Protein intake regulation in the weanling rat: Effects of additions of lysine,arginine and ammonia on the selection of gluten and energy

The effects of adding lysine, arginine and ammonia to gluten on the self-selection of protein and energy by the weanling rat simultaneously offered a choice of two diets differing only in gluten concentration (15 and 55%) were tested. Previous studies have shown that while lysine (6 g/100 g) additions to gluten decreased the amount of gluten selected by the rat from 40 to 20 g per 100 g of food eaten, selection was not related to the nutritional quality of the gluten. When graded levels of arginine (1.8, 3.6 or 7.2 g/100 g) were added to the gluten with or without lysine (0 or 6 g/100 g) the dietary protein selection was unaffected. The addition of ammonia (1.4 g/100 g as NH₄Cl) to gluten had initially the same effect as lysine (6 g/100 g) but with time protein intake returned to control levels. This effect of ammonia was unaltered by arginine additions. It is concluded that the mechanisms which lead to decreases in gluten selection caused by lysine or ammonia are not similar, and that the effects of lysine on gluten selection are not caused by an increased arginine requirement for urea cycle activity.     

Identification of detergents as components of wastewater sludge that modify the thermal stability of reovirus and enteroviruses.

The agent in wastewater sludge previously shown to reduce the heat required to inactivate reovirus (R. L. Ward and C. S. Ashley, Appl. Environ. Microbiol. 34:681--688, 1977) was "separated" from other sludge components and analyzed by infrared spectroscopy. The infrared spectrum of this material was quite similar to the spectra of commercial anionic detergents, and subsequent analyses of the fractionated sludge samples revealed that anionic detergents in sludge were copurified with the virucidal activity. Further measurements on the virucidal activities of specific detergents revealed that ionic detergents reduce the heat required to inactivate reovirus, that cationic detergents are more active than anionic, and that nonionic detergents are inactive. Several detergents were also shown to protect poliovirus and other enteroviruses against inactivation by heat. These results indicate that ionic detergents are the major component in wastewater sludge that reduce the thermal stability of reovirus and, in addition, that detergents are able to protect enteroviruses against heat.     

Identification of the virucidal agent in wastewater sludge.

Anaerobically digested sludge contains an agent that causes irreversible inactivation of poliovirus. It has now been shown that the agent responsible for this activity is ammonia. The effect of ammonia on poliovirus appears to be typical for picornaviruses, but reovirus, an enteric virus of another group, is quite resistant to this compound. Because ammonia is not virucidal in its charged state, it expresses significant activity only at pH values greater than 8. Therefore, increasing the pH of sludge should cause rapid inactivation of indigenous picornaviruses.     

Design optimization of continuous sterilizers

The development of a design of a continuous sterilization is considered with regard to practical data for temperature/time thermal deactivation of infecting organisms. An example of the optimization of the engineering design for capital and operating costs is given. Systems for continuous sterilization by membrane filtration are also considered.     

Characterisation of actI-homologous DNA encoding polyketide synthase genes from the monensin producer Streptomyces cinnamonensis

Summary Cloned DNA encoding polyketide synthase (PKS) genes from one Streptomyces species was previously shown to serve as a useful hybridisation probe for the isolation of other PKS gene clusters from the same or different species. In this work, the actI and actIII genes, encoding components of the actinorhodin PKS of Streptomyces coelicolor, were used to identify and clone a region of homologous DNA from the monensin-producing organism S. cinnamonensis. A 4799 by fragment containing the S. cinnamonensis act-homologous DNA was sequenced. Five open reading frames (ORFs 1–5) were identified on one strand of this DNA. The five ORFs show high sequence similarities to ORFs that were previously identified in the granaticin, actinorhodin, tetracenomycin and whiE PKS gene clusters. This allowed the assignment of the following putative functions to these five ORFS : a heterodimeric -ketoacyl synthase (ORF1 and ORF2), an acyl carrier protein (ORF3), a -ketoacyl reductase (ORF5), and a bifunctional cyclase/dehydrase (ORF4). The ORFs are encoded in the order ORFl-ORF2-ORF3-ORF5-ORF4, and ORFs-1 and -2 show evidence for translational coupling. This act-homologous region therefore appears to encode a PKS gene cluster. A gene disruption experiment using the vector pGM 160, and other evidence, suggests that this cluster is not essential for monensin biosynthesis but rather is involved in the biosynthesis of a cryptic aromatic polyketide in S. cinnamonensis. An efficient plasmid transformation system for S. cinnamonensis has been established, using the multicopy plasmids pWOR120 and pWOR125.     

