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Biomedical subjects

R Koller

Publications and source records attributed to R Koller.

At least 37 records · Page 2Linked to original sources
PubMed1999

Partial myotomy/myectomy of the trapezius muscle with an asleep-awake-asleep anesthetic technique for treatment of cervical dystonia. Technical note.

The authors describe a technique for performing partial sectioning and myectomy of the trapezius muscle in patients with severe cervical dystonia that is unresponsive to conservative treatment. Asleep-awake-asleep anesthesia allows intraoperative control of the sectioning procedure to avoid causing postoperative weakness of arm elevation above the horizontal plane. The procedure has been performed successfully in three patients. In all cases the dystonic posture of the shoulder and local pain were improved postoperatively. There were no new deficits. This technique can be used as an adjunct to other peripheral surgical procedures in patients with marked laterocollis and dystonic elevation and ante-version of the shoulder.

Anesthesia, General↗
PubMed1998

The impact of a muscle target organ on nerve grafts with different lengths--a histomorphological analysis.

The present study was done in order to evaluate the influence of a target muscle on the regenerative processes in long nerve grafts. In 21 rabbits the saphenous nerve was used as a nerve graft and coapted to the cut motor nerve of vastus medialis. The animals were separated into three groups with different graft lengths, namely 3, 5, and 7 cm. In a second stage the distal end of the graft (Graft.dist.) was coapted to the motor branch of rectus femoris. Cross sections of the normal vastus nerve and the Graft.dist. before and 7 months after the connection to rectus femoris were analyzed histomorphometrically. Before coaptation to the target organ mean fiber number in the Graft.dist. of the 3-cm-long grafts was 3380 and decreased to 2413 in the 7-cm-long grafts. Seven months after coaptation the results showed a statistically significant decrease of fibers in the Graft.dist. of group two and three and a distinct decrease of the fibers in group one. Summarizing, in a two-stage nerve grafting procedure the reinnervation of the muscle target organ leads to a down-regulation of fibers in the distal end of short and long nerve grafts.

Animals↗
PubMed1998

Experimental development of an electrically stimulated biological skeletal muscle ventricle for chronic aortic counterpulsation.

OBJECTIVE: The chronic shortage of donor organs for cardiac transplantation and the high costs for mechanical assist devices demand the development of alternative cardiac assist devices for the treatment of severe heart failure. Cardiac assistance by stimulated skeletal muscles is currently investigated as such a possible alternative. The goal of the presented study was to construct a newly designed biological skeletal muscle ventricle and to evaluate its possible hemodynamic efficacy in an acute sheep model. METHODS: A total of 14 adult sheep were used for acute experiments. The entire thoracic aorta including the aortic root was excised from a donor sheep. An aorto-pericardial pouch conduit (APPC) was created by enlarging the aortic circumference in its middle section with two strips of pericardium. This biological conduit was anastomosed in parallel to the descending aorta of a recipient sheep, using the aortic root as an inflow valve to the conduit. Stimulation electrodes were applicated to the thoracodorsal nerve and the latissimus dorsi muscle was detached from the trunk and wrapped around the pouch. ECG-triggered functional electrical stimulation was applied during cardiac diastole to simulate aortic counterpulsation. Stimulation was performed during various hemodynamic conditions. RESULTS: A standardised surgical procedure suitable for long term studies was established during six experiments. An APPC, with 70-80 mm filling volume, was found to be of optimal size. In another eight experiments, hemodynamic measurements were performed. Under stable hemodynamic conditions the stimulation of the biological skeletal muscle ventricle induced a significant increase of mean arterial pressure by 14% and mean diastolic pressure by 26%. During pharmacologically induced periods of cardiac failure, the stimulation of the APPC increased mean arterial pressure by 13% and mean diastolic pressure by 19%. In all eight experiments, the diastolic peak pressure reached supra-systolic values during stimulation. CONCLUSIONS: The results demonstrate the hemodynamic efficacy of this newly designed biological skeletal muscle ventricle as an aortic counterpulsation device. Chronic experiments using a preconditioned fatigue-resistant muscle will further help to evaluate its possible clinical significance.

Animals↗
PubMed1998

[Results of restoration of continuity in peripheral nerves in childhood and adolescence].

