Visual receptive-field properties of single cells in the rat superior colliculus

Receptive-field properties were studied in single cells in the visual layer of the albino rat's superior colliculus. All the samples (N = 195) were identified as one of the four classes (I-, II-, III- and IV-cells) which were established previously on the bases of the response properties to single shocks to the optic pathway and of the recording sites. The four classes were located more deeply in the superior colliculus roughly in the order of from I to IV. Response latencies to single shocks to the optic chiasm were shortest in the III-cells, intermediate in the II-cells and longest in the I- and IV-cells. These cell classes turned out to be different from each other in a number of visual properties. 1) Receptive-field centers in the I- and II-cells (N = 26 and 27, respectively) were of either the ON-OFF or the ON type. Of class III (N = 47), one subgroup (IIIa) consisted mostly of the OFF type whereas the other (IIb) was made up mostly of the ON-OFF type. About two-thirds of the IV-cells (71/95) were of either the ON, the OFF or the ON-OFF type; except for two cells, the rest were all of the moving-sensitive type. 2) The average size of the receptive-field center was small (5.4 degrees +/- 2.3 degrees) in the class I, intermediate in the classes II and III (8.1 degrees +/- 2.1 degrees and 7.1 degrees +/- 2.7 degrees, respectively) and large in the class IV (18.1 degrees +/- 15.9). 3) Responsiveness to moving light stimuli (speeds, 40 degrees--90 degrees/sec) decreased in the order of IIIa, II and IIIb, and I and IV. 4) Maintained activity was lower in the superficially located cells (I, II and IIIa) than in the deeply located ones (IIIb and IV).

Characteristics of optic nerve innervation in the rat superior colliculus as revealed by field potential analysis

With lightly anesthetized rats, field responses to single optic nerve (ON) and optic chiasm shocks were studied in superficial layers of the superior colliculus, i.e., St. zonale (SZ), St. griseum superficiale (SGS) and St. opticum (SO). Based upon characteristics in the depth profile of the field response within the superficial layers, we identified three zones of N3, N2, and N1 from the SZ in this order. The narrow N2-zone was localized around the middle part of the SGS and less distinct than the other two zones. The N3-zone was characterized by a N3-wave and the N1-zone with N1- and P3-waves. N3- and P3-waves were activated by slowly conducting ON fibers (5.0 +/- 1.4 and 4.2 +/- 0.6 m/sec, respectively) while the N1-wave was by fastest conducting fibers (16.3 +/- 4.1 m/sec). According to recent Golgi studies, hypothetical mechanisms underlying the three waves were proposed: the N3-wave was ascribed to the activities of small vertical fusiform cells in the SZ or the upper half of SGS, the N1-wave to those of narrow field vertical cells which predominate in the lower half of SGS, and the P3-wave to those of wide field vertical cells whose somata are in the lower half of SGS or in the SO. The N3-, N1-, and P3-waves were found to differ from each other in recovery function tested with double ON shocks as well as in the topographical analysis of amplitudes through a whole extent of the colliculus. The three systems represented by the three waves were suggested to play different roles in visual information processing within the superficial strata.

A four group classification of the rat superior collicular cells responding to optic nerve stimulation

With lightly anesthetized rats, activities of single cells responding to single optic nerve (ON) shocks were recorded from the superficial layers of the superior colliculus, i.e., St. zonale(SZ), St. griseum superficiale (SGS) and St. opticum (SO). According to response latencies and recording depths, four classes of cells were identified: I-, II-, III-, and IV-cells. Class I cells, recorded in the SZ or the upper half of SGS, were innervated by slowly conducting ON fibers of velocities slower than 4 m/sec. Class II cells, recorded from the middle part of the SGS, were innervated by ON fibers of intermediate velocity (4--8 m/sec). Class III cells, recorded from the lower half of SGS or the upper part of SO, were innervated by fast conducting ON fibers (faster than 8 m/sec). Class IV cells were recorded from the depth similar to the class III but they were innervated by slowly conducting fibers (4-1.7 m/sec). Class I cells revealed a long-lasting inhibition after initial excitation, being a sharp contrast with cells of classes II and III which were almost free from inhibition. Inhibition exerted upon class IV cells were of intermediate strength. Possible anatomical correlates of the four classes of cells and hypothetical modes of their ON innervation were discussed.

