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Biomedical subjects

J Murrell

Publications and source records attributed to J Murrell.

At least 19 recordsLinked to original sources
PubMed2006

Cholesterol, APOE genotype, and Alzheimer disease: an epidemiologic study of Nigerian Yoruba.

OBJECTIVE: To examine the relationship between cholesterol and other lipids, APOE genotype, and risk of Alzheimer disease (AD) in a population-based study of elderly Yoruba living in Ibadan, Nigeria. METHODS: Blood samples and clinical data were collected from Yoruba study participants aged 70 years and older (N = 1,075) as part of the Indianapolis-Ibadan Dementia Project, a longitudinal epidemiologic study of AD. Cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and triglyceride levels were measured in fasting blood samples. DNA was extracted and APOE was genotyped. Diagnoses of AD were made by consensus using National Institute of Neurologic Disorders/Stroke-Alzheimer's Disease and Related Disorders Association criteria. RESULTS: Logistic regression models showed interaction after adjusting for age and gender between APOE-epsilon4 genotype and biomarkers in the risk of AD cholesterol*genotype (p = 0.022), LDL*genotype (p= 0.018), and triglyceride*genotype (p = 0.036). Increasing levels of cholesterol and LDL were associated with increased risk of AD in individuals without the APOE-epsilon4 allele, but not in those with APOE-epsilon4. There was no significant association between levels of triglycerides and AD risk in those without APOE-epsilon4. CONCLUSIONS: There was a significant interaction between cholesterol, APOE-epsilon4, and the risk of Alzheimer disease (AD) in the Yoruba, a population that has lower cholesterol levels and lower incidence rates of AD compared to African Americans. APOE status needs to be considered when assessing the relationship between lipid levels and AD risk in population studies.

Aged↗
PubMed2005

Neuropsychological function in nondemented carriers of presenilin-1 mutations.

BACKGROUND: Prospective and case-control studies have demonstrated that memory loss and executive dysfunction occur early in Alzheimer disease (AD). OBJECTIVE: To investigate these observations by the study of persons at risk for autosomal dominant forms of AD. METHODS: Neuropsychological and genetic tests were performed on 51 nondemented at-risk members of 10 Mexican families with two distinct presenilin-1 (PS1) mutations. Test scores were compared between PS1 mutation carriers (MCs; n = 30) and noncarriers (NCs; n = 21) by analyses of variance, co-varying for family and specific mutation. Regression analyses were performed, taking into account age relative to the median age at dementia diagnosis in the family (adjusted age), gender, Beck Depression Inventory (BDI) scores, education, and number of APOE epsilon4 alleles. Subjects were divided into age tertiles and scores compared within these groups. Composite scores for Verbal Memory, Executive Function/Working Memory, Language, and Visuospatial Function were created, and these scores compared between MCs and NCs. RESULTS: MCs performed worse than NCs on the Mini-Mental State Examination, Trails Making Tests A and B, Delayed Recall of a 10-Word List, and Wechsler Adult Intelligence Scale WAIS Block Design. In multiple linear regression analyses, BDI score, gender, and number of APOE epsilon4 alleles did not consistently affect test scores. The differences seen between MCs and NCs were due to differences in the oldest tertile. MCs had lower Visuospatial and Executive Function/Working Memory but not Verbal Memory or Language composite scores. CONCLUSIONS: This study is consistent with findings in sporadic Alzheimer disease of early problems with memory, visuospatial function, and particularly with executive function in PS1 mutation carriers. Depression, gender, and presence of an APOE epsilon4 allele did not demonstrate large influences on neuropsychological performance.

Adolescent↗
PubMed2005

Fragmentations and reactions of the organophosphate insecticide Diazinon and its oxygen analog Diazoxon studied by electrospray ionization ion trap mass spectrometry.

The fragmentations and reactions of Diazinon and related compounds have been studied by electrospray ionization ion trap mass spectrometry. Several novel fragmentation and rearrangements have been observed, including an intramolecular thiono-thiolo rearrangement. The stability, in the gas-phase, of the protomers of 2-isopropyl-4-methyl-6-pyrimidinol has been demonstrated. The complexity of the gas phase ion processes observed suggest that, at present, caution should be exercised in using this approach for the analysis of environmental and other samples until our understanding of these processes increases considerably.

Diazinon↗
PubMed2004

Investigation into factors affecting precision in ion trap mass spectrometry using different scan directions and axial modulation potential amplitudes.

