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Biomedical subjects

A J Silver

Publications and source records attributed to A J Silver.

At least 19 recordsLinked to original sources
PubMed1992

Effects of peripheral hormones on memory and ingestive behaviors.

This article explores the mechanisms by which peripheral gastrointestinal hormones produce central nervous system effects on memory and feeding. Cholecystokinin produces its satiety effects and memory-enhancing effects by stimulating ascending vagal fibers. Hyperglycemia has been demonstrated to be a cause of memory dysfunction in persons with diabetes mellitus. A number of other hormones, such as amylin and bombesin, modulate both memory processing and feeding. The causes of the anorexia of aging are briefly reviewed.

Aging↗
PubMed1992

Role of the opioid system in the hypodipsia associated with aging.

OBJECTIVE: To compare the effects of the opioid antagonist, naloxone, on fluid ingestion in young and older males, in order to estimate the role of the opioid system in hypodipsia of older men. DESIGN: Single-blinded, randomized, cross-over, placebo-controlled study. SETTING: Outpatient Department of Veterans Affairs. STUDY PARTICIPANTS: Sixteen young subjects (aged 23 to 39) and eight older subjects (aged 69 to 75). All subjects were healthy, community-dwelling, non-smoking men, on no medications. INTERVENTION: Subjects were randomized to receive either placebo or naloxone on day one. Whichever substance the subject did not receive was given on day two with days one and two separated by at least a 2-week washout period. MAIN OUTCOME MEASURES: Fluid intake after overnight food and fluid deprivation, with placebo or naloxone injected in the morning. RESULTS: After overnight fluid deprivation, older individuals consumed 29% less fluid in 2 hours compared with younger individuals (ns). After overnight fluid deprivation and injection with naloxone 100 micrograms/kg, fluid intake was diminished by 42% (P less than 0.05) in young subjects compared with placebo, but only by 7% (ns) in older subjects. Subjective ratings did not differ significantly between young and old subjects. CONCLUSIONS: These preliminary data suggest that the opioid system plays a role in the drinking response in young subjects while failing to alter fluid intake in older subjects. Hypodipsia in older individuals may be due to a deficit in the opioid drinking drive.

Adult↗
PubMed1991

Effect of aging on fluid ingestion in mice.

The amount of fluid consumed by C57BL/6Nnia male mice 3, 12, and 25 months of age under various paradigms was studied. The old mice consumed less water during the dark cycle but not during the light cycle (12 h lights off; 12 h lights on). When thirst was induced by providing dry food pellets or after overnight fluid deprivation, old mice consumed significantly less water than younger mice over a one-hour period. When thirst was induced by administration of hypertonic saline, there were no age-related effects. Naloxone 7.5 mg/kg IP significantly suppressed drinking in 3- and 12-month-old mice, while 25-month-old mice did not show suppression. Dehydration-induced thirst is impaired in old mice, as it is in older humans. This may be related to the alteration in opioid mechanisms modulating thirst.

Aging↗
PubMed1991

The effect of recombinant human growth hormone on malnourished older individuals.

Malnutrition in the elderly is often unrecognized and untreated. Reduced secretion of growth hormone (GH) has been suggested as a cause of decreased muscle and bone mass with aging. This pilot study characterized the nutritional response of elderly malnourished subjects to recombinant human GH (rhGH). Subjects were included if they were over 60 years of age, if weight was more than 20% below average body weight (ABW), and if serum albumin concentration was less than 3.8 g/dL. Subjects were divided into two groups: one received 100 micrograms/kg rhGH (Protropin, Genentech) intramuscularly (IM) daily for 21 days; the other received a daily control injection of normal saline (Controls -C) (0.1 mL/kg IM) for the same period of time. During the 3-week period, mid-arm muscle circumference (MAMC) increased an average of 0.6 cm in GH patients but fell in C subjects. There was a non-significant trend to a decreased caloric intake in the control group. Weight increased an average of 4.95 lbs (2.2 kg) in the GH treated group, and decreased an average of 4.9 lbs (2.2 kg) in C subjects (P less than 0.05). Urinary nitrogen retention occurred only in the growth hormone treated subjects (P less than 0.05). Somatomedin C (IGF-1) rose significantly in those treated with GH (P less than 0.05), while there was no change in the control group. There was a significant association between weight change and IGF 1 concentration (r = 0.837, P less than 0.05). Neither clinical edema nor hyperglycemia was noted. These findings suggest that GH may be an effective way of maintaining and enhancing weight in malnourished older individuals.

Aged↗
PubMed1990

Secondary hypogonadism in older men: its relation to impotence.

