Cloning and expression of the amphibian homologue of the human PKD1 gene.

PKD1 is the gene responsible for autosomal dominant polycystic kidney disease (ADPKD) type 1 in humans. The PKD1 gene product is likely to be a calcium channel regulator. In this paper, we describe the isolation and characterization of the Xenopus homologue of the human PKD1 gene. We isolated and cloned genomic fragments corresponding to the amphibian homologue of PKD1 from a BAC library, and after sequencing the clones, we designed primers for the amplification of the transcript and sequenced 10 kb of ORF. The sequence of the putative protein clearly demonstrated that this gene is the homologue of human PKD1. Analysis of the tissue expression patterns of xPKD1 demonstrated a high level of expression in the kidney. A similar analysis in developing embryos and in an in vitro nephrogenic system suggests that xPKD1 is associated with, and probably involved in, the development of the amphibian pronephros.

Identification of various exon combinations of the ews/fli1 translocation: an optimized RT-PCR method for paraffin embedded tissue -- a report by the CWS-study group.

BACKGROUND: Chromosomal translocations t(11;22) (q24;q12) are characteristic of about 80-90 % of Ewing's sarcoma family of tumors [bone and soft tissue Ewing's sarcoma and peripheral neuroectodermal tumors (PNET)]. They generate ews/fli1 rearrangements showing great diversity in breakpoint exon combination. In about 5 % of Ewing's tumors, ews is fused to the erg gene at 21q22. The various chimeric proteins encoded may function as aberrant oncogenic transcription factors. These specific translocations can be used for exact molecular diagnosis in these poorly differentiated small round-cell tumors. Moreover, the prognostic relevance of different translocational variants has been previously suggested. Furthermore, the sensitive molecular detection of minimal metastatic and residual disease and its clinical significance can be evaluated. To address these questions more definitively in the large number of patients registered in multicenter studies, it is often necessary to access archival paraffin-embedded tumor tissue if no fresh or frozen tumor material is available for analysis by RT (reverse transcription)-PCR. Specific problems arise from formalin-fixed and paraffin-embedded tissue due to the degradation of RNA and insufficient extraction efficiency. Therefore, primer distance and product size are limited for successful PCR amplification. This conflicts with the requirement for identification of various possible exon combinations by PCR simultaneously using one single primer pair with larger distance. PATIENTS: We examined paraffin embedded soft part tumor tissue samples from 47 Ewing's tumor patients. Patients were treated according to either CWS (Cooperative Weichteilsarkomstudie, CWS-91 or CWS-96) or Euro-E.W.I.N.G. 99 therapy protocols. METHOD: We established a novel RT-PCR method, using 3 different exon specific sets of PCR primer pairs, selected according to the coding ews and fli1 nucleotide sequences (NCBI database), suitable for RT-PCR identification of variant ews/fli1 fusion transcripts in RNA isolated from formalin-fixed, paraffin-embedded tissue. For use in combination with ews -primer, an erg specific primer was selected to alternatively test for ews/erg fusion transcripts. As positive control for the integrity of isolated mRNA, we used the ubiquitously expressed gapdh transcript for RT-PCR amplification in each sample. RESULTS: In 31 cases (= 66 %) of 47 paraffin samples of Ewing's tumors analysed, gapdh control indicated adequate quality of RNA. In 16 cases no gapdh control fragment was amplifiable, nevertheless in 2 of these 16 samples distinct ews fusion products could be detected. In 23 cases we identified ews fusion transcripts. Thereof in 65 % ews exon 7 being fused to fli1 exon 6 (fusion type I), in 22 % to fli1 exon 5 (fusion type II). In 4 % each ews exon 10 being juxtaposed to fli1 either exon 6 or exon 5, respectively. An ews/erg fusion was detected in 4 % ( ews exon 7 fused to erg exon 6). In 10 samples, a gapdh fragment was amplified, but no ews/fli1 or - erg fusion transcript could be identified. The reference pathological review (I. L., Kiel, Germany) disproved the primary histopathology in 5 cases. CONCLUSIONS: Using our different sets of exon specific primer pairs, it was possible to detect 4 different breakpoints of ews/fli1 fusion transcripts and the ews/erg fusion by RT-PCR in RNA isolates from formalin-fixed, paraffin-embedded Ewing's tumor tissue. This method can be a very useful alternative in clinical situations (to ensure diagnosis and perform minimal metastatic and residual disease investigations) and in order to assess prognostic significance of translocation subtypes when no fresh tumor tissue is available.

