Quantum Barkhausen noise induced by domain wall cotunneling

Most macroscopic magnetic phenomena (including magnetic hysteresis) are typically understood classically. Here, we examine the dynamics of a uniaxial rare-earth ferromagnet deep within the quantum regime, so that domain wall motion, and the associated hysteresis, is initiated by quantum nucleation, which then grows into large-scale domain wall motion, which is observable as an unusual form of Barkhausen noise. We observe noncritical behavior in the resulting avalanche dynamics that only can be explained by going beyond traditional renormalization group methods or classical domain wall models. We find that this "quantum Barkhausen noise" exhibits two distinct mechanisms for domain wall movement, each of which is quantum-mechanical, but with very different dependences on an external magnetic field applied transverse to the spin (Ising) axis. These observations can be understood in terms of the correlated motion of pairs of domain walls, nucleated by cotunneling of plaquettes (sections of domain wall), with plaquette pairs correlated by dipolar interactions; this correlation is suppressed by the transverse field. Similar macroscopic correlations may be expected to appear in the hysteresis of other systems with long-range interactions.

Doppler Ultrasound Flow Reversal in the Superior Sagittal Sinus to Detect Cerebral Venous Congestion in Vein of Galen Malformation

BACKGROUND AND PURPOSE

Vein of Galen malformation is a rare congenital cerebrovascular malformation. In affected patients, increased cerebral venous pressure constitutes an important etiologic factor for the development of brain parenchymal damage. The aim of this study was to investigate the potential of serial cerebral venous Doppler measurements to detect and monitor increased cerebral venous pressure.

MATERIALS AND METHODS

This was a retrospective monocentric analysis of ultrasound examinations within the first 9 months of life in patients with vein of Galen malformation admitted at <28 days of life. Categorization of perfusion waveforms in the superficial cerebral sinus and veins into 6 patterns was based on antero- and retrograde flow components. We performed an analysis of flow profiles across time and correlation with disease severity, clinical interventions, and congestion damage on cerebral MR imaging.

RESULTS

The study included 44 Doppler ultrasound examinations of the superior sagittal sinus and 36 examinations of the cortical veins from 7 patients. Doppler flow profiles before interventional therapy correlated with disease severity determined by the Bicêtre Neonatal Evaluation Score (Spearman ρ = -0.97, P = < .001). At this time, 4 of 7 patients (57.1%) showed a retrograde flow component in the superior sagittal sinus, whereas after embolization, none of the 6 treated patients presented with a retrograde flow component. Only patients with a high retrograde flow component (equal or more than one-third retrograde flow, n = 2) showed severe venous congestion damage on cerebral MR imaging.

CONCLUSIONS

Flow profiles in the superficial cerebral sinus and veins appear to be a useful tool to noninvasively detect and monitor cerebral venous congestion in vein of Galen malformation.

Connections between constitutional mismatch repair deficiency syndrome and neurofibromatosis type 1

Constitutional mismatch repair (MMR) deficiency (CMMRD) is a rare childhood cancer susceptibility syndrome resulting from biallelic germline loss-of-function mutations in one of the MMR genes. Individuals with CMMRD have high risk to develop a broad spectrum of malignancies and frequently display features reminiscent of neurofibromatosis type 1 (NF1). Evaluation of the clinical findings of genetically proven CMMRD patients shows that not only multiple café-au-lait macules but also any of the diagnostic features of NF1 may be present in a CMMRD patient. This phenotypic overlap may lead to misdiagnosis of CMMRD patients as having NF1, which impedes adequate management of the patients and their families. The spectrum of CMMRD-associated childhood malignancies includes high-grade glioma, acute myeloid leukaemia or rhabdomyosarcoma, also reported as associated with NF1. Reported associations between NF1 and these malignancies are to a large extent based on studies that neither proved the presence of an NF1 germline mutation nor ruled-out CMMRD in the affected. Hence, these associations are challenged by our current knowledge of the phenotypic overlap between NF1 and CMMRD and should be re-evaluated in future studies. Recent advances in the diagnostics of CMMRD should render it possible to definitely state or refute this diagnosis in these individuals.

