The numerical analysis of fluid-solid interactions for blood flow in arterial structures. Part 1: A review of models for arterial wall behaviour

The structural response of a large artery is characteristically complex and includes the highly non-linear, history-dependent response of a nonhomogeneous anisotropic structure undergoing finite deformations. The mechanics of the arterial wall has been studied for nearly two centuries. The goals of such research range from the desire to have a basic knowledge and understanding of the mechanics and physiology of this complex structure to the need for data and methods for the design of arterial prostheses. In this paper, the models for arterial wall behaviour are critically reviewed. Firstly, the structure and general characteristics of the arterial wall are discussed. This is followed by a comprehensive review of the constitutive laws. Finally, structural analyses of the arterial wall by mathematical and numerical methods are discussed. Predictions using the authors' preferred models give focus to important issues, and in Part 2 the review and predictions are extended to the fluid solid coupled situation.

The numerical analysis of fluid-solid interactions for blood flow in arterial structures. Part 2: Development of coupled fluid-solid algorithms

In this paper, the authors extend their study of wall mechanics given in Part 1 to the overall problem of fluid-solid interactions in arterial flows. Fluid-solid coupling has become a specific topic in computational methods and applied mechanics. In this review, firstly, the effects of elasticity of blood vessels on wave propagation and local flow patterns in large arteries are discussed. Then, numerical techniques are reviewed together with the alternative coupled methods available in fluid--wall models. Finally, a novel numerical alogorithm combining two commercial codes for coupled solid/fluid problems is presented. As a consequence of the present studies, wall effects are now able to be included in predictions of haemodynamics in a clinical context.

Magnetic resonance image processing and structured grid generation of a human abdominal bifurcation

Magnetic resonance angiography (MRA) offers a non-invasive approach to the acquisition of anatomically accurate human arterial structure. Combining the latest computational fluid dynamics (CFD) techniques with clinical data from MRA, the detailed haemodynamics information in the human circulation system can be obtained. In this paper, a novel computer method is presented, which generates automatically a computational grid for a human abdominal bifurcation from a set of conventional MRA images. The method covers the complete sequence from MR image segmentation, 3-D model construction, grid generation, to grid quality evaluation. Results demonstrate that the computer program developed is capable of generating a good quality grid for human arterial bifurcations from MRA images with minimum user input. The resultant grid can be used directly for further computer simulation of the flow.

[The analysis of biological characteristics for the tissue-plasminogen activator (t-PA) mutant engineered cell line]

The morphology of t-PA mutant engineered cell line FSGGI48 is similar to that of CHO-dhfr- cell in polygon. When aminopterin (MTX) concentration is 5 x 10(-6) mol/L, a part of cells become slim, but they are still in polygon. Therefore, the morphology of FSGGI48 cell line is normal. The expression level is 4000 IU/10(6) cells/24 h in serum-free medium. The cell line is bequeathed for three months in vitro and revived after freezing three months, the greater part of cells are stable. The expression level is 3000-4000 IU/10(6) cells/24 h. The assay of tumorigenesis shows that the cells, cellular DNA and purified products don't form tumors in nude mice. The cell line hasn't been contaminated by mycoplasma. The results of chromosomal analysis show that the chromosomal number of CHO-dhfr- cell is 20 and the abnormal rate is 6%. FSGGI48 cell line is same as CHO-dhfr- cell in chromosomal number and the abnormal rate is 15%-18%, it is normal in scope. Therefore, the engineered cell line FSGGI48 is excellent.

[Discharge patterns of respiratory related neurones in the medial areas of nucleus retrofacialis of medulla]

Experiments were performed on rabbits and SD rats, both anesthetized with urethane (1.0 g/kg, i.v. or i.p.). Discharges of phrenic nerve and the diaphragmatic muscle electric activities were monitored. Discharge patterns of the respiration-related neurons (RRNs) in the medial area of nucleus retrofacialis (mNRF) were recorded and analyzed. Among the 249 RRNs recorded in the mNRF of the rabbits, 118 were inspiratory (I, 47.4%), 91 expiratory (E, 36.5%), and 40 phase-spanning (PS, 16.1%). Both I and E neurons could be further subdivided into 4 subtypes, the PS neurons into E-I and I-E type. In the 153 RRNs recorded in rats, 68 were I (44.5%), 55 E (35.9%), 30 PS (19.6%). It was found that a group of E-I PS neurons that fire preceding phrenic nerve respiratory activity are located in the mNRF, which was believed to be important in the generation of the basic respiratory rhythm.

