PubMed Health⌕ Search

Biomedical subjects

B Marquardt

Publications and source records attributed to B Marquardt.

At least 19 recordsLinked to original sources
PubMed2006

[Lumbar spinal stenosis].

Lumbal spinal stenosis is gaining more and more clinical relevance because of changing population structure and increasing demand on lifequality in the elderly. Current treatment recommendations are based on clinical experience, expert opinions and single studies rather than on proven evidence. The radiologic degree of stenosis does not correlate with the patients' clinical situation. It is not the main factor indicating surgery but rather the typical history and spinal claudication. Symptomatic patients with light to moderate complaints should undergo multimodal conservative treatment. Epidural injections, delordosating physiotherapy and medication are useful. In patients with severe symptomatic stenosis surgery is indicated after a conservative treatment of 3 months. Relevant pareses or a cauda equina syndrome are absolute indications for surgery. The general aim is to decompress sufficiently while maintaining or restoring segmental stability. A laminectomy is not necessarily required. In patients with accompanying degenerative Meyerding grade I-II spondylolisthesis or instability in functional radiographs, fusion or dynamic stabilisation are recommended in addition to decompression, depending on the patient's age and activity level.

Decompression↗
PubMed2005

Spectroscopic imaging of protein crystals in crystallization drops.

Automatic imaging and scoring of crystallization drops is an essential step in high-throughput crystallography. Presently, white-light images of crystallization drops are acquired robotically and the images are analyzed and scored using pattern recognition algorithms. However, the scoring part remains unreliable as crystals and microcrystals are not always recognized by existing feature-extraction and recognition algorithms. We propose a fundamental shift in crystal monitoring through spectroscopic imaging of crystallization drops. This method converts the problem of automatic crystal detection from one of pattern recognition into one of intensity (concentration) analysis. The latter can be more robust and reliable.

Crystallization↗
PubMed2004

Neuronal regeneration after application of radiofrequency energy to collagenous tissue is affected by limb immobilization: an in vivo animal study.

Despite widespread use of radiofrequency (RF)-shrinkage, there have been no studies on the influence of RF-energy on neural elements of collagenous tissue. The purpose of this study was to examine the effect of RF-shrinkage on neural structures of capsuloligamentous tissue and the recovery of neural elements under different postoperative treatment protocols. One patellar tendon of 46 New-Zealand-White rabbits was shrunk. Six rabbits were sacrificed immediately postoperative. Twenty rabbits were not immobilized, 10 were immobilized for 3 and 10 were immobilized for 6 weeks. A monoclonal antibody, specific against a neurofilament protein, was used to detect nerves and neural structures. Staining pattern of nerve fibres was significantly altered immediately postoperative. After 3 weeks the number of nerve fibres and bundles decreased significantly in immobilized and non-immobilized limbs. The loss of nerve fibres was significantly less in immobilized limbs. At 6 weeks the number of neural elements in immobilized limbs increased to the level of untreated control tissue. In non-immobilized limbs we found no recovery of neural elements 9 weeks postoperatively. At this time the number of nerve fibres and bundles was still significantly less compared to the untreated control limbs. RF-shrinkage causes significant alteration of neural elements. Under immobilization nerve fibres and bundles reach the level of normal untreated tissue. Careful rehabilitation is important after RF-shrinkage. Not only for biomechanical reasons, but also to allow the neural elements to recover, thermally modified tissue should be protected from normal physiologic loads.

Animals↗
PubMed2004

Immobilisation after radiofrequency-induced shrinkage of tendon. A histological study in rabbits.

Despite widespread use of radiofrequency (RF) shrinkage, there have been no animal studies on the effects of post-operative immobilisation on the histological properties of the shrunken tissue. We have therefore examined the role of post-operative immobilisation after RF shrinkage with special emphasis on the histological properties of collagenous tissue. One patellar tendon of 66 New Zealand White rabbits was shrunk. Six rabbits were killed immediately after the operation. Twenty rabbits were not immobilised, 20 were immobilised for three weeks and 20 for six weeks. Fibroblasts, collagen and vascular quality and density were evaluated on sections, stained by haematoxylin and eosin. Nine weeks after operation the histological properties were inferior to those of the contralateral control tendons. Shrunk tendons did not return to normal at any time after operation irrespective of whether the animals had been immobilised or not. All the parameters improved significantly between zero and three weeks after operation. Immobilised tendons tended to have a better and faster recovery. Careful rehabilitation is imperative after RF shrinkage. Immobilisation aids recovery of the histological properties. Our findings in this animal model support a period of immobilisation of more than three weeks.

