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Biomedical subjects

M Barnes

Publications and source records attributed to M Barnes.

At least 19 recordsLinked to original sources
PubMed2000

Fyn and Lyn phosphorylate the Fc receptor gamma chain downstream of glycoprotein VI in murine platelets, and Lyn regulates a novel feedback pathway.

Activation of platelets by collagen is mediated by the complex glycoprotein VI (GPVI)/Fc receptor gamma (FcR gamma chain). In the current study, the role of 2 Src family kinases, Fyn and Lyn, in GPVI signaling has been examined using murine platelets deficient in one or both kinases. In the fyn(-/-) platelets, tyrosine phosphorylation of FcR gamma chain, phopholipase C (PLC) activity, aggregation, and secretion are reduced, though the time of onset of response is unchanged. In the lyn(-/-) platelets, there is a delay of up to 30 seconds in the onset of tyrosine phosphorylation and functional responses, followed by recovery of phosphorylation and potentiation of aggregation and alpha-granule secretion. Tyrosine phosphorylation and aggregation in response to stimulation by collagen-related peptide is further attenuated and delayed in fyn(-/-)lyn(-/-) double-mutant platelets, and potentiation is not seen. This study provides the first genetic evidence that Fyn and Lyn mediate FcR immune receptor tyrosine-based activation motif phosphorylation and PLC gamma 2 activation after the ligation of GPVI. Lyn plays an additional role in inhibiting platelet activation through an uncharacterized inhibitory pathway. (Blood. 2000;96:4246-4253)

Animals↗
PubMed2000

Personal medical services. Friends and relations.

Personal medical services pilot schemes remain internally focused. In many areas hospital doctors' willingness to work with general practice has been hampered by chief executives' fear of loss of income. Health authorities have generally failed to take responsibility for the pilot schemes. There are some fears of the schemes creating inequity at local level.

Cooperative Behavior↗
PubMed2000

Primary care. This is your pilot speaking.

An evaluation of 14 personal medical services pilot schemes has found the GPs involved welcome the reduction in paperwork. The flexibility in funding of the schemes has allowed GPs greater leeway in managing their workload. Some of the financial risks of running a practice have been removed. It is questionable whether the schemes are fully using the freedoms envisaged. Some schemes reported a lack of support from their health authority.

Contract Services↗
PubMed2000

Botulinum toxin (Dysport) treatment of hip adductor spasticity in multiple sclerosis: a prospective, randomised, double blind, placebo controlled, dose ranging study.

OBJECTIVE: To define a safe and effective dose of Dysport for treating hip adductor spasticity. METHODS: Patients with definite or probable multiple sclerosis, and disabling spasticity affecting the hip adductor muscles of both legs, were randomised to one of four treatment groups. Dysport (500, 1000, or 1500 Units), or placebo was administered by intramuscular injection to these muscles. Patients were assessed at entry, and 2, 4 (primary analysis time-point), 8, and 12 weeks post-treatment. RESULTS: A total of 74 patients were recruited. Treatment groups were generally well matched at entry. The primary efficacy variables-passive hip abduction and distance between the knees-improved for all groups. The improvement in distance between the knees for the 1500 Unit group was significantly greater than placebo (p = 0.02). Spasm frequency was reduced in all groups, but muscle tone was reduced in the Dysport groups only. Pain was reduced in all groups, but improvements in hygiene scores were evident only in the 1000 Unit and 1500 Unit groups. Duration of benefit was significantly longer than placebo for all Dysport groups (p<0.05). Adverse events were reported by 32/58 (55%) Dysport patients, and by 10/16 (63%) placebo patients. Compared with the two lower dose groups, twice as many adverse events were reported by the 1500 Unit group (2.7/patient). The incidence of muscle weakness was higher for the 1500 Unit group (36%) than for placebo (6%). The response to treatment was considered positive by two thirds of the patients in the 500 Unit group, and by about half the patients in the other groups. CONCLUSION: Dysport reduced the degree of hip adductor spasticity associated with multiple sclerosis, and this benefit was evident despite the concomitant use of oral antispasticity medication and analgesics. Although evidence for a dose response effect was not statistically significant, there was a clear trend towards greater efficacy and duration of effect with higher doses of Dysport. Dysport treatment was well tolerated, with no major side effects seen at doses up to 1500 Units. The optimal dose for hip adductor spasticity seems to be 500-1000 Units, divided between both legs.

