Biomedical subjects

Lin Liu

Publications and source records attributed to Lin Liu.

At least 127 records · Page 7Linked to original sources

PubMed2004

[Preliminary proposal of the severity score system for maxillofacial injuries].

OBJECTIVE: A new injury severity score system was proposed in this study to evaluate maxillofacial injuries. METHODS: Based on AIS-90, all clinical samples were given diagnosis. Their month opening limitation, malocclusion and facial deformity were recorded as indices in scoring system. Severity injury scores for different groups and types were statistically. analyzed. RESULTS: It was demonstrated that there was a significant difference in scores between injuries of soft tissue and bone tissue and between different fracture groups. CONCLUSIONS: The proposed scoring was system useful to predict the cost of medical care and the days of in-patient, reliable, sensitive and specific in evaluation the maxillofacial injury severity.

Adolescent↗

PubMed2004

[Effects of anti-CXCR4 monoclonal antibody on adhesion and proliferation of human acute myelocytic leukemia cell line HL-60].

BACKGROUND & OBJECTIVE: Stromal cell derived factor-1 (SDF-1), excreted by bone marrow stromal cells, may be involved in shielding of marrow stromal cells from leukemia cells by binding to its receptor CXCR4, but the relation between SDF-1/CXCR4 axis and leukemia cells is unclear. This study was to inhibit activity of SDF-1 by anti-CXCR4 monoclonal antibody 12G5, observe changes of adhesion and proliferation of acute myelocytic leukemia cell line HL-60 co-cultivated with leukemic marrow stromal cells, and to assay potential of inhibiting SDF-1-driven processes on treating marrow residual disease. METHODS: HL-60 cells were co-cultured with leukemic marrow stromal cells, and 10 mug/ml 12G5 was added to block SDF-1 activity. Adhesive state, adhesion rate, apoptosis rate, and cell cycle of HL-60 cells were observed after incubation. Living conditions of HL-60 cells were detected by trypan blue exclusion, cell growth curve was protracted. RESULTS: Adhesion rate of 24-h 12G5-incubated HL-60 cells was (39.4+/-7.9)%, while that of control HL-60 cells was (51.4+/-5.9)% (P< 0.05). G0/G1, S, and G2/M phases of 24-h 12G5-incubated HL-60 cells were (55.2+/-4.9)%, (30.4+/-4.1)%, and (14.4+/-5.2)%, respectively, and apoptosis rate was (9.0+/-1.7)%; while those of control HL-60 cells were (44.7+/-2.2)%, (45.3+/-3.7)%, (10.0+/-2.6)%, and (4.0+/-2.4)%, respectively. T test showed that 12G5 induced more cells entering G0/G1 phase (P< 0.05), and increased cell apoptosis rate(P< 0.05). Compared with control HL-60 cells, survival rate and proliferation of 48-h 12G5-incubated HL-60 cells decreased markedly. CONCLUSION: 12G5 may inhibit adhesion ability and proliferation of HL-60 cells, thus inhibiting SDF-1 activity by 12G5 may be helpful to the treatment of marrow residual disease.

Antibodies, Monoclonal↗

PubMed2003

In vivo effects of arsenite on meiosis, preimplantation development, and apoptosis in the mouse.

