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Biomedical subjects

S F Perry

Publications and source records attributed to S F Perry.

139 records · Page 8Linked to original sources
PubMed1975

Diffusivity of various inert gases in rat skeletal muscle.

Krogh's diffusion constant (K) was determined for various inert gases in isolated rat abdominal muscle at 37 degrees C by measuring the amount of gas diffusing per unit time and partial pressure difference through a portion of the muscle of known surface area and thickness. The following mean values for K, in 10(-9) mmol-min-1-cm-1-torr-1, were obtained: C2H2, 42.2; N2O, 20.0; CHClF2, 18.8; H2, 1.67; He, 1.42; CH4, 1.27; SF6, 0.081. From Krogh's diffusion constant, the diffusion coefficient (D) was calculated using the solubility coefficient determined previously in the same preparation. The D values thus obtained were found to be about half the D values in water at 37 degrees C. Model calculations show that for gases with high lipid/water partition coefficient, D in tissues containing lipid is underestimated by this method. Graham's law (inverse proportionality between D and square root of molecular mass) was found to represent a useful approximation for these gases. A better correlation, however, was obtained between D and the molecular diameter.

Abdominal Muscles↗
PubMedDate not supplied

HCO3- dehydration by the blood of an elasmobranch in the absence of a Haldane effect.

We measured in vivo arterial PCO2 and CaCO2 in Scyliorhinus canicula and found them to be very low (approximately 1 Torr and 3 mmol l-1 respectively). In vitro, the Haldane effect was functionally absent, and there was no detectable beta-adrenergic Na+/H+ exchange, in contrast to teleosts. The HCO3- dehydration rate of the blood, measured by a radioisotopic assay (Wood and Perry, J. Exp. Biol. 157:349-366, 1991), was independent of steady-state deoxygenation or oxygenation, unaffected by rapid oxygenation, and insensitive to isoprenaline, amiloride, and removal of urea or TMAO. SITS and acetazolamide reduced the rate; HCO3-/Cl- exchange rather than intracellular carbonic anhydrase (CA) was the rate-limiting factor. The rate was not altered by steady-state plasma [HCO3-], but increased linearly with PCO2 and with RBC concentration, saturating at hematocrits > or = 15%. The rate in separated plasma accounted for approximately 50% of the whole blood rate, was higher than in trout plasma or saline, and was inhibited by acetazolamide. The presence of CA in the normally circulating blood plasma of dogfish may contribute to highly efficient CO2 excretion in vivo.

Adrenergic Agents↗
PubMedDate not supplied

Bronchial casts of human lungs using negative pressure injection.

Negative-pressure casting techniques have been used for obtaining silicone rubber casts of the avian respiratory system, which contains minute air capillaries, noncompressible hollow bones, and highly flexible air sacs. The possibilities of this technique for the study of human airway diseases, which present technical difficulties similar to those of avian lungs, are investigated here. Left lungs from patients with various obstructive lung diseases or with normal lungs were fixed at autopsy under 25 cm H2O airway pressure with 2.5% phosphate-buffered glutaraldehyde. Cannulated, isolated lobes were placed in a vacuum chamber, and Dow Corning 734 RTV silicone elastomer, diluted with 10% low-viscosity silicone oil, was introduced into the airways at--10 kPa. Following complete polymerization, the tissue was microdissected to reveal the lung cast in situ, and histological sections were obtained for correlative studies. The tissue was then macerated in 5.25% sodium hypochlorite. The total time from fixation to finished cast was 3-4 days. Linear shrinkage of the elastomer was less than 1% in glutaraldehyde or water and between 1 and 2% in bleach. The negative-pressure injection technique enabled complete and accurate filling of airways to the alveolar duct level at physiological pressures and provided good delineation of blind cavities such as obstructed airways or ecstatic mucous gland ducts. The technique proved useful for the study of obstructive lung disease and should also prove useful for modelling aerosol deposition in diseased lungs.

Bronchi↗
PubMedDate not supplied

Stereological determination of tracheal volume and diffusing capacity of the tracheal walls in the stick insect Carausius morosus (Phasmatodea, Lonchodidae).

First instars of Carausius morosus provide a good model for morphometric evaluation of the diffusing capacity between the tracheal system and hemolymph: air sacs are lacking, tracheoles do not penetrate the organs and muscles, and entire animals can be evaluated electron microscopically without subsampling. The tracheal volume makes up 1.3% of the volume of the whole insect excluding appendages. We calculated the lateral diffusing capacity for oxygen and carbon dioxide for five classes of tracheae according to their diameters, from 0.2 microm to 35 microm. The harmonic mean thickness of the tracheal epithelium is lowest in smallest tracheae and increases with increasing tracheal diameter. Although the smallest tracheae make up 70% (O2) and 60% (CO2) of the total diffusing capacity, the proximal four classes may also be significant in diffusion of oxygen and particularly of carbon dioxide. The suppression of the development of respiratory pigments in the evolution of terrestrial insects may have increased the relative importance of small tracheal elements for local oxygen consumption.

