Intermolecular histone H4 interactions in core nucleosomes

Chicken histone H4, labeled at methionine-84 with 1-N-pyrenyliodoacetamide, has been incorporated into a nucleosome-like particle with core length DNA and unmodified histones H2A, H2B, and H3. These synthetic nucleosomes exhibit properties very similar to those displayed by native particles and those labeled with other fluors. The emission spectrum of the pyrene-labeled nucleosome was characteristic of excited dimer (excimer) fluorescence, indicating that the single pyrene groups on the two H4 molecules are in close proximity in the reconstituted particle. Histone H4 was also labeled randomly at lysines with a group that contains two pyrene moieties separated by 12 A at most. Incorporation of this histone into nucleosome-like particles provides an excimer standard which does not depend on intermolecular interactions. The properties of the pyrene-containing nucleosome were examined as a function of ionic strength. It was found that the H4-H4 pyrene excimer fluorescence exhibited a cooperative disruption centered at 0.1 M NaCl which preceded increases in accessibility and environment polarity revealed by other fluors attached at the same site.     

Primary structure of the chromosomal protein HMb from the archaebacteria Methanosarcina barkeri

The amino acid sequence of the protein HMb, a protein of 93 residues (Mr 10757) which represents the major acid-soluble component of the Methanosarcina barkeri nucleoprotein complex, has been established from automated sequence analysis of the protein and from structural data provided by peptides derived from cleavage of the protein at aspartic acid, arginine and methionine residues. The protein HMb is mainly characterized by a high amount of charged residues (15% of acidic residues and 26.8% of basic residues) which are distributed all along the polypeptide chain. The amino acid sequence of the protein HMb is not homologous to any eubacterial, archaebacterial or eukaryotic chromosomal proteins known up to now.     

Tubulin pseudogenes as markers for hominoid divergence

Processed pseudogenes arise via unimolecular events that result in the integration of nonfunctional (and therefore non-selected) regions of DNA into the germ line. The sequence of such pseudogenes can be used as a novel form of evolutionary clock: the older a particular pseudogene, the more mutations it has acquired relative to the selectively constrained functional gene from which it was originally derived. We have used specific beta-tubulin gene probes to assay for the presence of fully sequenced processed pseudogenes in genomic DNA from various hominoid species. The data suggest that orangutan is more closely related to human, chimpanzee and gorilla than is generally believed.     

Influence of mixed culture conditions on yeast-wall hydrolytic activity of Bacillus circulans WL-12 and on extractability of astaxanthin from the yeast Phaffia rhodozyma

O kagbue , R.N. & L ewis , M.J. 1985. Influence of mixed culture conditions on yeast-wall hydrolytic activity of Bacillus circulans WL-12 and on extractability of astaxanthin from the yeast Phaffia rhodozyma. Journal of Applied Bacteriology 59 , 243–255.
In mixed culture Bacillus circulans WL-12 hydrolysed cell walls of Phaffia rhodozyma and rendered astaxanthin extractable from the yeast. pH control was critical to survival and lytic activity of the bacillus; the optimum range was 6.2–6.8. The optimum range of temperature was 20–24C. Glucose (1–2%) was efficient in minimizing catabolite repression of the lytic enzyme complex of the bacillus. Slow-feeding of glucose improved ultimate yields of lytic enzyme but did not acclerate yeast cell wall modification. A relatively high inoculum level of B. circulans accelerated modification of P. rhodozyma in the mixed culture: when the bacterial inoculum was four times that of the yeast, over 80% of total astaxanthin was extractable in 48 h. High bacterial inoculum size also stimulated yeast autolysis and necessitated early harvest of the mixed culture. Results obtained in shake flasks were duplicated in 5-litre fermentors and suggest that the mixed culture has potential industrial value for producing a biomass containing biologically-available astaxanthin. Extractability of astaxanthin was also achieved when mixed culture filtrate was incubated with pure cultured Phaffia cells. When suitably fortified with nutrients, the filtrate also supported simultaneous yeast growth and modification of the yeast cell walls. A scheme incorporating mixed culture with B. circulans WL-12 and re-use of culture filtrate has been proposed for enzymatic processing of Phaffia rhodozyma for inclusion in animal diets.     

