PubMed Health⌕ Search

Biomedical subjects

F J Silverblatt

Publications and source records attributed to F J Silverblatt.

At least 19 recordsLinked to original sources
PubMed1987

Autoradiographic study of tobramycin uptake by proximal and distal tubules of normal and pyelonephritic rats.

Multiple factors may modify the pharmacokinetics of aminoglycosides and affect their nephrotoxic potential. In the present study, the influence of Escherichia coli pyelonephritis on the renal handling of [3H]tobramycin was investigated. The accumulation of [3H]tobramycin in proximal and distal tubules in both normal and infected rats was compared. Following induction of pyelonephritis, disturbed intrarenal localization of the drug was noted. Grain counts were affected in both proximal and distal tubules. Decreased labeling was observed at all time intervals in the proximal tubules. Electron microscopy showed that radioactivity was associated mostly with lysosomes in both normal and infected rats 1 and 24 h following the injection of the drug. We could detect significantly higher amounts of drug in the distal tubules of the pyelonephritic kidney than the normal levels at 10 min and 24 h postinjection. The drug did not seem to be associated with any particular organelle and was evenly distributed within the distal tubular cells. The present study shows that the transport of tobramycin within the infected nephron is disturbed. These data might shed some light on the influence of infection on the intrarenal pharmacology of aminoglycosides.

Animals↗
PubMed1987

Stimulation of human polymorphonuclear leukocyte oxidative metabolism by type 1 pili from Escherichia coli.

We compared the degree to which Escherichia coli phase variants which do (T1P+ E. coli) or do not (T1P- E. coli) express type 1 pili (T1P) stimulate human polymorphonuclear leukocyte (PMN) oxidative activity. Unopsonized T1P+ E. coli stimulated the release of 0.20 to 0.24 nmol of H2O2 per 10(6) PMN per min and the consumption of 1.4 to 4.0 nmol of O2 per 10(6) PMN per min; no measurable PMN oxidative activity was stimulated by unopsonized T1P- E. coli. In the presence of serum opsonins, T1P+ E. coli stimulated the release of 1.12 to 1.16 nmol of H2O2 per 10(6) PMN per min and the consumption of 5.0 to 6.0 nmol of O2 per 10(6) PMN per min, whereas T1P- E. coli stimulated the release of 0.42 to 0.43 nmol of H2O2 per 10(6) PMN per min and the consumption of 0.6 to 2.0 nmol of O2 per 10(6) PMN per min. Although unaggregated T1P did not stimulate PMN, latex beads coated with T1P (T1P-latex) stimulated alpha-methylmannoside-inhibitable, opsonin-independent PMN oxidative activity. The activity stimulated by either T1P+ E. coli or T1P-latex was susceptible to inhibition by cytochalasin B. Latex particles coated with bovine serum albumin or mannose-resistant pili did not stimulate PMN. These data indicate that T1P+ E. coli stimulate PMN oxidative metabolism more effectively than do T1P- E. coli and that a similar PMN oxidative response follows cellular stimulation by either unopsonized T1P+ or opsonized T1P- E. coli. Furthermore, T1P-latex faithfully mimics the ability of T1P+ E. coli to stimulate PMN oxidative metabolism. Such particles may be useful in further analyses of cellular responses to T1P+ E. coli.

Concanavalin A↗
PubMed1987

An accurate method to obtain urine for culture in men with external catheters.

Results of urine cultures from 26 male nursing home patients wearing external catheters, collected by a simple standardized technique, were compared with culture results from the same patients obtained by sterile in-and-out catheterization. The culture results were the same in 22 (85%) of the matched specimens, and specimens collected by the standardized technique were 100% sensitive and 94% specific in detecting significant growth of pathogenic organisms. In contrast, 13 (57%) of 23 specimens collected from patients with external catheters by the nursing home staff using their routine technique yielded three or more organisms and were considered contaminated. These results suggest that it is possible to obtain a urine specimen that reflects bladder urine in the vast majority of patients with external catheters, and thus potentially avoid the need for in-and-out catheterization when diagnosing and planning treatment for urinary tract infections in this population.

Aged↗
PubMed1986

Effect of Tamm-Horsfall urinary glycoprotein on phagocytosis and killing of type I-fimbriated Escherichia coli.

