Biomedical subjects

C A Hassett

Publications and source records attributed to C A Hassett.

8 recordsLinked to original sources

PubMed1998

Recovery of muscle transfers replacing the total plantar flexor muscle group in rats.

In rats, combinations of plantar flexor muscles representing approximately 20, 40, 60, and 80% of the mass of the total plantar flexor group were transferred orthotopically in the absence of synergistic muscles and allowed to recover for 120 days. We hypothesized that, compared with their individual control values for structural and functional variables, the transfers would display a hierarchical array of deficits, proportional to their initial mass and, consequently, inversely proportional to the relative load on the transfers. Surprisingly, compared with their individual control values, each muscle transfer displayed deficits of 30-40% in muscle mass, total fiber cross-sectional area, and maximum isometric force, with the exception of the smallest transfer, the plantaris (PLN) muscle, which recovered 100% of its control value for each of these variables. Therefore, except for the PLN transfer, the muscle transfers studied displayed deficits similar in magnitude to those reported for muscles transferred in the presence of synergistic muscles. The greater recovery of the PLN transfer was attributed to the relatively large requirement for force production imposed on this transfer due to the average force requirements of the total plantar flexor group.

Animals↗

PubMed1997

Functional deficits in medial gastrocnemius grafts in rats: relation to muscle metabolism and beta-AR regulation.

This study tested the hypothesis that alterations in the metabolic integrity of grafted muscle contribute to its diminished ability to sustain power. Compared with control muscles, muscles studied 120 days after the grafting procedure had lower specific force and sustained power. The sustained power protocol resulted in a depletion of muscle glycogen in control (83%) and grafted (85%) animals. Grafts had lower pre- and poststimulation glycogen, diminished citrate synthase activity, and greater hexokinase activity. No differences were observed in phosphofructokinase activity, glucose transporter GLUT-4 content, fiber type, beta-adrenergic-receptor (beta-AR) density, or binding affinity. Isoproterenol-stimulated adenylyl cyclase activity was lower in grafted vs. control muscle, suggesting an uncoupling of the beta-AR-effector complex. Thus the diminished ability of the grafted muscle to sustain power may be explained, in part, by a decrease in energy available from glycogen stores and/or a decrease in oxidative capacity.

Adenylyl Cyclases↗

PubMed1996

Properties of single motor units in medial gastrocnemius muscles of adult and old rats.

1. The purpose of this study was to determine the role of motor unit remodelling in the deficit that develops in the maximum isometric tetanic force (Fo) of whole medial gastrocnemius (MGN) muscles in old compared with adult rats. The Fo values and morphological data were determined for MGN muscles and eighty-two single motor units in muscles of adult (10-12 months) and sixty-two units in those of old (24-26 months) F344 rats. During an unfused tetanus, fast and slow (S) motor units were identified by the presence and absence of sag, respectively. Fast-fatigable (FF) and fast-fatigue-resistant (FR) units were classified by fatigue indices less than or greater than 0.50, respectively. 2. For old rats, whole MGN muscle Fo was 29% less than the value of 11.2 N measured for adult rats. The deficit in whole muscle Fo of old rats resulted from equivalent decreases in the number of motor units, 16% smaller than the adult value of ninety-seven, and in the mean motor unit Fo value, 14% less than the adult value of 117 mN. 3. With ageing, little motor unit remodelling occurred in FR units, whereas the S and FF motor units demonstrated dramatic, but opposing, changes. For S units, the number of units remained constant, but the number of fibres per motor unit increased 3-fold from 57 to 165. In contrast, the number of FF units decreased by 34% and the number of fibres per motor unit of the remaining units decreased to 86% of the adult value of 333. The age-related remodelling of motor units appeared to involve denervation of fast muscle fibres with reinnervation of denervated fibres by axonal sprouting from slow fibres.

Aging↗

PubMed1994

Recovery of medial gastrocnemius muscle grafts in rats: implications for the plantar flexor group.

