CTLA-4 +49A/G polymorphism is associated with Behçet's disease in a Tunisian population

The involvement of excessive T-helper cell functions in the pathogenesis of Behçet's disease (BD) has been reported. Cytotoxic T-lymphocyte antigen-4 (CTLA-4) plays a role in T-cell downregulation. In this report, we investigated the possible association between BD patients and the CTLA-4 +49A/G polymorphism in Tunisian population. A total of 135 Tunisian BD patients and 151 healthy blood donors from the same geographic area were genotyped by polymerase chain reaction for the CTLA-4 +49 A/G polymorphism. A highly significant difference between Tunisian BD patients and healthy controls was found regarding the distribution of CTLA-4 +49 A allele [ P  < 10⁻⁷; χ² = 75.63; odds ratio (OR) = 4.63; 95% confidence interval (CI) = 3.20–6.72] and genotype frequencies ( P  < 10⁻⁷; χ² = 71.02). Furthermore, in the BD group, the A allele was predominant in males (76.3%) when compared with females (62%), ( P  = 0.014; χ² = 5.97; OR = 1.99; 95% CI = 1.10–3.59). No relationship was found between the studied genotype and clinical manifestations. Our results show a gene dose effect of the A allele on the BD. The A allele exerts a stronger effect on disease susceptibility in males compared with females.     

Dinucleotide repeat polymorphisms of RAD51, BRCA1, BRCA2 gene regions in breast cancer

Recent studies suggest that genetic polymorphisms of the DNA repair genes have been implicated in breast cancer risk. BRCA1 and BRCA2 , two breast cancer susceptibility genes, are essential to maintain chromosomal integrity. This is mediated via regulation of RAD51 during homologous recombination. Dinucleotide polymorphism repeats in the 15q14–21, 17q21 and 13q12–13 regions, where the RAD51 , BRCA1 and BRCA2 genes are located, respectively, have been evaluated. The polymorphism was determined using the following microsatellite markers: D15S118, D15S214, D15S1006, D17S855, D17S1323, D13S260 and D13S290. Genotypes containing the (CA)₁₇ or (CA)₁₉ alleles in the RAD51 region were found to be associated with a decreased breast cancer risk. Genotype containing the (CA)₁₇ allele in the 13q12–13 region was found to be associated with an increased breast cancer risk. The results indicate that dinucleotide CA repeat polymorphism at RAD51 and BRCA2 gene regions might be associated with genetic susceptibility to breast cancer.     

Association of PTPN22 gene functional variants with development of pulmonary tuberculosis in Moroccan population

Mycobacterium tuberculosis , the causal agent of pulmonary tuberculosis (TB), remains a major health problem throughout the world causing high mortality in humans. Previous studies showed that several genes may play crucial roles in susceptibility to TB. The PTPN22 gene encodes the lymphoid tyrosine phosphatase that has an important regulatory effect on T- and B-cell activation in immune response. The purpose of this study was to investigate the role of two functional missense single nucleotide polymorphisms (SNPs) of the PTPN22 gene region (R620W and R263Q) in the susceptibility to TB in the Moroccan population. A case–control association study was performed including 123 pulmonary TB patients and 155 healthy controls. All subjects were genotyped by TaqMan SNP genotyping assays. Regarding the PTPN22 R620W (C1858T) SNP, we observed a statistically significant difference in the distribution of the PTPN22 1885T allele between pulmonary TB patients and healthy controls (0.41% vs 3.2%, P  = 0.01, odds ratio (OR) = 0.14, 95% confidence interval (CI) = 0.01–0.93). With respect to the PTPN22 R263Q (G788A), we observed an increase of 788A allele frequencies in TB patients compared with those in healthy controls (3.65% vs 0.65%, P  = 0.01, OR = 5.85, 95% CI = 1.17–39.55). These results suggest that PTPN22 gene variants may affect susceptibility to TB in the Moroccan population.     

