Human immunodeficiency virus type 1 envelope glycoprotein molecules containing membrane fusion-impairing mutations in the V3 region efficiently undergo soluble CD4-stimulated gp120 release.

The ability of soluble forms of CD4 to induce gp120 release from the human immunodeficiency virus type 1 envelope glycoprotein complex may reflect molecular events associated with membrane fusion. The third hypervariable (V3) region of gp120 appears to play a role in fusion independent of CD4 binding. We demonstrate herein that envelope glycoprotein molecules rendered fusion defective by mutations in conserved residues within the V3 region nevertheless undergo efficient soluble CD4-induced gp120 release.     

Poly-(ADP-ribose) polymerase partially contributes to target cell death triggered by cytolytic T lymphocytes.

We hypothesized that CTL-induced target cell (TC) death is partially due to processes that follow the DNA damage in target cells and include the activation of poly-ADP-ribose transferase (PADPRT) by DNA strand breaks. According to this model, the activated PADPRT is expected to deplete NAD, ATP, and to contribute to the TC death. We used inhibitors of PADPRT and a PADPRT-deficient cell mutant, as well as other nucleated TC and SRBC to test the role of PADPRT in CTL-induced cytotoxicity. It is found that inhibitors of PADPRT (3-aminobenzamide, benzamide (aromatic amides)) and nicotinamide all inhibit the CTL-mediated lysis of both Ag-specific TC and of Ag-nonbearing TC. The effect of PADPRT inhibitors was not due to inhibition of the lethal hit delivery by CTL, because in parallel control experiments, the same inhibitors did not interfere with CTL-induced lysis of SRBC, cells that are devoid of nuclei and PADPRT. Moreover, the effect of inhibitors of PADPRT did not affect earlier stages of lethal hit delivery because 3-aminobenzamide and benzamide did not interfere with CTL-induced DNA fragmentation in TC at concentration which protected TC lysis. Importantly, a PADPRT-deficient cell line was also much more resistant to CTL-induced lysis as tested in retargeting (4 and 8 h) assays; this was expected if activation of PADPRT is indeed involved in TC death. Control experiments reveal that the relative resistance of the PADPRT-deficient cell mutant to CTL-induced lysis was not related to its impaired ability to form conjugates and to trigger CTL (as tested in granule exocytosis assay). In addition, PADPRT-deficient cells were as susceptible to CTL-induced DNA fragmentation as were the control cells; yet, they were resistant to CTL-induced 51Cr-release. Control cells and PADPRT-deficient mutant were equally susceptible to antibody+C'-mediated lysis. Our data support the view that the activation of PADPRT can contribute to the CTL-induced cytolysis of some TC, but is not involved in lysis of other TC, as evidenced by the ability of CTL to efficiently lyse SRBC. These data suggest that there could be multiple molecular pathways of TC death in CTL-mediated cytotoxicity and the relative contribution of PADPRT and/or other enzymes will reflect the individual make-up of a particular TC.     

Cerebral energy metabolism in immature and mature guinea pig fetuses during acute asphyxia.

In immature fetuses circulatory centralization caused by acute asphyxia is less effective than that in mature fetuses (Jensen & Berger, 1991). This suggests that cerebral oxygenation may be poor in immature fetuses during asphyxia. On the other hand cerebral oxygen consumption is lower in immature than that in mature fetuses. To determine, whether or not there is an imbalance between oxygen supply and demand in one or the other group, we compared the time course of the changes of cerebral concentrations of both high-energy phosphates and glycolytic intermediates between immature and mature guinea pig fetuses during acute asphyxia caused by arrest of uterine blood flow. The fall in the cerebral concentrations of adenosine triphosphate and glucose, and the rise in those of adenosine monophosphate and lactate were slower in immature than in mature fetuses. There were no differences between the levels of cerebral adenosine diphosphate and creatine phosphate of the two groups. From these results we conclude that during acute asphyxia the imbalance between cerebral oxygen supply and demand is less marked in immature than in mature fetuses.     

Chromosomal localization of two human zinc finger protein genes, ZNF24 (KOX17) and ZNF29 (KOX26), to 18q12 and 17p13-p12, respectively

Two members of the zinc finger Krüppel family, ZNF24 (KOX17) and ZNF29 (KOX26), have been localized by somatic cell hybrid analysis and in situ chromosomal hybridization to human chromosomes 18q12 and 17p13-p12, respectively. The mapping of ZNF29 together with the previously reported localization of ZFP3 suggests that a zinc finger gene complex is located on human chromosome 17p. ZNF29 maps centromeric to the human p53 tumor antigen gene (TP53). In the analogous murine position, the two mouse zinc finger genes Zfp2 and Zfp3 have recently been assigned to the distal region of mouse chromosome 11, the murine homolog of human chromosome 17. Both human zinc finger genes ZNF24 and ZNF29 are in chromosomal regions that have been noted to be deleted in neoplasms of the lung and of the central nervous system at chromosome 17p and in colorectal neoplasia at chromosomes 17p and 18q.     

