bluuebunny/crossref_metadata_2025 huggingface dataset:
Restoration of peak vascular conductance after simulated microgravity by maximal exercise
Authors: Engelke Keith A. , Convertino Victor A. , Doerr Donald F. , Maples Arthur B.
Published: March 2003

We sought to determine if (i) peak vascular conductance of the calf was reduced following prolonged exposure to simulated microgravity, and (ii) if maximal cycle ergometry performed at the end of microgravity exposure stimulated a restoration of peak calf vascular conductance. To do this, peak vascular conductance of the calf was recorded following ischaemic plantar flexion exercise to fatigue in seven men after 16 days of head‐down tilt (HDT) under two conditions: (i) after one bout of maximal supine cycle ergometry completed 24 h prior to performance of ischaemic plantar flexion exercise, and (ii) in a control (no cycle ergometry) condition. Following HDT, peak vascular conductance was reduced in the control condition (0·38 ± 0·02 to 0·24 ± 0·02 ml 100 ml−1 min−1 mmHg−1; P = 0·04), but was restored when subjects performed cycle ergometry (0·33 ± 0·05 to 0·28 ± 0·04 ml 100 ml−1 min−1 mmHg−1; P = 0·46). After HDT, time to fatigue during ischaemic plantar flexion exercise was not different from pre‐HDT 24 h after performance of exhaustive cycle ergometry (120 ± 24 vs. 122 ± 19 s), but was decreased in the control condition (116 ± 11 vs. 95 ± 8 s; P = 0·07). These data suggest that a single bout of maximal exercise can provide a stimulus to restore peak vascular conductance and maintain time to fatigue during performance of ischaemic plantar flexion exercise.
Effects of a sympathetic activation by lower body negative pressure on glucose and lipid metabolism
Authors: Henry  , Trueb  , Sartori  , Scherrer  , Jéquier  , Tappy
Published: March 2003

The effects of a sympathetic activation elicited by a lower body negative pressure (LBNP) (at −15 mmHg for 75 min) were assessed in 7 healthy subjects on two occasions: (i) in post‐absorptive conditions, and (ii) during glucose infusion (22·2 μmol kg−1 min−1). LBNP increased plasma norepinephrine concentration and heart rate. It did not alter whole‐body glucose metabolism (measured with [6,6‐2H]glucose) and glycerol turnover (measured with [1,1,2,3,3‐2H]glycerol). Interstitial glycerol concentrations were monitored with microdialysis in subcutaneous adipose tissue and in skeletal muscle. LBNP increased dialysate glycerol concentrations in muscle by 16% (P < 0·03) but not in adipose tissue in post‐absorptive conditions, and by 37% in adipose tissue (P < 0·05) but not in muscle during glucose infusion. These results indicate that an LBNP‐induced sympathetic activation (i) does not increase endogenous glucose production, and (ii) induces only a slight stimulation of lipolysis in adipose tissue during glucose infusion.
Prostaglandin inhibition causes an increase in reactive hyperaemia after ischaemic exercise in human forearm
Authors: Naylor  , Shoemaker  , Brock  , Hughson
Published: March 2003

The hypothesis that prostaglandins contribute to the reactive hyperaemia after 5 min of ischaemia or 5 min of ischaemic exercise was investigated in six men by inhibiting prostaglandin production with ibuprofen (1800 mg) and indomethacin (225 mg) over 24 h before testing. Blood flow was measured continuously in the baseline and after ischaemia by combined pulsed and echo Doppler as the product of velocity and cross‐sectional area. After 5 min of ischaemia, there were no differences in blood flow between placebo and the two drug conditions, except at 5 and 10 s when flow with indomethacin was greater than both placebo and ibuprofen. After 5 min of ischaemic exercise, blood flow was significantly greater as a consequence of increased vascular conductance in each of ibuprofen and indomethacin than placebo from 5 until 90 s of recovery. We conclude that prostaglandin inhibition had little or no effect on reactive hyperaemia after 5 min of circulatory occlusion alone, but that blood flow after ischaemic exercise was elevated due to increased vascular conductance when prostaglandin synthesis was inhibited.
Systolic and diastolic changes in human coronary blood flow during Valsalva manoeuvre
Authors: Federici  , Ciccone  , Gattullo  , Losano
Published: March 2003

Valsalva manoeuvre is reported to be sometimes successful for the relief of angina pectoris. The present study investigated how haemodynamic changes produced by Valsalva manoeuvre can interact to improve the relationship between cardiac work and coronary blood flow. Ten male subjects aged 53 ± 12 years (SD) were considered. Blood velocity in the internal mammary artery, previously anastomosed to the left descending coronary artery, was studied with Doppler technique. The subjects performed Valsalva manoeuvres by expiring into a tube connected to a mercury manometer, to develop a pressure of 40 mmHg. The arterial blood pressure curve was continuously monitored with a Finapres device from a finger of the left hand. During expiratory effort, an increase in heart rate and a decrease in arterial pulse pressure were followed by a more delayed and progressive increase in mean and diastolic pressures. Systolic blood velocity markedly decreased along with the reduction in pulse pressure and increase in heart rate. By contrast, diastolic and mean coronary blood velocities did not show any significant change. Since it is known that the Valsalva manoeuvre strongly reduces stroke volume and cardiac output, it is likely that a reduction in cardiac work also takes place. Since in diastole, i.e. when the myocardial wall is better perfused, coronary blood velocity did not show any significant reduction, it is likely that unchanged perfusion in the presence of reduced cardiac work is responsible for the relief from angina sometimes observed during Valsalva manoeuvre. It is also likely that the increase in heart rate prevents the diastolic and mean blood coronary velocity from decreasing during the expiratory strain, when an increased sympathetic discharge could cause vasoconstriction through the stimulation of the coronary α‐receptors.
The relation between mitral annulus motion and ejection fraction changes with age and heart size
Authors: Emilsson Kent , Wandt Birger
Published: March 2003

