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Biomedical subjects

C M Smith

Publications and source records attributed to C M Smith.

At least 109 records · Page 6Linked to original sources
PubMed1996

Unequal cleavage in leech embryos: zygotic transcription is required for correct spindle orientation in subset of early blastomeres.

Leech embryos undergo invariant sequences of equal and unequal cell divisions to give rise to identifiable progeny cells. While many of the early cleavages are under maternal control, the divisions of a subset of early blastomeres (the large cells of the D' lineage) are perturbed after the inhibition of zygotic transcription. Analysis of the different types of cells produced in embryos injected with the transcriptional inhibitor, alpha-amanitin, revealed that the symmetry of cell division is perturbed in these large D'-derived cells during this early period of development. These cells, which would normally undergo a series of equal and unequal cleavages, always undergo equal cleavages after the inhibition of zygotic transcription. It appears that zygotically transcribed gene product(s) are required in the large cells of the D' lineage to orient the mitotic spindles properly for these unequal cell cleavages.

Amanitins↗
PubMed1996

Cellular mechanisms of epiboly in leech embryos.

Gastrulation in leech embryos is dominated by the epibolic movements of two tissues: germinal bands, composed of segmental precursor cells, and an overlying epithelium that is part of a provisional integument. During gastrulation, the germinal bands move over the surface of the embryo and coalesce along the prospective ventral midline. Concurrently, the epithelium spreads to cover the embryo. We have begun to analyze the mechanisms involved in gastrulation in the leech by assessing the independent contributions of the epithelium and the germinal bands to these cell movements. Here we describe cellular events during epiboly in normal embryos and in embryos perturbed by either reducing the number of cells in the epithelium, or by preventing the formation of the germinal bands, or both. These experiments indicate that both the germinal bands and the epithelium are able to undergo epibolic movements independently, although each is required for the other to behave as in control embryos.

Animals↗
PubMed1996

Neurological complications of celiac disease: a rare but continuing problem.

Neurological complications are a recognized but unusual manifestation of celiac disease. We present here our experiences with four current cases. Age of patients at presentation with neurological signs varied from 7 to 67 yr. In one patient, the neurological disability developed before the diagnosis of celiac disease, whereas, in the other three, it occurred from months to 16 yr after the diagnosis had been established. One patient died of rapidly progressive neuromyopathy. The other three patients had combinations of cerebellar and posterior and lateral column abnormalities. All four patients developed neurological complications despite a strict gluten-free diet. In three of four patients, there was no improvement in duodenal histology on this diet. Treatment with vitamin B12, folic acid, or vitamin D failed to reverse the changes. No other nutritional deficiencies were found. Vitamin E levels were normal in two of three patients. One patient had no response to treatment with immunosuppressive drugs. The mechanisms responsible for these neurological complications are poorly understood, although patients whose duodenal histology fails to improve on a gluten-free diet may be at greater risk. There have been no real advances in the understanding of this condition since the original description nearly 30 yr ago.

Adult↗
PubMed1995

The division of neuronal progenitor cells during migration in the neonatal mammalian forebrain.

In the mammalian forebrain most neurons originate from proliferating cells in the ventricular zone lining the lateral ventricles. These neurons become postmitotic before they undergo migration to their final destinations. In this study we examined the proliferative and migratory properties of cells destined for the olfactory bulb that arise postnatally from progenitor cells situated at the anterior extent of the subventricular zone (SVZa). The SVZa-derived cells migrate along a stereotypical pathway to the olfactory bulb where they become interneurons. Using lineage tracers and the cell proliferation marker BrdU, we have demonstrated that SVZa-derived cells in the rat retain the capacity for division after migrating away from their initial site of generation. These cells also express a neuron-specific tubulin, recognized by the antibody TuJ1. These results suggest that, unlike other immature neurons, these SVZa-derived cells have made a commitment to become neurons before becoming postmitotic.

Animals↗
PubMed1995

Mapping eight new polymorphisms in 11q13 in the vicinity of multiple endocrine neoplasia type 1: identification of a new distal recombinant.

Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal dominant disorder that predisposes affected individuals to neoplasms of the parathyroid glands, endocrine pancreas, anterior pituitary, and carcinoids. The MEN1 locus has been localized by family studies to 11q13, flanked by markers PGA and D11S97. Eight new polymorphisms located in three separate radiation-reduced somatic cell hybrid segregation groups were developed. The order of the new markers, within the context of previously described loci, was determined by linkage analysis on the Venezuelan reference pedigree. Four independent MEN1 families, consisting of 57 affected individuals, and 70 individuals at-risk for the disease were genotyped. Sixteen people inherited a chromosome that shows recombination between a linked marker and the disease. The nearest proximal and distal markers that show recombination with the disease are D11S822 and GSTP1, respectively, thereby narrowing the candidate region for MEN1 by 50% on the distal side. Using these loci in haplotype analysis, an accurate presymptomatic molecular diagnostic test has been developed. These new markers in 11q13 linked to MEN1 also facilitate the genetic and physical characterization of this very gene-rich region.

Adolescent↗
PubMed1995

Relationship of actin filament assembly to clearance of fibrinogen gold, GPIIb-IIIa complexes on spread platelets.

The present study has evaluated the influence of high concentrations of cytochalasins B and E on the detergent-resistant actin levels in fully spread platelets by PAGE gel electrophoresis, and the effects of the two inhibitors of new actin filament assembly on translocation of fibrinogen gold (Fgn/Au) labelled GPIIb-IIIa receptors on the surface-activated cells. Concentrations of 10(-4) M and 10(-5) M cytochalasin B and E reduced detergent-resistant actin in fully spread platelets to levels present in resting discoid platelets in suspension. Despite reduction of actin filaments to levels in resting cells, cytochalasin B did not prevent translocation of Fgn/Au from platelet margins into channels of the open canalicular system (OCS). Similar concentrations of cytochalasin E completely blocked translocation of receptor-ligand complexes and produced a patching phenomenon not observed in previous studies. Rinsing of the spread cells to remove cytochalasin, followed by incubation of the treated platelets in Hank's buffered salt solution (HBSS) restored levels of detergent-resistant actin to those found in untreated, spread platelets. Resting grids of 10(-5) M cytochalasin E-treated platelets on drops of HBSS for 15 min restored their ability to clear FGN/Au linked to GPIIb-IIIa from exposed surfaces to the OCS, but 10(-4) M cytochalasin E-treated cells remained anergic after incubation on drops of HBSS. Thus a fully assembled cytoplasmic actin filament cytoskeleton does not appear to be essential for translocating receptor-ligand complexes on the platelet surface to the OCS, nor does its presence guarantee that the ability to clear GPIIb-IIIa receptors will be restored.

Actins↗
PubMed1995

Genetic and radiation-reduced somatic cell hybrid sublocalization of the human GSTP1 gene.

A number of related enzymes like glutathione S-transferases (GSTs) and fatty acid ethyl ester synthases (FAEESs) have been implicated in detoxification and drug resistance. The anionic class of GSTs, pi, and closely related FAEES-III exhibit tissue-specific and developmentally regulated expression, and the former has been shown to be overexpressed or amplified in a variety of tumors. The GSTP1 gene has previously been cloned and cytogenetically localized to human 11q13 by in situ hybridization. Using a series of previously described radiation-reduced somatic cell hybrids, we have sublocalized GSTP1 to 11q13. We isolated a genomic clone containing the entire GSTP1 gene and sequenced it. Analysis of the 5'region revealed 23 (TAAAA) tandem repeats interrupted by a single TA and TAA insertion. This repeat number differs among individuals. Eleven alleles in a mostly Caucasian sample were observed. This repeat has a polymorphism information content of 0.74. Linkage analysis of the Venezuelan reference pedigree places GSTP1 5 cM distal to PYGM and 4 cM proximal to FGF3 thereby providing a genetic marker half-way between these two loci. The sublocalization and genetic characterization of GSTP1 facilitates linkage analysis of several disease genes mapped to this chromosome band as well as the correlation of genetic and physical markers in the region.

