Spatial Analysis of Slowly Oscillating Electric Activity in the Gut of Mice Using Low Impedance Arrayed Microelectrodes

Smooth and elaborate gut motility is based on cellular cooperation, including smooth muscle, enteric neurons and special interstitial cells acting as pacemaker cells. Therefore, spatial characterization of electric activity in tissues containing these electric excitable cells is required for a precise understanding of gut motility. Furthermore, tools to evaluate spatial electric activity in a small area would be useful for the investigation of model animals. We thus employed a microelectrode array (MEA) system to simultaneously measure a set of 8×8 field potentials in a square area of ∼1 mm². The size of each recording electrode was 50×50 µm², however the surface area was increased by fixing platinum black particles. The impedance of microelectrode was sufficiently low to apply a high-pass filter of 0.1 Hz. Mapping of spectral power, and auto-correlation and cross-correlation parameters characterized the spatial properties of spontaneous electric activity in the ileum of wild-type (WT) and W/W^v mice, the latter serving as a model of impaired network of pacemaking interstitial cells. Namely, electric activities measured varied in both size and cooperativity in W/W^v mice, despite the small area. In the ileum of WT mice, procedures suppressing the excitability of smooth muscle and neurons altered the propagation of spontaneous electric activity, but had little change in the period of oscillations. In conclusion, MEA with low impedance electrodes enables to measure slowly oscillating electric activity, and is useful to evaluate both histological and functional changes in the spatio-temporal property of gut electric activity.     

A 5-bp Insertion in Mip Causes Recessive Congenital Cataract in KFRS4/Kyo Rats

We discovered a new cataract mutation, kfrs4, in the Kyoto Fancy Rat Stock (KFRS) background. Within 1 month of birth, all kfrs4/kfrs4 homozygotes developed cataracts, with severe opacity in the nuclei of the lens. In contrast, no opacity was observed in the kfrs4/+ heterozygotes. We continued to observe these rats until they reached 1 year of age and found that cataractogenesis did not occur in kfrs4/+ rats. To define the histological defects in the lenses of kfrs4 rats, sections of the eyes of these rats were prepared. Although the lenses of kfrs4/kfrs4 homozygotes showed severely disorganised fibres and vacuolation, the lenses of kfrs4/+ heterozygotes appeared normal and similar to those of wild-type rats. We used positional cloning to identify the kfrs4 mutation. The mutation was mapped to an approximately 9.7-Mb region on chromosome 7, which contains the Mip gene. This gene is responsible for a dominant form of cataract in humans and mice. Sequence analysis of the mutant-derived Mip gene identified a 5-bp insertion. This insertion is predicted to inactivate the MIP protein, as it produces a frameshift that results in the synthesis of 6 novel amino acid residues and a truncated protein that lacks 136 amino acids in the C-terminal region, and no MIP immunoreactivity was observed in the lens fibre cells of kfrs4/kfrs4 homozygous rats using an antibody that recognises the C- and N-terminus of MIP. In addition, the kfrs4/+ heterozygotes showed reduced expression of Mip mRNA and MIP protein and the kfrs4/kfrs4 homozygotes showed no expression in the lens. These results indicate that the kfrs4 mutation conveys a loss-of-function, which leads to functional inactivation though the degradation of Mip mRNA by an mRNA decay mechanism. Therefore, the kfrs4 rat represents the first characterised rat model with a recessive mutation in the Mip gene.     

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.     

Mechanism of How Salt-Gradient-Induced Charges Affect the Translocation of DNA Molecules through a Nanopore

Experiments using nanopores demonstrated that a salt gradient enhances the capture rate of DNA and reduces its translocation speed. These two effects can help to enable electrical DNA sequencing with nanopores. Here, we provide a quantitative theoretical evaluation that shows the positive net charges, which accumulate around the pore entrance due to the salt gradient, are responsible for the two observed effects: they reinforce the electric capture field, resulting in promoted molecule capture rate; and they induce cationic electroosmotic flow through the nanopore, thus significantly retarding the motion of the anionic DNA through the nanopore. Our multiphysical simulation results show that, during the polymer trapping stage, the former effect plays the major role, thus resulting in promoted DNA capture rate, while during the nanopore-penetrating stage the latter effect dominates and consequently reduces the DNA translocation speed significantly. Quantitative agreement with experimental results has been reached by further taking nanopore wall surface charges into account.     

