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Biomedical subjects

V Vijayan

Publications and source records attributed to V Vijayan.

12 recordsLinked to original sources
PubMed1997

Developing human biliary system in three dimensions.

BACKGROUND: In the development of the human biliary system, although the extrahepatic bile ducts develop from the embryonic hepatic diverticulum, there is increasing evidence to suggest that the intrahepatic bile ducts originate within the liver from the ductal plate. The ductal plate develops as a sheath of primitive biliary epithelium in the mesenchyme along the portal vein branches. Through an orderly process of selection and deletion, the ductal plate is remodelled into the adult system of anastomosing tubular bile ducts. The ductal plate remodelling process occurs at the porta hepatis between 11 and 13 weeks of gestation and progresses towards the periphery of the liver. METHODS: In this project, for the first time, we have used computerised three-dimensional reconstruction techniques to visualise the developing human biliary system. Paraffin-embedded tissue from eight human embryos or fetuses between 5.5 and 16 weeks of gestation were serially sectioned, and their images were aligned, digitised, and used for three-dimensional reconstruction. RESULTS AND CONCLUSIONS: Three-dimensional images of the extrahepatic and the intrahepatic biliary systems were obtained, and the following conclusions were drawn. (1) The intrahepatic biliary system, both at the porta hepatis and within the liver, developed from the ductal plate through a consistent pattern of remodelling. (2) Prior to the remodelling process, the ductal plate was of similar morphology irrespective of site and gestation. (3) The extrahepatic biliary system was in direct luminal continuity with the developing intrahepatic biliary system throughout gestation and did not show the presence of a "solid stage" in any of the embryos or fetuses studied.

Bile Ducts, Extrahepatic↗
PubMed1997

Development of alginate-based slow release formulation of Bacillus sphaericus for controlling Culex quinquefasciatus.

Seven types of formulations were prepared as granules using the larvicidal factor of Bacillus sphaericus and different concentrations of calcium alginate which was used as matrix to immobilize and entrap the active ingredient (ai). All formulations were tested in disused wells against Culex quinquefasciatus at the rate of 15 kg ai per hectare. Among the seven types tested, the type 2 which contained 5% calcium alginate as immobilizing agent, exhibited the maximum larvicidal activity. Persistent control in breeding was noticed for 8 weeks with this formulation type.

Alginates↗
PubMed1996

Prospective randomized study of sulindac versus calcium and calciferol for upper gastrointestinal polyps in familial adenomatous polyposis.

Eighteen patients with familial adenomatous polyposis (FAP) who had previously undergone colectomy but had upper gastrointestinal polyps were studied in a double-blind randomized crossover trial comparing sulindac with calcium and calciferol. Sulindac produced a reduction in the crypt proliferation index in the gastric epithelium of patients but did not significantly affect duodenal mucosa. Calcium with calciferol did not have any effects on crypt proliferation index in patients with FAP.

Adenomatous Polyposis Coli↗
PubMed1995

Distortion in TGF beta 1 peptide immunolocalization in biliary atresia: comparison with the normal pattern in the developing human intrahepatic bile duct system.

Biliary atresia is an important cause of neonatal obstructive jaundice in which there is inflammation, sclerosis and eventual obliteration of the bile duct system. Its onset may be antenatal, affecting the normal development of the biliary system. The intrahepatic biliary system is derived from the ductal plate, a sheath of cuboidal epithelium that appears at the hepatocyte-mesenchymal junction around the portal vein branches at 6 weeks gestation. This epithelial structure is moulded into a network of tubular bile ducts by the proliferating mesenchyme. Certain portions of the ductal plate are selected to become definitive bile ducts, while redundant biliary epithelium is deleted. The molecular dynamics controlling the intra-uterine development of the biliary system in humans are not yet clearly understood. Transforming growth factor-beta 1 is a cytokine that stimulates mesenchymal proliferation and inhibits epithelial growth, and has been shown to be important in organogenesis. In the present study, the pattern of TGF beta 1 peptide immunolocalization was investigated with the aid of computerized image analysis, in normal human bile duct development and in biliary atresia. TGF beta 1 peptide was detected within hepatocytes and ductal plate epithelium from 7 weeks gestation; increased TGF beta 1 immunoreactivity was present within the epithelium of developing bile ducts at 13 weeks gestation, and apical polarization of the cytokine was observed from 16 weeks gestation. In biliary atresia, the TGF beta 1 immunoreactivity pattern within the bile duct structures at the porta hepatis and within intrahepatic portal tracts resembled that of the primitive ductal plate, and there was no significant apical polarization. This may indicate a developmental arrest in the normal ductal plate remodelling process in biliary atresia, and suggests an underlying epithelial-mesenchymal interactive disorder.

