Impact of shear rate pattern on post-occlusive near-infrared spectroscopy microvascular reactivity.

The primary aim of the present study was to determine the impact of acute changes in shear rate patterns, in particular retrograde shear rate, on microvascular function in 15 healthy, young men and women as determined via the post-occlusive near-infrared spectroscopy (NIRS) microvascular reactivity response. Microvascular reactivity, via NIRS-derived measurements of post-occlusion tissue saturation index (TSI%) and total microvascular hemoglobin+myoglobin concentration ([Hb]total), were assessed in each participant before and immediately after exposure to a 30min retrograde shear treatment. Retrograde shear was achieved via a blood pressure cuff placed below the knee inflated to 75mmHg. One leg was exposed to the retrograde shear (Treatment leg) and the contralateral leg served as a non-treatment control. In the Treatment leg, significant increases in retrograde shear rate occurred during the retrograde intervention. Following the intervention, the area under the TSI% post-occlusion response curve, which represents the total microvascular reactivity response, and the absolute peak TSI% response were significantly increased compared to pre-intervention in the Treatment leg, but not the Control leg. The absolute peak [Hb]total response was significantly increased post-intervention in both legs. These results are in contrast to our hypothesis that 75mmHg cuff inflation, designed to increase retrograde shear rate in the femoral artery would negatively affect post-occlusive microvascular reactivity. These data suggest that the current method of increasing retrograde shear rate in the intact human does not adversely impact NIRS derived measurements of microvascular reactivity.

Gathering information to develop palliative care programs for Alaska's Aboriginal peoples.

Over an eight-year period, the authors conducted focus groups in six Alaska Aboriginal communities. They sought information about traditional ways of caring for the dying, current values and preferences surrounding death, the kind of support caregivers need, and how a palliative care program could assist families caring for loved ones in the community. Focus groups are a standard qualitative research tool for gathering information when a new program or service is planned. However, for Alaska's Aboriginal people living in remote settings, the standard focus group design is not useful. That design was modified to reflect cultural norms and communication methods while adhering to standards of qualitative research. Communities selected represented different groups of Alaska's Indigenous people; 84 Aboriginal elders participated. Culturally modified focus groups yielded rich and useful information about historical and traditional practices surrounding death. Participants also vocalized expectations and concerns regarding their own eventual deaths. The process of conducting six different focus groups throughout Alaska yielded valuable information about community engagement in Aboriginal communities.

DNA mismatch binding defects, DNA damage tolerance, and mutator phenotypes in human colorectal carcinoma cell lines.

DNA mismatch binding in vitro, resistance to DNA methylation damage, and spontaneous mutation rates were examined in human colorectal adenocarcinoma cell lines. Of 11 cell lines, 3 (DLD1, HCT15, and LoVo) were defective in mismatch binding. All three lines had a mutator phenotype. These properties indicate that DLD1 and HCT15 may, like LoVo, carry mutations in the mismatch recognition protein hMSH2. Mismatch binding was normal in the remaining eight lines, including HCT116 in which a second mismatch repair protein, hMLH1, is defective. Two lines, SW620 and SW48, did not express detectable levels of the DNA repair enzyme O6-methylguanine-DNA methyltransferase. SW620 exhibited the expected sensitivity to N-methyl-N-nitrosourea. In contrast, SW48 cells were highly resistant to N-methyl-N-nitrosourea and also slightly to methyl methanesulfonate, indicating that they are tolerant to DNA methylation damage. SW48 exhibited the spontaneous mutator phenotype and microsatellite instability that are hallmarks of a defect in mismatch repair. This cell line provides evidence for the association between methylation tolerance and defective mismatch correction in human colorectal carcinoma cells. The properties of methylation-tolerant, mismatch repair-defective cells identify possible selective pressures that might facilitate the natural selection of mismatch repair-defective tumors.

Spontaneous development of drug resistance: mismatch repair and p53 defects in resistance to cisplatin in human tumor cells.

The contributions of defective mismatch repair and mutated p53 to cisplatin resistance of human tumor cells were analysed. Mismatch repair defects were not associated with a predictable degree of resistance among several tumor cell lines. Repair defective variants of the A2780 ovarian carcinoma cell line which were isolated by selection for a methylation tolerant phenotype and did not express the hMLH1 mismatch repair protein, were highly resistant to cisplatin. Their cisplatin resistance was not a simple consequence of the mismatch repair defect. They were members of a drug-naive subpopulation of A2780 in which a silent hMLH1 gene accompanies a mutated p53. Two complementary approaches indicated that each defect contributes to cisplatin resistance independently and to a different extent. Firstly, separate introduction of a p53 defect into A2780 cells significantly increased their cisplatin resistance; defective hMLH1 provided less extensive protection. Secondly, azadeoxycytidine reactivation of the silent hMLH1 gene or expression of a transfected hMLH1 cDNA sensitized the doubly hMLH1/p53 deficient cells only slightly to cisplatin. Both approaches indicate that defective p53 status is a major determinant of cisplatin resistance and defective mismatch repair is a minor, and independent, contributor. The data have implications for the development of intrinsic cisplatin resistance.

