Search PubMed⌕ Search

Biomedical subjects

J D Smith

Publications and source records attributed to J D Smith.

At least 271 records · Page 15Linked to original sources
PubMed1985

Graviresponsiveness and abscisic-acid content of roots of carotenoid-deficient mutants of Zea mays L.

The abscisic-acid (ABA) content of roots of the carotenoid-deficient w-3, vp-5, and vp-7 mutants of Z. mays was analyzed using gas chromatography-mass spectrometry with an analysis sensitivity of 6 ng ABA g-1 fresh weight (FW). Roots of normal seedlings of the same lines were characterized by the following amounts of ABA (as ng ABA g-1 FW, +/- standard deviation): w-3, 279 +/- 43; vp-5, 237 +/- 26; vp-7, 338 +/- 61. We did not detect any ABA in roots of any of the mutants. Thus, the lack of carotenoids in these mutants correlated positively with the apparent absence of ABA. Primary roots of normal and mutant seedlings were positively gravitropic, with no significant differences in the curvatures of roots of normal as compared with mutant seedlings. These results indicate that ABA 1) is synthesized in maize roots via the carotenoid pathway, and 2) is not necessary for positive gravitropism by primary roots of Z. mays.

Abscisic Acid↗
PubMed1985

Clonal isolation of populations of gamma-glutamyl transpeptidase-positive and -negative cells from rat liver epithelial cells chemically transformed in vitro.

In a population of cultured rat liver epithelial cells transformed by 11 brief treatments with N-methyl-N'-nitro-N-nitrosoguanidine, 9% of the cells stained intensely for gamma-glutamyl transpeptidase (GGT). We have isolated from this phenotypically heterogeneous tumorigenic cell population 11 GGT-positive and 7 GGT-negative clonal subpopulations (from single cells) and have analyzed the ploidy and selected biochemical, histochemical, and growth properties of the cells in these clonal sublines. As compared to the GGT-negative strains and normal diploid rat liver epithelial cells, cells of the GGT-positive strains are larger in size, have greater DNA content, proliferate more slowly in culture, and have higher specific activities of NADH diaphorase, glucose-6-phosphate dehydrogenase, pyruvate kinase, and lactate dehydrogenase. The GGT-positive strains also show greater alteration and heterogeneity than do the GGT-negative strains in their ability to store glycogen and in their expression of lactate dehydrogenase isozymes. The results indicate that enzymatic changes commonly observed in "altered" hepatocytes in rat livers exposed to chemical carcinogens in vivo can also be produced in vitro in cultured hepatic epithelial cells by treatment with carcinogens. Moreover, treatment of a cell line with a chemical carcinogen generates a population of cells vastly heterogeneous in both their phenotypes and genotypes. Isolation of clonal subpopulations from the resulting cell line allows critical examination of the linkage and mechanistic relationship between tumorigenicity and many paratumorigenic phenotypes.

Animals↗
PubMed1985

Phenotypic and karyotypic changes induced in cultured rat hepatic epithelial cells that express the "oval" cell phenotype by exposure to N-methyl-N'-nitro-N-nitrosoguanidine.

A diploid population of cultured rat hepatic epithelial cells that expresses the "oval" cell phenotype was exposed briefly and repetitively to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and the effect on more than 20 phenotypic properties was evaluated during the neoplastic transformation of the population. MNNG treatments of this hepatic epithelial cell population resulted in a progressively increasing phenotypic alteration and heterogeneity including changes in specific activities of several cellular enzymes and expression of isozymes, synthetic functions, and various in vitro growth properties. Changes in phenotypic expression were clustered episodically and were associated with major karyotypic changes. The development of increasing phenotypic heterogeneity preceding and accompanying tumorigenicity in cultured liver epithelial cells in vitro and the specific phenotypes that occur resemble superficially the pattern of phenotypic changes that occur in hepatocytes during chemical hepatocarcinogenesis in vivo. The results of this study provide the basis for future investigations to further elucidate the mechanistic and linkage relationship between specific pretumorigenic and paratumorigenic phenotypes and tumorigenicity.

Animals↗
PubMed1984

Incorporation of serine into the phospholipids of phosphatidylethanolamine-depleted Tetrahymena.