Adult↗
PubMed1999

Human cathepsin V functional expression, tissue distribution, electrostatic surface potential, enzymatic characterization, and chromosomal localization.

Cathepsin V, a thymus and testis-specific human cysteine protease, was expressed in Pichia pastoris, and its physicokinetic properties were determined. Recombinant procathepsin V is autocatalytically activated at acidic pH and is effectively inhibited by various cysteine protease class-specific inhibitors. The S2P2 subsite specificity of cathepsin V was found to be intermediate between those of cathepsins S and L. The substrate binding pocket, S2, accepted both aromatic and nonaromatic hydrophobic residues, whereas cathepsins L and S preferred either an aromatic or nonaromatic hydrophobic residue, respectively. In contrast to cathepsin L, but similar to cathepsin S, cathepsin V exhibited only a very weak collagenolytic activity. Furthermore, cathepsin V was determined to be significantly more stable at mildly acidic and neutral pH than cathepsin L, but distinctly less stable than cathepsin S. A homology structure model of cathepsin V revealed completely different electrostatic potentials on the molecular surface when compared with human cathepsin L. The model-based electrostatic potential of human cathepsin V was neutral to weakly positive at and in the vicinity of the active site cleft, whereas that of cathepsin L was negative over extended regions of the surface. Surprisingly, the electrostatic potential of the human cathepsin V model structure resembled that of the model structure of mouse cathepsin L. These differences in the electrostatic potential at the molecular surfaces provide a reactivity determinant that may be the source of differences in substrate selectivity and pH stability. Cathepsin V was mapped to the chromosomal region 9q22.2, a site adjacent to the cathepsin L locus. The high sequence identity and the overlapping chromosomal gene loci suggest that both proteases evolved from an ancestral cathepsin L-like precursor by gene duplication.

Amino Acid Sequence↗
PubMed1999

An advanced generation of adenoviral vectors selectively enhances gene transfer for ovarian cancer gene therapy approaches.

OBJECTIVE: We hypothesized that incorporation of an integrin binding Arg-Gly-Asp (RGD)-containing peptide to the HI loop of the adenovirus fiber knob would allow enhanced, coxsackie-adenovirus receptor-independent gene transfer by modified Ad vector in the context of ovarian cancer. METHODS: Ovarian cancer cell lines, primary ovarian cancer cells, primary tumor explants, and mesothelial tissue were transfected with luciferase encoding adenovirus (AdCMVLuc) or a genetically modified adenovirus (Ad5lucRGD) which contained an RGD motif within the HI loop of the knob. The luciferase activity was measured and the transduction efficiencies of both viruses were compared. RESULTS: In all established ovarian cell lines and primary tumor cell samples there was dramatically augmented gene transfer observed with the Ad5lucRGD compared to AdCMVLuc. The enhanced gene transfer in ovarian cancer cell lines ranged from 2.5- to 471.6-fold, in ascites samples from 26.1- to 64.0-fold, and in tumor explants from 1.6- to 11.1-fold. Although gene transfer to normal mesothelial tissue was slightly augmented by RGD retargeting, the level of gene transfer was much lower than that seen in ovarian cancer cells. CONCLUSION: This study demonstrates that genetically altered adenoviruses with modified tropism are capable of more efficient gene transfer in the context of ovarian cancer. The higher level of transfer with respect to peritoneal mesothelium can be exploited to enhance the therapeutic index of interventions using adenoviral vectors. Studies are warranted, therefore, to determine the in vivo utility of this targeted vector approach in the context of gene therapeutic strategies for cancer of the ovary.

Adenoviridae↗
PubMed1999

Research in midwifery--the relevance of a feminist theoretical framework.

