Combining event scores to estimate the ability of competitors

Simulation was used to investigate the validities of nine measures of ability derived from scores of two or more competitive events. The measures were: raw means and least-squares means of raw scores, z scores, and normal scores; two measures derived from ranked scores; and the "personal-best" raw score. Simulations were performed for different numbers of competitors, events, and event entries, each for a range of validity of performance in a single event. A complete set of simulations was repeated for each of the following conditions: normal distribution of competitors' ability; skewed distribution of ability; event validity related to ability; validity, ability, and spread of scores differing between events; and events differing in difficulty. The raw mean of raw scores was generally the most valid measure. The personal best was comparable to the mean only when the number of entries approached one per competitor. The least-squares mean of raw scores had highest validity when events differed substantially in difficulty; it should therefore be used when events differ in length, or when event scores are affected by environmental conditions, judging bias, or by uneven matching of competitors in match-play sports.

Chelation therapy for intermittent claudication. A double-blind, randomized, controlled trial

BACKGROUND

The use of repeated intravenous infusions of EDTA, which has become known as "chelation therapy," has been promoted for treating intermittent claudication as well as a wide range of other disorders. Multiple reports of excellent results in large numbers of patients have encouraged the use of this regimen. The lack of well-controlled studies substantiating the benefits of this treatment has limited its use mainly to private clinics. The aim of the study was to assess the benefits of chelation therapy in patients with intermittent claudication.

METHODS AND RESULTS

A double-blind, randomized, controlled trial included 32 patients with intermittent claudication who were randomized to a treatment group (15) and a control group (17). Main outcome measures were subjective and measured walking distances and ankle/brachial pulse indices. Other outcome measures included lifestyle and subjective parameters of improvement, cardiac function, ECG, renal function, hematology, blood glucose, and lipid biochemistry. No clinically significant differences in main outcome measures between chelation therapy and placebo groups were detected up to 3 months after treatment. Measures of mood state, activities of daily living, and quality of life factors were not consistently affected by chelation therapy. An equal proportion (13%) of each group thought that they had received the active agent. The proportion of patients showing an improvement in walking distance was not significantly different between the chelation group (60%) and the control group (59%).

CONCLUSIONS

Chelation therapy has no significant beneficial effects over placebo in patients with intermittent claudication.

Respiratory responses of elite oarsmen, former oarsmen, and highly trained non-rowers during rowing, cycling and running

The position of the body and use of the respiratory muscles in the act of rowing may limit ventilation and thereby reduce maximal aerobic power relative to that achieved in cycling or running, in spite of the greater muscle mass involved in rowing. This hypothesis was investigated for three groups of male subjects: nine elite senior oarsmen, eight former senior oarsmen and eight highly trained athletes unskilled in rowing. The subjects performed graded exercise to maximal effort on a rowing ergometer, cycle ergometer and treadmill while respiratory minute volume (VE) and oxygen consumption (VO2) were monitored continuously. The VE at a given VO2 during intense submaximal exercise (greater than 75% of maximal VO2) was not significantly lower in rowing compared with that in cycling and treadmill running for any group, which would suggest that submaximal rowing does not restrict ventilation. At maximal effort, VO2, and VE for rowing were less than those for the other types of exercise in all the groups, although the differences were not statistically significant in the elite oarsmen. These data are consistent with a ventilatory limitation to maximal performance in rowing that may have been partly overcome by training in the elite oarsmen. Alternatively, a lower maximal VE in rowing might have been an effect rather than a cause of a lower maximal VO2, if maximal VO2 was limited by the lower rate of muscle activation in rowing.

Predictors of attainment in rhythmic sportive gymnastics

Correlates of attainment in rhythmic sportive gymnastics (RSG) were investigated in a cross-sectional study of 106 female gymnasts aged 7-27 years. Physical attributes were obtained by anthropometry and from tests of flexibility, leg power, maximum oxygen uptake and visuo-motor proficiency. Training and psychological measures were derived from self-administered questionnaires that included the Leadership Scale for Sport, Psychological Skills Inventory for Sport, General Health Questionnaire, Sport Competition Anxiety Test, and several questions on sport motivation and enjoyment. Attainment was expressed as competition grade level and mean performance score in 4 competitions. The best correlates of attainment were cumulative and current training time (r = 0.84-0.53). Age, lean body mass and composite measures of flexibility, leg power and visuo-motor proficiency were also significant correlates of attainment (r = 0.69-0.29), as were coach democratic and coach social behaviours (r = 0.41-0.28). The significant positive psychometric correlates of attainment were mental preparation, motivation by creativity, and several dimensions of enjoyment (r = 0.35-0.26); significant negative correlates were recent anxiety-depression and enjoyment of training (r = -0.34-(-)0.32). No previous study has identified the relative contributions of such a comprehensive range of physical, psychological and training measures to performance of a sport.

