The effects of lipid-lowering and antioxidant vitamin therapies on flow-mediated vasodilation of the brachial artery in older adults with hypercholesterolemia

OBJECTIVES

The goal of this study was to determine the long-term effects of statins and antioxidant vitamins on flow-mediated vasodilation of the brachial artery in older adults with hypercholesterolemia.

BACKGROUND

Lipid-lowering therapy and antioxidant vitamins improve endothelium-dependent vasodilation in young and middle-aged adults with hypercholesterolemia, but their effects in older adults are not known.

METHODS

Two double-blind, placebo-controlled studies were performed in individuals > or =70 years old with low-density lipoprotein cholesterol (LDL-C) > or =140 mg/dl. In the first study, 37 subjects were randomized to receive (group 1) pravastatin for six months then pravastatin and vitamin E for six additional months or (group 2) vitamin E for six months, then pravastatin and vitamin E for six additional months. In the second study, additional 17 subjects sequentially received simvastatin for six months, then simvastatin and vitamins C and E for six additional months. Flow-mediated vasodilation of the brachial artery was measured by high-resolution ultrasound.

RESULTS

At baseline, subjects in both studies were similar in age (mean +/- SD, 75.8 +/- 4.2 years), gender, systolic blood pressure, total cholesterol (261.6 +/- 37.4 mg/dl), LDL-C (180.3 +/- 28.1 mg/dl), high-density lipoprotein cholesterol and triglycerides levels. Flow-mediated vasodilation was severely impaired (2.2 +/- 3.9%). Both statins reduced total and LDL-C levels (p < 0.001); however, neither statin, antioxidant vitamin regimen nor the combination of statins and antioxidant vitamins improved flow-mediated vasodilation of the brachial artery. At baseline, nitroglycerin-mediated vasodilation also was impaired (10.7 +/- 5.6%) and did not change in either study.

CONCLUSIONS

Older adults with hypercholesterolemia have impaired flow-mediated vasodilation of the brachial artery that does not improve after one year of therapy with statins and antioxidant vitamins, despite significant lipid-lowering.

Using women's health research to develop women leaders in academic health sciences: the National Centers of Excellence in Women's Health

While the number of women entering U.S. medical schools has risen substantially in the past 25 years, the number of women in leadership positions in academic medicine is disproportionately small. The traditional pathway to academic leadership is through research. Women's health research is an ideal venue to fill the pipeline with talented women physicians and scientists who may become academic leaders in positions where they can promote positive change in women's health as well as mentor other women. The Office on Women's Health (OWH) in the U.S. Department of Health and Human Services has contracted with 18 academic medical centers to develop National Centers of Excellence in Women's Health. Emphasizing the integral link between women's health and women leaders, each of the Centers of Excellence must develop a leadership plan for women in academic medicine as part of the contract requirements. This paper describes the training programs in women's health research that have developed at five of the academic medical centers: the University of Wisconsin, Magee Women's Hospital, the University of Maryland, Medical College of Pennsylvania Hahnemann University, and the University of Illinois at Chicago. We discuss some of the challenges faced for both initiation and future viability of these programs as well as criteria by which these programs will be evaluated for success.

Age effects on the temporal evolution of isometric and swallowing pressure

BACKGROUND

The tongue plays a key role in bolus propulsion through the oropharyngeal chamber. In this study, possible age effects on the magnitude and timing of lingual pressure generation were analyzed.

METHODS

Oral pressure was measured during isometric and swallowing tasks for 10 elderly (mean age = 81 years) and 10 young (mean age = 51 years) subjects. Three trials each of the isometric task and swallows of three different boluses (3 ml semisolid, 3 ml liquid, and 10 ml liquid) were performed by each subject. The timing and magnitude of isometric and swallowing pressure generation along with the pattern of the swallowing pressure waveform were analyzed.

RESULTS

Whereas maximum lingual isometric pressures decreased with age (p < .001). no significant age difference was found for swallowing pressure. Time taken to reach peak pressure also was reduced with age in both the isometric task and swallows of liquid boluses (p < .05), while no significant age effect was found for semisolid swallows. Finally, only elderly subjects showed a pattern of liquid swallowing pressure generation in which multiple lingual gestures were required to reach peak pressure (termed "pressure building"), a pattern demonstrated by both young and elderly groups for semisolids.

CONCLUSIONS

Decreased lingual strength with age combined with unchanging swallowing pressure leads to a decreased "pressure reserve," perhaps leaving older individuals more at risk for dysphagia resulting from insults directly or indirectly to the swallowing system. Additionally, swallowing is generally "slowed" with age, apparently due to both central and peripheral factors, and this change may have an impact on bolus flow outcomes.

Hormone replacement therapy in prevention of morbidity and mortality in the older woman. Part IV: HRT and the aging brain, overall mortality, and individual decision-making

OBJECTIVES

The objective of this four part series is to review for the practicing clinician the extensive and sometimes contradictory literature on the effects of estrogen replacement therapy and hormone replacement therapy (HRT) in the postmenopausal woman. This final article reviews the role of long-term HRT in stroke, Alzheimer's disease (AD), and overall mortality as well as strategies to guide decision-making for the individual patient.

DESIGN

Studies reviewed were obtained through Medline searches, examination of citations in the articles reviewed from those searches, interviews with local experts in geriatrics, cardiology, and women's health.

CONCLUSIONS

Evidence for benefit from HRT in delaying onset of and preventing AD in aging women is inconclusive. No consistent trend for beneficial or harmful effect of HRT on stroke risk has been demonstrated. HRT does seem to be beneficial in decreasing overall mortality risk, especially in women with coronary heart disease risk factors. The overall health and functioning of the geriatric patient and the presence of co-morbid conditions must be factored into clinical decisions. The decision to initiate HRT is complex, requires thoughtful assessment of net benefit and risk for the individual patient, and should accommodate the individual's personal preferences. Forthcoming results from the Women's Health Initiative HRT trial and observational study will help resolve some of the ambiguities in this decision-making process.

Results of a gender-climate and work-environment survey at a midwestern academic health center

AND CLIMATE determine how faculty's perceptions of medical school gender climate differ by gender, track, rank, and departmental affiliation.

METHOD

In 1997, a 115-item questionnaire was sent to all University of Wisconsin Medical School faculty to assess their perceptions of mentoring, networking, professional environment, obstacles to a successful academic career, and reasons for considering leaving academic medicine. Using Fisher's exact two-tailed test, the authors assessed gender differences both overall and by track, rank, and departmental cluster.

