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Biomedical subjects

M Y Khan

Publications and source records attributed to M Y Khan.

At least 55 records · Page 3Linked to original sources
PubMed1992

Age related changes in the rat adrenal cortex.

The present study revealed that the growth of the rat adrenal gland was relatively slower than general body growth. However, growth of the cortex preceded that of the medulla. The parenchyma showed three usual zones but a fourth inconstant lipid-poor, zona intermedia between outer glomerulosa and middle fasciculata was also observed. In all cortical zones, the predominance of dark cells over the light cells occurred irrespective of the age groups studied. The advancing age replaced capsular cellular elements with fibrous ones whereas the mitotic activity of the parenchymal cells decreased and an increase in the intracellular lipid in the outer and ascorbic acid in the inner cortex was observed. The glycogen which was restricted mainly to the inner cortex remained unaffected by aging process while the acid phosphatase activity from the inner reticularis extended to the outer cortex in aged group.

Adrenal Cortex↗
PubMed1991

A rapid colorimetric assay for heparinase activity.

A rapid, sensitive, assay for enzymes that degrade heparin is described. The procedure is based on the interference of heparin with color development during the interaction of protein with the dye Coomassie brilliant blue. The loss of this property when the glycosaminoglycan is degraded by heparinase can be used to quantify activity of the enzyme in pure form, or in complex biological samples such as tissue homogenates or serum. The assay is also suitable for studying dependence of heparinase activity under conditions such as varying pH and temperature.

Colorimetry↗
PubMed1991

Unfolding-refolding behaviour of chicken egg white ovomucoid and its correlation with the three domain structure of the protein.

The urea and heat-induced unfolding-refolding behaviours of chicken egg white ovomucoid and its four fragments representing domains I, II + III, I + II and III were systematically investigated in 0.06 M sodium phosphate buffer (pH 7.0) by difference spectral measurements. The effect of temperature on ovomucoid and its fragments was also studied in 0.05 M sodium acetate buffer (pH 5.0) and in presence of 2 M urea at pH 7.0. Intrinsic viscosity data showed that ovomucoid and its different fragments did not lose any significant amount of their structure under mild acidic conditions (pH 4.6). Difference spectral results showed extensive disruption of the native structure by urea or temperature. Isothermal transitions showed single-step for domain I, domain I + II and domain III, and two-step having one stable intermediate, for ovomucoid and its fragment representing domain II + III. However, the presence of intermediate was not detected when the transitions were studied with temperature at pH 7.0. Strikingly, the single-step thermal transitions of ovomucoid and its fragment representing domain II + III, became two-step when measured either at pH 5.0 or in presence of 2 M urea at pH 7.0. Analysis of the equilibrium data on urea and heat denaturation showed that the second transition observed with ovomucoid or domain II + III represent the unfolding of domain III. The kinetic results of ovomucoid and its fragments indicate that the protein unfolds with three kinetic phases. A comparison of three rate constants for the unfolding of intact ovomucoid with that of its various fragments revealed that domain I, II and III of the protein correspond to the three kinetic phases having rate constants 0.456, 0.120 and 0.054 min-1, respectively. These data have led us to conclude: (i) the unusual stability of ovomucoid towards various denaturants, including temperature, is due to its domain III, (ii) initiation of the folding of the ovomucoid molecule starts from its NH2-terminal region which probably provides the nucleation site for the formation of the subsequent structure and (iii) domains I and II have greater mutual recognition between them as compared to the recognition either of them have with domain III.

Animals↗
PubMed1991

Interaction of fibronectin with heparin in model extracellular matrices: role of arginine residues and sulfate groups.

The interaction of heparin with the NH2-terminal domain of human plasma fibronectin was studied by using matrix-driven translocation, an assay for the adhesion of extracellular macromolecules with cell or particle surfaces within artificial collagen matrices. Partial desulfation of heparin rendered it ineffective in competitively inhibiting the interaction of the fibronectin NH2-terminal domain with heparin-coated particles, suggesting a role for sulfate groups of heparin in the interaction. Analysis of the fibronectin domain in terms of its primary structure, its proposed organization into "type I modules", and its hydrophilic and flexible segments led to the identification of several arginine-containing sites of potential interaction with the sulfate groups of heparin. Modification of increasing numbers of arginine side chains with 1,2-cyclohexanedione under mild conditions eventually led to decreases in translocation-promoting activity, and of heparin binding capacity as measured in a gel-shift assay, but the major portions of these functions were retained even when the four most accessible arginines (attributed to sites in and adjacent to the large loops of the type I modules) were modified. With the modification of additional arginines (attributed to sites in the small loops), both functions were lost. The peptide Gly-Arg-Gly, corresponding to a repeated determinant at the tips of two small loops, inhibited translocation, but arginine alone did not. Cleavage of the large loops by CNBr also led to loss of translocation-promoting activity. The correspondence between the molecular determinants of matrix-driven translocation and those previously found for mesenchymal morphogenesis indicates the utility of this system in the analysis of adhesive interactions of biological importance.