Blood glucose following training sessions in runners

The possibility that blood glucose reaches potentially dangerous concentrations following training sessions was investigated in 10 competitive runners. Blood glucose concentration was assayed in the first 60 min following a continuous run at moderate pace for 45 min, a continuous run at hard pace for 30 min, an interval training session for 15 min, and an incremental exercise test to maximum effort. Glucose concentration increased and remained high for up to 30 min following the hard-pace, interval and maximum-effort runs; maximum concentrations (mean +/- SD 6.8 +/- 1.1, 6.8 +/- 1.0, 7.8 +/- 1.1 mmol.l-1 respectively) were significantly higher (p < 0.05) than those of the moderate-pace run (4.9 +/- 0.4 mmol.l-1). A 10-min warm-down at moderate pace dramatically attenuated the surge in glucose concentration following 30 min of hard-pace running, but a pre-exercise carbohydrate snack had no effect. Level of glycation of haemoglobin in a venous blood sample (mean +/- SD 4.6 +/- 0.7 %) was normal. Thus transient elevations in blood glucose concentration following high-intensity training sessions are unlikely to damage body proteins.

Validation of subjective measures of fatigue after elective operations

OBJECTIVE

To find out if it was possible to evaluate postoperative fatigue by questionnaire.

DESIGN

Open study.

SETTING

University hospital.

SUBJECTS

23 patients about to undergo elective general surgical operations.

INTERVENTIONS

A questionnaire was filled in before, and 2-46 days after, operation.

MAIN OUTCOME MEASURES

Six measures of fatigue were derived from the questionnaire and validated objectively with changes in body weight, exercise tolerance (n = 10), or grip strength (n = 21).

RESULTS

The six measures all showed a significant increase after operation. The changes in fatigue correlated well, but there were differences in sensitivity to changes in perceived weakness compared with perceived tiredness. Each measure correlated significantly with either body weight, exercise tolerance or grip strength.

CONCLUSION

Questionnaires can provide reliable results in the assessment of postoperative fatigue.

Quantification of training in competitive sports. Methods and applications

The training of competitive athletes can be assessed by retrospective questionnaires, diaries, physiological monitoring and direct observation of training behaviour. Questionnaires represent the most economical, most comprehensive and least accurate method. Diaries are more valid, but their drawbacks for long term quantitative studies are poor compliance and difficulties in processing the data they generate. Physiological monitoring (of oxygen consumption, heart rate or blood lactate concentration) provides objective measures of training intensity, and direct observation gives valid measures of most aspects of training; however, these methods are impractical for continuous, long term use. Coaches and athletes quantify training for purposes of motivation, systematisation of training and training prescription, but there has been little study of the use of training quantification by these practitioners. Motivation and systematisation are probably achieved best with diaries. Direct observation appears to be the best method of ensuring compliance with a training prescription, although heart rate monitoring is also a promising method for prescribing endurance training intensity. Sport scientists quantify training to study its effects on the performance and health status of competitive athletes. Most studies have been descriptive rather than experimental, and unvalidated questionnaires have been the predominant method of assaying training. The main areas of research include performance prediction and enhancement, overtraining, reproductive dysfunction, injury, illness, and nutritional status. Training has substantial effects in all of these areas. There is a need for more experimental studies that utilise validated measures of training to investigate how to reduce sports injuries and enhance competitive sports performance. More attention could also be given to methodological issues of training quantification.

Training intensity of elite male distance runners

To quantify training intensity in 13 nationally ranked male distance runners, training heart rates, environmental factors, and motivational factors were recorded throughout a 6-8 wk period of normal training. Variation in motivational and environmental factors such as intended effort, terrain, and running with companions altered training session mean heart rates by up to 4.min-1 (standard deviation). Heart rates and blood lactate concentrations, recorded in a series of steady-state treadmill runs, were used to convert training session mean heart rates to mean training speeds (TS) and to derive a measure of the anaerobic threshold (AT, the treadmill speed at a blood lactate concentration of 4 mmol.l-1). TS (15.6 +/- 1.4 km.h-1, mean +/- SD) was considerably lower than AT (20.2 +/- 1.1 km.h-1) in all subjects (P less than 0.001). Relative TS (TS expressed as a fraction of AT) differed significantly (P less than 0.001) between subjects and correlated significantly with the distance of the event for which the subject was training (r = 0.59, P less than 0.05). Relative TS may therefore be determined by the subject's or coach's perception of the appropriate intensity for the event. If the AT is the optimum training intensity, these subjects have considerable scope for improvement.

