Nerve growth factor favours long-term depression over long-term potentiation in layer II–III neurones of rat visual cortex

Nerve growth factor (NGF) has been shown to regulate plasticity in the visual cortex of monocularly deprived animals. However, to date, few attempts have been made to investigate the role of NGF in synaptic plasticity at the cellular level. In the study reported here we looked at the effects of exogenously applied NGF on synaptic plasticity of layer II–III regular spiking (RS) neurones in visual cortex of 16- to 18-day-old rats. We found that local application of NGF converted high frequency stimulation (HFS)-induced long-term potentiation (LTP) into long-term depression (LTD). We showed that this shift of synaptic plasticity was also obtained with bath application of NGF during HFS. Application of NGF subsequent to HFS left LTP unaffected, conferring temporal constraints on NGF efficacy. NGF effects on LTP were mediated by TrkA receptors. Indeed, blockade of TrkA by monoclonal antibody prevented NGF from inducing LTD following HFS. Low frequency stimulation (LFS) elicited LTD in RS cells. We found that NGF or blockade of NGF signalling by anti-TrkA antibody did not change the amplitude of the LTD induced by LFS. Thus, the NGF effect is selective for synaptic modifications induced by HFS in RS cells. The present results indicate that NGF may modulate the sign of long-term changes of synaptic efficacy in response to high frequency inputs.     

Priming of Immunological Memory by Pneumococcal Conjugate Vaccine in Children Unresponsive to 23-Valent Polysaccharide Pneumococcal Vaccine

Pneumococcal polysaccharide vaccine (PPV) is of limited immunogenicity in infants and immunocompromised patients. Our prospective randomized controlled trial investigated whether priming with pneumococcal conjugate vaccine (PCV) induced specific immunological memory in previously nonresponders to PPV. Of a total of 33 children (2 to 18 years) with polysaccharide-specific immunodeficiency (PSI), group A (n = 16) received two doses of 7-valent PCV in a 4- to 6-week interval, and a booster dose of 23-valent PPV after one year. Group B (n = 17) received two doses of PPV in a 1-year interval exclusively. Specific antibody concentrations for serotypes 4, 5, 6B, 9V, 14, 18C, 19F, and 23F were determined (enzyme-linked immunosorbent assay) before and at 7 and 28 days after administration of the PPV booster and compared to an opsonophagocytosis assay. Of group A, 64 to 100% had antibody concentrations of ≥1 μg/ml on day 28 after the booster versus 25 to 94% of group B. Group A had significantly higher antibody concentrations for all PCV-containing serotypes already on day 7, indicating early memory response. Antibody concentrations were in accordance with functional opsonic activity, although opsonic titers varied among individuals. Pneumococcal vaccination was well tolerated. The incidence of airway infections was reduced after priming with PCV (10/year for group A versus 15/year for group B). Following a PPV booster, even patients primarily not responding to PPV showed a rapid and more pronounced memory response after priming with PCV.     

Growth factor-induced phosphorylation of c-ras p21 in normal hemopoietic progenitor cells

Normal murine hemopoietic progenitor cells (colony-forming cells, CFC), representing 0.2% of the bone marrow cell population, were purified to homogeneity by fluorescence-activated cell sorting. CFC require the presence of the murine hemopoietic regulator, granulocyte-macrophage-colony stimulating factor (GM-CSF) for survival, proliferation, and differentiation along the myeloid pathway. An analysis of protein phosphorylation in GM-CSF-stimulated CFC over a 20-hr period demonstrated three phosphoproteins of approximate MW 21 kd and pI 6.2, 5.7 and 5.2 p21-6.2 persisted for 14 hr, while p21-5.7 and p21-5.2 were only detected during the first 5 hr of the analysis. The phosphate turnover time in all three p21 proteins was less than 3 hr and p21-5.2 contains an alkaline-resistant phosphorylation site. Low levels of p21-6.2 were also detected in unstimulated CFC. The observation of these phosphoproteins led us to investigate c-ras p21 in CFC. Immune precipitation with the anti-Ha/Ki-ras p21 monoclonal antibody (Y13-259) showed that expression of c-ras p21 in CFC was independent of GM-CSF stimulation, but that phosphorylated c-ras p21 was present only after GM-CSF stimulation. CFC contained one-tenth of the amount of phosphorylated c-ras p21 per cell compared with v-Ha-ras-transformed fibroblasts. It is possible that the phosphorylation of c-ras p21 in CFC has a significant role in the growth factor-directed molecular cascade responsible for normal hemopoietic development.     