Mitral annulus motion (MAM) has recently been introduced as an index of left ventricular function. Several echocardiographic studies have shown good agreement between ejection fraction (EF) and MAM × 5, where MAM is the total mitral annulus motion, measured in mm, and EF is expressed as a percentage. This means that if MAM is used for estimation of left ventricular function, the conversion factor 5 is used, if the function is expressed as EF. In these studies, the mean age of the patients was over 60 years. The present study, including 102 patients, shows that in patients aged 20–40 years, the conversion factor is about 4·3, in patients aged 41–60 years it is about 4·6 and in patients aged 61–80 years it is about 5·0. It was also found that the ratio EF/MAM decreases with increasing height and left ventricular diameter, both variables closely connected to heart size. The results suggest that when MAM is used in assessment of left ventricular function, it is unwise to express the function in terms of EF. It is preferable to use MAM as a direct index of ventricular function, using reference values referred to aged and height. If the estimated function is expressed in terms of EF, different converting factors must be used depending on the age of the patients.
Well‐being and cerebral oxygen saturation during acute heart failure in humans
Authors: Madsen  , Nielsen  , Christiansen
Published: March 2003

Cerebral symptoms and near‐infrared spectrophotometry‐determined cerebral oxygen saturation (ScO2) were followed in patients treated for normotensive acute congestive heart failure. The reproducibility and normal range for ScO2 were established from 39 resting subjects without cardio‐respiratory disease: the ScO2 ranged from 55 to 78% with a coefficient of variation for triple determination of 6%. Patients rated cerebral symptoms on a scale with end‐points of 0 (best) and 10 (worst). In eight patients with acute heart failure, arterial oxygen tension increased during decongestive treatment, from 9·1 (4·9–10) to 10·4 kPa (7·3–17); median with range, as did arterial oxygen saturation, from 94 (48–97) to 97% (87–99) (P<0·02), whereas the mean arterial pressure, heart rate and arterial carbon dioxide tension remained unchanged. The cerebral symptom score improved from 8 (3–10) to 1 (1–9) and the ScO2 increased from 34 (20–58) to 50% (19–91) (P<0·02). A ninth patient presented with a silent but massive myocardial infarction: she was cerebrally obtunded with a ScO2 of 18% and soon died. In patients with normotensive acute heart failure and cerebral symptoms, cerebral oxygen saturation is low, and during successful treatment ScO2 increases with the well‐being of the patient.
The relation between ejection fraction and mitral annulus motion before and after direct‐current electrical cardioversion
Authors: Emilsson  , Wandt
Published: March 2003

Mitral annulus motion (MAM) and the relation between left ventricular ejection fraction (EF) and MAM has been shown to differ between patients with sinus rhythm and patients with atrial fibrillation. However, it has not been investigated how the relation between EF and MAM changes on direct‐current (DC) electrical cardioversion to sinus rhythm. Therefore, 31 consecutive patients on the waiting list for DC electrical cardioversion were examined by echocardiography before DC electrical cardioversion, and those who maintained sinus rhythm (13 patients) were examined again 4–8 weeks after cardioversion. The conversion factor (CF) (ratio EF/MAM) decreased from 8·4 ± 1·7 before to 5·8 ± 0·8 SD after cardioversion (P<0·001). The EF increased slightly (P<0·05) but the MAM had a much greater increase (P<0·001), resulting in the decrease in CF. There was no significant difference in CF between patients after cardioversion and age‐ and gender‐matched control patients with sinus rhythm, indicating that CF is normalized or almost normalized 4–8 weeks after cardioversion. This indicates that when MAM is used for investigation of the left ventricular function, and the function is expressed as EF, the same CF as in other patients with sinus rhythm can be used 4–8 weeks after DC electrical cardioversion.
Comparison of bioimpedance and radioisotope methods in the estimation of extracellular water volume before and after coronary artery bypass grafting operation
Authors: Kööbi  , Kähönen  , Koskinen  , Kaukinen  , Turjanmaa
Published: March 2003

To estimate extracellular water volume (ECW) changes in connection with coronary artery bypass grafting operation, simultaneous ECW estimations by 51Cr‐EDTA dilution and whole‐body bioimpedance techniques were performed in 15 patients. The assessments of ECW were compared with patients’ weighing results. Whole‐body bioimpedance‐derived ECW correlated significantly with 51Cr‐EDTA dilution‐based ECW in the pre‐operative period (r=0·74; P<0·005); the bias was 0·2 ± 1·1 l (±SD). In the post‐operative period, the agreement between these methods was poor, the bias being 0·5 ± 2·5 l, and no significant correlation between the methods was found (r=0·38; P>0·05). Whole‐body bioimpedance‐derived ECW changes correlated significantly with weight changes of the patient induced by the operation (r=0·52; P<0·05). 51Cr‐EDTA dilution‐based ECW changes correlated neither with weight changes (r=0·33; P>0·05) nor with bioimpedance‐derived ECW changes (r=0·03; P>0·05). Alterations in radioisotope tracer distribution and loss of it due to blood leakage in the post‐operative period were presumed to explain the discrepancy between dilution technique and weighing results. The results suggest that bioimpedance is a useful non‐invasive method for assessment of extracellular volume changes induced by coronary artery bypass grafting operations. 51Cr‐EDTA dilution‐based ECW determination is not suitable in related conditions.
Brozek two‐compartment model under‐estimates body fat in black female athletes
Authors: Thompson  , Moreau
Published: March 2003

