Cytosolic glutamine synthetase and not nitrate reductase from the green alga Chlamydomonas reinhardtii is phosphorylated and binds 14-3-3 proteins

The nitrate reductase activity from Chlamydomonas reinhardtii was not altered when extracts were incubated with yeast 14-3-3 proteins in the presence of Mg-ATP. However, the C. reinhardtii extracts contained 14-3-3 proteins capable of inhibiting the spinach nitrate reductase, raising the question of their physiological substrates. Two C. reinhardtii proteins of about 48 and 35 kDa were eluted from 14-3-3 affinity chromatography columns and bound to 14-3-3s in overlay assays. The 48-kDa protein corresponded to the cytosolic isoform of glutamine synthetase (GS1). The GSI was phosphorylated by a Ca2+-and calmodulin-dependent protein kinase partially purified from the alga. However, neither phosphorylation nor 14-3-3 binding seemed to change GS catalytic activity.

Population coding in spike trains of simultaneously recorded retinal ganglion cells

To achieve a better understanding of the parallel information processing that takes place in the nervous system, many researchers have recently begun to use multielectrode techniques to obtain high spatial- and temporal-resolution recordings of the firing patterns of neural ensembles. Apart from the complexities of acquiring and storing single unit responses from large numbers of neurons, the multielectrode technique has provided new challenges in the analysis of the responses from many simultaneously recorded neurons. This paper provides insights into the problem of coding/decoding of retinal images by ensembles of retinal ganglion cells. We have simultaneously recorded the responses of 15 ganglion cells to visual stimuli of various intensities and wavelengths and analyzed the data using discriminant analysis. Models of stimulus encoding were generated and discriminant analysis used to estimate the wavelength and intensity of the stimuli. We find that the ganglion cells we have recorded from are non-redundant encoders of these stimulus features. While single ganglion cells are poor classifiers of the stimulus parameters, examination of the responses of only a few ganglion cells greatly enhances our ability to specify the stimulus wavelength and intensity. Of the parameters studied, we find that the rate of firing of the ganglion cells provides the most information about these stimulus parameters, while the timing of the first action potential provides almost as much information. While we are not suggesting that the brain is using these variables, our results show how a population of sensory neurons can encode stimulus features and suggest that the brain could potentially deduce reliable information about stimulus features from response patterns of retinal ganglion cell populations.

Occupation and pancreatic cancer in Spain: a case-control study based on job titles. PANKRAS II Study Group

BACKGROUND

Occupational exposures may increase the risk of exocrine pancreatic cancer. This study aimed to identify occupations that in Spain may be associated with such risk.

METHODS

Incident cases of pancreatic cancer and hospital controls were prospectively identified and interviewed during their hospital stay. Occupational history was obtained by direct interview with the patient and was available for 164 (89%) of 185 pancreatic cancer cases and for 238 (90%) of 264 controls. Occupations were coded according to the Spanish version of the International Standard Classification of Occupations 1988.

RESULTS

A significant increased odds ratio (OR) was observed in men for 'physical, chemistry and engineering science technicians'. Elevated risks were also found for 'metal moulders, sheet-metal workers, structural metal workers, welders and related workers', 'painters and varnishers' and 'machinery mechanics and fitters'. 'Agricultural workers' did not present an increased risk for pancreas cancer in men. In women, however, high OR were observed for 'agricultural workers' and for 'textile and garment workers'. Most associations remained unchanged after considering long duration of the exposure and the period 5-15 years before diagnosis.

CONCLUSIONS

Few occupations were at increased risk for pancreatic cancer, and the associations observed are in accordance with previous studies. The increases in risk observed for women in agricultural and textile jobs, and for men in the manufacture of dyes and pigments may deserve further attention.

Meningoencephalitis associated with Globicatella sanguinis infection in lambs

Thirty lambs displayed symptoms of meningoencephalitis. An unusual gram-positive coccus was isolated in pure culture from the blood and brain samples from one of the affected animals, and phenotypic and phylogenetic characterization showed this to be Globicatella sanguinis. This is the first report of the isolation of G. sanguinis in pure culture from an animal infection.

