1. Measurements have been made of whole-body and skeletal muscle protein synthesis in fed and fasted adults with L-[1-13C]leucine. 2. The marked increase in whole-body synthesis on feeding largely reflects the changes in protein synthesis in muscle, which doubles on feeding, compared with a 40% increase in that of the rest of the body. 3. Skeletal muscle in fed man contributes more than half to total protein synthesis occurring in the whole body.

We have studied the effect of a pharmacological dose of testosterone enanthate (3 mg.kg-1.wk-1 for 12 wk) on muscle mass and total-body potassium and on whole-body and muscle protein synthesis in normal male subjects. Muscle mass estimated by creatinine excretion increased in all nine subjects (20% mean increase, P less than 0.02); total body potassium mass estimated by 40K counting increased in all subjects (12% mean increase, P less than 0.0001). In four subjects, a primed continuous infusion protocol with L-[1-13C]leucine was used to determine whole-body leucine flux and oxidation. Whole-body protein synthesis was estimated from nonoxidative flux. Muscle protein synthesis rate was determined by measuring [13C]leucine incorporation into muscle samples obtained by needle biopsy. Testosterone increased muscle protein synthesis in all subjects (27% mean increase, P less than 0.05). Leucine oxidation decreased slightly (17% mean decrease, P less than 0.01), but whole-body protein synthesis did not change significantly. Muscle morphometry showed no significant increase in muscle fiber diameter. These studies suggest that testosterone increases muscle mass by increasing muscle protein synthesis.

We performed two independent, randomised, controlled trials in order to assess the potential benefits of immediate weight-bearing mobilisation after rupture of the tendo Achillis. The first trial, on operatively-treated patients showed an improved functional outcome for patients mobilised fully weight-bearing after surgical repair. Two cases of rerupture in the treatment group suggested that careful patient selection is required as patients need to follow a structured rehabilitation regimen. The second trial, on conservatively-treated patients, provided no evidence of a functional benefit from immediate weight-bearing mobilisation. However, the practical advantages of immediate weight-bearing did not predispose the patients to a higher complication rate. In particular, there was no evidence of tendon lengthening or a higher re-rupture rate. We would advocate immediate weight-bearing mobilisation for the rehabilitation of all patients with rupture of the tendo Achillis.

1. We have investigated the effects of moderate long-term exercise on protein turnover in fed man by measuring the extent of whole-body nitrogen production, the labelling of urinary ammonia from ingested [15N]glycine and plasma, muscle and urine free amino acid concentrations. 2. Judged both from nitrogen production, and from the extent of 13CO2 production from ingested L-[1-13C]leucine, exercise causes a substantial rise in amino acid catabolism. 3. Amino acids catabolized during exercise appear to become available through a fall in whole-body protein synthesis and a rise in whole-body protein breakdown. After exercise, protein balance becomes positive through a rise in the rate of whole-body synthesis in excess of breakdown. 4. Studies of free 3-methylhistidine in muscle, plasma and urine samples suggest that exercise decreases the fractional rate of myofibrillar protein breakdown, in contrast with the apparent rise in whole-body breakdown.

We &pon a stlidy of the photophysical pro$nies of poly(p-phenylene vinylene), PPV, prepared in a way ihai gives an especially high degree of intrachaln order. optical absorption. photoluminescence. photoinduced absorption. and photoconductivity excimion spectra are presented and compared to data reported for leu well ordered wv. SpecM red shib, sharpening of spectral lines, and a msfer of oscillator strength into the vibronic p u n d slates of the electronic transitions are observe$ Photoinduced absorption due to long-lived charged excilations. previously reponed for Less ordered PPV. could not be detected in this material. Photoconductivity excitation specoa show a steep rise at the absorption edge with no appreciable offset between the onsets for photoconductio? and absorption, A very slow photocurrent component is observed, which we associate with lhe trapping and subsequent thermal release of Dhotocarriers.

