Search PubMed⌕ Search

Biomedical subjects

D A Hay

Publications and source records attributed to D A Hay.

At least 55 records · Page 3Linked to original sources
PubMed1987

Speech and language development in preschool twins.

While language, articulation and reading problems have been well documented in young twins, it is not clear how extensive such problems can be or how early in childhood they become evident. At the age of 30 months, twin boys in the La Trobe Twin Study were 8 months behind matched singletons and twin girls on expressive language and 6 months behind on verbal comprehension. They were also 5 months behind on symbolic play and this delay was closely related to language. "Secret" language characterised most of the twin boys but not the girls and the relation of this to articulation delays is discussed. To examine if exposure to other children helps the twin boys, 38-53 month old twins and singletons were matched on the Columbia Mental Maturity Scale at the time of starting preschool. The twin boys had more articulation problems and all twins scored much lower on a Sociability questionnaire completed by the teacher. After 8 months at preschool, all children had advanced in Sociability, but the twins remained just as far behind with poor Sociability relating to poor articulation. The role of intervention programs is discussed.

Articulation Disorders↗
PubMed1987

Early influences on the school social adjustment of twins.

The birth of twins is often accompanied by complications which may affect both twins equally (eg, prematurity) or which may establish differences between the twins (eg, one coming home from hospital first). Parents' ratings of behaviour may reflect and even perpetuate the influence of such variables and it is of interest to see if people less familiar with the twins' history can observe any long-term effects. In the La Trobe Twin Study teachers routinely complete the Bristol Social Adjustment Guide, an assessment of social maladjustment in children aged 5-16 years. Extreme prematurity and problems at delivery were generally associated with the Underreaction syndrome--the child who is unforthcoming, withdrawn and depressed. Withdrawal, depression and maladaptive behaviour to classroom peers were much more common among those twins discharged from hospital after the cotwin. A major mediating factor was that the parents admitted to greatly preferring the one to come home first. These raise questions both about the practice of bringing twins home separately (which occurred in 21% of the cases) and about intervening variables in studies of personality and temperament.

Adolescent↗
PubMed1987

Panic disorder: evidence for genetic vulnerability.

Many studies have suggested that a genetic predisposition to the development of panic disorder exists. These studies are examined and their limitations discussed. It is suggested that only by the analysis of comprehensive family and twin data, coupled with other measures such as the search for possible single gene association or linkage and study of the children of panic disorder patients, will the mechanism for the 'familiarity' noted in panic disorder patients be elucidated. Delineation of the mode of transmission of panic disorder may allow preventative intervention with those at risk before they develop panic.

Adoption↗
PubMed1984

The role of parental attitudes in the development of temperament in twins at home, school and in test situations.

In the La Trobe Twin Study, data are collected on temperament and social development in 3-15 year old twins and singletons from four different sources: questionnaires to parents covering development from birth to the present plus the Bristol Social Adjustment Guide completed by the teacher, Sattler's Behavior and Attitude Checklist completed by the tester, and the Qualitative Score on the Porteus Maze Test. Particular stresses are identified which the parents perceive as distinguishing a multiple from a singleton birth. Whereas they perceive no differences between the first and second-born in birth complications, the second-born is judged less favourably particularly in MZ pairs. The distinction continues in the later assessments by the teacher and tester, where in addition the male twins are seen as being different from other children both in cognition and in temperament. It is proposed that social and cognitive development of twins are interrelated and have two unique components, one related to the greater problems accompanying a multiple birth and the other to comparisons between cotwins.

Adolescent↗
PubMed1984

The high incidence of reading disability in twin boys and its implications for genetic analyses.

In 1975 the Australian Council of Educational Research (ACER) conducted a nationwide survey of literacy and numeracy in 10- to 14-year olds. A total of 297 of the 12875 children involved were twins. By age 14, only 42% of the twin boys achieved adequate standards of literacy compared with 71% of single-born boys. The deficit in twin girls was much less and twins of both sexes were only moderately behind in numeracy. A survey of 9-13-year-old twin boys in the La Trobe Twin Study (LTS) produced similar results with 75% being below average in reading skills and 23% behind by 18 months or more, despite above average IQs. The ACER data are corroborated by teachers' reports obtained in the same survey, which indicate also how few of the twins with problems are receiving remediation and the high incidence of classroom problems in spelling and reading reversals. The pattern of mistakes twins make on specific items in the ACER survey can be explained as resulting either from specific cognitive deficits or from problems in concentration. The same factors influence performance on different tasks, so that literacy and numeracy are much more closely interrelated in twins than in singletons, and also correlate more with a measure of verbal intelligence. Implications for genetic analysis of scholastic achievement are examined, centering around the different factor structure of abilities in twins and common family environmental effects which are unique to twins.

