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Biomedical subjects

J Baker

Publications and source records attributed to J Baker.

At least 37 records · Page 2Linked to original sources
PubMed2002

Numerical analysis of an anastomotic device.

The explicit dynamic finite element method was utilized to investigate the deformation behaviour of a woven wire mesh tubular device that is used in a side-to-side anastomotic procedure for achieving gastrointestinal anastomosis. The numerical model was initially verified by comparison to experimental results that were obtained using a specialized testing mechanism. Once validated, the finite element model (FEM) was parameterized to ascertain the influence of several device parameters on its deformation behaviour. The importance of these parameters, as related to its optimal design for use in minimally invasive surgery (MIS), was subsequently ascertained and discussed.

Anastomosis, Surgical↗
PubMed2002

Specific orofacial problems experienced by musicians.

BACKGROUND: Patients who play musical instruments (especially wind and stringed instruments) and vocalists are prone to particular types of orofacial problems. Some problems are caused by playing and some are the result of dental treatment. This paper proposes to give an insight into these problems and practical guidance to general practice dentists. METHOD: Information in this paper is gathered from studies published in dental, music and occupational health journals, and from discussions with career musicians and music teachers. RESULTS: Orthodontic problems, soft tissue trauma, focal dystonia, denture retention, herpes labialis, dry mouth and temporomandibular joint (TMJ) disorders were identified as orofacial problems of career musicians. Options available for prevention and palliative treatment as well as instrument selection are suggested to overcome these problems. CONCLUSIONS: Career musicians express reluctance to attend dentists who are not sensitive to their specific needs. General practitioner dentists who understand how the instruments impact on the orofacial structures and are aware of potential problems faced by musicians are able to offer preventive advice and supportive treatment to these patients, especially those in the early stages of their career.

Cumulative Trauma Disorders↗
PubMed2002

A rare complication of neonatal central venous access.

Total parenteral nutrition is often necessary for the survival of neonates, but obtaining central venous access can be very difficult. A case is reported in which malpositioning of a 27 gauge central venous catheter resulted in the misdiagnosis of necrotising enterocolitis and hypoglycaemia.

Catheterization, Central Venous↗
PubMed2001

Using PAC nested deletions to order contigs and microsatellite markers at the high repetitive sequence containing Npr3 gene locus.

Highly polymorphic di- and tetranucleotide repeats in and around Npr3, a potential candidate gene for hypertension, have been identified using a novel approach. Because this chromosomal site is rich in repetitive DNA and difficult to sequence, P1 artificial chromosomes were retrofitted with a loxP transposon to map the gene sequence within a clone using a series of nested deletions. Sequences from ends of deletions 1-3 kb apart identified a (CA)(20) and a (TA)(18)-(CA)(8) repeat 8 kb upstream and within an intron of Npr3, respectively. DNA from 17 individuals was analyzed for length polymorphisms in these and eight additional repeats identified in 200 kb of working draft sequence from this region in GenBank. The sequence contigs and microsatellite repeats from GenBank were ordered using the P1-derived artificial chromosome deletion series. Several of these repeats were found to vary considerably in length in the set of genomic DNA tested. Since this site in chromosome 5p has recently been implicated in disease in studies with genetically hypertensive rats, the microsatellite markers reported here will be useful for genetic analysis and may even be implicated in the disease process in humans. We discuss how these types of data are useful for interpreting draft DNA sequence coming out of the genome projects, and the utility of deletion clones as a resource for ordering contigs and gap filling.

Alleles↗
PubMed2001

Plunge waveforms from inspiralling binary black holes.

We study the coalescence of nonspinning binary black holes from near the innermost stable circular orbit down to the final single rotating black hole. We use a technique that combines the full numerical approach to solve the Einstein equations, applied in the truly nonlinear regime, and linearized perturbation theory around the final distorted single black hole at later times. We compute the plunge waveforms, which present a non-negligible signal lasting for t approximately 100M showing early nonlinear ringing, and we obtain estimates for the total gravitational energy and angular momentum radiated.

