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Biomedical subjects

S Laurberg

Publications and source records attributed to S Laurberg.

107 records · Page 6Linked to original sources
PubMed1987

Esophageal collagen content and mechanical strength after endoscopic sclerotherapy of esophageal varices. An experimental study in rabbits.

Twenty-five rabbits with esophageal varices were randomized to no treatment (n = 10) or endoscopic paravenous sclerotherapy of the varices (n = 15). Five other rabbits served as sham-operated controls. When they were killed, the mechanical strength and collagen content of the esophagus were determined at proximal, middle, and distal levels. The esophagus was examined histologically at proximal and distal levels. Animals treated by sclerotherapy showed histologic edema and inflammation of the esophageal wall after 2 days. This was not accompanied by any decrease in collagen content or mechanical strength. Ten days after sclerotherapy a slight but non-significant increase in collagen content and mechanical strength at middle and distal levels was observed. After 30 days the increase in collagen content at middle and distal levels was significant, and the mechanical strength was significantly increased at the middle level.

Animals↗
PubMed1986

Non-cholinergic afferents determine the distribution of the cholinergic septohippocampal projection: a study of the AChE staining pattern in the rat fascia dentata and hippocampus after lesions, X-irradiation, and intracerebral grafting.

The acetylcholinesterase (AChE) activity of the rat hippocampus and fascia dentata depends on an intact septohippocampal connection, and histochemical staining for AChE is commonly used to monitor the distribution of the cholinergic septohippocampal projection. It is also characteristic that the laminae of low or moderate to dense AChE staining in the hippocampus and fascia dentata coincide with the terminal fields of the major non-cholinergic, afferent pathways. While studying lesion-induced collateral sprouting and aberrant axonal growth of these pathways we observed that the AChE staining pattern changed in accordance with the reorganized distribution of the non-cholinergic pathways, and this occurred even without direct interfering with the septohippocampal projection itself. Widening and narrowing of the medial perforant path and mossy fiber terminal zones thus resulted in corresponding changes in the bands of AChE staining normally associated with these zones. Expansion of the commissural-associational hippocampodentate projections and the lateral perforant path was in a similar way paralleled by a widening of the AChE-poor zones which normally overlap with the termination of these projections. Observations of the same kind were made in intracerebral transplants of fascia dentata innervated by various host afferents, and in rats subjected to neonatal X-irradiation, where the mossy fiber projection is reduced and aberrant perforant pathways project into CA3 due to a reduced formation of granule cells. The observed sets of changes with linkage between the different non-cholinergic projections and the activity of AChE in their respective terminal fields were accordingly reproduced under several different experimental conditions. It could not be explained alone by interaction between the septal afferents and their target cells. We therefore conclude that the density and laminar distribution of the AChE activities within the hippocampus and fascia dentata are determined at least in part by the major afferent, non-cholinergic nerve connections. We suggest that the effect occurs through direct axonal interaction or through changes in the receptiveness of the common dentate and hippocampal target cells.

Acetylcholinesterase↗
PubMed1985

Cervical dorsal root ganglion cells with collaterals to both shoulder skin and the diaphragm. A fluorescent double labelling study in the rat. A model for referred pain?

Rat cervical spinal ganglion cells were retrogradely double-labelled with fluorescence dyes following injection of one dye into a cutaneous shoulder nerve and the other into the diaphragm. We suggest that the peripheral dichotomization of these ganglion cells could form the structural basis for the referred 'phrenic' pain in the shoulder region that can follow irritation of the diaphragm.

Animals↗
PubMed1984

Structure and function of aberrant perforant path synapses in the hippocampus of neonatally X-irradiated rats.

We have examined the functional and morphological characteristics of synapses made by perforant path fibres projecting from the entorhinal cortex to the medial zone of the dentate area in adult rats which had been X-irradiated at birth, a procedure which prevents the proliferation of granule cells in that zone. We provide ultrastructural evidence that perforant path fibres in this region make synaptic contact with dendritic spines, and demonstrate that these synapses generate functional responses when the perforant path is stimulated. The evidence suggests that aberrant functional connections are made with the elongated basal dendrites of pyramidal cells.

Animals↗
PubMed1983

Ectopic granule cells of hilus fasciae dentatae projecting to the ipsilateral regio inferior of the rat hippocampus.

Retrograde fluorescent tracing techniques were used in a search of projections from the hilus of fascia dentata to the Ammon's horn. We found that up to 5% of the neurons in the hilus project to the ipsilateral regio inferior. The projection originates from cells that morphologically resemble ectopic granule cells and terminates in the mossy fiber layer. We found no evidence for a projection from the hilus to the ipsilateral regio superior or the contralateral Ammon's horn.

Animals↗
PubMed1981

Lesion-induced sprouting of hippocampal mossy fiber collaterals to the fascia dentata in developing and adult rats.

