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Biomedical subjects

Y Guo

Publications and source records attributed to Y Guo.

At least 631 records · Page 35Linked to original sources
PubMed1991

[Electrocochleography in experimental animal model with acute hydrolabyrinth].

A desirable animal model of acute hydrolabyrinth was made by injecting artificial endolymph into the cochlear duct of guinea pigs. In 12 animals with intact Reissner membranes, the endolymphatic potential kept normal after injection of artificial endolymph, but their ECochG showed a rise of SP amplitude, a decrease in AP amplitude, an increase of SP/AP ratio, and a delay of N1 latency. In 7 animals with ruptured membranes, the EP significantly decreased. ECochG showed a decrease in hearing in all test frequencies, a distortion of SP-AP wave or even a loss of AP. Based on the results of our experiment, it can be assumed that the dominant -SP may be seen in the acute stage of endolymphatic hydrops without a rupture of Reissner membrane. Therefore, the dominant -SP may only be of value in the clinical diagnosis during an episodic vertigo and fluctuating hearing loss in Ménière disease.

Animals↗
PubMed1990

Effect of unsaturated phosphatidylethanolamine on the chain order profile of bilayers at the onset of the hexagonal phase transition. A 2H NMR study.

The quadrupolar splitting profiles of methylene groups along the acyl chains of perdeuteriated dimyristoylphosphatidylcholine (DMPC-d54) in mixtures with dioleoylphosphatidylethanolamine (DOPE) were studied by 2H NMR. The quadrupolar splittings, obtained for lipid mixtures in the bilayer state, were measured as functions of temperature and PE:PC ratio and were used to obtain the approximate gauche probabilities at a given chain position, pB. Ratios (R) of pB for C13, C12, and C11 relative to that of the plateau region were used to characterize the effect of increasing PE on the gauche content of PC chains. At all temperatures studied (including the bilayer to hexagonal phase transition region), for each ratio R (e.g., RC13/P), the relative gauche content of the DMPC chains was similar over the range of 25-85% PE. DOPE is viewed in simple terms as having a "conical" shape; if this geometry applies to the acyl chain region of the molecule, a greater lateral pressure would be expected toward the center of the bilayer as the PE content is increased, resulting in a decreased gauche content, relative to the plateau, of those methylene groups of PC. The failure to observe the predicted increase in lateral pressure has ramifications for the cone-shape molecular model. The overall "cone shape" of PE is seen to arise from the smaller size of the head-group relative to the acyl chains; however, the acyl chain region itself is not rigidly cone-shaped and is better represented by a flexible "balloon". These results were supported by small-angle X-ray diffraction, which showed a decreasing trend in the area per molecule with increasing PE content.

Deuterium↗
PubMed1990

New strategies for improving speech enhancement.

We describe two design strategies that could substantially improve the performance of speech enhancement systems. Results from a preliminary study of pulse recovery are presented to illustrate the potential benefits of such strategies. The first strategy is a direct application of a non-linear, adaptive signal processing approach for recovery of speech in noise. The second strategy optimizes performance by maximizing the enhancement system's ability to evoke target speech percepts. This approach may lead to better performance because the design is optimized on a measure directly related to the ultimate goal of speech enhancement: accurate communication of the speech percept. In both systems, recently developed 'neural network' learning algorithms can be used to determine appropriate parameters for enhancement processing.

Algorithms↗
PubMed1990

Increased levels of circulating interleukin 6 in burn patients.

The serum levels of interleukin 6 (IL-6) were determined in a population of burn patients. In all patients, IL-6 levels were increased over a 3-week interval with peak concentrations reached during the first week after injury. Patients receiving intravenous polymyxin B therapy according to a regimen designed to reduce endotoxemia manifested greatly reduced levels of both circulating endotoxins and IL-6. Certain patients not treated with polymyxin B showed extraordinarily large increases in IL-6 which were associated with lethal or life-threatening clinical complications. Increased IL-6 levels were also associated with decreased percentage of circulating T cells and corresponding increases in B cells. However, IL-6 did not produce any direct inhibitory effects in vitro on T cell representation or function.

