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Biomedical subjects

D Kendall

Publications and source records attributed to D Kendall.

31 records · Page 2Linked to original sources
PubMed1994

Staphylococci express a receptor for human transferrin: identification of a 42-kilodalton cell wall transferrin-binding protein.

Staphylococcus aureus and the coagulase-negative staphylococci are commonly responsible for peritonitis in renal patients undergoing continuous ambulatory peritoneal dialysis. To simulate growth conditions in vivo, staphylococci isolated from peritoneal infections were cultured in used human peritoneal dialysate (HPD). Immunoblotting experiments using cell wall preparations from these staphylococci revealed the presence of the host iron-binding glycoprotein transferrin bound to S. aureus, S. epidermidis, S. capitis, S. haemolyticus, and S. hominis but not to S. warneri or S. saprophyticus. Similar results were obtained by incubating broth-grown staphylococci with human transferrin, although, in contrast to S. aureus, the coagulase-negative staphylococci bound more transferrin after growth in iron-restricted broth. To determine whether the staphylococci express a saturable specific receptor for human transferrin, the interaction of human 125I-transferrin with the staphylococci was examined. Both S. aureus and S. epidermidis bound the radiolabelled iron-saturated ligand in a time- and concentration-dependent manner. From competition binding assays, the affinity (Kd) and number of receptors were estimated for S. epidermidis (Kd, 0.27 microM; 4,200 receptors per cell) and S. aureus (Kd, 0.28 microM; 4,200 receptors per cell). S. epidermidis but not S. aureus receptor activity was partially iron regulated. Human apotransferrin and iron-saturated transferrin and rabbit and rat transferrins competed equally well for the staphylococcal receptor. Bovine and porcine transferrins and ovotransferrin as well as human and bovine lactoferrins were much less effective at competing with human transferrin. Treatment of whole staphylococci with protease abolished transferrin binding, indicating the involvement of cell surface protein. Western blots (immunoblots) of cell wall preparations probed with human transferrin revealed the presence of a 42-kDa transferrin-binding protein common to both S. aureus and S. epidermidis. On Western strip blots, the binding of human transferrin to this protein was blocked by labelled human transferrin but not by albumin, immunoglobulin G, or bovine transferrin or ovotransferrin. To assess the conservation of the 42-kDa transferrin-binding protein, cell wall proteins of S. epidermidis, S. haemolyticus, S. capitis, S. hominis, S. warneri, and S. saprophyticus were Western blotted and probed with human transferrin. Only S. warneri and S. saprophyticus lacked the 42-kDa wall protein, consistent with their inability to bind transferrin. These data show that the staphylococci express a specific receptor for human transferrin based at least in part on a common 42-kDa cell wall protein.

Animals↗
PubMed1994

Integrin expression and localization in normal MDCK cells and transformed MDCK cells lacking apical polarity.

Epithelial cells polarize in response to contacts with the extracellular matrix and with neighboring cells. Interactions of cells with the extracellular matrix are mediated mainly by the integrin family of receptors. To begin to understand the role of integrins in polarization, we have investigated the expression and localization of three integrin families in the polarized Madin-Darby canine kidney (MDCK) epithelial cell line and in transformed MDCK cells lacking apical polarity. We find that MDCK cells express several beta 1 integrins, including alpha 2 beta 1, alpha 3 beta 1, and an unidentified integrin designated alpha x beta 1. The beta 1 integrins are the major receptors for collagens I and IV and laminin in MDCK cells, since a blocking anti-beta 1 antibody almost totally abolishes adhesion to these proteins. They also express a vitronectin receptor tentatively identified as alpha v beta 3, and the epithelial-specific integrin alpha 6 beta 4. The latter is not a laminin receptor in MDCK cells because a function blocking anti-alpha 6 antibody has no effect on cell adhesion to laminin. All three integrin families are expressed exclusively on both the basal and lateral surfaces, as determined by immunofluorescence microscopy and surface biotinylation. Transformed MDCK cells express beta 1 integrins as well as alpha v beta 3 and alpha 6 beta 4, but show alterations in the beta 1 family. Expression of alpha x is lacking, and the relative amount of the beta 1 subunit is diminished, resulting in the accumulation of Endo-H-sensitive alpha 3. In addition, surface biotinylation and immunofluorescence indicate that significant amounts of both alpha 2 beta 1 and alpha 3 beta 1 appear on not only the basolateral but also the apical plasma membrane. These results indicate that integrins are the major receptors for the extracellular matrix in MDCK cells, and that they may affect epithelial cell polarization by mediating not only cell-substratum but also cell-cell contacts.

Animals↗
PubMed1991

Multilayering and loss of apical polarity in MDCK cells transformed with viral K-ras.