RESULTS

Of the 836 faculty on tenure, clinician-educator, and clinical tracks, 507 (61%) responded. Although equal proportions of men and women had mentors, 24% of the women (compared with 6% of men; p < .001) felt that informal networking excluded faculty based on gender. Women's and men's perceptions differed significantly (p < .001) on 12 of 16 professional environment items (p < .05 on two of these items) and on five of six items regarding obstacles to academic success. While similar percentages of women and men indicated having seriously considered leaving academic medicine, their reasons differed: women cited work-family conflicts (51%), while men cited uncompetitive salaries (59%). These gender differences generally persisted across tracks, ranks, and departmental clusters. The greatest gender differences occurred among clinician-educators, associate professors, and primary care faculty.

CONCLUSIONS

Women faculty perceived that gender climate created specific, serious obstacles to their professional development. Many of those obstacles (e.g., inconvenient meeting times and lack of child care) are remediable. These data suggest that medical schools can improve the climate and retain and promote women by more inclusive networking, attention to meeting times and child care, and improved professional interactions between men and women faculty.

Hormone replacement therapy in prevention of morbidity and mortality in the older woman: part III: potential adverse effects of hormone replacement therapy

OBJECTIVES

The objective of this four part series is to review for the practicing clinician the extensive and sometimes contradictory literature on the effects of estrogen replacement therapy (ERT) and hormone replacement therapy (HRT) in the postmenopausal woman. This third article reviews HRT and the potential excess morbidity from breast cancer, endometrial cancer, venous thromboembolism (VTE), and coronary heart disease (CHD).

DESIGN

Studies reviewed were obtained through Medline searches, examination of citations in the articles reviewed from those searches,interviews with local experts in geriatrics, cardiology, and women's health.

CONCLUSIONS

Long-term HRT seems to be associated with a small increased risk for breast cancer. The risk of endometrial cancer in women with a uterus using ERT can be eliminated completely with the use of combination estrogen and progestin. HRT may be associated with a small increased risk for VTE; however, the absolute morbidity and mortality attributable to VTE is small and unlikely to impact the net benefit of HRT significantly. Although there is considerable data favoring a beneficial effect of HRT on CHD, initiation of HRT in women with established CHD may be associated with increased risk of adverse cardiac events in the first year after initiation. In counseling patients about the use of long-term HRT, the balance of these risks and the effect of co-morbid illness in the geriatric population should be addressed. Discussion of HRT and the aging brain (stroke, dementia), the net benefit of long-term HRT, and decision-making for the individual patient is forthcoming in the final article of this four-part series.

Managing dyslipidemia in older adults

OBJECTIVES

To summarize and critically review clinical trial data regarding dyslipidemia as a risk factor for coronary heart disease (CHD) and the efficacy and safety of lipid-lowering interventions in older adults. Based on these data, clinical recommendations for diagnosing and managing dyslipidemia in older adults are provided.

METHODS

Peer-reviewed journal articles were identified by a MEDLINE search and a review of journal article references. Studies that were performed exclusively in subjects older than 65 years or that included a large subgroup of older adults were included.

CONCLUSIONS

Elevated low density lipoprotein and total cholesterol levels are independent risk factors for CHD events in patients aged older than 65 years. Older adults have a higher risk of mortality attributable to hypercholesterolemia. Diet and lipid-lowering medications safely and effectively lower cholesterol levels in this age group. Exercise increases high-density lipoprotein cholesterol levels and decreases triglyceride levels. If accompanied by weight loss, exercise may reduce low-density lipoprotein and total cholesterol levels. Improving lipid levels in older adults with CHD decreases the risk of future coronary events by up to 45%, and significant effects on outcome measures may be observed within 2 years of the initiation of therapy.

Gender differences in acute myocardial infarction: the University of Wisconsin experience

OBJECTIVE

To investigate gender differences in baseline characteristics, presentation, and treatment of patients with acute myocardial infarction (MI) admitted to the University of Wisconsin Hospital Coronary Care Unit (CCU) over a 1-year period.

METHODS

A retrospective review was performed on the charts of all patients (n = 293) admitted to the CCU in 1996 with a discharge diagnosis of acute MI. In 83 women and 187 men with analyzable data (n = 270), 42 factors related to baseline characteristics, presentation, treatment, and outcomes were identified and analyzed for gender differences.

RESULTS

On average, women were 5 years older than men (p < .01). By univariate comparison, women were less likely than men to be smokers (p < .001); more likely to have underlying hypertension (p < .01), diabetes mellitus (p < 0.05), non-Q-wave infarctions (p < .01), and congestive heart failure (CHF, p < .05); and more likely to have received diuretics (p < .001) and ACE inhibitors (p < .01). While women were less likely than men to undergo coronary angiography (p < .05) and more likely to have echocardiograms (p < 0.05), rates of coronary artery bypass graft surgery, angioplasty, and the use of thrombolytics were similar for men and women. Clinical outcomes were similar in both groups. CHF, hypertension, and use of ACE inhibitors remained the only significant gender differences when data were adjusted for age.

CONCLUSION

Comparing men and women with acute MI at UW Hospital revealed some differences in clinical characteristics and management. Except for CHF, hypertension, and use of ACE inhibitors (all of which may be related), these differences disappeared when the data were adjusted for age. This is particularly notable for the disappearance of the difference in the use of coronary angiography between men and women. The comparable use of beta-blockers, aspirin, and nitrates, and the similar clinical outcomes in men and women, suggest less gender difference in MI management at UW Hospital than reported in other studies.

Effects of estrogen replacement therapy on the circadian rhythms of serum cortisol and body temperature in postmenopausal women

Estrogen replacement therapy (ERT) seems to enhance longevity in women. Both gender and aging have been shown to influence the regulation of circadian rhythms, yet little is known about the effect of ERT on circadian regulation. The aim of this study was to determine the effects of ERT (oral conjugated estrogen: Premarin, 0.625 mg) for 6-8 weeks on circadian serum cortisol by continuous blood sampling every 15 min for 24 h with simultaneous measurements of body temperature in six healthy postmenopausal women (range, 54-61 years). The results are presented as median values (range in quartiles). The circadian amplitude of cortisol increased during ERT from 20.20 (18.35, 23.61) to 25.97 (24.94, 27.74) microg/dL (p = 0.016), whereas the timing of nocturnal nadir and morning acrophase did not differ significantly. ERT lowered the 24-h body temperature from 37.03 degrees C (36.95 degrees C, 37.07 degrees C) to 36.90 degrees C (36.77 degrees C, 36.97 degrees C) (p = 0.038), but did not alter the peak and trough body temperatures significantly. These findings are noteworthy because the increased circadian amplitude of serum cortisol during ERT contrasts with the reduction in circadian amplitude seen with normal aging. The reduction in body temperature confirms the regulatory effect of ERT in thermoregulation and has implications regarding the correlation between basal metabolic rate and life span.

