Repeatability of adaptation in sunflowers reveals that genomic regions harbouring inversions also drive adaptation in species lacking an inversion

Local adaptation commonly involves alleles of large effect, which experience fitness advantages when in positive linkage disequilibrium (LD). Because segregating inversions suppress recombination and facilitate the maintenance of LD between locally adapted loci, they are also commonly found to be associated with adaptive divergence. However, it is unclear what fraction of an adaptive response can be attributed to inversions and alleles of large effect, and whether the loci within an inversion could still drive adaptation in the absence of its recombination-suppressing effect. Here, we use genome-wide association studies to explore patterns of local adaptation in three species of sunflower: Helianthus annuus, Helianthus argophyllus, and Helianthus petiolaris, which each harbour a large number of species-specific inversions. We find evidence of significant genome-wide repeatability in signatures of association to phenotypes and environments, which are particularly enriched within regions of the genome harbouring an inversion in one species. This shows that while inversions may facilitate local adaptation, at least some of the loci can still harbour mutations that make substantial contributions without the benefit of recombination suppression in species lacking a segregating inversion. While a large number of genomic regions show evidence of repeated adaptation, most of the strongest signatures of association still tend to be species-specific, indicating substantial genotypic redundancy for local adaptation in these species.

Role of curcumin on miR-26a and its effect on DNMT1, DNMT3b, and MEG3 expression in A549 lung cancer cell

CONTEXT

Most of the patients diagnosed with non-small cell lung cancer (NSCLC) are in their advanced stages and as a result might not be cured in spite of the advances in aimed therapy. In the recent years, the role of noncoding RNAs (ncRNAs) has been expanded to cancer as potential targets for RNA-based epigenetic therapies. Curcumin, as an active ingredient, is associated with epigenetic alterations, and it might modulate the expression of tumor suppressor and oncogenic microRNAs.

MATERIALS AND METHODS

In this study, we investigated the RNA-based epigenetic effects of curcumin on NSCLC, and the effect of curcumin on A549 cell viability was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The expression of miR-26a, MEG3, DNA methyltransferase 1 (DNMT1), and DNMT3 beta (DNMT3b) was assessed by quantitative polymerase chain reaction.

STATISTICAL ANALYSIS USED

Data analysis was done using Prism®6 software (GraphPad Software, Inc., La Jolla, CA, USA), and statistical analysis was performed using t-test between control and vitality samples.

RESULTS

The results showed a significant increase (P < 0.05) of miR-26a expression which in turn was associated with a significant decrease (P < 0.05) in expression of DNMTs and subsequently a significant increase in MEG3 expression (P < 0.05) in A549 cell line after adding curcumin in the media.

CONCLUSION

Considering all the data together, we could speculate the role of curcumin in ceasing the progression of cancer in its early stages and might be considered a potential drug for the treatment of NSCLC-derived lung cancer by establishing a meaningful relationship between epigenetic mechanisms and ncRNAs.

The genomics of linkage drag in inbred lines of sunflower

Crop wild relatives represent valuable sources of alleles for crop improvement, including adaptation to climate change and emerging diseases. However, introgressions from wild relatives might have deleterious effects on desirable traits, including yield, due to linkage drag. Here, we analyzed the genomic and phenotypic impacts of wild introgressions in inbred lines of cultivated sunflower to estimate the impacts of linkage drag. First, we generated reference sequences for seven cultivated and one wild sunflower genotype, as well as improved assemblies for two additional cultivars. Next, relying on previously generated sequences from wild donor species, we identified introgressions in the cultivated reference sequences, as well as the sequence and structural variants they contain. We then used a ridge-regression best linear unbiased prediction (BLUP) model to test the effects of the introgressions on phenotypic traits in the cultivated sunflower association mapping population. We found that introgression has introduced substantial sequence and structural variation into the cultivated sunflower gene pool, including >3,000 new genes. While introgressions reduced genetic load at protein-coding sequences, they mostly had negative impacts on yield and quality traits. Introgressions found at high frequency in the cultivated gene pool had larger effects than low-frequency introgressions, suggesting that the former likely were targeted by artificial selection. Also, introgressions from more distantly related species were more likely to be maladaptive than those from the wild progenitor of cultivated sunflower. Thus, breeding efforts should focus, as far as possible, on closely related and fully compatible wild relatives.

