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R J Schmidt

Publications and source records attributed to R J Schmidt.

At least 55 records · Page 3Linked to original sources
PubMed1995

Synthesis and biological evaluation of a new series of sterols as potential hypocholesterolemic agents.

A new series of sterols was synthesized and tested in a CHO cell-based LDL receptor/luciferase (LDLR/Luc) assay to investigate the capability of derepressing the transcription of LDL receptor promoter in the presence of 25-hydroxycholesterol. The effect of various substitutions on antagonizing the repressing effect mediated by 25-hydroxycholesterol was also studied in terms of regio- and stereochemistry, lipophilicity, steric bulk, and pi-electron density. Except 12, compounds active in the primary LDLR/Luc assay were not active in the secondary simian virus 40/luciferase (SV40/Luc) assay, demonstrating the specificity of their in vitro activity. Eight active compounds of various structural types were selected and screened in a [1-14C-acetate]cholesterol biosynthesis inhibition assay; none has shown any interference with the cholesterol biosynthesis in CHO cells. In hypercholesterolemic hamsters, generally, compounds that were active in vitro were active in vivo and vice versa, with the exception of three in vitro inactive compounds: 3 beta-ols 3a' and 3c' as well as 3-ketone 2a. Experimental results from the livers of hamsters revealed that the in vivo conversion of 3a' or 2a to 3a has in part contributed to the observed in vivo activity, and it is also anticipated that 3c' may similarly be converted to 3c in hamsters.

Animals↗
PubMed1995

A characterization of the MADS-box gene family in maize.

Studies on distantly related dicot plant species have identified homeotic genes that specify floral meristem identity and determine the fate of floral organ primordia. Most of these genes belong to a family characterized by the presence of a structural motif, the MADS-box, which encodes a protein domain with DNA-binding properties. As part of an effort to understand how such genes may have been recruited during the evolution of flowers with different organ types such as those found in maize, two members of this gene family in maize, ZAG1 and ZAG2, have been characterized previously. Here, the isolation and characterization of four new members of this gene family, designated ZAP1, ZAG3, ZAG4 and ZAG5, are described and the genetic map position of these and 28 additional maize MADS-box genes is determined. The first new member of this family appears to be the Zea mays ortholog of the floral homeotic gene APETALA1 (AP1) and has been designated ZAP1. One of these genes, ZAG4, is unusual in that its deduced protein sequence includes the MADS domain but lacks the K-domain characteristically present in this family of genes. In addition, its copy number and expression varies among different inbreds. A large number of maize MADS-box genes map to duplicated regions of the genome, including one pair characterized here, ZAG3 and ZAG5. These data underscore the complexity of this gene family in maize, and provide the basis for further studies into the regulation of floral organ morphogenesis among the grasses.

Amino Acid Sequence↗
PubMed1995

Molecular evolution of flower development: diversification of the plant MADS-box regulatory gene family.

Floral homeotic genes that control the specification of meristem and organ identity in developing flowers have been isolated from both Arabidopsis thaliana and Antirrhinum majus. Most of these genes belong to a large family of regulatory genes and possess a characteristic DNA binding domain known as the MADS-box. Members of this gene family display primarily floral-specific expression and are homologous to transcription factors found in several animal and fungal species. Molecular evolutionary analyses reveal that there are appreciable differences in the substitution rates between different domains of these plant MADS-box genes. Phylogenetic analyses also demonstrate that members of the plant MADS-box gene family are organized into several distinct gene groups: the AGAMOUS, APETALA3/PISTILLATA and APETALA1/AGL9 groups. The shared evolutionary history of members of a gene group appear to reflect the distinct functional roles these MADS-box genes play in flower development. Molecular evolutionary analyses also suggest that these different gene groups were established in a relatively short span of evolutionary time and that the various floral homeotic loci originated even before the appearance of the flowering plants.

Amino Acid Sequence↗
PubMed1995

Tosyl chloride.

Explore the source record for details and available documents.

