Cholesterol Interference in the Assessment of Vitamin D Status: A Canadian Health Measures Survey Biobank Project

BACKGROUND

Matrix effects are a known problem with immunoassays measuring serum 25-hydroxyvitamin D [25(OH)D].

OBJECTIVES

To determine if the inverse association between serum 25(OH)D and serum cholesterol concentrations is a function of assay method: Diasorin Liaison 25(OH) Vitamin D Total Assay (Liaison Total Assay), an immunoassay, compared with liquid chromatography tandem mass spectrometry (LC-MS/MS).

METHODS

Canadian Health Measures Survey data and biobank serum (White males aged 20-79 y, n = 392) were evaluated for bias in serum 25(OH)D using Bland-Altman plots. Differences in serum 25(OH)D (Liaison Total Assay - LC-MS/MS) were compared among non-HDL-cholesterol <4.2 (n = 295) compared with ≥4.2 (n = 97) mmol/L and total cholesterol groups <5.2 (n = 256) compared with ≥5.2 (n = 136) mmol/L, and associations tested between 25(OH)D and non-HDL-cholesterol or total cholesterol concentrations, using regression.

RESULTS

Serum 25(OH)D measured using Liaison Total Assay ranged from 10.7 to 137.0 nmol/L and 14.4 to 137.9 nmol/L by LC-MS/MS. Liaison Total Assay - LC-MS/MS showed a negative bias of 5.5 (95% limits of agreement -23.8, 12.7) nmol/L. Differences in 25(OH)D were -4.0 ± 9.0 (±SD) nmol/L if non-HDL-cholesterol was <4.2 mmol/L and -10.2 ± 8.7 nmol/L if ≥4.2 mmol/L (P < 0.0001). Differences in 25(OH)D, if total cholesterol was <5.2 mmol/L, were -3.4 ± 8.6 nmol/L and -9.6 ± 9.3 nmol/L if ≥5.2 mmol/L (P < 0.0001). Serum non-HDL-cholesterol (beta -3.17, P = 0.0014) and total cholesterol (beta -2.77, P = 0.0046) were inversely associated with Liaison Total Assay 25(OH)D (adjusted for age, fasting, and body mass index), but not with LC-MS/MS measured 25(OH)D. Interference by these lipoproteins was not eliminated by standardization of the Liaison Total Assay. Similar associations were observed with triglycerides as for the lipoproteins.

CONCLUSIONS

Total cholesterol inversely associates with 25(OH)D, which is likely due to elevated non-HDL-cholesterol lipoprotein or triglyceride interference with the Liaison Total Assay. This is important as elevated cholesterol is common, and an underestimation of vitamin D status could be an unnecessary cause for concern.

Fermentable Carbohydrates Differentially Affect Colon Tumor Formation in Azoxymethane-Induced Male Fischer 344 Rats

BACKGROUND

The role of fermentation compared with the source or type of the fermentable material in colon tumorigenesis remains an issue in refining the definition of dietary fiber (DF).

OBJECTIVE

The aim of this study was to investigate the fermentation and source-specific effects of various carbohydrates in a medium-term colon tumorigenesis model.

METHODS

Six-week-old male Fischer 344 rats were randomly allocated into 6 groups (n = 36/group) to receive either AIN-93G (control) or diets containing fructooligosaccharides, wheat bran (WB), oat bran (OB), polydextrose, or high-amylose maize starch (HAMS), each adjusted to contain a total DF concentration of 7% (wt:wt) and have a fermentability of 3% (wt:wt). After 2 wk, 24 rats/group received 2 subcutaneous doses of azoxymethane (at 15 mg/kg body weight) 1 wk apart while 12 rats/group were injected with a saline vehicle; all rats were maintained on the assigned diets for 24 wk postinjection and then killed. Colon tumor outcomes and pathology together with cecal short-chain fatty acid composition were assessed.

RESULTS

No tumors were found in saline-injected rats, and all subsequent analyses were restricted to azoxymethane-injected rats. Colon tumor incidence was significantly lower in the polydextrose (21%) and WB (13%) groups than in the control group (63%; P < 0.05) but not different from the fructooligosaccharide (58%), HAMS (46%), and OB (33%) groups. In comparison to the control group (8 proximal/31 total tumors), fermentable materials reduced the number of tumors (P < 0.05) originating in the proximal colon: HAMS (5/15), polydextrose (2/7), OB (2/9), fructooligosaccharides (1/21), and WB (1/3). The mean ± SEM number of tumors/tumor-bearing rats was significantly lower in the WB (1.00 ± 0.00), OB (1.13 ± 0.13), and HAMS (1.36 ± 0.15) groups than in the control group (2.07 ± 0.27; P < 0.02); other groups did not differ. The mean ± SEM tumor burden/diet group was lower in the WB (1.2 ± 0.7 mm2), polydextrose (6.7 ± 3.2 mm2), and OB (7.0 ± 3.0 mm2) groups than in the control (21.4 ± 5.9 mm2) and fructooligosaccharide (22.1 ± 7.1 mm2; P < 0.05) groups but not significantly different from the HAMS group (15.1 ± 6.1 mm2). Total cecal SCFA concentrations did not differ among diet groups (overall mean ± SEM: 81 ± 4 μmol/g wet weight).

CONCLUSION

The rate and extent of fermentation of the carbohydrate material as well as the characteristics of the material in the lumen of the lower gastrointestinal tract all appear to have an important role in tumor outcomes in the azoxymethane-induced rat colon tumorigenesis assay.

Gene expression and behaviour in mouse models of HD

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease, resulting in expansion of the CAG repeat in exon 1 of the HTT gene. The resulting mutant huntingtin protein has been implicated in the disruption of a variety of cellular functions, including transcription. Mouse models of HD have been central to the development of our understanding of gene expression changes in this disease, and are now beginning to elucidate the relationship between gene expression and behaviour. Here, we review current mouse models of HD and their characterisation in terms of gene expression. In addition, we look at how this can inform behaviours observed in mouse models of disease. The relationship between gene expression and behaviour in mouse models of HD is important, as this will further our knowledge of disease progression and its underlying molecular events, highlight new treatment targets, and potentially provide new biomarkers for therapeutic trials.

Five choice serial reaction time performance in the HdhQ92 mouse model of Huntington's disease

Huntington's disease is an autosomal dominant genetic disorder, with motor, cognitive and psychiatric symptoms. To date there is no cure. In order to understand better this disease and to develop novel treatments, many genetically modified animal models of Huntington's disease have been created. However, to utilize these models fully, appropriate functional assays need to be developed for behavioural assessments of the mice. Various facets of attention have been reported to be affected in Huntington's disease patients, and the Hdh(Q92/Q92) mice have been shown to have deficits on operant tasks which have attentional components. In the present study, the Hdh(Q92/Q92) mouse model is assessed on a well established test of attentional function, the operant 5-choice serial reaction time task (5-CSRT), in which the mice must respond with a nose poke to light stimuli presented randomly across a 5 hole light array to receive a reward. In the present paper, the Hdh(Q92/Q92) mice exhibited deficits on the 5-CSRT when pseudorandomly presented with stimuli of different durations. However, alterations in the pacing of the task, therefore requiring an increase in sustained attention, did not affect the Hdh(Q92/Q92) mice more than their wildtype littermates. This study indicates that the Hdh(Q92/Q92) mice may have deficits in aspects of attentional function, in particular disruption in the ability to maintain attention in the visuospatial domain, suggesting that this knock-in mouse model of Huntington's disease may be a relevant model of the disease for the testing of novel therapeutic interventions.

