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Biomedical subjects

W M Abraham

Publications and source records attributed to W M Abraham.

154 records · Page 9Linked to original sources
PubMed1975

Tension decline during isometric contractions without visual cues.

Subjects tried to maintain 15%, 30% and 50% maximum voluntary contraction (MVC) of their handgrip for 60 sec and 70% MVC for 30 sec. When the subjects watched the tension record, they could maintain the contraction for the required time. However, without visual cues (uncued), the tests resulted in a tension decline. Ae-alpha t described the tension decline in the 15% tests, Be-beta t the 70% test, while the form in the 30% and 50% tests was Ae-alpha t + Be-beta t. In all cases alpha and/or beta were found to be dependent on the starting tension. The electrical activity obtained from surface electromyograms did not increase during the uncued tests which would be expected if muscle fatigue were involved in the tension decline. Instead the electrical activity was directly proportional to the decline in tension suggesting that the fall in tension was not due entirely to muscle fatigue. 15% MVC uncued tests in which fatigue is known not to be a factor also showed a tension decline. Precooling the hand in an attempt to alter sensory input produced no systematic change from the original uncued tests, indicating that sensory information from the hand was probably not a major factor in the tension decline. It is suggested that during the uncued tests the fast component of the tension decline may be related to a sensory adaptation involving the Golgi tendon organs. The slow component is due to forearm muscle fatigue which is related to the ischemia produced during the isometric contractions.

Adult↗
PubMedDate not supplied

The effect of systemic hydration on normal and impaired mucociliary function.

Whether systemic hydration enhances the clearance of lower airway secretions in normal lungs and in lungs during antigen-induced bronchial obstruction was studied. In five conscious allergic sheep, tracheal mucus velocity (TMV) as an index of lower airway mucociliary clearance was measured before and serially for 60 minutes following intravenous infusion of 5% dextrose solution at volumes ranging from 5 to 35 ml/kg. None of these fluid regimens had a significant effect on TMV, although there was a tendency toward a slowing of TMV at the higher volumes of 25 and 35 ml/kg. After producing an acute allergic airway response by inhalation challenge with specific antigen, there was a decrease in mean TMV by 27% and 15% before sham infusion and infusion of 35 ml/kg of dextrose solution, respectively. During the subsequent 60-minute observation period, mucociliary transport was further impaired by dextrose infusion, with mean TMV being lower after dextrose infusion than after sham infusion at all times of measurement (P less than 0.05). The lowest value was reached 30 minutes after dextrose infusion (45% of control). It was concluded that systemic hydration does not significantly alter airway mucociliary transport in the normal state but further impairs mucociliary transport during allergic mucociliary dysfunction. This raises questions regarding the therapeutic role of systemic hydration in the treatment of children and adults who have bronchial asthma.

Animals↗
PubMedDate not supplied

Airway cell changes in tracheal lavage of sheep after ozone exposure.

We were interested in whether ozone (O3) could stimulate the migration of mast cells into the tracheal lumen. To test this we determined the effect of an acute O3 exposure on the types and relative numbers of cells recovered by tracheal lavage. Seven conscious sheep were intubated with an elongated nasotracheal tube. The trachea between the larynx and the cuff of the tracheal tube (15-20 cm) was lavaged repeatedly with 10-15-ml aliquots (total 350 ml) of 0.9% buffered (pH 7.4 saline, which contained the mast cell-stabilizer disodium cromoglycate (10 micrograms/ml). One hour after a baseline lavage, the sheep were exposed on separate occasions to either air (control) or 0.5 ppm O3 for 2 h. Lavages were repeated 24 h later. Cells were recovered from the lavage effluent by centrifugation across a saline/Ficoll Paque gradient. From part of this material we estimated total cells and total viable cells (with Trypan blue). The rest of the material was recentrifuged at 400 X g for 5 min, and cytological slides were made from the cell pellet. Slides were stained with Polichrome and Wright-Giemsa, and were analyzed by light microscopy. The percentages of epithelial cells, macrophages, lymphocytes, and mast cells were determined from a total count of 500 cells/slide. Differences in cell percentages between pre- and postexposure were calculated both for air and O3 exposures, and these differences were compared. Exposure to O3 resulted in an increased number of mast cells and lymphocytes when compared to the changes observed with air. It seems likely that the increase in number of luminal mast cells and lymphocytes following O3 exposure signals an enhanced inflammatory response and that these changes could contribute to O3-induced increased nonspecific airway hyperresponsiveness and susceptibility to allergic IgE-mediated airway reactions.

Animals↗
PubMedDate not supplied

Effect of an inhaled glucocorticosteroid (budesonide) on post-antigen induced increases in airway responsiveness.

We examined the effects of an inhaled glucocorticosteroid, budesonide, on antigen-induced early and late bronchial responses and the development 24 h after challenge of increased airway responsiveness to carbachol in allergic sheep. Six allergic sheep were used for this study and, on occasions separated by at least three weeks, they were treated: with placebo (treatment 1); 16 h and 20 min prior to antigen challenge with budesonide (treatment 2); 16 h and 20 min prior to and 8 h after antigen challenge with budesonide (treatment 3); or 16 h and 1 h prior to and 8 h after antigen challenge with budesonide (treatment 4). Airway responsiveness to carbachol was determined prior to and 24 h after antigen challenge by measuring specific lung resistance (sRL) after administering increasing doses of carbachol aerosol (0.5, 1 and 2.5% w/v) and determining the concentration of carbachol needed to increase sRL 150% over baseline (PC150). Placebo treatment did not affect the early or late increases in sRL after airway challenge with Ascaris suum antigen; 24 h after challenge, airway responsiveness to carbachol increased (p less than 0.05); at this time, PC150 was (mean +/- SEM) 0.88 +/- 0.15% as compared to 1.56 +/- 0.26% before challenge. Both treatments 2 and 3 blunted the early response to antigen and blocked the late response, but treatment 2 did not modify the antigen-induced increase in airway responsiveness, whereas treatment 3 did. Treatment 4 blocked both antigen-induced responses and was effective in blunting the increased airway responsiveness. These results suggest that antigen-induced increases in airway responsiveness: occur 24 h after a challenge in allergic sheep with early and late responses; can be blunted by budesonide; and are not dependent on the late response.

