Biomedical subjects

L A Opperman

Publications and source records attributed to L A Opperman.

25 records · Page 2Linked to original sources

PubMed1992

Ontogeny of calbindin-D28K and calbindin-D9K in the mouse kidney, duodenum, cerebellum and placenta.

The appearance of the calcium-binding proteins (CaBP-D28K and CaBP-D9K) in embryonic mice tissues was determined using a sensitive immunohistochemical assay. CaBP-D28K first appears in myenteric nerve plexuses of the duodenum on day E15, in duodenal villus cells on day E16, in Purkinje cells of the cerebellum on day E19, in cells of the mesonephric duct on day E11 and in the metanephric duct on day E12. CaBP-D9K first appears in enterocytes of the duodenum on day E18, in trophoblastic giant cells (TGC) of the placenta on day E10, and in the metanephric duct on day E15. A differential time of appearance and colocalization of the two CaBPs is demonstrated in the embryonic mouse kidney, suggesting either that vitamin D does not control both CaBPs in the foetus or that the vitamin D control is unequal. The early appearance and location of CaBP-D9K in TGCs may suggest that these cells play an important role in transplacental transfer of calcium.

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PubMed1990

Immunohistochemical localization of calbindins (28K and 9K) in the tissues of the baboon Papio ursinus.

An indirect immunoperoxidase procedure was used to detect the presence of calbindin-D28K and calbindin-D9K in the cerebellum, kidney, and duodenum of the baboon Papio ursinus. Antibodies to chick calbinding-D28K and to both rat and mouse calbindin-D9K were used. The cerebellum and kidney were shown to contain calbindin-D28K; the doudenum contained calbindin-D9K. In the cerebellum, positive staining was found in the Purkinje cells only; in the kidney, positive staining was found in the distal convoluted tubules, connecting tubules, and collecting tubules, extending deep into the medullary regions of the kidney. Staining in the duodenum was confined to the enterocytes of the villi, with no stain present in the crypt regions or goblet cells. Thus the baboon, a primate, contains the larger of the calbindins in both the cerebellum and kidney as does the human and monkey, but its distribution in the kidney is more generalized than that found in humans. The molecular weight of calbindin-D9K was found to be similar to that found in other animals. However, the calbindin-D28K from the baboon tissues appears to be slightly smaller than the protein found in other animals and may therefore be of similar size to the human calbindin-D28K (Mr 26,000).

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PubMed1990

Appearance during chick embryogenesis of vitamin D-dependent calcium-binding protein (calbindin-D28K).

The appearance of the vitamin D-dependent calcium-binding protein (calbindin-D28K) in embryonic chick tissues was determined using a sensitive immunohistochemical assay to elucidate the possible role of calbindin-D28K during embryogenesis. This protein first occurs in renal, cerebellar and intestinal cells during the final stages of maturation and/or differentiation. It is during this period of their development that these tissues become functional. On the basis of our observations, we suggest that the onset of cell function may be coupled with the appearance of calbindin-D28K.

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PubMed1980

Induction of supernumerary tracheal buds and the stimulation of DNA synthesis in the embryonic chick lung and trachea by epidermal growth factor.

Epidermal growth factor (EGF) has been found to stimulate DNA synthesis in both the trachea and bronchial tree of 5-day-old chick embryo lung rudiments in organ culture. After 20 h culture in the presence of 10 ng/ml EGF, the incorporation of tritiated thymidine into DNA is stimulated two- to three-fold following a 2 h labelling period, as revealed by scintillation counting. Autoradiographic data indicate that this stimulation is most marked in the epithelial tissue component of both the trachea and bronchial tree. Supernumerary "lung" buds have been induced in the normally unbranched tracheal epithelium by agarose pellets containing EGF, such buds having been previously induced only by grafting a variety of mesenchymal tissues alongside the tracheal epithelium. Since EGF has been shown to be a potent stimulator of tracheal DNA synthetic activity it is suggested that the induction of supernumerary buds by the EGF-agarose pellets is achieved through a localized stimulation of cell proliferation in the tracheal epithelium. These data would further suggest that the induction of supernumerary tracheal buds by various mesenchymal tissues is similarly due to a localized increase in mitotic activity resulting from the action of some mitotic stimulator substance(s) emanating from the inducing mesenchymal tissue. This conclusion may be extended to include normal bud formation which occurs during branching morphogenesis in several developing organ systems.

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PubMedDate not supplied

Cranial suture obliteration is induced by removal of transforming growth factor (TGF)-beta 3 activity and prevented by removal of TGF-beta 2 activity from fetal rat calvaria in vitro.

