Effect of hemodilution on ventilatory fluctuations of pulmonary capillary blood volume

By diluting the hematocrit (Ha) in the rabbit's circulation without changing its blood volume, we found that the ventilatory-induced fluctuation (delta rho) in the density of aortic blood and Ha (which was in the range of 8-39%) are related by this linear regression: delta rho = 0.63 g/l (-0.009 + Ha). In this hemodilution experiment, the rabbits were ventilated by an intermittent positive pressure of 6 mmHg at a frequency of 30-35 cycles/min. Based on the Fahraeus effect for capillary blood flows and the dispersion of the density indicator in the rabbit's central circulation, we computed from the fluctuation of the measured density within a ventilation cycle the fluctuation of pulmonary capillary blood volume and found it to be 4.1 +/- 0.4% of the capillary blood volume for all hematocrits. Since the same fluctuation in the airway pressure was used to induce the volumetric fluctuation, its independence of Ha indicates that the hemodilution has no effect on the viscoelasticity of pulmonary capillaries.     

蝮蛇抗栓酶对实验性动脉粥样硬化与PGI2／TXA2平衡影响的观察

通过用蝮蛇抗栓酶（Ｓｖａｔｅ）防治家兔动脉粥样硬化（ＡＳ）实验,发现Ｓｖａｔｅ能明显减轻家兔主动脉ＡＳ;同时能明显降低血液血栓素含量,能明显升高血液前列环素含量。以上血液检查结果与Ｓｖａｔｅ治疗心脑血管疾病时临床检查结果一致。说明Ｓｖａｔｅ有防治ＡＳ的作用,其机制与Ｓｖａｔｅ具有恢复前列环素／血栓素平衡的作用密切相关。     

Familial aggregation of blood pressure and anthropometric variables in patrilocal households

Fifty-three households in a small Indian fishing community were surveyed for blood pressure, pulse rate, and anthropometric measurements (height, weight, and three skinfolds). In addition to nuclear family relationships, correlations for extended family members and in-laws living within a common household were estimated by maximum likelihood. Based on likelihood ratio tests, the hypothesis that correlations among genetically unrelated pairs from the same household are zero is rejected for systolic blood pressure. Among genetically related individuals, the degree of relationship does not affect the magnitude of the blood pressure correlations. For the anthropometric measurements, family resemblance is significant only for first-degree relatives, except that the correlation for uncle-child pairs is significant for subscapular skinfold, and brother-in-law-sister-in-law pairs resemble each other for height and weight. The results suggest that common household environment is a significant determinant of blood pressure but not fatness in this population.     

Cerebral blood flow in split-brainstem rabbits

Cerebral blood flow (CBF), mean arterial pressure (MAP) and heart rate (HR) were recorded in anaesthetised, vagotomised, paralysed and artificially ventilated rabbits before and after a mid-sagittal section of the lower brainstem ("split-respiratory centre"). Splitting the medulla elicited first a small decrease and then an increase in CBF, a decrease in HR but no change in MAP. Hypoxia reduced CBF but did not modify MAP or HR. Hypercapnia did not significantly affect any of these parameters. It is concluded that a midline section of the rabbit's medulla and lower pons does not impair CBF and therefore the decrease in output from the respiratory controller, observed in split-brainstem animals, is not likely to be elicited by alterations in CBF.     

Cutaneous and subcutaneous blood flow measurement in rabbit's ear by epicutaneous diffusion of xenon 133. Influence of the arteriovenous anastomosis]

The cutaneous and subcutaneous blood flow measurement by a diffusible inert gas concerns theorically capillary nutritional flow. In clinical routine, where pathological openning of arteriovenous anastomosis is suspected, the blood flows measured by Xenon technic are often increased. The function of the shunts are displayed on the epuration curve obtained on a region where there are numerous: rabbit's ear.     

Is weight loss an effective treatment for hypertension? The evidence against

Although there are many studies reporting correlations between relative body weight and blood pressure, the correlations are generally of low order. Furthermore, these observational studies provide, at best, circumstantial evidence concerning the effect of weight reduction on elevated blood pressure. After outlining key methodologic criteria for testing the hypothesis that weight loss lowers blood pressure among hypertensive obese subjects, this article reviews the best intervention studies that are available. Despite the demonstration in these randomized trials that weight reduction programs can lower weight successfully, the results for blood pressure lowering are in considerable disagreement. Two studies reported significant lowering of both systolic and diastolic blood pressure, one found significant lowering of systolic pressure only, and two failed to find significant differences in either. The definitive study of substantial weight loss among patients receiving no other antihypertensive treatment or standardized medical treatment with long-term follow-up has yet to be done. At best, weight loss offers very limited benefit for overweight hypertensives. At worst, weight loss programs are expensive to run, cause considerable patient discomfort and may delay the implementation of more effective therapy.     

