Excitation of squid giant axons in hypotonic and hypertonic solutions

Excitability of intracellularly perfused squid giant axons was maintained in hypotonic solutions (down to 300 mOSM) and in hypertonic solutions (up to about 10 OSM), when osmolalities of internal and external solutions were adjusted to be equal with glycerol, glucose, or sucrose. Molar concentrations of ions were kept constant during one series of experiments. The resting potential and the amplitude of the action potential did not change in both hypotonic and hypertonic solutions. With reduction of osmolality, the duration of action potential decreased and the maximum rate of rise and conduction velocity increased. By raising osmolality, the duration was prolonged and the maximum rate of rise and the conduction velocity decreased. Effects of osmolality change were almost reversible. However, these effects were not directly related to the osmolality change but seemed to be related to the viscosity change of the solutions. When the osmolality of external solution was raised with NaCl (up to 2.6 M NaCl), the overshoot increased in porportion to the logarithm of the NaCl concentration. The slope of increase was about 50 mV/decade. However, the resting potential showed little change. With increase of the NaCl concentration, the duration of the action potential increased.     

A simple and rapid method for the determination of macrophage activating factor involving a new type of apparatus suitable for the measurement of macrophage chemiluminescence

A simple and rapid method for the determination of macrophage activating factor is described. A new type of apparatus suitable for the measurement of macrophage chemiluminescence was devised, and the effect of lymphokines on macrophage activities was studied by measuring phorbol myristate acetate-induced luminol-dependent chemiluminescence. An outstanding feature of the new apparatus is that the plastic dish used for the cell culture can be used as the vessel for the chemiluminescence reaction. When thioglycollate-elicited ICR mouse peritoneal macrophages were incubated with lymphokines, their ability to generate chemiluminescence increased rapidly, reaching a maximal level at about 4 h, and then it progressively decreased to the control level at 8 h. Although this increasing effect of lymphokines on macrophage chemiluminescence was short-lived, it could be seen at a relatively low concentration, at which lymphokine-mediated cytotoxic activity of macrophages was not observed.     

Structure of extrachromosomal circular DNAs generated by immunoglobulin light chain gene rearrangements

Recombination at the immunoglobulin kappa or lambda light chain locus generates extrachromosomal circular DNAs. We have isolated circular DNAs from adult mouse spleen cells and prepared a circular DNA clone library. We characterized four J kappa-positive and one J lambda 1-positive clones. The J kappa-clones contained both coding and signal joints of V kappa-J kappa joining, and the J lambda 1-clone contained a signal joint of V lambda 1-J lambda 1 joining. Genomic organization of the V kappa gene families used in these joints suggested the excision of circular DNA preceded by inversion. A specific dinucleotide (P) insertion in the coding joint was observed in two clones. Three coding joints were out of frame and one clone had an in-frame coding joint, although possibly combined with a pseudo-V kappa gene. These kappa-positive circular DNAs are possibly excised from the chromosome by secondary recombinations which replace non-productive primary rearrangements.     

Isolation and characterization of bacteriophage T3/T7 hybrids and their use in studies on molecular basis of DNA-packaging specificity

In vitro DNA-packaging systems of bacteriophages T3 and T7 packaged homologous DNA more efficiently than heterologous DNA. Packaging of phage DNA proceeds by way of concatemeric intermediates (H. Fujisawa, J. Miyazaki, and T. Minagawa (1978), Virology 87, 394-400). The conversion of mature homologous and heterologous DNAs to concatemers was efficient in both the T3- and T7-packaging systems. In vitro complementation experiments indicate that the gene 19 product (gp19) specifies which DNA enters the capsid. To identify DNA regions recognized by the packaging systems, T3/T7 hybrids were constructed and physical maps of the hybrid DNAs were determined by restriction enzyme analysis. By comparing restriction maps and in vitro packaging of hybrid DNAs, it is concluded that the sequence responsible for specificity of DNA packaging is confined within 5% of the ends of the T3 and T7 genomes.     

Met72Thr polymorphism of pigment epithelium-derived factor gene and susceptibility to age-related macular degeneration

Age-related macular degeneration (ARMD) is the most common cause of acquired blindness among the people of occupational age. Although the pathogenesis of ARMD is not fully understood, several studies suggest a possible contribution of a genetic factor in the development and progression of ARMD. Pigment epithelium-derived factor (PEDF), a glycoprotein that belongs to the superfamily of serine protease inhibitors, was first purified from the conditioned media of human retinal pigment epithelial cells as a factor with potent neuronal differentiating activity in human retinoblastoma cells. Recently, PEDF has been shown to be a highly effective inhibitor of angiogenesis in cell culture and animal models. In addition, PEDF has been found in the vitreous, and its levels were decreased in angiogenic eye diseases, thus suggesting that a loss of PEDF in the eye is functionally important in the pathogenesis of ARMD. A functional amino acid change, a methionine to threonine polymorphism (Met72Thr polymorphism) at codon 72 in exon 3 (T/C polymorphism) of the PEDF gene, that results in the formation of BsstSI restriction site, has recently been identified. Since it is well known that a single nucleotide polymorphism and resultant amino acid change often alters the activity or expression level of the target protein, we would like to propose here a novel hypothesis that the Met72Thr polymorphism (T/C polymorphism) of PEDF gene may be a genetic marker for ARMD. Are genotype and allele frequencies of the Met72Thr polymorphism (T/C polymorphism) different between the patients with or without ARMD? Is this polymorphism associated with disease severity and progression? If the answer is yes, does this Met72Thr polymorphism regulate the vitreous levels of PEDF? These clinical studies could provide us with information whether this genetic variant of the PEDF gene could present an attractive candidate susceptibility gene for ARMD.     