Determination of the source of immunoreactive relaxin in the cat

We have recently reported the secretory profile of relaxin throughout gestation in the cat. Because the appearance of relaxin begins at about Day 20 (Day O = ovulation) and because implantation begins shortly before this at Days 13-14, we hypothesized that relaxin was of feto-placental origin. To test this hypothesis, we used 4 experimental groups: 1) Control (laparotomy-only at Day 23 or 42, n = 4); 2) Early Ovariectomy (Ovx, bilateral ovariectomy between Days 23 and 26, n = 4); 3) Late Ovx (bilateral ovariectomy between Days 40 and 44, n = 4); 4) Tissue Removal (removal of feto-placental units, uterus, and one ovary on Days 16, 21, 28 and 35, n = 1 per day). Pregnancies were maintained in both Ovx groups by progesterone administration. Relaxin secretory patterns in Ovx groups were similar to the Control data. Relaxin was detectable in plasma beginning at about Day 20, with maximum concentrations reached by Day 30. Relaxin concentrations were highest (immunoactivity per mg tissue) in homogenates of placental tissues as compared to luteal, fetal, or uterine tissues. Altogether, these data indicate that the feto-placental unit is the source of relaxin in the cat.     

Properties of the binding of follicle-stimulating hormone to the fetal rat testis

Basic properties of the binding of [131I]-labeled rat FSH ([131I]rFSH) to the testicular homogenates of fetal rats were analyzed by micro-radioreceptor assay. Specific binding of FSH was detectable in the testicular preparations from 15.5-day fetuses, but it was very low. After 17.5 days of gestation, specific FSH binding was apparent in the testis and was effectively displaced by rat FSH but not by rat LH. The Scatchard plot analyses of the binding of FSH to the testicular preparations of fetuses showed straight lines similar to those of postnatal rats, suggesting the presence of a single class of binding sites. The mean dissociation constant (Kd) for FSH receptors in 17.5-day fetuses was 0.413 +/- 0.043 nM, which was significantly greater than that in postnatal rats at 50 days of age. However, the Kd in 19.5-day fetuses was not significantly different from those in 17.5-day fetuses and postnatal rats due to its considerable variance. The capacity of FSH binding sites was 0.51 +/- 0.01 fmol/testis in 17.5-day fetuses, which was significantly less than those of 19.5-day fetuses and postnatal rats.     

Induction of interdigitating reticulum cell-like differentiation in human monocytic leukemia cells by conditioned medium from IL-2-stimulated helper T-cells

Monocytic leukemia (MoL) cells were obtained from the peripheral blood of a patient in whom the leukemic cells infiltrating various lymphoreticular organs exhibited features intermediate between interdigitating reticulum cells (IDC) and ordinary phagocytic macrophages, whereas the leukemic cells in the peripheral blood were essentially monocytic and lacked such features. Peripheral blood CD4+ T-cells were established as an interleukin-2-dependent T-cell line. When the MoL cells were exposed for a few days to conditioned medium from the T-cell line, they extended several dendritic cytoplasmic projections and became intensely positive for HLA-DR antigen, cytoplasmic S-100β protein, and CD1 antigen. Functionally, the conditioned medium significantly down-regulated Fc-mediated and Fc-independent phagocytic activities, and the levels of lysosomal enzymes such as lysozyme and nonspecific esterase in the MoL cells. Moreover, the conditioned medium significantly up-regulated the accessory cell function of the MoL cells as measured by the primary allogenic mixed leukocyte reaction (MLR). Furthermore, the conditioned medium significantly down-regulated the expression of CD14 antigen. Biochemical analysis indicated that the factor responsible for these changes is a protein which is distinct from known human cytokines and whose molecular weight is approximately 31 kDa. These findings suggest that IDC are closely related the monocytic lineage and that helper T-cells play an important role in constructing the microenvironment of T-lymphoid tissues which is necessary for the differentiation and maturation of IDC.     

