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Biomedical subjects

F Qiao

Publications and source records attributed to F Qiao.

15 recordsLinked to original sources
PubMed2006

Evaluation of net energy expenditures of dairy cows according to body weight changes over a full lactation.

Equations that predict daily dry matter intake (DMI) of a lactating cow could be evaluated by comparing the predicted accumulation of energy in body weight (BW) over the course of lactation with the observed BW evolution. However, to do so requires that first the energy balance calculations from observed DMI are evaluated. The purpose of the work reported here was to determine the degree of deviation of predicted from observed BW, according to net energy for lactation (NE(L)) balance calculated from weekly observations of DMI, BW, and fat-corrected milk production in 21 sets of full-lactation data, and to determine an appropriate correction of the NE(L) bias for subsequent DMI prediction evaluations. When the National Research Council maintenance equation 0.08 x BW(kg)(0.75) was used in energy balance calculation, BW was overpredicted with an increasing difference between the cumulative predicted BW and observed BW as lactation progressed. Placing all the error of BW prediction into maintenance energy expenditures resulted in a best-fit equation of 0.096 +/- 0.003 Mcal/kg of BW(0.75). A time-dependent equation was also developed, in which weekly maintenance expenditures were determined as the NE(L) expenditure to yield a zero NE(L) balance and could be described by a second-order polynomial equation related to week of lactation (WOL) where maintenance NE(L) = [-0.0227(+/- 0.0098) x WOL2 + 1.352(+/- 0.456) x WOL + 78.09(+/- 4.92) Mcal/kg of BW(0.75)] x 10(-3). Average maintenance energy expenditure at the onset of lactation was approximately 0.08 Mcal/kg of BW(0.75), and this value increased to a plateau at wk 15 of lactation of approximately 0.098 Mcal/kg of BW(0.75). Standard deviations between data sets of weekly maintenance parameter estimates throughout lactation were large but consistent at approximately 25% of the mean. Revision of the maintenance energy expenditure estimate substantially improved BW prediction by the energy balance model. On average, the 0.096 Mcal of NE(L)/kg of BW(0.75) equation resulted in the best BW predictions, although substantial variation existed around this value.

Animals↗
PubMed2006

Prediction of dry matter intake throughout lactation in a dynamic model of dairy cow performance.

In the dynamic modeling of dairy cow performance over a full lactation, the difference between net energy intake and net energy used for maintenance, growth, and output in milk accumulates in body reserves. A simple dynamic model of net energy balance was constructed to select, out of some common dry matter intake (DMI) prediction equations, the one that resulted in a minimum cumulative bias in body energy deposition. Dry matter intake was predicted using the Cornell Net Carbohydrate and Protein System, Agricultural Research Council, or National Research Council (NRC) DMI equations from body weight (BW) and predicted fat-corrected milk yield. The instantaneous BW of cows at progressive weeks of lactation was simulated as the numerical integral of the BW change obtained from the predicted net energy balance. Predicted DMI and BW from each DMI equation, using either of 2 equations to describe maintenance energy expenditures, were compared statistically against observed data from 21 herd average published full lactation data sets. All DMI equations underpredicted BW and DMI, but the NRC DMI equation resulted in the minimum cumulative error in predicted BW and DMI. As a general solution to prevent predicted BW from deviating substantially over time from the observed BW, a lipostatic feedback mechanism was integrated into the NRC DMI equation as a 2-parameter linear function of the relative size of simulated body reserves and week of lactation. Residual sum of squares was reduced on average by 52% for BW predictions and by 41% for DMI predictions by inclusion of the negative feedback with parameters taken from the average of all 21 least squares fits. Similarly, root mean square prediction error (%) was reduced by 30% on average for BW predictions and by 23% for DMI predictions. Inclusion of a feedback of energy reserves onto predicted DMI, simulating lipostatic regulation of BW, solved the problem of final BW deviation within a dynamic model and improved its DMI prediction to a satisfactory level.

Adipose Tissue↗
PubMed2002

Milk synthetic response of the bovine mammary gland to an increase in the local concentration of arterial glucose.

