Search PubMed⌕ Search

Biomedical subjects

J Barnes

Publications and source records attributed to J Barnes.

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

A combination of subtherapeutic doses of chemically modified doxycycline (CMT-8) and a bisphosphonate (clodronate) inhibits bone loss in the ovariectomized rat: a dynamic histomorphometric and gene expression study.

Recent studies have demonstrated that tetracyclines can reduce bone loss in the ovariectomized (OVX) rat model of osteoporosis. In the current study, a non-antimicrobial, chemically modified doxycycline (CMT-8), alone or in combination with a bisphosphonate (Clodronate), was evaluated in this model. Forty-two, 6month old, female rats were randomly assigned to the following groups, (6/ group): a) sham/vehicle, b) OVX/vehicle; c) OVX/1 mg/day CMT-8; d) OVX/2 mg/day CMT-8, e) OVX/1 mg/week Clodronate; and f) OVX/1 mg/day CMT-8 + 1 mg/week Clodronate, CMT-8 was administered by oral gavage, Clodronate injected S/C. Following sham surgery or OVX, the rats were treated for 90 days with CMT-8 or vehicle alone, injected at three different times with fluorochrome labels, the rats were sacrificed, and the tibiae excised for analysis by dynamic bone histomorphometry. Femurs were aseptically removed and analyzed for collagen, collagenase and osteopontin mRNAs by Northern and dot blot analysis. As expected, OVX decreased trabecular bone volume (BV/TV by 73.8% vs. sham p<.01), and also reduced trabecular thickness, numbers, and increased spacing. Bone loss in the OVX animals was partially prevented with either 2 mg/day CMT-8 or 1 mg/wk Clodronate (p<.01), while the 1 mg/day CMT-8 had no effect. Interestingly, the efficacy of the combination therapy of CMT-8 and Clodronate was significantly better than either treatment by itself, maintaining bone mass and structural indices at levels identical to sham values. OVX rats mRNA for collagen, collagenase and osteopontin were elevated indicating high-turnover bone loss. Only COMBO therapy significantly reduced the collagenase and osteopontin mRNA. In summary, CMT-8 mono-therapy (2 mg) alone partially inhibited bone loss in this animal model of osteoporosis. However, 1 mg/day (CMT-8) monotherapy had no effect on bone loss or bone mRNA levels and when combined with Clodronate, interacted to increase efficacy. Thus, a combination of a suboptimal dose of CMT-8 and a bisphosphonate appears to increase the amount of bone by suppressing resorption in a model of osteoporosis.

Animals↗
PubMed2000

Catalytic activation of mitogen-activated protein (MAP) kinase phosphatase-1 by binding to p38 MAP kinase: critical role of the p38 C-terminal domain in its negative regulation.

Mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1) is the archetypal member of the dual-specificity protein phosphatase family, the expression of which can be rapidly induced by a variety of growth factors and cellular stress. Since MKP-1 protein localizes in the nucleus, it has been suggested to play an important role in the feedback control of MAP kinase-regulated gene transcription. Recently it has been demonstrated that the interaction of several cytosolic MAP kinase phosphatases with MAP kinases can trigger the catalytic activation of the phosphatases. It is unclear whether such a regulatory mechanism can apply to nuclear MAP kinase phosphatases and serve as an additional apparatus for the feedback control of MAP kinase-mediated gene expression. Here we have shown that MKP-1 associates directly with p38 MAP kinase both in vivo and in vitro, and that this interaction enhances the catalytic activity of MKP-1. The point mutation Asp-316-->Asn in the C-terminus of p38, analogous to the ERK2 (extracellular-signal-regulated kinase 2) sevenmaker mutation, dramatically decreases its binding to MKP-1 and substantially compromises its stimulatory effect on the catalytic activity of this phosphatase. Consistent with its defective interaction with MKP-1, this p38 mutant also displays greater resistance to dephosphorylation by the phosphatase. Our studies provide the first example of catalytic activation of a nuclear MAP kinase phosphatase through direct binding to a MAP kinase, suggesting that such a regulatory mechanism may play an important role in the feedback control of MAP kinase signalling in the nuclear compartment.

