Examination of the Montastraea annularis Species Complex (Cnidaria: Scleractinia) Using ITS and COI Sequences

: The Caribbean coral Montastraea annularis has recently been proposed to be a complex of at least three sibling species. To test the validity of this proposal, we sequenced the ITS region of the nuclear ribosomal RNA gene family (ITS-1, 5.8S, and ITS-2), and a portion of the mitochondrial DNA gene cytochrome c oxidase subunit I (COI) from the three proposed species (M. annularis, M. faveolata, and M. franksi) from Florida reefs. The ITS fragment was 665 nucleotides long and had 19 variable sites, of which 6 were parsimony-informative sites. None of these sites was fixed within the proposed species. The COI fragment was 658 nucleotides long with only two sites variable in one individual. Thus, under both the biological species concept and the phylogenetic species concept, the molecular evidence gathered in this study indicates the Montastraea annularis species complex to be a single evolutionary entity as opposed to three distinct species. The three proposed Montastraea species can interbreed, ruling out prezygotic barriers to gene flow (biological species concept), and the criterion of monophyly is not satisfied if hybridization is occurring among taxa (phylogenetic species concept).

Role of Arg100 and Arg264 from Anabaena PCC 7119 ferredoxin-NADP+ reductase for optimal NADP+ binding and electron transfer

Previous studies and the crystal structure of Anabaena PCC 7119 FNR suggest that the side chains of Arg100 and Arg264 may be directly involved in the proper NADP+/NADPH orientation for an efficient electron-transfer reaction. Protein engineering on Arg100 and Arg264 from Anabaena PCC 7119 FNR has been carried out to investigate their roles in complex formation and electron transfer to NADP+ and to ferredoxin/flavodoxin. Arg100 has been replaced with an alanine, which removes the positive charge, the long side chain, as well as the ability to form hydrogen bonds, while a charge reversal mutation has been made at Arg264 by replacing it with a glutamic acid. Results with various spectroscopic techniques indicate that the mutated proteins folded properly and that significant protein structural rearrangements did not occur. Both mutants have been kinetically characterized by steady-state as well as fast transient kinetic techniques, and the three-dimensional structure of Arg264Glu FNR has been solved. The results reported herein reveal important conceptual information about the interaction of FNR with its substrates. A critical role is confirmed for the long, positively charged side chain of Arg100. Studies on the Arg264Glu FNR mutant demonstrate that the Arg264 side chain is not critical for the nicotinamide orientation or for nicotinamide interaction with the isoalloxazine FAD moiety. However, this mutant showed altered behavior in its interaction and electron transfer with its protein partners, ferredoxin and flavodoxin.

Enhanced bradycardia induced by beta-adrenoceptor antagonists in rats pretreated with isoniazid

High doses of isoniazid increase hypotension induced by vasodilators and change the accompanying reflex tachycardia to bradycardia, an interaction attributed to decreased synthesis of brain gamma-aminobutyric acid (GABA). In the present study, the possible enhancement by isoniazid of bradycardia induced by beta-adrenoceptor antagonists was determined in rats anaesthetised with chloralose-urethane. Isoniazid significantly increased bradycardia after propranolol, pindolol, labetalol and atenolol, as well as after clonidine, but not after hexamethonium or carbachol. Enhancement was not observed in rats pretreated with methylatropine or previously vagotomised. These results are compatible with interference by isoniazid with GABAergic inhibition of cardiac parasympathetic tone. Such interference could be exerted centrally, possibly at the nucleus ambiguus, or peripherally at the sinus node.

