Disparate spinal and supraspinal opioid antinociceptive responses in beta-endorphin-deficient mutant mice

The role of endogenous opioid systems in the analgesic response to exogenous opiates remains controversial. We previously reported that mice lacking the peptide neurotransmitter beta-endorphin, although unable to produce opioid-mediated stress-induced antinociception, nevertheless displayed intact antinociception after systemic administration of the exogenous opiate morphine. Morphine administered by a peripheral route can activate opioid receptors in both the spinal cord and brain. However, beta-endorphin neuronal projections are confined predominantly to supraspinal nociceptive nuclei. Therefore, we questioned whether the absence of beta-endorphin would differentially affect antinociceptive responses depending on the route of opiate administration. Time- and dose-response curves were obtained in beta-endorphin-deficient and matched wild-type C57BL/6 congenic control mice using the tail-immersion/withdrawal assay. Null mutant mice were found to be more sensitive to supraspinal (i.c.v.) injection of the micro-opioid receptor-selective agonists, morphine and D-Ala(2)-MePhe(4)-Gly-ol(5) enkephalin. In contrast, the mutant mice were less sensitive to spinal (i.t.) injection of these same drugs. Quantitative receptor autoradiography revealed no differences between genotypes in the density of mu, delta, or kappa opioid receptor binding sites in either the spinal cord or pain-relevant supraspinal areas. Thus we report that the absence of a putative endogenous ligand for the mu-opioid receptor results in opposite changes in morphine sensitivity between discrete areas of the nervous system, which are not simply caused by changes in opioid receptor expression.

Effect of the mu-opioid agonist DAMGO on medial basal hypothalamic neurons in beta-endorphin knockout mice

The endogenous opioid neurotransmitter beta-endorphin (beta-END), a product of the proopiomelanocortin (POMC) gene, is strongly implicated in the control of the female reproductive cycle, stress responses, and antinociception. Using selective gene targeting, we have generated a strain of mice that do not express any beta-END. These mice exhibit both normal reproduction and normal basal and stress-induced hypothalamic-pituitary-axis activity, but exhibit a significantly attenuated opioid-mediated stress-induced analgesia. To further understand the cellular bases of these responses, we have studied mediobasal hypothalamic (MBH) neurons, including POMC neurons, using whole-cell patch recording in an in vitro slice preparation. Twenty-seven MBH cells were recorded in wild-type and 25 MBH cells were recorded in beta-END knockout mice. Neurons from both genotypes showed a significant positive correlation between DAMGO concentration (from 30 nM to 10 microM) and the induced outward K(+) current. The genotypes did not differ, however, in either the DAMGO-induced maximum outward current response or EC(50), or for the maximal response to the GABA(B) agonist baclofen. Furthermore, quantitative receptor autoradiography utilizing (3)H-DAMGO did not reveal any differences in total mu-opioid receptor binding between genotypes. Therefore, we conclude that the complete absence of beta-END throughout development did not alter either the expression of mu-opioid receptors or their coupling to K(+) channels in MBH neurons.

Chromosome pairing in Lolium perenne x L. temulentum diploid hybrids: genetic and cytogenetic evaluation

A Lolium perenne genotype (E5/2/5/10), which had been selected for low chiasma frequency over a number of generations and which was suspected of containing one or two heterozygous dominant genes with a significant effect on chiasma frequency, was crossed with L. temulentum (Ba3081) to create a hybrid population of 47 diploid plants. The mean chiasma or paired arm (PA) frequency of homoeologous chromosomes at meiosis in the population was 9.1/cell (1.3 PA/chromosome pair) with a distribution skewed towards high PA frequency. More than 90% of the hybrid chromosomes paired at meiosis in spite of the disparity in chromosome length and DNA quantity between the two species. Overall, the distribution of PAs between chromosomes for a given number of PAs/cell favoured the production of rod bivalents over ring bivalents and univalents, indicating that there is a mechanism present that maximizes the total number of bivalent associations formed. Molecular marker analysis using AFLPs and isoenzymes did not identify any clear major gene effect on PA frequency in the hybrid population. It was concluded that the control of PA frequency in E5/2/5/10 was not a simple genetic mechanism.

