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W J Costello

Publications and source records attributed to W J Costello.

8 recordsLinked to original sources
PubMed1990

Performance of Hereford and two-breed rotational crosses of Hereford with Angus and Simmental cattle: II. Carcass traits of steers.

Calf carcass traits were evaluated for Simmental (S) x Hereford (H) and Angus (A) x H crosses in two-breed rotations and for straightbred H. Data were grouped into seven dam breed categories: straightbred Hereford (H), F1 S x H cows (SH), S x H cows of low percentage H (SHS), S x H cows of high percentage H (HSH), F1 A x H cows (AH), A x H cows of low percentage H (AHA) and A x H cows of high percentage H (HAH). Straightbred H and crossbred SH, AH, SHS and AHA cows were mated to H bulls, HSH cows were mated to S bulls and HAH cows were mated to A bulls. Calves from the S x H rotation produced heavier carcasses with less fat, lower quality grade, larger longissimus area and increased estimated cutability compared to A x H calves. Some significant intergenerational differences were observed within rotations, particularly within S x H. Calves from HSH cows mated to S bulls produced carcasses with less fat cover, lower quality grade, larger longissimus muscle area and higher estimated cutability compared to calves from SHS dams mated to H bulls. Within both rotations, evaluation of carcass weight per day of age indicated that postweaning ADG was lower for generations for which H was the sire breed. Carcass traits of calves from SHS, HSH, AHA and HAH dam breed groups from the last 3 yr of the study when calves were fed under two different postweaning management systems were evaluated in a separate analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1989

Giant fiber activation of flight muscles in Drosophila: asynchrony in latency of wing depressor fibers.

In Drosophila, brain stimulation of the giant fiber pathway brings about highly stereotyped electrical responses in target muscles involved in the escape response. Both the order of muscle response and the latency of that response are predictable in wild-type flies. The neuronal circuit to the targets is well defined and has been used in the analysis of a number of mutant phenotypes, including induced anomalies in temperature-sensitive (ts) mutations such as shibire (shi). It has been assumed that the stereotyped response includes simultaneous activation of all six fibers of the wing depressor muscle, DLM, resulting in equal latencies for all fibers. We report here a small, but distinct, inherent difference in latency between two sets of DLM fibers in a proportion of two wild-type strains as well as in a strain carrying the ts mutation shi. This difference may occur on one or both sides of an individual, is stable over time, and persists when the motor axon is stimulated peripherally. These results, due to the circuit leading to the target, suggest that the difference in latency arises peripherally. In flies reared at the shi permissive temperature (22 degrees C), the difference is more common in shi than in wild-type flies; however, in shi flies reared at 18 degrees C, the prevalence resembles that of wild-type flies. This indicates a subtle expression of the shi defect even at the presumed permissive temperature of 22 degrees C. The difference in latency is similar to that induced in shi flies whose development is affected by pupal heat pulse. Thus, correct interpretation of differences in latency, e.g., in shi/wild-type mosaic flies or in flies with mutations affecting the GF pathway, requires recognition of the inherent asynchrony that can occur between DLM fibers.

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PubMed1986

Development of an indirect flight muscle in a muscle-specific mutant of Drosophila melanogaster.

Stripe (sr) is a highly specific mutant affecting only one of the indirect flight muscles, the dorsal longitudinal muscle (DLM). In the homozygous condition the DLM is reduced in size. In the hemizygous condition (sr/Df(3)sr) no DLM is present in the adult, though all other thoracic muscles are present. In the early stages of pupation, DLM development in sr/Df(3)sr is no different from that in wild type. Adult myocytes collect around target larval muscles and fuse to form myotubes; myofilaments are synthesized. Subsequently (35-hr pupa) the DLM commences to degenerate, forming random clumps of vacuolated muscle tissue. Adjacent muscles are unaffected and develop normally. In the adult a neuroma-like mass of nerve tissue is maintained where the DLM would normally be located. In this mass many abnormal synapses (hemisynapses) are seen: presynaptic specializations occur in the absence of any postsynaptic structure. Small remnants (less than 16-microns diameter) of muscle tissue are sometimes found in the neuroma-like mass. Such remnants resemble slow muscle, not the normal fast type of DLM. These data suggest a possible muscle origin from primary and secondary myotubes. The DLM motor axons are present in the neuroma-like mass, persisting even with the virtual degeneration of their end target. Thus, motoneurons and presynaptic specializations can survive independently of postsynaptic targets.

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PubMed1986

Suppression of the membrane defect by divalent cations in the Drosophila mutant shibire.

The single-gene mutant shibire (shits) is temperature-sensitive. It causes reversible paralysis at heat pulses greater than 29 degrees C by blocking synaptic transmission. The synapses of these heat-pulsed flies are depleted in vesicles but contain numerous cisternae. We report that such alterations in synaptic physiology and morphology of heat-pulsed flies can be suppressed by internal perfusion of salines with high concentrations (10-18 mM) of the divalent cations Ca2+ or Mg2+. Synaptic morphology in these perfused flies remains normal even when exposed to nonpermissive temperatures (greater than 29 degrees C); in addition, synaptic transmission maintains a high resistance to failure both in frequency and stimulus duration. We also observed many cisternae in close association with extrajunctional as well as with postsynaptic regions of the sarcolemma in heat-pulsed shits flies not perfused with the increased concentrations of divalent cations. Flies perfused with increased amounts of divalent cations lacked such cisternae in the sarcolemma. The evidence suggests that the divalent cations can mitigate an overall membrane defect expressed by the shits gene, perhaps by influencing lipid-phase transition behavior.

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PubMed1978

Experimental transformation of muscle fiber properties in lobster.

Like the chelipeds, the claw closer muscles of the adult lobster are asymmetric (dipmorphic). In the crusher claw the closer muscle is composed entirely of slow fibers, and in the cutter claw it has 65 to 75 percent fast fibers and 25 to 35 percent slow fibers. While claw placement in the adult is essentially random, it can be demonstrated in two ways that the muscle fiber properties are not genetically fixed: (i) if one claw is removed in the fourth and early fifth stages, the remaining closer muscle develops all slow muscle fibers, and (ii) if the animals are raised in smooth-bottomed containers, both claws can become cutter types, having closer muscles with more than 50 percent fast fibers. Thus, as in vertebrate skeletal muscle, the properties of lobster closer muscle fibers can be transformed by various experimental manipulations.

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PubMed1977

Development of the dimorphic claw closer muscles of the lobster Homarus americanus: L Regional distribution of muscle fiber types in adults.

1. The closer muscles of the dimorphic claws (chelipeds) were studied for the presence and location of fast and slow muscle fibers. 2. Cutter claws were composed of about 60-70% short sarcomere (less than 4 mum) fast fibers; the remainder was longer sarcomere (greater than 6 mum) slow and intermediate (4-6 mum) fibers. 3. Crusher claws were composed of a uniform population of long sarcomere (6-13 mum) slow and intermediate (4-6 mum) fibers. 4. There was a regional distribution of fibers in the cutter claw. Ventral fibers were predominantly slow. Dorsal fibers and central medial fibers were fast. Proximal and distal fibers in the medial section were usually mixed. 5. The regional distribution of cutter fibers correlates with previous physiological studies on the distribution of the fast and slow motor axons to these muscle fibers.

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