Paternal age and Down's syndrome genotypes diagnosed prenatally: No association in New York State data

Summary An investigation of a paternal age effect independent of maternal age was undertaken for 98 cases of Down's syndrome genotypes diagnosed prenatally compared to 10,329 fetuses with normal genotype diagnosed prenatally in data reported to the New York State Chromosome Registry. The mean of the difference (delta) in paternal age of cases compared to those with normal genotypes after controlling for maternal age, was slightly negative,-0.27 with a 95% confidence interval of-1.59 to +1.06. A regression analysis was also done in which the data were first fit to an equation of the type lny=(bx+c) and then to the equation ln y=(bx+dz+c) where y = rate of Down's syndrome, x = maternal age, z = paternal age, and b, d, and c are parameters. This also revealed no evidence for a paternal age effect. The value of d (the paternal age coefficient) was in fact slightly negative,-0.0058, with an asymptotic 95% confidence interval of-0.0379 to +0.0263. Lastly, multiple applications of the Mantel-Haenszel test considering various boundaries in paternal age also revealed no statistically significant evidence for a paternal age effect independent of maternal age. These results are at variance with claims of others elsewhere of a very strong paternal age effect detected in studies at prenatal diagnoses. Five different hypotheses are suggested which may account for discrepancies among studies to date in findings on paternal age effects for Down's syndrome: (i) there are temporal, geographic, or ethnic variations in paternal age effects, (ii) there is no paternal age effect and statistical fluctuation accounts for all trends to date; (iii) methologic artifacts have obscured a paternal age effect in some studies which did not find a positive outcome; (iv) methodologic artifacts are responsible for the positive results in some studies to date; (v) there is a rather weak paternal age effect independent of maternal age in most if not all populations, but because of statistical fluctuation the results are significant only in some data sets. The results of all data sets to date which we have been able to analyze by one year intervals are consistent with a mean delta of +0.04 to +0.48 and in the value of d (the paternal age coefficient) of +0.006 to +0.017, and it appears the fifth hypothesis cannot be excluded. Projections based on this assumption are presented.     

Phototactic responses in Haematococcus lacustris and its modification by light intensity and the carotenoid biosynthesis inhibitor Norflurazon

At fluence rates below 45 W· m^-2 cells of the flagellate stage of Haematococcus lacustris react only positively phototactically with a rather high degree of orientation (indicated by r values up to 0.66 with the Rayleigh test). The directedness of orientation decreases with decreasing irradiance. The degree of directedness of the phototactic response depends on the intensity of preirradiation: Low light intensity applied after strong light application results in a dark reaction (low r values), low light given after darkness stimulates a rather high degree of directedness of positive phototaxis. Weak blue light (=483 nm; 0.4 W · m^-2) stimulates positive phototactic response, whereas comparable red light (=658 nm; 0.5 W · m^-2) does not.Cells which were grown in a medium containing 10^-4 M Norflurazon (effective in inhibition of carotenoid biosynthesis) although maintaining motility completely lose the ability to react positively phototactically. The possible role of carotenoids in the phototactic orientation is discussed.     

Paternal age and trisomy among spontaneous abortions

Summary The relationship of paternal age to specific types of trisomy and to chromosomally normal loss was investigated in data drawn from a case-control study of spontaneous abortions. Differences in paternal age between karyotype groups and controls delivering after 28 weeks gestation were tested using an urn model analysis which adjusted, by regression, for maternal age and, by stratification, for the effects of design variables (payment status, phase of study) and demographic factors (language, ethnicity). The magnitude of paternal age differences was estimated using least squares regression analysis. For chromosomally normal cases there was no association with paternal age. Among the fourteen trisomy categories examined, four (7, 9, 18, 21) showed increased paternal age ( 1 year above expectation), three (13, 20, 22) showed decreased paternal age and the rest, including the most common, trisomy 16, showed negligible differences. Only the association with trisomy 22 was statistically significant (P = 0.012), with a predicted reduction in paternal age of 2.1 years (95% CI -4.9, -0.5 years). This association did not vary with maternal age, payment status, phase of study, language or ethnicity. Because previous observations are extensive, the relation of paternal age to trisomy 21 was examined further. The overall association was not significant ( = 0.8 years; 95% CI -0.8, 2.4 years). Moreover, there was evidence that the magnitude and direction of paternal age associations vary significantly within the sample, although not between subgroups defined on the basis of payment, phase of study, language or ethnicity. With respect to maternal age, the trend is towards a greater paternal age difference for trisomy 21 losses in younger women (P = 0.058). Given the number of tests performed, the finding for trisomy 22 and reduced paternal age could be due to chance. Among trisomy types, the direction of paternal age associations was not consistent for chromosomes grouped according to characteristics that might relate to the probability of nondisjunction, such as size, arm ratio, or nucleolar organizer region content, or to the potential viability of the trisomy. Thus, neither on statistical nor biological grounds do the data provide compelling evidence of paternal age effects on the trisomies found among spontaneous abortions, or on chromosomally normal losses.     

