Search PubMed⌕ Search

Biomedical subjects

J Robbins

Publications and source records attributed to J Robbins.

At least 199 records · Page 11Linked to original sources
PubMed1992

Oropharyngeal swallowing in normal adults of different ages.

In an effort to evaluate the effect of normal aging on oropharyngeal events of swallowing, 80 normal volunteers, stratified by gender into four age groups, were studied. Liquid and semisolid swallows were performed and recorded simultaneously using videofluoroscopy and manometry. Several parameters, including total duration of oropharyngeal swallowing, were significantly longer in the oldest age group than in any other age group. A delay in initiation of maximal hyolaryngeal excursion primarily accounted for the longer durations with increased age. Significant durational changes also were found as a function of bolus consistency and presence or absence of the manometry tube. Females had a longer duration of upper esophageal sphincter (UES) opening. The amplitude of pharyngeal pressures, duration of peak pharyngeal pressures, and rate of propagation of the contractions were not significantly different for age, gender, or consistency of bolus. No significant differences were found between age groups or between genders in UES pressure. Normal aging affects some parameters of swallowing, while others are preserved.

Adult↗
PubMed1992

Variations in thyroid hormone transport proteins and their clinical implications.

Variations in major thyroid hormone transport proteins may be inherited or acquired and may be associated with changes in serum concentration of the proteins or their affinity for thyroid hormones. These variations most frequently involve thyroxine-binding globulin (TBG), but changes in transthyretin and albumin are also observed. The consequent alteration of thyroid hormone-binding capacity in serum is associated with variations in total thyroid hormone concentration. Increased serum total thyroid hormone levels are found in subjects with TBG excess, familial dysalbuminemic hyperthyroxinemia, and transthyretin-associated hyperthyroxinemia. Conversely, diminished serum thyroid hormone values are observed in subjects with TBG deficiency, and decreased concentration or affinity of transthyretin and albumin is not associated with variations in serum concentrations of thyroid hormones. The transport protein-associated variations in serum total thyroid hormone concentrations do not reflect a change in thyroid status. Euthyroidism can be easily established in subjects with transport protein abnormalities by the normal free thyroid hormone and TSH concentrations. It is, however, crucial to select methods for free thyroid hormone measurement that are not affected by abnormalities of transport proteins. Some assays, such as the analog method, often provide artifactual and misleading results, which may lead to inappropriate and even detrimental treatments. The evolutionary advantage of TBG (and albumin) in terms of thyroid homeostasis still remains to be elucidated.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Structure-function relationships among the nickel-containing hydrogenases.

The enzymology of the heterodimeric (NiFe) and (NiFeSe) hydrogenases, the monomeric nickel-containing hydrogenases plus the multimeric F420-(NiFe) and NAD(+)-(NiFe) hydrogenases are summarized and discussed in terms of subunit localization of the redox-active nickel and non-heme iron clusters. It is proposed that nickel is ligated solely by amino acid residues of the large subunit and that the non-heme iron clusters are ligated by other cysteine-rich polypeptides encoded in the hydrogenase operons which are not necessarily homologous in either structure or function. Comparison of the hydrogenase operons or putative operons and their hydrogenase genes indicate that the arrangement, number and types of genes in these operons are not conserved among the various types of hydrogenases except for the gene encoding the large subunit. Thus, the presence of the gene for the large subunit is the sole feature common to all known nickel-containing hydrogenases and unites these hydrogenases into a large but diverse gene family. Although the different genes for the large subunits may possess only nominal general derived amino acid homology, all large subunit genes sequenced to date have the sequence R-X-C-X-X-C fully conserved in the amino terminal region of the polypeptide chain and the sequence of D-P-C-X-X-C fully conserved in the carboxyl terminal region. It is proposed that these conserved motifs of amino acids provide the ligands required for the binding of the redox-active nickel. The existing EXAFS (Extended X-ray Absorption Fine Structure) information is summarized and discussed in terms of the numbers and types of ligands to the nickel and the various redox species of nickel defined by EPR spectroscopy. New information concerning the ligands to nickel is presented based on site-directed mutagenesis of the gene encoding the large subunit of the (NiFe) hydrogenase-1 of Escherichia coli. Based on considerations of the biochemical, molecular and biophysical information, ligand environments of the nickel in different redox states of the (NiFe) hydrogenase are proposed.