Neurofibromatosis type 1 (NF1) and associated tumors

Neurofibromatosis type 1 (NF1) is a frequent neurocutaneous syndrome that predisposes for various benign and malignant tumors. Most characteristic are neurofibromas which occur in almost all NF1 patients at some point in lifetime. Although neurofibromas are benign tumors they can be disfiguring and plexiform neurofibromas may progress to malignant peripheral nerve sheath tumors. Overall survival rates of patients with these malignant tumors are poor. Other neoplasias frequently observed in NF1 patients are pilocytic astrocytomas, gastrointestinal stromal tumors, pheochromocytomas and juvenile myelomonocytic leukemia. Several other tumors have been reported in NF1 patients but it is unclear if there is a true association between the particular tumor type and NF1. Some of these tumors might be caused by a rare recessively inherited childhood cancer syndrome termed constitutive mismatch repair deficiency syndrome which shows certain phenotypic overlap with NF1 but includes a broad spectrum of tumors which usually do not occur in NF1. The development of NF1-associated tumors is largely explained by the underlying defect of the NF1 gene which results in activation of the RAS proto-oncogene- a key mechanism of tumorigenesis. Several downstream effectors of activated RAS as well as cooperating molecular pathways have been identified. These insights provide the basis to develop novel targeted treatment strategies which are urgently needed to improve the outcome for patients with NF1-associated malignancies.

[Transient splenial lesion in influenza A H1N1 2009 infection]

Severe neurologic complications have been rarely reported during novel pandemic influenza A(H1N1) virus infections. We describe the case of an 10-year-old boy with new onset seizures and proven influenza A(H1N1) 2009 infection showing a reversible hyperintense lesion in the splenium of the corpus callosum on T2-weighted and FLAIR magnetic resonance images without contrast enhancement. Transient splenial lesions have been described in the context of virus encephalopathy and do not require specific treatment.

[The TRPV1 channel as a target for the treatment of pain]

INTRODUCTION

Pain results from the processing of a large number of signals produced at different levels of the central and peripheral nervous system, which are generated in response to stimuli from the environment or from the organism itself. One of the strategies for generating new analgesics consists in studying the molecular bases that underlie the detection of painful stimuli, that is to say, the receptors. One receptor that plays a very important role in sensory and pain physiology is TRPV1, which is responsible for detecting mechanical, chemical and thermal stimuli. AIMS. The aim of this study is to discuss the structural and functional aspects of the TRPV1 channel, as well as its participation in certain pathological processes and the possible perspectives for clinical research.

DEVELOPMENT

TRPV1 activation in sensory neurons generates signals that reach the central nervous system, where they are interpreted as pain, as well as triggering the peripheral release of pro-inflammatory substances that make other neurons sensitive to subsequent stimuli. TRPV1 is a receptor that is structurally similar to other voltage-dependent ion channels, with the capacity to detect and integrate several different stimuli from the environment, such as dangerously high temperatures or irritants. Furthermore, the activity of this channel is linked to several signalling chains related with inflammatory processes.

CONCLUSIONS

The central role of TRPV1 in the physiology of pain will surely encourage the development of drugs aimed at this receptor which can be used in the treatment of several types of pain.

Aplasia cutis congenita of the scalp: how much therapy is necessary in large defects?

AIM

To show that local antibiotic management and a regular inspection of aplasia cutis congenita of the skull can give an excellent result.

METHOD

This case reports a girl born with aplasia cutis congenita of the skull presenting with a large aplasia of the epidermis, dermis, subcutaneous tissue and galea, including a bone defect without any additional risk factor, e.g. early eschar formation, cerebrospinal fluid leakage or uncommon dural blood vessels.

RESULTS

A primarily conservative treatment with local wet and antibiotic dressings together with a systemic antibiotic treatment for the first 2 wk led to an excellent result and thus prevented untimely operative and peri-operative procedures.

CONCLUSIONS

Here we have shown that conservative treatment might be an option, even if the wound diameter is greater than 1 cm(2), to prevent infants from any untimely operative procedure with an elevated operative risk if any additional risk factors are excluded.

