Spontaneous Separation in Idiopathic Vitreomacular Traction Syndrome Associated with Contralateral Full-Thickness Macular Hole

Purpose

Vitreomacular traction syndrome (VMTS) and full-thickness macular hole are two different well-known entities that on follow-up may be subjected to clinical modifications. Precisely, a spontaneous separation of idiopathic VMTS occurred in three eyes of three patients relieving in addition traction of the posterior hyaloid that had led also to a focal macular pigment epithelium detachment (RPE). An association to a full-thickness macular hole was observed in the contralateral eye of one of the patients.

Methods

This is a retrospective study of three patients evaluated with fluorescein angiography and documented with optical coherence tomography using the Stratus (OCT) model 3000, with scans analysis and protocols analysis, measuring the size and shape of vitreomacular adhesions, macular thickness changes before and after the spontaneous separation of the fractional posterior hyaloid adhesion. In addition, the vitreous was evaluated with contact lens slit lamp biomicroscopy and ultrasound. The associated contralateral macular hole in one of the patients was surgically treated.

Results

Two of the three eyes with spontaneous separation of the VMTS recovered 20/25 central visual acuity; the other eye maintained the initial 20/50 visual acuity. The treated macular hole recovered 20/100 corrected visual acuity.

Conclusions

Spontaneous separation of posterior hyaloid is a possible outcome during follow-up of idiopathic VMTS that can be well evaluated and documented with OCT while macular fluorescein angiography may be silent in cases like these presently reported. Central vision recovery can be excellent following the spontaneous separation, which releases anterior-posterior traction including on the retinal pigment epithelium and decreases macular thickness as measured with OCT. Therefore, regarding management, the indication for vitrectomy should be delayed awaiting the spontaneous release of vitreomacular traction in 4 to 6 months. The association between idiopathic VMTS in one eye and full-thickness macular hole in the opposite eye of one patient is an important pathophysiologic consideration.

Outcomes of Vitreoretinal Surgery for Retinal Detachment after LASIK for Myopia

PURPOSE

To report and compare outcomes of vitreoretinal surgery for repair of retinal detachment in myopic patients with and without previous laser-assisted in situ keratomileusis (LASIK).

METHODS

This is a descriptive retrospective observational study with a control group for comparison that consisted of the analysis of clinical and surgical charts of patients who underwent vitreoretinal procedures for retinal detachment at the Fundación Oftalmologica Nacional between January 1995 and December 2002. The authors identified those myopic patients who had previous history of LASIK and an age- and myopia-matched control group without refractive surgery.

RESULTS

The sample contains 24 myopic eyes of 22 patients with previous LASIK and 23 myopic eyes without previous LASIK in the control group, matched by age and myopia. Mean refractive error was -9.4 D before LASIK for the cases group and -11.2 for the control group. Poor preoperative best-corrected visual acuity was present in 71% of cases and 61% of controls (p=0.489). Macula off retinal detachment was found in 17 eyes in both groups. Five eyes required at least two procedures, achieving 91% (20 eyes) reattachments at the end of follow-up in each group. Final best-corrected visual acuity was better than 20/100 in 15 eyes (62.5%) in the LASIK group and 17 eyes (74 %) in the control group (p=0.659).

CONCLUSIONS

Retinal detachment in patients with previous myopic LASIK has similar characteristics as in myopic patients without refractive surgery. Current vitreoretinal surgery is of good prognosis as the retina was successfully reattached in most cases in both groups.

Evidence of conserved epitopes in variable region of VP8* subunit of VP4 protein of rotaviruses of P[8]-1 and P[8]-3 lineages

Although antibody responses to the human rotavirus VP4 protein have been reported, few studies have analyzed the specificity of these responses to the VP8* subunit. This study investigated antibody responses generated against the variable region of the VP4 protein (VP8* subunit) in children infected with rotavirus genotype P[8]. Recombinant VP8* subunit (rVP8*) and truncations corresponding aa 1-102 <br />(peptide A) and 84-180 (peptide B) of rotavirus strains P[8]-1 and P[8]-3 lineages were expressed in Escherichia coli and examined for antibody reactivity using ELISA and Western blot assays. Sera from infected children had IgG antibodies that reacted with full-length rVP8*, peptide A and B of both lineages, with stronger reactivity observed against peptide B. In addition, anti-strain Wa (P[8]-1) and anti-rVP8* (P[8]-3) rabbit polyclonal antiserum reacted against peptide B sequences of both lineages. These data indicate that the VP8* variable region of rotavirus belonging to P[8]-1 and P[8]-3 lineages have conserved epitopes recognized by antibodies elicited during natural infections.

Rheumatoid arthritis. New disease-modifying and anti-inflammatory drugs

Treatment options for rheumatoid arthritis (RA) are expanding as research has provided a more complete understanding of the pathophysiology of the disease. Three disease-modifying agents approved in the last 18 months for early intervention in RA are etanercept, leflunomide, and infliximab. For the relief of the signs and symptoms of RA, the new selective cyclooxygenase-2 (COX-2) inhibitors are joining the available nonsteroidal anti-inflammatory drugs. One COX-2 inhibitor is approved for use in RA, and another is under investigation for that indication. As a class, the COX-2 inhibitors offer efficacy similar to traditional NSAIDs but with less GI and platelet toxicity.

