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Biomedical subjects

N Tang

Publications and source records attributed to N Tang.

At least 37 records · Page 2Linked to original sources
PubMed2000

Studies of renal injury III: lipid-induced nephropathy in type II diabetes.

UNLABELLED: Studies of renal injury III: Lipid-induced nephropathy in type II diabetes. BACKGROUND: Nephrotoxicity from elevated circulating lipids occurs in experimental and clinical situations. We tested the hypothesis that lipid-induced nephropathy causes advanced renal failure in rats with type II diabetes and dyslipidemia. METHODS: First generation (F1) hybrid rats derived from the spontaneous hypertensive heart failure rat (SHHF/Gmi-fa) and the LA/NIH-corpulent rat (LA/N-fa) were studied for 41 weeks while being on specific diets. Group 1 (14 rats) ingested 11.5% protein, 47.9% fat, and 40.6% carbohydrate. Group 2 (8 rats) ingested 26.9% protein, 16.7% animal fat, and 56.4% carbohydrate, and group 3 (20 rats) ingested 20.2% protein, 40.4% soy and coconut oil, and 39.4% carbohydrate. RESULTS: Hyperglycemia was more severe in rat groups 1 and 2 than in group 3. In contrast, circulating cholesterol and hydroperoxide levels were highest in group 3, intermediate in group 2, and lowest in group 1. Group 3 had severe renal failure secondary to glomerulosclerosis and tubulointerstitial disease, with striking deposition of the lipid peroxidation stress biomarker 4-hydroxynonenal in glomeruli and renal microvessels. Moreover, in group 3, increased arterial wall thickness also connoted vascular injury. In contrast, the glycoxidation stress biomarkers pentosidine and carboxymethyl-lysine were preferentially localized to renal tubules of hyperglycemic rats in groups 1 and 2 and did not segregate with the most severe renal injury. Glomerular and interstitial fibrosis was accompanied by proportional increases in renal transforming growth factor-beta1 levels, which were threefold higher in the hypercholesterolemic rats of group 3 than in the hyperglycemic rats of group 1. CONCLUSIONS: Acquisition of non-nodular glomerular sclerosis and tubulointerstitial disease is dependent on lipoxidation stress in rats with type II diabetes. On the other hand, in the absence of hypercholesterolemia, prolonged glycoxidation stress does not appear to be uniquely nephrotoxic.

Animals↗
PubMed2000

Effects of single injection of methylazoxymethanol at postnatal day one on cell proliferation in different brain regions of male rats.

Methylazoxymethanol (MAM), an aglycone of cycasin extracted from Cycad seed, is reported to induce microencephaly in rats after prenatal or postnatal administration. Forty postnatal day (PND) 1 rats derived from 8 timed-pregnant rats were used to evaluate the effect of a single subcutaneous injection of MAM on PND 1 on cell proliferation in rat brain. All dams were fed NIH-31 diet. In the MAM-treated group, each pup received a single injection of MAM at 10 mg/kg body weight. In the control group, pups were injected with saline solution. Body weight of pups was recorded on PNDs 1, 7, 14, 21, 28, and 60. One male pup in each litter was removed for sacrifice by decapitation on PNDs 7, 14, 21, 28, and 60. The brain was removed and dissected to obtain the brain stem, caudate nucleus, cerebellum, frontal cortex, hippocampus, hypothalamus, and olfactory bulb. The percentage (%) of S-phase cells in the cell cycle for each region was measured as index of cell proliferation. A significant (p<0. 05) reduction in body weight was detected on PND 7. The % S-phase cells in cerebellum on PND 7 and olfactory bulb on PND 14 initially increased and then later decreased. There were significant decreases in the % S-phase cells in both cerebellum and caudate nucleus on PND 21 and olfactory bulb on PND 28. No significant changes were found in other brain regions in cell proliferation activity between the control and MAM-treated groups. The % of S-phase cells in cerebellum decreased 65% on PND 60 but lacked statistical significance due to small number of animals used in each group. The results indicated that a single injection of MAM at 10 mg/kg/body weight on PND 1 inhibited cell proliferation in the cerebellum in a manner that could lead to microencephaly.

Aging↗
PubMed1999

Nickel and cobalt reagents promote selective oxidation of Z-DNA.

