Microbial diversity and complexity in hypersaline environments: A preliminary assessment

The microbial communities in solar salterns and a soda lake have been characterized using two techniques: BIOLOG, to estimate the metabolic potential, and amplicon length heterogeneity analysis, to estimate the molecular diversity of these communities. Both techniques demonstrated that the halophilic Bacteria and halophilic Archaea populations in the Eilat, Israel saltern are dynamic communities with extensive metabolic potentials and changing community structures. Halophilic Bacteria were detected in Mono Lake and the lower salinity ponds at the Shark Bay saltern in Western Australia, except when the crystallizer samples were stressed by exposure to Acid Green Dye #9899. At Shark Bay, halophilic Archaea were found only in the crystallizer samples. These data confirm both the metabolic diversity and the phylogenetic complexity of the microbial communities and assert the need to develop more versatile media for the cultivation of the diversity of bacteria in hypersaline environments. Journal of Industrial Microbiology & Biotechnology (2002) 28, 48–55 DOI: 10.1038/sj/jim/7000175 Received 20 May 2001/ Accepted in revised form 15 June 2001     

The influence of tertiary structural restraints on conformational transitions in superhelical DNA.

This paper examines theoretically the effects that restraints on the tertiary structure of a superhelical DNA domain exert on the energetics of linking and the onset of conformational transitions. The most important tertiary constraint arises from the nucleosomal winding of genomic DNA in vivo. Conformational transitions are shown to occur at equilibrium at less extreme superhelicities in DNA whose tertiary structure is restrained than in unrestrained molecules where the residual linking difference alpha res (that part of the superhelical deformation which is not absorbed by transitions) may be freely partitioned between twisting and bending. In the extreme case of a rigidly held tertiary structure, this analysis predicts that the B-Z transition will occur at roughly half the superhelix density needed to drive the same transition in solution, other factors remaining fixed. This suggests that superhelical transitions may occur at more moderate superhelical deformations in vivo than in solution. The influence on transition behavior of the tertiary structural restraints imposed by gel conditions also are discussed.     

Characterization of the Binding of N-Methyl-4-Phenylpyridine, the Toxic Metabolite of the Parkinsonian Neurotoxin N-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine, to Neuromelanin

N-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) selectively destroys neuronal cell bodies in the neuromelanin-containing substantia nigra of humans and primates. We show that N-methyl-4-phenylpyridine (MPP+), the active metabolite of MPTP, binds to neuromelanin with high affinity. This binding increases at higher pH and is displaced most potently by divalent cations and antimalarial drugs. MPP+ bound intracellularly to neuromelanin may be stored and released gradually, resulting in subsequent damage to neurons of the substantia nigra.     

A synopsis of the obligate and facultative insect parasitic nematodes

A study of the pathogenicity of a cytoplasmic polyhedrosis virus of the gypsy moth, Porthetria dispar, was conducted. Third- and fourth-instar larvae were highly susceptible to the pathogen even when fed low dosages of polyhedra. Only 30–50% of the treated insects died of polyhedrosis, but the debilitating effects of the virus on larval and postlarval stages were remarkable. Pupal weights were consistently reduced. An inverse and, respectively, a direct, relationship was found between the size of diseased specimens and the developmental periods of larvae and pupae surviving to lethal infection. The highest infected male adults showed a lighter wing coloration. Structural abnormalities and melanotic abdominal inclusions, recorded in diseased adults, were more frequent in females than in males. The presence of melanotic inclusions in diseased females obtained from early larval infection experiments was associated with a greater pupal weight. Lower dosages were the most effective in producing larval mortality and reducing pupal weights and adult emergence. An interference phenomenon due to a mixed virus infection is suspected.     

