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Biomedical subjects

J Robbins

Publications and source records attributed to J Robbins.

At least 307 records · Page 17Linked to original sources
PubMed1983

Polymorphism of human thyroxine-binding globulin.

T4-binding globulin (TBG) consists of a single polypeptide chain containing 4 oligosaccharide units with an average of 10 terminal sialic acid residues. Isoelectric focusing (IEF) of TBG purified from pooled human plasma showed 4 main bands isoelectric at pH 4.2, 4.3, 4.5, and 4.6. Removal of 85% of carbohydrates by treatment with mixed glycosidases reduced these bands to 2, at pH 5.4 and 5.7. This residual microheterogeneity was not related to protein-ampholyte complexes, since it was still present in 8 M urea. It also did not represent an equilibrium mixture of interchangeable conformations, since each band obtained in the first dimension IEF gave a single spot when rerun in a second dimension. Therefore, the residual microheterogeneity of TBG after removal of carbohydrates can be attributed to variation in amino acid composition. Since genetic polymorphism of TBG was recently demonstrated, we further investigated whether the residual microheterogeneity was genetically determined. Plasma samples from 20 white donors and 17 black donors were labeled with [125I]T4 and submitted to IEF, followed by autoradiography. TBG-1, found in white donors and most black donors, showed the same 4 bands as TBG purified from pooled plasma. Two less frequent phenotypes were found in black individuals: TBG-2, with 4 bands at approximately pH 4.25, 4.45, 4.55, and 4.7; and TBG-1,2, having all of the bands present in TBG-1 and TBG-2. Electrophoretically homogeneous preparations of TBG of each type were obtained from 100 ml plasma; after deglycosylation, TBG-1 revealed 2 bands isoelectric at pH 5.4 and 5.7, TBG-2 had 2 bands at pH 5.7 and 5.9, and TBG-1,2 had 3 bands at pH 5.4, 5.7, and 5.9. The same TBG bands were found after neuraminidase treatment of whole plasma from the same donors. These data demonstrate two kinds of TBG polymorphism. The first is found in deglycosylated TBG from individual donors and is probably due to variation in amino acid composition. The second, also unrelated to the carbohydrate moiety, is a genetic polymorphism found in blacks.

Black People↗
PubMed1982

Thyroid nodules after high-dose external radiotherapy. Fine-needle aspiration cytology in diagnosis and management.

From 1974 to 1980, we studied six patients, five treated for Hodgkin's disease and one for a hemangioma, in whom thyroid nodules developed after high-dose (2,500 to 4,000 rad) thyroid radiation. Fine-needle aspiration cytology of the thyroid in five cases showed moderate to severe cellular atypia in four (three of whom had elevated serum thyrotropin levels) and mild atypia in one (who was overtly hypothyroid). In the four with marked atypia, surgical pathology disclosed Hashimoto's thyroiditis in one, diffuse hyperplasia and epithelial atypia in two, and a sclerosing papillary carcinoma in one. Among five patients who had total thyroidectomy, three had carcinoma (microscopic papillary, papillary-follicular, or sclerosing papillary) in addition to one or more follicular adenomas or colloid nodules. Thyroid nodules and neoplasia may be more common than previously appreciated in patients exposed to high-dose radiation.

Adenocarcinoma↗
PubMed1982

Thyroid hypofunction after exposure to fallout from a hydrogen bomb explosion.

Thyroid function was evaluated in the Marshallese who were accidentally exposed to fallout-containing radioiodine isotopes in 1954. Measurements of thyrotrophin (TSH, thyroid-stimulating hormone) levels and free thyroxine (T4) index (FT4I) have revealed that, among 86 persons exposed on Rongelap and Ailingnae atolls, 14 have shown evidence of thyroid hypofunction. This was first noted in some individuals about ten years after exposure. Only two of these showed clinical evidence of hypothyroidism. The most marked TSH elevations were noted in nine persons exposed when younger than 6 years, with estimated doses to the thyroid from 390 to 2,100 rad. Most of this group subsequently had surgery for removal of thyroid nodules. The remaining five cases have been noted more recently among 36 surviving adults exposed at an older age who showed no other detectable thyroid abnormalities. This group had received estimated thyroid doses ranging from 135 to 335 rad and showed modest elevation of serum TSH levels (6 to 9 microU/mL) and a slightly subnormal FT4I. No abnormalities were found in persons on Utirik who received substantially less radiation, and hypothyroidism was present in less than 1% of the control, unexposed Marshallese. The high prevalence of a thyroid hypofunction in these persons indicates that this condition, as well as thyroid nodularity, can be a delayed complication of exposure to early fallout from a nuclear explosion. The fact that a significant fraction of the radiation to the thyroid was from short-lived radioiodine isotopes (132I, 133I, 135I), as opposed to 131I, may account for the severity of the thyroid damage.

