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F Z Sun

Publications and source records attributed to F Z Sun.

17 recordsLinked to original sources
PubMed2001

Flowering plant sperm contains a cytosolic soluble protein factor which can trigger calcium oscillations in mouse eggs.

There is evidence showing that the sperm-induced Ca(2+) oscillations in mammalian eggs at fertilization are triggered by a sperm-derived protein factor. It was established recently that the activity of the putative sperm protein in causing Ca(2+) oscillations in mammalian eggs is not species-specific in vertebrates (1, 16). Here we report that cytosolic soluble extracts derived from flowering plant sperms in Brassica campestris can also induce fertilization-like Ca(2+) oscillations when microinjected into mouse eggs. The factor responsible for inducing Ca(2+) oscillations in the plant sperm was sperm-specific and heat- or trypsin-labile. Eight to ten sperm equivalents of the plant sperm extracts had enough activity to trigger Ca(2+) oscillations in mouse eggs. Our study suggests that, although plant and mammal are evolutionary divergent species, the activity of the putative sperm protein factor in triggering Ca(2+) signaling in mammalian eggs is not specific to the animal kingdom.

Animals↗
PubMed2001

Fine-scale mapping using Hardy-Weinberg disequilibrium.

Hardy-Weinberg disequilibrium (HWD) among affected individuals has recently been proposed for fine-scale mapping of disease susceptibility genes. We investigate the statistical properties of several available HWD measures and develop a new HWD measure J for fine-scale mapping. It is shown both theoretically and through simulations that the available HWD measures depend not only on the genetic distance between the marker locus of interest and the disease susceptibility locus, but also on the allele frequencies at the marker locus. On the contrary, the new measure is not affected by the allele frequencies at the marker locus under the following assumptions: (a) there is initial complete linkage disequilibrium between the marker and the disease loci, (b) there are no new mutations at the marker and the disease loci, and (c) the population under study is large. We develop a novel method to estimate the location of the disease susceptibility gene based on the HWD measure J. The estimator is robust to low mutation rates at the marker and the disease loci. We compare the standard error of the estimated disease gene loci using P excess for case-control studies with the standard error using J for case-only studies under various disease models. The newly developed method is successfully applied to a data set on hereditary haemochromatosis (HH).

Analysis of Variance↗
PubMed2000

Xenopus and chicken sperm contain a cytosolic soluble protein factor which can trigger calcium oscillations in mouse eggs.

There is evidence showing that at fertilization the sperm introduces into egg cytoplasm a protein-based cytosolic factor, which serves as the physiological trigger for inducing Ca(2+) oscillations in mammalian eggs. Here we show that sperm of nonmammalian vertebrates also contain a cytosolic protein factor that can induce Ca(2+) oscillations when introduced into mammalian eggs. We have observed that cytosolic extracts derived from Xenopus or chicken sperm could induce mouse eggs to undergo Ca(2+) oscillations similar to those induced by bovine sperm extracts. The factor responsible for inducing Ca(2+) oscillations was of high molecular weight and heat- or proteinase K-labile. We show that 0.5 chicken sperm-equivalents or 1-2 Xenopus sperm-equivalents of the extracts had enough activity to trigger Ca(2+) oscillations in mouse eggs. Our findings illustrate that although Xenopus, chicken, and mammals are evolutionarily divergent species, the function of the sperm protein factor in triggering Ca(2+) oscillations in mammalian eggs appears not to be species specific in vertebrates.

Animals↗
PubMed2000

Transmission/disequilibrium tests for quantitative traits.

The transmission/disequilibrium test (TDT) is a powerful method of locating disease genes. The TDT was originally proposed for use in studies of qualitative traits in families with both parents available. Recently, the TDT has been extended to studies of qualitative traits in sibships without parents available and in families with one parent available. It has also been extended for use in studies of quantitative traits in families with both parents available and in sibships with multiple offspring. In this paper, we first propose a new class of TDT-type tests for linkage in the presence of linkage disequilibrium for use in studies of families with both parents available. The TDT of Spielman et al. (1993) for qualitative traits and the TDT of Rabinowitz (1997) for quantitative traits are special cases of the new tests. Second, we propose a new class of TDT-type tests for linkage for use in studies of families with one parent available. Third, we study the validity and the power of the tests using simulations. Finally, we propose a method of combining data from different types of families. The combined test is valuable and allows researchers full use of the available data in detecting linkage between a marker locus and an unobservable quantitative trait locus. An important feature of the tests proposed in this paper is that no assumptions on the distribution of the quantitative traits are needed.

Computer Simulation↗
PubMed2000

Ca(2+) oscillations induced by a cytosolic sperm protein factor are mediated by a maternal machinery that functions only once in mammalian eggs.

