Production of interleukin 10 during malaria caused by lethal and nonlethal variants of Plasmodium yoelii yoelii

We investigated the induction of T-helper cell subsets during the course of lethal or nonlethal bloodstage Plasmodium yoelii 17X infection in C57BL/6 mice, which are relatively susceptible to these intraerythrocytic parasites. C57BL/6 mice infected with the nonlethal variant (PyNL) showed a moderate level of parasitemia and resolution of primary acute infection by week 4. Mice infected with the lethal variant (PyL) developed fulminating parasitemia and ultimately died. T-helper subset function was assessed during infection by determining the kinetics of in vitro production of the Th1-derived cytokine interferon-gamma (IFN-gamma) and the Th2-derived cytokine interleukin 10 (IL-10) by means of bioassay and enzyme-linked immunosorbent assay (ELISA), respectively. Spleen cells obtained from mice infected with PyL within the 1st week of infection produced high levels of IL-10 and IFN-gamma in response to malaria antigen. IL-10 also appeared in sera from PyL-infected mice at the same time at which the in vitro IL-10 response peaked. In contrast, spleen cells from mice infected with PyNL failed to produce IL-10 during the course of infection. CD4+ T-lymphocytes from mice infected with the lethal variant were a major source of IL-10, although non T-cells were also involved in the production of IL-10 during this malaria infection. In addition, the initial burst of IL-10 in response to malaria antigens was seen concomitantly with the production of IFN-gamma within the 1st week of infection. These results indicate that both Th1 and Th2 subsets of T-helper lymphocytes are activated during infection with the lethal variant of P. yoelii and support the contention of other investigators that a strong Th2 response early in infection is associated with the lethal outcome of malaria.

Immunogenicity of Leucocytozoon caulleryi sporozoites and their reactivity with specific immune sera

The immunogenicity of Leucocytozoon caulleryi sporozoites for chickens and their reactivity in vitro with specific immune sera were studied. Almost all of the chickens that had been immunized with the sporozoite antigens survived the sporozoite challenge. The degree of parasitemia observed in the immunized chickens was significantly lower than that found in the nonimmunized chickens. Specific antibodies against sporozoites were tested by the circumsporozoite precipitation (CSP) reaction. Antibodies were demonstrated in the sera of chickens that had been immunized with the sporozoite antigens or chickens that had recovered from a primary infection with L. caulleryi sporozoites. When viable mature sporozoites were incubated in vitro with serum from immune chickens, agglutination and a long, thread-like precipitate at one end of the sporozoite could be seen within a few minutes under a phase-contrast microscope. The effects of specific immune serum on the infectivity of sporozoites were examined by the sporozoite neutralization activity (SNA) test. Sporozoites that had been incubated in vitro with serum from immune chickens lost their infectivity to chickens. The CSP reaction and the SNA test in L. caulleryi infection were stage- and species-specific.

Vasospastic angina in a patient with Fabry's disease who showed normal coronary angiographic findings

It has been reported that coronary diseases in patients with Fabry's disease are induced by deposits in endothelial cells and coronary smooth muscle cells. Most of those are ischemia due to stenosis. This report describes a case of patient with Fabry's disease who showed severe vasospasms without coronary artery stenosis during acetylcholine loaded coronary angiography. In this case, a myocardial biopsy revealed that the deposits in the endothelial cells of the myocardial capillaries were lamellated appearance. Recently, it is reported that endothelial cell damage could be an important cause of coronary vasospasm. This case suggests that the some sort of functional disorder was induced by glyco-sphingolipid deposits in the coronary endothelial cells, and that this might have led to coronary artery spasms without the organic stenosis of coronary arteries.

Sperm immobilization antibodies in infertile male sera decrease the acrosome reaction: a possible mechanism for immunologic infertility

OBJECTIVE

To study the effect of sperm-immobilizing antibodies from male sera on spontaneous and A23187-induced acrosome reactions (AR).

