Properties of a prolactin receptor from the rabbit mammary gland

Receptors for human, simian, ovine, bovine and murine prolactin, human growth hormone and human placental lactogen have been identified in plasma-membrane-containing subcellular particles isolated from rabbit mammary glands. The association and dissociation of (125)I-labelled prolactin are time- and temperature-dependent processes, both being maximal at 37 degrees C. (125)I-labelled prolactin prepared by the enzymic iodination procedure with lactoperoxidase binds better to receptors than does the preparation obtained by using chloramine-t as the oxidizing agent. The binding of (125)I-labelled prolactin to receptors is strongly influenced by pH and ionic composition but not by many low-molecular-weight compounds tested, e.g. steroids, nucleotides and several drugs. Receptor activity is sensitive to trypsin and phospholipase C digestion, suggesting that protein and phospholipid moieties are essential for the binding of (125)I-labelled prolactin. The binding of (125)I-labelled prolactin to receptors is a saturable and reversible process. Scatchard and Lineweaver-Burk analyses suggest that (125)I-labelled prolactin has a high affinity for its receptor. Binding of (125)I-labelled prolactin to receptors does not result in the destruction of the hormone. Considerable prolactin-binding activity is also observed in subcellular fractions isolated from the adrenal gland, liver, ovary and kidney of the pregnant rabbit, a finding that is consistent with other reported actions of prolactin in these organs.     

Altered aggregational properties in a genetic variant of human glucose 6-phosphate dehydrogenase

The Tel Hashomer variant of human G6PD migrates as two prominent components during electrophoresis in several gel systems in which red cell G6PD from other males migrates predominantly as a single band. Since human males normally have but one X-chromosome, the extra band of this variant seemed an exception to earlier biochemical and genetic observations suggesting that human red cell G6PD is determined by a locus on the X chromosome. Results of the present studies indicate that the Tel Hashomer variant is unusually susceptible to the formation of a complex which has a higher molecular weight than normal G6PD and which represents the slow electrophoretic component. The conditions of formation and disruption of this complex in crude and purified Tel Hashomer preparations suggest that it results from the formation of disulfide bridges between molecules of Tel Hashomer G6PD.Supported by U.S. Public Health Service Research Grants AM-11065 and FR-5406 and Research Career Development Award 5 K3 AM 7992.     

Isologous Oxygen,Sulfur, and Selenium Compounds as Probes of Acetylcholine Receptors

Evidence is presented that while the conformations of acetylcholine and acetylthiolcholine are different, acetylthiolcholine and acetylselenolcholine are structurally and conformationally very similar. Experiments with sulfur and selenium isologs of acetylcholine, choline, and local anesthetics suggest that the active sites of receptors of the electroplax and of electric eel acetylcholinesterase are different, but are compatible with the postulate that acetylcholine receptors of axonal and synaptic excitable membranes are similar.     

Nature of Escherichia coli B(P1) Yielder Cells at the Time of Infection with Restricted T1

In the infection of Escherichia coli B(P1) with restricted T1, it was shown that yielder cells consist of both special and nonspecial cells. Special or predetermined yielders occurred only among the earliest yielders. In most instances, yielder-cell formation was most easily explained by assuming that the first step was a chance escape of the restricted phage DNA from the degrading enzyme of the restricting cell.     

Morphogenesis of Newcastle Disease Virus in Chorioallantoic Membrane

Chick embryo chorioallantoic membrane, infected with the Blacksburg strain of Newcastle disease virus, was examined with an electron microscope to investigate the sequence of viral-induced host cell alterations. These were evident mostly in the endodermal epithelial cells lining the allantoic sac and were divided arbitrarily into three stages. Stage 1 was characterized by commencement of cell hypertrophy and hyperplasia and presence of fewer cytoplasmic inclusion bodies normally found in the cells; in stage 2, juxtanuclear nucleocapsid-glycogen aggregates appeared, and there were increased numbers of microvilli; stage 3 was characterized by increased cytoplasmic density and evidence of viral assembly and release. The morphological features of viral assembly and the virion are also described.     

