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Biomedical subjects

Y Cai

Publications and source records attributed to Y Cai.

At least 91 records · Page 5Linked to original sources
PubMed2000

An electrical admittance based index of thoracic intracellular water during head-up tilt in humans.

During 50 degrees head-up tilt (HUT), the number of erythrocytes within the thorax has been shown to be reduced by approximately 25% and this level is retained during a maintained tilt, whilst that in the thigh increases by approximately 70%. To evaluate whether the electrical admittance of intracellular water (ICW) may be used to monitor this redistribution of red cells in humans, we determined the regional difference in the reciprocal value of the impedance at 1.5 and 100 kHz for the thorax (thoraxICW) and for the leg (legICW). In ten subjects all variables remained unchanged during head-down tilt but during HUT, presyncopal symptoms were induced in eight subjects after a mean of 27 (SEM 7) min as mean heart rate dropped from 85 (SEM 4) to 66 (SEM 3) beats x min(-1), mean arterial blood pressure from 80 (SEM 3) to 60 (SEM 5) mmHg, and mean oxygen saturation of venous blood from 76 (SEM 2)% to 73 (SEM 3)% (P < 0.05). The mean haematocrit increased from 50 (SEM 5)% to 52.5 (SEM 3.5)% (P < 0.01) and mean central venous pressure decreased during tilting (from a mean of 1 (SEM 1) to a mean of -1 (SEM 1) mmHg; P < 0.05) and returned to value at rest during the maintained tilt. Mean thoracic impedances increased by 7.0 (SEM 1.0) ohms (1.5 kHz) and 5.4 (SEM 1.2) ohms (100 kHz), and mean leg impedances decreased by 9.3 (SEM 1.2) ohms (1.5 kHz) and 3.1 (SEM 1.0) ohms (100 kHz) (P < 0.01). Mean thoraxICW decreased at 40 degrees HUT and remained reduced by 11 (SEM 2) S x 10(-4) (P < 0.05) until the presyncopal symptoms developed, at which time it was lower by 16 (SEM 2) S x 10(-4) (P < 0.01). Mean legICW increased from 97 (SEM 15) to 99 (SEM 15) S x 10(-4) (P = 0.08) during HUT but decreased during maintained tilt (to 94 (SEM 15) S x 10(-4); P < 0.05). The results suggested that during HUT, the difference in electrical admittance at a high and a low frequency current reflects the reduced number of red cells within the thorax.

Adult↗
PubMed2000

Influence of temperature on the distribution of blood in humans as assessed by electrical impedance.

This study investigated whether ambient temperature influences the distribution of blood as indicated by electrical impedance. In ten supine humans, the room temperature was raised from 14 to 35 degrees C. Skin temperature and blood flow on the thorax increased by 3.6 (SD 0.3) degrees C and 84 (SD 40)%, respectively, and by 9.8 (SD 1) degrees C and 115 (SD 45)%, respectively, on the extremities (P < 0.05). Cardiac output remained unchanged, ear temperature and heart rate became elevated, and the oesophageal temperature and mean arterial pressure decreased (P < 0.05). At five discrete frequencies (1.5. 5, 50, 100, 200 kHz) thoracic impedance was increased by 1.2 (SD 1) to 1.5 (SD 1) omega (P < 0.05). In contrast, total body impedance was reduced by 16.4 (SD 5) omega and leg impedance was reduced by 4.0 (SD 2) omega, while an index of intracellular water within the thorax (the difference between the admittances at 100 kHz and 1.5 kHz) was decreased by 10 (SD 1) x 10(-4)S (P < 0.05). The results would suggest that total body impedance is dominated by the impedance of the extremities. The increase in thoracic impedance and a decrease in leg impedance (as in total body impedance) could be explained by a redistribution of blood from the thorax to the extremities during heating. Such a translocation of blood was confirmed by a reduced impedance based index of intracellular water within the thorax.

Adult↗
PubMed2000

Twin-to-twin transfusion syndrome. Role of the fetal renin-angiotensin system.

