Search PubMed⌕ Search

Biomedical subjects

S K Guha

Publications and source records attributed to S K Guha.

At least 73 records · Page 4Linked to original sources
PubMed1977

Absorption spectra of bone.

Absorption spectra of human bone and its two major constituents (collagen and apatite) were obtained in the wavelength region extending from 2000 to 12,000 A. In the last two cases a minimum transmission (maximum absorption) was uniformly observed in the ultraviolet region. The two samples after exposure to ultraviolet radiations show a shift in the peak positions. Absorption peaks in the total bone spectra are not reproducible in its two constituents. After exposure to UV radiations the position of maximum absorption is displaced. A possible interpretation of the observed results is presented.

Apatites↗
PubMed1976

The synthesis and accumulation of polyamines in reproductive organs of the rat during pregnancy.

The pregnancy of the rat brings about profound changes of the accumulation, biosynthesis and biodegradtion of the polyamines putrescine, spermidine and spermine in the reproductive tissues. 1. In the ovary, the concentration of all polyamines increased markedly around the 12th day of pregnancy. In the uterus, only the concentration of spermine rose at that time. The concentration of purtrescine more than doubled in the fetal part of the placenta around the 15th day of pregnancy, while the low content of putrescine in the maternal placenta did not appreciably change during the progress of pregnancy. Both parts of rat placenta contained relatively high initial concentrations of spermine, which however, rapidly decreased until the term. 2. The activity of ornithine decarboxylase (EC 4.1.1.17) was remarkably high in the placental tissue. The fetal part of the placenta exhibited higher ornithine decarboxylase activity from the very beginning and the enzyme activity also remained at high levels throughout the pregnancy. The initially high orthine decarboxylase activity was very low in the uterus during the early days of pregnancy, however, rapidly increased a few days after the implantation. Uterine ornithine decarboxylase activity reached a maximum on day 12 to 14 of pregnancy and then swiftly decreased. 3. Both parts of the placenta contained high diamine oxidase (EC 1.4.3.6) activity, which, however, rapidly disappeared in the fetal part of the placenta. Although considerably decreasing, the activity of diamine oxidase still was remarkably high in the maternal placenta until the term. No diamine oxidase activity was found in the uterus of normally cycling rats. The enzyme activity was also undetectable in the uterus during the early pregnancy, but abruptly appeared on day 10 of pregnancy, reached a maximum around the 15th day of pregnancy, and therafter gradually decreased until the term. 4. The changes of activity of adenosylmethionine decarboxylase (EC 4.1.1.50) in the uterus and placental tissues resembled those changes found in ornithine decarboxylase activity. The activity of adenosylmethionine decarboxylase also rapidly decreased after day 12 of pregnancy. 5. Uterine diamine oxidase was partially purified (about 30-fold) and its substrate specificity was determined. Diamines putrescine, cadaverine and 1,3-diaminopropane served as most efficient substrates for the enzyme. Some evidence is presented as to indicate that also spermidine and spermine were oxidized by the enzyme, although at much slower rate than the diamines...

Amine Oxidase (Copper-Containing)↗
PubMed1976

In vivo motility of the unobstructed fallopian tube.

Current methods of recording the fallopian tube motility in vivo essentially measure the intraluminal pressure. Diametral change is another parameter which can provide additional useful information related to tubal function. A method for in vivo monitoring of diametral change without obstructing the lumen and based on the impedance measurement technique has been proposed. An in vitro comparison of wall displacement with transtubal electrical impedance change shows that the impedance changes reflect diametral changes. Another in vitro experiment in which the autorhythmicity of contractions was maintained by means of a perfusion bath indicates that the impedance changes are primarily due to the contraction of the circular muscles of the fallopian tube. These studies were followed up with long-term chronic implantations with dual probes on the isthmic and ampullar regions of the tube in female rabbits. Inpedance changes over periods as long as 6 mo could be readily obtained. Histological observations as well as fertility studies support the conclusion that the tube is minimally affected by the placement of the probes.

