The biology of pike, Esox lucius L., in a southern eutrophic lake

The biology of pike, Esox lucius L., in a southern productive lowland lake is described. Scales and opercular bones were difficult to read and interpret, and growth estimated had perforce to be based on scale readings. Growth of Slapton pike is average and intermediate between recorded extremes. Both male and female pike reached maximum condition in February, just prior to spawning. The population of pike of over 450 mm fork length in the lake was estimated at 870·6 ± 389·3 in 1975, and 950·4 ± 143.3 in 1976/77. This leads to the conclusion that the pike population has one of the highest biomasses per surface area of water ever recorded. Number of pike per unit area of surface was also high, despite the fact that a significant proportion of the population (fish under 450 mm) could not be adequately sampled. Mean instantaneous mortality rate was 0·53, and mean instantaneous survival rate was 0·59. The roach provided the main item of diet of the pike, with perch taken less readily. Immature pike ate a significant proportion of invertebrates, but roach was again a common feature of the diet of even small fish. Two spawning migrations were identified; at other times of the year, pike were non territorial. The majority of pike spawned in March. Fecundity of a sample of females was assessed. Overall sex ratio was 1:1.     

Effect of tween 80 on exploratory behavior and locomotor activity in rats

Exploratory behavior and locomotor activity is enhanced in male rat pups (aged 10 to 20 days) whose dams received a chronic dose (1.25 ml/l) of Tween 80 via their drinking water. This enhancement manifests itself during the diurnal period of the day. These data suggest that Tween 80 has an effect on the CNS which could lead to misinterpretation of results in toxicology studies that use this compound as a dosage vehicle.     

Purification and characterization of purple acid phosphatase from developing rat bone

Tartrate-resistant acid phosphatase active on nucleoside di- and triphosphate substrates was isolated from developing rat bone and purified 2500-fold. The enzyme concentration had a purple coloration and activity that was sensitive to reducing agents. Mild reducing agents such as ferrous ion and ascorbic acid caused loss of purple color and increased activity toward substrates severalfold; however, a strong reductant such as dithionite caused loss of both color and activity which were partially restored by addition of ferrous ion and ascorbic acid. Enzyme activity was homogeneous with protein during the final gel permeation steps of chromatography and gave an apparent molecular size of about 40,000 Da. Determination of iron in the most pure preparation revealed the presence of 1.3 atoms of iron per molecule of the tartrate-resistant enzyme E2. Other properties of the purified enzyme include a pI of approximately 9.5 and sensitivity to inhibition by ions of copper, zinc, fluoride, and molybdate. Antibody prepared to the pre-concanavalin A (Con A)-Sepharose purified enzyme reacted with all protein from the Con A step, but it did not react with tartrate-sensitive acid phosphatase from rat bone or with potato acid phosphatase. Purple acid phosphatase from rat bone has many properties that parallel the iron-containing purple acid phosphatases from rat spleen, bovine spleen, and pig uterine secretions.     

Growth-related expression of a double-stranded RNA-dependent protein kinase in 3T3 cells

Cultured mouse 3T3-F442A and 3T3-C2 fibroblasts exhibit a transient double-stranded RNA (dsRNA)-dependent phosphorylation of a 67,000-dalton protein (67K) without prior treatment with interferon (IFN). This phosphoprotein is similar but not identical to the dsRNA-dependent eukaryotic initiation factor-2 (eIF-2) alpha protein kinase (dsI), which regulates protein synthesis in rabbit reticulocytes. We have studied the relationship between cell growth and phosphorylation of the 67K protein (designated 3T3-dsRNA-dependent eIF-2 alpha kinase). A low level of dsRNA-dependent phosphorylation of 3T3-dsI was detectable in extracts prepared from cells not treated with IFN and grown at a low cell density. The phosphorylation of dsI and the phosphorylation of a 38K protein identified as the alpha-subunit (38K) of 3T3-eIF-2 (eIF-2 alpha) occurred concomitantly; the levels of these phosphorylations confluent and thereafter decreased markedly. Treatment of cells with IFN at all stages of growth resulted in an increase in phosphorylation of dsI. 3T3-F442A and 3T3-C2 fibroblasts were found to produce and secrete IFN at levels sufficient to induce an elevated dsI activity.     

Raman and infrared spectra of toxin gamma from the venom of the scorpion Tityus serrulatus

Toxin gamma is a basic, low-molecular-weight, neurotoxic protein, isolated from the venom of the Brazilian scorpion, Tityus serrulatus. Raman spectra (400-1800 cm-1 region) of this toxin in both the lyophilized state and in 0.1 M acetate buffer (pH 4.5) and the infrared spectrum (700-4000 cm-1 region) of a solid film were investigated. From the vibrational spectra, it can be concluded that the polypeptide backbone of toxin gamma consists of a mixture of the different secondary structures, with predominance of beta-sheet, followed by unordered structure and alpha-helix, with some evidence of beta-turn structures. The four disulfide bridges assume the gauche-gauche-gauche conformation of the CCSSCC fragments. The intensity ratio of the doublet at 853 and 828 cm-1 suggests that four out of the five tyrosine residues are exposed. The three tryptophan residues are exposed on the surface, and the single methionine residue assume the gauche-gauche conformation. Toxin gamma retains full activity in the pH 4.5-7.5 range, but is almost completely inactivated at pH 11.5.     

Mutual recognition between polymerized liposomes. IV. Polysaccharide-lectin system.

As a model of cell-cell recognition processes, the association processes of a polysaccharide (mannan)-carrying liposome with a lectin (Concanavalin A, Con A)-carrying polymerized liposome were followed by turbidimetry. The association process was strongly inhibited by the addition of a low molecular weight sugar, methyl-alpha-D-mannopyranoside, which shows that the association between the liposomes is due to the specific interaction between Con A and mannan. The association rate constant obtained was much smaller than the theoretical value for a diffusion-controlled binary association process. This implies that the association rate of liposomes is limited by the recognition between complementary ligands bound on the liposome surfaces. Another reason for the smaller association rate constant in the liposome-liposome system is the repulsive hydration effect. The effect of the surface density of the lectin immobilized on the liposome on the recognition was also examined.     

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.     

Decoding at the ribosomal A site: antibiotics, misreading and energy of aminoacyl-tRNA binding

The binding of Phe-tRNAPhe at the programmed ribosomal A site has been investigated using antibiotics that influence this binding in different ways. The adhesion of Phe-tRNAPhe, the consumption of GTP and the extent of the peptidyl transfer reaction were monitored. All of the five known misreading-inducing antibiotics that were tested stabilised the binding of Phe-tRNAPhe after its affixture to the A site by EF-Tu with GTP hydrolysis. The stabilisation was sufficient to overcome a single mismatch in the codon-anticodon interaction. Combinations of stabilising and destabilising influences were found to be additive, thus supporting the concepts: (1) that there is a 'correct' binding energy for aminoacyl tRNA in the A site, whose reduction hampers polypeptide synthesis and whose increase makes it inaccurate by by-passing proofreading; and (2) that the different antibiotics affect the bound aminoacyl tRNA at different points.