How does multi-set high-load resistance exercise impact neuromuscular function in normoxia and hypoxia?

This study examined whether hypoxia during multi-set, high-load resistance exercise alters neuromuscular responses. Using a single-blinded (participants), randomised crossover design, eight resistance-trained males completed five sets of five repetitions of bench press at 80% of one repetition maximum in moderate normobaric hypoxia (inspiratory oxygen fraction = 0.145) and normoxia. Maximal isometric bench press trials were performed following the warm-up, after 10 min of altitude priming and 5 min post-session (outside, inside and outside the chamber, respectively). Force during pre-/post-session maximal voluntary isometric contractions and bar velocity during exercise sets were measured along with surface electromyographic (EMG) activity of the pectoralis major, anterior deltoid and lateral and medial triceps muscles. Two-way repeated measures ANOVA (condition×time) were used. A significant time effect (p = 0.048) was found for mean bar velocity, independent of condition (p = 0.423). During sets of the bench press exercise, surface EMG amplitude of all studied muscles remained unchanged (p > 0.187). During maximal isometric trials, there were no main effects of condition (p > 0.666) or time (p > 0.119), nor were there any significant condition×time interactions for peak or mean forces and surface EMG amplitudes (p > 0.297). Lower end-exercise blood oxygen saturation (90.9 ± 1.8 vs. 98.6 ± 0.6%; p < 0.001) and higher blood lactate concentration (5.8 ± 1.4 vs. 4.4 ± 1.6 mmol/L; p = 0.007) values occurred in hypoxia. Acute delivery of systemic normobaric hypoxia during multi-set, high-load resistance exercise increased metabolic stress. However, only subtle neuromuscular function adjustments occurred with and without hypoxic exposure either during maximal isometric bench press trials before versus after the session or during actual exercise sets.

Flexible head-casts for high spatial precision MEG

BACKGROUND

In combination with magnetoencephalographic (MEG) data, accurate knowledge of the brain's structure and location provide a principled way of reconstructing neural activity with high temporal resolution. However, measuring the brain's location is compromised by head movement during scanning, and by fiducial-based co-registration with magnetic resonance imaging (MRI) data. The uncertainty from these two factors introduces errors into the forward model and limit the spatial resolution of the data.

NEW METHOD

We present a method for stabilizing and reliably repositioning the head during scanning, and for co-registering MRI and MEG data with low error.

RESULTS

Using this new flexible and comfortable subject-specific head-cast prototype, we find within-session movements of <0.25mm and between-session repositioning errors around 1mm.

COMPARISON WITH EXISTING METHOD(S)

This method is an improvement over existing methods for stabilizing the head or correcting for location shifts on- or off-line, which still introduce approximately 5mm of uncertainty at best (Adjamian et al., 2004; Stolk et al., 2013; Whalen et al., 2008). Further, the head-cast design presented here is more comfortable, safer, and easier to use than the earlier 3D printed prototype, and give slightly lower co-registration errors (Troebinger et al., 2014b).

CONCLUSIONS

We provide an empirical example of how these head-casts impact on source level reproducibility. Employment of the individual flexible head-casts for MEG recordings provide a reliable method of safely stabilizing the head during MEG recordings, and for co-registering MRI anatomical images to MEG functional data.

Analysis of simultaneous MEG and intracranial LFP recordings during Deep Brain Stimulation: a protocol and experimental validation

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Setup for MEG and intracranial recordings during Deep Brain Stimulation is described.

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Phantom experiment showed correct recovery of oscillatory sources despite artefacts.

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The method is applied to real data from a patient with Parkinson's Disease.

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Cortico-subthalamic coherence profiles on and off stimulation were comparable.

Background

Deep Brain Stimulation (DBS) is an effective treatment for several neurological and psychiatric disorders. In order to gain insights into the therapeutic mechanisms of DBS and to advance future therapies a better understanding of the effects of DBS on large-scale brain networks is required.

New method

In this paper, we describe an experimental protocol and analysis pipeline for simultaneously performing DBS and intracranial local field potential (LFP) recordings at a target brain region during concurrent magnetoencephalography (MEG) measurement. Firstly we describe a phantom setup that allowed us to precisely characterise the MEG artefacts that occurred during DBS at clinical settings.