Effect of H+ on spontaneous neuronal activity in the surface layer of the rat medulla oblongata in vitro

The effect of changing extracellular pH (pHe) on the spontaneous activity of neurons in brain slices taken from the ventral layer of the rat medulla oblongata was compared to the response of neurons in dorsal slices. In the ventral medulla, more than 50% of the neurons were excited by H+. These neurons were found just lateral to the pyramidal tract between the root of the hypoglossal nerve and the trapezoid body. In the dorsal medulla, low pHe caused an inhibition of activity in most neurons, although a few were excited. The fact that H+ elicted excitation predominantly in the ventral medullary substrate to respond to pHe changes. Depression of synaptic transmission within the neuronal network in the slice by reducing the [Ca2+]e and increasing the [Mg2+]e altered the nature of responses of neurons to H+: In the ventral medulla, the majority of neurons were inhibited by H+, whereas in the dorsal medulla more than 50% of neurons were excited. Therefore, "specificity" of the ventral medullary neurons seemed to be dependent upon intact synaptic connections. A possible role of acetylcholine-acetylcholinesterase system in the response of ventral medullary neurons to H+ is discussed.

[Two autopsy cases of adult central nervous system toxoplasmosis: light and electron microscopic studies (author's transl)]

Two autopsy cases of adult central nervous system toxoplasmosis were reported. Two cases treated with immunosuppressive agents and corticosteroids under a diagnosis of Hodgkin's disease were considered to be an acquired CNS toxoplasmosis associated with the underlying diseases. The first case, a 73 year old woman with Hodgkin's disease, showed toxoplasma lesions in the cerebrum. The second case, a 22 year old man with pulmonary tuberculosis, showed toxoplasma lesions in the cerebrum, basal ganglion, thalamus, cerebellum, pons, and medulla oblongatta. Each toxoplasma lesion showed small hemonecrotic softening. Toxoplasma cysts were seen around the hemonecrotic lesion. Encysted toxoplasma organisms were examined in detail with electron microscope.

A three-group classification of rat retinal ganglion cells: histological and physiological studies

In a whole mount preparation of the hooded rat retina, stained with methylene blue, the ganglion cell density was counted over the retina. The density ranged from 6200-6500/sq.mm to 1000-1500/sq.mm. The area with a density higher than 6000/sq.mm was called the central area and was centered at about 1 mm (20 degrees) away from the center of the optic disc, in the upper temporal quadrant. Based upon soma diameter histograms made for several locations with different eccentricities, ganglion cells were classified into three groups; large (L), medium-sized (M) and small (S). Relative frequencies of the three groups, on average, were 5, 28 and 67%, respectively. The absolute densities of S- and M-cells increase sharply towards the central area whereas the L-cells show a relatively flat distribution over the retina. The three-group classification of the retinal ganglion cells was supported by measuring their axonal conduction velocities. Single unit recordings were made from the retina and the lateral geniculate nucleus. In each case, two sites were chosen in the optic pathway for electrical stimulation: the optic chiasm and the superior coliculus in the retinal study, and the distal end of the optic nerve and the optic chiasm in the geniculate study. From differences of response latency to the two stimulating sites, conduction velocities of the optic nerve fibers were estimated. The average velocities for the L-, M- and S-axons determined by retinal recordings were 16.8, 11.4 and 6.3 m/sec and those determined by geniculate recordings 18.6, 12.0 and 5.2 m/sec.

pH sensitivity of cells located at the ventrolateral surface of the cat medulla oblongata in vitro

pH sensitivity of cells located at the ventral surface of the medulla oblongata was examined in a thin brain slice of the cat in vitro and the following results were obtained: (1) Transmembrane potential of the surface cells located in the area medial to the XIIth cranial nerve was reduced slightly by application of low pH solution; (2) In the rostral part of the area medial to the XIIth cranial nerve regular neuronal discharges could be observed extracellularly. The rate of firing of these cells was increased by lowering the external pH. These results were considered to support the idea the H+ receptor cells may exist in the surface layer of the ventral medulla.

Membranous glomerulonephritis associated with active liver cirrhosis both involved by HBs antigen

This is a case report of a 35-year-old female who showed a relatively short clinical course of severe liver cirrhosis and proteinuria. On light microscopical studies of autopsy material, besides active postnecrotic type liver cirrhosis, typical membranous glomerulonephritis was found. Immunofluorescent study disclosed not only clustered HBsAg (hepatitis type B surface antigen) in occasional hepatic cells but also beaded granular type deposition of HBsAg, IgG, IgM, IgA and complement C3 along renal glomerular basement membrane (GBM). Electron microscopical study disclosed multiple particulated material in occasional inclusion bodies of hepatic cells and in subepithelial and subendothelial dense deposits along the GBM. Enzymatic immunoelectron microscopical study confirmed these particles especially along the GBM being HBsAg themselves. It was concluded that HBsAg-Ab (antibody) complex was the pathogenetic factor responsible for the glomerular change of this particular case. Although HBsAg and Ab were examined to be negative in serum throughout the patient's clinical course, the possibility of the presence of circulating HBsAg-Ab complex in serum was discussed.