[Pharmacokinetic, bacteriological and clinical studies on meropenem in children]

Pharmacokinetic, bacteriological and clinical studies on meropenem (MEPM) were performed in children. The results are summarized as follows: 1. A total of 16 patients was treated with MEPM. Each dose was 20 mg/kg, and administration was made 3 times daily using 30-minute intravenous drip infusion for 5-28 days. Clinical efficacies of MEPM in 16 patients with bacterial infections (1 with purulent meningitis, 1 with suspected subdural abscess, 2 with suspected sepsis, 4 with pneumonia, 1 with acute maxillar sinusitis, 2 with cervical abscess, 1 with acute gastroenteritis, 2 with skin soft tissue infection and 2 with urinary tract infection) were evaluated as excellent in 7 patients, good in 8 patients and fair in 1 patient with an efficacy rate of 93.8%. Fourteen causative organisms found in 11 patients (Streptococcus pneumoniae in 4, Branhamella catarrhalis in 3, Staphylococcus aureus in 3, Group B Streptococcus in 1, Escherichia coli in 3) were all eradicated. No adverse reactions were observed in any of the 16 patients. 2. MICs of MEPM against 6 clinically isolated bacteria (B. catarrhalis 2, S. pneumoniae 3 and S. aureus 1) from children with bacterial infections were examined. MEPM showed good antibacterial activities. 3. Pharmacokinetic studies: Peak plasma concentrations of MEPM averaged 43.07 micrograms/ml (37.20-46.30 micrograms/ml) at dose of 20 mg/kg administered by 30-minute drip infusion. In the first 8 hours after administration, the urinary excretion rates of MEPM averaged 39.9% of the administered dose.(ABSTRACT TRUNCATED AT 250 WORDS)

c-Ha-ras containing 8-hydroxyguanine at codon 12 induces point mutations at the modified and adjacent positions

To determine the type of mutation induced by 8-hydroxyguanine in a mammalian system, we examined the mutations induced by a synthetic c-Ha-ras protooncogene containing 8-hydroxyguanine in the second position of codon 12 (GGC) in NIH3T3 cells. Transfection of this gene significantly increased the number of transformed foci. The c-Ha-ras gene present in these foci was analyzed by the polymerase chain reaction-restriction enzyme method. Interestingly, sequence analysis revealed random mutations at the modified site (G----T, G----A, and G----C) as well as mutations of the adjacent G on the 5'-side of 8-hydroxyguanine (G----A and G----T).

Two nucleotides next to the anticodon of cytoplasmic rat tRNA(Asp) are likely generated by RNA editing

The nucleotide sequences of major cytoplasmic tRNA(Asp) from rat liver and rat ascites hepatoma comprise a U32 and C33 next to the anticodon as was confirmed by different procedures. Additionally we identified a tRNA(Asp) with C32 and U33 in a minor proportion. We have shown earlier that the tRNA(Asp) gene is part of a cluster of tRNA genes which is amplified at least ten times in the rat nuclear genome. Six independent isolated clones display identical sequences in the coding region of the tRNA(Asp) gene which differ from tRNA(Asp) in having C32 and T33. Using a combination of single-strand conformation polymorphism (SSCP) analyses and direct sequencing of polymerase chain reaction (PCR) products we have now demonstrated that no variant allele of the tRNA(Asp) gene with T32 and C33 exists in the rat genome. Together with the RNA sequencing data these findings strongly indicate that major rat tRNA(Asp) is generated by post-transcriptional pyrimidine transitions at positions 32 and 33 and that the minor tRNA(Asp) is its unedited precursor.

cdc2-like kinase is associated with the retinoblastoma protein

The growth-suppressive activity of the retinoblastoma (RB) protein is suggested to be regulated by phosphorylation. In studies on the kinase that phosphorylates the RB proteins, we have previously found that RB proteins can be phosphorylated by purified cdc2 kinase. In this study, we noted that RB proteins immunoprecipitated from human cell lysates are weakly phosphorylated in the absence of purified cdc2 kinase. Immunoblot analysis showed the presence of p34cdc2 in the immunoprecipitates with anti-RB monoclonal antibody. In addition, the coprecipitated kinase was found to have the same substrate specificity as cdc2 kinase. The associated kinase activity was particularly high in cells arrested in G1/S and S phase by aphidicolin. Furthermore, RB proteins were shown to be phosphorylated in nuclear extracts by some endogenous cdc2-like kinase(s). These results suggest that cdc2-like kinase is the main kinase for phosphorylation of RB proteins in vivo.

