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L Steiner

Publications and source records attributed to L Steiner.

At least 37 records · Page 2Linked to original sources
PubMed1997

Annual risk for the first hemorrhage from untreated cerebral arteriovenous malformations.

To estimate the annual risk for the first hemorrhage, survival and life table statistics were used to analyze data from 2262 patients with cerebral arteriovenous malformations (AVM). We found that the risk for hemorrhage increases with increasing age. A validity test revealed, however, that life table statistics used on the total patient material underestimated the annual risk for hemorrhage, especially for patients 20-50 years of age. A method based on the fact that the distribution of the time at risk until the initial hemorrhage (= age at first rupture) reflects the risk for hemorrhage in untreated AVM was therefore also employed. The analysis yielded three conclusions: 1) the annual risk of hemorrhage increases with age; 2) small AVM are less prone to rupture; and 3) the risk of hemorrhage is higher in women during their fertile years as compared to males in the same age group. The risk related to age, AVM size and location assessed by survival statistics in the subgroup of patients with a known date for the initial hemorrhage gave similar results.

Adolescent↗
PubMed1997

Prediction of obliteration after gamma knife surgery for cerebral arteriovenous malformations.

OBJECTIVE: To define the factors of importance for the obliteration of cerebral arteriovenous malformations (AVMs), thus making a prediction of the probability for obliteration possible. METHODS: In 945 AVMs of a series of 1319 patients treated with the gamma knife during 1970 to 1990, the relationship between patient, AVMs, and treatment parameters on the one hand and the obliteration of the nidus on the other was analyzed. RESULTS: The obliteration rate increased both with increased minimum (lowest periphery) and average dose and decreased with increased AVM volume. The minimum dose to the AVMs was the decisive dose factor for the treatment result. The higher the minimum dose, the higher the chance for total obliteration. The curve illustrating this relation increased logarithmically to a value of 87%. A higher average dose shortened the latency to AVM obliteration. For the obliterated cases, the larger the malformation, the lower the minimum dose used. This prompted us to relate the obliteration rate to the product minimum dose (AVM volume)1/3 (K index). The obliteration rate increased linearly with the K index up to a value of approximately 27, and for higher K values, the obliteration rate had a constant value of approximately 80%. For the group of 273 cases treated with a minimum dose of at least 25 Gy, the obliteration rate at the study end point (defined as 2-yr latency) was 80% (95% confidence interval = 75-85%). If obliterations that occurred beyond the end point are included, the obliteration rate increased to 85% (81-89%). CONCLUSION: The probability of obliteration of AVMs after gamma knife surgery is related both to the lowest dose to the AVMs and the AVM volume, and it can be predicted using the K index.

Adolescent↗
PubMed1997

Six new DPB1 alleles identified in a study of 1,302 unrelated bone marrow donor-recipient pairs.

Six new DPB1 alleles were identified by PCR-SSOP methodologies in the course of a retrospective study of the role of HLA matching in the outcome of unrelated donor bone marrow transplantation. Sequencing confirmed that five of these alleles (DPB1*5901, *6801, *7101, *7201, and *7301) represent novel combinations of previously described sequence motifs in the variable regions of DPB1; the sixth (DPB1*7001) appears to result from a novel point mutation. These data support previous observations which suggest that multiple mechanisms, including segmental exchange and mutation, appear to be responsible for generating sequence diversity at the DPB1 locus. The extremely low discrepancy rate of 0.1% between the two laboratories which typed the samples, and the ability to predict the new sequences from probe hybridization patterns, indicate that SSOP is an accurate and efficient method for studying polymorphism at DPB1.

Alleles↗
PubMed1997

Radiosurgery for cerebral AVMs in children and adolescents: the neurobehavioral outcome.

Eight patients, ranging in age from 9 to 18 years, were treated for arteriovenous malformations using gamma knife radiosurgery and were evaluated an average of 6 years after treatment to record potential effects of radiosurgery on cognitive and neuropsychological performance. Tests for general intelligence, nonverbal intelligence, memory and its components, and attention performance were administered to patients and compared with test results of age-matched siblings or first cousins. No statistically significant difference was found between the performance of patients and controls in any of the tests administered. Additionally, a specially designed questionnaire completed by the patients, their parents, and their teachers revealed that the patients' emotional and relational behavior was stable and unchanged after treatment. No correlation was found between the neurocognitive test performance and the lesion volumes irradiated, but the lesion site was found to contribute to the type of deficit recorded after treatment. The less invasive nature of the radiosurgical approach, combined with the brevity or absence of hospitalization, presumably contributed to the patients successful physical, mental, and emotional recovery.