The structure of vitellogenin provides a molecular model for the assembly and secretion of atherogenic lipoproteins

The assembly of atherogenic lipoproteins requires the formation in the endoplasmic reticulum of a complex between apolipoprotein (apo)B, a microsomal triglyceride transfer protein (MTP) and protein disulphide isomerase (PDI). Here we show by molecular modelling and mutagenesis that the globular amino-terminal regions of apoB and MTP are closely related in structure to the ancient egg yolk storage protein, vitellogenin (VTG). In the MTP complex, conserved structural motifs that form the reciprocal homodimerization interfaces in VTG are re-utilized by MTP to form a stable heterodimer with PDI, which anchors MTP at the site of apoB translocation, and to associate with apoB and initiate lipid transfer. The structural and functional evolution of the VTGs provides a unifying scheme for the invertebrate origins of the major vertebrate lipid transport system.

[STRONGYLOIDES STERCORALIS: CLINICAL SEVERE FORMS ASSOCIATED TO HTLV-1 INFECTION]

A study was conducted in Lima to determine the HTLV-1 infection rate among patients with different clinical patterns of Strongyloidiasis. This study included 21 patients with Strongyloides Stercoralis (St St) hyperinfection (Group 1), and a group which consisted of sex and age matched asymptomatic healthy individuals whose stools were negative (Control Group Group 2). A third group included 33 patients with "probable hyperinfection", and another group of 63 patients with intestinal Strongyloidiasis, without evidence of systemic disease, was included. Serum from each studied individual was analized to find HTLV-1/II and ELISA; positive cases were confirmed by Western Blot. The hyperinfection rate was significantly higher [85.7% (18/21)] compared to the control group [4.7% (1/21)] p<0.001. Likewise, the "probable hyperinfection" group was considerably higher [69.7% (23/33)] in comparison to the control group p<0.01. The group with intestinal Strongyloidiasis was [10% (6/62)] lower than patients with Strongyloides hyperinfection, but did not differ significantly (p>0.05) from the control group. In this last group 3/6 were HTLV-1 positive, and their follow-up showed they developed hyperinfection forms. We conclude that severe forms of St St are considerably associated to HTLV-1 infection in adults and children over 5 years of age. No cases with HTLV-II were detected.

Strongyloides stercoralis hyperinfection associated with human T cell lymphotropic virus type-1 infection in Peru

A study was conducted in Lima, Peru to determine if patients with Strongyloides hyperinfection had human T cell lymphotropic virus type-1 (HTLV-I) infection. The study included patients with Strongyloides hyperinfection and a control group consisted of sex- and age-matched asymptomatic healthy individuals whose stools were negative for Strongyloides. A third group included patients with intestinal strongyloidiasis. Sera from each study subject were tested for HTLV-1/2I by an ELISA and Western blot. The HLTV-1 infection rates (85.7%, 18 of 21) were significantly (P < 0.001) associated with Strongyloides hyperinfection compared with the control group (4.7%, 1 of 21). The HTLV-1 rate (10%, 6 of 62) for patients with intestinal strongyloidiasis was significantly (P < 0.001) lower than patients with Strongyloides hyperinfection, but did not differ significantly (P > 0.05) from the control group. The association of HTLV-1 infection was observed among 17 of 19 patients more than 20 years of age and one of two younger patients. None had HTLV-2 infection. In conclusion, Strongyloides hyperinfection among Peruvian patients was highly associated with HTLV-1 infection.

Hydrophilic bile acids: prevention and dissolution experiments in two animal models of cholesterol cholelithiasis

The effects of beta-muricholic acid and hyocholic acid on cholesterol cholelithiasis were examined in two animal models. The following experiments were carried out: A) In a gallstone prevention study, prairie dogs were fed the lithogenic diet with or without 0.1% beta-muricholic or 0.1% hyocholic acid for eight weeks. B) In a second prevention study, hamsters were fed the lithogenic diet with or without 0.1% beta-muricholic acid or 0.1% hyocholic acid for six weeks. C) In a gallstone dissolution study, hamsters were fed the lithogenic diet for six weeks to induce stones; stone dissolution was examined during administration of a cholesterol-free purified diet with or without 0.1% beta-muricholic acid or 0.1% hyocholic acid. In the prevention study in prairie dogs (A), both bile acids failed to prevent stone formation, the cholesterol saturation index of bile was 0.89 in the lithogenic controls, remained unchanged with hyocholic acid and increased to 1.52 in the beta-muricholic acid group. In the prevention study in hamsters (B), beta-muricholic acid completely inhibited the cholesterol cholelithiasis (0% stone incidence); the cholesterol saturation index of bile was 1.78 (compared to lithogenic controls, 1.37). Hyocholic acid reduced stone incidence to 16% with a cholesterol saturation index of 0.98. In the dissolution study in hamsters (C), preexisting cholesterol gallstones were not dissolved by either hydrophilic bile acid after feeding these bile acids for an additional six weeks; at the end of the experiment, the cholesterol saturation indices were below unity.(ABSTRACT TRUNCATED AT 250 WORDS)

Chylomicron retention disease: exclusion of apolipoprotein B gene defects and detection of mRNA editing in an affected family

Chylomicron retention disease (CRD) is a rare autosomal recessive disorder characterized by the absence of post-prandial chylomicrons and apolipoprotein (apo) B-48 in sera from affected individuals. Apo B-100 is synthesized, and apo B-100-containing lipoproteins are present in sera. A crucial difference between the synthesis and secretion of apo B-containing lipoproteins from the liver and gut in man is the generation of apo B-48 by editing of apo B mRNA in the gut to create a premature stop-translation codon. In this study the hypothesis that CRD may represent an absence of editing of apo B mRNA in the gut was investigated. Two affected sisters were identified as having low cholesterol levels and an absence of post-prandial chylomicronemia. Segregation analysis in the family showed that the apo B locus is not the site of the defect. Using reverse transcription-polymerase chain reaction (RT-PCR), duodenal biopsy-mRNA from the affected sisters was isolated and analyzed. The apo B editing site was amplified after cDNA synthesis, and the products analyzed by the primer extension assay. The results show that editing of apo B mRNA is normal in patients with CRD. The data provides strong confirmation that the primary defect in CRD is not in the synthesis, or editing of apo B mRNA in the gut. More likely, the disease arises from a defect in a gene crucial to the assembly and/or secretion of the chylomicron particle.