Animals↗
PubMed2001

[Selective pre- intra- and postoperative bile duct diagnosis--an efficient and low complication regimen within the scope of laparoscopic cholecystectomy. Early and late results of a prospective study].

INTRODUCTION: The discussion of diagnostic pre- and intraoperative procedures of the common bile duct (CBD) for laparoscopic cholecystectomy is still open. METHODS: Results of a prospective study of 4000 laparoscopic cholecystectomies were evaluated, adhering to the concept of selective common bile duct examination. In 1999 an inquiry was performed on 1197 patients an average of 38.7 months postoperatively to judge this concept. RESULTS: Three hundred and nineteen patients (8%) examined preoperatively by ERC revealing a CBD stone in 126 cases. The morbidity of this procedure was 3.1%. In 0.18% a lesion of the common bile duct was documented following laparoscopic cholecysTectomy. A intraoperative cholangiography was performed in 67 patients (1.7%) because of unclear anatomy or to exclude a CBD stone. Perioperatively a CBD stone was found in 0.5% of cases. Additionally, in 0.3% the same problem occurred in the long-term follow-up, so that the risk for unknown CBD stones following the selective diagnostic concept is 0.8%. CONCLUSION: The concept of selective diagnostic procedures of the common bile duct shows a low morbidity with sufficient efficiency in avoiding CBD stones as well as duct lesions. Therefore it is recommended for routine use in laparoscopic cholecystectomy.

Cholangiography↗
PubMed1999

[Endoscopic hernia repair within the scope of a total management concept].

From 1991 until 1998 there were 1832 hernioplasties in 1696 patients. Endoscopic procedures as there were the Trans Abdominal Hernioplasty (TAPP) and the Totaly Extraperitoneal Hernioplasty (TEP) are increasing as the Lichtenstein procedure. This is in opposite to the Shouldice operation. Endoscopic treatment is highly accepted and the results are as good as with other operations. The analysis of our patients shows that there is an indication for all the different procedures. We clame to use the optimal operation for each individual patient depending on clear criteria. Principally there are still the Shouldice operation without a net for the youngers and the Lichtenstein operation in local anaesthesia for elder and risk patients recommended. All others, especially those with bilateral and recurrent hernia profit from endoscopic procedures. Advantages and disadvantages for TAPP and TEP are demonstrated.

Adult↗
PubMed1998

Incidence and time course of cardiovascular side effects during spinal anesthesia after prophylactic administration of intravenous fluids or vasoconstrictors.

UNLABELLED: We studied the time course of arterial hypotension and/or bradycardia requiring treatment during spinal anesthesia and compared the efficacy of i.v. fluid or vasoconstrictor administration for the prevention of these side effects. Patients (n = 1066) were randomly allocated to either a volume group (lactated Ringer's solution 15 mL/kg within 15 min before spinal anesthesia), a dihydroergotamine group (10 microg/kg i.m. 15 min before anesthesia), or a placebo group. All patients breathed O2-enriched air during spinal anesthesia (4 mL of plain 0.5% bupivacaine). With the placebo, there were side effects (mean incidence 22.9%) for up to 45 min after the start of anesthesia. Dihydroergotamine reduced the incidence of side effects, preferentially the late ones, more (mean incidence 11.8%) than fluid administration (mean incidence 16.9%), which was effective only during the first 15 min of anesthesia. Both heart rate and arterial pressure decreased within 15 min before the manifestation of symptoms. In a subgroup of patients, the incidence of side effects (8%) was greatly reduced by the intraoperative application of both sedatives and opioids. We conclude that cardiovascular side effects may occur at any time during spinal anesthesia. Fluid administration reduced the incidence of early events, but dihydroergotamine the late events. IMPLICATIONS: Cardiovascular side effects requiring treatment occurred at any time during spinal anesthesia in our placebo-controlled study, regardless of the prophylactic regimen (fluid infusions versus dihydroergotamine).

Adult↗
PubMed1995

Stimulation of MAP kinase by v-raf transformation of fibroblasts fails to induce hyperphosphorylation of transfected tau.

