K-Casein Suppresses Melanogenesis in Cultured Pigment Cells

The effects of bovine milk proteins on melanogenesis in B16 cells were examined. Both whey protein isolate and casein exhibited depigmenting properties. Among the major protein components of milk—including β-lactoglobulin, α-lactalbumin, α-, β-, and k-casein—only K-casein exhibited the depigmenting effect. However, the carboxyl terminal peptide of K-casein, glycomacropeptide, did not show this activity. Also, K-casein promoted the proliferation of the cells and inhibited the activity of tyrosinase in the cells. These results indicate that K-casein acts as a melanogenesis-suppressing modulator.     

Extensive size homoplasy at a microsatellite locus in the Japanese bumblebee, Bombus diversus

An extensive size homoplasy was found at microsatellite locus B11 of the bumblebee, Bombus diversus, in northern to central Honshu, Japan. A total of 16 alleles of different nucleotide sequences in five length morphs was obtained at B11 for this species. Of these alleles, five were 141 base pairs (bp) in length, five were 137 bp and four were 133 bp. Allele diversity in each length morph was high compared with previous studies. It is noteworthy that this extensive size homoplasy was found in a relatively small geographic area, in contrast to results from previous studies. Reconstruction of a median‐joining network revealed the complicated evolutionary process of the locus, involving insertion/deletion and point mutations. Preliminary estimation of the mutation rate of the B11 locus in B. diversus gives a value comparable to those estimated from experimental Drosophila populations. Effects of the extensive size homoplasy in population genetic studies is discussed.     

Characterization of microsatellite DNA markers in a critically endangered species,Mekong giant catfish,Pangasianodon gigas

Microsatellite DNA markers for a critically endangered Mekong giant catfish (Pangasianodon gigas Roberts and Vidthayanon, 1991) were developed from fin clips collected from captive fish using (GT)₁₅ probe. The number of alleles per locus ranged from two to four. The expected heterozygosities ranged from 0.13 to 0.68. Also, these primers were successfully amplified in four closely related species, Pangasius bocourti, Pangasius conchophilus, Pangasius larnaudii and Pangasius sanitwongsei with the number of alleles per locus ranged from 1 to 13, 1 to 16, 1 to 12 and 1 to 4, respectively. These markers should prove to be very useful for the evaluation of genetic diversity for this species and other related Pangasius species.     

Actin Degradation in the Metamorphosing Bullfrog Tadpole Tail

Degradation of tail muscle proteins was investigated during metamorphosis of Rana catesbeiana , tadpole. Regressing tail muscle contained actomyosin which was comparable to that of non-regressing tail muscle in its physico-chemical character, althouth the actomyosin content of the former tissue decreased as compared to the latter. However, when muscle proteins were extracted in the SDS-containing medium (TSM) and analyzed by SDS-polyacrylamide gel electrophoresis, we found that the protein band corresponding to actin disappeared completely during the late climax stage of metamorphosis. Detailed studies on this phenomenon showed that the apparent absence of actin on SDS-polyacrylamide gel electrophoresis was dependent upon the metamorphic stages of the tadpoles investigated. When TSM extract from the premetamorphic tadpole tail muscles which contained actin was incubated with the same extract from tadpoles of the climax stage, actin derived from premetamorphic tadpole disappeared on gel electrophoresis, indicating that tail muscle tissues of the climax stages contain the actin-degrading enzyme. Characterization of the enzyme was performed with a crude extract using actin prepared from rabbit thigh muscle as a substrate. Actin degrading activity showed incubation time- and temperature-dependency and the activity decreased gradually when the extract was preheated at increasing temperatures with the complete inactivation at 100°C. The major degradation products of actin hydrolysis by the enzyme had a Mr=28,000 and 14,000 which indicated the enzyme splits actin at a specific point. The activity had an optimum pH of 7.5 and was inhibited by leupeptin and iodoacetate and required the presence of a thiol reagent.     

