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Biomedical subjects

A Das

Publications and source records attributed to A Das.

At least 307 records · Page 17Linked to original sources
PubMed1991

Fine-needle aspiration cytology in the diagnosis of cysticercosis presenting as palpable nodules.

The cytologic findings in the fine-needle aspirate of 30 cases of cysticercosis presenting as palpable nodules are described. Essential for a diagnosis are identification of parasitic fragments. These include bluish fibrillary structures sometimes with honeycombing, tegument of parasite thrown into rounded wavy folds, and scolex with hooklets and hyaline membrane surrounding it. The inflammatory reaction consisted of eosinophils, neutrophils, lymphocytes, histiocytes, epithelioid cells, and giant cells in varying proportions.

Adolescent↗
PubMed1991

Stage-specific expression of plasmodial proteins containing an antigenic marker of the intraerythrocytic cisternae.

A monoclonal antibody, LWLI, recognized 3 proteins of 45, 50 and 102 kDa in Plasmodium falciparum-infected erythrocytes. The 45- and 50-kDa proteins were parasite-encoded and displayed markedly different peptide maps, indicating that they were distinct plasmodial polypeptides with a common antigenic epitope rather than differentially processed forms of a primary translational product. The 45-kDa protein was present throughout intraerythrocytic growth, while the 50-kDa molecule was not detected earlier than 11 h in the life cycle. The 102-kDa protein was only expressed in trophozoite- and schizont-infected red cells: its structural relationship to the 45- and 50-kDa proteins, if any, remains undefined. By indirect immunofluorescence and immunoelectron microscopy, LWLI bound to flattened intraerythrocytic cisternae exported into the erythrocyte cytoplasm. The results support the theory that proteins recognized by the antibody were concentrated in these compartments and their common antigenic epitope may serve as a marker for the cisternae. Stage-specific expression of LWLI reactive proteins implicates developmental regulation of cisternal functions during asexual parasite development.

Animals↗
PubMed1991

XH1--a new cervical carcinoma cell line and xenograft model of tumour invasion, 'metastasis' and regression.

A new cell line, XH1, has been derived from an invasive focally keratinising adenosquamous carcinoma of the cervix in a 32 year old patient. It has been maintained in long term monolayer culture for 26 months, and passaged over 100 times (much greater than 300 population doublings). It is aneuploid with a mean chromosome number of 78. Examination using two minisatellite hypervariable DNA probes has shown it to be different from other cell lines maintained in this laboratory and from HeLa. Two sublines, XH1a and XH1b, show marked differences in monolayer culture, growth in soft agar, and xenograft formation. XH1 and XH1a cells readily form subcutaneous xenografts, and lung colonies can be established by their intravenous injection. Subcutaneous injection of XH1b cells results in rapid cell growth for a few days after which the tumour undergoes degeneration and then regresses completely. The XH1 karyotype has many rearranged chromosomes. Parental XH1 cells and both sublines show integration of HPV16 into the genome.

Adult↗
PubMed1991

An ultrastructural comparison of dermo-epidermal separation techniques.

Dermo-epidermal separation through the lamina lucida is an essential technique for immunoblotting studies and for the diagnostic immunofluorescence of autoimmune bullous diseases. The most widely used methods of producing skin separation in the laboratory are suction blister induction and incubation in 1 molar sodium chloride. More recently the use of a proteolytic enzyme, thermolysin, has been described for this purpose. We examined the electron microscopic appearance of five suction blisters, five skin specimens separated by 1 M NaCl, and five treated with thermolysin. Both suction blister formation and treatment with 1 M NaCl resulted in a clean separation through the lamina lucida in all specimens examined. However specimens treated with thermolysin developed intra-epidermal separation in four cases without any lamina lucida separation in three. Suction blister formation was associated with hemidesmosome disruption. Incubation in 1 M NaCl remains the most reproducible, convenient, and reliable method of producing dermo-epidermal separation in the laboratory.

Basement Membrane↗
PubMed1991

Genetic differentiation and inversion clines in Indian natural populations of Drosophila melanogaster.

To study the genetic differentiation and inversion clines in Indian natural populations of Drosophila melanogaster, 14 natural populations (6 from the north and 8 from the south) were screened for chromosome inversions. The chromosomal analysis revealed the presence of 23 paracentric inversions, which include 4 common cosmopolitan, 4 rare cosmopolitan, 2 recurrent endemic, and 13 unique endemic (new inversions detected for the first time) inversions. The difference in karyotype frequencies between populations from the north and south were highly significant and the level of inversion heterozygosity was higher in populations from the south. Statistically significant negative correlations were found between each of the four common cosmopolitan inversions and latitude. These findings are in accord with results from other worldwide geographic regions and show that Indian populations of D. melanogaster have undergone considerable genetic differentiation at the level of inversion polymorphism.