Exploring the developmental overnutrition hypothesis using parental-offspring associations and FTO as an instrumental variable

Background

The developmental overnutrition hypothesis suggests that greater maternal obesity during pregnancy results in increased offspring adiposity in later life. If true, this would result in the obesity epidemic progressing across generations irrespective of environmental or genetic changes. It is therefore important to robustly test this hypothesis.

Methods and Findings

We explored this hypothesis by comparing the associations of maternal and paternal pre-pregnancy body mass index (BMI) with offspring dual energy X-ray absorptiometry (DXA)–determined fat mass measured at 9 to 11 y (4,091 parent–offspring trios) and by using maternal FTO genotype, controlling for offspring FTO genotype, as an instrument for maternal adiposity. Both maternal and paternal BMI were positively associated with offspring fat mass, but the maternal association effect size was larger than that in the paternal association in all models: mean difference in offspring sex- and age-standardised fat mass z-score per 1 standard deviation BMI 0.24 (95% confidence interval [CI]: 0.22 to 0.26) for maternal BMI versus 0.13 (95% CI: 0.11, 0.15) for paternal BMI; p-value for difference in effect < 0.001. The stronger maternal association was robust to sensitivity analyses assuming levels of non-paternity up to 20%. When maternal FTO, controlling for offspring FTO, was used as an instrument for the effect of maternal adiposity, the mean difference in offspring fat mass z-score per 1 standard deviation maternal BMI was −0.08 (95% CI: −0.56 to 0.41), with no strong statistical evidence that this differed from the observational ordinary least squares analyses (p = 0.17).

Conclusions

Neither our parental comparisons nor the use of FTO genotype as an instrumental variable, suggest that greater maternal BMI during offspring development has a marked effect on offspring fat mass at age 9–11 y. Developmental overnutrition related to greater maternal BMI is unlikely to have driven the recent obesity epidemic.     

Molecular basis for determining the sensitivity of eucaryotes to the antimitotic drug rhizoxin

Summary Rhizoxin, an antibiotic, exhibits potent anti-mitotic activity against most eucaryotic cells including those of higher vertebrates, plants and fungi by binding to -tubulin. ThebenA gene of three independently isolated rhizoxin-resistant (Rhi^r) mutants ofAspergillus nidulans was cloned, sequenced and compared with that of the wild-type, rhizoxin-sensitive (Rhi^s) strain. In all three Rhi^r mutants, the AAC codon for Asn-100 of thebenA -tubulin gene was altered to ATC, coding for Ile. Sequence displacement experiments confirmed that the substitution of Ile for Asn-100 confers resistance to rhizoxin in this organism. The amino acid sequences of -tubulin surrounding the 100th amino acid residue from the N-terminus including Asn-100 are highly conserved with a few exceptions. The fission yeastSchizosaccharomyces pombe and the budding yeastSaccharomyces cerevisiae are naturally occurring Rhi^r organisms whose -tubulin genes encode Ile and Val respectively at the 100th amino acid residue. The Ile-100 ofS. pombe and the Val-100 ofS. cerevisiae were altered to Asn using site-directed mutagenesis and gene displacement techniques. The resultant haploid strains of these two yeasts uniquely expressing -tubulin (Asn-100) instead of -tubulin (Ile-100 or Val-100) were found to be Rhi^s. Haploid yeast expressing -tubulin (Asn-100) is normal except for its sensitivity to rhizoxin. These results suggest that rhizoxin resistance has a common basis in both naturally occurring species and experimentally selected mutants in the substitution of Ile or Val for Asn-100 in -tubulin.     

Negative Effects of Paternal Age on Children's Neurocognitive Outcomes Can Be Explained by Maternal Education and Number of Siblings

Background

Recent findings suggest advanced paternal age may be associated with impaired child outcomes, in particular, neurocognitive skills. Such patterns are worrisome given relatively universal trends in advanced countries toward delayed nuptiality and fertility. But nature and nurture are both important for child outcomes, and it is important to control for both when drawing inferences about either pathway.

