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Biomedical subjects

Z Guan

Publications and source records attributed to Z Guan.

At least 109 records · Page 6Linked to original sources
PubMed1995

Zaprinast accelerates recovery from established acute renal failure in the rat.

Atrial natriuretic factor (ANF) has been demonstrated to be effective in the treatment of acute renal failure (ARF) in both rat and humans. The biological effects of ANF are presumed to be mediated by the generation of intracellular 3',5'-cyclic guanosine monophosphate (cGMP). Therefore, the current investigation examined whether zaprinast (M&B 22948), a guanosine 3',5'-cyclic monophosphate (cGMP)-specific phosphodiesterase inhibitor, would be effective in the treatment of established acute renal failure in the rat. Acute renal failure was induced by 60 minutes of bilateral renal artery clamping. Twenty-four hours after the ischemic insult, rats received either vehicle (5% Dextrose), zaprinast (0.03 or 0.3 mg/kg/min) or ANF24 (0.2 micrograms/kg/min) intravenously for four hours. Renal function, as measured by daily serum creatinine (days 1 to 7) and day 2 inulin clearances, was dramatically improved by zaprinast but not ANF treatment. Forty-eight hours post-renal ischemia, glomerular filtration rate (GFR) was 0.14 +/- 0.04 (ml/min/100 g body wt) in the vehicle and 0.94 +/- 0.29 in the zaprinast treated animals. To evaluate the mechanism by which zaprinast accelerated renal recovery, we measured regional blood flow in the postischemic rat kidneys during drug treatment with a laser doppler flowmeter. Both high and low dose zaprinast significantly increased cortical (17%) and outer medullary blood flow (40% and 60%), an effect not seen with ANF. In summary, zaprinast is effective in the treatment of established ischemic ARF. The mechanism by which zaprinast accelerates renal recovery is due to its unique ability to stimulate regional renal blood flow and increase intracellular cGMP in the setting of tissue ischemia.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1995

A minipig model for urodynamic evaluation of infravesical obstruction and its possible reversibility.

PURPOSE: The aim of our study was to create reproducible partial bladder outlet obstruction and to evaluate the resulting urodynamic changes. MATERIALS AND METHODS: Thirty-one female Yucatan microswine were randomly divided into obstructed and control groups. In the obstructed group of 21 animals, an artificial 4.5-cm. sphincter cuff was placed around the bladder neck. Fourteen of these minipigs were eventually deobstructed. In the controls (unobstructed sham-operated group), the sphincter cuff was removed prior to closure. Urodynamic measurements were conducted at 2, 4, 8 and 12 weeks postobstruction in conscious animals restrained in specially designed adjustable cages. RESULTS: (with all pressures in cm.H2O): 1) Unobstructed sham controls: Pdet,open 28.8 Pdet (Qmax) 22.5, Qmax 30.8 ml. per second, Pdet,isv 61.7, urethral resistance relation (URA) 7.7 cm.H2O, and Watts factor (WF) 4.7 W/m.2; 2) Obstructed group: Pdet,open 85.2; Pdet (Qmax) 94.4, Qmax 5.6 ml. per second, Pdet,isv 135.2, mean URA 74.3 cm.H2O and WF 13.5 W/m.2; 3) Deobstructed group: Pdet,open 39.9, Pdet (Qmax) 25.9, Qmax 25.0 ml. per second, Pdet,isv 58.0, mean URA 8.9 cm.H2O and WF 5.4 W/m.2. CONCLUSION: This animal model of reversible infravesical obstruction has given consistent and reproducible pressure flow data in the conscious, upright state.

Animals↗
PubMed1995

Effects of angiotensin II on plasma atrial natriuretic factor in nonpregnant and pregnant ewes.

