Isometric strength of the hip abductors and external rotators in athletes with and without patellar tendinopathy.

PURPOSE: This study aims to compare the isometric strength of hip abductors and external rotators in male athletes with and without patellar tendinopathy (PT), and to examine the correlation between hip strength, pain, and functional scores. METHODS: Sixty male athletes (30 with PT and 30 controls) were recruited from local volleyball and basketball teams. The isometric strength of the hip abductors and external rotators was quantified using a belt-stabilized handheld dynamometer. This study used the visual analog scale (VAS) and the Victorian Institute of Sport Assessment-Patella (VISA-p) questionnaire to measure the intensity of pain and functional scores in athletes with PT, respectively. RESULTS: The normalized isometric strength of the hip abductors and external rotators was significantly less in the PT group compared with controls. In subjects with PT, the normalized isometric strength was decreased by 22.0% (p = 0.000) in the hip abductors and by 20.0% in the hip external rotators (p = 0.004), compared with controls. Significant correlations were found between the normalized isometric strength of the hip abductors and intensity of pain (r = - 0.70; p < 0.05) and VISA-p score (r = 0.63; p < 0.05) in the affected leg in athletes with unilateral PT. CONCLUSIONS: Athletes with PT have decreased isometric strength in their hip abductors and external rotators when compared with controls. In subjects with unilateral PT, decreased isometric strength in the hip abductors is associated with greater intensity of pain and lower functional scores. Results of this study implied that hip muscle assessment and strengthening should be included for reconditioning and rehabilitation in athletes with PT.

Increase in passive muscle tension of the quadriceps muscle heads in jumping athletes with patellar tendinopathy.

To investigate the passive muscle tension of the quadriceps muscle heads in male athletes clinically diagnosed with patellar tendinopathy (PT) with those of healthy controls and explore the interplay between passive muscle tension and patellar tendon stiffness. Between November 2012 and December 2013, 66 male athletes (mean age of 21.1 ± 4.4 years) were examined using supersonic shear wave imaging technology. The passive tension of the vastus lateralis (VL) and rectus femoris (RF) muscles and patellar tendon stiffness were assessed. The shear elastic modulus of the VL muscle was increased by 26.5% (P < 0.001) in the subjects with PT when compared with the controls. Greater passive tension in the VL was associated with higher patellar tendon stiffness (r = 0.38; P = 0.001). The vastus lateralis muscle of the quadriceps shows increase in passive muscle tension in jumping athletes with patellar tendinopathy. These findings suggest that increase in muscle tension is not similar in the individual muscles of the quadriceps muscle. Traditional stretching of the whole quadriceps muscle might not be targeted to the tight muscle heads.

Alterations in mechanical properties of the patellar tendon is associated with pain in athletes with patellar tendinopathy.

PURPOSE: To compare tendon strain and stiffness between athletes with patellar tendinopathy and healthy controls, and explore whether the intensity of pain and dysfunction were related to the mechanical properties of the tendon. METHODS: Thirty-four male athletes with patellar tendinopathy and 13 healthy controls matched by age and activity levels were recruited. The in vivo mechanical properties of the patellar tendon were examined by ultrasonography and dynamometry. In subjects with patellar tendinopathy, the intensities of self-perceived pain (maximal pain in the past 7 days and pain during a single-legged declined-squat test) using the visual analogue scale and the assessment of functional disability using the Victorian Institute of Sport Assessment-patellar questionnaire, were collected. RESULTS: In subjects with patellar tendinopathy, tendon strain was significantly reduced by 22% (8.9 ± 3.7 vs. 14.3 ± 4.7%, P = 0.005) when compared with healthy controls. There was no significant group difference in tendon stiffness (P = 0.27). Significant negative correlations between tendon strain and the maximal self-perceived pain over 7 days (r = -0.37, P = 0.03), and pain during a single-legged declined-squat test (r = -0.37, P = 0.03) were detected. A trend of significant positive correlation was found between tendon stiffness and pain during a single-legged declined-squat test (r = 0.30, P = 0.09). CONCLUSION: Our findings show that tendon strain is reduced in athletes with patellar tendinopathy, and a lower tendon strain is associated with a greater magnitude of pain perceived.