Lifestyle behaviours during pregnancy

Lifestyle behaviours of 183 women before and during pregnancy were investigated by retrospective questionnaire in the first few days postpartum. The threshold of cigarette smoking for a reduction in birth weight was exceeded at full term by 17% of the women, but only 1% exceeded a similar threshold for alcohol consumption. Consumption below the recommended minimum level for one or more major food groups was reported by 35% of the women during pregnancy. Only 36% of the women were vigorously active before pregnancy, and only 13% remained so throughout pregnancy. Level of education was a significant predictor of healthy lifestyle behaviours. Concern for their baby's and their own health were the main reasons given for change in behaviour during pregnancy, while doctor's advice and antenatal classes were cited infrequently. A new approach to lifestyle enhancement by health professionals might promote desirable changes in relation to smoking and possibly also food consumption and physical activity.

The intensity of exercise in deep-water running

The intensity of exercise during 30-min sessions of continuous deep-water running at a "hard" pace was determined by monitoring oxygen consumption (VO2), respiratory quotient (RQ), heart rate, perceived physical effort and perceived aches and pains in the legs in eight competitive runners, six of whom had not previously practised the technique. The intensity was compared with that of 30-min runs on a treadmill at hard and "normal" training paces and a 30-min outdoor run at normal training pace. VO2 during the last session of deep-water running (73% of maximum VO2) was not significantly different from that of the treadmill hard run (78%), but was significantly higher than that of the treadmill normal run (62%). Similar results were obtained for RQ, perceived effort and pain. In contrast, heart rates for deep-water running were similar to those of normal training and significantly less than those of the treadmill hard run. The disparity between VO2 and heart rate for deep-water running may reflect cooling or increased venous return caused by water immersion. It is concluded that deep-water running can be performed at a sufficient intensity for a sufficient period to make it an effective endurance training technique.

Validation of the physical activity instrument for the Life in New Zealand national survey

A physical activity recall instrument suitable for self-administration by the adult New Zealand population was devised and validated for 140 subjects selected randomly from urban electoral rolls. Validation used bootstrapping to compare correlations between subjective measures derived from the instrument, the Stanford 7-day recall questionnaire and other questionnaires, and objective measures derived from an exercise test. Subjective measures were grouped as measures of high intensity activity, low intensity activity, or total activity metabolism. The high intensity measures correlated moderately with each other (mean r = 0.39), but poorly with metabolism and low intensity measures (r = 0.16, -0.02, respectively). The mean correlation between the metabolism and low intensity groups (r = 0.26) was similar to those within these groups (r = 0.31, 0.25, respectively). Thus, the high intensity measures formed a group distinct from the metabolism and low intensity groups, which represented similar measures. The objective measures that correlated with high intensity measures (mean r = 0.25) are predominantly recognized risk factors for cardiovascular disease; these did not correlate with the metabolism or low intensity measures (mean r = 0.03, -0.07, respectively). Activity measures from the instrument had mean correlations with subjective and objective measures that equaled or surpassed those of the Stanford measures from the same group. The authors conclude that 1) population health studies that assay physical activity should include well-defined measures of high intensity activity, and 2) valid measures of physical activity in the New Zealand population are achievable with this instrument.

Effect of low growth temperature on coupling between electron transport and proton flux in Vicia faba thylakoids

Coupling between electron transport and proton flux has been compared in chloroplasts from Vicia faba (cv. Windsor) plants grown at 20 and 5°C. Proton uptake by warm-grown thylakoids was sensitive to external pH and stimulated by micromolar adenine nucleotide above pH 7.0. Electron transport was modulated by pH, adenine nucleotide and energy transfer inhibitors (triphenyltin and Hg(2+) ). By contrast, proton uptake by cold-grown thylakoids was generally lower and was insensitive to micromolar ATP. The rate of non-phosphorylating electron flow in cold-grown thylakoids was relatively insensitive to pH and Hg(2+) and was not modulated by adenine nucleotides or triphenyltin. Stimulation of electron transport by phosphorylating conditions in cold-grown thylakoids was generally lower and insensitive to pH. It is concluded that the control of proton efflux through CF(0) -CF(1) differs in thylakoids of V. faba grown at warm and cold temperatures.

Competition for survival between motor units in mouse skeletal muscle

The soleus nerve on one side of neonatal mice was crushed and the soleus muscle on the same side was surgically reduced in size. Some animals also had their lumbar spinal nerve 5 (L5) cut and misdirected in the same operation. Three months later, the number of L5 and L6 soleus motor units in the operated muscles was counted electrophysiologically and the number of muscle fibers was counted histologically. The number of L6 motor units in reduced size muscles without L5 innervation was significantly greater than it was in muscles where both L5 and L6 motor units were present. This result supports the concept that motor neuron survival during development is dependent upon the number of muscle fibers available for innervation and the number of motor neurons competing to innervate them.

