Myosin light-chain expression during avian muscle development

Monoclonal antibodies to adult chicken myosin light chains were generated and used to quantitate the types of myosin light-chain (MLC) isoforms expressed during development of the pectoralis major (PM), anterior latissimus dorsi (ALD), and medial adductor (MA) muscles of the chicken. These are muscles which, in the adult, are composed predominantly of fast, slow, and a mixture of fiber types, respectively. Three distinct phases of MLC expression characterized the development of the PM and MA muscles. The first identifiable pase occurred during the period of 5-7 d of incubation in ovo. Extracts of muscles from the pectoral region (which included the presumptive PM muscle) contained only fast MLC isoforms. This period of exclusive fast light-chain synthesis was followed by a phase (8- 12 d of incubation in ovo) in which coexpression of both fast and slow MLC isoforms was apparent in both PM and MA muscles. During the period, the composition of both fast and slow MLC isoforms in the PM and MA muscles was identical. Beginning at day 12 in ovo, the ALD was also subjected to immunochemical analyses. The proportion of fast and slow MLCs in this muscle at day 12 was similar to that present in the other muscles studied. The third development phase of MLC expression began at approximately 12 d of incubation in ovo and encompassed the transition in MLC composition to the isoform patterns incubation in ovo and encompassed the transition in MLC composition to the isoform patterns typical of adult muscle. During this period, the relative proportion of slow MLC rose in both the MA and ALD and fell in the PM. By day 16, the third fast light chain, LC(3f), was apparent in extracts of both the PM and MA. These results show that there is a developmental progression in the expression of MLC in the two avian muscles studied from day 5 in ovo; first, only fast MLCs are accumulated, then both fast and slow MLC isoforms are expressed. Only during the latter third of development in ovo is the final MLC isoform pattern characteristic of a particular muscle type expressed.     

Effects of biuret content in urea and nitrogen source on the yield and composition of potato tubers

Summary Pot and field experiments were conducted at Simla and Daurala to investigate the effect of biuret content of urea and N source on the yield and composition of potato tubers. Soil application of urea containing biuret upto 1.0 per cent did not affect the yield. However, in foliar application of urea detrimental effect of biuret was recorded even at 0.5 per cent. In foliar application of urea, the removal of N, P, and K by tubers was reduced with increasing levels of biuret. In slightly acidic soil of Simla, performance of calcium ammonium nitrate and urea was at par with respect to potato yield, whereas in alkaline soil of Daurala, urea was comparatively inferior. In both soil types, the apparent recovery of N by tubers was higher with calcium ammonium nitrate than with urea. The efficaciousness of urea was increased by applying half of its dose to soil at planting and the other half as foliar sprays.     

Role of a pertussis toxin substrate in the control of lectin-induced cap formation in human neutrophils.

We have examined the role of GTP-binding proteins and the associated cyclic AMP- and calcium-related transduction mechanisms in the regulation of capping in human neutrophils. Pertussis toxin (PT), a probe for the GTP-binding protein Ni, abolished capping induced by fluorescein isothiocyanate-conjugated concanavalin A (Con-A), whereas cholera toxin, a probe for the GTP-binding protein Ns, was without effect. Consistent with the latter finding, ligands acting at receptors associated with the Ns protein, namely the prostaglandin E1 and beta-adrenergic agonists, were without effect on the capping reaction. The possible role of mobilization of internal calcium was evaluated by using Quin2-loaded cells. Calcium mobilization was observed at concentrations of Con-A which yielded optimal capping (10 micrograms/ml). Treatment with PT, phorbol myristrate acetate or 8-(NN-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) abolished both calcium mobilization and capping. Colchicine, which substantially enhanced capping, had no effect on calcium mobilization. At concentrations of the lectin above those required for capping, superoxide generation and enzyme release were noted. These reactions were less susceptible to inhibition by PT, effects being observed only on the Kact. for Con-A-mediated superoxide generation with little effect on the Vmax. The degree of PT-mediated inhibition for enzyme release with Con-A was much lower than that observed with fMet-Leu-Phe. Our results imply that a step involving Ni-mediated calcium mobilization, sensitive to phorbol myristate acetate, is essential to the regulation of capping; a distinct mechanism may be involved in colchicine-mediated enhancement of capping; and Ni may play a relative minor role in the regulation of lectin-mediated exocytosis.     

A step sensitive to pertussis toxin and phorbol ester in human neutrophils regulates chemotaxis and capping but not phagocytosis

Treatment of human neutrophils with pertussis toxin (PT) abolishes chemotaxis in response to either platelet-activating factor (PAF) or f-Met-Leu-Phe (FMLP), and capping induced via the concanavalin A (Con A) receptor. These functional effects are accompanied by the inhibition of calcium mobilization by PAF, FMLP and Con A. The agent phorbol 12-myristate-13-acetate (PMA) also inhibits chemotaxis and capping as well as calcium mobilization by these receptors. In sharp contrast, neither PT, cholera toxin (CT), nor PMA, inhibits the phagocytosis of non-opsonized and opsonized Candida albicans, sheep erythrocytes or fluorescent latex beads. Our results suggest that receptor-initiated chemotaxis and capping involve a step that is sensitive to PT and PMA, and that phagocytosis is not regulated in a similar fashion.     