Donor splice mutation generates a lipid-associated apolipoprotein B-27.6 in a patient with homozygous hypobetalipoproteinemia

We report the characterization of a new truncated apolipoprotein (apo) B, originally identified in the plasma of a homozygous proband and three heterozygous family members with hypobetalipoproteinemia. Using Western blotting, the truncated apoB species was estimated to be 27.5% the size of apoB-100. After fast protein liquid chromatography of plasma from the proband (CD) and mother (OS), the truncated apoB was eluted with particles whose sizes were between normal low and high density lipoproteins. Sequencing of exons 21-24, including the intron-exon boundaries, revealed a T-->C transition at +2 of intron 24, homozygous in CD and heterozygous in OS, thus disrupting the 5' donor splice site and interrupting the translation of serine. On the basis of this, the truncated protein was estimated to be approximately apoB-27.6. The reason for this approximation is that splice-junction mutations can generate different mRNA transcripts, and the truncated protein might represent a mixture of novel carboxy-terminal peptides, terminated by in-frame STOP codons. To date, apoB-27.6 is the smallest truncated species identified in plasma and associated with lipid. An explanation for this could be the hydrophobic nature of the novel carboxy-terminal peptides, which might enable stabilization of the particles by solubilization of sufficient lipid.

Metabolism of beta-muricholic acid in the hamster and prairie dog

The metabolism of beta-muricholic acid was investigated in the prairie dog and the hamster. Intravenous infusion into bile fistula hamsters showed that beta-muricholic acid was extracted by the liver and secreted into the bile (> 85% in 1 h). Hepatic extraction of this compound and cholic acid in the prairie dog was not as rapid as in the hamster. In the bile of the prairie dog, most (93%) of the administered beta-muricholic acid was present as the taurine conjugate. In the hamster, 28% of infused beta-muricholic acid was secreted in unconjugated form, 43% as the taurine conjugate, and 22% as the glycine conjugate. In both species, the administered compound underwent little biotransformation. After intraduodenal injection of [6 alpha-3H]-labeled beta-muricholic acid into bile fistula hamsters, the bile acid was rapidly secreted into the bile; more than 80% of the administered radioactivity was recovered in 3 h. In the prairie dog, biliary recovery after intraduodenal administration of either beta-muricholic acid (43% in 3 h) or cholic acid (22% in 3 h) was slower than in the hamster. After intragastric administration, more than 80% of beta-muricholic acid was recovered unchanged in feces of both animal species.

Genetic exclusion of apo-B gene in recessive abetalipoproteinemia

Abetalipoproteinemia is a recessive genetic disorder of unknown origin, which is characterized by absence of circulating apo-B-containing lipoproteins, malabsorption of intestinal fat, and degenerative neurological and retinal lesions. In this study, four families were analysed for genetic linkage between the abetalipoproteinemia phenotype and the apo-B genotype determined from polymorphisms of XbaI, MsPI, EcoRI and PvuII restriction sites and that of the 3'-minisatellite of the apo-B gene. The results definitively exclude mutation of the apo-B gene as a causal factor of abetalipoproteinemia in three families. Consanguinity of the parents in the fourth family made genotyping less conclusive.

Regulation of HMG-CoA reductase, apoprotein-B and LDL receptor gene expression by the hypocholesterolemic drugs simvastatin and ciprofibrate in Hep G2, human and rat hepatocytes

The comparative effects of simvastatin (a competitive inhibitor of HMG-CoA reductase) and ciprofibrate (another inhibitor of cholesterogenesis) on the incorporation of [14C]acetate and [3H]mevalonate into cholesterol HMG-CoA reductase activity, apo-B synthesis, LDL receptor, and their corresponding mRNAs, have been studied in the human hepatoma cell line Hep G2 and in human and rat hepatocytes in primary culture. Incubation of Hep G2 with simvastatin (0.01-1.5 microM) or ciprofibrate (25-100 microM) produced not only a marked inhibition of cholesterogenesis from [14C]acetate but also from [3H]mevalonate, an intermediate downstream of the HMG-CoA reductase reaction. However, in human and rat hepatocytes, cultured in similar conditions, simvastatin inhibited only the cholesterol synthesis from [14C]acetate, as expected. HMG-CoA reductase activity was greatly induced in Hep G2 and rat hepatocytes after incubation with simvastatin (up to 400% of controls), but not with ciprofibrate. Increased enzyme activity was accompanied by a higher cell content of reductase mRNA. Apo-B concentration in the medium of Hep G2 cells was 31% lower after 31 h incubation with simvastatin than in controls. However, neither simvastatin nor ciprofibrate modified the synthesis rate of apo-B or its mRNA level. Both LDL-receptor and its mRNA levels were raised by simvastatin at concentrations inhibiting cholesterol synthesis. Our data show that, in this human hepatoma cell line, HMG-CoA reductase competitive inhibition by simvastatin triggers a coordinate regulation of the expression of genes coding for reductase and LDL receptor but not for apo-B. Ciprofibrate, though efficient in inhibiting cholesterogenesis, did not induce the same regulatory reactions. The reason for this discrepancy is unknown.

