Biomedical subjects

D A Brown

Publications and source records attributed to D A Brown.

At least 73 records · Page 4Linked to original sources

PubMed2000

Synapse loss associated with abnormal PrP precedes neuronal degeneration in the scrapie-infected murine hippocampus.

Numbers of neurones, synapses and axon terminals were quantified in a murine scrapie model with severe hippocampal pyramidal cell loss, in which definite clinical scrapie is evident from 226 days post-infection (dpi) and death occurs around 250 dpi. Disease-specific PrP accumulations were first seen at 70 dpi (28% of the incubation period (IP)) in thalamus and as sparse foci within the stratum pyramidale of CA1. By 98 dpi (39% IP), PrP was seen in the stratum radiatum and was found at later stages throughout all levels of the hippocampus. At the ultrastructural level in the stratum radiatum of CA1, a decrease in the numbers of simple synapses from 84 dpi (34% IP) and in perforated synapses from 98 dpi (42% IP) was found using an unbiased stereological method, the disector analysis. Degeneration of axon terminals was found from 98 dpi (39% IP) onwards. Neuronal loss was detected in CA1 from 180 dpi (72% IP). The results suggest that the fundamental lesion in the hippocampus of ME7-infected mice is associated with PrP release from CA1 pyramidal neurones, which perturbs synaptic function and leads to degeneration of preterminal axons, and that subsequent pathological changes including neurone loss are sequelae to this initial insult.

Animals↗

PubMed2000

Contralateral movement and extensor force generation alter flexion phase muscle coordination in pedaling.

The importance of bilateral sensorimotor signals in coordination of locomotion has been demonstrated in animals but is difficult to ascertain in humans due to confounding effects of mechanical transmission of forces between the legs (i.e., mechanical interleg coupling). In a previous pedaling study, by eliminating mechanical interleg coupling, we showed that muscle coordination of a unipedal task can be shaped by interlimb sensorimotor pathways. Interlimb neural pathways were shown to alter pedaling coordination as subjects pedaling unilaterally exhibited increased flexion-phase muscle activity compared with bilateral pedaling even though the task mechanics performed by the pedaling leg(s) in the unilateral and bilateral pedaling tasks were identical. To further examine the relationship between contralateral sensorimotor state and ipsilateral flexion-phase muscle coordination during pedaling, subjects in this study pedaled with one leg while the contralateral leg either generated an extensor force or relaxed as a servomotor either held that leg stationary or moved it in antiphase with the pedaling leg. In the presence of contralateral extensor force generation, muscle activity in the pedaling leg during limb flexion was reduced. Integrated electromyographic activity of the pedaling-leg hamstring muscles (biceps femoris and semimembranosus) during flexion decreased by 25-30%, regardless of either the amplitude of force generated by the nonpedaling leg or whether the leg was stationary or moving. In contrast, rectus femoris and tibialis anterior activity during flexion decreased only when the contralateral leg generated high rhythmic force concomitant with leg movement. The results are consistent with a contralateral feedforward mechanism triggering flexion-phase hamstrings activity and a contralateral feedback mechanism modulating rectus femoris and tibialis anterior activity during flexion. Because only muscles that contribute to flexion as a secondary function were observed, it is impossible to know whether the modulatory effect also acts on primary, unifunctional, limb flexors or is specific to multifunctional muscles contributing to flexion. The influence of contralateral extensor-phase sensorimotor signals on ipsilateral flexion may reflect bilateral coupling of gain control mechanisms. More generally, these interlimb neural mechanisms may coordinate activity between muscles that perform antagonistic functions on opposite sides of the body. Because pedaling and walking share biomechanical and neuronal control features, these mechanisms may be operational in walking as well as pedaling.

Adult↗

PubMed2000

The transforming growth factor-ss superfamily cytokine macrophage inhibitory cytokine-1 is present in high concentrations in the serum of pregnant women.

Macrophage inhibitory cytokine-1 (MIC-1) is a recently described divergent member of the transforming growth factor-ss superfamily. MIC-1 transcription up-regulation is associated with macrophage activation, and this observation led to its cloning. Northern blots indicate that MIC-1 is also present in human placenta. A sensitive sandwich enzyme-linked immunosorbent assay for the quantification of MIC-1 was developed and used to examine the role of this cytokine in pregnancy. High levels of MIC-1 are present in the sera of pregnant women. The level rises substantially with progress of gestation. MIC-1 can also be detected, in large amounts, in amniotic fluid and placental extracts. In addition, the BeWo placental trophoblastic cell line was found to constitutively express the MIC-1 transcript and secrete large amounts of MIC-1. These findings suggest that the placental trophoblast is a major source of the MIC-1 present in maternal serum and amniotic fluid. We suggest that MIC-1 may promote fetal survival by suppressing the production of maternally derived proinflammatory cytokines within the uterus.

