长白猪、枫泾猪和它们的杂种后代Ag—NOR的研究

4头枫泾猪,3头长白猪和5头长白×枫泾杂一代的NOR平均数分别为3.88、2和2.95。33头长白×枫泾杂二代猪(杂一代互交后代),其中7头黑猪的NOR众数为4,平均数为3.85;9头白猪的NOR众数为2,平均数为2.25;14头白猪的NOR众数为3,平均数为2.86;3头花猪的NOR众数分别为4.3、3,平均数为3.65、3.00和3.08。根据长白、枫泾和长白×枫泾杂一代和杂二代的NOR数目的区别和变化,NOR的遗传符合孟德尔定律。根据NOR数目与毛色的高度相关,提出了决定猪的黑白毛色的基因位于8号染色体并与NOR连锁的假设。猪的毛色除由位于8号染色体上的毛色基因所决定外,还应受其它基因位点的影响。     

Different ventilation strategies alter surfactant responses in preterm rabbits.

The effect of ventilation strategy on in vivo function of different surfactants was evaluated in preterm rabbits delivered at 27 days gestational age and ventilated with either 0 cmH2O positive end-expiratory pressure (PEEP) at tidal volumes of 10-11 ml/kg or 3 cmH2O PEEP at tidal volumes of 7-8 ml/kg after treatment with one of four different surfactants: sheep surfactant, the lipids of sheep surfactant stripped of protein (LH-20 lipid), Exosurf, and Survanta. The use of 3 cmH2O PEEP decreased pneumothoraces in all groups except for the sheep surfactant group where pneumothoraces increased (P < 0.01). Ventilatory pressures (peak pressures - PEEP) decreased more with the 3 cmH2O PEEP, low-tidal-volume ventilation strategy for Exosurf-, Survanta-, and sheep surfactant-treated rabbits (P < 0.05), whereas ventilation efficiency indexes (VEI) improved only for Survanta- and sheep surfactant-treated rabbits with 3 cmH2O PEEP (P < 0.01). Pressure-volume curves for sheep surfactant-treated rabbits were better than for all other treated groups (P < 0.01), although Exosurf and Survanta increased lung volumes above those in control rabbits (P < 0.05). The recovery of intravascular radiolabeled albumin in the lungs and alveolar washes was used as an indicator of pulmonary edema. Only Survanta and sheep surfactant decreased protein leaks in the absence of PEEP, whereas all treatments decreased labeled albumin recoveries when 3 cmH2O PEEP was used (P < 0.05). These experiments demonstrate that ventilation style will alter a number of measurements of surfactant function, and the effects differ for different surfactants.     

Requirement for terminal cytochromes in generation of the aerobic signal for the arc regulatory system in Escherichia coli: study utilizing deletions and lac fusions of cyo and cyd.

Escherichia coli has two terminal oxidases for its respiratory chain: cytochrome o (low O2 affinity) and cytochrome d (high O2 affinity). Expression of the cyo operon, encoding cytochrome o, is decreased by anaerobic growth, whereas expression of the cyd operon, encoding cytochrome d, is increased by anaerobic growth. We show by the use of lac gene fusion that the expressions of cyo and cyd are under the control of the two-component arc system. In a cyo+ cyd+ background, expression of phi(cyo-lac) is higher when the organism is grown aerobically than when it is grown anaerobically. A mutation in either the sensor gene arcB or the pleiotropic regulator gene arcA almost abolishes the anaerobic repression. In the same background, expression of phi(cyd-lac) is higher under anaerobic growth conditions than under aerobic growth conditions. A mutation in arcA or arcB lowers both the aerobic and anaerobic expressions, suggesting that ArcA plays an activating role instead of the typical repressing role. Under aerobic growth conditions, double deletions of cyo and cyd lower phi(cyo-lac) expression but enhance phi(cyd-lac) expression. The double deletions also prevent elevated aerobic induction of the lct operon (encoding L-lactate dehydrogenase), another target operon of the arc system. In contrast, these deletions do not circumvent aerobic repression of the nar operon (encoding the anaerobic respiratory enzyme nitrate reductase) under the control of the pleiotropic fnr gene product. It thus appears that ArcB senses the presence of O2 by level of an electron transport component in reduced form or that of an nonautoxidizable compound linked to the process by a redox reaction, whereas Fnr senses O2 by a different mechanism.     

Transbilayer distribution and mobility of phosphatidylinositol in human red blood cells

The present studies describe the distribution of phosphatidylinositol (PI) within the membrane bilayer of the human red blood cell (RBC) as well as its transbilayer mobility. The membrane bilayer distribution was determined by measuring the hydrolysis of PI in the exterior leaflet of the RBC membrane using a PI-specific phospholipase C and by extraction of PI from the exterior leaflet using bovine serum albumin. The transbilayer mobility of PI was measured by following the fate of radiolabeled PI which was first incorporated into the outer leaflet of the RBC membrane. Our results indicate that PI is asymmetrically distributed in the membrane, with approximately 80% located in the inner and 20% in the outer leaflet of the bilayer. The rate of transbilayer mobility of PI is similar to that for certain molecular species of phosphatidylcholine and much slower than that reported for the aminophospholipids in the RBC membrane.     

