RNAi-mediated endogene silencing in strawberry fruit: detection of primary and secondary siRNAs by deep sequencing

RNA interference (RNAi) has been exploited as a reverse genetic tool for functional genomics in the nonmodel species strawberry (Fragaria × ananassa) since 2006. Here, we analysed for the first time different but overlapping nucleotide sections (>200 nt) of two endogenous genes, FaCHS (chalcone synthase) and FaOMT (O-methyltransferase), as inducer sequences and a transitive vector system to compare their gene silencing efficiencies. In total, ten vectors were assembled each containing the nucleotide sequence of one fragment in sense and corresponding antisense orientation separated by an intron (inverted hairpin construct, ihp). All sequence fragments along the full lengths of both target genes resulted in a significant down-regulation of the respective gene expression and related metabolite levels. Quantitative PCR data and successful application of a transitive vector system coinciding with a phenotypic change suggested propagation of the silencing signal. The spreading of the signal in strawberry fruit in the 3' direction was shown for the first time by the detection of secondary small interfering RNAs (siRNAs) outside of the primary targets by deep sequencing. Down-regulation of endogenes by the transitive method was less effective than silencing by ihp constructs probably because the numbers of primary siRNAs exceeded the quantity of secondary siRNAs by three orders of magnitude. Besides, we observed consistent hotspots of primary and secondary siRNA formation along the target sequence which fall within a distance of less than 200 nt. Thus, ihp vectors seem to be superior over the transitive vector system for functional genomics in strawberry fruit.

Long-term follow-up of standard microdiscectomy versus minimal access surgery for lumbar disc herniations

BACKGROUND

Surgery of lumbar disc herniations is one of the most common neurosurgical procedures. New surgical approaches and techniques are constantly evolving. We present our long-term follow-up results comparing standard open microdiscectomy (SOMD) and minimal access microdiscectomy (MAMD) for single-level lumbar disc herniations.

METHODS

Patients were randomized in two groups receiving either MAMD or SOMD. Physical and mental health and pain relief were assessed (ODI, SF-36 questionnaire, VAS leg and back pain). In addition, all patients received MR imaging for morphological evaluation of postoperative peridural scar tissue formation.

RESULTS

Of the 60 initial patients (SOMD: 30 pts, MAMD: 30 pts), 38 were available for long-term follow-up. Mean follow-up time was 33 months. Long-term follow-up revealed significant postoperative pain relief in both groups. Good to excellent results concerning physical and mental health and pain relief were achieved in both groups. Significantly less peridural scar tissue formation was observed in the MAMD patients, but without clinical impact.

CONCLUSION

MAMD is a feasible alternative to the standard open approach. Both groups show significant and long-lasting pain relief and good to excellent results regarding health-related quality of life. Congruent to our short-term results, we observed slightly but not statistically significant better clinical results in the MAMD group when compared to the SOMD group.

Photoinactivation of Escherichia coli (SURE2) without intracellular uptake of the photosensitizer

AIM

This study was performed to investigate the possibility to photodynamically inactivate Gram-negative bacteria without intracellular uptake of the photosensitizer. The efficiency of the photodynamic growth inhibition of Escherichia coli (SURE2) was proved in a comparative study of a neutral and a cationic photosensitizer.

METHODS AND RESULTS

We used confocal laser scanning microscopy (CLSM) to investigate the uptake of the photosensitizer by the bacteria to show that both chlorin e(6) and TMPyP are not accumulated in the cells. Fluorescence lifetime imaging (FLIM) and phototoxicity experiments were used to investigate the photodynamic inactivation of the Gram-negative bacteria. The phototoxicity experiments were carried out using a white light LED-setup to irradiate the bacterial suspensions. The viability of the bacteria was obtained by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-assay. For the cationic TMPyP, photodynamic inactivation without intracellular uptake was observed, whereas for chlorin e(6) such behaviour was not found.

CONCLUSIONS

It was proven that in general, it is possible to photodynamically inactivate Gram-negative bacteria without photosensitizer accumulation in the bacterial cells. This fact is especially interesting, considering that the development of resistances may be prevented, leaving the active components outside the bacterium.