Synthesis of 6 alpha-tritiated beta-muricholic acid for use as a molecular probe

Regioselective oxidation of methyl beta-muricholate to give the 6-ketoderivative is described. Stereoselective reduction of this ketone with tritiated NaBH4 furnishes labeled methyl beta-muricholate. The structure of all compounds was confirmed by infrared, 1H, and 13C nuclear magnetic resonance spectroscopy. Data obtained by circular dichroism and mass spectroscopy were in agreement with the structure of the ketone 3.

Regulation of chylomicron remnant uptake in the human hepatoma cell-line Hep G2. Role of the low-density lipoprotein receptor

Uptake and degradation of chylomicron remnants by the human hepatoma cell line Hep G2 was studied. Mesenteric lymph was collected from rats and injected into hepatectomized rats to obtain chylomicron remnants. This remnant preparation was taken up and catabolized by Hep G2 cells. The uptake process was dependent on cell growth and was regulated by compactin (a HMG-CoA reductase inhibitor) which suppresses cholesterol synthesis and by mevalonolactone, which enhances cholesterol synthesis. A monoclonal anti LDL receptor antibody blocked binding of chylomicron remnants to Hep G2 cells to a degree, which was comparable to but generally lower than the suppression of low-density lipoprotein binding. The results thus indicate that in Hep G2 cells, chylomicron remnant uptake is regulated, similarly to low-density lipoprotein uptake and that a significant part of the remnant uptake is mediated through the LDL receptor.

Anderson's disease: genetic exclusion of the apolipoprotein-B gene in two families

Anderson's disease is a recessive disorder characterized by intestinal fat malabsorption, absence of postprandial chylomicrons, and reduced levels of cholesterol, triglycerides, and apoproteins B, AI, and C. We have studied two families with, respectively, three and two children with Anderson's disease. Intestinal apo-B and apo-AIV mRNAs from two Anderson's patients were normal in size but their concentration was decreased fivefold compared with controls. After DNA digestion with seven restriction enzymes, restriction fragment length polymorphisms of apo-B gene did not show conclusive information except for Xba1, which revealed a lack of cosegregation between the restriction fragment length polymorphism and the Anderson's phenotype. Linkage analysis was performed using the polymorphism of the apo-B gene 3'minisatellite. Genomic DNA from parents and children was amplified by polymerase chain reaction using oligonucleotide primers flanking the apo-B gene 3'hypervariable locus. In both families each child inherited different apo-B alleles from at least one parent. According to the recessive mode of transmission of the disease, our results are incompatible with the involvement of the apo-B gene. More likely a posttranslational defect or a mutation in another gene encoding a protein essential for lipoprotein assembly or secretion may be involved.

[Familial hypobetalipoproteinemia. Familial study of 4 cases]

A familial study of four cases with hypobetalipoproteinemia is reported. Three members are heterozygous and one is homozygous. This congenital fat malabsorption in homozygous state is commonly associated with an absence of serum apoprotein B and LDL. Neuromuscular and ophthalmological signs are absent in this case. The major role of upper digestive endoscopy in the diagnostic procedure is emphasized. Histochemical and immunoenzymatic stains of enterocytes and intestinal organ culture show defective synthesis apo B in the homozygous patient. Studies of DNA polymorphism in the homozygous patient have shown that the apo B gene doesn't certain major insertions or deletions. These results are discussed.

Effect of probucol on the lipid composition of blood plasma, erythrocyte ghosts and liver membranes in mice

1. Probucol treatment of mice (0.6 g/kg) induced a decrease of cholesterol (CH) and total phospholipids (PLs) in blood plasma, erythrocyte ghosts, liver plasma and microsomal membranes. 2. The incorporation of [14C]acetate in the microsomal lipids of probucol-treated mice was lowered by 23% compared to controls. 3. Probucol administration induced a reduced specific activity of PLs, CH and CH esters, whereas in triacylglycerols it was augmented. 4. Phospholipase A2 and neutral sphingomyelinase activities were not enhanced, indicating that the catabolism of the membrane PL was not elevated.

Description of two different patients with abetalipoproteinemia: synthesis of a normal-sized apolipoprotein B-48 in intestinal organ culture

We describe here two patients, M. P. and S. L., with recessive abetalipoproteinemia. Analysis of restriction fragments of DNA from both patients using cDNA probes spanning the entire apolipoprotein B gene revealed no major insertions or deletions. Further, as defined by restriction fragment length polymorphism, abetalipoproteinemia, in these patients, did not appear associated with particular alleles of apolipoprotein B. Northern and dot blot analysis of intestinal mRNA of one patient (M. P.) revealed a normal-sized apolipoprotein B mRNA which was present in slightly reduced amounts. At the cellular level apolipoprotein B was detected in both intestinal and hepatic biopsies, of one patient (S. L.), by immunoenzymatic techniques using polyclonal and monoclonal antibodies to apolipoprotein B-48 and/or B-100. The level of apolipoprotein B-48 appeared to increase in the intestine after a fatty meal. In the other patient (M. P.), although no apolipoprotein B was detected in the enterocytes using similar immunoenzymatic techniques, organ culture experiments using [35S]methionine demonstrated the synthesis of a normal-sized apolipoprotein B-48 which appeared to be normally glycosylated. The glycosylation and processing of two intestinal membrane enzymes, sucrase-isomaltase and aminopeptidase N, were also normal. Although lipids and apolipoprotein B-48 were present intracellularly, no lipoprotein-like particles were observed by electron microscopy in the endoplasmic reticulum, the Golgi apparatus, or in the intercellular spaces of intestinal biopsies obtained in the fasted (M. P. and S. L.) or fed state (S. L.). The defect in these cases of abetalipoproteinemia, therefore, does not appear to involve the apolipoprotein B gene nor the synthesis or the glycosylation of the apolipoprotein but instead appears to involve some aspect of lipoprotein assembly or secretion.