Severe chronic urticaria is associated with elevated plasma levels of D-dimer

Background:  Patients with chronic urticaria (CU) frequently show signs of thrombin generation as a result of the activation of the extrinsic pathway of coagulation and signs of fibrinolysis as shown by slightly increased mean D-dimer plasma levels. Here, we studied patients with severe CU to see whether the activation of coagulation and fibrinolysis parallels the severity of the disease.
Methods:  Eight consecutive patients with severe exacerbations of CU and 13 with slight CU were studied. Plasma prothrombin fragment F₁₊₂ as well as D-dimer were measured by ELISA. Serum histamine-releasing activity was assessed by basophil histamine release assay. Seventy-four normal subjects were used as controls.
Results:  In patients with severe CU, median levels of both D-dimer (11.20 nmol/l) and F₁₊₂ (592 pmol/l) largely exceeded those found in patients with slight CU [D-dimer: 2.66 nmol/l ( P  = 0.001) and F₁₊₂: 228 pmol/l ( P  = 0.003)] and in normal subjects [D-dimer: 1.41 nmol/l ( P  = 0.0001) and F₁₊₂: 159 pmol/l ( P  = 0.0001)]. Sera from 25% of patients with severe CU and 31% of those with slight CU, but from none of normal subjects, showed in vitro histamine-releasing activity. D-dimer and F₁₊₂ levels were significantly correlated each other ( r  = 0.64, P  = 0.002) and with CU severity score ( r  = 0.80–0.90, P  = 0.0001), but no correlation was observed between serum histamine-releasing activity and coagulation parameters or severity score.
Conclusions:  Severe exacerbations of CU are associated with a strong activation of coagulation cascade and fibrinolysis. Whether this activation is the cause of CU or acts as an amplification system is still a matter of debate.     

Genetic variation in ORM1-like 3 (ORMDL3) and gasdermin-like (GSDML) and childhood asthma

Background:  A genome-wide association study identified ORM1-like 3 (orosomucoid 1-like 3, ORMDL3 ) as an asthma candidate gene. Single nucleotide polymorphisms (SNPs) in the region including ORMDL3 on chromosome 17q21 were related to childhood asthma risk and ORMDL3 expression levels in Europeans.
Objective:  We examined whether polymorphisms in ORMDL3 and the adjacent gasdermin-like ( GSDML ) gene associated with asthma in the genome-wide association study are related to childhood asthma and atopy in a Mexico City population.
Methods:  We genotyped rs4378650 in ORMDL3 and rs7216389 in GSDML in 615 nuclear families consisting of asthmatic children aged 4–17 years and their parents. Atopy was determined by skin prick tests to 25 aeroallergens.
Results:  Individuals carrying the C allele of rs4378650 or the T allele of rs7216389 had increased risk of asthma [relative risk (RR) = 1.73, 95% confidence interval (CI) 1.19–2.53, P  = 0.003 for one or two copies of rs4378650 C, and RR = 1.64, 95% CI 1.12–2.38, P  = 0.009 for one or two copies of rs7216389 T). Linkage disequilibrium between the two SNPs was high ( r ² = 0.92). Neither of the SNPs was associated with the degree of atopy. A meta-analysis of five published studies on rs7216389 in nine populations gave an odds ratio for asthma of 1.44 (95% CI, 1.35–1.54, P  < 0.00001).
Conclusions:  Our results and the meta-analysis provide evidence to confirm the finding from a recent genome-wide association study that polymorphisms in ORMDL3 and the adjacent GSDML may contribute to childhood asthma.     

Resolution of remodeling in eosinophilic esophagitis correlates with epithelial response to topical corticosteroids