Effects of habitual loading on patellar tendon mechanical and morphological properties in basketball and volleyball players.

PURPOSE: Tendon mechanical properties are linked to sports performance and tendon-related injuries, such as tendinopathy. Whether habitual loading, such as participation in regular jumping activities, would induce adaptation on tendon mechanical properties remains unclear. METHOD: Forty healthy subjects (10 sedentary, 15 volleyball players, and 15 basketball players) aged between 18 and 35 years were recruited. Supersonic shearwave imaging was used to measure the shear elastic modulus and thickness and cross-sectional area (CSA) of the proximal patellar tendons of both knees at 30° of flexion. RESULT: Significant group differences in tendon shear elastic modulus were found among the three groups. In the dominant leg, reduction in tendon shear elastic modulus by 18.9 % (p = 0.018) and 48.7 % (p = 0.000) were observed in the basketball and volleyball players, respectively, when compared with sedentary subjects. In the non-dominant leg, reduction in tendon shear elastic modulus were 27.3 % (p = 0.034) and 47.1 % (p = 0.02) in the basketball and volleyball players, respectively. The athlete groups were found to have larger CSA but with similar tendon thickness than sedentary group. The CSA were larger by 24-29 % and by 22-24 % in the basketball players and volleyball players, for the dominant and non-dominant legs, respectively (all p < 0.05). Age and body mass are related to tendon stiffness and CSA, particularly in the sedentary subjects. CONCLUSION: The proximal patellar tendon can undergo substantial adaptation on tendon mechanical and morphological properties when exposed in jumping sports. Intrinsic factors such as age and body mass could influence tendon properties.

Measurement of diabetic wounds with optical coherence tomography-based air-jet indentation system and a material testing system.

OBJECTIVE: Material testing system is a conventional but destructive method for measuring the biomechanical properties of wound tissues in basic research. The recently developed optical coherence tomography-based air-jet indentation system is a non-destructive method for measuring these properties of soft tissues in a non-contact manner. The aim of the study was to examine the correlation between the biomechanical properties of wound tissues measured by the two systems. METHOD: Young male Sprague-Dawley rats with streptozotocin-induced diabetic were wounded by a 6 mm biopsy punch on their hind limbs. The biomechanical properties of wound tissues were assessed with the two systems on post-wounding days 3, 7, 10, 14, and 21. Wound sections were stained with picro-sirius red for analysis on the collagen fibres. Data obtained on the different days were charted to obtain the change in biomechanical properties across the time points, and then pooled to examine the correlation between measurements made by the two devices. Qualitative analysis to determine any correlation between indentation stiffness measured by the air-jet indentation system and the orientation of collagen fibres. RESULTS: The indentation stiffness is significantly negatively correlated to the maximum load, maximum tensile stress, and Young's modulus by the material testing system (all p<0.05). The orientation of collagen changes with the indentation stiffness over time. CONCLUSION: Our findings support the use of optical coherence tomography-based air-jet indentation system to evaluate the biomechanical properties of wounds in a non-contact manner. It is a potential clinical device to examine the biomechanical properties of chronic wounds in vivo in a repeatable manner.

'Gear up and get ready': Collaborative curriculum for radiographers supporting percutaneous nephrolithotomy in the operating theatre.