Heterogeneity of alkaline phosphatases in different HeLa lines

Alkaline phosphatase (ALP) components in 8 cell lines of HeLa were examined. Line to line heterogeneity in ALP expression was observed using the criteria of electrophoretic mobility before and after neuraminidase treatment, heat stability, L-phenylanine inhibition, and reactivity against antiplacental ALP antiserum. Six lines contained a placentallike ALP isozyme and varying amounts of a liverlike ALP isozyme. One line contained a liverlike ALP isozyme only. One line contained a new ALP form which was clearly distinguished from the placental, liver, bone, and intestinal ALPs. Thus, derepression of the placental ALP structural locus appeared to have occurred in 6 of the 8 lines. However, where expressed, the placentallike ALP varied electrophoretically from line to line, and in only one case was the mobility identical to that of a common placental ALP phenotype. This phenotypic heterogeneity of the "derepressed' placentallike ALP contrasts markedly with the phenotypic stability of other enzymes expressed in HeLa cells.     

Stretch-induced injury in organotypic hippocampal slice cultures reproduces in vivo post-traumatic neurodegeneration: role of glutamate receptors and voltage-dependent calcium channels

The relationship between an initial mechanical event causing brain tissue deformation and delayed neurodegeneration in vivo is complex because of the multiplicity of factors involved. We have used a simplified brain surrogate based on rat hippocampal slices grown on deformable silicone membranes to study stretch-induced traumatic brain injury. Traumatic injury was induced by stretching the culture substrate, and the biological response characterized after 4 days. Morphological abnormalities consistent with traumatic injury in humans were widely observed in injured cultures. Synaptic function was significantly reduced after a severe injury. The N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 attenuated neuronal damage, prevented loss of microtubule-associated protein 2 immunoreactivity and attenuated reduction of synaptic function. In contrast, the NMDA receptor antagonists 3-[(R)-2-carboxypiperazin-4-yl]-propyl-1-phosphonic acid (CPP) and GYKI53655, were neuroprotective in a moderate but not a severe injury paradigm. Nifedipine, an L-type voltage-dependent calcium channel antagonist was protective only after a moderate injury, whereas omega-conotoxin attenuated damage following severe injury. These results indicate that the mechanism of damage following stretch injury is complex and varies depending on the severity of the insult. In conclusion, the pharmacological, morphological and electrophysiological responses of organotypic hippocampal slice cultures to stretch injury were similar to those observed in vivo. Our model provides an alternative to animal testing for understanding the mechanisms of post-traumatic delayed cell death and could be used as a high-content screen to discover neuroprotective compounds before advancing to in vivo models.     

Differential expression of the capsaicin receptor TRPV1 and related novel receptors TRPV3, TRPV4 and TRPM8 in normal human tissues and changes in traumatic and diabetic neuropathy

Background  

Transient receptor potential (TRP) receptors expressed by primary sensory neurons mediate thermosensitivity, and may play a role in sensory pathophysiology. We previously reported that human dorsal root ganglion (DRG) sensory neurons co-expressed TRPV1 and TRPV3, and that these were increased in injured human DRG. Related receptors TRPV4, activated by warmth and eicosanoids, and TRPM8, activated by cool and menthol, have been characterised in pre-clinical models. However, the role of TRPs in common clinical sensory neuropathies needs to be established.     

Non-equilibrium structural dynamics of supercoiled DNA plasmids exhibits asymmetrical relaxation

Many cellular processes occur out of equilibrium. This includes site-specific unwinding in supercoiled DNA, which may play an important role in gene regulation. Here, we use the Convex Lens-induced Confinement (CLiC) single-molecule microscopy platform to study these processes with high-throughput and without artificial constraints on molecular structures or interactions. We use two model DNA plasmid systems, pFLIP-FUSE and pUC19, to study the dynamics of supercoiling-induced secondary structural transitions after perturbations away from equilibrium. We find that structural transitions can be slow, leading to long-lived structural states whose kinetics depend on the duration and direction of perturbation. Our findings highlight the importance of out-of-equilibrium studies when characterizing the complex structural dynamics of DNA and understanding the mechanisms of gene regulation.