Physical activity of asthmatic and nonasthmatic children

Questionnaires examining behaviors and attitudes related to physical activity and asthma were administered to 408 urban schoolchildren aged 11-13 years. Asthmatics (16% of the sample) were more frequently active and were more anxious prior to exercise than nonasthmatics, but did not differ significantly from nonasthmatics in enjoyment of exercise or in physical self-concept. The motives for performing exercise or sport were similar in the two groups, although the asthmatics perceived less pressure to be active from parents or school than the nonasthmatics. It is concluded that asthmatic children have favorable behaviors and attitudes in relation to exercise and sport.

The meaning of "physical fitness"

The understanding of the term "physical fitness" was determined for a randomly selected sample (n = 94) of a population using a self-administered mailed questionnaire. Subjects were asked to state and give a reason for their perceived level of physical fitness, to state their perceived performance level in a number of physical fitness tests (muscular strength, daily physical work capacity, fatness, level of regular physical exercise, exercise speed, and body flexibility), and to rate how well these tests measure physical fitness. The reason most frequently stated for perceived level of physical fitness was the level of habitual physical activity (43%); significantly less frequently (P less than 0.01-0.0001) cited were reasons related to health (23%), physical performance (12%), and obesity (3%). The variation in perceived level of physical fitness was best explained by the variation in imagined regular exercise and fatness (r2 = 0.66, P less than 0.0001) with no significant additional contribution from imagined performance in remaining fitness tests. The measurement of regular exercise was most favored as a test of physical fitness. These results, taken together with evidence of the physical and psychological health benefits of regular exercise, imply that the most appropriate measure of physical fitness for the average person is an assessment of the habitual physical activity level.

An exercise performance test does not measure physical fitness for the average person

One hundred and thirty five members of the public who attended a medical school open day and who volunteered for a physical fitness assessment were asked to rate their own physical fitness and to give a reason for their rating; subjects then performed a submaximal exercise test for an estimation of maximum oxygen uptake. More than two-thirds of the reasons given for self-rating of fitness were related to level of regular exercise, while physical exercise performance, health or obesity each accounted for 10% or less of the reasons given. There was no significant correlation between self-rating of fitness and maximum oxygen uptake. It is concluded that for the average person an estimate of the level of regular exercise is likely to be a more appropriate measure of physical fitness than performance in an exercise test.

Polysomes from winter rye seedlings grown at low temperature : I. Size class distribution, composition, and stability

We have studied the influence of growth at low temperature on size class distribution, stability and composition of leaf cytoplasmic polysomes from rye seedlings (Secale cereale, cv Puma) grown at 5 degrees C and at 20 degrees C. Leaves of seedlings grown at 5 degrees C contain 2.7 times more cytoplasmic polysomes (expressed on a DNA basis) and the polysome size class distribution is skewed toward larger polysomes. These changes were more pronounced in the free polysome fraction than in the membrane-bound fraction. The melting point of the total ribosome fraction from cold-grown leaves was decreased by 3.7 degrees C. Electrophoresis did not reveal any difference in the rRNA or in core-ribosomal proteins (KCl nondissociable) following growth at low temperature. Some differences were noted in peripheral ribosomal proteins. This study is the first to examine the effect of growth at low and high temperatures on polysome metabolism using plants of similar developmental stage. Polysome quantity, polymerization, melting point and peripheral ribosomal proteins in rye seedlings are modified during growth at low temperature.

End-plate growth exceeds nerve terminal growth in juvenile mice

An electron microscopic investigation of neuromuscular synapses of the tensor fasciae latae muscle in juvenile mice was carried out to determine the relationship between the presynaptic (nerve terminal) and postsynaptic (end-plate plaque) elements during the major phase of postnatal growth. In the first month of life growth of the synapse was accompanied by a decrease in the size of pre- and postsynaptic elements in cross section. A decrease in the fraction of the width of end-plate plaque opposed by nerve terminal was also observed to age 2 months, and in older animal some end-plate plaques were completely unopposed by nerve terminal. This implies that end plates grow at a faster rate than nerve terminals and suggests that the availability of uninnervated, differentiated end plate permits or promotes nerve terminal growth.