As midwifery develops as a discipline and new models of care are introduced within maternity services, research activity and inquiry into practice and professional issues will be required. This paper suggests that an appropriate theoretical underpinning for research in midwifery is one that is based on feminist theory. It is argued that by adopting this approach, midwifery practice will focus on the needs of women and change in the provision of services for childbearing women will be in response to women's evaluation of existing services. By addressing the needs of women it is argued that the profession will also benefit, as the role of midwifery in the health care of childbearing women will be defined.

Female↗
PubMed1999

Hypertrophic response to hemodynamic overload: role of load vs. renin-angiotensin system activation.

Myocardial hypertrophy is one of the basic mechanisms by which the heart compensates for hemodynamic overload. The mechanisms by which hemodynamic overload is transduced by the cardiac muscle cell and translated into cardiac hypertrophy are not completely understood. Candidates include activation of the renin-angiotensin system (RAS) and angiotensin II receptor (AT1) stimulation. In this study, we tested the hypothesis that load, independent of the RAS, is sufficient to stimulate cardiac growth. Four groups of cats were studied: 14 normal controls, 20 pulmonary artery-banded (PAB) cats, 7 PAB cats in whom the AT1 was concomitantly and continuously blocked with losartan, and 8 PAB cats in whom the angiotensin-converting enzyme (ACE) was concomitantly and continuously blocked with captopril. Losartan cats had at least a one-log order increase in the ED50 of the blood pressure response to angiotensin II infusion. Right ventricular (RV) hypertrophy was assessed using the RV mass-to-body weight ratio and ventricular cardiocyte size. RV hemodynamic overload was assessed by measuring RV systolic and diastolic pressures. Neither the extent of RV pressure overload nor RV hypertrophy that resulted from PAB was affected by AT1 blockade with losartan or ACE inhibition with captopril. RV systolic pressure was increased from 21 +/- 3 mmHg in normals to 68 +/- 4 mmHg in PAB, 65 +/- 5 mmHg in PAB plus losartan and 62 +/- 3 mmHg in PAB plus captopril. RV-to-body weight ratio increased from 0.52 +/- 0.04 g/kg in normals to 1.11 +/- 0.06 g/kg in PAB, 1.06 +/- 0.06 g/kg in PAB plus losartan and 1.06 +/- 0.06 g/kg in PAB plus captopril. Thus 1) pharmacological modulation of the RAS with losartan and captopril did not change the extent of the hemodynamic overload or the hypertrophic response induced by PAB; 2) neither RAS activation nor angiotensin II receptor stimulation is an obligatory and necessary component of the signaling pathway that acts as an intermediary coupling load to the hypertrophic response; and 3) load, independent of the RAS, is capable of stimulating cardiac growth.

Angiotensin II↗
PubMed1999

Conditional survival among patients with carcinoma of the lung.

OBJECTIVE: One- and 5-year probabilities of survival or death change once a patient has already survived > or = 1 year after diagnosis. The current paper reports these probabilities for lung cancer patients according to histologic subtype, stage, and age at diagnosis. METHODS: Cumulative observed survival rates were calculated and compared among 95,283 patients with histologically confirmed lung cancer (diagnosed from 1983 to 1992 and followed through 1995) by the life-table method using population-based tumor registries participating in the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute. On the basis of the cumulative survival estimates, we derived the probability of death in the next year, conditioned on having already survived to the start of the year (annual hazards), and the probability of survival conditioned on having already survived > or = 1 year (conditional survival). These rates were reported according to histologic subtype, stage, and age groups. RESULTS: At the time of diagnosis, annual hazard rates differ greatly among histologic subtypes. However, by 5 years after diagnosis, the rates become similar. Bronchioloalveolar carcinoma displays the lowest annual hazards and small-cell carcinoma displays the highest annual hazards. Stage-age subcategories within histologic subtypes continue to show large differences in annual hazard rates. Five-year conditional survival probabilities are also reported, providing survival information that is consistent to that obtained from the annual hazards. CONCLUSIONS: One- and 5-year prognosis for lung cancer patients is influenced by years already survived and histology, stage, and age at diagnosis. Annual hazards and conditional survival provides useful and more relevant information than conventional survival estimates for patients and their physicians. These statistics can be directly obtained from cumulative survival estimates and should be more widely reported.

