The morphogenetic significance of the first quartet micromeres for the development of the snailBithynia tentaculata

Summary The significance of the first quartet of micromeres for the morphogenesis ofBithynia — a polar lobe-forming gastropod-has been studied by deletion experiments. After removal of the whole first quartet at the 8-cell stage a dorsoventrally organized veliger larva is formed. Apparently, an interaction between the animal micromeres and a vegetal macromere, which is essential for the origin of a dorsoventral organization in equally cleaving gastropods, is not required in polar lobe forming eggs. It is concluded that in these eggs dorsoventrality is determined by segregation of the polar lobe. The embryos, in which the first quartet has been removed, never develop head structures. This indicates that the capacity to form head structures is restricted to the first quartet of micromeres. Deletion of a specific first quartet micromere (1a, 1b, 1c or 1d) showed, however, that the individual cells of this quartet are not strictly determined right from their origin. Frequently regulative development was observed after removal of individual first quartet cells.     

Simulated removal trapping considered in connection with actual census data in small mammals

A record of simulated removal trapping of 50 samples drawn from N=50 under a design has been considered as to how it does contribute to practical censuses of small mammals. It follows that, for ordinary-density populations so far experienced, the removal census based on the theory may frequently lead to quite wrong estimates from single-plot data by the simplest method, and that the maximum likelihood method is doubtless better, but even this method may produce right estimates in about half of the cases, their standard error being of limited availability. Therefore pooling of data from many plots are desirous for such populations.     

The distribution of fluoride in some antarctic seals

Summary The aim of this investigation was to find out why some antarctic seals tolerate fluoride levels in their food (krill) that would be toxic to man. The fluoride content of different soft and hard tissues, urine and feces from 16 L. carcinophagus, 13 L. weddelli and 2 A. tropicalis (urine only) were determined by the fluoride sensitive electrode or by a photometric method (urine). Results and conclusions are following: All soft tissues have low concentrations of fluoride in the same range as soft tissues from non antarctic and non krill eating marine or terrestrial vertebrates. But within the soft tissues there are significant differences in the fluoride content (blood: 0.001 ppm F/dw — brain: 9.1 ppm F/dw). A special tolerance for fluoride of soft tissues can be excluded. Compared with man or weddell-seals the crabeater-seals store two times more fluoride in their skeleton. Hard structures that stop their mineralisation early in the development like teeth have only a relatively low fluoride content. For the same reason only neglectable amounts of fluoride could be detected in hair. Fluoride excretion by the kidneys is efficient and is — besides the storage of fluoride in the skeleton — the second mechanism to guarantee a good blood homoiostasis for fluoride. Until now it is impossible to decide how much fluoride from the food is resorbed by the digestive tract.     

Comparative chiasma analysis using a computerised optical digitiser

A new computerised technique has been devised for measuring the distribution of chiasmata along diplotene bivalents. The method involves the introduction into the field of view of the microscope, of a fine light spot which can be accurately manipulated along the chromosomes of each bivalent. The data recorded include (a) the positions of the chiasmata along the bivalent in terms of their relative distances from the centromere and (b) the individual bivalent and cellular chiasma frequencies. — The method has been applied to the analysis of chiasma distribution patterns in the two known species of the genus Caledia, C. species nova 1 and C. captiva and in two chromosomal races of the latter. Statistical tests indicate that within bivalents at least 40% of the comparative distribution patterns of chiasmata between races and species are significantly different. Similar comparisons between populations within races reveal only 18% significant differences. — The observed distribution patterns of chiasmata in this genus suggest that chiasma formation is sequential from centromere to telomere. — The variation in the frequency and distribution of chiasmata between races and species suggests that the interference distances between successive chiasmata are, at least partially, independent of chiasma frequency and position. — The interracial and interspecific differences in chromosome structure are correlated with changes in chiasma pattern.     

