Search PubMed⌕ Search

Biomedical subjects

B Burke

Publications and source records attributed to B Burke.

At least 73 records · Page 4Linked to original sources
PubMed1993

Targeting of the "insulin-responsive" glucose transporter (GLUT4) to the regulated secretory pathway in PC12 cells.

Insulin-activated glucose transport depends on the efficient sorting of facilitated hexose transporter isoforms to distinct subcellular locales. GLUT4, the "insulin-responsive" glucose transporter, is sequestered intracellularly, redistributing to the cell surface only in the presence of hormone. To test the hypothesis that the biosynthesis of the insulin-responsive compartment is analogous to the targeting of proteins to the regulated secretory pathway, GLUT4 was expressed in the neuroendocrine cell line, PC12. Localization of the transporter in differentiated PC12 cells by indirect immunofluorescence revealed GLUT4 to be in the perinuclear region and in the distal processes. Although, by immunofluorescence microscopy, GLUT4 co-localized with the endosomal protein transferrin receptor and the small synaptic vesicle (SSV) marker protein synaptophysin, fractionation by velocity gradient centrifugation revealed that GLUT4 was excluded from SSV. Immunoelectron microscopic localization indicated that GLUT4 was indeed targeted to early and late endosomes, but in addition was concentrated in large dense core vesicles (LDCV). This latter observation was confirmed by the following experiments: (a) an antibody directed against GLUT4 immunoadsorbed the LDCV marker protein secretogranin, as assayed by Western blot; (b) approximately 85% of secretogranin metabolically labeled with 35S-labeled sulfate and allowed to progress into secretory vesicles was coadsorbed by an antibody directed against GLUT4; and (c) GLUT4 was readily detected in LDCV purified by ultracentrifugation. These data suggest that GLUT4 is specifically sorted to a specialized secretory compartment in PC12 cells.

Animals↗
PubMed1993

Metastatic adenocarcinoma of an unknown primary site. A comparison of the relative contributions of morphology, minimal essential clinical data and CEA immunostaining status.

Measurement of the relative contributions of morphology alone; minimal essential clinical data; immunohistologic reactivity of a prototypic tumor marker, carcinoembryonic antigen (CEA); and the process by which a pathologist can identify the origin of a metastatic adenocarcinoma of unknown primary site is the subject of this report. To standardize the case material, we used an image digitizing and archival system to present 100 metastatic adenocarcinomas of known primary site as unknowns to two pathologists. The images were selected to show only gland-forming areas of the carcinomas and excluded all normal tissue elements. They were viewed, initially without, and then with, identification of gender and metastatic site. Subsequently, the results of immunoperoxidase staining for CEA, assessed independently by a third pathologist, were provided. Our analysis showed that, overall, the correct primary site was chosen as choice 1, 2, or 3 in 72% and 76%, and as choice 1 in 49% and 47% of cases, respectively. Accuracy was highest for prostatic, ovarian, and breast carcinomas, and lowest for upper-gastrointestinal tract, biliary tract, and pancreatic adenocarcinoma. Statistical analysis showed the largest increments in accuracy in the choice 1 prediction in each tumor category were achieved by provision of minimal essential clinical data. Knowledge of CEA status did not affect overall accuracy; however, it increased the odds of making the correct diagnosis for ovarian, colorectal, and endometrial (both pathologists) carcinomas, and for prostatic, pulmonary and esophago-gastric adenocarcinomas (one pathologist). The study exemplifies a model for the objective measurement of the contribution of ancillary studies, such as immunoperoxidase markers, to the accuracy of pathologic diagnosis.

Adenocarcinoma↗
PubMed1992

Maternal and fetal outcome after breast cancer in pregnancy.

We compared 118 women with breast cancer (119 pregnancies) with 269 nonpregnant control subjects matched on important prognostic factors. The distribution of breast cancer stages among the 118 pregnant women was compared with that among 5115 cases of breast cancer in women of reproductive age. Fetal outcome was compared with that of a control group matched for maternal age. Women having breast cancer in pregnancy were 2.5 times more likely to have metastatic disease (95% confidence interval 1.1 to 5.3) and had a significantly lower chance of having stage I disease (p = 0.015). Survival of pregnant women did not differ from that of the controls. Birth weights of babies born to women with breast cancer were significantly lower than those of control babies after gestational age was adjusted for (3010 +/- 787 vs 3451 +/- 515 gm, p = 0.016). The two stillbirths in 85 pregnancies that continued to term (2.4%) was not statistically different from the 1.1% rate for Ontario. We analyzed all 223 births occurring in women who had any form of cancer in the same hospital during the same 30 years. There were 10 stillbirths among these 223 cases (4.4%), significantly more than expected in Ontario (p less than 0.0005; relative risk of 4.23 with 95% confidence interval 2.0 to 7.8). Our data suggest that pregnant women are at a higher risk of presenting with advanced disease because pregnancy impedes early cancer detection.

