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Biomedical subjects

X L Yang

Publications and source records attributed to X L Yang.

At least 91 records · Page 5Linked to original sources
PubMed1997

[AMPA receptor desensitization and fast excitatory synaptic transmission].

AMPA(alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor, an ionotropic glutamate receptor subtype, mediates fast excitatory synaptic transmission in central nervous system. Recently, the distinct characteristics of AMPA receptor desensitization have been gradually revealed and a number of chemicals which selectively modulate AMPA receptor desensitization have been developed. Many lines of physiological and pharmacological evidence show that AMPA receptor desensitization plays an important role in fast excitatory synaptic transmission by affecting transmission efficacy of individual synaptic bouton, integrative functions of neuron, and synapse plasticity.

Benzothiadiazines↗
PubMed1997

[The selective suppression of GABA on cone-driven horizontal cells in carp retina].

Intracellular recordings were made from horizontal cells in the superfused, isolated carp retina and effects of GABA on rod- and cone-driven horizontal cells were studied. Bath-applied GABA (0.5-5 mmol/L) resulted in a hyperpolarization of dark membrane potential and a suppression of light responses of L-type cone horizontal cells. In 7 out of 10 cells tested the effects of GABA were completely blocked by bicuculline, an antagonist of GABAA receptors. In the presence of 0.5 mmol/L Co2+, 2 mmol/L GABA could not induce any change in dark membrane potential in 8 out of 12 cells, but cause slight depolarization in other 4 cells. These results suggest that the GABA effects may be mediated by GABAA receptors on cone terminals in the majority of the L-type cone horizontal cells. GABA had no effect on rod horizontal cells.

Animals↗
PubMed1996

Dietary sodium and potassium, socioeconomic status and blood pressure in a Chinese population.

The average total intake of sodium was 6.11 g in a Chinese urban diet and 6.49 g in the rural sample in China. Discretionary use of salt provided 53% of the total sodium intake in the urban and 63% in the rural diet. Sodium intakes derived from processed foods, soy sauce and monosodium glutamate were 17%, 16% and 6% respectively in the urban diet, and 4%, 16%, 2% respectively in the rural diet. The mean intake of potassium was 1.95 g in the urban and 1.83 g in the rural diet. Cereals and vegetables were the major sources of dietary potassium. The intakes of total sodium, salt and soy sauce decreased as educational level increased. Similar results were found in white-collar workers and blue-collar workers or farmers. Nevertheless, an inverse association between blood pressure and education was found. The results suggest that reduction in sodium intake, especially cooking salt, and increased potassium intake are needed for nutritional control of hypertension in population-based interventions aimed at all social classes.

Adult↗
PubMed1996

A comparative study of two techniques used in immediate postplacental insertion (IPPI) of the Copper T-380A IUD in Shanghai, People's Republic of China.

Chinese women in Shanghai who delivered vaginally and who chose to use an IUD for contraception received a Copper T-380A IUD inserted vaginally within 10 minutes after delivery of the placenta (i.e., immediate postplacental insertion, IPPI). Among them, 97.7% were primipara. The women were randomly divided into two groups: IUD inserted by hand and IUD via ring forceps. The follow-up rate of six months was 95.2%. Using Tietze's life table method and log rank test, the expulsion and other discontinuation rates were compared at three and six months postinsertion between these two different insertion techniques. Expulsions were the main reason for discontinuation. The six-month gross cumulative expulsion rates were 13.3 and 12.7 per 100 women in the hand-insertion group and ring forceps-insertion group, respectively. Discontinuation rates for medical removals (bleeding/pain) were 2.1 and 1.0 in these two groups, respectively. Neither of the differences was statistically significant (p > 0.05). No uterine perforation, infection or pregnancy occurred. The results suggest that these two different insertion techniques do not significantly affect discontinuation rates in vaginal IPPI using the TCu 380A, and the TCu 380A appears to be suitable for postpartum insertion in Chinese women. Other relevant issues, such as breastfeeding and IUD placement in uterine cavity, are also analyzed and discussed in this report.

Adult↗
PubMed1996

Successful treatment by percutaneous balloon angioplasty of Budd-Chiari syndrome caused by membranous obstruction of inferior vena cava: 8-year follow-up study.