A 55-kDa protein isolated from human cells shows DNA glycosylase activity toward 3,N4-ethenocytosine and the G/T mismatch

Etheno adducts in DNA arise from multiple endogenous and exogenous sources. Of these adducts we have reported that, 1,N6-ethenoadenine (epsilonA) and 3,N4-ethenocytosine (epsilonC) are removed from DNA by two separate DNA glycosylases. We later confirmed these results by using a gene knockout mouse lacking alkylpurine-DNA-N-glycosylase, which excises epsilonA. The present work is directed toward identifying and purifying the human glycosylase activity releasing epsilonC. HeLa cells were subjected to multiple steps of column chromatography, including two epsilonC-DNA affinity columns, which resulted in >1,000-fold purification. Isolation and renaturation of the protein from SDS/polyacrylamide gel showed that the epsilonC activity resides in a 55-kDa polypeptide. This apparent molecular mass is approximately the same as reported for the human G/T mismatch thymine-DNA glycosylase. This latter activity copurified to the final column step and was present in the isolated protein band having epsilonC-DNA glycosylase activity. In addition, oligonucleotides containing epsilonC.G or G/T(U), could compete for epsilonC protein binding, further indicating that the epsilonC-DNA glycosylase is specific for both types of substrates in recognition. The same substrate specificity for epsilonC also was observed in a recombinant G/T mismatch DNA glycosylase from the thermophilic bacterium, Methanobacterium thermoautotrophicum THF.

Protein-protein interaction in electron transfer reactions: the ferredoxin/flavodoxin/ferredoxin:NADP+ reductase system from Anabaena

Electron transfer reactions involving protein-protein interactions require the formation of a transient complex which brings together the two redox centres exchanging electrons. This is the case for the flavoprotein ferredoxin:NADP+ reductase (FNR) from the cyanobacterium Anabaena, an enzyme which interacts with ferredoxin in the photosynthetic pathway to receive the electrons required for NADP+ reduction. The reductase shows a concave cavity in its structure into which small proteins such as ferredoxin can fit. Flavodoxin, an FMN-containing protein that is synthesised in cyanobacteria under iron-deficient conditions, plays the same role as ferredoxin in its interaction with FNR in spite of its different structure, size and redox cofactor. There are a number of negatively charged amino acid residues on the surface of ferredoxin and flavodoxin that play a role in the electron transfer reaction with the reductase. Thus far, in only one case has charge replacement of one of the acidic residues produced an increase in the rate of electron transfer, whereas in several other cases a decrease in the rate is observed. In the most dramatic example, replacement of Glu at position 94 of Anabaena ferredoxin results in virtually the complete loss of ability to transfer electrons. Charge-reversal of positively charged amino acid residues in the reductase also produces strong effects on the rate of electron transfer. Several degrees of impairment have been observed, the most significant involving a positively charged Lys at position 75 which appears to be essential for the stability of the complex between the reductase and ferredoxin. The results presented in this paper provide a clear demonstration of the importance of electrostatic interactions on the stability of the transient complex formed during electron transfer by the proteins presently under study.

Lys75 of Anabaena ferredoxin-NADP+ reductase is a critical residue for binding ferredoxin and flavodoxin during electron transfer

Previous studies, and the three-dimensional structure of Anabaena PCC 7119 ferredoxin-NADP+ reductase (FNR), indicate that the positive charge of Lys75 might be directly involved in the interaction between FNR and its protein partners, ferredoxin (Fd) and flavodoxin (Fld). To assess this possibility, this residue has been replaced by another positively charged residue, Arg, by two uncharged residues, Gln and Ser, and by a negatively charged residue, Glu. UV-vis absorption, fluorescence, and CD spectroscopies of these FNR mutants (Lys75Arg, Lys75Gln, Lys75Ser, and Lys75Glu) indicate that all the mutated proteins folded properly and that significant protein structural rearrangements did not occur. Steady-state kinetic parameters for these FNR mutants, utilizing the diaphorase activity with DCPIP, indicate that Lys75 is not a critical residue for complex formation and electron transfer (ET) between FNR and NADP+ or NADPH. However, steady-state kinetic activities requiring complex formation and ET between FNR and Fd or Fld were appreciably affected when the positive charge at position of Lys75 was removed, and the ET reaction was not even measurable if a negatively charged residue was placed at this position. These kinetic parameters also suggest that it is complex formation that is affected by mutation. Consistent with this, when dissociation constants (Kd) for FNRox-Fdox (differential spectroscopy) and FNRox-Fdrd (laser flash photolysis) were measured, it was found that neutralization of the positive charge at position 75 increased the Kd values by 50-100-fold, and that no complex formation could be detected upon introduction of a negative charge at this position. Fast transient kinetic studies also corroborated the fact that removal of the positive charge at position 75 of FNR appreciably affects the complex formation process with its protein partners but indicates that ET is still achieved in all the reactions. This study thus clearly establishes the requirement of a positive charge at position Lys75 for complex formation during ET between FNR and its physiological protein partners. The results also suggest that the interaction of this residue with its protein partners is not structurally specific, since Lys75 can still be efficiently substituted by an arginine, but is definitely charge specific.