Nonvisual feeding in a visual planktivore,Xenomelaniris venezuelae

Summary Studies of the diel feeding patterns of the planktivorous fish, Xenomelaniris venezuelae, in Lake Valencia, Venezuela, revealed that, although the fish is primarily a diurnal feeder, it consumes substantial numbers of Chaoborus larvae and pupae at night. A number of fish species are known which feed on plankton at night, but these fish are filter feeders and their diets largely consist of relatively small, nonevasive prey. Chaoborus, however, is large and agile. Predation by Xenomelaniris in the dark was also studied experimentally. Captured fish were placed in completely darkened aquaria with zooplankton from Lake Valencia. After several hours the plankton was removed and examined for evidence of feeding. The fish were found to consume Chaoborus pupae and fourth instar larvae but not other types of prey. The mode of feeding by Xenomelaniris in the dark is unknown.     

Monoclonal antibodies against human abnormal (des-gamma-carboxy)prothrombin specific for the calcium-free conformer of prothrombin

A monoclonal antibody JO1 X 1 was prepared against human abnormal prothrombin using the hybridoma technique. The clone secreting this antibody was selected on the basis of the ability of this antibody to bind to abnormal prothrombin, but not to prothrombin, in the presence of calcium ions. The antibodies were purified by affinity chromatography in EDTA on columns of prothrombin-Sepharose. Bound antibodies were eluted with 15 mM CaCl2. The kinetics of dissociation of antibody from the antibody-prothrombin complex with the addition of calcium ions fit a first-order kinetic model. Increasing CaCl2 concentration increased the rate of antibody-prothrombin dissociation. Ca(II) and Mn(II) inhibited antibody-prothrombin interaction; half-maximal binding was observed at 0.9 and 4 mM, respectively. Mg(II) had little effect on antibody-antigen interaction. The JO1 X 1 antibody bound fragment 1, fragment (1-39), abnormal prothrombin, and prothrombin equivalently in the presence of EDTA, but did not bind to des(1-44)prothrombin in the presence of EDTA or prothrombin in the presence of CaCl2. These results indicate that the monoclonal antibody JO1 X 1 is conformation specific for the calcium-free conformer of prothrombin and directed against an antigenic determinant near the NH2 terminus of prothrombin expressed in the 1-39 region of the protein. This analysis provides confirmation of the presence of a metal-free conformer of prothrombin.     

Vagotomy and Pyloroplasty for Gastric Ulcer

In a series of 68 patients with gastric ulcer who were treated by vagotomy and pyloroplasty there were no operative deaths, though one patient who received massive transfusions died 14 weeks later from hepatic necrosis probably associated with serum hepatitis. Four patients developed recurrent peptic ulceration requiring further surgical treatment. The clinical condition of all but three of the remainder was satisfactory after an average follow-up period of three years and two months. Of the 14 patients who presented with an acutely bleeding gastric ulcer, one subsequently required gastrectomy for continued bleeding; in all the others the immediate and long-term results were satisfactory. Of 21 patients with a “high” ulcer and 29 with combined gastric and duodenal ulceration one (4·8%) and three (10%) respectively suffered recurrences. We conclude that vagotomy and pyloroplasty is a satisfactory form of treatment for a high or bleeding gastric ulcer, but that for all other gastric ulcers some form of gastric resection is preferable.     

On the spatial distribution, feeding and reproduction of the vermetid gastropod Dendropoma maximum

D. maximum is a dominant species of outer reef flats in the Red Sea, reaching densities of about 22/m² and biomass of 15.8 g dry tissue/m². A few individuals attached to loose rocks are found inside the breaker zone but they may have been dislodged by heavy seas from the outer reef flat. D. maximum feeds from a mucus net which is spread by wave action over the substratum. Hauling the net occurs at approximately 13 minute intervals throughout the 24 hours and lasts about two minutes. Neighbours with overlapping nets stimulate each other to haul and reduce feeding efficiency. The net is grasped by a pair of lateral jaws, tugged free of the substratum by rotation of the body and ingested by a zipper-like action of the lateral and marginal radula teeth. The robust, central and lateral teeth become worn, possibly while channelling out the substratum to accommodate new shell. Defaecation occurs about 2.4 times an hour, amounting to 10450 kcal/m²/y. Females may brood simultaneously at least 11 egg capsules at various stages of development, which are suspended by stalks from the roof of the shell and pass through a dorsal slit in the mantle. Each capsule contains–500 embryos which develop into larvae with simple, coiled shells 0.33 mm in diameter. There is no planktonic phase. Adult shells amount to 2.5 kg/m² on the outer reef flat, while dead shells are often occupied by blennies. Although D. maximum is not a specialized filter feeder, the highly developed ciliary mechanisms suggest that filtering may be an auxiliary feeding method.