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Biomedical subjects

R Li

Publications and source records attributed to R Li.

At least 361 records · Page 20Linked to original sources
PubMed1997

Development of the competence of bovine oocytes to release cortical granules and block polyspermy after meiotic maturation.

Bovine immature oocytes do not have the ability to block polyspermic penetration. The present study was conducted to determine whether this is correlated to cortical granule (CG) distribution and the competence of oocytes to release CG upon sperm penetration, and whether the ability of bovine oocytes to release CG develops during in vitro maturation. Fluorescein isothiocyanate-conjugated Lens culinaris agglutinin was used for detecting CG in immature and mature oocytes before and after sperm penetration and electric stimulation. The labeled oocytes were examined with laser confocal and fluorescent microscopes. The results show that CG exist as clusters in all immature oocytes. The CG were not released from immature oocytes exposed to electric pulse or penetrated by spermatozoa, resulting in 94% of oocytes being polyspermic. When immature oocytes were cultured for 22 h in vitro, 81% extruded the first polar body and reached metaphase II. In mature oocytes, 25% of oocytes showed CG clusters, 42% and 33% of oocytes showed partial and complete CG dispersion, respectively. When mature oocytes were inseminated in vitro, only 15% of oocytes were polyspermic. Cortical granule exocytosis occurred in 97% of oocytes after sperm penetration and 84% of oocytes released all of the CG 18 h after insemination. Electric pulse induced all of the mature oocytes to release CG but only 55% released all of their CG 18 h post stimulation. These results indicate that polyspermy in immature bovine oocytes is the result of the complete failure of the oocyte to release CG after sperm penetration. Bovine oocytes became competent to release CG by sperm penetration and electric stimulation after meiotic maturation. These results provide evidence that CG exocytosis plays an important role(s) in the establishment of the block to polyspermy in bovine oocytes.

Animals↗
PubMed1997

Human medulloblastoma gangliosides.

To establish a model system for the study of ganglioside metabolism of the human brain tumor, medulloblastoma, we have chemically characterized the gangliosides of the Daoy cell line. These cells contain a high concentration of gangliosides (143 +/- 13 nmol LBSA/10(8) cells). The major species have been structurally confirmed to be GM2 (65.9%), GM3 (13.0%), and GD1a (10.3%). Isolation of individual gangliosides homogeneous in both carbohydrate and ceramide moieties by reversed-phase HPLC and analysis by negative-ion fast atom bombardment collisionally activated dissociation tandem mass spectrometry have allowed us to unequivocally characterize ceramide structures. In the case of GM2, 10 major ceramide subspecies were identified: d18:1-hC16:0, d18:1-C16:0, d18:0-C16:0, d18:1-C18:0, d18:1-C20:0, d18:1-C22:0, d18:2-C24:1, d18:1-C23:1, d18:1-C24:1, and d18:1-C24:0. Taken together with previous studies, these findings in buman medulloblastoma cells support the view that high expression and marked heterogeneity of ceramide structure are general characteristics of tumor gangliosides, molecules which are shed by the tumor cells and which are biologically active in vivo.

Ceramides↗
PubMed1997

Second generation hepatitis C virus antibody-positive rate in children: investigation of the route of hepatitis C virus infection in children with no history of transfusion.

Hepatitis C virus (HCV) antibody and HCV-RNA screening was undertaken in 1864 children, aged from 0 to 15 years who did not have a history of transfusion. Anti-HCV was tested by the second generation enzyme-linked immunosorbent assay (ELISA). HCV RNA was examined by reverse transcriptase-nested polymerase chain reaction (PCR). Two of the 1864 children were positive for serum HCV RNA. They had no history of transfusion, no episodes of horizontal transmission, but the mother in each case was positive for serum HCV RNA, implying mother-to-infant infection. Eleven children who were positive for HCV antibody with low values and negative for serum HCV RNA were classified as belonging to the high bovine milk (composed primarily of casein)-specific IgG4 value group. This suggested that many of the children who were falsely positive for HCV antibody using ELISA had antibodies to casein.

Adolescent↗
PubMed1997

Risk factors differ for carotid artery plaque with and without acoustic shadowing. Atherosclerosis Risk in Communities Study Investigators.

