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Biomedical subjects

J Carr

Publications and source records attributed to J Carr.

At least 19 recordsLinked to original sources
PubMed2006

Autosomal dominant dystonia-plus with cerebral calcifications.

OBJECTIVE: To report genealogic, clinical, imaging, neuropathologic, and genetic data from a Canadian kindred with dystonia and brain calcinosis originally described in 1985. METHODS: The authors performed clinical examinations and CT and PET studies of the head and analyzed blood samples. One autopsy was performed. RESULTS: The family tree was expanded to 166 individuals. No individuals were newly affected with dystonia, but postural tremor developed in two. The mean age at symptom onset was 19 years. Eight individuals had dystonia: three focal, one segmental, one multifocal, and three generalized. Seven displayed additional signs: chorea, intellectual decline, postural tremor, and dysarthria. CT studies were performed on five affected and 10 at-risk family members. All affected individuals and eight at-risk individuals had brain calcinosis. PET scans in two individuals showed reduced D(1)- and D(2)-receptor binding and reduced uptake of 6-[(18)F]fluoro-l-dopa. Autopsy of one affected individual showed extensive depositions of calcium in the basal ganglia, thalamus, cerebral white matter, and cerebellum. No specific immunohistochemistry abnormalities were seen. Genome search data showed no evidence of linkage to the previously described loci IBGC1, DYT1, and DYT12. CONCLUSIONS: The phenotype of this family consists of dystonia-plus syndrome. Brain calcium deposits vary in severity and distribution, suggesting that calcifications alone are not entirely responsible for the observed clinical signs. Further studies are needed to elucidate the etiology of this heterogeneous group of disorders.

Adolescent↗
PubMed2005

Stability and change in cognitive ability over the life span: a comparison of populations with and without Down's syndrome.

BACKGROUND: Longitudinal studies show that in the general population IQ declines with age: early and rapidly in the case of performance IQ, later and more slowly in the case of verbal IQ. These populations have not apparently included people with intellectual disabilities (ID). METHOD: A literature search identified 11 studies, some cross-sectional and others longitudinal, which provided data on a variety of verbal and performance tests, over periods from 3 to 19 years, on older people with ID. Following statistical advice the results from the different tests were converted into the equivalent of, for verbal scores, British Picture Vocabulary Scale, and for performance scores, Leiter International Performance Scale, raw scores. Percentage change between earlier and later scores was then calculated. RESULTS: With one exception the studies considered tend to show verbal ability declining relatively more, and performance ability declining relatively less, than has been shown to occur in the general population. Potential confounding factors, such as population attrition, cohort effects, etc., are thought not to have affected these results. CONCLUSIONS: The pattern of change with age in verbal and performance ability appears different in people with ID from that seen in the general population. Some possible reasons for this difference are discussed.

Age Factors↗
PubMed2004

Neurosyphilis in the modern era.

OBJECTIVE: To review the nature of the presentation of neurosyphilis, the value of diagnostic tests, and the classification of the disease. METHODS: A retrospective review was carried out of the records of patients who had been identified as possible cases of neurosyphilis by a positive FTA-abs test in the CSF. The review extended over 10 years at a single hospital which served a population of mixed ancestry in a defined catchment area in the Western Cape province of South Africa. Patients were placed in predefined diagnostic categories, and clinical, radiological, and laboratory features were assessed. RESULTS: 161 patients met diagnostic criteria for neurosyphilis: 82 presented with combinations of delirium and dementia and other neuropsychiatric conditions, and the remainder had typical presentations such as stroke (24), spinal cord disease (15), and seizures (14). The average age of presentation ranged from 35.9 to 42.6 years in the different categories of neurosyphilis. Of those followed up, 77% had residual deficits from their initial illness. Cerebrospinal fluid (CSF) VDRL was positive in 73% of cases. CONCLUSIONS: The diagnosis of neurosyphilis can be made with reasonable certainty if there is an appropriate neuropsychiatric syndrome associated with a positive CSF VDRL. If the VDRL is negative, a positive FTA-abs in an appropriate clinical setting, associated with raised CSF cell count, protein, or IgG index, is a useful method of identifying neurosyphilis. Tabes dorsalis has become uncommon, but this is likely to be the only manifestation of neurosyphilis that has been altered during the antibiotic era.

Adolescent↗
PubMed2003

One-dimensional daisyworld: spatial interactions and pattern formation.