Journal Article↗
PubMed2001

Observation of a metastable periodic structure for the (001) surface of KTaO3 after cleaving in situ.

Helium atom diffraction experiments carried out under ultrahigh vacuum conditions on a freshly cleaved (001) surface of KTaO3 reveal metastable features which decay over a period of several hours. The initial He diffraction pattern contains large scattering intensity satellite peaks very close to the specular reflection beam. As time from cleaving elapses, the satellite intensities diminish virtually to zero while the specular intensity increases, and the diffraction pattern evolves into one consistent with the (1x1) bulk termination surface. The data are compared with model calculations for scattering from a series of terraces at two heights with a distribution of terrace lengths [Surf. Sci. 384, 15 (1997)].

Journal Article↗
PubMed2001

Expansion of cytolytic CD8(+) natural killer T cells with limited capacity for graft-versus-host disease induction due to interferon gamma production.

T cells with natural killer cell phenotype and function (NKT cells) have been described in both human and murine tissues. In this study, culture conditions were developed that resulted in the expansion of CD8(+) NKT cells from bone marrow, thymus, and spleen by the timed addition of interferon-gamma (IFN-gamma), interleukin 2 (IL-2), and anti-CD3 monoclonal antibody. After 14 to 21 days in culture, dramatic expansion of CD3(+), CD8(+), alphabetaT-cell receptor(+) T cells resulted with approximately 20% to 50% of the cells also expressing the NK markers NK1.1 and DX5. The CD8(+) NKT cells demonstrated lytic activity against several tumor target cells with more than 90% lysis by day 14 to day 21 of culture. Cytotoxicity was observed against both syngeneic and allogeneic tumor cell targets with the greatest lytic activity by the cells expressing either NK1.1 or DX5. The expanded CD8(+) NKT cells produce T(H)1-type cytokines with high levels of IFN-gamma and tumor necrosis factor alpha. Expansion of the CD8(+) NKT cells was independent of CD1d. Ly49 molecules were expressed on only a minority of cells. A single injection of expanded CD8(+) NKT cells was capable of protecting syngeneic animals from an otherwise lethal dose of Bcl1 leukemia cells. Expanded CD8(+) NKT cells produced far less graft-versus-host disease (GVHD) than splenocytes across major histocompatibility barriers, even when 10 times the number of CD8(+) NKT cells as compared to splenocytes were injected. This reduction in GVHD was related to IFN-gamma production since cells expanded from IFN-gamma knock-out animals caused acute lethal GVHD, whereas cells expanded from animals defective in fas ligand, fas, IL-2, and perforin did not. These data indicate that CD8(+) NKT cells expanded in this fashion could be useful for preserving graft-versus-leukemia activity without causing GVHD.

Animals↗
PubMed2001

Effect of pravastatin on frequency of fracture in the LIPID study: secondary analysis of a randomised controlled trial. Long-term Intervention with Pravastatin in Ischaemic Disease.

BACKGROUND: Statins inhibit the same biochemical pathway as aminobisphosphonates, therefore these cholesterol-lowering agents may have a beneficial effect on osteoporosis. This possibility has been supported by the finding that some statins also stimulate bone formation, and by observational studies suggesting that patients using statins have higher bone densities and lower fracture rates than controls. To assess whether statins have clinically significant effects on bone, we studied the frequency of fractures in a large randomised controlled trial of these agents. METHODS: 9014 patients (17% women, median age 62 years) with ischaemic heart disease were randomly assigned pravastatin 40 mg daily or placebo and followed up for a mean of 6.0 years. Fractures were ascertained from adverse-event reports. FINDINGS: 101 patients in the placebo group were admitted to hospital for fracture compared with 107 in the pravastatin group (hazard ratio 1.05 [95% CI 0.80-1.37]). When patients with fractures not necessitating hospital admission were added, the total number of patients having a fracture was 183 in the placebo group and 175 in the pravastatin group (0.94 [0.77-1.16]). Separate analyses for women alone and for individuals aged 65 years and over gave similar results. INTERPRETATION: These findings offer no support for the hypothesis that statins have a significant effect on fracture risk. However, this study was not of an osteoporotic population, and fracture rate, although clinically important, is an insensitive index of effects on bone. Statins should not be used to prevent osteoporosis until there is evidence for their efficacy based on randomised controlled trials.