Genome-Wide Association Mapping in Sunflower (Helianthus annuus) Reveals Common Loci and Putative Candidate Genes for Resistance to Diaporthe gulyae and D. helianthi Causing Phomopsis Stem Canker

Diaporthe gulyae and D. helianthi cause Phomopsis stem canker of sunflower (Helianthus annuus L.) in the United States. Because Phomopsis stem canker did not gain importance until the disease epidemic in 2010, limited studies were conducted to understand the genetic basis of sunflower resistance to D. gulyae and D. helianthi. The objectives of this study were to evaluate the United States Department of Agriculture cultivated accessions for resistance to D. gulyae and D. helianthi as well as to utilize genome-wide association studies (GWAS) to identify quantitative trait loci (QTLs) and putative candidate genes underlying those loci common to both organisms. For each fungus, 213 accessions were screened in a complete randomized design in the greenhouse and the experiment was repeated once. Six plants per accession were inoculated with a single isolate of D. gulyae or D. helianthi at four to six true leaves using the mycelium-contact inoculation method. At 15 days (D. gulyae) and 30 days (D. helianthi) postinoculation, accessions were evaluated for disease severity and compared with the susceptible confection inbred PI 552934. GWAS identified 28 QTLs common to the two fungi, and 24 genes overlapped close to these QTLs. Additionally, it was observed that the resistance QTLs derived mainly from landraces rather than from wild species. Seventeen putative candidate genes associated with resistance to D. gulyae or D. helianthi were identified that may be related to plant-pathogen interactions. These findings advanced our understanding of the genetic basis of resistance to D. gulyae and D. helianthi and will help develop resources for genomics-assisted breeding.

Expression complementation of gene presence/absence polymorphisms in hybrids contributes importantly to heterosis in sunflower

INTRODUCTION

Numerous crops have transitioned to hybrid seed production to increase yields and yield stability through heterosis. However, the molecular mechanisms underlying heterosis and its stability across environments are not yet fully understood.

OBJECTIVES

This study aimed to (1) elucidate the genetic and molecular mechanisms underlying heterosis in sunflower, and (2) determine how heterosis is maintained under different environments.

METHODS

Genome-wide association (GWA) analyses were employed to assess the effects of presence/absence variants (PAVs) and stop codons on 16 traits phenotyped in the sunflower association mapping population at three locations. To link the GWA results to transcriptomic variation, we sequenced the transcriptomes of two sunflower cultivars and their F₁ hybrid (INEDI) under both control and drought conditions and analyzed patterns of gene expression and alternative splicing.

RESULTS

Thousands of PAVs were found to affect phenotypic variation using a relaxed significance threshold, and at most such loci the "absence" allele reduced values of heterotic traits, but not those of non-heterotic traits. This pattern was strengthened for PAVs that showed expression complementation in INEDI. Stop codons were much rarer than PAVs and less likely to reduce heterotic trait values. Hybrid expression patterns were enriched for the GO category, sensitivity to stimulus, but all genotypes responded to drought similarily - by up-regulating water stress response pathways and down-regulating metabolic pathways. Changes in alternative splicing were strongly negatively correlated with expression variation, implying that alternative splicing in this system largely acts to reinforce expression responses.

CONCLUSION

Our results imply that complementation of expression of PAVs in hybrids is a major contributor to heterosis in sunflower, consistent with the dominance model of heterosis. This mechanism can account for yield stability across different environments. Moreover, given the much larger numbers of PAVs in plant vs. animal genomes, it also offers an explanation for the stronger heterotic responses seen in the former.

Genetic basis and dual adaptive role of floral pigmentation in sunflowers

Variation in floral displays, both between and within species, has been long known to be shaped by the mutualistic interactions that plants establish with their pollinators. However, increasing evidence suggests that abiotic selection pressures influence floral diversity as well. Here, we analyse the genetic and environmental factors that underlie patterns of floral pigmentation in wild sunflowers. While sunflower inflorescences appear invariably yellow to the human eye, they display extreme diversity for patterns of ultraviolet pigmentation, which are visible to most pollinators. We show that this diversity is largely controlled by cis-regulatory variation affecting a single MYB transcription factor, HaMYB111, through accumulation of ultraviolet (UV)-absorbing flavonol glycosides in ligules (the ‘petals’ of sunflower inflorescences). Different patterns of ultraviolet pigments in flowers are strongly correlated with pollinator preferences. Furthermore, variation for floral ultraviolet patterns is associated with environmental variables, especially relative humidity, across populations of wild sunflowers. Ligules with larger ultraviolet patterns, which are found in drier environments, show increased resistance to desiccation, suggesting a role in reducing water loss. The dual role of floral UV patterns in pollinator attraction and abiotic response reveals the complex adaptive balance underlying the evolution of floral traits.

