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Biomedical subjects

J O'Brien

Publications and source records attributed to J O'Brien.

At least 55 records · Page 3Linked to original sources
PubMed2001

Molecular cloning and pharmacological characterization of the canine B1 and B2 bradykinin receptors.

The dog is a valuable animal model in the study of the physiological role of both the B1 and B2 bradykinin receptors. To more thoroughly characterize the pharmacological properties of the canine kinin receptors we isolated the cDNA sequence encoding the B1 and B2 bradykinin receptor subtypes and overexpressed them in Chinese hamster ovary (CHO) cells. The cDNA sequence of the canine B1 bradykinin receptor encodes a protein comprised of 350 amino acids that is 76% identical to the human B1 bradykinin receptor. The cDNA sequence of the canine B2 bradykinin receptor encodes a protein of 392 amino acids that is 81% identical to the human B2 bradykinin receptor. The amino acid sequence of the canine B1 and B2 receptors are 35% identical. Pharmacological studies of the cloned receptors revealed that the agonist affinity of the dog B1 receptor is similar to the rodent B1 receptors, and differs from the human form in that there is no preference for the presence of the N-terminal Lys residue of [des-Arg10]Lys-bradykinin. Significantly, the B1 receptor antagonist [des-Arg9,Leu8]BK behaves as partial agonist on the cloned dog B1 receptor. The dog B2 receptor exhibits the 'classical' pharmacological properties of this receptor subtype.

Amino Acid Sequence↗
PubMed2001

New tools for oligonucleotide fingerprinting.

Oligonucleotide fingerprinting is an attractive, high-throughput complement to tag sequencing methods to determine the spectrum and abundance of genes in cDNA libraries. This method currently relies on the sequential hybridizations of short, radioactively labeled DNA oligonucleotides to clone arrays. Here, we describe a new environment that substantially improves this technology. Fluorescently labeled peptide nucleic acid (PNA) oligonucleotides are used as hybridization probes. Hybridization results are recorded with a large-field, high-resolution laser scanner developed for this purpose. Automated image analysis allows easy handling of large numbers of hybridization images. Signal interference effects, which limit the gridding density in the radioactive approach, are strongly reduced. The sensitivity of the fluorescence detection demonstrated permits the convenient use of nylon membranes. Hybridization data quality is improved, and its generation is substantially accelerated, simplified, and less expensive.

Autoanalysis↗
PubMed2001

Structural neuroimaging studies in late-life depression: a review.

Which patients presenting with depression in late life will progress to a dementia syndrome has been an important research question in recent times. In this paper we review selectively structural neuroimaging investigations of late-life depression (LLD) that have been performed over the past two decades. These studies indicate that there are neuroimaging changes commonly observed in LLD patients when compared to normal controls. Findings include ventricular enlargement and sulcal widening, and reduction in volume size of frontal lobes, hippocampus and caudate nucleus. White matter lesions are more common in depressed subjects and tend to be more severe. Some studies report these changes to be more pronounced in patients who present with late-onset depression (LOD) but this has been contradicted by other studies. Preliminary work suggests that these changes may be associated with a poor prognosis but there is a dearth of systematic, well-controlled longitudinal studies.

Aged↗
PubMed2001

A 1-year follow-up study of behavioral and psychological symptoms in dementia among people in care environments.

BACKGROUND: Behavioral and psychological symptoms in dementia (BPSD) are common and distressing for patients and caregivers, but little is known about the natural history of these symptoms, particularly among patients in care facilities. This information is essential for informed clinical management. We report a 1-year follow-up study of the prevalence, incidence, and outcome of the 3 main BPSD (agitation, depression, and psychosis) in care facilities. METHOD: 136 elderly residents with dementia (29% living in social care facilities and 71% in nursing home care) were assessed longitudinally on 2 occasions a year apart using a range of standardized psychiatric schedules, including the Neuropsychiatric Inventory. RESULTS: The overall prevalence of BPSD was stable over the year (76% at baseline and 82% at follow-up). Subjects with subclinical symptoms at baseline were more likely to develop clinically significant BPSD during follow-up than those who were symptom free (83% vs. 52%; Mann-Whitney U test, z = 2.36, p = .01). Agitation was the most common individual syndrome (55%). Although overall BPSD were persistent, > or = 45% of dementia patients with any of the major syndromes experienced resolution, indicating the development of different BPSD in many residents. There was no evidence that residents taking neuroleptics were more likely to experience resolution of BPSD than neuroleptic-free residents. CONCLUSION: BPSD are highly frequent and persistent among residents of care facilities with dementia. This emphasizes the need for ongoing treatment trials. The pattern of resolution with the development of new symptoms indicates that short focused periods of treatment may be a more effective management approach. In addition, the potential value in treating patients with subclinical BPSD to prevent the development of full-blown syndromes needs to be investigated.

