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Biomedical subjects

D Schmidt

Publications and source records attributed to D Schmidt.

At least 145 records · Page 8Linked to original sources

A risk-benefit assessment of therapies for Lennox-Gastaut syndrome.

The treatment of Lennox-Gastaut syndrome has been improved for some patients by the introduction of adjunctive therapy with newer anticonvulsants such as lamotrigine and topiramate and the availability of vagal nerve stimulation and the re-emergence of the use of the ketogenic diet in recent years. The place of standard anticonvulsants and the role of callosotomy needs to be re-evaluated in view of the new developments. Although recommendations for the treatment of patients with Lennox-Gastaut syndrome are difficult to make in the absence of direct head-on comparative trials, the following suggested treatment recommendations are based on the best evidence available. Medical treatment should start with valproic acid (sodium valproate) and be followed by adjunctive therapy with either lamotrigine or topiramate; clobazam can be added if necessary for better seizure control while trying to reduce the dose of the other anticonvulsants. If standard treatment does not achieve sufficient seizure control or proves to be intolerable, vagal nerve stimulation, ketogenic diet, felbamate, benzodiazepines such as clonazepam, and phenobarbital (phenobarbitone) are recommended as third-line choices. Further considerations include ethosuximide, methsuximide, corticotropin (adrenocorticotropic hormone) or corticosteroids, pyridoxine (vitamin B6) and vigabatrin. If adequate drug treatment and vagal nerve stimulation provide insufficient seizure control, partial callosotomy may be an option for the treatment of frequent, intractable and disabling drop attacks. These suggestions are based on the best evidence available and do not in any way exclude the use of other treatments if compelling individual risk-benefit considerations apply.

Algorithms↗

Prolonged exposure to intermittent alcohol vapors blunts hypothalamic responsiveness to immune and non-immune signals.

BACKGROUND: We have previously shown that long-term alcohol treatment blunts the ACTH response to alcohol itself, as well as to other stresses, and is accompanied by decreased pituitary responsiveness to vasopressin (VP), but not corticotropin-releasing factor (CRF). The present work aims to determine the relevance of changes in CRF and VP receptors in the pituitary gland and/or peptide stores of CRF neurons in the paraventricular nucleus (PVN) of the hypothalamus, the areas that are most directly involved in ACTH release. METHODS: Intact male rats were exposed to alcohol using a new vapor delivery system which enables individual rat housing in boxes. Alcohol treatment was delivered for 6 hr once daily (0700-1300), after which the rats were returned to their home cages where they had free access to food and water. Control rats were kept in similar boxes, but not exposed to alcohol. Total treatment time was 8 days. All animals were equipped with indwelling jugular cannulae that were used to monitor blood alcohol levels (BALs) as well as ACTH and corticosterone release throughout drug exposure. Due to the presence of a swivel, the animals' movements were not restricted or hindered by the presence of these cannulae. On the morning of day 9, the animals were decapitated under basal conditions or exposed to a neurogenic (mild electrofootshocks) or systemic [i.v. lipopolysaccharide (LPS)] stimulus. PVN neuronal responses, indicated by changes in mRNA concentrations of the immediate early genes (IEGs) c-fos and NGFI-B, and plasma ACTH levels were measured before and during endotoxemia or electrofootshocks. RESULTS: In the absence of alcohol, plasma ACTH and corticosterone remained at basal levels, indicating the absence of environment-induced stress. In rats exposed to alcohol, BALs were consistent and predictable, and we targeted peak values of about 200 mg%. At the end of the drug treatment period, there were no significant differences between CRF and VP receptor mRNA levels in the anterior pituitary of control and alcohol-treated rats. In contrast, alcohol treatment respectively decreased CRF and increased VP stores in the external zone of the median eminence. It also increased NGFI-B and c-fos transcripts in the magnocellular (m) portion of the PVN, but not the parvicellular (p) division of this nucleus under basal conditions (i.e., in the absence of shocks or LPS). After exposure to these stressors, on the other hand, all groups of rats showed significant increases in plasma ACTH levels as well as up-regulation of their PVN neuronal response, as indicated by changes in pPVN IEGs transcripts. However, these hormonal and neuronal responses were significantly blunted in animals pretreated with alcohol. CONCLUSIONS: Collectively, our results suggest that decreased PVN neuronal activation represents an important mechanism of the ability of long-term alcohol treatment to blunt the ACTH response to shocks or endotoxemia. In addition, the new system of alcohol delivery that we developed is practical and reliable, and has the significant advantage that it enables measurement of circulating hormone levels during drug exposure of the animals.

