Insulin Binding in Four Regions of the Developing Rat Brain

Specific insulin binding has been demonstrated in partially purified membranes prepared from four regions of the developing rat brain. Insulin binding to brain membranes demonstrated kinetics and hormonal specificity that were quite similar to those reported for traditional insulin target tissues (e.g., liver and adipose tissue), and binding was significantly correlated with receptor concentration. Binding in the olfactory bulbs, cerebrum, cerebellum, and hypothalamus all reached highest values at 15 days of postnatal life, with the olfactory bulbs generally showing the greatest binding at all ages studied. A temporal relationship was found between insulin binding to brain membranes in the postnatal rat and plasma membrane protein synthesis, especially in the cerebellum and olfactory bulbs.     

Characterization of Cyclic AMP-Dependent Phosphorylation of Neuronal Membrane Proteins

We examined the patterns of cyclic AMP-dependent protein phosphorylation in membranes prepared from rat cortical synaptosomes following gel electrophoresis and autoradiography. We determined the optimum pH (6.2), time (20 s), Mg2+ concentration (10 mM) and cyclic AMP concentration (5 microM) for the reaction. We also found that the detergents Triton X-100 and gramicidin S enhanced cyclic AMP-dependent protein phosphorylation. Inhibitors of the Na+, K+ ATPase (ouabain, NaF, vanadate) enhanced protein phosphorylation. This effect occurred in the presence but not in the absence of detergent. The addition of purified bovine brain cyclic AMP-dependent protein kinase catalytic subunit enhanced membrane protein phosphorylation. The addition of homogeneous neural (bovine brain) and non-neural (bovine skeletal muscle) cyclic AMP-dependent protein kinase type II regulatory subunit partially inhibited protein phosphorylation. Both neural and non-neural regulatory subunits behaved similarly. In addition to cyclic AMP-dependent phosphorylation, the alpha-subunit of pyruvate dehydrogenase (Mr = 41,000) is phosphorylated in a cyclic AMP-independent fashion. We also examined the phosphorylation pattern of membranes prepared from rat heart and found that the number of acceptor substrates was much less than that from the nervous system.     

Nematicides and Nonconventional Soil Amendments in the Management of Root-Knot Nematode on Cotton

Granular and liquid commercial humates, with micronutrients, and a microbial fermentation product were compared in several combinations with nematicides for their effects on cotton lint yield and root-knot nematode suppression. Fumigant nematicides effectively reduced cotton root galling caused by root-knot nematodes, and cotton lint yields increased. Organophosphates and carbamates were not effective. Occasionally, cotton lint yields were increased or maintained with combination treatments o f humates, micronutrients, and a microbial fermentation product, but galling o f cotton roots by root-knot nematodes was usually not reduced by these treatments.     

Phospholipid-Sensitive Ca2+-Dependent Protein Kinase Preferentially Phosphorylates Serine-115 of Bovine Myelin Basic Protein

Phospholipid-sensitive Ca2+ -dependent protein kinase (PL-Ca-PK) and cyclic AMP-dependent protein kinase (A-PK) both preferentially phosphorylated serine residues of bovine myelin basic protein (MBP). Tryptic peptide maps of MBP phosphorylated by PL-Ca-PK or A-PK, however, revealed different phosphopeptides, suggesting a difference in the intramolecular substrate specificity for the two enzymes. Serine-115 of MBP, in the sequence (-Arg-Phe-Ser(115)-Trp-), was found to be a preferred and probably major phosphorylation site for PL-Ca-PK. Because serine-115 of bovine MBP corresponds to serine-113 of rabbit MBP, an in vivo phosphorylation site reported by Martenson et al. (1983), and PL-Ca-PK is present at a very high level in brain and myelin, it is suggested that the enzyme may be responsible for the in vivo phosphorylation of this and other sites in MBP.     

Properties and Regional Distribution of Pyruvate Dehydrogenase Kinase in Rat Brain

A method is described to measure directly in rat brain the activity of pyruvate dehydrogenase kinase (PDHa kinase; EC 2.7.1.99), which catalyzes the inactivation of pyruvate dehydrogenase complex (PDHC, EC 1.2.4.1, EC 2.3.1.12, and EC 1.6.4.3). The activity showed the expected dependence on added ATP and divalent cation, and the expected inhibition by dichloroacetate, pyruvate, and thiamin pyrophosphate. These results, and the properties of pyruvate dehydrogenase phosphate phosphatase (EC 3.1.3.43), indicate that the mechanisms of control of phosphorylation of PDHC seem qualitatively similar in brain to those in other tissues. Regionally, PDHa kinase is more active in cerebral cortex and hippocampus, and less active in hypothalamus, pons and medulla, and olfactory bulbs. Indeed, the PDHa kinase activity in olfactory bulbs is uniquely low, and is more sensitive to inhibition by pyruvate and dichloroacetate than that in the cerebral cortex. Thus, there are significant quantitative differences in the enzymatic apparatus for controlling PDHC activity in different parts of the brain.     