Ants in their plants: Pseudomyrmex ants reduce primate,parrot and squirrel predation on Macrolobium acaciifolium (Fabaceae) seeds in Amazonian Brazil

Although plant‐inhabiting ants are known to act as effective deterrents to a variety of vertebrate and invertebrate herbivores, this has been reported only once before for primates, a group better known for their predation of ants. In the present study, we investigated the effects that colonies of Pseudomyrmex viduus ants living in individual Macrolobium acaciifolium (Fabaceae) trees have on the rates of visitation and fruit removal by four taxa of seed‐predating vertebrates: the primate Cacajao melanocephalus ouakary; macaws (Ara spp.); large parrots (Amazona spp.); and the Northern Amazonian red squirrel (Sciurus igniventris). We found that ant presence significantly reduced both rates of visitation and of fruit removal by C. m. ouakary. The same pattern of reduced fruit removal was also observed for other seed predators (parrots, macaws, and squirrels) but not for visitation rates (although this may be a result of the small sample size). This appears to be only the second‐known demonstration of the repellent effect of ants on primates and, indeed, the first for squirrels and psittacine birds. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 260–273.     

Tétraploïdie expérimentale chez le Triton Pleurodeles waltlii Michah.

Fischberg's method, thanks to which tetraploid individuals can be obtained, has been adapted to the newt Pleurodeles waltlii. — If at the beginning of the first furrow formation, the eggs are submitted for 10 minutes to a sudden increase in temperature (37.2–37.3°C), the embryos that subsequently develop are tetraploid in 100% of the cases. The percentage obtained of viable individuals is about 30% of the number of heated eggs. — A temperature treatment between 36.2 and 36.4°C applied at the same period and for the same length of time may lead to the formation of viable animals diplo-tetraploid mosaic. — Among adult tetraploids or diplo-tetraploid mosaic males and females can be found. — The cells of tetraploids can easily be distinguished from those of diploids by their larger size. Therefore, the former can be used as cellular markers.     

Improved screening method for beta-blockers in urine using solid-phase extraction and capillary gas chromatography—mass spectrometry

An improved screening method for beta-blockers in urine is proposed, involving enzymatic hydrolysis, solid-phase extraction and capillary gas chromatography—mass spectrometry. Several extraction methods for beta-blockers, such as conventional liquid—liquid and solid-phase extraction procedures, have been evaluated for at least eight beta-blockers. Additionally, the gas chromatographic properties and mass fragmentation of the trimethylsilyl—trifluoroacetyl, trifluoroacetyl and cyclic n-butylboronate derivatives of beta-blockers have been compared and evaluated with respect to their efficiency for screening urine. The resulting screening method proved to be a specific and sensitive procedure, enabling these analytes to be detected and identified up to 48 h after the administration of a dosage, usually encountered in doping cases.     

Liver stem cells: a two compartment system

Hepatocytes and biliary epithelia are phenotypically very dissimilar, but share a common ancestry. Hepatocytes regenerate very efficiently, and their division potential indicates that many of them are functional stem cells. When hepatocyte-damaging agents also impair the regenerative ability of surviving hepatocytes, a potential stem cell system of biliary origin is activated to generate new hepatocytes — a reversal of ontogeny. Now both bile duct derived cells and hepatocytes can be isolated from the liver, genetically modified in vitro and returned to their in vivo origins where, after considerable population expansion, they can function as hepatocytes — paving the way for ex vivo gene therapy.     

Gas chromatographic—mass spectrometric determination of plasma 5-fluorouracil after administration of 1-hexylcarbamoyl-5-fluorouracil to dogs and humans

A simple, sensitive and specific method for determining 5-fluorouracil (5-FU) in plasma after the administration of 1-hexylcarbamoyl-5-fluorouracil (HCFU) was developed using gas chromatography—mass spectrometry. Thymine was used as the internal standard. After removal of interfering substances with chloroform, diethyl ether and Amberlite XAD-2 resin, 5-FU and thymine were extracted with 16% n-propanol in diethyl ether and methylated with trimethylanilinium hydroxide. Fragment ions at m/e 158 and 154, the molecular ion of the dimethyl derivatives of 5-FU and thymine, respectively, were used to monitor 5-FU and thymine. The sensitivity of the method is 10 ng/ml, which is sufficient to determine the 5-FU levels in plasma after the administration of therapeutic doses of HCFU to patients.     

