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T Ren

Publications and source records attributed to T Ren.

At least 19 recordsLinked to original sources
PubMed2005

Genetic characterization of H5N1 avian influenza viruses isolated in southern China during the 2003-04 avian influenza outbreaks.

The recent H5N1 avian influenza outbreaks in Asia spread over more than 8 countries. It has caused enormous economic loss and grand challenges for the public health. During these breakouts we isolated three strains of H5N1 Avian Influenza Virus (AIV) from chickens and one from duck in different farms of Southern China. We completely sequenced these four AIVs. Molecular characterization demonstrated that these strains retain the reported H5N1 AIV sequence properties relevant to virus virulence and host adaptation. Phylogeny results demonstrated that three of these isolates (except A/Chicken/Guangdong/174/04) were closely linked to other H5N1 AIVs isolated from the recent H5N1 outbreaks in Asia. Six of 8 segments (except PA and M) of A/Chicken/Guangdong/174/04 also shares a close linkage to other H5N1 AIVs isolated from the recent H5N1 outbreaks. However, the PA gene of A/Chicken/Guangdong/174/04 and another H5N1 strain forms a distinct subgroup along with an H6N1 AIV, and the M gene of A/Chicken/Guangdong/174/04 shows a close linkage to some H5N1 AIVs from aquatic species in China. Our findings suggest that a new genotype of AIV (in addition to previous reported ones) was present during the 2003-04 Asian bird flu outbreaks and that continuing virus surveillance of AIVs be conducted to monitor the evolutionary paths of the A/Chicken/Guangdong/174/04-like AIVs.

Animals↗
PubMed2004

Spontaneous basilar membrane oscillation and otoacoustic emission at 15 kHz in a guinea pig.

A spontaneous otoacoustic emission (SOAE) measured in the ear canal of a guinea pig was found to have a counterpart in spontaneous mechanical vibration of the basilar membrane (BM). A spontaneous 15-kHz BM velocity signal was measured from the 18-kHz tonotopic location and had a level close to that evoked by a 14-kHz, 15-dB SPL tone given to the ear. Lower-frequency pure-tone acoustic excitation was found to reduce the spontaneous BM oscillation (SBMO) while higher-frequency sound could entrain the SBMO. Octave-band noise centered near the emission frequency showed an increased narrow-band response in that frequency range. Applied pulses of current enhanced or suppressed the oscillation, depending on polarity of the current. The compound action potential (CAP) audiogram demonstrated a frequency-specific loss at 8 and 12 kHz in this animal. We conclude that a relatively high-frequency spontaneous oscillation of 15 kHz originated near the 15-kHz tonotopic place and appeared at the measured BM location as a mechanical oscillation. The oscillation gave rise to a SOAE in the ear canal. Electric current can modulate level and frequency of the otoacoustic emission in a pattern similar to that for the observed mechanical oscillation of the BM.

Acoustic Stimulation↗
PubMed2004

Mechanisms regulating the development of the corpus callosum and its agenesis in mouse and human.

The development of the corpus callosum depends on a large number of different cellular and molecular mechanisms. These include the formation of midline glial populations, and the expression of specific molecules required to guide callosal axons as they cross the midline. An additional mechanism used by callosal axons from neurons in the neocortex is to grow within the pathway formed by pioneering axons derived from neurons in the cingulate cortex. Data in humans and in mice suggest the possibility that different mechanisms may regulate the development of the corpus callosum across its rostrocaudal and dorsoventral axes. The complex developmental processes required for formation of the corpus callosum may provide some insight into why such a large number of human congenital syndromes are associated with agenesis of this structure.

Agenesis of Corpus Callosum↗
PubMed2001

Increased Bcl-w expression following focally evoked limbic seizures in the rat.

Control of seizure-induced neuronal death may involve members of the Bcl-2 family of cell death regulating proteins. Bcl-w is a newly described anti-apoptotic member of this family that may confer neuroprotective effects. We therefore investigated Bcl-w expression in rat brain following focally evoked limbic seizures. Seizures were induced by unilateral microinjection of kainic acid into the amygdala of the rat and terminated after 40 min by diazepam. Constitutive Bcl-w expression was detected by Western blotting and immunohistochemistry. Bcl-w expression was increased 4-72 h following seizures within the injured hippocampus. Immunohistochemistry determined Bcl-w was predominantly expressed in neurons and seizures increased Bcl-w immunoreactivity within piriform cortex and surviving regions of the injured hippocampus. These data suggest Bcl-w may be involved in the modulation of seizure-induced brain injury.