Animals↗
PubMed1990

Characterization of the VirG binding site of Agrobacterium tumefaciens.

Expression of Agrobacterium tumefaciens virulence (vir) genes is dependent on the presence of a conserved 'vir box' sequence in their 5' nontranscribed regions. The location and number of these sequences vary considerably in different vir genes. Site-directed mutagenesis was used to identify the functional vir box(es) of virB, virC and virD. For virB expression both vir box B1 and B2 are required but only the vir box B1 is absolutely essential. Of the five vir boxes of virC and virD two are required for virC expression while only one vir box is required for virD expression. To investigate the minimum sequences necessary for vir gene induction a deletion derivative of virE that lacks the vir box region was used. This mutant is not induced by acetosyringone. The inducibility of this promoter was restored when a synthetic deoxyoligonucleotide dGTTTCAATTGAAAC was introduced at a location analogous to that of the wild type vir box sequence. Mutational analysis indicate that the functional vir box sequence is 14 residues in length, contains a dyad symmetry and has the consensus sequence d ryTncAaTTGnAaY [corrected] (r = purine, y = pyrimidine).

Base Sequence↗
PubMed1990

Efficient transformation of Agrobacterium tumefaciens by electroporation.

High-voltage electroporation was used to transform Agrobacterium tumefaciens strains A136 and A348, reaching the efficiency of 1-3 x 10(8) transformants/micrograms DNA. Transformation frequency was dependent on the electrical field strength and the pulse length. No significant reduction in transformation efficiency was observed when the transforming DNA contained sites sensitive to endonuclease AtuCI of A. tumefaciens.

DNA Restriction Enzymes↗
PubMed1990

Characterization of glucoamylase from Aspergillus terreus 4.

A strain of Aspergillus terreus 4 was found to show extracellular amylolytic activity and the amylase was identified as glucoamylase enzyme. The optimum temperature for the enzyme activity was 60% and it was stable at this temperature for 1 h. The enzyme was optimally active at pH 5.0 and stable between pH 3.0-8.0. Km values of glucoamylase for soluble starch, amylose and amylopectin were 5.9 mg/ml, 4.8 mg/ml and 2.6 mg/ml respectively.

Aspergillus↗
PubMed1990

Ultrastructural localization of extracellular matrix components in human retinal vessels and Bruch's membrane.

We have used the electron microscopic immunogold technique to localize precisely various extracellular matrix components in human retinal vessels and Bruch's membrane. Collagen types IV and V, laminin, and heparan sulfate proteoglycan core protein were localized in basement membranes of retinal capillaries. In addition to the capillary basement membrane components, collagen types I and III and fibronectin were found in the basement membranes of retinal arterioles and venules. The basement membranes of choriocapillaries and retinal pigment epithelial cells in Bruch's membrane also showed a similar distribution of the retinal capillary basement membrane components. Both the inner and outer collagenous layers of Bruch's membrane contained collagen types I and III along with fibronectin, whereas collagen type VI was mostly limited to the central elastic lamina. The precise localization and distribution of various extracellular matrix components in human retinal vessels and Bruch's membrane may be important for understanding their normal function as well as their alteration in disease.

Aged↗
PubMed1990

Hepatic vascular disease and portal hypertension in polycythemia vera and agnogenic myeloid metaplasia: a clinicopathological study of 145 patients examined at autopsy.

The pathogenesis of portal hypertension arising in patients with myeloproliferative disorders has been difficult to understand because liver biopsy findings often show minimal changes. It has been suggested that increased splenic blood flow, hepatic infiltration with hematopoietic cells or sinusoidal fibrosis may be important. We have reviewed the autopsy findings and clinical histories of 97 patients with polycythemia vera and 48 patients with agnogenic myeloid metaplasia collected from three institutions and from the Polycythemia Vera Study Group. Cirrhosis was present in seven patients, one of whom had bleeding varices. Esophageal varices were present clinically in 10 patients without cirrhosis (seven polycythemia and three agnogenic myeloid metaplasia). All of these patients had lesions in small or medium-sized portal veins and four had stenosis of the extrahepatic portal vein with histology compatible with organized thrombi. Nodular regenerative hyperplasia occurred in 14.6% and correlated closely with the presence of portal vein lesions. Thirty patients had greater than 500 ml of ascites, seven of these patients also had varices and six of them had hepatic vein thrombosis. Ascites also correlated with hepatic vein disease confined to small intrahepatic branches. No correlation was seen between hepatic hematopoietic infiltration and signs of portal hypertension. We conclude that esophageal varices are common and are almost always associated with portal vein lesions visible by light microscopy. These portal vein lesions, and the secondary effects of nodular regenerative hyperplasia and portal hypertension, are most likely a result of portal vein thrombosis in patients with myeloproliferative disorders.

Adult↗