Genetic and Environmental Factors Affecting Self-Rated Health from Age 16–25: A Longitudinal Study of Finnish Twins

We analyzed genetic and environmental determinants of self-rated health and its change from adolescence to early adulthood. Questionnaires were mailed to Finnish twins born 1975–1979 at ages 16, 17, and, on average, 25 years of age (N = 2465 complete twin pairs). The data were analyzed using quantitative genetic methods for twin data by the Mx statistical package. Heritability of self-rated health was greatest at age 16 (63%, 95% confidence intervals (CI) 56–67%, men and women together) and declined steadily to age 25 (33%, 95% CI 25–41%). The residual variation was due to unshared environments. Health ratings at different ages were modestly correlated (r = 0.33–0.61). These correlations were mainly due to genetic factors, but unshared environment also contributed to them. An important challenge for further research is to identify environmental influences contributing to self-rated health independently of, or in interaction with, genetic factors. Edited by Peter McGuffin and John Hewitt     

Heritability and Longitudinal Stability of Schizotypal Traits During Adolescence

The study investigated the genetic and environmental etiology of schizotypal personality traits in a non-selected sample of adolescent twins, measured on two occasions between the ages of 11 and 16 years old. The 22-item Schizotypal Personality Questionnaire- Child version (SPQ-C) was found to be factorially similar to the adult version of this instrument, with three underlying factors (Cognitive-Perceptual, Interpersonal-Affective, and Disorganization). Each factor was heritable at age 11–13 years (h ² = 42–53%) and 14–16 years old (h ² = 38–57%). Additive genetic and unique environmental influences for these three dimensions of schizotypal personality acted in part through a single common latent factor, with additional genetic effects specific to both Interpersonal-Affective and Disorganization subscales at each occasion. The longitudinal correlation between the latent schizotypy factor was r = 0.58, and genetic influences explained most of the stability in this latent factor over time (81%). These longitudinal data demonstrate significant genetic variance in schizotypal traits, with moderate stability between early to middle adolescence. In addition to common influences between the two assessments, there were new genetic and non-shared environmental effects that played a role at the later assessment, indicating significant change in schizotypal traits and their etiologies throughout adolescence.     

A Twin Study of the Genetics of High Cognitive Ability Selected from 11,000 Twin Pairs in Six Studies from Four Countries

Although much genetic research has addressed normal variation in intelligence, little is known about the etiology of high cognitive abilities. Using data from 11,000 twin pairs (age range = 6–71 years) from the genetics of high cognitive abilities consortium, we investigated the genetic and environmental etiologies of high general cognitive ability (g). Age-appropriate psychometric cognitive tests were administered to the twins and used to create g scores standardized within each study. Liability-threshold model fitting was used to estimate genetic and environmental parameters for the top 15% of the distribution of g. Genetic influence for high g was substantial (0.50, with a 95% confidence interval of 0.41–0.60). Shared environmental influences were moderate (0.28, 0.19–0.37). We conclude that genetic variation contributes substantially to high g in Australia, the Netherlands, the United Kingdom and the United States. Edited by Dick Rose.     

The RET proto-oncogene in medullary and papillary thyroid carcinoma

 The evolution of cancer is a multistep phenomenon, and multiple cellular genetic lesions are involved in the emergence of the malignant neoplasm. Several early events have been implicated in the neoplastic transformation of thyrocytes, and recent reports have described the involvement of specific genetic alterations in different types of thyroid neoplasms: ras point mutations are frequently observed in tumours with follicular histology, gsp – the mutated form of the alpha subunit of the Gs-protein – is encountered in up to 73% of papillary or follicular thyroid carcinomas, and a high prevalence of p53 point mutations has been found in anaplastic thyroid carcinomas but not in differentiated follicular tumours. More recent studies revealed that the RET proto-oncogene is involved in the oncogenesis of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) by activation of its tyrosine kinase either by point mutation or rearrangement. In this review the most important recently published data on alterations of the RET proto-oncogene in heritable and sporadic MTCs and in PTCs will be summarized. Emphasis will be directed to the pathophysiological mechanisms of tumour initiation, the indications and limitations of DNA testing, and the clinical implications of identified RET defects in thyroid lesions. Received: 9 January 1997 / Accepted: 17 February 1997     

Functional Connectivity and Quantitative EEG in Women with Alcohol Use Disorders: A Resting-State Study

