Observations on the potential across the rumen of the sheep

1. The electric potential difference between rumen contents and jugular venous blood was measured in anaesthetized sheep. In order to investigate the effect on the potential of changing the ionic concentrations within the rumen, the digesta were removed from the rumen and various salt solutions were substituted. The reticulo-rumen sac was isolated before the experiment by ligation of the oesophagus and the reticulo-omasal junction. 2. The observation of Dobson & Phillipson (1958) that the rumen contents are normally of the order of 30 mV negative to the blood was confirmed. 3. For potassium concentrations between 25 and 100 mM the potential at constant [Na+] varied linearly with log [K+]. With sulphate as the anion, the slope for a 10-fold concentration change was 39.7 +/- 3.0 mV when [Na+] was around 50 mM. The slope showed a tendency to increase when [Na+] was lowered, and to decrease when [Na+] was raised. 4. When chloride was substituted for sulphate, both the slope and the absolute size of the potential were slightly reduced. 5. When the sodium concentration was varied at constant [K+], the potential increased as an approximately linear function of [Na+]. At around 10 mM-K the mean slope was 0-32 +/- 0.07 mV/mM; at the highest potassium concentrations it fell to 0-13 +/- 0 05 mV/mM. 6. In most of these experiments isotonicity was maintained with sucrose. The results of a few tests in which Li+ was substituted for Na+ or K+ suggested that the rumen epithelium behaves in a relatively inert fashion towards this ion.

A survey of pediatric management of dyslipidemias in New England

We recently surveyed physicians attending the New England Pediatric Preventive Cardiology Society. Sixteen physicians who actively evaluated children with dyslipidemia completed questionnaires; at least one representative from six of the seven medical schools in New England was included. The survey elicited responses to five hypothetical cases of childhood dyslipidemia which were representative of the types of lipid problems commonly referred to pediatric lipid specialists. Diet modification was the initial treatment of choice of all participants. For any set of lipid values, postpubertal age increased the proportion of respondents who would have prescribed medication. When pharmacologic intervention was elected, resin binders (cholestyramine or cholestipol) and niacin were most commonly prescribed. The responses of the physicians showed considerable variation in the threshold for beginning medications. In summary, this survey suggests substantial variation in the approach to pharmacologic management of pediatric dyslipidemias in the New England region.