Animals↗
PubMed1995

Quality of well-being predicts survival in lung transplantation candidates.

Predictors of survival were evaluated among 74 patients selected for a lung transplantation program. Each patient received the quality of well-being scale, a utility-based outcome measure that gives a score on a continuum ranging from 0 (for dead) to 1.0 (for optimum function), and a measure of depressive symptoms (Beck depression inventory). Over the course of follow-up, 24 patients died (ranging from listing date, 3 to 1, 110 d). Of the 49 patients who received lung transplantation, 13 died. In a multivariate analysis, the most significant predictor of survival was quality of well-being (relative risk = 0.454, p < 0.05). Lung transplant status, when entered as a time-dependent covariate (a function of how long the patient waited for surgery) was not a significant predictor of survival (relative risk = 0.942, p > 0.05). Depression was not a significant predictor of survival (relative risk = 0.961, p > 0.05). We conclude that health-related quality of life is a significant predictor of survival for patients with serious lung diseases.

Humans↗
PubMed1995

Two missense mutations in the beta-globin gene can cause severe beta thalassemia. Hemoglobin Medicine Lake (beta 32[B14]leucine-->glutamine; 98 [FG5] valine-->methionine).

We studied the molecular basis of transfusion-dependent hemolytic anemia in an infant who rapidly developed the phenotype of beta thalassemia major. DNA sequence of one beta-globin gene of the proband revealed two mutations, one for the moderately unstable hemoglobin (Hb) Köln and another for a novel codon 32 cytosine-thymidine-guanine-->cytosine-adenine-guanine transversion encoding a leucine-->glutamine mutation. A hydrophilic glutamine residue at beta 32 has an uncharged polar side chain that could potentially distort the B helix and provoke further molecular instability. This new hemoglobin was called Hb Medicine Lake. Biosynthesis studies showed a deficit of beta-globin synthesis with early loss of beta-globin chains. An abnormal unstable hemoglobin, globin chain, or tryptic globin peptide was not present, demonstrating the extreme lability of this novel globin. Hb Medicine Lake mRNA was present, but an aberrantly spliced message was not. Absence of an abnormal beta-globin gene in the mother makes it likely that a de novo mutation occurred in the proband. The molecular pathogenesis of Hb Medicine Lake illustrates a mechanism whereby the phenotype of a genetic disorder, like the mild hemolytic anemia associated with a hemoglobinopathy, can be modulated by a coincident mutation in the same gene.

Amino Acid Sequence↗
PubMed1995

A polymorphism in the delta-aminolevulinic acid dehydratase gene may modify the pharmacokinetics and toxicity of lead.

Associations between the presence of a constitutional variant of delta-aminolevulinic acid dehydratase (ALAD-2) and lead concentrations in blood and bone, as well as between this allele and indices of kidney function, were investigated among 691 members of a construction trade union. The average blood lead level in this group was 7.78 micrograms/dl. No significant difference was observed in blood lead concentration in ALAD-2 carriers compared to those homozygous for the more common ALAD-1 allele (7.78 +/- 3.62 micrograms Pb/dl vs. 7.73 ( +/- 3.48 micrograms Pb/dl, respectively; p = 0.73). Bone lead was measured in a subset of 122 of the study subjects. Patella minus tibia lead concentrations for each individual averaged 3.35 +/- 11.99 micrograms Pb/g bone mineral in ALAD-1 homozygotes and 8.62 +/- 9.47 micrograms Pb/g bone mineral in ALAD-2 carriers (p = 0.06). Comparisons of blood urea nitrogen (BUN) and uric acid by genotype indicated elevated levels among ALAD-2 individuals (p = 0.03 and 0.07, respectively). In logistic regression models accounting for other variables potentially associated with BUN and uric acid levels, BUN was significantly associated with blood lead levels (p = 0.01). Associations of BUN and uric acid levels with ALAD-2 were of borderline statistical significance in these models (p = 0.06 and 0.07). Taken together, these results suggest that the ALAD-2 genotype may influence the pharmacokinetic distribution and chronic renal toxicity of lead, perhaps due to differential binding of lead to the variant protein.

