Regeneration of plants from long-term cultures of Oryza sativa L.

Root and embryo derived callus tissues of rice grown on sucrose alone as carbon source lost their ability to organise shoots by 75 and 100 days in culture respectively. Along with 2% sucrose, either 3% sorbitol or 3% mannitol was found to be necessary in the growth medium for the callus to regenerate whole plants over a period of 1400 days without any decline in the shoot forming ability. Our results indicated that incorporation of sorbitol or mannitol in the callus proliferating medium provides long-term totipotent rice cultures with a high frequency (50–60%) of shoot differentiation.     

Use of local electrostatic environments of cysteines to enhance formation of a desired species in a reversible disulfide exchange reaction

The role of electrostatic factors has been evaluated for the reversible disulfide exchange reaction between N-acetylcysteine (A) and a peptide fragment (B) comprising residues 85-114 of Kunitz soybean trypsin inhibitor. In A, the sulfhydryl group has a negative carboxyl neighbor on the cysteine itself. In B, the only charged group within five residues of the single cysteine at position 86 is the positive N-terminal amino group on residue 85. The concentrations of the monomers A and B and of the disulfides AA, AB and BB have been determined as a function of time in kinetic experiments at pH 7, 23 degrees C and ionic strengths of 20 mM and 1 M. At both ionic strengths the sulfhydryl acid dissociation constants Ka have been determined for A and B, as well as the four rate constants for the disulfide exchange reaction. The electrostatic effects are small in magnitude but occur in expected directions. Local cysteine environments enhance formation of the mixed disulfide (AB), having a favorable configuration of adjacent unlike charges and generate decreases in the AA and BB disulfides joining regions of identical charge. These experiments represent an initial step towards use of intrinsic protein functional groups to direct formation of specific disulfides in a synthetic protein.     

Partial purification and characterization of heat stable protein phosphatase inhibitor-2 from rabbit reticulocytes

Previous studies indicated that the species of type 1 and type 2 protein phosphatases (PP-1, PP-2) in rabbit reticulocytes are similar to those of rabbit skeletal muscle and rabbit liver. Reticulocyte PP-1 was found to be selectively inhibited by the heat stable protein phosphatase inhibitor-2 (I-2) from rabbit skeletal muscle. Of interest was the observation that muscle I-2 appeared to regulate protein synthesis in reticulocyte lysates by inhibiting an eIF-2 alpha phosphatase with type 1 properties. In this study we have characterized reticulocyte inhibitor-2 (I-2) and find that its properties are similar to those of skeletal muscle I-2. (i) Both I-2 species are stable to boiling and to acid treatment, and have similar chromatographic profiles on DEAE-cellulose and on Blue Sepharose CL-6B. (ii) The two I-2 species migrate electrophoretically as 26-28,000 dalton polypeptides in SDS-acrylamide gels. (iii) Both skeletal muscle I-2 and reticulocyte I-2 selectively inhibit isolated reticulocyte PP-1 and endogenous PP-1 in the lysate. (iv) Reticulocyte I-2 co-chromatographs with PP-1 on DEAE-cellulose, and over 90% of lysate I-2 can be isolated from this partially purified PP-1. (v) Both inhibitor-2 species are active in the unphosphorylated state, but upon addition to lysates, both are phosphorylated by endogenous cAMP-independent protein kinase(s). In addition a preliminary analysis using a polyclonal antibody against muscle inhibitor-1 confirmed biochemical analyses which indicate that lysates are deficient in inhibitor-1.     

Analyses of the splenic mRNA expressed by rabbits of different immunoglobulin kappa-light chain allotypes: conserved sequences in the 3' untranslated region and allotype-specific probes

The allelism of the structural genes for the complex rabbit b allotypes of immunoglobulin kappa-light chains has been questioned because of observations of unexpected phenotypic expression of "latent" allotypes. We find that the coding sequences of the b4 and b5 "alleles" are only 80% homologous for the last 60 nucleotides but there is a high degree of homology (96%) in the 3' untranslated region (3'DT). The high conservation of 3' DT region sequences enabled us to detect kappa-light chain mRNAs from rabbits of different genetic types (b4, b5, b9 and bbas) on northern blots and dot blots. We can distinguish mRNA encoding b9 and b5 allotypes on dot blots with b5 fragment-probes of known sequence and detect mRNA produced by unstimulated cultured splenic lymphocytes. Analyses of mRNA from cultured cells manipulated to enhance mRNA synthesis and production of unexpected or "latent" b allotypes can now be conducted.     

