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M Handler

Publications and source records attributed to M Handler.

18 recordsLinked to original sources
PubMed2004

Intracranial germ cell tumors: a single institution experience and review of the literature.

There is little literature to guide therapy in children and young adults with intracranial germ cell tumors. We present 17 consecutively diagnosed intracranial germ cell tumors at The Children's Hospital, Denver, from 1995 to 2001. Of 17 patients, 3 had considerable delay in diagnosis. Two with suprasellar tumors presented with dementia, blindness and pan-hypopituitarism and another with recurrent subarachnoid hemorrhage. Seven had germinoma, three were metastatic at diagnosis. Ten had non-germinomatous germ cell tumors (NGGCT), 5/10 were alpha feto-protein (AFP) positive only, one beta-human chorionic growth (betaHCG) factor positive only, 3 positive for AFP and betaHCG, and 1 malignant teratoma. Therapy for metastatic patients consisted of chemotherapy followed by craniospinal radiation (CSI). Patients with localized disease received chemotherapy followed by focal radiation. Two patients received chemotherapy only, one because she died of sepsis while receiving chemotherapy and one because of neurologic injury incurred during surgery parents elected for no therapy. Three patients have died, one of tumor recurrence, one from a remote complication of surgery and one of sepsis. Twelve patients are alive without evidence of disease from 10 to 68 months (median 31.5 months). All five children with only AFP positivity, treated with chemotherapy and focal radiation are alive without evidence of disease at 10, 16, 22, 41 and 41 months. Thus, there is little evidence that CSI is necessary in non-metastatic germinomas and AFP positive NGGCTs when combined chemotherapy and radiation therapy is used. However, complications of delayed diagnosis, surgery and chemotherapy are important causes of mortality, with only one patient dying of tumor.

Adult↗
PubMed2001

APP processing and synaptic plasticity in presenilin-1 conditional knockout mice.

We have developed a presenilin-1 (PS1) conditional knockout mouse (cKO), in which PS1 inactivation is restricted to the postnatal forebrain. The PS1 cKO mouse is viable and exhibits no gross abnormalities. The carboxy-terminal fragments of the amyloid precursor protein differentially accumulate in the cerebral cortex of cKO mice, while generation of beta-amyloid peptides is reduced. Expression of Notch downstream effector genes, Hes1, Hes5, and Dll1, is unaffected in the cKO cortex. Although basal synaptic transmission, long-term potentiation, and long-term depression at hippocampal area CA1 synapses are normal, the PS1 cKO mice exhibit subtle but significant deficits in long-term spatial memory. These results demonstrate that inactivation of PS1 function in the adult cerebral cortex leads to reduced Abeta generation and subtle cognitive deficits without affecting expression of Notch downstream genes.

Alzheimer Disease↗
PubMed2000

Presenilin-mediated modulation of capacitative calcium entry.

We studied a novel function of the presenilins (PS1 and PS2) in governing capacitative calcium entry (CCE), a refilling mechanism for depleted intracellular calcium stores. Abrogation of functional PS1, by either knocking out PS1 or expressing inactive PS1, markedly potentiated CCE, suggesting a role for PS1 in the modulation of CCE. In contrast, familial Alzheimer's disease (FAD)-linked mutant PS1 or PS2 significantly attenuated CCE and store depletion-activated currents. While inhibition of CCE selectively increased the amyloidogenic amyloid beta peptide (Abeta42), increased accumulation of the peptide had no effect on CCE. Thus, reduced CCE is most likely an early cellular event leading to increased Abeta42 generation associated with FAD mutant presenilins. Our data indicate that the CCE pathway is a novel therapeutic target for Alzheimer's disease.

Alzheimer Disease↗
PubMed2000

Role of presenilin-1 in murine neural development.

Our previous studies showed that presenilin-1 (PS1) is required for murine neural and skeletal development. Here we report that the reduction in the neural progenitor cells observed in the PS1-/- mouse brain is due to premature differentiation of progenitor cells, rather than to increased apoptotic cell death or decreased cell proliferation. In the ventricular zone of PS1-/- mice, expression of the Notch1 downstream effector gene Hes5 is reduced, and expression of the Notch1 ligand Dll1 is elevated, indicating reduced Notch signaling. These results provide direct evidence that PS1 is involved in the regulation of neurogenesis and Notch signaling during development.

Animals↗
PubMed2000

Presenilin-1 regulates neuronal differentiation during neurogenesis.

Mutations in Presenilin-1 (PS1) are a major cause of familial Alzheimer's disease. Our previous studies showed that PS1 is required for murine neural development. Here we report that lack of PS1 leads to premature differentiation of neural progenitor cells, indicating a role for PS1 in a cell fate decision between postmitotic neurons and neural progenitor cells. Neural proliferation and apoptotic cell death during neurogenesis are unaltered in PS1(-/-) mice, suggesting that the reduction in the neural progenitor cells observed in the PS1(-/-) brain is due to premature differentiation of progenitor cells, rather than to increased apoptotic cell death or decreased cell proliferation. In addition, the premature neuronal differentiation in the PS1(-/-) brain is associated with aberrant neuronal migration and disorganization of the laminar architecture of the developing cerebral hemisphere. In the ventricular zone of PS1(-/-) mice, expression of the Notch1 downstream effector gene Hes5 is reduced and expression of the Notch1 ligand Dll1 is elevated, whereas expression of Notch1 is unchanged. The level of Dll1 transcripts is also increased in the presomitic mesoderm of PS1(-/-) embryos, while the level of Notch1 transcripts is unchanged, in contrast to a previous report (Wong et al., 1997, Nature 387, 288-292). These results provide direct evidence that PS1 controls neuronal differentiation in association with the downregulation of Notch signalling during neurogenesis.