Inorganic arsenic, an environmental contaminant, produces a variety of stress responses in mammalian cells, including metabolic abnormalities accompanied by growth inhibition and carcinogenesis. Much of the toxicity of arsenic is known to stem from its uncoupling effects on mitochondria. Because previously we had shown that mitochondrial dysfunction can disrupt oocyte and embryo development, we investigated effects of arsenite on meiotic progression and early embryo development in mice. Six-week-old CD-1 mice were treated with 0 (solvent as control), 8 mg/kg (a dose previously established in mice as the maternal no-observed-adverse-effect level), and 16 mg/kg doses of sodium arsenite every 2 days for a total of seven i.p. injections ver a period of 14 days. The incidence of meiotic anomalies, characterized by spindle disruption and/or chromosomal misalignment, was significantly increased in arsenite-treated groups (25% after 8 mg/kg and 62.5% after 16 mg/kg), compared to normal metaphase II in control oocytes. Further, arsenite treatment significantly decreased cleavage rates of zygotes at 24 h, morula formation at 72 h, and development to blastocysts at 96 h in a dose-dependent manner. The total cell number in developed blastocysts did not differ significantly between the 8 mg/kg arsenite treatment and control groups, but was significantly reduced in the 16 mg/kg arsenite treatment group. Moreover, the percentage of apoptotic nuclei was significantly increased in blastocysts following 16 mg/kg arsenite treatment. These data suggest that arsenite causes meiotic aberrations, which may contribute to decreased cleavage and preimplantation development, as well as increased apoptosis.

Animals↗

PubMed2003

Protein nitration in rat lungs during hyperoxia exposure: a possible role of myeloperoxidase.

Several studies have suggested that exposure to hyperoxia causes lung injury through increased generation of reactive oxygen and nitrogen species. The present study was aimed to investigate the effects of hyperoxia exposure on protein nitration in lungs. Rats were exposed to hyperoxia (>95%) for 48, 60, and 72 h. Histopathological analysis showed a dramatic change in the severity of lung injury in terms of edema and hemorrhage between 48- and 60-h exposure times. Western blot for nitrotyrosine showed that several proteins with molecular masses of 29-66 kDa were nitrated in hyperoxic lung tissues. Immunohistochemical analyses indicate nitrotyrosine staining of alveolar epithelial and interstitial regions. Furthermore, immunoprecipitation followed by Western blot revealed the nitration of surfactant protein A and t1alpha, proteins specific for alveolar epithelial type II and type I cells, respectively. The increased myeloperoxidase (MPO) activity and total nitrite levels in bronchoalveolar lavage and lung tissue homogenates were observed in hyperoxic lungs. Neutrophils and macrophages isolated from the hyperoxia-exposed rats, when cocultured with a rat lung epithelial L2 cell line, caused a significant protein nitration in L2 cells. Inclusion of nitrite further increased the protein nitration. These studies suggest that protein nitration during hyperoxia may be mediated in part by MPO generated from activated phagocytic cells, and such protein modifications may contribute to hyperoxia-mediated lung injury.

Amino Acid Sequence↗

PubMed2003

Fusion of lamellar body with plasma membrane is driven by the dual action of annexin II tetramer and arachidonic acid.

Annexin II has been implicated in membrane fusion during the exocytosis of lamellar bodies from alveolar epithelial type II cells. Most previous studies were based on the fusion assays by using model membranes. In the present study, we investigated annexin II-mediated membrane fusion by using isolated lamellar bodies and plasma membrane as determined by the relief of octadecyl rhodamine B (R18) self-quenching. Immunodepletion of annexin II from type II cell cytosol reduced its fusion activity. Purified annexin II tetramer (AIIt) induced the fusion of lamellar bodies with the plasma membrane in a dose-dependent manner. This fusion is Ca2+-dependent and is highly specific to AIIt because other annexins (I and II monomer, III, IV, V, and VI) were unable to induce the fusion. Modification of the different functional residues of AIIt by N-ethylmaleimide, nitric oxide, or peroxynitrite abolished AIIt-mediated fusion. Arachidonic acid enhanced AIIt-mediated fusion and reduced its Ca2+ requirement to an intracellularly achievable level. This effect is due to membrane-bound arachidonic acid, not free arachidonic acid. Other fatty acids including linolenic acid, palmitoleic acid, myristoleic acid, stearic acid, palmitic acid, and myristic acid had little effect. AIIt-mediated fusion was suppressed by the removal of arachidonic acid from lamellar body and plasma membrane using bovine serum albumin. The addition of arachidonic acid back to the arachidonic acid-depleted membranes restored its fusion activity. Our results suggest that the fusion between lamellar bodies with the plasma membrane is driven by the synergistic action of AIIt and arachidonic acid.

