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Biomedical subjects

D Massaro

Publications and source records attributed to D Massaro.

At least 109 records · Page 6Linked to original sources
PubMed1977

Influence of insulin on amino acid uptake by lung slices.

We examined the transport of amino acids by rat lung slices using mainly 14C-labeled alpha-aminoisobutyric acid ([14C]AIB) as a nonmetabolized amino acid. We found that [14C]AIB is accumulated by the lung in an energy-dependent fashion against a concentration gradient. The uptake is saturable, stereospecific, and follows Michaelis-Menten kinetics suggesting enzyme or carrier mediation across the plasma membrane. Insulin increases the uptake of [14C]AIB and insulin plus glucose increases its uptake even more. The diffusion constant (KD) in the presence of glucose, insulin, or glucose plus insulin is the same, 0.29 h-1; the Vmax is also the same, 83.0 mmol-1-1-h-1, under these three conditions. The apparent Km is 14.0 mM with glucose, 9.0 mM with insulin, and 4.0 mM in the presence of glucose and insulin. We conclude that the uptake of [14C]AIB is increased by insulin, and insulin plus glucose, and, based on this kinetic analysis, this is due to an increased affinity of the transport sites for AIB (decreased Km, unchanged Vmax, and KD).

Amino Acids↗
PubMed1977

Protein metabolism by rat lung: influence of fasting, glucose, and insulin.

We studied protein metabolism by rat lung slices. We found that phenylalanine is not metabolized to other substances by the lung and that the rate of incorporation of L-[U-14C]phenylalanine into protein, calculated using its intracellular specific radioactivity, reached a maximum within 20 min and remained stable for the rest of a 3-h incubation. The rate of protein degradation, determined using [12C]phenylalanine as a marker, was linear over a 3-h incubation. Fasting for 3 days slowed the increase in lung protein content of fasted compared to nonfasted rats; there was also a decrease in protein synthesis and an increase in proteolysis. In fed rats, glucose, insulin, and glucose plus insulin did not alter protein synthesis. Glucose, insulin alone, and glucose plus insulin decreased proteolysis. We conclude that the in vitro system reflected changes in the in vivo protein content of the lung. Fasting decreases protein synthesis and increases proteolysis. Glucose and insulin alone modulate protein metabolism in the lung by acting on the degradative rather than the synthetic process.

Amino Acids↗
PubMed1977

Mitochondria of the pulmonary granular pneumocyte in different species.

We used stereologic methods to determine the surface density and surface-to-volume ratio of mitochondrial inner membranes and cristae in pulmonary granular pneumocytes of the mouse, rat, rabbit, and dog. We also measured mitochondrial length and width and calculated their volume. The surface density of the cristae and inner membrane and the mitochondrial volume have a direct linear correlation with the oxygen consumption of lung slices of the different species. We found an indirect linear correlation between the surface-to-volume ratio of the mitochondrial inner membrane and cristae and the lung's oxygen consumption in the different species.

Animals↗
PubMed1977

The oxygen consumption of rabbit lung slices after pneumothorax.

We produced a pneumothorax on the left side in rabbits and measured the oxygen consumption of lung slices from previously collapsed left and non-collapsed right lung immediately after in vitro re-expansion. After re-expansion, the oxygen consumptions of the previously collapsed and non-collapsed lung were almost identical, 162 +/- 6.7 and 168.6 +/- 9.6 microliter of oxygen consumed per hour per mg of deoxyribonucleic acid (mean +/- SE), respectively. We concluded that 3 days of collapse does not impair the oxidative metabolism of re-expanded lung.

Animals↗
PubMed1976

Influence of fasting on lung oxygen consumption and respiratory quotient.

We measured the oxygen consumption (QO2) of lung slices from rats and rabbits and the respiratory quotient (RQ) of lung slices from fed and fasted rats. The QO2 of lung slices is lowered within 24 h after the onset of food deprivation; this decrease in QO2 lasts during at least 2 additional days of fasting and is not eliminated by addition of glucose to the reaction medium. In fed rats the RQ of lung slices after 30 min of incubation without glucose is 0.75 +/- 0.01 (mean +/- SE) and 0.96 +/- 0.02 with glucose present. Fasting for 72 h lowers the RQ of lung slices after 30 min of incubation without glucose to 0.68 +/- 0.03; addition of glucose raises the RQ of lung slices from 72-h-fasted rats to 0.76 +/- 0.02. We conclude that fasting depresses lung oxidative metabolism. In the fed rat glucose is a major substrate for oxidative processes but in the fasting rat the oxidation of glucose is impaired and lipids are an important source of lung energy.

Animals↗
PubMed1976

Influence of thyroxine on adult rat lung oxygen consumption and ultrastructure.