Analyzing complex capture-recapture data in the presence of individual and temporal covariates and model uncertainty

SUMMARY

We consider the issue of analyzing complex ecological data in the presence of covariate information and model uncertainty. Several issues can arise when analyzing such data, not least the need to take into account where there are missing covariate values. This is most acutely observed in the presence of time-varying covariates. We consider mark-recapture-recovery data, where the corresponding recapture probabilities are less than unity, so that individuals are not always observed at each capture event. This often leads to a large amount of missing time-varying individual covariate information, because the covariate cannot usually be recorded if an individual is not observed. In addition, we address the problem of model selection over these covariates with missing data. We consider a Bayesian approach, where we are able to deal with large amounts of missing data, by essentially treating the missing values as auxiliary variables. This approach also allows a quantitative comparison of different models via posterior model probabilities, obtained via the reversible jump Markov chain Monte Carlo algorithm. To demonstrate this approach we analyze data relating to Soay sheep, which pose several statistical challenges in fully describing the intricacies of the system.

On the Bayesian estimation of a closed population size in the presence of heterogeneity and model uncertainty

We consider the estimation of the size of a closed population, often of interest for wild animal populations, using a capture-recapture study. The estimate of the total population size can be very sensitive to the choice of model used to fit to the data. We consider a Bayesian approach, in which we consider all eight plausible models initially described by Otis et al. (1978, Wildlife Monographs 62, 1-135) within a single framework, including models containing an individual heterogeneity component. We show how we are able to obtain a model-averaged estimate of the total population, incorporating both parameter and model uncertainty. To illustrate the methodology we initially perform a simulation study and analyze two datasets where the population size is known, before considering a real example relating to a population of dolphins off northeast Scotland.

Factors influencing soay sheep survival: a Bayesian analysis

This article presents a Bayesian analysis of mark-recapture-recovery data on Soay sheep. A reversible jump Markov chain Monte Carlo technique is used to determine age classes of common survival, and to model the survival probabilities in those classes using logistic regression. This involves environmental and individual covariates, as well as random effects. Auxiliary variables are used to impute missing covariates measured on individual sheep. The Bayesian approach suggests different models from those previously obtained using classical statistical methods. Following model averaging, features that were not previously detected, and which are of ecological importance, are identified.

Selective extra-dimensional set shifting deficit in a knock-in mouse model of Huntington's disease

People with early-stage Huntington's disease have been found to have a specific deficit in performing an extra-dimensional shift. To date no evidence of this deficit has been identified in transgenic or knock-in rodent models of the disease. The aim of the present paper then, was to test whether homozygous knock-in mice derived from the Hdh(CAG(150)) mouse line were impaired in any of five 2-choice discrimination tasks (simple, compound, compound reversal, intra-dimensional shift and extra-dimensional shift), and whether these mice were impaired at recalling these tasks on the following day. On the extra-dimensional shift task the Hdh(CAG(150)) homozygous mice required a greater number of trials to reach criteria than mice and the percentage of correct choices within the trials was also significantly reduced compared with the animals. For the recall tasks, a deficit for recalling the compound reversal test was found in the Hdh(CAG(150)) homozygous mice for both number of trials required to reach criteria and percentage of correct choices within the trials. Recall for the intra-dimensional shift task was also impaired in these animals when measured by the percentage of correct choices. Our results demonstrate a pronounced deficit in the Hdh(CAG(150)) mice not only on extra-dimensional shift performance in agreement with human studies, but also on recall tasks for both the compound reversal and the intra-dimensional shift tasks.

Social defeat increases alcohol preference of C57BL/10 strain mice; effect prevented by a CCKB antagonist

RATIONALE

In humans, social stress over long and short term can increase alcohol consumption, but the mechanisms involved are not understood.

OBJECTIVES

This study was conducted to examine the effects of social defeat, using the resident/intruder paradigm, on the alcohol preference of "low alcohol drinking" individuals in a colony of C57BL/10 strain mice and the effects of two anxiolytic drugs.

METHODS

Alcohol preference, in a two-bottle choice (8% v/v alcohol or water), was measured, in separate experiments, after either a single experience of social defeat by a resident male mouse, five consecutive daily defeat experiences or one experience per week for 4 weeks. Comparison was made with effects of repeated social defeat on the preference for dilute sucrose. In addition, the actions of the CCKB receptor antagonist, CAM1028, and of diazepam were examined on the effects of repeated defeat experiences.

RESULTS

Five consecutive daily defeat experiences had a slow onset effect in increasing alcohol preference and consumption, compared with five daily exposures to a novel environment. A single defeat, or one defeat per week, did not significantly alter alcohol preference or intake. There were no effects of five daily defeat experiences on sucrose preference or consumption. The effect of repeated defeats on alcohol preference was significantly decreased by administration of the CCKB receptor antagonist, CAM1028, prior to each experience, but not by corresponding administration of diazepam.

CONCLUSION

The results show that social stress increases alcohol intake in low alcohol preference C57BL/10 mice and suggest that CCK transmission may be involved in this effect.

Behavioural profiles of inbred mouse strains used as transgenic backgrounds. II: cognitive tests

One of the characteristic manifestations of several neurodegenerative diseases is the progressive decline in cognitive ability. In order to determine the suitability of six mouse strains (129S2/Sv, BALB/c, C3H/He, C57BL/6j, CBA/Ca and DBA/2) as transgenic background strains, we investigated the performance on a variety of tasks designed to identify subtle changes in cognition. In addition, a test of exploratory behaviour was used to probe the level of underlying anxiety in these mouse strains, as anxiety can be a confounding factor on behavioural performance generally. The C3H/He mice exhibited the least anxiogenic behavioural profile spending most time on the open arms of the maze, in contrast to the 129S2/Sv mice which spent the least amount of time in this location and were the quickest to move into a closed arm. The C3H/He mouse strain failed to acquire a visual discrimination task and failed to demonstrate learning on a water maze spatial learning task, in contrast to the CBA/Ca, DBA/2 and C57BL/6j strains which demonstrated a degree of learning in both tasks. No significant strain differences were identified on the object recognition task. These data, taken together, suggest that care must be taken when choosing cognitive tasks to be used with particular mouse strains and that task sensitivity must be considered as a critical element to research protocols with regard to these mouse strains.

Identification of the gene for Nance-Horan syndrome (NHS)

BACKGROUND

The disease intervals for Nance-Horan syndrome (NHS [MIM 302350]) and X linked congenital cataract (CXN) overlap on Xp22.

OBJECTIVE

To identify the gene or genes responsible for these diseases.

