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Biomedical subjects

W P Anderson

Publications and source records attributed to W P Anderson.

At least 19 recordsLinked to original sources
PubMed1992

Pet ownership and risk factors for cardiovascular disease.

OBJECTIVE: To compare risk factors for cardiovascular disease in pet owners and non-owners. DESIGN AND PATIENTS: Accepted risk factors for cardiovascular disease were measured in 5741 participants attending a free, screening clinic at the Baker Medical Research Institute in Melbourne. Blood pressure, plasma cholesterol and triglyceride values were compared in pet owners (n = 784) and non-owners (n = 4957). RESULTS: Pet owners had significantly lower systolic blood pressure and plasma triglycerides than non-owners. In men, pet owners had significantly lower systolic but not diastolic blood pressure than non-owners, and significantly lower plasma triglyceride levels, and plasma cholesterol levels. In women over 40 years old, systolic but not diastolic pressure was significantly lower in pet owners and plasma triglycerides also tended to be lower. There were no differences in body mass index and self-reported smoking habits were similar, but pet owners reported that they took significantly more exercise than non-owners, and ate more meat and "take-away" foods. The socioeconomic profile of the pet owners and non-owners appeared to be comparable. CONCLUSIONS: Pet owners in our clinic population had lower levels of accepted risk factors for cardiovascular disease, and this was not explicable on the basis of cigarette smoking, diet, body mass index or socioeconomic profile. The possibility that pet ownership reduces cardiovascular risk factors should therefore be investigated.

Animals↗
PubMed1992

Distribution of sympathetic neuroeffector junctions in the juxtaglomerular region of the rabbit kidney.

Two structurally distinct types of sympathetic axon (Type I and Type II) have recently been identified in the renal cortex of the rat and the rabbit. This study describes the distribution and density of the neuroeffector junctions made by these two types of axon on the different tissues from the juxtaglomerular region of the rabbit renal cortex. Immunohistochemical studies showed that tyrosine hydroxylase-positive axons were located only in regions adjacent to the arteries and arterioles in the renal cortex. Ultrastructural studies of the juxtaglomerular region indicated that both types of axon formed junctions on vascular smooth muscle cells, epithelial cells of proximal tubules and renin-secreting granular epithelioid cells. The density of neuromuscular junctions (18 x 10(3)/mm2 of vessel surface) was more than twice as high on the afferent arteriole as on the efferent arteriole or proximal tubules immediately adjacent to the glomerular arterioles (both about 6 x 10(3)/mm2). The junction density on granular epithelioid cells was much lower (about 2 x 10(3)/mm2) and were rarely observed on the distal tubule. Afferent arterioles preferentially received junctions from Type I axons at a relatively high density (14.2 x 10(3)/mm2) whereas junctions formed by Type II axons were less selectively distributed and occurred at lower densities on all other tissues (range, 1-6.3 x 10(3)/mm2). Presynaptic membrane specialisations were identified only at junctions on arterioles and granular epithelioid cells and occurred more frequently at Type I than at Type II junctions. The data suggest that the predominant effect of the sympathetic innervation in the juxtaglomerular region of the renal cortex is on the afferent arteriole and that the two axon types within the kidney may have different functions.

Animals↗
PubMed1992

Morphometric analysis of the actions of angiotensin II on renal arterioles and glomeruli.

To study the effects of angiotensin II on afferent and efferent arteriole diameters and on intraglomerular dimensions, angiotensin II (20 ng.kg-1.min-1) or saline vehicle was infused intravenously for 20 min into anesthetized rabbits pretreated with enalapril. Both kidneys were perfusion fixed (glutaraldehyde), and vascular casts were made of the right kidneys using methacrylate. Morphometric analysis of the left kidneys using transmission electron microscopy revealed no significant effects of angiotensin II within the glomerulus, including the degree of mesangial contraction. The diameters of the afferent and efferent arteriole casts from the right kidneys were measured at 20, 50, and 75 microns from the glomerulus by scanning electron microscopy. In the outer cortex the mean diameters of the afferent and efferent arterioles were 14.1 +/- 0.8 and 9.7 +/- 0.5 microns, respectively, in the angiotensin II-infused rabbits, significantly less than in the control (vehicle) rabbits, 17.0 +/- 0.7 microns (P less than 0.001) and 10.7 +/- 0.4 microns (P less than 0.005), respectively. Calculation of the relative changes in vascular resistance, however, indicated that the effects of angiotensin II on efferent arteriole resistance (average difference 2.4 +/- 1.2 units/microns) were significantly greater per unit length than the effects on afferent arteriole resistance (average difference 0.9 +/- 0.3 units/microns). Thus infused angiotensin II caused greater reduction in afferent arteriolar diameter than in efferent, but the calculated increase in vascular resistance per micron was greater in efferent vessels due to their smaller resting diameter.