Fluorescence urethroscopy following instillation of 5-aminolevulinic acid: a new procedure for detecting clinical and subclinical HPV lesions of the urethra.

OBJECTIVE: To report early clinical experience with intraurethral instillation of 5-aminolevulinic acid (ALA) for the detection of clinical lesions (condyloma acuminata) and subclinical human papillomavirus (HPV) lesions of the urethra, not visible by conventional endoscopy. SUBJECTS AND SETTING: Eighty-four men with clinical diagnosis of condyloma acuminata were examined for urethral HPV lesions at the Department of Urology, Ludwig Maximilian University, Munich, Germany. METHODS: The anogenital areas of the patients were thoroughly examined using a magnifying glass before and after application of 5% acetic acid. Conventional as well as fluorescence urethroscopy were performed 1 h after topical application of 0.1% ALA for 15 min. A sensitive colour charge-coupled device camera for fluorescence video inspection was used with spectral analysis. Biopsies were taken for histological examination and HPV detection by polymerase chain reaction (PCR). RESULTS: Forty-three of 84 men attending our clinic for condyloma acuminata had clinical HPV lesions of the urethra. Condylomas of the proximal urethra were found by conventional endoscopy in eight patients. Fluorescence urethroscopy detected additional subclinical lesions in 13 men. All lesions were HPV infections of the urethra confirmed histologically or by PCR. In nine of these subclinical urethra lesions low-risk HPV types (HPV6, 11, 34) were found. Four lesions were associated with high-risk types (HPV18, 31,52,58). CONCLUSIONS: Fluorescence urethroscopy is a promising diagnostic procedure for detecting subtle clinical and subclinical HPV lesions of the urethra, that are normally not visualized by conventional endoscopy. Generally, urethroscopy is recommended in all cases of externally visible condylomas of the urethra after therapy.

[Urethral condylomas. A therapeutic challenge]. / Harnröhrenkondylome. Eine therapeutische Herausforderung.

BACKGROUND AND OBJECTIVE: Very diverse treatment recommendations exist in the literature on HPV lesions of the urethra. There are no treatment guidelines from the specialist societies. Both these factors have led to a very wide spectrum of heterogeneous treatment strategies in hospitals and medical practices of various specialties. Primary and secondary treatment of urethral condylomata by practitioners as well as a specialized HPV center was evaluated. PATIENTS/METHODS: One hundred and five patients with condylomata of the urethra were studied. Most had been previously treated, often several times, by a variety of specialists. We treated all regardless of prior treatment status with laser therapy. RESULTS: A high percentage of patients treated with different methods in medical practices but also at our high-technology center sometimes showed serious treatment complications and numerous recurrences. Most established methods of treatment for condylomata on the external genitalia are not necessarily applicable to the urethra. CONCLUSIONS: About 20% of urethral condylomata can only be reached by endoscopy. Co-existing urethral malformations as well as complications of therapy are reasons for early cooperation with the urologist or HPV center.

Cloning and characterization of genes from Agrobacterium sp. IP I-671 involved in hydantoin degradation.

Cloning and sequencing of a 7.1 kb DNA fragment from Agrobacterium sp IP I-671 revealed seven open reading frames (ORFs) encoding D-hydantoinase, D-carbamoylase and putative hydantoin racemase, D-amino acid oxidase and NAD(P)H-flavin oxidoreductase. Two incomplete ORFs flanking the hydantoin utilization genes showed similarities to genes involved in transposition. Expression of the D-hydantoinase and D-carbamoylase gene in Escherichia coli gave mainly inactive protein concentrated in inclusion bodies, whereas homologous expression on an RSF1010 derivative increased hydantoinase and D-carbamoylase activity 2.5-fold and 10-fold, respectively, in this strain. Inactivation of the D-carbamoylase gene in Agrobacterium sp IP I-671 led to a complete loss of detectable carbamoylase activity whereas the low hydantoinase activity remaining after inactivation of the D-hydantoinase gene indicated the presence of a second hydantoinase-encoding gene. Two plasmids of 80 kb and 190 kb in size were identified by pulsed-field gel electrophoresis and the cloned hydantoin utilization genes were found to be localized on the 190 kb plasmid.