Amino Acid Sequence↗
PubMed1992

Kinetic and pharmacological properties of the M-current in rodent neuroblastoma x glioma hybrid cells.

1. The M-like current IK(M,ng) in differentiated NG108-15 mouse neuroblastoma x rat glioma hybrid cells has been studied using tight-seal, whole-cell patch-clamp recording. 2. When calculated from steady-state current-voltage curves, the conductance underlying IK(M,ng) showed a Boltzmann dependence on voltage with half-activation voltage Vo = -44 mV (in 3 mM [K+]) and slope factor (a) = 8.1 mV/e-fold increase in conductance. In 12 mM [K+] Vo = -38 mV and a = 6.9 mV. The deactivation reciprocal time constant accelerated with hyperpolarization with slope factor 17 mV/e-fold voltage change. 3. The reversal potential for deactivation tail currents varied with external [K+] as if PNa/PK were 0.005. 4. Steady-state current was increased on removing external Ca2+. In the presence of external Ca2+, reactivation of IK(M, ng) after a hyperpolarizing step was delayed. This delay was preceded by an inward Ca2+ current, and coincided with an increase in intracellular [Ca2+] as measured with Indo-1 fluorescence. Elevation of intracellular [Ca2+] with caffeine also reduced IK(M, ng). 5. IK(M, ng) was inhibited by external divalent cations in decreasing order of potency (mM IC50 in parentheses): Zn2+ (0.011) greater than Cu2+ (0.018) greater than Cd2+ (0.070) greater than Ni2+ (0.44) greater than Ba2+ (0.47) greater than Fe2+ (0.69) greater than Mn2+ (0.86) greater than Co2+ (0.92) greater than Ca2+ (5.6) greater than Mg2+ (16) greater than Sr2+ (33). This was not secondary to inhibition of ICa since: (i) inhibition persisted in Ca(2+)-free solution; (ii) La3+ did not inhibit IK(M, ng) at concentrations which inhibited ICa; and (iii) organic Ca2+ channel blockers were ineffective. Inhibition comprised both depression of the maximum conductance and a positive shift of the activation curve. Addition of Ca2+ (10 microM free [Ca2+]) or Ba2+ (1 mM total [Ba2+]) to the pipette solution did not significantly change IK(M, ng). 6. IK(M, ng) was reduced by 9-amino-1,2,3,4-tetrahydroacridine (IC50 8 microM) and quinine (30 microM) but was insensitive to tetraethylammonium (IC50 greater than 30 mM), 4-aminopyridine (greater than 10 mM), apamin (greater than 3 microM) or dendrotoxin (greater than 100 nM). 7. IK(M, ng) was inhibited by bradykinin (1-10 microM) or angiotensin II (1-10 microM), but not by the following other receptor agonists: acetylcholine (10 mM), muscarine (10 microM), noradrenaline (100 microM), adrenaline (100 microM), dopamine (100 microM), histamine (100 microM), 5-hydroxytryptamine (10 microM), Met-enkephalin (1 microM), glycine (100 microM), gamma-aminobutyric acid (100 microM) or baclofen (500 microM).(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1992

Mouse mammary tumor gene int-3: a member of the notch gene family transforms mammary epithelial cells.

Expression of a 2.3-kb RNA species is induced in mammary tumors as a consequence of insertional mutagenesis at the int-3 locus by the mouse mammary tumor virus. The nucleotide sequence and biological activity of this mammary tumor-specific int-3 RNA species were determined. It contains an open reading frame which encodes a 57-kDa protein. The translated protein possesses six nearly contiguous 32-amino-acid repeats which are related to a similar motif in the Saccharomyces cerevisiae cdc-10-encoded cell cycle protein. In addition, the int-3 cdc-10 repeats are bounded by the PEST amino acid sequence motif which is commonly found in proteins having a rapid turnover and may represent sites for phosphorylation. The int-3 cdc-10 repeat sequences are 50% identical to a portion of the intracellular domain of the neurogenic Drosophila notch gene product. Activation of expression of a recombinant int-3 genomic DNA fragment encoding the 2.3-kb RNA species in HC11 mouse mammary epithelial cells in vitro induces anchorage-independent growth in soft agar.

