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1.
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.  相似文献   
2.
Received: 23 June 1993 / Accepted in revised form: 15 September 1994  相似文献   
3.
Expression of the fragile X site fra(X)(q27.3) was studied in thymidine-prototrophic and auxotrophic human-mouse somatic cell hybrids. In these cells, low thymidylate stress, achieved by 5-fluoro-2'-deoxyuridine (FdU) treatment and by limiting the exogenous supply of thymidine (dT), induced fragile X expression. High thymidylate stress, produced by supplying excess amounts of dT, was also effective in inducing fragile X expression, even in a hybrid clone that retained a fragile X chromosome as the only human chromosome; addition of deoxycytidine (dC) completely abolished this effect. In contrast, 5-bromo-2'-deoxyuridine (BrdU) did not induce fragile X expression. Cell-cycle analysis of BrdU-deprived thymidine-auxotrophic hybrid cells indicated that one round of DNA replication under thymidylate stress conditions is sufficient for fragile X expression. Our results suggest that the expression is an intrinsic property of the fragile site itself, which is believed to be composed of replicon clusters with pyrimidine-rich DNA sequence(s).  相似文献   
4.
The membrane-bound acid alpha-glucosidase was purified partially (400-fold) from human placenta by solubilization with trypsin, concanavalin A-Sepharose chromatography, Ultrogel AcA-34 gel filtration, and Sephadex G-100 affinity chromatography. Two molecular forms of the enzyme were found in the final preparation of the purified enzyme. They were identical in molecular weight with a precursor (110 kDa) and an early intermediate form (105 kDa) of this enzyme. Also direct incubation of the membrane fraction without trypsin resulted in a release mainly of the 105 kDa form, which was inhibited by N-ethylmaleimide, but not by leupeptin, pepstatin or phenylmethylsulfonylfluoride. It was concluded that the precursor of acid alpha-glucosidase is an intrinsic membrane protein, which is transported into lysosomes after solubilization by proteolysis.  相似文献   
5.
A disposable filter unit containing a hydrophobic grid-membrane filter (HGMF) was developed. The unit is liquid tight to serve as a specimen transport container and, by removal of the funnel extender (175- or 300-ml capacity), the unit becomes less than the height of two stacked petri plates to save space during in situ incubation. The polyethylene mesh which supports the HGMF facilitates rinse removal of any substance(s) that would interfere with microbial growth. The correlations between a pour plate, a conventional square HGMF, and a disposable filter unit on microbial enumeration were examined. Characteristics (e.g., clumping, spreading, etc.) of some microorganisms limit the linear counting range to less than 1,000 CFU per filter.  相似文献   
6.
A simple method is described for picomole determinations of fatty acid metal salts. Fatty acid salts are directly labeled with 4-bromomethyl-7-methoxycoumarin in the presence of excess ethylenediaminetetraacetic acid tripotassium salt without any solvent extractions. The fluorescence derivatives of fatty acids are separated by reverse-phase high-performance liquid chromatography followed by fluorometric detection. The response of each fatty acid (C8-C18) calcium salt is linear from 1 to 50 micrograms/ml of samples. The detection limit is about 7 pmol. Good recoveries are obtained for the calcium salts of myrystic acid and soap (C8-C18, C18:1,2). The new method is successfully applied to the study on biodegradation of fatty acids in river water.  相似文献   
7.
A method for enzyme immunoassay of thyroid-stimulating hormone (TSH) is described, TSH was conjugated with horseradish peroxidase according to periodate oxidation method. Separation of the bound and free was obtained by double-antibody solid-phase technique using Sepharose 4B-anti-rabbit immunogiobulin G (IgG)-geat IgG. The fluorescence reaction using tyramine and hydrogen peroxide as substrates was used for the determination of enzyme activity in order to increase the sensitivity of enzyme immunoassay. The standard curve for serum TSH was satisfactory to recognize TSH concentrations as 0.06 μU/tube. TSH values obtained by this method correlated well with those obtained by radioimmunoassay (r, 0.96). The coefficients of variation were 1.8 to 5.3% (within assay) and 5.1 to 10.5% (between assay). The method is about equal to radioimmunoassay with respect to sensitivity. Since it requires minimal equipment and is less expensive than radioimmunoassay, it is possible to perform routine assays even in laboratories with limited facilities.  相似文献   
8.
We investigated the effects of exposure to diazinon, an organophosphate insecticide, on the expression of antioxidant and detoxification factors in the silkmoth. Exposure to diazinon resulted in induction of mRNA encoding manganese containing superoxide dismutase (SOD) and omega‐class glutathione S‐transferases (GST), whereas no changes were observed in catalase, other class of GST and acetylcholinesterase. Liquid chromatography showed that the amount of reactive oxygen species was increased, whereas the amount of glutathione was decreased in the silkmoth fat body after exposure to diazinon. These results suggest that SOD and omega‐class GSTs can contribute to organophosphate resistance in Lepidopterans.  相似文献   
9.
Immunohistochemical localization of substance P (SP), CGRP, VIP, neuropeptide Y (NPY), and somatostatin (SOM) in the carotid labyrinth were compared in some species of amphibians using the peroxidase-antiperoxidase method. Immunoreactivity of SP, CGRP, VIP, and NPY was found in the nerve fibers distributed in the intervascular stroma of the carotid labyrinth. SP, CGRP, and VIP immunoreactive varicose fibers were densely distributed in the peripheral portion of the carotid labyrinth. Some SP-immunoreactive fibers were distributed similarly to CGRP-immunoreactive fibers. The density of NPY and SOM immunoreactive varicose fibers was low. No immunoreactivity of enkephalins was observed in the labyrinth. The intensities of these peptides were varied from species to species. No glomus cells showed immunoreactivity for any of the 7 peptides studied. These results suggest that the vascular regulatory function, which is one of the possible functions of the carotid labyrinth, is controlled by the peptidergic mechanisms in addition to regulation through intimate apposition of glomus and smooth muscle cells (g-s connection).  相似文献   
10.
In vitro studies indicate that neomycin C is 50% as active as neomycin B against Staphylococcus epidermidis (ATCC 12228).  相似文献   
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