Amygdala↗
PubMed2001

Expanding cavitand chemistry: the preparation and characterization of [n]cavitands with n>=4.

The preparation of cavitands composed of 4, 5, 6, and 7 aromatic subunits ([n]cavitands, n=4-7) is described. The simple, two-step synthetic procedure utilized readily available starting materials (2-methylresorcinol and diethoxymethane). The two cavitand products having 4 and 5 aromatic subunits exhibited highly symmetric cone conformations, while the larger cavitands (n = 6 and 7) adopt conformations of lower symmetry. 1H NMR spectroscopic studies of [6]cavitand and [7]cavitand revealed that these hosts undergo exchange between equivalent conformations at room temperature. The departure of these two cavitands from cone conformations is related to steric crowding on their Ar-O-CH2-OAr bridges and is predicted by simple molecular mechanics calculations (MM2 force field). X-ray diffraction studies on single crystals of the [4]cavitand, [5]cavitand, and [6]cavitand hosts afforded additional experimental support for these conclusions.

Ethers, Cyclic↗
PubMed2001

Effect of ligustrazine on hematopoiesis in bone marrow transplantation mice.

The effect of Ligustrazine on the hematopoiesis after bone marrow transplantation (BMT) in allogenic BMT mice was investigated. After the typical mice model of allogenic BMT had been established, the mice were randomly divided into three groups: BMT group, Ligustrazine group and normal group. The BMT group was given normal saline (0.2 ml, twice a day) through gastric tube, while the Ligustrazine group was given Ligustrazine through gastric tube (0.2 ml, twice a day). At the 1st, 7th and 14th day after BMT, we observed the peripheral blood cells and bone marrow nuclear cells (BMNC), as well as the expression level of Heparan Sulfate (HS) and stromal cell derived factor-1 (SDF-1) on bone marrow sections by using immunohistochemistry (SABC-AP), the expression of CXCR4 on the BMNC. The results showed that on the 7th and 14th day, the peripheral blood white cells, platelets, BMNC and the expression levels of CXCR4, HS and SDF-1 were significantly higher in Ligustrazine group than in the BMT group (P < 0.05). It was concluded that Ligustrazine could promote hematopoiesis at the early stage of hematopoietic reconstitution after BMT.

Animals↗
PubMed2001

Basilar membrane vibration in the basal turn of the sensitive gerbil cochlea.

The basal membrane (BM) velocity responses to pure tones were measured using a newly developed laser interferometer microscope that does not require placing a reflecting object on the BM. It was demonstrated that the instrument is able to measure sub-nanometer vibration from the cochlear partition in the basal turn of the gerbil. The overall shape of the amplitude spectra shows typical tuning features. The 'best' frequencies (BFs) for the BM locations studied were between 14 kHz and 27 kHz, depending on the longitudinal position. For a given BM location, tuning sharpness was input level dependent, indicated by the Q(10dB), which varied from approximately 3 at low stimulus levels to near 1.5 at high input levels. At frequencies below BF, parallel amplitude/frequency curves across stimulus levels indicate a linear growth function. However, at frequencies near BF, the velocity increased linearly at low levels (<40 dB SPL) and became compressed between 40 and 50 dB SPL. Although the velocity gain for the frequency range below BF was a function of frequency, for a given frequency the gains were approximately constant across different levels. At frequencies near BF, the velocity gain at low sound pressure level was greater than that at a high sound pressure level, indicating a nonlinear negative relationship to stimulus level. The data also showed that the BF shifts toward the low frequencies with stimulus intensity increase. The phase spectra showed two important features: (1) at frequencies about half octave below the BF, phase slope is very small, indicating an extremely short delay; (2) the greatest phase lag occurs at frequencies near the BF, indicating a significant delay near this frequency range.

Acoustic Stimulation↗
PubMed2001

Electrically evoked otoacoustic emissions from apical and basal perilymphatic electrode positions in the guinea pig cochlea.

