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Biomedical subjects

F Gray

Publications and source records attributed to F Gray.

At least 19 recordsLinked to original sources
PubMed2006

Search for the invisible decay of neutrons with KamLAND.

The Kamioka Liquid scintillator Anti-Neutrino Detector is used in a search for single neutron or two-neutron intranuclear disappearance that would produce holes in the -shell energy level of (12)C nuclei. Such holes could be created as a result of nucleon decay into invisible modes (inv), e.g., n--> 3v or nn--> 2v. The deexcitation of the corresponding daughter nucleus results in a sequence of space and time-correlated events observable in the liquid scintillator detector. We report on new limits for one- and two-neutron disappearance: tau(n--> inv) > 5.8 x 10(29) years and tau (nn--> inv) > 1.4 x 10(30) years at 90% C.L. These results represent an improvement of factors of approximately 3 and >10(4) and over previous experiments.

Journal Article↗
PubMed2006

Dilation of Virchow-Robin spaces in CADASIL.

To precise the severity of dilated Virchow-Robin spaces (VRS) in CADASIL patients and to determine their correlation with clinical presentation and other abnormalities on cerebral Magnetic Resonance Imaging (MRI). Dilated VRS were previously associated with aging, hypertension, dementia, epilepsy or migraine. We already reported increased frequency of enlarged VRS in CADASIL patients when compared with family members without the affected haplotype. We analysed clinical and MRI data from 50 CADASIL patients collected prospectively in our center. The presence of dilated VRS was assessed in the subcortical white matter of temporal lobes, the centrum semi-ovale and the basal ganglia. Their severity in each region was evaluated according to the scale proposed by Heier. We compared the clinical data, the severity of white matter abnormalities and the presence of microbleeds in patients with and without dilated VRS. Seventy-eight percent of patients in our series had dilated VRS, mostly located in the lentiform nuclei (94%) and subcortical white matter of the temporal lobes (66%). The severity of these lesions was variable but not correlated neither to the extent of white matter abnormalities nor to the clinical presentation in our patients. Only the age was found to be related to the extent of dilated VRS. Dilated VRS are frequent in CADASIL and mostly located in the temporal white matter and basal ganglia. The dilation of perivascular spaces does not seem to be directly related to the occurrence of ischemic or hemorrhagic lesions in CADASIL. In contrast, the relation with age suggests that either aging, progression of vascular wall alterations during the course of the disease, or both of these processes can favour the extension of VRS in CADASIL.

Adult↗
PubMed2005

Experimental investigation of geologically produced antineutrinos with KamLAND.

The detection of electron antineutrinos produced by natural radioactivity in the Earth could yield important geophysical information. The Kamioka liquid scintillator antineutrino detector (KamLAND) has the sensitivity to detect electron antineutrinos produced by the decay of 238U and 232Th within the Earth. Earth composition models suggest that the radiogenic power from these isotope decays is 16 TW, approximately half of the total measured heat dissipation rate from the Earth. Here we present results from a search for geoneutrinos with KamLAND. Assuming a Th/U mass concentration ratio of 3.9, the 90 per cent confidence interval for the total number of geoneutrinos detected is 4.5 to 54.2. This result is consistent with the central value of 19 predicted by geophysical models. Although our present data have limited statistical power, they nevertheless provide by direct means an upper limit (60 TW) for the radiogenic power of U and Th in the Earth, a quantity that is currently poorly constrained.

Journal Article↗
PubMed2005

Measurement of neutrino oscillation with KamLAND: evidence of spectral distortion.

We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 nu (e) candidate events with energies above 3.4 MeV compared to 365.2+/-23.7 events expected in the absence of neutrino oscillation. Accounting for 17.8+/-7.3 expected background events, the statistical significance for reactor nu (e) disappearance is 99.998%. The observed energy spectrum disagrees with the expected spectral shape in the absence of neutrino oscillation at 99.6% significance and prefers the distortion expected from nu (e) oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2). A global analysis of data from KamLAND and solar-neutrino experiments yields Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2) and tan((2)theta=0.40(+0.10)(-0.07), the most precise determination to date.

Journal Article↗
PubMed2003

Effectiveness of dietary advice given by community dietitians to men with elevated blood cholesterol in a clinical setting: a pilot study.

OBJECTIVE: To compare the effect of two types of dietary advice given by community dietitians on subsequent dietary intake in Scottish men, over 8 weeks. DESIGN: A parallel design intervention study was employed. Twenty-five men with elevated blood cholesterol levels were randomly assigned to Group 1 (advice to reduce dietary fat only) or Group 2 (advice to reduce dietary fat and sugar). RESULTS: Neither group significantly reduced fat intakes, yet both groups self-rated their fat intake as being lower at the end than at the start of the study. Group 2 reduced per cent energy from sugar and increased per cent energy from starch without significantly changing per cent energy from total carbohydrate. No significant change in blood cholesterol levels were observed. CONCLUSIONS: Advice to reduce dietary fat was not effective in this group of subjects. Advice to reduce both fat and sugar resulted in a decrease in sugar intake only. Both groups wrongly rated their fat intake to be lower at the end of the study. This may be a barrier to further dietary advice.

