Models and tests of linkage and association studies of quantitative trait locus for multi-allele marker Loci

In this paper, we explore models and tests for association and linkage studies of a quantitative trait locus (QTL) linked to a multi-allele marker locus. Based on the difference between an offspring's conditional trait means of receiving and not receiving an allele from a parent at marker locus, we propose three statistics T(m), T(m,row) and T(m,col) to test association or linkage disequilibrium between the marker locus and the QTL. These tests are composite tests, and use the offspring marginal sample means including offspring data of both homozygous and heterozygous parents. For the linkage study, we calculate the offspring's conditional trait mean given the allele transmission status of a heterozygous parent at the marker locus. Based on the difference between the conditional means of a transmitted and a nontransmitted allele from a heterozygous parent, we propose statistics T(parsi), T(satur), T(gen) and T(m,het) to perform composite tests of linkage between the marker locus and the quantitative trait locus in the presence of association. These tests only use the offspring data that are related to the heterozygous parents at the marker locus. T(parsi) is a parsimonious or allele-wise statistic, T(satur) and T(gen )are satured or genotype-wise statistics, and T(m,het) compares the row and column sample means for offspring data of heterozygous parents. After comparing the powers and the sample sizes, we conclude that T(parsi) has higher power than those of the bi-allele tests, T(satur), T(gen), and T(m,het). If there is tight linkage between the marker and the trait locus, T(parsi) is powerful in detecting linkage between the marker and the trait locus in the presence of association. By investigating the goodness-of-fit of T(parsi), we find that T(satur) does not gain much power compared to that of T(parsi). Moreover, T(parsi) takes into account the pattern of the data that is consistent with linkage and linkage disequilibrium. As the number of alleles at the marker locus increases, T(parsi) is very conservative, and can be useful even for sparse data. To illustrate the usefulness and the power of the methods proposed in this paper, we analyze the chromosome 6 data of the Oxford asthma data, Genetic Analysis Workshop 12.

Linkage disequilibrium mapping of quantitative trait loci under truncation selection

As a dense map of single nucleotide polymorphism (SNP) markers are available, population-based linkage disequilibrium (LD) mapping or association study is becoming one of the major tools for identifying quantitative trait loci (QTL) and for fine gene mapping. However, in many cases, LD between the marker and trait locus is not very strong. Approaches that maximize the potential of detecting LD will be essential for the success of LD mapping of QTL. In this paper, we propose two strategies for increasing the probability of detecting LD: (1) phenotypic selection and (2) haplotype LD mapping. To provide the foundations for LD mapping of QTL under selection, we develop analytic tools for assessing the impact of phenotypic selection on allele and haplotype frequencies, and LD under three trait models: single trait locus, two unlinked trait loci, and two linked trait loci with or without epistasis. In addition to a traditional chi(2) test, which compares the difference in allele or haplotype frequencies in the selected sample and population sample, we present multiple regression methods for LD mapping of QTL, and investigate which methods are effective in employing phenotypic selection for QTL mapping. We also develop a statistical framework for investigating and comparing the power of the single marker and multilocus haplotype test for LD mapping of QTL. Finally, the proposed methods are applied to mapping QTL influencing variation in systolic blood pressure in an isolated Chinese population.

Comparing the efficacy of two fluorescent retrograde tracers in labeling the motor and sensory neuron populations of the rat sciatic nerve

We compared the efficacy with which the fluorescent tracers Fast Blue (FB) and Diamidino Yellow (DY) retrogradely label neutrons. Trace crystals were applied to the sciatic nerve exclusively (single label) or serially (double label). Unbiased cell counts showed that FB and DY label similar numbers of motoneurons (P=1.00, df 5) or DRG neurons (P=0.95, df 5) when applied exclusively. Plotting of motoneurons revealed a similar pattern of distribution of FB and DY labeled neurons. When the tracers were applied serially, 79% of labeled motoneurons and 77% of labeled DRG neurons were double-labeled irrespective of which tracer was applied first. Equal proportions of the remaining labeled neurons were single-labeled with FB or DY. These data show that FB and DY label equal numbers of motor and sensory neurons of the sciatic nerve following exclusive or serial application of tracers. These findings support the use of FB and DY together in serial fluorescent labeling experiments.