SIGNIFICANCE AND IMPACT OF THE STUDY

In a world with bacteria that gain the ability to withstand the effects of antibiotics and are able to transmit on these resistances to the next generation, it becomes necessary to develop new approaches to inhibit the growth of multi-resistant bacteria. The photodynamic inactivation of bacteria is based on a three-component system by which the growth of the bacterial cells is inhibited. The well-directed oxidative damage is initiated by visible light of a certain wavelength, which excites a nontoxic photoactive molecule, called photosensitizer. Its reaction with oxygen causes the generation of cytotoxic species like singlet oxygen, which is highly reactive and causes the inactivation of the growth of bacteria.

Differential expression of flavonoid 3'-hydroxylase during fruit development establishes the different B-ring hydroxylation patterns of flavonoids in Fragaria × ananassa and Fragaria vesca

Flavonoid 3'-hydroxylase (F3'H) was studied for the first time in different Fragaria species. The cDNA clones isolated from unripe and ripe fruits of Fragaria x ananassa (garden strawberry) and Fragaria vesca (wild strawberry) showed high similarity (99% at the amino acid level) to the publically available F. vesca genome sequence and no significant differences could be identified between species and developmental stages of the fruits. In contrast, the genomic F3'H clones showed differences in the non-coding regions and 5'-flanking elements. The recombinant F3'Hs were functionally active and showed high specificity for naringenin, dihydrokaempferol, and kaempferol, whereas apigenin was only a minor substrate. During fruit development, a clear difference in the F3'H expression was observed between F. × ananassa and F. vesca. While a drastic decline of F3'H expression occurred during fruit ripening in F. × ananassa, F3'H in F. vesca was highly expressed in all stages. This was reflected by the anthocyanin composition, which showed a prevalence of pelargonidin in ripe fruits of F. × ananassa, whereas F. vesca had a high content of cyanidin. Screening of 17 berry species for their anthocyanin and flavonol composition showed that the prevalence of monohydroxylated anthocyanins makes garden strawberry unique among all other fruit species indicating that selection of bright red color during strawberry breeding, which consumers typically associate with freshness and ripeness, has selected phenotypes with a special biochemical background.

Multifunctional flavonoid dioxygenases: flavonol and anthocyanin biosynthesis in Arabidopsis thaliana L

Flavonols and conditionally also anthocyanins, aside from flavonols, are the predominant polyphenols accumulated in various tissues of the model plant Arabidopsis thaliana L. In vitro experiments suggested that the dioxygenases involved in their biosynthesis, flavonol synthase and anthocyanidin synthase, are "multifunctional" enzymes showing distinct side activities. The in vivo relevance of the additional activities attributed to these enzymes, however, has remained obscure. In this review we summarize the most recent results and present final proof of the complementing activities of these synthases for flavonol and anthocyanidin formation in the model plant A. thaliana. The impact of their modification on the biosynthetic pathway and the pattern of flavonoids in different plant tissues are discussed.

Developmental, genetic and environmental factors affect the expression of flavonoid genes, enzymes and metabolites in strawberry fruits

The influence of internal (genetic and developmental) and external (environmental) factors on levels of flavonoid gene transcripts, enzyme activity and metabolites was studied in fruit of six cultivated strawberry (Fragaria x ananassa Duch.) genotypes grown at two Italian locations. Gene expression and enzyme activity showed development- and genotype-associated patterns, revealing gene coordination. Analysis clarified the regulation mechanism of the hydroxylation status of the B-ring of the major flavonoid pools and pointed out examples of genotype-specific post-transcriptional regulation mechanisms and key steps of pathway regulation in strawberry fruits. Metabolite profiles were strongly affected by development and genotype. Flavan-3-ols, their proanthocyanidin (PA) derivatives and anthocyanins were the most abundant metabolites. Flavonol levels and PA-associated traits (epicatechin/catechin ratio and mean degree of polymerization) showed significant environmental effects. Multivariate and correlation analyses determined the relationships among genes, enzymes and metabolites. The combined molecular and biochemical information elucidated more in depth the role of genetic and environmental factors on flavonoid metabolism during strawberry fruit development, highlighting the major impact of developmental processes, and revealing genotype-dependent differences and environmental effects on PA-related traits.