Detection of specific bacteriocin-producing lactic acid bacteria by colony hybridization

A colony hybridization method for detecting lactic acid bacteria encoding specific bacteriocins was developed. Specific PCR-generated probes were used to detect colonies of pediocin PA-1, lactococcin A, enterocin AS-48, nisin A and lacticin 481 producing strains. The probes were shown to be sensitive and specific for sequences belonging to the structural genes of the respective bacteriocins.

Involvement of blood serum in amphibian fertilization

A proteolytic enzyme secreted by the first portion of amphibian oviduct, pars recta, called oviductin in Xenopus laevis, causes ultrastructural alterations on the extracellular matrix of coelomic eggs, turning them susceptible to fertilization. Although great advances have been made in the field of reproduction, the molecular mechanisms responsible for the fusion between the egg and the sperm are yet to be understood. We have recently demonstrated the presence of proteins from pars recta fluid in blood serum and extracellular matrix of coelomic eggs in Bufo arenarum. Here we show, using immunofluorescence procedures, that blood serum components are present in the extracellular matrix of coelomic and pars recta fluid-conditioned eggs in Bufo arenarum. Furthermore, by assessing the neutralizing effect on the conditioning activity of pars recta fluid on coelomic eggs we found that antibodies against pars recta secretions and blood serum inhibited the effect of sperm-lysin on the vitelline envelope of conditioned oocytes and impaired fertilization by sperm. Thus, serum proteins appear to be implicated in the molecular events that lead to amphibian fertilization.

Involvement of glutamic acid 301 in the catalytic mechanism of ferredoxin-NADP+ reductase from Anabaena PCC 7119

The crystal structure of Anabaena PCC 7119 ferredoxin-NADP+ reductase (FNR) suggests that the carboxylate group of Glu301 may be directly involved in the catalytic process of electron and proton transfer between the isoalloxazine moiety of FAD and FNR substrates (NADPH, ferredoxin, and flavodoxin). To assess this possibility, the carboxylate of Glu301 was removed by mutating the residue to an alanine. Various spectroscopic techniques (UV-vis absorption, fluorescence, and CD) indicate that the mutant protein folded properly and that significant protein structural rearrangements did not occur. Additionally, complex formation of the mutant FNR with its substrates was almost unaltered. Nevertheless, no semiquinone formation was seen during photoreduction of Glu301Ala FNR. Furthermore, steady-state activities in which FNR semiquinone formation was required during the electron-transfer processes to ferredoxin were appreciably affected by the mutation. Fast transient kinetic studies corroborated that removal of the carboxylate at position 301 decreases the rate constant approximately 40-fold for the electron transfer process with ferredoxin without appreciably affecting complex formation, and thus interferes with the stabilization of the transition state during electron-transfer between the FAD and the iron-sulfur cluster. Moreover, the mutation also altered the nonspecific reaction of FNR with 5'-deazariboflavin semiquinone, the electron-transfer reactions with flavodoxin, and the reoxidation properties of the enzyme. These results clearly establish Glu301 as a critical residue for electron transfer in FNR.

Synergistic effect of nisin and the lactoperoxidase system on Listeria monocytogenes in skim milk

Nisin added at 10 or 100 IU/ml to ultra-high temperature processed (UHT) skim milk had no effect on counts of Listeria monocytogenes after 24 h at 30 degrees C, whereas addition of the lactoperoxidase system (LPS) resulted in counts of viable cells three log units lower than those of control milk after 24 h at 30 degrees C. Addition of nisin and LPS showed a synergistic effect and resulted in counts up to 5.6 log units lower than the control milk. When the two preservatives were added to actively growing cells of L. monocytogenes in two steps with a 2 h interval, their synergistic effect was enhanced. Counts of L. monocytogenes Ohio after 24 h at 30 degrees C in milk with nisin and LPS added together after 3 h of growth were 5.7 log units lower than the control milk. The difference in counts increased to 7.4 log units if LPS was added after 3 h and nisin after 5 h of growth. Similar but less pronounced effects were observed for the more resistant strain L. monocytogenes Scott A.

