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Biomedical subjects

G Reid

Publications and source records attributed to G Reid.

At least 127 records · Page 7Linked to original sources
PubMed1994

Comparison of cell lines deficient in antigen presentation reveals a functional role for TAP-1 alone in antigen processing.

Cytotoxic T lymphocytes (CTL) recognize antigenic peptides bound to major histocompatibility complex class I antigens on the cell surface of virus-infected cells. It is believed that the majority of peptides originate from cytoplasmic degradation of proteins assumed to be mediated by the "20S" proteasome. Cytosolic peptides are then translocated, presumably by transporters associated with antigen processing (TAP-1 and -2), into the lumen of the endoplasmic reticulum (ER) where binding and formation of the ternary complex between heavy chain, beta2-microglobulin (beta 2m) and peptide occurs. In this study, we have analyzed and compared the phenotype of two mutant cell lines, the thymoma cell line RMA-S and a small lung carcinoma cell line CMT.64, in order to address the mechanism that underlies the antigen processing deficiency of CMT.64 cells. Unlike RMA-S cells, vesicular stomatitis virus (VSV)-infected CMT.64 cells are not recognized by specific CTL. Interferon gamma (IFN-gamma) treatment of CMT.64 cells restores the ability of these cells to process and present VSV in the context of Kb. We show that although CMT.64 cells express a low level of beta 2m, the recognition of VSV-specific CTL is not restored by increasing the amount of beta 2m synthesized in CMT.64 cells. In addition, we find that CMT.64 cells express moderate levels of Kb heavy chain molecules, but most of it is unstable and rapidly degraded in the absence of IFN-gamma treatment. We infer that the antigen processing deficiency does not lie at the level of beta 2m or Kb production. We find also that the mRNAs for both TAP-1 and -2 are present in RMA and RMA-S cells but are absent in uninduced CMT.64 cells. Upon IFN-gamma induction, both mRNAs are highly expressed in CMT-64 cells. In addition, we find that the low molecular mass polypeptides 2 and 7, and additional components of the proteasome are induced by IFN-gamma in CMT-64 cells. Finally, introduction of the rat TAP-1 gene in CMT.64 cells restores CTL recognition of VSV-infected cells. These results indicate that a TAP-1 homodimer may translocate peptides in the ER and explain partially the CMT.64 defect and the RMA-S phenotype. These findings link a dysfunction in the transport and/or generation of antigenic peptides to the capacity of tumor cells to evade immunosurveillance and provide a unique model system to dissect this phenomenon.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Transport and expression in human melanomas of a transferrin-like glycosylphosphatidylinositol-anchored protein.

Melanotransferrin, also called p97, is a cell surface glycoprotein which was first described as a marker antigen for human melanoma cells. Although p97 has a striking structural similarity to human serum transferrin and lactoferrin, its function has not yet been determined. One feature that distinguishes p97 from the other members of the transferrin family is the presence of a stretch of 24 hydrophobic amino acids at the C terminus, previously assumed to form a proteinacious transmembrane domain. In this study, sensitivity to bacterial phosphatidylinositol-specific phospholipase C, biosynthetic labeling with [3H]ethanolamine, and partitioning in Triton X-114 are used to establish that p97 is expressed at the cell surface as a glycosylphosphatidylinositol-anchored protein. In addition, to gain insight into the intracellular transport of p97, biosynthetic transport studies were performed on a melanoma cell line. These studies resulted in the identification of an additional form of p97 which is found in the medium and which likely does not originate from an alternatively spliced form of the p97 mRNA. These findings, together with our recent observation of the co-localization of p97 and the transferrin receptor in brain capillary endothelium (W. A. Jefferies, M. R. Food, R. Gabathuler, S. Rothenberger, T. Yamada, and P. L. McGeer, manuscript submitted) raise important questions about the function of the two forms of p97 detected and the possible involvement of this protein in a cellular iron uptake mechanism that is independent from the transferrin/transferrin receptor system.

