Biomedical subjects

W T Butler

Publications and source records attributed to W T Butler.

At least 73 records · Page 4Linked to original sources

PubMed1991

Baylor's program to attract minority students and others to science and medicine.

To attract minority students and others to careers in medical practice and biomedical research and to prepare them for such careers, Baylor College of Medicine conducts a variety of summer enrichment programs and other programs to improve how science is presented to students in their preprofessional years from elementary grades through college. These efforts aim to increase the number of competitive candidates for medical school, particularly those from minority groups underrepresented in medicine. They entail close collaboration between the Baylor administration and faculty from Texas public schools and two-year and four-year colleges and universities. The authors discuss the rationale for these programs and comment about the need for institutional commitments of faculty and financial support. They note that these programs are an investment in the future and that longitudinal assessment is needed to determine their ultimate success.

Advertising↗

PubMed1991

Sialoproteins of bone and dentin.

Osteopontin (OPN), bone sialoprotein (BSP) and bone acidic glycoprotein-75 (BAG-75), are sialoproteins isolated from bone extracts that resemble each other in size and composition. OPN and BSP contain an RGD sequence (not proven but possible for BAG-75), suggesting that their biological functions involve interaction with cell membrane integrins. Dentin has small amounts of OPN and BSP but also contains a major sialic acid-rich protein, DSP that has an overall composition similar to the bone sialoproteins. It is possible that DSP plays a similar biological role in dentin as OPN, BSP, and BAG-75 play in bone. Future experimentation should shed further light onto the potential relationships of the four sialoproteins.

Animals↗

PubMed1990

Immunochemical comparison of transformation-associated protein and secreted phosphoprotein.

Transformation-associated protein (TAP) has been detected in MSV-M-transformed rat cell lines as glycosylated, weakly phosphorylated protein of molecular weight (Mr) 66,000 and 68,000. In the ts-MSV-M-transformed rat kidney cell line (6m2), the synthesis of TAP and the v-mos gene product is temperature-sensitive and accompanies the expression of transformation phenotypes. Therefore, TAP potentially plays a role in cellular transformation. On the other hand, SPP represents a family of glycosylated phosphoprotein with apparent Mr ranging from 42,000 to 69,000. SPP has been detected in osteoblasts and in avian and murine retrovirus-transformed rat and mouse epithelial cells. Therefore, the potential relatedness of TAP and SPP was studied. Using the 6m2 cells, we found that SPP was strongly phosphorylated and was synthesized at both the permissive (33 degrees C) and non-permissive (39 degrees C) temperatures. By contrast, TAP was weakly phosphorylated, and was synthesized, as we found previously, only at the permissive temperature of 33 degrees C. Furthermore, in 35S-methionine incorporation studies, TAP became heavily labelled whereas SPP was not (consistent with its amino acid composition having few methionine residues). Using 125I-TAP in both immunoprecipitation and radioimmunoassays, it was found that an antiserum raised against SPP did not cross-react with 125I-TAP. Additionally, SPP has now been found in many human and rodent cells, while TAP thus far has only been detected in MSV-transformed rat cells. These data suggest that structurally, TAP and SPP are not closely related phosphoproteins.

Animals↗

PubMed1990

Temporal and spatial patterns of transforming growth factor-beta 1 expression in developing rat molars.

Regulatory peptides of the TGF-beta family affect various aspects of embryonic development. Recent immunolocalization and in situ hybridization studies have demonstrated a specific time- and tissue-dependent expression of TGF-beta 1 in the developing mouse embryo. The purpose of this study was to evaluate the distribution of TGF-beta 1 within rat molars at different stages of development, using a well-characterized antibody, highly specific for TGF-beta 1, and immunohistochemical methods of detection. TGF-beta 1 was immunolocalized intensely within the ectodermally derived stellate reticulum and the mesenchyme of the dental papilla at the bell stage of development. Marked immunostaining was also evident in the papillary layer and the reduced dental organ subjacent to ameloblasts in the differentiation and secretory phases of amelogenesis. During the formation of coronal tissues and in the pre-eruptive phase, immunoreactive TGF-beta 1 was localized conspicuously within the dental follicle overlying the tooth germ. This temporospatial pattern of expression of TGF-beta 1 appears to correlate with specific events in morphogenesis, histogenesis and cytodifferentiation during tooth development.

