Biomedical subjects
Publications and source records attributed to K Rhodes.
As devices become smaller and bonds more critical, choosing the right adhesive system may be essential to the success of the device. This article investigates some adhesives and primers used to adhere difficult substrates.
Paediatricians were surveyed about baby walker knowledge, attitudes, and practice. Advising about walkers was associated with working in community paediatrics, treating walker related injuries, knowledge about walkers, and positive attitudes towards walker health promotion. Greater knowledge about walkers was associated with more negative attitudes to walkers. Educating paediatricians and parents about the risks of, and alternatives to using walkers is important.
Matrix metalloproteases (MMPs) and tissue inhibitors of metalloproteases (TIMPs) are involved in many cell migration phenomena and produced by many cell types, including neurons and glia. To assess their possible roles in brain injury and regeneration, we investigate their production by glial cells, after brain injury and in tissue culture, and we investigate whether they are capable of digesting known axon-inhibitory proteoglycans. To determine the action of MMPs, we incubated astrocyte conditioned medium with activated MMPs, then did western blots for several chondroitin sulphate proteoglycans. MMP-3 digested all five proteoglycans tested, whereas MMP-2 digested only two and MMP-9 none. To determine whether MMPs or TIMPs are produced by astrocytes in vitro, we tested both primary cultures and astrocyte cell lines by western blotting, and compared them with Schwann cells. All cultures produced at least some MMPs and TIMPs, with no obvious correlation with the ability of axons to grow on those cells. Both MMP-9 and TIMP-3 were regulated by various cytokines. To determine which cells produce MMPs and TIMPs after brain injury, we made lesions of adult rat cortex, and did immunohistochemistry. MMP-2 was seen to be induced in activated astrocytes through the whole thickness of the cortex but not deeper, but MMP-3 was not seen in the injured brain. TIMP-2 and TIMP-3 immunoreactivities were induced in activated astrocytes in deep cortex and the underlying white matter. In situ hybridisation confirmed induction of TIMP-2 in glia as well as neurons, but showed no expression of TIMP-4. These results show that both MMPs and TIMPs are produced by some astrocytes, but TIMP production is particularly strong, especially in deep cortex and white matter which is more inhibitory for axon regeneration. Conversely the MMPs produced may not be adequate to promote migration of cells and axons within the glial scar.
In the olfactory pathway, as in the limbs, branchial arches, and heart, mesenchymal/epithelial induction, mediated by retinoic acid (RA), FGF8, sonic hedgehog (shh), and the BMPs, defines patterning, morphogenesis, and differentiation. Neuronal differentiation in the olfactory epithelium and directed growth of axons in the nascent olfactory nerve depend critically upon this inductive interaction. When RA, FGF8, shh, or BMP signaling is disrupted, distinct aspects of olfactory pathway patterning and differentiation are compromised. Thus, a cellular and molecular mechanism that facilitates musculoskeletal and vascular development elsewhere in the embryo has been adapted to guide the differentiation of the olfactory pathway in the developing forebrain.
Explore the source record for details and available documents.
The human keratin 18 (K18) gene is expressed in a restricted but diverse subset of differentiated epithelial tissues and carcinomas. The 10-kilobase pair K18 gene contains all of the genetic information necessary for tissue-specific, copy number-dependent and integration site-independent expression in transgenic mice. We identified a 100-base pair regulatory element that activates the K18 proximal promoter in the presence of the previously identified first intron enhancer. Deletion of the element greatly diminished K18 expression. This regulatory element also has cryptic, AP-1-dependent promoter activity in the absence of the normal promoter, which results in 10-40-fold higher levels of K18 RNA expression in transgenic mice. The high activity of this cryptic promoter is dependent upon the first intron enhancer. These experiments define interactive regulatory regions of the K18 gene that modulate expression in diverse epithelial cell types and identify an unusual regulatory element with promoter activity that may be useful for high level heterologous gene expression in transgenic animals.