The purpose of this study was to compare percentage body fat (%BF) values of black female athletes calculated using the Heymsfield four‐compartment (4C), Brozek two‐compartment (2C) and Schutte models. Eleven collegiate athletes underwent total body water (TBW) assessment, hydrostatic weighing (HW) and dual energy X‐ray absorptiometry (DXA). Repeated‐measures ANOVA determined that the 4C model yielded %BF values (16·2 ± 1·5%) that were higher than the Brozek model (13·6 ± 1·7%) but similar to the Schutte model (16·7 ± 1·6%). The fat‐free mass density of the athletes (1·109 ± 0·002 kg l–1) was significantly higher than the value 1·1 kg l–1 assumed by the 2C model. We conclude that in lean black female athletes, the Brozek 2C model under‐estimates %BF, and that, if only HW is available, the Schutte model should be used to estimate %BF.
Cardiovascular responses during submaximal electrical stimulation‐induced leg cycling in individuals with paraplegia
Authors: Raymond Jacqui , Davis Glen M. , Van Der Plas Martinus
Published: March 2003

This study investigated the cardiovascular responses during electrical stimulation‐induced leg cycling (ES‐LCE) in people with paraplegia (PARA) compared with voluntary leg cycling (VOL) at similar levels of oxygen uptake in able‐bodied (AB) individuals. Six PARA with sensory and motor complete spinal cord lesions (T5–T9) and six AB participated in this study. Oxygen uptake (VO2), stroke volume (SV), heart rate (HR) and cardiac output (Q) were measured at rest and during submaximal, steady‐state leg cycling. At the highest power output achieved (9·2 ± 2·4 W for PARA versus 42·8 ± 1·0 W for AB), VO2 was augmented above resting levels to 0·75 ± 0·11 l min–1 in PARA and to 0·74 ± 0·07 l min–1 in AB. HR and SV were also increased during ES‐LCE in PARA (92·1 ± 8·6 beats min–1 and 93·9 ± 11·3 ml beat–1, respectively) and during VOL in AB (83·9 ± 9·2 beats min–1 and 89·7 ± 9·0 ml beat–1, respectively). At an equivalent submaximal VO2, HR and SV were not different between the two groups, however, Q was higher in PARA (6·6 ± 0·7 versus 4·1 ± 0·9 l min l–1ΔVO2). These data suggest that ES‐LCE at relatively low power outputs elicits increases in several cardiovascular variables in PARA. Furthermore, it is possible that ES‐LCE leads to a `hyperkinetic circulation' (a greater Q for a given VO2).
The cervical (Pap) smear—personal experience on both sides of the Atlantic
Authors: McKee G. T.
Published: March 2003

What's in a name? That which we call a rose

By any other name would smell as sweet.

Shakespeare, Romeo and Juliet
Ethnic factors in the pathology of the uterine cervix cervical screening: a population at variance with national targets
Authors: Ezra D. , Baithun S. I. , Dodd S. M. , Brown C. L.
Published: March 2003

Ethnic factors in the pathology of the uterine cervix cervical screening: a population at variance with national targets

In recent years, it has been noted that the rate of detection of high‐grade uterine cervical abnormalities by screening in the Newham and Tower Hamlets districts have been much lower than the national average. Whilst the national average for the detection rate of moderate and severe dyskaryosis has been around 1.6%, the detection rate in Newham and Tower Hamlets has consistently been substantially lower, at 0.6–1.0%. This discrepancy may be explained on demographic grounds. The ethnic make up of the two districts differs from the national average. Newham has a mixed ethnic structure: Moslem (11%), Asian non‐Moslem (12%) and other groups (77%). The population of Tower Hamlets is made up of Moslem (23%), Asian non‐Moslem (11%) and other groups (66%). In both districts, the rate of detection of moderate and severe dyskaryosis in these population subgroups between 1997 and 1999 was 0.57% for Moslem women, 0.52% for Asian non‐Moslem women and 1.18% for other women.
Personal view. Is it reality or an illusion that liquid‐based cytology is better than conventional cervical smears?
Authors: HERBERT AMANDA , JOHNSON JANE
Published: March 2003

Personal view. Is it reality or an illusion that liquid‐based cytology is better than conventional cervical smears?

