A new tool for the navigated placement of intracerebral chemotherapy catheters.

OBJECTIVE: The aim of this report is to illustrate a method for the precise placement of chemotherapeutic delivery catheters with the aid of computer-assisted navigation systems. MATERIALS AND METHODS: We have developed a cannula which can be referenced to our navigation system (BrainLab (®)) to advance and position catheters. The cannula has a length of 10 cm. In the case of a ventricular puncture, CSF will drain through holes at the tip and a side port of the cannula to caution the surgeon. The cannula is fixed to the BrainLab (®) adapter ML and navigated with a BrainLab (®) vector vision (®) system. Using the puncture software, the placement is planned and executed. After placing the cannula as planned, the mandrin is removed and the primed catheter moved forward. When resistance is felt the cannula is withdrawn over the catheter. Further catheters can be placed similarly. RESULTS: Initial phantom tests showed a good target accuracy. Clinically we have used the cannula in 7 cases with good accuracy. CONCLUSION: This newly designed tool is easy to handle and well integrated into the navigation system. It provides the means to place catheters precisely to the planned position. Potentially it can be combined with every navigation system using adaptable reference systems.

Structure of Bam HI endonuclease bound to DNA: partial folding and unfolding on DNA binding.

The crystal structure of restriction endonuclease Bam HI complexed to DNA has been determined at 2.2 angstrom resolution. The DNA binds in the cleft and retains a B-DNA type of conformation. The enzyme, however, undergoes a series of conformational changes, including rotation of subunits and folding of disordered regions. The most striking conformational change is the unraveling of carboxyl-terminal alpha helices to form partially disordered "arms." The arm from one subunit fits into the minor groove while the arm from the symmetry related subunit follows the DNA sugar-phosphate backbone. Recognition of DNA base pairs occurs primarily in the major groove, with a few interactions occurring in the minor groove. Tightly bound water molecules play an equally important role as side chain and main chain atoms in the recognition of base pairs. The complex also provides new insights into the mechanism by which the enzyme catalyzes the hydrolysis of DNA phosphodiester groups.

Entry points for catheter placement in convection-enhanced delivery--a retrospective anatomic analysis.

INTRODUCTION: Planning the trajectories for catheter positioning in convection-enhanced delivery (CED) is delicate. The bulk flow follows the path of least resistance. Additional factors such as the varying tumor location and the functional relevance of the surrounding brain areas add to complicate the trajectory planning even further. Therefore several criteria have been established, dealing with the correct general entry and target point position. The goal of our study was to analyze the trajectories for CED catheters placed in our department to find preferable entry point positions. METHODS: We retrospectively looked at 51 trajectories for CED catheters planned with neuronavigation during 2003-2005 for 21 patients with supratentorial malignant gliomas. We evaluated the entry points for their anatomic position, the functional relevance of the area and their parameter to reach the important white matter tracts for CED. This was done using the anatomic literature, macroscopical studies in our laboratory on human autopsy brains and MR imaging. RESULTS: Most tumors were located in the fronto-temporo-parietal region. For these locations catheters were predominantly placed via the superior parietal lobule and the superior frontal gyrus. Looking at the anatomic literature and our laboratory results we characterized these areas with properties predisposing them for catheter placement as having wide superficial gyri and few deep sulci. In addition, they have far less functional relevance than the surrounding eloquent areas. Most relevant white matter tracts can be reached from these entry points. Accordingly, we have defined 2 areas that appear most suitable as entry points in CED catheter placement: the superior parietal lobule and superior frontal gyrus. CONCLUSION: Inserting CED catheter via the described entry points will presumably save time in planning and reduce side effects.

Reversibility of venous sinus obstruction in idiopathic intracranial hypertension.

Elevated intracranial intravenous pressure seems to be of importance in pseudotumor cerebri syndromes, either as a cause (secondary intracranial hypertension) or as a consequence (idiopathic intracranial hypertension) of increased intracranial pressure. We present 3 case reports in which diagnostic imaging before and after CSF diversion provided evidence that narrowing of the transverse sinuses is a secondary phenomenon. Stent angioplasty of the venous sinuses should not be considered a therapeutic approach in these cases.

[Treatment of carotid artery aneurysms with covered stents]. / Aneurysmabehandlung der Arteria carotis interna mit gecoverten Stents.