Animals↗
PubMed1976

Decarboxylation of ornithine and adenosymethionine in rat ovary during pregnancy.

The activities of L-ornithine decarboxylase (EC 4.1.1.17) and S-adenosyl-L-methionine decarboxylase (EC 4.1.50) fluctuate markedly in rat ovary during the normal oestrous cycle. Ovarian ornithine and adenosylmethionine decarboxylases also showed profound changes during pregnancy of the rat. Both enzyme activities were remarkably low in the ovary through the first 11 days of pregnancy, but sharply increased at the time the placenta is formed in the rat. The enzyme activities remained elevated almost until term. It appears that the stimulated of polyamine synthesis in rat ovary, as reflected by the enhanced decarboxylation of ornithine and adenosylmethionine, is associated with the growth of the ovarian tissue rather than the secretory function of the corpus luteum during pregnancy.

Adenosylmethionine Decarboxylase↗
PubMed1976

A simple and inexpensive clinical whole body counter.

The conventional radioisotope scanner has been used as a whole body counter. The background index of the system is 10.9 counts per minute per ml of sodium iodide crystal. The sensitivity and derived sensitivity parameters have been evaluated and found to be suitable for clinical studies. The optimum parameters for a single detector at two positions above the lying subject have been obtained. It has been found that for the case of 131I measurement it is possible to assay a source located at any point in the body with coefficient of variation less than 5%. To add to the versatility, a fixed geometry for in-vitro counting of large samples has been obtained. The retention values obtained by the whole body counter have been found to correlate with those obtained by in-vitro assay of urine and stool after intravenous administration of 51Cr-albumin.

Background Radiation↗
PubMed1975

The effect of ultraviolet radiation on the electrical conductivity of human bone.

The electrical conductivity of intact bone, collagen and apatite mineral was determined in the region of moderately high fields. After exposure to ultraviolet (UV) radiation the conductivity of the specimens was redetermined. Following exposure marked decreases in electrical conductivity occurred in all specimens. The possible modes of interaction of UV radiation with bone are discussed. It is suggested that protonic conduction may be an important mode of charge transport in bone.

Apatites↗
PubMed1974

Transthoracic electrical impedance in cases of high-altitude hypoxia.

Changes in transthoracic electrical impedance (T.E.I.) due to high-altitude hypoxia (3,658 m) have been measured in 20 young, healthy Indian soldiers. They were first studied at sea level (198 m) and then rapidly transported by air to 3,658 m, where they were studied daily from day 1 to day 5 and then on days 8 and 10. The mean (+/-S.D.) T.E.I. at sea level (34.6+/-0.6Omega) fell sharply to 29.6+/-0.8Omega, 30.3+/-0.9Omega, and 30.5+/-1.1Omega on days 1, 2, and 3 (P <0.001) and levelled off at 31.5+/-0.7Omega on day 10, which was comparable to the mean value obtained in 13 persons permanently resident at high altitude (32.2+/-0.7Omega). Five sea-level residents who had acute mountain sickness (A.M.S.) or high-altitude pulmonary oedema (H.A.P.O.) had a still lower mean value (22.5+/-1.1Omega). One normal healthy subject who at sea level had a T.E.I. of 34.7Omega developed H.A.P.O. when the T.E.I. fell to 21.1Omega. Ninety minutes after the administration of 80 mg of intravenous frusemide the value increased to 35.5Omega. In another subject with A.M.S. who received 40 mg of frusemide intravenously the T.E.I. rose from 21.9 to 33.2Omega.Since the study was non-invasive the changes in impedance could not be correlated objectively with alterations in either pulmonary blood volume or pulmonary extravascular water space. In the subject, however, with x-ray evidence of H.A.P.O. and a low T.E.I. intravenous frusemide produced a marked rise in T.E.I. together with clearing of the chest x-ray picture within 24 hours, indicating an inverse relationship between impedance and thoracic fluid volume. It is suggested that with further objective verification in man the measurement of T.E.I. may be a potentially promising technique for the early detection of increased pulmonary fluid volume.

Adult↗