Effects of ischemic preconditioning on economy, VO2 kinetics and cycling performance in endurance athletes.

The aim of this study was to determine the effect of ischemic preconditioning (IPC) on several measures of aerobic function and 4-km cycling time-trial performance. An acute cross-over design was adopted involving eight well-trained cyclists (age 27.0 ± 7.0 years) who completed incremental and square-wave exercise tests for determination of peak O2 uptake (VO2peak), ventilatory threshold (VT) and moderate- and heavy-intensity domain VO2 kinetics, as well as 4-km time trials. All were preceded by IPC, or sham-IPC, involving repeated bouts of thigh blood flow occlusion, interspersed with reperfusion. There was no significant difference between IPC and sham-IPC with respect to VO2peak (4.4 ± 0.6 L min-1 vs 4.4 ± 0.5 L min-1, effect size - 0.01 ± 0.09), VT (3.4 ± 0.6 L min-1 vs 3.5 ± 0.5 L min-1, effect size 0.07 ± 0.28), cycling economy (4.9 ± 4.9%, ES 0.24 ± - 0.24, P > 0.05) or any moderate-domain VO2 kinetic parameter. During heavy-intensity exercise, a reduced end-exercise VO2, slow component amplitude and overall gain was observed following IPC compared to sham-IPC. Though not statistically significant, there was a possibly beneficial effect of IPC on 4-km time-trial mean power output (2.2 ± 2.0%; effect size: 0.18 ± 0.15, P > 0.05). The observed reduction in VO2 slow component and tendency for improved economy and 4-km time-trial performance, albeit small, suggests that acute IPC shows some potential as a performance-enhancing priming strategy for well-trained cyclists prior to high-intensity exercise.

Synaptic regeneration in identified neurons of the lamprey spinal cords.

Identified reticulospinal neurons whose giant axons were severed after spinal cord transection were filled with horseradish peroxidase. Whole mounts and serial-section light and electron micrographs show axon regeneration across the spinal lesion and the formation of new synapses. Normal swimming activity returns in the spinally transected animals, although the regenerated synapses are in atypical regions of the spinal cord.

Game performance and intermittent hypoxic training.

Live high-train low altitude exposure simulated by hypoxic devices may improve athletic performance. In this study, intermittent normobaric hypoxia was achieved with the GO2altitude hypoxicator to determine its effects on sea level performance in rugby players. Ten players were randomly assigned to two groups. Players in each group received 14 sessions of either hypoxic (10-15% O(2)) or normoxic (21% O(2)) exposure at rest over 14 consecutive days in a single blind fashion. Various performance measures were obtained consecutively in a single testing session pre- and post-exposure. Effects of hypoxic exposure on maximum speed and sprint times were trivial (<1.0%) but unclear (90% likely range, +/-5% to +/-9%). In rugby simulation, hypoxic exposure produced impairments of peak power in two scrums (15%, +/-8%; 9%, +/-7%) and impairments of time in offensive sprints (7%, +/-8%) and tackle sprints (11%, +/-9%). Pending further research, rugby players would be unwise to use normobaric intermittent hypoxic exposure to prepare for games at sea level.

Potentiation of M1 Muscarinic Receptor Reverses Plasticity Deficits and Negative and Cognitive Symptoms in a Schizophrenia Mouse Model.

Schizophrenia patients exhibit deficits in signaling of the M1 subtype of muscarinic acetylcholine receptor (mAChR) in the prefrontal cortex (PFC) and also display impaired cortical long-term depression (LTD). We report that selective activation of the M1 mAChR subtype induces LTD in PFC and that this response is completely lost after repeated administration of phencyclidine (PCP), a mouse model of schizophrenia. Furthermore, discovery of a novel, systemically active M1 positive allosteric modulator (PAM), VU0453595, allowed us to evaluate the impact of selective potentiation of M1 on induction of LTD and behavioral deficits in PCP-treated mice. Interestingly, VU0453595 fully restored impaired LTD as well as deficits in cognitive function and social interaction in these mice. These results provide critical new insights into synaptic changes that may contribute to behavioral deficits in this mouse model and support a role for selective M1 PAMs as a novel approach for the treatment of schizophrenia.

