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Biomedical subjects

D Brown

Publications and source records attributed to D Brown.

At least 343 records · Page 19Linked to original sources
PubMed1997

Cryptdin gene expression in developing mouse small intestine.

In rodents, the four intestinal epithelial cell lineages differentiate and become morphologically distinct during the first 2-3 postnatal wk. In studies reported here, reverse transcriptase-polymerase chain reaction (RT-PCR)-based assays detected Paneth cell defensin mRNAs in intestinal RNA from 1-day-old (P1) mice before crypt formation and maturation of the epithelium. Analysis of these defensin-coding RT-PCR products from P1 mice showed that 69% of clones sequenced coded for cryptdin-6, suggesting that it is the most abundant enteric defensin mRNA in the newborn. Paneth cell mRNAs, including cryptdins-4 and -5, lysozyme, matrilysin, and defensin-related sequences, also were detected in RNA from P1 mouse intestine. Unlike adult mice, where only Paneth cells are immunopositive for cryptdin, cryptdin-containing cells were distributed throughout the newborn intestinal epithelium and not in association with rudimentary crypts. Cryptdin immunoreactivity in the P1 mouse intestine was specific for intracellular granule contents, and immunofluorescent detection of cryptdins on mucosal surfaces suggested that the peptides are released into the intestinal lumen in P1 mice Defensin secretion may contribute to innate immunity of the neonatal intestine before the presence of distinguishable Paneth cells.

Aging↗
PubMed1997

Immunolocalization of AE2 anion exchanger in rat kidney.

The cellular and subcellular localizations of the AE2 anion exchanger in rat kidney have remained elusive despite detection of moderately abundant AE2 mRNA and AE2 polypeptide in all kidney regions. In this report a simple epitope unmasking technique has allowed the immunolocalization of AE2 antigenic sites in basolateral membranes of several rat kidney tubular epithelial cells. AE2 immunostaining was faint or absent in the glomerulus and proximal tubule, present in descending and ascending thin limbs, and stronger in the medullary thick ascending limb (MTAL). A lower staining intensity was found in cortical thick ascending limbs and even less in the distal convoluted tubule. In contrast, there was an enhanced staining in the macula densa. In principal cells (PC) of the connecting segment, AE2 was undetectable but gradually increased in intensity along the collecting duct, with strongest staining in inner medullary collecting duct (IMCD) PC. A sodium dodecyl sulfate-sensitive AE2-related Golgi epitope was also detected in some interstitial and endothelial cells of the inner medulla and in epithelial cells of IMCD and MTAL. Colchicine treatment of the intact animal altered the distribution of this Golgi-associated epitope but left plasmalemmal AE2 undisturbed. Reverse transcription-polymerase chain reaction detected AE2a, AE2b, and AE2c2 but not AE2cl transcripts in rat kidney mRNA. The results suggest a widespread occurrence of the AE2 protein in several renal epithelial cell types.

Animals↗
PubMed1997

Redistribution of villin to proximal tubule basolateral membranes after ischemia and reperfusion.

After ischemia and reperfusion, severe alterations in the cytoskeletal organization of renal tubular epithelial cells have been reported. These effects, accompanied by a modification in the polarized distribution of some membrane transport proteins, are especially evident in the proximal tubule. In normal proximal tubule cells, actin is concentrated in apical brush border microvilli, along with the actin-binding protein villin. Because villin plays an important role in actin bundling and in microvillar assembly but can also act as an actin-fragmenting protein at higher calcium concentrations, we examined the effects of ischemic injury and reperfusion on the distribution of villin and actin in proximal tubule cells of rat kidney. Using specific antibodies against villin and actin, we show that these proteins redistribute in parallel from the apical to the basolateral plasma membrane within 1 h of reperfusion after ischemia. Ischemia alone had no effect on the staining pattern. Repolarization of villin to the apical membrane begins within hours after reperfusion with enhanced apical localization over time during the period of regeneration. This apical repolarization of villin is accompanied by the migration of actin back to the apical membrane. These results show not only that villin may be involved in the initial disruption of the actin cytoskeleton during reperfusion injury but also that its migration back to the apical domain of these cells accompanies the reestablishment of a normal actin distribution in the brush border.

Actins↗
PubMed1997

Localization of the high-affinity glutamate transporter EAAC1 in rat kidney.