The activities of ETS transcription factors are modulated by posttranscriptional modifications and cooperation with other proteins. Another factor which could alter the regulation of genes by ETS transcription factors is DNA methylation of their cognate binding sites. The optimal activity of the keratin 18 (K18) gene is dependent upon an ETS binding site within an enhancer region located in the first intron. The methylation of the ETS binding site was correlated with the repression of the K18 gene in normal human tissues and in K18 transgenic mouse tissues. Neither recombinant ETS2 nor endogenous spleen ETS binding activities bound the methylated site effectively. Increased expression of the K18 gene in spleens of transgenic mice by use of an alternative, cryptic promoter 700 bp upstream of the enhancer resulted in modestly decreased methylation of the K18 ETS site and increased RNA expression. Expression in transgenic mice of a mutant K18 gene, which was still capable of activation by ETS factors but was no longer a substrate for DNA methylation of the ETS site, was fivefold higher in spleen and heart. However, expression in other organs such as liver and intestine was similar to that of the wild-type gene. This result suggests that DNA methylation of the K18 ETS site may be functionally important in the tissue-specific repression of the K18 gene. Epigenetic modification of the binding sites for some ETS transcription factors may result in a refractory transcriptional response even in the presence of necessary trans-acting activities.
An in vitro differentiation system utilizing retinoic acid (RA) treatment of pluripotent murine P19 embryonal carcinoma (EC) cells, which can be induced to differentiate into various cell types, was optimized for maximal induction of alpha 1 type I collagen (Col1a1) gene expression. Differentiation was associated with apoptotic death of the majority of cells, indicating that this in vitro system faithfully mimics the in vivo differentiation process. Col1a1 mRNA became detectable by RNase protection assay after 3 days of RA treatment and, after 6 days, reached a level comparable to that in NIH 3T3 fibroblasts. After induction of differentiation the Col1a1 gene remained transcriptionally active for extended periods of time even in the absence of RA. A minigene version of the murine Col1a1 gene was constructed that contains all of the so far known Col1a1 regulatory elements. This construct exhibited the correct expression pattern in stable transfection experiments: it was expressed in fibroblasts, but not in undifferentiated P19 EC cells, and it was transcriptionally activated after induction of differentiation. This experimental system should be a useful tool for dissecting the molecular mechanisms involved in the developmental activation and stage- and tissue-specific expression of the murine Col1a1 gene.
Several lines of evidence indicate that DNA methylation plays a role in the transcriptional regulation of the murine alpha 1(I) collagen gene. To study the molecular mechanisms involved, a reporter gene construct containing the alpha 1(I) promoter and part of the first exon linked to the luciferase gene (Col3luc) was methylated in vitro and transfected into murine fibroblasts and embryonal carcinoma cells. Methylation resulted in repression of the alpha 1(I) promoter in both cell types, although it was less pronounced in embryonal carcinoma cells than in fibroblasts. The extent of repression depended on the density of methylation. DNase footprint and mobility shift assays indicated that the trans-acting factors binding to the alpha 1(I) promoter and first exon are ubiquitous factors and that their DNA binding is not inhibited by methylation. Transfection of Col3luc into Drosophila SL2 cells together with expression vectors for the transcription factors Sp1 and NF-1 showed that DNA methylation also inhibits the alpha 1(I) promoter in nonvertebrate cells, although to a much lesser extent than in murine cells. However, Sp1 and NF-1 transactivated the unmethylated and methylated reporter gene in SL2 cells equally well, confirming that these factors can bind and transactivate methylated DNA and indicating that DNA methylation represses the alpha 1(I) promoter by an indirect mechanism. This was further confirmed by cotransfection experiments with unspecific methylated competitor DNA which partially restored the activity of the methylated alpha 1(I) promoter. Our results suggest that DNA methylation can inhibit promoter activity by an indirect mechanism independent of methyl-C-binding proteins and that in vertebrate cells, chromatin structure and methyl-C-binding proteins cooperatively mediate the transcriptional inhibitory effect of DNA methylation.
Explore the source record for details and available documents.
An approach for a frame-relay implementation is described which is intended to establish connectivity between the health care providers in the state of Connecticut with a gateway to the internet. While other health care networking efforts have based the interconnectivity efforts on direct connections to the internet for each institution, our design takes a more cost effective approach by establishing a private health care network with a single entry point to the internet. This will not only provide the advantages of internet connections to all participating providers, but it will also isolate intrastate patient care traffic from the internet, reserving internet traffic for those information needs not available within the statewide network. In addition to the network solution, an extensive user support infrastructure is also presented.