Concentrations of glucose in the external iliac artery feeding one udder half of 14 midlactation Holstein cows were increased by infusion to test the following three hypotheses of mammary function: 1) that mammary glands control their blood supply to maintain intracellular energy balance, 2) that milk precursors are taken out of capillary blood according to mass action kinetics, and 3) that the rate of milk component synthesis is dependent on its precursor's uptake from blood. The first seven cows received 20 g/h glucose during 10 h of infusion. Arterial concentrations of glucose were locally increased by only 10%, and the iliac plasma flow was not affected by glucose infusion, so the next seven cows were given 90 g/h glucose. Quantitative predictions resulting from the hypotheses were that arterial plasma flow would decrease by 32% with 90 g/h glucose infusion, glucose uptakes would increase and acetate, fatty acid, and amino acid uptakes decrease, and milk protein and fat yields and percentages would decrease. Iliac plasma flow decreased 16%, half of what was predicted, which suggests that other regulatory processes besides blood flow control took part in the response. Acetate and fatty acid uptakes by the mammary glands were reduced as predicted because of the lower blood flow, but an unexpected depression in extraction of plasma triacylglycerol also contributed to the reduced fatty acid uptake. Milk fat and protein yields were not affected by the exogenous glucose, falsifying the third hypothesis that milk component secretion is a function of uptake of its precursor. Milk fat and protein percentages declined with glucose infusion because of increased lactose synthesis and secretion of water into milk.

Animals↗
PubMed2001

Fanconi anemia proteins localize to chromatin and the nuclear matrix in a DNA damage- and cell cycle-regulated manner.

Fanconi anemia (FA) is a genetic disease characterized by congenital defects, bone marrow failure, and cancer susceptibility. Cells from patients with FA exhibit genomic instability and hypersensitivity to DNA cross linking agents such as mitomycin C. Despite the identification of seven complementation groups and the cloning of six genes, the function of the encoded gene products remains elusive. The FancA (Fanconi anemia complementation group A), FancC, and FancG proteins have been detected within a nuclear complex, but no change in level, binding, or localization has been reported as a result of drug treatment or cell cycle. We show that in immunofluorescence studies, FancA appears as a non-nucleolar nuclear protein that is excluded from condensed, mitotic chromosomes. Biochemical fractionation reveals that the FA proteins are found in nuclear matrix and chromatin and that treatment with mitomycin C results in increase of the FA proteins in nuclear matrix and chromatin fractions. This induction occurs in wild-type cells and mutant FA-D (Fanconi complementation group D) cells but not in mutant FA-A cells. Immunoprecipitation of FancA protein in chromatin demonstrates the coprecipitation of FancA, FancC, and FancG, showing that the FA proteins move together as a complex. Also, fractionation of mitotic cells confirms the lack of FA proteins in chromatin or the nuclear matrix. Furthermore, phosphorylation of FancG was found to be temporally correlated with exit of the FA complex from chromosomes at mitosis. Taken together, these findings suggest a role for FA proteins in chromatin and nuclear matrix.

Cell Cycle↗
PubMed2001

Milk composition responses to unilateral arterial infusion of complete and histidine-lacking amino acid mixtures to the mammary glands of cows.

To evaluate a close mammary infusion technique for the study of milk protein responses to blood amino acid profile, five early-lactation, multiparous Holstein cows were surgically fitted with catheters in both external iliac arteries. Animals were infused into one arterial catheter with five different solutions on 5 consecutive days in a Latin square design. Infusions began at 0800 h and continued until 1800 h. The five infusates were a 3% saline control, 15 g/h of complete amino acid mix, 15 g/h of imbalanced amino acid mix (minus His), 30 g/h of complete amino acid mix, and 30 g/h of imbalanced amino acid mix (minus His). Cows were fed a total mixed ration twice daily containing 16% crude protein and 1.7 Mcal/kg of net energy for lactation. Infusion of the complete amino acid mix elevated amino acid concentrations in arterial plasma two- to threefold but caused only a small dose-dependent increase in milk protein content and yield. Fat percentage in milk was decreased from 4.08 to 3.35% by the complete amino acid infusions so that the protein:fat ratio climbed from 0.76 on the control to 0.99 with 30 g/h of amino acid. Removal of His from the infusate caused plasma His concentrations to drop but had no effect on any other circulating amino acids. Milk composition was restored to control levels by removal of the single amino acid. A short-term circulating amino acid imbalance depresses milk protein percentage and increases milk fat content in dairy cows.

Amino Acids↗
PubMed2001

Human lens thioltransferase: cloning, purification, and function.