Chemical synthesis of oligodeoxynucleotide dumbbells

The chemical synthesis of DNA dumbbells is investigated by using two sequences, cyclo-d(GCG-T4-CGCCGC-T4-GCG) and cyclo-d(TTCC-T4-GGAATTCC-T4-GGAA). This method readily and inexpensively yields multimicromole quantities of circular DNA, allowing detailed structural and physical studies to be carried out. Linear oligomers of sequence d(GCG-T4-CGCCGC-T4-GCG) having either 3'- or 5'-phosphates were cyclized in 40% and 67% isolated yield, respectively, by using 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide. Formation of the circular product is confirmed by a 28 degrees C increase in the optical melting temperature, anomalously rapid electrophoretic migration, sequential nuclear Overhauser enhancements between protons of G1 and G20, and observed nuclear coupling between the ligated phosphorus and protons of both G1 and G20. cyclo-d(TTCC-T4-GGAATTCC-T4-GGCC) was synthesized from the corresponding linear 3'-phosphate in 80% yield by the same procedure. Chemical ligation is most effective for 3'-phosphorylated nick sites flanked by two purine bases.     

Purification and partial characterization of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase from Streptomyces clavuligerus.

delta-(L-alpha-Aminoadipyl)-L-cysteinyl-D-valine synthetase (ACVS) was purified from Streptomyces clavuligerus by a combination of salt precipitation, ultrafiltration, and anion-exchange chromatography. The final purified material gave two protein bands with molecular weights of 283,000 and 32,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Electrophoresis in nondenaturing gels gave a single protein band with an estimated molecular weight of 560,000. These results suggest that ACVS is a multimer composed of nonidentical subunits.     

Organization of the Hamster Cumulus Extracellular Matrix: A Hyaluronate-Glycoprotein Gel which Modulates Sperm Access to the Oocyte

The mammalian oocyte-cumulus complex contains an extracellular matrix rich in hyaluronate. Recently, the microstructure of the hamster cumulus extracellular matrix was described (52). In the present work, we investigated the organization of this matrix. We employed freeze-substitution methodologies to investigate ultrastructural effects of various treatments, including sperm enzymes, on the matrix. Protease treatment resulted in disruption with a loss of the fibrillar structures and some expansion; in contrast, hyaluronidase treatment completely solubilized the matrix. EDTA extraction revealed that the fibrils are composed of fine filaments. A discrete region of the matrix immediately surrounding the oocyte, the corona radiata, was resistant to EDTA disruption. We found that hyaluronate is an ubiquitous constituent of the microstructural elements of this extracellular matrix. The matrix exhibits a carbohydrate:protein ratio of approximately 2:1. SDS-PAGE revealed that glycosylated polypeptides are bound to the matrix. The lectins LCA and WGA had differing affinities for these polypeptides, and bound ubiquitously to the intact matrix. The present data suggest that glycoprotein-hyaluronate interaction is critical for maintenance of the cumulus extracellular matrix microstructure and for its physical properties.     

Surface Changes in Mild Steel Coupons from the Action of Corrosion-Causing Bacteria

Changes which occur on the surface of mild steel coupons submerged in cultures of an Fe(III)-reducing bacterium, isolated from corroded pipe systems carrying crude oil, were studied microscopically to investigate the interaction between the corrosion-causing bacterium and the corroding mild steel coupon. Under micro-aerobic conditions and in the absence of the bacteria, a dense, crystalline, amorphous coat formed on the surface of the steel coupons. In the presence of bacteria the surface coat was extensively removed, exposing the bare metal to the environment. After about 2 weeks of exposure, the removal of the surface coating was followed by colonization of the metal surface by the bacteria. Colonization was mediated by fibrous, exopolysaccharidic material formed by the bacteria. Extension of studies to other bacteria isolated from crude oil and corroded pipes reveals that the formation of exopolysaccharide fibers and possession of adherent properties are common characteristics of bacteria from crude oil systems.