The release of atrial natriuretic factor (ANF) is primarily determined by atrial stretch, but may also be modulated by circulating angiotensin II (AngII). During pregnancy, the circulating concentrations of both ANF and AngII are increased. To further define possible effects of AngII on ANF release, four doses of AngII (0.5, 5, 20, 40 ng.kg-1.min-1) were intravenously infused into five nonpregnant and five pregnant (105-140 days of gestation) ewes alone and during the simultaneous infusion of sodium nitroprusside at doses sufficient to abolish the pressor effects of AngII. Mean arterial pressure (MAP) was increased from 80 +/- 2 to a maximum of 121 +/- 5 mmHg (1 mmHg = 133.3 Pa) in nonpregnant ewes (p < 0.01) and from 79 +/- 2 to 116 +/- 4 mmHg in pregnant ewes (p < 0.01) over the range of AngII infusion. MAP was unaltered during AngII plus nitroprusside infusion, averaging 78 +/- 3 mmHg in nonpregnant ewes and 80 +/- 2 mmHg in pregnant ewes. Basal ANF was higher (p < 0.01) in pregnant sheep than in nonpregnant sheep. With AngII infusion alone, plasma ANF was increased from 13 +/- 2 to 42 +/- 4 fmol/microL in nonpregnant ewes (p < 0.01) and from 23 +/- 5 to 72 +/- 16 fmol/microL in pregnant ewes (p < 0.01). However, during AngII plus nitroprusside infusion, the increases in plasma ANF observed were completely abolished in both nonpregnant and pregnant ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1995

Control of atrial natriuretic factor by right and left atrial distension in pregnant sheep.

Previous studies of the atrial stretch-atrial natriuretic factor (ANF) relationship during pregnancy have employed volume expansion and measured only right atrial pressure (RAP). Consequently, we studied nonpregnant (n = 7) and 115- to 125-day pregnant (n = 7) sheep and assessed the ANF response to changes of RAP and left atrial pressure (LAP) induced by graded balloon inflation. Ewes prepared with vascular catheters and atrial balloons were studied after recovery from preparatory surgical procedures. The basal levels of mean arterial pressure (MAP, 83 +/- 3 mmHg), RAP (2.1 +/- 0.7 mmHg), LAP (4.7 +/- 0.9 mmHg), and heart rate (HR, 102 +/- 6 beats/min) were similar in nonpregnant and pregnant sheep. Pregnancy also resulted in elevation of ANF concentration from 25 +/- 6 to 57 +/- 4 fmol/ml. With right atrial distension, the RAP-ANF relationships were similar in both nonpregnant and pregnant sheep, with a 10-mmHg increase in RAP increasing ANF by an average of 95 +/- 9 fmol/ml. In nonpregnant sheep, the LAP-ANF relationship was more responsive than RAP-ANF because a 10-mmHg increase in LAP resulted in a 193 +/- 10 fmol/ml increase in ANF. Moreover, during pregnancy, the LAP-ANF relationship was significantly more sensitive because a 10-mmHg increase in LAP resulted in a 433 +/- 15 fmol/ml elevation of ANF. These data demonstrate that plasma ANF levels are more responsive to distension of the left atria than to the right. More importantly, the ANF response to left, but not right, atrial distension is enhanced by pregnancy.

Analysis of Variance↗
PubMed1995

[The effect of retinoic acid on DNA synthesis of fibroblast in vitro culture].

The effect of retinoic acid on DNA synthesis of fibroblast was studied in vitro culture. The results demonstrated that retinoic acid significantly (P < 0.01) inhibited the DNA synthesis of fibroblast in vitro culture and a dose-dependent relationship between DNA synthesis and retinoic acid concentration was observed. The possible mechanism of retinoic acid used for the treatment of scar was discussed.

Cells, Cultured↗
PubMed1995

Effects of acupuncture on immunoglobulins in patients with asthma and rheumatoid arthritis.