Animals↗
PubMed1998

Antisense targeting of perlecan blocks tumor growth and angiogenesis in vivo.

Perlecan, a ubiquitous heparan sulfate proteoglycan, possesses angiogenic and growth-promoting attributes primarily by acting as a coreceptor for basic fibroblast growth factor (FGF-2). In this report we blocked perlecan expression by using either constitutive CMV-driven or doxycycline- inducible antisense constructs. Growth of colon carcinoma cells was markedly attenuated upon obliteration of perlecan gene expression and these effects correlated with reduced responsiveness to and affinity for mitogenic keratinocyte growth factor (FGF-7). Exogenous perlecan effectively reconstituted the activity of FGF-7 in the perlecan-deficient cells. Moreover, soluble FGF-7 specifically bound immobilized perlecan in a heparan sulfate-independent manner. In both tumor xenografts induced by human colon carcinoma cells and tumor allografts induced by highly invasive mouse melanoma cells, perlecan suppression caused substantial inhibition of tumor growth and neovascularization. Thus, perlecan is a potent inducer of tumor growth and angiogenesis in vivo and therapeutic interventions targeting this key modulator of tumor progression may improve cancer treatment.

Animals↗
PubMed1998

Headache and Chiari I malformation in the pediatric population.

There has been disagreement regarding surgical intervention in treating pediatric patients with Chiari I malformation with headache as sole complaint. Therefore, we retrospectively reviewed our experience over a 6-year period, with patients less than 5 years of age (mean = 34.8 months) with radiographically confirmed Chiari I malformation. We identified 7 patients who presented with headaches as their only complaint. The headaches varied in location and severity. All patients were treated with posterior fossa decompression and syringosubarachnoid shunt when indicated. At follow-up, all patients were noted to have rapid clinical improvement (mean = 11.6 weeks) and remain asymptomatic. Our data suggest that patients less than 5 years of age with Chiari I malformation benefit from surgical decompression when presenting with a chief complaint of headache.

Arnold-Chiari Malformation↗
PubMed1997

Developmental expression of perlecan during murine embryogenesis.

Perlecan is a modular heparan sulfate proteoglycan that is an intrinsic constituent of all basement membranes and extracellular matrices. Because of its strategic position and unique structure, perlecan has been implicated in modulating the activity of various growth factors required for normal development and tissue homeostasis. To gain insights into the potential function of perlecan in vivo, we examined the spatiotemporal distribution of its mRNA and protein core during murine embryogenesis. We utilized a new affinity-purified antibody that recognizes specifically the protein core of perlecan together with an in situ RT-PCR approach to perform a systematic analysis of perlecan expression and deposition during murine ontogeny. Perlecan appeared early (E10.5) in tissues of vasculogenesis including heart, pericardium, and major blood vessels. Its early expression coincided with the development of the cardiovascular system. Subsequently (E11-13), the greatest deposition of perlecan occurred within the developing cartilage, especially the cartilage undergoing endochondral ossification, where it remained elevated throughout all the developmental stages, and up to adulthood. Interestingly, the mRNA levels of perlecan were always higher in all the vascularized tissues, principally within endothelial cells, while chondrocytes displayed relatively low mRNA levels. This suggests a higher biosynthesis and turnover rates in the blood vessels vis-à-vis those of cartilaginous and other mesenchymal tissues. During later stages of development (E13-17.5) perlecan mRNA levels progressively increased and its expression correlated with the onset of tissue differentiation of various parenchymal organs including the developing kidneys, lungs, liver, spleen, and gastrointestinal tract. The central nervous system showed no perlecan expression with the exception of the calvaria and choroid plexus. Collectively, the results indicate that perlecan may play crucial roles not only in vasculogenesis but also in the maturation and maintenance of differentiated tissues, including cartilage.

Animals↗
PubMed1997

Thrombin and its precursor in human cerebrospinal fluid.

