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Biomedical subjects

S Saha

Publications and source records attributed to S Saha.

At least 217 records · Page 12Linked to original sources
PubMed1990

Maternal mortality.

Maternal mortality in Chittaranjan Seva Sadan, Calcutta, in 1983, 1985 and 1986 was 2.45, 3.01 and 2.8 per thousand respectively. Abortion contributed a little in 1983 and 1985, whereas it was 15.7% in 1986. Haemorrhage was the commonest single cause of death in 1983 (28%) and 1985 (21.4%) as opposed to eclampsia in 1986 (28.9%). Infective hepatitis during pregnancy and labour was the commonest indirect cause of maternal mortality followed by anaemia. Usual difficulties like lack of antenatal care, multiparity, low socio-economical status, illiteracy, etc, in populated developing countries are responsible for this sad state of affairs in this country as well.

Female↗
PubMed1990

Biomechanical comparison of slotted and nonslotted interlocking nails in distal femoral shaft fractures.

The torsional and compressive biomechanical characteristics of slotted and nonslotted interlocking nails in distal femoral shaft fractures were evaluated. Slotted (Grosse-Kempf) and nonslotted (Russell-Taylor) locked nail systems were implanted in anatomic specimen femora, which were then tested in torsion and axial compression. For torsional studies, each femur was transversely sectioned distal to the isthmus; for axial loading, a distal 3-cm section of bone was removed. The mean peak torsional stiffness of the femora fixed with nonslotted nails was 0.955 Nm per degree, which was significantly greater than that (0.300 Nm per degree) for the femora fixed with the slotted nails. However, when loaded to failure in compression, the nonslotted nail group failed at a mean load of 2490 N compared with 3050 N for the group fixed with the slotted devices. These results could be due in part to the lesser rigidity of the slotted nail, which may have facilitated greater load sharing with bone and increased resistance to compression failure.

Biomechanical Phenomena↗
PubMed1989

Electric and dielectric properties of wet human cancellous bone as a function of frequency.

In this study the electrical and dielectric properties of wet human cancellous bone from distal tibiae were examined as a function of frequency and direction. The resistance and capacitance of the cancellous bone specimens were measured at near 100% relative humidity. The measurements were made in all three orthogonal directions at discrete frequencies ranging from 120 Hz to 10 MHz using an LCR meter. At a frequency of 100 kHz, the mean resistivity and specific capacitance for the thirty cancellous bone specimens were 500 ohm-cm and 8.64 pF/cm in the longitudinal direction, 613 ohm-cm and 15.25 pF/cm in the anterior-posterior direction, and 609 ohm-cm and 14.64 pF/cm in the lateral-medial direction. All electrical and dielectric properties except the resistivity and the impedance were highly frequency dependent for the frequency range tested. All electrical and dielectric properties were transversely isotropic as the values for the longitudinal direction were different from values obtained for the two transverse directions and properties in the two transverse directions were approximately similar.

Aged↗
PubMed1989

Activation of prophage P4 by the P2 Cox protein and the sites of action of the Cox protein on the two phage genomes.

Phage P2 induces the unrelated prophage P4. In this paper we show that this is due to the activation of the P4 late promoter PII by the P2 Cox protein. This is in contrast to the effects of Cox on P2, for which it is known from previous work that it acts as a repressor of the promoter Pc, which is responsible for expression of the immunity repressor C. The activator role of Cox was revealed by its effect on replication of P4 DNA and on the formation of chloramphenicol acetyltransferase when a promoterless cat gene was inserted downstream of the P4 PII promoter. DNase I protection studies revealed that the Cox protein binds to the repressor promoter Pc of phage P2 and to the promoter PII of phage P4. In the latter case the Cox protein binds upstream of the -35 region, in analogy to several other activators of promoters. A weak binding was found in the promoters Pe of phage P2 and Ple of phage P4. The Cox protein is a case of viral transactivation of the replication genes of one phage by a control protein of the other. However, the effects of the Cox protein are totally different in the two phages, repressive in one case and activating in the other.