DESIGN

Swim-up spermatozoa obtained from three fertile donors were incubated with 13 sera with sperm-immobilizing antibodies obtained from infertile men and three control sera obtained from healthy fertile males. Sperm acrosomes were examined by staining with pisum sativum agglutinin labeled with fluorescein isothiocyanate (30 micrograms/ml; Sigma Chemical Co., St. Louis. MO) as spontaneous and A23187 (used at a final concentration of 10 microM; Sigma Chemical Co.) induced.

RESULTS

The incidence of spontaneous AR of spermatozoa incubated with antisperm antibody positive male sera (6.2 +/- 0.7) was significantly (P < 0.001) lower than that of spermatozoa incubated with control sera (10.7 +/- 0.5). And the incidence of A23187-induced and -inducible (incidence of induced minus spontaneous) ARs of spermatozoa incubated with sperm antibody-positive male sera (12.4 +/- 1.9 and 6.2 +/- 1.9) was significantly lower (P < 0.001) than that of spermatozoa incubated with control sera (31.0 +/- 0.5 and 20.3 +/- 0.9). Sperm-immobilizing antibody-positive sera decreased spontaneous, A23187-induced, and inducible ARs.

CONCLUSIONS

Sperm-immobilizing antibodies from male sera interfere with fertilization by inhibiting the AR.

Rho-associated kinase, a novel serine/threonine kinase, as a putative target for small GTP binding protein Rho

The small GTP binding protein Rho is implicated in cytoskeletal responses to extracellular signals such as lysophosphatidic acid to form stress fibers and focal contacts. Here we have purified a Rho-interacting protein with a molecular mass of approximately 164 kDa (p164) from bovine brain. This protein bound to GTPgammaS (a non-hydrolyzable GTP analog).RhoA but not to GDP.RhoA or GTPgammaS.RhoA with a mutation in the effector domain (RhoAA37).p164 had a kinase activity which was specifically stimulated by GTPgammaS.RhoA. We obtained the cDNA encoding p164 on the basis of its partial amino acid sequences and named it Rho-associated kinase (Rho-kinase). Rho-kinase has a catalytic domain in the N-terminal portion, a coiled coil domain in the middle portion and a zinc finger-like motif in the C-terminal portion. The catalytic domain shares 72% sequence homology with that of myotonic dystrophy kinase and the coiled coil domain contains a Rho-interacting interface. When COS7 cells were cotransfected with Rho-kinase and activated RhoA, some Rho-kinase was recruited to membranes. Thus it is likely that Rho-kinase is a putative target serine/threonine kinase for Rho and serves as a mediator of the Rho-dependent signaling pathway.

Cholecystokinin-B/gastrin receptors mediate rapid formation of actin stress fibers

Specific receptors for brain-gut peptide hormones, cholecystokinin (CCK) and gastrin, are expressed in a variety of human tumor cells. CCK and gastrin promote the growth of NIH3T3 cells into which the CCK-B/gastrin receptor had been introduced via a eukaryotic expression vector. In this study, we have examined the effect of CCK-8 on the actin cytoskeleton by using two mouse fibroblast cell lines expressing human CCK-B/gastrin receptors. Treatment with very low concentration of CCK-8 (10(-10) M) induced the formation of actin stress fibers within one minute. Stress fiber formation increased for 30 min. In contrast, a potent mitogen for fibroblasts, platelet-derived growth factor (PDGF), initially induced membrane ruffling and, later, a weak formation of stress fibers. Microinjection of rho GDP dissociation inhibitor or Clostridium botulinum ADP-ribosyltransferase C3 which is known to impair the function of a small GTP-binding protein, rho p21, inhibited the stress fiber formation by CCK-8 as well as by PDGF. These results indicate that CCK-B/gastrin receptor could regulate stress fiber formation in a rho p21-dependent manner. The signals from CCK-B/gastrin receptor might affect cell growth as well as cell motility or adhesion by regulating the actin cytoskeleton.

