Muscle strength and soft tissue composition as measured by dual energy x-ray absorptiometry in women aged 18–87 years

Dual energy x-ray absorptiometry (DEXA) offers the possibility of assessing regional soft tissue composition, i.e. lean mass (LM) and fat mass : LM may be considered a measure of muscle mass. We examined age-related differences in LM, percentage fat (%fat) and muscle strength in 100 healthy non-athletic women aged 18–87 years. Relationships between muscle strength and leg LM in 20 elite female weight lifters and in 18 inactive women with previous hip fractures were also studied. The LM and %fat of the whole body, trunk, arms and legs were derived from a whole body DEXA scan. Isokinetic knee extensor strength (KES) and flexor strength (KFS) at 30° · s^–1 were assessed using an isokinetic dynamometer. The women aged 71–87 years had 35% lower KES and KFS than the women aged 18–40 years (P < 0.0001). Differences in LM were less pronounced. The LM of the legs, for instance, was 15% lower in the old than in the young women (P < 0.0001). In a multiple regression analysis with age, body mass, height and leg LM or KES as independent variables and KES or leg LM as the dependent variable, age was the most important predictor of KES (r _partial = −0.74, P < 0.0001). The same applied to KFS. Body mass, not age, was the most important predictor of leg LM (r _partial = 0.65, P < 0.0001) and of LM at all other measurement sites. The LM measured at different regions decreased equally with increasing age. The KES:leg LM ratio was negatively correlated with age (r = −0.70, P < 0.0001). The weight lifters had significantly higher KES:leg LM ratios than age-matched controls (+12%, P < 0.0001) and vice versa for the women with previous hip fractures (–36%, P < 0.0001). In conclusion, from our study it would seem that in healthy nonathletic women, age is a more important determinant of muscle strength than is LM as measured by DEXA. Muscle strengthening exercises and inactivity seem to have a considerably stronger influence on muscle strength than on LM. Accepted: 27 August 1996     

Accuracy and precision of dual-energy X-ray absorptiometry for body composition measurements in rhesus monkeys

Accuracy of body composition measurements by dual-energy X-ray absorptiometry (DXA) was compared with direct chemical analysis in 10 adult rhesus monkeys. DXA was highly correlated (r-values > 0.95) with direct analyses of body fat mass (FM), lean mass (LM) and lumbar spine bone mineral content (BMC). DXA measurements of total body BMC were not as strongly correlated (r-value = 0.58) with total carcass ash content. DXA measurements of body FM, LM and lumbar spine BMC were not different from data obtained by direct analyses (P-values > 0.30). In contrast, DXA determinations of total BMC (TBMC) averaged 15%, less than total carcass ash measurements (P = 0.002). In conclusion, this study confirms the accurate measurement of fat and lean tissue mass by DXA in rhesus monkeys. DXA also accurately measured lumbar spine BMC but underestimated total body BMC as compared with carcass ash determinations.     

Energetics during nursing and early postweaning fasting in hooded seal (Cystophora cristata ) pups from the Gulf of St Lawrence, Canada

In this study we measured growth and milk intake and calculated energy intake and its allocation into metabolism and stored tissue for hooded seal (Cystophora cristata) pups. In addition, we measured mass loss, change in body composition and metabolic rate during the first days of the postweaning fast. The mean body mass of the hooded seal pups (n = 5) at the start of the experiments, when they were new-born, was 24.3 ± 1.3 kg (SD). They gained an average of 5.9 ± 1.1. kg · day⁻¹ of which 19% was water, 76% fat and 5% protein. This corresponds to an average daily energy deposition of 179.8 ± 16.0 MJ. The pups were weaned at an average body mass of 42.5 ± 1.0 kg 3.1 days after the experiment was initiated. During the first days of the postweaning fast the pups lost an average of 1.3 ± 0.5␣kg of body mass daily, of which 56% was water, 16% fat and 28% protein. During the nursing period the average daily water influx for the pups was 124.6 ± 25.8 ml · kg⁻¹. The average CO₂ production during this period was 1.10 ± 0.20 ml · g⁻¹ · h⁻¹, which corresponds to a field metabolic rate of 714 ± 130 kJ ·  kg⁻¹ · day⁻¹, or 5.8 ± 1.1 times the predicted basal metabolic rate according to Kleiber (1975). During the postweaning fast the average daily water influx was reduced to 16.1 ± 6.6 ml · kg⁻¹. The average CO₂ production in␣this period was 0.58 ± 0.17 ml · g⁻¹ · h⁻¹ which corresponds to a field metabolic rate of 375 ± 108 kJ · kg⁻¹ · day⁻¹ or 3.2 ± 0.9 times the predicted basal metabolic rate. Average values for milk composition were 33.5% water, 58.6% fat and 6.2% protein. The pups drank an average of 10.4 ± 1.8␣kg of milk daily, which represents an energy intake of 248.9 ± 39.1 MJ · day⁻¹. The pups were able to store 73.2 ± 7.7% of this energy as body tissue. Accepted: 15 August 1996     

