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W Walker

Publications and source records attributed to W Walker.

At least 19 recordsLinked to original sources
PubMed2006

A genome-wide linkage scan for genes controlling variation in urinary albumin excretion in type II diabetes.

The main hallmark of diabetic nephropathy is elevation in urinary albumin excretion. We performed a genome-wide linkage scan in 63 extended families with multiple members with type II diabetes. Urinary albumin excretion, measured as the albumin-to-creatinine ratio (ACR), was determined in 426 diabetic and 431 nondiabetic relatives who were genotyped for 383 markers. The data were analyzed using variance components linkage analysis. Heritability (h2) of ACR was significant in diabetic (h2=0.23, P=0.0007), and nondiabetic (h2=0.39, P=0.0001) relatives. There was no significant difference in genetic variance of ACR between diabetic and nondiabetic relatives (P=0.16), and the genetic correlation (rG=0.64) for ACR between these two groups was not different from 1 (P=0.12). These results suggested that similar genes contribute to variation in ACR in diabetic and nondiabetic relatives. This hypothesis was supported further by the linkage results. Support for linkage to ACR was suggestive in diabetic relatives and became significant in all relatives for chromosome 22q (logarithm of odds, LOD=3.7) and chromosome 7q (LOD=3.1). When analyses were restricted to 59 Caucasian families, support for linkage in all relatives increased and became significant for 5q (LOD=3.4). In conclusion, genes on chromosomes 22q, 5q and 7q may contribute to variation in urinary albumin excretion in diabetic and nondiabetic individuals.

Adult↗
PubMed2005

Analysis of leukocyte binding to depletion filters: role of passive binding, interaction with platelets, and plasma components.

Since limited knowledge exists on the mechanisms which regulate cell binding to leukocyte removal filter surfaces, we investigated the binding patterns of leukocytes to individual layers of leukocyte depletion filters. After passage of 1 unit of whole blood, blotting of isolated filter layers on glass slides or elution of cells from filter layers revealed that most leukocytes were located within the first 10 of a total of 28 filter layers, peaking at layers 6 to 8, with granulocytes binding on average to earlier filter layers than lymphocytes. Leukocytes preincubated with inhibitors of actin activation showed unchanged distribution between filter layers, suggesting that cytoskeletal activation does not significantly contribute to their binding. When leukocytes were directly incubated with single filter layers, binding of up to 30% of input cells was recorded in the absence of Ca(2+). Immunohistological analyses showed colocalization of platelets and leukocytes, with co-clustering of platelets and leukocytes. Monocytes and to some degree lymphocytes but not granulocytes competed with platelets for filter binding. Precoating of filter layers with individual plasma components showed that hyaluronic acid, plasma type fibronectin, and fibrinogen all increased the binding of leukocytes compared with albumin coating. In conclusion, leukocytes can bind passively to filters in a process which does not require Ca(2+), which is independent of cytoskeletal activation and which may depend on individual plasma components. These results are of importance when new selective cell enrichment or depletion strategies through specific filters are envisaged.

Blood Cells↗
PubMed2005

The management and outcome of patients with germ-cell tumours treated in the Edinburgh Cancer Centre between 1988 and 2002.

AIMS: The aim of this retrospective analysis was to review the outcome of patients with germ-cell tumours treated in the Edinburgh Cancer Centre over the past 15 years, and to see whether there had been any changes over three 5-year cohorts. MATERIALS AND METHODS: Patients referred with gonadal and extra-gonadal primary germ-cell tumours, between 1988 and 2002, were identified from the departmental database, and survival by stage and prognostic group was analysed. RESULTS AND CONCLUSIONS: The proportion of patients with stage I seminoma has significantly increased. The good prognosis of patients with early stage disease is confirmed, with the outcome for some groups of patients being better than expected. There is a non-significant trend to improved results over the three 5-year cohorts. The outcome for patients with stage IV seminoma is worse than would be expected, but numbers are small. The poor prognosis of patients with non-seminomatous germ-cell tumours who fall into the International Germ Cell Consensus Classification (IGCCC) poor-prognostic group is confirmed. Failure of patients with metastatic non-seminomatous germ-cell tumours to achieve a complete response to initial therapy is shown to be a poor prognostic indicator.