Isolation of genes specifically expressed in flat revertant cells derived from activated ras-transformed NIH 3T3 cells by treatment with azatyrosine

We previously reported that mouse NIH 3T3 cells transformed by transfection of activated human c-Ha-ras become apparently normal upon treatment with the antibiotic azatyrosine. The revertant cells maintain their normal phenotype during prolonged culture in the absence of azatyrosine, although activated p21ras is still expressed. The normal phenotype induced by azatyrosine could be due to activation of expression of some cellular gene(s) in the cells that results in suppression of ras function. To identify the genes with increased expression in the revertant cells, we adopted differential screening of recombinants from a phage cDNA library made from mRNA of the revertant cells, hybridized with 32P-labeled cDNAs made from mRNAs of the ras-transformed NIH 3T3 cells and the revertant cells. Two clones thus isolated were found to be almost identical to the ras recision gene (rrg), which was identified as a tumor-suppressor gene by Contente et al. [Contente, S., Kenyon, K., Rimoldi, D. & Friedman, R. M. (1990) Science 249, 796-798]. Other genes identified were the collagen type III and rhoB genes. Approximately half the clones were found to contain a sequence corresponding to that of the murine retrovirus-like intracisternal A particle. We speculate that azatyrosine activates several cellular genes in the ras-transformed cells and that some of these genes, including rrg, act cooperatively to counteract ras function, resulting in reversion of the ras-transformed cells to the normal phenotype.

Histopathological reactions of calcium phosphate cement

Calcium phosphate cement (CPC) consisting of Ca4 (PO4)2O and CaHPO4 (2H2O) was recently developed. This study evaluated in vivo aspects of CPC and CPC mixtures compared to those of commercial hydroxyapatite (HP) and several endodontic materials: Grossman's cement (GC), calcium hydroxide-iodine paste (CHP) and gutta-percha plate (GP). Biocompatibility of subcutaneous implants in Donryu rats was evaluated after one month. Results showed very slight inflammatory reactions from CPC, CPC mixtures and HP. The materials were surrounded by thin fibrous connective tissues with a small number of lymphocytes and plasma cells. Severe inflammatory reactions were provoked by GC. Granulation tissues induced by CHP resembled those of pseudoxanthomatous granuloma. The GP material was encapsulated by relatively thick fibrous connective tissues with little inflammatory reactions.

Prolongation of canine epidural anesthesia by liposome encapsulation of lidocaine

The purpose of our study was to produce a long-acting lidocaine by using a liposome that would entrap the drug. Egg yolk phosphatidylcholine and cholesterol were used as liposome materials. After epidural administration, the pharmacodynamics and pharmacokinetics of liposomal and free lidocaine were studied in 20 dogs. Two percent liposomal or free lidocaine (3.0 mL) was injected into the lumbar epidural space. Nerve blocking effects were estimated by measuring somatosensory evoked potentials. Recovery time from the epidural block in the liposomal lidocaine group (170 +/- 49.5 min) was approximately three times longer than that in the free lidocaine group (61 +/- 18.1 min). The areas under the drug concentration-time curves (AUC0-infinity) and time to maximal concentration (Tmax) in the liposomal lidocaine group were significantly larger than those in the free lidocaine group. These results suggest that the prolongation of epidural blockade by liposomal lidocaine is caused by a slow release of the drug from liposomes. The present study suggests that liposomal lidocaine can be used as a long-acting local anesthetic.

Zonisamide blocks T-type calcium channel in cultured neurons of rat cerebral cortex

We investigated the effect of zonisamide, a new antiepileptic drug, on voltage-dependent Ca2+ currents in cultured neurons of rat cerebral cortex. Whole-cell voltage-clamp recordings demonstrated at least two distinct voltage-dependent Ca2+ currents: (1) a low-threshold, rapidly inactivating component, T-type Ca2+ current, which is sensitive to 100 microM Ni2+, and (2) a high-threshold, slowly inactivating (long-lasting) component, L-type Ca2+ current. Zonisamide, a new anticonvulsant effective against maximal electroshock (MES) seizures in mice reduced T-type Ca2+ current in a dose-dependent manner. The mean percentage of reduction was 59.5 +/- 7.2% at 500 microM, but zonisamide had no effect on L-type Ca2+ current. A methylated analog of zonisamide, which is ineffective against MES seizures in mice, was tested at a concentration of 500 microM, and reduced neither T-type nor L-type Ca2+ current. These findings suggest that the effects of zonisamide against MES seizures might occur through the reduction of T-type Ca2+ current. Because drugs that are effective against MES seizures are thought to prevent seizure discharge spread, T-type Ca2+ channels could underlie a cellular mechanism of spreading activity in epileptic seizures.