METHODS

Families with NHS were ascertained. The refined locus for CXN was used to focus the search for candidate genes, which were screened by polymerase chain reaction and direct sequencing of potential exons and intron-exon splice sites. Genomic structures and homologies were determined using bioinformatics. Expression studies were undertaken using specific exonic primers to amplify human fetal cDNA and mouse RNA.

RESULTS

A novel gene NHS, with no known function, was identified as causative for NHS. Protein truncating mutations were detected in all three NHS pedigrees, but no mutation was identified in a CXN family, raising the possibility that NHS and CXN may not be allelic. The NHS gene forms a new gene family with a closely related novel gene NHS-Like1 (NHSL1). NHS and NHSL1 lie in paralogous duplicated chromosomal intervals on Xp22 and 6q24, and NHSL1 is more broadly expressed than NHS in human fetal tissues.

CONCLUSIONS

This study reports the independent identification of the gene causative for Nance-Horan syndrome and extends the number of mutations identified.

Behavioural profiles of inbred mouse strains used as transgenic backgrounds. I: motor tests

One of the characteristic manifestations in several neurodegenarative diseases is the loss of voluntary motor control and the development of involuntary movements. In order to determine the suitability of six mouse strains as transgenic background strains we investigated performance on a variety of tasks designed to identify subtle changes in motor control. On both the accelerating and the staggered speed rotarod all six mouse strains performed well. However, latency to fall from the rod was sensitive to both rotarod speed and repeated exposure to the apparatus. Performance of the DBA/2 mouse strain was highly variable across the time points used. On the acoustic startle test CBA mice showed the greatest degree of reactivity to the acoustic startle stimuli with both the C57 and DBA showing the least. Complex strain differences were also identified on measures of habituation to the startle stimuli and variations in the prepulse noise level, and prepulse/startle delay. Gait analysis using the footprint test did not reveal strain differences on measures of base width, overlap or stride length but the 129S2/Sv strain took significantly longer to traverse the runway than the other mouse strains. Finally, the swim tank test detected complex strain differences in swim speed, and the number of fore- and hindpaw paddles required to swim the length of the tank. These data taken together suggest that choice of background strain is a crucial consideration for the repeated behavioural assessment of motor deficits in transgenic mouse models of disease.

Effects of corticosterone on place conditioning to ethanol

RATIONALE AND OBJECTIVE

Effects of corticosterone on place conditioning to ethanol were investigated in mice using two conditioning schedules; the conventional method and a rapid conditioning schedule in which exposure to the CS+ followed immediately on exposure to the CS-.

METHODS

Effects of administration of corticosterone, 10 mg/kg, on the acquisition of place conditioning produced by ethanol, 1-2.5 g/kg, were investigated using the conventional method of conditioning, with exposure to the CS+ and the CS- on alternate days, and also using the rapid conditioning method. Total and free blood corticosterone concentrations were measured after administration of ethanol and corticosterone.

RESULTS

In the conventional, alternate day, conditioning schedule, ethanol produced significant place preference at 2 and at 2.5 g/kg, but when these alcohol doses were given with corticosterone 10 mg/kg, significant place conditioning was not seen. In contrast, in the rapid, same day, conditioning schedule corticosterone significantly decreased the dose at which ethanol produced an apparent place preference, with significant place conditioning being seen with ethanol at 1 and 1.5 g/kg in combination with corticosterone, 10 mg/kg. Total and free corticosterone concentrations were increased after ethanol, 1.5 g/kg, compared with controls, and administration of corticosterone, 10 mg/kg, caused a significantly greater increase. There were no significant differences in spontaneous locomotor activity or brain alcohol concentrations between any of the treatment groups.

CONCLUSIONS

The effects of corticosterone on ethanol-induced place conditioning are substantially affected by the conditioning schedule used.

Combining demographic, environmental and genetic data to test hypotheses about colonization events in metapopulations

We describe a method for making inferences about the factors that influence colonization processes in natural populations. We consider the general situation where we have genetic data from a newly colonized population and also from I source populations that may have contributed individuals to the founding group that established the new population. The model assumes that p (biotic/abiotic) factors, G(1), ... ,G(p) may have influenced some individuals in some of the source populations to find a new habitat patch where they could establish a new population. The aim of the method is to determine the composition of the founding group and to ascertain if the aforementioned factors have indeed played a role in the colonization event. We investigate the performance of our method using simulated data sets and illustrate its application with data from the grey seal Halichoerus grypus. These applications demonstrate that the method can identify accurately those factors that are most important for the founding of new populations. This is the case even when genetic differentiation among source populations is low. The estimates of the contribution that each source population makes to the founding groups is somewhat sensitive to the degree of genetic differentiation but it is still possible to identify the sources that are the main contributors to the founding group, even when genetic differentiation is low (F(ST) = 0.01).

The analysis of ring-recovery data using random effects

We show how random terms, describing both yearly variation and overdispersion, can easily be incorporated into models for mark-recovery data, through the use of Bayesian methods. For recovery data on lapwings, we show that the incorporation of the random terms greatly improves the goodness of fit. Omitting the random terms can lead to overestimation of the significance of weather on survival, and overoptimistic prediction intervals in simulations of future population behavior. Random effects models provide a natural way of modeling overdispersion-which is more satisfactory than the standard classical approach of scaling up all standard errors by a uniform inflation factor. We compare models by means of Bayesian p-values and the deviance information criterion (DIC).

Model selection for integrated recovery/recapture data

Catchpole et al. (1998, Biometrics 54, 33-46) provide a novel scheme for integrating both recovery and recapture data analyses and derive sufficient statistics that facilitate likelihood computations. In this article, we demonstrate how their efficient likelihood expression can facilitate Bayesian analyses of these kinds of data and extend their methodology to provide a formal framework for model determination. We consider in detail the issue of model selection with respect to a set of recapture/recovery histories of shags (Phalacrocorax aristotelis) and determine, from the enormous range of biologically plausible models available, which best describe the data. By using reversible jump Markov chain Monte Carlo methodology, we demonstrate how this enormous model space can be efficiently and effectively explored without having to resort to performing an infeasibly large number of pairwise comparisons or some ad hoc stepwise procedure. We find that the model used by Catchpole et al. (1998) has essentially zero posterior probability and that, of the 477,144 possible models considered, over 60% of the posterior mass is placed on three neighboring models with biologically interesting interpretations.

Nimodipine prevents scopolamine-induced impairments in object recognition

The effects of acute administration of the dihydropyridine calcium channel antagonist, nimodipine, were studied on the actions of scopolamine in the object recognition test. Scopolamine at 0.125 mg/kg decreased the difference in the time spent exploring novel and familiar objects when given either 15 min before, or immediately after, exposure to objects. Administration of nimodipine at 10 mg/kg, or 1 mg/kg, at the same time as the scopolamine completely prevented the deleterious effects on memory in this task. This effect was seen when nimodipine and/or scopolamine were given prior to the object exposure and also when the drugs were given after the experience of seeing the objects. Nimodipine had no effects on performance when given in the absence of scopolamine. This lack of change in total time spent exploring the objects indicated that the effects of scopolamine and nimodipine were not due to changes in motor coordination or alertness. The results are discussed in the light of the role of cholinergic transmission in memory and the known actions of dihydropyridines on brain function.

