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41.
DN Dunham 《Canadian Metallurgical Quarterly》1997,27(3):171-182
Characterization of flow properties of an artificial ventricle may aid development of designs to minimize thrombosis. Techniques for determining two such flow properties, viz. ventricular clearance rate and ejection fraction, are compared and validated here for polyurethane and silicone rubber ventricles operated in a mock circulatory loop at various stroke volumes and pulse rates. Ventricular clearance rats were measured both by clinical radionuclide tracer techniques and by an optical tracer method. Ejection fractions were measured by radionuclide imaging and validated by direct measurements of flow rate and ventricular volume. Results from the two methods for ventricular clearance are in close agreement. The optical tracer method is superior in spatial resolution, convenience and economy, but the radionuclide tracer method for ejection fraction gives excellent agreement with the absolute measurements. 相似文献
42.
U Herrlinger CM Kramm KM Johnston DN Louis D Finkelstein G Reznikoff G Dranoff XO Breakefield JS Yu 《Canadian Metallurgical Quarterly》1997,4(6):345-352
Within the pituitary, folliculostellate (FS) cells are considered to regulate the intercellular communication between endocrine cells by paracrine mechanisms. One of the possible paracrine factors involved, could be interleukin-6 (IL-6) which is produced by these cells. Since IL-6 has been shown to be a growth factor of pituitary cells, we have determined whether IL-6 can also influence FS cell proliferation. To test this, a FS cell-like mouse pituitary cell line (TtT/GF cells) was used that exhibits most characteristics of normal FS cells. Under serum-free conditions the proliferation of TtT/GF cells is critically dependent on the initial seeding density: cells seeded at low density do not grow at all whereas cells seeded at high density proliferate with maximal doubling times of 34 hrs. Mouse IL-6 (mIL-6) stimulated only low density cell cultures in a dose and time dependent manner. For cells seeded at high density, exogenously added IL-6 may have failed to stimulate growth because of endogenously produced mIL-6. Conditioned medium from TtT/GF cells, in which mIL-6 concentrations up to 1017 pg/ml were measured, stimulated the proliferation of TtT/GF cells, indicating an autocrine growth stimulatory mechanism. A neutralizing mIL-6 antibody partially suppressed the growth of TtT/GF cells seeded at high density and partially reduced the growth stimulatory activity of TtT/GF conditioned medium. Thus, IL-6 is one but not the only factor that is involved in the autocrine growth stimulatory loop. The relevance of this mechanism for normal FS cells and its physiological consequence needs to be elucidated. 相似文献
43.
OBJECTIVE: To examine the occurrence of elevated personality disorder (PD) dimensional scores in a community sample of young adults as a function of the occurrence of Axis I disorders through age 18 years. METHOD: 299 individuals who had been interviewed regarding Axis I disorders twice while in adolescence (first when 14 through 18 years of age) were carefully assessed regarding Axis I and II psychopathology at age 24. RESULTS: The prevalence of PD diagnoses was relatively low (3.8% in participants with a history of Axis I versus 1.7% in participants with no Axis I history). The occurrence of all four Axis I diagnostic categories (major depression, anxiety disorders, disruptive behavior disorders, substance use disorders) in childhood and adolescence was associated with elevated PD dimensional scores. The likelihood of elevated PD dimensional scores increased as a function of the number of Axis I disorders. Elevated PD scores were significantly associated with a negative course of major depression. CONCLUSIONS: Although the rates of PDs were low, the findings suggest a substantial degree of association between early-onset Axis I disorders and Axis II psychopathology in young adulthood. More research is needed to develop assessment and treatment recommendations addressing the early manifestations of PDs. 相似文献
44.
45.
The comparative electrophysiological study of excitation process in heart with different types of organization have laid the foundation for solution of the problems of formation of cardioelectric field. It was shown, that the form of extracellular potentials on the epicardium correlated with different types of ventricle myocardial activation. Animals with the "flash" type of myocardial depolarization in most cases have the negative extracellular potentials in the greater part of the epicardial ventricular surface. Animals with the consecutive type of myocardial activation--the positive and biphase potentials. All myocardial layers (epicardial, intramural and endocardial) are electrophysiologically informative. 相似文献
46.
47.