Membrane phospholipid composition, fluidity and phospholipase A2 activity of human hepatoma cell line HepG2

1. Investigations have been carried out on the phospholipid composition, physical state and phospholipase A2 activity of plasma and microsomal membranes from HepG2 cells. 2. The results showed a great similarity in the physico-chemical properties of plasma and microsomal membranes from HepG2 cells. 3. The activity of phospholipase A2 was found to depend on the membrane physical state in both types of membranes.

A family with the Bardet-Biedl syndrome and diabetes mellitus

We studied a family with the Bardet-Biedl syndrome and diabetes mellitus. Two affected brothers and one affected sister were examined. Two older sisters with stigmata of the syndrome had died of unclear causes. The 18-year-old brother was obese, was mentally retarded, and had pigmentary retinopathy and insulin-dependent diabetes mellitus. The 16-year-old sister, who died in a diabetic coma during the course of the investigation, had polydactyly, hypogenitalism, obesity, mental retardation, and pigmentary retinopathy. The 8-year-old brother had all the features of the syndrome, but no overt diabetes mellitus. Electroretinography showed severe cone and rod dysfunction. Patients with the Bardet-Biedl syndrome should be screened for the presence of abnormalities in glucose metabolism.

Lipid and lipoprotein synthesis in isolated and cultured hepatocytes from lean and obese Zucker rats

Hepatocytes were isolated by EDTA perfusion of livers from lean (Fa/-) and obese (fa/fa) Zucker rats. Triacylglycerol (TG) and sn-glycerol 3-phosphate were increased in fa/fa hepatocytes, but free fatty acids, cholesterol and phospholipid concentrations were similar in both groups. In spite of an identical fatty acid uptake rate, glycerolipid synthesis was higher in obese compared to lean rat hepatocytes, and this difference remained for at least 2-3 days of culture. Triacylglycerol mass secretion was 2-fold higher in obese than in lean rat hepatocytes. This was confirmed by the higher incorporation of labeled glycerol and oleic acid into the medium TG fraction floating at density 1.006 g/ml. Density gradient ultracentrifugation of [14C]oleate-labeled lipoproteins showed that fa/fa hepatocytes secreted more TG-rich lipoproteins, and that 87% of the label was in the VLDL fraction compared with 67% in the medium of Fa/- hepatocytes. Decreased utilisation of leucine for protein synthesis in obese rat compared to lean rat hepatocytes was associated with enhanced leucine oxidation to CO2. [35S]Methionine incorporation showed an identical cell protein synthesis rate. Autoradiography after PAGE separation of secreted apolipoproteins (apoBh, Bl, apoA-VI, apoE, apoA-I, apoC) showed an identical pattern in both cell types.

Effects of ciprofibrate and fenofibrate on liver lipids and lipoprotein synthesis in normo- and hyperlipidemic rats

The plasma lipoprotein and liver lipid composition, and the lipid, cholesterol and apolipoprotein synthesis have been studied in normal and diet-induced hyperlipidemic rats, receiving ciprofibrate (2.5 mg/kg body weight) or fenofibrate (50 mg/kg b.w.) for 8 days. Ciprofibrate is about 25-fold more active than fenofibrate in reducing plasma triglyceride and cholesterol concentrations both in normolipemic and in hyperlipemic rats. In normolipemic rats ciprofibrate reduced the concentration and the lipid content of all lipoprotein classes. The incorporation of [14C]palmitate and [3H]leucine into the lipoproteins was reduced by ciprofibrate and fenofibrate. The reduction in lipoprotein production was confirmed by prevention of Triton-induced hyperlipemia. Liver and plasma cholesterol synthesis estimated by 3H2O and [14C]mevalonate incorporation indicated an inhibitory effect on HMG-CoA reductase. Administration of ciprofibrate or fenofibrate to rats fed a fat and cholesterol-rich diet partially prevented liver steatosis and hyperlipemia. Both drugs reduced the overproduction of lower density lipoproteins. The ratio of (VLDL + LDL)-cholesterol/HDL-cholesterol which was increased by the diet alone from 0.4 (normal) to 11 remained close to the normal value in the animals receiving ciprofibrate. In the hyperlipemic animals, ciprofibrate reduced the incorporation of [3H]oleate into the liver and plasma glycerolipid and increased cholesterol esterification. Ciprofibrate efficiently reduces plasma levels of cholesterol, triglyceride and phospholipid. Cholesterol and glycerolipid synthesis in the liver were significantly reduced leading to a lower lipoprotein secretion rate in both normolipidemic and diet-induced hyperlipidemic rats.

Lipid and lipoprotein metabolism in Hep G2 cells

Lipid composition, lipid synthesis and lipoprotein secretion by the Hep G2 cell line have been studied with substrate and insulin supplied under different conditions. The lipid composition of Hep G2 cells was close to that of normal human liver, except for a higher content in sphingomyelin (P less than 0.005) and a lower phosphatidylcholine/sphingomyelin ratio. Most of the [14C]triacylglycerols secreted into the medium were recovered by ultracentrifugation at densities of 1.006 to 1.020 g/ml. The main apolipoproteins secreted were apo B-100 and apo A-I. Hep G2 mRNA synthesized in vitro the pro-apolipoproteins A-I and E. Triacylglycerol secretion was 7.38 +/- 1.04 micrograms/mg cell protein per 20 h with 5.5 mM glucose in the medium and increased linearly with glucose concentration. Oleic acid (1 mM) increased the incorporation of [3H]glycerol into the medium and cell triacylglycerols by 251 and 899%, with a concomitant increment in cell triacylglycerols and cholesterol ester. Insulin (1 mU or 7 pmol/ml) inhibited triacylglycerol secretion and [35S]methionine incorporation into secreted protein by 47 and 28%, respectively, with a corresponding increase in the cells. Preincubation of cells with 2.5-10 mM mevalonolactone decreased the incorporation of [14C]acetate into cholesterol 6.2-fold, indicating an inhibitory effect on HMG-CoA reductase. It is concluded that in spite of some differences between Hep G2 and normal human hepatocytes, this line offers an alternative and reliable model for studies on liver lipid metabolism.