Arabidopsis thaliana expresses a second functional flavonol synthase

Arabidopsis thaliana L. produces flavonoid pigments, i.e. flavonols, anthocyanidins and proanthocyanidins, from dihydroflavonol substrates. A small family of putative flavonol synthase (FLS) genes had been recognized in Arabidopsis, and functional activity was attributed only to FLS1. Nevertheless, other FLS activities must be present, because A. thalianafls1 mutants still accumulate significant amounts of flavonols. The recombinant FLSs and leucoanthocyanidin dioxygenase (LDOX) proteins were therefore examined for their enzyme activities, which led to the identification of FLS3 as a second active FLS. This enzyme is therefore likely responsible for the formation of flavonols in the ldox/fls1-2 double mutant. These double mutant and biochemical data demonstrate for the first time that LDOX is capable of catalyzing the in planta formation of flavonols.

Characterization of major enzymes and genes involved in flavonoid and proanthocyanidin biosynthesis during fruit development in strawberry (Fragaria ×ananassa)

The biosynthesis of flavonoids and proanthocyanidins was studied in cultivated strawberry (Fragaria xananassa) by combining biochemical and molecular approaches. Chemical analyses showed that ripe strawberries accumulate high amounts of pelargonidin-derived anthocyanins, and a larger pool of 3',4'-hydroxylated proanthocyanidins. Activities and properties of major recombinant enzymes were demonstrated by means of in vitro assays, with special emphasis on specificity for the biologically relevant 4'- and 3',4'-hydroxylated compounds. Only leucoanthocyanidin reductase showed a strict specificity for the 3',4'-hydroxylated leucocyanidin, while other enzymes accepted either hydroxylated substrate with different relative activity rates. The structure of late flavonoid pathway genes, leading to the synthesis of major compounds in ripe fruits, was elucidated. Complex developmental and spatial expression patterns were shown for phenylpropanoid and flavonoid genes in fruits throughout ripening as well as in leaves, petals and roots. Presented results elucidate key steps in the biosynthesis of strawberry flavonoid end products.

Reinforcement effect of adhesively luted fiber reinforced composite versus titanium posts

OBJECTIVE

The aim of the present study was to investigate the influence of the rigidity of different post materials (titanium versus glass fiber reinforced composite [FRC]) on the fracture resistance of endodontically treated teeth (ETT).

METHOD

Forty-eight caries-free maxillary central incisors were randomly assigned to six groups (n=8). After endodontic treatment, teeth of four groups were flattened 2mm above and two groups at the cemento-enamel junction (CEJ). As control, specimens of one group received neither composite build-up nor post, and teeth were left empty (E). In another group only a resin composite build-up was placed (C). In two groups, both titanium and FRC posts were inserted. One group with titanium (2/T) and FRC (2/FRC) post received a 2mm deep ferrule preparation. For one group with titanium (0/T) and FRC (0/FRC) post no ferrule design was provided. All-ceramic crowns were adhesively luted on all specimens. Specimens were exposed to thermomechanical loading and finally statically loaded until failure.

RESULTS

The median fracture load values (min-max) were: E=317 (242-404); C=387 (335-475); 0/FRC=352 (0-440); 2/FRC=502 (326-561); 0/T=420 (0-548), 2/T=517 (416-653). Statistically significant differences were computed between E, C, 2/FRC, 0/T and 2/T; between C, 2/FRC and 2/T; between 0/FRC, 2/FRC and 2/T; between 0/T and 2/T regarding maximum fracture load.

SIGNIFICANCE

Fracture resistance of ETT is not influenced by the rigidity of the post material. The combination of ferrule preparation and endodontic post results in higher load resistance after TML than any other build-up design.

The effect of alveolar bone loss on the load capability of restored endodontically treated teeth: A comparative in vitro study

OBJECTIVES

The aim of the present investigation was to study the influence of a reduced bone support on the fracture resistance of endodontically treated teeth restored with glass fibre-reinforced posts (FRC).

METHODS

30 caries-free maxillary central incisors were divided into 3 groups (n=10). Endodontic treatment was performed. Teeth were flattened 2 mm above the cemento-enamel junction. Group I (control) simulated a clinical situation without horizontal bone loss. In group II a horizontal bone loss of 25% and in group III of 50% was simulated. All specimens received FRC posts and composite core restorations. All-ceramic crowns were adhesively cemented. Specimens were exposed to thermal cycling and mechanical loading (TCML) and finally statically loaded until failure in a universal testing machine (v=1 mm/min). Non-parametric tests were used to compare median fracture loads between groups. Fracture modes were compared using Fisher's exact test.