Abortion, Spontaneous↗
PubMed1992

The pathologic spectrum of the nephropathy associated with alpha 1-antitrypsin deficiency.

To further define the clinicopathologic spectrum and pathogenetic mechanism of the nephropathy associated with alpha 1-antitrypsin (A1AT) deficiency, we evaluated renal specimens from 34 patients with chronic hepatic disease, including 20 with A1AT deficiency (study patients), and correlated these findings with urinalysis evaluation. Glomerular lesions were noted in 79% (15 of 19) of A1AT patients with the PiZZ phenotype, including seven with mesangio-capillary glomerulonephritis (MPGN and focal segmental MPGN), six with mesangial proliferative glomerulonephritis (Mes GN), one with diffuse endocapillary proliferative glomerulonephritis (DPGN), and one with focal segmental mesangial proliferative glomerulonephritis with segmental necrosis (FS Nec GN). One A1AT patient with the PiMZ phenotype did not demonstrate glomerular abnormalities. Focal segmental Mes GN was found in 43% (six of 14) of patients in an age-matched group with chronic hepatic failure unrelated to A1AT deficiency. In nine study patients, glomerular pathology was noted in the presence of a normal urinalysis. Immunofluorescence studies revealed the presence of immunoproteins and the A1AT protein isoelectric forms, PiM and PiZ, in the subendothelial region of glomerular basement membranes in A1AT patients with MPGN, Mes GN, and DPGN. Our results emphasize the heterogeneity of glomerular lesions associated with A1AT deficiency and hepatic disease and the relatively high incidence of MPGN in these children. The presence of abnormal PiZ protein in the subendothelial region of the glomerular basement membrane in A1AT patients with glomerulonephritis suggests a possible role for this protein in the pathogenesis of this lesion.

Adolescent↗
PubMed1992

Analysis of epithelial and lymphoid phenotypic markers in relation to growth pattern of colorectal adenomas.

The relationship of villous to tubular adenomas is poorly understood and often difficult to characterize morphologically. A villous growth pattern in colorectal adenomas has been associated with a higher frequency of high-grade dysplasia. We compared phenotypic markers using immunoperoxidase techniques in paired samples of villous (75% to 100% villous) and pure tubular adenomas matched for size and degree of dysplasia, which were selected by review of 1,000 polyps from our files. The following monoclonal antibodies were used: CAM 5.2 and AE1/AE3 to cytokeratins; B18, D14, B7.1, and B7.8 to four distinct carcinoembryonic antigen epitopes; Leu-M1 and LN3 to HLA-DR antigen; LN2 to invariant chain class II major histocompatibility complex; LN1 and MB2 to B-cell markers; UCHL1 and MT1 to T-cell markers; Leu-7 to natural killer cells; Mac 387 to macrophages; S-100 to Langerhans-type cells; and a polyclonal antibody to secretory component. LN3 reactivity correlated with villous morphology and secretory component correlated with tubular morphology. Combined HLA-DR and secretory component expression discriminated between tubular and villous growth patterns in 12 of 15 pairs of adenomas (P less than .001). LN2 was expressed more frequently than LN3, but did not correlate with growth pattern. Neuroendocrine cells (Leu-7) were more frequent in tubular adenomas. Carcinoembryonic antigen epitopes did not relate to growth pattern. We did not confirm previously reported differences in cytokeratin expression. We concluded that among the markers tested, HLA-DR expression, which may have an immunologic basis, is most characteristic of colorectal adenomas that exhibit a villous growth pattern.

Adenoma↗
PubMed1992

Identification of a 200-kD, brefeldin-sensitive protein on Golgi membranes.