The zero-dimensional daisyworld model of Watson and Lovelock (1983) demonstrates that life can unconsciously regulate a global environment. Here that model is extended to one dimension, incorporating a distribution of incoming solar radiation and diffusion of heat consistent with a spherical planet. Global regulatory properties of the original model are retained. The daisy populations are initially restricted to hospitable regions of the surface but exert both global and local feedback to increase this habitable area, eventually colonizing the whole surface. The introduction of heat diffusion destabilizes the coexistence equilibrium of the two daisy types. In response, a striped pattern consisting of blocks of all black or all white daisies emerges. There are two mechanisms behind this pattern formation. Both are connected to the stability of the system and an overview of the mathematics involved is presented. Numerical experiments show that this pattern is globally determined. Perturbations in one region have an impact over the whole surface but the regulatory properties of the system are not compromised by transient perturbations. The relevance of these results to the Earth and the wider climate modelling field is discussed.

Climate↗
PubMed2003

Familial and sporadic Parkinson's disease usually display the same clinical features.

We examined the clinical features of familial (n = 26) and sporadic (n = 52) Parkinson's disease (PD) in patients presenting over the age of 40 years. Familial PD cases were tested for alpha-synuclein or parkin mutations as appropriate. No mutations were found in any of the families investigated. We found no between-group differences in the age at onset of PD, the pattern or severity of parkinsonian features, the dose of antiparkinsonian medications or treatment related complications. Cases of familial and sporadic PD in our cohort of patients display similar clinical features. This may suggest similar etiologies for both familial and sporadic PD.

Antiparkinson Agents↗
PubMed2003

Determinants of prognosis among black Africans with hypertensive heart failure.

One hundred and seven consecutive Black Africans hypertensive heart failure patients made of 52 Gambians and 55 Nigerians (51 males + 56 females) aged 53.6 +/- 12.1 years were followed-up for 12 months or till death. One-year survival curve was determined using Kaplan-Meiers method. The survivors and the deceased were compared using univariate and multivariate analysis. Mean blood pressures were 180.4 +/- 28.2 mmHg (range: 130-250 mmHg) systolic and 117.0 +/- 12.9 mmHg (range: 100-160 mmHg) diastolic. Duration of hypertension ranged from 0.5 to 23 years. The rate of undetected hypertension was 44%. Overall one-year survival rate was 71%. Twenty two percent of deaths occurred within the first 3 months of HHF. One-year survival rate among the survivors of this period was 89.4%. A strong negative correlation existed between cumulative survival and the duration of heart failure (y = 0.9812, x(2) = 0.1173, R = 0.965). Compared to the survivors, the deceased had significantly higher systolic blood pressure (191.9 +/- 32.2 mmHg versus 175.1 +/- 25.2 mmHg; P < 0.05), diastolic blood pressure (123.7 +/- 15.8mmHg versus 114.3 +/- 10.3 mmHg; P < 0.05), cardiothoracic index (69.2 +/- 3.9% versus 66.2 +/- 4.2%; P < 0.05) and serum creatinine (148.6 +/- 42.2 umol/L versus 113.8 +/- 36.4 umol/L; P < 0.05). Compared to the patients aged 40 or more years, patients aged below 40 years had significantly lower one-year survival rate (41.7% versus 74.1%; P < 0.05). One-year survival rate was significantly higher among patients on captopril medication than those without (75% versus 52.6%; P < 0.05). However, only serum creatinine had statistically differing values between the deceased and survivors (df = 1 SS = 10272, F = 7.60, p = 0.007). Basic clinical and biochemical parameters could therefore be useful prognostic markers in hypertensive heart failure.

Analysis of Variance↗
PubMed2002

Influenza virus carrying an R292K mutation in the neuraminidase gene is not transmitted in ferrets.

A model of influenza transmission has been established in ferrets in which wild-type influenza infection in a donor ferret can be transmitted sequentially to other ferrets. We have studied the transmission in ferrets of a clinical isolate of A/Sydney/5/97 (H3N2) carrying the neuraminidase 292K mutation compared with the corresponding wild-type virus from the same subject. Donor ferrets (n=four per group) were inoculated intranasally with mutant or wild-type virus and each housed with three naïve contact ferrets. All donor ferrets inoculated with wildtype virus were productively infected and transmitted virus to all 12 contacts, who in turn had high viral titres in their nasal washes. In contrast, only two of the donor ferrets inoculated with mutant virus were productively infected. There was little or no evidence that the two infected donor animals transmitted mutant virus to their contact animals. This ferret model has demonstrated that the mutant influenza virus with lysine at position 292 of the neuraminidase is of reduced infectivity and does not transmit under conditions in which the wild-type virus with arginine at position 292 readily transmits.

Animals↗
PubMed2002

Influenza virus carrying neuraminidase with reduced sensitivity to oseltamivir carboxylate has altered properties in vitro and is compromised for infectivity and replicative ability in vivo.