[Management of elderly patients with aneurysmal subarachnoid hemorrhage]

Clinical features of 61 elderly patients aged over 70 years with ruptured intracranial aneurysms were compared with those of 328 younger patients aged under 70 years. According to a policy of early operation, elderly patients with Hunt and Kosnik's grade I, II and younger patients with grade I, II, III were operated on in the acute stage. In elderly patients with grade III, IV and younger patients with grade IV, the indication for surgery was determined case by case. Surgery was performed on 29 patients (48%) in the elderly group and 277 patients (86%) in the younger group. Our conclusions are as follows: 1. Regarding cases of grade I, II and III of Hunt and Kosnik's classification, the rate of good outcome in the elderly group was similar to that in the younger group, following early surgery and meticulous post-operative care. 2. In the elderly group, no patient in cases of grade IV obtained good surgical outcome. 3. Symptomatic vasospasm was less frequent in elderly patients (18.8%) than in younger cases (37%). 4. Delayed operation was planned for some patients in the elderly group, but none of them underwent surgery because of rerupture of aneurysms and deterioration of general condition.

Alcohol interaction with high entropy states of macromolecules: critical temperature hypothesis for anesthesia cutoff

Nerve excitation generates heat and decreases the entropy (review by Ritchie and Keynes (1985) Q. Rev. Biophys. 18, 451-476). The data suggest the existence of at least two thermodynamically identifiable states: resting and excited, with a thermotropic transition between the two. We envision that nerve excitation is a transition between the two states of the excitation machinery consisting of proteins and lipids, rather than the sodium channel protein alone. Presumably, both proteins and lipids change their conformation at excitation. We proposed (Kaminoh et al. (1991) Ann. N.Y. Acad. Sci. 625, 315-317) that anesthesia occurs when compounds have a higher affinity to the resting state than to the excited state of excitable membranes, and that there is a critical temperature above which the affinity to the excited state becomes greater than to the resting state. When the temperature exceeds this critical level, compounds lose their anesthetic potency. We used thermotropic phase-transition of macromolecules as a model for the excitation process. Anesthetic alcohols decreased the main transition temperature of dipalmitoylphosphatidylcholine (DPPC) membranes and also the temperature of the alpha-helix to beta-sheet transition of poly(L-lysine). The affinity of alcohols to the high- and low-temperature states of the DPPC membranes were separately estimated. The difference in the affinity of n-alcohols to the liquid (high-temperature) and solid (low-temperature) states correlated with their anesthetic potency. It is not the total number of bound anesthetic molecules that determines the anesthesia, rather, the difference in the affinity between the higher and lower entropy states determines the effects. The critical temperatures of the long-chain alcohols were found to be lower than those of the short-chain alcohols. Cutoff occurs when the critical temperature of long-chain alcohols is below the physiological temperature, such that the anesthetic potency is not manifested in the experimental temperature range.

Ligand-induced functions of the epidermal growth factor receptor require the positively charged region asymmetrically distributed across plasma membrane

Many plasma membrane proteins, including the epidermal growth factor (EGF) receptor, possess basic regions on the cytoplasmic surface of the membrane. To examine the function of these positively charged regions, we constructed mutated EGF receptor genes lacking this region by substitution of the basic amino acid residues with 3 approximately 8 neutral Asn residues, or by their complete deletion. There was no significant difference in the affinities for EGF of the wild-type and mutant receptors which are produced in rodent fibroblasts through transfection. However, EGF-induced tyrosine phosphorylation of the receptor was strongly inhibited by removal of the 3 approximately 8 positively charged residues. On addition of EGF, cells expressing the mutant EGF receptors did not show morphological changes, whereas cells expressing the wild-type receptor did. These findings suggest that the positively charged regions of membrane proteins that are asymmetrically distributed on the cytoplasmic surface of the membrane may be required for the functions of membrane proteins in general.

