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T A Hamilton

Publications and source records attributed to T A Hamilton.

192 records · Page 11Linked to original sources
PubMed1979

Comparison of human alkaline phosphatase isoenzymes. Structural evidence for three protein classes.

The structural relationships among human alkaline phosphatase isoenzymes from placenta, bone, kidney, liver and intestine were investigated by using three criteria. 1. Immunochemical characterization by using monospecific antisera prepared against either the placental isoenzyme or the liver isoenzyme distinguishes two antigenic groups: bone, kidney and liver isoenzymes cross-react with anti-(liver isoenzyme) serum, and the intestinal and placental isoenzymes cross-react with the anti-(placental isoenzyme) antiserum. 2. High-resolution two-dimensional electrophoresis of the 32P-labelled denatured subunits of each enzyme distinguishes three groups of alkaline phosphatase: (a) the liver, bone and kidney isoenzymes, each with a unique isoelectric point in the native form, can be converted into a single form by treatment with neuraminidase; (b) the placental isoenzyme, whose position also shifts after removal of sialic acid; and (c) the intestinal isoenzyme, which is distinct from all other phosphatases and is unaffected by neuraminidase digestion. 3. Finally, we compare the primary structure of each enzyme by partial proteolytic-peptide 'mapping' in dodecyl sulphate/polyacrylamide gels. These results confirm the primary structural identity of liver and kidney isoenzymes and the non-identity of the placental and intestinal forms. These data provide direct experimental support for the existence of at least three alkaline phosphatase genes.

Adolescent↗
PubMed1979

Alkaline phosphates from human milk. Comparison with isoenzymes from placenta and liver.

Alkaline phosphatase was partially purified from human milk and its antigenic, functional and structural properties were characterized. By immunochemical and enzymic criteria, the enzyme resembled the alkaline phosphatase isoenzyme found in human liver. Two-dimensional electrophoretic analysis showed that the milk enzyme differed from the liver both in subunit molecular weight and in isoelectric point. These differences were shown to result from variation in sialic acid content.

Alkaline Phosphatase↗
PubMed1979

Human placental cell surface antigens:expression by cultured cells of diverse phenotypic origin.

The present work examined the expression of cell surface glycoprotein antigens in cultured human cell lines. The set of glycoproteins studied was defined by their immunoreactivity with antiserum developed to Triton-solubilized extracts of placental brush border membranes. Studies were performed using cell lines of trophoblastic (BeWo, JEG-3) and nontrophoblastic (Chang liver cells) origin, as well as diploid fibroblast cell lines (WI-38, GM-38). Antiplacental brush border antiserum reacts with at least 19 distinct antigens present in placental membrane preparations, each of which can be resolved and identified in two-dimensional electrophoresis. The subunit molecular weight and isoelectric point for all components were defined by their positions in the two-dimensional matrix. Thirteen of these could be detected among the five cell lines examined by lactoperoxidase-catalyzed cell surface iodination. One of these 13 antigens has been identified as the placental isoenzyme of alkaline phosphatase (PAP). The expression of this component is limited to choriocarcinoma cells and Chang liver cells and it is not present in diploid fibroblasts. Under normal circumstances expression of PAP is unique to the differentiated placenta but has been frequently demonstrated in both trophoblastic and nontrophoblastic neoplasms. Two other antigens are variably expressed among the different cell types examined in the present study and their presence or absence was independent of the trophoblastic, epithelial nontrophoblastic, or fibroblastic origin of the cells. Ten surface antigens were expressed in all five cell lines. Six of these had previously been found common to membranes from three adult differentiated tissues, including liver and kidney, as well as placenta (Wada et al, J Supramol Struc 10(3): 287-305, 1979). The presence of this set of antigens in cultured cells as well extends the possibility that these are ubiquitously expressed on human cell surfaces. Two other antigens observed in all cultured cells had been found in both placental and either kidney or liver membranes and may represent common functions shared by many tissues which are also necessary for growth in vitro. The two remaining placental antigens seen in all cultured cells have previously been shown to be absent in adult tissues. Their presence in cultured cells but not in the membranes of resting differentiated tissues may signify the expression of glycoproteins characteristic of trophoblasts in all cells adapted to growth in culture.