Adrenocorticotropic Hormone↗

[Comparison of PET and fMRI activation patterns durnig declarative memory processes].

AIM: In this study neuronal correlates of encoding and retrieval in paired association learning were compared using two different neuroimaging methods: positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). METHODS: 6 right-handed normal male volunteers took part in the study. Each subject underwent six 0-15-butanol PET scans and on fMRI study comprising four single epochs on a different day. The subjects had to learn and retrieve 12 word pairs which were visually presented (highly imaginable words, not semantically related). RESULTS: Mean recall accuracy was 93% in the PET as well as in the fMRI experiment. During encoding and retrieval we found anterior cingulate cortex activation, and bilateral prefrontal cortex activation in both imaging modalities. Furthermore, we demonstrate the importance of the precuneus in episodic memory. With PET the results demonstrate frontopolar activations whereas fMRI fails to show activations in this area probably due to susceptibility artifacts. In fMRI we found additionally parahippocampal activation and due to the whole-brain coverage cerebellar activation during encoding. The distance between the center-of-mass activations in both modalities was 7.2 +/- 6.5 mm. CONCLUSION: There is a preponderance of commonalities in the activation patterns yielded with fMRI and PET. However, there are also important differences. The decision to choose one or the other neuroimaging modality should among other aspects depend on the study design (single subject vs. group study) and the task of interest.

Adult↗

IPHIE: an International Partnership in Health Informatics Education.

Medical informatics contributes significantly to high quality and efficient health care and medical research. The need for well educated professionals in the field of medical informatics therefore is now worldwide recognized. Students of medicine, computer science/informatics are educated in the field of medical informatics and dedicated curricula on medical informatics have emerged. To advance and further develop the beneficial role of medical informatics in the medical field, an international orientation of health and medical informatics students seems an indispensable part of their training. An international orientation and education of medical informatics students may help to accelerate the dissemination of acquired knowledge and skills in the field and the promotion of medical informatics research results on a more global level. Some years ago, the departments of medical informatics of the university of Heidelberg/university of applied sciences Heilbronn and the university of Amsterdam decided to co-operate in the field of medical informatics. Now, this co-operation has grown out to an International Partnership of Health Informatics Education (IPHIE) of 5 universities, i.e. the university of Heidelberg, the university of Heilbronn, the university of Minnesota, the university of Utah and the university of Amsterdam. This paper presents the rationale behind this international partnership, the state of the art of the co-operation and our future plans for expanding this international co-operation.

Curriculum↗

[The role of L-3-I-123-iodine-alpha-methyltyrosine SPECT in cerebral gliomas].

L-3-I-123-iodine-alpha-methyltyrosine (IMT) is a I-123-labelled amino acid which has been used for single photon emission computed tomography (SPECT) of cerebral gliomas for more than a decade. IMT-SPECT is able to detect tumor infiltration independent of disruptions of the blood-brain barrier which is often difficult with computed tomography or magnetic resonance tomography. The method is useful to detect tumor recurrences and helps to distinguish gliomas from non-neoplastic brain masses. IMT-SPECT is thus a valuable tool in the diagnostic evaluation and in therapy planning of patients with cerebral gliomas.

Blood-Brain Barrier↗

A fluorescein angiographic study of branch retinal artery occlusion (BRAO) - the retrograde filling of occluded vessels.

