Ran is associated with chromosomes during starfish oocyte meiosis and embryonic mitoses.
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Anaphase↗
Biomedical subjects
P Stein
Publications and source records attributed to P Stein.
Reprogramming of gene expression during preimplantation development.
A fundamental problem in early mammalian development is the transformation of the highly differentiated oocyte into the totipotent blastomeres by the 2-cell stage. This remarkable transformation probably entails reprogramming the pattern of gene expression. The maternal-to-zygotic transition occurs during the 1-cell stage, i.e., 1-cell embryo is transcriptionally active. DNA replication is a likely locus of regulation, since DNA replication, with consequent nucleosome displacement, would serve to facilitate the access of maternally derived transcription factors to their cis-acting DNA-binding sequences. In fact, the first round of DNA replication is essential for the expression of two genes, eIF-1A and the transcription-requiring complex (TRC), as well as global transcription. A growing body of evidence suggests that a transcriptionally repressive state develops during the 2-cell stage. Interestingly, inhibiting the second round of DNA replication inhibits the decrease in expression of both the TRC and eIF-1A, as well as total endogenous gene expression. This repression may be linked to a change in chromatin structure, since treatment of 2-cell embryos with histone deacetylase inhibitors prevents the decrease in expression of the TRC and eIF-1A, and also inhibits the development of the transcriptionally repressive state for global gene expression. The findings that histone deacetylases can be targeted to chromatin provide a mechanism to link histone deacetylation with repression of gene expression. J. Exp. Zool. (Mol. Dev. Evol.) 285:276-282, 1999.
Animals↗
Cholesterol efflux-mediated signal transduction in mammalian sperm: cholesterol release signals an increase in protein tyrosine phosphorylation during mouse sperm capacitation.
We previously demonstrated that mouse sperm capacitation is accompanied by a time-dependent increase in protein tyrosine phosphorylation that is dependent on the presence of BSA, Ca2+, and NaHCO(3), all three of which are also required for this maturational event. We also demonstrated that activation of protein kinase A (PK-A) is upstream of this capacitation-associated increase in protein tyrosine phosphorylation. BSA is hypothesized to modulate capacitation through the removal of cholesterol from the sperm plasma membrane. In this report, we demonstrate that incubation of mouse sperm medium containing BSA results in a release of cholesterol from the sperm plasma membrane to the medium; release of this sterol does not occur in medium devoid of BSA. We next determined whether cholesterol release leads to changes in protein tyrosine phosphorylation. Blocking the action of BSA by adding exogenous cholesterol-SO-(4) to the BSA-containing medium inhibits the increase in protein tyrosine phosphorylation as well as capacitation. This inhibitory effect is overcome by (1) the addition of increasing concentrations of BSA at a given concentration of cholesterol-SO-(4) and (2) the addition of dibutyryl cAMP plus IBMX. High-density lipoprotein (HDL), another cholesterol binding protein, also supports the capacitation-associated increase in protein tyrosine phosphorylation through a cAMP-dependent pathway, whereas proteins that do not interact with cholesterol have no effect. HDL also supports sperm capacitation, as assessed by fertilization in vitro. Finally, we previously demonstrated that HCO-(3) is necessary for the capacitation-associated increase in protein tyrosine phosphorylation and demonstrate here, by examining the effectiveness of HCO-(3) or BSA addition to sperm on protein tyrosine phosphorylation, that the HCO-(3) effect is downstream of the site of BSA action. Taken together, these data demonstrate that cholesterol release is associated with the activation of a transmembrane signal transduction pathway involving PK-A and protein tyrosine phosphorylation, leading to functional maturation of the sperm.
Acrosome↗
Altered fetal cardiovascular responses to prolonged hypoxia after sinoaortic denervation.