Expression of Kin, a nuclear protein binding to curved DNA, in mammal and avian brains

Kin is a nuclear protein which presents cross-immunoreactivity with the bacterial RecA protein and which efficiently binds to curved DNA. This genomic interaction could be implied in DNA repair and illegitimate recombination in eukaryotic cells. Using immunocytochemistry with anti-RecA antibodies, we report the ubiquitous presence of the Kin protein in the CNS of mice and quails. However, some brain structures such as the hippocampal area, the locus coeruleus and Purkinje cells are preferentially immunolabelled and show some homologies between the two species. In conclusion, the expression of the Kin protein is preserved in the phylogeny of the brain of higher vertebrates.

Detection of enterocin AS-48-producing dairy enterococci by dot-blot and colony hybridization

The enterococci have traditionally been used as indicators of faecal contamination because they are common inhabitants of the human and animal intestinal tract. In addition, some strains are well documented as opportunistic pathogens, and have been implicated in endocarditis, infant diarrhoea and other conditions. However, other strains are widespread in foods, particularly in milk and dairy products, where they are considered desirable microflora. In fact, through their proteolytic and lipolytic abilities, they play an important role in cheese ripening, contributing to the development of the organoleptic properties characteristic of certain cheeses (Villani et al. 1993).

Production of antimicrobial substances is one of the mechanisms by which microorganisms can exert a probiotic effect in a host. In this context, a significant number of bacteriocin-producing enterococci of dairy origin have been isolated in recent years (Giraffa, 1995). Production of these antimicrobial peptides or proteins is a common phenotype among lactic acid bacteria, and this is the application of enterococcal bacteriocins of special interest in dairy systems. Firstly, they show activity against a broad spectrum of spoilage and pathogenic organisms of concern in dairy industries, such as Listeria monocytogenes. Secondly, they are inactivated by human gastric enzymes but not by some enzymes that, like rennet, are frequently used in dairy plants. Finally, their marked heat stability enables them to be used in a wide variety of dairy products (Giraffa, 1995).

The genes that encode the biosynthesis of some enterocins or enterococcins, such as enterocin AS-48 (Martínez-Bueno et al. 1994), have been sequenced, allowing their rapid detection by molecular biology techniques such as the polymerase chain reaction (PCR) (Joosten et al. 1997). Enterococcal bacteriocins that have been genetically characterized have been shown to be plasmid-encoded (Clewell, 1993).

In this paper, we report a simple method for the isolation of plasmid DNA from dairy enterococci, using a combination of lysozyme and glass beads (Frère, 1994; Reinkemeier et al. 1996) to achieve cell lysis. Plasmid DNA was used in dot-blot and Southern hybridization analyses to identify enterocin AS-48-encoding dairy enterococci by using a specific PCR-generated probe. In addition, a more rapid detection method based on colony hybridization was also developed.

Inhibitory activity of a nisin-producing starter culture on Listeria innocua in raw ewes milk Manchego cheese

The inhibitory activity of nisin-producing Lactococcus lactis subsp. lactis ESI 515 on the survival of Listeria innocua during ripening of raw ewes milk Manchego cheese was investigated. After 60 days of ripening, counts of L. innocua in cheese were 4.08 log units lower than the control when Lc. lactis subsp. lactis ESI 515 was used as a single-strain starter. Nisin activity was detected in cheeses manufactured with Lc. lactis subsp. lactis ESI 515 throughout the ripening period.