Detection of hepatitis G virus (HGV) RNA and antibodies to the HGV envelope protein E2 in a cohort of hemodialysis patients

An analysis of the evolution of hepatitis G virus (HGV) infection markers was performed for a cohort of 58 hemodialyzed patients. During follow-up (4.88 +/- 0.42 years), a group of these patients cleared their antibodies against the envelope protein E2 with (4 of 29 cases; 13.8%) or without (9 of 29 cases; 31%) the reappearance of viremia. This finding implies a temporally limited protection in patients previously infected with HGV.

Prospective randomized trial to evaluate the efficacy of a vaginal ring releasing progesterone for IVF and oocyte donation

A polysyloxane vaginal ring containing 1g of natural progesterone was developed as luteal supplementation for women treated with IVF-embryo transfer and for agonadal women participating in an oocyte donation programme. The ring provides continuous release of progesterone (10-20 nmol/l) for 90 days. The efficacy of this form of progesterone supplementation was evaluated in two multicentre prospective randomized trials. IVF-embryo transfer trial: After oocyte aspiration, 505 women were randomly allocated to progesterone supplementation with vaginal ring or i.m. progesterone (50 mg/day). The clinical pregnancy rate was 36.6% in both groups. Implantation rate was 15.9% in the vaginal ring and 16.0% in i.m. progesterone. Oocyte donation trial: After endometrial proliferation with micronized oestradiol, 153 women were allocated to progesterone replacement with a vaginal ring or i.m. progesterone (100 mg/day). Clinical pregnancy rate was 39.8 and 28.6% respectively. Implantation rate was significantly higher with the vaginal ring compared with i.m. progesterone (19.9 and 11.6% respectively, P = 0.006). The vaginal ring is a novel development which provides continuous release of progesterone for 90 days. In IVF-embryo transfer, its effectiveness is similar to daily i.m. injections. In oocyte donation the ring provides a progestative milieu which improves the implantation rate and eliminates the discomfort of daily i.m. injections.

Epidemiologic aspects of pediatric multiple trauma in a Spanish urban population

BACKGROUND/PURPOSE

Trauma is still the most frequent cause of mortality and disability in childhood and adolescence. An epidemiologic prospective study on children under 16 years of age with multiple trauma (MT) was conducted in a large Spanish urban university hospital over a 6-year period.

METHODS

Of 1,937 children admitted at the pediatric trauma unit for musculoskeletal injuries from March 1988 until March 1994, 56 patients including 37 boys and 19 girls had MT. MT was considered when at least 2 long bones were fractured or there was a fracture of 1 long bone combined with an injury of 4 other major anatomic regions (face and neck, thorax, abdomen, or neural system). The severity of injuries was evaluated according to the modified injury severity score (MISS).

RESULTS

Injury to pedestrians was the most frequent cause of MT (54%). The overall mortality rate of the series, including those children dying during transport to the hospital was 11.5%. The average MISS for the whole group was 15 (range, 5 to 59). Head trauma was the most frequent associated injury (52%), two thirds of which were considered minor injuries (Glasgow Coma Scale >15). Seventy-seven fractures were registered, 10% of which were open fractures. External fixation was the most common surgical technique among operated fractures. The average hospitalization period was 16 (median, 13; range, 1 to 150) days. Children with a MISS above 18 points showed a significant longer hospitalization period (mean, 31 +/- 45 days) as compared with those with MISS below 18 points (mean, 10 +/- 7 days; P < .05). There was a strong correlation between the MISS and both the period of hospitalization at the pediatric intensive care unit and the total length of hospital stay.

CONCLUSIONS

Pedestrian accidents caused by motor vehicles in children playing at the street contributed most significantly to MT in the urban pediatric population. Special care for prevention must be taken in the age group of 6 to 10 years. Head injury was the main cause of death in children with multiple trauma. MISS was found to be a good predictor of survival and duration of hospital stay in pediatric MT.