The effects of acupuncture on immunoglobulins in patients with asthma and rheumatoid arthritis were studied. After acupuncture, in 20 patients with asthma, IgG increased (P < 0.01), IgM and IgE decreased (both P < 0.01), while IgA did not change markedly (P > 0.05); in 12 patients with rheumatoid arthritis, after acupuncture IgG, IgA and IgM decreased (P < 0.05, 0.05, and 0.01, respectively), while IgE did not change evidently. The results observed in these 32 patients indicate that acupuncture exerts modulation action on immunoglobulins of the human body, and that patients with asthma and rheumatoid arthritis responded effectively to acupuncture therapy, the latter might be related to the reinforcement of the immunological function by acupuncture.

Acupuncture Therapy↗
PubMed1995

[Risk of malignant changes in hydatidiform mole complicated with pregnancy induced hypertension].

OBJECTIVE: To investigate the prognosis of patients of hydatidiform mole (HM) who complicated with pregnancy induced hypertension (PIH) and to suggest that PIH may serve as a risk factor for malignant change in molar pregnancy. METHODS: From 1962 to 1992, 161 patients of HM including 33 cases with PIH and 128 cases of normotension were managed and followed at the PLA General Hospital. The definition of malignant sequelae was that abnormal hCG level was lasting at least 8 weeks after molar evacuation or metastatic lesions was found. RESULTS: 15 of 33 patients with PIH developed metastatic invasive moles (45.5%) and 13 of them metastatic tumors were found before molar evacuation. 12 of 128 cases of normotension had malignant thanges including 1 choriocarcinoma and 11 invasive mole (9.4%) and among them only one had metastatic lesions before molar evacuation. CONCLUSIONS: The incidence (45.5%) of malignant changes in patients complicated with PIH was significantly higher than that in normotensive patients (9.4%) (P < 0.01). In addition, they had early metastatic lesions. This study suggests that PIH may serve as a risk factor for malignant change in molar pregnancy.

Adult↗
PubMed1995

[The relations of corneal, lenticular and total astigmatism].

PURPOSE: To determine the relations of corneal, lenticular and total astigmatism and the changes of the astigmatism with age. METHOD: Out-patients with refractive errors were refracted with retinoscope after using cycloplegic drops and measured the radii of anterior corneal curvature. RESULT: One hundred and ninety-four cases (382 eyes) with refractive errors were studied. Of the eyes 67.9% had regular corneal astigmatism, 68.1% irregular lenticular astigmatism and 60.7% regular total astigmatism, 88.5% of the corneal astigmatism has the same quality as the total astigmatism. The total astigmatism in 46% of the eyes included the summation of corneal and lenticular astigmatism, but in 41.3% of the eyes irregular lenticular astigmatism corrected the regular corneal astigmatism. The astigmatism of cornea, lens and total astigmatism changed from regular to irregular with the increase of age. The linear correlation analysis showed a positive correlation between the power of horizontal corneal refraction and age, and a negative corrlation between the power of vertical corneal refraction and age. CONCLUSION: The shape of cornea was the major cause of total astigmatism. The influence of lens on the total astigmatism was different. The reasons for the change of the total astigmatism from regular to irregular with the increase of age were the changes of the power of corneal refraction, particularly the increase of the power of horizontal corneal refraction and lenticular irregular astigmatism.

Adolescent↗
PubMed1994

Conscious minipig model for evaluating the lower urinary tract.

An animal model using minipigs to study urodynamic pressure flow relationships in the conscious animal is described. Port-catheters were implanted subcutaneously in the backs of 22 minipigs with access to the bladder (to measure intravesical pressure Pves) and to the peritoneal cavity (to measure abdominal pressure Pabd). The subtracted pressure (Pdet = Pves = Pabd) was recorded during the storage phase following Furosemide diuresis. Simultaneously, measurement of urinary flow (Q) during voiding was also recorded. Urodynamic studies were performed satisfactorily in all animals, and normal urodynamic profiles in minipigs were established. The minipig model allows reliable and reproducible measurement of pressure-flow parameters in a conscious state and in the natural posture.

Animals↗
PubMed1994

Gastric muscularis as a urinary sphincter.

