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H C Ludwig

Publications and source records attributed to H C Ludwig.

At least 19 recordsLinked to original sources
PubMed2006

Expression of glutathione S-transferase T1 (GSTT1) in human brain tumours.

Glutathione S-transferases (GSTs) play a central role in a number of metabolic processes. Glutathione S-transferase T1 (GSTT1) is a polymorphic cytosolic enzyme and a member of the theta class of GSTs. Typical substrates for GSTT1 are industrial compounds, such as dichloromethane and ethylene oxide. It has been shown that also chemotherapeutic drugs such as BCNU [i.e. 1,3-bis(2-chloroethyl)-1-nitrosourea] are efficiently inactivated by GSTT1. BCNU is a drug which is increasingly used locally in the chemotherapy of glioblastoma multiforme WHO grade IV. Therefore, if GSTT1 were expressed in neoplastic cells of brain tumours it could be a factor for chemoresistance. In order to clarify a possible role of GSTT1 in chemoresistance, as a first step, we localized this enzyme in malignant gliomas such as glioblastoma multiforme WHO grade IV and oligodendroglioma WHO grade II. Because of its polymorphism we first genotyped the samples for GSTT1 by PCR. Using in situ hybridization, we then demonstrated that GSTT1 transcripts are expressed in neoplastic cells of both tumour types. Immunohistochemistry revealed then that whereas neoplastic cells in glioblastoma multiforme WHO grade IV contain GSTT1, it was not localized in oligodendroglioma cells. Given the polymorphism of GSTT1 and its potential activity towards BCNU, the localization of GSTT1 in glioblastoma cells can be considered as a possible factor of non-homogeneous chemotherapy response among patients with different GSTT1 genotypes.

Adult↗
PubMed2005

Piezoelectric bone surgery: a revolutionary technique for minimally invasive surgery in cranial base and spinal surgery? Technical note.

OBJECTIVE: Piezoelectric surgery represents an innovative, ultrasonic surgery technique for performing a safe and effective osteotomy or osteoplasty that contrasts with the traditional hard and soft tissue management methods with rotating instruments. METHODS: Because of its physical and mechanical properties, the definitive clinical advantage of piezoelectric bone surgery with regard to precision cutting lies in the sparing of vital neurovascular bundles or general soft tissue and better visualization of the surgical field, thus suggesting its great safety. Piezoelectric bone surgery has been previously described only in oral and maxillofacial operative procedures in adults. RESULTS: Five children between the age of 6 and 84 months were operated on for craniosynostosis, tethered cord, and an extraconal intraorbital tumor. The usefulness of piezoelectric bone surgery during neurosurgical procedures is presented for these cases. This technique is especially recommended when there are anatomic difficulties because of poor intraoperative visibility or the presence of delicate anatomic structures. CONCLUSION: The present preliminary report (comprising illustrative case reports) demonstrates and introduces for the first time the utility of piezoelectric bone surgery in cranial base and spinal surgery in children. Until now, there has been no documented neurosurgical experience of this technique even in adults.

Craniosynostoses↗
PubMed2004

Expression of tyrosine kinases FAK and Pyk2 in 331 human astrocytomas.

The progression of malignancy from astrocytomas to glioblastomas remains clinically as well as histopathologically unpredictable. The focal adhesion kinase (FAK) and the proline-rich tyrosine kinase (Pyk2) show a high expression in glioma cell lines and have an influence on increased cell proliferation and migration of glioma cells in vitro and in vivo. The aim of this study was to correlate the coexpression of FAK and Pyk2 to the WHO grade of malignancy in human astrocytomas. Immunohistochemical staining scores of FAK and Pyk2 were analyzed in 331 astrocytomas and correlated to each other and to the WHO grade. Significant coexpression of FAK and Pyk2 in astrocytomas was demonstrated. Pyk2 expression occurred much more frequently and with higher expression scores within the different WHO grades. Beyond this, a significant correlation between the WHO grade of malignancy of astrocytomas and the expression of FAK, as well as of Pyk2, was detected. This connection and the roles of these two tyrosine kinases in the progression of tumors should be confirmed by further studies.

Astrocytoma↗
PubMed2000

The C1-C2 interface residue lysine 50 of pig kidney fructose-1, 6-bisphosphatase has a crucial role in the cooperative signal transmission of the AMP inhibition.

