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B H Chung

Publications and source records attributed to B H Chung.

At least 19 recordsLinked to original sources
PubMed1998

Glycosylation of human alpha 1-antitrypsin in Saccharomyces cerevisiae and methylotrophic yeasts.

Human alpha 1-antitrypsin (alpha 1-AT) is a major serine protease inhibitor in plasma, secreted as a glycoprotein with a complex type of carbohydrate at three asparagine residues. To study glycosylation of heterologous proteins in yeast, we investigated the glycosylation pattern of the human alpha 1-AT secreted in the baker's yeast Saccharomyces cerevisiae and in the methylotrophic yeasts, Hansenula polymorpha and Pichia pastoris. The partial digestion of the recombinant alpha 1-AT with endoglycosidase H and the expression in the mnn9 deletion mutant of S. cerevisiae showed that the recombinant alpha 1-AT secreted in S. cerevisiae was heterogeneous, consisting of molecules containing core carbohydrates on either two or all three asparagine residues. Besides the core carbohydrates, variable numbers of mannose outer chains were also added to some of the secreted alpha 1-AT. The human alpha 1-AT secreted in both methylotrophic yeasts was also heterogeneous and hypermannosylated as observed in S. cerevisiae, although the overall length of mannose outer chains of alpha 1-AT in the methylotrophic yeasts appeared to be relatively shorter than those of alpha 1-AT in S. cerevisiae. The alpha 1-AT secreted from both methylotrophic yeasts retained its biological activity as an elastase inhibitor comparable to that of alpha 1-AT from S. cerevisiae, suggesting that the different glycosylation profile does not affect the in vitro activity of the protein.

Amino Acid Sequence↗
PubMed1998

Synthesis and biological evaluation of 3-arylisoquinolines as antitumor agents.

To investigate the structure-activity relationship of 7,8-dimethoxy-2- methyl-3-(4,5-methylenedioxy-2-vinylphenyl)isoquinolin-1(2H) -one 2, diverse substituted 3-arylisoquinolines were synthesized and tested in vitro antitumor activity against five human tumor cell lines. The results showed a broad antitumor spectrum for a series of 3-arylisoquinolines.

Antineoplastic Agents↗
PubMed1998

Efficient production of intact human parathyroid hormone in a Saccharomyces cerevisiae mutant deficient in yeast aspartic protease 3 (YAP3).

When human parathyroid hormone (hPTH) is expressed as a secretory product in yeast, the main problem is the aberrant proteolytic cleavage that reduces the yield of intact protein. To overcome this problem, we developed an hPTH expression system using a host strain in which the YAP3 gene encoding yeast aspartic protease 3 (YAP3) was disrupted. After 48 h of culture, most of the hPTH secreted by the yap3 disruptant remained intact, whereas more than 90% of the hPTH secreted by the wild-type strain was cleaved. When the authentic hPTH was incubated in each of the culture supernatants of untransformed yap3 disruptant and wild-type strain, the proteolysis proceeded much more slowly in the culture supernatant of yap3 disruptant than in that of the wild type. The extent of hPTH proteolysis was also significantly reduced by the addition of pepstatin A, a specific aspartic protease inhibitor. The results suggest that YAP3 is involved in the internal cleavage of hPTH expressed in yeast. The correct processing of the intact hPTH secreted in the yap3 disruptant demonstrates that the yeast mutant lacking the YAP3 activity is a suitable host for the high-level expression of intact hPTH.

Aspartic Acid Endopeptidases↗
PubMed1998

Effect of the fat composition of a single meal on the composition and cytotoxic potencies of lipolytically-releasable free fatty acids in postprandial plasma.

