Notch signaling in T cell development

Notch signaling regulates cell fate decisions during development. Recent experiments suggest that Notch signaling is essential for initial commitment to the T cell lineage and may function together with signals from the pre-TCR and the TCR to regulate subsequent steps of T cell development.     

Δ9‐Tetrahydrocannabivarin suppresses in vitro epileptiform and in vivo seizure activity in adult rats

Purpose: We assessed the anticonvulsant potential of the phytocannabinoid Δ⁹‐tetrahydrocannabivarin (Δ⁹‐THCV) by investigating its effects in an in vitro piriform cortex (PC) brain slice model of epileptiform activity, on cannabinoid CB1 receptor radioligand‐binding assays and in a generalized seizure model in rats. Methods: Δ⁹‐THCV was applied before (10 μm Δ⁹‐THCV) or during (10–50 μm Δ⁹‐THCV) epileptiform activity induced by Mg²⁺‐free extracellular media in adult rat PC slices and measured using multielectrode array (MEA) extracellular electrophysiologic techniques. The actions of Δ⁹‐THCV on CB1 receptors were examined using [³H]SR141716A competition binding and [³⁵S]GTPγS assays in rat cortical membranes. Effects of Δ⁹‐THCV (0.025–2.5 mg/kg) on pentylenetetrazole (PTZ)–induced seizures in adult rats were also assessed. Results: After induction of stable spontaneous epileptiform activity, acute Δ⁹‐THCV application (≥20 μm ) significantly reduced burst complex incidence and the amplitude and frequency of paroxysmal depolarizing shifts (PDSs). Furthermore, slices pretreated with 10 μm Δ⁹‐THCV prior to induction of epileptiform activity exhibited significantly reduced burst complex incidence and PDS peak amplitude. In radioligand‐binding experiments, Δ⁹‐THCV acted as a CB1 receptor ligand, displacing 0.5 nm [³H]SR141716A with a Ki～290 nm , but exerted no agonist stimulation of [³⁵S]GTPγS binding. In PTZ‐induced seizures in vivo, 0.25 mg/kg Δ⁹‐THCV significantly reduced seizure incidence. Discussion: These data demonstrate that Δ⁹‐THCV exerts antiepileptiform and anticonvulsant properties, actions that are consistent with a CB1 receptor–mediated mechanism and suggest possible therapeutic application in the treatment of pathophysiologic hyperexcitability states.     

Long‐Term Effectiveness of Screening for Hearing Loss: The Screening for Auditory Impairment—Which Hearing Assessment Test (SAI‐WHAT) Randomized Trial

OBJECTIVES: To evaluate the effect of hearing screening on long‐term hearing outcomes in a general population of older veterans. DESIGN: Hearing loss in the elderly is underdetected and undertreated. Routine hearing screening has been proposed, but it is not clear whether screening identifies patients who are sufficiently motivated to adhere to treatment. A four‐arm randomized clinical trial was conducted to compare three screening strategies with no screening in 2,305 older veterans seeking general medical care. SETTING: Veterans Affairs Puget Sound Health Care System. INTERVENTIONS: The screening strategies were a tone‐emitting otoscope, a widely used questionnaire about hearing handicap, and a combination of both tools. MEASUREMENTS: Hearing aid use 1 year after screening. RESULTS: Of participants who underwent screening with the tone‐emitting otoscope, questionnaire, and combined testing, 18.6%, 59.2%, and 63.6%, respectively, screened positive for hearing loss (P<.01 for test of equality across three arms). Patients proceeded to formal audiology evaluation 14.7%, 23.0%, and 26.6% of the time in the same screening arms, compared with 10.8% in the control arm (P<.01 for test of equality across four arms). Hearing aid use 1 year after screening was 6.3%, 4.1%, and 7.4% in the same arms, compared with 3.3% in the control arm (P<.01). Hearing aid users experienced significant improvements in hearing‐related function and communication ability. CONCLUSION: In older veterans, screening for hearing loss led to significantly more hearing aid use. Screening with the tone‐emitting otoscope was more efficient. The results are most applicable to older populations with few cost barriers to hearing aids.     

Dicer controls CD8+ T-cell activation, migration, and survival

The RNaseIII enzyme Dicer is required for mature microRNA production. Although extensive investigation has been carried out to determine the role of Dicer/miRNAs in the immune system, their function in mature CD8(+) T cells has not been examined. We deleted Dicer in mature polyclonal and TCR transgenic CD8(+) T cells using either tat-cre or the distal lck promoter, which drives cre expression after the stage of positive selection. Following antigenic challenge by a pathogen infection in vivo, Dicer-deleted CD8(+) T cells failed to accumulate at the usual peak of the response. Surprisingly however, we found that deletion of Dicer in mature CD8(+) T cells allowed them to respond more rapidly than control cells to TCR stimuli in vitro. In response to anti-CD3 plus anti-CD28 stimulation, Dicer-deleted T cells up-regulated CD69 faster and entered the first mitosis earlier than control T cells. In addition, activated Dicer(-/-) cells failed to rapidly down-regulate CD69 when removed from the TCR stimulus. As a probable consequence of this sustained CD69 expression, Dicer(-/-) T cells showed defective migration out of the central lymphoid organs in vivo. We identify miR-130/301, which are dramatically up-regulated following T-cell activation, as able to down-regulate CD69 expression via binding to a conserved site in the 3'UTR of CD69 mRNA. Thus, cellular functions dependent on Dicer expression are not required for the early steps in CD8(+) T-cell activation, but are essential for their survival and accumulation.     

