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Biomedical subjects

M W Rampling

Publications and source records attributed to M W Rampling.

At least 19 recordsLinked to original sources
PubMed1999

Comparison of haemorrheological parameters and blood pressure in various breeds of dog.

Relationships between blood pressure and haemorrheological factors were examined in three groups of dogs characterised by different levels of blood pressure. The groups used were sight hounds (high pressure), retrievers (low pressure) and a mixed group with intermediate pressure. The three groups had different levels of haematocrit and blood viscosity at both high and low shear rates, with the sight hounds showing the highest and retrievers showing the lowest levels for each of the parameters. The plasma viscosities did not differ significantly between the groups. Blood pressure and blood viscosity or haematocrit were not correlated within dog groups, but when the dog groups were considered together, significant positive correlations existed between pressure and viscosity and pressure and haematocrit.

Animals↗
PubMed1999

Haemorheological disturbances in hypertension: the influence of diabetes and smoking.

Patients suffering from diabetes or hypertension commonly exhibit increased blood viscosity compared with healthy controls. This is primarily the result of elevated plasma fibrinogen concentration. Cigarette smokers also exhibit raised blood viscosity but in their case the main cause is a raised haematocrit. In this paper the effects of concurrent hypertension, diabetes and cigarette smoking on blood viscosity is reviewed. Evidence is presented that the haemorheological disturbances associated with each of these modalities are additive when present together in a subject.

Blood Viscosity↗
PubMed1998

A comparative study of the haemorheology of various breeds of dog.

Haemorheological parameters in nine breeds of dog were examined. Whole blood viscosity at both high and low shear rates differed significantly between the breeds with a 50% difference between the highest and lowest viscosity at high shear rate and a 140% difference at low shear rate. Athletic breeds (Greyhounds, Deerhounds) had the highest whole blood viscosities. Differences in viscosity correlated well with differences in haematocrit between breeds. When the blood samples were adjusted to a standard haematocrit (45%), there were no significant differences in viscosity. This implied that other rheological factors such as cellular deformability and plasma viscosity did not vary significantly between breeds, and direct measurement showed this to be the case.

Animals↗
PubMed1998

Haemorheology and the inflammatory process.

Many forms of tissue injury, whether due to physical or infectious sources, lead to the inflammatory response. During its course a wide variety of events takes place, including alterations in vascular contraction, in vascular permeability, in leucocyte activity and the initiation of the acute phase response. The last results in a leucocytosis and changes in the concentrations of a number of plasma proteins, including fibrinogen. They all cause alterations in haemodynamics, due in part to alteration in geometric resistance, but also to alterations in viscometric resistance as a result of changes in the haemorheological properties of the blood components locally and systemically. While some of these inflammation-induced changes are useful on a local level and assist in the resolution of the damaging factor and in tissue repair, the systemic haemorheological effects may lead to deleterious haemodynamics. Many of the effects are well documented but two new possibilities arise. One is the potential effects of fibrinogen heterogeneity on blood rheology, and the other the possible effects of leucocyte protease release on the aggregability of the red cell.

Hemorheology↗
PubMed1997

Effects of components of meals (carbohydrate, fat, protein) in causing postprandial exertional angina pectoris.

We have shown that unlike fat, protein, xylose, or water, the carbohydrate component of the meal accelerates myocardial ischemia, reduces exercise capacity, and is associated with a more rapid increase in the determinants of myocardial oxygen consumption than exercise in the fasting state. Our results suggest a role for a larger increase in sympathetic nervous activity and/or release of vasoactive gastrointestinal peptides after carbohydrate, but not fat or protein, meals in postprandial angina.

Angina Pectoris↗
PubMed1997

A novel instrument for studying the flow behaviour of erythrocytes through microchannels simulating human blood capillaries.