Giant condyloma of Buschke-Loewenstein in association with erythroderma

The Buschke-Loewenstein tumour is regarded as a type of verrucous carcinoma occurring on anogenital mucosal surfaces. The tumour is locally invasive but displays a benign cytology and rarely metastasizes. It is associated with human papillomavirus types 6 and 11. We describe a case of Buschke-Loewenstein tumour occurring in a 61-year-old man which behaved in a locally aggressive manner and was associated with human papillomavirus type 16 and erythroderma which proved resistant to treatment. The patient refused surgery and therapy with interferon alpha was ineffective. Chemotherapy with systemic cisplatin and 5-fluorouracil produced a partial response before the patient succumbed from gram-negative septicaemia.

Nerve growth factor increases L-type calcium current in pancreatic beta cells in culture

We analyzed the effect of culturing adult rat beta cells with NGF2.5 S for 5 to 7 days on macroscopic barium current (I(Ba)), and determined the role of Na and Ca channels on neurite-like process extension induced by NGF and dbcAMP, and by KCI depolarization. After five days in culture with 2.5S NGF, beta cells exhibit a 102% increase in I(Ba) density. This effect is on L-type calcium channels because most of the current is blocked by nifedipine. The application of NGF for 5 minutes to the cells deprived of the trophic factor for 24 hr further increases I(Ba) current by 91%. These results suggest that the trophic factor regulates I(Ba) by two different mechanisms, a) an increase in channel density and b) a rapid modulation of the channels already present in the membrane. Finally, we found that ion-channel activity modifies the growth of neurite-like processes. After 2 weeks in culture with high KCl, almost 14% of beta cells extend neurite-like processes and the most impressive effect is observed in the presence of KCl, NGF, and dbcAMP simultaneously, where nearly 60% of the cells extend neurite-like processes. Tetrodotoxin and nifedipine reduce the morphological changes induced by these agents.

Nerve growth factor increases insulin secretion and barium current in pancreatic beta-cells

We analyzed the effect of a brief exposure to nerve growth factor (NGF) on insulin secretion and macroscopic barium currents of single adult rat pancreatic beta-cells. After a 1-h exposure to NGF (50 ng/ml), single beta-cells show a 2.5-fold increase in the insulin secretion index in 5.6 mmol/l glucose and a nearly twofold increase in 15.6 mmol/l glucose compared with control cells. We have recently demonstrated that pancreatic beta-cells synthesize and secrete NGF. We analyzed the effect of endogenous NGF on insulin secretion by incubating islet cells in the presence of an anti-NGF monoclonal antibody for 1 h in different glucose concentrations. Although the basal insulin secretion index (5.6 mmol/l glucose) is not affected, glucose-stimulated insulin secretion (15.6 mmol/l glucose) is decreased by 41% in the presence of the antibody. This effect is mediated by the activation of the NGF receptor TrkA because the specific inhibitor of Trk phosphorylation K252a also blocks NGF-induced increase in insulin secretion, both in the presence and absence of exogenous NGF. Using the whole-cell variation of the patch-clamp technique, we found that cells exposed to NGF for 5 min exhibit a 32% increase in the average barium current density. These results suggest that the effects of NGF on insulin secretion are partially mediated by an increase in calcium current through Ca channels. These results further suggest that NGF plays an important autoregulatory role in pancreatic beta-cell function. Two targets of short-term NGF-modulation are insulin secretion and calcium-channel activity.

Mitotic recombination effects homozygosity for NF1 germline mutations in neurofibromas

Pure populations of neurofibroma-derived Schwann cells bearing both NF1 mutated alleles (NF1-/-) have been isolated from different neurofibromas showing loss of heterozygosity of nearly the entire 17q chromosome. By comparing molecular and fluorescent in situ hybridization analysis of these cells, we demonstrate mitotic recombination is the mechanism underlying this type of loss of heterozygosity leading to reduction to homozygosity of NF1 germline mutation.