At fertilization in mammals, the sperm activates the egg by inducing a series of oscillations in the intracellular free Ca(2+) concentration. There is evidence showing that this oscillatory event is triggered by a sperm-derived protein factor which diffuses into egg cytoplasm after gamete membrane fusion. At present the identity of this factor and its precise mechanism of action is unknown. Here, we studied the specificity of action of the sperm factor in triggering Ca(2+) oscillations in mammalian eggs. In doing so, we examined the patterns of Ca(2+) signaling in mouse eggs, zygotes, parthenogenetic eggs and maturing oocytes following the stimulation of bovine sperm extracts which contain the sperm factor. It is observed that the sperm factor could induce Ca(2+) oscillations in metaphase eggs, maturing oocytes and parthenogenetically activated eggs but not in the zygotes. We present evidence that Ca(2+) oscillations induced by the sperm factor require a maternal machinery. This machinery functions only once in mammalian oocytes and eggs, and is inactivated by sperm-derived components but not by parthenogenetic activation. In addition, it is found that neither InsP(3) receptor sensitivity to InsP(3) nor Ca(2+) pool size are the determinants that cause the fertilized egg to lose its ability to generate sperm-factor-induced Ca(2+) oscillations at metaphase. In conclusion, our study suggests that the orderly sequence of Ca(2+) oscillations in mammalian eggs at fertilization is critically dependent upon the presence of a functional maternal machinery that determines whether the sperm-factor-induced Ca(2+) oscillations can persist.

Animals↗
PubMed2000

[Pituitary adenylate cyclase activating polypeptide ameliorates the damage and inhibits the increase of intracellular calcium concentration in cultured hippocampal neurons induced by glutamate].

Hippocampal neurons cultured from 7 to 9 d in vitro were used to observe the effect of glutamate. Treatment of glutamate for 24 h greatly decreased neuronal survival and pretreatment with pituitary adenylate cyclase activating polypeptide (PACAP) significantly attenuated hippocampal neuron death induced by glutamate. Moreover, glutamate dose-dependently increased the intracellular calcium concentration in cultured hippocampal neurons, while PACAP inhibited the increase of intracellular calcium concentration induced by glutamate. PACAP 6-38, a specific PACAP type I receptor antagonist, completely inhibited the amelioration of glutamate induced death and the decrease of intracellular calcium concentration induced by PACAP in cultured hippocampal neurons. The data suggest that PACAP has a neuroprotective effect on the hippocampal neuronal damage induced by glutamate, which is related to an inhibition of glutamate-induced increase of intracellular calcium concentration and mediated by PACAP type I receptor.

Animals↗
PubMed1998

Spontaneous and fertilization-induced Ca2+ oscillations in mouse immature germinal vesicle-stage oocytes.

Mouse germinal vesicle (GV)-stage oocytes not only show Ca2+ oscillations in response to fertilization but also exhibit spontaneous Ca2+ oscillations during meiotic maturation in vitro. Spontaneous Ca2+ oscillations were entirely suppressed by microinjection of heparin (25 microM final intracellular concentration), an antagonist of inositol trisphosphate (IP3) receptor, whereas fertilization-induced Ca2+ oscillations were only partially inhibited by heparin even at a high dosage of 600 microM. Inhibition of endogenous IP3 generation by antagonizing phospholipase C using U73122 (20 microM final concentration) also failed to suppress the generation of fertilization-induced Ca2+ transients, suggesting that the two types of Ca2+ oscillations do not have the same dependence on IP3-induced Ca2+ release. In addition, spontaneous Ca2+ oscillations require the presence of intact GV whereas fertilization-induced Ca2+ oscillations are independent of the GV but require cytoplasm, since enucleation eliminated only spontaneous Ca2+ oscillations but not fertilization-induced Ca2+ oscillations. These results suggest that IP3-induced Ca2+ release is the primary mechanism responsible for spontaneous Ca2+ oscillations. Sperm-induced Ca2+ oscillations, however, may employ more complex mechanisms during fertilization.

Animals↗
PubMed1998

[Intracellular Ca2+ distribution and its role in mouse oocytes maturation].

To determine the role of calcium and calmodulin in mouse oocyte maturation, we examined the distribution of intracellular calcium during mouse oocyte maturation by using Mira Cal Imaging System. The calcium was present homogeneously in oocytes with intact germinal vesicle (GV) and accumulated around the nuclear region after GV breakdown(GVBD). The high level of calcium disappeared 6 hours later after GVBD. In the presence of 50 mumol/L BAPTA/AM, we failed to observe this phenomena. All eggs treated with 20 mumol/L W7, an antagonist of calmodulin, 50 mumol/L BAPTA/AM, a calcium chelator, could not develop to metaphase II (MII), although GVBD was not affected. We also detected the activity of a cytoplasmic maturation-promoting factor (MPF). W7 and BAPTA/AM had no effects on the rise of MPF activity in the course of maturation. We suggest that compartment distribution of calcium around nuclear region plays an important role in mouse oocyte maturation.