Ingestion of a meal increases plasma levels of triglyceride (TG)-rich lipoproteins through the secretion of intestine-derived chylomcirons and liver-derived very low density lipoproteins (VLDL). We have determined the effects of the fat composition of a single meal on the composition of TG in TG-rich lipoproteins (VLDL + chylomicrons) and circulating and lipolytically-releasable free fatty acids (FFA) in postprandial (PP) plasma and on the cytotoxic potencies of the lipolytically-released FFA to cultured arterial wall cells. PP lipemia was induced by feeding fasted normolipidemic human subjects with a meal rich in saturated fat (SF) and another meal rich in polyunsaturated fat (PUF), or vice versa; each meal provided 65% of energy as fat, and polyunsaturated to saturated fatty acid ratios (P/S) of the SF and PUF in the meals were 0.40 and 2.49, respectively. The mean P/S of TG in TG-rich lipoproteins (1.43) and circulating FFA (1.46) in 4 h PP plasma of PUF were significantly higher than those in PP plasma of SF (0.44 and 0.59, respectively) in fasting plasma (0.52 and 0.53, respectively). In vitro lipolysis of fasting and PP serum by purified bovine milk lipoprotein lipase (LpL) resulted in a marked (8.8-12.3-fold) increase in the serum FFA level. The P/S of serum FFA in postlipolysis fasting and PP serum were consistently higher than that of FFA or that of TG associated with TG-rich lipoproteins in prelipolysis fasting and PP serum, indicating that polyunsaturated TG in VLDL and/or chylomicrons is more susceptible than saturated TG to lipolysis. When postlipolysis serum was interacted with cultured endothelial cells and mouse peritoneal macrophages (MPM), the lipolytically-released FFA in PP serum of SF and PUF disrupted the barrier function of endothelial cells and were cytotoxic to cultured MPM; FFA in postlipolysis fasting serum was not cytotoxic. FFA in postlipolysis PP serum of PUF were consistently more potent than that in postlipolysis PP serum of SF. Further study showed that all long-chain monounsaturated FFA and polyunsaturated FFA, but not saturated FFA, incorporated into lipoproteins (LDL) were cytotoxic to cultured MPM. In conclusion, despite the generally well-accepted belief that SF is more atherogenic than PUF, the present study provides in vitro evidence that the lipolytic remnant products of TG-rich lipoproteins produced after a meal rich in PUF are more injurious to arterial wall cells than those produced after a meal rich in SF.

Adult↗
PubMed1998

In vitro production of beta-very low density lipoproteins and small, dense low density lipoproteins in mildly hypertriglyceridemic plasma: role of activities of lecithin:cholester acyltransferase, cholesterylester transfer proteins and lipoprotein lipase.

As a model for the formation of beta-very low density lipoproteins (VLDL) and small, dense LDL by the intraplasma metabolic activities in vivo, lipoproteins in fresh plasma were interacted in vitro with endogenous lecithin:cholesterol acyltransferase (LCAT) and cholesterylester transfer proteins (CETP) and subsequently with purified lipoprotein lipase (LpL). The LCAT and CETP reactions in a mildly hypertriglyceridemic (HTG) plasma at 37 degrees C for 18 h resulted in (1) esterification of about 45% plasma unesterified cholesterol (UC), (2) a marked increase in cholesterylester (CE) (+129%) and a decrease in triglyceride (TG) (-45%) in VLDL, and (3) a marked increase of TG (+ 341%) with a small net decrease of CE (-3.6%) in LDL, causing a significant alteration in the TG/CE of VLDL (from 8.0 to 1.9) and of LDL (from 0.20 to 0.93). The LDL in LCAT and CETP-reacted plasma is larger and more buoyant than that in control plasma. In vitro lipolysis of control and LCAT and CETP-reacted plasma by LpL, which hydrolyzed >90% of VLDL-TG and about 50-60% of LDL-TG, converted most of VLDL in control plasma (>85%) but less than half (40%) of VLDL in LCAT and CETP-reacted plasma into the IDL-LDL density fraction and transformed the large, buoyant LDL in the LCAT and CETP-reacted plasma into particles smaller and denser than those in the control plasma. The remnants that accumulated in the VLDL density region of the postlipolysis LCAT and CETP-reacted plasma contained apo B-100 and E but little or no detectable apo Cs and consisted of particles having pre-beta and beta-electrophoretic mobilities. The inhibition of LCAT during incubation of plasma, which lessened the extent of alteration in VLDL and LDL core lipids, increased the extent of lipolytic removal of VLDL from the VLDL density region but lowered the extent of alteration in the size and density of LDL. The LCAT, CETP and/or LpL-mediated alterations in the density of LDL in normolipidemic fasting plasma were less pronounced than that in mildly HTG plasma, but they became highly pronounced upon increase of its TG-rich lipoprotein level by the addition of preisolated VLDL or by the induction of postprandial lipemia. Although the effect of LCAT, CETP and LpL reactions in non-circulating plasma in vitro may be different from that in vivo, the above data suggests that the plasma TG-rich lipoprotein level and the extent of intraplasma LCAT, CETP, LpL and likely hepatic lipase (HL) reactions in vivo may play a role in determining the LDL phenotype.

