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21.
Bromocriptine administration in the form of slow-release injections to male blue foxes during March-May abolished the normal spring rise in plasma prolactin concentrations seen in May and June. The spring moult was prevented and the treated animals retained a winter coat of varied quality and maturity until the end of the study in August. Plasma testosterone concentrations fell normally from March until August. Testicular regression was, however, delayed, although there were individual variations in response. Estimation by DNA flow cytometry in early July of the relative numbers of haploid, diploid and tetraploid cells in the testis showed that, in the treated animals, 74-80% of the cells were haploid (maturing germinal cells), 4-6% tetraploid (mainly primary spermatocytes) and the rest diploid cells (somatic cells and the remaining germinal cell types). In the control males, however, no haploid cells were detected and the majority of cells were diploid (93-99%). At castration in August, histological examination revealed various stages of testicular regression in the treated and control animals.  相似文献   
22.
Laboratory studies compared the growth rate of Stenonema vicarium (Walker) nymphs on diets of detritus and natural stream periphyton. In three consecutive runs of the experiment, growth rates were consistently higher on periphyton (mean growth rate = 2.1% wet wt. d−1) than detritus (mean = 1.8% wet wt. d−1). The starting date of each run also significantly influenced growth rates. In each treatment growth rates generally decreased over the course of the 3 runs, and ca. one-half of the nymphs in the last run did not molt or grow. It appeared that growth of S. vicarium may be partially controlled by seasonal factors.  相似文献   
23.
AN AMPLIFICATION OF THE PHYLOGENETIC SPECIES CONCEPT   总被引:9,自引:0,他引:9  
Abstract— The goal of a phylogenetic species concept is to reveal the smallest units that are analysable by cladistic methods and interpretable as the result of phylogenctic history. We define species as the smallest aggregation of populations (sexual) or lineagcs (asexual) diagnosable by a unique combination of character states in comparable individuals (semaphoronts). A character state is an inherited attribute distributed among all comparable individuals (semaphoronts) of the same historical population, clade, or terminal lineage. This definition of species is character-based and pattern oriented. Evolutionary explanations of phylogenetic species are consistent with contemporary explanations of processes of speciation, but require only the assumption of nested hierarchical pattern. We discuss the compatibility of the phylogenetic species concept with various biological needs for species and justify its use at the exclusion of alternative species concepts.  相似文献   
24.
The diet of fork-tailed (Oceanodroma furcata) and Leach's storm-petrel(O.leucorhoa) was studied at Petrel Island, a small island northof Hippa Island in the Queen Charlotte Islands, British Columbiain 1983. The diet of the two storm-petrel species consistedmostly of the amphipod Paracallisoma coecus and fish. Most fisheswhich could be identified were myctophids, and may have beenacquired by storm-petrels at night. Fishes increased while P.coecusdeclined in importance as a food over the nestling season ofthe storm-petrels. The amount of oil also declined in the Leach'sstorm-petrel diet over the season. Since P.coecus contains muchoil, the seasonal decline of both P.coecus and oil was probablyassociated. Other less important foods were jellyfishes, copepods,isopods, euphausiids, shrimp, squid and octopus. Jellyfishes(Velella velella) only occurred in the diet of Leach's storm-petrels,which may relate to that storm-petrel feeding in open oceanwhere V. velella occurs most frequently. The most numerous copepodwas Neocalanus cristatus, which was only observed in the storm-petreldiet early on during the study period. An abyssal copepod, Bathycalanusbradyi, and the isopod Cirolana californiensis (tentativelyidentified, the latter only previously known from sea canyonsoff California) were surprising food items of storm-petrels.Most euphausiid prey consisted of Thysanoessa spinifera andEuphausia pacifica.  相似文献   
25.
We here report an enzyme linked immunosorbent assay (ELISA) and a scintillation proximity assay (SPA) for detection of the ganglioside FucGM1 in sera from small cell lung cancer (SCLC) patients. The SPA was more sensitive and reproducible than the ELISA. In this assay, monoclonal antibodies specific for FucGM1 were bound to SPA particles and incubated with labelled FucGM1 and 100 µl test-serum overnight, and counted in a -counter. The sensitivity was 0.2 ng. Seven out of twenty sera from SCLC patients were positive, whereas none of twenty sera from healthy individuals were positive for FucGM1. The SPA was more sensitive than the previously reported HPTLC as well as a direct ELISA.Abbreviations MAb monoclonal antibody - SPA scintillation proximity assay - HPTLC high performance thin layer chromatography - SCLC small cell lung cancer - FucGM1 Fuc1-2Gal1-3GalNAc1-4(NeuAc2-3)-Gal1-4Glc1-1Cer - ELISA enzyme linked immunosorbent assay - FCS foetal calf serum - PBS phosphate buffered saline  相似文献   
26.
