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Biomedical subjects

X H Yu

Publications and source records attributed to X H Yu.

At least 19 recordsLinked to original sources
PubMed1995

Intraocular viral replication after systemic murine cytomegalovirus infection requires immunosuppression.

PURPOSE: Human cytomegalovirus retinitis is the most common blinding complication of acquired immune deficiency syndrome. However, the pathogenesis of the disease is poorly understood. The authors sought to characterize intraocular viral replication after systemic murine cytomegalovirus (MCMV) infection in the normal and immunosuppressed Balb/c mouse. METHODS: Normal or immunosuppressed mice (400 rads radiation plus antilymphocyte serum) were infected intravenously with a recombinant MCMV (RM408) that carries an MCMV IE1 promoter--LacZ insert. In vivo MCMV replication and its tissue distribution were monitored by beta-gal activity with x-gal staining on frozen tissue sections of multiple organs harvested from infected mice at different time points after inoculation. RESULTS: MCMV replication within the eye can be detected in the immunosuppressed Balb/c mouse but not in the normal host. Intraocular viral replication was noted first, and most frequently, in the ciliary body and was mainly restricted to the uveal tract. Intraocular viral replication coincided with the peak of systemic viral replication; however, the neurosensory retina was spared. In contrast, supraciliary inoculation of MCMV in the immunosuppressed Balb/c mouse resulted in massive viral replication and destruction of the neurosensory retina. CONCLUSIONS: This study demonstrated that intraocular MCMV replication after systemic infection requires systemic immunosuppression. Furthermore, the ciliary body is the portal of entry for the virus within the eye. MCMV can replicate in the epithelium of the uvea and retinal pigment epithelium, but it does not replicate within the neurosensory retina. The absence of MCMV replication within the neurosensory retina is not caused by either a defect in the recombinant virus or the inability of the host tissue to support viral replication.

Animals↗
PubMed1995

Re-examination of the plasticity of the corticothalamic projection after unilateral neonatal lesion of the sensorimotor cortex in the rat: a phaseolus vulgaris-leucoagglutinin tracing study.

After unilateral lesion of the sensorimotor cortex in neonatal rats (postnatal days 2-4), the reorganization of the corticothalamic projection originating from the opposite intact sensorimotor cortex was studied. Three months after the lesion, the anterograde tracer phaseolus vulgaris-leucoagglutinin (PHA-L) was injected in the caudal forelimb area (CFA) of the intact opposite sensorimotor cortex to label the corticothalamic axons, in order to establish their trajectory as well as the distribution of their terminal fields in the thalamus. As previously reported, in addition to the standard ipsilateral corticothalamic projection, lesioned rats were characterized also by the presence of a contralateral corticothalamic projection, reaching the decorticate hemithalamus. There is some controversy in literature whether such bilateral corticothalamic projection is present in normal intact rats. On the basis of counts of axons crossing the midline to innervate the hemithalamus contralateral to the cortical injection, the present study provides evidence that the corticothalamic projection is indeed bilateral in normal rats, although the contralateral projection is sparse. Lesioned rats subjected to a similar small size PHA-L injection in the CFA of the intact opposite cortex showed a significantly increased contralateral corticothalamic projection. The number of labeled axons crossing the midline in the thalamus was, on average, five times higher in lesioned rats than in normal rats. It can be concluded that the contralateral corticothalamic projection from the CFA, observed after neonatal lesion of the opposite sensorimotor cortex, is not a novel projection resulting from the lesion, but rather an enhancement and extension of an existing, minor, projection present in normal rats. The enhancement of the crossing corticothalamic projection in lesioned rats is due to an increase of the number of crossing axons in the thalamus rather than to an increase of the degree of branching of the few axons present in control animals.

Animals↗
PubMed1994

Transcallosal connections of the distal forelimb representations of the primary and supplementary motor cortical areas in macaque monkeys.

