Biomedical subjects

Li Yang

Publications and source records attributed to Li Yang.

At least 109 records · Page 6Linked to original sources

PubMed2005

Isolation and characterization of a chlorpyrifos and 3,5,6-trichloro-2-pyridinol degrading bacterium.

A bacterium, isolated from contaminated soils around a chemical factory and named strain DSP3 was capable of biodegrading both chlorpyrifos and 3,5,6-trichloro-2-pyridinol. Based on the results of phenotypic features, phylogenetic similarity of 16S rRNA gene sequences, DNA G+C content, and DNA homology between strain DSP3 and reference strains, strain DSP3 was identified as Alcaligenes faecalis. Chlorpyrifos was utilized as the sole source of carbon and phosphorus by strain DSP3. We examined the role of strain DSP3 in the degradation of chlorpyrifos and 3,5,6-trichloro-2-pyridinol under different culture conditions. Parathion and diazinon could also be degraded by strain DSP3 when provided as the sole sources of carbon and phosphorus. An addition of strain DSP3 (10(8)cells g(-1)) to soil with chlorpyrifos (100 mg kg(-1)) resulted in a higher degradation rate than the one obtained from non-inoculated soils. Different degradation rates of chlorpyrifos in six types of treated soils suggested that soils used for cabbage growing in combination with inoculation of strain DSP3 showed enhanced microbial degradation of chlorpyrifos.

Alcaligenes faecalis↗

PubMed2005

Analysis of putative RNase P RNA from orthopoxviruses.

A putative RNase P RNA gene in camelpox virus, one of the orthopoxviruses, was cloned and transcribed in vitro. No RNase P activity could be detected in vitro from camelpox virus RNase P RNA alone, or by addition of the Escherichia coli RNase P protein subunit to reaction mixtures. Camelpox virus RNase P RNA reconstituted in vitro with camel or HeLa cell extracts, which were pre-treated with micrococcal nuclease to degrade the endogenous RNase P RNA, showed no RNase P activity. Vaccinia virus, another orthopoxvirus, showed no RNase P activity in vaccinia-infected HeLa cells, even though transcription of the vaccinia RNase P RNA could be identified in the cells by both Northern blot and RNase protection assay. Camelpox virus RNase P RNA inhibited an endogenous HeLa RNase P activity by 20% in our assays. The 5S RNA showed no significant inhibition in this assay.

Animals↗

PubMed2005

[Influence of taking aristolochic acid-containing Chinese drugs on occurrence of urinary transitional cell cancer in uremic uremic patients undergoing dialysis].

OBJECTIVE: To investigate the prevalence and clinical characteristics of urinary transitional cell cancer (TCC) in uremic patients undergoing dialysis who have history of taking aristolochic acid (AA)-containing Chinese drugs. METHODS: A questionnaire survey was conducted among 283 uremic patients with history of taking aristolochic acid (AA)-containing Chinese drug who were undergoing dialysis, 118 males and 165 females, aged 59 +/- 13 (22-88), to understand the drug-taking history, nephropathy-related situation, and prevalence and clinic TCC pathological features of TCC. RESULTS: Twenty-four of the 283 were suffering concomitant TCC with a prevalence rate of 8.48%. Sixty-six of the 283 patients had a history of taking AA-containing Chinese drugs, 22 of which had developed TCC with a prevalence rate of 33.3%, significantly higher than that among the 198 patients without a history of taking AA-containing Chinese drugs (1.0%, P < 0.01). Seventeen (94.4%) of the 18 TCC patients with a clear AA-taking history reported took the drug at routine doses for a long time, and 1 of the 18 patients took overdose of AA-containing drug. The average time between the beginning of taking AA-containing drugs and the occurrence of TCC was 10 years. TCC was found only in the patients with remnant urine > 100 ml after dialysis (8/38, 21.0%) and was not found in those with anuria after dialysis. The first symptom in the 18 TCC cases was intermittent painless hematuria. The positive rates of imageology and nuclear matrix protein (NMP)-22 detection were both more than 90%. Tumor was found in the urinary bladder or ureter (11/18, 61.2%). The relapse rate after routine surgery was 27.8%. CONCLUSION: With a very high prevalence of TCC, the patients with a history of taking AA-containing Chinese drugs should be monitored closely.

Adult↗

PubMed2005

Theoretical studies of the modulation of polymer electronic and optical properties through the introduction of the electron-donating 3,4-ethylenedioxythiophene or electron-accepting pyridine and 1,3,4-oxadiazole moieties.