This study was aimed at exploring the electroencephalographic features associated with alcohol use disorders (AUD) during a resting-state condition, by using quantitative EEG and Functional Connectivity analyses. In addition, we explored whether EEG functional connectivity is associated with trait impulsivity. Absolute and relative powers and Synchronization Likelihood (SL) as a measure of functional connectivity were analyzed in 15 AUD women and fifteen controls matched in age, gender and education. Correlation analysis between self-report impulsivity as measured by the Barratt impulsiveness Scale (BIS-11) and SL values of AUD patients were performed. Our results showed increased absolute and relative beta power in AUD patients compared to matched controls, and reduced functional connectivity in AUD patients predominantly in the beta and alpha bands. Impaired connectivity was distributed at fronto-central and occipito-parietal regions in the alpha band, and over the entire scalp in the beta band. We also found that impaired functional connectivity particularly in alpha band at fronto-central areas was negative correlated with non-planning dimension of impulsivity. These findings suggest that functional brain abnormalities are present in AUD patients and a disruption of resting-state EEG functional connectivity is associated with psychopathological traits of addictive behavior.     

Kinetics of capture and infection of infective larvae of trichostrongylides and free-living nematodes Panagrellus sp. by Duddingtonia flagrans

Duddingtonia flagrans, a nematode-trapping fungus, has been investigated as an agent for biological control against infective larvae of gastrointestinal nematode parasites of production animals. The initial process of nematode-trapping fungi infection is based on an interaction between the trap structure of the fungus and the surface of the nematode cuticle. This report investigates by light and scanning electron microscopy the kinetics of capture and infection during the interaction of D. flagrans with the infective larvae (L₃) of trichostrongylides and the free-living nematode Panagrellus sp. D. flagrans was cultivated for 7 days in a Petri dish containing agar–water. L₃ and Panagrellus sp. were inoculated in the Petri dishes and the samples consisting of agar–L₃–fungi and agar–Panagrellus sp.–fungi were collected after 10, 20, 30, 40, 50, 60, and 70 min and 3, 4, 5, 10, 15, 20, and 25 h of interaction. All samples were observed by light microscopy. The samples with 1, 5, 15, and 25 h of interaction were also analyzed by scanning electron microscopy. The interaction was monitored up to 25 h. An initial differentiation of predation structures was observed after 30 min of interaction. The presence of traps and of captured L₃ or Panagrellus sp. occurred after 70 min. The live captured nematodes were observed up to 3 h of interaction. However, after 4 h, all Panagrellus sp. were dead. It took 15 h of interaction for the fungus to invade the L₃, and the presence of hyphae inside the nematode near the region of penetration was evident. At this time, the hyphae had filled the whole body of Panagrellus sp. The complete occupation of the body of L₃ occurred at 20 h of interaction and with 25 h the nematode was completely damaged except for the cuticle. Although the double cuticle of L₃ slows the penetration of D. flagrans, it was possible to verify that the process of trap formation and capture occurs quickly when both nematodes were tested, suggesting that the organisms would eventually be killed once in contact with the fungi encouraging the use of the fungus as a biological control agent.     

The combination of <Emphasis Type="Italic">ApoCIII</Emphasis>, <Emphasis Type="Italic">hepatic lipase</Emphasis> and <Emphasis Type="Italic">hormono sensitive lipase</Emphasis> gene polymorphisms suggests an association with susceptibility to gestational hypertension

Dyslipidemia and insulin resistance contribute to the endothelial cell dysfunction in hypertensive disorders of pregnancy (HDP) and increase the long-term risk of cardiovascular disease (CVD). The genes linking susceptibility to gestational hypertension (GH) and/or preeclampsia (PE) to the long-term risk of CVD are still unknown. We evaluated the potential association between 14 polymorphisms from six genes involved in lipid metabolism and insulin action and the risk of HDP: namely the lipoprotein lipase (LPL), hepatic lipase (LIPC), hormone sensitive lipase (LIPE), cholesteryl ester transfer protein (CETP), ApoCIII and ApoE gene polymorphisms. Overall, 169 women with HDP [proteinuria (PE) and gestational hypertension without proteinuria (GH)] and 169 controls matched for age and year of delivery were genotyped. Homozygosity of the −514T allele of the −514C > T polymorphism (LIPC gene) decreased the risk of GH (OR = 0.17, CI₉₅: 0.02–0.76), while there were more −60G carriers of the −60C > G LIPE gene polymorphism (OR = 3.51, CI₉₅:1.02–12.10) among GH cases, but not in PE cases. The common ApoCIII two-locus −482CC/3238CC genotype was lower in women with GH compared with controls (OR = 0.53, CI₉₅: 0.3–0.9). The combined frequency of at-risk genotypes was higher in cases of GH compared with controls [one at-risk genotype: OR = 3.38 (95% CI: 0.48–41.8); two or more at-risk genotypes: OR = 7.14 (95% CI: 1.21–92.3, P = 0.01)], suggesting a gene-dose effect. We conclude that the combined effect of LIPC, LIPE and ApoCIII gene polymorphisms may increase the likelihood of GH, but seemingly not of PE.     

