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Biomedical subjects

K Richardson

Publications and source records attributed to K Richardson.

At least 19 recordsLinked to original sources
PubMed2006

Nonlinear optical properties of glasses in the system Ge/Ga-Sb-S/Se.

We report n2 measurements of selected chalcogenide glasses using a modified Z-scan technique. Measurements were made with picosecond pulses emitted by a 10 Hz Q-switched, mode-locked Nd:YAG laser at 1064 nm under conditions suitable to characterize ultrafast nonlinearities. The nonlinear index increases significantly up to 246 times the n2 for fused silica with an increase of SbS3 units and also very slightly with the replacement of Ge by Ga or S by Se. We have attributed the variation of n2 to the total number of electronic lone pairs and to the position of the absorption band gap, which are induced by the presence of GaS4 units or Se-Se bonds in the glass structure.

Journal Article↗
PubMed2006

A randomized, placebo-controlled trial of intermittent preventive treatment with sulphadoxine-pyrimethamine in Gambian multigravidae.

We investigated the ability of intermittent preventive treatment in pregnancy (IPTp) with sulphadoxine/pyrimethamine to prevent anaemia and low birthweight in Gambian multigravidae. Between July 2002 and February 2004, 2688 multigravidae living in a rural area of The Gambia received SP (1346 women) or placebo (1342 women) up to four times during pregnancy and were followed until 6-weeks post-partum. Shortly after delivery, 10.7% of women in the intervention group and 8.8% in the control group were severely anaemic [Hb < 7 g/dl, risk difference = 0.02 (95% CI -0.01, 0.04), P = 0.17]. The overall mean birthweight of infants born to women who had received SP (3103 g) was very similar to that observed in infants born to women in the control group [3075 g; difference = 28 g (95% CI -11 g, 67 g), P = 0.16]. However, among women who did not use a bednet (either insecticide treated or untreated), infants born to women who had received SP weighed more than infants born to women in the control group [3147 g vs. 3044 g; difference 143 g (95% CI 53 g, 232 g), interaction test P < 0.001]. This study did not show that IPTp with SP benefited Gambian multigravidae overall but that it may benefit a sub-group of women who do not use a bednet. In areas such as The Gambia, provision of insecticide-treated bednets to multigravidae may provide an adequate means of protection against malaria in pregnancy without the need for additional IPTp.

Adolescent↗
PubMed2006

Interferon-based combination anti-viral therapy for hepatitis C virus after liver transplantation: a review and quantitative analysis.

Recurrence of hepatitis C virus (HCV) infection after liver transplantation (LT) is universal. However, the efficacy, tolerability and safety of combination interferon and ribavirin (IFN-RIB) or peginterferon and ribavirin (PEG-RIB) anti-viral therapies post-LT are uncertain. We performed a comprehensive search of major medical databases (1980-2005) and conference proceedings (1996-2005). The main outcome measure was sustained virological response (SVR, undetectable HCV RNA) at 6 months. Summary estimates were calculated using random-effects models. Twenty-seven IFN-RIB and 21 PEG-RIB studies were included. IFN-RIB was associated with a pooled SVR rate of 24% (95% CI, 20-27%), while PEG-RIB was associated with an SVR rate of 27% (23-31%). Pooled discontinuation rates were 24% (21-27%) with IFN-RIB and 26% (20-32%) with PEG-RIB. The pooled rate of acute graft rejection was 2% (1-3%) with IFN-RIB and 5% (3-7%) with PEG-RIB. IFN-RIB and PEG-RIB therapies in HCV infection post-LT were associated with similar but overall low SVR and were poorly tolerated. The rate of acute rejection was small. The therapeutic advantage of PEG-RIB therapy observed in non-transplant chronic HCV infection appears to be attenuated post-LT. Clinical trials are needed to evaluate reasons for this post-transplant therapeutic disadvantage and to find strategies to ameliorate them.

Antiviral Agents↗
PubMed2003

Mapping and pyramiding of qualitative and quantitative resistance to stripe rust in barley.