Structural features are as important as sequence homologies inDrosophila heat shock gene upstream regions

Summary Pelham has shown that theDrosophila hsp 70 gene is not transcribed under heat shock conditions unless a given upstream region is present. Davidson et al. have recently compiled a list of sequences homologous to this region in otherDrosophila heat shock genes. They proposed that a set of unlinked genes, such as the heat shock genes, could be coordinately induced through an interaction in cis with a common regulatory molecule. That this interaction involves structural elements is suggested by the fact that these upstream regions share inverted repeats as well as areas of Z-DNA potential. Furthermore, using the Calladine-Dickerson rules for local helical parameters, we show that these regions share structural homology. This is significant because the presence of regions homologous to a derived consensus sequence does not necessarily imply structural similarity. Therefore, we suggest that these structural features are at least as important as the sequence homologies in enabling the heat shock response.     

Phytase production byAspergillus ficuum on semisolid substrate

Summary Phytase production byAspergillus ficuum was studied using solid state cultivation on several cereal grains and legume seeds. The microbial phytase was used to hydrolyze the phytate in soybean meal and cotton seed meal. Wheat bran, soybean meal, cottonseed meal and corn meal supported good fungal growth and yielded a high level of phytase when an adequate amount of moisture was present. The level of phytase production on solid substrate was higher than that obtained by submerged liquid fermentation. Higher levels of phosphorus (more than 10 mg Pi/100 g substrate) in the growth medium (static culture) inhibited phytase synthesis, and the degree of phosphorus inhibition was less apparent in semisolid medium than in liquid medium. A static cultivation on semisolid substrate produced a higher level of phytase (2-20-fold) than that obtained by agitated cultivation. The minimal amount of water required for growth and enzyme production on those substrates was about 15%, while the optimum level for phytase production was between 25 and 35% and that for cell growth was above 50%. Optimum pH for phytase production was between 4 and 6.A ficuum grew well on raw (unheated) substrate containing a minimal amount of water and produced as much phytase as on heated substrate. About half of the phytic acid in soybean meal and cottonseed meal was hydrolyzed by treatment withA. ficuum phytase.     

用双相电泳技术分析棉酚对大鼠成熟精子蛋白质组成的影响

本文首次将双相电泳(等电聚焦和SDS电泳)技术应用于对棉酚作用机理的研究。实验结果表明,棉酚能够改变大鼠成熟精子的蛋白质组成;同时也证明,双相电泳这一技术对棉酚的研究是有效的。     

Patterns of protein synthesis during the germination of pea axes,and the effects of an interrupting desiccation period

As germination of axes of Pisum sativum L. seeds progressed, profound quantitative and qualitative changes occurred in the patterns of protein synthesis. This was shown by fluorography of gels following two-dimensional polyacrylamide gel electrophoresis separation of [³⁵S]methioninelabelled proteins. The effects of desiccation during germination on these in-vivo protein-synthesis patterns were followed. Desiccation differentially affected the synthesis of proteins. Usually, however, upon rehydration following desiccation the types of proteins being synthesized were recognizable as those synthesized earlier during imbibition of control, once-imbibed axes: seeds imbibed for 8 h, and then dried, did not recommence synthesis of proteins typical of 8-h-imbibed control seeds, but rather of 4-h-imbibed control seeds. Seeds imbibed for 12 h, and then dried and rehydrated, synthesized proteins typical of 4-h-and 8-h-control seeds. Thus drying of germinating pea axes caused the proteinsynthesizing mechanism to revert to producing proteins typical of earlier stages of imbibition. Drying during germination never caused the seed to revert to the metabolic status of the initial mature dry state, however.Abbreviation DR dried and rehydrated     

The reserve proteins in the cells of mature cotyledons ofLupinus albus var.Lucky

Summary The nuclear DNA content of cotyledonary cells of two lupin seeds (L₁ and L₂) with markedly different total protein content, were investigated by scanning cytophotometry. Both seeds had polyloid nuclei with DNA levels varying between 8 C and 64 C, the majority being either 16 C or 32 C. The highest DNA levels were found in the abaxial and central cotyledonary zones of both seeds; seed L₂ had a higher ploidy level than L₁. It is shown that the volume of condensed chromatin (chromocenters) increased proportionally with the DNA content of the nucleus. A comparison was made between the distribution of protein, previously determined byLe Gal andRey (1986) and the DNA throughout the cotyledon. The L₂ seed, which has the highest total protein and the highest protein content per cell, also exhibited the greatest DNA content per cell. For both seeds, the r-value for association of DNA and protein content per cell was highly significant (0.98).