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Biomedical subjects

K A Marshall

Publications and source records attributed to K A Marshall.

At least 19 recordsLinked to original sources
PubMed2001

Effect of overexpression of BCL-2 on cellular oxidative damage, nitric oxide production, antioxidant defenses, and the proteasome.

Bcl-2 is a gene family involved in the suppression of apoptosis in response to a wide range of cellular insults. Multiple papers have suggested a link between Bcl-2 and oxidative damage/antioxidant protection. We therefore examined parameters of antioxidant defense and oxidative damage in two different cell lines, NT-2/D1 (NT-2) and SK-N-MC, overexpressing Bcl-2 as compared with vector-only controls. Bcl-2 transfectants of both cell lines were more resistant to H(2)O(2) and showed increases in GSH level and Cu/Zn-superoxide dismutase (SOD1) activity, but not in Mn-superoxide dismutase, glutathione peroxidase, or glutathione reductase activities. Catalase activity was increased in SK-N-MC cells. Overexpression of Bcl-2 did not significantly decrease levels of oxidative DNA damage (measured as 8-hydroxyguanine) or lipid peroxidation, but it decreased levels of 3-nitrotyrosine in both cell lines and protein carbonyls in SK-N-MC cells only. It also increased proteasome activity in both cell lines. We conclude that Bcl-2 raises cellular antioxidant defense status, but this is not necessarily reflected in decreased levels of oxidative damage to DNA and lipids. The ability of Bcl-2 overexpression to decrease 3-nitrotyrosine levels suggests that it may decrease formation of peroxynitrite or other reactive nitrogen species; this was confirmed as decreased production of NO(2)(-)/NO(3)(-) in the transfected cells and a fall in the level of nNOS protein.

Antioxidants↗
PubMed2001

Anchored reference loci in loblolly pine (Pinus taeda L.) for integrating pine genomics.

Anchored reference loci provide a framework for comparative mapping. They are landmarks to denote conserved chromosomal segments, allowing the synthesis of genetic maps from multiple sources. We evaluated 90 expressed sequence tag polymorphisms (ESTPs) from loblolly pine (Pinus taeda L.) for this function. Primer sets were assayed for amplification and polymorphism in six pedigrees, representing two subgenera of Pinus and a distant member of the Pinaceae, Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco). On average, 89% of primer sets amplified in four species of subgenus Pinus, 49% in one species of subgenus Strobus, and 22% in Douglas-fir. Polymorphisms were detected for 37-61% of the ESTPs within each pedigree. Comparative mapping in loblolly and slash pine (P. elliottii Englm.) revealed that ESTPs mapped to the same location. Disrupted synteny or significant disruptions in colinearity were not detected. Thirty-five ESTPs met criteria established for anchor loci. The majority of those that did not meet these criteria were excluded when map location was known in only a single species. Anchor loci provide a unifying tool for the community, facilitating the creation of a "generic" pine map and serving as a foundation for studies on genome organization and evolution.

Base Sequence↗
PubMed1999

Molecular parasites that evolve longer genomes.

Molecular parasites that utilize the replication machinery of cells or of in vitro amplification reactions have previously been characterized. By and large, these parasites have been smaller than the viruses or amplicons that gave rise to them. This is likely because shorter genomes can be replicated more quickly. In contrast, we have identified and characterized parasites of an isothermal amplification reaction that are longer than their parental molecules yet replicate much more efficiently. These results raise interesting questions regarding whether the optimal size of replicators reflects a trade-off between the information encoded in a parasite and the information encoded in the machinery replicating that parasite.

Base Sequence↗
PubMed1999

The neuronal toxicity of sulfite plus peroxynitrite is enhanced by glutathione depletion: implications for Parkinson's disease.

In Parkinson's disease (PD) and incidental Lewy body disease glutathione levels in the substantia nigra are decreased by 40-50%. Both peroxynitrite (ONOO ) and alterations in the metabolism of sulfur-containing amino acids have been implicated in PD and we have previously shown that sulfite and ONOO- exert synergistic toxicity to a neuronal cell line. This article presents data to show that this synergistic toxicity of sulfite and ONOO- is greatly enhanced by 50% depletion of cellular glutathione levels. The toxicity of sulfite is also slightly enhanced. Neurones with decreased glutathione may be at increased risk from sulfite and especially from the synergistic damaging effects of ONOO- and sulfite. Because sulfite is present normally in the brain as a product of cysteine metabolism, and because increased ONOO- formation has been reported in PD, these events might contribute to neuronal cell death.

Animals↗
PubMed1999

Training ribozymes to switch.

Ribozymes that are sensitive to cyclic nucleotides have been selected in vitro. Remarkably, the cGMP-dependent ribozymes are specifically activated by a factor of 5,000 - the largest allosteric ribozyme activation by a small molecule seen to date.

