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Biomedical subjects

G C Scott

Publications and source records attributed to G C Scott.

At least 37 records · Page 2Linked to original sources
PubMed1991

Transdermal delivery of the alpha 2-agonist clonidine does not alter airways responses to inhaled histamine or methacholine.

Previous studies have reported that the inhalation of the alpha 2-agonist clonidine decreases airways reactivity. Other studies have shown that oral doses of clonidine acutely increase airways reactivity to histamine, but not to methacholine. Recently, a transdermal clonidine delivery system (TTS) has been approved for use, and there is an increasing interest in using this system for management of postmenopausal and smoking cessation symptoms. To our knowledge, the effects of TTS on airways function in asthmatics have not been reported. The purpose of this study was to determine if use of TTS would alter airways reactivity. Six asymptomatic asthmatic subjects underwent a baseline methacholine challenge (M). In a double-blinded randomized crossover fashion, either a placebo or a TTS patch (TTS-1, 0.1 mg/day), was applied to the arm. Four days later, the challenge was repeated. After two to three days of washout, the alternate patch was applied, and a second challenge was performed. Several days later, a second baseline challenge was repeated. This sequence was then repeated using histamine (H). The patch was well tolerated by all subjects. There was no significant change in resting pulse or blood pressure, and for the group no change in airways reactivity to either M or H was noted. In conclusion, while use of TTS-1 does not improve airways function, its short-term use in asthmatics is not associated with an increase in airways reactivity.

Administration, Cutaneous↗
PubMed1990

Oscillatory and step response electromechanical phenomena in human and bovine bone.

Bone generates electrical potentials or strain-related potentials when mechanically deformed. These electrical potentials may be partially responsible for the remodeling process which bone experiences in response to mechanical loads. A large body of evidence suggests that streaming potentials are the dominant mechanism responsible for strain-related potential generation in fluid saturated bone. Recently, biphasic poroelastic theory has been coupled to electrokinetic theory in an attempt to further elucidate this mechanism. The work reported here expands the experimental evidence in support of this theory. Experimental results which characterize electrical and mechanical phenomena in both wide frequency oscillatory and step response testing of 47 human and bovine bone specimens are reported. These results also include data from experiments in which the viscosity and conductivity of the solutions permeating 10 human and bovine bone specimens were varied. A specially designed mechanical testing of bone specimens. Testing procedures, which were optimized for strain-related potential measurement, were developed. These included procedures for varying testing solution viscosity and conductivity. The experimental data was analyzed using descriptive and inferential statistical techniques and linear and nonlinear regression methods. The following objectives were established for the work reported here: (1) to confirm the existing experimental results; (2) to attempt to obtain a successful correlation between theoretically predicted and experimentally observed mechanical phenomena; (3) to extend the experimental results over the wider frequency range of 0.05-100 Hz; (4) to test the theory in the time domain; (5) to test the theory for changes in viscosity and conductivity of the permeating fluid; and (6) to extend the experimental testing to include human bone specimens. All of these objectives were met except that a highly variable correlation between the theoretically predicted and experimentally observed mechanical phenomena was obtained. Patterns in these data are explored and the possible causes of the highly variable correlation are discussed. The results strongly suggest an electrokinetic origin for the observed electrical potentials. The microporosity of bone appears to be the location in which this mechanism operates.

Aged↗
PubMed1990

Pulmonary talc granulomatosis in a cocaine sniffer.

The development of pulmonary granulomatosis following intravenous injection of medications intended for oral use has been well described previously. Talc is the most commonly implicated agent. We present a case of talc granulomatosis which developed in a patient following cocaine sniffing and suggest that this may be the cause of development of granulomata in drug addicts who deny any history of intravenous drug abuse.

Adult↗
PubMed1990

The relationship of resting ventilation to mouth occlusion pressure. An index of resting respiratory function.

In order to examine the relationship of mouth occlusion pressure (MOP), an index of central inspiratory neuromuscular drive, to age and sex and to resting ventilation (VE), measurements were made in the seated posture in 84 healthy, normal subjects (38 men, 46 women; ages 18-72 years, mean +/- SD = 39.8 +/- 14.5 years) and in 79 patients with either airways obstruction (n = 63) or restrictive lung disease (n = 16). In the normal subjects, there was no significant relationship between age or sex and MOP (expressed as P0.1), which is the mouth pressure developed against a complete occlusion at 0.1 s after the beginning of inspiration, and dP/dtmax, the maximal rate of rise of this pressure; mean +/- SD for P0.1 = 0.75 +/- 0.32 cmH2O, and dP/dtmax = 19.41 +/- 10.10 cmH2O/s. Similarly, there was no significant relationship between age or sex and VE/P0.1 or VE/dP/dtmax. In 99 percent of normal subjects (83 of 84), VE/P0.1 was greater than 8.0 L/min/cmH2O, whereas in only 1 of the 79 patients was the value greater than 7.9 L/min/cmH2O. While the mean values of P0.1 and dP/dtmax were significantly different between normal subjects and patients, there was considerable overlap, whereas the ratio VE/P0.1 or VE/dP/dtmax provided excellent differentiation between normal subjects and patients with lung disease. This index, which is easily measured and requires minimal patient cooperation, provides valuable information in the clinical assessment of ventilatory drive and lung mechanics.

