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R Cox

Publications and source records attributed to R Cox.

At least 145 records · Page 8Linked to original sources
PubMed1989

Chromosomal localization of murine interleukin-1 alpha and beta genes.

DNA analyses of mouse X Chinese hamster somatic cell hybrids and of recombinant inbred mouse strains have previously shown that the interleukin-1 alpha and beta genes are tightly linked on murine chromosome 2, approximately 4.7 cM distal to beta-2-microglobulin. In this study, using in situ chromosome hybridization, we show that the two interleukin-1 genes are located in the F region of murine chromosome 2 and discuss this physical map position in relation to conserved genetic linkage groups.

Animals↗
PubMed1989

DNA replication and cell cycle control in Xenopus egg extracts.

Aspects of the regulation of DNA replication and mitosis have been studied using a cell-free extract of Xenopus eggs. The extract is characterized by repeated cycles of DNA replication and mitosis, which are accompanied by periodic synthesis and degradation of cyclins as well as fluctuations in the level of Histone H1 kinase activity. DNA replication in this system is dependent upon the formation of a nucleus. However, while nuclear structures are clearly required for initiation, a complete nuclear membrane does not appear to be necessary. Indirect immunofluorescence and DIC microscopy indicate that nuclear reformation from chromosomes occurs asynchronously around individual chromatids. Lamin polymerization, biotin-11-dUTP incorporation and association of polymerases with chromatin occur before membrane formation is complete. S phase nuclei are typified by the co-distribution of both anti-DNA polymerase alpha and anti-PCNA antibodies as discrete spots of fluorescence which align the chromatin. However, as DNA replication is terminated, PCNA fluorescence fades and DNA polymerase alpha dissociates from the chromatin and is redistributed throughout the nucleoplasm. By inhibiting DNA replication with aphidicolin, both DNA polymerase alpha and PCNA remain associated with the chromatin throughout prolonged incubation. Under these conditions mitosis is delayed by up to 70 min, although both the general rate of protein synthesis and more importantly the rate of cyclin synthesis and histone kinase activation are unaffected. Upon nuclear envelope breakdown and lamin dispersal, cyclins degrade; however, no chromosomes are formed, and both PCNA and DNA polymerase alpha remain associated with the chromatin. Also, histone kinase activity is maintained at elevated levels.

Animals↗
PubMed1989

Inhibition of DNA methylation in Friend erythroleukemia cells by actinomycin D.

Actinomycin D caused the production of hypomethylated DNA in cultured Friend erythroleukemia cells at cell culture concentrations of 1-4 ng per ml. Inhibition of DNA methyltransferase in cell-free assays was kinetically complex, with mixed-type inhibition. Cornish-Bowden graphical analysis was used to derive a Ki of about 35 nmol Act D per mg DNA. Although nuclei from drug-treated cells were found to contain hypomethylated DNA and DNA methyltransferase could be extracted from the nuclei, the methyl-accepting ability of DNA in whole nuclei themselves was not elevated. We conclude that the low level of Act D bound to DNA in the nuclei is sufficient to prevent the remethylation of hypomethylated sites.

DNA↗
PubMed1989

Changes in collagen biosynthesis, types, and mechanics of aorta in hypertensive rats.

The purpose of this study was to relate changes in collagen composition with the mechanical properties of aortas of spontaneously hypertensive rats (SHRs). SHRs and normal Wistar-Kyoto (WKY) rats were killed at ages 6 and 20 weeks, and their aortas were removed. A portion of each aorta was used for determination of passive mechanical properties, and the remainder was incubated with carbon 14-labeled proline containing medium for 18 hours at 37 degrees C. After incubation, the tissues were lyophilized, and aliquots were used for sequential extraction with neutral salt, acetic acid, and pepsin at 4 degrees C. The pepsin extracts that contained most of the collagen were used for characterization of the collagen types and synthesis of collagen by the production of [14C]-labeled hydroxyproline. Collagen concentration decreased approximately 16% in both 6- and 20-week-old aortas, but collagen synthesis was about twofold higher in the aortas from both 6- and 20-week-old SHRs. Although type V collagen represented a minor fraction of total collagen (5%) in the aortas of WKY rats, it was twofold greater in the hypertensive animals. This increment in type V collagen in SHR aortas was accompanied by a reduction in the proportion of type I collagen, with no change in the proportion of type III. Study of the passive mechanical properties of the tissues showed that SHR aortas were stiffer compared with aortas of WKY rats, with a larger difference at 20 weeks than at 6 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1988

Functional activity of the two promoters of the myosin alkali light chain gene in primary muscle cell cultures: comparison with other muscle gene promoters and other culture systems.

