Noscapine does not show aneugenic activity in mouse oocytes

To clarify if noscapine has the ability to induce polyploidyin rodent germ cells in vivo, a cytogenetic study of mouse metaphaseII oocytes was conducted after oral treatment with noscapineat the doses of 20, 120 and 400 mg/kg. Plasma concentrationsof noscapine were measured by reversed-phase liquid chromatographyand UV detection in three satellite groups of mice up to 8 hafter administration of these doses. Thus, the relationshipof the maximum plasma concentration and the area under the curve(AUC) with that of meiotic progression could be established.Although noscapine was tested at the maximum tolerated dose,no delay of meiotic progression or induction of chromosome malsegregationcould be shown as no increase in the frequency of metaphaseI-arrested, polyploid or hyperploid oocytes were found. At thehighest dose only, noscapine affected the physiology of superovulationas shown by a significant decrease in the mean number of oocytesharvested per female. In view of the large span covered by thedoses tested, corresponding to concentrations far above thosedetected in humans, and the similarity between the pharmacokineticsof noscapine in mouse and humans, it is unlikely that noscapinerepresents a genetic risk for humans at therapeutic dosages. ²To whom correspondence should be addressed     

Chloral hydrate induced spindle aberrations, metaphase I arrest and aneuploidy in mouse oocytes

In view of tissue- and sex-specific differences in chemically-inducedaneuploidy, we analysed the effects of chloral hydrate (CH)on cell-cycle progression, spindle formation and aneuploidyin in vitro maturing mouse oocytes with cytogenetic and immunofluorescentmethods. CH blocks oocyte maturation irreversibly and concentrationdepend-ently. During culture in 125 µg/ml CH, germinalvesicle breakdown is delayed, and most oocytes become arrestedin meiosis I with bivalent chromosomes. Their spindles are asymmetricor attain fusiform poles. Oocytes which progress to metaphaseII also possess astral instead of barrel-shaped, anastral spindlesas characteristic for the controls. Resolution of chiasmatawithout polar body extrusion during exposure to 50 and 125 µ/mlCH results in significant rises in ‘diploid’ metaphaseII oocytes. Hyperplo-idy rates do not increase significantlyat any concentration of CH, but hypoploidy levels are elevatedat 125 µ/m\ CH. CH induces lagging of chromosomes duringtelophase I, inhibits spindle elongation in anaphase B and causeschromosome displacement from the spindle equator in metaphaseI and II. Oocytes also become irreversibly arrested in maturationwhen exposed to CH prior to resumption of maturation, or whenCH is present during the first or second 8 h of maturation.Therefore, these data show unequivocally that CH is a potentaneugen in female germ cells, affecting spindle shape, cytokinesisand cell-cycle progression. However, a metaphase I checkpointin mammalian oogenesis sensing disturbances in the spindle appearsto prevent nondisjunction efficiently in most oocytes. In thisin vitro model the aneugenic activity of drugs, critical periodsin oocyte maturation, threshold concentrations, and targetsof drug action can be directly assessed. ¹To whom correspondence should be addressed     

Synergism between gonadotrophins and vinblastine relative to the frequencies of metaphase I, diploid and aneuploid mouse oocytes

Ovulated oocytes are used to obtain estimates of germ cell aneuploidyfollowing in vivo treatment with various chemicals. Such studiescommonly use exogenous gonado-trophins to increase the numberof ovulated oocytes and to induce ovulation during specifictime periods. However, the gonadotrophin dosages have not beenevaluated relative to the possibility that synergistic and antagonisticinteractions may exist between the hormones and the chemicalbeing studied. We, therefore, studied the interactions of differenthormone dosages (5 IU pregnant mare's serum (PMS) and 2.5 IUhuman chorionic gonadotrophin (HCG), 7.5 IU PMS and 5 IU HCG,and 10 IU PMS and 7.5 IU HCG) alone (controls) and in combinationwith 0.2 mg/kg of the aneugen vinblastine sulfate (VBS) relativeto the number of oocytes ovulated, the frequencies of metaphaseI (MI), diploid and aneuploid oocytes. The results indicatedthat the proportions of oocytes ovulated were not significantly(P > 0.05) different among the various control and VBS groups.VBS, however, resulted in significantly (P < 0.01) higherlevels of MI oocytes than in controls. In the VBS-treated females,higher frequencies (P < 0.05) of MI oocytes were found inthe 7.5 IU PMS and 5 IU HCG and 10 IU PMS and 7.5 IU HCG groupsas compared to the 5 IU PMS and 2.5 IU HCG group. The frequenciesof diploid oocytes did not differ significantly (P > 0.05)within the control of VBS groups; whereas, when comparisonswere made between each control and VBS group, only the differencebetween the 5 IU PMS and 2.5 IU HCG groups was significant (P< 0.05). As expected, VBS resulted in higher (P < 0.01)levels of hyperploidy than in the controls. Following VBS, thefemales that received 7.5 IU PMS and 5 IU HCG had higher (P< 0.01) levels of hyperploidy than either the lower or higherhormone groups. We also found that significantly (P < 0.05)higher aneuploidy levels occurred in the 7.5 IU PMS and 5 IUHCG controls than in the controls that received 10 IU PMS and7.5 IU HCG. These findings suggest that gonadotrophin dosageinfluences oocyte chromosome segregation.     