Lipoprotein secretion in lean and obese Zucker female rats in vivo and in a single-pass-perfused liver preparation

The plasma lipoprotein composition as well as lipoprotein synthesis and secretion were studied in vivo and in a single-pass-perfused liver preparation in lean and obese Zucker rats. Compared with their lean littermates the levels in the plasma of very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL) + low density lipoprotein (LDL) and high density lipoprotein (HDL) were increased 4-, 2- and 2.5 fold, respectively, in obese rats. In these rats both VLDL and IDL + LDL were enriched in triglycerides, while the HDL were enriched in cholesterol. Although the VLDL and IDL + LDL protein concentrations were the same in lean and obese rats, the HDL protein concentration was 3-fold greater in the obese rats. Both the lean and obese rats incorporated similar amounts of [14C]leucine into total liver protein. However, obese rats incorporated 2.5-fold and 6-fold more [14C]leucine into VLDL and HDL in vivo, 2.7-fold and 1.7 fold more [35S]methionine in VLDL and HDL present in the perfusate, than did lean rats. The perfusate [35S]S-labelled apoproteins (apo-B100, B48; apo-E, apo-AI, apo-AIV and apo-C) were separated by gel electrophoresis and identified by autoradiography. Incorporation of [3H]glycerol into liver, VLDL, IDL + LDL and HDL triglycerides was 2-, 48-, 13- and 1.5-fold higher in obese than in lean rats, respectively. The [3H]-labelled triglycerides in VLDL and IDL + LDL present in the perfusate was 5.4-fold and 4.4-fold more in obese rat. There was no difference in the incorporation of [3H]glycerol into triglycerides of perfusate HDL between the two genotypes of rats. Thus, the hypertriglyceridaemia observed in obese Zucker rats results from very high synthetic rates of both the lipid and protein moieties of plasma lipoproteins. Before this study, no report of the simultaneous triglycerides and protein synthesis in vivo and in a single-pass-perfused liver preparations had been reported.

Synthesis and secretion of lipoproteins by human hepatocytes in culture

Confluent monolayers of normal human hepatocytes obtained by collagenase perfusion of liver fragments were incubated in a serum-free medium. Intracellular apolipoproteins apo AI, apo C, apo B, and apo E were detected between Day 1 and Day 6 of the culture by immunoenzymatic staining using polyclonal antibodies directed against these apoproteins and monoclonal antibodies directed against both forms of apo B (B100 and B48). Translation of mRNA isolated from these hepatocytes in an acellular system revealed that apo AI and apo E were synthesized as the precursor forms of mature plasma apo AI and apo E. Three lipoprotein fractions corresponding to the density of very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density lipoprotein (HDL) were isolated from the medium at Day 5 of culture and examined by electron microscopy after negative staining. VLDL and LDL particles are similar in size and shape to plasma lipoproteins; spherical HDL are larger than normal plasma particles isolated at the same density. Their protein represented 44, 19.5, and 36.5% respectively, of the total lipoprotein protein. The secretion rate of VLDL protein corresponded to that measured in primary cultures of rat hepatocytes. After incorporation of [3H]glycerol, more than 92% of the [3H]triglyceride secreted into the medium was recovered in the VLDL fraction. These results demonstrate that primary cultures of normal human hepatocytes are able to synthesize and secrete lipoproteins and thus could be a useful model to study lipoprotein metabolism in human liver.

The healing of colonic anastomoses after early intraperitoneal chemotherapy: an experimental study in rats

Early postoperative intraperitoneal administration of 5-fluorouracil (5-Fu) is a logical adjuvant treatment of patients with resectable colonic cancers. It is easier and less invasive than the intraportal administration of the drug. However, before applying the procedure to humans it must be demonstrated than it does not disturb the healing of recent colonic anastomoses. Colonic sutures were performed in 78 male Wistar rats. The animals then either served as controls or received intraperitoneal 5-Fu during 5 days starting on the first, third, or seventh postoperative day. No statistical difference was observed between treated and control groups when observing the incidence of anastomotic spontaneous disruptures, anastomotic healing strength, or the weight of the animals. It is concluded that early intraperitoneal 5-Fu administration does not impair the healing of recent colonic anastomoses in rats.

Hepatic transport of bile acids in the isolated perfused rat liver. Structure-kinetic relationship

We studied the transport kinetics of a series of bile acids from blood to bile in the isolated perfused rat liver in order to define better the relationship between chemical structure of bile acid molecules and efficiency of the overall hepatic transport process. BA studied were taurocholate (TC), glycocholate (GC), cholate (C), tauroursodeoxycholate (TUDC), ursodeoxycholate (UDC) and hyodeoxycholate (HDC). Estimates of intrinsic hepatic clearance (Cl(int)), maximal secretory rate (Vmax) were provided from the analysis of the relationship between bile acid removal rates and sinusoidal concentration under steady-state conditions. TC and TUDC had the highest Cl(int) (about 5 ml/min/g liver) and Vmax (about 800 nmol/min/g liver) followed in order by GC (1.71 ml/min/g liver; 442 nmol/min/g liver); C (1.25 ml/min/g liver; 252 nmol/min/g liver); HDC (0.86 ml/min/g liver; 238 nmol/min/g liver); UDC (0.72 ml/min/g liver; 176 nmol/min/g liver). The findings suggest that the efficiency of the overall hepatic transport of bile acids is highly dependent on their molecular structure and that conjugation has a more important effect on both Cl(int) and Vmax that the number or position of hydroxyl groups.