OBJECTIVE: To test the ability of gastric muscularis to act as a urinary sphincter in a rat model system. METHODS: Fourteen Long-Evans rats had an ileal conduit constructed joining the bladder to the ventral skin, creating urinary incontinence. A segment of gastric muscle maintained on its vascular pedicle was encircled around the conduit. The first 7 animals (group A) had both conduit and sphincter constructed simultaneously, whereas the remaining 7 animals had the conduit constructed first, followed by a two-week period of observation, after which gastric sphincters were added (group B). All animals were observed for urine leakage via the cutaneous stoma. At two weeks after sphincter placement, all animals underwent surgical exploration, pressure profilometry of the conduit, and histologic examination of the sphincter zone. RESULTS: Pressure profilometry demonstrated elevated pressures in the sphincter zone relative to baseline pressures in the conduit of all animals (group A: mean baseline, 4.8 cm water, mean maximum, 20.6 cm water; group B: mean baseline, 5.2 cm water, mean maximum, 18.1 cm water). At exploration, no intra-abdominal complications were noted in 13 of 14 animals. All conduits were easily catheterizeable and were found to be continent after they had been filled to capacity. The ileum and gastric segments were histologically found to be viable with no evidence of necrosis or ischemia. CONCLUSIONS: These preliminary results suggest that gastric muscularis may be a potential substitute urinary sphincter in the management of sphincteric urinary incontinence.

Animals↗
PubMed1994

Regulation of coenzyme Q biosynthesis.

The side-chain moiety of coenzyme Q is synthesized by a trans-prenyltransferase present in microsomes. Condensation of this moiety with the precursor ring takes place in the Golgi system. The enzymes involved, as well as the cytosolic geranylgeranyl-PP synthase, are regulated in an independent fashion. When the size of the farnesyl-PP pool is decreased or increased by employing appropriate inhibitors, the rate of CoQ synthesis is modified accordingly, indicating the dependence of trans-prenyltransferase activity on the level of intracellular substrate concentrations. Administration of peroxisome proliferators elevates CoQ concentrations not only in blood, but also in various tissues. Thus, it may be possible in the future to selectively increase CoQ concentrations in certain organs, without increasing the level of cholesterol.

Alkyl and Aryl Transferases↗
PubMed1994

The effects of gonadotropin on the phosphatidylinositol pathway in the primate corpus luteum.

The current study was designed to investigate the effects of gonadotropin on basal and prostaglandin (PG) F2 alpha-induced activity of the phosphatidylinositol pathway in corpora lutea (CL) of rhesus monkeys. Luteal progesterone production in vitro was significantly stimulated (P < 0.05) by human chorionic gonadotropin (hCG). Neither basal nor PGF2 alpha-induced phosphatidylinositol 4,5-bisphosphate hydrolysis was significantly influenced by hCG in CL of various ages (P > 0.10). Gonadotropin did induce a slight, yet sustained, increase (P < 0.05) in [Ca2+]i in approximately 70% of luteal cells. The maximal increase in [Ca2+]i in response to hCG (approximately 100 nM) was about one-tenth that induced by PGF2 alpha (approximately 1000 nM). hCG treatment did not alter (P > 0.10) the increase in [Ca2+]i induced by PGF2 alpha Treatment-induced changes in [Ca2+]i did not differ between small (17-21 microns) and large (23-28 microns) luteal cells. Therefore, luteolytic agents are more potent activators of the phosphatidylinositol pathway than luteotropins. This is consistent with the hypothesis that the phosphatidylinositol pathway is involved in primate luteal regression. The inability of hCG to acutely alter the responsiveness of this pathway to PGF2 alpha suggests that CG may rescue the CL of early pregnancy via a mechanism other than direct inhibition of the luteolytic actions of PGF2 alpha.

Animals↗
PubMed1994

[Herpes zoster keratoendotheliitis].

Herpes zoster keratoendotheliitis is related to autoimmunity or herpes zoster virus infection. It is characterised by K.P. and interstitial edema. The disease responds well to the administration of steroids and a good result is often achieved.