A high-density molecular map for ryegrass (Lolium perenne) using AFLP markers

AFLP markers have been successfully employed for the development of a high-density linkage map of ryegrass (Lolium perenne L.) using a progeny set of 95 plants from a testcross involving a doubled-haploid tester. This genetic map covered 930 cM in seven linkage groups and was based on 463 amplified fragment length polymorphism (AFLP) markers using 17 primer pairs, three isozymes and five EST markers. The average density of markers was approximately 1 per 2.0 cM. However, strong clustering of AFLP markers was observed at putative centromeric regions. Around these regions, 272 markers covered about 137 cM whereas the remaining 199 markers covered approximately 793 cM. Most genetic distances between consecutive pairs of markers were smaller than 20 cM except for five gaps on groups A, C, D, F and G. A skeletal map with a uniform distribution of markers can be extracted from this high-density map, and can be applied to detect and map QTLs. We report here the application of AFLP markers to genome mapping, in Lolium as a prelude to quantitative trait locus (QTL) identification for diverse agronomic traits in ryegrass and for marker-assisted plant breeding.

Racial inequality in active life among adult Americans

Is a shorter life with more years lived in poor health a defining attribute of the life cycle of disadvantaged groups? Based on the 1990 5% Public Use Microdata Survey, we develop life table models of healthy (or active) life for the major racial groups, by sex, in the United States. The analysis underscores the complexity of the relationship between morbidity and mortality in the population. For Asians, longer life is associated with fewer years lived in poor health. In contrast, Native Americans' relatively longer lives are accompanied by extended periods of chronic health problems. Of all racial groups, blacks live the fewest years, and they live a high proportion of those years with a chronic health problems. Hispanics also live substantially fewer years, yet the period of life they spend with a health problem is relatively compressed. Racial differences in the link between morbidity and mortality point to the importance of investigating how chronic diseases and disease prevention and treatment are related to active life across the population subgroups.

Career trajectories and older men's retirement

The idea of a long and stable career rewarded by retirement is a fixture of the American social ethos and political economy. The paradox is that many Americans' careers do not fit this image. Here, we examined how the structure of the career, as compared to only those circumstances proximate to retirement, is important for understanding career endings. Based on labor force histories drawn from the National Longitudinal Survey of Older Men, we observed that the occupational roles held through the mid and late career combine additively to influence retirement and disability experiences, with different conditions of work coming into play depending on the career stage. Occupational roles in the mid career also have long-term, indirect effects, operating through the onset of health problems and the adequacy of pension benefits. Although retirement and disability are not hinged to occupational mobility per se, these career endings are sensitive to major discontinuities in the career and work role in terms of unemployment and labor force mobility.

Inequality in men's mortality: the socioeconomic status gradient and geographic context

Lower mortality for older rural Americans, compared to urban residents, runs counter to rural-urban disparities in health care services and residents' socioeconomic resources. This paradox calls into question the ways in which community conditions influence mortality and contextualize the relationship between individuals' socioeconomic status and health. Drawing on 24 years of data from the National Longitudinal Survey of Older Men, we observe that rural older men's life expectancy advantages occur even after controlling for residential differences in social class and lifestyle factors. Our results also show that rural advantages in mortality coincide with a more equitable distribution of life chances across the social classes. The association between social class and mortality is strongest among urban men, arising from socioeconomic conditions throughout the life cycle.

Differentials in active life expectancy in the older population of the United States

This study clarifies the process by which mortality and disability interact to determine differences in active life expectancy by age, sex, race, and education for the U.S. population 70 years of age and over. The analysis is performed using data from the Longitudinal Study of Aging and multistate life tables constructed using the results of hazard models. Women spend more years than men both active and inactive at every age; however, the proportion of life that is expected to be active is smaller for women. These differences are largely due to mortality differences favoring women. Persons with less than a high school education have shorter total and active life expectancies but similar expected lengths of inactive life compared to those with more than a high school education. There are no significant race differences in total life expectancy for race-education groups of the older population; but Blacks have lower expected active life than non-Blacks because of worse functioning.

Race inequities in men's retirement

A multistate life table model is used to identify how labor force experiences and mortality determine the labor force participation rates (LFPRs) and the qualities of the retirement life cycle of Black and White older men. LFPRs and the life cycle measures are compared to assess inequities of retirement access for the racial groups. The results show that Blacks' lower LFPRs are a function of disability. Despite lower LFPRs than Whites, however, Blacks spend a greater portion of their lives both working and disabled, reducing the retirement period. Race differences in the retirement life cycle also are highly sensitive to mortality. Reducing Black mortality to that of Whites would substantially narrow the life cycle differences. The combination of higher disability and mortality rates among Blacks suggests that health is a key determinant of retirement inequity.