Methods and Findings

We examined cross-sectional patterns in six developmental outcome measures among children in the U.S. Collaborative Perinatal Project (n = 31,346). Many of these outcomes at 8 mo, 4 y, and 7 y of age (Bayley scales, Stanford Binet Intelligence Scale, Graham-Ernhart Block Sort Test, Wechsler Intelligence Scale for Children, Wide Range Achievement Test) are negatively correlated with paternal age when important family characteristics such as maternal education and number of siblings are not included as covariates. But controlling for family characteristics in general and mother''s education in particular renders the effect of paternal age statistically insignificant for most developmental measures.

Conclusions

Assortative mating produces interesting relationships between maternal and paternal characteristics that can inject spurious correlation into observational studies via omitted variable bias. Controlling for both nature and nurture reveals little residual evidence of a link between child neurocognitive outcomes and paternal age in these data. Results suggest that benefits associated with the upward trend in maternal education may offset any negative effects of advancing paternal age.     

High transmission of paternal plastid DNA in alfalfa plants demonstrated by restriction fragment polymorphic analysis

Summary A high frequency of paternal plastid transmission occurred in progeny from crosses among normal green alfalfa plants. Plastid transmission was analyzed by hybridization of radiolabeled alfalfa plastid DNA (cpDNA) probes to Southern blots of restriction digests of the progeny DNA. Each probe revealed a specific polymorphism differentiating the parental plastid genomes. Of 212 progeny, 34 were heteroplastidic, with their cpDNAs ranging from predominantly paternal to predominantly maternal. Regrowth of shoots from heteroplasmic plants following removal of top growth revealed the persistence of mixed plastids in a given plant. However, different shoots within a green heteroplasmic plant exhibited paternal, maternal, or mixed cpDNAs. Evidence of maternal nuclear genomic influence on the frequency of paternal plastid transmission was observed in some reciprocal crosses. A few tetraploid F₁ progeny were obtained from tetraploid (2n=4x=32) Medicago sativa ssp. sativa x diploid (2n=2x=16) M. sativa ssp. falcata crosses, and resulted from unreduced gametes. Here more than the maternal genome alone apparently functioned in controlling plastid transmission. Considering all crosses, only 5 of 212 progeny cpDNAs lacked evidence of a definitive paternal plastid fragment.Contribution No. 89-524-J from the Kansas Agricultural Experiment Station, Kansas State University, Manhattan     

CoMFA, HQSAR and molecular docking studies of butitaxel analogues with β-tubulin

Results from biochemical analyses for a series of 20 butitaxel analogues, paclitaxel and docetaxel were used to build two- and three-dimensional quantitative structure-activity relationship (QSAR) models in order to investigate the properties associated with microtubule assembly and stabilization. A comparative molecular field analysis (CoMFA) model was built using steric and electrostatic fields. The CoMFA model yielded an r² of 0.943 and a cross-validated r² (i.e. q²) of 0.376. Hologram quantitative structure-activity relationship (HQSAR) modeling of these same data generated an r² of 0.919 and a q² of 0.471. Contour maps used to visualize the steric and electrostatic contributions associated with activity or lack thereof were, as expected, localized to the varied position of the taxane system. Each analogue was docked successfully into a model of -tubulin derived from previously determined cryoelectron microscopy analyses of the tubulin / heterodimer. All analogues superimposed well with paclitaxel bound to the protein, as well as with each other. Defining the variable region of each structure as the ligand and docking it separately into the paclitaxel site revealed a modest correlation (r²=0.53) between activity and docking energy of all the compounds in the dataset. When only the butitaxel derivatives were considered, the correlation increased to 0.61. The mathematical models derived here provide information for the future development of taxanes.     