A novel instrument has been developed to study the microrheology of erythrocytes as they flow through channels of dimensions similar to human blood capillaries. The channels are produced in silicon substrates using microengineering technology. Accurately defined, physiological driving pressures and temperatures are employed whilst precise, real-time image processing allows individual cells to be monitored continuously during their transit. The instrument characterises each cell in a sample of ca. 1000 in terms of its volume and flow velocity profile during its transit through a channel. The unique representation of the data in volume/velocity space provides new insight into the microrheological behaviour of blood. The image processing and subsequent data analysis enable the system to reject anomalous events such as multiple cell transits, thereby ensuring integrity of the resulting data. By employing an array of microfluidic flow channels we can integrate a number of different but precise and highly reproducible channel sizes and geometries within one array, thereby allowing multiple, concurrent isobaric measurements on one sample. As an illustration of the performance of the system, volume/velocity data sets recorded in a microfluidic device incorporating multiple channels of 100 microns length and individual widths ranging between 3.0 and 4.0 microns are presented.

Adult↗
PubMed1994

Changes in hemorheology with fetal intravascular transfusion.

OBJECTIVE: Our aim was to determine the changes in fetal hemorheologic parameters caused by fetal intravascular transfusion for alloimmune anemia. STUDY DESIGN: Fetal blood samples were collected before and after 95 fetal transfusions in 31 women. Fetal hematocrit, whole-blood viscosity at a variety of shear rates, plasma viscosity, fetal fibrinogen, and fetal plasma proteins were measured. RESULTS: Fetal whole-blood viscosity increased, sometimes massively, with transfusion. The rise in viscosity was principally dependent on the rise in hematocrit, with a linear rise in hematocrit producing a linear rise in the logarithm of whole-blood viscosity, but was also affected by the amount of adult plasma proteins present in the donor blood. CONCLUSIONS: Rises in fetal whole-blood viscosity during transfusion can be minimized by using donor blood that has been serum depleted to a high hematocrit (> 90%) and by restricting the end hematocrit to 50% to 55%.

Blood Proteins↗
PubMed1994

The variation with gestational age of the rheological properties of the blood of the new-born.

A study has been made of the variation of blood viscosity and related factors with the gestational age of neonates from 24 weeks to normal term. Viscosity increases significantly over this period by 36% at high shear rate (128.5 s-1) and 250% at low shear (0.277 s-1). The high shear rate changes can be explained largely by the effects of variations in haematocrit and plasma viscosity. At low shear rate the same factors are involved together with changes in the plasma protein composition, in particular the age-related increase in the concentration of the proteins known to induce rouleaux formation. The variation in the degree of sialination of fibrinogen with gestational age may also play a part.

Albumins↗
PubMed1992

Contrast media-induced effects on blood rheology and their importance in angiography.

Factors which alter blood viscosity may have important consequences during angiography. The differential effects of various concentrations of five different radiocontrast media on the viscosity characteristics of erythrocyte-plasma suspensions were made over a range of applied shear rates. The results showed that, at both high and low shear rates, the rate of change of viscosity with contrast concentration differs markedly between the various types of contrast media. The conventional ionic monomers caused most disturbance to blood viscosity. The monoionic dimer hexabrix was least disturbing to the viscometric characteristics of blood, and the newer non-ionic monomers were intermediate in their effects. Significant effects on blood viscosity may be caused by radiocontrast agents during a number of in vivo angiographic situations, in particular: early after contrast bolus injection into large vessels, in the microcirculation after selective injections, and during angioplasty procedures.

Adult↗
PubMed1992

Decrease in erythrocyte glycophorin sialic acid content is associated with increased erythrocyte aggregation in human diabetes.

