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Biomedical subjects

J B Zhao

Publications and source records attributed to J B Zhao.

15 recordsLinked to original sources
PubMed2003

Shear modulus of porcine coronary artery: contributions of media and adventitia.

The epicardial coronary arteries experience significant torsion in the axial direction due to changes in the shape of the heart during the cardiac cycle. The objective of this study was to determine the torsional mechanical properties of the coronary arteries under various circumferential and longitudinal loadings. The coronary artery was treated as a two-layer composite vessel consisting of intima-medial and adventitial layers, and the shear modulus of each layer was determined. Eight porcine hearts were obtained at a local abattoir, and their right coronary and left anterior descending arteries were isolated and tested in vitro with a triaxial torsion machine (inflation, longitudinal stretch, and circumferential twist). After the intact vessel was tested, the adventitia was dissected away, leaving an intact media that was then tested under identical triaxial loading conditions. We proposed a biomechanical analysis to compute the shear modulus of the adventitia from the measured shear moduli of the intact vessel and the media. To validate our predictions, we used four additional hearts in which the shear modulus of the adventitia was measured after dissection of media. Our results show that the shear modulus does not depend on the shear stress or strain but varies linearly with circumferential and longitudinal stresses and in a nonlinear way with the corresponding strains. Furthermore, we found that the shear modulus of the adventitia is larger than that of the intact vessel, which is larger than the vessel media. These results may have important implications for baroreceptor sensitivity, circulation of the vasa vasorum, and coronary dissection.

Animals↗
PubMed2002

Severe partial ureteric obstruction in newborn rats can produce renal dysplasia.

OBJECTIVE: To investigate whether partial unilateral ureteric obstruction (PUUO) produces renal dysplasia in newborn rats. MATERIALS AND METHODS: Left mild (in 31) or severe (in 34) PUUO was induced in 2-day-old rats by embedding a quarter or two-thirds of the ureter into the psoas muscles, respectively. Sham-operated control rats (36) were assessed in parallel. Kidney morphology, renal parenchymal weight and histology were examined 24 weeks and 30 months afterward. RESULTS: There was significant pelvic dilatation in all obstructed kidneys; four kidneys were dysplastic in those severely obstructed, with a significant decrease in renal volume. There were three dysplastic kidneys after 6 months and one at 30 months. The in vitro dysplastic kidney weight was 36% of the control kidneys. Microscopy showed primitive glomerular and tubular structures, with renal parenchymal developmental disorganization and marked fibrosis. The glomeruli, tubules and collecting ducts were deficient in number and had often undergone cystic changes. Columnar tubular epithelium and peritubular mesenchymal collars were present. There was no renal dysplasia in the mildly obstructed and sham-operated rats. The parenchymal weight of the kidneys contralateral to the dysplastic kidneys was significantly higher than in the controls (P < 0.001). CONCLUSIONS: Severe PUUO can produce renal dysplasia in newborn rats. However, only 12% with severe obstruction had renal dysplasia, indicating that the cause of renal dysplasia might also be related to other factors.

Animals↗
PubMed2001

Remodeling of the zero-stress state of femoral arteries in response to flow overload.

The goal of this study is to quantitatively describe the remodeling of the zero-stress state of the femoral artery in flow overload. Increased blood flow, approximately as a unit step change, was imposed on the femoral artery by making an arteriovenous (a-v) fistula with the epigastric vein. The a-v fistula was created in the right leg of 36 rats, which were divided equally into six groups (2 days and 1, 2, 4, 8, and 12 wk after the fistula). The vessels in the left leg were used as controls without operative trauma. The in vivo blood pressure, flow, and femoral outer diameter and the in vitro zero-stress state geometry were measured. The in vivo shear rate at the endothelial surface increased approximately as a step function by approximately 83%, after 2 days, compared with the control artery. The arterial luminal and wall area significantly increased postsurgically from 0.15 +/- 0.02 and 0.22 +/- 0.02 mm(2) to 0.28 +/- 0.04 and 0.31 +/- 0.05 mm(2), respectively, after 12 wk. The wall thickness did not change significantly over time (P > 0.1). The opening angle decreased to 82 +/- 4.2 degrees postsurgically when compared with controls (102 +/- 4.4) after 12 wk and correlated linearly with the thickness-to-radius ratio. Histological analysis revealed vascular smooth muscle cell growth. The remodeling data are expressed mathematically in terms of indicial functions, i.e., change of a particular feature of a blood vessel in response to a unit step change of blood flow. The indicial function approach provides a quantitative description of the remodeling process in the blood vessel wall.

