Perceptual speed does not cause intelligence, and intelligence does not cause perceptual speed

There is ongoing debate whether the efficiency of local cognitive processes leads to global cognitive ability or whether global ability feeds the efficiency of basic processes. A prominent example is the well-replicated association between inspection time (IT), a measure of perceptual discrimination speed, and intelligence (IQ), where it is not known whether increased speed is a cause or consequence of high IQ. We investigated the direction of causation between IT and IQ in 2012 genetically related subjects from Australia and The Netherlands. Models in which the reliable variance of each observed variable was specified as a latent trait showed IT correlations of -0.44 and -0.33 with respective Performance and Verbal IQ; heritabilities were 57% (IT), 83% (PIQ) and 77% (VIQ). Directional causation models provided poor fits to the data, with covariation best explained by pleiotropic genes (influencing variation in both IT and IQ). This finding of a common genetic factor provides a better target for identifying genes involved in cognition than genes which are unique to specific traits.     

Effect of hydro-osmotic pressure on polycystin-2 channel function in the human syncytiotrophoblast

Polycystin-2 (PC2), one of the gene products whose mutations cause autosomal dominant polycystic kidney disease is a transient receptor potential (TRP)-type (TRPP2) Ca²⁺-permeable, non-selective cation channel. PC2 is localized in the plasma membrane, the primary cilium, and other cellular organelles of renal epithelial and other cells. Recent studies indicate that PC2 is involved in signal transduction events associated with the transient increase in cytosolic Ca²⁺. Proof of evidence now hinges on involvement of the PC2 channel in the transduction of environmental signals. PC2 is abundantly expressed in the apical membrane of human syncytiotrophoblast (hST), a highly intricate epithelial tissue, which is essential for the maternal–fetal transfer of solutes, including ions. Physical forces such as hydrostatic (H) and osmotic () pressure play important roles in placenta homeostasis. In this study, we provide new information on PC2 channel regulation in the hST by these environmental factors, and propose a model as to how they may trigger the activation of PC2. Using apical hST vesicles reconstituted in a lipid bilayer system, we found that a change in either H or modified PC2 channel activity. This stimulatory effect was no longer observed in hST vesicles pre-treated with the actin cytoskeleton disrupter cytochalasin D. As shown by immunofluorescence analysis PC2 co-localized with actin filaments in the vicinity of the plasma membrane. This co-localization was disrupted by cytochalasin D. Taken together, our findings indicate that physical forces exerted on cells regulate PC2 channel activity by a sensory mechanism involving the actin cytoskeleton.     

The genetic correlation between intelligence and speed of information processing

This study examined the contributions of genetic and environmental factors to the observed correlation between intelligence test scores and speed of information processing, based on data for same-sex adult twin pairs (age, 15–57). Verbal and performance IQ scores from the Multidimensional Abilities Battery, as well as 11 reaction-time measures derived from a battery of information-processing tasks, were available for 50 monozygotic and 32 dizygotic pairs of twins. Multivariate biometrical analyses were used to estimate genetic and environmental parameters underlying observed variances and covariances among intelligence test scores and a general speed of information-processing factor (based on a linear composite of the 11 reaction-time scores). A common-factor model with loadings on general speed of processing, verbal IQ, and performance IQ fit the data well. The common factor was influenced primarily by additive genetic effects, such that the observed relationships among the speed and IQ measures are mediated entirely by hereditary factors. There was additional specific genetic variance for Verbal IQ and specific shared-twin environmental variance for Performance IQ. However, twin similarity for general speed of processing was explained entirely by genetic factors related to intelligence. The results emphasize the importance of common, heritable, biological mechanisms underlying the speed-IQ association.This research was supported by funding from the Pioneer Fund, Inc.     

