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Biomedical subjects

A Yu

Publications and source records attributed to A Yu.

At least 73 records · Page 4Linked to original sources
PubMed1997

The role of recombinant platelet-activating factor acetylhydrolase in a neonatal rat model of necrotizing enterocolitis.

Previous studies have shown that the endogenous inflammatory mediator platelet-activating factor (PAF) plays an important role in the pathophysiology of neonatal necrotizing enterocolitis (NEC). This study was designed to investigate the role of the PAF-degrading enzyme acetylhydrolase (PAF-AH) in a neonatal rat model of NEC. To study the absorption, localization, and activity of human recombinant PAF-AH (rPAF-AH), newborn rats were treated with enteral rPAF-AH, and plasma and intestines were sampled at 8 and 24 h for determination of PAF-AH enzyme activity and rPAF-AH concentration using a specific enzyme-linked immunoassay. To study the effect of rPAF-AH on neonatal NEC, rats were treated with rPAF-AH via the enteral route every 3 h, and then subjected to formula feeding and asphyxia per an established neonatal rat protocol for NEC. Pretreatment with enteral rPAF-AH significantly reduced the incidence of NEC compared with controls (6/26 versus 19/26, p < 0.001). We found that enteral rPAF-AH administration resulted in significant intestinal PAF-AH activity but no circulating PAF-AH activity despite immunohistochemical localization of the administered rPAF-AH to the intestinal epithelial cells. These findings suggest that rPAF-AH is functional and stable in the gut of neonatal rats. We conclude that enteral administration of rPAF-AH remains locally active and reduces the incidence of NEC in our experimental animal model.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1997

Repression of hypoxia-reoxygenation injury in the catalase-overexpressing heart of transgenic mice.

Hypoxia-reoxygenation injury results at least in part from reactive oxygen free radicals. Catalase is a major enzyme involved in detoxification of hydrogen peroxide. The activity of catalase per gram of tissue in the heart is very low, being only about 2% that of liver in rodents and humans, which may be responsible for the high sensitivity of the heart to hypoxia-reoxygenation injury. The present study was undertaken to determine whether elevation of catalase specifically in the heart of transgenic mice could provide protection against hypoxia-reoxygenation injury. Transgenic mice with elevated cardiac catalase 60-fold higher than normal were selected, and the effects of catalase elevation on hypoxia-reoxygenation induced functional and morphological changes in isolated atria were determined. Catalase overexpression ameliorated reductions in contractile force and heart rate caused by hypoxia-reoxygenation, and eliminated reoxygenation-induced arrhythmia. The catalase-overexpressing transgenic atria were also highly resistant to hypoxia-reoxygenation-induced morphological alterations, as examined by electron microscopy. Use of cardiac catalase-overexpressing transgenic mice thus demonstrates that hydrogen peroxide is involved in hypoxia-reoxygenation cardiotoxicity, and that this mouse model provides a useful tool for study of free radical mechanism in the heart damage.

Animals↗
PubMed1996

Abundance and state of phosphorylation of the retinoblastoma gene product in human pituitary tumors.

Targeted disruptions of the retinoblastoma (Rb) gene result in a high frequency of pituitary tumors in heterozygous mice. While our group and others have reported that loss of heterozygosity (LOH) at the Rb locus in human pituitary tumors is rare, these studies have not excluded small inactivating Rb-gene abnormalities more frequently found in human tumors and undetectable by LOH-PCR assays. As a more sensitive means of detecting evidence of these lesions, we have performed Western-blot analysis of several human pituitary tumors to identify Rb loss at the protein level as well as truncated forms of the Rb protein frequently associated with Rb-gene mutations. In 24 tumors, Rb protein was detected at levels 1.4- to 3.9-fold those detected in normal postmortem pituitary. There was no evidence of truncated forms of the Rb protein and only the hypophosphorylated (active) form of the protein was detected in normal and in pituitary tumor specimens. To investigate the possibility of loss of function mutations in certain tumors resulting in the expression of stable, mutant, hypophosphorylated Rb protein, we further performed SSCP analysis of exons 20 through 24 corresponding to the pocket domain of the Rb protein. Of 20 pituitary tumors examined, no mobility shifts could be demonstrated in this analysis. Our findings provide further evidence that primary Rb inactivation is not common in human pituitary tumors. Our detection of only the hypophosphorylated form of the Rb protein probably reflects the low proliferative state of these tumors.

Base Sequence↗
PubMed1996

Frequent loss of the P16INK4a gene product in human pituitary tumors.

