Structural differences between somatic H2B and testis-specific TH2B histones of the rat

Testis-specific histone TH2B from rat testis showed a very similar tryptic map to somatic H2B from rat liver, indicating a common evolutionary origin. However, 5 peptide differences were detected between the 2 proteins, and the amino acid compositions of these distinctive peptides were determined.     

Gonadotrophin-releasing activity of histones H2A and H2B

We report that histones H2A and H2B possess gonadotrophin-releasing activity in vitro and assess the signal transduction pathways involved in these effects. Perifused and incubated rat anterior pituitary (AP) cells were used, and luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured by RIA. Perifusion of cells with histone H2A (30 μM) or histone H2B (30 μM), markedly stimulated LH release but failed to elicit any FSH response. Cells incubated with 6 or 30 μM histone H2A showed a dose- and time-dependent stimulatory effect on both LH and FSH release which was blocked by 1 μM peptide MB35, an 86–120 amino acid fragment of histone H2A. Incubation of pituitary cells with gonadotrophin-releasing hormone (GnRH) and histones H2A or H2B showed a stimulatory effect on LH and FSH release which was similar to the sum of the separate effects. Trifluoperazine, as well as ethylene glycol bis(b-aminoethyl ether) N,N,N′,N′-tetraacetic acid (EGTA), alone or in the presence of the calcium ionophore A23187, significantly reduced the response of AP cells to histones. Various cyclic adenosine monophosphate (cAMP) enhancers had no effect on histone-stimulated release of gonadotrophins in incubated AP cells. Our results confirm previous evidence that histones may act as hypophysiotrophic signals. Calcium- and diacylglycerol-associated pathways, but not cAMP, appear to participate in these effects. Received 11 August 1997; received after revision 20 January 1998; accepted 26 January 1998     

Stimulating effect of thromboxane B2 on isolated rat atria

Summary Thromboxane B₂ enhanced the beating frequency and the contractile tension of isolated rat atria. Both effects were inhibited by propranolol, by pretreatment with 6-hydroxydopamine, or after inhibition of prostaglandins synthesis with indomethacin and acetylsalicylic acid.This work has been supported by grant 6638 from CONICET (Argentina).     

Proinsulin C-peptide and its C-terminal pentapeptide: degradation in human serum and Schiff base formation with subsequent CO<Subscript>2</Subscript> incorporation

Processing of human proinsulin C-peptide and its C-terminal pentapeptide in blood serum was studied using reverse-phase HPLC and electrospray mass spectrometry. The results reveal degradation of both peptides, with a longer half-life for intact C-peptide than for the C-terminal pentapeptide. Products from C-peptide degradation were not distinguishable from the peptide background, suggesting endopeptidase degradation of C-peptide. In contrast, a set of products from the C-terminal pentapeptide were identifiable and corresponded to successive losses from the N terminus, showing that the pentapeptide is degraded by aminopeptidase in serum. Consistent with this finding, a slower degradation was found for the N-acetyl-protected pentapeptide. Removal of serum proteins by acetone precipitation produced N-terminally carbamate-modified C-peptide via a Schiff base intermediate (a ketimine with acetone), to which CO(2) was added and acetone removed, generating a cyclic side chain via anhydride formation. The modification was not seen with the pyroglutamate form of C-peptide, with the N-terminally acetylated C-peptide, or with a control peptide having N-terminal Phe, but was found with human C-peptide, its N-terminal tetrapeptide, and a rat C-peptide fragment (all with N-terminal Glu). Hence, the modification appears to require N-terminal Glu, but this is not the only prerequisite since the C-terminal pentapeptide and another control peptide (also starting with Glu) were not modified. A peptide aldimine Schiff base leading to CO(2) incorporation was detected with formaldehyde in NaHCO(3). The observation that C-peptide forms Schiff bases with ketones/aldehydes, enhancing covalent attachment of CO(2), may have biological implications.     

