A new description of arterial function: the compliance-pressure loop

Hypertension and atherosclerosis are associated with reduced arterial compliance, which is the principal component that reflects the dynamic behavior of the arterial system. Hence, change in arterial compliance has been used as a compass of arterial wall properties, as well as an effective parameter for assessing therapeutic treatment efficacy. The arterial compliance-blood pressure loop concept is introduced here for assessment of arterial function. Aortic pressure and flow were measured in experimental dogs during normal and acute hypertension. The compliance-pressure loops were constructed from pulsatile blood pressure waveforms and the corresponding compliances. The features of the loop are that, for any given heart beat, arterial compliance is seen to be maximal in early systole to facilitate ventricular ejection, compliance decreasing during the remainder of systole owing to increased blood pressure and reduced aortic flow, compliance in diastole increasing as pressure declines. The arteries are stiffer with reduced compliance in hypertension. Thus, the compliance-pressure loop can provide an effective characterization of the dynamic behavior of the arterial system in terms of pressure-flow relation and blood vessel properties.

Glycated haemoglobin and cardiovascular risk factors in Chinese subjects with normal glucose tolerance

Increased plasma glucose concentration is a predictive factor for mortality in both diabetic and non-diabetic subjects. Although glycated haemoglobin (HbA1c) is a useful index of mean blood glucose concentrations over the preceding 1 to 3 months, there are few data regarding its relationship to cardiovascular risk. We have examined the relationship between HbA1c and cardiovascular risk factors in 1280 subjects with normal glucose tolerance. Based on HbA1c tertiles (tertile 1: n = 427, 262 men and 165 women, HbA1c level: 2.9-4.7% in men and 3.2-4.2% in women; tertile 2: n = 426, 261 men and 165 women, HbA1c level: 4.7-5.1% in men and 4.2-4.6% in women; tertile 3: n = 427, 262 men and 165 women, HbA1c level: 5.1-6.7% in men and 4.6-6.9% in women), increasing HbA1c was associated with increasing age, blood pressure, waist-hip ratio, fasting and 2-h plasma glucose, 2-h insulin, cholesterol, low-density lipoprotein cholesterol, apolipoprotein B and urate concentrations. When age and sex were included as covariates, increasing HbA1c remained associated with increasing fasting and 2-h plasma glucose, 2-h insulin, total cholesterol, and low-density lipoprotein cholesterol concentrations. These findings emphasize the importance of hyperglycaemia, as reflected by HbA1c, as a continuum in the evaluation of cardiovascular risk. Furthermore, these findings support the hypothesis that cardiovascular disease risk commences with rising glucose concentrations before 'conventionally-defined' glucose intolerance occurs.

Gelatin nanoencapsulation of protein/peptide drugs using an emulsifier-free emulsion method

The nanoencapsulation of a model protein drug, bovine serum albumin (BSA), using gelatin as the matrix material is reported. Nanoencapsulation was conducted using a modified water-in-oil (w/o) emulsion method, which is emulsifier-free and simple. The nanoencapsulation product, BSA-containing gelatin nanoparticles, is characterized in terms of nanoparticle morphology, size and size distribution, water content, and in vitro protein release. The BSA-containing gelatin nanoparticles obtained from this nanoencapsulation process are nearly spherical and have a log-normal size distribution. The average diameter of the BSA-containing gelatin nanoparticles is approximately 840 nm. They can absorb 51-72% of water. In vitro release experiments demonstrate that BSA has been successfully encapsulated in, and can be released from the gelatin nanoparticles. The release of BSA from the gelatin nanoparticulate matrix follows a diffusion-controlled release mechanism. It is found that temperature affects both the water content and the BSA release rate of the gelatin nanoparticles.

Clozapine: a mimicry of phaeochromocytoma

OBJECTIVE

To report a case of clozapine-induced hypertension with raised urinary catecholamines.

CLINICAL PICTURE

A 27-year-old man fulfilling DSM-III-R criteria for catatonic schizophrenia was treated with clozapine. He later developed both hypertension and raised urinary catecholamines which mimicked phaeochromocytoma.

TREATMENT

Clozapine was withdrawn.

OUTCOME

Both blood pressure and urinary catecholamines normalised.

CONCLUSIONS

Clozapine may induce sympathetic hyperactivity.

Simple anthropometric indexes and cardiovascular risk factors in Chinese

OBJECTIVE

Obesity is a major public health problem due to its associations with multiple cardiovascular risk factors. Although there are sophisticated methods, such as imaging, to document total body fat and its distributions, anthropometric measurements remain important in clinical practice. We examined the relationships between cardiovascular risk factors and the three commonest anthropometric measurements for obesity, body mass index (BMI), waist-hip ratio (WHR) and waist circumference (WC), in Hong Kong Chinese subjects.

DESIGN AND SETTING

The data are obtained from a prevalence survey for glucose intolerance and lipid abnormality in a representative Hong Kong Chinese working population. All employees from a public utility company and a regional hospital were invited to participate.

SUBJECTS

There were 1513 subjects (910 men and 603 women, mean age +/- s.e.m.: 37.5 +/- 0.2 y). All of them had no significant past medical history.

MEASUREMENTS

BMI, WHR and WC of the 1513 subjects were assessed for their relationships with various cardiovascular risk factors. These include blood pressure, fasting and 2 h plasma glucose and insulin, glycated haemoglobin, total cholesterol, triglyceride, high density and low density lipoprotein cholesterol, and urine albumin concentration.

RESULTS

After age adjustment, all three anthropometric indexes were significantly correlated with the major cardiovascular risk factors in both men and women. When BMI, WHR and WC were analysed according to quartiles, there was a significant trend for blood pressure, plasma triglyceride, fasting and 2 h plasma glucose and insulin to increase, and high density lipoprotein cholesterol to decrease, with increasing obesity after adjustment for age and smoking. Using stepwise regression analysis with the three indexes as independent variables, most of the variance in blood pressure, plasma lipid, insulin, glucose and urinary albumin concentration were explained either by WC or WHR. In women, BMI was the main explanatory variable for reduced high density lipoprotein cholesterol.

CONCLUSIONS

In Hong Kong Chinese, BMI, WHR and WC provide important information in assessing cardiovascular risks. In men, central adiposity as reflected by WC and to some extent, WHR, explained most of the variance in blood pressure, plasma glucose, lipid, insulin and albuminuria. In women, all three indexes reflecting general and central obesity contribute to the variance in these risk factors.

