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Biomedical subjects

S R Khan

Publications and source records attributed to S R Khan.

142 records · Page 8Linked to original sources
PubMed1976

Tobramycin in treatment of infections due to Pseudomonas aeruginosa in patients with cystic fibrosis.

The effectiveness and safety of tobramycin against infections due to Pseudomonas aeruginosa in patients with cystic fibrosis were studied in 15 patients with moderate-to-severe exacerbation of chronic pulmonary infection. Seventeen courses of treatment were given. Tobramycin (5-7.5 mg/kg per day) was administered intravenously in three divided doses per day (seven to 21 days). All specimens of sputum yielded moderate-to-heavy growth of P. aeruginosa; all isolates were inhibited by 4 mug of tobramycin/ml, and in seven cases isolates were not inhibited by 4 mug of gentamicin/ml. The mean levels of tobramycin in the blood were 4.4 mug/ml 0.5-1 hr and 0.8 mug/ml 7.5-8 hr after administration. All patients received an antistaphylococcal agent before, during, and after therapy. All patients except for two received 750 mg of carbenicillin/kg per day intravenously in six divided doses and 1 g of carbenicillin in a mask for inhalation three times a day. Both clinical and radiological improvement was noted in all patients. The white blood cell count, which was elevated in seven patients, returned to normal, and levels of blood gases improved. P. aeruginosa was eliminated from the sputum in five cases. No adverse side effects were noted.

Adolescent↗
PubMed1970

Continued expression of the ribonucleic acid control gene during inhibition of Escherichia coli ribonucleic acid and protein synthesis.

The effect of the ribonucleic acid (RNA) control (RC) gene on the biosynthesis of viral RNA has been examined in an RC(str) and an RC(rel) host infected with R17 RNA bacteriophage under conditions in which host RNA and protein synthesis were inhibited by the addition of rifampicin. Methionine and isoleucine starvation depressed viral RNA biosynthesis in an RC(str) host but not in an RC(rel) host. However, histidine starvation had little effect on viral RNA and protein synthesis in both RC(str) and RC(rel) cells, although it had a marked effect on host protein and RNA synthesis in an RC(str) host. Chloramphenicol relieved the effect of amino acid starvation on viral RNA synthesis in an RC(str) host. It is concluded that stringent control of viral RNA biosynthesis does not require the continued biosynthesis of the RC gene product (RNA or protein) and that a preformed RC gene product can regulate the biosynthesis of the exogenous RNA. It is suggested that the amino acid dependence of viral RNA biosynthesis is due to its obligatory coupling with the translation of the viral coat protein which lacks histidine. It may be inferred that the amino acid requirement of bacterial RNA is due to its coupling with the translation of a host-specific protein (other than the RC gene product) which requires a full complement of amino acids. Since chloramphenicol is known to permit ribosome movement in the absence of protein synthesis, it is suggested that ribosome movement along the nascent RNA chain is a sufficient condition for the continuation of RNA synthesis.

Alanine↗
PubMed1968

Proflavine Uptake and Release in Sensitive and Resistant Escherichia coli.

Both Escherichia coli B and a proflavine-resistant mutant, E. coli B/Pr, took up the same amounts of proflavine when suspended in buffer containing the dye. In growth media, however, sensitive cells took up more proflavine than did resistant cells. Adding growth media or any one of several constituents of these media, including amino acids, glycerol, pyruvic acid, and metabolizable sugars, to resistant cells that had taken up proflavine in buffer caused them to lose the dye, but had less or no effect on sensitive cells. Certian salts caused an equal release of proflavine from resistant and sensitive cells. Proflavine released from resistant cells by glucose was not changed chemically. The effects of temperature and metabolic inhibitors suggest that proflavine uptake is a passive process but that its release may be an active one, dependent on metabolism. Glucose had more effect on the proflavine binding of E. coli B grown in a minimal medium than on that of cells grown in a complex medium. E. coli B was less susceptible to proflavine when growing in a minimal medium. The effects of other synthetic media on proflavine susceptibility of E. coli B were also studied. Deoxyribonucleic acid and envelopes from sensitive and resistant cells bound the same amounts of proflavine, and no difference was seen in the site of dye binding when sensitive and resistant cells that had taken up proflavine in buffer were sonically broken and fractionated. The results suggest that sensitive and resistant cells are equally permeable to proflavine but differ in the ease with which metabolites cause them to release bound proflavine. So far, however, these differences do not account completely for the ability of resistant cells to grow in high proflavine concentrations.