According to several studies, results after reconstructive procedures in children are generally superior compared to those in adults. In the present retrospective study, 20 patients after reconstruction of one or more major nerves in the upper limb (median, ulnar, and radial nerves) were examined. At the time of operation, the patients' age was 8.9 years on the average, the follow-up time ranged between 29 and 173 months. In six cases the nerve lesion had been treated by direct nerve coaptation, in 14 patients a primary or secondary nerve grafting procedure had been applied. The results were classified according to Millesi's examination system, which takes several factors such as mobility, sensibility, skill, and force of the hand into account. Besides two patients, one after reconstruction of the median and ulnar nerves by grafts with significant destruction of the muscles in the lower arm, and the second one after primary coaptation of the median and ulnar nerves in the elbow region, all patients showed a hand function of more than 70% according to Millesi's scoring system. In patients older than ten years at the time of the reconstructive procedure, results were slightly worse than in younger individuals. Children up to ten years of age were nearly always able to move their hand and fingers normally. The results after nerve grafting were sometimes even superior to those after primary neurorrhaphy. Therefore, the present study supports the findings of previous authors describing the excellent regenerative potential of the growing peripheral nervous system. Furthermore, Millesi's scoring system better revealed some subtle differences in hand function when compared to other classifications.

Adolescent↗
PubMed1998

[Effect of transplant length on functional and morphologic outcome of nerve transplantation--an experimental study].

BACKGROUND: The present study was done in order to clarify whether the sometimes poor results after the use of long grafts for nerve reconstruction are due to the length of the graft itself or due to the concomitant big defect in the soft tissues necessitating the use of long grafts. METHODS: In 22 rabbits, the saphenous nerve was used as a nerve graft. Animals were separated into three groups with different lengths of the grafts, namely 3 cm (group 1), 5 cm (group 2) and 7 cm (group 3). In one hindlimb, the proximal end of the graft was coapted to the motor nerve branch of vastus medialis. In a second step, the distal end of the graft was coapted to the nerve branch of rectus femoris. After a total period of 15 months the maximum tetanic tensions in the reinnervated rectus femoris and in the contralateral untreated muscle were determined. Biopsies of the graft and the motor branch distal to the graft were taken in order to count the number of regenerated myelinated nerve fibers. RESULTS: The average maximum tetanic tension in the rectus femoris muscle reinnervated by the 3 cm long graft was 27.2 N; in group 2 the force amounted to 20.4 N. In group 3, the maximum force was 17.6 N, which meant an average loss of 29% compared to the contralateral untreated muscle. In accordance with the functional results, the mean number of regenerated myelinated fibres in the rectus femoris motor branch decreased from 1683 in group 1 to 1136 in group 3. CONCLUSIONS: The results show that the length of the graft influences the results after nerve grafting to a certain extent, but a combination of other factors like concomitant soft tissue injury and destroyed target organs may also be responsible for some of the poor results after the clinical use of long nerve grafts.

Animals↗
PubMed1997

The influence of the graft length on the functional and morphological result after nerve grafting: an experimental study in rabbits.

Clinical experience shows that the results after the use of long nerve grafts for reconstruction are sometimes poor. Nevertheless several authors have stressed that the concomitant big defect in the soft tissues necessitating the use of long grafts is the reason for some of the failures. In 22 rabbits the saphenous nerve was used as a nerve graft. Animals were separated into 3 groups with different lengths of the grafts, namely 3 cm (group 1), 5 cm (group 2) and 7 cm (group 3). In the left hindlimb the proximal end of the graft was coapted to the cut motor nerve branch of vastus medialis. In a second stage the distal end of the graft was coapted to the nerve branch of rectus femoris. After a total period of 15 months the maximum tetanic tension in the reinnervated rectus femoris and in the contralateral unoperated muscle was determined. Biopsies of the graft and the motor branch distal to the graft were taken in order to count the number of regenerated myelinated nerve fibers. The average maximum tetanic tension in the rectus femoris muscle reinnervated by the 3 cm long graft was 27.2 N, in group 2 the force was 20.5 N. In group 3 the maximum force was 17.6 N, which meant an average loss of 29% compared to the contralateral unoperated muscle. The mean number of regenerated myelinated fibres distal to the graft in the rectus femoris motor branch was 1683 in group 1 and decreased to 1137 in group 3. The results show that the length of the graft influences the results after nerve grafting to a certain extent, but a combination of other factors like concomitant soft tissue injury and destroyed target organs may also be responsible for some of the poor results after the clinical use of long nerve grafts.

