Filopodia, spines, and the generation of synaptic diversity.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
S J Smith
Publications and source records attributed to S J Smith.
Fixation-off sensitivity as a model of continuous epileptiform discharges: electroencephalographic, neuropsychological and functional MRI findings.
A case of fixation-off sensitivity (FOS) in an asymptomatic adult is presented and studied as a model for continuous epileptiform discharges. Video-electroencephalographic (EEG) revealed continuous bilateral occipital spike wave discharges during elimination of central vision, which were shown to be associated with transitory cognitive impairment demonstrated by neuropsychological testing. Functional MRI showed activation of parieto-occipital and frontal brain areas during the fixation-off discharges. This localization was confirmed with 64-channel EEG source analysis. The applied methods provided additional information on the pathophysiology of epileptiform discharges.
Adult↗
The impact of uterine fibroid embolization on resumption of menses and ovarian function.
PURPOSE: To evaluate the effect of uterine fibroid embolization (UFE) on menstruation and ovarian function. METHODS: The authors performed an observational study of UFE for the treatment of symptomatic fibroids. All patients had regular predictable menses before intervention and none had clinical or laboratory findings of menopause. UFE was performed with use of standard methods with 355-700-microm-diameter polyvinyl alcohol (PVA) foam particles. The incidence of ovarian failure was calculated for women younger than 45 years and for those 45 years or older, based on retrospective stratification by age. The authors assessed statistical differences in ovarian failure between the two age groups with use of the X2 test. RESULTS: Sixty-six premenopausal women (age range, 30-55 years) underwent bilateral UFE and were followed for an average of 21 weeks (range, 12-77 weeks). In 56 of 66 (85%) patients, regular menses resumed after an average of 3.5 (range, 1-8) weeks. In 10 of 66 (15%) patients, regular menses did not resume. Clinical and biochemical findings consistent with ovarian failure and presumed menopause were seen in nine of 10 patients without resumption of menses (14% of total patients). Ovarian failure occurred in nine of 21 (43%) women older than 45 years and in none of the 45 women younger than 45 years (P < .05). There were no differences in presenting symptoms, amount of PVA used, or fibroid size between patients who did and did not resume menses. CONCLUSION: The majority of patients undergoing UFE will have resumption of menses, but the incidence of postprocedure ovarian failure is considerably higher than reported to date. Loss of menses induced by UFE is significantly more likely to occur in women older than 45 years.
Adult↗
Structure of the TPR domain of p67phox in complex with Rac.GTP.
p67phox is an essential part of the NADPH oxidase, a multiprotein enzyme complex that produces superoxide ions in response to microbial infection. Binding of the small GTPase Rac to p67phox is a key step in the assembly of the active enzyme complex. The structure of Rac.GTP bound to the N-terminal TPR (tetratricopeptide repeat) domain of p67phox reveals a novel mode of Rho family/effector interaction and explains the basis of GTPase specificity. Complex formation is largely mediated by an insertion between two TPR motifs, suggesting an unsuspected versatility of TPR domains in target recognition and in their more general role as scaffolds for the assembly of multiprotein complexes.
Amino Acid Sequence↗
Growth cone and dendrite dynamics in zebrafish embryos: early events in synaptogenesis imaged in vivo.
We used time-lapse fluorescence microscopy to observe the growth of Mauthner cell axons and their postsynaptic targets, the primary motor neurons, in spinal cords of developing zebrafish embryos. Upon reaching successive motor neurons, the Mauthner growth cone paused briefly before continuing along its path. Varicosities formed at regular intervals and were preferentially associated with the target regions of the primary motor neurons. In addition, the postsynaptic motor neurons showed highly dynamic filopodia, which transiently interacted with both the growth cone and the axon. Both Mauthner cell and motor neurons were highly active, each showing motility sufficient to initiate synaptogenesis.
Animals↗
Assembly of presynaptic active zones from cytoplasmic transport packets.
Little is known about presynaptic assembly during central nervous system synaptogenesis. Here we used time-lapse fluorescence imaging, immunocytochemistry and electron microscopy to study hippocampal neuronal cultures transfected with a fusion construct of the presynaptic vesicle protein VAMP and green fluorescent protein. Our results suggest that major cytoplasmic and membrane-associated protein precursors of the presynaptic active zone are transported along developing axons together as discrete packets. Retrospective electron microscopy demonstrated varied vesicular and tubulovesicular membrane structures. Packets containing these heterogeneous structures were stabilized specifically at new sites of dendrite- and axon-initiated cell-cell contact; within less than one hour, evoked vesicle recycling was observed at these putative nascent synapses. These observations suggest that substantial membrane remodeling may be necessary to produce the uniform vesicles typical of the mature active zone, and that many presynaptic proteins may be united early in their biogenesis and sorting pathways.