Amino Acid Sequence↗
PubMed1992

Thyroxine binding to the apolipoproteins of high density lipoproteins HDL2 and HDL3.

Four preparations of high density lipoprotein HDL2, five of HDL3, and purified apolipoproteins apoA-I, apoA-IV, and apoE were photoaffinity labeled with [125I]T4 and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Gels were also immunoblotted with antiserum against apoA-I, apoA-II, apoA-IV, apoE, or apo(a), and the immunostained membrane was then autoradiographed. In HDL2, the two major radioactive bands migrated near the origin of the resolving gel and at 28-31 kilodaltons (kDa). The first band, stained by anti-apo(a) and anti-apoB-100, accounted for 40-96% of the total radioactivity and was attributed to lipoprotein(a), which is isolated in the same density range as HDL2. The second band, stained by anti-apoA-I, accounted for 1-57% [41-95% after correction for contaminating lipoprotein(a)] of the [125I]T4 in the resolving gel. In HDL3, the major radioactive band was identified as apoA-I and contained 93-94% of the [125I]T4 in the resolving gel. Minor radioactive bands in both HDL2 and HDL3 were identified as apoA-II (17-18 kDa), apoA-II monomer (7-10 kDa), apoE (36-38 kDa), and apoAII-apoE heterodimer (46 kDa). In addition, HDL3 contained apoA-IV (43 kDa). Photoaffinity labeling of isolated apoA-IV and apoE showed that each protein interacted with [125I]T4. In both HDL2 and HDL3, photoaffinity labeling in the presence of unlabeled L-T4 (1-10 microM) showed inhibition, suggesting a Kd in the micromolar range. This inhibition varied among different apo bands of the same HDL2 or HDL3 preparation and among the same bands of different preparations. Labeling in the presence of heparin or other inhibitors of T4 binding to plasma proteins (furosemide, diclofenac, and mefenamic acid) showed that HDL2-associated apoA-I was more sensitive to inhibition than HDL3-associated apoA-I. In conclusion, 1) HDL2 and HDL3 carry T4 mainly through apoA-I and secondarily through apoA-II and apoE. The inter- and intrasubclass variations in T4 binding and sensitivity to inhibitors can be explained by the known heterogeneity of HDL particles and possible differences in conformation of the apo. The findings reported here, that apo other than apoA-I and apoB exhibit saturable binding of T4, suggest that thyroid hormone-lipoprotein interactions may have even wider physiological implications than previously appreciated.

Affinity Labels↗
PubMed1992

Effects of interleukin-6 on the expression of thyroid hormone-binding protein genes in cultured human hepatoblastoma-derived (Hep G2) cells.

T4-binding globulin (TBG) shares a high degree of homology with two serpin antiproteases, alpha 1-antichymotrypsin (ACT) and alpha 1-antitrypsin (AT), whose synthesis is increased during the acute phase phenomenon, which accompanies trauma, infections, and neoplasms. Interleukin-6 (IL-6) is believed to be the main effector of the acute phase response. When evaluated in human hepatoblastoma-derived (Hep G2) cells exposed to different doses of the recombinant human cytokine for variable time intervals, IL-6 caused a dose- and time-dependent decrease in the secretion of [35S]methionine-labeled TBG, transthyretin (TTR), and albumin. The secretion of ACT and AT was increased. These changes were not due to alterations in the secretory process, since the kinetics of secretion of newly synthesized proteins were not modified. IL-6 did, however, cause a decrease in the steady state levels of mRNA for TTR, TBG, and albumin and an increase in ACT and AT mRNAs. In addition, nuclear run-off assay demonstrated a decrease in the transcription of TTR, TBG, and albumin genes and an increased transcription of the ACT gene. Quantitation of the results showed that changes in the secretion of proteins, in steady state mRNA levels, and in gene transcription were superimposable for each protein, indicating that IL-6 exerts its effect on thyroid hormone-binding proteins mostly at the transcriptional level and that TTR is the thyroid hormone-binding protein showing the most pronounced negative regulation by IL-6. The opposite effect of IL-6 on TBG and the antiproteases, despite their structural homology, underscores gene divergence among these proteins.

