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Biomedical subjects

R M Smith

Publications and source records attributed to R M Smith.

At least 217 records · Page 12Linked to original sources
PubMed1993

Effect of environmental stress and surface treatment on resin-to-metal bonding.

This study compares the bond strength and durability of three metal surface treatments subjected to two types of environmental stress for both short- and long-term exposures. The luting resins Panavia and Comspan were applied to alumina-blasted, non-beryllium, nickel-chromium alloy coupons. Metal surface treatments consisted of either microscopic roughening by electrochemical etching, or one of two types of adhesives: a silanated silica coating (Silicoating) or a phosphate ester monomer (a component in the Panavia liquid). Shear bond strength was determined following short- or long-term exposure to either thermocycling in 6-60 degrees C water (2,672 cycles/7 days or 10,584 cycles/42 days) or storage in 37 degrees C water (7 or 42 days). Three-way ANOVA showed that both the type of environmental stress and the exposure time affected the bond strength of electroetched surfaces, but that only exposure time affected the two chemical adhesives (P < 0.05), regardless of the environmental stress used. In the short-term, the silica/silane coated surfaces produced and maintained the higher shear bond strengths (15.9 +/- 2.3 MPa). However, after 42 days the silica/silane bonds decreased 30% (to 11.3 +/- 2.2 MPa), while the phosphate ester bonds were essentially unchanged (11.4 +/- 3.0 at 4 days, 10.4 +/- 2.2 MPa at 42 days). Electroetched bonds were the weakest and decreased by 18% between 7 and 42 days in water (8.8 +/- 1.2 to 7.2 +/- 3.0 MPa) and 27% after 42 days of thermocycling (7.2 +/- 2.8 to 5.3 +/- 1.8 MPa).

Analysis of Variance↗
PubMed1992

O2- production by B lymphocytes lacking the respiratory burst oxidase subunit p47phox after transfection with an expression vector containing a p47phox cDNA.

The respiratory burst oxidase of phagocytes and B lymphocytes is a complicated enzyme that catalyzes the one-electron reduction of oxygen by NADPH. It is responsible for the O2- production that occurs when these cells are exposed to phorbol 12-myristate 13-acetate or other appropriate stimuli. The activity of this enzyme is greatly decreased or absent in patients with chronic granulomatous disease, an inherited disorder characterized by a severe defect in host defense against bacteria and fungi. In every chronic granulomatous disease patient studied to date, an abnormality has been found in a gene encoding one of four components of the respiratory burst oxidase: the membrane protein p22phox or gp91phox, or the cytosolic protein p47phox or p67phox. We report here that O2- production was partly restored to phorbol 12-myristate 13-acetate-stimulated Epstein-Barr virus-transformed B lymphocytes from a patient with p47phox-deficient chronic granulomatous disease by transfection with an expression plasmid containing a p47phox cDNA inserted in the sense direction. No detectable O2- was produced by untransfected p47phox-deficient lymphocytes or by p47phox-deficient lymphocytes transfected with an antisense plasmid. The finding that O2- can be produced by p47phox-deficient B lymphocytes after the transfer of a p47phox cDNA into the deficient cells suggests that this system could be useful for studying the function of mutant p47phox proteins in whole cells.

Amino Acid Sequence↗
PubMed1992

Direct stimulation of immediate-early genes by intranuclear insulin in trypsin-treated H35 hepatoma cells.

H35 hepatoma cells were treated with trypsin to abolish insulin binding and insulin-stimulated receptor kinase activity. Insulin was, however, internalized by fluid-phase endocytosis in trypsin-treated cells. Furthermore, nuclear accumulation of insulin was similar in control and trypsin-treated hepatoma cells. Northern blot analysis revealed insulin increased g33 and c-fos mRNA concentrations identically in control and trypsin-treated cells but had no effect on beta 2-microglobulin mRNA. Actinomycin D treatment prior to or after insulin addition demonstrated that insulin increased gene transcription and had no effect on mRNA degradation. These studies suggest that the accumulation of intact insulin in cell nuclei may be directly involved in the increased transcription of immediate-early genes.

