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Biomedical subjects

R J Smith

Publications and source records attributed to R J Smith.

At least 253 records · Page 14Linked to original sources
PubMed1995

Insulin receptor phosphorylation, insulin receptor substrate-1 phosphorylation, and phosphatidylinositol 3-kinase activity are decreased in intact skeletal muscle strips from obese subjects.

To determine whether the impaired insulin-stimulated glucose uptake in obese individuals is associated with altered insulin receptor signaling, we measured both glucose uptake and early steps in the insulin action pathway in intact strips of human skeletal muscle. Biopsies of rectus abdominus muscle were taken from eight obese and eight control subjects undergoing elective surgery (body mass index 52.9 +/- 3.6 vs 25.7 +/- 0.9). Insulin-stimulated 2-deoxyglucose uptake was 53% lower in muscle strips from obese subjects. Additional muscle strips were incubated in the basal state or with 10(-7) M insulin for 2, 15, or 30 min. In the lean subjects, tyrosine phosphorylation of the insulin receptor and insulin receptor substrate-1 (IRS-1), measured by immunoblotting with anti-phosphotyrosine antibodies, was significantly increased by insulin at all time points. In the skeletal muscle from the obese subjects, insulin was less effective in stimulating tyrosine phosphorylation (maximum receptor and IRS-1 phosphorylation decreased by 35 and 38%, respectively). Insulin stimulation of IRS-1 immunoprecipitable phosphatidylinositol 3-kinase (PI 3-kinase) activity also was markedly lower in obese subjects compared with controls (10- vs 35-fold above basal, respectively). In addition, the obese subjects had a lower abundance of the insulin receptor, IRS-1, and the p85 subunit of PI 3-kinase (55, 54, and 64% of nonobese, respectively). We conclude that impaired insulin-stimulated glucose uptake in skeletal muscle from severely obese subjects is accompanied by a deficiency in insulin receptor signaling, which may contribute to decreased insulin action.

Adult↗
PubMed1995

Dexamethasone enhances insulin-like growth factor-I effects on skeletal muscle cell proliferation. Role of specific intracellular signaling pathways.

IGF-I stimulation of cell proliferation and c-Fos expression in skeletal muscle cells is markedly enhanced by dexamethasone. The effect of dexamethasone is not mediated by changes in IGF-binding proteins, as evidenced by similar effects of dexamethasone on the actions of insulin, PDGF-BB, and the IGF-I analogue long R3IGF-I. Dexamethasone also does not alter autocrine IGF-II secretion by muscle cells. To investigate the mechanism of the augmentation of IGF-I action, the effects of dexamethasone on intracellular IGF-I signaling pathways were determined. In dexamethasone-treated cells, the levels of IGF-I receptor tyrosine phosphorylation and receptor-associated phosphatidylinositol 3-kinase activity were increased. Dexamethasone-treated cells also showed increased and prolonged tyrosine phosphorylation of the Shc proteins. In contrast, dexamethasone decreased both tyrosine phosphorylation and expression of insulin receptor substrate 1 (IRS-1) and IRS-1-associated phosphatidylinositol 3-kinase activity. Thus, distinct signaling pathways activated by the IGF-I receptor in skeletal muscle cells are differentially regulated by dexamethasone. Potentiation of IGF-I action correlates with increased IGF-I receptor-associated phosphatidylinositol 3-kinase activity and tyrosine phosphorylation of Shc, but appears to be independent of activation of the IRS-1/phosphatidylinositol 3-kinase signaling pathway.

Animals↗
PubMed1995

Langerhans' cell histiocytosis of the head and neck in children.

This is a retrospective analysis of a 29-year institutional experience with Langerhans' cell histiocytosis (LCH) in children. Cases of LCH were categorized by disease extent into three groups: group 1, with a solitary focus of LCH; group 2, with multiple non-vital organ foci; and group 3, with vital organ disease. Sixteen patients averaging 7.3 years of age and with 11.0 years of follow-up presented in group 1. One child experienced a spontaneous remission; all other children responded to local treatment. The skull was the most common site of involvement. Eight children averaging 4.6 years in age and with 8.0 years of follow-up presented in group 2; 3 children had diabetes insipidus. Treatment included radical surgery, radiotherapy, and chemotherapy; however, disease persisted in all patients. Iatrogenic complications were a significant cause of morbidity and mortality. Only 1 patient, 1 year of age, presented with lung and liver involvement (group 3). He died after a fulminant course. Current recommendations for diagnosis, evaluation, and treatment of LCH are discussed.