Urinary electrolyte excretion,alcohol consumption,and blood pressure in the Scottish heart health study.

As part of a study of risk factors for coronary heart disease 24 hour urine collections were obtained from 7354 men and women aged 40-59 selected at random from 22 districts throughout Scotland (Scottish heart health study). The mean of two standardised measurements of blood pressure was related to the reported consumption of alcohol and measurements of height, weight, pulse rate, and electrolyte excretion. Several significant correlations were found with both systolic and diastolic pressure, but only the coefficients for age, body mass index, and pulse rate were greater than 0.1. Alcohol consumption showed a weak positive correlation with blood pressure in men. Sodium excretion showed a weak positive correlation with blood pressure in both sexes, and potassium excretion showed weak negative correlations. In multiple regression analysis age, pulse rate, body mass index, alcohol consumption, and potassium excretion had significant independent effects but sodium excretion did not. Although measuring blood pressure twice on one occasion and 24 hour urinary sodium excretion only once may have weakened any potential correlation, the most likely explantation of these results is that the relation between sodium and blood pressure in the population is weak and that potassium and alcohol are of greater importance.     

Trimming a rabbit's nails

This column presents a step-by-step procedure for trimming a rabbit's nails. The technique requires only one person, who uses the rabbit's feedback to determine where to cut the nail, minimizing stress in the animal.     

Cutaneous vasomotion during REM sleep in the rabbit's ear, after alpha-receptor blockade

Cutaneous vasoconstriction in the rabbit's ear during REM sleep in a warm environment is not abolished by alpha-receptor blockade (phenoxybenzamine 6 mg/kg i.v.), thus confirming that the vasomotor response during REM sleep is independent of the activity of circulating catecholamines. The decrease in cardiac output during REM sleep may be responsible for the slight fall in transmural pressure which underlies cutaneous ear vasoconstriction during REM sleep.     

Evaluation of a new tail-cuff method for blood pressure measurements in rats with special reference to the effects of ambient temperature

We evaluated a recently developed tail-cuff apparatus for the indirect blood pressure measurement in rats with special reference to the effects of ambient temperature. For this purpose, we designed two preparations 1) an intact preparation to determine the effect of ambient temperature on blood pressure measurements and 2) an anesthetized and catheterized preparation for comparison of the values of blood pressure obtained by the indirect and by the direct method. This apparatus also required enough pulse volume oscillations to measure the accurate value of blood pressure. Sufficient pulse volume oscillations were obtained within 20 min at 30 and 40 degrees C. At 40 degrees C, the values of blood pressure, pulse rate and rectal temperature were significantly higher than those at 30 degrees C. Correlation between blood pressure and rectal temperature was significant, and blood pressure increased with rectal temperature dependently. The values of the indirect measurement were close to the values measured directly, and these correlations were highly significant. Thus, we showed the effects of temperature for indirect blood pressure measurement. This tail-cuff apparatus could measure the accurate value of indirect blood pressure without thermal stress at 30 degrees C.     

Blood pressure in first 10 years of life: the Brompton study.

OBJECTIVES--To determine the normal range of blood pressure and its pattern of change in the first 10 years of life. To estimate at what age (if any) children consistently appear in one part of the blood pressure distribution and at what age familial correlations in blood pressure become significant. DESIGN--Longitudinal cohort study. SETTING--South east England. SUBJECTS--2088 children of both sexes born consecutively in Farnborough Hospital, Kent, and their parents. MAIN OUTCOME MEASURE--Blood pressure measured by Doppler ultrasonography and sphygmomanometry. RESULTS--Systolic blood pressure rose from a mean of 88.5 mm Hg at age 6 months to 96.2 mm Hg at 8 years measured with a 8 cm cuff and from 89.1 mm Hg at age 5 years to 94.3 mm Hg at age 10 years measured with a 12 cm cuff. The larger cuff gave blood pressure readings about 6 mm Hg lower. This effect was independent of body weight and arm circumference. Diastolic blood pressure rose from 57.8 mm Hg at 5 years to 61.8 mm Hg at 10 years (12 cm cuff). There was only about 1 mm Hg difference between sexes. Blood pressure was correlated with weight, weight adjusted for height, height, and arm circumference at all ages studied. The correlation coefficient of repeated yearly measurements increased steadily with age from 0.28 at 2 years to 0.59 at 10 years. The correlation coefficients between child''s blood pressure and mother''s average blood pressure increased from 0.1 at age 1 year to 0.23 at age 10. CONCLUSIONS--Blood pressure changes relatively little between the ages of 6 months and 10 years. Yet because of the increasing strength of between occasion and family correlations, children are more consistently occupying a specific part of the blood pressure distribution as they grow older. Studies in children should help determine why some adults have hypertension and others do not.     

