Biomedical subjects

D Massaro

Publications and source records attributed to D Massaro.

At least 19 recordsLinked to original sources

PubMed1995

Sexual dimorphism in the architecture of the lung's gas-exchange region.

The lung's only vital function is to provide sufficient gas-exchange surface area (Sa) to meet the organism's needs for oxygen uptake (VO2) and carbon dioxide elimination. A direct linear relation between Sa and VO2 and an inverse linear relation between the size of the lung's gas-exchange units and the species mass-specific VO2 are strongly conserved across species. Within species, Sa increases in response to prolonged (weeks) elevation of VO2. We now report sex-dependent deviations from these relationships that seem to anticipate the need for increased gas-exchange capacity engendered in females by the metabolic demands of pregnancy and lactation. We found that although VO2 almost doubled in rats during pregnancy and lactation, Sa was the same in age-matched virgin, pregnant, and lactating females. However, at the onset of sexual maturity, virgin female rats and mice had higher mass-specific Sa than males of the same species although mass-specific VO2 was identical, within species, in both sexes. In addition, even though mass-specific VO2 was identical in males and females, alveoli were 30% and 50% smaller in female rats and mice, respectively, than males of the same species. We suggest the greater mass-specific Sa and smaller alveoli in females in spite of identical mass-specific VO2 as males were selected for evolutionarily; they help females meet the metabolic demands of reproduction without adding to the energy demands of these periods a requirement to form additional lung.

Animals↗

PubMed1992

Oxidation-reduction-sensitive binding of lung protein to rat catalase mRNA.

Air-breathing organisms experience an elevated concentration of oxygen mainly under two conditions. One occurs at birth when the O2 tension in the lung increases from approximately 25 torr present in utero to approximately 100 torr. The lungs, in particular, are also exposed to hyperoxia when oxygen is administered for therapeutic reasons. Under hyperoxic conditions, increased lung antioxidant enzyme activity is important for survival. The molecular basis for the increase in antioxidant enzyme gene expression under these circumstances is not well understood; in hyperoxia-exposed neonatal rats the elevation of lung catalase activity is not due to an increased rate of transcription but is associated with an increased concentration of catalase mRNA due to enhanced stability of the mRNA (Clerch, L.B., Iqbal, J., and Massaro, D. (1991) Am. J. Physiol. 260, L428-L433). We now show that neonatal rat lung protein forms specific complexes with catalase mRNA; this binding is redox-sensitive since when oxidizing agents are added binding is abolished but is restored by reducing agents. Our data also indicate lungs from hyperoxia-exposed rats have a larger proportion of catalase RNA-binding protein in oxidized form than lungs from air-breathing rats. This redox-sensitive binding of protein to catalase mRNA may be important in the control of catalase gene expression.

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PubMed1992

Endotoxin treatment protects rats against ozone-induced lung edema: with evidence for the role of manganese superoxide dismutase.

Ozone is a strong oxidizing agent that can cause lung damage and edema. There is evidence that it does so by causing peroxidation of membrane lipids. However, the elevation in lung activity of copper, zinc superoxide dismutase (Cu, ZnSOD), and manganese superoxide dismutase (MnSOD) during exposure to ozone suggests that increased production of superoxide could contribute to lung edema caused by ozone. This latter observation, and preliminary evidence that treatment of rats with endotoxin elevates lung activity of MnSOD without elevation of the activity of Cu, ZnSOD, catalase (CAT), or glutathione peroxidase (GP), led to the present study. We treated rats with endotoxin, exposed them to different concentrations of ozone, measured lung wet weight to dry weight ratio, thiobarbituric acid-reactive material (TBAR), and assayed lung tissue for Cu, ZnSOD, MnSOD, CAT, and GP activity. Our major findings are, (1) a strongly edemogenic concentration of ozone-lowered MnSOD activity; (2) endotoxin treatment of air-breathing rats did not decrease lipid peroxidation as indicated by the lung concentration of TBAR; (3) induction of increased MnSOD activity in lung by treatment with endotoxin was associated with virtually complete protection against an otherwise edemogenic concentration of ozone, with less lipid peroxidation, and with less loss of weight; and (4) this protection occurred without elevated Cu, ZnSOD, CAT, or GP activity.