Isolation and in vitro translation of polysomes from mature rye leaves

Cytoplasmic polysomes have been prepared from mature leaves of winter rye (Secale cereale L. cv Puma). This is the first time a method has been developed for isolation of highly polymerized polysomes from mature leaves. The degree of intactness of isolated plant polysomes has been determined by two independent but complementary methods: size class distribution by sucrose gradient centrifugation and in vitro translation. The polymerization of isolated polysomes was estimated by the ratio of the proportion of large polysomes to the proportion of small polysomes obtained from the profiles. Our results show that the composition of the optimal polysome isolation buffer for mature rye leaves is different from that reported for young tobacco and pea leaves. Polysomes were translated in vitro with the S-105 wheat germ fraction. The degree of polysome polymerization has a significant effect on their in vitro translation since both the incorporation of amino acid and the presence of high molecular weight polypeptides are proportional to the large polysomes/small polysomes ratio. This study emphasizes the need to evaluate isolation conditions carefully before proceeding with polysome studies in any particular tissue or in tissues under different physiological status.

Physical fitness of blind and sighted children

Twenty-seven children (age 7-17 years) with varying degrees of blindness but with no other known disorder were assessed for physical fitness. Twenty-seven randomly selected children with normal eyesight were also assessed. Maximum oxygen uptake (VO2max) was measured directly during a progressive exercise test on a treadmill. There was a significant and substantial reduction in VO2max in totally blind children (mean +/- standard deviation 35.0 +/- 7.5 ml X min-1 X kg-1) compared with normal children (45.9 +/- 6.6 ml X min-1 X kg-1). Partially sighted children had a significant but smaller reduction in VO2max. Fitness assessed by a step-test was significantly reduced in the visually impaired children, and skin-fold thickness was also significantly greater in totally blind children. The level of habitual physical activity for each child, as assessed by a questionnaire, correlated with VO2max (r = 0.53, p less than 0.0001). Blind children were significantly less active than normal children, and the difference between mean VO2max for blind and normal children became non-significant when their different activity levels were taken into account. It is concluded that totally blind children are less fit than other children at least partly because of their lower level of habitual activity.

Population biology of Ammophila breviligulata and Calamovilfa longifolia on Lake Huron sand dunes. II. Ultrastructure of organelles and photosynthetic properties

Organellar ultrastructure and photosynthetic properties of two grasses, Calamovilfa longifolia (Hook) Scribn. and Ammophila breviligulata Fern., growing on Lake Huron sand dunes were compared. Thylakoids of C. longifolia contained a relatively greater complement of the photosystem I (PSI) – chlorophyll a – protein complex, whereas thylakoids from A. breviligulata had a relatively greater complement of light-harvesting chlorophyll a + b complex. The chlorophyll a/b ratios of the mesophyll chloroplast thykaloids reflected the content of chlorophyll–protein complexes present in the membranes. Digitonin fractionation of mesophyll thylakoids from C. longifolia revealed that the PSI-enriched fraction contained more chlorophyll than the photosystem II (PSII) enriched fraction. Conversely, the PSII-enriched fraction accounted for the larger proportion of total chlorophyll in thylakoids from A. breviligulata. Whole chain electron transport (PSII + PSI) activity was greater in C. longifolia mesophyll thylakoids, at all light intensities. Chloroplast and mitochondrial ultrastructure were compared. The bundle sheath chloroplasts of C. longifolia contain extensive grana stacking and are distributed throughout the cell. The mitochondria of the bundle sheath and mesophyll cells are strikingly dimorphic. A suberin lamella is apparently absent from the bundle sheath cell walls. These results support the designation of C. longifolia as a C4 species of the nicotinamide adenine dinucleotide – malic enzyme type.

Effect of age and muscle type on regeneration of neuromuscular synapses in mice

A silver stain was used to investigate the regeneration of nerve terminals in mouse diaphragm, superior gluteus and tensor fasciae latae (TFL) muscles following nerve crush injury at different ages (9-530 days). The development of myelinated terminal branches and the development and elimination of terminal sprouts were little affected by age or muscle type following reinnervation. However, multiple axonal innervation developed on up to 50% of the gluteus and TFL muscle fibres, and this was subsequently eliminated only in the youngest animals.

Effect of nerve growth factor on intramuscular axons of neonatal mice

Newborn mice were given daily injections of nerve growth factor over the gluteus muscle. At age 9 days muscles were removed and stained to reveal intramuscular axons. Motor axons, and sensory axons of the Golgi tendon organs and muscle spindles were unaffected by nerve growth factor, but there was prolific growth of the small diameter axons that ramify over the surface of the muscle. These axons were sensory rather than sympathetic, since the degenerated following dorsal root ganglionectomy but not following sympathetic ganglionectomy. This finding supports the concept that nerve growth factor is involved in the development of sensory innervation of muscle.

