Progesterone and luteinizing hormone secretion following stress-induced interruption of constant estrus in aged rats

Concentrations of progesterone and luteinizing hormone (LH) were measured during the first diestrus and subsequent proestrus after constant estrous was interrupted by restraint stress. Stress stimulated an acute increase in serum progesterone. Although stress resulted in changes in vaginal cytology characteristic of normal estrous cycles, stress-treated constant estrous (CE) rats had no midcycle (diestrous day 1) elevation of progesterone and markedly lower LH and progesterone during the afternoon of proestrous than age-matched normally cycling controls. The majority of the treated rats resumed CE without completing a cycle. In a separate experiment, progesterone injection during proestrous resulted in increased LH secretion in aging rats with normal estrous cycles. These data indicate that decreased proestrous progesterone secretion may contribute to the decrease in neuro-endocrine stimulation of proestrous gonadotropin secretion in the aged rat and may be associated with the initiation of CE.

In vitro transcription of Drosophila actin and 70,000-dalton heat shock protein genes

Drosophila genomic DNAs containing a chromosomal locus 87C1 70,000-dalton heat shock protein gene, the locus 79B actin gene, and the 88F actin gene have been used as templates in an in vitro HeLa transcription system. RNA polymerase II-dependent transcription initiates from specific sites on the heat shock protein gene and the 79B actin gene. The locations of the transcription start sites were determined by two types of experiments: sizing of RNA runoff transcripts and S1 nuclease mapping of the 5' terminus of the in vitro transcripts. Transcription initiates at or near the in vivo initiation site of the heat shock protein gene and initiates at or near a site 14 nucleotides downstream of the in vivo start site of the 79B actin gene. The addition of the 79B actin, 88F actin, or heat shock protein templates to a HeLa extract transcription reaction precluded the transcription of a second template subsequently added. The exclusion occurs rapidly, within 15 s, is not dependent on transcription, and is only partially resistant to high concentrations of the second added template. We propose that stable protein-promoter complexes play an important role in maintaining exclusive transcription of the first template added in vitro.

Immune regulation in myasthenia gravis: evidence for an increased suppressor T-cell population

The production of anti-acetylcholine receptor antibodies in myasthenia gravis represents a persistent and unexplained break in self-tolerance. The studies reported here demonstrate an altered regulatory T-cell population with an increase in the percentage of circulating T-suppressor cells as defined by two independently developed murine monoclonal antibody markers. Leu 2a- and OKT8a-positive cells were significantly increased within the T-cell population in myasthenia gravis (25.0 +/- 6.4% versus 20.7 +/- 2.9% and 34.9 +/- 7.0% versus 26.0 +/- 3.2%, respectively) compared to an age- and sex-equivalent group. In addition, the circulating total T-cell population was reduced in myasthenia gravis. Patients with symptomatically uncontrolled disease (with or without immunosuppression) demonstrated significantly altered ratios of helper to suppressor T-cells, while patients whose myasthenia symptoms were controlled did not differ from normal subjects.

Temporal patterns of serum luteinizing hormone and testosterone and endocrine response to luteinizing hormone releasing hormone in aging male rats

Temporal patterns of serum testosterone and luteinizing hormone (LH) concentration and responsiveness to luteinizing hormone releasing hormone (LHRH) were measured in young (2 to 3 months), middle-aged (12 to 13 months), and aged (22 to 26 months) male rats. Average testosterone and LH concentrations, as well as individual sample variations, were higher in young than in middle-aged and aged rats and higher in middle-aged than in aged groups. In addition, the young group showed a diurnal pattern of serum testosterone concentration and greater ranges of LH and testosterone concentrations in individual blood samples. Young male rats showed greater increases in serum LH and testosterone than middle-aged and aged groups after intravenous LHRH, 1 and 5 ng/g of body weight. These data indicate that LH and testosterone secretion are progressively reduced in the aged male rat and suggest alterations in neuroendocrine control of pituitary gonadotropin secretion as the most important alteration in the gonadal control system in these animals.

Endogenous and interferon-augmented natural killer cell activity of human peripheral blood mononuclear cells in vitro. Studies of patients with multiple sclerosis, systemic lupus erythematosus or rheumatoid arthritis

Peripheral blood mononuclear cells (PBMC) of normal human donors are spontaneously cytotoxic for certain tumour-derived and virus-infected target cells. This so-called natural killing (NK) can be augmented by the action of interferons (IFN) and by IFN-inducers. In this study, we have compared both endogenous and augmented NK activity of normal donors with that of patients suffering from either multiple sclerosis (MS), systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA). Endogenous NK was assayed using an NK susceptible target cell (K562), and augmented NK using a target cell (WI-L2) which is lysed only by NK effector cells that have been pre-stimulated by IFN or IFN-inducers. While NK function appeared normal in RA patients, this study confirms previous reports of defective endogenous NK in many MS and SLE patients. In addition, anomalous IFN-augmented NK was also detected in many patients with these two diseases, indicating that defective NK function cannot always be corrected by IFN treatment in vitro. Analysis of IFN production, endogenous NK and IFN-augmented NK by individual patients with MS or SLE showed the defects in their IFN-NK systems to be highly selective, suggesting that individual components of this system may operate independently.