INTRODUCTION: Newly qualified radiographers often find working in the operating theatre (OT) challenging and intimidating. These perceptions, which inhibit confidence, may hinder their effectiveness in interprofessional teamwork, which may in turn adversely affect patient outcomes. A collaborative education programme was designed, building upon the foundations of competency-based education (CBE) and simulation-based mastery learning (SBML) to examine its potential in mitigating these perceptions. The objective of this research was to assess participants' experience and level of competency after attending the curated collaborative educational programme. METHODS: The programme was developed based on the Analysis, Design, Development, Implementation, and Evaluation (ADDIE) model and comprises two teaching and learning phases: educational session and simulation. A collaborative approach was undertaken to develop an assessment checklist for the interprofessional simulation. Requirements for the simulation, such as scenario design, information and storyboard, task trainer, logistics, and learners' briefing, debrief, and feedback, were identified and assembled. The radiographers' performance was recorded using a practical skills assessment checklist and a theory assessment. RESULTS: Twelve radiographers participated and showed improvement in their self-rating of learning objectives before and after the programme. The median (interquartile range) score achieved in the theory assessment, out of a possible of 11, was 9.00 (7.75-9.50). The median (interquartile range) score achieved in the simulation component, out of a possible of 16, was 15.00 (14.00-15.00). There was statistically significant difference in self-perceived performance in all learning objective domains. CONCLUSION: The findings from the programme were promising. The use of simulation and an assessment checklist proved to be useful learning tools in preparing newly qualified radiographers for work in the OT. IMPLICATIONS FOR PRACTICE: Assessment checklists are valuable tools that should be considered to facilitate teaching and learning. The use of interprofessional simulation activities can support radiographers in developing knowledge, professional skills, and clinical competency. It should be conducted in a timely manner to facilitate the introduction to role understanding and effective communication.

Motion control shoe affects temporal activity of quadriceps in runners.

OBJECTIVE: Delay onset of the vastus medialis obliquus (VMO) has often been reported to happen in people with patellofemoral pain (PFP). Previous studies revealed that a motion control shoe could check rearfoot pronation in overpronators. Literature suggested that movements of the lower leg could affect patellar tracking; thus motion control shoe may help prevent PFP by controlling excessive foot movements. This study aimed to compare the vasti muscle activities in people with excessive foot pronation when running with different footwear. METHODS: Twenty female subjects with rearfoot pronation >6 degrees were tested by running for 10 km on a treadmill on two separate days. During each test, subjects either wore a motion-control running shoe or a neutral running shoe. EMG activities of their right VMO and vastus lateralis (VL) were recorded. Their EMG onset timing and median frequency (MF) were compared between the two shoe conditions. RESULTS: A more significant delay in VMO onset of the running duty cycle was observed in the neutral shoe condition than in the motion control shoe (p<0.001). In the neutral shoe condition, the delay in VMO increased with running mileage (Pearson correlation = 0.948), whereas no such pattern was observed in the motion control shoe. A significant drop in MF of the quadriceps after the 10 km run in both shoe conditions was observed (p ranged from <0.001 to 0.008), and there was a larger drop in VMO MF when running with the neutral shoe. CONCLUSIONS: The findings suggest that the motion control shoe may facilitate a stable temporal activation of VMO during running.

Biofeedback exercise improved the EMG activity ratio of the medial and lateral vasti muscles in subjects with patellofemoral pain syndrome.

Patellofemoral pain syndrome (PFPS) is usually due to weakness of vastus medialis obliquus (VMO) resulting in abnormal patellar tracking. One of the objectives of rehabilitation is to strengthen the VMO so as to counterbalance the vastus lateralis (VL) action during normal activities. This study compared the effects of an 8-week exercise program with and without EMG biofeedback on the relative activations of VMO and VL. Twenty-six subjects with PFPS were randomly allocated into an "exercise" group (Group 1) and a "biofeedback+exercise" group (Group 2). Both groups performed the same exercise program but subjects in Group 2 received real time EMG biofeedback information on the relative activations of VMO and VL during the exercises. After 8 weeks of training, Group 1 had insignificant changes in their VMO/VL EMG ratio (p=0.355), whereas Group 2 had significantly greater VMO/VL EMG ratio (p=0.017) when performing normal activities throughout a 6-h assessment period. The present result reveals that the incorporation of an EMG biofeedback into a physiotherapy exercise program could facilitate the activation of VMO muscle such that the muscle could be preferentially recruited during daily activities.