Animals↗
Obesity resistance and multiple mechanisms of triglyceride synthesis in mice lacking Dgat.
Triglycerides (or triacylglycerols) represent the major form of stored energy in eukaryotes. Triglyceride synthesis has been assumed to occur primarily through acyl CoA:diacylglycerol transferase (Dgat), a microsomal enzyme that catalyses the final and only committed step in the glycerol phosphate pathway. Therefore, Dgat has been considered necessary for adipose tissue formation and essential for survival. Here we show that Dgat-deficient (Dgat-/-) mice are viable and can still synthesize triglycerides. Moreover, these mice are lean and resistant to diet-induced obesity. The obesity resistance involves increased energy expenditure and increased activity. Dgat deficiency also alters triglyceride metabolism in other tissues, including the mammary gland, where lactation is defective in Dgat-/- females. Our findings indicate that multiple mechanisms exist for triglyceride synthesis and suggest that the selective inhibition of Dgat-mediated triglyceride synthesis may be useful for treating obesity.
Absorption↗
Identification of peptide motifs recognized by a human IgG autoanti-IgE antibody using a phage display library.
BACKGROUND: The potential of murine monoclonal anti-IgE antibodies as long-term therapy for atopic diseases will have to rely, for the time being, on passive antibody administration. There is therefore considerable interest in developing a peptide-based vaccine for active immunization to elicit long-term protective anti-IgE antibodies in the patient. It has been shown that some human IgG autoanti-IgE antibodies have the ability to partially block the binding of IgE to Fc receptors such as Fc epsilonRI. Therefore, the epitopes recognized by such antibodies could have vaccine potential. OBJECTIVE: To determine the epitope specificity of one such human IgG anti-IgE antibody. METHODS: A 15-mer phage-peptide library was used to establish the epitope specificity of an IgG anti-IgE antibody isolated from the serum of an asthma patient. RESULTS: The SRPSP sequence, or part of it (i.e. RPS, RPSP, SPS or PSP), was present in all 18 phage-peptides that have been sequenced. This common motif was found to be within the human epsilon chain sequence Ser341-Thr355 near the N-terminus of the C epsilon3 domain. According to the human Fc epsilon model, the most accessible residues in this sequence are Arg342, Ile350, Arg351, Lys352 and Ser353. CONCLUSIONS: The present data should provide the molecular basis for the rational design of a suitable peptide immunogen (vaccine) for boosting the production of protective autoanti-IgE antibodies.
Amino Acid Motifs↗
Localization of iron transport and regulatory proteins in human cells.
The recent discovery of HFE, the MHC-Class-I-like gene mutated in up to 90% of patients with hereditary haemochromatosis, and the gene encoding the Nramp2/divalent metal transporter-1 (DMT-1) implicated in ferrous iron transport holds promise for a greater understanding of human iron metabolism. Since the HFE protein can be crystallized as a ternary complex with the transferrin receptor and iron-saturated transferrin, and DMT-1 expression is up-regulated in hereditary haemochromatosis, these proteins are likely to interact in a common pathway for human iron homeostasis. To investigate the cellular interactions between the cognate proteins encoded by these genes, we generated a panel of rabbit and avian antisera from human HFE and DMT-1 derived peptides. The antibodies were characterized by ELISA reactions and Western immunoblotting. Immunohistochemical staining showed that DMT-1 protein localized to the brush border of human duodenum where it is predicted to serve as the principal transporter of ferrous iron from the intestinal lumen. In the human cell lines, Caco-2 (small intestinal phenotype upon differentiation) and K562 (erythroleukaemic) HFE, in the presence of iron-saturated transferrin, co-localized with transferrin receptors in an early endosome compartment using confocal immunofluorescence microscopy. This interaction may be critical in small-intestinal crypt cells which express HFE, where it may function to modulate their intrinsic iron status thereby programming iron absorption by DMT-1 in the mature enterocyte. In undifferentiated Caco-2 cells, DMT-1 localized to a discrete late endosome compartment distinct from that occupied by HFE where, in addition to brush-border iron uptake, it may function to regulate the availability of iron delivery to intracellular iron pools. Disruption of the HFE gene as a result of mutations associated with hereditary haemochromatosis may thus impair homeostatic mechanisms controlling iron absorption within the small-intestine epithelium by a direct interaction with transferrin receptors and by subsequent alteration of DMT-1 expression. Identification of the molecular interactions of HFE with DMT-1 and other key components of the iron transport pathway has implications for a mechanistic understanding of the pathophysiology of human iron storage diseases as well as the regulation of normal iron balance.
