Interactions of the RAD7 and RAD23 excision repair genes of Saccharomyces cerevisiae with DNA repair genes in different epistasis groups

Summary The RAD7 and RAD23 genes of S. cerevisiae affect the efficiency of excision repair of UV-damaged DNA. We have examined the UV survival of strains carrying the rad7 or rad23 deletion mutation in combination with deletion mutations in genes affecting different DNA repair pathways. As expected, the rad7 and rad23 mutations interact epistatically with the excision repair defective rad1 mutation, and synergistically with the rad6 and rad52 mutations that affect the postreplication repair and recombinational repair pathways, respectively. However, the rad7rad6 and the rad23rad6 mutants exhibit the same level of UV sensitivity as the radlrad6 mutant. This observation is of interest since, in contrast to the rad7 or the rad23 mutations, the rad1 mutant is very UV sensitive and highly excision defective. This observation suggests that RAD6 and RAD7 and RAD23 genes compete for the same substrate during DNA repair.     

Organization of assembly factors Cbp3p and Cbp4p and their effect on bc 1 complex assembly in Saccharomyces cerevisiae

The bc₁ complex (complex III) of Saccharomyces cerevisae is composed of ten subunits that are assembled in the inner mitochondrial membrane. Cbp3p and Cbp4p are two mitochondrial proteins which are postulated to act as chaperones in bc₁ complex formation. Here, we show by blue native PAGE that cbp3 and cbp4 mutants are disturbed in complex III assembly and accumulate intermediate-sized forms of the complex. Moreover, deletion of CBP3 interferes with the formation of complex III/IV supracomplexes. Our studies show that Cbp3p and Cbp4p interact and are present in high-molecular-weight complexes, some of which might represent intermediates of complex III assembly. Overexpression of Cbp4p cannot substitute for the function of Cbp3p, but high-level expression of Cbp3p can partially compensate for the lack of Cbp4p. The finding that mitochondria of cbp3 and cbp4 mutants exhibit a wild-type lipid composition favors the idea that Cbp3p and Cbp4p are specific assembly factors for complex III rather than components of the mitochondrial lipid metabolism.     

Indices for the role played by regional flow resistance in blood pressure reflex

Summary An index, = (r/r)/(R/R), is proposed for assessment of the relative degree of participation of a regional flow resistance in a blood pressure reflex, wherer andR are regional and total peripheral resistances respectively and 's refer to their reflexive changes. For actual computation, =I (iP – Pi)/i(IP – PI), whereI=cardiac output,i=regional flow rate,P=mean arterial pressure. When the change in cardiac output is neglegible, the above equation is simplified as =1 – Pi/iP. Another index, = g/G = (Pi – iP)/(PI – IP), is introduced for the degree of contribution of a region to a reflex, whereg andG are regional and total conductances.i = 1. Some examples of application of the indices are presented.Supported in part by a grant from the Ministry of Education of Japan.     

Ultrasonography gives directly but noninvasively elastic characteristic of human tendon in vivo

To obtain an insight into tendon elasticity during human movement, a real-time ultrasonography was applied to the contracting tibialis anterior muscle. The insertion point of fascicles onto the aponeurosis was clearly visualized, and its position relative to a fixed marker on the skin moved proximally (1) according to the increasing dorsiflexion force (F) with a fixed ankle joint. Notably, the 1 – F relationship in the tendon was found to be quadratic in nature (F = c1²; c=1.48 2.24, r=0.985 0.992, n=9) as has been reported in the isolated tendon, although the F – 1 curves were slightly underestimated in comparison with the stiffness constant estimated from tendon architecture. This underestimation might be caused by changes in the height of the foot arch with the application of force.     

Effect of menstrual cycle and gender on ventilatory and heart rate responses at the onset of exercise

To clarify the luteal-follicular and male–female differences in ventilatory and heart rate responses at the onset of exercise, seven women and seven men performed voluntary exercise and passive movement for 20 s (brief voluntary exercise and brief passive movement) and voluntary exercise for 3 min (long voluntary exercise) in a sitting position. Voluntary exercise consisted of alternate flexion-extensions of both lower legs with a weight corresponding to about 2.5% of the subjects' body mass attached to each ankle, at a frequency of about 60 times min^–1. Passive movement was carried out without weights by experimenters pulling ropes attached to both of the subjects' ankles, in the same way as voluntary exercise. During these exercises and movements, minute inspiratory ventilation (_I) and heart rate (HR) were continuously measured by breath-by-breath and beat-to-beat techniques. We calculated relative changes of _I and HR (_I and HR). Additionally, we averaged _I and HR obtained during the exercise and movement for each subject, and performed a correlation analysis between the averaged _I and HR. It was clarified that: (1) _I and HR in the follicular phase were almost equal to those in the luteal phase; (2) there were no significant male–female differences in these parameters; (3) significant positive correlations were found in both genders only during brief voluntary exercise. We conclude that ventilatory and HR responses at the onset of voluntary exercise and passive movement are not affected by the menstrual cycle or gender.     