The twin-to-twin transfusion syndrome (TTS) results from an unbalanced blood supply through placental anastomoses in monochorionic twins. It induces growth restriction, renal tubular dysgenesis, and oliguria in the donor and visceromegaly and polyuria in the recipient. A better understanding of its pathophysiology could contribute to improving the management of TTS, which still carries a high perinatal mortality in both twins. As well as several other candidates, the renin-angiotensin system might be involved in TTS. To evaluate its role in the pathogenesis of the syndrome, we studied the kidneys of 21 twin pairs who died from TTS at 19 to 30 weeks, compared with 39 individuals in a control group, using light microscopy, immunohistochemistry, and in situ hybridization. The overexpression of the renin protein and transcript with frequent evidence of renin synthesis by mesangial cells was observed in the donor kidneys, presumably as a consequence of chronic renal hypoperfusion. This upregulation of renin synthesis might be beneficial to restore euvolemia. In severe cases of TTS, however, angiotensin-II-induced vasoconstriction acts as an additional deleterious factor by further reducing the renal blood flow in donors. In recipients, renin expression was virtually absent, possibly because it was down-regulated by hypervolemia. However, in addition to congestion and hemorrhagic infarction, there were severe glomerular and arterial lesions resembling those observed in polycythemia- or hypertension-induced microangiopathy. We speculate that fetal hypertension in the recipient might be partly mediated by the transfer of circulating renin produced by the donor, through the placental vascular shunts.

Female↗
PubMed2000

Glomerular expression of type IV collagen chains in normal and X-linked Alport syndrome kidneys.

Alport syndrome is an inherited nephropathy characterized by alterations of the glomerular basement membrane because of mutations in type IV collagen genes. COL4A5 mutations, causing X-linked Alport syndrome, frequently result in the loss of the alpha5 chains of type IV collagen in basement membranes. This is associated with the absence of the alpha3(IV) and alpha4(IV) chains and increased amounts of alpha1(IV) and alpha2(IV) in glomerular basement membranes. The mechanisms resulting in such a configuration are still controversial and are of fundamental importance for understanding the pathology of the disease and for considering gene therapy. In this article we studied, for the first time, type IV collagen expression in kidneys from X-linked Alport syndrome patients, using in situ hybridization and immunohistochemistry. We show that, independent of the type of mutation and of the level of COL4A5 transcription, both COL4A3 and COL4A4 genes are actively transcribed in podocytes. Moreover, using immunofluorescence amplification, we were able to demonstrate that the alpha3 chain of type IV collagen was present in the podocytes of all patients. Finally, the alpha1(IV) chain, which accumulates within glomerular basement membranes, was found to be synthesized by mesangial/endothelial cells. These results strongly suggest that, contrary to what has been found in dogs affected with X-linked Alport syndrome, there is no transcriptional co-regulation of COL4A3, COL4A4, and COL4A5 genes in humans, and that the absence of alpha3(IV) to alpha5(IV) in glomerular basement membranes in the patients results from events downstream of transcription, RNA processing, and protein synthesis.

Adolescent↗
PubMed2000

Inhibition of xanthine oxidase by some Chinese medicinal plants used to treat gout.

The enzyme xanthine oxidase catalyses the oxidation of hypoxanthine to xanthine and then to uric acid, which plays a crucial role in gout. A total of 122 traditional Chinese medicinal plants, selected according to the clinical efficacy and prescription frequency for the treatment of gout and other hyperuricemia-related disorders, have been evaluated for the enzyme inhibitory activity. Among the 122 methanol extracts derived from these species, 69 were shown to be inhibitory at 100 microg/ml, with 29 having greater than 50% inhibition. As to the equal amount of water extracts, 40 were disclosed to be active at 100 microg/ml, with 13 possessing more than 50% inhibition. At 50 microg/ml, 58 methanol and 24 water extracts exhibited inhibitory activity, with 15 of the former and two of the latter showing greater than 50% inhibition. The most active was the methanol extract of the twig of Cinnamomum cassia (Lauraceae) (IC(50), 18 microg/ml), which was followed immediately by those of the flower of Chrysanthemum indicum (Asteraceae) (IC(50), 22 microg/ml) and the leaves of Lycopus europaeus (Lamiatae) (IC(50), 26 microg/ml). Among the water extracts, the strongest inhibition of the enzyme was observed with that of the rhizome of Polygonum cuspidatum (Polygonaceae) (IC(50), 38 microg/ml). The IC(50) value of allopurinol used as a positive control was 1.06 microg/ml. The study demonstrated that the effects for these medicinal plants used for the gout treatment were based, at least in part, on the xanthine oxidase inhibitory action.

