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Biomedical subjects

S Sarkar

Publications and source records attributed to S Sarkar.

At least 271 records · Page 15Linked to original sources
PubMed1992

Insect sex chromosomes, XI. 3H-TdR induces random aberrations in the X chromosome(s) of Gryllotalpa fossor (Orthoptera).

The pattern of titrated thymidine (3H-TdR), a direct precursor of DNA, induced aberrations on the X chromosome of Gryllotalpa fossor was examined. 3H-TdR produced aberrations randomly distributed over the entire length of the X chromosome; breaks were observed in both the eu- and the heterochromatic arms of the X chromosome in both the sexes. Since the eu- and the heterochromatic arms cannot be distinguished cytologically in this insect, the presence of aberrations on both arms of the same X chromosome in the male and damage to both X chromosomes in the female indicate that both euchromatic and heterochromatic regions (facultative or constitutive) are equally liable to aberrations induced by H-TdR. This is in contrast to the non-random induction of aberrations by 3H-UdR, which causes chromosome damage due to the proximity of the labeled RNA to the DNA template during transcription.

Animals↗
PubMed1992

Antithrombotic effects of a platelet fibrinogen receptor antagonist in a canine model of carotid artery thrombosis.

BACKGROUND AND PURPOSE: Platelet-fibrin thrombi in the lumen of atherostenotic carotid arteries may underlie transient ischemic attacks and cerebral infarction. For this reason, we investigated the antiplatelet and antithrombotic effects of a novel and potent platelet fibrinogen receptor (glycoprotein IIb/IIIa) antagonist (SK&F 106760). METHODS: The effects of 0.1-3.0 mg/kg i.v. SK&F 106760 on platelet aggregation were examined ex vivo in canine platelet-rich plasma (n = 20). In addition, the antithrombotic effects of SK&F 106760 were compared with those of aspirin in an acute canine model of extracranial carotid artery thrombosis with high-grade stenosis. Sham-operated (n = 4), vehicle-treated (n = 6), SK&F 106760-treated (n = 8), aspirin-treated (n = 9), and SK&F 106760+aspirin-treated (n = 5) dogs were examined. RESULTS: The intravenous administration of SK&F 106760 caused a dose-related inhibition of ex vivo platelet aggregation. In the carotid artery thrombosis model, an occlusive thrombus formed at stenotic sites in the region of the carotid bifurcation. The thrombogenic process caused a progressive reduction in carotid blood flow and reduced the cortical microvascular perfusion and electroencephalographic power. Based on nuclear magnetic resonance spectroscopy, the occlusive events depleted the stores of high-energy phosphates (adenosine triphosphate and phosphocreatine) and increased the lactate concentration in the forelimb somatosensory area of the parietal cortex. In this model, the administration of 1 mg/kg i.v. SK&F 106760 prevented thrombosis of the stenotic carotid artery. Consequently, neurophysiological, cerebral hemodynamic, and metabolic parameters were all improved significantly in the SK&F 106760-treated group. No dog receiving SK&F 106760 reoccluded during the 1-hour posttreatment observation period. In contrast, thrombosis of the carotid artery was associated with neurophysiological deterioration in six of the nine dogs treated with 5 mg/kg i.v. aspirin. Both spontaneous and evoked (increased carotid stenosis) aspirin-resistant thrombosis were abolished by SK&F 106760 treatment. CONCLUSIONS: These results suggest that antagonism of fibrinogen binding to platelet glycoprotein IIb/IIIa (the final common pathway for aggregation) may represent a new and more effective antithrombotic approach to the treatment of cerebral transient ischemic attacks and infarction associated with extracranial carotid artery disease.

Animals↗
PubMed1992

The cytoplasmic translational inhibitory RNA of chick embryonic muscle: cloning and sequence of a subspecies which is antisense RNA.

A cytoplasmic translation inhibitory ribonucleoprotein (iRNP), about 10-12S in size and containing a heterogeneous class of RNA (iRNA) in the 60-140 nucleotide size range, has been previously isolated from 13-14 day old chick embryonic leg and breast muscle. Both iRNA and iRNA are potent inhibitors of mRNA translation in vitro. A cDNA library for iRNA was prepared in pUC18 vector. The 114 nucleotide insert of one clone was subcloned in pBluescript vector. The in vitro transcript of this insert (only the 5'-3' orientation and not the reverse orientation) showed inhibition of muscle poly(A)+ mRNA translation in vitro. The derived sequence of the iRNA indicates that it is a new sequence in which 27 nucleotides at the 3' and 5' ends can form base paired stem. Hybridization experiments and sequence analysis indicate that this iRNA has complementary (antisense) sequence to a highly conserved domain of the 28S eukaryotic rRNA and to a 5' leader segment of a muscle mRNA. These results suggest that iRNA mediated translational inhibition may act as a novel mechanism of controlling cellular mRNA levels in embryonic muscle and thus, acts in conjunction with the transcriptional control of myogenesis.