Differential association of the codon 72 p53 and GSTM1 polymorphisms on histological subtype of non-small cell lung carcinoma

Traditionally, non-small cell lung cancer (NSCLC) has been evaluated as a unique entity in genotyping studies. However, recent biological data suggest that different NSCLC subtypes, specifically adenocarcinomas (AC) and squamous cell carcinomas (SCC), differentially alter cancer behavior. Several studies have associated a p53 polymorphism at codon 72 with NSCLC susceptibility. This study investigated whether different p53 genotypes altered the overall risk of developing AC versus SCC. Polymorphisms in metabolizing enzymes, together with prolonged exposure to tobacco carcinogens, can result in accumulation of DNA damage; these effects may potentiate the effects of subtle differences in p53 function. Thus, interactions between polymorphisms of p53 and either GSTM1 or GSTT1 were also evaluated. We analyzed 1168 incident lung cancer cases and 1256 control subjects using multiple logistic regression. Histological data were available for 1144 cases (98%): 585 with AC, 284 with SCC, and 275 with other histological subtypes (large cell, small cell, mixed, and other). An increase in the NSCLC risk posed by the p53 Pro allele (versus Arg/Arg) was seen in AC compared with controls [adjusted odds ratio (OR), 1.36; 95% confidence interval (CI), 1.1-1.7] but not in SCC (adjusted OR, 1.04; 95% CI, 0.8-1.4). Among AC and SCC cancer patients, individuals with the GSTM1-null genotype had an OR of 1.80 (95% CI, 1.1-2.8; case-only analysis) of having AC versus SCC if they also carried a p53 Pro allele. We conclude that different genotype combinations of p53 and GSTM1 increase the risk of developing specific histological subtypes of NSCLC.

Surfactant protein (SP) B associations and interactions with SP-A in white and black subjects with respiratory distress syndrome

BACKGROUND

The etiology of respiratory distress syndrome (RDS) is multifactorial and/or multigenic. Surfactant protein A (SP-A) and/or SP-B genetic variants have been identified as risk or protection factors for RDS.

METHODS

We genotyped subjects with and without RDS for the SP-B intron 4 size variants (invariant (inv), deletion (del), insertion (ins) and for four (-18 (A/C), 1013 (A/C), 1580 (C/T), 9306 (A/G)) SP-B single nucleotide polymorphisms (SNP), to study case-control associations in black and white subjects. We also determined whether specific SP-B variants interact with RDS susceptibility or protective SP-A variants to enhance or reduce risk for RDS.

RESULTS

Based on odds ratio: (1) the SP-B intron 4 del variant in white subjects is more of an RDS risk factor for males and for subjects of 28 weeks <gestational age (GA)<33 weeks; (2) the SP-B intron 4 ins variant in black subjects is more of an RDS risk factor in females; (3) in white subjects, SP-A1 (6A(2)/6A(2)) or SP-A2 (1A(0)/1A(0) or 1A(0)/*) genotypes in subjects of certain GA and with a specific SP-B genotype (9306 (A/G) or del/*) are associated with an enhanced risk for RDS; (4) in black subjects, SP-A1 (6A3/6A(3) or 6A(3)/*) genotypes in subjects of 31 weeks < or = GA < or = 35 weeks and with the SP-B (1580 (T/T)) genotype are associated with a reduced risk for RDS.

CONCLUSIONS

The SP-B polymorphisms are important determinants for RDS. These may identify differences between black and white subjects, as well as, between males and females regarding the risk for RDS. Furthermore, SP-A susceptibility or protective alleles, in specific SP-B background, are associated, based on OR, with an increased or reduced risk for RDS.

