Effect of alterations in extracellular fluid volume on urinary kallikrein in the conscious rat.

The effect of alterations in extracellular fluid volume (ECV) and solute concentration on excretion of urinary kallikrein was examined in conscious Sprague-Dawley rats. Animals were given infusions of either dextrose and water, saline, or albumin according to a variety of protocols. These were designed to evaluate possible relationships between excretion of kallikrein, volume, sodium, and potassium. A reproducible pattern of kallikrein excretion was noted in all volume expanded groups. This consisted of a short lived increase during the initial hour of expansion with a subsequent fall to lower levels than baseline and a gradual recovery. To define the role of aldosterone in these studies, an adrenalectomized group and a group of appropriately prepared sham controls were expanded with saline. Adrenalectomy did not effect this pattern. We postulate a tubular "washout" phenomenon as the etiology of these observations. Results of these studies fail to demonstrate a consistent relationship between urinary volume, sodium, or potassium and the simultaneous amount of kallikrein found in the urine.

Alterations in systemic haemodynamics induced by atriopeptin III.

The mechanism of the hypotensive response to the intravenous administration of atriopeptin III was investigated in rats of the Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) Okamoto strains. Cardiac performance and the systemic haemodynamic response to acute volume loading were evaluated before and during atriopeptin infusion. Cardiac output was measured by a thermo-dilution technique in conscious rats, and left ventricular pressures with differential (dP/dt) calculations were obtained in anaesthetized animals. Bolus injections followed by a 1-h continuous infusion of atriopeptin caused a progressive decrease in mean arterial pressure (MAP) and cardiac output with no significant change in heart rate. In addition there was a transient decrease, maximal at 5 min, and a subsequent increase in peripheral resistance. Atriopeptin did not alter the maximal cardiac output achieved following acute volume expansion. In the anaesthetized animals, bolus injection with a subsequent 15-min continuous infusion of atriopeptin III significantly reduced left ventricular pressures, dP/dt and mean arterial pressure. Volume expansion fully restored intraventricular pressures and dP/dt while increasing mean arterial pressure toward baseline. We conclude that the steady decrease in mean arterial pressure produced by atriopeptin III is due to a decrease in cardiac output secondary to a fall in stroke volume caused by a lowered filling pressure.

Defining scholarship at the Uniformed Services University of the Health Sciences School of Medicine: A study in cultures.

Medical schools' long-awaited recognition of the varied contributions of their faculty has caused active dialogue and debate. The discourse centers on the best approach for incorporating a broader definition of scholarship, including professional service, into the traditional promotion and tenure processes. At the School of Medicine of the Uniformed Services University of the Health Sciences (USUHS), the majority of the clinical faculty also serve as active-duty uniformed medical officers, and the subject of how to appropriately recognize their varied contributions has long been contended. Concerns have been raised from all constituent groups that broadening the definition of scholarship at the USUHS has the potential to lower the standards of the academy and thus devalue faculty positions. The USUHS has viewed this challenge as a study in the integration of cultures. Institutional cultures include those of the academy, the military, government, basic science, and clinical science, and all the resulting permutations. A nine-year review of scholarship, promotion, and tenure at the USUHS has resulted in a document that supports the diverse missions of the university and appropriately rewards the accomplishments of its faculty. The dialogue continues, as the new document is subject to continuing review and ongoing critical analysis.

Correlation of changes in cardiac calcium channels with hemodynamics in Syrian hamster cardiomyopathy and heart failure.

We compared hemodynamics with [3H]nitrendipine (calcium channel) binding to cardiac membranes from Bio 14.6 cardiomyopathic Syrian hamsters at 4 and 10 months with their F1B controls. A 50% increase in the number (Bmax) of nitrendipine binding sites (calcium channels) was seen only in the 4 month old myopathic vs controls (Bmax = 468 +/- 11 vs 309 +/- 10 fmol/mg prot with no change in affinity (KD) (KD = .65 +/- .12 vs .75 +/- .14 nM), while no differences in Bmax or KD were seen at 10 months (Bmax = 375 +/- 9 vs 362 +/- 7 fmol/mg prot/KD = .82 +/- .18 vs .89 +/- .17 nM) myopathic vs control respectively. Hemodynamic studies revealed no significant differences in cardiac output, cardiac index, stroke volume, heart rate, mean arterial pressure, peripheral resistance, body weight, heart weight at 4 months, but a significant decrease in peripheral resistance (1120 +/- 360 vs 2080 +/- 240) increase in body weight (118 +/- 2 vs 94 +/- 2 grams) and heart weight (97 +/- 5 vs 78 +/- 2 gms/100 gms body weight) in 10 month myopathic vs control animals. We conclude that the onset of cardiomyopathy at 4 months is associated with a selective increase in calcium channel binding sites and heart failure at 10 months is associated with a relative decrease in these sites.

