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Biomedical subjects

B L Hamilton

Publications and source records attributed to B L Hamilton.

51 records · Page 3Linked to original sources
PubMed1976

Intranuclear bodies in neurons of the periaqueductal gray matter in the cat.

The nucleoplasm of neurons in the nucleus lateralis of the periqueductal gray matter in the cat contains fibrillar structures which have no limiting membranes. These intranuclear bodies are associated with neither the nucleolus nor the nuclear membrane and have two characteristic forms. The first, the rodlet, is a compact bundle of fibrils 2 to 8 nm in diameter. It is usually elongated in shape although it appears spherical when sectioned transversely. This rod-like structure appears to correspond to Roncoroni's rodlet or the accessory body of Cajal in light microscopy. The second and more commonly observed form is a long slender bundle of five rows of parallel fibrils. Although similar intranuclear structures have frequently been observed in the highly differentiated neurons of the sympathetic ganglia and the retina, this is the first report of their pbesence in the undifferentiated neurons of the isodendritic core of the brainstem.

Animals↗
PubMed1975

Mixed leukocyte culture reactivity in operationally tolerant rats: Relationship of lymphocyte-mediated reactivity and serum-blocking activity.

Tolerance to Brown Norway (BN) allografts was induced in Wistar Furth rats by neonatal inoculation of BN bone marrow cells or mixtures of (W/Fu x BN)F-1 hybrid spleen and bone marrow cells. Lymphoid cells from rats in which operational tolerance had been induced (maintenance of BN skin graft for more than 100 days) were studied for mixed leukocyte culture (MLC) reactivity. Peripheral blood lymphocytes from 10 of 25 W/Fu rats operationally tolerant to BN skin grafts showed MLC reactivity when exposed to BN antigens in vitro, implying that some degree of MLC reactivity is compatible with prolonged skin graft survival. These same rats also showed cytotoxic activity to BN fibroblasts in vitro regardless of their MLC status. MLC is quantitatively decreased and possibly qualitatively altered as compared to that of control W/Fu lymphocytes. The decrease was specific for the tolerated antigens. Serum from the tolerant rats inhibited cytotoxic but not normal MLC reactivity of W/Fu cells against BN antigens.

Animals↗
PubMedDate not supplied

Stress-induced changes in the function of the parasympathetic nervous system are mimicked by blocking GABA in the CNS of the cat.

The purpose of this study was to determine the effect of blockade of receptors for gamma-aminobutyric acid (GABA) in the forebrain, on vagal activity to the stomach and heart. This was done by injecting bicuculline (50 micrograms) into the lateral ventricle of the brain and restricting the drug to the forebrain ventricles by cannulating the cerebral aqueduct. Studies were performed in chloralose-anesthetized cats and gastric motility was monitored using extraluminal force transducers, sutured to the antrum and pylorus. Cardiac vagal activity was determined by noting the sinus bradycardia that developed from activation of the baroreceptor reflex induced by phenylephrine. Administration of bicuculline into the lateral ventricle of 7 animals produced increases in the minute motility index of 5.3 +/- 0.8 (antrum) and 13.9 +/- 2.1 (pylorus). This was associated with inhibition of baroreceptor-induced vagal bradycardia (i.e. -38 +/- 6.4 beats/min before bicuculline and -7.7 +/- 5.7 beats/min after bicuculline). These data indicate that a GABAergic mechanism in the forebrain may be important for controlling vagal outflow to both the stomach and the heart.

Animals↗