Quantitative model studies on the formation of aroma-active aldehydes and acids by strecker-type reactions.

Application of aroma extract dilution analysis on the volatiles formed by reacting glucose and L-phenylalanine (30 min, 100 degrees C) revealed the Strecker aldehyde, phenylacetaldehyde (PA), and, in addition, phenylacetic acid (PAA) as the two key odorants among the volatiles formed. Quantitative measurements on alpha-dicarbonyl formation revealed that the 3-deoxyosone and glyoxal were formed as the first prominent sugar degradation products, whereas 2-oxopropanal became predominant after approximately 4 h at 100 degrees C. Among the four alpha-dicarbonyls analyzed, 2-oxopropanal proved to be the most effective in generating PA as well as PAA from phenylalanine, but the reaction parameters significantly influenced the ratio of both odorants; for example, at pH 3.0 the ratio of PA to PAA was 3:1, whereas at pH 9.0 the ratio was 1:5. Furthermore, in the presence of oxygen and copper ions the formation of the acid was further increased. 3-Deoxyosone and glucosone were found to be effective precursors of phenylacetaldehyde, but neither was very effective in acid generation. On the basis of the results, a new oxygen-dependent formation pathway of the Strecker reaction is proposed.

Mechanisms for activation of aortic baroreceptor C-fibres in rabbits and rats.

In an earlier study, we examined the pressure-response characteristics of rat aortic baroreceptors with C-fibre (non-medullated) afferents. Compared with aortic baroreceptor fibres with A-fibre (medullated) afferents, the C-fibres were activated at higher pressures and discharged more irregularly when stimulated with a steady level of pressure. Here we examine the relationship between discharge and the aortic diameter in these two types of afferents in rats and rabbits. An in vitro aortic arch/aortic nerve preparation was used to record single-fibre activity simultaneously with aortic arch pressure and diameter. Diameter was measured using a highly sensitive non-contact photoelectric device. Baroreceptor discharge was characterized by stimulating the nerve endings with either slow pressure ramps from subthreshold to 200-250 mmHg, at a rate of rise of 2 mmHg s-1, or pressure steps from subthreshold to suprathreshold levels, at amplitudes of 110-180 mmHg. In response to these inputs, C-fibres in rabbits (conduction velocities= 0.8-2.2 m s-1) behaved much like those in rats. The C-fibres had significantly higher pressure thresholds (95 +/- 3 mmHg vs. 53 +/- 2 mmHg; mean +/- SEM), lower threshold frequencies (2.4 +/- 0.5 vs. 27.7 +/- 1.8 spikes s-1), lower maximum discharge frequencies (22.7 +/- 2.3 vs. 65 +/- 5.8 spikes s-1) and more irregular discharge in response to a pressure step when compared with A-fibres (conduction velocities of 8-16 m s-1). When plotted against diameter, C-fibre ramp-evoked discharge increased gradually at first, and then rose steeply at increasingly higher ramp pressures where aortic diameter became relatively constant. In contrast, A-fibre discharge was linearly related to diameter over a wide range of pressure. These results suggest two interpretations: (1) The relation between stretch and C-fibre discharge is highly non-linear, with a marked increase in sensitivity at large diameters. (2) C-fibres are stimulated by changes in intramural stress rather than stretch.

Vasopressin acts in the area postrema to attenuate the exercise pressor reflex in anesthetized cats.

