Inhibition of GTPase activating protein stimulation of Ras-p21 GTPase by the Krev-1 gene product

Krev-1 is known to suppress transformation by ras. However, the mechanism of the suppression is unclear. The protein product of Krev-1, Rap1A-p21, is identical to Ras-p21 proteins in the region where interaction with guanosine triphosphatase (GTPase) activating protein (GAP) is believed to occur. Therefore, the ability of GAP to interact with Rap1A-p21 was tested. Rap1A-p21 was not activated by GAP but bound tightly to GAP and was an effective competitive inhibitor of GAP-mediated Ras-GTPase activity. Binding of GAP to Rap1A-p21 was strictly guanosine triphosphate (GTP)-dependent. The ability of Rap1A-p21 to bind tightly to GAP may account for Krev-1 suppression of transformation by ras. This may occur by preventing interaction of GAP with Ras-p21 or with other cellular proteins necessary for GAP-mediated Ras GTPase activity.

Kinetics of interaction of nucleotides with nucleotide-free H-ras p21

A method is described for the convenient preparation of substantial quantities of nucleotide-free p21 or of 1:1 complexes with nucleotides other than GDP. The nucleotide-free protein has been used for kinetic studies of the binding of GDP and GTP, making use of the fluorescent analogues 3'-(methylanthraniloyl)-2'-deoxy-GDP and -GTP. Stopped-flow studies have led to the formulation of a two-step binding mechanism for both GDP and GTP, involving initial rapid but weak binding of the nucleotide followed by a relatively slow (10-20 s-1 at 25 degrees C; 3-5 s-1 at 5 degrees C) quasi-irreversible isomerization reaction. By use of a nonequilibrium competition method, guanosine and GMP have been shown to interact weakly but significantly with p21 (dissociation constants of 153 and 29 microM, respectively). The presence of guanosine or GMP at the active site of p21 leads to a marked stabilization of p21 against spontaneous denaturation when compared with the nucleotide- and nucleoside-free protein.

Proton NMR studies of transforming and nontransforming H-ras p21 mutants

One- and two-dimensional nuclear magnetic resonance spectroscopy (1D and 2D NMR) and site-directed mutagenesis were used to study the influence of mutations on the conformation of the H-ras oncogene product p21. No severe structural differences between the different mutants, whether they were transforming or nontransforming, could be detected. Initially, selective incorporation of 3,5-deuterated tyrosyl residues into p21 and 2D NMR were used to identify the resonances representing the spin systems of the imidazole rings of the three histidyl residues in the protein, of six of the nine tyrosyl rings, and of four of the five phenylalanyl rings. The spin systems of the phenyl rings of Phe28, Phe78, and Phe82 could be assigned by using mutant proteins, since no severe structure-induced spectral changes in the aromatic part of the spectra of the mutant proteins were detected. Sequence-specific assignments of the histidine imidazole resonances could be obtained by comparison of the distance information obtained by nuclear Overhauser enhancement spectroscopy (NOESY) experiments with the crystal structure. The change in the chemical shift values of the Hl' proton and the alpha-phosphate of the bound GDP in the NMR spectra of the p21(F28L) mutant and the 28-fold increase in the GDP dissociation rate constants of this mutant suggest a strong interaction between Phe28 and the p21-bound nucleotide. In solution, the p21-bound GDP.Mg2+ has an anti conformation, and the phenyl ring of Phe28 is close to the ribose of the bound GDP.Mg2+.

Interrelationships between serologic markers of immune activation and T lymphocyte subsets in HIV infection

Relationships among four serologic activation markers and T cell subsets were measured in HIV-seropositive former blood donors (N = 64) and seronegative controls (N = 61). Significant correlations were observed for the HIV group in pairwise comparisons of soluble IL-2 receptor (sIL-2R), beta 2-microglobulin (beta 2M), neopterin (NEOP), and soluble CD8 (sCD8). CD4 cell levels (number/microliter) in the HIV group showed significant negative correlation with all four serologic markers; CD8 cell levels, in contrast, showed no significant correlation with any serologic activation marker measured. Significant correlations were observed, however, among various cell surface activation markers and serologic activation markers. Specifically, the proportion of CD8 cells expressing CD45RA showed significant negative correlations with NEOP and B2M levels, whereas the proportion of CD8 cells expressing HLA-DR showed significant positive correlations with B2M and sIL-2R levels. Further, the proportion of CD8 cells expressing CD38 showed significant positive correlations with all four serologic activation markers. These findings indicate that sIL-2R, B2M, NEOP, and sCD8 show similar quantitative changes and correlational relationships to CD4 cell destruction in HIV infection; they differ, however, in their relationships to proportional changes in activated CD8 cell subsets.