Carrier Proteins↗
PubMed1998

Cellular uptake of stearic, oleic, linoleic, and linolenic acid and their effects on synthesis and secretion of lipids in Hep-G2 cells.

The present study was undertaken to examine the cellular uptake of stearic (18:0), oleic (18:1), linoleic (18:2), and linolenic acid (18:3), and their effects on synthesis and secretion of lipids in Hep-G2 cells. The cells were grown for 6 days in Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum. On day 7, cells were incubated in a serum-free DMEM containing 0.25-1.0 mM of 18:0, 18:1, 18:2 or 18:3. The cellular uptake of these fatty acids was almost linear during the 4 hr incubation period, and no significant differences were noted among the fatty acids tested, regardless of their degree of unsaturation. The treatment of cells with 1.0 mM of these fatty acids stimulated triglyceride (TG) synthesis nearly ten-fold and phospholipid (PL) synthesis approx, two-fold compared with those of the control. The lipoprotein-TG secretion also increased and was the highest with 18:1 followed in descending order by 18:2, 18:3, and 18:0. The fatty acid treatment of cells also significantly increased the incorporation of 14C-acetate into the cellular and lipoprotein cholesterol compared with that of the control (p < 0.05). In addition, notable changes occurred in the fatty acid composition of cellular and medium lipids, which were enriched with the particular fatty acid present in the incubation medium. The findings that 18:0, 18:1, 18:2, and 18:3 were taken up by Hep-G2 cells at almost identical rates demonstrate that differences in the cellular synthesis of lipids and their secretion are attributable to the metabolic specificity of those fatty acids, rather than variable rates of their uptake.

Acetates↗
PubMed1998

Potencies of lipoproteins in fasting and postprandial plasma to accept additional cholesterol molecules released from cell membranes.

To investigate the role of various lipoproteins in plasma to promote cholesterol efflux from cell membranes, potencies of lipoproteins in normolipidemic fasting and postprandial (PP) plasmas to accept additional cholesterol molecules from cell membranes were determined. We used red blood cells (RBCs) and lipoproteins in fresh blood as donors and acceptors of cell membrane cholesterol, respectively. When fresh fasting plasma (n=24) containing active lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer proteins (CETP) was incubated with a 3-fold excess of autologous RBCs at 37 degrees C for 18 hours, plasma cholesterol levels increased by 19.6% (38.5+/-14.2 mg/dL) owing to an exclusive increase in the CE level. Very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density lipoprotein (HDL) fractions retained 48.1%, 26.3%, and 25.6% of the net cholesterol mass increase in fasting plasma, resulting in 91%, 8%, and 21% increases in their cholesterol contents, respectively. The PP plasma was 1.3-fold more potent than fasting plasma in promoting cholesterol efflux from RBCs by associating excess cholesterol with chylomicrons, resulting in a 356% increase in the cholesterol content of chylomicrons. These increases in lipoprotein cholesterol content indicate that chylomicrons were about 3.9x, 44x, and 17x more potent than fasting VLDL, LDL, and HDL, respectively, in accepting additional cholesterol molecules released from RBCs. The capacity of PP plasma to promote cholesterol efflux from RBCs was significantly correlated with plasma cholesterol levels (r=0.60, P<0.005), triglycerides (r=0.68, P<0.001), chylomicrons (r=0.90, P<0.001), VLDL (r=0.65, P<0.001), and LDL (r=0.47, P<0.025) but not with the levels of HDL (r= -0.34, P<0.20). In fasting plasma containing a low level of VLDL and HDL, isolated chylomicrons supplemented to the plasma were approximately 9x more potent than HDL in boosting the capacity of plasma to promote cholesterol efflux from RBCs. This study indicates that chylomicrons in PP plasma are the most potent ultimate acceptors of cholesterol released from cell membranes and that a low HDL level is not a factor that limits the ability of PP plasma to promote cholesterol efflux from cell membranes. Our data obtained from an in-vitro system suggest that PP chylomicrons may play a major role in promoting reverse cholesterol transport in vivo, since the transfer of cholesterol from cell membranes to chylomicrons will lead to the rapid removal of this cholesterol by the liver. HDL in vivo may promote reverse cholesterol transport by enhancing the rapid removal of chylomicrons from the circulation, since the rate of clearance of chylomicrons is positively correlated with the HDL level in plasma.

