Antiallatotropins: inhibition of corpus allatum development

Treatment of newly eclosed adult milkweed bug (Oncopeltus fasciatus) females with precocene 2 prevents secretion of juvenile hormone by inhibition of postimaginal development of the corpus allatum. Ovarian development which is dependent upon juvenile hormone is prevented or reversed, depending upon the timing of precocene treatment. Juvenile hormone secretion is shown to be related to the development of the corpus allatum.     

Thyrotropin-releasing hormone: biosynthesis by rat hypothalamic fragments in vitro

Biosynthesis of thyrotropin-releasing hormone (L-pyroglutamyl-L-histidyl-L-proline amide) in vitro was studied. Rat hypothalamic fragments were incubated in Krebs-Ringer bicarbonate buffer that contained either (14)C-labeled proline, histidine, or glutamic acid (the three probable precursor amino acids,) and for control purposes each of 16 other naturally occurring amino acids. A number of labeled peptides were synthesized. With the use of synthetic thyrotropin-releasing hormone, detected by the Pauly reagent or with (125)1-labeled thyrotropin-releasing hormone as a marker, thin-layer chromatograms, paper electrophoresis, and carboxymethyl cellulose ion exchange chromatography revealed that only proline, histidine, and glutamic acid were consistently incorporated into peptides associated with the thyrotropin-releasing hormone region. This synthesizing activity was found in stalk median eminence, ventral hypothalamus. and dorsal hypothalamus but not in neural lobe or cerebral cortex. Because the biosynthetic peptide has identical properties with L-pyroglutamyl-L-histidyl-L-proline amide, it is probable that rat thyrotropin-releasing hormone is similar or identical to both bovine and porcine thyrotropin-releasing hormone and that the native material is present in the pyroglutamyl form in tissues.     

Random peptide libraries: a source of specific protein binding molecules

Libraries of random peptide sequences were constructed and screened to identify peptides that specifically bind to proteins. In one of these about 2 X 10(7) different 15-residue peptide sequences were expressed on the surface of the coliphage M13. Each phage encoded a single random sequence and expressed it as a fusion complex with pIII, a minor coat protein present at five molecules per phage. Phage encoding nine different streptavidin-binding peptide sequences were isolated from this library. The core consensus sequence was His-Pro-Gln and binding of these phage to streptavidin was inhibited by biotin. This type of library makes it possible to identify peptides that bind to proteins (or other macromolecules) that have no previously known affinity for peptides.     

No specific recognition of leader peptide by SecB, a chaperone involved in protein export

Most proteins destined for export from Escherichia coli are made as precursors containing amino-terminal leader sequences that are essential for export and that are removed during the process. The initial step in export of a subset of proteins, which includes maltose-binding protein, is binding of the precursor by the molecular chaperone SecB. This work shows directly that SecB binds with high affinity to unfolded maltose-binding protein but does not specifically recognize and bind the leader. Rather, the leader modulates folding to expose elements in the remainder of the polypeptide that are recognized by SecB.     

Estradiol: specific binding by pituitary nuclear fraction in vitro

The nuclear fraction of a homogenate of anterior pituitary has a marked binding affinity for estradiol but not for other hormonal steroids. Characteristics of the uptake of estradiol by pituitary nuclear fraction are like those reported for the uterus. Study in vitro will be useful in elucidating how direct estrogen feedback control of anterior pituitary function is mediated.     

Regulation of cockroach fat-body metabolism by the corpus cardiacum in vitro

Incubation in vitro of young, adult, male Leucophaea maderae fat body with extracts of corpora cardiaca or intact corpora cardiaca results in stimulation of oxygen consumption but reduction in carbon dioxide evolved from carbohydrate. The carbohydrate is preferentially used for trehalose synthesis, and the endogenous metabolism of the fat body appears to be supported by increased lipid utilization. A hormone from the corpus cardiacum is most likely responsible for these effects and may act at two points, at least, in the glycolytic pathway.     

Ciliary orientation: controlled by cell membrane or by intracellular fibrils?

The cirri of the ciliate Euplotes all asslumne the "reversed" orientation whenever the cell is depolarized and the "forward" orientation whenever the cell is hyperpolarized. Potenitial changes arise spontaneolusly or are induced by electrical or mechanical stimuli. The orientation responses of thte cirri are appatently independent of intracellular "neuromotor" fibrils previously assigned a coordinating function, as they persist after the fibrils are transected.     