Oseltamivir phosphate (Tamiflu, Ro 64-0796) is the first orally administered neuraminidase (NA) inhibitor approved for use in treatment and prevention of influenza virus infection in man. Oseltamivir phosphate is the pro-drug of the active metabolite oseltamivir carboxylate (Ro 64-0802). Extensive monitoring throughout the oseltamivir development programme has identified a very low incidence of patients who have carried drug-resistant virus. The predominant mutation seen is the substitution of arginine for lysine at position 292 of the viral NA. The fitness of clinically isolated influenza virus A/Sydney/5/97 (H3N2) carrying this mutation was markedly reduced in animal models of influenza virus infection. The infectivity and replicative abilities of R292K mutant virus were reduced by at least 2 logs in a mouse model of influenza infection and by 2 and 4 logs, respectively, in the ferret model. Pathogenicity of R292K influenza virus A/Sydney/5/97 was reduced in ferrets as measured by inflammatory and febrile responses at least in parallel to the decrease in replicative ability. The data indicate that the R292K NA mutation compromises viral fitness such that virus carrying this mutation is unlikely to be of significant clinical consequence in man.

Acetamides↗
PubMed2002

Tremor in Parkinson's disease.

Rest tremor is a common feature of Parkinson's disease, but its underlying pathophysiology remains unknown. This review hypothesizes that tremor is related to selective loss of components of the substantia nigra. The relative scarcity of tremor in related Parkinsonian conditions may indicate a dissociation associated with different pathological involvement of the substantia nigra and its connections. Connections of the subthalamic nucleus with the pallidum, modified by cortical and nigral inputs, allow for the transfer of tremorogenic activity to the thalamus. Thalamo-cortical interactions, tempered by cerebellar input, generate the final common pathway for tremor production.

Animals↗
PubMed2002

Sepsis in neonatal intensive care in the late 1990s.

AIM: To determine the incidence and clinical characteristics of sepsis in ventilated infants from an Australian neonatal intensive care unit (NICU) in the late 1990s. METHODS: Demographic data was collected from babies requiring assisted ventilation (AV) over the 6-month period from 1 July to 31 December 1998. Sepsis was divided into early onset sepsis (EOS; " 72 h of age) and late onset sepsis (LOS; >72 h of age), including both definite (culture-proven + abnormal markers) and probable (culture negative + abnormal markers) episodes. RESULTS: Two hundred and eleven babies required AV over this period. Of these, 64 (30.3%) had at least one infection, with 85 episodes of sepsis (40.3 episodes per 100 admissions requiring AV). There were 22 babies with 22 episodes of EOS, and 45 with 63 episodes of LOS. Three babies had both EOS and LOS. The rate of EOS was 10.4 infected infants (10.4 infections per 100 admissions requiring AV). The rate of LOS was 21.3 infected infants (29.9 infections per 100 admissions requiring AV). The rates of both EOS and LOS were higher than previously reported by Australian studies in the early 1990s. In both EOS and LOS, risk factors for infection were common. Group B streptococcus was the commonest cause of definite EOS. The mortality rate from sepsis in the EOS group was 14% (3/22). Coagulase-negative staphylococci were the commonest cause of LOS. The mortality rate from sepsis in the LOS group was 11% (5/45). CONCLUSIONS: EOS and LOS are significant problems in ventilated NICU infants in the late 1990s.

Australia↗
PubMed2001

Role of taurine in regulation of intracellular calcium level and neuroprotective function in cultured neurons.

Glutamate-induced excitotoxicity has been implicated as an important mechanism underlying a variety of brain injuries and neurodegenerative diseases. Previously we have shown that taurine has protective effects against glutamate-induced neuronal injury in cultured neurons. Here we propose that the primary underlying mechanism of the neuroprotective function of taurine is due to its action in preventing or reducing glutamate-induced elevation of intracellular free calcium, [Ca(2+)](i). This hypothesis is supported by the following findings. First, taurine transport inhibitors, e.g., guanidinoethyl sulfonate and beta-alanine, have no effect on taurine's neuroprotective function, suggesting that taurine protects against glutamate-induced neuronal damage through its action on the extracellular membranes. Second, glutamate-induced elevation of [Ca(2+)](i) is reduced to the basal level upon addition of taurine. Third, pretreatment of cultured neurons with taurine prevents or greatly suppresses the elevation of [Ca(2+)](i) induced by glutamate. Furthermore, taurine was found to inhibit the influx but not the efflux of (45)Ca(2+) in cultured neurons. Taurine has little effect on the binding of [(3)H]glutamate to the agonist binding site and of [(3)H]MDL 105,519 to the glycine binding site of the N-methyl-D-aspartic acid receptors, suggesting that taurine inhibits (45)Ca(2+) influx through other mechanisms, including its inhibitory effect on the reverse mode of the Na(+)/Ca(2+) exchangers (Wu et al. [2000] In: Taurine 4: taurine and excitable tissues. New York: Kluwer Academic/Plenum Publishers. p 35-44) rather than serving as an antagonist to the N-methyl-D-aspartic acid receptors.