One serious problem associated with polyfluorene and derivatives (PFs) as blue luminescent polymers is the significant energy barrier for hole or electron injections; thus they usually face charge injection and transport difficulties with the currently available cathode and anode materials. The incorporation of an electron-donating or -accepting unit is expected to improve the recombination of the charge carriers. In this paper, we apply quantum-chemical techniques to investigate three fluorene-based copolymers, copoly(2,5-ethylenedioxythiophene-alt-9,9'-dimethylfluorene) (PEF), copoly(2,5-pyridine-alt-9,9'-dimethylfluorene) (PPyF), and poly[(fluorene-2,7-diyl)-alt-(1,3,4-oxadiazole-2,5-diyl)] (PFO), in which Delta(H)(-)(L) [the energy difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), when n = infinity], the lowest excitation energies (E(g)), ionization potentials (IP), electron affinities (EA), and lambda(abs) and lambda(em) are fine-tuned by the regular insertion of electron-donating unit 3,4-ethylenedioxythiophene (EDOT) or electron-withdrawing units pyridine and 1,3,4-oxadiazole. The results show that the alternate incorporation of electron-donating moiety EDOT increases the HOMO energy and thus reduces the IPs, and consequently the hole injection was greatly improved. On the other hand, even though both kinds of charge carriers will improve the electron-accepting ability, the results show that electron-withdrawing moieties greatly facilitate the electron-transporting. Especially in PFO, the highly planar structural character resulted from the strong push-pull effect between the fluorene ring and the 1,3,4-oxadiazole ring and a weak interaction between the nitrogen and oxygen atoms in 1,3,4-oxadiazole ring and the hydrogen atom of the fluorene ring, significantly lowering the LUMO energy levels and thus improve the electron-accepting and transporting properties by the low LUMO energy levels.

Journal Article↗

PubMed2005

Regulated expression of functional external guide sequences in mammalian cells using a U6 RNA polymerase III promoter.

A regulatable promoter has been stably integrated into a human embryonic kidney cell line. The promoter is a pol III mouse promoter and is under the control of ponasterone A, an ecdysone inducer. The promoter controls transcription of an external guide sequence (EGS) targeted against Rpp38, a protein subunit of human RNase P, or of lamin A/C, a gene product located in the nucleus. The amounts of protein of both gene products are severely reduced when the EGSs are made. Several other, but not all, of the protein subunits of RNase P are also inhibited in both mRNA and protein levels when Rpp38 mRNA is targeted.

Animals↗

PubMed2005

Combination of low-dose gemcitabine and recombinant quail vascular endothelial growth factor receptor-2 as a vaccine induces synergistic antitumor activities.

Vascular endothelial growth factor receptor-2 (VEGFR-2) has been shown to play a major role in inducing the full spectrum of VEGF biological response which is essential for tumor angiogenesis. We have demonstrated that immunotherapy of tumors with a vaccine based on quail homologous VEGFR-2 (qVEGFR) was effective in providing both protective and therapeutic antitumor immunity in several tumor models in mice. The purpose of this study was to determine whether the combination therapy of low-dose gemcitabine with qVEGFR as a vaccine could inhibit tumor growth to a greater extent. To test this concept, H22 hepatoma and Lewis lung carcinoma models were established in BALB/c mice and C57BL/6 mice, respectively. Mice were treated with either qVEGFR as a protein vaccine, gemcitabine, or both agents together. qVEGFR or low-dose chemotherapy treatment individually resulted in tumor inhibition to a certain extent.Remarkably, the combination therapy resulted in synergistic antitumor activity. Histological examination revealed that there was endothelial deposition of immunoglobulins within tumor tissues from mice treated with vaccine or combination therapy, especially intratumor angiogenesis was suppressed more significantly for the combination group. Also, ELISPOT analysis showed that mice treated with either qVEGFR alone or in combination with low-dose chemotherapy produced similar amount of anti-VEGFR antibody-producing B cells, which suggested that low-dose gemcitabine did not suppress the host's immune response, but potentiated the antitumor activity of the qVEGFR vaccine. Furthermore, TUNEL staining demonstrated a significant increase in the number of TUNEL-positive cells in the combination group compared with those of other groups. The observations may provide a new bio-chemotherapeutic approach for cancer.

Animals↗

PubMed2005

Theoretical studies on the electronic and optical properties of two new alternating fluorene/carbazole copolymers.