Animals↗
PubMed1997

Deep accidental hypothermia and cardiac arrest--rewarming with forced air.

BACKGROUND: During the last two cold winters we have treated 5 severely hypothermic patients (temperature below 30 degrees C) with active external rewarming rather than with extracorporal circulation and heat exchanger. PATIENTS: Two patients were found in cardiac arrest, and 3 victims of mountain accidents suffered deep hypothermia without arrest. In one of them, ventricular fibrillation (VF) was converted successfully to a sinus rhythm at a core temperature of 25.9 degrees C. Both arrested patients developed an adequate hemodynamic state during resuscitation although they were at very low temperature. All the patients were warmed with a convective cover inflated with warm air of about 38 degrees C (Bair Hugger). The core temperature increased by approximately 1 degree C/h in all patients. During rewarming we observed neither an initial drop of the core temperature (afterdrop) nor cardiac arrhythmias. The outcome of all 5 patients was good without neurological sequelae. CONCLUSION: We conclude that external rewarming with forced air is a feasible alternative to cardiopulmonary bypass in severely hypothermic patients with electrical activity. This method can be used even in patients with VF because defibrillation can be successfully performed in deep hypothermia. Although after-drop during external rewarming is feared, we did not observe this phenomenon. Rewarming with forced air is inexpensive, easy to perform and direct access to the patient is possible at any time. It does not require heparinisation and can be used in hospitals where they do not have cardiopulmonary bypass facilities. Thus, this method is particularly useful in situations when the hypothermic patient cannot be transferred to a major medical center.

Accidents↗
PubMed1997

Repair of incisional hernias with expanded polytetrafluoroethylene.

OBJECTIVE: To find out the rates of recurrence after repair of incisional hernias with or without the implantation of a PTFE-patch. DESIGN: Open and retrospective study. SETTING: University hospital, Austria. SUBJECTS: 26 patients who had their incisional hernias repaired with a polytetrafluoroethylene (PTFE) patch and 70 for whom conventional methods were used. MAIN OUTCOME MEASURES: Absolute recurrence rate and the Kaplan-Meier estimate 24 months after the operation. Presence of risk factors. RESULTS: Three patients developed recurrences by 24 months in the PTFE group and 41 in the conventional group. The Kaplan-Meier estimate for the PTFE group was 13% and for the conservative group 63%. Women had significantly fewer recurrences than men (p < 0.05). Age, body mass index, and diameter of the defect were not significantly associated with an increased risk of failure. CONCLUSIONS: Insertion of a prosthesis can improve the results of surgical repair of incisional hernias.

Adult↗
PubMed1997

MuLV-insertional mutagenesis of c-myb and Mml1 in a murine model for promonocytic leukemia.

Analysis of retroviral integration sites in MuLV-induced promonocytic leukemias has determined that two genetic loci, c-myb and Mml1, can contribute to disease development but not in the same leukemia. Recent studies aimed at understanding the function of Myb in leukemia development have focused on the consequences of ectopic Myb expression on monocytic and granulocytic differentiation in vitro. In all instances Myb was shown to block growth arrest but not commitment to differentiation, a result which is consistent with observed effects of Myb in leukemia development. No effect of Myb protein truncation was observed in these studies although similar truncations are produced as a result of insertional mutagenesis. Common integration site, Mml1, was recently identified and mapped to mouse chromosome 10 within 1cM of c-myb. Despite its linkage to c-myb, Myb mRNA and protein expression appear to be unaffected in leukemias with Mml1 integrations.

Animals↗
PubMed1997

[Comparative studies of morphometric and functional results following reconstruction of motor nerves].

