Mutagenic effect of orally given AF-2 on embryonic cells in pregnant Syrian hamsters

Pregnant hamsters were given various doses of AF-2 by stomach tube; then the cells of their embryos were isolated and cultured in normal medium. Chromosome preparations were made within 24 h after the start of primary culture, and examined for chromosomal aberrations. Marked chromosomal abnormalities were observed in cells of embryos of animals treated with AF-2 at over 20 mg/kg. Samples of surviving cells were also cultured in normal medium for 48 h, and then selected in medium containing 8AG or 6TG. This treatment with AF-2 caused marked dose-dependent induction of 8AG- or 6TG-resistant mutations: mutant colonies were even obtained after a single treatment with 2 mg of AF-2 per kg. These results show that this is a sensitive and useful mammalian system for detecting environmental mutagens.     

A simple method for the isolation of basolateral plasma membrane vesicles from rat kidney cortex Enzyme activities and some properties of glucose transport

A procedure for preparing basolateral membrane vesicles from rat renal cortex was developed by differential centrifugation and Percoll density gradient centrifugation, and the uptake of d-[³H]glucose into these vesicles was studied by a rapid filtration technique. (Na⁺ + K⁺)-ATPase, the marker enzyme for basolateral membranes, was enriched 22-fold compared with that found in the homogenate. The rate of d-glucose uptake was almost unaffected by Na⁺ gradient (no overshoot).     

Stereoselectivity of the reduction of carvone and dihydrocarvone by suspension cells of Nicotiana tabacum

The biotransformation of foreign substrates with suspension cells of Nicotiana tabacum was tested with (4R)-(?)- and (4S)-(+)-carvones, (     

Possible role of coexpression of CD9 with membrane-anchored heparin-binding EGF-like growth factor and amphiregulin in cultured human keratinocyte growth

CD9 is a protein with 4 transmembrane domains, and functions as a cell surface antigen. We have previously reported that CD9 functions as an up-regulator of membrane-anchored heparin-binding EGF-like growth factor (proHB-EGF) activity, which is a potent mitogen as well as a soluble HB-EGF. Anti-CD9 antibodies can neutralize the juxtacrine activity of proHB-EGF when both CD9 and proHB-EGF are coexpressed. We demonstrated here: (1) the CD9 gene was transcribed and translated in the cultured human keratinocytes; (2) anti-CD9 antibody inhibited the approximately 50% growth of human keratinocytes in culture; (3) CD9 was coprecipitated with proHB-EGF and membrane-anchored amphiregulin (proAR), and (4) the transient coexpression of CD9 with proHB-EGF or proAR in mouse L cells up-regulated their juxtacrine growth factor activities. These results suggest that CD9 would make a heterodimer and/or trimer complex with proHB-EGF and proAR, and might cooperate with proHB-EGF and proAR for human keratinocyte growth in a juxtacrine manner. J. Cell. Physiol. 171:291–298, 1997. © 1997 Wiley-Liss, Inc.     

Ultrastructure of receptaculum seminis in Haemaphysalis longicornis (Acari: Ixodidae) in relation to inserted endospermatophore

The receptaculum seminis, opening into the female genital tract, is found only in the metastriate ixodid ticks. An endospermatophore that has been inserted into the female genital aperture at copulation is first stored in the receptaculum seminis, where spermiogenesis is completed before the sperm ascend the oviducts. The receptaculum seminis consists of a simple cuticularized epithelium. Epithelial cells in sexually matured females develop during feeding and become active in secretion. Secretions discharged from epithelial cells are released into the lumen of this organ through the cuticle and may act on the wall of the inserted endospermatophore. The fact that resumption of spermiogenesis (spermateleosis) has already occurred before destruction of the endospermatophore just after copulation suggests that secretions from epithelial cells of the receptaculum seminis are not the trigger of spermateleosis, but a destructive agent of the endospermatophore wall. J Morphol 231:143–147, 1997. © 1997 Wiley-Liss, Inc.     

Decreased expression of the mRNA for somatostatin in the periventricular nucleus of depression-model rats.

Expression of the mRNA for somatostatin (SRIF) in the periventricular nucleus (PeN), the level of SRIF in the stalk-median eminence (SME) and the concentration of growth hormone (GH) in the plasma were examined in depression-model rats in an attempt to confirm the hypothesis that SRIF neurons in the hypothalamus are hypofunctional in this model. We exposed male Wistar rats to intermittent walking stress for two weeks and then we measured their spontaneous running activity for 12 days. We divided the rats into a depression-model group and a partial-recovery group according to the spontaneous running activity of each rat after the termination of exposure to stress. Expression of SRIF mRNA in the PeN of the hypothalamus was monitored by in situ hybridization and relative levels were determined with an image analysis system. The relative level of expression of SRIF mRNA in the PeN was lower in rats in the depression-model group than in the control group and the partial-recovery group. The level of SRIF in the SME was lower and the plasma concentration of GH was higher in the depression-model group than in the other groups. Our findings suggest that reduced expression of mRNA for SRIF in the PeN might be associated with the pathophysiology of rats with this particular model of depression.     

Functional analysis of rat renal organic anion transporter OAT-K1: bidirectional methotrexate transport in apical membrane.

Renal organic anion transporter OAT-K1 was stably transfected in MDCK cells and examined for its transport characteristics and membrane localization. OAT-K1 mediated both uptake and efflux of methotrexate in the apical membranes. Immunoblotting showed that the apparent molecular mass of the expressed OAT-K1 was 50 kDa, which was comparable to that found in the rat renal brush-border membranes. The OAT-K1-mediated methotrexate transport was significantly inhibited in the presence of several organic anions such as folate and sulfobromophthalein. These findings suggest that OAT-K1 mediates bidirectional methotrexate transport across the apical membranes, and may be involved in the renal handling of methotrexate.     

Peptide Transporter in the Rat Small Intestine: Ultrastructural Localization and the Effect of Starvation and Administration of Amino Acids

Peptide transporter-1 is a H+/peptide cotransporter responsible for the uptake of small peptides and peptide-like drugs, and is present in the absorptive epithelial cells of the villi in the small intestine (duodenum, jejunum, and ileum). It has been localized to the apical microvillous plasma membrane of the absorptive epithelial cells of the rat small intestine using the immunogold electron microscopic technique. Digital image analysis of the jejunum revealed that the transporter protein was abundant at the tip of the villus and that the amount decreased from the tip of the villus to its base. The effect of dietary administration of amino acids and starvation on the expression of PepT1 in the jejunum was examined by immunoblotting and image analysis of immunofluorescence. Starvation markedly increased the amount of peptide transporter present, whereas dietary administration of amino acids reduced it. The gradient of the transporter protein along the crypt-villus axis was maintained under either condition. These observations show that it is specific to the microvillous plasma membrane and that its expression is regulated by the nutritional condition.