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Biomedical subjects

L Huang

Publications and source records attributed to L Huang.

At least 415 records · Page 23Linked to original sources
PubMed1996

Role of calf RTH-1 nuclease in removal of 5'-ribonucleotides during Okazaki fragment processing.

The role of the exonucleolytic activity of the calf 5' to 3' exo/endonuclease, a RAD2 homolog 1 (RTH-1) class nuclease, in lagging-strand DNA replication has been examined using model Okazaki fragment substrates. These substrates exemplify the situation in Okazaki fragment processing which occurs after the initiator RNA primer is cleaved off, and released intact, by calf RNase HI, leaving a single ribonucleotide at the 5' end of the RNA-DNA junction. This final RNA is then removed by the calf RTH-1 nuclease [Turchi et al. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 9803-9807]. The cleavage specificity of calf RTH-1 nuclease for different junction ribonucleotides was compared. These were removed without the usual requirement of calf RTH-1 for an immediately adjacent upstream primer. In most cases, the presence of an upstream DNA or RNA primer, separated from the monoribonucleotide-DNA segment by either a nick or a gap, reduced the efficiency of removal of the monoribonucleotide compared to the removal seen with no upstream primer. Substrates in which the monoribonucleotide-DNA segment had been replaced by an oligomer of the same sequence but consisting entirely of DNA also exhibited upstream primer inhibition. Results with various sequences indicated that the upstream primer is generally inhibitory for ribonucleotide removal but is sometimes neutral. For deoxynucleotide removal it could be stimulatory, neutral, or inhibitory. Possible reasons for the unexpected lack of upstream primer dependence have been explored. The ratio of RNase HI to RTH-1 was also shown to be critical for both enzymes to work together efficiently. These results suggest that regions of upstream primer inhibition within the genome may play a role in determining the mechanism by which mammalian Okazaki fragments are processed.

Animals↗
PubMed1996

A resonance Raman study of the C=N configurations of octopus rhodopsin, bathorhodopsin, and isorhodopsin.

The resonance Raman spectra of octopus rhodopsin, bathorhodopsin, and isorhodopsin at 120 K have been obtained as well as those of pigments regenerated with isotopically labeled retinals near the C14-C15 bond. Deuteration of the Schiff base nitrogen induces relatively large changes in the C-C stretch region between 1100 and 1300 cm-1, including a large frequency shift of the C14-C15 stretch mode located at 1206-1227 cm-1 in the three octopus species, as revealed by the Raman spectra of their 14,15-(13)C2 derivatives. Such results are different compared to those of the bovine pigments, in which no significant frequency shift of the C14-C15 stretch mode was observed upon Schiff base N deuteration. In an earlier Raman study of a Schiff base model compound which contained only one single bond adjacent to two double bonds, we have found that the stretch mode of this C-C single bond at 1232 cm-1 shifts up by 15 cm-1 and its intensity is also greatly reduced upon Schiff base N deuteration when the C=N configuration is anti [Deng et al., (1994) J. Phys. Chem. 98, 4776-4779]. The same study has also shown that when the C=N configuration is syn, the C-C stretch mode should be at about 1150 cm-1. Since the C14-C15 stretch mode frequency is relatively high in the spectra of octopus rhodopsin and bathorhodopsin (> 1200 cm-1) and since the normal mode pattern near the Schiff base is similar to the model, we suggest that the C=N configuration in these two species is anti. The different responses of the C14-C15 stretch mode to the Schiff base nitrogen deuteration in bovine and octopus pigments are due to the fact that the coupled C14-C15 stretch and the C12-C13 stretch motions in the model compound or in bovine rhodopsin are altered in octopus rhodopsin so that the stretch motion of the C14-15 bond is more localized, similar to the C-C stretch motion in the small Schiff base model compound. In clear contrast with the bovine rhodopsin Raman spectrum, which is very similar to that for the 11-cis-retinal Schiff base, the drastically different octopus rhodopsin spectrum indicates large protein perturbations on the C11=C12-C13 moiety, either by steric or by electrostatic interactions. Further studies are required to determine if such spectral differences indicate a difference of the energy conversion mechanism in the primary photochemical event of these two pigments.

Animals↗
PubMed1996

Biodistribution of clodronate and liposomes used in the liposome mediated macrophage 'suicide' approach.

