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Biomedical subjects

S Rohr

Publications and source records attributed to S Rohr.

At least 37 records · Page 2Linked to original sources
PubMed2000

Nonlinear changes of transmembrane potential caused by defibrillation shocks in strands of cultured myocytes.

Organization of cardiac tissue into cell strands and layers has been implicated in changes of transmembrane potential (DeltaV(m)) during defibrillation. To determine the shock-induced DeltaV(m) in such structures, cell strands of variable width [strand width (SW) = 0.15-2 mm] were grown in culture. Uniform-field shocks with variable strength [shock strength (SS) = 2-50 V/cm] were applied across strands during the action potential (AP) plateau, and DeltaV(m) were measured optically. Three different types of DeltaV(m) were observed. Small DeltaV(m) [<40%AP amplitude (APA)] were linearly dependent on SS and SW and were symmetrically distributed about a strand centerline with maximal positive and negative DeltaV(m) on opposite strand sides being equal. Intermediate DeltaV(m) (<200%APA) were strongly asymmetric with negative DeltaV(m) > positive DeltaV(m) because of a negative time-dependent shift of V(m) at the depolarized side of the strands. For large DeltaV(m) (>200%APA), a second time-dependent shift of V(m) to more positive levels was observed in the hyperpolarized portions of strands, causing reduction of the DeltaV(m) asymmetry. We conclude that during application of shocks to cell strands during the AP plateau, passive changes of V(m) were followed by two voltage- and time-dependent shifts of V(m), possibly reflecting changes of ionic currents or membrane electroporation.

Animals↗
PubMed1999

Management of common bile duct stones in a single operation combining laparoscopic cholecystectomy and perioperative endoscopic sphincterotomy.

BACKGROUND: Laparoscopic cholecystectomy (LC) has become the reference treatment for biliary lithiasis, but the management strategy for common bile duct stones (CBDS) remains a subject of controversy in the absence of an established consensus. While conventional surgery remains the reference treatment for CBDS, minimally invasive techniques are becoming more and more popular. These methods consist of the extraction of the common bile duct stones either exclusively by laparoscopy or by sequential treatment with endoscopic sphincterotomy (ES) followed by LC. The aim of this study was to evaluate the treatment of CBDS in a one-stage operation by laparoscopic cholecystectomy (LC) and perioperative endoscopic sphincterotomy. PATIENTS AND METHODS: Between January 1994 and March 1998, 44 patients, 20 male and 24 female, (sex ratio 1.2) with a median age of 57 years (range 28-84 years) were treated for suspected or confirmed CBDS. The CBDS were uncomplicated in 39 cases (88%) and associated with a complication in 5 cases (12%), namely, cholangitis (2 cases) or acute pancreatitis (3 cases). The perioperative ES was performed immediately after the LC during the same operative time, with perioperative cholangiography being systematically performed (1 failure). In 6 cases, a transcystic drain was left in place (to ensure complete evacuation of the CBDS postoperatively) when there were more than three stones and/or when they were larger than 6 mm. The patient was positioned in the left lateral position in order to perform the ES. RESULTS: Mean operative time for LC was 60 min, range 40-90 min. The general anesthesia was prolonged by 40 min in order to perform an ES (range 30-60 min). The perioperative ES was unsuccessful in one case (2%), due to the impossibility of catheterizing the papilla, the preoperative MR cholangiogram being normal. Immediate clearance of the CBD was achieved in 95% of the cases (42 p). In 2 cases, residual stone was found in the sixth day after cholangiography and was spontaneously evacuated as shown by 21st-day control. There was no mortality or postoperative complications. The duration of the postoperative hospitalization was 4.6 days (range 3-6). CONCLUSIONS: We believe that LC combined with perioperative ES is a quick, reliable, and safe technique for the treatment of CBDS during a single operative procedure, although this approach is limited by the proximity and availability of an endoscopic team.

