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Biomedical subjects

R E Scott

Publications and source records attributed to R E Scott.

At least 73 records · Page 4Linked to original sources
PubMed1988

Melanogenuria: laboratory evaluation of the qualitative Thormählen and ferric chloride tests and their clinical utility.

Malignant melanoma, a disease that is increasing in occurrence and medical concern, is characterized by the excretion of melanogens. Two qualitative tests are recommended for melanogen detection, the Thormählen test and the ferric chloride test. We evaluated the laboratory and clinical performance of these tests by subsequently re-evaluating 201 urine samples that had been submitted for routine melanogen analysis. We used (a) Thormählen, (b) ferric chloride, (c) small-scale thin-layer chromatography, and (d) spectrophotometry. Nearly 30% of Thormählen test results were equivocal. The ferric chloride test was of no value in itself or in categorizing equivocal Thormählen results as positive or negative. The small-scale chromatography was irreproducible. Prompt scanning of the Thormählen reaction product was helpful in classifying equivocal results. History review of 121 histopathologically diagnosed melanoma patients indicated that these qualitative assays were of no clinical value in the diagnosis or monitoring of melanoma patients.

Chlorides↗
PubMed1987

Polypeptide changes associated with loss of proliferative potential during the terminal event in differentiation.

The differentiation of murine mesenchymal stem cells occurs in nonterminal and terminal phases. In previous reports we established the characteristics of nonterminally differentiated cells and showed that transition from the nonterminal to the terminal state of differentiation can be induced by human plasma. We also showed that this transition is blocked by protein synthesis inhibitors and other pharmacological agents. In this paper, we have employed two-dimensional gel electrophoresis to evaluate changes in specific polypeptides that are induced when cells lose proliferative capacity associated with the terminal event in differentiation. Using silver staining procedures for analysis of electrophoretograms, we detected only seven major polypeptide differences between nonterminally differentiated and terminally differentiated cells. Six polypeptides were expressed only in preparations of terminally differentiated cells; these included two polypeptides identified in cytosolic fractions and four polypeptides identified in nuclear fractions. One polypeptide was also found to be selectively expressed only in nuclear fractions of nonterminally differentiated cells. Based on these observations we conclude that the loss of proliferative potential that occurs during the terminal event in mesenchymal stem cell differentiation is associated with changes in the composition of a limited number of specific polypeptides. We suggest that one or more of these polypeptides may be important in the regulation of cellular proliferation.

Adipose Tissue↗
PubMed1987

Analysis of the cardiovascular effects of arginine vasopressin in conscious dogs.

The effects of physiological elevations in arginine vasopressin on the cardiovascular system were studied in a group of nine conscious, chronically instrumented dogs. The animals were studied under normal conditions (plasma vasopressin, 4.1 +/- 0.4 pg/ml), after 24 hours of dehydration (plasma vasopressin, 7.3 +/- 1.5 pg/ml), after a 30-minute vasopressin infusion at 2.6 ng/kg/min (plasma vasopressin, 96.6 +/- 8.1 pg/ml). These increases in vasopressin concentration resulted in no change in arterial pressure and significant changes in the following: a 13 and 29% decrease in resting cardiac output during dehydration and acute infusion, respectively; a 26% reduction in heart rate during acute infusion; a 12 and 54% increase in total peripheral resistance during dehydration and acute infusion; a 16 and 22% reduction in mean circulatory filling pressure during dehydration and chronic vasopressin infusion. In addition, maximum pumping ability of the heart was reduced 16 and 31% during dehydration and acute infusion, respectively. These data suggest that elevations of vasopressin such as those occurring during dehydration or volume depletion potentially may affect cardiovascular performance by three mechanisms: greatly increasing resistance to flow, reducing heart rate, suppressing the pumping ability of the heart.

Animals↗
PubMed1987

The Ames Clinitek 200/Multistix 9 urinalysis method compared with manual and microscopic methods.

