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Biomedical subjects

R J Ellis

Publications and source records attributed to R J Ellis.

At least 73 records · Page 4Linked to original sources
PubMed1997

Neurocognitive impairment is an independent risk factor for death in HIV infection. San Diego HIV Neurobehavioral Research Center Group.

OBJECTIVE: To determine if mortality is increased in individuals with human immunodeficiency virus type 1 (HIV-1)-associated neurocognitive disorders less severe than frank dementia. DESIGN: A prospective cohort study; median duration of follow-up was 2.4 years. Kaplan-Meier analysis and Cox proportional hazards models were used to compare survival times according to neurocognitive classification. SETTING: University-based research unit. PARTICIPANTS: A volunteer sample of 414 individuals seropositive for HIV-1. Subjects were classified at their baseline evaluation as neuropsychologically (NP) normal or abnormal (impaired in > or = 2 NP test domains). A subgroup of NP abnormal subjects met operational criteria for HIV-associated minor cognitive motor disorder; the remaining subjects were designated NP impaired. Subjects with frank dementia were excluded. MAIN OUTCOME MEASURE: Mortality. RESULTS: At the baseline evaluation, 256 (62%) of 414 subjects were designated normal; 109 (26%). NP impaired; and 49 (12%), minor cognitive motor disorder. One hundred six participants (26%) died during follow-up. Compared with the NP normal group, the unadjusted relative risk (RR) of death for all NP abnormal subjects (minor cognitive motor disorder and NP impaired) was significantly increased (RR, 1.7; 95% confidence interval [CI], 1.2-2.6; P < .005). After adjusting for concurrently measured predictors of survival (CD4 lymphocyte counts, Centers for Disease Control and Prevention HIV disease classification, hemoglobin concentration, and serum beta 2-microglobulin) in proportional hazards models, mortality for all NP abnormal subjects remained elevated (RR, 1.8; 95% CI, 1.2-2.8; P < .01). The elevation in mortality risk for subjects with minor cognitive motor disorder was statistically significant (RR, 2.2; 95% CI, 1.2-3.8; P < .01); for NP impaired subjects it was marginally significant (RR, 1.6; 95% CI, 1.0-2.8; P = .06). CONCLUSIONS: The HIV-infected individuals with NP impairment had a higher risk of dying than those without impairment. This was particularly true for those meeting syndromic diagnostic criteria.

Adult↗
PubMed1997

Cerebrospinal fluid human immunodeficiency virus type 1 RNA levels are elevated in neurocognitively impaired individuals with acquired immunodeficiency syndrome. HIV Neurobehavioral Research Center Group.

To determine whether cerebrospinal fluid (CSF) viral burden measurements can assist in the evaluation of human immunodeficiency virus (HIV)-associated neurocognitive disorders, we quantified HIV type 1 (HIV-1) RNA in CSF. Because previous findings suggested that disease stage, lymphocytic pleocytosis, and HIV-1 RNA levels in plasma may influence CSF viral burden, these variables were examined as potential modifying factors. HIV-1 RNA levels were quantified by using a reverse transcriptase-polymerase chain reaction assay. Performance on a comprehensive neuropsychological (NP) battery was noted in 97 prospectively enrolled, HIV-infected subjects. Among subjects with acquired immunodeficiency syndrome (AIDS) (<200 CD4+ lymphocytes), NP impairment was associated with significantly higher CSF RNA levels (3.1 vs 1.8 log10 copies/ml; p = 0.02); most impaired subjects met criteria for HIV-associated dementia or minor cognitive-motor disorder. In subjects without AIDS, CSF RNA and NP impairment were unrelated. Before AIDS, CSF RNA was strongly correlated to plasma RNA and to pleocytosis, but in AIDS, CSF and plasma RNA were independent. In conclusion, we found elevated CSF HIV-1 RNA levels in NP impaired subjects with AIDS. Before AIDS, systemic viral replication, possibly through CD4+ mononuclear cell trafficking, may govern virus levels in CSF, whereas in AIDS, CD4 cell depletion may unmask a correlation between increased productive central nervous system HIV infection and clinical neurocognitive disorders.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Dendritic injury is a pathological substrate for human immunodeficiency virus-related cognitive disorders. HNRC Group. The HIV Neurobehavioral Research Center.

To determine the neuropathological substrate of human immunodeficiency virus (HIV)-associated neurocognitive disorders, we examined persons with acquired immunodeficiency syndrome before their death and related their antemortem neuropsychological performance to postmortem indicators of HIV encephalitis, viral burden, and presynaptic and postsynaptic neuronal injury. Of 20 prospectively examined cases, 9 were neurocognitively normal, 5 showed neuropsychological impairment, 5 had minor cognitive/motor disorder, and 1 was demented. Degree of neurocognitive impairment was strongly related to the amount of dendritic simplification based on microtubule-associated protein 2 immunohistochemical staining, somewhat less so to a semiquantitative viral burden score based on numbers of HIV gp41-immunoreactive cells, and much less so to the presence of multinucleated giant cells or microglial nodules. It appears that even milder neurocognitive impairment reflects microneuroanatomical injury to synaptic structures.