Administration, Inhalation↗
PubMedDate not supplied

Effects of a brief low-level exposure to the particulate fraction of diesel exhaust on pulmonary function of conscious sheep.

This study was undertaken to determine the effects of an acute low-level exposure to diesel exhaust particulate material on pulmonary function in conscious sheep. This was accomplished by measuring pulmonary mechanics, airway reactivity to increasing doses of aerosolized carbachol, and tracheal mucous velocity both prior to and immediately after exposure to the diesel exhaust particulates. The diesel exhaust particulate material was aerosolized by a fluidized-bed dust generator. The mass concentration of the dust ranged between 400 to 500 micrograms/m3 and a mass median aerodynamic diameter of 2.8 micrometers. The sheep breathed the diesel exhaust particulates for 30 min by means of a Plexiglas helmet. The particulates caused no material alteration in pulmonary resistance, airway reactivity to aerosolized carbachol, or static lung compliance when compared to pre-exposure values. Tracheal mucous velocity was likewise unaffected. In conscious sheep under the present exposure conditions, the diesel exhaust material administered as a respirable aerosol does not materially affect the function of the large airways, the elastic properties of the lung, nor tracheal mucous transport.

Airway Resistance↗
PubMedDate not supplied

Effects of nitric acid on carbachol reactivity of the airways in normal and allergic sheep.

The airway effect of a 4-hr exposure (via a Plexiglas hood) to 1.6 ppm nitric acid vapor were evaluated in seven normal and seven allergic sheep, i.e., animals that have a history of reacting with bronchospasm to inhalation challenge with Ascaris suum antigen. The nitric acid vapor was generated by ultrasonic nebulization of a 2% nitric acid solution. Airway effects were assessed by measuring the change in specific pulmonary flow resistance before and after a standard inhalation challenge with 2.5% carbachol aerosol. Nitric acid exposure did not produce bronchoconstriction in either group. Pre-exposure increases in specific pulmonary flow resistance after carbachol inhalation were 68% (SD +/- 13%) and 82% (SD +/- 35%) for the normal and allergic sheep, respectively. Within 24 hr, the largest post exposure increased in specific pulmonary flow resistance for the normal and allergic sheep were 108% [SD +/- 51% (P less than .06)] and 175% [SD +/- 87% (P less than .02)], respectively. We conclude that a short-term exposure to nitric acid vapor at levels below the industrial threshold limit (2 ppm), produces airway hyperreactivity to aerosolized carbachol in allergic sheep.

Airway Resistance↗
PubMedDate not supplied

Effect of atropine on tracheal mucociliary clearance and bacterial counts.

The purpose of this study was to determine if atropine, which has been shown to alter mucosal function, prolongs the persistence of inhaled bacteria in the trachea. In conscious sheep, bacterial counts in the trachea were determined by quantitative sterile brush cultures obtained before and serially after a controlled inhalation challenge with an aerosolized solution containing P. hemolytica (10(8) CFU X ml-1). The same animals were studied on two days, once without (control day) and once before and during intramuscular administration of 0.2 mg X kg-1 atropine sulfate at hourly intervals for up to 10 h (atropine day). On the control and atropine days, bacterial counts were zero before, and between 5 X 10(5) and 1.6 X 10(7) CFU X ml-1 immediately after inhalation of P. hemolytica. During the first 2 h after challenge, there was a similar semilogarithmic decline in bacterial counts on the control and atropine days despite the fact that mean tracheal mucociliary transport velocity remained unchanged on the control day, and ranged between 32% and 62% of baseline (p less than 0.05) during the 6-10 h post-drug observation period on the atropine day. However, the time to achieve sterility on the control day was less than or equal to 8 h in all animals, and greater than or equal to 8 h on the atropine day. We conclude that atropine prolongs the persistence of viable bacteria in the trachea. This effect of atropine may be related to an impairment of mucociliary clearance or to other alterations in mucosal function.

Aerosols↗
PubMedDate not supplied

A micro double capillary method for rheologic measurements of lower airway secretions.

We modified the double capillary method of Philipoff et al. [23] to allow rheologic measurements of lower respiratory secretions. The system consists of a precision bore stainless steel capillary (0.58 mm i.d., 5 mm length), a glass capillary (0.92 mm i.d., 15 mm length) and a sample holding tube (1.5 mm i.d., 15 mm length). This series of capillaries is connected to a long polyethylene catheter which permits advancing the system through the inner channel of a fiberoptic bronchoscope, and the placing of the sample holding tube into the lower airways for the aspiration of secretions under direct vision. The required sample volume is 20 microliter. The capillary is then removed from the fiberoptic bronchoscope and placed on a microscope stage; the movement of the meniscus of the sample under an applied vacuum as well as the elastic recoil of the sample after release of the vacuum are measured at body temperature. From this procedure, apparent viscosity (na) and shear elastic modulus (G) are calculated. The accuracy of the method was verified in vitro by using standard viscosity oils and a polymer solution of known elasticity. In five normal conscious sheep, na ranged between 200-3000 poises (shear rate: 0.06-1.0 s-1) and G between 17-83 dyn X cm-2. The micro double capillary method was found adequate for direct rheologic measurements of lower airway secretions.

Animals↗