Biomedical subjects

H Riml

Publications and source records attributed to H Riml.

4 recordsLinked to original sources

PubMed1990

Non-invasive in-vivo autoradiographic method to measure axonal transport in serotoninergic neurons in the rat brain.

We studied axonal transport of serotoninergic neurons by autoradiography following intravenous administration of alpha-[14C]methyl-L-tryptophan (alpha-[14C]MTrp). Autoradiograms obtained 24 h after intravenous injection of the tracer demonstrated clearly all raphe nuclei and the major ascending pathway, the medial forebrain bundle (MFB). From these autoradiograms it was clear that radioactivity traveling along the MFB had already reached the substantia nigra and ventrolateral geniculate body nuclei, terminal field. The whole route of the MFB was well visualized from an axial cross-section of a three-dimensional display of data. Autoradiograms obtained at 6 h after injection revealed only the caudal part of the MFB but all raphe nuclei were labelled, indicating that the tracer was in the process of being transported, probably as an alpha-methyl-5-hydroxytryptamine, via the MFB. The axonal transport rate was estimated from the brain autoradiograms of 4 rats killed 6 h after injection of the tracer. The mean distance of the tracer transported via the medial forebrain bundle in 4 rats was 3.8 +/- 0.4 (S.D.) mm, which corresponded to the level of the posterior to mid-hypothalamus. The axonal transport rate calculated from this distance from the medial raphe was 0.63 +/- 0.07 mm/h (14 mm/day). There was no significant difference in the axonal transport rate between the right and left side of the MFB.

Animals↗

PubMed1990

Formation and survival of a postsynaptic specialization in cultures of embryonic Xenopus nerve and muscle cells.

The formation and survival of nerve-induced clusters of acetylcholine receptors (AChRs) was monitored over a synaptogenic period of several days in cultures of myotomal muscle cells and spinal cord neurons derived from embryos of Xenopus laevis. AChRs were labeled with fluorescent alpha-bungarotoxin so that neurite-associated receptor patches (NARPs) could be viewed at daily intervals throughout the neuritic arbor of selected neurons. To avoid bleaching the NARPs and damaging the neurons, the intensity of the fluorescence excitation was reduced to 3%. Images were digitized and NARPs were measured with a computer-based image analysis system. Virtually all newly formed NARPs (greater than 90%) were detected at the same time as neurite-muscle contact and in the same proximal-distal sequence as neuritic growth. Those which formed in 6- to 13-day-old cocultures had similar distributions with respect to length, area, intensity, and area X intensity to those which formed in 1- to 2-day-old cocultures. NARPs exhibited variable daily changes in these parameters but on average they grew and reached close to their ultimate values within 1-2 days. Almost all (greater than 95%) survived as long as their contacts. In cases where NARP formation occurred on the same muscle on 2 or more different days, the ones which formed first were the most extensive. Spontaneous neurite withdrawal occurred mainly from young NARPs and resulted in their rapid disappearance. It is suggested that during the period when neurons grow and make new contacts with muscle cells there is no substantial change in their capacity to trigger the formation of new synaptic sites and maintain preexisting ones, and that the first-forming synapses on a muscle cell tend to be the largest because muscle cells have a limited capacity to generate postsynaptic membrane. Additional implications of the findings for synapse formation and elimination are discussed.

Animals↗

PubMed1990

Functional organization in the ferret visual cortex: a double-label 2-deoxyglucose study.

The functional organization of visual cortical area 17/18 of the ferret was studied using a double-label 2-deoxyglucose (2-DG) method. Animals were stimulated sequentially with moving gratings of 2 different orientations. Elongated orientational patches running roughly at a right angle into the area 17/18 border were seen. The orientation maps were similar in areas 17 and 18. When animals were stimulated with 2 orthogonally oriented gratings, activation patterns were not fully complementary but did not overlap. A complex pattern of partial overlap was observed, with orientations differing by 45 degrees. More gradual and more abrupt changes alternated frequently on a scale smaller than the average periodicity in the patterns. A cortical patch representing a given orientation was regularly surrounded by both neighboring and orthogonal orientations. The direction of the orientational changes reversed frequently in the immediate vicinity of any orientational patch. Orientation maps were compared with complete maps of retino-cortical projections obtained by transneuronal labeling with intravitreally injected tritiated proline. Ocular dominance in the binocular segment of both areas 17 and 18 was found to be organized into elongated ipsilateral islands in an almost contiguous contralateral projection. In area 18, the patches were wider than in area 17, and the ipsilateral islands were smaller in the regions representing the upper and central visual field than in those representing the lower visual field.

Animals↗

PubMed1988

Echinococcus multilocularis: relationship between persistent inflammation, serum amyloid A protein response and amyloidosis in four mouse strains.

LPS-hyporesponsive (C3H/HeJ) and LPS-sensitive (C57BL/6, CBA/J, C3H/HeSn) strains of mice were infected intraperitoneally with 50 alveolar hydatid cysts (AHC) to assess the effect of protracted severe inflammation on serum amyloid A protein (SAA) concentrations, splenic amyloid deposition, and pre- and postamyloidotic alterations in the splenic architecture. In general, the SAA concentrations in all the four mouse strains showed a moderate but steady increase throughout the course of infection. Splenic amyloid deposition commenced between 6 to 8 weeks postinfection (p.i.) when the SAA concentrations were relatively low and increased progressively until 12 weeks p.i. when 52 to 78% of the splenic parenchyma was obliterated. CBA mice which harbored the largest AHC throughout the 12-week course of infection showed the poorest SAA and amyloid responses; the situation was reversed in the C3H/HeSn strain. Histologically, most of the splenic follicles, during the stage of maximum amyloid deposition, appeared hypocellular. Their T-cell-dependent periarterial sinuses were either totally depleted of cells or contained plasma cells or myeloid cells. These results show that (a) there is no direct correlation between the intensity of inflammation, SAA concentrations, or amounts of amyloid deposition in either of the four mouse strains and (b) amyloidosis secondary to AHC infection differs from other experimental mouse models of amyloidosis in the magnitude of SAA elevation during the preamyloid phase.

Acute Disease↗