Genes and grocery stores.
Explore the source record for details and available documents.
Genetic Engineering↗
Biomedical subjects
T D Johnston
Publications and source records attributed to T D Johnston.
The influence of Weismann's germ-plasm theory on the distinction between learned and innate behavior.
Since the early twentieth century it has been common in both psychology and behavioral biology to draw a sharp distinction between learned and innate behavior, or elements of behavior. The persistence of this dichotomy may be attributed in part to the fundamental importance of the separation of inherited and acquired characters within neo-Darwinian evolutionary theory, one of the essential foundations for the modern study of behavior. A cornerstone of early neo-Darwinian thought was August Weismann's theory of the germ plasm, which proposed a segregation between germinal and somatic cells during development, thus ruling out the possibility that acquired characters could be inherited. This denial of Lamarckian hereditary mechanisms became one of the hallmarks of neo-Darwinism, as opposed to classical Darwinism. Within the neo-Darwinian framework it thus became important, as Weismann himself pointed out, to distinguish sharply between inherited and acquired characters. Although the dichotomy has frequently been criticized it remains tenacious, surfacing in different guises as older versions of it became terminologically unacceptable. The analysis offered here suggests that this tenacity may partly be explained by the implications of Weismann's germ-plasm theory, and its modern incarnation in the central dogma of molecular genetics, and by the central thematic position of those ideas in the neo-Darwinian foundations of modern behavioral biology.
Behavioral Sciences↗
Functional equivalence of hypothermia to specific clotting factor deficiencies.
Hypothermia prolongs clotting times when the tests are performed at hypothermic temperatures, in contrast to standard clinical tests performed at 37 degrees C. The relative impact of hypothermia on plasma clotting factor activity was investigated by determining the specific clotting factor deficiencies required to produce an equivalent effect. Clotting factor concentration curves were constructed for clotting factors II, V, and VII through XII using assayed reference plasma (ARP) diluted with specific factor-deficient plasmas (FDP). Prothrombin times and partial thromboplastin times were measured as appropriate for each factor at test temperatures ranging from 37 degrees to 25 degrees C using a modified fibrometer. The clotting times for each temperature with undiluted ARP were compared with the clotting times at 37 degrees C obtained with FDP dilution. Hypothermia at temperatures below 33 degrees C produces a coagulopathy that is functionally equivalent to significant (< 50% of normal activity) factor-deficiency states under normothermic conditions, despite the presence of normal clotting factor levels.
Blood Coagulation↗
Liver transplantation. The last ten years.
8960741 10 years have witnessed a number of changes in the liver transplant process. Key among these changes are the longer preservation times allowed with UW solution, the development of the new techniques for the transplantation of pediatric patients, and the reintroduction of xenotransplantation for both permanent and temporary hepatic support. Early referral and prompt transplant of patients are among the most important keys to successful transplantation. However, owing to the present organ allocation system and the lack of suitable organ donors, potential liver transplant recipients will continue to experience a significant mortality rate on the waiting list. In addition, owing to the long waiting times for suitable donor organs, many patients who would have been excellent low-risk candidates will deteriorate as their liver disease progresses and become high-risk patients for liver transplantation. Expanding the donor pool and modifying the present liver allocation system to shift the flow of organs to the better-risk patients will do more to improve the results of liver transplantation than any other change in the management and transplantation of patients with severe liver disease.
Actuarial Analysis↗
Special considerations in the transplant patient requiring other surgery.
The surgeon planning an operation on a transplant patient should regard the undertaking with healthy respect but not with fear. Immunosuppressive agents alter the patient's response to surgical stress and slow healing. The immunosuppressed state increases the patient's susceptibility to infection. For these reasons, certain precautions must be taken. But a careful surgeon can bring a transplant patient successfully through necessary surgery.
Humans↗
Hypertonic saline alters plasma clotting times and platelet aggregation.
