Agonist-induced activation of phospholipase D in bovine pulmonary artery endothelial cells: regulation by protein kinase C and calcium

Regulation of phospholipase D (PLD) activity was investigated in cultured monolayers of bovine pulmonary artery endothelial cells (BPAECs). Agonists such as bradykinin, histamine, vasopressin, alpha-thrombin, and adenosine triphosphate (ATP) stimulated up to 15-fold accumulation of phosphatidylethanol (PEt) in the presence of ethanol through PLD-catalyzed phosphatidyltransferase activity. To examine mechanisms of PLD regulation, we investigated the role of protein kinase C (PKC) and Ca2+ fluxes in agonist-induced PLD activation. The PKC activator 12-O-tetradecanoylphorbol-13-acetate (TPA, 100 nmol/L) produced up to a 25-fold increase in PEt formation in a time- and dose-dependent manner. PEt production was also stimulated by other cell-permeant PKC activators such as 1,2 dioctanoylglycerol and 1-oleyl-2-acetylglycerol, whereas inactive phorbol derivatives 4-alpha-phorbol-12,13-didecanoate and 4-beta-phorbol showed no effect. The effect of TPA on PEt accumulation was inhibited by the PKC inhibitors staurosporine (5 mumol/L, 95% inhibition) and sphingosine (10 mumol/L, 50% inhibition). TPA-induced PEt accumulation was almost completely abolished (> 95% inhibition) by PKC down-regulation accomplished by long-term treatment with 100 nmol/L TPA. In contrast, bradykinin- or ATP-induced phosphorus 32-labeled PA and [32P]-labeled PEt formation was only partially blocked (70% inhibition) by either staurosporine (10 mumol/L) or PKC down-regulation, suggesting that part of agonist-stimulated PLD activity may occur in the absence of PKC activation. An increase in Cai2+ appears to be involved in agonist-induced PLD activation as bradykinin-, ATP-, or Ca2+ ionophore-induced [32P]. PEt production was attenuated by either depletion of extra-cellular Ca2+ with EGTA or chelation of intracellular Ca2+ by BAPTA. TPA-mediated PEt accumulation was not affected by EGTA treatment, whereas BAPTA reduced TPA-mediated PEt formation by 50%. These results suggest that direct PKC activation is a potent stimulus for PLD activity and that the major pathway for agonist-induced PLD activation involves PKC activation and is dependent on an increase in intracellular Ca2+. Further, these studies suggest that agonist-induced PLD activation may also involve a PKC-independent mechanism.

Measurement of cardiovascular and renal function in unrestrained hamsters

We describe a preparation for measuring blood pressure, left ventricular end diastolic pressure, heart rate, and renal excretory variables (volume, electrolytes, glomerular filtration rate) in hamsters. The new approach offers an advantage over previously described methods by eliminating the problems associated with restraint. Hamsters were surgically implanted with venous and arterial catheters. A specially constructed bladder catheter, which allows flushing to minimize errors due to dead space and permits urine collection without restraining the animals, was also implanted. The hamsters were allowed to recover from surgery for 3 hours before being studied in a specially designed lucite housing unit. Representative results were obtained in cardiomyopathic and healthy hamsters.

Activation of endothelial cell phospholipase D by hydrogen peroxide and fatty acid hydroperoxide