Adolescent↗
PubMed1982

Isolation of multiple genomic sequences coding for chicken myosin heavy chain protein.

A genomic bank has been constructed using DNA isolated from a dystrophic strain of chickens. The library was screened for myosin heavy chain (MHC) sequences using a cDNA probe and 11 positive recombinants isolated. Identity of the clones was confirmed by positive RNA selection via hybridization of the clones with muscle RNA and subsequent translation of the hybridizable RNA in vitro. Restriction maps indicate that the clones can be divided into 7 distinct groups; some of these groups do, however, share similar or homologous sequences. Hydridization of the clones to RNA derived from leg, breast, heart, and brain reveals that all of the clones code for the muscle-specific MHC isoforms. These experiments also show that there are at least 3 size classes of MHC mRNA sequences, whose relative amounts appear to be modulated in a tissue- and developmental stage-specific manner.

Animals↗
PubMed1982

Effects of thyroxine binding on the stability, conformation, and fluorescence properties of thyroxine-binding globulin.

The effects of thyroxine (T4) on several molecular properties of human thyroxine-binding globulin (TBG) have been evaluated. Changes in the sedimentation constant and relaxation time indicate that TBG becomes more symmetric and compact when T4 is bound. This modification in structure is associated with an increase in the stability of TBG to denaturation by either acid or guanidinium chloride. T4 binding also produces changes in the emission and excitation spectra of TBG, reflecting different environments of the four tryptophanyl residues. T4 preferentially quenches residues in a less polar environment. In addition, it alters the effect of the collisional quencher, acrylamide, so as to indicate a shift in the environment of some of the exposed tryptophanyl residues.

Acrylamides↗
PubMed1982

Acoustic characteristics of voice production after Staffieri's surgical reconstructive procedure.

Selected phonatory variables for two laryngeal cancer patients were studied before and after total laryngectomy with reconstruction designed to restore phonation. Each subject performed five speaking tasks while simultaneous pneumographic and voice recordings were obtained. Measures of sound pressure level, fundamental frequency, vowel formant structure, frequency range, words per minute, maximum phonation time, and syllables per breath were compared pre- and post-operatively. Results indicate that for the post-surgical condition there was a reduction in intensity, frequency, and temporal measures for the two subjects studied. Results are analyzed and discussed in relation to variation within subjects and between subjects, and by comparison with the acoustic parameters of normal and esophageal talkers.

Aged↗
PubMed1982

Effect of thyroxine on molecular properties of native and dansylated thyroxine-binding globulin.

The effect of thyroxine (T4) on the stability of thyroxine-binding globulin (TBG) was investigated by examining intrinsic (tryptophan) or extrinsic (DNS) fluorescence as structural probes to demonstrate the presence of an induced conformation change. A thermal transition was observed at 55 degrees C for TBG by Trp fluorescence, which is evidence for heat denaturation, whereas no transition was observed in the same temperature range for TBG-T4. Acidification of DNS-TBG at pH 4.4 produced a decrease in both Trp and DNS fluorescence whereas DNS-TBG-T4 at the same pH showed a large change in DNS fluorescence but no change in Trp fluorescence. Low guanidinium chloride concentration unfolded the unliganded molecule as indicated by a decrease of Trp and DNS fluorescence, whereas the fully occupied TBG showed only a decrease of DNS fluorescence. Exposure of TBG and TBG-T4 to trypsin showed a twofold increase in the rate of tryptic hydrolysis for TBG-T4 indicating that T4 binding either increased the exposure to the solvent of some lysyl or arginyl residues or increased their susceptibility to the trypsin action. These data provide additional evidence that T4 binding enhances the molecular stability of TBG. An effect on TBG conformation which was previously described probably explains the increased stability. The decrease in dansyl fluorescence of DNS-TBG-T4 probably is due to a local effect of acid or GdmCl unrelated to protein unfolding.

