Die Wirkung länger dauernder Hydrochlorothiazid-Gaben auf die Plasma-Renin-Aktivität und die Aldosteron-Exkretionsrate bei Normalpersonen

Zusammenfassung Die Wirkung von Hydrochlorothiazid auf die Plasma-Renin-Aktivität (PRA) und die Aldosteron-Exkretionsrate (AER) wird bei 10 Normalpersonen untersucht. Gleichzeitig werden Bestimmungen der Serum- und Urinelektrolyte, des Hämatokrits und der Flüssigkeitsbilanz durchgeführt. In derjenigen Gruppe, die während 7 Tagen täglich 50 mg Hydrochlorothiazid (Esidrex®) erhielt, steigen die PRA am 2. und 4. Tag und die AER am 3. Tag nach Beginn der Diuretikagabe signifikant an, während am 6. bzw. am 7. Tag ein Abfall beider Parameter zur Norm einsetzt. Wesentliche Änderungen der Serumelektrolyte und des Hämatokrits werden nicht registriert. Die Stimulation des Renin-Angiotensin-Aldosteron-Systems (RAAS) kann mit einer erhöhten Natriurese und Diurese korreliert werden. Die Kaliurese steigt ebenfalls deutlich an, so daß der Na/K-Quotient im Urin unter 1 abfällt.In derjenigen Gruppe, die während 6 Wochen täglich 50 mg Hydrochlorothiazid erhielt, werden nach 2, 4 und 6 Wochen der Diuretikaverabreichung keine signifikanten Veränderungen der PRA, AER, Serumelektrolyte und des Hämatokrits festgestellt. Es entwickelt sich demnach unter längerdauernden Saluretikagaben kein sekundärer Hyperaldosteronismus.Die Wirkung sowohl einer Natriumrestriktion als auch einer saluretikainduzierten Natriumexkretion auf das RAAS wird besprochen. Schließlich werden die Möglichkeiten diskutiert, die einen Rückgang der Stimulation des RAAS trotz andauernder Diuretikagaben bewirken können.

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Summary The effect of hydrochlorothiazide on plasma renin activity (PRA) and aldosterone excretion rate (AER) were examined in 10 normal persons. At the same time, determinations of serum and urine electrolytes, of hematocrit and of fluid balance were carried out. In that group which recieved 50 mg hydrochlorothiazide (Esidrex®) daily for 7 days, the PRA rose significantly on the 2nd and 4th day and the AER on the 3rd day after the beginning of diuretic treatment. A decline to normal in both parameters set in on the 6th and 7th day, respectively. Considerable changes in serum electrolytes and hematocrit were not registered. The stimulation of the renin-angiotensin-aldosterone system (RAAS) could be correlated with elevated natriuresis and diuresis. Kaliuresis rose considerably as well so that the Na/K quotient in urine fell under 1.In that group which recieved 50 mg hydrochlorothiazide daily for a period of 6 weeks, no significant changes were noticed in PRA, AER, serum electrolytes or hematocrit after 2, 4 and 6 weeks of diuretic treatment. There was no development of secondary hyperaldosteronism under extended saluretic treatment.The effect of sodium restriction as well as saluretica-induced sodium excretion on the RAAS is discussed. Finally, the possibilities are discussed which can cause a retreat in stimulation of the RAAS despite extended treatment with diuretics.

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Diese Arbeit wurde durch die Hilfe des Schweizerischen Nationalfonds zur Förderung der wissenschaftlichen Forschung und der Stiftung zur wissenschaftlichen Forschung an der Universität Zürich ermöglicht.     

Hemodynamic profile of arpromidine and its F2-substituted derivatives in comparison to impromidine in congestive heart failure