Proximal upstream flanking sequences of the mouse myosin alkali light chain gene encoding MLC1F and MLC3F, the mouse alpha-cardiac actin gene and the chicken gene for the alpha-subunit of the acetylcholine receptor were linked to the bacterial chloramphenicol acetyl transferase (CAT) gene and transfected into primary cultures derived from mouse skeletal muscle or into myogenic cell lines. We demonstrate that the mouse MLC1F/MLC3F gene has two functional promoters. In primary muscle cultures, a 1200 bp sequence flanking exon 1 (MLC1F) and a 438 bp sequence flanking exon 2 (MLC3F) direct CAT activity in myotubes, but not in myoblasts or in non myogenic 3T6 and CV1 cells. Developmentally regulated expression is also seen with the alpha-cardiac actin (320 bp) and acetylcholine receptor alpha-subunit (850 bp) upstream sequences in the primary culture system. Transfection experiments with myogenic cell lines show different results with a given promoter construct, reflecting possible differences in the levels of regulatory factors between lines. Different muscle gene promoters behave differently in a given cell line, suggesting different regulatory factor requirements between these promoters.

Actins↗
PubMed1988

Validity and reliability of the Childhood Autism Rating Scale with autistic adolescents.

The validity and reliability of the Childhood Autism Rating Scale (CARS) for autistic adolescents was tested. In the first study, CARS scores for autistic children and adolescents (matched on nonverbal IQ, sex, and ethnicity) were compared. In the second study, a group of nonautistic, handicapped adolescents were administered the CARS and these scores were compared with those of a group of autistic adolescents (matched on age, nonverbal IQ, sex, and ethnicity). The CARS clearly discriminated the two adolescent groups, suggesting that the scale may be an adequate measure of autism in adolescence. Although the CARS total score did not discriminate the younger from older autistic subjects, some interesting age-related differences emerged for specific items. A recommendation is made for elimination of one of the items on the CARS that negatively correlates with the CARS total score for both autistic groups.

Adolescent↗
PubMed1988

Six complementation groups for ionising-radiation sensitivity in Chinese hamster cells.

The ionising radiation-sensitive mutants irs 1, irs 2, irs 3, xrs-1 (or xrs-7), EM7 and XR-1 were fused to wild-type cells or to each other in pairs to create hybrid cells. These hybrids were checked chromosomally and their X-ray sensitivity tested. Each mutant was found to be recessive to wild-type and to complement the X-ray sensitivity of the other mutants. Thus there appear to be at least 6 complementation groups for ionising radiation sensitivity in Chinese hamster cells.

Animals↗
PubMed1988

Preliminary molecular studies on two chromosome 2 encoded genes, c-abl and beta 2M, in radiation-induced murine myeloid leukaemias.

The majority of radiation-induced murine myeloid leukaemias are characterized by deletion and/or translocation of an interstitial region of chromosome 2, and there is evidence that such events may occur very early in myeloid leukaemogenesis. Analyses presented and discussed here on the structure and function of two possibly relevant chromosome 2 encoded genes (c-abl and beta 2M) lead to the preliminary conclusion that neither are directly involved nor activationally changed by the characteristic chromosome 2 rearrangements.

Animals↗
PubMed1988

Inhibition of DNA methylase activity by acrolein.

Acrolein, a reactive metabolite of cyclophosphamide, may be responsible for bladder cancer induced by cyclophosphamide. DNA methylase was isolated from the liver and urothelium of rats by high salt extraction of purified nuclei. Acrolein at 10 microM inhibited liver and bladder DNA methylase activity by 30-50%. Kinetic studies with the liver enzyme showed a competitive type of inhibition with a Ki of 6.7 microM. Both dithiothreitol and glutathione afforded protection to the enzyme when added to the assay. At near equimolar concentrations of glutathione to acrolein, the methylase retained 80-90% activity. An increase in DNA had no effect on the inhibition by acrolein, whereas increased amounts of protein protected against acrolein inhibition, suggesting that acrolein reacted with the DNA methylase protein. On the other hand, DNA that had been reacted with acrolein was unable to serve as a substrate for DNA methylase. As the DNA adducts increased the methylation of the DNA decreased. Thus, acrolein has the ability to react with DNA and the DNA methylase protein, either of which results in inhibition of DNA methylation.

Acrolein↗
PubMed1988

The value of the pre-clinic intravenous urogram in the earlier diagnosis of the cause of haematuria.

The early treatment of patients with bladder cancer reduces mortality. By arranging a pre-clinic intravenous urogram we reduced the time from receipt of the General Practitioner's referral letter to making a diagnosis from 85 to 67 days and saved on clinic time and resources. A further reduction to 52 days was made by not using any out-patient time at all. Significant saving of time and resources is possible without any disadvantage to the patient.

Ambulatory Care↗
PubMed1988

Urinary undiversion in young adults.

Eighteen patients who underwent urinary diversion in childhood were undiverted. There were three main groups: the neurologically intact bladder, the neuropathic bladder and the "occult" neuropathic bladder. The simplest procedure of anastomosing the proximal ureters to the distal ureters was preferred. The neuropathic group required excision of the bladder remnant and substitution with detubularised bowel. In four patients the renal function was progressively deteriorating pre-operatively and two have required transplants. Renal failure in one of these patients was accelerated by a post-operative anastomotic stenosis and infection, although his early post-operative anastomotic stenosis and infection, although his early post-operative course was uneventful.

Adolescent↗
PubMed1988

The control of DNA replication in a cell-free extract that recapitulates a basic cell cycle in vitro.