Ameloblasts↗

PubMed1990

China's quest for management of academic medicine.

The China Medical Board organized a management conference for the presidents of China's national medical universities. A three-person consulting team arranged by the Association of American Medical Colleges led the conference. Designed as a preliminary examination of the management problems faced by the national medical universities, the conference covered content similar to that of the AAMC Executive Development Seminars, including governance, financial management, faculty practice plans, technology transfer, information management, and organizational diagnosis. China's national medical universities are strategically managed by the Ministry of Public Health in Beijing, and for several years the ministry has increasingly decentralized the management and operational planning and control of these universities. The universities do not have enough properly trained personnel to absorb the additional management responsibilities, and the university presidents feel that they and their senior staffs need extensive training in adapting western-style management principles and practice to the Chinese setting.

Academic Medical Centers↗

PubMed1990

Histochemical localization of transforming growth factor-beta 1 in developing rat molars using antibodies to different epitopes.

In this study transforming growth factor-beta 1 (TGF-beta 1) has been immunolocalized in developing rat molars using two well characterized polyclonal antibodies, Anti-CC and Anti-LC, that recognize extracellular and intracellular TGF-beta 1, respectively. With immunohistochemical methods and the ABC-peroxidase system of detection, the growth factor was immunolocalized within the ectodermally derived enamel organ and the neural crest-derived dental papilla at the early and advanced bell stages of development. With Anti-CC, widespread and abundant extracellular TGF-beta 1 was found associated with the stellate reticulum and within central and apical regions of dental papilla mesenchyme. In contrast, Anti-LC localized TGF-beta 1 intensely within the cells of the outer dental epithelium. Moderate immunostaining for TGF-beta 1 with Anti-LC was also evident within the apical cytoplasm of inner dental epithelial cells and odontoblasts. These findings support the hypothesis that TGF-beta 1 may play a paracrine role in tooth development by regulating the epithelial-mesenchymal interactions that influence growth and cytodifferentiation events.

Animals↗

PubMed1989

Multiple forms of SppI (secreted phosphoprotein, osteopontin) synthesized by normal and transformed rat bone cell populations: regulation by TGF-beta.

Metabolic labeling has revealed that rat bone cell populations in culture synthesize several forms of the secreted phosphoprotein, SppI. Most cell populations produced two major [32PO4]-labeled forms that behaved anomolously on SDS-PAGE migrating at 60 kDa and 56 kDa on 10% gels and 55 kDa and 44 kDa on 15% gels. Minor forms of intermediate sizes were also resolved. In normal bone cells the 60 kDa form was predominant and was the only form produced by the clonal bone cell line, RCA 11, whereas the 56 kDa a form predominated in the transformed bone cell line, ROS 17/2.8. In all populations [35S]-methionine-labeling revealed SppIs at approximately 60 kDa but no 56 kDa form. Each form of SppI was specifically cleaved by thrombin which generated fragments of approximately 28 kDa. Transforming growth factor beta 1 increased SppI mRNA levels 3 to 6-fold within 24 h in the normal bone cells, but no increase occurred in the ROS 17/2.8 cells. The elevated expression of SppI was reflected in a selective increase in the synthesis of the [32PO4]-and [35S]-methionine-labeled 60 kDa SppIs.

Animals↗

PubMed1989

Transient expression of a chondroitin sulfate-related epitope during cartilage histomorphogenesis in the axial skeleton of fetal rats.