In order to determine the value of a reconstructive procedure in the peripheral nerve, experimental studies often evaluate the number and the diameter of myelinated nerve fibers as a parameter for the quality of regeneration. This study addresses the correlation between the number of fibers in a peripheral motor nerve after microsurgical reconstruction and the functional result, expressed as the force of the reinnervated muscle. In a total number of 24 sheep, the motor branch to the rectus femoris muscle was severed. The muscle was reinnervated either by direct neurorrhaphy or by nerve grafting, performed in three different ways (free grafting to the ipsilateral muscle, free grafting to the contralateral muscle, vascularized grafting to the ipsilateral muscle). In the final experiments, the muscle force in the reinnervated muscle was determined by supramaximal electrical stimulation. Number and diameter of myelinated nerve fibers were evaluated by computer-assisted morphometric analysis. Regression analysis of morphometric data and the muscle forces was calculated. No correlation was found between fiber numbers in the nerve graft and the maximal force. However, a positive correlation between the number of myelinated fibers in the motor branch distal to the site of coaptation and the functional result was observed in some cases. The diameter of myelinated fibers had no influence on the functional outcome.

Animals↗
PubMed1996

Mml1, a new common integration site in murine leukemia virus-induced promonocytic leukemias maps to mouse chromosome 10.

MuLV-induced myeloid leukemias (MML) having promonocytic characteristics are produced with high incidence in some strains of adult mice that are undergoing chronic peritoneal inflammation. Previously we showed that many leukemias have rearrangements of the c-myb locus due to insertional mutagenesis, however, we also identified a number of leukemias that had proviral integrations in the absence of c-myb rearrangement in the present study, a new locus, Mml1, was found to be a target of insertional mutagenesis in 10 of the promonocytic leukemias that lacked c-myb alterations. Chromosomal mapping studies, performed using progeny from interspecies backcross mice generated by mating (BALB/cAn x M. spretus)F1 females to BALB/cAN males, determined that Mml1 is located on the proximal end of mouse chromosome 10. Interestingly, there were no recombinants between c-myb and Mml1 in 101 backcross progeny and Mml1 was mapped approximately 20-25 kb upsteam of c-myb. Interestingly, c-myb mRNA and Myb protein are expressed at levels similar to the levels observed in myeloid progenitor cells, but are not overexpressed. It is anticipated that future experiments will determine whether Mml1 integration prevents down regulation of c-myb expression or activates another gene on chromosome 10.

3T3 Cells↗
PubMed1996

Role of a muscle target organ on the regeneration of motor nerve fibres in long nerve grafts: a synopsis of experimental and clinical data.

The importance of the muscle target organ as a promoting factor for nerve fibre regeneration in nerve grafts is still a subject of controversial discussion. In the last few years we published uniform results of experimental series in sheep and rabbits in which we investigated the biology of nerve fibre regeneration in long nerve autografts without connection to a target organ. Surprisingly, we found excellent regeneration of myelinated nerve fibres without the influence of a target organ through the whole length of the nerve graft, with an increase in the number of nerve fibres up to fourfold at the distal end. In the sheep series the additional contact with a muscle target organ for 6 months had a variable effect on the fibre population in the distal end of the nerve graft. The results of our planimetric analyses of nerve biopsies in patients with facial paralysis, who were treated by cross-face nerve grafting and free muscle transplantation, are extremely divergent from the results of our experimental series. Instead of an increase, we found a decrease in number of regenerating nerve fibres arriving at the distal end of the cross-face nerve graft down to 20%. Species-specific differences in the biology of nerve regeneration are discussed, together with their implications for the complex clinical situation of nerve grafting with or without the influence of a target organ.

Anastomosis, Surgical↗
PubMed1996

Retroviral insertional mutagenesis in murine promonocytic leukemias: c-myb and Mml1.

Studies have focused on two genetic loci, c-myb and Mml1, whose activation by retroviral insertional mutagenesis contribute to promonocytic leukemia in our acute monocytic leukemia (AMoL) model. Multiple mechanisms of activation of c-myb by retroviral insertional mutagenesis implicate both transcriptional deregulation and protein truncation in conversion of this proto-oncogene to an oncogene. Because transformation by c-Myb can be viewed as a block to differentiation our studies moved into two in vitro systems to evaluate effects of truncated forms of c-Myb on cytokine induced maturation of myeloid progenitors to the granulocyte and macrophage lineages. Deregulated expression of truncated and full length c-Myb did not result in maintenance of the myelomonocytic progenitor state but rather a block in differentiation at intermediate to late steps in the maturation processes of myelomonocytic cells. Our results argue that inhibition of differentiation is due to c-Myb's ability to maintain the proliferative state of cells. Interestingly, the phenotype of continuously proliferating monocytic cells resembles that of the tumor cell phenotype. Recently we identified a new target of integration, Mml1, which is rearranged in ten promonocytic leukemias that do not have c-myb rearrangements. This locus which was mapped to chromosome 10 is presently being characterized.

