7Li nuclear magnetic resonance study for the determination of Li+ properties in neuroblastoma SH-SY5Y cells

Lithium has been used clinically in the treatment of manic depression. However, its pharmacologic mode of action remains unclear. Characteristics of Li+ interactions in red blood cells (RBCs) have been identified. We investigated Li+ interactions on human neuroblastoma SH-SY5Y cells by developing a novel 7Li NMR method that provided a clear estimation of the intra- and extracellular amounts of Li+ in the presence of the shift reagent thulium-1,4,7,10-tetrazacyclododecane-N,N',N',N'-tetramethylene phosphonate (HTmDOTP4-). The first-order rate constants of Li+ influx and efflux for perfused, agarose-embedded SH-SY5Y cells in the presence of 3 mM HTmDOTP4- were 0.055 +/- 0.006 (n = 4) and -0.025 +/- 0.006 min(-1) (n = 3), respectively. Significant increases in the rate constants of Li+ influx and efflux in the presence of 0.05 mM veratridine indicated the presence of Na+ channel-mediated Li+ transport in SH-SY5Y cells. 7Li NMR relaxation measurements showed that Li+ is immobilized more in human neuroblastoma SH-SY5Y cells than in human RBCs.     

Characteristics of a fast transient outward current in guinea pig trigeminal motoneurons

A fast transient voltage dependent outward current (TOC) in trigeminal motoneurons (TMNs) was studied in guinea pig brainstem slices by use of sharp electrodes in combination with single electrode voltage clamp techniques. In solutions containing TTX, low Ca2+/Mn2+ and 20 mM TEA this current activated around -55 to -60 mV from holding potentials negative to resting potential, obtained its peak amplitude within 5 ms and decayed as a single exponential with a time constant of 6-8 ms. Half maximal values for inactivation and activation were -72 and -37 mV, respectively. Bath application of 5 mM 4-AP suppressed this current by approximately 90% and eliminated the early depolarizing transient membrane rectification observed in response to a constant depolarizing current pulse, prolonged the action potential duration, and reduced the threshold voltage and delay to onset of the action potential. It is suggested that this current resembles the typical A-current observed in many CNS neurons and, as a result of its voltage and time dependent properties, could contribute to control of motoneuronal discharge and timing of burst onset during rhythmical jaw movements. Therefore, any cellular models of masticatory activity should include the properties of this current.     

Effect of topical butyrate on rectal epithelial kinetics and mucosal enzyme activities

Public awareness and misunderstandings of lactose intolerance are at an all-time high. Many people erroneously believe they are lactose intolerant or develop gastrointestinal symptoms after intake of lactose. Consequently, lactose-containing foods such as milk and other dairy foods may be eliminated unnecessarily from the diet. Because these foods are a major source of calcium, low intake of them can compromise calcium nutriture. This, in turn, can increase the risk of major chronic diseases such as osteoporosis (porous bones) and hypertension. This review is intended to help dietetics professionals alleviate clients' fears about lactose intolerance and recommend dietary strategies to improve tolerance to lactose. Scientific findings indicate that the prevalence of lactose intolerance is grossly overestimated. Other physiologic and psychologic factors can contribute to gastrointestinal symptoms that mimic lactose intolerance. Scientific findings also indicate that people with laboratory-confirmed low levels of the enzyme lactase can consume 1 serving of milk with a meal or 2 servings of milk per day in divided doses at breakfast and dinner without experiencing symptoms. Several dietary strategies are available to help lactose maldigesters include milk and other dairy foods in their diet without experiencing symptoms.     

Lac/Tet dual-inducible system functions in mammalian cell lines

The Escherichia coli Lac repressor (Lac system) and tetracycline responsive promoter (Tet system) systems have been used individually to regulate gene expression at the cellular as well as the organismal levels. In this study, these two systems were combined (designated Lac/Tet dual-inducible system) to regulate two inducible genes simultaneously in a single cell. The isopropyl-beta-D-thiogalactopyranoside (IPTG) and tetracycline (used for the operation of the Lac and the Tet systems) were non-cytotoxic to the cells when added together into the cells at around the optimal concentrations (IPTG: < or = 5 mM; tetracycline: < 1.5 micrograms). The rate and efficiency of induction and repression of two inducible genes regulated by the Lac/Tet dual-inducible system were similar to the results obtained when one inducible gene is regulated by one inducible system in a single cell. The Lac/Tet dual-inducible system could function in many cell lines, which was demonstrated by regulating the expression of beta-galactosidase and luciferase reporter genes in five tumor cell lines by transient transfection analysis. The feasibility of introducing a second inducible system into an already established inducible cell line was confirmed. Finally, we showed that the Lac/Tet dual-inducible system functions at translational and at functional levels in a stable cell line named 7-4-b, which contains the Ha-ras and bc1-2 inducible genes. In conclusion, this study extends the application of prokaryotic inducible systems from the regulation of a single gene to two genes and helps clarify the relationship between two genes and the effects of two genes on the cells.     

The prolonged hematologic effects of a single injection of PEG-rHuMGDF in normal and thrombocytopenic mice

A single injection of > or =10 microg/kg PEG-rHuMGDF in mice causes a dose-dependent increase in circulating platelets beginning on day 3 and peaking on days 5-6. The mean platelet volume and platelet distribution width at doses > or =100 microg/kg initially increase in a dose-dependent fashion and later decrease. However, the mean platelet volume does not change when platelets are incubated with PEG-rHuMGDF in vitro. The number of marrow megakaryocytes increases in a dose-dependent fashion as early as day 1 and peaks on day 3. Marrow megakaryocyte colony-forming units (CFU-Meg) do not increase on days 1-3 at a dose of 100 microg/kg (a dose that increases platelet numbers two- to threefold and may be clinically relevant), but the relative frequency of high ploidy megakaryocytes and the proportion of large marrow megakaryocytes (29-50 microm in diameter) increases. After a dose of 1,000 microg/kg the percentage of megakaryocytes in mitosis peaks at 24-48 hours and the percentage of megakaryocytes incorporating BrdU is maximal at 48 hours, the relatively delayed peak of BrdU incorporation most likely representing endomitosis. The relative frequency of type II and III megakaryocytes peaks on days 3 and 4, respectively. Pharmacokinetic analysis of PEG-rHuMGDF shows peak serum concentrations at 2-4 hours and a terminal half-life of 11.4+/-2.5 hours. A single injection of PEG-rHuMGDF ameliorates carboplatin-induced megakaryocytopenia and thrombocytopenia in a dose-response dependent fashion. In conclusion, a single injection of PEG-rHuMGDF increases megakaryocyte and platelet production in normal and myelo-suppressed mice.     

Influence of Age on Antennal Response of Male Honey Bees, Apis mellifera, to Queen Mandibular Pheromone and Alarm Pheromone Component

Using a computer-controlled pheromone-puff delivery system with signal averaging, we investigated the change with age of the electroantennogram (EAG) response of drone (male) honey bees to queen mandibular pheromone (QMP) and an alarm pheromone component, isopentyl acetate (IPA). Drone antennae were significantly more sensitive than worker antennae to QMP, but there was no significant difference in response to IPA. Response to QMP was dose dependent and decreased gradually with the age of the drone. Drone response to IPA did not diminish significantly with age. Drones do not mature sexually or make their first flights until about 1 week old, so the ontogeny of their sensory responsiveness to queen pheromones does not reflect that of their behavior. It is unknown if drones exhibit any behavioral response to IPA. The signal-averaging system we describe could be used to improve resolution of low signal-to-noise ratio signals in other EAG studies.