[Detection of antiplatelet antibodies. The first one hundred samples studied]

Two types of platelet alloantigens are considered: type I, which refers to platelet alloantigens shared by platelets and other cells; and type II, which comprises the platelet-specific alloantigens. The Human Platelet Alloantigens (HPA) System consists of five diallelic alloantigens and eleven low frequency antigens. According to serological antigen capture assays, immunochemical methods and studies of Molecular Genetics, the glycoproteins (GP) of platelet membrane that are most frequently associated with antibodies are GPIIb-IIIa, GPIb-IX and GPIa-IIa. It is possible to detect platelet antibodies using different laboratory methods. Our experience was restricted to a solid phase system. In this method we used the indirect technique for the screening of alloantibodies and the direct technique for the detection of autoantibodies. The procedure with chloroquine solution was performed in order to differentiate between the presence of HLA and non-HLA platelet specific antibodies. Our comments are based on results obtained in a hundred samples tested throughout a period of eleven months and we briefly review the clinical features related to the diagnosis of autoimmune and alloimmune thrombocytopenia, drug-induced thrombocytopenia and other different factors of platelet destruction. The concepts of transfusional practice applied to emergency situations, platelet refractoriness strategy and the comprehensive management of patients are approached in this work.

The Chlamydomonas reinhardtii Nar1 gene encodes a chloroplast membrane protein involved in nitrite transport

A key step for nitrate assimilation in photosynthetic eukaryotes occurs within chloroplasts, where nitrite is reduced to ammonium, which is incorporated into carbon skeletons. The Nar1 gene from Chlamydomonas reinhardtii is clustered with five other genes for nitrate assimilation, all of them regulated by nitrate. Sequence analysis of genomic DNA and cDNA of Nar1 and comparative studies of strains having or lacking Nar1 have been performed. The deduced amino acid sequence indicates that Nar1 encodes a chloroplast membrane protein with substantial identity to putative formate and nitrite transporters in bacteria. Use of antibodies against NAR1 has corroborated its location in the plastidic membrane. Characterization of strains having or lacking this gene suggests that NAR1 is involved in nitrite transport in plastids, which is critical for cell survival under limiting nitrate conditions, and controls the amount of nitrate incorporated by the cells under limiting CO(2) conditions.

CD3delta couples T-cell receptor signalling to ERK activation and thymocyte positive selection

Thymocytes from mice lacking the CD3delta chain of the T-cell receptor (TCR), unlike those of other CD3-deficient mice, progress from a CD4- CD8- double-negative to a CD4+ CD8+ double-positive stage. However, CD3delta-/- double-positive cells fail to undergo positive selection, by which double-positive cells differentiate into more mature thymocytes. Positive selection is also impaired in mice expressing inactive components of the Ras/mitogen activated protein (MAP) kinase signalling pathway. Here we show that CD3delta-/- thymocytes are defective in the induction of extracellular signal-regulated protein kinase (ERK) MAP kinases upon TCR engagement, whereas activation of other MAP kinases is unaffected. The requirement for CD3delta maps to its extracellular or transmembrane domains, or both, as expression of a tail-less CD3delta rescues both ERK activation and positive selection in CD3delta-/- mice. Furthermore, the defect correlates with severely impaired tyrosine phosphorylation of the linker protein LAT, and of the CD3zeta chain that is localized to membrane lipid rafts upon TCR engagement. Our data indicate that the blockade of positive selection of CD3delta-/- thymocytes may derive from defective tyrosine phosphorylation of CD3zeta in lipid rafts, resulting in impaired activation of the LAT/Ras/ERK pathway.

[Study of association between the magnitude of sphincter hypotonia and esophageal motor disorders]

BACKGROUND

One of the most important factors involved in the pathophysiology of gastroesophageal reflux disease (GERD) is the lower esophageal sphincter rest pressure (LESRP), but these patients can have esophageal motor disorders (EMD).