Purification of carnosine synthetase from avian muscle by affinity chromatography and determination of its subunit structure.

An extract of chick pectoral muscle was prepared in which the level of carnosine synthetase (L-histidine; beta-alanine ligase (AMP-forming), EC 6.3.2.11) activity was approx. 10-times that of previous preparations. In affinity chromatography studies, this material was applied to a Cibracon blue-agarose column, and elution of carnosine synthetase by carnosine was attempted. Results indicated that the elution was not specific as the eluate contained large amounts of myosin. An (NH4)2SO4 fraction (21--30% satn.) of the crude extract was prepared which, in comparison to the crude extract, had a higher specific activity, was more stable on storage at 4 degrees C and had much lower myosin content. On affinity chromatography of this fraction, apparently homogeneous carnosine synthetase was eluted with carnosine, and the specific activity of the preparation was 1700-times that of the fresh crude extract. Amino acid analysis of the preparation indicated that it had a very high histidine content (141 per 1000 residues). On analysis of the preparation by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS), a polypeptide of Mr 119 000 was observed, whereas gel permeation chromatography of the native enzyme indicated an Mr of 250 000, suggesting that the native enzyme is a dimer.

Electrophysiological and morphological correlates of axotomy-induced deafferentation of the goldfish Mauthner cell.

Axotomy-induced changes in afferent synapses to the goldfish Mauthner cell have been analyzed with intracellular recordings and with electron microscopy. The studies encompassed 7-208 days after cervical spinal cord transection. The physiological findings suggest a persistent and specific reduction in excitatory chemical inputs to the soma and proximal lateral dendrite, with no changes in somatic inhibition or in the electrotonic and chemical inputs to the more distal regions of the lateral dendrite. Corroborative morphological evidence includes swelling of the M-cell soma, as indicated by a 35% increase in the length of its minor diameter, an increased spacing and a quantitatively lower density of terminals on the soma, and the appearance of astrocytic processes partially or completely engulfing the terminals in that region. Similar changes were observed on the inferior dendrites projecting from the ventral surface of the soma, although these dendrites do not exhibit the chromatolytic changes observed at the soma. In contrast, there are no noticeable changes in either the synaptic investment of the lateral dendrite or its ultrastructure. Quantitative and qualitative data support the conclusion that there is a restricted and specific reduction in the proximal excitatory inputs to the M-cell. The evidence also suggests that electrotonic junctions between afferents and the M-cell remain intact, functionally and structurally.

The arginine taste receptor. Physiology, biochemistry, and immunohistochemistry.

The amino acid, L-arginine (L-Arg), is a potent taste stimulus for the channel catfish, Ictalurus punctatus. Receptor binding studies demonstrated a high-affinity binding of L-Arg to putative taste receptor sites. This binding could be inhibited by preincubation of the tissue in the lectins Phaseolus vulgaris agglutinin (PHA) and Ricinus communis agglutinin I (RCA I). Neurophysiological studies demonstrated that the L-Arg receptor is a stimulus-gated ion channel type receptor whose conductance was stimulated by L-Arg and inhibited by D-arginine (D-Arg). To purify the receptor we subjected CHAPS solubilized partial membrane preparation from barbel epithelium to RCA I lectin affinity chromatography. The bound proteins were eluted with D-galactose. When these proteins were reconstituted into lipid bilayers, L-Arg activated single channel currents with conductances between 45 and 85 pS. Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the eluted protein showed a distinct band at approximately 83 kDa. Polyclonal antibodies raised against this 83-kDa band in guinea pigs reacted with numerous small (approximately 1 micron) sites within the taste pore of every taste bud when applied to fixed nonpermeabilized barbels. This observation suggests that the antibodies recognize an externally-facing epitope of the putative Arg receptor. The antibodies also inhibited L-Arg-stimulated currents in reconstitution studies. Sephacryl S-300 HR chromatography of the eluant from the affinity column showed a high molecular weight peak (> 700 kDa) which was recognized by the antibodies. Reconstitution of the protein from this peak into a lipid bilayer resulted in L-Arg-stimulated channels that could be inhibited by D-Arg. This high molecular weight component may be aggregates of the arginine taste receptor.