Aged↗
PubMed2000

Motion processing in autism: evidence for a dorsal stream deficiency.

We report that motion coherence thresholds in children with autism are significantly higher than in matched controls. No corresponding difference in form coherence thresholds was found. We interpret this as a specific deficit in dorsal stream function in autism. To examine the possibility of a neural basis for the perceptual and motor related abnormalities frequently cited in autism we tested 23 children diagnosed with autistic disorder, on two tasks specific to dorsal and ventral cortical stream functions. The results provide evidence that autistic individuals have a specific impairment in dorsal stream functioning. We conclude that autism may have common features with other developmental disorders and with early stages of normal development, perhaps reflecting a greater vulnerability of the dorsal system.

Adult↗
PubMed2000

Immune function and vaccine responses in healthy advanced elderly patients.

BACKGROUND: Decline in immune function has been reported to predictably accompany advancing age. However, to our knowledge, few studies have specifically characterized the rapidly expanding advanced elderly population or controlled adequately for concurrent diseases. OBJECTIVE: To assess whether successfully reaching an advanced age in good health is associated with preserved immune function. METHODS: We prospectively compared in vivo with in vitro variables of immune function in 29 healthy, independently living elderly subjects (mean age, 80 years; age range, 75-103 years) and in 21 healthy young control subjects (mean age, 29 years; age range, 25-35 years) in a Veterans Affairs Medical Center. RESULTS: In vivo, among elderly and young subjects, numbers of total white blood cells, monocytes, lymphocytes, and lymphocyte subsets (CD4(+) and CD8(+) T lymphocytes and CD20(+) B cells) were similar, as were levels of total serum IgG and IgM. Only levels of serum IgA were higher in the elderly subjects (3.0 vs 1.7 g/L; P=.001). Functionally, both groups showed vigorous responses to protein (tetanus and diphtheria toxoids) and polysaccharide (23-valent pneumococcal) vaccines. Although levels varied, the fold increases in vaccine antigen-specific IgG were not significantly different in young and elderly subjects, and the avidities of IgG to pneumococcal polysaccharides 14 and 19F were similar before and after vaccination. In vitro, proliferative responses of blood mononuclear cells to T-lymphocyte and B-cell mitogens (pokeweed mitogen, Staphylococcus aureus Cowan strain I, and S aureus Cowan strain I plus interleukin 2), and lipopolysaccharide-induced production of tumor necrosis factor alpha, were comparable in elderly vs young subjects. CONCLUSION: Successful aging, defined by reaching an advanced age with one's overall health intact, may be associated with preserved immune function and adequate responses to vaccines.

Adult↗
PubMed2000

End of life treatment decisions in people with dementia: carers' views and the factors which influence them.

OBJECTIVE: Treatment decisions in life threatening situations (TD) are poorly studied in people with dementia. METHOD: The carers of people with dementia were asked four TD questions, pertaining to cardiac resuscitation, intravenous fluids, oral antibiotics and intravenous antibiotics. The impact of key variables (age, dementia severity, psychiatric co-morbidity, physical illness, family relationship of carer) on TD were evaluated. RESULTS: Fifty carers participated, 46% wanted cardiac resuscitation, 60% wanted treatment with intravenous fluids, 52% wanted treatment with intravenous antibiotics and 60% wanted treatment with oral antibiotics. Agreement between questions was high (76 - 89%), suggesting that relatives were either for or against intervention. There was an association between more severe dementia and a reduced wish for intravenous antibiotics. None of the variables significantly influenced other TD. CONCLUSION: The 'global' view of carers, was not influenced greatly by key disease variables. There are potential implications for the way in which carers are used as proxy decision makers.

Aged↗
PubMed2000

Design and development of selective muscarinic agonists for the treatment of Alzheimer's disease: characterization of tetrahydropyrimidine derivatives and development of new approaches for improved affinity and selectivity for M1 receptors.