Background:  Esophageal remodeling occurs in eosinophilic esophagitis (EE) patients but whether the components of remodeling in the subepithelium are reversible by administration of topical oral corticosteroids is unknown.
Methods:  We quantitated the degree of lamina propria remodeling in esophageal biopsies obtained before and after at least 3 months of therapy with budesonide in 16 pediatric EE subjects. In addition, we investigated whether corticosteroid therapy modulated vascular activation (expression of VCAM-1; level of interstitial edema), TGFβ₁ activation (levels of TGFβ₁, phosphorylated Smad2/3), and performed a pilot analysis of a polymorphism in the TGFβ₁ promoter in relation to EE subjects who had reduced remodeling with budesonide therapy.
Results:  EE subjects were stratified based on the presence ( n  = 9) or absence ( n  = 7) of decreased epithelial eosinophilia following budesonide. Patients with residual eosinophil counts of ≤7 eosinophils per high power field in the epithelial space (responders) demonstrated significantly reduced esophageal remodeling with decreased fibrosis, TGFβ₁ and pSmad2/3 positive cells, and decreased vascular activation in association with budesonide therapy. Responders were more likely to have a CC genotype at the −509 position in the TGFβ₁ promoter.
Conclusions:  Reductions in epithelial eosinophils following budesonide therapy were associated with significantly reduced esophageal remodeling.     

Common CCR 5 Polymorphism in Stroke The CCR 5 Δ32 Polymorphism Differentiates Cardioembolism from Other Aetiologies of Ischaemic Cerebrovascular Diseases

Inflammation is involved in the development of atherosclerosis. The CC chemokine receptor 5 ( CCR5 ) initiates chemotaxis and modulates the inflammation secondary to atherosclerosis and related vascular diseases. The CCR5 Δ32 polymorphism influences the expression of CCR5 on the cell surface. The purpose of this study was to examine the effect of the Δ32 polymorphism in ischaemic cerebrovascular disease (ICVD). The CCR5 Δ32 polymorphism was genotyped in 1462 individuals: 562 ischaemic stroke (IS), 97 transient ischaemic attack (TIA) and in 803 healthy controls. All 659 ICVD patients were categorized according to the Trial of Org 10172 in Acute Stroke Treatment aetiological classification. The investigated subtypes were large artery atherosclerosis (LAA), cardioembolism (CE), small artery occlusion (SAO) and cryptogenic disease (CRYPT). Genotyping was performed with the TaqMan polymerase chain reaction. The Δ32 allele was less frequent in CE patients compared with LAA (OR, 0.4; 95% CI, 0.24–0.79; P  = 0.008), SAO (OR, 0.5; 95% CI, 0.29–0.84; P  = 0.01), CRYPT (OR, 0.5; 95% CI, 0.28–0.82; P  = 0.008) and controls (OR, 0.5; 95% CI, 0.36–0.82; P  = 0.002). Multiple logistic regression analysis showed that the Δ32 allele is associated with a lower risk for cardioembolic ICVD (OR 0.5; 95% CI, 0.28–0.75; P  = 0.002) when compared with ICVD of other causes. The Δ32 polymorphism of CCR5 may differentiate cardioembolism from the remaining causes of ICVD.     

Association of interferon gamma and interleukin 10 genes with tuberculosis in Hong Kong Chinese

Interferon gamma (IFN-gamma) and interleukin 10 (IL-10) are believed to play opposing roles in host immunity against mycobacterial infection. IFN-gamma activates macrophages, while IL-10 downregulates the expression of T helper type 1 cytokines, MHC class II antigens and costimulatory molecules on macrophages. Associations of IFN-gamma -179 (G/T), +874 (A/T), +875 miscrosatellite CA repeats and +4766 (C/T), and IL-10 -1082 (A/G), -819 (C/T) and -592 (C/A) with tuberculosis (TB) were investigated in 385 HIV-negative patients and 451 controls in a Hong Kong Chinese population. The frequency of a low IFN-gamma-producing +874 A/A genotype was significantly over-represented in the patient group (P<0.001, OR=3.79, 95% CI=1.93-7.45). We identified 10 alleles in the IFN-gamma CA repeats and observed a significant difference in allele frequency distribution between patients and controls (P<0.001). By grouping alleles into 12 and non-12 CA repeats, the non-12/non-12 genotype yielded a similar significant result (P<0.001, OR=4.56, 95% CI=2.21-9.43) as observed in +874 A/A genotype. Weak associations of the IL-10 GCC/- genotype (P=0.04) and the low IFN-gamma-producing A/A genotype (P=0.06) with TB relapse/extrapulmonary cases were found. This study suggests the possible role of interferon gamma in TB susceptibility.     