Results

Using the phantom recordings we demonstrate that with MEG beamforming it is possible to recover oscillatory activity synchronised to a reference channel, despite the presence of high amplitude artefacts evoked by DBS. Finally, we highlight the applicability of these methods by illustrating in a single patient with Parkinson's disease (PD), that changes in cortical-subthalamic nucleus coupling can be induced by DBS.

Comparison with existing approaches

To our knowledge this paper provides the first technical description of a recording and analysis pipeline for combining simultaneous cortical recordings using MEG, with intracranial LFP recordings of a target brain nucleus during DBS.

Cortical mechanisms of mirror therapy after stroke

BACKGROUND AND OBJECTIVE

Mirror therapy is a new form of stroke rehabilitation that uses the mirror reflection of the unaffected hand in place of the affected hand to augment movement training. The mechanism of mirror therapy is not known but is thought to involve changes in cerebral organization. We used magnetoencephalography (MEG) to measure changes in cortical activity during mirror training after stroke. In particular, we examined movement-related changes in the power of cortical oscillations in the beta (15-30 Hz) frequency range, known to be involved in movement.

METHODS

Ten stroke patients with upper limb paresis and 13 healthy controls were recorded using MEG while performing bimanual hand movements in 2 different conditions. In one, subjects looked directly at their affected hand (or dominant hand in controls), and in the other, they looked at a mirror reflection of their unaffected hand in place of their affected hand. The movement-related beta desynchronization was calculated in both primary motor cortices.

RESULTS

Movement-related beta desynchronization was symmetrical during bilateral movement and unaltered by the mirror condition in controls. In the patients, movement-related beta desynchronization was generally smaller than in controls, but greater in contralesional compared to ipsilesional motor cortex. This initial asymmetry in movement-related beta desynchronization between hemispheres was made more symmetrical by the presence of the mirror.

CONCLUSIONS

Mirror therapy could potentially aid stroke rehabilitation by normalizing an asymmetrical pattern of movement-related beta desynchronization in primary motor cortices during bilateral movement.

Between Thought and Expression, a Magnetoencephalography Study of the “Tip-of-the-Tongue” Phenomenon

“Tip-of-the-tongue” (TOT) is the phenomenon associated with the inaccessibility of a known word from memory. It is universally experienced, increases in frequency with age, and is most common for proper nouns. It is a good model for the symptom of anomia experienced much more frequently by some aphasic patients following brain injury. Here, we induced the TOT state in older participants while they underwent brain scanning with magnetoencephalography to investigate the changes in oscillatory brain activity associated with failed retrieval of known words. Using confrontation naming of pictures of celebrities, we successfully induced the TOT state in 29% of trials and contrasted it with two other states: “Know” where the participants both correctly recognized the celebrity's face and retrieved their name and “Don't Know” when the participants did not recognize the celebrity. We wished to test Levelt's influential model of speech output by carrying out two analyses, one epoching the data to the point in time when the picture was displayed and the other looking back in time from when the participants first articulated their responses. Our main findings supported the components of Levelt's model, but not their serial activation over time as both semantic and motor areas were identified in both analyses. We also found enduring decreases in the alpha frequency band in the left ventral temporal region during the TOT state, suggesting ongoing semantic search. Finally, we identified reduced beta power in classical peri-sylvian language areas for the TOT condition, suggesting that brain regions that encode linguistic memories are also involved in their attempted retrieval.