Cholinergic neurons degenerate in Alzheimer's disease, resulting in cognitive impairments and memory deficits, and drug development efforts have focused on selective M1 muscarinic agonists. 5-(3-Ethyl-1,2,4- oxadiazol-5-yl)-1,4,5,6-tetrahydropyrimidine trifluoroacetic acid (CDD-0102) stimulates M1 muscarinic receptors in rat brain [Messer, W.S., Jr., Abuh, Y.F., Liu, Y., Periyasamy, S., Ngur, D.O., Edgar, M.A., El-Assadi, A.A., Sbeih, S., Dunbar, P.G., Roknich, S., Rho, T., Fang, Z., Ojo, B., Zhang, H., Huzl, J.J., III, Nagy, P.I., 1997a. J. Med. Chem. 40, 1230-1246.] and improves memory function in rats with lesions of the basal forebrain cholinergic system. Moreover, CDD-0102 exhibits oral bioavailability, few side effects and low toxicity, and thus represents a viable candidate for clinical studies. Despite the development of functionally selective agonists such as xanomeline and CDD-0102, there is room for improvements in ligand affinity and selectivity. The high degree of amino acid homology within transmembrane domains has hindered the development of truly selective agonists. Site-directed mutagenesis, biochemical and molecular modeling studies have identified key amino acid residues such as Thr192 and Asn382 in the binding of agonist to M1 receptors [Huang, X.P., Nagy, P.I., Williams, F.E., Peseckis, S.M., Messer, W.S., Jr., 1999. Br. J. Pharmacol. 126, 735-745.]. Recent work has implicated residues at the top of transmembrane domain VI in the binding of muscarinic agonists and activation of M1 receptors [Huang, X.P., Williams, F.E., Peseckis, S.M., Messer, W.S., Jr., 1998. J. Pharmacol. Exp. Ther. 286, 1129-1139.]. Thus, residues such as Ser388 represent molecular targets for the further development of agonists with improved M1 receptor affinity, selectivity and activity.

Alzheimer Disease↗
PubMed2000

Anxiety, depression and psychosis in vascular dementia: prevalence and associations.

BACKGROUND: Little is known about psychiatric symptoms in Vascular dementia (VaD). METHOD: 92 patients with VaD, and 92 patients with Alzheimer's disease (AD) are reported. The evaluation included standardised measures of mood and psychosis. RESULTS: 72% of VaD patients and 38% of those with AD had two or more anxiety symptoms. VaD patients with severe dementia (94%) were the most likely to be anxious. Depression was also significantly more common in VaD patients (19% vs. 8%) whereas psychotic symptoms were prevalent in both dementias. CONCLUSION: Psychiatric symptoms are common in VaD, especially in patients with moderate or severe dementia. Rigorous assessment of psychiatric symptoms in VaD should be part of good clinical practice.

Aged↗
PubMed2000

Depression in the carers of dementia sufferers: a comparison of the carers of patients suffering from dementia with Lewy bodies and the carers of patients with Alzheimer's disease.

BACKGROUND: Depression has not previously been studied in the carers of patients suffering from dementia with Lewy Bodies (DLB). METHOD: Twenty-five DLB carers were matched with 75 AD carers, according to carer characteristics. A standardised assessment incorporated measures of cognition, depression, psychosis and behavioural disturbance. DLB (consensus criteria), and AD (NINCDS ADRDA criteria) were diagnosed using operationalised clinical criteria. Carer depression was diagnosed using the Research Diagnostic Criteria. RESULTS: The overall frequency of depression was similar in DLB and AD carers (28% vs. 31%). DLB carers were significantly more likely to experience a major depressive disorder (3/25 - 12% vs. 0/75 - 0% chi(2)=9.3, P=0.002, df 1), although the numbers were small. The severity of behavioural disturbance was associated with carer depression in the DLB carers and in the total sample. CONCLUSION: The severity of behavioural disturbance was significantly associated with depression in DLB carers.

Alzheimer Disease↗
PubMed2000

A simple and effective separation and purification procedure for DNA fragments using dodecyltrimethylammonium bromide.

In this work we describe a simple two step separation procedure for the separation and purification of short DNA fragments. The first step involves precipitating the DNA using the cationic surfactant dodecyltrimethylammonium bromide. Dodecyltrimethylammonium bromide, unlike cetyltrimethylammonium bromide will not precipitate DNA before complexation is complete thus providing a high purity DNA. The second step involves dissolution of the DNA-dodecyltrimethylammonium complex in 75% ethanol, followed by precipitation of the Sodium-DNA salt, by titrating in a salt solution. This method is particularly suited to purification of short fragments as it does not require high salt concentrations in the ethanol precipitation step, which can be damaging for short DNA. The ability of dodecyltrimethylammonium bromide to remove ethidium bromide from intercalation sites on the DNA is also discussed

Chemical Precipitation↗
PubMed2000

The centromeric part of the human NK gene complex: linkage of LOX-1 and LY49L with the CD94/NKG2 region.