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PubMed1992

Exposure of rats to ozone: evidence of damage to heart and brain.

Ozone is a strong oxidizing agent, and in many locations it is a major atmospheric pollutant. It is phytotoxic and an important cause of lung dysfunction in humans. Recently, a significant association has been established between total atmospheric oxidants, of which ozone is one, and daily cardiovascular mortality rates. In this article, we show that exposure of rats to ozone for 5 days, in a concentration found in major urban centers, results in an increased concentration of thiobarbituric acid-reactive material (an indicator of lipid peroxidation) in heart and brain tissue as well as elevated activity of catalase and glutathione peroxidase (enzymic scavengers of peroxides) in these tissues. We examined the heart anatomically and found evidence of extracellular and intracellular edema. These findings indicate that the heart and brain are damaged by a concentration of ozone present in major urban centers; they may have important implications for chronic illness and degenerative processes in humans.

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PubMed1992

Formation of alveoli in rats: postnatal effect of prenatal dexamethasone.

We administered a glucocorticosteroid (dexamethasone) or its diluent to pregnant rats on gestation days 17, 18, and 19. In male offspring we determined the lung's gas exchange surface area (S(a)), the average volume (v) of gas exchange saccules at age 2 days and alveoli at age 14 days, and their number (N) on these days. S(a), v, and N at 2 days and v at 14 days were not affected by the prenatal administration of dexamethasone. However, S(a) and N were lower in 14-day-old pups from dexamethasone-treated dams than in pups from diluent-treated dams. In separate experiments we found the responsiveness to prenatal dexamethasone, as a depressor of the postnatal increase in S(a), appeared earlier in female than male fetuses; it was present in female but not in male fetuses on days 16-18 and was found in male fetuses on days 17-19. We conclude 1) prenatal administration of dexamethasone diminishes the postnatal increase in S(a), 2) responsiveness to this action of dexamethasone occurs earlier in gestation in female than in male fetuses, and 3) prenatal dexamethasone does not effect the postnatal volume of an average alveolus but diminishes their number in male pups.

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PubMed1992

Rat lung antioxidant enzymes: differences in perinatal gene expression and regulation.

The lung activity of the antioxidant enzymes (AOEs) copper, zinc superoxide dismutase (Cu,Zn SOD), catalase (CAT), and glutathione peroxidase (GP), but not manganese superoxide dismutase (Mn SOD), increases in rats during late gestation; the concentrations of Cu,Zn SOD mRNA and CAT mRNA also rise. During early postnatal exposure to > 95% O2, the lung activity of Cu,Zn SOD, CAT, and GP increases. We now show 1) the lung concentration of Mn SOD mRNA and GP mRNA does not increase in late gestation; 2) Mn SOD activity and the concentration of its mRNA and of GP mRNA increase during exposure of neonatal rats to > 95% O2; and 3) as previously shown for CAT mRNA, the increase in lung concentration of the mRNAs for Cu,Zn SOD, Mn SOD, and GP during early postnatal hyperoxia occurs with a 70-80% prolongation of the half-life of these mRNAs. We conclude that 1) in late gestation the level at which lung AOE gene expression is regulated differs among the enzymes, 2) the level at which lung AOE gene expression is regulated shortly after birth in response to > 95% O2 is uniform among the enzymes, and 3) the lung's AOE response to neonatal hyperoxia is not merely a step-up of its prenatal regulation but involves different regulatory mechanisms based on increased stability of AOE mRNAs.

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PubMed1991

Rat lung antioxidant enzyme induction by ozone.

We exposed rats of different ages (weights approximately 45-300 g) to 0.7 ppm O3 for 1-5 days. At 5 days lungs of O3-exposed rats had higher activity of Cu,Zn superoxide dismutase (SOD), Mn SOD, catalase, and glutathione peroxidase than air-breathing rats; this greater activity was not due to blood-associated enzyme activity. The greater enzyme activity occurred with a higher concentration of the mRNA for each enzyme (Mn SOD not measured) without altered stability of these mRNAs. In adult rats the concentrations of these mRNAs were measured after 1, 3, and 5 days exposure to O3 and were elevated by day 3. The intergroup differences (air vs. O3) among antioxidant enzymes (AOEs) were unequal, and the intergroup differences in concentration of the specific AOE mRNA were greater than the differences in activity of their AOE. We conclude exposure to O3 led to greater expression of AOE genes; the increased expression was mediated pretranslationally probably at the level of transcription.