Flowers are an important part of how many plants reproduce. Their distinctive colours, shapes and patterns attract specific pollinators, but they can also help to protect the plant from predators and environmental stresses.

Many flowers contain pigments that absorb ultraviolet (UV) light to display distinct UV patterns – although invisible to the human eye, most pollinators are able to see them. For example, when seen in UV, sunflowers feature a ‘bullseye’ with a dark centre surrounded by a reflective outer ring. The sizes and thicknesses of these rings vary a lot within and between flower species, and so far, it has been unclear what causes this variation and how it affects the plants.

To find out more, Todesco et al. studied the UV patterns in various wild sunflowers across North America by considering the ecology and molecular biology of different plants. This revealed great variation between the UV patterns of the different sunflower populations. Moreover, Todesco et al. found that a gene called HaMYB111 is responsible for the diverse UV patterns in the sunflowers. This gene controls how plants make chemicals called flavonols that absorb UV light.

Flavonols also help to protect plants from damage caused by droughts and extreme temperatures. Todesco et al. showed that plants with larger bullseyes had more flavonols, attracted more pollinators, and were better at conserving water. Accordingly, these plants were found in drier locations.

This study suggests that, at least in sunflowers, UV patterns help both to attract pollinators and to control water loss. These insights could help to improve pollination – and consequently yield – in cultivated plants, and to develop plants with better resistance to extreme weather. This work also highlights the importance of combining biology on small and large scales to understand complex processes, such as adaptation and evolution.

Correlation Between Tympanosclerosis and Helicobacter pylori

Background:

Tympanosclerosis is a condition caused by calcification of tissues in the middle ear mucosa that sometimes results hearing loss. Helicobacter pylori is one of the pathological and etiologic factors in the development of tympanosclerosis.

Objectives:

The purpose of this study was to show the role of H. pylori in the different aspects of chronic suppurative otitis media using the polymerase chain reaction (PCR) technique.

Patients and Methods:

This case-control and cross-sectional study was performed on all patients with chronic otitis media, candidates for surgical operations, in 2013. They were allocated into the case group with tympanosclerosis and the control group without tympanosclerosis. During the surgical operation, biopsy was done from middle ear and the samples were studied to see if they contained H. pylori using the PCR method.

Results:

From a total of 19 patients with tympanosclerosis , 16 cases (84.2%) were H. pylori positive, while in the control group 15 (45.4%) cases out of the 37 cases were H. pylori positive, which showed a significant difference (P = 0.002). Age and gender of the patients, ear dryness and perforation size were not correlated with the presence or absence of H. pylori.

Conclusions:

There is a significant correlation between tympanosclerosis and H. pylori (P = 0.002). This correlation can single out H. pylori as a pathological factor in the development of tympanosclerosis; however, further studies are needed to prove this correlation.

Determining the Role of Helicobacter pylori in Chronic Sinus Infections Using the Polymerase Chain Reaction

Background:

Helicobacter pylori are becoming increasingly recognized as a possible pathological cause of chronic rhinosinusitis (CRS).

Objectives:

Considering the prevalence of CRS and its impact on quality of life, we decided to determine the role of H. pylori in chronic sinus infections by using the PCR technique.

Patients and Methods:

In a case-control analytical epidemiologic survey, the study population was selected by consecutive sampling from patients with CRS undergoing endoscopic sinus surgery during years 2010 - 2012. Patients were divided into two groups. The study group consisted of patients with CRS and the control group consisted of patients with nasal obstruction caused by concha bullosa, without inflammation or infection of the sinuses. Sampling was performed during surgery from the infected tissue and from the middle turbinate mucosa. Eventually, bacterial DNA was extracted and used for the PCR test, in order to isolate H. pylori.

Results:

Nine patients (18%) with CRS had H. pylori isolated from their samples whereas in the control group, H. pylori were only found in two patients (4%); this difference was statistically significant (P = 0.025). The indicator wasn’t statistically significant between males and females. There was no statistical correlation in relative frequency of H. pylori for different age groups (P > 0.05).