Adolescent↗
PubMed1995

Exercise-induced laryngomalacia.

Exercise-induced laryngomalacia (EIL) is characterized by severe dyspnea, stridor, and mild wheezing unresponsive to prophylactic treatment with beta-agonists and cromolyn sodium. Symptoms develop with extreme exertion, but resolve quickly as the degree of exercise is decreased. Diagnosis requires flexible fiberoptic laryngoscopy before, during, and after exercise. If the diagnosis of EIL is confirmed by laryngoscopy during maximal exercise, laser epiglottoplasty is effective in alleviating symptoms and improving the airway. However, because symptoms develop only during maximal exertion, EIL is unlikely to produce symptoms or functional disability in persons who lead relatively sedentary lives.

Child↗
PubMed1995

A comparison of rat small intestinal insulin and insulin-like growth factor I receptors during fasting and refeeding.

Insulin-like growth factor I (IGF-I) and insulin may be important regulators of intestinal growth. To investigate small intestinal IGF-I receptors (IGF-IR) and insulin receptors (IR) during intestinal cell atrophy and regeneration, we compared indexes of IGF-IR and IR expression in rat jejunum after 72 h of fasting and 24-72 h of enteral refeeding. Fasting induced intestinal atrophy, reduced plasma insulin and IGF-I concentrations, and markedly decreased jejunal IGF-I messenger RNA (mRNA) levels; these changes were reversed by refeeding. Fasting significantly increased jejunal specific insulin binding, IR content (to 230% of the fed control value), and the 9.6- and 7.4-kilobase IR mRNA transcript levels (to 202% and 218% of control values, respectively). These IR indexes rapidly decreased to control levels with refeeding. Levels of IGF-IR (by Scatchard analysis) and IGF-I-R mRNA were not significantly altered with fasting. The 11-kilobase IGF-IR mRNA transcript increased significantly during the first 24 h of refeeding (to 166% of the control value), and IGF-IR number rose 3-fold. We conclude that rat jejunal IR and IGF-IR are differentially regulated by nutrient availability. Up-regulation of jejunal IGF-I and IGF-IR expression during refeeding suggests a role for the IGF action pathway in gut trophic responses to enteral nutrients.

Animals↗
PubMed1995

Amplification of mitochondrial DNA from archival temporal bone specimens.

Archival temporal bone collections are an invaluable resource for studying the molecular genetics of many types of otopathology. The irreplaceable nature of temporal bone sections makes efficiency of DNA extraction of paramount importance. Several protocols are available for extracting DNA from fresh and preserved tissue. To establish the best protocol for reliably extracting DNA from celloidin-embedded temporal bone sections, a variety of DNA extraction techniques were tested. Using the optimum protocol, mitochondrial DNA fragments ranging in size from less than 100 base pairs to more than 400 base pairs were amplified, and the authenticity of polymerase chain reaction (PCR) products was confirmed through comparative sequence analysis.

Acetates↗
PubMed1995

Branchio-oto-renal syndrome.

Branchio-oto-renal syndrome is an autosomal-dominant disorder with branchial, otologic, and renal manifestations. The branchial manifestations are usually inconsequential; however, the hearing impairment and renal malformations can be significant. Appropriate evaluation of affected persons is necessary to minimize disease morbidity.

Audiometry, Pure-Tone↗
PubMed1995

A mononuclear cell dose of 3 x 10(8)/kg predicts early multilineage recovery in patients with malignant lymphoma treated with carmustine, etoposide, Ara-C and melphalan (BEAM) and peripheral blood progenitor cell transplantation.