One- and two-dimensional ESEEM spectroscopy of flavoproteins

One- and two-dimensional (1D and 2D) electron spin echo envelope modulation (ESEEM) spectroscopy was applied to study the flavin cofactors in the neutral semiquinone states of flavodoxin and ferredoxin-NADP+ reductase (FNR) from the cyanobacterium Anabaena PCC 7119, and the anionic semiquinone state of cholesterol oxidase from Brevibacterium sterolicum. High-resolution crystal structures are available for all these proteins. Three- and 4-pulse ESEEM and hyperfine sublevel correlation spectroscopy (HYSCORE) techniques at X-band were used. HYSCORE spectra showed correlations between transitions caused by interaction of the isoalloxazine unpaired electronic spin present in the semiquinone state with several nitrogen and hydrogen nuclei. Measurements of isotopic labeled samples ([15N]FMN flavodoxin and [2H]flavodoxin) allowed the assignment of all the detected transitions to nuclei belonging to the FMN cofactor group. Interactions of nitrogens in positions 1 and 3 of the isoalloxazine ring were determined to have isotropic hyperfine coupling constants in the 1-2 and 0.5-1 MHz ranges for all the different flavoprotein semiquinones studied. Information about the quadrupolar term of these nuclei was also obtained. An intense correlation in the negative quadrant was detected. It has been associated to the strongly interacting N(10) nucleus. The complete hyperfine term parameters (including the sign) were obtained from detailed analysis of this signal, being the quadrupolar parameter, K, also estimated. Another correlation in the HYSCORE spectra, corresponding to hydrogen bound to the N(5) position in neutral flavin semiquinones, was detected. Its interaction parameters were also determined. This study demonstrates that ESEEM spectroscopy, and in particular the HYSCORE technique, are of particular utility for detecting and assigning nuclear transition frequencies in flavoprotein semiquinones. Moreover, the results reported here are complementary to ENDOR studies, and both techniques together provide an important tool for obtaining information about spin distribution in the flavin ring of flavoproteins in the semiquinone state.

Inhibition of Listeria monocytogenes by enterocin 4 during the manufacture and ripening of Manchego cheese

The inhibitory effect of enterocin 4, a bacteriocin produced by Enterococcus faecalis INIA 4, on Listeria monocytogenes strains Ohio and Scott A during the manufacture and ripening of Manchego cheese was investigated. Raw ewe's milk was inoculated with ca 10(5) cfu ml-1 of L. monocytogenes and with 1% of a commercial lactic starter, 1% of an Ent. faecalis INIA 4 culture, or 1% of each culture. Manchego cheeses were manufactured according to usual procedures. Listeria monocytogenes Ohio counts decreased by 3 log units after 8 h and by 6 log units after 7 d in cheese made from milk inoculated with Ent. faecalis INIA 4 or with both cultures, whereas no inhibition was recorded after 60 d in cheese made from milk inoculated with commercial lactic starter. Listeria monocytogenes Scott A was not inhibited by enterocin 4 during cheese manufacture, but decreases of 1 log unit after 7 d and of 2 log units after 60 d were achieved in cheese made from milk inoculated with both commercial lactic starter and Ent. faecalis INIA 4.

Combined effect of bacteriocin-producing lactic acid bacteria and lactoperoxidase system activation on Listeria monocytogenes in refrigerated raw milk

The bactericidal activity of three bacteriocin-producing lactic acid bacteria alone and in combination with milk lactoperoxidase (LP) system activation against Listeria monocytogenes in refrigerated raw milk was studied. After 4 d at 4 degrees C, the population of L. monocytogenes in milk inoculated with bacteriocin-producing Lactococcus lactis subsp. lactis ATCC 11454, L. lactis subsp. lactis ESI 515 or Enterococcus faecalis INIA 4 was reduced by 0.21-0.24 log units. Activation of the LP system did not enhance inhibition at this temperature. After 4 d at 8 degrees C, L. monocytogenes levels in the non-activated LP system milk inoculated with L. lactis subsp. lactis ATCC 11454, L. lactis subsp. lactis ESI 515 or Ent. faecalis INIA 4 were reduced by 1.87, 1.54 and 1.11 log units compared to control milk, whereas in the activated LP system milk, this reduction was 1.99, 2.10 and 1.06, respectively. The higher nisin production by L. lactis subsp. lactis ESI 515 in milk with activated LP system than in non-activated LP system milk was responsible for the more pronounced decrease of L. monocytogenes counts in the former.