Pituitary tumors develop at a high frequency in retinoblastoma (Rb)-knockout mice; however, defects in the Rb gene are not common in human pituitary tumors. The inverse correlation of Rb and p16 defects in certain human tumors has led us to investigate the expression of p16 in human pituitary tumors as an indirect mechanism of Rb inactivation. By Western blot analysis, the p16 gene product was undetectable in 25 human pituitary tumors, whereas high levels of p16 could be demonstrated in 10 normal human pituitary specimens under the same conditions of protein extraction and immunoblotting. Similar results were obtained at the mRNA level with low to undetectable levels of p16 mRNA in 13 of 14 pituitary tumors relative to 5 normal pituitary specimens. Single-strand conformation polymorphism analysis of p16 exons 1 and 2 revealed no mobility shifts in 25 tumors; however, a quantitative differential PCR analysis revealed diminished amplification of p16 relative to a control gene in 3 of 25 tumors, suggesting homozygous p16 gene loss. We conclude that altered expression of the p16 gene product occurs at a high frequency in human pituitary tumors. This altered expression is not associated with frequent p16 mutation or gene loss, suggesting that alternative mechanisms of gene inactivation and/or altered regulation occur in the majority of these tumors.

Base Sequence↗
PubMed1996

Molecular and cellular responses to DNA damage in a murine pituitary adenoma cell line.

Loss of cell cycle control and the inability of the cell to repair DNA at cell cycle checkpoints results in the propagation of genetic lesions which ultimately leads to cancer. To further our understanding of these pathways in pituitary tumorigenesis, we have investigated the effects of DNA damage by gamma radiation in a murine pituitary adenoma (AtT20) cell line with attention to cell cycle checkpoint responses, the induction of apoptosis, and the expression of known regulators of these processes. Irradiated cells exhibited characteristic morphologic changes of apoptosis beginning at 24 h, which included cell shrinkage, chromatin condensation, and cytoplasmic vacuolization, yet the ability to exclude trypan blue was retained for several days. DNA fragmentation could be demonstrated by ethidium bromide staining beginning at 24 h post-irradiation. By propidium iodide staining and flow cytometry, irradiated cells demonstrated G1 and G2 arrest at 24 h, followed at 48 h by a shift to a sub-G1 position of the apoptotic cell population. The G1 arrest coincided with an induction of p53 protein by Western blot analysis which peaked at 4 h post-radiation and persisted beyond 48 h. Expression of c-myc in irradiated cells was found to progressively decrease at 12, 24, and 48 h. Basal expression of the bcl-2 gene in AtT20 cells was found to be 15-fold higher than in normal mouse pituitary by RNase protection assay. Bcl-2 mRNA and protein levels, however, remained unchanged at 24 and 48 h following gamma-irradiation, suggesting that apoptosis occurs independently of bcl-2 gene expression in these cells following this stimulus, as reported in other cell types. We conclude that AtT20 cells undergo G1 and G2 arrest following DNA damage and that a significant proportion of cells then undergo apoptosis. The G1 arrest at 24 h is concurrent with a strong induction of p53 protein, while c-myc expression progressively diminishes. Bcl-2 is highly expressed in this cell line. The absence of variation in bcl-2 expression during apoptosis could be related to its high basal level in these cells.

Adenoma↗
PubMed1996

Imidazoline receptor agonist drugs: a new approach to the treatment of systemic hypertension.

The imidazoline receptors have recently been discovered to be involved in central nervous system control of blood pressure (I-1 receptor) and in neuroprotection for cerebral ischemia (I-2 receptor). A new class of central-acting antihypertensive agents has been developed, the imidazoline receptor agonists (rilmenidine and moxonidine), which control blood pressure effectively without the adverse effects of sedation and mental depression that are usually associated with central-acting antihypertensives. This new generation of central-acting antihypertensive agents are highly selective for the imidazoline receptor, while having a low affinity for alpha 2-adrenergic receptors.

Animals↗
PubMed1996

The role of intra-operative duplex imaging in arterial reconstructions.