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PubMed1991

Perinatal rat lung catalase gene expression: influence of corticosteroid and hyperoxia.

Dexamethasone accelerates the late gestational rise in rat lung catalase activity; neonatal hyperoxia elevates rat lung catalase activity. We studied the regulation of catalase gene expression in these instances. Catalase mRNA/mg DNA increased to gestation day 22 and then fell to the concentration in adult lungs. The rate of transcription of catalase mRNA was higher on gestation day 22 than gestation day 19, whereas the half-life of catalase mRNA (approximately 7 h) was the same on both days. Dexamethasone given 48 and 24 h before expected birth (gestation 22 days) increased catalase mRNA concentration at days 20 and 22 without a change in catalase mRNA stability. Early postnatal hyperoxia (greater than 95% O2, 72 h) elevated catalase mRNA/mg DNA and doubled its half-life without changing its rate of transcription. We conclude the normal late gestational elevation of catalase activity and the increase of activity during prenatal dexamethasone treatment are regulated at the level of gene transcription. By contrast, the elevation of catalase activity during neonatal hyperoxia is mediated posttranscriptionally by increased catalase mRNA stability.

Aging↗

PubMed1991

Alveolar size, number, and surface area: developmentally dependent response to 13% O2.

Nonpregnant female rats were kept in 13% O2 for greater than 3 wk before being bred, throughout pregnancy, and, with their pups, after birth; control rats were only in air. The average volume (v), number (N) and surface area (Sa) of gas-exchange structures (saccules or alveoli) were estimated by stereological means. Saccule conversion to alveoli by septation between age 2 and 14 days was impaired in 13% O2 rats; there was less decrease in v (signifying less septation) and less increase in N (indicating the formation of fewer alveoli) in 13% O2 pups than in air pups. Between age 14 and 40 days, v rose 2-fold in air pups and 1.3-fold in 13% O2 pups; N increased 1.7-fold in air rats and 2.8-fold in 13% O2 rats. In other experiments, 23-day-old rats, previously only in air, were continued in air or were placed in 13% O2 until 44-days-old. At age 44 days, Sa was 25% and v 27% greater in 13% O2 rats than in air rats, but N was the same in both groups. We conclude there are multiple mechanisms for forming alveoli and increasing Sa and these mechanisms exhibit a developmentally dependent response to 13% O2.

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PubMed1990

Regulation of alveolar formation.

Postnatal formation of alveoli and their capillaries is essential to overall development. It enables pulmonary gas exchange to keep pace with the body's metabolism. Hormones, nutrition, and oxygen tension appear to regulate alveolar formation, perturbations of which may lead to normal variations in lung function or contribute to lung disease.

Animals↗

PubMed1990

Postnatal development of lung alveoli: suppression by 13% O2 and a critical period.

We studied the effect of 13% O2 on the development of the lung's gas-exchange region. Rats, acclimatized to 13% O2, remained in 13% O2 while pregnant, and were kept with their pups in 13% O2 until the pups were killed or were placed in air at age 15 days; other rats were always in air. Pups kept in 13% O2, unlike air pups, did not decrease mean chord length (Lm) or increase surface-to-volume ratio (S/V) of gas-exchange air spaces between age 2 and 14 days or by age 40 days. Rats placed in air at age 15 days did not change Lm or S/V even in air. Rats kept in 13% O2, and rats placed in air at age 15 days had fewer alveolar attachments to bronchioles than air rats. Gas-exchange air volume (VA) in 13% O2 rats was equal to or greater than in air rats; VA/kg was larger in 13% O2 than air rats. We conclude that maintenance of rats in 13% O2 during gestation and during the period alveoli are formed by septation blocks septation in a seemingly irrevocable manner. We suggest diminished septation decreases radial traction on conducting airways leading to increased VA/kg.

Aging↗

PubMed1989

Rat lung lectin gene expression is regulated developmentally and by dexamethasone.