A monoclonal antibody (MC21C), raised in mouse in response to a mixture of bone proteins, was found to exhibit a unique reactivity toward native chondroitin sulfate chains. Indirect immunofluorescence and immunoperoxidase assays were performed on tissue sections at different stages of fetal rat development, in order to investigate the distribution of the MC21C epitope during cartilage morphogenesis and differentiation. This extracellular marker was present in the sclerotome and its distribution subsequently followed the segmentation pattern of the precartilaginous vertebral column. In addition, changes in the MC21C-immunostaining pattern strongly correlated with the initial growth of the vertebrae. In the axial skeleton (spinal column, basis cranii), the immunostaining by MC21C was maximum in precartilaginous condensations and then rapidly disappeared during the process of chondrification. Also, the perinotochordal matrix was intensely immunostained.

Alcian Blue↗

PubMed1989

Cell attachment activity of the 44 kilodalton bone phosphoprotein is not restricted to bone cells.

Proteins that promote cell migration, attachment and spreading are considered to play an important role in the regulation of cell function. Recently, a 44 kilodalton bone phosphoprotein (44K BPP) was shown to enhance the attachment of gingival fibroblasts and osteoblasts in vitro. The potential importance of this attachment protein in the regulation of mineralized tissue homeostasis prompted us to evaluate its ability to promote the attachment and migration of several other cell types. All the fibroblast cell lines and non-transformed calvaria cell lines assayed exhibited enhanced attachment and spreading in response to 44K BPP. Rat osteosarcoma cells (ROS 17/2.8) expressing osteoblast-like features, exhibited enhanced attachment in response to 44K BPP, while non-osteoblast-like cells (ROS 25/1) obtained from the same osteosarcoma did not. Two epithelial cell lines, CCL4 and A431, demonstrated enhanced attachment when exposed to fibronectin or laminin, but not 44K BPP. Another epithelial-like cell line, HT 1080, derived from a fibrosarcoma, showed enhanced attachment in the presence of all three attachment proteins. Fibronectin, but not 44K BPP, promoted the chemotactic migration of fibroblasts. These studies indicate that the role of 44K BPP attachment protein in the regulation of cell behavior is not restricted to bone cells.

Animals↗

PubMed1989

Alteration of enamel proteins in hypomaturation amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a diverse group of disorders that affects primarily the enamel of teeth through a number of developmental processes. The purpose of this study was to characterize the enamel proteins in normal enamel and in hypomaturation AI enamel. Impacted teeth, which were at similar stages of development, were obtained for analysis from an individual with AI and from normal healthy controls. Evaluation of the amino acid profile and quantity of organic material collected showed that there was an excess of enamel protein material that had an amelogenin-like amino acid profile in mature hypomaturation AI enamel. The AI enamel protein content was 5%, while the control enamel had 0.1% protein (by weight). These findings indicate that the maturation process had been altered in this type of AI, and that maturation did not progress beyond the initial stages of secondary mineralization. Since this disorder is inherited as an autosomal recessive condition, it seems likely that the primary defect involves an abnormality in the mechanism for protein removal in enamel maturation.

Adolescent↗

PubMed1989

The nature and significance of osteopontin.