Adolescent↗
PubMed1995

Comparison study of DNA content of primary and metastatic lymph node lesions of colorectal cancer.

Abnormal DNA content or aneuploidy in cells usually indicates malignancy. In colorectal cancer aneuploidy has been shown to confer a poorer prognosis suggesting that aneuploid cancers are more aggressive. The mechanisms involved in the aggressive behaviour of an aneuploid tumour are still unknown. The aim of this study was to compare the patterns of aneuploidy of colorectal cancers and that of their corresponding lymph node metastases and to relate them to clinical outcomes. One hundred and one patients were studied, 81 (Dukes C) with lymph node metastasis only and 20 (Dukes D) with obvious distant metastasis as well. Forty-six (46.5%) of the tumours and an equal number of the lymph nodes were found to be aneuploid. Twenty-eight (60.9%) of the aneuploid tumours showed aneuploid metastasis and 18 (39.1%) showed diploid metastasis. Similarly, 37 (67.3%) of the diploid tumours showed diploid metastasis whereas 18 (32.7%) showed aneuploid metastasis. Local recurrence and distant metastasis were compared among the aneuploid and diploid primary tumours. Although there was no statistically significant difference, distant metastasis was more common in aneuploid tumour. Ploidy of the lymph node was not related to local recurrence or distant metastasis. We conclude that DNA ploidy by itself does not determine the metastatic potential of the tumour cell and that in about 50% of the tumours, the lymph node metastasis consists of clones of cells different from the primary tumours. We also conclude that the clinical outcome of the disease in terms of recurrence and metastasis cannot be predicted by the ploidy of the lymph node metastatic lesions.

Aneuploidy↗
PubMed1995

Effect of inorganic salts, soaps and detergents on dissolution and larvicidal activity of alginate formulation of Bacillus sphaericus.

Various inorganic salts and commonly used soaps and detergents were tested in the laboratory for their effect on the dissolution and larvicidal residual activity of a slow-release alginate encapsulated granular formation of Bacillus sphaericus. Fluoride, chloride and sulphate salts and a detergent powder affected the residual activity of this formulation drastically by rupturing it but did not effect its larvicidal activity. Nitrates and phosphates of sodium and potassium also had the same effect but to a moderate level. The safest concentration of these water impurities for effective functioning of the alginate encapsulated B. sphaericus formulation have been determined.

Alginates↗
PubMed1994

Role of cell kinetics from rectal scrapings in predicting risk of colorectal cancer.

It has been suggested that cells obtained from scrapings of rectal mucosa can be readily analysed by flow cytometry for DNA content. Aneuploidy, if detected in these cells, will indicate a field change in the rectal mucosa. If so, this could provide a convenient means of selective screening for colorectal cancer. Rectal scrapings were obtained and analysed from 90 patients (23 patients with cancer, 13 patients in whom the cancer had been resected, 21 patients with benign adenoma and 33 patients with normal colorectum). Only 1 normal patient, 3 cancer patients and 1 resected patient showed aneuploidy, the rest were diploid. S-phase analysis showed the highest S-phase (18.0%) in the adenoma group and lowest (12.7%) in the normal group. The difference was not statistically significant (P = 0.06). S-phase was significantly higher among normal males (16.3%) than normal females (9.2%) (P = 0.008). In the adenoma group, however, the females showed a slightly higher S-phase (18.4%) than the males (17.8%), suggesting that S-phase measurement may be important in the study of carcinogenesis. In conclusion, aneuploidy in cells obtained from rectal scrapings is not a useful marker for increased risk of colorectal cancer as it was found in only 13% of the cancer patients. S-phase studies show more promise and need to be more extensively studied.

Adenocarcinoma↗
PubMed1992

Gliotoxic actions of excitatory amino acids.