High precision anatomy for MEG

Precise MEG estimates of neuronal current flow are undermined by uncertain knowledge of the head location with respect to the MEG sensors. This is either due to head movements within the scanning session or systematic errors in co-registration to anatomy. Here we show how such errors can be minimized using subject-specific head-casts produced using 3D printing technology. The casts fit the scalp of the subject internally and the inside of the MEG dewar externally, reducing within session and between session head movements. Systematic errors in matching to MRI coordinate system are also reduced through the use of MRI-visible fiducial markers placed on the same cast. Bootstrap estimates of absolute co-registration error were of the order of 1 mm. Estimates of relative co-registration error were < 1.5 mm between sessions. We corroborated these scalp based estimates by looking at the MEG data recorded over a 6 month period. We found that the between session sensor variability of the subject's evoked response was of the order of the within session noise, showing no appreciable noise due to between-session movement. Simulations suggest that the between-session sensor level amplitude SNR improved by a factor of 5 over conventional strategies. We show that at this level of coregistration accuracy there is strong evidence for anatomical models based on the individual rather than canonical anatomy; but that this advantage disappears for errors of greater than 5 mm. This work paves the way for source reconstruction methods which can exploit very high SNR signals and accurate anatomical models; and also significantly increases the sensitivity of longitudinal studies with MEG.

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We introduce MEG coregistration scheme using 3D printed subject specific head casts.

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Using this scheme reduces relative/absolute coregistration errors to 1–2 mm levels.

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The ability to reposition between sessions results in high SNR data sets.

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At this level of coregistration error, we see a clear benefit for using individual cortical meshes.

Cholinergic enhancement of visual attention and neural oscillations in the human brain

Cognitive processes such as visual perception and selective attention induce specific patterns of brain oscillations [1–6]. The neurochemical bases of these spectral changes in neural activity are largely unknown, but neuromodulators are thought to regulate processing [7–9]. The cholinergic system is linked to attentional function in vivo [10–13], whereas separate in vitro studies show that cholinergic agonists induce high-frequency oscillations in slice preparations [14–16]. This has led to theoretical proposals [17–19] that cholinergic enhancement of visual attention might operate via gamma oscillations in visual cortex, although low-frequency alpha/beta modulation may also play a key role. Here we used MEG to record cortical oscillations in the context of administration of a cholinergic agonist (physostigmine) during a spatial visual attention task in humans. This cholinergic agonist enhanced spatial attention effects on low-frequency alpha/beta oscillations in visual cortex, an effect correlating with a drug-induced speeding of performance. By contrast, the cholinergic agonist did not alter high-frequency gamma oscillations in visual cortex. Thus, our findings show that cholinergic neuromodulation enhances attentional selection via an impact on oscillatory synchrony in visual cortex, for low rather than high frequencies. We discuss this dissociation between high- and low-frequency oscillations in relation to proposals that lower-frequency oscillations are generated by feedback pathways within visual cortex [20, 21].

Method for simultaneous voxel-based morphometry of the brain and cervical spinal cord area measurements using 3D-MDEFT

Purpose

To investigate whether a 3D-modified driven equilibrium Fourier transform (MDEFT)-based acquisition protocol established for brain morphometry also yields reliable information about the cross-sectional spinal cord area (SCA).

Materials and Methods

Images of brain and cervical cord of 10 controls and eight subjects with spinal cord injury (SCI) were acquired with the 3D-MDEFT-based imaging protocol and an 8-channel receive head coil. The new protocol was validated by two observers 1) comparing the SCA measured with the standard acquisition protocol (3D magnetization-prepared rapid acquisition gradient echo [MPRAGE] and dedicated spine coil) and the new protocol; and 2) determining the scan–rescan reproducibility of the new protocol.

Results

Scan–rescan reproducibility of SCA measurements with the MDEFT approach showed a similar precision for both observers with standard deviation (SD) <4.5 mm² and coefficient of variation (CV) ≤5.1%. Analysis of variance (ANOVA) revealed a main effect of observer and interaction between observer and scan protocol that could be primarily attributed to a small observer bias for MPRAGE (difference in SCA <2.1 mm²). No bias was observed for 3D-MDEFT vs. 3D-MPRAGE.

Conclusion

The 3D-MDEFT method allows for robust unbiased assessment of SCA in addition to brain morphology. J. Magn. Reson. Imaging 2010;32:1242–1247. © 2010 Wiley-Liss, Inc.