Amino Acid Sequence↗
PubMed1991

Potentiation of renal tumorigenicity by cyclosporine A in streptozotocin diabetic rats.

Male Wistar rats with streptozotocin induced diabetes were treated every third day with 10 mg/kg (13 rats) of cyclosporine A (CyA) for 20 weeks. At sacrifice, 7 of 13 rats (53.8%) demonstrated renal tumors. By contrast, only 2 of 16 streptozotocin diabetic rats (12.5%) without CyA demonstrated renal tumors. No tumors were noted in 10 non-diabetic control rats. These studies suggest that CyA potentiates renal tumorigenicity in streptozotocin diabetic rats.

Animals↗
PubMed1991

The salting-out behavior of human plasma fibronectin and its possible correlation with heparin-induced cryoprecipitation of the protein.

The solubility of human plasma fibronectin in concentrated ammonium sulfate solutions was measured at pH 7.0 and varying temperatures as well as at 25 degrees C and varying pHs. The salting-out parameters, KS and beta were found to increase linearly with temperature in the range 5 degrees-50 degrees C. KS-pH and beta-pH profiles were found to have maxima at pH 7.0. The dependence of both of the solubility parameters of plasma fibronectin on temperature and pH was thus found to be anomalous. The possibility of a correlation between the heparin-induced cryoprecipitation of fibronectin and the dependence of its solubility parameters on pH and temperature is considered. It is suggested that heparin-induced precipitation of human plasma fibronectin at low temperatures is caused by (i) a cold effect and (ii) conformational change in the protein due to heparin binding.

Ammonium Sulfate↗
PubMed1990

Unfolding transitions of fibronectin and its domains. Stabilization and structural alteration of the N-terminal domain by heparin.

Changes in the conformational state of human plasma fibronectin and several of its fragments were studied by fluorescence emission, intrinsic fluorescence polarization and c.d. spectroscopy under conditions of guanidinium chloride-and temperature-induced unfolding. Fragments were chosen to represent all three types of internal structural homology in the protein. Low concentration (less than 2 M) of guanidinium chloride induced a gradual transition in the intact protein that was not characteristic of any of the isolated domains, suggesting the presence of interdomain interactions within the protein. Intermediate concentrations of guanidinium chloride (2-3 M) and moderately elevated temperatures (55-60 degrees C) induced a highly co-operative structural transition in intact fibronectin that was attributable to the central 110 kDa cell-binding domain. High temperatures (greater than 60 degrees C) produced a gradual unfolding in the intact protein attributable to the 29 kDa N-terminal heparin-binding and 40 kDa collagen-binding domains. Binding of heparin to intact fibronectin and to its N-terminal fragment stabilized the proteins against thermal unfolding. This was reflected in increased delta H for the unfolding transitions of the heparin-bound N-terminal fragment, as well as decreased accessibility to solvent perturbants of internal chromophores in this fragment when bound to heparin. These results help to account for the biological efficacy of the interaction between the fibronectin N-terminal domain and heparin, despite its relatively low affinity.

Circular Dichroism↗
PubMed1990

An assay for heparin by decrease in color yield (DECOY) of a protein-dye-binding reaction.

The interference by heparin and some related molecules with the well-known Bradford dye-binding assay for proteins is used as the basis of a rapid, sensitive method for the quantitation of these polysaccharides. Whereas the available methods for the assay of glycosaminoglycans have lacked specificity for sulfated polyanions in general and for heparin in particular, the procedure described here distinguishes among different uronic acid derivatives and, when performed in conjunction with heparinase digestion or cetylpyridinium chloride precipitation, can be used to determine heparin content of complex biological samples.

Animals↗
PubMed1990

The relationship between new cardiac conduction defects and extension of valve infection in native valve endocarditis.

