Metabolism of prostaglandins in spontaneously hypertensive rats: NAD"-dependent 15-hydroxyprostaglandin dehydrogenase activity is decreased in kidney and increased in lung.

Renal, pulmonary and gastric NAD⁺-dependent 15-hydroxyprostaglandin dehydrogenase activities were determined in both spontaneously hypertensive and normotensive rats at 6 and 12 weeks of age. Renal enzyme activity in hypertensive rats was only 30–40% of that present in normotensive controls at both ages. In contract, pulmonary enzyme activity in hypertensive animals was twice as active as that in normal controls. There was no significant difference in gastric enzyme activity. NAD⁺-dependent 9-hydroxyprostaglandin dehydrogenase activity, the enzyme responsible for the conversion of vasoinactive PGF metabolites to PGE metabolites, also failed to show any difference in two types of rat kidneys. The results indicate that, in hypertension, prostaglandin inactivation is impaired in kidney but is facilitated in lung.     

Excitotoxic Brain Injury Suppresses Striatal High-Affinity Glutamate Uptake in Perinatal Rats

In immature rodent brain, the glutamate receptor agonist N-methyl-D-aspartate (NMDA) is a potent neurotoxin. In postnatal day (PND)-7 rats, intrastriatal injection of 25 nmol of NMDA results in extensive ipsilateral forebrain injury. In this study, we examined alterations in high-affinity [3H]glutamate uptake (HAGU) in NMDA-lesioned striatum. HAGU was assayed in synaptosomes, prepared from lesioned striatum, the corresponding contralateral striatum, or unlesioned controls. Twenty-four hours after NMDA injection (25 nmol), HAGU declined 44 +/- 8% in lesioned tissue, compared with the contralateral striatum (mean +/- SEM, n = 6 assays, p less than 0.006, paired t test). Doses of 5-25 nmol of NMDA resulted in increasing suppression of HAGU (5 nmol, n = 3; 12.5 nmol, n = 3; and 25 nmol, n = 5 assays; p less than 0.01, regression analysis). The temporal evolution of HAGU suppression was biphasic. There was an early transient suppression of HAGU (-28 +/- 4% at 1 h; p less than 0.03, analysis of variance, comparing changes at 0.5, 1, 2, and 3 h after lesioning); 1 or 5 days postinjury there was sustained loss of HAGU (at 5 days, -56 +/- 11%, n = 3, p less than 0.03, paired t test, lesioned versus contralateral striata).(ABSTRACT TRUNCATED AT 250 WORDS)     

Interaction of nitrogen dioxide with human plasma. Antioxidant depletion and oxidative damage.

Nitrogen dioxide (NO2.) is often present in inhaled air and may be generated in vivo from nitric oxide. Exposure of human blood plasma to NO2. caused rapid losses of ascorbic acid, uric acid and protein thiol groups, as well as lipid peroxidation and depletions of alpha-tocopherol, bilirubin and ubiquinol-10. No increase in protein carbonyls was detected. Supplementation of plasma with ascorbate decreased the rates of lipid peroxidation, alpha-tocopherol depletion and loss of uric acid. Uric acid supplementation decreased rates of lipid peroxidation but not the loss of alpha-tocopherol. We conclude that ascorbic acid, protein -SH groups, uric acid and alpha-tocopherol may be important agents protecting against NO2. in vivo. If these antioxidants are depleted, peroxidation of lipids occurs and might contribute to the toxicity of NO2..     

Induction of erythropoietin responsiveness in murine hematopoietic cells by the gag-myb-ets-containing ME26 virus.