A structural equation model of the relationship between muscle strength, balance performance, walking endurance and community integration in stroke survivors.

PURPOSE: To use structural equation modelling (SEM) to determine (1) the direct and indirect associations of strength of paretic lower limb muscles with the level of community integration, and (2) the direct association of walking endurance and balance performance with the level of community integration in community-dwelling stroke survivors. MATERIALS AND METHODS: In this cross-sectional study of 105 stroke survivors, the Subjective Index of Physical and Social Outcome (SIPSO) was used to measure the level of community integration. Lower-limb strength measures included isometric paretic ankle strength and isokinetic paretic knee peak torque. The Berg Balance Scale (BBS) and the 6-minute walk test (6MWT) were used to evaluate balance performance and walking endurance, respectively. RESULTS: SEM revealed that the distance walked on the 6MWT had the strongest direct association with the SIPSO score (ß = 0.41, p <0.001). An increase of one standard deviation in the 6MWT distance resulted in an increase of 0.41 standard deviations in the SIPSO score. Moreover, dorsiflexion strength (ß = 0.18, p = 0.044) and the BBS score (ß = 0.21, p = 0.021) had direct associations with the SIPSO score. CONCLUSIONS: The results of the proposed model suggest that rehabilitation training of community-dwelling stroke survivors could focus on walking endurance, balance performance and dorsiflexor muscle strengthening if the aim is to augment the level of community integration.

Intrinsic foot muscle volume in experienced runners with and without chronic plantar fasciitis.

OBJECTIVES: Plantar fasciitis, a common injury in runners, has been speculated to be associated with weakness of the intrinsic foot muscles. A recent study reported that atrophy of the intrinsic forefoot muscles might contribute to plantar fasciitis by destabilizing the medial longitudinal arch. However, intrinsic foot muscle volume difference between individuals with plantar fasciitis and healthy counterparts remains unknown. This study examined the relationship of intrinsic foot muscle volume and incidence of plantar fasciitis. DESIGN: Case-control study. METHODS: 20 experienced (≥5 years) runners were recruited. Ten of them had bilateral chronic (≥2 years) plantar fasciitis while the others were healthy characteristics-matched runners. Intrinsic muscle volumes of the participants' right foot were scanned with a 1.5T magnetic resonance system and segmented using established methods. Body-mass normalized intrinsic foot muscle volumes were compared between runners with and without chronic plantar fasciitis. RESULTS: There was significant greater rearfoot intrinsic muscle volume in healthy runners than runners with chronic plantar fasciitis (Cohen's d=1.13; p=0.023). A similar trend was also observed in the total intrinsic foot muscle volume but it did not reach a statistical significance (Cohen's d=0.92; p=0.056). Forefoot volume was similar between runners with and without plantar fasciitis. CONCLUSIONS: These results suggest that atrophy of intrinsic foot muscles may be associated with symptoms of plantar fasciitis in runners. These findings may provide useful information in rehabilitation strategies of chronic plantar fasciitis.

The double peak-to-peak analysis for determining EMG onset of muscle contraction.

PURPOSE: Identification of the onset of muscle contraction with EMG signal amplitude double of the baseline value (DP-P) has been recently reported for determining the temporal parameters of muscular activity. Due to its convenience, it is suitable for clinical application. However, there is a lack of report on the reliability and comparability of this method to other established methods. Therefore, this study examined the test-retest reliability of the DP-P method and compared it with an established method that used the mean + 3 standard deviations (mean + 3 s.d.) over the baseline value for muscles of the knee. METHODS: The onset of contraction of vastus medialis obliquus (VMO) and vastus lateralis (VL) of eleven able-bodied volunteers performing isometric knee extension at 50%, 75% and 100% of MVC in 30-minute and 7-day intervals were analyzed with both the DP-P and mean + 3 s.d. methods. RESULTS: The ICC for within-day measurements of DP-P method ranged from 0.64 to 0.86 and that for between-day measurements ranged from 0.63-0.81. The ICC values were higher with submaximal than maximal contractions. There was a consistent delay of about 3 ms in EMG onset detection with the DP-P as compared to the mean + 3 s.d method. CONCLUSION: The DP-P method is a reliable method for muscle onset determination but the absolute onset time of muscle contraction obtained from this method should not be directly compared with other methods such as the mean + 3 s.d.