Muscle size and motor unit survival in mice

The soleus muscles in neonatal and adult mice were surgically reduced in size on one side of the animal. The experimental and control muscles were excised 6-48 weeks later and the number of motor units in each muscle was estimated by stimulating the muscle nerve and counting step increments in the electromyogram recorded in vitro. Multiple innervation in individual muscle fibres was then assessed by intracellular recording and by visualization of end-plates in the light microscope with cholinesterase stain. Muscle fibres were counted in cross-sections of each muscle in the light microscope. Surgical reductions in the size of the muscle during the first 3 weeks of life produced correlated reductions in the number of motor units in the muscle. This could not be attributed to masking of motor units by multiple innervation, which was always less than 10% in these muscles. The loss of motor units was greatest following reduction in muscle size in newborn mice, whereas in 6-week-old mice there was no significant loss of motor units following the operation. Thus, survival of neonatal motor units shows an age-related dependence on the number of muscle fibres available for innervation. In control muscles there was a highly significant correlation between motor unit and muscle fibre numbers, which is consistent with the hypothesis that motor neurone survival during the embryonic period of cell death is dependent upon the number of muscle fibres available for innervation.

Axon growth in tendon organs of botulinum-paralyzed neonatal mouse muscles

Paralysis of neonatal mouse gluteus muscles with botulinum toxin stimulated the growth not only of motor nerve terminals but also of the terminals of the sensory axons innervating the tendon organs. However, the adult mouse tendon organ axons, unlike motor nerve terminals, did not sprout in response to paralysis.

Regeneration of mouse peripheral nerves in degenerating skeletal muscle: guidance by residual muscle fibre basement membrane

The part played by basement membrane in the guidance of peripheral nerve growth in vivo has been assessed by examining the capacity of degenerating mouse muscle to support the regeneration of the cut sciatic and saphenous nerves. Ethanol and formaldehyde-fixed gluteus maximus muscles were implanted around the contralateral cut nerves. The subsequent nerve growth into the degenerating muscle was assessed by silver staining after 3, 4 and 10 days. By 4 days, linear axonal growth was seen, parallel to the length of the muscle fibres, and coinciding with the onset of degeneration of the sarcoplasm. Transverse sections of the 10 day preparations showed that over 90% of linearly growing axons were located inside the remaining sheaths of muscle fibre basement membrane. This relationship was confirmed by electron microscopy of ruthenium red-stained preparations. Both motor and sensory axons were able to grow in this manner, for electrophysiological testing revealed the presence of motor axons from the sciatic nerve, while the saphenous nerve contains only sensory axons. Identical growth was seen at 10 days in muscles caused to degenerate by incubation in distilled water. However, linear growth did not occur in live-innervated and glutaraldehyde-fixed muscles, in which muscle fibre architecture was preserved. It is concluded that basement membrane derived from muscle can promote peripheral nerve regeneration. Furthermore, both motor and sensory axons show a strong preference for growth along its inner surface, the basal lamina.

Growth and development at cold-hardening temperatures. Chlorophyll–protein complexes and thylakoid membrane polypeptides

Chlorophyll–protein complexes of thylakoid membranes from rye plants (Secale cereale L. cv. Puma) grown at warm and cold-hardening temperatures were investigated by gel electrophoresis. Complex IV from cold-grown tissue was detectable in the presence of dodecyl sulfate if and only if solubilization and electrophoresis were performed at 4 °C, whereas complex IV from warm-grown material was detectable if membrane solubilization and electrophoresis were performed at either 4 or 23 °C in the presence of dodecyl sulfate. In the presence of octyl-β-D-glucopyranoside, the chlorophyll–protein complexes from cold-grown tissue were less stable at 23 °C than those from warm-grown tissue. Regardless of the detergent used, there was always more oligomer of the light-harvesting complex present in samples prepared from thylakoid membranes of warm-grown tissue than those from membranes of cold-grown tissue. It is concluded that the pigment–protein interaction in those complexes associated with photosystem II and the light-harvesting chlorophyll a/b – protein complex has been altered upon growth and development at cold-hardening temperatures.

Evidence for a motor nerve growth factor

We review the evidence that a motor nerve growth factor released from muscle has wide ranging effects on the development and maintenance of muscle innervation. The actions of this putative factor on motor neurons are analogous to the actions of the well known nerve growth factor (NGF) on sympathetic and sensory neurons.

Sprouting of mammalian motor neurones at nodes of Ranvier: the role of the denervated motor endplate

Treatment of the mouse gluteus maximus with the organophosphorus anticholinesterase ecothiopate, 4-aminopyridine and caffeine caused necrosis of the endplate region of the muscle fibres. When these drugs were given 12 h prior to partial denervation of the muscle there was a significant reduction in the amount of nodal sprouting seen 48 h after nerve section. No such reduction was seen if the drugs were given immediately after nerve section. In the former case both innervated and denervated fibres are necrotic; in the latter, only innervated fibres are necrotic. The amount of terminal sprouting was significantly increased in the former group, showing that the drug treatment and necrosis were not directly inhibitory to nerve growth. The reduction of nodal sprouting is therefore likely to be due to necrosis of denervated fibres; this supports the hypothesis that the denervated endplate is the source of a stimulus to nodal sprouting of motoneurones.