PURPOSE: Evaluation of the use of covered stents in treating pseudoaneurysms of the cervical and intracranial/extradural carotid artery and determination of the periprocedural and short- to mid-term complication rate. MATERIALS AND METHODS: 8 patients with 9 spontaneous dissecting aneurysms of the cervical carotid artery--5 of which were symptomatic--plus one patient with ofthalmoplegia due to an aneurysm of the cavernous carotid artery were studied. While the latter was treated with a PTFE-covered balloon-mounted stainless steel stent (Jostent/Graftmaster), a self-expanding PTFE-covered Nitonol Stent (Symbiot) was used in all other cases. Intervention was performed with local anesthesia. Aspirin and Clopidogrel were both used as antiplatelet drugs. Clinical signs and symptoms and vascular imaging with DS, MR, CT angiography and ultrasound were recorded during patient follow-up, with a mean follow-up period of 14.6 months (4 - 30). RESULTS: We were able to treat 8 out of 10 aneurysms (80%) using covered stents. The aneurysms were immediately occluded and the associated stenoses of the parent vessel were eliminated. No clinically relevant complications occurred during the procedure or in the follow-up interval. In two cases, elongation of the carotid artery prevented the stent from being positioned over the aneurysm neck. These cases were shown to be stable with the use of antiplatelet drugs. CONCLUSION: Covered stents can be used in the treatment of pseudoaneurysms of the carotid artery as an alternative to long-term antithrombotic medication or surgery. In our study treatment was effective (80%) and free of complications in the short- and mid-term follow-up. Possible indications, technique and the use of imaging modalities for patient follow-up are discussed.

Structure of restriction endonuclease bamhi phased at 1.95 A resolution by MAD analysis.

BACKGROUND: Type II restriction endonucleases recognize DNA sequences that vary between four to eight base pairs, and require only Mg2+ as a cofactor to catalyze the hydrolysis of DNA. Their protein sequences display a surprising lack of similarity, and no recurring structural motif analogous to the helix-turn-helix or the zinc finger of transcription factors, has yet been discovered. RESULTS: We have determined the crystal structure of restriction endonuclease BamHI at 1.95 A resolution. The structure was solved by combining phase information derived from multi-wavelength X-ray data by algebraic and maximum likelihood methods. The BamHI subunit consists of a central beta-sheet with alpha-helices on both sides. The dimer configuration reveals a large cleft which could accommodate B-form DNA. Mutants of the enzyme that are deficient in cleavage are located at or near the putative DNA-binding cleft. BamHI and endonuclease EcoRI share a common core motif (CCM) consisting of five beta-strands and two helices. It remains to be determined if other restriction enzymes also contain the CCM. CONCLUSIONS: The structure of BamHI provides the first clear evidence that there may be substantial structural homology amongst restriction enzymes, even though it is undetectable at the sequence level.

A mutant of BamHI restriction endonuclease which requires N6-methyladenine for cleavage.

Amino acid residues Asn116 and Ser118 of the restriction endonuclease BamHI make several sequence-specific and water-bridged contacts to the DNA bases. An in vivo selection was used to isolate BamHI variants at position 116, 118 and 122 which maintained sequence specificity to GGATCC sites. Here, the variants N116H, N116H/S118G and S118G were purified and characterized. The variants N116H and N116H/S118G were found to have lost their ability to cleave unmethylated GGATCC sequences by more than two orders of magnitude, while maintaining nearly wild-type levels of activity on the N6-methyladenine-containing sequence, GGmATCC. In contrast, wild-type BamHI and variant S118G have only a three- to fourfold lower activity on unmethylated GGATCC sequences compared with GGmATCC sequences. The N116 to H116 mutation has effectively altered the specificity of BamHI from an endonuclease which recognizes and cleaves GGATCC and GGmATC, to an endonuclease which only cleaves GGmATCC. The N116H change of specificity is due to the lowered binding affinity for the unmethylated sequence because of the loss of two asparagine-DNA hydrogen bonds and the introduction of a favorable van der Waals contact between the imidazole group of histidine and the N6-methyl group of adenine.

Genetic analysis of the base-specific contacts of BamHI restriction endonuclease.

Here, we investigate the highly specific interaction of the BamHI endonuclease with its cognate recognition sequence GGATCC by determining which amino acid residues can be substituted at the DNA interface while maintaining specificity. Mutational studies, together with the structural determination of the restriction endonuclease BamHI have revealed the amino acid residues which are involved in DNA catalysis and those which play a role in the specific binding of the enzyme to its cognate DNA recognition sequence. Amino acid residues N116, S118, R122, D154 and R155 are involved in DNA sequence recognition and are located in the major groove in close proximity to the nucleotide bases comprising the recognition sequence. Cassette mutagenesis of these amino acids, together with in vivo transcriptional interference selection, was used to identify an array of substitutions which maintain site-specific binding to the cognate GGATCC sequence. This approach has demonstrated the extent of acceptable variation among amino acid residues which are directly involved in site-specific binding. One variant, double mutant N116H, S118G was found to cleave DNA only when the adenine base in the recognition site is methylated.