Adult↗
PubMed1999

Optical recording of impulse propagation in designer cultures. Cardiac tissue architectures inducing ultra-slow conduction.

It has long been established that slow conduction constitutes one of the key mechanisms in the generation of cardiac arrhythmias. Also, it has been recognized that alterations in the cellular architecture of cardiac tissue can contribute to slow conduction. Based on the recent development of an experimental system permitting both the design of geometrically defined cardiac tissue structures in culture and the measurement of impulse propagation at the cellular level, we investigated the extent of conduction slowing along a tissue structure consisting of a cell strand releasing multiple side branches. This structure, which can functionally be looked upon as a series of interconnected current-to-load mismatches, gave rise to ultra-slow conduction (1-2 cm/s) that displayed a high margin of safety due to a "pull" and "push" effect exerted by the side branches on electrotonic current flow along the main strand. Under physiological conditions, such branching structures might contribute to slow conduction in the AV-node and, under pathophysiological conditions, to the precipitation of reentrant arrhythmias within minuscule tissue regions in a structurally remodeled myocardium. The results illustrate that the combination of patterned growth techniques and optical recording of transmembrane voltage are ideally suited to characterize systematically the relationship between tissue structure and impulse conduction.

Action Potentials↗
PubMed1999

Management of common bile duct stones by laparoscopic cholecystectomy and endoscopic sphincterotomy: pre-, per- or postoperative sphincterotomy?

BACKGROUND/AIMS: The aim of this study was to evaluate the treatment of common bile duct stones (CBDS) by endoscopic sphincterotomy (ES) and laparoscopic cholecystectomy (LC), ES being performed either pre-, per- or postoperatively. METHODS: Between January 1990 and June 1997, 386 patients with a median age of 60 (range 18-92) years were treated for suspected or confirmed CBDS. The CBDS were uncomplicated in 264 cases (70%) but associated with a complication in 122 cases (30%), namely, cholangitis (69 cases) or acute pancreatitis (53 cases). ES combined with LC was carried out in 233 cases (60%): ES was preoperative (sequential treatment in two stages) in 197 cases (51%); peroperative in 30 cases (7%), or postoperative in 6 cases (2%). Laparoscopic extraction was performed in 58 cases (15%) and conventional surgery in 82 cases (21%). RESULTS: With respect to sequential treatment, endoscopic retrograde cholangiography showed the presence of CBDS in 117 cases (60%) and preoperative ES allowed the release of the CBDS in 82% of these cases. The complication rate of sequential treatment was 8% (15 cases) after ES and 7% (13 cases) after LC, with 1 death (0.5%). A peroperative ES performed after LC enabled evacuation of the CBDS in 28 cases (93%) without any complications or mortality. Postoperative ES was successful in 100% of cases with residual lithiasis in 16% (1 case) and a complication rate of 16% (1 case). CONCLUSION: Along with conventional surgery and laparoscopic extraction, ES combined with LC represents an effective alternative in the management of CBDS. Since it can be performed peroperatively, it allows a one-stage, minimally invasive treatment of most uncomplicated CBDS.

Adult↗
PubMed1999

[Wound healing and hyperbaric oxygen. Experimental study of the angiogenesis phase in the rat].

Hyperbaric oxygen therapy (HBO) is widely reported as highly favourable to wound healing. The experimental models generally used to investigate its effects are difficult to set up and reliable quantification of the results obtained is rarely achieved. The underlying pathophysiological mechanisms occurring during HBO remain poorly understood and its mode of application for clinical practice is difficult to standardise. Our study was carried out to assess the contributions of oxygen and hyperbaric pressure on the initial steps of wound healing. It was based on qualitative and quantitative analysis of the development of the angiogenic process in a granulation tissue bud, using animals implanted with fibrin chambers, an in vivo model initially described by Dvorak in guinea pigs. In our study, rats were further submitted to HBO (OHB group) or hyperbaric air (Air-HB group) treatments. The control group (Control group) consisted of rats maintained in the treatment tank under normal atmospheric conditions. Nine specific parameters were determined and analysed during the course of the angiogenic process by classical histological techniques. The vascular density and the height of the bud were particularly examined at day 7, 14 and 21 following chamber implantation. At D7 the neovessel density and bud height were significantly higher in OHB group than in Air-HB or Control groups, thus confirming the beneficial effects of this treatment on the initial steps of wound healing. Nevertheless, the results reported herein also suggest a possible inhibitory effect of hyperbaric therapy alone on this very early process, although the pathophysiological significance of this effect on wound healing remains to be determined.

