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Biomedical subjects

R Gilbert

Publications and source records attributed to R Gilbert.

At least 19 recordsLinked to original sources
PubMed1992

A K+ current in Xenopus muscle cells which shows inactivation.

The purpose of this study was to describe an inactivating potassium current that is present in Xenopus muscle cells in culture. Whole cell currents were recorded from muscle cells grown in culture for 16-30 h. The majority of muscle cells had an outward current which inactivated during a 100 ms maintained depolarization. The outward current was reduced by tetraethylammonium or the aminopyridines, but not completely eliminated by either agent. Depolarizing prepulses reduced both the peak current and the late component of the current. The results suggest that by one day in culture these skeletal muscle cells develop an inactivating outward potassium current.

Animals↗
PubMed1992

Two classes of potassium currents in Xenopus muscle cells in young cultures.

The aim of the present study was to determine if both inactivating and non-inactivating potassium currents occur in skeletal muscle cells at early times in culture. Whole cell current was recorded from embryonic muscle cells within 4-10 h of plating. We found that in the cells which had an outward current, half had a current that did not inactivate and half had a current that inactivated during a maintained depolarization (100 ms). The two groups of cells did not differ in their age in culture or resting membrane potential. The results indicate that Xenopus skeletal muscle cells can acquire both types of outward potassium current early in culture life.

Animals↗
PubMed1992

Combined effect of infection and heavy wrapping on the risk of sudden unexpected infant death.

Three methods were used to investigate the role of infection in sudden unexpected infant death (SUD): (i) microbiological comparison of SUD victims and matched, live, community controls; (ii) postmortem classification of the contribution of infection to death; and (iii) case-control analysis of the relative risk associated with both infection and heavy wrapping. Limited sampling from the upper respiratory tract and gut in SUD victims and controls showed no significant excess of viral infection in the SUD victims (odds ratio = 1.98, 95% confidence interval (CI) 0.9 to 4.5). At postmortem examination, infection explained death in 3/95 babies and may have contributed to death in 37/95. Over 70 days of age, the combined presence of viral infection and wrapping in excess of 10 togs produced an odds ratio of SUD of 51.5 (95% CI 5.64 to 471.48) compared with wrapping of less than 6 togs. Viral infection was not a major risk factor as long as babies were lightly wrapped. In heavily wrapped babies the presence of a viral infection greatly increased the risk of SUD.

Bacterial Infections↗
PubMed1992

Health hazard of poorly regulated exposure during manufacture of cemented tungsten carbides and cobalt.

Forty two of 125 former workers in a factory in Syracuse, New York, which manufactured hard metal parts from tungsten carbide and cobalt, were studied by chest radiographs, spirometry, and plethysmographically determined lung volumes. The plant was closed in 1982 and the studies were performed in 1983-5. Recorded measurements of carbide dust concentrations were only mildly excessive by modern standards, but deceitful efforts to reduce the apparent concentration of dust were known to have occurred during an inspection by the Occupational Safety and Health Administration. Lung biopsies in four cases in the study and necropsy in one of the 83 cases not studied during life showed giant cell interstitial pneumonia and appreciable concentrations of tungsten carbide. This information indicates that exposure was substantial. Four workers had evidence of pulmonary fibrosis by chest radiographs; two of these workers had normal pulmonary function. Fourteen had abnormal pulmonary function, five of whom had a restrictive pattern, eight a pattern of air trapping, and one a combined pattern. Thus radiographic, or functional abnormalities, or both occurred in 16 of the 42 cases studied. No correlation with duration of exposure was established. Progressive clinically important disease (one fatal) has been found in four ex-workers, two in each of the restrictive and air trapping groups. These findings suggest that poorly regulated dust concentrations in a hard metals factory possibly cause pulmonary abnormalities and sometimes severe illness.

Adult↗
PubMed1992

A two-bag system for continuous measurement of oxygen uptake.

Collection of mixed expired gas in a bag has been a classic method for the estimation of VO2 during the steady state but has not been employed during unsteady state exercise in part because there is a need for suspending the acquisition of data during the period of gas analysis unless many bags are used. In this study a two-bag system is described in which one bag fills while the other is analyzed. Bag volume is under the control of the operator, and we employed volumes of 30 to 50 L. Thirty-one subjects were studied with this circuit in a progressive treadmill test. Although VO2 could be falsely elevated during periods of overbreathing, this source of error could be identified and its effect reduced if VO2 was plotted against both ventilation and power requirement. Plateau values of VO2 were identified only in six subjects and the ventilatory threshold in 16.

Adult↗
PubMed1991

Functional results of muscle flap closure for sternal infection.

