A comparative study of acute and chronic diseases induced by two subgroups of Theiler's murine encephalomyelitis virus

Theiler's murine encephalomyelitis viruses (TMEV) are divided into two subgroups on the basis of their different biological activities. The GDVII strain produces acute polioencephalomyelitis in mice, whereas the DA strain produced demyelination with virus persistence in the spinal cord. A comparative study of GDVII and DA strains suggested that low host immune responses are responsible for the development of acute GDVII infection and that the persistence of infected macrophages plays a crucial role in the development of chronic white matter lesions in DA infection. All 78 mice infected with GDVII died or became moribund by day 13, while none of 54 mice infected with DA died. In the acute stage, the distribution of viral antigens in the central nervous system (CNS) tissue was similar in both GDVII and DA infections, although the virus titer was higher in GDVII infection. In DA infection, a substantial number of T cells were recruited to the CNS on day 6 when they were virtually absent in GDVII infection. The titer of neutralizing antibody was already high on day 6 in DA infection but was negligible in GDVII infection. Development of chronic paralytic disease from day 35 of the DA infection was accompanied by focal accumulation of viral antigen-positive macrophages in the spinal white matter. In addition, whiter matter lesions comparable to those in chronic DA infection were induced in the spinal cord within 7 days after intracerebral injection of DA-infected murine macrophages.

Regulation of expression of the endothelial cell nitric oxide synthase

1. Recent studies have provided insight into how the expression of endothelial cell nitric oxide synthase (ecNOS) is regulated. 2. The promoter of ecNOS has several features that are compatible with a constitutively expressed, so-called 'house keeping' gene. These include absence of a TATA box and the presence of Sp1 binding sites located near the transcription start site. The promoter also contains a number of putative binding domains which suggests that it may be regulated by a variety of transcription factor mediated signals. 3. Studies of cultured endothelial cells suggest that ecNOS expression is modulated by shear stress, transforming growth factor beta, inhibition of protein kinase C and the state of proliferation. These experiments indicate that although the ecNOS is a 'constitutively expressed' gene, its content in the endothelium is subject to modest degrees of regulation that may have important physiological and pathophysiological implications.

Epidemiological analysis of tularemia in Japan (yato-byo)

A total of 1372 cases of tularemia observed in Japan since 1924 were analysed. More than 90% of the cases were reported in the north-eastern part of the main island of Japan. After World War II, more than 40 cases were reported yearly for 20 years. Since 1966, however, there have been less than 10 cases per year. Ninety-three % of the cases were caused by contact with infected wild rabbits. The pattern of monthly distribution showed a peak in December and also a lower peak in May. The number of patients older than 40 years of age and the proportion of cases in females have gradually increased. In the earlier survey periods almost 70% of the cases were engaged in agriculture but at present this rate is less than 50%. The changes in the occurrence of tularemia in Japan is thought to be related to the change of life style caused by the rapid growth of the Japanese economy after World War II.

[Cardiac output in patients in their 90's]

Cardiac output was measured by the thermodilution method in nine patients aged 90 to 97 years. The patients were capable of walking in their daily lives before the injury or admission to the hospital, after which they were scheduled for operations. The causes for operations were localized and did not markedly influence general conditions of the patients. After heart rate, arterial blood pressure and mental condition of the patients had been stabilized, their cardiac outputs were determined before the induction of anesthesia. The results are as follows: Cardiac output: 3.58 +/- 0.90 l.min-1, cardiac index: 2.72 +/- 0.57 l.min-1.m-2. Previously published reports in Japan and the results of this study about the relationship between cardiac index and age suggest that as a whole there is a tendency for the cardiac index to decrease with aging.