Use of a selectable marker regulated by alpha interferon to obtain mutations in the signaling pathway

We have selected mutations in genes encoding components of the signaling pathway for alpha interferon (IFN-alpha) by using a specially constructed cell line. The upstream region of the IFN-regulated human gene 6-16 was fused to the Escherichia coli guanine phosphoribosyltransferase (gpt) gene and transfected into hypoxanthine-guanine phosphoribosyltransferase-negative human cells. These cells express gpt only in the presence of IFN-alpha. They grow in medium containing hypoxanthine, aminopterin, and thymidine plus IFN and are killed by 6-thioguanine plus IFN. Two different types of mutants were obtained after treating the cells with mutagens. A recessive mutant, selected in 6-thioguanine plus IFN, was completely resistant to IFN-alpha but responded normally to IFN-gamma and, unexpectedly, partially to IFN-beta. A constitutive mutant, selected in hypoxanthine-aminopterin-thymidine alone, was abnormal in expressing endogenous genes in the absence of IFN. Both types revert infrequently, allowing selection for complementation of the defects by transfection.

Training general practioners in psychiatry - an icmr multi-centre study

The specialist psychiatric services available in India is insufficient to meet the mental health needs of the country. Training of general practitioners in psychiatry through short courses is one of the remedial strategies. In 1982-83, an ICMR Multi-Centre Project of Training in Psychiatry for Non-Psychiatrist Primary Care Doctors was successfully completed at Bangalore, Hyderabad and Vellore using the training methods developed at NIMHANS. This paper describes the training programme and the results.

Clinical vignettes for assessment of training general practitioners in psychiatry

Training of non-psychiatrist medical professionals in psychiatry through short courses is an urgent need recognised by the National Mental Health Policy. In order to improve the training programmes over a time, a suitable method of evaluation of the effect of training is essential. Such a method of evaluation was developed at NIMHANS using clinical vignettes. These vignettes were successfully used in the I. C. M. R. Multi-centre Project of Training non-psychiatrist primary care doctors in 1982-83. This paper describes the effectiveness of the clinical vignettes as tools of evaluating short training programmes.

Biochemical and crystallographic characterization of a complex of c-Ha-ras p21 and caged GTP with flash photolysis

The GTP binding domain of the c-Ha-ras protooncogene product (p21'c) and the corresponding region from an oncogenic mutant form of the protein in which glycine at position 12 has been replaced by valine [p21'(G12V)] have been crystallized with P3-1-(2-nitro)phenylethylguanosine 5'-O-triphosphate (caged GTP) at their active sites. The crystals give x-ray diffraction patterns to a resolution of better than 0.3 nm. Photolysis can be achieved in the crystal, after which GTP hydrolysis takes place at the rate expected from solution studies. Complete x-ray data sets have been obtained for the starting caged-GTP state and the final GDP state after photolysis and hydrolysis, demonstrating the feasibility of time-resolved structural investigations of the process of GTP hydrolysis.

Structure of the guanine-nucleotide-binding domain of the Ha-ras oncogene product p21 in the triphosphate conformation

The crystal structure of the guanine-nucleotide-binding domain of p21 (amino acids 1-166) complexed to the guanosine triphosphate analogue guanosine-5'-(beta, gamma-imido)triphosphate (GppNp) has been determined at a resolution of 2.6 A. The topological order of secondary structure elements is the same as that of the guanine-nucleotide-binding domain of bacterial elongation factor EF-Tu. Many interactions between nucleotide and protein have been identified. The effects of point mutations and the conservation of amino-acid sequence in the guanine-nucleotide-binding proteins are discussed.

C-terminal truncation of p21H preserves crucial kinetic and structural properties

The human c-Ha-ras protooncogene product p21C was truncated at the C terminus by 23 amino acids. The resulting G-binding domain, p21 (1-166) = p21C', can be crystallized as a complex with the slowly hydrolyzing GTP analogues guanosin-5'-[beta,gamma-imido]triphosphate, guanosin-5'-[beta,gamma-methylene]triphosphate, and guanosin-5'-O-(3-thiotriphosphate). We show here that this protein has biochemical properties very similar to those of the intact protein. Activating mutations in position 12 (Gly12----Val; Gly12----Arg) have the same effect on the properties of the truncated protein as on intact protein. Nuclear magnetic resonance (NMR) measurements show no apparent effect of the C-terminal deletion on the solution structure of p21. This suggests that neither the structure of the G-binding domain nor any of its biochemical properties are markedly influenced by the truncation.