Mismatch repair and p53 independently affect sensitivity to N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea.

The contributions of defective mismatch repair (MMR) and the p53-response to cell killing by N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea (CCNU) were evaluated. MMR defects were previously shown to be associated with CCNU sensitivity (G. Aquilina et al., Cancer Res., 58: 135-141, 1998). Unexpectedly, eight MMR-deficient variants of the A2780 human ovarian carcinoma cell line were 3-fold more resistant to CCNU than the MMR-proficient parental cells. The variants were members of a preexisting subpopulation of drug-resistant A2780 cells. In addition to deficient expression of the MMR protein hMLH1, an essential component of the hMutL alpha repair complex, the variants exhibited alterations in the expression of other genes that influence drug sensitivity. Although A2780 cells possess a wild-type p53 gene, all of the clones contained a heterozygous G to T tranversion at codon 172. This change resulted in a Val to Phe substitution and was associated with a constitutive production of high levels of p53, which was inactive as a transcriptional activator of bax and p21. The hMLH1/p53 defective variants displayed a less prominent cell cycle arrest and reduced apoptosis after CCNU treatment. In contrast, MMR-defective A2780 variants, which had a similar hMutL alpha defect but retained a wild-type p53, did exhibit the expected CCNU sensitivity. Expression of a dominant-negative p53val135 increased CCNU resistance of both MMR-proficient and MMR-deficient A2780 cells. Thus, defective MMR and p53 influence CCNU sensitivity in opposite directions. Their effects are independent, and sensitization by defective MMR does not require a functional p53 response.

The Spiritual History Scale in four dimensions (SHS-4): validity and reliability.

The goals of this study were to develop a valid, reliable measure of lifetime religious and spiritual experience and to assess its value in explaining late-life health. Procedures included semi-structured interviews with Duke Aging Center volunteers (n = 30), followed by structured interviews of a stratified, random sample of subjects (n = 157) from the Established Populations for Epidemiologic Studies of the Elderly at Duke University. Principal components analysis suggested four factors with favorable psychometrics. Health-impaired subjects reported a history of seeking/receiving divine aid (God Helped). At every level of impairment, Lifetime Religious Social Support and current religious attendance were positively correlated. Regardless of current attendance, subjects who reported higher Lifetime Religious Social Support received more instrumental social support. Healthy behaviors were associated with both God Helped and Lifetime Religious Social Support. Cost of Religiousness predicted depressive symptoms and impaired social support. Family History of Religiousness was unrelated to late-life health. Evaluation of the Spiritual History Scale in Four Dimensions (SHS-4) across geographical settings, cultural subgroups, age cohorts, and clinical samples is warranted.

Establishing a culturally sensitive palliative care program in rural Alaska Native American communities.

End-of-life programs that provide an option for patients to die at home are available in most U.S. communities. However, Alaska Natives living in remote Alaska villages often die alone in hospitals and nursing homes hundreds of miles away from home. The Bristol Bay Area Health Corporation (BBAHC), a tribal organization, is the sole provider of comprehensive primary care services to 34 Alaska Native villages located within a 46,000 square mile area in southwest Alaska. The closest tertiary care hospital is 329 air miles away in Anchorage. Because of the high cost of, and difficulties encountered in trying to deliver end-of-life care services to remote communities, a village-focused, culturally sensitive, volunteer and primary care program combined with a regionally based physician and home health nurse to deliver multi-disciplinary palliative care was developed. The Helping Hands Program blends cultural practices with contemporary palliative care medicine to allow Alaska Natives and others living in remote communities to be cared for at home through the end of life. Since the program was implemented in 1999, the percentage of home deaths for selected causes has changed from 33% in 1997 to 77% in 2001. The Anchorage-based Alaska Native Tribal Health Consortium (ANTHC) and the Alaska Native Medical Center (ANMC) have recognized the importance and success of the BBAHC program and are investigating expanding the program to other parts of Alaska. Centralizing the program in Anchorage will allow staff trained in palliative care to travel to regional Alaska Native hospitals to help train health care professionals.

Breast cancer risk factors among Hispanic women.