Poly(fluorene)-type materials are widely used in polymer-based emitting devices. During operation there appears, however, an additional emission peak at around 2.3 eV, leading to both a color instability and reduced efficiency. The incorporation of the carbazole units has been proven to efficiently suppress the keto defect emission. In this contribution, we apply quantum-chemical techniques to investigate two series of alternating fluorene/carbazole oligomers and copolymers poly[2,7-(N-(2-methyl)-carbazole)-co-alt-2,7-m(9,9-dimethylfluorene)], namely, PFmCz (m = 1,2) and gain a detailed understanding of the influence of carbazole units on the electronic and optical properties of fluorene derivatives. The electronic properties of the neutral molecules, HOMO-LUMO gaps (Delta(H-L)), in addition to the positive and negative ions, are studied using B3LYP functional. The lowest excitation energies (E(g)s) and the maximal absorption wavelength lambda(abs) of PFmCz (m = 1,2) are studied, employing the time-dependent density functional theory (TD-DFT). The properties of the two copolymers, such as Delta(H-L), E(g), IPs, and EAs were obtained by extrapolating those of the oligomers to the inverse chain length equal to zero (1/n = 0). The outcomes showed that the carbazole unit is a good electron-donating moiety for electronic materials, and the incorporation of carbazole into the polyfluorene (PF) backbone resulted in a broadened energy gap and a blue shift of both the absorption and photoluminescence emission peaks. Most importantly, the HOMO energies of PF1Cz and PF2Cz are both a higher average (0.4 eV) than polyfluorene (PF), which directly results in the decreasing of IPs of about 0.2 eV more than PF, indicating that the carbazole units have significantly improved the hole injection properties of the copolymers. In addition, the energy gap tends to broaden and the absorption and emission peaks are gradually blue-shifted to shorter wavelengths with an increase in the carbazole content in the copolymers. This is due to the interruption of the longer conjugation length of the backbone in the (F1Cz)(n) series.

Journal Article↗

PubMed2005

Theoretical study on electronic structure and optical properties of phenothiazine-containing conjugated oligomers and polymers.

The application of polyfluorenes in polymeric light-emitting diodes has been hampered because of the charge injection difficulties and the troublesome formation of a tailed emission band at long wavelengths (>500 nm) during device fabrication and operation, leading to both a color instability and reduced efficiency. The incorporation of the phenothiazine units has been proven to significantly enhance the hole injection and charge carrier balance and at the same time efficiently suppress the keto defect emission. In this contribution, we apply quantum-chemical techniques to investigate poly[10-(N-(2'-methyl)phenothiazine-3,7-diyl) and its fluorene copolymer poly[10-(N-(2'-methyl)phenothiazine-3,7-diyl)-co-alt-2,7-(9,9-dimethylfluorene)] (PFPTZ) and gain a detailed understanding the influence of phenothiazine units on the electronic and optical properties of fluorene derivatives. Density functional theory (DFT) and time-dependent DFT approaches are employed to study the neutral molecules, HOMO-LUMO gaps (Delta(H-L)), the lowest excitation energies (E(g)'s), positive and negative ions, as well as the IPs and EAs, focusing on the superiority of the electronic and optical properties attributed to the introduction of electron-donating moiety phenothiazine (PTZ) through comparing with pristine polyfluorene. The outcomes show that the highly nonplanar conformation of phenothiazine ring in the ground state preclude sufficiently close intermolecular interactions essential to forming aggregates or excimers. Furthermore, the HOMO energies lift about 0.4 eV, and thus, the IPs decrease about 0.3 eV in PFPTZ, suggesting the significant improved hole-accepting and transporting abilities, due to the electron-donating properties of phenothiazine ring by the presence of electron-rich sulfur and nitrogen heteroatoms and highly nonplanar characters, resulting in the enhanced performances in both efficiency and brightness compared with pristine polyfluorene. In addition, even though the introduction of electron-donating moiety PTZ onto fluorene leads to a slight bathochromic shift in absorption and emission spectra, the copolymer still exhibited strong blue emission.

Journal Article↗

PubMed2005

Cytotoxic and apoptotic activities of diarylheptanoids and gingerol-related compounds from the rhizome of Chinese ginger.

