Alterations of the immunosuppressive IL4I1 enzyme activity induced by naturally occurring SNP/mutations.

The immunosuppressive phenylalanine oxidase interleukin 4-induced gene 1 (IL4I1), primarily produced by antigen-presenting cells, inhibits T-cell proliferation and promotes the generation of Foxp3(+) regulatory T cells in vitro. Highly expressed by tumour-associated macrophages from human cancers, IL4I1 has a potential role in immune evasion from the anti-tumour immune response. We have reviewed single-nucleotide polymorphisms (SNPs) and mutations described for the exon 4 of the IL4I1 isoform 1, which is expressed in lymphoid tissue. Two of them were expressed in an exogenous system to analyse their effect on the enzymatic activity. The N92D SNP leads to a hyperactive enzyme, while the R102G mutation is hypomorphic. Moreover, we show that IL4I1 activity is not only directed against phenylalanine, as initially described, but also at a lower level against arginine. These data pave the way to more extensive analyses of the mutational state of IL4I1 in pathological conditions such as cancer, where its participation in immune system dysfunctions may have therapeutic implications.

Photochemical upconversion and triplet annihilation limit from a boron dipyrromethene emitter.

Non-coherent sensitized red-to-green upconversion has been achieved utilizing platinum(II) tetraphenyltetrabenzoporphyrin (PtTPTBP) as the triplet sensitizer and a nearly quantitatively fluorescent meso-(2,6-dichloropyridyl)-substituted boron dipyrromethene (Cl2PyBODIPY) chromophore (Φ = 0.99 in toluene) as the energy acceptor/annihilator in deoxygenated toluene. Dynamic Stern-Volmer analysis revealed that PtTPTBP phosphorescence as quenched by Cl2PyBODIPY occurs with a KSV of 108,000 M(-1), yielding a triplet-triplet energy transfer rate constant of 2.3 × 10(9) M(-1) s(-1). Using a non-coherent red light-emitting diode excitation source centered at 626 nm, the incident power dependence responsible for generating singlet BODIPY fluorescence in the green was shown to traverse quadratic to linear regimes, the latter being achieved near 60 mW cm(-2). These data were consistent with a photochemical upconversion mechanism being responsible for generating singlet fluorescence from the Cl2PyBODIPY chromophores through sensitized triplet-triplet annihilation (TTA). Integrated delayed fluorescence transients were utilized to reveal the TTA efficiency for the Cl2PyBODIPY chromophore and saturated near 46%, representing the lower limit for the TTA process. Kinetic modelling of the delayed fluorescence transient produced from 1.5 mJ laser pulses (λex = 615 nm) revealed a maximum limiting TTA efficiency of 64% for this upconverting composition, implying that this is indeed an extremely relevant acceptor/annihilator composition for photochemical upconversion.

Rare cardiomyopathies: diagnostic features.

Cardiomyopathies (CM) are an important and heterogeneous group of diseases affecting the myocardium. They can induce mechanical and/or electrical disorders and are due to a variety of causes, they frequently are genetic. However, since their high number and their clinical complexity, the identification is still a challenge. Echocardiography is a very useful tool in the assessment of CM. In this review we aim to define the typical clinical features and to discuss the main diagnostic tool, above all echocardiography that can help physicians in the correct assessment of CM.

[Megalencephalic leukoencephalopathy with cysts -the clinical importance in the genetic era]. / Leucoencefalopatía megalencefálica con quistes: importancia de la descripción clínica en la era genética.

INTRODUCTION: Megalencephalic leukoencephalopathy with cysts is a leukodystrophy of genetic origin that produces an alteration in the water and ion homeostasis in the brain, generating vacuolar forms and chronic oedema in the white matter with progressive neurological deterioration. It should be suspected in infants who present progressive macrocephaly during the first year of life, motor retardation and characteristic findings in magnetic resonance brain scans. CASE REPORT: We report the case of a girl who was followed up from the age of 9 months due to progressive macrocephaly and delayed psychomotor development and brain MRI findings consistent with megalencephalic leukoencephalopathy with cysts, and the appearance of epilepsy during its development. The usual genetic studies (new generation sequencing and array) were negative, but as the diagnostic criteria were met, a complementary messenger RNA and DNA study was conducted, which confirmed the presence of two pathogenic variants in MLC1. CONCLUSIONS: Megalencephalic leukoencephalopathy with cysts is a rare condition. Progressive macrocephaly in the first year of life, the absence of deterioration or slow deterioration, and the possibility of developing epilepsy, spasticity and ataxia are characteristic signs in its course. It is important for these patients to undergo an imaging test that shows findings that characterise this condition, which, together with the clinical features, makes it possible to differentiate it from other leukodystrophies and to establish a confirmatory diagnosis. Genetic studies can confirm the associated mutation that makes it possible to predict the clinicoradiological phenotype.