Differential activation of the murine laminin B1 gene promoter by RAR alpha, ROR alpha, and AP-1

RAR alpha, ROR alpha and AP-1 activated the transcription of the murine laminin B1 gene promoter, which consists of three core elements. Cotransfection experiments showed that AP-1-activated transcription is further stimulated by RAR alpha, but not by ROR alpha. Additionally, it was demonstrated by promoter mutagenesis that all of the three core elements are required for transactivation by RAR alpha and ROR alpha, while any one of them is dispensable for AP-1-activated transcription. These results suggest that the modes of transactivation of the laminin B1 promoter are different among the three transactivators.

An attempt to convert noncatalytic nucleotide binding site of F1-ATPase to the catalytic site: hydrolysis of tethered ATP by mutated alpha subunits in the enzyme

The alpha and beta subunits of F1-ATPase are homologous in primary structure and have similar folding topologies. The position of the essential Glu residue in the catalytic sites which reside in the beta subunits is occupied by a Gln residue in the noncatalytic nucleotide binding sites which reside in the alpha subunits. To test if an exchange of catalytic and noncatalytic binding sites is possible, we have replaced the Gln-Lys sequence in the noncatalytic binding site of the alpha subunit with Glu-Arg and, reciprocally, the Glu in the catalytic site of the beta subunit with Gln. The resultant mutant alpha3beta3gamma complex lost steady-state ATPase activity. However, HPLC analysis of tryptic digests of the mutant alpha3beta3gamma complex which had been photolabeled with 2-N3-[8-3H]ATP revealed that ATP tethered to the noncatalytic binding side was hydrolyzed, indicating that a primitive catalytic ability was generated at the alpha subunit by the introduced Glu.

Dense microspheres in normal horse brain

Here were report eosinophilic globular bodies referred to as dense microspheres (DMS), in the brains of normal horse in relation to the ageing process. The characteristic structures of DMS found in the horse were in similar to those previously reported in the human. The DMS were found predominantly in the neuropil of the cerebral cortex, and were shown histochemically to have a proteinaceous content. Electron microscopy showed that the DMS consisted of homogeneous electron-dense material bound by a single membrane and that they were found within the neuronal processes. In addition, immature or small DMS were observed, which seemed to be closely correlated with the endoplasmic reticulum.

[Five cases of hereditary high red cell membrane phosphatidylcholine hemolytic anemia in three families]

Five cases of hereditary high red cell membrane phosphatidylcholine hemolytic anemia in three families were described. All cases were clinically manifested by jaundice and splenomegaly. Hemolysis was evident from indirect hyperbilrubinemia, reticulocytosis and decrement of serum haptoglobin. Red blood cells showed morphological abnormalities such as poikylocytosis, anisocytosis and target cells on blood smears. Both direct and indirect Coombs' tests were negative. Ham test, sugar water test and hemoglobin electrophoresis showed no abnormalities. Osmotic fragility test showed decreased membrane fragility. Lipid analysis of red cell membrane showed increment of phosphatidylcholine content and decrement of sphingomyelin content, although plasma lipids were essentially normal. Influx and efflux of sodium through the red cell membrane were both increased. Splenectomy was performed without effect on one patient and the mother of other patients.

Effect of danazol on the immunocompetent cells in the eutopic endometrium in patients with endometriosis: a multicenter cooperative study

OBJECTIVE

To assess the effects of danazol on immunocompetent cells, human leukocyte antigen (HLA) expression, and adhesion molecules in the eutopic endometrium of patients with endometriosis.

DESIGN

Antigens were localized immunohistochemically in the endometria, before treatment and during treatment (2 months later).

PARTICIPANTS

Ten patients with laparoscopically proven endometriosis who consented to participate in this study were treated with 400 mg/d of danazol for 4 months. Forty-two infertile patients without endometriosis or adenomyosis served as controls.

RESULTS

Immunohistochemical analysis revealed significantly increased expression of the T cell subsets, macrophages, adhesion molecules, and HLA antigens in eutopic endometrium in patients with endometriosis compared with the infertile group. Treatment with danazol reduced the number of cells in T cell subsets, adhesion molecules, or HLA antigen expression, especially of gamma delta T cells, to 39.5% of the pretreatment value in patients with endometriosis.

CONCLUSIONS

Danazol had an immunomodulatory effect on the autoimmune response in endometrium associated with endometriosis.