The distribution and ultrastructure of sensory elements in the baroreceptor region of the truncus arteriosus of the lizard Trachydosaums rugosus

Summary The proximal truncus arteriosus of the lizard Trachydosaurus rugosus was studied with light-, fluorescence and electron-microscopical techniques. Three vessels comprised the truncus: the pulmonary, left aortic, and caroticoaortic arteries. Right and left truncal nerves, each derived from the ipsilateral vagus nerve, innervated the truncus, particularly its proximal 3 mm.Ultrastructurally, the nerves had a variety of appearances: some were clearly adrenergic, c-type or p-type. A number of profiles contained large numbers of mitochondria and were classified as sensory. Some profiles defied exact classification, having characteristics common to two different types of profile.Within the outer medial layers, profiles up to 7 m in diameter were found. These contained large numbers of mitochondria, myelin bodies and structures intermediate between the two. In addition, the profiles contained large amounts of glycogen and small numbers of vesicles. These nerve fibres were classified as baroreceptors, since they closely resemble carotid sinus and aortic arch baroreceptors in mammals.Large numbers of chromaffin cells were found, particularly in the common wall of the pulmonary and left aortic arteries. Many of these cells emitted a long tapering process, which sometimes entered a nearby nerve bundle. Sensory, p-type and c-type profiles, but not adrenergic profiles, made extensive close contacts with chromaffin cells.     

Association of specific immune response to pork and beef insulin with certain HLA-DR antigens in type 1 diabetes.

To test the association of HLA-DR antigens with high-responder and low-responder status to either beef or pork insulin, insulin antibodies in diabetic sera were separated into those with average low and those with average high affinity and their insulin-binding capacities for each insulin determined. Significantly less binding of pork insulin by the high affinity antibodies occurred in the group of patients with DR3 antigens compared with those with DR4 antigens (p less than 0.01) and DR3/4 antigens (p less than 0.01). The difference in the binding capacity of beef insulin by the high affinity antibodies between the groups with DR3 and DR4 antigens was less pronounced but still significant. The high-responder status of DR3/4 antigens to pork insulin suggests that the gene or genes associated with HLA-DR4, and responsible for a high response to pork insulin, are dominant to genes associated with HLA-DR3 and a low response. If extended to human insulin and different HLA-DR and HLA-B antigen patterns, these finding should help in the therapeutic selection of the appropriate insulin and thus reduce the induction of an anti-insulin response in patients with diabetes.     

Actin acetylation in Drosophila tissue culture cells

In a permanent cell line derived from Drosophila embryos, cytoplasmic actin is produced as an unstable precursor, which is subsequently converted to a stable form. This conversion results in a reduction in isoelectric point, with no apparent change in molecular weight. The conversion involves an enzymatic acetylation, and results in an insensitivity to aminopeptidase digestion, suggesting N-terminal blockage. Both the acetylated and unacetylated actins can participate in the assembly of F-actin, but with different efficiencies.This work was supported by a grant from the NIH (GM 22866).     

Human erythrocyte galactosyltransferase. Characterization, membrane association and sidedness of active site

Human erythrocyte UDPgalactose : 2-acetamido-2-deoxy-alpha-D-galactopyranosylpeptide galactose beta(1 lead to 3) transferase (Galactosyltransferase) has been characterized in terms of detergent and metal ion requirements. Michaelis constants for donor and acceptor substrates, inhibition constant for N-acetylgalactosamine, pH optimum and ionic strength effects. The assay thus optimized permits initial velocity measurements. Galactosyltransferase was shown to be membrane-bound by demonstrating its association with erythrocyte ghosts after high and low ionic strength treatments to remove weakly-associated proteins. In the absence of detergents, no activity was detectable in sealed ghosts and inside-out vesicles derived from erythrocyte membranes. Enzyme activation by detergents paralleled solubilization of membrane proteins. Both latency and solubilization studies indicated a substrate inaccessible active site for the enzyme in situ in the membrane. Galactosyltransferase activity in resealed ghosts, leaky ghosts and inside-out vesicles was resistant to the action of trypsin, chymotrypsin or pronase applied as single agents. A mixture of these proteases, however, strongly reduced the enzyme activity in inside-out vesicles and leaky ghosts, indicating a cytosolic orientation for the active site of the galactosyltransferase.