Adult↗
PubMed1989

Transdermal scopolamine attenuates methacholine-induced bronchospasm.

Anticholinergic agents have been widely used in the management of asthma. The use of scopolamine has been limited by significant side effects. Transdermal delivery of scopolamine (TS) has, however, been used successfully for the prevention of motion sickness. The purpose of this study was to determine if TS would decrease methacholine-induced bronchospasm in a group of subjects with mild asthma. Bronchoprovocational challenges with inhaled methacholine were performed on three separate occasions in 10 male subjects who each had a past history of asthma. After a baseline challenge, each subject received, in a double-blinded fashion, either a placebo patch or TS patch. The challenge was then repeated after at least 36 hours, and the alternate patch was then dispensed. The provocative dose producing a fall in FEV1 by 20% from baseline was then calculated by linear regression analysis. No significant change in baseline pulmonary function was noted with placebo patch or TS. With the use of TS, there was a small but significant increase in the provocative dose producing a fall in FEV1 by 20% from baseline for the group (p less than 0.05). In conclusion, we were able to demonstrate that a TS patch worn for a short period of time, can significantly decrease airway reactivity to methacholine in some patients with hyperactive airways.

Administration, Cutaneous↗
PubMed1989

Bronchoprovocational challenges in the assessment of the efficacy of therapeutic agents.

Bronchoprovocational challenge techniques are useful clinical and research tools for evaluating airway hyperreactivity. Not only are they useful in guiding management of patients with asthma, but also are commonly used to assess the efficacy of bronchodilating agents. The mechanisms involved in the development of bronchoconstriction are poorly defined, but continued work with challenge procedures may increase our understanding of the factors responsible for asthma. This paper will review some of the challenge techniques currently in use and outline the usefulness and limitations of these procedures.

Asthma↗
PubMed1989

Airways responsiveness determined by consecutive histamine challenges in asymptomatic asthmatics.

The effect of two consecutive histamine inhalation challenges on airways responsiveness was assessed in a group of eight nonsmoking nonmedicated asthmatics aged 19-27 yr. All subjects had a base-line forced expiratory volume in 1 s (FEV1) of greater than 80% of their predicted normal value before the initial challenge and were allowed to recover to greater than 95% of the initial base-line FEV1 value before the second challenge was initiated. The average airways recovery time after the first challenge was 44 min but ranged between 30 and 90 min. The mean +/- SD values of cumulative histamine dose units provoking a 20% decrease of the FEV1 from the buffer control value (PD20FEV1) were 10.79 +/- 5.95 determined with the first and 30.50 +/- 46.36 with the second challenge (P greater than 0.05). We conclude that sequential histamine challenges performed in mild asthmatics with closely controlled prechallenge airways function are well tolerated. Although some variance does exist in intersubject airways recovery time and in intra-subject histamine airways responsiveness determined by sequential challenges, our data do not support recent observations (J. Appl. Physiol. 63: 1572-1577, 1987) that histamine tolerance is a characteristic finding associated with bronchial asthma.

Adult↗
PubMed1989

The role of atmospheric pressure variation in the development of spontaneous pneumothoraces.

It has been postulated that spontaneous pneumothoraces (SP) develop because of rupture of subpleural blebs, and that atmospheric pressure changes (delta AP) may be contributory. A 5-year retrospective analysis of SP admissions was carried out to determine if delta AP do play a role in SP development. Using a 36-yr record of hourly delta AP, a normative background for delta AP was constructed. A fall in AP below the fifth, or a rise above the ninety-fifth percentile during these time periods, was classed as "unusual." Atmospheric pressure changes in the 4 days prior to SP were analyzed. The expected frequency of SP occurring by chance, if no relationship to delta AP existed, was also calculated. A total of 192 cases of SP was analyzed. Traumatic pneumothoraces were excluded. The majority of cases (72%) had been exposed to at least one "unusual" delta AP in the 4 days prior to onset of symptoms. Among those with four or more "unusual" exposures, SP occurrence was significantly more frequent than expected by chance alone (p less than 10(-10]. A strong positive association between delta AP and SP was not found in all cases, as delta AP are unlikely to be the only causative factor for SP. This finding of a relationship with ambient pressure changes lends support to the theory that SP develop as a result of rupture of subpleural blebs.

Adult↗
PubMed1989

BCG vaccination in leprosy: final results of the trial in Karimui, Papua New Guinea, 1963-79.

