Cerebral haemodynamic and electrocortical CO2 reactivity in pigs anaesthetized with fentanyl,nitrous oxide and pancuronium

Cerebral haemodynamic, metabolic and electrocortical reactivity to alterations in arterial CO₂, tension (PaCO₂) was assessed in seven mechanically ventilated juvenile pigs to test an experimental model designed for cerebral pharmacodynamic and pharmacokinetic studies. The animals were anaesthetized with fentanyl, nitrous oxide and pancuronium and sequentially normo- and hyperventilated over a 100-min period. Five measurements were made at 25-min intervals. The cerebral blood flow (CBF) was measured with the intraarterial ¹³³Xe technique and the cerebral metabolic rate for oxygen (CMRo₂) determined from CBF and the cerebral arteriovenous oxygen content difference. A linear correlation (r = 0.845) was found between CBF and PaCO₂. The cerebrovascular reactivity to hypocapnia (ΔCBF/ΔPaCO₂) was maintained throughout the experimental period and amounted to (95% confidence interval) 9.1 (7.1–11.1) ml · 100 g^-1 · min^-1 · kPa^-1 within the PaCO₂ range 3.3–6.3 kPa. The CMRo₂ was not influenced by hyperventilation. The baseline electroencephalographic (EEG) pattern was stable at normocapnia (mean PaCO₂ 5.6 kPa), whereas spectral values for delta and total average voltage increased significantly (P<0.05) at extensive hypocapnia (3.5 kPa). Maintenance of cerebral CO₂ reactivity and spectral EEG voltage at a stable plasma level of fentanyl is complementary to the cerebral haemodynamic and metabolic stability previously found at sustained normocapnia in this model.     

Hyperbaric oxygen reduces edema and necrosis of skeletal muscle in compartment syndromes associated with hemorrhagic hypotension

This study examined the effect of exposures to hyperbaric oxygen on the development of the edema and necrosis of muscle that are associated with compartment syndromes that are complicated by hemorrhagic hypotension. A compartment syndrome (twenty millimeters of mercury for six hours) was induced by infusion of autologous plasma in the anterolateral compartment of the left hind limb of seven anesthetized dogs while the mean arterial blood pressure was maintained at sixty-five millimeters of mercury after 30 per cent loss of blood volume. These dogs were treated with hyperbaric oxygen (two atmospheres of pure oxygen) and were compared with six dogs that had an identical compartment syndrome and hypotensive condition but were not exposed to hyperbaric oxygen. Forty-eight hours later, edema was quantified by measuring the weights of the muscles (the pressurized muscle compared with the contralateral muscle), and necrosis of muscle was evaluated by measuring the uptake of technetium-99m stannous pyrophosphate. The ratio for edema was significantly (p = 0.01) greater in dogs that had not been exposed to hyperbaric oxygen (1.15 +/- 0.01) than in the dogs that had been treated with hyperbaric oxygen (1.01 +/- 0.03), and the ratio for necrosis of muscle was also significantly (p = 0.04) greater in dogs that had not had hyperbaric oxygen (1.96 +/- 0.41) than in those that had been treated with hyperbaric oxygen (1.05 +/- 0.11). Comparisons were also made with the muscles of four normal control dogs and separately with the muscles of six normotensive dogs that had an identical compartment syndrome and normal blood pressure and were not treated with hyperbaric oxygen.(ABSTRACT TRUNCATED AT 250 WORDS)     

New experimental procedures to evaluate the biomechanical properties of healing canine medial collateral ligaments

Both clinical and animal studies have indicated that early mobilization and exercise may improve the healing of injured medial collateral ligaments (MCLs). To investigate these effects, transected canine MCLs were subjected to three different treatment regimens: (a) no surgical repair with 6 weeks mobilization; (b) surgical repair with 3 weeks immobilization followed by 3 weeks remobilization; and (c) surgical repair with 6 weeks immobilization. After sacrifice, knee laxity was measured in a newly designed varus-valgus (V-V) laxity device. Each knee was tested subsequently in tension to determine the structural properties of the femur-MCL-tibia complex (FMTC) and the mechanical properties of the healing MCL substance. It was found that the V-V laxity increased for all experimental knees, but that early mobilization enhanced joint stability. The structural properties of the FMTC and the mechanical properties of the MCL substance were also lower than the contralateral controls. Again, the early mobilization groups had better results.     

