Experimental candidiasis in liver injury

In an attempt to evaluate effects of liver injury and roles of iron metabolism on systemic fungal infection, experimental systemicCandida infection was produced in mice with galactosamine-induced liver injury. Survival rate and extent of fungal lesion are compared between mice with liver injury (Group 1) and ones without liver injury (Group 2). Median survival was 7 and 18 days in Group 1 and 2 respectively after 21 days observation. Mortality rate of Group 1 was significantly higher (P=0.05) than that of Group 2. This difference was reflected to the extent of fungal lesions in that they were extensive and disseminated, involving the multiple organs in Group 1 but predominantly localized to the kidneys in Group 2. UIBC (unbound iron binding capacity) and TIBC (total iron binding capacity), i.e., serum transferrin as well as serum iron levels were significantly lower in Group 1 as compared with those in Group 2. These results indicate that hepatic injury promotesCandida infectionin vivo and suggest that increased susceptibility toCandida in the presence of liver injury is, at least partially, attributable to low UIBC and/or TIBC.     

Three-dimensional solution structure of oryzacystatin-I, a cysteine proteinase inhibitor of the rice, Oryza sativa L. japonica

The three-dimensional structure of oryzacystatin-I, a cysteine proteinase inhibitor of the rice, Oryza sativa L. japonica, has been determined in solution at pH 6.8 and 25 degrees C by (1)H and (15)N NMR spectroscopy. The main body (Glu13-Asp97) of oryzacystatin-I is well-defined and consists of an alpha-helix and a five-stranded antiparallel beta-sheet, while the N- and C-terminal regions (Ser2-Val12 and Ala98-Ala102) are less defined. The helix-sheet architechture of oryzacystatin-I is stabilized by a hydrophobic cluster formed between the alpha-helix and the beta-sheet and is considerably similar to that of monellin, a sweet-tasting protein from an African berry, as well as those of the animal cystatins studied, e.g., chicken egg white cystatin and human stefins A and B (also referred to as human cystatins A and B). Detailed structural comparison indicates that oryzacystatin-I is more similar to chicken cystatin, which belongs to the type-2 animal cystatins, than to human stefins A and B, which belong to the type-1 animal cystatins, despite different loop length.     

Disruption of the epilepsy KCNQ2 gene results in neural hyperexcitability

Benign familial neonatal convulsion (BFNC) is a common idiopathic epilepsy with autosomal dominant inheritance. Recently, two novel voltage-dependent potassium channel genes, KCNQ2 and KCNQ3, were identified by positional cloning as being responsible for BFNC. Heterotetramers of the products of these genes form M-channels and regulate the threshold of electrical excitability of neurons. We disrupted the mouse KCNQ2 gene via gene targeting to study the relationship between KCNQ2 and epilepsy. Homozygous pups (KCNQ2 -/-) died within a few hours after birth owing to pulmonary atelectasis that was not due to the status of epileptic seizures, although their development was morphologically normal. Heterozygous mice had decreased expression of KCNQ2 and showed hypersensitivity to pentylenetetrazole, an inducer of seizure. These data indicate that the decreased expression of KCNQ2 might cause a hyperexcitability of the CNS, which accounts for the mechanism of BFNC.     

Synthesis of Very-Long-Chain Fatty Acids in the Epidermis Controls Plant Organ Growth by Restricting Cell Proliferation

Plant organ growth is controlled by inter-cell-layer communication, which thus determines the overall size of the organism. The epidermal layer interfaces with the environment and participates in both driving and restricting growth via inter-cell-layer communication. However, it remains unknown whether the epidermis can send signals to internal tissue to limit cell proliferation in determinate growth. Very-long-chain fatty acids (VLCFAs) are synthesized in the epidermis and used in the formation of cuticular wax. Here we found that VLCFA synthesis in the epidermis is essential for proper development of Arabidopsis thaliana. Wild-type plants treated with a VLCFA synthesis inhibitor and pasticcino mutants with defects in VLCFA synthesis exhibited overproliferation of cells in the vasculature or in the rib zone of shoot apices. The decrease of VLCFA content increased the expression of IPT3, a key determinant of cytokinin biosynthesis in the vasculature, and, indeed, elevated cytokinin levels. These phenotypes were suppressed in ipt3;5;7 triple mutants, and also by vasculature-specific expression of cytokinin oxidase, which degrades active forms of cytokinin. Our results imply that VLCFA synthesis in the epidermis is required to suppress cytokinin biosynthesis in the vasculature, thus fine-tuning cell division activity in internal tissue, and therefore that shoot growth is controlled by the interaction between the surface (epidermis) and the axis (vasculature) of the plant body.     