Most amino acids filtered by the glomerulus are reabsorbed in the kidney via specialized transport systems. Recently, the cDNA encoding a high-affinity glutamate transporter, EAAC1, has been isolated and shown to be expressed at high levels in the kidney. To determine the potential role of EAAC1 in renal acidic amino acid reabsorption, the distribution of EAAC1 mRNA and protein in rat kidney was examined. In situ hybridization revealed that EAAC1 mRNA is expressed predominantly in S2 and S3 segments of the proximal tubules and at low levels in the inner stripe of outer medulla and inner medulla. Polyclonal antibodies raised against the carboxy terminus of EAAC1 recognized a single band of approximately 70 kDa on Western blots of membrane protein from kidney cortex and medulla. Immunofluorescence microscopy revealed intense signals in the luminal membrane of S2 and S3 segments and weaker signals in S1 segments, descending thin limbs of long-loop nephrons, medullary thick ascending limbs, and distal convoluted tubules. These results are consistent with EAAC1 encoding the previously described apical high-affinity glutamate transporter in the kidney that mediates reabsorption of acidic amino acids in tubules beyond early proximal tubule S1 segments. Potential additional roles of EAAC1 in acid/base balance, cell volume regulation, and amino acid metabolism are discussed.

Amino Acid Transport System X-AG↗
PubMed1997

Slit diaphragm-reactive nephritogenic MAb 5-1-6 alters expression of ZO-1 in rat podocytes.

Monoclonal antibody (MAb) 5-1-6 identifies a 51-kDa protein (p51) on rat podocyte foot processes and causes severe complement- and leukocyte-independent proteinuria when injected into rats. In the studies reported here, we used various immunohistological techniques to define the precise location of p51 and its relationship to ZO-1, a known component of the podocyte slit diaphragm in adult rat glomeruli. Our results demonstrate that p51 and ZO-1 lie close to each other on opposite sides of the podocyte plasma membrane at the point of insertion of the slit diaphragm: ZO-1 on the cytoplasmic face and p51 on the slit diaphragm and adjoining outer leaflet of the plasma membrane bordering the filtration slits. In addition to their geographic proximity, there appears to be a relationship between p51 and ZO-1. After MAb 5-1-6 injection, there was a progressive decline in stainable ZO-1 in the podocytes of heavily proteinuric rats. In addition, Western blot analysis of glomerular lysates showed that the decline in staining was due to a loss of immunoreactive ZO-1 rather than redistribution or diffusion of the protein. Simultaneously, the distribution of glomerular-bound MAb 5-1-6 became more clumped, apparently because of partial endocytosis into a lysosomal compartment, while the slit diaphragms remained morphologically intact. These findings suggest that MAb 5-1-6 alters the molecular composition of the slit diaphragm and thereby affects the glomerular permeability barrier.

Animals↗
PubMed1997

Histochemical and ultrastructural characterization of primary cardiac chondrosarcoma.

A cardiac chondrosarcoma was found in the right atrium of a Golden Retriever dog. Macroscopically, the right atrial lumen was filled with a 6- x 12- x 8-mm white glossy mass, which was diffusely attached to the underlying myocardium. The mass was composed of spindle-shaped mesenchymal neoplastic cells loosely packed in light basophilic matrix, with focal areas of tightly packed cells in linear formation similar to the pattern of a growth plate. Tumor cells were positive when stained for vimentin and neuron-specific enolase, and weakly positive for S-100 protein. Ultrastructurally, neoplastic cells and abundant, dilate rough endoplasmic reticulum. Golgi apparatus, bundles of intermediate fibers, and primitive intercellular junctions between adjacent tumor cells. Based on morphologic, ultrastructural, histochemical, and immunohistochemical characteristics, this tumor was diagnosed as a chondrosarcoma.

Animals↗
PubMed1997

Role of V-ATPase-rich cells in acidification of the male reproductive tract.

