Effects of space flight on GLUT-4 content in rat plantaris muscle

 The effects of 14 days of space flight on the glucose transporter protein (GLUT-4) were studied in the plantaris muscle of growing 9-week-old, male Sprague Dawley rats. The rats were randomly separated into five groups: pre-flight vivarium ground controls (PF-VC) sacrificed approximately 2 h after launch; flight groups sacrificed either approximately 5 h (F-R0) or 9 days (F-R9) after the return from space; and synchronous ground controls (SC-R0 and SC-R9) sacrificed at the same time as the respective flight groups. The flight groups F-R0 and F-R9 were exposed to micro-gravity for 14 days in the Spacelab module located in the cargo bay of the shuttle transport system – 58 of the manned Space Shuttle for the NASA mission named ”Spacelab Life Sciences 2”. Body weight and plantaris weight of SC-R0 and F-R0 were significantly higher than those of PF-VC. Neither body weight nor plantaris muscle weight in either group had changed 9 days after the return from space. As a result, body weight and plantaris muscle weight did not differ between the flight and synchronous control groups at any of the time points investigated. The GLUT-4 content (cpm/μg membrane protein) in the plantaris muscle did not show any significant change in response to 14 days of space flight or 9 days after return. Similarly, citrate synthase activity did not change during the course of the space flight or the recovery period. These results suggest that 14 days of space flight does not affect muscle mass or GLUT-4 content of the fast-twitch plantaris muscle in the rat. Received: 25 March 1997 / Accepted: 18 August 1997     

Activation and Two Modes of Blockade by Strontium of Ca2+-activated K+ Channels in Goldfish Saccular Hair Cells

Effects of internal Sr²⁺ on the activity of large-conductance Ca²⁺-activated K⁺ channels were studied in inside-out membrane patches from goldfish saccular hair cells. Sr²⁺ was approximately one-fourth as potent as Ca²⁺ in activating these channels. Although the Hill coefficient for Sr²⁺ was smaller than that for Ca²⁺, maximum open-state probability, voltage dependence, steady state gating kinetics, and time courses of activation and deactivation of the channel were very similar under the presence of equipotent concentrations of Ca²⁺ and Sr²⁺. This suggests that voltage-dependent activation is partially independent of the ligand. Internal Sr²⁺ at higher concentrations (>100 μM) produced fast and slow blockade both concentration and voltage dependently. The reduction in single-channel amplitude (fast blockade) could be fitted with a modified Woodhull equation that incorporated the Hill coefficient. The dissociation constant at 0 mV, the Hill coefficient, and zd (a product of the charge of the blocking ion and the fraction of the voltage difference at the binding site from the inside) in this equation were 58–209 mM, 0.69–0.75, 0.45–0.51, respectively (n = 4). Long shut events (slow blockade) produced by Sr²⁺ lasted ∼10–200 ms and could be fitted with single-exponential curves (time constant, τ_l−s) in shut-time histograms. Durations of burst events, periods intercalated by long shut events, could also be fitted with single exponentials (time constant, τ_b). A significant decrease in τ_b and no large changes in τ_l−s were observed with increased Sr²⁺ concentration and voltage. These findings on slow blockade could be approximated by a model in which single Sr²⁺ ions bind to a blocking site within the channel pore beyond the energy barrier from the inside, as proposed for Ba²⁺ blockade. The dissociation constant at 0 mV and zd in the Woodhull equation for this model were 36–150 mM and 1–1.8, respectively (n = 3).     

Isolation and partial characterization of SSI-like protease inhibitors from Streptomyces

We attempted to screen a series of Streptomyces subtilisin inhibitor-like (SIL) proteins among several Streptomyces strains by using a highly sensitive assay system established by us. Of six randomly tested strains, four were found to produce SIL inhibitors as their major secreted proteins, suggesting that they might be distributed in a high frequency among this genus. Three inhibitors exhibited inhibition of both subtilisin BPN' and trypsin. Comparison of the amino terminal sequences of these isolated proteins with those of other reported SIL inhibitors revealed that the beta 1- and beta 2-sheets in SSI were highly conserved.     

Crystallization and preliminary diffraction studies of hydroxypyruvate reductase (D-glycerate dehydrogenase) from Hyphomicrobium methylovorum.

Two crystal forms of hydroxypyruvate reductase (D-glycerate dehydrogenase) from the methylotrophic bacterium Hyphomicrobium methylovorum have been grown from ammonium sulphate solutions. One crystal form is triclinic, with unit cell parameters a = 60.4 A, b = 60.5 A, c = 66.3 A, alpha = 102.3 degrees, beta = 113.7 degrees and gamma = 102.7 degrees, suggesting that a dimer (monomer M(r) 38,000) occupies the unit cell. This crystal form diffracts to beyond 2.4 A resolution and is suitable for crystallographic structure analysis.     

Efficient catalysis by pyridinium sulfonate in glycosylation involving an oxazoline intermediate derived from per-O-acetyl-N-acetyllactosamine andN,N′-diacetylchitobiose

New and facileN-acetyllactosaminidation andN,N-diacetylchitobiosylation with various alcohols, thiols, and sugar derivatives through the 1,2-oxazoline intermediates catalyzed by pyridiniump-toluenesulfonate were achieved.     

Pineal-dependent locomotor activity of lamprey,Lampetra japonica,measured in relation to LD cycle and circadian rhythmicity

Summary Locomotor activity of the river lamprey, Lampetra japonica, was investigated under a light-dark (LD 1212) cycle and under continuous dark conditions. Intact lampreys were entrained to the light:dark cycle. They were active mainly in the early half of the dark period and inactive in light period. The light:dark entrainment continued in 72.7% of lampreys after the removal of bilateral eyes, but additional pinealectomy made the entrainment disappear in all lampreys. When lampreys were pinealectomized with their eyes intact, light: dark entrainment was abolished in most cases. The results indicate that the pineal organ of the lamprey is a photoreceptive organ responsible for synchronizing locomotor activity to LD cycle. Under continuous dark conditions, the locomotor activity began to free-run with a period of 21.3 ± 0.9 h (mean ± SD, n = 53). This circadian rhythmicity was not affected by the removal of lateral eyes but was abolished by pinealectomy. The pineal organ appears to function as an oscillator, or as one of the oscillators, for the circadian locomotor rhythm of lampreys.Abbreviations DD continuous dark - LD light:dark     

Factors affecting experimental infection with Cryptococcus neoformans in mice with special reference to an endotoxic substance of C. neoformans

A close correlation was observed between body weight and length of the survival time of mice inoculated intravenously (i.v.) with Cryptococcus neoformans (p<0.001). An endotoxic substance of C. neoformans (Cr-ET) increased the susceptibility of mice to i.v. infection of C. neoformans only when more than 50 g of Cr-ET was injected i.v. 24 hours before infection. Intraperitoneal (i.p.) administration of dimethyl sulfoxide which is found to enhance bacterial infection did not enhance death rate of mice infected i.p. with C. neoformans.