Asparagine↗
PubMed2000

Impacts of urban levels of ozone on Pinus halepensis foliage.

Between May and September, 1996, seedlings of Pinus halepensis were placed at a site adjacent to an automated air pollution monitoring station within the urban area of Florence. Additional 'control' plants were placed in chambers ventilated with charcoal/Purafil(R)-filtered air. All trees were well watered throughout the whole experimental period. During the exposure period, ambient levels of sulphur dioxide were very low, whilst the accumulated hourly exposure to ozone above 40 ppb (i.e. AOT40) exceeded 20000 ppb h(-1) - peak hourly ozone concentrations rising to levels above 100 ppb. Trees exposed to ambient levels of air pollution exhibited typical symptoms of ozone damage (chlorotic mottle) on previous year needles toward the end of the summer. Similar symptoms were not observed on equivalent trees exposed to filtered-air, nor were visible symptoms accompanied by insect or pest infestation. Anatomical and ultrastructural observations made on symptomatic needles revealed degeneration in mesophyll cells bordering sub-stomatal cavities and alterations in chloroplast ultrastructure (fat accumulation, starch and tannin pattern modifications). These observations are consistent with the known effects of air pollutants (namely ozone) recorded in the literature. Findings are discussed in relation to the impacts of ozone on P. halepensis in the Mediterranean region.

Journal Article↗
PubMed2000

The functional neuroanatomy of implicit-motion perception or representational momentum.

BACKGROUND: When we view static scenes that imply motion - such as an object dropping off a shelf - recognition memory for the position of the object is extrapolated forward. It is as if the object in our mind's eye comes alive and continues on its course. This phenomenon is known as representational momentum and results in a distortion of recognition memory in the implied direction of motion. Representational momentum is modifiable; simply labelling a drawing of a pointed object as 'rocket' will facilitate the effect, whereas the label 'steeple' will impede it. We used functional magnetic resonance imaging (fMRI) to explore the neural substrate for representational momentum. RESULTS: Subjects participated in two experiments. In the first, they were presented with video excerpts of objects in motion (versus the same objects in a resting position). This identified brain areas responsible for motion perception. In the second experiment, they were presented with still photographs of the same target items, only some of which implied motion (representational momentum stimuli). When viewing still photographs of scenes implying motion, activity was revealed in secondary visual cortical regions that overlap with areas responsible for the perception of actual motion. Additional bilateral activity was revealed within a posterior satellite of V5 for the representational momentum stimuli. Activation was also engendered in the anterior cingulate cortex. CONCLUSIONS: Considering the implicit nature of representational momentum and its modifiability, the findings suggest that higher-order semantic information can act on secondary visual cortex to alter perception without explicit awareness.

Adult↗
PubMed2000

Hypnotherapy for smoking cessation.

BACKGROUND: Hypnotherapy is widely promoted as a method for aiding smoking cessation. It is proposed to act on underlying impulses to weaken the desire to smoke or strengthen the will to stop. OBJECTIVES: The objective of this review was to evaluate the effects of hypnotherapy for smoking cessation. SEARCH STRATEGY: We searched the Cochrane Tobacco Addiction Group trials register. SELECTION CRITERIA: We considered randomised trials of hypnotherapy which reported smoking cessation rates at least six months after the beginning of treatment. DATA COLLECTION AND ANALYSIS: Two reviewers extracted data on the type of subjects, the type and duration of the hypnotherapy, the nature of the control group,the outcome measures, method of randomisation, and completeness of follow-up. The main outcome measure was abstinence from smoking after at least six months follow-up in patients smoking at baseline. We used the most rigorous definition of abstinence in each trial, and biochemically validated rates where available. Subjects lost to follow-up were counted as smokers. Where possible, we performed meta-analysis using a fixed effects model. MAIN RESULTS: Nine studies compared hypnotherapy with 14 different control interventions. There was significant heterogeneity between the results of the individual studies, with conflicting results for the effectiveness of hypnotherapy compared to no treatment or to advice. We therefore did not attempt to calculate pooled odds ratios for the overall effect of hypnotherapy. There was no evidence of an effect of hypnotherapy compared to rapid smoking or psychological treatment. REVIEWER'S CONCLUSIONS: We have not shown that hypnotherapy has a greater effect on six month quit rates than other interventions or no treatment. The effects of hypnotherapy on smoking cessation claimed by uncontrolled studies were not confirmed by analysis of randomised controlled trials.