New conduction defects in the setting of native valve infective endocarditis (IE) are commonly believed to be associated with direct extension beyond the free valve area. At University Hospital in Newark, among 100 cases of IE, in none of five instances of associated conduction defects (excluding first-degree heart block) was this the case. In neither of two instances of direct extension of valve infection was this accompanied by a new conduction defect. To explore this relationship, autopsy, surgical, and echocardiographic findings from other institutions were combined with these data. Among 47 instances of new conduction defects in IE, only 60% could be related to direct extension of valve infection. The cause was coronary embolization in 4% and unknown in 36%. Among 119 cases of complicated valve lesions, significant conduction defects were documented by ECG in only 15%. In IE the appearance of new conduction abnormalities may often result from causes other than extension of valve infection. Furthermore, complicated valve lesions may often be present without electrocardiographic evidence, indicating interruption of normal conduction pathways.

Abscess↗
PubMed1990

Amorphisation of MgO single crystal specimens prepared by ion milling for transmission electron microscopy studies.

Single crystal MgO specimens having low load Vickers indentations were thinned in an ion milling machine employing a single ion gun, and their characteristics were investigated with optical microscopy and high voltage electron microscopy (HVEM). It was found that the state of cleanliness of the specimen chamber of the ion milling machine had a very marked influence on the quality of the thinned specimens. If the specimen chamber was not well cleaned before ion milling a fresh specimen, the latter tended to show amorphisation due to the deposition on the specimen of the debris left in the chamber from the previously ion-milled specimens. Such observations were made from MgO specimens ion milled in several different types of commercial ion milling machine employing a single gun. It is proposed that to obtain good-quality ion milled TEM specimens, it is important to clean the specimen chamber thoroughly prior to milling.

Magnesium Oxide↗
PubMed1990

Diabetic microangiopathy in KK mice. VI. Effect of glycemic control on renal glycoprotein metabolism and established glomerulosclerosis.

Twenty-three nonobese KK mice with abnormal tolerance to glucose, hyperinsulinemia with insulin resistance and human diabetic-like nephropathy were treated with either saline (12 mice) or glipizide, an oral hypoglycemic compound, 1 mg/kg, (11 mice) from 120 to 360 days of age. These mice develop significant increases in mesangial volume and matrix by 40 days of age. Oral glucose tolerance (OGTT), glucosyltransferase and N-acetyl-beta-glucosaminidase (enzymes involved in synthesis and degradation of kidney glycoproteins, respectively) in the kidney and serum, 24-hr proteinuria, and light microscopy studies of the kidney were performed. Glipizide-treated mice improved their OGTT. There was no difference in body weight; however, a 16% decrease (P less than 0.05) in kidney weight was observed in glipizide-treated mice. Both enzymes were significantly increased in the kidneys of mice treated with glipizide. No difference in serum enzymes was found between the two groups of mice. About 58% of the saline-treated mice had moderate glomerulosclerosis. By contrast, only 27% of glipizide-treated mice had moderate glomerulosclerosis. Also, a significant decrease in proteinuria was found in glipizide-treated mice. These data suggest that glipizide improves glucose metabolism, decreases kidney size, prevents kidney glycoprotein and mesangial matrix accumulation, and reduces proteinuria in type II diabetic KK mice. This indicates that good glycemic control prevents further progression of established diabetic nephropathy in animals.

Acetylglucosaminidase↗
PubMed1990

Dermatobia hominis myiasis masquerading as an infected sebaceous cyst.

In an apparently routine case, what appeared to be infected sebaceous cysts of the scalp turned out to harbour botfly larvae imported from a tropical country. Although the parasite Dermatobia hominis is not indigenous to the United States, cutaneous myiasis caused by the fly is fairly common in Central and South America, and several cases have been reported in people returning or emigrating from these regions. The authors therefore suggest that infection resulting from D. hominis invasion be considered in persons who present with furuncular lesions and give a history of travel to endemic areas.

Adult↗
PubMed1990

Further characterization of buffalo spleen cathepsin B.

Cathepsin B (EC 3.4.22.1) from buffalo spleen was isolated to homogeneity and its molecular weight was determined to be 25 KDa. The enzyme was found to be a glycoprotein having a total carbohydrate content of 7%. The NH2- and COOH-terminal amino acid residues were identified as Leu and Thr, respectively. The specific extinction coefficient, E1%1cm, of the enzyme was determined to be 13.2. The value of intrinsic viscosity and equivalent hydrodynamic radius of the enzyme were calculated to be 3.47 ml/gm and 2.34 nm, respectively. Polyclonal antibodies raised in rabbits were found to cross-react distinctly with the purified buffalo enzyme. Using BANA as substrate, the Km and Vmax values were determined to be 0.93 mM and 5.57 Units/mg, respectively. The buffalo enzyme was also found to be highly active against protein substrates, and the Km values for casein and BSA were measured to be 1.12 and 1.74 microM, respectively.