We have assessed the potential use of the mononuclear cell (MNC) content as the sole assessment of graft quality in 35 patients receiving BEAM (carmustine, etoposide, cytosine arabinoside, melphalan) chemotherapy and autologous peripheral blood progenitor cell (PBPC) transplantation for malignant lymphoma. PBPCs were mobilized with cyclophosphamide and granulocyte colony-stimulating factor (G-CSF), and each patient underwent two (n = 20) or three (n = 15) apheresis procedures. Median cell yields were 5.08 x 10(8) MNC/kg (range 1.59-15.70 x 10(8)) and 73.10 x 10(4) CFU-GM/kg (range 0.09-346.72 x 10(4)). All patients achieved hematologic recovery. Median days to neutrophils > or = 0.1 x 10(9)/L, neutrophils > or = 0.5 x 10(9)/L, and platelets > or = 25 x 10(9)/L were 11 (range 8-15), 13 (range 10-37), and 11 (range 7-41), respectively. A close correlation was observed between the MNC and CFU-GM dose (r = 0.79, p < 0.0001). We have previously defined a minimum threshold CFU-GM dose of 20 x 10(4)/kg for patients undergoing high-dose therapy. This corresponds with an MNC dose of 3 x 10(8)/kg. Comparison of engraftment in patients receiving 3 x 10(8) MNC/kg with those receiving lower doses demonstrated significantly longer times to recovery of neutrophils to > or = 0.5 x 10(9)/L and platelets to > or = 25 x 10(9)/L. All patients receiving an MNC dose of > or = 3 x 10(8)/kg achieved neutrophil and platelet recovery by days 12 and 24, respectively. These preliminary data demonstrate that for patients with lymphoma undergoing PBPC mobilization according to this protocol and treatment with BEAM chemotherapy, assessment of MNC dose alone is sufficient to predict early hematologic recovery. Additional assays such as CFU-GM or CD34+ cell counts may not be necessary if this MNC dose is reinfused.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

ROR gamma: the third member of ROR/RZR orphan receptor subfamily that is highly expressed in skeletal muscle.

In this study, we describe the identification and cloning of a novel member of the nuclear receptor superfamily. This orphan receptor, referred to as ROR gamma, belongs to the ROR/RZR subfamily. The open reading frame of ROR gamma encodes a protein of 560 amino acid residues with a predicted molecular mass of 63 kD. The amino acid sequence of ROR gamma exhibits a 50 and 51% identity with those of ROR alpha/RZR alpha and RZR beta, respectively, whereas the DNA-binding domains were 89% identical. ROR gamma was localized on human chromosome 1. Northern blot analysis using RNA from multiple tissues indicated that ROR gamma is expressed in several tissues but is most highly expressed in skeletal muscle.

Amino Acid Sequence↗
PubMed1994

Cloning and nucleotide sequence of the gene encoding dinitrogenase reductase (nifH) from the cyanobacterium Nostoc 6720.

The nucleotide sequence of the 3' end of the nifU coding sequence, the complete coding sequence of nifH and a substantial part of the 5' end of nifD coding sequence from Nostoc 6720 is presented. The coding sequences are highly conserved with those of Anabaena 7120 and Anabaena sp. L31. However the intergenic region between nifU and nifH contains two segments of short tandemly repetitive repeat sequences (STRRs) that differ from the STRR that is common to both Anabaena7120 and Anabaenasp. L31. Various sequence structures that are common to Nostoc 6720, the Anabaena strains and Plectonema boryanum are discussed.

Amino Acid Sequence↗
PubMed1994

cDNA cloning of the rat IGF I receptors: structural analysis of rat and human IGF I and insulin receptors reveals differences in alternative splicing and receptor-specific domain conservation.

IGF I and insulin receptors are homologous proteins that function in distinct physiological pathways. To define domains that might contribute to differences between IGF I and insulin receptors, we cloned the rat IGF I receptor cDNA and performed a comparative sequence analysis of specific functional domains in the two receptor types of rats and humans. Since alternative splicing has been shown to alter the activities of both IGF I and insulin receptors, we also examined the mRNA splicing patterns of the two receptors. The C-terminal region exhibits the lowest degree of amino acid homology between rat and human IGF I receptors (85%) and the tyrosine kinase domain the highest homology (98%). In the region corresponding to the CAG+/-alternative splicing site of the human IGF I receptor, a nucleotide change in the rat eliminates the alternative acceptor splice site. The rat IGF I receptor has no equivalent to the alternatively spliced exon 11 of the insulin receptor. The IGF I and insulin receptors are highly homologous in the tyrosine kinase domain (84%), but differ markedly in other specific regions (e.g., 22-26% homology in the transmembrane domain, 45% homology in the C-terminal domain). We speculate that these regions of divergent sequence may have roles in determining distinct signaling properties of IGF I and insulin receptors.

Alternative Splicing↗
PubMed1994

Two alternatively spliced forms of the human insulin-like growth factor I receptor have distinct biological activities and internalization kinetics.

