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Biomedical subjects

J D Smith

Publications and source records attributed to J D Smith.

At least 289 records · Page 16Linked to original sources
PubMed1983

Effect of modification of membrane phospholipid composition on the activity of phosphatidylethanolamine N-methyltransferase of Tetrahymena.

The activity of phosphatidylethanolamine N-methyltransferase is less than 10% of control levels in microsomes prepared from the ciliate protozoan Tetrahymena thermophila whose phospholipid composition had been altered by being cultured on media containing phosphonic acids. The primary modification obtained is decreased levels of phosphatidylethanolamine (J.D. Smith and D.A. Giegel, Arch. Biochem. Biophys., 206, 420-423 (1981) and 213, 595-601 (1982)). The enzyme protein is present in these cells at normal levels since addition of the substrate phosphatidylethanolamine to the assay system restores enzyme activity of the lipid-modified microsomes to control levels, while the enzyme from control microsomes is not affected by added phosphatidylethanolamine. The microsomal enzyme is inhibited by the anionic phospholipids cardiolipin, phosphatidylglycerol, and phosphatidylinositol and by lysophosphatidylethanolamine while it is activated only by phosphatidylserine in addition to the substrates phosphatidylethanolamine and phosphatidyldimethylethanolamine. The added phosphatidylethanolamine acts directly as a substrate for the methyltransferase rather than acting by merely stimulating utilization of endogenous lipid since added phosphatidyl[14C]ethanolamine is directly converted to phosphatidylcholine. The results suggest that the technique of phosphonic acid-induced modification of lipid composition will be useful for the study of other membrane-bound enzymes.

Animals↗
PubMed1983

The carcinogenic potential of twelve refined mineral oils following long-term topical application.

Twelve mineral oils, originating from naphthenic and paraffinic stocks and variously refined, were evaluated for their potential to induce cutaneous neoplasia in female CF1 mice. The oils were applied to the shorn dorsal skin for up to 78 weeks, using several different treatment regimes. The sole acid/earth refined naphthenic spindle oil was a moderately potent cutaneous carcinogen. By comparison, the 11 oils, processed by other refining routes, were less carcinogenic or non-carcinogenic to murine skin. Two of the 11 oils were weak cutaneous carcinogens viz, a naphthenic spindle oil refined only by mild hydrotreatment and a paraffinic spindle oil refined by mild solvent extraction and 'Ferrofining'. All 9 remaining oils had been solvent-extracted as part of the secondary refining process; none induced malignant tumours, although solitary benign tumours of the treated site were recorded after exposure to 3 oils. The cutaneous carcinogenic potential of the test oils did not correlate well with their potential to induce epidermal hyperplasia at the treated site. Consequently, hyperplasia caused after short term exposure is of little value for distinguishing between carcinogenic and non-carcinogenic oils.

Administration, Topical↗
PubMed1983

Early Events in Maize Seed Development : 1-Methyl-3-phenyl-5-(3-[trifluoromethyl]phenyl)-4-(1H)-Pyridinone Induction of Vivipary.

Preharvest sprouting or vivipary is induced in developing maize (Zea mays, inbred Tx 5855 and Va 35) seeds by fluridone, a pyridinone inhibitor of carotenoid biosynthesis. Fluridone has a maximal effect on vivipary at 11 days after pollination (DAP) and little effect at 13 DAP in the inbred maize line Tx 5855. Abscisic acid partially reversed the chemically induced vivipary. Though the precise mechanism of fluridone-induced vivipary is unknown, these results indicate that there are important developmental changes occurring at 11 DAP which reversibly commit the immature embryo to vivipary or dormancy.

Journal Article↗
PubMed1983

Fecal coliforms on environmental surfaces in two day care centers.

A survey of environmental surfaces in two Atlanta area day care centers was conducted to determine the prevalence of fecal coliform bacteria, considered a marker for the presence of fecal contamination which might contain pathogenic parasites, bacteria, or viruses. Fecal coliforms were found in 17 (4.3%) of 398 representative samples of building surfaces, furniture, and other objects. These surfaces may be involved in the chain of transmission of enteric diseases among children. Therefore, disinfection of inanimate objects, in addition to good handwashing, may be important in controlling the spread of enteric diseases in day care centers.

Child Day Care Centers↗
PubMed1983

Intracranial extension of nasal dermoids.

Nasal dermoid cysts with intracranial extension have been thought to be a rare entity. Seven new cases of nasal dermoid cyst with intracranial involvement were treated from 1975 through 1982 by combined otolaryngological-neurosurgical management. Preoperative radiological studies were helpful in predicting intracranial extension in only three cases. The extracranial lesion was resected by the otolaryngologist using surgical hemoclips to tag the dermoid remnant entering the cranium. These hemoclips were a helpful landmark for the neurosurgeon when resecting the intracranial extension through a bifrontal craniotomy approach. In four cases, the dermoid cyst entered the cranium through a persistent foramen cecum and lay within the falx in association with a bifid crista galli. We think that this entity is more common than was previously appreciated. Patients with a diagnosis of nasal dermoid should undergo polytomography or computed tomography of the glabellar area. Even when all x-ray studies are negative, neurosurgical preoperative evaluation and operative standby should be obtained before the otolaryngologist attempts the resection of a nasal dermoid cyst.

Adolescent↗
PubMed1983

Multiple organ system failure and infection in adult respiratory distress syndrome.