BACKGROUND: This study is a cost-benefit analysis of a less invasive method of intra-operative duplex imaging compared with the use of intra-operative angiogram (including C-arm fluoroscopy) in arterial reconstruction. METHODS: From September 1994 to May 1995, 93 intra-operative duplex imaging studies were performed. Duplex scanning results were recorded for carotid endarterectomy (35), iliac balloon angioplasty and stent placement (12), and infra-inguinal bypass (46). Average cost and time were calculated for each type of study. RESULTS: Thirty-four carotid endarterectomy patients (97%) had normal duplex findings. Three (9%) underwent intra-operative angiogram due to abnormal duplex findings and post-operative neurological deficit. In iliac balloon angioplasty and stent placement cases (12), both intra-operative duplex and C-arm post-stent angiography yielded comparable results in both normal (11) and abnormal (1) studies. In infra-inguinal bypass cases (46), 2 had abnormal duplex findings of the native vessels. Average time and cost required to perform intra-operative duplex studies is significantly less than that required for intra-operative angiogram or C-arm studies. CONCLUSION: Compared with traditional intra-operative angiography, the use of intra-operative duplex imaging is less expensive, less invasive, quicker, and equally accurate when used as an adjunct to access surgical results of arterial reconstructions.

Angioplasty, Balloon↗
PubMed1996

Localization and regulation by vitamin D of calcium transport proteins in rabbit cortical collecting system.

The 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]-induced expression of Na+/Ca2+ exchanger, Ca(2+)-adenosinetriphosphatase (Ca(2+)-ATPase), and calbindin-D28k was investigated in the rabbit distal nephron. Immunocytochemical studies in rabbit kidney sections revealed colocalization of the three Ca2+ transport proteins in the majority of cells in the distal nephron, including connecting tubules and cortical collecting ducts. Subsequently, rabbit connecting and cortical collecting tubule cells were immunodissected and cultured on permeable supports. Immunocytochemical analysis of the cultured cells by confocal microscopy revealed that Na+/Ca2+ exchanger and Ca(2+)-ATPase were present at the basolateral membrane, whereas calbindin-D28k was evenly distributed throughout the cytosol. Concomitant with an increase in Ca2+ transport, 1,25(OH)2D3 increased calbindin-D28k protein and RNA content two- to threefold, as determined by Northern and Western blotting. By contrast, neither Na+/Ca2+ exchanger nor Ca(2+)-ATPase RNA or protein content was noticeably altered. Our findings suggest that 1,25(OH)2D3 stimulation of transcellular Ca2+ transport in primary cultures of rabbit cortical collecting system cells involves an increase in the gene expression of calbindin-D28k but not of Na+/Ca2+ exchanger and Ca(2+)-ATPase.

Animals↗
PubMed1996

Re-evaluation of the mechanism and treatment of angina decubitus.

30 patients with angina decubitus (AD) were studied during hospitalization. These patients were found to have severe coronary artery obstructive lesions and an increase of myocardial oxygen consumption (MOC) before the onset to AD, indicating that AD belongs to the category of effort angina. 18 patients were investigated by continuous hemodynamic monitoring. Three patients had significant increase in pulmonary artery diastolic pressure (PADP) before the onset. In the other 15 patients, PADP increased slightly in 12 and remained unchanged in 3 cases before the onset. Left ventriculography showed ejection fraction (EF) > 45% in 25 of the 27 patients. These results indicate that left ventricular (LV) systolic dysfunction is not a major factor in the pathogenesis of AD. The patients with LVEDP > 12 mmHg constituted 60% of 25 patients with EF > 45%, suggesting that these patients had obvious LV diastolic dysfunction, which may be the major factor in the pathogenesis of AD. According to the results of our treatment, beta blockers may be used as the major form of treatment in the patients with AD.

Adult↗
PubMed1996

[Observation on the microstructure of sanyinjiao acupoint].

METHOD: Fresh adult limbs were divided into acupoint and control group. (1) H. E stain; (2) Cajal-Fauordky stain; (3) Lymph perfusion and section. RESULT: the sensery organs are multiple structures of nerves, blood and lymph etc. in the acupoint. There isn't significant difference (P > 0.05) for innervation of nerve, blood and lymph between the acupoint and other part. But there are some big nerve trunk in the tissues of the acupoint that play a different role in the reaction of human body.

Acupuncture Points↗
PubMed1995

The purine-rich trinucleotide repeat sequences d(CAG)15 and d(GAC)15 form hairpins.