A mAb AD7, raised against canine liver Golgi membranes, recognizes a novel, 200-kD protein (p200) which is found in a wide variety of cultured cell lines. Immunofluorescence staining of cultured cells with the AD7 antibody produced intense staining of p200 in the juxtanuclear Golgi complex and more diffuse staining of p200 in the cytoplasm. The p200 protein in the Golgi complex was colocalized with other Golgi proteins, including mannosidase II and beta-COP, a coatomer protein. Localization of p200 by immunoperoxidase staining at the electron microscopic level revealed concentrations of p200 at the dilated rims of Golgi cisternae. Biochemical studies showed that p200 is a peripheral membrane protein which partitions to the aqueous phase of Triton X-114 solutions and is phosphorylated. The p200 protein is located on the cytoplasmic face of membranes, since it was accessible to trypsin digestion in microsomal preparations, and is recovered in approximately equal amounts in membrane pellets and in the cytosol of homogenized cells. Immunofluorescence staining of normal rat kidney cells exposed to the toxin brefeldin A (BFA), showed that there was very rapid redistribution of p200, which was dissociated from Golgi membranes in the presence of this drug. The effect of BFA was reversible, since upon removal of the toxin, AD7 rapidly reassociated with the Golgi complex. In the BFA-resistant cell line PtK1, BFA failed to cause redistribution of p200 from Golgi membranes. Taken together, these results indicate that the p200 Golgi membrane-associated protein has many properties in common with the coatomer protein, beta-COP.

Animals↗
PubMed1992

The pathogenicity of two porcine rotaviruses differing in their in vitro growth characteristics and genes 4.

The pathogenicity of two rotavirus variants, 4F and 4S, obtained following adaptation to cell culture of rotavirus from a diarrhoeic pig in China, was compared by serial passage in 24 gnotobiotic piglets. The rotavirus variants have markedly different growth characteristics in vitro, and their genome profiles differ only in the relative migration of genes 4. Both cell culture-grown variants replicated to an equal extent in gnotobiotic piglets and neither caused disease, although weight gain was slightly affected in piglets inoculated with the 4F variant. During five serial pig-to-pig passages, variant 4F became highly pathogenic at the fourth and fifth passages, causing severe diarrhoea and weight loss, and premature death in two animals. Piglets inoculated with rotavirus variant 4S remained healthy during all passages although weight gain was slightly affected. Mean duration and peak infectivity titres of virus shedding were similar for both variants. Thus, variant 4F, which grew slowly and produced small plaques in vitro and had the faster migrating gene 4, was pathogenic in pigs, whereas variant 4S was apathogenic.

Adaptation, Biological↗
PubMed1992

Independent expression and assembly properties of heterologous lamins A and C in murine embryonal carcinomas.

The majority of cells derived from adult mammalian tissues contain three major species of nuclear lamin proteins, A, B and C. In contrast, embryonic cells including undifferentiated murine embryonal carcinomas, contain only B-type lamins, A and C appearing only after differentiation. Human lamins A or C have been introduced by transfection into undifferentiated P19 embryonal carcinomas. Twenty-four hours after transfection, both of these proteins were found to independently associate with the nuclear envelope as judged by immunofluorescence microscopy and at the same time were associated with a salt-resistant structure having solubility properties similar to those of the nuclear lamina. Biosynthetic experiments indicated that heterologous lamin A underwent processing to its mature molecular weight, an event which in adult type cells occurs after assembly into the lamina. Observations on mitotic cells demonstrate that either of the two human lamins will, independent of the other, become dispersed throughout the cytoplasm during prophase and subsequently reassemble at the nuclear periphery during telophase. Nuclear lamins A and C are not, however, equivalent in their abilities to incorporate into the nuclear lamina in these cells. Experiments involving cells arrested in S phase using thymidine suggest that lamin C, but not lamin A, requires progression through the cell cycle and probably mitosis for assembly into the nuclear lamina of P19 EC cells.

Animals↗
PubMed1991

Stage-specific expression of a family of proteins that are major products of zygotic gene activation in the mouse embryo.

Transcriptional activation of the embryonic genome occurs during the two-cell stage in the mouse embryo and is marked by the synthesis of a set of alpha-amanitin-sensitive proteins of Mr 73,000, 70,000, and 68,000. We have characterized these three proteins by two-dimensional gel electrophoresis of [35S]methionine radiolabeled two-cell embryos. Their isoelectric points range from 6.2 to 6.8 and their synthesis, which can constitute 5-10% of total protein synthesis, is restricted to the two-cell stage. These proteins are not heat shock proteins that have previously been reported as major products of transcriptional activation. Peptide mapping by limited proteolysis indicates that these three proteins are highly related to one another and the results of pulse-chase experiments indicate that they are likely to be degraded by the eight-cell stage. These proteins are nuclear-associated and insoluble in 2% Triton X-100/0.3 M KCl. Although these proteins share some features with somatic lamins--they exhibit solubility properties similar to somatic lamins--they do not cross-react with polyclonal antibodies to either lamins A/C or B, nor do they comigrate with somatic lamins on two-dimensional gels. Additional evidence that these proteins are not lamins is that although treatment of two-cell embryos with okadaic acid, which is an inhibitor of protein phosphatases 1 and 2A, results in precocious nuclear envelope breakdown, the proteins remain insoluble in 2% Triton X-100/0.3 M KCl.