Adolescent↗
PubMed2004

The effects of Donepezil on traumatic brain injury acute rehabilitation outcomes.

PRIMARY OBJECTIVE: To evaluate the effects of administering Donepezil during inpatient rehabilitation for individuals with TBI. RESEARCH DESIGN: Retrospective, age and injury severity matched, mixed between-within subjects analysis. METHODS AND PROCEDURES: Thirty-six patients with moderate-to-severe TBI admitted to acute rehabilitation within 90 days of injury. Main outcome measures included FIM cognitive total scores and rehabilitation lengths of stay. INTERVENTION: Initiation of Donepezil administration beginning at 5 mg daily. Dose titration and continuation based on perceived clinical response. MAIN OUTCOMES AND RESULTS: No differences in cognitive improvement were observed between the Donepezil treatment group and the matched control group. Sub-set analyses suggested that administration of Donepezil early in the rehabilitation stay was significantly related to higher rates of cognitive improvement. CONCLUSIONS: Preliminary evidence suggests that Donepezil administration early in the rehabilitation stay may have advantageous treatment effects. A prospective, randomized, placebo-controlled clinical trial with standard timing, dosage and treatment duration is recommended to further evaluate treatment efficacy.

Adult↗
PubMed2001

Comprehensive critical care education is critical to success.

Intensive and high-dependency care is currently receiving considerable attention, not least since the Department of Health review of adult critical care nursing and subsequent proposals for the development of a consistent and comprehensive critical care service (DoH 2000). The report highlights the need for policy changes at all levels and across all disciplines and makes several recommendations that are deemed essential for the future organization and delivery of critical care. Central to the proposed reforms is the availability of a skilled workforce, adequately prepared and appropriately trained to provide specialist care in a variety of settings where acutely ill patients are found. This paper considers the implications of 'comprehensive critical care' for pre- and post-registration nurse education and offers insight into programmes of learning that are tailored to meet the needs of the service and individuals. The paper draws upon three influential and timely publications, namely the Audit Commission report into critical care services, the English National Board (ENB) review of adult intensive/critical and high-dependency care programmes and the United Kingdom Central Council (UKCC) Commission for Education recommendations regarding 'fitness for practice'.

Critical Care↗
PubMed2001

Sex-associated hormones and immunity to protozoan parasites.

Numerous epidemiological and clinical studies have noted differences in the incidence and severity of parasitic diseases between males and females. Although in some instances this may be due to gender-associated differences in behavior, there is overwhelming evidence that sex-associated hormones can also modulate immune responses and consequently directly influence the outcome of parasitic infection. Animal models of disease can often recreate the gender-dependent differences observed in humans, and the role of sex-associated hormones can be confirmed by experimentally altering their levels. Under normal circumstances, levels of sex hormones not only differ between males and females but vary according to age. Furthermore, not only are females of reproductive age subject to the regular hormonal cycles which control ovulation, they are also exposed to dramatically altered levels during pregnancy. It is thus not surprising that the severity of many diseases, including those caused by parasites, has been shown to be affected by one or more of these circumstances. In addition, infection with many pathogens has been shown to have an adverse influence on pregnancy. In this article we review the impact of sex-associated hormones on the immune system and the development and maintenance of immunity to the intracellular protozoan parasites Toxoplasma gondii, Plasmodium spp., and Leishmania spp.

Animals↗
PubMed2001

Delivery of a cyclic adenosine 3',5'-monophosphate response element-binding protein (creb) mutant to seminiferous tubules results in impaired spermatogenesis.