Cytochalasin delays but does not prevent cell death from anoxia.

The role of alterations in the cytoskeleton in the anoxic death of cultured hepatocytes was evaluated with the use of cytochalasin B and colchicine. The addition of 50 microM Cytochalasin did, however, reduce the rate of accumulation of dead cells but was without effect on the number of cells that died. After 6 hours of anoxia in the presence of cytochalasin, 80% of the cells were dead. The same number of cells were dead after 4 hours in the absence of cytochalasin. Colchicine was without effect on the cell killing by anoxia. Cytochalasin also did not prevent the increase in the molecular order of the membranes of the anoxic hepatocytes as determined by electron spin resonance spectroscopy. In the presence or absence of cytochalasin, anoxia increased the order parameter, S, of hepatocytes spin-labeled with 12-doxyl stearic acid. These data indicate that changes in the organization of microfilaments that can be prevented by cytochalasin may aggravate the mechanisms mediating the anoxic death of the hepatocytes, but such mechanisms are essentially independent of these alterations in the cytoskeleton. The data do not exclude from a role in anoxic cell death other cytoskeletal changes that may not be affected by either cytochalasin or colchicine.     

Splenectomy modulates the immune response but does not prevent joint inflammation in a mouse model of RA

The spleen is the largest secondary lymphoid organ which is involved in the development of B cells and also in systemic (auto)immune responses. Using the recombinant human G1 domain-induced arthritis (GIA) model in splenectomized and control BALB/c mice, we investigated the role of the spleen in the induction and pathogenesis of autoimmune arthritis. Splenectomized mice developed GIA with a similar clinical picture to the control group. However, we observed significant alterations in the humoral and cellular immune responses in splenectomized mice. In the sera of the splenectomized mice, we found lower pro-inflammatory cytokine and anti-rhG1 IgM levels, but higher IL-4, anti-rhG1 IgG1 and anti-CCP and RF antibodies. The arthritis induction in the splenectomized group was associated with a significant expansion of activated helper T cells and an increase in the proportion of the circulating B1 and marginal zone B cell subsets. Importantly, immunization of the splenectomized mice with rhG1 induced the formation of germinal centers in the inguinal- and mesenteric lymph nodes (i/mLNs) which showed an active immune response to rhG1. Finally, both B and T cells from the mLNs of the splenectomized mice showed decreased intracellular Ca²⁺ signaling than those of the control group. Collectively, these findings indicate that the presence of the spleen is not critical for the induction of GIA, and in its absence the autoimmune arthritis is most likely promoted through the compensatory activity of the i/mLNs. However, our data implies the immunological role of the spleen in arthritis which could be further assessed in human RA.     

Reserpine does not prevent 3,4-methylenedioxymethamphetamine-induced neurotoxicity in the rat

3,4-Methylenedioxymethamphetamine (MDMA; 'Ecstasy') is a known neurotoxin to 5-hydroxytryptamine (5-HT) nerve terminals. Recent studies have suggested that endogenous dopamine (DA) and/or 5-HT may mediate the MDMA-induced neurotoxicity. The central monoamine stores of rats were significantly decreased with reserpine (5 mg/kg) prior to toxic injections of MDMA. Rats given MDMA (30 mg/kg) displayed significant decreases in the density of 5-HT nerve terminals labeled by [3H]paroxetine both with (51 +/- 8%) and without (43 +/- 20%) reserpine pre-treatment. These data suggest that the degeneration of 5-HT nerve terminals following MDMA is independent of the presence of endogenous stores of DA or 5-HT.     