Phosphatidylserine formation and decarboxylation are decreased in Tetrahymena in which phosphatidylethanolamine has been replaced by its isosteric analog 3-aminopropylphosphonolipid (1,2-diacylglyceryl-3-O-(3-aminopropylphosphonate). The combined activity of the phosphatidylethanolamine: serine phosphatidyltransferase/ phosphatidylserine decarboxylase complex in isolated mitochondria from lipid-altered cells [J. D. Smith and D. A. Giegel (1981) Arch. Biochem, Biophys. 206, 420-423] is about 20% of the activity in mitochondria from control cells. The enzyme activity in the lipid-altered mitochondria is stimulated by the addition of exogenous phosphatidylethanolamine to the assay system while the enzymes of the control mitochondria are not. In vivo the lipid-altered cells are able to incorporate radioactivity from [3-14C]- or [3-3H]serine into phosphatidylserine and phosphatidylcholine in amounts comparable to normal cells. Thus, under conditions of "stress" (e.g., the depletion of phosphatidylethanolamine), the phosphatidyltransferase is apparantly capable of utilizing other phospholipids besides its normal substrate phosphatidylethanolamine.

Animals↗
PubMed1984

A diploid epithelial cell line from normal adult rat liver with phenotypic properties of 'oval' cells.

A diploid epithelial cell line (termed WB-F344) was isolated from the liver of an adult male Fischer-344 rat and the phenotypic characteristics of the cells were studied. These cells measure approximately two-fifths the volume of freshly isolated hepatocytes. They are histochemically negative for glucose-6-phosphatase and weakly positive for gamma-glutamyl transpeptidase. They produce extensive intercellular reticulin fibers which stain immunocytochemically for fibronectin, and they synthesize both alpha-fetoprotein and albumin, but they do not accumulate glycogen particles. Ultrastructurally, they are polygonal cells with numerous intercellular desmosomes and nexus junctions, and they are partially surrounded by basement membrane-like material. Cytoplasmic organelles include few, but sometimes dilated profiles of rough endoplasmic reticulum, lysosomes, abundant free ribosomes, sparse smooth endoplasmic reticulum and Golgi membranes, microbodies, and small, pleomorphic mitochondria. They express A and C isozymes of aldolase, K isozyme of pyruvate kinase, LDH2 to LDH5 isozymes of lactate dehydrogenase, and 'fetal liver'-type alkaline phosphatase isozyme. When compared with the phenotypes of isolated and purified normal hepatocytes, biliary epithelial (ductular) cells and 'oval' cells isolated from livers treated with chemical carcinogens, the phenotypic properties of the liver epithelial cell line in culture most resemble those of the 'oval' cells.

Animals↗
PubMed1984

Argon laser treatment of hemangiomas in children.

Argon laser photocoagulation has become the treatment of choice for vascular cutaneous lesions of the head and neck. In children under age 12 years the results have been poor in more than 50% of cases. This is the result of limited response and increased risk of hypertrophic scarring. Except for infants with complications of capillary hemangiomas of infancy we would not recommend argon laser treatment in children under the age of 12.

Adolescent↗
PubMed1984

Nosocomial mycobacterial pseudoinfection in a Georgia hospital.

Nosocomial pseudoepidemics may be detected when clustering of pseudoinfections occur or when artificial clusters of real infection are observed. Nontuberculous mycobacteria were reportedly isolated from specimens obtained from seven patients at one hospital from October 1980 to January 1981. Because the patients' clinical illnesses were not uniformly consistent with mycobacterial disease, we hypothesized that pseudoinfections had occurred and searched for a common source of contamination. The investigation suggested that specimen contamination was associated with one microbiology laboratory technician: 6 of 22 (27%) specimens processed by that person were positive compared with 1 of 103 (1%) specimens processed by the other five technicians. However, a specific mechanism of contamination was not identified. Nosocomial pseudoepidemics associated with false infections should be suspected and investigated when clinical features and laboratory findings do not agree.

Adult↗
PubMed1984

Human infections with La Crosse virus in Georgia, 1982.

Eight cases of central nervous system infection due to La Crosse (California serogroup) virus were detected in Georgia children in 1982. The patients were residents of the state, without histories of travel away from the vicinities of their homes during the 30 days before the onset of their illnesses. All were hospitalized with a diagnosis of aseptic meningitis or encephalitis; none had sequelae. Onset dates were from May 1 to Aug 30. Distribution of cases within the state suggested that active transmission of La Crosse virus occurred at least in the southeast quadrant of the state. The epidemiology and natural cycle of La Crosse in the southeastern United States are briefly discussed.

Aedes↗
PubMed1984

Safety of prolonged administration of rimantadine hydrochloride in the prophylaxis of influenza A virus infections in nursing homes.