Processing of binaural stimuli by cat superior olivary complex neurons

Summary A method was developed to record stereotactically from the cat Superior Olivary Complex (SOC) using glass micropipettes. Sound stimulation was given through a closed system that permitted independent variation of interaural time (time) and intensity (int) differences. The most common binaural units found (n = 34) were ipsilateral excitatory, contralateral inhibitory (EI¹), cells of the Lateral Superior Olive (LSO). Some Medial Superior Olive (MSO) cells and presumed MSO ascending afferents were found but, as noted by other authors, we found it difficult to obtain single unit recordings from this nucleus. The LSO EI cells were mostly sensitive to higher frequencies and showed Peristimulus Time Histograms (PSTHs) consisting of a sharp On response followed by a plateau when stimulated with Best Frequency (BF) tone bursts or noise bursts. This On response was sensitive to time and int such that ipsilateral time lead or intensity increase resulted in a stronger response. The response reached a minimum around zero time or int. No sharp peaks or dips were seen in the physiological range needed for localization, instead the response increased with increasing ipsilateral lead or intensity to the maximum values tested (2048 s time, 30 dB int). In the physiological range the time and int response were complementary (both increasing response as ipsilaterality was increased). Provided enough sound energy in the unit's sensitive region was present, the same time curves were produced when BF tone bursts, masked tone bursts, sharp onset tone bursts or noise bursts were used. Changing the time of the carrier of the tone burst alone had no effect (except for one cell with a BF of 560 Hz), only the relative time of arrival of the stimulus envelope seemed to be important. In contrast to these LSO EI cells MSO-type units showed EI or EE predominantly low frequency phase-locked responses. When stimulated with interaurally phase shifted (pha) BF tones the unit response was a cyclic function of pha. Some cells (all that were tested, n = 6 including the 560 Hz LSO EI cell) showed these cyclic responses when stimulated with noise bursts or non-BF tones. However, these characteristic delays were not necessarily in the physiological range, i.e. we could find no evidence that these units were responding to time/pha values corresponding to a particular sound source direction. In both LSO and MSO it seems that integration of information higher in the CNS from a population of these cells is necessary for unambiguous coding of sound source direction. The time intensity trading ratios measured in two MSO type cells (11 and 26 /dB) were clearly different to those measured in LSO EI cells (n = 6, 99–550 s/dB). These ratios correspond approximately to those of the psychophysical time and int images measured by Hafter and Jeffress (1968).Supported by the Deutsche Forschungsgemeinschaft (SFB 45)     

Isolation of mutants lacking branched-chain amino acid transaminase

Variants of the Chinese hamster ovary cell have been isolated which can no longer grow when valine, leucine, or isoleucine is replaced in the culture medium by its respective -keto acid: -ketoisovaleric acid, -ketoisocaproic acid, or -keto--methylvaleric acid. These variants lack branched-chain amino acid transaminase activity. Evidence is presented indicating these variants to be single gene mutants. Genetic evidence is also presented confirming previous biochemical evidence that a single enzyme carries out transaminase functions on valine, leucine, and isoleucine. The branched-chain transaminase-deficient (trans^–)mutants can be reverted to wild-type behavior by treatment with mutagenic agents. These mutants promise to be useful in exploring regulatory mechanisms in biochemical, genetic, and cancer research.Trainee, U.S. Public Health Service Grant No. GM00781-17.     

Nucleotide sequence of dengue type 3 virus genomic RNA encoding viral structural proteins

Complementary DNAs to the 5 proximal region of the dengue virus type 3 RNA were cloned into bacterial plasmids and the nucleotide sequence of 3,000 bases from the 5 terminus of the genome were determined by DNA and RNA sequencing methods using dideoxy chain-termination reactions. Comparison of the nucleotide sequence thus obtained with those of other flavivirus genomes revealed significant homology existing in nucleotide sequence of the flavivirus genomes. When we compared amino acid sequence deduced from the nucleotide sequence with those of other flaviviruses, this genome region was found to include sequences encoding three viral structural proteins C, M, and E and a part of the viral nonstructural protein NS1 in this order in addition to the 5-noncoding sequence. The characteristics and functions of these proteins were discussed based on the deduced amino acid sequences and their hydrophobic profiles. The genetic relationship of flaviviruses was also discussed based on the genetic variation observed in their genomes.     