Cell recycling studies for α-amylase production by Bacillus amyloliquefaciens

Production of -amylase by a strain of Bacillus amyloliquefaciens was investigated in a cell recycle bioreactor incorporating a membrane filtration module for cell separation. Experimental fermentation studies with the B. amyloliquefaciens strain WA-4 clearly showed that incorporating cell recycling increased -amylase yield and volumetric productivity as compared to conventional continuous fermentation. The effect of operating conditions on -amylase production was difficult to demonstrate experimentally due to the problems of keeping the permeate and bleed rates constant over an extended period of time. Computer simulations were therefore undertaken to support the experimental data, as well as to elucidate the dynamics of -amylase production in the cell recycle bioreactor as compared to conventional chemostat and batch fermentations. Taken together, the simulations and experiments clearly showed that low bleed rate (high recycling ratio) various a high level of -amylase activity. The simulated fermentations revealed that this was especially pronounced at high recycling ratios. Volumetric productivity was maximum at a dilution rate of around 0.4 h^–1 and a high recycling ratio. The latter had to exceed 0.75 before volumetric productivity was significantly greater than with conventional chemostat fermentation.List of Symbols a proportionality constant relating the specific growth rate to the logarithm of G (h) - a ₁ reaction order with respect to starch concentration - a ₂ reaction order with respect to glucose concentration - B bleed rate (h^–1) - C starch concentration (g/l) - C ₀ starch concentration in the feed (g/l) - D dilution rate (h^–1) - D _E volumetric productivity (KNU/(mlh)) - e intracellular -amylase concentration (g/g cell mass) - E extracellular -amylase concentration (KNU/ml) - F volumetric flow rate (l/h) - G average number of genome equivalents of DNA per cell - k _l intracellular equilibrium constant - k ₂ intracellular equilibrium constant - k _s Monod saturation constant (g/l) - k ₃ excretion rate constant (h^–1) - k _d first order decay constant (h^–1) - k _gl rate constant for glucose production - k _st rate constant for starch hydrolysis - k _t1 proportionality constant for -amylase production (gmRNA/g substrate) - k ₁ translation constant (g/(g mRNAh)) - KNU kilo Novo unit - m maintenance coefficient (g substrate/(g cell massh)) - n number of binding sites for the co-repressor on the cytoplasmic repressor - Q repression function K₁/K₂Q1.0 - R ratio of recycling - R _s rate of glucose production (g/lh) - r _c rate of starch hydrolysis (g/(lh)) - R _eX retention by the filter of the compounds X: starch or -amylase - r intracellular -amylase mRNA concentration (g/g cell mass) - r _C volumetric productivity of starch (g/lh) - r _E volumetric productivity of intracellular -amylase (KNU/(g cell massh)) - r _r volumetric productivity of intracellular mRNA (g/(g cell massh)) - r _e volumetric productivity of extracellular -amylase (KNU/(mlh)) - r _s volumetric productivity of glucose (g/(lh)) - r _X volumetric productivity of cell mass (g/(lh)) - S ₀ free reducing sugar concentration in the feed (g/l) - S extracellular concentration of reducing sugar (g/1) - t time (h) - V volume (l) - X cell mass concentration (g/l) - Y yield coefficient (g cell mass/g substrate) - Y _E/S yield coefficient (KNU -amylase/g substrate) - Y _E total amount of -amylase produced (KNU) - substrate uptake (g substrate/(g cell massh)) - specific growth rate of cell mass (h^–1) - _d specific death rate of cells (h^–1) - _m maximum specific growth rate of cell mass (h^–1) This study was supported by Bioprocess Engineering Programme of the Nordic Industrial Foundation and the Center for Process Biotechnology, the Technical University of Denmark.     

Effect of Paternal Age on Reproductive Outcomes of In Vitro Fertilization

Although the adverse effects of maternal aging on reproductive outcomes have been investigated widely, there is no consensus on the impact of paternal age. Therefore, we investigated the effect of paternal age on reproductive outcomes in a retrospective analysis of 9,991 in vitro fertilization (IVF) cycles performed at the Reproductive Medicine Center of the Third Affiliated Hospital of Guangzhou Medical University (China) between January 2007 and October 2013. Samples were grouped according to maternal age [<30 (3,327 cycles), 30–34 (4,587 cycles), and 35–38 (2,077 cycles)] and then subgrouped according to paternal age (<30, 30–32, 33–35, 36–38, 39–41, and ≥42). The groups did not differ in terms of fertilization rate, numbers of viable and high-quality embryos and miscarriage rate when controlling maternal age (P >0.05). Chi-squared analysis revealed that there were no differences in implantation and pregnancy rates among the different paternal age groups when maternal age was <30 and 35–38 years (P >0.05). However, implantation and pregnancy rates decreased with paternal age in the 31–34 y maternal age group (P <0.05). Our study indicates that paternal age has no impact on fertilization rate, embryo quality at the cleavage stage and miscarriage rate. For the 30–34 y maternal age group, the implantation rate decreased with increased paternal age, with the pregnancy rate in this group being significantly higher in the paternal <30 y and 30–32 y age groups, compared with those in the 36–38 y and 39–41 y groups.     

