Biomedical subjects

R Skinner

Publications and source records attributed to R Skinner.

At least 37 records · Page 2Linked to original sources

PubMed2001

Dietary practices, attitudes, and physiological status of collegiate freshman football players.

The purpose of this study was to determine the dietary practices, attitudes, and physiological status of freshman collegiate football players. Thirty-one freshman football players at a National Collegiate Athletic Association division I school completed a self-administered nutrition screening questionnaire designed to determine their dietary practices and attitudes. Fasting blood samples were collected and height and weight were measured. The mean age of these athletes was 18 years. These players reported eating 3.6 times per day and on the average eating out 4.8 times per week. Fast food was the most common choice when eating out (55%). Of these athletes, 42% reported the use of dietary supplements, the most popular one being creatine (36%). Although more than 90% of the athletes recognized the importance of maintaining proper hydration status, greater than 50% believed that protein supplements were necessary for muscle growth and development, protein was the primary source of energy for muscle, and vitamin and mineral supplements increased energy levels. The plasma lipid profiles of the majority (76%) of the athletes were within normal ranges. The data suggest that these athletes may require education about healthy dietary practices and on the proper use of dietary supplements. This is not only important to help improve performance but to also promote healthy dietary practices in the long term.

Adolescent↗

PubMed2000

Conformational changes in serpins: II. The mechanism of activation of antithrombin by heparin.

Antithrombin, uniquely among plasma serpins acting as proteinase inhibitors in the control of the blood coagulation cascade, circulates in a relatively inactive form. Its activation by heparin, and specifically by a pentasaccharide core of heparin, has been shown to involve release of the peptide loop containing the reactive centre from partial insertion in the A sheet of the molecule. Here we compare the structures of the circulating inactive form of antithrombin with the activated structure in complex with heparin pentasaccharide. We show that the rearrangement of the reactive centre loop that occurs upon activation is part of a widespread conformational change involving a realignment of the two major domains of the molecule. We also examine natural mutants that possess high affinity for heparin pentasaccharide, and relate the kinetics of their interaction with heparin pentasaccharide to the structural transitions occuring in the activation process.

Amino Acid Sequence↗

PubMed2000

T-cell frequency analysis does not predict the incidence of graft-versus-host disease in HLA-matched sibling bone marrow transplantation.

BACKGROUND: Graft-versus-host disease (GVHD) is a major and sometimes fatal complication of allogeneic bone marrow transplantation (BMT). The prediction of GVHD remains an important issue in preventing morbidity and mortality after allogeneic BMT. In the past 10 years, there has been great interest in using the frequency analysis of alloreactive helper and cytotoxic T lymphocyte precursors (HTLp and CTLp) to detect recipient-specific alloreactivity and thus predict GVHD in HLA-matched related and unrelated BMT. However, the results remain controversial. The intention of the present study was to investigate whether alloreactive HTLp and CTLp frequencies measured in donor peripheral blood before BMT would be a useful predictor for the occurrence of acute GVHD after HLA-matched sibling BMT. METHOD: A combined limiting dilution assay was used to determine alloreactive HTLp and CTLp frequencies for 42 HLA-matched sibling patient/donor pairs. The pretransplantation host-reactive HTLp and CTLp frequencies were then correlated with post-transplantation clinical outcomes of acute GVHD. The association between HTLp/CTLp frequencies and the incidence of acute GVHD was determined using the Fisher's exact test. RESULTS: The mean values of HTLp and CTLp frequencies for this cohort of HLA-matched sibling patient/donor pairs were 1:321,322 (range 1:71,000 to 1:1000,000) and 1:195,260 (range 1:3,717 to 1:1000,000), respectively. Acute GVHD (> or =II) was observed in one of four patients with high (>1:100,000) HTLp frequencies and 20 of 36 patients with low (<1:100,000) HTLp frequencies. Similarly, 6 of 10 patients with high (>1: 100,000) CTLp frequencies and 14 of 29 patients with low (<1:100,000) CTLp frequencies developed acute GVHD (> or =II). The overall correlation between hostreactive HTLp/CTLp frequencies and the incidence of acute GVHD in this cohort of patients was 42.5% and 53.9%, respectively. There was no significant difference in the incidence of acute GVHD between the patients with either high or low host-reactive HTLp/ CTLp frequencies (P=0.331 and 0.716, respectively). The data were also analyzed separately for the adult patient group based on GVHD prophylaxis with either cyclosporine alone or the combination of cyclosporine and methotrexate. Within these two prophylaxis groups, neither HTLp nor CTLp frequencies correlated with acute GVHD. CONCLUSION: Host-reactive HTLp and CTLp frequency analysis did not provide informative prediction for the occurrence of acute GVHD after HLA-matched sibling BMT.