AIM

To assess an association between LESRP and the appearance of EMD in patients with GERD.

SUBJECTS AND METHODS

A cross-sectional study was conducted in 229 patients with GERD and 49 healthy controls. Forty five patients with LESRP < 6 mmHg and a mean age of 49 years were assigned to group 1, 128 patients with a LESRP between 6 and 12 mmHg and mean age of 47 years were assigned to group 2, 56 patients with a a LESRP > 12 mmHg and a mean age of 47 years were assigned to group 3 and group 4 was conformed by 49 healthy subjects aged 40 years old. Esophageal manometry was performed using previously published techniques.

RESULTS

There was a significant association between LESRP, waves amplitude and the frequency of tertiary waves.

CONCLUSIONS

Resting lower esophageal sphincter pressure is inversely proportional to the presence of esophageal motor disorders in patients with gastroesophageal reflux disease.

Marinomonas mediterranea MMB-1 transposon mutagenesis: isolation of a multipotent polyphenol oxidase mutant

Marinomonas mediterranea is a melanogenic marine bacterium expressing a multifunctional polyphenol oxidase (PPO) able to oxidize substrates characteristic for laccases and tyrosinases, as well as produce a classical tyrosinase. A new and quick method has been developed for screening laccase activity in culture plates to detect mutants differentially affected in this PPO activity. Transposon mutagenesis has been applied for the first time to M. mediterranea by using different minitransposons loaded in R6K-based suicide delivery vectors mobilizable by conjugation. Higher frequencies of insertions were obtained by using mini-Tn10 derivatives encoding kanamycin or gentamycin resistance. After applying this protocol, a multifunctional PPO-negative mutant was obtained. By using the antibiotic resistance cassette as a marker, flanking regions were cloned. Then the wild-type gene was amplified by PCR and was cloned and sequenced. This is the first report on cloning and sequencing of a gene encoding a prokaryotic enzyme with laccase activity. The deduced amino acid sequence shows the characteristic copper-binding sites of other blue copper proteins, including fungal laccases. In addition, it shows some extra copper-binding sites that might be related to its multipotent enzymatic capability.

The negative effect of nitrate on gametogenesis is independent of nitrate assimilation in Chlamydomonas reinhardtii

The effect of nitrate on gamete differentiation as well as on the expression of genes involved in gametogenesis, nitrogen scavenging, and nitrate assimilation has been analyzed in wild-type and mutant strains of Chlamydomonas reinhardtii. Nitrate prevented gamete formation from wild-type strains and caused a strong reduction in the number of zygotes recovered in genetic crosses between nitrate-assimilation-deficient mutants, thus suggesting that nitrate by itself is providing a negative regulatory signal for the sexual differentiation of the alga. Addition of nitrate at low concentrations to wild-type cells, after an initial period of nitrogen starvation, resulted in a drastic decrease in transcript levels of both nitrate-assimilation genes (NIA1 and NRT2;1) and genes induced after N-starvation (NCG2 and NCG4). This strong effect of nitrate was due to its assimilation products since it was not evident in nitrate-assimilation mutants. A slight negative effect of nitrate on NCG4 expression was only observed in the mutant. Nitrate by itself was also found to provide a negative signal for the expression of gamete-specific genes (GAS3 and GAS18) in mutants incapable of assimilating nitrate.

[Influence of housework on health and use of health services by employed women with paid work and homemakers]

OBJECTIVE

To analyse the association between housework, burden, health status, and health services use in women (employed and homemakers) in Cornellà de Llobregat (Spain).

METHODS

We included for analysis 520 women (employed and homemakers) aged 25 to 64 years old who were interviewed within the 1994 Cornellà Health Interview Survey.

RESULTS

Living with elderly persons and being more than 4 members at home was associated with a poorer health status in employed women, who also had a less frequent use of health services when they lived with elderly persons.

