Using Cu2O/ZnO as Two-Dimensional Hole/Electron Transport Nanolayers in Unleaded FASnI3 Perovskite Solar Cells

A Pb-free FASnI3 perovskite solar cell improved by using Cu2O/ZnO as two-dimensional-based hole/electron transport nanolayers has been proposed and studied by using a SCAPS-1D solar simulator. To calibrate our study, at first, an FTO/ZnO/MAPbI3/Cu2O/Au multilayer device was simulated, and the numerical results (including a conversion efficiency of 6.06%, an open circuit potential of 0.76 V, a fill factor parameter of 64.91%, and a short circuit electric current density of 12.26 mA/cm2) were compared with the experimental results in the literature. Then, the conversion efficiency of the proposed FASnI3-based solar cell was found to improve to 7.83%. The depth profile energy levels, charge carrier concentrations, recombination rate of electron/hole pair, and the FASnI3 thickness-dependent solar cell efficiency were studied and compared with the results obtained for the MAPbI3-containing device (as a benchmark). Interestingly, the FASnI3 material required to obtain an optimized solar cell is one-half of the material required for an optimized MAPbI3-based device, with a thickness of 200 nm. These results indicate that developing more environmentally friendly perovskite solar cells is possible if suitable electron/hole transport layers are selected along with the upcoming Pb-free perovskite absorber layers.

Effects of electron transport layer type on the performance of Pb-free Cs2AgBiBr6 double perovskites: a SCAPS-1D solar simulator-based study

Recently, due to the superior stability and lower risk of toxicity, the development of Pb-free halide double perovskite materials has revived excellent interest. In this work, Pb-free perovskite solar cells (PSCs) with ITO/ETL/Cs2AgBiBr6/Cu2O/Au multilayer structures with Cs2AgBiBr6 double perovskite as the solar light absorber layer, some electron transport layers (ETLs) and Cu2O as a hole transport layer have been introduced. Then, the effects of various thicknesses of the absorber layer and also ETL materials, like ZnO, C60, CdS, SnO2, phenyl-C61-butyric acid methyl ester (PCBM), and TiO2, on the device performance (including photoelectronic conversion efficiency (PCE), fill factor (FF%), short circuit current density (Jsc), and open-circuit voltage (VOC)) were examined with the help of a solar cell simulator (SCAPS-1D). It is noteworthy that, in the case of all ETL materials, the optimal thickness of the absorber layer was determined to be 400 nm. Then, the maximum PCE values of 20.08%, 17.63%, 14.07%, 12.11%, 14.94%, and 18.83% were obtained for the solar cells containing ZnO, C60, CdS, SnO2, PCBM, and TiO2 as the ETL, respectively. These results show that designing/developing Pb-free halide double perovskite devices having comparable PCEs with the Pb-based PSCs is feasible, provided that proper/compatible materials will be used in the multilayer structure of the next generations of solar cells.

Lead-free MAGeI3 as a suitable alternative for MAPbI3 in nanostructured perovskite solar cells: a simulation study

The lead is a heavy metal with hazardous impacts on environment and human life. Lead-free perovskite solar cells have attracted much attention in recent years, due to eco-friendly characteristics. Meanwhile, Pb-containing cells showed the highest efficiencies among the various types of cells. Hence, designing novel Pb-free solar cells with comparable or better performance than the Pb-containing ones is highly required. In this work, a lead-free methyl-ammonium-germanium-iodide (MAGeI₃)-based perovskite solar cell with ITO/TiO₂/MAGeI₃/Spiro-OMeTAD/Ag multilayer nanostructure has been proposed and its main characteristics including open-circuit voltage (V_OC) and power conversion efficiency (η) have been evaluated and compared with those of MAPbI₃-based cell, in simulation study. The V_OC and η of the MAGeI₃-based cell (1.18 V and 11.9%) have been found comparable with those of the MAPbI₃ one (1.10 V and 14.6%). These results can excite more attention to Ge as a more environment-friendly element than Pb, in highly efficient upcoming perovskite solar cells.

Cold Tolerance of the Tribolium castaneum (Coleoptera: Tenebrionidae), Under Different Thermal Regimes: Impact of Cold Acclimation

The red flour beetle, Tribolium castaneum (Herbst), is a serious pest of stored product worldwide. Cold tolerance or cold hardiness is an important ecophysiological trait related directly to survival, fitness, and distribution of insects. In this study, the effects of four thermal regimes, i.e., control (C), cold acclimation (CA), rapid cold hardening (RCH), and fluctuating-acclimation (FA), were examined for their effects on cold tolerance, supercooling point (SCP), lower lethal temperature (LLT), and chill-coma recovery time (CCRT) of the red flour beetle. In addition, changes in cryoprotectant (trehalose, sorbitol, and myo-inositol) levels were investigated under each thermal treatment. The results documented a substantial enhancement in the SCP, cold hardiness, and cryoprotectant levels of the adults of T. castaneum under CA regimes. The lowest SCP, highest trehalose and myo-inositol contents, and, subsequently, the greatest survival rate were observed in cold-acclimated beetles. In addition, coordination between cryoprotectant level, SCP, and cold tolerance of the pest was observed. The highest and lowest CCRT were observed at control and CA, respectively. In RCH regime with the highest impact, LLT reached the lowest level of -22°C. As most of the mortality of T. castaneum occurred at a temperature above the SCP, so this pest could be considered as a chill-susceptible insect.

