Biomedical subjects

M Carnes

Publications and source records attributed to M Carnes.

60 records · Page 4Linked to original sources

PubMedDate not supplied

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.

Activity Cycles↗

PubMedDate not supplied

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.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

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.

Academic Medical Centers↗

PubMedDate not supplied

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.

Journal Article↗

PubMedDate not supplied

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.

Journal Article↗

PubMedDate not supplied

The development of polymyositis in a patient with toxoplasmosis: clinical and pathologic findings and review of literature.

A 58 year old female was evaluated for fever, rash, myalgias, muscle weakness and cervical lymphadenopathy. She was found to have myositis on muscle biopsy, toxoplasmic lymphadenitis on lymph node biopsy, and markedly elevated IgM and IgG antibody titers to Toxoplasma gondii. The patient was treated with prednisone and a 2 month course of sulfadiazine and pyrimethamine. The patient improved over the next six months and has been followed for approximately a five year period. During this time, antibody levels to the toxoplasma antigen have significantly decreased but the patient has developed a chronic myositis indistinguishable from polymyositis.

Biopsy↗