The identification and location of sources of genetic resistance to plant diseases are important contributions to the development of resistant varieties. The combination of different sources and types of resistance in the same genotype should assist in the development of durably resistant varieties. Using a doubled haploid (DH), mapping population of barley, we mapped a qualitative resistance gene ( Rpsx) to barley stripe rust in the accession CI10587 (PI 243183) to the long arm of chromosome 1(7H). We combined the Rpsx gene, through a series of crosses, with three mapped and validated barley stripe rust resistance QTL alleles located on chromosomes 4(4H) (QTL4), 5(1H) (QTL5), and 7(5H) (QTL7). Three different barley DH populations were developed from these crosses, two combining Rpsx with QTL4 and QTL7, and the third combining Rpsx with QTL5. Disease severity testing in four environments and QTL mapping analyses confirmed the effects and locations of Rpsx, QTL4, and QTL5, thereby validating the original estimates of QTL location and effect. QTL alleles on chromosomes 4(4H) and 5(1H) were effective in decreasing disease severity in the absence of the resistance allele at Rpsx. Quantitative resistance effects were mainly additive, although magnitude interactions were detected. Our results indicate that combining qualitative and quantitative resistance in the same genotype is feasible. However, the durability of such resistance pyramids will require challenge from virulent isolates, which currently are not reported in North America.

Chromosome Mapping↗
PubMed2001

Drink and drug driving: what's the skipper up to?

OBJECTIVE: Since the introduction of random breath testing (RBT) in Australia there has been a significant reduction in drink driving, as measured by alcohol-related crashes. In contrast, the prevalence of drug-related road fatalities is on the increase. One strategy that targets drink- and/or drug-driving is the promotion of a designated driver or 'skipper'. This paper determines to what extent the 'skipper' is driving alcohol or drug-free. METHODS: A convenience sample of university students from The University of Western Australia completed a questionnaire that included questions on drug and alcohol use while driving as the designated 'skipper'. RESULTS: The mean age of the 286 participants was 21 years. Among the students who reported acting as the designated 'skipper' during the past 12 months, 26% of the students drove, as the designated 'skipper,' while feeling the effects of alcohol. Similarly, 18% of students who reported using drugs drove, as the 'skipper', while feeling the effects of the drug. Multivariate analysis identified that the presence of random drug testing would act as a deterrent for drug driving while the designated 'skipper'. CONCLUSION: Although three-quarters of designated 'skippers' do not drink and/or drug drive, a sizeable proportion of young drivers continue to place themselves and, more importantly, their passengers and the entire community at an elevated risk of injury. IMPLICATIONS: Campaigns that target the responsibility of the 'skipper' and that are included as part of drink-driving campaigns would be beneficial. It is premature to be making recommendations on random drug testing for drivers.

Adult↗
PubMed2001

The nursing outcomes classification: its relevance to school nursing.

Two surveys were conducted to determine school nurses' perceptions of the relevance of 190 outcomes developed by the Nursing Outcomes Classification (NOC) research team to school nursing practice. First, a national random survey of members of the National Association of School Nurses was conducted. Participants were asked to identify the percentage of children and families for whom school nurses affect health outcomes. Usable responses were returned from 227 school nurses (22% response rate). Ninety outcomes were perceived as relevant for 30% or more of children and families; 8 outcomes were perceived as relevant for 50% or more of children and families. A second survey--targeting state representatives attending a school nursing leadership meeting--was conducted using a revised version of the instrument. The legend was changed to degree of relevance to school nursing practice, with a response scale of 0 to 10. Usable responses were returned from 31 state representatives (41% response rate). The means of 172 of 190 outcomes were above 5 (median point on the 10-point scale of relevance). The findings of both surveys indicate that a large number of NOC outcomes are useful for documentation of the effectiveness of nursing interventions in school settings.

Adolescent↗
PubMed2000

Genetic control of susceptibility to UV-induced immunosuppression by interacting quantitative trait loci.