Regulation of endothelial cell nitric oxide synthase mRNA expression by shear stress

Shear stress enhances expression of Ca(2+)-calmodulin-sensitive endothelial cell nitric oxide synthase (ecNOS) mRNA and protein in bovine aortic endothelial cells (BAEC). The present studies were performed to investigate mechanisms responsible for regulation of ecNOS mRNA expression by shear stress and to determine if this induction of ecNOS mRNA is accompanied by an enhanced nitric oxide (NO) production. Shear stresses of 15 dyn/cm2 for 3-24 h resulted in a two- to threefold increase of ecNOS mRNA content quantified by Northern analysis in BAEC. Shear stresses (1.2-15 dyn/cm2) for 3 h resulted in an induction of ecNOS mRNA in a dose-dependent manner. In human aortic endothelial cells, shear stresses of 15 dyn/cm2 for 3 h also resulted in ecNOS mRNA induction. In BAEC, this induction in ecNOS mRNA was prevented by coincubation with actinomycin D (10 micrograms/ml). The K+ channel antagonist tetraethylammonium chloride (3 mM) prevented increase in ecNOS mRNA in response to shear stress. The ecNOS promotor contains putative binding domains for AP-1 complexes, potentially responsive to activation of protein kinase C (PKC). However, selective PKC inhibitor calphostin C (100 nM) did not inhibit ecNOS induction by shear stress. Finally, production of nitrogen oxides under both basal conditions and in response to the calcium ionophore A-23187 (1 microM) by BAEC exposed to shear stress was increased approximately twofold compared with cells not exposed to shear stress. These data suggest that ecNOS mRNA expression is regulated by K+ channel opening, but not by activation of PKC, and that shear not only enhances ecNOS mRNA expression but increases capacity of endothelial cells to release NO.

Correlation of the polysaccharide antigens of Francisella tularensis with virulence in experimental mice

Francisella tularensis gives rise to two distinct colony types, acriflavine agglutination test-positive (acf+) and -negative (acf-) colonies. The acf+ variants were exclusively low virulent in mice, while the acf- variants were shown to be either high or low virulent. Three fractions, phosphate-buffered saline-extractable without heating, with heating at 60 C, and with heating at 100 C, were obtained from cultures of both the acf+ and acf- variants on agar media, and the polysaccharide antigens in those fractions were quantitated. All of the highly virulent acf- variants possessed a large amount of the polysaccharide antigen in the fraction extractable with heating at 60 C. This antigen was not, however, detected in any of the acf+ variants and one low-virulent acf- variant. It was also detected in a very low amount in some other acf- variants with low virulence. The amount of this polysaccharide antigen was therefore shown to be correlated with bacterial virulence in mice.

Dietary correction of hypercholesterolemia in the rabbit normalizes endothelial superoxide anion production

BACKGROUND

We have shown that hypercholesterolemia increases vascular superoxide anion (O2-) production, which could be responsible for augmented inactivation of endothelium-derived vascular relaxing factor. We sought to determine whether this increased vascular O2- production is due to infiltration of macrophages into the intima and whether dietary treatment of hypercholesterolemia normalizes O2- production.

METHODS AND RESULTS

A specific and sensitive assay for O2- based on chemiluminescence of lucigenin was used; the amount of O2- produced by vascular ring segments was quantified based on known quantities of O2- produced by xanthine-xanthine oxidase standards. O2- production of aortic segments from normal rabbits (n = 9), cholesterol-fed rabbits (1% cholesterol diet for 1 month, n = 7), and rabbits fed a 1% cholesterol diet for 1 month followed by a normal diet for 1 month (regression rabbits, n = 5) was measured. At the end of these diets, serum cholesterol levels were 1.5 +/- 0.2, 26.0 +/- 3.9, and 1.8 +/- 0.5 mmol/L (58 +/- 6, 1000 +/- 150, and 71 +/- 19 mg/dL) in the normal, cholesterol-fed, and regression animals, respectively. Vessels from normal rabbits with endothelium produced 0.32 +/- 0.06 nmol O2-/mg dry wt per minute, whereas those without endothelium produced approximately twice as much O2- (0.66 +/- 0.12 nmol O2- mg dry wt per minute. Vessels with endothelium from cholesterol-fed rabbits produced 4.5-fold more O2- than vessels from normal animals. This increased production of O2- was normalized by endothelial removal. This increased production of O2- was not due to infiltration of macrophages in the intima, because there was no correlation between vascular O2- production and macrophage infiltration assessed by immunohistochemistry with use of a specific antibody against rabbit macrophage. O2- production by vessels from regression rabbits was similar to that observed in normal animals, and as in the normal rabbits, endothelial removal increased O2- production. Aortic rings from these animals also were studied in organ chambers. Dietary lowering of cholesterol dramatically improved vasodilator responses to acetylcholine and A23187 (P < .05 versus cholesterol-fed rabbits).

