Biomedical subjects

R A Schultz

Publications and source records attributed to R A Schultz.

At least 73 records · Page 4Linked to original sources

PubMed1988

A yeast DNA repair gene partially complements defective excision repair in mammalian cells.

The RAD10 gene of Saccharomyces cerevisiae is required for nucleotide excision repair of DNA. Expression of RAD10 mRNA and Rad10 protein was demonstrated in Chinese hamster ovary (CHO) cells containing amplified copies of the gene, and RAD10 mRNA was also detected in stable transfectants without gene amplification. Following transfection with the RAD10 gene, three independently isolated excision repair-defective CHO cell lines from the same genetic complementation group (complementation group 2) showed partial complementation of sensitivity to killing by UV radiation and to the DNA cross-linking agent mitomycin C. These results were not observed when RAD10 was introduced into excision repair-defective CHO cell lines from other genetic complementation groups, nor when the yeast RAD3 gene was expressed in cells from genetic complementation group 2. Enhanced UV resistance in cells carrying the RAD10 gene was accompanied by partial reactivation of the plasmid-borne chloramphenicol acetyltransferase (cat) gene following its inactivation by UV radiation. The phenotype of CHO cells from genetic complementation group 2 is also specifically complemented by the human ERCC1 gene, and the ERCC1 and RAD10 genes have similar amino acid sequences. The present experiments therefore indicate that the structural homology between the yeast Rad10 and human Ercc1 polypeptides is reflected at a functional level, and suggest that nucleotide excision repair proteins are conserved in eukaryotes.

Animals↗

PubMed1987

Microcell-mediated transfer of a single human chromosome complements xeroderma pigmentosum group A fibroblasts.

Chromosomes from an immortalized aneuploid human fibroblast cell line were randomly tagged with the selectable marker neo by transfection with the plasmid pSV2neo. Somatic cell fusions between transfected human cells and mouse A9 cells generated pools of G418-resistant human-mouse hybrid clones containing various numbers of human chromosomes. Microcell-mediated chromosome transfer from the hybrid pools to xeroderma pigmentosum complementation group A (XP-A) cells in culture and selection for G418-resistant colonies resulted in the identification of XP cells with enhanced resistance to ultraviolet radiation. Screening of subclones from selected pools of human-mouse hybrids facilitated the identification of hybrids containing a single neo-tagged human chromosome. Transfer of this chromosome to XP-A cells (but not to XP-F or XP-C cells) results in enhanced resistance to ultraviolet light and enhanced excision repair capacity. The identification of a single human chromosome that complements the phenotype of XP-A cells in culture provides the potential for genetic mapping of the complementing gene and for its isolation by molecular cloning.

Animals↗

PubMed1987

Cardiac glycoside poisoning in sheep caused by Urginea physodes (Jacq.) Bak. and the isolated physodine A.

Urginea physodes (Jacq.) Bak., a species closely related to or possibly synonymous with U. pusilla, is described and its distribution given. Four bufadienolides were isolated from U. physodes and the approximated LD50 and cumulative effect of some of them determined in guinea pigs. The most toxic one proved to be mildly cumulative. Typical signs of acute cardiac glycoside poisoning, involving the locomotory, gastro-intestinal, respiratory and cardiac system, were seen in the field cases and/or were experimentally induced by the plant. Similar signs could also be induced by injecting the isolated bufadienolide, physodine A, to a sheep.

Animals↗

PubMed1987

Experimental evidence that the active principle of the poisonous plant Thesium lineatum L.f. (Santalaceae) is a bufadienolide.

The toxicity of Thesium lineatum is confirmed in sheep. A toxic crystalline bufadienolide, with the suggested trivial name thesiuside, has been isolated from it. This is the first cardiac glycoside to be isolated from a member of the Santalaceae. The toxin appears to have no cumulative effect and the symptoms of intoxication and pathology in sheep are similar to that expected from acute cardiac glycoside intoxication.

Animals↗

PubMed1986

Molecular approaches to the study of nucleotide excision repair in eukaryotes.