Identification of ALOX5 as a gene regulating adiposity and pancreatic function

AIMS/HYPOTHESIS

We previously used an integrative genetics approach to demonstrate that 5-lipoxygenase (5-LO) deficiency in mice (Alox5 (-/-)) protects against atherosclerosis despite increasing lipid levels and fat mass. In the present study, we sought to further examine the role of 5-LO in adiposity and pancreatic function.

METHODS

Alox5 (-/-) and wild-type (WT) mice were characterised with respect to adiposity and glucose/insulin metabolism using in vivo and in vitro approaches. The role of ALOX5 in pancreatic function in human islets was assessed through short interfering RNA (siRNA) knockdown experiments.

RESULTS

Beginning at 12 weeks of age, Alox5 (-/-) mice had significantly increased fat mass, plasma leptin levels and fasting glucose levels, but lower fasting insulin levels (p<0.05). Although Alox5 (-/-) mice did not exhibit insulin resistance, they had impaired insulin secretion in response to a bolus glucose injection. Histological analyses revealed that Alox5 (-/-) mice had increased islet area, beta cell nuclear size, and numbers of beta cells/mm(2) islet (p<0.05), indicative of both hyperplasia and hypertrophy. Basal and stimulated insulin secretion in isolated Alox5 (-/-) islets were significantly lower than in WT islets (p<0.05) and accompanied by a three- to fivefold decrease in the expression of the genes encoding insulin and pancreatic duodenal homeobox 1 (Pdx1). Direct perturbation of ALOX5 in isolated human islets with siRNA decreased insulin and PDX1 gene expression by 50% and insulin secretion by threefold (p<0.05).

CONCLUSIONS/INTERPRETATION

These results provide strong evidence for pleiotropic metabolic effects of 5-LO on adiposity and pancreatic function and may have important implications for therapeutic strategies targeting this pathway for the treatment of cardiovascular disease.

Genetic locus in mice that blocks development of atherosclerosis despite extreme hyperlipidemia

The genes contributing to the common forms of atherosclerosis are largely unknown. One approach to dissecting complex traits such as atherosclerosis is to use animal models, such as the mouse, to map and characterize the genetic loci involved. We now report the identification of a locus for aortic lesion formation on mouse chromosome 6 that exhibits a highly significant lod score of 6.7 in a genetic cross between the susceptible strain, C57BL/6J, and the resistant strain, CAST/Ei. The locus was confirmed by constructing a congenic strain in which the chromosome 6 segment from CAST/Ei was transferred to a C57BL/6J background in a series of backcrosses. The congenic strain was almost completely resistant to diet-induced atherosclerosis. The chromosome 6 segment was also transferred onto the background of an LDL receptor-null mutation and resulted again in almost complete resistance to aortic lesion formation. This locus also influenced insulin levels but did not affect plasma lipoprotein levels, blood pressure, or body fat. The chromosome 6 gene, which we call Artles (for arterial lesions), did not affect endothelial cell responses to oxidized LDL, but lesion formation was partially reduced through bone marrow transplantation. The locus contains the candidate gene peroxisome proliferator-activated receptor-gamma, and the congenic mice exhibited significantly reduced expression of peroxisome proliferator-activated receptor-gamma.

Genetic control of HDL levels and composition in an interspecific mouse cross (CAST/Ei x C57BL/6J)

Strain CAST/Ei (CAST) mice exhibit unusually low levels of high density lipoproteins (HDL) as compared with most other strains of mice, including C57BL/6J (B6). This appears to be due in part to a functional deficiency of lecithin:cholesterol acyltransferase (LCAT). LCAT mRNA expression in CAST mice is normal, but the mice exhibit several characteristics consistent with functional deficiency. First, the activity and mass of LCAT in plasma and in HDL of CAST mice were reduced significantly. Second, the HDL of CAST mice were relatively poor in phospholipids and cholesteryl esters, but rich in free cholesterol and apolipoprotein A-I (apoA-I). Third, the adrenals of CAST mice were depleted of cholesteryl esters, a phenotype similar to that observed in LCAT- and acyl-CoA:cholesterol acyltransferase-deficient mice. Fourth, in common with LCAT-deficient mice, CAST mice contained triglyceride-rich lipoproteins with "panhandle"-like protrusions. To examine the genetic bases of these differences, we studied HDL lipid levels in an intercross between strain CAST and the common laboratory strain B6 on a low fat, chow diet as well as a high fat, atherogenic diet. HDL levels exhibited complex inheritance, as 12 quantitative trait loci with significant or suggestive likelihood of observed data scores were identified. Several of the loci occurred over plausible candidate genes and these were investigated. The results indicate that the functional LCAT deficiency is unlikely to be due to variations of the LCAT gene. Our results suggest that novel genes are likely to be important in the control of HDL metabolism, and they provide evidence of genetic factors influencing the interaction of LCAT with HDL.