Immunosuppression by inhibition of cellular adhesion mediated by leukocyte function-associated antigen-1/intercellular adhesion molecule-1 in murine cardiac transplantation

BACKGROUND

Donor alloantigen-specific tolerance to vascularized allografts can be induced by several treatments, but the immunological mechanism(s) of these effects remain unclear. One hypothesis is that allograft unresponsiveness is correlated with a shift in the pattern of expression of the T helper 1 versus T helper 2 T-cell cytokines. We report here an extensive analysis of murine cardiac allografts, during normal first set rejection and in mice treated with anti-adhesion molecule monoclonal antibodies (mAbs), a regimen that results in prolonged unresponsiveness.

METHODS

A combination of immunohistochemical staining with a panel of mAbs, and in situ hybridization with a panel of digoxigenin-labeled riboprobes, was performed on frozen-tissue sections of cardiac allografts.

RESULTS

In several strain combinations, injection of anti-leukocyte function-associated antigen-1 and anti-intercellular adhesion molecule-1, from day 0 to day 6 after transplantation, results in significant long-term survival. Examination of tolerated cardiac allografts by in situ hybridization and immunohistochemical staining shows an altered cytokine expression pattern, although the frequency of CD3 and CD4 cells is not dramatically reduced. These allografts show a decreased frequency of interferon-gamma and interleukin (IL)-2-expressing cells and a slightly increased frequency of cells expressing IL-4 and IL-10, compared with unmodified acute rejection. A direct role of these changes in T-cell cytokine expression is demonstrated by reversal of tolerance induction and rejection of the allograft by in vivo injection of either anti-IL-10 or anti-IL-4 mAb.

CONCLUSIONS

Although there are significant differences in the frequency of different cellular subsets and patterns of cytokine gene expression, these differences are quantitatively subtle, suggesting a delicately balanced immune response that can develop a pattern of specific unresponsiveness, with relatively minor alterations in the specific T-cell response.

Expression of exogenous NF-IL6 induces apoptosis in Sp2/0-Ag14 myeloma cells

NF-IL6 (or C/EBP beta) is a multifunctional transcription factor of the C/EBP family. To study the effects of exogenous expression of NF-IL6 on the growth of cells of hematopoietic tumors, we infected SP2/0-Ag14 myeloma cells with pLXSN recombinant retrovirus harboring the NF-IL6 cDNA. We found that the transfected cells revealed changes typical of the apoptosis and finally died. The expression of NF-IL6 protein was shown by a "supershift" assay in the NF-IL6-transfected cells. In controls, where cells were infected by the retroviral vector with a mutant NF-IL6 coding region as well as the vector without insert, no sign for expression of NF-IL6 and apoptosis was observed. Therefore, our work shows that the apoptosis of this myeloma cell line was induced by the exogenous NF-IL6 expression. This is significantly different from the apparent effects of NF-IL6 in leukemia cells and in fibroblasts. These facts indicate that NF-IL6 exerts different functions in different cell types. We discuss possible mechanisms for the NF-IL6-induced apoptosis.

[Clinical observation of Qi deficiency syndrome in 72 patients with chronic obstructive pulmonary disease treated with yiqi mianyi granule]

Seventy-two patients of chronic obstructive pulmonary disease (COPD) of Qi deficiency syndrome with abnormal immune indices were treated with Yiqi Mianyi Granule (YQMYG) and the efficacy was compared with 30 cases treated with Zhenqi Fuzheng Granule (ZQFZG) for control. Results showed that the marked effective rate of symptomatic improvement of Qi Deficiency in YQMYG group was 65.3%, the total effective rate was 93.1%. 88.6% of the immune indices lower than normal were corrected and 43.7% of them were normalized, while for indices higher than normal the rate were 78.2% and 52.9% respectively. These results suggested that YQMYG could improve the symptom of Qi Deficiency markedly, strengthen the cellular immunity, regulate the disorder of immune function, its therapeutic efficacy was obviously superior to ZQFZG (P < 0.05).