Role of the reticuloendothelial system in the catabolism of low density lipoprotein in the rat

The role of the reticuloendothelial system (RES) in receptor-independent catabolism of human low density lipoprotein (h-LDL) was evaluated in the rat in vivo after blockade of its phagocytic activity with gadolinium chloride (GaCl3). After blockade of the RES with GaCl3, the recovery of [125I] h-LDL in the liver of 17 alpha-ethinyl oestradiol-treated rats (EE-rats), was decreased by 37 and 16%, 15 and 60 min after h-LDL injection, respectively. This decrease did not result in a decreased LDL degradation which represented 14 and 55% of the injected dose in the two groups of rats after 15 and 60 min respectively, both on GaCl3 and control rats. Contrasting with EE-rats, the catabolism of h-LDL in untreated rats is much slower and takes place essentially through a receptor-independent mechanism. Six hours after the injection of [125I] h-LDL, 64% of the dose was degraded. This proportion decreased to 45% after blockade of the RES phagocytic activity. This 30 percent difference represents the proportion of h-LDL catabolized by receptor-independent mechanisms present in the Küpffer and endothelial cells. We conclude from our study that in the normal rat, the parenchymal cells of the liver on the one hand and the Küpffer and endothelial cells on the other hand contribute 70 and 30% respectively to the receptor-independent catabolism of low density lipoproteins in vivo.

beta-Muricholic acid; potentiometric and cholesterol-dissolving properties

Some physicochemical properties of beta-muricholic acid (3 alpha,6 beta,7 beta-trihydroxy-5 beta-cholanic acid), a major bile acid biosynthesized by rat liver, were determined and compared to those of ursodeoxycholic and chenodeoxycholic acids. From potentiometric studies, the following characteristics of beta-muricholic acid were shown: a low monomer solubility (13 microM), a high equilibrium precipitation pH (7.92 for 30 mM solution), an apparent critical micellar concentration of 4 mM, and a very low micellar capacity of the bile salt to dissolve the protonated bile acid. Sodium beta-muricholate solution (30 mM) poorly solubilized cholesterol, as indicated by a bile salt/cholesterol molar ratio of 1430, whereas saturation ratios obtained with chenodeoxycholate and ursoseoxycholate were 24 and 384, respectively. Sodium beta-muricholate (30 mM)/phosphatidylcholine/cholesterol mixtures contained non-micellar aggregates from very low cholesterol concentrations. At physiological phosphatidylcholine concentrations, sodium beta-muricholate (100 mM) dissolved cholesterol crystals via essentially lamellar liquid-crystal formation. These solubilizing properties might have important physiological relevance to the dissolution of cholesterol gallstones in man.

In vitro synthesis of apo-A-IV and apo-C by liver and intestinal mRNAs from lean and obese Zucker rats

The relative content and expression of mRNA coding for apolipoproteins A-IV and C in liver and intestinal cells have been studied in obese hyperlipemic (fa/fa) and lean (Fa/-) Zucker rats. The RNA were translated in a rabbit reticulocyte lysate system using 35S methionine as label. Apo-A IV and apo-C were immunoprecipitated with specific antibodies and characterized by electrophoresis and autoradiography. The content and expression of mRNA specific for apo-A-IV and apo-C was much higher and the liver of obese than of lean rats. The apo-A-IV and apo-C synthetic capacity of intestinal cells from fa/fa and Fa cells from fa/fa and Fa rats was similar suggesting that the lipoprotein overproduction, already described in obese Zucker rats, is mainly from hepatic origin.

Can hepatocytes proliferate when transplanted into the spleen? Demonstration by autohistoradiography in the rat

The aim of this work was to study hepatocyte multiplication after transplantation into the spleen, in order to apply this technique to the treatment of chronic liver disease. Hepatocytes isolated by an in situ collagenase perfusion technique in Wistar Furth rats were injected into the splenic parenchyma of three groups of syngeneic rats: controls with normal liver (group 1), 75% hepatectomies (group 2), and end-to-side portacaval shunts (group 3). The proliferation of transplanted hepatocytes was studied by autohistoradiography after the intraperitoneal administration of 0.6 microCi/g body weight of [3H]-thymidine, at 1, 3, 7 and 15 days after transplantation of hepatocytes. Significant incorporation of [3H]-thymidine by the transplanted hepatocytes during the study period was observed mostly in groups 2 and 3. The incorporation, although delayed was sustained and of greatest magnitude in the portacaval-shunted animals. The ability of transplanted hepatocytes to proliferate in the spleen, particularly after a portacaval shunt, indicates that this procedure may have therapeutic applications in the treatment of chronic liver disease.