Animals↗

PubMed2003

Gene silencing in mammalian cells by PCR-based short hairpin RNA.

RNA interference (RNAi) provides a powerful tool to silence genes in a sequence-specific manner in a variety of systems. However, not all sequences are effective in the RNAi-mediated gene silencing. In this study, we developed a polymerase chain reaction (PCR)-based RNAi strategy for a quick screening of small interfering RNA (siRNA) efficiency. This method utilized a two-step PCR to generate a chimeric DNA template containing the U6 promoter or cytomegalovirus promoter and short hairpin DNA. We demonstrated that the transfection of the PCR products into mammalian cells resulted in specific depressions of exogenous (luciferase, green fluorescent protein and beta-galactosidase) and endogenous (annexin II) gene expressions. This PCR strategy provides a rapid, easy and cheap approach for testing candidates siRNA sequences and is an attractive alternative to subcloning.

Animals↗

PubMed2003

Coevolutionary patterns in plasminogen activation.

The generation of plasmin by plasminogen (Pg) activators (PAs) is a physiologic process in animals that dissolves blood clots and promotes wound healing, blood vessel growth, and the migration of normal and cancerous cells. Pathogenic bacteria have evolved PAs [e.g., streptokinase (SK) and staphylokinase] that exploit the Pg system to infect animals. Animal PAs have a conserved ability to cleave a wide spectrum of animal Pgs, but the ability of bacterial PAs to cleave different animal Pgs is surprisingly restricted. We show that the spectrum of activity of an archetypal bacterial PA (SK) with animal Pgs can be profoundly altered by mutations that affect intermolecular complementarity at sites that participate in complex formation or substrate binding. Comparative sequence analysis of animal plasmins vs. close structural homologues (trypsin and chymotrypsin) that are not molecular targets for invading bacteria indicates that the sites in plasmin that interact with SK are preferentially targeted for mutation. Conversely, intermolecular contact sites in SKs that activate human Pg are more highly conserved than other loci in the molecule or than the same sites in other SKs that activate non-human Pgs. We propose that active modulation of intermolecular complementarity at sites of contact between SK and Pg may represent a competitive evolutionary strategy in a survival battle, whereby animals seek to evade bacterial invasion, and bacteria endeavor to invade their animal hosts.

Animals↗

PubMed2003

Oxidative stress contributes to arsenic-induced telomere attrition, chromosome instability, and apoptosis.

The environmental contaminant arsenic causes cancer, developmental retardation, and other degenerative diseases and, thus, is a serious health concern worldwide. Paradoxically, arsenic also may serve as an anti-tumor therapy, although the mechanisms of its antineoplastic effects remain unclear. Arsenic exerts its toxicity in part by generating reactive oxygen species. We show that arsenic-induced oxidative stress promotes telomere attrition, chromosome end-to-end fusions, and apoptotic cell death. An antioxidant, N-acetylcysteine, effectively prevents arsenic-induced oxidative stress, telomere erosion, chromosome instability, and apoptosis, suggesting that increasing the intracellular antioxidant level may have preventive or therapeutic effects in arsenic-induced chromosome instability and genotoxicity. Embryos with shortened telomeres from late generation telomerase-deficient mice exhibit increased sensitivity to arsenic-induced oxidative damage, suggesting that telomere attrition mediates arsenic-induced apoptosis. Unexpectedly, arsenite did not cause chromosome end-to-end fusions in telomerase RNA knockout mouse embryos despite progressively damaged telomeres and disrupting embryo viability. Together, these findings may explain why arsenic can initiate oxidative stress and telomere erosion, leading to apoptosis and anti-tumor therapy on the one hand and chromosome instability and carcinogenesis on the other.

