Characterization of third chromosome dominant alpha-methyl dopa resistant mutants (Tcr) and their interactions with l(2)amd alpha-methyl dopa hypersensitive alleles in Drosophila melanogaster

In Drosophila melanogaster two alleles at the Third chromosome resistance locus (Tcr; 3-39-6) were isolated in a screen of EMS mutagenized third chromosomes for dominant resistance to dietary alpha-methyl dopa, alpha-MD, a structural analogue of DOPA. Both alleles of Tcr are recessive lethals exhibiting partial complementation. Almost half (48.3%) of the Tcr40/Tcr45 heterozygotes die as embryos but some survive past adult eclosion. Both the embryonic lethal phenotype and the adult phenotype suggest that Tcr is involved in cuticle synthesis. Tcr mutants suppress the lethality of partially complementing alleles at the alpha-MD hypersensitive locus, l(2)amd. The viability of Tcr40/Tcr45, however, is not increased by the presence of a l(2)amd allele. The possibility that the Tcr and l(2)amd mutations reveal a catecholamine metabolic pathway involved in cuticle structure is discussed.     

Influence of blood parasites on the body mass of passeriform birds

Body masses of 3,739 birds representing immature and adult males and females of 15 species of passeriforms (both uninfected and infected with Haemoproteus spp. and Leucocytozoon spp.) were compared. There was some interaction among year, month and area of capture for several host species, but there was no discernible effect of either parasite genus on body mass. There were no effects due to high intensity parasitemia for eight host species examined. Either parasitism does not cause loss of body mass, or the techniques used were too insensitive to separate effects of parasitism from other natural causes.     

Standardized and simplified nomenclature for proteins common to all retroviruses.

We propose a revised standardized nomenclature for the proteins common to all retroviruses on the basis of biological function, enzymatic activity, and/or virion location data. (We do not discuss proteins specific for subfamilies or only some retroviruses.)     

Respiratory load compensation in neuromuscular disorders

First-breath ventilatory responses to graded elastic (delta E) and resistive (delta R) loads from 10 people with spinal muscular atrophy (SMA), 15 people with Duchenne muscular dystrophy (DMD), and 80 able-bodied people were compared. The SMA and DMD groups produced equal tidal volume, respiratory frequency, inspiratory duration (TI), expiratory duration, mean inspiratory airflow, and duty cycle responses to both delta E and delta R. Thus SMA (primarily a motoneuron disorder) and DMD (primarily a muscle disorder) have the same net effect on loaded breathing responses. The SMA and DMD groups failed to duplicate the normal group's short expirations during delta E, long inspirations during delta R, and thus, extended duty cycles during both delta E and delta R. The deficit in load compensation therefore was due to impaired regulation of respiratory timing (reflecting neural mechanisms) but not airflow defense (reflecting mechanical and neural mechanisms). One-fifth of the normal but none of the SMA or DMD subjects actively generated an "optimal" TI response (defined theoretically as TI greater than 160% control during large delta R and TI less than 75% control during large delta E). This lack of optimal responses, which is the same abnormality exhibited by quadriplegic people, suggests that SMA and DMD also impair human ability to discriminate between large delta R and delta E. These findings support the hypothesis that neuromuscular disorders can lead to disturbances in respiratory perception.     

Age and growth of tarpon,Megalops atlanticus,larvae in the eastern Gulf of Mexico,with notes on relative abundance and probable spawning areas

Synopsis Leptocephali were collected in June 1981 and July 1989 over the continental shelf and slope of the Florida west coast. Tarpon larvae ranged 5.5–24.4 mm standard length (SL) and were the second most abundant leptocephalus species. Sagittae examined with compound microscopes and scanning electron microscopy had increments that were presumed to be formed daily. Increment counts made using the two microscopic techniques were not significantly different. Estimated ages ranged 2–25 days with a growth rate (± standard error) of 0.92 ± 0.04 mm d^–1 The least squares linear regression equation SL = 2.78 + 0.92 (age in days) best described the relationship between estimated age and length. Adult tarpon appear to undergo a substantial spawning migration from inshore areas frequented during spring and summer to offshore spawning grounds. Spawning occurs during May, June, and July, although the spawning season may be of greater duration.     