OBJECTIVES: This study sought to report the long-term result (up to 8 years) of percutaneous transluminal balloon angioplasty (PTBA) for Budd-Chiari syndrome (BCS) caused by membranous obstruction of the inferior vena cava (MOVC). BACKGROUND: We previously reported on this nonoperative form of therapy in a smaller series of patients and found the short-term results to be excellent. METHODS: We studied the long-term results of PTBA in the treatment of BCS caused by MOVC in 42 patients who underwent PTBA with the Inoue balloon catheter between June 1988 and February 1996. There were 28 men and 14 women with a mean age of 35.6 years (range 16 to 56). MOVC was incomplete in 27 patients and complete in 15. PTBA was successful in 38 patients (91%). The longest follow-up period was 8 years. RESULTS: All 38 patients who successfully underwent PTBA showed marked symptomatic improvement. Immediately after PTBA, the diameter of the inferior vena cava at the MOVC increased from 1.7 +/- 2 to 19.9 +/- 3.5 mm (p < 0.0001), the caval pressure below the MOVC decreased from 23.6 +/- 8.5 to 12.0 +/- 6.5 mm Hg (p < 0.0001), and the enlarged liver size decreased from 6.5 +/- 1.5 to 2.0 +/- 1.5 cm below the right costal margin at the midclavicular line (p < 0.0001). Over a follow-up period of up to 8 years (7 to 8 years in 4 patients, 5 to 7 years in 12, 3 to 5 years in 11, 2 to 3 years in 6 and < 2 years in 9), MOVC returned in only 1 patient. This patient, our first, required a second PTBA 3 years later and a third 4.25 years after the second PTBA, in combination with stent placement for recurrence of stenosis. CONCLUSIONS: PTBA with the Inoue balloon catheter is an effective, safe and long-lasting alternative to surgical treatment of patients with BCS due to MOVC.

Adolescent↗
PubMed1996

Response sensitivity and voltage gain of the rod- and cone-horizontal cell synapses in dark- and light-adapted tiger salamander retina.

1. Rods, cones, and horizontal cells (HCs) were recorded in superfused, flat-mounted isolated retinas of the larval tiger salamander, Ambystoma tigrinum, under dark- and light-adapted conditions. 2. Under dark-adapted conditions, HC responses to dim 500-nm light stimuli were mediated only by rods. In the linear voltage range (near the dark potentials), the average response to a light step of 0.5 s (500 nm, 0.438 photons per micron2 per s) was 0.41 +/- 0.06 (SD) mV for rods and 1.86 +/- 0.52 mV for HCs. The step sensitivity of rods was approximately 0.94 mV per photon micron2 s, or 0.032 mV per activated rhodopsin molecule (Rh*) rod second, and the step sensitivity of HCs was approximately 4.25 +/- 1.19 mV per photon micron2 s or 0.14 +/- 0.04 mV per Rh* rod second. The chord voltage gain of the rod-HC synapse had an average value of 4.54 and a range from 2.68 to 7.32. 3. By the use of the spectral subtraction method, we found that the average cone-mediated HC response to a 750-nm light step that elicited an average cone response of 0.73 +/- 0.20 mV was 1.15 +/- 0.31 mV. The step sensitivity of cones under dark-adapted conditions was 0.0012 mV per photon micron2 s, and that of the cone-mediated-HC response was 0.0019 mV per photon micron2 s. The chord voltage gains of the cone-HC synapses under dark-adapted conditions had an average value of 1.58 and a range from 0.82 to 2.05. 4. Under light-adapted conditions (with a 500-nm/-2.40 background light, which desensitized rod responses but did not substantially reduce the cone responses), the cones had an average response to a light step of 0.5 s (500 nm/-3.3) of 0.78 +/- 0.09 mV, and this response did not vary with time. The HC response to the same light step had an average value of 3.95 +/- 3.41 mV 3 min after the background light onset, and it increased with time until reaching a steady-state value of 5.95 +/- 3.63 mV approximately 15 min after the background light onset. The average chord voltage gain of the cone-HC synapse under such light-adapted conditions was 5.06 at 3 min after background light onset and 7.63 at 15 min after background light onset. These values are approximately 3-5 times higher than the chord voltage gain of the cone-HC synapse under dark-adapted conditions. 5. The background-induced increase of the chord voltage gain of the cone-HC synapse suggests that similarly to the rod-HC synapse, the voltage gain of the cone-HC synapse in the tiger salamander retina can also be modulated by light. Additionally, our results suggest that certain time-dependent process(es) in the synaptic cleft or postsynaptic membrane may be responsible for such modulation. 6. In addition to determining the average values of response sensitivity and chord voltage gains of the rod- and cone-HC synapses, we studied the variation of these parameters among different HCs. HCs with higher rod-HC synaptic gain had lower cone-HC synaptic gain, and HCs with lower rod-HC synaptic gain exhibited higher cone-HC synaptic gain under both dark- and light-adapted conditions. This suggests that the rod-HC and cone-HC synaptic gains in HCs are complementary to each other, and voltage responses of all HCs under dark- or light-adapted conditions are of comparable amplitudes.

