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J W Rowe

Publications and source records attributed to J W Rowe.

At least 73 records · Page 4Linked to original sources
PubMed1987

Somatostatin does not alter insulin-mediated glucose disposal.

We examined the effect of somatostatin (SRIH) infusion on insulin-mediated glucose disposal (Rd) in normal young subjects (n = 8) to determine the influence of SRIH on insulin action. Paired 3-h euglycemic insulin clamp studies were performed in random order employing insulin alone (25 mU/m2 X min) or insulin with SRIH (250 micrograms/h) and replacement of basal glucagon (0.4 ng/kg X min). Basal plasma glucose, insulin, glucagon (IRG), and GH concentrations, hepatic glucose production, and Rd were similar on each occasion. Steady state (10-180 min) plasma insulin insulin alone, 283 +/- 10 (+/- SEM); insulin, IRG, and SRIH, 284 +/- 10 pmol/L) and glucagon levels (insulin alone, 84 +/- 7; insulin, IRG, and SRIH, 82 +/- 7 ng/L) were similar. Hepatic glucose production (insulin alone, 0.66 +/- 0.12; insulin, IRG, and SRIH, 0.78 +/- 0.48 mg/kg X min) and Rd (insulin alone, 8.16 +/- 0.62; insulin, IRG, and SRIH, 8.17 +/- 0.61 mg/kg X min) were not different at steady state. We conclude that SRIH infusion with glucagon replacement does not augment insulin-mediated glucose disposal in normal young subjects at physiological insulin levels.

Adult↗
PubMed1987

The emergence of geriatric assessment units. The "new technology of geriatrics".

Previous studies have suggested that geriatric assessment units may provide important benefits to the care of elderly persons. In early 1985 we surveyed personnel at 104 (91%) of the existing 114 geriatric assessment units associated with medical schools and Veterans Administration medical centers for information on the units' development and operation. Although almost 80% of the units were hospital based, most (61%) provided care for outpatients. Nearly half (47%) began operation in 1983 or later; of those in existence before 1983, two thirds have increased their capacity since then. The types of personnel and their training differed substantially among units. Fifty percent of the physicians had had no formal training in geriatrics. Of the 104 units, 99 (95%) did routine assessment. The estimated time spent per new patient in outpatient units was 2.7 +/- 2.1 (SD) hours. These data suggest that geriatric assessment units are proliferating rapidly, have differing structures, and consume substantial resources. Further efforts are needed to define their optimal structure, targets, and function.

Geriatrics↗
PubMed1987

Interface of geriatric medicine and geriatric psychiatry.

Proper care of rapidly growing numbers of elderly individuals, particularly the oldest-old, whose numbers are increasing more than any other subgroup, requires an integration of geriatric psychiatry and geriatric medicine on the clinical level. This dictates that educational programs at the medical school and residency level include both medical and psychiatric aspects of aging and that fellowship programs which are based in one discipline provide a meaningful exposure to the other. Nonetheless, it is highly unlikely that a single specialty of geriatrics will be developed which includes both psychiatry and medicine, and much more likely that the individual disciplines will maintain their identity and separate training programs. Specific clinical facilities being developed, such as geriatric assessment units and geriatric hospitals, will increasingly provide a creative environment for interdisciplinary interactions of psychiatrists and internists committed to the proper care of the elderly. It is through the experience of these emerging clinical units and joint clinical research programs that the further integration of the two subspecialties is likely to be forged.

Aged↗
PubMed1986

Cardiovascular and norepinephrine responses after meal consumption in elderly (older than 75 years) persons with postprandial hypotension and syncope.

Aging is associated with alterations in cardiovascular homeostasis that impair adaptation to common hypotensive stresses. Postprandial blood pressure (BP) reduction has been described in elderly subjects, but its clinical significance and pathophysiologic mechanisms are unknown. We have identified 8 elderly patients with meal-related syncope and large postprandial BP declines. To evaluate the role of sympathetic nervous system activity and insulin in the development of postprandial BP reduction, mean arterial BP, heart rate, plasma catecholamine and insulin responses to a high carbohydrate meal in these 8 syncope patients were compared with those of 7 young and 12 old nonsyncopal controls. By 60 minutes after the meal, mean arterial BP declined an average of 26 mm Hg (p = 0.001) in old syncope patients, in contrast to a decline of 9 mm Hg (p = 0.1) in elderly controls and no change in young controls. Young and old controls had significant, sustained increases in heart rate or plasma norepinephrine levels, or both, throughout the 90-minute postprandial period. However, elderly syncope patients had no significant change in heart rate and only an initial increase but subsequent sustained decrease in plasma norepinephrine levels that paralleled the marked mean arterial BP reduction. Insulin and glucose responses were not significantly correlated with mean arterial BP reduction. These findings demonstrate that compared with old and young controls, elderly patients with meal-related syncope have marked sustained declines in postprandial mean arterial BP associated with a failure to maintain compensatory norepinephrine levels and cardioacceleratory responses.