Ethanol↗
PubMed1994

Biocompatibility of potential wound management products: fungal mycelia as a source of chitin/chitosan and their effect on the proliferation of human F1000 fibroblasts in culture.

Aspergillus oryzae, Mucor mucedo, and Phycomyces blakesleeanus cultures were examined as sources of chitin/chitosan. The nitrogen content of the alkali-treated mycelia/sporangiophores of A. oryzae, M. mucedo, and P. blakesleeanus was 2.52, 3.61, and 6.27% w/w, which relates to an estimated chitin content of 37, 52, and 91%, respectively. The effect of these fungal materials on the rate of proliferation of human F1000 fibroblasts in culture was examined. At 0.01% w/v, all three materials exhibited significant (P < .05) proproliferant activity over a period of 13 days. However, at 0.05% w/v, P. blakesleeanus further enhanced cell proliferation, whereas A. oryzae and M. mucedo produced a significant (P < .05) antiproliferant effect. Higher concentrations of P. blakesleeanus (0.1 and 0.5%) caused marked inhibition of F1000 cell proliferation when measured on days 3 and 6. Only the proproliferant effect of these fungal materials appears to correlate to their chitin content. Furthermore, the cytomorphology of the fibroblasts indicated that P. blakesleeanus, and to a lesser extent M. mucedo, possessed cell attractant properties, again correlating with chitin content. If developed for use as wound management materials, the sporangiophores of P. blakesleeanus and the mycelium of M. mucedo could possibly promote the growth of fibroblasts and provide a matrix for their anchorage, thus contributing to the granulation phase of the healing cascade.

Aspergillus oryzae↗
PubMed1993

Toxicity of L-ascorbic acid to L929 fibroblast cultures: relevance to biocompatibility testing of materials for use in wound management.

Fibroblast cultures are often used to evaluate materials intended for medical use, cytotoxicity being taken as an indicator of bioincompatibility. Such an approach has previously been taken with ascorbic acid in determining its value in wound healing. We have now reexamined the toxicity of L-ascorbic acid to L929 fibroblast cells in culture. Concentrations of ascorbic acid between 0.5 mM and 11 mM were tested. At concentrations above 2 mM, ascorbic acid was found to inhibit cell proliferation, with cell viability decreasing as the concentration was increased. This effect could be prevented by the addition of either superoxide dismutase or catalase to the culture medium. Assays of glutathione and glutathione disulfide were carried out on 8 day old cultures exposed for 24 h to the same concentrations of ascorbic acid. A dose-related depletion of glutathione occurred whilst glutathione disulfide levels remained essentially constant. Lactate dehydrogenase and glucose-6-phosphate dehydrogenase activities were induced by ascorbic acid at all concentrations tested but the ratio of NADP to NADPH nevertheless increased as the concentration of ascorbic acid increased. Finally, ATP in cells from 8-day-old cultures became depleted in the presence of ascorbic acid at concentrations in excess of about 5 mM when assayed after 24 h incubation. These biochemical changes and the concomitant cytostatic/cytotoxic effects may be ascribed to the reactive oxygen species produced by the autoxidation of ascorbic acid in the culture medium. Ascorbic acid breakdown products appeared not to be directly involved. In addition, our results suggested that superoxide acted cooperatively with hydroxyl to elicit these effects on the fibroblasts. It is evident from this study that the microenvironment surrounding fibroblasts in culture may differ fundamentally from that surrounding fibroblasts in a healing wound, making it impossible to extrapolate directly to an in vivo situation and hence to make any recommendations from these results concerning the use of ascorbic acid in wound healing.

Adenosine Triphosphate↗
PubMed1993

A 168 bp derivative of Suppressor-mutator/Enhancer is responsible for the maize o2-23 mutation.