FSH binding to Sertoli cells is required for optimal production of sperm in mammals. The cAMP response element-binding protein (CREB) is a major mediator of FSH-induced changes in gene expression. To determine whether CREB is required for spermatogenesis, an adenovirus encoding a phosphorylation-defective CREB mutant (AdCREBm1) was used to inhibit CREB activity in Sertoli cells. Addition of AdCREBm1 to primary rat Sertoli cell cultures completely abolished induction of the CREB-regulated c-fos gene. Injection of an adenovirus encoding ss-galactosidase into the rat testis seminiferous tubules in vivo demonstrated that predominately Sertoli cells were infected by adenovirus. AdCREBm1-directed expression of CREBm1 in seminiferous tubules did not affect Sertoli cell viability, but resulted in the apoptosis of meiotic spermatocyte germ cells within 4 days of adenovirus injection into seminiferous tubules. Disrupted spermatogenesis, defined by at least a 75% reduction of round spermatids, was observed in 42 +/- 5.8% of seminiferous tubules 14 days after AdCREBm1 infection, whereas using this criteria, testes injected with a control adenovirus did not display disrupted spermatogenesis. These data demonstrate that AdCREBm1 causes apoptosis and elimination of germ cells and suggest that CREB is required to produce a Sertoli cell-derived factor that is critical for germ cell survival.

Animals↗
PubMed2000

Pulmonary endothelial permeability and circulating neutrophil-endothelial markers in patients undergoing esophagogastrectomy.

OBJECTIVE: Esophagogastrectomy is an established surgical treatment for esophageal malignancy. The postoperative period may be complicated by the development of acute lung injury syndromes and thus, may provide a useful model in which to study the early pathogenic mechanisms of inflammatory lung injury. DESIGN: Open, prospective study. SETTING: High dependency and intensive therapy units. PATIENTS: Eight healthy male volunteers and 20 patients in the early postoperative period INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The lung protein accumulation index (PAI) of radiolabeled transferrin was determined by using a portable, double-isotope system. The following circulating inflammatory markers-thought to reflect neutrophil-endothelial activation and injury including circulating neutrophil elastase-soluble L-, E-, and P-selectins and thrombomodulin and von Willebrand factor antigen were assayed from venous blood samples The PAI for healthy volunteers was median -0.5 (range, -1.73 to 0.27) x 10(-3)/min and for patients undergoing esophagogastrectomy -0.005 (range, -1.53 to 2.28) x 10(-3)/min. There was no statistical difference between the two groups. In the postesophagogastrectomy group, a significant elevation in circulating levels of neutrophil elastase, soluble P- and E-selectin, thrombomodulin, and von Willebrand factor antigen were observed relative to the control group but only circulating plasma elastase demonstrated a significant correlation with the PAI (r2 = .23, p =.03). CONCLUSIONS: The data suggest patients undergoing esophagogastrectomy develop a inflammatory response but this is not a surrogate of permeability and other factors are likely to determine persistent injury to the alveolar-capillary barrier function in this patient group.

Aged↗
PubMed2000

The CD40/CD40 ligand interaction is required for resistance to toxoplasmic encephalitis.

Since the CD40/CD40 ligand (CD40L) interaction is involved in the regulation of macrophage production of interleukin 12 (IL-12) and T-cell production of gamma interferon (IFN-gamma), effector cell functions associated with resistance to Toxoplasma gondii, the role of CD40L in immunity to this parasite was assessed. Infection of C57BL/6 mice with T. gondii results in an upregulation of CD40 expression on accessory cell populations at local sites of infection as well as in lymphoid tissues. Splenocytes from C57BL/6 mice infected with T. gondii for 5 days produced high levels of IL-12 and IFN-gamma when stimulated with toxoplasma lysate antigen, and blocking CD40L did not significantly alter the production of IFN-gamma or IL-12 by these cells. Similar results were observed with splenocytes and mononuclear cells isolated from the brains of chronically infected mice. Interestingly, although CD40L(-/-) mice infected with T. gondii produced less IL-12 than wild-type mice, they produced comparable levels of IFN-gamma but succumbed to toxoplasmic encephalitis 4 to 5 weeks after infection. The inability of CD40L(-/-) mice to control parasite replication in the brain correlated with the ability of soluble CD40L, in combination with IFN-gamma, to activate macrophages in vitro to control replication of T. gondii. Together, these results identify an important role for the CD40/CD40L interaction in resistance to T. gondii. However, this interaction may be more important in the control of parasite replication in the brain rather than the generation of protective T-cell responses during toxoplasmosis.

