ISSN:1663-2818    

DOI:10.1159/000184227

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1663-2818    

DOI:10.1159/000184228

出版商:S. Karger AG    

年代:1995

数据来源: Karger

ISSN:1663-2818    

DOI:10.1159/000184229

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The various hypothalamic nuclei show very different patterns of change in ageing. These patterns are a basis for changes in biological rhythms, hormones, autonomous functions or behavior. The suprachiasmatic nucleus (SCN) coordinates circadian and circannual rhythms. A marked seasonal and circadian variation in the vasopressin (AVP) cell number of the SCN was observed in relation to the variation in photoperiod. During normal ageing, the circadian variation and number of AVP-expressing neurons in the SCN decreases. The sexually dimorphic nucleus (SDN), intermediate nucleus or INAH-1 is localized between the supraoptic and paraventricular nucleus (PVN). In adult men the SDN is twice as large as in adult women. In girls, the SDN shows a first period of decreasing cell numbers during prepubertal development, leading to sexual dimorphism. During ageing a decrease in cell number is found in both sexes.The cells of the supraoptic nucleus and PVN produce AVP or oxytocin and coexpress tyrosine hydroxylase. These nuclei are examples of neuron populations that seem to stay perfectly intact in ageing. Parvicellular corticotropin-releasing-hormone (CRH)-containing neurons are found throughout the PVN. CRH neurons in the PVN are activated in the course of ageing, as indicated by their increase in number and AVP coexpression. Part of the infundibular (or arcuate) nucleus, the subventricular nucleus, contains hypertrophic neurons in postmenopausal women. The hypertrophied neurons contain neurokinin-B (NKB), substance P and estrogen receptors and probably act on LHRH neurons as interneurons. The NKB neurons may also be involved in the initiation of menopausal flushes. The nucleus tuberalis lateralis might be involved in feeding behavior and metabolism. It does not show any decrease in neuronal numbers in ageing. It is remarkable that the majority of the hypothalamic nuclei do not show signs of degeneration during ageing, but rather activation with the exception of the SDN and SCN.

ISSN:1663-2818    

DOI:10.1159/000184230

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Biological rhythms in blood variables are now fairly well documented in young healthy adults whereas reports in elderly subjects are few for obvious reasons including the difficulty of setting up a group of elderly subjects comparable in age and social background and moreover free of major liver, heart, kidney, bone or any other degenerative disease and consequently not requiring medication. We have observed that the parameters characteristic of the biological rhythm may be modified with ageing. However, the modifications are different from one function or variable to the next. Differences in acrophases, mesors and amplitudes could be demonstrated. For instance the acrophase may be phase-advanced in the elderly for plasma cortisol, DHEA-S, 18-OHDOC, the amplitude may be modified for testosterone, 18-OHDOC, proteins, melatonin, gonadotrophins. The administration as a function of time of drugs or agents used as a diagnostic tool made it possible to ascertain the importance of the time structure in this field. Both validity and interpretation of such administration depend upon the timing of the agent administration in the 24-hour scale. Therefore, the temporal organization of the subjects undergoing such treatments should be taken into account. In the near future this kind of investigation on various biological variables may lead to an improvement of the desired drug effects in elderly patients.

ISSN:1663-2818    

DOI:10.1159/000184231

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Circadian rhythmicity persists in healthy elderly subjects but a number of 24-hour rhythms are dampened and/or advanced in old age. The tendency for earlier sleep onset, earlier morning awakening and a more fragmented and more shallow sleep period is representative of these alterations. Other overt rhythms which have been shown to be of lower amplitude and/or phase-advanced are those of body temperature and of the peripheral levels of hormones such as cortisol, melatonin, TSH, testosterone, prolactin and GH. Mean hormonal levels are generally decreased, but overall cortisol secretion is increased with ageing. These modifications are likely to be partially due to alterations of the circadian central nervous system processes controlling circadian rhythmicity and sleep.

ISSN:1663-2818    

DOI:10.1159/000184232

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

In distinction to the course of reproductive ageing in women, men do not experience a rapid decline of Leydig cell function or irreversible arrest of reproductive capacity in old age. Hence, strictu sensu, the andropause does not exist. Nevertheless, both spermatogenesis and fertility as well as Leydig cell function do decline with age, as shown by a decrease of ± 35% of total and of 50% of free testosterone levels between the age of 20 and 80 years. The origin of this decline of Leydig cell function resides on the one hand in the testes, and is essentially characterized by a decreased number of Leydig (and Sertoli) cells and on the other hand in the hypothalamo-pituitary complex characterized by a decreased luteinzing hormone (LH) pulse amplitude, LH pulse frequency being maintained. As the responsiveness of the gonadotrophs to gonadotropin-releasing hormone (GnRH) remains unimpaired, one may assume that the amount of GnRH released at each pulse is also reduced, possibly as the consequence of a reduction of the cellular mass of GnRH neurones. Plasma levels of testosterone below the lower normal limit occur, however, only in a minority of elderly men from 7% in the age group 40-60, to 20% in the age group 60-80 and 35% in the age group over 80 years old. Factors influencing testosterone levels in elderly men are multiple: hereditary, environmental (obesity, stress), psychosocial (depression, smoking, drugs) or socioeconomical (diet, hygiene). Whether these elderly men should be substituted with androgens remains controversial. Beneficial effects, such as an increased feeling of well-being and fitness, increased muscle strength and endurance, decreased bone catabolism and increase of hematocrit, should be weighed against the risks of stimulation of growth of an occult, subclinical prostatic carcinoma (occurring with a high frequency in elderly males). Therefore, large scale androgen supplementation should await the results of well-controlled prospective studies