Clodronate (Cl2MBP; dichloromethylene-bisphosphonate)-containing liposomes are used to investigate the role of macrophages in immune and non-immune defense mechanisms by elimination of these macrophages followed by functional studies. The present studies characterize such liposomes in terms of the leakage of clodronate and the biodistribution of both the encapsulated drug and the liposomal carrier. The distribution of liposomes was studied using a radioactively labelled lipid phase marker (111In-DTPA-SA) and the distribution of the encapsulated drug was examined following injection of radioactively labelled clodronate (99mTc-Cl2MBP). Furthermore, the biodistribution of variously composed multilamellar liposomes (EPC/Chol molar ratio 7:1.3 or 7:7; EPC/Chol/PS 7:1.3:1 or 7:7:1; EPC/Chol/M 7:2:1; EPC/Chol/M-PE 7:2:1) after intravenous injection was investigated. The findings suggest that only one third of the originally entrapped clodronate was still encapsulated in the liposomes at the time of ingestion by the macrophages in the liver and spleen after intravenous injection of the clodronate containing liposomes. 3 h after injection no clodronate could be detected in the circulation.

Animals↗
PubMed1996

Reaction of the C30A mutant of trimethylamine dehydrogenase with diethylmethylamine.

The role played by the 6-S-cysteinyl-FMN bond of trimethylamine dehydrogenase in the reductive half-reaction of the enzyme has been studied by following the reaction of the slow substrate diethylmethylamine with a C30A mutant of the enzyme lacking the covalent flavin attachment to the polypeptide. Removal of the 6-S-cysteinyl-FMN bond diminishes the limiting rate for the first of the three observed kinetic phases of the reaction by a factor of 6, but has no effect on the rate constants for the two subsequent kinetic phases. The flavin in the C30A enzyme recovered from the reaction of the C30A enzyme with excess substrate is found to have been converted to the 6-hydroxy derivative, rendering the enzyme inactive. The noncovalently bound FMN of the C30A mutant enzyme is also converted to 6-hydroxy-FMN and rendered inactive upon reduction with excess trimethylamine, but not by reduction with dithionite, even at high pH or in the presence of the effector tetramethylammonium chloride. These results suggest that one significant role of the 6-S-cysteinyl-FMN bond is to prevent the inactivation of the enzyme during catalysis. A reaction mechanism is proposed whereby OH- attacks C-6 of a flavin-substrate covalent adduct in the course of steady-state turnover to form 6-hydroxy-FMN.

Binding Sites↗
PubMed1996

Partial inhibition of Na+/K+-ATPase by ouabain induces the Ca2+-dependent expressions of early-response genes in cardiac myocytes.

Exposure of neonatal rat cardiac myocytes to ouabain concentrations that caused partial inhibition of Na+/K+-ATPase but no loss of viability, increased c-fos and c-jun mRNAs and the transcription factor AP-1. The increased mRNAs were proportional to the extent of inhibition of Na+/K+-ATPase and the resulting rise in steady state intracellular Ca2+ concentration. The rapid and sustained increase of c-fos mRNA was shown to be due to increased transcriptional rate. Induction of c-fos by ouabain was prevented when either extracellular or intracellular Ca2+ was lowered and was attenuated by pretreatment of myocytes with a phorbol ester under conditions known to down-regulate protein kinase C. Exposure to ouabain for 24-48 h also increased total transcriptional activity and protein content of myocytes. The findings suggest that the same signal responsible for the positive inotropic action of ouabain, i.e. net influx of Ca2+ caused by partial inhibition of Na+/K+-ATPase, also initiates the rapid protein kinase C-dependent inductions of the early-response genes, the subsequent regulations of other cardiac genes by the resulting transcription factors, and stimulation of myocyte growth. Whether these hitherto unrecognized effects of cardiac glycosides are obtained in the intact heart and their relevance to the therapeutic uses of these drugs remain to be determined.

Animals↗
PubMed1996

Folate-targeted, anionic liposome-entrapped polylysine-condensed DNA for tumor cell-specific gene transfer.