To understand the mechanism of signal propagation involved in the cooperative AMP inhibition of the homotetrameric enzyme pig-kidney fructose-1,6-bisphosphatase, Arg49 and Lys50 residues located at the C1-C2 interface of this enzyme were replaced using site-directed mutagenesis. The mutant enzymes Lys50Ala, Lys50Gln, Arg49Ala and Arg49Gln were expressed in Escherichia coli, purified to homogeneity and the initial rate kinetics were compared with the wild-type recombinant enzyme. The mutants exhibited kcat, Km and I50 values for fructose-2,6-bisphosphate that were similar to those of the wild-type enzyme. The kinetic mechanism of AMP inhibition with respect to Mg2+ was changed from competitive (wild-type) to noncompetitive in the mutant enzymes. The Lys50Ala and Lys50Gln mutants showed a biphasic behavior towards AMP, with total loss of cooperativity. In addition, in these mutants the mechanism of AMP inhibition with respect to fructose-1,6-bisphosphate changed from noncompetitive (wild-type) to uncompetitive. In contrast, AMP inhibition was strongly altered in Arg49Ala and Arg49Gln enzymes; the mutants had > 1000-fold lower AMP affinity relative to the wild-type enzyme and exhibited no AMP cooperativity. These studies strongly indicate that the C1-C2 interface is critical for propagation of the cooperative signal between the AMP sites on the different subunits and also in the mechanism of allosteric inhibition of the enzyme by AMP.

Adenosine Monophosphate↗
PubMed2000

The influence of airway pressure changes on intracranial pressure (ICP) and the blood flow velocity in the middle cerebral artery (VMCA).

OBJECTIVE: Due to the exponential shape of the intracranial volume-pressure relation, simple measurement of epidural, parenchymal or intraventricular intracranial pressure (ICP) in traumatic brain injury (TBI) often fails to early recognize patients with a fulminant development of intracranial hypertension even during recently available methods of tissue PO2 and microdialysis measurements. One approach to this problem could be repetitive intracranial volume provocations to evaluate a trend of the intracranial elastance. Several previously published methods use invasive volume challenge through access to the cerebrospinal fluid (CSF). This pilot study describes changes in intracranial pressure due to variations of airway pressure with BIPAP ventilation maneuvers. PATIENTS AND METHODS: Ten patients with severe TBI were enrolled and completed the study. The inclusion was based on radiologic signs due to TBI in the first CT-scan and the clinical indication for insertion of an ICP monitoring device. Patients with elevated ICP above 20 mm Hg were excluded. The epidural ICP response together with haemodynamic parameters in relation to defined airway pressure changes (delta PAW) was detected. The influence of the duration of delta PAW was evaluated additionally. Data of central venous pressure (CVP), ICP, mean arterial pressure (MAP), cerebral perfusion pressure (CPP), airway pressure (PAW) and blood flow velocity of the middle cerebral artery (VMCA) were analyzed on the basis of differences between the maximum (inspiration) and minimum PAW values (expiration). RESULTS: Elevations of PAW in the range of 20 to 35 cm H2O resulted in changes of the ICPmean from 4.1 to 6.0 mm Hg (r = 0.9, p < 0.05). A correlation was estimated for the changes of systolic arterial pressure (Part) and CPPmean due to PAW variations which ranged between 4.5 and 11.6 mm Hg (r = 0.99, p < 0.05). Concerning the transcranial doppler measurements the data of changes of the blood flow velocity of the middle cerebral artery (VMCA) revealed a positive correlation to PAW with a r = 0.99, p < 0.05. CONCLUSIONS: Elevation of the venous outflow resistance and a transient increase in cardiac output have to be considered as mechanisms for transduction of transthoracic pressure changes to intracranial pressure variations. We conclude, that trends of changes in elastance can be derived from intermittent airway pressure variations. This can be useful in easy and on line dynamic monitoring of ICP in traumatic brain injury.

Air Pressure↗
PubMed1999

Elevated cerebral perfusion pressure and low colloid osmotic pressure as a risk factor for subdural space-occupying hygromas?