Very little is known about the molecular mechanism of nucleotide excision repair in eukaryotes. Studies on human cells have been stimulated by the availability of excision repair-defective cell lines from patients suffering from the autosomal recessive disease xeroderma pigmentosum (XP). Such studies have contributed significantly to an understanding of the genetic complexity of excision repair in human cells. However, to date, no human excision repair genes or gene products known to complement the repair defect in XP cells have been isolated. The yeast Saccharomyces cerevisiae is an interesting model for exploring the molecular mechanism of nucleotide excision repair in eukaryotic cells. As is true in human cells, multiple yeast genes are involved and at least five genes are required for the specific incision of UV-irradiated DNA in vivo. These five genes have been isolated by molecular cloning and the nucleotide sequences of four of them have been determined. Each of these cloned genes is being used for overexpression of protein.

Base Sequence↗

PubMed1986

Partial complementation of the UV sensitivity of E. coli and yeast excision repair mutants by the cloned denV gene of bacteriophage T4.

The denV gene of bacteriophage T4 was reconstituted from two overlapping DNA fragments cloned in M13 vectors. The coding region of the intact gene was tailored into a series of plasmid vectors containing different promoters suitable for expression of the gene in E. coli and in yeast. Induction of the TAC promoter with IPTG resulted in overexpression of the gene, which was lethal to E. coli. Expression of the TACdenV gene in the absence of IPTG, or the use of the yeast GAL1 or ADH promoters resulted in partial complementation of the UV sensitivity of uvrA, uvrB, uvrC and recA mutants of E. coli and rad1, rad2, rad3, rad4 and rad10 mutants of S. cerevisiae. The extent of denV-mediated reactivation of excision-defective mutants was approximately equal to that of photoreactivation of such strains. Excision proficient E. coli cells transformed with a plasmid containing the denV gene were slightly more resistant to ultraviolet (UV) radiation than control cells without the denV gene. On the other hand, excision proficient yeast cells were slightly more sensitive to killing by UV radiation following transformation with a plasmid containing the denV gene. This effect was more pronounced in yeast mutants of the RAD52 epistasis group.

Base Sequence↗

PubMed1986

Isolation and partial characterization of virus-transformed cell lines representing the A, G and variant complementation groups of xeroderma pigmentosum.

We have established viral-transformed, apparently permanent (immortalized) cell lines from diploid fibroblasts representative of normal and xeroderma pigmentosum (XP) A, G and variant individuals. The XP-G and XP-variant cells represent complementation groups not previously available as permanent lines. All the new permanent cell lines exhibit SV40 T-antigen expression. They are also aneuploid and have growth characteristics typical of viral transformants. They have retained the phenotypes of UV sensitivity, reduced repair synthesis or defective 'postreplication repair' appropriate to the XP complementation group they represent. Additionally, the new cell lines are all transfectable with the selectable plasmid pRSVneo. The XP-G and XP-variant cell lines show enhanced transfection with UV-irradiated plasmid DNA; a phenomenon previously reported for normal immortalized cells and for immortalized cells from the A and F complementation groups of XP.

Antigens, Viral, Tumor↗

PubMed1986

The efficacy of acetamide for the treatment of experimental Dichapetalum cymosum (gifblaar) poisoning in sheep.

High mortality of livestock is caused annually by the plant, Dichapetalum cymosum (gifblaar), in the Northern Transvaal. So far no therapeutic measures have been developed for the prevention or treatment of this poisoning. In this presentation, the efficacy of acetamide as therapy for experimental gifblaar poisoning was tested in 18 sheep. When 2.5-5 g/kg of acetamide was dosed to sheep at various intervals before and sometimes after the administration of 5 g/kg of gifblaar, 1 out of 5 survived, compared with 0 out of 2 controls. Dosing of 2 g/kg of acetamide before and/or simultaneously with or after 1 g/kg gifblaar prevented mortality as 5 out of 5 treated sheep survived compared with none of the 5 controls. The experiments indicate that acetamide has demonstrable therapeutic value as an antidote for the prevention of experimental gifblaar poisoning in sheep. Further investigations should determine the feasibility and applicability of these findings under field conditions in sheep and cattle.