Animals↗
PubMed1998

Slow conduction in cardiac tissue, I: effects of a reduction of excitability versus a reduction of electrical coupling on microconduction.

It was the aim of this study to characterize the spread of activation at the cellular level in cardiac tissue during conduction slowing, a key element of reentrant arrhythmias; therefore, activation patterns were assessed at high spatiotemporal resolution in narrow (70 to 80 microm) and wide (230 to 270 microm) linear strands of cultured neonatal rat ventricular myocytes, using multiple site optical recording of transmembrane voltage. Slow conduction was induced by graded elevation of [K+]o, by applying tetrodotoxin, or by exposing the preparations to the gap junctional uncouplers palmitoleic acid or 1-octanol. The main findings of the study are 4-fold: (1) gap junctional uncoupling reduced conduction velocity (range, 37 to 47 cm/s under control conditions) to a substantially larger extent before block (</=1 cm/s; ultra-slow conduction) than did a reduction of excitability (range, approximately 10 to 15 cm/s); (2) activation wavefronts during uncoupling meandered within the boundaries of the preparations, resulting in a pronounced additional slowing of conduction in wide cell strands; (3) at the cellular level, propagation during uncoupling-induced ultra-slow conduction was sustained by sequentially activated tissue patches, each of which consisted of a few cells being activated simultaneously; and (4) depending on the uncoupler used, maximal action potential upstroke velocities during ultra-slow conduction were either slightly (palmitoleic acid) or highly (1-octanol) depressed. Thus, depolarizing inward currents, the spatial pattern and degree of gap junctional coupling, and geometrical factors all contribute in a concerted manner to conduction slowing, which, at its extreme (0.25 cm/s measured over 1 mm), can reach values low enough to permit, theoretically, reentrant excitation to occur in minuscule areas of cardiac tissue (<<1 mm2).

Action Potentials↗
PubMed1998

Slow conduction in cardiac tissue, II: effects of branching tissue geometry.

In cardiac tissue, functional or structural current-to-load mismatches can induce local slow conduction or conduction block, which are important determinants of reentrant arrhythmias. This study tested whether spatially repetitive mismatches result in a steady-state slowing of conduction. Patterned growth of neonatal rat heart cells in culture was used to design unbranched cell strands or strands releasing branches from either a single point or multiple points at periodic intervals. Electrical activation was followed optically using voltage-sensitive dyes under control conditions and in elevated [K+]o (5.8 and 14.8 mmol/L, respectively; in the latter case, propagation was carried by the L-type Ca2+ current). Preparations with multiple branch points exhibited discontinuous and slow conduction that became slower with increasing branch length and/or decreasing inter-branch distance. Compared with unbranched strands, conduction was maximally slowed by 63% under control conditions (from 44.9+/-3.4 to 16.7+/-1.0 cm/s) and by 93% in elevated [K+]o (from 15.7+/-2.3 to 1.1+/-0.2 cm/s). Local activation delays induced at a single branch point were significantly larger than the delays per branch point in multiple branching structures. Also, selective inactivation of inward currents in the branches induced conduction blocks. These 2 observations pointed to a dual role of the branches in propagation: whereas they acted as current sinks for the approaching activation thus slowing conduction ("pull" effect), they supplied, once excited, depolarizing current supporting downstream activation ("push" effect). This "pull and push" action resulted in a slowing of conduction in which the safety was largely preserved by the "push" effect. Thus, branching microarchitectures might contribute to slow conduction in tissue with discontinuous geometry, such as infarct scars and the atrioventricular node.

