Characterisation of Na/K-ATPase, its isoforms, and the inotropic response to ouabain in isolated failing human hearts

OBJECTIVE

The aim was to determine whether failing human hearts have increased sensitivity to the inotropic and toxic effects of ouabain, and to examine alterations in Na/K-ATPase that might explain the observed higher ouabain sensitivity.

METHODS

For contractility studies, a total of 57 trabeculae were isolated from two non-failing (death from head injury) and 10 terminally failing, explanted human hearts. After the experiment, each trabecula was inspected under the light microscope for morphological alterations consistent with heart failure. Samples for biochemical and molecular studies were obtained from five non-failing and 13 failing hearts. Total Na/K-ATPase was measured in desoxycholate treated homogenates and expressed per unit of tissue wet or dry weight, DNA, protein, or myosin. Interference from residual bound digoxin due to previous therapy was excluded. The expression of the three alpha isoforms was studied at both the mRNA level using northern blots and the protein level by analysis of dissociation kinetics of the [3H]ouabain-enzyme complex.

RESULTS

Trabeculae showing morphological alterations and decreased contractility were sensitive to lower concentrations of ouabain (3-100 nM) than control trabeculae (100-1000 nM); the inotropic EC50 and the minimum toxic concentration were both reduced. [3H]Ouabain binding was significantly lower (p << 0.001) in failing than in non-failing hearts, at 293(SD 74) v 507(48) pmol.g-1 wet weight. No significant change was observed in maximum ATPase turnover rate, or in sensitivities to Na+, K+, vanadate, and dihydro-ouabain. All three alpha isoforms were expressed at the mRNA level in both normal and failing hearts.

CONCLUSIONS

This study shows conclusively, for the first time, that failing human hearts are more sensitive to ouabain. This may be at least partly due to a mean reduction of 42% (95% confidence interval, 26 to 56%) in the concentration of Na/K-ATPase (decrease in Na,K pump reserve), but not to an alteration in its catalytic properties or in its isoform composition.

Expression of Na,K-ATPase isoforms in human heart

The expression pattern of the multiple isoforms of Na,K-ATPase was examined in the human heart. Isoform specific oligonucleotide probes for the alpha 1, alpha 2, alpha 3 and beta 1 subunits were used to probe Northern blots. The adult human ventricle expresses mRNAs for all three alpha subunit isoforms in addition to beta 1 subunit mRNA.

Neurodevelopmental outcomes in children with HIV infection under 3 years of age

Following the introduction of combination antiretroviral therapy, children vertically infected with the human immunodeficiency virus (HIV-1) living in the developed world are surviving into adult life. This paper reviews the neurodevelopmental outcomes of 62 consecutively-presenting children with HIV-1 infection diagnosed before 3 years of age (32 males, 30 females; median age at presentation 6 mo). Neurological and developmental data are presented with immunological and virological responses to antiretroviral therapy. Fourteen children (22%) had abnormal neurological signs and 25 (40%) demonstrated significant developmental delay on standardized developmental assessments. Children presenting with more severe HIV-1 disease and immune compromise had significantly more abnormal neurological signs and developmental delays than children presenting with milder HIV-1 symptomatology. Immune function, control of HIV-1 viral replication, and growth parameters improved with antiretroviral therapy (median age at last follow-up 7 y 3 mo); however, abnormal neurological signs and significant gross motor difficulties persisted.

Effects of aromatase inhibition vs. testosterone in older men with low testosterone: randomized-controlled trial