We have developed a lipidic gene transfer vector, LPDII, where DNA was first complexed to polylysine at a ratio of 1:0.75 (w/w) and then entrapped into folate-targeted pH-sensitive anionic liposomes composed of dioleoyl phosphatidylethanolamine (DOPE)/cholesteryl hemisuccinate/folate-polyethlene glycol-DOPE (6:4:0.01 mol/mol) via charge interaction. LPDII transfection of KB cells, a cell line overexpressing the tumor marker folate receptor, was affected by both the lipid to DNA ratio and the lipid composition. At low lipid to DNA ratios (e.g. 4 and 6), LPDII particles were positively charged; transfection and cellular uptake levels were independent of the folate receptor and did not require a pH-sensitive lipid composition. Meanwhile, transfection and uptake of negatively charged LPDII particles, i.e. those with high lipid to DNA ratios (e.g. 10 and 12), were folate receptor-dependent and required a pH-sensitive lipid composition. The transfection activity of LPDII was lost when the inverted cone-shaped DOPE was replaced by dioleoyl phosphatidylcholine. LPDII particles with lipid to DNA ratios of 4, 6, 10, and 12 were approximately 20-30 times more active than DNA.3-beta-[N-(N',N'-dimethylethane)carbamoyl]cholesterol cationic liposome complexes in KB cells and were much less cytotoxic. On the sucrose gradient, LPDII particles had a migration rate in between those of the free DNA and the DNA.polylysine complex. An electron micrograph of LPDII showed a structure of spherical particles with a positively stained core enclosed in a lipidic envelope with a mean diameter of 74 +/- 14 nm. This novel gene transfer vector may potentially be useful in gene therapy for tumor-specific delivery.

Anions↗
PubMed1996

Deletion and mutation analyses of the P16/MTS-1 tumor suppressor gene in human ductal pancreatic cancer reveals a higher frequency of abnormalities in tumor-derived cell lines than in primary ductal adenocarcinomas.

The putative tumor suppressor gene p16/CDKN2 encodes a specific inhibitor of cyclin D-cyclin-dependent kinase 4 complexes important in cell-cycle regulation and has been found to be deleted or mutated in a variety of human cancers. Thirty microdissected primary human ductal pancreatic carcinomas from patients not subject to radiotherapy or chemotherapy prior to surgical resection of their carcinomas and 18 human pancreatic carcinoma cell lines were analyzed by single-strand conformation polymorphism (SSCP) and DNA sequence analyses and PCR-based deletion analyses for mutations and homozygous deletions of the p16/CDKN2 gene, respectively. Homozygous deletions of the gene were found in five cell lines, and nonpolymorphic SSCP and DNA sequence alterations were found within exon 1 in four cell lines and exon 2 in three lines, for an overall frequency of deletions and mutations of 66%. In contrast, homozygous deletions of p16/CDKN2 were observed in three primary pancreatic carcinomas, and five primary tumors revealed SSCP and/or sequence abnormalities in exon 1 (one case) and exon 2 (four cases), a mutation and deletion frequency of 27%. Immunoblotting analyses confirmed the absence of p16/MTS-1 expression in actively proliferating cell lines with a homozygous deletion of the gene and low-to-moderate levels of p16/MTS-1 expression in cell lines possessing a normal RB-1 gene or protein. These findings suggest that, although p16/CDKN2 may play a role in the pathobiology of pancreatic cancer, inactivation of this putative tumor suppressor gene occurs more frequently in cell lines than in primary ductal pancreatic carcinomas.

Adenocarcinoma↗
PubMed1996

Potentiation of cationic liposome-mediated gene delivery by polycations.

We discovered that several high molecular weight cationic polymers, such as poly(L-lysine) and protamine, can enhance the transfection efficiency of several types of cationic liposomes by 2-28-fold in a number of cell lines in vitro. Small polycations such as spermine and a cationic decapeptide derived from SV40 T-antigen were only moderately active. The addition of poly(L-lysine) and protamine dramatically reduced the particle size of the complex formed between DNA and cationic liposomes and rendered DNA resistant to the nuclease activity. The complexes composed of DNA, poly(L-lysine), and cationic lipids were purified from an excess of free liposomes with sucrose gradient ultracentrifugation. Purified complex formed at low cationic liposome ratio was poor in lipid content and only had weak transfection activity. Addition of free liposome to the purified complex significantly enhanced the transfection activity. In contrast, complexes formed at a higher initial ratio of liposome to DNA had a higher lipid content and were highly active in transfection; the activity was about 3-9-fold more active than the corresponding complex before purification. Negative stain EM studies revealed that the most active complexes prepared from 40 nmol of lipid, 0.5 micrograms of poly(L-lysine), and 1 microgram of DNA and purified by gradient ultracentrifugation were spherical, electron dense, small (< 100 nm in diameter) particles, and some of them were associated with lipid membranes. These highly active, stable, small-sized lipid/poly(L-lysine)/DNA complexes represent a new class of nonviral gene delivery vehicles that might be useful in gene therapy.