Action Potentials↗
PubMed1998

Activation of cardiac tissue by extracellular electrical shocks: formation of 'secondary sources' at intercellular clefts in monolayers of cultured myocytes.

This study investigated the activation of cardiac tissue by "secondary sources," which are localized changes of the transmembrane potential (Vm) during the application of strong extracellular electrical shocks far from the shock electrodes, in cultures of neonatal rat myocytes. Cell monolayers with small intercellular clefts (length, 45 to 270 microm; width, 20 to 70 microm [mean+/-SD, 54+/-13 microm]; n = 46) were produced using a technique of directed cell growth. Changes in Vm relative to the action potential amplitude (deltaVm/APA) were measured using a fluorescent voltage-sensitive dye and a 10 x 10 photodiode array. Shocks with voltage gradients of 4 to 18 V/cm were applied across the clefts during either the action potential (AP) plateau or diastole. During the AP plateau, shocks induced secondary sources in the form of localized hyperpolarizations and depolarizations in the regions immediately adjacent to opposite sides of the clefts. The strength of the secondary sources, defined as the difference of deltaVm/APA across a cleft, increased with increasing cleft length or increasing electrical field gradient. For shocks with a gradient of 8.5 V/cm, the estimated critical cleft length necessary to reach a Vm level corresponding to the diastolic threshold of excitation was 171+/-7 microm. Accordingly, shocks with average strength of 8.2 V/cm applied during diastole produced secondary sources that directly excited cells adjacent to the clefts when the cleft length was 196+/-53 microm (n = 14) and that failed when the cleft length was 84+/-23 microm (n = 9, P<.001). The area of earliest excitation in such cases coincided with the area of maximal depolarization induced during the plateau phase. These data suggest that small inexcitable obstacles may contribute to the Vm changes during the application of strong extracellular electrical shocks in vivo.

Animals↗
PubMed1998

[Results of fundoplication by laparoscopic approach in the treatment of gastroesophageal reflux. Apropos of 224 cases].

STUDY AIM: The aim of this paper is to evaluate prospectively immediate and 2-year results of laparoscopic fundoplicature (LF) for gastroesophageal reflux disease (GERD). PATIENTS AND METHODS: Patients presenting GERD who had been previously submitted to a long-term medical treatment were included in this study. Preoperative workup included upper GI tract endoscopy, esophageal manometry and 24-hour pHmetry. Standard surgical procedure incorporated a Nissen-Rossetti 360 degrees fundoplicature. Short vessels division (Nissen operation) was performed in case of high strength of the wrap and a partial fundoplicature (Toupet 270 degrees) was performed when motility disorders of the esophagus were demonstrated by manometry. Postoperative morbidity and results were evaluated, with a clinical appreciation at 3 and 22 months, and by manometry and pHmetry at 3 months. RESULTS: Two hundred and thirty-five patients were observed, and 224 included in the study (143 men and 92 women). Nissen-Rossetti fundoplication was performed in 169 cases (80%), Nissen in 30 (14%) and Toupet in 13 (6%). In 12 cases (5%). LF was converted to an open Nissen-Rossetti procedure. There was no hospital mortality and complications were noted in three cases (1.5%): pneumonia (n = 2) and gastroplegia (n = 1). With a mean 22-month follow up, among the 103 patients who answered to a questionnaire, the rate of relapse of GERD was 14%, dysphagia was present in 2% and four patients had been reoperated on (one for a slipped Nissen, one for a stenosis of the esogastric junction and two incisional hernias). CONCLUSION: On the basis of this experience, LF for GERD is a safe and efficient operation, with 86% of good results at 2 years.

Adult↗
PubMed1998

Optical recording system based on a fiber optic image conduit: assessment of microscopic activation patterns in cardiac tissue.