RESULTS

The median fracture load values (min/max) in [N] were: group I=501 (326/561), group II=422 (323/495); group III=352 (266/406), p=0.004. Two specimens in each group II and III failed during TCML. Statistical analysis revealed statistically significant differences between all test groups regarding maximum fracture load and mode of fracture.

CONCLUSIONS

The fracture resistance of endodontically treated teeth restored adhesively with a FRC post, composite core, and all-ceramic crown is dependent on the level of surrounding supporting periodontal bone. Loss of alveolar bone loss due to periodontal disease may lead to an increased risk of failure.

Load Capability of Excessively Flared Teeth Restored with Fiber-reinforced Composite Posts and All-ceramic Crowns

The fracture resistance of excessively flared endodontically-treated teeth (ETT) without ferrule preparation is not acceptable. Adhesively luted FRC posts with 2 mm ferrule are recommended.

Effect of incomplete crown ferrules on load capacity of endodontically treated maxillary incisors restored with fiber posts, composite build-ups, and all-ceramic crowns: an in vitro evaluation after chewing simulation

OBJECTIVE

The aim of this study was to compare the fracture resistance of endodontically treated maxillary central incisors with incomplete crown ferrules after chewing simulation.

MATERIAL AND METHODS

Forty caries-free maxillary central incisors were divided into 4 groups (n = 10). Endodontic treatment was performed. Teeth were decoronated 2 mm above the cemento-enamel junction (CEJ). Group I (control) provided a 360 degrees circumferential 2-mm ferrule. In group II, a 2-mm ferrule was present on the palatal aspect (status after occlusal overload), and in group III on the facial aspect (status after traumatic injury). In group IV, the ferrule was interrupted by bi-proximal cavitations (simulating caries treatment). The teeth received glass fiber reinforced posts and composite core restorations. All-ceramic crowns were adhesively cemented. Specimens were simultaneously exposed to thermal cycling and mechanical loading (1.2 million cycles; 6,000 cycles 5 degrees/55 degrees C) and finally statically loaded until failure in a universal testing machine (crosshead speed = 1 mm/min). For statistical analysis, the Kruskal-Wallis test was applied followed by the Mann-Whitney U-test as post hoc testing.

RESULTS

The median fracture load values (min./max.) were: group I = 502 (326/561), group II = 658 (280/827), group III = 899 (396/1176), and group IV = 360 (279/646). Analysis revealed statistically significant differences between test groups, except between groups I and IV and groups II and IV.

CONCLUSIONS

The fracture resistance of endodontically and post/core restored teeth is dependent on the degree of tooth conservation. An incomplete crown ferrule is associated with greater variation in load capacity and, despite high fracture values, inclines to fracture.

Hydride-Meisenheimer complex formation and protonation as key reactions of 2,4,6-trinitrophenol biodegradation by Rhodococcus erythropolis

Biodegradation of 2,4,6-trinitrophenol (picric acid) by Rhodococcus erythropolis HLPM-1 proceeds via initial hydrogenation of the aromatic ring system. Here we present evidence for the formation of a hydride-Meisenheimer complex (anionic sigma-complex) of picric acid and its protonated form under physiological conditions. These complexes are key intermediates of denitration and productive microbial degradation of picric acid. For comparative spectroscopic identification of the hydride complex, it was necessary to synthesize this complex for the first time. Spectroscopic data revealed the initial addition of a hydride ion at position 3 of picric acid. This hydride complex readily picks up a proton at position 2, thus forming a reactive species for the elimination of nitrite. Cell extracts of R. erythropolis HLPM-1 transform the chemically synthesized hydride complex into 2,4-dinitrophenol. Picric acid is used as the sole carbon, nitrogen, and energy source by R. erythropolis HLPM-1.