Low alcohol preference among the "high alcohol preference" C57/BL10 mice; factors affecting such preference

The effects of age, ethanol concentration and minor stress on the variation in alcohol preference of C57 strain mice were determined. In two bottle choice tests, an older population of mice contained slightly more low-preference mice than a younger population. A wide range of ethanol preference was consistently seen in young mice for 8% and 6% ethanol, but the previously reported biphasic pattern of distribution was revealed only with 8% ethanol. Very few animals showed high preference for concentrations of 10% or 12% ethanol. Moving low alcohol preference mice to a new location (but not repeated cage changing or ultrasonic noise) significantly increased the alcohol preference. Exploratory locomotor activity did not correlate with the subsequent alcohol consumption. Blood and brain alcohol concentrations showed that the differences in alcohol preference were not due to differences in metabolism of ethanol. The C57 strain mice with low preference for alcohol provides a valuable model for the study of the effects of minor stress on alcohol consumption.

Nimodipine prevents the effects of ethanol in tests of memory

The effects of acute administration of the dihydropyridine calcium channel antagonist, nimodipine, were studied on the actions of ethanol in the radial arm maze and the object recognition test. In the former test, the effects of the drugs were examined on the performance in finding the four baited arms, after previous training in this task. Ethanol, at 1 g/kg, increased both the number of re-entries into baited arms (counted as errors of working memory) and the total number of arm choices required to complete the task. Administration of nimodipine, 10 mg/kg, with the ethanol, completely prevented the deleterious effects on memory in this task, but had no effects on the performance when given in the absence of ethanol. In the object recognition task, ethanol, 1 g/kg, significantly decreased the differences in the time spent exploring novel and familiar objects. Nimodipine, 10 mg/kg, given with the ethanol, completely prevented this effect, but nimodipine alone had no effects. The lack of changes in total exploration times indicated that the effects of ethanol in these tests were not due to loss of motor co-ordination or of alertness. The results are discussed in the light of the known actions of the drugs on brain function.

Comparison of dietary fiber contents of selected baby foods from two major brands in Canada using three methods

Of the two major brands of baby foods in Canada, one reports lower dietary fiber values than the other, although the products appear to be similar. To investigate the reasons for this discrepancy, seven selected samples of baby foods from both brands were analyzed for total dietary fiber (TDF) according to the Mongeau (rapid Health Protection Branch; HPB) method. Two cereals were also analyzed by using the Prosky and the Englyst (nonstarch polysaccharide; NSP) methods as an internal check on the methodology as well as a means of investigating the reasons for the discrepancies. The sampling included at least four different lots of each product (cereals, fruits, vegetables, and legumes). Each lot was analyzed individually. The TDF values determined using the rapid HPB method were in agreement with those obtained by other dietary fiber methods. Comparison between manufacturer-reported and measured values showed that the low values reported in brand A products were due, in part, to under-reporting of TDF content: measured TDF values were significantly higher than manufacturer-reported values. For brand B products, the manufacturer-reported and measured TDF values were in general agreement. This shows that a large part of the discrepancy between the two brands was due to methodological problems associated with measuring TDF in brand A. Differences in TDF content were also apparent as shown by the fact that brand A TDF values were consistently lower than those of brand B when both were measured by the same method. The differences in TDF content were not explained by differences in the polysaccharide composition of the fiber residues or by differences in water content. Although the limited number of samples does not allow any general conclusion about the TDF content of specific brands, the results show that formulation and/or manufacturing differences may influence TDF values in processed baby foods.

Chronic infusion of nicotine can increase operant self-administration of alcohol

Effects of nicotine, administered by continuous infusion via osmotic minipumps, were studied on the operant self-administration of alcohol by rats, using a variable interval (15 s) schedule, and measuring the acquisition, maintenance, extinction and reinstatement of responding for alcohol. Doses of nicotine of 0.25, 1.25 and 7.5 mg/kg/24 h had no significant effects on the maintenance of responding for alcohol, but 5 mg/kg/24 h nicotine resulted in a significant increase in responding on the lever delivering the reward when water was substituted for the alcohol, indicating delayed extinction of responding. During infusion of 2.5 mg/kg/24 h nicotine, responding was significantly greater over the "sucrose-fading" training sessions, during acquisition of responding, when mixtures of alcohol and sucrose were provided as reward. When minipumps infusing 2.5 mg/kg/24 h nicotine were implanted after the alcohol responding had been acquired, the responding for alcohol increase during the first week of nicotine infusion, but corresponding nicotine infusion doses of 0.25, 1.25 and 7.5 had no significant effects. The results indicate that nicotine can increase operant responding for alcohol and this is crucially dependent on the dose of nicotine and the time of testing. The results have implications for the frequently encountered dependence on the combination of alcohol and nicotine.

Proposed phytic acid standard including a method for its analysis

A method is described that accurately and rapidly quantifies the free and total phosphorous content of a commercially available, purified, phytic acid preparation. This allows its use as a standard for phytic acid determinations in foods. The method involves a wet ashing step followed by phosphorous measurement with a 1-amino-2-naphthol-4-sulfonic acid-molybdate reagent in a microplate reader at 660 nm. The procedure can be performed in 3 h with as little as 50 mg sample.

Problems associated with measuring phytate in infant cereals

The inositol hexaphosphate (IP6) content of commercially available dried infant cereals was measured by ion pair high-pressure liquid chromatography (ion pair HPLC) and ion exchange high-pressure liquid chromatography (ion exchange HPLC). Large differences between methods were apparent: ion pair HPLC gave values 14 to 190-fold lower than the values from ion exchange HPLC. Poor recoveries of added IP6 (25 to 60%) by ion pair HPLC suggested that some component of the infant cereal was responsible for the difference. Further experimentation suggested that an excess of minerals (approximately 11 mg/g calcium and 0.3 mg/g iron) in these samples sequestered the endogenously low phytate content. This problem may be unique to samples with low IP6 and high mineral content as wheat bran was not problematic. These results suggest that ion exchange HPLC is the method of choice for measuring inositol phosphates in infant cereals.

On the Bayesian analysis of ring-recovery data

Vounatsou and Smith (1995, Biometrics 51, 687-708) describe the modern Bayesian analysis of ring-recovery data. Here we discuss and extend their work. We draw different conclusions from two major data analyses. We emphasize the extreme sensitivity of certain parameter estimates to the choice of prior distribution and conclude that naive use of Bayesian methods in this area can be misleading. Additionally, we explain the discrepancy between the Bayesian and classical analyses when the likelihood surface has a flat ridge. In this case, when there is no unique maximum likelihood estimate, the Bayesian estimators are remarkably precise.