Resistance of the dopamine D2L receptor to desensitization accompanies the up-regulation of receptors on to the surface of Sf9 cells.

Dopamine D2 receptor agonists are commonly used in the control of PRL-secreting adenomas, and the sensitivity of dopamine agonists during long term therapy is exquisite. However, the molecular mechanisms responsible for the maintenance of this cellular sensitivity to dopamine agonists remain poorly understood. In the present study, we examined the agonist-induced regulation of the human D2L receptor expressed to a specific activity of approximately 1 pmol receptor/mg protein in Sf9 insect cells. Treatment of D2L receptor-expressing cells with dopamine for up to 3 h resulted in no detectable change in the ligand-binding properties of the receptor and a approximately 120-fold reduction in the potency, but not the efficacy, of D2L receptors to mediate dopamine inhibition of forskolin-stimulated adenylyl cyclase activity. This resistance of the D2L receptor to agonist-induced desensitization was accompanied by a approximately 28% translocation of intracellular D2L receptors to the cell surface, as quantified by cellular fractionation and radioligand binding and visualized by whole cell immunocytochemical staining and confocal microscopy. Immunoblot analysis of the P2 membrane fraction revealed that surface D2L receptors comprised monomers and dimers. Treatment of D2L receptor-expressing cells with the protein synthesis inhibitor cycloheximide significantly reduced the basal expression level of receptors, but did not block the agonist-induced up-regulation of receptors. Longer periods of dopamine exposure for 24 h brought about a small increase in surface receptor density. However, when these studies were conducted in the presence of cycloheximide, receptor density was marginally reduced, suggesting that receptor synthesis accounts for the maintenance of cellular receptor density under these conditions. We conclude that the resistance of the D2L receptor-coupled adenylyl cyclase system to agonist-induced desensitization is attributed to the up-regulation of surface receptors after the translocation of existing intracellular receptors and de novo receptor synthesis.

Immunohistochemical and biochemical assessment of caspase-3 activation and DNA fragmentation following transient focal ischemia in the rat.

In the present study, we evaluated the time-course of caspase-3 activation, and the evolution of cell death following focal cerebral ischemia produced by transient middle cerebral artery occlusion in rats. Ischemia-induced active caspase-3 immunoreactivity in the striatum but not the cortex at 3 and 6 h time points post-reperfusion. Furthermore, using a novel approach to visualize enzymatic activity, deltaC-APP, a C-terminal cleavage product of APP generated by caspase-3, was found to immunolocalize to the same areas as active caspase-3. Double-labeling studies demonstrated co-localization of these two proteins at the cellular level. Further double-labeling experiments revealed that active caspase-3 was confined to neuronal cells which were still viable and thus immunoreactive for NeuN. DNA fragmentation, assessed histologically by terminal dUTP nick-end labeling (TUNEL), was observed in a small number of cells in the striatum as early as 3 h, but only began to appear in the cortex by 6 h. DNA fragmentation was progressive, and by 24 h post-reperfusion, large portions of both the striatum and cortex showed TUNEL positive cells. However, double-labeling of active caspase-3 with TUNEL showed only minimal co-localization at all time-points. Thus, caspase-3 activation is an event that appears to occur prior to DNA fragmentation. As a confirmation of the histological TUNEL data, 24 h ischemia also induced the generation of nucleosome fragments, evidenced by cell death enzyme-linked immunosorbent assay. Using a novel ischemia-induced substrate cleavage biochemical approach, spectrin P120 fragment, a caspase-specific cleavage product of alpha II spectrin, a cytoskeletal protein, was shown to be elevated by western blotting. Brain concentrations of both nucleosomes and spectrin P120 correlate with the degree of injury previously assessed by triphenyltetrazolium chloride staining and infarct volume calculation. Together, our findings suggest a possible association between caspase-3 activation and ischemic cell death following middle cerebral artery occlusion brain injury.

