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M R Karim

Publications and source records attributed to M R Karim.

14 recordsLinked to original sources
PubMed2001

Hemicholinium-3 mustard reveals two populations of cycling choline cotransporters in Limulus.

Cholinergic neurons have both a low-affinity and a high-affinity choline transport process. The high-affinity choline transport is sodium dependent and thus it can be referred to as choline cotransport. Choline cotransport has been shown to be up-regulated by neuronal activity. Protein kinase C has also been shown to regulate choline cotransport. Both forms of regulation appear to modulate transport by altering the numbers of choline cotransporters in the nerve terminal membrane. The present study centers on choline cotransporter trafficking in Limulus brain hemi-slice preparations. The competitive, reversible, non-permeant ligand, [3H]hemicholinium-3, was used in binding studies to estimate the relative number of choline cotransporters in plasma membranes. The hemicholinium-3 mustard derivative has been shown to be an irreversible, highly selective, non-permeant ligand for the choline cotransporter, and was also used. Hemicholinium-3 mustard binding to the choline cotransporter blocked [3H]choline transport and [3H]hemicholinium-3 binding. Antecedent elevated potassium exposure of cholinergic tissues has been shown to up-regulate choline transport by the recruitment of additional choline cotransporters to surface membranes. This treatment was also effective in the recruitment of cotransporters following maximal inhibition by hemicholinium-3 mustard of brain hemi-slices. Long-term washout of hemicholinium-3 mustard in hemi-slices resulted in a time-dependent restoration of choline cotransport. Full recovery occurred within 2h. In uninhibited slice preparations, both staurosporine and chelerythrine, protein kinase C inhibitors, stimulated choline uptake. However, within a 1-h washout recovery of uptake following hemicholinium-3 mustard inhibition, the staurosporine responsive but not chelerythrine responsive transport had returned. On the basis of these findings, we hypothesize the existence of two distinct populations of cycling choline cotransporters, which includes inactive or "silent" transporters.

Alkaloids↗
PubMed2001

Statistical analysis of marginal count failure data.

Manufacturers want to assess the quality and reliability of their products. Specifically, they want to know the exact number of failures from the sales transacted during a particular month. Information available today is sometimes incomplete as many companies analyze their failure data simply comparing sales for a total month from a particular department with the total number of claims registered for that given month. This information--called marginal count data--is, thus, incomplete as it does not give the exact number of failures of the specific products that were sold in a particular month. In this paper we discuss nonparametric estimation of the mean numbers of failures for repairable products and the failure probabilities for nonrepairable products. We present a nonhomogeneous Poisson process model for repairable products and a multinomial model and its Poisson approximation for nonrepairable products. A numerical example is given and a simulation is carried out to evaluate the proposed methods of estimating failure probabilities under a number of possible situations.

Algorithms↗
PubMed2001

Flow cytometric evaluation of antiviral agents against human herpesvirus 6.

Antiviral activities of acyclovir (9-[(2-hydroxyethoxy) methyl] guanine, ACV), penciclovir (9-[4-hydroxy-3-(hydroxymethyl) butyl] guanine, PCV), ganciclovir ([9-(1,3-dihydroxy-2-propoxy) methyl] guanine, GCV), and foscarnet (phosphonoformic acid, PFA) were determined against Human Herpesvirus 6 (HHV-6) by flow cytometric technique. The technique is based on the detection of gp116 antigen expression in virus infected cells. Susceptibility was defined in terms of drug concentration which reduced the number of cells expressing HHV-6 gp116 antigen with a mean fluorescent intensity (MFI) by 50% as compared to virus infected untreated cells. GCV was found to be most effective against HHV-6 followed by PFA, PCV and ACV. For HHV-6A, the mean 50% inhibitory concentrations (IC50) of GCV and PFA were found to be 3.4 microM and 34.7 microM respectively, whereas the IC50 of ACV and PCV were found to be 53.7 microM and 37.9 microM respectively. For HHV-6B, the IC50 of GCV and PFA were found to be 5.7 microM and 71.4 microM respectively, whereas the IC50 of ACV and PCV were found to be 119.0 microM and 77.8 microM respectively. Flow cytometry is a valuable technique for the evaluation of antiviral compounds against viruses including HHV-6.