Computer modeling of the effects of aortic valve stenosis and arterial system afterload on left ventricular hypertrophy

The degree of left ventricular hypertrophy is generally thought to reflect the severity of aortic stenosis. However, the compounded influence of arterial system load is poorly understood. We developed a computer model to investigate the effects of aortic valve stenosis in combination with various systemic arterial parameters in the development of left ventricular hypertrophy. Data show that an increased peripheral resistance and/or aortic valve resistance, results in an increase in left ventricular wall thickness and mass, while peak systolic wall stress remains constant. Changing arterial compliance to above normal level would not induce significant changes in wall thickness, while reduction in arterial compliance below normal would cause an increase in ventricular wall thickness. When a double load is imposed on the left ventricle by way of a stenotic valve and an increased arterial afterload, a greater and an aggregated increase in wall thickness results, hastening the hypertrophic process.

The effect of age on cardiovascular risk factors in Chinese women

Chinese women traditionally have a low incidence of coronary heart disease. However, information on cardiovascular risk factors in this population are relatively scarce. We examined these risk factors in 601 Hong Kong Chinese women (age+/-SEM, 38.5+/-0.4 years; range, 18-66 years) stratified into four age groups (group 1, < or =30 years; group 2, 31-40 years; group 3, 41-50 years; group 4, > or =51 years). Increasing age in Chinese women was associated with increased body mass index, waist-to-hip ratio, systolic and diastolic blood pressure, fasting plasma total cholesterol, triglyceride, low-density lipoprotein, apolipoprotein B, fasting and 2-h plasma glucose, glycated haemoglobin, fasting plasma insulin and urate concentrations. After adjustment for body mass index, waist-to-hip ratio and smoking, all these age-related associations remained statistically significant except for fasting plasma insulin concentration. There was a progressive increase with age in the prevalence of glucose intolerance, hypertension, dyslipidaemia and obesity. These prevalence rates further increased in subjects aged 51 years (the mean menopausal age in Asian women) or above. These findings suggest that age had an important and independent effect on cardiovascular risk in Chinese women and that, as in Caucasians, the onset of menopause might further increase this risk.

Vessel growth and collapsible pressure-area relationship

The role that the pattern of vessel wall growth plays in determining pressure-lumen area (P-A) and pressure-compliance curves was examined. A P-A vessel model was developed that encompasses the complete range of pressure, including negative values, and accounts for size given the fixed length, nonlinear elastic wall properties, constant wall area, and collapse. Data were obtained from excised canine carotid and femoral arteries, jugular veins, and elastic tubing. The mean error of estimate was 8 mmHg for all vessels studied and 2 mmHg for blood vessels. The P-A model was employed to examine two patterns of arterial wall thickening, outward growth and remodeling (constant wall area), under the assumption of constant wall properties. The model predicted that only outward wall growth resets compliance such that it increases at a given arterial pressure, explaining previously contradictory data. In addition, it was found that outward wall growth increases the lumen area between normal and high pressures. Remodeling resulted in lumen narrowing and a decrease in compliance for positive pressures.

A novel biodegradable system based on gelatin nanoparticles and poly(lactic-co-glycolic acid) microspheres for protein and peptide drug delivery

Gelatin nanoparticle-poly(lactic-co-glycolic acid) (PLGA) microsphere composites were prepared by encapsulating protein-loaded gelatin nanoparticles in PLGA microspheres. This encapsulation was conducted by using a phase separation method and a solvent extraction method. The average diameter of the gelatin nanoparticle-PLGA microsphere composites is between 160 and 175 microm. Protein loading efficiency is 93.2% for the nanoparticle-microsphere composite prepared by the phase separation method, while it is 31.31% for the composite prepared by the solvent extraction method. Protein release experiments indicate that this new composite system possesses sustained release characteristics. This system also demonstrates the capability of preventing the denaturation of protein drugs.

Improved heterologous expression of the white-rot fungal ligninase H8 by crossover linker mutagenesis

Using the crossover-linker mutagenesis method, the 5' noncoding region of the lambda ML-1 cDNA, which encodes the ligninase H8 isozyme of the white-rot fungus, Phanerochaete chrysosporium, was deleted with the simultaneous insertion of the putative Spodoptera frugiperda ribosome-binding sequence (RBS) (TATAAAT) directly in front of the translation-initiation codon of this gene. A recombinant baculovirus, pVL-Mu-H8, carrying the ligninase-H8 gene was successfully constructed, as determined by both sequence analysis and dot blot hybridization. A more than 18-fold increase in the expression of ligninase H8, compared to the previous pEV11-1A.3 recombinant baculovirus, was detected in the Sf-21 insect cells. This enzyme was detected within 3 d postinfection and was biologically active, capable of oxidizing the model lignin compound, veratryl alcohol. The molecular weight of the overexpressed 42 kD protein was similar to that of the native fungal ligninase-H8 isozyme and it also reacted specifically with the anti-H8 monoclonal antibody (MAb 2D4.9) in Western blot analysis.

Plasma fibrinogen concentration in a Chinese population

Plasma fibrinogen concentration has been shown to be a predictor of major cardiovascular events. Information on plasma fibrinogen amongst Chinese has been scanty. We examined the relationships between plasma fibrinogen concentration and cardiovascular risk factors in 988 chinese subjects who underwent 75 g oral glucose tolerance test for screening for glucose intolerance. The study involved a selected sample with subjects who had an history of gestational diabetes, delivery of big babies (birth weight > or = 4 kg), equivocal plasma glucose concentrations and subjects who were family members of diabetic patients. This was mainly a non-smoking (96.6%), non-drinking (98%) and non-exercising (99%) population of which 87% (n = 855) were female. Among the 988 subjects (age +/- S.D. 36.8 +/- 10.2, range 16-79 years), plasma fibrinogen concentration ranged from 1.40 to 9.90 g/l with a mean of 3.26 +/- 0.93 g/l. On stratification of the subjects into 4 quartiles based on plasma fibrinogen concentrations, we found that increased plasma fibrinogen was associated with older age, higher body mass index (BMI), systolic and diastolic blood pressure (BP), fasting and 2 h plasma glucose (PG), prevalence of diabetes, glycated haemoglobin (HbA1c) and triglyceride (TG) level. After adjustment for age and sex, increased plasma fibrinogen concentration remained associated with higher BMI, systolic BP, 2 h PG and TG level. On multivariate analysis using age, BMI, BP, TG, HbA1c and PG as independent variables, plasma fibrinogen was independently related to plasma TG concentration and HbA1c. With 1 S.D. change in TG concentration and HbA1c, there were 3.7 and 5.2% changes in plasma fibrinogen concentration respectively. These findings emphasize the close relationships between plasma fibrinogen and cardiovascular risk factors, in particular abnormal lipid and glucose metabolism.

Novel design of a regional myocardial force transducer

A novel force transducer was designed to measure the circumferential regional force developed in the ventricular myocardium in vivo. The transducer is composed of a frame, a carrier bar, and a cantilever spring. Two resistance strain gauges embedded on the spring serve as force-sensing elements. The output of a Wheatstone-bridge circuit, containing these two gauges and a temperature compensation resistor, is connected to a preamplifier. The main advantages of this prototype include the initial stretch-adjustment ability (physiologic 0) low temperature drift, high linearity (r = 0.99) with loads ranging from 0 to 100 g, and moderate sensitivity of 0.232 mV/V/g at room temperature. The transducer was validated with in-vivo canine experiments. The experimental results showed that this transducer can be used to reliably measure the myocardial force development during altered cardiac conditions, such as myocardial stunning and myocardial ischemia.

