Correction of keratoconus with rigid gas-permeable contact lenses

This study analyzed the feasibility of fitting keratoconus-affected corneas with nonkeratoconus rigid gas-permeable (RGP) contact lenses. We retrospectively studied patients with a diagnosis of keratoconus in the past 10 years who were fitted successfully with nonkeratoconus RGP lenses by the same physician. Results confirmed nonkeratoconus RGP lenses as the first-line correction tool. Additionally, we found a simple equation to speed the choice of the base curves of the lenses. The authors have stated that they do not have a significant financial interest or other relationship with any product manufacturer or provider of services discussed in this article.     

Ultrasound of soft tissue abnormalities of the extremities

Ultrasound may be the preferred initial diagnostic modality for the painful swollen extremity, the palpable extremity mass, and the injured extremity. The role of ultrasound in extremity soft tissue abnormalities, including muscle hemorrhage and injury, inflammatory processes, and soft tissue neoplasms, is the subject of this review.     

Inhibitory effect of islet amyloid polypeptide of glucose-induced proinsulin biosynthesis in rat insulinoma cells.

Islet amyloid polypeptide (IAPP) has been recently identified as the principal constituent of amyloid deposits in pancreatic islets of patients with type 2 (non-insulin-dependent) diabetes mellitus and causes insulin resistance in some target cells. In addition, glucose-induced insulin secretion is inhibited by IAPP. We studied the effect of IAPP on proinsulin biosynthesis in rat insulinoma (RINr) cells. Glucose at concentrations of 0, 15, 30, 60, 100, and 300 mg/dl stimulated proinsulin biosynthesis in a dose-responsive and and actino-mycin D-inhibitable manner after 6 h of incubation. At a glucose concentration of 300 mg/dl, IAPP decreased the mean responses of proinsulin biosynthesis to 61.2 and 29% at concentrations of 0.1 and 1 microM, respectively, compared with the IAPP-free control. In conclusion, IAPP inhibits glucose-induced proinsulin biosynthesis in RINr cells. IAPP might play an important role in the pathogenesis of type 2 diabetes mellitus.     

Two pharmacologically and kinetically distinct transient potassium currents in cultured embryonic mouse hippocampal neurons.

Transient potassium currents in mammalian central neurons influence both the repolarization of single action potentials and the timing of repetitive action potential generation. How these currents are integrated into neuronal function will depend on their specific properties: channel availability at the resting potential, activation threshold, inactivation rate, and current density. We here report on the voltage-gated transient potassium currents in embryonic mouse hippocampal neurons dissected at embryonic days 15-16 and grown in dissociated cell culture for up to 3 d. Two transient potassium currents, A-current and D-current, were isolated based on steady state inactivation and sensitivity to 4-aminopyridine (4-AP) and dendrotoxin (DTx). A-current had an activation threshold of approximately -50 mV and was half-inactivated at approximately -81 mV. A-current relaxations at voltages between -40 and +40 mV could be fit by single exponential functions with time constants of 20-25 msec; these time constants showed little sensitivity to voltage. In contrast, D-current had an activation threshold of between -40 and -30 mV and was half-inactivated at approximately -22 mV. D-current inactivation was voltage dependent; time constants of fitted exponential functions ranged from approximately 7 sec at -40 mV to 200 msec at +40 mV. A slower component of inactivation was also evident. D-current was preferentially blocked by 4-AP (100 microM) and DTx (1 microM). Operationally, A- and D-currents could be cleanly separated based on conditioning pulse potential and 4-AP sensitivity. Total transient potassium current amplitude increased during the time that neurons were in culture (recordings were made between 2 hr after dissociation and 3 d in culture). When normalized for cell capacitance (an index of membrane area), A-current density (pA/pF) decreased and D-current density increased, even during a period between days 1 and 3 when total transient current density remained constant. This observation suggests that A- and D-currents may be reciprocally modulated. Since blockade of D-current (with 100 microM 4-AP) increased both action potential duration and repetitive firing in response to constant current stimulation, long-term modulation of the A-current:D-current ratio may affect the excitability of hippocampal neurons.