PubMed Health⌕ Search

Biomedical subjects

F Rahemtulla

Publications and source records attributed to F Rahemtulla.

53 records · Page 3Linked to original sources
PubMed1987

Effects of variations in pH and hypothiocyanite concentrations on S. mutans glucose metabolism.

Hypothiocyanous acid (HOSCN) and hypothiocyanite (OSCN-) were generated by the antibody-independent salivary peroxidase (SP) system. The metabolism of Streptococcus mutans NCTC 10449 was examined by uniformly labeled glucose incorporation studies. We found that the SP-system causes a pH-dependent inhibition of 14C-labeled glucose uptake, and that the effects of HOSCN/OSCN- are bacteriostatic. The results also showed that, at low pH, bacteria required more time to recover fully from HOSCN/OSCN- inhibition. When control experiments were performed in the absence of HOSCN/OSCN-, but the pH was varied, we found a positive correlation between pH and the rate of 14C-glucose incorporation. The results also showed that pH did not affect the maximum incorporation of 14C-glucose, demonstrating that S. mutans can adapt to pH changes in the environment. Based on the data obtained, we postulate that the antibody-independent SP system plays an important role in the regulation of the metabolism of oral streptococci.

Glucose↗
PubMed1986

Specific assays for peroxidases in human saliva.

The peroxidase activity in human whole saliva is due to salivary peroxidase and, in some cases, myeloperoxidase; it is usually determined by spectrophotometric methods based on the rate of oxidation of chromogen substrates. Thiocyanate ion, a normal component of saliva, interferes with these kinetic assays by competing with the chromogen for the available oxidizing equivalents; this results in underestimation of peroxidase activity. Both salivary peroxidase and myeloperoxidase will catalyse the peroxidation of the thiocyanate ion; the product, hypothiocyanite ion, is a reactive oxidizing agent. We have developed an assay for total peroxidase activity in saliva, based on the rate of formation of hypothiocyanite, which is not affected by the concentrations of thiocyanate found in saliva. Myeloperoxidase will catalyse the peroxidation of the chloride ion but salivary peroxidase will not; the product of this in neutral solution is the hypochlorite ion, which is also a reactive oxidizing agent. The specific contribution was determined of myeloperoxidase to total peroxidase activity in saliva by measuring the rate of both hypochlorite and hypothiocyanite formation. Because the thiocyanate ion will compete with the chloride ion, the concentration of thiocyanate in saliva samples must be reduced below 0.05 mM prior to measurements of the rate of hypochlorite formation.

Humans↗
PubMed1985

Acidic glycoproteins from bovine compact bone.

Several acidic glycoproteins with apparent molecular weights of 85,000 (bone sialoprotein, BSP), 80,000, 67,000, 60,000, 40,000 (osteonectin) and 30,000 were isolated from adult bovine compact bone. About 20-25% of the 67 K preparation was serum albumin. This contaminant was removed by passing the protein through Blue Sepharose CL-6B; the material that emerged in the void volume of this affinity column contained the bone 67 K glycoprotein free of serum albumin. All six of the proteins had high amounts of aspartic and glutamic acid. The amino acid compositions of 80 K, 67 K, 40 K and 30 K glycoproteins were very similar. The 60 K glycoprotein had an amino acid content that differed from the others with notably higher proline, alanine and valine values. All six protein samples contained mannose, galactose, glucosamine, galactosamine and sialic acid, but no fucose. The carbohydrate contents varied from about 10% for osteonectin to 38% for BSP. Antibodies were raised against electrophoretically purified osteonectin and used in enzyme-linked immunosorbent assays (ELISA). In addition to reactivity with osteonectin, the antibodies displayed strong reactivity to 80 K and 30 K glycoprotein preparations, but did not react with 67 K or 60 K bone glycoproteins or bovine serum albumin. None of the acidic glycoproteins cross-reacted with antibodies to bovine serum albumin, bovine serum proteins or human alpha 2-HS-glycoprotein.

