Crystalline and disordered state of poly(dihexylsilylene) copolymers

A systematic comparison of random copolymers, derived from poly(dihexylsilylene) (PDHS) by incorporation of monomeric units with shorter unbranched alkyl side chains, has been carried out based on calorimetry, variable temperature UV spectroscopy, and ²⁹Si MAS (magic angle spinning) solid state NMR investigations. Also, hexylmethylsilylene units and branched monomers have been copolymerized. Up to 10% comonomer with shorter linear side chains (i. e., pentyl to propyl) could be incorporated into PDHS without impeding the all-trans order of the crystalline phase. In this case, the UV absorption maximum of the crystalline low-temperature phase was affected only slightly according to the length and fraction of the comonomer side chains. A less ordered crystal structure (λ_max = 345–355 nm) was observed when the content of comonomers with shorter side chains was about 20%. Yet, all these materials form conformationally disordered mesophases. A clear disordering transition and corresponding thermochromism was not observed any more when 50% of propyl side chains were incorporated. The order of the crystalline and the mesophase is also strongly perturbed if only a small fraction (4%) of the side chains are branched at C².     

Characterization of PaxA and its operon: a cohemolytic RTX toxin determinant from pathogenic Pasteurella aerogenes

Pasteurella aerogenes is known as a commensal bacterium or as an opportunistic pathogen, as well as a primary pathogen found to be involved in abortion cases of humans, swine, and other mammals. Using broad-range DNA probes for bacterial RTX toxin genes, we cloned and subsequently sequenced a new operon named paxCABD encoding the RTX toxin PaxA in P. aerogenes. The pax operon is organized analogous to the classical RTX operons containing the activator gene paxC upstream of the structural toxin gene paxA, which is followed by the secretion protein genes paxB and paxD. The highest sequence similarity of paxA with known RTX toxin genes is found with apxIIIA (82%). PaxA is structurally similar to ApxIIIA and also shows functional analogy to ApxIIIA, since it shows cohemolytic activity with the sphingomyelinase of Staphylococcus aureus, known as the CAMP effect, but is devoid of direct hemolytic activity. In addition, it shows to some extent immunological cross-reactions with ApxIIIA. P. aerogenes isolated from various specimens showed that the pax operon was present in about one-third of the strains. All of the pax-positive strains were specifically related to swine abortion cases or septicemia of newborn piglets. These strains were also shown to produce the PaxA toxin as determined by the CAMP phenomenon, whereas none of the pax-negative strains did. This indicated that the PaxA toxin is involved in the pathogenic potential of P. aerogenes. The examined P. aerogenes isolates were phylogenetically analyzed by 16S rRNA gene (rrs) sequencing in order to confirm their species. Only a small heterogeneity (<0.5%) was observed between the rrs genes of the strains originating from geographically distant farms and isolated at different times.     

Detection of DNA damage after hyperbaric oxygen (HBO) therapy

Hyperbaric oxygen HBO therapy is successfully used for the treatmentof a variety of conditions. However, exposure to high concentrationsof oxygen is known to induce damage to cells, possibly due toan increased oxygen radical production. As reactive oxygen speciesalso cause DNA damage, we investigated the DNA-damaging effectof HBO with the alkaline version of the single cell gel testcomet assay. Oxidative DNA base modifications were determinedby converting oxidized DNA bases to strand breaks using bacterialformamidopyrimidine-DNA glycosylase FPG, a DNA repair enzyme,which specifically nicks DNA at sites of 8-oxo-guanines andformamidopyrimidines. HBO treatment under therapeutic conditionsclearly and reproducibly induced DNA damage in leukocytes ofall test subjects investigated. Increased DNA damage was foundimmediately at the end of the treatment, while 24 h later, noeffect was found. Using FPG protein we detected significantoxidative base damage after HBO treatment DNA damage was detectedonly after the first treatment and not after further treatmentsunder the same conditions, indicating an increase in antioxidantdefences. DNA damage did not occur when the HBO treatment wasstarted with a reduced treatment time which was then increasedstepwise. ³To whom correspondence should be addressed     

