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Biomedical subjects

A Goldmann

Publications and source records attributed to A Goldmann.

At least 19 recordsLinked to original sources
PubMed1996

Biological activities of the nortropane alkaloid, calystegine B2, and analogs: structure-function relationships.

Calystegines, polyhydroxy nortropane alkaloids, are a recently discovered group of plant secondary metabolites believed to influence rhizosphere ecology as nutritional sources for soil microorganisms and as glycosidase inhibitors. Evidence is presented that calystegines mediate nutritional relationships under natural conditions and that their biological activities are closely correlated with their chemical structures and stereochemistry. Assays using synthetic (+)- and (-)-enantiomers of calystegine B2 established that catabolism by Rhizobium meliloti, glycosidase inhibition, and allelopathic activities were uniquely associated with the natural, (+)-enantiomer. Furthermore, the N-methyl derivative of calystegine B2 was not catabolized by R. meliloti, and it inhibited alpha-galactosidase, but not beta-glucosidase, whereas the parent alkaloid inhibits both enzymes. This N-methyl analog therefore could serve to construct a cellular or animal model for Fabry's disease, which is caused by a lack of alpha-galactosidase activity.

Bacteria↗
PubMed1995

Tissue characterisation of atherosclerotic carotid plaques by MRI.

Carotid artery plaques with intraplaque haemorrhage or atheromatous debris have been found to be associated with an increased risk of embolic stroke. Other methods have failed to detect plaque morphology, and it is not clear whether MRI allows differentiation between prognostically and therapeutically relevant plaque types. We examined 17 carotid bifurcation plaques which had been removed in toto by MRI. For quantifying MR signal intensities (I) the contrast-to-noise ratio (CNR) was used: (ITissue-IRef)/SDRef, with normal saline (0.9%) as reference (Ref) and the standard deviation (SD) of the noise. Measurements were correlated with the histopathological appearance of "simple plaques", consisting of fibrous intimal thickening, lipid deposits and/or atheromatous tissue with cholesterol crystals, largely calcified plaques, and "complicated plaques", containing recent intramural haemorrhage or friable atheromatous debris. Significantly different mean CNR could be measured in the three plaque types on T1- and T2-weighted sequences (p < 0.00001) and using the FLASH pulse sequence with a flip angle of 15 degrees (p < 0.001). With the T1-weighted sequence simple plaques showed a CNR of 4.4 +/- 2.3, calcified plaques -4.8 +/- 2.6 and complicated plaques 15.1 +/- 4.3. Using this technique, each single plaque could be correctly classified, an unalterable prerequisite for a clinical application. To date, motion artefacts due to patient movement or insufficiently triggerable vessel pulsation in combination with relative long acquisition times (6-7 min) have limited in vivo investigations. If these problems could be overcome, MRI might become a valuable technique for studying carotid plaque morphology.

Calcinosis↗
PubMed1994

Stereotactic and ultrasound guided minimal invasive surgery of subcortical cavernomas.

The experience of 7 operated patients with cavernous haemangiomas (CHa) and of 2 conservatively treated older patients is reported. There was no further postoperative neurological deficit, although 6 of the 7 patients had the CHa in an eloquent cerebral region. Two of the operated patients (22%) had several bleedings before surgery. In these cases seizures and visual field deficits remained. The relatively low rate of complications in our patient group was possible because an exact preoperative localisation helped to avoid a large traumatisation. This is possible with a stereotactic system or directly by CT guided skin marking. Intraoperative ultrasound was necessary in all cases because there was no landmark at the cerebral surface. The CHa was removed by a transsulcal microsurgical operation. A complete removal of the surrounding haemosiderin rim around the angioma seems necessary to avoid further seizures. The used technique has proved to be a simple and safe minimal invasive method.

Adolescent↗
PubMed1994

Endoscopic fenestration of the 3rd ventricular floor in aqueductal stenosis.

Six endoscopic fenestrations of the 3rd ventricular floor have been performed in patients with stenosis (SAS) of the aqueduct of Sylvius in our institute during the last two years. The endoscopic intraventricular landmarks were the Monro's foramen followed by the mamillary bodies. The fenestration instrument was a monopolar coagulation wire, the dilatation instrument was a balloon catheter. The patients included two newborns and four adults. The two newborns developed a recurrent hydrocephalus after 2 months. The four adults remained well after the operation. The only complication was edema (SIADH syndrome) in one case for 24 hours. Flow sensitised phase MRI showed a mirroring in the prestenotic CSF pulsation curve preoperatively. This, in combination with an increased intraventricular pulsation, is a sign of reduced capacity of the subarachnoid space at the cerebral surface. The postoperative patency of the fenestration with diminished intraventricular pulsation can be demonstrated with ECG retrogated phase MRI. There was a slow and incomplete decrease of the preoperative enlarged ventricular size. This operative method is a low-risk, minimal invasive alternative method to shunt implantation in adults with SAS.