On the use of log‐transformation versus nonlinear regression for analyzing biological power laws

Xiao and colleagues re‐examined 471 datasets from the literature in a major study comparing two common procedures for fitting the allometric equation y = ax^b to bivariate data (Xiao et al., 2011). One of the procedures was the traditional allometric method, whereby the model for a straight line fitted to logarithmic transformations of the original data is back‐transformed to form a two‐parameter power function with multiplicative, lognormal, heteroscedastic error on the arithmetic scale. The other procedure was standard nonlinear regression, whereby a two‐parameter power function with additive, normal, homoscedastic error is fitted directly to untransformed data by nonlinear least squares. Xiao and colleagues articulated a simple (but explicit) protocol for fitting and comparing the alternative models, and then used the protocol to examine each of the datasets in their compilation. The traditional method was said to provide a better fit in 69% of the cases and an equivalent fit in another 15%, so the investigation appeared to validate findings from a large majority of prior studies on allometric variation. However, focus for the investigation by Xiao and colleagues was overly narrow, and statistical models apparently were not validated graphically in the scale of measurement. The present study re‐examined a subset of the cases using a larger pool of candidate models and graphical validation, and discovered complexities that were overlooked in their investigation. Some datasets that appeared to be described better by the traditional method actually were unsuited for use in an allometric analysis, whereas other datasets were not described adequately by a two‐parameter power function, regardless of how the model was fitted. Thus, conclusions reached by Xiao and colleagues are not well supported and their paradigm for fitting allometric equations is unreliable. Future investigations of allometric variation should adopt a more holistic approach and incorporate graphical validation on the original arithmetic scale. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 1167–1178.     

Growth and removal of nitrogen and phosphorus by free-living and chitosan-immobilized cells of the marine cyanobacterium Synechococcus elongatus

This study investigated the growth rate of chitosan-immobilized cells of the marine cyanobacterium Synechococcus elongatus and its potential application in the removal of nitrogen and phosphorus for wastewater treatment. Immobilized cell cultures had a lag phase of growth due to the immobilization method, and their growth rate was similar to that of free-living cell cultures. Ammonia removal was higher in free cells (54%) than in immobilized cells (29%), but nitrate removal was similar in immobilized (38%) and free cells (44%); phosphorus removal was more efficient in free cells (88%) than in immobilized cells (77%). Chlorophyll a and protein content were higher in immobilized cells. Our study demonstrates that S. elongatus immobilized into chitosan capsules can remove nutrients and is able to maintain a growth rate comparable to that of free cells in culture.     

Resolution of heterogeneous charged antibody aggregates via multimodal chromatography: A comparison to conventional approaches

Clearance of aggregates during protein purification is increasingly paramount as protein aggregates represent one of the major impurities in biopharmaceutical products. Aggregates, especially dimer species, represent a significant challenge for purification processing since aggregate separation coupled with high purity protein recovery can be difficult to accomplish. Biochemical characterization of the aggregate species from the hydrophobic interaction and cation exchange chromatography elution peaks revealed two different charged populations, i.e. heterogeneous charged aggregates, which led to further challenges for chromatographic removal. This paper compares multimodal versus conventional cation exchange or hydrophobic chromatography methodologies to remove heterogeneous aggregates. A full, mixed level factorial design of experiment strategy together with high throughput experimentation was employed to rapidly evaluate chromatographic parameters such as pH, conductivity, and loading. A variety of operating conditions were identified for the multimodal chromatography step, which lead to effective removal of two different charged populations of aggregate species. This multimodal chromatography step was incorporated into a monoclonal antibody purification process and successfully implemented at commercial manufacturing scale. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:636–645, 2014     

Twin-core packed-bed reactors for organic-phase enzymatic esterification with water activity control