TITLE: Leucoencefalopatía megalencefálica con quistes: importancia de la descripción clínica en la era genética.Introducción. La leucoencefalopatía megalencefálica con quistes es una leucodistrofia de origen genético que produce una alteración de la homeostasis del agua e iones en el cerebro, generando formas vacuolares y edema crónico en la sustancia blanca con deterioro neurológico progresivo. Debe sospecharse en los lactantes que presentan macrocefalia progresiva durante el primer año de vida, retraso motor y hallazgos característicos en la resonancia magnética cerebral. Caso clínico. Niña en seguimiento desde los 9 meses por macrocefalia progresiva y retraso del desarrollo psicomotor con presencia en la resonancia magnética cerebral de hallazgos compatibles con leucoencefalopatía megalencefálica con quistes, y aparición de epilepsia en su evolución. Los estudios genéticos habituales (secuenciación de nueva generación y array) fueron negativos, pero, al cumplir los criterios diagnósticos, se procedió al estudio del ARN mensajero y el ADN complementario, que confirmó la presencia de dos variantes patogénicas en MLC1. Conclusiones. La leucoencefalopatía megalencefálica con quistes es una entidad infrecuente. Es característica la macrocefalia progresiva en el primer año de vida, la ausencia de deterioro o deterioro lento, y la posibilidad de desarrollar epilepsia, espasticidad y ataxia en su evolución. Cobra importancia en dichos pacientes la realización de una prueba de imagen que muestre hallazgos propios de la entidad, lo que, junto con la clínica, permite diferenciarla de otras leucodistrofias y establecer un diagnóstico confirmatorio. Los estudios genéticos pueden constatar la mutación asociada que posibilita predecir el fenotipo clinicorradiológico.

Inducible recruitment of Cdc42 or WASP to a cell-surface receptor triggers actin polymerization and filopodium formation.

BACKGROUND: Cdc42, a GTP-binding protein of the Rho family, controls actin cytoskeletal organization and helps to generate actin-based protruding structures, such as filopodia. In vitro, Cdc42 regulates actin polymerization by facilitating the creation of free barbed ends - the more rapidly growing ends of actin filaments - and subsequent elongation at these ends. The Wiskott- Aldrich syndrome protein, WASP, which has a pleckstrin-homology domain and a Cdc42/Rac-binding motif, has been implicated in cell signaling and cytoskeleton reorganization. We have investigated the consequences of local recruitment of activated Cdc42 or WASP to the plasma membrane. RESULTS: We used an activated Cdc42 protein that could be recruited to an engineered membrane receptor by adding rapamycin as a bridge, and added antibody-coupled beads to aggregate these receptors. Inducible recruitment of Cdc42 to clusters of receptors stimulated actin polymerization, resulting in the formation of membrane protrusions. Cdc42-induced protrusions were enriched in the vasodilator-stimulated phosphoprotein VASP and the focal-adhesion-associated proteins zyxin and ezrin. The Cdc42 effector WASP could also induce the formation of protrusions, albeit of different morphology. CONCLUSIONS: This is the first demonstration that the local recruitment of activated Cdc42 or its downstream effector, WASP, to a membrane receptor in whole cells is sufficient to trigger actin polymerization that results in the formation of membrane protrusions. Our data suggest that Cdc42-induced actin-based protrusions result from the local and serial recruitment of cytoskeletal proteins including zyxin, VASP, and ezrin.

Elucidation of a PTS-carbohydrate chemotactic signal pathway in Escherichia coli using a time-resolved behavioral assay.