The structural characteristics of Z-DNA were used to challenge the selectivity of guanine oxidation promoted by nickel and cobalt reagents. Base pairing and stacking within all helical structures studied previously had hindered access to guanine and limited its reaction. However, the Z-helix uniquely retains high exposure of guanine N7. This exposure was sufficient to direct oxidation specifically to a plasmid insert -(CG)(13)AATT(CG)(13)- that adopted a Z-conformation under native supercoiling. An alternative insert -(CG)(7)- retained its B-conformation and demonstrated the expected lack of reactivity. For a nickel salen complex made from a particularly bulky ligand, preferential reaction shifted to the junctions within the Z-DNA insert as is common for large reagents. Inactivation of the nickel reagents by high-salt concentrations prevented parallel investigations of Z-DNA, formed by oligonucleotides. However, the activity of Co(2+) was minimally affected by salt and consequently confirmed the high reactivity of 5'-p(CG)(4) in its Z-conformation. These reagents may now be applied to a broad array of targets, since their structural specificity remains predictable for both complex and helical assemblies of nucleic acids.

Chromium Alloys↗
PubMed1999

The effect of dietary fat on malondialdehyde concentrations in Fischer 344 rats.

The effects of dietary fat and age on the level of malondialdehyde (MDA), a product of lipid peroxidation, were investigated in cerebellum, kidney, and liver tissues of female Fischer 344 rats. Groups of rats were fed diets containing various levels of corn oil (3, 5, 10, 15, or 20%), starting at 57 days of age, for a duration of 2, 10, or 20 weeks. High fat diets are thought to promote tumor formation, diabetes, and cardiovascular diseases via induction of oxidation stress, and this can begin early in the lifespan. However, it was observed that rats chronically consuming 3 and 5% corn oil diets yielded significantly higher levels of MDA, as analyzed by high-performance liquid chromatography, compared with those fed higher fat diets. After 20 weeks of feeding, the concentration of MDA in each of the three organs studied showed no significant differences among rats consuming diets containing 10, 15, or 20% corn oil. The levels of MDA were highest in the cerebellum, followed by kidney, and lowest in liver. Over the 20-week feeding period, a decrease in MDA level in both cerebellum and liver was observed.

Aging↗
PubMed1999

Sequence-specific DNA cleavage by Fe2+-mediated fenton reactions has possible biological implications.

Preferential cleavage sites have been determined for Fe2+/H2O2-mediated oxidations of DNA. In 50 mM H2O2, preferential cleavages occurred at the nucleoside 5' to each of the dG moieties in the sequence RGGG, a sequence found in a majority of telomere repeats. Within a plasmid containing a (TTAGGG)81 human telomere insert, 7-fold more strand breakage occurred in the restriction fragment with the insert than in a similar-sized control fragment. This result implies that telomeric DNA could protect coding DNA from oxidative damage and might also link oxidative damage and iron load to telomere shortening and aging. In micromolar H2O2, preferential cleavage occurred at the thymidine within the sequence RTGR, a sequence frequently found to be required in promoters for normal responses of many procaryotic and eucaryotic genes to iron or oxygen stress. Computer modeling of the interaction of Fe2+ with RTGR in B-DNA suggests that due to steric hindrance with the thymine methyl, Fe2+ associates in a specific manner with the thymine flipped out from the base stack so as to allow an octahedrally-oriented coordination of the Fe2+ with the three purine N7 residues. Fe2+-dependent changes in NMR spectra of duplex oligonucleotides containing ATGA versus those containing AUGA or A5mCGA were consistent with this model.

Base Sequence↗
PubMed1999

Cardiopulmonary resuscitation in pediatric trauma patients: survival and functional outcome.

BACKGROUND: Although injury is the leading cause of cardiac arrests in children older than 1 year, few studies have examined the survival and functional outcome of cardiopulmonary resuscitation (CPR) in pediatric trauma patients. METHODS: A historical cohort of 957 trauma patients younger than 15 years who received CPR at the scene of injury or at the admitting hospital was constructed on the basis of the National Pediatric Trauma Registry. The rate of survival to discharge and factors related to survival were examined. Functional impairments were documented for surviving patients. RESULTS: The overall survival rate was 23.5%. With adjustment for the Injury Severity Score, the risk of fatality after CPR increased for children with systolic blood pressure below 60 mm Hg at admission (odds ratio [OR] 24.5, 95% confidence interval [CI] 8.6-69.3), for those who were comatose at admission (OR, 4.7; 95% CI, 1.9-11.6), for those with penetrating injury (OR, 4.4; 95% CI, 1.5-13.3), and for those with CPR initiated at the hospital (OR, 2.4; 95% CI, 1.5-3.9). Surviving patients stayed in hospitals for an average of 24.3 days; at discharge, 64% had at least one impairment in the functional activities of daily living. CONCLUSIONS: Survival outcome of CPR in pediatric trauma patients appears to be comparable to that reported in adults of mixed arrest causes. Future research needs to identify factors underlying the excess mortality associated with penetrating trauma.