CONCLUSION

Employed women have a higher probability of declaring a poor health status when their domestic workload is high.

Lack of effect of nitric oxide on KCl, acetylcholine and substance P induced contractions in ileal longitudinal muscle of the rat

The aim of this study was to determine whether an excess of nitric oxide (NO) (mimicked by addition of NO donors) might produce by itself changes in the contractile responses to acetylcholine (ACh), substance P (SP) and KCl in the longitudinal muscle of the rat ileum. We also studied the calcium handling properties of this tissue in presence of NO donors. The NO donors assayed sodium nitroprusside (SNP) and 3-morpholinosydnonimine hydrochloride (SIN-1), induced different responses. SNP caused an immediate contraction followed by a sustained relaxation, whereas SIN-1 induced an immediate relaxation followed by a contraction. Even after prolonged incubations (up to 90 min), the NO donors SNP and SIN-1 were unable to modify the ACh- and SP-concentration-response curves, as well as the response to 30 mM KCl. The nifedipine-resistant component of the ACh-induced contraction was not modified in presence of SNP. Cyclopiazonic acid (CPA) induced a contraction that was not modified when the tissue was pre-incubated with SNP. Nifedipine caused a sharp relaxation when added during the CPA-induced contraction and, when added previously, it reduced the CPA-induced contractile response. It is concluded that NO excess is not, by itself, responsible for the altered responses to KCl. ACh and SP. The contractility changes observed in the longitudinal muscle of the rat ileum during inflammation could rather be related to the presence of other inflammatory mediators.

[Social self-positioning as indicator of socioeconomic status]

OBJECTIVE

Self-perceived class results from directly questioning subjects about his or her social class. The aim of this investigation was to analyse self-perceived class in relation to other indicator variables of socioeconomic level.

METHODS

Data from the 1994 Catalan Health Interview Survey, a cross-sectional survey of a representative sample of the non-institutionalised population of Catalonia was used. We conducted a discriminant analysis to compute the degree of right classification when different socioeconomic variables potentially related to self-perceived class were considered. All subjects who directly answered the questionnaire were included (N = 12,245). With the aim of obtaining the discriminant functions in a group of subjects and to validate it in another one, the subjects were divided into two random samples, containing approximately 75% and 25% of subjects (analysis sample, n = 9,248; and validation sample, n = 2,997).

RESULTS

The final function for men and women included level of education, social class (based in occupation) and equivalent income. This function correctly classified 40.9% of the subjects in the analysis sample and 39.2% in the validation sample. Two other functions were selected for men and women separately. In men, the function included level of education, professional category, and family income (39.2% of classification in analysis sample and 37.2% in validation sample). In women, the function (level of education, working status, and equivalent income) correctly classified 40.3% of women in analysis sample whereas the percentage was 38.9% in validation sample. The percentages of right classification were higher for the highest and lowest classes.

CONCLUSION

These results show the utility of a simple variable to self-position within the social scale. Self-perceived class is related to education, income, and working determinants.

Role of architecture in determining passive electrical properties in gap junction-connected cells

The electrical properties of gap junction-connected cells were analysed in terms of their architectural organization. Two major architectural categories were considered: trees and rings. Trees are described by means of Bethe lattices (lattices with no rings) with arbitrary co-ordination and rings by two-dimensional periodic lattices with fourfold (square) or sixfold (triangular) co-ordination. The Bethe lattice is solved analytically by the transfer constant method, which allows the introduction of several physiologically relevant effects in a very simple manner. The experimental data for the length constant and the input resistance were fitted by varying the coupling and membrane resistances for various morphologies. The large variations in the length constant observed experimentally in two systems (turtle retina horizontal cells with and without dopamine and pancreatic beta-cells in the active and silent phases) could not be explained by means of the Bethe lattice, indicating that the cell arrangements form rings. Subsequent analysis by means of a linear chain and the square and triangular lattices showed the crucial relevance of architecture in deriving the electrical characteristics of gap junction-connected cells from experimental data.