Dispersal patterns and status change in a co‐operatively breeding cichlid Neolamprologus pulcher: evidence from microsatellite analyses and behavioural observations

Genetic techniques and long‐term behavioural observations were combined to investigate dispersal patterns and changes in social position in Neolamprologus pulcher , a co‐operatively breeding cichlid from Lake Tanganyika. Comparisons of genetic variance ( F _ST) across sub‐populations demonstrated that fish were genetically more similar to individuals from proximate sub‐populations compared to individuals from distant sub‐populations. Microsatellite analyses revealed year‐long philopatry for some individuals and that other individuals dispersed to new territories and sub‐populations. Individuals appeared to disperse farther (across many territories in a sub‐population or to new sub‐populations) to achieve breeding status. Non‐breeding group members (or helpers) were observed to inherit breeding positions and male breeders were replaced faster than female breeders. These results demonstrate that important and difficult to obtain life‐history information can be obtained from genetic sampling.     

Inactivation by gene disruption of 2‐cysteine‐peroxiredoxin in Synechocystis sp. PCC 6803 leads to increased stress sensitivity

2‐Cysteine‐peroxiredoxins (2‐CP) constitute a ubiquitous group of enzymes which reduce toxic alkyl hydroperoxides. In higher plants it was shown that the nuclear encoded 2‐CPs are posttranslationally imported into the chloroplasts, the site of most active oxidative metabolism in plants (Baier and Dietz 1997, Plant J. 12; 179‐190). The genome of the bluegreen alga Synechocystis (EMBL acc. # D64000) encodes a 2‐CP which shares 60% homology to higher plant 2‐CPs on the gene level and about 70% on the level of the mature protein. In order to elucidate the physiological significance of 2‐CPs for photosynthetic organisms, the 2‐CP gene was mutated in Synechocystis sp. PCC 6803 by insertion of a kanamycin gene cartridge. Following complete segregation mutant lines were analyzed for growth and photosynthetic parameters. The mutants revealed decreased growth rates as compared to the wild type. Growth inhibition was relieved after lowering the concentration of Fe or trace elements in the growth medium. Chlorophyll a fluorescence transients as induced by saturating light pulses were used as indicator for the state of photosynthesis. The effective quantum yield decreased at lower light intensities in the mutants as compared to the wild type Synechocystis . Simultaneously, electron transport rates saturated at lower light intensities in the mutants. These data provide the first evidence that 2‐CPs play a pivotal protective role in photosynthesis.     

A study of the relation between CP29 phosphorylation, zeaxanthin content and fluorescence quenching parameters in Zea mays leaves

The hypothesis that phosphorylation of the minor photosystem II antenna complex CP29 (CP34 formation) in Zea mays (cv. Dekalb DK300), under conditions of illumination and low temperature stress, may constitute a protective mechanism against photoinhibition, has been investigated. It is demonstrated that illumination at low temperature induces a marked increase in reversible non‐photochemical quenching yield of chlorophyll fluorescence, together with CP34 formation. These two parameters, however, are not related as CP34 dephosphorylates to CP29 in the dark, with a half‐time of about 10 min, while the enhanced non‐photochemical quenching yield is stable for many hours. The enhanced non‐photochemical quenching yield seems to correlate with zeaxanthin formation. The influence of CP34 formation on photoinhibition was also directly investigated. No measurable effect on this parameter could be observed after treatment with high light. It is concluded that CP34 is probably not directly involved in photoprotective processes.     

Long‐term patterns in growth of Oneida Lake walleye: a multivariate and stage‐explicit approach for applying the von Bertalanffy growth function

Total length ( L _T) and its inter annual variation of walleye Sander vitreus from Oneida Lake, New York, based on 51 years (1950–2000) of data for ages 1 to 7 years were analysed. Growth increased over time at young ages, did not change at intermediate ages and decreased at old ages. Total length at age increased over time to age 4 or 5 years, but was stable at older ages. Principle component analysis was used to study the pattern of variations in annual L _T increments among years. More than 92 and 91% of inter annual variability in growth was described by the first three principal components for males and females, respectively. The first principal component was a general indicator of annual growth at all ages, but was dominated by annual growth at intermediate ages. The second and third principal components represented contrasts among yearling L _T, yearling growth and growth at older ages. Therefore, changes in the three stage‐specific parameters, yearling L _T, yearling growth and asymptotic L _T, explained most of the variance in observed growth. Using these three stage‐specific parameters for the von Bertalanffy growth function facilitated interpretations of growth comparisons.     

