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Biomedical subjects

Vincent J Caiozzo

Publications and source records attributed to Vincent J Caiozzo.

24 records · Page 2Linked to original sources
PubMed2002

Effects of distraction on muscle length: mechanisms involved in sarcomerogenesis.

Although a great deal of interest has been given to understanding the mechanisms involved in regulating the radial growth that occurs because of resistance training, much less has been given to studying the longitudinal growth of skeletal muscle that occurs because of passive stretch. The current authors provide a brief overview of key issues relevant to the longitudinal growth of skeletal muscle that occurs during distraction osteogenesis. Specifically, five key issues are addressed: (1) the pattern of sarcomerogenesis during distraction; (2) sarcomerogenesis and altered expression of sarcomeric and nonsarcomeric genes; (3) the satellite cell hypothesis; (4) mitogenic factors; and (5) new approaches for studying the longitudinal growth of skeletal muscle. A discussion is provided that revolves around the concept of a negative feedback loop. One of the most interesting issues to be resolved in muscle biology is the role of satellite cells in regulating the growth of skeletal muscle. Currently, it is not known whether satellite cell activation is a prerequisite for the longitudinal growth of skeletal muscle. Gene chip analyses provide a paradoxical view, showing that distraction osteogenesis results in the upregulation of a gene, GADD45, involved with growth arrest and deoxyribonucleic acid destruction.

Animals↗
PubMed2002

Cellular and molecular responses to increased skeletal muscle loading after irradiation.

Irradiation of rat skeletal muscles before increased loading has been shown to prevent compensatory hypertrophy for periods of up to 4 wk, possibly by preventing satellite cells from proliferating and providing new myonuclei. Recent work suggested that stem cell populations exist that might allow irradiated muscles to eventually hypertrophy over time. We report that irradiation essentially prevented hypertrophy in rat muscles subjected to 3 mo of functional overload (OL-Ir). The time course and magnitude of changes in cellular and molecular markers of anabolic and myogenic responses were similar in the OL-Ir and the contralateral nonirradiated, overloaded (OL) muscles for the first 3-7 days. These markers then returned to control levels in OL-Ir muscles while remaining elevated in OL muscles. The number of myonuclei and amount of DNA were increased markedly in OL but not OL-Ir muscles. Thus it appears that stem cells were not added to the irradiated muscles in this time period. These data are consistent with the theory that the addition of new myonuclei may be required for compensatory hypertrophy in the rat.

Adaptation, Physiological↗
PubMed2002

Mechanical properties of rat soleus after long-term spinal cord transection.

The effects of a complete spinal cord transection (ST) on the mechanical properties of the rat soleus were assessed 3 and 6 mo post-ST and compared with age-matched controls. Maximal tetanic force was reduced by approximately 44 and approximately 25% at 3 and 6 mo post-ST, respectively. Similarly, maximum twitch force was reduced by approximately 29% in 3-mo and approximately 17% in 6-mo ST rats. ST resulted in faster twitch properties as evidenced by shorter time to peak tension (approximately 45%) and half-relaxation time (approximately 55%) at both time points. Maximum shortening velocity was significantly increased in ST rats whether measured by extrapolation from the force-velocity curve (approximately twofold at both time points) or by slack-test measurements (over twofold at both time points). A significant reduction in fatigue resistance of the soleus was observed at 3 (approximately 25%) and 6 mo (approximately 45%) post-ST. For the majority of the speed-related properties, no significant differences were detected between 3- and 6-mo ST rats. However, the fatigue resistance of the soleus was significantly lower in 6- vs. 3-mo ST rats. These data suggest that, between 3 and 6 mo post-ST, force-related properties tended to recover, speed-related properties plateaued, and fatigue-related properties continued to decline. Thus some specific functional properties of the rat soleus related to contractile force, speed, and fatigue adapted independently after ST.

Animals↗
PubMed2002

Altered diaphragm contractile properties with controlled mechanical ventilation.

This study shows that, over time, diaphragm inactivity with controlled mechanical ventilation (CMV) decreases diaphragm force and produces myofibril damage contributing to the reduced force. We measured in vivo and in vitro diaphragm contractile and morphological properties in 30 sedated rabbits grouped (n = 6) as follows: 1 or 3 days of CMV, 1 or 3 days of 0 cmH(2)O continuous positive airway pressure, and control. The CMV rate was set sufficient to suppress diaphragm electrical activity. Compared with the control group, phrenic-stimulated maximum transdiaphragmatic pressure did not decrease with continuous positive airway pressure but decreased to 63% after 1 day of CMV and to 49% after 3 days of CMV. The in vitro tetanic force decreased to 86% after 1 day of CMV and to 44% after 3 days of CMV. After 3 days of CMV, significant myofibril damage occurred in the diaphragm but not in the soleus. The decrease in tetanic force correlated with the volume density of abnormal myofibrils. We conclude that CMV had a detrimental effect on diaphragm contractile properties.

Anatomy, Cross-Sectional↗
PubMedDate not supplied

Myosin isoform expression and MAFbx mRNA levels in hibernating golden-mantled ground squirrels (Spermophilus lateralis).

Hibernating mammals present many unexplored opportunities for the study of muscle biology. The hindlimb muscles of a small rodent hibernator (Spermophilus lateralis) atrophy slightly during months of torpor, representing a reduction in the disuse atrophy commonly seen in other mammalian models. How torpor affects contractile protein expression is unclear; therefore, we examined the myosin heavy-chain (MHC) isoform profile of ground squirrel skeletal muscle before and after hibernation. Immunoblotting was performed first to identify the MHC isoforms expressed in this species. Relative percentages of MHC isoforms in individual muscles were then measured using SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). The soleus and diaphragm did not display differences in isoforms following hibernation, but we found minor fast-to-slow isoform shifts in MHC protein in the gastrocnemius and plantaris. These subtle changes are contrary to those predicted by other models of inactivity but may reflect the requirement for shivering thermogenesis during arousals from torpor. We also measured mRNA expression of the Muscle Atrophy F-box (MAFbx), a ubiquitin ligase important in proteasome-mediated proteolysis. Expression was elevated in the hibernating gastrocnemius and the plantaris but was not associated with atrophy. Skeletal muscle from hibernators displays unusual plasticity, which may be a combined result of the intense activity during arousals and the reduction of metabolism during torpor.

Animals↗