IL-1beta, BK, and TGF-beta1 attenuate PGI2-mediated cAMP formation in human pulmonary artery smooth muscle cells by multiple mechanisms involving p38 MAP kinase and PKA

We have previously shown that interleukin (IL)-1beta, transforming growth factor (TGF)-beta1, or bradykinin (BK) impair cAMP generation in response to prostacyclin analogs in human pulmonary artery smooth muscle (PASM), suggesting that inflammation can impair the effects of prostacyclin analogs on PASM in pulmonary hypertension. Here we explored the biochemical mechanisms involved. We found that IL-1beta, BK, and TGF-beta1 reduced adenylyl cyclase isoform 1, 2, and 4 mRNA, increased Galphai protein levels, and reduced prostacyclin receptor (IP receptor) mRNA expression. In contrast, Galphas protein levels were unchanged. Protein kinase A (PKA) (H-89, KT-2750, PKIm) and p38 mitogen-activated protein (MAP) kinase (SB-202190) inhibitors attenuated these effects, but protein kinase C (bisindolylmaleide) or phosphoinositol 3-kinase (LY-294002) inhibitors did not. Fluorescent kemptide assay and Western blotting confirmed that PKA and p38 MAP kinase were activated by IL-1beta, BK, and TGF-beta1. These studies suggest that IL-1beta, BK, and TGF-beta1 impair IP receptor-mediated cAMP accumulation by multiple effects on different components of the signaling pathway and that these effects are PKA and p38 MAP kinase dependent.

A cortical potential reflecting cardiac function

Emotional trauma and psychological stress can precipitate cardiac arrhythmia and sudden death through arrhythmogenic effects of efferent sympathetic drive. Patients with preexisting heart disease are particularly at risk. Moreover, generation of proarrhythmic activity patterns within cerebral autonomic centers may be amplified by afferent feedback from a dysfunctional myocardium. An electrocortical potential reflecting afferent cardiac information has been described, reflecting individual differences in interoceptive sensitivity (awareness of one's own heartbeats). To inform our understanding of mechanisms underlying arrhythmogenesis, we extended this approach, identifying electrocortical potentials corresponding to the cortical expression of afferent information about the integrity of myocardial function during stress. We measured changes in cardiac response simultaneously with electroencephalography in patients with established ventricular dysfunction. Experimentally induced mental stress enhanced cardiovascular indices of sympathetic activity (systolic blood pressure, heart rate, ventricular ejection fraction, and skin conductance) across all patients. However, the functional response of the myocardium varied; some patients increased, whereas others decreased, cardiac output during stress. Across patients, heartbeat-evoked potential amplitude at left temporal and lateral frontal electrode locations correlated with stress-induced changes in cardiac output, consistent with an afferent cortical representation of myocardial function during stress. Moreover, the amplitude of the heartbeat-evoked potential in the left temporal region reflected the proarrhythmic status of the heart (inhomogeneity of left ventricular repolarization). These observations delineate a cortical representation of cardiac function predictive of proarrhythmic abnormalities in cardiac repolarization. Our findings highlight the dynamic interaction of heart and brain in stress-induced cardiovascular morbidity.

Interleukin-1beta, transforming growth factor-beta1, and bradykinin attenuate cyclic AMP production by human pulmonary artery smooth muscle cells in response to prostacyclin analogues and prostaglandin E2 by cyclooxygenase-2 induction and downregulation of adenylyl cyclase isoforms 1, 2, and 4

Increased levels of inflammatory cytokines contribute to the pathophysiology of pulmonary hypertension. Prostacyclin (PGI2) analogues, which relax pulmonary vessels mainly through cAMP elevation, have a major therapeutic role. In this study, we show that prolonged incubation with bradykinin (BK), interleukin-1beta (IL-1beta), and transforming growth factor-beta1 (TGF-beta1) markedly impairs cAMP accumulation in human pulmonary artery smooth muscle cells in response to short-term incubation with prostaglandin E2 (PGE2) and the PGI2 analogues iloprost and carbaprostacyclin. A similar reduction in cAMP accumulation in response to a direct adenylyl cyclase activator, forskolin, suggested that the effect was attributable to downregulation of adenylyl cyclase. Reverse transcriptase-polymerase chain reaction studies showed downregulation of adenylyl cyclase isoforms 1, 2, and 4. The effect of IL-1beta, BK, and TGF-beta1 on cAMP levels was abrogated by the selective COX-2 inhibitor NS398. Furthermore, it was mimicked by prolonged incubation with the COX-2 product PGE2 and PGI2 analogues or the COX substrate arachidonic acid, suggesting that it was mediated by endogenous prostanoids produced by COX-2. Consistent with this, IL-1beta, BK, and TGF-beta1 all induced COX-2 and PGE2 release. These results show that BK, IL-1beta, and TGF-beta1 downregulate adenylyl cyclase in human pulmonary artery smooth muscle cells via COX-2 induction and prostanoid release. This suggests a novel mechanism whereby mediators and cytokines produced in pulmonary hypertension may impair the therapeutic effects of prostacyclin analogues such as iloprost and carbaprostacyclin.