We assayed 315 urine specimens by the Ames Clinitek 200/Multistix 9 semi-automated method and by corresponding standard methods (listed in parentheses) for the following analytes: protein (sulfosalicylic acid precipitation), glucose (Lilly Tes-Tape), ketones (Boehringer Mannheim Chemstrip K), leukocyte esterase (microscopic examination for leukocytes), blood (microscopic examination for erythrocytes), nitrite (microscopic examination for bacteria, Gram stain, or culture), and pH (pH meter). The Clinitek and standard methods agreed well at all concentrations for protein, ketones, and glucose. The Clinitek leukocyte esterase, nitrite, and blood methods were less sensitive than microscopic methods for detection of pyuria, bacteriuria, and hematuria, respectively. The Clinitek pH method produced falsely low pH values for urines with true pH less than 6.5, and falsely high values for urines with true pH greater than 6.5.

Autoanalysis↗
PubMed1986

Suppression of tumorigenicity by the cell-cycle-dependent control of cellular differentiation and proliferation.

The experiments described in this report were designed to determine if suppression of tumorigenicity can be mediated by cell-cycle-dependent mechanisms that control cellular differentiation and/or proliferation in mesenchymal stem cells of the 3T3 T type. These cells were employed because they possess distinct, well-characterized cell-cycle-dependent mechanisms to control both cellular differentiation and proliferation. To achieve our goal we developed by non-mutagenic procedures 23 clonal variants of 3T3 T stem cells that expressed one of 4 distinct phenotypes for the regulation of cellular differentiation and proliferation. Six clones expressed combined defects in the control of differentiation and proliferation; 6 expressed intact mechanisms to control proliferation but defects in the control of differentiation; and 3 expressed intact mechanisms to control differentiation but defects in the control of proliferation. Finally, 8 clones expressed no detectable phenotypic defects in the control of either differentiation or proliferation. Once isolated and characterized, each of these clones was assayed for its tumorigenic potential. The results establish that clones which express combined defects in the control of differentiation and proliferation are highly tumorigenic. By contrast, tumorigenicity is markedly suppressed in clones that maintain the ability to control their proliferation or their differentiation. Furthermore, clones that maintained the ability to control both proliferation and differentiation showed no evidence of tumorigenicity. These data are interpreted to suggest that stringently regulated control of cellular differentiation and/or proliferation can act as a cancer suppressor mechanism.

Animals↗
PubMed1986

Transforming growth factor type beta is a specific inhibitor of 3T3 T mesenchymal stem cell differentiation.

In the current studies we examined the effects of transforming growth factor type beta (TGF-beta) on the control of differentiation of BALB/c 3T3 T stem cells. We report that TGF-beta is a potent, reversible inhibitor of adipocyte differentiation (50% inhibition at approximately 0.06-0.08 ng/ml), while other biologically active polypeptides, such as epidermal growth factor (EGF), human growth hormone (hGH), and somatomedin C, have no specific effect on differentiation at even higher concentrations (200 ng/ml). We also report that TGF-beta inhibits differentiation in a cell cycle-dependent manner by its effect on a specific phase in the differentiation process. We therefore suggest that if TGF-beta is an important regulatory factor, one of its critical mechanisms of action may be its ability to inhibit the process of cell differentiation.

Adipose Tissue↗
PubMed1986

New techniques for the in vitro culture of human skin keratinocytes and perspectives on their use for grafting of patients with extensive burns.

Human keratinocytes can be cultured in vitro and used for autografting of the injured epidermis. In this article, we describe our culture methods for propagating autologous keratinocytes for grafting, and we present an overview of the questions raised by the use of such methods. Our culture method involves a two-phase technique. Phase 1 is performed in serum-free medium and yields large quantities of a homogeneous, highly proliferative, basal cell-like population. Phase 2 involves the induced formation of cohesive, stratified sheets of differentiated keratinocytes resembling normal epidermis that can be used for grafting. This two-phase technique was used for preparation of autografts for full-thickness wounds of a massively burned patient. Important questions about the functional potential of cultured keratinocytes and the long-term behavior of cultured epidermal autografts in vivo remain to be answered.

Adult↗
PubMed1986

Regulation of the terminal event in cellular differentiation: biological mechanisms of the loss of proliferative potential.