From a directed transposon tagging of the maize Opaque-2 gene (O2), we have isolated a stable mutant o2 allele, o2-23. Cloning and molecular analysis of the allele revealed a 168 nucleotide insertion in the third exon of o2. The sequence of this small insertion indicated identity with the 5' and 3' ends of the 8.3 kb Suppressor-mutator/Enhancer (Spm/En) transposable element. This represents the smallest deletion derivative of Spm (dSpm) thus far characterized in maize. Genetic crosses of plants homozygous for o2-23 with plants homozygous for both an o2 null allele (o2-R) and an autonomous Spm produce stable opaque seed having no apparent sectors of vitreous endosperm. DNA fragments of the size expected if the dSpm were to excise were not detectable by Southern analysis, suggesting that this element is unable to transpose. Northern analysis detected an o2-23 mRNA that was much more abundant in o2-23 seeds lacking Spm than in o2-23 seeds containing Spm, consistent with the idea that Spm transacting functions can suppress the accumulation of the o2-23 transcript.

Alleles↗
PubMed1993

An examination of the electromyographic fatigue threshold test.

The purpose of this investigation was to examine times to exhaustion at various percentages of the electromyographic fatigue threshold (EMGFT). Eight adult males [mean (SD), 21 (1) years] volunteered for the investigation. EMGFT was derived by determining the rate of rise in the electrical activity of the vastus lateralis [using integrated electromyography (iEMG)] over time (iEMG slope) for four fatiguing power outputs during cycle ergometry. The four power outputs were then plotted as a function of the four iEMG slope coefficients. The y-intercept of the power output versus iEMG slope coefficient graph was defined as the EMGFT. The intraclass correlation for repeated EMGFT tests was R = 0.65 (SEE = 7 W) and there was no significant (P > 0.05) difference between the mean (SD) values for test [260 (11) W] versus retest [262 (32) W]. Actual times to exhaustion were determined for work bouts at power outputs equal to 85, 100, 115, 130, and 145% of EMGFT. The mean (SD) times to exhaustion for these work bouts were 495 (231), 225 (72), 135 (35), 94 (17), and 72 (14) s, respectively. A power curve was derived using the mean power outputs and mean times to exhaustion from the five rides at various percentages of EMGFT. The power curve provided estimates of the power outputs which could be maintained for 30 and 60 min. There were significant (P < 0.05) differences between the mean EMGFT (260 W) and the power outputs which could be maintained for 30 (151 W) and 60 (125 W) min.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

OHP1: a maize basic domain/leucine zipper protein that interacts with opaque2.

OPAQUE2 (O2) is a regulatory gene that predominantly affects the expression of the 22-kD class of zein storage protein genes at the level of transcription. The O2 gene encodes a polypeptide belonging to the basic domain/leucine zipper (bZIP) class of transcriptional regulatory proteins. Our prior analyses have demonstrated that the O2 protein binds 22-kD zein gene promoters as a homodimer in vitro and have also suggested that O2 may bind as a heterodimer in vivo. To identify cDNAs encoding other bZIP motifs that might interact with O2, a portion encoding the bZIP motif from an O2 cDNA was used to screen an endosperm cDNA library. Sequence analysis of one isolated recombinant phage indicated the presence of a bZIP motif similar to O2. The protein product of this partial cDNA, designated OHP1, can bind the O2 target site both as a homodimer and in a heterodimeric complex with O2. Whole genome DNA gel blot analysis of maize recombinant inbreds revealed two strongly hybridizing restriction fragments, neither of which mapped close to any locus known to affect zein expression. RNA gel blot analysis revealed an approximately 1.7-kb transcript that is expressed in all organs examined except the female flower and is also expressed in endosperms homozygous for o2 and other mutations that affect zein expression (opaque7, floury2, and Defective endosperm b-30). Based on these results and previously reported data, we propose models to accommodate OHP1 in the regulation of zein gene expression by O2.

Amino Acid Sequence↗
PubMed1993

Identification and molecular characterization of ZAG1, the maize homolog of the Arabidopsis floral homeotic gene AGAMOUS.