The blood coagulation cascade proteolytic enzyme, thrombin, affects many cell types, including neurons and astrocytes, in which it prevents process outgrowth and induces significant morphological degeneration and even cell death. Since thrombin may contribute significantly to pathological conditions in the central nervous system (CNS), where it is synthesized locally, we measured the levels of thrombin and its precursor, prothrombin, in the cerebrospinal fluid (CSF) of 67 individuals from 6 groups: non-neurologic controls (NNC); spinal degenerative disease (SDD); peripheral nerve disease (PND); cerebrovascular, neuroimmune and seizure disorders and tumor (CNSD); traumatic brain injury (TBI) and neurodegenerative disorders (NDD). We employed a sensitive chromogenic assay utilizing the thrombin specific tripeptide substrate, S-2238, to evaluate CSF levels of thrombin and prothrombin. The latter estimated after its conversion to active enzyme by the snake venom prothrombinase, ecarin. No measurable active thrombin was detected in these CSF samples. However, activatable prothrombin was measured in all groups. The mean activatable prothrombin concentrations (in nM) were 7.26 +/- 3.39 (NNC); 8.85 +/- 3.09 (SDD); 6.78 +/- 2.58 (PND); 6.33 +/- 3.87 (CNSD); 5.10 +/- 1.86 (TBI), and 7.80 +/- 3.27 (NDD). Duncan's multiple comparison test showed significant reduction (p <0.05) in prothrombin levels of the TBI group. Our data suggests that the prothrombin zymogen gains access to the CSF, likely across either an intact or compromised blood-brain barrier (BBB), in increased amounts with age. Reduced levels in TBI patients may have diagnostic and/or prognostic value.

Adult↗
PubMed1988

Planning ventriculoperitoneal shunts in infants and small children.

A neurosurgeon planning a ventriculoperitoneal shunt in an infant or child must consider the question of how long a shunt to use in order to compensate for linear growth. Ideally, the system should be just long enough to accommodate the child's further development without being any longer than necessary. To approach the problem systematically, we used established criteria for prediction of growth to determining the catheter length required in adulthood. Our aim was to devise a simple 'rule of thumb' method for determining the catheter length necessary for maximal survival of a functioning shunt system.

Adolescent↗
PubMed1983

Acquired immunodeficiency syndrome: cerebral computed tomographic manifestations.

CT examination of the central nervous system was performed in 19 patients with acquired immunodeficiency syndrome (AIDS). Eighteen patients were homosexuals, and five drug abusers. Parenchymal and meningeal inflammations were seen in patients with intracranial manifestations of the disease. The most common demonstrable lesion in the parenchyma was toxoplasmosis, which produced ring enhancement, solid enhancement, and nonenhancing focal edema. The most common meningeal inflammation was cryptococcosis, which was diagnosed by examination of the cerebrospinal fluid and did not show specific CT changes. It is concluded that toxoplasmosis and cryptococcosis should be the first diagnostic consideration in patients with neurologic findings who have a history of homosexuality and/or intravenous drug abuse and previous unusual infections or anergy. A delayed contrast scan, single or double dose, appears to be the most accurate method of outlining the total extent of disease thereby helping to locate the best biopsy site for pretreatment diagnosis. Empirical institution of toxoplasmosis therapy is recommended in those cases in which CT findings are consistent with toxoplasmosis and the biopsy shows only nonspecific encephalitis. A biopsy of every parenchymal lesion is not considered necessary.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Intracerebral toxoplasmosis in patients with acquired immune deficiency syndrome.

The acquired immune deficiency syndrome (AIDS) is a recently described T-cell deficiency predisposing patients to a spectrum of opportunistic infections. Kaposi's sarcoma, and other neoplasms. It appears primarily among homosexual males and intravenous drug abusers, but is now being observed in other groups as well. The authors describe six adult patients with AIDS who developed intracranial toxoplasmosis. In four patients, diagnosis was made by brain biopsy, and in one by serology. These patients received a 90-day course of therapy with sulfadiazine, pyrimethamine, or both when tolerated, and improved neurologically. In one patient, the brain biopsy was nondiagnostic and the organism was identified at autopsy. On computerized tomographic and pathological follow-up studies the organism appeared to be eradicated by therapy. Early aggressive diagnostic study and prompt institution of therapy are imperative for reversal of neurological deficits. Despite cure of toxoplasmosis, the prognosis in patients with AIDS is poor; the mortality in this series was 67%. Isolation precautions should be taken by those caring for such patients.

Acquired Immunodeficiency Syndrome↗
PubMed1982

Severe thrombocytopenia as a result of contrast left ventricular angiography.

A case report of a 29-year-old Hispanic male who developed an acute thrombocytopenic reaction immediately following a cardiac catheterization using Hypaque-M radiographic dye. Laboratory studies immediately post-catheterization revealed a platelet count of 11,000 with a subsequent further drop to a low of 4,000. A need for the prompt identification and possible causes of this unusual reaction are discussed. Recovery occurred following treatment with corticosteroids.

Adult↗
PubMed1982

Results of testicular autotransplantation using the microvascular technique: experience with 8 intra-abdominal testes.

Children with intra-abdominal testes comprise a small group presenting for surgical management of the undescended testicle. During the last 4 years 6 children with 8 intra-abdominal testes have undergone testicular surgery. In 7 testicles the technique involved high intraperitoneal division of the testicular pedicle with reanastomosis of the distal spermatic artery and vein to the inferior epigastric artery and vein using the operating room microscope. Microsurgery on the 7 intra-abdominal testicles led to good results in 6 cases. In 1 testicle venous infarction occurred secondary to venous congestion. Although many children with intra-abdominal testes have been managed using the standard Stephens-Fowler technique, we believe that microsurgical reanastomosis will improve the previously reported results.

Adolescent↗