Adaptation, Physiological↗
PubMed1996

Relationship between CD44 expression and cell proliferation in epithelium and stroma of colorectal neoplasms.

The cell surface glycoprotein CD44 is expressed primarily in the region of cell replication in the lower crypt epithelium of colorectal mucosa, and its expression is markedly increased in colorectal neoplasms, suggesting that expression is linked to proliferation. The association between CD44 expression and replication in individual cells was therefore analyzed by double-label immunohistochemistry for CD44 and the cell-cycle-dependent protein proliferating cell nuclear antigen (PCNA). Enhanced expression of CD44 in colorectal neoplasms occurred not only in epithelial cells but also in stromal cells, including lymphocytes and macrophages. On a topographical basis, the cellular localization of CD44 and PCNA were commonly different. Quantitatively, in all cell types studied (epithelial cells and stroma of colorectal mucosa, adenomas, and carcinomas) PCNA was present most frequently in cells lacking CD44. Statistical analysis by logistic regression models indicated that cells negative for CD44 had a higher probability of being positive for PCNA than did cells positive for CD44 (P < 0.001). These data suggest that the enhanced level of CD44 in colorectal neoplasms is asynchronous with cell replication and reflects mechanisms that act on nonproliferative stromal lymphocytes and other mononuclear cells as well as the epithelial cells.

Adult↗
PubMed1996

[Differential effects of low calcium on signal transmission from rods and cones to horizontal cells in carp retina].

Intracellular recordings were made from neurons in the superfused isolated carp retina and the effects of calcium on synaptic transmission from cones and rods to horizontal cells were studied by changing the ionic composition of the external medium. When extracellular Ca2+ is lowered from 1.2 mmol/L to 0.1 mmol/L, both cone- and rod-horizontal cells (Cone-HC and Rod-HC) are depolarized, but light responsiveness of these cells are differentially affected: light responses of Cone-HCs are reduced in size, whereas those of Rod-HCs are significantly enhanced. In 0.1 mmol/L Ca2+, glutamate-isolated P III components, both photopic and scotopic, are enhanced, suggesting that the differential effects of low calcium on the horizontal cells must occur during signal transferring from photoreceptors to horizontal cells. Similar to the effect of 0.1 mmol/L Ca2+, phosphodiesterase inhibitor IBMX (50 mumol/L) is also capable of enhancing light responsiveness of both L-type Cone-HC and Rod-HC. These results suggest that the differential effects of low calcium on the two types of horizontal cells may be due to different changes in the calcium influx into the receptor terminals.

Animals↗
PubMed1995

[Novel GABAc receptors].

Considerable evidence has shown that there is a kind of special pharmacological GABA receptors in central nervous system, especially prominent along visual pathways. These receptors are neither antagonized by bicuculline nor activated by baclofen, but are activated selectively by the GABA analogue cis-4-aminocrotonic acid (CACA), its response did not show desensitization. These receptors have been termed GABAc receptors. It may play an important role in the visual information transmission and modulation of retinal rod pathway.

Animals↗
PubMed1995

Dietary survey in a Chinese population.