The heat increment of feeding in house wren chicks: magnitude, duration, and substitution for thermostatic costs

The heat increment of feeding (HIF), a transient postprandial increase in metabolic rate, is the energy cost of processing a meal. We measured HIF in house wren chicks (Troglodytes aedon) ranging in mass from 1.6 to 10.3 g. This mass range (age 2–10 days) spanned a transition from blind, naked, ectothermic chicks through alert, endothermic birds with nearly complete feathering. We fed chicks crickets (2.7–10% of chick body mass) and determined HIF from continuous measurements of oxygen consumption rate (O₂) before and after meals. At warm ambient temperatures (T _a) of 33–36 °C, the magnitude of HIF (in ml O₂ or joules) was linearly related to meal mass and was not affected by chick mass. HIF accounted for 6.3% of ingested energy, which is within the range of results for other carnivorous vertebrates. The duration of HIF was inversely related to chick mass; 10-g chicks processed a standard meal approximately twice as fast as 2-g chicks. HIF duration increased with increasing meal mass. The peak O₂ during HIF, expressed as the factorial increase above resting metabolism, was independent of body mass and meal mass. In large, endothermic chicks ( > 8 g), HIF substituted for thermoregulatory heat production at low T _a. Accepted: 11 December 1996     

Influence of soil hydric parameters on the winter cold hardiness of a burrowing beetle, Leptinotarsa decemlineata (Say)

This investigation examined the influence of soil moisture and associated parameters on the cold hardiness of the Colorado potato beetle (Leptinotarsa decemlineata Say), a temperate-zone species that overwinters in terrestrial burrows. The body mass and water content of adult beetles kept in sand at 4 °C varied over a 16-week period of diapause according to the substratum's moisture content. Changes in body water content, in turn, influenced the crystallization temperature (range −3.3 to −18.4 °C; n = 417), indicating that environmental moisture indirectly determined supercooling capacity, a measure of physiological cold hardiness. Beetles held in dry sand readily tolerated a 24-h exposure to temperatures ranging from 0° to −5 °C, but those chilled in sand containing as little as 1.7% water (dry mass) had elevated mortality. Thus, burrowing in dry soils not only promotes supercooling via its effect on water balance, but may also inhibit inoculative freezing. Mortality of beetles exposed to −5 °C for 24 h was lower in substrates composed of sand, clay and/or peat (36–52%) than in pure silica sand (78%) having an identical water content (17.0% dry mass). In addition to moisture, the texture, structure, water potential, and other physico-chemical attributes of soil may strongly influence the cold hardiness and overwintering survival of burrowing insects. Accepted: 10 September 1996     

Body fluid homeostasis and cardiovascular adjustments during submaximal exercise: influence of chewing coca leaves

 The present study was undertaken to determine the haematological and cardiovascular status, at rest and during prolonged (1 h) submaximal exercise (approximately 70% of peak oxygen uptake) in a group (n = 12) of chronic coca users after chewing approximately 50 g of coca leaves. The results were compared to those obtained in a group (n = 12) of nonchewers. At rest, coca chewing was accompanied by a significant increase in heart rate [from 60 (SEM 4) TO 76 (SEM 3) beats · min⁻¹], in haematocrit [from 53.2 (SEM 1.2) to 55.6 (SEM 1.1)%] in haemoglobin concentration, and plasma noradrenaline concentration [from 2.8 (SEM 0.4) to 5.0 (SEM 0.5) μmol · l⁻¹]. It was calculated that coca chewing for 1 h resulted in a significant decrease in blood [−4.3 (SEM 2.2)%] and plasma [−8.7 (SEM 1.2)%] volume. During submaximal exercise, coca chewers displayed a significantly higher heart rate and mean arterial blood pressure. The exercise-induced haemoconcentration was blunted in coca chewers compared to nonchewers. It was concluded that the coca-induced fluid shift observed at rest in these coca chewers was not cumulative with that of exercise, and that the hypovolaemia induced by coca chewing at rest compromised circulatory adjustments during exercise. Accepted: 29 October 1996     