Chemotaxis of Escherichia coli toward phosphotransferase systems (PTSs)-carbohydrates requires phosphoenolpyruvate-dependent PTSs as well as the chemotaxis response regulator CheY and its kinase, CheA. Responses initiated by flash photorelease of a PTS substrates D-glucose and its nonmetabolizable analog methyl alpha-D-glucopyranoside were measured with 33-ms time resolution using computer-assisted motion analysis. This, together with chemotactic mutants, has allowed us to map out and characterize the PTS chemotactic signal pathway. The responses were absent in mutants lacking the general PTS enzymes EI or HPr, elevated in PTS transport mutants, retarded in mutants lacking CheZ, a catalyst of CheY autodephosphorylation, and severely reduced in mutants with impaired methyl-accepting chemotaxis protein (MCP) signaling activity. Response kinetics were comparable to those triggered by MCP attractant ligands over most of the response range, the most rapid being 11.7 +/- 3.1 s-1. The response threshold was <10 nM for glucose. Responses to methyl alpha-D-glucopyranoside had a higher threshold, commensurate with a lower PTS affinity, but were otherwise kinetically indistinguishable. These facts provide evidence for a single pathway in which the PTS chemotactic signal is relayed rapidly to MCP-CheW-CheA signaling complexes that effect subsequent amplification and slower CheY dephosphorylation. The high sensitivity indicates that this signal is generated by transport-induced dephosphorylation of the PTS rather than phosphoenolpyruvate consumption.

[Contiguous gene deletion syndrome in Xp21: the association between glycerol kinase deficiency, congenital suprarenal hypoplasia and Duchenne's muscular dystrophy]. / Sindrome de deleción de genes contiguos en Xp21: asociación de deficiencia de glicerolcinasa, hipoplasia suprarrenal congénita y distrofia muscular de Duchenne.

INTRODUCTION: Complex glycerol kinase (GK) deficiency is a contiguous deletion of genes in Xp21 with loss of the locus for GK, for congenital adrenal hypoplasia (AHC) and/or for Duchenne's muscular dystrophy (DMD). We report the case of a 7-year-old patient with this rare disease. CASE REPORT: Our patient was a full-term male, with normal gestation and delivery, and no relevant family history. At the age of 11 days he presented a clinical picture of salt loss with lethargy, vomiting, metabolic acidosis, hypoglycaemia, hyponatraemia and hyperpotassaemia. Fluid therapy and treatment with corticoids was established. The patient's condition developed with moderate mental retardation and progressive muscular weakness. In the physical examination, the skull and face were seen to be 'hourglass' shaped. Decompensations associated to infectious processes and fasting hypoglycaemia, hydroelectrolytic disorders and ketoacidosis are all frequent. Lab findings showed a drop in cortisol levels, elevation of muscle enzymes, 'pseudohypertriglyceridaemia' and raised levels of glycerol in plasma and urine. Karyotype and neuroimaging tests were normal. A myopathic pattern was observed in the electromyogram. The genetic study confirmed the deletion in Xp21 of the genes responsible for DMD, the GK deficit and AHC. CONCLUSIONS: Early identification of this disease makes it possible to foresee the acute metabolic decompensations and to establish suitable genetic counselling. CK and triglyceride counts should be performed in all male patients that present a suprarenal hypoplasia; if levels are high, then it is necessary to confirm the raised glycerol values and to carry out a confirmatory genetic study.

[Endourological treatment of pelviureteric junction obstruction in paediatric patients: our experience]. / Tratamiento endourológico de la estenosis pieloureteral en la edad pediátrica: nuestra experiencia.

UNLABELLED: Endourological treatment of pelviureteric junction obstruction in paediatric patients: our experience. INTRODUCTION: Pelviureteric junction (PUJ) obstruction is the most common cause of hydronephrosis in the infancy. The gold standard of treatment is open pyeloplasty, but there is an ever greater tendency towards minimally invasive procedures. We present our serie of paediatric patients with endourologically treated PUJ obstruction, together with a review of the literature. MATERIAL AND METHODS: Retrospective, descriptive study of the children diagnosed of PUJ obstruction who were treated by an endourological technique in our centre between January 1988 and January 2005. We gathered data on 3 periods of time: 1st. Presurgical: age, sex, previous treatment, ultrasound (USS) and nuclear medicine (MAG-3) studies; 2nd. Surgical: type of procedure; 3rd. Surgical: recurrence or not and its treatment, and the current state of the patient. RESULTS: Seven children, with an age range of 13 months to 14 years, underwent operation using an endourological technique. The treatment was secondary in five of these patients, after open pyeloplasty, and was primary in 2 cases. The preoperative USS showed grade III dilatation in 3 and grade IV dilatation in 4, and the MAG-3 study showed type II curves in 6 and a type IIIb curve in 1. Three percutaneous endopyelotomies were performed and, by the retrograde approach, 3 balloon dilatations and one Acucise. With a mean follow-up of 37 months, 2 cases of recurrence (both in patients receiving secondary treatment) have been observed, one in whom a retrograde technique (balloon dilatation) was used and the other in a patient treated by an antegrade technique. The remaining five patients are asymptomatic and show no evidence of recurrence (71% of the patients). CONCLUSION: The endourological treatment of PUJ obstruction in paediatric patients is possible but must be individualised in each case. Larger, prospective studies need to be performed in order to reach conclusions.

