The role of intersegmental dynamics during rapid limb oscillations

The interactive dynamic effects of muscular, inertial and gravitational moments on rapid, multi-segmented limb oscillations were studied. Using three-segment, rigid-body equations of motion, hip, knee and ankle intersegmental dynamics were calculated for the steady-state cycles of the paw-shake response in adult spinal cats. Hindlimb trajectories were filmed to obtain segmental kinematics, and myopotentials of flexors and extensors at each of the three joints were recorded synchronously with the ciné film. The segmental oscillations that emerged during the paw-shake response were a consequence of an interplay between active and passive musculotendinous forces, inertial forces, and gravity. During steady-state oscillations, the amplitudes of joint excursions, peak angular velocities, and peak angular accelerations increased monotonically and significantly in magnitude from the proximal joint (hip) to the most distal joint (ankle). In contrast to these kinematic relationships, the maximal values of net moments at the hip and knee were equal in magnitude, but of significantly lower magnitude than the large net moment at the ankle joint. At both the ankle and the knee, the flexor and extensor muscle moments were equal, but at the hip the magnitude of the peak flexor muscle moment was significantly greater than the extensor muscle moment. Muscle moments at the hip not only acted to counterbalance accelerations of the more distal segments, but also acted to maintain the postural orientation of the hindlimb. Large muscle moments at the knee functioned to counterbalance the large inertial moments generated by the large angular accelerations of the paw. At the ankle, the muscle moments dominated the generation of the paw accelerations. At the ankle and the knee, muscle moments controlled limb dynamics by slowing and reversing joint motions, and the active muscle forces contributing to ankle and knee moments were derived from lengthening of active musculotendinous units. In contrast to the more distal joints, the active muscles crossing the hip predominantly shortened as a result of the interplay among inertial forces and gravitational moments. The muscle function and kinetic data explain key features of the complex interactions that occur between central control mechanisms and multi-segmented, oscillating limb segments during the paw-shake response.     

Testosterone in tropical birds: effects of environmental and social factors

Previous investigations suggest that male tropical birds have lower plasma testosterone concentrations than northern latitude species. To test whether this generalization is valid, we analyzed all currently available plasma testosterone data of tropical birds. We focused on peak breeding testosterone levels using phylogenetic and conventional statistics. Explanatory variables considered were social mating system, type of territoriality, breeding season length, and altitude. On average, tropical birds had lower mean peak testosterone levels than northern temperate birds. However, in several tropical species, testosterone levels were well within the range of northern latitude birds. Without controlling for phylogeny, breeding season length, type of territoriality, and altitude explained a significant proportion of the variance in testosterone levels. The shorter the breeding season, the higher the testosterone levels. Tropical birds that defend a breeding season territory had higher testosterone levels than birds that were year-round territorial or colonial, and testosterone levels were positively correlated with altitude. When controlling for phylogeny, only breeding season length predicted testosterone levels. In conclusion, we propose to refine previous notions of low plasma testosterone levels in tropical birds: short breeding seasons and perhaps environmental conditions at high altitudes precipitate conditions under which high testosterone levels are beneficial in the tropics.     

Developmental trajectories of overweight during childhood: role of early life factors

Objective: Our goal was to identify developmental trajectories of overweight in children and to assess early life influences on these trajectories. Research Methods and Procedures: Participants consisted of 1739 white, black, and Hispanic children who were younger than 2 years at the first survey and were followed up to 12 years of age. Repeated measures of overweight, defined as BMI ≥95th percentile, were used to identify overweight trajectories with a latent growth mixture modeling approach. Results: Three distinct overweight trajectories were identified: 1) early onset overweight (10.9%), 2) late onset overweight (5.2%), and 3) never overweight (83.9%). After adjustment for multiple potential risk factors, male gender [odds ratio (OR), 1.5; 95% confidence interval (CI), 1.0 to 2.2], black ethnicity (OR, 1.7; 95% CI, 1.1 to 2.6), maternal 25 ≤ BMI <30 kg/m² (OR, 2.2; 95% CI, 1.3 to 3.7) or ≥30 kg/m² (OR, 5.1; 95% CI, 2.9 to 9.1), maternal weight gain during pregnancy ≥20.43 kg (OR, 1.7; 95% CI, 1.0 to 2.9), and birth weight ≥4000 g (OR, 2.0; 95% CI, 1.2 to 3.4) were associated with an increased risk of early onset overweight. These risk factors, except maternal weight gain, exerted similar effects on late onset overweight. In addition, maternal smoking (OR, 1.6; 95% CI, 0.8 to 3.1) and birth order ≥3 (OR, 2.3; 95% CI, 1.0 to 5.2) were associated with an increased risk of late onset overweight only. Breastfeeding ≥4 months was associated with a decreased risk of both early (OR, 0.7; 95% CI, 0.3 to 1.3) and late onset overweight (OR, 0.7; 95% CI, 0.3 to 1.7). Discussion: Two trajectories of overweight and one never overweight group were identified. Early life predictors may have a significant influence on the developmental trajectories of overweight in children.     