Studies of risk factor differences between racial and ethnic groups within a population may be most valuable in delineating the etiology of breast cancer. Most studies of breast cancer risk factors have been conducted only among white women. We could not find any epidemiologic studies that investigated risk factors for breast cancer occurrence among Hispanic women. The Cancer and Steroid Hormone Study provided the opportunity to investigate risk factors for breast cancer among Hispanic women aged 20 to 54 years in a population-based case-control study of 148 case and 167 control subjects. The final multiple logistic regression analysis indicated that women who had a first-degree relative (mother or sister) with breast cancer were nearly twice as likely to have had breast cancer compared to women with no family history (OR = 1.89; 95% CI 1.10-3.16). Expected patterns of association between breast cancer and number of full-term pregnancies, age at first full-term birth, and benign breast disease, although not statistically significant, were observed. Unexpectedly, the results also suggested a reduced risk of breast cancer among Hispanic women associated with early age at menarche. These factors require further evaluation in larger studies among specific Hispanic subgroups.

Mycotic dermatitis in captive carpet snakes (Morelia spilotes variegata).

Geotrichum candidum was isolated from necrotic skin lesions in one of three captive carpet snakes (Morelia spilotes variegata). Hyphae and arthrospores morphologically consistent with this organism were present in histological preparations of lesions from the three snakes.

The healed diabetic foot. What next?

Reulceration of the healed diabetic foot must be prevented to end the cycle of degradation that leads to amputation in so many of these patients. Education, identification of risk factors, therapeutic shoe gear, prophylactic surgery, judicious physical examination, and follow-up by a multidisciplinary team can break this cycle. "Those who suffer losses due to diabetes are not just statistics on a chart. They are people whose talents and wisdom are needed and whose problems deserve our unified efforts. Together we can make life more just and more joyful for generations to come".

DNA mismatch binding and incision at modified guanine bases by extracts of mammalian cells: implications for tolerance to DNA methylation damage.

Two activities involved in separate pathways for correcting G.T mispairs in DNA have been assayed on duplex substrates containing modified guanine bases. The first, the G.T mismatch incision activity, is specifically involved in short-patch repair of mispairs arising via deamination of 5-methylcytosine. The second activity can be detected by its ability to bind to G.T mispairs and may initiate correction by a long-patch mechanism. 6-Thioguanine and O6-methylguanine paired with thymine were efficiently incised by cell extracts if the modified guanine was in a CpG dinucleotide. Incision was not observed when either purine was paired with cytosine. Extracts of cells that are tolerant both to methylation damage and to 6-thioguanine in DNA also incised 6-thioguanine.T and O6-methylguanine.T base pairs. The data suggest that this activity is unlikely to contribute significantly to the biological effects of O6-methylguanine in DNA. A defect in this pathway is therefore unlikely to explain the cross-resistance of tolerant cells to the two base analogs in DNA. In binding assays, 6-thioguanine.T base pairs were recognized efficiently and to an equivalent extent by the same protein complex as G.T mispairs. O6-Methylguanine.T base pairs were also recognized but with reduced efficiency. No binding was observed to 6-thioguanine.C or O6-methylguanine.C base pairs. Recognition by the binding complex was essentially independent of the base immediately 5' to the mismatched guanine but was somewhat more efficient if O6-methylguanine was preceded by a purine. Extracts of two tolerant lines with a known defect in G.T mismatch binding failed to form complexes with substrates containing the modified bases.(ABSTRACT TRUNCATED AT 250 WORDS)

Defective mismatch binding and a mutator phenotype in cells tolerant to DNA damage.

Acquired resistance to alkylating agents such as N-methyl-N-nitrosourea or N-methyl-N'-nitro-N-nitrosoguanidine results from the ability to tolerate the potentially cytotoxic methylated base O6-methylguanine (m6-G) in DNA. In the absence of repair by demethylation in situ, m6-G is probably lethal through its inappropriate processing by the cell. DNA mismatch correction is an attractive candidate for the processing function because although it is replicated, m6-G has no perfect complementary base. Thus, m6-G in DNA might provoke abortive mismatch repair and tolerance could subsequently arise through loss of a mismatch repair pathway. Mismatch correction helps maintain genomic fidelity by removing misincorporated bases and deaminated 5-methylcytosine from DNA, and its loss by mutation confers a mutator phenotype on Escherichia coli. Here we describe human and hamster cell lines that are tolerant to N-methyl-N-nitrosourea and are defective in a DNA mismatch binding activity. The loss of this activity, which acts on G.T mispairs, confers a mutator phenotype.

DNA replication arrest and tolerance to DNA methylation damage.

