Relaxation in ferret ventricular myocytes: unusual interplay among calcium transport systems.

Transport systems responsible for removing Ca2+ from the myoplasm during relaxation in isolated ferret ventricular myocytes were studied using caffeine-induced contractures. Internal calcium concentration ([Ca2+]i) was measured with the fluorescent calcium indicator indo-1, and the results were compared with our recent detailed characterizations in rabbit and rat myocytes. Relaxation and [Ca2+]i decline during a twitch in ferret myocytes were fast and similar to that in rat myocytes (i.e. half-time, t 1/2 approximately 100-160 ms). During a caffeine-induced contracture (SR Ca2+ accumulation prevented), relaxation was still relatively fast (t 1/2 = 0.57 s) and similar to relaxation in rabbit supported mainly by a strong Na(+)-Ca2+ exchange. When both the SR Ca2+ uptake and Na(+)-Ca2+ exchange are blocked (by caffeine and 0 Na+, 0 Ca2+ solution) relaxation in the ferret myocyte is remarkably fast (approximately 5-fold) compared with rabbit and rat myocytes. The decline of the Cai2+ transient was also fast under these conditions. These values were similar to those in rat under conditions where relaxation is due primarily to Na(+)-Ca2+ exchange. Additional inhibition of either the sarcolemmal Ca(2+)-ATPase or mitochondrial Ca2+ uptake caused only modest slowing of the relaxation of caffeine-induced contracture in 0 Na+, 0 Ca2+ (t 1/2 increased to approximately 3 s). In rabbit myocytes the relaxation t 1/2 is slowed to 20-30 s by these procedures. Even when the systems responsible for slow relaxation in rabbit ventricular myocytes are inhibited (i.e. sarcolemmal Ca(2+)-ATPase and mitochondrial Ca2+ uptake) along with the SR Ca(2+)-ATPase and Na(+)-Ca2+ exchange, relaxation and [Ca2+]i decline in ferret myocytes remain rapid compared with rabbit myocytes. Ca2+ taken up by mitochondria in rabbit myocytes during a caffeine contracture in 0 Na+, 0 Ca2+ solution gradually returns to the SR after caffeine removal, but this component appears to be much smaller in ferret myocytes under the same conditions. We tested for possible residual Ca2+ transport by each of the four systems which suffice to explain Ca2+ removal from the cytoplasm in rabbit (SR Ca(2+)-ATPase, Na(+)-Ca2+ exchange, sarcolemmal Ca(2+)-ATPase and mitochondrial Ca2+ uptake). We conclude that there is an additional calcium transport system at work in ferret myocytes. For this additional system, our results are most compatible with a trans-sarcolemmal Ca2+ transport, but neither a cation exchanger nor a Ca(2+)-ATPase with characteristics like that in other cardiac cells. This additional system appears able to transport Ca2+ nearly as fast as the Na(+)-Ca2+ exchange in rat ventricular myocytes.     

Osteopetrosis: MR characteristics at 1.5 T

Four patients with proved osteopetrosis (three with the infantile malignant form and one with the benign form) were examined with magnetic resonance imaging at 1.5 T. All patients were studied in the coronal and sagittal planes using both short and long repetition time/echo time sequences. The infantile malignant form was characterized by a complete lack of signal from the marrow alternating with a signal intensity equivalent to that of the intervertebral disks, resulting in a "stepladder" appearance. In the benign form or after successful marrow transplantation in the infantile malignant form, intermediate or high signal intensity in the vertebrae was noted, suggesting the presence of some marrow elements.     

Age and sex differences in the management of ischaemic heart disease

Objective

To investigate age and sex differences in the utilisation of hospital services for ischaemic heart disease.

Design

Analysis of routine mortality data and hospital activity data.

Setting

South West Thames Regional Health Authority.

Subjects

Residents of the South West Thames Regional Health Authority who in 1991 either died from ischaemic heart disease or were admitted to an NHS hospital in England and Wales with a main diagnosis of ischaemic heart disease.

Main outcome measures

Ratio of consultant episodes to deaths from ischaemic heart disease (as a proxymeasure of the utilisation of hospital care), and the percentages of consultant episodes in which further investigation (angiography or catheterisation) or revascularisation treatment (coronary artery bypass grafting or angioplasty) were carried out.

Results

The ratio of episodes to deaths was similar in men and women (odds ratio for men vs. women 0.96, 95% confidence intervals 0.90 to 1.03). The percentage of episodes in which further investigation was carried out was higher in men than women (odds ratio for men vs. women 1.46, 95% confidence intervals 1.25 to 1.70) as was the percentage of episodes in which revascularisation treatment was carried out (odds ratio for men vs. women 1.46, 95% confidence intervals 1.20 to 1.77). The ratio of episodes to deaths, the percentage of episodes in which further investigation was carried out, and the percentage of episodes in which revascularisation treatment was carried out all declined with age (all p values <0.001).

Conclusions

Women with ischaemic heart disease are as likely as men to be admitted to hospital, but afteradmission are less likely to undergo further investigation and revascularisation treatment. Elderly patients with ischaemic heart disease are less likely than younger patients to be admitted to hospital; after admission, they are also less likely to undergo further investigation and revascularisation treatment. Further research is needed to determine whether these age and sex differences in the use of hospital services are clinically justified.