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11.
Charlotte Gray 《CMAJ》1987,137(8):760-760D
Principles of Ethical Behaviour for all physicians, including those who may not be engaged directly in clinical practice. [List: see text] 相似文献
12.
Myobacterium avium LM1 was exposed to concentrations of 5-fluorouracil (5FU) that ranged from 0 to 100 g/ml. Growth inhibition was inversely proportional to the concentration of the drug. DNA was extracted from cells grown in medium that contained [14C]5FU, but no carrier. The [14C]DNA was enzymatically hydrolyzed to deoxyribonucleotides, which were separated and fractionated by high-performance liquid chromatography (HPLC). The isotope was located in 2-deoxycytidine 5-monophosphate (dCMP) and 2-deoxythymidine 5-monophosphate (dTMP), with dCMP containing the majority. There was no radioactivity at the elution times for 5-fluoro-2-deoxyuridine 5-monophosphate or 2-deoxyuridine 5-monophosphate. These results suggested that 5FU was dehalogenated and the uracil moiety ultimately converted into cytosine and thymine deoxyribonucleotides. Cells were grown in [3H]uracil, and [3H]DNA was extracted and analyzed by HPLC. The isotope was found only in the pyrimidine deoxyribonucleotides, with dCMP containing 4.1 times that in dTMP. Thus, it was demonstrated that uracil and dehalogenated 5FU were not directly incorporated into DNA, but rather converted to cytosine and thymine and then incorporated into DNA by a salvage pathway. 相似文献
13.
Summary [3H] thymidine incorporation into DNA of the parotid (PA) gland of adult and 20-day-old rats and into DNA of the pancreas (PANC) of 20-day-old rats was increased markedly following a 2-day regimen of isoproterenol (ISO) administration. However, when the submandibular-sublingual (SM-SL) glands had been removed just prior to initiation of the ISO injections, the [3H] thymidine incorporation into PA and PANC was inhibited, and cpm/mg protein of these organs was even lower than that of organs of untreated rats with SM-SL glands present. Removal of the PA glands just prior to initiation of the ISO regimen had no effect on the ISO-induced [3H] thymidine incorporation into DNA of PANC but partially inhibited that of the submandibular (SM) gland. It is suggested that the inhibitory effects on DNA and RNA synthesis that follow removal of SM-SL glands are attributable to the growth factors (epidermal growth factor and nerve growth factor) found in the rat SM gland. These factors appear to regulate normal DNA synthetic activity of exocrine glands as well as
1-adrenoceptor mediated DNA synthesis. Cellular hypertrophy induced by the ISO was less markedly affected by absence of the SM glands, but a partial inhibition of [3H] uridine incorporation into RNA of PA of adult rats also occurred when SM-SL glands were removed prior to initiation of the ISO-regimen. 相似文献
14.
Preston Gadson Judy McCoy Ann Charlotte Wikstrm Jan-Ake Gustafsson 《Journal of cellular biochemistry》1990,43(2):185-198
Exposure of fibroblasts derived from keloid tissues, desmoid and dermal tissue from individuals with Gardner's syndrome (GS) to dexamethasone resulted in the suppression of protein kinase C (PKC) activity and [3H]thymidine incorporation into DNA, and a 20-fold induction of glutamine synthetase activity. Treatment of GS and keloid fibroblasts with 0.1 microM dexamethasone for 36 h increased glucocorticoid receptor (GR) synthesis, as determined by [35S]methionine labeling and immunoprecipitation with a monoclonal antibody to the human GR. The suppression of PKC activity by dexamethasone was shown to result from a loss of protein mass as determined by immunoblotting using an antibody to PKC type III. In contrast to these results, exposure of fibroblasts isolated from normal tissues to dexamethasone did not result in the suppression PKC and [3H]thymidine incorporation, there was only a sixfold induction of glutamine synthetase, and a decrease of GR synthesis. As no primary receptor binding defect could be detected, the altered response of tumor cells to steroid-occupied receptor indicates a partial post-receptor binding defect in GS and keloid cells. 相似文献
15.
Sven E. G. Bystr?m Svend Erik Mathiassen Charlotte Fransson-Hall 《European journal of applied physiology and occupational physiology》1991,63(6):405-411
The physiological response to continuous and intermittent handgrip exercise was evaluated. Three experiments were performed until exhaustion at 25% of maximal voluntary contraction (MVC): experiment 1, continuous handgrip (CH) (n = 8); experiment 2, intermittent handgrip with 10-s rest pause every 3 min (IH) (n = 8); and experiment 3, as IH but with electrical stimulation (ES) of the forearm extensors in the pauses (IHES) (n = 4). Before, during, and after exercise, recordings were made of heart rate (HR), arterial blood pressure (BP), exercising forearm blood flow, and concentrations of potassium [K+] and lactate [La-] in venous blood from both arms. The electromyogram (EMG) of the exercising forearm extensors and perceived exertion were monitored during exercise. Before and up to 24 h after exercise, observations were made of MVC, of force response to electrical stimulation and of the EMG response to a 10-s test contraction (handgrip) at 25% of the initial MVC. Maximal endurance time (tlim) was significantly longer in IH (23.1 min) than in CH (16.2 min). The ES had no significant effect on tlim. During exercise, no significant differences were seen between CH and IH in blood flow, venous [K+] and [La-], or EMG response. The HR and BP increased at the same rate in CH and IH but, because of the longer duration of IH, the levels at exhaustion were higher in this protocol. The subjects reported less subjective fatigue in IH. During recovery, return to normal MVC was slower after CH (24 h) than after IH (4 h).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
16.
17.
18.