Animals↗
PubMedDate not supplied

Extracellular carbonic anhydrase in the dogfish, Squalus acanthias: a role in CO2 excretion.

In Pacific spiny dogfish (Squalus acanthias), plasma CO(2) reactions have access to plasma carbonic anhydrase (CA) and gill membrane-associated CA. The objectives of this study were to characterise the gill membrane-bound CA and investigate whether extracellular CA contributes significantly to CO(2) excretion in dogfish. A subcellular fraction containing membrane-associated CA activity was isolated from dogfish gills and incubated with phosphatidylinositol-specific phospholipase C. This treatment caused significant release of CA activity from its membrane association, a result consistent with identification of the dogfish gill membrane-bound CA as a type IV isozyme. Inhibition constants (K(i)) against acetazolamide and benzolamide were 4.2 and 3.5 nmol L(-1), respectively. Use of a low dose (1.3 mg kg(-1) or 13 micromol L(-1)) of benzolamide to selectively inhibit extracellular CA in vivo caused a significant 30%-60% reduction in the arterial-venous total CO(2) concentration difference, a significant increase in Pco(2) and an acidosis, without affecting blood flow or ventilation. No effect of benzolamide on any measure of CO(2) excretion was detected in rainbow trout (Oncorhynchus mykiss). These results indicate that extracellular CA contributes substantially to CO(2) excretion in the dogfish, an elasmobranch, and confirm that CA is not available to plasma CO(2) reactions in rainbow trout, a teleost.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMedDate not supplied

The effects of chronic hypoxia on the acute adrenergic stress response in the rainbow trout (Oncorhynchus mykiss).

We have investigated the effects of chronic hypoxia on the acute adrenergic stress response of adult rainbow trout (Oncorhynchus mykiss). The goal of this study was to determine whether a prior 5-d exposure of fish to lowered environmental oxygen levels (60 or 80 Torr) would influence the nature of catecholamine secretion from chromaffin tissue in situ. Using a saline-perfused posterior cardinal vein preparation, it was demonstrated that the basal (unstimulated) secretion of noradrenaline and adrenaline was increased at 60-Torr hypoxia. In response to cholinergic (carbachol-elicited) stimulation, noradrenaline and adrenaline secretion were significantly affected by prior exposure to hypoxia. The construction of dose response curves revealed that noradrenaline secretion was enhanced at the lowest doses of carbachol (1 - 5 x 10(-7) mol kg(-1)) and that this was reflected by an approximate 10-fold reduction in the ED50 (the dose of carbachol eliciting half-maximal noradrenaline secretion). The effect of chronic hypoxia on in situ carbachol-evoked adrenaline secretion was similar but less pronounced. The results of this study suggest that during chronic moderate hypoxia, increased basal catecholamine secretion and enhanced responsiveness of chromaffin cells to cholinergic stimulation, as well aiding the ongoing stress, may assist the physiological adaptations to subsequent bouts of more severe acute stress.

Adaptation, Physiological↗
PubMedDate not supplied

Extracellular carbonic anhydrase activity and carbonic anhydrase inhibitors in the circulatory system of fish.

Carbonic anhydrase activity in the extracellular fluid of lower vertebrates is considered to be minimal, either because of the absence of carbonic anhydrase or because of the presence of naturally occurring inhibitors. The presence of carbonic anhydrase activity and circulating inhibitors was measured in plasma and subcellular fractions of gill tissue in elasmobranchs and teleosts. Plasma carbonic anhydrase activity was confirmed in the former but in extremely low amounts, especially compared with activity in red cells. The activity was correlated with plasma iron concentration and red cell hemolysis, which suggests that it is a byproduct of endogenous hemolysis during red cell turnover. A subcellular fraction of dogfish gills rich in microsomes contained significantly higher carbonic anhydrase activity than previously found in teleosts, making elasmobranchs the only aquatic lower vertebrates to possess putative basolateral membrane-associated carbonic anhydrase in the gill vasculature. It is suggested that branchial membrane-associated carbonic anhydrase is correlated more with a pH and/or CO2-sensitive ventilatory drive than with the maintenance of resting CO2 excretion. The occurrence and effectiveness of plasma carbonic anhydrase inhibitors were highly species-specific, with the salmonids having the most potent inhibitor. Cross-reactivity of inhibitor to red cell carbonic anhydrase appeared to be related to phylogenetic proximity. Selection for the presence of carbonic anhydrase inhibitors in fish plasma appears to be the result of multiple physiological pressures, including preservation of red cell intracellular pH, ventilatory control, and red cell fragility.

Animals↗
PubMedDate not supplied

Nitrogen excretion and the cardiorespiratory physiology of the gulf toadfish, Opsanus beta.

