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B C Das

Publications and source records attributed to B C Das.

160 records · Page 9Linked to original sources
PubMedDate not supplied

Lipopeptides with improved properties: structure by NMR, purification by HPLC and structure-activity relationships of new isoleucyl-rich surfactins.

The biosynthesis of bacterial isoleucyl-rich surfactins was controlled by supplementation of L-isoleucine to the culture medium. Two new variants, the [Ile4,7]- and [Ile2,4,7]surfactins, were thus produced by Bacillus subtilis and their separation was achieved by reverse-phase HPLC. Amino acids of the heptapeptide moiety were analysed by chemical methods, and the lipid moiety was identified by beta-hydroxy anteiso pentadecanoic acid by combined GC/MS. Sequences were established on the basis of two-dimensional NMR data. Because conformational parameters issuing from NMR spectra suggested that the cyclic backbone fold was globally conserved in the new variants, structure-activity relationships were discussed in details on the basis of the three-dimensional model of surfactin in solution. Indeed, both variants have increased surface properties compared with that of surfactin, and this improvement is assigned to an increase of the hydrophobicity of the apolar domain favouring micellization. Furthermore, the additional Leu-to-Ile substitution at position 2 in the [Ile2,4,7]surfactin leads to a substantial increase of its affinity for calcium, when compared with that of [Ile4,7]surfactin or surfactin. This effect is assigned, from the model, to an increase in the accessibility of the acidic side chains constituting the calcium binding site. Thus, the propensities of such active lipopeptides for both hydrophobic and electrostatic interactions were improved, further substantiating that they can be rationally designed.

Amino Acids↗
PubMedDate not supplied

Blood lymphocyte culture system: quantitative analysis of X-ray-induced chromosome aberrations in man, muntjac and cattle.

Peripheral blood lymphocytes of 3 mammalian species, man, muntjac and cattle, which have various amounts of DNA and divergent karyotypes, were exposed to 100-400 rad of X-rays, and frequencies of dicentrics and other aberrations were analysed at first post-irradiation metaphases. During experiments, various preparative or physical and biological factors that could influence the yield of chromosome aberrations were taken into account. The frequency of dicentrics scored at first post-irradiation metaphases showed best fit to both linear and quadratic dose-response curves, y = a + bD and y = bD + cD2 with a high correlation coefficient of 0.98 (P less than 0.001). The frequency of dicentrics obtained at different post-irradiation fixation times did not show significant variation, indicating a homogeneous sensitivity of peripheral lymphocytes to X-irradiation. BrdU incorporation following X-irradiation showed no increase in the frequency of chromosome aberrations. The frequency of dicentrics in man, muntjac and cattle showed a close correlation with their DNA content, but no meaningful correlation was found between the yield of dicentrics and the chromosome arm number or the nuclear volume. The ratio of dicentric yields, 1.00:0.67:1.04 obtained in man, muntjac and cattle were comparable to the ratio of their DNA contents, 1.00: 0.65: 1.07. The base-line frequency of SCEs was similar in the 3 species and no significant variation in SCE frequency was noticed even after administration of 400 rad of X-rays.

Adult↗
PubMedDate not supplied

S4a + S5 with caudate lobe (S1) resection using the Taj Mahal liver parenchymal resection for carcinoma of the biliary tract.

Recently we have been performing S4a + S5 with total resection of the caudate lobe (S1) by using a dome-like dissection along the root of the middle hepatic vein at the pinnacle, which we refer to as the Taj Mahal liver parenchymal resection, for carcinoma of the biliary tract. This procedure offers the following advantages: (1) It allows total resection of the caudate lobe, including the paracaval portion (S9), and (2) because the cut surface of the liver is large, it allows intrahepatic jejunostomy to be performed more easily with a good field of view. The indications for this procedure include hilar bile duct carcinoma, gallbladder carcinoma, and choledochal cyst (type IVA). Because of the high rate of hilar liver parenchyma and caudate lobe invasion associated with hilar bile duct carcinoma, the liver must be resected. The Taj Mahal procedure is indicated in cases where extended liver resection is impossible. The dissection limits of this procedure are, on the left side, the B2+3 bifurcation at the right margin of the umbilical portion of the portal vein and, on the right side, the B8 of the anterior branch and the B6+7 bifurcation of the right posterior branch. This procedure could also be described as a reduced form of extended right hepatectomy and extended left hepatectomy. For gallbladder carcinoma, this procedure is indicated to ensure an adequate surgical margin and eradicate transvenous liver metastasis, particularly in cases of pT2 lesions. Hilar and caudate lobe invasion also occurs in liver bed-type gallbladder carcinoma, and bile duct resection and caudate lobe resection are required for the surgery to be curative. We performed this procedure in four cases of hilar bile duct carcinoma, five cases of gallbladder carcinoma, and one case each of choledochal cyst (type IVA) with carcinoma of the bile duct and gallbladder adenomyomatosis. Curative resection was possible in all except the patient with adenomyomatosis, and all of the patients are alive and recurrence free 10 to 37 months postoperatively. This procedure, in addition to preserving liver function, provides a wide field of view and facilitates reconstruction of multiple intrahepatic bile ducts. Thus it can be said to be a curative operation not only in patients considered high risk but also in those whose hilar bile duct carcinoma is limited to the bifurcation area (Bismuth type IIIa and IIIb) and in gallbladder carcinoma up to pT2 with slight extension on the hepatic side.