Modeling of mechanical dysfunction in regional stunned myocardium of the left ventricle

Reversible mechanical dysfunction of the myocardium after a single or multiple episode(s) of coronary artery occlusion has been observed in previous studies and is termed myocardial stunning. The hypothesis that stunning could be represented by a decrease in maximum available muscle force in the stunned region was examined by means of a mathematical model that incorporates series viscoelastic elements. A canine experimental model was also employed to demonstrate depressed contractility and a consistent delay of shortening in the stunned region. The mechanical model of the left ventricle was designed to include a normal and stunned region, for which the stunned region was allowed to have variable size. Each region consisted of a volume and time dependent force generator in parallel with a passive elastic force element. The passive elastic element was placed in series with a constant viscosity component and a series elastic component. The model was solved by means of a computer. Passive and active properties of each region could be altered independently. The typical regional measures of muscle performance such as percent shortening, percent bulge, percent thickening, delay of shortening, percent increase in end-diastolic length and other hemodynamic measures were computed. These results were similar to those observed in animal models of stunning. In addition, a nearly linear relationship with end-diastolic length and delay of shortening was predicted by the model. It was concluded that a decrease in the peak isovolumic elastance and augmentation of viscosity effect of creep during stunning can explain mechanical abnormalities of stunned myocardium.

Unstable radii in muscular blood vessels

A model of a muscular blood vessel in equilibrium that predicts stable and unstable control of radius is presented. The equilibrium wall tension is modeled as the sum of a passive exponential function of radius and an active parabolic function of radius. The magnitude of the active tension is varied to simulate the variable level of smooth muscle activation. This tension-radius relationship is then converted to an equilibrium pressure-radius relationship via Laplace's law. This model predicts the traditional ability to control the radius below a critical level of activation. However, when the active tension is raised above this critical level, the pressure-radius relationship (with pressure plotted on the ordinate and radius on the abscissa) becomes N shaped with a relative maximal pressure (Pmax) and a relative minimal pressure (Pmin). For this N-shaped curve, there are three equilibrium radii for any pressure between Pmin and Pmax. Analysis shows that the middle radius is unstable and thus cannot be maintained at equilibrium. Previously unexplained experimental data reveal evidence of this instability.

Analysis of effect of two concurrent ischaemic zones on left ventricular function

Left ventricular (LV) function due to two concurrent ischaemic zones (IZs) is investigated using a cardiovascular system model. The model comprises a three-compartment LV, the venous return and the arterial system. Haemodynamic responses of the LV to changes in the IZ size and myocardial contraction timings are explored. Results show that the greater the degree of asynschonisation is between the normal zone and the IZ, and the larger the ischaemic size, the more severe the LV dysfunction. Pre-load augmentation improves LV function. Model-predicted features are consistent with reported observations associated with myocardial ischaemia. The extent of the usefulness and limitations of this model is also discussed.

Serum bilirubin and cardiovascular risk factors in a Chinese population

BACKGROUND

Many risk factors for cardiovascular disease (CVD) have been identified. Recently an association between low concentration of serum bilirubin and increased risk of CVD has been reported. However, information on this topic remains scarce.

METHODS

We examined the relationships between serum bilirubin and CVD risk factors in 1508 Hong Kong Chinese. We divided the subjects into four quartiles based on serum bilirubin concentrations. Cardiovascular risk factors studied include age, sex, smoking, obesity glycaemic status and lipid indices.

RESULTS

Decreasing serum bilirubin concentration was associated with older age, increased prevalence of smoking, higher body mass index and systolic blood pressure, increased glycated haemoglobin, fasting and 2 h insulin, triglyceride, very-low-density lipoprotein and apolipoprotein B concentrations, and lower high-density lipoprotein concentration. Women had lower bilirubin concentrations than men. After adjustment for age, sex, smoking and insulin levels as covariates, the associations between serum bilirubin concentration and glycated haemoglobin, triglyceride, high-density lipoprotein and very-low-density lipoprotein persisted. The prevalence rates of abnormal glucose tolerance (impaired glucose tolerance or diabetes) were similar amongst the four quartiles of bilirubin concentrations. However, the mean bilirubin concentration was significantly lower in subjects with abnormal glucose tolerance (9.3 +/- 3.5 mumol/l, n = 178) than in normal subjects (10.1 +/- 5.2 mumol/l, n = 1330, P = 0.039). When analysed as a continuous variable by age-adjusted partial correlation coefficients, serum bilirubin concentration was inversely correlated with fasting insulin, triglyceride, very-low-density lipoprotein and glycated haemoglobin level.

CONCLUSIONS

There were close associations between low serum bilirubin concentration and increased CVD risk factors. Subjects with abnormal glucose tolerance also had lower serum bilirubin concentration than normal subjects. Some of these associations (body mass index, systolic blood pressure) could be explained by differences in insulin level. These relationships between bilirubin and CVD risk factors require further clarification, although abnormal intermediary metabolism and antioxidant deficiency may be possible linking factors.

Computer modeling of non-adjacent regional ischemic zones on ventricular function

Multiple regional myocardial ischemia that leads to depressed left ventricular (LV) function is commonplace. Quantitative analysis of the hemodynamic consequences, however, has been limited. We investigated this aspect using a novel computer model of the cardiovascular system. The model consists of an LV with two ischemic zones (IZs) and a normal zone (NZ), the preload, and the arterial system afterload. The IZ size and activation timing could be altered. Results show that the greater the size and activation asynchronization between NZ and IZ, the more severe the LV dysfunction. Increased preload during ischemia improved LV function. This computer model predicts features that agree well with reported experimental observations and is particularly useful for myocardial ischemic function analysis.

Thyrotoxic periodic paralysis in a Chinese population

We retrospectively evaluated the characteristics of adult patients admitted with thyrotoxic hypokalaemic periodic paralysis in Hong Kong. From 1984 to 1993, 45 Chinese adult patients were admitted with acute limb weakness, plasma potassium < or = 3.5 mmol/l and thyrotoxicosis confirmed by laboratory investigations. All but one were male. Seventy-five percent of attacks occurred between 9pm and 9am. Half of the attacks occurred between July and October (49.1%), most commonly in August (20%). Mean (+/- SEM) plasma potassium on admission was 2.17 +/- 0.08 mmol/l (range 1.1-3.5). In 15 episodes (27.3%), plasma potassium on recovery exceeded 5.0 mmol/l, while in three episodes (5.5%), potassium exceeded 6.0 mmol/l. No patient had a positive family history of thyrotoxic periodic paralysis. Only 28.9% had a known history of thyrotoxicosis before their first presentation with periodic paralysis. Twenty-seven (60%) had clinical evidence of thyrotoxicosis. Although all were biochemically thyrotoxic, 11.4% had only a mild degree of thyrotoxicosis (suppressed thyroid-stimulating hormone, high free thyroxine, but normal free triiodothyronine). One quarter of the patients had a normal erythrocyte zinc concentration, indicating either a short history of thyrotoxicosis or transient thyrotoxicosis. The diagnosis of thyrotoxic hypokalaemic paralysis should always be considered in Chinese patients with acute muscle weakness, especially in young males. Absence of clinical thyrotoxicosis does not exclude the diagnosis. Plasma potassium should be monitored carefully during treatment to prevent rebound hyperkalaemia.

