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Biomedical subjects

L Arnold

Publications and source records attributed to L Arnold.

At least 37 records · Page 2Linked to original sources
PubMed1997

My needlestick.

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Acquired Immunodeficiency Syndrome↗
PubMed1997

Metabolic effects of alterations in meal frequency in type 2 diabetes.

OBJECTIVE: The effects of altering meal frequency on measures of glucose and lipid metabolism in type 2 diabetes were examined by comparing isocaloric dietary regimens in which daily food intake was provided by three or nine meals each day. RESEARCH DESIGN AND METHODS: A total of 13 free-living men and women with type 2 diabetes or persistently impaired glucose tolerance participated in a randomized crossover study in which three- and nine-meal regimes were followed for 4-week periods. Fasting plasma lipid and lipoprotein, glucose and insulin concentrations were measured at weekly intervals and glucose, insulin, and triglyceride responses following a 75-g glucose load at weeks 2 and 4 of each diet period. Dietary intake was also recorded during these weeks. RESULTS: Nutrient intakes and all measures of carbohydrate and lipid metabolism were similar on the three- and nine-meal regimes. CONCLUSIONS: This longer-term study could not confirm the potential benefits of increased meal frequency suggested by comparable 4-week studies in type 2 diabetic individuals and acute experiments in individuals with diabetes. However, as there were no adverse effects of consuming nine meals per day, it would seem appropriate that meal frequency in those with type 2 diabetes should be left to personal choice, provided that energy balance is maintained.

Aged↗
PubMed1996

NMR evidence for helix geometry modifications by a G-U wobble base pair in the acceptor arm of E. coli tRNA(Ala).

A ribooligonucleotide duplex representing the acceptor stem of E. coli RNA(Ala) with a G3-U70 wobble base pair, which is the main identity element for the recognition by the alanine-tRNA synthetase, has been characterized by 2D-NMR, as having two sequence variants with a regular Watson-Crick G3-C70 and an I3-U70 wobble pair, respectively. As compared to a regular A-RNA, the G-U base pair gives rise to variations of the local helix geometry which are reflected in distinct local chemical shift changes. Structural differences between the duplex possessing an I3-U70 base pair and the wild-type G3-U70 sequence have also been found. The nucleotides in the ubiquitous single-stranded NCCA terminus display a surprisingly high degree of stacking order, especially between A73, C74, and C75.

Base Composition↗
PubMed1996

Presence of hypochlorite-modified proteins in human atherosclerotic lesions.

Oxidation of LDL may contribute to atherogenesis, though the nature of the in vivo oxidant(s) remains obscure. Myeloperoxidase, the enzyme responsible for hypochlorous acid/hypochlorite (HOCl) production in vivo, is present in active form in human atherosclerotic lesions, and HOCl aggregates and transforms LDL into a high-uptake form for macrophages in vitro. Here we demonstrate HOCl-modified proteins in human lesions using an mAb raised against HOCl-modified LDL that recognizes HOCl-oxidized proteins but does not cross-react with Cu2+-, malondialdehyde-, or 4-hydroxynonenal-modified LDL. This antibody detected significantly more material in advanced atherosclerotic lesions than normal arteries, even though azide and methionine were included during sample work-up to inhibit myeloperoxidase and to scavenge HOCl. The epitope(s) recognized was predominantly cell associated and present in monocyte/macrophages, smooth muscle, and endothelial cells. The intima and cholesterol clefts stained more heavily than the center of the thickened vessels; adventitial staining was apparent in some cases. Immunostaining was also detected in a very early lesion from an accident victim, beside healthy areas that were unreactive. LDL oxidized by HOCl in vitro, but not native LDL, effectively competed with the epitopes in lesions for antibody binding. Density centrifugation of plaque homogenates and Western blot analysis showed that, in the apo B-containing lipoprotein fraction, the mAb recognized protein(s) of molecular mass greater than apo B, similar to those produced during oxidation of LDL with HOCl in vitro. Three major proteins were recognized by the anti-HOCl-modified protein antibody but not by an anti-apo B antibody in the apo B-free fraction. Together, these results demonstrate HOCl-oxidized proteins in human atherosclerotic lesions, implicating this oxidant in LDL modification in vivo.

Arteriosclerosis↗
PubMed1996

Comparison of the solution and crystal conformations of (G + C)-rich fragments of DNA.

DNA fragments crystallize in an unpredictable manner, and relationships between their crystal and solution conformations still are not known. We have studied, using circular dichroism spectroscopy, solution conformations of (G + C)-rich DNA fragments, the crystal structures of which were solved in the laboratory of one of the present authors. In aqueous trifluorethanol (TFE) solutions, all of the examined oligonucleotides adopted the same type of double helix as in the crystal. Specifically, the dodecamer d(CCCCCGCGGGGG) crystalized as A-DNA and isomerized into A-DNA at high TFE concentrations. On the other hand, the hexamer d(CCGCGG) crystallized in Z-form containing tilted base pairs, and high TFE concentrations cooperatively transformed it into the same Z-form as adopted by the RNA hexamer r(CGCGCG), although d(CCGCGG) could isomerize into Z-DNA in the NaCl + NiCl2) aqueous solution. The fragments crystallizing as B-DNA remained B-DNA, regardless of the solution conditions, unless they denatured or aggregated. Effects on the oligonucleotide conformation of 2-methyl-2,4-pentanediol and other crystallization agents were also studied. 2-Methyl-2,4-pentanediol induced the same conformational transitions as TFE but, in addition, caused an oligonucleotide condensation that was also promoted by the other crystallization agents. The present results indicate that the crystal double helices of DNA are stable in aqueous TFE rather than aqueous solution.