The energetics of the interaction of BamHI endonuclease with its recognition site GGATCC.

The interaction of BamHI endonuclease with DNA has been studied crystallographically, but has not been characterized rigorously in solution. The enzyme binds in solution as a homodimer to its recognition site GGATCC. Only six base-pairs are directly recognized, but binding affinity (in the absence of the catalytic cofactor Mg(2+)) increases 5400-fold as oligonucleotide length increases from 10 to 14 bp. Binding is modulated by sequence context outside the recognition site, varying about 30-fold from the bes t (GTG or TAT) to the worst (CGG) flanking triplets. BamHI, EcoRI and EcoRV endonucleases all have different context preferences, suggesting that context affects binding by influencing the free energy levels of the complexes rather than that of the free DNA. Ethylation interference footprinting in the absence of divalent metal shows a localized and symmetrical pattern of phosphate contacts, with strong contacts at NpNpNpGGApTCC. In the presence of Mg(2+), first-order cleavage rate constants are identical in the two GGA half-sites, are the same for the two nicked intermediates and are unaffected by substrate length in the range 10-24 bp. DNA binding is strongly enhanced by mutations D94N, E111A or E113K, by binding of Ca(2+) at the active site, or by deletion of the scissile phosphate GpGATCC, indicating that a cluster of negative charges at the catalytic site contributes at least 3-4 kcal/mol of unfavorable binding free energy. This electrostatic repulsion destabilizes the enzyme-DNA complex and favors metal ion binding and progression to the transition state for cleavage.

Crystallization and preliminary X-ray analysis of restriction endonuclease BamHI-DNA complex.

Restriction endonuclease BamHI from Bacillus amyloliquefaciens has been co-crystallized with a 12 bp DNA fragment that encompasses its recognition site. The co-crystals diffract to at least 1.95 A resolution and belong to space group P2(1)2(1)2(1). The unit cell parameters are a = 108.8 A, b = 81.9 A, c = 68.8 A, consistent with one complex in the crystallographic asymmetric unit. The direction of the DNA appears to be along the b axis. In order to achieve end to end stacking of DNA, the complex must lie on the screw axis along b. A self-rotation function has determined the directions of the non-crystallographic 2-fold axes.

Cloning, analysis and expression of the HindIII R-M-encoding genes.

The genes encoding the HindIII restriction endonuclease (R.HindIII ENase) and methyltransferase (M.HindIII MTase) from Haemophilus influenzae Rd were cloned and expressed in Escherichia coli and their nucleotide (nt) sequences were determined. The genes are transcribed in the same orientation, with the ENase-encoding gene (hindIIIR) preceding the MTase-encoding gene (hindIIIM). The two genes overlap by several nt. The ENase is predicted to be 300 amino acids (aa) in length (34,950 Da); the MTase is predicted to be 309 aa (35,550 Da). The HindIII ENase and MTase activities increased approx. 20-fold when the genes were brought under the control of an inducible lambda pL promoter. Highly purified HindIII ENase and MTase proteins were prepared and their N-terminal aa sequences determined. In H. influenzae Rd, the HindIII R-M genes are located between the holC and valS genes; they are not closely linked to the HindII R-M genes.

Crystallization and preliminary X-ray analysis of restriction endonuclease FokI bound to DNA.

FokI is a type IIs restriction endonuclease which recognizes an asymmetric DNA sequence and cleaves DNA a short distance away from the sequence. The enzyme is bipartite in nature with its DNA recognition and cleavage functions located on distinct domains. We report here cocrystals of the complete FokI enzyme (579 amino acids) bound to a 20-bp DNA fragment containing its recognition sequence. The complex is amongst the largest protein-DNA complexes to be crystallized, and required macroseeding techniques for optimal crystal growth. The cocrystals diffract to at least 2.8 A in resolution and belong to space group P2(1) with unit cell dimensions of a=67.9 A, b=119.8 A, c=69.1 A, beta = 96.6 degrees. Using specific amino acid analysis we show that asymmetric unit contains a single FokI molecule bound to the 20-bp DNA fragment. This paper reports the first cocrystals of a type IIs restriction endonuclease.

Inhibition of GABAergic inhibitory postsynaptic currents by cannabinoids in rat corpus striatum.