The convulsant and anesthetic properties of cis-trans isomers of 1,2-dichlorohexafluorocyclobutane and 1,2-dichloroethylene

The differences in potencies of optical isomers of anesthetics support the hypothesis that anesthetics act by specific receptor interactions. Diastereoisomerism and geometrical isomerism offer further tests of this hypothesis but have not been explored. They are the subject of this report. We quantified the nonimmobilizing and convulsant properties of the cis and trans diastereomers of the nonimmobilizer 2N (1,2-dichlorohexafluorocyclobutane). Although the lipophilicity of the diastereomers predicts complete anesthesia at the partial pressures applied, neither diastereomer had anesthetic activity alone, and the cis form may have a small (10%) capacity to antagonize anesthesia, as defined by additive effects on the MAC (the minimum alveolar concentration required to suppress movement to a noxious stimulus in 50% of rats) of desflurane. Both diastereomers produced convulsions, the cis form being nearly twice as potent as the trans form: convulsant 50% effective dose (mean +/- SD) was 0.039 +/- 0.009 atmospheres (atm) for the purified cis and 0.064 +/- 0.009 atm for the purified trans isomer. The MAC value for cis-1,2-dichloroethylene equaled 0.0071 +/- 0.0006 atm, and MAC for trans-1,2-dichloroethylene equaled 0.0183 +/- 0.0031 atm. In qualitative accord with the Meyer-Overton hypothesis, the greater cis potency was associated with a greater lipophilicity. However, the product of MAC x solubility differed between the cis and trans isomers by 40%-50%. We conclude that neither the cis nor trans isomers of 2N have anesthetic properties, but isomerism does influence 2N's convulsant properties and the anesthetic properties of dichloroethylene. These isomeric effects may be as useful in defining receptor-anesthetic interactions as those found with optical isomers.

IMPLICATIONS

Cis-trans isomerism can influence the convulsant properties of the nonimmobilizer 2N (1,2-dichlorohexafluorocyclobutane) and the anesthetic properties of dichloroethylene. Such isomeric effects may be as useful as those found with optical isomers in defining receptor-anesthetic interactions.

Family-based transmission disequilibrium test (TDT) and case-control association studies reveal surfactant protein A (SP-A) susceptibility alleles for respiratory distress syndrome (RDS) and possible race differences

A key cause of respiratory distress syndrome (RDS) in the prematurely born infant is deficiency of pulmonary surfactant, a lipoprotein complex. Both low levels of surfactant protein A (SP-A) and SP-A alleles have been associated with RDS. Using the candidate gene approach, we performed family-based linkage studies to discern linkage of SP-A to RDS and identify SP-A susceptibility or protective alleles. Moreover, we performed case-control studies of whites and blacks to detect association between RDS and SP-A alleles. Transmission disequilibrium test (TDT) analysis revealed that the frequency of transmission (from parent to the offspring with RDS) of alleles 6A(2) and 1A(0) and of 1A(0)/6A(2) haplotype in RDS was increased, whereas transmission of alleles 1A(5) and 6A(4) and of haplotype 1A(5)/6A(4) was decreased. Extended TDT analysis further strengthened the observations made. The case-control studies showed that in whites or blacks with RDS the frequencies of specific genotypes, 1A(0) and 6A(2) or 1A(0), were increased, respectively, but the frequency of specific 6A(3) genotypes was increased in certain white subgroups and decreased in blacks. Regression analysis revealed gestational age (GA) and 6A(3) genotypes are significant factors in blacks with RDS. In whites with RDS, GA and antenatal steroids are important factors. The data together indicate linkage between SP-A and RDS; certain SP-A alleles/haplotypes are susceptibility (1A(0), 6A(2), 1A(0)/6A(2)) or protective (1A(5), 6A(4), 1A(5)/6A(4)) factors for RDS. Some differences between blacks and whites with regard to SP-A alleles may exist.

