Hypoxia-inducible factor 1α regulates branching morphogenesis during kidney development

The kidneys are exposed to hypoxic conditions during development. Hypoxia-inducible factor (HIF), an important mediator of the response to hypoxia, is believed to have an important role in development. However, the relationship between HIF and branching morphogenesis has not been elucidated clearly.     

The APC/C activator Cdh1 regulates the G2/M transition during differentiation of placental trophoblast stem cells

Differentiation of placental trophoblast stem (TS) cells to trophoblast giant (TG) cells is accompanied by transition from a mitotic cell cycle to an endocycle. Here, we report that Cdh1, a regulator of the anaphase-promoting complex/cyclosome (APC/C), negatively regulates mitotic entry upon the mitotic/endocycle transition. TS cells derived from homozygous Cdh1 gene-trapped (Cdh1^GT/GT) murine embryos accumulated mitotic cyclins and precociously entered mitosis after induction of TS cell differentiation, indicating that Cdh1 is required for the switch from mitosis to the endocycle. Furthermore, the Cdh1^GT/GT TS cells and placenta showed aberrant expression of placental differentiation markers. These data highlight an important role of Cdh1 in the G2/M transition during placental differentiation.     

Gelation Phenomena Induced by Alkali-alcohol Treatment of 7S and 11S Components in Soybean Globulins

Transparent gels containing about 2% protein were obtained by mixing alkaline dope solution of 7S or 11S soybean proteins with alcohol. The 7S component showed the ability to form a stronger gel than the 11S. This phenomenon depended on pH and alcohol concentration. In 66 % ethanol, the viscosity of the 7S and 11S reached maxima at pH 11.4 and 11.2, respectively. Above these pH levels where further unfolding and dissociation into subunits of the protein molecules occur, the viscosity decreased rather. The effectiveness of alcohol to increase viscosity increased in the order; n-butanol < tert-butanol < n-propanol < iso-propanol < ethanol < methanol. Alcohols having minor hydrophobicity were more effective for increasing viscosity, but ethylene glycol was ineffective. The addition of NaCl or 2-mercaptoethanol to ethanol-mixed alkaline dope solutions resulted in the remarkable increment of the viscosity, especially for the 7S.     

Extensin Secreted into the Culture Medium by Tobacco Cells I. Purification and Some Properties

The medium of 12-day-old culturs of tobacco cells (Nicotianatabacum L., var Xanthi; line XD-6S) contain c.a. 160mg/literof protein, of which 14% of the constituent ami no acids werefound to be hydroxyproline. By sequential column chromatographiesand CsCl density-gradient centrifugation, a basic hydroxyproline-richglycoprotein was purified from the medium and found to havean amino acid composition typical of extensin; with a high levelof hydroxyproline (33mole%), tyrosine (13%), and lysine (14%).The glycoprotein contained 42% (w/w) of sugars, among whicharabinose was the major component (85%). The proportion of thisextensin in the proteins in the culture medium was estimatedto be much higher than that of arabino-galactan protein (about5 times higher) on a protein basis, with extensin comprisingbetween 25% and 41%, and probably about 37% of the proteinsin the medium. (Received September 19, 1988; Accepted December 26, 1988)     

Immunohistochemical localization of proteoglycans in interstitial elements of human pancreas and biliary system

Summary The immunohistochemical localization of large proteoglycan and small proteoglycan was observed, using antibodies 2B1 and 6B6 (Sobueet al., 1988, 1989a), in fetal and adult pancreas and biliary system as well as in tumour tissues, obtained from 11 autopsies and 74 biopsies. The distribution of chondroitin 4- and 6-sulphate side chains, type I and IV collagen and elastin were also studied. In adult pancreas and all the biliary tracts examined, periductal fibrous tissues consisted mainly of dermatan sulphate small proteoglycan with networks of fibrous elements, which were composed of large proteoglycan, elastin, type I collagen and type IV collagen. In the interstitial components of cystadenoma of pancreas and biliary duct carcinoma, similar small proteoglycan-rich components were relatively abundant, although large proteoglycan was present in much larger amounts than that in non-neoplastic adult tissues. In some cholangiomas, the extra-and intracellular hyaline globules formed by the carcinoma cells were found to contain chondroitin sulphate large proteoglycan, laminin and fibronectin.The distribution of proteoglycans was observed to be different in the arterial walls of the interlobular tissues of the adult and the fetal pancreas. The biological significance of large and small proteoglycans in the interstitial connective tissues was discussed.     

New mutations fts-36, lts-33, and ftsW clustered in the mra region of the Escherichia coli chromosome induce thermosensitive cell growth and division.