Recent genetic and molecular studies in Arabidopsis and Antirrhinum suggest that mechanisms controlling floral development are well conserved among dicotyledonous species. To assess whether similar mechanisms also operate in more distantly related monocotyledonous species, we have begun to clone homologs of Arabidopsis floral genes from maize. Here we report the characterization of two genes, designated ZAG1 and ZAG2 (for Zea AG), that were cloned from a maize inflorescence cDNA library by low stringency hybridization with the AGAMOUS (AG) cDNA from Arabidopsis. ZAG1 encodes a putative polypeptide of 286 amino acids having 61% identity with the AGAMOUS (AG) protein. Through a stretch of 56 amino acids, constituting the MADS domain, the two proteins are identical except for two conservative amino acid substitutions. The ZAG2 protein is less similar to AG, with 49% identity overall and substantially less similarity than ZAG1 outside the well-conserved MADS domain. Like AG, ZAG1 RNA accumulates early in stamen and carpel primordia. In contrast, ZAG2 expression begins later and is restricted to developing carpels. Hybridization to genomic DNA with the full-length ZAG1 cDNA under moderately stringent conditions indicated the presence of a large family of related genes. Mapping data using maize recombinant inbreds placed ZAG1 and ZAG2 near two loci that are known to affect maize flower development, Polytypic ear (Pt) and Tassel seed4 (Ts4), respectively. The ZAG1 protein from in vitro translations binds to a consensus target site that is recognized by the AG protein. These data suggest that maize contains a homolog of the Arabidopsis floral identity gene AG and that this gene is conserved in sequence and function.

AGAMOUS Protein, Arabidopsis↗
PubMed1993

A study of hydrogen peroxide generation by, and antioxidant activity of, Granuflex (DuoDERM) Hydrocolloid Granules and some other hydrogel/hydrocolloid wound management materials.

The effect of Granuflex Hydrocolloid Granules (0.01-0.50% w/v) on the rate of proliferation of murine (L929) fibroblasts was examined. The dose-response curve showed a significant (P < 0.02) pro-proliferant effect at 0.05%, and a significant (P < 0.02) antiproliferant effect at 0.50%, mirroring the dose-response curve produced by hydrogen peroxide in the concentration range 10(-9) - 10(-4) mol/l. The antiproliferant effect at 0.20% w/v was abolished by catalase, suggesting that the biological activity of Granuflex was mediated by the in situ generation of hydrogen peroxide. Formation of hydrogen peroxide by Granuflex was confirmed by performing the scopoletin-horseradish peroxidase assay in the presence and absence of catalase. The total concentration of hydrogen peroxide detected was about 8 x 10(-6) mol/l (using 0.5% w/v Granuflex) after 48 h at 37 degrees C. In contrast, when hydrogen peroxide itself was added to L929 cultures, a similar antiproliferant activity was observed at concentrations between 10(-4) and 10(-5) mol/l. These results suggested that Granuflex was undergoing autoxidation in the culture medium, and hence that it might possess antioxidant activity. In assays for antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH), Granuflex, and two other hydrocolloid dressings (Comfeel Powder and Bard Absorption Dressing) showed significant ability to reduce DPPH to DPPH2. These three dressings also displayed superoxide scavenging activity in a nitroblue tetrazolium reduction assay. We conclude that, in addition to providing a moist wound-healing environment, Granuflex and certain other hydrocolloids might contribute to the establishment and maintenance of the reducing environment necessary for energy production and hence cell division.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Quantification of hydrogen peroxide generation by Granuflex (DuoDERM) Hydrocolloid Granules and its constituents (gelatin, sodium carboxymethylcellulose, and pectin).

The hydrogen peroxide generating capacity of Granuflex Hydrocolloid Granules and its constituents (porcine gelatin, sodium carboxymethylcellulose and pectin) was examined using the scopoletin-horseradish peroxidase assay in the presence and absence of catalase. Oxygen purging reduced the formation of hydrogen peroxide by 77-96%. The total concentrations of hydrogen peroxide detected were 1.9 x 10(-6), 1.2 x 10(-6) and 2.3 x 10(-6) mol/l for Granuflex, pectin and gelatin (using 0.5% w/v), respectively, after 48 h incubation in a phosphate buffer, pH 7.4, at 37 degrees C. No hydrogen peroxide was formed by sodium carboxymethylcellulose. The results indicate that hydrogen peroxide generation by Granuflex may be ascribed to its gelatin and pectin components, but not to the sodium carboxymethylcellulose. The release of low levels of hydrogen peroxide into the wound environment could conceivably contribute both to the inflammatory phase and to fibroblast proliferation, and hence to the granulation phase of wound healing.