Acyclovir↗
PubMed1995

A new mode of size-dependent separation of proteins by capillary electrophoresis in presence of sodium dodecyl sulfate and concentrated oligomeric dextran.

Capillary electrophoresis in presence of sodium dodecyl sulfate (SDS) and 10% w/v of oligomeric dextran with molecular weight of just above 1000 was found to be an efficient medium for size-dependent separation of proteins (Karim, M. R., Janson, J.-C., Takagi, T., Electrophoresis 1994, 15, 1531-1534). The separations were found to be highly reproducible, both with respect to the position and relative amounts of the peaks. No evidence for a network structure in the medium could be found on examination of the effect of dextran concentration and viscosity measurements. The separation mechanism appears to be different from sieving by a polymer network structure. In free solution, SDS-protein complexes with molecular weights > 10,000 migrate with almost the same mobilities, irrespective of their molecular weight (this behavior is called free draining). Such SDS-complexes of proteins or peptides with molecular weights < 10,000, however, tend to increase their negatively signed mobilities with decreasing molecular weight (Karim, M. R., Shinagawa, S., Takagi, T., Electrophoresis 1994, 15, 1141-1146). Our working hypothesis is that in presence of the oligomeric dextran, the range of deviation from the free-draining electrophoretic behavior extends to higher molecular weights, resulting in a novel separation made.

Circular Dichroism↗
PubMed1994

Size-dependent separation of proteins in the presence of sodium dodecyl sulfate and dextran in capillary electrophoresis: effect of molecular weight of dextran.

Dextran solutions are widely used as sieving medium in protein analysis by capillary electrophoresis in the presence of sodium dodecyl sulfate. We studied the effect of dextran molecular weight on the separation efficiency using different dextran preparations with wide and very narrow molecular weight distributions, in the range between 1270 and 2,000,000. Migration times and band broadening of proteins were significantly affected by the molecular weight of dextran. Migration times of proteins decreased as molecular weights of the dextrans decreased. Satisfactory separation of all the proteins was possible with all dextrans except those with molecular weights of 70,000 and 23,800 where bovine serum albumin and phosphorylase b failed to be separated. Unexpectedly rapid separation of all the proteins with enhanced resolution could be observed using two dextrans with a narrow molecular weight distribution, with molecular weights of 1270 and 5220. Clearly the use of dextran with higher molecular weight is not the only way to achieve efficient separation of proteins. The separation mechanism in the presence of the low molecular weight dextrans remains to be made clear in a future study.

Carbonic Anhydrases↗
PubMed1992

Generalized linear models with random effects; salamander mating revisited.

In recent years much effort has been devoted to extending regression methodology to non-Gaussian data, where responses are not independent. These methods for dependent responses are suitable for data from longitudinal studies or nested designs. However, use of these methods for crossed designs seems to have serious limitations due to the intensive computations involved because of the intractable nature of the joint distribution. In this paper, we cast the problem in a Bayesian framework and use a Monte Carlo method, the Gibbs sampler, to avoid current computational limitations. The flexibility of this approach is illustrated by analyzing the interesting salamander mating data reported by McCullagh and Nelder (1989, Generalized Linear Models, 2nd edition, London: Chapman and Hall).

Analysis of Variance↗
PubMed1990

Determination of water in ascorbic acid by the proton isoconcentration technique using the standard addition method.

Water has been extracted from ascorbic acid into a dry mixture of equal volumes of methanol-organic solvents (n-propanol, ethylene glycol or propylene carbonate) and was determined potentiometrically, using the calibration graph based on the large and systematic change in cell potential for addition of 0-1%, m/m water into a dry mixture of the above mentioned mixture containing 2 x 10(-3) M trifluoromethanesulphonic acid (TFMSA) using a combination pH glass electrode with silver-silver chloride reference electrode having tetraethylammonium chloride (TEACl) in methanol as a filling electrolyte. The method is fast, accurate, reproducible and simple for operation.

Ascorbic Acid↗
PubMed1986

[Simultaneous interventions of the bile ducts and intra-abdominal organs: what is indicated and when?].