BACKGROUND: Space-occupying subdural hygromas are a late complication of severe traumatic brain injury (TBI) and may delay the patient's recovery. To evaluate the risk factors involved, we performed a semiretrospective, -prospective analysis of three groups of patients, which differed with regard to the techniques used in the management of their cerebral perfusion pressure (CPP) and colloid osmotic pressure (COP) to determine the occurrence of space-occupying subdural hygromas. PATIENTS AND METHODS: Between 1989 and 1997 we examined 696 patients after a severe TBI: Group 1. 1989-1994 mean CPP: 67 (elevated for therapeutic reasons by catecholamines, if necessary), mean COP: 19. Group 2. January 1995-October 1996, mean CPP: 77, mean COP: 20. Group 3. November 1996-December 1997, mean CPP: 79, mean COP: 23 (elevated for therapeutic reasons by infusions of colloids). The groups were comparable for other criteria. RESULTS: Compared to Group 1, Group 2, with a high CPP but lower COP, showed a significantly higher (p < 0.01; chi2-test with correction of Yates) percentage of posttraumatic subdural hygromas with space-occupying aspects, clinical signs of bradycardia, hypertension and impaired consciousness requiring surgery (Group 1: 1.75%; Group 2: 10.46%; Group 3: 0%). In Group 3 we saw no patient with a space-occupying hygroma. CONCLUSION: We conclude that iatrogenic elevated CPP, which has been reported to be helpful in preventing secondary ischemic damage after a severe TBI, may be harmful to a patient if the COP is not maintained within physiological ranges.

Adult↗
PubMed1999

Suppression of kinetic AMP cooperativity of fructose-1,6-bisphosphatase by carbamoylation of lysine 50.

Selective treatment of pig kidney fructose 1,6-bisphosphatase with cyanate leads to the formation of an active carbamoylated derivative that shows no cooperative interaction between the AMP-binding sites, but completely retains the sensitivity to the inhibitor. By an exhaustive carbamoylation of the enzyme a derivative is formed that has a complete loss of cooperativity and a decrease of sensitivity to AMP. It was proposed that the observed changes of allosteric properties were due to the chemical modification of two lysine residues per enzyme subunit [Slebe et al. (1983), J. Protein Chem. 2, 437-443]. Studies of the temperature dependence of AMP sensitivity and the interaction with Cibacron Blue Sepharose of carbamoylated fructose 1,6-bisphosphatase derivatives indicate that the lysine residue involved in AMP sensitivity is located at the allosteric AMP site, while the lysine residue involved in AMP cooperativity is at a distinct location. Using [14C]cyanate, we identified both lysine residues in the primary structure of the enzyme; Lys50 is essential for AMP cooperativity and Lys112 appears to be the reactive residue involved in the AMP sensitivity. According to the fructose 1,6-bisphosphatase crystal structure, Lys50 is strategically positioned at the C1-C2 interface, near the molecular center of the tetramer, and Lys112 is in the AMP-binding site. The results reported here, combined with the structural data of the enzyme, strongly suggest that the C1-C2 interface is critical for the propagation of the allosteric signal among the AMP sites on different subunits.

Adenosine Monophosphate↗
PubMed1998

Glycerol gangliotomy of the second dorsal cervical root in rats: an experimental study to evaluate a minimal invasive approach for the treatment of the chronic cervicogenic headache.

Glycerol is a known agent in the therapy of chronic tic douloureux. It has been used for about 20 years in percutaneous, retrogasserian minimal-invasive rhizotomy, although the pharmacological mechanism of the pain relief involved remains unclear. To investigate glycerol treatment as a possible replacement for invasive approaches in the therapy of chronic cervicogenic headaches, we performed an experimental study on the pathomorphologic action of anhydrous glycerol injection into the second upper cervical dorsal root ganglion (DRG) of rats. Glycerol injections into the second cervical ganglion were investigated light- and electron-microscopically in a series of 40 rats for survival times of up to 30 days. We detected an unspecific overall effect on sensory neurons and satellite cells, as well as on myelinated and unmyelinated axons and Schwann cells. This could be detected after 5 days and sometimes led to degeneration of most of the neurons. Contralateral saline injections as a control showed no morphological effects. The loss of afferent fiber connections to the posterior horn of the myelon could be detected by immunohistochemical labeling of reactive astrocytes. Our results show a glycerol-induced deterioration of the cytoarchitecture of the neurons and their glial satellite cells. The effects on the ganglion cells appear to have been mediated by membrane disturbances and loss of glial integrity. These observations are contrary to previously reported results indicating the specific effect of glycerol on thin myelinated sensory axons.

Animals↗
PubMed1998

Optimized evaluation of a pulsed 2.09 microns holmium:YAG laser impact on the rat brain and 3 D-histomorphometry of the collateral damage.