A lesion-induced formation of an abnormal projection of hippocampal mossy fiber collaterals to the molecular layer of the fascia dentata was studied in rats. Both immature (1--30 days old) and adult rats were subjected to hippocampal and entorhinal lesions which alone or in combination removed one or more of the major afferents to the dentate molecular layer (commissural, associational, and perforant path). Some lesions in addition transected the main part of the mossy fibers en route from the dentate granule cells to the hippocampal pyramidal cells in regio inferior (CA3). The formation of aberrant mossy fiber terminals in fascia dentata (supragranular mossy fibers) was monitored by the histochemical Timm sulphide silver method, but the presence of aberrant terminals was also observed in the electron microscope. Abnormal amounts of supragranular mossy fiber terminals were found following entorhinal lesions of both immature and adult rats, but not following commissural lesions. Even larger amounts of aberrant terminals were, however, found in immature and adult rats subjected to lesions which removed most of the associational hippocampodentate projection by isolating columns of fascia dentata from major parts of the hilus (CA4). Pure transections of the fascia dentata perpendicular to its longitudinal septotemporal axis did not in itself cause aberrant supragranular terminals, although such lesions partially damaged the associational afferents. When the transections were combined with commissural lesions or entorhinal lesions or both, large amounts of supragranular terminals did, however, form at the denervated levels septal to the transection. After comparison of the amounts and distributions of the aberrant terminals found after the different lesions and in transplants of dentate tissue with different amounts of afferent input, we conclude that it is deafferentation of the dentate molecular layer, and not axotomy of the mossy fibers in the hilus of CA3 (pruning), that causes the aberrant growth of mossy fiber collaterals. Moreover, simultaneous removal of more than one afferent system seems to have a potentiating rather than a simple additive effect on the formation of supragranular mossy fibers.

Afferent Pathways↗
PubMed1981

Associational and commissural collaterals of neurons in the hippocampal formation (hilus fasciae dentatae and subfield CA3).

In rats, True Blue (or Granular Blue) was injected into the hippocampus of one hemisphere and Nuclear Yellow into a homotopic site of the hippocampus of the contralateral hemisphere. Following restricted injections into the septal part of area dentata fluorescent neurons were found in hilus fasciae dentate on both sides except for the most temporal 2 mm, while no fluorescent neurons were found in the Ammon's horn. Following restricted injections into the septal part of CA1, fluorescent CA3 pyramidal cells were found on both sides as far as 5.5--6.0 mm temporal to the injection, while no fluorescent neurons were seen in the hilus fasciae dentate. Hilus neurons simultaneously labeled with the True Blue and Nuclear Yellow were seen following injection of these substances into the area dentata of the two hemispheres, one tracer in each hemisphere, while double-labeled CA3 pyramidal cells were seen in cases with analogous injections in the septal part of CA1 of the two hemispheres. We conclude that the commissural and associational fibers to the area dentata and the Ammon's horn arise from neurons in the hilus and the CA3, respectively, and that at least some hilus and CA3 neurons have both an associational and a commissural branch.

Afferent Pathways↗
PubMed1979

Commissural and intrinsic connections of the rat hippocampus.

The commissural and intrinsic connections of the hippocampus were studied using the Fink-Heimer method and the horseradish peroxidase (HRP) uptake technique. A conspicuous septo-termporal gradient was found of the density of the commissural projection that passes through the psalterium ventrale to the Ammon's horn. The degeneration resulting from transection of the psalterium ventrale was most dense in the septal tip and decreased towards the temporal tip. The commissural and ipsilateral connections from the hilus fasciae dentatae (CA4) and regio inferior (CA3/CA2) were found to terminate in different parts of the hippocampus. The hilus fasciae dentatae gave rise to ipsilateral and commissural projections to the dentate area only. The regio inferior has ipsilateral and commissural projections to the Ammon's horn. A specific termination pattern was found of the projection from regio inferior to stratum radiatum of both the ipsilateral and contralateral regio superior (CA1) and regio inferior (CA2/CA3). At levels temporal to the lesion, the projection is primarily to the superficial part of stratum radiatum, while at levels septal to the lesion the terminal zone occupies the deep part of the layer. This pattern was not related to the position of the cells of origin, along the septo-temporal or subiculo-dentate axes. In general, the commissural projections showed the same degree of septo-temporal divergence as the ipsilateral projections. The only major difference in the terminal fields of the two sets projections to the Ammon's horn was that the terminal zone of the commissural projection to stratum oriens was always more dense than that of the ipsilateral projection to this layer, while an inverse gradient was seen in stratum radiatum. The projections from the septal and middle dorso-ventral parts of regio inferior differed. The temporal spread of the projections from the septal part was large while that from the projections arising at middle dorso-ventral levels was more restricted. Moreover, a longitudinal association path interconnecting different parts of the regio inferior along the septo-temporal axis was seen to arise only from the cells in the septal parts of the regio inferior. Each part of the regio inferior projected to all parts of stratum radiatum and oriens of the contralateral Ammon's horn. However, the projection to the contralateral regio inferior was most dense at the site homotopic to that lesioned. The ventricular part of regio inferior projected primarily to the contralateral stratum oriens of the Ammon's horn, while the part adjacent to the dentate area mostly supplied stratum radiatum.

