Biomedical subjects

J Y Duffy

Publications and source records attributed to J Y Duffy.

11 recordsLinked to original sources

PubMed2004

Cardiac abnormalities induced by zinc deficiency are associated with alterations in the expression of genes regulated by the zinc-finger transcription factor GATA-4.

Zinc (Zn) deficiency during pregnancy results in a wide variety of developmental abnormalities. The objective of this study was to determine if expression of cardiac developmental genes regulated by Zn-finger transcription factors could be modulated during dietary Zn deficiency. Rats were fed 0.5 (low Zn) or 90 (controls) microg Zn/g diet throughout pregnancy. Fetal development was examined and RNA isolated at gestation day (GD) 13 and 20. Cardiac abnormalities were detected at GD 20 in 82% of fetuses from dams fed low Zn diets compared with only 2% in controls. Cardiac developmental gene expression regulated by the Zn-finger transcription factor, GATA-4, was measured by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). In GD 13 and 20 hearts, two genes critical for heart development, alpha-myosin heavy chain (alpha-MHC) and cardiac troponin I (cTnI), were down-regulated in Zn-deficient fetuses. Expression of alpha-MHC was 66 and 40% lower at GD 13 and 20, respectively, in fetuses from dams fed low Zn diets compared with fetuses from control dams (p<0.05). Fetal cardiac TnI RNA levels were reduced 40 and 45% at GD 13 and 20 in the Zn-deficient group compared with controls (p<0.05). Fetal cardiac transcript levels of GATA-4 and MHox, a gene regulated by a helix-loop-helix transcription factor, whose expressions are not Zn-dependent, were unaffected by diet. These data indicated that alterations in gene regulation might be an underlying mechanism of cardiac abnormalities. Dysfunction of other Zn-dependent transcription factors may be an integral part of the extensive teratogenesis associated with Zn deficiency.

Abnormalities, Multiple↗

PubMed2001

Endothelin receptor blockade reduces ventricular dysfunction and injury after reoxygenation.

BACKGROUND: Reoxygenation of hypoxic myocardium during repair of congenital heart defects results in poor ventricular function and cellular injury. Endothelin-1 (ET-1), a potent vasoconstrictor that increases during hypoxia, may suppress myocardial function and activate leukocytes. The objective was to determine whether administration of an endothelin receptor antagonist could improve ventricular function and decrease cardiac injury after hypoxia and reoxygenation. METHODS: Fourteen piglets underwent 90 minutes of ventilator hypoxia, 1 hour of reoxygenation on cardiopulmonary bypass, and 2 hours of recovery (controls). Nine additional animals received an infusion of Bosentan, an ET(A/B) receptor antagonist, (5 mg/kg per hour) during hypoxia and reoxygenation. RESULTS: Right and left ventricular dP/dt in controls decreased to 78% and 52% of baseline, respectively, after recovery (p < 0.05). In contrast, Bosentan-treated animals had complete preservation of RV dP/dt and less depression of LV dP/dt. Bosentan reduced the hypoxia and reoxygenation-induced elevation of ET-1 and iNOS mRNA at the end of recovery (p < 0.05). Bosentan-treated animals had diminished myocardial myeloperoxidase activity and lipid peroxidation compared with controls (p < 0.05). Myocardial apoptotic index, elevated by hypoxia and reoxygenation, was lower in the Bosentan-treated animals (p < 0.05). CONCLUSIONS: Endothelin-1 receptor antagonism improved functional recovery and decreased leukocyte-mediated injury after reoxygenation. The reduction in cardiac cell death might also improve long-term outcome after reoxygenation injury.

Animals↗

PubMed2001

A decrease in intracellular zinc level precedes the detection of early indicators of apoptosis in HL-60 cells.

Low extracellular zinc concentrations have been associated with the induction of apoptosis. To assess the relationship between intracellular zinc concentration and the rate of apoptosis, cells were grown in media containing 0.5, 25, or 50 microM zinc and analyzed by flow cytometry or fluorescence microscopy. Cells grown in 0.5 microM zinc medium over 48 h showed a successive decrease in intracellular zinc concentration measured by the zinc-specific fluorophore, zinquin. After 18 h in 0.5 microM zinc medium, rhodamine 123 retention decreased. However, the addition of 10 microM zinc to the 0.5 microM medium before 16 h in culture restored rhodamine retention in the cells. After 30 h there was an increase in the number of cells cultured in 0.5 microM zinc medium that bound annexin V-FITC. These data indicated that decreased intracellular zinc concentration preceded early markers of apoptosis, with alterations in mitochondrial transmembrane potential preceding the loss of polarity in the cell membrane.

