Fluorescein-labeled antibody to rabbit pulmonary angiotensin-converting enzyme localized in the vascular endothelium of rabbit lung, liver, adrenal cortex, pancreas, kidney, and spleen. Epithelial cells of the renal proximal tubules were the only parenchymal cells among the organs studied that demonstrated immunoreactivity.

Rats were exposed to 98.5% oxygen at 765 torr for 6-72 hr. The pulmonary changes were investigatcd by electron microscopy and by morphomctric methods. A progressive thickcning of thc air-blood barrier, from the normal 1.5 to 3 # after 3 days, was duc primarily to enlargement of thc interstitial space by accumulation of edema which was replaced secondarily by cells and fibrin. This was accompanicd by destruction of about 50% of the capillaries. Morphomctric data allowed an cstimatc of the degree of impairment of lung function. The primary cellular damagc was located in endothelial cells which underwent cytoplasmic changes and, finally, fragmentation. In contrast, thc damage to the epithelial lining of alvcoli was relatively scarce compared to thc extcnsivc cndothclial changes. This pertained cven to severely damaged lungs with 65 % of the alveoli obliterated by a heterogeneous cxudatc. Possiblc causes for this apparently different reaction of epithelium (thc first target ccll) and cndothelium to toxic oxygen cffccts are discussed.

The localization of angiotensin converting enzyme (ACE) in the gonads of the normal rabbit was studied by immunofluorescence and immunoelectron microscopy. The enzyme is present in the cytoplasm of testicular spermatids and of epididymal and ejaculated spermatozoa, and on the surface of follicular and tubal oocytes. These findings support the hypothesis that ACE has a role in gamete maturation and in fertilization.

The effects of interaction between endothelial angiotensin converting enzyme (ACE) and goat anti-rabbit ACE (GtARbACE) antibodies were studied in rabbit glomeruli. IntroductionThe capillary wall of the renal glomerulus is composed of the visceral epithelial cells, the basement membrane, and the endothelial cells. The study of the interaction of antibodies with antigens present on the epithelial cells or in the basement membrane has provided considerable information concerning the morphological and immunocytochemical features of glomerular injury, as well as the in vivo processing of antibody to tissue antigens, and the characterization of mediators of inflammation. The earliest model studied was nephrotoxic glomerulonephritis, a proliferative and exudative injury induced by heterologous antibodies reactive with antigens of the basement membranes, including the glomerular basement membrane (1). The most recent model has been passive Heymann's glomerulonephritis (2-4), a membranous disease induced by heterologous antibody reactive with antigens expressed on the apical part ofthe epithelial cells of proximal convoluted tubules, and on the plasma mem-

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We screened African wild dogs ( Lycaon pictus ) in Kruger National Park, South Africa, for Mycobacterium bovis infection using an interferon-gamma release assay. We detected M. bovis sensitization in 20 of 21 packs; overall apparent infection prevalence was 83%. These animals experience high infection pressure, which may affect long-term survival and conservation strategies.

Angiotensin-converting enzyme has been solubilized from rabbit pulmonary particles and purified to homogeneity. The molecular weight of the native enzyme was estimated to be about 136,000 by glycerol gradient centrifugation, and a value of 140,000 was obtained for the reduced denatured protein by disc-gel electrophoresis in the presence of sodium dodecyl sulfate and 2-mercaptoethanol. The enzyme was found to be a glycoprotein with carbihydrate accounting for approximately 16% of its dry weight. The major sugar residues were identified as galactose, N-acetylglucosamine, and mannose, with smaller amounts of fucose and sialic acid. The homogeneous enzyme catalyzed the release of HisLeu from the COOH-terminus of angiotensin I and of Phe-Arg and Ser-Pro from that of bradykinin.The potent vasopressor octapeptide, angiotensin II, is derived by enzymatic cleavage of the COOH-terminal dipeptide HisLeu from angiotensin I, a relatively inactive decapeptide (for a recent review see ref. 1). An activity catalyzing this reaction was first isolated from horse plasma (2). However, subsequent studies on the metabolism of angiotensin I in vivo (3) have suggested that its physiologic conversion occurs in the lung, and is mediated by a particulate enzyme (4) directly accessible to the pulmonary circulation and thought to be a component of the vascular endothelium (5). Peptide inhibitors of this enzyme are known to block the conversion of angiotensin I to angiotensin II in vivo and have been reported to reverse hypertension in certain animal models (6, 7), thus implicating the enzyme as a potential therapeutic target. We have, therefore, purified angiotensin-converting enzyme directly from rabbit pulmonary particles. This report describes some unusual characteristics of the solubilized homogeneous enzyme.