Solar heat gain in a desert rodent: unexpected increases with wind speed and implications for estimating the heat balance of free-living animals

We quantified metabolic power consumption as a function of wind speed in the presence and absence of simulated solar radiation in rock squirrels, Spermophilus variegatus, a diurnal rodent inhabiting arid regions of Mexico and the western United States. In the absence of solar radiation, metabolic rate increased 2.2-fold as wind speed increased from 0.25 to 4.0 m·s^-1. Whole-body thermal resistance declined 56% as wind speed increased over this range, indicating that body insulation in this species is much more sensitive to wind disruption than in other mammals. In the presence of 950 W·m^-2 simulated solar radiation, metabolic rate increased 2.3-fold as wind speed was elevated from 0.25 to 4.0 m·s^-1. Solar heat gain, calculated as the reduction in metabolic heat production associated with the addition of solar radiation, increased with wind speed from 1.26 mW·g^-1 at 0.25 m·s^-1 to 2.92 mW·g^-1 at 4.0 m·s^-1. This increase is opposite to theoretical expectations. Both the unexpected increase in solar heat gain at elevated wind speeds and the large-scale reduction of coat insulation suggests that assumptions often used in heat-transfer analyses of animals can produce important errors.Abbreviations absorptivity of coat to solar radiation - kinematic viscosity of air (mm²·s^-1) - reflectivity of coat to solar radiation - a r _B expected at zero wind speed (s·m^-1) - A _P projected surface area of animal on plane perpendicular to solar beam (cm²) - A _SKIN skin surface area (cm²) - b Coefficient describing change in r _B with change in square-root of wind speed (s^1.5·m^1.5) - d hair diameter (m) - d characteristic dimension of animal (m) - D _H thermal diffusivity of air (m²·s^-1) - E evaporative heat loss (W·m^-2) - I probability per unit coat depth that photon will strike hair - k constant equalling 1200 J·m^-3·°C^-1 - l _C coat depth m) - l _H hair length (m) - M metabolic rate (W·m^-2) - n density of hairs of skin (m^-2) - Q _A solar heat gain to animal (W·m^-2) - Q _I solar irradiance intercepted by animal (W·m^-2) - RQ respiratory quotient - r _A thermal resistance of boundary layer (s·m^-1) - r _B whole-body thermal resistance (s·m^-1) - r _E thermal resistance between animal surface and environment s·m^-1) - r _R radiative resistance (s·m^-1) - r _S sum of r _B and r _E at 0.25 m·s^-1 (s·m^-1) - r _T tissue thermal resistance s·m^-1) - T _AIR air temperature (°C) - T _B body temperature (°C) - T _E operative temperature of environment (°C) - T _ES standard operative temperature of environment (°C) - u wind speed (m·s^-1)     

Light response of D1 turnover and photosystem II efficiency in the seagrassZostera capricorni

Biochemical and biophysical parameters, including D1-protein turnover, chlorophyll fluorescence, oxygen evolution activity and zeaxanthin formation were measured in the marine seagrassZostera capricorni (Aschers) in response to limiting (100 mol·m^–2·^–1), saturating (350 mol·m^–2·s^–1) or photoinhibitory (1100 mol·m^–2·s^–1) irradiances. Synthesis of D1 was maximal at 350 mol·m^–2·s^–1 which was also the irradiance at which the rate of photosynthetic O₂ evolution was maximal. Degradation of D1 was saturated at 350 mol·m^–2·s^–1. The rate of D1 synthesis at 1100 mol·m^–2·s^–1 was very similar to that at 350 mol·m^–2·s^–1 for the first 90 min but then declined. At limiting or saturating irradiance little change was observed in the ratio of variable to maximal fluorescence (Fv/Fm) measured after dark adaptation of the leaves, while significant photoinhibition occurred at 1100 mol·m^–2·s^–1. The proportion of zeaxanthin in the total xanthophyll pool increased with increasing irradiance, indicative of the presence of a photoprotective xanthophyll cycle in this seagrass. These results are consistent with a high level of regulatory D1 turnover inZostera under non-photoinhibitory irradiance conditions, as has been found previously for terrestrial plants.We would like to thank Professor Peter Böger (Department of Plant Biochemistry, University of Konstanz, Germany) for the kind gift of D1 antibodies. This work was partly supported by a University of Queensland Enabling Grant to CC.     