Effects of 3 days of carbohydrate supplementation on muscle glycogen content and utilisation during a 1-h cycling performance

This study compared the effects of supplementing the normal diets of six trained cyclists [maximal oxygen uptake O_2max) 4.5 (0.36)l · min⁻¹; values are mean (SD)] with additional carbohydrate (CHO) on muscle glycogen utilisation during a 1-h cycle time-trial (TT). Using a randomised crossover design, subjects consumed either their normal diet (NORM) for 3 days, which consisted of 426 (137) g · day⁻¹ CHO [5.9 (1.4) g · kg⁻¹ body mass (BM)], or additional CHO (SUPP) to increase their intake to 661 (76) g · day⁻¹ [9.3 (0.7) g · kg⁻¹ BM]. The SUPP diet elevated muscle glycogen content from 459 (83) to 565 (62) mmol · kg⁻¹ dry weight (d.w.) (P < 0.05). However, despite the increased pre-exercise muscle glycogen stores, there was no difference in the distance cycled during the TT [40.41 (1.44) vs 40.18 (1.76) km for NORM and SUPP, respectively]. With NORM, muscle glycogen declined from 459 (83) to 175 (64) mmol · kg⁻¹ d.w., whereas with SUPP the corresponding values were 565 (62) and 292 (113) mmol · kg⁻¹ d.w. Accordingly, both muscle glycogen utilisation [277 (64) vs 273 (114) mmol · kg⁻¹ d.w.] and total CHO oxidation [169 (20) vs 165 (30) g · h⁻¹ for NORM and SUPP, respectively] were similar. Neither were there any differences in plasma glucose or lactate concentrations during the two experimental trials. Plasma glucose concentration averaged 5.5 (0.5) and 5.6 (0.6) mmol · l⁻¹, while plasma lactate concentration averaged 4.4 (1.9) and 4.4 (2.3) mmol · l⁻¹ for NORM and SUPP, respectively. The results of this study show that when well-trained subjects increase the CHO content of their diet for 3 days from 6 to 9 g · kg⁻¹ BM there is only a modest increase in muscle glycogen content. Since supplementary CHO did not improve TT performance, we conclude that additional CHO provides no benefit to performance for athletes who compete in intense, continuous events lasting 1 h. Furthermore, the substantial muscle CHO reserves observed at the termination of exercise indicate that whole-muscle glycogen depletion does not determine fatigue at this exercise intensity and duration. Accepted: 25 November 1996     

The influence of either no fluid or carbohydrate-electrolyte fluid ingestion and the environment (thermoneutral versus hot and humid) on running economy after prolonged, high-intensity exercise

This study investigated the effects on running economy (RE) of ingesting either no fluid or an electrolyte solution with or without 6% carbohydrate (counterbalanced design) during 60-min running bouts at 80% maximal oxygen consumption (V˙O_2max). Tests were undertaken in either a thermoneutral (22–23°C; 56–62% relative humidity, RH) or a hot and humid natural environment (Singapore: 25–35°C; 66–77% RH). The subjects were 15 young adult male Singaporeans [V˙O_2max = 55.5 (4.4 SD) ml kg⁻¹ min⁻¹]. The RE was measured at 3 m s⁻¹ [65 (6)% V˙O_2max] before (RE1) and after each prolonged run (RE2). Fluids were administered every 2 min, at an individual rate determined from prior tests, to maintain body mass (group mean = 17.4 ml min⁻¹). The V˙O₂ during RE2 was higher (P < 0.05) than that during the RE1 test for all treatments, with no differences between treatments (ANOVA). The mean increase in V˙O₂ from RE1 to RE2 ranged from 3.4 to 4.7 ml kg⁻¹ min⁻¹ across treatments. In conclusion, the deterioration in RE at 3 m s⁻¹ (65% V˙O_2max) after 60 min of running at 80% V˙O_2max appears to occur independently of whether fluid is ingested and regardless of whether the fluid contains carbohydrates or electrolytes, in both a thermoneutral and in a hot, humid environment. Accepted: 30 October 1997     

