Biomedical subjects

Z Guan

Publications and source records attributed to Z Guan.

118 records · Page 7Linked to original sources

PubMed1992

Changes of brain response induced by simulated weightlessness.

The characteristics change of brain response was studied during 15 degrees head-down tilt (HDT) comparing with 45 degrees head-up tilt (HUT). The brain responses evaluated included the EEG power spectra change at rest and during mental arithmetic, and the event-related potentials (ERPs) of somatosensory, selective attention and mental arithmetic activities. The prominent feature of brain response change during HDT revealed that the brain function was inhibited to some extent. Such inhibition included that the significant increment of "40Hz" activity during HUT arithmetic almost disappeared during HDT arithmetic, and that the positive-potential effect induced by HDT presented in all kinds of ERPs measured, but the slow negative wave reflecting mental arithmetic and memory process was elongated. These data suggest that the brain function be affected profoundly by the simulated weightlessness, therefore, the brain function change during space flight should be studied systematically.

Adolescent↗

PubMed1992

Activation of the phosphatidylinositol pathway in the primate corpus luteum by prostaglandin F2 alpha.

The current study was designed to investigate the ability of prostaglandin F2 alpha (PGF2 alpha) to activate a second messenger system (phosphatidylinositol pathway) in corpora lutea (CL) of rhesus monkeys. Activation of this pathway was assessed by monitoring the hydrolysis of phosphatidylinositol to inositol phosphates. Since inositol triphosphate mobilizes intracellular Ca2+, intracellular free calcium concentrations ([Ca2+]i) were also assessed in individual cells by fura-2 fluorescence photometry. These responses to PGF2 alpha were measured in luteal cells collected from nonpregnant rhesus monkeys. CL were collected during the early (days 4-5 after estimated LH surge; n = 4), mid (days 8-9; n = 4), and late (days 13-14; n = 5) luteal phase and 1 day after in vivo hCG treatment (15 IU/dose, morning and evening), which began during the midluteal phase (n = 5). PGF2 alpha significantly increased the accumulation of inositol phosphates in all groups (P less than 0.05), except the midluteal phase (P = 0.07). The luteal sensitivity to PGF2 alpha, judged by phosphatidylinositol hydrolysis, was low in the early to midluteal phase compared to that in the late luteal phase and after in vivo hCG treatment. PGF2 alpha also caused a rapid, yet transient, increase in [Ca2+]i in a large proportion of primate luteal cells. The proportion of luteal cells that responded to PGF2 alpha with an increase in [Ca2+]i was smaller (P less than 0.05) in CL collected during the early luteal phase than in the other groups. Luteal progesterone production was inhibited by PGF2 alpha in CL collected after in vivo hCG. CL treated in vivo with hCG also displayed in vitro the largest increases in phosphatidylinositol hydrolysis and [Ca2+]i in response to PGF2 alpha. Therefore, this study demonstrates that PGF2 alpha is a potent activator of the phosphatidylinositol pathway in the primate CL. This activation is augmented as the luteal phase progresses and is influenced by in vivo hCG treatment. This study also provides evidence that the inhibitory effects of PGF2 alpha on progesterone production are associated with the activation of the phosphatidylinositol pathway.

Animals↗

PubMed1992

[Convergence insufficiency and asthenopia].

22 cases with convergence insufficiency (CI) were presented here. It is found that there was an important relationship between CI and asthenopia. The causes clinical findings, diagnostic criteria, treatment of CI and relation with asthenopia were discussed.

Adolescent↗

PubMed1991

Determination of Fura-2 dissociation constants following adjustment of the apparent Ca-EGTA association constant for temperature and ionic strength.