Electrophysiological consequences of activation of cannabinoid receptors have been mostly investigated on neuronal cell lines and on cells transfected with cannabinoid receptors. The aim of the present experiments was to study cannabinoid effects on identified neurons in situ. Electrically-evoked postsynaptic currents and voltage-dependent calcium currents were investigated in the principal neurons of the corpus striatum, the medium spiny neurons, with the patch-clamp method for brain slices. These neurons were chosen because they produce messenger RNA for cannabinoid receptors and because the density of cannabinoid binding sites in the striatum is high. Activation of muscarinic receptors by carbachol (10(-5) M) reduced inhibitory postsynaptic current amplitude by 67%. The synthetic cannabinoid receptor agonist R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4- benzoxazin-yl]-(1-naphtalenyl)methanone (WIN55212-2; 10(-8) to 10(-5) M) dose-dependently reduced striatal inhibitory postsynaptic currents; the maximum effect, inhibition by 52%, was observed at 10(-6) M. Another cannabinoid agonist, (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydr oxypropyl)cyclohexanol (CP55940; 10(-6) M), also reduced inhibitory postsynaptic currents, by 50%. The CB1 cannnabinoid receptor antagonist N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)4-methyl-3-pyra zolecarboxamide (SR141716A; 10(-6) M) had no effect when given alone but abolished the effect of WIN55212-2 (10(-6) M). WIN55212-2 (10(-6) M) did not change the current evoked by the GABA(A)-receptor agonist muscimol (10(-6) M). Activation of muscarinic receptors by carbachol (10(-5) M) inhibited voltage-dependent calcium currents by 21%, but the cannabinoid receptor agonist WIN55212-2 (10(-6) M) was without effect. The results show that activation of CB1 cannabinoid receptors reduces GABAergic inhibitory postsynaptic currents in medium spiny neurons of the corpus striatum: the likely mechanism is presynaptic inhibition of GABA release from terminals of recurrent axons of the medium spiny neurons themselves.

Neuropsychological testing to improve surgical management of patients with chronic hydrocephalus after shunt treatment.

AIM: To find out a practical neuropsychological tool for early and reliable outcome assessment in chronic hydrocephalus. In 30 patients (65 +/- 13 yrs.) 11 neuropsychological tests providing a wide range of psychomotor functions (visual and verbal attention, verbal memory and learning and visuomotor skills) were applied before (pre), one week (early) and 7 months (late) after shunting. After 7 months, clinical outcome was classified according to Stein and Langfitt. Statistics included factor analysis, logistic regression and non-parametric tests. Visual attention ("Digit-symbol"), verbal recall ("10-words-list") and motor precision ("line-tracing") were the most representative (and practical) tests (orthogonal loads > 0.9). These tests, in contrast to others, revealed significant differences between outcome groups concerning early postoperative changes: responder showed marked improvement in visual attention t-scores (47 +/- 8 vs. 41 +/- 8 (pre); p = 0.005) and motor precision scores (109 +/- 26 vs. 149 +/- 47 (pre); p = 0.03). Non-responder even decreased in verbal recall t-scores early after shunting (35 +/- 7 vs. 41 +/- 11 (pre); p = 0.007). By logistic regression, visual attention was most sensitive indicating shunt-response by early psychometric changes (p = 0.04). Psychomotor deficits in hydrocephalic patients can be represented by a few neuropsychological skills: visual attention, verbal recall and line tracing. Since they showed early post-operative differences regarding long-term response to shunting they may offer a practical and standardised method for reliable follow-up.

A case of ameloblastic carcinoma with pulmonary metastases.

A case initially thought to be ameloblastoma of the mandible which showed rapid local destruction and was demonstrated to have three pulmonary metastases post mortem 18 months after the first symptoms in the mandible. The diagnosis is now considered to be ameloblastic carcinoma. The difficulties in histological diagnosis and varying classifications of malignant odontogenic tumours is noted.

Differentiation of primary central nervous system lymphomas from high grade astrocytomas by qualitative analysis of the signal intensity curves derived from dynamic susceptibility-contrast magnetic resonance imaging.