Adult↗
PubMed2002

Expression of excitatory amino acid transporter-2 (EAAT-2) and glutamine synthetase (GS) in brain macrophages and microglia of SIVmac251-infected macaques.

Na+-dependent transporters for glutamate (excitatory amino acid transporters, EAATs) clear extracellular glutamate in the brain and prevent excitotoxic neuronal damage. Glutamine synthetase (GS) provides metabolic support for neurones by producing the neurotrophic amino acid glutamine. EAAT and GS expression has recently been demonstrated in macrophages and microglial cells in vitro, and in two models of acute inflammation in vivo. This observation might modify our current understanding of brain inflammation, which considers activated microglia and brain macrophages as the main neurotoxic cells through their production of a variety of neurotoxins, including glutamate. EAAT and GS expression by these cells would entail neuroprotective and neurotrophic properties, counterbalancing the deleterious consequences of microglial activation. Macaque infection by the simian immunodeficiency virus (SIV) is considered the most relevant model for human acquired immunodeficiency syndrome (AIDS), including chronic inflammation of the brain at the early asymptomatic stage of the infection, followed by an AIDS-like disease where neuronal death occurs. We studied the expression of EAAT-2 and GS in the brains of three SIVmac251-infected and two noninfected cynomolgus macaques. We found that both microglia and brain macrophages expressed EAAT-2 and GS in infected primates, suggesting that these cells might, like astrocytes, clear extracellular glutamate and provide glutamine to neurones. Microglia and macrophages could thus have neuroprotective and neurotrophic properties in addition to their production of neurotoxins. This finding might explain the contrast between early intense microglial activation and the late occurrence of neuronal apoptotic cell death, which is mainly observed at the terminal stage of the disease.

Animals↗
PubMed2002

[Hashimoto's encephalopathy: an anatomicoclinical observation].

Hashimoto's encephalopathy (HE) is a rare neurological complication of chronic lymphocytic thyroiditis. As its clinical presentation is aspecific, other etiologies of acute encephalopathy have to be ruled out. We report the case of a 29-year old woman with neuropsychiatric signs preceding coma, myoclonus and epileptic seizures. Clinical and electroencephalographic features were consistent with the diagnosis of new variant of Creutzfeldt-Jakob disease. However, high titres of antithyroid antibodies in serum directed towards the diagnosis of HE. Despite oral steroids, the patient died five months later. Neuropathological findings ruled out spongiform encephalopathy and disclosed aspecific activated microglia. Our observation suggests that this process could be involved in the pathogenesis of HE. Even in the absence of clinical dysthyroidism, HE diagnosis has to be suspected in the settings of acute encephalopathy associated with seric antithyroid antibodies.

Acute Disease↗
PubMed2001

Precise measurement of the positive muon anomalous magnetic moment.

A precise measurement of the anomalous g value, a(mu) = (g-2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. The result a(mu+) = 11 659 202(14) (6) x 10(-10) (1.3 ppm) is in good agreement with previous measurements and has an error one third that of the combined previous data. The current theoretical value from the standard model is a(mu)(SM) = 11 659 159.6(6.7) x 10(-10) (0.57 ppm) and a(mu)(exp) - a(mu)(SM) = 43(16) x 10(-10) in which a(mu)(exp) is the world average experimental value.

Journal Article↗
PubMed2001

Symmetrical necrosis of the solitary tract nuclei as a contributory cause of death.

A 64-year-old man died in spite of surgery 4 days after attempting suicide. He first tried to hang himself with a rope and when the hanging did not succeed, he cut his throat with a knife. The autopsy showed four sutured cervical wounds with laryngeal wounds but without associated important vascular injury. The neuropathological study revealed two watershed-type haemorrhagic infarcts, involving the left occipital lobe and the left cerebellum. It also showed a symmetrical necrosis of solitary tract nuclei in the medullary tegmentum. Such a lesion is likely to result from sudden acute transient circulatory failure and might have played a role in the secondary autonomous cardiac and respiratory dysfunctions following a non-lethal trauma.

Aged↗
PubMed2001

[Familial orthochromatic leukodystrophy: clinicopathological study of two cases].