Granular coated vesicles in the goldfish Mauthner cell following axotomy.

Axotomy of the goldfish Mauthner cell induces a marked increase in the occurrence of granular coated vesicles in close association with axosomatic synapses. This phenomenon, which persists for over 200 days, is discussed in relation to other morphological and physiological changes which occur over the same time period.

Two types of presynaptic configurations in insect central synapses: an ultrastructural analysis.

Two structurally distinct types of synapses have been identified in the cockroach metathoracic ganglion. The two synaptic types are distinguished on the basis of (a) the shape and position of the presynaptic density seen by serial thin sectioning and (b) the arrangement and location of vesicle attachment sites (VAS) on the presynaptic membrane obtained from replicas of aldehyde-fixed, freeze-fractured neuropile. Bar-type synapses in thin sections possess a long presynaptic density located in a trough or groove opposite the extracellular space between two contiguous postsynaptic processes. In freeze-fracture, this trough is flanked by two rows of vesicle attachment sites. The second synaptic conformation consists of rows of discrete dense projections located on the convexities of the presynaptic membrane, i.e., directly opposite a single postsynaptic process. This conformation has been correlated with groups of VAS linearly arranged also on the convexities of the presynaptic membrane. These structurally different synapses may represent functionally different contacts within the insect ganglion.

Organized projection of the goldfish saccular nerve onto the Mauthner cell lateral dendrite.

Application of horseradish peroxidase (HRP) to the proximal end of the transected saccular nerve in the goldfish results in uptake by fibers projecting to the distal half of the Mauthner (M) cell's lateral dendrite. More discrete HRP injections reveal an organized projection from the saccular nerve onto the lateral dendrite, as small groups of stained fibers terminate there in restricted regions. The possibility that this represents a tonotopic projection onto the M-cell is considered.

Na+ channel changes in the growth cone and developing nerve terminal.

Previous saxitoxin binding studies indicated two forms of the sodium channel in the fetal rat brain; a low-affinity precursor located in an internal membrane compartment, present exclusively in growth cones and a high-affinity mature form present in the plasmalemma of growth cones and characteristic of synapses. This raises the questions (1) of the presence or absence of the beta2 subunit in these channel forms and (2) of the developmental regulation of the the beta2 subunit. Antibodies against the alpha and beta2 channel subunits were used to probe Western blots of subcellular fractions from rat brains at embryonic day 18 (E18), pups at postnatal (P) days 7-25, and adults, as well as purified sodium channels from adult brain. In both synaptosomes and the purified sodium channel the beta2 antibody recognized the expected band at 38 kDa under reducing conditions. However, in contrast to the alpha subunit, this band was absent at E18 and became apparent only from P7 onwards. At the earlier time intervals a very prominent immunoreactive band of unknown identity was evident at 260--300kDa, which declined in intensity concomitant with the appearance of the 38 kDa beta2 band. These data indicate that beta2 subunits are regulated independently from alpha subunits, are absent in differentiating neurons, and hence are not necessary for insertion of the sodium channel into the plasmalemma, at least during early development of the neuron.

Axonal origin and purity of growth cones isolated from fetal rat brain.

The investigation of the molecular properties of nerve growth cones depends to a significant degree on their isolation from fetal brain in the form of 'growth cone particles' (GCPs). The availability of markers for developing axons and dendrites, as well as glial cells, has made it possible to characterize the GCP fraction in much greater detail than before and to optimize its yield. Marker analyses show that a member of the N-CAM family (5B4-CAM), synaptophysin, and especially GAP-43 and non-phosphorylated tau, are enriched in the GCP fraction. In contrast, MAP2 and, particularly, glial fibrillary acidic protein and vimentin are fractionated away from GCPs. Furthermore, GCP yield can be doubled relative to the original procedure, without compromising purity, by raising the sucrose concentration of the fractionation gradient's uppermost layer. The results indicate that GCPs are highly purified growth cone fragments with very little glial contamination, and that they are primarily of axonal origin.