Ginger is one of the most widely used spices and has been used in traditional oriental medicines for long time. Its extract and major pungent principles have been shown to exhibit a variety of biological activities. In order to find more active constituents and evaluate their structure-activity relationship (SAR) we isolated from the rhizomes of Chinese ginger (Zingiber officinale Roscoe) five new diarylheptanoids along with 20 known diarylheptanoids and gingerol-related compounds and studied their cytotoxic and apoptotic activities against human promyelocytic leukemia (HL-60) cells. It was found that compounds 1a, 2a, 5, 6a, 6b and 7 possess significant cytotoxicity against HL-60 cells (IC(50)<50 microM) and that the cytotoxic activity is associated with the cell apoptosis. SAR analysis demonstrates that the following structural determinants contribute critically to the enhancement of the activity: (i) acetoxyl groups at 3- and/or 5-positions of the side chain; (ii) the appropriate longer alkyl side-chain length; (iii) the ortho-diphenoxyl functionality on the aromatic ring; (iv) the alpha,beta-unsaturated ketone moiety in the side chain. These provide useful information for potential chemopreventive drug design.

Antineoplastic Agents, Phytogenic↗

PubMed2005

Multivariate analysis of TOF-SIMS spectra of monolayers on scribed silicon.

Static time-of-flight secondary ion mass spectrometry (TOF-SIMS) was performed on monolayers on scribed silicon (Si(scr)) derived from 1-alkenes, 1-alkynes, 1-holoalkanes, aldehydes, and acid chlorides. To rapidly determine the variation in the data without introducing user bias, a multivariate analysis was performed. First, principal components analysis (PCA) was done on data obtained from silicon scribed with homologous series of aldehydes and acid chlorides. For this study, the positive ion spectra, the negative ion spectra, and the concatentated (linked) positive and negative ion spectra were preprocessed by normalization, mean centering, and autoscaling. The mean centered data consistently showed the best correlations between the scores on PC1 and the number of carbon atoms in the adsorbate. These correlations were not as strong for the normalized and autoscaled data. After reviewing these methods, it was concluded that mean centering is the best preprocessing method for TOF-SIMS spectra of monolayers on Si(scr). A PCA analysis of all of the positive ion spectra revealed a good correlation between the number of carbon atoms in all of the adsorbates and the scores on PC1. PCA of all of the negative ion spectra and the concatenated positive and negative ion spectra showed a correlation based on the number of carbon atoms in the adsorbate and the class of the adsorbate. These results imply that the positive ion spectra are most sensitive to monolayer thickness, while the negative ion spectra are sensitive to the nature of the substrate-monolayer interface and the monolayer thickness. Loadings show an inverse relationship between (inorganic) fragments that are expected from the substrate and (organic) fragments expected from the monolayer. Multivariate peak intensity ratios were derived. It is also suggested that PCA can be used to detect outlier surfaces. Partial least squares showed a strong correlation between the number of carbon atoms in the adsorbate and the number it predicted.

Journal Article↗

PubMed2005

Overexpression of Stat3C in pulmonary epithelium protects against hyperoxic lung injury.

Acute lung injury is a side effect of therapy with a high concentration of inspired oxygen in patients. The molecular mechanism underlining this effect is poorly understood. In this study, we report that overexpression of Stat3C, a constitutive active form of STAT3, in respiratory epithelial cells of a doxycycline-controlled double-transgenic mouse system protects lung from inflammation and injury caused by hyperoxia. In this mouse line, >50% of transgenic mice survived exposure to 95% oxygen at day 7, compared with 0% survival of wild-type mice. Overexpression of STAT3C delays acute capillary leakage and neutrophil infiltration into the alveolar region. This protection is mediated at least partially through inhibition of hyperoxia-induced synthesis and release of matrix metalloproteinase (MMP)-9 and MMP-12 by neutrophils and alveolar resident cells. In some MMP-9(-/-) mice, prolonged survival was observed under hyperoxic condition. The finding supports a concept that activation of the Stat3 pathway plays a role to prevent hyperoxia-induced inflammation and injury in the lung.

Acute-Phase Proteins↗

PubMed2005

A modified method for generation of neural precursor cells from cultured mouse embryonic stem cells.

The pluripotency and high proliferative capacity of embryonic stem (ES) cells make them an attractive source of different cell types for biomedical research and cell replacement therapies. It has been demonstrated that ES cells can be induced into neural precursor cells (NPCs) under conditions. NPCs can be expanded in large numbers for significant periods of time to provide a reliable source of cells for transplantation in neurodegenerative disorders and injury of the central nervous system. This study describes a modified method for generation of NPCs from cultured mouse ES cells.

Alkaline Phosphatase↗

PubMed2005

[Study of calcium-phosphorous metabolism and intact parathyroid hormone levels in end stage renal disease patients].