Association of the leukocyte immunoglobulin G (Fcγ) receptor IIIa-158V/F polymorphism with inflammatory myopathies in Dutch patients

Leukocytes are involved in the pathogenesis of idiopathic inflammatory myopathies (IIMs). Immunoglobulin G (IgG) receptors (FcγR) link the specificity of IgG to the effector functions of leukocytes. Several FcγR subclasses display functional polymorphisms that determine in part the vigour of the inflammatory response. FcγRIIIa genotypes were differentially distributed among 100 IIM patients compared with 514 healthy controls with a significant increase of the homozygous FcγRIIIa-V-158 genotype (3 × 2 contingency table, χ² = 6.3, P  = 0.04). Odds ratios (ORs) increased at the addition of each FcγRIIIa-V-158 allele, in particular among patients with non-specific myositis and dermatomyositis {OR 2.1 [95% confidence interval (CI) 1.1–4.3] and 2.7 (95% CI 1.1–6.4) for FcγRIIIa-V/F158 and FcγRIIIa-V/V158 genotypes, respectively, using FcγRIIIa-F/F158 as a reference group}. These data suggest that the FcγRIIIa-V-158 allele may constitute a genetic risk marker for IIM.     

Effect of polymorphism in insulin locus and HLA on type 1 diabetes in four ethnic groups in Israel

This study examined a possible association of the insulin ( INS ) gene with type 1 diabetes (T1D) in patients and controls from four ethnic groups in Israel. We analyzed the distribution of −23 Hph I single nucleotide polymorphism (SNP) T/A alleles that correspond to INS variable number of tandem repeat short class I alleles (26–63 repeats) and class III alleles (141–209 repeats), respectively. The −23 Hph I T/T genotype was found to be positively associated with T1D in three Jewish groups (Yemenites: 93.9% patients vs 68.8% controls, P  = 0.0002; Ashkenazi: 80.6% vs 50.8%, P  < 10⁻⁴; Ethiopians: 75% vs 40.5%, P  = 0.002). The Yemenite healthy controls have the highest frequency of T allele from all Jewish groups studied (83.5% vs 68.8% in Ashkenazi and 64.3% in Ethiopians). The high frequency of a susceptibility allele in the Yemenites is in line with the high incidence of T1D in this population. No association was observed between T1D and the INS gene in Israeli Arabs studied (70.6% vs 66.7%). Variable incidence of T1D among different ethnicities in Israel is largely attributed to heterogeneous genetics. Human leukocyte antigen (HLA) results of our previous studies describing the susceptibility and protective haplotypes were used for combined analysis to determine possible interaction between the HLA and INS loci. Only in the Ashkenazi group such interaction was presented with statistical significance.     

T-Cell Epitope Mapping of the Borrelia garinii Outer Surface Protein A in Lyme Neuroborreliosis

We studied the T-cell reactivity to overlapping peptides of B. garinii OspA, in order to locate possible immunodominant T-cell epitopes in neuroborreliosis. Cells from cerebrospinal fluid (CSF) and blood from 39 patients with neuroborreliosis and 31 controls were stimulated with 31 overlapping peptides, and interferon-γ secreting cells were detected by ELISPOT. The peptides OspA_17–36, OspA_49–68, OspA_105–124, OspA_137–156, OspA_193–212 and OspA_233–252 showed the highest frequency of positive responses, being positive in CSF from 38% to 50% of patients with neuroborreliosis. These peptides also elicited higher responses in CSF compared with controls ( P  = 0.004). CSF cells more often showed positive responses to these peptides than blood cells ( P  = 0.001), in line with a compartmentalization to the central nervous system. Thus, a set of potential T-cell epitopes were identified in CSF cells from patients with neuroborreliosis. Further studies may reveal whether these epitopes can be used diagnostically and studies involving HLA interactions may show their possible pathogenetic importance.     

