Identification of viral ribonucleoproteins in the cytoplasm of murine cells chronically infected by a retrovirus.

Ribonucleoproteins were isolated from the cytoplasm of Friend-Eveline cells which produce the Friend virus complex, after a short labelling with [³H] uridine. These particles moved with a sedimentation coefficient of 53S in sucrose gradient and had a buoyant density of 1.46 g/cm³ in CsCl gradient. Analysis of their RNA content showed that they possessed a 35S major species having the size of the viral genome subunit. Moreover, a positive hybridization was observed when RNA of the 53S particles was annealed with viral complementary DNA. No such particles were found in cultures of uninfected murine cells suggesting that 53S RNPs have a viral origin.     

Oocyte-follicle cell relationships in a starfish

Summary The follicle cells which surround the oocytes of starfish are known to both release the hormone 1-methyladenine and to respond to it by an active movement which forms a component of the spawning response to the hormone. In Patiria miniata these flagellated cells are located peripheral to the oocyte and have long cytoplasmic processes which penetrate the vitelline layer to the egg surface to form an adhering zonule-like junction. Within the follicle cell cytoplasm are located elongate filamentous bands which appear to represent a component of the contractile mechanism that mediates follicle cell response to 1-methyladenine. These bands do not resemble the filaments of vertebrate smooth muscle cells (quantity, distribution and size of filaments; lack of dense bodies in the filament mass), nor the contractile units of the superficial epithelium of lower vertebrate follicles.This investigation was supported by grants HD-07194 and HD-12499 from the National Institutes of Health. We are indebted to Mr. James D. Huber for able technical assistance     

DNA FLOW CYTOMETRY OF ISOLATED KERATINIZED EPITHELIA: A METHODOLOGICAL STUDY BASED ON ULTRASONIC TISSUE DISAGGREGATION

Ultrasonication of keratinized, stratified, squamous epithelium, which had been separated from underlying tissue by means of acetic acid, resulted in disaggregation of all cellular layers in the epithelium, giving a suspension of single nuclei with mitoses preserved. This suspension was treated with RNAse and ethidium bromide for analysis by flow cytometry. From the resulting DNA histogram the G₁, S and G₂+ M fractions were estimated using the computer program of Fried (1976). Treatment with dithiothreitol before sonication increased the yield of nuclei in suspension and decreased the amount of debris and clumps, thereby suppressing overestimation of small S fractions. This method of preparation prior to DNA flow cytometry was useful for the study of the hamster cheek pouch epithelium and of normal and pathological human epidermis.     

Plasma membrane Ca2+ transport: stimulation by soluble proteins.

Inside-out membrane vesicles were prepared from human red blood cells. In the presence of ATP, these vesicles took up ⁴⁵Ca²⁺ against a chemical gradient. The active transport of Ca²⁺ was increased by addition of an activator protein of (Ca²⁺+Mg²⁺)-ATPase isolated from the membrane-free hemolysate of human red blood cells. A closely related protein, the protein modulator of cyclic AMP phosphodiesterase from bovine brain, also increased the rate of active transport of ⁴⁵Ca²⁺. Addition of the calcium ionophore A23187 caused a rapid efflux of ⁴⁵Ca²⁺ from loaded, inside-out vesicles. When La³⁺ was added to the system in the presence of activator protein, the uptake of ⁴⁵Ca²⁺ was inhibited. Results are compatible with the interpretation that activity of the plasma membrane Ca²⁺ pump may be modulated by certain cytoplasmic proteins.     

Ceruloplasmin Polymorphism and Parentage Test in Hereford Cattle

In recent years parentage control by means of blood grouping tests (blood and protein systems) has been required for bulls to be registered in the Danish Hereford Herd Book. Because the Hereford breed shows less variation in the blood and protein systems, the probability of excluding an incorrectly stated bull (or cow) is estimated to be some 15 % lower in Hereford than in Danish dairy breeds (RDM, SDM and Jersey).     

Ultrastructural evidence of maintenance of concanavalin A binding sites in enucleated mammalian cells

Mouse L cells were enucleated by centrifugation in cytochalasin B. Following enucleation, the enucleated cells were incubated in fresh medium for 30 min, 4, 20, or 24 h before being fixed for electron microscopy. After fixation the cells were incubated in concanavalin A and then horseradish peroxidase was bound to the ConA. Electron microscopy of these enucleates revealed that the concanavalin A-binding sites (CABS) are present on the cell surface of the enucleates even at 24 h after enucleation. Although the method does not detail the number of sites present, the inherent distribution of sites appears similar in normal and enucleated cells. Furthermore, the sites are still functional in that the live enucleated cells are agglutinated by ConA to the same extent as are normal L cells—about 80% agglutination in each instance. The results of this study indicate that surface CABS are maintained in the absence of a nucleus and they are still present even after the Golgi apparatus is morphologically disrupted. Turnover of these sites and their relationship to nuclear function are discussed.     

Identification of cyclopentenyl fatty acids by gas liquid chromatography and mass spectrometry

The straight chain fatty acids and the cyclopentenyl fatty acids present in the lipids of Hydnocarpus wightiana seeds were separated as their pyrrolidides by means of gas chromatography. A gas chromatography-mass spectrometry system confirmed the complete separation and permitted the identification of the individual components in the sample.     

Archaeal rRNA operons

Ribosomal RNA (rRNA) operons of the archaea reflect both the unity and the diversity of this third primary taxon. They have proven to be a rich source of both molecular biological and phylogenetic information.