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Biomedical subjects

D T Lowenthal

Publications and source records attributed to D T Lowenthal.

At least 55 records · Page 3Linked to original sources
PubMed1996

1H-MRS, MRI-based hippocampal volumetry, and 99mTc-HMPAO-SPECT in normal aging, age-associated memory impairment, and probable Alzheimer's disease.

OBJECTIVE: To better understand how to differentiate the "in vivo" normal aging brain from pathological conditions, namely dementia of the Alzheimer type (DAT), by means of magnetic resonance imaging (MRI), single photon emission computerized tomography (SPECT), and proton magnetic resonance spectroscopy (1H-MRS), to show neuroanatomical, perfusional and neurochemical details, respectively. DESIGN: 1H-MRS, MRI-based hippocampal volumetry and 99mTc-HMPAO SPECT were performed in healthy older subjects as well as patients suffering from age-associated memory impairment (AAMI) and dementia of Alzheimer type (DAT). SUBJECTS AND SETTING: Eighteen subjects were selected from those referred to an outpatient clinic for diagnostic evaluation of cognitive impairment entered the study. Six patients fulfilled NINCDS-ADRDA diagnostic criteria for DAT, six subjects were affected by AAMI, and six cognitively healthy subjects, selected from among relatives of the patients, were defined as controls. METHODS: The 1H-MRS and MRI studies were performed on a 1.5 Tesla NMR-imaging system equipped with a spectroscopy research package. SPECT scans were performed on a Gamma 11 computer system. FINDINGS: 1H-MRS showed significantly lower N-acetylasparatate concentration in DAT and AAMI compared with controls. Conversely, mean inositol concentration was significantly higher in DAT than in controls, whereas AAMI subjects registered intermediate values. MRI measurements showed significantly reduced volumes of hippocampal formations in DAT and AAMI groups compared with controls. Finally, 99mTc-HMPAO SPECT showed a significant frontal, temporo-parietal, and occipital hypoperfusion in DAT patients only. CONCLUSIONS: These findings support the hypothesis of a continuum among the three conditions studied, or at least between AAMI and DAT, where AAMI seems to be an early, monosymptomatic stage of Alzheimer disease. Accepting this view, it would be questionable to maintain the term "age-associated memory impairment" as a discrete entity.

Aged↗
PubMed1995

Effect of grapefruit juice on blood cyclosporin concentration.

Grapefruit juice increases blood concentrations of some dihydropyridine calcium-channel blockers, which are metabolised by the P450 enzymes that also metabolise cyclosporin. We evaluated, in a randomised cross-over study, the effect of grapefruit juice on blood cyclosporin concentrations in 14 healthy adults. Each subject was given oral cyclosporin 300 mg with 250 mL grapefruit juice, orange juice, or water. Area-under-the-curve (AUC) was significantly higher with grapefruit juice than with water or orange juice (means 7057, 4871, and 4932 ng h/mL, respectively; p < 0.0001). Thus grapefruit juice may provide a non-toxic and inexpensive alternative to drugs that are used to reduce cyclosporin dose.

Adolescent↗
PubMed1995

Hormonal responses in elders experiencing pre-syncopal symptoms during head-up tilt before and after exercise training.

BACKGROUND: Hormonal responses of elderly individuals experiencing pre-syncopal symptoms during head-up tilt testing (HUT) were compared with responses of nonsymptomatic subjects both before (T1) and after (T2) 6 months of endurance training. METHODS: Based on responses to HUT at T1, 35 men and women (ages 61-79 years) were placed into symptomatic and nonsymptomatic groups for analysis. Symptomatic subjects (n = 5) experienced lightheadedness, nausea, sweating, or syncope during T1 HUT but completed 15 minutes of HUT at T2. Training consisted of treadmill walking or stairclimbing 3 x/wk, 30-45 min/day, at 75-85% of maximal heart rate reserve. Adrenocorticotropic hormone (ACTH), vasopressin, aldosterone, norepinephrine, epinephrine, hemoglobin, and hematocrit were measured during supine rest prior to HUT, and either at the end of the 15-minute HUT or at symptom onset. Plasma volume (PV) was measured at supine rest; tilt-induced changes in PV were calculated from changes in hemoglobin and hematocrit. RESULTS: During T1 HUT, symptomatic subjects had greater increases in vasopressin and a greater rate of PV loss (p < .05). Increases in ACTH and aldosterone were greater in symptomatic subjects at T1 and T2, while increases in norepinephrine were greater at T2 (p < .05). Reductions in tilt-induced vasopressin concentration and a decreased rate of PV loss were seen at T2 in symptomatic subjects. CONCLUSIONS: T1 results from symptomatic subjects are consistent with greater stimulation of volume-sensitive receptors induced by a greater rate of fall in PV. Exercise training resulted in increased tilt tolerance for symptomatic subjects associated with reductions in vasopressin concentration and rate of PV loss during tilt.