Surfactant protein A and B genetic variants and respiratory distress syndrome: allele interactions

The contribution of multiple genetic components in disease pathogenesis is relevant to both diseases of multifactorial and/or multigenic etiology such as the respiratory distress syndrome (RDS) and to diseases where a single gene has been identified as the disease-causing gene. An example of the latter is cystic fibrosis (CF) where the disease-causing gene has been clearly identified as the CF transmembrane conductance regulator gene, but genetic variants of the mannose binding protein and surfactant protein A have been associated with disease severity in CF. The overall rationale for considering genetic contribution to disease pathogenesis is based on the premise that all diseases or deaths (except perhaps those resulting from trauma) have a genetic component. The difference in genetic contribution among various diseases is the percent contribution and the number of factors that make this contribution. Therefore, if the number of genetic contributors is small and the percentage of genetic contribution is high it may be less challenging to identify such factors. In this paper we summarize allele associations and discuss allele interaction of the surfactant protein genes in relation to RDS (the term allele and genetic variant will be used interchangeably).

Some features of intestinal absorption of intact fibrinolytic enzyme III-1 from Lumbricus rubellus

In order to investigate whether earthworm fibrinolytic enzyme III-1 (EFE-III-1) isolated from Lumbricus rubellus is capable of transporting into blood through intestinal epithelium and keeping its biological function in circulation, we have raised an antibody against EFE-III-1. The immunological results showed that 10-15% of intact EFE-III-1 was absorbed by the intestinal epithelium with the incubation chamber method [Vilhardt and Lundin, Acta Physiol. Scand. 126 (1986) 601-607]. The enzyme could be detected in the intestinal epithelial cells by immunohistochemistry. Furthermore, immunoreactive intact EFE-III-1 was found in serum or plasma after intraperitoneal injection of rats. Approx. 10% of the full-size enzyme could transport through the intestinal epithelium. The maximum remaining activity in blood could be assayed around 60 min after the intraperitoneal injection.

Quantitative modeling of suppression of IgG1, IgG2a, IL-2, and IL-4 responses to antigen in mice treated with exogenous corticosterone or restraint stress

Exposure to toxic chemicals often induces a neuroendocrine stress response leading to increased concentrations of a variety of potentially immunomodulatory mediators. Corticosterone is a major stress-induced mediator that can be immunosuppressive. However, the quantity of corticosterone exposure required to produce particular decrements in particular immunological parameters is not known. Mice treated with various dosages of exogenous corticosterone were compared to mice exposed to a psychogenic stressor (restraint). Cumulative corticosterone exposure in these mice, expressed as the area under the curve (AUC) of corticosterone concentration versus time, was used to develop quantitative models of the effects of corticosterone on the immunoglobulin (Ig) G1 and IgG2a responses to keyhole limpet hemocyanin (KLH) and sheep erythrocytes (sRBC). The production of interleukin (IL)-2 and IL-4 by splenocytes stimulated with KLH in culture was also evaluated. Linear regression models were derived that describe the relationship between the IgG1 and IgG2a responses to KLH. Restraint had a greater effect (at equivalent corticosterone AUC values) than exogenous corticosterone, suggesting that mediators in addition to corticosterone are important in suppression of the IgG1 and IgG2a response to KLH. The production of IL-2 and IL-4 by cultured splenocytes was mostly, but not always, consistent with the changes in IgG1 or IgG2a. For example, the regression lines for IgG2a (a Th1-driven response) and IL-2 (a Th1 cytokine) were not significantly different. The relationships between corticosterone AUC and the IgG1 and IgG2a responses to sRBC were nonlinear and characterized by enhanced responses at low to moderate AUC values. The quantitative models developed here have implications for risk assessment in immunotoxicology.

Individual variability in the zinc inducibility of metallothionein-IIA mRNA in human lymphocytes