Cholecystokinin-like systems in the chameleon brain

Immunohistochemical techniques were used to determine the distribution of cholecystokinin-8 (CCK8) immunoreactivity in the brain of the chameleon. In the telencephalon, CCK8-immunopositive somata were sparse and observed principally in the olfactory tubercle at the ventromedial edge of the rostral telencephalon and in the medial septum. Immunopositive fibers were observed mainly in the medial septal region and the ventral telencephalon. In the diencephalon, numerous CCK8-reactive fibers were densely concentrated in the periventricular region, the dorsolateral hypothalamus and the external zone of the median eminence. In the thalamus, labelled fibers were restricted to the peri-rotundal nuclei and the lateral part of the habenula. Immunoreactive cell bodies were observed in the medial part of the dorsal lateral geniculate nucleus, in the periventricular, ventral and lateral regions of the hypothalamus. In the mesencephalon, the densest accumulations of immunopositive fibers were observed in the area pretectalis, the periventricular gray matter, the medial tegmentum and the isthmus. Labelled neurons were observed in the deep, and occasionally intermediate, tectal layers and in the laminar nucleus of the torus semicircularis. In the rhombencephalon, labelled fibers were observed at the highest density in the central gray matter and the locus coeruleus; labelled somata were observed only in the nucleus of the tractus solitarius.

Electron-nuclear double resonance spectroscopy investigation of 4-hydroxybutyryl-CoA dehydratase from Clostridium aminobutyricum: comparison with other flavin radical enzymes

A FAD and [4Fe-4S]cluster-containing enzyme from Clostridium aminobutyricum catalyses the reversible dehydration of 4-hydroxybutyryl-CoA to crotonyl-CoA which involves the cleavage of an unactivated C-H bond at the beta-carbon. Transient oxidation of the substrate to an enoxy radical by FAD might facilitate the removal of this beta-proton, whereas no function could be attributed to the [4Fe-4S]cluster. In this paper the organic radical, which is formed by partial reduction of the enzyme with dithionite, was characterised as the neutral flavin semiquinone by EPR spectroscopy in H2O and D2O. The rapid electron-spin relaxation of the flavin semiquinone suggested a magnetic interaction with the [4Fe-4S]cluster. In order to obtain highly resolved information about nuclear spins in the vicinity of this paramagnetic centre, ENDOR spectroscopy was applied. The spectra were compared with those of the neutral semiquinone radicals of ferredoxin-NADP reductase and flavodoxin as well as with that of the anionic semiquinone radical of cholesterol oxidase. All ENDOR spectra showed strong couplings to the 8-methyl protons and to H-6 of the flavin. On addition of the substrates to the corresponding enzymes, the electron density changed significantly only at the 8-position. It decreased in the case of cholesterol oxidase and ferredoxin-NADP reductase, whereas an increase was observed with 4-hydroxybutyryl-CoA dehydratase. The results indicate an interaction of 4-hydroxybutyryl-CoA with the flavin as required by the proposed mechanism. Furthermore, the shift of electron density towards the benzoid ring of FAD in the dehydratase might be due to the location of the [4Fe-4S]cluster next to the 8-position as known from structurally characterised iron-sulfur flavoproteins.

[Risk factors and length of stay attributable to hospital infections of the urinary tract in general surgery patients]

BACKGROUND

Urinary tract infection (UTI) is the second frequent site of infection in surgical patients; nevertheless, its study has been frequently neglected. The main objective of this report is the analysis of risk factors for ITU in general surgery.

METHODS

A prospective study on 1,483 patients admitted at a service of general surgery for a 20-month study period has been carried out. The criteria used for diagnosing nosocomial were those of the CDC. Crude and adjusted for by logistic regression relative risks and its 95% confidence interval were estimated. To assess the length of stay attributable to UTI, infected patients were 1:1 matched with non-infected patients for surgical procedure, ASA score, age (+/- 10 years), emergency surgery, pre-operative stay, and urinary catheter.