NCAM expression by subsets of taste cells is dependent upon innervation

The expression of the neural cell adhesion molecule (NCAM) and distinct carbohydrate groups by cells of the taste buds of the rat vallate papilla was investigated by immunohistochemical and biochemical techniques. We employed antibodies against (1) the extracellular (mAb 3F4) and cytoplasmic (mAb 5B8) portions of the NCAM polypeptide, (2) the highly sialylated form of NCAM (mAb 5A5), (3) carbohydrate epitopes associated with glycosylated NCAM forms in the rat (mAb 2B8) or frog (mAb 9-OE) olfactory system, and also (4) the Lewis^b blood group carbohydrate epitope (mAb CO431). NCAM mRNA was demonstrated by polymerase chain reaction (PCR) in samples of the vallate papilla, suggesting the presence of NCAM in cells of the taste buds. Antibodies against NCAM (mAbs 3F4 and 5B8) recognized a subset (about 20%) of cells within the vallate taste buds; fibers of the glossopharyngeal nerve, including those innervating the gustatory epithelium, were NCAM immunoreactive. Taste bud cells did not express polysialic acid (mAb 5A5), but mAb 5A5 immunoreactivity was observed on fibers of the IXth nerve, including a few that entered the taste buds. All or nearly all of the cells within the vallate taste buds were immunoreactive to mAb 2B8, whereas mAbs 9-OE and CO431 reacted with subsets of cells. The carbohydrates recognized by mAbs 2B8 and 9-OE were also abundantly expressed in the ducts and acini of the lingual salivary glands. Bilateral crush of the IXth nerve resulted in the loss of expression of all of these molecules from the gustatory epithelium. If cells of the taste bud express NCAM during their final stage(s) of differentiation, then NCAM could play a role(s) in the growth of gustatory axons toward their target epithelial cells and in the recognition between the nerve fibers and mature taste receptor cells, or among the taste bud cells themselves. © 1993 Wiley-Liss, Inc.     

Spasticity and contracture. Physiologic aspects of formation

Disruption of the upper motor neuron inhibitory pathways by stroke, brain trauma, or spinal cord injury leads to muscle spasticity. Spasticity is characterized by increased muscle tone, hyperactive reflexes, and possible clonus or rigidity. The increased muscle tone may result in loss of joint motion, leading to contractures. Treatment of established contractures is difficult. Prevention of contractures by joint mobilization is emphasized as a goal in the management of patients with spasticity.     

A new antigen common to the rat nervous and immune systems: II. Molecular characterization

G5-IgG is a monoclonal antibody that binds specifically to some cells and tissues of the adult rat nervous and immune systems. The molecular nature of the G5 antigen from adult rat brain is described in this paper. G5 antigen in adult rat brain membrane fractions was trypsin-sensitive and heat-labile but not chloroform/methanol-soluble. It was solubilized by the nonionic detergent NP40 but not by 3 M KCl. Detergent-soluble rat brain particulate protein inhibited G5-IgG binding to glutaraldehyde-fixed rat brain particulate protein. Inhibitory activity could be removed by prior incubation with concanavalin-A agarose beads. Immunoprecipitates of enzymatically iodinated, detergent-solubilized brain particulate protein gave a single band on polyacrylamide gels of apparent molecular weight 95,000–105,000 daltons. A band of identical molecular weight was visualized in gels of unlabeled immune precipitates by ¹²⁵I-concanavalin A. These results strongly suggest that G5 is an integral membrane glycoprotein in adult rat brain.     

Normal ligament properties and ligament healing

There is still a long way to go to achieve the goals of ligament replacement through modification of normal, intrinsic ligament healing processes. We are learning about the biology of ligamentous tissues, including the problem of regeneration, and that in itself is an all-important first step toward seeking solutions.     

Ankle and knee position as a factor modifying intracompartmental pressure in the human leg

The objective of this study was to examine the effect of position of the knee and ankle on intracompartmental pressures in the leg. Slit catheters were introduced bilaterally into all four muscle compartments of the lower extremities of six healthy volunteers. Intracompartmental pressures were monitored with the catheters while the ankle joint was passively held in full dorsiflexion, full plantar flexion, or neutral with the knee flexed 90 or 10 degrees or fully extended. Statistical analysis revealed that intracompartmental pressure increased significantly in all four compartments when the ankle was passively dorsiflexed. Pressure in the superficial posterior and lateral compartments was dependent on knee position and in the deep posterior and anterior compartments it was independent of knee position. In addition, pressure in the deep posterior compartment decreased significantly when the ankle was placed in full plantar flexion, and that finding was independent of knee position. Anterior compartment pressure was not significantly elevated by full passive plantar flexion of the ankle.