BACKGROUND: For assessing the prognosis of a branch retinal artery occlusion (BRAO), examination of the arterial blood flow by fluorescein angiography is necessary. PATIENTS AND METHODS: In seven patients (mean age: 68.1, youngest 61, oldest 76 years old), with BRAO of varying involvement and extent, the disturbed retinal blood flow was demonstrated by this method. All the patients were subjected to Doppler sonography of the carotid arteries and all had a general medical examination. RESULTS: The most impressive sign was the retrograde filling of the retinal arterial and/or venous branches from the adjacent retinal vessels and capillaries. In four patients the visual acuity was better after the disappearance of the retinal edema. In one patient the visual field defect slightly decreased at follow-up. This means that not every patient with retrograde filling of dye in BRAO has a bad prognosis in terms of visual function. The extent and duration of the retrograde filling with dye and the arterial or venous passage varied from patient to patient. There was also delayed filling with an increased period of retention in an artery (which is an adverse sign in BRAO), and retrograde filling of the corresponding vein. This latter came from small adjacent veins, but the retrograde filling of an artery came from capillaries or from very small adjacent arterioles. All the patients showed signs of general systemic disease, such as occlusion or the presence of plaques in the carotid artery, absolute arrhythmia, arterial hypertension, patent foramen ovale, diabetes mellitus, hyperuricemia, Factor V mutation, homocysteinemia or coronary heart disease. CONCLUSION: Retrograde filling of the retinal arterial and/or venous branches means a kind of spontaneous healing compared to a condition with complete permanent obstruction of circulation. It is recommended that fluorescein angiography should be carried out for all patients with BRAO, in order to estimate the prognosis of the vascular occlusion. This is the first published record of consecutive pictures showing the retrograde filling of retinal arteries and/or veins with BRAO. In every patient with a BRAO an extensive medical and neurological examination (including echocardiography and Doppler sonography of the carotid arteries) is essential before planning the treatment.

Aged↗

Pharmacological characterization of morphine-6-sulfate and codeine-6-sulfate.

Morphine-6-sulfate (M6S) and codeine-6-sulfate (C6S) are mu-selective opiates which have been isolated from brain. M6S is an effective analgesic, with a 30-fold greater potency than morphine in the mouse radiant heat tailflick assay and similar to the active morphine metabolite morphine-6beta-glucuronide (M6G). M6S analgesia is reversed by 3-methoxynaltrexone at low antagonist doses which are inactive against morphine, suggesting that M6S may be acting through the same mechanisms as M6G. Consistent with this possibility, antisense mapping of the MOR-1 clone revealed that M6S analgesia was lowered by probes targeting exon 2 and not by targeting exon 1, a sensitivity profile similar to that of M6G and not morphine. C6S also has analgesic activity at doses approximately 10-fold greater than M6S. However, its characterization was impeded by the appearance of seizures at doses below full analgesic activity. Thus, M6S is a potent analgesic with pharmacological properties similar to M6G. C6S has limited utility due to its high level of toxicity.

Analgesics, Opioid↗

Immunohistochemical survey of migration of human anterior pituitary cells in developmental, pathological, and clinical aspects: a review.

Developmentally pathological conditions of the anterior pituitary cells include failed separation of the primary pituitary gland into sellar and pharyngeal ones, ectopic migration into the subarachnoid space, and basophil invasion into the posterior lobe although the last is a physiological phenomenon with pathological potentiality in certain circumstances. Pituitary primordium appears at about 4 weeks of gestation. One of the causes of the pituitary gland agenesis may be a formation of the primary hypothalamic ganglionic hamartoma just at the time of occurrence of the pituitary primordium, as analyzed in cases of Pallister-Hall syndrome. A double pituitary in a single individual is a rare malformation. Its pathogenesis is considered as a result of notochordal anomaly. In the 8th gestational week, the primary pituitary gland separates into sellar and pharyngeal parts. The disturbance of this histogenesis results in a rare pituitary malformation, a "pharyngosellar pituitary." Despite the failed separation in this case, differentiation of the pituitary cells proceeds and the hormone production of this malformed pituitary gland can be displayed immunohistochemically. In this case, the distribution of the different hormone producing cells was atypical, particularly in those of gonadotropic hormones and ACTH. Life-long existence of the pharyngeal pituitary is a normal anatomical state in humans. Cell differentiation (hormone production) in the pharyngeal pituitary occurs about 4-10 weeks later than in the sellar pituitary. In pharyngeal pituitary, all kinds of adenohypophyseal hormones are produced. Extracranial pituitary adenomas (with intact sellar pituitary), exclusively found in the nasopharynx, sphenoid sinus, and clivus, may occur from the pharyngeal pituitary while another tumorigenesis can develop from the residual tissue fragment in the craniopharyngeal canal. The "overshoot" of the adenohypophyseal cell migration in the distal part of the sellar pituitary is frequently observed in the leptomeninges of the peri-infundibular or peri-hypothalamic region as ectopic pituitary cell clusters that are apparently independent of the pars tuberalis. It is suggested that these cells, frequently found in "normal" individuals, may be one of the possible origins of the intracranial ectopic pituitary adenomas. However, the reason why a majority of the reported intracranial ectopic pituitary tumors are ACTH-adenomas remains unexplained, since the ectopic cells, found in "normal" individuals, consist of fairly different hormone-producing cells. A further enigmatic phenomenon is a "basophil invasion." ACTH-positive cells invade from the pars intermedia into the posterior lobe of the pituitary. This invasion increases in intensity and frequency according to increase in age. However, the invasion of ACTH cells is observed as early as in the fetal life. The invasive cells display occasionally cell atypia as well as mitotic activity. The origin of extremely rare pituitary adenomas inside the posterior lobe can be explained by the existence and proliferative activity of basophil invasion.

