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Biomedical subjects

C Caldwell

Publications and source records attributed to C Caldwell.

At least 19 recordsLinked to original sources
PubMed2001

Differential regulation of two alternatively spliced isoforms of hypoxia-inducible factor-1 alpha in activated T lymphocytes.

Cell adaptation to hypoxia is partially accomplished by hypoxia-inducible transcription factor-1 (HIF-1). Here we report the hypoxia-independent up-regulation of HIF-1 alpha subunit in antigen receptor-activated T cells. This is explained by a selective up-regulation of alternatively spliced mRNA isoform I.1 that encodes the HIF-1 alpha protein without the first 12 N-terminal amino acids. We show that both short (I.1) and long (I.2) HIF-1 alpha isoforms display similar DNA binding and transcriptional activities. Major differences were observed between these two HIF-1 alpha isoforms in their expression patterns with respect to the resting and activated T lymphocytes in hypoxic and normoxic conditions. The T cell antigen receptor (TCR)-triggered activation of normal ex vivo T cells and differentiated T cells results in up-regulation of expression of I.1 isoform of HIF-1 alpha mRNA without an effect on constitutive I.2 HIF-1 alpha mRNA expression. The accumulation of I.1 HIF-1 alpha mRNA isoform in T lymphocytes is also demonstrated during cytokine-mediated inflammation in vivo, suggesting a physiological role of short HIF-1 alpha isoform in activated lymphocytes. The TCR-triggered, protein kinase C and Ca(2+)/calcineurin-mediated HIF-1 alpha I.1 mRNA induction is protein synthesis-independent, suggesting that the HIF-1 alpha I.1 gene is expressed as an immediate early response gene. Therefore, these data predict a different physiological role of short and long isoforms of HIF-1 alpha in resting and activated cells.

Alternative Splicing↗
PubMed2001

Gene dose effect reveals no Gs-coupled A2A adenosine receptor reserve in murine T-lymphocytes: studies of cells from A2A-receptor-gene-deficient mice.

Agonist binding to extracellular A2A adenosine receptors (A2ARs) inhibits the activation of virtually all tested functions of T-cells and can induce apoptosis in thymocytes. The evaluation of levels of expression of these immunosuppressive receptors is expected to clarify whether the absence of spare A2ARs (no 'receptor reserve') might be one of the mechanisms of attenuation of the effects of extracellular adenosine on T-cells. A2A transcript is found in T-cells and functional receptors can be demonstrated, but the density of receptor on T-cells is too low to be detected by radioligand binding. Studies of direct radioligand binding to murine brain with the selective A2AR agonist [3H]CGS21680 (2-(4-[(2-carboxyethyl)-phenyl]ethylamino)-5'-N-ethylcarboxamidoadenosine) established that striata levels of A2AR are virtually absent from A2A knock-out mice. Mice that are heterozygous (A2AR+/-) for the A2AR express significantly decreased levels of A2AR. To test for the presence of spare receptors in T-cells we took advantage of this gene dose effect and examined whether the decrease in the number of receptors in thymocytes from A2AR+/- mice was proportionately reflected in a decrease in the functional cAMP response of T-cells to adenosine. cAMP accumulation and apoptosis induced by adenosine and by A2AR agonist are of a lower magnitude in T-cells from A2AR+/- heterozygous mice than in T-cells from A2AR+/+ littermate control mice. These results indicate that there is no A2AR reserve in murine T-cells. Strongly decreased adenosine-triggered cAMP increases were detected in thymocytes from A2AR-/- mice, suggesting that A2B adenosine receptors cannot fully compensate for the loss of A2ARs in murine T-cells. We conclude that the number of A2ARs is the limiting factor in determining the maximal cAMP response of T-lymphocytes to extracellular adenosine, thereby minimizing the immunosuppressive effects of extracellular adenosine.

Animals↗
PubMed2001

Effects of NSAIDs on cryoprobe-induced gastric ulcer healing in rats.