ME26 virus, which was generated by inserting the coding region of the acute avian leukemia-inducing virus E26 into a murine retrovirus vector, encodes a 135-kDa gag-myb-ets fusion protein. Amphotropic murine leukemia virus pseudotypes of ME26 virus induce a high incidence of erythroleukemia 2 to 4 months after injection into newborn NFS/N mice. Spleen cells from the majority of these mice proliferate to high levels in the presence of the erythroid hormone erythropoietin (Epo) and can easily be established as permanent Epo-dependent cell lines. The cell lines contain multiple copies of ME26 viral DNA and express viral message and protein. An Epo receptor mRNA of normal size can be detected in these cells, and binding studies reveal a single class of lower-affinity Epo receptor with an affinity for Epo that is in the range of that previously reported for erythroid cells. The ME26 virus-induced Epo-dependent cell lines, however, appear more immature than previously described erythroid cell lines and more closely resemble early hematopoietic precursor cells, suggesting that the virus may be activating the Epo receptor in hematopoietic cells that do not normally express it. Consistent with this idea, we are able to infect an interleukin-3-dependent myeloid cell line, FDC-P2, with ME26 virus and convert it to Epo dependence. The ME26 virus-infected FDC-P2 cells, even before growth on Epo, showed a large increase in the amount of Epo receptor mRNA. However, no ME26 viral integrations can be detected adjacent to the Epo receptor gene, indicating that the virus is not activating the Epo receptor gene by promoter/enhancer insertion. Our results are more consistent with the hypothesis that the gag-myb-ets-encoded viral fusion protein, which is known to bind DNA, is directly or indirectly activating the expression of the Epo receptor gene in these cells.     

The matrix protein of human immunodeficiency virus type 1 is required for incorporation of viral envelope protein into mature virions.

Accumulating evidence suggests that the matrix (MA) protein of retroviruses plays a key role in virus assembly by directing the intracellular transport and membrane association of the Gag polyprotein. In this report, we show that the MA protein of human immunodeficiency virus type 1 is also critical for the incorporation of viral Env proteins into mature virions. Several deletions introduced in the MA domain (p17) of human immunodeficiency virus type 1 Gag polyprotein did not greatly affect the synthesis and processing of the Gag polyprotein or the formation of virions. Analysis of the viral proteins revealed normal levels of Gag and Pol proteins in these mutant virions, but the Env proteins, gp120 and gp41, were hardly detectable in the mutant virions. Our data suggest that an interaction between the viral Env protein and the MA domain of the Gag polyprotein is required for the selective incorporation of Env proteins during virus assembly. Such an interaction appears to be very sensitive to conformational changes in the MA domain, as five small deletions in two separate regions of p17 equally inhibited viral Env protein incorporation. Mutant viruses were not infectious in T cells. When mutant and wild-type DNAs were cotransfected into T cells, the replication of wild-type virus was also hindered. These results suggest that the incorporation of viral Env protein is a critical step for replication of retroviruses and can be a target for the design of antiviral strategies.     

Fentanyl and medetomidine anaesthesia in the rat and its reversal using atipamazole and either nalbuphine or butorphanol.

The intraperitoneal injection of anaesthetic agents is a simple and convenient method of anaesthetizing rats. However, all of the anaesthetic combinations in current use which are administered by intraperitoneal injection produce prolonged sedation, and full recovery of consciousness may take several hours. Fentanyl, a mu agonist opioid, and medetomidine, an alpha 2-adrenoceptor agonist were mixed and administered as a single intraperitoneal injection. Combinations of 300 micrograms/300 micrograms/kg and 300 micrograms/200 micrograms/kg of fentanyl/medetomidine were shown to produce surgical anaesthesia in the rat. This anaesthetic regimen produced significant respiratory depression (P less than 0.01) and animals did not regain their righting reflex until 193 +/- 21 min (mean +/- 1 SD) after injection. Administration by intraperitoneal injection of atipamezole, a specific alpha 2-adrenoceptor antagonist (1 mg/kg) mixed with a mu antagonist/k agonist opioid (nalbuphine, 2 mg/kg or butorphanol 0.4 mg/kg), resulted in a rapid (less than 8 min) reversal of anaesthesia and the associated respiratory depression, and apparent full recovery of consciousness.     

A model for mercuric ion reduction in recombinant Escherichia coli

Plasmid-encoded mercuric reduction involves transfer of Hg(2+) across the cellular envelope and reduction to Hg(0) by the cytoplasmic mercuric reductase using NADPH. A mathematical model was developed for the binding and transfer of Hg(2+) by transport proteins and the subsequent reduction of Hg(2+). The values of the model parameters were determined using experimental data. The derived rate expressions were similar to the previously experimentally determined ones. The model predicted that a differential amplification of the transport protein relative to mercuric reductase expression levels may enhance the Hg(2+) reduction rate in whole cells.     