Acute Disease↗

PubMed2000

Conformational changes in serpins: I. The native and cleaved conformations of alpha(1)-antitrypsin.

The serpins (SERine Proteinase INhibitors) are a family of proteins with important physiological roles, including but not limited to the inhibition of chymotrypsin-like serine proteinases. The inhibitory mechan- ism involves a large conformational change known as the S-->R (stressed-->relaxed) transition. The largest structural differences occur in a region around the scissile bond called the reactive centre loop: In the native (S) state, the reactive centre is exposed, and is free to interact with proteinases. In inhibitory serpins, in the cleaved (R) state the reactive centre loop forms an additional strand within the beta-sheet. The latent state is an uncleaved state in which the intact reactive centre loop is integrated into the A sheet as in the cleaved form, to give an alternative R state. The serpin structures illustrate detailed control of conformation within a single protein. Serpins are also an unusual family of proteins in which homologues have native states with different folding topologies. Determination of the structures of inhibitory serpins in multiple conformational states permits a detailed analysis of the mechanism of the S-->R transition, and of the way in which a single sequence can form two stabilised states of different topology. Here we compare the conformations of alpha(1)-antitrypsin in native and cleaved states. Many protein conformational changes involve relative motions of large rigid subunits. We determine the rigid subunits of alpha(1)-antitrypsin and analyse the changes in their relative position and orientation. Knowing that the conformational change is initiated by cleavage at the reactive centre, we describe a mechanism of the S-->R transition as a logical sequence of mechanical effects, even though the transition likely proceeds in a concerted manner.

Amino Acid Sequence↗

PubMed2000

Stem cell transplantation in patients with severe congenital neutropenia without evidence of leukemic transformation.

Severe congenital neutropenia (CN) (Kostmann syndrome) is a hematologic disorder characterized by a maturation arrest of myelopoiesis at the promyelocyte/myelocyte stage of development. This arrest results in severe neutropenia leading to absolute neutrophil counts (ANC) below 0.2 x 10(9)/L associated with severe bacterial infections from early infancy. Data on over 300 patients with CN collected by the Severe Chronic Neutropenia International Registry (SCNIR) beginning in 1994 indicate that more than 90% of these patients respond to recombinant human granulocyte-colony stimulating factor (r-HuG-CSF) treatment with an ANC greater than 1. 0 x 10(9)/L. For patients who are refractory to r-HuG-CSF treatment and continue to have severe and often life-threatening bacterial infections, hematopoietic stem cell transplantation is the only currently available treatment. We report on a total of 11 patients with CN reported to the SCNIR who underwent transplantation for reasons other than malignant transformation between 1976 and 1998. Of these patients, 8 were nonresponders or showed only partial response to r-HuG-CSF treatment with ongoing infections. Results from these patients suggest that transplantation of stem cells from an HLA-identical sibling is beneficial for patients refractory to r-HuG-CSF. (Blood. 2000;95:1195-1198)

Adolescent↗

PubMed2000

Conformational changes in serpins: I. The native and cleaved conformations of alpha(1)-antitrypsin.

Amino Acid Sequence↗

PubMed2000

Outcome of 69 allogeneic stem cell transplantations for Fanconi anemia using HLA-matched unrelated donors: a study on behalf of the European Group for Blood and Marrow Transplantation.

Allogeneic stem cell transplantation is the only treatment that can restore a normal hematopoiesis in Fanconi anemia (FA). In this retrospective multicenter study, we analyzed the results of this approach using HLA-matched unrelated bone marrow donors, and tried to identify covariates predicting the outcome of the transplant. From January 1985 to June 1998, 69 FA patients were transplanted with unrelated HLA-matched donors. Patients' characteristics before and after transplant were provided by the European group blood and marrow transplant registry and were analyzed in collaboration with the European Fanconi Anemia Registry. The 3-year probability of survival was 33%. Extensive malformations, a positive recipient cytomegalovirus serology, the use of androgens before transplant, and female donors were associated with a worse outcome. Primary graft failures were observed more frequently when female donors were used, mainly because the grafts contained lower nucleated cell doses per kilogram of recipient body weight compared with grafts coming from male donors. The probability of grade III-IV acute graft-versus-host disease (GVHD) was 34%. Elevated serum alanine/aspartate transaminases before transplantation; limb, urogenital tract, or nephrologic malformations; and non-T-cell-depleted grafts were predictors of severe acute GVHD. This study shows the dramatic impact of preexisting congenital malformations on the outcome of FA patients transplanted with HLA-matched unrelated donors. If the use of T-cell depletion has led to a dramatic reduction of acute GVHD incidence, no significant outcome improvement was observed with this approach, mainly because of an increased risk of graft failure. (Blood. 2000;95:422-429)

Adolescent↗

PubMed2000

Auditory function is unaffected by treatment with ifosfamide in children and adolescents.