BACKGROUND: Failure of ulcer healing may be critically important to the development of serious gastrointestinal complications in patients on long-term NSAIDs. AIM: To determine the effect of indometacin, celecoxib, a cyclooxygenase-2-specific inhibitor, and nabumetone, a pro-drug, on ulcer healing rates in the rat. METHODS: Gastric ulcers were induced using a cryoprobe. An NSAID or a vehicle control was administered to groups of eight rats for 3 or 6 days (2 mg/kg indometacin, 9 mg/kg celecoxib or 40 mg/kg nabumetone). The ulcer area was measured and epithelial proliferation at the ulcer margins was measured histochemically. The effect of the drugs on intestinal prostaglandin levels was also assessed. RESULTS: The mean ulcer sizes in the four groups on day 3 were comparable. On day 6, control animals and those receiving nabumetone showed significant ulcer healing (P < 0.02), while the mean ulcer sizes in the indometacin (P < 0.01) and celecoxib (P < 0.02) groups were significantly larger than those in the control group. Higher doses of nabumetone (160 mg/kg), however, impaired healing. Intestinal prostaglandins were reduced (P < 0.01) only in indometacin-treated animals. The epithelial proliferation index was significantly lower among indometacin- (P=0.02) and celecoxib-treated (P=0.03) animals compared to controls at day 3. CONCLUSIONS: Celecoxib and indometacin both decreased the epithelial proliferative response and delayed healing of cryoprobe-induced gastric ulcers. In contrast, nabumetone impaired ulcer healing only at very high doses.

Animals↗
PubMed2001

Developmental and thermal regulation of the maize heat shock protein, HSP101.

The plant heat stress protein, Hsp101, and the yeast ortholog, Hsp104, are required to confer thermotolerance in plants and yeast (Saccharomyces cerevisiae), respectively. In addition to its function during stress, Hsp101 is developmentally regulated in plants although its function during development is not known. To determine how the expression of Hsp101 is regulated in cereals, we investigated the Hsp101 expression profile in developing maize (Zea mays). Hsp101 protein was most abundant in the developing tassel, ear, silks, endosperm, and embryo. It was less abundant in the vegetative and floral meristematic regions and was present at only a low level in the anthers and tassel at anthesis, mature pollen, roots, and leaves. As expected, heat treatment resulted in an increase in the level of Hsp101 protein in several organs. In expanding foliar leaves, husk leaves, the tassel at the premeiosis stage of development, or pre-anthesis anthers, however, the heat-mediated increase in protein was not accompanied by an equivalent increase in mRNA. In contrast, the level of Hsp101 transcript increased in the tassel at anthesis following a heat stress without an increase in Hsp101 protein. In other organs such as the vegetative and floral meristematic regions, fully expanded foliar leaves, the young ear, and roots, the heat-induced increase in Hsp101 protein was accompanied by a corresponding increase in Hsp101 transcript level. However, anthers at anthesis, mature pollen, developing endosperm, and embryos largely failed to mount a heat stress response at the level of Hsp101 protein or mRNA, indicating that Hsp101 expression is not heat inducible in these organs. In situ RNA localization analysis revealed that Hsp101 mRNA accumulated in the subaleurone and aleurone of developing kernels and was highest in the root cap meristem and quiescent center of heat-stressed roots. These data suggest an organ-specific control of Hsp101 expression during development and following a heat stress through mechanisms that may include posttranscriptional regulation.

Amino Acid Sequence↗
PubMed2000

Cloning, chromosomal sublocalization of the human soluble aminopeptidase P gene (XPNPEP1) to 10q25.3 and conservation of the putative proton shuttle and metal ligand binding sites with XPNPEP2.

