Decrease of blood pressure by ventrolateral medullary decompression in essential hypertension

BACKGROUND

About 20% of adults worldwide will develop hypertension. Studies and clinical observations suggest an association between hypertension and pulsatile compression of the ventrolateral medulla oblongata by a looping artery. We investigated whether neurosurgical microvascular decompression substantially decreases blood pressure long-term in patients with severe essential hypertension.

METHODS

We included eight patients who had received three or more antihypertensive drugs without adequate control of blood pressure, intolerable side-effects, or both. All patients underwent microvascular decompression at the root-entry zone of cranial nerves IX and X after neurovascular compression of the ventrolateral medulla oblongata was seen on magnetic-resonance angiography.

FINDINGS

3 months after surgery, blood pressure and antihypertensive regimens had decreased substantially in three patients. Four patients who were followed up for more than 1 year became normotensive, but their antihypertensive regimens remained the same as those at 3 months. One patient did not improve. No complications associated with decompression occurred. One patient experienced a transient vocal-cord paresis after the laryngeal part of the vagus nerve was manoeuvered during surgery.

INTERPRETATION

We showed a direct causal relation between raised blood pressure and irritation of cranial nerves IX and X. A subgroup of patients with essential hypertension may exist who have secondary forms of hypertension related to neurovascular compression at the ventrolateral medulla and who may be successfully treated with decompression.

Exhaustive exercise-induced tissue hypoxia does not change endothelin and big endothelin plasma levels in normal volunteers

Chronic hypoxia has been shown to increase plasma endothelin levels. The current study was undertaken to examine the effect of exercise-induced tissue hypoxia on plasma levels of endothelin-1 (ET-1) and its precursor big endothelin-1 (Big-ET-1). After approval by the local ethical committee an incremental dynamic exercise test was performed in 12 physically trained volunteers (aged 20 to 40 years), using an electrically braked bicycle ergometer. The protocol included a step-wise increase of the workload until a heart rate of 130/min was reached, followed by a maintenance period of 25 min, and a further step-wise increase until exhaustion. Blood was drawn before, at several time points during, and 5 min after termination of the study for determination of ET-1, Big-ET-1, plasma renin activity (PRA), angiotensin converting enzyme (ACE), norepinephrine, epinephrine, and lactate. Lactate levels at baseline were 14.5 +/- 1.6 mg/dL (mean +/- SEM), which increased to 76.5 +/- 4.8 mg/dL at the time of exhaustion (P < .01). Baseline values for ET-1 and Big-ET-1 were 0.264 +/- 0.061 and 0.637 +/- 0.130 fmol/ml, respectively, which remained essentially unaltered throughout the exercise test. PRA was 1.46 +/- 0.45 ng/mL/h before exercise and increased to 3.55 +/- 0.96 ng/mL/h at exhaustion (P < .001). Norepinephrine and epinephrine were also increased at exhaustion. The study demonstrates that exhaustive physical exercise with acute development of pronounced tissue hypoxia--in contrast to chronic hypoxia--does not influence the release of ET-1 or Big-ET-1 or the conversion of the precursor to the active compound. Unlike endothelin, circulating renin and the catecholamines were markedly stimulated by this maneuver.

Globin gene expression is reprogrammed in chimeras generated by injecting adult hematopoietic stem cells into mouse blastocysts

To elucidate whether the differentiation capacity of hematopoietic stem cells (HSCs) is influenced by specific microenvironments, adult mouse bone marrow-derived HSCs were injected into mouse blastocysts. Embryos developing from injected blastocysts contained donor-derived cells at various developmental stages, and progeny of the stem cells were detected in hematopoietic tissues. Thus, HSCs derived from an adult animal survive after injection into blastocysts and are able to participate in hematopoietic development. We further find that the erythroid progeny of transplanted adult HSCs express embryonic/fetal-type globin genes and, conversely, that embryonic and fetal progenitor cells transplanted into adult recipients transcribe the adult-type globin gene. Thus, the developmental potential of adult HSCs is evidently more plastic than previously thought, and the developmental stage of the hematopoietic microenvironment controls the developmental fate of transplanted progenitor cells.