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Adolescent↗

PubMed2000

Plasma coenzyme Q(10) in children and adolescents undergoing doxorubicin therapy.

The objective of this study was to test the hypothesis that doxorubicin treatment for cancer in childhood and adolescence causes a dose-related decrease in the concentration of plasma coenzyme Q(10). The concentration of plasma coenzyme Q(10) was measured before and after administration of doxorubicin in six patients, and before and after chemotherapy in six patients undergoing treatments that did not include doxorubicin. There was a significant increase in the concentration of plasma coenzyme Q(10) in post-treatment samples compared to pre-treatment samples in patients treated with doxorubicin (P=0.008; n=32), whereas there were no significant changes in plasma coenzyme Q(10) concentrations in patients treated with chemotherapy that did not include doxorubicin. (P=0.770; n=30). We hypothesise that the increase in plasma coenzyme Q(10) that was observed in patients undergoing doxorubicin treatment is due to release of coenzyme Q(10) from apoptotic or necrotic cardiac tissue. We conclude that the cardiotoxicity due to doxorubicin therapy does not involve acute myocardial depletion of coenzyme Q(10).

Adolescent↗

PubMed2000

Risk factors for nephrotoxicity after ifosfamide treatment in children: a UKCCSG Late Effects Group study. United Kingdom Children's Cancer Study Group.

The aim of this multicentre study was to document the nephrotoxicity associated with ifosfamide and evaluate risk factors in 148 children and young people with sarcomas who underwent investigation of renal function on one occasion each, at a median of 6 (range 1-47) months after completion of ifosfamide (median dose 62.0 (range 6.1-165.0) g/m2). Investigations included glomerular filtration rate (GFR), serum bicarbonate (HCO3) and phosphate (PO4), and renal tubular threshold for phosphate (Tmp/GFR). A clinically relevant nephrotoxicity score' was derived. GFR was < 90 ml/min/1.73 m2 in 61 of 123 evaluable patients, Tmp/GFR < 0.9-1.1 mmol/l (age-dependent) in 45/103, serum PO4 < 0.9-1.mmol/l (age-dependent) in 28/135, and serum HCO3 < 20 (< 18 in infants) mmol/l in 22/95. Of 76 fully evaluable patients: 50% had mild, 20% moderate and 8% severe nephrotoxicity. Higher total ifosfamide dose correlated significantly with greater glomerular and tubular toxicity (P < 0.01); other risk factors, including age at treatment, demonstrated no consistent significant independent effect. Chronic ifosfamide-related glomerular and proximal tubular toxicity were common in this large comprehensive study. Restriction of total ifosfamide dose to < 84 g/m2 will reduce the frequency of, but not abolish, clinically significant nephrotoxicity, whilst doses > 119 g/m2 are associated with a very high risk of severe toxicity.

Adolescent↗

PubMed1999

Dose-related nephrotoxicity of carboplatin in children.

This study investigated changes and the time course of these changes in renal function in children following treatment with carboplatin, and identified risk factors for nephrotoxicity. Glomerular and proximal renal tubular function were investigated before and up to 2 years after treatment in 23 children who received carboplatin. The main findings were reduced glomerular filtration rate (GFR), and increased renal tubular loss of magnesium, manifested by a low serum magnesium (S Mg). The mean fall in GFR was 22 ml min(-1) 1.73 m(-2) (P = 0.012), and in S Mg it was 0.17 mmol l(-1) (P = 0.0077). No patient had a clinically important reduction in GFR, and only one patient had symptomatic hypomagnesaemia. GFR and S Mg did not change over time after completion of treatment. Cumulative dose (CD) of carboplatin was inversely related to mean S Mg at the end of treatment (P = 0.031), and directly related to the fall in S Mg (P < 0.001). Calculated cumulative area under the plasma concentration versus time curve (AUC) of carboplatin was inversely related to S Mg after treatment (P = 0.004). Dose intensity (DI) of carboplatin was not shown to be related to S Mg following treatment. CD, AUC and DI of carboplatin were not related to GFR, nor change in GFR, after treatment. High CDs of carboplatin may be associated with evidence of renal damage qualitatively similar to but less severe than that caused by cisplatin. GFR and SMg should be carefully monitored when high CDs of carboplatin are used, or if carboplatin is combined with other nephrotoxic chemotherapy.

