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Biomedical subjects

M Schwarz

Publications and source records attributed to M Schwarz.

At least 271 records · Page 15Linked to original sources

Quinolinic acid lesion of the striatum induces impairment in spatial learning and motor performance in rats.

Injection of quinolinic acid (QA) into the striatum of rats is known to produce neuropathological and neurochemical alterations similar to those observed in Huntington's disease (HD). One clinical feature of HD patients is cognitive impairment. Two weeks after stereotaxic injection of either QA (240 nmol) or solvent in rats spatial learning was tested in the Morris water maze. QA lesioned animals required more time to find the hidden platform. The swim speed was reduced in all trials compared to the controls. The swim distance itself was longer and the amount of swim distance along the side wall was significantly higher in QA lesioned rats. The present results suggest that QA lesion of the striatum leads to deficit in motor performance and in spatial learning.

Animals↗

Comparison of somatosensory evoked potentials with striatal glucose consumption measured by positron emission tomography in the early diagnosis of Huntington's disease.

Both somatosensory evoked potentials (SEP) and striatal glucose consumption (rCMRGlc) measured by positron emission tomography (PET) have been reported to be abnormal early in the course of Huntington's disease (HD). To compare their diagnostic value, SEP and rCMRGlc were measured in a group of 18 first degree off-spring of HD families: 6 had manifest HD with chorea and the remaining 12 individuals were chorea-free subjects at risk for HD. In five patients with manifest disease, both SEP and striatal rCMRGlc were significantly abnormal, defined in SEP as having either a bilaterally absent frontal N30 amplitude or a reduction of the parietal N20/P25 amplitude below 1 microV on at least one side; in PET as exhibiting a reduction of the cerebellar ratio (CR) of both caudate and lentiform rCMRGlc below the 99% confidence limits of these variables determined in 20 normal volunteers. The remaining patient with manifest HD had questionably abnormal SEP and significantly reduced indices of striatal rCMRGlc. The five persons at risk for HD who had normal SEP also had normal striatal rCMRGlc; those three at-risk patients with abnormal SEP also had a reduction of the CR of both caudate and lentiform rCMRGlc. Of the remaining four individuals at risk for HD who had questionably abnormal SEP, three had CR values of striatal rCMRGlc in the normal range and one a reduction of the CR of lentiform rCMRGlc. In at-risk patients, the SEP diagnosis correlated significantly with caudate (r = -0.8; p < 0.002) and lentiform (r = -0.76; p < 0.005) rCMRGlc. These data indicate a parallel deterioration of SEP and striatal rCMRGlc early in the course of HD even before the development of chorea.

Adult↗

Remote microglial activation in the quinolinic acid model of Huntington's disease.

Intrastriatal injection of quinolinic acid (QA) in the rat leads to several structural and biochemical events which resemble neuropathological changes seen in the striatum of Huntington's disease patients. In the present experiment the accompanying microglial response in striatal projection areas following QA injection was studied immunocytochemically using monoclonal macrophage/microglial markers. After injection of 240 nmol of QA a marked microglial reaction was observed in the entire striatum, whereas injection of the same amount of solvent resulted only in a local microglial reaction around the injection site. Activated microglia were also found in the globus pallidus (GP), the entopeduncular nucleus (EP), the substantia nigra (SN), and the ventroanterior/ventrolateral, the ventromedial, and, in some rats, the reticular thalamic nucleus. The remote microglial reaction started in the first-order projection areas at Day 1 (GP) or Day 3 (EP, SN) and was found in the second-order projection areas (thalamic nuclei) by Day 5. Areas projecting to the striatum such as the amygdala and intralaminar thalamic nuclei remained free of activated microglia. It is concluded that a microglial response in striatal projection areas accompanies excitotoxic striatal injury. Anterograde degeneration of striatal projection neurons can explain the microglial activation in first-order projection areas but other mechanisms such as neuronal hyperexcitation following removal of inhibitory striatal input must be responsible for the rapid transsynaptic microglial activation seen in the thalamus.

Animals↗

Surgical treatment of posterior fossa tumors in infancy and childhood: techniques and results.