Chlorophyll-nutrient relationships in North Island lakes (New Zealand)

A model for the prediction of chlorophyll a in the near surface waters (1 m) of North Island lakes was developed using data from the literature and our own study of 12 North Island lakes. Annual geometric mean concentrations of chlorophyll a, total nitrogen and total phosphorus were used since no distinct growing season was discernable. Annual mean ratios of total nitrogen to total phosphorus in the near surface waters ranged between 10 and 59 (by weight). Strong correlations were obtained between log-transformed values of chlorophyll a and total nitrogen (r² = 0.53, n = 16), chlorophyll a and total phosphorus (r² = 0.71, n = 21), and between total nitrogen and total phosphorus (r² = 0.69, n = 16). However, after correcting for the high interdependency between total nitrogen and total phosphorus, only total phosphorus was found to be important in predicting chlorophyll concentrations. Much of the variance in the chlorophyll-phosphorus relation was attributable to differences in mean lake depth. Lakes with mean depths less than 11 m had significantly more chlorophyll a per unit of total phosphorus ( = 0.54 µg · µg^–1, SE = 0.05, n = 6) than lakes of greater mean depth ( = 0.17 µg · µg^–1, SE = 0.02, n = 14). When the effect of mean depth was taken into account, 89% of the variance in chlorophyll a was explained compared with 71% for the simple linear regression on total phosphorus alone.     

The fermentation of hexose and pentose sugars by Candida shehatae and Pichia stipitis

Summary The fermentation by Candida shehatae and Pichia stipitis of xylitol and the various sugars which are liberated upon hydrolysis of lignocellulosic biomass was investigated. Both yeasts produced ethanol from d-glucose, d-mannose, d-galactose and d-xylose. Only P. stipitis fermented d-cellobiose, producing 6.5 g·l^-1 ethanol from 20 g·l^-1 cellobiose within 48 h. No ethanol was produced from l-arabinose, l-rhamnose or xylitol. Diauxie was evident during the fermentation of a sugar mixture. Following the depletion of glucose, P. stipitis fermented galactose, mannose, xylose and cellobiose simultaneously with no noticeable preceding lag period. A similar fermentation pattern was observed with C. shehatae, except that it failed to utilize cellobiose even though it grew on cellobiose when supplied as the sole sugar. P. stipitis produced considerably more ethanol from the sugar mixture than C. shehatae, primarily due to its ability to ferment cellobiose. In general P. stipitis exhibited a higher volumetric rate and yield of ethanol production. This yeast fermented glucose 30–50% more rapidly than xylose, whereas the rates of ethanol production from these two sugars by C. shehatae were similar. P. stipitis had no absolute vitamin requirement for xylose fermentation, but biotin and thiamine enhanced the rate and yield of ethanol production significantly.Nomenclature _max Maximum specific growth rate, h^-1 - Q _p Maximum volumetric rate of ethanol production, calculated from the slope of the ethanol vs. time curve, g·(l·h)^-1 - q _p Maximum specific rate of ethanol production, g·(g cells·h) - Y _p/s Ethanol yield coefficient, g ethanol·(g substrate utilized)^-1 - Y _x/s Cell yield coefficient, g biomass·(g substrate utilized)^-1 - E Efficiency of substrate utilization, g substrate consumed·(g initial substrate)^-1·100     

Deducing the lateral distribution of proteins in lipid bilayer membranes

We consider four models of the lateral distribution of proteins in lipid bilayer membranes and study the fraction of lipids which are adjacent to at least one protein (adjacent lipids) and how this quantity depends upon protein concentration. The models are (i) hard hexagons free to move from one lattice site to another; (ii) hard disks moving on a continuum; (iii) a mixture of two sizes of nearly-hard disks moving on a continuum; (iv) a modification of (ii). The hexagons or disks represent proteins, while unocupied lattice sites or the remainder of the continuum represents lipids. In (iii) large disks represent proteins and small disks represent lipids. In (iv) some of the continuum between pairs of disks, where packing defects might occur, is not occupied by lipids. We find that an analytical expression for the adjacent lipids (Hoffmann et al. 1981), which is in excellent agreement with the results of the Hexagon model (i), breaks down at a packing density of f _A0.805, and we show by considering the hexagon pair correlation function, that this indicates the onset of random close packing, and that a transition to ordered close packing occurs at f _A=0.866. We thus obtain an operational definition for a random distribution of hexagons: distributions of packing densities0.805. We show that the Disk model (ii) gives results for adjacent lipids that are greater than the Hexagon model and compare these results to the Two Disk model (iii) which gives a result substantially less than the Hexagon model (Mountain et al. 1986). We show that the Modified Disk model (iv) gives results in essential agreement with the Hexagon model except for f _A0.77. Finally we discuss the general appearance of the motion restricted ESR spectrum and conclude that, of these four models, the Modified Disk or the Hexagon models best account for the data. We discuss why this is so with reference to the representation of a 3-dimensional membrane by a 2-dimensional plane.Abbreviations ESR Electron Spin Resonance     