Liquid‐based cytology (LBC) has been heralded as the way forward for cervical screening, and as the answer to many of its problems. It is already used as a sole method of cell preparation in many private clinics in the UK. It is being used for colposcopy smears in many NHS clinics and is now being piloted for primary screening in three screening centres in England, as well as one in Scotland and one in Wales. LBC has been welcomed as a new technology because it deals with the problem of specimen adequacy at source, removing responsibility for slide preparation and fixation from the clinician or nurse. It provides uniformly well‐fixed preparations that are free of inflammatory exudate and blood, and seem easier to screen than conventional smears. There are many articles in the world literature suggesting that LBC is more accurate than conventional screening, and it is thought likely to reduce the number of false negative tests.1 The main reasons for piloting LBC in the NHS Cervical Screening Programme (NHSCSP) lie in its potential for reducing screening times and for reducing the numbers of repeats for inadequate tests. LBC is expensive in terms of equipment, capital costs, maintenance, consumables, training, technical preparation time, transportation and disposal of liquid media. Its costs could be justified if they were offset by the money saved from reduced screening time and repeat tests, but only if its accuracy in terms of sensitivity and specificity were proven to be equal to or better than conventional cytology.1 Although that is generally held to be true by the public and medical profession alike, there is very little hard evidence to support it.
Phenotypic variation in adult morphology and pupal colour within and among families of the speckled wood butterfly Pararge aegeria
Authors: Van Dyck Hans. , Matthysen Erik. , Wiklund Christer
Published: March 2003

Abstract.1. Larvae from eggs of fifteen wild‐caught speckled wood females were reared individually under common conditions (LD 18:6 h and 17 °C) in the laboratory.

2. Pupal colour (green or brown) and the following adult morphological variables that are known or assumed to be related to behavioural variation (thermoregulation, flight, crypsis) were studied: size, relative thorax mass, area of yellow patches on the dorsal forewing, size of submarginal eyespots on the dorsal hindwing, colour of the dorsal thorax, dorsal basal wing, and dorsal distal wing.

3. The results of the breeding experiment indicate significant differences in adult morphological traits among families, sexes, and pupal colour types.

4. All adult morphological variables (except spot size and thorax colouration) differed significantly among families, suggesting genetic variation underlying the phenotypic variation. Heritabilities for these features were intermediate (0.38) to high (> 1).

5. Apart from known aspects (e.g. size), novel aspects of the sexual dimorphism were found: females had paler thoraxes than males, which relates to higher abundance of fur on the thorax and hence to thermoregulatory differences.

6. Green pupae produced larger individuals with a larger relative thorax mass than brown pupae. Green pupae produced adults with a paler basal wing colour in females, but not in males. These relationships are novel and suggest a trade‐off between juvenile and adult investment.
When host choice is a problem for a generalist herbivore: experiments with the whitefly, Bemisia tabaci
Authors: Bernays E. A.
Published: March 2003

1. Experiments with adult females of the whitefly, Bemisia tabaci, demonstrated that when mixtures of host plants were present, performance was reduced relative to that on the best of the host plants when presented alone.

2. Behavioural observations indicated that in the presence of a variety of plants, individuals moved more, switched between plants more frequently, and stayed feeding in one place for shorter periods of time, compared with the situation when single plant species were available.

3. The data are interpreted as a constraint on attentiveness in the presence of complex, mixed‐sensory stimuli.
An experimental test of potential host range in the ant parasitoidApocephalus paraponerae
Authors: Morehead Shellee A. , Feener Donald H.
Published: March 2003

1. The work reported here tested experimentally whether specialisation inApocephalus paraponeraewas due to physiological interactions that limit the parasitoid to the host antParaponera clavata. The suitability of other ant species as hosts was tested, and behavioural traits that may promote a high degree of specificity within this host–parasitoid system are discussed.

2. Data for development time, number of puparia, and adult eclosion success forA. paraponeraeovipositing in the regular hostP. clavataare provided. A new method for testing host suitability in parasitoids of ants is described. Eggs ofA. paraponeraewere transferred directly into potential ant hosts. The development time, number of puparia, and adults eclosed for the eggs transferred into other ant host species are compared with comparable data fromP. clavata.

3. Seven ant species within the Ponerinae are suitable for the development ofA. paraponerae. The potential host range is greater than the actual host range ofA. paraponerae. Flies are not limited solely by host suitability of related ant species for the development of larvae. Host location and acceptance behaviours are proposed as the primary reasons for host specialisation. The large size of the primary hostP. clavata, and the ability of multiple females to raise many offspring successfully from those hosts may influence the specialisation ofA. paraponeraeonP. clavata.
Interactions between the egg and larval parasitoids of a gall‐forming midge and their impact on the host
Authors: Briggs Cheryl J. , Latto John
Published: March 2003

1. The gall‐forming midgeRhopalomyia californicawas exposed experimentally to parasitism and predation during only the egg stage, during only the larval stage, during neither stage, or during both stages.

2. The combined action of natural enemies that attack during both the egg stage and the larval stage led to the lowest number of midges and total insects (midges + parasitoids) in the next generation, and the highest percentage parasitism.

3. The larval parasitoid killed a large fraction of hosts without producing new parasitoid offspring, while there is some indication that the egg parasitoid on its own tended to produce the most parasitoid offspring. The contrasting implications of host mortality versus parasitoid production for biological control are discussed.

4. Exposure to larval parasitoids resulted in a reduction in the number of egg parasitoid offspring produced, but exposure to the egg parasitoid did not affect the number of larval parasitoid offspring produced significantly.
Interactions of colonisation density and leaf environments on survival of Trioza eugeniae nymphs
Authors: Luft P. A. , Paine T. D. , Walker G. P.
Published: March 2003

1. Female eugenia psyllids Trioza eugeniae oviposit on the margins of expanding young Syzygium paniculatum leaves. The developing nymphs, feeding within pit‐shaped galls on the leaves, cause the leaves to become curled and deformed. The degree of leaf curling was correlated positively with densities of T. eugeniae nymphs.