CC chemokine receptor 5 Δ32 polymorphism in two independent cohorts of hepatitis C virus infected patients without hemophilia

Recently CC chemokine receptor 5 (CCR5) related immune mechanisms and a functional mutation of the CCR5 gene have been implicated in hepatitis C virus (HCV) infection in a cohort of predominantly hemophiliac patients. The present study investigated the frequency and clinical consequences of the CCR5 32 mutation in two genetically homogeneous populations of HCV infected patients with a different risk profile for infection. Genomic DNA samples from 333 German patients with chronic HCV infection were screened by PCR for the presence of the CCR5 32 polymorphism. In-hospital patients admitted for other diseases than viral hepatitis but with a comparable risk for HCV exposure were used as control population (n=125). Allele frequencies of CCR5 32 polymorphism did not differ significantly between the two groups (7.6% and 9.5%, respectively) and control subjects (10.4%), and did not deviate from Hardy-Weinberg equilibrium in any group. Furthermore, there were no major differences between patients with respect to HCV genotypes, viral loads, liver enzymes, or fibrosis scores in relation to the presence or absence of the heterozygous CCR5 32 mutation. Differences in inflammatory scores in liver biopsy samples and response to antiviral therapy in CCR5 32 heterozygotes in one cohort could neither be reproduced in the other group of patients nor when both cohorts were pooled. These results argue against a strong effect of the CCR5 32 deletion regarding these phenotypes. In conclusion, we found no increased frequency of the CCR5 32 polymorphism in two independent cohorts of patients with HCV infection but without hemophilia as the main risk factor for infection. As the major difference to investigations demonstrating an association between CCR5 32 and HCV infection is the selection of cases and controls, our study emphasizes the importance of epidemiological criteria for association studies of HCV infection.Abbreviations CCR CC chemokine receptor - HCV Hepatitis C virus - HIV Human immunodeficiency virus - HWE Hardy-Weinberg equilibrium     

Cupula displacement,hair bundle deflection,and physiological responses in the transparent semicircular canal of young eel

The transparent labyrinth of young eels (Anguilla anguilla L.) was used in toto for studying the configuration of cupula displacement, deflection of the hair bundle, and correlated changes in transepithelial voltage (TEV) and nerve activity (NA) in the semicircular canal. Microcapillaries were introduced into the canal through holes produced by a microthermocauter. Mechanical stimulation was applied either by injection of fluid into the ampulla or by electromagnetically displacing ferrofluid as a piston within the canal. Motion of individual kinocilia, stained cupulae or the ferrofluid piston was analysed by double-exposed microphotographs, photodiodes, or a video-system. The three-dimensional cupula displacement configuration was found to be piston-to diaphragm-like. Hair bundles at different sites on the crista exhibit differences in amplitude and time course of deflection. The transfer factor between shifts of the canal fluid and the tips of the kinocilia is 0.4–0.6. Displacements in opposite directions induce TEV and NA of opposite sign. Various tests confirmed TEV to reflect receptor potential responses. Nerve activity adapts to a tonic response with a time constant of 6.4s. No similar adaptation occurred in TEV. Stimulus-response curves of TEV- and NA-responses are similar and signoid in shape with saturation at ciliary deflections of roughly + 6° and –3°.     

Novel adenoviral vectors coding for GFP-tagged wtCFTR and ΔF508-CFTR: characterization of expression and electrophysiological properties in A549 cells

