Synthesis and in vitro bioactivity of C-terminal deleted analogs of human growth hormone-releasing factor

A series of C-terminal deleted analogs of human growth hormone-releasing factor (hGRF) with either an amidated or a free carboxylic acid C-terminus were synthesized by solid phase methodology. Their capacity to release growth hormone was tested on rat anterior pituitary cells in monolayer culture. A gradual decrease of bioactivity down to 23% relative to hGRF was noted when the C-terminal amino acids were deleted to hGRF (1-34)OH. Further deletions, however, did not decrease the bioactivity because the potencies of the fragments, hGRF(1-31)NH2, (1-30)NH2 and (1-29)NH2 remained at about 50% of that of hGRF. Continual deletion of residues to hGRF(1-23)NH2, (1-22)NH2 and (1-21)NH2 still yielded bioactive fragments with full intrinsic activity despite very low potency. Only with the deletion down to hGRF(1-19)NH2 did the bioactivity completely disappear. Thus, together with the data published in a previous paper (1), the minimal biologically active core of hGRF with full intrinsic activity comprises the fragment (3-21).     

New Family,Genus, and Species of Microsporida (Protozoa: Microsporida) from the Tropical Fire Ant,Solenopsis geminata (Fabricius) (Insecta: Formicidae)*

SYNOPSIS. A new species of Microsporida, Burenella dimorpha sp. n., representing a new family, Burenellidae fam. n. and genus, is described on the basis of light- and electron-microscope observations. The family is characterized by 2 sequences of sporogony, each sequence having morphologically different sporonts and spores. The parasite infects the tropical fire ant, Solenopsis geminata (Fabricius), producing distinct pathologic manifestations (clearing of the cuticle and eye malformation) and death in the pupal stage of development. Transmission of the infection per os to healthy S. geminata, to the Southern fire ant, Solenopsis xyloni McCook, and to the red and black imported fire ants, Solenopsis invicta Buren and Solenopsis richteri Forel, is reported.     

Characterization of L-threonine deaminase activity of guinea pig liver induced by a high protein diet

In a foregoing paper, we demonstrated that under equilibrated diet conditions, guinea pig liver L-threonine deaminase activity should be allocated to two distinct enzymes: a specific L-threonine deaminase without activity toward L-serine and a L-serine deaminase having a secondary activity toward L-threonine. In the present work, we observed that a high protidic diet caused an elevation of total threonine deaminase activity. Thus purification of guinea pig liver L-threonine deaminase was attempted, using ultracentrifugation, salt precipitation, heat treatment, ion exchange chromatography on DEAE Sephacel, Sephadex G 200 molecular sieve, 2 amino-2 methyl-1 propanol linked CH 4B Sepharose chromatography. The weak variations of the ratios of specific activities respectively toward L-threonine and L-serine observed at each stage of the purification procedure indicated that both activities are very likely supported by a single enzyme preexisting in the liver of guinea pigs fed an equilibrated diet. No isoenzyme was evidenced by polyacrylamide gel electrophoresis or DEAE Sephacel chromatography. Moreover, our purification procedure demonstrated that not only inducible L-threonine deaminase guinea pig liver activity was due to L-serine deaminase, but also that an initially existing specific L-threonine deaminase activity paradoxically disappeared with a protein rich diet.     

Effect of foliar‐applied potassium silicate on coffee leaf infection by Hemileia vastatrix

Coffee leaf rust, caused by Hemileia vastatrix, is the most devastating disease of coffee. Since limited information is available in the literature on silicon (Si) affecting plant diseases in coffee, this study was designed to investigate foliar application of potassium silicate (PS), a source of soluble (Si), on infection process of coffee leaf rust at the microscopic level. The foliar Si concentration for plants sprayed with water and PS has no significant difference (0.24 and 0.30 dag kg^?1, respectively). X‐ray microanalysis indicated that the deposition of Si on the leaves of the plants that were sprayed with PS was greater in comparison to the leaf samples from the plants sprayed with water. Rust severity on leaves of plants sprayed with water or sprayed with PS reached 44% and 32%, respectively, at 36 days after inoculation (dai). Plates of polymerised PS were observed on the leaf surfaces of the plants sprayed with the product, in contrast to its absence on the leaf surfaces of plants sprayed with water. At 36 dai, a greater number of uredia were observed on the leaf surfaces of plants sprayed with water in comparison to the leaf surfaces of plants sprayed with PS. On fractured leaf tissues that were sprayed with PS, less fungal colonisation was observed in comparison to the leaves of plants sprayed with water. In conclusion, the results of this study suggest that the effect of foliar‐applied Si on the control of the coffee leaf rust development may be attributed to the physical role of the polymerised PS, its osmotic effect against urediniospores germination, or both.     