Amino Acid Sequence↗
PubMed1996

Adsorption Behavior of Cationic and Nonionic Surfactant Mixtures at the Alumina-Water Interface.

The solution and interfacial behavior of surfactant mixtures was investigated using a cationic surfactant, tetradecyl trimethyl ammonium chloride (TTAC), and a nonionic surfactant, pentadecylethoxylated nonyl phenol (NP-15), with alumina as the substrate. The cationic TTAC adsorbed at the alumina-water interface as a result of electrostatic attraction at pH approximately 10 whereas the nonionic NP-15 did not. Interestingly, in the mixed surfactant system, the tetradecyl trimethyl ammonium chloride forced adsorption of the NP-15 as a result of hydrophobic interactions between the adsorbed surfactant chains at the alumina-water interface. The adsorption behavior was dependent upon the ratio of the two surfactants in the mixture as well as the order of addition. With an increase in TTAC content, the adsorption density of NP-15 increased and the isotherm shifted to lower surfactant concentrations. The adsorption of TTAC decreased under conditions of saturation adsorption due to the bulkiness of the coadsorbed NP-15 as well as competition for common adsorption sites. However, below saturation adsorption conditions, the adsorption of TTAC was increased due to synergistic interactions between the cationic and nonionic heads leading to reduced repulsion among the cationic headgroups. Zeta potential measurements showed that, with an increase of NP-15 in the mixtures, the positive charge of the TTAC was partially screened by the coadsorbed NP-15. Surface tension of the surfactant mixtures was also measured, and regular solution theory was used to model the interactions between the surfactants. Monomer concentrations obtained using the theory were correlated with the adsorption tendencies and it was seen that TTAC adsorption corresponded with its monomer concentration but that of NP-15 did not, suggesting the need for adequate theories for interactions between surfactants.

Journal Article↗
PubMed1996

Molecular and immunochemical analyses of RB1 and cyclin D1 in human ductal pancreatic carcinomas and cell lines.

Somatic mutations in the retinoblastoma-1 gene (RB1) and loss of RB1 protein function have been implicated in a number of human malignancies, but the role of RB1 gene and protein abnormalities in ductal pancreatic cancer (DPCA) is virtually unknown. We therefore analyzed expression of the RB1 protein immunohistochemically and/or by western blotting in a total of 54 sporadic and eight familial cases of archival and frozen DPCA and in 18 pancreatic carcinoma cell lines by using the antibodies RB-WL-1, 84-B3-1, and PMG3-245. Mutations in the RB1 promotor region and exons 13-21 of the RB1 gene were likewise examined by single-strand conformation polymorphism (SSCP) analyses and DNA sequencing of genomic DNA from 30 microdissected primary pancreatic tumors and the pancreatic carcinoma cell lines. Moreover, amplification and expression of a major regulatory component of RB1 function, cyclin D1, were assessed by southern and immunohistochemical analyses, respectively. The DPCAs were heterogeneous in both the intensity of RB1 nuclear staining and the percentage of immunoreactive cells. The tumors often had areas where RB1 staining was weak or absent adjacent to normal pancreatic tissue; however, only two of 32 archival cases and one of 30 frozen cases of DPCA completely lacked RB1 nuclear staining. Immunohistochemical and western blot analyses of 18 pancreatic carcinoma cell lines demonstrated the absence of RB1 expression in only two cell lines, Capan-1 and QGP-1. Analyses of the RB1 gene and promotor region by SSCP and DNA sequencing largely confirmed the immunochemical findings. Three of 30 primary carcinomas had abnormalities revealed by SSCP analyses. In one case a single base-pair deletion was confirmed in exon 18 and resulted in premature termination and the absence of detectable RB1 protein. A second case had TAC-->TTC missense mutation in exon 13. The third primary carcinoma could not be reliably sequenced because it had a low percentage of epithelial cells. The cyclin D1 gene was not amplified in any of the primary pancreatic tumors or cell lines examined. These immunochemical and molecular analyses of the RB1 tumor suppressor gene and cyclin D1 proto-oncogene in a large series of human pancreatic cancers and cell lines indicate that RB1 and cyclin D1 alterations occur during the development of some human DPCAs. Nevertheless, it is probable that alterations in cell-cycle regulation in DPCAs more frequently involve pathways other than those involving RB1 and cyclin D1.