Competition between ant species: outcome controlled by parasitic flies

Experimental evidence demonstrates that the parasitic phorid fly Apocephalus shifts the competitive balance between the ant species Pheidole dentata and Solenopsis texana by interfering with the defensive behavior of Pheidole dentata major workers (soldiers). This represents one of the first examples of a parasite affecting competitive interactions anmong terrestrial animals in natural communities. Similar complex interactions are probably common in many ant communities.     

Human melanoma proteoglycan: expression in hybrids controlled by intrinsic and extrinsic signals

Human malignant melanoma cells express specific chondroitin sulfate proteoglycans (mel-CSPG) on the surface, both in vivo and in vitro. Melanocytes in normal skin show no detectable mel-CSPG but can be induced to express the antigen when cultured in the presence of cholera toxin and the tumor promoter 12-O-tetradecanoylphorbol-13-acetate. Most other cell types do not express mel-CSPG either in vivo or in vitro. A study was designed to examine regulatory signals controlling mel-CSPG expression. The gene encoding mel-CSPG was mapped to human chromosome 15, and this chromosome was introduced into rodent cells derived from distinct differentiation lineages. Three types of mel-CSPG--expressing hybrids were found: (i) hybrids derived from human melanomas; (ii) hybrids derived from human cells that do not express mel-CSPG; and (iii) hybrids derived from human cells expressing mel-CSPG that are antigen-negative but that are induced to express mel-CSPG when cultured on extracellular matrix instead of plastic surfaces. Thus, mel-CSPG expression can be controlled both through intrinsic signals, provided by the differentiation program of the rodent fusion partner, and through extrinsic signals, provided by specific cell-matrix interactions.     

Synchronized moulting controlled by communication in group-living collembola

Group-living Collembola of the genus Hypogastrura coordinate their moulting by communication. Animals of different ages and moulting rhythms synchronized the moulting rhythms when combined in a single culture. This synchronization is apparently not dependent on external stimuli but is coordinated by chemical communication among these insects.     

Female germ cell aneuploidy and embryo death in mice lacking the meiosis-specific protein SCP3

Aneuploidy (trisomy or monosomy) is the leading genetic cause of pregnancy loss in humans and results from errors in meiotic chromosome segregation. Here, we show that the absence of synaptonemal complex protein 3 (SCP3) promotes aneuploidy in murine oocytes by inducing defective meiotic chromosome segregation. The abnormal oocyte karyotype is inherited by embryos, which die in utero at an early stage of development. In addition, embryo death in SCP3-deficient females increases with advancing maternal age. We found that SCP3 is required for chiasmata formation and for the structural integrity of meiotic chromosomes, suggesting that altered chromosomal structure triggers nondisjunction. SCP3 is thus linked to inherited aneuploidy in female germ cells and provides a model system for studying age-dependent degeneration in oocytes.     

Terminal saccharides on sperm plasma membranes: identification by specific agglutinins

Six specific agglutinins were used to identify the terminal sugar residues in the surface oligosaccharides of rabbit and hamster spermatozoa by specific agglutination. Species differences in epididymal sperm were found in the terminal residues, resembling alpha-D-mannose, D-galactose, N-acetyl-D-glucosamine, and N-acetyl-D-galactosamine. Species similarities were found in terminal residues, resembling L-fucose and N-acetylneuraminic acid. When ejaculated rabbit sperm were compared to epididyimal sperm, the latter were more agglutinable with a specific agglutinin recognizing N-acetyl-D-glucosamine.     

A multiubiquitin chain is confined to specific lysine in a targeted short-lived protein

The ubiquitin-dependent degradation of a test protein beta-galactosidase (beta gal) is preceded by ubiquitination of beta gal. The many (from 1 to more than 20) ubiquitin moieties attached to a molecule of beta gal occur as an ordered chain of branched ubiquitin-ubiquitin conjugates in which the carboxyl-terminal Gly76 of one ubiquitin is jointed to the internal Lys48 of an adjacent ubiquitin. This multiubiquitin chain is linked to one of two specific Lys residues in beta gal. These same Lys residues have been identified by molecular genetic analysis as components of the aminoterminal degradation signal in beta gal. The experiments with ubiquitin mutated at its Lys48 residue indicate that the multiubiquitin chain in a targeted protein is essential for the degradation of the protein.     