Vasoactive intestinal peptide increases intracellular cAMP and gonadotropin-alpha gene activity in JEG-3 syncytial trophoblasts. Constraints posed by desensitization.

Expression of the human chorionic gonadotropin (hCG)-alpha gene in placental trophoblasts is markedly stimulated by cAMP, a property preserved in a reporter plasmid containing its cAMP response elements (CREs) linked to the chloramphenicol acetyltransferase coding sequence (CRE alpha CAT). In search of a potential physiologic regulator of hCG gene expression via cAMP, we found that JEG-3 syncytial trophoblast cells have specific binding sites for vasoactive intestinal peptide (VIP) with dissociation constant of 1 nM. VIP maximally increased the transient expression of CRE alpha CAT and the expression of endogenous hCG-alpha mRNA in JEG-3 cells by 4- and 9-fold, respectively. Exposure of JEG-3 cells to 30 nM VIP increased cAMP levels 60-fold after 10-30 min, but cAMP rapidly declined thereafter. As a consequence of this desensitization, the effect of VIP on stimulation of both CRE alpha CAT and endogenous hCG-alpha and hCG-beta mRNA levels more closely resembled that of forskolin or 8-br-cAMP at time points much less than 24 h. Moreover, transient exposure to 8-br-cAMP was much less effective than 24 h of continuous incubation on CRE alpha CAT activity. We conclude that VIP rapidly increases cAMP content and activates hCG-alpha gene expression in JEG-3 cells, but sustained elevations in cAMP are necessary for maximal accumulation of this CRE-regulated gene product.     

Isolation and characterization of human glucose-6-phosphate isomerase isoforms containing two different size subunits

Previously undetected isoforms of human glucose-6-phosphate isomerase (GPI) have been isolated utilizing substrate-induced elution of the enzyme from spherical cross-linked phosphocellulose as an affinity ligand and subjected to a series of physical and chemical studies. The two major isoforms (1, 48%, pI 9.13; 2, 36%, pI 9.00) are homodimers of subunits of 63.2 kDa (Type-A) and are charge isomers, probably representing deamidation of specific Asn-Gly sequences as in other species. Isoform 3 (13%, pI 8.84) is a heterodimer composed of the Type-A subunit and a previously unreported larger subunit of 69.8 kDa (Type-B). Isoform 4 (3%, pI 8.62) is a BB-homodimer. Structural differences in the two types of subunits are also apparent from CNBr fragmentation patterns. Carbohydrate analyses show that, even though potential N- and O-linked glycosylation sites exist, the isoforms are not due to glycosylation. Recently recognized sequence similarities between GPI and the neurotropic lymphokine, neuroleukin (NLK) suggest that GPI and NLK are either derived from the same gene or represent modifications of the same protein. The possibility of NLK-GPI dimers exists, but the new isoforms identified in this study do not appear to represent hybrids of GPI subunits with mature NLK.     

Tumor necrosis factor-alpha enhances inhibitory effects of interleukin-1 beta on Leydig cell steroidogenesis

Human recombinant tumor necrosis factor-alpha (rTNF alpha) alone (up to 1000 units/ml) did not alter either basal or human chorionic gonadotropin (hCG)-induced testosterone formation in primary culture of rat Leydig cells. However, concomitant addition of rTNF alpha with human recombinant interleukin-1 beta (rIL-1 beta) enhanced the inhibitory effects of rIL-1 beta. The rIL-1 beta dose response curve was shifted to the left (IC50 changed from 1 ng/ml to 0.3 ng/ml). Even though rTNF alpha had no effect on testosterone formation, hCG-stimulated cyclic AMP formation was inhibited by rTNF alpha in a dose dependent manner. In the presence of both rTNF alpha and rIL-1 beta, hCG-induced cyclic AMP formation and binding of [125I]-hCG to Leydig cells were further inhibited. Testicular macrophages represent about 20% of the interstitial cells. TNF alpha and IL-1 may be produced locally by interstitial macrophages and have paracrine effects on Leydig cell function.     

Lipid conjugates of antiretroviral agents. II. Disodium palmityl phosphonoformate: anti-HIV activity, physical properties, and interaction with plasma proteins

Disodium palmityl phosphonoformate, a novel lipid phosphoester of the anti HIV agent phosphonoformate (foscarnet), inhibits HIV replication in H9 cells and syncytia formation in MOLT-3 cells as effectively as foscarnet itself, as shown by dose-response data from assays for expression of p17 and p24 viral antigens and syncytia formation. Protein binding studies indicate that in serum, the derivative exists bound to albumin and the lipoproteins, and would therefore be likely to exhibit improved serum lifetime in vivo.