Role of group II secretory phospholipase A2 in atherosclerosis: 1. Increased atherogenesis and altered lipoproteins in transgenic mice expressing group IIa phospholipase A2

Some observations have suggested that the extracellular group IIa phospholipase A2 (sPLA2), previously implicated in chronic inflammatory conditions such as arthritis, may contribute to atherosclerosis. We have examined this hypothesis by studying transgenic mice expressing the human enzyme. Compared with nontransgenic littermates, the transgenic mice exhibited dramatically increased atherosclerotic lesions when maintained on a high-fat, high-cholesterol diet. Surprisingly, the transgenic mice also exhibited significant atherosclerotic lesions when maintained on a low-fat chow diet. Immunohistochemical staining indicated that sPLA2 was present in the atherosclerotic lesions of the transgenic mice. On both chow and atherogenic diets, the transgenic mice exhibited decreased levels of HDLs and slightly increased levels of LDLs compared with nontransgenic littermates. These data indicate that group IIa sPLA2 may promote atherogenesis, in part, through its effects on lipoprotein levels. These data also provide a possible mechanism for the observation that there is an increased incidence of coronary artery disease in many chronic inflammatory diseases.

Genetic loci controlling body fat, lipoprotein metabolism, and insulin levels in a multifactorial mouse model

We analyzed the inheritance of body fat, leptin levels, plasma lipoprotein levels, insulin levels, and related traits in an intercross between inbred mouse strains CAST/Ei and C57BL/6J. CAST/Ei mice are unusually lean, with only approximately 8% of body weight as fat, whereas C57BL/6J mice have approximately 18% body fat. Quantitative trait locus analysis using > 200 F2 mice revealed highly significant loci (lod scores > 4.3) on chromosomes 2 (three separate loci) and 9 that contribute to mouse fat-pad mass for mice on a high-fat diet. Some loci also influenced plasma lipoprotein levels and insulin levels either on chow or high-fat diets. Two loci for body fat and lipoprotein levels (on central and distal chromosome 2) coincided with a locus having strong effects on hepatic lipase activity, an activity associated with visceral obesity and lipoprotein levels in humans. A locus contributing to plasma leptin levels (lod score 5.3) but not obesity was identified on chromosome 4, near the leptin receptor gene. These data identify candidate regions and candidate genes for studies of human obesity and diabetes, and suggest obesity is highly complex in terms of the number of genetic factors involved. Finally, they support the existence of specific genetic interactions between body fat, insulin metabolism, and lipoprotein metabolism.

Mapping a gene for combined hyperlipidaemia in a mutant mouse strain

Familial combined hyperlipidaemia (FCHL) is a common, multifactorial disorder associated with elevated levels of plasma triglyceride, cholesterol, or both. A characteristic feature is increased secretion of very low density lipoproteins (VLDL) and apolipoprotein B (apoB). Although FCHL is the most common cause of premature coronary artery disease (CAD), accounting for over 10% of cases, its aetiology remains largely unknown. One powerful approach to the dissection of complex genetic traits involves the use of animal models. We have identified a mouse strain, HcB-19/Dem (HcB-19), which exhibits hypertriglyceridaemia, hypercholesterolaemia and elevated levels of plasma apoB. Like FCHL patients, HcB-19 mice also exhibit increased secretion of triglyceride-rich lipoproteins, and their hyperlipidaemia becomes progressively more severe with age. It is likely that the hyperlipidaemia results from a mutation of a novel gene that arose during development of strain HcB-19. We mapped the hyperlipidaemia gene (Hyplip1) to the distal portion of mouse chromosome 3. This region is syntenic to human chromosome 1q21-q23, which has recently been shown to harbour a gene associated with FCHL in families from a Finnish isolate.

Amino terminus of apolipoprotein B suffices to produce recognition of malondialdehyde-modified low density lipoprotein by the scavenger receptor of human monocyte-macrophages