Restriction fragment length polymorphism (RFLP) analysis of bovine nuclear protein genes

Summary We have recently cloned both the bovine protamine (Krawetz et al. 1987, DNA 6: 47–57) and high mobility group (HMG-1) cDNAs (Pentecost and Dixon 1984, Bioscience Reports 4: 49–57). They have been used as probes for Restriction Fragment Length Polymorphism analysis of male-female pairs of different species and breeds, within the genus Bos. Utilizing this approach we have studied inheritance, chromosomal location and gene copy number of the bovine protamine and HMG-1 genes. This revealed that these nuclear protein genes are highly conserved suggesting that selective pressure has maintained their gene structures during evolution. A polymorphic Taq 1 restriction fragment was identified that was shown to be a heritable marker. These genes are not sex-linked and are present in a single copy for protamine and at least two copies for the HMG-1.     

Possible Phytoplasma Disease in Papaya (Carica papaya L.) from Baja California Sur: Diagnosis by Scanning Electron Microscopy

The symptoms of possible phytoplasma infection in introduced and local varieties of papaya were first noted in the Mexican state of Baja California Sur (BCS) during field surveys in 2002–2003. Phytoplasma structures were observed using scanning electron microscopy (SEM) in phloem sieve elements in diseased papaya plants, but not in healthy plants. They were rounded structures 400–1600 nm in diameter. This is the first report of the possible association of phytoplasmas with diseased papaya plants in BCS. The use of SEM for the primary detection of disease aetiology is discussed.     

Seasonal and interannual variation in the energetic condition of adult male Atlantic sharpnose shark Rhizoprionodon terraenovae in the northern Gulf of Mexico

One hundred and thirty Atlantic sharpnose shark Rhizoprionodon terraenovae livers were collected from April 1999 to October 2001 from inshore waters of the Mississippi Sound to investigate seasonal and inter‐annual variation in their energetic condition. A decline in the hepato‐somatic index ( I _H) was observed from 1999 to 2001. In addition, I _H, liver specific energy content and total energy content were lowest during the summer and highest during the spring and autumn, while liver water content was highest during the summer and lowest during the spring and autumn.     

Egg surface structure in the annual fishes Simpsonichthys (subgenera Ophthalmolebias and Xenurolebias) and Nematolebias (Teleostei: Cyprinodontiformes: Rivulidae): variability and phylogenetic significance

The surfaces of the egg chorion of nine species of Simpsonichthys , two of Nematolebias and eight other species of rivulids were studied with scanning electron microscopy revealing details of ornamentation that were previously undocumented. Surface structures of eggs of Simpsonichthys of the subgenus Ophthalmolebias are described for the first time: eggs of Simpsonichthys constanciae , Simpsonichthys perpendicularis , Simpsonichthys rosaceus and Simpsonichthys suzarti are ornamented with a very characteristic palm-like structure, that is restricted to these species among the rivulids examined. The surface of the egg chorion of Simpsonichthys bokermanni lacks the well-developed palm-like structure, but has a characteristic conical projection, distinct from the structures of other rivulids examined, that is proposed as homologous to the palm-like structure. Simpsonichthys bokermanni shares with Nematolebias papilliferus and Nematolebias whitei the presence of concentric rows of spiny projections around the micropylar region. Species of Simpsonichthys of the subgenus Ophthalmolebias , Simpsonichthys myersi (of the subgenus Xenurolebias ), and N. whitei share the presence of large rounded protuberances on the surface of the egg chorion. The phylogenetic significance of these features are evaluated and discussed in light of current knowledge about rivulid relationships.