Determinants of the energy cost of front-crawl swimming in children

The aim of the present study was to define the determinants of the energy cost of swimming (Cs) in children. Eleven healthy children [mean (SD) age: 12.42 (0.53) years] who practised 7.5–8.5 h·week^–1 volunteered to take part in this study. Anthropometric dimensions such as height (H), body mass (BM), hydrostatic lift (HL) and body surface area (SA) were measured. Forty-eight hours later when maximal oxygen consumption ( ) had been measured during 400 m of front-crawl swimming, Cs was measured over 200 m for three submaximal swimming speeds (0.9, 1.0 and 1.1 m·s^–1). Oxygen consumption (Douglas bag method), stroke frequency (SF) and stroke length (SL) were calculated during the last 50 m of each 200 m. The mean (SD) of the young swimmers was 2.19 (0.38) l·min^–1 at a maximal aerobic velocity of 1.19 (0.03) m·s^–1. The values of for Cs at 0.9 m·s^–1, 1.0 m·s^–1 and 1.1 m·s^–1 were 29.27 (3.13) ml·m^–1, 30.25 (3.68) ml·m^–1 and 32.91 (3.59) ml·m^–1, respectively. There was a significant increase in Cs with increasing swim speed. In addition, SF increased with velocity when SL remained constant. The values for SF at 0.9 m·s^–1, 1.0 m·s^–1 and 1.1 m·s^–1 were 31.28 (4.36) strokes·min^–1, 34.10 (5.09) strokes·min^–1 and 38.31 (5.90) strokes·min^–1, respectively. No significant correlation was obtained between Cs and the anthropometric or stroking parameters. It was concluded that for young swimmers, anthropometric characteristics, SF and SL are not good predictors of Cs in front-crawl swimming, and that further studies are needed to explore the influence of underwater torque on Cs in prepubertal children. Electronic Publication     

Effect of altitude training on serum creatine kinase activity and serum cortisol concentration in triathletes

In this investigation we evaluated the effect of a 5-week training program at 1860 m on serum creatine kinase (CK) activity and serum cortisol concentration in national-caliber triathletes for the purpose of monitoring the response to training in a hypobaric hypoxic environment. Subjects included 16 junior-level female (n = 8) and male (n = 8) triathletes who were training for the International Triathlon Union (ITU) World Championships. After an initial acclimatization period, training intensity and/or volume were increased progressively during the 5-week altitude training camp. Resting venous blood samples were drawn at 0700 hours following a 12-h overnight fast and were analyzed for serum CK activity and serum cortisol concentration. Subjects were evaluated before [7–10 days pre-altitude (SL 1)] and after [7–10 days post-altitude (SL 2)] the 5-week training camp at 1860 m. At altitude, subjects were evaluated within 24–36 h after arrival (ALT 1), 7 days after arrival (ALT 2), 18 days after arrival (ALT 3), and 24–36 h prior to leaving the altitude training camp (ALT 4). A repeated-measures analysis of variance was used to evaluate differences over time from SL 1 to SL 2. Compared to SL 1, serum CK activity increased approximately threefold (P < 0.05) within the initial 24–36 h at altitude (ALT 1), and increased by an additional 70% (P < 0.05) after the 1st week of altitude training (ALT 2). Serum CK activity remained significantly elevated over the duration of the experimental period compared to pre-altitude baseline levels. Serum cortisol concentration was increased (P < 0.05) at the end of the 5-week altitude training period (ALT 4) relative to SL 1, ALT 1 and ALT 3. These data suggest that: (1) the initial increase in serum CK activity observed in the first 24–36 h at altitude was due primarily to acute altitude exposure and was independent of increased training intensity and/or training volume, (2) the subsequent increases in serum CK activity observed over the duration of the 5-week altitude camp were probably due to the combined effects of altitude exposure and increased training load, and (3) the increase in serum cortisol concentration observed at the end of the altitude training camp reflects the additive effect of 5 weeks of altitude exposure in combination with a progressively increased training intensity and/or volume. Accepted: 5 June 1999     