Characterization of antigens of the nematodeNippostrongylus brasiliensis by monoclonal antibodies

Hybridomas secreting monoclonal antibodies toNippostrongylus brasiliensis antigens were generated by hybridization of IR983F myeloma cells with spleen cells from Lou/M/Wol rats infected with living third-stage larvae. Antibodies specific either for larval or worm antigens were identified by enzyme-linked immunosorbent assays withNippostronylus brasiliensis fragments, homogenates and secretions as antigens. The results demonstrate that all antibodies which recognized larval antigens (38 antibodies) also reacted with worm surfaces. Ten antibodies were specific only for worm antigens. Ten antibodies reacted with worm homogenate, three antibodies recognized components of worm secretion and 17 antibodies combined with acetylcholinesterase. The epitope specificity was investigated by the capacity of various glycosides, aminoacids,N-acetylneuraminic acid and phosphorylcholine to inhibit the binding to worm fragments. The analysis revealed that -methylglucoside, -methylmannoside,N-acetylglucosamine,N-acetylgalactosamine, fucose and the amino acids leucine, phenylalanine, tyrosine, serine, tryptophan did not combine with the antigen-binding sites of the antibodies. Proline, arginine and histidine, however, displayed inhibitory effects. WithN-acetylneuraminic acid as inhibitor three groups of antibodies could be discriminated. At a concentration of 10–20 mM, phosphorylcholine was a potent inhibitor for all antibodies.     

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     

Marek's Disease Virus Latent Protein MEQ: Delineation of an Epitope in the BR1 Domain Involved in Nuclear Localization

Marek's disease virus latent protein MEQ (MDV Eco Q) is abundantly expressed and consistently detected in MDV-induced tumors and cell lines. Deletion mutants were constructed to study the domain structure of MEQ. Four deletion mutants were obtained in the basic regions of MEQ, namely basic region 1 (BR1), basic region 2 (BR2), basic regions 1 and 2 (BR1 and 2), and the C-terminal (bZIP) domain. The BR1 and BR2 are nuclear localization signals and either is sufficient to cause transport of MEQ into the nucleus. In addition, the BR2 is also responsible for MEQ's nucleolar localization. A monoclonal antibody (Mab 23B46) was produced using recombinant fowlpox virus (rFPV) expressing MEQ (rFPV/MEQ) as a source of protein. The isotype of Mab 23B46 is IgG1 and immunoprecipitated a band in rFPV/MEQ infected cells with molecular weight of 60kDa specific to MEQ protein. We detected abundant expression of MEQ in (rFPV/MEQ), recombinant baculovirus (rBac) (rBac/MEQ), and lymphoid tumors induced by MDV. In order to delineate the epitope of MEQ reactive with Mab 23B46, we used four deletion mutants from the basic and bZIP domains. We found the deletions in the N-terminal region including BR1 (BR1), and (BR1 and 2) completely abolished the specific binding with Mab 23B46 as shown by Western blot analysis and immunofluoresence test. Deletion of BR2 (BR2) and the C-terminal (bZIP) domain had no effect on antibody binding. These data provide direct evidence that monoclonal antibody reactive epitope is localized in the BR1 domain of the molecule. Since both BR1 and BR2 domains contain sequences important for nuclear entry, we now have reagent to further study and elucidate the mechanism of MEQ's involvement in nuclear and nucleolar localization.     

Bioactive 5-Reduced 16α,17α-Cyclohexanoprogesterone Derivatives Weakly Interact with Proteins of the Soluble Uterine Fraction

We studied competitive activities of 16,17-cyclohexano-5- and 5-dihydroprogesterone in replacing ₃H-progesterone and ₃H-16,17-cyclohexano-6-methylprogesterone from protein complexes. Direct binding of ₃H-5-reduced derivatives with proteins of soluble fractions from rat and rabbit uteri was also assayed. Cd values for 5-reduced derivatives were in the micro- or submicromolar range. The data suggest that biological effects of these analogues are not mediated via soluble uterine receptors.     