This paper reports the clinico-pathological data in a French family with orthochromatic leukodystrophy. The parents were first cousins and had seven children. Among those, two sisters and one brother presented with neurological signs, with onset around the 5(th) decade, including a dementing syndrome of frontal type, a tetrapyramidal syndrome, seizures, and, in one sibling, a cerebellar syndrome. CT scan or MRI showed diffuse involvement of the white matter. The neurological signs worsened progressively leading to death within 11 and 22 months. Neuropathological examination was performed in two cases. It revealed characteristic orthochromatic leukodystrophy. In one case, the presence of pigmented macrophages and astrocytes was suggestive of Van Bogaert and Nyssen disease. However there were some atypical features including the absence of pigmented cells in the second case whose clinical course was shorter, and the cavitary appearance of the white matter changes with a relative increase in the number of oligodendrocytes raising the issue of a possible link between this condition and cavitary orthochromatic leukodystrophies.

Aged↗
PubMed2001

[Hereditary cerebral amyloid angiopathies].

Cerebral amyloid angiopathies are defined by the presence of amyloid substance in the walls of cerebral vessels. All amyloid substances have a particular physico-chemical structure, which imparts certain specific staining properties, but the biochemical composition of different amyloid types varies. Different forms of cerebral amyloid angiopathy have been identified, based on the biochemical nature of the protein deposited (e.g. beta-amyloid, cystatin C, transthyretin, gelsolin, amyloid protein Bri, prion protein). Some cerebral amyloid angiopathies are familial; these prompted genetic studies which in turn led to a better understanding of the genes coding for different amyloid proteins. As a group, cerebral amyloid angiopathies have certain neuropathological lesions in common. Infiltration by amyloid substance results in weakening of the small vessel walls and secondary complications responsible for changes such as microinfarcts and miliary haemorrhages in the cerebral cortex, lobar haemorrhages and/or leucoencephalopathy. These changes form the basis of the neurological complications: meningeal and cerebral haemorrhages, transient ischaemic episodes, vascular dementia. However each type of hereditary cerebral amyloid angiopathy has individual clinical and histopathological features reflecting the severity of arterial involvement, the extent of amyloid deposition within or outside the central nervous system, and the association with other neurodegenarative changes.

Alzheimer Disease↗
PubMed2000

Progressive multifocal leukoencephalopathy and oligodendroglioma in a monkey co-infected by simian immunodeficiency virus and simian virus 40.

A rhesus monkey experimentally inoculated with simian immunodeficiency virus (SIV) mac251 was killed 42 months later because of poor general condition. CD4 lymphocyte count which was 3,430/mm3 before inoculation, had decreased to 638/mm3 2 months before death. Neuropathological examination revealed changes characteristic of progressive multifocal leukoencephalopathy (PML) in the white matter of the cerebral hemispheres and brain stem. In situ hybridization was negative for JC virus but markedly positive for simian virus 40 (SV40) in the nuclei of many oligodendrocytes. Many oligodendrocytes also expressed p53. Within an area involved by PML, there was a densely cellular tumor with honeycomb appearance and elongated vessels characteristic of oligodendrogliomas. Within the tumor in situ hybridization for SV40 and immunocytochemistry for p53 were negative. Opportunistic infection by SV40 has been occasionally reported in experimentally SIV-infected monkeys resulting in PML or malignant astrocytoma. Association of JC virus-induced PML and astrocytomas has been reported in three human cases without AIDS. In those cases, as in our monkey, polyomaviruses (SV40 or JC virus) were expressed in the areas with PML but not in the glial tumor. Association of PML and oligodendroglioma has not been reported previously to our knowledge. The relationship between oligodendrocyte proliferation and polyomavirus infection of oligodendrocytes is unclear. Our findings suggest that binding of the viral protein to p53 may result in inactivation of the pro-apoptotic protein favoring the proliferation of a randomly occurring tumoral clone of oligodendrocytes.

Animals↗
PubMed2000

Neuronal apoptosis in human immunodeficiency virus infection.

Neuronal apoptosis has been shown to occur in HIV infection by a number of in vivo and in vitro studies, however, the cause of neuronal damage in AIDS is still unclear and its relationships with the cognitive disorders characteristic of HIV dementia remain a matter of debate. In this review, based on our experience, we analyse the techniques used to identify neuronal apoptosis on post-mortem AIDS brains and describe the relationships of neuronal apoptosis with the stage of disease, a history of HIV-dementia, the degree of productive HIV infection, microglial activation, blood-brain barrier involvement and axonal damage. We conclude that the severity of neuronal apoptosis in the cerebral cortex correlates with the presence of cerebral atrophy, but not with the cognitive disorders. There is no global quantitative correlation between neuronal apoptosis and HIV encephalitis, microglial activation or axonal damage. However we found some topographical correlation between these changes. We conclude that neuronal apoptosis and consequent neuronal loss, in HIV infected patients, are probably not related to a single cause. It seems likely that microglial activation, directly or indirectly related to HIV infection of the CNS, plays a major role in its causation possibly through the mediation of oxidative stress. Axonal damage, either secondary to microglial activation, or to the intervention of systemic factors may also contribute to neuronal apoptosis.

AIDS Dementia Complex↗