ISSN:1663-2818    

DOI:10.1159/000184233

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

A good body of experimental and clinical results has supported the existence of numerous reciprocal interactions among the nervous, endocrine and immune systems. Increasing evidence has been accumulated in the last years on the interaction between pituitary-thyroid hormones and the immune system on the basis of either the existence of receptors for thyreotropic and thyroid hormones on lymphocytes or the frequent immune alteration in physiological and pathological fluctuations of thyroid hormones. The data were obtained either in animals with experimentally induced hyper- or hypothyroidism or in humans with various hyperthyroid or hypothyroid situations. Conversely, immune-derived products such as lymphokines and monokines have been shown able to influence the pituitary-thyroid axis modulating either the thyroid hormone levels or the hormone/cytokine production by thyrocytes. The present paper aims at summarizing the data available on the existence of thyroid-immune interactions, and at analyzing the possible integration between pituitary-thyroid hormones and immune factors in favoring the development and maintenance of both thymic and peripheral immune efficiency. The relevance of pituitary-thyroid-immune interactions is discussed for its implication in the ageing process.

ISSN:1663-2818    

DOI:10.1159/000184234

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

In old mammals, including humans, the spontaneous growth hormone (GH) secretory pattern is markedly reduced resulting in lower amounts of GH released over 24 h, and the GH response to administration of GH-releasing hormone (GHRH) is reduced. In agreement with these in vivo findings, an impaired responsiveness to GHRH is evident in the pituitary of old male and female rats in vitro, and this is linked with a diminished stimulation of adenylate cyclase by GHRH. The poor GH responsiveness to GHRH in old mammals, which in the rat is coupled to a defective number of GHRH receptors in the somatotrophs, is likely due to a primary deficiency of GHRH availability, as implied by the diminished GHRH immunoreactivity and gene expression in and GHRH release from the hypothalamus of old rats. Attempts have been made to stimulate the sluggish somatotrophic function in elderly humans and dogs using GHRH; in either species positive results were obtained though, overall, it would seem that the GHRH hypofunction does not entirely account for the GH hyposecretory state during ageing. Concerning somatostatin, although the expression of this peptide decreases with age in the rat hypothalamus, secretion and activity of this hormone is increased, resulting in an altered relationship between GHRH and somatostatin gene expression and secretion. It is likely that defects, especially in catecholaminergic and cholinergic neurons, are instrumental in altering specific peptidergic neurons. Reportedly, catecholamines induce GH release by stimulating GHRH neurons and inhibiting somatostatin-releasing neurons; acetylcholine stimulates GH release via muscarinic receptors, in this way inhibiting the action of somatostatin neurons. In old beagle dogs short-term administration of the α2-adrenoceptor clonidine strikingly potentiated GHRH-stimulated GH release, thus implying that clonidine was acting via inhibition of hypothalamic release of somatostatin, and the combination GHRH plus clonidine was highly effective in restoring the pulsatile release of GH and plasma IGF-1 levels. The possibility is envisaged that GHRH or other GH-releasing peptides, e.g. GH-releasing hexapeptide (GHRP-6) and hexarelin, given in conjunction with compounds allegedly capable of reducing somatostatinergic function (clonidine, arginine) may be potent pharmacologic tools to reinstate in old humans GH secretion in a physiologic, pulsatile manner

ISSN:1663-2818    

DOI:10.1159/000184235

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Interactions between nutrition and the ageing process are a fascinating field of research. The assessment of the nutritional status is an important part of medical examination. Generally it is assumed that energy intake and energy expenditure decrease with age. In fact they vary widely and are very different in healthy, in sick or in institutionalized elderly. Nutritional requirements depend on many social and physiological factors in the free-living elderly population. Surveys indicate that dietary requirements are qualitatively grossly comparable to those in middle-aged adults. However the elderly are particularly at risk of marginal deficiencies of vitamins and trace elements. Today the early recognition of malnutrition is an important challenge. Its prevention may influence the evolution of nonspecific intercurrent disease and restore immunocompetence. Another challenge is to promote health by adequate recommendations in order to prevent deficiency diseases and to increase longevity. Some studies suggest that nutrition-based preventive medicine remains useful in the elderly. Caloric restriction, weight loss in case of obesity, decrease in blood lipids, increase in calcium intake which depend mainly of prior nutritional habits may have an effect in the elderly. However, prevention of protein caloric malnutrition is more relevant in the elderly.

ISSN:1663-2818    

DOI:10.1159/000184236

出版商:S. Karger AG    

年代:1995

数据来源: Karger