Circulating arginine vasopressin (AVP) can enhance baroreflex function via its action in the area postrema (AP). We tested the hypothesis that AVP acts in the AP to enhance baroreflex function during static contraction and, in turn, attenuates the exercise pressor reflex. Thus mean arterial blood pressure (n = 9) and heart rate (HR) (n = 9) during 30 s of electrically stimulated hindlimb contraction were compared before and after bilateral microinjections of 200 nl of the AVP V1-receptor antagonist d(CH2)5Tyr(Me)-AVP (V1x) (1 ng/nl) into the AP of the anesthetized cat. This protocol was repeated in three other cats in which sinoaortic denervation (SAD) was performed before any intervention. Injection of V1x into the AP had no effect on baseline blood pressure or HR. However, pressor and HR responses to static contraction were augmented by 44 +/- 10 and 29 +/- 9%, respectively. Static contraction also increased plasma AVP from 15.9 +/- 2.0 to 25.5 +/- 3.4 pg/ml. In the SAD cats, microinjection of V1x had no effect on contraction-induced increases in blood pressure or HR. These results suggest that baroreflex opposition of the reflex cardiovascular response to static contraction is enhanced by the action of AVP in the AP.

[Do employees in the rubber industry have an increased risk of laryngeal cancer?]. / Haben Arbeitnehmer in der Gummiindustrie ein erhöhtes Kehlkopfkrebsrisiko?

Blue collar workers in the rubber industry are exposed to a number of toxic and potentially carcinogenic substances. In the last years an increased incidence of laryngeal cancer has been found in this group of workers. Besides naphthylamine, asbestos, vulcanization fumes and especially nitrosamines have been considered as possible causative agents. The present paper reviews the most relevant epidemiological studies on this topic published within the last 12 years and includes 17 cohort studies and 5 cases control studies. Only some of these papers indicate an increased risk for head and neck cancer due to employment in the rubber industry. Further in most studies the reported standard mortality ratios or relative risk ratios were not increased significantly. In nearly all of these studies an adjustment was not made for alcohol and tobacco consumption to compromise findings.

Endothelium-mediated and direct actions of acetylcholine on rabbit aortic baroreceptors.

Effects of exogenous acetylcholine on single-unit aortic baroreceptors were studied using a rabbit in vitro aortic arch/aortic nerve preparation. The arch was perfused with Krebs-Henseleit solution at constant pressure while simultaneously recording arch diameter and baroreceptor discharge frequency. Administration of acetylcholine over a wide range of concentrations (10(-9) to 10(-4) mol/L) evoked multiple dose-dependent changes in baroreceptor activity. "Low" concentrations (< 10(-6) mol/L) consistently dilated arch and increased baroreceptor discharge (n = 11). These responses were prevented by prerelaxing smooth muscle with sodium nitroprusside (10(-7) mol/L, n = 6) and were augmented by precontracting smooth muscle with norepinephrine (0.5 x 10(-7) mol/L, n = 11). Thus, the baroreceptor responses were dependent quantitatively on the level of preexisting vasoactive tone. The responses also were antagonized by atropine (10(-7) mol/L, n = 6), which inhibits release of endothelium-derived relaxing factor (EDRF), and by N-monomethyl-L-arginine (10(-5) mol/L, n = 6), a specific blocker of nitric oxide formation (primary relaxing factor responsible for acetylcholine vasorelaxation). Hexamethonium was ineffective (n = 6). These results indicate that "low-dose" responses to acetylcholine were mediated solely by release of EDRF. In contrast, "high" concentrations of acetylcholine (> 10(-6) mol/L) constricted arch and reduced baroreceptor discharge in most units (66%). These responses were blocked by atropine, but not by hexamethonium, and were attributed to direct contraction of the smooth muscle. In the remaining baroreceptors (33%), discharge increased irrespective of changes in diameter or preexisting vasoactive tone, but not in the presence of hexamethonium. Therefore, some baroreceptors were stimulated chemically by acetylcholine (or an intermediary substance), probably through activation of nicotinic receptors on the sensory endings. The effects of acetylcholine on the baroreceptor pressure-frequency curve also were examined by injecting slow pressure ramps before and during acetylcholine treatment. Low concentrations that relaxed smooth muscle shifted the curve to lower pressures; high concentrations that contracted smooth muscle shifted the curve to higher pressures. Last, when acetylcholine was given with the diameter rather than the pressure held constant, the baroreceptor reciprocal responses to smooth muscle relaxation and contraction were directionally reversed but remained consistent with the changes in wall tension.(ABSTRACT TRUNCATED AT 400 WORDS)

Flow and thermal responses of aortic baroreceptors.