bcl-2 over-expression delays radiation-induced apoptosis without affecting the clonogenic survival of human prostate cancer cells

In this study we evaluated the effect of over-expression of the bcl-2 gene, a potent apoptosis suppressor, on radiation-induced apoptotic cell death in 2 human prostate cancer cell lines, androgen-independent PC-3 cells and androgen-sensitive LNCaP cells. Cells were transfected with the bcl-2 gene and bcl-2 transfectant clones isolated under neomycin selection; bcl-2 gene integration and level of mRNA and protein expression in the cloned transfectants were examined by Southern, Northern and Western blot analyses, respectively. Parental, neo control and bcl-2-expressing cells were exposed to single or fractionated doses of ionizing irradiation, and the cellular response to radiation was determined at 24, 48 and 72 hr post-irradiation, on the basis of: (i) loss of cell viability, (ii) clonogenic survival and (iii) induction of apoptotic DNA fragmentation. At 24 hr post-irradiation all cell lines, i.e., parental and bcl-2 transfectants, failed to form colonies, though the majority of bcl-2-expressing cells did not exhibit apoptotic morphology; bcl-2 over-expression in both cell lines reduced apoptosis 48 hr post-irradiation from 20-25% to 5% at a dose of 2,000 cGy. By 72 hr, bcl-2 over-expression afforded a 3-fold protection from radiation-induced apoptosis. There was no significant difference, however, in the clonogenic survival of the parental and bcl-2-expressing cells. Furthermore, there was a 24 hr delay in induction of the apoptosis marker gene SGP-2/TRPM-2 in the bcl-2-expressing cells, co-incidental with the delay in apoptotic DNA fragmentation.

Biological features of leukaemic cells associated with autonomous growth and reduced survival in acute myeloblastic leukaemia

The blast cells from up to 70% of patients with acute myeloblastic leukaemia exhibit a variable degree of autonomous growth in vitro, which is related to the production of autocrine growth factors. It has recently been established that patients with autonomous blast cell growth have both a lower remission rate and a higher relapse rate, compared to otherwise comparable patients whose blasts exhibit non-autonomous in vitro growth. In a group of 50 patients the actuarial disease-free survival for the autonomous growth group was 11% at 5 years compared to greater than 50% for the non-autonomous growth group. This data suggests that AML blasts with autocrine growth characteristics may be resistant to cytotoxic drug therapy. Here we present further data demonstrating that AML blasts with autonomous growth are relatively resistant to the induction of programmed cell death (apoptosis) and that this is related to the autocrine production of GM-CSF. Also AML blasts with autonomous growths have aberrant expression of genes associated with resistance to apoptosis induced by cytotoxic drugs. These include high expression of the bcl-2 oncoprotein and abnormalities of expression of the p53 tumour suppressor gene. Furthermore bcl-2 expression was found to be unregulated by both exogenous and autocrine GM-CSF suggesting that the documented negative prognostic effect of autonomous growth on treatment outcome in AML, is in part due to the regulatory effect of autocrine GM-CSF on bcl-2 expression, thus protecting cells from apoptosis induced by cytotoxic drug therapy.