Aged↗
PubMed2001

Reduction of stroke events with pravastatin: the Prospective Pravastatin Pooling (PPP) Project.

BACKGROUND: Stroke is a leading cause of death and disability. Although clinical trials of the early lipid-lowering therapies did not demonstrate a reduction in the rates of stroke, data from recently completed statin trials strongly suggest benefit. METHODS AND RESULTS: The effect of pravastatin 40 mg/d on stroke events was investigated in a prospectively defined pooled analysis of 3 large, placebo-controlled, randomized trials that included 19 768 patients with 102 559 person-years of follow-up. In all, 598 participants had a stroke during approximately 5 years of follow-up. The 2 secondary prevention trials (CARE [Cholesterol And Recurrent Events] and LIPID [Long-term Intervention with Pravastatin in Ischemic Disease]) individually demonstrated reductions in nonfatal and total stroke rates. When the 13 173 patients from CARE and LIPID were combined, there was a 22% reduction in total strokes (95% CI 7% to 35%, P:=0.01) and a 25% reduction in nonfatal stroke (95% CI 10% to 38%). The beneficial effect of pravastatin on total stroke was observed across a wide range of patient characteristics. WOSCOPS (West of Scotland Coronary Prevention Study, a primary prevention trial in hypercholesterolemic men) exhibited a similar, although smaller, trend for a reduction in total stroke. Among the CARE/LIPID participants, pravastatin was associated with a 23% reduction in nonhemorrhagic strokes (95% CI 6% to 37%), but there was no statistical treatment group difference in hemorrhagic or unknown type. CONCLUSIONS: Pravastatin reduced the risk of stroke over a wide range of lipid values among patients with documented coronary disease. This effect was due to a reduction in nonfatal nonhemorrhagic strokes.

Anticholesteremic Agents↗
PubMed2001

dbSNP: the NCBI database of genetic variation.

In response to a need for a general catalog of genome variation to address the large-scale sampling designs required by association studies, gene mapping and evolutionary biology, the National Center for Biotechnology Information (NCBI) has established the dbSNP database [S.T.Sherry, M.Ward and K. Sirotkin (1999) Genome Res., 9, 677-679]. Submissions to dbSNP will be integrated with other sources of information at NCBI such as GenBank, PubMed, LocusLink and the Human Genome Project data. The complete contents of dbSNP are available to the public at website: http://www.ncbi.nlm.nih.gov/SNP. The complete contents of dbSNP can also be downloaded in multiple formats via anonymous FTP at ftp://ncbi.nlm.nih.gov/snp/.

Animals↗
PubMed2001

Engineering hematopoietic grafts: purified allogeneic hematopoietic stem cells plus expanded CD8+ NK-T cells in the treatment of lymphoma.

