Biological evaluation of sphingomyelin analogues as inhibitors of sphingomyelinase

Seeking neutral sphingomyelinase inhibitors, we designed and synthesized hydrolytically stable analogues of sphingomyelin. These novel analogues replace the phosphodiester moiety of sphingomyelin with carbamate and urea moiety, resulting in inhibition of neutral sphingomyelinase. Compound 1 prevented ceramide generation and apoptotic neuronal cell death in a model of ischemia based on organotypic hippocampal slice cultures.     

A lone male chimpanzee in the wild: The survivor of a disintegrated unit-group

K Group, originally one of the two major study groups of chimpanzees since 1965 in the Mahale Mountains National Park, western Tanzania, was almost extinct by 1983: at most seven individuals remained in the group at the beginning of 1983. K Group continued to exist for more than four years, but in 1987 a male was left alone at the age of 15 after all the other chimpanzees of the group emigrated or disappeared. Since then he has been observed sporadically for more than five years only within the former range of K Group, without having any contact with the many resident chimpanzees of the neighboring M Group, the other major study group. The present observations reconfirm the strong philopatric tendency of adult male chimpanzees.     

Atrial natriuretic peptide (ANP): a study of ANP and its mRNA in cardiocytes,and of plasma ANP levels in non-obese diabetic mice

Summary Atrial natriuretic peptide (ANP) levels in cardiocytes and plasma were examined by using immunohistochemistry, electron microscopy, and radioimmunoassay in non-obese diabetic mice (NOD). Cardiocyte ANP mRNA expression was measured by the polymerase chain reaction method. ANP immunoreactivity in the auricular cardiocytes was more prominent in hyperglycemic mice (NOD-h) than in normoglycemic mice (NOD-n). Ultrastructural examination showed that auricular cardiocytes of the NOD-h group contained more cytoplasmic granules than cells of the NOD-n group. Ultrastructural morphometry indicated that the number of granules per auricular cardiocyte was significantly larger in the NOD-h group than in the NOD-n group. (P<0.01), whereas the granule diameter was significantly smaller in the NOD-h group (P<0.01). Radioimmunoassay showed that ANP levels in the NOD-h auricular cardiocytes were significantly higher than those in the NOD-n cardiocytes (P<0.01); the opposite was true in plasma. Cardiocyte ANP mRNA expression was lower in the NOD-h group than in the NOD-n group.     

Models of natural mutations including site heterogeneity

New computational models of natural site mutations are developed that account for the different selective pressures acting on different locations in the protein. The number of adjustable parameters is greatly reduced by basing the models on the underlying physical-chemical properties of the amino acids. This allows us to use our method on small data sets built of specific protein types. We demonstrate that with this approach we can represent the evolutionary patterns in HIV envelope proteins far better than with more traditional methods. Proteins 32:289–295, 1998. © 1998 Wiley-Liss, Inc.     

Synthesis of novel siRNAs having thymidine dimers consisting of a carbamate or a urea linkage at their 3' overhang regions and their ability to suppress human RNase L protein expression

In order to examine the effect of modifications at the 3' overhang regions of short interfering RNAs (siRNAs) on their gene-silencing activities, we designed and synthesized novel siRNAs having thymidine dimers consisting of a carbamate or a urea linkage at their 3' overhang regions. Suppression of human RNase L protein expression by these siRNAs was analyzed by immunoblot with RNase L-specific antibody. It was found that, at 24 h post-transfection, the modified siRNAs having the thymidine dimers with the carbamate and urea linkage suppress the protein expression 78 and 37 times more efficiently than that with the natural phosphodiester linkage, respectively. Furthermore, the siRNA containing the carbamate linkage was 37 times more resistant to nucleolytic degradation by snake venom phosphodiesterase than the siRNA consisting of the natural phosphodiester linkage. Thus, the RNA duplexes having the thymidine dimers with the carbamate or urea linkage at their 3' overhang regions will be promising candidates for novel siRNA molecules to down-regulate protein expression.     

A single-nucleotide polymorphism of SMARCB1 in human breast cancers

The gene SMARCB1 has been considered a candidate for a tumor-suppressor gene. Nucleotide alterations in SMARCB1 have been reported, primarily in association with malignant rhabdoid tumor cases. We carried out a search for mutations in SMARCB1 in 60 human gastro-intestinal tract carcinoma cases, 122 breast cancer cases, and 36 human cancer cell lines. A single-nucleotide polymorphism (SNP) at codon 152 with an amino acid change (Asn to Asp) was found in 2 of 122 (1.6%) breast cancer cases, and another SNP at codon 299 without an amino acid change was found in tumor and normal tissues from 7 (5.7%) cases. Codons 152 and 299 of SMARCB1 are localized near or within the binding site for the cMYC protein. The amount of immunoprecipitated cMYC protein was reduced in two different cell lines expressing the codon 152 polymorphic SMARCB1 clone compared with those expressing wild-type SMARCB1, regardless of the identical expression of SMARCB1 protein in both cell lines. Therefore, the SNP at codon 152 is considered to be one of the coding SNPs that alters the SMARCB1-cMYC complex, which regulates various tumor-suppressor related genes against cancer. In addition, we identified three types of splicing isoforms, a 27-bp deleted gene, a 51-bp inserted gene, and a consensus gene, in both carcinoma tissues and in normal tissues; however, no clinical significance was observed for those isoforms. We found a nucleotide change at codon 152 of SMARCB1 that may alter the amount of immunoprecipitated cMYC protein, but we finally determined that SMARCB1 is highly conserved in human solid carcinomas.     

Synthesis and bioactivities of novel 5,6-bis(4-methoxyphenyl)-2H-pyridazin-3-one derivatives: inhibitors of interleukin-1 beta (IL-1beta) production

New 5,6-bis(4-methoxyphenyl)-2H-pyridazin-3-one derivatives were prepared, and their abilities to inhibit IL-1beta production were evaluated. Some compounds showed potent inhibitory activity against IL-1beta production in HL-60 cells stimulated with lipopolysaccharide (LPS). The synthesis and structure-activity relationships of these compounds are described.     

The acquisition of stone-tool use in captive chimpanzees

In order to investigate the acquisition of stone-tool use to crack nuts, experiments were conducted with five captive chimpanzees, employing combinations of trial-and-error, and three types of observation learning of varied difficulty. Two adults and one sub-adult succeeded in acquiring this behavior in the tests where tool use was demonstrated by the experimenter, or by a successful chimpanzee. Analysis of their behavior patterns showed the adults' and sub-adult's process to success to be divided into three stages; these can be characterized as trial-and-error, understanding of the method, and learning the technique, respectively. A factor for distinguishing success from failure is whether or not a subject observes demonstrations with interest in the behavior itself. This interest, in turn, depends on the intensity of the desire for nuts. When released, the successful chimpanzees practiced the same behavior in a group of chimpanzees, and the behavior newly diffused to an infant. Unlike the adults, the infant did not go through the staged process but reached the solution through goal-directed trial-and-error.