Acetylcysteine↗

PubMed2003

Characterization of alpha-soluble N-ethylmaleimide-sensitive fusion attachment protein in alveolar type II cells: implications in lung surfactant secretion.

N-ethylmaleimide-sensitive fusion protein (NSF) and soluble NSF attachment protein (alpha-SNAP) are thought to be soluble factors that transiently bind and disassemble SNAP receptor complex during exocytosis in neuronal and endocrine cells. Lung surfactant is secreted via exocytosis of lamellar bodies from alveolar epithelial type II cells. However, the secretion of lung surfactant is a relatively slow process, and involvement of SNAP receptor and its cofactors (NSF and alpha-SNAP) in this process has not been demonstrated. In this study, we investigated a possible role of alpha-SNAP in surfactant secretion. alpha-SNAP was predominantly associated with the membranes in alveolar type II cells as determined by Western blot and immunocytochemical analysis using confocal microscope. Membrane-associated alpha-SNAP was not released from the membrane fraction when the cells were lyzed in the presence of Ca2+ or Mg2+ATP. The alkaline condition (0.1 M Na2CO3, pH 12), known to extract peripheral membrane proteins also failed to release it from the membrane. Phase separation using Triton X-114 showed that alpha-SNAP partitioned into both aqueous and detergent phases. NSF had membrane-bound characteristics similar to alpha-SNAP in type II cells. Permeabilization of type II cells with beta-escin resulted in a partial loss of alpha-SNAP from the cells, but cellular NSF was relatively unchanged. Addition of exogenous alpha-SNAP to the permeabilized cells increased surfactant secretion in a dose-dependent manner, whereas exogenous NSF has much less effects. An alpha-SNAP antisense oligonucleotide decreased its protein level and inhibited surfactant secretion. Our results suggest a role of alpha-SNAP in lung surfactant secretion.

Adenosine Triphosphate↗

PubMed2003

Severe cholestasis induced by cholic acid feeding in knockout mice of sister of P-glycoprotein.

Intrahepatic cholestasis is often associated with impairment of biliary bile acid secretion, a process mediated by the sister of P-glycoprotein (Spgp or Abcb11) also known as the bile salt export pump (Bsep). In humans, mutations in the Spgp gene are associated with a fatal childhood disease, type 2 progressive familial intrahepatic cholestasis (PFIC2). However in mice, the "knockout" of Spgp only results in mild cholestasis. In this study, we fed spgp(-/-) knockout mice with a cholic acid (CA)-supplemented diet to determine whether a more pronounced PFIC2-like phenotype could be induced. Such mice developed severe cholestasis characterized by jaundice, weight loss, elevated plasma bile acid, elevated transaminase, cholangiopathy (proliferation of bile ductules and cholangitis), liver necrosis, high mortality, and wide-ranging changes in the mRNA expression of major liver genes (16/36 examined). A surprising observation was that the bile acid output and bile flow in CA-fed mutant mice was significantly higher than anticipated. This suggests that the spgp(-/-) mice are able to utilize an alternative bile salt transport system. However, unlike Spgp, this system is insufficient to protect the knockout mice from cholestasis despite its high capacity. In conclusion, the spgp(-/-) mice provide a unique model to investigate molecular pathways associated with cholestasis and related diseases.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2003

Factor V Leiden and risk of ischemic stroke in nonvalvular atrial fibrillation: the AnTicoagulation and Risk Factors in Atrial Fibrillation (ATRIA) Study.