Renal denervation does not prevent dehydration-induced natriuresis in sheep

Normal sheep or sheep in which the renal nerves had been extirpated were deprived of water for 2 days in order to determine whether changes in renal nerve activity contribute to natriuresis during water deprivation. Both groups of sheep showed a considerable natriuresis throughout the period of water deprivation and increases in plasma osmolality and plasma Na concentration. Renal denervation, as indicated by the absence of catecholamine fluorescence in kidney sections, was extensive. Previous experiments have suggested cerebral involvement in the induction of dehydration-induced natriuresis. The present results indicate that the efferent pathway mediating this cerebral influence on renal sodium excretion does not involve the renal nerves, suggesting a hormonal mechanism as the likely pathway.     

Expression of mouse mammary tumor virus envelope protein does not prevent superinfection in vivo or in vitro.

Inbred mice expressing endogenous mouse mammary tumor virus envelope proteins can be infected with exogenous virus, and the mammary tumors that develop in these mice usually have many proviruses integrated in their genomes, indicating that this virus is not subject to receptor interference. We show here that transgenic mice expressing an exogenous mouse mammary tumor virus (C3H) envelope protein can still be infected with this virus. Moreover, cultured mammary gland cells expressing the mouse mammary tumor virus (C3H) envelope protein can be superinfected with pseudotyped viruses bearing that same protein. Thus cellular expression of the mouse mammary tumor virus envelope protein does not block superinfection in vivo or in vitro.     

Linomide does not prevent spontaneous autoimmune thyroiditis in NOD mice

Linomide is a potent immunomodulator and has been reported to prevent type 1 diabetes mellitus in non-obese diabetic (NOD) mice and to reduce the incidence of other autoimmune diseases in animal models. The mechanisms of action seem to involve antigen expression by down regulation of macrophage activity and to antagonise the activation of Th1 cells during the cellular immune response. With the purpose to investigate the effect of Linomide on the incidence of spontaneous autoimmune thyroiditis (AIT) in female NOD mice we administered Linomide in drinking water (100 mg/kg/day) to NOD mice from 5th to 19th week of age. The mice were sacrificed at the end of week 19. None of the mice developed diabetes during the study period. The incidence of thyroiditis was evaluated on paraffin HE-stained sections and graduated on a scale from 0 to 4. Thirty-two percent of 37 mice treated with Linomide developed thyroiditis compared to 45% of 22 controls (p=0.31, chi2 =1.00). Among the mice who developed thyroiditis no difference in the degree of thyroiditis was found. Therefore no beneficial effect of Linomide on the incidence of spontaneous AIT in NOD mice could be demonstrated.     

Beta-adrenergic blockade does not prevent hypoglycemia awareness in non-diabetic humans

This study's purpose was to test whether beta-adrenergic blockade reduces awareness of hypoglycemia. Six non-diabetic human adults received six experimental sessions each, one with each combination of intravenous propranolol (0.0, 0.05, and 0.15 mg/kg) followed by intravenous regular insulin (2 and 4 units). Physiological, biochemical, and symptom variables, and choice (was an active or an inactive substance administered?) were measured at 15, 30, and 45 min after insulin. Insulin dose and time after insulin administration significantly influenced choice, but propranolol did not significantly influence choice. Adrenergic symptoms were not prominent. These results may or may not apply to individuals with disorders of adrenergic function such as diabetic autonomic neuropathy.     

Aneuploidy in mouse metaphase II oocytes exposed in vivo and in vitro in preantral follicle culture to nocodazole