Adolescent↗

PubMed1999

Delayed engraftment and mixed chimerism after HLA-identical sibling donor BMT in Fanconi anaemia.

A 12-year-old girl with Fanconi anaemia (FA) received a bone marrow transplant from her HLA-identical brother following conditioning with cyclophosphamide (20 mg/kg), thoraco-abdominal radiation (TAI) (4 Gy) and equine anti-thymocyte globulin (ATG) (90 mg/kg). Engraftment was delayed and initially tenuous, and was followed by mixed chimerism (MC) over a follow-up period of 2 years. DNA analysis of engraftment was performed on whole peripheral blood and on separated granulocytes, B and T lymphocytes using PCR detection of CA tandem repeat polymorphisms. At 10 weeks post BMT, granulocytes were predominantly donor, but B and T lymphocytes recipient, in origin. Over the subsequent 90 weeks, granulocytes and B lymphocytes were donor-derived, whilst T cells showed persistent MC but with an increasing donor component. Marrow haemopoietic function (Hb, ANC and platelet count) improved gradually in parallel with a rise in the proportion of donor lymphocyte engraftment. We postulate that a population of recipient lymphocytes survived conditioning and in turn delayed the development of full donor chimerism. Although transient MC has been described after allogeneic BMT in FA, its association with delayed engraftment, and persistence for more than 1 year post BMT, has not been documented clearly.

Bone Marrow Transplantation↗

PubMed1999

The role of protective clothing in infection prevention in patients undergoing autologous bone marrow transplantation.

PURPOSE/OBJECTIVES: To determine the efficacy of cover gowns and shoe covers in the prevention of infection in patients undergoing autologous bone marrow transplantation (BMT). DESIGN: Randomized two-group controlled clinical trial. SETTING: Adult BMT unit of a university teaching hospital in the Southeastern United States. SAMPLE: 40 women and men receiving an autologous BMT for hematologic and solid tumor malignancies. Patients were assigned randomly to control or experimental groups. Thirty-one patients completed the study. Inclusion criteria required that patients be at least 18 years of age and not have received a previous autologous BMT. METHODS: Data were collected from the patients' medical records. Characteristics of the distributions for the main research variables were compared between the control group (caregivers who wore cover gowns and shoe covers) and experimental group (caregivers who wore no covers). MAIN RESEARCH VARIABLES: Time to first antibiotic treatment and length of antibiotic therapy. FINDINGS: Cover gowns and shoe covers worn by caregivers provided no benefit for this group of 31 patients. The differences in time to first antibiotic and length of antibiotic treatment were not statistically significant between the two groups. CONCLUSIONS: The mean and median number of hours to first antibiotic treatment for adult autologous BMT recipients in the control group exceeded the corresponding time for those in the experimental group by only one hour and four hours, respectively. The potential benefits and risks of cover gown and shoe cover usage by caregivers of autologous BMT recipients should be reexamined in larger randomized trials. IMPLICATIONS FOR NURSING PRACTICE: The elimination of cover gowns and shoe covers in caring for patients undergoing autologous BMT will save nursing time and hospital resources as well as eliminate one isolation barrier experienced by patients.

Adult↗

PubMed1998

The N-terminal segment of antithrombin acts as a steric gate for the binding of heparin.

The binding of heparin causes a conformational change in antithrombin to give an increased heparin binding affinity and activate the inhibition of thrombin and factor Xa. The areas of antithrombin involved in binding heparin and stabilizing the interaction in the high-affinity form have been partially resolved through the study of both recombinant and natural variants. The role of a section of the N-terminal segment of antithrombin, residues 22-46 (segment 22-46), in heparin binding was investigated using rapid kinetic analysis of the protein cleaved at residues 29-30 by limited proteolysis with thermolysin. The cleaved antithrombin had 5.5-fold lowered affinity for heparin pentasaccharide and 1.8-fold for full-length, high-affinity heparin. It was shown that, although the initial binding of heparin is slightly enhanced by the cleavage, it dissociates much faster from the cleaved form, giving rise to the overall decrease in heparin affinity. This implies that the segment constituting residues 22-46 in the N terminus of antithrombin hinders access to the binding site for heparin, hence the increased initial binding for the cleaved form, whereas, when heparin is bound, segment 22-46 is involved in the stabilization of the binding interaction, as indicated by the increased dissociation constant. When the heparin pentasaccharide is bound to antithrombin prior to incubation with thermolysin, it protects the N-terminal cleavage site, implying that segment 22-46 moves to interact with heparin in the conformational change and thus stabilizes the complex.