Conclusions:

There was a significant correlation between CRS and presence of H. pylori in sinonasal mucosa. This relationship may reflect the role of H. pylori as one of the pathogenic factors in the development of CRS. However, further studies are required to confirm this role.

Identification and validation of functional markers in a global rice collection by association mapping

Recent results indicate that marker-assisted selection is an effective approach to reduce the cost and to improve the efficacy and accuracy of selection in plant breeding. This study was conducted to identify and validate molecular markers linked to important breeding traits by association mapping. The association was evaluated between 81 molecular markers (STS, SSR, Indel, CAPS, and PCR-based SNP) and 15 morphological traits in a global panel of 100 rice (Oryza sativa) accessions. The population structure analysis identified three main subpopulations. Obvious kinship relationships were also detected between the rice accessions. Association analysis was performed based on the mixed linear model by considering population structure and family relatedness. In addition, the false discovery rate method was used to correct the multiple testing. A total of 47 marker-trait associations were identified, including 22 markers for 14 traits. Among all, the polymorphism at the loci DDR-GL was highly associated with grain characters (grain length, grain width, and length/width ratio). In addition, marker RM3148 was responsible for five important traits simultaneously. Results demonstrated that such informative markers can be very useful for rice breeding programs using marker-assisted selection. Moreover, the diverse populations of rice accessions are a valuable resource for association mapping of morphological traits.

First-line treatment of acute promyelocytic leukemia with arsenic trioxide without ATRA and chemotherapy

7073

Background: Standard treatment of APL is ATRA plus chemotherapy but Arsenic Trioxide (ATO) is most potent single agent against APL cells. Role of ATO in first line therapy of APL needs to clarify. Methods: Between may 2000 and September 2006,we treated 141 new cases of APL(Median age 28±12.8 y/o min=11,max=71) by 2 hours iv infusion of 0.15mg/kg ATO until complete remission. Trial approved by IRB and consent form obtained. Diagnosis was by clinical and morphologic characteristics and confirmed by cytogenetic and RT-PCR for detection of t(15,17) and presence of PML-RARa. After complete remission patients received consolidation by 28 days infusion of ATO for one or four courses.(one consolidation one month after CR and for some patients second, third and forth consolidations one month after first one and two another , one year and two year after CR) Results: : complete remission observed in 121 cases(85.8%) and early mortality rate was14.9%(most common cause of early mortality was APL syndrome,61.9%).Median follow up was 28 months. For patients who achieve to complete remission,one, two and three year disease free survival were 95.6%± 2%, 76.9±4% and 57± 6%,respectively. Many relapsed patients salvaged again with ATO alone so, two and three years overall survival for this cohort was 95.6%±2% and 83.7%±4%. Increasing number of consolidation from one to four couldn’t increase DFS or OS in one and two years after CR. Conclusions: ATO is effective in treatment of new cases of APL. Introduction of ATO in first line treatment of APL(with or without ATRA plus chemotherapy) needs a multi center randomized clinical trial.

No significant financial relationships to disclose.

Treatment of acute promyelocytic leukemia with arsenic trioxide without ATRA and/or chemotherapy

INTRODUCTION

Arsenic trioxide is effective and approved for treatment of relapsed or refractory acute promyelocytic leukemia (APL) cases resistant to all-trans retinoic acid (ATRA), but its effect on new cases of APL is not clear.

MATERIALS AND METHODS

We studied 111 patients with APL. Arsenic trioxide was infused at 0.15 mg/kg daily dose, until complete remission was achieved. Then, after 28 days of rest, arsenic trioxide was infused daily for 28 days as consolidation therapy. We studied minimal residual disease (MRD) by semi-sensitive reverse transcription polymerase chain reaction (RT-PCR) on peripheral blood samples.

RESULTS

Complete remission was observed in 95 patients (85.6%). With the median (range) follow-up period of 16.5 (1-57) months, 1- and 2-year disease-free survival was 88.3% and 63.7%, respectively; 24 patients relapsed, 19 of whom achieved a second complete remission, again by arsenic trioxide. Third and fourth remissions were seen in some relapsed patients, again by arsenic trioxide. For patients in complete remission, 1- and 3-year survival was 95.5% and 87.6%, respectively. MRD was positive in four (8.3%) out of 48 cases during 1 year after remission induction; three of them relapsed clinically.

CONCLUSIONS

Arsenic trioxide is effective as first-line treatment for APL. Results of arsenic trioxide combination therapy with chemotherapy/ATRA requires further study.