A proportion of the microtubule-associated protein, tau, is in an elevated state of phosphorylation in foetal and adult brain whereas all of the tau in paired helical filaments, which are characteristic of Alzheimer's disease is hyperphosphorylated; it is important therefore to elucidate the mechanisms that regulate tau phosphorylation. Here we describe results that show that although MAP kinase can hyperphosphorylate tau in vitro, activation of MAP kinase in transformed fibroblasts does not result in hyperphosphorylation of transfected tau, whereas glycogen synthase kinase-3 beta (GSK-3 beta) when co-transfected with tau does result in tau hyperphosphorylation. The findings imply that GSK-3 beta may be a stronger candidate than MAP kinase for inducing tau hyperphosphorylation in vivo.

3T3 Cells↗
PubMed1995

Kinase activities of c-Mos and v-Mos proteins: a single amino acid exchange is responsible for constitutive activation of the 124 v-Mos kinase.

The Mos protein kinase is a serine-/threonine-specific protein kinase with a crucial role in meiotic cell divisions in vertebrates. Several oncogenic derivatives of the c-Mos protein have been discovered in murine retroviruses. These proteins have acquired mutations and exhibit different degrees of protein kinase activity in vitro. In an attempt to understand the factors governing Mos protein kinase activity we have compared the kinase activities of the wild-type c-Mos protein and two v-Mos proteins (strain HT1 and MSV124) after expression in insect cells. Only the 124 v-Mos protein showed kinase activity in vitro as measured by autophosphorylation, vimentin phosphorylation or by phosphorylation and activation of MAP kinase kinase. By domain swapping and site-directed mutagenesis we identified a single point mutation in the 124 v-Mos protein (Arg145-->Gly) which is responsible for its constitutive activity. This residue is located in the alpha-helix C of the kinase domain close to the ATP binding fold and is conserved in all known c-Mos proteins. Introduction of the corresponding mutation into HT1 v-Mos and into murine c-Mos activated both proteins for autophosphorylation, vimentin phosphorylation and for signalling via MAP kinase kinase in vitro. We hypothesize that the Arg145-->Gly mutation found in 124 v-Mos mimicks a conformational change which might be an obligatory step in the activation of c-Mos in vivo.

Amino Acid Sequence↗
PubMed1994

Alzheimer's disease-like phosphorylation of the microtubule-associated protein tau by glycogen synthase kinase-3 in transfected mammalian cells.

BACKGROUND: Paired helical filaments (PHFs) are a characteristic pathological feature of Alzheimer's disease; their principal component is the microtubule-associated protein tau. The tau in PHFs (PHF-tau) is hyperphosphorylated, but the cellular mechanisms responsible for this hyperphosphorylation have yet to be elucidated. A number of kinases, including mitogen-activated protein (MAP) kinase, glycogen synthase kinase (GSK)-3 alpha, GSK-3 beta and cyclin-dependent kinase-5, phosphorylate recombinant tau in vitro so that it resembles PHF-tau as judged by its reactivity with a panel of antibodies capable of discriminating between normal tau and PHF-tau, and by a reduced electrophoretic mobility that is characteristic of PHF-tau. To determine whether MAP kinase, GSK-3 alpha and GSK-3 beta can also induce Alzheimer's disease-like phosphorylation of tau in mammalian cells, we studied the phosphorylation status of tau in primary neuronal cultures and transfected COS cells following changes in the activities of MAP kinase and GSK-3. RESULTS: Activating MAP kinase in cultures of primary neurons or transfected COS cells expressing tau isoforms did not increase the level of phosphorylation for any PHF-tau epitope investigated. But elevating GSK-3 activity in the COS cells by co-transfection with GSK-3 alpha or GSK-3 beta decreased the electrophoretic mobility of tau so that it resembled that of PHF-tau, and induced reactivity with eight PHF-tau-selective monoclonal antibodies. CONCLUSIONS: Our data indicate that GSK-3 alpha and/or GSK-3 beta, but not MAP kinase, are good candidates for generating PHF-type phosphorylation of tau in Alzheimer's disease. The involvement of other kinases in the generation of PHFs cannot, however, be eliminated. Our results suggest that aberrant regulation of GSK-3 may be a pathogenic mechanism in Alzheimer's disease.

Alzheimer Disease↗
PubMed1994

Signalling from TPA to MAP kinase requires protein kinase C, raf and MEK: reconstitution of the signalling pathway in vitro.