This study examines the role of the peripheral chemoreceptors in mediating fetal cardiovascular responses to prolonged hypoxia secondary to reduced uterine blood flow (RUBF). Fetal sheep were chronically instrumented for continuous heart rate (FHR), blood pressure (FBP), and carotid blood flow (CBF) measurements after bilateral sectioning of the carotid sinus and vagus nerves (denervated, n = 7) or sham denervation (intact, n = 7). Four days postoperatively, uterine blood flow was mechanically restricted, reducing fetal arterial oxygen saturation by 47.3% (P < 0.01). An initial bradycardia was observed in intact (184.0 +/- 10.7 to 160.5 +/- 10.7 beats/min, not significant) but not denervated fetuses, followed by a tachycardia (180.0 +/- 2.2 to 193.7 +/- 2.7 beats/min, P < 0.05). FHR increased in denervated fetuses (175.5 +/- 8.7 to 203. 0 +/- 17.9 beats/min, P < 0.05). FBP increased transiently in intact fetuses from 45.1 +/- 1.0 to 55.4 +/- 3.0 mmHg at 2 h (P < 0.01), whereas denervated fetuses demonstrated a decrease in FBP from 47.1 +/- 4.2 to 37.2 +/- 3.7 mmHg (not significant). CBF increased (P < 0. 05) in both intact and denervated fetuses from 39.3 +/- 2.8 and 29.7 +/- 3.8 ml. min-1. kg-1 to 47.7 +/- 0.4 and 39.1 +/- 0.3 ml. min-1. kg-1, respectively, whereas carotid vascular resistance decreased only in denervated fetuses (1.7 +/- 0.1 to 1.1 +/- 0.02 mmHg. ml-1. min. kg-1, P < 0.05). We conclude that the peripheral chemoreceptors play an important role in mediating fetal cardiovascular responses to prolonged RUBF.
Animals↗
[Effects of warm blood and clot crystalloid cardioplegia on the heart rate variability of canine].
The objectives of this study were to explore the mechanisms of cardiac autonomic system (CAS) impairment and to assess whether warm blood cardioplegia can prevent the decrease of heart rate variability (HRV) after CPB. Twelve adult mongrel dogs were divided into two groups. One group received warm blood cardioplegia and maintained at a systemic temperature of 38 degrees C throughout the experiment (WB group). The other received cold crystalloid cardioplegia at 31 degrees C and topical hypothermia (CC group). Anesthesia was induced and maintained with sodium pentobarbital and isoflurane. The heart was exposed through a right thorectomy. CPB was established using a single right atrial cannula. The arterial cannula was placed in the right femoral artery. The crossclamp time for both groups was 30 minutes. Serum potassium levels were normalized throughout the study. Each animal's ECG was continuously recorded for 24 hours before surgery and for the first five postoperative days (POD) using a two-channel Holter monitor. The data were analyzed for heart rate variability (TP = total power, 0.01-1.00; LF = low frequency, 0.04-0.15; HF = high frequency, 0.15-0.40; LF/HF). There were no differences in the preoperative values. In both groups the TP, LF, and HF decreased, compared to control (P < 0.05), with CC group having significantly lower TP, LF and HF than the WB group (P < 0.05). The LF/HF did not change both between groups and between before- and after-CPB in each group (P > 0.05). The mean heart rate at 24 hours (MHR) increased in both groups, compared to control (P < 0.05), with CC group having a significantly higher MHR than WB group (P < 0.05). The data suggest that CPB, with warm blood or cold crystalloid cardioplegia does not disturb the balance of CAS, but it causes the decrease of HRV, and warm blood cardioplegia can not prevent the impairment of HRV.
Animals↗
Heparin and low-molecular-weight heparin therapy for venous thromboembolism. The twilight of anticoagulant monitoring.