PURPOSE: To clone the human lens thioltransferase (TTase) gene and to purify, characterize and study the possible function of the recombinant human lens thioltransferase (RHLT). METHODS: The human lens TTase gene was cloned by using RT-PCR and verified by sequence and RNase protection assay. TTase overexpressed in Escherichia coli was isolated and purified to homogeneity by column chromatography and identified by Western blot analysis. The activity was assayed with a synthetic substrate hydroxyethyl disulfide. Its function in dethiolating and reactivating other key metabolic enzymes was studied by using pure glutathione S:-transferase (GST) and glutathione peroxidase (GPx) from commercial source and also with the cell extract of rabbit lens epithelial cells preexposed to H2O2. RESULTS: The cloned human lens TTase gene showed identical sequence to the TTase gene from other human tissues. The RNase protection assay displayed a single transcript from the total RNA of human lens epithelial cells. The purified RHLT had a molecular weight of 11.8 kDa and reacted positively with anti-pig liver TTase. It displayed similar structural, functional, and kinetic characteristics to those of TTases from other sources. It was shown that RHLT effectively regenerated the activities of GST and GPx, after each was inactivated by S-thiolation with cystine in vitro. Furthermore, RHLT was able to restore the activity of the oxidatively inactivated glyceraldehyde-3-phosphate dehydrogenase (G-3PD) in H2O2-exposed rabbit lens epithelial cells. CONCLUSIONS: The human lens TTase gene has been cloned for the first time. Its gene product showed the characteristics which support our speculation that TTase may play a major role in maintaining the homeostasis of lens protein thiols thus protecting against oxidative stress.

Amino Acid Sequence↗
PubMed2000

Modulation of lens glycolytic pathway by thioltransferase.

The observation that the level of S-thiolated proteins (protein-thiol mixed disulfides) was transiently increased in the lens epithelial cells correlation with the transient inactivation of glyceraldehyde-3-phosphate dehydrogenase (G-3PD), a key glycolytic enzyme, when the cells were treated with a bolus of hydrogen peroxide, prompted our speculation that G-3PD may have been transiently thiolated at the SH sensitive active center. In the meantime, thioltransferase (TTase), a thiol regulating enzyme, whose activity remained constant under the same condition, may be regulating G-3PD and other sulfhydryl-sensitive glycolytic enzymes through thiol-disulfide exchange reactions ( Lou et al., 1998 ). To prove this hypothesis, several purified glycolytic enzymes from a commercial source, including hexokinase (HK), G-3PD, pyruvate kinase (PK) and fructose 1,6-bisphosphatase (FBPase), an enzyme in gluconeogenesis, were made into protein-thiol mixed disulfide and used for this study. Glycolytic enzymes in cultured rabbit lens epithelial cells pre-exposed to H(2)O(2)(0.5 m M for 15 min) were also studied for this purpose. Recombinant human lens thioltransferase (RHLT), which was isolated and purified previously in this laboratory, reactivated these pure glycolytic enzymes inactivated by forming protein-S-S-gluthathione (PSSG), protein-S-S-cysteine (PSSC) or, protein-S-S-cysteamine after thiolating with oxidized glutathione, cystine or cystamine respectively. RHLT also reactivated these enzymes in the cell extract of cultured rabbit lens epithelial cells after being briefly exposed to 0.5 m M H(2)O(2). The S-thiolation and dethiolation of FBPase however, showed an opposite effect to that of glycolytic enzymes. These results suggest that TTase may participate in the repair process of glycolytic enzymes during oxidative stress and restore their activities in situ.

Adenosine Triphosphate↗
PubMed2000

Preliminary study on the cleavage of fusion protein GST-CMIV with palladium(II) complex.

A novel method for post-treatment of gene-engineered proteins is reported. A coden of Cys-His unit is introduced into the N-terminal of cecropin CMIV by using PCR. The gene is expressed in E. coli fused with GST. After purification, the fusion protein is cleaved by [Pd(en)(H2O)2]2+ at the His-Arg bond and the cecropin CMIV with antibacterial activity is obtained. The preliminary results held some promise of success for application of the palladium(II) complex as cleavage agent for the production of peptide drugs from gene-engineering fusion proteins.

Anti-Bacterial Agents↗
PubMed1999

Does glutathione-S-transferase dethiolate lens protein-thiol mixed disulfides?-A comparative study with thioltransferase.