Cranial suture morphogenesis requires soluble, heparin-binding factors secreted by the dura mater to resist premature osseous obliteration. Elevated levels of transforming growth factor (TGF)-beta 1, TGF-beta 2, and TGF-beta 3 have previously been noted in cranial sutures undergoing normal and premature sutural obliteration. To examine the role of TGF-beta s in regulating cranial suture morphogenesis, an established in vitro, serum-free, calvarial culture system was used. In this system, fetal rat coronal sutures undergo apparently normal suture morphogenesis in the presence of dura mater, but undergo osseous obliteration in the absence of dura mater. Neutralizing polyclonal antibodies to TGF-beta 1, TGF-beta 2, or TGF-beta 3 were added to cultures of fetal day 19 rat calvaria, which were harvested at 3, 4, or 5 days, processed for histology, sectioned, and examined. Coronal sutures from calvaria cultured in the presence of dura mater resisted obliteration, either alone or in the presence of TGF-beta 1 or TGF-beta 2 neutralizing antibodies. However, sutures from calvaria cultured in the presence of TGF-beta 3 neutralizing antibodies became obliterated. Conversely, sutures from calvaria cultured in the absence of dura mater became obliterated by bone, either alone or in the presence of neutralizing antibodies to TGF-beta 1 or TGF-beta 3. However, those sutures cultured in the presence of neutralizing antibodies to TGF-beta 2 were rescued from osseous obliteration.

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PubMedDate not supplied

Hyaluronan is essential for the expansion of the cranial base growth plates.

Exquisite control of chondrocyte function in the zone of hypertrophy results in expansive growth of cartilaginous growth plates, and is a prerequisite for normal skeletal lengthening. We hypothesize that hyaluronan-mediated hydrostatic pressure causes lacunae expansion in the zone of hypertrophy; an important mechanism in cartilaginous growth plate and associated skeletal expansion. The role of hyaluronan and CD44 in this mechanism was studied using organ culture of the bipolar cranial base synchondroses. Hyaluronan was present in the hypertrophic zones, pericellular to the hypertrophic chondrocytes, while no hyaluronan was detected in the resting, proliferating and maturing zones. This localization of hyaluronan was associated with increased lacunae size, suggesting that chondrocytes deposit and retain pericellular hyaluronan as they mature. In comparison, Toluidine Blue staining was associated with the territorial matrix. Hyaluronidase, the hyaluronan-degrading enzyme, and CD44, the receptor for hyaluronan which also participates in the uptake and degradation of hyaluronan, were co-localized within the zone of ossification. This pattern of expression suggests that cells in the early zone of ossification internalize and degrade hyaluronan through a CD44-mediated mechanism. Treatment of the cultured segments with either Streptomyces hyaluronidase or hyaluronan hexasaccharides inhibited lacunae expansion. These observations demonstrate that hyaluronan-mediated mechanisms play an important role in controlling normal skeletal lengthening.

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PubMedDate not supplied

Dura mater maintains rat cranial sutures in vitro by regulating suture cell proliferation and collagen production.

Craniosynostosis, the premature osseous obliteration of cranial vault sutures, can result from mutations in genes encoding components of growth factor signaling systems or the extracellular matrix (ECM). Little is known of the capacity of osteoprogenitor cells of the cranial sutures to divide or to synthesize ECM in situ. Osteoblasts derived from patients with prematurely fused sutures were reported to express alkaline phosphatase and osteocalcin at elevated levels, while proliferating at a rate comparable to control cells [DePollack et al., JBMR, 1996]; however, the suture osteoprogenitors, the population most likely to show proliferative abnormalities, were not present in the fused sutures used for this study. A model in which rat coronal sutures and associated bones develop normally in vitro, but in which sutures can be induced to fuse in the absence of dura mater, was used to examine cell proliferation and total protein synthesis in unfused sutures cultured in the presence of dura mater or in sutures induced to fuse in the absence of dura mater. Significantly increased cell proliferation was seen in suture cells prior to sutural obliteration, which returned to control levels as sutural fusion proceeded. Collagen synthesis in fusing sutures was elevated compared to non-fusing sutures and comparable to that seen in bone. Results indicated that in the absence of intercellular signals provided by the dura mater, suture cell proliferation increased initially, followed by increased synthesis of collagenous ECM within the suture and subsequent osseous obliteration of the suture. Thus factors originating in the dura mater affected suture cell proliferation and ECM production and were required for the maintenance of suture patency.

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