Activities of Daily Living↗
PubMed1998

Facial measurements for frame design.

Anthropometric data for the purpose of spectacle frame design are scarce in the literature. Definitions of facial features to be measured with existing systems of facial measurement are often not specific enough for frame design and manufacturing. Currently, for individual frame design, experienced personnel collect data with facial rules or instruments. A new measuring system is proposed, making use of a template in the form of a spectacle frame. Upon fitting the template onto a subject, most of the measuring references can be defined. Such a system can be administered by lesser-trained personnel and can be used for researches covering a larger population.

Anthropometry↗
PubMed1998

Ophthalmic anthropometry for Hong Kong Chinese adults.

A database of ophthalmic anthropometry is established which is useful for the design of spectacles for southeast Asian people. Statistical analysis reveals significant variations in the facial dimensions between male and female subjects. Results of the study are given separately for each sex and for the combined population. Hong Kong Chinese are found to have larger frontal angles, bigger angles of splay, and a less prominent bridge in the nose. Spectacle frames should be designed according to the targeted gender population, and to accommodate the characteristics of Asian faces.

Adolescent↗
PubMed1998

Mutations in the N terminus of the brome mosaic virus polymerase affect genetic RNA-RNA recombination.

Previously, we have observed that mutations in proteins 1a and 2a, the two virally encoded components of the brome mosaic virus (BMV) replicase, can affect the frequency of recombination and the locations of RNA recombination sites (P. D. Nagy, A. Dzianott, P. Ahlquist, and J. J. Bujarski, J. Virol. 69:2547-2556, 1995; M. Figlerowicz, P. D. Nagy, and J. J. Bujarski, Proc. Natl. Acad. Sci. USA 94:2073-2078, 1997). Also, it was found before that the N-terminal domain of 2a, the putative RNA polymerase protein, participates in the interactions between 1a and 2a (C. C. Kao, R. Quadt, R. P. Hershberger, and P. Ahlquist, J. Virol. 66:6322-6329, 1992; E. O'Reilly, J. Paul, and C. C. Kao, J. Virol. 71:7526-7532, 1997). In this work, we examine how mutations within the N terminus of 2a influence RNA recombination in BMV. Because of the likely electrostatic character of 1a-2a interactions, five 2a mutants, MF1 to MF5, were generated by replacing clusters of acidic amino acids with their neutral counterparts. MF2 and MF5 retained nearly wild-type levels of 1a-2a interaction and were infectious in Chenopodium quinoa. However, compared to that in wild-type virus, the frequency of nonhomologous recombination in both MF2 and MF5 was markedly decreased. Only in MF2 was the frequency of homologous recombination reduced and the occurrence of imprecise homologous recombination increased. In MF5 there was also a 3' shift in the positions of homologous crossovers. The observed effects of MF2 and MF5 reveal that the 2a N-terminal domain participates in different ways in homologous and in nonhomologous BMV RNA recombination. This work maps specific locations within the N terminus involved in 1a-2a interaction and in recombination and further suggests that the mechanisms of the two types of crossovers in BMV are different.

Amino Acid Sequence↗
PubMed1998

[Experimental study on regenerative capacity and form of corneal endothelial cells in the primate].

OBJECTIVE: To investigate the regenerative capacity and form of the corneal endothelial cells of the primate. METHODS: Chromosome, HE stainings and autoradiography were made for the cornea of human and monkey. RESULTS: After trauma, corneal endothelial cells of the adult monkey in vivo showed regenerative power. The regenerative form of corneal endothelial cells of the adult, infant and fetal primate was amitosis under both physiologic and pathologic conditions. CONCLUSION: The corneal endothelial cells of the primate have regenerative power, and the form is amitosis.

Adult↗
PubMed1998

Effects of isovolumetric hemodilution treatment and superoxide dismutase on ischemic reperfused hearts in rabbit.