香菇和侧耳属间原生质体的电融合研究

从培养在液体培养基中的香菇、美味侧耳和平菇的单核菌丝用酶法分离了原生质体。施加0.5MHz、500PV/cm的正弦波和μs、6000PV/cm方形脉冲的电场诱导下使其电融合。电融合后的融合子和原生质体在固体培养基上植板培养成菌落。在显微镜下检查融合子菌株菌丝的锁状联合选出从融合子长成的菌株。香菇和美味侧耳的融合菌株产生频率为61.53%,香菇和平菇的融合菌株产生频率为32.58%。根据融合菌株与亲本的拮抗作用和他们的过氧化物同工酶和酯酶同工酶的电泳酶谱与其亲本酶谱的不同,证实这些融合菌株是从融合的异核体生长成的。同时讨论了电融合方法和结果。     

Isolation and characterization of two novel rat ovarian lactogen receptor cDNA species

Two novel lactogen receptor cDNA clones (2.1 and 1.2 kb) were isolated from a rat ovarian cDNA library. Nucleotide sequence of the 2.1 kb clone codes for a 610 aa receptor (nonglycosylated mol. wgt. 66,000 D) with an extracellular domain, a transmembrane region and an intracellular domain, and exhibited significant overall similarity with the rat liver receptor (310 aa) and both rabbit mammary and human hepatoma receptors (616 and 622 aa). However, the ovarian lactogen receptor sequence contains a unique cytoplasmic domain of 110 aa and consensus sequences for both a tyrosine phosphorylation site and an ATP/GTP type A binding site, and thus has potential for signal transduction and mitogenic activity. The 1.2 kb clone codes for a truncated binding form of 150 aa that is identical with the ovarian long form over only the first 130 residues, and lacks the transmembrane region. Differences between long and short forms of the ovarian lactogen receptors and the truncated liver species may result from alternative splicing. The prolactin holoreceptor gene(s) has the potential for producing several receptor subtypes that differ in tissue-specific expression, size, compartmentalization and mode of signal transduction, and may subserve the divergent functions of prolactin in its several target cells.     

Isolation and partial characterization of a lactotransferrin receptor from mouse intestinal brush border

Several lines of evidence have recently suggested the occurrence of a specific lactotransferrin receptor in the small intestinal brush-border membrane in several animal species, which is thought to be involved in lactotransferrin-mediated intestinal iron absorption. We report here for the first time the isolation and partial characterization of this receptor from mouse intestinal brush border. The receptor has been purified to homogeneity by affinity chromatography on an immobilized human lactotransferrin column. The purified receptor was found to be active in that it binds iron-free and iron-saturated lactotransferrin with a Kd of 0.1 microM. Anti-receptor antibodies were prepared, and the receptor was further isolated by immunoaffinity chromatography in higher yield but in a denatured form. The purified receptor was revealed by sodium dodecyl sulfate-polyacrylamide electrophoresis to be a protein of about Mr = 130,000, consisting of a single polypeptide chain. The isoelectric point was determined to be 5.8. The receptor was further shown to bear concanavalin A and phytohemagglutinin L binding glycans. Digestion by N-glycanase and endo-N-acetyl-beta-D-glucosaminidase B led to a decrease of Mr = 25,000, while the endo-N-acetyl-beta-D-glucosaminidase H was uneffective, suggesting that the lactotransferrin receptor is mainly glycosylated by bi- and triantennary glycans. To gain further insight into the interaction of the receptor with lactotransferrin, namely, the number of ligand molecules bound per molecule of receptor, mouse lactotransferrin was cross-linked to its membrane-bound enterocyte receptor by use of radiolabeled sulfosuccinimidyl 3-[[2-(p-azidosalicylamido)ethyl]dithio]propionate (SASD).(ABSTRACT TRUNCATED AT 250 WORDS)