Adult↗

PubMed2000

Adiposity does not hinder the fitness response to exercise training in obese women.

BACKGROUND: This study examined how sedentary obese (OB) and normal weight (NW) women respond to exercise training; and if fitness levels of the OB and NW are comparable, in spite of differences in adiposity. METHODS: Sedentary OB (n=46, 48.5+/-1.5 yrs, BMI=35.9+/-0.8; mean+/-SEM) and NW (n=43, 48.3+/-1.7 yrs, BMI=21.7+/-0.2) women participated in a 14-week fitness program. RESULTS: There were no group differences in exercise adherence. No changes for either group were found for body weight or composition. Both groups improved similarly in aerobic fitness (VO2max), muscular strength (grip strength), muscular endurance (modified push-up), and flexibility (sit and reach). However, since norms for fitness are generally expressed relative to body weight (e.g. VO2max, ml x kg(-1) x min(-1); grip strength ratios), the OB women continued to be classified as unfit after exercise training, and categorized below the NW women in spite of having absolute scores for VO2max (OB=2.1+/-0.1, NW=1.8+/-0.1 l x min(-1)) and grip strength (OB=65.1+/-1.5, NW= 58.6+/-1.5 kg) that were higher than the NW women. CONCLUSIONS: The data suggest that OB women respond in a similar manner as NW women to exercise; that weight loss is not necessary for improved fitness; and that the OB are not less fit than the NW, but that low fitness scores for the OB are simply a reflection of the absolute scores being deflated because they are proportioned to body weight.

Exercise↗

PubMed1999

Targeted mutagenesis of DNA with alkylating RecA assisted oligonucleotides.

Site-specific mutation was demonstrated in a shuttle vector system using nitrogen mustard-conjugated oligodeoxyribonucleotides (ODNs). Plasmid DNA was modified in vitro by ODNs containing all four DNA bases in the presence of Escherichia coli RecA protein. Up to 50% of plasmid molecules were alkylated in the targeted region of the supF gene and mutations resulted upon replication in mammalian cells. ODNs conjugated with either two chlorambucil moieties or a novel tetrafunctional mustard caused interstrand crosslinks in the target DNA and were more mutagenic than ODNs that caused only monoadducts.

Alkylating Agents↗

PubMed1999

Glycosphingolipids are not essential for formation of detergent-resistant membrane rafts in melanoma cells. methyl-beta-cyclodextrin does not affect cell surface transport of a GPI-anchored protein.

Recent data suggest that membrane microdomains or rafts that are rich in sphingolipids and cholesterol are important in signal transduction and membrane trafficking. Two models of raft structure have been proposed. One proposes a unique role for glycosphingolipids (GSL), suggesting that GSL-head-group interactions are essential in raft formation. The other model suggests that close packing of the long saturated acyl chains found on both GSL and sphingomyelin plays a key role and helps these lipids form liquid-ordered phase domains in the presence of cholesterol. To distinguish between these models, we compared rafts in the MEB-4 melanoma cell line and its GSL-deficient derivative, GM-95. Rafts were isolated from cell lysates as detergent-resistant membranes (DRMs). The two cell lines had very similar DRM protein profiles. The yield of DRM protein was 2-fold higher in the parental than the mutant line, possibly reflecting cytoskeletal differences. The same amount of DRM lipid was isolated from both lines, and the lipid composition was similar except for up-regulation of sphingomyelin in the mutant that compensated for the lack of GSL. DRMs from the two lines had similar fluidity as measured by fluorescence polarization of diphenylhexatriene. Methyl-beta-cyclodextrin removed cholesterol from both cell lines with the same kinetics and to the same extent, and both a raft-associated glycosyl phosphatidylinositol-anchored protein and residual cholesterol showed the same distribution between DRMs and the detergent-soluble fraction after cholesterol removal in both cell lines. Finally, a glycosyl phosphatidylinositol-anchored protein was delivered to the cell surface at similar rates in the two lines, even after cholesterol depletion with methyl-beta-cyclodextrin. We conclude that GSL are not essential for the formation of rafts and do not play a major role in determining their properties.