Strukturspezifischer Abbau von Polypeptid-Metall-Komplexen. V. Abbau des Cu2+-Polymyxin-B-Komplexes durch NH2OH

Summary NH₂OH as well as H₂O₂ (previous results^3,4) decompose the Cu₂₊ complex of polymyxin B as can be shown with thin layer chromatography; the spots of the peptide fragments of both reactions were compared.     

热压烧结ZrB2／B4C陶瓷材料的组织与性能

以B4C、C、ZrO2为主要原料,采用反应热压法制备ZrB2／B4C陶瓷材料。通过对ZrB2／B4C陶瓷材料的显微组织及力学性能的综合分析,发现第二相ZrB2含量为20wt％时,材料具有较好的综合力学性能,相对密度为99．3％,维氏硬度为36．1GPa,抗弯强度为533．3MPa,断裂韧性为6．95MPa·m^1/2,比纯B4C陶瓷材料的性能均有所提高。材料为穿晶和沿晶断裂的混合断裂模式。     

Arylsulfatase B synthesis and clearance in inbred mouse strains

Arylsulfatase B activity levels were approximately 2-3-fold higher in adult C57BL/6J liver and kidney compared to corresponding tissues from A/J inbred mice. In vivo incorporation of tritiated leucine into C57BL/6J hepatic arylsulfatase B reached a maximum approximately 15 h after injection. The label was cleared from C57BL/6J arylsulfatase B with an apparent half-life of 36 h. The relative rates of synthesis of C57BL/6J and A/J arylsulfatase B were similar; however, the A/J enzyme was cleared more rapidly from liver tissue. C57BL/6J kidney arylsulfatase B appeared to be synthesized at a 2-3-fold higher rate than the corresponding A/J enzyme. These trends suggest genetic regulation of arylsulfatase B is effected through different means in liver and kidney from adult mice of these two inbred strains.     

多孔Cu2O／SnO2复合薄膜的制备及其可见光催化降解罗丹明B的性能

采用浸渍-沉积方法在电沉积的多孔Cu薄膜上修饰一层纳米SnO2,经低温热氧化处理制备出多孔Cu2O／SnO2复合多层薄膜。运用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X-射线粉末衍射仪（XRD）、紫外可见漫反射光谱（UV—vis DRS）和荧光光谱（FS）技术表征了薄膜的结构、形貌和光学性质。测试了薄膜在可见光下降解罗丹明B（RhB）的性能。结果表明,在30℃的0．2mol／LCuSO4＋1．5mol／L H2SO4镀液中,以1.5A／cm^2电流沉积20s得蓟的多孔Cu薄膜,在SnO2溶胶中浸渍10s并重复5次,再经空气气氛下100℃焙烧30min,锻得的多孔复夸薄膜显示良好的可见光催化降解RhB的性铯。     

COX-2与CYPlBl在人乳腺癌中的表达及意义

目的探讨人乳腺癌组织中COX-2和CYPlBl的表达规律及与临床病理特征的关系,对认识其在乳腺癌发生发展中的作用奠定初步病理学基础。方法应用免疫组织化学方法检测42例乳腺癌组织中COX-2和CYPlBl的表达情况,结合临床病理指标进行研究分析。结果在乳腺癌中COX-2和CYPIBl表达阳性率分别为78．6％和73．8％。COX-2的阳性表达与乳腺癌淋巴结转移、组织学分级显著相关（P〈0．05）;CYPlBI的阳性表达与组织学分级、ER表达显著相关（P〈0．05）。乳腺癌COX-2与CYPlBI表达呈正相关（r=0．481,P〈0．01）。结论人乳腺癌组织存在COX-2与CYPlBl的共同阳性表达,COX-2可能促进CYPlBl表达,共同作用参与乳腺癌的发生发展。     

Antigenic correlation between rat brain synaptic vesicles and rat bone marrow B lymphocytes.

Rabbit anti-rat brain synaptic vesicle serum reacted with thymocytes and B lymphocytes in cytotoxicity and immunofluorescence assays. Quantitative absorption analysis revealed that this antiserum contained antibodies specific for antigenic determinants on the surface membrane of a subpopulation of rat bone marrow B lymphocytes.     