UNLABELLED: The isovolumetric hemodilution treatment reduces ischemic injury and anti-radical interventions may reduce reperfusion injury. However, the effects of the treatment with both interventions have never been investigated. In the present study, anesthetized rabbits underwent 45 min of coronary artery ligation, which was followed by 180 min of reperfusion. Ten animals in each group received: (i) normal saline only; (ii) isovolumetric hemodilution with Dextran 40 during ischemia; (iii) superoxide dismutase (SOD) 1 min before and during reperfusion; and (iv) combined treatment with hemodilution and SOD. RESULTS: (1) compared with those of the control group, left ventricular peak pressure (LVP) and +/- dp/dt-max improved significantly in the animals which received hemodilution or SOD alone, and left ventricular systolic function of the animals with the combination therapy improved further; (2) infarct size averaged 54.4 +/- 2.6% of the risk region in controls and was significantly smaller in the rabbits that were treated with hemodilution (32.8 +/- 1.8%) (p < 0.05), with SOD (42.1 +/- 3.2%) (p < 0.05) and with the combination therapy (23.4 +/- 1.5%) (p < 0.01). Therefore, (1) in groups where either hemodilution during ischemia or removal of oxygen radicals during reperfusion was done left ventricular systolic function and salvaged ischemic reperfused myocardium improved significantly; (2) in this acute model, SOD improved left ventricular systolic and diastolic functions and reduced infarct size further when given to the animals that had been treated with hemodilution.

Animals↗
PubMed1996

The P58 cellular inhibitor complexes with the interferon-induced, double-stranded RNA-dependent protein kinase, PKR, to regulate its autophosphorylation and activity.

The 58-kDa protein, referred to as P58, is a cellular inhibitor of the interferon-induced, double-stranded RNA-activated protein kinase, PKR. The P58 protein inhibits both the autophosphorylation of PKR and the phosphorylation of the PKR natural substrate, the alpha subunit of eukaryotic initiation factor eIF-2. Sequence analysis revealed that P58 is a member of the tetratricopeptide family of proteins. Utilizing experimental approaches, which included coprecipitation or coselection of native and recombinant wild-type and mutant proteins, we found that P58 can efficiently complex with the PKR protein kinase. Attempts to map the P58 interactive sites revealed a correlation between the ability of P58 to inhibit PKR in vitro and bind to PKR. The DnaJ sequences, present at the carboxyl terminus of P58, were dispensable for binding in vitro, while sequences containing the eIF-2 alpha similarity region were essential for efficient complex formation. Furthermore, not all tetratricopeptide motifs were necessary for PKR-P58 interactions. Initial experiments to map the binding domains present in PKR showed that P58 complexed with PKR molecules that lacked the first RNA binding domain but did not bind to a PKR mutant containing only the amino terminus. These data, taken together, demonstrate that P58 inhibits PKR through a direct interaction, which is likely independent of the binding of double-stranded RNA to the protein kinase.

3T3 Cells↗
PubMed1996

[Assay of anti-corneal endothelial antibody after penetrating keratoplasty].

OBJECTIVE: To study the effective materials in the immune response and the humoral immunity in graft rejective reaction in the host after penetrating keratoplasty (PKP). METHODS: PK was performed on 2 groups of monkeys with a 5.5 mm button in a 5.0 mm bed. The heterogroup (human to monkey) had 4 monkeys, and homo-group (monkey to monkey) also 4. Nelken's method was modified. Two kinds of antigens, corneal endothelial and stromal antigens, had been made the first time. Enzyme linked immunosorbent assay (ELISA) was used to detect the anti-corneal endothelial antibody (ACEAb) in the serum and aqueous humor of the host. RESULTS: After PKP, the anti-corneal stromal antibody did not increase obviously, while the increase of ACEAb was distinct. CONCLUSION: Humoral immune response can occur in the host after PK, and the effective material is ACEAb.

Animals↗
PubMed1995

Biochemical and genetic analyses of the interaction between the helicase-like and polymerase-like proteins of the brome mosaic virus.

Replication of the three positive-strand genomic RNAs of brome mosaic virus requires the activities of the helicase-like 1a and the polymerase-like 2a proteins. One hundred fifteen amino acids of the 2a N-terminus and the 1a helicase-like region of over 50 kDa are both necessary and sufficient for 1a-2a interaction. Requirement of the large size of the 1a helicase-like domain suggests that higher order structures might be necessary for the protein's interaction with 2a. To explore the structural properties of 1a, we used limited proteolysis of in vitro-translated 1a protein. Treatment of 1a and its deletion derivatives with papain or trypsin revealed that the C-terminal helicase-like segment of approximately 50-60 kDa is highly resistant under our assay conditions to proteolysis, while the N-terminus is rapidly degraded. All tested mutations in the helicase-like region that renders this region protease-sensitive have previously been found to be defective for RNA replication in vivo. To complement the in vitro studies, we examined the interaction of the 1a helicase-like domain and the 2a N-terminus in yeast using the two-hybrid system. Mutations previously known to disrupt 1a-2a interaction also prevented interaction in yeast. Furthermore, results from two-hybrid analysis suggest that the structural domain mapped in vitro is important for 1a-2a interaction. Finally, we found that the helicase-like proteins of three other tripartite RNA viruses also contain equivalently located protease-resistant domains.