Immunological studies in senile dementia of the Alzheimer type: evidence for enhanced suppressor cell activity

To examine immunological variables in senile dementia of the Alzheimer type (SDAT), we compared SDAT patients with elderly and young controls with regard to concanavalin A (Con A)-induced suppression, lymphocyte proliferation, interferon production, and serum immunoglobulin levels. The results showed exaggerated Con A suppression and reduced lymphocyte proliferation in SDAT patients compared to elderly control subjects. Interferon production after stimulation by Con A and immunoglobulin levels did not differ between SDAT and elderly control subjects. The results suggest impaired immunoregulatory mechanisms in patients with SDAT that may be related to the cause or course of SDAT. Alternatively, these immunological changes may be secondary to pathological changes in the central nervous system.

Interferon responses of leukocytes in multiple sclerosis

In vitro interferon (IFN) responses of peripheral blood leukocytes to measles virus and to other IFN inducers were determined for multiple sclerosis patients and normal donors. The group mean IFN response to measles virus was significantly lower in patients (15 units) than in normal donors (100 units), and a greater proportion of the patients failed to exhibit a significant IFN response. This defect was not specific for measles virus and was also observed consistently in response to Newcastle disease virus, Poly(I).Poly(C), and concanavalin A. The level of IFN response was not related to the clinical stage of disease.

Selective decline in cellular immune response to varicella-zoster in the elderly

The incidence of herpes zoster rises markedly in the aged. We evaluated the hypothesis that cellular immunity to varicella-zoster (VZ) viral antigens may be impaired in aged subjects. We found that the lymphocyte proliferation to VZ antigen was less in older asymptomatic individuals than in normal young controls. In contrast, responses to other antigens did not differ. Antibody titers to VZ were similar in both young and old subjects. Impairment of cellular immunity to VZ, on a population basis, may contribute to the increased risk of herpes zoster in the elderly.

The effect of age on reproduction in repeatedly mated female rats

The effects of age and repeated pregnancies on reproduction were studied in Long-Evans rats. Indices of reproduction measured included estrous cycles, successful mating, numbers of rats producing litters, average litter size, average pup weight and serum LH-from a 4 pm proestrous blood sample. There were no differences in these reproductive parameters between rats with serial pregnancies initiated at 2 or 9 mo of age. The percentage of rats producing normal litters was reduced much faster than the percentage of successfully mated rats with normal ovarian cycles. Although 60% of the rats still had normal ovarian cycles and were mated at 17 mo of age, only one rat (4%) produced a litter. Increasing age and multiple pregnancies did not significantly affect the LH concentration of the proestrous blood sample or the average litter size or pup weight of the rats with successful pregnancies. These data suggest post-ovulatory loss of reproduction in the aging rat.

The changing urban-suburban distribution of medical practice in large American metropolitan areas

The twenty largest multi-county SMSAs in the U. S. were studied for trends in the suburbanization of medical practice from 1959 to 1974. Fifteen of them allowed a distinction between suburbs and central city on the county level according to criteria developed from a New York City pilot study. In all SMSAs, the density of hospital-based physicians was higher in central cities than in suburbs and still increasing more rapidly there, though hospital practice is also starting to grow in the suburbs at an appreciable rate. The same trends were found for physicians in non-patient care activities. Office based specialists in large Northeastern SMSAs increased much more rapidly in the urbanized suburbs than in the central cities. In the Southern and Western SMSAs, on the contrary, office-based specialists continued to increase rapidly in the central cities despite concentrations already far greater than in the Northeast. Suburban desities were growing more slowly in these areas. General practitioners declined uniformly everywhere, apparently simply by attrition. Implications of these trends for health care are discussed.

Hypothalamic LH-releasing activity in young and aged intact and gonadectomized rats

Hypothalamic LH-releasing activity content was measured in young (3-5 mo) and aged (22-26 mo) intact and gonadectomized male and female rats. Hypothalamic extracts (0.25, 0.5 and 1.0 hypothalamus equivalents) from young and aged rats were incubated with untreated hemisectioned rat pituitaries in medium 199. All hypothalamic extract treatments stimulated LH release from the incubated pituitaries. Increased amounts of hypothalamic extracts added to to the incubation medium proportionally increased LH release. There were no differences in LH release stimulated by young or aged hypothalamic extracts from either the intact or gonadectomized groups. In addition serum testosterone concentrations were reduced in the aged male rats and serum LH was lower in aged male and female rats than in the young groups. Although serum LH was increased after gonadectomy in all groups, the increase was of smaller magnitude in the aged rats. These data indicate significant alterations in the responsiveness of the hypothalamus to steroid feedback in the aged rat. Although the hypothalamus contains sufficient LH-releasing activity to stimulate higher levels of pituitary and gonadal endocrine function, aging effects on the neuroendocrine control mechanisms inhibit hypothalamic hormone function.

Serum testosterone and testicular response to HCG in young and aged male rats

Serum testosterone and testicular response to HCG was measured in young (3 - 6 mo) and aged (20 - 30 mo) male Long-Evans rats. Serum testosterone was measured by radioimmunoassays on serial blood samples taken before and after injections of HCG. Control group serum testosterone concentrations were lower in aged compared to young groups. Intravenous injection of 1, 5, and 20 IU of HCG increased serum testosterone in both age groups and testosterone remained elevated throughout the 150-min sampling interval. The increase in serum testosterone concentrations following acute HCG stimulation was greater in young than in aged rats. Serum testosterone concentrations and testicular response to intravenous HCG injections were increased to similar levels in young and aged male rats following 7 days of daily subcutaneous injections of 5 IU of HCG/100 gm bw. These data suggest that while testicular secretion and responsiveness is reduced with age, the aged male rat retains the capacity to secrete more testosterone than it normally maintains.