We have investigated oxidant-mediated stimulation of phospholipase D (PLD) activity in bovine pulmonary artery endothelial cells (BPAEC), prelabeled with [32P]orthophosphate or [32P]lysophospholipids. Treatment of cells incubated in Hanks' balanced salt solution (HBSS) containing 0.5% ethanol with hydrogen peroxide (H2O2) or linoleic acid hydroperoxide (18:2-OOH) enhanced the formation of 32P-labeled phosphatidylethanol (PEt) and phosphatidic acid (PA) in a dose- and time-dependent manner, indicating the activation of PLD. The H2O2- and 18:2-OOH-mediated PLD activation was not associated with cytotoxicity as determined by [3H]deoxyglucose release. The addition of ferrous chloride (50 microM) augmented H2O2-induced formation of [32P]PEt and [32P]PA about 2-fold, whereas the addition of the iron chelator desferoxamine blocked the potentiating effect of ferrous chloride. Replacement of the HBSS medium with Medium 199 containing 20% calf serum also potentiated the effect of H2O2-induced PLD activation. In addition to phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (PI) were readily hydrolyzed by PLD in response to H2O2 and 18:2-OOH treatment. The substrate specificity for oxidant-stimulated PLD activity differed from that observed in the presence of bradykinin or exhibited by agonist stimulation with 12-O-tetradecanoylphorbol 13-acetate (TPA) where PC was the major phospholipid hydrolyzed by PLD. The formation of PEt in the presence of H2O2 and 18:2-OOH was not abolished by chelation of either extracellular Ca2+ with EGTA (5 mM) or intracellular Ca2+ with 1,2-bis-(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid-acetoxymethyl ester (BAPTA-AM) (25 microM, 30 min). Furthermore, pretreatment of BPAEC with the protein kinase C (PKC) inhibitor staurosporine and down-regulation of PKC by chronic TPA treatment (100 nM, 18 hr) had no effect on H2O2-induced PLD activation, suggesting that PLD activation by H2O2 is independent of PKC activity. It is possible that H2O2- and 18:2-OOH-induced activation of PLD represents an important mechanism to produce PA and diacylglycerol in endothelial cells.

Interleukin 1-stimulated prostacyclin synthesis in endothelium: lack of phospholipase C, phospholipase D, or protein kinase C involvement in early signal transduction

The cascade of transmembrane signaling events that follow the occupancy of the interleukin 1 receptor remain poorly defined. We examined potential postreceptor transduction systems involved in human recombinant interleukin 1-beta-stimulated prostacyclin synthesis in human umbilical vein endothelium. Challenge of human umbilical vein endothelium monolayers with recombinant interleukin 1-beta resulted in dose- and time-dependent tritiated arachidonate release and prostacyclin synthesis consistent with phospholipase A2 activation. Prostacyclin synthesis after interleukin 1-beta (10 ng/ml) was detected 4 hours after stimulation and peaked at 16 to 24 hours. To examine whether interleukin 1-beta produced early activation of a phosphoinositide-specific phospholipase C, human umbilical vein endothelium monolayers were labeled with tritiated-2-myoinositol and inositol polyphosphates recovered after interleukin 1-beta stimulation. In contrast to the potent agonist, alpha-thrombin, interleukin 1-beta failed to significantly increase inositol phosphate production when examined for up to 4 hours. The absence of a significant increase in the Cai++ secretagogue, IP3, was confirmed in human umbilical vein endothelium monolayers loaded with the Ca++ photoprotein probe aequorin. Basal aequorin luminescence was unaltered after interleukin 1-beta (0 to 2 hours), whereas both alpha-thrombin and Ca++ ionophore A23187 produced rapid rises in Cai++. The intracellular Ca++ antagonist BAPTA and the extracellular Ca++ chelator EGTA produced significant inhibition of interleukin 1-beta-stimulated prostacyclin generation at 4 to 8 hours, suggesting either an indirect inhibitory effect of these agents on phospholipase A2 activity or that an increase in Ca++ may be a late event in the transduction scheme after interleukin 1 stimulation. Interleukin 1-beta-stimulated protein kinase C, phospholipase D, and adenylyl cyclase activities (0 to 4 hours) were unchanged from controls. Despite the absence of increased plasma membrane protein kinase C activity up to 4 hours after interleukin 1, pretreatment of human umbilical vein endothelium monolayers with staurosporine or phorbol myristate acetate (18 hours) to reduce protein kinase C activities, significantly attenuated the interleukin 1-stimulated prostanoid responses at 16 hours but not at 4 hours. Furthermore, short (5 minute) pretreatment with phorbol myristate acetate dramatically augmented interleukin 1-mediated prostacyclin responses in synergistic fashion, suggesting that protein kinase C may modulate interleukin 1 signal transducing pathways. In summary, these studies suggest that interleukin 1-beta-mediated endothelial cell phospholipase A2 activity and prostacyclin synthesis occur via a novel transducing pathway that does not involve early activation of phospholipase C, phospholipase D, or adenylate cyclase.(ABSTRACT TRUNCATED AT 400 WORDS)