Hydroxyl radical production in the reactions of copper-containing amine oxidases with substrates.

Solutions of porcine kidney diamine oxidase, PKDAO, and bovine plasma amine oxidase, BPAO, were saturated with the spin-trapping agent alpha-phenyl-N-t-butylnitrone, PBN, and incubated with cadaverine or benzylamine substrate, respectively, under aerobic conditions. EPR spectra due to trapped hydroxyl radicals were obtained for both enzymes with no evidence of superoxide formation. Under anaerobic conditions, hydroxyl radicals were formed only when H2O2 was present as well as substrate. Catalase prevented hydroxyl radical formation by PKDAO but not BPAO. The results indicate that hydroxyl radical is produced in the reaction of the product H2O2 with the reduced enzymes and therefore may be important in turnover-related enzyme degradation, but is not a true reaction intermediate.

Long-lifetime Ru(II) complexes for the measurement of high molecular weight protein hydrodynamics.

We describe the synthesis and characterization of two asymmetrical ruthenium(II) complexes, [Ru(dpp)2(dcbpy)]2+ and [Ru(dpp)2(mcbpy)]2+, as well as the water soluble sulfonated derivatives [Ru(dpp(SO3Na)2)2(dcbpy)]2+ and [Ru(dpp(SO3Na)2)2(mcbpy)]2+ (dpp is 4,7-diphenyl-1,10-phenanthroline, dcbpy is 4,4'-dicarboxylic acid-2,2'-bipyridine, mcbpy is 4-methyl,4'-carboxylic acid-2,2'-bipyridine, and dpp(SO3Na)2 is the disulfonated derivative of dpp) as probes for the measurement of the rotational motions of proteins. The spectral (absorption, emission, and anisotropy) and photophysical (time-resolved intensity and anisotropy decays) properties of these metal-ligand complexes were determined in solution, in both the presence and absence of human serum albumin (HSA). These complexes display lifetimes ranging from 345 ns to 3.8 microseconds in deoxygenated aqueous solutions under a variety of conditions. The carboxylic acid groups on these complexes were activated to form N-hydroxysuccinimide (NHS) esters which were used to covalently lable HSA, and were characterized spectroscopically in the same manner as above. Time-resolved anisotropy measurements were performed to demonstrate the utility of these complexes in measuring long rotational correlation times of bioconjugates between HSA and antibody to HSA. The potential usefulness of these probes in fluorescence polarization immunoassays was demonstrated by an association assay of the Ru(II)-labeled HSA with polyclonal antibody.

Childhood-onset systemic lupus erythematosus: antiphospholipid antibodies in 37 patients and their first-degree relatives.

OBJECTIVE: Antiphospholipid antibodies (aPL) are noted with increased frequency in patients with systemic lupus erythematosus (SLE). The main manifestations found to be associated with aPL are arterial and venous thrombotic events, thrombocytopenia, and recurrent pregnancy loss. This study is an attempt to define the incidence of aPL in patients with childhood-onset SLE and in their relatives and to correlate their presence with clinical manifestations, and especially, to evaluate the risk of thrombosis in aPL-positive subjects. METHODOLOGY: We studied 37 unrelated patients and 107 of their first-degree relatives. VDRL, IgG and IgM anticardiolipin, and IgG antiphosphatidylethanolamine antibodies were studied in all probands during periods of clinical remission and in first-degree relatives at the time of interview. Lupus anticoagulant had only been studied in probands during an SLE flare-up. RESULTS: Thirty-eight percent of probands and 19% of relatives were positive for at least one aPL, with little overlap between the different aPL studied. -No aPL-negative proband developed thrombosis. Two of the aPL-positive probands had thrombotic events before testing, and a third one showed thrombosis after testing. Only two probands had high levels of IgG aCL and showed thrombosis. The occurrence of aPL positivity in relatives was not always related to its presence in probands. None of the aPL-positive relatives had had thrombosis, but recurrent fetal loss was noted in one aPL-positive mother with SLE. Although there was a high frequency of SLE, SLE-like disease, auto-immune disorders or positive serological findings for lupus in first-degree relatives, many of these relatives did not test positive for aPL. CONCLUSION: The high levels of IgG aCL may be considered a risk factor for thrombosis. Findings in relatives suggest a multifactorial origin for autoimmune disease and antibody production.