Body piercing medical concerns with cutting-edge fashion

OBJECTIVE

To review the current information on medical complications, psychological implications, and legislative issues related to body piercing, a largely unregulated industry in the United States.

METHODS

We conducted a MEDLINE search of English language articles from 1966 until May 1998 using the search terms "body piercing" and "ear piercing." Bibliographies of these references were reviewed for additional citations. We also conducted an Internet search for "body piercing" on the World Wide Web.

MAIN RESULTS

In this manuscript, we review the available body piercing literature. We conclude that body piercing is an increasingly common practice in the United States, that this practice carries substantial risk of morbidity, and that most body piercing in the United States is being performed by unlicensed, unregulated individuals. Primary care physicians are seeing growing numbers of patients with body pierces. Practitioners must be able to recognize, treat, and counsel patients on body piercing complications and be alert to associated psychological conditions in patients who undergo body piercing.

Long-term efficacy of nonsurgical urinary incontinence treatment in elderly women

BACKGROUND

Although urinary incontinence affects up to 35% of community-dwelling elderly women, the long-term efficacy of conservative treatment in this population is unknown.

METHODS

Between April 1991 and January 1994, 81 community-dwelling women over age 60 underwent nonsurgical incontinence treatment that included pelvic muscle exercises, bladder retraining, estrogen replacement, biofeedback, functional electrical stimulation, and pharmacologic therapy. Information about intercurrent medical problems, urogynecologic diagnoses, treatment recommendations, and provider-documented outcome were collected from medical records. We mailed structured questionnaires evaluating persistent incontinence, treatment efficacy, interval therapy, and quality of life to women who had last attended clinic at least one year previously.

RESULTS

Fifty-three of 81 (65%) women, mean age (+/- SD) 76 +/- 8 years, returned the questionnaire. The mean follow-up interval was 21 +/- 8 months. At follow-up, 43% of women reported incontinence was not a problem or mild, 33% reported moderate incontinence, and 21% reported severe incontinence. When patients compared their initial with current incontinence severity, improvement was significant (p < .01). Genuine stress incontinence was diagnosed in 18 women, detrusor overactivity in 14, and mixed incontinence in 13. Improvement did not vary consistently by incontinence diagnosis. Older patients had more severe incontinence at presentation (r = .94, p = .02) and reported less improvement (r = .97, p < .01) than younger ones. However, the overall likelihood of improvement was greatest among patients with the most severe incontinence at presentation (r = .534, p < .001). Subjects considered pelvic muscle exercises, delayed voiding, and caffeine restriction most effective in reducing incontinence severity.

CONCLUSIONS

Elderly women derive long-term clinical benefit from nonsurgical incontinence therapy. Younger patients and those with more severe incontinence are most likely to respond to treatment.

Detecting iron deficiency in anemic patients with concomitant medical problems

OBJECTIVE

To determine the sensitivity and specificity of mean corpuscular volume, transferrin saturation, total iron-binding capacity, and ferritin level in determining iron deficiency in a population of anemic veterans with a wide variety of general medical diagnoses.

DESIGN

Retrospective chart review.

SETTING

Hospitals of the Department of Veterans Affairs in Madison and Milwaukee, Wisconsin.

PARTICIPANTS

One hundred one anemic veterans with any medical condition who underwent bone marrow aspiration and serum iron studies.

MEASUREMENTS AND MAIN RESULTS

Using the presence or absence of bone marrow hemosiderin as the reference standard, the sensitivity and specificity of the following serum iron indicators were calculated: mean corpuscular volume, transferrin saturation, total iron-binding capacity, and ferritin level. Of these patients, 41 (40.6%) were categorized as iron deficient, with no stainable bone marrow hemosiderin. A serum ferritin level < or =100 microg/L provided the best sensitivity (64.9%) and specificity (96.1%) for evaluating iron stores in this patient population. When performed within 24 hours of bone marrow examination, a serum ferritin level < or =100 microg/L was 100% accurate in separating iron-deficient from iron-sufficient patients. None of the other serum iron indicators alone or in combination performed better than ferritin level alone.

CONCLUSIONS

In a population of anemic veterans with a wide variety of concomitant medical problems, a serum ferritin level < or =100 microg/L was optimal for determining iron deficiency. This is higher than the ferritin level of < or =50 microg/L cited in standard textbooks as evidence of iron deficiency in patients with inflammation, infection, or malignancy.

Intensive venous sampling of adrenocorticotropic hormone in rats with sham or paraventricular nucleus lesions

Adrenocorticotropic hormone (ACTH) secretion from the anterior pituitary is predominantly regulated by corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) synthesized in neurons of the paraventricular nucleus (PVN) of the hypothalamus. Secretion of ACTH occurs in pulsatile bursts. To explore the relationship between hypothalamic control and the pulsatile pattern of ACTH secretion, we measured ACTH in 2 min blood samples over 4 h in rats with intact and lesioned PVN during hypovolemic-stress or control conditions and also measured median eminence (ME) levels of CRH, AVP, and oxytocin (OT). Mean plasma ACTH was highest in the sham lesioned-hypovolemic group, lowest in the sham lesioned-control group and intermediate in the two PVN-lesioned groups. CRH in the ME was negligible in the lesioned animals and correlated with OT and AVP. Pulsatile secretion was observed despite PVN ablation. Visual inspection of composite time series suggested different temporal patterns of ACTH secretion. Principal components analysis of the individual ACTH time series revealed three significant eigenvectors which correlated differentially with the three treatment groups. Neither lesioned group had the steep rise over 10 min seen in plasma ACTH in the non-lesioned groups. Delayed ACTH rise after 30-60 min occurred in all but the sham control group. Our data suggest that CRH is responsible for immediate secretion of ACTH in response to hypovolemic stress and that regulators from non-PVN sites may be responsible for more delayed secretion of ACTH in this setting. The persistence of ME AVP and OT levels in the face of > 90% reduction in ME CRH levels leaves open the question of a role for one or both of these peptides in the delayed ACTH response following stress onset and in the generation of pulsatile ACTH secretory bursts.