Malondialdehyde, a product of lipid peroxidation, produces threshold conversion of low density lipoprotein (LDL) to a form recognized by type I and type II scavenger receptors of monocyte-macrophages. To investigate whether localized domains of human apoB-100 protein provide recognition determinants, we tested the ability of several different apoB-bearing particles to interact with the scavenger receptor of human monocyte-macrophages. Genetically engineered, carboxyl-terminally truncated apoB proteins assembled into lipoprotein form were labeled by fluorescent dye. Fluorescence microscopy and quantitative fluorescent spectrophotometry showed that purified particles containing as little as 23% of the apoB amino-terminus were internalized by the scavenger receptor after, but not before, malondialdehyde modification. There was no recognition of the particles by the LDL receptor. Similar results were obtained with human plasma LDL homozygous for carboxyl-terminally truncated apoB-45.2. Liposome-incorporated fusion protein containing apoB residues 547-735 displayed specific uptake by the scavenger receptor without modification by malondialdehyde. In contrast, fusion proteins containing apoB residues 3,029-3,133 or a short amino terminal segment failed to interact. Thus, primary sequence presented by residues 1-1,084 sufficed to produce recognition of modified LDL by the scavenger receptor. These receptor-combining domains were sequestered when secreted in lipoprotein form and were expressed upon malondialdehyde modification. When packaged exogenously in liposome form, fusion protein containing apoB residues 547-735, containing approximately 4% of the primary sequence, mediated scavenger receptor-dependent uptake and hydrolysis. Our findings provide an additional function or the amino-terminal region of apoB and demonstrate that primary sequence presented by the first 2% of apoB-100 protein suffices to produce recognition on malondialdehyde-modified LDL by the scavenger receptor of human monocyte-macrophages.

Genetic regulation of cholesterol homeostasis: chromosomal organization of candidate genes

As part of an effort to dissect the genetic factors involved in cholesterol homeostasis in the mouse model, we report the mapping of 12 new candidate genes using linkage analysis. The genes include: cytoplasmic HMG-CoA synthase (Hmgcs 1, Chr 13), mitochondrial synthase (Hmgcs 2, Chr 3), a synthase-related sequence (Hmgcs 1-rs, Chr 12), mevalonate kinase (Mvk, Chr 5), farnesyl diphosphate synthase (Fdps, Chr 3), squalene synthase (Fdft 1, Chr 14), acyl-CoA:cholesterol acyltransferase (Acact, Chr 1), sterol regulatory element binding protein-1 (Srebf1, Chr 8) and -2 (Srebf2, Chr 15), apolipoprotein A-I regulatory protein (Tcfcoup2, Chr 7), low density receptor-related protein-related sequence (Lrp-rs, Chr 10), and Lrp-associated protein (Lrpap 1, Chr 5). In addition, the map positions for several lipoprotein receptor genes were refined. These genes include: low density lipoprotein receptor (Ldlr, Chr 9), very low density lipoprotein receptor (Vldlr, Chr 19), and glycoprotein 330 (Gp330, Chr 2). Some of these candidate genes are located within previously defined chromosomal regions (quantitative trait loci, QTLs) contributing to plasma lipoprotein levels, and Acact maps near a mouse mutation, ald, resulting in depletion of cholesteryl esters in the adrenals. The combined use of QTL and candidate gene mapping provides a powerful means of dissecting complex traits such as cholesterol homeostasis.

Genetic factors in lipoprotein metabolism. Analysis of a genetic cross between inbred mouse strains NZB/BINJ and SM/J using a complete linkage map approach

A genetic cross was constructed from two parental inbred strains of mice, NZB/BINJ and SM/J, which differ markedly in their plasma lipoprotein levels. Plasma lipid and apolipoprotein values were measured in 184 F2 progeny on a normal chow diet and on an atherogenic diet. Genetic markers were typed at 126 loci spanning all chromosomes except the Y. Statistical analysis revealed significant linkage or suggestive linkage of lipoprotein levels with markers on a number of chromosomes. Chromosome 1 markers were linked to levels of total cholesterol (lod 5.9) and high density lipoprotein (HDL) cholesterol (lod 8.1), chromosome 5 markers were linked to levels of total cholesterol (lod 6.7) and HDL cholesterol (lod 5.6), and chromosome 7 markers were linked to levels of total plasma triglycerides (lod 5.1) and free fatty acids (lod 5.6). Plasma apoAII levels were linked to the apoAII gene (lod score 19.6) and were highly correlated with plasma HDL cholesterol levels (r = 0.63, P = 0.0001), indicating that apoAII expression influences HDL cholesterol levels. Molecular studies suggested that structural differences in the apoAII polypeptide of the two strains may contribute to differences in clearance of the protein.

Localization of murine macrophage inducible nitric oxide synthase to mouse chromosome 11

There are at least three distinct nitric oxide (NO) synthase genes. Brain and endothelial NO synthases are constitutively synthesized, while NO synthase is inducible by cytokines in macrophages. We have utilized a backcross of (C57BL/6J x Mus spretus) x C57BL/6J to map the inducible NO synthase (Nos2). We report the chromosomal mapping of Nos2 to mouse chromosome 11, 3.3 cM proximal to Scya2.