Medial gastrocnemius (MGN) muscles were grafted in 18 rats and evaluated at 60, 90, and 120 days after the operation. Our purpose was to investigate the degree of recovery of the vascularized MGN grafts and the entire plantar flexor muscle group. Compared with control values, muscle mass and maximum force of MGN grafts were decreased by 33 and 38% at 60 days, 22 and 32% at 90 days, and 13 and 15% at 120 days. At 60 and 90 days, the deficits in maximum force for the entire plantar flexor muscle group, including the graft, were 29 and 17%, respectively. No difference was observed at 120 days. At 60 days, the deficit in the total mass of the plantar flexor group was 14% compared with control values, but by 90 days no deficit was observed. The restoration of normal plantar flexor group structure and function indicates that the degree of recovery attained by MGN grafts, although not complete, was sufficient to ensure that the performance of the total muscle group was not compromised.

Adaptation, Physiological↗

PubMed1990

Comparative study of survival of autologous adipose tissue taken and transplanted by different techniques.

In recent years, adipocytes obtained by suction-assisted lipectomy have been used for implantation by injection methods. This study is designed to assess the appearance of suctioned and excised adipose tissue and its survival after being injected or implanted into different tissues (0.5 cc into the rectus muscle and 0.5 cc into the dorsal ear skin) of New Zealand White rabbits. The results showed that significant numbers of adipocytes were ruptured after suction procedures. The intact cells represented approximately 10 percent of the fat cell population. Fat cells in aspirated and excised samples remained intact and did not differ histologically. After being injected into tissue, adipocytes appeared to survive better for a short term in a more vascularized bed (rectus muscle) than in a low vascular area (ear dermis). Long-term studies at 6- to 9-month intervals revealed transplanted adipose tissue, taken by suction or excision, being replaced with fibrosis, although cystic spaces and only a small number of surviving adipocytes were still present. Insulin did not show any protective effects on survival of the adipocytes during their transplantation.

Adipose Tissue↗

PubMed1989

Modified hematoxylin and eosin staining method for epoxy-embedded tissue sections.

A modified hematoxylin and eosin staining method for glutaraldehyde fixed, osmium tetroxide postfixed, and epoxy resin (Medcast Resin) embedded tissue is described. Two microns thick sections of human and animal tissues are treated with 4% H2O2 for 4 minutes, washed, dryed, and then flooded with Gill's III hematoxylin in a moist chamber at 37 degrees C for 90 minutes. Subsequent steps are: washing; bluing in ammonia water for 1 minutes; washing again and staining in 1% eosin Y alcoholic solution for 5 minutes; rinsing in 100% ethanol; drying and mounting with Permont. This procedure is quick, easy and successful in demonstrating both color scale and quality similar to hematoxylin and eosin stains obtained in standard paraffin sections.

Animals↗

PubMed1989

Regional differences in capillary density of the normal human dermis.

Quantitative study of the capillary density of normal dermis of 113 biopsy specimens taken from 20 body sites from 6 cadavers was carried out. Histologic quantification of dermal capillaries using the alkaline phosphatase method to delineate vascular endothelium and automated image analysis demonstrates statistically significantly greater capillary density in the head-face/neck region both in the papillary and reticular dermis than in the lower parts of the body. The smallest numbers of the dermal capillary density were noted in the calf and shin areas. These data support the hypothesis that random-pattern skin flaps can be safely raised longer in the face and neck than in other parts of the body.

Aged↗

PubMed1988

Endothelial cell crystalloids in newborn human foreskin.

This study describes the presence of crystalline inclusions in the endothelial cells of foreskins. They were found in 9 normal full-term newborn infants, without maternal medication or complication during pregnancy and delivery. These cytoplasmic crystalloids occurred in 10% of endothelial cells of small blood vessels. The diameter of the inclusions ranged from 0.3 to 1.5 micron and they appeared as round, oval, hexagonal or irregular polygonal in shape. These inclusions were surrounded by a triple membrane and their contents demonstrated granular, homogeneous and crystalloid-like material with a regular periodicity of dense and less dense layers measuring about 20-25 nm. Similar crystalloids in the endothelial cells were observed in the normal upper lip skin of a 6-week-old girl, although they were present in much smaller numbers than in foreskin. No endothelial inclusions were found in normal skin taken from 11 body areas in 29 patients aged 2.5 to 56 years. The nature and function of these cytoplasmic crystalloids are unknown.

Adolescent↗