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Biomedical subjects

L Klein

Publications and source records attributed to L Klein.

At least 199 records · Page 11Linked to original sources
PubMed1981

Steady-state relationship of calcium-45 between bone and blood: differences in growing dogs, chicks, and rats.

In young animals that had received multiple doses of calcium-45, a constant ratio of calcium-45 specific activity in blood to that in bone was found in growing dogs and chicks but not in rats. This steady-state relationship of calcium-45 between bone and blood suggests that during growth in dogs and chicks most of the skeletal calcium is in an active state of turnover. In growing rats, after the first 2 weeks of life, the blood/bone ratio of calcium-45 decreases due to a decrease in bone resorption.

Age Factors↗
PubMed1981

Effect of lactation and calcium deficiency, and of fluoride intake, on bone turnover in rats: isotopic measurements of bone resorption and formation.

The rates of bone formation and resorption were investigated, using isotopic measurements, in calcium-deficient lactating rats and compared to those of calcium-sufficient non-lactating animals. Bone formation was measured by 3H-proline uptake and 3H-hydroxyproline formation, and resorption was measured by the loss of previously incorporated 3H-tetracycline, in whole humerus. The effect of 50 ppm fluoride in the drinking water on both parameters was also examined. The stress of lactation and calcium deficiency significantly increased the rates of bone resorption and formation, but the increase in resorption was greater than in formation which resulted in a net decrease in bone mineral and matrix. Fluoride had no effect on various parameters measured.

Animals↗
PubMed1981

Polarizing light microscopy of intestine and its relationship to mechanical behaviour.

The polarizing optical microscope has been used to observe morphologically the effect of stress on rat and bovine intestine. Collagen fibres about 6 micrometers in diameter were found to be biaxially oriented at approximately +30 degrees and -30 degrees to the longitudinal direction. The fibres are arranged in layers with the fibres in each layer densely packed in parallel undulating arrays. The undulations give rise to the extinction pattern observed in the polarizing optical microscope. The initial response to stress is straightening of the fibres. Gradual straightening of the fibres is related to the increasing stiffness of the tissue observed in the stress--strain relationship. Once the fibres ares straightened, the biaxial orientation of the fibres produces higher strength in the longitudinal direction than in the transverse direction. This organization of intestinal collagen fibres has not been reported previously and is not observed in other biaxial tissues such as skin and aorta. Thus, intestine is a unique tissue for studying the relationship of mechanical behaviour to structure and organization of collagen.

Animals↗
PubMed1981

Behavioral and cardiorespiratory responses to 4-aminopyridine in healthy awake horses.

4-Aminopyridine was administered in incremental IV doses to healthy horses to evaluate cardiorespiratory and behavioral effects. Doses of 100 micrograms/kg produced apparent sensory discomfort, manifested by wiggling or curling of the lips and tongue, arching or stretching the neck, snorting, squealing, and coughing. At cumulative dosages of 300 to 500 micrograms/kg, muscle tremors, a stilted gait, and signs of excitement occurred. Once signs of excitement occurred, additional administration of 4-aminopyridine resulted in prolonged excitement consisting of severe muscle tremors and exaggerated responses to external stimuli. Heavy sedation with xylazine provided nearly complete relief from these effects. 4-Aminopyridine could be a useful adjunct to treatment of botulism in horses; however, administration of doses in excess of 300 to 500 micrograms/kg may cause severe CNS excitatory effects.

4-Aminopyridine↗
PubMed1980

Acceptance of amniocentesis by low-income patients in an urban hospital.

A study was made of increased accessibility of genetic services to low-income obstetric patients in Atlanta, Georgia. The proportion of black patients averaged 83%. Of 522 patients counseled from August, 1976, through 1978, 157 were offered amniocentesis, and 95 (61%) elected the procedure. For most of the patients (120, or 76%) who were eligible for amniocentesis, age (greater than or equal to 35 years at delivery) was an indication; and of these, only six (5%) had any prior knowledge of genetic risk. During the same time interval, 188 patients over 35 years of age who initiated prenatal care too late for prenatal diagnosis were counseled in the hospital after delivery; 101 (54%) indicated that they would have accepted amniocentesis. The conclusion was that (1) genetic services are acceptable to this socioeconomic group, and (2) accessibility and publicity are needed to promote utilization in this population.

Amniocentesis↗
PubMed1980

Regression of atherosclerotic plaques in rhesus monkeys. Angiographic, morphologic, and angiochemical changes.

On a diet with high levels of cholesterol and sucrose, a beta-lipoproteinemia developed in rhesus monkeys that is similar to type II human hyperlipidemia. Lesion regression appeared in response to drastic lowering of serum cholesterol (SC) levels. This experiment analyzed angiochemical responses on the addition of a bile-acid sequestrant to continued atherogenic feeding, which resulted in ranges of moderate cholesterolemia that mimick those that occur in man. After two years of atherogenic diet, fatty fibrous plaques were demonstrated in ten monkeys; then cholestyramine resin, 1.5 g/100 g of the atherosclerotic diet, was added to the food of eight monkeys, whereas two served as controls during a 12-month regression period. Six adult control monkeys that did not receive the atherosclerotic diet were also killed. Seven experimental animals overall showed plaque regression when SC level fell from 400 +/- 130 to 237 +/- 74 mg/dL; one animal showed angiographic combinations of progression and regression. Angiochemical evaluation demonstrated discordant data with instances of decreased plaque cholesterol content and increased levels of collagen. On the average, plaque regression and final composition were related to absolute levels of SC reduction induced by cholestyramine. Regression required that the threshold levels of cholesterol be below 200 mg/dL. Plaques regressed mainly by lipid absorption; in this experiment and, in particular, arterial segments, collagen content sometimes increased.

