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Biomedical subjects

R Brown

Publications and source records attributed to R Brown.

At least 109 records · Page 6Linked to original sources
PubMed2001

Clonidine-induced vasoconstriction in awake volunteers.

UNLABELLED: We evaluated the vasomotor effects of clonidine in awake subjects with an intact central cardiovascular regulatory system. To determine the lower limit of the vasoconstrictive effect of clonidine in awake volunteers, we blocked sympathetic innervation to the left arm by anesthetizing the brachial plexus. We then measured arterial blood pressure and vasoconstriction via finger volume plethysmography measuring infrared light transmitted through a fingertip (LTF). LTF values obtained from the left arm were compared with those from the neurally intact right arm during four progressively increasing IV doses of clonidine, targeting plasma clonidine concentrations of 0.3, 0.45, 0.68, and 1.0 ng/mL. Clonidine decreased systolic blood pressure (P < 0.004) from 135 +/- 8 mm Hg to 115 +/- 8 mm Hg and heart rate (P = 0.0017) from 68 +/- 7 mm Hg to 61 +/- 10 mm Hg. Clonidine decreased LTF by -12% +/- 11% (P < 0.0001) less than preinfusion values at the 0.68 ng/mL target concentration in the right hand. In contrast, in the left hand, clonidine increased LTF significantly more than (P < 0.0001) preinfusion values at all target concentrations, with a maximal increase of 30% +/- 7%. We conclude that IV clonidine, at doses that decrease arterial blood pressure, causes arterial vasoconstriction in awake subjects. IMPLICATIONS: IV clonidine, at doses that decrease blood pressure, causes arterial vasoconstriction in awake subjects. These data suggest that an alpha-2 agonist with a high alpha-2a/alpha-2b selectivity should provide more profound sedative and analgesic effects with less undesirable vasoconstrictive effects.

Adrenergic alpha-Agonists↗
PubMed2001

Hemoglobin desaturation after succinylcholine-induced apnea: a study of the recovery of spontaneous ventilation in healthy volunteers.

BACKGROUND: Because of the rapid recovery of neuromuscular function after succinylcholine administration, there is a belief that patients will start breathing sufficiently rapidly to prevent significant oxygen desaturation. The authors tested whether this belief was valid. METHODS: Twelve healthy volunteers aged 18-45 yr participated in the study. After preoxygenation to an end-tidal oxygen concentration greater than 90%, each subject received 5 mg/kg thiopental and 1 mg/kg succinylcholine. Oxygen saturation (SaO2) was measured at both a finger and an ear lobe (beat to beat). During the period of apnea and as they were recovering, the volunteers received continuous verbal reassurance by the investigators. If the SaO2 decreased below 80%, the volunteers received chin lift and, if necessary, assisted ventilation. The length of time the subject was apneic and level of desaturation were related by linear regression analysis. One hour after recovery and again 1 week later, subjects were asked a series of questions regarding their emotional experience. RESULTS: In six volunteers, SaO2 decreased below 95% during apnea; in four, SaO2 decreased below 80%, necessitating chin lift and assisted ventilation in three. Apnea time was significantly longer in volunteers who reached SaO2 less than 80% than in those who did not (7.0+/-0.4 and 4.1+/-0.3 min, respectively), and there was a significant correlation between the length of time the subject was apneic and the magnitude of desaturation. CONCLUSIONS: Spontaneous recovery from succinylcholine-induced apnea may not occur sufficiently quickly to prevent hemoglobin desaturation in subjects whose ventilation is not assisted.

Adolescent↗
PubMed2001

Corynebacterium mooreparkense sp. nov. and Corynebacterium casei sp. nov., isolated from the surface of a smear-ripened cheese.

