Biomedical subjects

S Saha

Publications and source records attributed to S Saha.

296 records · Page 17Linked to original sources

PubMedDate not supplied

Menstrual irregularity and stress fractures in collegiate female distance runners.

From 240 questionnaires, we investigated the prevalence of stress fractures in competitive collegiate female long distance runners and its relationship to menstrual history. The runners were divided into three groups according to their menstrual history: very irregular 69/240 (0 to 5 menses/year), irregular 51/240 (6 to 9 menses/year), and regular 120/240 (10 to 13 menses/year). Stress fractures occurred in 49% of the very irregular runners, 39% of the irregular runners, and 29% of the regular runners. The majority of the stress fractures occurred in the tibia. Runners who had never used oral contraceptives were over twice as likely to have had a stress fracture when compared with runners who had used oral contraceptives for more than 1 year. These data suggest that female distance runners who have a history of irregular or absent menses and who have never used oral contraceptives may be at an increased risk for developing a stress fracture. When amenorrheal runners were separated from the very irregular group, an alarming trend was noted in eating behavior disorders. Forty-seven percent of the amenorrheal group, 20% of the one to five menses/year group, 10% of the irregular group, and 7% of the regular group admitted to an eating behavior disorder.

Adult↗

PubMedDate not supplied

Do patients choose physicians of their own race?

This study seeks to determine whether minority Americans tend to see physicians of their own race as a matter of choice or simply because minority physicians are more conveniently located within predominantly minority communities. Using data from the Commonwealth Fund 1994 National Comparative Survey of Minority Health Care, we found that black and Hispanic Americans sought care from physicians of their own race because of personal preference and language, not solely because of geographic accessibility. As minority populations continue to grow, the demand for minority physicians is likely to increase. Keeping up with this demand will require medical school admissions policies and physician workforce planning to include explicit strategies to increase the supply of underrepresented minority physicians.

Adult↗

PubMedDate not supplied

Functional analysis of conserved motifs in type III restriction-modification enzymes.

EcoP1I and EcoP15I are members of type III restriction-modification enzymes. EcoPI and EcoP15I DNA methyltransferases transfer a methyl group from S-adenosyl-L-methionine (AdoMet) to the N6 position of the second adenine residues in their recognition sequences, 5'-AGACC-3' and 5'-CAGCAG-3' respectively. We have altered various residues in two highly conserved sequences, FxGxG (motif I) and DPPY (motif IV) in these proteins by site-directed mutagenesis. Using a mixture of in vivo and in vitro assays, our results on the mutational analysis of these methyltransferases demonstrate the universal role of motif I in AdoMet binding and a role for motif IV in catalysis. All six cysteine residues in EcoP15I DNA methyltransferase have been substituted with serine and the role of cysteine residues in EcoP15I DNA methyltransferase catalysed reaction assessed. The Res subunits of type III restriction enzymes share a distant sequence similarity with and contain the motifs characteristic of the DEAD box proteins. We have carried out site-directed mutagenesis of the conserved residues in two of the helicase motifs of the EcoP1I restriction enzyme in order to investigate the role of motifs in DNA cleavage by this enzyme. Our findings indicate that certain conserved residues in these motifs are involved in ATP hydrolysis while the other residues are involved in coupling restriction of DNA to ATP hydrolysis. Taken collectively, these results form the basis for a detailed structure-function analysis of EcoP1I and EcoP15I restriction enzymes.

Adenosine Triphosphate↗

PubMedDate not supplied

Bioengineers, health-care technology and bioethics.

Technology has created moral dilemmas in recent years creating an increased interest in the field of bioethics, which affects engineers in biomedicine, physicians, other health-care professionals, and society in general. For example devices like the kidney dialysis machine or Nuclear Magnetic Resonance (NMR) diagnostic scanner demonstrate state-of-the-art capabilities, yet they are very expensive. Therefore, standards of the past involving health care and allocation of resources are changing, and professionals must be aware of this change, as well as the responsibility for complete testing and review during the research and development process of medical devices. In this paper, we illustrate technological impact and stress the necessity of an understanding of ethics in order to deal effectively with product liability, conflicts of interests, and allocation of scarce resources. Hopefully, this will result in awareness and education in ethics and professional responsibilities.

Bioethical Issues↗

PubMedDate not supplied

Analysis of the current distribution in bone produced by pulsed electro-magnetic field stimulation of bone.

Pulsed electromagnetic stimulation is being increasingly used by orthopaedic surgeons to treat non-unions and congenital pseudoarthrosis. In this paper a theoretical model is developed to analyze the distribution of induced current in bone due to a pulsed electromagnetic field, produced by a pair of Helmholtz coils. The result shows that the induced current density is dependent of the electrical properties of bone, geometry of the coils and their location.

Bone and Bones↗

PubMedDate not supplied

A pulsed electromagnetic stimulator for bone-growth studies.

A variable-pulse electromagnetic pulse generator has been developed to study the effect of the magnetic field on bone growth. The unit's repetition frequency can be varied from 2 to 200 Hz, and the peak current that it can drive is 10 A. The duty cycle of the pulse can be varied in steps of 10, 12.5, 17, 25, 50, 75, 83, 87.5, and 90% and is independent of the repetition frequency. The trailing edge of the output pulse can be controlled to produce any desired voltage-time pulse characteristic. This decay adjustment makes it possible to generate a variable-pulse frequency spectrum.

Amplifiers, Electronic↗

PubMedDate not supplied

A noncontacting electromagnetic device for the determination of in vivo properties of bone.

A noncontacting, electromagnetic device to monitor stress waves in bone has been developed. Since bone exhibits piezoelectric-like behavior, a propagating stress wave in bone generates both electric and magnetic fields. The present device detects the magnetic field and thus provides a measure of the stress-wave amplitude in the bone. Excised dry and wet human femora, as well as a model system consisting of a bar of strongly piezoelectric ceramic, were examined using the device. Magnetic signals associated with elastic waves were also recorded in the long bones of human volunteers. Since the observed signals are not perturbed by the mechanical quality of the soft tissue over the bone, the device may be used to quantitatively assess the mechanical properties of bone in vivo.

Bone Diseases↗

PubMedDate not supplied

Anticancer activities of 2,5,8,9-substituted 6-oxo-1,2,3,4,5,6-hexahydrophenanthridines on multi-drug-resistant phenotype cells.

Lycorine is a member of the alkaloid group from the bulb of the amaryllidaceae. This drug has been reported to have anticancer activity. Several synthetic intermediates obtained during the synthetic study of anticancer drugs based on the lycorine structure, were tested for anticancer activity using three cell lines: L1210 and HL60 cell lines which were resistant (R) or sensitive (S) to adriamycin. The two synthetic intermediates, 2-acetoxy- and 2-hydroxy-5-allyl-8,9-methylenedioxy-6-oxo-1,2,3,4,5,6-hexahydr ophenanthridine (1 and 2), both had anticancer activity in all three cell lines. However, the LD50 for the precursors was about 20 fold greater than for the native lycorine. Both 1 and 2 were cytotoxic to the adriamycin-resistant cell line, indicating that these drugs are not affected by the multidrug resistance factors. When low doses of the compounds were used, the HL60R cell line could be induced to differentiate to a cell which expressed a macrophage specific protein. These results suggest that phenanthridines 1 and 2 can be used on cells which are resistant to adriamycin, and that one mechanism of action is the induction of differentiation.

Animals↗