Amino Acids↗
PubMed1985

Proteoglycans of adult bovine compact bone.

Proteoglycans of bovine compact bone were purified by chromatography of the formic acid precipitate of an EDTA extract. The sequential chromatographic steps consisted of gel filtration on Sepharose CL-6B in 4-M guanidine HCl, ion-exchange chromatography on DEAE-Sephacel in 4-M urea and rechromatography on Sepharose CL-6B in 4-M guanidine HCl. The preparation consisted of a relatively small proteoglycan (Kav = 0.4 on Sepharose CL-6B) containing about 40% protein, 21% hexuronic acid, 23% galactosamine and lesser amounts of other monosaccharides. The core protein was shown by gradient NaDodSO4 gel electrophoresis, electrotransfer and immunodetection to be monodispersed with an Mr = 45,000. Analysis of glycopeptides obtained after papain digestion of the proteoglycan and separation from glycosaminoglycan chains by gel chromatography, indicated that both N-linked and O-linked oligosaccharides were present. The glycosaminoglycan chains liberated by papain digestion eluted from Sepharose CL-6B as a broad peak with Kav = 0.50, slightly ahead of the position of elution of bovine nasal cartilage glycosaminoglycans (Kav = 0.52); the bone glycosaminoglycans are thus slightly larger than those from cartilage and smaller than the ones attached to fetal bone proteoglycans. These chains were totally susceptible to chondroitinase AC II, a procedure that yielded unsaturated disaccharides corresponding predominantly to chondroitin-4-sulfate, and to a lesser extent chondroitin-6-sulfate. Antisera raised against adult bone proteoglycans cross-reacted with core protein of bone proteoglycan (obtained after chondroitinase digestion) but not with papain digested proteoglycan. In addition, they cross-reacted with core protein and trypsin-liberated, chondroitin sulfate rich region (AlTAl) derived from cartilage proteoglycans and, to a lesser extent, rat bone proteoglycans. No cross-reactivity could be detected to Smith-degraded cartilage proteoglycans, bone acidic glycoproteins or serum proteins.

Amino Acids↗
PubMed1985

Ultrastructural and biochemical characterization of glycosaminoglycans in HNK-1-positive large granular lymphocytes.

Natural killer (NK) cells are large granular lymphocytes (LGLs) that contain distinct lysosomal granules. The present study was undertaken to determine if these lysosomes contain glycosaminoglycans (GAGs) similar to those previously described in myeloid cells. Mononuclear cells from human blood were stained with HNK-1 fluoresceinated monoclonal antibody, and the NK cell population reactive with this antibody were isolated with a fluorescence-activated cell sorter (FACS). Specific staining of sulfated macromolecules with the cationic reagent, high iron diamine, was observed in the lysosomal granules of 90% of the HNK-1 positive cells. Staining in the same location was also observed in the unsorted LGLs, presumed to be NK cells, and intense staining of the cell surface was also a prominent feature of these cells. Surface staining was not evident in the majority of the FACS-separated NK cells. Digestion with chondroitinase ABC or treatment with nitrous acid reduced the staining in both locations; after sequential treatment with both chondroitinase and nitrous acid, little or no staining was seen. The presence of chondroitin sulfate (and/or dermatan sulfate) and heparan sulfate was also shown by the finding that incubation of the isolated NK cells with 35S-sulfate yielded cell-associated radiolabeled macromolecules with the characteristics of these two groups of GAGs. Of the labeled GAG pool, 60% was degraded by chondroitinase and 40% was susceptible to nitrous acid treatment. LGLs of a patient with Chediak-Higashi syndrome was also stained, and intracellular sulfate staining was clearly localized to the enlarged granules, supporting the conclusion that the lysosomes are the major site of intracellular accumulation of GAGs in normal NK cells.