Aged↗
PubMed1995

Effect of 6 months of exercise training on cardiovascular responses to head-up tilt in the elderly.

The purpose of this investigation was to evaluate the effect of 6 months of exercise training on cardiovascular responses to 70 degrees head-up tilt (HUT) in the elderly. Forty-four elderly men and women (ages 60-82 years) were assigned to endurance training alone (n = 18), endurance training in combination with selected resistance exercises (n = 17), or to a non-exercising control group (n = 9). Head-up tilt testing at the start (T1) and end (T2) of 26 weeks of training consisted of 30 min of supine rest, 15 min of 70 degrees HUT, and 15 min of supine recovery. Endurance training consisted of uphill treadmill walking or stair climbing exercise 3 times per week, 30-45 min/day, at 75-85% of maximal heart rate reserve. In addition, the endurance/resistance group completed one set of 8-15 repetitions of biceps curl (BC), triceps extension (TE), and leg press, 3 times per week. After 26 weeks, increases in VO2max averaged 16.2% and 12.3% for endurance and endurance/resistance groups, respectively. In addition, the endurance/resistance group increased BC and TE strength by 25.3% and 26.1%, respectively. Results from the HUT test indicated that only the endurance group increased supine resting stroke volume (SV) and cardiac output (Q) from T1 to T2; however, SV and Q during HUT were not augmented as a result of training. Training did not affect heart rate, blood pressure, or peripheral resistance responses at rest or during HUT in any of the groups. These results suggest that 6 months of endurance training, alone or in combination with selected resistance exercises, is not detrimental to blood pressure controlling mechanisms to head-up tilt in the elderly.

Aged↗
PubMed1995

Clinical problem-solving in geriatric medicine: obstacles to rehabilitation.

This case illustrates how multifactorial medical, neurological and psychiatric conditions can synergistically effect the functional status of elderly individuals. This case also illustrates how iatrogenically induced illness, most commonly in the form of drug therapy, can significantly affect patients' conditions and their progress in rehabilitative therapies. This case also illustrates how the atypical presentation of disease in the elderly, as well as the medical ramifications of rehabilitative therapies, need to be strongly considered during trials at functional rehabilitation. More importantly, however, this case demonstrates how even a community-based geriatrician can be instrumental in recognizing the need of more appropriate evaluations in elderly patients with functional disabilities and how even in the setting of a multidisciplinary team there can still be a consulting relationship, with each person seeing the patient individually and communicating with other members of the team as necessary. Although each team member may have a specific area of expertise, there is still a very important role for the geriatrician to play in making sure that all the different components of the rehabilitation and the medical care proceed in a way that will provide the most favorable outcome for the patient.

Aged↗
PubMed1995

Effect of training on blood volume and plasma hormone concentrations in the elderly.