Pulsatile adrenocorticotropic hormone: an overview

Adrenocorticotropic hormone (ACTH) is secreted by corticotrophic cells in pulsatile bursts. This paper reviews the extant literature on the phenomenon of pulsatile ACTH after addressing basic issues of hormone pulsatility in neuroendocrine systems. The following themes emerged from reviewing 51 studies measuring plasma ACTH at intervals of 20 min or less: marked inter-individual variability in the pattern of ACTH, the dependence of pulse identification on sampling frequency, the similarity in ACTH pulse amplitude and frequency across species, and the predominance of amplitude over frequency changes in ACTH pulses in altered physiological states. As the hypothalamic-pituitary-adrenocortical (HPA) axis plays a critical role in orchestrating adaptation and survival, the ability to modulate the shape of ACTH signals may prove to be an important means of transmitting complex information to ACTH responsive cells. The clinical and neurobiological significance of temporal alterations in ACTH secretion represents an area for future investigation.

Geriatric assessment: making it work in primary care practice

Geriatric assessment has become an established part of medical practice, a trend driven by the growing population of older patients, positive patient outcomes, and increase interest in controlling healthcare cost. Geriatric assessment is a diagnostic process that can be performed in a variety of clinical settings, including the primary care office. The interdisciplinary assessment team usually includes at least three members: a physician, a nurse,and a social worker. Patients who appear to derive the greatest benefit are over age 75, have mild to moderate disabilities, may be at risk of nursing home placement, and may have a poor social network. For optimal effectiveness, assessment must be coupled with a comprehensive therapeutic plan and long-term follow-up.

Neuroendocrine and cardiovascular effects of serotonin: selective role of brain angiotensin on vasopressin

Central serotonin (5-HT) and angiotensin (ANG II) stimulate arginine vasopressin (AVP), oxytocin (OT), and adrenocorticotropin (ACTH) secretion and increase blood pressure. Studies were conducted in conscious rats to determine whether neuroendocrine activation by 5-HT requires a brain angiotensinergic intermediate pathway. In the first study, ANG II formation was inhibited by the angiotensin-converting enzyme inhibitor enalapril before injection of the 5-HT releaser/uptake inhibitor d-fenfluramine. Fenfluramine (2 mg/kg ip) stimulated AVP, OT, corticosterone, and prolactin (PRL) secretion (P<0.01). Enalapril (60 mg/l in drinking water for 4 days and 10 mg/kg ip 2 h before the rats were killed) inhibited only the AVP response (P<0.01) to d-fenfluramine. In the second study, the effect of intracerebroventricular injection of the 5-HT2A/2C antagonist LY-53857 (10 microgram), or the ANG II AT1 antagonist DuP-753 (10 microgram), on intracerebroventricular 5-HT (10 microgram)-stimulated AVP, OT, ACTH, PRL, renin secretion, mean arterial pressure (MAP) and heart rate (HR) was tested. LY-53857 inhibited the AVP, OT, and ACTH responses to 5-HT (P<0.01), whereas DuP-753 inhibited only the AVP response (P<0.01). Intraventricular injection of 5-HT increased MAP and decreased HR. The MAP response was not affected by LY-53857 or DuP-753, and at no time did MAP decline below starting levels. The decreased HR was inhibited by LY-53857 but not by DuP-753. These results demonstrate that 5-HT-induced AVP secretion is mediated selectively via brain angiotensinergic mechanisms by way of the AT1 receptor.

Symposium on geriatric care:

Academic geriatricians are challenged to develop clinical programs which meet needs in the area of patient care as well as medical student and resident education and research. The creation of such programs within tertiary care institutions can be complex based on existing, traditional styles of care, the increasing demand for geriatric education and the fiscal reality of caring for frail, complex patients. In this article we discuss how five such institutions have met this challenge.

Menopause and the aging female reproductive system

Only in this century have so many women lived beyond reproductive age. Cultural upheavals in industrial nations have made reproduction an option, a hygienic issue, and the ending of reproductive capacity a crisis of aging. A woman's hormonal milieu changes during her climacteric and beyond with multiple potential symptomatic consequences. Treatment with hormones can ameliorate the symptoms of menopause and potentially decrease the risk for the long-term consequences of the menopause. Objective scientific data for absolutes regarding hormone replacement therapy are lacking, but, increasingly, this epoch in the physical and emotional life of a woman is being defined by new cultural expectations.

Apparent seasonal rhythms in hypothalamic neuropeptides in rats without photoperiod changes

An apparent seasonal or circannual rhythm in the hypothalamic content of CRF, TRH, neurotensin, and neuromedin N has been observed in 12 separate monthly coherts (n = 10@ or 130 total) adult, male Sprague-Dawley rats obtained at the same time each month from a single commercial supplier and held under constant (12:12) photoperiod conditions since birth. Both annual and 4-month (terannual) harmonics can be statistically discerned in these apparent rhythms, which exhibit cycles containing concentration changes up to 3-fold the lowest levels across the year (CRF increases 390%, TRH increases 173%, neurotensin increases 136%, and neuromedin N increases 150%). Hypothalamic somatostatin did not exhibit these statistically significant robust rhythms nor did any peptide in regions outside the hypothalamus. These data indicate that a mechanism allowing enhanced or diminished physiological availability of these regulatory neuropeptides at different times of the year may exist and may display distinct cycles even in the absence of normal photoperiod cues. Possible regulatory responses of pituitary receptor populations for these hypothalamic peptides must be considered. As certain of these neuropeptides also appear to be altered in the cerebrospinal fluid of patients with major depression or schizophrenia, similar hypothalamic cyclic changes may underly psychiatric symptoms with seasonal periodicity.