CONCLUSIONS

Dietary lowering of cholesterol not only improves endothelium-dependent vascular relaxation but also normalizes endothelial O2- production. Decreases of O2- production by dietary lowering of cholesterol not only may improve vasomotor control but also may improve other aspects of vascular integrity in atherosclerosis.

Molecular regulation of the bovine endothelial cell nitric oxide synthase by transforming growth factor-beta 1

The promoter region of the endothelial cell nitric oxide synthase (ecNOS) gene contains potential response elements for transforming growth factor-beta 1 (TGF beta 1). TGF beta 1 plays an important role in the pathogenesis of atherosclerosis, vascular hypertrophy, and angiogenesis. We therefore sought to determine whether TGF beta 1 might modulate ecNOS expression in bovine aortic endothelial cells (BAEC). TGF beta 1 increased ecNOS mRNA in a dose-dependent manner. TGF beta 1 also increased ecNOS protein content. The production of nitrogen oxides (NOx), assessed by chemiluminescence, and nitric oxide synthase activity, assessed by arginine/citrulline conversion were increased in TGF beta 1-treated cells. Transcriptional activity of the 5'-flanking promoter region of the ecNOS gene was increased by TGF beta 1, as assessed by transfection with promoter/luciferase constructs. Deletion analysis suggested that the TGF beta 1-response element was present between nucleotides -1269 and -935 from the first transcription start site, in which a putative nuclear factor-1 (NF-1) binding site existed. Gel shift assays showed that nuclear protein(s), immunologically similar to CCAAT transcription factor/NF-1, bound to the putative NF-1 binding site in a sequence-specific manner. Mutation of the putative NF-1 binding site in the promoter/luciferase construct significantly decreased the responsiveness to TGF beta 1. In conclusion, TGF beta 1 increases ecNOS expression associated with an increase in production of NO in BAEC. This response is probably mediated by transcriptional activation of the ecNOS gene promoter.

Mechanisms of coronary hyperconstriction in response to serotonin induced by X-irradiation in miniature pigs: increased constrictive response of medial smooth muscle

Experimental and clinical studies suggest that X-irradiation to the coronary artery may enhance vasoconstrictive response. This study aimed to clarify the effect of X-irradiation on the vasomotor response of porcine coronary artery. X-ray (15 Gy) was selectively irradiated to the left anterior descending coronary artery (LAD) in 14 Göttingen miniature pigs. The coronary vasomotor responses to serotonin at the irradiated site (LAD) and the control site (the left circumflex artery; LCX) were assessed by quantitative arteriography before and 1 h and 1, 2, and 4 weeks after X-irradiation. At 2 weeks, endothelium-dependent vasodilation in response to substance P was also evaluated arteriographically in vivo. At 2 weeks, isometric tension studies were performed to evaluate the constrictive responses of medial muscle strips and endothelium-dependent relaxation. Coronary vasoconstriction in response to serotonin was enhanced 1 week after, and further augmentation was noted 2 and 4 weeks after X-irradiation. Endothelium-dependent vasodilation in response to substance P in vivo was preserved 2 weeks after X-irradiation. Coronary arteriography showed no organic stenosis at the irradiated site. In vitro studies demonstrated that medial muscle strips of the irradiated site showed hypercontraction in response to serotonin and that endothelium-dependent relaxation in response to serotonin and substance P was preserved at the irradiated site. A histological study revealed no appreciable changes of the endothelial cells or intimal thickening.(ABSTRACT TRUNCATED AT 250 WORDS)