Optical recording of transmembrane voltage changes with the use of potentiometric dyes has opened the possibility of determining spatial patterns of electrical activity in excitable tissues. To follow such activation patterns on the cellular/subcellular level in heart cell cultures, a recording system was developed that features both high spatial resolution (4-200 microm) and high temporal resolution (uncertainty in the determination of delays between fast rising signals of +/-1 micros). Central to the system is a fiber optic image conduit consisting of 379 individual optical fibers. At one end the fibers are fused to form an input window that matches the size of the field of view of the microscope. At the other end, the fibers are loose, permitting a selectable subset to be connected to 80 discrete photodetectors. This design allows the sensitive area of the imager to be adapted to regions of interest in a given preparation, thus making optimal use of the limited number of detectors. Furthermore, by using a second fiber optic imager, individual photodetectors can be assigned to different optical ports, thus providing the means for fast and simultaneous dual-emission wavelength measurements. This feature permitted the elimination of motion artifacts arising from the myocytes without the use of contraction-suppressing drugs.

Action Potentials↗
PubMed1998

[Pseudo-acute surgical abdomen and acute leukemia].

The so-called pseudo-acute abdomen has been reported in acute leukemia, both at diagnosis or relapse. The clinical presentation may be misleading and life-threatening, due to the possible infiltration of any abdominal viscera. The authors present a series of eight patients and emphasize the management specificities of such patients and the possibility of long-term remissions, regardless of the severity of the initial presentation.

Abdomen, Acute↗
PubMed1998

[Laparoscopic treatment of gastroesophageal reflux using fundoplication. Midterm results].

UNLABELLED: The aim of this study was to see whether the results of surgical treatment of gastroesophageal reflux disease (GERD) by laparoscopic fundoplication were satisfactory and stable over time. PATIENTS AND METHODS: From July 1992 to September 1996, 161 patients with medical treatment-dependent GERD were operated. 17 patients were excluded from the study (conversion or immediate laparotomy). The group of 144 patients included consisted of 92 men and 52 women with a mean age of 50 (25-77 years). The preoperative work-up included endoscopy, esophageal manometry and 24-hour pH monitoring. The surgical procedures were complete fundoplication without section of the short vessels (Nissen-Rossetti: 122 cases), with section of the shorts vessels (Nissen: 18 cases), or partial fundoplication of 270 degrees (Toupet: 4 cases). The patients were reviewed clinically 3 months after the operation, with repeat manometry and pH monitoring; yearly survey was performed. RESULTS: There was no postoperative mortality. The morbidity consisted of 2 respiratory complications (1.5%) with good recovery. With a follow-up of 3 and 21 months, the dysphagia rate was 24 vs 2% of patients (p < 0.05), the rate of gas bloat syndrome was 18% vs 21% (n.s.), and the GERD recurrence 6% vs 14% (p < 0.05). The mean time to recurrence was 8 months. 2 patients were reoperated: one for incisional hernia and one for slipped-Nissen. CONCLUSION: The results of laparoscopic treatment of GERD with fundoplication procedures at 2 years follow-up showed an 86% cure rate of GERD control and 94% satisfaction rate for the patients who were investigated.

Adult↗
PubMed1997

Paradoxical improvement of impulse conduction in cardiac tissue by partial cellular uncoupling.

Generally, impulse propagation in cardiac tissue is assumed to be impaired by a reduction of intercellular electrical coupling or by the presence of structural discontinuities. Contrary to this notion, the spatially uniform reduction of electrical coupling induced successful conduction in discontinuous cardiac tissue structures exhibiting unidirectional conduction block. This seemingly paradoxical finding can be explained by a nonsymmetric effect of uncoupling on the current source and the current sink in the preparations used. It suggests that partial cellular uncoupling might prevent the initiation of cardiac arrhythmias that are dependent on the presence of unidirectional conduction block.

Action Potentials↗
PubMed1997

Involvement of the calcium inward current in cardiac impulse propagation: induction of unidirectional conduction block by nifedipine and reversal by Bay K 8644.