Adenocarcinoma↗
PubMed1998

Tissue restricted expression of two human Frzbs in preadipocytes and pancreas.

Frzb is a newly discovered family of secreted glycoproteins that function to modulate signaling activity of Wnt. Frzb proteins share sequence homology with the extracellular domain of the Wnt receptor (frizzled) and are capable of binding to Wnt. Thus, Frzb functions to antagonize Wnt activity by sequestering Wnt and preventing its binding to the frizzled receptor. Since the initial identification of bovine and human Frzb, several related members of this family have been isolated from rodent and human. In this paper, we describe the cloning and expression of two human frzb homologues termed hFRP-1b and hFRP-2. These human FRPs share significant homology to mouse sFRP-1 and sFRP-2 (55 and 98% identity at amino acid level, respectively). Northern blot experiments revealed that these Frzb homologues have highly restricted tissue distribution. hFRP-1b is exclusively expressed in pancreatic tissue while high levels of hFRP-2 were found in adipose tissue. In addition, low levels of hFRP-2 were also observed in other tissues including heart, pancreas and muscle. Remarkably, FRP-2 is predominantly expressed in un-differentiated preadipocytes in both rodent and man. The expression of FRP-2 is also significantly reduced in fat pads from obese mice. Taken together, these data indicate that distinctive members of the Frzb family exhibit different expression patterns in vivo, suggesting their ability to modulate diverse aspects of Wnt signaling. The expression and dysregulation of sFRP-2 in fat and obesity also suggest a potential roles on the Wnt signaling pathway in the pathology of obesity and related metabolic diseases. Molecular cloning and expression of these Frzbs will allow detailed molecular and biochemical analysis of Wnt-Frzb interaction and their impact on Wnt-Frizzled receptor signal transduction.

3T3 Cells↗
PubMed1998

Crystal structure of recombinant human tissue kallikrein at 2.0 A resolution.

Human tissue kallikrein, a trypsin-like serine protease involved in blood pressure regulation and inflammation processes, was expressed in a deglycosylated form at high levels in Pichia pastoris, purified, and crystallized. The crystal structure at 2.0 A resolution is described and compared with that of porcine kallikrein and of other trypsin-like proteases. The active and S1 sites (nomenclature of Schechter I, Berger A, 1967, Biochem Biophys Res Commun 27:157-162) are similar to those of porcine kallikrein. Compared to trypsin, the S1 site is enlarged owing to the insertion of an additional residue, cis-Pro 219. The replacement Tyr 228 --> Ala further enlarges the S1 pocket. However, the replacement of Gly 226 in trypsin with Ser in human tissue kallikrein restricts accessibility of substrates and inhibitors to Asp 189 at the base of the S1 pocket; there is a hydrogen bond between O delta1Asp189 and O gammaSer226. These changes in the architecture of the S1 site perturb the binding of inhibitors or substrates from the modes determined or inferred for trypsin. The crystal structure gives insight into the structural differences responsible for changes in specificity in human tissue kallikrein compared with other trypsin-like proteases, and into the structural basis for the unusual specificity of human tissue kallikrein in cleaving both an Arg-Ser and a Met-Lys peptide bond in its natural protein substrate, kininogen. A Zn+2-dependent, small-molecule competitive inhibitor of kallikrein (Ki = 3.3 microM) has been identified and the bound structure modeled to guide drug design.

Amino Acid Sequence↗
PubMed1997

Glycoprotein VI is the collagen receptor in platelets which underlies tyrosine phosphorylation of the Fc receptor gamma-chain.

We have recently shown that collagen activates platelets through a pathway dependent on the Fc receptor gamma-chain and the tyrosine kinase Syk. We report here that the Fc receptor gamma-chain and the candidate collagen receptor glycoprotein VI (GPVI) co-associate. Furthermore, cross-linking GPVI stimulates a similar pattern of tyrosine phosphorylation to that stimulated by collagen, including tyrosine phosphorylation of Fc receptor gamma-chain. These results support a model where GPVI couples collagen-stimulation of platelets to phosphorylation of the Fc receptor gamma-chain leading to activation of Syk and phospholipase Cgamma2.

Blood Platelets↗