Alternative Splicing↗
PubMed1994

Activating effect of the flavonoid phloretin on Ca(2+)-activated K+ channels in myelinated nerve fibers of Xenopus laevis [corrected].

The effects of the flavonoid phloretin on K+ channels in amphibian myelinated nerve were studied by patch clamping. The open probability of Ca(2+)-activated K+ channels was greatly increased by external phloretin (10-200 microM) due to a shift of the membrane potential for half-maximal activation, E50, of -63.9 mV (80 microM phloretin). Open times were prolonged and closed times shortened. Channel activation by phloretin developed slowly (tau on = 33.4 s) and its washout was even slower (tau off,1 = 4.7 and tau off,2 = 183.2 s). In contrast, submillimolar phloretin blocked two delayed rectifier K+ channels (I and F) whereas the gating of the ATP-sensitive and the flickering K+ channel were unaffected. Phloretin may directly affect the voltage sensor of K+ channels.

Adenosine Triphosphate↗
PubMed1994

Adhesion of lactobacilli to urinary catheters and diapers: effect of surface properties.

Thirteen strains of lactobacilli were tested for their ability to adhere to commercial devices used in the urinary tract. Although it appeared that the most hydrophilic organisms adhered in highest numbers, there was no significant correlation between water contact angle and adhesiveness to catheters. Five organisms tested were found to be highly adherent to Huggies commercial diapers. Loss in hydrophobicity upon serial culture of Lactobacillus fermentum B-54 was not due to a proteinaceous S layer, although protein involvement per se cannot be ruled out. It was evident that, not only can members of the normal female urogenital flora adhere to commonly used commercial prostheses, but their ability to attach is related to hydrophilic as well as hydrophobic surface components.

Adult↗
PubMed1994

Applications from bacterial adhesion and biofilm studies in relation to urogenital tissues and biomaterials: a review.

The urogenital tract, particularly of the adult female, is the habitat for many species of microorganisms. These populations are in a state of flux, are susceptible to disruption by antibiotics and spermicides, and are exposed to many different biomaterial substrata. Infections of the genital area and bladder are common, and are invariably initiated by microbial adhesion to surfaces. This review examines the actual and potential applications to industry and to patients emerging from the study of bacterial adhesion to surfaces.

Anti-Bacterial Agents↗
PubMed1994

Sudden infant death syndrome (SIDS): disordered brown fat metabolism and thermogenesis.

Foster found areas with the highest incidence of SIDS in USA in 1983-1984 coincided with the highest areas recorded with the highest incidence of goitre in First World War troops (1). Reid compared the two populations described as having the highest incidence of SIDS worldwide. Both were selenium deficient areas (King County WA, USA and Canterbury, New Zealand). Besides being a selenium livestock responsive area, Canterbury school children, prior to 1925, had a 56% incidence of goitre (2-6). Brown adipose tissue (BAT) synthesises fatty acids from glucose. BAT is a major tissue in fatty acid metabolism for the generation of heat (7). BAT has the specific property of converting thyroxine (T4) to triodothyronine (T3) via Type II deiodinase enzyme. There is a many fold increase in the activity of this deiodinase in BAT after exposure of rats to sudden cold, which is greatly impaired in selenium deficient animals (7). The accepted picture of SIDS worldwide is that there is an increased incidence in infants of young smoking mothers. The incidence peaks in the second and third month of life, in winter and as latitude increases.

Adipose Tissue, Brown↗
PubMed1994

Do antibiotics clear bladder infections?

An examination of transitional bladder epithelial cells from 69 urine specimens from 23 spinal cord injury patients showed the presence of adherent bacterial biofilms in 66 cases (96%). All patients were receiving antimicrobial therapy, primarily trimethoprim-sulfamethoxazole (41 of 69), without any apparent effect on the bladder colonization. The large number of bacteria that emerged with highly virulent and potentially multi-drug resistant characteristics, especially Enterococcus faecalis (33% of isolates), was of concern. These findings raise questions about the proved efficacy and effectiveness of antibiotics against uropathogenic biofilms adherent to tissues.