Aneuploidy tests are important in evaluating genetic hazards especially when chemical exposures are suspected to affect the fidelity of chromosome segregation in oocytes and embryos. In the current study, a newly established method, mouse preantral follicle culture, was employed to grow oocytes in vitro within follicles. The sensitivity of in vitro grown follicle enclosed oocytes was compared with oocytes maturing in vivo in the ovary. In both the cases, oocytes were exposed to the cytostatic chemical, nocodazole, from the time of hormonally stimulated resumption of meiosis. The in vivo study revealed a significant decrease in the number of ovulated mouse oocytes and an increase in meiosis I-arrested and hyperploid metaphase II oocytes at a single i.p. dose of 70 mg/kg body weight of nocodazole. A significant increase was also observed in the number of meiosis I-arrested and hyperploid mouse oocytes from preantral follicle culture, when they were cultured in the presence of >or=30 nM nocodazole during the final stages of maturation. This concentration is slightly lower than that previously shown to induce nondisjunction in denuded mouse oocytes or in cultured human lymphocytes. The higher sensitivity of the in vitro matured oocytes from preantral follicle culture than that of denuded oocytes may be related to a synergistic adverse influence of nocodazole on the oocyte, on somatic cell integrity and on cell-cell communication, which possibly also affects ovulation in vivo. When expressed in molarity relative to the mouse weight, the effective dose of the acute exposure in vivo is 3-4 orders of magnitude higher than the lowest effective concentration employed continuously in vitro. Reduced bioavailability of nocodazole to the target cells due to its poor water solubility may contribute to this difference. Preantral follicle culture can be helpful in analysing mechanisms in chemically induced aneuploidy in mammalian oogenesis, and in predicting the consequences of chemical exposures in vivo.     

Neutrophil depletion does not prevent indomethacin-induced ulceration of the rat gastric antrum

Indomethacin-induced ulceration of the rat gastric antrum is paralleled by an increase in blood neutrophil numbers and of neutrophil infiltration into the antrum. Thus, in this study, neutrophil depletion has been employed to study the potential role of neutrophils in the pathogenesis of indomethacin-induced ulceration of the rat gastric antrum. Pretreatment with an anti-neutrophil serum (ANS) induced a near complete neutropaenia and inhibition of neutrophil infiltration into the gastric antrum (as assessed by antral LTB₄ release). In contrast, ANS pretreatment did not alter the area of indomethacin-induced mucosal damage detected microscopically.

Our results suggest that, in contrast to published reports examining fundic ulceration, neutrophil infiltration does not contribute to the ulcerogenic effects of indomethacin in the rat gastric antrum.

     

Long-term endurance training does not prevent the age-related decrease in left ventricular relaxation properties

AIM: Diastolic filling dynamics in the long-term endurance trained elderly has previously been examined by transmitral flow velocity, which has been shown to be preload dependent. The aim of this study was to assess the effect of long-term endurance training on left ventricular (LV) relaxation in older individuals by using pulsed tissue Doppler imaging. METHODS: Fourteen master athletes with a history of intensive long-term endurance training, 14 aged-matched sedentary controls and 15 young adult men underwent standard Doppler echocardiography and pulsed Doppler tissue imaging, performed in four-chambers apical view, by placing a sample volume at the level of the mitral annulus. RESULTS: Stroke volume was significantly higher and heart rate lower in master athletes compared with aged-matched sedentary subjects. Transmitral Peak E velocity and ratio E/A were significantly higher in master athletes, but did not reach the values of young men. Peak LV wall motion during the early filling phase, an index of LV relaxation, were significantly higher in young men than in both groups of older individuals. However, similar values were obtained between master athletes and sedentary counterparts. CONCLUSIONS: Our data provide evidence that long-term training does not reduce the age-related decline in LV relaxation properties in humans. This finding implies that other mechanisms, such as increased LV filling pressures due to expanded blood volume, are probably responsible for the higher contribution of early diastolic filling to LV filling in master athletes compared with their sedentary counterparts. However this hypothesis needs to be confirmed.     

Blockade of nitric oxide formation does not prevent glutamate-induced neurotoxicity in neuronal cultures from rat hippocampus.

This study examined the role of nitric oxide (NO) in glutamate-induced, N-methyl-D-aspartate (NMDA) receptor-mediated neurotoxicity in rat hippocampal neuronal cultures grown under serum-free conditions. Formation of cGMP was used as an indirect measure of NO formation. Neuronal cell degeneration was monitored by measuring the release of lactate dehydrogenase (LDH). Neuronal cells showed a 4-fold increase in cGMP formation and release of LDH upon exposure to 30 microM glutamate. cGMP formation was fully inhibited by 1 microM nitro-arginine (N-Arg), 100 microM hemoglobin or 1 microM MK-801. In the presence of 1 microM MK-801, glutamate induced neither cGMP formation nor neuronal cell degeneration. However, when NO formation was inhibited by means of 100 microM N-Arg, glutamate still induced neurotoxicity. Therefore, in serum-free hippocampal cultures glutamate neurotoxicity occurs notwithstanding complete inhibition of the NO-synthase enzyme by N-Arg. Our data provide evidence that NO, synthesized upon glutamate exposure, has not a primary toxic action in pure hippocampal neuronal cultures.     