Ultraviolet B radiation (290-320 nm) initiates a dose and wavelength dependent down-regulation of cell-mediated immunity which is critical in experimental ultraviolet radiation (UV) carcinogenesis, preventing immune attack on highly antigenic UV-induced tumors. UV-induced immunosuppression has been demonstrated in humans and may be a risk factor for skin cancer. In this study, we have investigated genetic linkage of the autosomal loci controlling this trait. Previously, we had derived a model describing control of susceptibility to UV-induced immunosuppression in inbred mice by unlinked interacting autosomal and X-linked loci. A genome-wide scan using MIT microsatellite markers was carried out on 100 backcross (BALB/c x (BALB/c x C57BL/6) F1) mice derived from the inbred strains BALB/c (low susceptibility) and C57BL/6 (high susceptibility) and tested for systemic UV-induced immunosuppression of a contact hypersensitivity response. The values for % suppression for each animal and the genotype data were used to investigate genetic linkage by multiple regression analysis. Significance was assessed using the permutation test. Both main effects and interactive effects were investigated, first with each genotype marker singly, and secondly, in a novel approach using markers pairwise. A joint model was derived in which all loci and pairs of loci identified were included simultaneously in a multiple regression model. This model indicates four quantitative trait loci (QTLs) with significant main effects, one on chromosome 10 which decreased susceptibility to UV-induced immunosuppression and QTLs on chromosomes 6, 17 and 1 which increased susceptibility. Additionally, loci on chromosomes 14 and 19 showed significant interaction with the locus on chromosome 1. Further investigation indicated a potential three-way interaction involving the loci on chromosomes 1, 14 and 19.

Animals↗
PubMed1999

GIGANTEA: a circadian clock-controlled gene that regulates photoperiodic flowering in Arabidopsis and encodes a protein with several possible membrane-spanning domains.

Flowering of Arabidopsis is promoted by long days and delayed by short days. Mutations in the GIGANTEA (GI) gene delay flowering under long days but have little or no effect under short days. We have now isolated the GI gene and show that it encodes a novel, putative membrane protein. By comparing the sequence of the Arabidopsis gene with that of a likely rice orthologue and by sequencing mutant alleles, we identify regions of the GI protein that are likely to be important for its function. We show that GI expression is regulated by the circadian clock with a peak in transcript levels 8-10 h after dawn. The timing, height and duration of this peak are influenced by daylength. We analysed the interactions between GI and the LHY, CCA1 and ELF3 genes, previously shown to affect daylength responses; we show that the rhythmic pattern of GI expression is altered in the elf3, CCA1-OX and lhy genotypes, and that CCA1 and LHY expression are reduced by gi mutations. Our results are consistent with the idea that GI plays an important role in regulating the expression of flowering time genes during the promotion of flowering by photoperiod.

Alleles↗
PubMed1999

Comparison of the effects of asparaginase administered subcutaneously versus intramuscularly for treatment of multicentric lymphoma in dogs receiving doxorubicin.

OBJECTIVE: To determine the effectiveness and safety of asparaginase administered s.c. versus i.m. for treatment of multicentric lymphoma in dogs receiving doxorubicin. DESIGN: Prospective study. ANIMALS: 49 dogs with multicentric lymphoma. PROCEDURE: Dogs were treated with doxorubicin every 3 weeks, for a total of 5 treatments, and were given 3 weekly treatments of asparaginase, s.c. or i.m. Using high-performance liquid chromatography, mean plasma asparagine, aspartic acid, glutamine, and glutamic acid concentrations were determined in dogs before and during treatment with asparaginase (10,000 U/m2 of body surface area, once a week for 3 weeks). Asparaginase was administered s.c. in 23 dogs and i.m. in 26 dogs. Variables evaluated included time to response to chemotherapy, remission and survival times, and clinical and serum biochemical indicators of toxicoses. RESULTS: Using the World Health Organization's staging system for lymphoma, 30 dogs were in clinical stage III and 19 were in clinical stage IV. One week after asparaginase treatment, plasma asparagine concentrations were low and plasma aspartic acid, glutamine, and glutamic acid concentrations were high. Differences in plasma amino acid concentrations were not found between s.c. and i.m. groups. For dogs in clinical stage IV, i.m. administration of asparaginase significantly decreased the number of days to complete remission, compared with s.c. administration (8 vs 17 days, respectively). For dogs in clinical stage III, i.m. administration favorably increased the duration of first remission (191 vs 103 days) and survival time (289 vs 209 days). Overall, dogs treated i.m. had a faster response to chemotherapy (9 vs 15 days), a longer remission (191 vs 109 days), and a longer survival time (286 vs 198 days), compared with all dogs treated s.c. Asparaginase toxicoses were not observed regardless of the route of administration. CLINICAL IMPLICATIONS: For dogs with multicentric lymphoma that are receiving doxorubicin, i.m. treatment with asparaginase is more effective than s.c. treatment.

Animals↗
PubMed1999

Laryngeal swabs for diagnosing tuberculosis.

