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Biomedical subjects

S K Basu

Publications and source records attributed to S K Basu.

At least 55 records · Page 3Linked to original sources
PubMed1995

Mapping of phase response properties of monopolar ECG voltages.

In the present investigation an attempt has been made to study the phase response properties of monopolar chest lead ECG voltages. Using a generator model of the heart an equivalent circuit of ECG network has been developed. The equivalent impedance between WCT and probe electrode has been determined by reduction techniques. From this equivalent impedance the phaser characteristics of monopolar ECG voltages have been analysed for change in probe electrode locations. The source of the generated voltage, i.e., the heart, will develop a different voltage for its different condition. There will also be a change in impedances. Thus for the normal subject the distribution of the phaser of the ECG voltages will be different from that of the abnormal one. A software tool has been developed to evaluate the relative phase response of ECG voltages. The data acquisition of monopolar ECG records of chest leads V1 to V6 from chart recorder has been done with the help of AutoCAD application package. The harmonic constituents of ECG voltages have been evaluated at each harmonic plane and the phase characteristics have been studied in polar coordinate for normal subjects as well as for a typical case. An interesting result has been observed in typical cases which are indicated in the paper.

Algorithms↗
PubMed1995

Physico-chemical properties and biological activities of erythromycin nalidixate.

Erythromycin nalidixate was prepared by combining nalidixic acid with erythromycin base. Thin-layer chromatographic studies and infrared absorption spectrum confirmed homogeneity of the new salt. The salt is very soluble in nonpolar solvent and freely soluble in polar solvent. The salt is quite stable at room temperature (30 +/- 1 degrees C). The antimicrobially active dose of the salt was found to be 820 micrograms/mg. Serum protein binding amounted to 85% and was reversible. LD50 in mice was found to be 371.5 mg/kg when the intraperitoneal route was used.

Animals↗
PubMed1995

Fate of DNA targeted to hepatocytes by asialoglycoprotein polylysine conjugates.

The data indicate that partial hepatectomy results in a decrease in degradation of targeted DNA. This appears to be due to an inhibition of the endocytotic pathway shortly after hepatectomy and is associated with the accumulation of targeted DNA within a population of light endosomal vesicles. It is likely that these vesicles serve as a reservoir from which targeted DNA gradually escapes and can be found in the nucleus. The DNA targeted to liver is capable of expressing the marker gene, and the DNA in the vesicles is transfection competent, suggesting that a substantial portion is intact. Overall, the receptor-mediated delivery system is highly efficient in transporting foreign DNA to liver cells. Partial hepatectomy and the ensuing cellular events provide a means of inhibiting the degradative portion of the endocytotic pathway. Pharmacological agents that can mimic the cellular processes that occur after partial hepatectomy may be useful in increasing the duration of foreign gene expression without the trauma of surgery.

Animals↗
PubMed1994

Enhanced intracellular delivery of doxorubicin by scavenger receptor-mediated endocytosis for preferential killing of histiocytic lymphoma cells in culture.

A conjugate of the antineoplastic drug doxorubicin (DXR) with maleylated bovine serum albumin (MBSA) was taken up by a human histiocytic lymphoma cell line (U937) through the high efficiency process of scavenger receptor-mediated endocytosis resulting in a sixfold higher intracellular concentration of the drug compared to that obtained when the free drug was administered. Compared to the free drug, the drug conjugate showed significantly higher cytotoxicity towards U937 cells presumably because of intracellular availability of a pharmacologically active form of the drug. The intracellular product released after lysosomal degradation of the drug conjugate was chromatographically identical to free DXR. These findings merit serious consideration in the development of new chemotherapeutic agents for the treatment of histiocytic malignancies.

Albumins↗
PubMed1994

Low-level X-ray exposures on rat skin. Hyperkeratinization and concomitant changes in biometal concentration.

Integumentary structures naturally are more exposed to solar radiation than other body tissues, so there is a big question regarding the biological threshold of skin in respect to low-dose ionizing radiation. In this study, adult male albino rats were exposed chronically to low-dose (0.015 cGy/sec) X-rays for 9 and 18 mo, with total X-ray dose of 2.025 and 4.050 cGy, respectively. In both the dose groups, hyperkeratinization was noted in skin by transmission electron microscopic (TEM) study. Atomic absorption spectrometric (AAS) study revealed decreased zinc concentration (p < 0.01), increased iron concentration (p < 0.001), and status quo cadmium concentration. Moreover, the ratio between zinc and iron became highly depleted in both the irradiated groups. Hence it may be stated that chronic low-level X-rays induce redistribution of biometals in the skin. Nevertheless, specific concentrations of biometals indicate the risk-prone status of irradiated skin.

