Biomedical subjects

B C Ritchie

Publications and source records attributed to B C Ritchie.

At least 37 records · Page 2Linked to original sources

PubMed1975

Epithelial surfaces of the trachea and principal bronchi in the rat.

The epithelial surfaces in the trachea and principal bronchi of healthy rats were examined by scanning electron microscopy. A system of four cell types, ciliated, microvillous, brush, and goblet cells, in this order of frequency, were found and intermediate type cells were not seen. An extensive area of the surface examined was covered by densely ciliated epithelium. The presence of other cell types beneath the cilia was confirmed by transmission electron microscopy. Areas up to 1 mm in diameter and randomly distributed were observed where microvillous cells predominated and only occasional ciliated cells were found. Most ciliated cells in these areas were adjacent to glandular openings or goblet cells. The larger microvilli of the brush cells were arranged in a coronal configuration elucidated by the scanning electron microscope. Preparatory techniques recently introduced for the examination of soft tissue in the scanning electron microscope facilitated the confirmation of cell types present and the microarchitecture of the epithelial surface.

Animals↗

PubMed1975

Diaphragmatic activity and lung liquid flow in the unanesthetized fetal sheep.

For some time it has been suggested that breathing movements are made "in utero" and recently measurements of tracheal pressure and lung liquid flow in chronic fetal preparations have led to the hypothesis that rapid changes in these parameters are the result of respiratory muscle activity. To test this hypothesis diaphragmatic electrical activity was measured in seven chronic unanesthetized fetal sheep preparations and correlated with lung liquid flow and tracheal pressure. Diaphragmatic activity led to a fall of tracheal pressure and movement of a small volume of lung liquid into the lung. After the activity ceased, tracheal pressure returned to normal and flow diminished to zero or was directed out of the lung. The breathing pattern was unassociated with the net movement of lung liquid out of the lung. A histogram of the interval between breaths revealed a changing pattern of activity throughout gestation. The pattern was significantly altered after premature delivery of one animal with a respiratory problem. These observations provide evidence that respiratory muscles are active "in utero" and that the pattern of activity changes throughout gestation.

Animals↗

PubMed1975

Modification of respiratory center output in the unanesthetized fetal sheep "in utero".

Diaphragmatic electromyographic activity, tracheal and amniotic fluid pressures, lung liquid flow, and carotid and jugular venous pressures were measured on eight fetal lambs who survived for periods of 9-43 days postoperatively. The fetal gestational age ranged from 98 to 113 days at operation. Respiratory center output of the fetus as indicated by electromyographic activity was modified by the following stimuli. It was suppressed by anesthesia and fetal hypoxia (Pao2 = 12 mmHg), tonically reduced by lung inflation, and stimulated by cyanide injections (150-600 mug) into the fetal jugular vein. Neuromuscular transmission to the diaphragm was blocked with d-tubocurarine (0.2-0.6 mg). These experiments indicate that central and motor pathways to the diaphragm are sufficiently mature by 101 days in the fetal sheep to permit their output to be modified by chemical and mechanical stimuli.

Amniotic Fluid↗

PubMed1975

Effect of ventilation on pulmonary blood volume of the fetal lamb.

Blood volume changes in the fetal lung following the onset of ventilation were studied by isotopic measurement of red blood cell and plasma volume in rapidly frozen lungs of ten near term fetal lambs. Total pulmonary blood volumes of fetal lambs ventilated with 3% O2 and 7% CO2 in nitrogen (so that blood gas levels were little changed from fetal values), or with air, were compared with measurements in unventilated lambs. Regional correlations of blood volume and blood flow (measured with isotope-labeled microemboli) within the lungs were also examined. Total pulmonary blood volume averaged 5.6 ml/kg body weight in unventilated fetal lambs and was approximately 43% greated in fetal lambs after 5-20 min of air ventilation, but not significantly different in lambs ventilated with 3% O2 and 7% CO2 in nitrogen. Thus it is ventilation with air, rather than the introduction of gas into the alveoli, which enlarges the fetal pulmonary vascular bed. Regional pulmonary blood volume and blood flow were correlated, though poorly, in air-ventilated lungs, but not in lungs ventilated with 3% O2 and 7% CO2 in nitrogen; this suggests that a common factor may operate to increase both blood flow and blood volume in the fetal lung following the introduction of air.

Animals↗

PubMed1974