Comparative Nuclear Magnetic Resonance Studies of Diffusional Water Permeability of Red Blood Cells from Different Species. XII. Dog (<Emphasis Type="BoldItalic">Canis familiaris</Emphasis>) and Cat (<Emphasis Type="BoldItalic">Felis domestica</Emphasis>)

The diffusional water permeability (P _d ) of dog and cat red blood cell (RBC) membrane has been monitored by a doping nuclear magnetic resonance (NMR) technique on control cells and following inhibition with p-chloromercuribenzene sulphonate (PCMBS). The values of P _d were in the case of cat RBC ∼3.0 × 10⁻³ cm/s at 15 °C, 3.5 × 10⁻³ cm/s at 20 °C, 4.2 × 10⁻³ cm/s at 25 °C, 4.4 × 10⁻³ cm/s at 30 °C and 5.9 × 10⁻³ cm/s at 38 °C. In case of dog RBC the values of P _d were higher ∼3.8 × 10⁻³ cm/s at 15 °C, 4.6 × 10⁻³ cm/s at 20 °C, 5.0 × 10⁻³ cm/s at 25 °C, 5.9 × 10⁻³ cm/s at 30 °C and 7.9 × 10⁻³ cm/s at 37 °C. Systematic studies of the effect of PCMBS on water diffusion indicated that in the case of dog RBCs the maximal inhibition was reached in 15–30 min with 1 mm PCMBS, whereas in the case of cat RBCs in 60 min with 1 mm PCMBS or in 30 min with 2 mm PCMBS. The values of maximal inhibition in the case of cat RBC were in the range of 55–60% at 15 °C, 60–68% at 20 °C and 25 °C, 50–60% at 30 °C and 50–55% at 37 °C. In the case of dog RBC the corresponding values were higher, 75–80% at 15 °C, 70–80% at 20 °C and 25 °C, 65–70% at 30 °C and 55–60% at 37 °C. The basal permeability to water was estimated to be ∼1 × 10⁻³ cm/s −2 × 10⁻³ cm/s in the range of temperatures of 25–37 °C. The activation energy of water diffusion E _a,d was ∼19 kJ/mol for the dog RBC and ∼23 kJ/mol for the cat RBC. After incubation with PCMBS the values of E _a,d increased, reaching 40 kJ/mol in conditions of maximal inhibition of water exchange. The membrane polypeptide electrophoretic pattern of dog and cat RBCs has been compared with its human counterpart. Dog and cat RBCs contained higher amounts of spectrin (band 1 and 2) and lower amounts of bands 4.4, 4.2, band 5 and band 7 compared to human RBCs. Band 4.9 was decreased only in the cat RBCs, whereas band 6 was decreased only in the dog RBCs. Correspondence and offprint requests to: Gheorghe Benga, Department of Cell and Molecular Biology, ‘Iuliu Haţieganu’ University of Medicine and Pharmacy, 6 Pasteur St, 3400 Cluj-Napoca, Romania. Tel:/Fax: 40–64–194373; e-mail: GBenga@personal.ro; gbenga@umfcluj.ro     

Investigating the relationship between fetus EEG,respiratory, and blood pressure signals during maturation using wavelet transform

In this study, we introduce the fast wavelet transform as a method for characterizing maturational changes in electrocortical activity, respiratory activity, and blood pressure in fetal lambs in early (110–122 days), mid (123–135 days), and late (136–144 days) third trimester (term 145 days). Each recording was 2 hr in duration. Wavelet decomposition was performed for six sets of parametersD _2j where 1≤j≤6. The six series wavelet transforms represent the following signal frequency bands: 1. 16–32 Hz; 2. 8–16 Hz; 3. 4–8 Hz; 4. 2–4 Hz; 5. 1–2 Hz; 6. 0.5–1 Hz. In the early group, power in the electrocephalogram (EEG) was highest in the fourth wavelet band, with relatively low power in the other bands. Increase in gestational age was characterized by increased power in all four wavelet bands. Power in the first wavelet band was significantly increased during low-voltage fast activity (LVFA) in the late group. The respiratory and blood pressure signals showed common frequency components with respect to time and were coincident with the LVFA EEG signal. Respiratory activity was only observed during some of the LVFA periods and was completely absent during high-voltage slow activity (HVSA) EEG. The respiratory signal showed dominant power in the fourth wavelet band, and less power in the third and fifth band. The blood pressure signal was also characterized by dominant power in the fourth wavelet band. This power was significantly increased during periods of respiratory activity. These results suggest a strong relationship between fetal EEG, blood pressure, and breathing movements.     

