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B Mielke

Publications and source records attributed to B Mielke.

At least 19 recordsLinked to original sources
PubMed2000

In vivo functional analysis of the daughter of sevenless protein in receptor tyrosine kinase signaling.

One mechanism used by receptor tyrosine kinases to relay a signal to different downstream effector molecules is to use adaptor proteins that provide docking sites for a variety of proteins. The daughter of sevenless (dos) gene was isolated in a genetic screen for components acting downstream of the Sevenless (Sev) receptor tyrosine kinase. Dos contains a N-terminally located PH domain and several tyrosine residues within consensus binding sites for a number of SH2 domain containing proteins. The structural features of Dos and experiments demonstrating tyrosine phosphorylation of Dos upon Sev activation suggested that Dos belongs to the family of multisite adaptor proteins that include the Insulin Receptor Substrate (IRS) proteins, Gab1, and Gab2. Here, we studied the structural requirements for Dos function in receptor tyrosine kinase mediated signaling processes by expressing mutated dos transgenes in the fly. We show that mutant Dos proteins lacking the putative binding sites for the SH2 domains of Shc, PhospholipaseC-gamma (PLC-gamma) and the regulatory subunit of Phosphoinositide 3-kinase (PI3-K) can substitute the loss of endogenous Dos function during development. In contrast, tyrosine 801, corresponding to a predicted Corkscrew (Csw) tyrosine phosphatase SH2 domain binding site, is essential for Dos function. Furthermore, we assayed whether the Pleckstrin homology (PH) domain is required for Dos function and localization. Evidence is provided that deletion or mutation of the PH domain interferes with the function but not with localization of the Dos protein. The Dos PH domain can be replaced by the Gab1 PH domain but not by a heterologous membrane anchor, suggesting a specific function of the PH domain in regulating signal transduction.

Amino Acid Sequence↗
PubMed1996

Anatomic details of intradural channels in the parasagittal dura: a possible pathway for flow of cerebrospinal fluid.

OBJECTIVE: The absorption of cerebrospinal fluid occurs primarily by means of arachnoid granulations (AG) in the superior sagittal sinus (SSS) and the lacunae laterales (LL) in the parasagittal dura. Previous descriptions of this region suggest a network of intradural channels, but finer details of extent and relationship between channels and AG were not addressed. Therefore, we undertook an anatomic study of cadaveric parasagittal dura. METHODS: The SSS and parasagittal dura of 20 formalin-fixed adult cadavers and 15 autopsy specimens from patients ranging in age from 18 weeks of gestation to 80 years were studied by use of a light microscope, a scanning electron microscope, and corrosion casting. Intradural injections into the parasagittal region were performed in two formalin-fixed and four autopsy specimens from adults by use of normal saline and corrosion casting. RESULTS: Extensive networks of intradural channels from 0.02 to 2.0 mm in diameter were noted in all of the specimens. Channels either were connected to the SSS at intervals along the side wall or drained directly into the LL, which extended up to 3 cm from midline. Channels lined with endothelium stained positive for Factor VIII, as did the endothelium of the LL and SSS. In some places, the network of channels seemed to coalesce to form LL. The underside of the dura was coarse and trabeculated where the channels were abundant, and AG were interdigitated between these trabeculae. In regions of the dura where channels were sparse or absent, the dural underside was smooth and lacked AG. Underlying cortical veins opened directly into the SSS and were unrelated to intradural channels. Intradural parasagittal injections from the epidural side accessed the SSS by way of channels using pressures between 0 and 20 cm H2O at 1.5 ml/min. CONCLUSION: These channels may represent a pathway for the flow of cerebrospinal fluid from AG to the SSS.

Adolescent↗
PubMed1994

Anti-myelin basic protein and anti-proteolipid protein specific forms of multiple sclerosis.