Recent improvements in the methods of clinical trials and the use of accurate objective tests to detect venous thromboembolism have made possible a series of randomized trials to evaluate various treatments for venous thromboembolism. The results of these trials have resolved many of the uncertainties a clinician confronts in selecting an appropriate course of anticoagulant therapy. These trials have shown that the intensity of both initial heparin treatment and long-term anticoagulant therapy must be sufficient to prevent unacceptable rates of recurrence of venous thromboembolism. Patients with proximal deep vein thrombosis who receive inadequate anticoagulant therapy have a risk of clinically evident, objectively documented recurrent venous thromboembolism that approaches 20% to 25%. The need for therapy with heparin and the importance of monitoring blood levels of the effect of heparin have been established. The importance of achieving adequate heparinization was suggested by a nonrandomized trial in 1972 and randomized trials in the 1980s have confirmed this finding. Furthermore, randomized trials have demonstrated the importance of achieving adequate heparinization early in the course of therapy. Unfractionated intravenous heparin has provided an effective therapy for more than half a century, but the need to monitor therapy and establish therapeutic levels is a fundamental problem. It is evident that validated heparin protocols are more successful in establishing adequate heparinization than intuitive ordering by the clinician. However, even with the best of care using a heparin protocol, some patients treated with intravenous heparin will receive subtherapy. In this context, subtherapy reflects a practical limitation of the use of unfractionated heparin, rather than a poor standard of care. Furthermore, it is recognized that the practical difficulties associated with heparin administration are compounded by the substantive practical difficulties of standardizing APTT testing and the therapeutic range. Our findings emphasize the confounding effect that initial heparin treatment has on long-term outcome. In future trials of longterm therapy, it is imperative that the initial therapy is of adequate intensity and duration; failure to administer adequate initial treatment may lead to a poor outcome that is falsely attributed to the long-term therapy under evaluation. Therapy with low-molecular-weight heparin, which does not require monitoring and dose finding, is the likely practical solution to these dilemmas. Based on the experience of difficulties achieving adequate therapy with subcutaneous unfractionated heparin dosing, we administered a low-molecular-weight heparin formulation in a single daily dose, rather than splitting the treatment into 2 equal doses. The initial intensity of therapy was thereby maximized. Therapy with low-molecular-weight heparin proved to be better than therapy with unfractionated heparin.
Animals↗
Stage-dependent redistributions of acetylated histones in nuclei of the early preimplantation mouse embryo.
In the preimplantation mouse embryo, activation of the embryonic genome is accompanied by a transient enrichment of histone H4 acetylated at lysines 5, 8, and 12 at the nuclear periphery (Worrad et al., 1995: Development 121:2949-2959). In the present report, we use laser-scanning confocal microscopy and a new panel of antibodies to define the distribution of specific acetylated isoforms of the other three core histones in mouse embryos at the 1- to 4-cell stage. We find that histone H3 acetylated at lysine 9 and/or 18 (H3.Ac9/18) and the single acetylated form of H2A (H2A.Ac5) become transiently enriched at the nuclear periphery in the 2-cell embryo. In contrast, H3.Ac14, H3.Ac23, and acetylated H2B, like H4.Ac16, remain distributed throughout the nucleoplasm. The staining intensity with antisera to H3.Ac9/18, even at the periphery was weak compared to that obtained with antisera to acetylated H4. A brief period of culture, however, in the presence of the inhibitor of histone deacetylases trichostatin A (TSA) or trapoxin increased labeling. Thus, the steady-state level of H3.Ac9/18 at the nuclear periphery and H3.Ac14 and H3.Ac23 in the nuclear interior is relatively low, but turnover remains high. The localization of selected acetylated isoforms of H3 and H2A at the nuclear periphery was independent of ongoing transcription or of cytokinesis, but did require DNA replication. We propose a model in which the selective, replication-dependent acetylation and deacetylation of zygotic chromatin at the nuclear periphery mediates the programming of zygotic transcription.
Acetylation↗
Dysfunctional variants and the structural biology of the serpins.
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Animals↗
Regulation of ovarian follicle differentiation in gonadotrophin-stimulated rats.
The aim of the present study was to investigate the regulation of the in vitro DNA synthesis of ovarian cells recovered from prepubertal rats 48 h after administration of pregnant mare's serum gonadotrophin alone (granulosa cells) or followed by human chorionic gonadotrophin (luteal cells). Isolated granulosa cells were cultured in serum-free medium, different stimuli added for periods of 48 h, and 3H-thymidine incorporation was measured. Both follicle-stimulating hormone (FSH) and luteinizing hormone (LH) inhibited 3H-thymidine incorporation by cultured granulosa cells in a dose-dependent manner (FSH: 10, 100, 200 ng/mL = 26, 41, 49% inhibition, respectively; LH: 0.1, 1, 10 ng/mL = 11, 37, 75% inhibition, respectively). On the other hand, estradiol was found to stimulate 3H-thymidine incorporation in granulosa cells (Estradiol: 5, 50, 500 ng/mL = 17, 37, 76% stimulation, respectively). In luteal cells, the rate of basal 3H-thymidine incorporation was very low (granulosa cells: 2560 +/- 310; luteal cells: 661 +/- 92 cpm/100,000 cells) and not modified by any stimulus. To determine the possible production of an inhibitory growth factor by the early corpus luteum, 3H-thymidine incorporation by granulosa cells was assessed in the presence of 10% conditioned media (CM) recovered from luteal cell cultures. A marked inhibition both in basal and estradiol-stimulated 3H-thymidine incorporation was observed (74 and 76% of inhibition, respectively). Results suggest that an inhibitory growth factor produced by luteal cells after luteinizing gonadotrophin stimulus could be involved in the differentiation of growing follicles to corpus luteum.