Quantitative representation of local forest composition in forest‐floor pollen assemblages

1 We compared modern pollen assemblages from 60 moss polster sites in northern New York with forest composition data within 20–120 m of the sites using extended R ‐value (ERV) models, which correct for non‐linearities arising from use of pollen percentage data. Our sites were concentrated in two regions, one dominated by Tsuga and hardwood ( Acer , Betula , Fagus ) forests, and the other by Tsuga , Pinus , Betula , Acer and Quercus forests.
2 Our results confirm that forest‐floor pollen assemblages are dominated by pollen originating from trees growing more than 20 m from the site of deposition. However, our results suggest that background pollen percentages were overestimated by Jackson & Wong in 1994, owing to unusually high Pinus pollen production in the year of their sampling.
3 Expansion of our vegetation sampling radius from 20 to 120 m resulted in modest but consistent improvement in model fit and a decrease in background pollen percentages.
4 ERV model parameters (slope and background) differed substantially between the two study regions, primarily owing to differences in background pollen productivity and dispersal from regional sources.
5 High background pollen percentages may lead to poor estimation of calibration parameters in regions of complex vegetation patterns. Expansion of the vegetation sampling radius to reduce the background component may lead to better parameter estimates.
6 Calibration of pollen–vegetation relationships requires definition of the vegetation term so that it approximates the vegetation sampled by the pollen assemblages. Critical challenges are to define better the appropriate vegetation sampling area and distance‐weighting functions for application to pollen–vegetation calibration.     

Inter‐individual differences in rates of routine energy loss and growth in young‐of‐the‐year juvenile Atlantic cod

Inter‐individual differences in rates of routine (non‐feeding) metabolism and growth were evaluated in young‐of‐the‐year (YOY) juvenile Atlantic cod Gadus morhua . Rates of O₂ consumption, CO₂ production and ammonia (TAN) excretion were measured in 64, 25–43 mm standard length ( L _S) YOY growing at different rates (0·27–0·47 mm day⁻¹) in a common rearing tank. Parameter rates ( y ) increased allometrically ( y = a·M^b ) with increasing body mass ( M ) with b ‐values for O₂ production, CO₂ consumption and TAN excretion equal to 0·81, 0·89 and 0·56, respectively. In some cases, residuals from these regressions were significantly negatively correlated to fish growth rate. In no cases did residuals of parameter rates increase with increasing growth rate. These data suggest that, during unfed periods, relatively fast‐growing fish were more metabolically efficient than slower‐growing fish from the same cohort. The fish condition factor, derived from     , also significantly decreased with increasing growth rate. Results indicated differences in both the rates of routine energy loss and the patterns of growth allocation among YOY Atlantic cod. Since these physiological attributes were positively correlated with growth rate, they may be indicative of 'survivors' in field populations.     

Inter‐ and intra‐observer variation in the reporting of cervical smears: specialist cytopathologists versus histopathologists

One hundred and ten cervical smears were circulated to five specialist consultant cytopathologists and five consultant histopathologists. Of these smears, 100 were randomized and re‐circulated. The cytopathologists reported endocervical cells and wart virus infection more frequently than the histopathologists, although neither group showed good inter‐observer agreement for either assessment. Apart from smear adequacy and the presence of endocervical cells, both groups showed good intra‐observer agreement in all the parameters measured. This suggests that overall individuals were applying their own personal criteria with consistency over time, although a previous study had shown considerable lack of inter‐observer agreement among the histopathologists on the grade of dyskaryosis and the management recommendation. The results indicate that specialist cytopathologists bring a different viewpoint to the reporting of cervical smears than histopathologists. They also show a lack of standardization in the reporting of smears despite the guidelines issued by the British Society for Clinical Cytology.     

c‐erbB‐2 and p53 expression in breast cancer fine needle aspirates

The aim of this study was to co‐evaluate c‐ erbB ‐2 and p53 protein expression in breast cancer fine needle aspirates (FNA) and to compare this with histological variables and the immunohistochemical phenotype of the tumours. Furthermore, we assessed the relationship of c‐ erbB ‐2 and p53 immunocytochemical expression to tumour prognostic factors. We examined 124 breast cancer FNAs and 79 matched surgical specimens using the avidin–biotin complex (ABC) and the alkaline phosphatase immunocytochemical techniques. C‐ erbB ‐2 immunopositivity was detected in 37.9% of the FNAs, while 31.7% were positive for p53. A statistically significant correlation was observed between p53 negativity and absence of c‐ erbB ‐2 immunostaining in the FNAs ( P =0.0007). Smears from infiltrating ductal carcinomas tended to be more frequently positive for p53 (36.7%) than those from lobular carcinomas (11.7%) ( P =0.054). In matched tumour tissues, c‐ erbB ‐2 was positive in 16.7% and p53 in 19% of cases. The immunocytochemical results for both c‐ erbB ‐2 and p53 were significantly correlated with the immunohistochemical results. There was no correlation between c‐ erbB ‐2 and p53 immunostaining, in both FNAs and tissues, and patients' menopausal status, tumour size, grade and lymph node status.     