An amide conjugate of o-methoxybenzoic acid and aspartic acid has been isolated from bean leaves. After extraction and methylation of plant material, this compound was isolated as two isomeric monoethyl monomethyl esters. The ethylation of the aspartyl carboxyl groups was shown to be a likely result of an extraction procedure utilising acidified ethanol, the methylation of the aromatic hydroxy of the methoxy group to be due to the derivatisation procedure. Studies with pentafluorobenzylation confirmed that the endogenous compound is o-hydroxybenzoylaspartate.  相似文献   
27.
A fusion of human lymphocytes released from regional lymph nodes of papillary adenocarcinoma of lung cancer with mouse myeloma P3-X63-Ag8-U1 cells resulted in a stable hybridoma-secreting human IgM antibody (NCC-1004) that reacts with a large proportion of squamous cell carcinomas of lung and esophagus as well as carcinoma of thyroid glands. However, the antibody also reacts with normal red blood cells, B lymphocytes, and a few other limited loci in normal tissues such as the basal cells of bronchial epithelium and the basal cell layer of stratified squamous epithelium, as well as endothelium and alveolar lining epithelium. The antigen defined by NCC-1004 has been characterized as blood group i antigen on the basis of the following results. The antibody preferentially agglutinates cord erythrocytes in contrast to adult erythrocytes. The agglutination was obvious at 4 degrees C, but diminished greatly at 37 degrees C, and was enhanced after sialidase treatment. The antibody specifically reacts with lacto-norhexaosylceramide (nLc6) and sialosyllacto-norhexaosylceramide (IV3NeuAcnLc6), but does not react with lacto-neotetraosylceramide (nLc4), sialosyllacto-neotetraosylceramide (IV3NeuAcnLc4), lacto-isooctaosylceramide (IV6Gal beta 1----4GlcNAcnLc6; I antigen), and other standard glycolipids so far tested. The properties of the antibody and its antigen are identical to those previously described for the i blood group system. Inasmuch as the hybridoma was established by hybridization of lymphocytes derived from regional lymph nodes of lung cancer, and the antigen was found in the patient's lung cancer tissue, the i antigen in lung cancer is probably recognized as a tumor-associated antigen by the host's immune cell system.  相似文献   
28.
Summary Primary cultures of newborn mouse epidermal cells proliferate rapidly and with a high growth fraction for several months when grown in medium with low calcium (0.02 to 0.1 mM). Addition of calcium to levels generally used in culture medium (1.2 mM) was followed by rapid changes in the pattern of proliferation. By using a combination of technics (a stathmokinetic method, autoradiography, [3H]thymidine incorporation into DNA, DNA flow cytometry) it was found that cell flux was blocked for 5 to 6 h, followed by a short rise in the mitotic rate at 10 h, and a gradual fall in all growth parameters until about 32 h after the calcium switch. There was no accumulation of cells in any particular cell cycle phase. The results indicate that the calcium switch is followed by a strong reduction in cell flux from G1 whereas the majority of the cells that had left G1 at the time of the switch completed one cell division before cessation of all proliferative activity. Both before and after the switch the primary epidermal cultures consisted of one diploid and one tetraploid G1 DNA stemline that seemed to react in the same way to calcium. This work reported in this paper was undertaken during the tenure of an American Cancer Society-Eleanor Roosevelt-International Cancer Fellowship awarded by the International Union Against Cancer (K. E.). The project was supported by funds partly provided by the International Cancer Research Data Bank Program of the National Cancer Institute, National Institutes of Health, Bethesda, MD, under contract N01-C0-65341 (International Cancer Research Technology Transfer) and partly by the International Union Against Cancer (O.P.F.C.).  相似文献   
29.
30.
To determine whether the micronucleus makes essential contributions during asexual reproduction, observations were made on cells of Euplotes octocarinatus from which the micronucleus had been removed with a micropipette. Most cells underwent one postenucleation division, then became arrested in macronuclear G1, slowed down in food uptake, developed macronuclear deformations, and finally died. Such cells could be rescued if a micronucleus was reimplanted before macronuclear deformations had developed. When provided with a new micronucleus, cells initiated macronuclear DNA synthesis about 12-16 h later. The data suggest that the micronucleus is involved in the control of the cell's transition from macronuclear G1 to S, and a model is proposed which postulates that in Euplotes macronuclear DNA synthesis is initiated when a micronucleus-encoded "initiator protein" has accumulated to a critical amount.  相似文献   
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