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Biomedical subjects

C Roberts

Publications and source records attributed to C Roberts.

At least 217 records · Page 12Linked to original sources
PubMed1996

Functional characterization of the 5-HT terminal autoreceptor in the guinea-pig brain cortex.

1 In guinea-pig cerebral cortical slices in vitro we have shown that the rank order of potency of 5-hydroxytrptamine (5-HT), 5-carboxamidotryptamine and sumatriptan for inhibition of electrically stimulated [3H]-5-HT release correlates well with published data on their 5-HT1D receptor binding affinities. 2 Both the non-selective 5-HT1D receptor antagonist, methiothepin and the selective 5-HT1D receptor antagonist, N-[4-methoxy-3-(4-methyl-1-piperazinyl]phenyl]-2'-methyl-4'- (5-methyl-1,2,4-oxadiazole-3-yl) [1,1-biphenyl]4-carboxamide (GR127935) increased stimulated [3H]-5-HT release per se and also attenuated agonist-induced inhibition of [3H]-5-HT release. GR127935 (10 nM-100 nM) produced a pA2 of 9.0 against 5-HT, which is consistent with its 5-HT1D receptor binding affinity. 3 From these findings we conclude that, in guinea-pig cerebral cortex, the 5-HT terminal autoreceptor is of the 5-HT1D receptor subtype. However, three observations suggest the presence of multiple terminal autoreceptors: shallow inhibition curves to the agonists; a shallow Schild slope of GR127935 antagonism and differences in the maximal responses to 5-HT between whole cortex and frontal cortex.

Animals↗
PubMed1996

Analysis of diaphragm EMG signals: comparison of gating vs. subtraction for removal of ECG contamination.

The diaphragm electromyogram (EMGdi) conveys information relating to the mechanisms of respiration; however, electrocardiogram (ECG) contamination can compromise the accuracy of data derived from this signal. We examine the EMGdi recorded from anesthetized spontaneously breathing dogs via implanted electrodes to assess the extent of the error introduced by the ECG contamination and the effectiveness of ECG gating in reducing this error. Because ECG subtraction has been shown to generate accurate results for such applications, it is used as the gold standard. Analysis of variance methods are employed to compare results derived from the EMGdi data after ECG subtraction with corresponding results derived from the original data and from the data after ECG gating. Estimates of EMGdi variables obtained by using subtraction and gating techniques were not significantly different, indicating that gating can be employed on these signals to reduce ECG contamination without affecting the accuracy of the derived data. Results also show that at EMG-to-ECG power ratios > 13.3 dB, ECG contamination does not significantly affect estimates of the EMGdi variables.

Animals↗
PubMed1996

The physiological effects of alcohol misuse.

Alcoholism is costly both in human and monetary terms. A thorough nursing assessment will lead to early detection and treatment. Further tissue damage and suffering can be reduced by early intervention.

Alcoholism↗
PubMed1996

Birth-weight percentiles by gestational age, Connecticut 1988-1993.

Extreme birth weights are associated with increased infant mortality and morbidity. Identifying infants of extreme birth weight is important for both clinical assessment and public health research. This study aimed to produce charts of birth-weight percentiles by gestational age for male and female, black and white infants in Connecticut. Data were obtained from registrations of live births to Connecticut residents in Connecticut, 1988-1993. During this period 263,032 births were registered to black and white women. Birth weight was missing in only 90 records but gestational age was missing in 29,865 (11%) records. An additional 0.5% of births were excluded because the recorded birth weight was an extreme outlier for the recorded gestational age. Birth records with missing gestational age had lower mean birth weights and proportionately more births < or = 1500 g when compared to birth records where gestation was reported; however the magnitude of the differences was small. Our charts provide population-based birth-weight percentiles by gestational age based on the most recent Connecticut birth data available. They are the most appropriate population norms available for Connecticut clinicians and researchers.

Birth Weight↗
PubMed1995

A survey of job stress and job satisfaction among DSAs in the north-west of England.

This study was a survey of job stress and job satisfaction among DSAs in general practice in the north-west of England during 1993. The results suggest that severe overall job stress and dissatisfaction were not prevalent but do present an important problem for a minority. The chief sources of stress are ranked. Those which caused moderate to severe stress were: running behind time, feeling under-valued by the dentist and handling difficult patients. Those experiencing greater stress outside work were more likely to report stress within it. Having a regular staff meeting, an annual salary review and a clear job description were associated with significantly less job stress.

Adult↗
PubMed1995

A mechanism for pentamidine-induced hyperkalemia: inhibition of distal nephron sodium transport.