Are HLA antigens a risk factor for acute GVHD in thalassemic patients receiving HLA-identical stem cell transplantation?

We retrospectively evaluated the association between risk factors and acute graft-versus-host disease (aGVHD) among 182 beta thalassemia patients who received 73 peripheral blood stem cell (PBSC) or 109 bone marrow transplants from HLA-identical siblings between 1991 and 2003. The relationship between the severity of aGVHD was examined for the following factors: HLA antigens, age, sex, ABO mismatch, sex mismatch (between recipient and donor), thalassemia class, graft source, transplant cell dose, CD3+ cell dose, conditioning regimen, GVHD prophylaxis, neutrophil engraftment duration, and blood product transfusions using univariate and multivariate analyses. Overall 61 (34%) patients developed clinical grade III or grade IV aGVHD. Univariate analysis confirmed an increased risk of severe aGVHD, which was associated with HLA-A11, HLA-A26, and PBSCT (P=.04, .03, and .03, respectively). The risk of aGVHD was reduced in the presence of HLA-A3 (P=.03). Multivariate analysis confirmed the increased risk of aGVHD associated with HLA-A11 (P=.04), HLA-A26 (P=.01), and a short-period neutrophil recovery (P=.009). In this study HLA-A11, HLA-A26, PBSCT, and a short neutrophil engraftment period were probable risk factors and HLA-A3 a probable protective factor associated with severe aGVHD. These data may provide useful guidelines to choose strategies for treatment and prevention.

Thyroid, parathyroid, gonadal, and pancreatic β-cell function after bone marrow transplantation with chemotherapy-only conditioning

INTRODUCTION

Radiation and cytotoxic chemotherapy can provoke short- and long-term endocrine dysfunction. We studied the prevalence of thyroid, parathyroid, gonadal, and pancreatic beta-cell function in patients undergoing bone marrow transplantation (BMT).

MATERIALS AND METHOD

Forty-six patients (12 women, 34 men), aged 1.5 to 49 years (mean, 15.1 years), were evaluated for thyroid, parathyroid, gonadal, and pancreatic beta-cell function before and 3, 6, and 12 months after BMT with a little busulfan-cyclophosphamide conditioning regimen.

RESULTS

Thyroid and parathyroid function was unaltered by BMT. Leydig cell function was normal in 11 adult men (G5P5) before and at 3, 6, and 12 months after BMT, but injury to the germinal epithelium (oligo- or azoospermia) was seen before and 12 months after BMT. There was no relationship between serum FSH and germinal epithelial injury. Maturation was normal in six boys (G2P2 or G3P3 at BMT) 12 months post-BMT. Primary hypogonadism was seen in four adult women (B5P5) after BMT. One 14-year-old girl continued to have regular menstrual periods during the 24 months after BMT. Another girl (P1B1 pre-BMT) developed ovarian failure 12 months post-BMT. Pancreatic beta-cell function was normal pre- and post-BMT in 12 thalassemic patients with serum ferritin > 1000 ng/mL.

CONCLUSION

BMT with chemotherapy-only conditioning seems primarily to affect gonadal function, without having any significant effect on thyroid, parathyroid, or pancreatic beta-cell function.

Esophageal cancer in Iran

Esophageal cancer is among the 10 most frequent cancers in the world. Iran is one of the known areas with a high incidence of esophageal cancer. Most of the patients in Iran have been reported from the north and northeast regions of the country. In one survey by the Iran Cancer Institute, 9% of all cancers and 27% of gastrointestinal cancers were esophageal carcinoma. The male to female ratio was 1.7/1. The distal portion of the esophagus is involved more often than other parts. Consumption of wheat flour, exposure to residues from opium pipes, drinking hot tea, and chewing nass (a mixture of tobacco, lime, ash, and other ingredients) are the suspect etiologic agents for esophageal cancer in Iran. Dysphagia, weight loss, anorexia, abdominal pain, and odynophagia are the common symptoms and signs of Iranian patients with esophageal cancer. For clinical staging, chest computed tomographic scanning is performed. Adenocarcinoma of the esophagus is not as common in Iran as in western countries. Public education, nutritional support, and eradication of opium addiction may decrease the morbidity and mortality that result from esophageal cancer. Surgery has traditionally been the mainstay of esophageal cancer treatment in Iran. Radiotherapy is mainly used postoperatively. The usual combination chemotherapy regimen is cisplatin plus flurouracil (5-Fu). Semin Oncol 28:153-157.