Three new mutants of Escherichia coli showing thermosensitive cell growth and division were isolated, and the mutations were mapped to the mra region at 2 min on the E. coli chromosome map distal to leuA. Two mutations were mapped closely upstream of ftsI (also called pbpB), in a region of 600 bases; the fts-36 mutant showed thermosensitive growth and formed filamentous cells at 42 degrees C, whereas the lts-33 mutant lysed at 42 degrees C without forming filamentous cells. The mutation in the third new thermosensitive, filament-forming mutant, named ftsW, was mapped between murF and murG. By isolation of these three mutants, about 90% of the 17-kilobase region from fts-36-lts-33 to envA could be filled with genes for cell division and growth, and the genes could be aligned.     

Localization of cytochrome P-450 in the colonic mucosa of 3-methylcholanthrene-pretreated and untreated rats An immunohistochemical study

Summary Immunohistochemical localization of cytochrome P-450 in the colonic mucosa of 3-methylcholanthrene-pretreated and untreated rats was studied by indirect fluorescent antibody staining technique. A polyclonal antibody for cytochrome P-450_MC purified from hepatic microsomes of 3-methylcholanthrene-pretreated rats was used for this experiment. A strong immunofluorescence was found to be localized in the cytoplasm of the surface epithelium of the mucosa in the colon of 3-methylcholanthrene-pretreated rats. A faint immunofluorescence was also observed in the epithelium of untreated rats. 7-Ethoxycoumarin O-deethylase activity of colonic microsomes was significantly enhanced by 3-methylcholanthrene-pretreatment in parallel with an increase in the intensity of immunostaining for cytochrome P-450_MC in Western blotting analysis. This is the first report on the localization of cytochrome P-450 in the colonic mucosa.     

Optimal seasonal timing of univoltine and bivoltine insects

This study examines the optimal seasonal timing of the life cycle for univoltine and bivoltine insects, assuming that resource availability has a peak in the middle of a year and is symmetric around it. Results show that if the growth rate increases in proporrion to the bodyweight, bivoltine life cannot be optimal. If the growth rate is a power function of the bodyweight with a power smaller than unity, a symmetric bivoltine solution can be the optimal provided that the resource availability has a plateau in the middle of the season. If the resource availability has a sharp peak, the optimal pattern is an asymmetric bivoltine solution in which the larval periods of two generations differ in length. The bivoltine life cycle is more likely to be superior to the univoltine one if: growth is fast, suitable growing season is long, biomass loss during nonlarval stages is small, and egg size is small.     

Molecular cloning of the gene of a penicillin-binding protein supposed to cause high resistance to beta-lactam antibiotics in Staphylococcus aureus.

A novel penicillin-binding protein, PBP-2' (Mr about 75,000), is known to be induced in excessively large amount by most beta-lactam compounds in cells of a clinically isolated strain of Staphylococcus aureus, TK784, that is highly resistant to beta-lactams and also most other antibiotics. This protein has very low affinities to most beta-lactam compounds and has been supposed to be the cause of the resistance of the cells to beta-lactams. A 14-kilobase DNA fragment was isolated from the cells that carried the gene encoding this penicillin-binding protein and also a genetically linked marker that is responsible for the resistance to tobramycin. This DNA was cloned on plasmid pACYC184 and was shown to cause both production of PBP-2' and resistance to tobramycin in Escherichia coli cells. However, the formation of PBP-2' in E. coli was only moderate and was independent of normal inducer beta-lactams. The PBP-2' formed in the E. coli cells showed slow kinetics of binding to beta-lactams similar to that of PBP-2' formed in the original S. aureus cells and gave a similar pattern of peptides to the latter when digested with the proteolytic V8 enzyme of S. aureus.     

Peptidoglycan synthetic activities in membranes of Escherichia coli caused by overproduction of penicillin-binding protein 2 and rodA protein

Penicillin-binding protein (PBP)-2 and the RodA protein are known to function in determining the rod shape of Escherichia coli cells. Peptidoglycan biosynthetic reactions that required these two proteins were demonstrated in the membrane fraction prepared from an E. coli strain that overproduced both of these two proteins and which lacked PBP-1B activity (the major peptidoglycan synthetase activity in the normal E. coli membranes). The cross-linked peptidoglycan was synthesized from UDP-N-acetylmuramylpentapeptide and UDP-N-acetylglucosamine in the presence of a high concentration of cefmetazole that inhibited all of PBPs except PBP-2. The peptidoglycan was synthesized via a lipid intermediate and showed up to 30% cross-linking. The cross-linking reaction was strongly inhibited by the amidinopenicillin, mecillinam, and by other beta-lactam antibiotics that have a high affinity for PBP-2, but not by beta-lactams that had very low affinity for PBP-2. The formation of peptidoglycan required the presence of high levels of both PBP-2 and the RodA protein in the membranes, but it is unclear which of the two proteins was primarily responsible for the extension of the glycan chains (transglycosylation). However, the sensitivity of the cross-linking reaction to specific beta-lactam antibiotics strongly suggested that it was catalyzed by PBP-2. The transglycosylase activity of the membranes was sensitive to enramycin and vancomycin and was unusual in being stimulated greatly by a high concentration of a chelating agent.