Enzyme Inhibitors↗
PubMed2000

Accurate monitoring of blood loss: thoracic electrical impedance during hemorrhage in the pig.

BACKGROUND: Cardiovascular variables are closely regulated in that they remain relatively stable during minor hemorrhage. We considered that such stability would make these variables less accurate for monitoring a blood loss. In contrast, thoracic electrical impedance would be unlikely to be a regulated variable and could serve as a non-invasive monitor of a volume deficit. METHODS: In 10 pigs bled (0-24 ml kg(-1)) and retransfused (to 28 ml kg(-1)) during halothane anesthesia, the magnitude of the electrical impedance, cardiovascular, blood gas and temperature variables, atrial natriuretic peptide and near infrared spectroscopy of the leg muscles were recorded. RESULTS: During hemorrhage and retransfusion, the median correlations between changes in the magnitude of the thoracic impedance and the external blood loss ranged from 0.97 to 0.98 with an individual range from 0.80 to 1.0. These correlation coefficients were higher and their ranges were lower than correlations established for any other measured parameter. CONCLUSION: During hemorrhage and retransfusion in the halothane anesthetized pig, a change in the magnitude of thoracic electrical impedance appears to be an accurate and also non-invasive monitor of a blood volume deficit.

Anesthesia, Inhalation↗
PubMed2000

Cardiac defects and renal failure in mice with targeted mutations in Pkd2.

PKD2, mutations in which cause autosomal dominant polycystic kidney disease (ADPKD), encodes an integral membrane glycoprotein with similarity to calcium channel subunits. We induced two mutations in the mouse homologue Pkd2 (ref.4): an unstable allele (WS25; hereafter denoted Pkd2WS25) that can undergo homologous-recombination-based somatic rearrangement to form a null allele; and a true null mutation (WS183; hereafter denoted Pkd2-). We examined these mutations to understand the function of polycystin-2, the protein product of Pkd2, and to provide evidence that kidney and liver cyst formation associated with Pkd2 deficiency occurs by a two-hit mechanism. Pkd2-/- mice die in utero between embryonic day (E) 13.5 and parturition. They have structural defects in cardiac septation and cyst formation in maturing nephrons and pancreatic ducts. Pancreatic ductal cysts also occur in adult Pkd2WS25/- mice, suggesting that this clinical manifestation of ADPKD also occurs by a two-hit mechanism. As in human ADPKD, formation of kidney cysts in adult Pkd2WS25/- mice is associated with renal failure and early death (median survival, 65 weeks versus 94 weeks for controls). Adult Pkd2+/- mice have intermediate survival in the absence of cystic disease or renal failure, providing the first indication of a deleterious effect of haploinsufficiency at Pkd2on long-term survival. Our studies advance our understanding of the function of polycystin-2 in development and our mouse models recapitulate the complex human ADPKD phenotype.

Animals↗
PubMed2000

Middle cerebral artery blood velocity during exercise with beta-1 adrenergic and unilateral stellate ganglion blockade in humans.