Aged↗
PubMed1986

Syncope in institutionalized elderly: the impact of multiple pathological conditions and situational stress.

We conducted a prospective study to identify clinical factors which predispose institutionalized elderly to syncope. Over 3 years, 97 patients (mean age = 87 +/- 6 y) developed syncope. On clinical evaluation, diagnoses fell into two categories: specific diseases including myocardial infarction (6%) and aortic stenosis (5%); and situational stresses including drug-induced hypotension (11%), postprandial syncope (8%), defecation syncope (7%) and postural hypotension (6%). Clinical variables derived from the history, physical examination, and laboratory evaluation of these patients were compared to those of 118 non-syncopal age-matched subjects evaluated in similar fashion. Multivariate analysis identified five independent statistically significant correlates of syncope: coronary artery disease (p = 0.0003), functional impairment (p = 0.006), postural blood pressure reduction (p = 0.003), aortic stenosis (p = 0.008), and insulin therapy (p = 0.03). Syncope patients were more likely than controls to have two or more coexistent factors (p = 0.0001). Syncope in institutionalized elderly is often due to the interaction of multiple coexistent clinical abnormalities which impair cardiovascular compensation for common situational stresses.

Age Factors↗
PubMed1986

Splanchnic factors enhance the norepinephrine response to oral glucose in aged man.

Oral glucose has been shown to increase sympathetic nervous system (SNS) activity more in old than in young subjects. In contrast intravenous glucose during euglycemic hyperinsulinemia increases SNS activity in young but not in old subjects. To evaluate the role of splanchnic factors in this discrepancy, we employed a modification of the glucose clamp technique in 6 young (24-39 years) and 8 old (65-83 years) normal males. Each subject underwent two studies in which insulin was infused at 120 mU/m2 X min for 3 h and either oral glucose (50 gms) or water was given 60 min after initiating insulin. Euglycemia was maintained in all studies. When compared to control drink, oral glucose elevated norepinephrine in old (p less than 0.01), but not in young subjects. The difference between old and young was significant (p less than 0.02). When compared to control drink, oral glucose increased pulse rate and double product in the young, and pulse rate in the old. These results indicate that oral glucose activates the SNS in the elderly via splanchnic mechanisms independent of changes in circulating levels of glucose or insulin.

Administration, Oral↗
PubMed1986

Insulin resistance and regulation of serum amino acid levels in myotonic dystrophy.

To quantify the degree of whole body insulin resistance in patients with myotonic dystrophy and to determine if these same patients display signs of a whole body decrease in the action of insulin on amino acid uptake and glucose disposal, three separate 120 min studies employing the euglycaemic insulin clamp technique (20, 80 and 200 m-units min-1 m-2) were performed on five ambulatory patients with myotonic dystrophy. The results were compared with findings obtained in identical studies in 21 normal volunteers. Myotonic dystrophy patients showed a slower, less marked decline in the serum concentration of insulin sensitive amino acids (threonine, valine, leucine, isoleucine, tyrosine, phenylalanine) during all three insulin infusions compared with normals. The greatest difference occurred at the low physiological elevations of insulin produced by the 20 m-units min-1 m-2 infusion. Alanine levels fell significantly below baseline in patients with myotonic dystrophy after 60 and 120 min of insulin infusion with all three rates of insulin infusion. Normal subjects had only a minimal, insignificant decline in arterialized alanine concentrations during the three different insulin infusions. Creatinine adjusted rates of whole body glucose disposal were 30-40% lower in the myotonic dystrophy group at all three doses of insulin compared with the normals. This demonstrates that their insulin resistance was not due simply to a reduction in muscle mass. The overall pattern of findings in these studies of patients with myotonic dystrophy indicates that there is a whole body derangement in the regulation of circulating amino acid levels by insulin as well as a marked decrease in the action of this hormone in stimulating glucose uptake by target tissues.

Adult↗
PubMed1986

Insulin dose-dependent reductions in plasma amino acids in man.