OBJECTIVES: To assess food pattern and nutrition profile aiming at planning population-based nutrition intervention for chronic diseases control. DESIGN: A randomized survey. SETTING: The survey was carried out in Tianjin, one of the three largest cities in China. SUBJECTS: 3683 subjects aged 15-64 years old were selected by a random stratified multilevel cluster sampling. INTERVENTION: The diet was assessed by food weighing plus consecutive individual 3 day food records. RESULTS: Distinct differences in dietary pattern and nutrient intakes were found between subjects living in urban and rural areas. The diet of urban people was richer in fat and high quality protein compared with the diet of rural people. Low intakes of vitamin A, calcium, riboflavin, and zinc were found in both areas, the situation being worse in the rural areas. The sodium intake and sodium:potassium ratio was very high in both areas. Cholesterol intake was much higher among the urban people. CONCLUSION: The study suggests that integrated nutrition intervention is needed to prevent insufficient intake of some nutrients and control dietary risk factors related to chronic diseases.

Adolescent↗
PubMed1995

Relationship between serum lipids and dietary and non-dietary factors in a Chinese population.

OBJECTIVES: To describe the distribution of serum lipids and examine the relationship between serum lipids and dietary and non-dietary factors. DESIGN: A randomised survey. SETTING: The survey was carried out in Tianjin, China. SUBJECTS: Altogether 680 subjects were screened. Forty-nine of those were excluded but 314 men and 317 women remained. INTERVENTION: The serum lipids were measured by enzymatic methods. The diet was assessed by food weighing plus consecutive individual 3-day food records. RESULTS: The mean cholesterol concentrations were 4.08 and 3.94 mmol/l in men and women respectively. The mean high-density lipoprotein cholesterol (HDL-C) levels were 1.24 and 1.35 mmol/l, and the mean triglyceride levels were 1.48 and 1.20 mmol/l. The energy intake derived from fat was approximately 29% (6.9% from saturated fat) and the polyunsaturates:saturates ratio of the diet was 1.3 in both sexes. Multiple regression analyses showed that no association was discovered between serum lipids and dietary variables. Age and body mass index (BMI) were strong and independent predictors of serum lipids in both sexes. BMI was positively related to serum total cholesterol, triglyceride and low-density lipoprotein cholesterol (LDL-C), and inversely related to HDL-C. Education was a predictor only in men. Men with a higher education had more coronary heart disease risk factors than men with lower education attainment. CONCLUSION: The Chinese have favourable serum lipid profiles and dietary fat pattern. No relationship was found between lipids and dietary variables, which warrants further studies because these relationships have not been investigated previously in any Chinese population.

Adolescent↗
PubMed1994

CD44 expression in colorectal adenomas is an early event occurring prior to K-ras and p53 gene mutation.

Neoplastic progression of colorectal epithelial cells from benign adenomas to malignant carcinomas appears to result from a series of genetic alterations involving both oncogenes and tumor suppressor genes. This progression was recently found to be associated with expression of splice variant isoforms of CD44, a cell surface hyaluronate receptor implicated in carcinogenesis. In this study we examined the relationship of CD44 expression to somatic genetic events in the adenoma-carcinoma sequence: point mutation of K-ras in codons 12 and 13 and overexpression of p53 protein as a marker of gene mutation. Among 22 small adenomas, CD44 was present in 9 (41%), of which only 1 contained a K-ras mutation. CD44 was absent in the other 2 small adenomas positive for K-ras mutation or p53 overexpression. In contrast to the early expression of CD44 in small adenomas, mutations of K-ras and p53 were detected preferentially in large adenomas and late-stage adenomas containing carcinoma. The frequent expression of CD44 prior to K-ras and p53 gene alterations in colorectal neoplasia suggests that activation of CD44 gene expression is related to earlier events in the adenoma-carcinoma sequence, possibly cell activation and proliferation following APC gene mutation or alteration of DNA methylation.

Adenoma↗
PubMed1994

Expression of CD44 in human lung tumors.