Essential role of MARCKS in cortical actin dynamics during gastrulation movements

Myristoylated alanine-rich C kinase substrate (MARCKS) is an actin-binding, membrane-associated protein expressed during Xenopus embryogenesis. We analyzed its function in cytoskeletal regulation during gastrulation. Here, we show that blockade of its function impaired morphogenetic movements, including convergent extension. MARCKS was required for control of cell morphology, motility, adhesion, protrusive activity, and cortical actin formation in embryonic cells. We also demonstrate that the noncanonical Wnt pathway promotes the formation of lamellipodia- and filopodia-like protrusions and that MARCKS is necessary for this activity. These findings show that MARCKS regulates the cortical actin formation that is requisite for dynamic morphogenetic movements.     

Internal ribosome entry segment-mediated translation during apoptosis: the role of IRES-trans-acting factors

During apoptosis, there is a reduction in translation initiation caused by caspase cleavage of several of the factors required for the cap-dependent scanning mechanism. Under these circumstances, many proteins that are required for apoptosis are instead translated by the alternative method of internal ribosome entry. This mechanism requires the formation of a complex RNA structural element and in the presence of internal ribosome entry segment (IRES)-trans-acting factors (ITAFs), the ribosome is recruited to the RNA. The interactions of several ITAFs with IRESs have been investigated in detail, and several mechanisms of action have been noted, including acting as chaperones, stabilising and remodelling the RNA structure. Structural remodelling by PTB in particular will be discussed, and how this protein is able to facilitate recruitment of the ribosome to several IRESs by causing previously occluded sites to become more accessible.     

Induction of emotional states during oral reading of texts with different emotional valence and EEG power dynamics in frequency bands beta2 and gamma

EEG power in frequency bands beta2 (18.5-29.5 Hz) and low gamma (30-40 Hz) was compared for situations while reading aloud with the technique "self-regulative utterance" texts as follow: a text with neutral emotional-semantic dominant; literary texts with either a positive or a negative emotional-semantic dominant; personal texts--recollections with similar dominants. Two groups of healthy subjects participated--a group of actor students (N=22) and a group of non-actor students (N=23). EEG power values in the states of emotiogenic texts reading are reproducibly differed with statistical significance from those in the state of reading ofa non-emotiogenic text. States of reading emotionally-positive texts are characterized by increases of EEG power in these bands, while those for emotionally negative texts--by decreases if compared with the state of emotionally neutral reading.     

The emotional counting Stroop: a task for assessing emotional interference during brain imaging

The emotional counting Stroop (ecStroop) is an emotional variant of the counting Stroop. Both of these tasks require a motor response instead of a spoken response for the purpose of minimizing head movement during functional MRI (fMRI). During this task, subjects report, by button press, the number of words (1-4) that appear on a screen, regardless of word meaning. Neutral word-control trials contain common words (e.g., 'cabinet' written three times), while interference trials contain emotional words (e.g., 'murder' written three times). The degree to which this task represents a true 'Stroop' interference task, in the sense that emotional words will increase motor-response times compared with neutral words, depends upon the subjects of the study and the words that are presented. Much research on the emotional Stroop task demonstrates that interference effects are observed in psychopathological groups in response to words that are specific to their disorder, and in normal subjects when the words are related to current concerns endorsed by them. The ecStroop task described here will produce reaction time-interference effects that are comparable to the traditional color-naming emotional Stroop. This protocol can be completed in approximately 20 min per subject. The protocol described here employs neutral words and emotional words that include general-negative words, as well as words specific to combat-related trauma. However, this protocol is amenable to any emotional word lists.     