Somatic NF1 mutational spectrum in benign neurofibromas: mRNA splice defects are common among point mutations

Neurofibromas, benign tumors that originate from the peripheral nerve sheath, are a hallmark of neurofibromatosis type 1 (NF1). Although loss of heterozygosity (LOH) is a common phenomenon in this neoplasia, it only accounts for part of the somatic NF1 mutations found. Somatic point mutations or the presence of "two hits" in the NF1 gene have only been reported for a few neurofibromas. The large size of the NF1 gene together with the multicellular composition of these tumors has greatly hampered their molecular characterization. Here, we present the somatic NF1 mutational analysis of the whole set of neurofibromas studied by our group and consisting in 126 tumors derived from 32 NF1 patients. We report the identification of 45 independent somatic NF1 mutations, 20 of which are reported for the first time. Different types of point mutations together with LOH affecting the NF1 gene and its surrounding region or extending along the 17q arm have been found. Among point mutations, those affecting the correct splicing of the NF1 gene are common, coinciding with results reported on germline NF1 mutations. In most cases, we have been able to confirm that both copies of the NF1 gene are inactivated. We have also found that both somatic and germline mutations can be expressed at the RNA level in the neoplastic cells. Furthermore, we have observed that the study of more than one tumor derived from the same patient is useful for the identification of the germline mutation. Finally, we have noticed that the culture of neurofibromas and their fibroblast clearance facilitates LOH detection in cases in which it is difficult to determine.

Schwann cells harbor the somatic NF1 mutation in neurofibromas: evidence of two different Schwann cell subpopulations

Neurofibromas are one of the most characteristic features of neurofibromatosis type 1 (NF1), an inherited autosomal-dominant neurogenetic disorder affecting 1 in 3500 individuals worldwide. These benign tumors mainly consist of Schwann cells (SCs) and fibroblasts. Recent evidence demonstrates that somatic mutations at the NF1 gene are found in neurofibromas, but it has not been demonstrated whether SCs, fibroblasts and/or both cell types bear a somatic loss of NF1. We recently established a cell culture system that allows selective expansion of human SCs from neurofibromas. We cultured pure populations of SCs and fibroblasts derived from 10 neurofibromas with characterized NF1 mutations and found that SCs but not fibroblasts harbored a somatic mutation at the NF1 locus in all studied tumors. Furthermore, by culturing neurofibroma-derived SCs under different in vitro conditions we were able to obtain two genetically distinct SC subpopulations: NF1(-/-) and NF1(+/-). These data strongly support the idea that NF1 mutations in SCs, but not in fibroblasts, correlate to neurofibroma formation and demonstrate that only a portion of SCs in neurofibromas have mutations in both NF1 alleles.

Long-term culture and characterization of human neurofibroma-derived Schwann cells

Neurofibromas are benign tumors arising from the peripheral nerve sheath and are a typical finding in neurofibromatosis type 1 (NF1). Schwann cells are the predominant cell type in neurofibromas and thus are supposed to play a major role in the pathogenesis of these tumors. It is not known, however, if NF1 mutations in Schwann cells result in an altered phenotype that subsequently leads to tumor formation. To characterize the biological properties of neurofibroma-derived Schwann cells we developed cell culture techniques that enabled us to isolate Schwann cells from neurofibromas and grow them in vitro for several weeks without significant fibroblast contamination. Neurofibroma-derived Schwann cells were characterized by altered morphology, heterogeneous growth behavior, and increased expression of the P0 antigen while several other features of normal human Schwann cells were retained. We conclude that neurofibroma-derived Schwann cells exhibit a distinct phenotype in vitro but that the observed abnormalities by themselves are insufficient to explain neurofibroma formation. Application of our improved culture conditions makes neurofibroma-derived Schwann cells readily available for further studies to define their role in tumorigenesis in neurofibromatosis type 1.

Distinction among neuronal subtypes of voltage-activated sodium channels by mu-conotoxin PIIIA

The functional properties of most sodium channels are too similar to permit identification of specific sodium channel types underlying macroscopic current. Such discrimination would be particularly advantageous in the nervous system in which different sodium channel family isoforms are coexpressed in the same cell. To test whether members of the mu-conotoxin family can discriminate among known neuronal sodium channel types, we examined six toxins for their ability to block different types of heterologously expressed sodium channels. PIIIA mu-conotoxin blocked rat brain type II/IIA (rBII/IIA) and skeletal muscle sodium current at concentrations that resulted in only slight inhibition of rat peripheral nerve (rPN1) sodium current. Recordings from variant lines of PC12 cells, which selectively express either rBII/IIA or rPN1 channel subtypes, verified that the differential block by PIIIA also applied to native sodium current. The sensitivity to block by PIIIA toxin was then used to discriminate between rBII/IIA and rPN1 sodium currents in NGF-treated PC12 cells in which both mRNAs are induced. During the first 24 hr of NGF-treatment, PN1 sodium channels accounted for over 90% of the sodium current. However, over the ensuing 48 hr period, a sharp rise in the proportion of rBII/IIA sodium current occurred, confirming the idea, based on previous mRNA measurements, that two distinct sodium channel types appear sequentially during neuronal differentiation of PC12 cells.