Acetamides↗

PubMed1985

Studies on gene transfer and reversion to UV resistance in xeroderma pigmentosum cells.

We have examined several parameters which address the feasibility of complementing the UV-sensitive phenotype of xeroderma pigmentosum (XP) fibroblasts by gene transfer. We present a comparative study which demonstrates that, relative to immortalized cells, human diploid cells are poor recipients for gene transfer. As measured by both transient and stable expression assays, diploid fibroblasts were completely refractory to DNA transfer by calcium phosphate coprecipitation and exhibited substantially reduced levels of expression following gene transfer by fusion with E. coli protoplasts. We also examined the significance of reversion of the phenotype of UV sensitivity in SV40-immortalized XP-A cell lines. In addition to confirming a previous report of reversion to wild-type levels of UV resistance at a frequency of approximately 10(-7), we have attempted to facilitate the identification of XP-A cells complemented with genomic DNA by employing less stringent selection schemes and cotransfection of a selectable marker. Under these conditions, we observed an increased frequency of reversion and were unable to identify true transfectants.

Cell Line↗

PubMed1985

Isolation and characterization of and some observations on poisoning by bufadienolides from Cotyledon orbiculata L. var. orbiculata.

The approximate LD50 and cumulative effect of 4 bufadienolides, isolated from Cotyledon orbiculata, were determined in guinea-pigs. Two of the bufadienolides proved to be mildly cumulative. One of the mildly cumulative bufadienolides induced subacute intoxication with some signs of krimpsiekte when injected intravenously into a sheep over 13 days. In the sheep, the paralysis was accompanied by signs of malaise, such as electrocardiographic changes and ruminal stasis.

Animals↗

PubMed1984

Mechanoreceptors in human cruciate ligaments. A histological study.

We obtained human cruciate ligaments at the time of total knee replacement and from autopsy and amputation specimens, and examined histological sections of the ligaments for the presence of mechanoreceptors using the Bodian, Bielschowsky, and Ranvier gold-chloride stains for axons and nerve-endings. The cruciate ligaments obtained at the time of total knee replacement were too distorted by disease processes to be of use. The autopsy and amputation specimens, however, contained fusiform mechanoreceptor structures measuring 200 by seventy-five micrometers, with a single axon exiting from the capsule of the receptor. One to three receptors were found at the surface of each ligament beneath the synovial membrane, and were absent from the joint capsules and menisci. Morphologically the receptors resembled Golgi tendon organs, and it seems likely that they provide proprioceptive information and contribute to reflexes inhibiting injurious movements of the knee. This is the first histological demonstration of mechanoreceptors in human cruciate ligaments.

Aged↗

PubMed1983

Nucleotide sequence analysis of the proviral genome of avian myelocytomatosis virus (MC29).

The nucleotide sequence of the integrated proviral genome of avian myelocytomatosis virus (MC29) coding for gag-myc protein has been determined. By comparison of this nucleotide sequence with the helper virus as well as the c-myc region, it was possible to localize the junction points between helper viral and v-myc sequences. These studies demonstrate that (i) the large terminal repeat sequence of MC29 is very similar to that of Rous sarcoma virus, (ii) the viral genome has suffered extensive deletions in the gag, pol, and env genes, (iii) the gag region can code for p19, p10, and part of p27, (iv) the recombination between viral and cellular sequences occurred in the coding region of p27 such that the open reading frame extends for an additional stretch of 1,266 base pairs, resulting in a gag-myc hybrid protein, (v) the open reading frame terminated within the v-myc region 300 bases upstream of v-myc-helper viral junction, and (vi) the v-myc helper-viral junction at the 3' end occurred in the middle of env gene, rendering it defective.

Amino Acid Sequence↗

PubMed1983

Use of an Escherichia coli mutant strain permits measurement of single-stranded apurinic-apyrimidinic endonuclease in crude extracts: studies with untransformed cells and cells transformed with plasmids containing the uvrC gene.