Linkage mapping of 40 randomly isolated liver cDNA clones in the mouse

We report the chromosomal mapping of 43 loci for 40 randomly isolated mouse liver cDNA clones by linkage analysis in an interspecific backcross of ((C57BL/6J x Mus spretus) x C57BL/6J). The clones were sequenced from both sides and a subset was examined for expression in various mouse tissues. Fifteen of the 40 mapped cDNA clones are either identical or strongly related to known sequences in GenBank, while 25 represent new genes. Additional loci mapped in this cross include 53 simple sequence repeat polymorphisms and 40 restriction fragment length variants from previously characterized cDNA markers. Nine homologous human genes were identified for 7 mouse liver cDNA clones. One clone that maps to mouse chromosome 3 (D3Ucla1) identified a novel homologous segment (synteny) on human chromosome 18q23 (D18S372E). These studies provide linkage mapping and initial characterization of random cDNA clones that may provide a resource for the positional candidate cloning of disease genes.

Chromosomal organization of mammalian POU domain factors

We present the chromosomal locations in mouse of eight new members of the mammalian POU domain family of transcriptional regulators. Chromosomal assignments were made for Brn-1 (Chr 1), Brn-2 (Chr 4), Brn-4 (Chr X), Brn-3.0 (Chr 14), Brn-3.1 (Chr 18), Brn-5.0 (Chr 15), Skn-1a/i (Chr 9), and Sprm-1 (Chr 13) in addition to the previously reported Pit-1 (Chr 16), Tst-1 (Chr 4), Oct-3/4 (Chr 17), Oct-1 (Chr 1), and Oct-2 (Chr 7) genes. Several conclusions have emerged from this analysis. First, among the most highly related family members (Brn-1, Brn-2, Brn-4, and Tst-1; Brn-3.0 and Brn-3.1; Oct-1, Oct-2, and Skn-1a/i) no chromosomal linkage is noted. Second, no clusters of genes are observed, irrespective of homology. Finally, no obvious linkages to genes for known additional regulatory factors with a specific origin of cell type are apparent. Thus, members of this large gene family, presumably arising as duplication events from common ancestral genes, apparently function in distinct chromosomal milieu under independent regulation. Some of these newly localized genes map in close proximity to existing mouse mutations.

Two members of the S-lac lectin gene family, LGALS1 and LGALS2, reside in close proximity on human chromosome 22q12-q13

S-lac lectins are a family of soluble lactose-binding proteins thought to function in the control of cell growth. We now report the chromosomal mapping of two members of the family, termed L-14-I and L-14-II, to the q12-q13 region of human chromosome 22, suggesting the possibility of a cluster of genes for lactose-binding proteins.

Influence of the apoA-II gene locus on HDL levels and fatty streak development in mice

Previous studies have shown that distal mouse chromosome 1 contains the apolipoprotein AII (apoAII) gene, encoding the second most abundant apolipoprotein in high density lipoproteins (HDLs), as well as a gene termed Ath-1 that controls aortic fatty streak development and HDL cholesterol levels in response to a high-fat, high-cholesterol diet. We report genetic studies confirming that the genes are distinct. Using molecular markers for mouse chromosome 1, we have further mapped the two genes, and our results indicate that they are separated by a minimum of 2 cM. We also report evidence that in mice on a low-fat chow diet, the apoAII gene locus influences HDL cholesterol levels. Thus, statistical analysis of two sets of recombinant inbred strains revealed concordant segregation patterns of HDL cholesterol levels and the apoAII gene locus. The effect of apoAII expression on HDL cholesterol levels was further tested by using a congenic strain that exhibits increased apoAII synthesis in comparison to the background strain. The results support the concept that increased synthesis of apoAII results in increased HDL cholesterol levels. Unexpectedly, increased expression of apoAII appeared to promote rather than retard aortic fatty streak development.

Cloning of the human cholesterol 7 alpha-hydroxylase gene (CYP7) and localization to chromosome 8q11-q12

Cholesterol 7 alpha-hydroxylase (7 alpha-hydroxylase) is a microsomal cytochrome P450 that catalyzes the first step in bile acid synthesis. In this paper, we describe the cloning, characterization, and chromosomal mapping of the human 7 alpha-hydroxylase gene (CYP7). The gene spans 10 kb and contains six exons and five introns. The exon-intron boundaries are completely conserved between the human and rat genes. Sequencing of the 5' flanking region revealed consensus recognition sequences for a number of liver-specific transcription factors. The human CYP7 gene was mapped to chromosome 8q11-q12 using both mouse-human somatic cell hybrids and in situ chromosomal hybridization studies. A total of four single-stranded conformation-dependent DNA polymorphisms and an Alu sequence-related polymorphism were identified. Of the individuals analyzed, 80% were heterozygous for at least one of these five polymorphisms. The localization and characterization of the human 7 alpha-hydroxylase gene, as well as the identification of polymorphisms, provide the molecular tools necessary to investigate the role of this gene in disorders of cholesterol and bile acid metabolism.