Humans↗
PubMed2000

The selectin superfamily: the role of selectin adhesion molecules in delayed cerebral ischaemia after aneurysmal subarachnoid haemorrhage.

Cerebral ischaemia and reperfusion injury may be exacerbated by leukocyte recruitment and activation. Adhesion molecules play a pivotal role in leukocyte recruitment. We report a prospective study of the potential role of the selectin family of adhesion molecules (E-, P- and L-selectin) in delayed cerebral ischaemia (DID) following aneurysmal subarachnoid haemorrhage. In patients with good grade SAH, we have compared serum concentrations of E-, P- and L-selectin, between patients who do, and do not develop delayed cerebral ischaemia. There was no difference in E-selectin concentration between the two groups (44.0 ng/ml vs. 37.4 ng/ml). Serum P-selectin concentration was significantly higher in patients with DID compared to those patients without DID (149.5 ng/ml vs. 112.9 ng/ml, p = 0.039). Serum L-selectin concentrations were significantly lower in patients with DID (633.8 ng/ml vs 897.9 ng/ml, p = 0.013). We conclude that P- and L-selectin are involved in the pathogenesis of DID following aneurysmal subarachnoid haemorrhage. The results of this study do not elucidate the exact role of each selectin in DID.

Brain↗
PubMed2000

Simulating ozone detoxification in the leaf apoplast through the direct reaction with ascorbate.

This paper presents a mathematical model which enables the semi-quantification of ozone (O3) detoxification, based upon the direct reaction of the pollutant with ascorbate (ASC) located in the aqueous matrix associated with the cell wall (i.e. the apoplast). The model describes the uptake of ozone into the leaf and its direct reaction with ASC, taking into consideration the regeneration of dehydroascorbic acid in the cytosol, the rate of replenishment of cell wall ASC and the distribution of ASC between sub-cellular compartments based upon the permeability of biomembranes to the neutral species, ascorbic acid and the pH of various sub-cellular compartments. The importance of various physico-chemical characteristics (e.g. stomatal conductance, mesophyll cell wall thickness and tortuosity, chloroplast volume, apoplast pH, ASC:O3 reaction stoichiometry) in mediating the flux of ozone to the plasmalemma is analysed. Model simulations, supported by experimental observations, suggest that the ASC concentration in the leaf apoplast is high enough to scavenge a significant proportion of the O3 taken up into the leaf interior, under environmentally relevant conditions. However, there is considerable variation between taxa in the potential degree of protection afforded by apoplastic ASC, emphasizing the need for an improved understanding of the reaction chemistry of O3 in the cell wall.

Ascorbic Acid↗
PubMed2000

Cortical activity during rotational and linear transformations.

Neuroimaging studies of cortical activation during image transformation tasks have shown that mental rotation may rely on similar brain regions as those underlying visual perceptual mechanisms. The V5 complex, which is specialised for visual motion, is one region that has been implicated. We used functional magnetic resonance imaging (fMRI) to investigate rotational and linear transformation of stimuli. Areas of significant brain activation were identified for each of the primary mental transformation tasks in contrast to its own perceptual reference task which was cognitively matched in all respects except for the variable of interest. Analysis of group data for perception of rotational and linear motion showed activation in areas corresponding to V5 as defined in earlier studies. Both rotational and linear mental transformations activated Brodman Area (BA) 19 but did not activate V5. An area within the inferior temporal gyrus, representing an inferior satellite area of V5, was activated by both the rotational perception and rotational transformation tasks, but showed no activation in response to linear motion perception or transformation. The findings demonstrate the extent to which neural substrates for image transformation and perception overlap and are distinct as well as revealing functional specialisation within perception and transformation processing systems.

Adult↗
PubMed2000

Qualitative interview study of communication between parents and children about maternal breast cancer.

