Mitral valve prolapse: a review of the syndrome with emphasis on current antibiotic prophylaxis.

Mitral valve prolapse syndrome (MVPS) is the name given to the heart valve abnormality described by Barlow over two decades ago. This condition is of particular importance to the dentist as these patients are thought to be at risk of developing infective endocarditis with routine dental procedures which may cause gingival bleeding. This paper is an updated version of an article that originally appeared in the University of Toronto Dental Journal in 1990. In 1984, guidelines for antibiotic prophylaxis were provided by the American Heart Association (AHA). More current prophylactic regimens are also presented, with emphasis on the current recommendations of the AHA, recently published in December of 1990.     

Determination of the diastolic function of the left ventricle in post-infarction patients using a complex echocardiographic index

The diastolic function of 25 patients with ischemic heart disease was studied by both digitized M-mode and Doppler echocardiography. The control groups were a group of healthy subjects and patients with hypertension, resp. There was a significant difference in the diastolic parametres of the healthy and the diseased groups. The altered diastolic function of the latter showed, however, little variation. A new complex diastolic index was formed from the parametres involved in Doppler and M-mode echocardiography. It contains early and late diastolic filling rates, the isovolumic relaxation period, and the diametric change of the left ventricle during the isovolumic relaxation period. This index allowed us to separate the altered diastolic functions of patients with ischemic heart disease from those with left ventricular hypertrophy.     

Age-Related Cancellous Bone Loss in the Proximal Femur of Caucasian Females

The purpose of this investigation was to directly define the age-related intrafemoral variations in cancellous bone density, bone mineralization and rate of bone loss in a cadaveric population of Caucasian female femoral necks and trochanters. Forty-three Caucasian female femora were obtained and divided into premenopausal, postmenopausal and elderly age groups. The neck and trochanter were removed, and cores of cancellous bone were taken from the superior, middle and inferior regions; volume fraction and ash fraction were determined for each core. The cancellous bone volume fraction of the neck was significantly greater than that of the trochanter, as was that of the inferior region of the neck compared with the superior and middle regions at all age groups (p<0.05). The mean neck/trochanter and neck inferior/superior volume fraction ratios did not change with age; however, the variance increased with age (p<0.001). This increasing variability with age suggests that there may be a subpopulation of individuals within the elderly Caucasian population with a significantly different intrafemoral bone density distribution than was present prior to menopause. This study identified no mineralization changes with age in the cancellous bone of the proximal femur (p>0.05). The influence of increased neck/trochanter and neck inferior/superior ratios on femoral neck integrity and fracture prediction is of interest and requires further investigation. Received: 8 April 1999 / Accepted: 18 October 1999     

The rhythmic properties of the motor system

The resonance properties of the motor control circuits are basic features of the motor system. From our results, it can be concluded that, when the normally existing suppression mechanism weakens, external stimuli or internal impulses may elicit oscillations in the circuits according to the resonant frequency, and tremor will appear. It seems that the resonant frequency is between 5 and 8 Hz, as demonstrated by rhythmic voluntary movement, rhythmic elicited reflex movement and rhythmic modulated voluntary movement modulated by the stimulation of the central motor system.     

Denervation Diuresis and Renin Secretion in the Anaesthetized Dog

Abstract Simultaneous determinations of renal sodium excretion and renin secretion have been performed on 10 anaesthetized dogs, 1–2 weeks after unilateral splanchnicotomy ("renal denervation"). Under basal conditions, urine flow and sodium excretion were increased, renal venous renin activity (RVRA) and secretion decreased on the denervated side. During isotonic volume expansion a quantitative increase in denervation diuresis and natriuresis occurred while RVRA in denervated kidneys decreased further and the secretion rate became negative. Regardless of the absolute differences in water and sodium excretion between intact and denervated kidneys, RVRA and the output of the latter amounted to about 60 per cent of the intact kidney values. Both sodium reabsorption and renin production seem to be neurally regulated; their interrelationship is discussed.