Evaluation of a new recombinant BCG which contains mycobacterial antigen ag85B-mpt64(190-198)-mtb8.4 in C57/BL6 mice

Tuberculosis (TB) caused by Mycobacterium tuberculosis continues to be one of the major public health problems in the world. The eventual control of this disease will require the development of a safe and effective vaccine. Bacille Calmette-Guerin (BCG), the only vaccine against TB, is not perfect for its limited ability to protect against the adult form of TB. Some improvements of TB vaccines relied to strengthening the immunogenicity and/or persistence of genetically modified recombinant BCG (rBCG) strain. Antigen 85B (Ag85B) and Mtb8.4 are importantly immunodominant antigens of M. tuberculosis , and both are very promising vaccine candidate molecules. MPT64_190–198, is presented to CD8⁺ T cells during mycobacterial infections. In this study, we combined these above genes into one recombinant gene of ag85B–mpt64 _190–198 –mtb8.4 . Then we constructed the new rBCG containing this united gene. This rBCG can induce an increased Th1-type immune response in mice, characterized by an elevated level of interferon-γ in antigen-stimulated splenocyte culture and a strong IgG2a antibody response. Also, it can elicit longer immune responses than BCG. The results show that this rBCG is a promising candidate for further study.     

Response linearity in primary auditory cortex of the ferret

The responses of neurons within the primary auditory cortex (A1) of the ferret elicited by broadband dynamic spectral ripple stimuli were examined over a range of ripple spectral densities and ripple velocities. The large majority of neurons showed modulated responses to these stimuli and responded most strongly at low ripple densities and velocities. The period histograms of their responses were subjected to Fourier analysis, and the ratio of the magnitudes of the f ₁ and f ₀ (DC) components of these responses were calculated to give a quantitative index of response linearity. For 82 out of 396 neurons tested (20.7%) this ratio remained above 1.0 over the entire range of ripple densities and velocities. These neurons were classified as 'consistently linear'. A further 134/396 (33.8%) of neurons maintained an f ₁/ f ₀ ratio above 1.0 for either a range of ripple densities at a fixed ripple velocity, or over a range of ripple velocities at a specific ripple density, and were classified as 'locally linear'. Interestingly, for the superficial layers of the primary auditory cortex, consistently linear and locally linear neurons outnumbered nonlinear neurons by a 2:1 ratio. The converse was true for the deep layers. Unlike in primary visual cortex, where f ₁/ f ₀ ratios have been reported to exhibit a bimodal distribution with a minimum at   f ₁/ f ₀≈ 1  , f ₁/ f ₀ ratios for A1 are unimodally distributed with a peak at   f ₁/ f ₀≈ 1  .     

Correlation among urinary eosinophil protein X, leukotriene E4, and 11-dehydrothromboxane B2 in patients with spontaneous asthmatic attack

Various kinds of cells and their mediators are thought to be involved in the pathogenesis of bronchial asthma. However, changes in each mediator or relationship among mediators during an asthmatic attack have not been well documented. In this study, to clarify whether eosinophil protein X (EPX) is a marker which is distinct from leukotriene E₄ (LTE₄), or 11-dehydrothromboxane B₂ (11DTXB₂), we measured the urinary excretion of EPX, LTE₄, and 11DTXB₂ in 14 asthmatics who were admitted to the hospital with either an acute asthmatic attack or status asthmaticus. These patients included eight atopic and six non-atopic types of bronchial asthma, with a median age of 34.0 years. Urinary excretion of EPX was significantly high on admission with the asthmatic attack, and returned to control levels 175 [122 –384] μg/day when the patients were in the improved state (1036–317 μg/day, P  < 0.01). Similar findings were observed in LTE₄ (155–59 ng/day, P  < 0.01) and 11DTXB₂ (991–442 ng/day, P  < 0.01). No significant differences in values were observed between atopic and non-atopic types of asthma in all three substances. When the individual data during the attack state were analysed, a significant correlation was observed between changes (%) in urinary EPX and those in urinary LTE₄, but no such relationship was observed between changes (%) in urinary EPX and those in urinary 11DTXB₂. These results suggest that measuring urinary EPX levels may be a useful marker for the understanding and management of the disease.     