Osteopontin is an acidic glycoprotein of about 41,500 daltons that has been isolated from rat, human and bovine bone. It is rich in aspartic acid, glutamic acid and serine and contains about 30 monosaccharides, including 10 sialic acids. Several types of data suggest that the carbohydrate is present as 1 N-glycoside and 5-6 O-glycosides while the phosphate is present as 12 phosphoserines and 1 phosphothreonine. The cDNA sequence indicated the presence of a Gly-Arg-Gly-Asp-Ser- (GRGDS) amino acid sequence identical to a cell binding sequence in fibronectin, and suggested that osteopontin might function as a cell attachment factor. This conclusion is supported by a number of studies showing that the protein promotes attachment and spreading of fibroblasts and osteoblasts to substratum, and that this attachment is inhibited by RGD-containing peptides. Despite this evidence that it contains an RGD recognition sequence and probably interacts with the family of receptors known as integrins, it appears that osteopontin does not possess a collagen-binding domain. Osteopontin is synthesized by preosteoblasts, osteoblasts and osteocytes, is secreted into osteoid and is incorporated into bone. The expression at an early developmental stage is an indication that osteopontin is an important component in the formation of bone. The level of synthesis of osteopontin by osteoblasts in culture is increased by treating these cells with 1,25-dihydroxyvitamin D3 and TGF-beta. The effect of these agents is at the transcriptional level. In addition to bone cells, osteopontin is synthesized by extraosseous cells in the inner ear, brain, kidney, and deciduum and placenta. It is also synthesized by odontoblasts, certain bone marrow cells and hypertrophic chondrocytes. Studies with several fibroblast and epithelial-derived cell lines in culture indicate that secretion of osteopontin can be dramatically increased when these cells are treated with phorbol esters, growth factors and hormones. However, osteopontin does not appear to be expressed by mesenchymal cells, fibroblasts, epidermal cells or by most epithelial cells in vivo.

Amino Acid Sequence↗

PubMed1988

Transcriptional regulation of osteopontin production in rat osteosarcoma cells by type beta transforming growth factor.

Type beta transforming growth factor (TGF beta) was shown to regulate the production of several extracellular matrix proteins. Osteopontin (OP) is a recently discovered bone matrix protein which was shown to promote the attachment of osteoblastic rat osteosarcoma ROS 17/2.8 cells to their substrate. We examined the effects of TGF beta on OP production and OP mRNA in ROS 17/2.8 cells. Four-day treatment with 4 ng/ml TGF beta 1 increased substantially the level of osteopontin in the cell culture media, as estimated by immunoblotting. Metabolic labeling showed that this effect was associated with a 3-4-fold increase in OP biosynthesis. TGF beta 1 also increased, in a dose-dependent manner starting at 0.4 ng/ml, the steady-state level of OP mRNA. The increase in OP mRNA was first detected 48 h after the addition of TGF beta 1 and lasted at least until 120 h. The half-life of OP mRNA, estimated in the presence of 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, was about 10 h and was not altered by TGF beta 1. On the other hand, the increase in OP mRNA was blocked by actinomycin D. Nuclear run-on assays indicated that TGF beta 1 increased the rate of transcription of the OP gene. Examination of hormonal interactions showed that TGF beta 1 opposed or compensated for the reduction in OP mRNA produced by dexamethasone and that TGF beta 1 did not further augment OP mRNA levels which had been increased by 1,25-dihydroxyvitamin D3 treatment. TGF beta 2 had similar effects on OP gene expression as TGF beta 1. In conclusion, TGF beta promotes the production of osteopontin in the osteoblastic osteosarcoma cells through a pathway which is at least in part mediated by transcriptional events.

Animals↗

PubMed1988

44-kDal bone phosphoprotein (osteopontin) antigenicity at ectopic sites in newborn rats: kidney and nervous tissues.

Previous immunohistochemical data have shown that the 44-kDal bone phosphoprotein (44K BPP, also called sialoprotein I or oestopontin) recently isolated in our laboratory was synthesized by osteoblasts and osteocytes and was expressed early during differentiation of bone-forming cells. We report here the presence of 44K BPP antigenicity at certain ectopic sites, namely, the proximal-convoluted tubule of the kidney, neurons, sensory and secretory cells in the internal ear. To insure specificity and reproducibility, different immunohistochemical methods were used and affinity-purified antibodies against two separate preparations of pure 44K BPP were tested. In the cells of the proximal-convoluted tubule, 44K BPP immunoreactivity was observed within apical endocytotic vacuoles and within lysosomes. This staining thus correlates with the degradation of the 44K BPP epitope which we previously demonstrated to occur in serum. On the other hand, in the neurons of the acoustic ganglion and the sensory cells of the macula, 44K BPP immunoreactivity was associated with the Golgi apparatus indicating synthesis and secretion by these cells. The finding that the 44K BPP (or a structurally related molecule) is synthesized by neurons and neuroepithelial cells deserves further investigation with respect to a possible embryologic relationship between neuroectodermal cells and the precursors of some bone forming-cells of the skull.

