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Biomedical subjects

R Marcus

Publications and source records attributed to R Marcus.

323 records · Page 18Linked to original sources
PubMed1968

Apparent production of 2 types of antibdoies by a single cell.

Immunization of mice with bacterial, sheep red cells coated with antigen resulted in apparent production of antibody-forming plaques with specificities for both hemolysis and bactericidal activity. The secondary response for production of these bifunctional types of plaques could be induced by red blood cells or bacteria alone. A significant mutual suppression of immune response between the two immunizing agents was observed.

Animals↗
PubMedDate not supplied

Translumbar coronary and brachiocephalic arteriography using a modified Desilets-Hoffman sheath.

A translumbar sheath is described that is suitable for performance of selective coronary and brachiocephalic arteriography when the extremity arteries are blocked. The sheath has been adapted to a needle and catheter, which are introduced as a unit into the aorta at the T-12 level. With the needle and catheter removed, the sheath can be used safely to exchange catheters for left ventriculography and selective studies of branches of the thoracic aorta without excessive retroperitoneal bleeding.

Aorta, Thoracic↗
PubMedDate not supplied

Bone mineral density in older non-Hispanic Caucasian and Mexican-American women: relationship to lean and fat mass.

PRIMARY OBJECTIVE: The prevalence of osteoporotic fracture is higher in non-Hispanic Caucasian (NHC) than Mexican-American (MA) women in the USA. The present study examined bone mineral density (BMD) in these two ethnic groups and the association between BMD and body composition. RESEARCH DESIGN: Cross-sectional. SUBJECTS: Sixty-two NHC and 54 MA women, aged 60-86 years, with a body mass index (kgm(-2)) of <30. METHODS: BMD (gcm(-2)) of the spine (L2-4), hip (femoral neck, trochanter, Ward's triangle) and whole body was determined by dual-energy X-ray absorptiometry (DXA). Bone mineral-free lean mass (LM) and fat mass (FM) and several ratios of body fat distribution were also assessed by DXA. RESULTS: There was no difference in age (NHC, 69.5+/-0.7; MA 69.5+/-0.9 years; mean +/- SEM) or body mass, but MA women were shorter with a higher truncal adiposity (p < 0.001). There was no significant difference in BMD between groups, however, adjusting for height resulted in higher hip and whole body BMD in MA women (p < 0.01). When volumetric bone density was calculated (bone mineral apparent density; BMAD, gcm(-3)), a trend for higher values in MA women was observed at the femoral neck (p = 0.018). LM contributed independently to BMD at the spine and hip in NHC women, with FM also contributing at the femoral neck. In MA women, LM was an independent contributor to lumbar spine and trochanter BMD, and both LM and FM contributed to whole body BMD. However, the effects of LM and FM were removed in both groups when BMD was adjusted for body or bone size, the only exception being at the trochanter in NHC women. CONCLUSIONS: These results indicate that MA women have higher bone density at the proximal femur than NHC women, which may partially account for their lower rate of hip fracture. Further, differences in bone density between the two ethnic groups do not appear to be dependent on soft-tissue composition.

Aged↗
PubMedDate not supplied

Analysis of athletic performance with prophylactic ankle devices.

We evaluated the effect of different ankle support devices on athletic performance. Thirty varsity college athletes were tested with both ankles supported by taping, Swede-O brace, Kallassy brace or left unsupported. The athletes performed four events: broad jump, vertical leap, 10 yard shuttle run, and 40 yard sprint. The events and appliances were randomized to prevent bias by fatigue. Compared to the results when no support was used, ankle taping resulted in a significant decreased performance in the vertical jump (4%), shuttle run (1.6%), and sprint (3.5%) (P less than 0.05). Use of the Swede-O brace decreased performance in the vertical jump (4.6%), broad jump (3.6%), and time of the sprint (3.2%). Results using the Kallassy brace showed a decrease in the vertical jump (3.4%) when compared to no support. The test results of the shuttle run with taping were slower than the Kallassy brace (P less than 0.05). Wearing the Swede-O brace caused the athletes' broad jump distance to decrease more than the Kallassy brace (P less than 0.05). Subjective questionnaires supported the Kallassy brace as the most comfortable support and the one that decreased performance the least. Taping of the ankles is universally accepted for ankle prophylaxis. This study has shown a decrease in performance when ankles are taped compared to ankles with no protection. Since the decreases in performance caused by ankle braces are minor, this should not be used as a criterion for selection of prophylactic support compared to taping.

Ankle Injuries↗
PubMedDate not supplied

Unique dermal and subcutaneous botryoid rhabdomyosarcoma associated with mature renal tissue: is this an extrarenal Wilms' tumor?

A unique dermal and subcutaneous botryoid rhabdomyosarcoma admixed with ectopic mature renal tissue, overlying the left lateral lumbosacral region of a 41/2-year-old girl is reported. The tumor was devoid of blastemal or immature epithelial elements and nephrogenic rests. The relationship of this lesion to an extrarenal Wilms' tumor with exclusive myogenous differentiation is discussed.

Cell Transformation, Neoplastic↗
PubMedDate not supplied

Mechanobiology of femoral neck structure during adolescence.

Understanding femoral neck structure may be critical to preventing fractures at this site. We examined the correlates of changes in the femoral neck during adolescence. Dual energy x-ray absorptiometry measurements of proximal femora were made in 101 Caucasian youths (ages 9 to 26 years). Relationships were examined between developmental parameters (age, pubertal stage, height, body mass, lean mass, and fat mass) and femoral structure (bone mineral content, bone mineral density, neck width, cross-sectional area, and cross-sectional strength). Lean body mass was the best predictor of femoral neck structure, explaining 53-87 percent of the variance, and was independent of gender. Body mass only explained 51-79 percent of the variance. Previously we found body mass to be the strongest predictor of femoral mid-diaphyseal cross-sectional properties. These findings suggest that trabecular bone of the femoral neck may be more responsive to its mechanical environment than the cortical diaphysis. In addition, lean body mass may be a more reliable predictor of muscle loading than body mass.

Absorptiometry, Photon↗
PubMedDate not supplied

Musculoskeletal health and the older adult.

A decline in muscle mass and function, and in the mass and integrity of the skeletal system, are well-known consequences of aging. These changes impinge on the functional performance required for independent living and contribute to frailty and fracture risk. Resistance exercise has been shown to be an effective mode to circumvent age-related changes in the muscular system, although the benefit of exercise on bone mass in the aging skeleton is comparatively modest at best. This brief review highlights results from several studies that we have undertaken in older adults, examining aspects of the resistance training prescription as well as the potential beneficial role of hormones. What is common to all of these studies is the high degree of residual plasticity that remains in aging skeletal muscle. Risk factors for falls and fracture include reduced bone mass, muscle weakness, impaired balance, and lessened visual acuity. Among these, only muscle strength is reliably enhanced with resistance exercise, which may aid in reducing hip fracture risk as well as improving the ability to undertake daily activities and maintain independence.

Adaptation, Physiological↗