Temperature regulation of glucose metabolism in red blood cells of the freeze-tolerant wood frog

The low-temperature metabolism of erythrocytes from the freeze-tolerant frog Rana sylvatica was investigated by (13)C and (31)P NMR spectroscopy. Erythrocytes readily took up high concentrations of the natural cryoprotectant, glucose, at both high (12 and 17 degrees C) and low (4 degrees C) temperatures but glucose was apparently not metabolized at 4 degrees C. Strong inhibition of glucose catabolism at low temperature would facilitate the maintenance of the very high concentrations of glucose (approximately 200 mM) that are accumulated to provide cryoprotection during freezing in wood frogs. Analysis of (13)C labeling of glycolytic intermediates at 4 degrees C showed mixing of label primarily in hexose (fructose) and hexose phosphate (glucose 6-phosphate, fructose 6-phosphate) pools but little label incorporation into triose phosphate intermediates. These data are consistent with a profound low-temperature-induced inhibition of phosphofructokinase (PFK). Investigations into potential PFK control mechanisms were undertaken. (31)P NMR analysis showed that the intracellular pH of erythrocytes increased from 7.0 to 7.3 as temperature decreased from 17 to 4 degrees C in a manner consistent with alphastat regulation. This change is exactly opposite to that expected if overall PFK activity was regulated by changes in cellular pH since PFK is less active at lower pH values in vitro. Other factors must, therefore, operate to regulate PFK at lower temperatures.

Effect of dietary fat on whole body fatty acid synthesis in weanling rats

The effect of dietary fat on body composition, whole body lipogenesis, and enzyme activity was measured in rats over the first 16 weeks post-weaning. Rats were fed either a low fat (5% w/w fat) or high fat (20% w/w fat) diet for the first 4 weeks. After this time all rats were fed the low fat diet. The results showed no significant effect of diet on the rate of fat synthesis over the first 8 weeks of the experiment. However, the activities of the enzymes of fatty acid synthesis [glucose 6-phosphate dehydrogenase, malic enzyme, adenosine triphosphate-citrate lyase, acetyl-coenzyme A carboxylase (ACCX), fatty acid synthetase] were dependent on the age and dietary status of the animals. The exact pattern depended on the specific enzyme and the tissue source. No significant differences in pyruvate dehydrogenase (PDH) activity were observed. Mathematical analysis of the enzyme activities suggested that ACCX and PDH were the most likely sites of fat synthesis regulation. In addition, an examination of body composition and overall weight retention showed that the "weight increasing" effect of a high fat diet could be completely reversed by subsequent feeding of a low fat diet. However, the reversal required an additional 12 weeks. Interestingly, at this time the rats switched from a high fat to a low fat diet had a lower body weight and lower body fat content than rats fed a low fat diet throughout the course of the experiment.

Metabolic adjustments during daily torpor in the Djungarian hamster

Djungarian hamsters (Phodopus sungorus) acclimated to a short photoperiod (8:16-h light-dark cycle) display spontaneous daily torpor with ad libitum food availability. The time course of body temperature (Tb), metabolic rate, respiratory quotient (RQ), and substrate and enzyme changes was measured during entrance into torpor and in deep torpor. RQ, blood glucose, and serum lipids are high during the first hours of torpor but then gradually decline, suggesting that glucose is the primary fuel during the first hours of torpor, with a gradual change to lipid utilization. No major changes in enzyme activities were observed during torpor except for inactivation of the pyruvate dehydrogenase (PDH) complex in liver, brown adipose tissue, and heart muscle. PDH inactivation closely correlates with the reduction of total metabolic rate, whereas in brain, kidney, diaphragm, and skeletal muscle, PDH activity was maintained at the initial level. These findings suggest inhibition of carbohydrate oxidation in heart, brown adipose tissue, and liver during entrance into daily torpor.

Monitoring phospholipid signaling pathways: recipes from the experts

Phospholipid Signaling Protocols Edited by Ian M. Bird. Totowa, Humana, 1998, $79.50 (xii +380 pages), ISBN 0-896-03491-7.

Role of transforming growth factor-beta1 in the suppressed allostimulatory function of AIDS patients

BACKGROUND

The T-cell stimulatory function of accessory cells isolated from peripheral blood lymphocytes of AIDS patients has been reported to be suppressed. These patients also have elevated levels of the immunosuppressive factor transforming growth factor (TGF)-beta1 in their serum and plasma.

OBJECTIVE

To explore the role of TGF-beta1 in the loss of accessory cell function of peripheral blood lymphocytes from AIDS patients.

METHODS

Fluorescent labeled anti-TGF-beta1 and confocal microscopy were used to detect the presence of TGF-beta1 on the cell membrane of dendritic cells. To assess the role of TGF-beta1 in the inhibition of accessory cell function in AIDS, antibodies against TGF-beta1 or the TGF-beta1 type III receptor, beta-glycan, were added to a mixed lymphocyte reaction.

RESULTS

TGF-beta1 was detected on the cell membrane of dendritic cells isolated from AIDS patients. The addition of blocking antibodies against either TGF-beta1 or beta-glycan restored the T-cell stimulatory function to accessory cells from these patients.

CONCLUSIONS

T-cell stimulatory function was not irreversibly lost in AIDS patients. Our data suggested that beta-glycan-TGF-beta1 immunosuppressive complexes may contribute to the suppression of accessory cell function in these patients.

Protein kinase C from rainbow trout brain: identification and characterization of three isozymes

Free and membrane-associated fractions of protein kinase C (PKC) from rainbow trout (Onchorynchus mykiss) brain tissue were separated by hydroxylapatite chromatography and characterized kinetically. In both resting fish and in fish swum to exhaustion, approximately 40% of the total PKC activity was bound to membranes. Quantification of the three distinct hydroxylapatite chromatography peaks (PKC types gamma, beta and alpha) in cytosolic and membrane fractions revealed different isozyme distributions. The cytosolic fraction contained 21% PKC type gamma, 52% PKC type beta and 27% PKC type alpha. The membrane-associated fraction contained 23% PKC type gamma, 28% PKC type beta and 49% PKC type alpha. Kinetic characterization of the three isozymes showed that PKC type gamma was almost completely activated by Ca2+ alone whereas PKC type beta and PKC type alpha were 40% and 60% activated by Ca2+. Full activity for all enzymes was observed only in the presence of phosphatidylserine and diacylglycerol. Differences in the kinetic constants for the three isozymes were also apparent. PKC type gamma had a much lower affinity for Histone III-S when compared with PKC types beta and alpha (100 micrograms/ml as compared with 1.7 and 5.7 micrograms/ml). PKC type gamma also had a lower affinity for calcium (0.22 microM) when compared with PKC type beta (0.08 microM) and PKC type alpha (0.05 microM). PKC type alpha had a lower affinity for phosphatidylserine (8.6 micrograms/ml) when compared with PKC type gamma (0.37 microgram/ml) and PKC type beta (0.89 microgram/ml).

Glycolytic controls in estivation and anoxia: a comparison of metabolic arrest in land and marine molluscs

Facultative metabolic rate depression is the common adaptive strategy underlying various animal mechanisms for surviving harsh environmental conditions. This strategy is common among molluscs, enabling animals to survive over days or even months in the absence of oxygen or under extremely dry conditions. The large reductions in metabolic rate during estivation and anoxia can translate into considerable energy savings when dormant animals are compared to active animals. A complex metabolic coordination is required during the transition into the dormant state to maintain cellular homeostasis and involves both energy-consuming and energy-producing pathways. With regard to energy-producing pathways, several different mechanisms have been identified that participate in controlling flux. One such mechanism, enzyme phosphorylation, can have a wide-ranging effect. For example, phosphorylated enzymes exhibit altered substrate, activator, and inhibitor affinities. This effect may be magnified by changes in the concentrations of allosteric effectors, such as fructose 2,6-bisphosphate, that occur during hypometabolic states. Changes in fructose 2,6-bisphosphate are related to changes in enzyme phosphorylation through changes in the relative activity of phosphofructokinase-2. Alterations in glycolytic enzyme binding can also be brought about through changes in enzyme phosphorylation. The present review focuses on identifying hypometabolism-related changes in enzyme phosphorylation as well as characterizing the mechanisms involved in mediating these phosphorylation events.