An improved method for the quantitation of cellular migration: Role of αvβ3 integrin in endothelial and smooth muscle cell migration

The present study was undertaken to develop a simple and improvedmethod for the accurate quantitation of cellular migration and to examinethe role of v3 integrins in different cellular migration. Usingour newly developed micro-volume chemotaxis assay, we developed an improvedquantitative method to measure in vitro chemotaxis of smooth muscle orendothelial cells toward different extracellular matrix proteins. Theconvenience in setup and counting of migrated cells using this methodallows for large capacity screening and for various research applicationswith other cells as well. The signal. to noise ratios were in the range of10/1, along with about 10–20% intra- or inter-assayvariabilities. Using this method, we have determined that eithervitronectin at 0.4 µg/well or osteopontin at 0.4 µg/well areselective v3 chemoattractants for endothelial or smooth musclecells (0.5 × 105 cells/well). Additionally, a selective v3small molecule peptiddomimetic, monoclonal antibody LM609, or an anti-3 (v3/II3) anti-body, c7E3 demonstratedmaximal inhibition of cellular migration toward vitronectin or osteopontin.These data suggest the potential utility of this method in assessing therole of various mechanisms in cellular migration and also suggests the potential implication of an v3 antagonist in blocking pathologicalprocesses involving endothelial or smooth muscle cell adhesion/migration.     

Serum creatine kinase activity following forearm flexion isometric exercise

Summary The purpose of this study was to 1) compare serum creatine kinase (CK) activity following two forearm flexion isometric exercise regimens differing in work to rest ratio, and 2) examine the CK response to a repeated bout of isometric exercise. Eleven males were tested on two sessions (bouts) spaced 1 week apart. For bout 1, five subjects (group A) performed a forearm flexion isometric exercise consisting of 40 10-s maximal contractions with 20-s inter-trial rests (1020), while six (group B) performed 40 maximal 10-s contractions with 5-s inter-trial rests (105). The increase in serum CK activity following the 1020 exercise (143%) was significantly greater than that following the 105 exercise (52%). The 1020 exercise was also associated with greater tension generation over trials. One week later, both groups performed a bout of 1020 exercise. A substantial reduction in the serum CK response was found following this second bout. The data suggest that for bout 1 the isometric exercise associated with the greater overall tension levels resulted in the greater CK response. However, when the 1020 exercise was repeated 1 week later, a substantial reduction in the CK response was found which was unrelated to the tension generated.This study was supported by a University Faculty Research Grant No. 2-03021     

Neutropenia: Antibiotic combinations for empiric therapy

During the last two decades the mortality from gram-negative septicemia in neutropienic patients with serious underlying disease has declined from 85 % to less than 20 %. Many factors seem responsible for this trend: (a) the development of potent broad-spectrum antimicrobial agents. (b) aggressive clinical approaches to empiric therapy entailing the use of antibiotics before results of cultures are known. (c) better supportive care, (d) improved treatment of underlying disease. Controversy persists about the choice of optimum regimens: clinical studies to date show major differences in evaluation criteria, particularly in the definition of response. The largest and most convincing studies of gram-negative bacteremia still favor the use of antibiotic combinations in patients with profound, persistent neutropenia.     

Measurement ofN τ-methylhistamine concentrations in plasma and urine as a parameter for histamine release during anaphylactoid reactions

N -methylhistamine concentrations in plasma and urine were determined using a newly developed simultaneous determination for histamine andN -methylhistamine, based on isotope dilution mass fragmentography. Three groups of patients were investigated: patients receiving intravenously-administered iodamide for excretory urography, patients receiving a wasp-sting challenge, and patients treated with an intravenously-administered muscle relaxant. In all patients showing a distinct systemic anaphylactic or anaphylactoid reaction histamine andN -methylhistamine concentrations were found to be elevated. From the results of this study it can be concluded thatN -methylhistamine in plasma and urine is a good parameter for histamine release, and that the determination of this histamine metabolite are less hampered by possible artefacts (due to basophil disrupture, a very short half-life time or bacterial production) than determinations of histamine itself.     

Characterization ofcpd-1 andcpd-2 mutants which affect the activity of orthophosphate regulated cyclic phosphodiesterase inNeurospora

