(14C)Glucosamine incorporation into specific products in the nerve ending fraction in vivo and in vitro

The products ofin vivo andin vitro incorporation of radioactive glucosamine into glycoproteins associated with the nerve ending (synaptosome) fraction were studied by polyacrylamide gel electrophoresis and also by gel filtration of glycopeptides derived from these glycoproteins by pronase digestion.Afterin vivo labeling for 1 h a heterogeneous group of [¹⁴C]glucosamine labeled glycoproteins was found associated with the nerve ending fraction. The predominant [¹⁴C]glucosamine containing glycopeptide derived by pronase digestion of the nerve ending fraction had an apparent molecular weight of 1250. It constituted a larger percentage of the labeled glycopeptides associated with the nerve ending fraction, as compared with other subcellular fractions. After 4 h ofin vivo labeling other glycopeptides constituted a greater percentage of the total labeled glycopeptides derived from the nerve ending fraction. This suggests that a different group of [¹⁴C]glucosamine containing glycoproteins were now relatively abundant in nerve endings. Presumably they had arrived by axoplasmic transport to the nerve endings.Afterin vitro labeling the nerve ending fraction incorporated [¹⁴C]glucosamine more actively than the microsomal or mitochondrial fractions. The radioactive products found upon polyacrylamide gel electrophoresis of the nerve ending fraction appeared to be less heterogeneous than afterin vivo labeling. Upon pronase digestion a single class of labeled glycopeptides was found with the same apparent molecular weight as the predominant labeled glycopeptide in the nerve ending fraction afterin vivo labeling.The results indicate that some [¹⁴C]glucosamine is incorporated into specific products by components of the nerve ending fraction and that this glycosylation cannot readily be attributed to contamination with other particles containing glycosyl transferases. Other glucosamine containing products are apparently transported to the nerve endings after glycosylation in the nerve cell body.     

Characterizing the need for mechanical ventilation following cervical spinal cord injury with neurologic deficit

BACKGROUND: Patients who sustain cervical spinal cord injury (C-SCI) with neurologic deficit may require a definitive airway and/or prolonged mechanical ventilation. The purpose of this study was to characterize factors associated with a high risk for respiratory failure and/or the need for mechanical ventilation in C-SCI patients. METHODS: Patients with C-SCI and neurologic deficit admitted to a Level I Trauma Center between July 1, 2000 and June 30, 2002 were retrospectively reviewed for demographics, level and completeness of neurologic deficit, need for definitive airway, need for tracheostomy, need for mechanical ventilation at hospital discharge (MVDC), and outcomes. The level and completeness of injury were defined by American Spinal Injury Association standards. RESULTS: One hundred nineteen patients with C-SCI and neurologic deficit were identified over this period. Of these, 45 were identified as complete C-SCI: 12 (27%) patients had levels of C1 to C4; 19 (42%) had a level of C5; and 14 (31%) had levels of C6 and below. There were 37 males and 8 females. There were 36 blunt and 9 penetrating injuries. The average age of these patients was 40 +/- 21, and the average ISS was 45+/-22. Eight of the patients with complete C-SCI died, for a mortality of 18%. Of the 37 survivors, 92% received a definitive airway, 81% received tracheostomy, and 51% required MVDC. All patients with complete injuries at the C5 level and above required a definitive airway and tracheostomy, and 71% of survivors required MVDC. Of the patients with complete injuries of C6 and below, 79% received a definitive airway, 50% required tracheostomy, and 15% of survivors required MVDC. Only 35% of incomplete injuries required a definitive airway, and only 7% required tracheostomy. CONCLUSIONS: The need for definitive airway control, tracheostomy, and ventilator dependence is significant, especially for patients with high complete C-SCI. Based on these results we recommend consideration of early intubation and tracheostomy for patients with complete C-SCI, especially for those with levels of C5 and above.     

Differential effects of halothane and isoflurane on lumbar dorsal horn neuronal windup and excitability

Background. Windup of spinal nociceptive neurones may underlietemporal summation of pain, influencing the minimum alveolarconcentration (MAC) of anaesthetics required to prevent movementto supramaximal stimuli. We hypothesized that halothane andisoflurane would differentially affect windup of dorsal hornneurones. Methods. We recorded 18 nociceptive dorsal horn neurones exhibitingwindup to 1 Hz electrical hindpaw stimuli in rats. Effects of0.8 and 1.2 MAC isoflurane and halothane were recorded in thesame neurones (counterbalanced, crossover design). Windup wascalculated as the total number of C-fibre (100–400 mslatency) plus afterdischarge (400–1000 ms latency) spikes/20stimuli (area under curve, AUC) or absolute windup (C-fibreplus afterdischarge–20xinitial response). Results. Increasing isoflurane from 0.8 to1.2 MAC did not affectAUC, but increased absolute windup from 429 (62) to 618 (84)impulses/20 stimuli (P<0.05) and depressed the initial C-fibreresponse from 14 (3) to 8 (2) impulses (P<0.05). Increasinghalothane from 0.8 to1.2 MAC depressed AUC from 690 (79) to537 (65) impulses/20 stimuli (P<0.05) and the initial responsefrom 18 (2) to 13 (2) impulses (P<0.05), but absolute windupwas not affected. Absolute windup was 117% greater during 1.2MAC isoflurane compared with 1.2 MAC halothane. Conclusions. Windup was significantly greater under isofluranethan halothane anaesthesia at 1.2 MAC, whereas the initial C-fibreresponse was suppressed more by isoflurane. These findings suggestthat these two anaesthetics have mechanistically distinct effectson neuronal windup and excitability.     

A murine model of congenital toxoplasmic retinochoroiditis

A histopathological study of toxoplasmic retinochoroiditis in 39 eyes of mice infected in utero with Toxoplasma gondii and sacrificed at 16 weeks post-partum showed a wide variation in the pattern of tissue destruction. The changes in individual eyes were graded from mild to severe; Toxoplasma cysts were present in the retina and optic nerve in each grade. In the least affected eyes, Toxoplasma cysts were rarely seen and the disease was limited to a low grade uveitis and retinal lymphocytic perivasculitis. In the more severely affected eyes, there was focal, sectorial or total retinal destruction with secondary degeneration in the lens. In some eyes inflammatory destruction of the outer retina was associated either with a paucity of cells, or with lymphocytic infiltration or with plasma cell infiltration; giant cell granulomatous reactions were rare. In the most severely affected eyes the retina was necrotic and calcified. The findings illustrate the complexity of toxoplasmic retinochoroiditis and suggest that autoimmunity may play a part in the disease process.