Acute-Phase Reaction↗
PubMed1992

Effects of bradykinin on ion conductances in NG108-15 neuroblastoma x glioma hybrid cells recorded with patch-clamp electrodes.

Under whole-cell recording, bradykinin (BK) produced an initial outward membrane current followed by an inward current in voltage-clamped NG108-15 cells. The initial outward current was associated with a rise in intracellular Ca2+ and was accompanied by the opening of Ca(2+)-dependent K(+)-channels recorded with a cell-attached patch electrode. This current was inhibited by intracellular Mg2+. The inward current was associated with inhibition of the voltage-dependent K(+)-current IK(M). These effects accord with those previously observed in microelectrode-impaled cells, with the difference that BK produced much more pronounced and long-lasting desensitization in the patch-clamped cells.

Acetylcholine↗
PubMed1992

Pelvic radioiodine uptake in a rectal wall teratoma after thyroidectomy for papillary carcinoma.

A 30-yr-old woman with previously resected papillary thyroid carcinoma was found to have a pelvic lesion which concentrated radioiodine. By performing simultaneous 131I whole-body and 99mTc-methylene diphosphonate bone scans, we found the lesion to be in soft tissue between the sacrum and bladder. Radioiodine therapy was postponed so that the lesion, a benign teratoma of the rectal wall, could be surgically removed. Prior to laparotomy, the patient received a second tracer dose of 131I so that the lesion could be located at surgery with a hand-held gamma detector. A postoperative whole-body 131I scan confirmed that the lesion had been removed, thus reducing the absorbed radiation that would have been received by the ovaries during radioiodine therapy. Although the lesion contained both thyroid and gastric epithelium, accumulated 131I was limited to the area with thyroid follicles.

Adult↗
PubMed1992

The movement of thyroid hormones in the central nervous system.

Thyroid hormones in the central nervous system (CNS) present a number of complexities which include a marked difference in hormone effects on the developing brain compared to the mature brain, extensive regional heterogeneity within the brain, and alternate ways by which the hormones gain entry to the CNS and its cells. Furthermore, most of the T3 found within brain cells is derived from the T4 that they have accumulated. This brief review concerns the movement of the thyroid hormones as they leave the bloodstream and make their way into and through the CNS. There are many sites for potential control of thyroid hormone transport into the central nervous system. The blood brain barrier and the choroid plexus may work in tandem as two parallel resistors subjected to different controls to maintain brain interstitial levels of thyroid hormone at near constant levels. Thyroid hormone may enter neurons directly from the interstitial fluid or indirectly from the glial cells. Nonetheless, both neurons, perhaps at the synaptosome, and glial cells are capable of transporting and concentrating thyroid hormones at physiological levels.

Animals↗
PubMed1992

Passive administration of antibody against retinal S-antigen induces electroretinographic supernormality.

Electroretinographic supernormality, affecting both the a- and b-waves of the electroretinogram (ERG), occurs consistently before the onset of experimental autoimmune uveoretinitis (EAU) in rabbits and rats. To investigate the possible role of antibody to S-antigen (S-ab) in this phenomenon, affinity-purified polyclonal rat S-ab was injected intravenously into normal rats and administered to isolated rat eyecup preparations by bolus perfusion. In both situations, ERG supernormality was observed. The effect in vivo peaked 90 min after injection, and ERG changes in vitro were observed within 15 sec. The ERG response in vivo and in vitro was dose dependent and was abolished in vivo by pretreatment with cyproheptadine (a serotonin antagonist). The ERG was not affected in either system by a control rat antibody (antiovalbumin) or by murine monoclonal or rabbit polyclonal antibodies to S-antigen. The induction of ERG supernormality in vivo and in vitro by homologous S-ab indicates the operation of species-specific mechanisms both involving and bypassing the blood-retinal barrier and highlights a significant role for humoral autoimmunity in the pathogenesis of S-antigen-induced EAU in the rat.

Animals↗
PubMed1991

Tissue-specific regulation of the alpha-myosin heavy chain gene promoter in transgenic mice.