Thrombin stimulation of human endothelial cell phospholipase D activity. Regulation by phospholipase C, protein kinase C, and cyclic adenosine 3'5'-monophosphate

The activation of membrane-bound phospholipase D (PLD) resulting in the generation of phosphatidic acid (PA) is increasingly recognized as an integral event in the initiation of a variety of cellular responses. We explored whether alpha-thrombin is a physiologic agonist for PLD activation in human umbilical vein endothelial cells (HUVEC). HUVEC monolayers were labeled with [32Pi] and PLD activity determined by formation of the PLD metabolite [32P] phosphatidylethanol (PEt) in the presence of 5 g/L ethanol by thin-layer chromatography. alpha-Thrombin rapidly (1 minute) increased PA and PEt formation in a dose-dependent manner (10(-6) to 10(-10)) with maximal PLD stimulation achieved with 10 nmol/L alpha-thrombin producing a threefold to fourfold increase in PA and a sixfold to eightfold increase in PEt over controls at 15 minutes. Esterolytically active zeta-thrombin (10 nmol/L) and gamma-thrombin (1 mumol/L), but not inactive DIP-alpha-thrombin (1 mumol/L) also increased PLD activity. The role of Ca2+ flux in human endothelial cell PLD activation was investigated and PEt formation was significantly enhanced by Ca2+ ionophores A23187 and ionomycin (1 mumol/L, three-fold to fourfold increase in PEt). Alpha-Thrombin-stimulated PEt formation was abolished (greater than 90% inhibition) with chelation of intracellular calcium (Ca2+i) by pretreatment with BAPTA-AM (25 mumol/L, 30 minutes) but only mildly attenuated (30% inhibition) by removal of extracellular calcium (Ca2+E) with EGTA (5 mmol/L). The protein kinase C (PKC) inhibitor staurosporine reduced alpha-thrombin-induced PEt formation in a dose-dependent manner (10 mumol/L, 78% inhibition) and PKC downregulation with chronic PMA treatment (18 hours) also resulted in marked inhibition of alpha-thrombin-induced PEt formation. Neither pertussis nor botulinum C bacterial toxins significantly altered alpha-thrombin-induced PLD responses. In contrast, similar pretreatment with cholera toxin (1 microgram/mL, 60 minutes) consistently augmented alpha-thrombin-stimulated PLD activity by 50% to 90%. Comparable results were observed with agents which increased cAMP such as forskolin, 8-bromo cAMP, or dibutyryl cAMP and cholera toxin augmentation was abolished by 2-dideoxyadenosine, a competitive inhibitor of adenylyl cyclase activity. These studies demonstrate that alpha-thrombin is a potent stimulus for human PLD-mediated PA formation and that cyclic adenosine nucleotides modulate agonist-induced cellular PLD activity. In this model of PLD activation, alpha-thrombin receptor occupancy leads to the breakdown of phosphatidylinositol 4,5-bisphosphate catalyzed by phospholipase C producing the Ca2+ secretagogue IP3 and DAG.(ABSTRACT TRUNCATED AT 400 WORDS)

Role of protein kinase C in the regulation of prostaglandin synthesis in human endothelium