Annexin A5↗

PubMed2001

Cellular and molecular aspects of myocardial dysfunction.

Disruption of any one of a large number of balanced systems that maintain cardiomyocyte structure and function can cause myocardial dysfunction. Such disruption can occur either in response to acute stresses such as cardiac surgery with cardiopulmonary bypass and cross-clamping of the aorta or because of more chronic stresses resulting from factors such as genetic abnormalities, infection, or chronic ischemia. Several currently available therapies such as beta-adrenergic receptor agonists and antagonists, phosphodiesterase inhibitors, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and other agents affect cardiomyocytes in ways that are more far reaching than initially appreciated when these agents were first introduced into clinical practice. As our knowledge and understanding of myocardial dysfunction increases, particularly in the neonatal and pediatric patient, we will be able to further target interventions to highly specific perturbations of cellular function and individual genetic variability.

Acute Disease↗

PubMed2000

Hyperoxia for management of acid-base status during deep hypothermia with circulatory arrest.

BACKGROUND: Which blood gas strategy to use during deep hypothermic circulatory arrest has not been resolved because of conflicting data regarding the advantage of pH-stat versus alpha-stat. Oxygen pressure field theory suggests that hyperoxia just before deep hypothermic circulatory arrest takes advantage of increased oxygen solubility and reduced oxygen consumption to load tissues with excess oxygen. The objective of this study was to determine whether prevention of tissue hypoxia with this strategy could attenuate ischemic and reperfusion injury. METHODS: Infants who had deep hypothermic circulatory arrest (n = 37) were compared retrospectively. Treatments were alpha-stat and normoxia (group I), alpha-stat and hyperoxia (group II), pH-stat and normoxia (group III), and pH-stat and hyperoxia (group IV). RESULTS: Both hyperoxia groups had less acidosis after deep hypothermic circulatory arrest than normoxia groups. Group IV had less acid generation during circulatory arrest and less base excess after arrest than groups I, II, or III (p < 0.05). Group IV produced only 25% as much acid during deep hypothermic circulatory arrest as the next closest group (group II). CONCLUSIONS: Hyperoxia before deep hypothermic circulatory arrest with alpha-stat or pH-stat strategy demonstrated advantages over normoxia. Furthermore, pH-stat strategy using hyperoxia provided superior venous blood gas values over any of the other groups after circulatory arrest.

Acid-Base Imbalance↗

PubMed2000

Acute hypoxia and reoxygenation impairs exhaled nitric oxide release and pulmonary mechanics.

OBJECTIVE: Changes in exhaled nitric oxide levels often accompany conditions associated with elevated pulmonary vascular resistance and altered lung mechanics. However, it is unclear whether changes in exhaled nitric oxide reflect altered vascular or bronchial nitric oxide production. This study determined the effects of acute hypoxia and reoxygenation on pulmonary mechanics, plasma nitrite levels, and exhaled nitric oxide production. METHODS: Ten piglets underwent 90 minutes of hypoxia (fraction of inspired oxygen = 12%), 1 hour of reoxygenation on cardiopulmonary bypass, and 2 hours of recovery. Five additional animals underwent bypass without hypoxia. Exhaled nitric oxide, plasma nitrite levels, and pulmonary mechanics were measured. RESULTS: Exhaled nitric oxide decreased to 36% of baseline by end hypoxia (34 +/- 14 vs 12 +/- 9 ppb, P =.005) and declined further to 20% of baseline at end recovery (7 +/- 6 ppb). Aortic nitrite levels decreased from baseline during hypoxia (from 102 +/- 13 to 49 +/- 7 micromol/L, P =.05) but returned to baseline during recovery. Pulmonary arterial nitrite also decreased during hypoxia (from 31.4 +/- 7.8 to 22.9 +/- 9.5 micromol/L, P =.04) and returned to baseline at end recovery. Decreased production of exhaled nitric oxide was associated with impaired gas exchange (alveolar-arterial gradient = 32 mm Hg at baseline and 84 mm Hg at end recovery), decreased pulmonary compliance (6.6 +/- 0.9 mL/cm H(2)O at baseline, 5.0 +/- 0.7 mL/cm H(2)O at end hypoxia, and 5.4 +/- 0.7 mL/cm H(2)O at end recovery), and increased inspiratory airway resistance (41 +/- 4 cm H(2)O. L(-1). s(-1) at baseline, 56 +/- 4.9 cm H(2)O. L(-1). s(-1) at end hypoxia, and 50 +/- 5 cm H(2)O. L(-1). s(-1) at end recovery). CONCLUSIONS: A decrease in exhaled nitric oxide persisted after hypoxia, and plasma nitrite levels returned to baseline on reoxygenation, indicating that alterations in exhaled nitric oxide during hypoxia-reoxygenation might be unrelated to plasma nitrite levels. Furthermore, decreased exhaled nitric oxide corresponded with altered pulmonary mechanics and gas exchange. Reduced exhaled nitric oxide after hypoxia-reoxygenation might reflect bronchial epithelial dysfunction associated with acute lung injury.