Hypertonic (7.5%) saline (HS) is advocated for resuscitation of injured and burned patients. Recent animal studies indicate that HS increases bleeding during uncontrolled hemorrhage, although the mechanisms for this are unclear. To investigate potential anticoagulant effects of HS (without dextran), normal human plasma was serially diluted with either HS or normal (0.9%) saline (NS). Prothrombin times (PT), activated partial thromboplastin times (APTT), and platelet aggregation studies were performed. Significant (p less than 0.05) deteriorations in clotting tests and platelet aggregation developed when 10% or more of normal plasma was replaced by HS, whereas there was no effect from similar NS dilutions. Strong correlations were observed between clotting test changes and sodium concentrations (R2 greater than 0.80, p less than 0.0001). Thus, HS exhibits anticoagulant activity, but not at the usual small volumes necessary to produce hemodynamic improvement. Nevertheless, the anticoagulant effect may be more pronounced with ongoing clotting factor losses or with the addition of dextran.
Blood Coagulation↗
Neophenogenesis: a developmental theory of phenotypic evolution.
An important task for evolutionary biology is to explain how phenotypes change over evolutionary time. Neo-Darwinian theory explains phenotypic change as the outcome of genetic change brought about by natural selection. In the neo-Darwinian account, genetic change is primary; phenotypic change is a secondary outcome that is often given no explicit consideration at all. In this article, we introduce the concept of neophenogenesis: a persistent, transgenerational change in phenotypes over evolutionary time. A theory of neophenogenesis must encompass all sources of such phenotypic change, not just genetic ones. Both genetic and extra-genetic contributions to neophenogenesis have their effect through the mechanisms of development, and developmental considerations, particularly a rejection of the commonly held distinction between inherited and acquired traits, occupy a central place in neophenogenetic theory. New phenotypes arise because of a change in the patterns of organism-environment interaction that produce development in members of a population. So long as these new patterns of developmental interaction persist, the new phenotype(s) will also persist. Although the developmental mechanisms that produce the novel phenotype may change, as in the process known as "genetic assimilation", such changes are not necessary in order for neophenogenesis to occur, because neophenogenetic theory is a theory of phenotypic, not genetic, change.
Animals↗
Sibling inhibition of hoarding in postweaning hamster pups (Mesocricetus auratus).
If hamster pups are placed in individual cages at weaning (21 days of age) they begin to hoard food immediately; within 2-6 days, they hoard 90% of the food they take from their food dish in the course of a 1-hr test, consuming only 10% of it. Pups that remain with their littermates after weaning in large group cages do not hoard food until they are placed in individual cages, when hoarding starts immediately. The inhibitory effect of littermates is just as pronounced in hamsters that have been allowed to hoard food in individual cages for 14 days after weaning and are then regrouped into litters. If litters are housed in divided cages that prevent physical interactions among littermates, but allow the interchange of olfactory, auditory, and some visual cues, hoarding is suppressed to an intermediate level. These results show that the presence of siblings inhibits the expression of hoarding, partly as a result of direct physical interactions and partly through the agency of sensory cues. The onset of hoarding following the dispersal of young from the nest cannot be explained as a motivational consequence of the young no longer having access to the mother's food hoard.
Aging↗
Development of visually controlled maternal preferences in Peking ducklings.
The interaction between natural visual and auditory stimulation in the control of filial behavior was studied in domestic mallard (Peking) ducklings during the first 3 days of postnatal life. Visual imprinting at 24 hr resulted in a visual preference for the familiar model over an unfamiliar model in each of two choice tests, one at 48 hr and one at 72 hr, but only if both models were silent. If both models emitted a recording of the mallard maternal call, the visual preference was found only in the later (72-hr) test. Visuomotor experience between training and testing was found to be essential for the development of the visual preference at 72 hr, but the required experience was of a very general nature. Either a choice test with silent models or a period of social rearing (between 24 and 72 hr) provided effective experience. Thus, the ability to show a visual preference in the presence of the maternal call at 72 hr depends on experience, but not necessarily on further exposure to the imprinting object or to any specific aspects of the test situation. These results demonstrate the importance of normal visual, motor and/or social experience to the development of the visual control of filial behavior in ducklings.
Age Factors↗
Effects of social experience on visually imprinted maternal preferences in Peking ducklings.