Aging in men is associated with loss of bone mass, impaired physical function and altered body composition. The objective of this proof-of-concept randomized, double-blind, placebo-controlled, parallel-group, single-center trial was to determine the relative effects of testosterone (T) and estradiol (E(2)) on bone mineral density, body composition, and physical performance in older men. The primary outcome was lumbar spine bone mineral density (BMD), and secondary outcomes were body composition, muscle strength, gait speed, and sex hormone concentrations. Forty three men (age range, 65-82 years; mean age 71 years) with low total T levels <350 ng/dL were randomized to one of three groups: 5 g transdermal testosterone gel (TT) (N = 16), anastrozole (AI) 1 mg (N = 14) or placebo daily (N = 13) for 12 months. Outcomes were assessed at baseline, 3, 6, and 12 months. Both TT and AI increased serum TT levels (>500 ng/dL, p < 0.05) compared to baseline; T values remained stable throughout the duration of the trial. At 12 months, TT improved the primary outcome of lumbar spine BMD (p < 0.01).Both interventions improved knee strength at 12 months compared to baseline (p < 0.05) while lean body mass significantly increased only in the AI group at 6 and 12 months (1.49 ± 0.38 kg, p < 0.01; 1.24 ± 0.39 kg, p < 0.05, respectively) compared to baseline. Interestingly, TT improved fast gait speed at 3 and 12 months (p < 0.01, p < 0.05, respectively). In summary, this proof-of-concept study confirms that aromatization of T is required for maintaining BMD in older men with low-T levels. The trial also uncovered the novel finding that aromatization of T is required for improvement in fast gait speed, an observation that needs to be verified in future studies.

Effect of stationary guiding vanes on improvement of the washout behind the rotor in centrifugal blood pumps

In centrifugal pumps, there always exists an area of stagnation between the rear of the rotor and the rear housing wall that promotes thrombus formation around the axle. Some current devices overcome the problem by using holes in the rotor plane, leading to increased hydrodynamic losses and shear stress. In this study, a simple apparatus was developed to overcome this problem. Guiding vanes were fixed to the rear housing wall. These vanes decrease the tangential velocity of the fluid and thus the centrifugal force, leading to an increased secondary flow toward the axle. The effect of such vanes was studied in videographic and ultrasound studies. An increase of washout and mixing between the flow layers could be demonstrated (stay time < 200 msec versus several seconds without vanes). In the first animal experiment using nonoptimized vanes, there was no thrombus at the back plane or the seal, and only a small thrombus at the transition between axle and rotor. Hemolysis was slightly elevated (3.2 mg/dl versus 2.5 mg/dl in control experiments). In conclusion, it is highly likely that this simple system will improve the flow characteristics in centrifugal pumps.

The child in the family--responding to AIDS and HIV

This study examines the psychosocial needs of children with AIDS and HIV infection based on a cohort of 18 infected children. Fifteen of the children live with their mothers, nine of whom are single mothers. For 14 children the mother is HIV +ve and for a further 8 the father is also HIV +ve. Many children have siblings (10), but only one of these is infected. Close family and grandparents are rarely involved in care and only one child, the oldest, is aware of parental and personal HIV status. Where children attend school or preschool centres none have been informed of the child's HIV infection. Cultural issues are prevalent, especially marked when English is not the first language (n = 10) which renders obstacles for counselling and developmental appraisal. Children in this group are hospitalized more frequently than the parents. Child and parental hospitalization is problematic. Three case situations arising in this group are described in some detail to highlight the nature of the emotional challenges facing carers and service providers.

Reduced cardiac myofibrillar Mg-ATPase activity without changes in myosin isozymes in patients with end-stage heart failure

In this study we tested the hypothesis that reduced myofibrillar ATPase activities in end-stage heart failure are associated with a redistribution of myosin isozymes. Cardiac myofibrils were isolated from left ventricular free wall from normal human hearts and hearts at end-stage heart failure caused by coronary artery diseases, cardiomyopathy or immunological rejection. The hearts had been excised in preparation for a heart transplant. Myofibrillar Ca2(+)-dependent Mg-ATPase and myosin Ca2(+)- and K+EDTA-ATPase activities were compared. Possible changes in myosin isozyme distribution in the diseased heart were investigated using polyacrylamide gel electrophoresis of native myosin in the presence of pyrophosphate. Significant reduction in myofibrillar Ca2(+)-dependent Mg-ATPase with no changes in the sensitivity of the myofibrils to Ca2+ was observed in heart with coronary artery diseases (25.2 to 27.1% at pCa 5.83 to pCa 5.05), cardiomyopathy (21.1 to 25.5% at pCa 5.41 to pCa 5.05), and in the immunologically rejected heart (18.4 to 22.8% at pCa 5.41 to pCa 5.05). Significantly lower myosin Ca2(+)-ATPase was observed with coronary artery diseases only and myosin K-EDTA activities did not differ in diseased and normal hearts. Polyacrylamide gel electrophoresis of native myosin from the normal and three models of end-stage heart failure revealed two distinct bands in the human left ventricle and one diffuse band in the human right atria. No apparent differences in myosin isoenzyme pattern were observed between the normal and diseased hearts. Further evaluation is needed to clarify the ATPase nature of the two bands.