2. High relative humidity increased persistence of nymphs on leaves at low insect densities, but persistence did not differ between high or low relative humidity conditions when nymphal densities were high and leaves were greatly curled.

3. Direct insolation increased nymphal mortality. Nymphs on the abaxial leaf surface in the direct sun had lower mortality than similarly exposed nymphs on the adaxial leaf surface.

4. Field populations showed high preference for abaxial leaf surfaces and a stronger preference for shaded adaxial surfaces than for exposed adaxial surfaces.

5. Adverse environmental conditions of direct insolation and low relative humidity may be mitigated by leaf curl associated with moderate populations, however competition at high nymphal density supersedes any potential benefit arising from leaf curling and has a negative effect on nymphal survival.
Do parasitoids diversify in response to host‐plant shifts by herbivorous insects?
Authors: Cronin James T. , Abrahamson Warren G.
Published: March 2003

1. For herbivorous insects, the incorporation of a novel host into the diet, and subsequent formation of distinct host associations (races), is thought to be a significant early step in the speciation process. While many studies have addressed this issue, virtually nothing is known about the evolutionary response of natural enemies to herbivore host‐race formation.

2. The hypothesis that the parasitoid wasp Eurytoma gigantea (Hymenoptera: Eurytomidae) has formed host races in direct response to the host shift and subsequent host‐race formation by its host, the gallmaker Eurosta solidaginis (Diptera: Tephritidae) was tested. Emergence time, mating preference, and female oviposition preference were determined for parasitoids derived from galls of each Eurosta host race.

3. Male and female E. gigantea overlap broadly in their emergence times from each Eurosta host race, suggesting that there is no phenological barrier to gene flow.

4. In choice experiments, female parasitoids did not mate assortatively: females that emerged from one Eurosta host race were equally likely to mate with males from either Eurosta host race.

5. Oviposition behaviour experiments revealed that female parasitoids do not prefer to oviposit on their host race of origin and that there is no overall preference for one host race, even though fitness is higher when parasitoids are reared from Eurosta galls of the Solidago gigantea host race than when reared from Eurosta galls of the Solidago altissima host race.

6. These results suggest that E. gigantea has not diverged in parallel with its host in response to the herbivore host‐plant shift. Further studies are needed before the ubiquity of this diversification mechanism can be evaluated fully.
Nourishment affects colony demographics in the paper waspPolistes metricus
Authors: Hunt J. H. , Dove M. A.
Published: March 2003

Abstract 1. Colony survivorship and numbers of nest cells, pupae, and adult females were monitored throughout the nesting season for a cohort of 78 colonies of the paper waspPolistes metricusSay. Thirty‐nine colonies received a twice‐weekly nourishment supplement of honey during pre‐emergence and early emergence phases of the colony cycle; 39 colonies were unsupplemented controls.

2. Colony survivorship was unaffected by the supplemental nourishment. Loss of colonies to predation differed among three sites but was unaffected by supplementation.

3. Honey‐supplemented colonies constructed more nest cells than did control colonies but this effect was not expressed until after supplementation had ceased.

4. Honey‐supplemented colonies produced more pupae than did control colonies but the number of adult females at nests did not differ between supplemented and control colonies. Because honey‐supplemented colonies had more offspring but fewer of them remained as workers at the nest, honey supplementation led to a lower frequency of workers and corresponding higher frequency of reproductives than in control colonies.

5. In a second year of study, colony survivorship and numbers of nest cells, pupae, and adult females were monitored from late pre‐emergence until the end of the nesting season for a cohort of 32 colonies ofPolistes metricus. In 16 colonies, trophallactic saliva was taken from final‐instar larvae on nine dates in the late pre‐emergence and early emergence periods; 16 colonies served as controls.

6. Saliva‐diminished colonies had lower survivorship, fewer nest cells, fewer pupae, and fewer adult females at the nest than did control colonies.

7. These results show that variation in nourishment in the early to mid phases of the colony cycle can have significant effects on the subsequent colony demographics ofPolistes metricuspaper wasps.
Facultative bacterial endosymbionts benefit pea aphids Acyrthosiphon pisum under heat stress
Authors: Montllor Clytia B. , Maxmen Amy , Purcell Alexander H.
Published: March 2003

Abstract 1. Natural populations of pea aphids in California contain at least two facultative bacterial secondary symbionts (pea aphid secondary symbiont, PASS, or pea aphid rickettsia, PAR) in a range of frequencies throughout the state.

2. Two pea aphid clones without either of these facultative associates failed to reproduce in the first 8 days after the final moult if they had been heat‐stressed for a period of about 4 h at 39 °C as 1‐day‐old larvae in the laboratory.

3. Aphids infected artificially with PASS, however, were able to produce up to 48% of the normal complement of offspring produced by PASS‐positive aphids that had not been heat‐stressed. Clones infected artificially with PAR did not have the same advantage as those with PASS after heat stress.

4. In aphids without PASS or PAR, heat stress reduced the number of bacteriocytes (in which the obligate primary symbiont, Buchnera, resides) to 7% of non‐heat‐stressed aphids, while aphids with only PASS retained 70% of their bacteriocytes. Bacteriocytes in aphids with PAR but not PASS were reduced to 42% of controls.

5. When larvae were heat‐stressed as older instars (5 days old), a similar pattern emerged, though the effect of heat stress was less extreme. Clones containing PASS produced the most offspring, three to 14 times as many as aphids without PASS or PAR. Aphids with PAR only, or PASS and PAR together, had reduced or no advantage over aphids without facultative symbionts.