Topography and immunogenicity of bluetongue virus VP7 epitopes

The core of bluetongue virus (BTV) consists of ten dsRNA viral genome segments and five proteins, including two major (VP7 and VP3) and three minor (VP1, VP4 and VP6) components. The major core protein VP7 is believed to be an important structural constituent because it interacts, not only with the underlying core protein VP3, but also with two outer capsid proteins (VP2 and VP5). In this communication we summarise data on the mapping of at least six different epitopes of VP7 distributed along the molecule. Two of the six epitopes have not been mapped previously. The accessibility of these epitopes in intact virions and core particles was analysed using immunoelectron microscopy. The epitope located near the N-terminus of VP7 was accessible at the surface of intact virions and core particles. Epitopes in other parts of the VP7 molecule were detected weakly in core particles but not in intact virions. These results support the proposal that VP7 molecules are orientated with their N-terminus accessible on the surface of either the particle or at least one of the three different channels observed by cryoelectron microscopy in the outer capsid layer. Analysis of the immune response to BTV-infected or -immunised sheep and rabbits to three selected epitopes, which are located in different regions of the VP7 molecule, demonstrated that all of them were recognised by the animals tested. These results provided further molecular evidence suggesting that VP7 is indeed a major immunogenic antigen ideal for BTV antibody detection.

Sequence analyses and antigenic epitope mapping of the putative RNA-directed RNA polymerase of five U.S. bluetongue viruses

We determined the complete nucleotide sequences of the cognate L1 double-stranded RNA segments of bluetongue virus (BTV) serotypes 2, 11, 13, and 17, which encode the putative RNA-directed RNA polymerase VP1. Each L1 gene contained 3944 nucleotides and was 10 bases shorter than the previously reported L1 gene of BTV 10. A single open reading frame which could encode the reported VP1 protein, 1302 amino acids in size, began with an initiation codon at nucleotides 12-14 and a termination codon at nucleotides 3918-3920. Analyses of the nucleotides of L1 genes and the deduced amino acid sequences of VP1 proteins of the five U.S. BTV serotypes indicated that the most recently isolated BTV-2 serotype from Florida was more distantly related than BTV-10, 11, 13, and 17, which were isolated primarily in the western U.S.A. The results are consistent with our hypothesis that BTVs-10, -11, -13, and -17 are derived from a single and common gene pool, and that BTV-2 belongs to a second, distinct gene pool. These genetic distinctions also reflected well with the known geographic distribution of the five U.S. BTV serotypes in North America. This putative RNA-directed RNA polymerase (149 KDa) was a basic protein, and the deduced amino acid sequences of the VP1 proteins contained seven highly conserved hydrophobic domains and many other sequence motifs which were also found in other known RNA polymerases. Four immunodominant but linear antigenic epitopes conserved among the VP1 of five U.S. BTVs were also been identified and mapped using monospecific oligoclonal antibodies.

Arterial wave propagation phenomena, ventricular work, and power dissipation

The effects of wave propagation phenomena, namely global reflection coefficient (gamma G[omega]) and pulse wave velocity (Cph), are studied in a model of the coupled left ventricle/arterial system. The left ventricle consists of a time-varying elastance, while the arterial system is modeled as a single, uniform, elastic tube terminating in a complex load. Manipulation of model parameters allowed for the precise control of gamma G(omega) and Cph independent of each other, peripheral resistance, and characteristic impedance. Reduction of gamma G(omega) and Cph were achieved through increases in load compliance and tube compliance, respectively. The equations describing the system were solved for left ventricular and aortic pressures and aortic flow. From these, stroke volume (SV), left ventricular stroke work (SW), and steady (Ws), oscillatory (Wo), and total power dissipation (Wt) in the arterial system were calculated. An index of arterial system efficiency was the ratio Wo/Wt (%Wo), with lower values indicating higher efficiency. Reduction of gamma G(omega) yielded initial increases in Ws, while Wo increased for the entire range of gamma G(omega), resulting in increased %Wo. This reduced efficiency is imposed on the ventricle, resulting in increased SW without increased SV. On the other hand, decreased Cph yielded in a steady increase in Ws and a biphasic response in Wo, resulting in reduced %Wo for most of the range of reduced Cph. These results suggest that differential effects on arterial system efficiency can result from reductions of gamma G(omega) and Cph. In terms of compliance, changes in arterial compliance can have different effects on efficiency, depending on where the compliance change takes place. Reasons for these results are suggested, and the role of distributed compliances is raised as a new problem.

Characterization of heterologously expressed recombinant retinoic acid receptors with natural or synthetic retinoids

The first step in retinoid action is binding to their nuclear receptors. Therefore, characterization of binding characteristics of retinoids is of major importance. Human retinoic acid receptors alpha (hRAR alpha), hRAR beta, and mouse RAR gamma (mRAR gamma) were expressed heterologously in Escherichia coli as a recombinant glutathione S-transferase (GST) fusion protein. The expressed fusion proteins were functional and bound specifically to the all-trans-retinoic acid (RA). The dissociation constants (Kd) for RA were 1.4 nM for GST-hRAR alpha, 1.4 nM for GST-hRAR beta, and 3.3 nM for GST-mRAR gamma, respectively. The fusion proteins were further used for competitive displacement assays to determine the displacement constant (DC50) for other selected retinoids. All-trans-RA and 4-oxo-all-trans-RA have high affinity with all three receptors (DC50 = 0.8-55 nM). The 13-cis RA binds to hRAR alpha with low affinity, but not to other RARs evaluated here. All-trans-N-ethylretinamide, all-trans-retinylacetate, and an ethyl ester of tetrahydronaphthalene derivative had no affinity to any RARs. The hRAR alpha and mRAR gamma receptors did not bind a naphthalene carboxylic acid derivative of RA, but hRAR beta binds this chemical with high affinity. Results indicated that the three recombinant proteins were functional in binding various RA congeners. The affinity and binding data of these retinoids were compared to their observed teratogenic activity.