Animals↗
PubMed1991

Renal preservation after warm ischemia using oxygen free radical scavengers to prevent reperfusion injury.

Oxygen free radicals damage kidneys and accumulate during the period of preservation prior to transplantation. We hypothesized that a perfusate containing either an oxygen free radical scavenger such as ceruloplasmin, or an iron-chelating agent such as deferoxamine, would improve kidney preservation. Thirty-eight mongrel dogs underwent autotransplantation of the left kidney after 30 min of warm ischemia and 48 hr of machine perfusion (MOX-100, Water Instruments, Rochester, MN) at 5 degrees C and pH of 7.4. The right kidney was removed at the time of autotransplantation. Four blind code-labeled preservation solutions were tested. SGF-I was used for the control group (Group 1, n = 13), and the remaining animals were transplanted with kidneys preserved with one of three solutions modified from the basic SGF-I solution: Group 2, SGF-I plus deferoxamine (656 mg/liter), n = 8; Group 3, SGF-I ceruloplasmin enriched (72 mg/dl), n = 8; and Group 4, SGF-I ceruloplasmin reduced (3.4 mg/dl), n = 9. Serum creatinine levels were measured daily for 2 weeks and survival curves for each of the four groups were estimated by the Kaplan-Meier method. Peak mean serum creatinine levels +/- standard errors in Groups 1 through 4 were 12.6 +/- 1.97, 7.8 +/- 0.90, 7.1 +/- 1.26, and 8.2 +/- 1.09, respectively. Repeated measures analysis of variance showed statistically significant differences between the groups with respect to their serum creatinine profiles (Wald's test x2 with 3 df = 22.39, P value less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Differential expression of basement membrane collagen in membranous nephropathy.

Membranous nephropathy (MN) is characterized by subepithelial immune complex formation and progressive thickening of the glomerular basement membrane (GBM). Kidney tissues from 21 patients stratified according to morphology (stage I: 5 patients; stage II: 5 patients, stage III: 11 patients) were studied by immunohistochemical techniques using antibody probes to matrix components of recently described (novel) chains of type IV collagen [alpha 3(IV)NC, alpha 4(IV)NC, Alport antigen] and of traditional type IV collagen [alpha 1(IV)NC, alpha 2(IV)NC, 7S(IV), triple helix]; as well as laminin B2, nidogen and fibronectin. In Stage I, there were no detectable changes when compared with normal tissue. In Stage II and early Stage III, the subepithelial projections of GBM (spikes) and the thickened GBM consisted predominantly of the novel type IV collagen chains as well as laminin B2 and nidogen, with no detectable changes in traditional type IV collagen. In late Stage III, an increase in the latter was observed in the subendothelial region of the thickened GBM with narrowing of the capillary lumen. At this stage, there was close apposition of novel and traditional type IV collagen molecules. The expression of these two groups of molecules is spatially and temporally distinct during the evolution of MN. It is hypothesized that immune complex formation in the subepithelial region of the GBM leads to increased formation of the novel type IV collagen network by visceral epithelial cells resulting in the formation of spikes and thickening of GBM between and surrounding immune deposits. These changes precede and are distinct from detectable alterations in traditional type IV collagen. With progression and time, the deposits become embedded in the novel collagen network and increased subendothelial formation of traditional type IV collagen molecules occurs with narrowing of the capillary lumen.

Antibodies, Monoclonal↗
PubMed1991

Presumptive invasive Chrysosporium infection in a bone marrow transplant recipient.

Chrysosporium species caused an invasive infection in an 18-year-old patient following allogeneic sibling bone marrow transplant for T lineage acute lymphoblastic leukemia. This infection began as a facial swelling and extended into the central nervous system. Fungal disease spread rapidly despite antifungal agents. An autopsy showed fungal involvement of brain, lungs, liver and kidneys.

Adolescent↗
PubMed1990

On the cell-free association of lamins A and C with metaphase chromosomes.