The present study specifically addresses the role of protein kinase C (PKC) activation in human endothelial cell Ca2+ mobilization, a response that is functionally coupled to the production of the potent arachidonate (AA) metabolite, prostacyclin (PGI2). Phorbol 12-myristate 13-acetate (PMA), alpha-thrombin, and sodium fluoride (NaF), a direct G-protein activator, produced a rapid and time-dependent translocation of PKC from the cytosol to the membrane. Activation of PKC by brief pretreatment of human umbilical vein endothelial cell (HUVEC) monolayers with PMA resulted in the inhibition of NaF-induced inositol phosphate increases and attenuation of both alpha-thrombin- and NaF-activated increases in intracellular Ca2+ (Ca2+i). Ca2+ mobilization induced by ionophore A23187 was not affected by PKC preactivation, suggesting PKC-dependent negative feedback inhibition of phosphatidylinositol (PI)-specific phospholipase C (PLC). Agonist-stimulated AA release and PGI2 synthesis in PMA-pretreated cultured human endothelial cells, however, was potentiated, and the enhanced PGI2 synthesis produced by A23187, NaF, and alpha-thrombin was dependent upon the dose of PMA. Treatment of HUVEC monolayers with an intracellular Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N'N'-tetraacetic acid-acetoxymethylester (BAPTA-AM), dramatically reduced alpha-thrombin-, NaF-, and A23187-induced PGI2 synthesis, demonstrating the importance of Ca2+i availability in PGI2 synthesis. BAPTA pretreatment did not inhibit PMA-induced PKC activation, and BAPTA-mediated inhibition of agonist-stimulated PGI2 synthesis was partially attenuated by prior PMA pretreatment. Staurosporine, a potent PKC inhibitor, at concentrations that inhibited PKC-induced phosphorylation of histone-1, augmented both alpha-thrombin- and NaF-induced production of inositol phosphates but markedly inhibited alpha-thrombin-, NaF-, and A23187-induced PGI2 synthesis. The downregulation of PKC activity by prolonged PMA treatment (18 h) produced similar inhibition of PGI2 synthesis by these agonists (approximately 50% inhibition). These studies indicate that the integrated phospholipase A2 and PLC activities are under complex regulation by factors that include both PKC activation and [Ca2+i]. PKC exerts dual effects on prostaglandin synthesis via negative regulation of Gp-coupled PI-specific PLC and positive feedback regulation of AA release and PGI2 synthesis. PKC is thus a critical determinant in the regulation of human endothelial cell prostaglandin synthesis by both receptor-mediated and G-protein-dependent cellular activation.

Effect of zinc ion on the interaction of some amino acid compounds of copper(II) with hydrogen peroxide

Reaction of elemental copper and zinc powder mixtures with glycine (NH2.CH2COOH; HA) or aspartic acid (NH2CHCOOHCH2COOH; H2B) (in 1:1:2 ratio, respectively) in the presence of excess hydrogen peroxide (H2O2) at 50 degrees C, results in the formation of a new mixed metal peroxy carbonate compound corresponding to formula [Cu(Zn)2(O2(2-) (CO3)2(H2O)4], while the same reaction with elemental copper powder alone yields merely peroxy amino acid compounds having the formula [Cu(O2(2-)) (HA)2(H2O)] and [Cu(O2(2-)) (H2B) (H2O)2] for glycine and aspartic acid, respectively. These compounds have been characterized by elemental analysis, ESR, and electronic and IR spectra. It is interesting to note that both amino acids are converted to carbonate in the presence of zinc alone. A method analogous to that described above, for the reaction of elemental copper, zinc powder mixtures with succinic acid [(CH2COOH)2] or acetic acid (CH3COOH) in excess H2O2, on the other hand, gave a product essentially comprising copper succinate or acetate, respectively. These observations suggest an interesting and perhaps important phenomenon by which only the simple amino acids such as glycine and aspartic acid are converted to carbonates while their corresponding carboxylic acids form only their respective salts.

Localization of the human gene for the type I cyclic GMP-dependent protein kinase to chromosome 10

We have recently characterized cDNAs and genomic DNA fragments for human type I cGMP-dependent protein kinase (cGK). By probing human x hamster hybrid cell lines with a 1.2-kb intron fragment from the human type I cGK gene, we identified a 5.9-kb BglII restriction fragment and localized it to human chromosome 10. In situ hybridization analyses using 3H-labeled cDNA and genomic DNA probes for the human type I cGK to human metaphase chromosomes supported the somatic cell hybrid data and indicated that the gene (PRKG1B; protein kinase, cGMP-dependent) maps to 10p11.2----q11.2.

