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L Chan

Publications and source records attributed to L Chan.

At least 397 records · Page 22Linked to original sources
PubMed1987

Chicken apolipoprotein A-I: cDNA sequence, tissue expression and evolution.

Using an antibody against chicken apolipoprotein (apo) A-I, we identified multiple cDNA clones for the protein in two intestinal cDNA libraries in lambda gt11. The complete nucleotide sequence of chicken apoA-I cDNA was determined. The sequence predicts a mature protein of 240 amino acids, a 6-amino acid propeptide and an 18-amino acid signal peptide. Using a 32P-cDNA probe, we detected the presence of apoA-I mRNA in 21 day old chicken intestine, liver, kidney, spleen, breast muscle and brain. The primary sequence of apoA-I contains numerous tandem repeats of 11 and 22 residues in a manner similar to the mammalian proteins. Our analysis of apoA-I sequences from human, rabbit, dog, rat, and chicken indicates that the rate of amino acid substitution is considerably faster in the rat lineage than in other mammalian lineages.

Amino Acid Sequence↗
PubMed1987

Structure and expression of dog apolipoprotein C-II and C-III mRNAs. Implications for the evolution and functional constraints of apolipoprotein structure.

The complete cDNAs for canine apolipoprotein (apo) C-II and C-III have been cloned in the plasmid vector, pUC-18, and the phage vector, lambda gt11. With 32P-labeled nick-translated cDNAs as hybridization probes, apoC-II and apoC-III mRNAs were found to be expressed in canine liver, jejunum, ileum, colon, pancreas, spleen, ovary, and bladder at the following relative concentrations: 100, 35, 30, 10, 15, 5, 30, and 2% for apoC-II, and 100, 35, 15, 2, 20, 5, 30, and 5% for apoC-III. Neither mRNA was detected in canine brain, kidney, lung, muscle, oviduct, uterus, or testis. Both mRNAs are approximately 700 nucleotides in length. Complete sequence analysis revealed that apoC-II mRNA codes for a protein of 101 amino acid residues including 22 residues in the signal peptide and 79 residues in the mature peptide region. ApoC-III mRNA codes for a protein of 100 amino acid residues, including 20 in the signal peptide and 80 residues in the mature peptide region. It contains a single cysteine residue in position 54. Secondary structural analysis shows the presence of two regions each of amphipathic helix for apoC-II (residues 14-33 and 44-63) and apoC-III (residues 16-33 and 50-69). Computer analysis of the amphipathic helical regions demonstrates the importance of variation in the dihedral angles of the side chains in the charge microenvironment of the helices. Statistical analysis of sequence similarities between human apoC-II, apoC-III, apoA-II, apoA-I, apoE, and apoA-IV, and dog apoC-II and apoC-III, and rat apoC-III, apoA-II, apoA-I, apoE, and apoA-IV indicates that all these proteins have evolved rapidly, especially in the rat in which apoC-III has evolved at three times the rate in man and dog. Further, the shorter apolipoproteins, apoA-II, apoC-II, and a-poC-III, have evolved more rapidly than the longer ones, apoA-I, apoE, and apoA-IV. Some regions in the individual apolipoproteins are better conserved than others. The rate of evolution of individual regions seems to be related to the stringency of their functional requirements.

Amino Acid Sequence↗
PubMed1987

Atrial natriuretic factor (ANF) levels are elevated in rats bearing rejecting heart-lung allografts.

Intra-abdominal heart-lung grafts were transplanted into 8 rats across a major histocompatibility barrier. Four of the 8 rats were treated with Cyclosporin A (CsA) to prevent rejection. Atrial natriuretic factor (ANF) levels measured 6 days after transplantation revealed a significantly (p less than .005) higher mean ANF concentration in rats bearing a rejecting heart-lung allograft (642 +/- 148.0 pg/ml) compared to rats bearing a heart-lung allograft not undergoing rejection (200.8 +/- 13.07 pg/ml). ANF might be a useful noninvasive marker in the diagnosis of rejection in heart and heart-lung transplants.

Animals↗
PubMed1987

Rotavirus gastroenteritis. Clinical and laboratory features and use of the Rotazyme test.