[Waiting times and death on the waiting list for coronary artery bypass operation. Experiences in Munich with over 1,000 patients]

Short-term and long-term results are the classical parameters for quality assurance in coronary artery bypass graft surgery (CABGS). In contrast, waiting times and the inherent risks of waiting lists are usually neglected. Although the problem of "death on the waiting list" is generally known, related publications are scarce. Therefore, in January 1994, we started a prospective study to document the waiting times and the occurrence of severe complications in our patients waiting for CABGS. Between January 1, 1994 and July 31, 1996, we catheterized 1125 patients with indication for CABGS. 968 patients had social health insurance (SOCL); 157 patients were privately insured (PRIV). The urgency of CABGS was classified as "emergent", "ery urgent" and "less urgent" according to the clinical experience of the responsible cardiologists. All emergency cases could be operated the same day. 69% of the very urgent SOCL patients had to travel beyond the Munich area to be operated, while 84% of the respective PRIV patients were operated in Munich. SOCL patients were therefore separated from their families 4.3 times more frequently then PRIV. Not so urgent SOCL cases were separated from their families 1.8 times more often than PRIV. The mean waiting time for SOCL was 39.5 +/- 39.1 days in 1994, 34.9 +/- 31.5 days in 1995 and 22.7 +/- 16 days in 1996. The corresponding values of PRIV are 19.1 +/- 16.2, 19.8 +/- 14.1 and 17.2 +/- 12.6 days. The risk of dying while waiting for CABGS was 1.3% per month (15/1125). The reduction of waiting times by the factor of two between 1994 and 1996 did not, however, influence the death on the waiting list, because all deaths occurred within 4 weeks after diagnostic catheterization. Our results show that triage practices for patients requiring CABGS are not reliable. To minimize the risk of the "death on the waiting list", CABGS must be offered within a week after diagnostic coronary angiography, even for "elective" cases.

Marker pattern instabilities as a major cause of reproducibility problems in two-dimensional DNA fingerprinting

Two-dimensional (2-D) DNA fingerprinting is a promising technique for multilocus analysis of eukaryotic genomes. It has been successfully applied to the detection of DNA variation in tumors, to linkage analyses and to genomic comparisons of inbred mouse strains. However, there are still problems with inter-gel comparisons of 2-D DNA typing patterns as documented by the inter-gel reproducibility rates reported in the literature, which range from 84 to 98%. The basis for standardization in almost all of these studies has been a set of lambda fragments (digested separately with the restriction enzymes HaeIII, RsaI, Bg/I) that produces a spot pattern scattered across the gel. These spots are used as markers for gel comparisons. Since we noticed considerable variations in the marker spot patterns, we evaluated the properties of the lambda marker using both computer simulation and an empirical analysis of forty independent consecutive gels from our laboratory. We explain the instabilities of the spot pattern on the basis of the melting properties of the individual lambda fragments. A subset of spots is presented that has been stable in all our experiments. Only this set of spots should be used for gel standardization purposes until a new, completely reproducible marker becomes available. Finally, suggestions for an improved marker system are made.

The kinetic of the oxidation of InSn48

The oxidation of InSn48 has been investigated at partial pressures between 10(-8) Pa and 10(+4) Pa over a temperature range from 22 ( degrees )C to 250 ( degrees )C with different analytical methods. The oxide film contains a mixture of several oxides, although indium oxide forms preferentially. Below the melting point a logarithmic growth, and above this, a parabolic growth of the oxide film has been observed. The oxide film formed in air at 250 ( degrees )C does not become thicker than 50 nm in the first 5 min of oxidation.

In vitro neuronal production and differentiation by precursor cells derived from the adult human forebrain

It has traditionally been held that the adult brain is incapable of significant self-repair, due in part to its inability to generate new neurons. Nevertheless, rodents and birds have been found to harbor neural precursor cells in adulthood. We asked whether the adult human brain might retain such precursors, by culturing samples of temporal lobe under conditions permissive for neuronal differentiation, while exposed to 3H-thymidine. Adult human temporal lobe cultures, derived from cortex, subcortex, and periventricular subependymal zone (SZ), were incubated for 7-28 d, stained for neuronal and glial antigens, and autoradiographed. Neuron-like cells were found in explant outgrowths and monolayer dissociates of SZ and periventricular white matter, but not cortex; they expressed neuronal antigens including MAP-2, MAP-5, NF, and N-CAM, and were GFAP-. Neurons responded to K+ depolarization with rapid and reversible increases in intracellular Ca2+, with much greater increments than those noted in glia. Although most neurons were not 3H-thymidine labeled, a small number of MAP-2+ and MAP-5+/GFAP- cells did incorporate 3H-thymidine, suggesting neuronal production from precursor mitosis. Rare 3H-thymidine+ neurons were also found in cultures of subventricular white matter; in these, GFAP+ astrocytic mitogenesis was common, while O4+ oligodendrocytes, although the predominant cell type, were largely postmitotic. Thus, the adult human forebrain harbors precursor cells that retain the potential for neuronal production and differentiation in vitro.