Mapping and characterization of antigenic epitopes and the nucleic acid-binding domains of the VP6 protein of bluetongue viruses

Heterologously expressed VP6 and truncated VP6 proteins of bluetongue virus (BTV) serotype 11 purified to near homogeneity were used for structure and function analyses. The yield of the expressed VP6 was host cell dependent. Six antigenic epitopes of VP6 of BTV were identified and mapped by immunoblot analyses and enzyme-linked immunosorbent assay with oligoclonal antibodies. These determinants were surface accessible and conserved among the cognate VP6 proteins of five U.S. BTV serotypes. The amino acid sequences and sizes of these six antigenic epitopes were determined, and their precise locations were also mapped and confirmed by deletion analyses. The nucleic acid binding activities of VP6, confirmed by electrophoretic mobility shift assay, were concentration dependent. The binding activities and affinities of the purified expressed VP6 protein towards double-stranded RNA and double-stranded DNA were similar. Two domains of VP6, corresponding to three of the six antigenic epitopes, were responsible for the nucleic acid binding activities and have been mapped within 28 amino acids near the middle and 11 residues near the carboxyl terminus of VP6 by electrophoretic mobility shift assay and deletion mutant analyses. Synthetic oligopeptides corresponding to these three regions also exhibited similar concentration-dependent nucleic acid binding activities.

Analyses and conservation of sequences among the cognate L3 segments of the five United States bluetongue viruses

We determined the complete nucleotide sequences of the cognate L3 double-stranded RNA (ds-RNA) segments of bluetongue virus (BTV) serotypes 2, 11, and 13 encoding the major viral inner capsid protein, VP3. Each cognate L3 segment was 2772 nucleotides long and contained a single open reading frame (ORF) with an initiation codon at nucleotides #18-20 and a termination codon at nucleotides #2721-2723. This ORF can encode the 901-amino acid VP3 protein (103 kDa) with a calculated isoelectric point of 6. Phylogenetic analyses using both the nucleotide and the deduced amino acid sequences of the L3 cognate gene of the five US BTV serotypes indicated that the BTV-2 serotype recently isolated in Florida was more distantly related than BTV-10, 11, 13 or 17. The five US BTV serotypes were derived apparently from two distinct gene pools, findings consistent with their current geographic distribution in North America.

Differential effects of wave reflections and peripheral resistance on aortic blood pressure: a model-based study

It has been generally accepted that arterial system wave reflections act to increase aortic blood pressure and the load placed on the left ventricle. Using a mathematical model of the coupled left ventricle-arterial system, we predict that this is not the case. With the model, two aspects of wave reflection, the global reflection coefficient [TG(omega)] and the pulse wave velocity (cph), were adjusted independently. In addition, TG(omega) and cph could be altered independently of the direct-current properties of the arterial system model. Reduction of TG(omega) yielded increases in stroke volume (SV) as well as in peak systolic (Ps), diastolic (Pd), and mean aortic (Pao) pressures and, hence, increased the load on the left ventricle. SV and Pao increased only in the range where strong reflection occurs. Reduced cph also yielded higher pressures, whereas increased cph resulted in reduced Pao and Pd but increased Ps. The changes in pressures and SV in response to altered TG(omega) and cph were relatively small compared with absolute levels. Simulated vasoconstriction and vasodilation further demonstrated the much greater importance of peripheral resistance on pressure and SV levels and lead to the prediction that pressure reduction in vasodilation occurs not because of, but in spite of, reduced wave reflections. We conclude that these results have not yet been observed experimentally, because reflection cannot yet be separated from the direct-current properties of the arterial system; therefore wave reflections themselves have not yet been adequately studied in the intact animal.

Arterial compliance and its pressure dependence in hypertension and vasodilation

Arterial compliance has been recognized to be pressure-dependent. Its variation due to changing systolic and diastolic blood pressures in hypertension and subsequent vasodilation has not been investigated. The authors examined this aspect by combining an animal experiment and a recently established nonlinear windkessel model of the arterial system that incorporates a pressure-dependent arterial compliance, C(P). Aortic pressure and flow were simultaneously measured in experimental dogs during control and during methoxamine-induced hypertension and nitroprusside-induced vasodilation. A numerical procedure was implemented to compute the nonlinear compliance and account for the pressure dependence. Results show that within the cardiac cycle, C(P) reached its maximum at end-systole and increased in diastole when diastolic aortic pressure decayed. The magnitude of C(P) and its variation within the cardiac cycle was larger at low pressures, while the reverse was found when blood pressure was high. C(P) decreased significantly in hypertension and increased during subsequent vasodilation.

Pathogenesis of gall stones in Crohn's disease: an alternative explanation

The increased prevalence of gall stones in Crohn's disease is thought to be related to depletion of the bile salt pool due either to terminal ileal disease or after ileal resection. This study was designed to examine whether this hypothesis is correct and explore alternative explanations. Two hundred and fifty one randomly selected patients (156 females, 95 males, mean age 45 years) were interviewed and screened by ultrasonography to determine the prevalence of gall stones in a large population of patients with Crohn's disease. Sixty nine (28%) patients had gall stones proved by ultrasonography (n = 42), or had had cholecystectomy for gall stone disease (n = 27). The risk factors for the development of gall stones including sex, age, site, and duration of disease, and previous intestinal resection were examined by multivariate analysis. Age and duration of disease were positive risk factors for gall stones and were covariables. The site of disease and of previous intestinal resection did not predispose to gall stones. Previous surgery was an independent risk factor for the development of gall stones, the risk increasing with number of laparotomies. It is suggested that mechanisms other than ileal dysfunction may predispose to gall stones. Postoperative gall bladder hypomotility with biliary sludge formation may be precursors of gall stone formation in patients with Crohn's disease.

Conservation of the segment 4 gene sequence and of a leucine zipper motif in VP4 among five US bluetongue viruses

Full-length cDNA copies of the segment 4 (M1) genes of US Bluetongue viruses serotype-2, -10, -11, -13, and -17 were selectively amplified using genomic double-stranded RNA segments from purified BTV virions as templates and a modified polymerase chain reaction (Clamp-R). They were then cloned into pUC19 plasmids and both strands of several clones were sequenced. The length of all five segment 4 genes is 1981 nucleotides, which is 30 nucleotides shorter than that of the BTV serotype-10 reported by Y. Yu, A. Fukusho, and P. Roy (Nucleic Acids Res. 15, 7206 (1987)). The 5'- and 3'-noncoding regions of all five segment 4 genes are identical among all serotypes. The plus sense strand of the BTV segment 4 gene, which encodes the VP4 protein, possesses a single long open reading frame with an initiation codon (ATG) at nucleotides 9-11 and a stop codon (TAA) at nucleotides 1941-1943. This open reading frame encodes for a protein of 644 amino acid residues with a predicted molecular weight of about 75 kDa and a pI of +7 to +7.9. A potential leucine zipper motif was detected near the carboxyl terminus of the deduced VP4 amino acid sequence. The phylogenetic analysis using the sequences of these five cognate segment 4 genes is consistent with the results of our previous phylogenetic studies of cognate genome segments 5, 6, 8, 9, and 10. Serotype-10, -11, -13, and -17 are closely related and serotype-2 is the most distantly related among the five US BTV serotypes.