The olfactory system as a model for the analysis of the contribution of gene expression to programmed cell death

The process of programmed cell death is frequently attenuated by inhibitors of protein and RNA synthesis. This implies that gene expression is necessary for the active elimination of some cell types. Genes such as bcl-2 and bax have been implicated in the direct control of cell death, while cellular immediate-early genes (cIEGs), such as c-fos and c-jun have been repeatedly associated with neuronal degeneration. We are using the olfactory neuroepithelium as a model system to investigate the role that expression of such genes might play in cell death. The advantages of this system is that even in the adult, there is spontaneous degeneration of olfactory receptor neurons followed by their replacement by the division and differentiation of precursors. Furthermore, the receptor neurons can be induced to die synchronously by removal of the olfactory bulb or intranasal administration of toxic agents. We have generated fos-lacZ and jun-lacZ transgenic mice that can be used to assess expression of c-fos and c-jun following these various manipulations. In addition, a line of transgenic mice has been derived that express Bcl-2 under the control of the olfactory receptor protein promoter. These mice have high levels of Bcl-2 selectively in receptor neurons of the primary neuro-epithelium and vomeronasal organ. Since in some circumstances, Bcl-2 can protect against programmed cell death these mice are being assessed for neuronal turnover under basal conditions and following olfactory bulbectomy.

Use of random PCR (RAPD) technology to analyse phylogenetic relationships in the Lolium/Festuca complex

The RAPD PCR technique has been employed to investigate phylogenetic relationships between species of the genera Lolium and Festuca. Several decamer primers were used to generate patterns from groups of genotypes of several different species. The degree of band sharing was used to evaluate genetic distances between species and to construct a phylogenetic tree which is in good overall agreement with classical taxonomy, but contains a number of novel insights. The degree of homoplasy inherent in this approach has been investigated using Southern hybridization. These results are discussed in the context of current work in molecular biosystematics.

The relationship between retirement life cycle changes and older men's labor force participation rates

This study probes the utility of older men's labor force participation rates (LFPRs) as indicators of the work-to-retirement transition. Specific attention is directed at how shifts in the retirement life cycle are related to LFPRs. Based on Current Population Survey data for the 1970s, a life table modeling approach showed that LFPRs are relatively weak indicators of the work-to-retirement transition. This was demonstrated by the relative stability in older men's age profiles of LFPRs despite significant changes in the timing and "organization" of the work-to-retirement transition. The 1970s evidenced a contraction of the main career and the expansion of both post-retirement work activity and retirement, yet none of these changes substantially altered the age profiles of older men's labor force participation rates.

Changing mortality and morbidity rates and the health status and life expectancy of the older population

This paper demonstrates the consequences of changes in mortality and health transition rates for changes in both health status life expectancy and the prevalence of health problems in the older population. A five-state multistate life table for the mid-1980s provides the baseline for estimating the effect of differing mortality and morbidity schedules. Results show that improving mortality alone implies increases in both the years and the proportion of dependent life; improving morbidity alone reduces both the years and the proportion of dependent life. Improving mortality alone leads to a higher prevalence of dependent individuals in the life table population; improving morbidity alone leads to a lower percentage of individuals with problems in functioning.

Induction of immediate early genes by cyclic AMP in primary cultures of neurons from rat cerebral cortex

In this paper, we tested whether physiological activators of the cAMP second messenger pathway in primary cultures of neurons from rat cerebral cortex directly induce c-fos and other immediate early gene (IEG) transcription factors. We have found that brief (30 s to 2 min) stimulation of neurons with vasoactive intestinal peptide (VIP) and SKF-38393, a D1-dopaminergic receptor agonist, potently increased mRNA levels for the IEGs c-fos, jun-B, and NGFI-A, with weaker increases for c-jun. This action was mimicked by forskolin and dibutyryl cAMP. IEG induction by VIP and dibutyryl cAMP was not blocked by excitatory amino acid receptor antagonists or by blockers of dihydropyridine-sensitive calcium channels. Moreover, calcium-free medium did not modify IEG induction by dibutyryl cAMP, suggesting that cAMP can directly regulate IEG expression in differentiated neurons independently of calcium.