Glutamine transaminase K and omega-amidase activities in primary cultures of astrocytes and neurons and in embryonic chick forebrain: marked induction of brain glutamine transaminase K at time of hatching

Glutamine transaminase K and omega-amidase activities are present in the chick brain and in the brains of adult mice, rats, and humans. However, the activity of glutamine transaminase K in adult mouse brain is relatively low. In the chick embryo, cerebral glutamine transaminase K activity is low between embryonic days 5 and 17, but by day 23 (day of hatching) activity rises dramatically (> 15-fold). Cerebral omega-amidase activity is relatively high at embryonic day 5 but lower between days 5 and 17; at embryonic day 23 the activity rises to a maximum. Both glutamine transaminase K and omega-amidase are present in cultured chick, rat, and mouse astrocytes and neurons. For each species, the activity of glutamine transaminase K is higher in the astrocytes than in the neurons. The activity of omega-amidase is about the same in the cultured chick astrocytes and neurons but significantly higher in rat astrocytes than in rat neurons. The data suggest that the rise in brain glutamine transaminase K activity in the chick embryo at hatching correlates with maturation of astrocytes. Glutamine transaminase K may be involved in glutamine cycling in astrocytes. Glutamine transaminase K appears to be a major cysteine S-conjugate beta-lyase of the brain and may play a role in the neurotoxicity associated with exposure to dichloroacetylene and perhaps to other toxins.

Glutamine transaminase K and omega-amidase activities in primary cultures of astrocytes and neurons and in embryonic chick forebrain: marked induction of brain glutamine transaminase K at time of hatching

Glutamine transaminase K and omega-amidase activities are present in the chick brain and in the brains of adult mice, rats, and humans. However, the activity of glutamine transaminase K in adult mouse brain is relatively low. In the chick embryo, cerebral glutamine transaminase K activity is low between embryonic days 5 and 17, but by day 23 (day of hatching) activity rises dramatically (> 15-fold). Cerebral omega-amidase activity is relatively high at embryonic day 5 but lower between days 5 and 17; at embryonic day 23 the activity rises to a maximum. Both glutamine transaminase K and omega-amidase are present in cultured chick, rat, and mouse astrocytes and neurons. For each species, the activity of glutamine transaminase K is higher in the astrocytes than in the neurons. The activity of omega-amidase is about the same in the cultured chick astrocytes and neurons but significantly higher in rat astrocytes than in rat neurons. The data suggest that the rise in brain glutamine transaminase K activity in the chick embryo at hatching correlates with maturation of astrocytes. Glutamine transaminase K may be involved in glutamine cycling in astrocytes. Glutamine transaminase K appears to be a major cysteine S-conjugate beta-lyase of the brain and may play a role in the neurotoxicity associated with exposure to dichloroacetylene and perhaps to other toxins.

Vitamin E, ascorbate, glutathione, glutathione disulfide, and enzymes of glutathione metabolism in cultures of chick astrocytes and neurons: evidence that astrocytes play an important role in antioxidative processes in the brain