Neurofibromin, the neurofibromatosis type 1 Ras-GAP, is required for appropriate P0 expression and myelination

The neurofibromatosis type 1 (NF1) gene product, neurofibromin, regulates activation of the Ras intracellular signaling pathway in Schwann cells. Schwann cells purified from mouse embryos with null mutations in the Nf1 gene increase expression of the major myelin glycoprotein P0. v-Ras expression in cultured Schwann cells partially mimics loss of Nf1, suggesting a role for Ras in upregulation of P0 expression in Nf1-deficient cells. We tested whether loss of Nf1 alters the ability of Schwann cells to form myelin. No significant changes in myelin formation resulted when Nf1-deficient or v-Ras-expressing Schwann cells were cultured with normal neurons. Yet, in organotypic cultures of neurons, Schwann cells, and fibroblasts without neurofibromin, myelination was dramatically reduced. We suggest that Nf1-dependent signaling cascades in neurons and/or fibroblasts, as well as Schwann cells, are required for normal myelination.

MRI abnormalities in neurofibromatosis type 1 (NF1): a study of men and mice

Hyperintense lesions on T2-weighted MR images of the brain, predominantly located in the basal ganglia, the brainstem and cerebellum, are a frequent finding in patients with neurofibromatosis type 1. Nature and significance of these lesions are still unknown so that the term 'unidentified bright objects' (UBOs) has been introduced to allow an unbiased description. We analyzed brain MRI scans of 31 children with definite diagnosis of neurofibromatosis type 1 according to the NIH criteria. High-intensity lesions on T2-weighted images were present in 86% of the patients. They did not correlate to other MRI findings such as optic pathway gliomas and were not indicative of intellectual impairment. Additionally, brain MR imaging of Nf1 knockout mice was performed to find out if similar abnormalities are present in this animal model. A total of 9 Nf1 knockout mice was examined on a dedicated animal MRI scanner at 4.7 Tesla but no evidence of high-signal intensity lesions on T2-weighted images was found. Therefore, the Nf1 mouse model seems to be unhelpful in providing further insights into the histological basis of hyperintense MRI abnormalities in NF1 patients.

Pancreatic beta cells synthesize and secrete nerve growth factor

Differentiation and function of pancreatic beta cells are regulated by a variety of hormones and growth factors, including nerve growth factor (NGF). Whether this is an endocrine or autocrine/paracrine role for NGF is not known. We demonstrate that NGF is produced and secreted by adult rat pancreatic beta cells. NGF secretion is increased in response to elevated glucose or potassium, but decreased in response to dibutyryl cAMP. Moreover, steady-state levels of NGF mRNA are down-regulated by dibutyryl cAMP, which is opposite to the effect of cAMP on insulin release. NGF-stimulated changes in morphology and function are mediated by high-affinity Trk A receptors in other mammalian cells. Trk A receptors are present in beta cells and steady-state levels of Trk A mRNA are modulated by NGF and dibutyryl cAMP. Taken together, these findings suggest endocrine and autocrine roles for pancreatic beta-cell NGF, which, in turn, could be related to the pathogenesis of diabetes mellitus where serum NGF levels are diminished.

