Canine conjoined twinning: A pathoanatomical study of a Lhasa Apso symmetrical cephalothoracopagus.

A female pair of conjoined twins of the Lhasa Apso canine breed was subjected to tomographic and anatomical examinations. The twins had only one head and neck. The two ribcages were joined, extending to the umbilicus, with duplicated structures thereafter. They had three thoracic limbs and two pelvic girdles with four limbs, as well as a number of abnormalities in their internal organs. The data obtained were compared with the rare canine cases reported so far and with human cases.

Can different levels of S-R practice influence sequence learning? An investigation into the context of a perceptual-motor sequence learning task.

The main aim of the present study was to evaluate on a serial reaction time task the effect of stimulus-response (S-R) practice on sequence learning. The experiment used a pointing task which allowed recording reaction times and movement times. The basic manipulation consisted in varying the amount of S-R practice prior to sequence practice. Two main findings from this study may be highlighted. Firstly, the benefit from extensive S-R practice was mainly observed in the random practice phase. Secondly, S-R learning and sequence learning were reflected by different components of performance. The movement times were selectively sensitive to the acquisition of S-R regularities whereas the reaction times were selectively sensitive to the acquisition of sequence regularities. The implications of these results on the comprehension of the sequence learning mechanism were then discussed.

Differential effects of task complexity on contextual interference in a drawing task.

A large number of studies demonstrated the beneficial effects of contextual interference (CI) created by a random practice of different task variations during training on the retention and transfer of motor skills. Current interpretations of this phenomenon assume that random practice engages the subjects in deep and elaborate processing of movement related information, whereas blocked practice results in more superficial processing leading to poorer performance on later retention and transfer tests. According to this line of interpretation, we hypothesised that the complexity of the task to be learned could modulate the effects of CI. If the task is sufficiently complex, it could force the subjects to rely on such elaborate processing, and the beneficial effects of the intertask interference created by random practice could be obscured in that case. We tested this hypothesis by analysing the effects of practice schedule (random vs. blocked), on the acquisition, retention and transfer of learning in a drawing task where subjects had to reproduce accurately, without visual control, geometrical patterns presented on a video screen, as a function of task complexity defined by the number of segments (two, three or four) of each pattern. The results indicated a clear beneficial effect of random over blocked practice on delayed retention and transfer. However, this CI effect was only observed in subjects who learned the simplest movements, and was not observed in subjects who practised the more complex task. These results are discussed in terms of intratask interference created by the planning of multiple movements and the processing of knowledge of results (KR) when the number of drawing movements is increased. These findings support the assumption that the level of cognitive effort in which the subjects are engaged during training is a main factor influencing long-term retention and transfer of motor skills.

Acid exposure enhances sporulation of certain strains of Clostridium perfringens.

A gastroenteritis results when Clostridium perfringens is ingested in high numbers and sporulates releasing enterotoxin in the intestines. Since the organism must pass through the stomach, its ability to form spores may be affected by the acidic environment. Five strains of C. perfringens were exposed to acidic conditions and then assessed for survival and their ability to form spores. An acidic pH environment kills the bacteria over time but surviving cells are able to recover and form spores. Two of the five strains demonstrated enhanced sporulation following a 30-min exposure to a pH 2 environment. For four of the strains tested, enterotoxin concentrations were higher from acid-exposed cells than from untreated cells. Exposure to a pH 3.5 environment did not affect sporulation when compared to an untreated control. Bacteria in the stationary phase of growth were the most able to resist the acid and sporulate. The results indicate that some strains will produce more spores and enterotoxin following exposure to an acidic environment.

Age influence on attitudes of office workers faced with new computerized technologies: a questionnaire analysis.

The study of Bue and Gollac (1988) provided evidence that a significantly lower proportion of workers aged 45 years and over make use of computer technology compared with younger ones. The aim of the present survey was to explain this fact by a more intensive analysis of the older workers' attitude with respect to the computerization of work situations in relation to other individual and organizational factors. Six hundred and twenty office workers from 18 to 70 years old, either users or non-users of computerized devices, were asked to complete a questionnaire. The questions allowed the assessment of various aspects of the workers' current situation, such as the computer training they had received, the degree of consultation they were subjected to during the computerization process, their representation of the effects of these new technologies on working conditions and employment, the rate of use of new technologies outside the work context, and the perceived usefulness of computers for their own work. The analysis of the questionnaire revealed that as long as the step towards using computer tools, even minimally, has not been taken, then attitudes with respect to computerization are on the whole not very positive and are a source of anxiety for many workers. Age, and even more, seniority in the department, increase such negative representations. The effects of age and seniority were also found among users, as well as the effects of other factors such as qualification, education level, type and rate of computer use, and size of the firm. For the older workers, the expectation of less positive consequences for their career, or even the fear that computerization might be accompanied by threats to their own employment and the less clear knowledge of how computers operate, appeared to account for a significant part of the observed age and seniority differences in attitudes. Although the difference in the amount of computer training between age groups was smaller than expected, the study revealed that one third of the users never received any specific training, and that many of those who benefited from it were trained for only a few days. Consultation of the staff during the computerization process also appeared to be poor, to apply mostly to the best trained and qualified workers, and to be more highly developed in small companies. The results are discussed in the light of more qualitative data recorded during the survey. They suggest the need to increase information, training and involvement of all personnel from the very first stages of computerization (or other technical changes) in order to lessen fears and the feeling of disruption, which are particularly obvious among the oldest workers.