Animals↗
PubMed1992

Gastric transposition & deltopectoral flap for peristomal recurrence following total laryngectomy--a case report.

Stomal recurrence following laryngectomy presents a difficult problem with an incidence of 8.3-15%. Wide excision of the recurrence with mediastinal dissection, although the operation of choice,m is technically demanding and has a high morbidity and mortality. We recommend a technically easier procedure for reconstruction after palliative excision and present a case to illustrate it.

Anastomosis, Surgical↗
PubMed1992

Prevalence of thumb sucking in children of Calcutta.

The prevalence study of thumb digital sucking carried out on 3-12-year- old 2517 children, 1293 boys & 1224 girls, with different socio-economic status, belonging to villages, suburbs and city areas of Calcutta revealed that non-nutritional sucking habit was predominantly seen in cities, and bottle feeding was found to be the main cause of this habit; in 3-6-year-old children the prevalence of the habit was more in boys than girls but it persisted more in boys with increase in age.

Bottle Feeding↗
PubMed1992

Detection of human papilloma virus types 16 & 18 DNA in cervical lesions of Indian women using in situ hybridization.

Fifty one biopsies from women with malignant lesions of the uterine cervix and 9 biopsies fron non-malignant lesions were examined for the presence of HPV 16 and 18 DNA sequences by in situ hybridization method using 35S-labelled DNA probes. HPV 16 DNA sequences were detected in 82.4 per cent biopsies from women with malignant lesions, whereas HPV 18 DNA was detected in only 3 biopsies which were also positive for HPV 16 DNA. Two biopsies from non-malignant lesions were positive for HPV 16 DNA only. Data were also analysed according to the histologic type of cancer. It was observed that no significant correlation existed between HPV types and different histologic types of cervical cancer.

DNA Probes, HPV↗
PubMed1992

Pharmacokinetics of oxytetracycline in presence of calcium gluconate in goats.

The concentration of oxytetracycline (OTC) in plasma, after single dose i.v. administration at 10 mg kg-1, was determined during pre and post induced-hypercalcemia in goats. The pharmacokinetic variables were then calculated. Hypercalcemia caused several changes in the determined variables. The CPmax and CPmin of OTC observed at 0.08 and 4 hr in normal goats were respectively 34.50 +/- 1.65 and 1.19 +/- 0.14 micrograms ml-1, while the CPmax and CPmin of OTC in presence of calcium at 0.08 and 8 hr were 20.81 +/- 2.18 and 1.04 +/- 0.05 micrograms ml-1 respectively. Hypercalcemic state in goats increased t1/2 (alpha) (0.19 +/- 0.02 hr), t1/2 (beta) (2.77 +/- 0.03 hr), AUC (37.67 +/- 0.83 micrograms x hr x ml vd (area) (1.07 +/- 0.03 L kg-1) and vd (ss) (0.95 +/- 0.04 L kg-1) values of OTC compared to normal goats. The semilogarithmic plot of plasma level-time profile of OTC administered i.v. showed biphasic decline suggestive of two compartment open model 'kinetics' in both normal and hypercalcemic animals.

Animals↗
PubMed1992

Rh segregation distortion: an artifact of ascertainment bias?

On the basis of Rh blood group data on mother-child pairs collected from the maternity clinic of a hospital in Chile, Valenzuela and Harb postulated that there is a significant segregation distortion at the Rh locus. For data collected from a hospital, biases of ascertainment cannot be ruled out. For the Rh blood group locus, there is a strong possibility of preferential admission of Rh(-) pregnant women, especially of those Rh(-) women with Rh(+) husbands. We show that the evidence of segregation distortion vanishes when the possibility of such preferential admissions are taken into account.

Adult↗
PubMed1991

Captopril renography in the diagnosis of renal artery stenosis: accuracy and limitations.