We have constructed a strain of Escherichia coli that is defective in exonuclease VII and uracil-DNA glycosylase activities. This strain (xse ung) facilitates the quantitation of single-stranded apurinic-apyrimidinic endonuclease activity in crude extracts. Quantitative comparisons of single-stranded apurinic-apyrimidinic endonuclease activity under conditions in which uvrC protein is overexpressed showed no differences, suggesting that single-stranded apurinic-apyrimidinic endonuclease and uvrC protein are probably distinct.

Bacterial Proteins↗

PubMed1983

Krimpsiekte and acute cardiac glycoside poisoning in sheep caused by bufadienolides from the plant Kalanchoe lanceolata Forsk.

Three toxic bufadienolides , one characterized as hellibrigenin 3-acetate, have been isolated from Kalanchoe lanceolata Forsk. Typical signs of cardiac glycoside poisoning, involving the gastro-intestinal, neuromuscular and cardiovascular systems, could be induced by drenching the milled plant to sheep. Such signs could also be induced by dosing the bufadienolides to sheep or by injecting them into both guinea-pigs (subcutaneously) and sheep (intravenously). The specific paretic syndrome, krimpsiekte , on the other hand, was reproduced only by the repeated intravenous administration of smaller doses of the 2 unknown bufadienolides to sheep. Histopathological examination revealed a mild to severe multifocal cardiomyopathy in sheep receiving plant material or bufadienolides .

Acute Disease↗

PubMed1983

The experimental production of krimpsiekte in sheep with Tylecodon grandiflorus (Burm.f.) Toelken and some of its bufadienolides.

Six bufadienolides were isolated from Tylecodon grandiflorus ( Burm .f.) Toelken . The paretic syndrome, krimpsiekte , could be induced in sheep either by repeated oral administration of small quantities of plant material or the intravenous injection of small quantities of certain bufadienolides . A mild to moderate, acute to subacute, multifocal cardiomyopathy was evident in sheep poisoned by both the plant and the bufadienolides .

Animals↗

PubMed1982

The treatment of Urginea sanguinea Schinz poisoning in sheep with activated charcoal and potassium chloride.

An 80% survival rate was achieved when sheep which received lethal doses of Urginea sanguinea were treated with activated charcoal at 5 g/kg and potassium chloride at 1 g/kg body mass per os. A brief description of U. sanguinea poisoning and of the mechanism of cardiac glycoside action is given. Clinical examinations, ECG recordings and serum potassium levels were done to monitor developing signs of poisoning.

Animals↗

PubMed1982

Prevalence of antibodies to Haemophilus pleuropneumoniae in Iowa swine.

The prevalence of complement-fixing (CF) antibodies to Haemophilus pleuropneumoniae in Iowa swine was determined by testing samples collected randomly from each of 9 crop-reporting areas (9 to 12 counties) in Iowa in approximate proportion to the number of swine marketed annually from each area. For testing, a pooled antigen composed of serotypes 1 to 5 of H pleuropneumoniae was used in a modified direct Microtiter complement-fixation test. Of 7,348 sera tested, 2,362 or 32.1% had CF antibodies (titer greater than or equal to 1:4) to the organism. On a herd basis, 417 of 597 herds or 68.8% had at least 1 animal with CF antibodies (titer greater than or equal to 1:4) to the organism. The clinical problem with H pleuropneumoniae has become significant in recent years, but by no means is the overt disease as prevalent as animals or herds with CF antibodies to the organism.

Animals↗

PubMed1982

The treatment of Moraea polystachya (Thunb) KER-GAWL (cardiac glycoside) poisoning in sheep and cattle with activated charcoal and potassium chloride.

Six out of 6 steers survived a lethal dose of Moraea polystachya (blue tulp) when treated with activated charcoal alone and 3 out of 4 wethers survived when treated with activated charcoal plus potassium chloride. Barbeque charcoal was not of therapeutic value. An increase in the level of serum potassium served as indicator of acute poisoning in only a third of the animals.

Animals↗