Dopamine D1 receptor distribution in Sf9 cells imaged by confocal microscopy: a quantitative evaluation.

A c-myc epitope-tagged human dopamine D1 receptor (c-myc D1 receptor) was expressed in Sf9 cells and its cellular distribution under basal conditions and after exposure to the agonist dopamine was examined. In the basal state, immunofluorescently labeled c-myc D1 receptors imaged by confocal microscopy appeared as a bright ring of label predominantly on the cell surface, and to a lesser extent as intracellular clusters of label. This pattern of receptor distribution was confirmed by radioligand-binding assays on plasma membrane and light membrane fractions using the D1 receptor-antagonist [3H]-SCH-23390. After exposure to dopamine, c-myc D1 receptors were redistributed on the cell surface, changing from a continuous ring to a discontinuous pattern of label. Analysis of fluorescence intensity and three-dimensional computer reconstruction of labeled receptors revealed a 30% decrease in surface labeling with no decrease in total number of receptors confirmed by radioligand-binding analysis. These findings constituted the first direct evidence of agonist-induced D1 receptor internalization. The results showed that the combination of confocal microscopy and three-dimensional reconstruction can be used to visualize and assess receptor distribution in Sf9 cells.

The identification of NP25: a novel protein that is differentially expressed by neuronal subpopulations.

A novel gene encoding a 25-kDa neuronal-specific protein, here named 'NP25', has been isolated as a cDNA clone from rat brain. The sequence of the NP25 cDNA reveals a single open reading frame that encodes a primary translation product of 206 amino acids. A search of the protein sequence databank indicates that NP25 is significantly homologous with three recently discovered muscle proteins: SM22 alpha, mp20 and calponin. The gene is specifically and ubiquitously expressed in the rat brain and has conserved sequences among chicken, rat, mouse and human. Rat brain NP25 was identified by Western blot using an antiserum elicited against trpE-NP25 fusion protein. On pH gradient electrophoresis, NP25 was separated into at least two isoforms with similar molecular weights. Immunocytochemistry and in situ hybridization demonstrated that NP25 was differentially expressed by neuronal subpopulations of the rat central nervous system. The highest concentration of NP25 protein was localized in central amygdaloid nuclei and glomeruli in the granule layer of cerebellum. The wide and differential distribution of NP25 in the brain suggests that it may play a particular important role in the function of specific neuronal systems.

Dopamine receptor agonist reduces ethanol self-administration in the ethanol-preferring C57BL/6J inbred mouse.

This report experimentally examined whether the genetically determined low nigrostriatal/mesolimbic dopaminergic activity in the C57BL/6J (herein referred to as C57) inbred mouse mediated the congenital high risk for ethanol abuse (ethanol consumption and ethanol preference) in this model. C57 mice pretreated with dopamine D1 receptor agonist ((+)-SKF-38393) or dopamine D2 receptor agonist (bromocriptine) to augment synaptic dopamine availability exhibited marked 76% and 38% reductions in voluntary ethanol intake in comparison to untreated controls. Dopamine receptor agonist administration resulted in changes in dopamine D1 and D2 receptor mRNA in the cell bodies and dopamine D1 and D2 receptor densities principally in the afferent targets of nigrostriatal/mesolimbic dopamine neurons. Dopamine receptor agonists promoted a decrease of striatal dopamine D1 and D2 receptor densities and corresponding down-regulation of olfactory tubercle dopamine D1 and D2 receptor mRNA abundance. Dopamine receptor agonist-induced increases in forebrain dopaminergic activity was compensated with increased dopamine D2 receptor density and correspondingly higher dopamine D2 receptor mRNA content in the brain stem. When bromocriptine was administered to ethanol-sensitized mice, it was ineffective in reducing voluntary ethanol abuse. In these mice, treatment with the dopamine D2 receptor antagonist haloperidol led to a 28% reduction in the absolute amount of ethanol consumed, but not in voluntary ethanol preference. These data indicated that nigrostriatal/mesolimbic dopamine D1-D2 receptor mechanism(s) mediating the potential for becoming high ethanol drinking on exposure to ethanol are distinct from factors mediating voluntary ethanol drinking after sensitization to ethanol. These data constitute direct evidence supporting a dopamine hypothesis for ethanol abuse in the genetically ethanol-preferring C57 mouse.