Nuclear envelopes have previously been shown to assemble spontaneously around endogenous chromosomes in cell-free homogenates of mitotic Chinese hamster ovary cells. In order to further analyze the mechanisms underlying nuclear envelope reformation and the functions of the individual nuclear lamin polypeptides, a fractionated cell-free nuclear envelope reassembly system involving purified chromosomes and either a postchromosomal supernatant or a cytosol fraction from mitotic cells has been devised. Results obtained with this fractionated system show that lamins A and C will associate with the surfaces of chromosomes in the absence of lamin B and membranes, this association being inhibitable by ATP-gamma-S. However, in the absence of membranes chromatin decondensation never occurs. Using the reversible swelling of chromosomes in low ionic strength buffers lacking divalent cations as the basis of a simple assay, it is demonstrated that the association of lamins A and C with the surfaces of chromosomes has a pronounced and easily observable effect on chromatin organization.

Animals↗
PubMed1990

Early bladder outlet obstruction in fetal lambs induces renal dysplasia and the prune-belly syndrome.

A model of posterior urethral valves in fetal lambs was developed in order to evaluate the effect of intrauterine urinary obstruction on the developing kidney. Complete urethral obstruction was induced in five fetal lambs at 43 to 45 days of gestation. Two control fetal lambs underwent sham operations. At full term (140 days), two of the five experimental lambs and both control lambs were available for postmortem examination. Results of gross and histological examination of the control lambs were normal. In contrast, the kidneys of the experimental lambs were markedly asymmetrical in size. Histological examination of the kidneys in experimental lambs showed cystic dilatation of the collecting ducts and occasional cystic dilatation of Bowman's spaces, features compatible with obstruction. Also noted were peripheral cortical cysts and primitive tubules lined with cuboidal epithelium and surrounded by fibromuscular collarettes, characteristic of renal dysplasia. One of the infant lambs had many characteristics of the prune-belly syndrome, including a wrinkled, markedly distended abdomen, deficient abdominal wall musculature, flared chest wall, limb deformities, and undescended testes. These results suggest that early in utero urethral obstruction (at the beginning of the second third of gestation) causes renal dysplasia. The results also support the hypothesis that the prune-belly syndrome results from abdominal distention that occurs early in gestation.

Abdominal Muscles↗
PubMed1990

Microwave: practical cost-effective method for sterilizing urinary catheters in the home.

We used a standard microwave oven to sterilize red rubber catheters used for intermittent self-catheterization. Catheters were incubated for sixty minutes in a suspension of microorganisms isolated from the urine of patients with urinary tract infections. For each trial, 6 catheters were removed from their respective suspensions, placed in separate plastic freezer bags, distributed evenly in a microwave oven (avoiding cold spots), and microwaved simultaneously for twelve minutes. A control catheter was not microwaved. Two strains of each microorganism were tested. The urinary isolates were Escherichia coli, Klebsiella sp., Proteus sp., Enterobacter sp., Pseudomonas sp., Streptococcus sp., Staphylococcus sp., and Candida sp. In each experiment, all 6 catheters were sterilized. Repeat sterilization in the microwave oven did not affect the integrity of the catheters or the plastic bags. A water heat sink of constant volume was employed. A home microwave oven may be used as a method to sterilize red rubber catheters for reuse with a recommended time of twelve minutes at full power. This technique makes aseptic intermittent self-catheterization a practical possibility.

Bacteriuria↗
PubMed1990

Identification of a Golgi-associated protein that undergoes mitosis dependent phosphorylation and relocation.

By means of a monoclonal antibody (BH3), we have identified a 57-kD protein (p57) that in interphase is restricted largely to the perinuclear region of the cell. Double label immunofluorescence microscopy suggests localization of p57 to the Golgi complex and associated membranous structures. Protease protection experiments and chemical extractability indicate that p57 is a peripheral membrane protein exposed to the cytoplasm. p57 displays unique behavior during mitosis. At the end of G2 or in early prophase, p57 leaves the perinuclear region and accumulates very rapidly within the nucleus, at a time when the nuclear envelope is still intact and before nuclear lamina disassembly. This relocation of p57 coincides with its hyperphosphorylation on serine and threonine residues. After nuclear envelope breakdown p57 becomes uniformly distributed throughout the mitotic cytoplasm until in late telophase when it returns to its perinuclear location and is once again excluded from the nucleus. The behavior of p57 during mitosis suggests that it may play a role in the cellular reorganization evident during mitotic prophase.

Animals↗