Optical urethrotomy--experience in Oman

Over a 4-year period 170 men with urethral strictures were treated with optical urethrotomy; 80% required no further treatment during the 2-year follow-up; 2 patients with urethral fistulae associated with stricture were also treated successfully.

[Cryoimmunotherapy of herpetic and metaherpetic keratitis]

In 11 patients with relapsing herpetic keratitis and metaherpetic ulcers cryoimmunotherapy, as recommended by Amoils, was applied. Under instillation anaesthesia three cryocycles were made using a temperature of -80 degrees on the entire area of the lesion with subsequent instillation of 60 drops (1 drop per minute) of serum obtained from 15 ml of the patient's blood mixed with 5 ml gamma globulin. In all 11 patients progression of the disease was arrested, though it could not be checked by previous conservative therapy. The cornea cleared and vision improved. The method is effective, simple and expands therapeutic procedures which can be used in these tiresome conditions.

Crystallization and preliminary X-ray analysis of the human c-H-ras-oncogene product p21 complexed with GTP analogues

The catalytic domain (amino acid residues 1 to 166) of the human ras-oncogene product p21 complexed with the GTP analogues beta,gamma-imido-GTP (GMPPNP), beta,gamma-methylene-GTP (GMPPCP), and guanosine-5'-(gamma-thiotriphosphate) (GTP gamma S) have been been crystallized. Crystals of the GMPPNP and GMPPCP complexes are well suited for high resolution X-ray crystallography. They belong to space group P3(1)21 (or its enantiomorph P3(2)21) with unit cell axes a=b=40.3 A and c = 162.2 A.

Staphylococcus saprophyticus urease: characterization and contribution to uropathogenicity in unobstructed urinary tract infection of rats

We studied the biochemical properties of the urease of Staphylococcus saprophyticus and the possible role of the urease in experimental urinary tract infections. For this purpose, the nonhemagglutinating and nonadherent strain 9325, which was isolated from a case of symptomatic urinary tract infection, was used. The urease was shown to have a Km of 6.64 mM urea and a Vmax of 4.59 mumol NH3.min-1.mg-1. The enzyme was inhibited by acetohydroxamic acid in a noncompetitive manner. By means of Sephacryl S-300 column chromatography, we determined a mean molecular weight (+/- standard error of the mean) of 420,000 +/- 16,000. To assess the contribution of S. saprophyticus urease to uropathogenicity, a urease-negative mutant was constructed by nitrosoguanidine mutagenesis. In the rat model of ascending unobstructed urinary tract infection, higher numbers of CFU.gram of tissue-1 and more-severe lesions were detected with the parent strain. Moreover, bladder stones were found in animals infected with the urease-positive strain only. Interestingly, the difference in mean bacterial counts of the bladders was found to be significant by the Wilcoxon two-sample test (P less than 0.05), whereas that between the kidney bacterial counts was not. Immunoblot studies revealed a faint antibody response in rats infected with the mutant strain, although bacteria could still be detected in the kidneys after 7 days. Sera of animals challenged with the parent strain reacted strongly with many antigens of S. saprophyticus. Our data indicate that urease is a major factor for invasiveness of S. saprophyticus, especially in the tissue of the bladder, whereas persistence in the urinary tract and nephropathogenicity of this organism are governed by factors other than urease.

ras p21 protein promotes survival and fiber outgrowth of cultured embryonic neurons

Although evidence obtained with the PC12 cell line has suggested a role for the ras oncogene proteins in the signal transduction of nerve growth factor-mediated fiber outgrowth, little is known about the signal transduction mechanisms involved in the neuronal response to neurotrophic factors in nontransformed cells. We report here that the oncogene protein T24-ras, when introduced into the cytoplasm of freshly dissociated chick embryonic neurons, promotes the in vitro survival and neurite outgrowth of nerve growth factor-responsive dorsal root ganglion neurons, brain-derived neurotrophic factor-responsive nodose ganglion neurons, and ciliary neuronotrophic factor-responsive ciliary ganglion neurons. The proto-oncogene product c-Ha-ras also promotes neuronal survival, albeit less strongly. No effect could be observed with truncated counterparts of T24-ras and c-Ha-ras lacking the 23 C-terminal amino acids including the membrane-anchoring, palmityl-accepting cysteine. These results suggest a generalized involvement of ras or ras-like proteins in the intracellular signal transduction pathway for neurotrophic factors.