Evidence that ACTH secretion is regulated by serotonin2A/2C (5-HT2A/2C) receptors

The present study characterized the serotonin (5-HT) receptor subtypes mediating adrenal corticotropic hormone (ACTH) and corticosterone responses to 5-HT agonists in conscious rats. The 5-HT2A/5-HT2C agonist (+/-(-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HC1 (DOI) increased plasma ACTH and corticosterone in a dose-dependent manner. The 5-HT2A/5-HT2C antagonist ritanserin (0.01 and 0.1 mg/kg sc) inhibited the DOI-induced increase in plasma ACTH, but not corticosterone. Low doses of spiperone (0.01 and 0.1 mg/kg sc) significantly reduced the ACTH response to DOI. Because spiperone has a higher affinity for 5-HT2A than 5-HT2C receptors, these data suggest that DOI stimulates ACTH secretion through 5-HT2A receptors. 5-methoxy-3-[1,2,3,4-tetrahydro-4-pyridinyl]-1H-indole (RU 24969) is a potent 5-HT1A/1B and moderate 5-HT2C agonist that also has been suggested to release 5-HT. However, p-chlorophenylalanine (PCPA) did not reduce the effect of RU 24969 on plasma ACTH, suggesting that RU 24969 only acts as a direct agonist. 6-methyl-1-[1-methylethyl]ergoline-8-carboxylic acid (LY53857) injected into the lateral cerebral ventricles (i.c.v.) inhibited the ACTH, but not corticosterone response to peripheral injection of RU 24969, suggesting that central 5-HT2A/2C receptors mediate the ACTH response. LY53857 injection (i.c.v.) also inhibited the effect of p-chloroamphetamine (i.c.v.) on plasma ACTH. However, the corticosterone response was not inhibited by LY53857, suggesting a distinct location of 5-HT receptors regulating corticosterone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Coincident plasma ACTH and corticosterone time series: comparisons between young and old rats

Senescence is accompanied by a reduced ability to respond to a variety of physical and behavioral stressors. A sizable literature has been devoted to the interplay between hypothalamic-pituitary-adrenocortical axis dysfunction and senescence; yet, the precise interactions remain an enigma. Adrenocorticotropic hormone (ACTH) is secreted in pulsatile bursts generating complex signals in the plasma compartment that must be "read" by adrenocortical cells in order to initiate appropriate secretory responses. We have previously demonstrated subtle differences between young and old rats in the pattern of fluctuations in plasma ACTH concentrations over time, despite no difference in mean levels. The present work addressed the physiological significance of these differences in the plasma ACTH signal by analyzing the corresponding plasma corticosterone concentration time series and the relationship between these two hormones over time. Time series of integrated 10-min ACTH and corticosterone concentrations were collected over 4 h at the time of diurnal activation and analyzed in the time and frequency domains. The time of onset of the diurnal surge occurred 20 min later in old rats, and the ratio of corticosterone to ACTH was less at the time of onset and peak of the diurnal surge. Corticosterone levels were lower in old rats and mean ACTH and corticosterone levels were correlated in young but not old rats, as were maximum levels of the two hormones. Cross-correlation of ACTH and corticosterone time series and comparison of spectra were consistent with smoother fluctuations in plasma corticosterone in old animals with less variability at time scales less than 55 min. We conclude that age may be associated with a delay in diurnal activation of the HPA axis, a loss of sensitivity of adrenal corticosterone secretion to plasma ACTH levels, and a relative loss of high frequency variability in the corticosterone signal, as seen in many physiological systems with age.

Model simulations of ACTH pulsatility

Using high intensity venous sampling (1-2 min integrated intervals) we have observed rapid (< 10 min) large amplitude (up to 80 pg/ml) fluctuations in plasma ACTH concentrations in addition to variations at longer time scales. We developed a mathematical model to assess whether plausible physiological explanations could account for our observations and compared model simulations with time series from two human subjects. Three key features enabled the model to accurately simulate the observed time series. 1) The pattern of instantaneous secretory events comprising a pulse followed a Poisson process during baseline activity and rapidly shifted to a step function pattern during a pulsatile episode. 2) The fraction of secreted ACTH shunted between a fast and slow clearance mechanism varied biphasically between baseline and pulsatile states. 3) A brief rate-sensitive suppression of secretion was invoked when secretory rates increased above a threshold amount.

High intensity venous sampling reveals subtle alterations in plasma adrenocorticotropin patterns in old rats

Dysregulation of the hypothalamic-pituitary-adrenocortical axis has been theoretically linked to the processes of aging for decades. To investigate the effects of age on high frequency rhythms of plasma ACTH at the time of circadian activation, integrated 2-min blood samples were collected over 4 h in 10 young and 14 old rats with simultaneous plasma volume replacement. Plasma ACTH time series were analyzed in the time and frequency domains. Relative to young rats, old rats had a significantly later onset of the diurnal surge, more spectral power (R2) at lower frequencies, a lack of correlation between the slope of the spectral background continuum and the R2 at periods less than approximately 11 min, a stretching of the time scale in the composite spectra by 18.5%, and an amplitude reduction of the major composite spectral peak by 31%. These findings support the existence of subtle, but significant, alterations in the pattern of plasma ACTH with age and a delayed response of the hypothalamic-pituitary-adrenocortical axis to circadian activation. The differences in spectra suggest a weaker coupling with age between the high frequency signal input (that may reflect depolarization of groups of corticotrophs) and the system response, which could account for the delay in onset of the diurnal surge seen in the time domain.

The role of serotonergic neurons in intravenous hypertonic saline-induced secretion of vasopressin, oxytocin, and ACTH

This study tested the effect of brain serotonin (5-HT) depletion on the secretion of oxytocin (OT), vasopressin (VP), and adrenocorticotropin (ACTH) due to an osmotic load. The 5-HT neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) was used to deplete brain 5-HT. The OT, VP, and ACTH osmotic sensitivity (slope of delta[OT]/delta[Osm]) and the osmotic threshold (X intercept of delta[OT]/delta[Osm]) were evaluated. Depletion of brain 5-HT decreased the OT osmotic sensitivity by > 80% (p < 0.001) without changing the OT osmotic threshold. Brain 5-HT depletion had no effect on the VP osmotic sensitivity and increased the VP osmotic threshold from 287.8 +/- 1.5 to 293.1 +/- 2.0 mOsm/kg (p < 0.05). The plasma ACTH increase due to infusion of hypertonic saline was not affected by brain 5-HT depletion. Brain 5-HT depletion significantly (p < 0.01) decreased the pituitary content of OT and VP by 38 and 32%, respectively, without changing ACTH content. These results provide evidence for a functional role of serotonergic neurons in osmoregulation of plasma and pituitary concentration of OT and VP, but not ACTH.

Effect of cocaine injections on the neuroendocrine response to the serotonin agonist MK-212

This study was undertaken to examine whether several of the hormones that can be released by activation of serotonin receptors will be affected by long-term cocaine administration. Male rats received cocaine injections (15 mg/kg, IP) twice daily for 7 days. Forty-two hr after the last cocaine injection, the rats were challenged with increasing doses (0, 1, 5, 10 mg/kg, IP) of the 5-HT1/5-HT2 agonist MK-212 (6-chloro-2-[1-piper-azinyl]-pyrazine). The following observations were made: (1) cocaine reduced the rate of body weight gain; (2) cocaine inhibited the stimulatory effect of MK-212 on plasma vasopressin, oxytocin, and prolactin concentrations and on plasma renin activity and concentration; (3) cocaine did not inhibit the stimulatory effect of MK-212 on plasma ACTH or corticosterone concentrations. The data indicate that a wide-spectrum 5-HT (serotonin) agonist such as MK-212 can reveal differential neuroendocrine responses. This effect could be related to cocaine-induced changes in the different 5-HT receptor subtypes that regulate the secretion of these hormones.