Patients with the adult respiratory distress syndrome and multiple organ system failure have a high mortality rate despite extensive supportive therapy. We evaluated the role of multiple organ system failure and infection in 37 consecutive survivors of the syndrome, and 47 consecutive nonsurvivors on whom autopsies were done. Failure of the central nervous, coagulation, endocrine, gastrointestinal, and renal systems was common in all patients but was more frequent in those who died. Major infections occurred in 46 nonsurvivors and 22 survivors. All patients with bacteremia who had a clinically identified site of infection survived, whereas all patients with bacteremia without a clinically identified site of infection died. Autopsy results of the latter group showed infections requiring surgical drainage for complete therapy. Patients clinically septic but without bacteremia and without a clear site of infection were shown at autopsy to have pneumonia. Multiple organ system failure was more common in infected (93%) than noninfected (47%) patients. Vigorous evaluation and treatment of infection in patients with the adult respiratory distress syndrome may improve survival.

Autopsy↗
PubMed1982

Sequences of four tRNA genes from Caenorhabditis elegans and the expression of C. elegans tRNALeu (anticodon IAG) in Xenopus oocytes.

Four tRNA genes have been identified in cloned segments of Caenorhabditis elegans DNA by tRNA hybridisation and expression after injection into Xenopus laevis oocyte nuclei. From DNA sequencing these are (with DNA anticodon sequences) tRNAAsp (GTC), tRNALeu (AAG), tRNALys (CTT) and tRNAPro (TGG). Their flanking DNA sequences are compared. Two identical tRNALys (CTT) genes from different regions of the genome have quite unrelated 5' flanking sequences. The tRNA synthesised in Xenopus oocytes after injection of the tRNALeu cloned DNA has the modified anticodon IAG. The tRNALeu gene precursor transcript from injected oocytes has short 5' and 3' additional sequences and lacks certain of those modified bases found in the processed tRNA.

Animals↗
PubMed1982

Toxigenic isolates of Fusarium sporotrichioides obtained from hay in Saskatchewan.

An isolate of Fusarium sporotrichioides Sherbakoff obtained from hay from Kindersley, Saskatchewan, and producing metabolites toxic to insect larvae, rats, and mice was cultured on sterile rye grain and extracted with ethyl acetate. The most toxic fraction derived from column chromatography on silica gel was purified by thin-layer chromatography of silica gel and elution of the main band. This compound was identified as T-2 toxin by comparison with the pure chemical by thin-layer chromatography and, after crystallization, by determination of melting point, infrared spectrum, and nuclear magnetic resonance spectrum. This work demonstrates that strains of F. sporotichioides capable of producing T-2 toxin may be present on hay in western Canada.

Animal Feed↗
PubMed1982

A general method for heterokaryon detection using resonance energy transfer and a fluorescence-activated cell sorter.

A simple and general labeling method has been adapted for the rapid detection and isolation of heterokaryons soon after somatic cell fusion. The method involves prelabeling each parental cell type by adding one of two hydrophobic fluorescent probes, F18 or R16, to the culture medium. These probes are nontoxic, nonmutagenic, and do not inhibit either cellular replication or the efficiency of fusion. Following polyethylene glycol (PEG)-induced fusion, heterokaryons are identified on a cell sorter as cells showing fluorescence as a result of nonradiative resonance energy transfer (RET) between the two fluorochromes. Optimal conditions are described for the unambiguous detection of heterokaryons by fusion-induced RET. The value of this method lies in the universal applicability of F18 and R16 as simple and direct membrane labels for any pair of parental cells, even those lacking selectable genetic markers or detectable antigenic differences. This potential for heterokaryon selection in any cell cross should significantly expand the range of cell types amenable to investigation through somatic cell genetics, while the rapidity of the method should facilitate the study of early events following fusion.

Animals↗
PubMed1981

Lectins mimic insulin in the induction of tyrosine aminotransferase.

Various lectins were found to induce tyrosine aminotransferase in H-35 rat hepatoma cells grown in monolayer culture. Wheat germ agglutinin gave a maximal induction of tyrosine aminotransferase 6 hours after its addition. The induction time course was similar to that elicited by insulin. Fourteen micrograms of wheat germ agglutinin per milliliter gave half-maximal enzyme induction and 50 micrograms per milliliter gave the maximal response. The induction of tyrosine aminotransferase by wheat germ agglutinin was additive with the induction by either dexamethasone or dibutyryl adenosine 3',5'-monophosphate, but was not additive with the tyrosine amino transferase induction by insulin. Wheat germ agglutinin also mimicked insulin in the inhibition of cellular protein degradation in the absence of serum. The insulin-like effects of lectins should be considered in lectin-mediated manipulations such as agglutination.

Animals↗
PubMed1981

Treatment of airway obstruction in Pierre Robin syndrome. A modified lip-tongue adhesion.

Pierre Robin syndrome is a triad of micrognathia, glossoptosis, and cleft palate that results in upper airway obstruction and feeding problems. This syndrome occurred in six cases; five of these cases required surgical correction to alleviate the airway problems. A modification of the Douglas lip-tongue adhesion was used to prevent the problem of early separation of the adhesion. The patients have had resolution of the airway and feeding problems, with early discharge from the hospital. There has been minimal morbidity and no mortality associated with the procedure.

Airway Obstruction↗