We studied the oxygen consumption (QO2) of lung slices and the ultrastructure of the pulmonary granular pneumocyte in rats whose level of circulating thyroxine was altered. Rats given thyroxine for 6 days (1.0 mg-kg-1-day-1) and sacrificed on the 7th day had a serum thyroxine level of 18.9 +/- 2.7 mug/100 ml (mean +/- SD); rats given diluent alone for 6 days had a serum thyroxine level of 4.67 +/- 0.53 mug/100 ml. Rats subjected to a sham thyroidectomy has a serum thyroxine level of 7.27 +/- 1.47 mug/100 ml, whereas rats subjected to thyroidectomy had a serum thyroxine level of 1.13 +/- 0.55 mug/100 ml when sacrificed. The QO2 of lung slices from rats with high levels of circulating thyroxine was significantly greater than that of rats that received diluent alone. The QO2 of slices from rats whose thyroid glands were excised was significantly lower than the QO2 of slices from sham-operated rats. We did not find quantitative ultrastructural differences in granular pneumocyte mitochondria and lamellar bodies of rats given thyroxine compared to rats given diluent or between rats subjected to sham thyroidectomy compared to rats whose thyroid glands were removed.

Animals↗
PubMed1976

The effect of betamethasone on pressure-volume characteristics of nonfetal rat lungs.

Betamethasone was administered to rats for 28 days, and body weight, lung weight, and descending pressure-volume relations were measured in their excised lungs. In rats treated with corticosteroid, lung and body weights increased less rapidly than in control rats, but the ratio of lung wet weight to body weight and the per cent dry weight remained the same in both groups. The absolute lung volume was significantly greater at each pressure in the control rats; but when expressed per lung weight, the lungs of rats treated with corticosteroid held more air. When corrected for lung size, the only difference in the lung pressure-volume curves between groups existed at transpulmonary pressures of 0 and 5 cm H2O, where the lungs of the rats treated with betamethasone contained more volume, whether inflated with air or with saline. We concluded that betamethasone administered to nonfetal rats has little influence on the lung's pressure-volume characteristics, which cannot be ascribed to differences in lung size.

Animals↗
PubMed1976

Hemorrhagic hypotension and the lung: in vitro respiration.

We examined the O2 consumption and respiratory quotient of lung slices from rats whose mean blood pressure was decreased to approximately 40 mm Hg for 1 hour by hemorrhage and from control rats that were handled in the same manner but were not bled. The in vitro O2 consumption of lung slices from the hypotensive rats was lower than the O2 consumption of slices from control rats; exogenous glucose did not alter these differences. In the absence of exogenous glucose, the (mean +/- SE) respiratory quotient of lungs from control rats was 0.75 +/- 0.01; from hypotensive rats 0.78 +/- 0.01 (P less than 0.05). Glucose increased the respiratory quotient of lung slices from control rats to 0.95 +/- 001 but increased the respiratory quotient of slices from hypotensive rats to only 0.86 +/- 0.01. We concluded that hemorrhagic hypotension decreases lung O2 consumption and alters substrate metabolism by the lung.

Animals↗
PubMed1976

Oxygen consumption by rat lung after in vivo hyperoxia.

We studied the influence of 48 and 96 hours of in vivo hyperoxia (O2 greater than 98 per cent) on O2 consumption by rat lung slices. After 48 hours of hyperoxia, lung O2 consumption expressed per mg of deoxyribonucleic acid or per left lung decreased to approximately 70 per cent of that of lungs from rats exposed to compressed air. After 96 hours of hyperoxia, there was no difference in lung O2 consumption per mg of deoxyribonucleic acid between rats exposed to O2 and those exposed to air, but lung O2 consumption per left lung was higher in rats exposed to O2 than in those exposed to compressed air. Lung ribonucleic acid content and the ratio of ribonucleic acid to deoxyribonucleic acid were significantly increased after 96 hours of hyperoxia. We concluded that the rate of lung metabolism is altered after in vivo exposure to high PO2.

Animals↗
PubMed1975

Intraspecies differences in lung metabolism and granular pneumocyte mitochondria.

The authors used waltzing and nonwaltzing mice to examine granular pneumocyte mitochondria and lung oxygen consumption and protein synthesis. They found that the oxygen consumption of lung slices from waltzing mice is higher than that of lung slices from nonwaltzing mice. The volume density of granular pneumocyte mitochondria is higher in waltzing than nonwaltzing mice as is their number per 100 mum-3 of cytoplasm. The mean, length, width, volume and surface density of individual mitochondria are the same in both groups. The incorporation of [14-C]leucine by lung slices into protein in a surface active lung fraction is greater in lung slices from waltzing than nonwaltzing mice. This difference occurs in the face of similar levels of free leucine in both groups. The authors conclude that there are intraspecies differences in lung oxygen consumption and protein synthesis and in the volume density and number of granular pneumocyte mitochondria.

Animals↗
PubMed1975

Lung oxygen consumption and mitochondria of alveolar epithelial and endothelial cells.