Ten isolates each of two different bacterial species isolated from the surface of a smear-ripened cheese were found to exhibit many characteristics of the genus Corynebacterium. The isolates were Gram-positive, catalase-positive, non-spore-forming rods that did not undergo a rod/coccus transformation when grown on complex media. Chemotaxonomic investigation revealed that the strains belonged unambiguously to the genus Corynebacterium. Their cell walls contained arabinose, galactose and short-chain mycolic acids (C22 to C36) and their peptidoglycan contained meso-diaminopimelic acid. The G+C content of the DNA was 51-60 mol%. MK-9 (H2) was the principal menaquinone. The 16S rDNA sequences of four isolates of each bacterium were determined and aligned with those of other members of the coryneform group. Phylogenetic analysis showed that the strains represented two new sublines within the genus Corynebacterium; Corynebacterium variabile and Corynebacterium ammoniagenes were their nearest known phylogenetic neighbours. Corynebacterium variabile and Corynebacterium ammoniagenes showed the highest levels of sequence homology with the isolates; however, DNA-DNA hydridization studies indicated that the Corynebacterium strains isolated from the cheese smear did not belong to either Corynebacterium variabile or Corynebacterium ammoniagenes (26 and 46% chromosomal similarity, respectively). On the basis of the phylogenetic and phenotypic distinctiveness of the unknown isolates, it is proposed that the bacteria be classified as two new Corynebacterium species, for which the names Corynebacterium mooreparkense sp. nov. and Corynebacterium casei sp. nov. are proposed. Type strains have been deposited in culture collections as Corynebacterium mooreparkense LMG S-19265T (= NCIMB 30131T) and Corynebacterium casei LMG S-19264T (= NCIMB 30130T).

Biomass↗
PubMed2001

Microbacterium gubbeenense sp. nov., from the surface of a smear-ripened cheese.

Phenotypic and phylogenetic studies were performed on 11 strains of a Microbacterium-like organism isolated from the surface of a smear-ripened cheese. The isolates were Gram-positive, catalase-positive, facultatively anaerobic, oxidase-negative, non-spore-forming, non-motile, small, slender rods and grew in 12% (w/v) NaCl. Chemotaxonomic investigation revealed that all the isolates belonged unambiguously to the genus Microbacterium. They contained type B1 peptidoglycans with L-lysine as the diamino acid and glycolyl acyl types; rhamnose and galactose were the cell wall sugars. The G+C content ranged from 69 to 72 mol%. The major menaquinones were MK-11 and MK-12 and the major fatty acids were anteiso C15:0 and C17:0 and iso C16:0. Phylogenetic analysis of the 16S rRNA sequences of four isolates showed that they represented a new subline in the genus Microbacterium, with Microbacterium barkeri as their nearest phylogenetic neighbour. M. barkeri showed the highest sequence similarity to the isolates; however, DNA-DNA hybridization showed that the isolates had only 38% chromosomal similarity to M. barkeri. Based on the phylogenetic and phenotypic distinctiveness of the isolates, it is proposed that they be classified as a new Microbacterium species, for which the name Microbacterium gubbeenense sp. nov. is suggested. The type strain has been deposited as LMG S-19263T (= NCIMB 30129T). The GenBank accession number for the 16S rDNA sequence of the type strain is AF263563.

Actinomycetales↗
PubMed2001

Blue calls--time for a change?

Prior alert via a landline telephone ("blue call") is commonly used to warn accident and emergency (A&E) departments of the impending arrival of a seriously ill or injured patient. There are no published indications for making such calls or validated protocols on message content. Submitted telephone information has the potential for distortion as it is passed through the control centre resulting in inappropriate resource allocation. This study focuses on the quality and content of the message in the context of the available patient details as well as reviewing the clinical indications for the call. Data were collected on patients for whom "blue calls" were made to an A&E department over three months of 1998. Patients with life threatening conditions who were brought by non-blue light ambulance were identified during the same period. Similar details were collected on these critical patients. Of the 189 "blue calls" with complete details, 73% were admitted, (12% to ITU) and 18% died. Sixty nine per cent of cases were medical, 26% trauma and 5% obstetric. Pre-hospital observations were missing for 25% of patients (excluding patients in cardiac arrest), suggesting that the decisions to make a pre-alert call may have been based on subjective criteria in a significant minority. Information given over the telephone invariably included age, sex and presenting complaint but details of the current condition of the patient were included in only 11%. On reviewing pre-hospital information, a consultant in A&E and an ambulance paramedic judged that a prior alert was justified in 93% but additional information would be helpful in 52% of cases to correctly mobilise resources. Seventy five "clinically critical" patients were found in the three months of the study. Clinically critical patients were patients who had no prior alert, transported by ambulance, who were subsequently admitted to intensive care, theatre, or other high dependency areas. They included 27 patients with symptoms of a myocardial infarction. These patients may have benefited from prior alert. A protocol is suggested to provide criteria for making a prior alert to the A&E department via a landline connection. A standardised message structure would be used using vital signs and mechanism of injury or type of illness to assist in hospital preparation.