Clinical and laboratory features of 86 infants admitted with diarrhea and dehydration were evaluated prospectively. Human rotavirus (HRV) infection was documented in 35 infants (41%) by the Rotazyme test. Those with HRV gastroenteritis (HRV+ group) had a shorter duration of diarrhea prior to admission, more severe dehydration on presentation, and a longer hospital course than the HRV-negative (HRV-) group. Vomiting, fever, upper respiratory tract symptoms, otitis media, and cough were present in equal numbers of infants in both groups. The HRV+ infants had lower serum bicarbonate and higher serum albumin, alanine aminotransferase, aspartate aminotransferase, and uric acid concentrations than did the HRV- infants. Serum uric acid levels greater than 10 mg/dL (590 mumol/L) were present in 69% of HRV+ vs 29% of HRV- infants. The Rotazyme test was found to be a valuable tool in diagnosis; testing on two days increased the yield from 74% to 97% of all infants finally diagnosed as HRV+. The optimal time for testing was within the first five days of illness.

Diarrhea, Infantile↗
PubMed1987

31P nuclear magnetic resonance study of acute renal dysfunction in rat kidney transplants.

31P NMR spectroscopy was used to study renal allografts in rats subjected to allograft rejection, cyclosporine toxicity, ischemia, and ureteral obstruction. Parameters of relative peak areas and intracellular pH were accurately distinguished among the different causes of graft dysfunction. Ureteral obstruction was clearly identified by elevations in the phosphodiester/urine phosphate peak. Ischemia and rejection were both associated with increases in inorganic phosphates and phosphomonesters and decreases in the beta-phosphate peak of adenosine triphosphate but were distinguishable from each other by differences in intracellular pH which was normal in rejected allografts (7.33 +/- 0.07, n = 3) but low in ischemic allografts (7.00 +/- 0.05, n = 3, P less than 0.05). Grafts insulted with cyclosporine toxicity were not distinguishable from normal allografts by any of the parameters studied. These data suggest that 31P NMR spectroscopy may have potential clinical application in differentiating among the causes of graft failure of human renal allografts.

Animals↗
PubMed1987

Comparison of the natriuretic response to atriopeptin III and loop diuretic in the isolated perfused rat kidney.

1. Isolated rat kidneys were perfused at a constant perfusion pressure of 90 mmHg to study the natriuretic effects of atriopeptin III (AP-III) and to compare these effects with those of frusemide. AP-III (1 microgram) or frusemide (1 mg) were added to the perfusate (100 ml) after two 15 min control collection periods. 2. Compared with the control group, AP-III and frusemide increased urinary sodium excretion (UNa V, 5.6 +/- 1.1 and 4.6 +/- 0.6 vs control 1.8 +/- 0.3 mumol min-1 g-1, mean +/- SEM, P less than 0.01 and P less than 0.05, respectively), fractional sodium excretion (FENa, 4.8 +/- 1.1 and 6.7 +/- 0.8 vs control 2.0 +/- 0.2%, P less than 0.05 and P less than 0.001, respectively) and potassium excretion (UKV, 3.2 +/- 0.3 and 3.0 +/- 0.3 vs control 1.5 +/- 0.3 mumol min-1 g-1, both P less than 0.01). However, AP-III, but not frusemide, increased glomerular filtration rate (820 +/- 55 vs 590 +/- 24 microliter min-1 g-1, P less than 0.01) and urine flow rate (V 97.5 +/- 8.0 vs 44.1 +/- 5.2 microliter min-1 g-1, P less than 0.001). Calculated distal delivery of sodium (CNa +/- CH2O, 76.6 +/- 6.8 vs 30.7 +/- 3.8 microliter min-1 g-1, P less than 0.005) as well as fractional distal delivery of sodium [(CNa +/- CH2O)/CIn, 9.4 +/- 0.9 vs 5.1 +/- 0.6%, P less than 0.01] were increased by AP-III, but not frusemide.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

P-31 nuclear magnetic resonance spectroscopic evaluation of heterotopic cardiac allograft rejection in the rat.

