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Repeated bouts of eccentric muscle contractions were used to examine indirect indices of exercise-induced muscle damage and adaptation in human skeletal muscle. Twenty-four subjects (18 females, 6 males) aged 20.0 +/- 1.4 years (mean +/- S.D.) performed an initial bout of either 10 (n = 7), 30 (n = 9) or 50 (n = 8) maximum voluntary eccentric contractions of the knee extensors, followed by a second bout of 50 contractions 3 weeks later using the same leg. Muscle soreness was elevated after all bouts (P < 0.05, Wilcoxon test), although the initial bout reduced the soreness associated with the second bout. Force loss and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio were observed after all exercise bouts (P < 0.01). Serum creatine kinase activity was elevated following the initial bouts of 30 and 50 repetitions (P < 0.01), but there was no increase following 10 repetitions. No increase in serum creatine kinase activity was observed in any group following the second bout of contractions (P > 0.05). We conclude that skeletal muscle adaptation can be brought about by a single bout of relatively few eccentric muscle contractions. Increasing the number of eccentric muscle repetitions did not result in an increased prophylactic effect on skeletal muscle.

Indirect indices of exercise-induced human skeletal muscle damage and connective tissue breakdown were studied following a single bout of voluntary eccentric muscle contractions. Subjects (six female, two male), mean (SD) age 22 (2) years performed a bout of 50 maximum voluntary eccentric contractions of the knee extensors of a single leg. The eccentric exercise protocol induced muscle soreness (P < 0.05 Wilcoxon test), chronic force loss, and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio [P < 0.01, repeated measures analysis of variance (ANOVA)]. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) activities were elevated (P < 0.01, repeated measures ANOVA) following the bout. The mean (SD) CK and LDH levels recorded 3 days post-exercise were 2815 (4144) IU.l-1 and 375 (198) IU.l-1, respectively. Serum alkaline phosphatase activity showed no changes throughout the study, and a non-significant increase (P = 0.058, repeated measures ANOVA) in pyridinoline was recorded following the bout. Urinary hydroxyproline (HP) and hydroxylysine (HL) excretion, expressed in terms of creatinine (Cr) concentration, increased after exercise (P < 0.05 and P < 0.01, respectively, repeated measures ANOVA). An increased HP:Cr was recorded 2 days post-exercise and HL:Cr was increased above baseline on days 2, 5, and 9 post-exercise. This indirect evidence of exercise-induced muscle damage suggests that myofibre disruption was caused by the eccentric muscle contractions. Elevated urine concentrations of indirect indices of collagen breakdown following eccentric muscle contractions suggests an increased breakdown of connective tissue, possibly due to a localised inflammatory response.

Indices of human skeletal muscle contractile function were examined in nine subjects for up to 9 days following a single bout of stimulated eccentric exercise. Eccentric muscle actions of the knee extensor muscles were evoked by percutaneous electrical myostimulation (PES). Delayed onset muscle soreness (DOMS), elevated serum creatine kinase activity, chronic force loss, and a decline in the 20:100 Hz force ratio were observed in the days postexercise. The exercised knee extensor muscles demonstrated an impaired ability to respond to PES. This was evident by an increased time delay between the start of 100 Hz PES and the onset of contraction immediately postexercise [22.3 (SD 15.9)%, P < 0.01] and 3 days postexercise [14.9 (SD 18.1)%, P < 0.05]. Muscle relaxation rates appeared unaffected by the eccentric exercise protocol, where the muscles showed no differences in the time between the end of PES and the onset of relaxation (P > 0.05). During the days following the exercise, no significant differences were observed in the time between the start of contraction and attainment of 70% of the mean tetanic force following a single 1-s pulse of PES. Similarly, no significant differences were observed in the time between the start of relaxation and attainment of 70% of the total relaxation during the same time. The increased delay in excitation-contraction coupling observed immediately postexercise and 3 days after the exercise, may reflect a damage-induced delay in action potential propagation. Muscle relaxation rates postexercise remained unchanged, which would seem to indicate normal functioning of the sarcoplasmic reticulum, suggesting this was not the site of failure in excitation-contraction coupling.

Glutaminase activity in intact mitochondria from rat liver is activated by spermine, as indicated both by increased glutamate production from glutamine and by increased respiration with glutamine as sole substrate. Glutaminase activity assayed in membranes from frozen-thawed mitochondria, is activated by spermine about 6-fold at physiological concentrations of its other effectors (NH4+ at 0.7 mM, Pi 5 mM) and at pH 7.4. Spermine decreased the apparent Km for glutamine from 38 to 15 mM at 5 mM Pi, and increased the sensitivity of the enzyme for phosphate activation so that the concentration required for 50% stimulation decreased from 15 to 4 mM. Half-maximal spermine effects occurred at 0.15 mM, which is in the physiological range. Spermine was effective in the presence of physiological concentrations of Mg2+. We suggest that spermine may be a physiological activator of hepatic glutaminase.