Nutrient limitations and their implications on the effects of atmospheric deposition in coastal dunes; lime‐poor and lime‐rich sites in the Netherlands

1 A survey of plant and soil parameters was carried out in dry dune grasslands along the Dutch coast in the lime‐ and iron‐poor Wadden district and initially lime‐ and iron‐rich Renodunaal district, in order to detect differences in nutrient availability related to soil characteristics and potential sensitivity to atmospheric deposition of nitrogen.
2 Plant biomass and phosphorus pools in the shoot were higher in the Wadden district. The low foliar nitrogen concentrations and nitrogen/phosphorus ratios in the Wadden district suggested nitrogen‐limitation, while in the Renodunaal district there appeared to be a balanced supply of both nitrogen and phosphorus.
3 Soil pH, soil organic matter, soil nitrogen and phosphorus concentrations and total amounts were generally higher in the Renodunaal district. In both districts mineral phosphorus decreased with acidification and phosphorus oxalate (iron and aluminium bound) increased.
4 In the Wadden district iron is present primarily in iron–organic matter complexes, which leads to reversible binding of phosphorus. In the Renodunaal district large amounts of iron (hydr)oxides occur and at high pH may contribute to reversible phosphorus‐sorption, but at low pH this probably leads to immobilization of phosphorus.
5 While pools of soil phosphorus are low in the Wadden district, the phosphorus availability may be relatively high due to the comparatively loose nature of phosphorus‐sorption. As a result the area may be nitrogen‐limited and grass‐encroachment may thus have resulted from atmospheric deposition of nitrogen.
6 In the Renodunaal district, atmospheric deposition probably only accelerates grass‐encroachment, because deposition of acid and nitrogen increases the availability of both nitrogen and phosphorus and maintains the 'co‐limitation'.     

Enhancement of pH‐resistant iron‐binding activity in supernatants of rainbow trout blood leucocytes by in vitro treatment with phorbol‐12‐myristate‐13‐acetate

Leucocyte lysates from rainbow trout Oncorhynchus mykiss showed an iron‐binding activity that was retained even if the samples were exposed to an acid pH (4·5). Iron‐binding activity of leucocyte supernatants was enhanced by the presence of 1 μg ml⁻¹ phorbol‐12‐myristate‐13‐acetate in the cell medium.     

Attributable risk estimation from case-control data via logistic regression.

By fitting an unconditional logistic regression model to unmatched case-control data, an estimate of the joint population attributable risk for the factor included is obtained. This estimate and its asymptotic variance can easily be computed from the intercept parameter and its asymptotic variance. A generalization to the analysis of stratified data with large strata enables the calculation of stratum-specific attributable risks and their variances via stratum-specific intercept parameters. If sampling of cases is independent of strata, an estimate of the summary attributable risk and its asymptotic variance may be obtained as a weighted sum of the stratum-specific attributable risks.     

Characterization of Microcirculation in Multiple Sclerosis Lesions by Dynamic Texture Parameter Analysis (DTPA)

Objective

Texture analysis is an alternative method to quantitatively assess MR-images. In this study, we introduce dynamic texture parameter analysis (DTPA), a novel technique to investigate the temporal evolution of texture parameters using dynamic susceptibility contrast enhanced (DSCE) imaging. Here, we aim to introduce the method and its application on enhancing lesions (EL), non-enhancing lesions (NEL) and normal appearing white matter (NAWM) in multiple sclerosis (MS).

Methods

We investigated 18 patients with MS and clinical isolated syndrome (CIS), according to the 2010 McDonald''s criteria using DSCE imaging at different field strengths (1.5 and 3 Tesla). Tissues of interest (TOIs) were defined within 27 EL, 29 NEL and 37 NAWM areas after normalization and eight histogram-based texture parameter maps (TPMs) were computed. TPMs quantify the heterogeneity of the TOI. For every TOI, the average, variance, skewness, kurtosis and variance-of-the-variance statistical parameters were calculated. These TOI parameters were further analyzed using one-way ANOVA followed by multiple Wilcoxon sum rank testing corrected for multiple comparisons.