The HIV-1 gp120 envelope protein has the intrinsic capacity to stimulate monokine secretion

Results and conclusions concerning the ability of HIV glycoprotein (gp) 120 to stimulate monokine secretion have been equivocal, based on observations using natural gp120 derived from infected human cells and a Chinese hamster ovary (CHO) cell-derived recombinant fusion protein. Current studies were designed to determine whether differences in recombinant gp120 proteins could result in failure to trigger monokine production. We found that natural gp120 could stimulate monocytes to release TNF-alpha, IL-1 beta, IL-6, and granulocyte-macrophage-CSF, and this effect could be blocked with soluble CD4. Full-length rgp120 either expressed from an adenovirus vector and purified from infected human cells, or derived from CHO cells, could function similarly. In contrast, full-length recombinant envelope protein expressed in a baculovirus system and a CHO cell-derived recombinant fusion protein tested previously, consistently failed to stimulate monokine production. The stimulatory capacity of both natural and full-length CHO cell-derived gp120 was eliminated by heating at 100 degrees C, and could be blocked with excess CHO cell-derived gp120 fusion protein. Inasmuch as the baculovirus-expressed gp120 and the CHO cell-derived recombinant fusion protein can bind to CD4, these results suggest that HIV gp120 binding to CD4 on the monocyte surface may of itself be insufficient for stimulation of monokine secretion. Therefore, primary protein structure, as well as posttranslational protein modifications, may determine this activity.

The HIV-1 gp120 envelope protein has the intrinsic capacity to stimulate monokine secretion

Results and conclusions concerning the ability of HIV glycoprotein (gp) 120 to stimulate monokine secretion have been equivocal, based on observations using natural gp120 derived from infected human cells and a Chinese hamster ovary (CHO) cell-derived recombinant fusion protein. Current studies were designed to determine whether differences in recombinant gp120 proteins could result in failure to trigger monokine production. We found that natural gp120 could stimulate monocytes to release TNF-alpha, IL-1 beta, IL-6, and granulocyte-macrophage-CSF, and this effect could be blocked with soluble CD4. Full-length rgp120 either expressed from an adenovirus vector and purified from infected human cells, or derived from CHO cells, could function similarly. In contrast, full-length recombinant envelope protein expressed in a baculovirus system and a CHO cell-derived recombinant fusion protein tested previously, consistently failed to stimulate monokine production. The stimulatory capacity of both natural and full-length CHO cell-derived gp120 was eliminated by heating at 100 degrees C, and could be blocked with excess CHO cell-derived gp120 fusion protein. Inasmuch as the baculovirus-expressed gp120 and the CHO cell-derived recombinant fusion protein can bind to CD4, these results suggest that HIV gp120 binding to CD4 on the monocyte surface may of itself be insufficient for stimulation of monokine secretion. Therefore, primary protein structure, as well as posttranslational protein modifications, may determine this activity.

Membrane-associated phospholipase D activity in rat sciatic nerve

Rat sciatic nerve contains a membrane-bound phospholipase D that catalyzes the hydrolysis of exogenous phosphatidylcholine (PC) to phosphatidic acid (PA) and choline. The enzyme is associated with a particulate fraction consisting primarily of microsomes and myelin. This fraction also contains phosphatidate phosphohydrolase activity leading to the production of diacylglycerols (DAG). The phosphohydrolase activity can be completely inhibited by NaF. Hydrolysis of exogenous PC requires detergent and is linear up to about 40 micrograms of protein at a pH optimum of 6.5. In the absence of NaF, the sum of PA and DAG increases linearly for 40 min, whereas in its presence, PA production is linear for only 15 min. At optimum conditions, PC hydrolysis proceeds at 15 nmol/h/mg of protein. Addition of increasing amounts of ethanol to the incubation system leads to the generation of increasing amounts of phosphatidylethanol, indicating transphosphatidylation activity. At an ethanol concentration of 0.4 M, phosphatidylethanol represents about one-half of the reaction products generated at approximately the same rate of enzymic activity observed in the absence of ethanol. Higher ethanol concentrations are inhibitory.