Human soluble ("cytosolic") aminopeptidase P (hsAmP) is an aminoacylprolyl hydrolase (EC 3.4.11.9) present in all tissues yet examined. hsAmP is related in terms of catalytic specificity to an ectoenzyme, membrane aminopeptidase P (hmAmP), which is largely limited in distribution to endothelia and brush border epithelia. Although both enzymes can degrade oligopeptides having N-terminal Xaa-Pro- moieties, hsAmP and hmAmP are of relatively low sequence homology. Recently, it has been shown that the two enzymes are not products of splice variants of the same gene. How hsAmP relates to hmAmP has clinical significance in that both can inactivate bradykinin, and AmP deficiency states have been described. The hmAmP gene (XPNPEP2) is disposed at chromosome Xq25, a disposition with clear meaning in terms of inheritance of hmAmP deficiencies. To further explore similarities and differences between hsAmP and hmAmP, the present study was begun to determine the chromosomal disposition of the hsAmP gene. Here we show that the gene is sublocalized on chromosome 10q25.3. We also show that hsAmP and hmAmP contain homologous blocks of sequence common to members of the "pita bread-fold" protein family, of which Escherichia coli methionine aminopeptidase is the prototype. The prototype is known to contain a proton shuttle and five divalent metal ligands, counterparts of which we identify in the homologous blocks of sequence in both hsAmP and hmAmP and compare to E. coli aminopeptidase.

Amino Acid Sequence↗
PubMed2000

A presurgical psychosocial intervention for breast cancer patients. psychological distress and the immune response.

OBJECTIVE: The present study evaluated the feasibility and potential immunological benefit of a presurgical intervention for breast cancer patients. METHODS: Forty-one newly diagnosed breast cancer patients were randomized into control (standard care) and intervention groups. In addition to standard care, intervention group members received a two-session psychosocial intervention. Blood was drawn at three timepoints: (1) at preintervention; (2) at postintervention/presurgery; and (3) at postsurgery. RESULTS: Examination of the immunological data revealed evidence of suppression of interferon-gamma (IFN-gamma) in the control group over time, but not in the intervention group. Secondary findings related to psychological assessment generally paralleled the IFN-gamma results. CONCLUSION: The relevance and applicability of these findings to future breast cancer intervention research is detailed.

Adult↗
PubMed2000

Serum levels of vascular endothelial growth factor in preeclamptic and normotensive pregnancy.

The purpose of these studies was first to determine if vascular endothelial growth factor (VEGF), a vascular permeability agent, is increased in the serum of women with preclinical and clinical preclampsia (PE), and second to determine how these levels change after delivery. Twenty preeclamptic and 25 normotensive women at term consented to have blood taken pre- and post-delivery. Ten preeclamptic, 10 gestational hypertensive, and 28 normotensive women had blood collected respectively at 12, 20, and 30 weeks gestation and predelivery. Serum was extracted from all samples, and VEGF concentrations were determined by radioimmunoassay. Predelivery, the median serum VEGF concentration in the preeclamptic group was 51.7 ng/mL, and in the control group the concentration was 13.9 ng/mL (P<0.0001). Serum VEGF concentrations fell within 24 hours of delivery in both groups, which resulted in median values of 3.8 ng/mL and 3.2 ng/mL respectively (P<0.3). At 12 and 20 weeks, there was no significant difference between the serum VEGF concentrations in the 3 groups (P<0.3, 0.052 respectively). At 30 weeks, prior to the onset of clinical PE, the serum VEGF levels in the eventual preeclamptic group were elevated significantly compared with the gestational hypertensive and normotensive groups (P<0.001). Predelivery serum VEGF concentrations were significantly elevated in the preeclamptic group and were similar to those in the first study (P<0.0001). These findings suggest that VEGF may be important in the pathophysiology of PE and has the potential to act as a preclinical marker for the condition.

Adult↗
PubMed1999

Etiology and outcome for 295 patients with acute liver failure in the United States.