Effects of cholesterol uptake from high-density lipoprotein on bile secretion and 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity in perfused rat liver.

Small aliquots of rat high-density lipoproteins (HDL) (388 +/- 67 nmol lipoprotein cholesterol) were labeled with [14C]cholesterol and administered as a bolus to perfused rat livers. Bile and perfusate samples were collected for 2 hours at 30-minute intervals. After perfusion, both the microsomes and lipid extracts were prepared from the livers. Lipid composition was examined in both liver and microsomes, and 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase activity was evaluated in microsomes. Basal values of bile flow, lipid composition, and enzyme activity were evaluated using livers in which perfusion was discontinued before injecting the lipoprotein. In some experiments, the effect of perfusion per se was assessed by infusing saline instead of lipoprotein. After 10 minutes of lipoprotein perfusion, 50% of cholesterol administered was taken up by the perfused liver. During infusion, transient but significant increases in both bile flow and bile steroid secretion were observed. Cholesterol administration, even if rapid, represented less than 0.4% of total liver cholesterol content. However, this was enough to significantly increase the cholesterol to phospholipid (CH/PL) molar ratio in liver microsomes and at the same time decrease HMG-CoA reductase activity. In conclusion, the main response of the perfused liver to HDL cholesterol infusion is a reduced activity of the rate-limiting enzyme in cholesterol biosynthesis, due to the shift in the microsomal CH/PL molar ratio. A small proportion of the infused cholesterol enters bile as cholesterol and bile salts.

Characterization of the response of growth and differentiation to lipoproteins and agents affecting cholesterol metabolism in murine neuroblastoma cells.

Treatment with mevinolin, a competitive inhibitor of HMGCoAR, the key enzyme of isoprenoid metabolism, causes the arrest of proliferation and the differentiation of a neuroblastoma cell line (N18TG2). Mevalonate and high density lipoproteins partially restore growth. Cholesterol synthesis in the presence of mevinolin remains active, because in these cells the key enzyme HMG-CoA reductase is not completely inhibited by this drug. The fact that cell growth is reduced, while cholesterogenesis remains active, suggests that mevinolin acts by interfering with the synthesis of some unknown compound, other than cholesterol, which is necessary for proliferation.

Two-photon excitation of ethidium bromide labeled DNA.

We examined the steady state and time-resolved emission of DNA stained with ethidium bromide (EB) when excited with 90 fs pulses from a mode-locked titanium sapphire laser. Over the wavelength range from 840 to 880 nm EB-DNA was found to display two-photon excitation, with a cross-section near 7 x 10(-50) cm4s/photon. Frequency-domain intensity decay measurements revealed similar multi-exponential intensity decays for one- and two-photon excitation. Time-resolved anisotropy decay measurements revealed similar correlation times, but different amplitudes as has been observed previously for two- versus one-photon excitation. These results indicate that two-photon excitation of EB-DNA can be accomplished with the fundamental output of a Ti:sapphire laser without obvious heating or perturbation of the DNA.

A long-lifetime Ru(II) metal-ligand complex as a membrane probe.

A luminescent metal-ligand complex, [Ru(bpy)2(dppz)]2+, (where dppz is dipyrido[3,2-a:2',3'-c] phenazine), was used as a photoluminescence probe for investigating submicrosecond lipid dynamics in a dipalmitoyl-L-alpha-phosphotidylglycerol (DPPG) model bilayer system. The luminescence of [Ru(bpy)2(dppz)]2+ in buffer is completely quenched but becomes luminescent when intercalated into DPPG vesicles. The experimental results show that the emission intensity of [Ru(bpy)2(dppz)]2+ intercalated into DPPG vesicles increases dramatically as temperature is increased towards the lipid phase transition temperature. This effect is abolished in bilayers containing a high concentration (> 30 mol%) of cholesterol, suggesting this probe is sensitive to the membrane composition. Frequency-domain emission intensity decays, measured as a function of increasing temperature towards the lipid phase transition temperature (2 to 57 degrees C), display two major lifetime components. The short lifetime disappears at temperatures well above the phase transition temperature. A comparison of oxygen quenching with iodide quenching suggests the heterogeneity of probe location at temperatures well below the lipid phase transition temperature and the homogeneity of probe location at temperature well above the lipid phase transition temperature. [Ru(bpy)2(dppz)]2+ displays polarized emission, enabling the study of membrane dynamics. The long decay time displayed by this probe allows measurement of the overall rotational correlation time of lipid vesicles on the microsecond time-scale. Because of the long lifetime, polarized emission, and background free nature of the photoluminescence measurements, [Ru(bpy)2(dppz)]2+ has numerous applications in the biophysical studies of membranes.