Identification and localization of a serotypic neutralization determinant on the VP2 protein of bluetongue virus 13

We have used a serotype-specific monoclonal antibody to locate a neutralization epitope on the outer capsid protein, VP2, of the bluetongue virus 13. This surface-accessible region of the virion was recognized by a monoclonal antibody, D24.15, which exhibited serotype-specific neutralizing activity as determined by plaque reduction assay. In Western blots, this monoclonal antibody reacted only with the VP2 of bluetongue virus 13, but not with any of the other US BTV serotypes. Competition with sequence-specific synthetic peptides identified only one linear synthetic peptide (EMDD-DETEYE), corresponding to amino acids 642-651 of VP2 of bluetongue virus 13 that could block both the neutralizing activity of MAb D24.15 and its specific binding to VP2 of BTV-13. However, oligoclonal antibody against this synthetic peptide did not exhibit any neutralizing activity. These data suggest that the serotype-specific neutralization determinant of the outer capsid protein VP2 is located on the surface of the BTV-13 virion and represents the major component of a conformational epitope.

Glycosylation of the major outer capsid protein of bluetongue viruses

The major outer capsid protein, VP5, of five US bluetongue viruses, was found to be glycosylated. Enzymatic removal of the carbohydrate moiety did not affect the electrophoretic mobility of VP5 in SDS-PAGE, indicating the presence of only short and possibly unbranched oligosaccharide chains. The surface accessibilities and immunogenic specificities of two conformational-dependent antigenic epitopes on VP5 of BTV were not affected by deglycosylation. Selective binding of those lectins which have well-defined sugar specificities suggests that the potential short N-linked carbohydrate chain present on BTV VP5 might be composed of sialic acid alpha(2-6)-N-acetylgalactosamine-beta(1-3)-galactose-beta(1-4)-N- acetylglucosamine-beta(1-2)-mannose-N-acetylglucosamine-Asn. In accordance with the standard nomenclature, BTV-VP5 should now be termed GP5 due to the presence of the carbohydrate moiety.

High-sequence conservation among the United States bluetongue viruses cognate M2 genes which encode the nonstructural NS1 tubule protein

Full-length cDNA copies of the M2 gene of BTV-2, -11, and -13 serotypes obtained by a modified polymerase chain reaction (Clamp-R) were cloned into pUC19 plasmid. The entire nucleotide sequences of each M2 gene were determined and compared with BTV-10 and BTV-17, thus completing the sequencing of these cognate M2 gene segments from all five U.S. BTV serotypes. Each M2 segment contained 1769 nucleotides, a single open reading frame (ORF) with an initiation codon at nucleotides 35-37, and a termination codon at nucleotides 1691-1693. This ORF can encode the 552-amino-acid NS1 protein (64 KDa) which has an isoelectric point of 7. Analyses of the nucleotide and deduced amino acid sequences of the five U.S. BTV serotypes indicated that the most recently isolated BTV-2 serotype was more distantly related than BTV-10, -11, -13, or -17. Analyses of the evolutionary relatedness of the cognate M2 genes by codon positions indicate that the rate of mismatch accumulations in the first and second base codon positions are less than 4%. However, the mismatch accumulations in the third base codon position are quite evident (23%) when BTV-2 serotype was compared with the other U.S. BTV serotypes. This suggests that BTV-2 has separated from the other four U.S. serotypes long before they themselves diverged. These data also indicate that the five U.S. BTV serotypes were apparently derived from two distinct gene pools that reflected geographic distribution in North America.

Feedback effects in heart-arterial system interaction

Dynamic arterio-ventricular interaction in terms of left ventricle elastance and nonlinear arterial system compliance, pulse wave reflections and coronary blood flow was investigated, combining the use of analog models of the circulation with data from animal experiments. Results show that dynamic factors, as well as "feedback" effects are important.

Repeated reflection of waves in the systemic arterial system

Traditional analysis of pulse-wave propagation and reflection in the arterial system treats measured pressure and flow waves as the sum of a single forward wave (traveling away from the heart) and a single backward wave (traveling toward the heart). The purpose of this study was to develop a more general wave reflection theory that allows repeated reflection of these waves. The arterial system was modeled as a uniform viscoelastic tube terminating in a complex load with reflections occurring at the tube load interface and the heart tube interface. The resulting framework considers the forward wave to be the sum of an initial wave plus a series of antegrade waves. Similarly, the backward wave is the sum of a series of retrograde waves. This repeated reflection theory contains within it the traditional forward/backward wave reflection analysis as a special case. In addition, the individual antegrade and retrograde waves, at the tube entrance, are shown to be independent of the tube length. Aortic pressure and flow data, from dog experiments, were used to illustrate the phenomenon of repeated reflections. Alteration of the arterial system loading conditions, brought about through pharmacological intervention, affected the number and morphology of repeated waves. These results are compared with those found in traditional forward/backward reflection analysis.

Iontophoretically enhanced transdermal delivery of an ACE inhibitor in induced hypertensive rabbits: preliminary report

Both conventional direct current (DC) and pulsed-mode DC constant-current iontophoresis were used to investigate enhanced transdermal delivery of the angiotensin-converting enzyme (ACE) inhibitor captopril to rabbits with acutely induced hypertension. Passive transdermal captopril administration and pulsed DC constant-current iontophoresis of the vehicle were studied as control experimentation. Mean arterial pressure (MAP) was not significantly (p > 0.05) altered following passive transdermal delivery of captopril (n = 4) or after iontophoretic delivery of the vehicle alone (n = 4). Pressure reduction was evident within 10 minutes of iontophoretic enhancement of transdermal captopril delivery. DC mode constant-current (n = 4) iontophoretic transdermal captopril administration caused MAP to fall by 21% from a mean hypertensive level of 66 +/- 5 mmHg to a mean post-treatment level of 52 +/- 6 mmHg (p < 0.05) within 60 minutes. Pulsed DC mode constant-current (n = 4) iontophoresis of captopril caused mean MAP to fall on average by 27% from 62 +/- 6 to 45 +/- 5 mmHg (p < 0.05), also within 60 minutes. This paper provides the first report on the enhanced efficiency during iontophoretic delivery of an ACE inhibitor. We have concluded that both modes of constant-current iontophoresis of captopril offer a safe and effective means of pressure reduction in rabbits with induced hypertension and that there is no significant difference in efficacy between the two forms of enhanced delivery. These results have potential applications for enhanced transdermal delivery of ACE inhibitors in humans.