Explore the source record for details and available documents.
A total of 4,952 articles published in 1970, 1975, 1980, 1985, and 1990 in the areas of developmental, clinical, physiological, and social psychology were reviewed for the purpose of assessing various indicators of sexism in human psychological research. Significant changes in sex of first author, sex of participants, sexist language, and inappropriate generalization indicated that sexism has clearly diminished in the past two decades. Despite these improvements, however, the data revealed continued evidence of discriminatory practices, suggesting that efforts to eliminate sexism must be strengthened if psychology is to be a nonsexist discipline.
Regulatory elements contributing to the tissue-specific regulation of the murine alpha 1(I) collagen (Colla1) gene have previously been identified in its promoter region and first intron. Because several lines of evidence indicate that DNA methylation may be involved in the tissue-specific regulation of Colla1 gene expression, we have analyzed the methylation status of the 5' region of the gene by restriction analysis and a methylation-dependent PCR assay. All sites tested were unmethylated in sperm DNA. The region surrounding the start site of transcription was partially or completely methylated in undifferentiated embryonal cell lines, suggesting that it may be marked by de novo methylation during early embryonic development. In differentiated cells and adult tissues, the Colla1 promoter was completely demethylated in collagen-producing and some nonproducing cells, and partially methylated in other nonproducing cells. The first intron was unmethylated in collagen-producing as well as nonproducing cells. Only sites in the first exon showed an inverse correlation with transcriptional activity, i.e., they were unmethylated in cells that express the gene, but predominantly methylated in cells that do not. Our results indicate that the methylation status of a small area (less than 1 kb) downstream of the Colla1 promoter, but not of the promoter itself or the first intron, may be critical for transcriptional activity of the promoter, presumably through an indirect mechanism.
We have analyzed the transcriptional activity of cellular target sequences for Moloney murine leukemia virus integration in mouse fibroblasts. At least five of the nine random, unselected integration target sequences studied showed direct evidence for transcriptional activity by hybridization to nuclear run-on transcripts prepared from uninfected cells. At least four of the sequences contained multiple recognition sites for several restriction enzymes that cut preferentially in CpG-rich islands, indicating integration into 5' or 3' ends or flanking regions of genes. Assuming that only a minor fraction (less than 20%) of the genome is transcribed in mammalian cells, we calculated the probability that this association of retroviral integration sites with transcribed sequences is due to chance to be very low (1.6 x 10(-2]. Thus, our results strongly suggest that transcriptionally active genome regions are preferred targets for retrovirus integration.
Of primary interest in the present study was the assessment of the association between several contextual factors, including chronic stress, exercise, alcohol, nicotine, and caffeine intake, and the self-report of perimenstrual symptoms. Two hundred and eleven women completed questionnaires designed to assess chronic stress, perimenstrual symptoms, and physical health. The results indicated that stress accounted for a significant amount of the variance in perimenstrual symptoms. Stress, however, accounted for a substantially greater amount of variance in scores on a general health measure than in self-reports of perimenstrual symptoms. Of those lifestyle variables assessed, only duration of current level of strenuous exercise was associated with perimenstrual symptoms to a meaningful extent.
Renal biopsies were performed on 21 of 27 Melanesian patients presenting with significant proteinuria in Vanuatu from 1983 to 1985. All patients had more than 2 g of proteinuria per 24 hours or clinical evidence of the nephrotic syndrome. The average age of the patients who were biopsied was 31 years. Three of the 21 patients had evidence of active malaria at the time of presentation, and all of these patients had Plasmodium falciparum. Renal histopathology revealed that six patients (29%) had amyloidosis and five patients (24%) had mesangiocapillary glomerulonephritis (type 1). Of particular note was the fact that only one patient had membranous glomerulonephropathy and only one patient had minimal change nephrotic syndrome, the two most common lesions reported in nephrotic patients in Europe and the United States. Thus, the spectrum of renal histopathology in patients presenting in Vanuatu with significant proteinuria is very different from that seen in Western Countries.
Explore the source record for details and available documents.