The L-isoaspartyl/D-aspartyl protein methyltransferase gene (PCMT1) maps to human chromosome 6q22.3-6q24 and the syntenic region of mouse chromosome 10

We have mapped the genes for the human and mouse L-isoaspartyl/D-aspartyl protein carboxyl methyltransferase (EC 2.1.1.77) using cDNA probes. We determined that the human gene is present in chromosome 6 by Southern blot analysis of DNA from a panel of mouse-human somatic cell hybrids. In situ hybridization studies allowed us to confirm this identification and further localize the human gene (PCMT1) to the 6q22.3-6q24 region. By analyzing the presence of an EcoRI polymorphism in DNA from backcrosses of C57BL/6J and Mus spretus strains of mice, we localized the mouse gene (Pcmt-1) to chromosome 10, at a position 8.2 +/- 3.5 cM proximal to the Myb locus. This region of the mouse chromosome is homologous to the human 6q24 region.

Mechanisms controlling competence gene expression in murine fibroblasts stimulated with minimally modified LDL

Mildly oxidized low density lipoprotein (minimally modified low density lipoprotein [MM-LDL] is capable of inducing gene expression in cells of the artery wall. In this study, we investigated the mechanisms that control the mRNA expression of JE, KC, c-myc, and c-fos in quiescent mouse L-cell fibroblasts stimulated with MM-LDL. The data demonstrate that MM-LDL induces increases greater than or equal to 20-fold in the levels of transcripts of these genes within 15-60 minutes. Of the four genes examined, JE and KC mRNA showed the greatest response to MM-LDL. The pattern of induction by MM-LDL is distinct from that observed in fibroblasts stimulated with serum, a known inducer of these genes. Treatment with cycloheximide (10 micrograms/ml) did not block the MM-LDL-induced increase in the mRNA levels of these genes. The increase of JE and KC mRNA levels in response to MM-LDL could be blocked by treatment with actinomycin D (5 micrograms/ml). In nuclear runoff studies, MM-LDL increased the transcription rate of JE and KC at 4 hours by 13-fold and fivefold, respectively. Small but reproducible stimulations of c-fos and c-myc transcription by MM-LDL were also observed. In addition, the half-life of JE mRNA was increased after addition of MM-LDL to fibroblasts, suggesting that the MM-LDL-induced accumulation of these mRNAs might be accomplished by both transcriptional and posttranscriptional mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential accumulation of intimal monocyte-macrophages relative to lipoproteins and lipofuscin corresponds to hemodynamic forces on cardiac valves in mice

We have studied the distribution of monocyte-macrophages, lipids, and lipoproteins in sections of aorta and aortic valves from mice fed an atherogenic diet. By immunocytochemical analysis with Mac-1 and F4/80 antibodies, apolipoprotein B antibody, and oil red O staining, three discrete regions were identified: 1) the aortic wall of the sinus of Valsalva, which contained deposits of lipid that colocalized with lipoproteins and monocyte-macrophages; 2) the sides of the aortic valve leaflets facing the ventricle, which did not contain lipids or lipoproteins but which were lined with macrophages that colocalized with lipofuscin; and 3) the sides of the leaflets facing the aorta, which did not contain lipids, lipoproteins, monocyte-macrophages, or lipofuscin deposits. This pattern of distribution resembles the expected distribution of mechanical forces, especially those of systolic blood flow, which in the three areas are predominantly 1) low-shear disturbed flow, 2) high-shear laminar flow, and 3) low-shear laminar flow, respectively. These findings suggest that lesions in the mouse closely resemble early atherosclerotic lesions in humans and other primates with respect to monocyte-macrophage and lipoprotein accumulation. The results also strikingly demonstrate that the accumulation of monocyte-macrophages and lipoproteins can occur independently, with spatial differences corresponding to the distribution of hemodynamic forces.

Minimally modified low density lipoprotein is biologically active in vivo in mice

Minimally modified low density lipoprotein (MM-LDL), derived by mild iron oxidation or prolonged storage at 4 degrees C, has been shown to induce certain inflammatory responses in vascular cells in tissue culture. These include induction of monocyte (but not neutrophil) adherence to endothelial cells (EC), induction of EC production of colony stimulating factors (CSF), and induction of EC and smooth muscle cell production of monocyte chemotactic protein (MCP-1). To test for biologic activity in vivo, microgram quantities of MM-LDL were injected into mice, sera were assayed for CSF activity, and tissues were subjected to Northern analysis. After injection of MM-LDL, CSF activity increased approximately 7-26-fold but remained near control levels after injection of native LDL. Essentially all of the induced CSF activity was due to macrophage CSF as judged by antibody inhibition. Injection of MM-LDL into a mouse strain (C3H/HeJ) that is resistant to bacterial LPS gave similar results, indicating that the induction of CSF was not due to contaminating LPS and suggesting that there are differences in the pathways by which LPS and MM-LDL trigger cytokine production. In addition, after injection of MM-LDL, mRNA for JE, the mouse homologue of MCP-1, was markedly induced in various tissues, but was not induced after injection of native LDL. We conclude, therefore, that MM-LDL is biologically active in vivo and may contribute to the early stages of atherosclerosis by acting as an inflammatory agent.