The accurate calibration of Fura-2 fluorescence in living cells is dependent upon the apparent dissociation constant (Kd) of Fura-2 for Ca2+. If Ca-EGTA calibration buffers are used to construct an in vitro calibration curve, then the calculated value of the apparent Ca-EGTA association constant (K'CaEGTA) will have an important influence on the Kd of Fura-2 and thus the calculated free [Ca2+] in cells. In order to simulate experimental conditions, the individual proton and Ca2+ association constants for EGTA in these experiments were adjusted for both ionic strength and temperature using a semi-empirical form of the Debye-Huckel limiting law and the Van't Hoff isochore, respectively, as described by Harrison and Bers. The modified individual binding constants were then employed in the calculation of K'CaEGTA using the SPECS computer program of Fabatio. At pH = 7.05, ionic strength = 0.15 M, temp = 20 degrees C, K'CaEGTA = 3.232 x 10(6) M-1; at pH = 6.84, temp = 36 degrees C, K'CaEGTA = 1.652 x 10(6) M-1. These values differed substantially from those obtained with unadjusted individual association constants. Calibration buffers of varying [Ca2+] were prepared using the corrected values of K'CaEGTA, and Fura-2 fluorescence ratios were measured during superfusion of these buffers in the experimental chamber at both 20 degrees C and 37 degrees C. The Kd of Fura-2 for Ca2+ was determined to be 236 nM at 20 degrees C and 285 nM at 37 degrees C, utilizing the value of K'CaEGTA adjusted by the method of Harrison and Bers.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗

PubMed1991

The effects of elevation and depletion of intracellular free calcium on progesterone and prostaglandin production by the primate corpus luteum.

The role of the phosphatidylinositol second messenger system in luteal regulation has not been extensively studied, particularly in the primate. The objectives of this study were (1) to further characterize the response of the primate CL to the calcium ionophore A23187, in terms of intracellular free calcium concentrations ([Ca2+]i) and progesterone (P) production; and (2) to assess the effects of depleting, as well as elevating, available calcium on luteal P and prostaglandin (PG) production. The response to A23187, in terms of [Ca2+]i, was measured by fura-2 fluorescence microscopy of single small and large luteal cells. A23187 significantly increased [Ca2+]i in both cell types (p less than 0.01). P production (basal and hCG-stimulated) by dispersed primate luteal cells incubated for various times (1-8 h) with and without A23187 was measured. Treatment with A23187 rapidly (within 1-2 h) attenuated (p less than 0.05) the time-dependent increase in basal and hCG-stimulated P production. Luteal P and PG production following treatment with the calcium ionophore, ionomycin, alone or in combination with additional CaCl2, was also monitored. Treatment with ionomycin (p less than 0.01) and CaCl2 (p less than 0.01) inhibited luteal P production. In contrast, treatment with ionomycin stimulated (p less than 0.01) luteal PG production. To determine the effects of Ca2+ depletion on luteal function, P and PG production by cells incubated for 2 and 8 h in the absence and presence of the Ca(2+)-chelator EGTA was measured. Luteal production of both P and PG was inhibited by 8-h treatment with EGTA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

[Obliterative peripheral retinal vascular disease in children].

Obliterative peripheral retinal vascular disease in children is a rare disease. Only 4 cases had been reported abroad. No case of this disease was reported in China before. This paper reported a 13-year-old girl suffering from this disease in both eyes. Neovascular glaucoma of her left eye has developed and that of her right eye was still in early stage. Fluorescein angiography changes, diagnosis and differential diagnosis, pathogenesis and treatment of the disease were discussed.

Adolescent↗

PubMed1990

A case of hemolytic disease of the newborn caused by anti-Hro and anti-e.

A Chinese woman of blood group B, D- and her husband of blood group AB, CCDee were examined. The woman had not been transfused before. Their first two babies died. Anti-Hro and anti-e were found in the mother's serum. During her third pregnancy, the titer of antibodies went up quickly, approximately one titer per month. After 36 weeks of pregnancy, the baby was delivered by Caesarean section. The cord blood Hb was 88 g/L, his red blood cell count 2.7 x 10(12)/L, and total bilirubin 114.6 mol/L. The baby was of blood group AB, and CDe-D-genotype. Exchange transfusion was begun 2.5 hours after birth. O, ccDEE washed red cells together with group AB plasma were used. Two days later, 70 ml washed O, ccDEE concentrated red cells were administered. The baby is alive and in good health.

Erythroblastosis, Fetal↗

PubMed1989

Hyperthyroid adult rat cardiomyocytes. II. Single cell electrophysiology and free calcium transients.