Animals↗
Triglyceride synthesis: insights from the cloning of diacylglycerol acyltransferase.
Although the biochemistry of triglyceride synthesis has been studied for decades, an understanding of the molecular processes involved has been lacking. The recent cloning of a gene encoding acyl coenzyme A : diacylglycerol acyltransferase, an enzyme that catalyses the final step in triglyceride synthesis, has opened this area to molecular investigation and has begun to provide new insights into triglyceride metabolism.
Acyltransferases↗
Idiopathic generalized epilepsy presenting with hemiconvulsive seizures.
PURPOSE: Unilateral seizures, or hemiconvulsive attacks, are motor seizures with tonic and/or clonic phenomena that involve only one side of the body. METHODS: We describe three adolescents who presented with hemiconvulsive seizures and were found to have 3-cps generalized spike-and-wave discharges on ictal and/or interictal EEG. All had normal neuroimaging studies. Two patients had been previously treated with carbamazepine, which led to a partial response in one patient. RESULTS: All three patients, however, are now seizure free on either sodium valproate or a combination of sodium valproate and lamotrigine. We believe the electroclinical diagnosis is that of idiopathic generalized epilepsy. CONCLUSIONS: Idiopathic generalized epilepsy presenting with hemiconvulsive seizures has not, to our knowledge, been previously described. However, the correct diagnosis of an idiopathic generalized seizure disorder, as opposed to a partial seizure disorder, has important treatment implications. The possible mechanism of hemiconvulsive seizures in idiopathic generalized epilepsy is discussed.
Adolescent↗
Innate immunity to amebic liver abscess is dependent on gamma interferon and nitric oxide in a murine model of disease.
Evidence from in vitro studies suggests that gamma interferon (IFN-gamma) and nitric oxide (NO) are important in host defense against the protozoan parasite Entamoeba histolytica. We used SCID mice with targeted disruption of the IFN-gamma receptor gene and mice with targeted disruption of the gene encoding inducible NO synthase to show that IFN-gamma plays a role in the innate immunity to amebic liver abscess seen in SCID mice while NO is required for control of amebic liver abscess in immunocompetent mice.
Animals↗
Characterisation of a mouse monoclonal anti-idiotype reactive with a V region sequence commonly used by human immunoglobulins.
BACKGROUND: A mouse monoclonal antibody (2C7/IgG2b kappa) has been described recently, which is directed against the major house dust mite allergen Der p 1, and whose epitope specificity is representative of a major component of the human IgE anti-Der p 1 response. AIMS: To characterise an anti-idiotypic antibody (2G10/IgG1 kappa) raised against monoclonal antibody 2C7 as surrogate human IgE anti-Der p 1. METHODS: The specificity of the anti-idiotype antibody 2G10 was determined by competitive inhibition experiments using human and mouse immunoglobulins of known VH gene families. The epitope recognised by monoclonal antibody 2G10 was located on the molecular model of the Fv (fragment variable) region of monoclonal antibody 2C7. RESULTS: The data suggest that monoclonal antibody 2G10 is directed against a crossreactive idiotype on human IgE that is shared by polyclonal IgG. Competitive inhibition studies against human immunoglobulins, representative of VH2, VH3, and VH4 gene families, showed that monoclonal antibody 2G10 is mostly likely to be directed against sequences encoded by either VH3 or VH4 genes. The fact that monoclonal antibody 2G10 binds to the humanized (complementarity determining region (CDR) grafted) CAMPATH-1H antibody, but not to the original rat CAMPATH-1 YTH34.5.6 antibody, indicates that it is directed against a framework region rather than the CDRs. Analysis of amino acids in the VH region for charge, hydrophobicity, and accessibility suggests that reactivity with monoclonal antibody 2G10 is defined by a hexapeptide spanning residues 74-79 within framework region 3. CONCLUSION: The anti-idiotype monoclonal antibody 2G10 could potentially be used as a probe for determining the contribution of the VH3 and VH4 gene segments to antigenic specificity.