Protein S-thiolation is a process in which under oxidative stress, vulnerable sulfhydryl groups of proteins are conjugated to non-protein thiols such as glutathione (GSH) or cysteine resulting in the formation of protein-thiol mixed disulfides, protein-S-S-glutathione (PSSG) and protein-S-S-cysteine (PSSC). This process spontaneously disrupts the redox homeostasis of the cells, which in turn leads to functional disturbances in the respective tissue. In the ocular lens, such modification of proteins may trigger a cascade of events starting with the alteration of protein conformation, protein/enzyme deactivation, protein-S-S-protein aggregation and eventually lens opacification or cataract. Generally, the first line of defense system in the cells protects the lens proteins against such damage. Recent studies in our laboratory have shown that in addition to this defense system, lens cells also possess a well developed system to repair the oxidative damage to the lens proteins. We have identified this repair system as thioltransferase (TTase) and have proved that TTase by its dethiolase activity reverses the protein S-thiolation process which returns the oxidatively damaged lens proteins/enzymes to their original reduced state and restores their physiological functions. We investigated if this repair mechanism was mediated by enzymes other than TTase. We studied glutathione S-transferase (GST) and report here for the first time the cloning, high level expression, and purification of human lens mu and pi isoforms of GST. A comparative study of recombinant human lens TTase and GST (mu and pi) on their dethiolating abilities using lens crystallin-thiol mixed disulfides showed that the lens TTase is 60-70% more efficient in the dethiolation/repair process than GST. When TTase and GST were tested in conjunction for the dethiolation of thiol mixed disulfides, there was no significant enhancement of dethiolase activity. These findings suggest that TTase by itself is an efficient enzyme in the dethiolation/repair process and hence can be considered a crucial system to counteract oxidative stress in the lens.

Amino Acid Sequence↗
PubMed1998

Cloning, high level-expression and characterization of human lens thioltransferase.

Polymerase chain reaction (PCR) primers, directed against the nucleotide sequence of pig liver thioltransferase (PLTT) were used to amplify human lens thioltransferase (HLTT) from a pool of human lens cDNA. The 520 bp PCR fragment obtained was cloned unidirectionally into pCR 3.1-Uni vector and sequenced. The cDNA sequence of the lens thioltransferase had 98% and 87% homology to pig liver and human placental thioltransferases (TTase) respectively. Nhe1 and EcoR1 fragment of the recombinant PCR 3.1-Uni vector was subcloned in pET 23a Expression vector. High level expression of HLTT was accomplished in Escherichia coli and the expressed protein was characterized by immunoblot analysis with anti PLTT and N-terminal amino acid sequence analysis. The recombinant enzyme efficiently dethiolated protein thiol mixed disulfides conjugated to both cystine (PSSC) and glutathione (PSSG) and had a significant dehydroascorbate reductase activity. Human lens thioltransferase thus displayed structural and functional characteristics identical to pig liver and human placental thioltransferases.

Amino Acid Sequence↗
PubMed1996

Modified ligands to FA and FB in photosystem I. Proposed chemical rescue of a [4Fe-4S] cluster with an external thiolate in alanine, glycine, and serine mutants of PsaC.

The FB and FA electron acceptors in Photosystem I (PS I) are [4Fe-4S] clusters ligated by cysteines provided by PsaC. In a previous study (Mehari, T., Qiao, F., Scott, M. P., Nellis, D., Zhao, J., Bryant, D., and Golbeck, J. H. (1995) J. Biol. Chem. 270, 28108-28117), we showed that when cysteines 14 and 51 were replaced with serine or alanine, the free proteins contained a S = 1/2, [4Fe-4S] cluster at the unmodified site and a mixed population of S = 1/2, [3Fe-4S] and S = 3/2, [4Fe-4S] clusters at the modified site. We show here that these mutant PsaC proteins can be rebound to P700-FX cores, resulting in fully functional PS I complexes. The low temperature EPR spectra of the C14XPsaC.PS I complexes (where X = S, A, or G) show the photoreduction of a wild-type FA cluster and a modified FB' cluster, the latter with g values of 2.115, 1.899, and 1.852 and linewidths of 110, 70, and 85 MHz. Since neither alanine nor glycine contains a suitable side group, an external thiolate provided by beta-mercaptoethanol has likely been recruited to supply the requisite ligand to the [4Fe-4S] cluster. The EPR spectrum of the C51SPsaC.PS I complex differs from that of the C51APsaC.PS I or C51GPsaC.PS I complexes by the presence of an additional set of resonances, which may be derived from the serine oxygen-ligated cluster. In all other mutant PS I complexes, a wild-type spin-coupled interaction spectrum appears when FA and FB are simultaneously reduced. Single turnover flash studies indicate approximately 50% efficient electron transfer to FA/FB in the C14SPsaC.PS I, C51SPsaC.PS I, C14GPsaC.PS I, and C51GPsaC.PS I mutants and less than 40% in the C14APsaC.PS I and C51APsaC.PS I mutants, compared with approximately 76% in the PS I core reconstructed with wild-type PsaC. These data are consistent with the measurements of the rates of cytochrome c6-NADP+ reductase activity, indicating lower rates in the alanine mutants. It is proposed that the chemical rescue of a [4Fe-4S] cluster with a recruited external thiolate at the modified site allows the mutant PsaC proteins to rebind to PS I and to function in forward electron transfer.