The goal of the present neuroanatomical study in macaque monkeys was twofold: (1) to clarify whether the hand representation of the primary motor cortex (M1) has a transcallosal projection to M1 of the opposite hemisphere; (2) to compare the topography and density of transcallosal connections for the hand representations of M1 and the supplementary motor area (SMA). The hand areas of M1 and the SMA were identified by intracortical microstimulation and then injected either with retrograde tracer substances in order to label the neurons of origin in the contralateral motor cortical areas (four monkeys) or, with an anterograde tracer, to establish the regional distribution and density of terminal fields in the opposite motor cortical areas (two monkeys). The main results were: (1) The hand representation of M1 exhibited a modest homotopic callosal projection, as judged by the small number of labeled neurons within the region corresponding to the contralateral injection. A modest heterotopic callosal projection originated from the opposite supplementary, premotor, and cingulate motor areas. (2) In contrast, the SMA hand representation showed a dense callosal projection to the opposite SMA. The SMA was found to receive also dense heterotopic callosal projections from the contralateral rostral and caudal cingulate motor areas, moderate projections from the lateral premotor cortex, and sparse projections from M1. (3) After injection of an anterograde tracer (biotinylated dextran amine) in the hand representation of M1, only a few small patches of axonal label were found in the corresponding region of M1, as well as in the lateral premotor cortex; virtually no label was found in the SMA or in cingulate motor areas. Injections of the same anterograde tracer in the hand representation of the SMA, however, resulted in dense and widely distributed axonal terminal fields in the opposite SMA, premotor cortex, and cingulate motor areas, while labeled terminals were clearly less dense in M1. It is concluded that the hand representations of the SMA and M1 strongly differ with respect to the strength and distribution of callosal connectivity with the former having more powerful and widespread callosal connections with a number of motor fields of the opposite cortex than the latter. These anatomical results support the proposition of the SMA being a bilaterally organized system, possibly contributing to bimanual coordination.

Animals↗
PubMed1994

Blood-contacting properties of polydimethylsiloxane polyurea-urethanes.

A series of polyurethanes was synthesized from amino-terminated polydimethylsiloxane oligomers of two molecular weights. The oligomers had been extended with hexane diisocyanate to give internal urea linkages in the soft segment. These polymers have been shown to have higher tensile properties over similar polymers without the internal urea linkages due to the greater phase mixing and interfacial bonding between the hard and soft segment microdomains. The surface properties of these materials were evaluated by dynamic contact angle measurements and the blood compatibility by a canine ex vivo series shunt. The silicone-urea polyurethanes had favourable blood-contacting properties compared to a polyetherurethane. The polymers composed of the higher molecular weight silicone oligomers had the least platelet and fibrinogen deposition.

Animals↗
PubMed1994

Time-varying adaptive filters for evoked potential estimation.

Adaptive implementation of an optimal time-varying filter (TVF) for evoked potential (EP) estimation is addressed in this paper. A data-adaptive scheme is used, which converges asymptotically to the optimal TVF solution. Two basic adaptive TVF's (ATVF's) are first introduced, namely least mean square (LMS) ATVF and recursive least-squares (RLS) ATVF. The latter converges much faster than the former. Since the basic ATVF's usually require a relatively large set of response trials to get a meaningful solution, a reduced-order ATVF is further presented and the corresponding LMS and RLS (including a fast RLS) adaptive algorithms are developed. To save memory, a truncated Fourier expansion is suggested to express approximately the time-sequenced weight-vectors of the ATVF's, resulting in a simplified reduced-order ATVF. Finally, extensive simulations are provided to confirm the superior performance of the ATVF's. The present ATVF's can be used as prefilters for latency-corrected average (LCA) processing to obtain more informative estimates of EP signals.

Adult↗
PubMed1994

Peak component latency-corrected average method for evoked potential waveform estimation.

A peak component latency-corrected average (PC-LCA) method consisting of three steps is presented for estimating the evoked potentials (EP) in the human brain. The present PC-LCA is essentially an alternative version of the original LCA method developed by McGillem et al. It first uses a time-varying adaptive filter as a preprocessor to suppress the ongoing EEG and to enhance the EP. Then, the statistics of mean latencies and amplitudes of the EP peak components are estimated by a peak detection and alignment procedure. The final waveform estimate is obtained by superimposing the estimated mean peak components on background information and subsequently fitting a truncated Fourier series using the fast Fourier transform (FFT). Consistent estimates of the EP peak component information are established based on asymptotic analysis of the PC-LCA. Finally, real-time implementation of the PC-LCA is considered, and the superior performance of the PC-LCA method is confirmed by detailed numerical results.

Electroencephalography↗
PubMed1993

Effects of oligoethylene oxide monoalkyl(aryl) alcohol ether grafting on the surface properties and blood compatibility of a polyurethane.