Paraneoplastic limbic encephalitis in two teenage girls

Paraneoplastic neurological disorders represent remote effects of cancer without invasion of tumor cells into the nervous system. Limbic encephalitis is a distinct entity mostly associated with small-cell carcinoma of the lung. We present the cases of two teenage girls who were admitted with clinical symptoms typical for limbic encephalitis. In the course of the disease, they exhibited characteristic evolutionary changes of brain MRI abnormalities. Onset of neurological symptoms and type of underlying neoplasia were different in both patients. In one girl the initial workup led to the diagnosis of nodular sclerosing Hodgkin disease which so far had not caused any symptoms besides the described neurological abnormalities. A diagnostic brain biopsy showed inflammatory changes and excluded invasion of malignant cells into the central nervous system. The other patient had been diagnosed with a small cell carcinoma of the ovary several months before neurological and brain MRI abnormalities were observed. This is the first report in which clinical picture, evolution of MRI abnormalities, and--in one case--characteristic neuropathological changes are suggestive of paraneoplastic limbic encephalitis in two adolescent girls.

Nerve growth factor increases sodium current in pancreatic beta cells

Nerve growth factor (NGF) induces neuritelike process outgrowth in cultured adult pancreatic beta cells. DbcAMP partially mimics this effect on cell morphology, and both compounds act synergistically to promote neuritelike process outgrowth. To determine if NGF- and dbcAMP-induced differentiation was accompanied by changes in beta cell electrical activity, we studied the macroscopic Na current of adult rat beta cells identified with the reverse hemolytic plaque assay and cultured for one week with these factors. After 5-7 days, beta cells cultured in the presence of 2.5S NGF exhibited a 48% increase on the macroscopic Na current, which was due to an increase on Na current density. We did not observe changes on voltage dependence of current activation, nor on steady-state inactivation. Although dbcAMP also promotes changes on beta cell morphology, it did not affect the Na current density.

Neuron-like phenotypic changes in pancreatic β-cells induced by NGF, FGF, and dbcAMP

We studied the effects of nerve growth factor (NGF), fibroblast growth factor (FGF), and dibutyryl-cAMP (dbcAMP) on rat pancreatic β-cell morphology and of NGF and dbcAMP on insulin secretion. After 2 wk in culture, nearly 3% of β-cells extended neurite-like processes spontaneously; when cells were treated with NGF, almost 30% of them extended processes. In the presence of dbcAMP, almost all β-cells flattened, and the extension of neurite-like processes was more pronounced in fetal than in adult cells. The most prominent effect, regardless of age, was observed in cells treated with NGF and dbcAMP together, since the percentage of neurite-like bearing β-cells increased to 50%. β-cells cultured under these conditions maintained their immunoreactivity to insulin and nearly all β-cells and their neurite-like processes were also positive to GABA, tubulin, tau protein, and N-CAM. FGF increased the percentage of adult β-cells bearing neurite-like processes to 13%, and FGF and dbcAMP applied together to 40%. β-cells treated with NGF and dbcAMP for 5 to 7 d preserved their capability to secrete the hormone in response to different extracellular glucose concentrations. Insulin secretion of dbcAMP-treated β-cells was 2.5-fold higher than in control cells. NGF-treated cells were able to discriminate between different glucose concentrations, a property lost in control cells with time in culture.

Neurofibromin-deficient fibroblasts fail to form perineurium in vitro

To identify cell type(s) that might contribute to nerve sheath tumors (neurofibromas) in patients with neurofibromatosis type 1, we generated cell cultures containing neurons. Schwann cells and fibroblasts from transgenic mouse embryos in which the type 1 neurofibromatosis gene was disrupted by homologous recombination (Brannan et al. (1994) Genes Development, 8,1019-1029). Normal fascicle formation by perineurial cells failed to occur in the absence of neurofibromin. Fascicles were reduced in number and showed abnormal morphology when normal neurons and Schwann cells were cultured up to 37 days with fibroblasts lacking neurofibromin. Proliferation was increased in a majority of fibroblast cell strains analyzed from embryos lacking neurofibromin. These observations suggest that mutations in the neurofibromatosis type I gene affect fibroblast behavior that might contribute to neurofibroma formation in patients with neurofibromatosis type 1.