OBJECTIVE: To examine parents' communication with their children about the diagnosis and initial treatment of breast cancer in the mother. DESIGN: Qualitative interview study within a cross-sectional cohort. SETTING: Two breast cancer treatment centers. PARTICIPANTS: 32 women with stage I or stage II breast cancer with 56 school-aged children. Main outcome measures Semistructured interview regarding timing and extent of communication with children about the diagnosis and initial treatment of the mother's illness, reasons for talking to children or withholding information, and help available and requested from health professionals. RESULTS: Women were most likely to begin talking to their children after their diagnosis had been confirmed by biopsy, but a few waited until after surgery or said nothing at all. Family discussion did not necessarily include mention of cancer. There was considerable consistency in the reasons given for either discussing or not discussing the diagnosis. The most common reason for not communicating was to avoid children's questions, particularly those about death. Although most women had helpful discussion with a physician concerning their illness, few were offered help with talking to their children; many would have liked help, particularly the opportunity for both parents to talk to a health professional with experience in understanding and talking to children. CONCLUSION: Parents diagnosed with cancer or other serious illnesses should be offered help to think about whether, what, and how to tell their children and about what children can understand, especially as they may well be struggling themselves to come to terms with their illness.

Adolescent↗
PubMed2000

Does ascorbate in the mesophyll cell walls form the first line of defence against ozone? Testing the concept using broad bean (Vicia faba L.).

Broad bean (Vicia faba L.) plants were exposed, in duplicate controlled environment chambers, to charcoal/Purafil-filtered air (CFA-grown plants) or to 75 nmol mol(-1) ozone (O(3)) for 7 h d(-1) (O(3)-grown plants) for 28 d, and then exposed to 150 nmol mol(-1) O(3 )for 8 h. The concentration of ascorbate (ASC) was determined in leaf extracellular washing fluid (apoplast) and in the residual leaf tissue (symplast) after 0, 4 and 8 h acute fumigation, and after a 16 h "recovery" period in CFA. Changes in stomatal conductance were measured in vivo in order to model pollutant uptake, while the light-saturated rate of CO(2) assimilation (A:(sat)) was recorded as an indicator of O(3)-induced intracellular damage. Measurements of A:(sat) revealed enhanced tolerance to 150 nmol mol(-1) O(3) in plants pre-exposed to the pollutant compared with equivalent plants grown in CFA, consistent with the observed reduction in pollutant uptake due to lower stomatal conductance. The concentration of ASC in the leaf apoplast (ASC(apo)) declined upon O(3)-treatment in both CFA- and O(3)-grown plants, consistent with the oxidation of ASC(apo) under O(3)-stress. Furthermore, the decline in ASC(apo) was reversible in O(3)-grown plants after a 16 h "recovery" period, but not in plants grown in CFA. No significant change in the level and/or redox state of ASC in the symplast (ASC(symp)) was observed in plants exposed to 150 nmol mol(-1) O(3), and there was no difference in the constitutive level of ASC(symp) between CFA- and O(3)-grown plants. Model calculations indicated that the reaction of O(3) with ASC(apo) in the leaves of Vicia faba is potentially sufficient to intercept a substantial proportion (30-40%) of the O(3)entering the plant under environmentally-relevant conditions. The potential role of apoplastic ASC in mediating the tolerance of leaves to O(3) is discussed.

Air Pollutants↗
PubMed1999

Treatment of osteoporosis with MMP inhibitors.

