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Biomedical subjects

M Taylor

Publications and source records attributed to M Taylor.

At least 559 records · Page 31Linked to original sources
PubMed1985

Characterization of human IgG Fc receptors.

A murine monoclonal antibody, KuFc79, has been developed that reacts with human IgG Fc receptors on monocytes, B lymphocytes, and granulocytes. The specificity of KuFc79 for Fc receptors was demonstrated by the ability of Fab fragments to block Fc-mediated phagocytosis by monocytes. This finding was further substantiated by the decrease of KuFc79 binding to monocytes and granulocytes (58 and 70%, respectively) after modulation of surface IgG receptors with aggregated IgG. In addition, Fab KuFc79-conjugated Sepharose was used to isolate functional IgG Fc-binding molecules from soluble extracts of the human monocyte-like cell line U937. By immunoprecipitation, it was further shown that KuFc79 immunoprecipitated molecules of 42,000 and 70,000 daltons from U937 and a human lymphoblastoid cell line, SB. A lower m.w. species of approximately 33,000 was also precipitable from granulocytes. Extensive microheterogeneity of these molecules was noted by isoelectric focusing, which appears to be due to differential sialation.

Animals↗
PubMed1984

The local environment of metal sites in intracellular granules investigated by using X-ray-absorption spectroscopy.

We report the use of X-ray-absorption spectroscopy (x.a.s.) to study the local atomic environment of cations in intracellular granules from the hepatopancreas of Helix aspersa. Both the calcium K-edge in these concretions and the manganese K-edge in doped specimens were measured. Electron-microprobe measurements confirm that the introduced Mn2+ is concentrated in irregular growths on the surfaces of the granules. The near-edge structure (x.a.n.e.s.) of calcium is similar to that of manganese, indicating that the oxygen-co-ordination spheres of both cations share a similar symmetry. From the extended structure (e.x.a.f.s.) the metal-oxygen bond lengths of 0.230 nm (2.30A) for Ca-O and 0.218 nm (2.18A) for Mn-O [+/- 0.004 nm (0.04A)] were determined, reference being made to a variety of model compounds. The low density of the granules (2.07 g/cm3), together with the local atomic distribution, suggest an open hydrated structure for these phosphate deposits. Detailed analysis of the distribution of nearest-neighbour oxygen atoms demonstrates that this is asymmetric and considerably broader for Ca2+ than for Mn2+. Compared with the model compounds, the Ca2+ environment in the granules is similar to that observed in Ca2P2O7. I.r. spectra indicate the presence of condensed phosphate groups in the granules, with the strong possibility these are pyrophosphate (P2O7(4-) groups.

Animals↗
PubMed1984

In vivo effect of volume expansion on rectal gland function. I. Humoral factors.

The spiny dogfish Squalus acanthias responds to volume expansion by increasing the rate of chloride secretion by its rectal gland. The response is elicited by intravascular infusion of either isotonic shark Ringer solution, a 1 M hypertonic sodium chloride solution, or an isotonic hyponatremic solution containing equal volumes of shark Ringer solution and 10% mannitol. The effect of volume expansion was evoked in explanted glands connected to a host fish only by the arterial supply, indicating that the response is mediated by a humoral factor. The explanted gland responded to theophylline (2.5 X 10(-3) M) and adenosine 3',5'-cyclic monophosphate (5 X 10(-4) M) by increasing the rate of secretion of chloride by an amount similar to that induced by volume expansion of the perfusing fish. Theophylline at concentrations (10(-6) to 5 X 10(-5) M) that are known to inhibit the effect of adenosine in isolated perfused glands failed to inhibit the effect of volume expansion on explanted glands. Somatostatin (4.5 X 10(-6) M), which inhibits the effect of vasoactive intestinal peptide (VIP) in the isolated perfused gland, completely prevented the secretory response to volume expansion in explanted glands. Volume expansion is a major stimulus for chloride secretion by the rectal gland. The effect is mediated by a humoral factor that appears to be VIP.

Animals↗
PubMed1984

In vivo effect of volume expansion on rectal gland function. II. Hemodynamic changes.

Intravascular volume expansion causes a 300% increase in the rate of fluid secretion from, and blood flow to, the in vivo rectal gland of the spiny dogfish Squalus acanthias. Similar increases are also observed in explanted rectal glands perfused through a catheter from the dorsal aorta of a volume-expanded dogfish. Stimulation of rectal gland secretion by volume expansion is not associated with a change in the ratio of chloride secreted to oxygen consumed by the rectal gland and the oxygen extraction ratio, suggesting that an increase in blood flow is necessary to support the increased rate of chloride secretion. Perfusion of the explanted gland with bumetanide (10(-4) M) completely inhibits the secretory response to volume expansion but does not prevent the increase in blood flow. Bumetanide also inhibits dibutyryl adenosine 3',5'-cyclic monophosphate- and theophylline-induced increases in chloride secretion but does not inhibit the hyperemic response. Somatostatin inhibits the secretory response of the explanted gland to volume expansion but does not prevent the increase in blood flow. Although an increase in blood flow is necessary to support the increased energy requirement of enhanced transport, the secretory response and the increase in blood flow appear to be independently regulated and mediated, at least in part, by humoral factors.