Human myelin basic protein (hMBP) and proteolipid protein (PLP) were used as antigens in a solid-phase radioimmunoassay to determine relative frequencies of anti-MBP and anti-PLP in cerebrospinal fluid (CSF) of optic neuritis and multiple sclerosis (MS) patients. Forty-nine of 55 patients with optic neuritis had increased CSF anti-MBP and the remaining 6 had increased anti-PLP. Of 385 MS patients, MS relapse: 173 of 180 patients had increased anti-MBP, 5 of the remaining 7 patients had elevated anti-PLP, and 2 had neither of these autoantibodies. Progressive MS: 111 of 116 patients had increased anti-MBP in either free and/or bound form, of the remaining 5 patients 4 had increased anti-PLP, and 1 had neither anti-MBP nor anti-PLP. MS remission: 15 of 87 patients had somewhat increased anti-MBP, none had anti-PLP. IgG was purified by affinity chromatography from necropsy central nervous system (CNS) tissue samples of 4 individual patients with clinically definite and neuropathologically confirmed MS. Three of these 4 patients who had increased levels of CSF anti-MBP also had increased anti-MBP titers in CNS tissue-extracted IgG. The fourth patient who had anti-PLP in CSF also had anti-PLP in brain tissue IgG. These autoantibodies were not detected simultaneously in any patient. These results suggest that there are at least two immunologically distinct forms of MS, i.e., a common form highly associated with anti-MBP and more frequent prominent inflammatory characteristics in CSF and CNS, and an infrequent form associated with anti-PLP in CSF and tissue, and less abundant inflammation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Attempted experimental modification of the postlaminectomy membrane by local instillation of recombinant tissue-plasminogen activator gel.

A prospective, randomized, blinded trial involving 25 adult mongrel dogs was performed to evaluate whether placement of a fat graft or local instillation of recombinant tissue-plasminogen activator gel (rt-PA) could modify the development of a postlaminectomy membrane. One component of the study involved the performance of a lumbar laminectomy and placement of gel rt-PA, free fat, or no tissue placement over the exposed dura mater. Three months later the animals were killed and sections of spine were removed en bloc, decalcified, and examined histologically. No significant differences were found in the degree of cellular fibrosis or heavy collagen production. A similar laminectomy at another lumbar level was also followed by gel rt-PA, free fat, or no tissue placement. Three months after surgery, surgery was performed again at this level immediately before death. There were no differences in the adhesiveness of the laminectomy membrane to dura mater or roots. It was concluded that the local instillation of gel rt-PA after laminectomy did not inhibit scar formation or scar adherence to the dura mater.

Adipose Tissue↗
PubMed1993

Bcl-2 gene rearrangements in primary B-cell lymphoma of the gastrointestinal tract reveal follicular lymphoma as a subtype.

The principal objective of this study was to investigate whether follicular center cell lymphomas occur among B-cell lymphoma of mucosa-associated lymphoid tissue (MALT). We used a molecular genetic/immunohistochemical approach and analysed 21 cases with the primary site in the gastrointestinal tract. Only two bcl-2 gene rearrangements were detected in our series and were found in two out of seven lymphomas with a nodular growth pattern. A chromosomal translocation t(14;18) was demonstrated by comigration of rearranged bcl-2 and JH sequences in one of these two cases. Additionally, both lymphomas showed bcl-2 protein positive neoplastic follicles, CD10 expression, and lack of vimentin. Therefore, these two cases were defined as follicular lymphomas. In contrast to the two follicular lymphomas of MALT, three other, nodular growing, bcl-2 protein positive lymphomas were found to have no bcl-2 gene rearrangements, to be CD10 negative and to express vimentin. These three lymphomas might be composed of neoplastic extrafollicular cells which secondarily invaded reactive follicles. We conclude that the presence of bcl-2 protein positive follicles is consistent with both a follicular and extrafollicular origin of a B lymphoma of MALT. However, the detection of a bcl-2 gene rearrangement is the most valuable criterion in such a situation, and additional immunophenotypic criteria, such as CD10 expression and lack of vimentin within the neoplastic population, further substantiate the diagnosis of a follicular lymphoma in MALT.

Adult↗
PubMed1992

Increasing radiation dose intensity using hyperfractionation in patients with malignant glioma. Final report of a prospective phase I-II dose response study.

We attempted to show a dose effect relationship for radiation therapy by treating patients harbouring malignant glioma with increasing doses of radiation in a step-wise fashion. We postulated that no increase in delayed toxicity would be seen because we used hyperfractionation technique. Between January 1981 and December 1988 we treated 280 patients three times daily at 4 hour intervals. 100 patients received a total dose of 6141 cGy, 73 patients received 7120 cGy, and 107 patients received 8000 cGy. CCNU was given at the time of tumor progression following radiotherapy. Median time to tumor progression was 28 weeks for patients who received 6141 cGy, 27 weeks for patients who received 7120 cGy and 36 weeks for patients who received 8000 cGy. Median survival was 46 weeks for patients who received 6141 cGy, 38 weeks for patients who received 7120 cGy and 45 weeks for patients who received 8000 cGy. There was no statistically significant difference in either time to tumor progression or survival among the three treatment arms and no dose response effect was seen. There was no increase in delayed radiation toxicity when the total radiation dose was increased up to 8000 cGy.