A method for the removal of water and the control of water activity, a _w, during enzymatic esterification is the use of salt hydrate pairs. When this technique is used on a laboratory scale, the recovery and reuse of the salt are not critical. Potential problems, such as the reactivity of some salts, can also be overcome simply by substituting another salt. However, if this technique is to be used on a larger scale, economic constraints would require salt recovery and restric the range of salts that could be used. In this article a twin-core packed-bed reactor — used for the esterification of an equimolar mixture of decanoic acid and dodecanol catalysed by lipase from Candida rugosa — which facilitates salt recovery and permits a _w control without direct contact between immobilized enzyme and salt, has been described. a _w control was maintained by using suitable salt hydrate mixtures in the inner core of the reactor. The substrate mixture was esterified by pumping it through the outer core of the reactor, which contained enzyme immobilized on a macroporous polypropylene support. Complete conversion, albeit at different rates, was obtained with a _w buffering at 0.48 and 0.8 by using hydrates of Na₄P₂O₇ and Na₂HPO₄.     

Mutual support and selection between branches of damaged plants

Snow (1931) showed that the fate of a branch of a plant that had suffered local herbivory could be determined by correlative effects of other branches. This neglected work was continued in the current study, herbivory being simulated by the removal of leaves of different ages from pea plants with two branches. A damaged branch was suppressed when an undamaged alternative branch was present; otherwise the damage never prevented continued development. The removal of mature leaves had a smaller effect than the removal of immature, expanding leaves. When leaves were removed from both branches it was the branches that suffered less damage to their immature leaves that continued shoot development. Branches from which all photosynthetic leaves were repeatedly removed developed only when they retained their immature leaves and remained dominant, inhibiting the development — but not the photosynthesis — of the other branch on the same plant. Accounting for these results requires mechanisms that compare the different branches of the plant and select for development the ones that have the greatest potential for future, rather than present, photosynthesis. It is concluded that a compartmentalized or sectorial distribution of essential substrates can be modified by correlative relations that are probably mediated by hormones.     

Simultaneous high-performance liquid chromatographic determination of urinary metabolites of benzene, nitrobenzene, toluene, xylene and styrene

A high-performance liquid chromatographic method is described for the simultaneous determination of six urinary metabolites of several aromatic chemicals: phenol (from benzene), hippuric acid (from toluene), 3-methylhippuric acid (from xylene), mandelic and phenylglyoxylic acid (from styrene) and 4-nitrophenol (from nitrobenzene). Reversed-phase liquid chromatography was performed in an isocratic mode at 1 ml/min on a 5-μm C₁₈ column using two mobile phases: (A) acetonitrile—1% phosphoric acid (10:90); (B) acetonitrile—1% phosphoric acid (30:70). Phase A separates the six metabolites well, but phase B allows to a more rapid and reproducible simultaneous determination of phenolic compounds than phase A. For these compounds a prior enzymic hydrolysis step using Helix pomatia juice is performed to hydrolyse their sulphate and glucuronate conjugates. The reproducibility and the specificity are both excellent. Furthermore, the method is rapid, economical and easily automated. The proposed method appears very suitable for the routine monitoring of workers exposed to these chemicals on the basis of the biological threshold limit values.     

Riparian Conservation Facilitated Expansion of Gray Hawks

Desert riparian ecosystems are among the most threatened biodiversity hotspots in the United States, and efforts to conserve them have been increasing. In 2010–2011 and 2014–2016, we examined shifts in the distribution, habitat characteristics, diet, nest success, and productivity of the gray hawk (Buteo plagiatus), 25 years after a Riparian National Conservation Area was established along the San Pedro River in Arizona, USA, to determine how the removal of grazing and agriculture may have affected the ecosystem. The gray hawk population increased and expanded from mesquite (Prosopis spp.)-dominated areas that they historically occupied into areas that were dominated by grassland. In contrast with the 1990s, percent of mesquite cover in pairs' territories did not correlate with their productivity. Gray hawk diets also included more mammals in our study period, particularly in territories with more grassland. We propose that conservation measures created habitat for gray hawks in areas that were previously unsuitable by allowing grasslands to regenerate and become habitat for their prey, and that management strategies in the San Pedro Riparian National Conservation Area could serve as a model for conservation of other desert riparian ecosystems. © 2020 The Wildlife Society.     