Importance of pathway formation for nodal sprout production in partly denervated muscles

Experiments were carried out to investigate possible factors controlling nodal sprout growth in partly denervated mouse gluteal muscles. Pretreatment of the muscle with botulinum toxin for up to 20 days, which produces denervation-like change and elicits terminal and nodal sprouting, increased reinnervation by terminal sprouting after partial denervation but did not alter the rate of reinnervation by nodal sprouts. This implies that nodal sprout growth is not limited by the development of an adequate growth stimulus from denervated muscle. A disto-proximal gradient of degeneration was observed in denervated intramuscular nerves in the electron microscope, suggesting that nodal sprout growth may be modulated by the availability of endoneurial pathways sufficiently degenerated to permit reinnervation by nodal sprouts, although the initial outgrowths from nodes of Ranvier may appear in response to a growth stimulus from denervated muscle.

Formation of chloroplast pigments in a temperature-sensitive, virescent mutant of maize

Pigment levels and greening responses have been examined in a temperature-sensitive virescent 16 mutant of maize with a temperature threshold of 25 °C for greening. Expansion of tissue at 20 °C leads to a reduction of protochlorophyll level as well as carotenoids and chlorophyll. Seedlings will not green at 20 °C under low-intensity intermittent or continuous light. Chlorophyll is formed at 20 °C in the light following etiolation at 28 °C. These results suggest that absence of chlorophyll in the virescent seedling at temperatures below the threshold is not due to loss of the protective function of carotenoids and consequent photooxidation of chlorophyll.

Neuromuscular transmission at terminals of sprouted mammalian motor neurones

Motor nerve sprouting was induced in the tensor fasciae latae muscle of mice by partial denervation produced either by cutting (to prevent reinnervation) or crushing (to allow subsequent reinnervation) spinal nerve L4 unilaterally. The quantum content (m) of endplate potentials recorded intracellularly in vitro in the presence of high-Mg2+ and low-Ca2+ ion concentrations was determined up to 400 days later in non-reinnervated, reinnervated and contralateral control muscles. The muscles were then either fixed and stained with silver and cholinesterase for light microscopy, or fixed and examined in the electron microscope. The average value of m in control muscles increased by 4-5-fold as the animals matured in the 4 months following the operations. The average value of m at terminals of sprouted motor neurones in the absence of reinnervation also increased with time after partial denervation but was always less than the value in the corresponding control muscle. In electron micrographs of muscles following L4 section the nerve terminals closely apposed on average only two-thirds of the proportion of junctional folds apposed to terminals in control muscles. When muscles were reinnervated following L4 crush the average value of m at terminals of sprouted and reinnervating motor neurones equalled and sometimes exceeded m in contralateral control muscles. A proportion of muscle fibres had endplate potentials from reinnervating and sprouted axons, and the silver stain showed that these muscle fibres were innervated at the site of the original endplate. At these endplates the fraction of the total quantum content contributed by presumed sprout terminals fell significantly in the 4 months following L4 crush. It is concluded that: (i) in the absence of reinnervation, sprout terminals grow in size but a significant number never occupy all endplate site available to them; and (ii) in the presence of reinnervation axons terminals share some endplates with sprout terminals and grow at the expense of the sprout terminals which are eventually withdrawn from some shared endplates.

Short- and long-term effects of paralysis on the motor innervation of two different neonatal mouse muscles