Initial clinical experience with the Baylor-Nikkiso centrifugal pump

Recently, a newly developed centrifugal pump, the Baylor-Nikkiso pump, was approved for clinical use in the United States. This pump is the most compact centrifugal pump with a priming volume of only 25 ml. Although it is small, this pump can provide a flow of 4 L/min against a total pressure head of 300 mm Hg at 3,000 rpm. In vitro and in vivo validation of the Baylor-Nikkiso pump has proved that this pump could effectively reduce blood trauma even under high total head pressure. In addition, 48-h durability tests with biventricular bypass using calves verified the reliability of shaft sealing and antithrombogenicity. Clinical trials of the Baylor-Nikkiso pumps have been initiated in our department. This pump provides flows of 60-70 ml/kg/min with stable hemodynamic conditions. No leakage of thrombus formation was observed. The results of the initial clinical experience of the Baylor-Nikkiso pump suggest that it is suitable for cardiopulmonary bypass surgery.

In vitro analysis of the floating mode phenomenon in the Free Impeller Gyro Pump

The Free Impeller Gyro Pump was designed based on a new concept of free impeller, in which the rotational shaft and the mechanical bearings were completely eliminated from the impeller. Due to this characteristic design, a phenomenon occurred in which the impeller lifted off the bottom of the pump housing in a certain range of pumping conditions during the initial in vitro studies (floating mode). We studied this floating mode in detail using a Hall effect position sensor to monitor the impeller position. A Hall sensor signal recorded on the strip chart, which represents the distance between the impeller top and the pump ceiling, proved the existence of the floating mode. By analyzing the data in detail, it was also verified that the floating mode was composed of three subdivided phases: latent, transitional, and dominant. Furthermore, stability of the impeller rotation in the floating mode against the change of pump orientation was also exhibited in this study. These results suggests that the Free Impeller Gyro Pump should possess high antithrombogenicity, atraumatic features, no bearing wear, and stable performance when operated within the range of the floating mode.

[Evaluation of preoperative blood preparation and blood consumption for implementation of type and screen and maximum surgical blood order schedule]

We analyzed preoperative blood preparation and intraoperative blood transfusion in Kagawa Prefectural Central Hospital and evaluated the effectiveness of maximum surgical blood order schedule (MSBOS) and Type and Screen (T&S). Forty seven kinds of surgery were performed on 1,283 cases from May, 1991 to April, 1992. Transfusion was performed in 179 cases of them. All of 1,884 units of blood that had been prepared, were crossmatched and 1,078 of them were actually transfused. The Crossmatched to Transfused ratio (C/T ratio) was 1.71. If we adopted MSBOS and T&S in 13 elective surgery, 766 units of blood and labour work for preoperative blood preparation could have been saved. MSBOS and T&S are beneficial for efficient usage of blood transfusion in surgery.

Vasoreactivity and restenosis after coronary angioplasty in the atherosclerotic pig model

BACKGROUND

The effect of coronary angioplasty on coronary spasm remains unknown. We examined the effects of balloon angioplasty, using an oversized balloon, on coronary hypercontraction and eventual restenosis in a pig model of coronary spasm.

METHODS

We performed balloon angioplasty, using an oversized balloon at the site of coronary spasm superimposed on atherosclerosis with 6 (group A, n = 14) or 1 (group B, n = 14) atmospheres of inflation pressure in miniature pigs. Using coronary angiography we assessed the coronary basal diameter and diameter change in response to histamine and serotonin before, immediately after, and 4 weeks after angioplasty. Histological examinations were performed immediately after and 4 weeks after the angioplasty.