A reduced ability to increase cardiac output (CO) during exercise limits blood flow by vasoconstriction even in active skeletal muscle. Such a flow limitation may also take place in the brain as an increase in the transcranial Doppler determined middle cerebral artery blood velocity (MCA V(mean)) is attenuated during cycling with beta-1 adrenergic blockade and in patients with heart insufficiency. We studied whether sympathetic blockade at the level of the neck (0.1% lidocaine; 8 mL; n=8) affects the attenuated exercise - MCA V(mean following cardio-selective beta-1 adrenergic blockade (0.15 mg kg(-1) metoprolol i.v.) during cycling. Cardiac output determined by indocyanine green dye dilution, heart rate (HR), mean arterial pressure (MAP) and MCA V(mean) were obtained during moderate intensity cycling before and after pharmacological intervention. During control cycling the right and left MCA V(mean) increased to the same extent (11.4 +/- 1.9 vs. 11.1 +/- 1.9 cm s(-1)). With the pharmacological intervention the exercise CO (10 +/- 1 vs. 12 +/- 1 L min(-1); n=5), HR (115 +/- 4 vs. 134 +/- 4 beats min(-1)) and delta MCA V(mean) (8.7 +/- 2.2 vs. 11.4 +/- 1.9 cm s(-1) were reduced, and MAP was increased (100 +/- 5 vs. 86 +/- 2 mmHg; P < 0.05). However, sympathetic blockade at the level of the neck eliminated the beta-1 blockade induced attenuation in delta MCA V(mean) (10.2 +/- 2.5 cm s(-1)). These results indicate that a reduced ability to increase CO during exercise limits blood flow to a vital organ like the brain and that this flow limitation is likely to be by way of the sympathetic nervous system.

Adolescent↗
PubMed2000

Identification and enumeration of oleic acid and linoleic acid hydrating bacteria in the rumen of sheep and cows.

The diversity and population densities of facultative anaerobic bacteria with the capacity to hydrate oleic acid and linoleic acid in the rumen of sheep and dairy cows were determined. The screening of representative colonies, from rumen fluid plated aerobically on a range of agar media, revealed that sheep rumen fluid contained hydration-positive strains of Streptococcus, Staphylococcus, Enterococcus, Lactobacillus and Pediococcus, whereas cow rumen fluid contained hydration-positive strains of Streptococcus, Lactobacillus and Staphylococcus. Mean counts of facultative anaerobic bacteria in sheep and cattle rumen were log10 7.29 and log10 6.40, respectively, and were independent of diet. Approximately 56% of facultative anaerobic bacteria were able to hydrate oleic and/or linoleic acid in anaerobic broth culture. For both sheep and cows, the most numerous hydration-positive isolates were strains of Strep. bovis. The results, which are the first to show that pediococci have the capacity to hydrate unsaturated fatty acids, suggest that lactic acid bacteria are the major unsaturated fatty acid hydrating bacteria in the rumen.

Animals↗
PubMed2000

Decreased expression of SPRR3 in Chinese human oesophageal cancer.

cDNA fragments that were differentially expressed between human oesophageal carcinomas and matched normal adjacent mucosa were isolated using an improved mRNA differential display technique. One of them was identified as the 3'-untranslated region of SPRR3 and was homologous to the esophagin cDNA. Northern blot, dot blot and reverse transcription-polymerase chain reaction (RT-PCR) analyses revealed that SPRR3 expression was lost in three cell lines of oesophageal carcinoma and was dramatically decreased in 54 out of 57 primary oesophageal carcinomas compared with adjacent normal mucosa. Esophagin has been shown to be down-regulated in western oesophageal carcinomas. The data suggest that esophagin is probably the protein product of the gene SPRR3 and that altered mRNA expression of SPRR3/esophagin is a frequent event in the development of Chinese oesophageal cancer.

3' Untranslated Regions↗
PubMed2000

Bifidobacterium lactis Meile et al. 1997 is a subjective synonym of Bifidobacterium animalis (Mitsuoka 1969) Scardovi and Trovatelli 1974.

Bifidobacterium lactis JCM 10602T (T = type strain) and Bifidobacterium animalis JCM 1190T were found to be phenotypically similar. These strains were subjected to investigation of their genetic relationships. The 16S rRNA sequence of B. animalis JCM 1190T was aligned with that of other Bifidobacterium species. B. animalis and B. lactis were the most closely related species in the phylogenetic tree and showed a high similarity in sequences (98.8%). The levels of DNA-DNA hybridization between the type strains of B. lactis and B. animalis ranged from 85.5 to 92.3%, showing that they represent a single species. It is proposed that B. lactis should be considered as a junior subjective synonym of B. animalis.