Animals↗
Ten steps to creative decision making.
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Decision Making↗
Effect of streptozotocin-induced diabetes on phosphodiesterase activity in rat luteal cells.
The present studies were carried out to characterize the cAMP-phosphodiesterase enzyme (PDE) in luteal cells recovered from pseudopregnant rats with streptozotocin-induced diabetes. A significant increase in the specific activity of the enzyme was detected in luteal cells from diabetic rats (Group D) with respect to control rats (Group C). This increase could not be prevented by insulin therapy (Group I). Luteal cells from Groups C and D rats responded in vitro to insulin by increasing their PDE activity (% of stimulus of specific activity: C = 75%, D = 110%). However, in cells isolated from Group I, the hormone caused an inhibition of PDE activity (% of inhibition of specific activity: 48%). When cytosolic fractions from Groups C, D and I were submitted to ion exchange chromatography, two PDE activity peaks could be observed and the activity of the different fractions was increased in the presence of Ca2+ and calmodulin. Nevertheless, the Ca(2+)-calmodulin effect was much lower in the extracts from Groups D and I than for controls. Kinetic studies of luteal PDE showed nonlinear Lineweaver-Burk graphs with two apparent ATP hydrolysis sites. Similar K(m) values were found for PDE from groups C, D, and I, whereas the Vmax2 for the enzyme was higher in Groups D and I. The endogenous concentration of cAMP, measured by RIA, showed no significant differences among Groups C, D, and I. On the basis of these results, we conclude that the specific activity of PDE is significantly increased in luteal cells from streptozotocin-induced diabetic animals, which could explain the previously described reduction in LH-stimulated progesterone production by luteal cells in diabetic rats.
3',5'-Cyclic-AMP Phosphodiesterases↗
A deficit of chondroitin sulfate proteoglycans on the bladder uroepithelium in interstitial cystitis.
OBJECTIVES: To investigate the abundance of chondroitin sulfate proteoglycans at the bladder lumenal and subepithelial surfaces in bladder biopsies derived from patients with interstitial cystitis (IC) and controls. METHODS: Tissue sections derived from biopsies from 31 IC patients and 24 pathologically normal control sections were labeled for proteoglycans using the 2B6 anti-"stub" antibody and detected by immunohistochemistry. RESULTS: On the lumenal surface, 5 of 31 (19%) IC sections were positive for proteoglycans versus 14 of 24 (58%) control sections (P = 0.00011). At the basal surface, 5 of 19 IC patients were positive versus 7 of 12 controls (P = 0.032). CONCLUSIONS: A deficit of bladder lumenal and basal proteoglycans is associated with IC. The deficit in basal layer proteoglycans suggests an altered urothelial differentiation program. The lumenal deficit suggests that the charge-dependent exclusion of ions from the bladder surface is compromised in IC.
Chondroitin Sulfates↗
Determining laboratory value: Part 1.
This article will describe how to determine a fair market value for a dental laboratory. Part one addresses how to define fair market value, how value is perceived and how to prepare for laboratory evaluation. Part two, to be printed in April, will address how to apply an appropriate valuation methodology to determine worth.
Financial Audit↗
Determining laboratory value: Part 2.
This article describes how to determine a fair market value for a dental laboratory. Part one defined fair market value, addressed how value is perceived and how to prepare for laboratory evaluation. Part two addresses how to apply an appropriate valuation methodology to determine worth.
Accounting↗
Association of depression with reduced heart rate variability in coronary artery disease.