Animals↗

PubMed1988

Developmental expression of 44-kDa bone phosphoprotein (osteopontin) and bone gamma-carboxyglutamic acid (Gla)-containing protein (osteocalcin) in calcifying tissues of rat.

New aspects of the distribution and developmental appearance of the 44-kDa bone phosphoprotein (44K BPP, also called sialoprotein I or osteopontin) and bone gamma-carboxyglutamic acid (Gla)-containing protein (BGP, also called osteocalcin) during osteogenesis and dentinogenesis were investigated with immunocytochemical techniques using monospecific, affinity-purified polyclonal antibodies. Sections from newborn rat incisors and from various bone anlagen of newborn animals and fetuses were processed for detection of 44K BPP or BGP antigenicity. In addition, histochemical reactions for detection of alkaline phosphatase or calcium salts were performed on a number of the sections. The 44K BPP appears to be synthesized and secreted by chondrocytes only in the areas of cartilage-to-bone transition; these cells could participate indirectly in the process of bone formation by providing a suitable scaffold onto which primary marrow osteoblasts attach and spread. During osteogenesis, 44K BPP is found in bone-forming cells almost concomitantly with the appearance of alkaline phosphatase and before osteoid deposition, whereas BGP is still absent during early stages of mineralization. We hypothesize that this dramatic difference between the developmental appearance of 44K BPP and BGP reflects the delayed expression of the BGP gene relative to that of 44K BPP. In long-term cultures of bone marrow from adult mice, some fibroblastic cells expressed the 44K BPP phenotype; these cells could represent early osteogenic progenitor cells. Some experiments also suggested that, as with BGP, 44K BPP or an immunologically related protein is synthesized by some odontoblasts and secreted into predentin, prior to the onset of mineralization.

Alkaline Phosphatase↗

PubMed1987

Isolation, characterization, and biosynthesis of a phosphorylated glycoprotein from rat bone.

A phosphorylated glycoprotein was purified from the mixture of proteins extracted by demineralization of rat bone with 0.5 M EDTA in 4 M guanidinium chloride. A high level of purity for the preparation was indicated by a single band on sodium dodecyl sulfate (SDS)-gradient gel electrophoresis, sedimentation equilibrium ultracentrifugal data, and by automated Edman degradation results. The molecular weight of the phosphoprotein was shown to be about 44,000 by sedimentation equilibrium analyses in 4 M guanidinium chloride, even though an Mr of 75,000 was obtained by 5-15% SDS-polyacrylamide gel electrophoresis. Subsequent analysis by 15% SDS-polyacrylamide gel electrophoresis gave an Mr of 45,000. Analytical data showed that the protein contained 16.6% carbohydrate, possibly including 1 N-linked oligosaccharide and 5-6 O-linked oligosaccharides. The aspartic acid- and glutamic acid-rich protein contained about 300 amino acid residues including 1 phosphothreonine and 12 phosphoserine residues. Alkaline beta-elimination/NaBH4 reduction data showed that the phosphate obtained by complete acid hydrolysis prior to amino acid analysis was equivalent to the phosphate subject to alkaline beta-elimination. In this experiment, the losses of serine plus threonine exceeded the amount of phosphate liberated by 5-6 residues/protein. These serine and threonine residues probably represent O-linked oligosaccharides, since the protein contained about this number of N-acetyl-galactosamine residues. That the phosphoprotein is synthesized and secreted by osteoblast-like cells was shown with cultures of clonal rat osteosarcoma cells. After pulsing with 32PO4 the proteins secreted into the medium were precipitated with trichloroacetic acid and the radiolabeled proteins were immunoadsorbed. A protein migrating in the same position, on 5-15% SDS-polyacrylamide gel electrophoresis (i.e. with an Mr = 75,000) and on 15% gels (Mr = 45,000), as the phosphoprotein obtained from bone could be specifically immunoprecipitated.