Neurological visual fields.

Neurological visual field defects represent lesions to the visual pathway, some of which may be life-threatening. It is, therefore, crucial that optometrists understand how to diagnose these lesions, so they may know when, and to whom to refer the patient. The following cases illustrate the management of patients with lesions to the prechiasmal, chiasmal, and postchiasmal visual pathway.

Expanded eye care in the Veterans Administration hospital setting.

Over the past decade a greater number of optometrists can be found practicing in hospitals, health maintenance organizations, health clinics and other multipractitioner group settings. The impetus enabling optometry to practice in such settings is based in part on cost effectivity. Optometrists in Veterans Administration (VA) hospitals have been in the forefront in this movement to provide the full range of primary eye care services, and in becoming an integral part of the hospital/medical community.

Acute renal failure secondary to vascular occlusion by a retroperitoneal plasmacytoma.

A case of acute renal failure secondary to bilateral renal vein occlusion by a retroperitoneal plasmacytoma is described. The use of low-risk radiographic techniques including radionuclide venography and a computerized axial tomography (CAT) scan made a rapid and accurate diagnosis possible. Fatal hemorrhage occurred following tumor erosion and perforation of the vena cava. In patients with multiple myeloma, and clinically apparent retroperitoneal tumor, vascular compromise should be considered in the differential diagnosis of acute renal insufficiency.

Atrial natriuretic factor (ANF 103-126) enhances volume- and pressor-induced heart rate response in the conscious rat.

The reduction in blood pressure due to ANF(103-126) fails to elicit reflex cardioacceleration in the conscious rat. To examine baroreflex sensitivity, the effect of ANF(103-126) on the heart period (HP) response to rapid central volume expansion and to alterations in mean arterial pressure (MAP) induced by bolus injections of phenylephrine and sodium nitroprusside was assessed. ANF(103-126) significantly augmented the bradycardic response induced by acute volume expansion from 426 +/- 21 to 391 +/- 23 beats min-1 versus 421 +/- 23 to 405 +/- 24 without ANF(103-126). Baroreflex sensitivity was defined by the ratio of the change in heart period to the maximal change in mean arterial pressure. The dose of ANF(103-126) utilized did not affect basal heart rate or the magnitude of the mean arterial pressure response to phenylephrine but did significantly enhance the nitroprusside-induced decrease in mean arterial pressure. Baroreceptor sensitivity to phenylephrine was significantly increased by ANF(103-126): 0.997 +/- 0.07 (ms mmHg-1) during ANF(103-126) vs 0.613 +/- 0.08 during vehicle. The total duration of the heart rate response to phenylephrine was also prolonged. In contrast, ANF(103-126) did not alter the baroreceptor sensitivity (1.45 +/- 0.3 vs 1.43 +/- 0.2 ms mmHg-1) or duration of heart rate response to nitroprusside. In the conscious rat, ANF(103-126) modifies the heart rate response to changes in mean arterial pressure and acute central volume expansion. This action appears to be dependent on stimulation of cardiac vagal afferents.

Neuropeptide Y is a potent vasoconstrictor and a cardiodepressant in rat.