Cardiac adaptation of sarcomere dynamics to arterial load: a model of hypertrophy

In the past, the dynamics of the left ventricle were studied by its response to altered venous and arterial load for a given heart. This led researchers to propose the concept of an arterioventricular match or optimal point of function. The model of this paper reverses that idea by fixing preload and afterload while computing cardiac function due to altered left ventricular size or shape, resulting from modification of the number of parallel and series sarcounits. A mathematical model of physiological hypertrophy is introduced. Series and parallel arrangements of sarcounits constitute a cylindrical model of the left ventricle. Filling occurs from a venous reservoir with constant pressure through a valve, while ejection takes place into a three-element model of the systemic arterial system through another valve. It is found that the dynamics of the myofibrils can be matched to those of the left ventricle by choosing a ventricular shape that results in a minimum in myocardial O2 consumption (MVO2) for any constant ventricular load. A unique solution for the size of the ventricle results if the rate of MVO2 is specified. The model is able to predict correctly hypertrophy due to hypoxia and due to pressure (concentric) and volume (eccentric) overloads.

Evolutionary analyses of five US bluetongue viruses using the cognate S2 genes

Full-length cDNA copies of S2 genes (segment 8), coding for non-structural protein 2 (NS2) of bluetongue virus serotypes 2, 11, 13 and 17 were selectively synthesized by a modified polymerase chain reaction (Clamp-R) and cloned into the PstI site of the pUC19 plasmid. Each of these S2 cognate genes was 1125 nucleotides in length with an initiation and a termination codon at nucleotides 20-22 and 1082-1084, respectively, resulting in a long open reading frame capable of coding for a protein of 354 amino acids. The deduced amino acid sequence of NS2 protein had a high concentration of lysine and contained a relatively low number of tryptophan and histidine residues. There was a highly conserved hydrophilic region at the carboxyl termini of predicted NS2 proteins in all five BTV serotypes, even though the amino acid sequence in this region in BTV-2 was more variable than in the other four serotypes. There was significant sequence homology of the cognate S2 genes at both the nucleotide and the amino acid levels. Phylogenetic analyses using the S2 gene sequences indicated that BTV-10, -11, -13 and -17 were more closely related and BTV-2 was the most distantly related serotype among the five US bluetongue viruses.

Production and characterization of recombinant lignin peroxidase isozyme H2 from Phanerochaete chrysosporium using recombinant baculovirus

Recombinant Phanerochaete chrysosporium lignin peroxidase isozyme H2 (pI 4.4) was produced in insect cells infected with a genetically engineered baculovirus containing a copy of the cDNA clone lambda ML-6. The recombinant enzyme was purified to near homogeneity and is capable of oxidizing veratryl alcohol, iodide, and, to a lesser extent, guaiacol. The Km of the recombinant enzyme for veratryl alcohol and H2O2 is similar to that of the fungal enzyme. The guaiacol oxidation activity or any other activity is not dependent upon Mn2+. The purified recombinant peroxidase is glycosylated with N-linked carbohydrate(s). The recombinant lignin peroxidase eluted from an anion exchange resin similar to that of native isozyme H1 rather than H2. However, the pI of the recombinant enzymes is different from both H1 and H2 isozymes. Further characterization of native isozymes H1 and H2 from the fungal cultures revealed identical N-terminus residues. This indicates that isozymes H1 and H2 differ in post-translational modification.

Comparative sequence analyses of the cognate structural protein VP6 genes of five US bluetongue viruses

The S3 segment (the small segment 3), encoding the structural protein, VP6, from the five United States (US) prototype bluetongue virus (BTV) serotypes were amplified by the Clamp-R method and cloned as full-length entities. The complete nucleotide sequence of each cognate gene segment was determined. Each cognate S3 segment of BTV-10, 11, 13 and 17 was 1049 nucleotides long and contained an open reading frame (ORF) capable of encoding a 325-amino acid protein. However, the S3 segment of BTV-2, which also contained 1049 nucleotides, had a longer 5'-non-coding region of 99-nucleotide and contained an ORF capable only of encoding a 301-amino acid protein. Comparative analyses of the predicted amino acid sequences of S3 segments of BTV-2, 10, 11, 13 and 17 revealed that VP6 was unusually high in glycine and contained few aromatic amino acids, but a high concentration of charged amino acids, which is a characteristic of a hydrophilic protein. Phylogenetic analyses indicated that BTV-11, 13 and 17 were more closely related than the other two US BTV serotypes. BTV-2 was the most distantly related.

Epitopic mapping of linear and conformation-dependent antigenic determinants on GP5 of five U.S. bluetongue viruses

Two distinct antigenic determinants of the major outer capsid protein, GP5, of five U.S. bluetongue viruses have been identified and mapped using monoclonal and oligoclonal antibodies. One antigenic site, identified by oligoclonal antibody AK-15, was found to be common and conserved in all five U.S. BTV serotypes. This linear epitope was located between amino acid residues 175 and 189 (ALQREAAERSEDEIK). The second determinant identified by monoclonal antibody 34.7 was present in BTV-2, -10, -11, and -17 but absent in BTV-13. The binding of this monoclonal antibody to GP5 could be blocked specifically by one of three short synthetic peptides located among amino acid residues 33-42 (KAAERFAESE), 159-168 (EKILKEEDSK), and 206-215 (EIERDGMQEE), indicating that this antigenic determinant is conformation-dependent. Oligoclonal antibody (AK-15) reacted with denatured GP5 immobilized on nitrocellulose membrane after Western transfer as well as with native GP5 present on the surface of purified BTV virions. Monoclonal antibody (34.7) reacted only with denatured GP5 but not native GP5 using an ELISA assay. However, these two antigenic epitopes alone did not elicit detectable neutralizing antibodies as determined by plaque reduction assay.

Sequence conservation among the cognate nonstructural NS3/3A protein genes of six bluetongue viruses

Full-length cDNA copies of segment 10 genes of bluetongue virus serotypes 2, 11, 13 and 17 were synthesized by the Clamp-R method and inserted into the plasmid pUC19. The complete nucleotide sequences of these four cognate genes were sequenced and determined to be 822 nucleotides in length, smallest of the 10 genes in the bluetongue virion. These four cognate gene segments contained two in-phase and overlapping open reading frames capable of coding for two non-structural proteins of 229 and 216 amino acids with net charges of +4.5 and +5.5, respectively, at neutral pH. Comparative analyses of the predicted amino acid sequences of bluetongue virus serotypes 1, 2, 10, 11, 13 and 17 revealed (i) a high degree of sequence homology and conservation, (ii) a single conserved tryptophan located at residue 159, (iii) the presence of two conserved cysteines at residues 137 and 181 and two potential N-linked glycosylation sites at residues 63-65 and 150-152, (iv) a cluster of six prolines within a 15-amino acid region near the amino terminus, and (v) the longest 3' noncoding sequence of 113 bases among the 10 bluetongue viral genes. Phylogenetic analyses indicated that BTV-10 and -11 are very closely related and BTV-2 is the distantly related serotype of the five US bluetongue virus serotypes.