Cell-free extracts prepared from Xenopus eggs support chromosome decondensation and pronuclear formation on demembranated sperm heads. 32P-dCTP pulse-labelling studies demonstrate that DNA synthesis occurs in multiple bursts of 30-40 min in extracts containing pronuclei, each burst being followed by a period of 20-50 min during which no synthesis occurs. Density substitution with bromodeoxyuridine indicates that the synthesis in each burst is semiconservative and results from new initiations, and that, following multiple bursts of synthesis, reinitiation events can occur. Changes in nuclear morphology have been characterized in the extract by phase-contrast microscopy and by fluorescence microscopy following pulse labelling with biotin-11-dUTP and staining with anti-lamin antibodies. Lamin accumulation occurs as DNA decondenses and parallels the acquisition of membrane structures. Biotin-11-dUTP incorporation is first observed in small nuclei having decondensed DNA and an extensive lamina. While DNA synthesis is occurring nuclei remain relatively small, but rapid swelling accompanied by chromosome condensation occurs when biotin incorporation ceases. Nuclear swelling and chromatin condensation is followed by nuclear membrane breakdown, lamin dispersal and chromosome formation. Mitosis lasts for approximately 20 min. Nuclear reassembly is recognized by the appearance of membrane vesicles around small pieces of decondensed DNA, which parallels the appearance of lamin islands within a chromatin mass. These 'islands' incorporate biotin, indicating that DNA synthesis is occurring, and apparently fuse as larger S-phase nuclei are formed. Extensive protein synthesis occurs for at least 4 h in most extracts. This synthesis is required for the initiation of mitotic events and the reinitiation of DNA synthesis.

Animals↗
PubMed1987

Periodic DNA synthesis in cell-free extracts of Xenopus eggs.

Cell-free extracts prepared from unfertilized eggs of Xenopus laevis support DNA synthesis on sperm pronuclei. Continuous labelling studies using [3H]dCTP and pulse labelling studies using [32P]dCTP demonstrate that synthesis occurs in short bursts of 40 min, which are punctuated by periods of 20-40 min during which no synthesis occurs. Density substitution experiments using bromodeoxyuridine demonstrate that this synthesis involves the initiation of replication and reveals that re-initiation events can occur following multiple bursts of replication. The periodic properties of these extracts are sensitive to protein synthesis inhibitors.

Animals↗
PubMed1987

An in vitro system for the study of tracheal epithelial cells.

Enzymatically dissociated hamster tracheal epithelial (HTE) cells were cultured on collagen coated Millicell filters. Within 3-5 days after being placed in culture large numbers of ciliated and mucus cells began to appear. By 1 week the HTE cells closely resembled those seen in vivo, i.e. columnar morphology and organelle polarity. After 4 weeks in vitro the HTE cultures were still able to maintain the polarity and overall columnar morphology found in in vivo tissue. There was, in addition, no apparent degradation of the collagen substrate. Auto-radiographic data indicated that there was an initial period of high DNA synthesis during the first 3 days in vitro. This was followed by a second phase in which, by day 6, the amount of DNA synthesis was greatly reduced. Analysis of the numbers of ciliated cells relative to non-ciliated cells demonstrated that between days 5 and 8 there was an increase in the percentage of ciliated cells, suggesting that cellular differentiation (i.e. ciliogenesis) follows cellular proliferation. The results of this study show that when HTE cells are grown on collagen-coated Millicell filters there is a significant improvement in cell growth and morphology yielding cells that are very similar to those present under in vivo conditions. Moreover, since there is no degradation of the collagen substrate, HTE cultures may be suitable for long-term studies of respiratory tract epithelia.

Animals↗
PubMed1987

Isolation and cross-sensitivity of X-ray-sensitive mutants of V79-4 hamster cells.

The V79-4 Chinese hamster line was mutagenized and surviving clones screened for X-ray sensitivity using a replica microwell technique. One slightly sensitive clone and 3 clearly sensitive clones were isolated from approximately 5000 screened, and designated irs 1 to irs 4. The 3 more sensitive clones showed different responses to the genotoxic agents mitomycin C (MMC), ethyl methanesulphonate (EMS) and ultraviolet light (UV). irs 1 showed considerable sensitivity to all the agents tested, in the order MMC much greater than EMS greater than UV. irs 2 and irs 3 had similar sensitivities to EMS and to UV (EMS greater than UV) but irs 3 was more sensitive than irs 2 to MMC. None of these mutants is identical in phenotype to previously published mutants.

Animals↗
PubMed1987

Ileal loop diversion in women with incurable stress incontinence.

Eighteen women with incurable stress incontinence underwent ileal loop urinary diversion. Eight patients required surgical revision of their stomas. Another eight patients required the formation of iatrogenic vesicovaginal fistulas but subsequently underwent cystectomy for persistent vesical discharge. Twelve patients with a psychiatric history underwent a total of 29 further operations after diversion compared with a total of six operations for the six patients without a psychiatric history. Urinary diversion is an unsatisfactory solution to the problem of incurable stress incontinence and the relationship between psychiatric disorders and incurable stress incontinence requires further study.

Adult↗