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Biomedical subjects

R G Thompson

Publications and source records attributed to R G Thompson.

At least 19 recordsLinked to original sources
PubMed1992

Detection of nicotinic receptor ligands with a light addressable potentiometric sensor.

The nicotinic acetylcholine receptor, purified from Torpedo electric organ, was coupled to a light addressable potentiometric sensor (LAPS) to form a LAPS-receptor biosensor. Receptor-ligand complexes containing biotin and urease were captured on a biotinylated nitrocellulose membrane via a streptavidin bridge and detected with a silicon-based sensor. Competition between biotinylated alpha-bungarotoxin and nonbiotinylated ligands formed the basis of this assay. This biosensor detected both agonists (acetylcholine, carbamylcholine, succinylcholine, suberyldicholine, and nicotine) and competitive antagonists (d-tubocurarine, alpha-bungarotoxin, and alpha-Naja toxin) of the receptor with affinities comparable to those obtained using radioactive ligand binding assays. Consistent with agonist-induced desensitization of the receptor, the LAPS-receptor biosensor reported a time-dependent increase in affinity for the agonist carbamylcholine as expected, but not for the antagonists.

Animals↗
PubMed1991

Pharmacological specificity of a nicotinic acetylcholine receptor optical sensor.

The pharmacological specificity of a nicotinic acetylcholine receptor (nAChR) optical biosensor was investigated using three fluorescein isothiocyanate (FITC)-tagged neurotoxic peptides that vary in the reversibility of their receptor inhibition: alpha-bungarotoxin (alpha-BGT), alpha-Naja toxin (alpha-NT), and alpha-conotoxin (GI) (alpha-CNTX). Kinetic analysis of the time course of binding of FITC-neurotoxins to the nAChR-coated fiber gave association rate constants (k+1) of 8.4 x 10(6) M-1 min-1 for FITC-alpha-BGT, 6.0 x 10(6) M-1 min-1 for FITC-alpha-NT and 1.4 x 10(6) M-1 min-1 for FITC-alpha-CNTX. The dissociation rate constants (k-1) for the three neurotoxins were 7.9 x 10(-3) min-1. 4.8 x 10(-2) min-1 and 8.0 x 10(-1) min-1 for FITC-alpha-BGT. FITC-alpha-NT and FITC-alpha-CNTX, respectively. The equilibrium dissociation constant (Kd) values for the three toxins. calculated from these rare constants, were similar to published values obtained from tissue responses or ligand binding assays. The optical signal generated by FITC-alpha-NT binding to the nAChR-coated fiber was effectively quenched by agonists and antagonists of the nAChR but not by most of the tested agonists and antagonists of muscarinic cholinergic, adrenergic, glutamatergic, serotonergic, dopaminergic or GABAergic receptors. Interestingly, 5-hydroxy-tryptamine, haloperidol and (+)cis-methyldioxolane gave significant inhibition of FITC-alpha-NT binding to the immobilized receptor. Equilibrium constants of inhibition (Ki) for d-tubocurarine (d-TC) and carbamylcholine (carb) were determined from competition studies using FITC-alpha-CNTX. FITC-alpha-NT or FITC-alpha-BGT as probes for receptor occupancy. When the more reversible probe FITC-alpha-CNTX was used, the Ki value for d-TC was an order of magnitude lower than those determined using the less reversible probes. Ki values for carb however, were independent of the FITC-toxin probe used.

Biosensing Techniques↗
PubMed1990

Opal phytoliths found on the teeth of the extinct ape Gigantopithecus blacki: implications for paleodietary studies.

Identification of opal phytoliths bonded to the enamel surface of the teeth of Gigantopithecus blacki indicates that this extinct ape had a varied diet of grasses and fruits. By using the scanning electron microscope at magnifications of 2000-6000x specific opal phytoliths were observed and photographed on the fossilized teeth of an extinct species. Since opal phytoliths represent the inorganic remains of once-living plant cells, their documentation on the teeth of Gigantopithecus introduces a promising technique for the determination of diet in extinct mammalian species which should find numerous applications in the field of paleoanthropology as well as vertebrate paleontology.

Animals↗
PubMed1990

Biosynthetic human growth hormone in the treatment of growth hormone deficiency.