Since more than 20 years CO2 and Nd:YAG lasers are established in the microsurgery of the nervous system. CO2 lasers can be used handheld, but may be focused on the target area by mirror optics and sideports of the operating microscope's micromanipulator. Nd:YAG lasers have the disadvantage of deep penetration into the brain and provocation of a large collateral damage. The need is for a fibre conducted solid system for surgery in delicate areas as for brain stem surgery. Fibre conduction of near infrared lasers allows better exposure of the target area compared to hollow wave guides or mirror equipment. Fibres can be tapered and modified according to the purpose. The holmium:YAG (Ho:YAG) laser has acquired interest by introducing the system into microsurgery of parenchymal tissue. They have not been proven yet sufficiently for neurosurgical tasks. The effort to minimalize the collateral tissue damage has to be maximalized in the surgery of nervous tissue and functional low redundant brain stem or spinal cord tissue. Volumetric data may be more precise in comparison to depth and width data of the laser lesion even when the different levels of the tissue interaction have to be analyzed for estimation of the real side effects in nervous tissue. We have used 50-800 ml delivered Ho:YAG single pulses in cortical areas of Sprague-Dawley rats and investigated the different lesion zones by volumetric data. The functional lesion zone was detected and measured by immunohistological staining of the heat shock protein HSP 72. For further reduction of the focus area, we have used tapered 400 to 200 microns fibres.

Animals↗
PubMed1997

[Trigeminal neuralgia as symptom of an infratentorial space-occupying process].

UNLABELLED: Despite excellent technical means of imaging the posterior fossa by magnetic resonance imaging (MRI), some infratentorial space-occupying processes still remain undiscovered, especially if they present only slight symptoms or imitate typical different diseases. METHODS: We analysed the data of 334 patients who were admitted because of infratentorial space-occupying processes in the years 1986 to 1995. RESULTS: There were six patients with trigeminal neuralgia caused by infratentorial tumors. In only one was the tumour previously diagnosed. All suffered from tic douloureux; two had undergone operative treatment. Mean latency from first symptoms until diagnosis was 48 months. On admission all patients presented at least slight neurological deficits. Postoperatively, the patients remained pain-free. CONCLUSION: Because the prognosis of operative treatment and the occurrence of postoperative deficits depend on tumour size, we advocate MRI examination in every patient presenting tic douloureux, even without additional neurological signs.

English Abstract↗
PubMed1995

Bedside measurement of the third ventricle's diameter during episodes of arising intracranial pressure after head trauma. Using transcranial real-time sonography for a non-invasive examination of intracranial compensation mechanisms.

Using transcranial real-time sonography, changes in the axial diameter of the third ventricle during manoeuvres, which increased intracranial pressure (ICP), were measured in 28 patients with moderate to severe head injury. The measurements were correlated with ICP measured by epidural pressure monitoring. We observed reductions in diameter ranging from 0.3 to 1.1 mm with rises in intracranial pressure of at least 5 mm in 22 patients of whom only one died. In 6 additional patients, no changes in diameter were seen, and 5 of the 6 died. We interpret that poor outcome as a measurable inability for the brain to expel cerebrospinal fluid into extracerebral compartments during increased ICP. Transcranial real-time sonography may provide additional information about intracranial cerebral fluid dynamics and compliance.

Adolescent↗
PubMed1994

Immunohistochemical and electronmicroscopic effects of a new 2.1 microns Ho:YAG laser on the rat brain.

Using an experimental animal model, the thermal single-pulse lesion derived from a mid-infrared 1.0 Joule 300 microns fibre-conducted Holmium: Yttrium-Aluminum-Garnet (Ho:YAG) laser was examined, with special emphasis on the orientation and depth of the tissue reaction. Performing biparietal craniotomy in Sprague-Dawley rats weighing 250-300 g, both hemispheres were targeted by different radiant exposures from 20 to 140 J/cm2 derived from a 600-800 microsecond single pulse. After survival periods of one to 30 days, the animals were sacrificed and both hemispheres were processed for light- and electronmicroscopic investigations. To resolve the depth and orientation of the tissue reaction regarding the localization of reactive astrocytes, we looked for the expression of glial proteins like glial fibrillary acidic protein (GFAP), Vimentin and S 100 with a three-step biotin-avidin immunoperoxidase method. Neuronal and secondary axonal damage was investigated by labelling Neurofilament and Synaptophysin. The tissue reaction beneath the ablated material, consisting of a vacuolation and coagulation zone resulting from heat diffusion, was further elucidated by localization of the heat shock protein (HSP 72 kilo Dalton). Revealing the extension of reactive astrocytes and the degree of the electronmicroscopically depicted glial oedema, the depth of the tissue damage was estimated to reach about 700 microns beneath laser excision. Since McKenzie predicted the depth of tissue damage beneath CO2 and YAG laser excisions in a theoretical mathematical model, the authors were able to develop a sensitive model for testing new laser systems and as a promising instrument for neurosurgery.