Inhibition of DNA replication by different DNA damaging agents has been investigated in HeLaMR cells and a methylation damage-tolerant variant HeLa5A1. In synchronous HeLaMR and HeLa5A1 cells exposed to N-ethyl-N-nitrosourea or ionizing radiation in mid-G1 phase, DNA synthesis was inhibited in the following S phase. N-methyl-N-nitrosourea-induced replication inhibition in HeLaMR cells was delayed until the second S phase after treatment. In contrast, N-methyl-N-nitrosourea treatment of HeLa5A1 cells affected neither the timing nor the extent of the first or second S phases. Both radiation and chemical treatment inhibited replication of an episomal plasmid and of genomic DNA in unison. Inhibition was observed at levels of DNA damage that did not directly damage the plasmid molecules. Thus, DNA replication inhibition occurs immediately after ionizing radiation or ethylation damage, but methylation damage requires processing through one cell cycle to generate an inhibitory signal. The inhibitory signal appears to act in trans on undamaged DNA. Although methylation-tolerant cells are responsive to inhibition after gamma-irradiation, methylation damage does not produce inhibitory signals to which they respond.

A mismatch recognition defect in colon carcinoma confers DNA microsatellite instability and a mutator phenotype.

We have analyzed spontaneous mutations in the adenine phosphoribosyltransferase gene of Chinese hamster clone B cells that exhibit a mutator phenotype because of defective mismatch binding. The mutator phenotype conferred increases in a limited number of mutational classes. The rates of transitions and most transversions were not significantly increased. The rates of A to T transversions and -2 frameshifts were strikingly elevated. These mutations were in repeated elements and 5 of 9 of the frameshifts were dinucleotide deletions in DNA sequences resembling microsatellites. The mismatch binding protein that is defective in the mutator line is a G-T mismatch recognition factor. Band-shift analysis indicated that the preferred substrate for the mismatch recognition protein is duplex DNA containing an extrahelical mono- or dinucleotide within repeated sequences. In agreement with a role in preventing minus frameshifts, a defective binding protein conferred an instability in clone B microsatellite DNA. A mismatch binding defect was also detected in Lo Vo, a human colorectal carcinoma cell line. Extracts of clone B or a second mismatch binding-deficient line, Raji-F12, did not complement Lo Vo extracts, indicating that these lines share a common defect. Our data provide a mechanistic explanation for the relation between defective mismatch recognition and the microsatellite instability of human colon cancer.

hMSH2-independent DNA mismatch recognition by human proteins.

Two distinct mismatch binding activities are detected using bandshift assays with human cell extracts and DNA with mispairs at defined positions. One requires hMSH2 protein and is absent from extracts of LoVo cells, which contain a partial deletion of the hMSH2 gene. The second activity is independent of hMSH2 and is present at normal levels in LoVo and three other cell lines, which are defective in in vitro hMSH2-dependent binding. The two mismatch recognition activities are distinguished by their sensitivity to polycations and can be resolved by chromatography on MonoQ. hMSH2-independent activity has been purified extensively from wild-type cells and from a cell line deficient in hMSH2-dependent binding. The purified material preferentially recognizes A-C, some pyrimidine-pyrimidine mismatches, and certain slipped mispaired structures. Binding exhibits some sequence preferences. The similar properties of the two mismatch binding activities suggest that they both contribute to mismatch repair.

Mismatch repair and differential sensitivity of mouse and human cells to methylating agents.

The long-patch mismatch repair pathway contributes to the cytotoxic effect of methylating agents and loss of this pathway confers tolerance to DNA methylation damage. Two methylation-tolerant mouse cell lines were identified and were shown to be defective in the MSH2 protein by in vitro mismatch repair assay. A normal copy of the human MSH2 gene, introduced by transfer of human chromosome 2, reversed the methylation tolerance. These mismatch repair defective mouse cells together with a fibroblast cell line derived from an MSH2-/- mouse, were all as resistant to N-methyl-N-nitrosourea as repair-defective human cells. Although long-patch mismatch repair-defective human cells were 50- to 100-fold more resistant to methylating agents than repair-proficient cells, loss of the same pathway from mouse cells conferred only a 3-fold increase. This discrepancy was accounted for by the intrinsic N-methyl-N-nitrosourea resistance of normal or transformed mouse cells compared with human cells. The >20-fold differential resistance between mouse and human cells could not be explained by the levels of either DNA methylation damage or the repair enzyme O6-methylguanine-DNA methyltransferase. The resistance of mouse cells to N-methyl-N-nitrosourea was selective and no cross-resistance to unrelated DNA damaging agents was observed. Pathways of apoptosis were apparently intact and functional after exposure to either N-methyl-N-nitrosourea or ultraviolet light. Extracts of mouse cells were found to perform 2-fold less long-patch mismatch repair. The reduced level of mismatch repair may contribute to their lack of sensitivity to DNA methylation damage.