In the current study, we examined the effects of minocycline on the osteopenia of ovariectomized (OVX) aged rats using the marrow ablation model. This injury induces rapid bone formation followed by bone resorption in the marrow cavity. Old female rats were randomly divided into five groups: sham, OVX, OVX + minocycline (5-15 mg/day, orally), OVX + 17 beta-estradiol (25 micrograms/day, subcutaneously), and OVX + both agents. Rats were OVX, treated with minocycline and/or estrogen, followed by marrow ablation. Bone samples were collected 16 days post-marrow ablation. X-ray radiography of bones operated on showed that treatment of OVX old rats with minocycline increased bone mass in diaphyseal region. Diaphyseal bone mineral density (BMD) was measured by DEXA scan. Diaphyseal BMD of OVX rats was increased 17-25% by treatment with 5-15 mg of minocycline or 17 beta-estradiol. The effects of minocycline and estrogen treatments on the expression of osteoblast and osteoclast markers were also examined. Northern and dot blot analysis of RNA samples showed that treatment of OVX aged rats with minocycline increased the expression of type I collagen (COL I) (49%) and decreased that of interleukin-6 (IL-6) (31%). In contrast, estrogen treatment decreased the expression of interleukin-6 (IL-6) (39%), carbonic anhydrase II (CA II) (36%), and osteopontin (OP) (37%). Neither minocycline nor 17 beta-estradiol had an effect on the expression of osteocalcin (OC) and alkaline phosphatase (AP). To elucidate the mechanism by which minocycline prevented the loss of bone in OVX aged rats, we examined the colony-formation potential of bone marrow stromal cells in ex vivo cultures. Minocycline stimulated the colony-forming efficiency of marrow stromal cells derived from old animals. We have therefore concluded that the modest increase in BMD noted in OVX aged rats, in response to minocycline treatment, may be due to a change in bone remodeling that favors bone formation; and the anabolic effect of minocycline is likely due to its effect on the expression of COL I and/or the metabolism of osteoprogenitor cells.

Absorptiometry, Photon↗
PubMed1999

Actions of bFGF on mitogenic activity and lineage expression in rat osteoprogenitor cells: effect of age.

Rat osteoprogenitor cells were used to examine the effects of bFGF on DNA synthesis and the expression of osteoblast (OB)-related genes. bFGF, as low as 0.1 ng/ml, stimulated DNA synthesis. bFGF also increased the mRNA level of osteopontin (OP) and decreased that of type I collagen (COL I). When cultures were grown in dexamethasone (DEX) to induce OB lineage commitment, the expression of COL I, alkaline phosphatase (AP) and OP was greatly enhanced. Subsequent incubation with bFGF partially negated the stimulatory effect of DEX on AP and COL I mRNAs. bFGF also inhibited the expression of osteocalcin mRNA in cells grown in 1,25(OH)2D3 and DEX. Combined effects of bFGF with IGF-I or PDGF on DNA synthesis and OP expression were examined. bFGF + IGF-I, but not bFGF + PDGF, was more effective than PDGF alone. By comparing cells from adult and old animals, we found that bFGF-induced mitogenic activity was reduced significantly with age. In contrast, the effect of bFGF on the expression of OB genes was not significantly altered by age. These findings suggest that bFGF plays a dual role as a local positive and negative regulator on proliferation and osteogenic lineage expression, respectively, in osteoprogenitor cells, and that the mitogenic activity in response to bFGF was impaired in aging.

Aging↗
PubMed1999

The functional anatomy of the McCollough contingent colour after-effect.

We report two functional magnetic resonance imaging (fMRI) experiments which reveal a cortical network activated when perceiving coloured grids, and experiencing the McCollough effect (ME). Our results show that perception of red-black and green-black grids activate the right fusiform gyrus (area V4) plus the left and right lingual gyri, right striate cortex (V1) and left insula. The ME activated the left anterior fusiform gyrus as well as the ventrolateral prefrontal cortex, and in common with colour perception, the left insula. These data confirm the critical role of the fusiform gyrus in actual and illusory colour perception as well as revealing localized frontal cortical activation associated with the ME, which would suggest that a 'top-down' mechanism is implicated in this illusion.

Adult↗
PubMed1999

Relatives' lived experiences of complementary therapies in a critical care department--a phenomenological study.

This phenomenological study examined relatives' lived experiences of complementary therapies in the Department of Critical Care Medicine at Royal Hobart Hospital. Participants in the study, 20 relatives of critically ill patients, were involved in a non-structured, audiotaped interview. Subsequently, transcripts were analysed using a phenomenological transformative process to identify common themes in the text. Study findings suggested four emerging conceptual categories, which with further analysis uncovered the essence of the phenomenon as extending and enriching a caring atmosphere.

Adolescent↗