Cultures of neonatal Type I astrocytes of the rat were exposed to a series of excitatory amino acid analogs to identify those compounds that were gliotoxic. In addition to L-alpha-aminoadipate, a previously identified gliotoxin, L-homocysteate, L-serine-O-sulfate, L-alpha-amino-4-phosphonobutyrate and L-alpha-amino-3-phosphono-propionate were also found to induce a sequence of degenerative events that led to the lysis of the astrocytes. Cellular injury was assessed by quantifying the activity of lactate dehydrogenase present in the surviving astrocytes. Prior to lysis, the cells went through a succession of distinctive morphological changes, the most prominent of which involved nuclear alterations. The nuclei appeared swollen, contained "pale" or "watery" nucleoplasm and exhibited a very prominent nuclear membrane and obvious nucleoli. These astrocytes appeared quite similar in appearance to the Alzheimer's Type II astrocytes, principally associated with the pathology of hepatic encephalopathy. The nuclear anomalies, which are thought to be indicative of cellular damage and compromised function, were also produced by the endogenous transmitters L-glutamate and L-aspartate, although with time, the affected astrocytes appeared to recover and return to normal morphology, without lyzing. These findings suggest that excessive levels of excitatory amino acids may induce cellular damage to astrocytes, as well as neurons. Once damaged, the resulting reductions in astrocyte function may further contribute to CNS losses and the overall pathology attributed to the excitatory amino acids.

Alzheimer Disease↗
PubMed1991

Metabolites of fungi & actinomycetes active against mosquito larvae.

Extracellular secondary metabolites from 350 fungi and 94 actinomycetes were screened for larvicidal activity against Culex quinquefasciatus, Anopheles stephensi and Aedes aegypti. Of them, 133 fungal metabolites and 35 from actinomycetes were active. Two from Streptomyces sp. and one from Paecilomyces sp. were highly active with LC50 value of 1-3 microliters/ml. The metabolites were more toxic to C. quinquefasciatus than to A. stephensi or Ae. aegypti larvae.

Actinomycetales↗
PubMed1990

Incidence, clinical features and epidemiology of rotavirus gastro-enteritis in hospitalized children.

Two hundred and eighteen patients with acute gastro-enteritis (GE) and 67 controls (patients admitted during the period of study for illness other than (GE) were included in this study. Their stool samples were subjected to the following tests to detect the presence of rotavirus: enzyme-linked immunosorbent assay (ELISA), latex agglutination and electron microscopy. Samples positive by any one or more of the above methods were considered positive for rotavirus and were subjected to polyacrylamide gel electrophoresis of viral RNA. Rotavirus was detected in 59 (27.1%) of the 218 GE samples and four (6%) of the control samples. ELISA was the most sensitive test and could detect viral antigen long after the other methods failed to do so.

Child↗
PubMed1990

Pulmonary membrane diffusing capacity and capillary blood volume in tropical eosinophilia.

Pulmonary membrane diffusing capacity (Dm) and pulmonary capillary blood volume (Vc) measurements were carried out in 21 patients with untreated tropical eosinophilia and 21 healthy controls matched for age, sex, height, and smoking habit. The mean single breath transfer factor (Dco) and the mean membrane diffusing capacity were significantly lower (p less than 0.001) in patients with tropical eosinophilia compared with control subjects. However, the mean capillary blood volume was not significantly different (p greater than 0.2). The positive correlations between Dm and transfer factor (r = 0.825), between Dm and effective alveolar volume (VA) (r = 0.721), and between Dco and VA (r = 0.774) were also highly significant (p less than 0.001) in study patients prior to treatment. These data suggest that reduction in single breath transfer factor in untreated tropical eosinophilia may be due to a reduction in membrane diffusing capacity, which in turn may be due to a reduction in area of membrane available for diffusion, as evidenced by the significantly reduced VA (p less than 0.001) in these patients. Since pulmonary capillary blood volume was normal, the pulmonary perfusion was within normal limits. Following three weeks of treatment with diethylcarbamazine citrate, although there was a significant rise in single breath transfer factor (p less than 0.001) and membrane diffusing capacity (p less than 0.05), both Dco (p less than 0.01) and Dm (p less than 0.01) continued to be significantly lower than those of control subjects. However, pulmonary capillary blood volume did not show any change (p greater than 0.2).

Adult↗