Animals↗
PubMed1993

Biocompatibility of wound management products: a study of the effects of various polysaccharides on murine L929 fibroblast proliferation and macrophage respiratory burst.

An in-vitro screening method to examine the biocompatibility of materials used in wound management has been evaluated. This involved the use of a macrophage respiratory-burst assay and a fibroblast proliferation assay to represent respectively the inflammatory and the granulation phases in wound healing. Standard polysaccharides (calcium and sodium alginates, l-carrageenan, chitin, chitosan lactate, chondroitin sulphate and pectic acid) were used as test compounds. None of the polysaccharide samples caused a significant increase in L929 fibroblast cell numbers relative to control after 6 days incubation. The overall effect of exposure of the fibroblast cultures to the alginates, carrageenan and chondroitin sulphate was an extension of lag phase followed by an enhanced rate of cell proliferation in the logarithmic phase. Only calcium and sodium alginates and chondroitin sulphate enhanced the respiratory burst activity of murine macrophages; l-carrageenan and chitosan lactate were markedly inhibitory. The results suggest that a macrophage activity assay should be included as part of an in-vitro screening program to evaluate the biocompatibility of wound management materials and to detect intrinsic biological activity.

Alginates↗
PubMed1993

Perturbation of glutathione status and generation of oxidative stress in mouse skin following application of contact allergenic sesquiterpene lactones and isothiocyanates.

1. The sensitizing or non-sensitizing status of selected sesquiterpene lactones and isothiocyanates was confirmed in mouse by open epicutaneous application. 2. Glutathione status of mouse skin was determined 12 h after lactone/isothiocyanate application; glutathione S-transferase activity also was determined 12 h after lactone application. 3. NAD(P)H utilization by rat liver microsomal preparations exposed to the sesquiterpene lactones and isothiocyanates was measured. 4. A correlation was observed between sensitizing status and the ability to perturb glutathione status, to induce glutathione S-transferase activity, and to stimulate NAD(P)H utilization. 5. It was concluded that sensitizing sesquiterpene lactones and isothiocyanates could induce oxidative stress in mouse skin, possibly as a result of their reductive metabolism.

Administration, Cutaneous↗
PubMed1993

Effective continuous ambulatory peritoneal dialysis following abdominal aortic aneurysm repair.

OBJECTIVE: To review a single center's experience with the initiation and maintenance of continuous ambulatory peritoneal dialysis (CAPD) in 8 patients with a history of abdominal aortic aneurysm repair (AAAR). DESIGN: Retrospective case review with long-term follow-up. PATIENTS (OR PARTICIPANTS): Eight patients with multiple medical problems including a history of abdominal aortic aneurysm repair and end-stage renal failure who received peritoneal dialysis catheters between December 1986 and July 1991. MAIN OUTCOME MEASURES: Success of catheter implantation and maintenance of continuous ambulatory peritoneal dialysis; incidence of peritoneal infection and long-term complications; overall clinical course. RESULTS: Over five years 8 patients with a history of reconstructed abdominal aortic aneurysm received peritoneal dialysis catheters without complication and dialyzed successfully for 88 patient-months in total. Three patients had a total of five episodes of peritonitis, at an incidence of 0.68 episodes per patient per year, a rate not significantly different from that of our overall CAPD patient population (1.09) and that reported by other groups. CONCLUSION: Our experience suggests that historical AAAR poses no significant risk to and should not preclude the implementation of continuous ambulatory peritoneal dialysis. Indeed, CAPD offers a safe and optimal dialytic alternative for patients with historical abdominal aortic aneurysm repair in whom compromised cardiovascular hemodynamics may significantly influence morbidity and survival.

Aged↗