Alkaline Phosphatase↗

PubMed1999

Two types of K(+) channel subunit, Erg1 and KCNQ2/3, contribute to the M-like current in a mammalian neuronal cell.

The potassium M current was originally identified in sympathetic ganglion cells, and analogous currents have been reported in some central neurons and also in some neural cell lines. It has recently been suggested that the M channel in sympathetic neurons comprises a heteromultimer of KCNQ2 and KCNQ3 (Wang et al., 1998) but it is unclear whether all other M-like currents are generated by these channels. Here we report that the M-like current previously described in NG108-15 mouse neuroblastoma x rat glioma cells has two components, "fast" and "slow", that may be differentiated kinetically and pharmacologically. We provide evidence from PCR analysis and expression studies to indicate that these two components are mediated by two distinct molecular species of K(+) channel: the fast component resembles that in sympathetic ganglia and is probably carried by KCNQ2/3 channels, whereas the slow component appears to be carried by merg1a channels. Thus, the channels generating M-like currents in different cells may be heterogeneous in molecular composition.

Animals↗

PubMed1999

betagamma dimers derived from Go and Gi proteins contribute different components of adrenergic inhibition of Ca2+ channels in rat sympathetic neurones.

1. Using perforated-patch recordings, we have examined the part played by endogenous G-protein subunits in the alpha2-adrenoceptor-mediated inhibition of N-type Ca2+ currents in sympathetic neurones. 2. Two components of ICa inhibition by noradrenaline were recorded: a prominent, high affinity and voltage-dependent pertussis toxin (PTX)-sensitive pathway and a minor, low affinity and mostly voltage-insensitive PTX-resistant pathway. 3. PTX-sensitive inhibition was reduced by microinjection of antibodies against either GalphaoA,B or Galphai1,2. The voltage-dependent fraction of inhibition was reduced by anti-Galphao but not by anti-Galphai antibody. 4. Antisense depletion of GalphaoA led to a marked reduction of noradrenaline-induced inhibition and voltage dependence. By contrast, Galphai depletion attenuated noradrenergic modulation without affecting the voltage dependence. 5. Expression of the betagamma-binding agents beta-adrenergic receptor kinase 1 (C-terminus, betaARK1C-ter) or Galphai1 with a Cys3 to Ser mutation partially prevented noradrenergic inhibition while alpha-transducin abolished it. Residual inhibition was mostly voltage independent in cells expressing betaARK1C-ter but was strongly reversed by depolarization in Galphai1 Cys3Ser-expressing cells. 6. Expression of the PTX-resistant Galphai1 Cys351Ile mutant in cells treated with PTX restored alpha2-adrenoceptor inhibition. This restored inhibition was weakly reversed by depolarization. Both the degree and voltage dependence of inhibition were correlated with the level of expression of the Galphai1 Cys351Ile subunit. 7. Our findings identify betagamma dimers associated with GalphaoA and Galphai as mediators of the PTX-sensitive alpha2-adrenoceptor-mediated inhibition of N-type Ca2+ channels. Different betagamma combinations may account for the differential voltage-dependent effects of Go and Gi on ICa.

Animals↗

PubMed1999

Selective activation of heterologously expressed G protein-gated K+ channels by M2 muscarinic receptors in rat sympathetic neurones.

1. G protein-regulated inward rectifier K+ (GIRK) channels were over-expressed in dissociated rat superior cervical sympathetic (SCG) neurones by co-transfecting green fluorescent protein (GFP)-, GIRK1- and GIRK2-expressing plasmids using the biolistic technique. Membrane currents were subsequently recorded with whole-cell patch electrodes. 2. Co-transfected cells had larger Ba2+-sensitive inwardly rectifying currents and 13 mV more negative resting potentials (in 3 mM [K+]o) than non-transfected cells, or cells transfected with GIRK1 or GIRK2 alone. 3. Carbachol (CCh, 1-30 microM) increased the inwardly rectifying current in 70 % of GIRK1+ GIRK2-transfected cells by 261 +/- 53 % (n = 6, CCh 30 microM) at -120 mV, but had no effect in non-transfected cells or in cells transfected with GIRK1 or GIRK2 alone. Pertussis toxin prevented the effect of carbachol but had no effect on basal currents. 4. The effect of CCh was antagonized by 6 nM tripitramine but not by 100 nM pirenzepine, consistent with activation of endogenous M2 muscarinic acetylcholine receptors. 5. In contrast, inhibition of the voltage-activated Ca2+ current by CCh was antagonized by 100 nM pirenzepine but not by 6 nM tripitramine, indicating that it was mediated by M4 muscarinic acetylcholine receptors. 6. We conclude that endogenous M2 and M4 muscarinic receptors selectively couple to GIRK currents and Ca2+ currents respectively, with negligible cross-talk.