Adolescent↗
PubMed1984

Biochemical and ultrastructural integrity of the saphenous vein conduit during coronary artery bypass grafting. Preliminary results of the effect of papaverine.

Factors associated with early and late graft patency related to aorta-coronary artery bypass grafting with a reversed segment of saphenous vein are clinically important. The present investigation examines the biochemical and electron microscopic integrity of this venous conduit intraoperatively with regard to pharmacologic manipulation with papaverine. Portions of saphenous vein were analyzed in 22 patients undergoing coronary artery bypass operations. Levels of a stable derivative of prostacyclin, 6-keto-PGF1 alpha, were measured by radioimmunoassay. Scanning as well as transmission electron microscopy was also performed. In particular, the efficacy of local vein treatment with papaverine, a phosphodiesterase inhibitor, was evaluated. We found that levels of 6-keto-PGF1 alpha in venous effluent showed a biphasic response with initial elevation followed by a relative depression after papaverine exposure. There were no such changes observed in veins subjected to a balanced electrolyte solution (Plasma-Lyte). In addition, levels of the platelet-inhibitory substance 6-keto-PGF1 alpha in venous tissue were less in papaverine-treated veins than those found in veins treated only with the balanced electrolyte solution (Plasma-Lyte). Furthermore, evidence for ultrastructural damage was also somewhat greater in the papaverine-treated group. An alternative method of dilating the saphenous vein after harvesting, which involves the creation of the proximal aorta-coronary anastomosis first and gentle finger manipulation subsequently, appeared to minimize venous injury. Under present clinical conditions, it appears that some amount of injury is inevitable during harvesting and suturing of the human saphenous vein during coronary bypass grafting.

6-Ketoprostaglandin F1 alpha↗
PubMed1984

Selected views of early heart development by scanning electron microscopy.

This tutorial on cardiac development is designed to acquaint the novice student of embryology with the key events that occur during cardiogenesis. Each of the following events is depicted through a series of scanning electron micrographs which convey the spatial relationships between minute, yet essential structures: fusion of paired heart tubes; looping; partitioning of the common atrium, the atrioventricular canal, the primitive ventricle and the outflow tract. The cellular and biochemical mechanisms responsible for these events cannot be adequately determined nor illustrated by SEM and therefore will not be considered in detail herein.

Animals↗
PubMed1983

Endocytic activity in embryonic cardiac cushion mesenchyme in vivo and in collagen gel lattices.

Mesenchymal cells, termed cushion tissue (CT) cells, are the principal cellular elements in atrioventricular (AV) endocardial cushions, the latter constituting AV septal and valvular primordia in the embryonic heart. Atrioventricular canals of 2 1/2 day chick embryo hearts were explanted onto collagen gel lattices, wherein cushion endothelial cells acquired the characteristics of CT cells and invaded the gel. The endocytic activity of in situ CT cells was compared to that of gel-cultured CT cells by exposing appropriate preparations to horseradish peroxidase (HRP), cationized ferritin (CF) or to lysozyme. Stimulation by these exogenous proteins resulted in phagocytosis. In addition, all three markers were associated with coated pits, smooth surfaced vesicles (45-60 nm), C- or cup-shaped structures and other lysosomal elements, but were excluded from Golgi cisternae and their entire vesicle population. In CT cells, HRP does not act solely as a "content" marker that reflects fluid-phase uptake. Instead it appears to follow adsorptive endocytic pathways. The endocytic behavior of in vivo and in vitro cushion tissue cells appears to be the same. Endogenous endocytic activity may reflect in part membrane retrieval, which counterbalances the extensive exocytosis observed in these cells.

Animals↗
PubMed1983

The La Trobe Twin Study: a genetic approach to the structure and development of cognition in twin children.

Twins are particularly useful for developmental behavior genetics, if adequate consideration is given to the possibilities of twin-singleton differences and of data from twins being unrepresentative of the entire population. As an alternative to existing analyses in the developmental behavior genetics of cognition, the covariance structure analysis method in biometrical genetics involving twins and other relatives has the potential for dissecting the determinants of the structure of cognitive abilities and how these change during childhood, as well as checking on the adequacy of twin data. Designed with these aims in mind, the La Trobe Twin Study is a mixed longitudinal analysis of 1,356 twins, their siblings, and cousins, who are followed between the ages of 3 and 15 years on a battery of physical and behavioral tests. The criteria for choosing behavioral tests in such a project are discussed, along with the comprehensive series of questionnaires necessary to examine the children's development in the context of the stresses a multiple birth may impose on a family. In discussion of methods of analysis, 2 points are emphasized: (1) Twin-singleton differences are specific to particular abilities rather than being general, and (2) the incidence of family changes and stresses in such that these should be considered among the environmental effects on development along with the more usual indices of family environment.