A water-soluble luminescence oxygen sensor.

We developed a water-soluble luminescent probe for dissolved oxygen. This probe is based on (Ru[dpp(SO3Na)2]3) cl2, which is a sulfonated analogue of the well-known oxygen probe (Ru[dpp]3)cl2. The compound dpp is 4,7-diphenyl-1,10-phenanthroline and dpp(SO3Na)2 is a disulfonated derivative of the same ligand. In aqueous solution in the absence of oxygen (Ru[dpp(SO3Na)2]3)cl2 displays a lifetime of 3.7 microseconds that decreases to 930 ns on equilibrium with air and 227 ns on equilibrium with 100% oxygen. The Stern-Volmer quenching constant is 11,330 M-1. This high oxygen-quenching constant means that the photoluminescence of Ru(dpp[SO3Na]2)3cl2 is 10% quenched at an oxygen concentration of 8.8 x 10(-6) M, or equilibration with 5.4 torr of oxygen. The oxygen probe dissolved in water displays minimal interactions with lipid vesicles composed of dipalmityl-L-alpha-phosphatidyl glycerol but does appear to interact with human serum albumin. The absorption maximum near 480 nm, long lifetime and large Stokes' shift allow this probe to be used with simple instrumentation based on a light-emitting diode light source, allowing low-cost oxygen sensing in aqueous solutions. To the best of our knowledge this is the first practical water-soluble oxygen sensor.

Long-lifetime lipid rhenium metal-ligand complex for probing membrane dynamics on the microsecond timescale.

We report the luminescence and spectral properties of a phospholipid analogue containing a long-lifetime luminescent rhenium metal-ligand complex (MLC) covalently linked to the amino group of phosphatidyl ethanolamine. When incorporated into synthetic membranes, this lipid probe displays intensity decay times near 3 microseconds. Importantly, the probe displays highly polarized emission with a maximal fundamental anisotropy of 0.33. This probe is expected to have numerous applications for studies of microsecond diffusion and dynamics of membranes.

Mevalonate-derived proteins in liver regeneration.

Sixteen hours after partial hepatectomy in the rat, the synthesis of mevalonate (MVA) is not committed to produce cholesterol and only partially utilized for dolichol formation. In order to investigate the fate of MVA in this replicative system, slices of the remaining liver were incubated with 5-3H-MVA. Labeled proteins from whole liver and purified nuclei were analyzed after extensive delipidation and separation by SDS-PAGE. Many MVA-derived proteins were identified at 16 hours, while only two labelled peptides were detectable at 24 hours. The radioactivity was localized in covalently bound lipid moieties. A highly labeled 26 kD peptide was detectable in the nucleus at 16 hours, suggesting its involvement in the cell cycle progression.

Seasonal commitment of HMGCoA reductase activity to vitellogenin production.

In female frogs (Rana Esculenta) during gametogenesis the cholesterol synthesized in the liver by 3-hydroxy-3-methylglutaryl coenzyme A reductase is mostly exported into the blood and taken up by the oocytes. In order to understand the fate of the neosynthesized cholesterol, female and male frogs and estrogenized male controls were injected with the labelled precursor 14C mevalonate. In females and in estrogenized controls, mevalonate-derived radioactivity is found in a plasmatic lipoprotein that has been identified as vitellogenin by immunological detection. The increased 3-hydroxy-3-methylglutaryl coenzyme A reductase activity present in females in Fall is likely to be committed to provide cholesterol for the lipidation of this cholesterol-rich protein.

Effect of HDL1 infusion on biliary secretion in perfused rat liver.

The effects of HDL1 lipoprotein infusion on biliary lipid secretion were studied in the in vitro model of rat perfused liver. A strong increase in bile flow was observed during and after lipoprotein infusion. This caused a significant rise in cholesterol, phospholipid and bile salt secretions. However, only the percentage of cholesterol increased with respect to the other bile lipids. The changes observed in the cholesterol/phospholipid molar ratio values of liver membrane subfractions (i.e., liver plasma membrane, mitochondria plus lysosomes and microsomes) isolated from the perfused rat liver after HDL1 administration were not significant.