AIDS-Related Opportunistic Infections↗
PubMed1996

Revisiting the Anfinsen cage.

In the past five years, ideas about protein folding inside cells have changed as a results of experiments with the chaperonin family of molecular chaperones. The folding of at least some proteins is no longer regarded as a spontaneous energy-independent process, but as involving transient interactions with chaperonin ATPases that serve to increase the efficiency of correct folding within the highly crowded intracellular environment. This review discusses in an historical context one model for how the chaperonins function. This model suggests that proteins fold inside cells in the same way as they do in pure dilute solution, but that they do so inside macromolecular Anfinsen cages that serve as sequestration devices to prevent and reverse unproductive interactions.

Adenosine Triphosphate↗
PubMed1996

Protein folding in the cell: competing models of chaperonin function.

The long-standing view that polypeptide chains newly synthesized inside cells fold spontaneously to their functional conformations in an energy-independent fashion derives from the observation that many pure denatured proteins will refold spontaneously in vitro when the denaturant is removed. This view is being challenged by the alternative proposal that in vivo many chains need to be helped to fold correctly by preexisting proteins acting as molecular chaperones, some of which hydrolyse ATP. The need for molecular chaperones arises because of the high concentrations of transiently interacting protein surfaces inside cells permit the formation of incorrect nonfunctional structures. The best-studied family of molecular chaperones are called the chaperonins, the archetypal examples being the GroEL and GroES proteins of Escherichia coli. The chaperonins increase the yield of correctly refolded polypeptide chains, both by decreasing their propensity to aggregate with one another and by allowing polypeptides kinetically trapped in incorrect conformations to make fresh attempts to refold into the functional conformations. The mechanisms by which the chaperonins achieve these remarkable results are currently under debate. This review surveys competing models for chaperonin action, and emphasizes the importance when evaluating these models of considering the intracellular environment in which the chaperonins have evolved to function.

Chaperonin 10↗
PubMed1996

Extrapyramidal motor signs in clinically diagnosed Alzheimer disease.

We reviewed clinical case series published over a 10-year period addressing the cross-sectional frequency, incidence, and diagnostic and prognostic significance of extrapyramidal signs (EPS) in Alzheimer disease (AD). The review was prompted by recent reports of Lewy body (LB) pathology in the brains of many AD patients and the association of LB pathology with clinical parkinsonism in AD. In the clinical case series reviewed, we evaluated several possible determinants of prevalent EPS, including neuroleptic use, EPS assessment technique, and dementia severity. Neuroleptics were a well recognized cause of parkinsonism in these reports, though some failed to document the frequency of neuroleptic use. Assessment methods were also important: Studies using structured clinical research scales to rate EPS reported higher frequencies than studies employing routine neurological examination. The relationship between parkinsonism and dementia severity was complex. Some studies found bradykinesia, facial masking, and parkinsonian postural changes even in mildly demented, neuroleptic-naive AD patients. Rigidity, on the other hand, became increasingly common as dementia progressed. AD patients with EPS showed faster cognitive and functional decline and earlier death than those without EPS, even after consideration of differences in initial dementia severity. In the differential diagnosis of dementia with parkinsonism, LB disease in its various forms, including AD with LB, is the principal diagnostic consideration. Future studies of parkinsonism in AD should employ standardized clinical rating scales and should exclude patients on neuroleptics or analyze their results separately. Investigators should report frequencies for individual parkinsonian signs in addition to the overall prevalence of EPS to facilitate meaningful comparisons across studies.

Alzheimer Disease↗
PubMed1996

Cerebral amyloid angiopathy in the brains of patients with Alzheimer's disease: the CERAD experience, Part XV.

We studied the frequency, severity, and clinical correlations of cerebral amyloid angiopathy (CAA) in 117 CERAD subjects with autopsy-confirmed AD. Eighty-three percent showed at least a mild degree of amyloid angiopathy. Thirty of 117 brains (25.6%) showed moderate to severe CAA affecting the cerebral vessels in one or more cortical regions. These brains also showed a significantly higher frequency of hemorrhages or ischemic lesions than those of subjects with little or no amyloid angiopathy (43.3% versus 23.0%; odds ratio = 2.6, 95% CI = 1.1 to 6.2) High CAA scores also correlated with the presence of cerebral arteriosclerosis and with older age at onset of dementia. Our findings suggest that factors contributing to non-AD-related vascular pathology (e.g., atherosclerosis) may play a role in amyloid deposition in cerebral vessels in AD.

