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Biomedical subjects

D Troyer

Publications and source records attributed to D Troyer.

52 records · Page 3Linked to original sources
PubMed1988

What do two-year-olds know about the sizes of things?

Knowledge about the sizes of things is an integral part of object concepts. In 5 experiments, we examined 2-, 3-, 4-year-olds' and adults' internalized representations of the sizes of buttons, plates, and shoes. We found that 3- and 4-year-olds had accurate knowledge of the typical sizes of buttons and plates. 2-year-olds' knowledge of plate and button sizes was more fragile; however, they demonstrated accurate internal representations of the sizes of shoes. The studies provide new empirical evidence about the young child's knowledge of the sizes of 3 everyday objects. The findings also suggest that the size of an object may be more accurately represented if its size is highly relevant for the object's intended function.

Attention↗
PubMed1986

Reduction of blood pressure and restoration of T-cell immune function in spontaneously hypertensive rats by food restriction and/or by treadmill exercise.

The studies were carried out to compare the effects of food restriction and/or treadmill exercise on the development of high blood pressure and to compare immune function in spontaneously hypertensive rats (SHR). The results demonstrate that moderate food restriction from weaning or a regular treadmill exercise not only maintains significantly lower blood pressure, but also increases T-cell proliferative response against mitogens which is found to be significantly depressed in SHR fed ad libitum. A significant loss of T-cell subpopulation such as W3/25+ T helper cells and OX8+ non-helper T-cells occurring in mice fed ad libitum were restored to normal levels, including IL-2 response, in food-restricted SHR. Our results suggest that both food restriction and/or physical exercise is effective in modulating the blood pressure and increasing T-cell immune functions in SHR.

Animals↗
PubMed1985

Contractile properties of cultured glomerular mesangial cells.

The glomerular mesangium is composed of matrix material and at least two cell types. One is a bone marrow-derived phagocyte and the other is a smooth muscle-like cell. The phagocytic cell represents approximately 3-7% of the total mesangial cell population. The other, more abundant, cell type appears to be contractile and therefore has been proposed to play a role in regulating the surface area for filtration, one component of the ultrafiltration coefficient, Kf. In this review we discuss the contractile properties of cultured mesangial cells as well as the phenotypic alterations that lead to loss of isotonic contraction after prolonged culture.

Angiotensin II↗
PubMed1984

A collagen-like glycoprotein of the extracellular matrix is the undegraded form of type VI collagen.

The 140 000-dalton collagenous glycoprotein (CGP) from calf aorta and ligament characterized by Gibson & Cleary (1982) [Gibson, M.A., & Cleary, E.G. (1982) Biochem. Biophys. Res. Commun. 105, 1288-1295] has been studied. In the electron microscope, rotary-shadowed CGP molecules appear similar to the dimers of type VI collagen (short-chain collagen, intima collagen) described by other authors [Furthmayr, H., Wiedemann, H., Timpl, R., Odermatt, E., & Engel, J. (1983) Biochem. J. 211, 303-311] except that they have larger globular domains. As shown by gel electrophoresis, pepsin treatment of CGP at 4 degrees C either before or after reduction releases polypeptide chains corresponding in size to those of type VI collagen. Electron microscopic examination shows that pepsin digestion of nonreduced CGP removes the outer globular domains, reduces the size of the inner ones, and separates the paired central strands. The residual structures look like type VI collagen dimers. When intact CGP is reduced, monomers with two large globular ends are obtained. Pepsin digestion of monomers removes most or all of both globular domains. In immunoblots, CGP and its pepsin-derived fragments react with antibodies directed against type VI collagen. The results indicate that type VI collagen is an integral component of CGP.

Amino Acids↗
PubMed1982

Trimming selected areas of embedments for electron microscopy--dead simple.

Precision trimming of specific areas of plastic embedments can be accomplished without having to find the specimen detail in the block face itself. The desired area is located in a thick section of the pretrimmed block. The position of the area in the section is evaluated using an ocular micrometer. The block is then mechanically trimmed in the ultramicrotome in such a way that the amount of plastic removed from each of its sides is determined from the magnitude of the knife advance. The procedure can be used in connection with inclined blocks if the microtome head can be rotated behind the specimen orientation arc.

Microscopy, Electron↗
PubMed1980

Giant neurons and associated synapses in the peripheral nervous system of whip spiders.

Whip spiders (Amblypygi) are arachnids with a specialized first pair of legs. These legs are unusually long (20-25 cm) and are not used for walking. Instead their lengthy tarsi (7-8 cm) are covered with thousands of sensory hairs (mechano- and chemoreceptors). The legs thus resemble antennae of insects. Each sensory hair is associated with 4-40 neurons whose axons are grouped together to form two large tarsal nerves. The nerves contain about 23 000 sensory axons. Whereas most of the axons measure only 0.1-0.2 microns in diameter, a few are exceptionally large (3-20 microns). These are giant fibres. Their large somata are located in specific segments of the tarsi. The branched dendrites of the giant neurons receive hundreds of chemical synapses, presumably from the sensory axons of the hair sensilla. Since stimulation of the tarsal tip elicits fast withdrawal reaction (greater than or equal to 80 ms), it is likely that the giant fibres provide the pathway for the rapid conduction of nerve impulses to the motor centres of the C.N.S. The system is comparable to the giant fibre system of certain insects. In contrast, however, the giant interneurons and associated synapses of whip spiders are not located in the C.N.S., but lie some 20 cm removed in the periphery. Thus, some primary sensory information already becomes processed in the peripheral nervous system, before it reaches the C.N.S.

Animals↗