P-31 nuclear magnetic resonance (NMR) spectroscopy was used to evaluate heterotropic cardiac allograft rejection in the rat. To enable optimal application of NMR spectroscopy for the in vivo study of myocardial metabolism in the transplanted organ, an accessory heart transplantation to groin in the rat was used. The allografts were studied in a 1.89 Tesla horizontal bore magnet. Each spectrum was obtained by Fourier transform of 512 scans using 60-degree pulses with 2-sec delays. Changes in phosphocreatine (PCr), adenosine 5-triphosphate (ATP), and inorganic phosphate (Pi) and intracellular pH as determined by P-31 NMR were compared with rejection process as judged by histological studies. Allografts treated with cyclosporine (CsA) did not show any rejection (NR) and had relatively high levels of PCr, and low levels of Pi. Allografts that did not receive any CsA revealed both vascular and cellular rejection. These rejected allografts (R) had relatively low levels of PCr and high levels of Pi. It is concluded that P-31 NMR spectroscopy may have potential application to the clinical diagnosis of cardiac allograft rejection.

Adenosine Triphosphate↗
PubMed1987

Role of beta-lactamase in in vivo development of ceftazidime resistance in experimental Pseudomonas aeruginosa endocarditis.

Two ceftazidime-resistant variants of Pseudomonas aeruginosa (PA-48, PA-60), obtained from cardiac vegetations of rabbits with endocarditis receiving ceftazidime therapy, were studied for mechanisms of resistance. Both resistant variants were stably derepressed for the type Id beta-lactamase, which was ceftazidime inducible in the parental strain (PA-96) used to initially infect the rabbits. There was no evidence of ceftazidime bioinactivation by the resistant strains, and their outer membrane permeabilities were comparable to those of the parental strain. No alterations were observed in patterns of outer membrane proteins or membrane lipopolysaccharides in the resistant variants as compared with the parental strain. Penicillin-binding protein patterns of the resistant variants revealed the absence of penicillin-binding protein 4 in both, with acquisition of a new protein of higher apparent molecular weight in PA-60. Calculation of the rate of appearance of ceftazidime in the periplasm at sub-MICs suggested that slow enzymatic hydrolysis of the beta-lactam, rather than nonhydrolytic trapping, was the major explanation for the induced resistance in vivo in strains PA-48 and PA-60.

Animals↗
PubMed1987

In vitro and in vivo protective effect of atriopeptin III on ischemic acute renal failure.

The effect of atriopeptin III (AP-III) on ameliorate ischemic acute renal failure was first examined in the isolated perfused kidney. Isolated rat kidneys were clamped for 1 h and reperfused for 30 min without therapy and then perfused with either 0 (control) or 100 micrograms/dl AP-III. In this system AP-III significantly improved renal plasma flow (39.6 +/- 2.4 vs. 32.2 +/- 2.1 ml/min per g; P less than 0.05) inulin clearance (182.6 +/- 49.2 vs. 24.6 +/- 6.2 microliters/min per g; P less than 0.05), urine flow (52.9 +/- 12.1 vs. 7.1 +/- 0.8 microliters/min per g, P less than 0.01), and net tubular sodium reabsorption (21.2 +/- 6.6 vs. 2.9 +/- 0.9 mumol/min per g, P less than 0.05) as compared with control. A second series of in vivo studies experiments were performed using 1 h of bilateral renal artery clamping followed by an intravenous infusion of either saline alone (control) or AP-III (0.20 microgram/kg per min) for 60 min. The results demonstrated that inulin clearance (244.4 +/- 25.1 vs. 15.8 +/- 8.2 microliters/min per 100 g; P less than 0.01), urine flow (23.1 +/- 5.9 vs. 1.1 +/- 0.5 microliters/min per 100 g; P less than 0.01), and net tubular sodium reabsorption (38.9 +/- 4.7 vs. 4.3 +/- 1.6 mumol/min per 100 g; P less than 0.01) were significantly higher in AP-III-treated rats than controls during the hour of AP-III infusion. In 1 h posttreatment study this significant protective effect of AP-III was documented to persist. In more chronic studies animals treated acutely with AP-III had lower serum creatinine concentration at 24 h (1.8 +/- 0.3 vs. 3.3 +/- 0.4 mg/dl; P less than 0.01) and 48 (1.0 +/- 0.2 vs. 2.4 +/- 4.0 mg/dl; P less than 0.01) after the 60 min of ischemia than controls. Renal adenosine triphosphate regeneration as assessed by P-31 nuclear magnetic resonance during reflow was also significantly improved in AP-III-treated animals at 1 h (3.03 +/- 0.30 vs. 1.45 +/- 0.40 mumol/g dry wt; P less than 0.05) and 2 h (3.98 +/- 0.46 vs. 1.80 +/- 0.05 mumol/g dry wt; P less than 0.01) or reflow as compared with control rats. Thus, AP-III significantly ameliorates ischemic acute renal failure both in vitro and in vivo in the rat.

