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Biomedical subjects

W E Bakewell

Publications and source records attributed to W E Bakewell.

16 recordsLinked to original sources
PubMed1995

Altered regulation of surfactant phospholipid and protein A during acute pulmonary inflammation.

Biochemical changes in the pulmonary surfactant system caused by exposure to toxicants are often accompanied by an influx of inflammatory cells into the lungs. We have investigated the possibility that the inflammatory and surfactant biochemical effects might be connected. Co-treatment with dexamethasone, a synthetic anti-inflammatory glucocorticoid, mitigated the increases in free cells and total intracellular surfactant phospholipid normally seen in animals given silica alone, suggesting a relationship between the free cell population of the alveoli and the surfactant system during alveolitis. Furthermore, we have investigated whether induction of the surfactant system is a universal response to alveolar inflammation. Inflammation was induced in the lungs by intratracheal injections of titanium dioxide, silica, bleomycin or lipopolysaccharide (LPS) suspended in isotonic saline. Inflammatory cell and surfactant responses were measured at 3 days and 14 days following injection. There was a distinct alveolar inflammatory cell profile following administration of each agent, at each time point, indicating a dynamic inflammatory cell population during the course of the study. Furthermore, surfactant phospholipid and protein A (SP-A) pools exhibited unique responses to the inflammatory agents. Only silica-treated lungs maintained elevated levels of surfactant phospholipids and SP-A throughout the course of the experiment. We conclude that both the surfactant components and the inflammatory cell population of the alveoli undergo dynamic changes following treatment with these inflammatory agents and that activation of the surfactant system is not a universal response to alveolar inflammation, since surfactant components were not always elevated during times of increased alveolar cellularity. The unique inflammatory cell infiltrate elicited by silica is of particular interest in that surfactant components were elevated throughout the course of the experiment in this group. Indeed, we have shown that the size of the intracellular pool of surfactant is directly proportional to the number of polymorphonuclear leukocytes but not alveolar macrophages or lymphocytes in the alveoli following silica treatment. Finally, our data suggest that the phospholipid and SP-A components of surfactant respond differentially to the pulmonary toxicants in this study.

Animals↗
PubMed1995

Detection of candidates for cancer cell motility inhibitory protein in the Dunning adenocarcinoma model.

The more differentiated components of a primary tumor may produce substances that reduce the growth rate and metastatic potential of more aggressive components. In the Dunning R-3327 prostatic adenocarcinoma model, cancer cell motility is required for metastatic potential. Medium conditioned by the non-motile, non-metastatic G subline contains proteins of molecular weight 50-100 kDa that inhibited the motility of the highly motile, highly metastatic MAT-LyLu subline. G subline-conditioned medium was separated by DEAE-cellulose chromatography using a linear gradient of 0-0.5 M NaCl in 100 mM Tris at pH 8.3. The motility inhibitory activity of G-conditioned medium was localized to column fractions 51-70 that contained 18% of the applied protein and only 6.5% of the proteins secreted by the G cells. Analysis of pooled fractions 51-60 and 61-70 by two-dimensional gel electrophoresis identified five protein families, with a total of 12 charged proteins of molecular weights approximating 66, 54, 50, 41 and 34 kDa, that were not present or present in reduced quantities in column fractions that did not inhibit motility. Isolation and identification of motility inhibitory protein may prove it the first substance discovered that is produced by a more differentiated component of a neoplasm that directly inhibits a metastasis-associated property.

Adenocarcinoma↗
PubMed1995

Bile duct-specific lectins, Dolichos biflorus agglutinin and peanut agglutinin, as probes in mouse hepatocarcinogenesis.