Expression of c-fms proto-oncogene product by ovarian cancer cell lines with effects of macrophage colony-stimulating factor on proliferation

We studied the production of macrophage colony-stimulating factor (M-CSF) and the expression of c-fms mRNA, an M-CSF receptor, in four human ovarian cancer cell lines. All four cell lines expressed c-fms mRNA while three secreted M-CSF into the culture medium. The exogenous administration of M-CSF caused no significant enhancement of cellular proliferation in any cell line. Interestingly, the proliferation of KK cells was not affected by anti-M-CSF antibody. These results, taken together with the fact that ovarian cancer cells simultaneously produce M-CSF and c-fms, suggest that an autocrine mechanism may modulate cellular proliferation.

Regulation of dopamine D2 receptor affinity by cholecystokinin octapeptide in fibroblast cells cotransfected with human CCKB and D2L receptor cDNAs

Alteration in dopamine (DA) and/or cholecystokinin (CCK) transmission in the CNS may be of relevance for schizophrenia. Previous findings in striatal membranes give indications of a modulation of DA D2 receptor affinity by CCKB receptor activation. In the present study receptor binding studies were performed in a mouse fibroblast cell line (L-hD2l/CCK), expressing both human D2 receptors (long form, D2L) and human CCKB receptors, and binding sites for [3H]CCK-8S (sulfated CCK octapeptide), the D2 agonist [3H]NPA and the D2 antagonist [3H]raclopride were found and characterized in saturation and competition experiments. 1 nM of CCK-8 caused a significant 38% increase in the KD value of the D2 agonist [3H]NPA binding sites in the L-hD2l/CCK cell membranes. This change was blocked by the CCKB receptor antagonist PD 134308 (50 nM). Furthermore, 1 nM of CCK-8 increased the KD value of the D2 antagonist [3H]raclopride binding sites by 34% (P < 0.05) in the L-hD2l/CCK cell membranes. Control cells (L-hD2l cells) expressing D2L receptors showed no specific [3H]CCK-8S binding sites and no modulation by CCK-8 of the D2L receptors. These findings indicate a modulation of the D2L receptor affinity by activation of the CCKB receptor also when they are coexpressed in a fibroblast cell line. One possible explanation of these data may include a receptor-receptor interaction between the CCKB and D2L receptors.

Structural asymmetry of F1-ATPase caused by the gamma subunit generates a high affinity nucleotide binding site

The alpha 3 beta 3 gamma and alpha 3 beta 3 complexes of F1-ATPase from a thermophilic Bacillus PS3 were compared in terms of interaction with trinitrophenyl analogs of ATP and ADP (TNP-ATP and TNP-ADP) that differed from ATP and ADP and did not destabilize the alpha 3 beta 3 complex. The results of equilibrium dialysis show that the alpha 3 beta 3 gamma complex has a high affinity nucleotide binding site and several low affinity sites, whereas the alpha 3 beta 2 complex has only low affinity sites. This is also supported from analysis of spectral change induced by TNP-ADP, which in addition indicates that this high affinity site is located on the beta subunit. Single-site hydrolysis of substoichiometric amounts of TNP-ATP by the alpha 3 beta 3 gamma complex is accelerated by the chase addition of excess ATP, whereas that by the alpha 3 beta 3 complex is not. We further examined the complexes containing mutant beta subunits (Y341L, Y341A, and Y341C). Surprisingly, in spite of very weak affinity of the isolated mutant beta subunits to nucleotides (Odaka, M., Kaibara, C., Amano, T., Matsui, T., Muneyuki, E., Ogasawara, K, Yutani, K., and Yoshida, M. (1994) J. Biochem. (Tokyo) 115, 789-796), a high affinity TNP-ADP binding site is generated on the beta subunit in the mutant alpha 3 beta 3 gamma complexes where single-site TNP-ATP hydrolysis can occur. ATP concentrations required for the chase acceleration of the mutant complexes are higher than that of the wild-type complex. The mutant alpha 3 beta 3 complexes, on the contrary, catalyze single-site hydrolysis of TNP-ATP rather slowly, and there is no chase acceleration. Thus, the gamma subunit is responsible for the generation of a high affinity nucleotide binding site on the beta subunit in F1-ATPase where cooperative catalysis can proceed.