Testosterone secretion during early pregnancy in mares

We have characterized the testosterone secretion pattern during the first 80 d of pregnancy in mares and determined the sources that contribute to circulating testosterone levels during this period. Ten untreated, pregnant mares (Group 1), 10 altrenogest-treated, pregnant mares (Group 2), and 10 altrenogest-treated, pregnant mares in which the CL was eliminated by administration of PGF-2alpha on Day 16 (Group 3) were used in this study. Complete luteolysis occurred following PGF-2alpha administration in all mares in Group 3. Six of the 10 mares in Group 3 did not have an active CL until after Day 60 of pregnancy (Group 3a) and were included in the analysis. The remaining four mares developed a new CL on Days 32, 40, 43 and 49 of pregnancy and were excluded from analysis. Mares without a functional CL (Group 3a) had significantly lower testosterone concentrations than mares with a functional CL (Groups 1 and 2), during the period before equine chorionic gonadotropin (eCG) secretion. At the onset of eCG secretion, testosterone concentrations increased rapidly but the rate of increase decreased with time in mares with a functional CL (Groups 1 and 2). In mares without a functional CL (Group 3a), testosterone concentrations did not increase at the onset of eCG secretion but increased at a gradually increasing rate after Day 50. The lower testosterone concentration in mares without a functional CL before eCG secretion suggests that the CL contributes significantly to the circulating testosterone concentration during the period before eCG secretion. The close time relationship between the onset of eCG secretion and the increase in testosterone secretion in mares with a functional CL and the lack of a testosterone increase in pregnant mares without a functional CL suggest that the increase in testosterone secretion after Day 35 of pregnancy is the result of eCG-stimulated, luteal testosterone synthesis.     

Testosterone and behaviour during extinction in chicks

Testosterone-injected and control male chicks, in their second week of life, were observed during eight (massed) 1-min extinction trials of a runway response for a food reward. The hormone produced no overall differences in extinction rates but the following changes in behaviour were observed: first, increased frequency of contact with the empty food dish (pecking the outside, scratching, and treading); secondly, increased frequency of fixated gazing at the walls; thirdly, decreased looking up from the runway; and fourthly, increased head shaking. These results were discussed in relation to effects of testosterone on attack and attention.     

The role of emotional labour in oncology

Oncologists and related health care professionals (HCPs) do not only have to follow professional protocols in their everyday work, but also have to communicate proper attitudes towards patients suffering from malignant diseases. This task is often a heavier load than the implementation of professional activities themselves. The present article is based on a survey on HCP work motivation, employment parameters and correlations with emotional labour. Fifty oncology HCPs at Debrecen University Medical Health Sciences Centre volunteered to participate in this survey containing 20 simple-choice questions. More than 90 percent of HCPs make an effort to hide their emotional state, giving way to possible negative side effects. The survey showed significant differences between the level of emotional labour of those working in the field of oncology longer or shorter than ten years. Surface and deep emotional labour is more frequent among professionals already working in oncology for a longer period of time. This can serve us with explanation to the burn-out syndrome so frequent in this profession. To diminish the load of emotional labour, healthcare institutes have to aim at hiring employees that spontaneously fit the emotional and behavioural norms facing them, and do not need officially prescribed behavioural norms for everyday work. Their constant need for respect and appreciation of their values must be kept in mind, because the capability of genuine emotional labour diminishes parallel to the number of years spent in work.     

Testosterone and prolactin are associated with emotional responses to infant cries in new fathers

