Spontaneous miniature hyperpolarizations of presynaptic nerve terminals in the chick ciliary ganglion

Intracellular recordings from presynaptic nerve terminals in the chick ciliary ganlion revealed the presence of spontaneous miniature hyperpolarizations in virtually all (86%) nerve terminals examined. These spontaneous events appeared as small, brief hyperpolarizations at resting potential and were observed to increase or decrease as the membrane potential was depolarized or hyperpolarized from rest, respectively. The hyperpolarizing potentials were sensitive to blockade by tetraethylammonium and Ba²⁺, while caffeine increased then abolished these events. The voltage fluctuations were unaffected by tetrodotoxin, low Ca²⁺ external solution or the synaptic blockers, picrotoxin and strychnine. These spontaneous, transient, miniature hyperpolarizations may be due to the brief and co-ordinated activation of between 15–60 Ca²⁺-dependent K⁺ channels following the release of Ca²⁺ from internal stores.     

The role of chromosomal translocation (15;19) in the carcinoma of the upper aerodigestive tract in children

OBJECTIVE: To further evaluate the role of chromosomal translocation (15;19) in the presentation of the carcinoma (CA) of the upper aerodigestive tract. STUDY DESIGN AND SETTING: A retrospective study at a tertiary care pediatric medical center. RESULTS: Seven patients with a mean age of 12 years presented with CA of nasopharynx (N = 2), sinonasal region (N = I), parotid gland (N = 2), or larynx (N = 2). Treatments included combinations of surgery (N = 5), chemotherapy (N = 5), and radiation therapy (N = 4). One patient with sinonasal CA and one patient with laryngeal CA had chromosomal translocation (15;19); these patients both died of their disease with a mean survival of 6 months. The 5 patients without translocation (15;19) responded well to treatment and are disease-free with a mean follow-up of 47 months. CONCLUSION: The preliminary results appear to indicate poor prognosis associated with the presentation of chromosomal translocation (15;19) despite aggressive multi-modality treatment. Further investigation is needed to better understand the cause and relationship of the translocation (15;19) and aggressive behavior of these tumors.     

Tumor necrosis factor-induced mortality is reversed with cyclooxygenase inhibition.

OBJECTIVE: The authors hypothesized that TNF would induce eicosanoid synthesis, and a cyclooxygenase inhibitor would attenuate both eicosanoid synthesis and improve survival in an LD90 TNF-induced (150 ng/kg/i.v./5 min) mortality model. SUMMARY BACKGROUND DATA: Tumor necrosis factor is a cardinal mediator in sepsis; however, little is known about its effects on arachidonate metabolism. METHODS: Conscious male rats with carotid arterial and jugular venous catheters were randomized for mortality: group I, TNF alone (150 kg/i.v./15 min, n = 30); group II, ibuprofen (30 mg/kg/i.v. at t = -20 and +240 min), plus TNF, (n = 28); and for hemodynamics, eicosanoid synthesis, blood gases: group III, TNF alone, (n = 8); group IV, ibuprofen + TNF (n = 8); group V, monoclonal antibody to TNF plus TNF (n = 8). Mortality was determined at 4-72 hr. Other parameters determined over 4 hours (0, 5, 60, 120, 240 min). RESULTS: TNF stimulated synthesis of (a) TXB2 (71 +/- 30 pg/ml, mean +/- SE at base vs. 117 +/- 18 at 4 hr, p < 0.02); (b) PGE2 (70 +/- 6 pg/ml at base vs. 231 +/- 68 at 4 hr, p < 0.02); (c) 6PGF (52 +/- 6 pg/ml at base vs. 250 +/- 80 at 4 hr, p < 0.02). Ibuprofen significantly (p < 0.05) inhibited eicosanoid synthesis from TNF. TNF-induced mortality (87%, 26/30) was dramatically decreased with ibuprofen (11%, 3/28), at 4, 24, and 72 hr (p < 0.01). Monoclonal antibody to TNF prevented all abnormalities and had 100% survival. Hemodynamic events were similar in both groups, but metabolic acidosis was attenuated with ibuprofen. CONCLUSIONS: TNF stimulates arachidonic acid metabolism in vivo. A cyclooxygenase inhibitor attenuates eicosanoid synthesis and dramatically improves survival. TNF appears to have different effect on tissues that synthesize certain eicosanoids. Hypotension from TNF is not mediated via the eicosanoids. TNF-induced mortality, like endotoxemia/sepsis may be mediated, in part, via arachidonic acid metabolites. These new findings support the notion that cyclooxygenase inhibitors may be used as adjunctive therapy in clinical sepsis.     

Indomethacin-induced augmentation of insulin release

The effect of indomethacin, a potent prostaglandin synthetase inhibitor upon portal venous glucose, glucagon, and insulin, was examined in eight glucose-loaded, nondiabetic adult male mongrel dogs, by examining the response of each animal to a standard enteral glucose challenge with and without indomethacin pretreatment. Mean portal venous insulin rose after glucose loading with the rise after indomethacin pretreatment being significantly greater (P < 0.001) and more prolonged than that seen in the control group. Mean basal glucagon was increased with indomethacin pretreatment relative to controls (P < 0.01) and remained so throughout the measurement period. The glucose tolerance curves generated in control and indomethacin pretreatment groups were of normal contour and magnitude, and indistinguishable from one another. The effects seen are presumably the consequence of prostaglandin synthetase inhibition and imply that prostaglandins may play a suppressor role in modulating the insulin response to a glucose challenge.