In a collective of 72 children with tumors of the posterior fossa, the preoperative diagnosis, operation planning and performance, and use of additional procedures, like the preliminary ventricular drainage and interventriculostomy are described. The extent of intra- and postoperative complications is given. Postoperative lethality was 0% in the group operated on between 1979 and 1991. The responsible factors are discussed. The findings support the opinion of ALBRIGHT (1989) that the prognosis for such patients is most promising in the hands of a specialist in pediatric neurosurgery.

Adolescent↗

Tethered cord after spina bifida aperta: a longitudinal study of somatosensory evoked potentials.

Progressive neurological deterioration may occur after meningomyelocele repair. Magnetic resonance imaging almost invariably demonstrates a conus medullaris in an abnormally low position, whether neurological symptoms develop or not. Surgery of a secondary tethered cord is indicated when progression of neurological symptoms is documented. We performed a longitudinal study of posterior tibial nerve somatosensory evoked potentials (SSEPs) in children and adolescents after neonatal meningomyelocele repair. All patients were able to walk. Declining or negative posterior tibial nerve SSEPs were recorded in 15 patients; 14 of these had clinical signs of a secondary tethered cord. After surgery of the tethered cord, the SSEPs improved in 8 of 10 patients. Posterior tibial nerve SSEPs may contribute to the diagnosis of secondary tethered cord. After untethering, the evoked potentials demonstrate recovery of spinal cord function and might help to delineate prognosis.

Adolescent↗

The operative treatment of spinal deformities in MMC.

The results of the operative treatment of scoliosis in 12 patients with MMC and in two patients with associated severe kyphosis are presented. In scoliosis only multi-segmental methods combined with ventral procedures allow a postoperative care without brace or cast. The angle before and after operation with the CDI or CDI/VDS procedures averaged 80.3 degrees and 38.2 degrees respectively (mean corrections of 41.5 degrees and 51.6%). The results show that patients with scoliosis with MMC had a approximately 30% greater preoperative angle than patients with idiopathic scoliosis. An early operation (in progressive curves with more than 30 degrees) may reduce the number and severity of complications.

Adolescent↗

Development of scoliosis in myelomeningocele. Differences in the history caused by idiopathic pattern.

The natural history of scoliosis in the literature concerning the idiopathic and neuromuscular scoliosis in myelomeningocele patients (MMC) are compared to our own results in 12 patients with MMC and 89 patients operated because of an idiopathic scoliosis. According to known experiences the natural history of scoliosis in MMC is progression even after the end of growth. The chance of developing a scoliosis increases with the patients, age and the level of the lesion. The higher the level of paralysis the more common is a spinal deformity. In literature the progression rate of MMC scoliosis is 2.5-3.5 degrees per year, with the idiopathic pattern 0.5-0.65 degrees per year after end of growth. Our own results of surgically treated patients show a rate of progression of 6.2 degrees per year in MMC. The surgical treatment must start before a severe spinal deformity has developed because of the higher rate of operative complications.

Adolescent↗

A further case of acute nonlymphocytic leukemia with tetrasomy 8.

In very rare patients tetrasomy of chromosome 8 is observed as the only karyotypic event. We present a 74-year-old man with acute monocytic leukemia (FAB M5) displaying 46,XY/48,XY, +8, +8 in unstimulated bone marrow cells. The patient died 2 weeks after diagnosis. Tetrasomy 8 appears to identify a subgroup of acute nonlymphocytic leukemia. It may indicate a poor prognosis.

Aged↗

Non-NMDA-mediated transmission of somatosensory-evoked potentials in the rat thalamus.

Somatosensory-evoked potentials (SEPs) were recorded from the somatosensory cortex of pentobarbital-anesthetized rats, in response to single electrical stimulation of the contralateral forelimb. The effects of microapplication of the selective N-methyl-D-aspartate (NMDA) antagonist, (-)-2-Amino-7-phosphonoheptanoate (AP7), and of the specific non-NMDA antagonist, 6,7-Dinitro-quinoxaline-2,3-dione (DNQX), in the ventrobasal thalamic nucleus on the amplitudes and latencies of cortical potentials were measured. The injection of DNQX resulted in a decrease in amplitude and an increase in the latency of cortical SEPs. These effects were a) dose dependent over the range 0.1 to 1.0 nmol, b) specific for non-NMDA receptors, and c) site specific. In contrast, microapplications of AP7 did not affect the SEPs. The present findings support the hypothesis that non-NMDA receptors in the ventrobasal thalamic nucleus are involved in the transmission of cortical SEPs.