Adolescent↗
PubMed1991

Development of a large-animal human brain tumor xenograft model in immunosuppressed cats.

A large-animal model was developed to facilitate the noninvasive investigation of the effect on the human glioma-derived D-54 MG (glioblastoma multiforme) continuous cell line of a variety of therapeutic regimens. Twenty random-bred male cats were inoculated intracerebrally with 1 x 10(7) D-54 MG tumor cells after being initiated on one of three preparatory regimens of cyclosporin A p.o. Reproducible success of D-54 MG xenotransplantation (100%, 6 of 6 cats) was achieved only after pretreatment with 120 mg cyclosporin A p.o. (24-30 mg/kg) daily for greater than or equal to 10 days prior to tumor implantation. High-performance liquid chromatography-derived whole blood cyclosporin A 12-h trough levels of greater than or equal to 640 ng/ml were seen in successful implants. Lesions ranging from 2 to 20 mm in diameter were seen in cats sacrificed 27-44 days after implantation with no growth seen in control animals. Histopathological examination revealed the tumors to be well-circumscribed anaplastic intracerebral tumors with some invasion into surrounding host parenchyma. Perivascular lymphocytic cuffing was observed, but intratumoral lymphocytic infiltration was minimal. Gadolinium-EDTA-enhanced nuclear magnetic resonance imaging provided accurate tumor localization in T1-weighted images (TE 26 ms; TR 600 ms). Biochemical tests of kidney, liver, and hematological function were within normal limits, although 10% (2 of 20) of the animals developed gingival hyperplasia, and 5% (1 of 20) developed intussusception. The reproducible growth of the D-54 MG human glioblastoma cell line in a large-animal model eliminates many of the limitations associated with the standard nude mouse/rat model, thereby providing a novel test bed for a variety of imaging modalities as well as for drug immunoconjugate localization and toxicity studies.

Animals↗
PubMed1991

Histomorphologic and immunophenotypic spectrum of primary gastro-intestinal B-cell lymphomas.

In order to compare primary gastro-intestinal (GI) B-cell lymphomas histomorphologically and immunophenotypically with orthologous steps of B-cell differentiation within the mucosa-associated lymphoid tissue (MALT) of the GI tract, a comprehensive panel of well characterized leucocyte differentiation antigens was composed. It comprised immunoglobulin constituents CD5, CD10, CD11c, CD20, CD23, CD24, CD30, CDw32, CD38, CD39, CDw75, CD76, and vimentin. These antigens yield characteristic immunoprofiles for the following B-cell compartments of the MALT, per se closely linked to cytologically distinct B-cell phenotypes: mantle zone (MZ), extrafollicular compartment (EF), follicle center (FC), and plasma-cell compartment (PC). An unselected series of 31 MALT B lymphomas (13 of low and 18 of high grade malignancy) was classified histologically in routine preparations and subsequently characterized immunohistochemically using fresh frozen tissue, monoclonal antibodies (MAbs) against the antigen panel listed above, and an indirect immunoperoxidase method. The final classification considered both morphology and immunoprofile of tumor cells. Ten tumors were "typical" in both respects: 2 closely corresponded to MZ, 5 to EF, 2 to FC and 1 to PC. The remaining 21 cases were characterized as "atypical" because of anaplastic cytology and/or abnormal co-expression and/or loss of antigens. A hybrid EF/FC phenotype was most frequently observed together with centrocyte-like or centrocytic anaplastic cytology of tumor cells. We conclude that MALT B-cell neoplasia comprises a broad spectrum of histo- and immunophenotypes ranging from well differentiated forms closely mimicking normal B-cell development to highly abnormal tumors which cannot be subclassified.

Antibodies, Monoclonal↗
PubMed1990

Identity of HML-1 antigen on intestinal intraepithelial T cells and of B-ly7 antigen on hairy cell leukaemia.