Comparison of neuroendocrine and behavioral effects of ipsapirone, a 5-HT1A agonist, in three stress paradigms: immobilization, forced swim and conditioned fear

Ipsapirone is an anxiolytic drug and a serotonin1A (5-HT1A) agonist. The aim of the present study was to investigate the effects of low doses of ipsapirone on the hormonal and behavioral response to three stress procedures: immobilization, forced swim and conditioned emotional response (CER). We examined the effect of ipsapirone (0.1, 0.5 or 1.0 mg/kg) on plasma renin concentration (PRC), adrenal corticotropic hormone (ACTH), corticosterone, prolactin and defecation in rats exposed to immobilization, forced swim or CER stress. All three stressors significantly elevated all the hormone levels (P less than 0.01). Immobilization-induced elevations of PRC, and corticosterone were inhibited by the highest doses of ipsapirone (0.5 and 1 mg/kg, i.p.). However, ipsapirone did not modify the immobilization-induced elevations of plasma ACTH, prolactin or defecation. Ipsapirone was relatively ineffective at reducing the endocrine responses to forced swim. Ipsapirone reduced some, but not all of the hormonal responses to CER stress. CER-induced elevations of corticosterone and prolactin were not inhibited by ipsapirone. However, the ACTH response to CER was significantly (P less than 0.01) inhibited by all doses of ipsapirone and the highest dose of ipsapirone attenuated the renin response. In contrast with the hormonal responses, ipsapirone inhibited all of the behavioral responses to CER stress. Ipsapirone inhibited CER-induced freezing behavior and defecation, while dose-dependently reversing the suppressive effect of CER on exploring, grooming and rearing behaviors. In conclusion, there is a dissociation between the influence of ipsapirone on the endocrine and behavioral responses to CER stress. Ipsapirone also has differential effects on the neuroendocrine response to the three stressors studied. Ipsapirone was most effective in attenuating the hormonal responses to CER, followed by immobilization and swim stress. Of the hormones studied, the stimulation of renin secretion after exposure to the three stressors was most sensitive to ipsapirone, while corticosterone and prolactin were the least sensitive to ipsapirone.

A comparison of a two-wheeled walker and a three-wheeled walker in a geriatric population

OBJECTIVE

There are few data on the effect of walkers on gait and mobility or on comparisons of different walker types. We compared a commonly used 4-legged, 2-wheeled walker and a newer 3-legged, 3-wheeled walker in measures of gait, mobility, and patient satisfaction.

DESIGN

Cross-over controlled trial.

SETTING

In the Physical Therapy Department of a Veterans Affairs hospital.

PARTICIPANTS

Subjects were 15 male and female frail elderly veterans (mean age, 82 years), both inpatients and outpatients, consecutively enrolled from a sample of 35 patients referred to the Physical Therapy Department for mobility problems. Subjects met the following criteria: age 65 or over, ambulatory, no prior use of a wheeled walker, stable medical condition, and informed consent.

INTERVENTION

Subjects were evaluated without either walker and with each of the two walkers on a 15-foot walkway and a 60-foot obstacle course. Subjects were asked which walker they preferred.

OUTCOME MEASURE

Outcome measures were stride length on the walkway, time on an obstacle course, and walker preference.

RESULTS

Stride length was 1.4 inches (3.6 cm) greater with the 3-wheeled walker than with the 2-wheeled walker (P = 0.016 by Wilcoxon signed-rank test). Time on the obstacle course was 16.0 seconds less with the 3-wheeled walker than the 2-wheeled walker (P = 0.002). The 3-wheeled walker was subjectively preferred.

CONCLUSIONS

The 3-wheeled walker appears to have a greater positive impact on gait and mobility than the 2-wheeled walker.

Prior chronic exposure to cocaine inhibits the serotonergic stimulation of ACTH and secretion of corticosterone

The effect of long-term pretreatment with cocaine on serotonergic regulation of ACTH (adrenocorticotropic hormone; corticotropin) and secretion of corticosterone in rats was investigated. The following observations were made: (1) Pretreatment with cocaine had no significant effect on basal levels of ACTH and corticosterone in plasma. However, cocaine caused a reduction in the ability of the 5-HT (5-hydroxytryptamine, serotonin) releaser p-chloroamphetamine (PCA) to increase corticosterone in plasma, 42 hr after the last injection of cocaine. (2) Exposure to cocaine for 7 days was sufficient to produce a maximal inhibition of the PCA-induced increase in ACTH in plasma. (3) The inhibitory effect of cocaine on PCA-induced release of ACTH was more marked than on corticosterone. (4) Conversely, the dose-dependent stimulatory effect of two 5-HT1 agonists, RU 24969 (5-methoxy-3-(1,2,3,4-tetrahydro-4-pyridinyl)-1H-indole) and m-CPP (m-chlorophenylpiperazine), on ACTH and corticosterone was not reduced by 7 days of exposure to cocaine. Taken together, these findings indicate that pretreatment with cocaine reduced the function of serotonergic nerve-terminals but not postsynaptic receptors, that stimulate ACTH and secretion of corticosterone.

Pulsatile ACTH and cortisol in goats: effects of insulin-induced hypoglycemia and dexamethasone

Insulin-induced hypoglycemia is a metabolic stress that stimulates secretion of adrenocorticotropic hormone (ACTH) and cortisol in a number of animal species. Dexamethasone is a potent synthetic glucocorticoid that suppresses the secretion of ACTH and cortisol. Both ACTH and cortisol exhibit complex secretory patterns demonstrating ultradian and circadian rhythms. This work investigated the pattern of ACTH and cortisol response to hypoglycemia in goats and the effect of dexamethasone on this response. Five goats were pretreated with dexamethasone (0.1 mg/kg) and 5 with saline. Blood samples were taken every 2 min for 60 min before and 60 min after administration of insulin (2.5 IU/kg, i.v.). Immunoreactive ACTH and cortisol were measured in all samples and glucose in selected samples. Data sets were analyzed for significant pulses with the Cluster Analysis program. Complete data sets were compared as well as those for each 30-min interval. Plasma glucose was lower than preinsulin levels at 10 min, declined rapidly between 10 and 30 min, and remained low 30-60 min after insulin injection in both treatment groups. Controls showed a rapid rise in ACTH and cortisol beginning 30 +/- 10 min postinsulin. The increase in mean plasma hormone levels during hypoglycemia was predominantly due to an increase in amplitude of secretory pulses for ACTH and cortisol compared with the 30 min before insulin. Dexamethasone significantly lowered mean ACTH and cortisol levels and prevented alteration in plasma ACTH and cortisol secretion during hypoglycemia but did not totally ablate pulsatile activity of either hormone. The amplitude of ACTH and cortisol pulses was significantly decreased by dexamethasone treatment. The frequency of cortisol but not ACTH pulses was also significantly decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