To determine the responsiveness of new fathers and non-fathers toward infant cues, we exposed fathers and non-fathers to infant cries and to control stimuli and we measured affective, heart-rate, and endocrine responses, including salivary testosterone and cortisol and plasma prolactin concentrations prior to and after cry presentations. We found that (1) fathers hearing the cry stimuli felt more sympathetic and more alert compared to groups who did not hear the cries or to non-fathers who heard the cries; (2) fathers and non-fathers with lower testosterone levels had higher sympathy and/or need to respond to the infant cries than fathers with higher testosterone levels; (3) fathers with higher, as opposed to lower, prolactin levels were also more alert and more positive in response to the cries; (4) fathers hearing the cry stimuli showed greater percentage increase in testosterone than fathers not hearing the cry stimuli; (5) experienced fathers hearing the cries showed a greater percentage increase in prolactin levels compared to first-time fathers or to any group of fathers hearing control stimuli; finally, (6) partial correlations with parity and experience entered as a covariates indicated that both experience and testosterone contributed to the variance in fathers' affective responses to infant cries. Taken together, these results indicate that, as with a number of other biparental species, human fathers are more responsive to infant cues than are non-fathers and fathers' responses to infant cues are related to both hormones and to caregiving experience.     

The role of ecological factors in controlling vegetation dynamics on long temporal scales

Abstract

The pattern of change in the Holocene forests of Europe is outlined and discussed in the light of external and internal forcing factors. Forests are seen as non-linear, dynamic systems, that are, at any point in time, unique and changing. In the absence of human activity, potential forcing factors during the Holocene include (i) climate, (ii) soil development, and (iii) internal forest dynamics. Climate is influential through exerting control on the floristic pool from which forests developed. Current results indicate that the role of soil development is likely to have been minor, but may have slowed rate of invasion and increase of some mid- and late-Holocene forest dominants. Forest change following spread and increase then forces soil change. Internal processes of forest dynamics include competition among existing species, and interactions between existing species and potential invading species. The patterns of interaction may be detectable through rates of change and patterns of increase seen in pollen records. Such processes are seen as being the dominant influence on the pattern of change and the development of forest. Forested systems, such as those in Europe, are strongly influenced by historical events, such as the mid-Holocene decline of elm. Forest composition is likely to be similar, in the broadest terms, from one interglacial to another, but always to vary in detail. The interaction of individuals, populations and environmental variables ensures that, although deterministic, prediction of change will always be difficult.     

Follicle selection in cattle: dynamics of follicular fluid factors during development of follicle dominance.

Follicle diameter deviation during follicular waves in cattle begins with a reduction in growth rates of developing subordinate follicles, in contrast to the maintenance of a constant growth rate by a developing dominant follicle. In experiment 1, the temporal changes encompassing deviation in concentrations of follicular fluid factors relative to one another in the three largest follicles (F1, F2, and F3) were studied. Follicular fluid samples were collected when F1 reached diameter ranges of 7.0-7.9, 8.0-8.9, 9.0-9.9, and 10.0-10.9 mm (n = 12 per range). The first increase (P < 0.05) in the difference between F1 and F2 for estradiol occurred at the 8.0- to 8.9-mm range, which was one range earlier than for diameter (P < 0.05). Free insulin-like growth factor (IGF)-1 concentrations in F1 were similar among diameter ranges, but concentrations in F1 were higher (P < 0.05) than in F2 for each range except 7.0-7.9 mm. Concentrations of free IGF-1 in F2 decreased (P < 0.05). No significant differences were detected in concentrations of progesterone, androstenedione, total inhibin, and inhibin-A. Averaged over follicles, inhibin-B decreased (P < 0.05) between the 8.0- to 8.9- and 10.0- to 10.9-mm ranges, and activin-A increased (P < 0.05) between the 7.0- to 7.9- and 9.0- to 9.9-mm ranges. However, no differences were found among follicles. In experiment 2, changes associated with the development of dominance by F2 were studied using ablation of F1 at the beginning of expected deviation (F1, 8.5 mm; Hour 0) as the reference point. Follicular fluid factors were compared at Hour 12 between F2 of a control group (F1 intact; n = 10) and an ablated group (F1 ablated; n = 10). Diameter (P < 0.02), estradiol (P < 0.001), free IGF-1 (P < 0.002), and progesterone (P < 0.003) were greater and IGF-binding protein-2 was lower (P < 0.01) in F2 of the ablated group at Hour 12. No differences were detected in concentrations of androstenedione, total inhibin, and inhibin-A. The results of the two experiments indicated, on a temporal basis, that intrafollicular changes in estradiol and the IGF system, but not in the inhibin/activin system, could account for a reported greater FSH responsiveness by the future dominant follicle than by the future subordinate follicles by the beginning of diameter deviation in cattle.