Journal Article↗
PubMedDate not supplied

Different secretory IgA antibody responses after immunization with inactivated and live poliovirus vaccines.

The influence on secretory IgA antibody levels in milk and saliva of vaccination with oral, live poliovirus vaccine ( OPV ) and inactivated poliovirus vaccine (IPV) was studied. IPV, especially the antigen-rich Dutch vaccine, more often induced increases in antibody titers in milk (50%) than did OPV (26%) (P less than .01). OPV more often decreased the antibody levels in milk (40%) than did IPV (10%) (P less than .01). It was striking that mainly high prevaccination titers were decreased. The increases of IgA antibody in saliva were less striking. IPV caused increases as often in milk as in saliva, whereas OPV more often induced increases in IgA antibody in saliva, but there was a poor correlation between the changes in antibody titers in milk and those in saliva.

Antibodies, Viral↗
PubMedDate not supplied

Disclosure of HIV status to medical providers: differences by gender, "race," and immune function.

OBJECTIVE: The authors used data from a larger study to explore differences by gender, self-reported racial identification, and immune function in disclosure of HIV-positive serostatus to medical providers (dentists, family doctors, and emergency room [ER] and obstetrics-gynecology [ob/gyn] providers). METHOD: The authors analyzed interview responses from a convenience sample of African American and white men and women receiving HIV medical care at urban hospitals and clinics in St. Louis. Missouri. RESULTS: Of 179 respondents using at least one of three types of providers, 124 (69%) disclosed their HIV status to all applicable types of providers, 39 (22%) disclosed to only one or two types of providers, and 16 (9%) did not disclose to any of these types of providers. "Race" and CD4 count, but not gender, were independently associated with disclosure to dentists, family doctors, and ER providers in multivariate logistic regression analyses. CONCLUSIONS: Differences in disclosure rates, especially among patients who may be asymptomatic, suggest a need for public health education of both medical providers and patients with HIV.

Adolescent↗
PubMedDate not supplied

Intestinal colonization with Enterobacteriaceae in Pakistani and Swedish hospital-delivered infants.

Rectal cultures from Swedish and Pakistani hospital-delivered newborn infants were analysed regarding the early acquisition of enterobacteria. Swedish infants were delivered vaginally, Pakistani infants were delivered either vaginally or by caesarean section. The Swedish infants were all breast-fed, whereas breastfeeding was incomplete and often started late among the Pakistani infants. Both groups of Pakistani infants were more rapidly colonized with enterobacteria than were the Swedish infants. Cultures from Swedish infants seldom yielded more than one kind of enterobacteria; E. coli and Klebsiella were most frequently isolated. E. coli dominated in both Pakistani groups, but especially caesarean section delivered infants were in addition often colonized with Proteus, Klebsiella, Enterobacter or Citrobacter species. Breastfeeding from the first day of life reduced colonization with Klebsiella/Enterobacter/Citrobacter. The results suggest that environmental exposure, delivery mode and early feeding habits all influence the early intestinal colonization with enterobacteria.

Breast Feeding↗
PubMedDate not supplied

Origin of cells in the coronary intima during acute vascular rejection of the transplanted human heart.