Animals↗
PubMed1994

Trace metal levels of X-ray technicians' blood and hair.

Medical X-ray technicians are exposed to low-level ionizing radiation in their occupational field. There are very few data on low-dose radiation effects. The present study was designed to estimate few vital trace metals (Zn, Cu, Fe) in indicator tissues (blood and hair) of X-ray technicians and non-X-ray technicians (hospital employees were used as controls) by Atomic Absorption Spectrometry (AAS). This analysis noted a significant increase in Zn, Cu, and Fe concentrations in X-ray technicians' hair. But in blood, Zn and Cu were depleted, whereas Fe was increased. Such changes in trace metal concentrations among X-ray technicians were noted where occupational exposure to radiation was for longer than three years. Through composite risk analysis, by using Zn:Fe as an indicator, it was noted that blood gave a stronger indication than hair in analyzing and estimating risk.

Adult↗
PubMed1994

Alteration of spermatozoal structure and trace metal profile of testis and epididymis of rat under chronic low-level X-ray irradiation.

This study investigates the short-term as well as long-term effects of low-level X-ray irradiation on the Spermatozoal structure and trace metal (Zn, Fe, Cu, and Cd) contents in the testis and epididymis of whole-body irradiated albino rats. Male rats were exposed to 0.675, 1.350, 2.700, and 4.050 cGy of X-ray intermittently in 45, 90, 180, and 270 equal fractions (each fraction of 0.015 cGy s-1), respectively. SEM study had revealed numerous fusiform swelling in sperm tail in most of the x-irradiated groups. Moreover, in 2.700 and 4.050 cGy dose groups, the tail sheath of several sperm were eroded out. In the TEM study, damage in microtubules of sperm tail in 4.050 cGy irradiated group was noted. The AAS study showed a transient increase in Zn content in 0.675 and 1.350 cGy dose groups, but its concentration was decreased in 2.700 and 4.050 cGy dose groups. Fe concentration was increased in all the cases in comparison to that of control group. Nevertheless, Cu and Cd contents were increased mostly in 2.700 and 4.050 cGy doses. Thus present findings probably throw some light regarding mammalian response threshold at low-level X-ray irradiation. Moreover, it raises questions regarding the validity of "safe dose ionizing radiation."

Animals↗
PubMed1993

Enhancement of tumouricidal activity of daunomycin by receptor-mediated delivery. In vivo studies.

A conjugate of the antineoplastic drug daunomycin (DNM) with maleylated bovine serum albumin (MBSA) bound to the transformed cells of a macrophage lineage with high affinity and saturation kinetics through scavenger receptors present on the surface of macrophages. Binding of MBSA-DNM by these cells led to efficient internalization and degradation of the ligand. When injected into mice, the drug conjugate was cleared rapidly from the circulation and accumulated in the macrophage-rich tissues, viz. liver, lung and spleen. MBSA-DNM suppressed the growth of J774A.1 tumour cells in BALB/C mice at much lower dosages of DNM relative to the free form of the drug. Thus, 50% reduction of the tumour mass was elicited by 0.8 micrograms of DNM in the conjugated form, whereas approximately 28 micrograms of the drug in the free form was necessary to achieve a similar antitumour effect. These findings merit serious consideration in the development of new chemotherapeutic agents for the treatment of histiocytic malignancies that involve cells of macrophage lineage bearing the scavenger receptors.

Animals↗
PubMed1993

Detection of structural and trace metal changes in scalp hair of radiographers.

Human scalp hair samples were collected from 24 medical radiographers and from 24 nonradiographers (control group) of matching age groups belonging to both sexes. Changes in zinc, copper, and iron content, as well as structural morphology of hair, were studied by atomic absorption spectrometry and scanning electron microscopy, respectively. Such studies revealed increases in zinc, copper, and iron concentrations along with varied types of cuticular damage in the radiographers' hair compared to that of nonradiographers. Present observations indicate the possibility of radiation hazards for radiation workers.

Adult↗
PubMed1993

Collagen, zinc & iron contents of rat skin irradiated with chronic low-dose X-ray.