The purpose of this investigation was to determine the effects of 6 months of endurance training on resting plasma (PV) and blood volume (BV), and resting hormone and electrolyte concentrations in the elderly. Thirty-eight elderly men and women (ages 60-82 yr) were assigned to endurance exercise training (N = 29) or to control (N = 9) groups. Resting plasma levels of adrenocorticotropic hormone, vasopressin, aldosterone, norepinephrine, epinephrine, sodium, potassium, and protein were measured at the start (T1) and end (T2) of 26 wk of training. PV measurement was performed using the Evan's blue dye technique. Endurance training consisted of uphill treadmill walking or stairclimbing exercise 3 times.wk-1, 30-45 min.d-1, at 75-84% of maximal heart rate reserve. The exercise group increased VO2max by 11.2% (P < or = 0.05) and increased resting PV and BV by 11.2% and 12.7% (P < or = 0.05), respectively. Hormone and electrolyte levels in the exercise group remained unchanged; all variables were unchanged in the control group. These results are similar to findings in younger individuals. Because plasma hormone concentrations were maintained despite a chronically elevated BV, endurance training in healthy, elderly subjects may be associated with a resetting of volume receptors.

Adrenocorticotropic Hormone↗
PubMed1994

Moderate- and high-intensity exercise lowers blood pressure in normotensive subjects 60 to 79 years of age.

To investigate the effects of exercise intensity on resting blood pressure (BP) in normotensive elderly subjects, 44 sedentary healthy subjects aged 60 to 79 years of age were studied during 6 months of walking exercise. Subjects were ranked according to maximal oxygen consumption and randomly stratified to groups that trained at 70% (n = 19) or 80% to 85% (n = 14) of maximal heart rate reserve, or to a control group (n = 11) that did not train. Initial BP was established during a 2- to 3-week control period. During the first 3 months, both exercise groups progressed to 70% of heart rate reserve for 40 minutes 3 times each week. The moderate-intensity group continued to train at 70% (45-minute duration) for an additional 3 months, whereas the high-intensity group progressed to training at 85% of heart rate reserve (35-minute duration). Maximal oxygen consumption increased (p < or = 0.05) during the initial 3 months in both exercise groups (25.2 to 28.1 ml.kg-1.min-1 and 26.3 to 29.3 ml.kg-1.min-1) and continued to increase (p < or = 0.05) after 3 additional months of training, but the increase was greater (p < or = 0.05) in the high-intensity group (28.1 to 29.4 ml.kg-1.min-1 and 29.3 to 32.8 ml.kg-1.min-1). Systolic BP decreased (p < or = 0.05) similarly at 6 months in both training groups (120 to 111 mm Hg and 120 to 112 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Effects of caffeine or ethanol on treadmill performance and metabolic responses of well-trained men.

The effects of caffeine and ethanol on treadmill performance and metabolic responses to exercise were determined in four trained runners. Caffeine (2.5 mg.kg-1 body weight) or ethanol (25 ml) in 150 ml of grapefruit juice (total volume) or grapefruit juice (placebo) was randomly administered 10 minutes prior to and at 30 minutes of a 60 minutes treadmill run. The speed and grade of the treadmill was adjusted to elicit an average oxygen consumption of 80-85% of the subject's maximal oxygen consumption. All subjects completed the treadmill run for the caffeine and placebo conditions. Three of the four subjects could not complete the treadmill run following the second administration of ethanol. Exercise heart rate was significantly greater for the ethanol condition than for the placebo condition. Exercise oxygen consumption was greater following ethanol administration than for placebo, but the differences were not significant. Blood glucose rose significantly between 0 and 30 minutes of treadmill running for all three conditions. Between 30 minutes of treadmill running and either 60 minutes or the time of termination of the exercise, blood glucose decreased significantly by 24% following the second ethanol treatment. Plasma fatty acid, triglyceride, creatine phosphokinase, and renin contents followed expected exercise changes with a blunting of the rise of plasma fatty acids at 30 minutes of exercise for the ethanol condition. It was concluded that the administration of ethanol adversely influenced treadmill exercise performance by eliciting a hypoglycemic effect between 30 minutes and the termination of the exercise.

Adult↗
PubMed1994

Metabolic and nutritional considerations for exercising older adults.

Age-associated declines in REE and the thermogenesis of activity result in lower energy requirements in older adults. Regular aerobic exercise and resistive exercise programs will increase ones daily energy expenditure and may preserve or increase the lean body mass which has been shown to decrease with increasing age. Further, regular resistive exercise programs may improve bone mineral density and ambulation in older adults. Normal age-associated changes in gastrointestinal function and the addition of exercise may require some modification of nutrient intake. However, in the absence of gastrointestinal disease, these modifications should not be great for healthy sedentary older adults. Protein intake should be at least 1.0 g/kg body weight for older adults especially, physically active older adults.