Cell Membrane↗
PubMed1984

Incorporation of [35S]sulphate into glycosaminoglycans by mineralized tissues in vivo.

To investigate the metabolism of proteoglycans in young growing rats, calvaria, incisors, femoral diaphysis and metaphysis were labelled in vivo for 0.5-72 h with [35S]sulphate. At each time point the specific radioactivity, expressed as c.p.m. of [35S]sulphate/micrograms of uronic acid, of papain-resistant macromolecules in each tissue was determined. The identity of the glycosaminoglycans was established by the use of specific enzymic and chemical methods of degradation. Incorporation of the label into each tissue was maximal at 12 h; it then declined to 50-75% of that value by 72 h. Chondroitin sulphate was the predominant glycosaminoglycan in each tissue, representing 80-96% of the total; heparan sulphate comprised 2-14% of the total; in general, radioactive material sensitive to keratanase comprised less than 1% of the total. The relative amount of labelled chondroitin sulphate increased, whereas that of heparan sulphate decreased, with increasing time of incorporation. These data show that 25-50% of the newly synthesized glycosaminoglycans are lost from mineralizing tissues, during the time in which the newly secreted organic matrix becomes mineralized.

Animals↗
PubMed1984

Isolation and partial characterization of proteoglycans from rat incisors.

Newly synthesized proteoglycans of rat incisors were labelled in vivo for 6h with [35S]-sulphate in order to facilitate their detection during purification and characterization. Proteoglycans were extracted from non-mineralized portions (predentine) of rat incisors with 4M-guanidinium chloride and subsequently from dentine by demineralization with a 0.4M-EDTA solution containing 4M-guanidinium chloride. Both extractions were performed at 4 degrees C in the presence of proteinase inhibitors. Purification of proteoglycans was achieved with a procedure involving gel-filtration chromatography, selective precipitation of phosphoproteins, affinity chromatography and ion-exchange chromatography. Two proteoglycan populations were found in the initial extract (Pd-PG I and Pd-PG II), whereas only one fraction (D-PG) was obtained after demineralization. The minor proteoglycan fraction from the first extract, Pd-PG I, although not totally characterized, differed sharply from the other proteoglycans in that it had a larger molecular size with larger glycosaminoglycan chains composed of chondroitin 4- and 6-sulphate isomers. In contrast, the major proteoglycans Pd-PG II and D-PG had smaller hydrodynamic sizes with smaller glycosaminoglycan chains (but larger than those from bovine nasal cartilage proteoglycans) composed exclusively of chondroitin 4-sulphate. The major proteoglycans were incapable of interacting with hyaluronic acid. In general, the amino acid compositions of the major proteoglycans of rat incisors resembled that of bovine nasal cartilage proteoglycans, but the former had lower proline, valine, isoleucine, leucine, and higher aspartic acid, contents.

Amino Acids↗
PubMed1983

Metabolism of rat bone proteoglycans in vivo.

Former evaluations of the role of proteoglycans in mineralization have neglected to address the possibility that the metabolism of proteoglycans may be of significance in this regard. This problem was studied by using radiolabeling in vivo of rat calvaria with [35Sulphate for 2-72 h and a sequential extraction procedure to yield two pools of newly synthesized proteoglycans: one obtained from non-mineralized tissue by extraction with guanidinium chloride (GdmCl) and another obtained only after demineralization with EDTA. Total radioactivity in calvaria was maximal after 12 h of incorporation, but by 36 h had declined to a level that was about 55-65% of maximum. Radioactivity in the GdmCl extract declined steadily after 12 h, whereas that in the EDTA extract remained constant until 36 h, when it began to increase. Each extract contained a minor proteoglycan that eluted at the void volume (Vo) of a Sepharose CL-6B column. Unlike in the EDTA extract, this proteoglycan gradually disappeared from the GdmCl extract. Each extract also contained a major, smaller proteoglycan, with a Kav. of 0.24 and 0.36 in the GdmCl and EDTA extracts respectively. Papain digestion of each extract yielded glycosaminoglycan chains with Kav. values of 0.32 and 0.50 on CL-6B in the GdmCl and EDTA extracts respectively. Digestion of each extract with chondroitinase ABC and chondroitinase AC showed that the glycosaminoglycans were of similar disaccharide composition, with about 85% being 4-sulphated and the remainder 6-sulphated and/or iduronic acid-containing. These data suggest that about 45% of the newly synthesized proteoglycans are removed from the tissue during the course of mineralization.