Alkaline Phosphatase↗
PubMed1979

Regulation of alkaline phosphatase expression in human choriocarcinoma cell lines.

The coincident expression of two structurally distinct isoenzymes of human alkaline phosphatase was demonstrated in two independently derived gestational choriocarcinoma cell lines. These proteins were shown to have enzymatic, antigenic, and physical-chemical properties resembling those of isoenzymes from term placenta and adult liver. The regulation of these isoenzymes has been studied during the exposure of both cell lines to 5-bromodeoxyuridine and dibutyryl cyclic AMP. The responses of the alkaline phosphatase isoenzymes to these agents have also been compared with the response of another protein phenotypic to placenta, the alpha subunit of chorionic gonadotropin. The results show that (i) the separate structural genes coding for placental and liver alkaline phosphatases are regulated in a noncoordinate fashion; (ii) both alkaline phosphatase genes respond independently of the alpha subunit; and (iii) the induction of the placental type isoenzyme occurs via at least two independent pathways.

Alkaline Phosphatase↗
PubMed1979

Identification of transferrin receptors on the surface of human cultured cells.

We have examined the binding of human transferrin to cultured human choriocarcinoma cell lines and to detergent extracts of such cells. The results indicate the presence of a high-affinity saturable binding site (Ka = 4.25 x 10(8) M-1) that is specific for transferrin. This receptor has also been detected on three other human cell lines of different phenotypic origin, including Wil-2 (splenic lymphocytes of B-cell origin), RPMI-2650 (a quasi-diploid nasopharyngeal carcinoma), and WI-38 (embryonic lung fibroblasts). By using anti-human transferrin antiserum to immunoprecipitate the receptor-transferrin complex from detergent extracts of cells containing saturating levels of transferrin followed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, a single polypeptide of 90,000 daltons has been identified as a subunit of the putative transferrin receptor. The protein shows immunochemical identity and coelectrophoreses in sodium dodecyl sulfate gels with a cell surface glycoprotein subunit, previously identified in placental brush border membrane preparations, on all human cultured cell lines examined. These results suggest that the recent demonstration of transferrin dependence of maximal cell growth in culture [e.g., Hutchings, S.E. & Sato, G.H. (1978) Proc. Natl. Acad. Sci. USA 75, 901-904] is mediated through expression of this glycoprotein receptor.

Cell Line↗
PubMed1977

Amino acid control of stable RNA synthesis in Friend leukemia cells in relation to intracellular purine nucleoside triphosphate levels.

Histidinol is known to cause deacylation of histidyl-tRNA in cultured mammalian cells, thereby producing a functional deprivation of histidine. Such deprivation of an essential amino acid is known to produce various effects, including inhibition of tRNA synthesis and of nucleolar RNA synthesis and processing. It has been proposed [Grummt, F. & Grummt, I. (1976) Eur. J. Biochem. 64, 307-312] that this response to amino acid deprivation is mediated by decreases in GTP and ATP pool sizes caused by a deacylated-tRNA-dependent hydrolysis of GTP. In contrast, we find that Friend leukemia cells treated with histidinol show no significant changes in GTP or ATP pool sizes, although this treatment does produce the expected inhibition of rRNA and tRNA synthesis.

Adenosine Triphosphate↗
PubMed1976

Biosynthesis of mammalian transfer RNA. Evidence for regulation by deacylated transfer RNA.