The quantitative relationship between insulin and plasma amino acid (AA) levels were characterized in five healthy young men during euglycemic insulin infusions (6, 10, 30, and 400 mU . m-2 . min-1). The endogenous production and disposal of glucose were determined for the 6 mU . m-2 . min-1 insulin infusion using 6,6-dideuteroglucose. While 8 of 10 AA decreased in a dose-responsive pattern to increasing levels of insulin, alanine and glycine concentrations remained unaffected. For isoleucine and proline, the insulin levels required for a half-maximal response were less than for glucose disposal (P less than 0.05), but, for all other insulin-influenced AA, the levels required were similar to those for glucose disposal. These studies indicate that insulin sensitivity of AA is similar to that of glucose disposal and that AA responses to insulin exhibit a physiologically relevant, dose-response relationship.

Adult↗
PubMed1986

Maintenance of carotid baroreflex function in advanced age in the rat.

To evaluate the influence of age per se on the carotid sinus baroreceptors in the absence of hypertension and atherosclerosis, we employed the Fischer 344 rat model. In 14 adult (A, 6-9 mo) and 9 senescent (S, 24-26 mo) normotensive male Fischer 344 rats the left carotid sinus region was vascularly isolated with sinus nerve intact and perfused with oxygenated modified Kreb's solution. Simultaneous measurements of intrasinus pressure and femoral arterial pressure response were obtained during linear pressure increases (20-200 mmHg) in the vascularly isolated sinus. There was no age difference in base-line arterial pressure or heart rate. Both age groups demonstrated similar positive relations between basal femoral arterial pressure and the magnitude of the femoral pressure response to equivalent carotid sinus pressures. There were similar estimated sinus volumes at onset of systemic response (39 +/- 1, A; 39 +/- 1 microliter, S), time to initial systemic pressure response (9 +/- 1, A; 7 +/- 1 s, S), mean rates of femoral pressure decline (1.8 +/- 0.3, A; 2.1 +/- 0.3 mmHg/s, S), and return to base line (1.5 +/- 0.3, A; 1.4 +/- 0.3 mmHg/s, S) as well as magnitudes of systolic (25 +/- 3, A; 26 +/- 4 mmHg, S) and diastolic (21 +/- 2 A; 22 +/- 4 mmHg, S) pressure drops. Thus, in the Fischer 344 rat model of aging, which differs from the human in that it is not complicated by hypertension or atherosclerosis, carotid sinus baroreflex function appears to be well maintained in senescence.

Aging↗
PubMed1986

The effect of age and sodium depletion on cardiovascular response to orthostasis.

To test the hypothesis that normal age-related limitations in cardiovascular homeostasis may become clinically significant under stress, the cardiovascular response to postural change was assessed in six young and six old healthy subjects before and after modest diuretic-induced sodium depletion. Before diuresis, systolic blood pressure was maintained (from 110 +/- 4 to 113 +/- 6 mm Hg) while heart rate increased 22% (from 67 +/- 2 to 82 +/- 5 beats/min) at 3 minutes after 60-degree upright tilt in young subjects. After a significant diuretic-induced weight reduction and natriuresis, the young again maintained systolic blood pressure (from 110 +/- 4 to 110 +/- 6 mm Hg) and increased heart rate 49% (from 68 +/- 2 to 101 +/- 5 beats/min; p less than 0.05, compared with prediuresis values) in response to the same postural stimulus. During the prediuresis tilt, the older subjects showed no change in systolic blood pressure (from 132 +/- 4 to 134 +/- 6 mm Hg) and a 9% increase in heart rate (from 68 +/- 3 to 74 +/- 2 beats/min). After a similar significant weight reduction and sodium loss, the older subjects showed a significant reduction in systolic blood pressure (from 132 +/- 6 to 108 +/- 6 mm Hg; p less than 0.05) and a 17% increase in heart rate (from 69 +/- 4 to 81 +/- 3 beats/min; p less than 0.05) during tilt compared with values in young subjects. Three of six elderly subjects noted postural symptoms. These results suggest that, although the healthy old may appear well compensated under optimal conditions, decreased cardiovascular reserve renders them susceptible to postural change following mild sodium depletion.

Adult↗
PubMed1986

The dawn phenomenon does not occur in normal elderly subjects.