The relation of the reproductive endocrine system to impotence in older men was examined by measuring the concentrations of testosterone (T), bioavailable testosterone (BT), LH, and PRL and body mass index (BMI) in 57 young controls (YC), 50 healthy potent older controls attending a health fair (HF), and 267 impotent patients (SD). The SD and HF had markedly reduced mean T and BT values compared to YC. When adjusted for age and BMI there was no difference in BT between potent and impotent older men. The percent BT was much higher in YC than in the older groups. While the percent BT rose significantly with increased T in YC, it was inversely related to T in the older subjects, suggesting that increased sex hormone-binding globulin binding was a primary event leading to a low BT. Forty-eight percent of HF and 39% of SD were hypogonadal, as defined by a mean BT of 2.5 SD or more below the mean of YC (less than or equal to 2.3 nmol/L). Ninety percent of these had LH values in the normal range, suggesting hypothalamic-pituitary dysfunction. Thirty-four SD and six each of YC and older control volunteers (OC) underwent GnRH testing. Older subjects showed impaired responsiveness to GnRH compared to YC. A low basal LH level correlated very highly with hyporesponsiveness to GnRH. Thus, secondary hypogonadism and impotence are two common, independently distributed conditions of older men.

Aged↗
PubMed1990

Aging and risks for dehydration.

The elderly are at increased risk for dehydration and associated fluid and electrolyte imbalances. Changes in functional and mental status, medication effects, and changes in the aging renal system all may be factors. Furthermore, hypodipsia, or insensibility to thirst, may be a physiologic process of aging. These and other risk factors are presented, along with a guide to the management of dehydration in the elderly.

Aging↗
PubMed1989

Evidence for a physiological role for CCK in the regulation of food intake in mice.

The effects of L-364,718, a cholecystokinin receptor antagonist, on cholecystokinin octapeptide-induced inhibition of food, and its effect on food intake when given alone, were studied in mice using several different feeding paradigms. In all studies, L-364,718 (100 micrograms/kg, 1.0 mg/kg) reversed the ability of cholecystokinin octapeptide to decrease food intake. L-364,718 enhanced food consumption compared with controls in nonfasted mice (100 microgram/kg) and in prefed mice (50, 100, 250 micrograms/kg). The number of reinforcements, using a lever press, was also enhanced by L-364,718 (100 micrograms/kg) compared with control. In other paradigms, L-364,718 failed to enhance food intake. These results are compatible with the suggestion that cholecystokinin may play a physiological role in the regulation of food intake.

Animals↗
PubMed1988

Nutrition in the elderly.

Nutritional modulation is one approach to successful aging. In animals, dietary restriction increases life span. Alterations in the macronutrient and micronutrient constituent of the diet can modulate gene expression. Anorexia is common in elderly persons. The results of studies in animals suggest that aging is associated with a decrease in the opioid feeding drive and an increase in the satiating effect of cholecystokinin. Unrecognized depression is a common, treatable cause of anorexia and weight loss in elderly persons. Protein synthesis decreases in elderly persons; nevertheless, nitrogen balance can be maintained in patients with fairly low intakes of protein. Carbohydrate intolerance is common and may be modulated by nutritional intervention and physical activity. The role of cholesterol in the development of heart disease in very old persons is controversial. Homebound and institutionalized elderly persons often do not expose their skin to sunlight; because the skin of older persons has a decreased ability to form vitamin D, the vitamin D status in these persons is precarious and they are at risk for osteopenia. Vitamins are often abused by elderly persons. Drug administration alters the vitamin requirements of persons. Borderline zinc state has been associated with deteriorating immune function, especially in persons who have diabetes mellitus or who abuse alcohol. Zinc administration appears to protect against the deteriorating vision associated with age-related macular degeneration. Selenium deficiency seems to be associated with an increased prevalence of cancer.

Aged↗
PubMed1988

Nutritional status in an academic nursing home.

Inadequate nutrition is a major problem facing the elderly today. Despite seemingly appropriate meal standards and dietary supervision, patients in long-term care facilities remain at risk for developing malnutrition. Various nutritional parameters including weight loss, percentage average body weight, serum albumin levels, anthropometrics, and skin testing were examined in 130 patients in an academic nursing home, two thirds of whom were over the age of 65 years. Functional status including type of feeding and associated diseases was also determined. The data show that nutritional risk factors are similar among different age-groups in nursing home patients. A significant proportion of our patients lost weight while maintaining their serum albumin levels. Despite this, there appears to be less evidence of malnutrition among patients in the academic nursing home compared with other nursing home settings studied.

Aged↗
PubMed1988

MR imaging of pseudotumor cerebri.

Eleven obese young women with idiopathic pseudotumor cerebri were studied with high-field-strength (1.5 T) MR imaging to demonstrate increased water content in the brains of such patients. Heavily T2-weighted studies were obtained for 10 patients, and balanced (long TRs, short TEs, spin density, proton density) pulse sequences were obtained for four patients. We examined the studies of morphologically normal periventricular white matter and developed a white matter water index to determine if a slight increase in signal was present that could be ascribed to low levels of edema. Comparison was made to an age-matched control group. We also examined five patients with sodium MR imaging. Two of the 11 patients had focal areas of increased signal in their periventricular white matter. Presumably, these are areas of increased edema above the background that could not be detected on the CT scan. The white matter water index for the normal controls was an average of 0.479 (+/- 0.015), while that of the pseudotumor cerebri group was 0.520 (+/- 0.016). This indicates an increase in the white matter water signal. We believe this represents a diffuse low level of edema. These findings are consistent with previous estimates of the increase in brain water in patients with idiopathic pseudotumor cerebri. The patients with focally abnormal proton studies demonstrated similar abnormalities on their sodium studies.

Adult↗