A total of 309 previously untreated children with growth hormone deficiency (GHD) (219 boys, 90 girls; mean age 8.4 +/- 3.9 years, range 1.5-19 years) were treated for up to 3 years in an ongoing trial designed to examine the long-term efficacy and safety of biosynthetic somatropin (rhGH). The children were treated with rhGH, 0.06 mg/kg (0.16 IU/kg) three times weekly. In the prepubertal children, the mean height velocity increased during the first year from 3.8 +/- 1.8 cm/year to 8.9 +/- 2.2 cm/year (n = 188). During the second and third years, their height velocities were 7.1 +/- 1.1 (n = 147) and 6.3 +/- 1.2 cm/year (n = 64), respectively. The height velocity SDS increased from -2.5 +/- 1.9 before treatment to 3.1 +/- 2.6 during the first year of treatment in the prepubertal children. The mean pretreatment height velocity in those with idiopathic GHD (3.8 +/- 1.6 cm/year) did not differ from that in children with organic GHD (3.8 +/- 2.3 cm/year). In addition, the height velocities during the first year of therapy did not differ significantly with respect to the aetiology of GHD. For the children who entered puberty during the study, the mean height velocity increased from 3.0 +/- 1.7 cm/year before treatment to 8.4 +/- 2.3 cm/year during the first year of rhGH therapy. In the first year, the height velocity of children with a bone age of less than 5 years (9.4 +/- 2.3 cm/year) was significantly greater than that in children with a bone age of 5-10 years (8.4 +/- 1.8 cm/year) or greater than 10 years (7.8 +/- 2.2 cm/year: p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Resonance Raman studies of Escherichia coli sulfite reductase hemoprotein. 1. Siroheme vibrational modes.

Resonance Raman (RR) spectra are reported for the hemoprotein subunit (SiR-HP) of Escherichia coli NADPH-sulfite reductase (EC 1.8.1.2) in various ligation and redox states. Comparison of the RR spectra of extracted siroheme and the mu-oxo FeIII dimer of octaethylisobacteriochlorin with those of mu-oxo FeIII octaethylchlorin dimer and mu-oxo FeIII octaethylporphyrin dimer demonstrates that many siroheme bands can be correlated with established porphyrin skeletal modes. Depolarization measurements are a powerful tool in this correlation, since the 45 degrees rotation of the C2 symmetry axis of the isobacteriochlorin ring relative to the chlorin system results in reversal of the polarization properties (polarized vs anomalously polarized) of bands correlating with B1g and B2g modes of porphyrin. Various SiR-HP adducts (CO, NO, CN-, SO3(2-] show upshifted high-frequency bands, characteristic of the low-spin state and consistent with the expected core size sensitivity of the skeletal modes. Fully reduced unliganded SiR-HP (both siroheme and Fe4S4 cluster reduced) in liquid solution displays RR features comparable to those of high-spin ferrous porphyrins; on freezing, the RR spectrum changes, reflecting an apparent mixture of siroheme spin states. At intermediate reduction levels in solution a RR species is observed whose high-frequency bands are upshifted relative to oxidized and fully reduced SiR-HP. This spectrum, thought to arise from the "one-electron" state of SiR-HP (siroheme reduced, cluster oxidized), may be due to S = 1 FeII siroheme.

Binding Sites↗
PubMed1989

Chlamydia trachomatis infection in late pregnancy: a prospective study.

During a 1-year period, 3309 women were screened in pregnancy for Chlamydia trachomatis infection. A cervical swab was taken and chlamydial antigen was detected, using a monoclonal antibody ELISA technique, in 198 women (6%). The prevalence of chlamydial infection was high in women under 20 years (14.5%), single women (14.2%) and black women (16.8%). Binomial regression of these data estimates a relative risk of 2.9 for women under 20 years compared with women aged 25 and over. There was an interaction between race and marital status with a high risk in single white and single asian women (2.3, 4.5 respectively) but a similar risk in black single and black married women (3.0, 4.0 respectively). Parity and social class did not effect the prevalence of antigen carriage. There was no demonstrable effect of maternal antigen carriage on outcome of pregnancy, gestation or admission to neonatal unit. Infants of 174 antigen-positive mothers were followed-up. Tissue culture for Chlamydia trachomatis was positive in 43 (24%) infants. Complications occurred in 23 (53%): 17 had conjunctivitis, three had lower respiratory tract infection and three both complications. Amongst 131 chlamydia-negative infants, complications occurred in 21 (16%). Since this infection, in infants, responds promptly to erythromycin therapy, screening and treatment in pregnancy will convey little benefit in prevention of perinatal morbidity or perinatal mortality.