Bifidobacterium↗
PubMed2000

Hepatocyte-specific mutation establishes retinoid X receptor alpha as a heterodimeric integrator of multiple physiological processes in the liver.

A large number of physiological processes in the adult liver are regulated by nuclear receptors that require heterodimerization with retinoid X receptors (RXRs). In this study, we have used cre-mediated recombination to disrupt the mouse RXRalpha gene specifically in hepatocytes. Although such mice are viable, molecular and biochemical parameters indicate that every one of the examined metabolic pathways in the liver (mediated by RXR heterodimerization with PPARalpha, CARbeta, PXR, LXR, and FXR) is compromised in the absence of RXRalpha. These data demonstrate the presence of a complex circuitry in which RXRalpha is integrated into a number of diverse physiological pathways as a common regulatory component of cholesterol, fatty acid, bile acid, steroid, and xenobiotic metabolism and homeostasis.

Animals↗
PubMed2000

Electrical admittance for filling of the heart during lower body negative pressure in humans.

To evaluate whether electrical admittance of intracellular water is applicable for monitoring filling of the heart, we determined the difference in intracellular water in the thorax (Thorax(ICW)), measured as the reciprocal value of the electrical impedance for the thorax at 1.5 and 100 kHz during lower body negative pressure (LBNP) in humans. Changes in Thorax(ICW) were compared with positron emission tomography-determined C(15)O-labeled erythrocytes over the heart. During -40 mmHg LBNP, the blood volume of the heart decreased by 21 +/- 3% as the erythrocyte volume was reduced by 20 +/- 2% and the plasma volume declined by 26 +/- 2% (P < 0.01; n = 8). Over the heart region, LBNP was also associated with a decrease in the technetium-labeled erythrocyte activity by 26 +/- 4% and, conversely, an increase over the lower leg by 92 +/- 5% (P < 0.01; n = 6). For 15 subjects, LBNP increased thoracic impedance by 3.3 +/- 0.3 Omega (1.5 kHz) and 3.0 +/- 0.4 Omega (100 kHz), whereas leg impedance decreased by 9.0 +/- 3.3 Omega (1.5 kHz) and 6.1 +/- 3 Omega (100 kHz; P < 0.01). Thorax(ICW) was reduced by 7.1 +/- 1.9 S. 10(-4) (P < 0.01) and intracellular water in the leg tended to increase (from 37.8 +/- 4.6 to 40.9 +/- 5.0 S. 10(-4); P = 0.08). The correlation between Thorax(ICW) and heart erythrocyte volume was 0.84 (P < 0.05). The results suggest that thoracic electrical admittance of intracellular water can be applied to evaluate changes in blood volume of the heart during LBNP in humans.

Adult↗
PubMed2000

Contributions of ion conductances to the onset responses of octopus cells in the ventral cochlear nucleus: simulation results.

The onset response pattern displayed by octopus cells has been attributed to intrinsic membrane properties, low membrane impedance, and/or synaptic inputs. Although the importance of a low membrane impedance generally is acknowledged as an essential component, views differ on the role that ion channels play in producing the onset response. In this study, we use a computer model to investigate the contributions of ion channels to the responses of octopus cells. Simulations using current ramps indicate that, during the "ramp-up" stage, the membrane depolarizes, activating a low-threshold K(+) channel, K(LT), which increases membrane conductance and dynamically increases the current required to evoke an action potential. As a result, the model is sensitive to the rate that membrane potential changes when initiating an action potential. Results obtained when experimentally recorded spike trains of auditory-nerve fibers served as model inputs (simulating acoustic stimulation) demonstrate that a model with K(LT) conductance as the dominant conductance produces realistic onset response patterns. Systematically replacing the K(LT) conductance by a h-type conductance (which corresponds to a hyperpolarization-activated inward rectifier current, I(h)) or by a leakage conductance reduces the model's sensitivity to rate of change in membrane potential, and the model's response to "acoustic stimulation" becomes more chopper-like. Increasing the h-type conductance while maintaining a large K(LT) conductance causes an increase in threshold to both current steps and acoustic stimulation but does not significantly affect the model's sensitivity to rate of change in membrane potential and the onset response pattern under acoustic stimulation. These findings support the idea that K(LT), which is activated during depolarization, is the primary membrane conductance determining the response properties of octopus cells, and its dynamic role cannot be provided by a static membrane conductance. On the other hand, I(h), which is activated during hyperpolarization, does not play a large role in the basic onset response pattern but may regulate response threshold through its contribution to the membrane conductance.