Animals↗

PubMed1999

Role of lipid modifications in targeting proteins to detergent-resistant membrane rafts. Many raft proteins are acylated, while few are prenylated.

Sphingolipid and cholesterol-rich Triton X-100-insoluble membrane fragments (detergent-resistant membranes, DRMs) containing lipids in a state similar to the liquid-ordered phase can be isolated from mammalian cells, and probably exist as discrete domains or rafts in intact membranes. We postulated that proteins with a high affinity for such an ordered lipid environment might be targeted to rafts. Saturated acyl chains should prefer an extended conformation that would fit well in rafts. In contrast, prenyl groups, which are as hydrophobic as acyl chains but have a branched and bulky structure, should be excluded from rafts. Here, we showed that at least half of the proteins in Madin-Darby canine kidney cell DRMs (other than cytoskeletal contaminants) could be labeled with [3H]palmitate. Association of influenza hemagglutinin with DRMs required all three of its palmitoylated Cys residues. Prenylated proteins, detected by [3H]mevalonate labeling or by blotting for Rap1, Rab5, Gbeta, or Ras, were excluded from DRMs. Rab5 and H-Ras each contain more than one lipid group, showing that hydrophobicity alone does not target multiply lipid-modified proteins to DRMs. Partitioning of covalently linked saturated acyl chains into liquid-ordered phase domains is likely to be an important mechanism for targeting proteins to DRMs.

Acylation↗

PubMed1999

M-channel gating and simulation.

Single potassium M-channels in rat sympathetic neurons have multiple voltage-dependent kinetic components in their activity: short, medium, and long closed times (tau(CS), tau(CM), and tau(CL)) and short and long open times (tau(OS) and tau(OL)). All five components can be detected in cell-attached patches, but only four of them (tau(CS), tau(CM), tau(OS), and tau(OL)) in excised patches (, J. Physiol. (Lond.). 472:711-724; 1996, Neuron. 16:151-162; 1996, Neuropharmacology. 35:933-947). Analysis of the burst structure of activity recorded from cell-attached and excised inside-out patches showed it to be consistent with the sequential kinetic scheme C(L) left arrow over right arrow O(S) left arrow over right arrow C(M) left arrow over right arrow O(L) left arrow over right arrow C(S). Using this scheme and experimentally determined kinetic parameters, we successfully simulated the activity of M-channels both under steady-state conditions and during depolarizing voltage steps. Consistent with the characteristic behavior of macroscopic M-current, ensemble currents constructed from simulated M-channels had exponential activation and deactivation, with no delays, when tested in the range between -50 and -20 mV.

Animals↗

PubMed1999

Children's recall of medical experiences: the impact of stress.

OBJECTIVE: The study compared children's reports of two medical events, to assess the effects of the type of event on children's recall. Additionally, the study examined the effect of props on children's event reports. METHOD: Twenty children between the ages of 37 and 67 months were interviewed following either a voiding cysto-urethrogram (VCUG) or a pediatric assessment (PA) at a hospital. Interviews were conducted between 6 and 8 days after the event and included a doll and prop items. RESULTS: Ratings of stress were significantly higher for children who underwent the VCUG than those who underwent the PA. Children who experienced the VCUG procedure reported more correct information than the children who experienced the PA. Age was correlated with the total amount of correct information reported. Stress levels were correlated with both errors and accuracy of information. CONCLUSIONS: Children who experienced a stressful medical procedure remembered more than children who experienced a neutral medical event, although this increase in amount recalled was at the expense of accuracy. These findings suggest that stress impacts negatively on recall: however, the unique and structured nature of the VCUG procedure compared to the PA, and the familiarity of the PA prop items to the children who experienced the VCUG procedure, may also have contributed to differences in recall of the two events.

Child, Preschool↗

PubMed1999

Osteonecrosis of the temporomandibular joint: correlation of magnetic resonance imaging and histology.