Little information is available on acute liver failure (ALF) in the United States. We gathered demographic data retrospectively for a 2-year period from July 1994 to June 1996 on all cases of ALF from 13 hospitals (12 liver transplant centers). Data on the patients included age, hepatic coma grade on admission, presumed cause, transplantation, and outcome. Among 295 patients, 74 (25%) survived spontaneously, 121 (41%) underwent transplantation, and 99 (34%) died without undergoing transplantation. Ninety-two of 121 patients (76%) survived 1 year after transplantation. Acetaminophen overdose was the most frequent cause (60 patients; 20%), followed by cryptogenic/non A non B non C (NANBNC; 15%), idiosyncratic drug reactions (12%), hepatitis B (10%), and hepatitis A (7%). Spontaneous survival rates were highest for patients with acetaminophen overdose (57%) and hepatitis A (40%) and lowest for those with Wilson's disease (no survivors of 18 patients). The transplantation rate was highest for Wilson's disease (17 of 18 patients; 94%) and lowest for autoimmune hepatitis (29%) and acetaminophen overdose (12%). Age did not differ between survivors and nonsurvivors, perhaps reflecting a selection bias for patients transferred to liver transplant centers. Coma grade on admission was not a significant determinant of outcome, but showed a trend toward affecting both survival and transplantation rate. These findings on retrospectively studied patients from the United States differ from those previously gathered in the United Kingdom and France, highlighting the need for further study of trends in each country.

Acetaminophen↗
PubMed1999

Automatic karyotyping of metaphase cells with overlapping chromosomes.

Image analysis research aimed at analyzing images of banded, human chromosomes is described. An experimental automated karyotyping system (AKS) has been assembled. The goal of the system is to label the chromosomes from a metaphase image with minimal human intervention. The AKS is unique in that it is designed to automatically process cells containing overlapping chromosomes. It also has four novel algorithmic features: the use of cross section sequence graphs, an over-segmentation-based segmentation strategy, the use of the 'pale path' concept for banded chromosomes and the application of mathematical programming for cell-level chromosome classification in cells with overlapping chromosomes. System performance was analyzed using a variety of metaphase images exhibiting various levels of overlapping chromosomes.

Algorithms↗
PubMed1998

Analysis of translation elongation factors from wheat during development and following heat shock.

Translational activity in plants undergoes rapid changes during developmental stages such as seed formation and germination, and during abiotic stresses such as heat shock, hypoxia and wounding. We examined the protein levels and isoelectric state of two components of the translation machinery, elongation factor (EF) 1 alpha and 2, to determine their roles in the regulation of translation. We found that the apparent protein levels of EF1 alpha increase relative to the EF2 levels which decline slightly during the development of the wheat seed. During germination, high levels of these factors are present in seedling tissues known to be actively engaged in translation; however, no differences in isoelectric state were observed during germination. As an example of abiotic stress, heat shock had little impact on the apparent levels of EF1 alpha or EF2 present in wheat leaves, nor were changes in the number or levels of isoforms observed.

Germination↗
PubMed1998

Prognostic significance of the bcl-2 apoptotic family of proteins in primary and recurrent cervical cancer.

bcl-2 is one of a family of genes that control the apoptotic threshold of a cell. bcl-2 protein and its anti-apoptotic homologue, mcl-1, with the pro-apoptotic protein, bax, are thought to function by forming homo- and heterotypic dimers that then control the progression to apoptosis. p53 is also involved as a down-regulator of bcl-2 and a promoter of bax. To determine the effect of these apoptotic mechanisms, we used immunohistochemistry to determine the prognostic significance of the expression of bcl-2, mcl-1, bax and p53 in primary and recurrent cervical cancer. Tissues from 46 patients with primary cervical cancer and 28 women with recurrent carcinoma were stained for bcl-2, mcl-1, bax and p53. Kaplan-Meier survival analysis was performed using the log-rank test for differences between groups. In the primary disease group, positive staining for bcl-2 was associated with a better 5-year survival (bcl-2 +ve, 84% vs bcl-2 -ve, 53%, P = 0.03). Positive staining for p53 was associated with a survival disadvantage (p53 +ve, 4-year survival 38% vs p53 -ve, 4-year survival 78%, P = 0.02). mcl-1 and bax staining were not useful as prognostic indicators in primary disease. No marker was prognostic in recurrent disease. Positive bcl-2 staining defines a group of patients with primary disease with a good prognosis. p53, an activator of the bax promoter, identifies a group with a worse outcome. In recurrent disease, none of the markers reflected prognosis.

Adult↗