Biochemical properties of Ha-ras encoded p21 mutants and mechanism of the autophosphorylation reaction

Kinetic studies performed on p21H guanine nucleotide complexes with and without Mg2+ show that point mutations at positions 12, 59, and 61 each have a different effect on the rate of nucleotide dissociation. Double mutants with a combination of these amino acid substitutions reveal that the effects of each mutation on these kinetics are interactive (nonadditive) for positions 12 and 59 and approximately additive for the positions 12 and 61. The magnitude and direction of the effects seen are dependent on the nature of the nucleotide and whether or not the complexes contain Mg2+. All the mutants have reduced GTPase activity. It is also shown that the autophosphorylation reaction velocity is of first order with respect to the protein concentration and that this reaction is an intramolecular one, which takes place as a side reaction of the GTPase reaction. The autophosphorylation is not reversible under the experimental conditions. The covalently bound phosphate does not decrease the nucleotide-binding ability of the protein nor does it change the relative affinity of the protein for GTP versus GDP. The results are discussed in terms of the structural model and function of p21H.

Evaluation of disposable cartridges for trace enrichment from aqueous solutions

Selected aromatic hydrocarbons, phthalate esters, and food, drug and cosmetic (FD&C) dyes are isolated from aqueous solutions with Chrom-Prep PRP-1 and Sep-Pak C18 cartridges. The Chrom-Prep cartridges demonstrate greater adsorption capacity for model aromatic hydrocarbons and phthalate esters than Sep-Pak C18 cartridges; however, the latter exhibits greater capacity for the FD&C dyes, which have breakthrough volumes that are a function of pH. Both cartridge types show a small amount of analyte leakage during the trace enrichment step, which is measured by monitoring the cartridge effluents for the presence of 14C-labeled solute. Two PRP-1 cartridges connected in tandem reduce the amount of activity in the effluent by approximately one half.

Characterisation of the metal-ion-GDP complex at the active sites of transforming and nontransforming p21 proteins by observation of the 17O-Mn superhyperfine coupling and by kinetic methods

Kinetic studies on the interaction of three Ha-ras-encoded p21 proteins with GDP and MgGDP have yielded values for the association (10(6)-10(7) M-1 s-1) and dissociation (10(-3)-10(-5) s-1) rate constants at 0 degrees C. Dramatic differences in the rate constants were not observed for the three proteins. Under non-physiological conditions (absence of Mg2+), the rate constant for GDP release was an order of magnitude faster for the viral protein p21v than for the cellular form p21c or the T24 mutant p21t, but this was reduced to a factor of about 3 in the presence of Mg2+. In all cases, there was an increase of about one order of magnitude in the rate of GDP release on removing magnesium. The binding affinities ranged from 5.7 X 10(10) M-1 for p21c to 1.3 X 10(11) M-1 for p21v. Electron paramagnetic resonance (EPR) measurements on Mn2+ bound together with stereospecifically 17O-labelled GDP showed direct coordination of a beta-phosphate oxygen to the metal ion with a superhyperfine coupling constant of 0.16-0.22 mT, but no interaction with the alpha-phosphate oxygens at the active site of all three proteins. The association constant of Mn(II) to p21 proteins in the absence of nucleotides was estimated to be greater than 10(5) M-1. In agreement with the EPR results, experiments on the metal ion dependence of the binding of thiophosphate analogs of GDP provided further evidence for the absence of direct coordination of the metal ion to the alpha-phosphate group. These results have been used to construct a model for the interactions of Mg X GDP with the active site of p21 proteins.

Cost containment in a statutory health insurance scheme by substitution of outpatient for inpatient care? The case of the Bavarian Contract

Among manifold attempts at containing the rapid growth of health care expenditure, one which attracted considerable attention was the 1979 agreement between Bavarian sick-funds and the office-based physicians of Bavaria that, in some ways, reshaped the remuneration scheme for ambulatory medical treatment. This so-called 'Bavarian Contract' tried to approach cost containment by initiating transsectoral substitution processes in favour of outpatient medical care and to the disfavour of, above all, the hospital sector of the health care system. This paper deals with the question whether in Bavaria (between 1979 and 1983/84) the structure of services and prescriptions was modified in a way that indicates the occurrence of substitution processes as intended by the 'Bavarian Contract'; also, whether there is any evidence of cost containment effects brought about the intensifying the ambulatory services of office-based physicians. The study results provide some weak hints at substitution processes in favour of ambulatory services; but there is no evidence that expanding ambulatory medical services may help to contain the growth of health care expenditure.