A major benefit of allogeneic hematopoietic cell transplantation (HCT) in the treatment of malignancies is the graft-versus-tumor (GVT) effect conferred by lymphocytes contained within the graft. However, lymphocytes can also induce the potentially lethal complication of graft-versus-host disease (GVHD). We have previously reported a method of generating large numbers of ex vivo activated and expanded T cells with antitumor activity after culture with interferon-y, cross-linking antibodies to CD3, and interleukin-2. Murine splenocytes expanded under these conditions are a heterogeneous population of which approximately 20% to 60% of cells express natural killer (NK)-cell markers (NK1.1 and DX5) and display major histocompatibility complex (MHC)-unrestricted antitumor activity. Here we demonstrate the in vivo antitumor activity of this population of expanded CD8+ NK-T cells when transplanted across MHC barriers into tumor-bearing hosts. In cotransfer studies with purified allogeneic hematopoietic stem cells, expanded CD8+ NK-T cells confer GVT activity with minimal to no GVHD. In vitro studies show that, although expanded NK-T cells lyse normal allogeneic bone marrow cells, they preferentially mediate cytolysis against tumor targets. These cells persist in the peripheral circulation of host animals for at least 3 weeks posttransfer. GVT activity is dependent on perforin, but not on Fas-ligand. We conclude that expanded CD8+ NK-T cells may serve as a valuable adjuvant population for allogeneic HCT because they mediate GVT effects with minimal GVHD.

Animals↗
PubMed2001

Power output of legs during high intensity cycle ergometry: influence of hand grip.

Traditionally, leg cycle ergometry is used to assess the power output of the lower limbs. However, it is suspected that the upper body makes a significant, albeit as yet unknown, contribution to the measured power output, and as such, the lean mass of the whole body should be considered during ergometric assessment. To test this idea, indices of mechanical power output were obtained from 11 subjects during high intensity leg cycle ergometry tests (20 second duration; 75 grams per kilogram total body mass) using two protocols: one with a standard handle-bar grip (with grip) and one with supinated wrists (without-grip). Peak mechanical power, mean mechanical power, fatigue index and total mechanical work values were calculated for each subject during each test and the sample mean differences associated with the two protocols were compared using paired Student t-tests. The with-grip protocol yielded significantly greater peak mechanical power output than the without-grip protocol (886+/-124 W and 815+/-151 W, respectively), suggesting a significant upper body contribution to the maximum power output measured for the legs. As a first step towards quantifying the upper body involvement during leg cycle ergometry, surface electromyography of the forearm musculature was measured in a twelfth subject whilst performing each of the test protocols. During the with-grip ergometer tests, the intensity of electrical activity in the forearm musculature was similar, if not greater than, the intensity of electrical activity recorded for the forearm musculature during 100% maximum voluntary hand grip-dynamometer contractions, suggesting maximum isometric-type forearm muscle contraction during the with-grip leg ergometry tests. These findings suggest that the performance of traditional-style leg cycle ergometry requires a muscular contribution from the whole body. As such, researchers should be mindful of this, both in terms of the allocation of ergometer loads, and in the analysis of blood-borne metabolites.

Adult↗
PubMed2001

Identification of some rabbit allergens as lipocalins.

Rabbits are frequently used as laboratory animals or kept as domestic pets. Rabbit serum albumin and a 17-kDa protein referred to as Ory c 1 have previously been reported as allergens. Several other allergenic proteins have been recognized by crossed immuno-electrophoresis but have not been characterized. The aim of this study was to characterize the allergenic proteins present in rabbit saliva, urine and fur on the basis of molecular size and, where possible, to determine their amino acid sequences. Extracts from the male New Zealand white rabbit were used for developing specific direct RAST and RAST inhibition assays. Proteins in the extracts were separated by SDS-PAGE and the individual allergens identified by immunoblotting with serum from rabbit-allergic individuals. The N-termini of four allergens were sequenced. Saliva was the most potent extract. In total, 26 protein bands were recognized as allergens in the three extracts: 12 in saliva, seven in urine and seven in fur. Their molecular weights ranged from an 8-kDa species in saliva to an 80-kDa protein in urine. The N terminal sequences of an 18 kDa and a 21-kDa species in saliva, were identified as lipocalins with sequence similarity to a recently described odourant binding protein. This is the first evidence that allergens from the rabbit are members of the lipocalin superfamily of proteins, suggesting that similar mechanisms may be involved in eliciting the allergic response to rabbits. The 18 kDa allergen from saliva may be the previously named rabbit allergen, Ory c 1.