405 surgical interventions had been carried out simultaneously on the biliary tract and other intraperitoneal organs from 1960 to 1984. The patients were divided into three groups. Concerning group A and B (58 patients) the indication for that double-operation was absolute. The range of postoperative wound infections was 10.3%, complications were noted in 24.1%. Lethality rate was 6.8%, hospitalisation took place for 17.7 days. Concerning group C (347 patients) without absolute indication for surgical treatment on the biliary tract and another intraperitoneal organ wound infections subsequent to operating occurred in 5.7%, lethality rate was 2.3%. Complications could be seen in 12.1% and hospital treatment continued for 15.5 days. Principally occasional operations and surgical treatment carried out simultaneously should be avoided.

Abdomen↗
PubMed1985

Synergistic antiviral effects of acyclovir and vidarabine on herpes simplex infection in newborn mice.

277 5-7-day-old white Swiss mice were infected intranasally with Herpes simplex virus type 2 (HSV2) to mimic disseminated herpetic infection in human newborns. The antiviral efficacy of acyclovir, vidarabine and specific antiserum (SAS) alone and in combination was assessed. A significant increase in survival rate (52%) was observed with the combination of acyclovir (80 mg/kg/day) and vidarabine (125 mg/kg/day) compared to either compound (24 and 6%, respectively) when therapy was begun 30 h after infection and continued daily for the next 4 days. Combinations of acyclovir, vidarabine and SAS had less protective effect (8%) than acyclovir with SAS (32%) or vidarabine with SAS (12%). No improvement was observed in survival rate of HSV2-infected mice treated with SAS as compared with controls (0% and 5%, respectively). These results suggest the enhanced antiherpes effect in newborn mice is due to synergism of acyclovir and vidarabine, a combination deserving further evaluation for the treatment of HSV2 infections in humans.

Acyclovir↗
PubMed1983

In vitro activity of U-57930E against anaerobic bacteria and its comparison with clindamycin, ampicillin, carbenicillin and tetracycline.

The in vitro activity of U-57930E, a pipecolic acid amide of clindamycin, was compared with those of clindamycin, ampicillin, carbenicillin and tetracycline against 321 anaerobic clinical isolates. The MIC (micrograms/ml) of U-57930E that inhibited 95% Bacteroides fragilis, Peptococcus prevotii, B. melaninogenicus and P. asaccharolyticus was 0.0625; 0.03125 for Peptostreptococcus anaerobius, B. vulgatus, Propionibacterium and Peptococcus species. Clindamycin, on the other hand, gave MIC values of 0.5 microgram/ml for B. fragilis, P. prevotii and P. asaccharolyticus, 0.25 for Propionibacterium sp. All strains of Clostridium perfringens were inhibited by 0.5 microgram/ml of U-57930E. Both clindamycin and U-57930E showed similar MIC values for all strains of Fusobacterium nucleatum and Propionibacterium acnes tested. The MIC values for ampicillin, carbenicillin and tetracycline were within the expected range. U-57930E had a 4 approximately 8 fold lower MIC than clindamycin and is significantly active against anaerobic bacteria.

Ampicillin↗
PubMed1981

A rapid method for the detection of tryptophanase in anaerobic bacteria.

A total of 633 anaerobic bacteria were examined for tryptophanase production using a rapid method which distinguishes within 5 to 180 minutes between anaerobes that contain tryptophanase and those that do not. Of the 196 tryptophanase-positive isolates tested, 99% showed tryptophanase activity within 2 hours as compared with 94.4% in 24 hours by a conventional method. A total of 299 tryptophanase-negative organisms were tested. Ninety three percent of these remained negative after 24 hours as compared with 95.3% when tested within a 24-h conventional method. Additional information was obtained on the sensitivity of this test and the time-dependent production of indole by tryptophanase.

Bacteria↗
PubMedDate not supplied

Electrophoretic mobilities of the complexes between sodium dodecyl sulfate and various peptides or proteins determined by free solution electrophoresis using coated capillaries.

Electrophoretic mobilities of various proteins or peptides complexed with sodium dodecyl sulfate (SDS) were determined by free solution capillary electrophoresis. The complexes formed between SDS and protein polypeptide showed electrophoretic mobilities virtually insensitive to the protein molecular weight. On the other hand, scattered and larger negative electrophoretic mobilities were observed for peptides of molecular weights less than 10000. Mobility differences as small as 0.3-3% among the three differently modified derivatives of bovine serum albumin could also be successfully determined due to the high resolving power of capillary electrophoresis.

Amino Acid Sequence↗