The effects of very low-dose X-ray on collagen and Zn and Fe contents of rat skin were studied. CFS male rats were exposed to chronic, intermittent low dose X-radiation at the dose rate of 0.015 cGy/sec/day (7 days irradiation alternating with 7 days rest) for periods of three months and six months. Transmission electron microscopy showed hyalinization collagen on days 180 and 360 in the six months group. Atomic absorption spectrometry revealed significantly decreased zinc levels (P < 0.001) only on day 360 in six months group whereas iron increased significantly (P < 0.001) in all treated groups. This radiation induced redistribution of zinc and iron and subsequent changes in dermal collagen possibly confirm the hazardous effect of long term exposure to X-rays. Our findings also provide some information on the mammalian response threshold at low dose X-irradiation.

Animals↗
PubMed1993

Use of hydroxylamine in improving radio protection of a combination of 5-hydroxy L-tryptophan and a thiol compound (AET) in small mammals.

Radioprotective effectiveness has been evaluated by 30 day survival studies and protection to bone-marrow cells in mice after radiation exposure and this has been further established by 24 hr deoxycytidine excretion in urine of rats following 5 Gy whole body gamma irradiation and protection to superoxide dismutase enzyme in marrow cells and red blood corpuscles. Radioprotective effectiveness as well as the duration of radioprotection have been improved by the administration (ip) of hydroxylamine (20 mg/kg), a decarboxylase inhibitor, prior to the use of a combination of 5-hydroxy L-tryptophan (5-HTP, 70 mg/kg) and 2-aminoethylisothiuronium bromide hydrobromide (AET, 20 mg/kg) ip in small mammals before whole body gamma irradiation.

5-Hydroxytryptophan↗
PubMed1993

Cholesterol side-chain cleavage by immobilized cells of Rhodococcus equi DSM 89-133.

Side-chain cleavage of sterol and extracellular cholesterol oxidase activity were investigated using viable cells of R. equi DSM 89-133 immobilized in polyacrylamide gel. In batch culture, immobilized cells were active in side-chain cleavage of cholesterol for more than 30 days. Free or immobilized cells were incapable of side-chain cleavage in the absence of 2,2' dipyridyl; cholesterol oxidase was, however, produced in both the cases. Maximal activity of the immobilized cells was 60 to 70% of the free cells.

2,2'-Dipyridyl↗
PubMed1993

Experience in elective hepatic resection.

A study was conducted on 35 elective hepatic resections performed by one surgical team over a period of 5 years with 14% postoperative mortality. The indications for hepatic resection were primary hepatocellular carcinoma in 20 cases (57%) and metastatic tumours from colorectal cancer in 12 cases (34%). Underlying cirrhosis of liver was found co-existent in 35% of patients of hepatocellular carcinoma. The 3-year actuarial survival rate after resection for HCC and metastatic tumour was 30% and 42% respectively.

Adolescent↗
PubMed1992

Scavenger-receptor-mediated delivery of daunomycin elicits selective toxicity towards neoplastic cells of macrophage lineage.

Transformed cells of macrophage lineage such as J774A.1, P388D1 and IC21 take up and degrade a conjugate of the antineoplastic drug, daunomycin, with maleylated BSA with high efficiency and saturation kinetics through the scavenger receptors expressed on the surface of these cells. By contrast, transformed cells of non-macrophage lineage, namely L929, EL4, Bowes melanoma and CHO (Chinese-hamster ovary), do not take up and degrade the conjugate, indicating that these cells are scavenger-receptor-deficient. In the conjugated form, about 0.1 microM-daunomycin cause 50% inhibition in the uptake of [3H]thymidine by the receptor-bearing J774A.1 cells, whereas the receptor-deficient Bowes-melanoma cells are not affected. Free daunomycin (0.1 microM) does not significantly affect the uptake of [3H]thymidine by either cell type. Treatment of cells derived from intraperitoneal tumours induced in BALB/C mice by J774A.1 cells with 0.4 microM-daunomycin in the conjugated form for 5 h abolished their ability to form tumours in BALB/C mice. By contrast, transplantation of untreated cells or cells treated with free daunomycin under identical conditions led to tumour formation and subsequent death of the BALB/C mice. These results indicate that this modality for selective elimination of scavenger-receptor-bearing neoplastic cells may be useful for the treatment of histiocytic malignancies in which cells of macrophage lineage turn malignant.

Albumins↗