Cell Cycle↗
PubMed1992

The cytosolic components of the respiratory burst oxidase exist as a M(r) approximately 240,000 complex that acquires a membrane-binding site during activation of the oxidase in a cell-free system.

Sodium dodecyl sulfate (SDS) treatment of a mixture of cytosol and plasma membranes from resting neutrophils resulted in the activation of the respiratory burst oxidase, a complicated enzyme that catalyzes the production of O2- from NADPH and oxygen. Activation was accompanied by translocation to the plasma membranes of the oxidase components p47phox and p67phox, which in resting cytosol were found in a M(r) approximately 240,000 complex. This translocation, which appeared to take place without a major change in the size of the cytosolic complex, did not occur if the membranes lacked cytochrome b558, and was inhibited by the peptide PRGV-HFIFNK, a sequence found near the carboxyl terminus of cytochrome b558 that was known from earlier work to inhibit O2- production by the cell-free system (Rotrosen, D., Kleinberg, M. E., Nunoi, H., Leto T., Gallin, J. I., and Malech H. L. (1990) J. Biol. Chem. 265, 8745-8750). Cytosols pretreated with the cross-linking agents 3,3'-dithiobis(sulfosuccinimidyl) propionate (DTSSP) (cleavable by 2-mercaptoethanol) and bis-(sulfosuccinimidyl) suberate (not cleavable by 2-mercaptoethanol) lost most of their ability to support O2- production in the cell-free system, and oxidase components from DTSSP-treated cytosol failed to translocate to the plasma membrane. When DTSSP-treated cytosols were incubated with 2-mercaptoethanol, however, both O2- production and translocation were partly restored, indicating that the functional impairment in DTSSP-treated cytosols was probably due at least in part to a restriction in the conformational mobility of the cross-linked peptide chains in the approximately 240,000 complex. These findings provide further support for the idea that the cytosolic components of the respiratory burst oxidase exist in the form of a approximately 240,000 complex, and suggest that the exposure of this complex to SDS induces a structural change that may or may not be associated with the loss of an inhibitory subunit too small to cause a detectable change in the size of the complex. This SDS-induced change allows translocation to take place by creating a membrane-binding site on the surface of the complex.

Adult↗
PubMed1992

Abomasal dilatation and impaction in two Hampshire rams.

Two adult Hampshire rams, unrelated and from separate farms, were examined for the cause of intermittent bloat and, or anorexia which lasted for three to six weeks and caused depression and cachexia. The rumen of each ram was hypermotile and ballottement of the ventral abdomen of each animal revealed an enlarged doughy viscus. Mild prerenal azotaemia, hypokalaemia with metabolic alkalosis, and high rumen chloride concentrations were evident. One ram died during the induction of anaesthesia for an abomasotomy and the other was euthanased after unsuccessful medical therapy. The abomasum of each ram was four to six times larger than that of a normal adult ram and filled with coarse, semi-moist, impacted ingesta. This abnormality was clinically identical to the abomasal emptying syndrome which has been described only in the Suffolk breed.

Abomasum↗
PubMed1992

Risk factors for hypertension in Kimberley aborigines.

OBJECTIVE: To determine physical, biochemical and lifestyle factors associated with high blood pressure among Aborigines in the Kimberley region. DESIGN: Blood pressure and electrocardiographic (ECG) abnormalities in an age and sex stratified random sample of the Aboriginal population were related to other observations and measurements made at the same time specifically for the purpose of these comparisons. SETTING: A field study in which subjects were interviewed and measurements made mostly in community clinics. PARTICIPANTS: All 249 men and 241 women from the prevalence study were included although only complete data sets for the various comparisons were analysed. INTERVENTIONS: A sample of venous blood was obtained in addition to physical measurements and information at interview. MAIN OUTCOME MEASURES: Statistical analysis of the relationships between blood pressure or hypertension and alcohol consumption, plasma gamma-glutamyl transpeptidase (GGT) activity, use of tobacco, body mass index (BMI, kg/m2) and non-fasted plasma cholesterol level. Hypertension was defined as systolic blood pressure of 160 mmHg or greater or diastolic blood pressure of 95 mmHg or greater. RESULTS: High blood pressure in Aboriginal men below 30 years was associated both with current drinking status and with circulating GGT level. There was a positive association of diastolic hypertension with consumption of alcohol in middle aged men (30 to 49 years) and in older women. Drinking was highly prevalent among men, especially below 30 years, but was less prevalent among women. Both systolic and diastolic blood pressure were positively related to BMI across the population but obesity (BMI greater than or equal to 30 kg/m2) was highly prevalent only among middle-aged women. Both systolic and diastolic blood pressure were positively and strongly related to plasma cholesterol level independently of the latter's relationship to age and BMI. CONCLUSION: The high prevalence of drinking among Aboriginal men and of obesity among Aboriginal women involves a risk of hypertension. The association between plasma cholesterol and blood pressure in Aboriginal men and women may be relevant to the demonstrated link between systolic hypertension and ischaemic heart disease.