Clonidine suppression test revisited

BACKGROUND

The diagnosis of pheochromocytoma may be difficult because the clinical picture is variable.

OBJECTIVE

The purpose of this paper is to report our experience and to review the published data on the diagnostic significance and risks of the clonidine suppression test in the diagnosis of pheochromocytoma.

PATIENTS AND METHODS

114 patients were evaluated for pheochromocytoma using the clonidine suppression test.

RESULTS

The diagnosis was established in four patients. Overall accuracy of the test in our own series was 98% when the normal response to clonidine was defined as total plasma catecholamines of less than 500 ng/L, or less than 70% of the baseline value. No serious complication was noted.

CONCLUSION

Our data and the published series demonstrate that the clonidine suppression test is accurate and safe in patients with suspected pheochromocytoma.

Elevated serum cyclophilin levels in patients with severe sepsis

Several cytokines are considered to be important mediators in the pathophysiology of sepsis. Cyclophilins (Cyps), the main binding proteins for the immunosuppressive drug cyclosporine A, have been suggested to function as cytokines. This study was conducted to determine (i) if serum Cyp levels were elevated in critically ill patients suffering from either sepsis or other life-threatening diseases and (ii) if so, whether there was an association between Cyp levels and a certain diagnosis and/or outcome. Serum samples of 45 patients (22 severe sepsis, 23 other diagnoses) and 17 healthy controls were prospectively analyzed by an enzymatic assay using the ability of cyclophilins to catalyze cis/trans isomerisation of peptidylprolyl-peptide bonds (PPIase activity). In addition, western blotting was applied to differentiate both isoforms. PPIase activity was significantly higher in patients with severe sepsis than in patients with other diagnoses (P = 0.004) or in healthy subjects (P = 0.001). There was no difference between healthy subjects and other critically ill patients (P = 0.067). Elevated PPIase activity was associated with high mortality (P = 0.03). It is concluded that Cyps might play a role, probably as mediators in the pathophysiology of sepsis or as symptoms of diagnostic value.

Effects of early and late antihypertensive treatment on extracellular matrix proteins and mononuclear cells in uninephrectomized SHR

The efficacy of an early and late treatment with the angiotensin converting enzyme inhibitor lisinopril or the angiotensin II receptor blocker ICI D8731 was investigated in uninephrectomized spontaneously hypertensive rats (SHR). Rats that underwent uninephrectomy (UNX) at six weeks of age were randomly assigned to receive no treatment, lisinopril shortly after UNX, lisinopril starting 16 weeks after UNX, ICI D8731 shortly after UNX, and ICI D8731 starting 16 weeks after UNX. Blood pressure was normalized with both treatments. After six months inulin clearance was not significant different, while proteinuria and prevalence of interstitial fibrosis were significantly reduced in all treatment groups. Immunohistochemical studies revealed an interstitial, periglomerular and perivascular increase of extracellular matrix proteins in all rats, but a markedly reduced expression of collagen I, IV and fibronectin after early and late treatment compared to untreated controls. We found a significant reduction of infiltrating macrophages and T-lymphocytes in all treated animals compared to untreated controls after 2, 4 and 6 months. Especially early treatment was associated with lower numbers of infiltrating cells. Both treatments reduced proliferation of tubular and interstitial cells. There were no striking differences with regard to nephroprotection between the ACE inhibitor and angiotensin II receptor blocker. These findings show that both treatments have beneficial effects on kidney structure and function. They suggest that both ACE inhibition and angiotensin II blockade decrease renal cell proliferation and suppress the infiltration of mononuclear cells that may trigger expression of extracellular matrix proteins and progressive nephrosclerosis.