Post-inhibitory excitation of adenosine on neurotransmission in guinea pig hippocampal slices

The postsynaptic field potential (population spike potential; PS) was recorded from the granule cell layer of guinea pig hippocampal slices. Adenosine at low concentrations ranging from 10 nM to 1 microM enhanced the amplitude of PS, whereas at concentrations over 10 microM it inhibited the neurotransmission. There appeared to be a rebound phenomenon after the removal of adenosine at inhibitory concentrations and the amplitude of the PS overshot the initial amplitude (we called this post-inhibitory excitation; PIE). Neither depressants such as gamma-aminobutyric acid (GABA; 1 mM) nor sodium pentobarbital (100 microM) by itself induced PIE. After application of GABA or sodium pentobarbital together with adenosine (0.1 microM), however, removal of all agents could induce the PIE. PIE as well as the excitatory effect of adenosine at low concentrations was counteracted by application of H-7 (100 microM), melittin or polymyxin B, potent protein kinase C (PKC) inhibitors, suggesting that the excitatory effect of adenosine is mediated by a metabolic process involving PKC. These results indicate that PIE induced by adenosine at high concentrations is due to a mechanism similar to the excitatory effect induced by adenosine at low concentrations, and that during application of adenosine at high concentrations the excitation is masked by its potent inhibitory effect.

[Changes in dementia after shunt surgery for normal pressure hydrocephalus]

In order to investigate the pathogenesis of normal pressure hydrocephalus (NPH), dementia was analyzed with regard to the characteristic preoperative picture, the time when dementia improved, and what aspect of dementia was improved, retrospectively. Twenty seven patients of NPH were divided into two groups; young adult group: patients under 64 years old and geriatric group: patients above 65 years old. We found that the only difference found between these two groups was severity in dementia grading, higher in geriatric group. Postoperative course or complications did not differ. Dementia in NPH was not an essential impairment of intellectual ability, but was characterized by the subset symptoms of dementia, such as decrease in spontaneity and interest, slowness and paucity of thought and action. Improvement of memory followed postoperative recovery of these subset symptoms which was observed at earliest three days after shunt surgery. We postulate that recovery of dementia in NPH is associated with not only a decrease in intracranial pressure but also an improvement in the microcirculation of the brain or an improved metabolism.

Acute renal failure following hypokalemic rhabdomyolysis due to chronic glycyrrhizic acid administration

A 72-year-old man developed acute renal failure (ARF) following severe hypokalemic rhabdomyolysis. The hypokalemia was due to chronic glycyrrhizin (glycyrrhizic acid) administration. Although glycyrrhizin-induced hypokalemic rhabdomyolysis has been occasionally reported, the association of this type of rhabdomyolysis with ARF has not been described. In the present case, there was a sensitivity to glycyrrhizin the preceding renal insufficiency, and dehydration which was thought to have contributed to ARF. It should be recognized that elderly patients with such predisposing factors may be susceptible to a rapid deterioration of renal function after glycyrrhizin-induced hypokalemic rhabdomyolysis.

X-ray crystal structures of transforming p21 ras mutants suggest a transition-state stabilization mechanism for GTP hydrolysis

RAS genes isolated from human tumors often have mutations at positions corresponding to amino acid 12 or 61 of the encoded protein (p21), while retroviral ras-encoded p21 contains substitutions at both positions 12 and 59. These mutant proteins are deficient in their GTP hydrolysis activity, and this loss of activity is linked to their transforming potential. The crystal structures of the mutant proteins are presented here as either GDP-bound or GTP-analogue-bound complexes. Based on these structures, a mechanism for the p21 GTPase reaction is proposed that is consistent with the observed structural and biochemical data. The central feature of this mechanism is a specific stabilization complex formed between the Gln-61 side-chain and the pentavalent gamma-phosphate of the GTP transition state. Amino acids other than glutamine at position 61 cannot stabilize the transition state, and amino acids larger than glycine at position 12 would interfere with the transition-state complex. Thr-59 disrupts the normal position of residue 61, thus preventing its participation in the transition-state complex.