Allergens↗
PubMed2001

Central orexin-A activates hypothalamic-pituitary-adrenal axis and stimulates hypothalamic corticotropin releasing factor and arginine vasopressin neurones in conscious rats.

The effects of centrally injected orexin-A on plasma adrenocorticotropin (ACTH) and corticosterone levels and corticotropin releasing factor (CRF) and arginine vasopressin (AVP) mRNA in the parvocellular cells of the paraventricular nucleus (PVN) of the rat were investigated. In animals implanted previously with a lateral brain ventricle and femoral artery cannula, a single i.c.v. injection of orexin-A (10 microg/rat) resulted in a rapid, significant increase in plasma ACTH and corticosterone concentrations. Plasma ACTH reached a peak (12.5-fold greater than basal levels) at 30 min, which was maintained over 120 min before declining towards control levels by 240 min. Plasma corticosterone concentrations reached a peak (6.7-fold greater than basal levels) at 30 min. Orexin-A at a higher dose (30 microg/rat) also produced a rapid increase in plasma ACTH and corticosterone concentrations. The area under the curve for plasma levels of ACTH was similar for both doses of orexin-A. In a second study, orexin-A (10 microg/rat) was injected i.c.v. and brains and pituitaries were rapidly removed after 240 min. In situ hybridization histochemistry revealed that CRF and AVP mRNA levels were significantly increased in the parvocellular cells of the PVN. Pro-opiomelanocortin mRNA levels in the pituitary gland were not significantly elevated in response to orexin-A. These results suggest that orexin-A is able to act centrally to activate the hypothalamic-pituitary-adrenal axis involving stimulation of both CRF and AVP expression.

Adrenocorticotropic Hormone↗
PubMed2001

The innervation of the triangular fibrocartilage complex: nitric acid maceration rediscovered.

Injury to the triangular fibrocartilage complex (TFCC) is frequently implicated in the etiology of ulnar-sided wrist pain. This study examines the nervous anatomy of the TFCC using a nitric acid maceration technique and attempts to correlate this information with known tear patterns. Ten fresh frozen cadaveric specimens were studied in detail. Gross dissection of each upper-extremity specimen included removal of all flexor and extensor tendons. After identification and labeling with permanent color of the ulnar nerve, dorsal sensory branch of the ulnar nerve, posterior interosseous nerve, anterior interosseous nerve, and median nerve, an en bloc excision of the distal radioulnar region was performed. Digestion of the soft tissue was performed with nitric acid at sequential concentrations of 50% and 33% for 9 of 10 specimens. The digestion was halted by immersing the specimen in a mixture of 10% formaldehyde and 1% glycerine. After removal of bone, the specimens were fixed in paraffin, sectioned, and stained with hematoxylin and eosin. Nine of the 10 specimens were studied microscopically to determine the contribution of the grossly identified nerves to each zone of the triangular fibrocartilage complex as defined by Palmer's classification of acute TFCC tears. The anterior interosseous, median, and superficial radial nerves did not contribute to the innervation of the TFCC. The intraarticular course of the peripheral nerves could not be defined in the one specimen that was not digested with nitric acid. Nitric acid maceration is a rediscovered technique for identifying the nervous anatomy of soft tissues. The study showed that the triangular fibrocartilage complex is innervated by branches of the posterior interosseous, ulnar, and dorsal sensory ulnar nerves in a fairly consistent manner. Improved treatment of TFCC tears may result from an enhanced understanding of the supporting structures' innervation and mechanical function.

Cartilage, Articular↗
PubMed2001

Gastrointestinal mucormycosis in a renal transplant patient.

The clinical course and management of a rare case of gastrointestinal mucormycosis occurring in a renal transplant patient are presented. The diagnosis was made on pathological examination of surgically resected tissue from the colon, spleen and stomach. The patient did not survive the infection. To the best of our knowledge, this is the 11th reported case of gastrointestinal mucormycosis in a solid organ transplant patient. The pathophysiology, incidence and prognosis of this disease are discussed.

Animals↗