Angiotensin II↗
PubMed1991

Glomerular ultrafiltration in rabbits with superficial glomeruli.

The determinants of glomerular ultrafiltration in superficial glomeruli of a strain of English cross-breed rabbits have been studied using micropuncture techniques. Mean arterial blood pressure in the anaesthetised rabbits was 70 +/- 2 mmHg. The glomerular filtration rate in the kidney prepared for micropuncture was 4.4 +/- 0.4 ml/min, the filtration fraction was 22 +/- 1% and renal blood flow was 33 +/- 3 ml/min, and these values were comparable to values in conscious rabbits. Glomerular capillary pressure (Pgc) averaged 31 +/- 1 mmHg, the single-nephron glomerular filtration rate (SNGFR) averaged 25 +/- 2 nl/min, and the mean ultrafiltration pressure (calculated using the whole-kidney filtration fraction) averaged 7 +/- 1 mmHg. A net positive pressure at the efferent end of the glomerular capillaries (4.4 +/- 0.9 mmHg) indicated that a state of filtration pressure disequilibrium existed, under the experimental conditions of this study, in rabbit glomeruli. The calculated glomerular ultrafiltration coefficient (Kf) was 0.08 +/- 0.01 nl s-1 mmHg-1. Thus, compared to the Munich-Wistar rat, SNGFR is lower in the rabbit. This reflects the substantially lower glomerular ultrafiltration pressure in the rabbit, although this was offset partially by a higher Kf.

Animals↗
PubMed1991

Two types of sympathetic axon innervating the juxtaglomerular arterioles of the rabbit and rat kidney differ structurally from those supplying other arteries.

Ultrastructural analyses of serial thin sections have revealed two structurally different types of sympathetic axon innervating the afferent and efferent juxtaglomerular arterioles and the intralobular arteries in the outer cortex of the rabbit kidney. Both types of axon have also been found in association with an afferent arteriole in rat kidney. One axon type consists of relatively large diameter unmyelinated axons bearing varicosities in the form of slight expansions. The varicosities have a distinct structural zonation: synaptic vesicles occupy the expansion which faces the smooth muscle cells, whereas the rest of the axon is filled with numerous microtubules. The other axon type has varicosities containing vesicles and mitochondria but few microtubules. The varicosities are generally small and the intervaricosities very thin. The relationship of both axon types with support cells and/or basal lamina is sometimes poorly defined. Both axon types are catecholaminergic as their vesicles take up 6-hydroxydopamine and both types form junctions with arteriolar smooth muscle cells. As well as differing from each other, both types of intrarenal axon differ in several respects from those which innervate other arterial vessels.

Animals↗
PubMed1991

Significance of cardiovascular hypertrophy in the development and maintenance of hypertension.

The amplifier properties associated with the structural changes in the heart and resistance vessels in chronic hypertension together play a major role in maintaining the elevated blood pressure (BP) in chronic hypertension, which is greater than that of the initiating cause. In patients with primary hypertension, long-term antihypertensive drug therapy causes substantial regression of the structural changes, as assessed by normalization of the total peripheral resistance (including the nonautonomic component) and of the left ventricular (LV) mass. Reversal of LV hypertrophy (LVH) took considerably longer than reversal of the vascular changes and the more complete the reversal of LVH, the slower the rate of redevelopment of hypertension upon cessation of treatment. We observed no change in sympathetic activity or in renin-angiotensin-aldosterone levels during the redevelopment phase and we hypothesized that the cardiovascular amplifiers played a role in pathogenesis. This hypothesis was examined in spontaneously hypertensive rats (SHRs), where the vascular amplifier properties were developed substantially by 4 weeks of age, i.e., before the development of hypertension, whereas LVH occurred pari passu the rise in BP. When young SHRs were treated with enalapril for brief periods, there was almost complete long-term regression of vascular amplifier properties, but attenuation of LVH and hypertension were both smaller and more transient. In 4-week-old SHRs, complete abolition of sympathetic activity had a minimal effect on vascular amplifier properties, but affected LVH. Our findings suggest that LVH is as important in both the development and maintenance of hypertension as the structurally determined amplifier properties of the resistance vessels.