Differentiation of Cucumber mosaic virus isolates by hybridization to oligonucleotides in a microarray format

A system for microarrays was developed to detect and differentiate Cucumber mosaic virus (CMV) serogroups and subgroups. The coat protein genes of 14 different isolates were amplified using cy3-labelled generic but species-specific primers. These amplicons were hybridized against a set of five different serotype and subgroup specific 24-mer oligonucleotides bound to an aldehyde-coated glass slide via an aminolinker. The results of the hybridization revealed that the method allowed a clear differentiation of the 14 different CMV isolates into the serogroupes 1 and 2, and in addition was able to assign 9 out of 10 different serogroup 1 isolates correctly into subgroups 1a and 1b. This differentiation was not possible by RFLP analysis with the restriction enzyme MspI. The use of amplicons larger than 700 base pairs and their successful differentiation by hybridization to specific oligonucleotides opens avenues to highly parallel, yet sensitive assays for plant viruses.     

Lysine and collagen

The amount of lysine in collagen is only 3 or 4% of total aminoacids, but it has an important function in the constitution of the cross-links between the molecules to built the fibrils and the fibers of collagen. For this function, some lysine molecules must be hydroxylated and other oxidized to aldehyde compounds. Some deficits in these metabolic pathways are responsible for heritable diseases of the connectivite tissue as types IV and IX of the Ehlers-Danlos syndrome, lathyrism, the Menkes kinky hair syndrome, Cutis-Laxa or the type II of osteogenesis imperfecta. The contribution to fibrosis is also discussed.     

The amygdala is part of the behavioural reinforcement system modulating long-term potentiation in rat hippocampus

Long-term potentiation (LTP) in the dentate gyrus can be modulated and prolonged by emotional/motivational influences when concurrently activated. A similar effect on LTP can be obtained by stimulating the amygdala, suggesting that this limbic structure might be part of the neural system involved in behavioural reinforcement. To confirm this we have performed a series of experiments in which the basolateral amygdala was either temporary inactivated by injection of lidocaine or permanently lesioned electrolytically. Both manipulations completely blocked the reinforcing effect of a motivational stimulus (drinking after 24-h deprivation) on LTP at the perforant pathway-dentate gyrus synapses, whilst leaving intact the non-reinforced potentiation. These results demonstrate that the basolateral amygdala is a key structure within the system involved in the modulatory interaction between the affective status of the animal and the mechanisms of functional plasticity.     

THE ROLE OF RAPID SLIDE CULTURE IN THE DIAGNOSIS AND MANAGEMENT OF PULMONARY TUBERCULOSIS

Rapid slide culture method using human blood medium was utilized for the primary culture of Mycobacterium tuberculosis and the results obtained were compared with results of smear examination of sputum specimens from fresh cases of pulmonary tuberculosis. Smear and rapid slide culture results of a total of 320 patients were analyzed. Slide culture was positive in 104 cases whereas smears were positive in 90 cases. Early culture confirmation in 7 days coupled with positivity better than smear examination, makes rapid slide culture a better method for diagnosis.KEY WORDS: Mycobacterium tuberculosis, Rapid slide culture, Bacteriological techniques, Colony count microbial     

(+)-alpha-[11C]Dihydrotetrabenazine PET imaging in familial paroxysmal dystonic choreoathetosis

Clinical observations suggest a disturbance of striatal dopaminergic function in familial paroxysmal dystonic choreoathetosis (PDC). The authors used PET with [11C]dihydrotetrabenazine (DTBZ) to study striatal dopaminergic innervation in PDC. The results did not reveal abnormal DTBZ binding potential in PDC striatum. This suggests that dopaminergic abnormalities, if present, may be due to altered regulation of dopamine release or to postsynaptic mechanisms, rather than to an altered density of nigrostriatal innervation.