Anesthesia↗

Cost-benefit analysis of the work-up for pancreatic cancer.

We reviewed the records of 126 patients with pancreatic cancer to assess the value of diagnostic tests. The most commonly performed studies were computed tomography (CT) (97% of patients), endoscopic retrograde cholangiopancreatography (ERCP) (44%), and fine-needle aspiration (FNA) (41%). Of 34 patients who were found to have a mass in the body or tail of the pancreas on CT, 13 underwent ERCP; the results found by ERCP did not affect the management of the patients, whereas the results of FNA in 12 patients eliminated the need for operation. Of 14 patients with suspected metastases as evidenced by CT, the results of 3 ERCPs had no impact, whereas 5 of 7 patients who had FNAs avoided operation. Of five patients with normal results on CT, three had an ERCP that identified tumor. Of 26 patients with atypical CTs, the results of 12 of 16 ERCPs and 3 of 5 FNAs confirmed cancer. In contrast, in 48 patients with a mass in the head of the pancreas and biliary dilatation, ERCP did not alter the patients' management; only 3 of 14 patients who had FNAs avoided operation. Thus, the results of ERCP rarely altered the management of the patient when the CT showed a mass but was useful when the scan was normal or atypical. FNA was helpful in patients with cancer in the body or tail of the pancreas or with suspected metastases and in confirming the diagnosis when the CT was inconclusive.

Adenocarcinoma↗

Absence of frontal somatosensory evoked potentials in Huntington's disease.

A fast route for transmission of deep and cutaneous afferent information to the frontal cortex is well established in non-human primates. Whether the incoming cortical information gives rise to early frontal somatosensory evoked potentials (SEPs) in humans is still a matter of contention. We attempted to solve this question by investigating the topography of SEP generators evoked by median nerve stimulation in 30 healthy subjects and in 30 patients suffering from Huntington's disease, who are known to have reduced SEP amplitudes. Using an earlobe reference, SEPs were recorded with an array of either five surface electrodes over the contralateral parietal cortex or 32 electrodes distributed over the whole scalp. In normal subjects analysis of frontal potentials revealed an early positive (P22) and negative (N30) component which could not be explained by generators located in the parietal cortex. Apart from the reduction of parietal components (N20, P25) frontal P22 and N30 were diminished or absent in Huntington's disease patients. Frontal potentials were even reduced in those patients who had parietal SEP amplitudes within the range of normal subjects. These frontal changes are similar to those reported in other basal ganglia disorders. Basal ganglia dysfunction might therefore be associated with changes of frontal SEP components.

Adult↗

Development of hydroxysteroid sulfotransferase-deficient lesions during hepatocarcinogenesis in rats.

Rat liver cytosolic hydroxysteroid sulfotransferases form highly reactive sulfuric acid esters from some benzylic alcohols, such as 1-hydroxymethylpyrene. In this study we examined the expression of hydroxysteroid sulfotransferase a (STa) in carcinogen-induced enzyme-altered, presumably preneoplastic, rat liver foci. Female Wistar rats were given a single i.p. injection of diethylnitrosamine (0.15 mumol/g body wt) 1 day after birth to induce the liver foci. After weaning, rats were given 1-hydroxymethylpyrene or phenobarbital continuously in their diet (250 or 500 p.p.m. respectively) for a total of 120 days. Carcinogen-induced liver foci were identified by a change in the marker enzyme adenosine triphosphatase. Immunohistochemical staining of consecutive sections using an anti-STa rabbit antibody demonstrated that STa was expressed at decreased levels in most of the adenosine triphosphatase-negative liver foci. This effect was observed in both 1-hydroxymethylpyrene- and phenobarbital-treated animals. The decrease in STa content in enzyme-altered foci may lead to a selective advantage of the preneoplastic cells in the presence of agents that are able to form reactive sulfuric acid esters, such as 1-hydroxymethylpyrene. In some diethylnitrosamine/phenobarbital-treated rats, a small number of atypical foci were observed, most of them showing enhanced expression of STa and unchanged to moderately increased ATPase activity.