Amplification of the C-erbB-2(HER-2/neu) proto-oncogene in ovarian carcinomas

C-erbB-2(HER-2/neu) proto-oncogene is mainly expressed in epithelial tissue and activated due to its amplification. Amplification of the C-erbB-2 proto-oncogene has been associated with poor prognosis in human ovarian cancer. Our study was to examine whether amplification is more frequently observed in ovarian cancer, or it is associated with poor prognosis of human ovarian cancer in China. The DNA of ovarian cancers was extracted and consequently digested with restriction endonuclease EcoRI, electrophoresed in 0.8% agarose gels and blotted onto nitrocellulose filter with Southern transferring method. It was then hybridized with a 32P-labelled C-erbB-2 probe and subsequently underwent autoradiography. The result has shown that the C-erbB-2(HER-2/neu) gene was amplified in 8 of 26 human ovarian cancers (30.8%). The clinical data showed that all of the 8 cases with the amplified C-erbB-2 were in their advanced stage (III-IV). Five of the patients died from 2 to 4 months after operation. These data suggest that amplification of the C-erbB-2 gene may play a role in the pathogenesis of ovarian carcinoma; it is frequently observed in advanced ovarian cancer and is associated with poor prognosis for these patients.

Cyclosporin A-induced autoimmune disease in mice

The immunosuppressive drug cyclosporin A (CsA) disrupts the process of thymic ontogeny and repertoire selection in the alpha beta T cell population. Although treatment with this agent does not cause overt abnormalities in adult animals by itself, in lethally irradiated rats reconstituted with syngeneic bone marrow cells, CsA treatment results in an autoimmune syndrome. In this report, a modified protocol is described to obtain a similar, but distinctive, pathologic syndrome in mice. The key elements of this protocol are stringent elimination of mature T cells from the bone marrow cells used to reconstitute the irradiated recipients and the use of high doses of CsA over a long course (6 wk) after irradiation. CsA treatment inhibits both the positive and negative selection of alpha beta thymocytes in normal young mice as well as in irradiated, T cell-deficient bone marrow-transplanted mice. An increased frequency of "forbidden" V beta 11 T cells is detected in these animals, but it is not clear that these cells are the actual initiators of the inflammatory lesions. In mice of several inbred strains treated by this protocol, striking inflammatory lesions develop in the colon, with less intense, but significant lesions in liver, stomach, and pancreas. Unlike allogeneic graft-vs-host disease, no lesions are found in the small intestine. Examination of these lesions by immunohistochemistry demonstrates that the lesions are composed primarily of T cells and macrophages, with focal aggregates of small B cells present. The same pattern of inflammatory lesions can be adoptively transferred with lymphoid cells from the CsA-treated animals at the peak of lesion development to irradiated syngeneic recipients. The transfer of active lesions is blocked by the co-transfer of normal syngeneic T cells to these recipients. Although similar to the previously described system in rats, these findings emphasize several novel features. In mice, we find an absolute requirement for the elimination of mature T cells from the bone marrow source to develop active inflammatory lesions. The particular tissues affected are also distinctive, especially the unusual feature of severe inflammation in the colon, but no involvement of the small intestine. The mechanism by which the presence of normal T cells suppresses the development of active autoimmunity in this model may have implications for the etiology of localized inflammatory lesions in general.

Cyclosporin A-induced autoimmune disease in mice

The immunosuppressive drug cyclosporin A (CsA) disrupts the process of thymic ontogeny and repertoire selection in the alpha beta T cell population. Although treatment with this agent does not cause overt abnormalities in adult animals by itself, in lethally irradiated rats reconstituted with syngeneic bone marrow cells, CsA treatment results in an autoimmune syndrome. In this report, a modified protocol is described to obtain a similar, but distinctive, pathologic syndrome in mice. The key elements of this protocol are stringent elimination of mature T cells from the bone marrow cells used to reconstitute the irradiated recipients and the use of high doses of CsA over a long course (6 wk) after irradiation. CsA treatment inhibits both the positive and negative selection of alpha beta thymocytes in normal young mice as well as in irradiated, T cell-deficient bone marrow-transplanted mice. An increased frequency of "forbidden" V beta 11 T cells is detected in these animals, but it is not clear that these cells are the actual initiators of the inflammatory lesions. In mice of several inbred strains treated by this protocol, striking inflammatory lesions develop in the colon, with less intense, but significant lesions in liver, stomach, and pancreas. Unlike allogeneic graft-vs-host disease, no lesions are found in the small intestine. Examination of these lesions by immunohistochemistry demonstrates that the lesions are composed primarily of T cells and macrophages, with focal aggregates of small B cells present. The same pattern of inflammatory lesions can be adoptively transferred with lymphoid cells from the CsA-treated animals at the peak of lesion development to irradiated syngeneic recipients. The transfer of active lesions is blocked by the co-transfer of normal syngeneic T cells to these recipients. Although similar to the previously described system in rats, these findings emphasize several novel features. In mice, we find an absolute requirement for the elimination of mature T cells from the bone marrow source to develop active inflammatory lesions. The particular tissues affected are also distinctive, especially the unusual feature of severe inflammation in the colon, but no involvement of the small intestine. The mechanism by which the presence of normal T cells suppresses the development of active autoimmunity in this model may have implications for the etiology of localized inflammatory lesions in general.