Simvastatin does not prevent acute cardiac allograft rejection in CD28-deficient mice

Background  

Heterotopic cardiac transplantation in mice was used to determine whether complementary immunomodulation by statins prevents lymphocyte function-associated antigen (LFA)-1-dependent acute allograft rejection in vivo.     

Short-term subcutaneous insulin treatment delays but does not prevent diabetes in NOD mice

Despite encouraging results in the NOD mouse, type 1 diabetes prevention trials using subcutaneous insulin have been unsuccessful. To explain these discrepancies, 3-week-old NOD mice were treated for 7 weeks with subcutaneous insulin at two different doses: a high dose (0.5 U/mouse) used in previous mouse studies; and a low dose (0.005 U/mouse) equivalent to that used in human trials. Effects on insulitis and diabetes were monitored along with immune and metabolic modifications. Low-dose insulin did not have any effect on disease incidence. High-dose treatment delayed but did not prevent diabetes, with reduced insulitis reappearing once insulin discontinued. This effect was not associated with significant immune changes in islet infiltrates, either in terms of cell composition or frequency and IFN-γ secretion of islet-reactive CD8(+) T cells recognizing the immunodominant epitopes insulin B(15-23) and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)(206-214). Delayed diabetes and insulitis were associated with lower blood glucose and endogenous C-peptide levels, which rapidly returned to normal upon treatment discontinuation. In conclusion, high- but not low-dose prophylactic insulin treatment delays diabetes onset and is associated with metabolic changes suggestive of β-cell "rest" which do not persist beyond treatment. These findings have important implications for designing insulin-based prevention trials.     

Pravastatin does not prevent antiphospholipid antibody-mediated changes in human first trimester trophoblast function

STUDY QUESTION: What is the effect of pravastatin on antiphospholipid antibody (aPL) modulation of human first trimester trophoblast function? SUMMARY ANSWER: Pravastatin does not prevent the effects of aPL on human first trimester trophoblast cell function. WHAT IS KNOWN ALREADY: Antiphospholipid syndrome (APS) is associated with recurrent pregnancy loss and late pregnancy complications, such as pre-eclampsia, owing to direct targeting of the placenta by aPL. While treatment with heparin reduces the rate of pregnancy loss, the risk for severe pre-eclampsia remains high. Thus, there is a need to find alternative treatments for the prenatal management of patients with APS. Statins have recently been shown to prevent aPL-mediated fetal loss in mice but their effects on a human pregnancy model of APS have not yet been studied. DESIGN, DATA COLLECTION, METHODS: The human first trimester trophoblast cell line, HTR8, and human first trimester trophoblast primary cultures were incubated with or without a mouse anti-human beta 2 glycoprotein I (β(2)GPI) monoclonal antibody in the presence or absence of pravastatin. Cytokine and angiogenic factor secretion were measured by enzyme-linked immunosorbent assay and multiplex analysis. Cell migration was measured using a colorimetric two-chamber migration assay. MAIN FINDINGS: Using the human first trimester trophoblast cell line, HTR8, pravastatin significantly augmented, compared with no treatment, aPL-dependent secretion of interleukin (IL)-8 (P< 0.05), IL-1β (P< 0.05) and soluble endoglin (P< 0.01) but had no effect on aPL-induced up-regulation of vascular endothelial growth factor, placenta growth factor or growth-related oncogene alpha secretion. Furthermore, pravastatin alone limited basal HTR8 cell migration (P< 0.01), and did not mitigate the adverse effect of aPL on trophoblast migration. Pravastatin also had no impact on the secretion of pro-inflammatory cytokines and angiogenic factors by primary human first trimester trophoblast cells exposed to aPL. LIMITATIONS AND WIDER IMPLICATIONS OF THE FINDINGS: While our in vitro findings suggest that pravastatin may not be effective in preventing pregnancy complications in patients with APS, the in vivo condition may be more complex, and thus, more studies are needed to determine the effectiveness of pravastatin in the prevention of aPL-associated pregnancy complications in humans. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the American Heart Association.