Amino Acid Sequence↗
Mast cell-eosinophil-fibroblast crosstalk in allergic inflammation.
Explore the source record for details and available documents.
3T3 Cells↗
Massive xanthomatosis and altered composition of atherosclerotic lesions in hyperlipidemic mice lacking acyl CoA:cholesterol acyltransferase 1.
Inhibitors of acyl CoA:cholesterol acyltransferase (ACAT) have attracted considerable interest as a potential treatment for atherosclerosis. Currently available inhibitors probably act nonselectively against the two known ACATs. One of these enzymes, ACAT1, is highly expressed in macrophages in atherosclerotic lesions, where it contributes to foam-cell formation. In this study, we examined the effects of selective ACAT1 deficiency in two mouse models of atherosclerosis. In the setting of severe hypercholesterolemia caused by deficiency in apoE or the LDL receptor (LDLR), total ACAT1 deficiency led to marked alterations in cholesterol homeostasis and extensive deposition of unesterified cholesterol in the skin and brain. Bone marrow transplantation experiments demonstrated that ACAT1 deficiency in macrophages was sufficient to cause dermal xanthomas in hyperlipidemic LDLR-deficient mice. ACAT1 deficiency did not prevent the development of atherosclerotic lesions in either apoE-deficient or LDLR-deficient mice, despite causing relatively lower serum cholesterol levels. However, the lesions in ACAT1-deficient mice were atypical in composition, with reduced amounts of neutral lipids and a paucity of macrophages in advanced lesions. Although the latter findings may be associated with increased lesion stability, the marked alterations in cholesterol homeostasis indicate that selectively inhibiting ACAT1 in the setting of severe hyperlipidemia may have detrimental consequences.
Animals↗
A double-blind placebo-controlled study of botulinum toxin in upper limb spasticity after stroke or head injury.
OBJECTIVE: To assess dose-response relationships to a single dose of botulinum toxin 'A' in upper limb spasticity associated with stroke or head injury. DESIGN: A double-blind placebo-controlled randomized dose ranging study. SETTING: A regional centre for neuroscience and a neurorehabilitation outpatient clinic. SUBJECTS: Twenty-one hemiplegic patients with troublesome upper limb spasticity. Nineteen with stroke and two with head injury. MAIN OUTCOME MEASURES: Spasticity (modified Ashworth), range of movement, posture (postural alignment and finger curl), disability (upper body dressing time and Frenchay Arm Test), patient-reported global assessment scale. RESULTS: Combining data from all doses of botulinum toxin there was a significant reduction in spasticity at the wrist and fingers associated with a greater range of passive movement at the wrist and less finger curl at rest. There was a tendency for a further reduction in spasticity at elbow and wrist to occur with increasing dose but not for finger spasticity or curl. Effects present at six weeks were lost by 12 weeks except for a small improvement in elbow range of movement at the 1,500 Mu dose. There was no change in upper limb disability but a significant increase in patients' global assessment of benefit. CONCLUSION: Botulinum toxin produced beneficial effects in spasticity and passive range of movement in the hemiplegic upper limb. Increasing the dose increased the magnitude of response for impairments in some muscle groups but had little effect on duration of response.
Adult↗
The role of affect on the perception of disability in multiple sclerosis.
OBJECTIVE: To determine the prevalence of depression in multiple sclerosis in the community and to assess how the presence of depression affects patients' perception of their disability. DESIGN: Consecutive case series. SETTING: The study was carried out at a regional multiple sclerosis (MS) clinic. SUBJECTS: Eighty-eight patients with MS. MAIN OUTCOME MEASURES: Patients were asked to complete the following questionnaires: Hospital Anxiety and Depression Scale (HADS), Beck Depression Inventory (BDI), Rankin Scale of Disability/Handicap (completed by patient and physician to assess relative perceived disability) and two visual analogue scales (coping ability and perceived service adequacy). RESULTS: Thirty-nine per cent were case level for depression using the BDI criteria of Sullivan; 17% were case level for depression (34% borderline case) and 34% case level for anxiety on HADS. Depressed patients using both BDI and HADS criteria were three times more likely than nondepressed patients to perceive their disability as being greater than the physicians' perception (p < 0.001). CONCLUSION: Depression is common in MS and adversely affects patients' perception of their disability.
Affect↗