BACKGROUND: Atrial fibrillation is a major cause of cardioembolic stroke. Since atrial and venous pressures are similar, genetic variants that promote venous thromboembolism may increase the risk of atrial thrombi and subsequent stroke in atrial fibrillation. METHODS: We conducted a nested case-control study of the association between the presence of factor V Leiden polymorphism and incident ischemic stroke within a prospective cohort of 13,559 adult patients with diagnosed nonvalvular atrial fibrillation between July 1, 1996 and December 31, 1997. Incident cases with ischemic strokes were identified through August 31, 1999 and matching stroke-free controls were enrolled. RESULTS: One hundred thirty-seven case patients with incident stroke and 214 controls were enrolled. Cases were older, more likely to be women, and more likely to have a prior stroke, heart failure, hypertension, diabetes, and coronary disease. The factor V Leiden polymorphism was present in 5.8% of cases and 3.7% of controls (P = 0.36). Among non-anticoagulated patients, 7/96 (7.3%) case patients and 3/81 (3.6%) control subjects were heterozygous for factor V Leiden (Odds Ratio 2.1 [95% CI: 0.5-8.4]). Adjustment for known stroke risk factors did not significantly change the observed association in non-anticoagulated patients (adjusted OR 1.9 [0.5-8.0]). CONCLUSIONS: Within a large nested case-control sample of patients with atrial fibrillation, factor V Leiden was not significantly associated with risk of stroke. However, given the suggestive nature of our findings, further study in even larger numbers of patients is needed to clarify the impact of factor V Leiden on stroke risk in atrial fibrillation.

Aged↗

PubMed2003

Effect of nitric oxide on lung surfactant secretion.

Lung surfactant is secreted from epithelial type II cells into alveolar airspace in response to airborne and circulating stimuli. Nitric oxide (NO) can be generated by constitutive and inducible nitric oxide synthases (cNOS and iNOS) in pulmonary endothelial and epithelial cells. The authors therefore examined the effects of NO on lung surfactant secretion using an isolated perfused rat lung model and primary culture of type II cells. Infusion of L-N(G)-nitroarginine methyl ester (L-NAME) (100 micro M), an inhibitor of cNOS and iNOS, via pulmonary circulation for 90 minutes resulted in a decrease of lung surfactant secretion (1.55%+/-0.15% in control versus 0.79%+/-0.16% in L-NAME-treated lungs, P <.05). However, aminoguanide, an inhibitor of iNOS, had no effect, indicating that the decline of lung surfactant secretion is due to the specific blockage of cNOS rather than iNOS activity in perfused lungs. A reduction of cGMP level by 1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (25 micro M), a specific inhibitor of guanylyl cyclase, inhibited surfactant secretion by 64%. Furthermore, KT5823 (1 micro M), an inhibitor of protein kinase G, depressed surfactant secretion by 40%. These results suggest that physiological concentrations of NO are required for lung surfactant secretion and NO-mediated secretion is at least partly via a rise of cGMP level and activation of protein kinase G. In primary culture of alveolar type II cells, spermine NONOate (SPER/NO), a NO donor, increased basal phosphatidylcholine (PC) secretion in a dose-dependent manner. Maximal stimulation was observed at 1 micro M. However, in the ATP-stimulated type II cells, SPER/NO displayed a biphasic effect on PC secretion. At low concentrations (0.1 to 1 micro M), SPER/NO increased ATP-stimulated PC secretion, whereas at a high concentration (100 micro M), SPER/NO inhibited the secretion. The results suggest that NO may play an important role in lung surfactant secretion.

Animals↗

PubMed2003

Ultrastructure of type II alveolar epithelial cells in rats with acute respiratory distress syndrome.

OBJECTIVE: To observe the ultrastructure of type II alveolar epithelium cells of rats with experimental acute respiratory distress syndrome (ARDS). METHODS: Rat models of ARDS were established via oleic acid injection, and the type II alveolar epithelium was isolated and purified to observe the changes in the ultrastructure of the cells under transmission electron microscope. RESULTS: Observation under transmission electron microscope revealed evidently decreased lamellar bodies in type II alveolar epithelial cells leading to vacuolation in rats with ARDS. CONCLUSION: After proper isolation and purification, the morphological changes in type II alveolar epithelial cells can be more easily observed, and the changes in the lamellar bodies suggest that type II cells play an important role in ARDS.