Synthesis and biological activity of novel cephalosporins containing a (Z)-vinyl dimethylphosphonate group.

A series of cephalosporins containing a novel 7-[2-(Z)-(2-amino-thiazol-4- yl)-3-(dimethoxy-phosphoryl)-acryloylamino] group were prepared and their antibacterial activity measured against a range of pathogens. In general the compounds displayed a broad spectrum of activity against both Gram positive and Gram negative organisms, except Pseudomonas aeruginosa. Activity against the latter could be achieved by introducing a catechol moiety at the 3 position of the cephalosporin. The methyl phosphonates in general were stable to a wide range of beta-lactamases, including the TEM enzymes and the Enterobacter cloacae P99 chromosomal enzyme. In addition, they showed the advantage of being highly water soluble.

A biomechanical study of the effects of growth hormone in experimental fracture healing.

In 65 mature Wistar rats a Kirschner wire was introduced into the medullary cavity of each femur. A closed transverse mid-shaft fracture of one femur was produced by a three-point bending technique. Subsequently the mechanical characteristics of the healing fracture, including the torque and angle of twist required to take the callus to its yield point and to ultimate failure, were compared with those for the opposite femur of each rat. Controls were killed in groups at two, three, four, five and seven weeks. Test animals were given bovine growth hormone in a daily dose of five milligrams before being killed in groups at two, three and four weeks. A significant increase in torque index was found in the two-week group of test animals but not in subsequent groups. No evidence was found that growth hormone given alone could produce an overall shortening of the healing time in fresh fractures.

The effect of streptomycin, oxytetracycline, tilmicosin and phenylbutazone on spermatogenesis in bulls.

To determine whether declining semen quality associated with health problems may be due to certain antibiotic or anti-inflammatory treatments, semen was collected 3 times per week for up to 42 d from 6 normal bulls after treatment with oxytetracycline, tilmicosin, dihydrostreptomycin, or phenylbutazone. No adverse effects on semen quality were observed.

The value of revision surgery after initial amputation of an upper or lower limb.

The value of revision surgery when carried out more than six weeks after initial amputation of the upper or lower limb was assessed. When performed for stump and/or phantom limb pain alone, only 33/95 (35%) obtained satisfactory results after one revision; 25/95 (26%) of the patients required four or more surgical procedures without relief of pain. However, when carried out for local specific pathology, the results of surgical revision were 100% successful, even if the procedure had to be repeated once in 15% (28/189) of this group of patients. Transcutaneous nerve stimulation appeared to offer no long lasting relief of pain following amputation surgery.

The value of stump split skin grafting following amputation for trauma in adult upper and lower limb amputees.

One hundred and twenty adult patients were reviewed in whom split skin grafts were applied to the stump following traumatic amputation of the upper limb (44 amputees) or lower limb (76 amputees). The average follow-up period was seven and a half years after initial amputation. There was delay in prosthetic fitting in all patients. Approximately one third of patients complained of occasional minor ulceration, controlled by removing the prosthesis for a few days or modification of the prosthesis. Further revision surgery, including excision of the grafted skin often combined with proximal bone resection, but not removal of the proximal joint, was necessary in 29% of below-elbow amputees and approximately 50% of below and above-knee amputees. At the above-elbow level, use of skin grafts allowed prosthetic fitting because of preservation of sufficient length of the stump. Despite the fact that revision surgery may often be necessary, split skin grafting has a definite place in the early management of the stump following traumatic limb amputation in the adult. Preservation of stump length with the knee or elbow joint allows easier rehabilitation and lower energy expenditure when using the prosthesis. Partial foot amputation, when combined with skin grafting usually requires subsequent revision to a more proximal level to obtain a satisfactory result.

Students' anxiety in a senior thesis course.

The State-Trait Anxiety Inventory was administered on Weeks 8, 12, and 15 of a semester to 16 students enrolled in a senior thesis course. State anxiety scores were elevated when oral presentations began and declined following the presentations. Trait anxiety scores remained constant across test administrations. The influence of situational variables on students' anxiety was discussed.