Adenosine Triphosphatases↗

N-methyl-D-aspartate (NMDA)-mediated muscle relaxant action of dextromethorphan in rats.

The present study examined whether the antitussive agent dextromethorphan, which is an antagonist at the N-methyl-D-aspartate (NMDA) receptor, depresses spinal reflexes in rats. Injection of both the specific NMDA antagonist (-)-2-amino-7-phosphonoheptanoate and of dextromethorphan dose-dependently reduced the magnitude of the polysynaptic flexor reflex without affecting the monosynaptic H-reflex. In contrast, the non-NMDA antagonist 6,7-dinitroquinoxaline-2,3-dione depressed the H-reflex in a dose-dependent manner without affecting the flexor reflex. The depressant effect of dextromethorphan on the flexor reflex was prevented by co-administration with NMDA but not with the non-NMDA agonist alpha-amino-3-hydroxy-5-terthyl-4-isoxazole-propionic acid. These data suggest that dextromethorphan exerts a muscle relaxant action via the NMDA receptor.

2-Amino-5-phosphonovalerate↗

Impaired acetylcholine-mediated vasodilation in patients with congestive heart failure. Role of endothelium-derived vasodilating and vasoconstricting factors.

BACKGROUND: The vasodilatory response to intra-arterial administration of acetylcholine is reduced in patients with congestive heart failure compared with that of normal subjects. The reduced response to acetylcholine may be related to decreased endothelial release of nitric oxide, interaction with peripheral alpha-adrenergic transmission, or production of cyclooxygenase-dependent vasoconstricting substances. The extent to which each of these mechanisms contributes to the reduced vasodilatory response to acetylcholine in patients with congestive heart failure is not known. METHODS AND RESULTS: Thirty-one patients with congestive heart failure (New York Heart Association functional class II-III) and five age-matched normal subjects were studied. Regional vascular responses in the forearm to infusions of acetylcholine, an endothelium-dependent vasodilator (10(-7) to 10(-5) mol/L) and nitroglycerin, an endothelium-independent vasodilator (10(-6) mol/L) in the brachial artery were determined with venous occlusion plethysmography before and after regional alpha-adrenergic blockade with intra-arterial phentolamine (25 micrograms/min) and systemic cyclooxygenase with oral indomethacin (50 mg). Administration of phentolamine significantly increased resting baseline forearm blood flow in 11 patients with congestive heart failure (2.9 +/- 0.4 to 5.4 +/- 0.8 mL.min-1.100 mL-1) and normal subjects (4.6 +/- 0.3 to 11.3 +/- 2.1 mL.min-1.100 mL-1). Before administration of phentolamine, intra-arterial infusions of acetylcholine 10(-7), 10(-6), and 10(-5) mol/L increased forearm blood flow to 4.0 +/- 1.0, 6.0 +/- 1.7, and 16.1 +/- 4.0 mL.min-1.100 mL-1, respectively, in patients with congestive heart failure and to 14.7 +/- 6.2, 20.2 +/- 4.7, and 38.7 +/- 7.9 mL.min-1.100 mL-1, respectively, in normal subjects. After administration of phentolamine, the vasodilatory responses to intra-arterial infusions of acetylcholine and nitroglycerin did not change in either patients or normal subjects. Administration of indomethacin did not alter resting forearm blood flow in 15 patients with congestive heart failure (2.7 +/- 0.4 to 2.7 +/- 0.4 mL.min-1.100 mL-1) or normal subjects (4.6 +/- 0.3 to 5.4 +/- 0.8 mL.min-1.100 mL-1). Administration of indomethacin significantly increased the vasodilatory response to infusion of acetylcholine by an average of 39% in patients with congestive heart failure but did not change the vasodilatory response to acetylcholine in normal subjects. In patients with congestive heart failure, baseline forearm blood flow and the vasodilatory responses to intra-arterial infusions of acetylcholine and nitroglycerin were significantly less than those of normal subjects both before and after administration of phentolamine and indomethacin. CONCLUSIONS: The reduced vasodilatory response to intra-arterial infusion of acetylcholine in patients with congestive heart failure probably results from several coexistent abnormalities in peripheral vascular function, including abnormal production of cyclooxygenase-dependent vasoconstricting factor, impaired endothelial release of nitric oxide, and decreased vascular smooth muscle responsiveness to cyclic GMP-mediated vasodilation.