Phenotypic variation in seasonal adjustments of testis size, body weight, and food intake in deer mice: role of pineal function and ambient temperature

We investigated pineal function as well as reproductive and energetic characteristics in male deer mice (Peromyscus maniculatus) that differentially respond to short photoperiod with full, partial or no gonadal regression. In mice at both high (23 °C) and low temperature (1 °C), these phenotypic differences in reproductive responses to short days were not reflected by differences in urinary excretion of 6-sulphatoxy-melatonin, the main metabolite of pineal melatonin. Neither duration nor amplitude or phase-angle of nocturnal peaks in 6-sulphatoxymelatonin significantly differed between reproductive phenotypes at either temperature. Differences in testis size were, however, associated with different energy requirements. In gonadally regressed males only, food intake and body weight were significantly (P < 0.01) reduced by up to 29% and 13% respectively. Chronic cold exposure (5 °C) had no effect on the proportion of males undergoing testicular regression under short days, but caused a general elevation in body weights among all mice (P < 0.05). Phenotypic differences in body weight and food intake were maintained in the cold. Together, these results suggest that within-population variation of reproductive responses in male deer mice is based on post-pineal differences in the regulation of gonadal function, and that phenotypic characteristics in reproductive and energetic responses to short days are largely unaffected by ambient temperature. Accepted: 2 October 1995     

Effects of hydration state on hormonal and renal responses during moderate exercise in the heat

The effects of hydromineral hormones and catecholamines on renal concentrating ability at different hydration states were examined in five male volunteers while they performed three trials. Each of these trials comprised a 60-min exercise bout on a treadmill (at 50% of maximal oxygen uptake) in a warm environment (dry bulb temperature, 35°C; relative humidity, 20–30%). In one session, subjects were euhydrated before exercise (C). In the two other sessions, after thermal dehydration (loss of 3% body mass) which markedly reduced plasma volume (PV) and increased plasma osmolality (osm_pl), the subjects exercised either not rehydrated (Dh) or rehydrated (Rh) by drinking 600 ml of mineral water before and 40 min after the onset of exercise. During exercise in the Dh compared to C state, plasma renin, aldosterone, arginine vasopressin (AVP), noradrenaline and adrenaline concentrations were increased (P < 0.05). A reduction in creatinine clearance and urine flow was also observed (P < 0.05) together with a decrease in urine osmolality, osmolar clearance and sodium excretion, while free water clearance increased (P < 0.05). However, compared to Dh, Rh partially restored PV and osm_pl and induced a marked reduction in the time courses of both the plasma AVP and catecholamine responses (P < 0.05). Values for renal water and electrolyte excretion were intermediate between those of Dh and C. Plasma atrial natriuretic peptide presented similar changes whatever the hydration state. These results demonstrate that during moderate exercise in the heat, renal concentrating ability is paradoxically reduced by prior dehydration in spite of high plasma AVP levels, and might be the result of marked activation of the sympatho-adrenal system. Rehydration, by reducing this activation, could partially restore the renal concentrating ability despite the lowered plasma AVP. Accepted: 23 April 1997     

Aged-Related Changes in Body Composition and Association between Body Composition with Bone Mass Density by Body Mass Index in Chinese Han Men over 50-year-old

Objectives

Aging, body composition, and body mass index (BMI) are important factors in bone mineral density (BMD). Although several studies have investigated the various parameters and factors that differentially influence BMD, the results have been inconsistent. Thus, the primary goal of the present study was to further characterize the relationships of aging, body composition parameters, and BMI with BMD in Chinese Han males older than 50 years.

