Dichroism of bacteriochlorophyll in cells of the photosynthetic bacterium Rhodopseudomonas palustris

1. The dichroism was measured at varied wavelengths of polarized light in “intact” cells of Rhodopseudomonas palustris and in films of air-dried lamellar fragments of the bacterium.     

Chain conformation of copoly(γ-methyl D,L-glutamate)

Copolymers of γ-methyl D - and L -glutamates with various D /L ratios were prepared. Infrared absorption spectra of solid films were measured and sums of right- and left-handed helix contents were determined from intensities of amide V bands. Farultraviolet absorption spectra and optical rotatory dispersion of these copolymers in solutions are used to ascertain their helical character. Chain conformations of DL -copolypeptides are discussed.     

Activation of phospholipase C by the agonist U46619 is inhibited by cromakalim-induced hyperpolarization in porcine coronary artery.

We measured inositol 1,4,5-trisphosphate (IP3) production, intracellular calcium concentration ([Ca2+]i) and force of contraction induced by a thromboxane A2 analogue U46619 in porcine coronary artery to elucidate the relaxant effect of a K+ channel opener cromakalim. Cromakalim (10 microM) significantly inhibited the production of IP3, Ca2+ release from intracellular stores and contraction induced by 300 nM U46619. The inhibitory effect of cromakalim on IP3 was blocked by a K+ channel blocker tetrabutylammonium (TBA, 3 mM) and counteracted by 20 mM KCl-induced depolarization. These results suggest that the hyperpolarization of the plasma membrane by cromakalim inhibits the activation of phospholipase via the stimulation of the thromboxane A2 receptor to result in vasodilation.     

SFA-1, a novel cellular gene induced by human T-cell leukemia virus type 1, is a member of the transmembrane 4 superfamily.

A novel cellular gene termed SFA-1 was isolated by differential hybridization of a cDNA library, using probes obtained from an adult T-cell leukemia cell line in comparison with probes obtained from normal CD4+ T cells and the MOLT-4 cell line. The mRNA of the SFA-1 gene is approximately 1.6 kb in size and encodes a protein of 253 amino acids, containing four putative transmembrane domains, a number of cysteine residues, and one potential N-glycosylation site in a major hydrophilic region between the third and fourth transmembrane domains. Expression of the SFA-1 gene was either absent or present at a low level in lymphoid cells but was up-regulated after transformation by human T-cell leukemia virus type 1 and transactivated by Tax. SFA-1 was broadly expressed in many human cell types and conserved in different species. Computer-aided comparison showed that SFA-1 had significant sequence homology and common structural features with members of the transmembrane 4 superfamily. SFA-1 antigen was detected as a 29-kDa membrane protein by immunoblotting, using anti-SFA-1 monoclonal antibody.     

Comparison of muscle force,muscle endurance,and electromyogram activity during an expedition at high altitude

Handgrip force (HF), maximal pinch force (MF), muscle endurance (ME), and the median power frequency (MdPF) of the activity shown in the electromyogram (EMG) were studied at various altitudes in eight normal healthy subjects. MF and ME were measured between the index finger and thumb, and all measurements were obtained at altitudes ranging from 610 to 4860 m during an expedition in the Qinghai Plateau in China. With the change in altitude HF, ME, and MF showed no significant change. Compared to the MdPF at 2260 m on ascent, the MdPF at other altitudes showed a significant decrease (P<0.01). Thus, we conclude that muscle performance (HF, MF, and ME) was not affected by the environment at high altitude. However, MdPF was affected and the mean MdPF at 610 m after the expedition did not recover to initial values of MdPF. We suggest these results may have been affected by fatigue and chronic exposure to the hypobaric hypoxic environment, since the members of the expedition party expressed feelings of sluggishness and fatigue after the expedition.     

Filial cannibalism by mouthbrooding males of the cardinal fish,Apogon doederleini, in relation to their physical condition

Synopsis Paternal brood cannibalism was observed in a population ofApogon doederleini in Shikoku Island, Japan. Of 361 egg masses mouthbrooded by males, 47 disappeared within a day of spawning. A stomach check with a syringe ascertained that they had been consumed by the males. The frequency of this cannibalism increased as the breeding season advanced. As males completed 4–7 breeding cycles in a breeding season and spent 80% of the time mouthbrooding without taking ordinary food, their physical condition deteriorated greatly late in the breeding season. We concluded that parental physical condition is an important factor in the occurrence of brood cannibalism.     

Postnatal reorganization of actin filaments and differentiation of intercellular boundaries in the rat aortic endothelial cells

Postnatal change in the distribution of actin filaments in endothelial cells was studied in the rat aorta by use of rhodamine-phalloidin staining and confocal laser scanning microscopy. Endothelial cells of the rat aorta possessed two populations of actin filament bundles, namely, peripheral bands at the cell border and stress fibers running longitudinally in the cytoplasm. Aortic endothelial cells of the neonatal rat contained only stress fibers, whereas those of the 10-day-old rat developed both peripheral bands and stress fibers. After 20 days of age, aortic endothelial cells had predominantly peripheral bands with occasional stress fibers around the branch orifices. During postnatal development the length density of stress fibers in aortic endothelial cells decreased, whereas individual stress fibers in endothelial cells were shortened. Electron-microscopic observation revealed that the high intercellular boundaries of aortic endothelial cells at birth decreased in height and developed cytoplasmic interdigitations after 20 days of age. The occurrence of peripheral bands at the cell border is thought to be closely related to formation of cytoplasmic interdigitation which strengthens the mechanical connection between endothelial cells against increasing transmural pressure. Expression of stress fibers in aortic endothelial cells of the neonatal rat is supposed to be affected by longitudinal elongation of the developing aorta, whereas their postnatal decrease is though to be correlated with the change of fluid shear stress loaded in the aortic endothelium.