Interspecific interactions and diet of sympatric juvenile brook charr, Salvelinus fontinalis, and adult ninespine sticklebacks, Pungitius pungitius

Breeding male ninespine sticklebacks, Pungilius pungitius , are highly aggressive toward juvenile brook charr. Salvelinus fontinalis , in the Matamek River, Québec. Field observations revealed that such aggression was always initiated by the sticklebacks and only if the charr approached their nests or free-swimming fry. There was considerable overlap in diet in August, but not in June and July, suggesting competition for food is possible under some circumstances.
In laboratory stream tanks, we compared frequency of intraspecific and interspecific aggression of single and mixed species groups over a range of densities. There was no simple relationship between aggression and density for either species, although significant differences in aggression occurred among fish in some of the different density conditions.     

Unusually high-level expression of a foreign gene (hepatitis B virus core antigen) in Saccharomyces cerevisiae

As a model system for the study of factors affecting gene expression, hepatitis B virus core antigen (HBcAg) has been expressed in the yeast Saccharomyces cerevisiae. The singularly high levels of expression achieved are approx. 40% of the soluble yeast protein. The HBcAg polypeptides are present as 28-nm particles which are morphologically indistinguishable from HBcAg particles in human plasma and are highly immunogenic in mice. The plasmid construction employed to achieve these very high levels of expression utilizes the constitutively active yeast promoter from the GAP491 gene which is fused in a way that all non-translated sequences flanking the HBcAg coding region are yeast-derived. Hybrid constructions containing 3'-nontranslated viral DNA (yeast 5') or 5'-nontranslated viral DNA (yeast 3') as well as a construction with both 5'- and 3'-nontranslated viral DNA also have been made. A comparison of these constructions for levels of HBcAg expression indicates that the strongest contributor to the high levels of protein is the presence of 5'-flanking sequences which are yeast-derived; secondarily, a significant improvement can be achieved if the 3'-flanking sequences also are yeast-derived. The high abundance of HBcAg in the highest producer is explicable in part on the basis of the very high stability in yeast cells of HBcAg polypeptides. Analysis of the HBcAg coding sequence reveals a very low index of codon bias for S. cerevisiae, largely discounting codon usage as a contributor to the high level of protein obtained.     

Sequences required for delivery and localization of the ADP/ATP translocator to the mitochondrial inner membrane.

The ADP/ATP translocator, a transmembrane protein of the mitochondrial inner membrane, is coded in Saccharomyces cerevisiae by the nuclear gene PET9. DNA sequence analysis of the PET9 gene showed that it encoded a protein of 309 amino acids which exhibited a high degree of homology with mitochondrial translocator proteins from other sources. This mitochondrial precursor, in contrast to many others, does not contain a transient presequence which has been shown to direct the posttranslational localization of proteins in the organelle. Gene fusions between the PET9 gene and the gene encoding beta-galactosidase (lacZ) were constructed to define the location of sequences necessary for the mitochondrial delivery of the ADP/ATP translocator protein in vivo. These studies reveal that the information to target the hybrid molecule to the mitochondria is present within the first 115 residues of the protein. In addition, these studies suggest that the "import information" of the amino-terminal region of the ADP/ATP translocator precursor is twofold. In addition to providing targeting function of the precursor to the organelle, these amino-terminal sequences act to prevent membrane-anchoring sequences located between residues 78 and 98 from stopping import at the outer mitochondrial membrane. These results are discussed in light of the function of distinct protein elements at the amino terminus of mitochondrially destined precursors in both organelle delivery and correct membrane localization.     

Further studies of glycosylation and intracellular transport of lactase-phlorizin hydrolase in rat small intestine.