Alpha-Globulins↗
PubMed1981

A spin label study of the thyroid hormone-binding sites in human plasma thyroxine transport proteins.

The binding site topographies of the three thyroid hormone-transporting proteins in human serum--prealbumin, thyroxine binding globulin, human serum albumin--have been studied with the aid of five spin-labeled analogs of L-thyroxine in which the distance between the phenolic hydroxyl and the nitroxide nitrogen ranged from 17 to 23 A. In the presence of prealbumin, the electron spin resonance spectrum of 3-([alpha-carboxy-4-(4-hydroxy-3,5-diiodophenoxy)-3,5-diiodophenethyl]-carbamoyl)-2,2,5,5-tetramethyl-3-pyrrolinl-yloxy-ethyl ester revealed the presence of a highly immobilized spin label. As the chain length between the thyroxyl moiety and the pyrroline ring was increased, the mobility of the nitroxide group in the prealbumin-bound labels increased. If the spin labels bind in an extended conformation, the thyroxine-binding site was estimated to be approximately 21 A in depth. This finding is consistent with the known crystal structure of prealbumin and suggests that the solution and crystal conformations of the protein are very similar. In contrast to prealbumin, the thyroxine-binding site on thyroxine-binding globulin was found to be more open and possibly deeper. Human serum albumin has two binding sites for thyroxine, one of which has a higher affinity and is deep enough to accommodate a molecule that is 23 A in length. The lower affinity site is somewhat shallower and probably wider, as thyroxine spin labels bound to this site exhibited greater mobility.

Binding Sites↗
PubMed1981

Characterization of a macrolide, lincosamide, and streptogramin resistance plasmid in Staphylococcus epidermidis.

A strain of Staphylococcus epidermidis was transduced to erythromycin resistance, and all of the transductants exhibited the macrolide, lincosamide, streptogramin B resistance phenotype. Curing and antibiotic disk studies also indicated that these resistances were controlled by a single plasmid determinant and were constitutive. Agarose gel electrophoresis of plasmid deoxyribonucleic acid (DNA) from donor, cured, and transduced strains showed that a single plasmid was responsible. This plasmid, designated pNE131, was examined for sequence homology to two other plasmids, pE194 and p1258, from Staphylococcus aureus, which also code for erythromycin resistance. DNA from plasmids pNE131 and pE194 hybridized with one another, but no extensive homology to pI258 with either pNE131 or pE194 was found. Restriction endonuclease digests of pNE131 and pE194 showed no common fragments. However, sequence homology was localized to the nucleotides in pE194 that code for the 29,000-dalton protein responsible for erythromycin resistance. pNE131 was calculated to have 2,220 base pairs and is the smallest naturally occurring plasmid with a known function yet reported in S. epidermidis.

Anti-Bacterial Agents↗
PubMed1981

Observations of fouling biofilm formation.

Fouling biofilm development was monitored in a completely mixed tubular recycle reactor. A unique sampling system allowed direct (brightfield, epifluorescence, and scanning electron photomicroscopy) and indirect (increased fluid frictional resistance) observations of biofilms. Low fluid velocity (138.5 cm/s) experiments had shorter induction times and biofilm matrixes which included firmly adherent filamentous bacteria. High fluid velocity (265.4 cm/s) experiments had longer induction times with firmly adherent filamentous bacteria present only after the accumulation of extracellular materials. In both cases the fluid frictional resistance increased after filamentous bacteria became a permanent part of the biofilm.

Adhesiveness↗
PubMed1981

Thyroid hormone metabolism in primary cultured rat hepatocytes. Effects of glucose, glucagon, and insulin.