Adolescent↗
PubMed1994

Sympathetic nervous system: aging and exercise.

Both aging and exercise are associated with alterations in regulation of catecholamines. With aging, elevated circulating catecholamines at rest and after stress may result in increased sympathetic nervous system activity. The ability of the catecholaminergic system of older subjects to respond and adapt to environmental challenges is altered during aging. One consequence of these changes may be the increased prevalence of hypertension with age. Exercise training reduces both systolic and diastolic blood pressure in young and elderly hypertensive subjects. The reduction in catecholamine synthesis after training may be linked to the beneficial effects of exercise in hypertensive individuals.

Adrenal Medulla↗
PubMed1994

Effects of exercise on age and disease.

This overview on the integration of exercise into the life-style of the healthy elderly summarizes data on the effects of physical activity on both coronary risk factors and age-induced changes in both cardiac and noncardiac organ systems. It appears that many of the diseases associated with age as well as aging itself can be either treated or blunted by an active life-style. Cardiac, pulmonary, musculoskeletal and metabolic-endocrine changes associated with age and/or disease can show a change in progression as a result of physical activity. This overview sets the tone for the symposium, which covers in depth many of the specific areas affecting the quality of life of the elderly. The exercise prescription is described in this paper and expanded upon in subsequent papers of this symposium, and it is on the basis of these recommendations that many of the age-related changes and risk factors may be forestalled or rectified.

Aged↗
PubMed1994

Influences of age and exercise on glucose metabolism: implications for management of older diabetics.

The well-characterized decline in glucose tolerance during aging is due primarily to impaired insulin-mediated glucose uptake in peripheral tissues. Elderly persons with reduced insulin sensitivity are predisposed to the development of non-insulin-dependent diabetes mellitus (NIDDM), which is common in the geriatric population. Numerous studies suggest that exercise and physical training increase insulin sensitivity in young adult and middle-aged nondiabetics, older subjects with impaired glucose tolerance, and middle-aged persons with NIDDM. These investigations provide presumptive evidence that elderly persons with NIDDM may benefit from exercise training, although no published studies have specifically addressed the effects of exercise in older diabetics. Physical activity may also be effective in preventing the development of NIDDM. In addition, exercise training improves several cardiovascular risk factors, such as plasma lipid abnormalities, hypertension, and obesity. The risks of exercise in older diabetics include hypoglycemia in insulin-treated patients, exacerbation of preexisting cardiovascular disease, and worsening of long-term diabetic complications. Any exercise prescription in the older diabetic must be individualized to the patient's physical capabilities, limitations, and preferences.

Aged↗
PubMed1994

Exercise training and prescription for the elderly.

Most exercise programs designed for healthy persons older than 65 emphasize fitness development, but the maintenance of functional capacity and quality of life are equally important. The basic guidelines for frequency, intensity, and duration of training and the mode of activity recommended by the American College of Sports Medicine for healthy adults are also appropriate for the elderly. The difference in the exercise prescription for the elderly participant is the manner in which it is applied. Given that the elderly person is more fragile and has more physical-medical limitations than the middle-aged participant, the intensity of the program is usually lower while the training frequency and duration are increased. The mode of training should avoid high-impact activities, and the progression of training should be more gradual. The prescribed training heart rate for the elderly at 40% to 80% of maximal heart rate reserve is slightly lower than the 50% to 85% recommended for young and middle-aged participants, but its relationship to relative metabolic work (50% to 85% of maximal oxygen uptake) and rating of perceived exertion are similar to those found for younger participants. Because of the importance of maintaining muscle mass and bone in middle and old age, a well-rounded program including strength/resistance exercise of the major muscle groups is recommended. Hence the exercise prescription for the elderly should emphasize low to moderate intensity and low-impact activities, avoid heavy static-dynamic lifting, and allow a gradual progression in training.

Activities of Daily Living↗
PubMed1993

Effect of ethanol on metabolic responses to treadmill running in well-trained men.