Base Sequence↗
PubMed1989

Carcinoid tumors of the gastrointestinal tract: a 44-year experience.

We retrospectively studied 112 patients treated for gastrointestinal carcinoid tumors between 1942 and 1986. The three most common sites were jejunum-ileum (27%), rectum (27%), and appendix (21%), followed by colon (12%), duodenum (9%), and stomach (4%). Seventy-five percent of patients had localized disease, primarily in the rectum and appendix. Colon and small bowel tumors were often manifested with metastatic disease. Complete surgical excision of all localized disease was curative in 94% of patients. Corrected five- and ten-year survival rates were 90% and 58%, respectively, in cases of localized disease, whereas in stage III disease, the rates were 46% and less than 30%, respectively. All patients with liver metastasis died within 25 months. A second malignancy, most often adenocarcinoma of the colon, occurred in 25% of patients. Carcinoid syndrome was found in 6% of patients. The best survival rates were noted for appendiceal and rectal carcinoids, and the worst for colon and stomach carcinoids.

Actuarial Analysis↗
PubMed1989

Immunobiological relationships among new cholera toxins produced by CT gene-negative strains of Vibrio cholerae O1.

The enterotoxic activities of partially purified new cholera toxins (NCT) prepared from the CT gene-negative strains of Vibrio cholerae serotype O1 isolated from cases of diarrhoea in man and from diverse environmental sources were assayed in the rabbit ileal-loop model and the toxin unit was calculated in micrograms of protein content. The secretory activities of one unit of homologous and heterologous enterotoxins were completely neutralised by 2.5 units of crude antiserum raised against one NCT preparation. In immunodiffusion tests, the NCT preparations from all strains tested gave precipitin bands against one antiserum showing reaction of complete identity. Thus, the present study clearly demonstrated that NCTs elaborated by CT gene-negative strains of V. cholerae O1 are immunobiologically similar.

Cholera Toxin↗
PubMed1989

Analysis of mechanical factors affecting fixation of olecranon fractures.

Fractures of the most distal part of the olecranon process differ from more proximal fractures because a plane of instability exists between the humerus and the radial head. Thus, the fixation of these fractures must resist the deforming forces of the forearm flexor muscles. The investigators fixed 10 paired cadaver ulnae with either the tension-band wire technique or a one-third tubular plate, and tested the specimens to simulate the effect of the biceps and brachialis muscles. The average maximum fixation stiffness for specimens fixed with the one-third tubular plate was found to be 163 N/mm compared with 53 N/mm for the tension-band wire group. This study indicates that for fractures of the distal part of the olecranon, fixation with screws and a one-third tubular plate affords better resistance to the forces applied by the brachialis and the biceps brachii than the tension-band wire technique.

Biomechanical Phenomena↗
PubMed1989

Neutralisation of the new cholera toxin by antiserum against crude enterotoxin of cholera toxin gene-positive Vibrio cholerae 01 in rabbit ileal loop model.

The enterotoxicity of the new cholera toxin (NCT) prepared from cholera toxin gene-negative (CT-) V. cholerae 01 strains isolated from human diarrhoeal and environmental sources was assayed in rabbit ileal loops and the toxin unit was calculated to be 24 micrograms of protein. The enterotoxicity of the NCT preparations were completely neutralised by the antiserum raised against the enterotoxin preparation from the CT+ V. cholerae 01 strain 569B at 1 in 16 dilution in ileal loops. The antiserum contained 1 unit of antitoxin in 85 x 10(-4) ml amount. The data indicate that the antiserum prepared against the enterotoxin of CT+ strain contains antibody against the NCT and can neutralise the toxin in vivo. The observations also suggest that CT+ strains liberate the NCT simultaneously with CT and the latter gets eliminated during the process of purification.

Animals↗
PubMed1988

Visualisation of CGRP and ChAT-like immunoreactivity in identified trigeminal neurones by combined peroxidase and alkaline phosphatase enzymatic reactions.