We evaluated the safety of rimantadine hydrochloride (RH) prophylaxis in a double-blind, placebo-controlled trial in three nursing homes during a community epidemic of influenza A (H3N2). Although daily monitoring of the 35 participants revealed an association between RH administration (100 mg twice a day) and the development of nausea and anxiety (P less than 0.05), these and other potential side effects were transient and were rarely considered to be clinically significant. Serum RH levels measured at the end of the trial (mean, 1,159 ng/ml) were nearly three times higher than those measured previously in younger individuals, suggesting that lower dosages may be indicated for the elderly.

Adamantane↗
PubMed1984

Variability in lung collagen amounts after prolonged support of acute respiratory failure.

In order to identify correlates of fibrosis in acute respiratory failure, autopsies were performed on 16 patients who died after an episode of more than two weeks' duration, and the left lower lung lobe was obtained for biochemical measurements. The average amount of lobar collagen in one group of patients was nearly three times that in another group. Both groups had been mechanically ventilated for the same length of time and could not be distinguished by primary diagnosis. However, the group with increased collagen had received nearly twice the level of positive end-expiratory pressure and had received an inspired oxygen fraction of more than 0.4 for twice as long as the normal collagen group. Examination of complications and other aspects of therapy did not reveal clearcut differences between the groups. Examination of the same clinical data in a group of patients who had survived an episode of similar duration indicated that survivors differed from the high collagen group in inspired oxygen levels.

Adolescent↗
PubMed1984

Growth, graviresponsiveness and abscisic-acid content of Zea mays seedlings treated with fluridone.

Ten-d-old seedlings of Zea mays L. cv. Tx 5855 treated with 1-methyl-3-phenyl-5-(3-[trifluoromethyl]phenyl)-4-(1H)-pyridinone (Fluridone) were analyzed for abscisic acid (ABA) content using high-performance liquid chromatography with an analysis sensitivity of 2.5 ng ABA g-1 fresh weight (FW). Seedlings were divided into three portions: leaves, detipped roots, and root tips (terminal 1.5 mm). Control plants (water treatment only; no Fluridone) were characterized by the following amounts of ABA: leaves, 0.114 +/- 0.024 (standard deviation) microgram ABA g-1 FW; detipped roots, 0.260 +/- 0.039 +/- microgram ABA g-1 FW; root tips, no ABA detected. We did not detect any ABA in tissues of Fluridone-treated plants. Primary roots of treated and untreated seedlings were strongly graviresponsive, with no significant differences between the curvatures or the growth rates of primary roots of Fluridone-treated and control seedlings. These results indicate that 1) Fluridone completely inhibits ABA synthesis, and 2) ABA is not necessary for positive gravitropism by primary roots of Zea mays.

Abscisic Acid↗
PubMed1984

Colony-forming ability in calcium-poor medium in vitro and tumorigenicity in vivo not coupled in clones of transformed rat hepatic epithelial cells.

The ability of eukaryotic cells in culture to proliferate in calcium-poor medium has been found to characterize populations of transformed cells, but the relationship between this phenotypic property and tumorigenicity at the cellular level is unclear. Thus, we have isolated 14 clonal subpopulations, based on their ability to colonize in calcium-poor medium, from a parental tumorigenic rat hepatic epithelial cell line which was transformed by multiple exposures to N-methyl-N'-nitro-N-nitrosoguanidine. These clonal subpopulations of cells were tested for their ability to grow in soft agar, to express gamma-glutamyl transpeptidase activity, and to form tumors upon back-transplantation into isogeneic newborn rats. The results indicated that clonal subpopulations of cells selected by their ability to grow in calcium-poor medium were phenotypically heterogeneous for gamma-glutamyl transpeptidase activity and anchorage-independent growth, and, more importantly, they were not more tumorigenic than the phenotypically heterogeneous parental cell line. This observation suggests that the capability of cultured hepatic epithelial cells to grow in calcium-poor medium is not tightly coupled to the tumorigenic phenotype.

Animals↗
PubMed1983

A human tRNAGlu gene of high transcriptional activity.

A mixture of low molecular weight RNAs, in which only tRNAs were radiolabelled, was used as a hybridisation probe to select for tRNA-like sequences within a bank of human genomic DNA in lambda Charon 4A. A restriction enzyme digest of one of the selected lambda Charon 4A recombinants contained two fragments (2.4 Kb & 1.8 Kb) which hybridised tRNA and which, when subcloned into pAT153, were transcribed in Xenopus oocyte nuclei. Analysis of the subcloned 2.4 Kb fragment, which was of remarkably high transcriptional activity, revealed the presence of a single gene for tRNAGlu in the middle of the fragment. The sequence immediately preceding the gene has the potential for forming a tRNA-like structure.

Base Sequence↗