Human polymorphonuclear leukocytes (PMN) ingest type I (mannose sensitive) fimbriated Escherichia coli even in the absence of antibody, complement, or other serum opsonins. Our studies suggest that the Tamm-Horsfall urinary glycoprotein (THP) interferes with serum-independent ingestion. Electron micrographs showed that dissolved THP adhered to type I fimbriae and formed a pseudocapsule around bacteria bearing type I fimbriae. Phase-variant bacteria grown on blood agar neither expressed fimbriae nor bound THP. Affinity column chromatography demonstrated mannose-sensitive binding between purified type I fimbriae and purified THP. The ability of human PMN to bind and ingest type I-fimbriated E. coli was diminished if the bacteria had been coated by exposure to THP at physiologic concentrations. At 1 h, PMN were associated with an average of 2.62 uncoated bacteria, but with only 0.18 coated bacteria (P less than 0.001). alpha-Methyl mannoside blocked the observed effect of THP on binding and phagocytosis in a dose-dependent fashion: increased mannoside led to increased blocking. PMN preincubated with THP were able to bind and phagocytose normally. There did not appear to be any significant clumping of bacteria in suspension to account for these effects. Bactericidal assays with leukocytes in suspension demonstrated protection of THP-coated bacteria. At 1 h, PMN killed 42% of noncoated E. coli (a decrease of 0.24 log), but the number of THP-coated bacteria increased by 75% (an increase of 0.24 log). These observations may partially explain the virulence of E. coli in the bladder and kidney, where serum activity is low and THP is abundant.

Adhesiveness↗
PubMed1986

The surface of virulent Treponema pallidum: resistance to antibody binding in the absence of complement and surface association of recombinant antigen 4D.

The binding of immunoglobulin G present in syphilitic immune rabbit serum, syphilitic human serum, and rabbit antiserum to purified recombinant Treponema pallidum antigen 4D by T. pallidum, Nichols strain, was studied by immunoelectron microscopy. Treponemes were incubated with antiserum under the conditions of the T. pallidum immobilization test, in which T. pallidum-specific antibody renders the organism nonmotile and avirulent only in the presence of complement after a 16-h incubation period in an anaerobic environment. Antibody was not demonstrable on the surface of T. pallidum incubated with nonimmune rabbit serum or normal human serum in the presence of complement. Similarly, in the absence of complement, little or no antibody was found on the treponemal surface after incubation with syphilitic immune rabbit serum, syphilitic human serum, or rabbit antiserum directed against the recombinant 4D antigen. The addition of complement to syphilitic immune rabbit serum, syphilitic human serum, and anti-4D antibody resulted in immobilization and the deposition of antibody on the entire surface of the immobilized organisms. These results corroborate earlier work by other investigators demonstrating the resistance of freshly isolated T. pallidum to antibody binding in a variety of serological tests. Detection of 4D antigen on the surface of immobilized T. pallidum strongly implies that the use of T. pallidum immobilization test conditions provides a means to demonstrate the association of individual surface antigens on virulent T. pallidum. The resistance of T. pallidum to antibody binding may be relevant to the pathogenesis of syphilis.

Animals↗
PubMed1986

Change in degree of type 1 piliation of Escherichia coli during experimental peritonitis in the mouse.

To determine whether expression of type 1 pili varies during the course of Escherichia coli infection in vivo, mice were injected intraperitoneally with 5 X 10(7) CFU of piliated or nonpiliated phase variants per ml, and the degree of piliation was measured in peritoneal exudate by an enzyme-linked immunosorbent assay inhibition method. In the animals challenged with the piliated bacteria, the numbers of organisms increased a log over 9 h and the amount of pilus antigen decreased from 3 to 0.075 micrograms/10 bacteria. After a 4-h delay, nonpiliated bacteria also increased by one log over 9 h; however, the amount of piliation remained virtually undetectable. Piliated E. coli were more virulent than nonpiliated variants in this model (50% lethal dose of 7.5 X 10(6) versus 3 X 10(7), respectively). The difference was significantly reduced by prior passive immunization with rabbit serum containing high titers of antipili antibody. Piliated bacteria adhered in significantly greater numbers to isolated mouse peritoneal membranes than did nonpiliated variants (15,400 +/- 2,700 versus 1,300 +/- 700 bacteria/mm2, respectively; P = 0.05). Adherence was inhibited by the presence of 0.1 M alpha methyl mannose (1,500 +/- 1,800 bacteria/mm2, P = 0.01). These results confirm the results of previous qualitative studies showing that phase variation of type 1 pili occurs in vivo and suggest that these pili may confer an initial advantage for growth of E. coli in the peritoneal cavity, presumably by fostering colonization of the peritoneal serosal surface.