The metallothionein-III gene (MT-IIA) is a major member of the human MT gene family. Metallothioneins (MTs) are low-molecular-weight, cysteine-rich proteins that bind and detoxify heavy metals. At least two different MT-IIA polymorphisms have been identified in humans, one or both of which may affect susceptibility to metal toxicity. The purpose of this study was to investigate whether these different genotypes affect the inducibility of MT-IIA mRNA in human lymphocytes treated with zinc (Zn), the major known inducer of MT-IIA in vitro. Fresh lymphocytes obtained from 16 healthy volunteers, aged 23-38 yr, were genotyped for the MT-IIA gene and tested for expression. A 43.5-bp HindIII-Taql fragment of the MT-IIA promoter was used to probe for the two known polymorphisms (a 7.8-kb vs. a 5.3-kb fragmnent, and a 1.7-kb vs. a 1.6-kb fragment). The allele frequencies of the 16 subjects were 14%, for 5.3-kb allele and 19% for 1.6-kb allele. In Northern blotting experiments, MT-II mRNA levels were induced over a wide range of Zn concentrations during 2-h exposures; specifcally, levels increased by 9- to 115-fold with exposure to 100 microM ZnCl, and by 16- to 311-fold with exposure to 200 microM ZnCl2. However, no significant differences in MT-IIA inducibility were found between the 7.8/5.3-kb allele pair (n = 4) and the 7.8/7.8-kb allele pair (n = 12) or between the 1.7/1.6-kb allele pair (n = 5) and the 1.7/1.7-kb allele pair (n = 11). Thus. MT-IIA is strongly inducible by Zn in human lymphocytes, but individual variations exceed those that can be attributed to the known promoter-region polymorphisms.

Quantitative analysis of the neuroendocrine-immune axis: linear modeling of the effects of exogenous corticosterone and restraint stress on lymphocyte subpopulations in the spleen and thymus in female B6C3F1 mice

The effects of exogenous corticosterone and restraint stress on the number and percentage of lymphocyte subpopulations in the spleen and thymus were evaluated. The data were used to generate linear models that describe the relationship between these parameters and the area under the corticosterone concentration vs time curve (AUC). Comparison of the models revealed that the number of nucleated cells in the spleen was decreased similarly by exogenous corticosterone and restraint (at equivalent corticosterone AUC values). However, exogenous corticosterone caused a greater decrease in cell number in the thymus than it did in the spleen. Corticosterone preferentially depleted CD4+CD8+ cells in the thymus, whereas the same corticosterone exposure produced by restraint stress did not. In the spleen, cell number for all major cell types was decreased by both treatments, but there were minor differences in the change in percentage of some subpopulations induced by exogenous corticosterone as compared to restraint. The models derived here provide quantitative data that indicate the magnitude of corticosterone and stress-induced effects on lymphocyte populations in the spleen and thymus. These results have mechanistic implications, and they may be useful in future efforts to extrapolate from mouse to human by completing a risk assessment parallelogram.

Crystallization and preliminary X-ray analysis of earthworm fibrinolytic enzyme component A from Eisenia fetida

Earthworm fibrinolytic enzyme component A, a protein which functions both as a direct fibrinolytic enzyme and a plasminogen activator, was purified from the earthworm Eisenia fetida. Diffraction-quality single crystals of the protein were grown by the hanging-drop vapour-diffusion technique with ammonium sulfate as a precipitant. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 40.6, b = 127.5, c = 129.2 A and three molecules per asymmetric unit. The data set reached a resolution of 1.95 A.

Development of an affordable diaphragmatic pump for cardiopulmonary bypass: an in vivo evaluation

A new diaphragmatic pump (L-Y pump) and its drive unit were developed in our institute. The pump has a priming volume of 80 ml. The pump housing is 72 mm in diameter and 42 mm in height. Its total weight is 139 g. To assess and confirm the function and controllability of this pump, comparative studies of cardiopulmonary bypass (CPB) with L-Y pump (group A) and conventional roller pump (Group B) were performed using dogs. Both pumps provided pump flow of 90 to 100 ml/kg/min. The hemodynamics of both groups were stable and within the normal range. No leakage or thrombus formation was observed in the L-Y pump. All biochemistry data showed no significant differences between the 2 groups. This data demonstrated low plasma-free hemoglobin levels in the L-Y pump group; after 120 min of CPB, mean plasma free hemoglobin levels were 48.7 +/- 8.6 mg/dl in the roller pump group and 21.4 +/- 7.1 mg/dl in the L-Y pump group, and minimal hemolysis was indicated. In conclusion, this L-Y pump and its controller system might be useful for CPB in terms of its low hemolysis and good pump quality. This pump demonstrated easy manipulation, good controllability, and provided a sufficient pulsatile flow. This pump is suitable not only for CPB, but also as a long-term circulatory support system.