Four novel SPG3A/atlastin mutations identified in autosomal dominant hereditary spastic paraplegia kindreds with intra-familial variability in age of onset and complex phenotype

Mutation of the atlastin gene ( SPG3A ) is responsible for ∼10% of autosomal dominant hereditary spastic paraplegia (AD-HSP) cases. The goal of this study was to identify novel disease causing atlastin mutations. Atlastin nucleotide variations were detected by direct sequencing of all 14 exons in 70 autosomal dominant (AD), 16 single sibship and 14 sporadic spastic paraplegia patients. Six mis-sense mutations (four of which were novel) were identified in six unrelated AD-HSP kindreds in exons 4, 7 and 8 of the atlastin gene. One kindred with a novel mutation showed variability in clinical phenotype and age of onset. Mutations are predicted to decrease GTPase activity, cause morphological abnormalities of the endoplasmic reticulum and prevent maturation of the Golgi complex resulting in impaired vesicle trafficking. Our study significantly adds to the spectrum of mutations and clinical phenotype of SPG3A . We advocate that all spastin mutation negative AD-HSP kindreds should be screened for pathogenic atlastin mutations regardless of age of onset or phenotypic complexity.     

Twitch depression and train-of-four ratio after antagonism of pancuronium with edrophonium, neostigmine, or pyridostigmine

During N2O-O2-halothane anesthesia pancuronium (3 mg/70 kg) was antagonized with neostigmine (2.5 or 5 mg/70 kg), pyridostigmine (10 or 20 mg/70 kg), or edrophonium (50 or 100 mg/70 kg) in 36 human subjects (6 in each group). Reversal was attempted at 10% spontaneous recovery of muscle twitch, which was measured using train-of-four stimulation. When first twitch tension was less than 70% of the control it was found that for the same tension, the train-of-four ratio was greater with edrophonium than with neostigmine, and greater with neostigmine than with pyridostigmine. It was concluded that the three antagonists have different mechanisms of action. In comparison with neostigmine, edrophonium is more and pyridostigmine is less effective at presynaptic (or fade) receptors.     

Vecuronium in renal failure

Neuromuscular blockade during surgery was provided with vecuronium in 24 adult patients in end-stage renal failure and in 21 normal patients who served as controls. Dose response curves were constructed which showed that the effective doses required to produce 50, 90 and 95 per cent neuromuscular blockade in patients with renal failure were 27.5, 43 and49fig-kg-1 respectively. These were not significantly different from the doses of 31, 49 and 57 fig-kg-1 in the normal patients. Repeated small dosesof0.01 mg’kg-1 hada significantly longer duration of action and were associated with some cumulation in the renal failure group. Recovery from the block occurred rapidly after neostigmine, was no different in renal failure and was not associated with recurarization. It is concluded that, when given to subjects in renal failure, vecuronium offers advantages over established agents such as shorter duration of action and easy reversibility.     

Responses of small rabbit pial arteries in vitro.

An in vitro method for measuring changes in isometric force of vessels as small as 100 microns in outer diameter was used to determine whether the adrenergic mechanism of small pial arteries is the same as the large arteries of the circle of Willis. Fluorescence histology demonstrated the rich noradrenergic innervation of small branches of the middle cerebral artery. In spite of this rich innervation, contractile responses to transmural stimulation (TNS) were much smaller than maximum responses to histamine. An insensitivity to exogenous norepinephrine was shown which could account for this small response to TNS. In the presence of low concentrations of histamine, responses to TNS were increased. Thus, small pial arteries have characteristics similar to larger cerebral arteries.     

Direct effect of interleukin 2 on chronic lymphocytic leukaemia B cell functions and morphology.

The functional and morphological changes induced by recombinant interleukin 2 (IL-2) were studied in purified B cells from patients with untreated B chronic lymphocytic leukaemia (B-CLL). In eight of nine patients, purified B-CLL cells increased their DNA synthesis in response to IL-2 without preactivation in vitro. This response, studied in detail in three patients, was dose dependent and reached a maximum on day 5 or 6. IL-2 induced or increased IgM secretion in cultures from five of the nine patients studied. Two of this responsive group were particularly interesting as IL-2 not only stimulated IgM secretion but also induced the secretion of IgG. Immunoglobulin production was invariably monoclonal. B CLL cells incubated with IL-2 showed distinct morphological changes including an increase in the size of cytoplasm and enlargement of nuclei together with the appearance of nucleoli. These changes were present in all IL-2 treated cultures but were more pronounced in those containing immunoglobulin secreting cells. None of the IL-2 induced changes appeared to correlate with the clinical stage of the disease or the level of Tac antigen expression on the freshly isolated CLL B cells.     

Pituitary metastasis from malignant bronchial carcinoid

Metastases from a carcinoid tumor to the pituitary gland have, to our knowledge, not been described. We present a 49-year-old woman diagnosed as having a primary carcinoid tumor arising in the submucosa of a large bronchus who 8 years later presented with multiple metastases including one to the pituitary gland, which was in partial failure of pituitary function. This case illustrates than when confronted with a pituitary tumor resembling an adenoma but negative for pituitary hormones, the possibility of a metastasis from a carcinoid tumor should be considered.