The value of smear and culture of laryngeal swabs as a method of confirming pulmonary tuberculosis was investigated in Indian children. A total of 116 children with 'suspected' tuberculosis had a Mantoux test and chest X-ray. Of these, 51 had a positive Mantoux and/or chest X-ray compatible with tuberculosis, and this group had two laryngeal swabs taken on each of 3 consecutive days. The Mantoux test was positive in 37 (73%) of the 51 'probable' cases. Chest X-ray was abnormal in 36 (71%) cases and compatible with tuberculosis in 20 (39.7%). Mycobacterium tuberculosis was cultured from laryngeal swabs in 14 (28%) children and in another three children smears were positive but culture-negative. The overall confirmation rate for tuberculosis was 33%. Laryngeal swabs are a simple method of confirming tuberculosis and may be undertaken in out-patients.

Adolescent↗
PubMed1999

National survey to identify the nursing interventions used in school settings.

A national survey of members of the National Association of School Nurses was conducted to identify interventions from the Nursing Interventions Classification (NIC) that are used by school nurses. Usable responses were returned from 522 school nurses. The findings were that 163 interventions were used, on the average, from every day to once a year, and all but three interventions were used by one or more respondents. Certain interventions were significantly associated with special education or grade level of children served by nurses. It is concluded that the NIC is a useful tool to standardize documentation for school nursing.

Adult↗
PubMed1998

Constitutive properties of adult mammalian cardiac muscle cells.

BACKGROUND: The purpose of this study was to determine whether changes in the constitutive properties of the cardiac muscle cell play a causative role in the development of diastolic dysfunction. METHODS AND RESULTS: Cardiocytes from normal and pressure-hypertrophied cats were embedded in an agarose gel, placed on a stretching device, and subjected to a change in stress (sigma), and resultant changes in cell strain (epsilon) were measured. These measurements were used to examine the passive elastic spring, viscous damping, and myofilament activation. The passive elastic spring was assessed in protocol A by increasing the sigma on the agarose gel at a constant rate to define the cardiocyte sigma-versus-epsilon relationship. Viscous damping was assessed in protocol B from the loop area between the cardiocyte sigma-versus-epsilon relationship during an increase and then a decrease in sigma. In both protocols, myofilament activation was minimized by a reduction in [Ca2+]i. Myofilament activation effects were assessed in protocol C by defining cardiocyte sigma versus epsilon during an increase in sigma with physiological [Ca2+]i. In protocol A, the cardiocyte sigma-versus-epsilon relationship was similar in normal and hypertrophied cells. In protocol B, the loop area was greater in hypertrophied than normal cardiocytes. In protocol C, the sigma-versus-epsilon relation in hypertrophied cardiocytes was shifted to the left compared with normal cells. CONCLUSIONS: Changes in viscous damping and myofilament activation in combination may cause pressure-hypertrophied cardiocytes to resist changes in shape during diastole and contribute to diastolic dysfunction.

Actin Cytoskeleton↗
PubMed1998

Gel stretch method: a new method to measure constitutive properties of cardiac muscle cells.

Diastolic dysfunction is an important cause of congestive heart failure; however, the basic mechanisms causing diastolic congestive heart failure are not fully understood, especially the role of the cardiac muscle cell, or cardiocyte, in this process. Before the role of the cardiocyte in this pathophysiology can be defined, methods for measuring cardiocyte constitutive properties must be developed and validated. Thus this study was designed to evaluate a new method to characterize cardiocyte constitutive properties, the gel stretch method. Cardiocytes were isolated enzymatically from normal feline hearts and embedded in a 2% agarose gel containing HEPES-Krebs buffer and laminin. This gel was cast in a shape that allowed it to be placed in a stretching device. The ends of the gel were held between a movable roller and fixed plates that acted as mandibles. Distance between the right and left mandibles was increased using a stepper motor system. The force applied to the gel was measured by a force transducer. The resultant cardiocyte strain was determined by imaging the cells with a microscope, capturing the images with a CCD camera, and measuring cardiocyte and sarcomere length changes. Cardiocyte stress was characterized with a finite-element method. These measurements of cardiocyte stress and strain were used to determine cardiocyte stiffness. Two variables affecting cardiocyte stiffness were measured, the passive elastic spring and viscous damping. The passive spring was assessed by increasing the force on the gel at 1 g/min, modeling the resultant stress vs. strain relationship as an exponential [sigma = A/k(ekepsilon - 1)]. In normal cardiocytes, A = 23.0 kN/m2 and k = 16. Viscous damping was assessed by examining the loop area between the stress vs. strain relationship during 1 g/min increases and decreases in force. Normal cardiocytes had a finite loop area = 1.39 kN/m2, indicating the presence of viscous damping. Thus the gel stretch method provided accurate measurements of cardiocyte constitutive properties. These measurements have allowed the first quantitative assessment of passive elastic spring properties and viscous damping in normal mammalian cardiocytes.