Electrospray ionization mass spectra obtained from different scan directions are observed to be dependent on the axial modulation potential amplitudes used for resonant ejection and on the positive deviation caused by higher even-multipole fields present in most commercial ion traps. The axial modulation voltage influences the dissociation of ions during resonant ejection and the observed mass shifts. The higher even-multipole fields in commercial ion traps are known to influence resonant ejection from the ion trap and can cause a loss in mass resolution for peaks in reverse scan mass spectra compared with that obtained by the forward scan. However, along with the dissociation of ions during resonant ejection causing a loss in resolution, the possibility of resolving an isotopic distribution is also shown to be influenced by the mass shifts caused by the space charge. These mass shifts differ depending on the scan direction employed. A significant loss in resolution can also result from resonant ejection using non-optimal axial modulation voltages. We also present results showing the ejection of ions at betaz = 1/2 using the reverse scan mode without the axial modulation voltage. Ion ejection at betaz = 1/2 is uncommon in commercial (stretched ion traps) with the conventional analytical scan without the use of a frequency of the axial modulation voltage corresponding to this non-linear resonance.

Cytochromes c↗
PubMed2004

Female preclinical presenilin-1 mutation carriers unaware of their genetic status have higher levels of depression than their non-mutation carrying kin.

OBJECTIVES: To study depressive symptoms in preclinical presenilin-1 (PS1) related Alzheimer's disease. METHODS: Participants were 33 Mexican women at risk for inheriting PS1 mutations who were not demented. They were interviewed, underwent cognitive testing, and completed the Beck depression inventory (BDI). PS1 mutation status was determined. Mean BDI scores were compared between PS1 mutation carriers and non-carriers. The percentage of subjects who reported seeing a psychiatric professional, and the percentage complaining of memory loss were compared between groups. Regression analysis was used to determine whether mutation status predicted BDI scores after adjusting for age, education, mini-mental state examination, and subjective memory function. RESULTS: PS1 mutation carriers (n = 17) scored significantly higher than non-carriers (n = 16) on the BDI (mean score, 14.4 v 6.5, p = 0.017); 24% of mutation carriers and 12.5% of non-carriers admitted having sought help from a psychiatric professional (NS). Mutation status remained a significant predictor of BDI scores after adjusting for potential covariates. Though not demented, mutation carriers tended to score lower than non-carriers on several neuropsychological tests. CONCLUSIONS: Depressive symptoms can occur early in the course of PS1 related Alzheimer's disease, at least in women. This supports the hypothesis that depression may occur as a direct result of the neuropathology underlying Alzheimer's disease.

Adult↗
PubMed2003

Investigations into the use of a reverse scan in a quadrupole ion trap mass spectrometer.

The forward scan (i.e. an increasing RF voltage ramp for the mass-selective instability scan) is commonly used as an analytical scan for ion detection with quadrupole ion trap instruments. A number of phenomena have been observed while using this scan technique. These include space charge effects resulting in the delayed ejection of ions from the ion trap, and the fragmentation of fragile ions producing very broad peaks. Here the use of a reverse scan (i.e. a decreasing RF voltage ramp) is examined to determine the effect of the above phenomena in this acquisition method. With regard to space charge effects, the apparent reduction of the carbon isotope spacing below one Thomson (for singly charged ions) that is observed with the forward scan is now replaced by an apparent increase in this spacing. The reverse scan, which optimizes at lower axial modulation ejection voltages than the forward scan, allows for the intact ejection of fragile ions under its typical operating conditions whereas the forward scan results in fragmentation. Reducing the axial modulation voltage for the ejection of ions in the forward scan results in less dissociation of the fragile ions during ion ejection, but with the observation of ghost peaks due to incomplete ejection of all of the ions at the resonance ejection condition. While performing the reverse scan experiment, the formation of product ions from dissociation of the MH(+) ion has also been observed.

Journal Article↗
PubMed2003

"Fast excitation" CID in a quadrupole ion trap mass spectrometer.

Collision-induced dissociation (CID) in a quadrupole ion trap mass spectrometer is usually performed by applying a small amplitude excitation voltage at the same secular frequency as the ion of interest. Here we disclose studies examining the use of large amplitude voltage excitations (applied for short periods of time) to cause fragmentation of the ions of interest. This process has been examined using leucine enkephalin as the model compound and the motion of the ions within the ion trap simulated using ITSIM. The resulting fragmentation information obtained is identical with that observed by conventional resonance excitation CID. "Fast excitation" CID deposits (as determined by the intensity ratio of the a(4)/b(4) ion of leucine enkephalin) approximately the same amount of internal energy into an ion as conventional resonance excitation CID where the excitation signal is applied for much longer periods of time. The major difference between the two excitation techniques is the higher rate of excitation (gain in kinetic energy) between successive collisions with helium atoms with "fast excitation" CID as opposed to the conventional resonance excitation CID. With conventional resonance excitation CID ions fragment while the excitation voltage is still being applied whereas for "fast excitation" CID a higher proportion of the ions fragment in the ion cooling time following the excitation pulse. The fragmentation of the (M + 17H)(17+) of horse heart myoglobin is also shown to illustrate the application of "fast excitation" CID to proteins.