We examined oxygen consumption by lung slices and measured the volume density of mitochondria of granular pneumocytes, alveolar type I cells, and alveolar capillary endothelial cells in several species. We found that lung oxygen consumption (mu-1 02 times h-1 times mg DNA-1) varies inversely with the log of animal body weight and with the species alveolar diameter and directly with the species respiratory rate. The volume density of granular pneumocyte mitochondria show a direct linear correlation with the lung's oxygen consumption and the species respiratory rate, and an inverse linear correlation with the species alveolar diameter. The volume density of mitochondria in type I alveolar epithelial cells and capillary endothelial cells, considered together, did not differ in the two species studied (mouse and rat). We conclude that there are interspecies differences in oxygen consumption by lung cells and that granular pneumocytes contribute to these differences. We suggest that, at least part of these differences, are related to interspecies differences in surfactant secretory activity.

Animals↗
PubMed1975

Influence of cycloheximide on the lung.

We examined the time course of the influence of cycloheximide on descending pressure-volume curves of excised lungs and on protein and lecithin synthesis and oxygen consumption by lung slices. We also looked at the influence of cycloheximide on granular pneumocyte ultrastructure. Excised lungs from cycloheximide-treated animals are more compliant than controls. After ventilation with air, lungs from control and cycloheximide animals show increased retractive forces and a shift to the right of the deflation P-V curve. Incubation at 38 degrees C for 30 min reverses these changes in control lungs, but not in lungs from cycloheximide-treated rabbits. There is no change in liquid delfation P-V curves after cycloheximide. Cycloheximide causes an immediate decrease of 50% in incorporation of radioactive leucine into protein by lung slices. Incorporation of radioactive palmitate into lecithin and oxygen consumption are also decreased by 50% 6 h after cycloheximide. Lamellar bodies in granular pneumocytes are smaller after cycloheximide. Cycloheximide causes a significant increase in the surface density of the lamellar body envelope. Cytoplasmic area of granular pneumocytes is increased after cycloheximide.

Animals↗
PubMed1975

In vivo protein secretion by lung. Evidence for active secretion and interspecies differences.

The present study is an attempt to determine (a) if the lung actively secretes protein into the surface-active fraction of lung lavage returns; (b) if there are interspecies differences in this secretory activity; and (c) if the amount of nonradioactive protein in the lavage surface-active fraction shows interspecies variation. I found that pilocarpine stimulates the release of radioactive protein into the lavage surface-active fraction of rabbits and that this pilocarpine effect is completely blocked by atropine. Inhibition of lung oxygen consumption by iodoacetate is associaged with a dose-dependent inhibition of the pilocarpine-induced secretion. Microtubules may be involved in this secretory process because colchicine inhibits the pilocarpine effect. Of the radioactive protein in the total surface-active fraction (tissue plus lavage returns), a greater percent appears in the lavage surface-active fraction at 2 and 4 h, after a pulsed injection [U-14C] leucine, in the mouse than in the rat, which in turn has a greater amount than the rabbit. There is also a difference in the amount of nonradioactive protein per square meter of alveolar surface area in the lavage surface-active fraction of different species: mouse greater than rabbit greater than cat greater than dog. The amount of nonradioactive protein per square meter of alveolar surface area in the lavage surface-active fraction is directly proportional to the species respiratory rate; the log of the nonradioactive protein in the lavage surface-active fraction is inversely proportional to the log of the species alveolar diameter. I conclude that the lung actively secretes protein into the lavage surface-active fraction, that this secretion is under neurohumoral regulation, and that respiratory rate and alveolar size may influence this secretory activity and the amount of protein in this surface-active fraction.

Animals↗
PubMed1975

Stereologic evaluation of granular pneumocyte lamellar bodies in different species.

Lamellar bodies in individual pulmonary glanular pneumocytes in the species examined (mouse, rat, rabbit, and dog) have virtually the same volume density with respect to the cytoplasmic volume as estimated by stereological techniques. The surface-to-volume ratio for these structures also fail to show any interspecies variation in these species.

Animals↗
PubMed1974

Adaption to hyperoxia. Influence on protein synthesis by lung and on granular pneumocyte ultrastructure.

We studied the influence of prolonged exposure to hyperoxia (O(2) > 98%) on protein synthesis and on the ultrastructure of the granular pneumocyte. To study protein synthesis, as indicated by l-[U-(14)C]-leucine incorporation into protein, lung slices were incubated with radioactive leucine and a surface-active fraction was obtained by ultracentrifugation of lung homogenates. We found that, following an initial depression in protein synthesis after 48 h of hyperoxia, protein synthesis in rats exposed to oxygen for 96 h rose to greater than control levels. This increase in protein synthesis was noted in whole lung protein and in protein present in the surface-active fraction. Stereologic ultrastructural analysis of granular pneumocytes revealed that the lamellar bodies occupy the same percentage of cytoplasmic volume in oxygen-exposed and control rats after 96 h; a previous study had shown lamellar bodies of oxygen-exposed rats to occupy less volume than those of control rats after 48 h of exposure at which time protein synthesis was also depressed. After 96 h of exposure there is a greater amount of rough endoplasmic reticulum in the granular pneumocytes of oxygen-exposed rats. These studies show that after 96 h of hyperoxia the lung has recovered its ability to synthesize protein including protein in the surface-active fraction and that these biochemical changes are associated with consistent ultrastructural alterations in the granular pneumocyte.

Adaptation, Biological↗