To determine whether the dawn phenomenon occurs in normal elderly subjects and thus contributes to the progressive mild fasting hyperglycemia of aging, we examined the effect of physiological insulin levels on glucose disposal and hepatic glucose production (HGO) between 0530 and 0800 h, and 0930 and 1200 h. Paired euglycemic insulin clamp studies (8 mU/m2 X min) were performed on healthy old subjects (n = 5), employing [3H]glucose methodology to measure glucose production and disposal rates. Basal plasma insulin, GH, glucagon, and cortisol levels, and HGO and glucose disposal rates were similar before each study. Steady state plasma insulin values were slightly, but not significantly, lower during the dawn study [dawn: 20.3 +/- 1.1 (SE); control: 23.5 +/- 2.1 microU/ml, P = 0.08]. Insulin clearance rates were higher during the dawn study (dawn: 523 +/- 16; control: 430 +/- 19 ml/m2 X min, P less than 0.01). Maximum glucose disposal rates (dawn: 3.10 +/- 0.24; control: 3.03 +/- 0.23 mg/kg X min) and minimum HGO levels (dawn: 0.83 +/- 0.09; control: 0.62 +/- 0.03 mg/kg X min) were not significantly different in each part of the study. There was a significant decrease in plasma GH during the dawn (P less than 0.01, analysis of variance) but not the control studies. There was no difference in cortisol levels during the euglycemic clamp between the dawn and control studies. The mean decrement in glucagon during the insulin infusion was similar in each part of the study. We conclude that the dawn phenomenon does not occur in healthy elderly subjects despite an increase in insulin clearance during the dawn period.

Aged↗
PubMed1985

Intra-individual variability in postural blood pressure in the elderly.

Orthostatic hypotension, an age-related phenomenon, has been associated with hypertension and body weight variability. To evaluate the relative contributions of blood pressure elevation and abnormalities in extracellular volume regulation to orthostatic hypotension, elderly institutionalized subjects (mean age = 87 +/- 7 years), taking no cardiovascular medications, underwent measurement of body weight (n = 15) and first morning supine and standing blood pressures (n = 19), 12-13 times per subject over a 2-4 week period. There was a wide day-to-day variability in postural systolic blood pressure change (coefficient of variation = 533%) and a strong negative correlation between each day's postural change in systolic blood pressure and basal supine blood pressure (r = -0.55, P less than 0.0001). There was no association between postural blood pressure change and heart rate response or body weight changes, which were very small over the duration of the study (coefficient of variation = 0.6%). Elderly individuals have intact homeostatic mechanisms for the control of standing pressure when basal blood pressure is normal. Postural hypotension in the elderly is a variable phenomenon related to elevations in basal blood pressure.

Age Factors↗
PubMed1985

Influence of age on cardiovascular reflex response in anesthetized rats.

To test the hypothesis that aging is associated with an altered hemodynamic response to physiological (nonpharmacological) stimuli, such as postural change and intravascular volume perturbations, we studied the adult (A, 6 mo) and senescent (S, 24 mo) Fischer 344 rat, a mammalian aging model not influenced by atherosclerosis or hypertension. Special emphasis was placed on the afferent limb of the baroreceptor reflex arc, an area not previously studied with respect to age. The base-line heart rate (HR), systemic arterial pressure (SAP), pulmonary arterial pressure (PAP), and carotid sinus nerve activity were not influenced by age. Following postural change (60 degrees upward tilt), the old animals demonstrated a greater drop in systolic pressure (-11 +/- 2, A; -21 +/- 4 mmHg, S; P less than 0.05), but there was no significant change in HR in either group. In response to a controlled withdrawal of 0.5 ml, the A had a greater reduction in systolic pressure (-29 +/- 4, A; -12 +/- 3 mmHg, S; P less than 0.01), whereas HR or PAP did not change; both groups showed a similar decrease in nerve activity. After infusions of 0.5 and 1.0 ml, the systolic and diastolic pressure changes were greater (P less than 0.02), and the changes in nerve activity appeared to be slightly more prolonged in the A compared with the S. Thus the response to changes in intravascular volume and posture are altered with age, and differences in volume-mediated venovasomotor reflex response may contribute to these age-related changes in the rat.

Aging↗
PubMed1985

Insulin-mediated reduction of whole body protein breakdown. Dose-response effects on leucine metabolism in postabsorptive men.