Peroxidative modification of phospholipids in myocardial membranes

Rat heart myocardial membranes exposed to the free radical generating system, Fe2+/ascorbate, undergo lipid peroxidation as evidenced by the accumulation of thiobarbituric acid-reactive substances, loss of polyunsaturated fatty acids from phospholipids, and formation of conjugated dienes and fluorescent substances. In addition, the treated membranes exhibit a dramatic decrease in extractable phospholipids. This decrease is even more pronounced in individual phospholipid classes isolated by high-performance liquid chromatography. The decrease in lipid phosphorus under oxidant stress is accompanied by an increase in the phosphorus content of the aqueous phase after Folch extraction and by an even greater increase of phosphorus in the protein residue. In addition, increased amounts of saturated and monounsaturated fatty acyl groups are found in the protein residue of Fe2+/ascorbate-treated membranes. Extraction of the oxidant-treated membranes with acidic solvents does not enhance the recovery of phospholipids and neither does treatment with detergents, trypsin, and chymotrypsin prior to lipid extraction. However, treatment with the bacterial protease, Pronase, markedly enhances the recovery of phospholipids from the peroxidized membranes. These results indicate that membrane phospholipids undergoing free radical-induced peroxidation may form lipid-protein adducts, which renders them inextractable with lipid solvents.

An unusual presentation of cardiac tamponade

A case of pericardial effusion with tamponade that presented as an acute abdomen is described.

Mechanism of phospholipidosis in amiodarone pulmonary toxicity

Amiodarone therapy can be complicated by life-threatening pulmonary toxicity and is invariably associated with characteristic morphologic changes in the lung consistent with a severe phospholipidosis. To determine possible mechanisms, this study utilizes a unique in vitro cell culture model of amiodarone pulmonary toxicity and demonstrates that amiodarone can directly induce an accumulation of phospholipids within bovine pulmonary artery endothelial (BPAE) cells during the first 24 hr using amiodarone concentrations equivalent to concentrations found in the blood and lungs of human subjects. For example, amiodarone at 7.5 microM during a 24-hr incubation increases [32P]orthophosphate incorporation into phospholipids from 193 +/- 10 X 10(3) dpm/10(6) cells to 266 +/- 19 X 10(3) dpm/10(6) cells (P less than .01). A generalized increase in all phospholipids occurs after amiodarone treatment of the cultured cells; however, several specific phospholipids including phosphatidylinositol, phosphatidic acid and bis(monoacylglycerol) phosphate are all significantly increased to a greater extent than other phospholipids. Furthermore, the data indicate that amiodarone is a potent inhibitor of lysosomal phospholipase A1 and A2 activities derived from the BPAE cells; whereas, amiodarone has no effect on phospholipase A1 and A2 activities from the BPAE microsomal fraction. Thus, this study demonstrates phospholipids accumulate in cultured BPAE cells exposed to amiodarone and provides direct evidence that the drug initiates a specific and nearly complete inhibition of phospholipid degradation by lysosomal phospholipase A1 and A2 suggesting a similar process may occur in vivo in the lungs of subjects with amiodarone pulmonary toxicity.

Molecular cloning and predicted full-length amino acid sequence of the type I beta isozyme of cGMP-dependent protein kinase from human placenta. Tissue distribution and developmental changes in rat