1. Sialic acid moieties of erythrocyte membrane glycoproteins are the principal determinants of the negative charge on the cell surface. The resultant electrostatic repulsion between the cells reduces erythrocyte aggregation and hence the low shear rate viscosity and yield stress of blood. 2. Using g.c.-m.s., a decrease in sialic acid content has been observed in the major erythrocyte membrane glycoprotein, glycophorin A, obtained from nine diabetic patients compared with that from seven normal control subjects [median (range): 3.30 (0.01-11.90) versus 18.60 (3.20-32.60) micrograms/100 micrograms of protein, P less than 0.02]. 3. Erythrocyte aggregation, measured by viscometry as the ratio of suspension viscosity to supernatant viscosity (LS/S) in fibrinogen solution, was increased in ten diabetic patients compared with ten normal control subjects (mean +/- SEM, 37.6 +/- 1.3 versus 33.8 +/- 0.6, P less than 0.02). 4. In the patients in whom both viscometry and carbohydrate analysis were performed, the decrease in erythrocyte glycophorin sialylation and the increase in erythrocyte aggregation in fibrinogen solution were related statistically (LS/S correlated negatively with glycophorin sialic acid content, r = 0.73, P less than 0.05). 5. Decreased glycophorin sialylation provides an explanation at the molecular level for increased erythrocyte aggregation and it may be important in the pathogenesis of vascular disease in diabetes.

Adult↗
PubMed1991

Blood rheology and fibrinogen in children with familial hypercholesterolaemia.

Whole blood and plasma viscosity, red cell aggregability and deformability, and plasma fibrinogen have been compared between 16 children aged between 6 and 18 years with heterozygous familial hypercholesterolaemia (FH) and 16 controls individually matched for age and sex. Mean (SD) plasma cholesterol was 7.19 (1.23) mmol/l in the patients and 4.31 (0.84) mmol/l in the controls. This was due to a similar difference in low density lipoprotein (LDL) cholesterol, while triglycerides and high density lipoprotein (HDL) cholesterol were similar between groups. No differences were seen in any of the rheological parameters between the two groups. This suggests that the rheological abnormalities seen in adults with FH are not a direct consequence of their hyperlipidaemia, and may instead be a reflection of their more extensive atherosclerosis.

Adolescent↗
PubMed1991

Haemorheological changes in the very short term after abstention from tobacco by cigarette smokers.

A study was made of the haemorheological changes that took place in the days immediately following tobacco withdrawal from cigarette smokers. In both males and females substantial and persistent reductions in blood viscosity occurred within 2 d, the fall at high shear rate corresponding to about 8% while at low shear rate it was approximately twice as much. These changes were due partly to a fall in packed cell volume (PCV), but also to reductions in total plasma protein and fibrinogen concentrations which led to reductions in plasma viscosity and rouleaux formation. These plasma protein-related changes were less pronounced in the female group. The results indicate that, even in the very short-term, abstention from cigarettes leads to substantial improvements in the haemorheological profile of heavy smokers.

Adult↗
PubMed1990

Properties of thrombolytic agents in vitro using a perfusion circuit attaining shear stress at physiological levels.

A perfusion circuit was designed to investigate in vitro some of the factors which may influence the success of thrombolytic treatment in vivo. The rate of lysis of clotted plasma and different types of artificial thrombi (fibrin thrombi or whole blood thrombi) was measured in citrated plasma or whole blood under static conditions or under shear stress equivalent to the arterial or venous circulation. With both streptokinase (SK) and tissue-type plasminogen activator (t-PA) the rate of lysis of fibrin thrombi and whole blood thrombi was reduced significantly, when compared to the conventional plasma gel clot model (25-fold and 8-fold, respectively). This occurred particularly with SK which showed a reduction (4-fold) in potency relative to t-PA under these conditions. Lysis of thrombi by both activators was observed to be faster in plasma than whole blood, and also faster with whole blood thrombi than fibrin thrombi. High shear stress, generally, caused a reduction in the rate of lysis of fibrin thrombi and an increase in the rate of lysis of whole blood thrombi compared to lysis rates under static conditions. Under all conditions of flow the lysis rate observed at 50 units t-PA per ml was much faster than that at 500 units per ml unlike the conventional plasma gel clot model.

Fibrin↗
PubMed1990

Abnormalities of blood rheology in familial hypercholesterolaemia: effects of treatment.