Amino Acid Sequence↗
PubMed1995

Determinants of emergency department procedure- and condition-specific universal (barrier) precaution requirements for optimal provider protection.

STUDY OBJECTIVE: To determine potential blood and body fluid (B/BF) contacts with specific body areas associated with procedures commonly performed in the emergency department and to thereby delineate appropriate procedure-specific precautions. DESIGN: Prospective, observational study assessing procedure-related B/BF contacts by use of stratified, blocked sampling of shifts. PARTICIPANTS: ED patients in an inner-city tertiary care university hospital. RESULTS: Of 2,529 procedures performed in 1,025 patients, 1,621 (64%) were associated with barrier-protected or unprotected B/BF contact; 92% involved blood or bloody BF. Chest tube placement, lumbar puncture, and examination of the bleeding patient all resulted in B/BF contact with the facial area. All of the 18 procedure categories observed, with the exception of i.m. injection, resulted in B/BF contact with hands. Many procedures resulted in contact with the body or feet. Procedure type, provider, length of time, number of procedures per patient, and successful completion were each independently associated with B/BF contact. Number of attempts, adverse conditions, and triage acuteness were not associated with increased likelihood of contact. CONCLUSION: Virtually all ED procedures require gloves. Barrier protection for the body may be appropriate for all but the simplest procedures. Protection for the face seems appropriate, especially in invasive procedures such as lumbar puncture or physical examination of the bleeding patient. This study, along with other published data, has aided development of detailed guidelines for appropriate barrier precautions to be taken for common ED procedures.

Adolescent↗
PubMed1995

Trends in human immunodeficiency virus (HIV) infection among a patient population of an inner-city emergency department: implications for emergency department-based screening programs for HIV infection.

Personnel of inner-city emergency departments (EDs), which are frequently the only source of medical care for many patients, may be in a unique position to detect human immunodeficiency virus (HIV) infection earlier than personnel at other recommended screening sites. To assist development of ED-based screening strategies for HIV infection, we undertook a serosurvey of HIV infection in adult patients attending an ED during a 6-week period in 1992 using an identity-unlinked technique and compared our findings with data collected similarly in 1988. Of 1,606 patients, 183 (11.4%) were HIV-positive, compared with 6.0% in 1988. Seroprevalence rates of HIV infection among patients only at risk of heterosexual transmission increased more than fourfold (7% to 30.3%). CD4+ cell counts were higher in those patients with undiagnosed HIV infection than in those with known HIV infection. Targeting minority patients aged 25-44 years, intravenous drug users, and those patients at heterosexual risk would have identified 87% of patients with new HIV infection, while requiring screening of 41% of the study sample. Targeted voluntary screening programs in certain EDs would likely detect significant numbers of new early HIV infections.

Adolescent↗
PubMed1994

The 58,000-dalton cellular inhibitor of the interferon-induced double-stranded RNA-activated protein kinase (PKR) is a member of the tetratricopeptide repeat family of proteins.

PKR is a serine/threonine protein kinase induced by interferon treatment and activated by double-stranded RNAs. As a result of activation, PKR becomes autophosphorylated and catalyzes phosphorylation of the alpha subunit of protein synthesis eukaryotic initiation factor 2 (eIF-2). While studying the regulation of PKR in virus-infected cells, we found that a cellular 58-kDa protein (P58) was recruited by influenza virus to downregulate PKR and thus avoid the kinase's deleterious effects on viral protein synthesis and replication. We now report on the cloning, sequencing, expression, and structural analysis of the P58 PKR inhibitor, a 504-amino-acid hydrophilic protein. P58, expressed as a histidine fusion protein in Escherichia coli, blocked both the autophosphorylation of PKR and phosphorylation of the alpha subunit of eIF-2. Western blot (immunoblot) analysis showed that P58 is present not only in bovine cells but also in human, monkey, and mouse cells, suggesting the protein is highly conserved. Computer analysis revealed that P58 contains regions of homology to the DnaJ family of proteins and a much lesser degree of similarity to the PKR natural substrate, eIF-2 alpha. Finally, P58 contains nine tandemly arranged 34-amino-acid repeats, demonstrating that the PKR inhibitor is a member of the tetratricopeptide repeat family of proteins, the only member identified thus far with a known biochemical function.

Amino Acid Sequence↗