A Ca2+- and Voltage-Dependent Cl- -Sensitive Anion Channel in the Chara Plasmalemma: A Patch-Clamp Study

The inside-out patch-clamp technique was applied to the plasmolyzedplasmalemma of inter-nodes of Chara corallina without enzymatictreatment. We found two different types of channel activitythat were CP^–-sensitive. Both types of channel were Ca²⁺-dependent.However, the one that exhibited greater dependence on Ca²⁺ ionswas the focus of our studies, and we named it the Ca²⁺-dependentCP^–-sensitive anion channel. When the concentration ofCa²⁺ ions on the cyto-plasmic side was 1.0 µM, the Ca²⁺-dependentCP^–-sensitive channel opened most frequently between approximately–80 and –100 mV. At 10 µM Ca²⁺, it openedless frequently, and at 0.1 µM Ca²⁺ it scarcely openedat all. These observations indicate that the anion channel ofinterest is voltage-dependent over a restricted range of concentrationsof Ca²⁺ ions. The dependence on Ca²⁺ and voltage of the channelcan explain the behavior of the excitable Ca²⁺-activated Cl^–channel in the Chara plasmalemma. The channel activity was blockedby several antagonists of calmodulin. ⁴ Present Address: Department of Biology, College of GeneralEducation, Osaka University, Toyonaka, 560 Osaka, Japan (Received October 8, 1990; Accepted April 4, 1991)     

Detection of 1-nitropyrene in yakitori (grilled chicken)

Pieces of raw chicken with or without a marinating sauce were grilled over a city gas flame, extracted with benzene-ethanol (4:1) by ultrasonication and fractionated into diethyl ether-soluble neutral, acidic and basic fractions. The mutagenicity of these fractions was measured with Salmonella typhimurium strains TA100, TA98, TA98NR and TA98/1,8-DNP6 in the presence and absence of a 9000 X g post-mitochondrial supernatant from Aroclor 1254-treated Sprague-Dawley rat liver (S9 mix). The basic fraction of yakitori without the sauce was more mutagenic than the other fractions for S. typhimurium strain TA98 in the presence of S9 mix. This is probably due to the presence of amino acid or protein pyrolysates. However, when the chicken was grilled with the sauce, the basic fraction showed lower mutagenicity for strain TA98 in the presence of S9 mix than did the same fraction without the sauce. The neutral fraction of yakitori with sauce showed high mutagenicity for strain TA98 in the absence of S9 mix, but low mutagenicity for strains TA98NR and TA98/1,8-DNP6, suggesting that this fraction might contain nitropyrenes (NPs). The neutral fraction of yakitori was analyzed by high-performance liquid chromatography (HPLC). The neutral fraction of the chicken grilled with the sauce for 3, 5 and 7 min contained 3.8, 19 and 43 ng, respectively, of 1-NP per gram of yakitori accounting for 3.0, 2.7 and 1.3%, respectively, of the total mutagenicity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tripolyphosphate is an alternative phosphodonor of the selective protein phosphorylation of liver microsomal membrane

Two proteins (Mr = 145,000 and Mr = 130,000) of rat liver microsomal membrane are selectively phosphorylated in a characteristic biphasic time course by incubating the membrane with [gamma-32P]ATP in the absence of exogenously added Mg2+ (Lam, K. S., and Kasper, C. B. (1980) J. Biol. Chem. 255, 259-266). This endogenous phosphorylation system was solubilized with Triton X-100 and fractionated by chromatography with DEAE-cellulose and Sepharose 4B. The resulting preparation lacked both ATPase and inorganic pyrophosphatase activity, but retained its original character: the first phase occurred in the presence of ATP but the second phase was initiated after its depletion, implying the presence of a phosphodonor other than ATP. The putative phosphoryl donors were demonstrated to be ATP in the first phase and in the second phase tripolyphosphate, which is present in [gamma-32P]ATP preparations as a radioactive impurity. The latter conclusion was corroborated by results showing that tripolyphosphate purified from a commercial [gamma-32P]ATP and chemically synthesized [32P] tripolyphosphate were both capable of phosphorylating the two proteins and that the unlabeled tripolyphosphate competed effectively against the phosphodonor. A rapid dephosphorylation was observed in both phases upon removal of substrates during the reaction, indicating that there is a continuous turnover of the phosphoryl groups being transferred to the proteins. The second phase of phosphorylation maintained by the tripolyphosphate was shown to be reversibly inhibited by micromolar levels of ATP, ADP, and nonhydrolyzable analogues of these compounds. The implications of this unique phosphorylation system are discussed.