Acute Kidney Injury↗
PubMed1987

P-31 nuclear magnetic resonance spectroscopic study of obstructive uropathy in the rat.

P-31 nuclear magnetic resonance (NMR) spectroscopy of the rat kidney with ureteral ligation resulted in a rapid and major increase in a peak resonating at 7096.63 +/- 0.65 Hz from the reference frequency of phosphorus (32.60 MHz). This corresponded to an increase in the concentration of the substance responsible for peak X from 0.34 +/- 0.04 mumol/g wet weight in normal kidneys to 1.45 +/- 0.27 mumol/g wet weight in unilaterally obstructed kidneys and 2.00 +/- 0.34 mumol/g wet weight in bilaterally obstructed kidneys at 3 h (P less than 0.01). Further NMR studies performed with in vivo kidneys and tissue extracts revealed that inorganic phosphate in the urine, resonating at a lower frequency due to the acid pH environment, was responsible for the increase in this peak. These findings may prove to be of fundamental interest as well as potential clinical significance.

Adenosine Triphosphate↗
PubMed1987

Human apolipoprotein B: analysis of internal repeats and homology with other apolipoproteins.

Apolipoprotein B (apoB) is the major protein component of plasma low density lipoproteins (LDL) and, through its binding to the LDL receptor, it plays a prominent role in lipoprotein metabolism and in the development of atherosclerosis. Specially developed computer programs were applied to detect potential internal repeats in the human apoB sequence and homology of some of these repeats with other apolipoproteins. The simultaneous computer alignment of several (repeated) sequences, carried out in an iterative way to generate consensus sequences, showed the presence of repeated amphipathic helical regions and of repeated hydrophobic proline-rich domains. Extensive Monte-Carlo statistics were used to demonstrate the statistical significance of the internal repeats. Both classes of repeats may contribute to the specific lipid-binding characteristics of apoB. Additional homology, detected between apoB and apoE, the other apolipoprotein-ligand of the LDL receptor, further defined the structural requirements for this receptor-ligand interaction. The computer programs developed in this study should also be useful for detecting internal repeats in other proteins.

Amino Acid Sequence↗
PubMed1987

Effects of adenosine triphosphate depletion in the isolated perfused rat kidney.

Glycerol or fructose (40 mM) was added to the control perfusate and renal function was observed in the isolated perfused rat kidney during nonischemic perfusions or perfusions following 30 min of clamp ischemia. Addition of glycerol or fructose resulted in lowering adenosine triphosphate (ATP) levels to 62 and 35%, respectively, of levels achieved with control perfusate under nonischemic conditions (p less than 0.01). Total adenine nucleotides (TAN) were also lowered to 67% with glycerol and 61% with fructose of control values under nonischemic conditions (p less than 0.05). However, physiologic parameters of renal plasma flow and inulin clearance were essentially unaffected by either glycerol or fructose. Following ischemia, glycerol and fructose reduced ATP levels to 51 and 37% and TAN levels to 67 and 65%, respectively, of values seen with control perfusate. However, recovery of renal plasma flow and inulin clearance were uneffected by the addition of either glycerol or fructose. Thus, a 33-65% reduction in renal tissue ATP by glycerol or fructose does not appear to have a deleterious effect on organ function in the basal state or during recovery from an ischemic insult in the isolated perfused rat kidney.

Adenine Nucleotides↗
PubMed1986

Determination of the molecular mass of apolipoprotein B-100. A chemical approach.

Apolipoprotein B-100 (apo B-100) is the protein ligand in low-density lipoproteins that binds to a specific cell-surface receptor. Its molecular mass has been a subject of controversy. We have determined the molecular mass of the protein by a chemical approach. After complete CNBr cleavage, the C-terminal fragment of apo B-100 was purified by reverse-phase h.p.l.c. Amino acid N- and C-terminal analyses confirm that this peptide represents the C-terminal peptide as deduced from the DNA sequence of a human apo B-100 cDNA clone. A chemically synthesized peptide was used to determine the recovery of the peptide (74.72%). On the basis of these data, the molecular mass of apo B-100 was determined to be 496.82 +/- 24.84 kDa.