Animals↗
PubMed1991

Renovascular hypertension: information from experiments using conscious dogs.

1. Evidence from experiments in conscious, instrumented dogs shows that hypertension from renal artery stenosis is due to: (i) the stimulus, the mechanical resistance of the stenosis; and (ii) the secondary responses to this, especially angiotensin II (initially) and cardiovascular hypertrophy. 2. The hydraulic resistance of the stenosis is responsible for about 20-25% of the rise in blood pressure. 3. Angiotensin II is initially the most important secondary response to the stenosis. Within days, however, other as yet undetermined factors become dominant in the maintenance of the hypertension. The most important of these factors is probably cardiovascular hypertrophy. 4. These secondary factors are homeostatic, in that they mitigate the effects of stenosis on renal function.

Angiotensin II↗
PubMed1991

Evidence for a renomedullary vasodepressor system in rabbits and dogs.

Renal perfusion was increased in anesthetized rabbits and dogs by using an extracorporeal circuit. When left kidney perfusion pressure was raised in rabbits (145-240 mm Hg), arterial pressure fell by 1.34 +/- 0.20 mm Hg/min. Pretreatment of the rabbits with 2-bromoethylamine hydrobromide, which destroyed the renal medulla, abolished the fall in arterial pressure (-0.08 +/- 0.08 mm Hg/min) in response to increased renal perfusion pressure. In dogs (with blockade of autonomic ganglia by pentolinium, converting enzyme inhibition [captopril/enalaprilat], and surgical renal denervation), increasing renal perfusion pressure to 170-220 mm Hg resulted in a fall in arterial pressure by 0.32 +/- 0.03 mm Hg/min (or by 28.9 +/- 3.1 mm Hg over a 90-minute period). Mean arterial pressure did not change significantly in identically prepared dogs not subjected to increased renal perfusion pressure, whereas pretreatment of dogs with bromoethylamine abolished the hypotensive response to increased renal perfusion pressure. Thus, the hypotensive response to increased renal perfusion was dependent on the presence of an intact renal medulla, but hypotension still occurred in the presence of converting enzyme inhibition, autonomic ganglion blockade, and renal denervation. The results provide in vivo evidence in two species that a vasodepressor factor from the renal medulla is released in response to increased renal perfusion.

Animals↗
PubMed1979

Sex offenders: three personality types.

Analyzed by a Q-type factor analysis MMPI profiles of 92 sex offenders institutionalized for psychiatric evaluation, which yielded three basic MMPI profile types. Altogether 88 of the 92 Ss coult be categorized into one of three types characterized by profile peaks on F,Sc; Pd,MA; or D,PD. Analysis of background information, social history items, nature of present crime, primary diagnosis, and ward observations revealed significant differences among the types. Of particular interest was the finding that the primary diagnosis for 85% of the "F,Sc" MMPI type was "no mental disorder" in spite of the fact that this group showed significantly more disturbed behavior on the ward (anxiety, depression, suspicion, and manic excitement) and had uniquely degraded their victims. The fact that two-thirds of these persons who had F scores greater than or equal to 80 and 50% denied the crime may have inadvertently affected diagnostic decisions.

Adult↗
PubMed1979

Acute renal haemodynamic and renin-angiotensin system responses to graded renal artery stenosis in the dog.

