The size and quality of muscle specimens obtained by use of a percutaneous biopsy technique were studied. All biopsies were performed under local anesthesia, using an 11-gauge biopsy needle. The mean +/- SEM size of specimens obtained from 128 biopsies of the semitendinosus muscles of 16 Alaskan Huskies was 23.8 +/- 4.4 mg. All biopsy specimens were of sufficient quality to permit histochemical differentiation of the fiber types by use of myosin ATPase staining. An additional 8 biopsy specimens were obtained from 1 dog and analyzed for muscle glycogen content. These specimens contained 50.6 +/- 7.2 mmol of glucose/kg of muscle wet weight. This modified biopsy procedure was free of notable complications, and repeatable use produced specimens of adequate size and quality for histologic and biochemical analysis. It is concluded that this procedure is a safe and reliable alternative to open biopsy for diagnosis and management of neuromuscular, metabolic, and nutritional myopathies.

We examined the electromyographic activity of the costal portion of the diaphragm and the transverse abdominal and external oblique muscles in 6 chronically instrumented awake adult horses during eupneic breathing during 2 levels of hypercapnia (fractional concentration of inspired CO2; FICO2 = 0.4 and 0.6), and during 2 levels of hypocapnic hypoxia (FIO2 = 0.15 and 0.12). Using the inert gas technique, we also measured the end-expiratory lung volumes of the 6 horses during eupnea, 6% CO2 challenge, and 12% O2 breathing. During eupneic breathing, phasic electrical activity of these 3 muscles was always present and was preceded by the onset of mechanical flow. At progressive levels of hypercapnia, the magnitude of inspiratory and expiratory electrical activity increased, and for the expiratory muscles, this recruitment coincided with significant (P < 0.05) increases in peak expiratory gastric pressure. However, during hypocapnic hypoxia, differential recruitment patterns of the respiratory muscles were found. The electrical activity of the diaphragm increased in magnitude and occurred sooner relative to the onset of mechanical flow. The magnitude and onset of abdominal expiratory activity failed to increase significantly during these episodes of hyperpnea and this pattern of activity coincided with decrements in peak expiratory gastric pressure. Despite alterations in muscle recruitment patterns during these hyperpneic episodes, end-expiratory lung volume remained unchanged. Thus, we conclude that adult horses respond similarly to awake dogs during peripheral and central chemoreceptor stimulation.

Blood flow to the semitendinosus muscle was studied in 12 dogs after ligation of either the proximal or distal vascular pedicle and elevation of the muscle from its normal position. Using 25-micrometer-diameter radioactive microspheres, flow was measured at rest, h and 18 days after muscle elevation and pedicle ligation. Mean blood flow in the proximal region of the muscle 6 and 18 days after ligation of the caudal gluteal (proximal) pedicle was not significantly different from mean blood flow calculated in the middle and distal regions of the muscle. There was also no significant difference in mean blood flow among proximal, middle, and distal regions of the muscle, 6 and 18 days after ligation of the distal caudal femoral (distal) pedicle. There was significantly (P < 0.05) increased blood flow between group-A (ligation of caudal gluteal artery) and group-C (operated-control) muscles, 6 and 18 days after surgery. There was no loss of muscle fiber striations or nuclei, or presence of fibrous tissue that might have indicated ischemic necrosis in any of the experimental groups. These results indicate that the entire semitendinosus muscle can be sustained by the blood flow from either of its 2 vascular pedicles, which reinforces its potential as a muscle flap.

The degree and type of tissue reactivity and the absorption of a new suture material was determined by implantation within rat gluteal muscles. Amount and type of tissue inflammatory reaction was compared among the new suture material, polypropylene, and coated polyamide. Histologic evaluation of the tissues in which sutures were implanted indicated that the new suture material, polypropylene, and coated polyamide had similar amounts and types of reaction at 30 days or less after implantation, but differed after 30 days. The new suture material and polypropylene had an inflammatory reaction zone measuring less than 25% of the high-power field after 60 days, but the coated polyamide still induced reaction greater than 45% of the field at 90 days. At 60 and 90 days after implantation, the new suture material and polypropylene induced a mature fibrous reaction; the reaction to coated polyamide was either immature fibrous or granulomatous, depending on whether there was rupture of the suture coat. There was no observable absorption of the new suture material at 90 days. This study indicated that the new suture material is nonabsorbable and is minimally reactive in rat muscle. The tissue reactions induced by this suture material are similar to those of polypropylene and significantly less than those induced by coated polyamide after 30 days following implantation.