Methoxyphenylethylamines as substrates for type A and type B monoamine oxidase

Summary 4-Methoxyphenylethylamine was found to be a specific substrate for type B monoamine oxidase (MAO) in rat brain mitochondria, whereas 3,4-dimethoxyphenylethylamine was common for both types of MAO. These results suggest that O-methylation in the para-position increases the preference of the substrate for type B MAO, while a methoxy-group in the meta-position contributes to the substance being a type A substrate.     

Identification of thromboxane B2 in guinea-pig uterine homogenates

On the basis of gas chromatographic and mass spectrometric evidence, thromboxane B2 has been identified in incubates of homogenised guinea-pig uterus.     

Antigenic correlation between rat brain synaptic vesicles and rat bone marrow B lymphocytes

Summary Rabbit anti-rat brain synaptic vesicle serum reacted with thymocytes and B lymphocytes in cytotoxicity and immunofluorescence assays. Quantitative absorption analysis revealed that this antiserum contained antibodies specific for antigenic determinants on the surface membrane of a subpopulation of rat bone marrow B lymphocytes.This work was supported by the Republic of Serbia Research Fund, Belgrade.     

Prolactin and growth hormone releasing activity of [D-Met2, Pro5]-enkephalinamide in the rat after systemic administration

Summary The growth hormone (GH) and prolactin releasing (PRL) activity of [D-Met², Pro⁵]-enkephalinamide (EKNH₂), an opioid peptide analog with higher opiate agonist activity that morphine, was compared in the unanesthetized male rat to those of equimolar doses of morphine upon systemic injection. EKNH₂ proved to be a higher PRL, but not GH, releaser than the opiate alkaloid.     

Effect of the administration of (d-Ala)2methionine-enkephalin on the serotonin metabolism in rat brain

Summary The effect of cerebroventricular injection of [D-Alanine] methionine-enkephalin (DALA), a synthetic analog of met-enkephalin, on the serotonergic system of rat brain has been studied. This opioid peptide caused an increase in 5HT turnover which was particularly evident in the limbic forebrain. This effect was completely antagonized by naloxone pretreatment.Acknowledgments. Support received from Tecnofarmaci, Rome, is gratefully acknowledged.     

Distribution of type A and B monamine oxidase activities in the central nervous system of rat and chick.

The distribution of type A and B monamine oxidase (MAO) activities in the central nervous system (CNS) of rat and chick was investigated using 5-hydroxytryptamine and beta-phenylethylamine as specific substrates. The distribution of type A MAO was similar to that of type B MAO in rat CNS, but quite different in chick CNS. This may be ascribed to the difference in animal species. The major part of MAO activity in the spinal cord was found to be type A.     

A C-terminally elongated form of PHI from porcine intestine

A C-terminally elongated form of peptide histidine isoleucine amide (PHI) was isolated from porcine intestine based on its effect on cAMP production in IMR-32 cells. The structure was determined by amino acid sequence analysis of tryptic fragments and by mass spectrometry. The peptide has 42 amino acid residues like those described from human, rat and mouse, but the amino acid sequence of the C-terminal extension of pig PHI is unique. Unlike the other peptides, it has a C-terminal Ala and it differs at five positions from the human form and at six positions from the rat form, while the human and the rat forms differ by only two substitutions. To avoid confusion arising from different C-terminal residues, a unifying nomenclature is proposed: PHI-27 for the hormone and PHI-42 for the elongated product.     

Pancreastatin (33–49) enhances the priming effect of glucose in the rat pancreas

Short-term exposure to glusoe increases insulin secretion during subsequent stimulation. We investigated the effect of the new regulatory peptide pancreastatin on this priming effect of glucose in the perfused rat pancreas. Pancreastatin (33–49) at a concentration of 10^–8 M inhibited insulin release when stimulated by glucose at a concentration of 16.7 mM. However, after a second pulse of 16.7 mM glucose, pancreastatin potentiated the priming effect of glucose on insulin secretion. The modulation of insulin secretion by pancreastatin results in a potentiation of the priming effect of glucose in the rat pancreas, suggesting a role for pancreastatin in the adaptation of the B cell to glucose-stimulated insulin secretion.