Low heritability in morphological characters of Tengmalm's owls: The role of cyclic food and laying date?

Summary In parent—offspring regressions, high heritability estimates of characters may simply be due to common environment: the resemblance between the living conditions of parents and their offspring in species showing restricted natal dispersal. In vole-eating Tengmalm's owls (Aegolius funereus), the natal dispersal and breeding dispersal of adult females are wide (up to > 1000 km and > 500 km, respectively), whereas adult males are resident. We found that body measurements of 183 recruits born in western Finland were independent of parental age and vole abundance in the birth year. Early-laid eggs produced longer winged recruits than late-laid eggs. The wing lengths of the daughters showed a significant positive regression on the wing length of their mothers, but the removal of the maternal effect via laying date lowered this relationship. The development time of offspring to the first autumn might also be crucial for morphological characters of females in their later life. Significant regressions were not found between the wing length of the son and his father. The mother—daughter regression was small for laying date, but positive (p = 0.08) for clutch size. These results suggest low heritability in breeding and morphological characters of owls and this low heritability may enable plastic adjustment to optimize fitness at any stage in a fluctuating environment. Nonadditive genetic variance also creates variation between offspring characters that are not genetically correlated with the parents and may explain these low heritability estimates.     

Differential staining of polytene chromosome bands in Chironomus by Giemsa banding methods

Two Giemsa banding methods (C banding and RB banding) are described which selectively stain the centromere bands of polytene salivary gland chromosomes in a number of Chironomus species. — By the C banding method the polytene chromosome appearance is changed grossly. Chromosome bands, as far as they are identifiable, are stained pale with the exception of the centromere bands and in some cases telomeres, which then are intensely stained reddish blue. — By the RB method the centromere bands are stained bright blue, whereas the remainder of the polytene bands stain red to red-violet. — Contrary to all other species examined, in Chironomus th. thummi numerous interstitial polytene chromosome bands, in addition to the centromere regions, are positively C banded and blue stained by RB banding. In the hybrid of Ch. th. thummi x Ch. th. piger only those interstitial thummi bands which are known to have a greater DNA content than their homologous piger bands are C banding positive and blue stained by the RB method whereas the homologous piger bands are C banding negative and red stained by RB banding. Ch. thummi and piger bands with an equal amount of DNA both show no C banding and stain red by RB banding. — It seems that the Giemsa banding methods used are capable of demonstrating, in addition to centromeric heterochromatin, heterochromatin in those interstitial polytene chromosome bands whose DNA content has been increased during chromosome evolution.     

Interspecific variation in the defensive responses of obligate plant-ants: experimental tests and consequences for herbivory

The aggressive behavior of ants that protect plants from herbivores in exchange for rewards such as shelter or food is thought to be an important form of biotic defense against herbivory, particularly in tropical systems. To date, however, no one has compared the defensive responses of different ant taxa associated with the same plant species, and attempted to relate these differences to longer-term efficacy of ant defense. We used experimental cues associated with herbivory—physical damage and extracts of chemical volatiles from leaf tissue—to compare the aggressive responses of two ant species obligately associated with the Amazonian myrmecophyte Tococa bullifera (Melastomataceae). We also conducted a colony removal experiment to quantify the level of resistance from herbivores provided to plants by each ant species. Our experiments demonstrate that some cues eliciting a strong response from one ant species elicited no response by the other. For cues that do elicit responses, the magnitude of these responses can vary interspecifically. These patterns were consistent with the level of resistance provided from herbivores to plants. The colony removal experiment showed that both ant species defend plants from herbivores: however, herbivory was higher on plants colonized by the less aggressive ant species. Our results add to the growing body of literature indicating defensive ant responses are stimulated by cues associated with herbivory. However, they also suggest the local and regional variation in the composition of potential partner taxa could influence the ecology and evolution of defensive mutualisms in ways that have previously remained unexplored.