Adolescent↗
PubMed1997

[Frequency and etiology of calf losses and calf diseases in cow-calf farms. I. Methods of data collection, calf mortality, and calf morbidity].

An observational study was initiated to provide general information on calf health and estimates of frequency and of economic impact of calf diseases in farms with extensive beef production. The study was planned as a cohort study and included all calves born during the calving season of 1993/94 in 105 cow-calf farms in western Switzerland. The total preweaning mortality was 8.5% (123 calves out of 1452 calvings); 2.5% of the calves were stillborn, and 6.0% died or were euthanized before weaning. Forty-four percent of all losses were recorded in the perinatal period (i.e. the first 48 hours p. p.). The average preweaning mortality among liveborn calves at farm level was 6.1%. A large variation in mortality was observed from farm to farm (0-50%). In 50% of the post mortem analyses, respiratory disease was diagnosed as the cause of death. Twenty-two percent of all calves were treated at least once by a veterinarian. Thirty-six percent of all treatments were performed because of diarrhea, 26% because of respiratory disease and 15% because of umbilical problems. From birth to weaning age, the average treatment costs including calving assistance, medication and prophylactic measures were SFr, 23.80 per calf.

Aging↗
PubMed1997

[Frequency and etiology of calf losses and calf diseases before weaning in cow-calf farms. II. Microbiological and parasitological diagnoses in diarrheic calves].

Diarrhea is the most frequently diagnosed disease in Swiss cow-calf farms. During an longitudinal study conducted in 105 cow-calf farms in Switzerland in 1993-95, blood and fecal samples were collected from diarrheic calves and from calves that died because of diarrhea. Campylobacter spp. were detected in 42%, E. coli (VTEC) in 32%, rotavirus in 33%, coronavirus in 13%, coccidia in 43% and helminths in 8% of the cases. In some samples Yersinia pseudotuberculosis were isolated. The BVD-virus antigen was not detected in any of the calves examined. In most cases concurrent infection with several enteropathogens was diagnosed. Specific causes of diarrhea were therefore difficult to establish. The bacteriological findings of this study have implication for food safety: VTEC, Campylobacter spp. Yersinia spp. and cryptosporidia are considered as potential causes on zoonoses.

Animals↗
PubMed1997

[Frequency and etiology of calf losses and calf diseases in cow-calf farms. III. seroprevalence of selected diseases and prevalence of endoparasites and weaning age].

In a cross sectional study in 38 cow-calf farms blood and fecal samples were taken from 207 calves at an age of 8-10 months and their darms, in order to determine the seroprevalence of Leptospira hardjo, Coxiella burnetii, Toxoplasma gondii and the presence of the BVD-Antigen as well as the prevalence of endoparasites. The study was conducted in fall 1994 at the end of the grazing period. Eggs or larvaes of gastrointestinal helminths were detected in 74% of calves that were dewormed before the grazing period and in 88% of untreated calves. The difference between the two groups was statistically significant. In 83% of the weaned calves oocysts of Eimeria spp. were diagnosed. No significant difference in weight gain was observed between animals without endoparasites and animals infected with either helminths and/or Eimeria. In cows the prevalence was 61.5% for helminths and 45.7% for Eimeria spp. In calves the seroprevalence was 4% for Leptospira hardjo, 0.5% for Coxiella burnetii and 14.0% for Toxoplasma gondii. The seroprevalence in cows were 18% for Leptospira hardjo, 7.6% for Coxiella burnetii and 14.3% for Toxoplasma gondii. The prevalence of the BVD-Virus antigen was 0.5% for calves and cows.

Aging↗
PubMed1996

Occlusion of the anterior cerebral artery after Gamma Knife irradiation in a rat.