Results

Tissue- and time-dependent differences were observed in the dynamics of computed texture parameters. Sixteen parameters discriminated between EL, NEL and NAWM (pAVG = 0.0005). Significant differences in the DTPA texture maps were found during inflow (52 parameters), outflow (40 parameters) and reperfusion (62 parameters). The strongest discriminators among the TPMs were observed in the variance-related parameters, while skewness and kurtosis TPMs were in general less sensitive to detect differences between the tissues.

Conclusion

DTPA of DSCE image time series revealed characteristic time responses for ELs, NELs and NAWM. This may be further used for a refined quantitative grading of MS lesions during their evolution from acute to chronic state. DTPA discriminates lesions beyond features of enhancement or T2-hypersignal, on a numeric scale allowing for a more subtle grading of MS-lesions.     

Diffusion in the littoral zone: scoping emergence times and movement to essential habitat for young‐of‐year brook trout in lakes

Factors governing the process of dispersal of lake‐spawned brook trout ( Salvelinus fontinalis ) young‐of‐year (YOY) appear drastically different from those governing dispersal in more commonly studied stream salmonids. Rather than dispersal being highly density‐dependent and the result of territoriality and aggression, in brook trout it may be density‐independent and driven by a common need for coldwater habitat for summer survival. Emerging fish travel great distances from single spawning sites on lakes to cold groundwater habitat. Movement is a gradual, one‐dimensional diffusion around lake margins and represents a very unique and simplified natal dispersal pathway allowing for dispersal rates, distances, and factors controlling these parameters to be measured. We predicted timing of the emergence period for brook trout alevins from lake spawning sites using the known relation between water temperature and emergence times for salmonids. Emergence and dispersal was then observed in the field by visually estimating YOY density in segments of the littoral zone throughout the dispersal period. Fluxes in density in these sections were used to estimate rate of YOY spread. YOY behaviour and body condition was also assessed across the wave of spatial spread. We are working towards a spatially explicit model to identify critical groundwater rearing habitat needing protection from forestry activities.     

Interaction between photoperiod, photosynthesis and ethylene formation in tomato plants (Lycopersicon esculentum cv. Ailsa Craig and ACC‐oxidase antisense pTOM13)

Wild‐type and ACC‐oxidase antisense tomato plants ( Lycopersicon esculentum Mill. cv. Ailsa Craig and pTOM13) were grown in environment‐controlled rooms for 21 days under photoperiods of 8, 16 or 23.5 h at an irradiance of 300 µmol m⁻² s⁻¹. Photosynthetic pigments, photosynthesis, soluble carbohydrates, starch and ethylene were measured on the last fully expanded leaf. Increasing the photoperiod from 8 to 16 h stimulated all measured growth parameters in both cultivars. However, when the photoperiod was increased to 23.5 h, foliar yellowing and deformation were observed in the wild‐type Ailsa Craig whereas no change was observed in pTOM13. It was not possible to relate these foliar changes in Ailsa Craig to destruction of the photosynthetic apparatus by excess carbohydrate levels in the leaves. Because pTOM13 was antisense to ACC‐oxidase. it is proposed that yellowing and deformation in leaves of wild‐type tomato plants grown under long photoperiods may be caused by stress ethylene induced by a long photoperiod.     

Does light intensity affect self‐feeding and food wastage in group‐held rainbow trout and white‐spotted charr?

The self‐feeding rhythms of rainbow trout Oncorhynchus mykiss and white‐spotted charr Salvelinus leucomaenis were studied when group‐held fishes ( n  = 10 per group) were fed using self‐feeders under two different light intensities (50 lx, 16 μW cm⁻² and 700 lx, 215 μW cm⁻²) during the light phase of the light‐dark cycle. Food wastage was also measured. At 50 lx, all groups of rainbow trout learned to operate the self‐feeder within 4 days, whereas it took up to 25 days for all groups at 700 lx. In contrast, all groups of white‐spotted charr learned self‐feeding within 17 days, irrespective of light intensity. These results, although non‐significant, suggest that lower light intensities can stimulate instrumental learning in rainbow trout, but not white‐spotted charr. In rainbow trout, the total number of trigger actuations for the entire experimental period was significantly higher at 50 rather than 700 lx, although this may have been related to delayed learning at 700 lx. There was no significant effect in white‐spotted charr. Growth rate (assessed using the thermal growth coefficient) was also higher in rainbow trout but not white‐spotted charr at 50 rather than 700 lx, although this difference was non‐significant. Light intensity had no significant effect on food wastage in either rainbow trout or white‐spotted charr, and it did not appear to affect the proportion of trigger actuations during the light phase. Clear diurnal feeding rhythms were observed in both species and these were classified into four categories: uniform, dawn, dusk and crepuscular. At 50 lx, fish from both species generally fed in temporally localized periods at either dawn and dusk, whilst feeding was predominantly uniform during the light phase at 700 lx.     