Adenomyoma↗
PubMedDate not supplied

Telomerase-A molecular marker for cervical cancer screening.

Cervical cancer is one of the most common cancers in women and can be routinely screened for by the Papanicolaou smear. Screening for HPV high-risk types 16 and 18 has augmented the sensitivity of this test, but still some cases remain undetected. We have investigated the utility of assaying telomerase activity as a possible screening marker for cervical cancer. Telomerase activity was studied in relation to HPV 16/18 infection, Papanicolaou smear cytopathology, and biopsy histopathology in a total of 88 subjects, consisting of 29 cervical cancer cases, 19 control hysterectomy samples, 16 precancerous cervical scrapes, 6 cervical samples from other gynecological malignancies, and 18 normal healthy cervical scrapings. Telomerase activity was detected in 96.5% of cervical tumor samples and in 68.7% of premalignant cervical scrapings but was not detected in control hysterectomy samples and in cervical scrapings of normal healthy controls. Telomerase assay had a diagnostic accuracy of 95.8 in tissue samples, 79.1 in scrapings and 91.2 in all. Whereas HPV-16/18 subtyping had a diagnostic accuracy of 89.5% in tissue samples, 70.5% in scrapings, and 82.1% in all. There was also 71% agreement between telomerase activity and HPV-16/18 infection. The absence of telomerase activity in cervical scrapes from healthy women indicated the potential of telomerase to serve as a good screening marker for the early diagnosis of cervical cancer. For the first time we have also shown the ability of telomerase to detect micro and probably occult metastasis in gynecological malignancies.

Adult↗
PubMedDate not supplied

Surgical anatomy of the medial segment (S4) of the liver with special reference to bile ducts and vessels.

BACKGROUND/AIMS: Resection of the inferior area of the medial segment (S4a) plus S5 with preservation of the superior area of the medial segment (S4b) is being performed to manage hilar bile duct carcinoma and pT2 type gallbladder carcinoma, and thus, attention has been focused on the surgical anatomy of the medial segment of the liver to identify the specific vessels and bile ducts of the areas of that segment to be resected and to be preserved. METHODOLOGY: Anatomical study of the bile duct, portal vein, middle hepatic vein, and middle hepatic artery to the medial segment branches of the liver (S4) was performed in a total of 171 specimens comprised of 71 adult cadavers, and 100 liver casts. RESULTS: 1) Two main types of bile duct branches of the medial segment (B4) were recognized. Type I included the branches which joined to the left hepatic duct on the hilar duct side (35.5%), and type II included the branches that joined on the peripheral side (54.6%). Several subtypes were also found in both types. The B2-B3 confluence was mostly on the left (41.7%) or posterior (42.7%) to the umbilical portion (UP) of the portal vein, and to the right of the UP (hilar side) in only 15.6%. 2) The portal vein of the medial segment branches (P4): P4a branched from the right angle and upper right border of the UP in every specimen. The most common morphology was 1 large and 2-3 small branches (41%). P4b was almost always found to branch posterior to the UP and lower than P4a, and the most common morphology was 1 large and 0-1 small branches (57.8%). 3) The middle hepatic vein: In 83.2% a common trunk was observed at the confluence with the inferior vena cava, and 8 types of the middle hepatic vein were recognized. 4) The middle hepatic artery: It arose from the left hepatic artery in 61.5%, from of the right hepatic artery in 27.5%, from the proper hepatic artery in 5.5%, and from both the left and the right hepatic artery in 5.5%. CONCLUSIONS: The detailed vascular and bile duct anatomy of S4 is described. This study should be helpful in identifying the specific vessels and bile ducts of the areas of the medial segment to be resected and to be preserved, thereby facilitating resection of the medial segment.

Adult↗
PubMedDate not supplied

Ultrastructural study of the remnant liver after extensive hepatectomy in dogs; especially morphological alterations of sinusoidal endothelial cells.

BACKGROUND/AIMS: To investigate the role of sinusoidal endothelial cells in the mechanism of the remnant liver dysfunction after extensive hepatectomy, morphological alteration of sinusoidal endothelial cells and cytoprotective effects of prostaglandin I2 analog were studied by ultrastructural analysis. METHODOLOGY: Mongrel dogs (n = 24) were divided into 3 groups according to the extent of hepatectomy and the use of prostaglandin I2 analog preoperatively. Group 1: 70% hepatectomy (n = 8), Group 2: 84% hepatectomy (n = 8), and Group 3: 84% hepatectomy with administration of prostaglandin I2 analog, preoperatively (n = 8). Morphology of hepatic sinusoidal endothelial cells was examined after hepatectomy in all cases. RESULTS: Group 2: Enlargement of the sinusoidal endothelial fenestrations was transitorily occurred immediately after hepatectomy, but were dramatically decreased in size 24 h after the operation. Most sinusoidal endothelial cells were destroyed and separated from the sinusoidal wall. Fibrin deposits and sludge were found in the Disse's space and sinusoidal lumens, resembling liver failure at 24 h after the operation. Group 1 and 3: sinusoidal endothelial fenestrations remained slightly enlarged at 24 h after the operation, but fibrin deposits or sludge were not observed in sinusoidal lumens. CONCLUSIONS: Our data suggest that extensive hepatectomy changed the morphology of sinusoidal endothelial cells. Administration of prostaglandin I2 analog helped maintain structural integrity of sinusoidal endothelial cells, improved hepatic microcirculation and thus served to reduce remnant liver dysfunction.

Animals↗