E1/E3-deleted adenoviral vectors expressing an N-terminal green fluorescent protein (GFP) reporter gene fused to either wtCFTR (H5.040CMVEGFP-wtCFTR) or F508-CFTR (H5.040CMVEGFP-F508CFTR) were generated. To characterize the expression and activity, A549 cells were infected with vectors expressing GFP-tagged and non-tagged forms of CFTR and F508CFTR. CFTR activity was assayed in cell-attached and excised patches. For H5.040CMVEGFP-wtCFTR, forskolin-dependent outward current was observed in cell-attached patches from 56 of 67 GFP-positive cells. Single-channel conductances, open probability, mean open and mean closed time values for GFP-CFTR and CFTR were not significantly different. After excision, GFP-CFTR activity required ATP and exhibited a linear I-V relationship. For H5.040CMVEGFP-F508CFTR, media were supplemented with 5 mM butyrate 16 h after infection. Forskolin-dependent outward current was observed in cell-attached patches from 21 of 30 butyrate-treated GFP-positive cells and 0 of 8 GFP-positive cells without butyrate. Single-channel conductances, open probability, mean open and mean closed time values for GFP-F508CFTR and F508CFTR were not significantly different. However, the increase in open probability with genistein was significantly smaller for GFP-F508CFTR than for F508CFTR. In excised patches, GFP-F508CFTR activity required ATP and exhibited a linear I-V relationship. Despite the consistent detection of GFP-CFTR and GFP-F508CFTR channels in the plasma membrane by patch clamping, GFP fluorescence was observed only in intracellular regions and was not altered by butyrate. The data show that high levels of functional GFP-tagged CFTR channels can be expressed with these adenoviral vector constructs.     

The yeast phosphotyrosyl phosphatase activator protein,yPtpa1/Rrd1, interacts with Sit4 phosphatase to mediate resistance to 4-nitroquinoline-1-oxide and UVA

We previously reported the isolation of mutants hypersensitive to the genotoxic agent 4-nitroquinoline-1-oxide, a potent inducer of oxidative stress. One of the mutants was defective in a gene designated yPTPA1, encoding a protein related to the human phosphotyrosyl phosphatase activator hPTPA, which is believed to play a role in activating the serine/threonine phosphatase PP2A. Yeast yptpa1 mutants are also sensitive to the UVA component of sunlight known to produce reactive oxygen species, suggesting a role for yPtpa1 in oxidative stress response. We now report the characterization of another 4-nitroquinoline-1-oxide-sensitive mutant, EBY20. We show that this mutant is defective in the SIT4 gene encoding a catalytic subunit of the PP2A phosphatases and that sit4 mutants exhibit hypersensitivity to 4-nitroquinoline-1-oxide and UVA, but not to UVC at 254 nm. Like the yptpa1 mutants, sit4 mutants are also defective in the repair of 4-nitroquinoline-1-oxide-induced DNA lesions. Genetic analysis revealed that both yPtpa1 and Sit4 function in the same pathway to protect cells against the lethal effects of 4-nitroquinoline-1-oxide and UVA. Moreover, we demonstrate that yPtpa1-affinity columns specifically retain Sit4, confirming a previous report that these two proteins indeed belong to a complex. Cellular localization studies using GFP-tagged proteins reveals that yPtpa1 is localized to the cytoplasm and the nucleus, while the Sit4 protein shows an intense staining spot in the cytoplasm and diffused staining in this organelle. We suggest that the yPtpa1–Sit4 complex may participate in a novel mechanism that mediates repair of oxidative DNA damage caused by 4-nitroquinoline-1-oxide and UVA.     

The REV2 gene of Saccharomyces cerevisiae: cloning and DNA sequence

Summary The REV2 gene of Saccharomyces cerevisiae was cloned and sequenced; it contains an open reading frame of 1985 bp with a coding potential of 662 amino acids. Interruption of the chromosomal REV2 gene by integrating the URA3 gene coupled with partial deletion of the 3 terminal region produced viable haploid rev2 mutants. This indicates that the REV2 gene is non-essential for growth. The rev2 mutant is slightly more UV-sensitive than strains carrying various rev2 alleles (rev2-1, rev2x, rad5-1, rad5-8). The putative Rev2 protein is probably a globular protein containing a highly conserved nucleotide-binding site and two zinc-finger domains.     

Mutations suppressing the effects of a deletion of the Phosphoglucose isomerase gene PGI1 in Saccharomyces cerevisiae

Summary A mutant with a deletion covering the phosphoglucose isomerase gene PGI1, allele pgi1, can only grow on a medium containing fructose and low concentrations of glucose whereas growth is completely inhibited by glucose concentrations higher than 0.4%. This was used to select suppressor mutants restoring growth on synthetic media with 2% glucose as the sole carbon source. One complementation group, SPG1, was defined by recessive mutations. The ability to grow on glucose media was strictly dependent on functional mitochondria. The generation time of the selected mutants on YEP glucose was 6–8 h. No ethanol was formed from glucose and the levels of respiration were very high. These phenotypes were also observed in single pgi1 mutants when growing on fructose media supplemented with 0.4% glucose. The other glycolytic enzymes, the enzymes of the glucose-6-phosphate oxidation pathway as well as catabolite repression were normal in suppressed pgi1 mutants. The suppressor mutation alone caused no abnormal phenotype. The results suggest that the spg1 suppressor mutations allow S. cerevisiae pgi1 mutant strains to grow on glucose by using the Pentose-P cycle in combination with unusual strong respiration.     