Animals↗
PubMed1996

Changes in distribution of labile zinc in mouse spermatozoa during maturation in the epididymis assessed by the fluorophore Zinquin.

The Zn(II)-specific fluorophore Zinquin was used to determine the regional distribution of free or loosely-bound Zn(II) in mouse spermatozoa. Spermatozoa from the testes exhibited bright fluorescence over the entire head; those from the caput epididymides generally fluoresced more brightly in the post-acrosomal region; and spermatozoa from the caudae epididymides fluoresced less brightly, with foci of fluorescence over the sperm head which were lost after extraction with Triton X-100 and hence appeared to be membrane-associated. Treatment of cauda sperm with sodium dodecyl sulfate resulted in a bright uniform Zinquin fluorescence in the heads, similar to that observed in caput sperm, indicating that the two types of sperm have similar amounts of head Zn(II) but that the availability of Zn(II) for binding Zinquin is different. By contrast, the intensity of tail fluorescence was similar in spermatozoa from different regions of the male reproductive tract and was largely unaffected by Triton X-100 extraction, consistent with an intracellular location. Similar differences were observed between caput sperm and cauda sperm in the rat. It is concluded that visualization and measurement of free or loosely-bound Zn(II) in subcellular compartments of spermatozoa should facilitate investigation of the role of this metal in the development and function of spermatozoa and abnormalities that might accompany infertility and Zn(II) deficiency.

Animals↗
PubMed1994

Changes in intracellular calcium concentration in bovine oocytes following penetration by spermatozoa.

The pattern of changes in intracellular calcium concentration ([Ca2+]i) in bovine oocytes after penetration by spermatozoa was determined. Dynamic video imaging, using Fura-2 as a probe for intracellular free calcium, showed that activation of oocytes by spermatozoa induced multiple transient increases in [Ca2+]i with a spike interval of 24.2 +/- 7.3 min, and that the early transient increases were propagated throughout the oocytes in the form of a wave. Calcium transients at fertilization are involved in the induction of cortical granule exocytosis and the resultant block to polyspermy. The hypothesis that the inhibition of Ca2+ release from inositol trisphosphate-sensitive stores would inhibit exocytosis and increase polyspermy was tested by injecting oocytes before fertilization with heparin, a potent inhibitor of inositol trisphosphate-activated Ca2+ release. There was no significant difference after fertilization in either [Ca2+]i spikes or in polyspermy rates between control and experimental groups injected with low molecular mass heparin up to a final cytoplasmic concentration of 400 mumol l-1. We conclude that inositol trisphosphate-independent Ca2+ stores may be mobilized during the fertilization of bovine oocytes.

Animals↗
PubMed1993

[Analgesic effect and gastro-intestinal motility inhibitory action of 3-hydroxy-4-methoxy-acetophenone from Cynanchum paniculatum (Bunge) Kitagawa].

3-Hydroxy-4-methoxy-acetophenone (HMA) isolated from Cynanchum paniculatum was found to have analgesic effect and inhibitory action on the gastro-intestinal motility. The effect and action were equivalent to that of paeonol, HMA displayed a very low degree of antibacterial activity against Escherichia coli and Shigella flexneri.

Acetophenones↗
PubMed1992

A comparison of intracellular changes in porcine eggs after fertilization and electroactivation.

The experiments compare intracellular changes in porcine eggs induced by electrical activation with those induced by sperm penetration. Adequate electrostimulation induces changes in both cortical granule exocytosis and protein synthesis similar to those induced by sperm during fertilization. However, ionic changes induced by electrostimulation differ markedly from those initiated at fertilization. Thus, dynamic video imaging using Fura-2 as a Ca2+ probe provides evidence that parthenogenetic activation induced by electrostimulation is initiated by a single sharp rise in the concentration of intracellular free calcium ([Ca2+]i) in the egg. The intracellular Ca2+ transient increase is triggered by an influx of extracellular Ca2+ immediately after electrostimulation. The amplitude of the intracellular Ca2+ transient increase is a function both of the extracellular Ca2+ concentration and of electric field parameters (field strength and pulse duration). Imaging demonstrates further that a single electrical pulse can only induce a single Ca2+ transient which usually lasts three to five minutes; no further Ca2+ transients are observed unless additional electrical stimuli are applied. By contrast, sperm-induced activation is characterised by a series of Ca2+ spikes which continue for at least 3 hours after sperm-egg fusion. The pattern of Ca2+ spiking after fertilization is not consistent during this period but changes both in frequency and amplitude. Overall, the results demonstrate that, although electrostimulation induces both cortical granule exocytosis and protein reprogramming in porcine eggs, it does not reproduce the pattern of [Ca2+]i changes induced by sperm entry at fertilization.