Specialized proton-secreting cells play important physiological roles in a variety of tissues. On the basis of the immunocytochemical detection of carbonic anhydrase and V-ATPase in distinct epithelial cells of the epididymis and vas deferens, we predicted that the vacuolar V-ATPase that is located on the apical membrane of these cells should be a major contributor to luminal acidification in parts of the male reproductive tract. Physiological studies using the proton-selective vibrating probe in the vas deferens confirmed this hypothesis. As discussed recently, maintenance of the pH of the reproductive tract is probably under tight physiological control, by analogy with the situation in the kidney. Manipulation of luminal pH might, therefore, provide a point of intervention for the regulation of male fertility. In addition, it is possible that some cases of unexplained male infertility might result from defective acidification, resulting either from pathological states or potentially from environmental factors that may inhibit proton secretory pathways.

Animals↗
PubMed1997

Physical activity and women in the United States: an overview of health benefits, prevalence, and intervention opportunities.

Despite decades of physical activity research and interventions conducted on men, very little is known about the patterns of physical activity among US women. Rates from several national surveys show much lower rates of physical activity for women than for men. Among women, rates may vary by socioeconomic status. Studies relating physical activity and experience with heart disease, cancer, osteoporosis, and mental health are discussed. Interventions in the workplace and the community may increase the level of physical activity among US women. A history of not participating in exercise and lack of time for this activity appear to be important constraints for many women. The Surgeon General's Report on physical activity sanctioned future research on specific groups, such as women. Applied research coupled with community and workplace policies that support women's efforts to be more physically active may decrease the rates of some chronic diseases in this population.

Exercise↗
PubMed1997

Outcome and analysis of the surgical management of esthesioneuroblastoma.

OBJECTIVE: The aim of this study was to evaluate the effectiveness of combined radical surgical resection and radiotherapy for the treatment of esthesioneuroblastoma, a rare malignant neoplasm accounting for 1 to 5% of malignant neoplasms of the nasal cavity. METHOD: A 10-year review of 12 patients treated at our institution suggests that primary treatment consisting of a combined otolaryngologic/neurosurgical craniofacial approach results in good local control with relatively low morbidity and complication. Patients tend to present with advanced stage disease because of the nonspecific presenting signs and symptoms. Eighty-three percent of the patients were treated with combined surgery and radiation. RESULTS: Seventy-five percent of the patients are free of disease with an average follow-up time of 54 months. Based on our experience in anterior skull base surgery (zone I), we strongly advocate the pericranial flap for dural reconstruction. Postoperative complications occurred in 25% of the cases with no postoperative deaths. CONCLUSION: Failure analysis suggests that radical surgical resection combined with radiotherapy provides the best chance of disease control.

Adolescent↗
PubMed1997

Lymphocyte and macrophage phenotypes in chronic hepatitis C infection. Correlation with disease activity.

The pathogenesis of chronic hepatitis C and the mechanisms underlying progressive liver disease in patients with chronic hepatitis C infection are poorly understood. To demonstrate which inflammatory cells might be responsible for the necroinflammatory damage in chronic hepatitis C infection, we have correlated the phenotype of the intrahepatic lymphocytes and macrophages with histological activity in liver biopsy and explant specimens from 19 patients with chronic hepatitis C infection. In all stages of disease, more CD8+ than CD4+ lymphocytes were found. However, histologically active versus histologically mild hepatitis was associated with a trend toward greater parenchymal concentrations of CD4+ lymphocytes (0.71 +/- 0.27 per 10(4) microns 2 versus 0.35 +/- 0.15; not significant), significantly less parenchymal CD8+ lymphocytes (0.90 +/- 0.1 versus 1.70 +/- 0.3; t = 2.32, P = 0.03) and a greater parenchymal CD4/CD8 ratio (4.1 +/- 2.8 versus 0.91 +/- 0.3; t = 1.65, P = 0.07). No difference was found in the number of cells containing cytotoxic granules between the two groups. Greater numbers of CD4+ lymphocytes were found in liver biopsy specimens with little or no staining for hepatitis C virus antigen (1.47 +/- 0.88 versus 0.27 +/- 0.27; t = 2.28, P < 0.05). No significant differences were found in the macrophage subsets between the three stages of disease. Our data suggest that active histological disease in chronic hepatitis C infection may be associated with an increase in CD4+ lymphocytes and suggest that CD4+ T cells may play an important role in the hepatic injury in these patients.

CD4-CD8 Ratio↗
PubMed1997

Protein kinase A phosphorylation is involved in regulated exocytosis of aquaporin-2 in transfected LLC-PK1 cells.