Animals↗
PubMed1980

Direct measurement of bone resorption and calcium conservation during vitamin D deficiency or hypervitaminosis D.

When bone is remodeled during the growth of a given size bone to a larger size, some bone is resorbed and some is deposited. Much of the resorbed bone mineral, calcium, can be reutilized during bone formation. The net and absolute effects of normal growth, vitamin D deficiency, or vitamin D excess were compared on bone resorption, bone formation, and calcium reutilization. Growing chicks were prelabeled extensively with three isotopes: (45)Ca, [(3)H]tetracycline, and [(3)H]proline. Data were obtained weekly during 3 weeks of control growth, vitamin D deficiency, or vitamin D overdosage while on a nonradioactive diet. Bone resorption as measured by increases in the marrow (inner) diameter of the midshaft of the femur and humerus and by the weekly losses of total [(3)H]tetracycline and [(3)H]collagen per whole bone was not significantly different among any of the groups studied. The data indicated that the high rate of cortical bone resorption in experimental chicks was not increased above that observed in experimental chicks was not increased above that observed in control chicks. Vitamin D deficiency had little effect on the total (45)Ca in whole bones, whereas vitamin D-treated chicks lost 40% of their (45)Ca. Thus, vitamin D overdosage resulted in a decrease of (45)Ca reutilization, whereas vitamin D deficiency resulted in an apparent increase of (45)Ca reutilization. Both vitamin D-deficient and vitamin D-treated chicks had a decreased accumulation of dietary calcium per whole bone. The insufficient mineral mass in vitamin D-deficient chicks resulted from the indirect inhibition of bone mineralization due to the low intestinal absorption of calcium rather than from a change in bone resorption. In vitamin D-treated chicks the apparent bone atrophy and net loss of (45)Ca from bone resulted from inhibiting bone matrix formation and mineralization instead of increasing bone resorption. The constancy of bone resorption under these experimental conditions suggests that bone mineralization is the major regulator of bone mass.

Animals↗
PubMed1980

Intraoperative external pneumatic calf compression to afford long-term prophylaxis against deep vein thrombosis in urological patients.

In a prospective randomized study of patients undergoing open urological operations, we found external pneumatic compression (EPC) of the calves applied in the operating room and recovery room as effective in reducing deep vein thrombosis as EPC continued during convalescence until resumption of ambulation. Provided early postoperative ambulation is practiced, intraoperative EPC appears to be adequate prophylaxis and equivalent to long-term EPC for prevention of deep venous thrombosis in urological patients.

Adult↗
PubMed1979

Effect of regenerated endothelium on collagen content in the injured artery.

Collagen content and intimal thickness were measured in endothelialized and nonendothelialized zones of the aorta in rabbits for 30 days after a standard embolectomy balloon injury. A large increase in collagen content and intimal thickness were seen in the arterial wall covered by regenerating endothelium. In areas devoid of endothelial coverage, minimal intimal thickness occurred; no measurable increase in collagen content was measured. Interaction between arterial smooth muscle cells and regenerated endothelium appear to be necessary for collagen accumulation and intimal thickening after arterial injury and repair.

Animals↗
PubMed1978

Fetal rat bone in organ culture: effect of bone growth and bone atrophy on the comparative losses of 45Ca and 3H-tetracycline.

Fetal rat bones were cultured in either growth-inducing or resorption-inducing media to study mineral losses during bone growth and atrophy in vitro. Whole radii and ulnae from 19-day-old fetal rats, prelabeled with 45Ca and/or 3H-tetracycline, were cultured intact or cut, and then digested by collagenase to obtain the calcified portion of the bones. Three- to five-fold more 3H-tetracycline than 45Ca was lost from the calcified portion when the bones were cultured for 4 days in growth-inducing media. Similar small amounts of 45Ca were lost from live and killed bones, but more 3H-tetracycline was lost from live bones than from killed bones. More 3H-tetracycline was released into the growth medium with a low concentration of calcium (0.5 mM) than when the calcium concentration was high (1.0 mM); no significant difference was seen in the release of 45Ca into the medium at different calcium concentrations. Larger amounts of both isotopes were lost when the prelabeled bones were cultured in resorption-inducing media than in growth-inducing media. When parathyroid hormone stimulated bone resorption in a resorption-inducing medium, equal proportions of both isotopes and bone collagen were lost. Greater losses of 3H-tetracycline than of 45Ca suggest that 45Ca was conserved locally during the resorption that accompanies bone growth, but not during resorption that accompanies bone atrophy.

Animals↗
PubMed1978

Antecedents of teenage pregnancy.

Antecedent factors operative in the causation of adolescent pregnancy include: The sexuality of contemporary society, especially the media. Prolongation of educational any vocational preparation in industrialized western society. Normal physical maturation at an early age. Peer and social pressure. Low expectations of life among minority and economically poor individuals. The conspiracy of silence surrounding sexuality and the inability of society to admit and deal realistically with the sexual activity of adolescents. Failure to provide sex education, clarification of values, family-life education, preparation for parenthood, and knowledge of birth-control and family-planning services targeted to teenagers, including adolescent males. Psychological and emotional problems. Failure to provide available and accessible early pregnancy-detection services with adequate counseling and support services. Failure to provide abortion services. Failure to provide supportive services to adolescents who have a child in order to prevent repeated pregnancy. Pregnancy, childbearing, and motherhood represent ultimate feminine fulfillment to many in our society, and unless attainable expectations and desirable alternatives are available, adolescents will continue to see little reason to postpone pregnancy and childbearing.

Adolescent↗