1. The aims of this study were 1) to determine whether the impulse activity in rabbit aortic baroreceptors (BRs) was influenced by changes in nonpulsatile flow through the aortic lumen and 2) to examine the BR and aortic arch responses to changes in temperature. 2. An in vitro aortic arch-aortic nerve preparation was used to record suprathreshold steady-state discharge in a total of 29 single-unit BRs from 12 New Zealand white rabbits. Changes in BR frequency were measured relative to control and were recorded simultaneously with aortic arch pressure, flow, temperature, diameter, and calculated wall shear stress (Sw). 3. With pressure held constant, stair-step increases in flow (3-18 ml/min) constricted the arch and evoked two types of BR responses: activation in most units (15 of 17 BRs tested) and inhibition in 2 units. The activation response appeared closely related to the changes in flow and Sw, but also appeared related to uncontrolled changes in perfusate temperature. 4. When the effects of temperature were examined more closely with pressure and flow held constant, controlled step increases in temperature (between 32 and 42 degrees C) constricted the arch and again evoked two BR responses: activation in 11 of 14 BRs tested and inhibition in 3 units. The Q10 for the activation response was 1.55 +/- 0.08 (mean +/- SE), which was not significantly different from the Q10 for activation when temperature varied with flow (1.65 +/- 0.1, P < 0.05). Thus the effect of temperature on most BRs was directionally and quantitatively similar in the presence and absence of changes in flow. 5. Last, when flow was examined over a wide range (15-515 ml/min) with temperature and pressure held constant, stair-step increases in flow failed to produce any change in BR frequency in each of 15 fibers tested (10 arches). The lack of response was not due to a functionally damaged preparation because the usual BR and aortic arch responses to pressure and to drug-evoked vasoconstriction (norepinephrine) and endothelial-mediated vasodilation (acetylcholine) were intact. 6. These results demonstrate that aortic BRs in rabbits are not sensitive to flow and thus are not likely influenced by fluctuations in cardiac output apart from associated changes in pressure. The aortic BRs are affected directly by variations in temperature and in some cases indirectly by temperature-related vasoconstriction. The effects of temperature may have important implications for neural control of the circulation when core temperature varies because of physiological and environmental stress.

Discharge characteristics and rapid resetting of autoactive aortic baroreceptors in rats.

1. An in vitro aortic arch-aortic nerve preparation was used to characterize the pressure-discharge properties of aortic 'autoactive' baroreceptors (aBRs), a functionally unique group of baroreceptors that discharge continuously below pressure threshold (Pth). These units contrast to more familiar 'quiescent' BRs (qBRs) that are silent below Pth. This study also examined whether aBRs rapidly reset to sustained changes in mean arterial pressure (MAP), and whether they respond to local vasoconstriction, as found in qBRs. 2. Pressure-discharge curves were constructed using slow pressure ramps (2 mmHg s-1) in a total of fifty-four aBRs and sixty-four qBRs from fifty-three Wistar-Kyoto rats. Rapid resetting was tested by comparing the curves before and 15 min after adjusting MAP to selected levels between 40 and 180 mmHg. Response curves were also compared before and after constricting the arch with 10(-8) M angiotensin II. 3. Compared to qBRs, aBRs had significantly lower Pth values (83 +/- 2 versus 91 +/- 2 mmHg, mean +/- S.E.M., P < 0.05) but similar threshold frequencies (13 +/- 1 versus 16 +/- 2 Hz), higher saturation pressures (138 +/- 4 versus 123 +/- 2 mmHg) but similar saturation frequencies (55 +/- 3 versus 55 +/- 3 Hz), and lower suprathreshold sensitivities (slope of linear region: 1.1 +/- 0.1 versus 1.4 +/- 0.1 Hz mmHg-1) but wider operating ranges (57 +/- 4 versus 35 +/- 3 mmHg). 4. The aBRs rapidly reset to changes in MAP (n = 16), and the extent of resetting (delta Pth/delta MAP = 0.26) was similar to that in qBRs (0.23). 5. Vasoconstriction had no effect on aBR subthreshold discharge (n = 5), but inhibited suprathreshold responses to pressure much like that in qBRs. 6. These results suggest that aortic aBRs may extend the range of the baroreflex, but probably do not improve its sensitivity to transient fluctuations in pressure or its ability to correct changes in mean pressure over extended periods. 7. Subthreshold discharge in aBRs appears to be an intrinsic property of these units, which was not affected by resetting or changes in vascular tone. At suprathreshold pressures, contraction of local smooth muscle modulates the aBRs and qBRs in a similar fashion by mechanically unloading the sensory endings.