Whole body protein turnover was measured in six normal adults using a model based on a primed constant infusion of [2H5]phenylalanine and, independently, by an established method of a primed constant infusion of [1-13C]leucine. Isotopic plateau in plasma was achieved within 2 h for [2H5]phenylalanine and, in four of the subjects who received a priming dose of [2H4]tyrosine, for [2H4]tyrosine. In all subjects whole body protein turnover measured with the phenylalanine model (mean protein synthesis, 2.65 +/- (SD) 0.16 g.kg-1.24 h-1; catabolism, 3.58 +/- 0.26 g.kg-1.24 h-1) was similar to that measured using the leucine model (synthesis, 3.09 +/- 0.27 g.kg-1.24 h-1; catabolism, 3.70 +/- 0.35 g.kg-1.24 h-1). Mean forearm fractional muscle protein synthesis calculated by the phenylalanine model was 0.06 +/- 0.03%/h, which compares closely with literature values derived by other methods. The phenylalanine model allows the rapid assessment of whole body and muscle protein turnover from plasma samples alone, obviating the need for measurement of expired air CO2 production or enrichment.

Quadriceps muscle protein turnover was assessed in the post-absorptive state in six men immediately after the end of unilateral leg immobilization (37 +/- 4 days) in a plaster cast after tibial fracture. A primed-constant intravenous infusion of L-[1-13C]leucine was administered over 7 h. Quadriceps needle biopsies, taken bilaterally at the end of the infusion, were analysed for muscle protein leucine enrichment with 13C. Quadriceps muscle protein synthetic rate, calculated from the fractional incorporation of [13C]leucine into protein compared with the average enrichment of blood alpha-ketoisocaproate, was 0.046 +/- 0.012%/h in the uninjured leg, but was only 0.034 +/- 0.007%/h in the quadriceps of the previously fractured leg (P less than 0.05, means +/- SD). Muscle RNA activity (i.e. protein synthetic rate per RNA) fell from 0.27 +/- 0.08 microgram of protein synthesized h-1 microgram-1 of RNA in the control leg to 0.14 +/- 0.03 microgram of protein synthesized h-1 microgram-1 of RNA in the immobilized leg (P less than 0.02). Immobilization was associated with a significant atrophy of type I muscle fibres (mean diameter 69.5 +/- 21 microns immobilized, 81.1 +/- 18 microns control, P less than 0.05), but no significant change occurred in type II fibre diameter. Mean quadriceps fibre volume calculated from the values for fibre diameter and percentage of each fibre type, was smaller in the injured leg by 10.6%; this value was near to the calculated difference in muscle thigh volume (calculated from thigh circumference and skin-fold thickness) which was less by 8.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

t fichbereich Physikalische atemie und Zentmm fir Materialwisenschaften der Philipps-UnivmiI?it, Hans-MeeaweinSuasse, D-W-3550 Marburg, Federal Republic of m a w t Cavendish Labontoly, Madingley Road, Cambridge (B3 OWE, LIK § University Chemical Iaboratoly, Lenstield Road, Cambridge 032 lEw, UK Reoeived 10 August 1992 AbstrncL Iowvmperature site-selective B u o r e m c e (SSF) spectrasmw is employed tostudy morphological eEests on the mnfomation of plyfpphenylene nnylene) (PW) and its phenyl-sutstituted, soluble derivative poly(phenylphenylenwiny1ene) (PPW). Samples of W V prepared as spincoated thin films and *retch-aligned free-slanding films, and samples of ww prepared a a t 61ms and as blends with @y(methyImethaclylate) and polycarbonate have been studied. The l~cults that we prerent are mnsislent with the notion that each polymer sample mnsists o f an m y of ordered chain segments whose avenge length renests the perfection of the loa1 structure. The satistical distribution of the segment lengths is Rsponsible for inhomogeneous broadening of the optical spenra (ataorption and emission). m e dominant electronic ucitation aeated by photoexcitation a m the r-r' energy gdp is a singlet exiton that can execute a nndom Wdlk among the chain segments. SSF specwascqy allows us to distinguish the mntributious to the apparent fluorescence Stokes shift that arise from energy relaxation though ucitation raigntion (specfral diffusion) and from svUctural relaxation of the polymer main (selflocalization). The stluctunl mntribution Lo the Stokes shift approaches zem in well aligned P W and m c h e s values of up to 500 an-' in highly disordered P P W films. The SF method also prmides a means of asesing the BRent 01 phase separation that occurs m ww blends