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Biomedical subjects

H W Taeusch

Publications and source records attributed to H W Taeusch.

At least 91 records · Page 5Linked to original sources
PubMed1975

Glucocorticoid prophylaxis for respiratory distress syndrome: a review of potential toxicity.

Much evidence suggests that glucocorticoids may increase the rate of lung development during late fetal life, and thereby decrease the risk of respiratory distress syndrome if the fetus is born prematurely. Results of human and animal studies are basically in agreement. The risks of this form of therapy are less well examined, especially in human studies. This review briefly outlines studies that relate to toxicity so that the "risk/benefit ratio" of this form of therapy may be assessed.

Animals↗
PubMed1975

Surfactant inactivation by hyperventilation: conservation by end-expiratory pressure.

Hyperventilation, defined as repeated hyperinflations, for three hours in open-chested anesthetized cats increased elastic recoil and elevated minimum surface tension of lung extracts as measured on a surface film balance. Equivalent hyperventilation from an elevated lung volume did not alter the pressure-volume relationships. When a mixture of [3H]glycerol and [14C]palmitate had been injected 17 h before the three hour period of phyerventilation, an increase in the ratio of specific activity in wash to tissue lecithin occurred in the hyperventilated cats compared to controls. These findings suggest that hyperventilation promotes release of surface active material from tissue to alveolus, but the released material is inactivated. The application of 2.5 cmH2O positive end-expiratory pressure prevented the adverse effects of hyperventilation. The same increase in wash to tissue lecithin occurred during this study; since the material was appropriately surface active, we conclude that the positive end-expiratory pressure prevented its inactivation.

Animals↗
PubMed1975

Spontaneous phrenic nerve activity in the exteriorized fetal lamb.

Phrenic nerve activity and tracheal pressure changes were recorded in four exteriorized fetal lambs (120-135 days gestation) from lightly anesthetized ewes to study possible mechanisms involved in the establishment of rhythmical breathing patterns. Two types of spontaneous neural activity were found. The first consisted of high-frequency multiunit bursts (mean duration 820 ms; range 450-2,500 ms) that preceded a gasp. Individual units within these bursts reached peak discharge frequencies as high as 40 impulses/s. The second type of neural activity consisted of single-unit, low-frequency (1-14 impulses/s), irregular background discharges lasting up to several seconds without changes in tracheal pressure. Occasionally, higher frequency bursts of single-unit activity were detected that were also unassociated with tracheal pressure changes. The data indicate that the neural correlate of a fetal gasp includes high-frequency synchronized bursting activity in the phrenic nerve. In addition, background phrenic activity can be detected in the exteriorized fetal lamb that reflects central nervous activity in the absence of tracheal pressure changes.

Animals↗
PubMed1975

Prolonged sympathetic activation and pulmonary surfactant: absence of effect in anesthetized cats.

Cats were anesthetized with either sodium pentobarbital or ketamine hydrochloride, paralyzed, and artifically ventilated. The stellate ganglion was electrically stimulated for one hour (10 V, frequency = 10 per sec, and 0.5 to 1.0 msec pulse duration), alternating periods of stimulation and rest of 20 sec each, while control animals were sham operated. After stimulation, static deflation pressure-volume relationships of the excised lungs were compared. Regardless of the anesthetic used, no change in static lung compliance was found between experimental and control groups, and one hour of stellate stimulation did not produce significant changes in lung volumes at maximum distending pressures, in lung weight/body weight ratios, or in minimum surface tension measurements of lung extracts. We concluded that prolonged intermittent stimulation of the stellate ganglion does not alter significantly the function of alveolar surfactant.

Anesthesia, General↗
PubMed1975

Pulmonary pressure- volume relationships after corticotropin (ACTH) and salin injections in fetal rabbits.

ACTH mixed with barium sulfate injected into fetal rabbits on day 24 of a 31-day gestation was associated with increased lung maturity compared with lungs of noninjected controls when assessed by deflation pressure-volume curves and lung weight to body weight ratios measured on day 27. Fetuses injected with saline and barium sulfate also had accelerated (although somewhat less) lung maturation, perhaps from an ACTH-mediated response to stress. The ACTH group LA) maintained the largest lung volumes on deflation, followed by the saline group (B), the ACTH controls (C), and the saline controls (D). Volumes (percentage of total lung capacity) between the two injected groups and their controls (A versus C; B versus D) were significantly different at transthoracic pressures of 15, 10, 7, 4, 0, and -2 cm water (p less than 0.05). Volumes (percentage of total lung capacity) between the ACTH group and the saline group (A versus B) and between the two controls groups (C versus D) were not significantly different. Wet lung weight to body weight ratios were significantly different between the injected groups and their respective controls, between the two injected groups, and between the two control groups.

Adrenocorticotropic Hormone↗
PubMed1973

A combined scanning and transmission electron microscopic study of alveolar epithelial development of the fetal rabbit lung.

Scanning and transmission electron microscopy were used to study the epithelial surface development in fetal rabbit lungs. At 20 to 22 days of gestation, microvilli of the epithelial cells were scarce on the luminal surface but were concentrated along the cellular borders which had well-formed apical tight junctions and desmosomes. The epithelial intercellular spaces were frequently wide, and the basement membrane was thin and discontinuous, suggesting that transport or exchange of metabolites across the epithelium occurred easily. Attenuation of cytoplasm started at 26 days of gestation, and the cytoplasmic processes overlapped each other in various ways, so that both autonomous expansion and passive forces may be involved in attenuation of the pulmonary epithelial cells. The lining cells of the alveolus-like structures during late gestation and in the newborn rabbit showed pits with 0.1 to 0.5 mu diameters which probably reflected active production and release of osmiophilic bodies in the type 2 cells and increased micropinocytosis in the type 1 cell. No "gaps" between the epithelial cells were found to account for the resorption of lung liquid.

Animals↗
PubMedDate not supplied

Inactivation of pulmonary surfactant and the treatment of acute lung injuries.

Inactivation of pulmonary surfactant may be important in acute lung injury and acute respiratory distress syndrome. Treatment of surfactant dysfunction by instilling exogenous surfactants may improve gas exchange and pulmonary mechanics. Surfactants used for treatment vary in their attributes and effects, so when various surfactants are considered for therapy, resistance to inactivation is an important consideration. Animal models of acute lung injury exist in which the relative merits of surfactants can be compared. We hypothesize that the surfactants most resistant to inactivation in vitro will be the ones that are most effective in treatment of animal models of acute lung injury. Surfactants with higher concentrations of surfactant proteins specificallly A, B, and C) are more resistant to inactivation. Nonionic polymers mimic surfactant proteins in preventing surfactant inactivation under some conditions. Adding nonionic polymers to surfactant containing minimal amounts of SP-B and SP-C markedly improves lung function of animals with lung injury. Making surfactants more "inactivation-proof" may improve surfactant therapy of acute lung injuries.

Adult↗