Correction of bone marrow failure in dyskeratosis congenita by bone marrow transplantation

Dyskeratosis congenita is recognized by its dermal lesions and constitutional aplastic anemia in some cases. We report successful allogeneic bone marrow transplantation in two siblings with this disease from their sister, and their long term follow-up. We used reduced doses of cyclophosphamide and busulfan for conditioning instead of total body irradiation. Also, we report late adverse effects of transplantation which are not distinguishable from the natural course of disease.

Prognostic factors in bone marrow transplantation for beta thalassemia major: experiences from Iran

This study concerns the effects of several pre-transplant features on outcome for patients with beta thalassemia major who underwent bone marrow transplantation (BMT). Seventy patients with beta thalassemia major underwent bone marrow transplantation during the period 1991-1997 in Shariati Hospital in Tehran, Iran. The survival and rejection curves levelled off at 8 and 18 months after transplantation at 82.6% and 11.4%, respectively. Pre-transplant clinical features (age, serum ferritin, portal fibrosis, hepatomegaly and quality of chelation therapy) were examined for their effects on survival and recurrence of thalassemia in this group of patients who were less than 16 years old. Increasing age, presence of portal fibrosis and increasing serum ferritin were significantly associated with reduced probability of survival (P = 0.0047, P = 0.016 and P = 0.024, respectively). Hepatomegaly and inadequate pre-transplant chelation therapy which were documented as poor prognostic factors in previous studies, were not evaluable in this study. We also showed the benefits of transplanting more than 5.5 x 10(8)/kg cells in this group of patients with no increase in complications.

Bone marrow transplantation in Iran

Seventy-three BMT procedures (42 allogeneic-BMT, 30 autologous-BMT, 1 syngeneic transplant) were undertaken at the Shariati Hospital in Tehran between March 1991 and November 1993. Allogeneic-BMT was performed for thalassaemia major (n = 23), AML in complete remission (n = 3), severe aplastic anaemia (n = 7), CML (n = 7), dyskeratosis congenita (n = 2) and Fanconi anaemia (n = 1). Conditioning regimens comprised busulphan (BU) plus cyclophosphamide (CY) or CY only. Thirty-two (78%) of the 43 patients remain alive 1-34 months after BMT. Twelve patients died: the causes of death were haemorrhagic cystitis (n = 1), CMV pneumonitis (n = 1), GVHD (n = 3), infection (n = 3), rejection (n = 1), VOD (n = 2) and hepatitis (n = 1). Autologous-BMT was performed for patients with AML in CR (n = 16), ALL in CR (n = 9), lymphoma in relapse (n = 3), Ewing sarcoma (n = 1) and multiple myeloma (n = 1). The median age was 18 years. Conditioning regimens were Ara C plus CY, etoposide plus CY and high-dose melphalan. Sixteen (54%) of the 30 patients survive, 14 in continuous complete remission. The causes of death were relapse (AML (n = 7), ALL (n = 4), lymphoma (n = 1)), VOD (n = 1) and infection (n = 1).

Isolation of high-density lipoproteins by immunoaffinity column chromatography from hog plasma

High density lipoprotein (HDL) was isolated from hog plasma by a simple immunoaffinity column chromatography procedure using immobilized anti-apolipoprotein AI. The composition of HDL isolated by immunoaffinity chromatography was nearly identical to that of a control sample that was isolated by an alternate method utilizing ultracentrifugation and gel chromatography. The HDL isolated by immunoaffinity chromatography had a larger number of polypeptide components that the control as indicated by acrylamide gel electrophoresis in the presence of urea. When the HDL isolated by immunoaffinity chromatography was applied to a heparin-agarose column the amount of protein retained was approximately twice that of the control. These findings indicate that the ultracentrifugation procedure probably induced the loss of apolipoprotein E containing components from the HDL complex.