Animals↗
PubMed1979

Autoradiography of gentamicin uptake by the rat proximal tubule cell.

Rats were injected with 25 microCi (14.2 microgram) of tritiated gentamicin and were killed 10 min, 1 hour, or 24 hours after the injection. Renal tissue was preserved by intravascular perfusion of a glutaraldehyde-containing solution. In a preliminary experiment, glutaraldehyde was found to fix gentamicin to bovine serum albumin, and this property probably accounted for the negligible loss of label during specimen preparation. By light microscopy, gentamicin appeared to be confined almost entirely to the proximal tubules. Autoradiographic grains appeared initially over the apical cytoplasm of the proximal tubule cells and, with time, moved progressively into the interior of the cell. Electron-microscopy revealed that the grains were associated with apical vesicles at 10 min and lysosomes at 1 and 24 hours. The specificity of labeling was confirmed by quantitative grain analysis. These results indicate that gentamicin is transported into the proximal tubule cell by pinocytosis and becomes sequestered in lysosomes. This process may account for the accumulation of myeloid bodies in the proximal tubule lysosomes of gentamicin-treated rats, but whether this mechanism contributes the nephrotoxicity of this drug cannot be ascertained at this time.

Animals↗
PubMed1979

Effect of pili on susceptibility of Escherichia coli to phagocytosis.

The degree of piliation of 20 clinical isolates of Escherichia coli was correlated with their susceptibility to phagocytosis by human polymorphonuclear leukocytes. Piliation was quantitated by negative staining, and phagocytosis was quantitated by a monolayer technique. Ingestion was confirmed by electron microscopy. In the absence of source of opsonins, there was a positive correlation between the degree of piliation and susceptibility to phagocytosis (y = 0.83x + 19.58; correlation coefficient = 0.65; P < 0.01). Heavily piliated strains were no longer phagocytized after their pili were removed by ultraviolet irradiation. Phagocytosis was reduced 75% in the presence of 0.1 M d-mannose, an agent which competitively inhibits binding of pili to cell surfaces. l-Mannose, d-glucose, and d-galactose were much less inhibitory. The viability of piliated organisms was reduced by 1 log after 1 h of incubation with polymorphonuclear leukocytes. Addition of 10% fresh human serum increased both the rate and completeness of killing. These observations suggest that polymorphonuclear leukocytes may interact with the pili of E. coli to promote phagocytosis. This phenomenon may have clinical relevance in situations where normal opsonic activity is poor, such as the renal medulla.

Binding Sites↗
PubMed1979

Ultraviolet irradiation disrupts somatic pili structure and function.

Three piliated bacterial species were exposed to ultraviolet light (7 X 10(3) microW/cm2), and the effect of increasing duration of irradiation on the integrity of the somatic pili was quantitated by negative-stain electron microscopy. Heavily piliated Proteus mirabilis became devoid of pili after 20 min of irradiation, but Escherichia coli and Neisseria gonorrhoeae required 40 min for complete depiliation. Partially purified proteus pili underwent progressive loss of structural integrity with increasing doses of irradiation as determined by negative staining and nephelometry, suggesting that ultraviolet light exerted an effect directly on the pili themselves. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that new, small molecular weight fragments appeared after irradiation of purified E. coli pili, suggesting that cleavage of the peptide chain rather than disassociation of pilin monomers accounted for the loss of pili structure. Ultraviolet irradiation also inhibited the ability of piliated bacteria to bind to human buccal epithelial cells. These observations indicate that the ultrastructural integrity and function of pili can be disrupted by ultraviolet light.

Dose-Response Relationship, Radiation↗
PubMed1979

Antipili antibody affords protection against experimental ascending pyelonephritis.