Differences in the prevalence of a TaqI RFLP in the 3' flanking region of the α1-proteinase inhibitor gene between asthmatic and non-asthmatic black and white South Africans

The prevalence of the Taq I(-) allele in variants of α₁-proteinase inhibitor (α₁PI) was investigated in a group of 28 black asthmatic patients and 32 black control individuals, and was compared to 43 white asthmatic patients and 32 white control individuals. The plasma concentration of α₁PI was determined in eight black and 14 white asthmatics without the Taq I(-) allele, and compared to seven black and three white asthmatics with the Taq I(-) allele. Alpha-1-PI concentration was also determined in 10 black and 29 white control individuals without the Taq I(-) allele and compared to seven black and three white controls with the Taq I(-) allele. There was a highly significant difference in the frequency of the Taq I(-) allele between black South Africans (24.1%) and white South Africans (6%) (p<0.00001) and a significant difference in the frequency of the Taq I(-) allele between black asthmatics and white asthmatics (p = 0.0004) and between black controls and white controls (p = 0.011). The Taq I(-) allele was significantly associated with the Ml(Val²¹³) variant as compared to the Ml (Ala²¹³) of α₁PI (p = 0.0042). There was no difference in the concentration of α₁PI between the asthmatics (black and white) lacking the Taq I(-) allele and the asthmatics (black and white) with the allele. However, a significant increase in plasma α₁PI concentration was found in the asthmatics compared to the controls (p = 0.011). The Taq I(-) allele did not seem to interfere with the basal expression of α₁PI in the groups of asthmatic patients in this study.     

Tyrosine kinases enhance the function of glycine receptors in rat hippocampal neurons and human α1β glycine receptors

Glycine receptors (GlyRs) are transmitter-gated channels that mediate fast inhibitory neurotransmission in the spinal cord and brain. The GlyR β subunit contains a putative tyrosine phosphorylation site whose functional role has not been determined. To examine if protein tyrosine kinases (PTKs) regulate the function of GlyRs, we analysed whole-cell currents activated by applications of glycine to CA1 hippocampal neurons and spinal neurons. The role of a putative site for tyrosine phosphorylation at position 413 of the β subunit was examined using site-directed mutagenesis and expression of recombinant (α₁β^Y413F ) receptors in human embryonic kidney (HEK 293) cells. Lavendustin A, an inhibitor of PTKs, depressed glycine-evoked currents ( I _Gly) in CA1 neurons and spinal neurons by 31 % and 40 %, respectively. In contrast, the intracellular application of the exogenous tyrosine kinase, cSrc, enhanced I _Gly in CA1 neurons by 56 %. cSrc also accelerated GlyR desensitization and increased the potency of glycine 2-fold (control EC₅₀= 143 μ m ; cSrc EC₅₀= 74 μ m ). Exogenous cSrc, applied intracellularly, upregulated heteromeric α₁β receptors but not homomeric α₁ receptors. Substitution mutation of the tyrosine to phenylalanine at position β-413 prevented this enhancement. Furthermore, a selective inhibitor of the Src family kinases, PP2, down-regulated wild-type α₁β but not α₁β^Y413F receptors. Together, these findings indicate that GlyR function is upregulated by PTKs and this modulation is dependent on the tyrosine-413 residue of the β subunit.     