The rate of tRNA synthesis in cultured Friend leukemia cells has been examined as a function of the variation in polyribosome structure produced by treatment with a variety of inhibitors of protein synthesis. The results indicate, in contrast to the conclusions of Bölcsföldi (Bölcsföldi, G. (1974) Exp. Cell Res., 88, 231--240), that no necessary relationship exists between the ribosome distribution and the rate of tRNA synthesis. Alternatively, it is observed that inhibitors of tRNA aminoacylation cause, in all cases, a decrease in the rate of tRNA synthesis whereas drugs which may stimulate the aminoacylation of tRNA cause, in all cases, an elevation of the rate of tRNA synthesis. It is concluded that tRNA synthesis in mammalian cells may be regulated by the relative levels of acylated and deacylated tRNA.

Animals↗
PubMedDate not supplied

Dexamethasone selectively regulates LPS-inducible gene expression in murine peritoneal macrophages.

Our laboratory has recently described the characterization of three distinct cDNAs (designated C7, D3 and D8) encoding genes whose expression is induced in murine peritoneal macrophages by treatment with inflammatory stimuli such as IFNs and lipopolysaccharide (LPS). Sequence analysis of full-length cDNA for C7 suggests that this encodes the murine homologue of the human IFN gamma-inducible protein IP-10. Partial sequence analysis of D3 and D8 cDNAs has revealed no significant homology with known sequences. Treatment of macrophages with the corticosteroid hormone dexamethasone (Dex) suppressed LPS-induced gene expression in a selective manner, having little or no effect on induced D3 mRNA levels, but markedly inhibiting the accumulation of both C7 and D8 mRNAs. The suppression of LPS-induced C7 and D8 mRNAs was dose-dependent in the range 0.01-10 microM Dex. Furthermore, the inhibitory effect was corticosteroid-specific because testosterone, beta-estradiol and progesterone had no effect on gene expression when used at comparable doses. Inhibition of protein synthesis did not abolish the suppressive activity of Dex, indicating that no intermediate Dex-inducible protein was necessary to suppress the expression of LPS-inducible genes. When macrophages were treated with Dex after initiation of LPS treatment, the suppressive effects were diminished in a time-dependent fashion. However, even when the hormone was added as much as 2 h after LPS, sensitive gene expression was still markedly inhibited. Finally, Dex inhibited the transcription of genes encoding C7 and D8 mRNAs when administered 15 min before LPS but had little effect when added 1 h after LPS.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Cisplatin chemotherapy for treatment of thyroid carcinoma in dogs: 13 cases.

The medical records of 13 dogs (10 spayed females, one intact male, one castrated male, and one dog of unknown gender) with histopathologically diagnosed thyroid carcinoma that were treated with cisplatin chemotherapy were reviewed. The mean age was 10.6 years. Three of the dogs were beagles. One dog had a c-cell medullary carcinoma, while the remaining 12 had follicular thyroid carcinoma. Eight of 13 dogs had tumors greater than 5 cm in diameter. In all 11 tumors for which information was available in the medical record, the masses were attached to underlying tissue. One dog underwent a complete remission, six had partial remissions, three had stable disease, and three had progressive disease. The mean time between initiation of cisplatin chemotherapy and development of progressive disease was 223.7 days (median, 202 days), with a mean survival time of 191.8 days (median, 98 days).

Adenocarcinoma, Follicular↗
PubMedDate not supplied

Topical tretinoin improves photoaged skin. A double-blind vehicle-controlled study.

In a 16-week randomized, double-blind, vehicle-controlled study of topical tretinoin in the treatment of photoaging, all patients applied topical tretinoin to one forearm and vehicle cream to the other. Half of the patients received tretinoin to the face, and half received vehicle cream. All 30 patients who completed the study showed statistically significant improvement in photoaging on the tretinoin-treated forearms, but not on the vehicle-treated forearms. Fourteen of the 15 patients who received tretinoin to the face had improvement in photoaging, whereas none of the vehicle-treated patients' faces improved, a statistically significant difference in response between the two groups. Statistically significant histologic changes were seen in forearm skin treated with tretinoin, but not with vehicle cream. Side effects were limited to irritation of tretinoin-exposed skin.

Administration, Cutaneous↗