PURPOSE: The purpose of this study was to determine the sensitivity, specificity, and clinical usefulness of renography performed in combination with captopril administration ("captopril renography") in diagnosing renal artery stenosis. PATIENTS AND METHODS: Fifty-five patients with suspected renal artery stenosis underwent renography prior to performance of renal angiography. Renography was performed on two consecutive days using technetium-99m-diethylenetiamine pentaacetic acid (DTPA) as an index of glomerular filtration rate and iodine-131-orthoiodohippurate (OIH) as an index of renal blood flow. Captopril (25 mg orally, crushed) was administered 1 hour before the second study. Renal artery stenosis was defined as a stenosis exceeding 70%. Renographic criteria were then established, retrospectively, to differentiate renal artery stenosis from essential hypertension based on (1) asymmetry of function and (2) the presence of captopril-induced changes. RESULTS: Renal artery stenosis was detected in 35 of 55 patients (21 with unilateral and 14 with bilateral stenosis). Three criteria were established for diagnosing renal artery stenosis: (1) a percent uptake of DTPA by the affected kidney of less than 40% of the combined bilateral uptake, (2) a delayed time to peak uptake of DTPA, which was more than 5 minutes longer in the affected kidney than in the contralateral kidney, (3) a delayed excretion of DTPA, with retention at 15 minutes, as a fraction of peak activity, more than 20% greater than in the contralateral kidney. The presence of one or more of these criteria was diagnostic of renal artery stenosis, with a sensitivity and specificity of 71% and 75%, respectively before captopril administration, and 94% and 95% after captopril administration. Lesser degrees of asymmetry (i.e., uptake of 40% to 50%) had very poor diagnostic specificity. Among patients with bilateral stenoses, asymmetry identified the more severely affected kidney, but the presence or absence of stenosis in the contralateral kidney could not be reliably determined. When pre- and post-captopril studies were compared, the presence of captopril-induced scintigraphic changes was a highly specific finding for renal artery stenosis, but occurred in only 51% of the cases. OIH scintigraphy provided similar results, with slightly lower sensitivity and specificity. CONCLUSION: Asymmetry of DTPA uptake, time to peak uptake, or retention seen on a single post-captopril renogram is a highly sensitive and specific finding in detecting renal artery stenosis but does not distinguish unilateral from bilateral disease. If renograms are obtained both before and after captopril administration, the presence of captopril-induced change is a highly specific finding for the detection of renal artery stenosis, but the sensitivity of this finding is low.

Antihypertensive Agents↗
PubMed1991

Patterns of regional lymph node metastases from cutaneous melanomas of the head and neck.

A consecutive series of 111 patients treated between 1964 and 1989 with primary cutaneous malignant melanoma of the head and neck and histologically proven regional metastases was reviewed to determine the patterns of nodal metastases. The primary sites were grouped in the following categories: face (34), anterior scalp (25), anterior neck (16), posterior scalp (15), ear (11), and posterior neck (10). All patients underwent radical neck dissection: 80 of the procedures were therapeutic and 31 elective. A total of 106 specimens were positive for metastases. Thirty-three of the 57 patients undergoing parotidectomy had positive results for metastases (14 of 20 in therapeutic parotidectomies and 19 of 37 in elective parotidectomies). Based on the incidence of involvement of the parotid gland and the patterns of lymph node metastases from levels I through V, three observations are made. Patients undergoing regional lymphadenectomy for primary melanomas on the ear, face, and anterior scalp should be considered for parotidectomy. The use of selective limited neck dissection for elective regional lymphadenectomy appears justified based on the location of the primary site. In patients undergoing therapeutic neck dissection, a complete neck dissection should be performed due to the unpredictable distribution of lymph node metastases to the cervical lymph nodes.

Female↗
PubMed1991

Descriptive epidemiology of intravenous heroin users--a new risk group for transmission of HIV in India.

India is considered to have a low incidence of HIV infection so far. Nevertheless, an epidemic of HIV infection has been reported recently among intra-venous drug users (IVDUs) in Manipur, a north-eastern state of India, bordering Myanmar (Burma). This report describes the epidemiology of intravenous drug abuse in the state of Manipur. Four hundred and fifty IVDUs were interviewed. Their age (median 24 years) and sex patterns (95% male) differ from those reported from western countries. It is estimated that there may be approximately 15,000 such addicts in a population of 1.8 million and 50% of them could be positive for HIV. Knowledge of AIDS and its transmission is significantly higher among the addicts than non-addict controls. Free availability of heroin was found to be the major factor responsible for the high rate of addiction. It is presumed that two other neighbouring States which are well-connected to Manipur and also have a common border with Myanmar (part of the 'Golden Triangle') may have a similar problem with HIV infection.

Acquired Immunodeficiency Syndrome↗