Quantitative and sustained suppression of renal sympathetic nerve activity by left atrial distension in conscious dogs

In order to investigate the interrelations between left atrial pressure (Pla) and renal sympathetic nerve activity (RSNA) and heart rate (HR), Pla was increased by a balloon both in conscious sham-operated and cardiac-denervated dogs. RSNA was decreased and HR was increased with increasing Pla in sham-operated dogs. The reflex changes in RSNA and HR induced by the stimulation of atrial receptors persisted for at least 15 min. There was a consistent relationship between Pla and RSNA which could be described by a single exponential equation: % RSNA = 80.0(1–e^{–0.395 Pla}), or by a linear equation when Pla was less than 6 mmHg; %RSNA=-13.5Pla–2.25. The relationship between Pla and HR can be described by a single exponential equation: HR = 86.5(1–e^{–0.125 Pla}). A significant linear relationship between RSNA and HR was obtained during a graded left atrial distention (%RSNA=-1.08HR–17.7). In cardiac-denervated dogs, RSNA tended to increase and HR remained constant during the left atrial distention. These results indicate that left atrial receptors regulate RSNA and HR in both a quantitative and sustained manner in conscious sham-operated dogs.     

Trait anxiety,submaximal physical exercise and blood androgens

Summary This study evaluates the relationship between trait anxiety and both androgen and gonadotrophic hormone levels at rest and during severe physical exercise. Twelve volunteers were selected among 160 untrained male collegial students and classified as anxious (N=6) or non-anxious (N=6) subjects according to their scores on three trait-anxiety tests (STAI, IPAT, 16 PF). Serum ⁴-androgen (testosterone and ⁴-androstenedione), ⁴-androgen (DHEA and DHEA-SO₄) and gonadotrophin (LH and FSH) concentrations were measured by radioimmunoassay before, during and after 20 minutes of intensive bicycle exercise (80% of maximal heart rate). Results indicate significantly lower serum ⁴-androgens in anxious subjects before exercise. However, for each subject and irrespective of his anxiety level, all measured serum androgen concentrations increased significantly during exercise, although ⁴-androstene-dione remained lower in anxious subjects than in non-anxious ones. Serum LH concentrations (but not FSH) were signicantly higher in anxious subjects throughout the observation periods. However, exercise induced in each subject a significant decrease in the serum level of both gonadotrophic hormones. The results suggest that trait anxiety level may constitute an important factor that affects both pre-exercise and exercise serum androgen concentrations in untrained subjects.     

Distribution of a 27-bp deletion in the band 3 gene in South Pacific islanders

Distribution of a 27-bp deletion in the band 3 gene (B327) that causes Southeast Asian/Melanesian ovalocytosis has scarcely been studied in remote insular Southeast Asia and New Guinea. Here the presence of the B327 was surveyed among a total of 756 subjects from the indigenous populations inhabiting New Guinean islands and remote insular Southeast Asia by using a polymerase chain reaction method. In remote insular Southeast Asia where Austronesian-speaking peoples inhabit, the B327 frequency ranged between 0.04 and 0.15. In New Guinea Island, hinterland or Papuan groups showed the absence of the B327 or a very low gene frequency (0.01 in the Gidra) of the B327. However, groups of the coastal regions (Asmat, Sorong, and others) and of the nearby islands (Biak and Manus) where Austronesian infiltration had occurred showed substantial frequencies of the deletion (0.02–0.09). It is likely that the B327 was introduced into this region about 3,500 years ago with the arrival of Austronesian-speaking peoples. Once being introduced, the B327 may have been selected because of its resistance against malaria, while founder effect and genetic drift might have occurred in the New Guinean tribes with small population size, which helped to generate a variety of the B327 frequencies.     