1. A study was made of short- and long-term effects of paralysis induced by type A botulinum toxin on the development of innervation of mouse muscles. The toxin was injected locally over the tensor fasciae latae (t.f.l.) and gluteus muscles at various times after birth, and the innervation was later examined by intracellular recording and by a histological technique using a reduced silver stain for axons.2. Paralysis induced at 0-4 days of age delayed but did not prevent the eventual elimination of nearly all focal multiple innervation in gluteus muscle fibres, whereas in t.f.l. up to 50% of the fibres remained focally innervated by more than one axon for at least 120 days. There was an associated reduction in the number of muscle fibres in t.f.l. of between 50 and 70%. The biggest reduction in the number of gluteus fibres was under 40%.3. In the t.f.l., paralysis begun at 6-9 days caused the extent of single-site polyneuronal innervation to increase above the level existing at the time of paralysis. Histologically this increase was seen to be due at least in part to the stimulation of nodal sprout growth from a limited number of nodes.4. Motor nerve terminal sprouts were evoked by paralysis at all ages. In mice injected before 4 days of age recovery from the toxin occurred rapidly and without the formation of ectopic synapses by sprouted motor terminals; however, intrafusal motor nerves also sprouted and established a permanent ectopic innervation on surrounding extrafusal muscle fibres.5. The following conclusions are drawn. (a) In some but not all muscles, neonatally induced paralysis can not only temporarily halt elimination of polyneuronal innervation but actually lead to an increase; it is suggested tentatively that this occurs only during the neonatal period because of the availability at that time of endoneurial pathways associated with normal polyneuronal innervation, rather than because of any special neuronal growth potential then. (b) Permanent establishment of focal polyneuronal innervation is due not to stability of presynaptic elements maintained past a critical developmental stage but is associated with substantial losses of muscle fibres, leading to a high ratio of nerve fibres to muscle fibres.

The distribution of nodal sprouts in a paralysed or partly denervated mouse muscle

The right gluteus maximus muscles of young adult mice were paralysed with botulinum toxin for up to 21 days or partly denervated by spinal root section for up to 63 days; the intramuscular and extramuscular nerves were then examined in the electron microscope in thin sections of tissue fixed conventionally or stained with zinc iodide-osmium tetroxide. Contralateral muscles were also examined as controls. The distribution of nodal sprouts in the nerves of the paralysed or partly denervated muscles was determined by calculating the mean ratios of unmyelinated to myelinated axons in nerve profiles containing different numbers of myelinated axons (intact or degenerating) and comparing these with control ratios. In paralysed muscles there was a significantly higher proportion of nerve profiles containing one or two unmyelinated axons alongside a single myelinated axon. Nerve profiles containing two or more myelinated axons did not show any increase in the proportion of unmyelinated axons. Thus, there is probably nodal sprouting in paralysed muscles which is restricted to the most distal nodes of the intramuscular nerves. In muscles partly denervated for 8 days there were significant increases in the proportion of unmyelinated axons in nerve profiles which had contained up to 5-10 myelinated axons. After 21 days of partial denervation, similar increases may have occurred in the larger intramuscular nerve profiles and after 63 days there were large increases in the proportion of unmyelinated axons in the main intramuscular nerve branches and in the extramuscular nerve. Nodal sprouting in response to partial denervation is therefore localised initially to the smaller, more distal nerve branches; at later times, some sprouts probably grow slowly in a disto-proximal direction along denervated Schwann cell pathways. The existence of nodal sprouts in paralysed muscles and their restricted distribution in paralysed and partly denervated muscles suggest that the nodal sprouting stimulus is produced by the muscle and acts only at distal nodes.

Comparison of effects of denervation and botulinum toxin paralysis on muscle properties in mice

1. The properties of denervated and fully innervated but paralysed soleus and extensor digitorum longus (e.d.l.) muscles were compared in mice.2. Muscles were paralysed by single or repeated injections of botulinum toxin into the right lower leg. Contralateral muscles were denervated at the same time by sciatic nerve section. Muscles were excised 3-20 days later and direct and indirect isometric twitch and tetanic tensions measured in vitro. ACh sensitivity was assessed from isometric contractions to various concentrations of bath-applied ACh perchlorate.3. Denervated muscles as expected from the work of others developed sensitivity to ACh earlier and more rapidly than paralysed muscles. A transient peak of sensitivity was reached after 7 days of denervation in soleus and after 8 days in e.d.l. However 2 days later the sensitivity of muscles fully paralysed to nerve twitch and tetanic stimuli was not significantly different from that of denervated muscles.4. In both e.d.l. and soleus the direct tetanus/twitch ratios declined in paralysed and denervated muscles. The decline was initially more rapid in denervated than paralysed soleus, but the ratios for paralysed and denervated muscles were not significantly different after 10 days in either muscle. By this time there were no differences in the absolute strengths of the paralysed and denervated muscles.5. It is concluded that the ACh sensitivity and dynamic properties of fully paralysed mouse muscles become equal to those of denervated muscles once the acute effects associated with nerve degeneration are past. This result is consistent with the idea that normal neuronal control of extrajunctional mammalian skeletal muscle properties is mediated solely by means of activity.

Nerve growth from nodes of Ranvier in inactive muscle

Paralysis of mouse gluteus maximus muscles with botulinum toxin not only evoked the expected sprouting from nerve terminals but also induced growth from some nodes of Ranvier close to the endplate region. This finding shows that nerve degeneration is not essential for nodal sprouting and supports the hypothesis that inactive muscle liberates a motor nerve growth factor.