Immunoprecipitation of radioiodinated hairy cell leukaemia (HCL) cell lysates with monoclonal antibody (MoAb) HML-1, originally reported to recognize intraepithelial T cells, and with MoAb B-ly7, originally reported to react with HCL, led to identical biochemical characteristics. In SDS-PAGE under reducing conditions, a major band of 143 kDa, a broad band ranging from 112 to 122 kDa, and two additional faint bands of 175 and 100 kDa could be determined. Deglycosylation of N-linked sugar moieties by treatment of immunoprecipitates with endoglycosidases indicated that the two main protein cores of the antigen are predominantly if not exclusively glycosylated by complex and hybrid types of oligosaccharide chains. Competitive binding inhibition demonstrated that both MoAb are directed against different epitopes. Immunohistochemically, the staining patterns obtained with both MoAb in normal tissues, in T- and B-cell lymphomas, and in HCL were identical except for a single case of HCL which was HML-1-/B-ly-7+. We conclude that MoAb HML-1 and B-ly7 recognize the same antigen.

Antibodies, Monoclonal↗
PubMed1990

Monoclonal antibody HML-1, a marker for intraepithelial T cells and lymphomas derived thereof, also recognizes hairy cell leukemia and some B-cell lymphomas.

Current views regard monoclonal antibody HML-1 as an exquisite marker for intraepithelial T cells and primary intestinal and cutaneous T-cell lymphomas. We show that HML-1 reacted with 11 of 12 cases of hairy cell leukemia, with 1 of 13 cases of primary gastrointestinal B-cell lymphoma, and with an unclassified large-cell B lymphoma of the thoracic wall. We conclude that HML-1 is not restricted to the T-cell lineage and that the HML-1 antigen is expressed in a small subset of both T- and B-cell neoplasms.

Antibodies, Monoclonal↗
PubMed1989

Brain tolerance to middle cerebral artery occlusion during hypotension in primates.

The aim of this study was to determine the duration of middle cerebral artery occlusion required to produce significant ischemic damage when the occlusion occurs during controlled systemic hypotension. In 21 anesthetized cynomolgus monkeys, an IV infusion of sodium nitroprusside was used to lower the mean arterial blood pressure to 45-50 mmHg for 90 minutes. Middle cerebral artery occlusion for 15, 30, 45, or 60 minutes was performed during the hypotensive period. Neurological function was then evaluated every 8 hours for a total of 72 hours. At the end of the observation period, the monkeys were again anesthetized, magnetic resonance imaging was performed, and the brain was perfused with 10% buffered formalin. Neurological deficits were observed after 30 minutes, but not after 15 minutes, of middle cerebral artery occlusion, and rapidly increased in incidence and severity when the duration of occlusion was increased. After 60 minutes of occlusion, all the monkeys exhibited severe deficits. Four monkeys died during the observation period--two in each of the 45- and 60-minute occlusion groups. Histopathological examination revealed that little or no ischemic damage resulted from a 15-minute occlusion during hypotension. However, severe ischemic damage began to occur after only 30 minutes of occlusion, and all monkeys subjected to middle cerebral artery occlusion for 60 minutes developed extensive regions of infarction. The size and incidence of these infarctions correlated well with the lesions observed in the magnetic resonance images. These results demonstrate that the duration of middle cerebral artery occlusion that produces cerebral infarction in primates is drastically reduced when the occlusion occurs at hypotensive levels commonly employed during neurovascular surgical procedures.

Animals↗
PubMed1988

Brain hemorrhage associated with methanol poisoning.

We recently treated seven patients who were victims of accidental methanol intoxication. Five of the seven patients died within 72 h of hospital admission. The two survivors were discharged from the hospital without visual or neurologic impairment. Hemorrhagic necrosis of the brain was found on CT scan and at autopsy in two patients who died. This complication of methanol intoxication prompted us to review our experience with this poison since 1980. Of 45 methanol intoxication patients treated in our ICU, CT scan was performed in 21, and brain hemorrhage was documented in six, thereby giving an incidence of at least six of 45 or 13.5%. Although hemorrhagic and nonhemorrhagic putamenal necrosis has been described from methanol poisoning previously, we postulate that heparinization during hemodialysis may contribute to brain hemorrhage complicating methanol poisoning and recommend the use of artificial kidneys with albumin-primed biocompatible membranes so that heparin administration during hemodialysis can be minimized.

Adolescent↗
PubMed1987

Effect of clot removal at 24 hours on chronic vasospasm after SAH in the primate model.

