Environmental stress and bacterial infection in channel catfish, Ictalurus punctatus Rafinesque

Channel catfish, Ictalurus punctatus , were injected intraperitoneally with a sublethal dose of Aerornonas hydrophila and then stressed for 144 h by being maintained either in a dissolved oxygen concentration of 1·5 mg/1, 1·2 mg/1 total ammonia, and/or 6·5 mg/1 free CO₂ with a continuous inflow of water. A significant difference in percentage of mortality was noted between treatments ( P < 0·05). The trunk kidneys of surviving stressed fish had significantly higher total bacterial counts than non-stressed controls. A. hydrophila was isolated from 67% of the stressed fish and 9% of the control fish. Edwardsiella tarda , apparently endemic in the population, was isolated from 43% of the stressed fish and 7% of the control fish. Histopathological lesions were in the gills, liver, spleen, trunk kidney, and head kidney of stressed fish, but not control fish.     

Liver microsome phospholipids and cytochrome P.450 conceptration in phenobarbital treated rats fed on different diets

Liver microsomal concentration of cytochrome P.450 is increased in animals which are fed diets rich in polyunsaturated fatty acids. On the other hand, the effects of phenobarbital are more important when the dietary fat is more unsaturated. The unsaturation index in liver microsomal phosphatidylcholines depends on the unsaturation of the dietary fats. The treatment with phenobarbital constantly results in a decrease of the unsaturation index of fatty acids both in lecithins and cephalins. The importance of the liver microsomal cytochrome P.450 increase and the importance of the unsaturation index decrease in liver microsomal lecithins, both promoted by phenobarbital, are in good agreement.     

The role of follitropin and lutropin on the ovarian function in rats

Adult cycling female rats were treated with antisera to highly purified human follitropin and lutropin for eight days. The effect of this treatment on thein vitro steroidogenic response of the ovarian cells isolated from these rats to follitropin and lutropin has been investigated. Neutralisation of follitropin did not have significant effect on steroid production in response to lutropin. However, neutralisation of lutropin resulted in a very significant inhibition of response to both follitropin and lutropin.     

Clinical effectiveness of biologics in clinical practice

TNF inhibitors are currently considered both effective and cost-effective in patients with active rheumatoid arthritis (RA), particularly in patients who have not responded fully to methotrexate. There is substantial doubt about the cost-effectiveness of TNF inhibitors as initial treatment for active RA. New data from the National Data Bank for Rheumatic Diseases now question the current consensus in methotrexate failures. The data suggest that in routine clinical practice TNF inhibitors provide only modest incremental benefits over best conventional therapy. If confirmed, these observational studies suggest that the economic argument underpinning the widespread use of TNF inhibitors in established RA is unsustainable.     

The Ultrastructure of Tetrasporogenesis in the Marine Red Alga Chondria tenuissima (Good, et Woodw.) (Ceramiales, Rhodomelaceae)

Tetraspore development has been studied in Chondria tenuissimausing light and electron microscopy. The transformation of tetrasporangialmother cells into mature tetrasporangia involves a series ofstructural changes, especially of dictyosomes and of the nucleus.The youngest stage of tetrasporogenesis consists of a uninucleatetetraspore mother cell with synaptonemal complexes present duringearly prophase of meiosis I. Mitochondria are aggregated aroundthe nucleus, dictyosome activity is low, and proplastids occurin the peripheral cytoplasm. The cleavage furrows are initiatedalmost concomitantly with commencement of meiosis. When thecleavage furrows are initiated, spherical bodies bounded bytwo membranes are found within the cytoplasm; they develop intovacuoles with fibrillar contents (fv₁), which increase in sizeduring tetraspore development by fusing with each other andwith Golgi vesicles. The Golgi vesicles and the vacuoles withfibrillar contents (fv₁) contribute material to the developingtetraspore wall. During the middle stage of tetraspore formationthe vacuoles with fibrillar contents (fv₁) are dominant, dictyosomeactivity increases, as well as the number of plastids and mitochondria;starch formation also increases. Stacked cisternae of the endoplasmicreticulum are found within the peripheral part of the nucleus.The same nuclear structures are also observed in tetrasporangiaof the marine red alga Gastroclonium clavalum. The final stageis characterized by the disappearance of vacuoles with fibrillarcontents (fv₁) and of the stacked ER within the nucleus, presenceof straight, large dictyosomes which produce cored vesicles,an abundance of starch grains and by the formation of fullydeveloped chlorqplasts. The cored vesicles contain Thiéry-positivematerial and contribute to the formation of vacuoles with fibrouscontents (fv₂) as they are dominant in the tetraspores beforetheir liberation. Rhodophlyla, Chondria, tetrasporogenesis, ultrastructure, Golgi apparatus     

The inhibition of phospholipase A2 by manoalide and manoalide analogues

Manoalide, a natural product from sponge, displays anti-inflammatory activity in vivo. Previous work has shown that manoalide is also a potent covalent inhibitor of the extracellular phospholipase A2 from cobra venom and that the inhibition correlated with a pH-dependent change in manoalide (Lombardo and Dennis (1985) J. Biol. Chem. 260, 7234-7240). Manoalide contains two rings and the opening of either would produce an alpha,beta-unsaturated aldehyde. The cobra venom phospholipase A2 may be able to catalyze the opening or isomerization of one of these rings, raising the possibility that manoalide is acting as a suicide substrate. To ascertain the role of the gamma-lactone ring in the inhibition, we have now investigated a synthetic manoalide analogue, 3(cis,cis-7,10)-hexadecadienyl-4-hydroxy-2-butenolide (HDHB) which contains only the alpha,beta-unsaturated gamma-lactone ring. We have found that the closed and open forms are in rapid equilibrium between pH 4 and 9 with the cyclic form being preferred at acidic pH values and the open cis form preferred at pH 9.5. When the pH is raised above 12, the alpha,beta double bond isomerizes to form trans-HDHB. Once the trans compound is formed, it is stable at all pH values and does not recyclize to the gamma-lactone ring. The observed pKa of 7.7 found for the inhibition of manoalide agrees well with the transition of the closed to the cis form of the gamma-lactone ring. Kinetic experiments with the HDHB compound show that under conditions in which the cis and closed form of the inhibitor are present in equal molar ratios, HDHB is not an irreversible inhibitor, but reversibly competes with substrate. However, the kinetics of this inhibition are complex and do not follow either pure competitive or non-competitive inhibition. The trans-HDHB exhibits similar complex kinetic but is several times more potent. The distinct differences between the behavior of manoalide and HDHB clearly indicate that while the gamma-lactone ring may play an important role in manoalide inhibition, it alone does not produce irreversible inhibition.     

Is the mitochondrial precursor protein apocytochrome c able to pass a lipid barrier?

To obtain insight into the role of lipids in the translocation of extramitochondrially synthesized proteins, we studied the ability of apocytochrome c to pass lipid bilayers. With polyacrylamide gel electrophoresis, the digestion of externally added apocytochrome c by trypsin, enclosed in lipid vesicles, was followed. The experiments demonstrate that apocytochrome c is able to pass a lipid barrier and this process shows both a lipid- and protein specificity. The most probable molecular mechanisms involved in this phenomenon are discussed.