The ability of antipili antibody to prevent ascending urinary tract infection was investigated in rats. One group of rats was immunized passively with rabbit antisera to purified pili and challenged by intravesicular inoculation of 5 x 10(7) heavily piliated Escherichia coli. Only 2 of 14 immunized animals developed cortical abscesses as compared to 13 of 15 control rats given normal rabbit serum (P equals 0.0001). The mean log titer of bacteria in the kidneys of the immunized rats was 0.85 vs. 6.08 in the controls (P less than 0.005). A second group was actively immunized with pili. 3 of 16 immunized animals became infected as compared to 10 of 15 controls (P equals 0.01). The mean log titers were 2.13 and 4.54, respectively (P less than 0.01). A third group was passively immunized and challenged with a strain that had different O, K, and H antigens but shared pili antigens. Abscesses occurred in 4 of 15 immunized animals as compared to 13 of 15 controls (P equals 0.001). The mean log titers were 2.37 and 5.63, respectively (P less than 0.005). These results indicate that antipili antibody protects rats against ascending urinary tract infections.

Animals↗
PubMed1979

Binding of 125I-insulin to the isolated glomeruli of rat kidney.

To investigate a possible action of insulin on the glomerulus, the binding 125I-insulin to the isolated glomeruli prepared from rat kidney was examined. When incubated at 22 degrees C, 125I-insulin binding proceeded with time and reached a steady state at 45 min at which time nonspecific binding was less than 25% of total binding. A small fraction of 125I-insulin was degraded during incubation. This binding was specific to insulin in that it was inhibited by unlabeled porcine and beef insulins and to a lesser extent by porcine proinsulin and desalanine-desasparagine insulin, but not by glucagon, parathyroid hormone, vasopressin, calcitonin, and angiotensin II. Increasing concentrations of nonlabeled insulin displaced 125I-insulin binding in a dose-dependent fashion. Scatchard plot of the data was curvilinear consistent with either two classes of receptors with different affinities or a single class of receptors that demonstrate negative cooperativity. The addition of excess nonlabeled insulin to the glomeruli preincubated with 125I-insulin resulted in a rapid dissociation of approximately or equal to 70% of bound 125I-insulin. Insulin decreased the increments in glomerular cyclic AMP levels by epinephrine and by prostaglandin E2, but not those by histamine. These data showed the presence of specific insulin receptors in the glomeruli, and that insulin action may be, at least in part, through modulation of glomerular cyclic AMP concentrations. Such action of insulin may underlie the alteration in glomerular ultrafiltration and the glomerular ultrafiltration and the development of glomerular lesions in diabetes mellitus, a disease in which insulin deficiency or the tissue resistance to insulin exists.

Angiotensin II↗
PubMed1978

Influence of pili on the virulence of Proteus mirabilis in experimental hematogenous pyelonephritis.

The ability of heavily and lightly piliated Proteus mirabilis to infect the renal parenchyma was compared in a model of hematogenous pyelonephritis. Cortical abscesses occurred in 13 of 24 rats injected with lightly piliated P. mirabilis but in none of 24 rats challenged with heavily piliated organisms (P less than 0.001). Lightly and heavily piliated organisms were cleared from the vasculature equally rapidly and were also delivered to the kidney in equal numbers. During the first 24 hr, however, titers of the lightly piliated organisms in the kidney increased by 4 logs, whereas the heavily piliated P. mirabilis were virtually all eliminated. Pili are believed to mediate attachment to cell surfaces, and heavy piliation has been correlated with enhanced virulence when P. mirabilis invades the kidney across the pelvic mucosa. The results in this study suggest, however, that pili may adversely affect bacterial survival within the renal parenchyma.

Animals↗
PubMed1978

Evaluation of an office method of detecting bacteriuria.

Although catheter-associated UTI continues to be the leading cause of nosocomial infection, epidemiological investigation of catheter use in many hospitals may be precluded by the reluctance of the laboratory to process the large number of urine cultures. We have evaluated the use by Nurse Epidemiologists of Bacturcult tubes for such purposes. The urine of 111 catheterized patients was cultured daily using both the Bacturcult and streak plate method until significant bacteriuria developed (greater than 10(5) colonies/ml). Bacturcult proved as accurate as the conventional technique in detecting bacteriuria. In contrast to previous studies, the daily incidence of infection rose with increasing duration of catheterization. Concomitant antibiotic usage reduced the risk of infection but selected out multi-drug resistant organisms. Older age and procedural errors also increased the risk of infection. The study took 150 hours to complete and cost about $250. It is concluded that Bacturcult is an accurate, simple and relatively inexpensive method of detecting bacteriuria and could be useful for investigating the epidemiology of catheter-associated infections in community hospitals.

Adult↗