BACKGROUND: It is well established that alterations in the expression of cell surface glycoproteins occur during the course of tumorigenesis and can be detected immunohistochemically. However, no consistent markers of malignancy in mouse hepatocellular tumors have yet been identified. EXPERIMENTAL DESIGN: Lectin histochemistry, using three bile duct-specific lectins, Dolichos biflorus agglutinin (DBA), peanut agglutinin (PNA) and soybean agglutinin (SBA), and anti-epidermal keratin immunohistochemistry, was conducted on formalin-fixed, paraffin-embedded tissues of a spectrum of benign and malignant hepatocellular proliferative lesions of mice, including hepatocholangiocarcinomas. DBA- and PNA-binding glycoproteins in normal livers and in bile and liver tumors of mice were verified by SDS-PAGE and Western blot analysis. RESULTS: Normal bile duct cells stained strongly with DBA but minimally to moderately with PNA and SBA. DBA-positive tumor cells were present in 96% of hepatocholangiocarcinomas, 89% of hepatocellular carcinomas, and 35% of hepatocellular adenomas. In comparison, 43% of hepatocholangiocarcinomas, 37% of hepatocellular carcinomas, and 24% of hepatocellular adenomas exhibited PNA staining. SBA did not specifically stain tumor cells. Normal hepatocytes and those in altered foci were consistently negative for these three lectins. Keratin-positive staining was found only in normal bile ductular cells and ductal elements in 70% of hepatocholangiocarcinomas. Electrophoresis and Western blot analysis demonstrated that, in normal livers, DBA and PNA bound to the 13- to 16-kDa and 27- to 30-kDa glycoproteins believed to be of bile duct cell origin and commonly present in hepatocellular adenomas, hepatocellular carcinomas, and hepatocholangiocarcinomas, with strongest expression in the last. In addition, hepatocholangiocarcinomas had the same high molecular mass glycoprotein (> 200 kDa) labeled with DBA as detected in bile. CONCLUSIONS: Our results suggest that some malignant hepatocytes, especially in mouse hepatocholangiocarcinomas, have the potential of biliary differentiation. DBA is a sensitive marker for malignant hepatocytes in mice.

Adenoma↗
PubMed1993

Confocal laser scanning immunofluorescence microscopy of the pulmonary surfactant system. Association of surfactant protein A with the nucleus of the alveolar type II cell.

BACKGROUND: Localization of surfactant protein A (SP-A) to nucleus of type II cells isolated from the lungs of rats has been reported. Data suggested that most SP-A was located within lamellar bodies of the type II cell; however, some SP-A was found in other cytoplasmic regions of the cell and in particular in the nucleus. EXPERIMENTAL DESIGN: Type II cells and type II cell nuclei isolated from the lungs of rats were reacted with affinity-purified antibodies against SP-A. Location of SP-A was determined by using fluorescein isothiocyanate-labeled secondary antibodies and the distribution of fluorescence examined by using a laser scanning microscope fitted with a confocal aperture. Two-dimensional electrophoresis followed by Western blotting was used to separate and identify type II cell nuclear proteins. RESULTS: Nuclei were isolated from type II cells obtained from elastase-digested rat lungs and examined for the presence of SP-A. The nuclei contained both focal and diffuse deposits of SP-A. Some regions within the nuclear matrix (in particular the nucleolus) appeared to be relatively devoid of SP-A. The perinuclear membrane stained intensely for SP-A where optical sectioning showed its presence as a patchwork of punctate deposits. Analysis of the SP-A associated with the nucleus by two-dimensional electrophoresis revealed that it consisted of a family of proteins with molecular masses of 26, 32, and 36 kDa and pI 5.1. Biosynthesis of nuclear SP-A in primary cultures of type II cells was sensitive to inhibitors of glycosylation resulting in the presence of only the lowest molecular weight unprocessed form. CONCLUSIONS: These data indicate that three basic forms of SP-A are associated with the nucleus of the type II cell and are especially concentrated on the perinuclear membrane.

Animals↗
PubMed1991

Application of confocal scanning laser microscopy in experimental pathology.

Confocal scanning laser microscopy (CSLM) represents an exciting new tool for scientific disciplines which focus on mechanistic studies such as experimental pathology. Enhanced resolution in the specimen plane and rejection of out-of-focus fluorescence flare allow analysis of specific nucleic acid sequences, enzymes, structural macromolecules, and cellular homeostasis utilizing fluorescent probes. Four different experimental applications are discussed which utilize CSLM to evaluate pathological processes at the subcellular, cellular, and tissue levels. Programmed cell death, or apoptosis, is a natural process of significance both during development and as a response to toxic stimuli. CSLM-imaging of nuclei of human B lymphoblastoid cells following exposure to a monofunctional alkylating agent suggests that the degradation of chromatin characteristic of apoptosis may occur in asymmetric patterns. Surfactant apoprotein-A is the major non-serum protein component of pulmonary surfactant and is essential for the extracellular function of surfactant. CSLM of alveolar type II cells suggests that apoprotein-A is present in both the cytoplasm, predominantly in lamellar bodies, and in the nucleus. The tumor promoter, phorbol myristate acetate, rapidly stimulated the formation of vacuoles in human neutrophils. CSLM using Lucifer Yellow as a probe suggests that cylindrical vacuoles are formed by fluid-phase pinocytosis. The blood-nerve barrier (BNB) in peripheral nerves may be an important target during toxin-induced neuropathies. Ricin-induced permeability of the BNB in the rat was rapidly visualized by CSLM as leakage of fluorescein isothiocynate (FITC)-dextran into the endoneurial compartment.