Time course of enzyme changes after a switch from a high-fat to a low-fat diet

This study was conducted to determine the time course of metabolic changes associated with a switch from a high-fat to a low-fat diet in rats. Adult rats, maintained on a high-fat diet (42% of energy from fat) for 4-5 weeks were switched to a low-fat diet (11% of energy from fat), and the activities of several liver enzymes were followed. Three different phases could be distinguished. The early phase, complete by 2 days after the switch in diets, included an increase in the activity of glucose 6-phosphate dehydrogenase (pentose phosphate pathway), an increase in pyruvate kinase and pyruvate dehydrogenase activities (terminal end of the glycolytic pathway) and an increase in ATP-citrate lyase and fatty acid synthetase (fatty acid synthesis pathway). The early phase also included a decrease in the activity of phosphoenolpyruvate carboxykinase (PEPCK, gluconeogenesis) and a lower branched-chain amino acid dehydrogenase activity (BCAADH, branched-chain amino acid degradation). The concentration of the allosteric phosphofructokinase regulator, fructose 2,6-bisphosphate (Fru-2,6-P2, glycolysis), decreased during the early phase. An intermediate phase could also be discerned between 3 and 10 days after the switch in diets. In this phase, the decreased Fru-2,6-P2 concentration and the decreased PEPCK and BCAADH activities observed in the early phase were reversed. The late phase occurred 10 days after the dietary switch and was characterized by an increase in the activities of glucokinase (glycolytic pathway) and glycogen phosphorylase (associated with glycogenolysis) and by a decrease in glutamate dehydrogenase, PEPCK and BCAADH activities. These measurements indicate that at least 20 days are required before metabolic changes associated with a switch in diet are complete.

Finite mixture models for proportions

Six data sets recording fetal control mortality in mouse litters are presented. The data are clearly overdispersed, and a standard approach would be to describe the data by means of a beta-binomial model or to use quasi-likelihood methods. For five of the examples, we show that beta-binomial model provides a reasonable description but that the fit can be significantly improved by using a mixture of a beta-binomial model with a binomial distribution. This mixture provides two alternative solutions, in one of which the binomial component indicates a high probability of death but is selected infrequently; this accounts for outlying litters with high mortality. The influence of the outliers on the beta-binomial fits is also demonstrated. The location and nature of the two main maxima to the likelihood are investigated through profile log-likelihoods. Comparisons are made with the performance of finite mixtures of binomial distributions.

Glycolytic enzyme binding in Otala lactea hepatopancreas: effect of taxol, colchicine and cytochalasin B and D on the in vivo enzyme distribution

The effect of cytoskeleton modulators on glycolytic enzyme binding was examined in the hepatopancreas of Otala lactea in an attempt to identify potential cellular binding sites. Binding was followed by measuring phosphofructokinase (PFK), aldolase (ALD), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and pyruvate kinase (PK) distribution between low speed pellets (12,000 xg), high speed pellets (100,000 xg) and high speed supernatants. Taxol (which stabilizes microtubules), colchicine (which destabilizes microtubules) and cytochalasin B and D (which destabilize F-actin filaments) were added to the homogenate prior to centrifugation. Addition of taxol increased the amount of PFK associated with the high speed pellet. Cytochalasin B and D reduced the binding of PFK and PK to the low speed pellet. ALD and GAPDH binding were unaffected by any treatment. Lowering the pH of the crude homogenate increased PFK binding to the low speed pellet by 33%. This effect could be reversed by addition of cytochalasin B and D suggesting that pH influences the PFK-F-actin interaction in vivo. The differential binding response of PFK, PK, ALD and GAPDH to added effectors suggests that, in the cell, PFK and PK are bound to different subcellular structural elements than are ALD and GAPDH.

Enzymes of carbohydrate metabolism in young and adult rats fed diets differing in fat and carbohydrate

Glycogen content as well as glycolytic, gluconeogenic and fatty acid synthesis enzyme activities were monitored in young and adult male rats fed diets differing in fat content: 11% (low), 22% (medium) and 42% (high) of total energy from fat. The results showed significant differences in the responses of young and adult rats to changes in dietary fat and carbohydrate. In young animals, increasing dietary fat decreased total liver glycogen phosphorylase (GP), pyruvate kinase (PK), glycerol 3-phosphate dehydrogenase, glucose 6-phosphate dehydrogenase, malic enzyme (ME), ATP-citrate lyase (ATP-CL) and fatty acid synthase (FAS). Increasing dietary fat also affected enzyme levels in other tissues: hexokinase (HK) and pyruvate dehydrogenase (PDH) activities decreased whereas skeletal muscle PK activity increased. The pattern of enzyme changes was similar in livers of fed adults with the exception that liver GP was not affected by dietary manipulations. Overnight food deprivation decreased liver glucokinase (GK), ME, ATP-CL, and FAS activities and increased liver phosphoenolpyruvate carboxykinase (PEPCK) and phosphofructokinase in both young and adult animals. In young animals, food deprivation also: (i) reduced liver GK and PK, (ii) increased kidney PEPCK, (iii) decreased muscle PEPCK and (iv) decreased kidney PDH. Food-deprived adults had increased skeletal muscle PEPCK and kidney glycogen synthetase as well as decreased kidney PEPCK muscle GP activity. These differences suggest that young animals are somewhat more responsive to changes in dietary manipulations. They also show that overnight food restriction causes a more profound metabolic re-organization in younger than in older animals.

Purification and characterization of a protein phosphatase that dephosphorylates pyruvate kinase in an anoxia tolerant animal

A protein phosphatase that dephosphorylates pyruvate kinase (PK) in vitro was purified and characterized from the foot muscle of the anoxia tolerant gastropod mollusc Busycon canaliculatum. Purification involved three steps: negative chromatography through Blue Dextran and CM Sephadex, affinity chromatography on DEAE Sephadex and gel exclusion chromatography on Sephacryl S-400. Pyruvate kinase phosphatase (PK-Pase) activity was monitored by following changes in PK I50 values for L-alanine that had previously been linked to changes in the degree of PK phosphorylation. The purified PK-Pase gave a single band on SDS-polyacrylamide gel electrophoresis with a molecular weight of 41 +/- 1 kdaltons. Isoelectric focusing analysis showed that the PK-Pase had an isoelectric point of 4.2 +/- 0.1. Kinetic analysis showed that the enzyme was a Type 2C protein phosphatase with a pH optimum of 6.5. Maximal activity required the presence of magnesium ions (KM = 7.9 +/- 0.6 microM) although high concentrations of Mg2+ were inhibitory (I50 = 2.3 +/- 0.4 mM). The protein phosphatase activity was not affected by either spermine, cAMP, cGMP, potassium phosphate, tartrate, NaF, HgCl2, citrate or concentrations of CaCl2 less than 10 mM. The enzyme could also use ATP, ADP, and GTP as substrates.