We report here a method that allows simultaneous visualisation of two antigens within single neurones. In essence this involves the combined use of horseradish peroxidase and alkaline phosphatase reactions to visualise two markers. Using this method we show that ChAT-and CGRP-like immunoreactivity can be co-localised within single neurones of the V to VII motor nuclei. In the case of the V motor nucleus, we show that each marker can be localised in motoneurones labelled with horseradish peroxidase.

Abducens Nerve↗
PubMed1988

Changes in plasma gangliosides in relation to tumor growth and their tumor-enhancing effect.

Gangliosides in the plasma of Ehrlich ascites tumor-bearing mice showed changes, both quantitative and qualitative, with progress of tumor. Quantitative changes assessed by chemical estimation indicated a gradual increase of gangliosides up to day 6 of tumor growth followed by a decline leading to a level below the normal by day 12. Qualitative changes studied by thin-layer chromatography indicated appearance of new gangliosides in the plasma of tumor-bearing mice, which were absent from normal plasma. One of these gangliosides appears to be of tumor-cell origin. Gangliosides obtained from tumor-bearing mouse plasma enhanced tumor growth when adoptively transferred with tumor cells into normal mice.

Animals↗
PubMed1987

The cox protein of bacteriophage P2 inhibits the formation of the repressor protein and autoregulates the early operon.

The cox gene is the first gene of the early operon of bacteriophage P2. The early promoter Pe and the repressor promoter Pc are located close to each other and in such a way that their transcripts have opposite polarity and show an overlap of about 30 nucleotides. The expression of the early operon and of the C gene was studied in vivo by using fusions to a promoterless cat (chloramphenicol acetyl transferase) gene. The results show that the Cox protein negatively autoregulates the early operon and inhibits the formation of the repressor C. By measuring the efficiency of plating of a series of P2 virulent deletion mutants on bacteria carrying a cloned cox gene, the site of action of the Cox protein was mapped within the Pe-Pc region. The stimulatory effect of the C protein on expression of the Pc promoter was found to be due to inhibition of transcription from Pc; this was demonstrated by mutating Pe which showed that loss of transcription from Pe stimulated transcription from Pc. Hence, this is a case of regulation of gene expression by convergent transcription. By cloning the region C-Pe-Pc-cox such that the cat and kan genes are expressed from Pc and Pe, respectively, it was shown that only one of the resistances (Cm and Km) was expressed. This mimics the choice between lysogeny and lytic growth of the phage. The 'lysogenic' state was very stable whereas the 'lytic' state flipped to the 'lysogenic' at a somewhat higher frequency. The presence of a cloned cox gene drastically stimulated the formation of free phage from a P2-lysogen and dramatically reduced the frequency of lysogenization after P2 infection. We conclude that the pleiotropic effects of the cox (control of excision) gene, namely effects on lysogenization, formation of free phage and site-specific P2 recombination, can be explained by the effect of the Cox protein on the activity of the promoters Pc and Pe.

Amino Acid Sequence↗
PubMed1987

Autoregulation of bacteriophage P2 repressor.

The immunity repressor of bacteriophage P2 regulates the two convergent promoters, Pe and Pc, located in the early control region. Pe is the early promoter which is negatively regulated by the repressor. It was found, by DNase I protection studies, that the P2 repressor enhances the binding of RNA polymerase to Pc. Furthermore, under in vivo conditions the transcription initiated at Pc, measured as chloramphenicol acetyl transferase gene expression, is low in the absence of repressor but is stimulated by low repressor levels. With increasing repressor concentrations transcription from the Pc promoter decreases. Thus, the P2 repressor both negatively and positively regulates its own promoter.

Base Sequence↗
PubMed1987

Thermal analysis of the bone surface induced by laser radiation.

High energy laser has emerged to be an important surgical tool in medical technology. However, the application of laser energy to drill or cut a bone is still in an experimental state. In order to estimate the adequacy of laser heating of bone surface and at the same time minimize the damage to the bone tissue, we developed a mathematical model of the temperature distribution in bone due to laser irradiation. The thermal analysis shows that the temperature distribution depends on several parameters, including the density, the specific heat, and the thermal conductivity of the osseous tissue.

Bone and Bones↗