Adult↗
PubMed1993

Calystegins, a novel class of alkaloid glycosidase inhibitors.

The alkaloid extract from roots of naturally growing Convolvulus arvensis, purified by ion-exchange chromatography, showed significant inhibitory activity toward beta-glucosidase and alpha-galactosidase. The demonstrated occurrence of polyhydroxy-nortropane alkaloids, the calystegins, in C. arvensis and their structural similarity to known polyhydroxy alkaloid glycosidase inhibitors, suggested that these might be responsible for the observed activity. Pure calystegins, isolated from transformed root cultures of the related plant species Calystegia sepium, were tested for glycosidase inhibitory activity. The purity of the alkaloids was established by gas chromatography and their identity confirmed by their mass spectrometric fragmentation patterns. The trihydroxy alkaloid, calystegin A3, was a moderately good inhibitor of beta-glucosidase (Ki = 4.3 x 10(-5) M) and a weak inhibitor of alpha-galactosidase (Ki = 1.9 x 10(-4) M). An increased level of hydroxylation, as in the tetrahydroxy calystegins B, consisting of 27% calystegin B1 and 73% calystegin B2, resulted in greatly enhanced inhibitory activity. The calystegins B were potent inhibitors of beta-glucosidase (Ki = 3 x 10(-6) M) and alpha-galactosidase (Ki = 7 x 10(-6) M). These levels of activity are comparable with those of the polyhydroxy indolizidine alkaloids castanospermine and swainsonine toward alpha-glucosidase and alpha-mannosidase, respectively, and of the polyhydroxy pyrrolizidine alkaloid australine toward alpha-glucosidase. The calystegins therefore compose a new structural class of polyhydroxy alkaloids, the nortropanes, possessing potent glycosidase inhibitory properties.

Alkaloids↗
PubMed1993

[The postoperative MR tomographic findings following the removal of a hypophyseal adenoma].

36 patients with pituitary adenomas were examined via MRI to describe physiological changes and to visualise a residual tumour. Pre- and postoperative examinations included T1- and T2-weighted SE sequences. T1-weighted images were obtained in sagittal and coronal orientation pre- and post-Gd-DTPA application and T2-weighted images in coronal orientation. In 12 cases a residual tumour was found. Its signal intensity and contrast enhancement were similar to those of the primary tumour. Implanted material could be distinguished by localisation, decrease in volume and different signal intensity. The behaviour of contrast enhancement was helpful, since implanted material showed a rim enhancement. In our experience a sensitive imaging protocol in the follow-up of operated pituitary adenomas would be an early examination three months postoperatively followed by a control examination after one year. Information on the size and localisation of the primary tumour and the performed operative procedure is essential.

Adenoma↗
PubMed1993

[MR-myelography of the lumbar spine using a PSIF sequence: first experiences].

A rapid gradient-echo acquisition (PSIF) was used to delineate the lumber spine. Because this sequence is heavily T2 weighted the cerebrospinal fluid shows a bright signal, the myelon has a poor signal. 5 healthy volunteers and 5 patients with suspected lumbar disc herniation were examined by this technique. All MR myelograms were compared with spin-echo sequences (sagittal and transversal slices). All lumbar disc herniations which were recognized by MRI were also delineated by MR myelography.

Adult↗
PubMed1992

Plesiomonas shigelloides sepsis and meningoencephalitis in a neonate.

A newborn infant is described who presented with septicaemia and meningoencephalitis caused by Plesiomonas shigelloides, a Gram-negative rod belonging to the family Vibrionaceae. The patient in this case, the first to be documented in Europe, developed multilocular lysis of the brain despite immediate treatment with antibiotics active in vitro. A cranial CT revealed garland-like calcifications and a large amount of medullary necrosis was seen on MRI.

Bacteremia↗
PubMed1992

[Abdominal sonography in primary diagnosis of blunt abdominal trauma].