Adolescent↗
PubMed2001

Wild type Huntingtin reduces the cellular toxicity of mutant Huntingtin in mammalian cell models of Huntington's disease.

OBJECTIVES: Recent data suggest that wild type huntingtin can protect against apoptosis in the testis of mice expressing full length huntingtin transgenes with expanded CAG repeats. It is not clear if this protective effect was confined to particular cell types, or if wild type huntingtin exerted its protective effect in this model by simply reducing the formation of toxic proteolytic fragments from mutant huntingtin. METHODS: We cotransfected neuronal (SK-N-SH, human neuroblastoma) and non-neuronal (COS-7, monkey kidney) cell lines with HD exon 1 (containing either 21 or 72 CAG repeats) construct DNA and either full length wild type huntingtin or pFLAG (control vector). RESULTS: Full length wild type huntingtin significantly reduced cell death resulting from the mutant HD exon 1 fragments containing 72 CAG repeats in both cell lines. Wild type huntingtin did not significantly modulate cell death caused by transfection of HD exon 1 fragments containing 21 CAG repeats in either cell line. CONCLUSIONS: Our results suggest that wild type huntingtin can significantly reduce the cellular toxicity of mutant HD exon 1 fragments in both neuronal and non-neuronal cell lines. This suggests that wild type huntingtin can be protective in different cell types and that it can act against the toxicity caused by a mutant huntingtin fragment as well as against a full length transgene.

Animals↗
PubMed2001

Abolished tubuloglomerular feedback and increased plasma renin in adenosine A1 receptor-deficient mice.

The hypothesis that adenosine acting on adenosine A1 receptors (A1R) regulates several renal functions and mediates tubuloglomerular feedback (TGF) was examined using A1R knockout mice. We anesthetized knockout, wild-type, and heterozygous mice and measured glomerular filtration rate, TGF response using the stop-flow pressure (P(sf)) technique, and plasma renin concentration. The A1R knockout mice had an increased blood pressure compared with wild-type and heterozygote mice. Glomerular filtration rate was similar in all genotypes. Proximal tubular P(sf) was decreased from 36.7 +/- 1.2 to 25.3 +/- 1.6 mmHg in the A1R+/+ mice and from 38.1 +/- 1.0 to 27.4 +/- 1.1 mmHg in A1R+/- mice in response to an increase in tubular flow rate from 0 to 35 nl/min. This response was abolished in the homozygous A1R-/- mice (from 39.1 +/- 4.1 to 39.2 +/- 4.5 mmHg). Plasma renin activity was significantly greater in the A1R knockout mice [74.2 +/- 14.3 milli-Goldblatt units (mGU)/ml] mice compared with the wild-type and A1R+/- mice (36.3 +/- 8.5 and 34.1 +/- 9.6 mGU/ml), respectively. The results demonstrate that adenosine acting on A1R is required for TGF and modulates renin release.

Adenosine↗
PubMed2001

Effects of tidal volume stretch on airway constriction in vivo.

Tidal stresses are thought to be involved in maintaining airway patency in vivo. The present study examined the effects of normal stresses exerted by the lung parenchyma during tidal ventilation on recovery from agonist-induced airway constriction. In seven anesthetized dogs, one lung was selectively ventilated with a Univent endotracheal tube (Vitaid, Lewiston, NY). Airway tone was increased either transiently (intravenous bolus) or continuously (intravenous infusion) with methacholine (MCh). During one-lung ventilation, changes in the airway size of both lungs were measured for up to 40 min during recovery from constriction by using high-resolution computed tomography. After recovery to baseline, the alternate lung was ventilated, and the protocol was repeated. The absence of tidal stresses led to an attenuated recovery from either transient or steady-state airway constriction. The effectiveness or lack thereof of normal tidal stress in stabilizing airway size may be one factor that contributes to the lack of reversal with tidal breathing and deep inspiration seen in asthmatic subjects.

Animals↗
PubMed2001

Neural compensations after lesion of the cerebral cortex.