Induction of mutation of a synthetic c-Ha-ras gene containing hypoxanthine

The second base of codon 61 of a synthetic c-Ha-ras gene was replaced with a hypoxanthine residue in a site-specific manner. Transfection of this gene into NIH3T3 cells by the calcium phosphate procedure resulted in increased focus formation. Total DNA was extracted from transformed cells, and the sequences of the inserted c-Ha-ras DNA were analyzed by the polymerase chain reaction-single-strand conformation polymorphism method. Mutations with A (or hypoxanthine) to G transition were detected exclusively. These results suggest that the synthetic c-Ha-ras gene can be used for investigations of mutagenesis caused by DNA lesions.

Lack of effect of islet amyloid polypeptide on hepatic glucose output in the in situ-perfused rat liver

Islet amyloid polypeptide (IAPP), a novel peptide isolated from islet amyloid deposits in patients with insulinoma and non-insulin-dependent diabetes mellitus (NIDDM), has been reported to be cosecreted with insulin from pancreatic beta cells and to inhibit glucose uptake and glycogen synthesis in muscle tissue in vitro. We investigated the effects of the synthesized, rat-amidated form of IAPP on hepatic glucose output, and IAPP extraction, using an in situ flow-through perfusion system in rats to elucidate the actions of IAPP on the liver. The IAPP (10(-8) mol/L) alone had no effects on the hepatic glucose release. Infusion of 6 x 10(-11) mol/L glucagon alone resulted in an expected elevation in glucose production (30.0 +/- 1.7 mumol/35 min/g liver). Insulin (3 x 10(-10) mol/L) submaximally decreased the glucagon-stimulated glucose production to 73% (from 30.0 +/- 1.7 to 22.0 +/- 1.4 mumol/35 min/g liver; n = 7, P less than .01). A simultaneous infusion of 10(-8) mol/L IAPP did not influence the glucagon-stimulated glucose production (27.6 +/- 1.2 mumol/35 min/g liver) or the insulin-dependent inhibition of glucagon-stimulated glucose production (22.6 +/- 1.3 mumol/35 min/g liver). IAPP extraction by the liver in a single passage was minimal, in contrast to approximately 50% hepatic insulin extraction. These results indicate that IAPP does not play any important role in modulating glycogen metabolism in the liver.

Giant basal prolactinoma extending into the nasal cavity

An unusual case of a giant prolactinoma extending to the nasopharynx and nasal cavity is presented. A 35-year-old man admitted for nasal obstruction and visual disturbances was found to have bilateral anosmia, right homonymous hemianopsia, and a right hemiparesis. The serum prolactin level was 13,300 ng/mL. Radiological examination revealed a large mass invading the skull base and extending into the suprasellar region and the left frontal lobe superiorly and into the nasopharynx inferiorly. Subtotal removal was done through a bilateral orbitofrontal craniotomy, which was followed by radiotherapy and bromocriptine administration. Immunohistochemical analysis confirmed a prolactinoma. The rarity of such a tumor, its location and extension, and the usefulness of magnetic resonance imaging and immunohistochemistry are stressed. Pertinent literature is reviewed.

[Münchhausen syndrome with severe iron deficiency anemia]

A patient with Münchhausen syndrome who had severe iron deficiency anemia (IDA) is reported. A 31 year-old female presented with irregular genital bleeding. However, gynecological examination disclosed no evidence of specific disorders causing bleeding. Tests for bleeding tendency and hemolysis were all negative. Although massive bleeding was absent, she had three episodes of a rapid fall in Hb level associated with marked fatigue and weakness, and subsequently rapidly developed serious IDA afterwards. Factitious bleeding was strongly suspected. Blood transfusion performed when the patient was not being watched failed to increase Hb, while transfusions given while the patient was watched were effective. She was not cooperative throughout the hospital course and was discharged on her own request. In outpatient clinic, the diagnosis was confirmed by the evidence that she diluted her own blood samples.

1H-NMR assignment and secondary structure of human insulin-like growth factor-I (IGF-I) in solution

Human insulin-like growth factor-I (IGF-I) was studied by two-dimensional 1H-NMR spectroscopy. Resonance assignments were obtained for all the backbone protons and almost all of the sidechain protons of the total 70 amino acid residues, using sequence-specific assignment procedures. The secondary structure elements of human IGF-I were identified by investigation of the sequential and medium range NOEs as a preliminary step in determining the three-dimensional structure of this protein by means of distance geometry calculations. The typical NOEs of d alpha beta(i,i + 3) and d alpha N(i,i + 3), as well as the successive strong NOEs of dNN connectivities and slowly exchanging amide protons confirmed the presence of three helical segments corresponding to the sequence regions, Ala8-Cys18, Gly42-Cys48, and Leu54-Cys61, and the existence of a beta-turn in the Gly19-Gly22 region. Our results definitely indicate that the secondary structure of human IGF-I in solution is consistent with that of insulin in the crystalline state.