Adolescent↗
PubMed1981

Ultrastructure of the developing vascular system in the puppy kidney.

The present study defined the ultrastructural features of peritubular capillary development. Two-day-old beagle puppies and adult dogs were perfused with 2.5% glutaraldehyde and routinely prepared for light and transmission electron microscopy. Some of the fixed tissue was subsequently used to make freeze-fracture replicas. The outer cortex of the puppy kidney possessed large, thick-walled vessels best termed sinusoidal capillaries instead of the small caliber vessels (peritubular capillaries) noted in the adult. These sinusoidal vessels showed extensive overlapping of the endothelium with isolated patches of fenestrae. Their luminal surfaces were irregular, owing to prominent ridges and sporadic bulges of endothelium. The basement membrane of most vessels was not present. Interstitial spaces were filled with mesenchymal cells and cells closely resembling pericytes. The diameter of the fenestrae of vessels throughout the cortex was similar; however, the number of fenestrae per micrometer of endothelium increased significantly from outer to inner cortex. Vessels of the inner cortex were also immature when compared to the adult. From these morphological findings, it was apparent that a true peritubular capillary system does not exist in the two-day-old puppy. Ultrastructural features of these vessels suggested reduced permeability characteristics.

Animals↗
PubMed1980

Genetics in the analysis of behaviour.

Behaviour genetics has developed rapidly in the last two decades and has now gone far beyond the stage of merely measuring the extent to which individual differences on a particular behaviour can be attributed to genetic factors. This paper discusses the uses to which genetics can be put in efficient experimental design, in determining the generality of results and, most importantly, in the simultaneous analysis of several behaviours and their relationship to each other and to physical and biochemical parameters. Because the principles of genetics apply to all organisms, the first animal discussed is Drosophila, the vinegar fly, which is a vital tool in genetics but which has met with scant attention among psychologists. Drosophila has some unique advantages such as the sex mosaic technique for studying sexual behaviour, but most of the discussion concerns learning and the extent to which parallels can be found between Drosophila and the vertebrates, both in terms of process and of genetic control. It is demonstrated how strain differences and the response to artificial selection can distinguish between learning and other components of behaviour. Drosophila are also used to explain how the type of genetic control can suggest the way in which natural selection acts upon the particular behaviour and further examples from rodents are discussed to show that this is a general result across species. There are many inbred strains and selection lines of mice and rats and examples from a wide range of behaviours illustrate the advantages of using such stocks. The concept of the 'behavioural phenotype' is explained, where genetic differences on a wide range of behaviours are considered, rather than just focusing on one behaviour or one response to a particular drug or environmental treatment. Many different aspects of open-field behaviour, learning and mother-infant interaction are used as examples of this concept. The extent of genotype-environmental interaction is considered, since the possibility that each genotype will have a unique response to a brief discussion of human behaviour genetics, since here again the concern is not just with the trivial question of measuring 'heritability', but rather with how such information can be used to understand behaviour. The final suggestion is that psychology may gain by having more contact not only with geneticists, but also with the ecologists concerned with the significance of behavioural differences in the wild.

Aggression↗
PubMed1979

Maturation of the proximal tubule in the puppy kidney: a comparison to the adult.

Two- to four-day-old beagle puppy kidneys were preapred for transmission and scanning electron microscopy and compared to similarly prepared adult tissues. Proximal tubules of puppy kidneys which contained nephrons in various stages of differentiation were examined and maturational changes were described. Lateral surface contours of proximal tubular cells were initially smooth and relatively unfolded, but progressively acquired complex processes that may be recognized as lateral ridges and lateral-basal processes. Basal projections began as short, stubby processes and gradually took on either a narrow, plate-like or finger-like appearance. Mitochondria lysosomes and apical vacuoles increased in number as the tubules matured. Mitochondria lacked orientation in outer cortical tubules, but exhibited some vertical arrangement within basal processes in inner cortical tubules. Despite features indicating advanced maturation of tubules in the inner cortex, puppy kidneys lacked the lipid droplets characteristic of the adult. Thus, differentiation of this portion of the developing nephron into S1, S2 and S3 segments was not possible at day 4. Morphometric analyses of the lateral and basal membrane surface concentration of proximal convulted tubules from the puppy revealed all cells to have a significantly smaller membrane area than that of the adult. However, the inner cortical cells of the puppy had a greater surface concentration than those of the outer cortex. The reduced transport capacity of the puppy proximal tubule may be realted to the lack of segmentation and/or reduced lateral-basal surface area.

Animals↗