Schwann cells from neurofibromin deficient mice exhibit activation of p21ras, inhibition of cell proliferation and morphological changes

Schwann cells are thought to be abnormal in type 1 neurofibromatosis (NF1) and to contribute to the formation of benign and malignant tumors in this disease. To test the role of the NF1 gene product neurofibromin as a Ras-GTPase activating protein in Schwann cells, and to study the effect of the loss of neurofibromin on Schwann cell proliferation, we isolated Schwann cells from mice with targeted disruption of NF1. The properties of these neurofibromin deficient cells were strikingly similar to those of v-ras expressing rat Schwann cells with normal levels of neurofibromin. The similarities included: growth inhibition, noted as a decrease in cell division in response to glial growth factor 2 (GGF2) and of neuronal contact; morphological changes such as the appearance of elaborated processes; and elevated levels of Ras-GTP. Furthermore, Ras-GTP levels in the neurofibromin deficient Schwann cells were consistently elevated in response to GGF2 treatment. In contrast to these results, introduction of v-ras into a Schwannoma cell line (RN22) led to cell transformation. We conclude that neurofibromin functions as a major regulator of Ras-GTP in Schwann cells; however, mutation in NF1 by itself is unlikely to explain the hyperplasia observed in Schwann cell tumors in NF1 disease.

Effect of transforming growth factor-beta 1 and -beta 2 on Schwann cell proliferation on neurites

Mechanisms regulating Schwann cell proliferation during development are unclear. Schwann cell division is known to be driven by an unidentified mitogen present on the surface of axons, but it is not known whether other molecules play a role in regulating this proliferation. Transforming growth factor-beta (TGF-beta) which is found in the developing peripheral nervous system (PNS) and is mitogenic for neuron-free Schwann cells in vitro could be involved. We have investigated the effects of TGF-beta 1, TGF-beta 2 and antibodies to TGF-beta 1 and TGF-beta 2 on axon driven Schwann cell proliferation. Rat embryonic dorsal root ganglion neurons (DRG) neurons and Schwann cells from the sciatic nerve were isolated, purified and recombined in vitro. Confirming earlier reports by others, we observed that TGF-beta 1 and TGF-beta 2 added to the culture medium stimulated the proliferation of Schwann cells in the absence of neurons. However, when added to neuron-Schwann cell co-cultures, TGF beta caused a variable response ranging from no effect to moderate inhibition of Schwann cell proliferation in different experiments. A stimulation of Schwann cell proliferation by TGF beta was never observed in neuron-Schwann cell co-cultures. Antibodies to TGF-beta 1 and TGF-beta 2 did not influence axon driven Schwann cell proliferation. To further determine the role of TGF-beta in Schwann cell proliferation and myelination, we studied Schwann cell proliferation in cultures from mice in which the TGF-beta 1 gene was delected by homologous recombination. Neuron-Schwann cell cultures from wild-type, heterozygous and homozygous mice were used. No differences were observed in either Schwann cell proliferation or myelination between cultures obtained from homozygous mutants and their heterozygous and wild-type controls. These findings suggest that TGF-beta does not function as a part of the mitogenic mechanism presented by neurons to Schwann cells, but that the presence of active TGF beta in the cellular environment might regulate the degree of proliferation induced by neuronal contact.

Extended deep vein and inferior vena cava thrombosis in a 15-year-old boy: successful lysis with recombinant tissue-type plasminogen activator 2 weeks after onset of symptoms

We present the case of a 15-year-old boy with thrombosis of the inferior vena cava, the femoral, inguinal, and renal veins of unknown origin. Although the thrombosis was 2 weeks old, thrombolytic therapy with recombinant tissue-type plasminogen activator (maximum dosage: 0.4 mg/kg/h) was started as this appeared to be the only change to re-establish normal kidney function. After 1 week, treatment was discontinued because of generalized bleeding. At this time, the infrarenal inferior vena cava was again patent with complete lysis of all other clots. Phlebography 3 months after lysis documented an abnormal renal vein, a tubular, subhepatical stenosis of the inferior vena cava and a large collateral vessel between the inferior vena cava and the azygos vein.

