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Biomedical subjects

B Lauritzen

Publications and source records attributed to B Lauritzen.

24 records · Page 2Linked to original sources
PubMed1987

Cell junctions and membrane specializations in the ventricular zone (germinal matrix) of the developing sheep brain: a CSF-brain barrier.

Cell junctions in the ventricular zone (germinal matrix) of the embryonic and foetal sheep brain were examined with thin-section and freeze-fracture electron microscopy. Neuroependymal cells in the early ventricular zone (days 19-40 of embryonic development, gestation period 147 days) exhibit a novel arrangement of cell junctions that connect adjacent neuroependymal cells at their lateral cell membranes next to the ventricular system. Small but typical gap junctions were also identified from the earliest stages examined. In serial thin sections and using a goniometer with a tilting device, the cell contacts showed a tight junction-like appearance of close and continuous fusion between neighbouring cell membranes. However, they were not arranged in a belt-like fashion close to the ventricular surface, but spiralled from the ventricular pole of the cells along the lateral cell membrane towards the deeper parts of the ventricular zone. Their freeze fracture appearance was different from that of single-stranded tight junctions in that the dimensions of their ridges and grooves were generally greater and the E-face grooves contained many particles. The junctions were especially prominent where more than two cells made contact. At mid-gestation they were less prominent than earlier and at 125 days gestation the neuroependymal layer was replaced by a mature-looking normal ependymal layer in which individual ependymal cells were connected by zonulae adherentes and large gap junctions; orthogonal arrays were also prominent. The close contact between gap junctions and single-stranded junctions found early in gestation suggests that there may be some developmental relation between these two membrane specializations. The transient single-strand junctions presumably form the morphological basis for a recently described CSF-brain barrier in the early foetal sheep brain. They may also have some mechanical function in anchoring neighbouring cells together in the region of the developing brain where cells are continuously dividing and migrating.

Animals↗
PubMed1987

Co-localization of parathyroid hormone and secretory protein-I in bovine parathyroid glands: a double immunocytochemical study at the electron microscopical level.

Secretory protein-I (SP-I), also known as chromogranin A, is an acidic glycoprotein of unknown function that is found in large amount in the secretory granules of all endocrine and neuroendocrine cells, but not in exocrine or epithelial cells. It is cosecreted with parathyroid hormone (PTH) and by immunocytochemical staining has been reported to exist in the same subcellular structures of the gland. In the present study we have used the colloidal gold-double immunocytochemical technique at the ultrastructural level to precisely define the locales of SP-I and PTH in the bovine parathyroid cell. SP-I and PTH were co-localized to the same secretory granules. The patterns for both gold labels were diffuse ones throughout the granule and suggested that there was a general association of SP-I and PTH. There was little or no localization of the SP-I at the secretory granule membrane. The results support the concept that SP-I is responsible for stabilization of PTH within the secretory granules.

Animals↗
PubMed1979

Double replica technique applied to choroid plexus from early foetal sheep: completeness and complexity of tight junctions.

Choroid plexuses from early and late sheep foetuses were examined by an improved freeze-fracture technique and the use of double-replicas to define the structure of the tight junction network of the epithelial cells. 'Complex' strands which consist of two normal parallel strands separated by a single row of pits or particles are defined and demonstrated in complementary faces. Since this strand variety was encountered in the same proportion in the different development stages investigated, it could not be correlated with changes in permeability. It is more likely that the 'complex' strands are associated with the transfer of gap junction particles within the membrane. The question of the significance of discontinuities in P face ridges was also resolved by the double replica technique: the few discontinuities which were observed could be accounted for by particles in the complementary E faces. Furthermore, approximately the same number of such junction displacements was found in early and late stages which makes it unlikely that this phenomenon could contribute to changes in permeability. Thus it has not been possible so far to relate any structural feature of the tight junction network in developing choroid plexus epithelial cells with the reported changes in permeability of the blood-C.S.F. barrier.

Animals↗
PubMed1979

Primary results after resection and anastomosis for mid-rectal cancer with a new stapling instrument. A preliminary report.

Early results after resection with primary anastomosis for cancer of the mid-rectum using a new stapling instrument are reported. 20 patients with an adenocarcinoma 7-12 cm from the anal verge were operated. On patient died postoperatively from respiratory complications but with no sign of anastomotic dehiscence. One patient had a clinically recognizable leakage which closed spontaneously within 2 days. Three patients had roentgenologically demonstrable leakage but no clinical symptoms. On examination, 1-3 months after the operation, all patients were continent for feces as well as for gas and none had more than four bowel movements per day. Resection and anastomosis by means' of the stapling instrument is practicable even at the lowest level, and is far less time consuming and does not require the same degree of training as low anterior resection with conventional suture anastomosis.

Adenocarcinoma↗