Metabolite and enzyme contents of freeze-clamped liver of the marine fish Stenotomus chrysops

Hepatic metabolites and enzymes in the marine fish, scup or porgy (Stenotomus chrysops), were determined in freeze-clamped tissue taken either within a day of removing fish from their natural habitat or after scup were held in captivity for 6-8 months. The same determinations were made for liver from fed or 48 hr-starved rats (Mus norvegicus albinus). Compared with rat liver, both groups of fish had, per gram of liver, higher contents of AMP, inorganic phosphate, glucose, glucose-6-phosphate, malate, glutamate and NH4+. ATP was lower in fish liver, and ADP, lactate and pyruvate contents were similar in rats and fish. Fish held in captivity had significantly lower pyruvate, alpha-ketoglutarate, and cytosolic free NAD+/NADH and higher cytosolic free NADPH/NADP+. These decreases were similar to those seen when starved rats were compared with fed ones. In scup liver, glucose-6-phosphate dehydrogenase was 3-8 times, malic enzyme about 2 times, and alanine aminotransferase 2-4 times higher than those activities in rat liver. Those results and a higher cytosolic free NADPH/NADP+ are consistent with the liver being the major site of lipogenesis in fish.     

Characterization of cardiac innervation in the nudibranch,Archidoris montereyensis

Summary The heart of the nudibranch mollusc Archidoris montereyensis is regulated by a small number of powerful effector neurons located in the right pleural and visceral ganglia. Two identifiable neurons in the pleural ganglion, a heart excitor (pl_HE) and a heart inhibitor (Pl_HI), are especially important regulators of cardiac function in that low levels of spontaneous activity in either cell significantly alters the amplitude and rate of heart contractions. These neurons have extensive dendritic arbors within the right pleural ganglion and branching axonal processes within the visceral ganglion. The visceral ganglion also contains a heart excitor neuron (V_HE) and at least two heart inhibitor neurons (V_HI cells), but their influence on cardiac activity is weaker than that of the pleural ganglion cells. All of these heart effector cells appear to be motor neurons with axons that terminate predominately in the atrio-ventricular valve region of the heart via the pericardial nerve. The simplicity and strength of these neuronal connections to the heart of Archidoris make this a favorable preparation for studies of cardiac regulation.Abbreviations Pl _HE pleural ganglion heart excitor neuron - Pl _HI pleural heart inhibitor neuron - V _HE visceral ganglion heart excitor neuron - V _HI cells, visceral heart inhibitor neurons - V _K visceral kidney excitor neuron - V _G visceral gill excitor neuron     

Cytochrome P-450 isozymes from the marine teleost Stenotomus chrysops: their roles in steroid hydroxylation and the influence of cytochrome b5

Two new cytochrome P-450 forms were purified from liver microsomes of the marine fish Stenotomus chrysops (scup). Cytochrome P-450A (Mr = 52.5K) had a CO-ligated, reduced difference spectrum lambda max at 447.5 nm, and reconstituted modest benzo[a]pyrene hydroxylase activity (0.16 nmol/min/nmol P-450) and ethoxycoumarin O-deethylase activity (0.42 nmol/min/nmol P-450). Cytochrome P-450A reconstituted under optimal conditions catalyzed hydroxylation of testosterone almost exclusively at the 6 beta position (0.8 nmol/min/nmol P-450) and also catalyzed 2-hydroxylation of estradiol. Cytochrome P-450A is active toward steroid substrates and we propose that it is a major contributor to microsomal testosterone 6 beta-hydroxylase activity. Cytochrome P-450A had a requirement for conspecific (scup) NADPH-cytochrome P-450 reductase and all reconstituted activities examined were stimulated by the addition of purified scup cytochrome b5. Cytochrome P-450B (Mr = 45.9K) had a CO-ligated, reduced difference spectrum lambda max at 449.5 nm and displayed low rates of reconstituted catalytic activities. However, cytochrome P-450B oxidized testosterone at several different sites including the 15 alpha position (0.07 nmol/min/nmol P-450). Both cytochromes P-450A and P-450B were distinct from the major benzo[a]pyrene hydroxylating form, cytochrome P-450E, by the criteria of spectroscopic properties, substrate profiles, minimum molecular weights on NaDodSO4-polyacrylamide gels, peptide mapping and lack of cross-reaction with antibody raised against cytochrome P-450E. Cytochrome P-450E shares epitopes with rat cytochrome P-450c indicating it is the equivalent enzyme, but possible homology between scup cytochromes P-450A or P-450B and known P-450 isozymes in other vertebrate groups is uncertain, although functional analogs exist.     

Molecular and genetic analysis of factors controlling host range in Agrobacterium tumefaciens

Summary We have investigated the factors which contribute to the host specificity of a tumor inducing plasmid of Agrobacterium, pTiAg162, which confers a narrow host range. Determinants both within the T-DNA and virulence regions contribute to host specificity. Within the T-DNA a defective cytokinin biosynthetic gene limits host range. Nucleotide sequence analysis revealed a large deletion in the 5 coding region of this gene when compared with the homologous gene from the wide host range tumor inducing plasmid, pTiA6. Introduction of the wide host range cytokinin biosynthesis gene into the T-DNA of the limited host range strain expanded the host range and suppressed the rooty morphology of tumors incited by the limited host range strain. Two genes from the virulence region of the wide host range plasmid, designated virA and virC, must also be introduced into the limited host range strain in order to restore a wide host range phenotype. The wide host range strain is avirulent on some cultivars of Vitis plants on which the limited host range strain induces tumors. This avirulence is apparently due to a hypersensitive response in which infected plant cells are killed at the site of inoculation. Mutations within the virC locus of the wide host range plasmid prevented the hypersensitive response and allowed the formation of tumors by the wide host range strain.     

Organic free radical levels in seeds and pollen: The effects of hydration and aging

In view of their possible role in oxidative deterioration of seeds and pollen, organic free radicals were measured by electron spin resonance in embryonic axes and cotyledons of soybean [ Glycine max (L.) Merr], embryo and endosperm fractions of corn [ Zea mays L.] and pollen of cattail [ Typha latifolia L.]. A pronounced decline in the radical signal ensued when hydration increased above about 7% (wet weight basis) in both the seed materials and in pollen. Moderate hydration of the soybean axis followed by drying led to a small decrease in organic free radicals compared to untreated material, especially if the desiccation step was performed under nitrogen. In a comparison of soybeans of various ages under normal storage, organic free radical levels in the axis showed little or no increase with age. In marked contrast, over 5 days of accelerated aging at 40°C and near-saturating humidity, organic radical levels approximately doubled in the axis. This pronounced increase in free radical content was not associated with a decrease in the proportion of polyunsaturated fatty acids. The data suggest that hydration of seed and pollen causes a release of free radicals from the trapped state.     

A vehicle for the introduction of transposons into plant-associated pseudomonads

A recombinant plasmid with wide-host-range transfer functions, narrow-host-range replication functions, and carrying a kanamycin-resistant transposon transferred kanamycin resistance to a number of plant-associated pseudomonads. Southern hybridization studies suggest that only a small portion of the plasmid, coinciding with the location of the transposon, is present in the kanamycin-resistant Pseudomonas derivatives. The plasmid sequences appear to be inserted at a number of different sites in the recipient genome. This plasmid can thus be used as a vehicle for the introduction of transposons into some plant-associated pseudomonads and should be useful in both genetic and ecological studies of these bacteria.