Adolescent↗
PubMed1994

Use of adhesion counts to help predict symptomatic infection and the ability of fluoroquinolones to penetrate bacterial biofilms on the bladder cells of spinal cord injured patients.

There were three objectives to the present study: (1) compare the bladder infection rate and extent of biofilm formation for seven untreated spinal cord injured (SCI) patients and seven given prophylactic co-trimoxazole, (2) identify a level of bacterial adhesion to bladder cells which could be used to help predict symptomatic infection, and (3) determine from in vivo and in vitro studies whether fluoroquinolones were effective at penetrating bacterial biofilms. The results showed that the infection rate had not changed with the introduction of prophylaxis. However, the uropathogenic population had altered subsequent to the introduction of prophylaxis with E. coli being replaced by E. faecalis as the most common cause of infection. In 63% of the specimens from asymptomatic patients, the bacterial counts per cell were < 20, while 81% of specimens from patients with at least one sign and one symptom of urinary tract infection (UTI) had > 20 adherent bacteria per bladder cell. Therefore, it is proposed that counts of > 20 bacteria adherent to sediment transitional epithelial bladder cells may be predictive of symptomatic UTI. Clinical data showed that fluoroquinolone therapy reduced the adhesion counts to < 20 per cell in 63% of cases, while trimethoprim-sulfamethoxazole only did so in 44%. Further in vitro testing showed that ciprofloxacin (0.1, 0.5 and 1.0 micrograms/ml) partially or completely eradicated adherent biofilms from 92% of spinal cord injured patients' bladder cells, while ofloxacin did so in 71% cases and norfloxacin in 56%. These findings have important implications for the detection and treatment of bacteriuria in spinal cord injured patients.

Adult↗
PubMed1994

Effects of ciprofloxacin, norfloxacin, and ofloxacin on in vitro adhesion and survival of Pseudomonas aeruginosa AK1 on urinary catheters.

Pretreatment of urinary silicone latex catheters in vitro with 0.1 and 0.5 microgram of ciprofloxacin per ml for 1, 24, and 48 h significantly reduced the adhesion and survival of the clinical isolate Pseudomonas aeruginosa AK1. UV spectroscopy and high-performance liquid chromatography confirmed the presence of ciprofloxacin adsorbed onto the catheters and showed that up to 56% of the drug leached into the surrounding fluid within 24 h. Scanning electron microscopy demonstrated that the adherent organisms were malformed and elongated after exposure to ciprofloxacin. Transmission electron microscopy showed the presence of fimbriae on the bacterial surfaces, but there was no conclusive evidence of changes in the fimbriae upon exposure to ciprofloxacin. It was found that a significant eradication of 24-h Pseudomonas biofilms could be achieved with ciprofloxacin as well as with ofloxacin and norfloxacin. Preincubation of catheters with 50- and 100-micrograms/ml concentrations of ciprofloxacin resulted in up to a 99% reduction in the number of adherent bacteria in comparison with the reduction on control catheters. In addition, adherent biofilms were eradicated by 24 h of challenge with 50 and 100 micrograms of ciprofloxacin per ml at pH 7.0 and 5.5. Results of these in vitro studies suggest that there could be a clinical role for fluoroquinolones in preventing and treating urinary tract infections associated with P. aeruginosa adherence to prosthetic devices.

Anti-Infective Agents↗
PubMed1994

Displacement of Enterococcus faecalis from hydrophobic and hydrophilic substrata by Lactobacillus and Streptococcus spp. as studied in a parallel plate flow chamber.