1. The acute renal haemodynamic and renin-angiotensin system responses to graded renal artery stenosis were studied in chronically instrumented, unanaesthetized dogs. 2. Stenosis was induced over 30 sec by inflation of a cuff around the renal artery to lower distal pressure to 60, 40 or 20 mmHg, with stenosis maintained for 1 hr. This resulted in an immediate fall in renal vascular resistance, but over the next 5--30 min both resistance and renal artery pressure were restored back towards prestenosis values. Only transient increases in systemic arterial blood pressure and plasma renin and angiotensin levels were seen with the two milder stenoses. Despite restoration of renal artery pressure, renal blood flow remained reduced at all grades of stenosis. 3. Pre-treatment with angiotensin I converting enzyme inhibitor or sarosine1, isoleucone8 angiotensin II greatly attenuated or abolished the restoration of renal artery pressure and renal vascular resistance after stenosis, and plasma renin and angiotensin II levels remained high. Renal dilatation was indefinitely maintained, but the normal restoration of resistance and pressure could be simulated by infusing angiotensin II into the renal artery. 4. The effective resistance to blood flow by the stenosis did not remain constant but varied with changes in the renal vascular resistance.

Angiotensin II↗
PubMed1978

The role of vasopressin in blood pressure control and in experimental hypertension.

1. The role of vasopressin in blood pressure control and in the pathogenesis of one-kidney Goldblatt hypertension in the conscious dog was investigated. 2. Infusion of synthetic arginine vasopressin to elevate plasma levels approximately five-fold caused bradycardia in normal dogs and increase in mean arterial blood pressure in dogs with pharmacological autonomic blockade. 3. A similar degree of elevation of plasma vasopressin concentration was observed after mild non-hypotensive haemorrhage. 4. Renal artery constriction in unilaterally-nephrectomized dogs caused a rise in plasma renin activity and only a doubling of plasma vasopressin concentration, but a marked rise in mean arterial blood pressure. 5. Vasopressin may play a role in normal cardiovascular homeostatic responses, but its role in the pathogenesis of this form of hypertension is unlikely to be significant.

Animals↗
PubMed1977

Leakage of dl-propranolol from cerebrospinal fluid to the bloodstream in the rabbit.

Intracerebroventricular (i.c.v.) injection of 500 microgram of dl-propranolol in the conscious rabbit in a rise in mean arterial pressure followed by a small but significant fall (3.2 +/- 1.4 mm Hg between 2 and 4 hours after injection), as has been observed by others. The same dose injected i.v. resulted in a lowering of mean arterial pressure of 6.0 +/- 2.4 mm Hg between 2 and 4 hours after injection. After i.c.v. injection there was a rapid rise in plasma propranolol concentration. Ten minutes after i.c.v. injection the concentration of 80% of the level reached after giving the same dose i.v. After i.c.v. injection there was significant blockade of cardiac beta adrenoreceptors for at least 2 hours. This blockade was determined from the degree of attenuation of isoproterenol-induced tachycardia in rabbits subjected to presynaptic sympathetic nerve block with guanethidine and to vagal block with methscopolamine. Because of the rapid leakage of propranolol from cerebrospinal fluid to plasma it is not possible by means of the technique of i.c.v. injection of the drug to differentiate between central nervous and systemic mechanisms contributing to the lowering of blood pressure.

Animals↗
PubMed1976

Normalizing the MMPI.

Effective psychological services require recognition of a client's strengths as well as weaknesses. Personality tests such as the MMPI, however, focus attention upon the abnormal and deviant attributes of personality. Therefore, a psychologist should have an understanding of various adaptive behaviors that may be indicated by moderately elevated MMPI scale scores. Because most of the literature deals with the pathological ramifications of scale elevations, the authors developed a conceptual perspective of counterpart descriptors for each MMPI clinical scale. These descriptors are presented so that apparently contradictory sets of behaviors for elevated scores on any given scale can be viewed on a continuum from adaptive to maladaptive behavior. An armamentarium of MMPI personality traits should include positive as well as negative considerations to provide a fully comprehensive basis for the formulation of realistic assessments of human potentialities.

Behavior↗
PubMed1976

Effects of the sympathetic nervous system and the adrenal medullary hormones on dog hind limb blood flow after haemorrhage.

