Lack of effect of supplementation with essential fatty acids on bone mineral density in healthy pre- and postmenopausal women: two randomized controlled trials of Efacal v. calcium alone.

Randomized controlled trials of the effects of the dietary supplement Efacal (Scotia Pharmaceuticals Plc, Guildford, Surrey, UK) v. Ca only on total body bone mineral density (BMD) and markers of bone turnover were conducted in healthy pre- and postmenopausal women separately. Total daily dose for 12 months for the Efacal groups was: Ca 1.0 g, evening primrose oil 4.0 g and marine fish oil 440 mg; and for the control groups was: Ca 1.0 g. Reported compliance was better than 90% in both age groups. For the forty-three premenopausal women (age range 25-40 years), initial mean total body BMD values were similar for Efacal and control groups and both groups showed highly significant mean increases of about 1%; however, there were no significant between-group differences for the changes in BMD or markers of bone turnover. For the forty-two postmenopausal women (age range 50-65 years), initial mean total body BMD values were again well-matched across treatment groups. Both Efacal and control groups showed highly significant decreases in total body BMD of about 1%, but again there were no significant between-group differences in total body BMD or markers of bone turnover. Possible confounding variables such as initial total body BMD were explored but had no effect on the outcome in either age group. Nail quality improved in both age groups and in both Efacal and control groups. Again, there was no significant difference between treatment groups. No evidence was found to support a beneficial effect of Efacal on BMD in these women.

Pre- and postmenopausal women have different bone mineral density responses to the same high-impact exercise.

The effects of a vertical jumping exercise regime on bone mineral density (BMD) have been assessed using randomized controlled trials in both pre- and postmenopausal women, the latter stratified for hormone replacement therapy (HRT). Women were screened for contraindications or medication likely to influence bone. The premenopausal women were at least 12 months postpartum and not lactating; the postmenopausal women had been stable on, or off, HRT for the previous 12 months and throughout the study. BMD was measured blind using dual-energy X-ray absorptiometry at the spine (L2-L4) and the proximal femur. The exercise consisted of 50 vertical jumps on 6 days/week of mean height 8.5 cm, which produced mean ground reactions of 3.0 times body weight in the young women and 4.0 times in the older women. In the premenopausal women, the exercise resulted in a significant increase of 2.8% in femoral BMD after 5 months (p < 0.001, n = 31). This change was significantly greater (p < 0.05) than that found in the control group (n = 26). In the postmenopausal women, there was no significant difference between the exercise and control groups after 12 months (total n = 123) nor after 18 months (total n = 38). HRT status did not affect this outcome, at least up to 12 months. It appears that premenopausal women respond positively to this brief high-impact exercise but postmenopausal women do not.

Changes in blood volume distribution between legs and trunk during halothane anaesthesia.

To assess the influence of halothane anaesthesia on the distribution of blood volume in supine humans, we used albumin labelled with 99mTc to measure blood volume distribution along the craniocaudal axis. We studied 6 volunteers in the supine position before, during and after anaesthesia with 1% halothane and 66% nitrous oxide. Using collimated detectors above and below the subject, counts were obtained from the legs, pelvis, abdomen, rib cage and head, with the arms excluded. During anaesthesia, the proportion of counts detected in the legs increased, but failed to achieve significance (P = 0.059). On recovery from anaesthesia, leg counts decreased significantly. Counts in the abdomen and rib cage decreased significantly during anaesthesia and the abdomen counts increased again on recovery (P = 0.036 for all changes). These results confirm other studies of the vascular effects of halothane, and do not support the hypothesis that blood volume redistributes from the legs to within the chest wall during anaesthesia.

Ultrasound and dual X-ray absorptiometry measurement of the calcaneus: influence of region of interest location.

Ultrasound measurements of the calcaneus are related to incidence of osteoporotic fracture. Such measurements are generally made at fixed coordinates relative to a footplate. This study compares measurements at an anatomically located region of interest (ROIanat) and at fixed coordinates (ROIfixed), with bone mineral density measurements, in 84 postmenopausal women. Bone mineral density (BMD) was assessed using dual energy X-ray absorptiometry at both ROIs as well as at lumbar spine and femoral neck. Broadband ultrasound attenuation and velocity of sound were measured using a CUBA system at ROIanat and ROIfixed. Additionally, broadband ultrasound attenuation at ROIfixed was measured using a Walker Sonix instrument. Mean bone mineral density, broadband ultrasound attenuation and velocity of sound did not differ significantly between ROIfixed and ROIanat, although broadband ultrasound attenuation by Walker Sonix (81.4 +/- 14.6 dBMHz-1) was significantly (P < 0.001) greater than that by CUBA (63.7 +/- 14.2 dBMHz-1). The relationship between broadband ultrasound attenuation and BMD differed significantly between the 2 ROIs and the correlation of this relationship was significantly greater at ROIfixed than at ROIanat(r = 0.74 versus 0.46, P < 0.01). The differing relationship may reflect structural variation at different regions. ROI selection may thus be a possible confounding factor in ultrasound measurement.

Errors due to non-uniform distribution of fat in dual X-ray absorptiometry of the lumbar spine.

Errors in spinal dual X-ray absorptiometry (DXA) were studied by analysing X-ray CT scans taken for diagnostic purposes on 20 patients representing a wide range of fat content. The mean difference between the fat thickness over the vertebral bodies and that over a background area in antero-posterior (AP) scanning was 6.7 +/- 8.1 mm for men and 13.4 +/- 4.7 mm for women. For lateral scanning the mean fat thickness difference was only 4 mm for both sexes, but the dispersion was greater, with a standard deviation of 15 mm. To relate these differences to errors in bone mineral, measurements were made of the bone mineral equivalence of fat-equivalent materials on DXA machines from three manufacturers. 10 mm of adipose tissue was equivalent to -0.043 g/cm2 of hydroxyapatite. For AP scanning a non-uniform fat distribution leads to a mean overestimate of 0.029 g/cm2 for men and 0.057 g/cm2 for women. The error exceeded 0.1 g/cm2 in 10% of slices. For lateral scanning the error exceeded 0.1 g/cm2 (about 15% of normal) in a quarter of slices.

Estimation of the magnitude of the error in bone mineral measurement due to fat: the effect of machine calibration.

An inhomogeneous fat distribution across the spine introduces an error into the measurement of bone mineral density by dual photon absorptiometry. Various published estimates of the mean error lie between 3 and 10%. This paper shows that while an estimate of the absolute error is sensitive to the attenuation coefficients entered for bone the relative or percentage error is independent of the bone calibration. This suggests that a re-evaluation is necessary of some of the published conclusions.

Tuberculin anergy in clinically normal individuals. I. Lymphokine and lymphocyte transformation studies.

Tuberculin anergy was demonstrated in a number of clinically normal individuals who, on being immunized with Bacillus Calmette-Guérin (BCG), failed to demonstrate a positive Mantoux skin test. Lymphoid cells from these anergic subjects when stimulated with purified protein derivative (PPD) in vitro did not produce macrophage migration inhibition factor (MIF). Lymphocyte transformation studies demonstrated that while Mantoux-positive, non-BCG immunized Mantoux-negative and anergic individuals could all undergo blast cell transformation in the presence of PHA, only lymphoid cells from Mantoux-positive and a proportion of anergic people were capable of blast cell transformation when cultured with PPD. These results suggest that more than one mechanism may account for tuberculin anergy in clinically normal people operating at the level of lymphokine production and in some cases lymphocyte transformation.