Electron microscopic evidence for the thick filament interconnections associated with the catch state in the anterior byssal retractor muscle of Mytilus edulis

The anterior byssal retractor muscle (ABRM) of a bivalve mollusc Mytilus edulis is known to exhibit catch state, i.e. a prolonged tonic contraction maintained with very little energy expenditure. Two different hypotheses have been put forward concerning the catch state; one assumes actin-myosin linkages between the thick and thin filaments that dissociate extremely slowly (linkage hypothesis), while the other postulates a load-bearing structure other than actin-myosin linkages (parallel hypothesis). We explored the possible load-bearing structure responsible for the catch state by examining the arrangement of the thick and thin filaments within the ABRM fibers, using techniques of quick freezing and freeze substitution. No thick filament aggregation was observed in the cross-section of the fibers quickly frozen not only in the relaxed and actively contracting states but also in the catch state. The thick filaments were, however, occasionally interconnected with each other either directly or by distinct projections in all the three states studied. The proportion of the interconnected thick filaments relative to the total thick filaments in a given cross-sectional area was much larger in the catch state than in the relaxed and actively contracting states, providing evidence that the thick filament interconnection is responsible for the catch state.     

Androgen-dependent atypical fibromas spontaneously arising in the skin of Djungarian hamsters (Phodopus sungorus)

Spontaneous atypical fibromas that arose in the thoracoabdominal skin of one aged female and 31 aged male Djungarian hamsters (Phodopus sungorus) were examined histologically, immunohistochemically, and ultrastructurally. The normal skin from both sexes obtained at various intervals until the age of 12 months was examined, as were the tumors. These tumors were composed of ganglion cell-like (GL) cells that had one or two ovoid nuclei, basophilic foamy cytoplasm, and various amount of collagen fibers between the cells. The tumor cells had positive reaction to vimentin and androgen receptor (AR); the stromal collagen fibers reacted positively with the antibody against collagen type I or III. Ultrastructurally, the tumor cells had abundant rough endoplasmic reticulum in the cytoplasm. On the other hand, small nests of the cells mimicking tumor GL cells were present in the dermal layer to the panniculus of the normal thoracoabdominal skin of adult males, but were seldom found in adult females. The morphologic and immunohistochemical features of these tumor GL cells were basically similar to those of normal skin GL cells, although the former had a certain degree of atypia. These results suggest that atypical skin fibroma in the Djungarian hamster is an androgen-dependent tumor and originates from skin GL cells.     

Plasma orexin-A-like immunoreactivity in patients with sleep apnea hypopnea syndrome

Orexin-A (hypocretin-1), a neuropeptide produced in hypothalamus, stimulates arousal. We studied plasma concentrations of orexin-A-like immunoreactivity (orexin-A-LI) in 156 patients with sleep apnea hypopnea syndrome (SAHS) and 22 control subjects. Plasma orexin-A-LI levels were significantly decreased in 156 patients with SAHS (4.4+/-0.15 pmol/l, mean+/-S.E.) as compared with controls (5.3+/-0.45 pmol/l). The levels were decreased in parallel with the severity of sleep-related respiratory disturbance and magnitude of sleep fragmentation. These findings raise the possibility that a low plasma level of orexin-A-LI may be a marker to show the severity of the disease in patients with SAHS.     

Inhibition of recombinant dipeptidyl peptidase III by synthetic hemorphin-like peptides

In order to find the most effective antagonist for dipeptidyl peptidase III degrading enkephalin, we synthesized hemorphin-like pentapeptides with aliphatic or aromatic amino acids at the N-termini, such as VVYPW, LVYPW, IVYPW, YVYPW, FVYPW and WVYPW. Among those pentapeptides, IVYPW and WVYPW showed the strongest inhibitory activity toward rDPP III. The K(i) values of IVYPW and WVYPW were 0.100+/-0.011 and 0.126+/-0.015 microM (mean+/-S.E.), respectively. The order of K(i) values was Ile> or =Trp>Phe> or =Tyr>Leu>Ala>Val>Ser>Gly. rDPP III activity is inhibited in a non-competitive manner by these peptides. The peptide VYPW did not inhibit rDPP III activity, but the sequence is essential for the expression of inhibitory activity.     

The crucial role of caspase-9 in the disease progression of a transgenic ALS mouse model

Mutant copper/zinc superoxide dismutase (SOD1)-overexpressing transgenic mice, a mouse model for familial amyotrophic lateral sclerosis (ALS), provides an excellent resource for developing novel therapies for ALS. Several observations suggest that mitochondria-dependent apoptotic signaling, including caspase-9 activation, may play an important role in mutant SOD1-related neurodegeneration. To elucidate the role of caspase-9 in ALS, we examined the effects of an inhibitor of X chromosome-linked inhibitor of apoptosis (XIAP), a mammalian inhibitor of caspase-3, -7 and -9, and p35, a baculoviral broad caspase inhibitor that does not inhibit caspase-9. When expressed in spinal motor neurons of mutant SOD1 mice using transgenic techniques, XIAP attenuated disease progression without delaying onset. In contrast, p35 delayed onset without slowing disease progression. Moreover, caspase-9 was activated in spinal motor neurons of human ALS subjects. These data strongly suggest that caspase-9 plays a crucial role in disease progression of ALS and constitutes a promising therapeutic target.     

Nested PCR for detection of mutans streptococci in dental plaque

AIMS: Mutans streptococci such as Streptococcus mutans and Streptococcus sobrinus have been implicated in human dental caries. In an attempt to develop a rapid and sensitive method for detecting Strep. mutans and Strep. sobrinus in dental plaque, a nested PCR amplification based on the 16S rRNA gene was employed. METHODS AND RESULTS: A universal set of PCR primers for bacterial 16S rRNA gene was introduced for the first PCR, and then two sets of primers specific for the 16S rRNA gene sequences of either Strep. mutans or Strep. sobrinus were used for the second PCR. Eighteen plaque samples were analyzed, and a nested PCR was shown to be more sensitive for detecting Strep. mutans and Strep. sobrinus than direct PCR. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The 16S rRNA gene-based nested PCR method is a rapid and sensitive method for the detection of mutans streptococci, and may also be suitable for carrying out large-scale studies on the cariogenicity of mutans streptococci.     

A missense mutation (GGC[435Gly]-->AGC[Ser]) in exon 8 of the CYP11B2 gene inherited in Japanese patients with congenital hypoaldosteronism

OBJECTIVES: To clarify the underlying molecular mechanism of corticosterone methyl oxidase type II (CMO II) deficiency, Japanese patients newly diagnosed with CMO II deficiency were investigated. METHODS: We analyzed the patients' genomic DNA sequence on all 9 exons of the CYP11B2 gene. In addition, restriction fragment length polymorphism (RFLP) analysis and expression studies were performed. RESULTS: The analysis showed that the patients homozygously retained a missense mutation, Gumacr;GC[435Gly]-->Aumacr;GC[Ser], in the CYP11B2 gene. Expression studies indicated that the steroid 18-hydroxylase/oxidase activities of the mutant enzyme were substantially reduced. CONCLUSION: These results support the hypothesis that this mutation causes CMO II deficiency in the patients, and are in accordance with our theory that the partial loss of P-450(C18) activities causes CMO II deficiency.