Pulmonary serotonin 5-HT3-sensitive afferent fibers modulate renal sympathetic nerve activity in rats

Cardiopulmonary reflexes with vagal afferents may control volume homeostasis by influencing renal nerve activity. Such reflexes can be stimulated mechanically and chemically, e.g., by serotonin 5-HT). We have demonstrated that stimulation of epicardial 5-HT3 receptors inhibits renal sympathetic nerve activity (RSNA) by a cardiorenal reflex. We now tested the hypothesis that pulmonary 5-HT3-sensitive vagal afferent fibers participate in the control of renal nerve activity. Two sets of experiments were performed. First, the responses of multifiber RSNA, heart rate (HR), and blood pressure (BP) to the 5-HT3-receptor agonist phenylbiguanide (PBG; 10 microg iv) were recorded in the presence of intact pulmonary afferents. Abdominal afferents were removed by subdiaphragmatic vagotomy. Cardiac afferents were blocked by intrapericardial injection of 10% procaine. Second, the responses of 25 single vagal pulmonary afferent C fibers to PBG were assessed. PBG decreased BP, HR, and RSNA (-90 +/- 8%). When cardiac afferents were blocked by procaine, BP and HR failed to decrease in response to PBG; however, the RSNA decrease was still -48 +/- 8%. Single fibers generally responded to PBG by a slight increase in firing rate. A distinct subset of fibers (5 of 25) showed an activity increase of >15 Hz that preceded changes in BP and HR. The decreased RSNA in the absence of cardiac and abdominal vagal afferents and the strong response of 20% of pulmonary single fibers to intravenous PBG suggest that pulmonary fibers play a role in a 5-HT3 serotenergic reflex. Thus pulmonary serotonin could influence the neural control of renal function.

[The first manifestations of Schönlein-Henoch purpura in a 74-year-old female patient with hyperthyroidism]

HISTORY AND CLINICAL FINDINGS

A 74-year-old woman had for 3 weeks suffered from watery diarrhoea and diffuse abdominal pain. She felt restless, had a subfebrile temperature (37.8 degrees C), tachycardia and a blood pressure of 190/90 mmHg. Shortly after admission petechiae were found over the lower legs and she complained of joint pains.

INVESTIGATIONS

Laboratory tests established hyperthyroidism. Skin biopsy showed leukocytoclastic vasculitis. Tests for antinuclear antibodies, antistreptolysin titre, rheumatoid factors, cryoglobulins and TSH-receptor antibodies were negative, immunoglobulin A (IgA) was raised.

TREATMENT AND COURSE

As a drug-induced vasculitis was suspected treatment was started with methylprednisolone, 100 mg daily. Proteinuria (5.6 g daily) indicated renal biopsy, which revealed focal glomerulonephritis with deposits of IgA, fibrin/fibrinogen and complement factor 3. Gastroscopic biopsy, performed after an episode of gastrointestinal bleeding, demonstrated necrotizing vasculitis, confirming the diagnosis of Schönlein-Henoch-purpura (SHP). As the patient's condition rapidly worsened, cyclophosphamide was started additionally (2 mg/kg). She died on the 17th hospital day from acute cardiac failure.

CONCLUSION

The lethal course of the disease in this elderly patient illustrates a previously not reported close temporal and clinical relationship between SHP and hyperthyroidism.

Experimental studies on the role of intercellular adhesion molecule-1 and lymphocyte function-associated antigen-1 in hypertensive nephrosclerosis

T helper cells and macrophages infiltrate into the renal cortical interstitium during the course of hypertensive nephrosclerosis. To investigate the mechanisms of mononuclear cell infiltration, we examined the expression of the intercellular adhesion molecule-1 (ICAM-1) and its counterpart lymphocyte function-associated antigen-1 (LFA-1) in the progression of hypertensive renal injury. We studied nonclipped kidneys of two-kidney, one clip renovascular hypertensive and sham-operated control rats immunohistochemically at 4, 7, 14, and 28 days after clipping (n = 5 per group and time point). Systolic pressure was significantly elevated by day 7 (154 +/- 4 versus 117 +/- 6 mm Hg in sham, P < .05). The development of hypertension resulted in a progressive increase of ICAM-1 expression in the perivascular and interstitial areas of the renal cortex and on proximal tubular brush borders. Only a few glomeruli showed augmented ICAM-1 staining. Increased ICAM-1 was associated with an accumulation of LFA-1-positive mononuclear cells in the perivascular region (day 14: 15 +/- 4 versus 2 +/- 0.2 cells/mm2 in sham, P < .005) and intertubular region (127 +/- 11 versus 32 +/- 3 cells per millimeter squared in sham, P < .005). The maximum was obtained at day 14 and remained elevated until day 28. In addition, the number of interstitial LFA-1-positive infiltrating cells was related to the degree of interstitial and tubular ICAM-1 expression and correlated with blood pressure (r = .75, P < .001, n = 18). Our data suggest that ICAM-1 is involved in the recruitment of macrophages/lymphocytes via specific interaction of ICAM-1 and LFA-1 in this model of hypertensive target-organ damage.