Genotypic differences in brain dopamine receptor function in the DBA/2J and C57BL/6J inbred mouse strains.

The propensity for high ethanol preference and high ethanol consumption (herein referred to as ethanol abuse) may be a consequence of a congenital deficit in central dopaminergic activity. This hypothesis was examined in the ethanol-avoiding DBA/2J (DBA) and ethanol-preferring C57BL/6J (C57) inbred mouse strains. Endogenous dopamine D1 and D2 receptor functions differed between strains in the nigrostriatal/mesolimbic dopamine system. At the level of the forebrain, the C57 mouse exhibited higher dopamine D1 and D2 receptor mRNA abundance and elevated dopamine D1 and D2 receptor densities in the striatum compared to DBA mouse. A likely explanation for these observations might be that higher dopamine receptor gene expression could be a consequence of low synaptic dopamine activity. Accordingly, we found higher striatal dopamine-sensitive adenylyl cyclase activity in the C57 mouse. The C57 mouse exhibited an enhanced dopamine D1-D2 receptor link as suggested by an enhanced up-regulation of striatal dopamine D2 receptor mRNA following dopamine D1 receptor blockade with SCH-23390 compared to DBA mouse. At the level of the mesencephalon and hind brain, the C57 mouse had lower dopamine D2 receptor mRNA in the medulla pons, and correspondingly lower midbrain and medulla pons dopamine D2 receptor densities. Adenylyl cyclase activities in these regions were similar to the DBA mouse suggesting that the coupling of these dopamine D2 receptors could be a factor regulating their function. Strain differences in dopamine D2 receptor function were also observed in the diencephalic dopamine system. The C57 mouse exhibited lower dopamine D2 receptor density in the hippocampus and lower dopamine D2 receptor mRNA abundance and lower adenylyl cyclase activity in the hypothalamus. Changes in brain dopamine receptor gene expression following ethanol intake inferred an increase in the activities of central dopamine pathways in both the DBA and C57 mouse supporting an association between dopamine receptor function and ethanol drinking. These lines of evidence provide a basis for the hypothesis that a genetically determined brain dopaminergic deficit mediated by dopamine D1-D2 receptor mechanisms may be involved in at least a part of the risk for ethanol abuse in the C57 inbred mouse strain.

Genotypic differences in mesolimbic enkephalin gene expression in DBA/2J and C57BL/6J inbred mice.

The DBA/2J and C57BL/6J (herein referred to as DBA and C57) inbred mouse strains exhibit low and high predispositions for voluntary ethanol consumption, respectively, but the neurobiological basis underlying this differential drug vulnerability remains poorly understood. Comparison of endogenous brain proenkephalin gene expression showed the C57 mouse, compared to the DBA mouse, had lower preproenkephalin mRNA abundance, proenkephalin concentration and processed [Met5]enkephalin-immunoreactive peptide levels in the mid brain. No strain differences in enkephalin gene expression was observed in the striatum, hypothalamus, or medulla pons. Neurochemical analysis of C57 mice, following high voluntary ethanol consumption (approximately 17 g/kg/day), revealed markedly higher enkephalin gene expression in the striatum and mid brain compared to ethanol-naive animals. These findings suggested that mesolimbic enkephalin is augmented following ethanol consumption, and that endogenous low enkephalin biosynthesis may be associated with an increased vulnerability for ethanol abuse. However, the neurobiological basis of this behaviour may not be quite this simple. C57 mice pretreated with the dopamine receptor agonist, bromocriptine, had reduced striatum and mid brain preproenkephalin mRNA levels, and showed a 41% lower voluntary ethanol consumption compared to controls. We conclude that functional connectivity exists between enkephalin and dopamine systems, and although low mesolimbic enkephalin may predispose to high ethanol preference, dopamine is a more important determinant than enkephalin in the hierarchy of neurotransmitter pathways that mediate the increased vulnerability for ethanol consumption in the C57 mouse.