A new form of vena caval interruption

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The epidemiology of childhood asthma in Red Deer and Medicine Hat, Alberta

OBJECTIVES

To document the prevalence of asthma among school-aged children in two Alberta communities, to understand host and indoor environmental factors associated with asthma, and to compare these factors between the two communities.

DESIGN

A cross-sectional study with a nested, case-control follow-up.

SETTING

Red Deer and Medicine Hat, Alberta.

PATIENTS AND METHODS

Questionnaires were sent to families of children aged five to 19 years in Red Deer (n=5292) and Medicine Hat (n=5372) to identify children with current asthma. A random sample of 592 children with current asthma and 443 with no history of asthma constituted a case-control population; they were followed up by telephone to obtain responses to the European Respiratory Health Survey and, in children with current asthma, the Pediatric Quality of Life Questionnaire.

RESULTS

Cross-sectional response rates were 84% and 73% for Red Deer and Medicine Hat, respectively. The prevalence of asthma was higher in Medicine Hat (17.0%) than in Red Deer (12.8%). In the follow-up study, factors associated with the presence of asthma were parental asthma or allergies, number of siblings, presence of cats, serious respiratory illnesses before five years of age, sex, age, presence of mould and/or mildew and use of a gas cooking stove. The presence of mould and/or mildew was a significant risk factor in Red Deer but not in Medicine Hat.

CONCLUSIONS

Asthma prevalence among school children in Red Deer was consistent with recently published Canadian data; the prevalence in Medicine Hat was higher than expected, especially given the low relative humidity. Risk factor data are consistent with other studies in that parental asthma, especially maternal asthma, was a significant predictor of childhood asthma. Cats in the house (both communities) and environmental tobacco smoke (Medicine Hat only) were significantly less common among children with asthma, suggesting that preventive actions may have been taken in the homes of some children with asthma.

Testosterone vs. aromatase inhibitor in older men with low testosterone: effects on cardiometabolic parameters

Testosterone (T) replacement is being increasingly offered to older men with age-related decline in testosterone levels. The effects of long-term testosterone replacement and aromatase inhibition (AI) on glucose homeostasis and cardiometabolic markers were determine in older non-diabetic men with low testosterone levels. Men ≥65 years, mean age 71 ± 3 years with serum total T < 350 ng/dL were randomized in a double-blind, placebo-controlled, parallel-group, proof-of-concept trial evaluating the effects of 5 g transdermal testosterone gel (TT) (n = 10), 1 mg anastrozole (n = 10) or placebo (n = 9) daily for 12 months. Homeostatic Model Assessment of insulin resistance (HOMA_IR ) was the primary outcome. Secondary outcomes included OGIS in response to OGTT, fasting lipids, C-reactive protein (CRP), adipokines, and abdominal and mid-thigh fat by computed tomography. All outcomes were assessed at baseline and 12 months. After 12 months, absolute changes in HOMA_IR in both treatment arms (TT group: -0.05 ± 0.21); (AI group: 0.15 ± 0.10) were similar to placebo (-0.11 ± 0.26), as were CRP and fasting lipid levels. Adiponectin levels significantly decreased in the TT group (-1.8 ± 0.9 mg/L, p = 0.02) and abdominal subcutaneous fat (-60.34 ± 3.19 cm² , p = 0.003) and leptin levels (-1.5 ± 1.2 ng/mL, p = 0.04) were significantly lower with AI. Mid-thigh subcutaneous fat was reduced in both treatment arms (TT group: -4.88 ± 1.24 cm² , p = 0.008); (AI group: -6.05 ± 0.87 cm² , p = 0.0002). In summary, in this proof-of-concept trial, changes in HOMA_IR AI were similar in all three groups while the effects of intervention on subcutaneous fat distribution and adipokines were variable. Larger efficacy and safety trials are needed before AI pharmacotherapy can be considered as a treatment option for low T levels in older men.