Definition of TCR recognition sites on Ld-tum complexes

The P911 variant of the P815 mastocytoma was shown by Lurquinet al. (Cell 58:293,1989) to elicit rapid tumor rejection ina syngeneic host. This rejection was mediated by L^d-restrictedcytotoxic T lymphocytes (CTL) for which targets could be sensitizedby the synthetic peptide designated tum^– (P91A^–.12–24).In a previous study, T cell clones specific for L^d-tum^–complexes displayed very restricted TCR usage and a characteristicTCR motif in the V CDR3 region, predicted to interact with peptide.However, in contrast to the majority of L^d peptide Uganda thatare nonamers, the tum^– peptide is a 13-mer and its sequencedoes not fit the Ld binding motif. Thus, to define shorter versionsof the tum^– 13-mer and residues involved in TCR recognition,nonamer derivatives were synthesized and compared in severaldifferent binding and functional assays. From these comparisons,the peptide TQNHRALDL was found to be the optimal nonamer. CTLrecognition of Ala-substituted analogues of this peptide indicatedthat the Hls and Arg residues at positions 4 and 5 are importantfor TCR contact We propose that these basic residues of thetum^– peptide interact with the previously defined acidicresidues in the CDR3 region of several TCR known to recognizeLd-tum^– complexes.     

A Multivariate Twin Study of Autistic Traits in 12-Year-Olds: Testing the Fractionable Autism Triad Hypothesis

Autistic traits—social impairment, communication impairment, and restricted and repetitive behaviors and interests—are heritable in the general population. Previous analyses have consistently reported limited genetic and environmental overlap between autistic trait domains in samples assessed in middle childhood. Here we extend this research to parent-report data for 12-year-olds. Data from 5,944 pairs in the Twins Early Development Study were analyzed to explore the domain-specific heritability and degree of shared genetic and environmental influences across different autistic traits in the general population and among individuals scoring in the top 5% of each domain. Sex differences in the etiological estimates were also tested in these analyses. Autistic traits were moderately to highly heritable (0.58–0.88) at age 12. Bivariate genetic correlations in the full sample (0.18–0.40) and the extremes (0.24–0.67), as well as even lower unique environmental correlations, all suggested considerable fractionation of genetic and environmental influences across autistic trait domains, in line with previous findings.     

Information Communication Networks in Severe Traumatic Brain Injury

In this study we explored the use of coherence and Granger causality (GC) to separate patients in minimally conscious state (MCS) from patients with severe neurocognitive disorders (SND) that show signs of awareness. We studied 16 patients, 7 MCS and 9 SND with age between 18 and 49 years. Three minutes of ongoing electroencephalographic (EEG) activity was obtained at rest from 19 standard scalp locations, while subjects were alert but kept their eyes closed. GC was formulated in terms of linear autoregressive models that predict the evolution of several EEG time series, each representing the activity of one channel. The entire network of causally connected brain areas can be summarized as a graph of incompletely connected nodes. The 19 channels were grouped into five gross anatomical regions, frontal, left and right temporal, central, and parieto-occipital, while data analysis was performed separately in each of the five classical EEG frequency bands, namely delta, theta, alpha, beta, and gamma. Our results showed that the SND group consistently formed a larger number of connections compared to the MCS group in all frequency bands. Additionally, the number of connections in the delta band (0.1–4 Hz) between the left temporal and parieto-occipital areas was significantly different (P < 0.1%) in the two groups. Furthermore, in the beta band (12–18 Hz), the input to the frontal areas from all other cortical areas was also significantly different (P < 0.1%) in the two groups. Finally, classification of the subjects into distinct groups using as features the number of connections within and between regions in all frequency bands resulted in 100% classification accuracy of all subjects. The results of this study suggest that analysis of brain connectivity networks based on GC can be a highly accurate approach for classifying subjects affected by severe traumatic brain injury.     