The effects of hyperthyroidism on electrophysiological properties and intracellular free calcium transients in single adult rat cardiomyocytes were studied using conventional microelectrodes and time-resolved single cell fura-2 fluorescence microscopy. Under control conditions, resting membrane potentials and triggered action potentials were not different in euthyroid and hyperthyroid myocytes. Calcium transients produced by electrical stimulation, however, were markedly abbreviated in hyperthyroid myocytes. During a train of stimuli, the duration of the calcium transients at half peak amplitude (half time) was 124 +/- 14 ms at the fifth beat in hyperthyroid cells vs. 287 +/- 35 ms in euthyroid cells. Isoproterenol (1 microM) prolonged time to 50% repolarization (APD50) of the action potentials and increased the peak calcium transients in both euthyroid and hyperthyroid myocytes. It also shortened the half time of the calcium transients in euthyroid myocytes but had little effect on the half time in hyperthyroid cells. These data are consistent with the electrophysiology and mechanical performance in intact euthyroid and hyperthyroid cardiac tissues, and the intrinsic changes in hyperthyroid tissues can therefore be illustrated in single ventricular myocytes. Furthermore, the results suggest that alterations in intracellular calcium handling by sarcoplasmic reticulum may account for contractile changes of the heart induced by hyperthyroidism.

Action Potentials↗

PubMed1985

Acinetobacter calcoaceticus septicemia in patients with cancer.

At our institution, 95 cases of Acinetobacter septicemia occurred over a ten-year period (1973 to 1982) in patients being treated for cancer. In 24 patients the infection was polymicrobial, while Acinetobacter ssp was the only offending pathogen in 71 patients. In 76 patients (80%), the infection was related to an indwelling central venous catheter (CVC). A sharp increase in the frequency of Acinetobacter septicemia was noticed in the years 1981 and 1982 and coincided with a marked increase in the number of indwelling CVCs in use. Acute leukemia and breast cancer were the malignancies most commonly associated with Acinetobacter septicemia. The isolates of Acinetobacter calcoaceticus from the patients in this study were highly susceptible to the aminoglycosides and moderately susceptible to trimethoprim-sulfamethoxazole (TMP-SMX), carbenicillin, and tetracycline. Seventy-nine patients recovered from their infection with removal of the CVC and antimicrobial chemotherapy. Acinetobacter sp was the cause of death in none of the 16 patients who died. A calcoaceticus is an important nosocomial pathogen causing infections predominantly in immune compromised patients and frequently associated with indwelling catheters.

Acinetobacter Infections↗

PubMedDate not supplied

Effect of hemostatic agents in canine gastric serosal blood vessels.

The efficacy of various sclerotherapeutic agents in the control of acute bleeding, via subserosal injection, was assessed in 10 dogs. Blood flow rate (BFR) from severed gastric serosal vessels (diameter, 1.6 to 2.2 mm) was measured for 3 min (ml/min) for a control group and the agent used. The agents tested were 5 ml of normal saline (NS), 5 ml of 3% hypertonic saline (HS), 5 ml of 1:10,000 epinephrine in NS, 5 ml of 1:10,000 epinephrine/HS, 5 ml of 1:20,000 epinephrine/HS, 2 ml of old thrombin "cocktail" (thrombin, cephapirin + 1% tetradecyl), and 2 ml of fresh thrombin cocktail (total seven). One agent was tested per dog; there were one to two dogs in each subgroup. All of the agents showed significant reduction in BFR (except old thrombin) when compared with BFR of control vessels. The reduction ranged from 30% to more than 75% after 1:10 epinephrine/HS. Complete hemostasis was achieved in up to 47% of vessels using 1:20 epinephrine/HS. Overall, the epinephrine solutions achieved the best results. No systemic effects were observed with the use of any of the agents. Histological studies showed that epinephrine caused mild tissue damage, whereas the cocktail caused significant tissue necrosis. This serosal vessel model permits comparison of the effectiveness of each agent; however, clinical extrapolation to mucosal vessels in a patient and the long-term histological changes are not known.

Animals↗