Bradykinin increases myocardial contractility: relation to the Gregg phenomenon.

Bradykinin (BK) is reportedly produced in the heart during ischemia. Because BK has been shown to activate cardiac afferent nerves thought to be nocioceptors, we tested whether BK might alter myocardial shortening, which potentially could contribute to afferent nerve stimulation. In open-chest dogs, BK (1-10 micrograms) was injected into the left anterior descending (LAD) coronary artery while wall motion in the LAD and control circumflex regions was monitored. Wall motion was measured with midwall segment gauges (sonomicrometer crystals) placed in the hoop direction. Blood pressure, heart rate, left ventricular pressure, first derivative of left ventricular pressure, and LAD coronary flow also were monitored. At 15-20 s after injection, which was before circulation of the peptide caused blood pressure to change, BK decreased maximum end-diastolic and minimum end-systolic segment lengths and increased maximum shortening fraction in LAD region. No change was observed in circumflex region. The response was not eliminated by bilateral vagotomy or subsequent stellate ganglionectomy, indicating that it was not neurally mediated. The response closely paralleled changes in coronary flow, was mimicked by intracoronary injection of adenosine, and was reduced or absent if flow was already elevated by previous injection of adenosine. When BK eventually reached the systemic circulation, the resultant hypotension further reduced shortening in LAD region, with directionally similar effect in circumflex region. These results suggest that BK can increase regional shortening by enhancing coronary flow (Gregg phenomenon) as well as by altering global ventricular function through systemic hypotension. Such changes in shortening may contribute to stimulation of cardiac afferent nerves.

Contrasting effects of vasopressin and angiotensin II on rabbit aortic baroreceptors.

Arginine vasopressin (AVP) reportedly enhances, whereas angiotensin II (ANG II) attenuates, baroreflex control of the circulation. Here we examine whether these responses can be attributed, in part, to local actions on myelinated baroreceptor (BR) afferents, either directly or via changes in vascular tone. An in vitro rabbit aortic arch/aortic nerve preparation was used to study regularly discharging presumably myelinated BRs under controlled static and pulsatile pressures. At constant suprathreshold pressures, AVP (10(-13) M to 10(-6) M) had no effect on arch diameter or BR frequency, whereas equimolar concentrations of ANG II evoked dose-dependent vasoconstriction and associated BR inhibition. Differences were not caused by limited diffusion to BR endings lying outside the media, since similar results were obtained with either luminal or adventitial applications. AVP also had no effect on diameter or discharge in arches preconstricted with norepinephrine, whereas acetylcholine (ACh) relaxed the arch and thereby increased BR activity. These results eliminate possible AVP-induced endothelium-dependent vasodilation or potentiation of adrenergic vasoconstriction that would not be evident in isolated arches lacking tone. Finally, AVP did not sensitize BRs to changes in pressure, since ramp-evoked pressure-discharge curves remained constant and pulsatile discharge in response to sine-wave pressure inputs was unaltered. ANG II, however, shifted pressure-discharge curves to higher pressures and, with pulsatile inputs at constant mean pressure, reduced peak and average discharge firing rates. In conclusion, AVP has no apparent peripheral effect on aortic myelinated BRs in rabbits that could contribute to amplification of the baroreflex when AVP levels are elevated. In contrast, ANG II can inhibit BR firing as a consequence of local vasoconstriction, which may contribute to attenuation of the reflex when ANG II levels are elevated.