Sites of microtubule reorganization in tobacco BY-2 cells during cell-cycle progression

Summary The sites of microtubule (MT) reorganization were examined in synchronized tobacco BY-2 cells. The MTs of these cells were completely destroyed by a combined cold and drug treatment at 0 °C with 100 M propyzamide for 3 h. After the cells were washed and cultured at 30 °C, the reorganization of MTs was observed in detail. Sites for MT reorganization at each stage of the cell cycle were identified on the cell cortex and nuclei, the mitotic apparatus, the nuclei (or the nuclei and cell cortex), and the cell cortex in the S-G₂ phase, M phase, M/G₁ interface, and g₁ phase, respectively. The polypeptide synthesis elongation factor (EF)-1 is co-localized with these sites of MT reorganization. At some stages, microfilaments (MFs) were found to be involved in the reorganization of MTs. Based on these results, the mode of MT reorganization during cell cycle progression is discussed.Abbreviations EF-1 elongation factor 1 - MAP microtubule-associated protein - MF microfilament - MIs mitotic indices - MT microtubule     

Infectivity of different genotypes of human Blastocystis hominis isolates in chickens and rats

Most Blastocystis hominis isolates from humans are believed to be potentially zoonotic. This is because B. hominis isolates found in a variety of other host species have been found to have identical or relatively similar genotypes to those found in human isolates. However, the transmission of human B. hominis isolates to other animals has not been confirmed experimentally. In this study, the infectivity associated with several unique human Blastocystis genotypes (subtypes 2, 3, 4 and 7) was therefore investigated by infecting chickens and rats with two isolates of each subtype experimentally. The results showed that one isolate of subtype 4 and one isolate of subtype 7 was capable of infecting both chickens and rats, while two isolates of subtype 2, another isolate of subtype 4, and another isolate of subtype 7 could only infect chickens. Conversely, two isolates of subtype 3 failed to infect either of the animals. These results confirmed that several genotypes from human isolates could infect chickens and/or rats, indicating that chickens and rats are suitable experimental animal models for studying the zoonotic potential of human Blastocystis isolates.     

Biosynthesis of a novel transformation-sensitive heat-shock protein that binds to collagen. Regulation by mRNA levels and in vitro synthesis of a functional precursor

The synthesis of a major collagen-binding glycoprotein of molecular weight 47,000 was previously shown to be altered by malignant transformation as well as by heat shock in chick embryo fibroblasts (Nagata, K., and Yamada, K.M. (1986) J. Biol. Chem. 261, 7531-7536 and Nagata, K., Saga, S., and Yamada, K.M. (1986) J. Cell Biol. 103, 223-229). In this paper, we examined the synthesis of this heat shock protein (hsp47) in terms of possible functional precursors and its regulation after heat shock and transformation by Rous sarcoma virus. Actinomycin D inhibited the induction of hsp47 after heat shock. Messenger RNAs purified from chick embryo fibroblasts (CEF), heat-treated CEF, and transformed CEF were analyzed in an in vitro translation system. In vitro translated products readily bound to gelatin-Sepharose, and levels were increased after heat shock and decreased after transformation. The increase in mRNA after heat shock was shown more directly by Northern assay using a synthetic oligonucleotide probe. We identified two putative precursors of hsp47 using an in vitro translation/processing system and tunicamycin: one is a 42-kDa primary translation product and the second is a 41-kDa polypeptide lacking signal peptide and carbohydrate moieties. Both of these precursors are biologically active as determined by gelatin-binding activity, in contrast to the lack of binding activity of precursors in several other membrane-associated receptor systems.