Animals↗
PubMed2001

Fragmentation and reactions of two isomeric O-alkyl S-(2-dialkylamino)ethyl methylphosphonothiolates studied by electrospray ionization/ion trap mass spectrometry.

An initial investigation into the electrospray ionization ion trap mass spectrometry (ESI/ITMS) of simple organophosphorus compounds [1] demonstrated that detailed structural information could be obtained by sequential fragmentation of the ions using collision induced dissociation (CID). Several novel fragmentations/rearrangements were observed and it was apparent that the full potential of this approach could not be exploited until a more detailed understanding of the ion fragmentations was obtained. Such an understanding will only result from a detailed study of a wide range of compounds. The present paper describes the investigation of two isomeric organophosphates of particular relevance to chemical warfare convention (CWC) considerations.

Chemical Warfare Agents↗
PubMed1996

Report of a critical recombination further narrowing the TSC1 region.

A large tuberous sclerosis multigenerational family segregating with markers on chromosome 9q from the TSC1 region was studied with a new highly polymorphic marker (designated A6) from the region. A critical affected person showed recombination with the marker, eliminating approximately 100 kilobases from the telomeric end of the critical region, which contains three genes and three to four additional exons for which the associated genes have not been delineated. This information serves to further the search for the TSC1 gene.

Blotting, Southern↗
PubMed1995

A 500-kilobase region containing the tuberous sclerosis locus (TSC1) in a 1.7-megabase YAC and cosmid contig.

A complete overlapping clone map of a 1.7-Mb region from DBH to D9S67 that includes the TSC1 candidate region has been constructed. The map includes YAC and cosmid clones, contains STS approximately every 50 kb on average, and establishes the order of five previously unordered loci. The overall physical length of this segment of chromosome 9q34 (1.7 Mb) is significantly less than expected compared to its estimated genetic length (approximately 10 cM). Consequently, the physical length of the TSC1 candidate region is substantially less than predicted by a genetic distance of approximately 2 cM.

Base Sequence↗
PubMed1994

Endoglin, a TGF-beta binding protein of endothelial cells, is the gene for hereditary haemorrhagic telangiectasia type 1.

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by multisystemic vascular dysplasia and recurrent haemorrhage. Linkage for some families has been established to chromosome 9q33-q34. In the present study, endoglin, a transforming growth factor beta (TGF-beta) binding protein, was analysed as a candidate gene for the disorder based on chromosomal location, expression pattern and function. We have identified mutations in three affected individuals: a C to G substitution converting a tyrosine to a termination codon, a 39 base pair deletion and a 2 basepair deletion which creates a premature termination codon. We have identified endoglin as the HHT gene mapping to 9q3 and have established HHT as the first human disease defined by a mutation in a member of the TGF-beta receptor complex.

Amino Acid Sequence↗
PubMed1994

Disposition of a mixed meal by the conscious dog.

The disposition of a mixed meal administered intragastrically was examined in 13 24-h-fasted conscious dogs, using the arteriovenous (AV) difference technique (and isotopic methods in 6 dogs). Postprandial net gut output totaled (in g of glucose equivalents) 42 +/- 6 glucose, 3 +/- 0.3 lactate, 2 +/- 0.2 alanine, and 0.2 +/- 0.0 glycerol. The gut oxidized 2 +/- 1 g of glucose, and 0.2 +/- 0.1 g remained within the intestinal lumen. Of the administered glucose 68 +/- 6% were accounted for, and volatile fatty acid production by the gut (n = 1) accounted for at least an additional 4%. Of the labeled glucose in the meal 82 +/- 5% appeared in the systemic circulation, an apparent overestimate of absorption of glucose from the meal. Cumulative net hepatic uptakes (in g of glucose equivalents) were 4.1 +/- 3.1 glucose, 12.1 +/- 2.1 gluconeogenic amino acids, and 1.5 +/- 0.2 glycerol. Net hepatic glycogen synthesis and lactate and CO2 production accounted for 6.2 +/- 4.1, 9.3 +/- 2.8, and 1.6 +/- 0.8 g of glucose equivalents, respectively. In summary, the AV difference method could account for the gut disposition of about two-thirds of the meal glucose. Nonsplanchnic tissues disposed of threefold more glucose than the liver. Net hepatic uptake of glucose equivalents as gluconeogenic amino acids was threefold > glucose uptake, and net hepatic uptake of gluconeogenic amino acids was > net gut release of gluconeogenic amino acids. In conclusion, the net hepatic uptake of glucose and gluconeogenic substrates provided adequate carbon for net hepatic synthesis of glycogen and production of lactate and CO2. In a net sense, peripheral tissues must have been the source of some of the gluconeogenic carbon taken up by the liver after the meal.