Transgenic animals as a tool for studying the effect of the c-myc proto-oncogene on cardiac development

Transgenic animals provide a model system to elucidate the role of specific proteins in development. This model is now being used increasingly in the cardiovascular system to study cardiac growth and differentiation. During cardiac myocyte development a transition occurs from hyperplastic to hypertrophic growth. In the heart the switch from myocyte proliferation to terminal differentiation is synchronous with a decrease in c-myc mRNA abundance. To determine whether c-myc functions to regulate myocyte proliferation and/or differentiation, we examined the in vivo effect of increasing c-myc expression during fetal development and of preventing the decrease in c-myc mRNA expression that normally occurs during myocyte development. The model system used was a strain of transgenic mice exhibiting constitutive expression of c-myc mRNA in cardiac myocytes throughout development. Increased c-myc mRNA expression is associated with both atrial and ventricular enlargement in the transgenic mice. This increase in cardiac mass is secondary to myocyte hyperplasia, with the transgenic hearts containing greater than twice as many myocytes as nontransgenic hearts. The results of this study indicate that constitutive expression of c-myc mRNA in the heart during development results in enhanced hyperplastic growth, and suggest a regulatory role for the c-myc protooncogene in cardiac myogenesis.     

Actinomycin D induced DNase I hypersensitivity and asymmetric structure transmission in a DNA hexadecamer.

DNase I cleavage rates and nmr chemical shifts are shown to change for DNA sequences distal to an intercalated actinomycin D molecule in a duplex hexadecamer upon drug binding. Both sets of observations suggest that the source of these changes is a DNA-mediated structural response. The nmr results imply the response is transmitted preferentially in a 5'-to-3' direction from the drug binding site. An inequivalent response of the two strands to a ligand-induced conformational change immediately suggests a mechanism for distinguishing the sense and antisense strands of DNA.     

Secretion of biologically active leech hirudin from baculovirus-infected insect cells.

The thrombin inhibitor, hirudin, from the leech Hirudo Medicinalis, is the most powerful natural anticoagulant known. It has been characterized as a polypeptide of 65 amino acids which exhibits its anticoagulant properties by binding tightly and specifically to alpha-thrombin. The potency and specificity of hirudin have generated interest on its possible use in the treatment or prophylaxis of various thrombotic diseases. We have used the baculovirus expression system to efficiently produce active hirudins in insect cells. The Autographa californica nuclear polyhedrosis virus has proved useful as a helper-independent viral expression vector for high-level production of recombinant proteins in cultured insect cells. Hirudin variants (HV1 and HV2) were produced in infected insect cells as secreted proteins by joining their coding sequences to the leader peptide sequence of the vescicular stomatitis virus G protein. The recombinant products were biologically active and, interestingly, N-terminal sequencing of HV1 revealed that the heterologous leader peptide is correctly removed.     

Morphometry of feline neutrophil granule genesis

During neutrophil granule genesis, the formation of primary granules is generally thought to be limited to the promyelocyte stage; whereas synthesis of secondary granules is thought to occur only at the myelocyte stage. This hypothesis was tested morphometrically in feline neutrophils that are known to contain both granule types. Marrow specimens obtained from six cats were stained with peroxidase for identification of neutrophil primary granules and counterstained with periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) for identification of secondary granules. By regression analysis using arithmetic models, numbers of cytoplasmic granules in 311 cells were correlated with the degree of nuclear chromatin condensation, which was shown to be an adequate parameter for cell maturation. Promyelocytes and myelocytes had similar mean numbers of peroxidase-positive granules per unit area. A significant increase (p less than or equal to 0.0001) in the numbers of peroxidase-positive granules was noted between the metamyelocyte and the mature neutrophil stage, despite the lack of peroxidase activity in endoplasmic reticulum and Golgi lamellae. By contrast, a significant increase of peroxidase-negative granules between the metamyelocyte and the mature neutrophil stage was not clearly established with these methods. The increase in peroxidase-positive granules may indicate continued production of peroxidase-containing granules and/or redistribution of peroxidase among lysosomal organelles in late feline neutrophils.