OBJECTIVE: To investigate the state of calcium-phosphorus metabolism and serum intact parathyroid hormone (iPTH) levels in end stage renal disease (ESRD) patients, to analyze clinical characters, and to provide scientific basis for clinical treatment. METHODS: The data of 100 ESRD patients who received hemodialysis in Peking University First Hospital from January 2000 to July 2003 were analyzed retrospectively. RESULTS: (1) The levels of serum total calcium were adjusted by serum albumin. There were 15 patients with hypocalcemia and 85 patients with normocalcemia or hypercalcemia. 31.8% of the latter took calcium-containing phosphate binders or/and vitamin D. In the 14 patients with hypocalcemia and 58 patients without low serum calcium who did not take calcium-containing phosphate binders or/and vitamin D, we found the levels of carbon dioxide combining power (CO(2)CP) were lower in the group of hypocalcemia (P<0.05), at the same time, there were no significant differences in age and the levels of serum phosphorous, creatinine and iPTH between the two groups. (2) Hyperphosphataemia occurred in 81 patients (81%). (3) The levels of serum iPTH were lower than 100 ng/L in 18 patients (18%) and higher than 300 ng/L in 46 patients (46%), the most common cause of the former was chronic tubular-interstitial nephropathy and that of the latter was chronic glomerulonephritis, excluding the patients who took calcium-containing phosphate binders or/and vitamin D. There were no significant differences in age and the levels of serum calcium, phosphorous and CO(2)CP between the two groups. Multiple regression analyses indicated the levels of serum calcium were in negative correlation with the levels of serum iPTH (r=-0.275, P=0.006). CONCLUSION: Hyperphosphataemia is one of the outstanding characters in ESRD patients and nearly 50% of all the patients develop secondary hyperparathyroidism. The serum calcium levels are correlative with acidosis besides calcium-containing phosphate binders or/and vitamin D.

Adolescent↗

PubMed2005

Theoretical investigation of optical and electronic property modulations of pi-conjugated polymers based on the electron-rich 3,6-dimethoxy-fluorene unit.

Poly(fluorene)-type materials are widely used in polymer-based emitting devices. One of the drawbacks of light-emitting diodes based on polyfluorene derivatives is the injection of holes from the anode due to the high ionization potential (IP) of most derivatives. Substitution by electron-donating alkoxy substituents or by adding charge carriers on the conjugated polymer's backbone produces a remarkable influence on its electrical and optical properties. In this contribution, we apply quantum-chemical techniques to investigate a family of pi-conjugated polymers with substituted dimethoxy groups at the 3,6 positions of the fluorene ring, namely, poly(2,7-(3,6-dimethoxy-fluorene)(PDMOF), poly(2,7-(3,6-dimethoxy-fluorene)-co-alt-fluorene (PDMOFF), and poly(2,7-(3,6-dimeth-oxy-fluorene)-co-alt-2,5-thiophene (PDMOFT). The electronic properties of the neutral molecules, HOMO-LUMO gaps (Delta(H)(-)(L)), in addition to the positive and negative ions, are studied using the B3LYP functional. The lowest excitation energies (E(g)) and the maximal absorption wavelength lambda(abs) of PDMOF, PDMOFF, and PDMOFT are studied by employing time-dependent density functional theory (TD-DFT) and the ZINDO semiempirical method. The IP, EA, and E(g) values of each polymer were obtained by extrapolating those of the oligomers to the inverse chain length equal to zero ((1)/(n)() = 0). The influence of the presence of methoxy groups on the fluorene moiety on the ionization potential is especially emphasized. The outcomes show that the HOMO energies of these systems under study increase by about 0.4 eV and the IP values decrease by about 0.3 eV compared to those of the corresponding polyfluorene. Both effects result in a reduction of the energy barrier for the injection of holes in related polymeric light-emitting devices and should contribute to the enhancement of their performances. Because of the cooperation with thiophene in PDMOFT, which results in a good planar conformation, both the hole-creating and electron-accepting abilities are improved.

Journal Article↗

PubMed2005

Theory of light propagation incorporating scattering and absorption in turbid media.

A general theoretical approach to the description of light propagating through turbid media is proposed. The theory is a modification of the two-flux model of Kubelka-Munk (KM), extending its applicability to media systems containing an absorptive component. The modified KM model takes into account the influence of internal scattering on the total path length and accommodates a wide range of absorption influences. Experimental results obtained for dyed-paper systems illuminated by diffuse light are demonstrated to be qualitatively and quantitatively reproduced by the theory.