To investigate the association of gender, ethnicity, and several cardiovascular risk factors with carotid artery plaque and plaque with acoustic shadowing in a population-based sample, high-resolution B-mode ultrasonography was used to characterize lesions in the common and internal carotid arteries, and at the carotid bifurcation in 12,796 US men and women, aged 45 to 64 years, participating in the Atherosclerosis Risk in Communities Study (ARIC) baseline survey. In multiple logistic regression analyses, male gender (odds ratio and 95% confidence interval: 1.52 [1.39-1.67]) and increased total (1.47 [1.32-1.63]) and low-density-lipoprotein cholesterol (1.49 [1.34-1.65]) levels were statistically significantly associated only with the presence of plaque. In contradistinction, smoking (2.22 [1.79-2.75]) and hypertension (1.54 [1.30-1.82]) were additionally associated with acoustic shadowing. Hyperfibrinogenemia (1.33 [1.12-1.59]) was associated only with lesions accompanied by acoustic shadowing. While ethnicity associations with plaque alone varied across the artery segments, among those with plaque, being white was uniformly associated with acoustic shadowing. After multivariable adjustment, high-density-lipoprotein cholesterol was not associated with either manifestation of atherosclerosis. In conclusion, differences were seen in the associations of established cardiovascular risk factors with discretely characterized carotid artery plaque lesions, according to the presence or absence of acoustic shadowing suggestive of mineralization of plaque.

Carotid Artery, Common↗
PubMed1997

Evolutionary conservation and predicted structure of the Drosophila extra sex combs repressor protein.

The Drosophila extra sex combs (esc) protein, a member of the Polycomb group (PcG), is a transcriptional repressor of homeotic genes. Genetic studies have shown that esc protein is required in early embryos at about the time that other PcG proteins become engaged in homeotic gene repression. The esc protein consists primarily of multiple copies of the WD repeat, a motif that has been implicated in protein-protein interaction. To further investigate the domain organization of esc protein, we have isolated and characterized esc homologs from divergent insect species. We report that esc protein is highly conserved in housefly (72% identical to Drosophila esc), butterfly (55% identical), and grasshopper (56% identical). We show that the butterfly homolog provides esc function in Drosophila, indicating that the sequence similarities reflect functional conservation. Homology modeling using the crystal structure of another WD repeat protein, the G-protein beta-subunit, predicts that esc protein adopts a beta-propeller structure. The sequence comparisons and modeling suggest that there are seven WD repeats in esc protein which together form a seven-bladed beta-propeller. We locate the conserved regions in esc protein with respect to this predicted structure. Site-directed mutagenesis of specific loops, predicted to extend from the propeller surface, identifies conserved parts of esc protein required for function in vivo. We suggest that these regions might mediate physical interaction with esc partner proteins.

Amino Acid Sequence↗
PubMed1997

The murine C'-terminally alternatively spliced form of p53 induces attenuated apoptosis in myeloid cells.

The onset of p53-dependent apoptosis results from the accumulation of damaged DNA. Recently, it was shown that the C' terminus of the p53 protein plays a central role in sensing damaged DNA. In our present study, we examined the role of the C' terminus in the induction of apoptosis. A temperature-sensitive (ts) mutant of the alternatively spliced form of p53 (p53AS-ts) and the ts mutant of the regularly spliced form (p53RS-ts) were used to generate series of stable clones with increasing amounts of p53 protein. Apoptotic patterns induced by either the regularly spliced p53 product (p53RS) or a C'-terminally alternatively spliced p53 product (p53AS) were compared. We found that although both forms of p53 induced apoptosis following expression of the wild-type protein conformation, the kinetics were different. Apoptosis induced by the p53AS protein was attenuated compared to that induced by p53RS. The delay in the manifestation of the apoptotic features following p53AS expression was in agreement with a delay in the regulation of the expression of apoptosis-related genes. The observation that p53 with an altered C' terminus is still capable of inducing apoptosis suggests that the actual onset of the apoptotic process most probably involves structural domains other than the C' terminus of the p53 molecule. However, the fact that the apoptotic activity mediated by the p53AS product was slower than that mediated by the p53RS product suggests that the C' terminus indeed exerts a certain control on the apoptotic activity of the p53 molecule.

Alternative Splicing↗
PubMed1997

Use of measurements of ethanol absorption from stomach and intestine to assess human ethanol metabolism.

Controversy exists concerning the site (stomach vs. liver) and magnitude of first-pass metabolism of ethanol. We quantitated gastric and total ethanol absorption rates in five male subjects and utilized these measurements to evaluate first-pass metabolism. Gastric emptying of ethanol (0.15 g/kg) was determined via a gamma camera and gastric absorption from the ratio of gastric ethanol to [14C]polyethylene glycol. Gastric absorption accounted for 30% and 10% of ethanol administered with food and water, respectively. With food, estimated gastric mucosal ethanol concentrations fell from 19 to 5 mM over 2 h. Calculations using these concentrations and kinetic data for gastric alcohol dehydrogenase showed <2% of the dose underwent gastric metabolism. Application of observed ethanol absorption rates to a model of human hepatic ethanol metabolism indicated that only 30% and 4% of the dose underwent first-pass metabolism when administered with food and water, respectively. We conclude that virtually all first-pass ethanol metabolism occurs in the liver and first-pass metabolism accounts for only a small fraction of total clearance.