The plasma membrane H+‐ATPase from maize roots is phosphorylated in the C‐terminal domain by a calcium‐dependent protein kinase

A protein kinase activity associated with maize root plasma membranes was partially purified and characterized. Biochemical properties, such as calcium dependence, inhibition by calmodulin antagonists, and absence of calmodulin stimulation, indicated that the enzyme belongs to the calcium‐dependent protein kinase (CDPK) family. By means of an in‐gel phosphorylation assay the molecular mass of active polypeptides was determined: two bands of 55 and 51 kDa became labelled. The same proteins were also immunodecorated by monoclonal antibodies against soybean CDPK. Results from in vitro assays demonstrated that maize H⁺‐ATPase was a suitable substrate for this protein kinase and that the phosphorylation site was located at the C‐terminal domain of the enzyme. This result was confirmed by using as substrate in phosphorylation assays the isolated C‐terminal domain of the H⁺‐ATPase expressed in Escherichia coli as a glutathione‐transferase fusion protein.     

Membrane lipid dynamics and lipid peroxidation in the early stages of low‐temperature sweetening in tubers of Solanum tuberosum

Sugar accumulation and membrane lipid parameters associated with membrane permeability in chilling injury and senescence were followed in the early stages of low‐temperature sweetening in Solanum tuberosum tubers to monitor their dynamics. Norchip, a low‐temperature sweetening‐susceptible potato cultivar, and North Dakota 860‐2, a low‐temperature sweetening‐tolerant selection, were stored for 55 days at 4 and 12°C. Sugar accumulations were not linear and were characterized by fluctuations or cycles over storage time. Sucrose cycling and accumulation were greatest for Norchip tubers stored at 4°C as compared to the other treatments. Increases in membrane permeability were not detected by increases in electrolyte leakage. No significant changes in the phospholipid, galactolipid, free sterol levels or phospholipid to free sterol ratio were observed. The double bond index obtained from the fatty acid profiles of the total lipid fraction decreased significantly (decreased unsaturation) for Norchip tubers at 4°C over time. Free fatty acid and diene conjugation values fluctuated and increased over time for all treatments with greater amplitude of fluctuations observed for Norchip tubers stored at 4°C. These latter effects may be due to the high levels of lipid acyl hydrolase and lipoxygenase found in potato tubers. When free fatty acid and diene conjugation values were plotted with glucose accumulation over time, a possible relationship among the variables was revealed. The observed peroxidation products could relate low‐temperature stress and the resultant low‐temperature sweetening to chilling injury and drought stress. The anti‐oxidative potential of potato tubers should be considered for future cultivar development as a mechanism to lessen the severity or rate of low‐temperature sweetening development.     

Isolation, characterization and significance of papaya β‐galactanases to cell wall modification and fruit softening during ripening

β‐Galactosidases (EC 3.2.1.23) from ripe papaya ( Carica papaya L. cv. Eksotika) fruits having galactanase activities were fractionated by a combination of cation exchange and gel‐filtration chromatography into three isoforms, viz., β‐galactosidase I, II and III. The native proteins of the respective isoforms have apparent molecular masses of 67, 67 and 55 kDa, each showing one predominant polypeptide upon SDS‐PAGE of about 31 and 33 kDa for β‐galactosidases I and III, respectively, and of 67 kDa for β‐galactosidase II. The β‐galactosidase I protein, which was undetectable in immature fruits, appeared to be specifically accumulated during ripening. The β‐galactosidase II protein was present in developing fruits, but its level seemed to decrease with ripening. β‐Galactosidase I seemed to be an important softening enzyme; its activity increased dramatically (4‐ to 8‐fold) to a peak early during ripening and correlated closely with differential softening as related to position in the fruit tissue. The inner mesocarp tissue was softer, and its wall pectins were modified earlier and firmness decreased more rapidly during ripening compared to the outer mesocarp tissue. β‐Galactosidase II also may contribute significantly to softening because of its ability to catalyse increased solubility and depolymerization of pectins as well as through its ability to modify the alkali‐soluble hemicellulose fraction of the cell wall. The physiological significance of both β‐galactosidase isoforms may partly be attributed to their functional capacity as β‐(1,4)‐galactanases.