Human plasma has been demonstrated to contain factors that induce the sequential expression of nonterminal and terminal adipocyte differentiation in 3T3 T mesenchymal stem cells. We now report the development of methods for the isolation of purified populations of nonterminally differentiated cells and terminally differentiated cells, and we show that it is possible to experimentally induce transition from the nonterminal to the terminal state of differentiation. With this model system it is therefore now possible to examine the biological and molecular processes associated with the terminal event in differentiation, i.e., the irreversible loss of proliferative potential. In this regard, we demonstrate that transition from the nonterminal to terminal state of differentiation is a complex metabolic process that consists of at least two steps and that this process can be triggered by pulse exposure to an inducer for approximately 12 h but that approximately 24-48 h is required for the process to be completed. The data also establish that induction of the terminal event in differentiation requires protein synthesis but not RNA and DNA synthesis. These and additional results suggest that loss of proliferative potential associated with the terminal event in cellular differentiation is a distinct regulatory process, and we suggest that defects in this regulatory process may be of etiological significance in the pathogenesis of specific human diseases, especially cancer.

1-Methyl-3-isobutylxanthine↗
PubMed1986

Two functionally distinct classes of growth arrest states in human prokeratinocytes that regulate clonogenic potential.

Rapidly growing normal human neonatal prokeratinocytes (HPK) cultured in serum-free medium can be induced to undergo either reversible or irreversible growth arrest at distinct cell cycle states. Reversible G1 arrest was induced by culture of low-density cells in human lymphocyte conditioned medium, by culture in high-density stationary phase conditioned medium, and by culture in isoleucine-deficient medium. Irreversible arrest of HPK growth predominantly in G1 was induced by culture in growth factor-deficient medium. Irreversible arrest of HPK growth in G1 and G2 was also induced by culture in suspension in methylcellulose prepared in complete MCDB 153 medium or by culture in serum-containing medium. Finally, the drug razoxane was employed to induce irreversible arrest of HPK in G2. These data establish that there are 2 distinct classes of growth arrest states for HPK and suggest that each arrest mechanism may serve a unique role in the control of keratinocyte differentiation in normal cells. It is also possible that the development of selective defects in either of these processes could be of etiologic significance in certain epidermal disease states.

Cell Cycle↗
PubMed1986

Stabilization and purification of the secondary metabolism specific enzyme, m-hydroxybenzylalcohol dehydrogenase.

m-Hydroxybenzylalcohol dehydrogenase (EC 1.1.1.97), a secondary metabolism associated protein from stationary phase cultures of Penicillium urticae, was stabilized in crude extracts prior to purification. Stabilization studies resulted in the formulation of an optimal cell breakage and purification buffer. This buffer increased the enzyme's in vitro half-life at 30 degrees C from 14 to over 800 min which greatly aided purification and enhanced yields. Purification was achieved by salt fractionation, size-exclusion chromatography, affinity chromatography, and ion-exchange chromatography. The 1200-fold purified protein gave only one major band by sodium dodecyl sulphate - polyacrylamide gel electrophoresis.

Alcohol Oxidoreductases↗
PubMed1986

Manganese and antibiotic biosynthesis. I. A specific manganese requirement for patulin production in Penicillium urticae.

The effect of trace metal nutrition on the functioning of the patulin biosynthetic pathway in submerged cultures of Penicillium urticae (NRRL 2159A) was examined by both chromatographic and enzymological means. Comprehensive metal ion analysis showed generally low levels of contaminating metal ions in media components. Of eight metal ions examined, only manganese strongly influenced secondary metabolite production. In control cultures or cultures deficient in calcium, iron, cobalt, copper, zinc, or molybdenum, pathway metabolites appeared in the medium at about 25 h after inoculation. The first pathway-specific metabolite, 6-methylsalicylic acid, accumulated only transiently before being converted to patulin whose concentration steadily increased. In manganese-deficient cultures, however, 6-methylsalicylic acid continued to accumulate, with only minor amounts of patulin being produced. Additionally, a marker enzyme for the pathway showed only 0-20% of control activity. Clear dose responses (patulin versus manganese) were found in different media, with no effect on growth yield. Addition of manganese to depleted cultures at 18, 26, or 36 h resulted in increasing marker enzyme activity and patulin concentrations. It is concluded that manganese exerts a specific, positive effect on patulin biosynthesis and may in some way control the section of the patulin pathway occurring after 6-methylsalicylic acid.

Acyltransferases↗
PubMed1986

Manganese and antibiotic biosynthesis. II. Cellular levels of manganese during the transition to patulin production in Penicillium urticae.