Adult↗
PubMed1992

Prevalence of hypertension in Kimberley aborigines and its relationship to ischaemic heart disease. An age-stratified random survey.

OBJECTIVE: To determine the age-specific prevalence of systolic and diastolic hypertension and of electrocardiographic abnormalities in the Aboriginal population of the Kimberley region of Western Australia. DESIGN AND SETTING: Age and sex stratified random samples of the Aboriginal population of the Kimberley region were selected and located. Measurements were made of systolic and diastolic blood pressure and electrocardiograms (ECG) were recorded. Hypertension was defined as a systolic blood pressure of 160 mmHg or greater or diastolic blood pressure of 95 mmHg or greater. ECG abnormalities were classified by the Minnesota system. PARTICIPANTS: Measurements were made on 249 men and 241 women distributed in seven age bands above 15 years and representing 78% of the selected men and 76% of the selected women. INTERVENTIONS: In addition to ECG and blood pressure, measurements were made of height and weight and information was obtained on medication, smoking, drinking and diet. A sample of venous blood was obtained. MAIN OUTCOME MEASURES: The data obtained on blood pressure, hypertension and ECG abnormalities were compared with existing data on Caucasian and Aboriginal Australians. RESULTS: Aboriginal men below the age of 30 years showed particularly high blood pressure compared with Caucasian men. The overall prevalence of hypertension in Aboriginal men 50 years of age and older was 45%. The prevalence of hypertension among Aboriginal women increased sharply from 35 years of age with a maximum between 55 and 65 years. The overall prevalence of hypertension in women 50 years of age and older was 50%. By regression, the average systolic/diastolic blood pressure at 40 years was 137/85 mmHg for men and 135/83 mmHg for women. ECG abnormalities indicating ischaemic heart disease (IHD) were more prevalent in both male and female Aborigines than had been found for Caucasians in 1966. In both sexes IHD and especially code 1.1 indicating myocardial infarct were associated with systolic hypertension. CONCLUSIONS: The prevalence of both systolic and diastolic hypertension and of probable IHD was two to three times higher in Kimberley Aborigines than in Caucasian Australians. ECG evidence of infarct was significantly related to systolic hypertension in both sexes.

Adolescent↗
PubMed1992

Ca2+/calmodulin-dependent NO synthase type I: a biopteroflavoprotein with Ca2+/calmodulin-independent diaphorase and reductase activities.

NO synthase (NOS; EC 1.14.23) catalyzes the conversion of L-arginine into L-citrulline and a guanylyl cyclase-activating factor (GAF) that is chemically identical with nitric oxide or a nitric oxide-releasing compound (NO). Similar to the other isozymes of NOS that have been characterized to date, the soluble and Ca2+/calmodulin-regulated type I from rat cerebellum (homodimer of 160-kDa subunits) is dependent on NADPH for catalytic activity. The enzyme also possesses NADPH diaphorase activity in the presence of the electron acceptor nitroblue tetrazolium (NBT). We investigated the requirements of NOS and its content of the proposed additional cofactors tetrahydrobiopterin (H4biopterin) and flavins, further characterized the NADPH diaphorase activity, and quantified the NADPH binding site(s). Purified NOS type I Ca2+/calmodulin-independently bound the [32P]2',3'-dialdehyde analogue of NADPH (dNADPH), which, at near Km concentrations during 3-min incubations was utilized as a substrate and at higher concentrations or after prolonged incubations and cross-linking inhibited NOS activity. The NADPH diaphorase activity was Ca2+/calmodulin-independent, required higher NADPH concentrations than NOS activity, and was affected by dNADPH to a lesser degree. Divalent cations interfered with the diaphorase assay. Per dimer, native NOS contained about 1 mol each of H4biopterin, FAD, and FMN, classifying it as a biopteroflavoprotein, and incorporated 1 mol of dNADPH. No dihydrobiopterin (H2biopterin), biopterin, or riboflavin was detected. These findings suggest that NOS may share cofactors between two identical subunits via high-affinity binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMed1992