Photoaffinity labeling and partial purification of the putative plant receptor for the fungal wilt-inducing toxin,fusicoccin

The high-affinity fusicoccin-binding protein (FCBP) was solubilized from plasma-membrane vesicles prepared from leaves of Vicia faba L. by aqueous two-phase partitioning. Conditions for the solubilization of intact FCBP-radioligand complexes were worked out. About 60–70% of the complexes can be solubilized with 50–60 mM nonanoyl-N-methylglucamide in the presence of 1 mg· ml^-1 soybean phosphatidylcholine, type IV S, and 20% (v/v) glycerol at pH 5.5. The slow dissociation of the radioligand, 9-nor-fusicoccin-8-alcohol-[³H] from the FCBP at low temperatures permits the purification of FCBP-radioligand complexes at 4–10° C by fast protein liquid chromatography on anion-exchange and gel permeation columns. The FCBP, extracted from plasma membranes with cholate and chromatographed in the presence of this detergent, gave an apparent molecular mass (M_r) of 80±20 kDa on gel permeation columns under the conditions used. By comparison of the elution profiles of the fraction most enriched in FCBP-radioligand complexes with polypeptide patterns obtained on sodium dodecyl sulfate-polyacrylamide gels, a polypeptide with an M_r of approx. 34kDa co-separated with the radioactivity profile. A second, faint band of approx. 31 kDa was sometimes also observed co-electrophoresing. Photoaffinity labeling of plasma-membrane vesicles with the new compound 9-nor-8[(3,5-[³H]-4-azidobenzoy)ethylenediamine]-fusicoccin ([³H]ABE-FC) and subsequent separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis labeled a single band with an M_r of 35±1 kDa. Labeling in this band was strongly reduced when the membranes were incubated with [³H]ABE-FC in the presence of 0.1–1 M fusicoccin. From our data, we conclude (i) that the 34-35-kDa polypeptide represents the FCBP and (ii) that in detergent extracts of plasma membranes this polypeptide is probably present as a di- or trimeric structure.Abbreviations ABE-FC [(4-azidobenzoyl)-ethylenediamine]-fusicoccin - ABE-NHS (4-azidobenzoyl)-N-hydroxysuccinimide ester - FC fusicoccin - FCBP fusicoccin-binding protein - FCol 9-norfusicoccin-8-alcohol - MAB monoclonal antibody - Mega-9(10) nonanoyl(decanoyl)-N-methylglucamide - M_r apparent molecular mass - PMSF phenylmethyl-sulfonyl fluoride - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - TCA trichloroacetic acid - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol     

Genetic control of seed proteins in wheat

Summary Electrophoretic profiles of crude protein extracts from seed of F₁ hybrids and reciprocal crosses among diploid, tetraploid and hexaploid wheats were compared with those of their respective parental species. The electrophoretic patterns within each of three pairs of reciprocal crosses, T.boeoticum X T.urartu, T.monococcun X T. urartu and T.dicoccum X T. araraticum, were different from one another but were identical with those of their respective maternal parents. Protein bands characteristic of the paternal parents were missing in F₁ hybrid seed suggesting that the major seed proteins in wheat were presumably regulated by genotype of the maternal parent rather than by the seed genotype. However, in another three pairs of reciprocal crosses, T.boeoticum X T. durum, T.dicoccum X T.aestivum and T. zhukovskyi x T. aestivum, protein bands attributable to the paternal parents were present in the F₁ hybrid seeds indicating that the seed proteins were not always exclusively regulated by the maternal genotype. The expression of paternal genomes is presumably determined by dosage and genetic affinity of the maternal and paternal genomes in the hybrid endosperm. The maternal regulation of seed protein content is probably accomplished through the maternal control over seed size. The seed protein quality may, however, depend upon the extent of expression of the paternal genome.     