Amino Acid Sequence↗
PubMed1986

Changes in apolipoprotein A-I mRNA level in the liver of rats with experimental nephrotic syndrome.

In previous studies we had shown that: one of the most specific feature of hyperlipoproteinemia found in rats with experimental nephrotic syndrome is the accumulation of apolipoprotein A-I-rich HDL in plasma and this disorder is associated with an overproduction of apolipoprotein A-I by the liver. The present study was designed to investigate whether the increased hepatic synthesis of apolipoprotein A-I was due to an accumulation of functionally active apolipoprotein A-I mRNA in liver of nephrotic rats. Hepatic mRNA was translated in vitro by rabbit reticulocyte lysate in the presence of [35S]methionine and in vitro synthesized apolipoprotein A-I, albumin and apolipoprotein E were immunoprecipitated by specific rabbit IgG. In nephrotic rats the amount of in vitro synthesized apolipoprotein A-I was almost twice that found in the controls, suggesting that functionally active apolipoprotein A-I mRNA was increased in liver of nephrotic rats. To confirm that this difference in apolipoprotein A-I mRNA activity was due to an actual increase of hepatic apolipoprotein A-I mRNA sequences, we performed nucleic acid hybridization experiments (northern blot) using several cloned cDNA probes (rat and human apolipoprotein A-I, rat apolipoprotein E and apolipoprotein A-II). The results indicate that in nephrotic rats the amount of hybridizable apolipoprotein A-I mRNA sequences was about 3-fold higher than that in controls. In contrast, there was no difference in the amount of hybridizable apolipoprotein A-II and apolipoprotein E mRNA sequences, indicating that the change in apolipoprotein A-I mRNA induced by the nephrotic state was specific for this mRNA.

Animals↗
PubMed1986

The complete cDNA and amino acid sequence of human apolipoprotein B-100.

We have determined the complete sequence of apolipoprotein (apo) B-100 cDNA. It is 14.1 kilobases in length and codes for a 4563-amino acid protein, including a 27-amino acid signal peptide and a 4536-amino acid mature protein. Further, we identified 2366 residues of apoB-100 by direct sequence analysis of apoB-100 tryptic peptides. The mature peptide is characterized by high hydrophobicity (0.916 kcal/residue) and predicted beta-sheet content (21%). Dot matrix analysis revealed the presence of many long internal repeats in apoB-100. The mature peptide contains 25 cysteine residues, 12 of which are in the N-terminal 500 residues. Twenty potential N-linked glycosylation sites were identified, of which 13 were proven to be glycosylated, and 4 were found not to be glycosylated by direct analysis of tryptic peptides. Our findings on apoB structure provide a basis for future experimentation on the role of apoB-100-containing lipoproteins in atherosclerosis.

Amino Acid Sequence↗
PubMed1986

Structure and evolution of the apolipoprotein multigene family.

We present the complementary DNA and deduced amino acid sequence of rat apolipoprotein A-II (apoA-II), and the results of a detailed statistical analysis of the nucleotide and amino acid sequences of all the apolipoprotein gene sequences published to date: namely, those of human and rat apoA-I, apoA-II and apoE, rat apoA-IV, and human apoC-I, C-II and C-III. Our results indicate that the apolipoprotein genes have very similar genomic structures, each having a total of three introns at the same locations. Using the exon/intron junctions as reference points, we have obtained an alignment of the coding regions of all the genes studied. It appears that the mature peptide regions of these genes are almost completely made up of tandem repeats of 11 codons. The part of mature peptide region encoded by exon 3 contains a common block of 33 codons, whereas the part encoded by exon 4 contains a much more variable number of internal repeats of 11 codons. These genes have apparently evolved from a primordial gene through multiple partial (internal) and complete gene duplications. On the basis of the degree of homology of the various sequences, and the pattern of the internal repeats in these genes, we propose an evolutionary tree for the apolipoprotein genes and give rough estimates of the divergence times between these genes. Our results show that apoA-II has evolved extremely rapidly and that apoA-I and apoE also have evolved at high rates but some regions are better conserved than the others. The rate of evolution of individual regions seems to be related to the stringency of their functional requirements.

Amino Acid Sequence↗