Stimulation of the cochlea with sinusoidal current results in the production of an otoacoustic emission at the primary frequency of the stimulus current. In this study we test the hypothesis that the wide frequency response from round window (RW) stimulation is due to the involvement of a relatively large spatial segment of the organ of Corti. Tonotopically organized group delays would be evident from perilymphatic electrode locations that restrict the spatial extent of hair cell stimulation. Monopolar and bipolar-paired stimulus electrodes were placed in perilymphatic areas of the first or third cochlear turns and the electrically evoked otoacoustic emissions (EEOAE) produced by these electrodes were compared to that from the RW monopolar electrode in the anesthetized guinea pig. Current stimuli of 35 microA RMS were swept across the frequency range between 60 Hz and 100 kHz. The EEOAE was measured using a microphone coupled to the ear canal. It was found that the bandwidth of EEOAEs from RW stimulation extended to at least 40 kHz and was a relatively insensitive to electrode location on the RW. The group delay of the EEOAE from stimulation at the RW membrane (corrected to stapes motion) was about 53 micros. First and third turn stimulations from electrode placements in perilymph near the bony wall of cochlea yielded narrower band EEOAE magnitude spectra but which had the same short group delays as for RW stimulation. A confined current (from a bipolar electrode pair) applied close to the basilar membrane (BM) in the first turn produced the narrowest frequency-band magnitude emissions and a mean corrected group delay of 176 micros for a location approximately 3 mm from the high frequency end of the BM (corresponding to about the 18 kHz best frequency location). Bipolar electrodes in the third turn scala tympani produced low pass EEOAE magnitude functions with corrected group delays ranging between approximately 0.3 and 1 ms. The average phase slopes did not change with altered cochlear sensitivity and postmortem. These data indicate that the EEOAE from RW stimulation is the summed response from a wide-tonotopic distribution of outer hair cells. A preliminary model study indicates that short time delayed emissions are the result of a large spatial distribution of current applied to perilymphatic locations possibly giving rise to "wave-fixed" emissions.

Animals↗
PubMed2001

Nitric oxide distribution and production in the guinea pig cochlea.

Production sites and distribution of nitric oxide (NO) were detected in cochlear lateral wall tissue, the organ of Corti and in isolated outer hair cells (OHCs) from the guinea pig using the fluorescent dye, 4,5-diaminofluorescein diacetate. Fluorescent signal, indicating the presence of NO, was found in the afferent nerves and their putative endings near inner hair cells (IHCs) and putative efferent nerve endings near OHCs, the IHCs and OHCs, the endothelial cells of blood vessels of the spiral ligament, the stria vascularis, and the spiral blood vessels of the basilar membrane. An increased NO signal was observed following exposure to the substrate for NO, L-arginine, while exposure to NO synthase inhibitors resulted in a decrease in NO signal. Observation of OHCs at the subcellular level revealed differentially strong fluorescent signals at the locations of cuticular plate, the subcuticular plate region, the infranuclear region, and the region adjacent to the lateral wall. The findings indicate the presence of NO in the cochlea and suggest that NO may play an important role in both regulating vascular tone and mediating neurotransmission in guinea pig cochlea.

Afferent Pathways↗
PubMed2001

Quinine-induced alterations of electrically evoked otoacoustic emissions and cochlear potentials in guinea pigs.

Quinine is a well-known ototoxic drug which may affect portions of the auditory system with different biochemical effects, causing reversible hearing loss and tinnitus. Recent investigations indicate that quinine at high concentrations can act directly on cochlear outer hair cells to affect their motility and the mechanical response of the basilar membrane. This study aimed to investigate the effect of quinine on the electromotility of outer hair cells in vivo by means of measuring the electrically evoked otoacoustic emissions (EEOAEs), and the relationship between EEOAE and hearing sensitivity alterations in guinea pigs. Quinine was infused into the scala tympani with concentrations between 0.05 and 5 mM. An alternating current (35 microA RMS) swept from 400 Hz to 40 kHz was applied to the round window to evoke the EEOAE. The compound action potential (CAP), cochlear microphonic (CM) and summating potential (SP) were also measured. Results show that quinine affects the EEOAE in a dose-dependent manner and that its effects are reversible. Two aspects of the EEOAE were affected by quinine, depending on concentration: (1) the 'fine structure' only for concentrations below 0.1 mM and (2) the overall amplitude and the 'fine structure' for concentrations above 0.1 mM. At 5 mM the fine structure was completely absent and the mean amplitude of the EEOAE greatly decreased. Multiple component analysis shows the short delay component of the EEOAE is related to the mean value of the amplitude spectrum while the long delay component is related to the fine structure. The alterations of the EEOAE are roughly comparable to that of the cochlear potentials. A 'threshold concentration' for quinine's effects was found at 25 microM. CAP was significantly affected at 25 microM while EEOAE, CM and SP were not. Enhancement of the EEOAE amplitude was noticed in five out of 20 animals in the current study. The enhancement appears only related to the EEOAE mean level or short delay component. The results suggest that quinine can affect in vivo electromotility of outer hair cells at low concentration and therefore change the cochlear amplifier performance via an effect on electro-mechanical transduction. Its effects on the cochlear spiral ganglion neurons and/or their presynaptic process are also suggested, and these are speculated to be the primary sites for quinine's effects on the auditory system.