Adult↗
PubMed1998

Telomerase: a potential marker of bladder transitional cell carcinoma in bladder washes.

Telomerase is an enzyme that immortalizes cells by maintaining a constant telomere length. Here, telomerase activity in bladder washes was analyzed and compared with the final pathological diagnosis in 23 patients with bladder transitional cell carcinoma (TCC). Bladder washes and normal tissues were obtained from each patient prior to transurethral resection of bladder tumor. Telomerase activity was detected using telomeric repeat amplification protocol assay based on PCR. Cytological diagnosis of centrifuged cells from bladder washes was made using Papanicolau's stain. Results demonstrated that telomerase activity was detected in 95.7% of both cancer tissues and bladder washes. In normal tissues, telomerase activity was not detected in 22 of 23 samples. Regarding cytological diagnosis, only 69.6% of bladder wash samples had positive cytology. Moreover, in five cases of grade 1 TCC, only 20% of the cytological specimens were positive for malignancy, whereas 80% showed positive telomerase activity. These results demonstrate that telomerase activity is detectable in a majority of human bladder cancer tissues and bladder washes obtained from patients with TCC. In addition, results of this study suggest that the presence of telomerase in bladder washes may be a specific marker of bladder cancer, especially in low-grade tumors.

Aged↗
PubMed1997

Lack of effect of vitamin E on cholesteryl ester transfer and lipoprotein composition in cholesterol-fed rabbits.

The concentration and activity of cholesteryl ester transfer protein (CETP) is increased in plasma in hypercholesterolemic humans and in experimental animals fed cholesterol. While the concentration of lipo-proteins appears to be the major determinant of CETP activity, we have found previously that dietary measures and pharmacologic agents that alter their lipid composition reduce the activity of CETP in plasma (CET). Since vitamin E is lipophilic and is incorporated into lipoproteins, we have examined the question of whether it too attenuates CET in cholesterol-fed New Zealand White rabbits prior to and 14 weeks after treatment with differing doses (5, 15, 30, 45 mg/kg) of vitamin E. Plasma triglycerides (TG), cholesterol (TC) and phospholipids (Lys, Sph, Lec, PI, PE) all increased significantly to a comparable degree in the rabbits fed cholesterol compared to those fed chow (p < 0.05; p < 0.01); the levels achieved were similar in the vitamin E-treated and untreated groups. As was observed with plasma lipids, cholesteryl ester transfer (CET) was accelerated to the same degree in each of the cholesterol-fed groups independent of whether they received vitamin E compared to chow-fed controls (p < 0.01) and the distribution of cholesterol in apo-B containing lipoproteins (VLDL, IDL, and LDL) was similar in the vitamin E-treated and untreated groups. These findings indicate that vitamin E has no discernible effect on CET when cholesterol levels are markedly elevated.

Animals↗
PubMed1997

Telomerase activity: a potential marker of bladder transitional cell carcinoma in bladder washes.