Parental reports of emotional and behavioural difficulties on the SDQ for school-age children with vertically acquired HIV infection living in London

This study uses a screening questionnaire (the Strengths and Difficulties Questionnaire, SDQ) to indicate levels of parental or carer concern about behavioural or emotional difficulties in a representative group of school-age children with vertically acquired HIV attending London clinics. Fourteen per cent of the total 107 children screened were reported to have behavioural and emotional difficulties scoring in the "abnormal" range. Older children tended to have higher scores. Overall, levels of reported difficulties were found to be similar to those reported for other chronic childhood illnesses and slightly higher than in the general child population.

Parental HIV discordancy and its impact on the family

There is little or no available information on the effect of HIV discordancy in heterosexual relationships on different family members. A review of case notes was carried out on all families who had a child referred to the paediatric HIV service/family clinic at St Mary's Hospital between January 1991 and March 1996. The children had been exposed to HIV infection because they were born to HIV-positive women. There was HIV discordancy in more than one-fifth of the parents' relationships. In over 46% of the relationships, the HIV status of the natural or birth father was not known because he was either untested or unavailable. It is likely that not all of these men are infected and the number of discordant couples is greater. There were more discordant couples where the man and woman came from different ethnic groups. Consideration of the potential impact of discordancy on individual men, women and children is discussed.

Incidence and nature of feeding problems in young children referred to a paediatric HIV service in London: FEAD screening

A detailed screening assessment was carried out on two matched groups of young children; one group was HIV-infected and the other was not. Screening included assessments of growth, development and food intake. Parents were also interviewed about their child's feeding and mealtime behaviours. Half of the HIV-infected children were reported with serious feeding problems; significantly higher than in the uninfected group. More of the children in the HIV-infected group were found to have poorer growth and developmental weaknesses than in the uninfected group. A combination of physical and psychological factors are suggested as contributing to these feeding difficulties. Early monitoring of feeding behaviours, daily routines and food intake, together with systematic growth and developmental measures are suggested as important components in the care and management of HIV-infected children.

Community support to families living with HIV in London: an agency overview

In 1996 a structured questionnaire, relating to services provided, was completed by 12 agencies providing support to families with HIV in London. A wide range of information, practical and therapeutic services were available from these agencies but these usually had a primary focus on supporting the adults in these families. Only one agency had been set up specifically to offer a direct service for children within their own home or community. Services for children within most agencies consisted of organized child care or social activities, often provided to enable parents to access other services at the centre. Concern was frequently expressed that the normal and emotional needs, especially of older children, were not being met. Many children attending events at these agencies were unaware of the diagnosis or the reasons for attending these centres. Implications are discussed on how future development of services in the voluntary and statutory sector will need to address the specific and changing needs of infected and affected children.

The effectiveness of communication groups in day nurseries

This project, run by a speech and language therapist and a clinical psychologist, took place in three inner city day nurseries. A group of children over whose communication there was concern were assessed on both formal (verbal and non-verbal) and informal (observational) measures. At each nursery these children were divided into two matched groups: intervention and control. The intervention consisted of communication groups run jointly with nursery staff. These small groups focused on promoting communication through play. On reassessment the children attending the communication groups had made significantly more improvement than the controls on both formal and informal measures. In particular, the number and quality of children's interactions, their underlying ability to focus on tasks and their knowledge of basic concepts appeared to benefit from the intervention. The study, therefore, provides strong evidence for the efficacy of such interventions in enhancing communication development in a real-life setting.

Paediatric HIV infection

HIV and AIDS have made a huge global impact, permeating the social, cultural, and economic fabric of almost all nations. The first cases of HIV infection in children were reported in the late 1980s and numbers have since risen steadily throughout the world, with some of the poorest and least developed countries experiencing the highest prevalence. Combined drug regimes have changed the course of HIV-related illness and brought increased survival to those for whom treatment is available. With this, however, have come fresh concerns relating to drug resistance, treatment adherence, and the risk of second-generation vertical transmission as HIV-infected children now survive into adulthood and beyond. The psychological literature has addressed issues such as the direct effect of HIV on child development, social and cultural attitudes, family functioning and support, affected children and orphans of HIV-infected parents, sexual health education, disclosure of diagnosis, and long-term clinical management. The outcome for those living in wealthier countries is optimistic, but the spread of this virus in the rest of the world and its impact on family life and social and political systems remains of great concern.