RESULTS

Before angioplasty, histamine- and serotonin-induced hypercontraction was reproducibly noted at the atherosclerotic site. Immediately after angioplasty, the coronary diameter became larger (P < 0.01) than before angioplasty in group A, but there was no significant difference in group B. The hypercontraction in group A was abolished immediately after and 4 weeks after angioplasty, whereas the hypercontraction in group B was unchanged. Histological examination revealed medial necrosis immediately after and medial fibrosis 4 weeks after angioplasty, which were more prominent in group A. Four weeks after angioplasty, the magnitude of restenosis was greater in group A than in group B.

CONCLUSIONS

Angioplasty using an oversized balloon with the higher atmosphere of inflation pressure abolished coronary hypercontraction immediately after and 4 weeks after angioplasty, which probably resulted from the irreversible damage to medial smooth muscles; however, this did not prevent restenosis.

Regulation of endothelial constitutive nitric oxide synthase by protein kinase C

Protein kinase C (PKC) plays a key role in a variety of signal transduction processes. The promoter region of the endothelial constitutive nitric oxide synthase (ecNOS) gene contains a transcriptional factor AP-1 binding element. In the present study, we sought to determine the effect of PKC inhibition on the expression of ecNOS in cultured bovine aortic endothelial cells (BAEC). The PKC inhibitor staurosporine (10 to 100 nmol/L) increased the expression of ecNOS mRNA, assessed by Northern analysis, in a dose-dependent manner. A newly developed, more specific PKC inhibitor, chelerythrine (1 to 3 mumol/L), also increased the level of ecNOS mRNA. Incubation of BAEC with phorbol 12-myristate 13-acetate (100 nmol/L) for 24 hours, which downregulates PKC, increased ecNOS mRNA expression. The protein content of ecNOS, assessed by Western analysis, was also increased in staurosporine-treated or chelerythrine-treated BAEC. The release of nitrogen oxides from staurosporine-treated or chelerythrine-treated cells both under basal conditions and in response to calcium ionophore A23187 was significantly increased (P < .05). In conclusion, the present study suggests that regulation of ecNOS is mediated by PKC. The increased release of nitric oxide induced by PKC inhibition may play a protective role against atherogenic process.

Clinical evaluation of the oscillometric blood pressure monitor in adults and children based on the 1992 AAMI SP-10 standards

OBJECTIVE AND METHODS

A noninvasive blood pressure monitor (model BP8800MS, Colin Medical Instruments Corp., San Antonio, TX) that uses the oscillometric principle was evaluated against the manual auscultatory method in 85 adults and 85 children following the requirements of the 1992 AAMI SP-10 standard. This was the first evaluation study of the electronic sphygmomanometers according to the new AAMI standards.

RESULTS

In adult subjects, the mean difference and standard deviation of the differences between the oscillometric and auscultatory methods were 2.81 +/- 5.35 mm Hg (mean +/- SD) for systolic and 0.04 +/- 4.90 mm Hg for diastolic; in children, they were 3.18 +/- 5.96 mm Hg for systolic and -0.82 +/- 5.24 mm Hg for diastolic. Excellent correlation between the oscillometric and auscultatory methods, particularly the diastolic pressure, is due to usage of the Phase V Korotkoff's sounds for auscultatory detection of the diastolic pressure, increased accuracy of the two observers' measurements, and proper selection of cuff sizes depending on the mid-arm circumference. Five different-sized cuffs were used in this study. The cuff-width-to-midarm circumference ratio was adjusted to be 0.4 or larger to minimize the measurement error associated with mismatch of cuff-size/arm-size relationship. The distribution of errors associated with each cuff was nearly the same.