Summary Enzymatic and genetic characterization ofcpd-1 andcpd-2, which exhibit rhythmic conidiation in liquid media and on solid media, were described with band (bd) strain as a reference.Cpd-1 andcpd-2 showed reduced growth in orthophosphate-free cyclic 3,5-AMP media, whilebd showed wild-type level of growth in the media. In low-phosphate media,cpd-1 andcpd-2 produced 19.2% and 9.8% of orthophosphate-regulated cyclic phosphodiesterase (cPDase) in culture media, while bd produced 123%. The intracellular levels of cPDase with K_m of 1 × 10^–5 M in high-phosphate media incpd-1, cpd-2 and bd were about 20%, 15%, and 10% of that in wild-type, respectively. In low-phosphate media, roughly equal levels of cPDase with K_m of 1 × 10^–5 M were produced in all strains, whereas the production of cPDase with K_m of 2 × 10^–3 M was reduced incpd-2, and that of cPDase with K_m of 1 × 10^–2 was reduced incpd-1 andcpd-2. The levels of intracellular cyclic 3,5-AMP incpd-1, cpd-2, andbd in high-phosphate media were 13.1%, 10.1%, and 69.6% of that in wild-type. Adenylate cyclase activity incpd-1, cpd-2, bd, andcr-1 was 69.3%, 34.0%, 63.2%, and 20.3% of that of wild-type (74A). The levels of Mg⁺⁺-stimulated cyclic phosphodiesterase incpd-1, cpd-2, bd, andcr-1 at 0.2M cyclic 3,5-AMP were 199%, 137%, 329%, and 293% of that of wild-type. It was suggested thatcpd-1, cpd-2, andbd are the genes controlling the levels of enzymes for cyclic 3,5-AMP.Cpd-I was mapped on LG IVR 19.4% distal topyr-2 andcpd-2 was mapped on LG IL 5.6% proximal toarg-1.     

Structural elements in adenovirus cores. Studies by means of freeze-fracturing and ultrathin sectioning

Summary Rod-like elements have been observed in adenovirions after freeze-fracturing of purified, semi-purified and intra-cellular adenovirus type 5. Their rod-like shape was clearly demonstrated by means of stereomicrographs. Ultrathin sections prepared in parallel with the freeze-fracture replicas revealed linear structures such as ribbons, rings or rods in up to 30 per cent of the semi-purified or intracellular virus particles. These observations indicate that the main structural element in the adenovirus interior is a linear structure either fragmented into 5 to 6 rods or folded 5 to 6 times to fit into the inner space of the virion.With 7 Figures     

αv Integrins mediate adhesion and migration of breast carcinoma cell lines

Integrins with the _v subunit are involved in cell adhesion and cellular signaling. Some _v integrins have been associated with tumor progression and dissemination. The objective of this study was to assess the contribution of _v integrins to the adhesive and migratory behavior of cells derived from breast carcinoma (BCA). The expression and function of _v integrins was characterized in three BCA cell lines which exhibit different metastatic potentials. These include MCF-7 cells which metastasize inefficiently, MDA-MB-231 cells, which have a moderate metastatic potential, and MDA-MB-435 cells, which metastasize extensively. Each cell type displays a different repertoire of _v integrins on the cell surface. The complement of _v integrins on each cell type influences their ability to adhere and migrate. The most striking difference among these cell lines was the expression of the _{v3 3} integrin. The highly metastatic MDA-MB-435 cells express substantial levels of this receptor, whereas MDA-MB-231 and MCF-7 cells do not. The MDA-MB-435 cells showed a greater ability to adhere and to migrate and this functional difference can largely be attributed to the expression of _v3 integrin. This characterization is a first step toward determining the role of _v integrins in animal models of BCA metastasis, and lends support to the hypothesis that the _v3 integrin can be a contributing factor in metastatic disease. © Rapid Science 1998     

Measurement of urinary Nτ-methylhistamine excretion: Correlation of a newly developed radioimmunoassay (RIA) with gas chromatography mass spectrometry (GCMS)

A newly developed radioimmunoassay (RIA, Y) for the determination of urinary N-methylhistamine concentrations was correlated with gas chromatography mass spectrometry (GCMS, X). In 34 urine samples, with histamine and N-methylhistamine levels within our reference values, the correlation was: Y=1.47X–0.245 mol/l (r=0.92;p-slope 0.0001). In 14 pathological urine samples, derived from patients with mastocytosis and having upper reference values, the correlation was: Y=1.75X–1.02 mol/l (r=0.93;p-slope 0.001). In spite of the greater specificity of the monoclonal antibody for N-methylhistamine compared with that of histamine, relatively high urinary histamine concentrations gave a false positive influence on the RIA results, which was 100% when the histamine/N-methylhistamine ratio was about 19. Clear cases of mastocytosis can be diagnosed, using the RIA-kit, but for a more precise N-methylhistamine value GCMS analyses will remain necessary.     