The natural killer (NK) gene complex is a genomic region containing lectin-type receptor genes. We have established a contig of PAC and BAC clones comprising about 1 Mb of the centromeric part of the NK gene complex. This region extends from the LOX-1 gene, which encodes a receptor for oxidized LDL and was found within 100 kb telomeric of the STS marker D12S77, contains the CD94 and NKG2 NK receptor genes and reaches beyond D12S852 on the proximal side. In this part we have mapped the human LY49L gene, a homologue of the rodent Ly49 genes, which encode important MHC class I receptors for the regulation of NK cell activity in rodents. The LY49L gene is localized 100 to 200 kb centromeric of the NKG2 gene cluster and 300 to 400 kb telomeric of the STS marker D12S841. Genomic sequencing of the complete gene including promoter and intron sequences confirmed that the structure is similar to the mouse Ly49 genes. Screening of several cDNA libraries did not detect any transcripts of putative additional human LY49 genes. In addition, in the course of these studies several EST sequences were localized in the region, one immediately upstream of the LY49L gene.

Antigens, CD↗
PubMed2000

Investigation of the Alamar Blue (resazurin) fluorescent dye for the assessment of mammalian cell cytotoxicity.

We show here the identity of Alamar Blue as resazurin. The 'resazurin reduction test' has been used for about 50 years to monitor bacterial and yeast contamination of milk, and also for assessing semen quality. Resazurin (blue and nonfluorescent) is reduced to resorufin (pink and highly fluorescent) which is further reduced to hydroresorufin (uncoloured and nonfluorescent). It is still not known how this reduction occurs, intracellularly via enzyme activity or in the medium as a chemical reaction, although the reduced fluorescent form of Alamar Blue was found in the cytoplasm and of living cells nucleus of dead cells. Recently, the dye has gained popularity as a very simple and versatile way of measuring cell proliferation and cytotoxicity. This dye presents numerous advantages over other cytotoxicity or proliferation tests but we observed several drawbacks to the routine use of Alamar Blue. Tests with several toxicants in different cell lines and rat primary hepatocytes have shown accumulation of the fluorescent product of Alamar Blue in the medium which could lead to an overestimation of cell population. Also, the extensive reduction of Alamar Blue by metabolically active cells led to a final nonfluorescent product, and hence an underestimation of cellular activity.

Animals↗
PubMed2000

When texture takes precedence over motion in depth perception.

Both texture and motion can be strong cues to depth, and estimating slant from texture cues can be considered analogous to calculating slant from motion parallax (Malik and Rosenholtz 1994, report UCB/CSD 93/775, University of California, Berkeley, CA). A series of experiments was conducted to determine the relative weight of texture and motion cues in the perception of planar-surface slant when both texture and motion convey similar information. Stimuli were monocularly viewed images of planar surfaces slanted in depth, defined by texture and motion information that could be varied independently. Slant discrimination biases and thresholds were measured by a method of single-stimuli binary-choice procedure. When the motion and texture cues depicted surfaces of identical slants, it was found that the depth-from-motion information neither reduced slant discrimination thresholds, nor altered slant discrimination bias, compared to texture cues presented alone. When there was a difference in the slant depicted by motion and by texture, perceived slant was determined almost entirely by the texture cue. The regularity of the texture pattern did not affect this weighting. Results are discussed in terms of models of cue combination and previous results with different types of texture and motion information.

Analysis of Variance↗
PubMed2000

Information theoretical probe selection for hybridisation experiments.

MOTIVATION: The choice of probes is an important feature of hybridisation experiments. In this paper we present an algorithm that optimises probes with respect to a training set of sequences based on Shannon entropy as a quality criterion. The practical motivation for our algorithm is oligonucleotide fingerprinting, a method for the simultaneous identification of sequences (cDNA or genomic DNA) by their hybridisation tags according to a set of short probes such as octamers, although the algorithm is of course not restricted to that application. RESULTS: We can show that our method is superior to the selection of probes according to their frequencies, which is a widely used strategy, and to randomly chosen probe sets. The quality of probe sets is assessed by a simulation pipeline that entails the set of probes as a simulation parameter. The performance of probe sets trained on sequences from different organisms shows additionally that probes should be chosen with regard to the organism under analysis. Case studies are presented on how constraints (G+C-content, complexity of the individual probes) influence the selection process. AVAILABILITY: A description of the oligonucleotide fingerprinting pipeline is published on our web-page http://www.molgen.mpg.de/ approximately ag_onf/met.htm. An executable of the algorithm and probe lists designed for human and rodents can be downloaded from the ftp-site ftp://ftp.molgen.mpg.de/pub/mpimg/probe_design/.

Algorithms↗