Volume flow,hydraulic conductivity and electrical properties across bovine tracheal epithelium in vitro: Effect of histamine

Volume flow (J _v), potential difference (), shortcircuit current (i ₀) and electrical resistance (R) were measured simultaneously across bovine tracheal epithelium in vitro. Under basal conditions, with no applied hydrostatic or osmotic pressure gradient (P=0, =0), no spontaneousJ _v was observed. was 31±2 mV (lumen negative),i ₀ 161±8 A cm^–2 andR 202±9 cm²,n=50. When a was applied, by adding 20–80 mM sucrose into the medium bathing either the luminal or the serosal side of the tissue, a linear relationship was found between andJ _v toward the lumen or toward the serosa. The apparent hydraulic conductivity (apparentL _p) was 4.6–4.910^–6 cm s^–1 atm^–1. Histamine 10^–4 M did not induce any spontaneousJ _v under basal conditions and had no effect oni ₀ nor onR. However, histamine caused a 100% increase inJ _v elicited by sucrose gradients. It was concluded that histamine exerts a selective action on the hydraulic conductivity of bovine tracheal epithelium. Experiments using H₁-receptors antagonists (diphenhydramine, dimetindene, chloropyramine) and H₂-antagonists (cimetidine, metiamide) or a H₂-agonist (impromidine) showed that the increase ofL _p induced by histamine was mediated via H₂-receptors.Supported by the Swiss National Foundation (SNF), grant no. 3.5880.79     

Effects of the order of running and cycling of similar intensity and duration on pulmonary diffusing capacity in triathletes

To study the pathophysiological mechanisms involved in the decrease of post-triathlon diffusing capacity (DLco), blood rheologic properties (blood viscosity: _b; changes in plasma volume: PV) and atrial natriuretic factor (ANF) were assessed in ten triathletes during cycle-run (CR) and run-cycle (RC) trials at a metabolic intensity of 75% of maximal oxygen consumption (O_2max). The DLco was measured before and 10 min after trials. ANF and PV were measured at rest, after the cycle and run of CR and RC trials, and at the end of and 10 min after exercise. RC led to a greater DLco decrease, a lower ANF concentration and a lower PV than did CR, whereas for both CR and RC _b was increased throughout exercise and 10 min after. In addition, after CR the DLco decrease was inversely correlated (r=–0.764; P<0.01) with PV. The association of decreased plasma volume, increased _b, and lower ANF concentrations after RC suggested that lower blood pulmonary volume may have caused the greater decrease in Dlco as compared with CR. The inverse correlation between PV and DLco reinforces the hypothesis that fluid shifts limit the post-exercise DLco decrease after the CR succession in triathletes. Lastly, cycling in the crouched position might increase intra-thoracic pressure, decrease thorax volume due to the forearm position on the handlebars, and weaken peripheral muscular pump efficacy, all of which would limit venous return to the heart, and thus result in low pulmonary blood volume. Compared with cycling, running appeared to induce the opposite effects.     

The growth and signalling defects of the ggs1 (fdp1/byp1) deletion mutant on glucose are suppressed by a deletion of the gene encoding hexokinase PII

Yeast cells defective in the GGS1 (FDP1/BYP1) gene are unable to adapt to fermentative metabolism. When glucose is added to derepressed ggs1 cells, growth is arrested due to an overloading of glycolysis with sugar phosphates which eventually leads to a depletion of phosphate in the cytosol. Ggs1 mutants lack all glucose-induced regulatory effects investigated so far. We reduced hexokinase activity in ggs1 strains by deleting the gene HXK2 encoding hexokinase PII. The double mutant ggs1, hxk2 grew on glucose. This is in agreement with the idea that an inability of the ggs1 mutants to regulate the initiation of glycolysis causes the growth deficiency. However, the ggs1, hxk2 double mutant still displayed a high level of glucose-6-phosphate as well as the rapid appearance of free intracellular glucose. This is consistent with our previous model suggesting an involvement of GGS1 in transport-associated sugar phosphorylation. Glucose induction of pyruvate decarboxylase, glucoseinduced cAMP-signalling, glucose-induced inactivation of fructose-1,6-bisphosphatase, and glucose-induced activation of the potassium transport system, all deficient in ggs1 mutants, were restored by the delection of HXK2. However, both the ggs1 and the ggs1, hk2 mutant lack detectable trehalose and trehalose-6-phosphate synthase activity. Trehalose is undetectable even in ggs1 strains with strongly reduced activity of protein kinase A which normally causes a very high trehalose content. These data fit with the recent cloning of GGS1 as a subunit of the trehalose-6-phosphate synthase/phosphatase complex. We discuss a possible requirement of trehalose synthesis for a metabolic balance of sugar phosphates and free inorganic phosphate during the transition from derepressed to fermentative metabolism.     