Modeling and predicting selected immunological effects of a chemical stressor (3,4-dichloropropionanilide) using the area under the corticosterone concentration versus time curve

Many chemicals and drugs can induce a neuroendocrine stress response that can be immunosuppressive. Mathematical models have been developed that allow prediction of the immunological impact of such stress responses in mice on the basis of exposure to the important stress-related mediator corticosterone. The area under the corticosterone concentration vs. time curve (AUC) has been used as an indicator of cumulative corticosterone exposure in these modeling studies. In the present study, an immunotoxicant known to induce a stress response, 3,4-dichloropropionanilide (propanil), was evaluated to determine if corticosterone AUC values are related to suppression of immunological parameters in mice treated with this chemical. Linear relationships between corticosterone AUC values and suppression of the following parameters were noted in B6C3F1 female mice: thymus cellularity and thymus subpopulation percentages, splenic subpopulation percentages, natural killer cell activity, MHC class II protein expression, and IgG1 and IgG2a antibody responses to antigen. Linear models derived in previous studies using mice treated with exogenous corticosterone or with restraint stress effectively predicted the immunological effects of 3, 4-dichloropropionanilide on the basis of corticosterone AUC values. The models derived using immobilization stress were more effective (r(2) for observed vs. predicted = 0.90) than the models derived using mice treated with exogenous corticosterone (r(2) for observed vs. predicted = 0.65). This was expected, because most stressors induce a variety of immunomodulatory mediators, not just corticosterone. These findings have implications for risk assessment in immunotoxicology.

The p53 codon 72 polymorphism and lung cancer risk

The p53 tumor suppressor gene frequently is mutated in many forms of human carcinomas. A common polymorphism occurs at codon 72 of exon 4, with two alleles encoding either arginine (CGC) or proline (CCC). This p53 polymorphism reportedly is associated with lung cancer susceptibility. However, not all investigations have been consistent, and this hypothesized association remains controversial. We tested the hypothesis that the Pro/Pro genotype is associated with increased lung cancer risk in a large case-control study of lung cancer that included 482 cases and 510 controls from the Massachusetts General Hospital in Boston, Massachusetts. DNA from peripheral blood samples was examined by PCR-RFLP. Pro/Pro homozygotes were found more frequently in adenocarcinomas (cases, 16.4%; controls, 12.0%; P = 0.03). The prevalence of the Pro/Pro homozygous genotype increased in frequency with increasing pack-years of smoking. The combined susceptible genotype homozygous Pro/Pro and heterozygous Arg/Pro was associated with a 1.45-fold higher risk of adenocarcinoma compared with Arg/Arg genotype (95% confidence interval = 1.01-2.06; P = 0.04) after adjustment for relevant variables. Lung adenocarcinoma risk increased with the presence of one or both variant alleles across smoking strata. In addition, at each level of smoking (except nonsmoker and light smoker), the risk associated with smoking was higher for the population with the combined variant (Arg/Pro + Pro/Pro) genotype. The risk for the combined genotype was associated with tobacco exposure status. In conclusion, the codon 72 germ-line polymorphism (Arg/Pro) of the common tumor suppressor gene p53 contributes to heritable susceptibility for smoke-induced lung adenocarcinoma. The modifications by p53 polymorphism and pack-years resulted in an increased risk of the susceptible genotype to lung adenocarcinoma. The p53 gene may modulate the response to environment carcinogens and thereby affect the risk of developing lung adenocarcinoma.

[The research and manufacture of the pneumatic left ventricular assist pump]

The manufacturing methods and testing results of the pneumatic left ventricular assist pump(L-Y pump) are introduced in this paper. The results demonstrate that L-Y pump is reliable, biocompatible and in keeping with the clinical requirements.