The metabolic effects of ethanol on treadmill performance were determined in four trained runners. Ethanol in doses of 25 mL in 150 mL of grapefruit juice (total volume) or grapefruit juice was randomly administered 10 minutes before and at 30 minutes of a 60-minute treadmill run. The speed and grade of the treadmill was adjusted to elicit an average oxygen consumption (VO2) of 80 to 85% of the subjects' VO2max. Three of the four subjects could not complete the treadmill run after the administration of ethanol. Administration of ethanol resulted in significant increases in the heart rate responses to treadmill running above those for the placebo grapefruit treatment. VO2 was higher after ethanol administration than the placebo grapefruit juice treatment, but these values were not significant. Blood glucose content rose significantly between 0 and 30 minutes of treadmill running for both the ethanol and placebo grapefruit juice treatments. Between 30 minutes of treadmill running and the termination of the exercise, the blood glucose level decreased significantly by 24% after the second ethanol treatment at 30 minutes of exercise. Plasma fatty acid, triglyceride, creatine phosphokinase, and renin contents followed expected exercise changes. It was concluded that the administration of ethanol adversely influenced treadmill exercise performance by eliciting a hypoglycemic effect between 30 minutes and the termination of the exercise.

Administration, Oral↗
PubMed1993

The influence of food on the absorption and metabolism of drugs.

Food-drug interactions can lead to a loss of therapeutic efficacy or toxic effects of drug therapy. Generally, the effect of food on drugs results from a reduction in the drug's bioavailability; however, an alteration in drug clearance can occur due to the effect of certain foods on drug metabolism. The proportion of adverse drug reactions due to food-drug interactions is not known and unfortunately only when a serious adverse drug reaction follows a food-drug interaction does the matter usually receive any significant attention. In order to improve therapeutic efficacy and to help prevent adverse drug reactions, it is necessary that clinicians be knowledgeable of the important food-drug incompatibilities and risk factors related to the increased likelihood of developing an adverse drug reaction due to food-drug interactions.

Biological Availability↗
PubMed1993

The use of transdermal clonidine in the hypertensive patient with chronic renal failure.

The efficacy of transdermally administered clonidine was evaluated in twenty-four patients with mild-to-moderate hypertension (seated diastolic blood pressure 95-115 mmHg) and renal impairment. Patients were initially treated with oral clonidine; the dose was titrated until the seated diastolic pressure fell below 90 mmHg or a minimum 10% reduction in baseline was achieved. Oral clonidine produced a significant decrease in both systolic and diastolic blood pressure; mean seated diastolic blood pressure decreased 16.9 mmHg from baseline. When transdermal clonidine was substituted for twice daily dosage of oral clonidine, blood pressure decreases were fully maintained. Sixteen patients completed three months of stable-dose transdermal therapy. The results suggest that, in mild-to-moderate hypertensive patients with chronic renal impairment, blood pressure can be controlled with a once-weekly application of transdermal clonidine as effectively as with oral clonidine. Mean diastolic blood pressure was decreased approximately 17% during clonidine therapy independent of the severity of renal dysfunction or route of clonidine administration.

Administration, Cutaneous↗
PubMed1992

Influence of exercise and age on myocardial beta-adrenergic receptor properties.

The bradycardia following physical training may be mediated by an alteration in beta-adrenergic receptor number or agonist affinity. We characterized the interaction between age and exercise on myocardial beta-adrenergic receptor number and agonist affinity in 4- and 24-month-old F344 rats to test the hypothesis that the effects of training should be blunted in older rats. beta-adrenergic receptor density was unchanged with age or training. The total number of receptors per heart increased with age due to increased ventricle weight. With training, in the senescent rats the total number of receptors decreased due to a reduced amount of homogenate protein recovered from the ventricle, the significance of which is unknown. The receptor agonist dissociation constant for isoproterenol was determined in both the absence and presence of beta,gamma-imidoguanosine 5'-triphosphate [Gpp(NH)p] and did not change with age or training. Neither training nor age influenced beta-adrenergic receptor characteristics, suggesting that training bradycardia is not mediated by an alteration in beta-adrenergic receptors.

Aging↗