Action Potentials↗
PubMed2001

Synthesis of galactosyl compounds for targeted gene delivery.

Cell-specific DNA delivery offers a great potential for targeted gene therapy. Toward this end, we have synthesized a series of compounds carrying galactose residues as a targeting ligand for asialoglycoprotein receptors of hepatocytes and primary amine groups as a functional domain for DNA binding. Biological activity of these galactosyl compounds in DNA delivery was evaluated in HepG2 and BL-6 cells and compared with respect to the number of galactose residues as well as primary amine groups in each molecule. Transfection experiments using a firefly luciferase gene as a reporter revealed that compounds with multivalent binding properties were more active in DNA delivery. An optimal transfection activity in HepG2 cells requires seven primary amine groups and a minimum of two galactose residues in each molecule. The transfection activity of compounds carrying multi-galactose residues can be inhibited by asialofetuin, a natural substrate for asialoglycoprotein receptors of hepatocytes, suggesting that gene transfer by these galactosyl compounds is asialoglycoprotein receptor-mediated. These results provide direct evidence in support of our new strategy for the use of small and synthetic compounds for cell specific and targeted gene delivery.

Animals↗
PubMed2001

Recording depth of the heterodyne laser interferometer for cochlear vibration measurement.

Measurement of the cochlear partition vibration as a function of the optical-axis (z-axis) position in the gerbil cochlea showed that the velocity distributes over a range of more than 300 microm, which is larger than the thickness of the cochlear partition. This finding suggests that the recording depth (RD) of the heterodyne interferometer probably is not as small as reported in the literature. In the current experiment, the RD of the heterodyne laser interferometer was studied by measuring the velocity of a vibrating mirror as a function of the z-axis position. Results demonstrate that the optical sectioning characteristic, measured by the intensity of the reflected laser beam as a function of the z-axis position, is not able to correctly estimate the RD of the heterodyne interferometer: the RD is much larger than optical sectioning, indicating a poor spatial resolution along the z axis.

Animals↗
PubMed2000

Synthesis and evaluation of vitamin D-based cationic lipids for gene delivery in vitro.

A new panel of steroidal cationic lipids has been synthesized for gene delivery. Using commercially available vitamin D2 (calciferol) or vitamin D3 (cholecalciferol) as hydrophobic motifs and a variety of cationic head groups as binding sites for negatively charged phosphate groups in DNA, we demonstrated that the transfection activity of the synthetic vitamin D-based cationic lipids 1d, 2d formulated with dioleoylphosphatidylethanolamine (DOPE) as a co-lipid is comparable to that of 3-(-[N-N',N'-dimethylaminoethane)carbamoyl]cholesterol (DC-Chol). These synthetic lipids are effective in transfecting a variety of cell lines. These results suggest that vitamin D-based cationic lipids are useful transfection reagents for in vitro gene transfer studies.

3T3 Cells↗
PubMed2000

Deltamethrin induces altered expression of P53, Bax and Bcl-2 in rat brain.