Previous studies [Büller, Montgomery, Sasak & Grand (1987) J. Biol. Chem. 262, 17206-17211] have demonstrated that lactase-phlorizin hydrolase is inserted into the microvillus membrane (MVM) as a large precursor of approx. 220 kDa, which then undergoes two proteolytic cleavage steps to become the 130 kDa mature MVM protein. In order to assess the role of glycosylation in intracellular transport, the processing of this enzyme has been studied in the presence of castanospermine, an inhibitor of N-linked oligosaccharide modification and subsequent treatment with two endoglycosidases, endo-beta-N-acetyl-glucosaminidase (endo-H) and peptide:N-glycosidase-F (N-glycanase). We now show that the intracellular precursor (205 kDa) undergoes carbohydrate processing (220 kDa) and transport to the MVM where its further proteolytic cleavage is as described. Treatment of the intracellular 205 kDa precursor with either endo-H which cleaves only high-mannose N-linked oligosaccharides, or with N-glycanase, which cleaves both high-mannose and complex N-linked oligosaccharides, results in the conversion of the 205 kDa protein band to one of 195 kDa. These data suggest that the 205 kDa precursor contains only high-mannose N-linked carbohydrates, and that the unglycosylated nascent protein is 195 kDa. In the presence of castanospermine, an intracellular precursor of approx. 210 kDa is observed. When treated with endo-H or N-glycanase, this form also produces a protein of 195 kDa. The transport of the intracellular precursor to the MVM and further proteolytic processing is not blocked by the inhibitor. However, all MVM forms of lactase-phlorizin hydrolase show an increase of approx. 5 kDa. Treatment of these three MVM forms with endo-H indicates the increased presence of high mannose oligosaccharides in comparison with non-castanospermine-treated forms. The susceptibility to endo-H of the 130 kDa MVM band synthesized in the absence of castanospermine implies the presence of high-mannose N-linked oligosaccharides in the mature form of lactase-phlorizin hydrolase. Incubation of these MVM forms with N-glycanase further reduces their electrophoretic mobility, indicating the presence of complex N-linked oligosaccharides in the MVM forms, in contrast with the intracellular precursor. Altered glycosylation reduces but does not abolish intracellular transport of lactase-phlorizin hydrolase to the MVM.     

Ontogeny of vision in the Antarctic fish Pagothenia borchgrevinki (Nototheniidae)

Summary Pagothenia borchgrevinki ranging in size from 63 to 245 mm were captured from beneath sea ice in McMurdo Sound by fishing and diver collection. Changes in ocular morphology with increasing body size were measured, and assessed in relation to ingested prey. Relative eye size was highest among smaller fish (<100mm total length), and declined with increasing fish size. This was accompanied by a decrease in cone density in the retina from a maximum of 14,200 mm^–2 in the smallest fish examined (63 mm), to 1000 mm^–2 in a 220 mm long fish. Theoretical acuity was lowest among fish at either end of the size range examined (minimum separable angle 40–50) but approximately constant over the remainder of the size range (25–40). Rod density also decreased with increasing body size but rod numbers per unit visual arc were relatively constant, except in the smallest fish, where angular rod density was low. The same prey taxa occurred in fish of all sizes; however, prey items smaller than about 1.5 mm were not taken by fish of any body size.     

Energy status of the rapidly paced canine myocardium in congestive heart failure.

Rapid ventricular pacing (RVP) is used as an experimental model of congestive heart failure (CHF). The purpose of this study was to determine the energy status of the dog myocardium after the development of CHF via chronic RVP. The myocardium had a significantly lower (P < 0.05) energy charge (EC) during CHF (0.63 +/- 0.01) than in sham-operated controls (0.82 +/- 0.02). This was due to significant differences in concentrations in ATP (-48%), ADP (29%), and AMP (275%) in the RVP group. However, the total adenine nucleotide pool was not different between groups. Myocardial lactate concentration was also similar. Glycogen was significantly lower (P < 0.05) by 20% at peak CHF. The adenine nucleotides were similar among the different myocardial layers (endo-, mid-, and epicardium). The administration of enalapril (an inhibitor of angiotension-converting enzyme) to decrease vascular resistance had no effect on the myocardial energy status of CHF dogs. These findings suggest that the lower EC in CHF animals is not the result of subendocardial ischemia. Also, lower EC is not associated with endogenous glycogen depletion or increased lactate concentration. The energy status of the myocardium in RVP-induced CHF is unlike that seen in ischemia-induced heart failure. This suggests that CHF in RVP is not vascular in origin.     

How far does prophylaxis against infection in total joint replacement offset its cost?