Absorption↗
PubMed1997

Blood pressure response to chronic episodic hypoxia: role of the sympathetic nervous system.

Previous studies in several strains of rats have demonstrated that 35 consecutive days of recurrent episodic hypoxia (7 h/day) cause an 8- to 13-mmHg persistent increase in diurnal systemic blood pressure (BP). Carotid chemoreceptors and the sympathetic nervous system have been shown to be necessary for development of this BP increase. The present study was undertaken to further define the role of renal artery sympathetic nerves and the adrenal medulla in this BP increase. Male Sprague-Dawley rats had either adrenal medullectomy, bilateral renal artery denervation, or sham surgery. Rats from each of these groups were subjected to episodic hypoxia for 35 days. Control groups received either compressed air or were left unhandled. Adrenal demedullation or renal artery denervation eliminated the chronic diurnal mean BP response (measured intra-arterially) to episodic hypoxia, whereas sham-operated controls continued to showed persistent elevation of systemic BP. Plasma and renal tissue catecholamine levels at the end of the experiment confirmed successful adrenal demedullation or renal denervation in the respective animals. The chronic episodic hypoxia-mediated increase in diurnal BP requires both intact renal artery nerves as well as an intact adrenal medulla.

Adrenal Medulla↗
PubMed1997

Analysis of the hypervariable region of hepatitis C virus E2/NS1 gene in an infant infected by blood transfusion.

We investigated the sequential change in the hypervariable region 1 (HVR 1) of hepatitis C virus (HCV) E2/NS1 gene in an infant. He was transfused with 160 mL of blood containing the HCV (0.7 Meq/mL) on the 6th d after birth and subsequently developed chronic viremia. At 16 mo, the HVR1 amino acid sequences of HCV observed in the infant's sera were very similar to those from the donor (his maternal grandfather) on the day of transfusion. However, highly variable amino acid sequences of HVR1 were observed throughout infancy. These results demonstrate that an adaptive response of HCV to evade host immunity seems to occur, as in adult cases, even in early infancy when the ability to produce humoral immunoglobulin is thought to be low.

Amino Acid Sequence↗
PubMed1997

Lindane, an inhibitor of gap junction formation, abolishes oocyte directed follicle organizing activity in vitro.

Folliculogenesis in the ovary begins before birth with the formation of primordial follicles consisting of an oocyte in the resting meiotic prophase surrounded by a layer of undifferentiated granulosa cells. At each menstrual cycle a subset of these follicles is selected and undergoes growth and differentiation leading to ovulation and corpora lutea formation or apoptosis. We have previously described an in vitro model of rat follicular development in which the organization of three-dimensional antral-follicles requires FSH and activin A. Here we report that, in this system, the oocyte is required for follicle morphogenesis and requires gap junctions to direct the morphological arrangement of the surrounding granulosa cells.

Activins↗
PubMed1997

Follicle-stimulating hormone induces terminal differentiation in a predifferentiated rat granulosa cell line (ROG).

The divergent commitment of ovarian granulosa cells to either proliferation and differentiation or programmed cell death directly reflects the process of follicular dominance and atresia. This process is regulated by FSH and local paracrine factors. To further analyze the role of FSH and intraovarian factors in follicular selection, we have established a rat ovarian granulosa (ROG) cell line from prepubertal (p14) rats. ROG cells are cultured in serum-free medium with activin A, but without FSH. ROG cells bind FSH and respond to FSH by a burst of cell proliferation and increased progesterone secretion. These results support the hypothesis that activin, but not FSH, is an important factor in the maintenance of immature granulosa cells. After exposure of ROG cells to FSH, withdrawal of FSH from the cultures results in apoptotic cell death. ROG cells start active membrane blebbing by 2 h after FSH withdrawal, and most cells die within 7 h. Thus, FSH-induced ROG cells differentiate into a more mature granulosa phenotype, which is nonmitotic and dependent on FSH for survival. The ROG cell line may thus provide a good in vitro model of follicular selection.

Animals↗
PubMed1997

Homology of E2 gene in 8 child-mother pairs infected with hepatitis C virus.