Animals↗
PubMed1976

Further studies on the metabolism of D-glucose anomers in pancreatic islets.

The alpha and beta anomers of commercially available D-(5-3H) glucose were separated by miniaturized Hudson-Dale procedures based on precipitation with acetic acid. Reflectometric measurements of the reactivity with matrix-bound glucose oxidase showed that the preparations were about 90 per cent pure with respect to anomeric composition. Nonradioactive anomers separated by the same procedures were analyzed by optic polarimetry and gas chromatography. The preparations were about 90 per cent pure with respect to anomeric composition and produced no peaks but D-glucose on trimethylsilylation and chromatography. Microdissected pancreatic islets of noninbred ob/ob-mice exhibited a linear production of 3H2O for three to nine minutes when incubated with 6 mM alpha-D-(5-3H) glucose, beta-D-(5-3H) glucose, or D-(5-3H) glucose in anomeric equilibrium; the three glucose preparations did not differ in their rate of conversion to 3H2O. The rate of 3H2O production increased with glucose concentration (3-21 mM) during incubations for three minutes and, again, there was no evidence for the metabolic activity's being dependent on the anomeric composition of the labeled sugar. When microdissected islets were perifused without glucose and suddenly exposed to 5-6 mM alpha-D-glucose or beta-D-glucose, the concentration of glucose-6-phosphate rose within five minutes and did not differ significantly between experiments with alpha-D-glucose and beta-D-glucose. In the same perifusion experiments, only alpha-D-glucose caused a pronounced stimulation of insulin secretion, the difference from beta-D-glucose being significant. The results indicate that the recognition of glucose as an insulin secretagogue does not only involve metabolism by glucose-6-phosphate. The possible roles of the sorbitol pathway and of hypothetical regulatory sites for the glucose molecule ("receptors") are briefly discussed.

Animals↗
PubMedDate not supplied

Bone response to titanium alloy implants placed in diabetic rats.

Although dental implants continue to provide consistent and predictable treatment options for most patients, some people with uncontrolled systemic disease may be denied implant treatment. Diabetes is one such disease. According to the U.S. Centers for Disease Control and Prevention, diabetes is a leading cause of blindness, kidney failure, and amputations of the lower extremities. These complications result from microvascular disturbances associated with diabetes. The effect of diabetes on the healing of titanium implants has not been well established. In this study of 32 rats, diabetes was induced in 16 animals by injection of streptozotocin (65 mg/kg); the remaining 16 animals served as controls. Titanium alloy implants were placed in the tibiae of all 32 rats using standard surgical techniques. Implants healed for 14 days. Blood samples were obtained for serum glucose, osteocalcin, and alkaline phosphatase analyses. Implants were retrieved and processed for histomorphometric analyses. Three quantities were measured using light microscopy, video capture, and computer analysis: percent osseointegration (i.e., linear bone interface), associated bone volume percent, and contact frequency. Diabetic animals demonstrated significantly less osseointegration than controls. However, bone volume percent in diabetic animals was about 4 times greater than controls. Biochemical analyses were mixed; diabetic animals demonstrated increased serum osteocalcin levels compared to controls but decreased alkaline phosphatase. Based on the results of this study, it was concluded that the bone response associated with titanium alloy implants in the tibiae of diabetic rats is uniquely different from controls.

Alkaline Phosphatase↗