Selection of a cost effective method of prophylaxis against infection for patients undergoing total joint replacement was shown to depend on the number of arthroplasties performed each year at individual hospitals. When 100 arthroplasties were performed each year the prophylactic use of systemic antibiotics minimised the total costs of the department—that is, the combined costs of prophylaxis and reoperation for deep sepsis. Some departments also used local antibiotic prophylaxis in the form of polymethylmethacrylate cement impregnated with gentamicin or a combination of systemic and local prophylaxis at almost as low a total cost and with comparable effect.Selection of a method of prophylaxis should not be determined solely on the basis of reducing costs. When a value was assigned to the effects of loss of health an economic optimum was established that allowed selection of a more costly method of prophylaxis together with further reductions in the incidence of infection and the need for reoperation.     

Influence of Bipyridylium Compounds on Microsomal Mixed-Function Oxidation Activities

The two principal bipyridyl herbicides, paraquat and diquat, were investigated for their influence on microsomal mixed-function oxidation (MFO) activities and on NADPH oxidation rates in lung, liver, and kidney preparations. In lung microsomal preparations, benzphetamine N-demethylation was found to be inhibited by paraquat and diquat in a concentration-dependent manner, but ethylmorphine N-demethylation was unaffected by these bipyridyls. In liver microsomal fractions, both benzphetamine and ethylmorphine N-demethylases were inhibited by paraquat and diquat. Neither bipyridyl affected MFO activity in kidney preparations. A kinetic investigation of the enzyme inhibition showed that only V_max was affected by paraquat and diquat, providing the first evidence for noncompetitive inhibition by the bipyridyls. In all microsomal preparations, NADPH oxidation was stimulated significantly by paraquat and to an even greater extent by diquat in the absence or presence of benzphetamine or ethylmorphine. The influence of MFO substrates on the stimulation varied widely among the three organ systems. In lung, paraquat- or diquat-mediated stimulation of NADPH oxidation was equal in the absence of MFO substrates and in the presence of ethylmorphine, but the stimulation was increased in the presence of benzphetamine. Stimulation of NADPH oxidation by the bipyridyls, in liver as well as in kidney preparations, was equal in all situations in the absence of MFO substrates and in the presence of benzphetamine or ethylmorphine, although the quantity of this stimulation was greater in liver than in kidney fractions. It is apparent that the bipyridyls are potent stimulators of in vitro NADPH oxidation in microsomal preparations from several organs. The quantity of the NADPH oxidation stimulation seems to be a decisive factor in the inhibition of xenobiotic metabolism. Whether the stimulation of NADPH oxidation and the noncompetitive inhibition of xenobiotic metabolism play a significant role in bipyridyl toxicity are under further investigation.     

Microbial degradation of n-alkyl tetrahydrothiophenes found in petroleum.

Although n-alkyl-substituted tetrahydrothiophenes are found in nonbiodegraded petroleums, they are not found in petroleums which have undergone biodegradation in their reservoirs. These observations suggested that this group of compounds with alkyl chain lengths from approximately C10 to at least C30 is biodegradable. Two of these sulfides, 2-n-dodecyltetrahydrothiophene (DTHT) and 2-n-undecyltetrahydrothiophene, were synthesized, and their biodegradabilities were tested by using five gram-positive, n-alkane-degrading bacterial isolates. The alkyl side chains of these compounds were oxidized, and the major intermediates found in 2-n-undecyltetrahydrothiophene- and DTHT-metabolizing cultures were 2-tetrahydrothiophenecarboxylic acid (THTC) and 2-tetrahydrothiopheneacetic acid (THTA), respectively. Four n-alkane-degrading fungi were also shown to degrade DTHT, yielding both THTA and THTC. Quantitation of tetrahydrothiophene ring-containing products in 28-day-old bacterial and fungal cultures suggested that THTC and THTA were metabolized further to unidentified products. In addition, two of the bacterial isolates were shown to degrade a mixture of n-alkyl tetrahydrothiophenes isolated from Bellshill Lake crude oil.     

Trichloroethylene metabolism by microorganisms that degrade aromatic compounds.

Trichloroethylene (TCE) was metabolized by the natural microflora of three different environmental water samples when stimulated by the addition of either toluene or phenol. Two different strains of Pseudomonas putida that degrade toluene by a pathway containing a toluene dioxygenase also metabolized TCE. A mutant of one of these strains lacking an active toluene dioxygenase could not degrade TCE, but spontaneous revertants for toluene degradation also regained TCE-degradative ability. The results implicate toluene dioxygenase in TCE metabolism.