Expression of p21 proteins in Escherichia coli and stereochemistry of the nucleotide-binding site

v-Ha-ras encoded p21 protein (p21V), the cellular c-Ha-ras encoded protein (p21C) and its T24 mutant form p21T were produced in Escherichia coli under the control of the tac promoter. Large amounts of the authentic proteins in a soluble form can be extracted and purified without the use of denaturants or detergents. All three proteins are highly active in GDP binding, GTPase and, for p21V, autokinase activity. Inhibition of [3H]GDP binding to p21C by regio- and stereospecific phosphorothioate analogs of GDP and GTP was investigated to obtain a measure of the relative affinities of the three diphosphate and five triphosphate analogs of guanosine. p21 has a preference for the Sp isomers of GDP alpha S and GTP alpha S. It has low specificity for the Sp isomer of GTP beta S. Together with the data for GDP beta S and GTP gamma S these results are compared with those obtained for elongation factor (EF)Tu and transducin. This has enabled us to probe the structural relatedness of these proteins. We conclude that p21 seems to be more closely related to EF-Tu than to transducin.

Failure of electrical myofeedback to augment the effects of physiotherapy in stroke

Electromyographic biofeedback has been used with some success to treat patients with disturbances of muscle tone resulting from neurological disease. The aim of this study was to incorporate electrical myofeedback as an integral part of a physiotherapeutic regime designed to improve quality of movement and function in limbs weakened or paralysed by stroke. A portable, inexpensive E. M. G. biofeedback machine was used. Stainless steel skin electrodes were applied which needed minimal skin preparation. Twelve adults, (five male, seven female, mean age 44.2 years and 51.3 years respectively) who were referred for treatment due to weakness of limb muscles due to disease of the brain or spinal cord, were treated. The mean time from onset of incidence to treatment was 75.5 days. Each patient received six weeks of treatment. This was divided into two phases. Phase 1, (weeks 1, 2, 3) and phase 2 (weeks 4, 5, 6). Physiotherapy, and physiotherapy with biofeedback was randomly allocated to either phase. Each patient acted as his/her own control. A validated assessment was carried out by an independent therapist at the start of treatment, after three weeks and after six weeks of treatment. General function, knee function, range of movement of the affected side and timed tests were measured. Results show an overall improvement in general function. The second phase of treatment was slightly more favourable to improvement, but there was no indication that biofeedback significantly improved the outcome. In three tests it was equally significant to the physiotherapy applied; in one test it improved the effectiveness of physiotherapy and in one test it reduced the effectiveness of physiotherapy. This suggests that a six week course of physiotherapy improved muscular function and range of movements in patients with weakness due to upper motor neurone disease, but that these effects are not enhanced by myofeedback.

Nosocomial infections due to Pseudomonas aeruginosa: review of recent trends

The role of Pseudomonas aeruginosa in nosocomial infections occurring since 1975 is reviewed. Data from the National Nosocomial Infections Study conducted by the Centers for Disease Control, from individual medical centers, and from the literature were used to compare the relative frequency of occurrence of nosocomial infection caused by P. aeruginosa with that of infection caused by other gram-negative bacilli. The relative frequency of P. aeruginosa as a nosocomial pathogen has increased, although wide variations are seen among individual medical centers. P. aeruginosa continues to be a major pathogen among patients with immunosuppression, cystic fibrosis, malignancy, and trauma. While Staphylococcus aureus has become the predominant pathogen in some large burn centers, P. aeruginosa is the most important gram-negative pathogen. Periodic review of the epidemiology of P. aeruginosa infection is warranted in view of the changing incidence of infection caused by this organism.

Asymptomatic urethral gonorrhoea in men

Over a period of nine months 203 cases of urethral gonorrhoea were seen in 188 men. In 36 (17%) of the cases there were no symptoms, and in 14 (7%) the symptoms were considered so mild that the patients thought medical care was unnecessary. The symptomless patients and those with mild symptoms were found only as a result of efficient contact tracing. This high incidence illustrates the importance of good contact tracing and careful investigation.

Abnormal forms of Trichomonas vaginalis

Abnormal forms of Trichomonas vaginalis have been demonstrated by both conventional and scanning electron microscopy after inoculation of media with clinical material from cases of trichomonal vaginitis. Twenty-six cases of vaginitis have been studied; 10 of them showed the abnormal forms of trichomonads after growth in a modification of the medium described by Bushby and Copp (1955), while 16 showed only normal forms.