Genetic basis of resistance to zonate leaf spot disease in forage sorghum

Summary Generation mean analysis was carried out for ten crosses between two resistant and two susceptible parents to find the genetic basic of resistance to zonate leaf spot disease in forage sorghum. In all crosses except one, at least one type of non-allelic interaction was present. Both additive and dominance gene effects were significant for most crosses. Duplicate type epistasis was present for the inheritance of this disease. Resistance to this disease revealed overdominance. Appropriate breeding plans were suggested to exploit the disease resistance.     

A comparative kinetic study of bovine calmodulin-dependent cyclic nucleotide phosphodiesterase isozymes utilizing cAMP, cGMP and their 2'-O-anthraniloyl-,2'-O-(N-methylanthraniloyl)-derivatives as substrates

Calmodulin-dependent 3',5'-cyclic nucleotide phosphodiesterase (EC 3.1.4.17) Mr 63,000 and Mr 60,000 from the brain as well as Mr approximately 59,000 species from the heart, have been compared with respect to their steady-state kinetic parameters for the hydrolysis of cAMP, cGMP and their 2'-O-anthraniloyl- and 2'-O-(N-methylanthraniloyl)-derivatives. Kinetic studies with the native substrates indicate high Mr brain enzyme to be cGMP specific whereas low Mr brain and heart enzymes to be nonspecific. In addition, the isozymes studied here appear to be kinetically distinct from those previously isolated form bovine brain tissues. Substitution at 2'-O-position of the cyclic nucleotides gave rise to Vmax values ranging 1-11% of those observed with the native substrates, with minimal effect on Km. The isozymes with exception of heart isoform gave higher Km and Vmax with the anthraniloyl derivatives. This effect is thought to be related to the formation of an intramolecular hydrogen bond which leads to decreased electrostatic interactions between the active-site side chains and the pseudo-substrates.     

The Mitochondrial Genomes of the Nudibranch Mollusks,Melibe leonina and Tritonia diomedea,and Their Impact on Gastropod Phylogeny

The phylogenetic relationships among certain groups of gastropods have remained unresolved in recent studies, especially in the diverse subclass Opisthobranchia, where nudibranchs have been poorly represented. Here we present the complete mitochondrial genomes of Melibe leonina and Tritonia diomedea (more recently named T. tetraquetra), two nudibranchs from the unrepresented Cladobranchia group, and report on the resulting phylogenetic analyses. Both genomes coded for the typical thirteen protein-coding genes, twenty-two transfer RNAs, and two ribosomal RNAs seen in other species. The twelve-nucleotide deletion previously reported for the cytochrome oxidase 1 gene in several other Melibe species was further clarified as three separate deletion events. These deletions were not present in any opisthobranchs examined in our study, including the newly sequenced M. leonina or T. diomedea, suggesting that these previously reported deletions may represent more recently divergent taxa. Analysis of the secondary structures for all twenty-two tRNAs of both M. leonina and T. diomedea indicated truncated d arms for the two serine tRNAs, as seen in some other heterobranchs. In addition, the serine 1 tRNA in T. diomedea contained an anticodon not yet reported in any other gastropod. For phylogenetic analysis, we used the thirteen protein-coding genes from the mitochondrial genomes of M. leonina, T. diomedea, and seventy-one other gastropods. Phylogenetic analyses were performed for both the class Gastropoda and the subclass Opisthobranchia. Both Bayesian and maximum likelihood analyses resulted in similar tree topologies. In the Opisthobranchia, the five orders represented in our study were monophyletic (Anaspidea, Cephalaspidea, Notaspidea, Nudibranchia, Sacoglossa). In Gastropoda, two of the three traditional subclasses, Opisthobranchia and Pulmonata, were not monophyletic. In contrast, four of the more recently named gastropod clades (Vetigastropoda, Neritimorpha, Caenogastropoda, and Heterobranchia) were all monophyletic, and thus appear to be better classifications for this diverse group.     

A discrete class of intergenic DNA dictates meiotic DNA break hotspots in fission yeast

Meiotic recombination is initiated by DNA double-strand breaks (DSBs) made by Spo11 (Rec12 in fission yeast), which becomes covalently linked to the DSB ends. Like recombination events, DSBs occur at hotspots in the genome, but the genetic factors responsible for most hotspots have remained elusive. Here we describe in fission yeast the genome-wide distribution of meiosis-specific Rec12-DNA linkages, which closely parallel DSBs measured by conventional Southern blot hybridization. Prominent DSB hotspots are located ~65 kb apart, separated by intervals with little or no detectable breakage. Most hotspots lie within exceptionally large intergenic regions. Thus, the chromosomal architecture responsible for hotspots in fission yeast is markedly different from that of budding yeast, in which DSB hotspots are much more closely spaced and, in many regions of the genome, occur at each promoter. Our analysis in fission yeast reveals a clearly identifiable chromosomal feature that can predict the majority of recombination hotspots across a whole genome and provides a basis for searching for the chromosomal features that dictate hotspots of meiotic recombination in other organisms, including humans.