CONCLUSIONS

The 1992 AAMI SP-10 standards offer a thorough evaluation of the oscillometric sphygmomanometer by enforcing more stringent criteria on (1) agreement between two observers, (2) wide spectrum of blood pressure from hypertensive (above 180 mm Hg) to hypotensive, and (3) data analysis. The oscillometric blood pressure monitor evaluated in this study meets the specifications of the new AAMI SP-10 standards and can offer an accurate, automatic, and noninvasive measure of both systolic and diastolic blood pressure in adults and children. It can safely replace the manual or automatic auscultatory system in various clinical settings.

Physiologic consequences of increased vascular oxidant stresses in hypercholesterolemia and atherosclerosis: implications for impaired vasomotion

During the past 8 years, it has become apparent that endothelium-dependent vascular relaxation is abnormal in a variety of disease states, including hypercholesterolemia, atherosclerosis, diabetes, hypertension, and following heart transplantation. Our laboratory and several others have examined dysfunctional regulation of vasomotor tone in hypercholesterolemia and atherosclerosis. These studies have led to the concepts that altered regulation of vasomotion by the endothelium (1) is an early development in atherosclerosis, (2) involves both large vessels (with overt atherosclerosis) and the microcirculation (in which atherosclerosis does not develop), and (3) can be reversed by lipid-lowering strategies. The mechanisms for the abnormalities underlying this form of endothelial dysfunction are likely multifactorial, but a major underlying factor appears to be increased oxidant degradation of endothelium-derived nitric oxide. In this review we examine the evidence supporting this conclusion and consider the implications of these findings.

Inhibitory effects of aspirin on coronary hyperreactivity to autacoids after arterial balloon injury in miniature pigs

We examined the effects of aspirin on coronary hyperreactivity to autacoids after arterial balloon injury in miniature pigs. Coronary vasoconstriction induced by histamine and serotonin were examined angiographically before, 1 h, 1 week, and 1 month after balloon injury in 29 hypercholesterolemic miniature pigs. The animals were divided into three groups: group A, no treatment (n = 16); group B, pretreated with aspirin 50 mg/day for 2 days before injury (n = 7); and group C, treated with aspirin 50 mg/day for 2 days before and 5 days after injury (7 days in all) (n = 6). In group A, coronary vasoconstriction induced by autacoids was significantly greater at the injured than at the noninjured site at all times examined (p < 0.01). Hyperconstriction induced by the autacoids 1 h after injury were significantly less in groups B and C than in group A (p < 0.01). Hyperconstriction induced by autacoids 1 week after injury were significantly less in group B than in group A (p < 0.01) and were significantly less in group C than in group A (p < 0.01) or group B (p < 0.05). Treatment with aspirin for 2 or 7 days had no effect on the constrictive responses at the injured site 1 month after injury or on those at the noninjured site at all times examined. These results suggest that platelet-vessel wall interaction may play an important role in coronary hyperconstrictive responses to autacoids 1 h and 1 week after injury.

The endothelial cell nitric oxide synthase: is it really constitutively expressed?

During the past two years, the enzyme responsible for production of endothelium-derived nitric oxide, the endothelial cell NO synthase (ecNOS) has been cloned and the gene encoding this enzyme isolated, cloned and its structure characterized. This research has provided direction for a variety of studies of regulation of the ecNOS. Several features of the ecNOS are compatible with a constitutively expressed, poorly regulated gene, including absence of a TATA box and numerous SP-1 sites. The promoter also contains a number of putative binding domains which suggest that it may be regulated by a variety of transcription factor mediated signals. In this review we will discuss evidence to support the concept that the ecNOS is a constitutively expressed gene subject to a modest degree of regulation by important physiological influences.

[The pathomechanisms of virus-induced demyelination]

The pathomechanisms of virus-induced demyelination have been widely studied, especially in animal models, in order to elucidate the pathogenesis of a human demyelinating disease, multiple sclerosis. The recent development of molecular biology has partially defined the genomic segment responsible for demyelination in some viruses. It is, however, still unclear, how such a segment causes demyelination. Three main issues have been addressed regarding the mechanisms of demyelination, i.e., oligodendrocyte lytic viral infection, immune-mediated demyelination with oligodendrocyte viral infection, and immune-mediated demyelination without oligodendrocyte viral infection. Immune responses of the host are, therefore, critical, as well as viral replication and propagation in virus-induced demyelination.