Aluminum↗
PubMed1991

Results of various methods to investigate the function of postmortem human and bovine basilar arteries.

Cerebral vasospasm is a serious complication for patients suffering from acute nontraumatic subarachnoid hemorrhage (SAH). Despite numerous efforts to analyze the multifactorial pathomechanisms, it is still unclear whether vasospasm is a primary result caused by the release of vasoactive mediators or a secondary event due to severe destructions of the vessel architecture. This study was designed in order to investigate the reactivity of postmortem human basilar arteries upon exogenous vasoconstrictors, to study time-dependent changes in vessel morphology and to control responsiveness to agonists and selective antagonists. Therefore, isolated rings and spirally cut strips of bovine- and human basilar arteries were incubated with exogenous vasoconstrictors and specific antagonists (Daltroban, Ketanserin). Light and electron microscopic studies were performed in order to analyze the morphological changes in vessel tissues. Our results suggest that postmortem human basilar arteries are a suitable pharmacological tool studying the effects of contractile mediators.

Animals↗
PubMed1987

Heavy riboflavin synthase of Bacillus subtilis. Primary structure of the beta subunit.

Heavy riboflavin synthase is a 1,000,000-Da protein catalyzing the last two reactions of riboflavin biosynthesis. The enzyme complex consists of 60 beta subunits (Mr = 16,200) and approximately three alpha subunits (Mr = 23,000). beta subunits were isolated and cleaved with cyanogen bromide. Fragments were isolated and further digested with trypsin and staphylococcal protease. Peptides were isolated by high performance liquid chromatography. Sequences were determined by automated liquid-phase Edman degradation. The complete sequence of the beta subunit (154 amino acids) was established by direct sequencing of the NH2 terminus, sequencing of overlapping peptides, and carboxypeptidase degradation of the COOH terminus. The sequence shows no detectable homologies to other proteins. A computer prediction of secondary structure elements indicates 34% alpha helix and 30% beta sheet.

Amino Acid Sequence↗
PubMed1986

Heavy riboflavin synthase from Bacillus subtilis. Quaternary structure and reaggregation.

Heavy riboflavin synthase of Bacillus subtilis was purified by a simplified procedure. The enzyme is a complex protein containing about 3 alpha-subunits (23.5 X 10(3) Mr) and 60 beta-subunits (16 X 10(3) Mr). The 10(6) Mr protein dissociates upon exposure to pH values above neutrality. Phosphate ions increase the stability at neutral pH. The dissociation induced by exposure of the enzyme to elevated pH is reversible in phosphate buffer at neutral pH. The stability of the enzyme at elevated pH values is greatly enhanced by the substrate analogue, 5-nitroso-6-ribitylamino-2,4(1H, 3H)-pyrimidinedione. Electron micrographs of negatively stained enzyme specimens show spherical particles with a diameter of 15.6 nm. Various immunochemical methods show that the alpha-subunits are not accessible to antibodies in the native molecule. The native enzyme is not precipitated by anti-alpha-subunit serum, and riboflavin synthase activity is not inhibited by the serum. However, these tests become positive at pH values that lead to dissociation of the enzyme. Subsequent to dissociation of the native enzyme at elevated pH values, the beta-subunits form high molecular weight aggregates. These aggregates form a complex mixture of different molecular species, which sediment at velocities of about 48 S and 70 S. The average molecular weight was approximately 5.6 X 10(6). Homogeneous preparations have not been obtained. Electron micrographs show hollow, spherical vesicles with diameters of about 29 nm. The substrate analogue 5-nitroso-6-ribitylamino-2,4(1H, 3H)-pyrimidinedione can induce the reaggregation of isolated beta-subunits with formation of smaller molecules, which are structurally similar to native riboflavin synthase. A homogeneous preparation of reaggregated molecules was obtained by renaturation of beta-subunits from 6.4 M-urea in the presence of the ligand. The sedimentation velocity of this aggregate is about 7% smaller than that of the native enzyme. The molecular weight is 96 X 10(4). Electron micrographs show spherical particles with a diameter of about 17.4 nm. Inspection of the micrographs tentatively suggests the presence of a central cavity. It appears likely that these molecules, which are devoid of alpha-subunits, have the same number and spatial arrangement of beta-subunits as the native enzyme. All data are consistent with the hypothesis that the native enzyme consists of a central core of alpha-subunits surrounded by a capsid-like arrangement of beta-subunits. The number of beta-subunits and the shape of the protein suggest a capsid-like arrangement of beta-subunits.(ABSTRACT TRUNCATED AT 400 WORDS)

Bacillus subtilis↗