Functional improvement after cortical injury can be stimulated by various factors including experience, psychomotor stimulants, gonadal hormones, and neurotrophic factors. The timing of the administration of these factors may be critical, however. For example, factors such as gonadal hormones, nerve growth factor, or psychomotor stimulants may act to either enhance or retard recovery, depending upon the timing of administration. Nicotine, for instance, stimulates recovery if given after an injury but is without neuroprotective effect and may actually retard recovery if it is given only preinjury. A related timing problem concerns the interaction of different treatments. For example, behavioral therapies may act, in part, via their action in stimulating the endogenous production of trophic factors. Thus, combining behavioral therapies with pharmacological administration of compounds to increase the availability of trophic factors enhances functional outcome. Finally, anatomical evidence suggests that the mechanism of action of many treatments is through changes in dendritic arborization, which presumably reflects changes in synaptic organization. Factors that enhance dendritic change stimulate functional compensation, whereas factors that retard or block dendritic change block or retard compensation.

Animals↗
PubMed2001

Discitis in young children.

Discitis is uncommon in children and presents in different ways at different ages. It is most difficult to diagnose in the uncommunicative toddler of one to three years of age. We present 11 consecutive cases. The non-specific clinical features included refusal to walk (63%), back pain (27%), inability to flex the lower back (50%) and a loss of lumbar lordosis (40%). Laboratory tests were unhelpful and cultures of blood and disc tissue were negative. MRI reduces the diagnostic delay and may help to avoid the requirement for a biopsy. In 75% of cases it demonstrated a paravertebral inflammatory mass, which helped to determine the duration of the oral therapy given after initial intravenous antibiotics. At a mean follow-up of 21 months (10 to 40), all the spines were mobile and the patients free from pain. Radiological fusion occurred in 20% and was predictable after two years. At follow-up, MRI showed variable appearances: changes in the vertebral body usually resolved at 24 months and recovery of the disc was seen after 34 months.

Anti-Bacterial Agents↗
PubMed2001

Two forms of intergroup discrimination with positive and negative outcomes: explaining the positive-negative asymmetry effect.

The minimal group paradigm is widely used for the study of intergroup discrimination. Reliably, group members show in-group favouritism in the allocation of positive outcomes but not in the allocation of negative outcomes. Less frequently investigated has been the withdrawal of positive and negative outcomes in the minimal paradigm. In this minimal group experiment the method of discrimination (allocation vs. withdrawal) and valence of outcomes (positive vs. negative) were combined in a 2 x 2 design (N = 57). Participants showed significant in-group favouritism only in the allocate (+) condition, less in withdrawal (-), and none at all in the remaining two cells (where parity predominated). Measures of subgroup and superordinate category identification paralleled these findings, and their inclusion as covariates in the analyses of favouritism and parity measures eliminated the previously significant interactions, thus implicating recategorization as the process mediating positive-negative asymmetry effects in intergroup discrimination.

Adolescent↗
PubMed2001

Nationalism and patriotism: national identification and out-group rejection.

It is argued that the differentiation between nationalism and patriotism proposed in the literature can be seen as analogous to judgments based on different types of comparisons: intergroup comparisons with other nations are associated with intergroup behaviour that corresponds to nationalism, whereas temporal or standard comparisons are linked with behaviour that corresponds to patriotism. Four studies (N = 103, 107, 96 and 105) conducted in Germany and Britain examined the hypothesis that national identification and in-group evaluation only show a reliable relationship with out-group rejection under an intergroup comparison orientation. Participants were primed with either an intergroup comparison, a temporal comparison or no explicit comparison orientation. A subsequent questionnaire assessed in-group (own country) identification, in-group evaluation (i.e. national pride) and rejection of national out-groups. Across all four studies, both in-group identification and in-group evaluation show a stronger correlation with out-group derogation if participants were primed with an intergroup comparison orientation compared to temporal and control conditions. Results are discussed with regard to nationalism and patriotism as well as Hinkle and Brown's (1990) model on relational vs. autonomous orientations.

Adolescent↗
PubMed2001

Quality of life--ageing and Down syndrome.

This article, based on pilot qualitative research, examines the quality of life of people with Down syndrome who are in the upper age bracket (45-70 years). Through use of a questionnaire, the current life experience and interests of a small group of individuals are noted, along with some of their perceptions concerning their past and present, including their views on the ageing process. Recommendations are made particularly in relation to the need to recognise the principles of variability, perception and choice, while providing support to encourage dignified and active lifestyles.

Adult↗