Allosteric Regulation↗
PubMed1998

Toxic effects of sulphite in combination with peroxynitrite on neuronal cells.

Sulphite is widely used as a preservative and antioxidant in foods, beverages, and pharmaceuticals. Endogenous sulphite is generated during the normal metabolism of sulphur-containing amino acids, and alterations in sulphur amino acid metabolism occur in some neurodegenerative diseases. In particular, sulphite oxidase deficiency produces severe mental retardation, seizures, spastic quadriparesis, dislocated lenses, and early death. Exposure of a neuronal cell line (rat mesencephalic cells) to high levels of sulphite induced a time-dependent decrease in viability. Peroxynitrite was also toxic to this cell line, and sulphite affected the toxicity of ONOO-. Sulphite concentrations of < or = 0.5 mM markedly potentiated cell damage induced by 200 microM ONOO-. We propose that sulphite can act as a neurotoxic agent, especially in combination with peroxynitrite. Sulphite radicals may be involved in the neurotoxic effect.

Animals↗
PubMed1997

Upregulation of the anti-apoptotic protein Bcl-2 may be an early event in neurodegeneration: studies on Parkinson's and incidental Lewy body disease.

Apoptosis and oxidative stress have been suggested to be involved in Parkinson's disease (PD). However, whether this is a cause or consequence of neurodegeneration is unknown. Incidental Lewy Body disease (ILBD) appears to be a presymptomatic form of Parkinson's disease where individuals are neurologically normal, but after post-mortem examination pathology similar to Parkinson's disease is present. Thus, ILBD can be used to examine the early stages of the pathological process in PD. We investigated the levels of Bcl-2, an anti-apoptotic protein known to decrease cell death induced by several mechanisms, including oxidative stress. Our data show that Bcl-2 is significantly raised in the basal ganglia regions of PD patients as compared to age-matched controls. A similar trend is also found in ILBD. We propose that Bcl-2 increases in some brain regions as an early event and that these brain regions are under a stress for perhaps many years before any symptomatic changes occur.

Age Factors↗
PubMed1996

Evaluation of the antioxidant activity of melatonin in vitro.

Melatonin is being increasingly promoted as a treatment for "jet lag" and insomnia and has been suggested to act as an antioxidant in vivo. The antioxidant and potential pro-oxidant activities of melatonin were investigated in vitro. Melatonin was able to scavenge hypochlorous acid (HOCl) at a rate sufficient to protect catalase against inactivation by this molecule. Melatonin could also prevent the oxidation of 5-thio-2-nitrobenzoic acid by HOCl. Melatonin decreased the peroxidation of ox-brain phospholipids with a calculated IC50 of (210 +/- 2.3) microM. In contrast, serotonin which also scavenged HOCl, was much more effective in decreasing phospholipid peroxidation (IC50 15 +/- 5 microM). Both compounds reacted with trichloromethylperoxyl radical (CCl3O2) with rate constants of (2.7 +/- 0.2) x 10(8) and (1.2 +/- 0.1) x 10(8)M-1 s- respectively. Melatonin did not scavenge superoxide radical and weakly protected DNA against damage by the ferric bleomycin system. By contrast serotonin was weakly pro-oxidant in the ferric-bleomycin system and strongly pro-oxidant in the Fe(3+)-EDTA/H2O-deoxyribose system. Solubility restrictions precluded examination of melatonin in this system. Our data show that melatonin exerts only limited direct antioxidant activities.

Animals↗
PubMed1996

Managing cancer pain: basic principles and invasive treatments.

Severe pain associated with cancer continues to be a substantial problem for patients, physicians, and the health-care system. During the past 2 decades, major advances have occurred in the understanding of the pathogenesis of pain. Likewise, considerable advances have occurred in the conceptualization of and clinical approach to cancer pain. This article briefly summarizes the basic principles of the treatment of cancer pain and in particular describes the World Health Organization 3-step "analgesic ladder" for the treatment of cancer pain. In addition, several invasive approaches for managing various refractory cancer pain syndromes are discussed.

Drug Therapy, Combination↗
PubMed1995

A mutation hotspot in the chloroplast genome of a conifer (Douglas-fir: Pseudotsuga) is caused by variability in the number of direct repeats derived from a partially duplicated tRNA gene.