6. Aphids of all clones that had been heat‐stressed as later instars gave birth to a variable number of stillborn offspring. Aphids without facultative symbionts produced the most stillborn larvae.

7. Field studies showed a higher incidence of PASS in aphids collected in California in summer compared with aphids from the same sites collected 2–4 months earlier. The difference was significant in two of three widely dispersed locations.
Caste‐specific N and C isotope ratios in fungus‐growing termites with special reference to uric acid preservation and their nutritional interpretation
Authors: Tayasu I. , Hyodo F. , Abe T.
Published: March 2003

Abstract 1. Nitrogen and carbon isotope ratios and uric acid concentrations in fungus‐growing termites (Isoptera: Termitidae: Macrotermitinae), sampled in Cameroon and Thailand, were determined in order to compare castes that are known to differ in behaviour and feeding habits.

2. Nitrogen isotope ratios (δ15N) were either not significantly changed or lower in workers compared with the diet (the fungus combs), whereas carbon isotope ratios (δ13C) were higher in worker termites than in the fungus combs.

3. In old workers, δ15N values were unexpectedly low and correlated negatively with whole‐body uric acid concentrations. This indicates that older workers retain uric acid, which has a low δ15N value, to conserve nitrogen within the colony and, furthermore, that older colony members may ultimately be consumed by younger conspecifics.
Fitness advantage from nuptial gifts in female fireflies
Authors: Rooney Jennifer , Lewis Sara M.
Published: March 2003

Abstract 1. In many insects, males provide nuptial gifts to females in the form of spermatophores, sperm‐containing structures produced by male accessory glands.

2. The work reported here examined the influence of both spermatophore number and spermatophore size on female reproductive output in two related firefly beetles, Photinus ignitus and Ellychnia corrusca (Coleoptera: Lampyridae). Based on differences in adult diet, male spermatophores were predicted to increase female reproductive output to a greater extent in P. ignitus than in E. corrusca.

3. Female fecundity was significantly higher in triply mated females than in singly mated females in both species, with no difference between mating treatments in female lifespan or egg hatching success. No effects of second male spermatophore size on fecundity, lifespan, or egg hatching success were detected in either species.

4. These results suggest a direct fitness advantage from multiple mating for females in both species, although enhanced fecundity may be due either to allocation of spermatophore nutrients to eggs or to other substances transferred within the spermatophore acting as oviposition stimulants.
Opposing survivorship and fecundity effects of host phenology on the gall‐forming aphid Hormaphis hamamelidis
Authors: Rehill Brian , Schultz John
Published: March 2003

Abstract  1. This study examined the synchronisation and roles of host and insect phenology for fundatrices of the gall‐forming aphid Hormaphis hamamelidis, which forms galls on the leaves of the understorey tree Hamamelis virginiana.

2. Host and insect phenologies varied widely among years and individual host trees.

3. Most winter eggs (≈ 85%) hatched before budbreak and galls could be initiated but in 2 years there was no inherent risk for earlier hatching fundatrices in terms of greater mortality. Egg hatch was not synchronised tightly with host trees but instead seemed to occur well in advance of budbreak as a conservative, bet‐hedging strategy to ensure the opportunity to form galls.

4. Fundatrices that formed galls later had higher fecundity, contrary to typical patterns for insects that feed on the first flush of leaves in temperate forests, where later herbivores have lower fecundity. Also, unlike many other systems, trees that had later budbreak had greater densities of galls.
Differential vulnerability of prey to an invading top predator: integrating field surveys and laboratory experiments
Authors: Woodward Guy , Hildrew Alan G.
Published: March 2003

Abstract1. A new top predator, the dragonflyCordulegaster boltonii, invaded Broadstone Stream (U.K.) in the mid‐1990s. This provided a rare opportunity to assess the impact of a new, large carnivore on a community that has been studied since the 1970s and has one of the most detailed food webs yet published. The vulnerability of the resident species to the invader was assessed by integrating experiments, which examined discrete stages in the predation sequence, with empirical survey data.

2. Although the new predator preyed on nearly every macro‐invertebrate in the food web, vulnerability varied considerably among prey species. Size‐related handling constraints initially set the predator's diet, resulting in strong ontogenetic shifts, with progressively larger prey being added while small prey were retained in the diet, as predators grew. Within the size range of vulnerable prey, encounter rate limited the strength of predation, with mobile, epibenthic species being most at risk. Contrary to most studies of interactions between freshwater predators (usually stoneflies) and prey (usually mayflies), the new predator did not elicit avoidance responses from its prey, probably because it combined a highly cryptic feeding posture with an extremely rapid attack response.

3. The invader exploited its prey heavily in experiments, even at prey densities orders of magnitude above ambient. In the field,electivityreflected prey availability, as determined by mobility and microhabitat use, rather than prey abundance or active predator choice. Consequently, the invader had skewed effects within the prey assemblage, with sedentary, interstitial species being far less vulnerable than more active, epibenthic species, some of which, including a previous top predator, have declined markedly since the invasion.