The phorbol ester PMA/TPA (phorbol 12-myristate 13-acetate) is a potent tumor promoter which mimics distinct intracellular signalling events triggered by activated growth factor receptors, e.g. the activation of MAP kinases. The largest known family of TPA-binding proteins comprise members of the protein kinase C (PKC) family although other TPA-binding proteins outside the PKC family have recently been identified. In this report we addressed the mechanism and the pathway by which TPA induces the activation of MAPkinases. Using recombinant proteins and in vitro phosphorylation reactions we identified the components in the signal transduction pathway from TPA to MAPkinase and we show that the activation of MAPkinase by TPA requires the presence of protein kinase C, c-raf and the MAPkinase activator MEK. We also find that the activation of raf autophosphorylation in vitro correlates with the ability of Raf to signal to MAPkinase. Thus the activation of Raf by PKC apparently can trigger the same signalling pathway as oncogenic Raf or Raf activation by ras in combination with tyrosine phosphorylation.

Animals↗
PubMed1992

Sequence of a rat cDNA encoding the ERK1-MAP kinase.

Mitogen-activated protein (MAP) kinases are cytoplasmic and/or nuclear protein kinases which are activated by one or several signal transduction pathways from the cell surface into the nucleus. Their activity is regulated by phosphorylation on Tyr as well as on Ser/Thr residues. A cDNA encoding the rat ERK1 member of the MAP kinase family was isolated and sequenced. The longest cDNA consisted of 1875 nucleotides and coded for a polypeptide of 380 amino acids with a predicted M(r) of 42987.

Amino Acid Sequence↗
PubMed1991

[Neurologic complications after bone marrow transplantation].

The retrospective study presented here reports clinical, electrophysiological and CT-data from 21 patients who underwent bone marrow transplantation for leukemia or aplastic anemia between 1980 and 1985. The aim of the investigation, which was performed at the end of 1986, was to elucidate whether antineoplastic drugs and radiation can result in long-term damage of the central nervous system. In 9 patients we observed neurological signs (1 leukencephalopathy, 5 cerebellar symptoms). Seven patients revealed dysrhythmia in the EEG and five had delayed latencies of visual evoked potentials. Eight patients exhibited pathological changes in CT (3 atrophy of supratentorial structures, 3 periventricular lucencies, 2 a combination of both). The results indicate that long-term damage to the CNS may be encountered after successful bone marrow transplantation.

Adolescent↗
PubMed1987

[Anaphylactic shock].

Symptoms, therapy, and outcome of 49 cases of anaphylactic reaction are presented. Epinephrine (0.5-2.0 mg) did not produce any circulatory improvement but induced severe dysrhythmias and even ventricular fibrillation. Neither epinephrine nor prednisolone (2 g) prevented shock development, neurologic sequelae, or fatal outcome. Rapid infusion of 2000 ml 50% colloid (dextran 70 or starch, m.w. 450,000) with 50% Ringer's lactate, however, reliably restored circulation within 30 min. If elevated, airway resistance dropped in conjunction with colloid administration rather than with any other drug. Impairment of the pulmonary circulation is found to be the initial feature of anaphylaxis, manifested by a rise in pulmonary vascular resistance; then stroke volume and systemic blood pressure fall as left heart filling is reduced. Many findings indicate a high blood viscosity with resulting capillary occlusion: rapid clotting; low levels of factors I, II, V, VIII, and X; low plasma protein, which may be only 50% of its normal value; thrombocytopenia; and aggregation of white blood cells with fibrin in small lung vessels. Blood and plasma vanish from the circulation and appear to be sequestered in the pulmonary capillaries as the initial response to the antigen; later, the whole body is affected. Congestion and pain in the lymph nodes indicate that the lymphatic system may also become involved. On the basis of hemoconcentration, a blood volume deficiency in the range of 30% has been calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaphylaxis↗
PubMed1984

Rupture of intracranial aneurysms during angiography and CT: coincidental or causal event? A case report.

The rare event of rupture of a saccular aneurysm of the internal carotid artery during cerebral angiography and of a fusiform aneurysm of the basilar artery following contrast enhanced CT are reported. Whereas some angiographic findings point at a causal relationship between rupture of the aneurysm and the examination procedure itself, this relationship between possible contrast medium effects and rupture of the basilar artery aneurysm during CT remains uncertain. Possible mechanisms are discussed.

Adult↗
PubMed1981

[Experiences with 31 anaphylactoid reactions (author's transl)].

31 Anaphylactoid reactions to Dextran, Propanidid, Althesin, Ampicillin and Mepivacaine are reported. By rapid infusion of Ringer lactate and colloid solutions to an amount of 2,000-3,000 ml circulation could be restored in 30 minutes. Prednisolone did not reveal positive effects. After administration of epinephrine in 3 of 4 cases more negative than positive effects were seen.

Adolescent↗