In this study we report the isolation and characterization of three overlapping cDNA clones for the type I beta isozyme of cGMP-dependent protein kinase (cGK) from human placenta libraries. The composite sequence was 3740 nucleotides long and contained 58 nucleotides from the 5'-noncoding region, an open reading frame of 2061 bases including the stop codon, and a 3'-noncoding region of 1621 nucleotides. The predicted full-length human type I beta cGK protein contained 686 amino acids including the initiator methionine, and had an estimated molecular mass of 77,803 Da. On comparison to the published amino acid sequence of bovine lung I alpha, human placenta I beta cGK differed by only two amino acids in the carboxyl-terminal region (amino acids 105-686). In contrast, the amino-terminal region of the two proteins was markedly different (only 36% similarity), and human I beta cGK was 16 amino acids longer. In a specific region in the amino-terminus (amino acids 63-75), 12 out of 13 amino acids of the human I beta cGK were identical to the partial amino acid sequence recently published for a new I beta isoform of cGK from bovine aorta. Northern blot analysis demonstrated a human I beta cGK mRNA, 7 kb in size, in human uterus and weakly in placenta. An mRNA of 7 kb was also observed in rat cerebellum, cerebrum, lung, kidney, and adrenal, whereas an mRNA doublet of 7.5 and 6.5 kb were observed in rat heart. Comparison of Northern and Western blot analyses demonstrated that the mRNA and protein for cerebellar cGK increased during the development of rats from 5 to 30 days old, whereas the 6.5 kb mRNA in rat heart declined.

Biosynthesis and processing of human immunodeficiency virus type 1 envelope glycoproteins: effects of monensin on glycosylation and transport

When human immunodeficiency virus type 1 envelope glycoproteins were expressed in 293 cells by using a recombinant adenovirus expression vector, the envelope precursor (gp160) was initially glycosylated by cotranslational addition of N-linked high-mannose oligosaccharide units to the protein backbone and then cleaved to gp120 and gp41. The subunits gp120 and gp41 were then further modified by the addition of fucose, galactose, and sialic acid, resulting in glycoproteins containing a mixture of hybrid and complex oligosaccharide side chains. A fraction of glycosylated gp160 that escaped cleavage was further modified by the terminal addition of fucose and galactose, but the addition of sialic acid did not occur, consistent with the notion that it is compartmentalized separately from the gp120 envelope protein. Processing and transport of gp160 were blocked by the monovalent ionophore monensin, which at high concentrations (25 microM and above) was a potent inhibitor of the endoproteolytic cleavage of gp160; at lower concentrations (1 to 10 microM), it selectively blocked the secondary glycosylation steps so that smaller products were produced. Monensin (1 microM) treatment also resulted in a reduction in syncytium formation, which was observed when recombinant infected cells were cocultivated with CD4-bearing HeLa cells. The infectivity of human immunodeficiency virus type 1 was also reduced by monensin treatment, a decrease that may be due to incompletely glycosylated forms of gp120 that have a lower affinity for the CD4 receptor.

Factors involved in specific transcription by mammalian RNA polymerase II. Role of factors IID and MLTF in transcription from the adenovirus major late and IVa2 promoters

The role of the adenovirus major late upstream transcription factor (MLTF) in transcription from the adenovirus major late and the IVa2 promoters was studied. The transcription initiation site of the IVa2 promoter is located 210 nucleotides upstream from the CAP site of the major late promoter. Transcription from these two promoters occurs on different DNA strands. Thus, this divergent transcription suggests that the same factor could simultaneously regulate the expression of two different genes. This was investigated utilizing a reconstituted transcription system in vitro. The addition of MLTF to reaction mixtures containing the purified general transcription factors and the major late promoter resulted in a 10-12-fold stimulation of transcription. This stimulation was because of an increase of the stability of the preinitiation complex. MLTF allowed DNA template molecules to undergo multiple rounds of transcription. MLTF also stimulated transcription from the adenovirus-encoded IVa2 promoter. Surprisingly, reconstitution experiments indicated that transcription from the IVa2 promoter which does not have a TATA sequence required all the previously described general transcription factors, including TFIID, the TATA binding protein. The requirement for TFIID was demonstrated by reconstitution experiments as well as by oligonucleotide competition experiments. The implications of this observation are discussed.