Animals↗

PubMed2003

Effect of Zn7-metallothionein on oxidative stress in liver of rats with severe thermal injury.

AIM: Using the model of burned animal with delayed resuscitation to study antagonistic effect of Zn7-metallothionein (Zn7-MT) on oxidative stress in the liver of rats suffered from severe thermal injury on skin. METHODS: To compare the changes in antioxidant concentrations and antioxidative enzyme activities in the liver or plasma of burned rats with or without Zn7-MT in resuscitation fluid by biochemical assay. RESULTS: After injury, glutathione concentration was progressively decreased with time. At 24 h after injury, activities of glutathione reductase and glutathione peroxidase in the liver of burned rats were increased and then decreased at 48 h postburn. Alpha-tocopherol in plasma was reduced at 24 h and malondialdehyde in the liver was increased significantly postburn. MT and MT-1 mRNA expression in burned rats were activated. Taken together, oxidative stress in the liver of burned rats occurred. Exogenous Zn7-MT attenuated the changes in antioxidant concentrations and antioxidative enzyme activities in the liver or plasma of burned rats. The effect of Zn7-MT was in a concentration-dependent manner and the concentration of 10 micromol/L was the most effective. Exogenous Zn7-MT also inhibited MT-1 mRNA overexpression and increased MT protein concentration. CONCLUSION: Zn7-MT effectively antagonized oxidative stress in the liver of rats with severe thermal injury.

Animals↗

PubMed2003

[Associations of Rsa I polymorphism at the 5' flanking region of CYP2E1 and PON2 148 polymorphism in neonates with preterm delivery].

The objective is to investigate whether Rsa I polymorphism at the 5' flanking region of cytochrome P450 2E1 gene (CYP2E1) and paraoxonase 2 gene polymorphism (PON2 148) in neonates are associated with preterm delivery. Using standard questionnaires, 209 singleton live born mother-neonate pairs (include preterm cases and term controls) were investigated by the trained field workers with cross-sectional survey at the hospitals in Anqing, Anhui Province, China. Epidemiological and clinical data and blood samples were obtained from 209 mother-neonate pairs. CYP2E1 homozygous wild-type (+/+) is not associated with a shortened gestation among neonates, compared with CYP2E1 homozygous mutant-type (-/-)/CYP2E1 heterozygote (+/-) before and after adjustment confounders, however, PON2 Ala148Ala homozygote is significantly associated with a shortened gestation among neonates. When Rsa I polymorphism at the 5' flanking region of CYP2E1 and PON2 148 polymorphism were considered jointly, a significant shortened gestation was observed among neonates with the combined genotype of CYP2E1 homozygous wild-type and PON2 Ala148Ala homozygote. In conclusion, Rsa I polymorphism at the 5' flanking region of CYP2E1 in neonates is not associated with preterm delivery, however, PON2 148 polymorphism in neonates is significantly associated with preterm delivery. Furthermore, the gene interaction between Rsa I polymorphism at the 5' flanking region of CYP2E1 and PON2 148 polymorphism in neonates is significantly associated with preterm delivery.

5' Flanking Region↗

PubMed2003

[Saccharomyces cerevisiae B5 efficiently and stereoselectively reduces 2'-chloroacetophenone to R-2'-chloro-1-phenylethanol in the presence of 5% ethanol].