The efficacy of BCG vaccine in preventing the clinical manifestations of leprosy in a tuberculosis-free area of Papua New Guinea is reported. Between 1963 and 1966 a total of 5356 subjects, randomized to receive BCG or saline inoculations, were examined for leprosy before the vaccination and surveillance was continued until 1979. BCG afforded 48% protection against clinical leprosy, being most effective against borderline tuberculoid leprosy and in children vaccinated when under 15 years old. Protection was evident within 12 months in those vaccinated between the ages of 10 and 15 years but was delayed in other age groups. There was evidence for accelerated manifestations of tuberculoid leprosy in children vaccinated when under 5 years of age. Tuberculin sensitivity was more likely to be sustained following multiple BCG inoculations; vaccinees with sustained tuberculin sensitivity had the lowest incidence of leprosy, but protection was also evident in tuberculin-negative vaccinees. These results may have implications for ongoing trials of leprosy vaccine incorporating BCG.

Adolescent↗
PubMed1989

Large cell lymphoma presenting as a coronal penile lesion.

Although the majority of penile malignancies are primary epithelial carcinomas, consideration of secondary involvement, especially from lymphoma, is important, since there are alternatives to the standard therapeutic approach of penile amputation.

Aged↗
PubMed1985

How many spirograms for a histamine challenge?

Several reports have shown that a prior deep inspiration exerts a blunting effect on pharmacologically induced bronchoconstriction. Inspiration to total lung capacity is a mandatory requirement for valid determination of the FEV1, and thus, the FEV1 may underestimate the magnitude of induced airway obstruction. The present study was designed to assess the effect that the performance and separate analysis of 2 consecutive FEV1 maneuvers (FEV(1)1, FEV(1)2), obtained at different levels of histamine-induced bronchoconstriction, may have on the final interpretation of a histamine challenge. Eight asymptomatic nonsmoking asthmatics (mean age, 24 yr; range, 19 to 27 yr) underwent a total of 16 histamine challenges. Paired FEV1 measurements (FEV(1)1, FEV(1)2) were obtained after inhalation of buffer solution (control) and 3 min after inhalation of aerosolized, serially diluted, histamine diphosphate solutions. A significant airways response (FEV1 decreasing by 20% or more from the control value) was observed in all subjects after inhalation of 5 mg/ml of histamine or less, indicating histamine airway hypersensitivity. At lower doses of histamine the mean values for FEV(1)1 and FEV(1)2 were similar to the control value. At higher histamine doses FEV(1)2 was consistently higher than FEV(1)1 (p = 0.007) and exceeded FEV1 1 by a mean of 9% after inhalation of the provocational histamine concentration; delta FEV1(FEV(1)2-FEV(1)1) was correlated with the log10 of cumulative inhaled histamine dose units (p = 0.040). Assuming that the difference between corresponding FEV1 determinations at a given level of induced bronchoconstriction is a direct consequence of changes in lung mechanics induced by deep inspiration, we are led to conclude that during histamine inhalation challenges, only 1 spirogram should be performed at each level of induced bronchoconstriction.

Adult↗
PubMed1984

Food preferences of dogs housed in testing-kennels and in consumers' homes: some comparisons.

This work assessed the extent to which the food preferences of dogs housed in testing-kennels are representative of those reported for dogs housed in consumers' homes. Experiment 1 compared two-pan preference data from kennel-dogs and home-dogs fed canned, semi-moist, or dry food products. Kennel- and home-dogs performed similarly on the canned-products test, but differed significantly on the semi-moist and dry products tests. Experiment 2 demonstrated that the discrepancies between kennel- and home-dogs were likely due to differences in feeding history prior to the test. Experiment 3 showed that the effects of prefeeding with a single food are relatively short-lived in kennel-dogs, lasting for only a few days. In home-dogs preferences were more stable.

Animal Feed↗
PubMed1983

The influence of a feed additive level of virginiamycin on the course of an experimentally induced Salmonella typhimurium infection in broilers.

The purpose of this study was to determine the effect of virginiamycin on the course of an experimentally induced infection of Salmonella typhimurium in broilers. Several parameters were evaluated, including effects on the persistence and duration of shedding of the infecting Salmonella organism and its antibiotic resistance patterns. Virginiamycin was administered to the experimentally infected group for 8 weeks in feed at concentrations of 25 g/ton. This was compared to an infected control group not receiving the antibiotic. No effects were exhibited by virginiamycin on Salmonella typhimurium shedding and antibiotic resistance patterns.

Animals↗
PubMed1982

Cancer reporting in Papua New Guinea: 1958-70 and 1971-78.

In 1958, a cancer registry was established in Papua New Guinea for a population of 2 million who had remained in near isolation for millenia until recently. This report includes cancer data for 1970 through 1978. During those years, the registrations increased from 200 to 600. The reasons for this increase and the patterns of reporting over the entire 21-year period are examined. The data offered us opportunities to examine changes in case findings according to geography, time, and sex. Genuine differences in cancer incidence and pattern within this diverse country, mainly between the highland and lowland regions, were studied, particularly concerning oral, skin, liver, and penile cancers, and Burkitt's lymphoma. The controversy remains over the relationship of oral cancer and chewing of substances other than tobacco; but in this country, at least, a chew consisting only of areca nut mixed with lime must be held suspect. With the emergence from isolation, profound socioeconomic changes are occurring in this country; the patterns of cancer must change also, and we may be seeing the beginning of this already. Possible fruitful areas for further detailed studies are indicated.

Burkitt Lymphoma↗