Stringent requirement for Ca2+ in the removal of Z-lines and alpha-actinin from isolated myofibrils by Ca2+-activated neutral proteinase

Treatment of isolated myofibrils with Ca2+-activated neutral proteinase (CANP) results in specific removal of Z-line and of alpha-actinin. To investigate the ionic requirement for these processes, we measured Z-line removal by phase-contrast and interference microscopy and alpha-actinin removal by sodium dodecyl sulphate/polyacrylamide-gel electrophoretic analysis of myofibrillar proteins. The proteolytic digestion of native purified proteins was measured directly on polyacrylamide gels and by the fluorescamine technique. We found that the removal of Z-line and alpha-actinin as well as the release of proteolytic degradation products from isolated myofibrils by CANP occur only in the presence of Ca2+; Sr2+, Ba2+, Mn2+, Mg2+, Co2+ and Zn2+ are all ineffective. In contrast with this stringent requirement for Ca2+, the proteolytic activity of CANP measured with denatured casein, native and denatured haemoglobin, native actin and tropomyosin also occurs in the presence of other bivalent cations, in the following order: Ca2+ greater than Sr2+ greater than Ba2+. These data suggest that only Ca2+ can produce the conformational change in myofibrils that renders them susceptible to the action of CANP, whereas its proteolytic activity is stimulated by several bivalent ions.     

Effect of prostaglandins on ornithine decarboxylase activity in the testis of immature rat

Intratesticular injection of prostaglandin E₂(PGE₂) and F_2α (PGF_2α) caused stimulation of ornithine decarboxylase (ODC) activity in the testis of immature rats. PGE₂ at a dose of 10 μg per testis was maximally effective 2 hours after the injection. Dibutyryl cyclic AMP (cAMP) and 1 methyl, 3-isobutyl xanthine (MIX), a phosphodiesterase inhibitor, also stimulated ODC activity. Simultaneous injection of PGE₂ and FSH or LH caused additional stimulation of ODC activity. Similarly injection of PGE₂ in addition to cAMP or MIX also caused increased stimulation of ODC. Indomethacin (IM, 60 μg/testis) inhibited LH, FSH or cAMP induced ODC activity. However, IM at the same dose inhibited the synthesis of total proteins. These results suggest that PGE₂ and PGF_2α stimulate the activity of ODC. The action of prostaglandins may be independent of the action of gonadotropic hormones. cAMP appears to mediate the action of prostaglandins in the testis of rat.     

Uptake of fertilizer nitrogen and soil nitrogen by rice using15N-labelled nitrogen fertilizer

Data from five field experiments using labelled nitrogen fertilizer were used to determine the relative effects of soil nitrogen and fertilizer nitrogen on rice yield. Yield of grain was closely correlated with total aboveground nitrogen uptake (soil+fertilizer), less closely correlated with soil nitrogen uptake and not significantly correlated with fertilizer nitrogen uptake. When yield increase rather than yield was correlated with fertilizer nitrogen uptake, the correlation coefficient was statistically significant.Contribution from the Laboratory for Flooded Soils and Sediments, Agronomy Dept., Louisiana Agri. Exper. Sta., Louisiana State Univ., Baton Rouge, LA 70803, and Univ. of Florida, Agricultural Research and Education Center, Sanford, FL 32771.     

Studies on groundnut hypocotyl exudates and the behaviour ofRhizoctonia solani in influencing the disease

Summary The behaviour ofRhizoctonia solani on the surface of groundnut seedling hypocotyls was studied at different stages of growth. Characteristic variation in the growth and production on infection cushions was observed. No infection cushions were observed as the seedling reaches the age of three weeks. Hypocotyl exudates were collected at various stages of growth and analysed for total phenols, carbohydrates and ninhydrin positive compounds. The exudates were also analysed for individual amino acids, sugars and organic acids. Gradual decline in the total quantities of various compounds was observed with age. Quantitative and qualitative change in the individual compounds was also evident and some of the compounds were not at all detected as age increases. The possible correlation between the exudation and behaviour of the fungus on host surface is discussed.     

Secretion granules of transplantable pancreatic acinar carcinoma of rat.

Secretion granules of the rat transplantable pancreatic acinar carcinoma and of normal rat pancreas were isolated by differential centrifugation. Analysis of the granule content by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and isoelectric focusing procedures combined with specific enzyme assays indicated essential qualitative similarities between normal and neoplastic secretory proteins, suggesting retention of enzymic differentiation in this pancreatic acinar carcinoma. Accordingly, this epithelial tumor should serve as an important model for examination of regulatory mechanisms in cell differentiation and neoplasia.     

Clinical experience in 1040 patients with double-velour knitted Dacron vascular prostheses: With particular reference to dilatation and aneurysm formation

Recent reports of dilatation and aneurysm formation in Dacron fabric grafts have prompted us to review our experience with 1040 patients who received Meadox-Cooley double-velour knitted grafts over a 47-month period. Bifurcation grafts were used in 398 patients with aorto-femoral occlusive disease and in 203 patients with aortoiliac occlusive disease. Straight tube grafts were implanted in 310 patients with abdominal aortic aneurysms. Small caliber straight tube grafts were used for femoral-femoral bypass in 112 patients. The remaining 17 patients received double-velour grafts for restoration of the renal (14) and superior mesenteric (3) artery circulation. In a review of patients, no dilatation or aneurysm formation was disclosed by clinical examination, sonography or aortography.