The intergenic region between the mouse alpha-myosin heavy chain (MHC) and beta-MHC genes was analyzed in terms of its ability to drive gene expression in transgenic mice. Earlier, we reported that the entire intergenic region was sufficient to direct expression of the bacterial chloramphenicol acetyl transferase reporter gene in a tissue-specific and developmental stage-specific manner. Additional transgenic lines have been generated which include two deletions. The first deletion, alpha-3, which lacks the distal 2.5 kilobase pairs of the upstream region, is competent to direct tissue- and developmental-specific expression of the transgene. A larger deletion, in which only 138 base pairs upstream of the transcriptional start site remain, shows no chloramphenicol acetyltransferase activity in either muscle or non-muscle tissue. Tissue surveys of transgene expression indicated low levels of activity in the lung, and analyses via the polymerase chain reaction confirmed the presence of the endogenous alpha-MHC gene transcripts in this tissue. Subsequently, an alpha-MHC gene-specific riboprobe was used to detect the cognate transcripts in lung sections by in situ hybridization. The data show that, in the lung, the transcripts are localized to the thick intimal wall of the veins and venules.

Animals↗
PubMed1991

Molecular basis of thyroid hormone regulation of myelin basic protein gene expression in rodent brain.

Regulation of myelin basic protein (MBP) gene expression by thyroid hormone has been investigated in rodent brain. Quantitation of the 4 major alternatively spliced transcripts by RNase protection assay showed that the individual mRNAs, corresponding to MBP isoforms 21.5, 18.5, 17, and 14 kDa, were decreased from 2- to 17-fold at all ages studied (4-60 days) in hypothyroid animals when compared to euthyroid, but the timing of onset of expression was not altered. MBP mRNA was also reduced in young adult rats thyroidectomized at the age of 5-6 weeks and was restored to normal by thyroxine administration. Nuclear run-off assays showed that the rate of MBP gene transcription is dependent on thyroid state. Co-transfection of MBP (-256/+1)-chloramphenicol acetyltransferase chimeric gene with a plasmid expressing thyroid hormone receptor alpha, and in the presence of 3,5,3'-triiodothyronine, into NIH3T3 or NG108-15, increased chloramphenicol acetyltransferase expression 4-fold. Using a footprinting technique and Spodoptera frugiperda 9 (Sf9) nuclear extract infected with baculovirus expressing TR alpha, we have identified a single DNA-binding site (-186/-163) for the receptor. A part of this region contains the AGGACA sequence found in thyroid hormone-responsive elements of other 3,5,3'-triiodothyronine-regulated genes. Our finding of a specific hormone-receptor interaction with the MBP promoter region is the first direct demonstration of a thyroid hormone-responsive element in a brain-specific gene.

Animals↗
PubMed1991

Myosin heavy chain gene expression in mouse embryoid bodies. An in vitro developmental study.

Embryoid bodies (EBs) are obtained when mouse pluripotential embryonic stem cells are grown in the absence of an embryonic fibroblast feeder layer. Seven- to 9-day-old EBs undergo rhythmical, spontaneous contractions and express the appropriate tissue- and developmental stage-specific cardiac and skeletal myosin heavy chain (MHC) genes. To study the expression patterns of these MHC genes in vitro we isolated and partially sequenced the cDNAs expressed in EBs such that specific oligonucleotides suitable for polymerase chain reaction analyses and appropriate riboprobes for in situ hybridizations could be made. The data show the beta-cardiac gene is expressed first during EB development (days 3 and 4), and alpha-cardiac gene expression begins at approximately day 8. A similar pattern of expression is also detected during mouse embryogenesis in utero. Only those EBs that expressed both the alpha- and beta-cardiac transcripts contracted. In situ hybridization of EBs using riboprobes shows that the spatial distribution of the cardiac MHC transcripts differs. No expression of the genes was detected in day 8 or older nonbeating EBs. These data suggest that developing EBs closely mimic the pre- and early postsomitic patterns of in vivo expression of the cardiac MHC genes and thus provide a useful system in which to study early aspects of mammalian cardiogenesis.

Amino Acid Sequence↗
PubMed1991

Thyroid cancer: a lethal endocrine neoplasm.