Two alternatively spliced human insulin-like growth factor I (IGF I) receptor mRNA transcripts have been described that differ by three nucleotides (CAG) starting at position 2829. This results in an amino acid coding sequence change from Thr-Gly to Arg in the extracellular portion of the receptor beta subunit. To investigate the functional significance of this sequence difference, we obtained full-length cDNAs for the CAG+ and CAG- receptor forms, transfected CHO cells, and isolated multiple clones expressing approximately equal numbers of receptors (0.57-0.73 x 10(6) receptors/cell). The two receptors bound IGF I with similar affinity (Kd approximately 1.7 nM), but the CAG- form exhibited an approximately 2-fold increase in IGF I stimulation of receptor autophosphorylation, insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation, thymidine incorporation, and IRS-1-associated phosphatidylinositol 3-kinase activity. In contrast to its higher signaling activity, the rate of receptor-mediated internalization of IGF I by the CAG-receptor was decreased by 50% in comparison with the CAG+ receptor. We conclude that proteins corresponding to the two alternatively spliced human IGF I receptor transcripts are biologically active, but have distinct signaling properties. These experiments further indicate a previously unrecognized role for the extramembranous portion of the beta subunit in receptor signaling and internalization.

Alternative Splicing↗
PubMed1994

Clinical diagnosis of the Usher syndromes. Usher Syndrome Consortium.

The Usher syndromes are genetically distinct disorders which share specific phenotypic characteristics. This paper describes a set of clinical criteria recommended for the diagnosis of Usher syndrome type I and Usher syndrome type II. These criteria have been adopted by the Usher Syndrome Consortium and are used in studies reported by members of this Consortium.

Diagnosis, Differential↗
PubMed1994

Degrees of freedom in interspecific allometry: an adjustment for the effects of phylogenetic constraint.

The data used in studies of bivariate interspecific allometry usually violate the assumption of statistical independence. Although the traits of each species are commonly treated as independent, the expression of a trait among species within a genus may covary because of shared common ancestry. The same effect exists for genera within a family and so on up the phylogenetic hierarchy. Determining sample size by counting data points overestimates the effective sample size, which then leads to overestimating the degrees of freedom that should be used in calculating probabilities and confidence intervals. This results in an inflated Type 1 error rate. Although some workers (e.g., Felsenstein [1985] Am. Nat. 125:1-15) have suggested that this issue may invalidate interspecific allometry as a comparative method, a correction for the problem can be approximated with variance components from a nested analysis of variance. Variance components partition the total variation in the data set among the levels of the nested hierarchy. If the variance component for each nested level is weighted by the number of groups at that level, the sum of these values is an estimate of an effective sample size for the data set which reflects the effects of phylogenetic constraint. Analysis of two data sets, using taxonomy to define levels of the nested hierarchy, suggests that it has been common for published studies of interspecific allometry to severely overestimate the number of degrees of freedom. Interspecific allometry remains an important comparative method for evaluating questions concerning individual species that are not similarly addressed by the format of most of the newer comparative methods. With the correction proposed here for estimating degrees of freedom, the major statistical weakness of the procedure is substantially reduced.

Analysis of Variance↗
PubMed1994

Purification, properties, and subcellular localization of foxtail mosaic potexvirus 26-kDa protein.

The open reading frame 2 (ORF2) of the potexviral genome encodes a 24- to 26-kDa protein which is part of the "triple gene block," a group of overlapping ORFs also present in the genomes of the carla-, hordei-, and furoviruses. The product of these ORFs is believed to play a role in the cell-to-cell movement of the viruses in host plants. The amino acid sequences of the homologous ORF2 products encoded by these related viruses suggest that they specify NTP binding and possibly helicase activities. We have used an Escherichia coli expression system to produce significant amounts of the 26-kDa protein (p26) encoded by foxtail mosaic potexvirus ORF2. p28 was purified to near homogeneity by conventional purification methods and some of its biochemical properties were determined. We present evidence that p26 is an ATP, CTP, and RNA binding protein with apparent ATPase activity. Western blot analysis of infected plant extracts using a polyclonal antiserum produced against p26 indicates that it is a relatively stable protein maintained at high levels for at least 6 days following its peak level of expression. Moreover, it is found predominantly in the soluble fraction of infected tissues. An immunocytochemical analysis of infected Chenopodium quinoa leaves reveals that p26 is exclusively associated with cytoplasmic inclusions in proximity to but distinct from aggregates of viral particles.

Adenosine Triphosphatases↗