The Fura-2 transient can show two types of voltage dependence at 36°C in ventricular myocytes isolated from the rat heart

We used the whole-cell patch-clamp method to investigate the voltage dependence of the L-type Ca current (I _Ca,L) and intracellular Ca (Ca_i) transient in ventricular myocytes isolated from the rat heart. Intracellular Ca was monitored using Fura-2 and the experiments were carried out at 36° C. We measured I _Ca,L by using a caesium-based internal dialysis solution to eliminate interfering K currents. The voltage dependence of peak I _Ca,L amplitude was bell-shaped: I _Ca,L was maximal at +10 mV and declined at more positive potentials. When I _Ca,L was integrated over the first 25 ms to estimate the magnitude of Ca entry, this had a very similar voltage dependence to peak I _Ca,L. In all cells, phasic Fura-2 transients were abolished by 5 μM ryanodine (a blocker of the sarcoplasmic reticulum, SR) showing that the Fura-2 transient provided an index of the magnitude of SR Ca release. For experiments measuring the Ca_i transient, we used a K-based internal dialysis solution to preserve normal excitation-contraction coupling. In 30–40% of cells, we found that the Fura-2 transient had a bell-shaped voltage dependence. This suggests that, in these cells, the primary trigger mechanism for Ca-induced Ca-release might have been Ca entry via I _Ca,L. In the remaining 60–70% of cells, the voltage dependence of the Fura-2 transient was not bell-shaped. The Fura-2 transient reached a maximum with a pulse to +10 mV, and the amplitude of the transient did not decline significantly at more positive potentials to this. In cells with a non-bell-shaped voltage dependence of the Fura-2 transient, pulses to potentials as far positive as +140 mV elicited phasic Fura-2 transients. Since this potential exceeded the Nernst potential for Ca, it was unlikely there was any tigger Ca entry via I _Ca,L at this potential. This would suggest that, in these cells, another trigger for SR Ca release (in addition to I _Ca,L) might be present. We conclude that rat ventricular myocytes, produced using a standard isolation technique and under standard recording conditions, can show either a bell-shaped or a sigmoidal voltage dependence of the Fura-2 transient. Received: 13 October 1995/Received after revision and accepted: 10 January 1996     

Genetic Covariation Between Brain Volumes and IQ,Reading Performance,and Processing Speed

Although there has been much interest in the relation between brain size and cognition, few studies have investigated this relation within a genetic framework and fewer still in non-adult samples. We analyzed the genetic and environmental covariance between structural MRI data from four brain regions (total brain volume, neocortex, white matter, and prefrontal cortex), and four cognitive measures (verbal IQ (VIQ), performance IQ (PIQ), reading ability, and processing speed), in a sample of 41 MZ twin pairs and 30 same-sex DZ twin pairs (mean age at cognitive test = 11.4 years; mean age at scan = 15.4 years). Multivariate Cholesky decompositions were performed with each brain volume measure entered first, followed by the four cognitive measures. Consistent with previous research, each brain and cognitive measure was found to be significantly heritable. The novel finding was the significant genetic but not environmental covariance between brain volumes and cognitive measures. Specifically, PIQ shared significant common genetic variance with all four measures of brain volume (r _g = .58–.82). In contrast, VIQ shared significant genetic influence with neocortex volume only (r _g = .58). Processing speed was significant with total brain volume (r _g = .79), neocortex (r _g = .64), and white matter (r _g = .89), but not prefrontal cortex. The only brain measure to share genetic influence with reading was total brain volume (r _g = .32), which also shared genetic influences with processing speed.     

The effect of age on the power/duration relationship and the intensity-domain limits in sedentary men