The anterior cerebral artery of rats was irradiated at the level of the circle of Willis by Gamma Knife with a maximum dose of 25, 50, or 100 Gy. Occlusion of the anterior cerebral artery was observed in one rat which was followed for 20 months after irradiation of 100 Gy. Cerebral infarction was found at the midline-frontal region and the cingulate gyrus. Arterial wall thickening with fibrosis, splitting of the internal elastic membrane, luminal organized thrombus, and migration of smooth muscle cells into the thrombus were observed. In the anterior cerebral artery, thrombus formation seemed to occur after the endothelial injury and this may play a prominent role for occlusion. In small arteries, various changes were observed in the irradiated tissue. These included fibrosis and thrombus, thickened smooth muscle layer, lymphocytic infiltration, and thickening of vessel wall with fibrosis and fibrinous thrombosis with leakage of fibrin into the surrounding tissue after different doses of radiation and at different observation times. These changes were comparable to the ordinary vascular response to injury including healing vasculitis and arteriosclerosis.

Animals↗
PubMed1996

Accuracy of an experimental stereotactic system for MRI-based gamma knife irradiation in the rat.

Stereotactic devices for experimental Gamma Knife irradiation and magnetic resonance imaging (MRI) have recently been developed for experimental studies using rats [6,7]. The present study examined the accuracy of these devices using the following two approaches. In the first approach, Gamma Knife irradiation was performed using the stereotactic device with targets based on a standard stereotactic atlas. Gadolinium-enhanced T1-weighted magnetic resonance imaging was performed using the MRI stereotactic device. Animals were then sacrificed after Evans blue injection, and the rat brain was sliced using an attachment to the stereotactic device. The center coordinates of the gadolinium-enhanced area from the MRI and Evans blue-stained area from the tissue sections were obtained using a computer-assisted image analysis system. These coordinates were compared with the target coordinates planned from the stereotactic atlas. In the second approach, a thermoluminescence dosimeter was implanted in the rat brain. Stereotactic MRI was performed using the stereotactic MRI device, and the coordinates of the implant were obtained. Gamma Knife irradiation was then performed at this target using the stereotactic device. The absorbed dose was measured and compared with the planning dose. These experiments demonstrated a spatial error of 0.6 mm (standard error +/- 0.07) between Gamma Knife irradiation based on a comparison of the atlas coordinates and the lesion, and a spatial error of 1.0 mm (standard error +/- 0.13) based on a comparison of the stereotactic MR images and the lesion. Gamma Knife irradiation based on MR images using the stereotactic device demonstrated a maximum error of 10% in absorbed dose at the target center. Together, the stereotactic devices for Gamma Knife irradiation and magnetic resonance imaging provide useful tools for Gamma Knife research in an animal model.

Animals↗
PubMed1996

Histological changes in the normal rat brain after gamma irradiation.

Radiation-induced changes in the parietal cortex of Wistar rats were observed at various time points after gamma surgery. Maximum dosages of 50, 75, and 120 Gy were given at the iso-center of the radiation using a 4-mm collimator. Conventional histochemical and immunocytochemical analyses, and computer-assisted videomicroscopy were utilized to examine perfusion-fixed brain tissue. Irradiation at a dosage of 50 Gy elicited morphological changes of astrocytes in the parietal cortex at 3 months. Vasodilatation became obvious at 12 months; fibrin deposition was observed in the dilated capillary wall. Neither leakage of Evans Blue from the vasculature into the tissue nor necrosis was observed across the 12 month observation period. Irradiation at a dosage of 75 Gy resulted in morphological changes of astrocytes within 1 month. Dilatation of vessels and capillary thickening were observed at 3 months. Evans Blue leakage and necrosis were observed at 4 months after 75 Gy irradiation. At this time, the walls of arterioles became thickened by subintimal accumulation of fibrin and hyaline substance; this sometimes resulted in occlusion of the lumen. Significant hemispheric swelling was observed at 4 months. Irradiation at a dosage of 120 Gy elicited changes in astrocytic morphology within 3 days. Evans Blue leakage into the tissue was observed by 3 weeks. Vasodilation became marked at this time point and rarefaction was observed in the irradiated cortex. Necrosis was observed at 4 weeks, however, no significant swelling was observed. Taken together, these findings demonstrate time-dependent and dosage-dependent changes in normal cerebral tissue after Gamma Knife irradiation. These results provide a basis for gauging the impact of gamma surgery in regions of eloquent tissue. An enhanced understanding of the cellular responses to radiosurgery will contribute to developing and evaluating future applications for gamma surgery.