Sympathetic modulation of rabbit aortic baroreceptors in vitro.

Previous studies indicate that sympathetic efferent nerves to the carotid sinus can modulate carotid sinus baroreceptor (BR) activity. There are, however, no studies that demonstrate this in the aortic arch. Since application of exogenous norepinephrine to the aortic arch can alter BR activity, we examined whether electrically stimulating the efferent innervation would likewise be effective. We used an in vitro preparation from anesthetized rabbits. This consisted of the aortic arch and sections of the aortic afferent and sympathetic efferent nerves. The aorta was perfused at a constant pulseless pressure set 10-15 mmHg above BR pressure threshold, and aortic diameter was measured with a photoelectric device. We electrically stimulated the efferent innervation with 1-ms duration constant-voltage pulses, while simultaneously recording aortic pressure, diameter, and BR discharge. In 12 of 18 BRs, discharge decreased with vasoconstriction and subsequently recovered with vasorelaxation. This BR inhibition was blocked when constriction was prevented with the alpha-adrenergic antagonist prazosin (10(-6) M). In the remaining six BRs, discharge increased in five units and remained constant in one unit; however, the excitation occurred only during and a few seconds after the stimulus period. Discharge then fell below control while aortic constriction persisted and subsequently increased back to control with aortic relaxation. In this second group of fibers, treatment with the smooth muscle relaxant sodium nitroprusside (10(-6) M) prevented BR inhibition but not excitation. Lastly, BR responses were eliminated if the efferent nerve was crushed but not cut, indicating that the sensory endings were not activated directly by electrotonic current spread.(ABSTRACT TRUNCATED AT 250 WORDS)

Dual effects of norepinephrine and mechanisms of baroreceptor stimulation.

The aim of this study was to determine the mechanism of action of norepinephrine (NE) on arterial baroreceptors (BRs), with the focus on regularly discharging, presumably myelinated fibers. With the use of an in vitro aortic arch/aortic nerve preparation from rats, BR single-fiber discharge was recorded simultaneously with aortic pressure and diameter. At constant suprathreshold pressure, NE had two dose-dependent effects. Inhibition was produced at low concentrations (10(-10)-10(-7) M), whereas excitation was produced at high concentrations (10(-6)-10(-5) M). Inhibition was attributed to BR unloading since the response was consistent with the fall in diameter, was mimicked by angiotensin II (10(-10)-10(-6) M), and was prevented by pretreatment with the smooth muscle relaxant sodium nitroprusside (10(-6) M) or the selective alpha 1-adrenergic antagonist, prazosin (10(-6) M). Excitation was attributed to direct activation of the BR endings since this response was independent of changes in diameter, was not mimicked by angiotensin II, and was not prevented by sodium nitroprusside but was blocked by prazosin. These results indicate that NE has two modes of action, one mediated by contraction of local vascular smooth muscle and the other due to direct excitation of the nerve endings. It was also found that BR discharge at given diameters decreased more when pressure was lowered (smooth muscle passive) than when the aorta constricted (smooth muscle active). Furthermore, if diameter was held constant during smooth muscle contraction, discharge increased, as opposed to decreasing at constant pressure. These later results suggest that BR responses to vasoactive agents reflect not only changes in wall dimension but perhaps changes in wall tension and/or the coupling relation between BR and smooth muscle structures.

[Growth behavior of microvein and artery grafts]. / Wachstumsverhalten von Mikrovenen- und -arterieninterponaten.