Decreased heart rate (HR) variability is an independent risk factor for mortality in cardiac populations. Clinical depression has also been associated with adverse outcomes in patients with coronary artery disease (CAD). This study tests the hypothesis that depressed patients with CAD have decreased HR variability compared with nondepressed CAD patients. Nineteen patients with angiographically documented CAD and either major or minor depression were compared with a sample of nondepressed CAD patients according to age, sex, and smoking status. All patients underwent 24-hour Holter monitoring, and the standard deviation of all normal-to-normal intervals was used as the primary index of HR variability. HR variability was significantly lower in depressed than nondepressed patients (90 +/- 35 vs 117 +/- 26 ms; p < or = 0.01), even after adjusting for relevant covariates. Thus, decreased HR variability may help explain the increased risk for cardiac mortality and morbidity in depressed CAD patients.
Aged↗
Association between heart rate variability and training response in sedentary middle-aged men.
The effect of exercise training on heart rate variability (HRV) and improvements in peak oxygen consumption (VO2peak) was examined in sedentary middle-aged men. The HRV and absolute and relative VO2peak of training (n = 19) and control (n = 15) subjects were assessed before and after a 24-session moderate intensity exercise training programme. Results indicated that with exercise training there was a significantly increased absolute and relative VO2peak (P < 0.005) for the training group (12% and 11% respectively) with no increase for the control group. The training group also displayed a significant reduction in resting heart rate; however, HRV remained unchanged. The trained subjects were further categorized into high (n = 5) and low (n = 5) HRV groups and changes in VO2peak were compared. Improvements in both absolute and relative VO2peak were significantly greater (P > 0.005) in the high HRV group (17% and 20% respectively) compared to the low HRV group (6% and 1% respectively). The groups did not differ in mean age, pretraining oxygen consumption, or resting heart rate. These results would seem to suggest that a short aerobic training programme does not alter HRV in middle-aged men. Individual differences in HRV, however, may be associated with VO2peak response to aerobic training.
Adult↗
Colon transit scintigraphy using oral indium-111-labeled DTPA. Can scan pattern predict final diagnosis?
Colon transit scintigraphy (CTS) was performed in 100 consecutive patients with idiopathic constipation using oral indium-111-labeled DTPA. Criteria were defined to allow classification of studies as normal, slow transit constipation (STC), or obstructed defecation (OD). Results were compared with final clinical diagnosis in 100 and findings of defecating proctography in 70. Of those with a scintigraphic diagnosis of STC, this was also the final diagnosis in 75% (33 of 44), and the scintigraphic diagnosis of OD was confirmed in 61% (17 of 28). Of 28 normal or equivocal scans, the final diagnosis was STC in only two (4%) but OD in 10 (21%). Fifty-four percent of patients with STC and 71% with OD had abnormal proctograms. The correlation between CTS and proctography was mediocre, occurring in 54% of patients. CTS has a valuable role in the diagnostic work-up of patients with idiopathic constipation.
Aged↗
In vivo regulation of the steroidogenic activity of rat luteal cells by insulin.
The aim of the present study was to determine the long-term effects of insulin treatment on luteal cell function. For this purpose, superovulated prepubertal rats were treated with insulin (group I) or vehicle (group C) for 9 days. Serum progesterone (P4) levels were increased in the insulin-treated group (55 +/- 10 vs 134 +/- 31 ng/ml, P < 0.05). Isolated luteal cells were incubated 3 h, and P4 and 20 alpha-hydroxy-progesterone (20 alpha-OH-P) were measured in the incubation media. A decrease in P4 levels and an increase in 20 alpha-OH-P values [P4 (ng/ml): C = 26.6 +/- 0.3; I = 20 +/- 2; 20 alpha-OH-P (ng/ml): C = 62 +/- 2; I: 120 +/- 7; P < 0.01] were observed in group I. In addition, progestagen (P4 + 20 alpha-OH-P) levels were higher in group I (C = 88 +/- 2; I = 140 +/- 9 ng/ml; P < 0.001). When cytochrome P450scc contents were measured by immunoblotting, a marked increase was observed in luteal cells obtained from group I. LH receptor numbers were decreased in luteal cells isolated from group I (C = 388,834 +/- 14,146; I = 303,057 +/- 13,392 sites/cell; P < 0.001) with a concomitantly diminished LH responsiveness. It is concluded that in vivo treatment of superovulated rats with insulin increases luteal progestagen production by increasing the content of cytochrome P450scc.
20-alpha-Dihydroprogesterone↗