4. By examining the predation sequence in detail and integrating surveys with experiments, species traits and system characteristics that determine the strength of trophic interactions may be identified, and their potential importance in natural food webs assessed. In so doing, greater insight can be gained into which species (and systems) will be most vulnerable to invading or exotic predators, an imperative in both pure and applied ecology.
The influence of host plant diversity and food quality on larval survival of plant feeding heteropteran bugs
Authors: Di Giulio Manuela , Edwards Peter J.
Published: March 2003

Abstract. 1. In a laboratory experiment, the influence of host plant diversity and food quality, in terms of nitrogen content, on the larval survival of two oligophagous bug species (Heteroptera, Miridae: Leptopterna dolobrata L., Notostira erratica L.) was investigated. Both species are strictly phytophagous and capable of feeding on a wide range of grass species. Moreover, they typically change their host plants during ontogenesis; it has been suggested that this behaviour is a response to the changing protein content of the hosts.

2. To investigate the importance of host plant diversity for these insects, the development of insects reared on grass monocultures was compared with that on mixtures of four grass species. In addition, the host grasses were grown under two nitrogen regimes to test whether nitrogen content is the key factor determining host plant switching.

3. Both species had a significantly higher survival rate when feeding on several host plants but only L. dolobrata showed a significant response to food nitrogen content. Furthermore, there was no correlation between the nitrogen content of the host plants and the survival rate of N. erratica larvae.

4. The study suggests that at least some Stenodemini need a variety of host plants during larval development but that the level of host plant nitrogen is not the main factor responsible for the observed diversity effect.
Nucleopolyhedroviruses of forest and western tent caterpillars: cross‐infectivity and evidence for activation of latent virus in high‐density field populations
Authors: Cooper Dawn , Cory Jenny S. , Theilmann David A. , Myers Judith H.
Published: March 2003

Abstract. 1. Cyclic population dynamics of forest caterpillars are often associated with epizootics of nucleopolyhedrovirus, but it is not known how these viruses persist between generations or through the fluctuations in host population density.

2. To explore the question of virus persistence at different phases of the population cycle, the nucleopolyhedroviruses of two species of tent caterpillar that co‐occur in British Columbia, Canada, Malacosoma californicum pluviale (western tent caterpillar) and Malacosoma disstria (forest tent caterpillar), were characterised. The cross‐infectivity of the viruses in these two host species was investigated to determine whether there might be a route for virus persistence via the alternative host species. Any virus produced in the cross‐infections was characterised to confirm true cross‐infection or to ascertain whether cross‐inoculation triggered latent virus persisting within the population.

3. The virus associated with forest tent caterpillars (MadiNPV) did not infect western tent caterpillars from low‐density populations, nor did it trigger a latent virus infection; however, inoculation of forest tent caterpillars from high‐density populations with virus from western tent caterpillars (McplNPV) resulted in viral infection, but without a dose–response relationship.

4. Analysis of DNA profiles of virus resulting from cross‐infection of the forest tent caterpillar with McplNPV, revealed that 88% of these infections were caused by MadiNPV rather than McplNPV; however the virus from all 44 infected individuals was identical and differed in DNA profile from the stock MadiNPV used for cross‐infection. This suggests strongly that forest tent caterpillars from high‐density field populations harbour a latent, persistent, or sublethal form of MadiNPV that was triggered by exposure to nucleopolyhedrovirus from the western tent caterpillar.

5. Virus was not activated in western tent caterpillars collected over 2 years of late population decline and the first year of population increase.
Biological warfare in the garden pond: tadpoles suppress the growth of mosquito larvae
Authors: Mokany Allie , Shine Richard
Published: March 2003

Abstract. 1. Although tadpoles and mosquito larvae may compete for scarce resources in natural freshwater systems, the mechanisms involved in such competition remain largely unstudied.

2. Replicated artificial ponds were set up to examine the role of pathogenic interference (water‐borne growth inhibitors) in two tadpole–mosquito systems from south‐eastern Australia. One system comprised taxa that are commonly sympatric in freshwater ponds (tadpoles of Limnodynastes peronii and larvae of Culex quinquefasciatus) while the other comprised species that co‐occur in brackish water ponds (tadpoles of Crinia signifera and larvae of Ochlerotatus australis).

3. Water that had previously contained tadpoles suppressed the rates of survival and pupation of mosquito larvae in both systems. Fungicide reduced or eliminated this effect, suggesting that the growth inhibitors may be fungal organisms (possibly the yeast Rhodotorula glutinis) from tadpole faeces. Fungicide also enhanced growth rates of tadpoles.

4. These results suggest that interference competition between tadpoles and mosquito larvae is mediated by other organisms in some ecological systems.
Species richness and parasitism in an assemblage of parasitoids attacking maize stem borers in coastal Kenya
Authors: Zhou Guofa , Overholt William A. , Kimani‐Njogu Susan W.
Published: March 2003

Abstract.1. Parasitoids were reared from four species of lepidopteran stem borer collected in maize in southern coastal Kenya from 1992 to 1999. The stem borers included three native species,Sesamia calamistisHampson,Busseola fuscaFuller, andChilo orichalcociliellus(Strand), and one exotic borer,Chilo partellus(Swinhoe). A total of 174 663 caterpillars was collected, of which 12 645 were parasitised.

2. Twenty‐six primary parasitoid species were reared from the exotic borer,C. partellus, indicating a rapid accumulation of native parasitoids on the alien borer.

3. The three most abundant parasitoids were the larval parasitoidsCotesia sesamiaeCameron,Cotesia flavipes(Cameron), and the pupal parasitoidPediobius furvusGahan. The pupal parasitoidDentichasmias busseolaeHeinrich and the larval parasitoidGoniozus indicusAshmead were also common. All used an ingress‐and‐sting method of attack.