Animals↗
PubMed1996

Neuroimaging studies of postobliteration nidus changes in cerebral arteriovenous malformations treated by gamma knife radiosurgery.

BACKGROUND: Following radiosurgical treatment, the majority of patients with arteriovenous malformations (AVMs) are periodically examined by means of computed tomography (CT) and magnetic resonance imaging (MRI) to assess the attainment of nidus obliterations, as well as adverse radiation effects in the surrounding brain. However, few neuroimaging studies of the long-term results following complete obliterations, confirmed by angiography, have been published to date. METHODS: CT, MRI, magnetic resonance (MR) angiographic and angiographic images, obtained after angiographic confirmation of complete nidus obliteration, were reviewed in 11 AVM patients treated with gamma knife radiosurgery. The period between angiographic confirmation of nidus obliteration and these most recent examinations was 12-84 months (mean, 29 months). RESULTS: In ten patients who were assessed by CT, the obliterated nidus was shown to be isodense (eight cases). A significant time-related decrease in contrast enhancement was observed within 1 to 2 postobliteration years (five/seven cases). Eight patients were evaluated by MRI. On T1-weighted imaging, the nidus was shown to be hypointense (six cases) or a mixture of hypointense and isointense areas (two cases). On T2-weighted imaging, nidus intensity varied more than than observed on T1-weighted imaging, and time-related intensity increases were observed (two/seven cases). No flow-signal void was demonstrated in any of these cases. In four of the seven cases, in which serial postobliteration follow-up MRI studies were conducted, significant gadolinium enhancement persisted 3 years or more after obliteration (maximum of 7 years). No vascular abnormalities were demonstrated in seven patients who were assessed by conventional angiography and/or MR angiography. CONCLUSIONS: Radiosurgery-induced changes in a nidus may continue for several years after angiography has shown complete AVM obliteration.

Adolescent↗
PubMed1996

Effect of Gamma Knife surgery on the risk of rupture prior to AVM obliteration.

The incidence for hemorrhage in non-obliterated arteriovenous malformations (AVM) during the first two years following Gamma Knife (GK) surgery was compared to the calculated incidence in untreated patients. There was a decrease in the incidence of hemorrhage as compared to the natural course. This difference was statistically significant. The actual number of hemorrhages during the first two years was 49 in a series of 1604 patients. Additionally, 41 hemorrhages occurred beyond the two years following treatment over the entire follow up time span of up to 24 years. For the first two years the calculated incidence was roughly two times higher than the observed incidence. This impact on the natural history was detectable already within six months after the treatment for the malformations totally covered with at least 25 Gy. The relation between a high minimum and a high average dose on the one hand and a lower risk for hemorrhage on the other hand was statistically significant. Low treatment doses and high age correlated to a higher risk. Neither hemorrhage prior to treatment nor time interval between presenting hemorrhage and treatment seemed to influence the risk for post treatment hemorrhage. The risk for permanent neurological deficit or death due to AVM rupture during the latency period between the time of treatment and total nidus obliteration was less than 0.5% for small AVM and 2-4% for large ones during the first two years. Of the 24 patients with sequelae following AVM rupture after treatment 14 died and 10 remained with neurological deficit of different degrees. However, all survivors were self sufficient.

Adult↗
PubMed1995

Calreticulin--the potential autoantigen in celiac disease.

Monoclonal antibodies to gliadin were recently found to cross-react with epitopes on rat enterocytes. Two molecules of mol. mass 62 and 66 kDa were isolated from enterocyte lysates by affinity chromatography using antigliadin monoclonal antibodies. The N-terminal amino acid sequence of the 62-kDa protein was determined to be XXXIYFKEQFLD. This amino acid sequence corresponds to amino acid sequence of rat calreticulin. The presence of calreticulin in enterocyte lysates was further confirmed using anticalreticulin serum. Anticalreticulin serum was also used to investigate the reactivity of isolated rat calreticulin. To analyze whether gliadin and calreticulin share similar epitopes recognized by anticalreticulin antibodies, synthetic dodecapeptides derived from the amino acid sequence of alpha gliadin were used in competitive ELISA assay. Two gliadin peptides, QEQVPLVQQQQF and YQLLQELCCQHL, were found to inhibit the binding of rabbit anti-rat calreticulin sera to rat calreticulin. The significant correlation was detected between IgA anticalreticulin and antigliadin antibodies (r = 0.827; P < 0.001) in celiac patients.

