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991.
Corpus luteum function in the cycling and the pregnant rhesus monkey (Macaca mulatta) was evaluated through short term in vitro studies of progesterone production by suspensions of collagenase-dispersed luteal cells in the presence and absence of exogenous gonadotropin (human chortonic gonadotropin, HCG). Cells from mid-luteal phase of the menstrual cycle secreted progesterone, as measured by accumulation of this hormone in the incubation medium, and responded to the addition of 100 ng HCG/ml with a marked increase in progesterone secretion above basal level (63.7 ± 13.1 versus 24.7 ± 5.5 ng progesterone/ml/5 × 104cells/ 3 hr, X ± S.E., n = 6; p < 0.05). However, luteal cells from early pregnancy (23–26 days after fertilization) secreted significantly less progesterone than cells of the non-fertile menstrual cycle (3.6 ± 2.4 versus 24.7 ± 5.5 ng/ml/5 × 104 cells/3 hr, n = 3; p < 0.05) and did not respond to HCG with enhanced secretion. By mid-pregnancy (108–118 days gestation) luteal cells exhibited partially renewed function, and near the time of parturition (163–166 days gestation) basal and HCG-stimulated progesterone secretion (30.2 ± 5.6 and 63.0 ± 13.0 ng/ml/5 × 104 cells/3 hr, respectively; n = 3) was equivalent to that of cells from the luteal phase of the non-fertile menstrual cycle. The data suggest that following a period around the fourth week of gestation, when steroidogenic activity is markedly diminished, the corpus luteum of pregnancy progressively reacquires its functional capacity and at term exhibits gonadotropin-sensitive steroidogenesis similar to that of the corpus luteum of the menstrual cycle.  相似文献   
992.
Richard J. Wang 《Cell》1976,8(2):257-261
A temperature-sensitive mammalian cell line has been isolated which grows and divides normally at the permissive temperature of 33°C. When incubated at 39°C, the nonpermissive temperature, interphase cells continue to enter a prophase-like state. Chromatin-like material condenses and coalesces into dark-staining clumps rather than into discernible chromosomes. Disappearance of the nuclear boundary is observed, but re-formation of the boundary around the clumps fails to occur. Incorporation of labeled precursors reveals a decrease in protein synthesis which is accompanied by a slower decrease in DNA synthesis. Approximately 0.2% of the mutant cells revert in their capability of growth and cell division at 39°C. These “revertants” are found to contain a higher number of chromosomes. The isolation of this mutant is based on the initial observation that the cells become rounded at the nonpermissive temperature. The cell-rounding process characteristic of mitotic cells should serve as a useful marker in the isolation of mitotic mutants.  相似文献   
993.
Observations of 8 groups each containing three adult spiny mice (Acomys cahirinus) revealed that instances of chasing and physical displacement were quite common, while fighting and biting were rarely observed. The relationships between the most frequent behavioral categories were presented in a correlation matrix. In a second, study, ♀♀ tested in their home cages were dominant over ♂♂ In the ♂♂ home cages, however, no differences in the frequency of ♀ vs. ♂ aggression were observed. More instances of aggression were observed in the cages of the ♀♀ than in the cages of the ♂♂.  相似文献   
994.
Summary The electron-dense capsule tip (apical cap) of sea anemone and coral spirocysts is of a different structure than the capsule wall. The capsule wall is composed of a double layer of fiber-like materials which cross each other at roughly right angles. The innermost layer is characterized by numerous serrations, the tips of which project into the lumen of the capsule. Within each serration, a band of finely cross-striated material encircles the capsule at right angles to its longitudinal axis. The membrane lining the lumen of the capsule appears to be continuous with the wall of the undischarged thread. The outer capsule wall layer consists of closely spaced microfilaments (cnidofilaments) which are oriented in the longitudinal axis of the capsule. The cnidofilaments appear to merge with the apical cap material. Contrary to some previous reports in the literature, it has been found that spirocysts normally discharge by eversion, as do nematocysts. The relationship of the capsule wall sub-structure to the spirocyst discharge process is discussed.Thanks are due Dr. Cadet Hand for the use of the facilities of the Bodega Marine Laboratory of the University of California and B. Miller, F. Doroshow, C. Bigger, G. Chapman and E. Chang for expert technical assistance. The use of the facilities of the Electron Microscope Laboratory and Electronics Research Laboratory of the University of California at Berkeley and the Eelectron Microscope Laboratory of the Florida State University is gratefully acknowledged. Part of this work was made possible by NSF Grant GB-40547 to the senior author  相似文献   
995.