Animals↗
PubMed2001

Digital particle image velocimetry investigation of the pulsating flow around a simplified 2-D model of a bileaflet heart valve.

BACKGROUND AND AIM OF STUDY: Strong interactions are believed to exist between the pulsating valvular flow and the valve leaflet motions. Hinge position, indicated by d/W (d = distance between the two axes of the hinge pivots; W = width of the testing section in the middle plane), plays a critical role in MHV performance. An optimized hinge position for a bileaflet heart valve can be identified as a design criterion for better valve performance. METHODS: A two-dimensional (2-D) digital particle image velocimetry (DPIV) system was used to map the transient flow field of a simplified 2-D model of a bileaflet heart valve with a hydraulic diameter enlarged three-fold under pressure waveforms which was expanded based on Womersley number and Euler number considerations. Six different hinge positions were investigated. RESULTS: At extreme hinge positions (d/W <0.2 or d/W >0.3), large-scale and long-duration stagnation of flow was found in the central orifice, and instability and highly disturbed flow was noted in plots of velocity vectors. CONCLUSION: The transient flow pattern in the vicinity of the valve was greatly affected by the hinge position of moving leaflets. An optimum d/W in the range 0.2-0.3 yielded good velocity field and opening and closing behaviors.

Blood Flow Velocity↗
PubMed1999

A steady flow analysis on the stented and non-stented sidewall aneurysm models.

As part of a general investigation on the effects of blood flow patterns in sidewall aneurysm, in vitro steady flow studies on rigid aneurysm models have been conducted using Particle Image Velocimetry over a range of Reynolds number from 200 to 1600. Above Reynolds number 700, one large recirculating vortex would be formed, occupying the entire aneurysmal pouch. The centre of the vortex is located at region near to the distal neck. A pair of counter rotating vortices would however be formed at Reynolds numbers below 700. For all the aneurysm models considered, the vortex strength, in general, is stronger at higher Reynolds numbers but lower at larger aneurysm size. Maximum strength of the vortex is about 15% of the bulk mean velocity in the upstream parent tube. Estimates of the wall shear stresses are derived from the near wall velocity measurements. Highest level of wall shear stresses always appears at the distal neck of the aneurysmal pouch. Stents and springs of different porosity have been used to dampen the flow movement inside the aneurysm so as to induce the possible formation of thrombosis. It is found that the flow movement inside the aneurysmal pouch can be suppressed to less than 5% of the bulk mean velocity by both devices. Furthermore, regions of high wall shear stresses at the distal neck could also be suppressed by almost 90%. The present results would be useful for further improvements in stent (or spring) technology.

Aneurysm↗
PubMed1994

Alpha and beta thalassaemia among Chinese children in Guangxi Province, P.R. China: molecular and haematological characterization.

We have studied nearly 100 patients with beta-thalassaemia major and 60 patients with Hb H disease who were attending the Haematology Clinic of Guangxi Medical College. Treatment of the patients was limited and only a few patients with beta-thalassaemia major received blood transfusion(s). As a result, the severe anaemia has led to early death at 3-4 years for beta zero-thalassaemia homozygotes, and 8-12 years for beta(+)-thalassaemia homozygotes. Four beta-thalassaemia alleles are responsible for nearly 90% of all beta-thalassaemia chromosomes. This information has resulted in the initiation of a prenatal testing programme at the local level. The patients with Hb H disease maintained a haemoglobin level of 6-10 g/dl and early death was infrequently observed. The --SEA deletion was the major type of alpha-thalassemia-1, while three smaller deletions (-2.7, -3.7 and -4.2 kb) and two nondeletional alpha-thalassaemia determinants (Hbs Constant Spring and Quong Sze) were the alpha-thalassaemia-2 types.

Alleles↗
PubMed1994

[The pathology of Joseph's disease in a Chinese family: a report of two autopsy cases].