The time to fatigue (t) in response to high-intensity constant-load exercise decreases hyperbolically with increasing power (W˙), at least in active and younger individuals [i.e. (W˙−θ_F)t=W′, where θ_F is the critical power asymptote and W′ is the curvature constant]. Little is known, however, about the combined effects of age and sedetarity on these parameters. We therefore evaluated 17 non-trained males (9 aged 60–75 years and 8 aged below 30 years) who underwent ramp-incremental cycle ergometry and, on different days, 4 high-intensity constant-load tests to t. Compared to their younger counterparts, the older subjects presented significantly lower maximum oxygen uptake (i.e. the maximum value of oxygen uptake attained at the end of a progressive exercise with the subject exerting a presumably maximal effort, μV˙O₂), estimated lactate threshold (V˙O₂θ_L), V˙O₂θ_F, and W′ (P < 0.05). Interestingly, however, both V˙O₂θ_L and V˙O₂θ_F, when expressed as a percentage of μV˙O₂, were higher in older than in younger men [61.8 (6.2)% versus 45.4 (4.6)% and 87.8 (7.3)% versus 79.0 (8.2)%, P < 0.05, respectively]. Therefore, age was associated with an increase in the relative magnitude of the “moderate”, sub-θ_L exercise-intensity domain (+30.4%), mainly at the expense of the “very-heavy”, supra-θ_F domain (−56%). Our results demonstrate that age and sedentarity are associated with: (1) marked reductions in both the aerobic (θ_F) and anaerobic (W′) determinants of the W˙/t relationship, and (2) changes in either the absolute or relative magnitudes of the exercise-intensity domains. These findings are consistent with the notion that endurance-related parameters are less diminished with ageing than the maximal capacity, thereby mitigating the deleterious effects of senescence in the functional capacity. Accepted: 5 April 2000     

Heritability of Self-reported Phobic Fear

Twin studies on fear and phobia suggest moderate genetic effects. However, results are inconclusive regarding the presence of dominant genetic effects and sex differences. Using an extended twin design, including male and female twins (n = 5,465) and their siblings (n = 1,624), we examined the genetic and environmental influences on blood-injury, social, and agoraphobic fear and investigated their interaction with sex and age. Data of spouses (n = 708) of twins were used to evaluate assortative mating for the three fear dimensions. Results showed that there was no assortative mating for blood-injury, social and agoraphobic fear. Resemblance between biological relatives could be explained by additive and non-additive genetic effects for blood-injury and agoraphobic fear in all participants, and social fear in participants aged 14–25 years. For social fear in participants aged 26–65 only additive genetic effects were detected. Broad-sense heritability estimates ranged from 36 to 51% and were similar for men and women. Edited by John K Hewitt.     

Genes and Developmental Stabiltiy of Aggressive Behavior Problems at Home and School in a Community Sample of Twins Aged 7–12

Though behavioral genetic studies of aggression have implicated heritable and environmental factors, there is limited understanding of how these factors influence aggression across different settings and over time. Ratings for 732 twins were collected from parents and teachers during middle childhood and early adolescence. Total aggression scores on the Child Behavioral Checklist (CBCL) and Teacher Report Form (TRF) were examined at each age, across both settings, and developmentally. In this sample, aggressive behavior was moderately to largely heritable at each age within the home (.76–.84) and school (.42–.61). Across each age, ratings by parents and teachers were moderately correlated (.19–.36). Genetic and environmental effects that were limited to a particular setting were important etiological factors for aggressive behavior consistently within each setting, while only genetic factors influenced levels of aggression across both settings. Stability during these ages was due to genetic effects common to each age and the persistence of child-specific environmental experiences within each setting. These results suggest that genetic and environmental influences on children’s aggressive behavior are largely setting specific. Levels of aggression seen consistently across both settings are due to genetic influences. Developmentally stable levels of aggressive behavior result from genetic influences common to all ages and individual environmental influences whose effects persist across ages.Edited by Danielle Posthuma     

Length Adaptation of the Passive-to-Active Tension Ratio in Rabbit Detrusor

The passive and active length–tension (L–T _p and L–T _a) relationships in airway, vascular, and detrusor smooth muscles can adapt with length changes and/or multiple contractions. The present objectives were to (1) determine whether short-term adaptation at one muscle length shifts the entire L–T _a curve in detrusor smooth muscle (DSM), (2) compare adaptation at shorter versus longer lengths, and (3) determine the effect of adaptation on the T _p/T _a ratio. Results showed that multiple KCl-induced contractions on the descending limb of the original L–T _a curve adapted DSM strips to that length and shifted the L–T _a curve rightward. Peak T _a at the new length was not different from the original peak T _a, and the L–T _p curve shifted rightward with the L–T _a curve. Multiple contractions on the ascending limb increased both T _a and T _p. In contrast, multiple contractions on the descending limb increased T _a but decreased T _p. The T _p/T _a ratio on the original descending limb adapted from 0.540 ± 0.084 to 0.223 ± 0.033 (mean ± SE, n = 7), such that it was not different from the ratio of 0.208 ± 0.033 at the original peak T _a length, suggesting a role of length adaptation may be to maintain a desirable T _p/T _a ratio as the bladder fills and voids over a broad DSM length range.