Methods

The present study was a retrospective analysis of the body composition, BMI, and BMD of 358 Chinese male outpatients between 50 and 89 years of age that were recruited from our hospital between 2009 and 2011. Qualified subjects were stratified according to age and BMI as follows: 50–59 (n = 35), 60–69 (n = 123), 70–79 (n = 93), and 80–89 (n = 107) years of age and low weight (BMI: < 20 kg/m²; n = 21), medium weight (20 ≤ BMI < 24 kg/m²; n = 118), overweight (24 ≤ BMI < 28 kg/m²; n = 178), and obese (BMI ≥ 28 kg/m²; n = 41). Dual-energy X-ray absorptiometry (DEXA) was used to assess bone mineral content (BMC), lean mass (LM), fat mass (FM), fat-free mass (FFM), lumbar spine (L1-L4) BMD, femoral neck BMD, and total hip BMD. Additionally, the FM index (FMI; FM/height²), LM index (LMI; LM/height²), FFM index (FFMI; [BMC+LM]/height²), percentage of BMC (%BMC; BMC/[BMC+FM+LM] × 100%), percentage of FM (%FM; FM/[BMC+FM+LM] × 100%), and percentage of LM (%LM; LM/(BMC+FM+LM) × 100%) were calculated. Osteopenia or osteoporosis was identified using the criteria and T-score of the World Health Organization.

Results

Although there were no significant differences in BMI among the age groups, there was a significant decline in height and weight according to age (p < 0.0001 and p = 0.0002, respectively). The LMI and FFMI also declined with age (both p < 0.0001) whereas the FMI exhibited a significant increase that peaked in the 80-89-years group (p = 0.0145). Although the absolute values of BMC and LM declined with age (p = 0.0031 and p < 0.0001, respectively), there was no significant difference in FM. In terms of body composition, there were no significant differences in %BMC but there was an increase in %FM (p < 0.0001) and a decrease in %LM (p < 0.0001) with age. The femoral neck and total hip BMD significantly declined with age (p < 0.0001 and p = 0.0027, respectively) but there were no differences in L1-L4. BMD increased at all sites (all p < 0.01) as BMI increased but there were declines in the detection rates of osteoporosis and osteopenia (both p < 0.001). A logistic regression revealed that when the medium weight group was given a BMI value of 1, a decline in BMI was an independent risk factor of osteoporosis or osteopenia, while an increase in BMI was a protective factor for BMD. At the same time, BMD in L1-L4 exhibited a significant positive association with FMI (p = 0.0003) and the femoral neck and total hip BMDs had significant positive associations with FFMI and LMI, respectively (both p < 0.0001).

Conclusions

These data indicate that LMI and FFMI exhibited significant negative associations with aging in Chinese Han males older than 50 years, whereas FMI had a positive association. BMD in the femoral neck and total hip declined with age but an increased BMI was protective for BMD. LMI and FFMI were protective for BMD in the femoral neck and total hip.     

Walking performance and economy in chronic heart failure patients pre and post exercise training

The effect of a 3-week exercise programme on performance and economy of walking was analysed in 16 male patients with chronic heart failure [mean age 51.8 (SD 6.9) years, height 174.9 (SD 6.3) cm, body mass 75.3 (SD 11.5) kg, ejection fraction 20.8 (SD 5.0)%]. They were submitted to a cardiopulmonary exercise test on a cycle ergometer and a 6-min walking test on a treadmill before and after the period of exercise training. The training programme consisted of interval cycle (five times a week for 15 min), and treadmill ergometer training (three times a week for 10 min) at approximately 70% cycling peak oxygen uptake (O_2peak) and supplementary exercises (three times a week for 20 min). Compared to the pre values cycling O_2peak [11.9 (SD 2.9) vs 14.0 (SD 2.3) ml ·  kg^–1 · min^–1], maximal self paced walking speed [0.68 (SD 0.33) vs 1.16 (SD 0.30) m · s^–1], and net walking power [2.16 (SD 0.89) vs 2.73 (SD 0.91) W · kg^–1] had increased (P < 0.01) while net energy cost [3.31 (SD 0.66) vs 2.33 (SD 0.38) J · kg^–1 ·  m^–1] had decreased (P < 0.001) after the training period. Approximately 42% of the increase of walking speed resulted from a higher walking power output, whereas approximately 58% corresponded to a positive effect on walking economy. The improvement in walking economy was a function of an increase in walking velocity itself and a result of a more efficient walking technique. These results would indicate that in patients with marked exercise intolerance, adequate exercise training programmes could contribute to favourable metabolic changes with positive effects on the economy of motion. Accepted: 29 August 1996     

Cold induced vasodilatation and cardiovascular responses in humans during cold water immersion of various upper limb areas