If Peking ducklings are given social experience with agemates after their initial exposure to a maternal imprinting model (a stuffed mallard hen) their subsequent maternal preferences in simultaneous choice tests are different from those of isolate-reared ducklings. Early in development (at 48 hr after hatching), they show a visual preference for the mallard over a redhead model, a difficult discrimination that isolated birds do not make (Experiment I). However, later in development (at 72 hr after hatching) the social experience interferes with the birds' maternal preferences, in that socially reared birds do not show a visual preference for the mallard over a pintail model, a preference that isolated birds do show at that age (Experiment II). It was found that it is the later social experience with agemates (between 48 and 72 hr) that actively interferes with the preference for the mallard model, because birds that have had only early social experience with agemates (between 24 and 48 hr) prefer the familiar mallard to the pintail model at both 48 and 72 hr (Experiment III). The conventional view of visual imprinting is that it serves to establish a maternal bond that does not require further experience with the mother to be maintained. Our results suggest that in the natural situation, where potentially interfering social stimulation is provided by siblings, continual exposure to the mother may be necessary to maintain the maternal bond even after it has been established.
Age Factors↗
Visual preferences of imprinted ducklings are altered by the maternal call.
This study determined whether the visual characteristics of a familiar (imprinted) model or the auditory characteristics of the species maternal call are more important in determining the maternal preferences of visually imprinted ducklings. Domestic mallard (Peking) ducklings were visually imprinted to a stuffed model of a mallard duck during a 30-min following trial at 24 hr after hatching. Simultaneous choice tests between the familiar mallard model and an unfamiliar red-and-white striped box at 48 hr and 72 hr confirmed the efficacy of the imprinting procedure: When both models were silent, subjects preferred to follow the familiar mallard model. However, when a recording of the mallard maternal assembly call was played from a speaker mounted inside the red box, subjects imprinted to the mallard preferred to follow the unfamiliar box rather than the familiar mallard model (Experiment 1). That preference was not due merely to the audiovisual stimulation provided by athe box, since when a recording of intermittent tones was played from the mallard model, subjects imprinted to the mallard still preferred to follow the red box emitting the mallard call (Experiment 2). Playing only the tones from the red box disrupted the stability of the subjects' imprinted preferences between the first and second tests but did not produce a preference for the box (Experiment 3). These results show that the mallard maternal call is more important than visual experience with an inanimate model in determining the maternal preferences of visually imprinted Peking ducklings.
Animals↗
Compensation for substrate elasticity in the kinematics of leaping by infant pigtailed macaques (Macaca nemestrina).
The means whereby animals adapt their locomotor behavior to variation in environmental conditions is an important and neglected problem in the area of motor control. To investigate this problem, young (3-month-old) pigtailed macaques (Macaca nemestrina) were filmed leaping a fixed distance from both rigid and elastic take-off supports. Sixteen of 17 subjects exhibited substantial invariance in the trajectories described by the major joints of the hind limb (hip, knee and ankle) during the leap. By contrast, the patterns of angular joint movement varied between performances involving the rigid and elastic supports. Maintaining invariant joint trajectories may enable the leaping animal to land safely at the target and prepare for subsequent action, and requires compensation for substrate elasticity. This compensation is effected, in part, by changing the patterns of joint flexion and extension.
Adaptation, Physiological↗
Middle temporal cortical visual area and visuospatial function in Galago senegalensis.
Bushbabies with lesions restricted to the middle temporal (MT) area and animals with larger extrastriate lesions including area MT were compared with normal control animals on test of visuospatial localization and discrimination learning. Ablation of area MT was sufficient to produce impairments in directing behavior appropriately on the basis of visuospatial cues. Extension of the lesion into areas 18 and 19 produced more profound deficits. Retardation in learning a stripe discrimination problem was correlated with the extent of damage to the geniculostriate system. It is hypothesized that area MT is important in achieving and maintaining fixation on a target whereas cortical areas 18 and 19 are necessary for establishing the location of stimulation in visual space.
Animals↗
Crisis intervention skills. Part II: Putting the skills to work.
Explore the source record for details and available documents.
Aged↗
Theoretical considerations in the adaptation of animal communication systems.
Explore the source record for details and available documents.
Adaptation, Biological↗
A spontaneous neuropathy of free-ranging Japanese macaques.
Thirteen cases of a spontaneous neuropathy were observed among 150 free-ranging Japanese snow monkeys (Macaca fuscata). Necropsy of 4 individuals revealed lesions in the peripheral and central nervous systems. Pathologic changes were associated with ingestion of coyotillo berries (Karwinskia humboldtiana).
Animals↗
Septic hemodynamics produced by infusion of endotoxin.
Explore the source record for details and available documents.
Animals↗