A series of oligoethylene oxide monoalkyl(aryl) alcohol ethers was grafted on to the backbone of a polytetramethylene oxide (PTMO)-based polyurethane, in an attempt to improve its biocompatibility. Each polyurethane contained a different pendant chain grafted to the urethane nitrogen atoms. The grafted chains consisted of various short lengths of hydrophillic oligomeric poly(ethylene oxide) (PEO) spacer segments and alkyl/aryl hydrophobic terminal groups. By using the 1H-NMR (nuclear magnetic resonance) technique, the extent of grafting was found to range from 7 to 12 mol% substitution of the urethane hydrogen groups. The surface properties of these materials were evaluated using high-vacuum, air-equilibrated and water-equilibrated methods. X-ray photoelectron spectroscopy (XPS) and static and dynamic contact angle experiments were performed. XPS showed that all of the grafted polyurethane surfaces contained higher ratios of C1s to O1s than the base polyurethane. These C:O contents correlate with the C:O ratios of the grafted chains. Dynamic contact angle analysis showed larger contact angle hysteresis for the grafted polyurethanes. The grafted polyurethanes generally exhibit lower complement activation, measured by an in vitro assay for C3a. A canine ex vivo arteriovenous series shunt was used to monitor platelet and fibrinogen deposition on these polymers. The incorporation of short ethylene oxide spacer segments with terminal C18 linear alkyl chains resulted in an improved short-term (up to 15 min) blood compatibility compared to the underivatized polyurethane. At longer blood contact times, all the grafted polyurethanes were more thrombogenic than the base polyurethane. In addition, there was no observable correlation between the material surface properties and the blood contact response.

Absorption↗
PubMed1993

[Protective effect of nerve growth factor on cholinergic neurons corpus striatum of new born rat subjected to hypoxia-ischemia].

Cerebral hypoxia-ischemia was produced in 7 day old rats by right common carotid artery occlusion combined with systemic hypoxia. In the hypoxic-ischemic group animals, striatal ACh contents on both sides were reduced to a significant extent in commensurate to AChE histochemical image analysis. All these changes could be restored to normal control by a protection dose (50 micrograms) of NGF intraventricularly injected.

Acetylcholine↗
PubMed1991

Expression of isoforms of internal Ca2+ pump in cardiac, smooth muscle and non-muscle tissues.

Smooth muscle and several non-muscle tissues contain mRNA for an alternative splice of the mRNA for the cardiac sarcoplasmic reticulum (SR) Ca,Mg-ATPase. Based on amino acid composition deduced from cDNA sequences the cardiac isoform (Ic) is 110 kDa while the smooth muscle and the non-muscle isoform (Is) is 115 kDa. This prediction in their molecular masses was tested at the protein level in rabbit stomach, aorta, uterus and vas deferens smooth muscles; stomach mucosa, brain, liver, kidney and heart. The major species of the acylphosphates formed in the presence of Ca2+ and electrophoresed in acid SDS-acrylamide gels were 5 kDa smaller for the heart (Ic) than those for all the other tissues (Is). The size difference was also confirmed in Western blots using a monoclonal antibody which binds to both Is and Ic. Thus consistent with the mRNA splices for the internal Ca2+ pumps previously reported to be present in these tissues, rabbit heart expresses predominantly the Ca2+ pump protein Ic and the various smooth muscle, mucosa, brain, liver and kidney express mainly the isoform Is.

Animals↗
PubMed1991

Physical and blood contacting characteristics of propyl sulphonate grafted Biomer.

Propyl sulphonate groups were grafted on to the backbone of Biomer, a polyetherurethaneurea, in an attempt to improve its blood-contacting properties. The bulk, surface and blood-contacting properties of this series of sulphonated polymers were evaluated. Differential scanning calorimetry and dynamic mechanical analysis indicated that propyl sulphonate incorporation increased the microphase separation of the polymers. The ultimate tensile strength was also increased with sulphonation at the expense of the polymer's extensibility. Dynamic contact angle analysis showed that, in water, the sulphonated Biomer surfaces were more polar than the Biomer sample indicating the propyl sulphonate groups were enriched at the surface. Canine ex vivo blood-contacting results showed that the incorporation of propyl sulphonate groups dramatically reduced the number and activation of platelets adherent to the polymer surface. In addition, fibrinogen deposition increased with increasing sulphonate content, despite the low level of platelet activation.

Animals↗
PubMed1991

Skeletal development and formation of osteoclast-like cells from in situ progenitors in fetal mouse metatarsals cultured in chemically defined medium.