The displacement of Enterococcus faecalis 1131 from hydrophobic and hydrophilic substrata by isolates of Lactobacillus casei 36 and Streptococcus hyointestinalis KM1 was studied in a parallel plate flow chamber. The experiments were conducted with either 10 mM potassium phosphate buffer or human urine as the suspending fluid, and adhesion and displacement were measured by real-time in situ image analysis. The results showed that E. faecalis 1131 was displaced by lactobacilli (31%) and streptococci (74%) from fluorinated ethylene propylene in buffer and that displacement by lactobacilli was even more effective on a glass substratum in urine (54%). The passage of an air-liquid interface significantly impacted on adhesion, especially when the surface had been challenged with lactobacilli (up to 100% displacement) or streptococci (up to 94% displacement). These results showed that the parallel plate flow system with real-time in situ image analysis was effective for studying bacterial adhesion and that uropathogenic enterococci can be displaced by indigenous bacteria.

Adult↗
PubMed1994

Influence of dextrose dialysis solutions on adhesion of Staphylococcus aureus and Pseudomonas aeruginosa to three catheter surfaces.

Peritonitis is serious problem associated with continuous ambulatory peritoneal dialysis. The process can be initiated by intraluminal contamination and colonization of the peritoneal cavity as well as by bacterial adhesion to biomaterials, including catheters and exit site dressings. The aim of this study was to determine the degree to which two pathogenic organisms could adhere to three biomaterial surfaces, and the extent to which dextrose concentration influenced the binding and survival. Using a 24-hour in vitro assay, it was found that the Staphylococcus aureus strain consistently adhered significantly better than the Pseudomonas aeruginosa isolate, and only the adhesion of the latter was decreased with higher concentrations of dextrose in dialysis solutions. Electron microscopy demonstrates that within this short time period, bacterial biofilms had begun to form on the catheter surfaces.

Bacterial Adhesion↗
PubMed1993

Metabolic disorders of cattle.

Goldberger discovered human pellagra was a non-infectious disease, affecting mostly the small and the timid in overcrowded institutions. Symptoms were diarrhoea, dermatitis and dementia. The staff and older children escaped the disease. They ate the meat and left the small and timid with the gravy. The 'Goldberger syndrome' is observed during competitive feeding of livestock, in ketotic animals and in the zinc depleted which are lethargic and pick all day at their feed. The pellagra preventative factor was later found to be nicotinic acid, derived from the amino acid tryptophan. Deficiencies of copper, magnesium, vitamin B6 (activated by a zinc kinase) inhibit the conversion of tryptophan to nicotinic acid. Stresses, including liver diseases, malabsorption, iron overload, porphyria, marasmus, cold stress, pregnancy, lactation, antibiotics and sulfa drugs, all increase dietary needs of nicotinic acid. Elevated free fatty acids and ketone bodies in the blood are associated with ketosis, zinc depletion and the pre-diabetic state. There is a diminished uptake of glucose by the tissues, a condition also found in parturient paresis of dairy cows when elevated hydrocortisone promotes insulin resistance and hyperglycaemia. This defect in insulin response leads to a diabetic-like state. The major predisposing factor in parturient paresis of dairy cows is hypocalcaemia. Gut absorption of dietary calcium may not meet the primary demands of lactation initiation until bone calcium mobilisation is established.

Animals↗
PubMed1993

Bacterial biofilm formation on the bladder epithelium of spinal cord injured patients. II. Toxic outcome on cell viability.