OBJECTIVE: Preoperative differentiation between primary central nervous system lymphoma (PCNSL) and high grade astrocytoma (HGA) on conventional magnetic resonance imaging (MRI) can be difficult and even impossible. However, differentiation is important to guide therapeutic strategy. Several authors have reported the leakage pattern in dynamic susceptibility-contrast (DSC)-MRI in PCNSL. It describes the shape of the signal intensity curve which does not return to the baseline after the first pass of the bolus of contrast agent but crosses above it and sometimes even slopes up. In this retrospective study, our goal was to define the sensitivity and specificity of this sign. MATERIAL AND METHODS: Patients with first ever diagnosed PCNSL and HGA who were treatment naive and received DSC-MRI were included. In all patients, a histological specimen was available. Patients did not receive corticosteroids prior to imaging and were HIV negative. The presence of a leakage pattern was assessed by two neuroradiologists working in consensus and correlated with the histological diagnosis. RESULTS: Nine patients with PCNSL (2 women, 7 men, age 59 ± 10 years) and 14 patients with HGA (3 women, 11 men, age 58 ± 17 years) were included. Six of the patients with PCNSL exhibited a leakage pattern, while only two patients with HGA did (P = 0.0227, Fischer's exact test). Sensitivity was 0.67, and specificity was 0.86. DISCUSSION: Although the leakage pattern does not prove PCNSL, it is an important diagnostic clue and can be easily assessed.

Does routine MR contrast enhancement correlate with internal thrombosis in cerebral cavernous malformations? A radiological-histopathological correlation in a case series.

OBJECTIVES: It is well known that cerebral cavernous malformations (CCMs) present with variable degrees of contrast enhancement on routine magnetic resonance imaging (MRI) studies. This is attributed to the presence of a low flow vascular architecture in these lesions. The aim of this preliminary study was to determine whether an additional reason for the different degree of contrast enhancement could be the degree of internal thrombosis. MATERIAL AND METHODS: Fourteen consecutive patients with surgically removed CCMs were included. In all patients, standard preoperative MRI (1.5 Tesla, T1 weighted images without and with contrast agent, slice thickness 5 mm, 0.1 mmol gadolinium/kg body weight, and delay ∼5 minutes) and a histological specimen were available. The degree of contrast enhancement (none, little, moderate, and marked) was rated by two independent neuroradiologists blinded to the results of histopathology. The degree of internal thrombosis (none, little, moderate, and marked) was rated by a neuropathologist blinded to the results of MRI. RESULTS: Contrast enhancement was visible in six (43%) CCMs (Cohen's κ = 0.76 or substantial). The degree of contrast enhancement was not dependent on the degree of internal thrombosis (P = 0.1, Fisher's exact test) and did not correlate with it (r = 0.06, P = 0.83, Pearson's correlation coefficient). CONCLUSION: The flow characteristics of CCMs seem to be the main factor contributing to the degree of contrast enhancement while the degree of internal thrombosis does not influence their contrast affinity.

A subarachnoid haemorrhage primarily presenting as Terson's syndrome.

We present a case of a subarachnoid haemorrhage due to a ruptured basilar artery aneurysm in a 61-year-old woman. She presented with visual deterioration as the only clinical sign, no previous episodes of headache were reported. Fundoscopy showed a bilateral vitreous haemorrhage. A consecutively performed cranial computer tomography demonstrated subarachnoid bleeding. Further diagnostics revealed a basilar artery aneurysm that was successfully treated with coil embolisation. As a scarring of the vitreous bodies developed, they had to be removed. The patient's eyesight improved gradually and no further complications occurred.

Acute subdural hematoma in the elderly; clinical and CT factors influencing the surgical treatment decision.

OBJECTIVE: Acute subdural hematomas (aSDH) are severe traumatic brain injuries. Older patients have a higher mortality rate. In the present study the computed tomography (CT) and neurological deficits caused by aSDH were used as prognostic factors to define the outcome and surgical treatment indication in older patients. METHODS: The affect of the Glasgow Coma Scale (GCS) score on initial presentation, pupil abnormalities, parenchymal lesions, SDH-thickness, midline shift and intracranial pressure (ICP) in the outcome of older patients (>or=65 years old) admitted to our hospital between 1993 and 2006 with aSDH was evaluated. The outcome was assessed with the Glasgow Outcome Scale (GOS). The data were collected retrospectively. Statistical analysis was performed with Chi-square test and ANOVA. RESULTS: Older patients have a high mortality after aSDH. A low GCS score (3-8), pupil abnormalities, the presence of contusions and subarachnoid bleeding, midline shift>aSDH thickness as well as a highly elevated ICP>40 mmHg are unfavorable factors in the prognosis of aSDH. CONCLUSION: Patients with a GCS of 13-15 can be observed clinically (the expected outcome is very good). Comatose patients (GCS 3-8) with bilateral dilatation of the pupils should not be operated (very high mortality rate). If the GCS score is <13 and both pupils or only one are reactive to light and the midline shift<10 mm, surgery is indicated. If the midline shift is >10 mm and aSDH thickness>midline shift, surgery is also indicated. If in the same patient group midline shift>SDH thickness and ICP>40 mmHg, surgery is not indicated.