Animals↗
PubMed1990

Ovomucoid domains: preparation and physico-chemical characterization.

Four fragments of ovomucoid representing its individual domains and their different combinations were prepared by peptic and cyanogen bromide cleavages of the protein. The fragments corresponding to domains I + II, II + III, I and III of the parent ovomucoid molecule, were found to be homogeneous by gel filtration and polyacrylamide gel electrophoresis in presence and absence of SDS. Various physico-chemical properties of these proteins, such as molecular weight, NH2- and COOH-terminal amino acid residues, sugar content, isoionic pH, specific extinction coefficient, fluorescence emission spectra, intrinsic viscosity, frictional coefficient, Stokes radius, diffusion coefficient and geometrical mean radius were determined. Analysis of the results on trypsin inhibitory activity of ovomucoid and its different fragments suggested that only domain II is involved in the antitryptic activity of the inhibitor. Optical characteristics of these fragments indicate that they are devoid of tryptophan residues. The hydrodynamic properties suggest that intact ovomucoid and two of its fragments (domain I + II and domain II + III) are significantly different from those of typical globular proteins and are asymmetric in nature. However, the shape of the two remaining fragments representing domains I and III of the intact protein appeared to be compact and globular. Furthermore, domain II of ovomucoid has been suggested to primarily contribute towards the apparent asymmetry in the intact protein.

Animals↗
PubMed1989

On the origin of the positive band in the far-ultraviolet circular dichroic spectrum of fibronectin.

The genesis of the positive bands in the far-ultraviolet circular dichroic spectra of human plasma fibronectin and its 31-kDa NH2-terminal heparin-binding fragment was studied. Spectra of ester derivatives of tyrosine, tryptophan, and phenylalanine and of model mixtures of these derivatives in which they are present in the same ratios as in the proteins indicate that all the aromatic side chains make substantial contributions to composite positive bands with maxima several nanometers below those of the proteins. In the presence of solvent perturbants such as polyethylene glycol and ethylene glycol, the bands of the model mixtures are red-shifted to the approximate positions they have in the spectra of the proteins. No additional red shift is seen with solvent perturbation of the proteins, suggesting that the conditions leading to this effect are satisfied within the proteins. A separate effect of solvent perturbation, an increase in amplitude of the positive band, occurs equally in solutions of free aromatic amino acid derivatives and in the proteins. This effect is used to estimate the relative accessibility of the chromophores of fibronectin and its fragment to different perturbants. The possible influence of protein secondary structure on the amplitude of the positive circular dichroic band is discussed.

Circular Dichroism↗
PubMed1989

Adenosquamous-cell carcinoma of the ovary: report of a case with positive peritoneal fluid cytology.

Cytologic examination of peritoneal fluid showed only malignant squamous cells, without revealing adenocarcinomatous cell components, in a patient who had an endometrioid adenosquamous-cell carcinoma of the ovary. Histologic examination of the ovary demonstrated diffuse squamous-cell carcinoma with rare foci of endometrioid and abortive malignant glands, as well as isolated mucin-positive cells. The cytologic differential diagnosis of malignant squamous cells in peritoneal fluid and the pathogenesis of squamous-cell carcinoma of the ovary are discussed.

Adenocarcinoma↗
PubMed1989

New outlook on pericardial substitution after open heart operations.

The difficulties of reoperation owing to adhesions are well known. Clinical attempts to solve this problem using synthetic materials or glutaraldehyde-fixed pericardial xenograft have been less than satisfactory. Although experimental animal results have been good, they have not considered the influence of cardiopulmonary bypass (CPB) on adhesion formation. This study addressed the influence of CPB on the formation of adhesions and evaluated biodegradable polyglycolic acid as a material to reduce adhesions and as a pericardial substitute. Forty-five weanling sheep received implants of pericardial xenograft and polyglycolic acid with and without CPB. The pericardial xenograft showed no adhesions when implanted without CPB, but severe adhesions formed and a thick fibrinous layer covered the heart when CPB was used, making identification of coronary arteries at reoperation very difficult. The polyglycolic acid mesh implanted without CPB was absorbed and replaced with newly formed host collagen. With CPB, the polyglycolic acid was more rapidly absorbed, and a thinner layer of host collagen formed. Therefore, future animal studies must include CPB. In agreement with reported clinical results, glutaraldehyde-fixed pericardial tissue implanted with CPB resulted in severe epicardial reaction and therefore is not an ideal pericardial substitute.

Animals↗