Retention reproducibility of basic drugs in high-performance liquid chromatography on a silica column with a methanol-high-pH buffer eluent. Changes in selectivity with the age of the stationary phase.

The long-term reproducibility of the separation of basic drugs by high-performance liquid chromatography using a silica column with a methanol-high-pH eluent was examined. The relative capacity factors of specific tertiary amines changed systematically compared with the other drugs on storage of the columns for 1 year. The changes were enhanced on storing the column in mobile phase and were accelerated by prolonged washing with water. A comparison of freshly packed columns suggested that similar changes also occurred with the dry silica on storage. These effects may be a contributor to previously observed batch-to-batch differences in the silica.

Caffeine↗
PubMed1992

Nonreceptor mediated nuclear accumulation of insulin in H35 rat hepatoma cells.

We previously demonstrated that insulin accumulated in the nucleus in several cell types and partially characterized the uptake mechanisms and pathways in H35 rat hepatoma cells. Nuclear accumulation of insulin was energy independent, time, temperature, and insulin concentration dependent, but apparently nonsaturable. This study investigated further the initial endocytotic pathways that contribute to the nuclear accumulation of insulin using trypsin treatment of the cells to prevent insulin binding to its plasma membrane receptor. Total cell-associated, intracellular, and nuclear insulin were compared in control and trypsin-treated H35 hepatoma cells. Trypsin treatment markedly decreased total cell-associated and intracellular insulin as well as the nuclear accumulation of insulin when cells were incubated with 2.8 ng/ml insulin. When the cells were incubated with 100 ng/ml insulin, trypsin treatment totally inhibited insulin binding to the plasma membrane for at least 90 min. However, intracellular accumulation of insulin was reduced by only 50% at 60 min, and trypsin treatment failed to inhibit the nuclear accumulation of insulin. Chemical extraction and Sephadex G-50 chromatography revealed nuclear associated insulin in trypsin-treated cells was identical to that in control cells incubated with either 2.8 or 100 ng/ml insulin. These results suggest that a nonreceptor mediated uptake pathway, i.e., fluid-phase endocytosis, contributed significantly to the nuclear accumulation of insulin at high insulin concentrations, but at lower insulin concentrations the receptor-mediated pathway predominated. No matter which initial endocytotic route was used to internalize insulin, the insulin apparently associated with the same nuclear matrix proteins. This association of insulin with the nuclear matrix may be involved in regulation of nuclear events such as cell growth and differentiation or gene transcription.

Animals↗
PubMed1992

Colocalization of transforming growth factor-alpha and a functional epidermal growth factor receptor (EGFR) to the inner cell mass and preferential localization of the EGFR on the basolateral surface of the trophectoderm in the mouse blastocyst.

Results of previous studies suggested that responses of mouse blastocysts to TGF-alpha/EGF treatment are mediated by EGF receptors (EGFR) located on the apical surface of the trophectoderm (TE). We report here results of experiments using gold-labeled EGF that confirm the presence of these apically located EGFRs. In addition, immunoelectron microscopy (IEM) studies using anti-EGFR antibodies indicate that the receptor is preferentially distributed on the basolateral surface of the TE. Furthermore, the receptor is also present on the inner cell mass (ICM) and is likely to be functional, since treatment of isolated ICMs with TGF-alpha affects [35S]methionine uptake and incorporation into acid-insoluble material. IEM was also used to demonstrate that EGF, which is not synthesized by the mouse preimplantation embryo, is present in both the oviduct and the uterus. Maternally derived EGF is present in both ICM and TE cells in freshly isolated blastocysts, but is present in greatly reduced amounts following overnight culture of blastocysts in vitro. Last, IEM was also used to demonstrate that TGF-alpha is preferentially localized to the ICM and polar TE. The co-localization of TGF-alpha and functional EGFRs to the ICM and polar TE suggests potential autocrine, juxtacrine, and paracrine roles for TGF-alpha in blastocyst development.