禽流感病毒血凝素HA的可变性解析

以重组的蒙古鸭H5N2禽流感病毒A/Duck/Mongolia/54/01的血凝素HA蛋白的cDNA为模板,进行PCR随机突变,表达只有单个氨基酸突变的H5HA基因共计38个.根据红细胞吸附反应,分析这些突变HA的功能,仍然具有红细胞吸附活性的单个氨基酸突变的HA约占89%,说明H5HA单个氨基酸突变的容许率是相当高的.HA1区突变数目大约是HA2区的两倍.对失去红细胞吸附功能和某些仍然拥有红细胞吸附功能的HA及单个氨基酸突变的位置与结构的关系进行探讨.有两个位点氨基酸突变了两次,但都不影响红细胞吸附功能,对红细胞吸附功能的影响,似乎主要由位置决定,而不是取决于取代的氨基酸的种类.位点179位和122位的突变是不允许的;位点179位于H5N1的受体结合区域RBD内,122位位于A抗原决定簇区附近,推测在H5HA三维结构上,这两个位点位于HA分子的内部,维持着H5HA的结构.HA1Cys位点4和HA2Cys位点148的突变是不允许的.这两个Cys正好形成HA1和HA2连接的桥梁,对维持H5HA结构也是相当重要的.本实验中HA先后失去了三个糖基化位点,但并不影响吸附红细胞的功能.总之,通过实验分析以研究某些氨基酸改变的效果,寻找关键位点是否突变,可以作为评估H5N1野毒株大流行潜力的分子标志.     

TISSUE DEGRADATION PATTERNS OF AMPHIBIAN TADPOLE TAIL: HISTOLOGICAL AND BIOCHEMICAL STUDIES

The pattern of tissue degradation in the tadpole tail of the bullfrog, Rana catesbeiana , was studied histologically and biochemically. Tadpoles at four metamorphic stages (premetamorphic stage, stage XIII; prometamorphic stage, stage XVIII; early to middle climax stage, stage XXII; late climax stage, stage XXIII) were examined. In the histological study, tissues were stained by two different methods, i.e., Masson's trichrome stain and Van Gieson's stain. The results are summarized as follows: 1) Muscle tissues degenerated earlier thatn connective tissues; 2) Collagen density increased as tissue degraded; 3) At stage XXIII, degenerating and fragmented muscle tissues, surrounded by connective tissues, were seen, and 4) At the late climax stage, cell density was greatly increased as compared to preceding stages.
The biochemical studies are summarized as follows; 1) The general catabolic pattern of tail proteins seems to differ between the premetamorphic and late climax stages; 2) The total hydroxyproline content per unit wet weight of the tail increased significantly at the late climax stage as compared to the premetamorphic stage, supporting the histological observations, and 3) Collagen degradation products were obtained at the late climax stage on Sephadex G-75 columns.     

STUDIES ON FORMATION OF γ-GLUTAMYLAMINES IN RAT BRAIN AND THEIR SYNTHETIC AND CATABOLIC ENZYMES

γ-Glutamylation of p-tyramine, noradrenaline, dopamine and serotonin in rat brains was demonstrated by intraventricular injections of the radioactive amines and isolation of the γ-glutamylamines from the acidic extract of the rat brains. Formation of these γ-glutamylamines was proved to be catalysed by γ-glutamyltranspeptidase prepared from both rat kidney and brain. However, these compounds were degraded by γ-glutamylcyclotransferase of rat brain, but not by the emzyme of rat kidney.     

Isolation and characterization of microsatellite DNA loci for endangered fish,Japanese huchen (Hucho perryi)

Japanese huchen, Hucho perryi, is an endangered fish in Japan. In order to promote a conservation program for this species, it is necessary to evaluate its genetic diversity and population genetics. For this purpose, we designed 15 primers containing dinucleotide microsatellite regions and examined their allelic variation using a total of 23 wild individuals collected from two different localities. Eight loci showed moderate allelic variation ranging from two to four alleles, with expected heterozygosities from 0.043 to 0.548. These markers will be useful for the assessment of genetic variation for this species.