Antithrombin III↗

PubMed1998

Implications for function and therapy of a 2.9 A structure of binary-complexed antithrombin.

The crystal structure of a binary complex of human antithrombin with a peptide of the same sequence as its reactive loop (P14-P3) has been determined at 2.9 A. The peptide binds as the middle strand s4A in the A beta-sheet, homologously to that of the reactive loop in the latent and cleaved forms of antithrombin. Peptide binding results in the complete expulsion of the hinge region of the loop from the A beta-sheet although the conformation differs from that of heparin-activated antithrombin. The 36-fold increase in the rate of reaction of the binary complex with factor Xa indicates that full loop expulsion alone is not sufficient for complete heparin activation of antithrombin but that this is also dependent on the overall conformation of the molecule. Previous studies have demonstrated that reactive loop peptides can block or reverse the polymerisation of serpins associated with cirrhosis and thrombosis. The antithrombin binary complex structure defines the precise localisation of the blocking peptide in a serpin and provides the basis for rational drug design for mimetics that will prevent polymerisation in vivo and so ameliorate the associated disease.

Amino Acid Sequence↗

PubMed1998

Acute changes in urine protein excretion may predict chronic ifosfamide nephrotoxicity: a preliminary observation.

PURPOSE: To evaluate proteinuria occurring early after ifosfamide therapy and to assess the use of changes in proteinuria in the prediction of severe chronic nephrotoxicity. METHODS: One-dimensional sodium dodecyl sulphate polyacrylamide gel electrophoresis was used to characterize urine protein excretion in 12 children with solid tumours before and after the first course of ifosfamide treatment, and in 24 healthy children. Chronic nephrotoxicity was evaluated at 6 months after ifosfamide treatment and graded as none, mild, moderate or severe. RESULTS: Urine from healthy children and from 10 of 12 patients before ifosfamide therapy showed a protein band with a molecular weight (95.4 kDa) corresponding to that of Tamm-Horsfall protein but no lower molecular weight proteins. After the first course of ifosfamide this 95.4-kDa protein was lost in six of ten patients with a concomitant appearance of a low molecular weight proteinuria (< 70 kDa) in eight. Tamm-Horsfall protein was lost in two of five patients who subsequently developed no or mild nephrotoxicity and in four of five patients who subsequently developed moderate or severe nephrotoxicity. CONCLUSIONS: Early subclinical changes in urine protein excretion after ifosfamide, manifested by a loss of Tamm-Horsfall protein excretion, may be predictive of subsequent chronic nephrotoxicity.

Adolescent↗

PubMed1998

An atlas of serpin conformations.

The serpins are a family of proteins that inhibit chymotrypsin-like serine proteinases, with an unusual mechanism involving a large conformational change known as the stressed-->relaxed (S-->R) transition. This article is a guide to the known serpin conformations and their biological significance.

Amino Acid Sequence↗

PubMed1998

Cisplatin dose rate as a risk factor for nephrotoxicity in children.

The purpose of the study was to evaluate the incidence, risk factors and changes in severity with time of cisplatin nephrotoxicity in children. A total of 35 children underwent measurement of glomerular filtration rate (GFR) and tubular function after completion of cisplatin chemotherapy. No child received ifosfamide. A clinically relevant 'nephrotoxicity score' was derived from GFR and serum magnesium. Follow-up studies were performed in 16 children at 1 year and in 15 at 2 years after cisplatin. Considerable interpatient variability in nephrotoxicity was observed. Treatment was modified in three patients because of nephrotoxicity. GFR was low in 18 out of 31 patients. Proximal nephron toxicity caused hypomagnesaemia in ten patients and hypocalcaemia in five patients. Elevated urinary N-acetylglucosaminidase excretion was seen in 22 out of 30 children, indicating subclinical tubular toxicity. Nephrotoxicity was less severe in children who received cisplatin courses at a dose rate of 40 mg m(-2) day(-1) than in those who received higher dose rates (P < 0.005), but there was no correlation with total dose received. Follow-up studies revealed partial recovery of GFR (P < 0.05). Glomerular and proximal nephron toxicity are common in children treated with cisplatin, and more severe at higher dose rates. Despite partial recovery of GFR, the long-term outcome of nephrotoxicity remains unknown and careful monitoring of chronic toxicity is necessary.

Adolescent↗