Animals↗
PubMed2001

Characterization of full-length HIV type 1 subtype C sequences from South Africa.

Four full-length genome subtype C sequences from South Africa, three of which are being used for vaccine development, were characterized. Three isolates were obtained from recently infected individuals in KwaZulu/Natal: Du151, Du422, and Du179. A fourth isolate, CTSc2, was obtained from an individual residing in Cape Town. All four strains used the CCR5 coreceptor, although Du179 also used CXCR4. The four isolates clustered within subtype C, but the three Du isolates formed a subcluster with a bootstrap value of 100%, with CTSc2 outside the subcluster. None of the strains showed evidence of intersubtype recombination, as expected from the predominance of subtype C in South Africa. All 4 isolates had a 16-amino acid truncation on the 3' end of the Rev protein, identified in other subtype C isolates. Like many other subtype C strains, Du151, Du422, and Du179 had three NF-kappa B-binding sites in the LTR; however, CTSc2 had only two.

Genome, Viral↗
PubMed2001

Coronary artery imaging using contrast-enhanced 3D segmented EPI.

The purpose of the work was to evaluate the effectiveness of extracellular contrast media in improving MR coronary angiography using breath-hold segmented echo-planar imaging (SEPI). Two protocols were designed to optimize the inversion recovery-prepared contrast-enhanced SEPI method. In 15 healthy volunteers, significant improvements in signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, and length of visualization were observed post-contrast. The method with two targeted scans to cover the left and right arteries, respectively, following separate 20-mL contrast injections, was found to yield thinner slices and longer right coronary artery (RCA) visualization than a single scan following a 40-mL contrast injection without compromising SNR and CNR. In conclusion, extracellular contrast media substantially improves the delineation of coronary arteries with SEPI. J. Magn. Reson. Imaging 2001;13:676-681.

Adult↗
PubMed2001

Contrast-enhanced coronary MR angiography: relationship between coronary artery delineation and blood T1.

Contrast-enhanced coronary angiography has become an important technique for magnetic resonance (MR) coronary artery imaging. However, the relationship between the quality of the coronary artery images and blood T1 has not yet been fully explored. In this paper, we assessed this relationship in an animal model by using a prototypical blood pool agent. With accumulated injections of this agent, the blood T1 would be maintained at different levels. The measured blood T1 values in vivo were 147 +/- 3, 82 +/- 6, 48 +/- 4, 40 +/- 3, and 30 +/- 8 msec (N = 7). Fixed and variable flip angle schemes were used in coronary artery imaging. The signal to noise ratios (SNR) of coronary arteries were measured and the image quality was assessed. It was found that blood T1 less than 80 msec might be desired. No statistically significant difference was observed between two flip angle schemes. There was better vessel definition using variable flip angle at blood T1 lower than 50 msec. Understanding this relationship may be beneficial to optimizing image protocol and/or design of blood pool contrast agents for contrast-enhanced coronary angiography.

Animals↗
PubMed2001

Three-dimensional MR pulmonary perfusion imaging and angiography with an injection of a new blood pool contrast agent B-22956/1.

Initial evaluation of a new blood pool agent, B-22956/1, for pulmonary imaging was performed in five domestic pigs with artificial embolism. Pre-embolism 3D pulmonary perfusion images were first acquired by injecting an extravascular agent, gadoteridol. The pulmonary arteries of the pigs were then occluded by the artificial emboli. Post-embolism perfusion scans were subsequently performed by injecting B-22956/1. Additional post-embolism high-spatial-resolution angiograms were also acquired. Parenchyma perfusion deficits were well depicted in the post-embolism perfusion maps. The post-embolism angiography clearly revealed the location and extent of the filling defects in the pulmonary vessels. Signal intensities of perfusion maps on the normal parenchyma were significantly improved (30%) by using B-22956/1, in comparison with perfusion images using gadoteridol (P < 0.01). Many pulmonary angiograms with approximately equal contrast could be obtained even at 22 minutes after the injection of B-22956/1. Our initial results indicate that blood pool agent B-22956/1 may provide opportunities for whole-lung-coverage perfusion mapping and additional high-resolution target angiograms after a single injection.

Animals↗