Equilibrium enzymes in metabolic pathways

It is commonly believed that certain reactions in a metabolic sequence may be at or close to equilibrium because of the large excess of catalytic capacity compared to the flux through these enzyme loci. Simple algebraic manipulations can show that the equilibrium and steady state conditions are mutually exclusive. However, solution of the complete reaction schemes for model "equilibrium" reactions shows that they can remain far from equilibrium even though the ratio of enzyme flux to steady state flux through the overall pathway is high. These calculations show that a reaction's proximity to equilibrium depends on the overall flux through the enzyme locus as well as on the kinetic parameters of the other enzymes in the pathway. Thus, combinations of kinetic parameters may exist that allow certain reactions to approach equilibrium but these conditions are not universal.

Protein kinase involvement in land snail aestivation and anoxia: protein kinase A kinetic properties and changes in second messenger compounds during depressed metabolism

In response to environmental stress (low water, low oxygen) snails sharply suppress their metabolic rate, a process that is coordinated at the molecular level by reversible protein phosphorylation of key enzymes and functional proteins. Factors affecting protein kinase activity are, therefore, critical to metabolic suppression. Changes in the concentration of protein kinase second messenger compounds were followed over the first 24 h of aestivation and anoxia exposure in the terrestrial snail Otala lactea (Muller) (Pulmonata, Helicidae). The results showed declining concentrations of cyclic AMP over the first 24 h of anoxia exposure and aestivation in foot. Cyclic AMP concentrations in hepatopancreas transiently decreased with the lowest concentration observed at 4 h in both anoxic and aestivating animals. A transient increase in foot muscle cyclic GMP concentrations was apparent 4 h after the start of aestivation whereas a slow, steady increase was seen in anoxic foot muscle. Foot muscle 1,4,5-inositol triphosphate (IP3) concentrations decreased transiently during anoxia exposure and aestivation. Hepatopancreas IP3 concentrations were significantly lower in 24 h anoxic snails and foot IP3 concentrations were significantly lower in 24 h aestivating snails. Kinetic characterization of purified PKA catalytic subunit was also performed. Snail PKA catalytic subunit had an absolute requirement for Mg2+ ion but was inhibited at Mg2+ concentrations above 0.5 mM. Increasing concentrations of neutral salts and phosphate also inhibited activity although the inhibition by phosphate appeared to be specific since the inhibition constant (I50 = 39 mM) was much lower than that of the neutral salts (I50 approximately 240 mM). The enzyme exhibited a broad pH optimum between pH 6.5-8.5. Arrhenius plots gave an activation energy of 13.3 kcal/mol corresponding to a Q10 value of 2.3. The relationship between these results and temporal control of enzyme phosphorylation is discussed.

Activation of multiple transcription factors and fos and jun gene family expression in cells exposed to a single electric pulse

We report that exposure of cells to a single electric pulse (250-1250 V/cm) results in the rapid and persistent activation of the DNA binding activities of a number of transcription factors, including AP-1, SP1, AP-2, and NF-kappa B, and the transient expression of select members of the fos and jun gene families. Induction of gene expression occurs primarily at the level of transcription, although c-jun expression also appears to be regulated posttranscriptionally. Interestingly, maximal induction of gene expression is detected at electrical field strengths that do not result in pore formation in the plasma membrane and that do not significantly affect cell viability. Exposure of cells to electric pulses does not result in the activation of HSF1 DNA binding activity, or the induction of hsp70 or p53 protein synthesis, indicating that the induction of fos and jun gene expression is not coincident with protein or DNA damage. The results of these studies suggest that electrical pulses may represent a novel mechanism for inducing the activities of multiple transcription factors and the expression of select members of the fos and jun gene families.

A comparison of methods for determining total body protein

The aim of the study was to find the optimal method (with respect to convenience and accuracy) for determining total protein in whole-body homogenates of rats. Three different protein extraction methods and five different protein concentration methods were assessed. The results were compared against a reference value measured by complete amino acid analysis after acid hydrolysis. The data demonstrated that extraction with 5% (w/v) sodium dodecylsulfate (SDS) in 0.5 N NaOH was far superior to that with water alone or to 6 N guanidine-HCl. A comparison of the Biuret, Bradford, and bicinchoninic acid methods on the SDS-NaOH-extracted samples showed that the Biuret method was optimal, giving a value that was 90% of the reference value with a small variation (2.4% of the mean). The Kjeldahl method gave the correct protein concentration only when a nitrogen factor of 5.51 +/- 0.03 (N = 5) was applied. The results suggest that extraction with SDS-NaOH followed by the Biuret procedure is a good method for measuring protein concentrations in whole body rat homogenates.

Protein phosphorylation patterns during aestivation in the land snail Otala lactea

Protein phosphorylation patterns were investigated in whole tissues and subcellular fractions of active and aestivating Otala lactea (Müller) (Pulmonata, Helicidae). Measurement of overall protein phosphorylation showed that incorporation of 32P increased until the second day after injection and remained constant for the remaining 4 days of the time course. Comparison of tissues from aestivating and active snails on day 3 showed a decreased protein phosphorylation in aestivating snails (44% of active). No differences in total and protein-associated radioactivity for foot, mantle or haemolymph were observed. Subcellular fractionation of the hepatopancreas localized the changes to plasma membrane, microsomal, and cytosolic fractions: values for aestivating animals were reduced to 71, 37 and 58% of the corresponding active values. Separation of the individual subcellular fractions on isoelectric focusing columns revealed differences in the phosphate incorporation patterns. Plasma membrane from aestivating animal hepatopancreas had a lower overall level of incorporation and fewer radioactive peaks in the pH 7-10 region than did the plasma membrane fraction from active animals. SDS-PAGE analysis of plasma membrane fractions from active and aestivating snails showed a relative decrease in phosphorylation between 60-80 kDa and 30-40 kDa. IEF analysis of cytosolic proteins from aestivating snail hepatopancreas also showed peaks of radioactivity that were apparently shifted by 0.3 pH units toward higher pI values. Increased phosphate incorporation was observed at a peak that corresponded to the pI value for pyruvate kinase in aestivating snails but definite assignment of peaks was not possible. SDS-PAGE analysis of cytosolic proteins showed an aestivation-related decrease in relative protein phosphorylation between 30-35 kDa and 40-45 kDa. A relative increase in phosphorylation during aestivation was observed for proteins between 16-22 kDa.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for aestivation specific proteins in Otala lactea