Leaf development in Lolium temulentum L.: characterization of a slow-to-green mutant

A nuclear-gene mutation of the C3 grass Lolium temulentum L., which arose following cell suspension culture and plant regeneration, is manifested as delayed and incomplete greening, which occurs from the leaf tip downwards. Many plastids in the mutant exhibit abnormal morphology when examined by transmission electron microscopy; the plastid outer envelope lacks integrity and thylakoids, while still stacked, are spread over a wide area surrounded by diffuse stromal contents. These aberrant plastids can coexist with apparently normal chloroplasts in the same cell of mutant plants. Levels of chlorophyll a and b, and carotenoids, are all lower in the mutants than in normal Lolium temulentum. Leaf length, absolute growth rate, and number of cells per unit length at the leaf base, are greatly reduced (20-30% the normal values) in slow-to-green plants, but relative growth rate, duration of leaf growth, length of cell division zone and proportion of cells dividing are little affected. This novel mutant is a potentially valuable resource for studying interrelationships between photosynthetic function and leaf extension growth in grasses.

Differential induction of immediate early genes by excitatory amino acid receptor types in primary cultures of cortical and striatal neurons

In primary cultures of neurons from cerebral cortex and striatum, 30 s stimulation with the excitatory amino acid glutamate elicited a 5 to 9-fold increase in immediate early gene (IEG) mRNAs. Glutamate increased c-fos, c-jun, jun-B, and NGFI-A (zif/268) mRNAs by binding to both alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptor types, and increased c-fos, jun-B, and NGFI-A mRNAs by binding to the metabotropic receptor. NMDA receptor activation elicited IEG expression by a transmembrane calcium influx; AMPA receptor-induced depolarization played a permissive role for the opening of the NMDA receptor channel. The protein kinase C (PKC) inhibitor H-7 (but not inhibitors of cyclic nucleotide-dependent and calcium/calmodulin-dependent protein kinases) partially blocked IEG expression induced by glutamate.

Induction of the c-fos proto-oncogene in rat amygdala during unconditioned and conditioned fear

Induction of the nuclear proto-oncogene c-fos in rat amygdala was investigated 30-40 min following the presentation of mild footshocks (unconditioned fear) or of contextual cues associated with similar footshocks 24 h earlier (conditioned fear). Initially, it was found that handling rats for the first time elevated c-fos mRNA levels, but this response could be blocked completely by repeated handling. Unconditioned and conditioned fear both elevated amygdala c-fos mRNA dramatically above control levels.

Induction of the c-fos proto-oncogene during opiate withdrawal in the locus coeruleus and other regions of rat brain

Opiate regulation of the nuclear proto-oncogene c-fos was studied in the locus coeruleus (LC) and other regions of rat brain by immunoblotting, northern blotting, and in situ hybridization procedures. Precipitation of opiate withdrawal in rats, which is known to increase LC firing rates 4-fold, led to a two- to three-fold increase in levels of mRNA and protein for c-fos in the LC 1-2 h after initiation of withdrawal. In contrast, levels of c-fos expression were decreased in LC from rats treated acutely or chronically with morphine but not experiencing withdrawal, conditions under which LC firing rates are depressed. Similar regulation of c-fos expression during opiate withdrawal was found in the amygdala, ventral tegmentum, nucleus accumbens, neostriatum, and cerebral cortex, but not in a number of other brain regions studied, which included the hippocampus, dorsal raphe, periaqueductal gray, and paragigantocellularis. In the LC and some other brain regions, induction of c-fos during opiate withdrawal was associated with a parallel induction of c-jun, another nuclear proto-oncogene, which, like c-fos, is expressed rapidly in brain in response to certain extracellular stimuli. The results demonstrate a novel use of c-fos in neuropharmacology, namely to map neuronal pathways and neuronal cell types activated in response to acute and chronic opiate administration and during opiate withdrawal, as well as in response to other psychotropic drug treatments.

Work and retirement among a cohort of older men in the United States, 1966-1983

Multivariate increment-decrement working life tables are estimated for a cohort of older men in the United States for the period 1966-1983. The approach taken allows multiple processes to be simultaneously incorporated into a single model, resulting in a more realistic portrayal of a cohort's late-life labor force behavior. In addition, because the life table model is developed from multivariate hazard equations, we identify the effects of sociodemographic characteristics on the potentially complex process by which the labor force career is ended. In contrast to the assumed homogeneity of previous working life table analyses, the present study shows marked differences in labor force mobility and working and nonworking life expectancy according to occupation, class of worker, education, race, and marital status. We briefly discuss the implications of these findings for inequities of access to retirement, private and public pension consumption, and future changes in the retirement process.