Subthreshold stimulation of a serotonin 5-HT3 reflex attenuates cardiovascular reflexes

Volume-sensitive and chemosensitive cardiopulmonary reflexes modulate volume homeostasis via renal sympathetic nerve activity (RSNA). Blunting of volume-sensitive cardiopulmonary reflexes is associated with volume retention, e.g., in hypertension, whereas the role of chemosensitive cardiopulmonary reflexes is largely unknown. To elucidate the possible role of chemosensitive cardiopulmonary reflexes in control of volume homeostasis, we investigated whether subthreshold stimulation of 5-HT3 receptors modulates the control of RSNA by volume-sensitive cardiopulmonary reflexes or the arterial baroreceptor reflex in rats. Phenyl biguanide (PBG) was infused intravenously to stimulate 5-HT3 receptors. Higher doses of PBG lowered RSNA, but a dose of 6 micrograms/min, given as a background infusion throughout the experiment, did not change arterial pressure, heart rate (HR), or RSNA. Ten minutes after beginning the 6 micrograms/min PBG infusion, a 15-min volume expansion (0.9% saline, 5 or 10% body weight) was started to stimulate volume-sensitive cardiopulmonary reflexes. In separate experiments, 5-min ramp infusions of methoxamine and nitroglycerin to stimulate the arterial baroreceptor reflex (evaluated by a 4-parameter logistic regression) were performed 15 min after beginning the PBG background infusion (6 micrograms/min). During PBG infusion, the RSNA responses to volume expansions were significantly impaired (5% body weight: PBG -6 +/- 6%, n = 7 vs. control -39 +/- 9%, n = 6, P < 0.001; 10% body weight: PBG -33 +/- 6%, n = 8 vs. control -52 +/- 5%, n = 7, P < 0.05). The 5-HT3 receptor antagonist odansetron (GR-38032F) abolished these effects of PBG. The maximum HR gain of the arterial baroreceptor reflex was impaired but the arterial baroreceptor control of RSNA was unaffected by PBG background infusion. We conclude that 5-HT3-serotonergic cardiopulmonary chemoreceptors blunt the RSNA decrease to volume loading. This mechanism may facilitate volume retention when cardiac serotonin is increased.

Preeclampsia -- a state of sympathetic overactivity

BACKGROUND

Preeclampsia is characterized by a marked increase in peripheral vascular resistance leading to an increase in blood pressure, but the triggering mechanisms are unclear.

METHODS

To determine whether augmented sympathetic vasoconstrictor activity may be an important mechanism in mediating the increase in vasomotor tone, we measured postganglionic sympathetic-nerve activity in the blood vessels of skeletal muscle by means of intraneural microelectrodes in nine women with preeclampsia, eight normotensive pregnant women, six normotensive nonpregnant women, and seven nonpregnant women with hypertension, both at rest and during noninvasive cardiovascular-reflex testing (with the Valsalva maneuver and the cold pressor test).

RESULTS

The mean (+/-SE) rate of sympathetic-nerve activity in the normotensive pregnant women (10+/-1 bursts per minute) was not significantly different from that in normotensive nonpregnant women (12+/-2 bursts per minute) or hypertensive nonpregnant women (15+/-3 bursts per minute). In contrast, the rate of sympathetic-nerve activity in the patients with preeclampsia (33+/-3 bursts per minute) was more than three times as high as that in the normotensive pregnant women (P<0.05) and more than twice as high as in the group of nonpregnant women with hypertension (P<0.05). Hemodynamic and sympathetic-nerve responses to both reflex tests did not differ significantly among the four groups. Six patients with preeclampsia were studied again after delivery; mean sympathetic-nerve activity at that time had decreased significantly from the value during pregnancy (from 36+/-4 to 13+/-2 bursts per minute, P<0.01), as had mean arterial pressure (from 118+/-3 to 96+/-1 mm Hg, P<0.01).

