Biomedical subjects
Publications and source records attributed to M M Mullins.
Rollerblading is increasingly popular in the UK. Over 12 weeks, we treated 29 patients of whom 34 per cent required operative intervention. There was a wide range of injuries, those of the radius being most common, and some (e.g. femoral and pelvic fractures) being quite severe. The value of protective equipment is discussed.
To ascertain the effect of aldosterone on body fluid volumes in neonatal, prehypertensive spontaneously hypertensive rats (SHR), we studied these animals at 12 days using age-matched Wistar-Kyoto (WKY) as normotensive controls. Some pups of each strain were treated with spironolactone (1.5 micrograms/g body wt) on days 10-12. Total body water (TBW, by dessication) and extracellular fluid (ECF, Na2 35SO4 space) volumes were significantly larger in SHR than in WKY, whereas plasma volumes (125I-serum albumin space) were not different. Thus the enlarged ECF was due to preferential expansion of the interstitial fluid (ISF) space. Treatment of SHR with spironolactone reduced TBW and ISF to values not different from untreated WKY and also reduced plasma volume to some extent. These results indicate 1) significant ISF volume expansion occurs in SHR prior to elevation of blood pressure, and 2) the previously observed elevation in plasma aldosterone in SHR at this age probably mediates the volume expansion.
The effects of a natriuretic factor contained in extracts of the atrial myocardium on an isolated renal Na+, K+-ATPase enzyme system were evaluated. Ultrafiltrates (molecular weight less than 30,000) of boiled extract of rat atria and ventricles were prepared. Infusion of 100 microliters of the atrial ultrafiltrate into bioassay rats resulted in a prompt, short-lived natriuresis and diuresis. However, addition of 100 microliters of the atrial ultrafiltrate to 900 microliters of a suspension containing Na+, K+-ATPase had no significant effect on enzymatic activity. Similarly, ultrafiltrates of ventricular extract also had no significant effect on Na+, K+-ATPase activity. These results indicate that the atrial natriuretic factor does not alter renal tubular sodium reabsorption by directly inhibiting the Na+, K+-ATPase enzyme system.
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The ability of 6- to 7-, 12- to 13-, and 16- to 17-wk-old spontaneously hypertensive rats (SHR) to excrete an acutely administered, isotonic saline load (equivalent to 4.5% body wt) was evaluated. Female SHR from two different colonies were studied. Age-matched female Wistar (W) and Wistar-Kyoto (WKY) rats served as controls. At age 6 wk, the fraction of administered Na+ load excreted by either SHR colony after 60 min was significantly lower than in the Wistar rats but not significank, one colony of SHR excreted significantly more sodium after 60 min than the other rats. Glomerular filtration rate during control periods was positively correlated with age in one SHR colony; no age-related changes were observed in glomerular function in the other groups. These data 1) suggest that WKY rats are more appropriate than the Wistar rats as controls for renal function in the SHR, 2) demonstrate that the ability of the SHR to excrete an acutely administered sodium load is equal to or greater than normotensive WKY controls, and 3) demonstrate that with respect to renal function parameters, the SHR is not a homogenous strain.
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