Phosphorylation modulates the activity of the ATP-sensitive K channel in the ventromedial hypothalamic nucleus

Regulation of the ATP-sensitive K⁺ (K-ATP) channel was examined in cell-attached and inside-out membrane patches of freshly isolated neurons from the ventromedial hypothalamic nucleus (VMN) of 7–14 day old male Sprague–Dawley rats. When inside-out patches were exposed to symmetrical K⁺, the reversal potential was −2.85±1.65 mV, the single channel conductance 46 pS, and the total conductance varied as a multiple of this value. Glucose (10 mM) reversibly inhibited channel activity in cell-attached preparations by 81%. In the presence of 0.1 mM ADP, 10, 5, and 1 mM ATP reversibly inhibited VMN K-ATP channels in inside-out patches by 88, 83, and 60%, respectively. This inhibition was not dependent on phosphorylation since 5 mM AMPPNP, the non-hydrolyzable analog of ATP, reversibly inhibited channel activity by 67%. Relatively high concentrations of glibenclamide (100 μM) also reversibly inhibited VMN K-ATP channel activity in cell attached and inside-out patches by 67 and 79%, respectively. Finally, the non-specific kinase inhibitor H7 (200 μM) decreased channel activity by 53% while the non-specific phosphatase inhibitor microcystin (250 nM) increased channel activity by 218%. These data suggest that while the inhibitory effect of ATP is not phosphorylation dependent, phosphorylation state is an important regulator of the VMN K-ATP channel.     

The effect of intramuscular stanozolol on fibrinolysis and blood lipids

The effects of a single 50 mg intramuscular injection of the anabolic steroid stanozolol (Stromba) on fibrinolysis, blood coagulation and lipids was evaluated in 12 healthy male volunteers. Significantly increased plasminogen activator levels (p < 0.05) was noted 24 hours following the injection and these remained elevated for one week. Plasminogen levels increased significantly by day two (p < 0.01) and remained elevated for three weeks. HDL cholesterol fell (p < 0.01) and both total and LDL cholesterol increased (p < 0.05) when measured one month post injection. Stanozolol appears to have therapeutic potential as an activator of the fibrinolytic system when given by intramuscular injection.     

The enhancement of adenyl cyclase by steroid therapy in shock.

Hepatic and intestinal adenyl cyclase activity were measured after a single pulse injection of epinephrine or glucagon into normal dogs and into dogs subjected to hemorrhagic shock. The results indicated that hemorrhagic shock abolishes the increase in adenyl cyclase activity seen in normal animals following epinephrine and significantly reduces that induced by glucagon. These changes are reflected in the glucose production from the liver induced by these hormones. The response of adenyl cyclase to the in vitro addition of epinephrine or glucagon, as well as the nonspecific stimulator of adenyl cyclase, sodium fluoride, showed that it is the receptor site of the enzyme which is affected primarily by shock. The treatment of dogs with 30 mg/kg of methylprednisolone following the reinfusion of shed blood significantly improved the response of adneyl cyclase to epinephrine in both liver and intestine, and this improvement was reflected in the glucose production by the liver in response to the hormone.     

Internalization of gonadotropin-releasing hormone receptors (GnRHRs): does arrestin binding to the C-terminal tail target GnRHRs for dynamin-dependent internalization?

Activation of seven-transmembrane receptors is typically followed by desensitization and arrestin-dependent internalization via vesicles that are pinched off by a dynamin collar. Arrestins also scaffold Src, which mediates dynamin-dependent internalization of beta2-adrenergic receptors. Type I mammalian gonadotropin-releasing hormone receptors (GnRHRs) do not rapidly desensitize or internalize (characteristics attributed to their unique lack of C-terminal tails) whereas non-mammalian GnRHRs (that have C-terminal tails) are rapidly internalized and desensitized. Moreover, internalization of Xenopus (X) GnRHRs is dynamin-dependent whereas that of human (h) GnRHRs is not, raising the possibility that binding of arrestin to the C-terminal tails of GnRHRs targets them to the dynamin-dependent internalization pathway. To test this we have compared wild-type GnRHRs with chimeric receptors (XGnRHR C-terminal tail added to the hGnRHR alone (h.XtGnRHR) or with exchange of the third intracellular loops (h.Xl.XtGnRHR)). We show that adding the XGnRHR C-terminal tail facilitates arrestin- and dynamin-dependent internalization as well as arrestin/green fluorescent protein translocation, but Src (or mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase) inhibition does not slow internalization, and h.XtGnRHR internalization is slower than that of the hGnRHR. Moreover, arrestin expression increased XGnRHR internalization even when dynamin was inhibited and h.Xl.XtGnRHR underwent rapid arrestin-dependent internalization without signaling to G(q/11). Thus, although the C-terminal tail can direct GnRHRs for arrestin- and dynamin-dependent internalization, this effect is not dependent on Src activation and arrestin can also facilitate dynamin-independent internalization.     

Levels of plasma cyclic AMP and insulin in cardiac surgery.

Cyclic AMP is a common second messenger for a variety of hormones such as catecholamine, glucagon, and growth hormone, which are affected by cardiac surgery. Changes in plasma cyclic AMP level may thus reflect an altered hormonal milieu. The effects of open-heart surgery on plasma cyclic AMP and its relation with serum insulin were studied in 33 adult patients who underwent cardiac surgery with cardiopulmonary bypass. Plasma cyclic AMP levels were markedly elevated during cardiopulmonary bypass and returned toward normal within several days after the operation. The serum insulin concentration remained low, and no positive correlation was found with plasma cyclic AMP level. The responses were similar in patients who had aorta-coronary bypass grafts and those who had valve replacements.     

When hearing aids go bad: an FM success story

Both clinical and research findings support the effectiveness of frequency-modulated (FM) technology among individuals who continue to encounter significant communication problems despite the use of conventional hearing instruments. The use rate of FM devices throughout the nation, however, remains disappointingly low. The authors present a case of a longtime hearing aid user whose hearing aids provided decreasing benefit as his hearing impairment increased to the extent that cochlear implantation was considered. Through the establishment of patient-specific treatment goals, the provision of appropriate FM technology as verified through real-ear measurements, and careful and deliberate counseling and follow-up, this patient was able to realize significant communication benefits as reported through several self-assessment measures. The cost-benefit implications of FM technology versus cochlear implantation are discussed.