Gulf toadfish, Opsanus beta, are facultatively ureotelic and can excrete the majority of their nitrogenous waste as urea. Urea excretion occurs in "pulses." The hypothesis that pulsatile urea excretion reflects sudden, transient, generalized increases in the branchial conductance was investigated by the simultaneous monitoring of cardiorespiratory variables, oxygen uptake, and whole-body urea, ammonia, and/or 3H2O effluxes. The direct monitoring of both expired branchial water and water exiting a respirometer demonstrated that urea pulses were derived from the gills. No significant changes in ventilation or cardiac frequency, oxygen uptake, or ammonia efflux were observed during natural urea pulses, refuting the hypothesis that pulsatile urea excretion reflects pulsatile increases in the generalized diffusive properties of the gill for solute transfer. An alternative model for pulsatile urea excretion postulates that the gill urea permeability is increased periodically by the insertion and/or activation of specific urea transporters into gill cell membranes. Pulsatile urea excretion was abolished by pretreatment with the cytoskeletal-disrupting agent colchicine; colchicine may block trafficking of urea transporter-containing vesicles. Exocytosis of water following the fusion of vesicles with gill cell membranes could explain the significantly elevated 3H2O efflux observed during urea pulses.

Animals↗
PubMedDate not supplied

Proton pumps in fish gill pavement cells?

The gill epithelium which comprises several types of cell faces multiple functions (O2/CO2 transfer, acid-base balance and ionic regulation). Little is known of the respective cellular localization of these functions. TEM examination of the catfish gill shows, in pavement cells, cytoplasmic vesicles and apical pits, both ornamented with studs reminiscent of the proton pumps observed in H+ secretory epithelia. Ornamented apical pits are more frequently observed in acidotic fish. Taking together with our previous studies, this finding suggests that pavement cells play an important role, in addition to transfer of gas, by secreting protons. A new model of gill exchanges is proposed.

Animals↗
PubMedDate not supplied

The frog brainstem preparation as a model for studying the central control of breathing in tetrapods.

Our frog brainstem preparation revealed mechanisms for the central control of breathing that are in many ways similar to those of mammals. Thus, the basic control mechanisms for air-breathing appear to have been present in the Devonian common ancestors of frogs and mammals and may be common to all lung-breathing vertebrates. LOCATION: The in vitro frog brainstem, including motor nuclei of cranial nerves V to X, maintains frequency and ratio of fictive buccal oscillations to fictive lung inflation episodes comparable with that of the living animal. In this preparation, transection caudal to V abolishes spontaneous discharge in X but slow, spontaneous discharge in V may remain. Independent central pattern generation is present in the left and right half-brainstems. CHEMOSENSITIVITY: The frequency of fictive lung inflations increases with decrease in pH within the physiological range. RESPONSE TO GLUTAMATE: Biphasic response, consisting of a pause, followed by a dramatic increase in the frequency of fictive inspirations and positive baseline deflection, followed, in turn, by slow return of the baseline to the control level with frequency remaining above control as long as glutamate is applied. Local application reveals glutamate-sensitive sites in the ventral reticular formation. RESPONSE TO SUBSTANCE P AND PHYSALAEMIN: Similar to glutamate but the frequency of fictive inspirations decreases below control values. RESPONSE TO STRYCHNINE: The normal temporal sequence in firing of motor neurons of cranial nerves is disrupted and all nerves are synchronously active. The firing sequence of respiratory neurons is consistent with a grouping possibly homologous to the mammalian inspiratory, post-inspiratory and expiratory phases.

Animals↗
PubMedDate not supplied

Multiple sclerosis with medullary plaques and fatal sleep apnea (Ondine's curse).

We report 2 patients with multiple sclerosis (MS) who were symptomatic but ambulatory, and died in their sleep. Sleep studies in 1 patient showed hypercarbia and hypoxia accompanying sleep. In both cases autopsy showed plaques of multiple sclerosis in the medulla oblongata, incompletely involving the neuroanatomic areas of the medullary reticular formation controlling automatic breathing. A systematic analysis of the location of the plaques in relation to areas known to be important in breathing control revealed that the regions corresponding to the ventral nuclear complex of respiratory control in animals were incompletely and unilaterally involved in both cases. Close correlation with nuclei that have been demonstrated in animal experiments to be important in descending respiratory control of phrenic and intercostal musculature was not possible due to possible differences in anatomy between animals and humans, and the fact that plaques of MS affect axons of passage and spare neuronal cell bodies. Nevertheless, the cases clearly illustrate that patchy, unilateral lesions of the medullary reticular formation in humans can give rise to sleep disordered breathing. The cases also illustrate the risk of death during sleep in MS patients with demyelination in the medulla oblongata, and demonstrate the need to carefully examine the medulla in MS patients if they die unexpectedly during sleep.

Adult↗