蛋白质交联与食品蛋白配料功能性的研究进展

为研究蛋白质交联技术对蛋白质的功能性作用,对国内外食品体系中蛋白质交联的研究状况进行了系统回顾。首先,围绕食品蛋白配料最重要的两种功能性(乳化性、凝胶性),分析了"蛋白-蛋白"与"蛋白-糖"两种交联类型各自对乳化功能及凝胶功能的促进作用;其次,进一步探讨了不同蛋白质交联对热稳定性、亲水性、成膜性、发泡性和其他食品配料的常见加工性能的影响。研究表明:多数与蛋白质有关的交联对食品蛋白配料功能均产生积极作用,且针对"蛋白-蛋白"交联的研究多于"蛋白-糖"交联;国内外有关蛋白质交联的研究涵盖了动物、植物、乳和蛋等主要食品蛋白源,且多数集中在对单一蛋白源的研究,而对混合蛋白源的研究相对匮乏;今后应针对蛋白质交联机理,特别是加工过程中蛋白自然氧化进行深入探索,将蛋白源应用范围进一步扩展到低值蛋白、加工副产物及混合蛋白源。     

蛋白质交联与食品蛋白配料功能性的研究进展

为研究蛋白质交联技术对蛋白质的功能性作用,对国内外食品体系中蛋白质交联的研究状况进行了系统回顾。首先,围绕食品蛋白配料最重要的两种功能性(乳化性、凝胶性),分析了蛋白-蛋白与蛋白-糖两种交联类型各自对乳化功能及凝胶功能的促进作用;其次,进一步探讨了不同蛋白质交联对热稳定性、亲水性、成膜性、发泡性和其他食品配料的常见加工性能的影响。研究表明:多数与蛋白质有关的交联对食品蛋白配料功能均产生积极作用,且针对蛋白-蛋白交联的研究多于蛋白-糖交联;国内外有关蛋白质交联的研究涵盖了动物、植物、乳和蛋等主要食品蛋白源,且多数集中在对单一蛋白源的研究,而对混合蛋白源的研究相对匮乏;今后应针对蛋白质交联机理,特别是加工过程中蛋白自然氧化进行深入探索,将蛋白源应用范围进一步扩展到低值蛋白、加工副产物及混合蛋白源。     

Norepinephrine biosynthesis inhibition: effects on memory in mice

Diethyldithiocarbamate, a dopamine beta hydroxylase inhibitor, decreases biosynthesis of norepinephrine in the brain. The effects of this inhibitor coincide with alterations in memory as demonstrated in single-trial passive avoidance in C57BL/6J mice.     

Malignant melanoma: specific immunity induced by bacillus Calmette-Guérin in BALB-c mice

Previous treatment of BALB/c mice with bacillus Calmette-Guérin (BCG) will significantly protect them against intramuscular challenge of S-91 melanoma but not against a mammary carcinoma or a methylcholanthrene-induced sarcoma. Lymphocyte-mediated cytotoxicity studies correlate with in vivo data in showing that BCG-immune lymphocytes are specifically cytotoxic to S-91 melanoma target cells but not to the carcinoma or sarcoma target cells.     

Cucurbitacins: specific insect attractants in Cucurbitaceae

In vivo studies of cucurbitacins, the bitter principles present in Cucurbitaceae, indicated a quantitative relation between the concentrations of cucurbitacin in the plant and the degree of insect feeding. In vitro studies demonstrated the attractiveness of these compounds when they were separated from influences of other components of the host plants.     

Plant development: regulation by protein degradation

Many aspects of eukaryotic development depend on regulated protein degradation by the ubiquitin-proteasome pathway. This highly conserved pathway promotes covalent attachment of ubiquitin to protein substrates through the sequential action of three enzymes called a ubiquitin-activating enzyme (E1), a ubiquitin-conjugating enzyme (E2), and a ubiquitin-protein ligase (E3). Most ubiquitinated proteins are then targeted for degradation by the 26S proteasome. Recent studies have also shown that the ubiquitin-related protein RUB/Nedd8 and the proteasome-related COP9 signalosome complex cooperate with the ubiquitin-proteasome pathway to promote protein degradation. Most of these components are conserved in all three eukaryotic kingdoms. However, the known targets of the pathway in plants, and the developmental processes they regulate, are specific to the plant kingdom.     

Metachronal Limb Movements by Artemia salina: Synchrony of Male and Female during Coupling

Studies of the metachronal rhythms of Artemia salina reveal that limb movements of the male and female are synchronous during precopulatory coupling. Synchrony is an adaptation which maintains efficiency in locomotion, respiration, and feeding. The male acts as the pacemaker for the pair and drives the female at a higher rate than she exhibits when alone.