The radionuclide 54MnCl2 was used to examine the cellular manganese content of submerged cultures of Penicillium urticae NRRL 2159A. Liquid-scintillation spectroscopy allowed sensitive detection of isotopic manganese in both normally supplemented and manganese-deficient cultures. The cellular manganese content in supplemented cultures showed three distinct phases, including a period of uptake that coincided with the time of transition to antibiotic biosynthesis. Such an uptake was not seen for manganese-deficient cultures, but addition of normal quantities of unlabelled manganese to the media appeared to stimulate uptake. Preliminary characterization shows this manganese uptake is not inhibited by other metal ions, does not require metabolic energy or a protein component, but is disrupted by changes in incubation temperature. The significance of these observations is discussed in the light of recent work on the requirement for manganese for antibiotic biosynthesis in this organism.

Manganese↗
PubMed1986

Manganese and antibiotic biosynthesis. III. The site of manganese control of patulin production in Penicillium urticae.

Although manganese had been shown to be an essential requirement for patulin biosynthesis, its site of action was unknown. Four possibilities were considered. A manganese requirement for the second pathway enzyme, a decarboxylase, was discounted since mid and late pathway intermediates were not converted to patulin in manganese-deficient cultures. A major disruption in primary metabolism and hence secondary metabolism was discounted since eight primary metabolism enzymes showed no evidence of unusual changes in specific activity when normal and manganese-deficient cultures were compared. Inhibitor studies using actinomycin D and cycloheximide showed that there was no activation of preexisting enzyme proteins and that manganese did not influence translation. The inhibitor studies did show, however, that manganese exercised its effect on patulin biosynthesis by influencing the coordinate appearance of pathway enzymes though an effect at the level of transcription.

Alcohol Oxidoreductases↗
PubMed1986

An ultrastructural examination of Penicillium urticae during the transition to antibiotic biosynthesis.

The ultrastructure of Penicillium urticae mycelium was compared at various stages of submerged growth to examine changes associated with the onset of antibiotic biosynthesis. Penicillium urticae was shown to be a normal eukaryotic, septate, filamentous fungus with a variety of subcellular components. Younger mycelia possessed a denser cytoplasm which gave way to a more granular and vacuolated cytoplasm as the organism made the transition into antibiotic biosynthesis. An increase in the thickness, and perhaps the structural complexity, of the cell wall also occurred over the transition. There was evidence of a glycocalyx surrounding the hyphae. Discrete granules, termed peripheral particles, appeared and increased in number over the transition. Their biochemical content and possible involvement in patulin production was tested by examining P. urticae after growth in media of different composition, and by examining the ultrastructure of a patulin minus mutant, P3. The significance of these observations in relation to patulin production is discussed.

Cell Membrane↗
PubMed1986

Reversible inhibition of normal human prokeratinocyte proliferation by type beta transforming growth factor-growth inhibitor in serum-free medium.

Type beta transforming growth factor-growth inhibitor (TGF beta/GI) causes normal human prokeratinocytes to arrest growth predominantly in the G1 phase of the cell cycle within 48 h after log phase cultures are exposed to the factor in serum-free medium. The growth arrest induced by TGF beta/GI is reversible because the cells from treated cultures can be replated into fresh medium and grown into large colonies. Normal prokeratinocytes are demonstrated to secrete TGF beta/GI-like molecules into the culture medium and to have specific cell surface receptors for this molecule. In contrast, a human squamous cell carcinoma, SCC-25, does not arrest growth when exposed to TGF beta/GI. These cells, unlike the normal prokeratinocytes, do not exhibit detectable cell surface receptors for the factor.

Blood↗
PubMed1986

Vasculitis in hairy cell leukemia: review of literature and consideration of possible pathogenic mechanisms.

Systemic vasculitis is an unusual but recently recognized complication of hairy cell leukemia. We studied this relationship further in an attempt to better understand pathogenetic mechanisms of vasculitis. We examined the records of 129 cases of hairy cell leukemia seen at the Mayo Clinic between 1976 and 1983, and identified 2 cases with evidence of systemic vasculitis. The first of these cases is discussed in detail. Immunologic studies were performed but we were unable to demonstrate the presence of shared antigen on hairy cells and endothelial cells. The literature is reviewed and reports of this association are summarized. Possible mechanisms of vascular injury are discussed.

Adult↗