Animals↗
PubMed1997

Structure-function relationships in interphotoreceptor retinoid-binding protein (IRBP).

PURPOSE: Interphotoreceptor retinoid binding protein (IRBP) binds hydrophobic ligands in the retina. The polypeptide consists of 1230 amino acids in four 300 amino acid long repeats. We asked whether each of the four repeats can bind one retinoid or fatty acid analog. Our rationale was to make protein variants from the human cDNA bearing one or more of the repeats and examine binding capacities and dissociation constants. METHODS: Proteins were characterized by SDS-PAGE, western blotting, N-terminal sequencing, and CD spectroscopy. Binding properties with all-trans-retinol and 16-anthryloxy-palmitic acid (16-AP) were characterized by ligand fluorescence enhancement and curve fitting. RESULTS: Binding capacities varied according to the length of each protein. Each repeat possesses the capability of binding retinol and 16-AP. CONCLUSIONS: The data contrast with the idea that two or more repeats are needed to bind one molecule of ligand. Each repeat binds a retinoid and fatty acid analog, suggesting that each has multiple ligand binding sites or one binding site with affinity for different ligands. Last, these data fit well with the current model of multiple binding sites in IRBP derived from quadruplication of an ancestral monomeric binding protein.

Animals↗
PubMed1997

Relevance of NANDA and health promotion diagnoses to school nursing. National Association of School Nurses.

This is a report of a national survey of 490 members of the National Association of School Nurses which described the relevance of 109 nursing diagnoses approved by NANDA (1992) and 29 health promotion (wellness) diagnoses developed by the authors. The relevance of these 138 nursing diagnoses for school nursing was determined by the percent of participants who checked "Yes" for the diagnostic categories they observed in their practice and for which they provided one or more interventions. More than half of the sample checked "Yes" for 67 NANDA diagnoses; health promotion diagnoses were checked "Yes" by 45% to 89% of the sample. The implications are that NANDA and health promotion diagnoses are relevant to school nursing and could readily be incorporated into practice to facilitate data collection that supports both the funding of school nurses and program development for children, families, and school staff.

Adult↗
PubMed1997

The effect of suture type on meniscus repair. A clinical analysis.

To test the hypothesis that use of permanent suture for meniscus repair allows longer, more stable fixation and more complete healing than absorbable suture, 89 patients (90 meniscus repairs) undergoing repair between 1990 and 1993 were evaluated. Eight patients were lost to follow-up, leaving 81 patients with 82 meniscal repairs. All patients underwent meniscus repair with either absorbable or permanent suture and were re-evaluated at an average of 24.1 months follow-up. The tears were within 5 mm of the peripheral meniscal rim and communicated with the peripheral blood supply (either red-red or red-white zone). Group 1 (absorbable suture) was comprised of 50 patients (38 males and 12 females; 19 right and 31 left knees). There were 36 medial and 14 lateral repairs. Group 2 (permanent suture) was comprised of 31 patients with 32 meniscus repairs (23 males and 8 females; 17 right knees and 14 left knees). There were 23 medial and 9 lateral meniscus repairs. Follow-up consisted of objective (clinical examination, range of motion, McMurray test, detectable swelling, locking, and joint-line tenderness) and subjective evaluations (15 question series of visual analog scales). Success or failure of the meniscal repair was based on the degree of symptoms present at follow-up. Group 1 had 9 failures, while Group 2 had none. All of the failures were rescoped and required additional surgical procedures. Group 1 had higher scores on all subjective questions. Data were analyzed using the two-sample t-test and the chi-squared test. The absolute failure rate was statistically significant. In this study, menisci repaired with permanent sutures had a lower incidence of clinical symptoms and a much lower failure rate. Thus, permanent suture is recommended for meniscus repair as it appears to allow for longer and more stable fixation, permitting more complete maturation and remodeling of the meniscus.

Absorption↗