The structures of single-stranded (ss) oligonucleotides containing (CAG)15 [ss(CAG)15] or (GAC)15 [ss(GAC)15] were examined. At 10 degrees C, the electrophoretic mobilites of the two DNAs were similar to ss(CTG)15, a DNA that forms a hairpin containing base paired and/or stacked thymines. At 37 degrees C in 50 mM NaCl, single-strand-specific P1 nuclease cleaved the G33-G36 phosphodiesters of ss(GAC)15, and the G32-A34, G35-C36 phosphodiesters of ss(CAG)15 (where the loop apex of both DNAs = A34). Electrophoretic mobility melting profiles indicated that the melting temperature (Tm) of ss(CAG)15 in low (approximately 1 mM Na+) ionic strength was 38 degrees C. In contrast, the Tm of ss(GAC)15 was 49 degrees C, a value similar to the Tm of ss(CTG)15. These results provide evidence that ss(GAC)15 and ss(CAG)15 form similar, but distinguishable hairpin structures.

Base Sequence↗
PubMed1995

The trinucleotide repeat sequence d(CGG)15 forms a heat-stable hairpin containing Gsyn. Ganti base pairs.

To investigate potential structures of d(CGG/CCG)n that might relate to their biological function and association with triplet repeat expansion diseases (TREDs), electrophoretic mobility, chemical modification, and P1 nuclease studies were performed with a single-stranded (ss) oligonucleotide containing (CGG)15 [ss(CGG)15]. The results suggest that ss(CGG)15 forms a hairpin with the following features: (i) a stem containing Gsyn. Ganti base pairs; (ii) at > or = 200 mM K+, CGG repeats on the 5' portion of the stem base-paired to GCG repeats on the 3' side (referred to as the (b) alignment); and (iii) heat stability (Tm = 75 degrees C in low ionic strength). At < or = 100 mM K+, dimethyl sulfate reactions indicated that the hairpin in the (b) alignment was in equilibrium with another structure, presumably a hairpin in the alternative (a) alignment (CGG repeats on the 5' portion of the stem base-paired to CGG repeats on the 3' portion of the stem). Molecular dynamics simulations suggested that the loop region of the (a) alignment contained two guanines stacked on top of one another. The same guanines in the (b) alignment were base-paired in a syn-anti arrangement. We propose that the stability of the loop partially determines the stem alignment.

Base Sequence↗
PubMed1995

Acute depletion of serotonin down-regulates serotonin transporter mRNA in raphe neurons.

Serotonin transporter (5-HTT) mRNA and 5-HTT sites were measured 3 days after treatment with p-chlorophenylalanine, a tryptophan hydroxylase inhibitor. While 5-HTT mRNA levels decreased (P < 0.001) in the dorsal raphe nucleus, 5-HTT binding sites remained unchanged, suggesting that an acute depletion of 5-HT may induce an increase in the turnover of 5-HTT mRNA without affecting protein levels at 3 days.

Animals↗
PubMed1995

Detection of polyomaviral DNA sequences in normal and adenomatous human pituitary tissues using the polymerase chain reaction.

BACKGROUND: Tumor viruses are known to have a role in the pathogenesis of many types of benign and malignant human tumors. The possible roles of these viruses in the development of human pituitary tumors have not been investigated. METHODS: The polymerase chain reaction was used to screen human pituitary tumors for human papillomaviral (HPV) and Polyomaviral DNA sequences. Sets of consensus primers, which are capable of amplifying HPV Types 16, 18, and 33 and polyomavirus BK, JC, and SV40, were used in these experiments. RESULTS: Amplification products were not detected using HPV consensus primers in 30 tumors. Twenty-six of 30 tumors demonstrated an amplification product with polyomaviral primers that hybridized to SV40 and BK internal probes and was confirmed to be SV40 in one tumor by direct sequencing. Ten normal postmortem pituitary samples then were examined similarly with Polyomaviral consensus primers; 8 of 10 normal samples demonstrated a similar amplification product that also hybridized with SV40 and BK internal probes by Southern blotting. Polyomaviral DNA sequences in normal and tumor samples were not present at levels detectable by genomic Southern blotting. Expressed viral protein (large T antigen) was not demonstrated in positive samples by Western blot analysis. CONCLUSIONS: These findings, that polyomaviral DNA sequences are detectable at low levels in certain normal tissues, are in agreement with those of other groups and, to the authors' knowledge, serve as the first report of polyomaviral latency in human pituitary tissue. A role for polyomaviruses in pituitary tumorigenesis could not be established in this analysis.

Adenoma↗
PubMed1995

The trinucleotide repeat sequence d(GTC)15 adopts a hairpin conformation.

