Lymphocyte subsets in cord blood of preterm infants: effect of antenatal steroids

The objective of this study was to evaluate prospectively the influence of gestational age (GA) and short-term antenatal steroids on total lymphocyte count and lymphocyte subsets in cord blood from preterm infants. Two-color flow cytometric analyses of lymphocyte subsets were performed on cord blood collected from 67 infants. These infants were grouped according to GA: group I (term, n = 19); group II (GA 33-37 weeks, n = 25); group III (GA <33 weeks, n = 23). The mean absolute lymphocyte counts (ALC) in groups I, II and III were 5.6 +/- 2.5 x 10(3)/ microl, 4.3 +/- 1.5 x 10(3)/ microl and 3. 5 +/- 1.8 x 10(3)/ microl respectively. The mean values for CD4+ lymphocytes in groups I, II and III were 2.7 +/- 0.8 x 10(3)/ microl, 2.0 +/- 0.8 x 10(3)/ microl and 1.6 +/- 0.9 x 10(3)/ microl respectively. Mean values for CD8+ lymphocytes were 0.9 +/- 0.3 x 10(3)/ microl, 0.6 +/- 0.3 x 10(3)/ microl and 0.5 +/- 0.3 x 10(3)/ microl respectively. With decreasing GA, there was a statistically significant decrease in ALC (p = 0.0035), CD4+ lymphocytes (p = 0. 0013) and CD8+ lymphocytes (p = 0.0064). We then evaluated the effect of antenatal steroids, now routinely administered to women with preterm onset of labor to facilitate fetal lung maturation, and found that after adjusting for GA, infants of women on antenatal steroids had significantly fewer ALC (p = 0.0001), CD4+ lymphocytes (p = 0.02) and CD25+ lymphocytes (p = 0.03). In this population of infants, the decreased number of lymphocytes seen at younger GAs is associated with antenatal steroid use.

Lung angiotensin receptor binding characteristics during the development of monocrotaline-induced pulmonary hypertension

Alterations in lung angiotensin converting enzyme (ACE) activity in monocrotaline (MCT)-induced pulmonary hypertension in rats have suggested a pathophysiologic role for angiotensin II (AII) in pulmonary vascular remodeling. ACE inhibitors suppress MCT-induced pulmonary hypertension; however, losartan, an angiotensin type 1 (AT1) receptor antagonist, was without impact. The present study examined AII receptor binding characteristics by radioligand binding during the development of MCT-induced pulmonary hypertension. Saturation binding isotherms for [125I]AII binding to membrane preparations from rat lung were performed at 4, 10, and 21 days following a single injection of MCT (60 mg/kg) or saline vehicle. Right ventricular hypertrophy, an index of pulmonary hypertension, increased at 21 days post-MCT. Saturation binding isotherms revealed a single, high affinity site for [125I]AII binding in lung membranes from MCT-treated and control rats, with no change in receptor affinity or density during the development of pulmonary hypertension. Competition displacement binding demonstrated that the AT1 receptor predominates in lung membranes from control rats, with no alterations in AII receptor subtype distribution following MCT treatment. In summary, these results suggest that the AT1 receptor subtype predominates in rat lung and does not contribute to the development of MCT-induced pulmonary hypertension.

Pulmonary mechanical and immunologic dysfunction in a murine model of AIDS

Human immunodeficiency virus-infected patients occasionally exhibit alveolar septal wall thickening and decreases in gas diffusion capacity, but the mechanism underlying these abnormalities is unknown. The present study evaluated septal wall thickness and gas exchange properties in a murine model of the acquired immunodeficiency syndrome and determined whether there were alterations in lung lymphocyte deposition and activation that could contribute to changes in respiratory structure and function. Although alveolar septal wall thickness did not differ from control at 1, 2, and 4 wk postimmunosuppressive virus infection, at 8 wk after infection, septal wall thickness was substantially increased. Immunohistochemical evaluation at this time revealed marked increases in the septal wall deposition of fibronectin and collagen type IV. Pulmonary function tests on anesthetized mice with virus-induced septal wall thickening demonstrated that, although total lung capacity, compliance, and functional residual capacity were unaltered, diffusion capacity for carbon monoxide was significantly impaired. A diffuse nonspecific interstitial pneumonitis was present in lungs of immunodeficient mice, and flow cytometry indicated that both lymphocytes and macrophages were activated. Reverse transcriptase-polymerase chain reaction analysis of lung lymphocytes demonstrated enhanced mRNA expression for several cytokines known to affect lung structure. These results show that impaired gas exchange occurs in a murine model of acquired immunodeficiency syndrome and suggest that such alterations may be mediated by elaboration of cytokines from activated lung lymphocytes and macrophages.

Angiotensin-converting enzyme in organs of air-breathing fish

Angiotensin-converting enzyme (ACE) was measured in tissue homogenates from the African lungfish and six species of air-breathing teleosts (Heteropneustes fossilis, Clarias batrachus, Channa gachua, Anabas testudineus, Notopterus chitala, and Monopterus cuchia) using a standard spectrophotometric assay. In most species, the highest levels of ACE activity were found in the respiratory organs (gills and/or accessory respiratory organs). ACE was also found in heart and kidney tissues from most species and occasionally in liver. Converting enzyme was not found in skin or skeletal muscle from any species and only in blood from H. fossilis and brain from C. batrachus. Captopril, a potent inhibitor of mammalian ACE, inhibited enzymatic activity from all tissues except C. gachua heart and liver and A. testudineus heart. As fish make the transition from aquatic to aerial respiration the gill microcirculation is usually reduced in size and the accessory respiratory organs become elaborated and occupy a more central position in the vascular tree. The presence of ACE in accessory respiratory organs of air-breathing fish appears to greatly enhance the metabolic efficiency of this enzyme on circulating substrates.