Recognition of a sequestered self peptide by influenza virus-specific CD8+ cytolytic T lymphocytes

The Ag receptors on CD8+ CTL recognize foreign antigenic peptides associated with cell surface MHC class I molecules. Peptides derived from self proteins are also normally presented by MHC class I molecules. Here we report that an H-2Kd-restricted murine CD8+ CTL clone directed to an influenza hemagglutinin epitope can recognize a peptide derived from the murine mitochondrial aconitase enzyme in association with H-2Kd molecules. Surprisingly, this self peptide is not normally displayed on the cell surface associated with the restricting MHC class I molecule. Several lines of evidence suggest that this self peptide, although requiring association with the Kd molecule for CTL recognition, is not associated with this or other MHC class I allele under physiologic conditions in intact cells. Rather, it is sequestered in the cytoplasm associated with a carrier protein and is released only upon cell disruption. These results suggest a means of restricting the entry of self peptide into the class I pathway. In addition, this finding raises the possibility that self peptides sequestered within the cell can, after release from damaged cells, interact with MHC class I molecules on bystander cells and trigger autoimmune injury by virus-specific CTLs during viral infection.

A method for processing fluorescent labelled tissue into methacrylate: a qualitative comparison of four tracers

A technique for preserving fluorescence in retrogradely labelled neurons embedded in resin was developed. Four retrograde tracers were tested, Fast Blue (FB); Diamidino Yellow (DY); tetramethylrhodamine dextran (fluoro-ruby) (TMRD) and fluorescein dextran (fluoro-emerald) (FD). These tracers were applied to the cut end of the sciatic nerves in rats either by: (a) direct application of tracer crystals, or (b) dipping the nerve into an aqueous solution containing the tracer. Each lumbar spinal cord was removed and dehydrated by one of two methods: (a) conventional alcohol dehydration, or (b) dehydration through a graded series of aqueous methacrylate infiltration solutions (inert dehydration). Specimens were embedded in methacrylate and horizontal sections cut. The location of labelled motoneurons was mapped using a fluorescence microscope. Direct application of tracer crystals labelled more motoneurons than dipping. Fast Blue labelled considerably more motoneurons than tetramethylrhodamine. Labelling by all tracers was retained following methacrylate embedding. Fast Blue and Diamidino Yellow required inert dehydration, while tetramethylrhodamine dextran and fluorescein dextran were preserved using conventional dehydration. These results indicate that tissue labelled with commonly used fluorescent tracers can be processed and embedded in methacrylate, thereby permitting quantitative analysis by modern stereological methods.

Quantitative relationships between the suppression of selected immunological parameters and the area under the corticosterone concentration vs. time curve in B6C3F1 mice subjected to exogenous corticosterone or to restraint stress

The neuroendocrine response to stressors increases the concentration of several endogenous mediators, some of which are immunosuppressive. However, quantitative aspects of these effects have been overlooked. Although it should be possible to predict the degree of suppression of particular immunological functions by measuring the concentrations of stress-related mediators such as corticosterone, this cannot be done with data presently available. This study was designed to develop regression models to predict the relationship between the area under the corticosterone concentration vs. time curve (AUC) and two immunological parameters. Models were developed using mice treated with exogenous corticosterone and mice subjected to various periods of restraint stress. The latter treatment was included to determine if the effects of corticosterone were different from those of corticosterone in association with the other mediators induced in a restraint-stress response. Models relating corticosterone AUC to expression of MHC class II proteins on splenocytes were very similar, whether the corticosterone was exogenous or produced as part of a restraint-stress response. This was also true for splenic natural killer (NK) cell activity. However, MHC class II expression was more sensitive to the effects of corticosterone or restraint than was NK cell activity. The corticosterone and restraint models predicted the previously published effect of a chemical stressor (ethanol) on MHC class II expression, but neither model predicted the suppression of NK cell activity by ethanol. These results have mechanistic implications, which are discussed in the context of previous studies. The quantitative models described here should be useful in determining and predicting the stress-related portion of chemical-induced immunosuppression. In addition, these models provide quantitative data essential for a complete understanding of stress-induced immunosuppression.