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Biomedical subjects

A Hein

Publications and source records attributed to A Hein.

At least 73 records · Page 4Linked to original sources
PubMed1982

Morphologic demonstration of two stages in the development of type II collagen-induced arthritis.

The infrapatellar fat pad, fibrous synovium, and cartilage joint surfaces of the tibia, patella, and femur of the knee joints of 17 normal rats and 38 rats with type II collagen-induced arthritis were examined by light and electron microscopy. In the normal animals, the synovium covering the fat pad was structurally variable in that the mesothelium was flattened and two to three cell layers thick in the central region but rounded and three to five layers thick at the tibial and patellar ends. Large vacuoles were more numerous in the synovial cells at either end of the fat pad, and these cells contained less endoplasmic reticulum than those in the central region. The fibrous synovium consisted of a flattened mesothelium composed of cells similar to those found in the central region of the fat pad. The normal cartilage was not covered by a mesothelium. Knees from animals immunized with collagen showed no structural changes until 5 days after immunization, when fibrin could be detected in the synovium by immunofluorescence. By day 12, fibrin deposition was found throughout the synovium covering the fat pad and fibrous tissue, as well as over the cartilage. In addition, hyperplasia of the synovium over the soft tissues was present, and synovial cells extended over the cartilage. On day 19, in approximately 20 per cent of the animals, inflammatory infiltrates, composed of mixtures of polymorphonuclear leukocytes and mononuclear cells, were observed within the synovium covering the soft tissues. Infiltrates were also seen at the edges of the cartilage. When the 80 per cent of the animals that did not have cellular infiltrates were examined 30 days after immunization, neither hyperplasia nor fibrin deposition were seen by light microscopy. By day 45, in 20 per cent of the animals, the synovium was hyperplastic, and granulation tissue, scarring, and granulomata were found in the soft tissues. It is concluded that there are two distinct stages in the development of this synovial disease--the first is characterized by hyperplasia and fibrin deposition, and the second by the presence of inflammatory infiltrates.

Animals↗
PubMed1981

Light and electron microscopic appearance of rat peritoneal mast cells adhering to schistosomula of Schistosoma mansoni by means of complement or antibody.

Metrizamide-gradient purified rat peritoneal mast cells were allowed to adhere to schistosomula of S. mansoni that had been preincubated in either minimum essential medium with 5% fetal calf serum (MEM/FCS), heat-inactivated serum from rats 8 weeks after cercarial infection (IRS) fresh normal rat serum as a source of complement (NRS), or IRS and NRS. Adherence was evaluated in sections 0.3 micrometers thick. The preincubation conditions favoring cell adherence were IRS + NRS greater than NRS greater than IRS greater than MEM/FCS. Greater adherence was seen at 60 min than at 10 min. Discharge of mast cell granulates was seen infrequently, was not greater in adherent than nonadherent cells, was not increased by any preincubation condition, and did not occur against the parasite's surface, as would be expected if antigen, antibody, and surface receptors were aggregated there. Electron microscopic examination showed that attachment to the parasite occurred through electron-dense material which was usually fibrillar in appearance. Membrane fusion, such as is seen between human neutrophils and schistosomula, did not occur.

Animals↗
PubMed1980

Recovery of forelimb placing after lateral hypothalamic lesions in the cat: parallels and contrasts with development.

Recovery of forelimb placing after lateral hypothalamic lesions in the cat is similar in several respects to the development of placing in kittens. In both recovery and development, the sequence in which sensory systems acquire control over placing is the same: vestibular--proprioceptive--tactile--visual. In addition, within each sensory modality, placing is initially sluggish, exaggerated in amplitude, and susceptible to rapid habituation. Unlike development, however, the recovery of visually guided placing does not require visuomotor experience.

Age Factors↗
PubMed1980

Secretion in dissociated human pulmonary mast cells. Evidence for solubilization of granule contents before discharge.