Chronic dehydration stone disease

A study was made of 819 patients attending a metabolic stone clinic. A firm diagnosis was made in 708 (86%) and in 132 of these (19%) the diagnosis was thought to be chronic dehydration. The records were available for study for 87 males and 11 females in the chronic dehydration group. The mean age at presentation was 43 years. The causes of chronic dehydration were hot climate (62%), with hot occupation and low water intake almost equal in second place. In patients with a single cause of chronic dehydration, 57% also had a dietary risk factor for urolithiasis and this was most commonly high oxalate intake. Following dietary advice, the mean urinary volume increased from 1720 to 2475 ml/24 h. This was accompanied by a rise in mean urinary calcium from 6.02 to 6.96 mmol/24 h, presumably due to the calcium in the additional water drunk. Urinary oxalate did not change significantly. The mean follow-up time was 4.85 years and the stone recurrence rate was low. It was concluded that chronic dehydration is a common cause of urolithiasis; this can be treated satisfactorily by increasing water intake plus dietary advice in certain cases.

Beta-receptor-adenylate cyclase coupling in hypoxic neonatal rat ventricular myocytes

This study investigated the influence of hypoxia on alterations in the beta-adrenergic receptor-adenylate cyclase system. Cultured neonatal rat ventricular myocytes were subjected to normoxia (incubator PO2 135-145 mmHg) or hypoxia (incubator PO2 0-14 mmHg) and, in crude membrane preparations, beta-receptor binding properties were measured with [125I]iodocyanopindolol and adenylate cyclase activity by radioimmunoassay. Hypoxia of 30 min in duration caused no alteration in beta-receptor density (Bmax 75 +/- 11 vs. 71 +/- 12 fmol/mg protein) but increased adenylate cyclase activity under basal conditions and during stimulation with l-isoproterenol, 5'-guanylimidotriphosphate [Gpp(NH)p] 5 X 10(-5) M, NaF 10(-4) M, and forskolin 10(-4) M. For example, isoproterenol 10(-5) M + guanosine 5'-triphosphate (GTP) 5 X 10(-5) M gave 221 +/- 34 vs. 143 +/- 11 pmol.min-1.mg protein-1, P less than 0.05 hypoxia vs. normoxia. After 60 min of hypoxia, adenylate cyclase activity was no longer increased. Hypoxia of 120-150 min duration increased Bmax by 64% (73 +/- 8 to 120 +/- 11 fmol/mg protein, P less than 0.05 vs. normoxia) but decreased adenylate cyclase activity during stimulation with isoproterenol, NaF 10(-4) M, and forskolin 10(-4) M. For example, isoproterenol 10(-5) M + GTP 5 X 10(-5) M gave 107 +/- 12 vs. 148 +/- 11 pmol.min-1.mg protein-1, P less than 0.05 hypoxia vs. normoxia. Reoxygenation for 15 min following 120-150 min of hypoxia reversed the increased beta-receptor numbers and decreased adenylate cyclase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of a potentially reversible increase in beta-adrenergic receptors in isolated, neonatal rat cardiac myocytes with impaired energy metabolism

Previous studies have reported that the numbers of beta- and alpha-adrenergic receptors increase in ischemic myocardium. In vivo studies have raised questions regarding the mechanisms involved in the adrenergic receptor alterations and the consequences of these alterations. The purpose of this study was to evaluate potential relationships among beta-adrenergic receptor changes, high energy phosphate reduction, and severity of cell injury in cultured neonatal rat myocytes treated with metabolic inhibitors. The potential for reversal of the receptor changes also was addressed. Binding parameters were measured using [125I]iodocyanopindolol. After 4 hours incubation in potassium cyanide and 2-deoxyglucose, there was a 43% increase in beta-adrenergic receptor number, 41% decrease in adenosine triphosphate, and minimal morphological change in myocytes. Twenty-four hours after removal of the inhibitors, myocytes exhibited a return to normal of the receptor number and adenosine triphosphate level. Iodoacetate treatment for up to 3 hours resulted in marked reduction in adenosine triphosphate and increasing severity of cell injury. The number of beta-adrenergic receptors was unchanged at 1.2 hours, increased at 1.5-2 hours, and decreased at 3 hours. Thus: beta-adrenergic receptor density increases during relatively early stages of injury in metabolically impaired myocytes with reduced adenosine triphosphate levels and decreases subsequently, after the myocytes become irreversibly injured; the increased beta-adrenergic receptor density in moderately injured myocytes can be reversed upon removal of the injurious agent and restoration of the cellular adenosine triphosphate level; and changes in catecholamines mediated by an intact nervous system are not required for an increase in beta-adrenergic receptor density in the setting of impaired energy metabolism.