Amino Acid Sequence↗
PubMed1995

Enhanced magnetic resonance imaging of the rat brain using a stereotactic device with a small head coil: technical note.

A stereotactic device (SDM) was developed for performing consistent magnetic resonance imaging (MRI) of the rat brain. The SDM was developed by adapting a radiofrequency transmit/receive head coil of 4.4 cm inner diameter (quadrature birdcage head coil), and utilizing partial acrylic construction for the positioning elements. The small head coil provides improved resolution and accuracy of the image, while the stereotactic holder permits repeatable and accurate imaging of identified brain structures. This system provides several advantages over existing experimental MRI devices. The SDM ensures that the head is always placed in the center of the coil in a uniform fashion. Standardized positioning of the skull optimizes image quality and provides a consistent orientation of the brain. In addition, a widely-utilized coordinate system described by Paxinos and Watson can be employed to assist in the identification of structures and to facilitate surgical planning. The SDM is compatible with a recently-developed stereotactic device for radiosurgery with the Gamma Knife, thus permitting the planning and performance of experimental radiosurgery using the same coordinate system. The SDM also provides the ability to perform MRI and radiosurgery at different times, thus avoiding the need for prolonged anesthesia during an experimental study. Finally, the SDM allows repeated MRI of the same, identifiable positions in the brain during longitudinal experimental studies. The utility of this device is demonstrated here by examining the time course of cerebral damage that evolved within a radiosurgical focus after gamma irradiation.

Animals↗
PubMed1995

Failure in management of pituitary tumors discussion of 3 cases.

Three patients with pituitary adenomas (ACTH-secreting, non-secretory, and multi-secretory) with unfavorable course, in spite of repeated microsurgery, drug therapy, as well as radiotherapy and radiosurgery, are presented. Each case was re-evaluated for possible flaws in management. Two of the invasive tumors continued to grow, in spite of correct management. The third patient with a pituitary adenoma underwent microsurgical resection, and later following a false positive finding of recurrence, received radiotherapy and underwent radiosurgery. The lesion actually was chronic inflammatory tissue.

Adult↗
PubMed1995

Gamma knife surgery for craniopharyngioma.

We present our results of Gamma Knife surgery for craniopharyngioma in nine patients. The current status of surgery, radiation therapy, intracavitary instillation of radionucleides and Gamma Knife surgery in the management of craniopharyngiomas is discussed.

Adolescent↗
PubMed1995

Gamma Knife radiosurgery in cerebral arteriovenous malformations: postobliteration nidus changes observed on neurodiagnostic imaging.

Computed tomographic (CT), magnetic resonance (MR), MR angiographic and angiographic images, obtained after complete nidus obliteration had been angiographically confirmed, were reviewed in 9 patients who had undergone Gamma Knife treatment for cerebral arteriovenous malformations (AVMs). The period between angiographic confirmation of nidus obliteration and the most recent examinations was 12-84 months (mean 29 months). The patients ranged in age from 9 to 54 years (mean 22 years). There were 6 females and 3 males. In 8 patients, the obliterated nidus was shown on CT to be isodense. Calcification was identified in 3 patients, 1 of whom had not shown calcification on CT before treatment. Contrast enhancement of the nidus was seen in 6 patients, in 5 of whom a significant time-related decrease in contrast enhancement was observed following nidus obliteration. In 6 patients, T1-weighted MR imaging showed a hypointense nidus in 4 cases, both hypo- and isointense in 1 and isointense in 1. T2-weighted imaging showed a more varied nidus intensity than was seen on T1-weighted imaging. No flow signal void was demonstrated in any of these cases. After gadolinium administration, the nidus was enhanced in all cases, markedly in 4 and moderately in 2. In 5 of the 6 cases a time-related decrease in gadolinium enhancement was observed following nidus obliteration. This change was, however, less significant than that observed on contrast-enhanced CT. Angiography and/or MR angiography showed no vascular abnormalities in 7 patients. These results show that radiosurgery-induced changes in a nidus may continue for several years after angiography has shown complete AVM obliteration. These late changes can be considered to involve further obliteration of the remaining or recanalizing vessels, reflecting an ongoing process from coagulation necrosis to liquefaction necrosis.

Adolescent↗