The frequency of genetic homology of hepatitis C virus (HCV) E2 gene in 8 child-mother pairs was investigated. The route of HCV infection of all children suggested mother-to-child infection by their past history. In this study, we analyzed at least 5 complementary DNA (cDNA) clones for each case. In 6 of the 8 (75%) child-mother pairs, for the region between hypervariable region (HVR)-1 and HVR-2, the similarity of the nucleotide sequence of all 5 cDNA clones between each child and the mother was higher than that between the child and the other children, the other mothers and the sequences from GenBank. One of the 8 (13%) child-mother pairs showed a great similarity in parts of all cDNA clones. This was also confirmed by phylogenetic analyses of the sequences of cDNA clones from families and that from GenBank. These results suggested that the homology search of nucleotide sequence of this region was useful to confirm mother-to-child transmission of HCV.

Amino Acid Sequence↗
PubMed1997

Structure of music may influence cognition.

Classical music has been said to enhance cognition, which effect may be related to musical structure. 19 subjects who listened to highly structured music scored somewhat higher afterwards on cognitive performance than the 15 who listened to less structured music. Since this did not reach statistical significance, other as yet unidentified factors may also be involved.

Acoustic Stimulation↗
PubMed1997

[An improvement on the adhesive electrode recording device].

An improved device of the adhesive electrode for recording the bioelectrical potential of animal's syncytial tissue is described in this paper. The main feature of the new device is to place a small chamber between the syringe for building negative pressue and the adhesive electrode. This chamber can keep the electric connection between amplifier and the tissue being recorded, and be placed near the tissue. The negative pressure can be conducted from the syringe by a plastic tube, so the syringe can be placed in any place where it doesn't affect the experiment. By using this new device, good results can be achieved when bioelectrical potential of hearts or gastric muscle of molluscan snails or frogs etc. is recorded. This simple and easy-operating device is practically valuable on studies of the normal functions and pharmacological effects in small animal's syncytial tissues such as heart, and gastric muscle.

Action Potentials↗
PubMed1997

[Study on the effect of different disease courses on pre- and post-operative visual acuity in cases with congenital cataract].

OBJECTIVE: To study the effect of different disease courses on the visual acuity of congenital cataracts. METHOD: 876 cases with five kinds of human congenital cataract have been studied. RESULTS: It has been found that the preoperative visual acuity (VA) is closely related to the length of disease course. The longer the course of disease, the worse the VA. When the disease courses were shorter than one year, the most serious reduction of preoperative VA was found in the patients with congenital total cataract. When the disease courses were within one to four years, the most remarkable reduction of VA was found in patients with congenital dense nuclear cataract (CDNC). When the disease courses were longer than four years, except the congenital anterior polar cataract, the VA in all the other four kinds of cataracts were decreased significantly. It is indicated that the postoperative VA highly depends on the preoperative VA. In the group with disease courses shorter than one year, this relationship is the most remarkable. Some kinds of congenital cataract showed accelerated changes in preoperative VA, especially in the CDNC. CONCLUSION: It is suggested that the key point to get better visual function in cases with congenital cataract should be to discover and treat the patients as early as possible.

Adolescent↗
PubMed1997

[Transferrin subtyping of human semen, semen stain, vaginal fluid and mixed stain using isoelectric focusing and immunoblotting].

Transferrin (Tf) is an important genetic marker for personal identification in forensic science. We examined the subtypes in human semen, semen stain, vaginal fluid and mixed stain using isoelectric focusing and immunoblotting method(IEFIB). The results showed that, Tf subtypes of 8 semen and semen stain samples stored at room temperature for up to 32 weeks were the same as those in sera. Tf subtypes of 17 vaginal fluid and 4 mixed stain containing few semen were not detected. Tf Subtyping of 1 mixed stain containing enough semen was successful by using IEFIB. These results indicate that Tf is stable in semen stain. The Tf subtyping in semen stain and mixed stain containing enough semen can be carried out by using IEFIB method.

Exudates and Transudates↗
PubMed1997

[Chemical studies on peptidepolysaccharides of Ganoderma lucidum (W. Curt. Fr.) Karst].

Seven homogeneous peptidepolysaccharides have been obtained from the fruit-body of Ganoderma lucidum. The main constituents are TGLP-2, TGLP-3, TGLP-6 and TGLP-7, whose molecular weights are 20.9 x 10(4), 4.5 x 10(4), 3.2 x 10(4) and 10 x 10(4) respectively. TGLP-2 is a heteroglycan peptide, TGLP-3 and TGLP-6 are glycan peptides and TGLP-7 is a galactan peptide.

Drugs, Chinese Herbal↗