Amino Acids↗
PubMed1994

Clinical characteristics in a kindred with early-onset Alzheimer's disease and their linkage to a G-->T change at position 2149 of the amyloid precursor protein gene.

Patients from five generations of a family developed presenile Alzheimer's disease (AD) early in the fifth decade. Recent memory, information-processing speed, sequential tracking, and conceptual reasoning were the earliest cognitive functions affected. Language and visuoperceptual skills were largely spared early in the course of the disease. Later, there were progressive cognitive deficits and inability to perform the activities of daily living. Death occurred, on average, 6 years after onset. Three autopsies in affected members revealed cerebral amyloid deposits and neurofibrillary tangles. Clinical and pathologic features were typical for familial AD. Direct DNA sequencing revealed a G-->T change at position 2149 of the amyloid precursor protein (APP) gene that resulted in the substitution of phenylalanine for valine in the transmembrane domain of the mature protein. This mutation was present in DNA from all four examined affected individuals and linked to the disease with a lod score of 3.25, and was the most probable cause of AD in this family.

Adult↗
PubMed1993

RFLP analysis for APP 717 mutations associated with Alzheimer's disease.

Familial Alzheimer's disease (FAD) has been shown to be associated with three distinct point mutations within the same codon of the amyloid precursor protein (APP) gene. The mutation identified in the Indiana kindred is a G-->T transversion at the first position of the codon for amino acid 717, resulting in a substitution of phenylalanine for valine in the APP protein. Screening of persons at risk for the APP Phe-717 mutation using a variation of the polymerase chain reaction identified nine positives among 34 tested. In addition, DNA from 145 FAD subjects were tested for the three known APP 717 mutations.

Alzheimer Disease↗
PubMed1992

Spectrum of amyloid beta-protein immunoreactivity in hereditary Alzheimer disease with a guanine to thymine missense change at position 1924 of the APP gene.

We studied neuropathologically 3 patients of a previously unreported kindred of presenile Alzheimer disease (AD), characterized by a G to T mutation at base pair 1924 (695 transcript) of the amyloid precursor protein gene. Classic features of presenile AD are observed. Neurofibrillary tangles with paired helical filaments as well as neuritic plaques are found in large number in neocortex and hippocampus. beta-Protein deposits in meningeal and parenchymal vessels are present, but not severe. Prominent subpial ribbon-like deposits are detected with antibodies to a 28-residue synthetic peptide; however, only occasionally can they be seen in thioflavin S treated sections. Along with a mild involvement of vessels, as demonstrated by beta-protein immunolabeling, parenchymal involvement is also seen in the cerebellar molecular layer. In the course of the study, we have not detected neuropathologic changes, which are mutation specific. Further investigations of familial Alzheimer disease with known genetic mutations will clarify whether correlations exist between specific mutations and neuropathologic phenotypes.

Adult↗
PubMed1991

A mutation in the amyloid precursor protein associated with hereditary Alzheimer's disease.

Alzheimer's disease is a form of localized amyloidosis characterized by cerebral cortical amyloid plaques, neurofibrillary tangles, and amyloid deposits within the walls of leptomeningeal vessels. Although most cases of Alzheimer's disease are sporadic, kindreds with autosomal-dominant inheritance of the syndrome suggest that a single mutation may be important in pathogenesis. Direct sequencing of DNA from a family with autopsy-proven Alzheimer's disease revealed a single amino acid substitution (Phe for Val) in the transmembrane domain of the amyloid precursor protein. This mutation correlates with the presence of Alzheimer's disease in all patients in this study, and may be the inherited factor causing both amyloid fibril formation and dementia.

Alzheimer Disease↗
PubMed1991

Preparation and crystallization of human transthyretin (prealbumin) variants.

Naturally occurring variants of human serum transthyretin (prealbumin) have been prepared by recombinant DNA methods and crystallized from ammonium sulfate solutions to give crystals suitable for x-ray crystallographic analysis. Included are variants which are known to be associated with familial amyloidotic polyneuropathy. Dyes which have been used as histochemical stains to identify amyloid tissue deposits: Congo Red, Methylene Blue and Bromophenol Blue, have been co-crystallized with the transthyretin variants. Congo Red was found to be very selective while Methylene Blue actually assisted in the formation of crystals. All crystal forms which were examined were isomorphous to the structure of normal transthyretin.

Base Sequence↗