The efficacy of complete clot removal 24 hours after subarachnoid hemorrhage (SAH) in the prevention of chronic cerebral vasospasm was evaluated in monkeys in a blind randomized controlled trial. Twenty-four monkeys were randomized to one of three groups to undergo sham-operation (sham-operated group), clot placement only (clot group), or clot placement and removal (clot-removal group). By means of standard microsurgical techniques, the major cerebral vessels bilaterally were dissected free of arachnoid. An autologous hematoma averaging 5 gm was placed around the vessels in the subarachnoid spaces in the clot and clot-removal groups. Saline solution was instilled in the subarachnoid spaces of the sham-operated group. All animals underwent reoperation 24 hours after the first procedure. In the clot-removal group, the hematoma was evacuated. In the sham-operated and clot groups, the incision was simply closed again after 3 hours of anesthesia. Indices monitored before and 7 days after SAH induction included neurological status, angiographic cerebral vessel caliber, and arterial blood pressure. All animals were evaluated with magnetic resonance imaging (MRI); representative animals were evaluated with computerized tomography (CT) brain scans. There were no neurological deficits in either the sham-operated or the clot-removal groups. One animal in the clot group developed a progressive delayed ischemic deficit on Day 5 after SAH. A second animal in this group died suddenly on Day 4 post-SAH. An autopsy revealed a recent infarct in the territory of the superior cerebellar artery. Clinical findings correlated with MRI and CT images. Significant vasospasm (25% to 100% reduction in vessel caliber) was present on Day 7 in 100% of the clot animals (p less than 0.01). There was no significant vasospasm (p greater than 0.05) on Day 7 in either the sham-operated or the clot-removal groups. A large volume of clot placed bilaterally resulted in a 25% incidence of delayed ischemic deficit. Evacuation of subarachnoid hematoma within 24 hours of SAH prevented the development of chronic vasospasm and delayed ischemic deficit in the primate model.

Animals↗
PubMed1985

Multiple daily fractionated radiation therapy and misonidazole in the management of malignant astrocytoma. A preliminary report.

Various attempts have been made to improve the effectiveness of radiation in the treatment of cerebral malignant astrocytomas. A trend favoring multiple daily fractionated (MDF) radiation therapy over conventional single daily fractionated (CF) radiation therapy was identified in our previous study. In order to assess the effect of MDF with and without misonidazole, a province-wide prospective randomized trial was initiated in January 1981. By March 1984, 124 patients with histologically verified grade III and IV astrocytomas were randomized to CF (5800 cGy/6 weeks/30 fractions), MDF (6141 cGy/4.5 weeks/69 fractions at 89 cGy every 3-4 hours, three times a day) and MDF in combination with misonidazole (1.25 g/m2 three times weekly for the first 3 weeks). Thirty-eight patients were randomized to CF, 43 patients to MDF, and 43 patients to MDF and misonidazole. At the preliminary assessment in July 1984, the median survival time was 27 weeks for the CF group, 39 weeks for the MDF group and 49 weeks for MDF and misonidazole group. The 1-year actuarial survival rate from surgery was 20% for CF group, 41% for MDF group, and 45% for MDF and misonidazole group. There is a statistically significant difference (P less than 0.001) between the CF and MDF group. However, the addition of misonidazole does not significantly alter survival.

Adolescent↗
PubMed1985

Photoradiation therapy of 9L-gliosarcoma in rats: hematoporphyrin derivative (types I and II) followed by laser energy.

Suspensions of 9L-gliosarcoma cells were inoculated into the brain or flank of rats and photoradiation therapy (PRT) was applied to the resulting tumors. The PRT consisted of hematoporphyrin derivative (HpD), type I or II, followed by single-fiber laser energy 24, 48, or 72 h later. Necrotic foci in brain tumors were most numerous following laser exposure 24 h after HpD; they were more than twice as common, and with less damage to healthy tissue, after HpD II than after HpD I with the same laser dose. Neither lifespan nor the final weight of brain tumor was affected by the type of HpD or whether PRT was applied once or twice. In rats with flank tumor, multiple PRT (up to X 4) did not delay tumor growth; also, 11 of 12 PRT-treated flank tumors grew after implantation at various sites in healthy rats. We conclude that HpD II is a more effective photosensitizer than HpD I. However, the value of PRT will be limited until a lethal dose of laser energy can be delivered throughout a tumor without destroying vital healthy tissue.

Animals↗