Animals↗
PubMed2000

Ultrasound-guided percutaneous thrombin injection for femoral artery pseudoaneurysms.

We reviewed 13 cases of ultrasound-guided thrombin injection of femoral pseudoaneurysms. All cases occurred within a 17-month period from January 1998 through May 1999 and were complications of femoral artery puncture. Immediate total thrombosis occurred in nine of 13 patients. Twenty-four-hour follow-up ultrasound in seven patients revealed no recurrence of pseudoaneurysm. Two of 13 patients required operative repair. One pseudoaneurysm thrombosed with 15 minutes of compression after injection and one case required a second injection. No cases of arterial thrombosis were noted. Ultrasound-guided thrombin injection for femoral artery pseudoaneurysm represents a safe and effective alternative to operative repair.

Aged↗
PubMed2000

[Effects of ob genotype on early development in mice].

OBJECTIVE: To study the effects and the extent of dominance of ob gene on early development in mice. METHODS: ob genotypes, wild type (+/+), hybrid type (ob/+) and mutant type (ob/ob), were detected by polymerase chain reaction and restrict endonuclease technique. Body weight of mice was recorded daily for the first seventh weeks of life. Their wet weight of white adipose tissue (WAT) and brown adipose tissue (BAT) was compared at the 7th, 14th and 24th days after birth. RESULTS: Body weight of ob/ob mice increased rapidly two weeks after birth and reached two times of that of +/+ and ob/+ mice seven weeks after birth. WAT of ob/ob mice was significantly higher than that of +/+ and ob/+ mice 24 days after birth. Effect of ob genotype on BAT was earlier than that on WAT. Body weight and WAT of ob/+ mice ranged between those of +/+ and ob/ob mice. Dominance index, reflecting the effect of ob gene on body weight, ranged from 1.0 - 0.5 within the first two weeks after birth, appearing co-dominance. And, dominance index approximated to 0.0 six weeks after birth, appearing almost complete recession. CONCLUSION: Effect of ob gene on body weight and WAT initiated two weeks after birth and increased with age, developing gradually from co-dominance to recession in their early life.

Adipose Tissue, Brown↗
PubMed1999

IL-18 and CD28 use distinct molecular mechanisms to enhance NK cell production of IL-12-induced IFN-gamma.

NK cells play an important role in innate immune resistance, particularly through synthesis of the pro-inflammatory cytokine IFN-gamma. This study compares the abilities of the cytokine IL-18 and the costimulatory cell surface molecule CD28 to enhance IL-12-driven IFN-gamma production by NK cells. Studies with other cytokines (IL-1beta, IL-6, TNF-alpha, IL-15) showed that IL-18 or anti-CD28 treatments were the most efficient inducers of IFN-gamma when combined with IL-12. The ability of IL-18 to enhance IFN-gamma was shown to be dependent on the presence of IL-12. Similarly, although anti-CD28 stimulation alone could enhance IFN-gamma synthesis, this effect was significantly increased in the presence of IL-12. Although neither method of costimulation required de novo protein synthesis for their effects on IFN-gamma mRNA expression, these molecules used distinct mechanisms. Specifically, nuclear run-on analysis revealed that IL-18 in combination with IL-12 enhanced the rate of transcription of the IFN-gamma gene. Conversely, treatment with anti-CD28 plus IL-12 did not significantly up-regulate the rate of transcription of the IFN-gamma gene, but stabilized IFN-gamma mRNA expression within NK cells. These findings illustrate costimulatory pathways that result in potent IFN-gamma responses by NK cells and show that although IL-18 and anti-CD28 can enhance the synthesis of IL-12-driven IFN-gamma, they employ molecular mechanisms that are distinct from one another.

Animals↗
PubMed1999

Fatal infantile cardioencephalomyopathy with COX deficiency and mutations in SCO2, a COX assembly gene.