Animals↗
PubMed1984

Mycobacterium bovis infection in primates in Dublin Zoo: epidemiological aspects and implications for management.

An outbreak of tuberculosis in non-human primates was successfully contained in the isolation area of Dublin Zoo. A Mayotte lemur, a lion-tailed macaque, a Patas monkey and a Siamang gibbon developed tuberculosis, and Mycobacterium bovis was isolated from all but the lemur, from which lesions were not cultured. Procedures for the prevention of tuberculosis in primate collections and for the management of outbreaks are discussed. The need for typing of the isolated pathogen is emphasized.

Animals↗
PubMed1984

Tubular transport and metabolism of cimetidine in chicken kidneys.

Renal tubular transport and renal metabolism of [14C]cimetidine (CIM) were investigated by unilateral infusion into the renal portal circulation in chickens (Sperber technique). [14C]CIM was actively transported at a rate 88% that of simultaneously infused p-aminohippuric acid, and its transport was saturable. The following organic cations competitively inhibited the tubular transport of [14C]CIM with decreasing potency: CIM, ranitidine, thiamine, procainamide, guanidine and choline. CIM inhibited the transport of [14C]thiamine, [14C]amiloride and [14C]tetraethylammonium. During CIM infusion, two renal metabolites, CIM sulfoxide and hydroxymethylcimetidine, were found in urine. When CIM sulfoxide was infused, its transport efficiency was 32% and not saturable. CIM sulfoxide did ot inhibit the simultaneous renal tubular transport of p-aminohippuric acid or tetraethylammonium. CIM is transported by the organic cation transport system and the kidney metabolizes CIM. Transport of CIM and other cationic drugs could produce a drug interaction to alter drug excretion.

Animals↗
PubMed1984

How two-year-old children interpret proper and common names for unfamiliar objects.

The linguistic form class of a word and the kind of object the word refers to both provide information for discovering whether a new noun refers to an object as a category member (e.g., a dog) or as an individual (e.g., Lassie). This study investigated children's use of both syntactic (i.e., form class) and semantic (i.e., type of referent) information, clarifying and extending work summarized by Macnamara. Although widely accepted, past results were inconclusive because (1) children were taught new words for objects they could already name, and (2) the earlier procedure lacked appropriate distractor items. This work eliminated these problems by using unfamiliar objects and a revised testing procedure. 32 2-year-olds were each taught 1 new noun. Linguistic form class (presence or absence of an article) and type of referent (animal-like or blocklike toy) were varied between groups. Children's interpretations of the new nouns were assessed by asking the subjects to select the named toy from an array of 4 toys (e.g., "Point to Zav"). With animal-like toys, Macnamara's claim that children interpret common nouns as category names, and proper nouns as individual names, was supported. With blocklike toys, children in our study interpreted a common noun as a category name, but there was a tendency for children in the proper noun condition to choose a particular stuffed animal as the new noun's referent rather than the named blocklike toy. These results show that 2-year-old children use both linguistic form class and their knowledge about real-world objects to interpret new words.

Child, Preschool↗
PubMed1984

Seeing and believing: children's understanding of the distinction between appearance and reality.

When young children are asked questions about objects with misleading appearances, they make two kinds of errors: (1) phenomenism--they report appearance when asked to report reality; and (2) intellectual realism--they report reality when asked to report appearance. Two studies with 3-year-old children tested the hypothesis that phenomenism errors predominate when children are asked about objects' real and apparent properties, whereas intellectual realism errors predominate when children are asked about objects' real and apparent identities. The results of these studies provided some support for the property-identity hypothesis; children's appearance-reality judgments about properties tended to differ from those about identities. More phenomenism errors were elicited when the stimuli were described to the children in terms of their properties than when the very same stimulus objects were described in terms of their identities. Identity tasks were not found to elicit predominantly intellectual realism errors, although the data showed trends in this direction. The implications of these results for theories about young children's tendency to accept things in terms of their perceptual characteristics were briefly discussed.

Child Development↗
PubMed1983

Isolation, characterization and comparison of mammalian epidermal prekeratins.

1. The lower living layers of mammalian epidermis contain a cytoplasmic tonofilament protein, prekeratin, believed to be the precursor of the keratin which is found in the outer dead cell layer or stratum corneum. 2. Prekeratin is distinguished by its property of being extractable from epidermis homogenized in the presence of citric acid trisodium citrate buffer pH 2.65. 3. In the present study we have compared the epidermal prekeratins from ten mammalian species and have shown them to be of similar amino acid composition. 4. Conditions have been established for studying the immunology of these insoluble proteins and examination of their immunological properties has shown that they are similar to one another but that their antigenic determinants are different from those of callus keratin. 5. The SDS polyacrylamide gel electrophoretic patterns of these proteins differ widely and we have also demonstrated anatomical site variation by this method.

Amino Acids↗
PubMed1983

Chronic boric acid poisoning in infants.