Aged↗
PubMed1995

The HNRC 500--neuropsychology of HIV infection at different disease stages. HIV Neurobehavioral Research Center.

The present study examined neuropsychological (NP) functioning and associated medical, neurological, brain magnetic resonance imaging (MRI), and psychiatric findings in 389 nondemented males infected with Human Immunodeficiency Virus-Type 1 (HIV-1), and in 111 uninfected controls. Using a comprehensive NP test battery, we found increased rates of impairment at each successive stage of HIV infection. HIV-related NP impairment was generally mild, especially in the medically asymptomatic stage of infection, and most often affected attention, speed of information processing, and learning efficiency; this pattern is consistent with earliest involvement of subcortical or frontostriatal brain systems. NP impairment could not be explained on the bases of mood disturbance, recreational drug or alcohol use, or constitutional symptoms; by contrast, impairment in HIV-infected subjects was related to central brain atrophy on MRI, as well as to evidence of cellular immune activation and neurological abnormalities linked to the central nervous system.

AIDS Dementia Complex↗
PubMed1995

Site directed chromosomal marking of a fluorescent pseudomonad isolated from the phytosphere of sugar beet; stability and potential for marker gene transfer.

A plasmid-free, non-pathogenic, ribosomal RNA group 1 fluorescent pseudomonad, Pseudomonas fluorescens SBW25, was selected from the microflora of sugar beet (Beta vulgaris) and modified to contain constitutively expressed marker genes. By site directed homologous recombination a KX cassette [kanamycin resistance (kanr) and catechol 2,3 dioxygenase (xylE)] and a ZY cassette [lactose utilization (lacZY, beta-galactosidase, lactose permease)] were introduced at least 1 Mbp apart on the 6.6 Mbp bacterial chromosome. Separate sites were selected to provide sensitive detection methods and allow assessments of marker gene stability of the genetically modified micro-organism (GMM), SBW25EeZY6KX, when it colonized the leaves and roots of sugar beet plants following seed inoculation.

Base Sequence↗
PubMed1993

ATP induces large quaternary rearrangements in a cage-like chaperonin structure.

BACKGROUND: The chaperonins, a family of molecular chaperones, are large oligomeric proteins that bind nonnative intermediates of protein folding. They couple the release and correct folding of their ligands to the binding and hydrolysis of ATP. Chaperonin 60 (cpn60) is a decatetramer (14-mer) of 60 kD subunits. Folding of some ligands also requires the cooperation of cpn10, a heptamer of 10 kD subunits. RESULTS: We have determined the three-dimensional arrangements of subunits in Rhodobacter sphaeroides cpn60 in the nucleotide-free and ATP-bound forms. Negative stain electron microscopy and tilt reconstruction show the cylindrical structure of the decatetramer comprising two rings of seven subunits. The decatetramer consists of two cages joined base-to-base without a continuous central channel. These cages appear to contain bound polypeptide with an asymmetric distribution between the two rings. The two major domains of each subunit are connected on the exterior of the cylinder by a narrower bridge of density that could be a hinge region. Binding of ATP to cpn60 causes a major rearrangement of the protein density, which is reversed upon the hydrolysis of the ATP. Cpn10 binds to only one end of the cpn60 structure and is visible as an additional layer of density forming a cap on one end of the cpn60 cylinder. CONCLUSIONS: The observed rearrangement is consistent with an inward 5-10 degrees rotation of subunits, pivoting about the subunit contacts between the two heptamers, and thus bringing cpn60 domains towards the position occupied by the bound polypeptide. This change could explain the stimulation of ATPase activity by ligands, and the effects of ATP on lowering the affinity of cpn60 for ligands and on triggering the release of folding polypeptides.

Journal Article↗
PubMed1993

The general concept of molecular chaperones.

This introductory article proposes a conceptual framework in which to consider the information that is emerging about the proteins called molecular chaperones, and suggests some definitions that may be useful in this new field of biochemistry. Molecular chaperones are currently defined in functional terms as a class of unrelated families of protein that assist the correct non-covalent assembly of other polypeptide-containing structures in vivo, but which are not components of these assembled structures when they are performing their normal biological functions. The term assembly in this definition embraces not only the folding of newly synthesized polypeptides and any association into oligomers that may occur, but also includes any changes in the degree of either folding or association that may take place when proteins carry out their functions, are transported across membranes, or are repaired or destroyed after stresses such as heat shock. Known molecular chaperones do not convey steric information essential for correct assembly, but appear to act by binding to interactive protein surfaces that are transiently exposed during various cellular processes; this binding inhibits incorrect interactions that may otherwise produce non-functional structures. Thus the concept of molecular chaperones does not contradict the principle of protein self-assembly, but qualifies it by suggesting that in vivo self-assembly requires assistance by other protein molecules.

Chaperonins↗