Evidence for internal autocrine regulation of growth in acute myeloblastic leukemia cells

Blast cells from 70% of patients with acute myeloid leukemia (AML) show some evidence of in vitro autonomous growth, which appears to be related to the autocrine secretion of growth factors, particularly granulocyte-macrophage colony-stimulating factor (GM-CSF). In the majority of cases, the growth factors appear to be involved in classical extracellular autocrine or paracrine loops with neutralizing antibodies to the relevant cytokine inhibiting growth. In a minority, however, antibodies do not inhibit growth despite evidence of secretion of the cytokine. There is evidence for intracellular autocrine loops in murine leukemic cell lines. In this study, we wished to investigate for the presence of such intracellular loops involving GM-CSF in AML blast cells. Blast cells from 11 patients with AML were cultured in the presence of either neutralizing GM-CSF antibody or an antisense oligonucleotide directed against GM-CSF. We also studied the effect of the oligonucleotide on the autonomous growth of cells whose production of GM-CSF had been apparently abolished by either interleukin-1 receptor antagonist (IL-1Ra) or following blast cell purification using the CD34 antigen. The autonomous growth of the blast cells from nine of the 11 patients was inhibited by the antisense oligonucleotide (but not by the control sense oligonucleotide). However, only six of the nine were inhibited by the anti-GM-CSF antibody. Similarly, in one patient whose CD34 purified blast cells continued to show a high degree of autonomous growth but did not produce detectable GM-CSF, growth was inhibited by the antisense oligonucleotide but not by antibody, while in another patient whose cells were inhibited by IL-1Ra with, again, loss of detectable GM-CSF, growth could be further inhibited by the addition of the oligonucleotide but not the antibody. These studies provide evidence that intracellular autocrine loops involving GM-CSF are involved in the autonomous growth of some AML blast cells.

Regulation of Bcl-2 expression and apoptosis in acute myeloblastic leukaemia cells by granulocyte-macrophage colony-stimulating factor

Previous studies have shown that the bcl-2 gene encodes a mitochondrial protein which can inhibit the onset of apoptosis induced by withdrawal of trophic factors or by antitumour drugs. In some malignant cells bcl-2 expression has been demonstrated to be regulated by specific trophic factors which act to suppress apoptosis. Here we have investigated the effect of exogenous and autocrine granulocyte-macrophage colony-stimulating factor (GM-CSF) on both bcl-2 expression and apoptosis in acute myeloid leukaemia (AML) cells. Blasts from 31 patients with AML were studied, this included 21 patients whose cells exhibited variable degrees of autonomous growth in culture and ten patients with non-autonomous growth. Blasts with autonomous growth expressed significantly higher levels of bcl-2 protein, the intensity of fluorescence expressed as soluble fluorochrome per cell was 40.9 +/- 3.6 x 10(3) (mean +/- SD); this compared with an intensity of bcl-2 expression of 19.3 +/- 2.4 x 10(3) for blasts with non-autocrine growth (p < 0.0001 by Mann-Whitney analysis). Blasts with non-autocrine growth rapidly lost viability following 48 h of culture due to the onset of apoptosis. In these cells apoptosis was suppressed by the addition of GM-CSF and bcl-2 protein expression was found to be significantly upregulated. In contrast blasts from patients with autonomous growth and autocrine GM-CSF production failed to show any features of apoptosis in culture. In these cells bcl-2 expression was significantly downregulated following neutralization of autocrine GM-CSF by antibodies. We conclude that bcl-2 expression in AML cells is regulated by GM-CSF, and suggest that the previously demonstrated negative prognostic effect of autocrine growth as a determinant of treatment outcome in AML is in part due to the effect of autocrine GM-CSF in upregulating bcl-2 expression.

Decreased retinoblastoma protein expression in acute myeloblastic leukaemia is associated with the autonomous proliferation of clonogenic blasts