Phosphorylation of caldesmon by smooth-muscle casein kinase II

Summary A caldesmon kinase activity was partially purified from an extract of chicken gizzard smooth muscle by sequential chromatography on columns of DEAE-Sephacel, MonoQ and Superose 12. This kinase was identified as casein kinase II by Western blotting using peptide-directed antibodies raised against the , and subunits of human casein kinase II; the smooth muscle enzyme consisted of similar subunits of M_r 43 000 (), 39 000 (), and 27 000 (). Phosphorylation of caldesmon and casein by smooth muscle casein kinase II was optimal at 0.1 M NaCl, did not require second messengers, and was inhibited by heparin. The kinase utilized either GTP or ATP as a substrate. Caldesmon was phosphorylated to 1 mol P_i mol^-1 caldesmon by smooth muscle casein kinase II with a K_m for caldesmon of 4.9 M. Two-dimensional thin-layer electrophoresis indicated phosphate incorporation into both serine and threonine. All the incorporated phosphate was recovered in the N-terminal peptide (residues 1–152) generated by cleavage at cysteine 153 with 2-nitro-5-thiocyanobenzoic acid. Purification of tryptic phosphopeptides and N-terminal sequencing revealed two principal sites of phosphorylation: serine 73 and threonine 83. The following four synthetic peptides corresponding to this domain of caldesmon were examined as substrates of casein kinase II: A = RRREVNAQNSVAEEE; B = AQNSVAEEE; C = RSTDDEAA; D = SVAEEETKRSTDDE. Interestingly, only peptides C and D were phosphorylated and both only at threonine. Phosphorylation of intact caldesmon did not affect the pattern of chymotryptic digestion suggesting that it does not induce a significant conformational change in the protein substrate. Phosphorylation also had no effect on the binding of caldesmon to actin or on the caldesmon-mediated inhibition of actomyosin MgATPase activity. However, phosphorylation completely abolished the interaction of caldesmon with immobilized smooth muscle myosin. These results are consistent with the localization of the myosin-binding domain near the N-terminus of caldesmon and of the actin-binding domain near the opposite end of the elongated molecule. Casein kinase II may therefore play a role in regulating caldesmon-myosin interaction and the ability of caldesmon to cross-link actin and myosin filaments in smooth muscle.     

Negative accumulated oxygen deficit during heavy and very heavy intensity cycle ergometry in humans

The concept of the accumulated O₂ deficit (AOD) assumes that the O₂ deficit increases monotonically with increasing work rate (WR), to plateau at the maximum AOD, and is based on linear extrapolation of the relationship between measured steady-state oxygen uptake (O₂) and WR for moderate exercise. However, for high WRs, the measured O₂ increases above that expected from such linear extrapolation, reflecting the superimposition of a "slow component" on the fundamental O₂ mono-exponential kinetics. We were therefore interested in determining the effect of the O₂ slow component on the computed AOD. Ten subjects [31 (12) years] performed square-wave cycle ergometry of moderate (40%, 60%, 80% and 90% ), heavy (40%), very heavy (80%) and severe (110% O_{2 peak}) intensities for 10–15 min, where is the estimated lactate threshold and is the WR difference between and O_{2 peak}. O₂ was determined breath-by-breath. Projected "steady-state" O₂ values were determined from sub- tests. The measured O₂ exceeded the projected value after ~3 min for both heavy and very heavy intensity exercise. This led to the AOD actually becoming negative. Thus, for heavy exercise, while the AOD was positive [0.63 (0.41) l] at 5 min, it was negative by 10 min [–0.61 (1.05) l], and more so by 15 min [–1.70 (1.64) l]. For the very heavy WRs, the AOD was [0.42 (0.67) l] by 5 min and reached –2.68 (2.09) l at exhaustion. For severe exercise, however, the AOD at exhaustion was positive in each case: +1.69 (0.39) l. We therefore conclude that the assumptions underlying the computation of the AOD are invalid for heavy and very heavy cycle ergometry (at least). Physiological inferences, such as the "anaerobic work capacity", are therefore prone to misinterpretation.