Direct observation of hydrogen-bond exchange within a single water dimer.

The dynamics of water dimers was investigated at the single-molecule level by using a scanning tunneling microscope. The two molecules in a water dimer, bound on a Cu(110) surface at 6 K, were observed to exchange their roles as hydrogen-bond donor and acceptor via hydrogen-bond rearrangement. The interchange rate is approximately 60 times higher for (H2O)2 than for (D2O)2, suggesting that quantum tunneling is involved in the process. The interchange rate is enhanced upon excitation of the intermolecular mode that correlates with the reaction coordinate.

Infection of macaques with an R5-tropic SHIV bearing a chimeric envelope carrying subtype E V3 loop among subtype B framework.

To establish simian/human immunodeficiency virus (SHIV) clones bearing a chimeric envelope carrying subtype E V3 loop among subtype B envelope, four subtype E V3 sequences were substituted into SHIV(MD14), a SHIV clone bearing an envelope derived from a CXCR4 (X4)/CCR5 (R5)-dual tropic subtype B HIV-1 strain. SHIV-TH09V3, an only V3-chimera clone capable of replicating in human and macaque peripheral blood mononuclear cells (PBMCs), was propagated in pig-tailed macaque PBMCs and in cynomolgus macaque splenic mononuclear cells. The propagated virus stocks were intravenously inoculated into respective macaque species. SHIV-TH09V3 infected both macaque species as shown by plasma RNA viremia, isolated viruses from PBMCs and plasma, and antibody production against viral proteins. To assess how the substituted V3 sequence affected coreceptor usage, SHIV-TH09V3 stocks propagated in vitro and after isolation from macaques were verified for their corecepor usage by GHOST cells assay. SHIV-TH09V3 maintained R5-tropic phenotype both in vitro and after isolation from macaques, in contrast to the X4/R5-dual tropic SHIV(MD14). This indicates the substituted V3 sequence among the backbone of SHIV(MD14) governs coreceptor usage. Future study of infecting macaques with SHIV-TH09V3 and SHIV(MD14) will focus on differences of the outcome caused by the different V3 sequences in connection with coreceptor usage.

Decline in the HIV-1 isolation rate in Japan: a 12-year observation.

Since 1988, we have isolated HIV-1 from 614 HIV-1-infected persons (total sample=2,785) in Japan. During the past 12 years, we have found a decline in the HIV-1 isolation rate in Japan, with two identifiable turning points, 1991-1992 and 1996-1997. The two turning points correspond to shifts in anti-HIV-1 therapy. These findings suggest that HIV-1 in Japan is currently biologically well controlled, probably due to anti-HIV-1 therapy. On the other hand, this decline is inconsistent with the recent increase of genetic drug-resistant HIV-1 in Japan. Further studies are needed to clarify mechanisms that might explain the discrepancy.

A highly pathogenic simian/human immunodeficiency virus with genetic changes in cynomolgus monkey.

A highly pathogenic simian/human immunodeficiency virus (SHIV), designated C2/1, was obtained by serum passages in cynomolgus monkeys of p-SHIV, an SHIV strain that contains the env gene of pathogenic human immunodeficiency virus type 1 89.6. CD4+ lymphocyte depletion was induced within 1 week of the SHIV-C2/1 infection in peripheral blood as well as in various lymphoid organs in all the animals tested, with symptoms of diarrhoea and no increase in body weight, followed by intense viraemia. Serum antibody against Env protein was detected from 4 weeks after the virus infection, while the anti-Gag antibody response was absent in the SHIV-C2/1-infected animals. In contrast, both anti-Gag and anti-Env antibody responses were present in animals infected with p-SHIV or the non-pathogenic SHIV-MN. Sequencing of the env gene of isolates of SHIV-C strains showed conserved amino acid changes in the Env C2 and V3 regions that included changes to negatively charged amino acids, in the cytoplasmic region of gp41 that included a 42 amino acid deletion, and in the Nef protein. The pathogenic SHIV-C2/1-monkey model suggests that virus-specific pathogenicity in SHIV infection may be associated with the absence of anti-Gag antibody responses in animals and may be caused by genetic changes during serum passage in vivo.

Neoadjuvant chemotherapy followed by concurrent chemotherapy and radiotherapy for locally advanced esophageal carcinoma with bulky upper abdominal lymphadenopathy. Case report.

A 60-year old male patient who had locally advanced esophageal carcinoma with bulky upper abdominal lymphadenopathy underwent neoadjuvant chemotherapy consisting of 5-fluorouracil (5-FU) and cisplatin (CDDP), followed by concurrent radiotherapy and chemotherapy using protracted low-dose continuous infusion of 5-FU and CDDP. The treatment brought about complete remission in the primary lesion and good partial remission in the upper abdominal lymphadenopathy. He subsequently underwent trans-hiatal esophagectomy after one cycle of adjuvant chemotherapy because local recurrence was suspected. Histopathologic study of the resected specimen demonstrated no malignant tissue in the primary lesion and the lymph nodes. The patient is still alive and disease-free at 26+ months. This result suggests that neoadjuvant chemotherapy followed by concomitant chemotherapy and radiotherapy for patients who have locally advanced squamous cell carcinoma of the esophagus with intensive abdominal lymphadenopathy may offer some chance for sterilization of local and regional metastases and longer survival.

Cloning of a Drosophila melanogaster homologue of the mouse type-I bone morphogenetic proteins-2/-4 receptor: a potential decapentaplegic receptor.

The Drosophila melanogaster (Dm) decapentaplegic (dpp) gene product plays an essential role during several stages of Dm development. The DPP protein is a member of the transforming growth factor-beta (TGF-beta) superfamily and an orthologue of mammalian bone morphogenetic proteins (BMP-2 and -4). Recently, a cDNA clone encoding the mouse Ser/Thr kinase receptor specific for BMP-2/-4 (mTFR11) was isolated. Here, we describe the deduced primary structure, the cytogenetic position and expression pattern of the Dm homologue of mTFR11 (DTFR), a putative DPP receptor. The cytogenetic position of the Dm dtfr gene was mapped to 25D. DTFR has striking homology to mTFR11, especially in the cytoplasmic domain (approx. 63%), including a Ser + Gly-rich box that is characteristic of type-I receptors for the TGF-beta superfamily. Although the amino acid (aa) sequence of the extracellular domain is less conserved than that of the cytoplasmic domain, the extracellular domains of these two molecules were more homologous (approx. 27%) to each other than any other receptors for the TGF-beta superfamily. The spacing of Cys residues in the extracellular domain, which is considered crucial to ligand specificity, is highly conserved in these two receptors. During Dm embryonic development, its expression pattern changes in a dynamic fashion with high levels of expression in mesoderm and midgut, with some relation to dpp mutant phenotypes.

Mechanism of action of the new orally active cephalosporin FK027.

The mechanism of action of a new orally active cephalosporin, FK027, was compared to that of cephalexin and cefaclor to elucidate its excellent antibacterial activity against Gram-negative bacteria. FK027 showed very high affinity for the penicillin-binding proteins (PBPs) 3, 1a and 1bs of Escherichia coli whereas cephalexin showed fairly high affinity for PBPs 1a, 4 and 3. The ability of FK027 to penetrate the outer membranes of E. coli and Enterobacter cloacae was less than that of cephalexin and cefaclor. However, FK027 was extremely stable to both plasmid-mediated penicillinases and chromosomal beta-lactamases except the Bacteroides fragilis enzyme and its stability was superior to that of cephalexin and cefaclor. These results indicate that the potent antibacterial activity of FK027 is based on its enhanced affinity for the target enzymes and its high stability to beta-lactamases.