OBJECTIVES: To determine whether pentamidine directly affects the transport of renal ions and thus provides a mechanism for hyperkalemia, which develops in as many as 100% of patients with the acquired immunodeficiency syndrome (AIDS) who receive pentamidine for more than 6 days. DESIGN: Transepithelial and single-channel electrical measurements were made on two models of distal-nephron ion transport: an amphibian distal-nephron cell line (A6) and primary cultures of rabbit cortical collecting tubules. RESULTS: Luminal bath application of pentamidine to A6 monolayers inhibited the amiloride-sensitive, short-circuit current with a 50% inhibitory concentration of 700 microM (five experiments). In the principal cell apical membranes of cortical collecting tubule primary cultures, amiloride-sensitive, 4-picosiemen Na+ channels in cell-attached patches were also identified. When the luminal membrane was directly exposed to 1.0 microM of pentamidine in the patch pipette solution, channel activity decreased by 40% (11 experiments). Channel inhibition rapidly reversed with washout of intrapipette pentamidine (four experiments). In contrast, replacement of either the luminal bath outside the patch pipette (four experiments) or the serosal bath (five experiments) with pentamidine did not significantly affect Na+ channel activity in the patches. CONCLUSIONS: Luminal or "urinary" pentamidine inhibits distal nephron reabsorption of Na+ by blocking apical Na+ channels in a manner similar to "potassium-sparing" diuretics (for example, amiloride and triamterene). This results in a decrease in the electrochemical gradients that drive secretion of distal nephron K+. Because pentamidine is eliminated through urinary excretion, this renal tubular effect provides a mechanism for pentamidine-induced hyperkalemia.

Animals↗
PubMed1995

Psychological and rheumatic symptoms of women requesting silicone breast implant removal.

In this case series, we describe the psychological and rheumatic symptoms of 52 women requesting breast implant removal. Main outcome measures include psychological evaluation with the Brief Symptom Inventory and the Beck Depression Inventory. Clinical evaluation was performed using a rheumatic symptom survey. Results noted elevation of all Brief Symptom Inventory subscales (highest in Somatization and Obsessive-Compulsive), and the Beck Depression Inventory showed mild depression. Rheumatic survey noted a mean of 12 of 23 symptoms. In conclusion, psychological distress and mild depression are noted in this group, who also may experience rheumatic symptoms of connective tissue disease. There was a moderate positive correlation between rheumatic symptoms and psychological distress.

Breast Implants↗
PubMed1995

Analysis of the inherent error of the TMS-1 Topographic Modeling System in mapping a radially aspheric surface.

The potential spherical bias of the Topographic Modeling System (TMS) in measuring a radially aspheric surface was investigated. The radii of curvature of an ellipsoidal surface were measured experimentally using the TMS, and calculated using both an instantaneous radius of curvature formula and a spherically biased algorithm for comparison. Measurements were made aligned and under four conditions of misalignment. A sphere with the same radius of curvature as the apex of the ellipsoid was used to document the fundamental performance of the system. The TMS demonstrated increasing error from center to periphery in measurement of an ellipsoid with 7.5 mm apical radius of curvature and 0.5 eccentricity. Greater than 3 D of error was present at 4 mm from the apex. The misalignment error was small compared to the inherent error in the system performance. The TMS does not accurately measure the instantaneous radii of curvature of an ellipsoidal surface due to an inherent spherical bias. In addition, the spherically biased system may not detect subtle shifts in curvature in the peripheral regions, causing potentially inaccurate reconstruction of patterns of curvature.

Algorithms↗
PubMed1995

Neuropsychological function and MRI abnormalities in neurofibromatosis type 1.

This study investigated the relationship between MRI abnormalities and cognitive function in neurofibromatosis type 1.40 children aged eight to 16 years underwent comprehensive neuropsychological, medical and neuroradiological assessments. MRI scans revealed a characteristic pattern of T2-weighted signals ('UBOs') located primarily in the basal ganglia, brainstem and cerebellum in 25 of the children. Reductions in global IQ, attention, and visuopatial and executive functions were shown to occur in association with the presence of UBOs. These findings establish a link between changes in neuropsychological functions and MRI abnormalities in NF-1, and further support neuropathological findings which suggest that UBOs may be a manifestation of delayed or disordered myelination.

Adolescent↗
PubMed1995

Temporal recovery of short-term repopulating HSC subpopulations in marrow following schedule-dependent administrations of IL-1 alpha and M-CSF.

Studies were carried out to establish the temporal effects of abbreviated administrations of IL-1 and IL-1 plus M-CSF as rescue agents on multipotential and short-term repopulating hematopoietic stem cell (HSC) subpopulations in murine marrow treated with a myelosuppressive dose of 150 mg/kg 5-FU. The recovery kinetics for high-proliferative-potential colony-forming cells (HPP-CFC), CFU-S8 and -S12, and both CFU-M and CFU-G compartments were monitored over a 14-day interval in 5-FU-treated bone marrow (FUBM) following daily cytokine injections over a 4-day interval. Both IL-1 and the coadministration of IL-1 and M-CSF rapidly enhanced the recovery of the HPP-CFC in FUBM to supranormal levels and maintained these levels for extended intervals. Moreover, since M-CSF was unable to influence the recovery of the HSC subpopulations in FUBM by itself, the results of the two cytokines amounted to a synergistic effect on the recovery of the HPP-CFC in FUBM and a reduction of severe neutropenia in the myelosuppressed animal. Scheduling studies demonstrated that these synergistic effects were restricted to those schedules in which M-CSF was coadministered with IL-1 during the first 2 days of cytokine rescue. Finally, the recovery curves generated for the HSC and CFU-M subpopulations in response to IL-1 (with or without M-CSF) also suggest that these cytokines may conceivably alter the normal balance between proliferation and differentiation within CFU-S8 and -S12 during the accelerated recovery of hematopoiesis in FUBM.

Animals↗