The structure of a single-stranded (ss) oligonucleotide containing (GTC)15 [ss(GTC)15] was examined. As a control, parallel studies were performed with ss(CTG)15, an oligonucleotide that forms a hairpin. Electrophoretic mobility, KMnO4 oxidation and P1 nuclease studies demonstrate that, similar to ss(CTG)15, ss(GTC)15 forms a hairpin containing base paired and/or stacked thymines in the stem. Electrophoretic mobility melting profiles performed in approximately 1 mM Na+ revealed that the melting temperature of ss(GTC)15 and ss(CTG)15 were 38 and 48 degrees C respectively. The loop regions of ss(GTC)15 and ss(CTG)15 were cleaved by single-strand-specific P1 nuclease at the T25-C29 and G26-C27 phosphodiester bonds respectively (where the loop apex of the DNAs is T28). Molecular dynamics simulations suggested that in ss(GTC)15 the loop was bent towards the major groove of the stem, apparently causing an increased exposure of the T25-C29 region to solvent. In ss(CTG)15 guanine--guanine stacking caused a separation of the G26 and C27 bases, resulting in exposure of the intervening phosphodiester to solvent. The results suggest that ss(GTC)15 and ss(CTG)15 form similar, but distinguishable, hairpin structures.

Base Sequence↗
PubMed1995

Hairpin properties of single-stranded DNA containing a GC-rich triplet repeat: (CTG)15.

Although triplet repeat DNA sequences are scattered throughout the human genome, their biological function remains obscure. To aid in correlating potential structures of these nucleic acids with their function, we propose their classification based on the presence or absence of a palindromic dinucleotide within the triplet, the G + C content, and the presence or absence of a homopolymer. Five classes of double-stranded (ds) triplet repeats are distinguished. Class I repeats, which are defined by the presence of a GC or CG palindrome, have the lowest base stacking energies, exhibit the lowest rates of slippage synthesis [Schlötterer and Tautz (1992) Nucleic Acids Res., 20, 211] and are uniquely associated with triplet repeat expansion diseases. The six single-stranded (ss) triplet repeats within Class I also have the potential to form hairpin structures, as determined by energy minimization. To explore the possibility of hairpin formation by ss Class I triplet repeats, studies were performed with a ss oligonucleotide containing 15 prototypic CTG repeats [ss (CTG)15]. Electrophoretic, P1 nuclease and KMnO4 oxidation data demonstrate that ss (CTG)15 forms a hairpin containing base paired and/or stacked thymines in the stem. Potential functions of hairpins containing Class I triplet repeats are discussed with respect to protein translation and mRNA splicing. Further, potential roles of hairpin structures in triplet repeat expansion events are discussed.

Base Composition↗
PubMed1995

Arrhythmias after cardioverter-defibrillator implantation: comparison of epicardial and transvenous systems.

Surgery for implantable cardioverter-defibrillators can cause postoperative exacerbation of ventricular and atrial arrhythmias. It is not known whether the techniques of electrode implantation (epicardial vs transvenous) influence the incidence of arrhythmia exacerbation. We reviewed the postoperative course of 229 consecutive patients who received either epicardial (n = 119) or transvenous (n = 110) implantations from 1984 to 1994. Exacerbation of ventricular tachycardia (VT) was defined as an increase in the number of sustained VTs during the postoperative versus the preoperative 2 weeks. Of the entire cohort, 18 patients (8%) developed exacerbation of VT after operation, which was more frequent in patients with epicardial than with transvenous implantations (12% vs 4%, p < 0.03, odds ratio 3.5, 95% confidence interval 1.0 to 13.2). New-onset atrial fibrillation occurred in 15% of patients with epicardial versus 1% of those with transvenous implantations (p = 0.00005, odds ratio 19.4, 95% confidence interval 2.7 to 86.7). These differences persisted after excluding patients with concurrent cardiac surgery. Preoperative occurrence of arrhythmias was the strongest independent predictor for postoperative occurrence (p < 0.01 for VT, p < 0.0001 for atrial fibrillation). Epicardial implantation (p = 0.03) and a history of myocardial infarction (p = 0.04) were independent predictors for postoperative VT exacerbation, whereas epicardial implantation (p < 0.05) and concurrent coronary bypass surgery (p = 0.0001) were independent predictors for postoperative new atrial fibrillation. Perioperative discontinuation of antiarrhythmic drugs did not influence postoperative VT exacerbation. Epicardial implantation was associated with longer length of hospital stay than transvenous implantation (p = 0.0005), independent of age, left ventricular ejection fraction, and concurrent cardiac surgery.

Aged↗