In this study we investigated the effects of deltamethrin on the expression of P53, Bax and Bcl-2 in rat brain. Immunohistochemical analysis demonstrated that the immunoreactivity for P53 was markedly increased in the cerebral cortex and hippocampus at 5 h after deltamethrin treatment, and maintained at an increased level at 24 and 48 h, whereas little immunoreactivity for P53 was seen in the same brain regions of control rats. The immunostaining for Bax was also elevated in the same brain regions, showing the same time course of P53 expression after deltamethrin treatment. However, the immunolabeling for Bcl-2 was markedly decreased at 24 h after a transient increase at 5 h following deltamethrin treatment. These results indicate that deltamethrin leads to the persistent increase of P53 and Bax expression and transient elevation of Bcl-2 expression, resulting in an increased ratio of Bax to Bcl-2, which may contribute to apoptotic cell death in rat brain following deltamethrin treatment.

Animals↗
PubMed2000

Quantitative measure of multicomponents of otoacoustic emissions.

A method for quantitatively measuring measuring multicomponents of otoacoustic emissions (OAE) was developed in this study. The method is based on the rationale that, if the acoustic emission is a vector sum of multicomponents coming from different locations in the cochlea, each component will show a delay. The proposed method consists of the following steps: (1) the amplitude and phase of the emission is measured when the emission frequency is swept; (2) the real part of the spectrum is obtained based on the amplitude and phase spectra; and (3) the real part of the emission spectrum is then analyzed using a Fourier transform to extract the multiple components. The theoretical basis and practical procedure of this method are described, and in vitro and in vivo tests are used to demonstrate the validity of the method. Preliminary data demonstrate the multicomponents of the extracochlear electrically evoked otoacoustic emission (EEOAE).

Acoustic Stimulation↗
PubMed2000

Fine structure and multicomponents of the electrically evoked otoacoustic emission in gerbil.

Like the acoustically evoked distortion product otoacoustic emissions (DPOAE), the amplitude spectrum of the extracochlear electrically evoked otoacoustic emission (EEOAE) also shows peaks and valleys, which are termed the fine structure (FS) of the EEOAE. The hypothesis that the FS of the EEOAE is generated by multiple wave interactions in the cochlea is investigated by examining the relationship between the FS and the multiple-delay components of the EEOAE. The bulla of the gerbil was exposed using a ventral surgical approach. One pole of a bipolar electrode was placed in the round window niche, and the other pole on the surface of the first cochlear turn. A microphone was used to measure electrically evoked sound pressure change in the ear canal. A recently developed multicomponent analysis method was used to detect the EEOAE multiple delays. It was found that the FS is the spectral representation of the multiple-delay components. The relative power of a prominent long delay component (LDC) shows a negative relationship to the electrical stimulus level. Both the FS and the LDC were abolished by intravenous furosemide. Reconstructed signals showed that mathematical removal of the EEOAE LDC also completely eliminated the FS. These data demonstrate that the FS and the EEOAE multicomponents are properties of normal cochlear mechanics in a healthy ear and that the FS is a manifestation of the multicomponents. The findings in this study strongly indicate that the FS of the EEOAE evoked by extracochlear electrical stimulation is generated by wave interaction in the cochlea. The similarity between the EEOAE FS and the DPOAE FS suggests that they may share the same mechanism.

Animals↗
PubMed2000

Structural basis of DOTMA for its high intravenous transfection activity in mouse.

Eleven structural analogues of two known cationic lipids, N-[1-(2, 3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA) and N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTAP) were synthesized and utilized to evaluate the structural characteristics of DOTMA for its high intravenous transfection activity. Using a CMV-driven expression system and luciferase gene as a reporter, the transfection activity of these analogues was evaluated in mice using tail vein injection. Results concerning the structure-activity relationship with regard to the influence of the backbone, relative position between head group and the hydrophobic chains on the backbone, linkage bonds, as well as the composition of the aliphatic chains revealed that cationic lipids which give a higher in vivo transfection activity share the following structural characteristics: (1) cationic head group and its neighboring aliphatic chain being in a 1,2-relationship on the backbone; (2) ether bond for bridging the aliphatic chains to the backbone; and (3) paired oleyl chains as the hydrophobic anchor. Cationic lipids without these structural features had lower in vivo transfection activity. These structural characteristics, however, did not significantly influence their in vitro transfection activity. The contribution that cationic lipids make to the overall in vivo transfection activity is likely to be determined by the structure of DNA/lipid complexes and by the outcome of the interaction between the DNA/lipid complexes and blood components upon intravenous administration.

Animals↗