Adult↗
PubMed1989

Chlamydia trachomatis infection in infants: a prospective study.

In a prospective study of Chlamydia trachomatis infection in pregnancy, 198 mothers positive for chlamydial antigen were identified; the infants of 174 were followed for up to six months and C trachomatis was recovered in cell culture from 43 infants (25%). Conjunctivitis occurred in significantly more infants who were positive for C trachomatis (20 of 43, 47%) than in those who were negative (18 of 131, 14%). There were also significantly more lower respiratory tract infections among infants with positive cultures (six of 43, 14%, compared with three of 131, 2%). The chlamydial antigen enzyme linked immunosorbent assay (ELISA) was positive in 61 of 131 infants from whom C trachomatis was not recovered in cell culture. False positive results were usually associated with the isolation of Staphylococcus aureus from samples of pharyngeal aspirate. Our results confirm that C trachomatis infection is a common cause of neonatal conjunctivitis, and respiratory infection in the first few months of life, with an incidence of 8.2/1000 live births. Because the infection is easily treated by oral erythromycin, however, screening during pregnancy is not warranted.

Chlamydia Infections↗
PubMed1989

Biosynthetic human growth hormone: current status and future questions.

Human growth hormone derived from human pituitaries resulted in excellent growth in children with growth hormone deficiency but limited supplies in many countries prevented treatment of all children, delayed the onset of therapy, and/or forced the use of doses that may have been less than optimal. Recent advances in technology allow the production of byosynthetic human growth hormone (hGH) by recombinant methods resulting in increased supplies of hormone. More than 200 previously untreated children with growth hormone deficiency have been evaluated for two years or longer while receiving biosynthetic natural sequence hGH (somatropin). The mean growth velocity of 3.6 cm/yr prior to therapy increased to 8.8 cm/yr after one year and 7.25 cm/yr in the second year. Growth response was inversely related to age when calculated as cm/yr. This response paralleled the normal decrease in growth velocity as children approach puberty. Children with hGH deficiency who had previously received replacement hGH were enrolled in a double-blind study using either 0.06 or 0.10 mg/kg thrice weekly for 12 months. Growth rate was significantly greater with the higher dose during the first six months but not during the second six month period. The use of a higher dose of hGH must be individualized as not all patients have accelerated growth with the increased dose and the mean group response is not permanent. Multiple questions remain unanswered after three decades of treating growth hormone deficiency. Are the current criteria for diagnosis of growth hormone deficiency appropriate? What dose of hGH is correct? Do children need increases in replacement therapy as their height approaches normal?(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1979

Triglyceride concentrations: the disaccharide effect.

The mean 24-hour or integrated concentration of triglyceride is significantly higher when dietary sucrose is provided rather than an equivalent amount of its component monosaccharides, glucose and fructose. In contrast, the plasma triglyceride concentration after a 12-hour fast is not significantly different.

Adult↗
PubMed1979

Serum cholesterol and triglycerides in children with growth hormone deficiency.

To test the hypothesis that hyperlipidemia is characteristic of growth hormone deficiency in childhood, we have measured serum cholesterol and triglyceride concentrations in 24 euthyroid children with growth hormone deficiency. Although modest elevations of cholesterol and/or triglyceride above the 95th percentile for age, race, and sex were present in 46% of the children studied, the mean (+/- 1 SD) cholesterol of 173 +/- 36 mg/dl and the mean triglyceride of 80 +/- 42 mg/dl were not significantly different from published normal mean values. Administration of human growth hormone for 4 mo to 15 of these subjects did not alter these mean cholesterol and triglyceride values, but did result in a marked improvement in the growth rate. Some individuals (n = 6) with a subnormal growth response to therapy and/or a low serum thyroxine and high serum cholesterol were treated for an additional 4 mo with growth hormone and thyroid hormone together. There was a statistically significant decrement in serum cholesterol in this group. We conclude that modest hyperlipidemia does exist in some children with growth hormone deficiency. Subclinical hypothyroidism may play a role in the hypercholesterolemia of some children, as may growth hormone deficiency itself. Any association of growth hormone and lipid metabolism remains to be clarified.

Adolescent↗
PubMed1979

Triglyceride integrated concentrations: effect of variation of source and amount of dietary carbohydrate.