CD44 is an integral membrane glycoprotein that functions as a receptor for the extracellular matrix glycan, hyaluronan. Here we report that CD44 is a novel biomarker for non-small cell lung tumors, squamous metaplasia of the lung, and activated type II pneumocytes. We have examined the expression of CD44 in 12 human lung tumor cell lines and 23 fixed, paraffin-embedded lung cancers. CD44 transcription and translation is consistently high among non-small cell tumors (5 of 5 cell lines, 10 of 14 tumors) but rare in small cell tumors (1 of 6 cell lines, 0 of 9 tumors). In normal lung, CD44 was confined to the surface of bronchial basal cells and alveolar macrophages. Squamous metaplasia of the lung showed strong CD44 immunoreactivity. Resting type II pneumocytes were largely CD44 negative but rows of active, surfactant-secreting type II cells had significant amounts of CD44 located on lateral surfaces of adjacent cells. The correlation between CD44 and the non-small cell phenotype was further demonstrated in studies of a cultured small cell lung cancer line induced to exhibit characteristics of a non-small lung cancer by infection with v-Ha-ras. Following ras gen insertion, these cells showed a 40-fold increase in CD44 expression. The CD44 detected in lung cancer cells throughout these studies was predominantly the "standard" rather than the "variant" species. Taken together, these results suggest that CD44 is a protein expressed on non-small cell lung tumors, squamous metaplasia, and activated type II cells. In addition, CD44 in cultured small cell lung cancer cells is transcriptionally activated following differentiation by the ras oncogene. The fact that immunohistochemistry can be used to discriminate among the cell types makes CD44 a valuable new marker for lung neoplasia.

Antigens, Surface↗
PubMed1994

Effects of prolonged darkness on light responsiveness and spectral sensitivity of cone horizontal cells in carp retina in vivo.

Light responses of cone- and rod-driven horizontal cells were recorded intracellularly from opened eyes of intact, immobilized carp and the effects of prolonged darkness on these cells were examined. When the retina was left in the dark, responses of cone horizontal cells to a moderate test flash presented once every 10 min gradually and steadily decreased in size (dark suppression effect). Following a repetitive presentation of the test flash, the light responsiveness of the cells was enhanced. In contrast, the rod horizontal cells did not show the dark suppression effect and the light responsiveness of these cells increased in the dark. Effects of prolonged darkness on the spectral sensitivity of L-type and R/G-type cone horizontal cells were also studied. The spectral sensitivity of L-type cells, determined just after background illumination was extinguished, agreed reasonably well with that of red-sensitive (R-) cones, but it matched better that of green-sensitive (G-) cones when determined in prolonged darkness. We further show that depolarizing responses of R/G-type cone horizontal cells to long-wavelength flashes, driven by R-cones, were abolished after prolonged darkness. Taken together, these results suggest that input from R-cones converging onto the cone horizontal cells is more significantly suppressed after prolonged dark adaptation than input from G-cones. Due to the suppression of the R-cone input, enhancement of responses of the L-type cone horizontal cells to long-wavelength stimulation in the presence of a green background light was no longer seen after prolonged darkness.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Synaptic transmission from rods to rod-dominated bipolar cells in the tiger salamander retina.

Synaptic transmission between photoreceptors and bipolar cells was studied in dark-adapted tiger salamander retinas. Based on the relative light sensitivity, bipolar cells, either depolarizing (DBC) or hyperpolarizing (HBC), fell into two groups: one receives inputs primarily from rods (rod-dominated bipolar cells, DBCR and HBCR) and the other receives inputs primarily from cones (cone-dominated bipolar cells, DBCC and HBCC). The input-output relations of the rod-DBCR and rod-HBCR synapses were determined by plotting the voltage responses of the rod and DBCR (or HBCR) to dim 500-nm light steps, which polarizes only the rods but not the cones. The slope gains of both synapses were the highest near the dark rod voltage (-2.5 for the rod-DBCR synapse and 4.0 for the rod-HBCR synapse), and they (the absolute values) became progressively smaller at more hyperpolarized rod voltages.

Acclimatization↗
PubMed1993

Effects of GABA on horizontal cells in the tiger salamander retina.

Application of gamma-aminobutyric acid (GABA) slows down the horizontal cell response time course (HCRRT) and induces membrane depolarization in horizontal cells (HCs) after synaptic inputs are blocked by Co2+. We present evidence that suggests both effects are probably mediated by GABAA receptors which open chloride channels in the HC membrane. In any given concentration of GABA, ranged from 0 to 100 microM, the HC membrane potential (VHC) in saturating light and in the presence of 100 microM Co2+ are identical. This result suggests that GABA in both light and 100 microM Co2+ opens the same amount of chloride channels (same gCl) so that VHC determined by chloride and leak conductances has the same value. Higher concentrations of Co2+ (> 300 microM) not only blocks synaptic transmission from photoreceptors to HCs, but also acts as an antagonist that suppresses the GABA-mediated depolarization in HCs.

Ambystoma↗