Development and evaluation of antithrombogenic centrifugal pump: the Baylor C-Gyro Pump Eccentric Inlet Port Model

The Baylor C-Gyro Pump Eccentric Inlet Port Models (C1E) have been developed aiming for a long-term centrifugal ventricular assist device (VAD) as well as a cardiopulmonary bypass pump. The eccentric inlet port models are characterized by their unique inlet port and secondary impeller vanes. An inlet female pivot bearing, which was fixed to a supporting bar in the prototype model, is directly embedded into the ceiling of the pump casing. An inlet port is then placed off-center to avoid the bearing area, and it is angled between 0 to 90 degrees from the upright position. In addition, small secondary vanes were incorporated into the impeller bottom to accelerate the washout flow behind the impeller. These features attained design objectives proposed for higher antithrombogenicity: a seal-less pump chamber, no stationary parts in the blood path, and acceleration of the secondary flow behind the impeller. The first in vivo experiment using C1E pumps showed excellent antithrombogenicity for up to 18 days when the experiment ceased due to severe infection in the calf.

Does hematocrit affect in vitro hemolysis test results? Preliminary study with Baylor/NASA prototype axial flow pump

The effect of hematocrit (Ht) on in vitro hemolysis test results (i.e., index of hemolysis) was evaluated using a Baylor/NASA prototype axial flow pump. Red blood cell suspensions of six different Ht (5, 10, 15, 20, 30, 40%; n = 30) were prepared and used for this evaluation. The pump was operated for 60 min under 5 L/min flow conditions, and blood samples were taken every 10 min to measure plasma free hemoglobin levels. The normalized index of hemolysis (NIH) was calculated using the regression line slope between time and plasma free hemoglobin level, and relationships between NIH and Ht or hemoglobin (Hb) were checked. NIH and Ht had a statistically significant (p < 0.0001) correlation with a coefficient of fit of 0.976, and NIH and Hb had a statistically significant (p < 0.0001) correlation with a coefficient of fit of 0.976. To reduce the effect of Ht, NIH/Ht was proposed and compared with a modified index of hemolysis (MIH), which was normalized by the Hb level of blood. NIH/Ht and MIH had a poor correlation with Ht (coefficient of fit, 0.608) and Hb (coefficient of fit, 0.577), respectively. When blood that has a wide range of Ht or Hb values is used for in vitro hemolysis tests, NIH/Ht is suggested for use as an index of hemolysis to evaluate the hemolysis characteristics of rotary blood pumps because MIH has no dimension and it requires Hb values. In contrast, NIH/Ht has a dimension of g/100 L, which is quite understandable, and it does not require measurement of Hb levels of blood; it is therefore cost-effective.

The Baylor total artificial heart. Flow visualization studies

To analyze the flow patterns of the left blood chamber of the Baylor total artificial heart (TAH) and to evaluate influences of the inflow valve angle to the flow patterns, flow visualization studies were performed. The inflow valve angle of the left housing was changed by 20 degrees orthogonal to the inflow tube, and comparison studies of the modified and unmodified models were made. For evaluating sectional flow patterns, a laser light was used, the clear transparent housing was scanned segmentally, and flow patterns were recorded on high contrast film for measuring flow velocities. A signal was used that synchronized the timing of the camera shutter to the pusher-plate movement signal. With the modified 20 degree inflow valve direction, there were better closing characteristics of the inflow valve leaflets. At the same time, we could successfully reduce the vortex formation at the inflow port, which may cause thrombus formation. We also have improved the washout during the diastolic phase in not only the bottom area, but in the entire pumping chamber. This flow visualization setup is simple and inexpensive. It is useful not only for validation of global flow patterns, but also for validation of local flow velocities of various blood pumps.