Synthesis and processing of human immunodeficiency virus type 1 envelope proteins encoded by a recombinant human adenovirus

A recombinant adenovirus was constructed by inserting the human immunodeficiency virus type 1 (HIV-1) envelope gene downstream from the early region 3 (E3) promoter of adenovirus type 5 (Ad5), replacing the coding sequences of E3. The recombinant virus replicated as efficiently as the parent virus in all cell lines tested. Human cells infected with the recombinant virus synthesized the HIV-1 envelope precursor gp160, which was efficiently processed to the envelope glycoproteins gp120 and gp41. A human T-lymphoblast line (Molt-4) infected with the recombinant virus expressed HIV-1 envelope glycoproteins on the cell surface, leading to syncytium formation. The envelope gene was expressed from the E3 promoter at early times after infection and at late times from the major late promoter. When cotton rats were infected with the recombinant virus, antibodies against the HIV-1 envelope glycoproteins could be expressed in an immunoreactive form by the recombinant adenovirus, further illustrating the usefulness of adenoviruses as expression vectors.

Passive hemagglutination test for detection of antibodies to human immunodeficiency virus type 1 and comparison of the test with enzyme-linked immunosorbent assay and Western blot (immunoblot) analysis

A passive hemagglutination test (PHA) was developed for detecting antibodies to human immunodeficiency virus type 1 (HIV-1) utilizing sheep erythrocytes cross-linked with purified envelope glycoprotein (gp160) of HIV-1. In an analysis of 216 human serum samples, 100% correlation was observed in 86 reactive and 124 nonreactive serum samples between PHA and commercial enzyme-linked immunosorbent assays and Western blot (immunoblot) analysis. Serum samples from gp160-immunized chimpanzees also reacted equally well in PHA. The test is simple, rapid, and inexpensive, thus providing an alternate, quick method of detecting HIV antibodies. These advantages and the thermal stability of the reagents that are used make this an attractive alternative for detecting prior exposure of individuals to HIV-1.

Evidence for the incorporation of [32P]orthophosphate into leaf inositol phospholipids

Leaf discs of brinjal, tomato, sugar cane and maize rapidly incorporated [32P]orthophosphate into total phospholipids. Analyses of the labelled lipid extracts by thin-layer chromatography, autoradiography and comparison with inositol phospholipid standards demonstrated the labelling of phosphatidylinositol monophosphate and phosphatidylinositol bisphosphate in addition to other phospholipids. The presence of polyphosphoinositides was further confirmed by deacylation of phosphatidylinositol monophosphate and phosphatidylinositol bisphosphate and separation of the water-soluble products, glycerophosphoinositol phosphate and glycerophosphoinositol bisphosphate by formate exchange chromatography. Incorporation of [32P]orthophosphate into inositol phospholipids was time-dependent, with monoester phosphate groups attaining isotopic equilibrium within 90 min of incubation. After 2 h, incorporation of label into phosphatidylinositol, phosphatidylinositol monophosphate and phosphatidylinositol bisphosphate was about 15, 10 and 3%, respectively, of the total phospholipids. The ratio of radioactivity in phosphatidylinositol/phosphatidylinositol monophosphate/phosphatidylinositol bisphosphate was about 5:5:1 in brinjal leaves. However, this ratio may be an overestimate of the amounts of inositol phospholipids present, as other lysophospholipids may comigrate with standards.

Radiographic performance of two different total hip cemented arthroplasties. A survivorship analysis

Detailed serial radiographic analysis of the femoral and acetabular components of 367 Charnley (cobalt-chrome alloy) and 383 STH (titanium alloy) primary cemented total hip prostheses was conducted. The follow-up of the Charnley prosthesis ranged from 1 to 16 years (mean follow-up, 9 years), and for the STH from 1 to 11 years (mean follow-up, 80 months). Both single period and survivorship analyses were done to evaluate the radiographic performance. The analysis revealed that the curved STH prostheses' overall radiographic performance was less satisfactory than the Charnley prostheses. However, the STH with a straight stem had significantly better radiographic performance compared with the Charnley prostheses in all parameters except in the incidence of bone-cement radiolucent lines.