Age and segmental differences in 5-hydroxytryptamine-induced hypersecretion in the pig small intestine

5-Hydroxytryptamine is a mediator in cholera toxin-induced hypersecretion in the small intestine. Our hypothesis is that the hypersecretion induced by 5-hydroxytryptamine in the small intestine decreases with increasing age and in an aboral direction in the small intestine. In vivo, measuring accumulated fluid in ligated loops, the apparent maximal efficacy of the 5-hydroxytryptamine-induced jejunal secretion in pig neonates was 4.8±1.1 mg·mg^–1 dry loop·45 min^–1. The apparent maximal efficacy decreased by 23% and 63% in young and adult pigs, respectively, compared with neonates. In vitro, measuring changes in short-circuit current in Ussing chambers, the apparent maximal efficacy was 66.7±4.8 A·cm^–2 in neonates and was reduced by 30% and 57% in young and adult pigs, respectively. Young pigs were used in the segmental study. The apparent maximal efficacy in vivo was 3.7±0.5 mg·mg^–1 dry loop and decreased by 22% and 56% in the mid and distal small intestine, respectively. By contrast, in vitro the apparent maximal efficacy was elevated by 56% to 72.0±5.0 A·cm^–2 in the distal compared with the proximal part. In conclusion, the secretory response to 5-hydroxytryptamine in pig small intestine decreases with increasing age and in the aboral direction according to in vivo results. We suggest that the decrease in sensitivity to 5-hydroxytryptamine can explain a part of the reduced secretory response to cholera toxin with age and in the aboral direction of the small intestine.Abbreviations ASF pituitary peptide antisecretory factor - AMP cyclic adenosine monophosphate - CT cholera toxin - E _max apparent maximal efficacy - EC enterochromaffine ENS enteric nerve system - 5-HT 5-hydroxytryptamine serotonin - LT heat-labile - E. coli enterotoxin - PD electrical potential difference - R tissue resistance - SCC short-circuit current - VIP vasoactive intestinal peptide     

The Impact of Paternal and Maternal Smoking on Semen Quality of Adolescent Men

Background

Maternal smoking during pregnancy has been reported to negatively impact sperm counts of the sons. Sufficient data on the effect of paternal smoking is lacking.

Objectives

We wished to elucidate the impact of maternal and paternal smoking during pregnancy and current own smoking on reproductive function of the male offspring.

Methods

Semen parameters including sperm DNA integrity were analyzed in 295 adolescents from the general population close to Malmö, Sweden, recruited for the study during 2008–2010. Information on maternal smoking was obtained from the Swedish Medical Birth Register, and regarding own and paternal smoking from questionnaires. The impacts of maternal, paternal and own smoking were evaluated in a multivariate regression model and by use of models including interaction terms. Totally, three exposures and five outcomes were evaluated.

Results

In maternally unexposed men, paternal smoking was associated with 46% lower total sperm count (95%CI: 21%, 64%) in maternally unexposed men. Both paternal and maternal smoking were associated with a lower sperm concentration (mean differences: 35%; 95%CI: 8.1%, 55% and 36%; 95%CI: 3.9%, 57%, respectively) if the other parent was a non-smoker. No statistically significant impact of own smoking on semen parameters was seen.

Conclusions

Prenatal both maternal and paternal smoking were separately associated with some decrease in sperm count in men of whom the other parent was not reported to smoke.     

Food dependence and energetics of freeliving nematodes

Summary The food dependence of larval duration, fecundity and the intrinsic rate of natural increase follow a hyperbolic form, which can for the former be described by the Michaelis-Menten function.Maximal larval duration at 20° C is 62 h, maximal fecundity is 153 eggs per female and r _max is 1.136 per day. The lower food threshold is 10⁸ E. coli cells·ml^-1 (=0.06 mg dry weight·ml^-1) for larval growth and 2·10⁸ cells·ml^-1 for reproduction and r. 50% of maximal performances (K _s ) are attained at 5·10⁸ and 7.5·10⁸ cells·ml^-1 respectively.Reproductive effort at dense food is highest immediately after maturation (e.g. 50% of the total eggs produced by a female are laid within 2 days after onset of egg production). At lower food densities the reproductive effort is delayed.Larval mortality increases strongly below 10⁹ cells·ml^-1.The results reported sofar were obtained with E. coli cells which were harvested at the phase of decreasing population growth in batch cultures. With cells from the exponential and the stationary phase, performances are increased and decreased respectively. This is partly due to differences in bacterial biomass per unit cell, partly an expression of the change of nutritive value of bacterial cells with growth phases.