Identification of a putative target for Rho as the serine-threonine kinase protein kinase N

Rho, a Ras-like small guanosine triphosphatase, has been implicated in cytoskeletal responses to extracellular signals such as lysophosphatidic acid (LPA) to form stress fibers and focal contacts. The form of RhoA bound to guanosine triphosphate directly bound to and activated a serine-threonine kinase, protein kinase N (PKN). Activated RhoA formed a complex with PKN and activated it in COS-7 cells. PKN was phosphorylated in Swiss 3T3 cells stimulated with LPA, and this phosphorylation was blocked by treatment of cells with botulinum C3 exoenzyme. Activation of Rho may be linked directly to a serine-threonine kinase pathway.

Perioperative respiratory management with fiberoptic bronchoscopy in pediatric living-related liver transplantation

BACKGROUND

Perioperative respiratory complications have been one of the largest obstacles to pediatric management of pediatric liver

METHODS

The roles of fiberoptic bronchoscopy in perioperative respiratory management of pediatric liver transplantation were studied retrospectively.

RESULTS

In a group of 162 children who underwent pediatric living-related liver transplantation, 44 underwent 222 bronchoscopic procedures for diagnostic and therapeutic purposes during the perioperative period. Major indications for bronchoscopy were atelectasis/retention of airway secretion (n = 27), pneumonia (n = 19), pulmonary edema (n = 8), airway stenosis (n = 7), and airway bleeding (n = 6). Visualization of the airway was helpful in diagnosing respiratory complications; in seven infants, bronchoscopy revealed tracheobronchial stenosis that other diagnostic modalities failed to detect. In 16 of 19 patients with pneumonia, specimens taken by bronchoscopy were positive for specific pathogens. Bronchoscopy also proved to have significant therapeutic value, especially in airway cleaning; bronchial suctioning resulted in immediate reexpansion of the collapsed lung in 16 of 20 cases of atelectasis. No complications were noted other than severe hypoxia and bradycardia in one infant.

CONCLUSIONS

Fiberoptic bronchoscopy is a safe and useful modality for perioperative respiratory management in pediatric liver transplantation.

Control of gastric pH with ranitidine in patients with Crohn's disease receiving total parenteral nutrition. Comparison of two intravenous regimens

Eleven patients with Crohn's disease in remission who were receiving total parenteral nutrition (TPN) underwent continuous intragastric 24-h pH monitoring before and during ranitidine administration. The patients were randomly allocated to receive 200 mg/day (group 1) or 400 mg/day (group 2) of ranitidine by continuous infusion. The mean basal 24-h gastric pH was sustained at a low value. After raintidine administration, the mean pH increased significantly both in group 1 (from 2.13 to 3.28) and in group 2 (from 1.91 to 3.36), with the mean holding-time at pH-3 also increasing significantly in both groups. There were no differences in the mean pH or holding-time at pH-3 between the two groups during ranitidine administration; however, the plasma ranitidine concentration was significantly higher in group 2. These findings indicate that the continuous infusion of a standard dose of ranitidine exerted a maximal inhibitory effect on the sustained hyperacidity induced by TPN, but that this infusion was unable to maintain the intragastric pH level at above 3.5.

[Cholecystokinin-B/gastrin receptor is a novel molecular probe for human small cell lung cancer]

Cloning of CCK-B/gastrin receptor cDNAs showed that they possess the feature of serpentine G protein coupled receptors. In this study, the receptor mRNA was detected selectively in all SCLCs (10 cases) with a RT-PCR assay. By contrast, it was detectable in only one of thirteen squamous cell carcinomas or twenty-one adenocarcinomas of lung. Thus, CCK-B/gastrin receptor has been demonstrated to provide a novel molecular marker for the diagnosis of small cell lung cancer (SCLC) by using biopsy specimens.