Mammalian cytochrome c oxidase (COX) catalyses the transfer of reducing equivalents from cytochrome c to molecular oxygen and pumps protons across the inner mitochondrial membrane. Mitochondrial DNA (mtDNA) encodes three COX subunits (I-III) and nuclear DNA (nDNA) encodes ten. In addition, ancillary proteins are required for the correct assembly and function of COX (refs 2, 3, 4, 5, 6). Although pathogenic mutations in mtDNA-encoded COX subunits have been described, no mutations in the nDNA-encoded subunits have been uncovered in any mendelian-inherited COX deficiency disorder. In yeast, two related COX assembly genes, SCO1 and SCO2 (for synthesis of cytochrome c oxidase), enable subunits I and II to be incorporated into the holoprotein. Here we have identified mutations in the human homologue, SCO2, in three unrelated infants with a newly recognized fatal cardioencephalomyopathy and COX deficiency. Immunohistochemical studies implied that the enzymatic deficiency, which was most severe in cardiac and skeletal muscle, was due to the loss of mtDNA-encoded COX subunits. The clinical phenotype caused by mutations in human SCO2 differs from that caused by mutations in SURF1, the only other known COX assembly gene associated with a human disease, Leigh syndrome.

Amino Acid Sequence↗
PubMed1998

Characterization of PKA isoforms and kinase-dependent activation of chloride secretion in T84 cells.

Chloride exit across the apical membranes of secretory epithelial cells is acutely regulated by the cAMP-mediated second messenger cascade. To better understand the regulation of transepithelial chloride secretion, we have characterized the complement of cAMP-dependent protein kinase (PKA) isoforms present in the human colonic epithelial cell line T84. Our results show that both type I and type II PKA are present in T84 cells. Immunoprecipitation of 8-azido-[32P]cAMP-labeled cell lysates revealed that the major regulatory subunits of PKA were RIalpha and RIIalpha. In addition, immunogold electron microscopy showed that RIIalpha labeling was found on membranes of the trans Golgi network and on apical plasma membrane. In contrast, RIalpha was randomly distributed throughout the cytoplasm, with no discernible membrane association. Northern blot analysis of T84 RNA revealed that Calpha was the predominantly expressed catalytic subunit. Short-circuit current measurements were performed in the presence of combinations of site-selective cAMP analog pairs to preferentially activate either PKA type I or PKA type II in intact T84 cell monolayers. Maximal levels of chloride secretion (approximately 100 microA/cm2) were observed for both type I and type II PKA-selective analog pairs. Subsequent addition of forskolin was unable to further increase chloride secretion. Thus activation of either type I or type II PKA is able to maximally stimulate chloride secretion in T84 colonic epithelial cells.

Affinity Labels↗
PubMed1997

SCID mice reconstituted with IL-4-deficient lymphocytes, but not immunocompetent lymphocytes, are resistant to cutaneous leishmaniasis.

To characterize the roles of lymphoid- and non-lymphoid-derived IL-4 during cutaneous infection with Leishmania mexicana, the disease was monitored in SCID mice reconstituted with splenocytes from either immunocompetent BALB/c mice or IL-4-deficient BALB/c mice. Whereas following s.c. infection with L. mexicana no lesion growth was observed in BALB/c IL-4(-/-) mice and lesion growth was significantly inhibited in SCID mice, rapid initial lesion growth occurred in both SCID IL-4(+/+) and SCID IL-4(-/-) reconstituted mice. However, after 3 to 4 wk of infection, lesions in SCID IL-4(-/-) but not SCID IL-4(+/+) reconstituted mice began to heal. This paralleled a developing Th1-like phenotype and parasite clearance in the former group and a developing Th2-like phenotype in the latter group. Lesion sites from the healing SCID IL-4(-/-) mice expressed the inducible nitric oxide synthase, whereas the SCID IL-4(+/+) mice with progressive disease did not. These findings indicate that non-lymphocyte-derived IL-4 may play a role in initiating lesion growth following cutaneous infection with L. mexicana, but the presence of lymphocyte-derived IL-4 is essential for disease progression, and in its absence, lesions heal due to a developing Th1 phenotype.

Animals↗