Acetylcholine↗

[Regulation of cytokine production by human T-lymphocytes in allergic immune response].

A network of cytokines regulates the growth and function of the cells of the immune system. T cells possess a dominant role in this network since they are the main source of many cytokines. The production of different cytokines is specifically regulated by means of cell interactions and cytokines and depends largely on the state of differentiation of the T cell. The production of certain cytokines is, therefore, restricted to defined subpopulations of T cells. IL2, IL4, IL5, IL10, IL12 and Interferon gamma (IFN gamma) play a central role in allergic immune response. The production of these cytokines can be restricted to specialized T cells. Two different types of differentiated T cells can be characterised according to the pattern of cytokine production of T cells: IL2 and IFN gamma are typically produced by T helper 1 (Th 1) cells, whereas predominantly T helper 2 (Th 2) cells produce IL4, IL5 and IL10. The selective activation of either Th 1 or Th 2 type cells depends on the antigen and is influenced by cytokines produced partly by antigen-presenting cells and partly by T helper cells. Typically, allergens induce an immune response which is dominated by Th 2 cells. These cells then stimulate the production of IgE by B cells.

Adult↗

[Securing the airway in children with the Morquio-Brailsford syndrome].

Mucopolysaccharidosis IVA (Morquio-Brailsford syndrome) results from an inborn deficiency of n-acetyl-galactosamine-6-sulphate sulphatase. Clinical features include skeletal deformities with hypoplasia or absence of the odontoid process of the axis. The resulting atlanto-axial subluxation compresses the spinal cord, resulting in cervical myelopathy. Without treatment, quadriplegia ensues sooner or later; consequently, surgical decompression and dorsal fusion of the cervical vertebrae is recommended, either prophylactically or therapeutically. Anaesthesiological management must focus on protection of the airway without compromising integrity of the cervical spinal cord; quadriplegia subsequent to positioning of the head under anaesthesia has been reported. We have performed fiberendoscopic nasotracheal intubation in a 23-month-old child presenting for neurosurgical treatment of cervical myelopathy resulting from Morquio-Brailsford syndrome. CASE REPORT. A 23-month-old girl (84 cm, 11 kg) with Morquio-Brailsford syndrome presented for surgical decompression and dorsal fusion of the cervical spine. Pre-anaesthetic examination revealed enamel defects, chronic bronchitis, and splenomegaly; the neck was immobilised with a collar. Radiological examinations (X-ray and NMR) revealed narrowing of the atlanto-occipital and atlanto-axial spaces (Fig. 1) and compression of the cervical spinal cord (Figs. 2 and 3). Pre-anaesthetic medication consisted of midazolam juice (4 mg). After establishing intravenous access, atropine (0.5 mg), midazolam (1 mg), and ketamine (10 mg) were administered. A 22 Fr nasopharyngeal airway (Wendl) was lubricated with local anaesthetic gel and introduced into the right nostril; oxygen was administered through a probe to the left nostril. The Wendl-airway was then removed, another 5 mg ketamine was administered, and a 3.5-mm flexible fiberendoscope--over which a 20 Fr armored tube was slipped--was introduced through the right nostril. With the child spontaneously breathing, the glottis was visualised and the fiberscope introduced into the trachea (Fig. 4); 1 mg midazolam and 35 mg ketamine was administered and the endotracheal tube was advanced through the nose into the trachea, utilizing the fiberscope as a guide. The distance between endotracheal tube and carina was assessed endoscopically, the fiberscope withdrawn, and the tube connected to the breathing system. Pulse oxymetric readings were 98% during induction of anaesthesia including endotracheal intubation. Anaesthesia was continued with enflurane, alfentanil, midazolam, and atracurium; 315 min after induction the trachea was extubated and the child discharged to the paediatric intensive care unit. The postsurgical course was uneventful, and the child resumed co-ordinated gait. DISCUSSION. Airway management in patients with mucopolysaccharidoses may be extremely difficult. Recommended methods such as blind nasal intubation are not feasible in small children. Anaesthetic management in children younger than 2 years with Morquio-Brailsford syndrome presenting for cervical spine surgery has not yet been described. Fiberoptically guided nasotracheal intubation is a means of airway management that does not require repositioning of the head and may be performed with the stabilising collar left in place (Fig. 4); preservation of cervical spinal cord integrity may hence be assumed. Analgosedation with ketamine and midazolam allows sufficient spontaneous breathing and--to some extent--maintenance of protective laryngeal reflexes. In conclusion, anaesthetic management of patients with Morquio-Brailsford syndrome is a challenge that is further increased by extending indications for surgical intervention to include infants. With respect to protecting the airway, fiberoptic nasotracheal intubation of the spontaneously breathing child is our method of choice.