Reproductive life of French-Canadians in the 17-18th centuries: a search for a trade-off between early fecundity and longevity.

One of the predictions derived from Williams' (1957) evolutionary theory of senescence is the existence of a trade-off between early fecundity and longevity. The population register of the French immigrants to Québec in the 17th century and of the first Canadians in the 17th and 18th centuries was used to detect such a trade-off in a noncontraceptive human population living at a time when longevity had not been prolonged by medical care and was not artificially shortened by wars, epidemics, or other external causes. No evidence for such a trade-off could be detected in these populations which had not yet reached the demographic transition phase (i.e., the historical period when longevity began to be extended and the progeny began to be reduced). Results are discussed in connection with the various studies aiming to test the Williams' theory.

Astronaut behavior in an orbital flight situation: preliminary ethological observations.

Following the ethological approach, astronaut behavior is divided into "observable" motor acts which make possible its quantitative description. Frame-by-frame analysis of current videotape recordings shows that the behavioral adaptation to weightlessness is achieved through various processes. Among these are new motor acts and stereotyped movements (successive movements of head, eye, arm, and hand), reversal and reorganization of the sequence of the motor acts to form new patterns (head and eye movements upward or downward), construction of a particular cognitive image of the astronaut's own world (more compensatory regulations than anticipatory processes), and the relationship between postures and orientations according to the proximate visual environment. Furthermore, the present analysis confirms physiological data showing a redistribution of activity between flexor and extensor muscles, and a differential adaptation of vestibulo-ocular reflexes. Thus, this approach suggests new physiological experiments and enables the prediction of behavioral changes occurring during adaptation in microgravity.

Changes in cuticular hydrocarbon composition in relation to age and sexual behavior in the female Calliphora Vomitoria (Diptera).

Qualitative and quantitative changes in epicuticular hydrocarbon synthesis/release were observed during the first gonadotrophic cycle of Calliphora vomitoria. Up to 12 hours after eclosion, hydrocarbon synthesis/release is low, with little change in the relative proportions of the compounds detected. At 24 hours there is a marked increase in hydrocarbon synthesis/release, especially in the monomethylalkanes (both absolute and relative amounts). Between 48 and 72 hours, hydrocarbon synthesis stabilizes. At 83 hours, two hydrocarbon patterns can be distinguished, depending on the state of receptiveness of the females. The results show for the first time that differences in age, sexual attractiveness and receptivity are accompanied by characteristic changes in cuticular n-alkanes and mono-methylalkanes.

Acquisition and retention of habituation as a function of intertrial interval duration during training in the blowfly.

The influence of the duration of the interval between successive stimulations during habituation training on the dynamics of motor response decrement and its retention over time has been studied in the blowfly, Calliphora vomitoria . The intertrial interval (ITI) duration during training was either 7, 15, 30, 60 or 120 seconds. After a rest period of 30 minutes, a second session was given with the same ITI duration of 30 seconds for all groups. The response decrement observed during training is faster the longer the ITI duration. At the end of this session, the lower response level is reached with an ITI of 60 seconds. After the rest period, the lower responsiveness is observed in the animals which have been trained with the longer ITI. These results are discussed with reference to the dual-process theory of habituation, which can account for the results obtained during training, and memory-centered models to interpret the influence of ITI duration on retention performance.

Habituation of cardiac and motor responses to a moving visual stimulus in the blowfly (Calliphora vomitoria).

The relation between heart activity and locomotor behavior was studied in tethered blowflies (Calliphora vomitoria) by simultaneous recording of the electrocardiogram and the electromyogram. Motor activity resulted in an inhibition of forward beating of the heart. In the case of visual stimulation by movement of black stripes, this inhibition anticipated the motor activity. When this visual stimulation was repeated, motor and cardiac responses waned, but optocardiac response remained present a long time after the disappearance of the optomotor response. These results support the hypothesis of the participation of cardiac activity disturbances in preparatory processes for motor activity in insects.