In vitro fertilization of in vitro matured oocytes obtained from the follicles without hCG exposure for prevention of severe ovarian hyperstimulation syndrome: a case report

We aspirated ovarian follicles of an infertile patient who encountered a great risk of ovarian hyperstimulation (OHSS) during her ovulation-induction cycle, which had been stimulated with gonadotropins, in order to avoid OHSS without interrupting the treatment. If this action were to yield a considerable number of immature oocytes, some of which were to achieve in vitro maturation and subsequent fertilization, this method could be an alternative to conventional ovulation-induction methods for patients who repeatedly present imminent signs of hyperstimulation. However, the number of oocytes collected from the patient was disappointingly low, even though a large number of follicles were thoroughly aspirated. One of these oocytes was matured in vitro in a medium containing 30% follicular fluid and granulosa cells of mature follicles, fertilized, cryopreserved, and transferred in a later artificial cycle; but pregnancy was not achieved. A low number of recovered oocytes from patients in this situation might be a factor that greatly limits the clinical applications of this method.

Five new anthocyanins, ternatins A3, B4, B3, B2, and D2, from Clitoria ternatea flowers

Five new ternatins 1-5 have been isolated from Clitoria ternatea flowers, and the structures have been determined by chemical and spectroscopic methods as delphinidin 3-malonylG having 3'-GCG-5'-GCG, 3'-GCG-5'-GC, 3'-GCGCG-5'-GC, 3'-GCGC-5'-GCG, and 3'-GCGC-5'-GC side chains, respectively, in which G is D-glucose and C is p-coumaric acid. Pigment 1 had symmetric 3',5'-side chains. Compounds 3 and 4 are structural isomers. These ternatins were shown to form an intramolecular stacking between the aglycon ring and the 3',5'-side chains in solution.

Stimulatory effect of zinc-chelating dipeptide on deoxyribonucleic acid synthesis in osteoblastic MC3T3-E1 cells

Whether deoxyribonucleic acid (DNA) synthesis in osteoblastic MC3T3-E1 cells is stimulated by zinc, an activator of bone formation, was investigated in vitro. After subculture for 3 days, the cells were cultured for up to 3 days (72 h) with zinc sulfate or zinc-chelated dipeptide (beta-alanyl-L-histidinato zinc; AHZ) in the range of 10(-7) to 10(-5) M. The culture with zinc compounds (10(-5) M) produced a significant increase of cell number, DNA content, and protein concentration in the cells, as reported previously. The culture with zinc compounds (10(-6) and 10(-5) M) clearly stimulated DNA synthesis in the homogenate, when it was estimated by the incorporation of [3H]deoxythymidine 5'-triphosphate into the DNA in the homogenate of cells. The AHZ effect was greater than that of zinc sulfate. The culture together with cycloheximide (19(-6) M) completely abolished the zinc compounds (10(-5) M)-induced increase of DNA synthesis in the cells, suggesting that the zinc compound effect is based on a newly synthesized protein component. Moreover, when zinc sulfate (10(-7) and 10(-6) M) or AHZ (10(-8) to 10(-5) M) was added into the reaction mixture with the homogenate of cells cultured without zinc compounds, the DNA synthesis was clearly increased. The effect of addition of zinc compounds (10(-6) M) on the DNA synthesis was completely inhibited by the presence of staurosporine (10(-8) M), an inhibitor of protein kinase C, or okadaic acid (10(-7) M), an inhibitor of protein phosphatase. The present study demonstrates that zinc compounds have a stimulatory effect on DNA synthesis in osteoblastic cells.

[Chest wall reconstruction using polyester mesh]

From January 1987 through December 1994, we performed chest wall reconstruction using the polyester mesh in 15 patients with lung cancer, 11 with empyema after open drainage, 8 with chest wall tumor and 1 with radiation dermatitis and costal chondritis. Twenty five patients were resected 3 or more ribs. Chest wall defects were reconstructed with the polyester mesh covered with Gore-Tex soft tissue patch. Twenty two cases passed more than a year without signs of infection and follow-up averaged 27.6 months. Polyester mesh was removed due to bronchial fistula (3 cases), deformities (3 cases) and abscess formation (1 case). In these cases, polyester mesh was well incorporated and had no foreign body change. In conclusion, the polyester mesh seems to be a dependable prosthetic material for chest wall reconstruction.