Suppression of UV-induced mutations by wild-type p53 protein in human osteosarcoma cells

We have examined whether the tumour suppressor p53 protein suppressedUV-induced mutations in the hypoxathine-guanine phosphoribosyltransferase (HPRT) gene and in the supF gene of the shuttlevector plasmid pMY189. We used human osteosarcoma Saos-LP12cells, in which wild type (wt) p53 protein was induced by treatmentwith isopopyl-(ß-D-thiogalactopyranoside. The inductionof wt p53 protein suppressed UV-induced mutations but not spontaneousmutations in the HPRT gene. The frequency of UV-induced mutationsinduced by UV-irradiation of the plasmid was also significantlylower in cells with induced wt p53 protein than in the uninducedcells. In addition, we found that frequency of G : C to A :T transition mutations which occurred at the 3' base pair ofdipyrimidine sites were significantly lower in the cells withinduced wt p53 protein than in the uninduced cells. These findingssuggestthat wt p53 protein may play roles in modulating DNArepair pathway, resulting in the suppression of UV-induced mutations. ¹To whom correspondence should be addressed     

Synthesis and side-chain crystallization of comb-like polymers obtained from isopropenyl-1,3,5-triazines carrying two,three, and four long alkyl groups

Monomers containing several octadecyl groups, e.g., 2-isopropenyl-4,6-bis(octadecylamino)-1,3,5-triazine ( 2 ), 2-dioctadecylamino-4-isopropenyl-6-octadecylamino-1,3,5-triazine ( 3 ) and 2,4-bis(dioctadecylamino)-6-isopropenly-1,3,5-triazine ( 4 ) were prepared by the alkylation reaction of 2,4-diamino-6-isopropenyl-1,3,5-triazine ( 1 ) with 1-bromooctadecane in the presence of sodium hydride. In the free-radical homopolymerization of these monomers, the polymer yield of 3 was lower than that of 2 due to a decrease in the ceiling temperature, and the polymerization of 4 did not proceed. Copolymerizations of these monomers with styrene or methyl methacrylate were carried out and the monomer reactivity ratios (r₁ and r₂) were determined. The monomer reactivity decreased with increasing the number of octadecyl groups in the monomers. Crystallinity of the octadecyl side chains in the resulting comb-like polymers was evaluated by differential scanning calorimetry.     

Acarbose is a promising therapeutic strategy for the treatment of patients with nonalcoholic steatohepatitis (NASH)

The metabolic syndrome is strongly associated with insulin resistance and has been recognized as a cluster of risk factors for cardiovascular diseases such as visceral obesity, hypertension, and diabetes. There is a growing body of evidence to show that nonalcoholic steatohepatitis (NASH) is the hepatic manifestation of insulin resistant patients with the metabolic syndrome. Indeed, insulin resistance increases adipocyte lipolysis and subsequently elevates circulating free fatty acids, thus stimulating the accumulation of fatty acids in the liver (hepatic steatosis). Fatty acids elicit reactive oxygen species generation, thereby promoting disease progression to NASH by both lipid peroxidation and inflammatory cytokine production. Postprandial hyperglycemia, one of the characteristic features of insulin resistance, also induces oxidative stress generation, being involved in dysfunction of pancreatic beta cells and vascular wall cells in the metabolic syndrome. Recently, STOP-NIDDM trial revealed that acarbose (Glucobay), an alpha-glucosidase inhibitor, improved postprandial hyperglycemia and subsequently reduced the risk of development of type 2 diabetes and newly diagnosed hypertension in patients with impaired glucose tolerance. In this study, acarbose treatment was also found to reduce body mass index and waist circumference in these patients. Furthermore, a meta-analysis of seven long-term studies has also shown that intervention with acarbose improved triglyceride levels, body weight and systolic blood pressure and subsequently prevented myocardial infarction in type 2 diabetic patients. Since acarbose improves postprandial hyperglycemia by delaying the release of glucose from complex carbohydrates in the absence of an increase in insulin secretion, the beneficial aspects of acarbose could be ascribed to improvement of insulin sensitivity in these patients. Given the pathological link between NASH and insulin resistance, we would like to hypothesize here that acarbose may become a promising therapeutic strategy for the treatment of patients with NASH. Does acarbose treatment improve steatohepatitis histologically? Is the extent of histological improvement by acarbose parallel to that of insulin sensitivity in these patients? Large clinical trials will provide us with more definite information whether acarbose treatment can improve insulin sensitivity and resultantly reduce the risk of progression of liver diseases in patients with NASH.