Base Sequence↗
PubMed1996

Phenotyping of esterase D and acid phosphatase by rapid isoelectric focusing on PhastSystem.

A rapid isoelectric focusing method on PhastSystem was applied to investigate the distribution of esterase D (ESD) and acid phosphatase (ACP) phenotypes in 152 and 112 unrelated healthy donors, respectively, from the Han population in Beijing. Laboratory-made gels with a pH range of 5.0-7.0 and 5.0-8.0 were used for analysis of ESD and ACP, respectively, with 1 microliter sample loading. The running time was 30-40 min. Gene frequencies for ESD were 0.6809 for ESD*1 and 0.3191 for ESD*2, (sigma chi 2 = 0.8586 and P > or = 0.50); gene frequencies of ACP were 0.2009 for ACP*A, 0.7991 for ACP*B, (sigma chi 2 = 1.7892 and P > 0.20), with good agreement between the observed and the expected values.

Acid Phosphatase↗
PubMed1996

Subtyping of group-specific component and protease inhibitor by rapid isoelectric focusing on PhastSystem.

A rapid method on PhastSystem was used to investigate the distribution of group-specific component (GC) and protease inhibitor (PI) subtypes and their gene frequencies from 190 unrelated healthy donors of the Han population in Beijing. Laboratory-made gels (pH 4.5-5.4 and pH 4.2-4.9) were used for analysis of GC and PI, respectively. Sample loading was 1.5 microliters. The separation and visualization time was 0.5 h in each. Gene frequencies were as follows: GC*1F = 0.4891, GC*1S = 0.2432, GC*2 = 0.2678; rare GC variants were discovered in seven cases. The results for PI were: PI*M1 = 0.7542, PI*M2 = 0.1808, PM*M3 = 0.0650. Good agreement between the observed and expected values in both GC and PI subtyping (for GC, sigma chi 2 = 1.4043, 0.7 < P < 0.8; for PI, sigma chi 2 = 1.1233, 0.7 < P < 0.8) was obtained.

Gene Frequency↗
PubMed1996

Chronic exposure of neonatal cardiac myocytes to hydrogen peroxide enhances the expression of catalase.

The adaptive response of antioxidant enzymes to oxidative stress in the heart has not been investigated. Because H2O2 is considered to play a major role in reperfusion injury to the heart, this study was undertaken to examine if H2O2 alters the expression of these enzymes in the rat neonatal myocytes. H2O2 was continuously generated by the addition of glucose oxidase to the culture medium. Both the activity and the mRNA for catalase were increased following incubation of neonatal myocytes with non-toxic concentrations of glucose oxidase. The induction of mRNA preceded the enhancement of activity, and both remained elevated after 24 h incubation. Nuclear run-on assay indicated that the transcriptional rate for catalase mRNA was increased. The same treatment did not alter the activities for total superoxide dismutase and Se-glutathione peroxidase. The results suggest that H2O2-induced expression of catalase was in part due to transcriptional activation. It further implies that the induction of catalase may play an important role in protecting hearts from ischemic/reperfusion injury.

Animals↗
PubMed1996

Architectural design and tools to support the transparent access to hospital information systems, radiology information systems, and picture archiving and communication systems.

The fragmentation of the electronic patient record among hospital information systems (HIS), radiology information systems (RIS), and picture archiving and communication systems (PACS) makes the viewing of the complete medical patient record inconvenient. The purpose of this report is to describe the system architecture, development tools, and implementation issues related to providing transparent access to HIS, RIS, and PACS information. A client-mediator-server architecture was implemented to facilitate the gathering and visualization of electronic medical records from these independent heterogeneous information systems. The architecture features intelligent data access agents, run-time determination of data access strategies, and an active patient cache. The development and management of the agents were facilitated by data integration CASE (computer-assisted software engineering) tools. HIS, RIS, and PACS data access and translation agents were successfully developed. All pathology, radiology, medical, laboratory, admissions, and radiology reports for a patient are available for review from a single integrated workstation interface. A data caching system provides fast access to active patient data. New network architectures are evolving that support the integration of heterogeneous software subsystems. Commercial tools are available to assist in the integration procedure.

Computer Systems↗
PubMed1996

A concept-based retrieval system for thoracic radiology.