Amino Acids↗

PubMed1987

Mechanism of fibroblast attachment to bone extracellular matrix: role of a 44 kilodalton bone phosphoprotein.

While the exact mechanisms regulating bone homeostasis are unknown, it is generally accepted that factors with the capacity to regulate cell attachment and spreading play a role in osteogenesis. A 44 kDa bone phosphoprotein (44K BPP), isolated from rat bone and synthesized by osteoblasts, was evaluated for its role in attachment and spreading of fibroblasts. In uncoated plates, enhanced cell attachment and spreading were observed when fibroblasts were exposed to the 44K BPP. The attachment properties of the bone phosphoprotein are different from those of fibronectin, in that the 44K BPP did not promote cell attachment in type I collagen wells, as was seen with fibronectin. Also, 44K BPP continued to enhance cell attachment up to 24 h, whereas cell attachment declined in time with cells exposed to fibronectin. Cycloheximide did not alter 44K BPP promotion of cell attachment, indicating that de novo protein synthesis was not required. These studies suggest that the 44K BPP is important in the regulation of cell attachment and spreading at sites of mineralization.

Bone and Bones↗

PubMed1987

A comparative immunocytochemical study on the subcellular distributions of 44 kDa bone phosphoprotein and bone gamma-carboxyglutamic acid (Gla)-containing protein in osteoblasts.

Bone gamma-carboxyglutamic acid (Gla)-containing protein (BGP or osteocalcin) and 44 kDa bone phosphoprotein (44K BPP, also called Sialoprotein I or osteopontin) have been localized at the ultrastructural level in osteoblasts from woven bones of newborn rats. Frozen, undecalcified sections of periodate-lysine-paraformaldehyde fixed specimens were incubated with affinity purified, monospecific antibodies against BGP or 44K BPP. The sites of the antigen-antibody reaction were demonstrated by the avidin-biotin-peroxidase complex method using the Hanker-Yates reagent as a peroxidase substrate. In some cases immunostaining could only be achieved after detergent treatment. The immunostained sections were then flat-embedded in Epon 812 and processed for electron microscopy. Strong specific intracellular labeling was obtained with both antibodies, but the patterns of staining differed significantly: BGP antigenicity was mainly located in the endoplasmic reticulum (ER), whereas 44K BPP behaved as a Golgi-specific antigen. In both cases, however, we found no evidence for immunostained secretory vesicles. There was no correlation between the expression of BGP by osteoblasts and the morphological aspect of these cells, their apparent degree of polarization with respect to the bone matrix, or their relation with the mineralized phase.

Animals↗

PubMed1987

Immunocytochemical localization of gamma-carboxyglutamic acid-containing proteins (osteocalcin) in rat bone and dentin.

Gla-protein or osteocalcin is one of the most abundant noncollagenous matrix proteins found in bone and dentin. The present study describes, with high resolution, the intracellular and extracellular distribution of Gla-protein in alveolar bone and incisor dentin. Sections of tissues embedded in Lowicryl K4M were incubated with rabbit antibodies to rat dentin Gla-protein. The site of the specific antigen-antibody reaction was revealed by the protein A-gold complex. Labeling was detected over bone and dentin while fewer gold particles were present over prebone and predentin. Gold particles were also seen over the protein synthetic organelles (rough endoplasmic reticulum, Golgi apparatus) of osteoblasts and odontoblasts. These findings confirm, with improved resolution, previous light immunohistochemical studies, and offer the possibility to examine the secretory pathway of the protein.

Alveolar Process↗