In an experimental study with young rats the authors were able to prove that arterial and venous grafts show almost normal growth. With respect to patency rate, growth and integrity of the vessel wall the results with arterial grafts were more satisfactory than those with venous grafts. Examination of thirty-four patients who had undergone replantation or transplantation in infancy or childhood, showed that after digital replantation the extremities grew almost normally and that there was no indication of lag in vessel growth. Three times a slight change in growth after major limb replantations was found, in one case there was a slight increase in growth and in another case the growth was considerably diminished. In the latter there had been total destruction of the epiphyseal line. One large replantation was examined by angiography and normal development of the venous grafts was found.

Photoelectric caliper for noncontact measurement of vascular dynamic strain in vitro.

A photoelectric device is described for in vitro semicontinuous contact-free measurement of vascular dynamic strain. The vessel's optical image is projected onto a pair of linear photodiode arrays by use of a projection lens and a set of mirrors. Each array's video signal indicates a focused image of the vessel edge as a steep change of the light intensity. Edge location is defined as the midpoint of the intensity drop across the edge. Knowing the interdiode distance (16 micron), the location of the edge can be determined by counting the number of diodes up to the midpoint. Given both edge locations and the distance between arrays, diameter can be electronically computed. The output voltage is calibrated with a metric grid in place of the vessel and is linearly related to diameter. Resolution varies with magnification and may be on the order of 1 micron, depending on the strain amplitude and the initial unstressed vessel caliber. Frequency response is determined by the array scanning rate and is uniform well beyond the range of physiological considerations.

Role of vessel wall in acute resetting of aortic baroreceptors.

Previously we found that baroreceptor (BR) pressure-frequency (PF) curves rapidly (5 min) reset to changes in mean arterial pressure (MAP) exclusive of sympathetic efferents or circulating hormones. Since BRs are mechanically coupled to vessel wall structures, resetting may be due to changes in the wall. This was examined using an in vitro rat aortic arch-aortic nerve preparation and a photoelectric device to measure arch diameter. Pressure-diameter (PD) curves were constructed at selected MAPs following the resetting protocol used previously [Am. J. Physiol. 244 (Heart Circ. Physiol. 13): H672-H680, 1983]. Overall there was no consistent relationship between the PD curves and MAP, which was in sharp contrast to BR PF resetting. To determine if smooth muscle tone could affect aortic or BR function, the arch was constricted or relaxed with norepinephrine (NE) or sodium nitroprusside (NP), respectively. BR PF and aortic PD curves were constructed before and after drug treatment. NE reduced and NP increased discharge at given pressures. Diameter-frequency (DF) plots were not altered by either drug. PD and PF curves at constant MAP were stable after the initial responses to NP relaxation were completed. Subsequent MAP elevations in NP reset BRs to higher pressures, whereas PD curves shifted to lower pressures. Hence, DF plots shifted to higher diameters. These results show that neither smooth muscle activity nor mechanical changes in the whole wall can account for BR rapid resetting. The process probably occurs in the receptors.

Rapid resetting of aortic baroreceptors in vitro.

Pressure-response characteristics of arterial baroreceptors (BR) were shown recently to be reset following a 15- to 20-min change in mean arterial pressure (MAP); the curves shifted in the direction of the MAP change. To characterize this rapid BR resetting process more precisely than in vitro studies allow, we utilized an in vitro aortic arch-aortic nerve preparation from Wistar-Kyoto rats. Pressure ramps were used to determine the discharge response curves of single BRs following exposure to precisely controlled conditioning pressures. Rapid resetting occurred in all BRs and followed an exponential time course with a 3- to 5-min time constant. The reset curves were stable for 1 h and were completely reversible. The curves were shifted along the pressure axis in a parallel manner, i.e., pressure threshold (Pth) changed but slope and mean asymptotic discharge were unaltered. In experiments lasting as long as 7 h in which more than two MAP steps were possible, in vitro rapid resetting was a very consistent and reproducible process. Quantitatively, the extent of resetting (delta Pth/delta MAP) averaged 0.33 over an MAP range of 40-160 mmHg. In vitro resetting therefore appears very similar to that observed in vivo, suggesting that the conditioning pressure is the primary, perhaps the sole, determinant of resetting. Resetting occurred at subthreshold MAPs, demonstrating action potentials are not a prerequisite. Efferent neural or hormonal influences are also not required.