In general, the fast sodium inward current (INa) is regarded as the main inward current ensuring fast and safe excitation of the normally polarized working myocardium. However, under conditions of locally delayed excitation in the millisecond range, the slow inward current (ICa) might additionally contribute to the success of impulse propagation. This hypothesis was tested in patterned growth cultures of neonatal rat ventricular myocytes, which consisted of narrow cell strands connected to large rectangular cell monolayers, where INa or ICa could be modified in the narrow cell strand adjacent to the expansion by a microsuperfusion system. As assessed during antegrade (strand-->expansion) propagation under control conditions using a system for multiple site optical recording of transmembrane voltage (MSORTV), this cell pattern gave either rise to local activation delays at the expansion ranging from 0.5 to 4 ms (dcontrol), or it induced undirectional conduction blocks (UCBs) in the antegrade direction. Irrespective of the size of dcontrol, suppression of the sodium current with tetrodotoxin confined to the cell strand adjacent to the expansion invariably induced UCB in the antegrade direction. If dcontrol was > 1 ms, UCB could also be elicited by suppression of ICa alone with nifedipine. Conversely, if UCB was present under control conditions, the inclusion of Bay K 8644 in the microsuperfusion established successful bidirectional conduction. These results suggest that ICa can be critically important for the success of impulse propagation across abrupt expansions of excitable tissue even if INa is not concurrently depressed.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1997

[Acute pancreatitis and ectopic pancreas].

We report the case of a 28-year-old woman with a pancreatic heterotopia presenting with a history of acute pancreatitis. Symptoms were epigastric pains. Abdomino-pelvic CT Scan revealed a tumor located in gastro-duodenal area. Exploratory surgery was performed, and the segment containing the mass was resected. Histopathologic examination of the lesion revealed heterotopic pancreatic tissue without malignancy.

Acute Disease↗
PubMed1997

[Value of absorbable clips in laparoscopic cholecystectomy. A randomized prospective study].

Most surgeons use metal clips in laparoscopic cholecystectomy. The aim of this prospective randomized controlled study was to evaluate the efficacy of absorbable clips in elective laparoscopic cholecystectomy. One hundred consecutive patients with symptomatic gallstones without complications were randomized into groups; group T had two metal clips (titan clip ETHICONR), group R (laproclipR Davis and Geck) had one absorbable clip applied on the cystic duct and cystic artery. The patients were followed for one year. There was no difference between the two groups concerning operative time, hospital stay and postoperative complications. The absorbable clips seem to be as effective as metal clips in providing hemostasis in cystic artery and in cystic duct ligation.

Adult↗
PubMed1997

[Outcome of surgical treatment of cancer of the stomach. Report of 330 cases].

The study concerned 330 cases of gastric adenocarcinoma operated from January 1969 to June 1996. Clinical, histological and therapeutic features were analyzed and compared during 3 periods (Group 1: 1969-79, Group 2: 1979-88, Group 3: 1989-96). The aim was to evaluate changes and results occurred in gastric carcinoma. The median age was 65 +/- 11 year (range 25-90), the sex ratio 2. The most common location was in the lower third of the stomach and the cancer was often far advanced (71 percent of stages III and IV). Subtotal gastrectomy was replaced by total gastrectomy and large lymph node dissection was systematically performed in group 3. Curative resection rate increased from 28 to 60 percent between group 1 and group 3. Despite the more radical surgery, post-operative mortality rates decreased respectively 22%, 9%, 8% for the groups 1, 2, 3 (p < 0.01) and global morbidity remained stable while the rate of intra-abdominal infection have changed in group 3 (4.8% vs 2.7% and 2.1% in respectively groups 1 and 2; p = ns). Two year survival rates were 20% for group 1.25% for group 2 and 35% for group 3 (p < 0.01). This results can be considered as encouraging but have to be confirmed at 5 year survival.

Adenocarcinoma↗