Acoustic Stimulation↗
PubMed2000

Dysregulated expression of ebaf, a novel molecular defect in the endometria of patients with infertility.

We recently described the expression of ebaf, a novel member of the transforming growth factor-beta superfamily in human endometrium. ebaf messenger ribonucleic acid was expressed in late secretory and menstrual endometria. Here, we show that ebaf is secreted as 42-, 34-, 28-, and 14-kDa proteins into the conditioned medium of transfected cells, endometrial fluid, and serum. The amount of secreted proteins was markedly reduced during the implantation window in the endometria and sera of normal fertile subjects. The expression of ebaf was dysregulated in the endometria of a subset of women with infertility during the receptive phase of the menstrual cycle. Abundant secreted protein was present in the endometria of these women during the implantation window. During the critical period of endometrial receptivity, ebaf protein was more abundant in patients with endometriosis who did not conceive than in patients who became pregnant. These findings show that ebaf is a secreted product and is released into body fluids. Some types of infertility are associated with dysregulated expression of ebaf in human endometrium, suggesting that a molecular defect in uterine receptivity may be identified using such a marker protein.

Adult↗
PubMed2000

[The role of membrane-type 1 matrix metalloproteinase in the invasion and metastasis of hepatocellular carcinoma].

OBJECTIVE: To study the role of membrane-type 1 matrix metalloproteinase (MT(1)-MMP) in the invasion and metastasis of hepatocellular carcinoma (HCC), and find a method to judge the invasion and metastasis of HCC through MT(1)-MMP. METHODS: RT-PCR was used to study the expression of MT(1)-MMP mRNA in the HCC and in HCC nude mice model with higher metastasis potential (LCI-D20) and lower metastasis potential (LCI-35), and statistical methods were used to analyse the association between the expression of MT(1)-MMP mRNA and the pathological indexes of HCC. RESULTS: MT(1)-MMP mRNA was expressed by all the normal liver tissue (1.12 +/- 0.73), HCC (3.51 +/- 0.97), surrounding liver parenchyma (1.19 +/- 0.57), tumor embolus, and HCC nude mice model with LCI-D20, LCI-D35. The overexpression of MT(1)-MMP mRNA in HCC, embolus, LCI-D20 was related to the invasion and metastasis of HCC. The expression of MT(1)-MMP mRNA in HCC being higher than that in surrounding liver parenchyma was an important index to judge the invasion and metastasis of the HCC. CONCLUSION: MT(1)-MMP is related to the invasion and metastasis of HCC. The expression of MT(1)-MMP mRNA in HCC being higher than that in surrounding liver parenchyma could be acted as an important index to judge the invasion and metastasis of HCC.

Animals↗
PubMed2000

Studies of MAL gene in human esophageal cancer by RNA in situ hybridization.

OBJECTIVE: To observe the expression of MAL gene mRNA in esophageal cancer tissue and adjacent epithelial mucosa. METHODS: Non-radioactive RNA in situ hybridization. RESULTS: MAL gene was expressed in all epithelia of 33 matched samples but only in 8 of esophageal cancer tissues. Differential expression between esophageal cancer tissues and adjacent epithelia was not related to clinical parameters. CONCLUSION: Down-regulation of MAL may be an important event in the development of esophageal cancer.

Down-Regulation↗