We have compared the performance of an off-axis (knife-edge) photorefractor with that of an on-axis (isotropic) system. Normal infants and children between the ages of 8 and 208 weeks were photographed with each camera both with and without cycloplegia. Refractive errors were estimated for each technique based on equations derived from ray-tracing. These refractions were compared to the results of retinoscopy under cycloplegia. Sensitivity and specificity of the two photorefraction systems were evaluated as a function of the magnitude of meridional hyperopia defined by retinoscopy. We also examined the effect of varying the photorefraction screening criterion. Thirteen percent of the infants in the screening sample presented with +3.50 diopters or more of meridional hyperopia. Using this level of ametropia as a referral criterion, the sensitivity and specificity of the off-axis system for infants without cycloplegia were 83% and 72%, respectively. For the on-axis system, sensitivity and specificity values were 85% and 53%. The use of cycloplegics did not significantly improve the performance of either system, but rather their use degraded the specificity of the on-axis system in the presence of moderate refractive errors. The results of the present study indicate that both on- and off-axis systems are effective in identifying highly ametropic infants, but that the off-axis system results in significantly fewer false positives. Moreover, the off-axis system has the advantages of an inherently greater dynamic range for a fixed camera design, and also more easily interpreted photographs.

The alternatives in the management of infantile glaucoma refractory to conventional treatment are quite limited and unrewarding. We did a retrospective study of 49 patients (53 eyes) under 12 years of age with advanced, uncontrolled glaucoma who each underwent implantation of a single-plate Molteno implant in one stage. Over the follow-up period ranging from 6 months to 3 years (mean 18 months), 36 of the 53 eyes (68%) had an intraocular pressure less than or equal to 21 mm Hg and were considered a success. Fourteen eyes (26%) required further glaucoma surgery, 2 eyes developed severe chronic hypotony, and 1 eye lost light perception following endophthalmitis. The number of anti-glaucoma medications was decreased from a mean of 2 (+/- 1) to 1 (+/- 1). The probability for success of the Molteno implant in controlling glaucoma increased with the age of the patient. Six eyes (11%) were late failures, most probably due to fibrous encapsulation of the bleb. Complications observed were: prolonged hypotony and flat anterior chamber, retinal detachment, migration of the tube, erosion of the tube through the conjunctiva, and an ingrowth of fibrous tissue in the anterior chamber. We consider the Molteno implant to be a reasonable option in the management of difficult cases of infantile glaucoma.

Monocular and binocular grating acuities were measured using a swept spatial frequency visual evoked potential (VEP) technique in a group of fifteen infants with esotropia and alternating fixation. Both monocular and binocular acuity measures fell significantly below the mean for age-matched normals. Infants with esotropia and alternating fixation did not have significant interocular acuity differences.

Refractive errors were determined photographically in a group of infants and children and were compared to conventional cycloplegic retinoscopy. The refractor consisted of a mirror telephoto lens and strobe flash designed to mimic the action of a retinoscope. Significant amblyogenic conditions such as anisometropia and high isoametropia were detectable. Strabismus and media opacities were also recordable. The technique provides a potential mass suited for infants.

Kaakinen (1979) presented a method of measuring refractive error and ocular alignment by simultaneous photography of corneal and fundus reflexes. As presented, the technique was unable to detect refractive errors of less than 2-3 diopters (Howland 1980; Kaakinen 1979). We demonstrate that the use of a catadioptric lens and a long working distance can improve sensitivity to less than 1.0 D. Refractions of a model eye, an accommodating eye and ametropic eyes indicate that refractive errors greater than 0.75 D are readily detectable. The improvement in sensitivity achieved by the present system is attributable to a reduction of the angle between the flash source and the entrance pupil of the photorefractor.

A 14-year-old native of Ethiopia with previously treated onchocerciasis moved to California where he was examined for evidence of persisting nematode infestation. Skin and conjunctival biopsy specimens initially disclosed no abnormalities. Subsequently, conjunctival nodules developed, and a biopsy specimen of one of these revealed microfilariae of Onchocerca volvulus lying adjacent to a necrotic eosinophilic granulomatous inflammatory nodule. To our knowledge, nodules of this type have not heretofore been reported to be a notable feature of ocular onchocerciasis. This type of inflammation has a relationship to degenerating microfilaria in onchocerciasis and in other nematode infestation.