In vivo effects of insulin on plasma leucine and alanine kinetics were determined in healthy postabsorptive young men (n = 5) employing 360-min primed, constant infusions of L-[1-13C]leucine and L-[15N]alanine during separate single rate euglycemic insulin infusions. Serum insulin concentrations of 16.4 +/- 0.8, 29.1 +/- 2.7, 75.3 +/- 5.0, and 2,407 +/- 56 microU/ml were achieved. Changes in plasma 3-methyl-histidine (3-MeHis) were obtained as an independent qualitative indicator of insulin-mediated reduction in proteolysis. Hepatic glucose output was evaluated at the lowest insulin level using D-[6,6-2H2]glucose. The data demonstrate a dose-response effect of insulin to reduce leucine flux, from basal values of 77 +/- 1 to 70 +/- 2, 64 +/- 3, 57 +/- 3, and 52 +/- 4 mumol(kg X h)-1 at the 16, 29, 75, and 2,407 microU/ml insulin levels, respectively (P less than 0.01). A parallel, progressive reduction in 3-MeHis from 5.8 +/- 0.3 to 4.3 +/- 0.3 microM was revealed. Leucine oxidation estimated from the 13C-enrichment of expired CO2 and plasma leucine (12 +/- 1 mumol[kg X h]-1) and from the 13C-enrichment of CO2 and plasma alpha-ketoisocaproate (19 +/- 2 mumol[kg X h]-1) increased at the 16 microU/ml insulin level to 16 +/- 1 and 24 +/- 2 mumol(kg X h)-1, respectively (P less than 0.05 for each), but did not increase at higher insulin levels. Alanine flux (206 +/- 13 mumol(kg X h)-1) did not increase during the clamp, but alanine de novo synthesis increased in all studies from basal rates of 150 +/- 13 to 168 +/- 23, 185 +/- 21, 213 +/- 29, and 187 +/- 15 mumol(kg X h)-1 at 16, 29, 75, and 2,407 microU/ml insulin levels, respectively (P less than 0.05). These data indicate the presence of insulin-dependent suppression of leucine entry into the plasma compartment in man secondary to a reduction in proteolysis and the stimulation of alanine synthesis during euglycemic hyperinsulinemia.

Adult↗
PubMed1985

Counterregulatory responses to insulin-induced glucose reduction in the elderly.

The impact of age on counterregulatory responses to moderate reductions in blood glucose induced by a constant insulin infusion (20 mU/m2 X min) was studied in normal young (n = 7; aged 20-42 yr) and old (n = 7; aged 66-77 yr) nonobese subjects. Insulin was infused until the whole blood glucose level fell to or below 60 mg/dl. This required an infusion time of 39 +/- 3 (+/- SE) min in the young and 36 +/- 3 min in the old. Mean basal glucose [young, 88 +/- 2 (+/- SE); old, 88 +/- 2 mg/dl), minimum glucose (young, 51 +/- 2; old, 54 +/- 1 mg/dl), time to nadir (young, 48 +/- 3; old, 44 +/- 3), and time to recovery were similar in both groups. Maximal (young, 40.3 +/- 2.3; old, 42.1 +/- 3.3 microU/ml) insulin levels were also similar. Basal and maximal levels of glucagon, epinephrine, and GH were similar in the two groups. Although basal norepinephrine values were higher in the old subjects (young, 243 +/- 38; old, 364 +/- 23 pg/ml; P = 0.02), increments above basal during reduction in blood glucose were not affected by age. Basal cortisol values were similar (young, 13.7 +/- 1.4; old, 14.0 +/- 0.7 micrograms/dl), but maximum cortisol responses were slightly greater in the old subjects (young, 14.6 +/- 1.0; old, 17.7 +/- 0.9 micrograms/dl; P = 0.03). These studies indicate that hormonal responses and counterregulatory efficiency during modest reductions in blood glucose are preserved in healthy elderly subjects.

Adult↗
PubMed1985

Metabolic response to three years of continuous, basal rate intravenous insulin infusion in type II diabetic patients.

We studied two obese type II diabetic patients before, during, and after 3 yr of continuous iv insulin infusion, delivered by means of totally implanted insulin infusion pumps. Tolerance of the devices was excellent, and no side-effects or episodes of significant hypoglycemia occurred. Glycosuria was eliminated, and mean 24-h plasma glucose and hemoglobin A1c levels decreased in both patients and remained in or near the normal range for 3 yr. Improvements were also noted in serum triglyceride concentrations and vitreous fluorescein concentrations after iv fluorescein injection. Euglycemic insulin clamp studies showed that no significant change in glucose disposal rate occurred after 6 and 12 months of treatment. However, some improvement in insulin secretion during hyperglycemic insulin clamp studies occurred in both patients after 6 months of insulin infusion. Evaluation of the insulin-glycerol mixture used in the pump revealed that moderate degradation of insulin occurred in the pump during the 21-day flow cycle, resulting in 6-12% increases in fasting blood glucose levels; in addition, higher mol wt species of immunoreactive insulin were present in the patients' serum. We conclude that long term continuous iv infusion of insulin using a totally implantable infusion pump is practical in type II diabetic patients, is acceptable to patients, and is capable of providing near-normal glycemic control.

Blood Glucose↗