The enzyme telomerase maintains a constant telomere length in immortalized cells, allowing unlimited cell proliferation. Almost all cancer cells express telomerase activity. However, little data is available regarding the role of telomerase activity in the detection of bladder cancer with a bladder wash specimen. We detected telomerase activity in a bladder wash specimen of bladder cancer and normal tissues, and compared them with final pathologic diagnosis. Twenty-three patients with transitional cell carcinoma (TCC) of the bladder were enrolled in our study. A bladder wash specimen was obtained before transurethral resection of the bladder (TURB) and normal and cancer tissues from the same patients during TURB. Telomerase activity was analyzed in each specimen a using telomeric repeat amplification protocol (TRAP) assay based on polymerase chain reaction (PCR) technique. Cytologic diagnosis was performed using Papanicolaou's stain with cytocentrifuged cytology preparation. We observed telomerase activity in 95.7% (22/23) of bath cancer tissues and bladder wash specimens; only one case did not express telomerase activity. Telomerase activity was undetected in all normal tissues except one, which was obtained from a patient with carcinoma in situ. A total of 69.6% (16/23) of wash specimens were positive in cytopathologic diagnosis. The accuracy of cytopathologic diagnosis in pathologic grade 2 or 3 was relatively high (83.3%, 15/18). However, in five cases of grade 1 TCC only 20% (1/5) of cytologic diagnosis was positive whereas the telomerase activity of wash specimens was detected in 80% (4/5). Our data demonstrates that not only the majority of human bladder cancer tissues, but also the bladder wash specimens obtained from patients with TCC, expressed telomerase activity. It indicates that telomerase activity may be a reliable marker in detecting bladder cancer especially in cases with a low grade that bladder wash cytology can miss.

Aged↗
PubMed1996

High-level secretion of human alpha 1-antitrypsin from Saccharomyces cerevisiae using inulinase signal sequence.

The use of a proper signal sequence is one of the major determinants for the efficient secretion of heterologous proteins from yeast. The signal sequence derived from inulinase (INU1A) of Kluyveromyces marxianus was evaluated in directing the secretion of a human glycoprotein, alpha 1-antitrypsin (alpha 1-AT), from Saccharomyces cerevisiae. A yeast expression vector for alpha 1-AT was constructed by placing the coding sequence of human alpha 1-AT fused with the INU1A signal sequence downstream of the GAL10 promoter. S. cerevisiae transformants harboring the expression vector secreted about 70% of the total alpha 1-AT synthesized into the culture media. The intracellularly retained form of alpha 1-AT was mostly unglycosylated, whereas the secreted protein had high mannose-type glycosylation. The fed-batch cultivation of the recombinant yeast achieved a high-cell density, leading to the secretion of biologically active alpha 1-AT up to 75 mg l-1. The secreted protein was purified and subjected to N-terminal sequencing, which confirmed that the secreted alpha 1-AT was processed correctly at the Kex2 cleavage site as expected from the sequence of INU1A signal peptide. The results suggest that the inulinase signal sequence is useful for the high-level secretion of relatively large glycoproteins, such as human alpha 1-AT, from S. cerevisiae.

Amino Acid Sequence↗
PubMed1996

A PCR-RFLP method for the detection of activated H-ras oncogene with a point mutation at codon 12 and 61.

To investigate the incidence of the H-ras gene activation in bladder tumor and the feasibility of using urinary washout samples for screening, a series of 33 human bladder tumors and their preoperatively collected urinary washout samples were screened using a mutant specific PCR-RFLP (polymerase chain-restriction fragment length polymorphism) to detect a point mutation of the H-ras gene. Five tumors were found to harbor H-ras mutations where two tumors had a glycine to valine (G-->T) change in codon 12 and three tumors had a glutamine to lysine (C-->A) change in codon 61, respectively. Moreover, we could also detect the same point mutations of the H-ras gene in corresponding urine washout samples. The incidence of H-ras mutation in Korean bladder cancer was estimated at approximately 15.2%. In conclusion, a mutant specific PCR-RFLP method for the detection of H-ras gene mutation is useful for screening or postoperative follow-up of bladder tumor due to its simplicity and high specificity even in urinary samples.

Base Sequence↗
PubMed1996

Effects of nitric oxide on detrusor relaxation.