To study the physiological responses induced by immersing in cold water various areas of the upper limb, 20 subjects immersed either the index finger (T1), hand (T2) or forearm and hand (T3) for 30 min in 5°C water followed by a 15-min recovery period. Skin temperature of the index finger, skin blood flow (Q_sk) measured by laser Doppler flowmetry, as well as heart rate (HR) and mean arterial blood pressure (ˉBP_a) were all monitored during the test. Cutaneous vascular conductance (CVC) was calculated as Q_sk / ˉBP_a. Cold induced vasodilatation (CIVD) indices were calculated from index finger skin temperature and CVC time courses. The results showed that no differences in temperature, CVC or cardiovascular changes were observed between T2 and T3. During T1, CIVD appeared earlier compared to T2 and T3 [5.90 (SEM 0.32) min in T1 vs 7.95 (SEM 0.86) min in T2 and 9.26 (SEM 0.78) min in T3, P < 0.01]. The HR was unchanged in T1 whereas it increased significantly at the beginning of T2 and T3 [+13 (SEM 2) beats · min⁻¹ in T2 and +15 (SEM 3) beats · min⁻¹ in T3, P < 0.01] and then decreased at the end of the immersion [−12 (SEM 3) beats · min⁻¹ in T2, and −15 (SEM 3) beats · min⁻¹ in T3, P < 0.01]. Moreover, ˉBP_aincreased at the beginning of T1 but was lower than in T2 and T3 [+9.3 (SEM 2.5) mmHg in T1, P < 0.05;  +20.6 (SEM 2.6) mmHg and 26.5 (SEM 2.8) mmHg in T2 and T3, respectively, P < 0.01]. The rewarming during recovery was faster and higher in T1 compared to T2 and T3. These results showed that general and local physiological responses observed during an upper limb cold water test differed according to the area immersed. Index finger cooling led to earlier and faster CIVD without significant cardiovascular changes, whereas hand or forearm immersion led to a delayed and slower CIVD with a bradycardia at the end of the test. Accepted: 26 November 1996     

Directionality of the tympanal vibrations in a cicada: a biophysical analysis

1. Laser vibrometry and acoustic measurements were used to study the biophysics of directional hearing in males and females of a cicada, in which most of the male tympanum is covered by thick, water filled tissue “pads”. 2. In females, the tympanal vibrations are very dependent on the direction of sound incidence in the entire frequency range 1–20 kHz, and especially at the main frequencies of the calling song (3–7 kHz). At frequencies up to 10 kHz, the directionality disappears if the contralateral tympanum, metathoracic spiracle, and folded membrane are blocked with Vaseline. This suggests some pressure-difference receiver properties in the ear. 3. In males, the tympanal vibrations depend on the direction of sound incidence only within narrow frequency bands (around 1.8 kHz and at 6–7 kHz). At frequencies above 10–12 kHz, the directionality appears to be determined by diffraction, and the ear seems to work as a pressure receiver. The peak in directionality at 6–7 kHz disappears when the contralateral timbal, but not the tympanum, is covered. Covering the thin ventral abdominal wall causes the peak around 1.8 kHz to disappear. 4. Most observed tympanal directionalities, except around 1.8 kHz in males, are well predicted from measured transmissions of sound through the body and measured values of sound amplitude and phase at the ears at various directions of sound incidence. Accepted: 18 October 1996     

Identification of plant volatiles activating single receptor neurons in the pine weevil (Hylobius abietis)

Naturally produced plant volatiles, eliciting responses of single olfactory receptor neurons in the pine weevil, have been identified by gas chromatography linked with mass spectrometry. The receptor neurons (n = 72) were classified in 30 types, according to the compound which elicited the strongest response in each neuron, 20 of which compounds were identified. Most potent for 14 types of neurons (n = 50) were monoterpenes, including bicyclic (e.g. α-pinene, camphor and myrtenal) for 8 types (n = 32), monocyclic (limonene, carvone, α-terpinene) for 3 types (n = 12) and acyclic (e.g. β-myrcene and linalool) for 3 types (n = 6). Other compounds eliciting strongest responses of a neuron were five sesquiterpenes, including α-copaene and a farnesene-isomer, and an anethole type which has no biosynthetic relationship with terpenes. Within one type, receptor neurons with quite selective responses to the most potent compound as well as neurons with additional responses to several, structurally similar compounds were found, indicating that the neurons may have the same functional types of membrane receptors, but different sensitivities. Response spectra of neurons within the bicyclic-, mono-cyclic and acyclic types showed more overlapping than across the neuron types. Minimal overlapping response spectra was found between monoterpene and sesquiterpene neurons. The results suggest that this structure-activity relationship is significant for encoding plant odour information in the pipe weevil. Accepted: 6 January 1997     