Female↗

Inhibition of chloroplast ATPase by the K+ channel blocker alpha-dendrotoxin.

Possible structural and functional similarities between the channel part, CF0, of chloroplast ATPase (CF0CF1) and ion channels permeable to monovalent cations were investigated using high-affinity toxins mainly targeted against voltage-sensitive K+ channels. In particular, the effect of the K(+)-channel blocker alpha-dendrotoxin and the crude scorpion venom of Leiurus quinquestriatus hebraeus (LQ venom) on ATP synthesis in thylakoid membranes and in CF0CF1-containing liposomes was characterised. Alpha-dendrotoxin (K(i) approximately 5.05 microM) and the LQ venom (K(i) approximately 1.55 micrograms/ml) specifically inhibited ATP synthesis in thylakoid membranes and in CF0CF1-containing liposomes. Our results show that alpha-dendrotoxin and peptides of the LQ venom with an apparent molecular mass of about 4.0 kDa, probably isoforms of charybdotoxin, specifically bind to CF0CF1. This binding was reversible and induced a high leak conductance for H+ through CF0. The Ca(2+)-dependent ATPase activity of the isolated soluble part of CF0CF1 (CF1) was completely inhibited by 1 microM alpha-dendrotoxin, while the crude LQ venom, at concentrations up to 10 micrograms/ml, had no affect on ATPase activity. The concentration dependence of the inhibition by alpha-dendrotoxin indicates that approximately 2 mol alpha-dendrotoxin bind/mol CF0CF1 and 1 mol alpha-dendrotoxin/mol CF1. Known inhibitors of H(+)-flow-through CF0 acted in the presence of alpha-dendrotoxin synergistically. Dicyclohexylcarbodiimide and venturicidin, in contrast to their known effect of blocking H(+)-flow-through CF0, increased the leak conductance through CF0 in the presence of alpha-dendrotoxin drastically. This uncoupling effect indicates that their normal mode of blocking is a secondary effect. Binding of the inhibitors to their respective sites apparently does not affect the proton pathway in CF0, but induces a conformation which closes the channel part for H+. Protein sequence comparison between the known binding site of charybdotoxin in the shaker K+ channel from Drosophila [MacKinnon, R. & Heginbotham, L. (1990) Neuron 5, 767-771] and the choroplast ATPase showed that subunit III reveals a significant similarity (64%) in parts of its sequence (Gln28-Leu53) to the helix 5 and helix 6 (S5-S6) linker region (Ala413-Cys462; the charybdotoxin-binding site) of the shaker K+ channel. According to secondary-structure predictions, the homologous sequences in subunit III and the shaker K+ channel represent putative hydrophilic loops connecting two transmembrane alpha-helices. Apparently the shaker K+ channel and subunit III share significant topological features in these hydrophilic loops which may be part of the respective channel entrance.

Adenosine Triphosphatases↗

Carcinogen-specific mutational pattern in the p53 gene in ultraviolet B radiation-induced squamous cell carcinomas of mouse skin.

We have examined 35 epidermal tumors induced in mice of four different strains by chronic exposure to ultraviolet B radiation for the presence of aberrations in the p53 tumor suppressor gene. Polymerase chain reaction products from p53 exons 5 to 8 were screened by single-strand conformation polymorphism analysis and sequencing. Base substitutions were found in seven tumors (20%). All mutations occurred at dipyrimidine sequences; most frequent were C-->T single base and CC-->TT tandem transitions suggesting the involvement of UV radiation in the genesis of the mutations. Three base substitutions were located at codon 148, and all dipyrimidine-derived mutations occurred at sites where the sequence is present in the nontranscribed DNA strand, indicating some site and strand specificity of the ultraviolet B-induced p53 mutations.

Animals↗