4.Cotesia flavipes, introduced into Kenya in 1993, was found in all seasons from 1997 onwards, and has become the most abundant stem borer larval parasitoid in the area. A native congener,Cotesia sesamiae, appeared in all seasons from 1992 to 1999. Together, these two parasitoids accounted for 83.3% of the parasitised borers.

5. Thirty parasitoid species were recovered in Kilifi district, 27 in Kwale, and 15 in Taita Taveta. Parasitism was much greater in Taita Taveta district than in Kilifi or Kwale districts.
Preliminary survey for insects associated with Bursaphelenchus xylophilus in Portugal
Authors: Sousa E. , Naves P. , Bonifácio L. , Bravo M. A. , Penas A. C. , Pires J. , Serrão M.
Published: March 2003

The detection of Bursaphelenchus xylophilus in Pinus pinaster trees in Portugal in 1999 led the official services to implement exceptional and urgent control measures to prevent the spread of the pest. Because the pest is vector‐transmitted, special attention was paid to the insects associated with infested trees. A survey comprising 21 species of insects, from six families, with a total of 1367 specimens, was made in order to evaluate their possible role as vectors of the nematode in Portugal. Five insect species were found to carry other Bursaphelenchus spp., but only Monochamus galloprovincialis was associated with B. xylophilus.
Impact of recombinant human growth hormone treatment on psychological profiles in hypopituitary patients with adult‐onset growth hormone deficiency
Authors: Giusti  , Meineri  , Malagamba  , Cuttica  , Fattacciu  , Menichini  , Rasore  , Giordano
Published: March 2003

Background

We examined the effect of growth hormone (GH) administration on the psychological capacity and sense of well‐being in 25 patients with adult‐onset GH‐deficiency (GHD).

Methods

Very low dosages (0.5–1.0 UI day−1 s.c. at bed‐time) of recombinant human (rh)‐GH (n = 13; aged 50 ± 15 years, mean ± SD) or placebo (n = 12, 53 ± 14 years) were given at random for a 6‐month period. Quality of life was assessed by using the Italian version of the self‐rating Kellner Symptom Questionnaire (KSQ) and the Hamilton Depression Scale (HDS).

Results

No difference in insulin‐like growth factor I (IGF‐I) levels was noted between groups on entry to the study. A significant increase in IGF‐I (month 0 56.2 ± 10.4 μg L−1 vs. month 6 125.7 ± 16.7 μg L−1; P < 0.001) levels was noted only in the rh‐GH‐treated group. There was no difference in overall scores on the KSQ between the rh‐GH‐treated and control groups on entry. A slight, non‐significant, decrease in overall scores was noted in both groups of subjects. Subsection analysis of items from the KSQ did not show significant differences in either group during the 6‐month period. A significant decrease (month 0 28 ± 1 vs. month 6 25 ± 1; P = 0.02) in the HDS score was noted in rh‐GH‐treated but not in placebo‐treated patients. There was a significant correlation (rs, –0.56, P = 0.05) between increase in IGF‐I levels and decrease in HDS scores in rh‐GH treated patients.

Conclusion

The data demonstrate that low rh‐GH dosages significantly improve psychological profiles as rated by HDS evaluation in adult‐onset patients with GHD. On the other hand, a 6‐month period of treatment does not produce any significant differences in quality of life as measured by KSQ between treated patients and placebo controls.
Inhibitory effects of hyperglycaemia on fed jejunal motility: potential role of hyperinsulinaemia
Authors: Byrne  , Pluntke  , Wank  , Schirra  , Arnold  , Göke  , Katschinski
Published: March 2003

Background

Acute hyperglycaemia is known to inhibit jejunal interdigestive motility. This study was undertaken to establish the effects of hyperglycaemia on fed jejunal motility and small intestinal transit time, and to establish if the effects of hyperglycaemia are mediated in part by hyperinsulinaemia

Methods

Nine healthy male volunteers were studied in random order using three experimental conditions: (a) euglycaemic clamp (glucose 5 mmol L−1); (b) hyperglycaemic clamp (glucose 15 mmol L−1); and (c) euglycaemic hyperinsulinaemic clamp (glucose 5 mmol L−1). Fed jejunal motility was induced by an intrajejunal perfusion of lipid (Lipofundin medium‐chained triglyceride 10%) at 1.5 mL min−1 (1.5 kcal min−1) for 180 min through the most proximal port of a manometry catheter (eight ports spaced at 2‐cm intervals) located just distal to the ligament of Treitz. One minute after starting the lipid perfusion, 15 g of lactulose dissolved in 20 mL of tap water was infused. Small intestinal transit time was measured by the hydrogen breath test.

Results

Acute hyperglycaemia reduced the total number of jejunal contractions and progradely propagated contractions, the motility index (P < 0.05) and the mean amplitude of contractions and delayed intestinal transit time. Hyperinsulinaemia reduced the total number of jejunal contractions, motility index (P < 0.05) and intestinal transit time.

Conclusions

Thus, hyperinsulinaemia may contribute to the inhibitory effects of hyperglycaemia on jejeunal motility. In addition, this study demonstrated that intrajejunal infusion of lipid stimulates sustained glucagon‐like peptide‐1 release. In contrast to fat‐induced gastric inhibitory polypeptide release, this glucagon‐like peptide‐1 release is not inhibited by exogenous or endogenous hyperinsulinaemia (P = 0.59).