This conference focuses on the controversies about managing thyroid cancer, emphasizing the possibility that the treatment of patients with potentially fatal thyroid cancer may be improved. Although the mortality rate from thyroid cancer is low, it is the highest among cancers affecting the endocrine glands (excluding the ovary). Exposure to radiation during childhood in the 1930s and 1940s increased the incidence of but not the mortality from thyroid cancer, because these tumors are mainly papillary cancers developing in young adults. These rates may change as the exposed cohort ages. Risk factors that increase mortality include older patient age and the growth characteristics of the tumor at diagnosis, the presence of distant metastases, and cell type (for example, the tall-cell variants of papillary cancer, follicular cancer [to be distinguished from the more benign follicular variant of papillary cancer], medullary cancer, and anaplastic cancer). Local metastases in lymph nodes do not seem to increase the risk for death from papillary cancer, but they do increase the risk for death from follicular and medullary cancer. In the latter, mortality is decreased by the early detection and treatment of patients with the familial multiple endocrine neoplasia syndrome 2a. There are excellent tumor markers for differentiated cancer of the parafollicular and of the follicular cells (serum calcitonin and serum thyroglobulin levels, respectively). Measuring the calcitonin level allows early diagnosis of familial medullary cancer, whereas measuring the thyroglobulin level, although useful only after total thyroidectomy, allows early recognition of recurrence or metastases of papillary or follicular cancer. Initial surgery, protocols for follow-up, and the use of radioiodine for the ablation of any residual thyroid and the treatment of metastatic cancer are discussed. Because these tumors resist currently available chemotherapy regimens, possible ways to increase the effectiveness of radioiodine therapy are considered as are new approaches to treatment.

Carcinoma↗
PubMed1991

Isolation and characterization of the mouse cardiac myosin heavy chain genes.

Two mouse genomic libraries were probed in order to isolate the murine cardiac myosin heavy chain (MHC) genes. Two overlapping cosmid clones that encode the cardiac genes were isolated. One of them encompasses the entire alpha-cardiac MHC gene, its 5'-flanking region and approximately 10 kilobase pairs (kb) of the 3'-end of the beta-cardiac MHC gene which we determined is located approximately 4 kb upstream of the alpha-cardiac MHC gene. Four clones isolated from a bacteriophage library were found to overlap with the 5'-region of the cosmid clones, and sequence analysis confirmed that the 5'-end of the beta-cardiac MHC gene was contained within one of the clones. Primer extension and polymerase chain reaction (PCR) analyses were used to define the transcriptional start site and the 5'-organization of the alpha-cardiac MHC gene. This region exhibits greater than 90% homology to the corresponding nucleotides of the rat alpha-cardiac MHC gene. To assess the importance of the intergenic region in directing expression of the alpha-cardiac MHC gene, a fragment containing the 3'-end of the beta-cardiac gene and the 5'-end of the alpha-cardiac gene was linked to a chloramphenicol acetyltransferase gene and used to generate transgenic mice. Analyses of the chloramphenicol acetyltransferase (CAT) activity in two lines indicate that the intergenic region is sufficient to properly direct expression in a tissue-specific manner.

Animals↗
PubMed1991

The naphthalenesulphonamide calmodulin antagonist W7 and its 5-iodo-1-C8 analogue inhibit potassium and calcium currents in NG108-15 neuroblastoma x glioma cells in a manner possibly unrelated to their antagonism of calmodulin.

Patch clamp techniques were used to record voltage-sensitive calcium and potassium currents from NG108-15 cells. N-(6-aminohexyl)-5-chloro-1-naphthalene- sulphonamide (W7), a calmodulin (CaM) antagonist and its more potent (10 times) 5-iodo-1-C8 analogue (J8) inhibited these currents in a dose-dependent manner. The inhibition was not dependent on internal or external Ca2+. W7 was about four times more potent as an inhibitor of the transient potassium current (IC50 = 8 microM) than of the M-current or of the calcium current. J8 was also selective for the potassium currents (IC50 values: transient current 4 microM, M-current 11 microM) compared to the calcium current (IC50 36 microM). It is suggested that the inhibition does not result from an anti-CaM action of the compounds.

Animals↗