Current digital information systems in radiology are insufficient to accommodate the retrieval needs of academicians. Significant efforts are required in retrieving clinical cases for teaching and research. We describe a prototype system that supports intelligent case retrieval based on a combined specification of patient demographics, radiologic findings, and pathologic diagnoses. The documents for these cases can be distributed among multiple heterogeneous data bases. The system features automatic indexing of radiology and pathology reports, a comprehensive lexicon for thoracic radiology, an interface to a hospital information system, radiology information system, and picture archiving and communication systems, and a graphical user interface for query formulation and results visualization. The prototype system was developed within the domain of thoracic radiology involving patients with lung cancer.

Abstracting and Indexing↗
PubMed1996

In vivo antitumor activity of cis-bis-neodecanoato-trans-R,R-1, 2-diaminocyclohexane platinum(II) formulated in long-circulating liposomes.

A lipophilic cisplatin derivative, cis-bis-neodecanoato-trans- R,R-1,2-diaminocyclohexane platinum (II) (NDDP), was formulated in liposomes composed of phosphatidylcholine (PC) and cholesterol (Chol) additionally containing monosialoganglioside (Gm1) or polyethyleneglycol conjugated to phosphatidylethanolamine (PEG-PE). These NDDP-containing long-circulating liposomes were examined for in vivo antitumor activity using the mouse RIF-1 solid tumor as a target residing outside the reticuloendothelial system (RES). Biodistribution studies, using C3H/HeJ mice and 111In-labelled DTPA-SA as a lipid marker, showed that the activity of GM1 and PEG-PE in prolonging the circulation times of liposomes was preserved in the presence of 3.0 mol% of NDDP in the liposome membranes. The high levels of liposomes remaining in the blood for PC/Chol/GM1 and PC/Chol/PEG3000-PE liposomes were associated with high levels of platinum in the blood as determined by atomic absorption spectrophotometry. These NDDP-containing long-circulating liposomes showed approximately a three-fold increase in tumor accumulation as compared to the conventional PC/Chol liposomes. In vitro cytotoxicity studies using RIF-1 tumor cells showed that the presence of PEG-PE, but not Gm1, significantly enhanced the cytotoxicity of liposomal NDDP. RIF-1 tumor-bearing C3H/HeJ mice were treated twice with 25 mg/kp NDDP in various liposomal formulations on days 12 and 16 after tumor cell inoculation. A significant reduction in the tumor growth rate was observed when NDDP was formulated in PC/Chol/PEG3000-PE liposomes which support both efficient tumor accumulation and enhanced cytotoxicity of liposomal NDDP. On the other hand, NDDP formulated in PC/Chol/GM1 liposomes, which display only a high tumor accumulation, had no effect on the tumor growth rate. Furthermore, NDDP formulated in dimyristoylphosphatidylglycerol (DMPG)-containing liposomes, exhibiting in vitro cytotoxicity comparable to NDDP formulated in PC/Chol/PEG3000-PE liposomes, but showing poor tumor accumulation, was also not effective. These results indicate a potential effectiveness of NDDP formulated in PEG-PE-containing liposomes for therapy of tumors in non-RES organs.

Animals↗
PubMed1996

Endotoxin induces PAF production in the rat ileum: quantitation of tissue PAF by an improved method.

PAF (platelet-activating factor) is an endogenous mediator of endotoxin (LPS) shock and intestinal injury. In the present study we used an improved method to quantitate intestinal PAF after LPS injection. Both column and thin layer chromatography (TLC) were used to purify PAF. We found that using C18 column eluted sequentially with 10% acetic acid, ethyl acetate and 70% ethanol, yielded consistent results. TLC yielded falsely high PAF values, possibly from an unknown tissue lipid which co-migrated with PAF, or from toxic ingredients in the silica gel. Moreover, addition of optimal amounts of Tween-20 or ethanol in the bioassay samples enhanced PAF solubility and markedly improved PAF recovery. Lastly, dilution and heparinization of platelet-rich plasma greatly improved the sensitivity of the bioassay. The overall PAF recovery under these optimal conditions was 70-80%. We found that LPS (2-10 mg/kg, iv, 90 min) stimulated PAF production in the rat ileum, but not in the jejunum and colon. The difference in PAF production did not correlate to the numbers of sequestered neutrophils (reflected by myeloperoxidase levels) after LPS injection. This selective PAF production may account for the special vulnerability of the ileum to develop injury during endotoxemia.

Animals↗