As a follow up to our first study of 10 spinal cord injured patients, a further 8 patients were investigated over 2 months for biofilm formation on their bladder epithelial cells and for evidence that these uropathogens damage the host bladder. All the patients were found to be colonized with uropathogens, regardless of whether or not they were receiving antibiotics. Using vital staining, it was discovered that there was a significant reduction (33%) in bladder cell viability in the presence of bacterial biofilms compared to controls. This was not associated with cell turnover rates. In vitro tests showed a similar reduction in cell viability when uropathogens were incubated with bladder cells. In addition, white cell counts were significantly elevated in the patients' urine, indicative of an infectious and/or inflamed state. There was no difference between symptomatic and asymptomatic patients in their mean bacterial adhesion counts. Patients were just as likely to be symptomatic as asymptomatic when on antibiotics. In summary, the presence of virulent organisms in the bladder does adversely affect the host, even when the patient has insignificant signs and symptoms of infection, thereby raising concerns over the decision not to treat the patient. Unless specific antibiotics are used which eradicate adherent biofilms from the bladder, the treatment of symptomatic patients will only impact upon the signs and symptoms in some patients, and not alter their susceptibility to reinfection.

Adult↗
PubMed1993

Cor pulmonale and silicosis: a necropsy based case-control study.

The presence of cor pulmonale at death in relation to other factors such as emphysema, silicosis, and thromboembolism was analysed in a case-control study of 732 South African gold miners. Marked emphysema was the highest risk factor with an odds ratio of 21.32 (95% confidence interval (95% CI) 5.02-90.7), then extensive silicosis (OR 4.95, 95% CI 2.92-8.38) and thromboembolic disease (OR 1.92, 95% CI 1.37-2.69). Age and smoking were not significant predictors of cor pulmonale.

Aged↗
PubMed1993

Ion channels in human axons.

1. Until now, no direct electrophysiological information has been available on the molecular basis of human nerve excitability. We here report patch-clamp recordings, both single- and multichannel, from acutely dissociated human axons. 2. Voltage-dependent sodium channels with a conductance gamma = 13 pS (measured in Ringer at room temperature) are found in the nodal area. 3. There are several types of voltage-dependent potassium channels: I channels (gamma = 34 pS), F channels (gamma = 50 pS), and channels with small conductance (gamma = 7-9 pS, all measured in high potassium solution). Most of them are closely similar to those already reported in Xenopus and rat axons; in addition a 200-pS, calcium-dependent potassium channel, similar to that in Xenopus, is present. 4. Differences between the electrical behavior of human axons and those of other species are probably not due to the presence of fundamentally different channel types, but may be due to differences in channel density or distribution. 5. As well as increasing our understanding of the basis of excitability in human nerve, this method may prove useful in the investigation of inherited and other human neuropathies.

Axons↗
PubMed1993

Adhesion of three Lactobacillus strains to human urinary and intestinal epithelial cells.

Three strains of urogenital lactobacilli were found to adhere in phosphate buffered saline to human uroepithelial cells in vitro according to thermodynamic principles, and to adhere in culture medium to intestinal cells with no such correlation. The most hydrophilic strain (water contact angle 54 degrees) L. casei RC-17 was the most adherent to uroepithelial (118 bacteria per cell) and intestinal cells (165 bacteria per cell). A direct correlation was found between bacterial hydrophilicity and adhesion to uroepithelial cells for the three strains tested. An extracellular adhesin, which appeared to be proteinaceous, and a trypsin-insensitive cell wall adhesin were identified. It was evident that high levels of bacterial retention could be reproduced in vitro, perhaps indicating the potential colonizing capacity of these strains in vivo.

Adult↗
PubMed1992

Correlation between hydrophobicity and resistance to nonoxynol-9 and vancomycin for urogenital isolates of lactobacilli.

Seven clinical isolates of lactobacilli were found to be relatively hydrophobic with a mean water-contact angle of 66 +/- 15 degrees, and to be susceptible to 1% nonoxynol-9 and vancomycin. However, seven other strains were relatively hydrophilic with a mean water-contact angle of 32 +/- 13 degrees, and found to be resistant to 25% nonoxynol-9 and vancomycin. Thus, the surface properties of lactobacilli that influence susceptibility to antimicrobial agents may involve surface hydrophobicity. Possibly the penetration barrier posed by the cell surface towards these two nonionic antimicrobials is lower for hydrophobic cells than for hydrophilic cells.

Adult↗