Biological Factors↗
PubMed1990

[Ultrastructural observation of acute cerebral ischemia pathological changes after carotid ligation in rats].

This study reported the ultrastructural changes of acute cerebral ischemia in rats. The pathological changes 120 min and 180 min after ligation of both carotid arteries in 12 rats were observed. The results show the cytotoxic swelling and edema of the neurons and astrocytes, particularly edema of glial processes were more marked than neurons, also perivascular edema was rather severe, but the lesion-of the structure of the vessel was very mild. Swelling and edema of astrocytes and its processes are of importance consideration of the mechanism of acute cerebral ischemia. The latter was briefly discussed.

Animals↗
PubMed1990

[An analysis of survivals of lung cancer in Beijing during 1977-1982].

An Survival analysis include sex, age, diagnosis bases, treatment and survival status. Of lung cancer cases during 1977-1982 in 4 districts covering a population of 2.3 million in Beijing was studied by using Kaplan-Meier and Cox regression methods. Survival curves of 3005 lung cancer cases came down alongside the time last; and came down alongside the growth of age except the age group younger than 40 years. In addition, sieved result of complex factors, the authors got a model of six covariable. The survival time was obviously effected by age, type of pathology, complication in lung, state of metastasis, operation treatment and radiotherapy.

Adult↗
PubMed1990

[Prenatal diagnosis of Duchenne muscular dystrophy by fetoscopic muscle biopsy. Report of a case].

A needle muscle biopsy through a fetoscope for the antenatal diagnosis of Duchenne muscular dystrophy (DMD) was reported the mother was a carrier of 30 years old with a family history of Duchenne muscular dystrophy. Her brother died of DMD and her son had suffering from DMD. At 17 weeks of her second gestation, an amniotic puncture was performed. The cellular chromosome was found to be a male fetus (46,xy). At 20 weeks of her gestation, a needle muscle biopsy of the male fetus was performed under fetoscopy and turned out to be Duchenne muscular dystrophy. At 23 weeks, a male fetus was born with induced labor. The pre and postnatal muscles were examined under the light and electron--microscopes. The large hyaline round fibres were positive for calcium. There was evidence of a break down of the basement membranes, appearance of A and I bands and fragmentation of Z bands. Myofibrils were replaced by thin filaments. The diagnosis of Duchenne muscular dystrophy was established on the basic of these findings. This was considered the first case of antenatal fetal Duchenne muscular dystrophy diagnosed with the aid of fetoscope and needle muscle biopsy.

Abortion, Induced↗
PubMed1990

[Chemical constituents of Isodon parvifolia (Batalin) Hara].

Twelve compounds were isolated from the leaves and stems of Isodon parvifolia. This paper deals with the isolation and identification of two diterpenes epinodosinol (I), lasiodonin (II) and two triterpenes alpha-amyrin (XI a) and beta-amyrin (XI b).

Antineoplastic Agents, Phytogenic↗
PubMed1989

Superconducting properties of copper oxide high-temperature superconductors.

The equations for the magnon pairing theory of high-temperature copper-oxide-based superconductors are solved and used to calculate several properties, leading to results for specific heat and critical magnetic fields consistent with experimental results. In addition, the theory suggests an explanation of why there are two sets of transition temperatures (T(c) approximately 90 K and T(c) approximately 55 K) for the Y(1)Ba(2)Cu(3)O(6+x) class of superconductors. It also provides an explanation of why La(2-x)Sr(x)CuO(4) is a superconductor for only a small range of x (and suggests an experiment to independently test the theory). These results provide support for the magnon pairing theory of high-temperature superconductors. On the basis of the theory, some suggestions are made for improving these materials.

Journal Article↗
PubMed1989

Sequential observation of clinical and karyotypic evolution in a patient with myelodysplastic syndrome.

This paper reports an interesting case of myelodysplastic syndrome (MDS), whose bone marrow karyotype at diagnosis was 46, XY, t(16;17) (q12;q25). Fourteen months later, the disease transformed into erythroleukemia, and several correlative clones with hyperdiploid appeared at the same time. Thus, we consider that detecting karyotypic evolution may help evaluate the prognosis of MDS.

Anemia, Refractory↗