Adenoma↗

Two mechanisms for the non-MHC-linked resistance to spontaneous autoimmunity.

Genetic susceptibility and resistance to most autoimmune disorders are associated with highly polymorphic genes of the MHC and with non-MHC-linked polygenic modifiers. It is known that non-MHC-linked polymorphisms can override or enhance the susceptibility to an autoimmune disease provided by pathogenic MHC genes, but the mechanisms remain elusive. In this study, we have followed the fate of two highly diabetogenic beta cell-specific T cell receptors (Kd and I-Ag7 restricted, respectively) in NOR/Lt mice, which are resistant to autoimmune diabetes despite expressing two copies of the diabetogenic MHC haplotype H-2g7. We show that at least two mechanisms of non-MHC-linked control of pathogenic T cells operate in these mice. One segregates as a recessive trait and is associated with a reduction in the peripheral frequency of diabetogenic CD8+ (but not CD4+) T cells. The other segregates as a dominant trait and is mediated by IL-4- and TGF-beta1-independent immune suppressive functions provided by lymphocytes that target diabetogenic CD4+ and CD8+ T cells, without causing their deletion, anergy, immune deviation, or ignorance. These results provide explanations as to how non-MHC-linked polymorphisms can override the susceptibility to an autoimmune disease provided by pathogenic MHC haplotypes, and demonstrate that protective non-MHC-linked genes may selectively target specific lymphoid cell types in cellularly complex autoimmune responses.

Amino Acid Sequence↗

Autoantigen-independent deletion of diabetogenic CD4+ thymocytes by protective MHC class II molecules.

Some MHC class II genes provide dominant resistance to certain autoimmune diseases via mechanisms that remain unclear. We have shown that thymocytes bearing a highly diabetogenic, I-Ag7-restricted beta-cell-reactive TCR (4.1-TCR) undergo negative selection in diabetes-resistant H-2g7/x mice by engaging several different antidiabetogenic MHC class II molecules on thymic (but not peripheral) hemopoietic cells, independently of endogenous superantigens. Here we have investigated 1) whether this TCR can also engage protective MHC class II molecules (I-Ab) on cortical thymic epithelial cells in the absence of diabetogenic (I-Ag7) molecules, and 2) whether deletion of 4.1-CD4+ thymocytes in I-Ab-expressing mice might result from the ability of I-Ab molecules to present the target beta-cell autoantigen of the 4.1-TCR. We show that, unlike I-Ag7 molecules, I-Ab molecules can restrict neither the positive selection of 4.1-CD4+ thymocytes in the thymic cortex nor the presentation of their target autoantigen in the periphery. Deletion of 4.1-CD4+ thymocytes by I-Ab molecules in the thymic medulla, however, is a peptide-specific process, since it can be triggered by hemopoietic cells expressing heterogeneous peptide/I-Ab complexes, but not by hemopoietic cells expressing single peptide/I-Ab complexes. Thus, unlike MHC-autoreactive or alloreactive TCRs, which can engage deleting MHC molecules in the thymic cortex, thymic medulla, and peripheral APCs, the 4.1-TCR can only engage deleting MHC molecules (I-Ab) in the thymic medulla. We therefore conclude that this form of MHC-induced protection from diabetes is based on the presentation of an anatomically restricted, nonautoantigenic peptide to highly diabetogenic thymocytes.