Blood flow in the carotid artery during breath-holding in relation to diving bradycardia

The present study investigated the mechanism of diving bradycardia. A group of 14 healthy untrained male subjects were examined during breath-holding either out of the water (30–33°C), in head-out immersion, or in whole-body submersion (27–29°C) in a diving pool. Blood velocity, blood volume flow in the carotid artery, diastolic blood pressure and electrocardiogram were measured and recorded during the experiments. The peak blood velocity increased by 13.6% (P < 0.01) and R-wave amplitude increased by 57.1% (P < 0.005) when the subjects entered water from air. End-diastolic blood velocity in the carotid artery increased significantly during breath-holding, e.g. increased from 0.20 (SD 0.02) m · s⁻¹ at rest to 0.33 (SD 0.04) m · s⁻¹ (P < 0.001) at 50.0 s in breath-hold submersion to a 2.0-m depth. Blood volume flow in the carotid artery increased by 26.6% (P < 0.05) at 30 s and 36.6% (P < 0.001) at 40 s in breath-hold submersion to a 2.0-m depth. Diastolic blood pressure increased by 15.4% (P < 0.01) at 60 s during breath-holding in head-out immersion. Blood volume flow, and diastolic blood pressure increased significantly more and faster during breath-holding in submersion than out of the water. There was a good negative correlation with the heart rate: the root mean square correlation coefficient r was 0.73 (P < 0.001). It was concluded that an increased accumulation of blood in the aorta and arteries at end-diastole and decreased venous return, caused by an increase in systemic peripheral resistance during breath-holding, underlies diving bradycardia. Accepted: 22 November 1996     

The effect of gender on left ventricular function immediately after the wingate test

The effect of gender on left ventricular systolic function and exercise haemodynamics in healthy young subjects was studied during 30-s all-out sudden strenuous dynamic exercise. A group of 22 men [19.3 (SD 1) years] 20 women [19.1 (SD 1) years] volunteered to participate in this study. Two-dimensional direct M-mode and Doppler echocardiograph studies were performed with the subject in the sitting position. The Doppler examination of flow was located with continuous-wave, interrogating ascending aorta measurements. The subjects completed the study without showing any electrocardiograph abnormalities. An interaction effect with stroke volume (P < 0.05) was characterized by a decrease in the men and an increase of stroke volume in the women. Cardiac output rose significantly (P < 0.05) up to 14.5 (SD 6) l · min⁻¹) for the men and 12.1 (SD 4) l · min⁻¹ for the women compared to the rest values [5.8 (SD 0.4) and 4.7 (SD 0.5) l · min⁻¹, respectively]. Flow velocity integral and acceleration time differed significantly between the two groups at rest (P < 0.05). During exercise these differences showed an interaction effect (P < 0.05). These results would indicate that normal men and women respond to sudden strenuous exercise by reducing their left ventricular systolic function, with a significantly greater decrease in women (P < 0.05). The gender differences in the haemodynamic responses during the present study, may, as suggested by others, be attributable to differences in energy metabolism. In addition, changes in Doppler parameters of aortic flow, haemodynamics and blood pressure responses during sudden strenuous exercise differed markedly from those seen before with endurance exercise. Accepted: 8 January 1997     

Seed dispersal in Cakile edentula var. lacustris : decoupling the fitness effects of density and distance from the home site