Detection of HIV-1 antiretroviral resistance from patients with persistently low but detectable viraemia

We modified the Abbott diagnostics HIV-1 Viroseq version 2 assay trade mark in order to detect the presence of HIV-1 drug resistance mutations in patients with viraemia below 1000 copies/ml of plasma. One hundred and forty-four patients with a detectable HIV-1 plasma viral load below 1000 copies/ml were selected and HIV-1 genetic analysis carried out using a modification of the Abbott Diagnostics Viroseq 2.0 assay trade mark. The procedure differs from the standard protocol in that a nested PCR amplification step was introduced. The oligonucleotide primers for the first round of PCR were those supplied in the RT-PCR module of the kit. The nested PCR primers were primers A and H taken from the sequencing module. One hundred and twenty-eight out of 144 (89%) plasma samples with an HIV-1 viral load of less than 1000 copies/ml (ranging from 54 to 992 copies) were successfully sequenced. HIV-1 genotypes were obtained from 68 out of 81 (84%) samples with a viral load of greater than 50 but less than 300 copies/ml and 60/63 (95%) of samples with a viral load of greater than 300 but less than 1000 copies/ml. Serial dilution of a sample with a high viral load did not affect the detection of resistance mutations. Multiple sequencing of samples with low viral load did not result in detection of additional mutations, although, in one sample the K103N mutation was detected in 3/6 replicates while wild-type was detected in 2/6 and a mixture of wild-type/mutant in 1/6. Samples from patients infected with both clade B and non-B clades of HIV-1 could be genotyped at low copy number. Modification of the Abbott Viroseq assay allows reproducible sequencing of the HIV-1 genome from patients with low, but detectable, plasma virus burden.     

Pathophysiology of dementias and implications for therapy

Dementia is characterized clinically by progressive cognitive decline, often with impairment of memory. The pathology of dementias is either focal as with infarcts in Vascular Dementia or diffuse as typified by Alzheimer's disease. In many cases of Alzheimer's disease there is a mixture of focal infarcts and diffuse changes. Diffuse pathology in dementias comprises mainly intracellular and extracellular protein deposits. Intracellular inclusions are of tau protein (Alzheimer's disease; and some frontotemporal dementias), alpha-synuclein (Dementia with Lewy bodies) and huntingtin (Huntington's disease). Soluble and insoluble peptides also accumulate in the extracellular spaces of brain parenchyma in dementias with diffuse pathology, mainly amyloid-beta (Abeta) in parenchymal plaques and in artery walls as cerebral amyloid angiopathy (Alzheimer's disease and Dementia with Lewy bodies). Insoluble prion protein (PrP) is deposited in brain parenchyma in Creutzfeldt-Jakob disease and other insoluble amyloid peptides accumulate in brain and vessel walls infamilial dementias. The pattern of extracellular deposits in brain and artery walls suggests that there is a failure of elimination of peptides, such as Abeta along perivascular interstitial fluid drainage pathways ("lymphatics") from the aged brain and in Alzheimer's disease. Such failure may be due to reduced pulsations as arteries stiffen with age and cerebrovascular disease. Immunization against Abeta removes insoluble deposits of Abeta from brain parenchyma and may allow improved clearance of soluble Abeta. Reducing cerebrovascular disease and facilitating elimination of Abeta along perivascular drainage routes may offer long-term preventative measuresfor both Vascular Dementia and for Alzheimer's disease.     

Reversal or reduction of glutamate and GABA transport in CNS pathology and therapy

A dysfunction of amino acid neurotransmitter transporters occurs in a number of central nervous system disorders, including stroke, epilepsy, cerebral palsy and amyotrophic lateral sclerosis. This dysfunction can comprise a reversal of transport direction, leading to the release of neurotransmitter into the extracellular space, or an alteration in transporter expression level. This review analyses the role of glutamate and GABA transporters in the pathogenesis and therapy of a number of acute and chronic neurological disorders.     

9q34 loss of heterozygosity in a tuberous sclerosis astrocytoma suggests a growth suppressor-like activity also for the TSC1 gene

Tuberous sclerosis is an autosomal dominant disease whose characteristicfeature is the development of multiple hamartomas in a varietyof organs and tissues. Two major loci have been identified sofar: TSC1 on chromosome 9q34 and TSC2 on chromosome 16p13.3.Loss of heterozygosity at 16p13.3-associated markers has beenrecently observed in hamartomatous lesions of some tuberoussclerosis patients. Here we report the first evidence of lossof heterozygosity at the TSC1 critical region in a giant cellastrocytoma of a familial tuberous sclerosis case. Segregationanalysis showed that the 9q34 haplotype lost carried the putativenormal TSC1 gene. These data support the hypothesis of botha germline and somatic loss-of-function mutation for the developmentof tuberous sclerosis hamartomas and suggest a tumor-suppressor-likeactivity also for the TSC1 gene product. Finally, the possiblesignificance of a second small region of loss of heterozygosityat 9p21, found in the same astrocytoma, is discussed.     

The impact of working life on health behavior: the effect of job strain on the cognitive predictors of exercise

The theory of planned behavior (TPB) and R. A. Karasek's (1979) job strain model were used to investigate the predictors of exercise in a group of employees. A total of 241 employees completed an initial questionnaire; 1 week later 213 employees responded to a questionnaire measuring behavior. Employees in high-strain jobs did significantly less exercise than those in low-strain jobs, although they did not intend to do less, suggesting that work may impede the intention implementation. Intenders who failed to exercise had significantly higher work demands and lower exercise self-efficacy than intenders who succeeded in exercising. Work also affected exercise indirectly through self-efficacy. Thus, work may be a target for behavior change intervention because of its impact at 2 stages of the TPB.