Serum carbonic anhydrase III,an enzyme of type I muscle fibres,and the intensity of physical exercise

The effects of 30 min running with stepwise increasing intensity (exhaustive, energy demand approx. 50 100% ofVO_2max), 60 s supramaximal running (anaerobic, 125% ofVO_2max) and 40–60 min low-intensity running (acrobic, 40–60% ofVO_2max) on serum concentration of muscle-derived proteins were studied in 5 male and 5 female elite orienteerers. S-Carbonic anhydrase III (S-CA III) was used as a marker of protein leakage from type I (slow oxidative) muscle fibres and S-myoglobin (S-Mb) as a non-selective (type I+II) muscular marker. The fractional increase in S-CA III (S-Ca III) was 0.37±0.09 (mean±SEM,p<0.001), 0.10±0.05 (N. S.) and 0.46±0.09 (p<0.001) 1 h after exhaustive, anaerobic and aerobic exercise, respectively. The corresponding values for S-Mb were 1.45±0.36 (p<0.001), 0.39±0.13 (p<0.01) and 0.67±0.18 (p<0.001). The value for the S-CA III/S-Mb ratio was 0.68±0.03 after the acrobic exercise, but only 0.25–0.26 (p vs. aerobic exercise <0.001) after the two high-intensity forms of exercise. Since type I fibres of skeletal muscle are known to be responsible for power production during low-intensity exercise, whereas fibres of both type I and type II are active at higher intensities, the S-CA III/S-Mb ratio may depend on the recruitment profile of type I vs. type I+II fibres.     

Exogenous gene expression and growth regulation of hematopoietic cells via a novel human artificial chromosome

A number of gene delivery systems are currently being developed for potential use in gene therapy. Here, we demonstrate the feasibility of 21qHAC, a newly developed human artificial chromosome (HAC), as a gene delivery system. We first introduced a 21qHAC carrying an EGFP reporter gene and a geneticin-resistant gene (EGFP-21qHAC) into hematopoietic cells by microcell-mediated chromosome transfer. These HAC-containing hematopoietic cells showed resistance to geneticin, expressed EGFP and retained the ability to differentiate into various lineages, and the EGFP-21qHAC was successfully transduced into primary hematopoietic cells. Hematopoietic cells harboring the EGFP-21qHAC could still be detected at two weeks post-transplantation in immunodeficient mice. We also showed effective expansion of hematopoietic cells by introducing the 21qHAC containing ScFvg, a gp130-based chimeric receptor that transmits growth signals in response to specific-antigen of this receptor. All of these results demonstrate the usefulness of HAC in gene therapy.     

Relationship between muscle architectural features and oxygenation status determined by near infrared device

This study tested whether regional differences in oxygenation status could result from differences in muscle fiber architecture. Architectural properties, oxygen supply, and consumption in the medial head of the gastrocnemius muscle (GM) were determined in vivo in six men using B-mode ultrasound and functional near infrared (NIR) imaging devices. Fascicle length, fascicle angle, NIR-O₂ saturation (deoxygenated Hb or oxygenated Hb), and NIR-blood volume (sum of deoxygenated and oxygenated Hb) were obtained in the distal and proximal portions of the GM at rest and during contraction. Exercise consisted of 2 min of standing plantar flexion at 1 Hz with an additional load of 50% of each subjects weight. Plantar flexion produced larger decreases (: difference between rest and exercise values) in NIR-O₂ saturation [mean saturation (SD) of 0.14 (0.05) vs 0.07 (0.04) optical density units] and NIR-blood volume [mean saturation (SD) of –0.23 (0.08) vs –0.13 (0.04) optical density units] in the distal compared with the proximal portion (P<0.05 for all comparisons). It also produced larger changes () in fascicle length [mean length (SD) of –16.5 (4.7) vs –8.2 (4.2) mm] and fascicle angle (mean angle (SD) of 10.8 (1.4)° vs 3.9 (2.1)°] in the distal compared with the proximal portion (P<0.05 for all comparisons). There were significant correlations between NIR-O₂ saturation and fascicle length (r=–0.84, P<0.05), and between NIR-O₂ saturation and fascicle angle (r=–0.90, P<0.05), between NIR-blood volume and fascicle length (r=0.91, P<0.05), between NIR-blood volume and fascicle angle (r=–0.85, P<0.05). In conclusion, the plantar flexion exercise produced regional differences in oxygenation status consistent with regional differences in muscle architecture.