PURPOSE: Recently we (1994) reported the photo-induced adequate nitric oxide (PIANO) system, in which an NO- or NO2-carrying molecule which has been photoactivated to release NO, could be exploited to investigate the role of NO in various smooth muscle functions. This study was designed to characterize the effect of nitric oxide (NO) exploiting PIANO on rat detrusor relaxation by isometric tension recording and measuring changes in cGMP content. MATERIALS AND METHODS: Exposure to ultraviolet light was used (1 to 60 seconds) to evoke PIANO in the presence of streptozotocin, an NO-carrier, and N omega-nitro-L-arginine (L-NOARG), an NO2-carrier. During relaxation the cyclic guanosine monophosphate (cGMP) content was measured by radioimmunoassay. RESULTS: Rat detrusor strips were reversibly relaxed upon NO generation via PIANO. Pyrogallol, an O2 generator, significantly (p < 0.01) diminished PIANO-mediated relaxation. During PIANO-mediated relaxation, the tissue level of cyclic GMP significantly (p < 0.05) increased over that of the control. Furthermore, methylene blue, a guanylate cyclase inhibitor, significantly (p < 0.01) inhibited both the relaxation and the increase of cGMP. CONCLUSION: We concluded that rat detrusor muscle was capable of responding to NO, and these findings might lead to a treatment for bladder instability and detrusor hyperreflexia, by the use of intravesical instillation of NO donors.

Animals↗
PubMed1996

Probing structure and function of VLDL by synthetic amphipathic helical peptides.

Class A amphipathic helical peptides have been shown to mimic many properties of exchangeable apolipoproteins. The three analogs of the class A amphipathic peptides were used to probe the structure and function of human very low density lipoproteins (VLDL): 1) 18 residue peptide possessing a single helical domain (18A) with the sequence Asp-Trp-Leu-Lys-Ala-Phe-Tyr-Asp-Lys-Val-Ala-Glu-Lys-Leu-Lys-Glu-Ala-Phe; 2) two domains of 18A separated by a Pro (37pA); and 3) and 18A analog with the end groups protected to increase helicity (Ac-18A-NH2). Upon incubation of the peptides with VLDL at a peptide to VLDL, (protein) ratio of 1:1, the 37pA and Ac-18A-NH2 were able to displace most of apolipoprotein (apo) Cs and E from VLDL without alteration in its lipid composition and morphology while 18A had minimal effect. The extent of displacement was a function of the peptide to VLDL ratio. The rank order of displaceability of apolipoproteins on VLDL was apoE > C-III > C-II. The displacement of apoE and/or Cs from VLDL by peptides variably affected the ability of VLDL to interact with purified bovine milk lipoprotein lipase (LpL) and cultured macrophages. Treatment of VLDL with Ac-18A-NH2 markedly lowered its reactivity to LpL and its ability to induce lipid accumulation in cultured macrophages: however, treatment of VLDL with 37pA or 18A only minimally lowered their abilities. Ac-18A-NH2 treatment of VLDL resulted in the increase of apparent K(m) and a decrease of Vmax for lipoprotein lipase (LpL)-catalyzed hydrolysis of VLDL triglycerides. When an artificial triglyceride emulsion was used as a substrate of LpL, 37pA, but not Ac-18A-NH2, activated LpL. The above data indicate that 1) amphipathic helical peptides can alter the metabolic and functional properties of VLDL by dissociating the functionally important exchangeable apolipoproteins from VLDL as well as by acting as a functional element of VLDL after their incorporation; and 2) the class A amphipathic peptides having different lipid-associating properties exert significantly different effect on VLDL function.

Amino Acid Sequence↗
PubMed1995

Oxidized low-density lipoproteins delay endothelial wound healing: lack of effect of vitamin E.

The purpose of this study was to examine the influence of oxidized low-density lipoprotein (oxLDL) on endothelial regrowth in an in vitro wounding model and the possible protection afforded by vitamin E (E). Endothelial cells grown on micropore filters were wounded by scraping and allowed to reestablish growth on denuded areas in the presence of LDL or oxLDL (25-200 micrograms/ml), linoleic acid (FA, 90 microM) or linoleic acid hydroperoxide (OFA, 15 microM) for 24 h. Some monolayers were pretreated with 25 microM E for 24 h. Transendothelial albumin movement was used as a measure of endothelial barrier function and as an indicator of endothelial monolayer regrowth. Exposure to levels of oxLDL as low as 25 micrograms/ml for 24 h resulted in depressed endothelial monolayer regrowth, whereas native LDL was without effect and pre-enrichment with 25 microM E offered no protection. In comparison, E pre-enrichment improved endothelial regrowth to control levels in FA- and OFA-treated cultures, unlike oxLDL-treated cultures. It is concluded that circulating oxLDL may reduce regrowth of wounded endothelium and supplemental E may not offer protection. Moreover, fatty acids or their hydroperoxides are unlikely to be involved in this effect.