The cell-agglutinating activity of soluble beta-galactoside-binding proteins (lectins) is developmentally regulated in several mammalian organs. Little is known of the alterations in gene expression that underlie this developmental regulation. Rat lung contains a dimeric beta-galactoside-binding protein that exhibits a postnatal peak of hemagglutination activity caused in part by an increased rate of lectin synthesis. We now report rat lung lectin mRNA concentration increased to a peak at age 6 days; dexamethasone treatment aborted this increase. Southern blot analysis is compatible with the presence of more than one lectin gene. However, two lines of evidence indicate that we measured a single gene product: 1) only one lectin of subunit Mr 14,000 is present in rat lung (Biochemistry 27: 692-699, 1988), and 2) in Northern blot analysis of RNA, the lectin cDNA hybridized with only one mRNA species. Our present findings, taken with prior studies of lectin synthesis, indicate that the postnatal increase in lectin synthesis is mediated pretranslationally and by an increased efficiency of translation. Dexamethasone treatment impairs the increase of lectin mRNA concentration but increases translational efficiency.

Aging↗

PubMed1989

Endotoxin increases lung Cu,Zn superoxide dismutase mRNA: O2 raises enzyme synthesis.

Administration of endotoxin to adult rats increases lung Cu,Zn superoxide activity after 72 h of exposure to greater than 95% O2. The increased activity is brought about mainly by a faster rate of Cu,Zn superoxide dismutase synthesis; rats treated with endotoxin but not exposed to hyperoxia do not exhibit these findings (Hass, Frank, and Massaro, J. Biol. Chem. 257: 9379-9383, 1982). We now report that 48 h after treatment of adult rats with endotoxin there was a decreased rate of Cu,Zn superoxide dismutase synthesis by lung slices from air- and O2- exposed rats, although, in both groups, the lung concentration of Cu,Zn superoxide dismutase mRNA was increased approximately 45%. Exposure of endotoxin-treated rats to greater than 95% O2 or air for an additional 24 h (72 h all told) resulted in continued elevation of Cu,Zn superoxide dismutase mRNA only in lungs of O2- exposed rats. In vitro exposure of lung slices from air-breathing saline- or endotoxin-treated rats to 95% O2 for 6 h led to an increased rate of Cu,Zn superoxide dismutase synthesis only in slices from endotoxin-treated rats. We conclude that endotoxin treatment leads to an increased concentration of Cu,Zn superoxide dismutase mRNA in rat lungs, but a sustained elevation of the mRNA, and its translation into an increased rate of Cu,Zn superoxide dismutase synthesis requires exposure of the lung to hyperoxia.

Animals↗

PubMed1989

Brief perinatal hypoxia impairs postnatal development of the bronchiolar epithelium.

We placed pregnant rats in 10% O2 on the last day of gestation for less than or equal to 9 h plus 1-2 h (with their pups) after the onset of delivery. In the pups this brief perinatal hypoxia led to an altered cellular composition of the bronchiolar epithelium that persisted at least to age 30 days; it was characterized by a higher nuclear numerical density (Nvn) of Clara cells, a lower Nvn of ciliated cells, and a lower percentage and Nvn of Clara cells in mitoses compared with control rats. The perinatal hypoxia also led to a significantly lower volume and volume density of the secretory apparatus (rough endoplasmic reticulum and secretory granules) on day 7 in 10% O2-born rats. The data on the Nvn of Clara and ciliated cells and on Clara cell mitoses are consistent with the notion that exposure to 10% O2 impaired the differentiation of Clara cells into ciliated cells and this impairment persisted well beyond the period of exposure.

Aging↗

PubMed1989

Short-term perinatal 10% O2 alters postnatal development of lung alveoli.

We studied the effect of breathing 10% O2 for less than or equal to 9 h by rat dams during the last day of gestation and (with their pups) for 1-2 h immediately after birth on the development of the lung's gas exchange region in the pups. Our major finding is that this brief stress resulted in substantially altered lung development noted at age 7 days and still partially present at age 30 days. In particular, perinatal hypoxia slowed the postnatal increase of lung volume, delayed septation of the large gas exchange saccules, diminished the increase of the gas exchange surface area, but accelerated thinning of the wall of the gas exchange structures. The changes produced by briefly breathing 10% O2 had as great an effect on these aspects of lung development as the same prenatal exposure to 10% O2 plus continuous postnatal exposure to 10% O2 for 7 days. Breathing 10% O2 had a particularly strong effect on alveolar wall thinning, since 2 h of breathing 10% O2 immediately after birth, without prenatal hypoxia, accelerated thinning of the alveolar wall.