Adult↗
PubMed1994

Partial purification and characterization of maize-leaf pyruvate, orthophosphate dikinase regulatory protein: a low-abundance, mesophyll-chloroplast stromal protein.

The C4 mesophyll-chloroplast stromal enzyme pyruvate, orthophosphate dikinase (PPDK) regulatory protein (RP) catalyzes the activation/dephosphorylation and inactivation/phosphorylation of PPDK. This bifunctional converter enzyme has been partially purified from maize leaf extracts approximately 100-fold to a final specific PPDK-inactivation activity of 3-10 units PPDK/min/mg protein and an overall recovery of 1-5%. Purification of active RP was accomplished by (NH4)2SO4 fractionation and sequential column chromatography on dye-ligand and size-exclusion or FPLC-based anion-exchange matrices. Immunoblot analyses of size-exclusion and anion-exchange fractionated preparations indicate that NADP-malate dehydrogenase (MDH) and ribulose-bisphosphate carboxylase/oxygenase are major contaminants, respectively. During sequential dye-ligand and anion-exchange chromatography, RP activity copurifies with a approximately 48-kDa polypeptide on silver-stained denaturing gels. Both RP activities are readily detected in maize mesophyll-chloroplast stromal extracts, but unlike stromal PPDK and NADP-MDH, the putative, approximately 48-kDa RP polypeptide is barely detectable in silver-stained gels. Our collective data indicate that RP constitutes < 0.04% of the total soluble maize-leaf protein and < 1% of its target enzyme, contrary to a previous report. PPDK-inactivation and -activation activities are quantitatively equivalent in light- and dark-adapted maize-leaf tissue rapidly extracted and assayed at either pH 7.0 or 8.0, suggesting that the opposing RP activities are not regulated differentially by reversible covalent modification or pH effects.

Chloroplasts↗
PubMed1994

Comparison of testosterone metabolism in benign prostatic hyperplasia and human prostate cancer cell lines in vitro.

Pathways of testosterone metabolism in tissue slices and cell suspensions of human benign hyperplastic prostate (BPH) tissue and human prostate cancer cell lines (DU145, HPC-36M, PC-3/MA2 and LNCaP) were investigated. Thin layer chromatography analysis was used to identify the following tritiated metabolites: testosterone, 5 alpha-dihydrostestosterone (DHT), 5 alpha-androstane-3 alpha/3 beta-17 beta-diol (androstanediols), 4-androstene-3,17-dione (androstenedione) and 5 alpha-androstanedione. The predominant pathway for testosterone metabolism in BPH was via 5 alpha-reductase producing 5 alpha-dihydrotestosterone (71% and 75% total metabolites in slices and suspensions incubated for 24 h, respectively). The cancer cell lines DU145 and HPC-36M resembled BPH by metabolizing testosterone predominantly to DHT (68% and 82% total metabolites, respectively), although the rate of metabolism was much lower in the cell lines (0.099 and 0.05 pmol testosterone/mg protein/h in DU145 and HPC-36M) compared to the BPH cell suspensions (6.4 pmol testosterone/mg protein/h). In contrast, PC-3/MA2 contained high 17 beta-HSD activity forming large amounts of 4-androstene-3,17-dione (84% total metabolites), converting testosterone at a rate faster (12.8 pmol testosterone/mg protein/h) than the BPH cell suspensions. LNCaP rapidly converted testosterone exclusively to a glucuronide conjugate (7.4 pmol testosterone/mg protein/h), although after incubation with [3H]-4-androstene-3,17-dione, 5 alpha-reductase activity was demonstrated. LNCaP was the only cell line whose growth and colony-forming ability was stimulated by testosterone and DHT. BPH and all the cell lines tested had 5 alpha-reductase activity, but only the prostate tissue and the cell lines DU145 and HPC-36M converted testosterone predominantly to DHT.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