Genetic variability in response to dietary calcium

Supplemental dietary calcium has been shown to reduce blood pressure in spontaneously hypertensive rats while restricted calcium diets cause an elevation in blood pressure. This latter nutrient effect has been enhanced by modest sodium restriction and is associated with a reduction in serum ionized calcium concentration. To determine whether alterations of dietary calcium and sodium have a similar influence on blood pressure in genetically normotensive rats, Fisher 344, Wistar Furth, and ACI rats were fed either a low (0.1%) calcium, low (0.25%) sodium diet or normal (1.0%) calcium, normal sodium (0.45%) diet from 4 weeks of age through 29 weeks of age. Indirect measurements of systolic blood pressure showed that only the Fisher 344 rats consistently responded to the low calcium/low sodium diets with an elevation of blood pressure. There was considerable variation in serum electrolytes across strains in the normal diets but all three strains experienced a reduction in ionized calcium and an elevation in phosphorus and magnesium on the restricted diets. In the Fisher 344 rats there were significant (p less than .05) inverse correlations among systolic blood pressure and serum ionized and total calcium concentrations and positive correlations among systolic blood pressure, phosphorus, and magnesium. There was no significant correlation between serum electrolytes and blood pressure in the other two strains. The data indicate that there is genetic variability in the blood pressure response to alterations in dietary calcium and sodium. The pattern of change in serum electrolytes across strains suggests that diet-induced alterations of serum electrolytes, specifically calcium, are not necessarily predictive of a pressor response. It would appear that some other calcium-sensitive physiological process involved in blood pressure regulation must respond differentially to calcium availability across strains.     

Muscle strength and body composition as determinants of blood pressure in young men

The correlations of blood pressure to various indices of muscularity and fatness were studied in 183 young healthy men (mean age 19.7, SD 2.1 years). Systolic pressure showed significant positive correlations with body fat percentage, isometric strength of trunk extensors, body mass index, lean body mass, strength of leg extensors, heart rate, and the sum of four skinfolds. Diastolic pressure had significant positive correlations with body mass index, lean body mass, body fat percentage, sum of skinfolds, strength of leg extensors, strength of trunk extensors, and age. A stepwise selective multiple regression analysis for systolic pressure resulted in four significantly correlating variables: body fat percentage (p less than 0.001), heart rate (p less than 0.01), lean body mass (p less than 0.05), and strength of trunk extensors per kg body weight (p less than 0.05). For diastolic pressure the analysis resulted in two explaining variables: body mass index (p less than 0.001) and age (p less than 0.05). In a regression equation with 13 variables the strength of trunk flexors was negatively correlated with diastolic pressure. It is concluded that both fatness and muscularity are factors related to blood pressure in young men. The muscularity effect is more clearly associated with trunk and leg extensor strength.     

Sodium and potassium intake and blood pressure.

Sodium and potassium intakes were increased in normotensive volunteers to assess the effects on their blood pressures. An approximately threefold increase in sodium intake for eight days had no effect on the blood pressures of seven volunteers, while a two-stage increase in potassium intake, by about 40% for eight days and a further 55% for 14 days, had no effect on the blood pressures of 21 volunteers. Renal electrolyte excretions and the blood pressures of all 28 subjects showed no statistically significant correlations between either sodium or potassium excretion and blood pressure. A weak negative correlation was found between the sodium: potassium ratio and systolic pressure. The small reductions in sodium intake and increases in potassium intake that might be achieved through propaganda and changes in food processing are unlikely to lower mean blood pressure in Western societies.     

Analgesic and cardiovascular effects of centrally administered substance P

Substance P (SP) injected intracerebroventricularly (ICV) into rabbits caused dose-related thermal analgesia with the maximum effect after 2 micrograms. The analgesia was measured by timing the withdrawal of the rabbit's ear from an infrared beam. Equimolar amounts of the related peptides physalaemin and eledoisin-related peptide also caused analgesia, but the SP N-terminal fragment (1-9) was inactive. This suggests that the analgesic message of SP resides within the C-terminal fragment. The analgesia caused by each peptide developed more rapidly but did not last as long as that after central injection of beta-endorphin. In separate experiments, 2 micrograms SP injected ICV increased blood pressure and decreased heart rate. The analgesic, bradycardic and pressor responses to central administration of SP were opposite to effects of peripherally administered SP, described previously. These results indicate that the effect induced by SP depends upon its specific neuroanatomical site of action.     