Hypobetalipoproteinemia with accumulation of an apoprotein B-like protein in intestinal cells. Immunoenzymatic and biochemical characterization of seven cases of Anderson's disease

We describe here seven cases (from five kindreds) of Anderson's disease, which is characterized by diarrhea, steatorrhea, hypobetalipoproteinemia with low levels of cholesterol, triglycerides, and phospholipids, and failure to secrete chylomicrons after a fat meal. Enterocytes isolated from intestinal biopsies of patients after overnight fast showed numerous fat droplets, a histological picture resembling that of abetalipoproteinemia. Immunoenzymatic staining of the enterocytes demonstrated large amounts of material that reacted with a polyclonal antiserum to apolipoprotein B. Further, the immunoreactive material was found to react with several different monoclonal antibodies capable of recognizing both the B100 and B48 forms of apoprotein B, but not with any of several monoclonal antibodies capable of recognizing only B100. This suggests that the material in the enterocytes is the B48 form of apoprotein B or a fragment thereof. Additional findings included decreased low density lipoprotein levels with an abnormal chemical composition, abnormal high density lipoprotein2 (HDL2) and HDL3 particle size distributions, and an abnormal HDL apoprotein composition. Increased amounts of proteins having electrophoretic mobilities similar to apo E and the E-AII complex were present. Finally, some cases exhibited additional protein components of apparent molecular weights between 17,000 and 28,000, which was similar to some cases of abetalipoproteinemia. These findings demonstrate that Anderson's disease is not due to the absence of synthesis of intestinal apo B and suggest that it is more complex than previously thought, affecting all the lipoprotein classes.

Phospholipid-transfer proteins in human liver and primary liver carcinoma

Investigations have been carried out on phospholipid-transfer activity of the cytosol and the phospholipid composition of subcellular membranes from human liver and primary liver carcinoma. In both human liver and primary liver carcinoma cytosolic fractions, the transfer activity for phosphatidylcholine (PC), phosphatidylethanolamine (PE) and sphingomyelin has been observed for the first time. The transfer rate of PC and PE in normal human liver was almost equal, whereas sphingomyelin-transfer activity was much slower. In carcinoma cells, the transfer activity for PE and PC was significantly enhanced, while sphingomyelin transfer remained unchanged. Comparative investigations with HepG2 cultured cells have revealed a high PE-transfer activity in this cell line. Parallel with the phospholipid-transfer activity modifications in neoplasic cells, changes in the phospholipid composition of microsomes and mitochondria have been observed. The content of PC and PE in hepatocarcinoma cells was decreased in microsomes, while in the mitochondria it was increased. The possible role of the phospholipid-transfer proteins in the maintenance of membrane composition and structure is discussed.

Metabolism of doxorubicin and epirubicin in adult human hepatocytes in culture

Epirubicin is the only anthracycline to be metabolized in humans through a glucuronidation pathway which is not observed in laboratory animals. In search of a model for the experimental study of this metabolism, we have observed that human hepatocytes in culture exhibited this pathway and could be of interest for the understanding of the metabolism of this new drug.

Fecal bile acid excretion and liver cholesterol synthesis after sucralfate and cholestyramine administration in the rat

The relative ability of the resin cholestyramine and sucralfate (disucrose octasulfate) to bind bile acids in the gastro intestinal tract and increase fecal bile acid excretion has been studied in normal rats under standard diet. Plasma and liver cholesterol concentrations and in vitro cholesterol synthesis from 14C-acetate by liver slices, have been determined before and after one and three weeks of drug administration (0.5 or 1.0 g/100 g food). Plasma and liver cholesterol levels were unchanged after one week of treatment, but a moderate decrease in liver cholesterol content was observed after 3 weeks administration of cholestyramine and, to a lesser extent of sucralfate. Both drugs increase fecal bile acid excretion with a definitely higher effect of cholestyramine at either dose or period of administration. However, the resin produced a higher bile acid excretion after one week than after three weeks, whereas sucralfate effect increases with the time of administration. In vitro cholesterogenesis was clearly increased by cholestyramine and moderately by sucralfate although 14C-acetate incorporation into cholesterol was not quantitatively correlated to the amount of bile acid excreted in feces. The potential interest of sucralfate as bile acid sequestrant and hypocholesterolemic agent in man deserves further investigations.

Free fatty-acid uptake by isolated rat hepatocytes

In isolated rat hepatocytes, the rate of palmitic acid binding and uptake is directly related to the concentration of free fatty acid (FFA) in the medium. After their entry into the cell, FFA are immediately incorporated into cellular phospholipids and triglycerides and no accumulation of free fatty acids can be demonstrated inside the cell. The rate of free fatty-acid uptake remains unchanged after incubation in a 2 mM KCN containing medium, indicating that in the range of fatty-acid concentrations used in this study, this phenomenon does not require energy.

Glucuronidation of bile acids in human liver, intestine and kidney. An in vitro study on hyodeoxycholic acid

The activities of UDP-glucuronyl transferase(s) in homogenates and microsomal preparations of human liver, kidney and intestine were tested with hyodeoxycholic acid (HDC). The various kinetic parameters of the UDC-glucuronidation were determined from time course experiments. In both liver and kidney preparations, HDC underwent a very active metabolic transformation: liver Km = 78 microM, Vmax = 3.3 nmol . min-1 . mg-1 protein; kidney Km = 186 microM, Vmax = 9.9 nmol . min-1 . mg-1 protein. To our knowledge this is the first observation of both an extensive and comparable bile acid glucuronidation occurring in renal and hepatic tissues.

Isolation of rat hepatocytes with EDTA and their metabolic functions in primary culture

Isolated hepatocytes from adult rat liver were prepared after dissociation of the liver with EDTA. The morphological appearance, viability (94.5%) and yield (1.76.10(7) cells/g liver) compare well with those of previously described methods using collagenase. Differentiated functions of the hepatocytes in primary culture such as albumin secretion (10.9 micrograms/mg cell protein/d) and triglyceride synthesis and secretion are maintained. Induction of triglyceride synthesis and secretion by oleic acid takes place to an extent similar to that observed in vivo and liver perfusion. Particles with a lipid composition resembling circulating very low density lipoproteins are secreted into the medium. These characteristics demonstrate the ability of hepatocytes isolated with EDTA and subsequently used in primary culture to retain complex and highly differentiated functions of the intact liver.