Neuropeptide Y (NPY) is contained in and coreleased with norepinephrine (NE) from sympathetic nerves innervating vascular and cardiac tissues. The effects of NPY infusion on systemic hemodynamics and cardiac performance were compared with those of NE in conscious and pentobarbital sodium-anesthetized rats. A 10-min infusion of NPY (2 nmol.kg-1.min-1) decreased cardiac index (CI) 20% and stroke volume index (SVI) 9% with increases of 20% in mean arterial pressure (MAP) and 48% in total peripheral resistance (TPR). Conversely, NE (1.0 microgram.kg-1.min-1) increased SVI 14%, MAP 29%, and TRP 26%, with no change in CI. Heart rates decreased similarly (approximately 60 beats/min) but only NE-induced bradycardia was reversible by methylatropine nitrate. In anesthetized rats NPY (0.1 nmol.kg-1.min-1) increased left ventricular end-diastolic pressure (LVEDP) 20 +/- 10 mmHg (means +/- SD, n = 7) and decreased dP/dt by 8 +/- 6%. NE (0.07 microgram.kg-1.min-1) produced an equivalent pressor response, however, dP/dt rose 22 +/- 10% whereas LVEDP increased significantly less than with NPY. Thus NPY is a potent vasoconstrictor exerting similar effects to NE on MAP and TPR but, unlike NE, possesses negative inotropic and chronotropic activity.

Acute oliguric renal failure due to ibuprofen overdose.

We have described a patient who had acute oliguric renal failure after ingesting a single large overdose of ibuprofen. This patient had no predisposing underlying disease, and subsequently had complete resolution of renal failure.

Influenza immunization in patients with chronic renal disease.

Patients receiving long-term hemodialysis (23) and patients with moderate to severe renal impairment and without hemodialysis (14) were immunized with inactivated influenza A/New Jersey/76 whole virus vaccine. Fourfold or greater increases in hemagglutinating-inhibiting antibody (HAI) titers occurred in 94% of controls, 93% of nondialyzed patients with chronic renal disease, and 87% of patients with continual hemodialysis. Postimmunization geometric mean titers in both groups of patients were equivalent to those of controls. The proportion of patients responding to vaccine was independent of levels of creatinine clearance, and the presence of preimmunization HAI titers also had no effect on frequency of seroconversion. Though some element of immunologic suppression is associated with chronic renal disease, it is not reflected in the humoral antibody response to influenza A/New Jersey/76 vaccine.

Response of chronic renovascular hypertension to surgical correction or prolonged blockade of the renin-angiotensin system by two inhibitors in the rat.

1. Removal of the renal artery constriction but not of the clipped kidney restored the blood pressure to normal levels in Goldblatt two-kidney rats with hypertension of more than 4 months' duration. 2. Despite the differences in blood pressure response, both surgical procedures lowered plasma renin concentration to normal or below normal values. 3. Administration of the oral converting enzyme inhibitor SQ 14 225 produced a marked fall in blood pressure in Goldblatt kidney rats with chronic hypertension. However, a prolonged infusion of the angiotensin II antagonist saralasin was quite ineffective. The difference in response to the two inhibitors may have been due to bradykinin potentiation by the converting enzyme inhibitor. 4. Although plasma renin is often elevated in Goldblatt two-kidney rats with hypertension of more than 4 months' duration, the renin-angiotensin system plays no role in the maintenance of blood pressure at this stage.

Vasodepressor property of the converting enzyme inhibitor captopril (SQ 14 225): the role of factors other than renin-angiotensin blockade in the rat.

1. The peptide converting enzyme inhibitor captopril was given (1.25 mg/kg intravenously) to normal and nephrectomized rats and rats with renovascular and deoxycorticosterone hypertension. 2. Captopril lowered blood pressure to a small extent in normal and nephrectomized rats. Bradykinin infusion in nephrectomized animals, however, potentiated the vasodepressor action of captopril. 3. Captopril produced a major blood pressure fall in the early stages of Goldblatt two-kidney one-clip hypertension: even when hypertension had been present for more than 4 months, a substantial vasodepressor action was seen. Rats with deoxycorticosterone-induced hypertension also showed a significant blood pressure fall. 4. Captopril was given to salt-loaded and salt-depleted rats in which the renin-angiotensin system had been blocked by infusion of the competitive angiotensin II antagonist saralasin. Captopril still lowered blood pressure in the salt-depleted group. 5. Captopril lowers blood pressure in situations where the renin-angiotensin system is not responsible for blood pressure maintenance. Further, the fall in blood pressure produced in Goldblatt two-kidney one-clip hypertension is greater than would be predicted on the basis of renin-angiotensin blockade. It is likely therefore that captopril lowers blood pressure by an action additional to angiotensin blockade. Bradykinin potentiation is one possible mechanism by which this may take place.