We determined the DNA sequence of a 2.7-kb cpDNA XbaI fragment from douglas-fir [Pseudotsuga menziesii (Mirb.) Franco]. RFLPs revealed by the 2.7-kb XbaI clone were observed to vary up to 1 kb among species within the genus Pseudotsuga and up to 200 bp among trees of P. menziesii. The polymerase chain reaction (PCR) allowed the locus of polymorphism to be identified, and the variable region was then sequenced in a second Douglas-fir tree, a single tree of a related species, Japanese Douglas-fir (P. japonica), and in a species lacking a mutation hotspot in the region, Pinus radiata (Monterey pine). The locus of polymorphism is characterized by hundreds of base pairs of imperfect, tandem direct repeats flanked by a partially duplicated and an intact trn Y-GUA gene. The duplication is direct in orientation and consists of 43 bp of the 3' end of trnY and 25 bp of its 3' flanking sequence. Tandem repeats show high sequence similarity to a 27-bp region of the trnY gene that overlaps one end of the duplication. The two trees of Douglas-fir sequenced differed by a single tandem repeat unit, whereas these trees differed from the Japanese Douglas-fir sequenced by approximately 34 repeat units. Repetitive DNA in the Pseudotsuga cpDNA hotspot was most likely generated at the time of the partial trnY gene duplication and these sequences expanded by slipped-strand mispairing and unequal crossing-over.

Base Sequence↗
PubMed1994

Accumulation of HL-60 leukemia cells in G2/M and inhibition of cytokinesis caused by two marine compounds, bistratene A and cycloxazoline.

The effects on the cell cycle of two biologically active compounds, bistratene A and cycloxazoline, from the marine ascidian Lissoclinum bistratum were studied in HL-60 human leukemia cells using flow cytometry. Both compounds were shown to cause an apparent accumulation of cells in the G2/M phase. This effect was shown to be both time- and dose-dependent. At the longer time points (30 and 48 h after addition of the compounds) polyploidy was apparent. The fate of cells labeled in the S phase with 5-bromo-2'-deoxyuridine (BrdUrd) was analysed using a bivariate BrdUrd/PI (propidium iodide) technique. Bistratene A and cycloxazoline treatment prevented the majority of BrdUrd-labeled cells from progressing through to the G1 phase. Approximately 50% of the cells were delayed at G2/M, and a significant proportion of cells appeared to be polyploid. Light and electron microscopy revealed the presence of multinucleated cells accounting for the apparent polyploidy. The progression of cells out of the G1 phase was also examined by synchronising cells with mimosine and releasing them from mimosine block in the presence of bistratene A. There was no evidence of a block at the G1/S phase transition or through the S phase since DNA synthesis was not inhibited. The mechanism by which these compounds interfere with cytokinesis is presently unknown but, in the case of bistratene A, may be linked to altered phosphorylation of cellular proteins involved in cell-cycle control.

Acetamides↗
PubMed1993

Breast-feeding reduces maternal lower-body fat.

The effect of breast-feeding on maternal anthropometric measures during the first 6 postpartum months was studied in 24 women. Mothers, who were seen in the hospital shortly after delivery and at monthly intervals thereafter, kept a record of their infant-feeding practices and provided three 24-hour dietary recalls per month. The women were placed in one of three groups according to their infant-feeding practices: breast-feeding exclusively, combination of breast- and formula-feeding, and formula-feeding only. Changes in anthropometric variables at 6 months postpartum were similar in the three groups, but mothers who breast-fed exclusively or partially had significantly larger reductions in hip circumference measurements (3.6% and 3.1%, respectively) and were less above their prepregnancy weights at 1 month postpartum (7.8% and 8.5% above prepregnancy weight, respectively) than mothers who fed formula exclusively (0.68% reduction in hip circumference and 13.7% above prepregnancy weight). Our findings indicate that a woman's choice of infant-feeding practice influences postpartum anthropometric changes, but these effects may be temporary.

Anthropometry↗
PubMed1990

Structure-activity relationships of the lissoclinamides: cytotoxic cyclic peptides from the ascidian Lissoclinum patella.

Two new lissoclinamides (lissoclinamides 7 and 8) have been isolated from the aplousobranch ascidian Lissoclinum patella. These lissoclinamides are cyclic heptapeptides with the same structural features as lissoclinamides 4 and 5 reported earlier, containing an oxazoline ring, one proline, one valine, two phenylalanine residues, and thiazole and/or thiazoline rings. All four peptides have the same sequence of amino acids around the ring and differ from one another only in their stereochemistry or the number of thiazole and thiazoline rings. The cytotoxicities of the compounds were tested with human fibroblast and bladder carcinoma cell lines and normal lymphocytes. Slight changes in structure resulted in marked differences in the cytotoxicities of these compounds. The most potent is lissoclinamide 7, containing two thiazoline rings, which rivals didemnin B in cytotoxicity in vitro.

Animals↗
PubMed1990

Hand infections in the diabetic and the diabetic renal transplant recipient.

We present a series of 41 diabetic patients with severe tissue destruction and deformity secondary to hand infections. Thirty (73%) of the patients showed propagation of the infection to bone, tendons, or deep palmar spaces, and 26 of 41 (63%) required amputations. Sixty-three percent of the cultures were mixed; pure Staphylococcus aureus accounted for only 12%. Diabetics who were renal transplant recipients were at increased risk, with a 100% amputation rate and an average hospitalization of 41 days. Recommendations for management of diabetic hand infections are given to reduce the mortality and morbidity in these patients.

Adult↗