Acute vascular rejection of the coronary arteries in human heart transplants is characterized by a lymphocytic infiltrate and a thickened intima that contains numerous highly vacuolated cells. The origin of the vacuolated cells has been controversial. In this immunocytochemical and electron microscopic study of four patients with acute vascular rejection, the predominant cells in the coronary artery intima were host-derived lymphocytes and highly vacuolated smooth muscle cells. Lymphocytic infiltrates were composed of T cells with variable numbers of B cells. Macrophages were infrequent. Smooth muscle cells were identified by their reactivity to muscle-specific actin and ultrastructural features of a peripherally displaced elongated nucleus associated with abundant myofibrils. In addition, the vacuolated cells did not react with endothelial factor 8-related antigen or Ulex europaeus agglutinin, as would be expected of endothelial cells. The cytoplasmic vacuoles present in the smooth muscle cells appear to be swollen endoplasmic reticulum containing watery fluid consistent with the hypothesis that they result from altered ion movement across the plasma membrane in response to cellular injury.

Constriction, Pathologic↗
PubMedDate not supplied

Acute vascular rejection of the coronary arteries in human heart transplantation: pathology and correlations with immunosuppression and cytomegalovirus infection.

Prior studies of vascular rejection in transplanted human hearts have stressed the importance of accelerated coronary arteriosclerosis (chronic vascular rejection). We, however, have had four patients with sudden onset of acute heart failure within 90 days of transplantation who have died without significant myocardial interstitial rejection or the concentric intimal thickening with dense collagen that is typical of chronic vascular rejection. In contrast, the coronary arteries in our patients had a prominent lymphocytic infiltrate, a loosely organized intimal thickening composed of smooth muscle cells, and extensive endothelial injury. We believe that these changes define acute vascular rejection of the coronary artery. In 14 transplanted hearts obtained consecutively, at autopsy or at a second transplant procedure, graft failure was caused by acute coronary vascular rejection in six cases and by chronic coronary vascular rejection in one case. The remaining seven patients showed no evidence of vascular rejection and died primarily of sepsis. Cytomegalovirus (CMV) disease was present in 6 of 7 patients with vascular rejection, of which 43% were CMV-negative recipients of hearts from CMV-positive donors. The adoption of a triple-drug protocol, in which azathioprine was added to cyclosporine and prednisone, reduced the incidence of acute vascular rejection from 27% to 8%. We conclude that acute coronary vascular rejection may be initially seen as global cardiac ischemia in the absence of significant interstitial myocardial rejection. Further, acute vascular rejection should be pathologically distinguished from chronic vascular rejection, although both are probably stages in the natural history of immune-mediated vascular injury.

Acute Disease↗
PubMedDate not supplied

Oxalate and calcium oxalate crystals are injurious to renal epithelial cells: results of in vivo and in vitro studies.

Calcium oxalate (CaOx) nephrolithiasis was induced in male Sprague-Dawley rats by administration of 0.75% ethylene glycol. Urinary excretion of lactate dehydrogenase (LDH) was used as a marker of cellular injury. Lipid peroxides (LP), as marker for free radical injury, were measured as malondialdehyde (MDA) in urine and the kidneys. Urinary oxalate (Ox), LDH, LP, CaOx crystals, and renal LP and CaOx crystal deposits were examined on day 0, 5, 30 and 60 of the experiment. There were significant differences between control and experimental rats in all the parameters except LDH which did not show a significant increase after 15 days. Subconfluent cultures of MDCK and LLCPK1 cells were exposed to various concentrations of oxalate and/or 500 fg/ml CaOx crystals. Cell viability was assayed by trypan blue exclusion, cellular injury was determined by measuring LDH in the media, and free radical injury was measured as MDA contents of the cells. On exposure to both Ox and/or CaOx crystals trypan blue exclusion decreased and LDH and MDA increased significantly in both tissue cultures. LLC-PK1 appeared more sensitive. The results indicate that both oxalate and calcium oxalate crystals are injurious to renal epithelial cells in the kidneys as well as in culture.

Animals↗