The morbidity and mortality of infection after median sternotomy have been substantially reduced with the advent of treatment by wide sternal resection and muscle flap closure. A study was performed comparing the cardiorespiratory function of 13 such patients before and after operation as well as with a control group of 15 patients who underwent similar procedures without complication. The groups were comparable in preoperative pulmonary function, though more patients in the study group had evidence of chronic lung disease. Patients were studied 2 to 39 months after the original procedure. Late postoperative pulmonary function test results, exercise tolerance, and oxygen uptake were not significantly different between the groups, and pulmonary function test results were unchanged in those patients who were tested preoperatively. We conclude that muscle flap reconstruction for sternal infection can be expected to give good long-term functional results. Exercise tolerance and pulmonary function may not differ from a control group of cardiac surgical patients, despite the altered composition of the chest wall. Patients with chronic lung disease may be more prone to have this complication.

Aged↗
PubMed1991

Subglottic laryngeal closure for aspiration.

Aspiration may be life threatening, particularly in those patients with severe central neurological disease. From such a group of patients, several were identified who had severe laryngeal dysfunction and aspiration. The majority of patients in this subgroup existed in a neurologically vegetative state. In an attempt to reduce the degree of aspiration they experienced, the procedure of subglottic laryngeal closure was performed. Essentially, the operation is designed to isolate the tracheal airway from the incompetent larynx. The aim is to protect the lower airway from pharyngeal contamination. In all 5 patients there was a marked improvement in general and pulmonary health.

Adult↗
PubMed1991

The effect of progressive exercise on the equilibrium rebreathing cardiac output method.

The equilibrium CO2 rebreathing method has been used in the study of exercise cardiac output (Q) in health and disease, but the requirement for a steady state has usually limited its application to step function exercise. This limits testing to only a few levels of exertion in a laboratory session. We have devised a treadmill test where the grade is flat at the beginning and rises continuously at 1%.min-1 after stable measurements are obtained during level walking. The walking speed is determined by the subject's comfort and tolerance for fast walking. In series I seven normal subjects were studied with this protocol, and an automated system was employed for estimation of Q and oxygen uptake (VO2). For comparison of steady state and progressive tests, an interpolation method was devised which furnished a value of Q (progressive) that could exist at the value of VO2 obtained during the steady state. The average difference in Q so estimated between the steady state and the unsteady state was 0.3 l.min-1, SD = 1.7. This difference was less than the difference between averages of duplicate values of Q obtained during the steady state (1.11.min-1, SD = 16), and the difference between the two differences was not significant. Based on 51 determinations of Q and VO2 in eight normal subjects the unsteady state procedure furnished an average value of the relation slope of delta Q/delta VO2(-1) of 4.8 l.l-1. We conclude that the equilibrium CO2 method can be used to depict the Q, VO2 relationship over the range of VO2 at which rebreathing is tolerable.

Adult↗
PubMed1990

Inward rectifier potassium current on embryonic Xenopus muscle cells at different times in culture.

Whole cell current recordings of Xenopus muscle cells in 1-day-old cultures revealed an inward K+ current, with properties similar to the inward rectifier of adult muscle. However, at the earliest ages (less than 10 h in culture) the time-dependent decline in the current amplitude, indicative of a depletion of extracellular K+, was not present. The change in the time-dependent decline of the current amplitude may result from a change in the channel itself or a change in the distribution of the channel in the membrane.

Animals↗
PubMed1990

Interaction between bedding and sleeping position in the sudden infant death syndrome: a population based case-control study.

OBJECTIVE: To determine the relation between sleeping position and quantity of bedding and the risk of sudden unexpected infant death. DESIGN: A study of all infants dying suddenly and unexpectedly and of two controls matched for age and date with each index case. The parents of control infants were interviewed within 72 hours of the index infant's death. Information was collected on bedding, sleeping position, heating, and recent signs of illness for index and control infants. SETTING: A defined geographical area comprising most of the county of Avon and part of Somerset. SUBJECTS: 72 Infants who had died suddenly and unexpectedly (of whom 67 had died from the sudden infant death syndrome) and 144 control infants. RESULTS: Compared with the control infants the infants who had died from the sudden infant death syndrome were more likely to have been sleeping prone (relative risk 8.8; 95% confidence interval 7.0 to 11.0; p less than 0.001), to have been more heavily wrapped (relative risk 1.14 per tog above 8 tog; 1.03 to 1.28; p less than 0.05), and to have had the heating on all night (relative risk 2.7; 1.4 to 5.2; p less than 0.01). These differences were less pronounced in the younger infants (less than 70 days) than the older ones. The risk of sudden unexpected death among infants older than 70 days, nursed prone, and with clothing and bedding of total thermal resistance greater than 10 tog was increased by factors of 15.1 (2.6 to 89.6) and 25.2 (3.7 to 169.0) respectively compared with the risk in infants of the same age nursed supine or on their side and under less than 6 tog of bedding. CONCLUSIONS: Overheating and the prone position are independently associated with an increased risk of sudden unexpected infant death, particularly in infants aged more than 70 days. Educating parents about appropriate thermal care and sleeping position of infants may help to reduce the incidence of the sudden infant death syndrome.