IgE responses to Dermatophagoides pteronyssinus native major allergens Der p 1 and Der p 2 during long-term specific immunotherapy

We investigated by ELISA the IgE response to whole extract of the house-dust mite Dermatophagoides pteronyssinus (Dp) and to the native major allergens, Der p 1 and Der p 2, in sera from 18 adult patients (group A) with Dp-allergic asthma before ( t ₀) and 1, 2, 3, and 4 ( t ₁– t ₄) years after subcutaneous specific immunotherapy (SIT). A qualitative reduction ( P =0.05) of the IgE responses to Dp and Der p 2 was observed from t ₁ to t ₄, but a highly statistical significant decrease appeared at t ₃, ( P < 0.01). With regard to Der p 1 IgE values, the immunotherapy induced a significant decrease ( P < 0.01) at t ₃, but not before. In group A, the IgE responses to Der p 1 and Der p 2 were not correlated at t ₀ ( r _s=0.31; P = 0.2l) but were correlated at t₃ ( r _s= 0.78; P=0.001). We also examined sera from 14 adult patients (group B, same SIT schedule as group A) who were without respiratory symptoms at the end of the third year (t₃) of Dp SIT. At this time ( t ₃), there were no significant differences in Der p 1 and Der p 2 IgE levels between group A and group B.     

Cerebral non-oxidative carbohydrate consumption in humans driven by adrenaline

During brain activation, the decrease in the ratio between cerebral oxygen and carbohydrate uptake (6 O₂/(glucose +  ¹/₂  lactate); the oxygen–carbohydrate index, OCI) is attenuated by the non-selective β-adrenergic receptor antagonist propranolol, whereas OCI remains unaffected by the β₁-adrenergic receptor antagonist metroprolol. These observations suggest involvement of a β₂-adrenergic mechanism in non-oxidative metabolism for the brain. Therefore, we evaluated the effect of adrenaline (0.08 μg kg⁻¹ min⁻¹ i.v. for 15 min) and noradrenaline (0.5, 0.1 and 0.15 μg kg⁻¹ min⁻¹ i.v. for 20 min) on the arterial to internal jugular venous concentration differences (a-v diff) of O₂, glucose and lactate in healthy humans. Adrenaline ( n = 10) increased the arterial concentrations of O₂, glucose and lactate ( P < 0.05) and also increased the a-v diff for glucose from 0.6 ± 0.1 to 0.8 ± 0.2 m m (mean ± s.d. ; P < 0.05). The a-v diff for lactate shifted from a net cerebral release to an uptake and OCI was lowered from 5.1 ± 1.5 to 3.6 ± 0.4 ( P < 0.05) indicating an 8-fold increase in the rate of non-oxidative carbohydrate uptake during adrenaline infusion ( P < 0.01). Conversely, noradrenaline ( n = 8) did not affect the OCI despite an increase in the a-v diff for glucose ( P < 0.05). These results support that non-oxidative carbohydrate consumption for the brain is driven by a β₂-adrenergic mechanism, giving neurons an abundant provision of energy when plasma adrenaline increases.     

Temperature change does not affect force between regulated actin filaments and heavy meromyosin in single-molecule experiments

The temperature dependence of sliding velocity, force and the number of cross-bridges was studied on regulated actin filaments (reconstituted thin filaments) when they were placed on heavy meromyosin (HMM) attached to a glass surface. The regulated actin filaments were used because our previous study on muscle fibres demonstrated that the temperature effect was much reduced in the absence of regulatory proteins. A fluorescently labelled thin filament was attached to the gelsolin-coated surface of a polystyrene bead. The bead was trapped by optical tweezers, and HMM–thin filament interaction was performed at 20–35°C to study the temperature dependence of force at the single-molecule level. Our experiments showed that there was a small increase in force with temperature  ( Q ₁₀= 1.43)  and sliding velocity  ( Q ₁₀= 1.46)  . The small increase in force was correlated with the small increase in the number of cross-bridges  ( Q ₁₀= 1.49)  , and when force was divided by the number of cross-bridges, the result did not depend on the temperature  ( Q ₁₀= 1.03)  . These results demonstrate that the force each cross-bridge generates is fixed and independent of temperature. Our additional experiments demonstrate that tropomyosin (Tm) in the presence of troponin (Tn) and Ca²⁺ enhances both force and velocity, and a truncated mutant, Δ23Tm, diminishes force and velocity. These results are consistent with the hypothesis that Tm in the presence of Tn and Ca²⁺ exerts a positive allosteric effect on actin to make actomyosin linkage more secure so that larger forces can be generated.