Animals↗
PubMed1991

Confocal laser scanning immunofluorescence microscopy of lamellar bodies and pulmonary surfactant protein A in isolated alveolar type II cells.

We have determined the distribution of surfactant protein A (SP-A) in isolated type II cells from the lungs of rats by using immunofluorescence in conjunction with a laser scanning microscope fitted with a confocal aperture. Because of the very narrow depth of field of this microscope (less than 0.4 microns) in the confocal format, we were able to optically section type II cells and determine both the distribution of SP-A in the type II cell and the distribution of the lamellar bodies. The location of SP-A was determined by using fluorescein isothiocyanate-labeled secondary antibodies and the lamellar body distribution by using the lipid soluble fluorescent stain Phosphine 3R. SP-A was detected in the cytoplasm of type II cells as asymmetrically distributed punctate fluorescent bodies that resembled lamellar bodies in terms of size, number, and distribution within the cytoplasm of the cell. Most of the SP-A was located within bodies of the type II cell. Diffuse patches of fluorescence were seen in other cytoplasmic regions as well as the number of the cell. We conclude that SP-A is localized primarily, but not exclusively, in lamellar bodies of type II cells and that laser scanning microscopy is a much superior technique for the localization of SP-A than conventional microscopy in terms of both sensitivity and resolution.

Animals↗
PubMed1990

Induction of surfactant protein (SP-A) biosynthesis and SP-A mRNA in activated type II cells during acute silicosis in rats.

The synthesis of the major surfactant protein, SP-A, was studied in activated alveolar type II cells isolated from the lungs of rats exposed to silica by intratracheal instillation. Exposure of rats to silica resulted in large increases in the levels of disaturated phosphatidylcholine and SP-A in the extracellular and intracellular surfactant compartments. Isolated type II cells were used to determine if the observed increases in SP-A were associated with increased SP-A synthesis. Type II cells were isolated by a combination of elastase digestion, centrifugal elutriation, and differential adherence on IgG-coated petri dishes. Type II cells from silica-treated lungs were separated into two populations, designated type IIA and type IIB. The type IIB, or activated population, consisted of type II cells that were larger than normal type II cells and, in addition, contained larger and more numerous lamellar bodies than normal type II cells. Type IIB cells contained 4.3-fold higher levels of SP-A compared to normal type II cells. SP-A synthesis was measured by incubating freshly isolated cells with [35S]Translabel (70% [35S]methionine, 15% [35S]cysteine) for up to 4 h in methionine-free medium, followed by immunoprecipitation of newly synthesized protein. The rate of SP-A synthesis was increased approximately 6.7-fold in the activated type II cells. Analysis of the newly synthesized protein by one-dimensional SDS-PAGE indicated three intracellular forms of SP-A with molecular weights of approximately 26,000, 30,000, and 34,000. In type II cells from control rats, the 34-kD protein accounted for approximately 93% of the newly synthesized SP-A after 4 h of incubation; only a small amount of radioactivity was associated with the lower molecular weight species. The increased biosynthesis of SP-A in the activated type II cells was associated with a 7.3-fold increase in the level of SP-A mRNA. These results indicate that the content and synthesis of SP-A are both highly elevated in activated type II cells and that these increases may be due to increased levels of SP-A mRNA.

Animals↗
PubMed1980

Incremental validity of the new MCAT.

The authors investigated the power of the New Medical College Admission Test (MCAT) to predict performance of first-year medical students at the University of North Carolina. The approach was to compute the additional variance in performance explainable by the New MCAT after the effects of other routinely available admissions variables were taken into account. This incremental validity of the New MCAT was found to be substantial, with performance prediction improved by 23 to 38 percent, and was higher in this range when nationally standardized performance measures were employed as the outcome variable. Also several predictor variables--including two New MCAT subtests--were found to have significant polynomial relationships to the outcome measures; Use of polynomials in the regression procedure increased the overall accuracy of the prediction but did not affect the incremental validity of the New MCAT.

Achievement↗
PubMed1975

Stress polycythemia--a pathophysiologic study.

Two patients with "Gaisböck syndrome" (stress polycythemia) were found to have been under chronic "stress" with REM sleep decrease, decreased nocturnal ADH-like activity and consequent nocturnal water loss. The role of REM decrease with chronic "stress" in causing secondary decrease in nocturnal ADH-like activity was emphasized as the means by which "stress" caused the blood volume changes seen with these two patients. Some factors that possibly could play a role in the pathophysiology of this syndrome were ruled out and other factors not studied here were considered for future investigation.

17-Hydroxycorticosteroids↗