Animals↗

Risk assessment of a former military base contaminated with organoarsenic-based warfare agents: uptake of arsenic by terrestrial plants.

Organoarsenic-based chemical warfare agents (CWAs) such as the sternutators diphenylchloroarsine (CLARK I), diphenylcyanoarsine (CLARK II) or phenyldichloroarsine (PFIFFIKUS) still pose a notable risk in countries where former military bases that have stored these weapons have not yet been reclaimed. In fact, this is the case for many countries of Eastern Europe and the CIS. One of the most important military bases of the former Third Reich, the Heeresmunitionsanstalt I and II, is situated close to the German-Polish border at Loecknitz (Fig. 1). The German army stored and decanted different compounds of CWAs at this military base until 1945. When the Soviet Army destroyed the base in 1946, large amounts of CWAs and other organoarsenic compounds polluted the soil. Today up to 250 g (!) of arsenic may be found in 1 kg of soil at some places in this area. Since 1991, a Government Working Group has been working on the risk assessment in order to define the scope of reclamation measures. This study investigates the contamination and the uptake of arsenic by plants because little is known about the bioavailability and metabolism of sternutators and their constituents. The total arsenic concentration of nine different species of terrestrial plants with at least six samples per species is presented. In spite of the considerable arsenic contamination of the soil (mean value 923 mg arsenic/kg soil) the plant contamination remained comparably low. The median value of arsenic contamination of the above-ground organs of velvet grass, Holcus lanatus, was 0.7 mg/kg dry wt. and the mean value was 4.3 mg/kg dry wt. due to some highly contaminated samples. The highest arsenic concentration registered was 26 mg/kg dry wt. in a sample of H. lanatus, which was most probably caused by soil particles adhering to the plant. The chemical structure of the arsenic compounds carried by the above-ground plant organs has been determined by gas chromatographic investigations and showed an uptake of triphenyl arsine by the plants.

Arsenic↗

[Otorhinolaryngologic findings in Horton temporal arteritis. Review of the literature and case report].

Otorhinolaryngological findings of a temporal arteritis frequently occur in the beginning and/or course of the disease. A purulent sinusitis can be a sign of recurrence of the arteritis and was diagnosed in a 77-year-old woman with known disease that had been biopsied 6 years earlier. Puncture of the maxillary sinus was considered necessary, but no bacteria were found in purulent sinus discharge. When antibiotic treatment failed to bring about a resolution of the inflammatory condition, steroid therapy was begun and the patient recovered within a few days in response to this treatment. The clinical findings in this case show that early diagnosis and treatment by the otorhinolaryngologist are necessary in order to prevent severe complications of the disease.

Aged↗

[Serum concentration of anticonvulsants. Practical guidelines for measuring and useful interpretation. Therapy Committee of the German Section of the International Epilepsy League].

The clinical relevance of being informed on the serum concentration of antiepileptic drugs has been judged very differently during the last decades. Therefore the Commission on the treatment of epilepsy (German section of the International League against Epilepsy) had the task to outline the importance of therapeutic monitoring of anticonvulsant serum concentrations. The possibility of determining the serum concentration of anticonvulsants induced the elaboration of "therapeutic drug level ranges". The usefulness of determining serum concentrations of antiepileptic drugs in clinical management of patients with epilepsy depends decisively on the following questions: Can the efficacy of antiepileptic drug treatment be increased by serum concentration monitoring? Can the rate of adverse effects of antiepileptic drugs be reduced by serum concentration monitoring? Clinical experience suggests numerous indications of therapeutic drug monitoring, scientific studies however, supporting these empirical guidelines are not available. Therefore, therapeutic drug monitoring may be restricted for some special situations which have to be justified in every single case. Tailored determinations with specific purposes are e.g.: resistance to therapy, including suspected irregular intake; suspected intoxication, particularly during combined therapy; the possibility of significant changes in the dosage-serum concentration relationship (interactions with other drugs, unusual pharmacokinetics in childhood, in pregnancy etc.).

Adult↗

Neuronal correlates of encoding and retrieval in episodic memory during a paired-word association learning task: a functional magnetic resonance imaging study.