We have previously shown that blasts from some patients with acute myeloblastic leukaemia (AML) grow autonomously in vitro and that this growth pattern is related to the production of autocrine growth factors including granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin-1 beta. However, another potential mechanism of autonomous growth involves the deletion of growth inhibitory molecules. One such inhibitory protein is the product of the retinoblastoma (Rb) gene which is expressed in normal haemopoietic cells and functions in cell cycle control and as a transcriptional repressor. Deletion of the Rb gene has been reported in various types of malignancy. We have examined the expression of the Rb gene product in blasts from 39 patients with AML by Western analysis. Using an antibody, Rb (Ab-2) which recognizes the C-terminal region, 11/39 samples (28%) failed to express Rb protein. The results of the Western blot analysis were confirmed by flow cytometry using a second antibody, Rb (Ab-1), against residues 300-380 of the Rb protein. Samples from seven of the 11 Rb-negative cases were studied for the expression of Rb mRNA; Rb mRNA was absent in four and three cases were positive. Analysis of the growth characteristics of these cells showed that blasts from 24/39 cases (62%) had partially or totally autonomous growth in a blast cell colony assay. Of these 24 samples with autonomous growth, 10 (41%) were Rb protein negative; in contrast, of the 15 cases with non-autocrine growth only one was Rb protein negative (7%, P < 0.05). Also, in Rb positive blasts, suppression of Rb protein production using an antisense oligonucleotide significantly increased proliferation of clonogenic AML blasts, confirming that the Rb protein acts as a negative regulator of growth in AML blasts. Our data suggest that deletion of Rb protein expression is frequently found in AML and is associated with the acquisition of autocrine growth characteristics, possibly as the consequence of derepression of genes involved in growth control and cytokine production.

Expression of different conformations of p53 in the blast cells of acute myeloblastic leukaemia is related to in vitro growth characteristics

Expression of the wild-type p53 gene has an important role in cell differentiation, maturation and apoptosis. Mutation of the p53 gene is associated with tumour development and mutant p53 can promote cell proliferation. Recently wild-type p53 has been demonstrated to exist in two conformational variants: one acting as a suppressor (PAb240-/PAb1620+) and one as a promoter (PAb240+/PAb1620-) of cell proliferation. We have analysed the expression of p53 by flow cytometry in blast cells from 34 patients with acute myeloblastic leukaemia in relationship to the proliferation characteristics of these cells in a clonogenic assay. Blasts from three out of 34 patients did not express p53 using the antibodies: PAb421, PAb1801, PAb240 and PAb1620. The remaining 31 samples expressed p53 detected by PAb240 which recognises mutant p53 and is predicted to recognise wild-type p53 in the promoter conformation. Blasts from 19 out of 31 cells which expressed PAb240 co-expressed PAb1620, expression of PAb1620 was associated with non-autonomous growth in vitro. In contrast, the majority of blasts with the p53 phenotype of PAb240+/PAb1620- or which lacked p53 expression exhibited autonomous growth characteristics in vitro. Furthermore expression of PAb1620 in blasts with autonomous growth cells could be detected following growth inhibition using monoclonal antibodies against autocrine growth factors. Our data demonstrate that in AML cells, p53 conformation is related to the growth characteristics of the cells and is regulated by either exogenous or autocrine haematopoietic growth factors.

Role of autocrine and paracrine production of granulocyte-macrophage colony-stimulating factor and interleukin-1 beta in the autonomous growth of acute myeloblastic leukaemia cells--studies using purified CD34-positive cells

The blast cells from some patients with acute myeloblastic leukemia (AML) proliferate autonomously in vitro. We have previously identified four groups of AML blasts based upon their growth characteristics in vitro, in particular the degree of autonomous growth. We have now measured the production of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-1 beta (IL-1 beta) by AML cells with different growth characteristics, using two sensitive enzyme-linked immunosorbent assays. Our results show a correlation between the capacity of AML blasts to produce GM-CSF and IL-1 beta and the ability to grow autonomously in vitro. Blasts from cells with no autonomous growth (n = 5) secreted low or undetectable amounts of GM-CSF and IL-1 beta. Blasts with totally autonomous growth (n = 10) secreted the highest levels of GM-CSF (mean 2469 pg/10(3) cells) and IL-1 beta (mean 3156 pg/10(6) cells). Whereas blasts with partially autonomous growth (n = 9) secreted intermediate levels of GM-CSF (mean 270 pg/10(6) cells) and IL-1 beta (mean 931 pg/10(6) cells). In order to determine whether GM-CSF production was autocrine or the consequence of paracrine secretion by differentiated leukemic cells, we studied the degree of autonomous growth and production of GM-CSF by CD34-positive blasts from eight patients whose unfractionated cells produced GM-CSF. We found that CD34-positive blasts from six of these cases grew autonomously to a degree comparable to that of the unfractionated cells, and that CD34-positive blasts produced GM-CSF either autonomously or in response to recombinant IL-1 beta. Our data suggests that in the majority of cases, CD34-positive blasts are capable of autonomous growth and autocrine GM-CSF production, however this is variably regulated by the paracrine production of IL-1 beta by CD34-negative cells.