200 patients with blunt abdominal trauma were scanned by ultrasound primarily. 152 showed a normal sonographic examination. In 24 patients an organic injury was visualised. These 20 splenic injuries, 2 lesions of the kidney, 1 splenic and renal lesion and 1 hepatic and splenic rupture were confirmed by CT in 9 cases, by laparotomy in 9 cases, by sonographic follow-up in 2 cases. 23 patients showed an intraabdominal fluid collection, in 16 patients a decrease was seen by ultrasound. 7 patients were directly operated on because of a visible increase of intraabdominal fluid. The lesions consisted of 3 hepatic ruptures, 2 retroperitoneal bleedings. Ultrasound is a reliable tool in the diagnosis of blunt abdominal trauma on the day of admittance and in the evaluation of injuries in respect of operative or conservative management.

Abdominal Injuries↗
PubMed1992

[Magnetic resonance tomography of the liver with TurboFLASH and segmented acquisition. Fast imaging with flexible image contrast].

The value of a fast imaging sequence in diagnosing focal liver lesions was assessed in 43 patients. The sequence (TurboFLASH with segmented acquisition) allows the acquisition of T1- and T2-weighted images within a breath-hold interval. Lesion-liver contrast was compared with T2-weighted spin-echo, T1-weighted gradient-echo, and single shot TurboFLASH sequences. All lesions that were seen with the latter sequences were also visible on the segmented TurboFLASH images. Contrast on the segmented TurboFLASH images was similar to that of T2-weighted spin-echo sequences and superior to T1-weighted gradient-echo sequences. Signal of fat could be nulled at an inversion time of 10 ms, signal from liver tissue could be nulled at an inversion time of 300 ms. By minimising the liver signal, the lesions could be "highlighted". This was not possible with the other imaging sequences. The segmented TurboFLASH technique allows breath-hold imaging of the liver with arbitrary image contrast. The lesion-liver contrast is comparable to time-consuming T2-weighted spin-echo sequences.

Biopsy, Needle↗
PubMed1992

[Magnetic resonance tomographic imaging of pulsatile CSF movement in communicating hydrocephalus before and after shunt placement].

16 patients with hydrocephalus communicans and 5 healthy volunteers were examined to demonstrate the pattern of the pulsatile CSF flow. After implantation of a CSF shunt system the same patients were examined again to show the influence of the shunt on the CSF pulsations. We used a flow-sensitised, cardiac-gated 2D FLASH sequence and analysed the phase and magnitude images. It could be shown that most patients (n = 12) had a hyperdynamic pulsatile flow preoperatively. After shunt implantation the pulsatile CSF motion and the clinical symptoms were improved in 8 of these patients. MRI of pulsatile CSF flow movement seems to be a helpful noninvasive tool to estimate the prognosis of a shunt implantation in patients with hydrocephalus communicans.

Adult↗
PubMed1992

[Stent-supported percutaneous therapy of iliac vein stenosis following operative thrombectomy and placement of a shunt].

Among 15 patients with acute thrombotic disease of pelvic veins who had been submitted to operative thrombectomy and creation of arteriovenous fistula in the groin, 12 presented with stenotic lesions 3 months later. These stenoses were submitted to percutaneous angioplasty. If angioplasty failed, percutaneous placement of a vascular stent (wall stent) was performed immediately (n = 7). Stenting in cross-over-technique proved practicable in all cases. Secondary stenotic disease in the exclusively dilated area was observed in 3/5 cases and was also treated with a wall stent. In one patient with recurrent stenoses who refused stenting, extended thrombosis occurred after occlusion of the AV-fistula. At mid-term PTA was successful in only two cases. Intimal hyperplasia was observed in only one wall stent treated patient. Percutaneous treatment of iliacal stenoses in patients with postthrombotic syndrome may be performed safely under the protective effect of the fistula. With the presented technique, patency of pelvic veins could be restored in 11/12 patients with postoperative significant venous stenoses.

Adult↗
PubMed1992

Improved time-of-flight MR angiography of the brain with magnetization transfer contrast.

The authors hypothesized that magnetization transfer contrast (MTC) could be used to improve flow contrast in time-of-flight (TOF) magnetic resonance (MR) angiography. Two- and three-dimensional flow-compensated gradient-echo images were obtained with and without MTC. MTC images were obtained by applying low-power radio-frequency (RF) radiation with a frequency offset from the bulk "free" water resonance frequency before the excitation RF pulse. The signal intensity of stationary tissue decreased as the power applied for the MTC pulse was increased. A smaller decrease occurred in venous signal intensity as measured in the superior sagittal sinus, and less change was seen in the arterial signal intensity as measured in the middle cerebral artery. Cerebrospinal fluid showed no MTC effect. The use of MTC improved small-vessel depiction on maximum-intensity projection images. The authors conclude that use of MTC can substantially enhance the quality of TOF MR angiography of the brain.

Adult↗