Adrenal Cortex Hormones↗
PubMed1993

Remeasurement of electrosprayed proteins in the trapped ion cell of a Fourier transform ion cyclotron resonance mass spectrometer.

A single population of multiply charged protein ions formed by electrospray ionization (ESI) is subjected to multiple Fourier transform ion cyclotron resonance (FTICR) excitation and detection events without promoting ion loss from the trapped ion cell. This nondestructive approach to mass spectrometric detection will allow detection limits to be significantly reduced by averaging the repetitive time-domain response that follows each excitation event. Under appropriate conditions, unit remeasurement efficiency is observed for large proteins; for example, 250 consecutive remeasurements of a single population of bovine albumin dimer ions (MW 132,532) yield the expected 16-fold improvement in signal-to-noise ratio compared to a single measurement. Examples presented include a 14-fmol sample of horse myoglobin (MW 16,951), which yields a 15:1 S/N for 50 remeasurements compared to a single scan S/N of 2:1 and a 30-fmol sample of bovine albumin dimer which exhibits a S/N of 25:1 for 50 remeasurements compared to a single scan S/N of 3:1. Of both practical and theoretical interest is the observation of a rapid collision-mediated homogeneous relaxation process that can return these large ions to the center of the cell within a few hundred milliseconds after excitation.

Animals↗
PubMed1993

Mechanisms through which gangliosides inhibit PDGF-stimulated mitogenesis in intact Swiss 3T3 cells: receptor tyrosine phosphorylation, intracellular calcium, and receptor binding.

Several potential mechanisms through which gangliosides could modulate PDGF-stimulated events in Swiss 3T3 cells were studied using intact cells. Of the gangliosides studied, at low micromolar concentrations GM2 was the only one that inhibited PDGF-stimulated DNA synthesis, but GT1b was the most potent between 25 and 100 microM; GM1 was generally the least effective, and GD1a and GM3 had intermediate effects. All gangliosides tested inhibited the PDGF-stimulated increases in free intracellular calcium concentrations ([Ca2+]i) with the rank order of potency being GM1 > or = GT1b > GM2 > GM3. PDGF stimulated phosphorylation on tyrosine of a protein with apparent M(r) = 170 kDa which was immunoprecipitated by an anti-PDGF receptor (beta) antibody, indicating that it is a PDGF receptor. Preincubating the cells with specific gangliosides inhibited tyrosine phosphorylation of this protein in a dose-responsive fashion with the following rank order of potency GD1a = GT1b > GM1 > GM2 > GM3. Autoradiography showed that this was due to a decrease in the proportion of cells synthesizing DNA, and a time study showed that ganglioside did not delay entry of the cells into S phase. These effects were not due to gangliosides interfering with PDGF binding to its receptor because results of competitive binding studies showed that none of the gangliosides studied had an effect on either receptor number or affinity, and did not bind to PDGF in solution. These results show that gangliosides affect several specific components of the complex responses to PDGF in intact cells. The relative effectiveness of individual gangliosides, however, varied among the different cellular and molecular responses. This is interpreted to mean that specific gangliosides modulate to different degrees several molecular mechanisms which converge on the common biological response of mitogenesis, and suggests that gangliosides as a family of molecules may function as coordinators of different molecular events involved in complex cellular processes.

3T3 Cells↗
PubMed1992

Gangliosides inhibit platelet-derived growth-factor-stimulated increases in intracellular calcium in Swiss 3T3 cells.

Individual Swiss 3T3 cells stimulated by platelet-derived growth factor delivered by means of a picopump device respond with a brisk, large, and sustained increase in intracellular calcium concentration ([Ca2+]i). Preincubation of cells with either GM1 or GT1b gangliosides inhibited the proportion of responding cells and caused a dose-related diminution in the magnitude of the increase in [Ca2+]i. This effect of ganglioside is probably part of the mechanism through which gangliosides exert their biological effects, including inhibition of platelet-derived growth-factor-induced mitogenesis.

3T3 Cells↗