Localization of monocyte chemotactic protein-1 gene (SCYA2) to human chromosome 17q11.2-q21.1

Monocyte chemotactic protein-1 (MCP-1) is a member of the small inducible gene (SIG) family. It has been shown to play a role in the recruitment of monocytes to sites of injury and infection. By analysis of a panel of somatic cell hybrids, we have localized the MCP-1 gene, designated SCYA2, to human chromosome 17. In situ hybridization confirmed this assignment and further localized the gene to 17q11.2-q21.1.

Dietary regulation of fibrinolytic factors

W examined the short-term effects of a high-complex carbohydrate, low fat diet on the plasmin-dependent fibrinolytic pathway. A population of 27 adult American Caucasians exposed to the diet for 3 weeks showed highly significant reductions in the levels of plasminogen (P = 0.0001), tissue plasminogen activator (tPA) (P = 0.0001) and plasminogen activator inhibitor (tPAI) (P = 0.0017). Fibrinogen levels also decreased, but the changes did not reach statistical significance (P = 0.07). In contrast, the levels of the Lpa(a) lipoprotein, a potential inhibitor of fibrinolysis, remained remarkably constant despite a marked decrease in the levels of apolipoprotein B, a major constituent of Lp(a). Correlations between the levels of tPA, tPAI and plasma triglyceride were observed among the individuals both before and after the dietary challenge. Although the mechanisms responsible for the effects are unknown, the dramatic responsiveness of the thrombolytic pathway to dietary challenge is likely to be of importance in understanding the etiology of coronary artery disease and other vascular disorders.

Regulation of rat liver 3-hydroxy-3-methylglutaryl coenzyme A synthase and the chromosomal localization of the human gene

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase was purified to homogeneity from rat liver cytoplasm. The active enzyme is a dimer composed of identical subunits of Mr = 53,000. The amino acid composition and the NH2-terminal sequence are presented. Partial cDNA clones for the enzyme were isolated by screening of a rat liver lambda gt11 expression library with antibodies raised against the purified protein. The identity of the clones was confirmed by hybrid selection and translation. When rats were fed diets supplemented with cholesterol, cholestyramine, or cholestyramine plus mevinolin, the hepatic protein mass of cytoplasmic synthase, as determined by immunoblotting, was 25, 160, and 1100%, respectively, of the mass observed in rats fed normal chow. Comparable changes in enzyme activity were observed. Approximately 9-fold increases in both HMG-CoA synthase mRNA mass and synthase mRNA activity were observed when control diets were supplemented with cholestyramine and mevinolin. When rats were fed these two drugs and then given mevalonolactone by stomach intubation, there was a 5-fold decrease of synthase mRNA within 3 h. These results indicate that cytoplasmic synthase regulation occurs primarily at the level of mRNA. This regulation is rapid and coordinate with that observed for HMG-CoA reductase. The chromosomal localization of human HMG-CoA synthase was determined by examining a panel of human-mouse somatic cell hybrids with the rat cDNA probe. Interestingly, the synthase gene resides on human chromosome 5, which has previously been shown to contain the gene for HMG-CoA reductase. Regional mapping, performed by examination of a series of chromosome 5 deletion mutants and by in situ hybridization to human chromosomes indicates that the two genes are not tightly clustered.

Human apolipoprotein B: chromosomal mapping and DNA polymorphisms of hepatic and intestinal species

Apolipoprotein B (apoB) is the major protein component of low-density and very-low-density lipoproteins. We have recently isolated nonoverlapping cDNA clones for apoB and confirmed their identity by sequence comparisons. We now report the mapping of the human apoB gene (APOB) to the p23-p24 region of chromosome 2 by examination of human-mouse somatic cell hybrids and by in situ hybridization to human chromosomes. Thus, APOB is unlinked to members of the dispersed gene family encoding other apolipoprotein species or to the gene encoding the low-density lipoprotein receptor. Hybridization analysis with genomic DNA and liver and intestinal mRNA suggests that APOB encodes both the high-molecular-weight form of apoB (apoB100) incorporated into very-low-density lipoproteins in liver and the lower-molecular-weight form (apoB48) incorporated into chylomicrons in intestine. Restriction fragment length polymorphisms of APOB have been identified and should prove useful in examining the possibility that genetic variations of APOB are involved in dyslipoproteinemias and atherosclerosis.

Human apolipoprotein B: identification of cDNA clones and characterization of mRNA

Apolipoprotein B (apoB) is a major protein component of low density and very low density lipoproteins. Because of its large size and heterogeneity, molecular studies of apoB have been difficult, and its structure and regulation remain poorly understood. We now report the identification of human apoB cDNA clones by antibody screening of hepatoma libraries in the expression vector lambda gt11. Both oligo(dT) primed and random primed libraries were constructed and screened with polyclonal antibodies to intact apoB, as well as with antibodies raised against a synthetic peptide based on the limited amino acid sequence available for apoB. The identity of the clones was unambiguously established by comparisons of the cloned cDNA sequences with apoB amino acid sequences. The clones hybridize to an exceptionally large 20 kb mRNA that is present in liver and intestine but not other tissues examined, consistent with the distribution expected from protein biosynthetic studies. The properties of the mRNA have implications for the biogenesis of the multiple apoB molecular weight forms secreted by liver and intestine.