Animals↗
PubMed1978

Benzodiazepine receptor in brain.

The evidence that the brain possesses specific receptors for benzodiazepines is summarized. Further we present a series of brain lesion experiments in rats showing that specific neuronal destructions by 6-hydroxydopamine, kainic acid in the striatum, X-ray irradiation of the hippocampus, intraperitoneal 3-acetyl-pyridine or hemisection at the thalamic level do not reduce the level of benzodiazepine receptors in striatum, hippocampus, cortex or cerebellum. These results show that the benzodiazepines are not positioned on dopamine or noradrenaline terminals, cholergic or GABA-ergic neurons in the striatum, granular cells in the hippocampus or climbing fibers in the cerebellum.

Animals↗
PubMed1977

Commissural connections of the dentate area in the rat.

The commissural connections of the area dentata were investigated with the Fink-Heimer silver impregnation method and the commissural terminals in the hilus of the fascia dentata further studied by electron microscopy of anterograde degeneration. The commissural endings in the molecular layer were found to terminate as previously reported by others. In addition it was shown that the hilus also receives a significant commissural input. The commissural afferents to both the molecular layer and the hilus terminate along the full rostro-caudal extent of the area dentata, but with varying densities. The degeneration in the molecular layer is maximal dorso-rostrally and declines in the caudo-ventral direction, whereas the degeneration in the hilus varies inversely. The commissural terminals in the hilus make asymmetrical contacts with dendritic spines and to a lesser extent with dendritic stems. Dark, but otherwise apparently normal terminals with the features of mossy fiber boutons, were encountered in low numbers in both decommissurated and control animals. The commissural projection to the dentate area originates in the opposite hilus and possibly the adjacent part of CA3 (CA3c). Fibers from middle dorso-basal levels of the hilus to the opposite molecular layer are distributed more rostrally than ventrally relative to the level of the source of the fibers.

Animals↗
PubMedDate not supplied

Brain grafts can restore irradiation-damaged neuronal connections in newborn rats.

Immature rat brain tissue grafted to the brain of other immature and adult rats can survive and establish nerve connections with the host brains. In addition to facilitating the study of factors involved in the formation of central neural connections, brain grafts may also be used to substitute damaged or maldeveloped neurones. With exceptions in the visual system, the restoration of specific central neural connections has to date involved grafts of cholinergic and monoaminergic neurones, which have good regenerative capacity. In the present study, rat hippocampal neurones were damaged by neonatal X-ray irradiation and replaced by transplantation of normal, developing neurones of the same type. The grafted neurones (dentate granule cells) are not cholinergic or monoaminergic, but when appropriately located in the host hippocampal region they established specific and highly ordered afferent and efferent connections with the damaged host brain. Moreover, simultaneous demonstration of afferent and efferent transplant pathways showed that serial host-transplant-host connections had formed, restoring the normal neuronal circuitry initially disrupted by the irradiation.

Animals↗
PubMedDate not supplied

Bursting strength of experimental colonic anastomoses. A methodological study.

This study was performed to evaluate the validity of the bursting strength test of experimental anastomoses. By a combination of measuring the intraluminal physiological pressure during the test procedure with a radiological detection of the anastomosed intestinal segment until disruption it was demonstrated that the bursting pressure is a meaningful parameter since the maximum pressure equals the time of anastomotic leak. At day 6 60% of the tested segments disrupted outside the anastomotic line. This indicates that the bursting strength test is not a valid measure for determining the strength of colonic anastomoses after the 4th to 5th postoperative day. Moreover, the bursting wall tension parameter was evaluated. Assessment of the anastomotic radius demonstrated significant differences when the anastomotic radius at disruption was determined from the amount of inflated contrast compared with the radius detected radiologically. These differences had the effect that the wall tension at burst compared with the wall tension determined from direct radius measurement on day 4 was 61% higher than the wall tension determined from the amount of inflated contrast with no correction for elongation of the tested segment, and 36% higher than the wall tension determined from the amount of inflated contrast and corrected for elongation of the segment. No differences in the bursting strength were found between inflation rates of 2.5 and 5.0 ml.min-1. In conclusion, the bursting strength test is a meaningful parameter since the maximum physiological pressure equals the time of anastomotic radiological disruption, and the bursting pressure is a more exact parameter for measuring the bursting strength than the bursting wall tension.

Anastomosis, Surgical↗