Growth-associated modifications of low-molecular-weight thiols and protein sulfhydryls in human bronchial fibroblasts 总被引:2,自引:0,他引:2
Luigi Atzori Jeannette M. Dypbukt Kristina Sundqvist Ian Cotgreave Charlotte C. Edman Peter Moldus Roland C. Grafstrm 《Journal of cellular physiology》1990,143(1):165-171
The thiol redox status of cultured human bronchial fibroblasts has been characterized at various growth conditions using thiol-reactive monobromobimane, with or without the combination of dithiotreitol, a strong reducing agent. This procedure has enabled measurement of the cellular content of reduced glutathione (GSH), total glutathione equivalents, cysteine, total cysteine equivalents, protein sulfhydryls, protein disulfides, and mixed disulfides. Passage of cells with trypsin perturbs the cellular thiol homeostasis and causes a 50% decrease in the GSH content, whereas the total cysteine content is subsequently increased severalfold during cell attachment. During subsequent culture, transient severalfold increased levels of GSH, protein-bound thiols, and protein disulfides are reached, whereas the total cysteine content gradually declines. These changes in the redox balance of both low-molecular-weight thiols and protein-bound thiols correlate with cell proliferation and mostly precede the major growth phase. When the onset of proliferation is inhibited by maintenance of cells in medium containing decreased amounts of serum, the GSH content remains significantly increased. Subsequent stimulation of growth by addition of serum results in decreased GSH levels at the onset of proliferation. In thiol-depleted medium, proliferation is also inhibited, whereas GSH levels are increased to a lesser extent than in complete medium. Exposure to buthionine sulfoximine inhibits growth, prevents GSH synthesis, and results in accumulation of total cysteine, protein-bound cysteine, and protein disulfides. For extracellular cystine, variable rates of cellular uptake correlate with the initial increase in the total cysteine content observed following subculture and with the GSH peak that precedes active proliferation. The results strongly suggest that specific fluctuations in the cellular redox balance of both free low-molecular-weight thiols and protein sulfhydryls are involved in growth regulation of normal human fibroblasts. 相似文献
19.
Charlotte L. Branchaud Cynthia G. Goodyer Harvey J. Guyda Yves Lefebvre 《In vitro cellular & developmental biology. Plant》1990,26(9):865-870
Summary We have compared hormone production by early gestation and term human placental trophoblasts cultured in Ham's F10 medium
containing 10% fetal bovine serum with that by cells cultured in serum-free HB102 medium. Mean daily production of progesterone
on Days 3 to 7 was approximately 25% less by both early gestation and term cells cultured in HB102 as compared to Ham's F10,
but production was maintained at a stable level for at least 7 d longer than the cells in Ham's. Estradiol production from
10−6
M dehydroepiandrosterone by both early gestation and term cells was comparable in both media. Human placental lactogen production
on Days 3 to 7 was 40% less by cells cultured in HB102. Human chorionic gonadotropin (hCG) output by early gestation cells
was also 50% less in HB102 but term cells in HB102 produced twice as much hCG as those in Ham's F10. 3B-Hydroxysteroid dehydrogenase
(3BHSD) activity in early gestation and term cells and 11B-hydroxysteroid dehydrogenase (11BHSD) activity of early gestation
cultures was comparable in the two media. 11BHSD activity was decreased in the term cultures, and this decrease was more marked
in Ham's than in HB102. Sulfatase and aromatase activities in the early gestation cultures were comparable in both media;
sulfatase activity was comparable and aromatase activity only 20% less in the term cells cultured in HB102. These results
indicate that serum-free HB102 supports differential function of human trophoblast cells and is useful for studies of placental
activity for as long as 14 d in culture. 相似文献
20.
The details of spermatogenesis and spermiogenesis are described forOphryotrocha puerilis. The ultrastructure of mature sperm is shown forO. puerilis, O. hartmanni, O. gracilis, O. diadema, O. labronica, andO. notoglandulata. Clusters of sixteen cells each are proliferated by two stem cells in each setigerous segment ofO. puerilis representing the very early stages of both oogenesis and spermatogenesis. In each spermatocyte-I cluster, the cells are interconnected
by cytoplasmic bridges. Early, clusters are enveloped by peritoneal sheath cells. These transient gonad walls break down prior
to meiosis. The meiotic processes may start in the clusters with the cells still interconnected, or during breakdown of the
original cluster, giving rise to smaller subclusters of both spermatocytes I and spermatocytes II with various numbers of
cells. Finally, spermatid tetrads are present. As spermiogenesis progresses, the tetrads disintegrate. Golgi vesicles in both
spermatocytes and spermatids contain electron-dense material, presumably preacrosomal. The acrosome is formed by such vesicles.
In the six species studied here, the acrosomes appear to be of a similar overall structure but are of different shape. Centrioles
are usually located beneath the acrosome. The distal centriole forms the basal body of a flagellum-like cytoplasmic process.
The microtubules of these flagellar equivalents do not show a normal ciliar arrangement. The flagellar equivalent appears
to be non-motile. InO. hartmanni and inO. notoglandulata, a flagellar equivalent is missing. Microtubules originating from the proximal end of the distal centriole stretch to the
nuclear envelope. This feature appears to be especially conspicuous inO. puerilis and inO. labronica. InO. labronica and inO. notoglandulata, bundles of microtubules paralleling the cell perimeter appear to stabilise the sperm. Various numbers of mitochondria are
either randomly distributed around the nucleus or accumulate on one side, often directly under the acrosome.
Parts of the present paper were presented at the 2nd International Polychaete Conference, Copenhagen 1986 and at the 3rd International Polychaete Conference, Long Beach, Ca. 1989. 相似文献