High resolution spectral analysis of plasma adrenocorticotropin reveals a multifactorial frequency structure

Time series of plasma ACTH concentrations were analyzed with a high resolution spectral analysis program based on digital Fourier transforms. Both coherent signal and stochastic aspects of the time series were analyzed. Samples were collected at 2- and 15-min intervals in control rats and rats immunoneutralized against CRH. The individual and composite spectral distributions revealed significant structure at both the higher and lower ranges of frequencies studied, with multiple periodicities between 4-220 min in both groups. CRH immunoneutralization consistently reduced the amplitude by 82% and compressed the frequency distribution for waveforms with periods longer than 15 min by 23%. A systematic break in the slopes of the background continua occurred between 10 and 15 min in the 2-min time series. This break was unaffected by CRH immunoneutralization. Digital Fourier transform analysis of our ACTH time series suggests a system with a more complex high frequency structure than has previously been appreciated. Our analyses suggest a biological system with the following characteristics: 1) both a fast and a slow response to a fairly constant unspecified fast forcing; 2) the slow response is initiated by the fast response and represents an imperfect integration due to feedback processes; 3) CRH alters the ability of the fast forcing to elicit a slow response without altering the fast response or ACTH clearance; and 4) this alteration consists of both amplitude and frequency modulation in the signal output. This view of ACTH secretion suggests an adaptive and energy-efficient system.

Effects of immunoneutralization of corticotropin-releasing hormone on ultradian rhythms of plasma adrenocorticotropin

ACTH, like other anterior pituitary peptide hormones, is secreted episodically and demonstrates both circadian and ultradian rhythms. CRH is the major regulator of ACTH release from the pituitary corticotroph. To determine the dependence of ACTH ultradian rhythms on CRH, passive immunoneutralization was used to block the activity of endogenous CRH in rats with indwelling venous catheters. Blood was sampled at 2- and 15-min intervals while blood volume was replaced. Plasma ACTH was measured by RIA. Time-series analysis of plasma ACTH concentrations was performed with PULSAR and Cluster Analysis. The 2 min data demonstrated secretory bursts approximately every 20 min. CRH immunoneutralization had no effect on the frequency of these pulses, but significantly reduced their amplitude. This was the case for raw data as well as data in which lower frequency variation had been filtered out. The 15 min data demonstrated pulsatile secretion, with a secretory episode approximately every 100 min. This lower frequency rhythm was also observed when high frequency components were filtered out of the 2 min data series. Analysis of the 15 min and the filtered 2 min time series showed this rhythm to be almost totally ablated by CRH immunoneutralization. These results suggest that CRH is responsible for amplitude modulation of an underlying CRH-independent rhythm and that through intermittent amplitude modulation of this rhythm a lower frequency rhythm is generated. Comparison between treatment groups of pulses identified by PULSAR or Cluster Analysis yielded similar results, but the programs were discordant with each other. This is the first in vivo evidence of pulsatile ACTH secretion independent of CRH, the first report demonstrating that different ultradian rhythms of ACTH may be regulated by different mechanisms, and the first comparison of PULSAR and Cluster Analysis on plasma ACTH time series.

The effects of stress on plasma ACTH and corticosterone in young and aging pregnant rats and their fetuses

Compared to younger rats, old rats exhibit prolonged elevations of plasma ACTH and corticosterone (CORT) in response to stress. In addition, CORT crosses the placenta. To investigate whether fetuses of older rats may be exposed to higher concentrations of CORT during development than fetuses of young rats, we compared the effects of stress on hypothalamic-pituitary-adrenal (HPA) axis function in young and aging pregnant rats and their 19-day-old fetuses. The plasma of the mothers and fetuses was assayed for ACTH and CORT by radioimmunoassay. Both young and aging pregnant rats showed a significant increase in plasma ACTH and CORT immediately after exposure to stress. However, aging rats had more prolonged elevations of ACTH and CORT than young rats. This suggests that, like old male rats, aging pregnant rats have an alteration in feedback inhibition of the HPA axis. Prolonged elevation of CORT was also seen in fetuses of aging mothers. These results have important implications concerning the effects of stress during pregnancy at different maternal ages, and for the potential deleterious consequences of prolonged prenatal elevation in stress hormones on the offspring of aging females.

Neuroendocrine evidence for denervation supersensitivity of serotonin receptors: effects of the 5-HT agonist RU 24969 on corticotropin, corticosterone, prolactin and renin secretion

Serotonergic stimulation can increase the secretion of several hormones through the involvement of different serotonin (5-HT) receptor subtypes. RU 24969, a 5-HT agonist with highest affinity at 5-HT1A and 5-HT1B receptors, increased plasma renin activity (PRA) and plasma renin concentration (PRC) as well as plasma corticosterone and prolactin concentrations in a dose-dependent manner. Inasmuch as 5-HT2 receptors mediate the serotonergic stimulation of renin secretion, we examined the ability of two selective 5-HT2 antagonists, ritanserin and LY53857, to inhibit the neuroendocrine effects of RU 24969. To determine whether the 5-HT receptors which are involved in the stimulation of these hormones are pre- or postsynaptic, RU 24969 was also injected to rats whose brain serotonergic neurons were chemically destroyed by i.c.v. injection of 5,7-dihydroxytryptamine. Both ritanserin and LY53857 blocked the effect of RU 24969 on PRA and PRC, but did not inhibit the RU 24969-induced elevation in plasma corticosterone concentrations. Ritanserin did not inhibit the effect of RU 24969 on prolactin levels, but LY53857 produced a partial inhibition of the RU 24969-induced elevation of prolactin concentrations. In rats with chemical lesions of serotonergic neurons the dose-response curves of RU 24969 for PRA and PRC as well as corticotropin, corticosterone and prolactin shifted to the left, suggesting functional up-regulation of postsynaptic 5-HT receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma adrenocorticotropic hormone in the rat demonstrates three different rhythms within 24 h