DA Emmerson KA Turner DN Foster NB Anthony KE Nestor 《Canadian Metallurgical Quarterly》1997,76(11):1563-1568
The activity of ornithine decarboxylase (ODC), an enzyme associated with cellular growth and protein synthesis, was examined in breast muscle, liver, and intestinal tissues of turkeys during a short-term period of feed withdrawal (FW) and following refeeding. Turkeys from a randombred control line were reared under standard management practices to 3 wk of age in battery brooders. Feed was then withdrawn from FW birds for a 48-h period, after which feed was consumed ad libitum. Control birds consumed feed ad libitum throughout the test period. Tissues were collected from 12 birds per treatment following 24 and 48 h of FW and at 6, 12, 24, and 48 h following refeeding for later determination of tissue ODC activity. Activity of ODC was greater in tissue from the small intestine than in liver tissue and both had greater activity than that exhibited by breast muscle. Short-term FW and refeeding produced differential responses in ODC activity of the three tissues examined. Feed withdrawal resulted in a reduction of ODC activity in intestinal tissue, whereas activity was unaffected for liver or breast muscle tissues. Compensatory increases in ODC activity were observed in liver and intestinal tissues; however, the increase was both more rapid and transitory in small intestine than in liver tissue. The ODC activity in breast muscle was largely unaffected by short-term FW and refeeding. Patterns of ODC activity in liver during FW and refeeding closely resembled patterns observed for absolute and relative liver weight. Thus, the results of the present experiment demonstrate that short-term FW and refeeding influence underlying growth mechanisms of supply organs, such as hepatic and intestinal tissue, in addition to affecting overall growth and muscle development. 相似文献
48.
M Winey CL Mamay ET O'Toole DN Mastronarde TH Giddings KL McDonald JR McIntosh 《Canadian Metallurgical Quarterly》1995,129(6):1601-1615
The three dimensional organization of microtubules in mitotic spindles of the yeast Saccharomyces cerevisiae has been determined by computer-aided reconstruction from electron micrographs of serially cross-sectioned spindles. Fifteen spindles ranging in length from 0.6-9.4 microns have been analyzed. Ordered microtubule packing is absent in spindles up to 0.8 micron, but the total number of microtubules is sufficient to allow one microtubule per kinetochore with a few additional microtubules that may form an interpolar spindle. An obvious bundle of about eight interpolar microtubules was found in spindles 1.3-1.6 microns long, and we suggest that the approximately 32 remaining microtubules act as kinetochore fibers. The relative lengths of the microtubules in these spindles suggest that they may be in an early stage of anaphase, even though these spindles are all situated in the mother cell, not in the isthmus between mother and bud. None of the reconstructed spindles exhibited the uniform populations of kinetochore microtubules characteristic of metaphase. Long spindles (2.7-9.4 microns), presumably in anaphase B, contained short remnants of a few presumed kinetochore microtubules clustered near the poles and a few long microtubules extending from each pole toward the spindle midplane, where they interdigitated with their counterparts from the other pole. Interpretation of these reconstructed spindles offers some insights into the mechanisms of mitosis in this yeast. 相似文献
49.
PURPOSE: To evaluate antro-pyloric canal dimensions from early prematurity to full-term gestational age. MATERIALS AND METHODS: Ninety infants with no signs of regurgitation or vomiting were studied 3-5 days after birth. Their gestational ages ranged from 26 to 41 weeks (mean 33.7 weeks) and the body weight from 670 to 4150 g (mean 2067 g). Antro-pyloric muscle thickness, canal length and canal width were measured. RESULTS: A positive correlation between gestational age, muscle thickness (R = 0.71, P < 0.001), length (R = 0.63, P < 0.001) and width (R = 0.42, P < 0.001) was found. Furthermore, a positive correlation between body weight, muscle thickness (R = 0.82, P < 0.001) length, (R = 0.67, P < 0.001) and width (R = 0.55, P < 0.001) was observed. CONCLUSIONS: This study shows that antro-pyloric canal dimensions increase with gestational age. Moreover, it provides normal values for muscle thickness, canal length and canal width from the early gestation to full term. 相似文献
50.
CA Awoniyi D Roberts DN Veeramachaneni BS Hurst KE Tucker WD Schlaff 《Canadian Metallurgical Quarterly》1998,70(3):440-447
OBJECTIVE: To determine reproductive sequelae in female rats after in utero and lactational dietary exposure to genistein. DESIGN: Experimental animal study. SETTING: University laboratory. ANIMAL(S): Sprague Dawley rats. INTERVENTION(S): Pregnant rats were fed control rat chow or rat chow incorporated with genistein (approximately 50 microg/d) beginning on day 17 of gestation and continuing until the end of lactation (postpartum day 21). Genistein-exposed female pups were divided into two groups on day 21. One group continued to receive a genistein-added diet (G70); the other group was changed to a control diet (Ex-G). At necropsy (days 21 and 70), blood and reproductive tissues were collected. MAIN OUTCOME MEASURE(S): Serum levels of gonadotropins and gonadal steroids and histopathologic examination of the ovaries. RESULT(S): The weight of the ovaries and uterus and serum levels of E2 and progesterone in genistein-exposed rats on day 21 (G21) were significantly reduced compared with control rats. On day 70, serum levels of E2, progesterone, LH, and FSH were similar in all groups. Atretic follicles and secondary interstitial glands were more common in G70 and Ex-G rats compared with control rats. Cystic rete ovarii was observed in some G70 and Ex-G rats. CONCLUSION(S): Our data indicate that in utero and lactational exposure to dietary genistein adversely affects reproductive processes in the adult female rat. 相似文献