Flow studies in canine artery bifurcations using a numerical simulation method

Three-dimensional flows through canine femoral bifurcation models were predicted under physiological flow conditions by solving numerically the time-dependent three-dimensional Navier-stokes equations. In the calculations, two models were assumed for the blood, those of (a) a Newtonian fluid, and (b) a non-Newtonian fluid obeying the power law. The blood vessel wall was assumed to be rigid this being the only approximation to the prediction model. The numerical procedure utilized a finite volume approach on a finite element mesh to discretize the equations, and the code used (ASTEC) incorporated the SIMPLE velocity-pressure algorithm in performing the calculations. The predicted velocity profiles were in good qualitative agreement with the in vivo measurements recently obtained by Jones et al. The non-Newtonian effects on the bifurcation flow field were also investigated, and no great differences in velocity profiles were observed. This indicated that the non-Newtonian characteristics of the blood might not be an important factor in determining the general flow patterns for these bifurcations, but could have local significance. Current work involves modeling wall distensibility in an empirically valid manner. Predictions accommodating these will permit a true quantitative comparison with experiment.

Human influenza A (H1N2) viruses isolated from China

Reassortant influenza A viruses bearing H1 haemagglutinin and N2 neuraminidase were isolated from humans in China between December 1988 and March 1989. As primary isolation of influenza A (H1N2) viruses from humans had not been reported previously, it was of interest to determine the genetic origin of these virus isolates. The haemagglutinins of the H1N2 viruses were antigenically and genetically related to those of H1 viruses isolated world-wide since 1986, and the neuraminidases of these viruses were antigenically and genetically related to those of recent H3N2 viruses. Partial sequencing of each gene segment of three of the H1N2 viruses revealed that all gene segments except that encoding the haemagglutinin gene were derived from virus of the H3N2 subtype. Sequence differences amongst the neuraminidase, nucleoprotein and nonstructural genes of these three H1N2 reassortant viruses as well as the isolation of reassortants in seven laboratories over a 4 month period make it unlikely that the H1N2 viruses are laboratory artefacts. The spread of these reassortant viruses to other countries has not yet been documented.

[The influence of sodium ferulate on hypotensive effect and urinary excretion of TXB2 after captopril in essential hypertensive patients]

In the present study, the influence of sodium ferulate (SF) on hypotensive effect and urinary excretion of TXB2 after captopril (CAP) was observed in 44 patients with essential hypertension. A single oral dose of CAP (50 mg) decreased mean arterial pressure (MAP) from 16.25 +/- 0.85 to 13.65 +/- 1.14 kPa, n = 28, (P less than 0.01), and increased urinary TXB2 excretion significantly from 119.12 +/- 57.12 to 183.32 +/- 78.61 pg/min, n = 16, (P less than 0.05). The administration of SF 300 mg/d for one day did not affect the MAP. CAP in combination with SF induced a decrease both in MAP from 16.33 +/- 1.14 to 13.83 +/- 1.77 kPa, n = 16, (P less than 0.01) and urinary TXB2 excretion from 155.89 +/- 69.64 to 133.43 +/- 60.01 pg/min, n = 16, (P greater than 0.05) though the latter was not so significant. Compared with the administration of CAP alone, the combination of CAP and SF induced stronger hypotensive effect (P less than 0.05) and the increased urinary TXB2 excretion could be inhibited by SF, but the inhibition to angiotensin converting enzyme was the same. These results suggested that the increased urinary TXB2 excretion by CAP can be inhibited and the hypotensive effect of CAP is potentiated by SF in essential hypertensive patients.

A review of the numerical analysis of blood flow in arterial bifurcations

Arterial bifurcation flow has been of special interest for some years because of its important role in the formation of atherosclerotic plaques and thrombi. To investigate the flow phenomena analytically, four major factors need to be accommodated--the three-dimensionality of a general bifurcation, the pulsatile nature of the laminar flow, the distensibility of the arterial wall and the non-Newtonian character of the blood. In this review, both engineering and medical aspects of each factor are carefully surveyed. It is demonstrated that the latest generation of computational fluid dynamics codes can treat this problem area and that it is both feasible and desirable to investigate the effects of each independent factor.