Alanine↗
PubMed1995

Modified ligands to FA and FB in photosystem I. I. Structural constraints for the formation of iron-sulfur clusters in free and rebound PsaC.

Cysteines 14, 21, 34, 51, or 58 in PsaC of photosystem I (PS I) were replaced with aspartic acid (C21D and C58D), serine (C14S, C34S, and C51S), and alanine (C14A, C34A, and C51A). When free in solution, the C34S and C34A holoproteins contained two S = 1/2 ground state [4Fe-4S] clusters; all other mutant proteins contained [3Fe-4S] clusters and [4Fe-4S] clusters; in addition, there was evidence in C14S, C51S, C14A, and C51A for high spin (S = 3/2) [4Fe-4S] clusters, presumably in the modified site. These findings are consistent with the assignment of C14, C21, C51, and C58, but not C34, as ligands to FA and FB. The [4Fe-4S] clusters in the unmodified sites in C14S, C51S, C14A, and C51A remained highly electronegative, with Em values ranging from -495 to -575 mV. The [3Fe-4S] clusters in the modified sites were driven 400 to 450 mV more oxidizing than the native [4Fe-4S] clusters, with Em values ranging from -98 mV to -171 mV. A C14D/C51D double mutant contains [3Fe-4S] and S = 1/2 [4Fe-4S] clusters, showing that the 3Cys.1Asp motif is also able to accommodate a low spin cubane. When C34S, C34A, C14S, C51S, C14A, and C51A were rebound to P700-FX cores, electron transfer to FA/FB was regained, but functional reconstitution has not yet been achieved for C21D, C58D, or C14D/C51D. These data imply that PsaC requires two iron-sulfur clusters to refold, one of which must be a cubane. Since two [4Fe-4S] clusters are found in all reconstituted PS I complexes, the presence of two cubanes in free PsaC may be a necessary precondition for binding to P700-FX cores.

Amino Acid Sequence↗
PubMed1995

[Uteroplacental blood flow monitoring by color Doppler flow imaging in pregnancy induced hypertension].

The uteroplacental blood flow was monitored using color Doppler flow imaging (CDFI) in 31 cases of pregnancy induced hypertension (PIH) and 71 cases of normal pregnancy. At the same time the values of serum estriol (E3), human placental lactogen (hPL), thromboxane (TXB2), 6-KP and TXB2/6-KP ratio were measured. The results showed that time average velocity (TAV) and volume of blood flow (Q) of uterine and umbilical arteries in PIH cases were much lower than those in normal pregnant women and fetuses (P < 0.05). After treatment with magnesium sulfate and qingxintong there was a marked improvement in placental blood flow. TAV and Q of uterine and umbilical arteries was also increased (P < 0.05). In PIH cases the E3 and hPL levels were much lower, while the ratio of TXB2/6-KP was significantly higher than that in normal pregnancy. Using CDFI to observe the velocity and volume of uteroplacental blood flow can monitor the blood supply of uterus and placenta. It is a valuable predictive index of fetal and placental function.

Acetophenones↗
PubMed1990

Ring chromosome 21 transmitted from mother to daughter: its stability in a lymphoblastoid cell line.

A female infant with a high-pitched cry and hypertelorism but an otherwise normal facies was found to have the karyotype 46,XX,r(21)(p11.2q22.3). The r(21) was transmitted from the phenotypically normal mother. In both cases, the structure and behavior of the r(21) were rather stable in peripheral lymphocyte cultures. This stable nature of the r(21) was also confirmed in a lymphoblastoid cell line derived from the proband, where the normal-sized r(21) was persistent in most cells in prolonged culture for at least 5 months.

Abnormalities, Multiple↗