Animals↗
PubMed1996

Vienna phrenic pacemaker--experience with diaphragm pacing in children.

Eight children, five boys and three girls, aging from 2 to 13 years (M = 9 +/- 3) were treated with the "Vienna phrenic pacemaker". Indication for implantation was central alveolar hypoventilation syndrome (CAH) in one case and total ventilatory insufficiency due to high cervical cord or brain stem lesion (SCI) in seven cases. Four electrodes were applied to each phrenic nerve via sternotomy. Both hemidiaphragms were paced synchronously with increasing duty cycles to condition the diaphragms for continuous electrophrenic respiration (EPR). EPR could be performed successfully in all children but one. Four children could achieve chronical EPR, one is in conditioning period. Two patients could not be discharged from hospital due to parental neglect and died after two and three years of intermittent stimulation. Six children could be discharged from hospital, two of them died after one and four years of chronic pacing. In one case tracheotomy could be closed definitively. Ventilatory insufficiency due to CAH and SCI can be treated even in children with diaphragm pacing, provided the indication for implantation, containing medical and social aspects, was made correctly. Diaphragm pacing probably will not lengthen life of severely injured children but it can increase the quality of their life and therefore should be preferred to positive pressure mechanical ventilation.

Adolescent↗
PubMed1996

Influence of different conditioning methods on force and fatigue resistance in chronically stimulated skeletal muscles.

A study was undertaken to compare different conditioning methods for the transformation of latissimus dorsi muscle into a fatigue resistant one for application in circulatory assist. In ten sheep four electrodes were sutured to the epineurium of the left thoracodorsal nerve for indirect electrical stimulation of the latissimus dorsi muscle. In six sheep a "carousel stimulation," a special multichannel stimulation, in combination with a recently developed conditioning protocol was used for muscle conditioning (multichannel method). In four sheep, a conventional stimulation protocol using single channel stimulation was applied for transformation of the muscle (single channel method). The final experiments were carried out when fatigue resistance was obtained. The maximum tetanic forces at different preloads were determined and fatigue resistance was tested during 20 minutes of continuous stimulation. Both conditioning patterns led to fatigue-free chronic stimulation. Muscles conditioned by multichannel stimulation exhibited between 20% and 33% less force than the contralateral unconditioned muscles, whereas in the single channel group this loss was between 32% and 43%. Thus, the multichannel method revealed relatively superior in preserving muscle force for chronic stimulation.

Animals↗
PubMed1996

[Circulatory support by an electrically stimulated muscle flap. Experimental experiences].

Functional electrical stimulation of the latissimus dorsi muscle flap for circulatory assistance extends the traditional concept of using this flap for reconstructive procedures into the field of cardiac surgery. It requires a transformed muscle which is able to contract for long periods of time without fatigue. Two main groups of experiments have been carried out in sheep. In six sheep the latissimus dorsi muscle (MLD) was transformed into a fatigue-resistant muscle by the means of multichannel stimulation of the supplying motor nerve. After that, stimulation of MLD at a frequency of 70 contractions per minute could be performed continuously without significant muscle fatigue. The loss of maximal force caused by the conditioning procedure was about one third of the initial force. In a second series of acute experiments the MLD was used for cardiomyoplasty. The muscle was divided into two parts which were wrapped around the heart in two different forms. The resting tension of the muscle was preserved. EKG-synchronous stimulation resulted in an increase in left ventricular pressure between 12 and 53%. The increase in arterial pressure was between 10,6 and 58%.

Animals↗
PubMed1996

[Results of occlusion of large or recurrent incisional hernias with polytetrafluoroethylene].

In 48 patients who were suffering from recurrent or large abdominal incisional hernias the defect in the abdominal wall was closed by the implantation of a patch of polytetrafluoroethylene. Patients were examined 22 months postoperatively on the average. In 5 cases recurrence had occurred (10.4%). The estimated rate of recurrence two years postoperatively amounted to 14%. As this is significantly lower than after conventional techniques without alloplastic materials, the closure of incisional hernias by PTFE is an important alternative for the management of difficult abdominal incisional hernias.

Adult↗