Ubiquitous presence in mammalian cells of enzymatic activity specifically cleaving 8-hydroxyguanine-containing DNA

Here we report the finding of enzymatic activity that specifically cleaves DNA containing 8-hydroxyguanine (oh8Gua) residues in various mammalian cells. To detect this activity, we used a synthetic double-stranded DNA containing a single oh8Gua at a defined position as the substrate, and analyzed the products of enzymatic digestion by polyacrylamide gel electrophoresis. Two cleavage sites near the oh8Gua residue were detected with partially purified fractions from cow brain and rat liver, and also with preparations from all mammalian tissues examined. These results suggest that enzymatic activity for the removal of oh8Gua from DNA is widely distributed in mammalian cells.

Inhibition of chemical carcinogenesis in vivo by azatyrosine

A single painting of 7,12-dimethylbenz[a]anthracene on the skin of transgenic mice harboring the human protooncogene c-Ha-ras induced papillomas at 100% incidence after 20 weeks (M. Izawa et al., unpublished data). Application of L-beta-(5-hydroxy-2-pyridyl)alanine (azatyrosine) to the skin at a dose of 2 mg/mouse once every 3 days after initiation with 7,12-dimethylbenz[a]anthracene greatly reduced the percentage incidence, number per mouse, and size of papillomas. Injection of methylnitrosourea i.p. into transgenic mice induced papillomas in the forestomach after 12 weeks (2 to 12 papillomas/mouse) at 100% incidence (K. Ando et al., Cancer Res., 52: 978-982, 1992). Administration of azatyrosine i.p. at a dose of 2 mg/mouse once every 2 days for 12 weeks after initiation with methylnitrosourea completely prevented the formation of forestomach papillomas. These results clearly indicated that azatyrosine inhibits chemical carcinogenesis in vivo.

Possible role of surface potential in the gating mechanism of Ca2+ channels in cat adrenal chromaffin cells: studies with fura-2 microfluorometry

The cytosolic free Ca2+ concentration ([Ca]in) in isolated cat chromaffin cells was measured by fura-2 microfluorometry. During 30 mM KCl depolarization or sucrose substitution for NaCl, a reduction in external Ca2+ concentration under optimal conditions paradoxically caused a rise in [Ca]in and, in separate experiments, in catecholamine secretion. The results support a previously suggested role of surface potentials in the gating mechanism of Ca2+ channels.

A glutamic acid residue at position 31 of Ras protein is essential to the signal transduction for neurite outgrowth of PC12 cells and the stimulation of GTPase activity by GAPRas

The roles of residues at positions 23-31 adjacent to the 'effector region' and residues at positions 61-65 in a phosphoryl binding loop of the human c-Ha-ras protein were studied by changing each residue of the normal (Gly-12 type) and oncogenic (Val-12 type) Ras proteins to the corresponding residue of the K-rev-1 protein. Firstly, the signal-transducing activities of the mutant Ras proteins of Val-12 type were examined by analysis of their ability to induce neurite outgrowth of phaeochromocytoma (PC12) cells upon expression of the mutant ras gene. Thus, replacement of Glu-31 by Lys was found to impair the signal-transducing activity of the oncogenic Ras protein. Furthermore, it was shown that expression of the Gly-12----Val/Glu-31----Lys mutant Ras protein in PC12 cells suppresses neurite outgrowth induced either by microinjection of the oncogenic Ras protein or by addition of nerve growth factor to the medium. As for the Glu-31----Lys mutant Ras protein (Gly-12 type), the GTPase activity in the presence of GTPase-activating protein for Ras (GAPRas) is much lower than that of the normal Ras protein, whereas the intrinsic GTPase activity is nearly the same as that of the normal Ras protein. Therefore, Gly-31 is one of the determinants for the signal transduction and the correct interaction with GAPRas. On the other hand, the GTPase activity of the Gln-61----Thr mutant Ras protein (Gly-12 type) is negligibly low both in the absence and in the presence of GAPRas.