Primary cultured adult rat hepatocytes were used to study regulation of thyroid hormone deiodination. Control studies showed that these cells survived for at leas 4 d, during which time they actively deiodinated both the phenolic (5'-) and non-phenolic (5-) rings of L-thyroxine (T4),3,5,3'-triiodo-L-thyronine, and 3,3',5'-triiodothyronine. Increasing the substate concentration caused a decrease in fractional iodide release and a corresponding increase in conjugation with sulfate and glucuronide. Propylthiouracil strongly inhibited the 5'-deiodinase activity and caused only a slight decrease in 5-deiodinase activity. Thus, these monolayer-cultured cells preserved many of the properties of normal hepatocytes. Incubation with combinations of insulin, glucagon, and/or glucose for 5 h showed that insulin stimulated T4 5'-deiodination, whereas glucagon inhibited the insulin stimulation but had no effect in the absence of insulin. Glucose had no effect and did not alter the effect of the hormones. The insulin-enhanced deiodination increased between 1 and 5 h, which suggests that the previous inability to demonstrate an insulin effect was due to the short survival of the in vitro liver systems used in those studies. The present data suggest that the inhibition of T4 5'-deiodination observed during fasting, and its restoration by refeeding, may be related to the effects of feeding on insulin and glucagon release rather than on glucose per se.

Animals↗
PubMed1981

Sulfate transfer to thyroid hormones and their analogs by hepatic aryl sulfotransferases.

The transfer of sulfate to thyroid hormones and their analogs by a monkey hepatocarcinoma cell extract was compared to this reaction as catalyzed by two homogeneous aryl sulfotransferases from rat liver. The thyroid hormones 3,5,3'-triiodo-L-thyronine and L-T4 as well as analogs of these hormones, were used as substrates. While these compounds vary widely in their capacity as sulfate acceptors, the catalytic abilities of the three enzyme preparations generally reflect a broad pattern of overlapping specificity. The finding that T4 is a very poor substrate, that 3'-iodothyronine and 3,3'-diiodothyronine are very good substrates, and that T3 is intermediate in its acceptor activity probably explains the relative sulfation of these compounds in vivo and by living hepatocytes. (Endocrinology 108: 454, 1981)

Animals↗
PubMed1981

Glutathione deficiency induced by cystine and/or methionine deprivation does not affect thyroid hormone deiodination in cultured rat hepatocytes and monkey hepatocarcinoma cells.

To elucidate the recently advanced hypothesis that glutathione [L-gamma-glutamyl-L-cysteinyl glycine (GSH)] regulates deiodinating enzyme activities, accounting for the decreased conversion of T4 to T3 in the liver of fetal and starved animals, we investigated thyroid hormone metabolism in GSH-depleted neoplastic and normal hepatocytes. In monkey hepatocarcinoma cells, intracellular total GSH decreased below 10% of the control value (approximately 25 micrograms/mg protein) when cells were grown for 44 h in medium deficient in cystine and methionine or in cystine alone. The latter finding indicated that transsulfuration from methionine to cysteine was defective in these neoplastic cells. In primary cultured adult rat hepatocytes, on the other hand, the transsulfuration pathway was intact, and total GSH decreased below 10% of control (approximately 20 micrograms/mg protein) only in cells grown in cystine- and methionine-deficient medium. In both cell types, the oxidized GSH fraction remained constant (2-5% of total). Incubation with 125I-labeled T4 and T3, followed by chromatography, was used to evaluate 5-deiodination in hepatocarcinoma cells and both 5- and 5'-deiodination in normal hepatocytes. Deiodination was not decreased by GSH deficiency in either case, but was actually increased in hepatocarcinoma cells. This resulted from an increase in the Vmax of 5-deiodinase related to growth arrest. Diamide at 2 mM reversibly inhibited both 5'- and 5'-deiodination in rat hepatocytes, accompanied by decreased total GSH as well as increased GSH disulfide (27% of total). The data suggest that GSH is so abundant in the liver that hepatocytes can tolerate a greater than 90% decrease in intracellular concentration without any change in thyroid hormone deiodination and indicate that altered thyroid hormone metabolism in the fetus and in starvation cannot be accounted for by a decreased hepatic GSH concentration.

Animals↗