Complete genomic sequences of the GP5 protein gene of bluetongue virus serotype 11 and 17

The complete nucleotide sequences of full-length copies of genomic segment 6 or M3 of US bluetongue virus serotype 11 and 17 consisted of 1638 nucleotides. The plus-strand contained an open reading frame for a protein of 526 amino acids which was equivalent to about 59,000 Da, similar to the molecular weight of GP5 as determined by SDS-PAGE analysis. This long open reading frame was flanked by a 5' non-coding region of 29 nucleotides and a 3' non-coding region of 28 bases. When the predicted amino acid sequences of GP5 of BTV-11 and -17 were aligned and compared with those of BTV-2, -10, -13, -1AU and -1SA, four major highly conserved domains interrupted by several variable regions were detected. The potential significance of these discrete domains is discussed. Evolutionary and phylogenetic characteristics of these US BTV serotypes were consistent with our finding concerning BTV-1AU and -1SA.

Temporal relationship between left ventricular and arterial system elastances

Arterial compliance is an important component of ventricular afterload. Although its pressure dependence has been recognized, its temporal relationship to ventricular elastance (Elv(t)) has not been established. We investigated this in five open chest anesthetized dogs where simultaneous aortic pressure and flow and left ventricular pressure were measured. Elv(t) was derived using an elastance-resistance model of the left ventricle assuming an ejection fraction of 0.50 and a dead volume (Vd) of 3.0 mL. The nonlinear pressure-dependent compliance (C(P)) of the arterial system was incorporated in a three-element Windkessel model and determined by accurate prediction of aortic pressure from aortic flow. The resulting arterial elastance (Eas(t)) was computed as Eas(t) = 1/C(P). Results show that Eas(t) reaches a minimum value at or near the start of ventricular ejection and attains its peak value at or near the same time maximum LV elastance (Emax) is reached, at end-systole. Finally, numerical simulation of the model demonstrates its ability to adequately reproduce measured pressure and flow. Thus, the arterial system, in terms of elastance, is dynamically and temporally coupled to the left-ventricle during ejection.

Heterologous expression and characterization of an active lignin peroxidase from Phanerochaete chrysosporium using recombinant baculovirus

The cDNA clone lambda ML-1 encoding one of the extracellular lignin peroxidases from the white rot fungus, Phanerochaete chrysosporium, was heterologously expressed in an active form using a recombinant baculovirus system. The glycosylated extracellular form of the recombinant protein contained the ferriprotoporphyrin IX moiety and was capable of oxidizing both iodide and the model lignin compound, veratryl alcohol. In comparative peroxidase assays using guaiacol and Mn(II), the recombinant lignin peroxidase did not appear to be Mn(II) dependent. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that the heterologously expressed peroxidase had an apparent molecular weight similar to that of the native fungal isozyme H8. The elution profile of the active recombinant enzyme derived by ion-exchange chromatography and immunoblot analysis using an anti-H8 monoclonal antibody provided further evidence that the lambda ML-1 DNA encodes the lignin peroxidase H8.

Diastolic mechanics and the origin of the third heart sound

The third heart sound (S3) is observed for various hemodynamic conditions in both the normal and diseased heart. A theory is proposed in which myocardial viscoelasticity is primarily responsible for S3. A mathematical model is developed based on the mechanical aspects of diastolic function: nonlinear elasticity, viscoelasticity, and pressure generation. The model is provided as an electrical analogy of the left ventricle and circulatory system. S3 is predicted for the normal heart and the heart with dilated cardiomyopathy. An elevation of S3 intensity is indicated for cardiomyopathy, as is often observed in the clinic. S3 is produced experimentally by volume loading of the open-chest canine preparation and mathematically by imposing the conditions of volume loading on the model. Consistency of theory and experiment imply that it is valid to attribute S3 to myocardial viscoelasticity. The animal whose heart possessed the largest constant of viscoelasticity produced the greatest level of S3, in both cases. Nonlinear ventricular compliance is not found to be an essential requirement for sound generation, although increased compliance led to an increase in sound. S3 is predicted to change in response to venous return, ventricular stiffness, contractility, heart rate, and duration of contraction, as observed by others. In general, the coupling of these quantities to S3 is explained in terms of an excitation of viscous properties of the ventricle.

Ssp RF1, a novel class-II restriction endonuclease from Synechococcus RF-1 recognizing 5'TT/CGAA-3'

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Similar pressure pulse propagation and reflection characteristics in aortas of mammals

Similar pressure and flow waveforms recorded in mammalian aortas suggest that pulse transmission characteristics may also be similar. We examined the validity of this hypothesis, utilizing allometric equations of pertinent hemodynamic parameters and a model of the arterial system. Results show that both the reflection coefficient and the propagation constant times the aortic length are essentially invariant across the mammalian species investigated. Resolved forward and reflected propagating waves are also similar. These findings suggest that the arterial system in these mammals indeed functions in a similar manner.

Bluetongue virus evolution: sequence analyses of the genomic S1 segments and major core protein VP7

The S1 segments, encoding the group-specific antigen, VP7, from the five United States prototype BTV serotypes were cloned as full-length entities. The nucleotide and deduced amino acid sequences of segment S1 of BTV-2 were determined and compared with BTV-10, -11, -13, and -17, completing the sequencing of this cognate gene segment from all five US BTV serotypes. Each segment is 1156 bp long and contains an open reading frame encoding the 349-amino acid VP7 protein. Most (greater than 94%) of the amino acids of VP7 among the serotypes are conserved, including the location (position 255) of a single lysine residue. Secondary structure analyses of VP7 predict a putative eight-stranded beta-barrel between amino acid positions 150 and 250, a structure similar to that observed in ssRNA viruses. The S1 genes are flanked by conserved 5' and 3' noncoding regions. Stem-loop structures are predicted at the 3' end of each gene (nucleotide positions 1058-1097). The S1 segments of BTV-2, -10, -11, and -17 have greater than 93% of the nucleotides conserved, while less than 80% of their bases are identical with BTV-13. Analyses of nucleotide mismatches in each codon position of the VP7 open reading frame, transition frequencies, and evolutionary distances show that of the five, BTV-13 is the most distantly related and that BTV-10 and -17 are the most closely related serotypes. Evolutionary distance calculations of segment L2 from BTV-10, -11, and -17 concur with these observations. Comparison of this relationship with hybridization data of segment M3, which codes for VP5, suggests that BTV-17 has evolved by a combination of genetic drift and genomic reassortment. The data also indicate that the five US BTV serotypes are derived from two distinct gene pools. Evolution distances were used to estimate an evolution rate of 2.2 x 10(-3) nucleotide substitution/site/year for BTV segment S1. This rate is similar to the genes of retroviruses and implies an absence of RNA polymerase proofreading activity for dsRNA viruses.