Changes in [35S]methionine protein labeling patterns were examined by following incorporation into the acid precipitate protein fraction of land snails, Otala lactea (Müller) (Pulmonata, Helicidae). Labeled proteins were analyzed by SDS polyacrylamide gel electrophoresis and isoelectric focusing columns. Snails in four different physiological states were compared: active controls, short term aestivating snails (injected and allowed to enter aestivation), long term aestivating snails (aestivated for 14 days, injected, and maintained in the aestivating state), and snails aroused after aestivation (aestivated, injected, and aroused). Protein associated radioactivity was measured over a 7 day time course post injection. Autoradiographic analysis of SDS-polyacrylamide gels showed increases in the radioactivity of four proteins: 91 kDa (hepatopancreas, day 1 in long term aestivating animals), 50 kDa (hepatopancreas, day 2 in short term aestivating snails), 70 kDa and 30 kDa (foot, day 2 in short term aestivating animals). Hepatopancreas and foot from day 1 long term aestivating and day 2 short term aestivating animals were also analyzed by isoelectric focusing columns. Several pH-specific differences were apparent when controls and aestivating animals were analyzed. In particular a peak of radioactivity was observed at pH 5.05 in 1 d long term aestivating hepatopancreas and at pH 4.30 in 2d short term aestivating animals. Several differences were noted in foot with no specific pattern emerging. SDS-polyacrylamide gel electrophoresis analysis of the hepatopancreas peaks showed the appearance of several bands with increased radioactivity, including the 91 kDa and 50 kDa proteins described above. These results suggest that O. lactea aestivation specific proteins may be involved in the transition to a depressed metabolic state.

A program for analyzing enzyme rate data obtained from a microplate reader

A computer program (microplate analysis [MPA] program) is described that allows manipulation of kinetic data obtained from a microplate reader. It is particularly useful for obtaining enzyme velocities from microplate data. Data can be displayed either as an 8 x 12 grid which shows all microplate wells at low resolution or as single enzyme progress curves which show the reaction time course in greater detail and allow data manipulation (single curve mode). In the single curve mode, the X-axis of the progress curves can be displayed either as discrete time points numbered from the first to the last or as real time in seconds. The program can calculate the maximum, minimum or initial reaction rate by either linear or robust regression. In the single curve mode, the user can control the range of data points included in the regression analysis and the number of data points over which the rate is averaged. In this way, the maximum (or minimum) rate within a specific range of data can be determined. The major advantage of the MPA program is that the range settings are specific to each well. This gives the user complete control over the presentation and calculation of the kinetic data. The MPA program requires an AS-CII file containing data blocks of 96 sequential absorbance readings for each time point and the time interval between successive absorbance readings.

Effect of anoxia on isolated turtle tissues: is the response to anoxia mediated by protein kinase second messengers?

Organ slices from the turtle Trachemys scripta elegans were incubated under aerobic and anoxic conditions to examine the effect of protein kinase (PrK) second messengers in potentiating the biochemical responses to anoxia exposure. Incubating liver slices from aerobic animals under anoxic conditions produced biochemical changes exactly similar to those observed in vivo: phosphofructokinase (PFK) was more sensitive to citrate inhibition and the percentage of glycogen phosphorylase (GP) in the active a form increased. On the other hand, incubating brain and heart tissue slices under anoxic conditions produced no changes in PFK and GP kinetic constants. Addition of PrK second messengers (dibutyryl-cAMP or Ca2+ plus phorbol myristate acetate) to the incubated tissues did not promote anoxia-associated changes in aerobically incubated tissues nor did they prevent anoxia-associated changes in anaerobically incubated tissues. These results suggest that unidentified external hormonal signals mediate heart and brain responses to anoxia. It is also apparent that cAMP and Ca2+ plus phospholipid do not play a role in bringing about the anoxia-induced changes in PFK, GP and fructose 2,6-bisphosphate in liver of turtles.

Metabolic depression in land snails: in vitro analysis of protein kinase involvement in pyruvate kinase control in isolated Otala lactea tissues

Isolated tissues from the land snail Otala lactea were used to examine the relationship between protein kinase activity and phosphorylation-induced changes associated with metabolic depression. Hepatopancreas and foot muscle were removed from active and estivating land snails and incubated in vitro under aerobic and anoxic conditions. Pyruvate kinase (PK), cAMP-dependent protein kinase (PKA), and protein kinase second messenger compounds (cyclic AMP and inositol 1,4,5-triphosphate) were measured after incubating the tissues for 4 hours. Pyruvate kinase from the hepatopancreas of active snails was phosphorylated during anoxic incubations as indicated by changes in the I50 value for L-alanine. However, measurements of PKA activity and of cellular cAMP concentrations suggested that PKA activity was lower in these incubated tissues. When foot muscle was used as the tissue source, incubation under anoxic conditions produced no changes in PK activity even though PKA activity was drastically reduced. Analysis of changes in inositol 1,4,5-triphosphate concentrations after tissue incubation showed that they were not consistent with changes in PK activity in either organ. These results suggest that PKA and Ca2+/phospholipid-dependent protein kinase C do not phosphorylate PK during anoxia in land snails. The differences between values measured in incubated tissues and those measured in vivo suggest that isolated O. lactea tissues are not a good in vitro model system for studying metabolic changes associated with depressed metabolism.

De novo protein synthesis and protein phosphorylation during anoxia and recovery in the red-eared turtle

Changes in de novo protein synthesis and protein phosphorylation were monitored during anoxia and recovery in the red-eared slider Trachemys (= Pseudemys) scripta elegans. Time courses of 35S-radiolabeled methionine incorporation into acid-precipitable material showed an increase up to 5 h postinjection and remained constant after this time. Comparison of the total and acid-precipitable 35S label incorporation into tissues from 20-h control, anoxic, and recovering animals showed differences between these groups: total radioactivity in brain was 2.9-fold lower in recovering turtles, whereas protein-associated radioactivity was 2.4-fold higher in anoxic liver, 2.3-fold lower in recovering skeletal muscle, and 3.7-fold lower in recovering brain tissue. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of radiolabeled proteins showed the existence of a newly synthesized protein band (relative molecular mass = 72 kDa) that was apparent only in 20-h recovering liver and skeletal muscle. Use of 32P labeling to monitor changes in protein phosphorylation patterns during anoxia revealed 1.6-, 1.4-, and 1.5-fold increases in 32P incorporation in anoxic brain, heart, and liver, respectively. Changes in protein phosphorylation were localized to the plasma membrane and cytosolic fractions in brain and to the cytosolic fraction in liver.

An improvement in the pyruvate dehydrogenase complex assay: a high-yield method for purifying arylamine acetyltransferase

A new method for purifying arylamine acetyltransferase (AAT) has been devised using polyethylene glycol fractionation and hydroxylapatite chromatography. The new procedure gives a final yield of approximately 70% based on activity in crude homogenates and can be performed in a single day. This represents a threefold higher yield than previous methods. The procedure may be used to purify AAT from pigeon, chicken, and duck livers with equivalent yield of the final enzyme. However, the preparation from pigeon liver is preferred because of the sevenfold higher activity in this tissue. Nevertheless, if fresh pigeon livers cannot be acquired, calculations reveal that the preparation from chicken liver is comparable to that from pigeon liver acetone powder with respect to total activity obtained per gram wet weight starting material. One can also calculate that the chicken liver preparation is approximately 40 times cheaper than that from pigeon liver acetone powder, making the preparation of AAT from fresh chicken livers a good alternative when pigeon livers are not available.