Mast cells were enzymatically dissociated from human lung fragments that had been sensitized with serum from human allergic to ragweed and were enriched by isopyknic and velocity gradient sedimentation. Electron microscope examination showed that the mast cells were well preserved at the end of the dissociation and isolation and that the majority of their secretory granules contained crystalline structures. These structures exhibited three patterns--scrolls, gratings, and lattices--which all could be found in the same granule. The period of crystalline structures was found to be bimodal, with maxima at 150 and 75 A. Both periods were observed in gratings that had been tilted and in scrolls that had been cut obliquely, indicating that the various gross patterns are composed of the same basic substructure. After the mast cells were stimulated by rabbit anti-human IgE to release histamine, the contents of the granule were transformed from a crystalline to an amorphous state, and only granules with amorphous contents were seen discharging from the cell. Clusters of intermediate filaments were present around the granules with amorphous contents, both deep in the cytoplasm and discharging at the cell surface. Discharge occurred both by fusion of granule membranes with the plasma membrane and by fusion of granule membranes with other granule membranes that ultimately were continuous with the plasma membrane. After discharge, the granule residue was fibrillar. Cells challenged with anti-human IgE in calcium-free medium neither released histamine nor demonstrated morphologic changes in their granules. We conclude that the crystalline state represents a storage form for materials that are solubilized before fusion of the granule membrane with the plasma membrane and discharge.

Antibodies, Anti-Idiotypic↗
PubMed1979

Eye movements initiate visual-motor development in the cat.

Visually naïve kittens turn their eyes toward visual targets but lack other visual-motor coordinations. Light-reared animals were able to mediate guided behaviors with an immobilized eye, but animals with the eye immobilized before initial exposure to a lighted environment were not. Eye movement is implied to play an essential role in visual-motor development.

Animals↗
PubMed1976

Recovery of function in cat visual cortex following prolonged deprivation.

Evidence that there is a critical period during which response characteristics of neurons in visual cortex of the cat may be influenced has been provided in several studied, which suggest that the period of influence is restricted to the first few months of life. Using a somewhat different experimental procedure, we have obtained evidence that cortical units retain plasticity long after the end of this period has passed. In our procedure prolonged visual deprivation was followed by exposure in a normal visual environment. The animals were maintained throughout the first year of life either in total darkness or in an enclosure illuminated intermittently by a strobe light. Following the period of deprivation, electrophysiologic recordings were taken from some of these animals. The remaining cats were permitted 6-12 months in a normally-illuminated environment prior to recording. Cats of the same age reared from birth in a normally lit environment were also recorded. Cortical neurons in cats deprived of any normal visual experience rarely show orientation selective responses. In animals allowed subsequent normal visual experience about one-half of the units studied exhibited this property. This level of response specificity is intermediate between that of normally-reared and recently-deprived animals. While most cortical units in normally-reared cats exhibited direction selectivity, this property is rarely observed in the "recovery" cats. A number of unit types which are rarely observed in either normal or totally deprived animals were encountered in cats that had normal exposure following prolonged deprivation. A convergent strabismus was observed, in contrast with the divergent strabismus often shown by cats immediately following prolonged visual deprivation. This shows that ocular alignment as well as cortical unit properties can remain plastic in the adult.

Blindness↗
PubMed1975

Cats raised in a one-directional world: effects on receptive fields in visual cortex and superior colliculus.

Cats were reared in a visual environment in which irregularly-shaped patches of luminescent paint moved constantly leftward. The distribution of preferred directions and orientations of cortical neurons in these cats was examined. Most cortical neurons encountered had leftward components in their preferred directions, and although no anisotropy of orientation was present in the rearing environment, most cortical neurons responded optimally to stimuli oriented at or near vertical. Variations in the strength of the induced bias of direction and orientation were noted among the different subclasses of cortical neurons. Preferred velocities of cortical neurons did not appear matched to the velocity of stimuli in the rearing environment. The ocular dominance distribution among cortical neurons in the unidirectional cats was skewed toward the contralateral eye relative to normal cats. The distribution of preferred directions in collicular neurons was largely unaltered by the rearing procedures employed. As in normal cats, units in the left colliculus more frequently responded best to rightward stimulus movement while those in the right colliculus preferred leftward movement. The ocular dominance distribution among collicular units was somewhat skewed toward the contralateral eye.

Animals↗
PubMed1973

Cats reared in stroboscopic illumination: effects on receptive fields in visual cortex.

Cats were reared in a light-tight box in which the only source of illumination was a 9-musec strobe flash every 2 sec. This allowed them to experience visual form but they did not experience visual movement. Receptive-field properties of single units in area 17 of the visual cortex of cats reared in stroboscopic illumination (strobe-reared) were compared with properties of units in area 17 of normally reared cats. In strobe-reared cats both direction selectivity and orientation selectivity were greatly reduced relative to normally reared cats, and some units in the strobe-reared cats responded only to strobe flashes.

Animals↗