Animals↗
PubMed1991

Nuclear-cytoplasmic interactions during ovine oocyte maturation.

The present studies have been undertaken to investigate the interactions that occur between the nucleus and cytoplasm of ovine oocytes at various stages during meiotic maturation. We report that the nucleus of ovine fully grown dictyate stage oocytes can be efficiently removed by a microsurgical enucleation procedure. It is demonstrated that between the initiation of maturation and germinal vesicle breakdown certain newly synthesized polypeptides are selectively sequestered in the oocyte nucleus and the major sequestered polypeptide has a relative molecular mass of 28,000, which represent at least 9% of the total labelled polypeptides transferred to the oocyte nucleus during the first 4 h of maturation. The experiments provide evidence that the removal of the oocyte nucleus at various times before germinal vesicle breakdown (GVBD) does not prevent the major series of changes in protein synthesis that occurs after entry into a metaphase. We conclude therefore that the mixing of the nucleoplasm and cytoplasm is not essential for the initiation or progression of the protein reprogramming process during maturation. In addition, the experiments show that the development of the ability to condense chromatin during ovine oocyte maturation is independent of the oocyte nucleus. The combined results strongly support the hypothesis that the extensive series of translational changes that occur in oocytes during maturation are controlled by cytoplasmic rather than nuclear factors.

Animals↗
PubMed1985

Supervised intermittent chemotherapy for pulmonary tuberculosis in a rural area of China.

In order to ensure regularity of ambulatory treatment of new cases of pulmonary tuberculosis, a fully supervised intermittent chemotherapy regimen was tried in two rural counties of Beijing. The bare-foot doctors of the village health co-operatives were designated to administer and supervise treatment. The regimen consisted of isoniazid and streptomycin daily for 1 month, then every 3 days for 5 months and then every 5 days for a total of 12 or 18 months. For smear-negative cases the daily phase was omitted. The compliance rate among 229 patients in 1 year was 99.4%. The sputum conversion rate among 104 cases harbouring sensitive bacilli was 95.2%. Discontinuation of the regimen due to side-effects as necessary in 3 cases (1.3%). Since 1979, this treatment programme has been adopted in the whole rural area of Beijing, and the coverage rate among newly diagnosed smear-positive cases in 1983 reached 90%. A reserve regimen consisting of rifampicin and ethambutol for patients who do not convert their sputum after 6 months of treatment with isoniazid and streptomycin was added. The overall conversion rate achieved in 1981 was 97.8%. The average overall cost of drugs for each patient treated in this treatment programme was 49 yuan (RMB), about $24.00 U.S.

Adolescent↗
PubMedDate not supplied

The effect of castration and androgen replacement on rat pituitary follicle stimulating hormone investigated by reversed-phase high performance liquid chromatography.

Rat follicle stimulating hormone (rFSH) was analysed in extracts of rat anterior pituitary using a newly developed separation method of reversed-phase high performance liquid chromatography (RP-HPLC) and post-column detection of immunoreactivity (rFSH-IR) by radioimmunoassay (RIA) or immunoprecipitation with a specific anti-rFSH antibody. Good separation of rFSH was achieved on a Waters Radial-Peak 8MBC18 cartridge with a linear (60 min) gradient from 10-60% acetonitrile at constant 0.1% trifluoroacetic acid concentration. The elution profiles of radioiodinated purified rFSH [(125I)rFSH] as well as extracts of adult male and female rat pituitaries contained two main immunoreactive components (peaks 1 and 2) which eluted at 16-17 min and 21 min respectively. In the (125I)rFSH elution profile, the peaks of immunobinding corresponded to two major peaks of radioactivity. The male pituitary showed greater binding to anti-rFSH-serum of peak 1 and 2 eluate compared to female pituitary. At day 20 after orchidectomy, the amount of immunoreactive rFSH (rFSH-IR) increased in both peaks (by 30% in peak 1 and 180% in peak 2); however, the rFSH-IR level in peak 2 appeared to be more variable compared with that in peak 1. Subcutaneous implantation of 5 mg or 15 mg of dihydrotestosterone (DHT) at the time of orchidectomy prevented the post-castration elevation of rFSH-IR at 10 and 20 days after surgery. The precise nature and physiological significance of the two elution peaks are not clear at this time; however, only peak 2 showed immunoreactivity with anti-rLH-alpha-subunit antibody (AFP 87713681) and the elution time of peak 2 coincided with that of (125I) rLH-alpha subunit (AFP-7264 B).(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