Biomedical subjects
Publications and source records attributed to B R Pynn.
A case of traumatic mandibular fracture with associated unilateral anterior dislocation of the temporomandibular joint in a child is described. Although anterior dislocation is common, this combination of fracture and separate dislocation to our knowledge has not been reported in a young child. The unusual management required in this case is discussed.
Subcutaneous emphysema is an uncommonly reported complication of routine dentistry. Two cases are presented, one occurring during root canal therapy and the second during routine restorative dentistry. The etiology and consequences of this phenomenon are reviewed, and the prompt recognition and management of this condition are discussed.
In order to establish the relationship among intraoperative ischemia time, the recovery of contractile function, muscle fiber morphometry, and capillary geometry following free muscle transfer, 15 male dogs underwent unilateral, orthotopic free transfer of the left gracilis muscle with microneurovascular anastomosis. Intraoperative ischemia time varied from 0 to 4 hours. After a recovery period averaging 14 months, isometric contractile function was measured in the transfers and the contralateral, control muscles. Muscle fiber type composition, fiber size, and capillary geometry were quantified from histochemical sections. Transferred and control muscles had similar type I fiber percentages, type I fiber sizes, and capillary densities. Type II fiber sizes were reduced in transfers relative to controls. There was no significant effect of intraoperative ischemia on any morphometric variable. Although contractile function was generally reduced after free, vascularized transfer, there was only a weak correlation between the recovery of tetanic tension and type I fiber percentage (r = 0.53, P less than 0.05). It is concluded that free, vascularized muscle transfer results in minimal disturbance of muscle fiber type composition, fiber size, or capillary supply and that the diminished contractile function observed in this setting is still largely unexplained.
The purpose of this study was to document the recovery of isometric contractile function following tourniquet ischemia. Male Wistar rats (N = 27) were subjected to unilateral hindlimb tourniquet ischemia of 0 hr (control, N = 6), 1 hr (N = 5), 2 hr (N = 5), 3 hr (N = 5) and 4 hr (N = 3). Following a 2-week recovery period, isometric force measurements were made from both gastrocnemii of each rat with the contralateral limb acting as the control side. Each muscle was analyzed for maximal twitch (Pt, N/g), maximal rate of rise of twitch tension (DP/dt, N/sec), time to peak tension (TPT, msec), half relaxation time (RT 1/2, msec), maximal tetanus (P0, N/g, at 100 Hz), and fatigue (Burke Fatigue Protocol). Pt, P0, and DP/dt were significantly different from control values (P less than 0.05) for all hours of tourniquet ischemia. A strong negative correlation (P less than 0.001) was found for twitch (R = -0.84), tetanus (R = -0.78), and maximal rate of force development (R = -0.83) with respect to increasing hours of ischemia. The recovery of isometric twitch and tetanic function following tourniquet ischemia is inversely related to the ischemic interval. This study quantified the relationship between muscle ischemia and recovery of function following a 2-week interval and stresses the functional physiological changes which occur in skeletal muscle following tourniquet ischemia.
The purpose of this study was to determine whether there were differences in skeletal muscle properties in the hindlimb muscles of different types of dogs. Muscle samples were obtained from the gracilis, sartorius cranial head, sartorius caudal head and tibialis anterior muscles of mixed-breed and hound-type dogs and Beagles. Fiber type, fiber size and capillary morphometry determinations of each muscle from each dog were made from sections stained for myofibrillar ATPase activity. Individual animals were bilaterally symmetric for all measured variables. Fiber type, fiber size and capillary geometry varied between dogs of a given type and muscles within a given dog. There were no differences between dog types for fiber type or fiber size; significant variation in log(muscle)/log(body) mass ratios between dog types was observed for all muscles. The results indicate that for a given muscle, significant variation can occur in skeletal muscle characteristics between different types of dogs and that these differences can be independent of differences in exercise history.