(R)-chlorprenaline, a selective activator of beta2 receptor and an effective drug for bronchitis and asthma, is industrially prepared from (R)-2'-chloro-1-phenyl-ethanol. In this communication, we describe (1) the identification of Saccharomyces cerevisiae B5 as an effective host for stereoselective reduction of 2'-chloroacetophenone to (R)-2'-chloro-1-phenyl-ethanol; (2) the presence of ethanol enhances the conversion; and (3) the biochemical factors that effect the yield of the product. Among the four yeast strains capable of reduction 2'-chloroacetophenone to (R)-2'-chloro-1-phenyl-ethanol we screened, Saccharomyces cerevisiae B5 showed the highest activity and stereoselectivity, and was used for the subsequent study. The effect of the presence of methanol, ethanol, 2-propanol, 1-butanol, glucose, glycerol and lactic acid was first investigated, as it was previously reported that they increased the yield and stereoselectivity of the reaction. The addition of the co-substrate methanol, ethanol, 2-propanol, 1-butanol, glucose and glycerol favored the formation of the 2'-chloroacetophenone to (R)-2'-chloro-1-phenyl-ethanol. Lactic acid inhibited the enzyme activity. Ethanol is the best co-substrate among the seven co-substrates and under the optimum concentration of 5% , the yield of (R)-2'-chloro-1-phenyl-ethanol was increased from 17% to 74%. The oxidation of ethanol regenerates NADH required for the reduction. The effects of the reaction time, pH, cell concentration, substrate concentration and temperature on the reduction were investigated next. The enantiometric excess of (R)-2'-chloro-1-phenyl-ethanol reached 100% under the optimal condition: pH8.0, 25 degrees C and 5% ethanol. The product yield went up with the increasing Saccharomyces cerevisiae B5 concentration and reached 100% when the cell dry weight was 10.75 mg/mL and 2'-chloroacetophenone was 6.47 mmol/L. The yield of (R)-2'-chloro-1-phenyl-ethanol decreased sharply with the increase of substrate concentration, as the high concentration of substrates is toxic to the cell and inhibits the activity of reductases. The aerobic cultivation of the yeast and shaking during the reaction increased the yield of (R)-2'-chloro-1-phenyl-ethanol. The yeast can be reused up to 15 times. This research paves the way for economical preparation of chiral 2'-chloroacetophenone to R-2'-chloro-1-phenylethanol.

Ethanol↗

PubMed2002

Direct synthesis of uniform hollow carbon spheres by a self-assembly template approach.

Hollow carbon spheres (50-100 nm) have been synthesized by a self-assembly approach using hexachlorobenzene and Na. NaCl which generated during the reaction has been successfully exploited as a template for the direct synthesis of porous carbon materials, which can be subsequently removed from carbon product by annealing above 1400 degrees C.

Journal Article↗

PubMed2002

An essential role for functional telomeres in mouse germ cells during fertilization and early development.

Late generations of telomerase-null (TR(-/-)) mice exhibit progressive defects in highly proliferative tissues and organs and decreased fertility, ultimately leading to sterility. To determine effects of telomerase deficiency on germ cells, we investigated the cleavage and preimplantation development of embryos derived from both in vivo and in vitro fertilization of TR(-/-) or wild-type (TR(+/+)) sperm with either TR(-/-) or TR(+/+) oocytes. Consistently, fertilization of TR(-/-) oocytes with either TR(+/+) or TR(-/-) sperm, and TR(-/-) sperm with TR(+/+) oocytes, resulted in aberrant cleavage and development, in contrast to the normal cleavage and development of TR(+/+) oocytes fertilized by TR(+/+) sperm. Many (>50%) of the fertilized TR(-/-) eggs developed only one pronucleus, coincident with increased incidence of cytofragmentation, in contrast to the normal formation of two pronuclei and equal cleavage of wild-type embryos. These results suggest that both TR(-/-) sperm and oocytes contribute to defective fertilization and cleavage. We further found that a subset (7-9%) of telomeres was undetectable at the ends of some metaphase I chromosomes from TR(-/-) spermatocytes and oocytes, indicating that meiotic germ cells lacking telomerase ultimately resulted in telomere shortening and loss. Dysfunction of meiotic telomeres may contribute to aberrant fertilization of gametes and lead to abnormal cleavage of embryos, implying an important role of functional telomeres for germ cells undergoing fertilization and early cleavage development.

Animals↗