The effects of viral Kirsten ras oncogene expression on the polarized phenotype of MDCK cells were investigated. Stable transformed MDCK cell lines expressing the v-K-ras oncogene were generated via infection with a helper-independent retroviral vector construct. When grown on plastic substrata, transformed cells formed continuous monolayers with epithelial-like morphology. However, on permeable filter supports where normal cells form highly polarized monolayers, transformed MDCK cells detached from the substratum and developed multilayers. Morphological analysis of the multilayers revealed that oncogene expression perturbed the polarized organization of MDCK cells such that the transformed cells lacked an apical--basal axis around which the cytoplasm is normally organized. Evidence for selective disruption of apical membrane polarity was provided by immunolocalization of membrane proteins; a normally apical 114-kD protein was randomly distributed on the cell surface in the transformed cell line, whereas normally basolateral proteins remained exclusively localized to areas of cell contact and did not appear on the free cell surface. The discrete distribution of the tight junction-associated ZO-1 protein as well as transepithelial resistance and flux measurements suggested that tight junctions were also assembled. These findings indicate that v-K-ras transformation alters cell-substratum and cell-cell interactions in MDCK cells. Furthermore, v-K-ras expression perturbs apical polarization but does not interfere with the development of a basolateral domain, suggesting that apical and basolateral polarity in epithelial cells may be regulated independently.

Animals↗
PubMed1988

Ornithine decarboxylase activity in Barrett's esophagus: a potential marker for dysplasia.

Ornithine decarboxylase activity is known to be increased in certain premalignant conditions. We determined the activity of this enzyme in mucosal biopsy specimens from 15 patients with Barrett's esophagus. Ornithine decarboxylase was greater in Barrett's mucosa than in squamous esophageal or gastric mucosa. In Barrett's mucosa from 4 patients with dysplasia, the enzyme activity was greater than in 11 patients without dysplasia (1.6 +/- 0.35 vs. 0.19 +/- 0.08 U/mg protein; p less than 0.005). Increased ornithine decarboxylase activity in biopsy specimens of Barrett's mucosa may represent a marker for dysplasia.

Barrett Esophagus↗
PubMed1986

Pancreas transplantation.

The data on vascularized pancreas transplant cases reported to the old American College of Surgeons/National Institutes of Health Organ Transplant Registry from December 17, 1966, through December 31, 1984, are summarized in this article. Also described is the experience at the University of Minnesota, where more than one fifth of the transplants have been performed. The authors conclude that pancreas transplantation is now an effective treatment for human diabetes.

Diabetes Mellitus↗
PubMed1982

Fasting plasma glucose and glycosylated haemoglobin levels in the assessment of diabetic control in non-insulin-dependent diabetes in the young.

Response to diet and drug therapy was assessed in a group of 85 Indian patients with non-insulin-dependent diabetes in the young (NIDDY). There was a significant decrease in fasting plasma glucose (FPG) values on therapy (pretreatment 13.3 +/- 0.5 mmol/l; post-treatment 9,7 +/- 0,4 mmol/l) (P less than 0,001). Prior to therapy the majority of patients had either moderate (40%) or severe (59%) diabetes; on therapy, the majority had either mild (21%) or moderate (62%) diabetes. Estimation of glycosylated haemoglobin (Hb A1) levels revealed that control was excellent (Hb A1 less than 10%) in 47% of patients and excellent or adequate (Hb A1 less than 12%) in 78%. Hb A1 levels correlated significantly with the FPG value (r = 0,78; P less than 0,001). In 8 patients with iron deficiency anaemia the HB a1 level did not fall within the correlation norms between Hb A1 and FPG. Treatment of the anaemia restored the correlative norms. Hb A1 levels were significantly higher in patients with microvascular complications (12,1 +/- 0,8%) than in those without any vascular complications (10,3 +/- 0,3%) (P less than 0,01).

Blood Glucose↗
PubMed1970

Facial paralysis.

Explore the source record for details and available documents.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Eating disorders and insulin-dependent diabetes mellitus.

The eating disorders anorexia nervosa and bulimia nervosa have been reported to occur in Type I diabetes mellitus. Although prevalence estimates vary, the most rigorous studies yield rates similar to the population at large. Intentional insulin omission is more common, especially in young diabetic women, and at times may indicate an eating disorder in Type I diabetic patients. Both diagnosable eating disorders and intentional insulin omission are associated with worse glycemic control and higher rates of secondary diabetic complications. Recognition of these conditions, followed by carefully coordinated treatment involving both diabetes care providers and mental health providers, is necessary to improve treatment outcome.

Adolescent↗
PubMedDate not supplied

Variability of deoxynivalenol measurements in barley.

Deoxynivalenol (DON), a toxin produced by Fusarium fungi, can occur in many cereal grains. If wet climatic conditions coincide with the flowering period of plant development, circumstances are favorable for the fungi infection. Because the presence of DON in barley can have significant economic consequences to barley producers, commercially available test kits are used to measure DON in shipments throughout marketing channels. The quantity of barley sampled from a lot and used to measure DON can vary widely, depending on where the test is conducted. The Grain Inspection, Packers and Stockyards Administration of the U.S. Department of Agriculture specifies that a minimum of 100 g of grain must be processed to measure DON. Other laboratories may use more or less grain. A study undertaken to measure the variability among measurements of different sample sizes found no detectable differences in variability attributable to sample size. It was concluded that the variability among DON concentrations in samples from the lot was small relative to that introduced by the measurement process (combined sample preparation and analysis). A separate experiment investigated variation among samples taken from a lot, variation among subsamples taken from ground samples, and variation among multiple replicated measurements of an extract. On 10 lots, all 3 sources were significant contributors to variation. Stratification of DON within lots was hypothesized as a source of variation of DON measurements. Tests indicated that some stratification may exist.

Hordeum↗