There is considerable evidence that congestive heart failure (CHF) is paralleled by a decrease in the number of sarcolemmal β-receptors due to excessive levels of circulating endogenous catecholamines [1, 2]. In contrast, the myocardial H₂-receptor system is not affected. The first clinically available specific H₂-receptor agonist impromidine proved to be a potent inotrope in patients with CHF which were insensitive to catecholamine stimulation [3, 4]. Though the overall results of these initial studies were beneficial, the narrow therapeutic range, high costs of synthesis and the arrhythmogenic potential of impromidine limited its broad clinical application in large scale clinical trials. Recently developed phenylpyridylalkylguanidines [5] were investigated underin vitro andin vivo conditions in the guinea pig under physiologic and pathophysiologic conditions using impromidine as reference. Compounds tested were arpromidine and the difluorinated analogues BU-E-75 and BU-E-76, all guanidine-type H₂-agonists with additional H₁-antagonistic properties due to a pheniramine like moiety. In the isolated perfused heart, all three new compounds were more potent in increasing cardiac contractile force and coronary flow but less effective on heart rate and less arrhythmogenic. The same could be established underin vivo conditions where BU-E-76 was more potent than BU-E-75, arpromidine and impromidine, respectively, in augmenting LV dp/dt, LVP, cardiac output and systemic blood pressure, but all compounds were revealed to have less chronotropic and arrhythmogenic potential. In the vasopressin-induced acute heart failure model, BU-E-76 and BU-E-75 normalized within minutes all contractile parameters in contrast to arpromidine and impromidine. It is thus concluded that these new H₂-receptor agonists may represent a promising therapeutic improvement for treatments of CHF patients, with a cardiovascular profile superior to impromidine and conventional catecholamines.

     

The pharmacological stimulation of NMDA receptors via co-agonist site: an fMRI study in the rat brain

d-Serine has been proposed as an endogenous modulator at the co-agonist glycine-binding site of N-methyl-d-aspartate (NMDA) receptors. There is still some debate as to whether this site is saturated in vivo, but it seems likely that this depends on regional differences in local glycine or d-serine concentrations. In order to identify areas where the co-agonist site was not fully activated in vivo, we studied the effect of intraperitoneal d-serine administration in the rat brain using functional magnetic resonance imaging (fMRI). Using contrast agent injection, the variations in the relative cerebral blood volume (CBVrel) in several regions of interest were evaluated. d-Serine (50 mg/kg) elicited a significant statistical increase in the CBVrel in the hippocampus. This effect was inhibited by the specific full antagonist of the co-agonist glycine site L-701,324 indicating that the hippocampal activation occurred through the binding of the agonist d-serine to the glycine-binding site of NMDA receptors. This result demonstrates that in the hippocampus, the co-agonist sites of NMDA receptors are not endogenously saturated under our experimental conditions, suggesting an important role of d-serine in the modulation of receptor function in the hippocampus.     

Nursing constraint models for electronic health records: a vision for domain knowledge governance

Various forms of electronic health records (EHRs) are currently being introduced in several countries. Nurses are primary stakeholders and need to ensure that their information and knowledge needs are being met by such systems information sharing between health care providers to enable them to improve the quality and efficiency of health care service delivery for all subjects of care. The latest international EHR standards have adopted the openEHR approach of two-level modelling. The first level is a stable information model determining structure, while the second level consists of constraint models or 'archetypes' that reflect the specifications or clinician rules for how clinical information needs to be represented to enable unambiguous data sharing. The current state of play in terms of international health informatics standards development activities is providing the nursing profession with a unique opportunity and challenge. Much work has been undertaken internationally in the area of nursing terminologies and evidence-based practice. This paper argues that to make the most of these emerging technologies and EHRs we must now concentrate on developing a process to identify, document, implement, manage and govern our nursing domain knowledge as well as contribute to the development of relevant international standards. It is argued that one comprehensive nursing terminology, such as the ICNP or SNOMED CT is simply too complex and too difficult to maintain. As the openEHR archetype approach does not rely heavily on big standardised terminologies, it offers more flexibility during standardisation of clinical concepts and it ensures open, future-proof electronic health records. We conclude that it is highly desirable for the nursing profession to adopt this openEHR approach as a means of documenting and governing the nursing profession's domain knowledge. It is essential for the nursing profession to develop its domain knowledge constraint models (archetypes) collaboratively in an international context.     

