High sensitivity of porcine cerebral arteries to endothelin

Summary The threshold concentration of endothelin to induce contractions in porcine cerebral arteries (anterior cerebral, Willis ring and basilar artery) was lower than those for coronary and renal arteries. The median effective concentrations (ED₅₀) of endothelin in cerebral arteries were also significantly lower than those for coronary and renal arteries. There was no significant difference in the sensitivity to endothelin among cerebral arteries, or between coronary and renal arteries. The maximal percentage of contractions induced by endothelin, as compared to that induced by 10^–1 M potassium chloride, was not significantly different between the arteries.     

Mechanism of frost heave by film water migration under temperature gradient

Conclusions Based on the principle of freezing point superposition, a model for predicting unfrozen water content is worked out and it can consider the influences of five factors: soil variation, water content, temperature, solution concentration and overburden pressure. The difference of values between determination and calculation is less than 3 %. According to the curve of unfrozen water content vs. temperature and initial freezing point and temperature at the cold end of soil body, a way for estimating ice segregation temperature is presented. The difference of values between determination and calculation is less than 0.3°C. The thickness of frozen fringe changing with time has three models. The calculation method needs further study.     

Circles in spermatocyte chromatin loops. Electron microscopy and AgAs-NORs studies.

We describe the production of circles in chromomeric loops during the pachytene stage of the spermatocytes. These circles are found attached to chromatin or already free in the nucleoplasm. Each circle measures an average of 3700 A in circunference. We suggest that such circles might indicate the presence of tandem repetitions.     

Mutation of ARX causes abnormal development of forebrain and testes in mice and X-linked lissencephaly with abnormal genitalia in humans

Male embryonic mice with mutations in the X-linked aristaless-related homeobox gene (Arx) developed with small brains due to suppressed proliferation and regional deficiencies in the forebrain. These mice also showed aberrant migration and differentiation of interneurons containing gamma-aminobutyric acid (GABAergic interneurons) in the ganglionic eminence and neocortex as well as abnormal testicular differentiation. These characteristics recapitulate some of the clinical features of X-linked lissencephaly with abnormal genitalia (XLAG) in humans. We found multiple loss-of-function mutations in ARX in individuals affected with XLAG and in some female relatives, and conclude that mutation of ARX causes XLAG. The present report is, to our knowledge, the first to use phenotypic analysis of a knockout mouse to identify a gene associated with an X-linked human brain malformation.     

Effects of vitamin B12 on plasma melatonin rhythm in humans: Increased light sensitivity phase-advances the circadian clock?

Vitamin B12 (methylcobalamine) was administered orally (3 mg/day) to 9 healthy subjects for 4 weeks. Nocturnal melatonin levels after exposure to bright light (ca. 2500 lx) were determined, as well as the levels of plasma melatonin over 24 h. The timing of sleep was also recorded. Vitamin B12 was given blind to the subjects and crossed over with placebo. We found that the 24-h melatlonin rhythm was significantly phase-advanced (1.1. h) in the vitamin B12 trial as compared with that in the placebo trial. In addition, the 24-h mean of plasma melatonin level was much lower in the vitamin B12 traial than with the placebo. Furthermore, the nocturnal melatonin levels during bright light exposure were significantly lower in the vitamin B12 trial than with the placebo. On the other hand, vitamin B12 did not affect the timing of sleep. These findings raise the possibility that vitamin B12 phase-advances the human circadian rhythm by increasing the light sensitivity of the circadian clock.     

Construction of Multilayer Porous Scaffold Based on Magnetically Guided Assembly of Microfiber

This paper proposes a novel method of magnetically guided assembly to construct multilayer porous scaffold for three-dimensional cell culture by apply magnetic microfibers. Microfibers are composed of biocompatible and biodegradable alginate solution with homogeneous magnetic nanoparticles, which are continuously spun from a microfluidic device by precise pressure control of the syringe pump. Magnetic nanoparticles enable the control of magnetic field on microfibers. Meanwhile, magnetized device combining with a round permanent magnet are utilized to guide the distribution of spouted microfibers. The device is composed by pure iron wire arrays and wax, which stimulates powerful magnetic flux density and magnetic field gradients for the capture and assembly of microfibers.Thus, magnetic microfibers are spun on desired places of the magnetized device by motion control of the micromanipulation robot, and precise locations are adjusted by magnetic force couple with the assist of glass micropipette. Afterwards, microfibers are spatially organized by periodic magnetic force and crossed layer-by-layer to form micro-pore structure with both length and width of 650 μm. Finally,the authors construct a multilayer microfiber-based scaffold with high porosity to provide a satisfactory environment for long-term cell culture. The experimental results demonstrate the effectiveness of the proposed method.