Interleukin-1 is one factor which regulates autocrine production of GM-CSF by the blast cells of acute myeloblastic leukaemia

The role of interleukin-1 (IL-1) as a regulator of the autonomous growth of the blast cells of acute myeloid leukaemia (AML) has been studied on samples isolated from 15 patients. In nine out of 10 patients with evidence of partial autonomous blast cell growth. IL-1 further stimulated cell growth in both suspension culture and in a clongenic assay. IL-1 also stimulated cell growth in two out of three cases with no evidence of autonomous growth whereas no additional stimulation was observed in two cases with totally autonomous growth. In blast cells stimulated by IL-1, synthesis of granulocyte-macrophage colony stimulating factor (GM-CSF) was increased and the proliferative response to IL-1 was inhibited by an antibody to GM-CSF. In all samples with evidence of autonomous growth, blast cell conditioned medium (BCCM) contained IL-1 activity (range 0.7-74.2 units ml) and a polyclonal antibody to IL-1 markedly inhibited autonomous growth in four samples. BCCM from three of these four samples contained GM-CSF, the synthesis of which was suppressed when BCCM was prepared in the presence of anti-IL-1. Our data suggests that endogenous IL-1 is an important factor in the regulation of the production of GM-CSF and hence of autonomous growth of AML blasts, but that other mechanisms regulating GM-CSF production may exist.

Endogenous interleukin-1 can regulate the autonomous growth of the blast cells of acute myeloblastic leukemia by inducing autocrine secretion of GM-CSF

We have studied peripheral blood blast cells from a patient with acute myeloblastic leukemia (AML) whose cells proliferated autonomously at high cell density, but only in the presence of adherent cells. At low cell density in suspension culture and in a clonogenic assay, blast cell growth was stimulated by recombinant granulocyte macrophage colony stimulating factor (GM-CSF) and recombinant interleukin-1 (IL-1) independently. The response to rIL-1 was inhibited (less than 90%) by anti-GM-CSF, suggesting that the proliferative response to IL-1 was mediated by GM-CSF. This was supported by experiments which demonstrated that blast cell conditioned medium prepared in the presence of IL-1 contained GM-CSF activity which stimulated the growth of normal granulocyte-macrophage precursors (CFU-GM) and of homologous GM-CSF responsive AML blasts. As IL-1 but no GM-CSF activity was detected in BCCM prepared without exogenous IL-1 and a neutralizing antibody to IL-1 inhibited the autonomous growth of blasts in suspension culture, we conclude that the endogenous secretion of IL-1 by leukemic cells stimulated autocrine GM-CSF secretion, inducing autonomous growth of the blast cell population.

Anthropometric and training variables related to 10km running performance

Sixty male distance athletes were divided into three equal groups according to their personal best time for the 10km run. The runners were measured anthropometrically and each runner completed a detailed questionnaire on his athletic status, training programme and performance. The runners in this study had similar anthropometric and training profiles to other distance runners of a similar standard. The most able runners were shorter and lighter than those in the other two groups and significantly smaller skinfold values (P less than 0.05). There were no significant differences between the groups for either bone widths or circumferences but the elite and good runners had significantly higher ponderal indices (P less than 0.05) than the average runners, indicating that they are more linear. Elite and good runners were also less endomorphic but more ectomorphic than the average runners. The elite runners trained more often, ran more miles per week and had been running longer (P less than 0.05) than good or average runners. A multiple regression and discriminant function analysis indicated that linearity, total skinfold, the type and frequency of training and the number of years running were the best predictors of running performance and success at the 10km distance.

Albinism Induced by Substituted Benzoic Acids

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