The investigation of memory function using functional magnetic resonance imaging (fMRI) is an expanding field of research. The aim of this study was to demonstrate brain-activity patterns related to a word-pair association task employing a whole-brain EPI sequence. Six right-handed, healthy male volunteers (mean age: 27.5 years) took part in the study. fMRI was performed at a field strength of 1. 5 Tesla with 26-32 slices parallel to the AC-PC line, depending on individual brain size. Distributed brain regions were activated in episodic encoding and retrieval with similarities, but also (distinct) differences in activation patterns. Bilateral prefrontal cortical areas were involved when comparing encoding as well as retrieval to the reference condition (nonsense words). Furthermore, activation was observed in cerebellar areas during encoding, and activation in bilateral parietal areas (precuneus and inferior parietal cortex) was differentially more pronounced during retrieval. The activation of left dorsomedial thalamus during retrieval of high imagery-content word-pair associates may point to the role of this structure in episodic retrieval. The direct cognitive subtraction of encoding minus retrieval yielded a differentially larger left prefrontal activation. There was a differentially higher right prefrontal activation during retrieval than during encoding, underlining the proposed right/left asymmetry for episodic memory processes.

Adult↗

[Arterial occlusion of the eye in infectious endocarditis].

BACKGROUND: Infectious endocarditis can lead to embolic arterial retinal occlusions. Which therapy is indicated? RESULTS: A 33-year-old man suddenly became blind in his left eye as the result of a central retinal artery occlusion (CRAO). This occurred during high-dosage treatment for infectious endocarditis that had been diagnosed 3 weeks earlier. The echocardiogram showed distinct vegetation and an abscess on the aortic valve. The CRAO together with the ultrasound findings was considered an absolute indication for surgery of the aortic valve. During this emergency operation, a 2 cm deep abscess cavity was found between the mitral and aortic valves. After removal of the abscess, together with the infected valve, a prosthetic valve was inserted. Following the operation, the patient made an uneventful recovery. The antibiotic treatment was continued for several months. The left eye remained sightless. No recurrence of infectious endocarditis occurred during the follow-up of 2 1/4 years. A branch retinal arterial occlusion occurred in the right eye of a 35-year-old man who had suffered from chronic infectious endocarditis for several months. Insufficiency of more than one valve had been diagnosed on several occasions. The patient, a drug-addict, had refused surgical treatment on each occasion. After 3 months, the right eye became completely blind owing to CRAO. Following high-dosage treatment with antibiotics, the infectious endocarditis was healed. The right eye remained blind. One year later the patient died. CONCLUSION: Retinal arterial occlusion of embolic origin in a patient with infectious endocarditis is an indication for immediate medical and/or surgical treatment. This is of particular importance if there is ultrasound evidence of an abscess in the valve area.

Abscess↗

Pharyngeal pituitary: development, malformation, and tumorigenesis.

The development of the pharyngeal pituitary (PhP) in the fetal period was morphologically and, for the first time, immunohistochemically examined. PhP, found in every individual, begins its hormone production at the 17-18th week of gestation, that is, 4-8 weeks later than that of sellar pituitary (SP). Only 1 of 25 examined fetuses without any stigmata of developmental anomalies showed a residual pituitary fragment in the craniopharyngeal canal (craniopharyngeal pituitary, CPhP). An adult case of a rare clivus pituitary adenoma that we examined is demonstrated in discussing its relationship to PhP. Extracranial ectopic pituitary adenomas in the literature describe an exclusively sphenoid sinus/nasopharyngeal/clivus location of the tumor. Their location corresponded exactly with that of PhP, so that the origin of the tumors can be reasonably speculated as PhP, although another origin, e.g., CPhP, can not be excluded. A variety of malformations of PhP, although very rare, have been described for the fist time during the systemic examination of 16 fetuses with different cranioneural malformations, such as agenesis, unseparated PhP from SP (pharyngosellar pituitary), fragmentation, and residual pituitary tissue in the open craniopharyngeal canal. However, developmental anomaly of PhP was not specifically associated with cranioneural malformations except in cases of chromosomal aberrations. The hormone production in PhP in malformation cases tended to be retarded. Absence of SP was recorded in 50% of anencephalics in the literature; however, PhP was identified in all anencephalics in our series, independent of the existence of SP. This supports the opinion that agenesis of SP in anencephalics seems to be false information.

Adenoma↗