CONCLUSIONS

Preeclampsia is a state of sympathetic overactivity, which reverts to normal after delivery. Our data indicate that the increases in peripheral vascular resistance and blood pressure that characterize this disorder are mediated, at least in part, by a substantial increase in sympathetic vasoconstrictor activity.

Angiotensin II-induced hypertension: effects on central and peripheral atrial natriuretic peptide

Angiotensin (Ang) II and atrial natriuretic peptide (ANP) have opposing effects on blood pressure, sympathetic activity, vasopressin and ACTH secretion, salt appetite, and drinking. We observed their interaction by infusing Ang II (7.2 nmol/h) into the peritoneum (i.p.) or into the lateral ventricle (i.c.v.) of rats with osmotic minipumps for seven days. At sacrifice, rats receiving Ang II-i.c.v. had a systolic blood pressure of 184 +/- 3 (SEM) mmHg, those receiving Ang II-i.p. had 159 +/- 5 mmHg (p < 0.05), while controls had 109 +/- 2 and 110 +/- 2 mmHg, respectively (p < 0.05). Drinking and urine volume increased similarly in rats receiving Ang II by either route, while Uosm decreased. Renin (PRA) values were lower (p < 0.05) in rats receiving Ang II-i.c.v. (0.7 +/- 0.2 ng Ang l/ml/h) or Ang II-i.p. (0.9 +/- 0.2) than in the respective controls (2.3 +/- 0.7 and 2.0 +/- 0.3). Plasma ANP values with Ang II-i.c.v. (18 +/- 1.6 pg/ml) or with Ang II-i.p. (49 +/- 6) were also lower (p < 0.05) than respective controls (89 +/- 12, 76 +/- 4). Vasopressin (AVP) concentrations in the plasma were not influenced by the regimens. In the brain, the ANP contents in areas of the so-called AV3V-region (organum vasculosum laminae terminalis, preoptic periventricular nucleus, medial preoptic nucleus) were similarly and significantly reduced by both Ang II-i.c.v. and Ang II-i.p.. ANP values were also reduced in the median eminence by both types of Ang II-treatment, while ANP concentrations in the supraoptic nucleus were increased. The data show that Ang II infusions producing a chronic rise in blood pressure exert similar effects on drinking behavior, PRA, and ANP concentrations in blood and brain. The AV3V area may be pivotal to both models.

Expression of angiotensin-converting enzyme in renovascular hypertensive rat kidney

We hypothesized that the gene expression of angiotensinogen, angiotensin-converting enzyme, and angiotensin II type 1 receptor, in addition to renin, is increased in kidneys after renal artery stenosis. Two-kidney, one clip renovascular hypertension was initiated in Sprague-Dawley rats by clipping of the left renal artery; control rats were sham operated. Blood pressure was not changed for the first 2 days after clipping but was elevated on day 4 (mean arterial pressure, 104 +/- 4 versus 87 +/- 2 mm Hg in sham-operated control rats, P < .002) and increased further during the next 24 days. Rats were killed 2, 4, 7, 14, and 28 days after clipping or sham operation, and poly(A)(+)-purified renal cortical RNA was analyzed by Northern blotting. Autoradiographs were quantitated by densitometry and normalized for the expression of a housekeeping gene. Renin expression was increased in the clipped kidney (by 149% on day 2) and decreased in the nonclipped kidney (by 82% on day 2), compared with kidneys of control rats. Expression of the angiotensin-converting enzyme was increased in clipped kidneys from the first day after clipping (158%) and throughout the experiment (66% on day 28), but was unchanged or slightly decreased in nonclipped kidneys. Angiotensinogen mRNA showed little change. Angiotensin II type 1 receptor expression was decreased in nonclipped kidneys but unchanged during the first 7 days in clipped kidneys. Our results show that components of the renin-angiotensin system other than renin are also differentially expressed in clipped kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurotransmitters and neuropeptides in the baroreceptor reflex arc: connections between the nucleus of the solitary tract and the ventrolateral medulla oblongata in the rat