Secretion of adrenocorticotropic hormone (ACTH) by the anterior pituitary is rhythmic and episodic, as reflected by fluctuations in plasma concentrations of ACTH. The present work was designed to further characterize the patterns of ACTH secretion that occur simultaneously within a 24-hour period in the rat. To accomplish this, blood collection protocols with sampling intervals of 2 min, 15 min, and 4 h were used in awake, chronically cannulated rats. Plasma samples were assayed for immunoreactive ACTH, and resultant data were analyzed for significant pulsatile secretory episodes. We observed three different patterns of ACTH secretion within a 24-hour period. Circadian variation occurred with peak plasma ACTH levels in the early evening. In addition, plasma ACTH exhibited two types of episodic variation: (1) episodic bursts with variable amplitudes that occurred approximately three times per hour which have been referred to as 'micropulses', and (2) prolonged elevations of plasma ACTH that occurred approximately 14 times in 24 h which have been referred to as 'larger ultradian' secretory episodes. These latter episodes appeared to consist of groups of relatively high amplitude micropulses. The physiological significance, functional interactions, and location of the controlling oscillator(s) of these different rhythms remain to be determined.

Isolation of a complementary DNA encoding a chitinase with structural homology to a bifunctional lysozyme/chitinase

An extracellular, acidic chitinase was purified to homogeneity from tobacco necrosis virus-infected leaves of Cucumis sativis. The amino acid sequences of the intact protein and of peptides isolated following endoproteinase Lys-C digestion, cyanogen bromide cleavage, and trypsin digestion were determined. Oligonucleotide probes derived from this sequence were used to isolate a cDNA clone encoding this protein. No significant homology was found between this chitinase and either the basic chitinase isolated from bean or tobacco or the chitinase isolated from Serratia marcescens; however, strong homology was found between the cucumber chitinase and a lysozyme/chitinase from Parthenocissus quinquifolia. The induction of the protein by tobacco necrosis virus infection or salicylate was found to be at the level of RNA accumulation. Genomic Southern analysis indicates that a single gene in the cucumber genome encodes this protein.

Immunoneutralization of corticotropin-releasing hormone prevents the diurnal surge of ACTH

To determine whether CRH is required for the evening rise in plasma ACTH, rats were injected at 0800 hr with CRH antiserum (anti-CRH) or normal rabbit serum (NRS). Blood samples were taken through venous catheters at 0800 hr before treatment and at 1300, 1700, and 2100 hr. Plasma was assayed for immunoreactive ACTH and corticosterone. There was no significant difference in pretreatment values between the two groups. Immunoneutralization of CRH abolished the rise in plasma ACTH seen at 1700 hr in the NRS group but had little effect on earlier levels. The diurnal elevation in plasma corticosterone continued after anti-CRH treatment, but peak levels occurred earlier. Plasma ACTH and corticosterone were significantly correlated at the time of the diurnal surge, but not at 0800 hr or 1300 hr in the NRS controls or at any time point in the anti-CRH group. These results suggest that CRH is required for the diurnal surge of plasma ACTH. They also confirm previous observations by others that the adrenal cortex does not require active CRH or a diurnal surge of ACTH in order to exhibit a significant diurnal increase in secretion of corticosterone, and that factors other than CRH may be relatively more active than CRH in regulation of ACTH secretion during the time of circadian inactivity.

Pulsatile ACTH secretion: variation with time of day and relationship to cortisol

It has long been known that ACTH is secreted in an episodic fashion demonstrating circadian and ultradian rhythms. High intensity venous sampling has recently revealed that in addition to these larger ultradian fluctuations in hormone levels, plasma ACTH in rats demonstrates high frequency, low amplitude oscillations which have been called "micropulses." These micropulses were not detected in previous studies due to sampling intervals of greater than 5 minutes. To investigate the presence of these ACTH micropulses in a primate species, blood samples were drawn from six chair-restrained rhesus monkeys at one-minute intervals for up to 70 minutes and plasma was assayed for immunoreactive ACTH. To assess the variation in ACTH micropulse parameters with time of day and the relationship to cortisol secretion, four of the monkeys were sampled for three 70-minute periods beginning at 0530, 1100, and 1730 hours, and plasma was assayed for immunoreactive ACTH and cortisol. Analysis of the data revealed that ACTH and cortisol are secreted in micropulses in rhesus monkeys with marked individual variation in the pattern of secretion and a concurrence of approximately 75% of ACTH and cortisol micropulses. Difference in pulse amplitude but not frequency appeared to contribute to the circadian variation in mean ACTH levels and a sampling interval of two minutes appeared to be adequate for accurately identifying micropulses of ACTH.

Changes in mean plasma ACTH reflect changes in amplitude and frequency of secretory pulses

ACTH is secreted in an episodic manner from the anterior pituitary. Unanesthetized rats with indwelling jugular and femoral venous cannulae were continuously bled and simultaneously infused with isotonic fluid by peristaltic pump. Two-minute blood samples were collected for up to five hours in 8 male rats. ACTH was measured by radioimmunoassay. The resulting time series were analyzed for significant secretory pulses with the PULSAR program. Elevations or declines in mean plasma ACTH levels were associated with significant changes in amplitude and frequency of secretory pulses.

Immunocytochemical distribution of luteinizing hormone in rat central nervous system

This paper presents the first detailed localization of luteinizing hormone (LH)-containing cells and fibers in the rat central nervous system. These immunoreactive elements were identified by four LH antisera, two directed against the intact LH molecule and two against LHb. Cell bodies, immunoreactive for LH were found throughout the rostral-caudal extent of the hypothalamic arcuate and ventromedial nuclei, the periarcuate area ventral to the ventromedial nucleus, and the retrochiasmatic area. Immunopositive fibers were traced to numerous structures within the brain including discrete regions of the hypothalamus, septal area, nucleus of the diagonal band, bed nucleus of stria terminalis, amygdala, thalamus, periaqueductal gray, raphe nuclei, brainstem reticular nuclei, locus ceruleus, parabrachial nucleus, dorsal motor nucleus of vagus, and the nucleus of the solitary tract, with a few fibers extending into spinal cord central gray. This pattern of fiber distribution corresponds closely with those described for fibers containing several other anterior pituitary hormones. The extensive projection for LH may provide neuroanatomical substrate mediating reproductive events as it does in the pituitary, or it may serve some modulatory function in brain which is independent of its role in reproduction.