Acute Disease↗

PubMed1997

Repeated administration of alpha-hederin results in alterations in maternal zinc status and adverse developmental outcome in the rat.

The administration of alpha-hederin, an inducer of metallothionein, results in a secondary zinc deficiency that may be an important maternally mediated mechanism of developmental toxicity. Previous studies have shown adverse developmental outcome with a single administration of alpha-hederin to rats on gestation day (GD) 8 or 11. The objective of this study was to determine whether dosing of alpha-hederin throughout organogenesis would result in a sustained elevation of maternal hepatic metallothionein and subsequent developmental abnormalities. Rats were administered dosage levels of 0 (vehicle only), 20, or 30 mumol/kg from GD 6-15. Maternal hepatic metallothionein levels were 10-fold higher on GD 16 in the treatment groups than the controls. Consequently, liver zinc concentrations increased 60% and 54%, whereas plasma levels decreased 23% and 33% in the 20 and 30 mumol/kg treatment groups, respectively. At GD 20, mean fetal weights of the treatment litters were 11% less than control litters. The administration of alpha-hederin resulted in a threefold increase in the number of offspring that exhibited developmental abnormalities, including visceral and skeletal malformations. Following an oral pulse of 65Zn subsequent to treatment with 0 or 20 mumol/kg of alpha-hederin, the distribution of 65Zn to the liver of treated dams was twice that of controls, whereas the radiolabeled zinc apportioned to the decidua and uterus decreased by 44%. Furthermore, the 65Zn detected in the embryos from treated dams was 70% lower than in embryos from control dams. In conclusion, low doses of a metallothionein inducer administered to the dam from GD 6-15 resulted in a sustained elevation of hepatic metallothionein and a subsequent redistribution of zinc leading to a decrease in the zinc available to the embryo and ultimately to adverse development of the offspring. Repeated dosing throughout organogenesis, as required in regulated safety assessment testing, increased the severity of the effects previously observed with single large dosages of the toxicant administered during midgestation.

Animals↗

PubMed1997

Expression of a plasmin/trypsin Kunitz inhibitor by pig trophoblast.

Under the influence of progesterone, the porcine uterus synthesizes plasmin/trypsin inhibitor (PTI), a low molecular weight protein (M(r) approximately 14,000) belonging to the Kunitz family of proteinase inhibitors. Here it is demonstrated that mRNA for the same protein is produced by the developing trophoblast during early pregnancy and by the placenta throughout gestation. The transcript for PTI was represented in approximately 0.1% of total phage plaques of a day 13-17 porcine conceptus cDNA library. It shared 99% nucleotide sequence identity with the cDNA isolated from the uterine library and encoded a 112-amino-acid protein identical to the uterine-produced PTI, which has a well-defined Kunitz domain comprised of 64 residues at its amino terminus. Northern analysis and in situ hybridization studies confirmed that expression of PTI by the conceptus begins as early as day 10 of pregnancy and is continued in placental tissues until at least day 90 of gestation. Expression was trophoblast specific at day 20 of gestation, as in situ hybridization detected no mRNA in the embryo. The pattern of PTI expression during pregnancy is consistent with a role either in controlling trophoblast invasiveness or in inhibiting proteinases with trypsin-like specificity released by immune or inflammatory cells.