Vasopressin-dependent translocation of aquaporin-2 (AQP2) between intracellular vesicles and the plasma membrane has been demonstrated in vivo and in vitro. Furthermore, the vasopressin-induced increase in apical membrane water permeability of renal principal cells is dependent on a rise in intracellular adenosine 3',5'-cyclic monophosphate and activation of protein kinase A (PKA). To determine whether trafficking of AQP2 is dependent on PKA phosphorylation, we first examined the effect of the PKA-inhibitor N-(2[[3-(4-bromophenyl)-2-propenyl]-amino]-ethyl)-5-isoquinolinesulfonam ide (H-89) on AQP2 translocation in transfected LLC-PK1 cells. Vasopressin-induced membrane insertion of AQP2 was completely inhibited by pretreatment of the cells for 60 min with H-89. This reagent also caused a dense accumulation of AQP2 in the Golgi region. Next, LLC-PK1 cells were stably transfected with AQP2 cDNA in which the PKA phosphorylation site, Ser256, was replaced with alanine (S256A). S256A-AQP2 was not phosphorylated in vitro by PKA, and S256A-AQP2 was mainly localized to intracellular vesicles in the basal condition, similar to wild-type AQP2. However, after stimulation with vasopressin or forskolin, the cellular distribution of S256A-AQP2 remained unchanged. In addition, the usual vasopressin-induced increase in endocytosis seen in AQP2-transfected cells was not observed in S256A-AQP2-transfected cells. These results demonstrate that the Ser256 PKA phosphorylation site is possibly involved in the vasopressin-induced trafficking of AQP2 from intracellular vesicles to the plasma membrane and in the subsequent stimulation of endocytosis.

Animals↗
PubMed1997

Polarized expression of membrane proteins in renal epithelial cells: involvement of specialized transport vesicles and intracellular pathways.

The polarized insertion of membrane proteins in epithelial cells is a highly regulated process that involves the coordinated interaction of many subsets of intracellular proteins. Thus, like cog-wheels in a complex machine, the different parts of the trafficking pathway must work together to ensure the correct functioning of an individual cell and of the entire epithelium in which it resides. The individual portions of the trafficking pathway include (1) sorting of membrane proteins into the correct apically or basolaterally targeted vesicles at the level of the trans-Golgi network; (2) delivery of these vesicles to their correct membrane destination by the microtubular (and probably the actin) cytoskeleton; (3) fusion of the vesicles with the appropriate membrane domain via a complex set of fusion proteins. This review has briefly outlined some of these processes and has used examples from the kidney to illustrate their importance to normal renal function.

Animals↗
PubMed1997

Surveillance of measles in England and Wales: implications of a national saliva testing programme.

The impact of a mass vaccination campaign against measles-rubella in England and Wales was assessed using the results of a saliva test for measles-specific IgM, which was offered to all notified cases of measles. By means of clinical data supplied by the reporting doctors, we estimated the sensitivity and specificity of various clinical case definitions in predicting a confirmed case. A saliva sample was obtained within the appropriate time period for 3442/7574 (45.4%) of notified cases; the proportion confirmed by saliva testing was low and fell from 67/681 (9.8%) at the start of the campaign to 1/373 (0.3%) after 35 weeks. The specificity of all clinical case definitions was low, but was highest at 41.1% (95% confidence interval, 39.2-43.0%) for the definition similar to that recommended in the USA. Extrapolating from cases observed during ongoing surveillance permits estimation of an annual notification rate for nonmeasles rash and fever illness. For countries with good measles control, a clinical case definition is too nonspecific for accurate surveillance. Laboratory confirmation of suspected measles cases is required and saliva testing is an acceptable method. The continued sensitivity of measles surveillance in England and Wales requires that the incidence of notified rash and fever illness and the proportion of cases in which measles infection was excluded by laboratory testing be monitored.

Adolescent↗
PubMed1997

The status of restorative dental materials.

The ideal restorative material should enable teeth which have suffered trauma or have been damaged during the removal of caries, to be restored to their original function and appearance. At the same time a seal should develop between the material and the tooth such that bacteria-laden fluids cannot permeate the dentine and reach the pulp. Few, if any, of the materials currently available fulfil these requirements. This short series will consider the current status of each.

Composite Resins↗