Microwave properties of cryoprotectants

The values of the dielectric constant and of the loss tangent for pure samples of DMSO, ethylene glycol, and glycerol were determined over the temperature range of + 15 to −70 °C. An operating frequency range of 1.45 to 1.55 GHz was used, allowing direct application of the results of both 0.915 and 2.450 GHz studies. Strong temperature dependencies were found, with peaks and irregularities occuring at subfreezing temperatures. In order to design a suitable cryoprotective system for the long term preservation of whole organs, the effect of cryoprotectant concentration on microwave properties must be known.     

The two visual pigments of the gecko: The labile behavior

Summary This report describes five selected experiments that describe the labile behavior of pigment-521 of the Tokay gecko and the relatively more stable properties of the second photopigment, pigment-467, of the same retina. Prepared in the chloride-deficient state, P521 is sensitive to mild temperature increases, is destroyed by NH₂OH and NaBH₄ in the dark, responds top-hydroxymercuribenzoate by a spectral shift to shorter wavelengths, exchanges some of its 11 -cis retinal for the 9 -cis isomer in the dark, and reacts to added chloride and nitrate by spectral shifts to longer and shorter wavelengths, respectively. Dissolved in Triton-X-100 it is irreversibly destroyed by only moderate increases in temperature. In all these responses, chloride ions act specifically to protect the pigment. Pigment-467, in contrast, is less sensitive to temperature, is not bleached by NH₂OH and NaBH₄ in the dark, does not exchange its prosthetic group and responds neither to chloride nor to nitrate by the typical P521 effects. With regard to molecular stability and access to the chromophoric structure there appears to be a dual system in the gecko retina with P521 showing similarities to the cone pigment iodopsin; P467 to rhodopsin. It is pointed out that this dual system may be associated with certain responses of the gecko retina that indicate physiological duality. This is the case even though there are no rods and cones, in the classical sense, in the gecko retina.Abbreviations PMB p-hydroxymercuribenzoate - DTT dithiothreitol, Cleland's reagent This work was supported by grant EY-02178 from the National Institutes of Health     

Electron Microscopic Observations of Mouse Brain Infected with Bunyamwera Group Arboviruses

Ultrathin sections of brain tissue from mice infected with three Bunyamwera group arboviruses, Bunyamwera, Tensaw, and Maguari, were examined by electron microscopy. In all three cases, virus was observed budding from membranes into intracytoplasmic cisternae. Mature virus was found accumulated within these distended cisternae and in extracellular spaces. The three viruses were morphologically indistinguishable; particles were round or oval, 98 nm in diameter, and had a closely adherent irregular envelope.     

Fossilized fungi as evidence of continental drift

According to Wegener (1912), about 200 million years ago the once unitary land mass that he named Pangea, became fragmented into the several continents. Subsequently these continents have continued to drift.The present account deals with the occurrence of fossilized fungal remains in Chattanooga shale and such fossils are interpreted as evidence of the occurrence of continental drift. Chattanooga shale consists of two materials, shale and the highly carbonized remains of a floating, aquatic, green plant, Conodontophyta chattanoogae, that now is an extinct, nonpetrified fossil. The remains of this fossil became compressed between layers of finegrained shale. When a piece of shale is struck with a hammer it breaks apart at the bedding planes and thus exposes fossilized Conodontophyta tissues. By examination with a dissecting microscope, the fungal remains may be seen to occur on the Conodontophyta tissues. Fragments of the carbonized tissues are filled with hyphae and with dark fungal nodules. When these nodules are removed with a dissecting needle tipped with Canada balsam and are mounted on a microscope slide, and pressure is applied to the coverglass, the nodules break apart. The parts consist of hyphae, spores, and ascocarps. These fungi are like some of the species presently in soils of the several continents. Fossil fungi as well as present-day widely distributed ones therefore may be regarded plausibly as evidence of the occurrence of continental drift.