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Isometric contractile function was studied after recovery in free, vascularized muscle transfer subjected to graded periods of intraoperative ischemia. Fifteen dogs had orthotopic replantation of their left gracilis muscles, with intraoperative ischemia times grouped as 0 (n = 3), 1 to 2 (n = 3), 2 to 3 (n = 4), or 3 to 4 (n = 5) hours. After recovery (mean 61.8 weeks), isometric twitch and tetanic tension and fatigue measurements were made in the replants and in the contralateral, control gracilis. On the average, replants were found to produce significantly less twitch (0.32 +/- 0.13 versus 0.49 +/- 0.24 N/g) and 75 Hz tetanic tension (2.2 +/- 0.9 versus 3.4 +/- 0.5 N/g) than controls. However, in several individual replants, 100% of control maximal tetanic tension was observed. Intraoperative ischemia time of up to 4 hours was not correlated with functional return. It is concluded that (1) full recovery is possible after free muscle transfer; (2) intraoperative ischemia, if less than 4 hours long, is not the primary determinant of functional recovery; and (3) factors besides intraoperative ischemia must be operative in producing the variability in recovery seen in this setting.
The fiber type, fiber size, and capillary geometric features were determined from the center of the proximal half of the left and right semitendinosus muscles in 5 mixed-breed dogs, 5 hound-type dogs, and 5 Beagles. There were no significant differences between the left and right muscles of each dog. Comparisons among the 3 groups of dogs revealed that the hound-type dogs had the largest fibers (type I and type II); however, the 3 groups were similar in their fiber-type percentages and their capillary geometric features.
A modified ATPase method for the simultaneous demonstration of capillaries and fiber types in skeletal muscle is presented. Muscle biopsies were obtained from mice, hamsters, rats, cats, and dogs, quick frozen, and sectioned at 8 microns in a cryostat. The frozen slides were fixed in a neutral formalin solution at 4 C for 5 min, and then incubated at 37 C for 1 hr in a medium containing ATP, Pb2+, and Ca2+ in a tris-maleate buffer (pH 7.2). Dilute (NH4)2S was used as a developer. To test the reliability of the proposed method, serial sections of each biopsy were stained separately for capillaries (amylase-PAS method) and for fiber types by a standard myosin ATPase (m-ATPase) method. Fiber type percent and capillary parameters were determined for each biopsy. No difference in results was observed for parameters determined using the modified ATPase method compared to the standard capillary and fiber type staining methods. This modified technique is therefore suitable for the simultaneous demonstration of capillaries and fiber types in skeletal muscle.
A modified isolated canine gracilis model of acute complete muscle ischemia was developed and then tested metabolically and histologically in 25 animals to assess its validity. In each dog, both gracili were isolated on their major vascular pedicles. One muscle underwent ischemia and reperfusion by placing and removing microvascular clips on the artery and vein. The other gracilis muscle was used as a control. Total muscle blood flow measurements, blood samples, and muscle biopsies were taken every other hour for up to 11 hr after preparation. The fiber-type profile of the gracilis was determined bilaterally using a myosin ATPase stain (n = 10). The results verified these hypotheses: after surgical preparation, the right and left muscles in the same dog are equivalent metabolically, after a 2-hr stabilization period, gracilis blood flow, oxygen and glucose uptake, lactate release, and tissue glycogen, lactate, phosphocreatine, and ATP levels remain within normal limits and unchanged for the next 9 hr, the surgical isolation of the gracilis muscle on a single vascular pedicle does not result in significant metabolic changes, in this model, a 2-hr ischemia is reversible, but a 7-hr ischemia results in irreversible ischemic injury. As well, fiber-type profile, muscle blood flow, and metabolic parameters can very significantly among animals supporting the necessity of a contralateral control. Therefore, this modified gracilis muscle model with its contralateral muscle as a control is suitable for acute skeletal muscle ischemia experiments of at least 9-hr duration.
A model for the study of neovascularization with a normal epigastric free flap set into an irradiated defect in the Fischer F344 rat is presented. In this model, both the administration of radiation and the flap transfer mimic the clinical situation. Significantly less tissue survives loss of the complete vascular pedicle at the second to fourth days following flap creation in rats with an irradiated bed. Later survival is not different from controls. Delayed neovascularization is proposed as the mechanism responsible for this effect during the period corresponding to the onset of the late phase of the response to skin radiation in rats. That neovascularization does occur, although delayed, suggests that the induced endarteritis may not be as important as previously suggested.
Electromagnetic flowprobe calibration must be done under controlled conditions similar to those encountered experimentally. This in situ calibration apparatus is simple in design, inexpensive, and provides pressure and flow conditions analogous to those found in small veins in vivo.