PURPOSE: The aims of this study were to investigate whether osteonecrosis affects the mandibular condyle and to determine whether this condition could be diagnosed with magnetic resonance imaging (MRI). MATERIALS AND METHODS: The study was based on 50 temporomandibular joints in 44 patients in whom MRI and surgery were performed for painful internal derangements. At the time of surgery, a core biopsy specimen was obtained from the marrow of the mandibular condyles, and the histological observations were correlated to T1-(proton density) and T2-weighted MR images. RESULTS: Histological evidence of osteonecrosis was found in nine joints (18%). Bone marrow edema, which may be a precursor of osteonecrosis, was found in nine other joints. The MRI was 78% sensitive and 84% specific for the diagnosis of osteonecrosis of the mandibular condyle. However, the positive predictive value was only 54% because of a number of false-positive MRI diagnoses. CONCLUSION: Osteonecrosis can affect the mandibular condyle, and this condition can be diagnosed with MRI. A combination of edema and sclerosis of the bone marrow was the most reliable MRI sign of osteonecrosis. The cause, its clinical significance, and the need for treatment are unknown.

Adult↗

PubMed1999

Dual coupling of heterologously-expressed rat P2Y6 nucleotide receptors to N-type Ca2+ and M-type K+ currents in rat sympathetic neurones.

1. The P2Y6 receptor is a uridine nucleotide-specific G protein-linked receptor previously reported to stimulate the phosphoinositide (PI) pathway. We have investigated its effect in neurones, by micro-injecting its cRNA into dissociated rat sympathetic neurones and recording responses of N-type Ca2+ (I(Ca(N))) and M-type K+ (I(K(M))) currents. 2. In P2Y6 cRNA-injected neurones, UDP or UTP produced a voltage-dependent inhibition of I(Ca(N)) by approximately 53% in whole-cell (disrupted-patch) mode and by 73% in perforated-patch mode; no inhibition occurred in control cells. Mean IC50 values (whole-cell) were: UDP, 5.9+/-0.3 nM; UTP, 20+/-1 nM. ATP and ADP (1 microM) had no significant effect. Pertussis toxin (PTX) substantially (approximately 60%) reduced UTP-mediated inhibition in disrupted patch mode but not in perforated-patch mode. 3. Uridine nucleotides also inhibited I(K(M)) in P2Y6 cRNA-injected cells (by up to 71% at 10 microM UTP; perforated-patch). Mean IC50 values were: UDP, 30+/-3 nM; UTP, 115+/-12 nM. ATP (10 microM) again had no effect. No significant inhibition occurred in control cells. Inhibition was PTX-resistant. 4. Thus, the P2Y6 receptor, like the P2Y2 subtype studied in this system, couples to both of these two neuronal ion channels through at least two different G proteins. However, the P2Y6 receptor displays a much higher sensitivity to its agonists than the P2Y2 receptor in this expression system and higher than previously reported using other expression methods. The very high sensitivity to both UDP and UTP suggests that it might be preferentially activated by any locally released uridine nucleotides.

Animals↗

PubMed1999

Bicyclic monoterpene diols induce differentiation of S91 melanoma and PC12 pheochromocytoma cells by a cyclic guanosine-monophosphate-dependent pathway.

Previously, we showed that 5-norbornene-2,2-dimethanol (5-NBene-2,2-DM) is an effective inducer of melanogenesis in cultured cells and guinea-pig skin [Brown et al. (1998) J. Invest. Dermatol., 110:428-437]. This study shows that 2,3-cis/exo-pinanediol (2,3-cs/ex-PinD) is a more effective inducer of melanogenesis than 5-NBene-2,2-DM in S91 mouse melanoma cells. Furthermore, 2,3-cs/ex-PinD appears to penetrate guinea-pig skin better than 5-NBene-2,2-DM and to induce higher levels of pigmentation. Both 5-NBene-2,2-DM and 2,3-cs/ex-PinD induce synthesis of nitric oxide (NO) in S91 cells, and the melanogenic activity of both compounds is reduced by inhibitors of the NO/cyclic guanosine monophosphate (cGMP)/protein kinase(PK) G signaling pathway, but not by inhibitors of the PKC or PKA pathways. Thus, these bicyclic monoterpene diols appear to induce melanogenesis by the same pathway in S91 cells as that shown previously for ultraviolet radiation in melanocytes (Romero-Graillet et al. (1996) J. Biol. Chem., 271:28052-28056). These compounds also induce NO synthesis, neurite outgrowth, and tyrosine hydroxylase activity in PC12 pheochromocytoma cells. Neurite outgrowth in PC12 cells is blocked by the guanylate cyclase inhibitor, LY83583 (6-anilino-2,8-quinolinequinone), indicating that, similar to S91 cells, the induction of morphological differentiation of PC12 cells by bicyclic monoterpene diols is regulated by a cGMP-dependent pathway.