RESULTS

33 patients (2.2%) developed UTI. In crude analysis, UTI risk was significantly associated with urethral catheter (and its duration), advanced age, severity of illness (McCabe-Jackson scale, ASA score, number of diagnoses), type of surgical wound, intrinsic risk of infection (measured by the SENIC and NNIS indices). Stepwise logistic regression analysis selected three independent predictors: urethral catheter, age and pre-operative stay. All urinary drain-ages were open. UTI prolonged hospital stay 4.7 days (95% Cl 3.4-6.2). The use of closed drain-age systems would eliminate 6 UTIs. Assuming a cost per day of hospital stay of $250 the use of closed systems would save $7,000 (IC 95%, 5300-9300).

CONCLUSION

The use of closed systems for urethral catheters is cost-saving.

Presenilin 1 interaction in the brain with a novel member of the Armadillo family

One approach to understanding the function of presenilin 1 (PS1), is to discover those proteins with which it interacts. Evidence for a function in developmental patterning came from C. elegans, in which a PS homologue was identified by screening for suppressors of a mutation in Notch/lin-12, a gene which specifies cell fate. However, this genetic experiment cannot determine which proteins directly interact with PS1. Therefore, we utilized the two hybrid system and confirmatory co-immunoprecipitations to identify a novel catenin, termed delta-catenin, which interacts with PS1 and is principally expressed in brain. The catenins are a gene family related to the Armadillo gene in Drosophila, some of which appear to have dual roles-they are components of cell-cell adherens junctions, and may serve as intermediates in the Wingless (Wg) signaling pathway, which, like Notch/lin-12, is also responsible for a variety of inductive signaling events. In the non-neuronal 293 cell line, PS1 interacted with beta-catenin, the family member with the greatest homology to Armadillo. Wg and Notch interactions are mediated by the Dishevelled gene, which may form a signaling complex with PS1 and Wg pathway intermediates to regulate the function of the Notch/lin-12 gene.

Acute brain swelling during removal of supratentorial cystic lesion caused by contralateral extradural hematoma: case report

BACKGROUND

Protrusion of the cortex through a bone flap in the course of surgery is a very serious event and, if it persists, the procedure must be suspended, the cause sought, and the problem resolved.

CASE DESCRIPTION

We report the case of a 13-year-old boy whose brain underwent sudden swelling during removal of a supratentorial cystic lesion. The operation was suspended at once and an emergency CT scan was performed. It revealed a large contralateral extradural hematoma, which was removed immediately.

CONCLUSIONS

We considered the following possible mechanisms of the emergency: bleeding of bone at the site of the supposed piercing by the headrest pin and/or a vacuum mechanism consequent upon removal of the large cystic lesion. Our aims are to emphasize the importance of gauging the thickness of a child's skull before fixing the head in the headrest, especially when chronic intracranial hypertension is present, and the need to suspend the operation for CT scanning in the event of uncontrollable brain swelling.

Enrichment of glutamate-like immunoreactivity in the retinotectal terminals of the viper Vipera aspis: an electron microscope quantitative immunogold study

A post-embedding immunogold study was carried out to estimate the immunoreactivity to glutamate in retinal terminals, P axon terminals and dendrites containing synaptic vesicles in the superficial layers of the optic tectum of Vipera. Retinal terminals, identified following either intraocular injection of tritiated proline, horseradish peroxidase (HRP) or short-term survivals after retinal ablation, were observed to be highly glutamate-immunoreactive. A detailed quantitative analysis showed that about 50% of glutamate immunoreactivity was localized over the synaptic vesicles, 35.8% over mitochondria and 14.2% over the axoplasmic matrix. The close association of immunoreactivity with the synaptic vesicles could indicate that Vipera retino-tectal terminals may use glutamate as their neurotransmitter. P axon terminals and dendrites containing synaptic vesicles, strongly gamma-aminobutyric (GABA)-immunoreactive, were shown to be also moderately glutamate-immunoreactive, but two to three times less than retinal terminals. Moreover, in P axon terminals, the glutamate immunoreactivity was denser over mitochondria than over synaptic vesicles, possibly reflecting the 'metabolic' pool of glutamate, which serves as a precursor in the formation of GABA.