An in vitro model system is described, using metatarsal explants from 15-day mouse embryos (E15) cultured in serumless chemically defined medium, to study fetal skeletal development with particular emphasis on de novo osteoclast formation. The normal pattern of growth and differentiation observed in vitro, assessed by ultrastructure and morphometry, demonstrate a permissive local environment which replicates physiologic temporal and spatial relationships which exist in vivo. The population of committed osteoclast progenitors present in E15 metatarsals form osteoclasts and precursors which have cytochemical and ultrastructural features, as well as kinetics of formation, that are similar to that which occurs in vivo. The responsiveness of osteoclast formation to the effects of added 1,25(OH)2D3 illustrates that controlled manipulation enables one to exploit the system for investigating the role of cytokines, growth factors and osteotropic hormones in skeletal development and osteoclast ontogeny.

Animals↗
PubMed1991

Calcitonin receptor expression and its regulation by 1 alpha-25-dihydroxyvitamin D3 during de novo osteoclast formation in organ cultures of fetal mouse metatarsals.

Organ cultures of 15-day embryonic mouse metatarsals cultured in serumless, chemically-defined medium were used to investigate the influence of 1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) on calcitonin receptor (CTR) expression in osteoclasts formed from in situ progenitors. CTR expression was demonstrated in tartrate-resistant acid phosphatase-positive (TRAP+) osteoclasts and their precursors. The expression of TRAP preceded that of CTR and was first observed in cells identified as osteoclast precursors. Not all TRAP+ precursors were CTR+ and from 40 to 60% of newly formed osteoclasts lacked CTR. Treatment with 1,25(OH)2D3 increased precursor numbers without affecting CTR expression, whereas both the numbers and the percentage of newly formed osteoclasts expressing CTR was increased by 1,25(OH)2D3. Grain count analysis revealed that this increased percentage of newly formed CTR+ osteoclasts were cells with low and medium levels of CTR expression. This apparent down-regulation of CTR expression in newly formed osteoclasts may help to explain the 'escape' of osteoclastic bone resorption from the inhibitory effects of calcitonin.

Acid Phosphatase↗
PubMed1991

[Scanning electron microscopic observations on Clonorchis sinensis cercariae].

The surface structure of Clonorchis sinensis cercariae was observed under scanning electron microscope. The cercaria was of the parapleuro-lophocercous type. The measurements of the cercariae were as follows: body 137-240 x 62-90 microns, tail 320-470 x 21-34 microns, oral sucker 27-46 x 23-33 microns. The ventral sucker was incompletely developed and much smaller than the oral one. The whole body surface was covered with backward pointing spines. Four horizontal rows of oral spines were found around the mouth opening of the oral sucker. These spines diminished in size with the distance of the rows from the opening and their numbers were 12, 18, 19 and 18 respectively. Transverse and longitudinal plicae formed from tegument were found on the surface of the tail, being in connection with dorsal and ventral fins along posterior half of the tail. Many sensory structures or papillae were observed on the body. They were of three different types: 1) papillae with long or short cilia distributed widely on the body surface and around the mouth opening, the number of papillae with cilia on the body surface being greater than that described by Komiya et al (1940); 2) a few sensory fossa on the tail, measuring 1.0 x 0.6 microns; 3) a few ring-type papillae with knob on the body surface with pore of 0.5 micron in diameter.

Animals↗
PubMed1990

[Ultrastructural changes in the body wall and gut of Clonorchis sinensis in rats after albendazole treatment].

The effect of albendazole on the body wall and gut of Clornorchis sinensis was studied with transmission and scanning electron microscopes after albendazole administration to rats infected with Chonorchis sinensis at a single dose of 150 mg/kg. The results showed that swelling and adhesion of the projections of the tegument and gut microvilli occurred 1h after medication. Necrosis and disruption of the projections and the gut microvilli were seen at the 24th h. By the 72nd h, detachment of the partial projections were seen. The dynamic process of the damages observed on the tegument was identical with that of the gut microvilli (Figs. 1-10).

Albendazole↗
PubMed1989

[A comparative study on the structure and growth of the dentoskeleton and soft-tissue in normal occlusion].

A study of hard tissue and soft tissue contour and growth on normal occlusion among Chinese population was made by means of computerized radiographic cephalometrics. Correlation analysis and polygon methods were applied to analyse the profile contour. The result showed that the dento-skeletal pattern and integumental contour were not necessarily alike, the diversity could be quite prominent. As to the growth change features in soft-tissue and hard-tissue structure, we found that the growth behavior of the lips seemed to show a tendency to follow the dental structure directly. The bony profile tended to become less convex with aging, while the soft-tissue profile remained stable in its degree of convexity.

Adolescent↗