Simulated microgravity triggers characteristic morphology and stress response in Saccharomyces cerevisiae

Reduction of gravity results in changes in gene expression and morphology in the budding yeast Saccharomyces cerevisiae. We studied the genes responsible for the morphological changes induced by simulated microgravity (SMG) using the yeast morphology data. We comprehensively captured the features of the morphological changes in yeast cells cultured in SMG with CalMorph, a high-throughput image-processing system. Statistical analysis revealed that 95 of 501 morphological traits were significantly affected, which included changes in bud direction, the ratio of daughter to mother cell size, the random daughter cell shape, the large mother cell size, bright nuclei in the M phase, and the decrease in angle between two nuclei. We identified downregulated genes that impacted the morphological changes in conditions of SMG by focusing on each of the morphological features individually. Gene Ontology (GO)-enrichment analysis indicated that morphological changes under conditions of SMG were caused by cooperative downregulation of 103 genes annotated to six GO terms, which included cytoplasmic ribonucleoprotein granule, RNA elongation, mitotic cell cycle phase transition, nucleocytoplasmic transport, protein–DNA complex subunit organization, and RNA localization. P-body formation was also promoted under conditions of SMG. These results suggest that cooperative downregulation of multiple genes occurs in conditions of SMG.     

Yeast Lrg1p acts as a specialized RhoGAP regulating 1,3-beta-glucan synthesis.

Selection of an extragenic suppressor of fks1-1154 Deltafks2, mutations in the catalytic subunits of yeast 1,3-beta-glucan synthase (GS) conferring temperature-sensitivity, led to the LRG1 gene, which was originally identified as a LIM-RhoGAP homologous gene. Mutations in the LRG1 gene restore impaired 1,3-beta-glucan synthesis in the fks1-1154 Deltafks2 mutant as well as that in rho1-2, a temperature-sensitive mutant of Rho-type GTPase that functions as a regulatory subunit of GS. Two-hybrid analyses of Lrg1p, which contains a sequence conserved among Rho GTPase-activating proteins (GAPs), revealed its specific interactions with the active form of Rho1p. Among eight potential yeast RhoGAPs, Lrg1p is the only member that negatively regulates GS activity: mutations in the rest of GAPs, including bem2, Deltabem3, Deltasac7, Deltabag7, Deltarga1, Deltarga2 and Deltargd1, do not suppress impairment of 1,3-beta-glucan synthesis. Analyses of Mpk1p phosphorylation revealed the inability of Lrg1p to regulate the Pkc1p-MAP kinase cascade, a distinct Rho1p-regulating signalling pathway known to be affected by the GAPs, Bem2p and Sac7p. Thus, different groups of Rho1p GAPs control the activity of different Rho1p-effector proteins.     

Ultrastructure of immotile spermatozoa obtained from infertile male patients

We sometimes experienced infertile patients whose sperms had no motility but were not stained by Eosin Y. In this paper we report five cases of so-called "immotile spermatozoa". The ultrastructure of sperm tails was examined by transmission electrone microscope (TEM). These cases were selected from the out-patient population who attended infertility clinic of our department. The semen analyses showed that all the cases had sperm motility below 1% and more than 90% of the spermatozoa were proven alive. Family history revealed that one case had an infertile sibling. None of them had situs inversus, bronchiectasis and chronic sinusitis which are classic trias of Kartagener's syndrome. They had no symptoms of upper respiratory tract infection which was caused by the abnormality in the flagella of the respiratory tract. The TEM pictures of sperm tails showed partial deletion of inner dynein arms in two cases, lack of central microtubular doublets (so-called 9 + 0) in two cases and disarrangement of microtubular doublets in one case. For the treatment of these cases there is no effective means but AID. However, the rapid progress of IVF-ET techniques and a report that the spermatozoa from Kartagener's syndrome had showed penetration into eggs encouraged us to think the micromanipulation of spermatozoa with IVF-ET as a hopeful option of the treatment in the near future.     

An analysis of reverse osmotic characteristics of American-standard type tubular module

Reverse osmosis experiments were carried out with a TM-5-14 tubular module to obtain its reverse osmotic characteristics. Analysis of the data based on the general equations proposed by Ohya and Sourirajan (5) gives membrane characteristic constants, A = 0.845 x 10^?6 g·mole H₂O/cm²·atm·s, and (D_AM/ kδ) = 1.38 x 10^-5cm/sec. The experimental data of mass transfer coefficients agree well with the equation proposed by Linton and Sherwood (7).     

An analysis of reverse osmotic characteristics of ROGA-4000 spiral-wound module

Reverse osmosis experiments were carried out with a ROGA-4000 Spiral-Wound module to obtain its reverse osmotic characteristics. Analysis of the data based on the general equations proposed by Ohya and Sourirajan (10) gives membrane characteristic constants, A = 1.24 × 10^-6 g mole H·₂O/cm²·atmsec, and (D_AM /kδ) = 2.3 × 10^-5 cm/sec, which show the membrane belongs to the CA-NRC-18 type family. The experimental data of mass-transfer coefficients always show about 35% lower values than the theoretical value of laminar flow between flat parallel membranes proposed by Kimura and Sourirajan (12).     

Interband-resonant light modulation by intersubband-resonant lightin undoped quantum wells

Interband-resonant light modulation by intersubband-resonant light in undoped quantum wells is investigated. Theoretical calculation for the modulation is carried out by considering not only the excitonic interband-transition but also the continuous level transition between the conduction and valence bands. The modulation characteristics are compared with those of the modulation using n-doped quantum wells. The possibility of the modulation using undoped quantum well is successfully shown by real-time single-shot experiment using Ti-Al₂O₃ and CO₂ lasers for interband- and intersubband-resonant lights at room temperature     

Theory of spectral linewidth of external cavity semiconductor lasers

A new formula of the spectral linewidth of external cavity semiconductor lasers is proposed, with which linewidth narrowing with the optical feedback is discussed. It is shown that in the limit of large external cavity length, the linewidth caused by the phase diffusion due to spontaneously emitted photons becomes dominant and the linewidth decreases proportionally to the inverse of the external cavity length.     

Preparation of lamellar hybrid inorganic–organic films of layered titanate and cationic or anionic surfactants

Hybrid inorganic–organic films were fabricated from aqueous colloidal solutions of a layered titanate salt and cationic and anionic surfactants. Cetyltrimethylammonium bromide and dodecyl phosphate were used as cationic and anionic surfactants, respectively. When the substrates dip-coated with mixtures of the titanate salt colloids and the surfactants were treated with steam in a closed vessel, hybrid inorganic–organic films with a lamellar structure were fabricated. Although the titanate layers have a negative charge, the hybrid inorganic–organic films consisting of the titanate layer and the anionic surfactant could be obtained, as well as the ones including the cationic surfactants.