We report 7 infants suffering from seizures induced by chronic boric acid ingestion. The boric acid was given by dipping a soother in a proprietary borax and honey mixture. The babies have remained well since the mixture was withheld.

Borates↗
PubMed1982

Regulation of sugar transport in cultured diploid human skin fibroblasts.

The regulation of hexose transport under glucose-starvation conditions was studied in cultured human skin fibroblasts. Glucose starvation enhanced the transport of 2-DG and 3-0-methyl-D-glucose (3-OMG) but not of L-glucose. Glucose-starvation enhanced transport was inhibited by cytochalasin B (10 microM). The starvation-induced change in 2-DG transport was due to an increase in the Vmax of both the high and low affinity transport sites (2.8- and 2.4-fold, respectively) with no effect on their Kms. The presence of 5.55 mM glucose, fructose, or L-glucose in the medium resulted in transport increases similar to those seen in glucose-starved cells, while the presence of 5.55 mM glucose, mannose, or 3-OMG repressed 2-DG transport. Glucose-starvation enhancement of 2-DG transport was blocked by cycloheximide (20 micrograms/ml) but not by actinomycin D (0.03 microgram/ml) or alpha-amanitin (3.5 microM). Readdition of glucose (5.55 mM) for six hours to glucose-starved cells led to a rapid decrease in hexose transport that could be blocked by cycloheximide but not actinomycin D. Although readdition of 3-OMG to glucose-starved cells had little effect on reversing the transport increases, glucose plus 3-OMG were more effective than glucose alone. Serum containing cultures (10% v/v) of glucose-fed or glucose-starved cells exhibited rapid decreases in 2-DG transport when exposed to glucose-containing serum-free medium. These decreases were prevented by employing glucose-free, serum-free medium. The data indicate that hexose transport regulation in cultured human fibroblasts involves protein synthesis of hexose carriers balanced by interactions of glucose with a regulatory protein(s) and glucose metabolism as they affect the regulation and/or turnover of the carrier molecules.

3-O-Methylglucose↗
PubMed1982

Mechanisms of dietary modification of aflatoxin B1 carcinogenesis.

Trout were fed a range of dietary components which altered their carcinogenic response to aflatoxin B1 (AFB1). Dietary protein at levels substantially exceeding nutritional requirements were synergistic with AFB1. Cyclopropene fatty acids (CPFA) were carcinogenic when fed alone at 20 or 55 ppm, and synergistic when fed with AFB1. In contrast, several flavonoid and indole compounds, especially beta-naphthoflavone (beta-NF) and indole-3-carbinol, inhibited the carcinogenic response when fed prior to and along with AFB1. The mechanisms by which some of these dietary factors modulate AFB1 carcinogenesis were investigated. Dietary beta-naphthoflavone was shown to substantially induce the levels of mixed function oxidase (MFO) activities assayed in vitro. These changes were accompanied by alterations in AFB1 metabolism and binding in freshly isolated hepatocytes. AFB1 incubated in hepatocytes freshly isolated from fish fed beta-NF diet was metabolized more rapidly, showed enhanced rates of detoxication reactions, and decreased accumulation of AFB1-DNA adducts compared to control hepatocytes. These results suggest that beta-NF inhibits AFB1 carcinogenesis at least in part by altering MFO activities such that detoxication is enhanced and initial DNA damage by AFB1 is reduced. In contrast, high dietary protein is a synergist for AFB1 carcinogenesis, and this appears to occur primarily by enhancing the transformation probability for AFB1-initiated genome damage. Fish treated with AFB1 as embryos and then reared on high protein diets had substantially higher incidences of hepatocellular carcinoma (86%) than similarly treated fish fed normal protein diet (44%) or high protein controls without AFB1 exposure (0-2%). The synergistic behavior of dietary CPFAs also appears to partially involve enhanced transformation following DNA damage by AFB1. Fish exposed as embryos to AFB1 and then fed CPFA-containing diets are known to show promotion effects similar to the high protein results (Hendricks, J.D., Proc. 11th Int. Symp. of the Princess Takamatsu Cancer Research Fund, in press.) However, factors other than promotion are involved in the synergism between CPFA and AFB1. Preliminary studies indicate that dietary CPFAs repress MFO activities and depress DNA damage by AFB1 in vitro. If this occurs in vivo, then the net synergistic effect of dietary CPFAs would involve depression of initial AFB1-induced DNA damage, but highly efficient promotion of transformation from the remaining lesions.

Aflatoxin B1↗
PubMed1982

[Incidence of lung cancer and age at death in silicosis deaths of the Swiss National Accident Insurance Fund, 1960-1978].

The frequency of lung carcinoma among the deaths of silicotics registered by the Swiss National Accident Insurance Fund from 1960 to 1978 has been compared with the causes of death of all Swiss males during the same period. The PMR, while underestimating the true risk, is significantly raised among foundry workers. SMR's for lung cancer (estimated by comparing the numbers of pulmonary and non-pulmonary malignancies) are elevated among foundry workers, miners, workers in ceramic and miscellaneous industries. Only the stone/slate industry has not yielded a significant excess of lung cancers.

Age Factors↗