The effect of changes in the amount of dietary carbohydrate (45 or 65% of total energy) and in the source of carbohydrate (sucrose or corn syrup) on plasma triglyceride and cholesterol concentrations was studied in eight healthy males. Subjects ingested each of the four formula diets for 10 days in a latin square sequence. Diet-induced response was assessed by measurement of plasma lipid concentrations in blood obtained after overnight fast and by measurement of the mean plasma lipid concentrations--designated the integrated concentration--of blood obtained by 24 hr continuous blood withdrawal. The fasting plasma triglyceride concentration increased significantly during ingestion of the high carbohydrate diet (P less than 0.005) but was not significantly influenced by the source of carbohydrate calories. The 45% carbohydrate diets induced larger meal associated plasma triglyceride variation than 65% diets. Sucrose-containing diets induced significantly higher plasma triglyceride integrated concentrations than corn syrup diets, whether provided as 45% (P less than 0.05) or 65% (P less than 0.005) of total energy. Diet-induced changes in fasting or integrated plasma cholesterol concentration were minimal.

Adult↗
PubMed1979

Bystander-initiated cardiopulmonary resuscitation in the management of ventricular fibrillation.

We assessed the influence of bystander-initiated cardiopulmonary resuscitation upon outcome in 316 consecutive patients treated for out-of-hospital ventricular fibrillation. Of 109 patients who received bystander-initiated cardiopulmonary resuscitation, 47 (43%) were ultimately discharged home. Of 207 patients for whom resuscitation was delayed until arrival of fire department personnel, 43 (21%) survived (P less than 0.001). Improved survival was largely due to a reduction in subsequent hospital mortality rather than to a higher rate of initially effective resuscitation. In a separate analysis of 118 patients treated at a single institution after resuscitation, the reduced hospital mortality reflected a decrease in deaths due to shock and to anoxic encephalopathy. In addition, neurologic dysfunction was significantly less common if bystanders had initiated cardiopulmonary resuscitation. Bystander participation in cardiopulmonary resuscitation represents an important adjunct to a rapid-response emergency care system.

Consciousness↗
PubMed1979

A new method of patellectomy for patellofemoral arthritis.

Total patellectomy, although it has a biomechanical disadvantage in that it may lead to a degree of quadriceps weakness, is frequently indicated in selected patients. Numerous different techniques of performing patellectomy have been described. In this paper, we present a technique of performing a patellectomy in which the continuity of the quadriceps mechanism is not disrupted and the vastuc medialis is advanced. Twenty-six patients (twenty-nine knees) in whom the procedure was performed were studied retrospectively. The findings in this series showed 90 per cent good or excellent results, two cases of extensor lag, an average of 118 degrees of knee flexion, minimum quadriceps atrophy with good strength, and minimum postoperative immobilization. The method presented has the important advantage of an easier, smoother postoperative knee-rehabilitation period, which is extremely advantageous in elderly patients.

Adolescent↗
PubMed1978

Endogenous norepinephrine and serotonin within the hippocampal formation during the development and recovery from septal hyperreactivity.

Fluorometric analysis of serotonin (5-HT) and norepinephrine (NE) content of the hippocampal formation revealed that biogenic amines are distributed heterogeneously in the dorsoventral axis, and that NE also exhibits a heterogeneous distribution in the medial-lateral direction while 5-HT does not. Dissection of the hippocampus into its dorsal and ventral halves shows that both NE and 5-HT exhibit higher concentrations in the ventral hippocampus in comparison to its dorsal counterpart. A dissection which separated the cell fields CA 1 and 2 from CA 3 and 4 and the dentate gyrus showed NE to be the highest in the latter region, while 5-HT was uniformly distributed between the two regions. Taken together, these data indicate that NE is more highly concentrated in the CA 3 and 4 and dentate area of the ventral hippocampus while 5-HT concentration differences are apparent only in a dorsal-ventral dissection. Concentrations of NE and 5-HT in the dorsal and ventral hippocampus were also determined at 1, 3, 6, 11, 16, 24, and 30 days following a lesion to the septal nuclei. The results demonstrate that biogenic amine levels in the dorsal hippocampus achieve maximal depletion earlier than do their ventral counterparts, and that percent depletion is greater for 5-HT than NE in both dorsal and ventral areas. On the first day following septal lesions, 5-HT is increased above normal levels. Sixteen days after septal lesion, 5-HT is substantially depleted below normal levels. In addition, by 30 days, 5-HT shows significant return toward normal levels from its earlier depleted state. Behavioral changes related to sensory reactivity correlate with the relative decreases of NE and 5-HT following septal lesions.

Animals↗