In activity assays of labeled compounds by liquid scintillation spectrometer, the effects due to sample sorption to the counting vial may be excluded by the use of the Triton X-100-toluene-based mixture in a 1:2 ratio by volume. For the ratio (v/v) of water to this mixture within the interval 1:4 to 1:1, the counting rates in particular channels, corrected to the disintegration half-time, are constant.  相似文献   
996.
Macromolecular synthesis was studied in individual liver cells rendered permeable to macromolecules and charged molecules by treatment with toluene. Toluene-treated cells were compared to intact cells with regard to their ability to synthesize protein, RNA, and DNA. The permeable cells catalyzed the incorporation of amino acids into protein in a system which was sensitive to cycloheximide. Maximal incorporation required the addition of tRNA, ATP, GTP, an energy source and various cations. RNA synthesis also took place in these cells and was inhibited by actinomycin D. Maximal incorporation required all four ribonucleoside triphosphates, an energy-generating system, and Mn2+, K+, and F?. The toluene-treated cells also were active for DNA synthesis when Ca2+ was present to induce endonucleolytic cleavage of the endogenous DNA. For maximal synthesis, all four deoxyribonucleoside triphosphates, ATP, K+, Mg2+, polyamines, and mercaptoethanol were required. These studies serve to emphasize the potential usefulness of toluene treatment for studying biosynthetic processes in mammalian cells.  相似文献   
997.
Mouse fibroblast (L-929) cells, in culture, synthesized and secreted into the growth medium a vitamin B12-binding substance which was identical to mouse transcobalamin II (TC II) as judged by the following criteria: (i) gel filtration on Sephadex G-200, (ii) ion-exchange chromatography on DEAE-cellulose and CM-cellulose, and (iii) the ability to facilitate cellular B12 uptake by L-929 cells. The secretion of mouse fibroblast binder was blocked by cycloheximide and puromycin; and in both cases the cells' ability to secrete this binder was partially restored when the inhibitor was removed. Within 30 h after the cells were exposed to [57Co]B12 bound to mouse serum TC II (Mr ~ 38,000) the [57Co]B12 was bound to a large molecular weight intracellular binder (Mr ~ 120,000) which was not released into the culture medium. During this same incubation period, the cells released free [57Co]B12 and [57Co]B12 bound to a protein which had the same elution volume as mouse serum TC II on Sephadex G-200.  相似文献   
998.
999.
We describe a simple method for locating tryptophanyl-tRNA synthetase (E.C. 6.1.1.2) on cellulose acetate gels (Cellogel) following electrophoresis. Employing electrophoretic conditions which result in the separation of mouse and human tryptophanyl-tRNA synthetases, we have analyzed extracts of a number of independently derived mouse-human somatic cell hybrids and subclones derived from these hybrids for the presence of human tryptophanyl-tRNA synthetase. Electrophoretic patterns of hybrid extracts which contain human tryptophanyl-tRNA synthetase exhibit three bands. This is consistent with published evidence that the enzyme from mammalian cells is a homologous dimer. The electrophoretic patterns derived from some hybrids are unusual in that the human and hybrid bands of activity are more intense than the mouse band from the same hybrid. An analysis of hybrid cells and extracts indicates that human tryptophanyl-tRNA synthetase segregates with human chromosome 14 and with the only enzyme marker which has previously been assigned to this chromosome, nucleoside phosphorylase.R. M. D. was supported by a postdoctoral fellowship from the Damon Runyon Fund for Cancer Research. The work described was supported in part by grants from Cancer Research Campaign, the Medical Research Council, and NATO.  相似文献   
1000.
Peripheral blood lymphocytes from healthy humans formed stable E rosettes with sheep erythrocytes (SRBC) at 37°C after culture with phytohemagglutinin or the divalent cation ionophore A23187. Cells manifesting this phenomenon exhibited “blast” morphology, appeared by 16 hr of culture, increased dramatically in percentage and absolute number by 62 hr, and persisted in large numbers for the duration of culture (182 hr). Unstimulated lymphocytes formed rosettes at 4°C but not at 37°C. Increased “stickiness” due to surface-bound lectin mitogen was not the cause of rosette formation at 37°C.Formation of E rosettes at 37°C has previously been considered a property of lymphocytes less differentiated than the circulating T cell (e.g., thymocytes, leukemic lymphoblasts). The present findings indicate that this property can be “reexpressed” during blastogenesis in culture.This observation also demonstrates technical problems associated with the use of SRBC to quantitate lymphocytes with complement receptors (B cells) by the EAC rosette assay in culture. False positives resulted from 37°C E rosette formation, but this was overcome by replacing the SRBC with guinea pig erythrocytes in the EAC assay.  相似文献   
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