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Biomedical subjects

A K Das

Publications and source records attributed to A K Das.

At least 127 records · Page 7Linked to original sources
PubMed1995

A simple chemical synthesis of the ether analog of lysophosphatidylcholine and platelet-activating factor.

A simple chemical procedure for synthesis of 1-O-alkyl-(rac or sn)-glycero-3-phosphocholine (alkyl analog of lysophosphatidylcholine, II) and platelet activating factor (PAF), 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (III) has been described. The key step of the method is the decomposition of 1-O-hexadecyl-3-diazohydroxyacetone (A. K. Hajra, T. V. Saraswathi and A. K. Das, 1983. Chem. Phys. Lipids. 33: 179-193) with phosphocholine to synthesize 1-O-hexadecyl dihydroxyacetone-3-phosphocholine (I). Conditions for this phosphorolysis were studied with respect to the reaction medium, temperature, and optimum proportion of the reactants. Compound (I) was quantitatively reduced with NaBH4 to synthesize (II) which was acetylated to prepare compound (III). Phospholipase A2 hydrolysis of compound (III) followed by separation of the products afforded the unreacted sn-3-hexadecyl isomer (III) and sn-1-hexadecyl isomer (II) which was acetylated to PAF. The structures of the compounds were verified by NMR and FAB-MS spectra, and their biological activities were determined by measuring the release of serotonin from rabbit blood platelets in response to different doses of these compounds. The suitability of the method as a general technique for synthesis of different ether phosphoglycerides is discussed.

Animals↗
PubMed1994

Human erythrocyte membrane protein 4.2 is palmitoylated.

Protein 4.2 is a major protein of the human erythrocyte membrane. It has previously been shown to be N-myristoylated. After labeling of intact human erythrocytes with [3H]palmitic acid, radioactivity was found to be associated with protein 4.2 by immunoprecipitation of peripheral membrane proteins extracted at pH 11 from ghosts with anti-(4.2) sera, followed by SDS/PAGE and fluorography. The fatty acid linked to protein 4.2 was identified as palmitic acid after hydrolysis of protein and thin-layer chromatography of the fatty acid extracted in the organic phase. Protein 4.2 could be depalmitoylated with hydroxylamine, suggesting a thioester linkage. Depalmitoylated protein 4.2 showed significantly decreased binding to protein-4.2-depleted membranes, compared to native protein 4.2.

Blood Proteins↗
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↗
PubMed1994

A temporal query system for protocol-directed decision support.

Chronus is a query system that supports temporal extensions to the Structured Query Language (SQL) for relational databases. Although the relational data model can store time-stamped data and can permit simple temporal-comparison operations, it does not provide either a closed or a sufficient algebra for manipulating temporal data. In this paper, we outline an algebra that maintains a consistent relational representation of temporal data and that allows the type of temporal queries needed for protocol-directed decision support. We also discuss how Chronus can translate between our temporal algebra and the relational algebra used for SQL queries. We have applied our system to the task of screening patients for clinical trials. Our results demonstrate that Chronous can express sufficiently all required temporal queries, and that the search time of such queries is similar to that of standard SQL.

Clinical Protocols↗
PubMed1994

Total bladder replacement by detubularised sigmoid colon segment.

A preliminary report of 3 cases of carcinoma bladder is presented in whom, after radical cystoprostatectomy, a low pressure neobladder is created from detubularised pelvic colon, with subsequent colo-urethral anastomosis. In selected cases, this is a feasible procedure with good patient acceptance as the normal body image is maintained. Also the low pressure neobladder ensures protection to the upper urinary tract from backpressure damage.

Adult↗
PubMed1994

Synthesis and anthelmintic activity of 3-substituted 5-methylthio-isoxazoles.

Isoxazole derivatives have been shown to possess antiparasitic activity. In the present study, 3-substituted 5-methylthio-isoxazoles were synthesized and tested for anthelmintic activity, along with some other isoxazoles which have been reported but not tested earlier. Nine compounds (2a, 2b, 2e, 2g, 2u, 3a, 3b, 3e and 3f) showed activity against both A. ceylanicum and N. dubius in vitro. Twelve compounds (2a, 2b, 2d, 2e, 2f, 2h, 2l, 2n, 2o, 2u, 3d and 3e) showed activity against N. dubius in vivo, a parasite of veterinary importance.

Ancylostoma↗
PubMed1994

A temporal-abstraction mediator for protocol-based decision-support systems.

The inability of many clinical decision-support applications to integrate with existing databases limits the wide-scale deployment of such systems. To overcome this obstacle, we have designed a data-interpretation module that can be embedded in a general architecture for protocol-based reasoning and that can support the fundamental task of detecting temporal abstractions. We have developed this software module by coupling two existing systems--RESUME and Chronus--that provide complementary temporal-abstraction techniques at the application and the database levels, respectively. Their encapsulation into a single module thus can resolve the temporal queries of protocol planners with the domain-specific knowledge needed for the temporal-abstraction task and with primary time-stamped data stored in autonomous clinical databases. We show that other computer methods for the detection of temporal abstractions do not scale up to the data- and knowledge-intensive environments of protocol-based decision-support systems.

Artificial Intelligence↗
PubMed1994

Knowledge-based temporal abstraction for diabetic monitoring.

We have developed a general method that solves the task of creating abstract, interval-based concepts from time-stamped clinical data. We refer to this method as knowledge-based temporal-abstraction (KBTA). In this paper, we focus on the knowledge representation, acquisition, maintenance, reuse and sharing aspects of the KBTA method. We describe five problem-solving mechanisms that solve the five subtasks into which the KBTA method decomposes its task, and four types of knowledge necessary for instantiating these mechanisms in a particular domain. We present an example of instantiating the KBTA method in the clinical area of monitoring insulin-dependent-diabetes patients.

Artificial Intelligence↗
PubMed1993

Cardiac autonomic function in fibrocalculous pancreatic diabetes.

Cardiac autonomic function was evaluated in 23 patients with fibrocalculous pancreatic diabetes (FCPD). Though none of the patients had any symptoms referable to autonomic dysfunction, 5 had abnormal heart rate responses. The variability in the heart rate in response to deep breathing was the earliest abnormality found in our patients. Four of the 5 patients had clinical evidence of neuropathy while all 5 had retinopathy and overt nephropathy. We therefore conclude that the autonomic nervous system can be involved in patients with FCPD even as early as 2 years after the onset of the disease, and thus that evaluation of the autonomic nervous system should be part of the routine evaluation of all patients with FCPD.

Adolescent↗
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↗