Animals↗
PubMed1995

Lipolysis-induced partitioning of free fatty acids to lipoproteins: effect on the biological properties of free fatty acids.

Free fatty acids (FFA) released during the lipolysis of triglyceride (TG)-rich lipoproteins in vivo are generally believed to be bound to serum albumin. When hypertriglyceridemic (HTG) sera were lipolyzed in vitro by purified bovine milk lipoprotein lipase (LpL), there was an 11- to 18-fold increase in serum FFA levels, and a major portion (> 80%) of the FFA in serum was partitioned to lipoprotein fractions. The greatest portion (33%) of FFA in lipolyzed HTG serum was associated with newly formed flocculent remnants that banded just below low density lipoproteins (LDL) in the density gradient tube. Very low density lipoprotein (VLDL), LDL, and high density lipoprotein (HDL) fractions in lipolyzed HTG serum contained 18- to 29-times more FFA molecules than those in prelipolysis serum. Analysis of the fatty acyl chain composition of FFA in lipolyzed HTG serum showed that the extent of partitioning of saturated FFA into the lipoprotein fractions relative to that of polyunsaturated FFA was about 4.5- to 11-times greater than that partitioned into the free protein fraction; most (84%) of FFA partitioned into flocculent remnants were saturated fatty acids. In vivo lipolysis of TG-rich lipoproteins in HTG subjects, induced by heparinization, resulted in only a small (2.8-fold) increase in serum FFA and little or no increase in the partitioning of FFA to lipoproteins. However, in vitro incubation of the postheparin serum at 37 degrees C for 90 min resulted in a 2.9- to 6.8-fold increase in the serum FFA level and the partitioning of > 66% of total serum FFA into lipoprotein fractions. Studies of the interaction of various plasma fractions from control and in vitro lipolyzed HTG serum with cultured mouse peritoneal macrophages (MPM) showed that FFA partitioned to lipoprotein fractions were highly cytotoxic to cultured MPM, whereas FFA partitioned to albumin at a 10 x greater concentration were not cytotoxic. The cytotoxic potencies of FFA bound to lipoproteins and albumin were further compared after in vitro incorporation of FFA (oleic acids) into LDL and to albumin. FFA bound to LDL but not to albumin were cytotoxic to cultured MPM; the cytotoxicity of FFA bound to LDL was more closely related to the FFA to LDL-cholesterol molar ratio than to the total FFA concentration in the culture dish. The ability of FFA bound to LDL and albumin to induce foam cell formation was studied in THP-1 monocyte-derived macrophages, which were less susceptible to cytotoxicity produced by FFA bound to LDL than MPM.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Photo-induced adequate nitric oxide (PIANO)-mediated relaxation in isolated rabbit corpus cavernosum.

1. We further investigated our earlier proposal that NO- and NO2-carrying molecules potentiate photorelaxation using isolated rabbit corpus cavernosum. 2. Corporal smooth muscle, in the presence or absence of endothelium, relaxed only slightly upon u.v. light (366 nm) irradiation. But, NO- and/or NO2-containing compounds such as streptozotocin and NG-nitro-L-arginine methyl ester significantly (P < 0.01) enhanced photorelaxation in this tissue. In addition, NG-nitro-D-arginine methyl ester, known to lack inhibitory action on NO synthase, showed concentration-dependent potentiation of the photorelaxation. 3. Oxygen radical generating system via xanthine+xanthine oxidase and guanylate cyclase inhibitor, methylene blue, significantly (P < 0.05) inhibited the streptozotocin-potentiated photorelaxation. 4. Nitrite was accumulated by photolysis of streptozotocin, NG-nitro-L-arginine methyl ester and NG-nitro-D-arginine methyl ester, in a concentration and exposure time-dependent manner. 5. These observations indicate that NO is a potent relaxant of rabbit corpus cavernosum and further support our hypothesis that NO is released by photolysis from NO- and NO2-carrying molecules.

Animals↗