Whole blood and plasma viscosity, red cell aggregability and deformability, and plasma fibrinogen have been compared between 20 patients with heterozygous familial hypercholesterolaemia (FH), without clinical arterial disease, and 20 age- and sex-matched controls. Plasma fibrinogen was elevated in FH, associated with increased whole blood viscosity at low shear rate, plasma viscosity and red cell aggregation. At high shear rate blood viscosity was not elevated, and red cell deformability was normal. The effect of 12 weeks double blind treatment with cholestyramine 16-24 g/day, pravastatin 20 mg b.i.d. or placebo on blood rheology was studied in 17 FH patients. Mean plasma cholesterol fell significantly by 24.7% with pravastatin and 21.5% with cholestyramine, the latter also causing a significant 42% rise in triglyceride. Pravastatin, but not cholestyramine, caused a significant fall in plasma viscosity and fibrinogen, but no change was seen in whole blood rheology. This suggests that the rheological abnormalities in FH are at least partly related to the plasma lipid levels and hence reversible with treatment.

Adult↗
PubMed1990

Acute changes in atherogenic and thrombogenic factors with cessation of smoking.

Tobacco smoking is associated with alterations in several factors considered to be important in the atherosclerotic process. Thirty chronic smokers were studied 2 weeks before and 2 weeks after complete tobacco withdrawal. Significant reductions in fibrinogen, haematocrit, plasma viscosity and whole blood viscosity as well as a significant increase in HDL-cholesterol were observed. As these factors are important in both atherogenesis and thrombogenesis, these observations may give insight into tobacco-induced atherosclerotic disease and may be responsible for the more rapid reduction in the incidence of cardiovascular disease that is believed to occur after stopped smoking.

Adult↗
PubMed1989

Tuberculin sensitivity and an interaction of leucocyte and plasma factors involving fibrinogen.

Lysates of blood leucocytes from strong tuberculin-positive reactors contained smaller particles of insoluble protein-rich material than did similar preparations from negative donors. The phenomenon was dependent on the presence of small quantities of plasma in the original leucocyte suspensions: when this was removed or replaced by serum both groups of donors produced particles of the smaller size. When the experiments were repeated in the presence of 125I-fibrinogen, larger particle size was found to be associated with an increased proportion of radioactivity becoming firmly bound to the insoluble material. These findings are likely to reflect differences in the levels of procoagulant, proteolytic enzymes or associated activities in the cells or plasma of the two groups.

Adult↗
PubMed1989

A comparison of the rheologic properties of neonatal and adult blood.

A number of studies have indicated that the rheologic properties of neonatal blood are different from those of the adult. The frequent administration of blood components to the neonate during intensive care make it important that these differences be established and their causes understood. The purpose of this study was to make a detailed comparison of the rheologic properties of neonatal and adult blood, with particular emphasis on low shear rate viscosity and rouleaux-related phenomena. The viscometric data was obtained from seven preterm (PT) and 18 normal term (NT) babies and compared with those from 18 adults (A). In the present study, viscometry was performed over a wide range of shear rates, from about 0.3 to 130 s-1, and the low shear rate data were compared with direct measurement of rouleaux formation using the Myrenne Erythrocyte Aggregometer. A major factor leading to the viscometric differences observed was the high hematocrit common in the newborn (46.8 +/- 2.1% PT, 52.8 +/- 6.1% NT, 44.1 +/- 2.5% A males, 40.5 +/- 1.9% A females). However, this tended to be compensated for by the lower plasma viscosity (1.05 +/- 0.07 mPas PT, 1.23 +/- 0.14 mPas NT, 1.34 +/- 0.08 mPas A--no sex difference) and reduced rouleaux formation observed in the newborn and more marked in the preterm baby. The lowered levels of red cell aggregation were found not to be due to cellular differences between the adults and the babies but rather to differing plasma components. The presence of the fetal variant of fibrinogen and low levels of immunoglobulins, especially IgM and IgA, are likely to be of particular importance.

Adult↗