The contributions of the sympathetic nervous system and the adrenal medullary catecholamines to the response of dog hind limb resistance vessels to haemorrhage were examined. Anaesthetized dogs were bled either 30% or 45% of blood volume. There was little difference between the vascular conductance response in untreated hind limbs and sympathectomized limbs. Conductance in limbs that had been both sympathectomized and alpha-adrenergically blocked with phenoxybenzamine was markedly above that of untreated limbs. Blood flow in both the untreated limbs and the sympathectomized limbs was closely similar to that predicted from the pressure-flow curve for the hind limbs obtained in non-bled dogs. Flow was higher than predicted in the limbs with combined sympathectomy and alpha-adrenergic blockade. It is concluded that the sympathetic nervous system exerted little vasoconstrictive influence after haemorrhage, but that circulatory catecholamines exerted a strong vasoconstrictive influence that was opposed in the normal limbs by an almost equally powerful vasodilatory force of undetermined origin.

Animals↗
PubMed1976

Action of propranolol on arterial pressure and on cardiovascular reflexes.

In the rabbit, administration of 500 mug (+/-) propranolol into the lateral cerebral ventricle resulted in rapid leakage of drug into the blood. The drug produced a small reduction in blood pressure at 2 and 4 hours after injection but because of the rapid leakage, this could have been due to its peripheral actions. To investigate possible central mechanisms of action which were independent of peripheral effects, we tested the action of intravenously administered propranolol on the reflex rise in TPR evoked in rabbits by graded Valsalva-like manoeuvres. This was performed in unanaesthetised rabbits with Doppler flowmeters for measuring cardiac output. Graded expiratory pressures (EP) were applied to the inlet and outlet tubes of the tracheotomised animal's respiratory valve and to the cuff around their thorax and abdomen. Administration of propranolol at two levels (168 +/- 35 ng/ml, and 240 +/- 33 ng/ml) for 1 hour had no effect on slope and threshold of the EP-TPR relationship. By contrast to the minimal effects on the reflex with propranolol, the EP-related rise in TPR was attenuated by clonidine. We conclude that propranolol does not lower blood pressure in the rabbit by attenuating sympathetic constrictor activity.

Animals↗
PubMed1975

Rapid estimation of pulmonary extravascular water with an instream catheter.

An arterial catheter-bearing external conductivity electrodes and a thermistor was used for measurement of lung thermal volume (LTV) by the double-indicator method. Ten milliliters of 3% saline at room temperature were injected, dilution curves measured, and LTV calculated as mean transit time difference, less thermistor time constant, times cardiac output (CO). Comparisons were made, in dogs, between LTV, pulmonary extravascular lung water with Evans blue and tritiated water (PEVWtho), and weighed lung water (WLW). Pulmonary edema was induced with dextran and epinephrine. CO was measured by thermodilution in both the pulmonary artery (PA) and aorta (AO) and dye dilution in the AO. CO from dye dilution was compared with thermodilution (aortic detection) to detect irreversible loss of thermal indicator. Comparisons showed good correspondence of dye and thermal curves (Y = 0.91X - 0.16 1/min; r = 0.93). LTV is about 120% of WLW in near normal lungs, 90% of WLW in extreme edema. PEVWtho was 60-70% WLW.

Animals↗
PubMed1975

The effects of phlebotomy, hemodilution and autologous transfusion on systemic oxygenation and whole blood utilization in open heart surgery.

Blood utilization in 400 consecutive adult patients undergoing a wide variety of cardiovascular operations requiring cardiopulmonary bypass was documented following institution of: 1) complete oxygenator hemodilution; 2) intraoperative phlebotomy and autologous transfusion; 3) infusion of residual oxygenator red cells; and 4) use of reconstituted frozen cells in patients whose blood type was uncommon. These techniques have resulted in an average utilization of 4.8 units of blood per adult patient. Fourteen patients required no blood at all and a total of 259 patients required less than 5 units of blood during their entire hospital course. Physiologic effects of this blood program and hemodilution were evaluated in ten patients and the results indicate that marked reduction of red cell mass by hemodilution with hypothermia and low flow perfusion is not detrimental to satisfactory whole blood oxygenation during open heart surgery.

Adolescent↗