Base Composition↗
PubMed1996

The unusual X-form DNA in oligodeoxynucleotides: dependence of stability on the base sequence and length.

X-form is an unusual double helix of DNA adopted by poly(dA-dT) or (dT-dA)4 at high concentrations of CsF. On the other hand, poly(dA), poly(dT), (dA-dT)4 and most other DNAs do not adopt this conformer. Here we demonstrate that the X-form is strongly destabilized by GC pairs or even minute perturbations of the alternating pyrimidinepurine sequence. For example, the 30-mer d(TATAAT)5, containing five tandem repeats of the Pribnow box, fails to isomerize into the X-form. After (dT-dA)4, the 16-mer (dT-dA)8 is shown to be the second most predisposed oligodeoxynucleotide in the (dT-dA)n series to isomerize into the X-form while the duplex lengths corresponding to n = 3,5,6,7,9,12 and 20 make the X-form unstable even in the strictly alternating (dT-dA)n sequence. Consequently, the (dT-dA)n duplex length is also a crucial factor of the X-form stability on the oligodeoxynucleotide level. We discuss a possibility that the X-form is a solution counterpart of the D-form adopted in dehydrated poly(dA-dT) fibers because properties of these two conformers are remarkably similar in many respects.

Base Sequence↗
PubMed1996

UV light-induced crosslinking of short DNA duplex strands: nucleotide sequence preferences and a prominent role of the duplex ends.

By various doses of UV light, we irradiated 32 short DNA duplexes having between 12 and 40 nucleotide residues in length, and monitored the induced crosslinks between the complementary DNA strands by denaturing polyacrylamide gel electrophoresis. The experiments revealed that the crosslinking was strongest with the alternating sequence of T and A and weaker with the alternating sequence of T and G (C and A in the complementary strand). On the other hand, GC blocks of any sequence provided undetectable amounts of interstrand crosslinks even at the highest doses of UV irradiation. The amount of crosslinked strands logarithmically increased with the UV dose but it did not depend on the oligonucleotide concentration, ionic strength, divalent magnesium or manganese cations and pH at least within the examined regions of the experimental conditions, unless the oligonucleotide denatured or isomerized into a unimolecular foldback. The extent of crosslinking also did not depend on the (dT-dA)n duplex length to indicate that the crosslink was predominantly localized at a specific duplex locus. Experiments with (dT-dA)8 "mutants" in which AT pairs were systematically replaced by GC pairs at various molecule positions, revealed that the crosslinking predominantly occurred at the oligo(dT-dA) duplex ends. The crosslinking is a direct method to detect duplexes of DNA, which is here, for example, demonstrated with the heteroduplex of (dT-dA)12 and (dT-dA)16.

Electrophoresis, Polyacrylamide Gel↗
PubMed1996

Early discharge and home care after unplanned cesarean birth: nursing care time.

OBJECTIVE: This study examined the mean nursing time spent providing discharge planning and home care to women who delivered by unplanned cesarean birth and examined differences in nursing time required by women with and without morbidity. DESIGN: A secondary analysis of nursing time from a randomized trial of transitional care (discharge planning and home follow-up) provided to women after cesarean delivery. SETTING: An urban tertiary-care hospital. PATIENTS: The sample (N = 61) of black and white women who had unplanned cesarean births and their full-term newborn was selected randomly. Forty-four percent of the women had experienced pregnancy complications. INTERVENTIONS: Advanced practice nurses provided discharge planning and 8-week home follow-up consisting of home visits, telephone outreach, and daily telephone availability. OUTCOME MEASURE: Nursing time required was dictated by patient need and provider judgment rather than by reimbursement plan. RESULTS: More than half of the women required more than two home visits; mean home visit time was 1 hour. For women who experienced morbidity mean discharge planning time was 20 minutes more and mean home visit time 40 minutes more. CONCLUSIONS: Current health care services that provide one or two 1-hour home visits to childbearing women at high risk may not be meeting the education and resource needs of this group.

Adolescent↗
PubMed1996

The evolving nature of perinatal nursing.

Current and future health-care trends create many challenges for perinatal nurses. A new mind set is required for the profession not only to accommodate the paradigm shift but provide leadership in designing a new future for health care. Interestingly, it has been predicted that the movement toward achieving healthier communities will result in a decentralized, community-based, nonhierarchical system that will not be male dominated. Nurses will be called on to participate in the development and implementation of health-care programs rather than assume a passive, recipient role. On the brink of the 21st century, nursing is in a position to emerge as a leader in providing cost-effective, needs-based, health-care services aimed at improving the health status of a community.

Humans↗
PubMed1995

Relationship of mitochondrial function and cellular adenosine triphosphate levels to pMC540 and merodantoin cytotoxicity in MCF-7 human breast cancer cells.

In previous studies we have reported that preactivated merocyanine 540 (pMC540) and its chemically synthesized isolates merocil and merodantoin mediate their preferential cytotoxicity towards certain types of malignant cells including human breast cancer cells in vitro and in vivo. The mechanism of cytotoxic action appears to be, in part, via initial interaction with topoisomerase II leading to apoptosis. To further build upon these findings we now show that pMC540 and merodantoin disrupt mitochondrial morphology and function in intact MCF-7 human breast cancer cells as seen by their causing the release of rhodamine 123 from prestained cells, a rapid reduction in ATP levels, inhibition of succinate dehydrogenase activity and oxygen consumption. These data suggest that mitochondria may also be an important target for the cytotoxic action of pMC540 and merodantoin mediated through disruption of the energy balance.

Adenosine Triphosphate↗