Bacteriochlorophyllgehalt und Proteinmuster der Thylakoide von Rhodospirillum rubrum während der Morphogenese des Photosynthese-Apparates

Zusammenfassung Der Zusammenhang zwischen dem spezifischen Bacteriochlorophyllgehalt der Zellen und der Thylakoidmorphogenese wird an Rhodospirillum rubrum untersucht. Bei der Induktion des Photosynthese-Apparates wird zunächst Bacteriochlorophyll synthetisiert, obgleich noch keine Thylakoide gebildet werden (1. Phase). Werden Thylakoide ausgebildet, so steigt der spezifische Bacteriochlorophyllgehalt der Thylakoide in Abhängigkeit vom spezifischen Bacteriochlorophyllgehalt der Zellen an, bis ein Wert von 12–13 g Bacteriochlorophyll je mg Zellprotein erreicht ist (2. Phase). Während der Wert für die Zellen darüber hinaus weiter erhöht werden kann, bleibt der Wert der Thylakoide konstant bei 100 g Bacteriochlorophyll je mg Thylakoid-Protein (3. Phase). Isolierte Thylakoide aus Zellen mit niedrigem Bacteriochlorophyllgehalt besitzen geringere Durchmesser als Thylakoide aus Zellen mit höheren Werten. Auch hinsichtlich der Zusammensetzung der Thylakoide in Abhängigkeit von den steigenden Bacteriochlorophyllgehalten bei induzierten Zellen konnten Unterschiede festgestellt werden. Ähnlich wie die spezifischen Bacteriochlorophyllgehalte der Thylakoide, nähern sich die verschiedenen Proteinbausteine der Thylakoide einem festen Verhältnis zueinander, das sich oberhalb von 10–14 g Bacteriochlorophyll je mg Zellprotein nicht mehr ändert. Mit Zunahme des Bacteriochlorophyllgehaltes der Zellen steigt der Gehalt an thylakoidspezifischen Proteinen in den Membranen an und der Anteil der für die Cytoplasmamembran spezifischen Komponenten nimmt ab.

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The bacteriochlorophyll content and protein composition of chromatophores (=thylakoids) of Rhodospirillum rubrum during morphogenesis of the photosynthetic apparatus

Summary The correlation between the specific bacteriochlorophyll content of whole cells and the morphogenesis of chromatophores was investigated in Rhodospirillum rubrum. During the first phase after induction of the photosynthetic apparatus bacteriochlorophyll is synthesized without formation of chromatophores. In a second phase chromatophores increases in a linear correlation to the specific bacterichlorophyll content of the cells. In a third phase, when the specific bacteriochlorophyll content of the cells has reached 12–13 g/mg protein, the specific bacteriochlorophyll content of the chromatophores remains constant (100 g/mg protein). Isolated chromatophores from the second phase have smaller diameters, than chromatophores from the third phase. The composition of the protein compounds of isolated chromatophores changes during the development of the chromatophores in a similar fashion as the specific bacteriochlorophyll content of chromatophores does change. With increasing bacteriochlorophyll content of the cells the chromatophore specific proteins in the membranes increase whereas proteins specific for the cytoplasmic membrane decrease until both reach a constant level.

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Verwendete Abkürzungen BChl. Bacteriochlorophyll     

Rumen Microbial Ecology in Mule Deer

Mule deer rumen microbial populations from animals in the natural habitat in Utah and from captive deer fed various rations were studied. The microorganisms were characterized on the basis of morphology and Gram reaction. Rumen samples contained 13 identifiable types of bacteria and one genus of ciliate protozoa (Entodinium). Highest rumen bacterial populations were produced on rations containing barley. No differences in proportions of ruminal bacteria in the various morphological groups could be detected when animals were fed either natural browse plants or alfalfa hay. The total numbers of bacteria were similar for animals feeding on controlled diets of browse or hay and those in the natural habitat. Numbers of some bacterial types were directly related to ciliate protozoal numbers, whereas others were inversely related. Highest rumen ciliate protozoal populations were observed on rations containing barley. No differences in protozoal populations were noted between diets containing only browse or hay. Seasonal variations were noted in ciliate protozoal numbers from deer feeding in the natural habitat. The total number of ciliate protozoa decreased in the fall and winter and remained low until spring. There were indications that salt in the deer diet favorably affected rumen ciliate protozoa. Rather than revealing direct deer management applications, this study serves to stimulate and illuminate new approaches to research in range and wildlife nutrition.