A novel GTPase-activating protein for R-Ras

R-Ras, belonging to the Ras small GTP-binding protein superfamily, has been implicated in regulation of various cell functions such as gene expression, cell proliferation, and apoptotic cell death. In the present study, we purified an R-Ras-interacting protein with molecular mass of about 98 kDa (p98) from bovine brain cytosol by glutathione S-transferase (GST)-R-Ras affinity column chromatography. This protein bound to GTP gamma S (guanosine 5'-(3-O-thio)triphosphate, a nonhydrolyzable GTP analog).R-Ras but not to GDP.R-Ras, GTP gamma S.R-Ras with a mutation in the effector domain (R-RasA64), GTP gamma S.Ha-Ras, or GTP gamma S.RalA. We obtained a cDNA encoding p98 on the basis of its partial amino acid sequences. The predicted protein consists of 834 amino acids whose calculated mass, 95,384 Da, is close to the apparent molecular mass of p98. The amino acid sequence shows a high degree of sequence similarity to the entire sequence of Gap1m, one of the GTPase-activating proteins (GAP) for Ha-Ras. A recombinant protein consisting of the GAP-related domain of p98 fused to maltose-binding protein stimulated GTPase activity of R-Ras, and showed a weak effect on that of Ha-Ras but not that of Rap1 or Rho. These results clearly indicate that p98 is a novel GAP for R-Ras. Thus, we designated this protein as R-Ras GAP.

The alpha 3 beta 3 gamma complex of the F1-ATPase from thermophilic Bacillus PS3 containing the alpha D261N substitution fails to dissociate inhibitory MgADP from a catalytic site when ATP binds to noncatalytic sites

ATP hydrolyses by the wild-type alpha 3 beta 3 gamma and mutant (alpha D261N)3 beta 3 gamma subcomplexes of the F1-ATPase from the thermophilic Bacillus PS3 have been compared. The wild-type complex hydrolyzes 50 microM ATP in three kinetic phases: a burst decelerates to an intermediate phase, which then gradually accelerates to a final rate. In contrast, the mutant complex hydrolyzes 50 microM or 2 mM ATP in two kinetic phases. The mutation abolishes acceleration from the intermediate phase to a faster final rate. Both the wild-type and mutant complexes hydrolyze ATP with a lag after loading a catalytic site with MgADP. The rate of the MgADP-loaded wild-type complex rapidly accelerates and approaches that observed for the wild-type apo-complex. The MgADP-loaded mutant complex hydrolyzes ATP with a more pronounced lag, and the gradually accelerating rate approaches the slow, final rate observed with the mutant apo-complex. Lauryl dimethylamide oxide (LDAO) stimulates hydrolysis of 2 mM ATP catalyzed by wild-type and mutant complexes 4- and 7.5-fold, respectively. The rate of release of [3H]ADP from the Mg[3H]ADP-loaded mutant complex during hydrolysis of 40 microM ATP is slower than observed with the wild-type complex. LDAO increases the rate of release of [3H]ADP from the preloaded wild-type and mutant complexes during hydrolysis of 40 microM ATP. Again, release is slower with the mutant complex. When the wild-type and mutant complexes are irradiated in the presence of 2-N3-[3H]ADP plus Mg2+ or 2-N3-[3H]ATP plus Mg2+ and azide, the same extent of labeling of noncatalytic sites is observed. Whereas ADP and ATP protect noncatalytic sites of the wild-type and mutant complexes about equally from labeling by 2-N3-[3H]ADP or 2-N3-[3H[ATP, respectively, AMP-PNP provides little protection of noncatalytic sites of the mutant complex. The results suggest that the substitution does not prevent binding of ADP or ATP to noncatalytic sites, but rather that it affects cross-talk between liganded noncatalytic sites and catalytic sites which is necessary to promote dissociation of inhibitory MgADP.