GSH, GSSG, vitamin E, and ascorbate were measured in 14-day cultures of chick astrocytes and neurons and compared with levels in the forebrains of chick embryos of comparable age. Activities of enzymes involved in GSH metabolism were also measured. These included gamma-glutamylcysteine synthetase, GSH synthetase, gamma-glutamyl cyclotransferase, gamma-glutamyltranspeptidase, glutathione transferase (GST), GSH peroxidase, and GSSG reductase. The concentration of lipid-soluble vitamin E in the cultured neurons was found to be comparable with that in the forebrain. On the other hand, the concentration of vitamin E in the astrocytes was significantly greater in the cultured astrocytes than in the neurons, suggesting that the astrocytes are able to accumulate exogenous vitamin E more extensively than neurons. The concentrations of major fatty acids were higher in the cell membranes of cultured neurons than those in the astrocytes. Ascorbate was not detected in cultured cells although the chick forebrains contained appreciable levels of this antioxidant. GSH, total glutathione (i.e., GSH and GSSG), and GST activity were much higher in cultured astrocytes than in neurons. gamma-Glutamylcysteine synthetase activity was higher in the cultured astrocytes than in the cultured neurons. GSH reductase and GSH peroxidase activities were roughly comparable in cultured astrocytes and neurons. The high levels of GSH and GST in cultured astrocytes appears to reflect the situation in vivo. The data suggest that astrocytes are resistant to reactive oxygen species (and potentially toxic xenobiotics) and may play a protective role in the brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobic transformation of 2,4,6-trinitrotoluene (TNT)

A sulfate-reducing bacterium using trinitrotoluene (TNT) as the sole nitrogen source was isolated with pyruvate and sulfate as the energy sources. The organism was able to reduce TNT to triaminotoluene (TAT) in growing cultures and cell suspensions and to further transform TAT to still unknown products. Pyruvate, H2, or carbon monoxide served as the electron donors for the reduction of TNT. The limiting step in TNT conversion to TAT was the reduction of 2,4-diamino-6-nitrotoluene (2,4-DANT) to triaminotoluene. The reduction proceeded via 2,4-diamino-6-hydroxylaminotoluene (DAHAT) as an intermediate. The intermediary formation of DAHAT was only observed in the presence of carbon monoxide or hydroxylamine, respectively. The reduction of DAHAT to triaminotoluene was inhibited by both CO and NH2OH. The inhibitors as well as DANT and DAHAT significantly inhibited sulfide formation from sulfite. The data were taken as evidence for the involvement of dissimilatory sulfite reductase in the reduction of DANT and/or DAHAT to triaminotoluene. Hydrogenase purified from Clostridium pasteurianum and carbon monoxide dehydrogenase partially purified from Clostridium thermoaceticum also catalyzed the reduction of DANT in the presence of methyl viologen or ferredoxin, however, as the main reduction product DAHAT rather than triaminotoluene was formed. The findings could explain the function of CO as an electron donor for the DANT reduction (to DAHAT) and the concomitant inhibitory effect of CO on triaminotoluene formation (from DAHAT) by the inhibition of sulfite reductase.(ABSTRACT TRUNCATED AT 250 WORDS)

Processing of amplitude modulated sounds in the medial geniculate body of squirrel monkeys

The responses of single and multi units in the medial geniculate body of the squirrel monkey (Saimiri sciureus) to modulation frequency, modulation depth and changes in absolute intensity of sinusoidally amplitude modulated (AM) sounds were studied. Both spike-frequency and spike rate modulation were used as a measure for neuronal response. Spike rate modulation was derived from FFT (Fast-Fourier-Transformation) analysis of the PSTHs. In all cases (N = 133) spike rate modulation was shown to be dependent on the stimulus modulation frequency: Most neurons responded best to one modulation frequency, i.e., they showed a modulation transfer function with bandpass characteristic; only a few displayed a low pass or multiple peaked transfer characteristic. The majority of the neurons responded best in a range from 4 to 64 Hz, with a peak at 32 Hz and a median at 16 Hz. Such modulation frequencies are common in parts of the species vocal repertoire.

Corticostriatal cells in comparison with pyramidal tract neurons: contrasting properties in the behaving monkey

Antidromically identified neurons projecting to the putamen (CPNs) and pyramidal tract neurons (PTNs) were recorded from motor and premotor cortex of a monkey which performed a load-bearing task with the wrist. CPNs appeared as a uniform population with very slowly conducting axons and low spontaneous activity. In contrast to PTNs, they exhibited weak, mostly insignificant correlation with graded steady-state forces, responded to torque perturbations with remarkably long latency, and seemed to discharge much later with active movement. Collateral branching of PTNs to the putamen was found to be infrequent (1%). We suggest that the putamen receives a cortical message that is strikingly different from that sent down the pyramidal tract.