Amino Acid Sequence↗

PubMed1995

Regulation and regulatory role of proteinase inhibitors.

Excess or ill-timed proteolytic events have, of necessity, to be restrained. Therefore, there are partner proteinase inhibitors to most of the known mammalian enzymes that cleave peptide bonds, a situation that implicates the inhibitors in a myriad of normal as well as pathological processes. Here, what is currently known about the regulatory functions, the mode of action, and the control of gene expression of the commoner extracellularly acting proteinase inhibitors is reviewed. The review covers four families of serine proteinase inhibitors: the serpins, the Kunitz, Kazal, and leukoproteinase inhibitors, which overlap considerably in the range of their specificities but differ considerably in their respective structures and likely functions. There then follows a description of the growing family of metalloproteinase inhibitors (usually known by the acronym TIMP), the structurally varied cysteine proteinase inhibitors, and finally alpha 2-macroglobulin, a large multisubunit inhibitor, that is relatively catholic in its range of targets. The review concludes with two short sections, the first an overview of the acute phase response, which features several proteinase inhibitors from the different families discussed earlier, and the second, our prediction of where this research field is headed over the next decade.

Animals↗

PubMed1994

Selective cloning of cDNA for secretory proteins of early embryos. Identification of a transiently expressed kunitz domain protein from preimplantation sheep trophoblast.

The preimplantation ovine conceptus transiently secretes several proteins, including a type I interferon (IFN-tau), that are likely involved in establishment of pregnancy. A method has been developed to identify proteins produced simultaneously with IFN-tau. An antiserum against total ovine conceptus secretory proteins, from which IFN-tau and proteins common to maternal uterine tract secretions had first been removed, was used to immunoscreen cDNA libraries created from mRNA of days 13 and 15 ovine conceptuses. This approach has allowed several unique cDNA to be identified, including one particularly abundant transcript for a novel member of the Kunitz family of serine protease inhibitors. This cDNA encodes a 265-amino acid protein with a 20-amino acid signal sequence. A 64-amino acid Kunitz domain occupies the carboxyl terminus. It is preceded by two similar repeats of 84 residues that bear no obvious similarity to any sequences present in the protein data banks. The protein present in conceptus secretions (M(r) of approximately 14,000) represents only the carboxyl terminus of the molecule. The mRNA for this putative proteinase inhibitor was confined to trophectoderm and was highly expressed for only a few days (approximately 13-18) of development. A similar transcript was detected during the days 17-21 period in cattle embryos. Despite their high expression, no proteinase-inhibitory activity can so far be ascribed to either the ovine or bovine proteins. The P1 residue, an asparagine, is not represented in any other known Kunitz inhibitors.

Amino Acid Sequence↗

PubMed1992

Influence of somatotropin on lipid metabolism and IGF gene expression in porcine adipose tissue.

The present study was designed to evaluate the effects of porcine somatotropin (pST) treatment (2 mg/day) and dietary fat (10%) separately and in combination on the metabolic activity of subcutaneous adipose tissue, serum adipogenic activity, and insulin-like growth factor (IGF) gene expression within adipose tissue from growing 5- to 6-mo-old barrows. This study attempted to determine how these factors might contribute to the reported changes in adiposity of treated swine. Biopsies of adipose tissue were collected after 28 days of treatment following anesthesia with thiopental sodium (15 mg/kg iv). Somatotropin inhibited in vitro glucose oxidation and lipogenesis in adipose tissue but did not affect fatty acid esterification. Adipogenic activity of serum was not altered by pST treatment. Subcutaneous adipose tissue contained mRNA for IGF-I and -II, and pST administration increased the abundance of IGF-I mRNA. Dietary fat had no effect on these variables. Thus somatotropin reduces glucose metabolism in porcine subcutaneous adipose tissue. Preadipocyte proliferation and differentiation are not affected by somatotropin through its actions on systemic factors. Dietary fat provides no additional benefit in combination with pST administration to affect accretion of adipose tissue in growing swine.

Adipose Tissue↗