Age Factors↗
PubMed1990

Salmonella colonization in commercial pet turtles (Pseudemys scripta elegans).

An epidemiological survey was conducted on two commercial turtle farms in southern Louisiana to determine the reason for an apparent increase in the prevalence of Salmonella spp. in turtle hatchlings at the time of pre-export certification examination. Pond water was consistently found to be contaminated (6/36 samples) with either Salmonella newport, S. arizonae, or S. poona. Environmental specimens obtained from eggs and turtle hatcheries (204 specimens) failed to yield Salmonella spp. A sample comprising 197 hatchlings, derived from a batch previously demonstrated to be contaminated, showed a salmonella prevalence of 12%, with S. arizonae and S. poona the only serotypes isolated. Four serotypes of Salmonella sp. isolated by a certifying laboratory in 1988, and 20 salmonella isolates obtained from hatchling turtles, were all resistant to gentamicin. The emergence of gentamicin resistance in Salmonella spp. isolated from turtles will reduce the effectiveness of preventive measures in use in Louisiana since 1984.

Animals↗
PubMed1990

Post-test probability of asthma following methacholine challenge.

Using recently published data, a nomogram was constructed to estimate the likelihood of asthma following methacholine challenge. Based on Bayes' theorem, the nomogram makes use of the sensitivity and specificity of methacholine challenge to calculate the post-test probability of asthma once the physician makes a determination of the pretest probability, that is, the likelihood of asthma before the test results are considered. A family of curves is presented to cover several levels of cumulative breath units at which the test could become positive, and a single curve is presented for a negative test after 224 cumulative breath units. Separate curves are presented for smokers and nonsmokers. The estimate of pretest probability is most crucial in negative tests where likelihood of asthma is considered high, and in positive tests in patients in whom asthma is considered unlikely. Although these curves will not apply precisely to a different data base, the concept of the relationship between pretest and post-test probability helps in the interpretation of the test results and stresses the importance of using all available information in making a diagnosis.

Asthma↗
PubMed1989

Reactive airways dysfunction syndrome presenting as a reversible restrictive defect.

A 25-year-old farm worker developed acute bronchopneumonia after heavy exposure to a respiratory irritant in a silo. He recovered from the acute episode but then experienced chronic dyspnea and fatigue. Pulmonary function testing showed small lung volumes with a normal ratio of 1 s forced expiratory volume/forced vital capacity (restrictive defect). This defect improved markedly with bronchodilator treatment and changed to a mixed obstructive/restrictive defect with methacholine challenge. We believe that this is an example of the reactive airways dysfunction syndrome manifested by a restrictive rather than obstructive defect. Constriction of airways at the bronchiole or alveolar duct level is the most likely cause of the syndrome.

Adult↗
PubMed1989

Calcium current in embryonic Xenopus muscle cells in culture.

We have investigated the appearance of calcium current in Xenopus muscle cells in 1- to 6-day-old cultures. Whole cell currents were recorded using a patch-clamp amplifier with sodium and potassium replaced with tetraethylammonium and cesium, respectively, and BaCl2 used in place of CaCl2. When the muscle membrane was depolarized above -30 mV, a slow inward current was activated, the current reached a peak amplitude near 0 mV, and an outward current became apparent above +10 mV. This slow current was enhanced by adding barium or Bay K 8644 to the extracellular recording solution and was blocked by the addition of cobalt, cadmium, or the dihydropyridines nifedipine or (+)PN 200-110. Taken together these results indicate the presence of an inward calcium current mediated through L-type channels. Thirty-one percent of the cells examined on the first day in culture showed no discernible slow inward current; however, as the age of the culture increased, all cells showed slow inward current and there was an increase in the amplitude of the current. A small proportion of the muscle cells (5 out of 34) also showed a fast activating and inactivating inward current. This current, which activated at more hyperpolarized potentials (-40 mV) was only present when 5 mM ATP was included in the internal recording solution. It also appeared to be mediated through a calcium channel but not a dihydropyridine, sensitive channel.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1988

Chemical synthesis, cloning and expression in mammalian cells of a gene coding for human tissue-type plasminogen activator.

A 1610-bp DNA duplex coding for human tissue-type plasminogen activator has been chemically synthesized using the phosphoramidite procedure, adapted for a custom-built gene synthesizer. The synthesizer, which was designed for both simplicity and speed, permits the rapid construction of relatively large genes and compares favorably in speed with alternative cDNA isolation procedures. The plasminogen activator gene has been expressed in mammalian cells and shown to produce authentic protein by an immuno-activity assay.

Base Sequence↗