Cloning and expression of apolipoprotein B, the major protein of low and very low density lipoproteins

We report the cloning of cDNAs for rat liver apolipoprotein B (apo B) and the use of the cloned sequences to examine apo B expression at the level of mRNA in rat tissues. Fifteen putative apo B clones were identified by antibody screening of a rat liver cDNA library in the lambda gt11 expression vector. The identity of the clones was confirmed by immunological studies of the fusion protein products. All clones appear to contain sequences found only in apo B PI, the high molecular weight form of rat liver apo B. Blotting studies show that the clones hybridize to a single 20-kilobase liver mRNA species, sufficiently large to encode the entire apo B PI peptide, which is estimated to be 400 kDa in size. Apo B PI mRNA is abundant in liver and present in lower amounts in intestine but is absent in a variety of other tissues examined. This tissue distribution is consistent with that expected from studies on the in vivo synthesis of apo B. One clone, corresponding to a 240-base segment of the apo B PI mRNA, was sequenced and found to exhibit homology with a short region of rat apo E mRNA. Analysis of the secondary structure of the corresponding peptide did not show the preponderance of amphipathic alpha-helical structures characteristic of other apolipoproteins examined thus far.

Interaction of rat liver lysosomal membranes with actin

Membranes were prepared from lysosomes purified 80-fold by centrifugation in a discontinuous metrizamide gradient. When salt-washed membranes were combined with rabbit muscle actin, an increase in viscosity could be measured using a falling ball viscometer. The lysosomal membrane-actin interaction was actin- and membrane-concentration dependent and appeared to be optimal under presumed physiological conditions (2 mM MgCl2, 1 mM MgATP, neutral pH, and free calcium concentration less than 10(-8) M). The actin cross-linking activity of the membrane was optimal at pH 6.4. The interaction was maximal between 10(-7) and 10(-9) M free calcium ions and inhibited by approximately 50% at concentrations of calcium greater than 0.5 x 10(-7) M. The actin-lysosomal membrane interaction was destroyed if the membranes were pretreated with Pronase, or if the membranes were purified in the absence of protease inhibitors. The interaction was not destroyed if membranes were washed with high salt or extracted with KCl and urea. In addition, a sedimentation assay for the actin-lysosomal membrane interaction was also performed to corroborate the viscometry data. The results suggest the existence of an integral lysosomal membrane actin-binding protein.

Contact-site cross-linking agents

Contact-site cross-linking agents comprise a heterogeneous grouping of cross-linkers which share the common property of being able to cross-link only very closely juxtaposed residues in macromolecular complexes. We have defined contact-site cross-linking arbitrarily as the covalent joining of residues such that they are constrained to a distance which is equivalent to or less than their closest possible steric approach prior to becoming linked (1). We recognize two classes of contact-site cross-linkers, bridge type and zero-length type. The former, such as formaldehyde, become incorporated during cross-linking as one-atom bridges. The latter, such as the carbodiimides, operate as condensing agents with the result that the cross-linked residues become interjoined directly. Contact-site cross-linkers have been used in several ways as specific probes of both the static and dynamic aspects of macromolecular structure. They can yield precise structural information about macromolecular contacts when actual sites of cross-linking are determined by peptide or nucleotide mapping techniques. In this way exact contacts between histones in the nucleosome, between protein and RNA in the ribosome, and between RNA polymerase and DNA have been determined. Contact-site cross-linkers have also been used to probe the perturbation of contacts following macromolecular conformational changes. Certain histone-histone 'cross-linkable' sites are rendered unreactive after induction of chromatin conformational changes thus serving to localize sites of perturbation.

Histon-histone interactions within chromatin. Preliminary location of multiple contact sites between histones 2A, 2B, and 4

The contact-site cross-linkers tetranitromethane, UV light, formaldehyde, and a monofunctional imido ester have been used to generate a collection of histone-histone dimers and trimers from nuclei and chromatin. Four different H2B-H4 dimers have been isolated. Preliminary CNBr peptide mapping has shown that all are cross-linked at different positions that are apparently clustered within the C-terminal regions of these histones. Similarily, two different H2A-H2B dimers and two different H2A-H2B-H4 trimers have been partially characterized. The data suggest a functional map for H2B in which the N-terminal third interacts with DNA, the middle third interacts with H2A, and the C-terminal third interacts with H4. We hope, by pursuing this type of analysis, to develop a detailed understanding of each histone-histone binding interaction through saturation cross-linking of the binding sites.