Prostaglandin D synthase (beta-trace) in healthy human sleep

STUDY OBJECTIVES: The prostaglandin D system plays an important role in animal sleep. In humans, alterations in the prostaglandin D system have been found in diseases exhibiting sleep disturbances as a prominent symptom, such as trypanosoma infection, systemic mastocytosis, bacterial meningitis, major depression, or obstructive sleep apnea. Assessment of this system's activity in relation to human physiologic sleep was the target of the present study. DESIGN: Serum concentrations of lipocalin-type prostaglandin D synthase (L-PGDS, former beta-trace), and plasma levels of the pineal hormone melatonin were measured in 20 healthy humans (10 women, 10 men; aged: 23.3 +/- 2.39 years) at 4-hour intervals over a period of 5 days and nights, which included physiologic sleep, rapid eye movement sleep deprivation, and total sleep deprivation. In addition, the serum L-PGDS and plasma melatonin levels of 6 subjects were determined under conditions of bright white (10,000 lux) or dark red light (< 50 lux) in a crossover design during total sleep deprivation. Nocturnal blood sampling was performed by a through-the-wall tube system. L-PGDS was measured by an automated immunonephelometric assay, and melatonin was analyzed by direct radioimmunoassay. RESULTS: Serum L-PGDS concentrations showed marked time-dependent changes with evening increases and the highest values at night (P < .0005). This nocturnal increase was suppressed during total sleep deprivation (P < .05), independent of external light conditions and melatonin secretion. Rapid eye movement sleep deprivation had no impact on circulating L-PGDS levels. CONCLUSIONS: The circadian L-PGDS pattern and its suppression by total sleep deprivation indicate an interaction of the prostaglandin D system and human sleep regulation. L-PGDS measurements may well provide new insights into physiologic and pathologic sleep regulation in humans.     

Cell membrane destabilizes progressively during repetitive mechanical rupture events

The postfusion oscillation cycle method of electrofused cells was applied to red blood cell membranes to induce repetitive membrane ruptures and test the mechanical membrane resistance against sequential events of membrane strain and rupture. After producing doublets from pairs of electrofused cells, they entered the oscillation cycle, providing a sequence of at least four consecutive colloidosmotic-driven rupture events. Different gradations of colloidosmotic pressure loads between 3230 Pa and 8640 Pa were established with various buffer types. The independence of buffer type and geometrical and mechanical observations has been verified independently for both parts of the oscillation sequence. With decreasing colloidosmotic inducement, caused by repetitive oscillation cycles, an increasing susceptibility of the cell membrane against membrane rupture was measurable. Since side-effects had been eliminated, it could be concluded that the cell membrane resistance against repetitive mechanical ruptures decreases.     

Serum pregnancy-specific beta1-glycoprotein before embryo transfer is related to endometrial thickness and to outcome prognosis in women undergoing in-vitro fertilization treatment

We have previously observed the repeated presence of low but detectable amounts of the trophoblast marker pregnancy-specific beta1-glycoprotein (SP1) in the serum of some women undergoing in-vitro fertilization (IVF) treatment around the time of oocyte retrieval. The occurrence of these signals seemed to be restricted to a defined group of patients which also showed a lower pregnancy success rate in a preliminary study. To test our hypothesis we have analysed 173 consecutive cycles leading to an embryo transfer. Fifty-four cycles (31%) had a serum SP1 level of at least 0.1 ng/ml between days embryo transfer -5 and embryo transfer (group A). Five pregnancies were obtained in this group (pregnancy rate = 9.3%), while in group B, defined by the absence of detectable SP1 before embryo transfer (119 cycles), 36 ongoing pregnancies were achieved (30.3%). Ten of the 41 pregnancies were achieved in 33 first-time non-pregnant patients undergoing further attempts during the study period. Again the pregnancy rate was higher in the first-time group B women (9/23 versus 1/10 for group A). Patients tended to remain in their groups A or B, the latter being associated with a better immediate as well as subsequent chance for pregnancy. Group A cycles had a significantly lower endometrial thickness two days before oocyte retrieval than group B (P = 0.0011). We postulate that the presence of an unknown, maternal and progesterone- or follicle stimulating hormone-independent factor in some patients could stimulate tonic ectopic SP1 synthesis and at the same time negatively influence endometrial development.      

Norepinephrine transporter (NET) promoter and 5'-UTR polymorphisms: association analysis in panic disorder

Several biochemical and pharmacological studies suggest that the catecholaminergic system involving the norepinephrine transporter (NET) is relevant for the pathogenesis of panic disorder. Three single nucleotide polymorphisms in the promoter or untranslated 5' region of the NET gene were investigated by means of RFLP analysis in a sample of 115 German patients with panic disorder and 115 matched controls. Statistical analysis failed to show association with the overall diagnosis of panic disorder. In the subgroup of patients with panic disorder without agoraphobia, however, two polymorphisms were found to be associated with the disease (G/C (rs2397771): p < 0.05; T/C (rs2242446): p < 0.01). While our data do not support a major function of the NET gene in the development of panic disorder, it may play a role in the subgroup of panic disorder without agoraphobia.