Characterization of lecithin-cholesterol acyltransferase from human plasma. 3. Chemical properties of the enzyme

The polypeptide molecular weight of lecithin-cholesterol acyltransferase (LCAT) (45000) was obtained by deducting the weight of carbohydrate moiety (25%, w/w) from the total molecular weight of 60000. LCAT was found to have a relatively high content of glutamic acid, aspartic acid, glycine, and leucine residues and four half-cystines. The carbohydrate content was found to be about 25% (w/w): hexoses, 13%; hexosamines, 6.2%; and sialic acid, 5.4%. The total number of 408 amino acid residues per mole and the mean residue weight of 110.3 were found. From fluorescence spectroscopy analysis, 6-7 mol of tryptophan were found per mole of LCAT in 10 mM phosphate (pH 7.4). However, when LCAT was digested by the mixture of chymotrypsin and pronase the tryptophan residues increased to 10-11 mol/mol of LCAT, which agrees well with data obtained previously by ultraviolet absorption spectroscopy. A partial specific volume of 0.707 mL/g was determined by compositional analysis. Human LCAT was found to have a relatively high extinction coefficient (E1%1cm) of 21 at 280 nm and neutral pH. Two residues of cysteine per mole of LCAT were estimated both in the presence or absence of sodium dodecyl sulfate by titration with 5,5'-dithiobis-2-nitrobenzoic acid. The enzyme showed a lower tendency to staining with Coomassie blue R-250 than bovine serum albumin. The enzyme was rapidly inactivated by diisopropyl fluorophosphate (DFP), regardless of whether the free sulfhydryl were blocked or not. The enzyme was also irreversibly inhibited by cysteine above concentrations of 1 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Study of the lecithin: cholesterol acyltransferase reaction with liposome and high density lipoprotein substrates

The activity of highly purified preparations of human plasma lecithin: cholesterol acyltransferase were stabilized by precipitating the enzyme with ammonium sulfate and using the dilutions of the particulate lecithin: cholesterol acyltransferase suspension for enzyme assays. Ammonium sulfate concentrations in the assay mix up to 0.1 M had no significant effect on lecithin: cholesterol acyltransferase activity. The basic enzymatic properties of lecithin: cholesterol acyltransferase were investigated using liposomes and high density lipoprotein (HDL) substrates. pH optima for both substrates was approximately 8.0. The temperature dependence of lecithin: cholesterol acyltransferase activity resulted in non-linear Arrhenius plots with both substrates. The activity vs. temperature (degrees C) curves showed slight inflections at 30 degrees C, which may have been due to the relatively rapid inactivation of the enzyme above this temperature. HDL3 was found to be a better substrate than HDL or HDL2. HDL3 was also considerably better than egg phosphatidylcholine/cholesterol liposomes as an lecithin: cholesterol acyltransferase substrate. Addition of HDL2 to a reaction mix of enzyme and HDL3 indicated that HDL2 acts as an inhibitor of cholesterol esterification in this system.

A study of the interaction of lecithin: cholesterol acyltransferase with subfractions of high density lipoproteins

High density lipoproteins (HDL) were isolated by a chromatographic procedure and subsequently fractionated on a DEAE cellulose (DE-52) column. Four fractions were separated and analyzed for lipid and protein composition and molecular weight. During ion exchange chromatography, one of the four fractions consistently coincided with lecithin:cholesterol acyltransferase (LCAT) activity. When the HDL fractions were incubated with highly purified LCAT preparations, the LCAT activity showed a dependence on unesterified cholesterol concentrations. The HDL subfraction eluting at the highest ionic strength was found to be the best substrate for LCAT. This subfraction exhibited apoprotein and lipid composition similar to HDL3 and contained 31% of the total apoprotein D present in all the subfractions. A positive correlation was found between LCAT activity and the cholesteryl ester/unesterified cholesterol ratio, and a negative correlation was found between LCAT substrate potential and apparent molecular weight of the HDL subfractions when these subfractions were incubated with LCAT. No correlation was apparent between LCAT activity, and the phospholipid/unesterified cholesterol ratio or with the apoA-I/apoA-II ratio.U

A novel chromatographic method for the preparation of high density lipoproteins

High density lipoproteins (HDL) were isolated by a procedure employing polyanion precipitation and column chromatography. The product polyanion precipitation and column chromatography. The product was free of low denisty lipoproteins (LDL) but serum albumin (HSA) was still present. The remaining HSA was removed by an immunoadsorbent column. The HDL isolated by our method was compared to another HDL preparation isolated from the same plasma sample by the combination of ultracentrifugation and gel chromatgraphy. It was found to have approximately the same lipid and protein composition as the HDL isolated by conventional techniques. Minor differences included a higher phospholipid and apoprotein E content and lower triglyceride and ApoC II content of the HDL isolated by column chromatography. The method described here is considerably less tedious than earlier techniques, can be scaled up without substantial increase in labor and results in an approximately 30% higher yield than the method described by Rudel et al.