Structural analysis of the correlations of genetic markers with physiological indices

The structure of phenotypic and genetic correlations between ABO blood groups, MN, Rh(D), haptoglobins and concentration indications of the total cholesterol, of sugar curve, the levels of systolic and diastolic arterial pressure was studied in twins by the method for cluster analysis (121 monozygotic twin pairs, 120 dizygotic like sex twin pairs and 107 pairs of unlike sex twins). No correlation between the systems analysed and their indications on the phenotypic level was observed. By analysis of genetic correlations, the existence of correlations between the Rh system and arterial pressure, and the total cholesterol concentration, as well as between the ABO system and sugar concentration indexes, was established. Possible genetic causes for correlations obtained are being discussed.     

Autologous perfusion of an isolated rabbit gastrointestinal tract.

Most perfusion techniques rely on mechanical means to provide blood flow to the isolated organ for maintaining its physiological conditions. The approach usually requires a complicated mechanical system with the associated problems of blood type matching and prevention of blood cell damage. This paper describes a gastrointestinal tract perfusion technique that uses the rabbit's own cardiopulmonary system as the autologous blood supply source. The technique allows for the removal of the complete intestinal loop from the abdominal cavity of the rabbit, and maintains its blood circulation through silastic tubing connections of the catheterized portal vein and cranial and caudal mesenteric arteries. An alternative perfusion site that uses the aorta as the arterial blood supply and the vena cava as the venous return also is described. The isolated perfused GI tract may then be placed in a separate test environment for controlled experiments. For an acute animal test, the approach was found to be a convenient alternative to conventional approaches.     

Comparison of performance of various sphygmomanometers with intra-arterial blood-pressure readings.

Seven types of sphygmomanometer were used in random order on each of nine hypertensive patients and the readings compared with simultaneous intra-arterial blood-pressure recordings. All the devices gave significantly different values for systolic pressure, and only two measured diastolic pressure without significant error. Systolic pressure was consistently underestimated (range 31-7 mm Hg), and all but one instrument overestimated diastolic pressure (range 10-2 mm Hg). The variability of readings was least with the standard mercury sphygmomanometer and the random-zero machine, while with some of the more automated devices single readings were in error up to -68/33 mm Hg. The strong correlations found between intra-arterial and cuff systolic pressures with all devices tested and significant correlations for diastolic pressure with all but one device indicate that, with one possible exception, the sphygmomanometers would give accurate results where a change in blood pressure was the main concern.     

Relationship of body size and body mass to blood pressure: sex-specific and developmental influences.

The relationship of body mass and body fat distribution to blood pressure has been recognized for many years. This relationship has formed the basis for much additional research, including the impact of growth and developmental factors on blood pressure levels. Blood pressure in children is related to somatic growth and is tied to increases in height, skeletal maturation, and sexual maturation. Sexual and ethnic differences in blood pressure levels are already apparent during childhood and may also be related to the process of growth and sexual maturity. Body size exerts a profound influence on a variety of physiological functions, including blood pressure and the onset of sexual maturity. In general, studies have reported a strong linear relationship between height and blood pressure and between body mass and blood pressure such that tracking correlations from childhood to adulthood for both blood pressure and body mass index are significant for most sex and ethnic groups. Studies evaluating the effects of hormone replacement therapy on post-menopausal women have thus far generated results suggesting that the age-related rise of blood pressure is not due directly to hormonal changes associated with menopause. The interrelated effects of growth, maturation, body weight, and body fat are influenced by both genetic and environmental factors. Environmental influences may modify relationships established much earlier, perhaps as early as prenatally, during infancy, or during early childhood. Directions for future research and implications resulting from the complex relationship between body weight and blood pressure are discussed.     

Phenotypic variability and correlation between skinfold thickness and arterial pressure level]

Contribution of genetic and environmental factors in phenotypic variability of blood pressure level and skinfold thickness, and phenotypic correlation between these characters was calculated on the basis of familial correlations. It was shown that genetic determinant explains considerable portion of blood pressure level and skinfold thickness variability. Among common environmental effects, the factors affecting one generation are important with regard to variability of these characters. Maternal effect is expressed in the variability of systolic and diastolic blood pressure. Correlation between blood pressure level and triceps skinfold thickness is determined by genetic factors, whereas that between blood pressure level and subscapular skinfold thickness is mediated by environmental factors. The results obtained may be applied in populational prevention of cardiovascular disease.