This is the first pathology report on Joseph's disease in China, based on autopsies of 2 members of the Huang family. The main pathological changes were chiefly located in the central nervous system including globus pallidus and Luy's body, cerebellar dentate nucleus, cranial nerve motor nuclei of brain stem, substantia nigra and red nuclei, and also there were severe loss of neurons in the anterior horn and Clarke's nuclei; severe demyelinization of cerebellospinal tract and degeneration with demyelinization of the peripheral nerves accompanied by neurogenic skeletal muscular atrophy. It is concluded that the pathologic characteristics were similar to those found in Europe, United States and Japan.

Adult↗
PubMed1994

[Morphological study on 40 cases of alcoholic liver disease].

Morphological changes in liver biopsies from 40 alcoholic patients were studied, 20 of which being ordinary alcoholics (40-80g ethanol/day) and the other 20 being heavy drinkers (above 80g ethanol/day for over 20 years). All being male who have neither type B nor type C hepatitis. The basic morphological changes observed being: 1. Liver cell degeneration including fatty degeneration & focal ballooning, decrease in liver cell size, occasional giant mitochondrion and Mallory's body formation. 2. Focal necrosis with neutrophil infiltration. 3. Pericellular fibrosis of liver cells, hepatic fibrosis and early cirrhosis. Alcoholic liver disease can be divided into 5 types: I. alcoholic fatty liver (AFL), II. alcoholic hepatitis (AH), III. alcoholic hepatic fibrosis (AHF), IV. alcoholic liver cirrhosis (ALC), V. slight alcoholic liver disease (SALD). The degree of liver damage (liver cell necrosis and hepatic fibrosis) is closely related to the amount of daily ethanol intake. The progression of liver damage observed in our study is much milder than reports from Europe, the U.S. and Japan.

Adult↗
PubMed1990

Immunoglobulin deposits in diabetic microangiopathy. Observations in autopsy materials.

Non-enzymatic glycosylation of vascular wall collagen is considered to be most important in the pathogenesis of diabetic microangiopathy, and glycosylated collagens are reported to bind immunoglobulins in vivo. We investigated the occurrence of IgG or IgM deposits in the microvasculature of certain organs of diabetics using routine autopsy materials. Glomerular capillary basement membrane/endothelium was often positive for IgM in diabetics. Endothelial cells of glomerular capillaries were positive for HLA-DR in 6 of 16 diabetics and in 2 of 11 controls. This was associated with IgM or IgG deposits in 5 cases. In the esophagus and/or tongue of diabetics, IgG was frequently deposited in the microvasculature. In total, IgG deposits were found in 13 of 16 diabetics, either in the esophagus or the tongue, but in only 3 of 16 controls. The difference was significant at p less than 0.005. These observations suggest that deposition of immunoglobulins is a component of diabetic microangiopathy. Differences in expression of HLA-DR in glomeruli between diabetics and non-diabetics remain to be explored.

Adult↗
PubMed1989

[Ultrastructural studies on the spermatogenesis in diploid and triploid types of Paragonimus westermani].

Diploid and triploid types of Paragonimus westermani were compared in the aspect of ultrastructure of spermatogenesis. The results showed that the process of spermatogenesis in the diploid type was normal. The cells at every stage are well developed. A great number of morphologically and functionally normal spermatozoa could be formed. On the other hand, the process of spermatogenesis in the triploid type was abnormal, the cells at every stage developed abnormally. They were apparently degenerated or vacuolated, lacking organelles. The cytophore was broken into small particles. No normal spermatozoa were found (Figs. 1-5).

Animals↗
PubMed1989

[Comparative study on chromosome C-banding in diploid and triploid types of Paragonimus westermani].

Diploid and triploid types of Paragonimus westermani had similar chromosomal karyotypes, however, they differed in chromosome c-band patterns. Two of three homologues of the triploid resembled those of the diploid in c-banding pattern, while the remaining chromosomes showed a different pattern. Heterogeneity in homologues was observed especially in chromosome Nos. 2, 3, 5, 6 and 7 (Fig. 1, 2). In the diploid chromosome specimen, mitotic and meiosic phases were observed, while only the mitotic phase was found in the triploid chromosome.

Animals↗