A factorial design of three densities of siblings at three local distances from seed parents was employed to distinguish effects of density from effects of dispersal distance on lifespan and fruit production of Cakile edentula var. lacustris, a plant with heteromorphic seeds. The segmented fruits produce two seed types: proximal and distal, with distal seeds having greater mass and greater dispersibility. Effects of longer distances (0.5 km and 30 km) on lifespan and fruit production were investigated using plants at low density. The prediction was tested that the greater seed mass of distal seeds increases fitness when seeds are dispersed into sites of unknown quality away from the home site or when seeds are dispersed to low density. High density caused earlier mortality and lower probability of reproduction. Distance from the maternal plant did not influence lifespan or reproduction at distances of 15 m or less, but lifespan was longer 0.5 km from the home site. No interaction was detected between the effects of density and distance on either lifespan or total fitness. Environmental conditions that influence fitness did not vary as a function of dispersal distance in this system, and favorable conditions at the home site did not persist between generations. Therefore, selection on dispersion patterns in natural conditions is likely to be through effects of density rather than dispersal distance. Proximal seeds had greater reproduction than distal seeds at the home site, and distal seeds had greater reproduction at the more distant sites (but not the most distant site), as expected, but these performance differences could not be attributed to differences in mass between the two seed types. Reduced seed mass was favored at the most distant site, but larger seed mass was favored most strongly at low density. Seeds that are dispersed to low density are larger, suggesting that although kin selection may limit the effectiveness of individual selection to increase seed mass under conditions of sibling competition, density-dependent individual selection on seed mass, rather than distant-dependent selection, also contributes to the observed associations among seed type, seed mass and dispersal ability. Received: 21 October 1996 / Accepted: 4 December 1996     

Short latency vestibular evoked potentials in the Japanese quail (Coturnix coturnix japonica)

Short-latency vestibular-evoked potentials to pulsed linear acceleration were characterized in the quail. Responses occurred within 8 ms following the onset of stimuli and were composed of a series of positive and negative peaks. The latencies and amplitudes of the first four peaks were quantitatively characterized. Mean latencies at 1.0 g ms⁻¹ ranged from 1265 ± 208 μs (P1, N = 18) to 4802 ± 441 μs (N4, N = 13). Amplitudes ranged from 3.72 ± 1.51 μV (P1/N1, N = 18) to 1.49 ± 0.77 μV (P3/N3, N = 16). Latency-intensity (LI) slopes ranged from −38.7 ± 7.3 μs dB⁻¹ (P1, N = 18) to −71.6 ± 21.9 μs dB⁻¹ (N3, N = 15) and amplitude-intensity (AI) slopes ranged from 0.20 ± 0.08 μV dB⁻¹ (P1/N1, N = 18) to 0.07 ± 0.04 μV dB⁻¹ (P3/N3, N = 11). The mean response threshold across all animals was −21.83 ± 3.34 dB re: 1.0 g ms⁻¹ (N = 18). Responses remained after cochlear extirpation showing that they could not depend critically on cochlear activity. Responses were eliminated by destruction of the vestibular end organs, thus showing that responses depended critically and specifically on the vestibular system. The results demonstrate that the responses are vestibular and the findings provide a scientific basis for using vestibular responses to evaluate vestibular function through ontogeny and senescence in the quail. Accepted: 18 January 1997     

Temperature regulation and metabolism of an Australian bat, Chalinolobus gouldii (Chiroptera: Vespertilionidae) when euthermic and torpid

The thermal and metabolic physiology of Chalinolobus gouldii, an Australian vespertilionid bat, was studied in the laboratory using flow-through respirometry. Chalinolobus gouldii exhibits a clear pattern of euthermic thermoregulation, typical of endotherms with respect to body temperature and rate of oxygen consumption. The basal metabolic rate of euthermic Chalinolobus gouldii is approximately 86% of that predicted for a 17.5-g mammal and falls into the range of mass-specific basal metabolic rates ascribed to vespertilionid bats. However, like most vespertilionid bats, Chalinolobus gouldii displays extreme thermolability. It is able to enter into torpor and spontaneously arouse at ambient temperatures as low as 5 °C. Torpid bats thermoconform at moderate ambient temperature, with body temperature ≈ ambient temperature, and have a low rate of oxygen consumption determined primarily by Q ₁₀ effects. At low ambient temperature (< 10 °C), torpid C. gouldii begin to regulate their body temperature by increased metabolic heat production; they tend to maintain a higher body temperature at low ambient temperature than do many northern hemisphere hibernating bats. Use of torpor leads to significant energy savings. The evaporative water loss of euthermic bats is relatively high, which seems unusual for a bat whose range includes extremely arid areas of Australia, and is reduced during torpor. The thermal conductance of euthermic C. gouldii is less than that predicted for a mammal of its size. The thermal conductance is considerably lower for torpid bats at intermediate body temperature and ambient temperature, but increases to euthermic values for torpid bats when thermoregulating at low ambient temperature. Accepted: 22 August 1996