Desensitization, phosphorylation and palmitoylation of the human dopamine D1 receptor.

The regulation and post-translational modifications of the human dopamine D1 receptor were studied in the baculovirus-eukaryotic cell expression system. Baculovirus constructs containing either the DNA encoding the dopamine D1 receptor or a DNA encoding a c-myc epitope tagged dopamine D1 receptor (c-myc-dopamine D1 receptor) were used to infect Spodoptera frugiperda (Sf9) insect cells. Expressed dopamine D1 and c-myc-dopamine D1 receptors bound agonists and antagonists with affinities and a rank order of potency characteristic of a classical dopamine D1 receptor pharmacological profile. In membrane preparations from cells expressing c-myc-dopamine D1 receptor, the photoaffinity label [125I](3-methyl-2-[4'-azidophenyl]-2,3,5-tetrahydro-2H-3-benzazepine) ([125I]MAB) bound specifically upon photolysis. A major broad band of approximately 48 kDa was detected. This species was identified in immunoblots by the monoclonal antibody raised against the c-myc epitope of c-myc-dopamine D1 receptor was isolated by immunoprecipitation from whole cells and was shown to be post-translationally modified by phosphorylation and palmitoylation. Exposure of cells expressing c-myc-dopamine D1 receptor to dopamine for 15 min resulted in a reduction in the maximal dopamine stimulated adenylyl cyclase activity, which was accompanied by an increased phosphorylation of the receptor and a rapid redistribution of surface c-myc-dopamine D1 receptor as detected by in situ immunofluorescence. Dopamine exposure also resulted in an increased level of incorporation of [3H]palmitic acid into the receptor. Thus, we provide the first evidence that the human dopamine D1 receptor undergoes agonist-dependent desensitization, phosphorylation and palmitoylation.

Long-term study of the biochemistry and biomechanics of anterior cruciate ligament-patellar tendon autografts in goats.

This study examined the change in type-III collagen concentration and hydroxypyridinium crosslink density of anterior cruciate ligament-patellar tendon autografts and their correlations with Young's modulus of the anterior cruciate autografts and anterior cruciate controls for as long as 3 years after surgery. Fifteen adult female goats (two control and 13 experimental) were tested. Each experimental animal received an anterior cruciate ligament-patellar tendon autograft to the right knee. These animals were tested at 0 (n = 2), 6 (n = 2), 12 (n = 2), and 24 (n = 1) weeks and 1 (n = 3) and 3 (n = 3) years after surgery. After mechanical testing, the anterior cruciate autograft and control tissues were analysed for type-III collagen concentration and hydroxypyridinium crosslink density. The results of sodium dodecyl sulfate gel electrophoresis showed a trend of initial increase in the percentage of type-III collagen in the anterior cruciate ligament autografts and a subsequent decrease after 24 weeks following surgery. There was a nonsignificant (p > 0.05) negative correlation between type-III collagen concentration and Young's modulus. The hydroxypyridinium crosslink density was highest at 1 year after surgery. There was a significant (p < 0.05) positive correlation between hydroxypyridinium crosslink density and Young's modulus in the anterior cruciate autografts and controls. This suggests that hydroxypyridinium crosslink density has a good linear relationship with the material strength of the anterior cruciate ligament autograft and hence could be used as an objective guide for rehabilitation with anterior cruciate autografts.