Amino Acids↗
PubMed1992

Value of radiograph audit in an accident service department.

In our accident service department all trauma radiographs are reported acutely and those misinterpreted by the casualty officers are presented at the daily clinicoradiological conference. We have reviewed this practice over a 6-month period. From over 25,000 patients attending the accident service, 16,246 radiographs were requested and reported. Of these, 456 (2.8 per cent) were considered to have been potentially misinterpreted. The errors included 167 (1 per cent) missed fractures, 55 (0.3 per cent) suspected fractures and 72 (0.4 per cent) false-positive diagnoses of fracture. Subsequently, 114 (0.7 per cent) patients required recall for treatment or further imaging. Incorrect diagnoses were seen most frequently in the more commonly injured anatomical sites--the ankle, wrist, foot, elbow and hand. However, the incidence of misinterpretation was highest in examination of the fingers, especially in children. We believe that these low figures are principally the result of involving both orthopaedic surgeons and radiologists at the formal daily conference. We regard our system of audit as beneficial to patients' care and anticipate reduced litigation which may offset the increased cost of audit.

Child↗
PubMed1992

Insulin, insulin-like growth factors and glucose transporters: temporal patterns of gene expression in early murine and bovine embryos.

mRNA phenotyping by the reverse transcription-polymerase chain reaction (RT-PCR) method was used to compare the patterns of expression of insulin and insulin-like growth factor (IGF) ligand and receptor genes in preimplantation bovine embryos with those established previously for preimplantation murine embryos. In the early bovine embryo, transcripts for IGF-I, IGF-II and mRNAs encoding receptors for insulin, IGF-I and IGF-II were all detectable at all embryo stages from the 1-cell zygote to the blastocyst. In the mouse, IGF-II ligand and receptor mRNAs were not expressed until the 2-cell stage, and the insulin and IGF-I receptor mRNAs were not detectable until the 8-cell stage. Since transcriptional activation of the embryonic genome occurs at the 8- to 16-cell stage in the bovine embryo and at the 2-cell stage in the murine embryo, it is suggested that these transcripts are products of both the maternal and embryonic genomes in the bovine embryo whereas in the mouse they are present only after activation of the embryonic genome. Transcripts for insulin were not detected in preimplantation embryos of either species. Colloidal-gold immunocytochemistry with antibodies directed against the insulin receptor, IGF-I receptor and IGF-I ligand has confirmed the presence of these molecules in bovine blastocysts. RT-PCR and indirect immunofluorescence procedures demonstrated that the glucose transporter (GLUT) isoform 1 is present in murine embryos from the oocyte to blastocyst stage whereas GLUT 2 expression begins at the 8-cell stage.

Animals↗
PubMed1992

Sitting balance in spinal deformity.

A computerized pressure plate system was used to analyze the sitting pressure distribution and balance of 100 subjects with both normal and abnormal spines. Normal subjects had a balanced sitting posture with the weight taken evenly on each ischial tuberosity. Patients with idiopathic scoliosis showed significant sitting imbalance especially in the presence of lumbar curves. Bracing improved the sitting balance and stability in most patients. Abnormal sitting patterns were seen with the spinal deformities of myelodysplasia or cerebral palsy. Some patients with severe scoliosis had very asymmetric patterns, which correlated with their loss of sitting stability. The kyphosis of myelodysplasia produced an abnormal tripod sitting pattern due to pelvic flexion and a hyperlordosis of cerebral palsy a pubic sitting pattern due to pelvic extension. The patients studied after spinal fusion also had poor sitting balance and occasionally persisting decubitus ulceration.

Cerebral Palsy↗