Absorption↗

PubMed2005

Gold nanoparticle-modified etched capillaries for open-tubular capillary electrochromatography.

The use of gold nanoparticles in conjunction with etched capillary-based open-tubular capillary electrochromatography (OTCEC) to improve the efficiency of separation and the selectivity between selected solutes is described. The fused-silica capillaries (50-microm i.d.) were etched with ammonium hydrogen difluoride, followed by prederivatization of the new surface with (3-mercaptopropyl)trimethoxysilane (MPTMS) for the immobilization of dodecanethiol gold nanoparticles, for OTCEC. The electrochromatography of a "reversed-phase" test mixture and of selected polycylic aromatic hydrocarbons was investigated, and efficient separations and high theoretical plate numbers per meter were obtained. The electroosmotic flow characteristics of the etched gold nanoparticle capillary, unetched gold nanoparticle capillary, bare capillary, and etched bare capillary were studied by varying the percentage of organic modifier in buffer, buffer pH, and separation voltage. Optical microscopy and scanning electron microscopy were used to examine the process of etching and modification and the surface features of the etched gold nanoparticle capillary. The results confirm that dodecanethiol gold nanoparticles bonded on the etched inner wall of the fused-silica capillary can provide sufficient solute-bonded phase interactions to obtain OTCEC separations with reproducible retention, as well as characteristic reversed-phase behavior, even with the inner diameter of the capillary of 50 microm.

Capillary Electrochromatography↗

PubMed2005

First reaction of a bare silicon surface with acid chlorides and a one-step preparation of acid chloride terminated monolayers on scribed silicon.

Methyl-terminated and acyl chloride terminated monolayers are produced when silicon is scribed under mono- and diacid chlorides, respectively. To the best of our knowledge, this is the first report of the reaction between a bare silicon surface and acid chlorides. This reaction takes place by wetting the silicon surface in the air with the acid chloride and scribing. Scribing activates the silicon surface by removing its passivation layer. We propose that scribed silicon abstracts chlorine from an acid chloride to form an Si-Cl bond and that the resulting acyl radical diffuses back to the surface to condense with the surface and form an alkyl monolayer. X-ray photoelectron spectroscopy (XPS) confirms the presence of chlorine and shows a steady increase in the amount of carbon with increasing alkyl chain lengths of the acid chlorides. Time-of-flight secondary ion mass spectrometry shows SiCl(+) species and a steady increase in representative hydrocarbon fragments with increasing alkyl chain lengths of the acid chlorides. XPS indicates that diacid chlorides react primarily at one of their ends to create acyl chloride terminated surfaces in a single step. The resulting surfaces are shown to react with various amines (piperazine, morpholine, and octylamine) and a protein. Calculations at Hartree-Fock and density functional theory levels are consistent with the proposed mechanism.

Journal Article↗

PubMed2005

Maternally inherited nonsyndromic hearing loss is associated with the T7511C mutation in the mitochondrial tRNASerUCN gene in a Japanese family.

We report here the characterization of a Japanese family with maternally transmitted nonsyndromic hearing loss. Fourteen of 21 matrilineal relatives in this family exhibited early or late-onset/progressive but noncongenital hearing impairment with a wide range of severity, ranging from severe to normal hearing. The age-of-onset varies from 3 to 30 years. Sequence analysis of the complete mitochondrial genome in one matrilineal relative of this family revealed the presence of T7511C mutation and other variants. However, the levels of heteroplasmy of T7511C mutation did not correlate with the severity and age-of-onset of hearing loss in this family. Furthermore, none of other mtDNA variants are evolutionarily conserved and implicated to have significantly functional consequence. The absence of the ND1 T3308C and tRNA(Ala) T5655C mutations in this Japanese family but the presence of these mtDNA mutations in an African family with a high penetrance seems to account for different penetrance between two pedigrees. Incomplete penetrance in this family indicates the involvement of modulatory factors in the phenotypic expression of hearing impairment associated with the T7511C mutation. Here, two known variants G79A and G109A in the GJB2 gene were identified in the hearing-impaired and normal hearing matrilineal relatives of this Japanese family. However, the lack of correlation in the severity and age-of-onset in hearing impairment with homozygous or heterozygous G79A or G109A or combination of both variants in the GJB2 gene in those subjects with hearing impairment and normal hearing indicates that those variants of GJB2 gene may not be a modifier of the phenotypic effects of the T7511C mutation in those subjects. Thus, the phenotypic variability in this family is due to the involvement of other modifier factor(s).

Age of Onset↗