Animals↗

PubMed1999

Phase reversal of biomechanical functions and muscle activity in backward pedaling.

Computer simulations of pedaling have shown that a wide range of pedaling tasks can be performed if each limb has the capability of executing six biomechanical functions, which are arranged into three pairs of alternating antagonistic functions. An Ext/Flex pair accelerates the limb into extension or flexion, a Plant/Dorsi pair accelerates the foot into plantarflexion or dorsiflexion, and an Ant/Post pair accelerates the foot anteriorly or posteriorly relative to the pelvis. Because each biomechanical function (i.e., Ext, Flex, Plant, Dorsi, Ant, or Post) contributes to crank propulsion during a specific region in the cycle, phasing of a muscle is hypothesized to be a consequence of its ability to contribute to one or more of the biomechanical functions. Analysis of electromyogram (EMG) patterns has shown that this biomechanical framework assists in the interpretation of muscle activity in healthy and hemiparetic subjects during forward pedaling. Simulations show that backward pedaling can be produced with a phase shift of 180 degrees in the Ant/Post pair. No phase shifts in the Ext/Flex and Plant/Dorsi pairs are then necessary. To further test whether this simple yet biomechanically viable strategy may be used by the nervous system, EMGs from 7 muscles in 16 subjects were measured during backward as well as forward pedaling. As predicted, phasing in vastus medialis (VM), tibialis anterior (TA), medial gastrocnemius (MG), and soleus (SL) were unaffected by pedaling direction, with VM and SL contributing to Ext, MG to Plant, and TA to Dorsi. In contrast, phasing in biceps femoris (BF) and semimembranosus (SM) were affected by pedaling direction, as predicted, compatible with their contribution to the directionally sensitive Post function. Phasing of rectus femoris (RF) was also affected by pedaling direction; however, its ability to contribute to the directionally sensitive Ant function may only be expressed in forward pedaling. RF also contributed significantly to the directionally insensitive Ext function in both forward and backward pedaling. Other muscles also appear to have contributed to more than one function, which was especially evident in backward pedaling (i.e. , BF, SM, MG, and TA to Flex). We conclude that the phasing of only the Ant and Post biomechanical functions are directionally sensitive. Further, we suggest that task-dependent modulation of the expression of the functions in the motor output provides this biomechanics-based neural control scheme with the capability to execute a variety of lower limb tasks, including walking.

Adult↗

PubMed1999

Speed-dependent reductions of force output in people with poststroke hemiparesis.

BACKGROUND AND PURPOSE: Movement is slow in people with poststroke hemiparesis. Moving at faster speeds is thought by some researchers to exacerbate abnormal or unwanted muscle activity. The purpose of this study was to quantify the effects of increased speed on motor performance during pedaling exercise in people with poststroke hemiparesis. SUBJECTS: Twelve elderly subjects with no known neurological impairment and 15 subjects with poststroke hemiparesis of greater than 6 months' duration were tested. METHODS: Subjects pedaled at 12 randomly ordered workload and cadence combinations (45-, 90-, 135-, and 180-J workloads at 25, 40, and 55 rpm). Pedal reaction forces were used to calculate work done by each lower extremity. Electromyographic activity was recorded from 7 lower-extremity muscles. RESULTS: The main finding was that net mechanical work done by the paretic lower extremity decreased as speed increased in all subjects. The occurrence of inappropriate muscle activity on the paretic side, however, was not exacerbated in that the vastus medialis muscle on the paretic side did not show a consistent further increase in its prolonged activity at higher speeds. The mechanics of faster pedaling resulted in greater net negative mechanical work because, at higher pedaling rates, the prolonged vastus medialis muscle activity is present during a greater portion of the cycle. CONCLUSION AND DISCUSSION: The lessened force output by the paretic limb is mainly the result of the inherent mechanical demands of higher-speed pedaling and not due to exacerbation of impaired neural control.

Aged↗

PubMed1999

Minimally invasive coronary artery bypass grafting for myocardial muscle bridging.

Myocardial bridging is a congenital anomaly of the left anterior descending coronary artery (LAD), which is associated with myocardial ischemia and infarction, cardiac arrhythmias, and sudden cardiac death. Two cases are reported of symptomatic myocardial bridging refractory to medical management treated by minimally invasive coronary artery bypass grafting without cardiopulmonary bypass. We conclude that minimally invasive coronary artery bypass techniques are appropriate alternatives to endovascular stent placement, muscle bridge division, or aortocoronary grafting with cardiopulmonary bypass for the management of symptomatic myocardial bridging.

Adult↗