Grey dynamic model of predicting the long-term effects of drugs and its application to pirenzepine

In an attempt to approach the quantification of the dynamics of drug effects and the prediction of the long-term effects of drugs, a grey dynamic model was proposed and it was applied to predict the long-term effects of pirenzepine on pupils and peripheral leukocytes in dogs. The inconsiderable relative errors between the predicted and observed values suggest that the model-based equations for pupil diameter, neutrophils (%) and lymphocytes (%) which, obtained by fitting the data measured before and during initial 16 wk experiment, are acceptable for predicting the effects after 20- and 24-wk treatment with the drug.

Effect of cyclosporin A on the ontogeny of different T cell sublineages in chickens

We have used a panel of murine mAb against chicken TCR and associated molecules to study the effect of cyclosporin A (CsA) on the ontogeny of the different sublineages of T cells. After injection of CsA (20 mg/kg/day from day 0 to 20) we observed a significant suppression of the normal maturation of the TCR2 (alpha beta TCR) cells in their transition from cortical CD4+CD8+ thymocytes to the mature single positive cells in the thymus medulla. The TCR3 subpopulation, a distinct form of alpha beta-like TCR in chickens, was inhibited from initially developing within the cortex by CsA, indicating that the TCR3 subpopulation is functionally distinct from the TCR2+ cells. In contrast, the maturation and peripheral emigration of TCR1 (gamma delta TCR) cells was unaffected by CsA treatment. Mature splenic T cells sorted for either TCR1+ or TCR2+ subsets were equally sensitive to CsA blockade of Con A-stimulated mitogenesis, indicating that there is no inherent difference in CsA sensitivity between these sublineages. Furthermore, no difference was detected in the expression of class II MHC Ag in thymi of birds treated with olive oil vs CsA. Inasmuch as the mechanism of CsA action appears to involve inhibition of TCR initiated signal transduction for lymphokine synthesis, these data indicate that a similar signaling is involved in thymic repertoire selection for TCR2. The lack of an effect on TCR1 cell maturation suggests that the TCR1 repertoire may not undergo selection in the thymus as do TCR2+ cells.

Effect of cyclosporin A on the ontogeny of different T cell sublineages in chickens

We have used a panel of murine mAb against chicken TCR and associated molecules to study the effect of cyclosporin A (CsA) on the ontogeny of the different sublineages of T cells. After injection of CsA (20 mg/kg/day from day 0 to 20) we observed a significant suppression of the normal maturation of the TCR2 (alpha beta TCR) cells in their transition from cortical CD4+CD8+ thymocytes to the mature single positive cells in the thymus medulla. The TCR3 subpopulation, a distinct form of alpha beta-like TCR in chickens, was inhibited from initially developing within the cortex by CsA, indicating that the TCR3 subpopulation is functionally distinct from the TCR2+ cells. In contrast, the maturation and peripheral emigration of TCR1 (gamma delta TCR) cells was unaffected by CsA treatment. Mature splenic T cells sorted for either TCR1+ or TCR2+ subsets were equally sensitive to CsA blockade of Con A-stimulated mitogenesis, indicating that there is no inherent difference in CsA sensitivity between these sublineages. Furthermore, no difference was detected in the expression of class II MHC Ag in thymi of birds treated with olive oil vs CsA. Inasmuch as the mechanism of CsA action appears to involve inhibition of TCR initiated signal transduction for lymphokine synthesis, these data indicate that a similar signaling is involved in thymic repertoire selection for TCR2. The lack of an effect on TCR1 cell maturation suggests that the TCR1 repertoire may not undergo selection in the thymus as do TCR2+ cells.

[Dynamic changes in depolarization of action potentials by high frequency stimulation in guinea pig papillary muscles]

The effect of high frequency stimulation on rate-dependent depression of depolarization of action potentials was studied with computer and standard microelectrode techniques in guinea pig papillary muscles. After increasing driving frequency from 0.5 to 6 Hz, decreases in Vmax, APA and OS were found. Changes of upstroke velocity during phase 0 between driving frequency 6 and 0.5 Hz could be described as a parabola. The rate-dependent depression of depolarization was exaggerated by tetrodotoxin (TTX), particularly during the accelerating period of phase 0. A progressive decline in Vmax, which could be fitted by a power function curve, was observed after changing driving frequency from 1 to 5 Hz. TTX significantly influenced the decline in Vmax and the regression coefficients in fitted equations.