Unified rate-dependent atrioventricular nodal function: Consistent recovery and fatigue properties revealed with S1S2S3 protocols and different recovery indexes

BACKGROUND: Rate-dependent nodal properties are commonly assessed with premature protocols performed at different basic rates. Because characteristics of responses differ with recovery time index, the true nature of nodal rate-dependent properties is elusive. OBJECTIVES: The purpose of this study was to reveal consistent nodal rate-dependent properties regardless of selected recovery index. METHODS: With S(1)S(2)S(3) protocols, we independently varied basic and pretest cycle lengths and thereby distinguished cumulative from noncumulative effects of rate on nodal conduction time in rabbit heart preparations. Nodal responses to 30 basic and pretest cycle length combinations (five with identical basic and pretest cycles as in standard protocols) were analyzed using both atrial (AA) and His-atrial (HA) intervals as recovery index. RESULTS: AA and HA curves had an identical shape for any of 30 steady-state conditions. When assessed with constant pretest cycle lengths, cumulative effects (fatigue) of shortened basic cycle lengths were also independent of recovery index. Shortening of pretest cycle length at fixed basic rates led to apparent inhibitory and facilitatory effects when assessed with AA and HA curves, respectively. These effects vanished when a single long cycle was inserted after the pretest cycle. In all responses including those obtained with standard protocols, combined effects of basic and pretest cycle lengths set nodal conduction time. CONCLUSION: S(1)S(2)S(3) protocols reveal consistent nodal recovery and fatigue properties regardless of recovery index used. Changes in nodal function curves arising from the use of different recovery indexes mainly depend on pretest effects. This study provides a new approach to a unified interpretation of nodal recovery and fatigue properties.     

Neuroprotective effect of taurine in 3-nitropropionic acid-induced experimental animal model of Huntington's disease phenotype

An experimental animal model of Huntington's disease (HD) phenotype was induced using the mycotoxin 3-nitropropionic acid (3-NP) and was well characterized behaviorally, neurochemically, morphometrically and histologically. Administration of 3-NP caused a reduction in prepulse inhibition (PPI) of acoustic startle response, locomotor hyper- and/or hypoactivity, bilateral striatal lesions, brain oxidative stress, and decreased striatal gamma-aminobutyric acid (GABA) levels. Taurine is a semi-essential beta-amino acid that was demonstrated to have both antioxidant and GABA-A agonistic activity. In this study, treatment with taurine (200 mg/kg daily for 3 days) prior to 3-NP administration reversed both reduced PPI response and locomotor hypoactivity caused by 3-NP injection. Taurine pretreatment also caused about 2-fold increase in GABA concentration compared to 3-NP-treated animals. In addition, taurine demonstrated antioxidant activity against oxidative stress induced by 3-NP administration as evidenced by the reduced striatal malondialdehyde (MDA) and elevated striatal glutathione (GSH) levels. Histochemical examination of striatal tissue showed that prior administration of taurine ahead of 3-NP challenge significantly increased succinate dehydrogenase (SDH) activity compared to 3-NP-treated animals. Histopathological examination further affirmed the neuroprotective effect of taurine in 3-NP-induced HD in rats. Taken together, one may conclude that taurine has neuroprotective role in the current HD paradigm due, at least partly, to its indirect antioxidant effect and GABA agonistic action.     

Language impairment in dementia: impact on symptoms and care needs in residential homes

BACKGROUND: Impairment of language skills affects the level of functioning of an individual, interferes with effective communication and can result in development of disruptive behaviour. Social skills and capacity for self care may be compromised. Few studies have evaluated the impact of language problems on symptoms and socialization in people with dementia in care environments. METHOD: 315 elderly residents with dementia (29% living in nursing homes, 71% in social care facilities) were assessed using standardized psychiatric schedules including the Sheffield Screening Test for Acquired Language Disorders and Neuropsychiatric Inventory. Dementia Care Mapping was undertaken at random in at least 50% of residents in each facility. RESULTS: Expressive language impairment was associated with the presence of delusions even when severity of dementia was controlled for (p=0.02) and showed a tendency of association with depression (p=0.06). Receptive language difficulties were strongly associated with presence of Aberrant Motor Behaviour, even controlling for severity of dementia (p=0.04). Decreased participation in social activities was correlated with both expressive (p=0.048) and receptive aspects of language (p<0.01) but social withdrawal was only correlated with receptive language difficulties (p=0.01). CONCLUSION: Language disorders are associated with both behavioural and psychological symptoms of dementia even when severity of dementia is controlled for. Patients' needs in communication skills should be addressed earlier to help them maintain social interactions and reduce the impact on behavioural problems and patients' quality of life.     

Control of essential hypertension with captopril, an angiotensin converting enzyme inhibitor.

1 Captopril, an orally active angiotensin converting enzyme inhibitor, was compared with hydrochlorothiazide (HCT) in the treatment of mild and moderate essential hypertension. 2 Twenty outpatients received no antihypertensive therapy for 2 weeks, after which they were given placebo for 8 weeks. Since their diastolic blood pressure remained above 100 mm Hg, they were then randomized to receive either captopril (twelve patients) or HCT (eight patients) for a 4-week titration period. If the supine diastolic blood pressure (SDBP) was normalized, (less than or equal to 90 mm Hg) by the end of titration period, the established regimen was continued for an 8-week maintenance period; if not, the alternate drug was added in increasing doses for up to 4 weeks and the combined therapy was maintained for the remaining 4 weeks. 3 After the first 4 weeks of therapy, both groups showed a statistically significant decrease in both systolic and diastolic blood pressure. Normalization of SDBP occurred in 75% of patients treated with captopril alone, and the addition of HCT produced normalization in the remainder. HCT alone resulted in normalization of SDBP in 50% of patients and the blood pressure of the remaining patients was normalized after the addition of captopril. 4 Captopril given orally, either alone or in conjunction with HCT, is an effective agent for the control of mild and moderate essential hypertension. 5 In our series the main side effects encountered were vertigo and dizziness, transient eosinophilia, a rise of BUN and or/a rise of SGPT or SGOT.