Aging↗

PubMed1989

New "rest period" protocol for inducing tolerance to high O2 exposure in adult rats.

We report a new protocol for inducing marked tolerance to prolonged exposure to hyperoxia in adult rats that entails the use of a single "rest period" between exposures to a usually lethal concentration of O2. Exposure of adult rats to greater than 95% O2 for 48 h followed by a rest in air, or a rest even in 50-75% O2, consistently resulted in 100% survival with evidence of only slight pulmonary edema during continuation of exposure to greater than 95% O2 for 3-7 more days (7-day survival for rats rested in room air for 24 h = 23/23; for rats rested in 50-75% O2 for 24 h = 27/27; for continuously O2-exposed control rats = 0/11). Induction of tolerance to hyperoxia was associated with significant increases in the lungs' antioxidant enzyme activities during the reexposure to greater than 95% O2 following the rest period. The molecular means by which the events in this protocol lead to increased lung antioxidant enzyme activity is only partially known, but because of the marked tolerance produced, the elucidation of the mechanisms must be important to our understanding of tolerance to hyperoxia.

Animals↗

PubMed1989

Alveolar dimensions and number: developmental and hormonal regulation.

We used three-dimensional reconstruction 1) to determine the effect of treating rats with dexamethasone, from age 4 to 13 days, on alveolar volume (v) and number (Na) and 2) to determine if v, Na, or both change between age 14 and 60 days. At age 14 days, v, Na, and gas exchange surface area (Sa) were (2.7 +/- 0.3) x 10(4) microns3, (20.2 +/- 2.1) x 10(6), and 832 +/- 29 cm2, respectively, in diluent-treated rats; in dexamethasone-treated 14-day-old rats the same parameters were (7.5 +/- 1.1) x 10(4) microns3, (9.9 +/- 1.6) x 10(6), and 733 +/- 16 cm2, respectively. At age 60 days, v, Na, and Sa were (7.1 +/- 0.4) x 10(4) microns3, (60.8 +/- 4.1) x 10(6), and 4,495 +/- 187 cm2 in diluent-treated rats and in rats treated with dexamethasone from age 4 to 13 days, v, Na, and Sa at age 60 days were (15.9 +/- 2.4) x 10(4) microns3, (25.8 +/- 3.8) x 10(6), and 3,424 +/- 203 cm2. We conclude that treatment with dexamethasone from age 4 to 13 days (the period of normal septation) resulted in larger alveoli at age 14 and 60 days, and in diluent- and dexamethasone-treated rats the increase in Sa between age 14 and 60 days is due, at least in part, to the formation of new alveoli.

Aging↗

PubMed1989

Rat lung Cu,Zn superoxide dismutase. Isolation and sequence of a full-length cDNA and studies of enzyme induction.

The synthesis of Cu,Zn SOD by rat lung increases spontaneously in the fetus in late gestation and during exposure of neonatal and adult rats to greater than 95% O2. To explore the regulation of these increases, we measured rat lung Cu,Zn SOD synthesis and activity. We also cloned and sequenced a rat lung Cu,Zn SOD cDNA that was used to measure Cu,Zn SOD mRNA concentration. We found that (a) under normal gestational and postgestational conditions the synthesis of this enzyme was regulated pretranslationally; (b) the increased synthesis that occurs under hyperoxia (greater than 95% O2), was pretranslationally mediated in otherwise unmanipulated neonatal rats but translationally controlled in hyperoxic adult rats; and (c) in lungs of rats made tolerant to greater than 95% O2 by allowing 24 h rest in air after an initial 48 h in greater than 95% O2, the increased Cu,Zn SOD synthesis that occurred during the second period of hyperoxia was regulated pretranslationally. We conclude Cu,Zn SOD gene expression in the lung is developmentally regulated under normal conditions and in response to an oxidant challenge. Tolerance, whether endogenous or induced, appears to require the accumulation of increased amounts of Cu,Zn SOD mRNA.

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