The primary baroreceptor area (nucleus of the solitary tract-NTS) is anatomically interconnected with the rostral ("vasomotor area") and the caudal ("vasodepressor area") ventrolateral medulla by a well-defined arc of neuronal pathways. The chemical character and the direction of these pathways have been investigated with immunohistochemical and neurochemical techniques in intact and brainstem-operated rats. The transection of the neuronal arc resulted in an accumulation of tyrosine hydroxylase immunoreactivity in a small group of cells in the NTS adjacent to the area postrema, ipsilateral to the knife cut. Decreased angiotensinogen mRNA and atrial natriuretic peptide concentrations were measured in the ventrolateral medulla after the cut, and an accumulation of angiotensin II-immunoreactivity was found in neuronal perikarya in the ipsilateral NTS. Intracranial vagotomy caused marked depletions in glutamate levels in the subcommissural portion of the NTS and in the caudal ventrolateral medulla but nowhere else in the brainstem investigated including the rostral ventrolateral medulla.

New Three- and Tetraoxygenated Coumarin Glucosides from the Mosses Atrichum undulatum and Polytrichum formosum

Atrichum undulatum as well as Polytrichum formosum are containing each six different coumarin glycosides of which three are common to both species. From the nine different glycosides eight are new natural compounds. The structures have been elucidated spectroscopically.

Posterior fossa neurovascular anomalies in essential hypertension

Intraoperative observations, necropsy, and angiographic studies support the presumption that neurovascular compression of the left ventrolateral medulla may cause neurogenic hypertension. Pulsatile irritation of the ventrolateral medulla at the root-entry zone of cranial nerves IX and X increases blood pressure in animals. To identify and assess the distribution of neurovascular compression at the ventrolateral medulla in human beings, we did a prospective single-blind study in 24 patients with essential hypertension, in 14 patients with renal hypertension, and in 14 normal subjects. To detect neurovascular compression, we used axial and coronal double-echo and magnetic-resonance angiography sequences. Blood pressure control and duration of hypertension were not different in the two groups of patients. 20 patients with essential hypertension had magnetic tomographic evidence of left-sided neurovascular compression at the ventrolateral medulla; 2 patients with renal hypertension and 1 of the normal subjects had a positive finding on the left. On the right side, we found signs of neurovascular compression in 4 patients with essential hypertension, in 4 with renal hypertension, and in 2 of the normal subjects. With magnetic resonance tomography, it is possible to evaluate the neurovascular relations in the posterior fossa and detect neurovascular compression at the ventrolateral medulla. These data in living subjects give further evidence of an association between neurovascular compression at the left ventrolateral medulla and essential hypertension.

Impaired cardiovascular reflexes precede deoxycorticosterone acetate-salt hypertension

We hypothesized that impaired cardiopulmonary reflexes but not altered baroreceptor reflexes precede deoxycorticosterone acetate (DOCA)-salt hypertension. Uninephrectomized rats were given either DOCA and 0.9% NaCl as drinking water, 0.9% NaCl alone, or tap water. We measured mean blood pressure, heart rate, and renal sympathetic nerve activity. After 8 days, mean blood pressure was not different in DOCA-salt and control rats. Volume-sensitive cardiopulmonary reflexes were tested by intravenous volume loading with saline (10% body weight in 15 minutes), which decreased renal sympathetic nerve activity without changing mean blood pressure or heart rate. This response was blunted in DOCA-salt rats. Chemosensitive cardiopulmonary reflexes were tested by 15-minute infusions of the serotonin 5-HT3 agonist phenylbiguanide, which decreased renal sympathetic nerve activity without changing mean blood pressure or heart rate. Sustained decreases in renal sympathetic nerve activity occurred during phenylbiguanide infusion in controls but were blunted over time in DOCA-salt rats. The arterial baroreflex responses to graded infusions of methoxamine and nitroprusside were analyzed by sigmoidal curve fitting. There were no differences in gain of renal sympathetic nerve activity or heart rate between the groups. Thus, DOCA-salt rats exhibit impaired cardiopulmonary reflexes before the onset of hypertension; the volume-sensitive reflexes are more severely affected than chemosensitive reflexes. The arterial baroreceptor reflex is unaltered. The decreased sensitivity of cardiopulmonary reflexes may contribute to DOCA-salt hypertension.