A new test method for biochemical analysis of plasmalogens in dried blood spots and erythrocytes from patients with peroxisomal disorders

Measurement of plasmalogens is useful for the biochemical diagnosis of rhizomelic chondrodysplasia punctata (RCDP) and is also informative for Zellweger spectrum disorders (ZSD). We have developed a test method for the simultaneous quantitation of C16:0, C18:0, and C018:1 plasmalogen (PG) species and their corresponding fatty acids (FAs) in dried blood spots (DBS) and erythrocytes (RBC) by using capillary gas chromatography-mass spectrometry. Normal reference ranges for measured markers and 10 calculated ratios were established by the analysis of 720 and 473 unaffected DBS and RBC samples, respectively. Determination of preliminary disease ranges was made by using 45 samples from 43 unique patients: RCDP type 1 (DBS: 1 mild, 17 severe; RBC: 1 mild, 6 severe), RCDP type 2 (DBS: 2 mild, 1 severe; RBC: 2 severe), RCDP type 3 (DBS: 1 severe), RCDP type 4 (RBC: 2 severe), and ZSD (DBS: 3 severe; RBC: 2 mild, 7 severe). Postanalytical interpretive tools in Collaborative Laboratory Integrated Reports (CLIR) were used to generate an integrated score and a likelihood of disease. In conjunction with a review of clinical phenotype, phytanic acid, and very long-chain FA test results, the CLIR analysis allowed for differentiation between RCDP and ZSD. Data will continue to be gathered to improve CLIR analysis as more samples from affected patients with variable disease severity are analyzed. The addition of DBS analysis of PGs may allow for at-home specimen collection and second-tier testing for newborn screening programs.

Clinical, biochemical and genetic characteristics of MOGS-CDG: a rare congenital disorder of glycosylation

PURPOSE

To summarise the clinical, molecular and biochemical phenotype of mannosyl-oligosaccharide glucosidase-related congenital disorders of glycosylation (MOGS-CDG), which presents with variable clinical manifestations, and to analyse which clinical biochemical assay consistently supports diagnosis in individuals with bi-allelic variants in MOGS.

METHODS

Phenotypic characterisation was performed through an international and multicentre collaboration. Genetic testing was done by exome sequencing and targeted arrays. Biochemical assays on serum and urine were performed to delineate the biochemical signature of MOGS-CDG.

RESULTS

Clinical phenotyping revealed heterogeneity in MOGS-CDG, including neurological, immunological and skeletal phenotypes. Bi-allelic variants in MOGS were identified in 12 individuals from 11 families. The severity in each organ system was variable, without definite genotype correlation. Urine oligosaccharide analysis was consistently abnormal for all affected probands, whereas other biochemical analyses such as serum transferrin analysis was not consistently abnormal.

CONCLUSION

The clinical phenotype of MOGS-CDG includes multisystemic involvement with variable severity. Molecular analysis, combined with biochemical testing, is important for diagnosis. In MOGS-CDG, urine oligosaccharide analysis via matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry can be used as a reliable biochemical test for screening and confirmation of disease.

Locoregional delivery of CAR-T cells in the clinic

Cellular therapies utilizing T cells expressing chimeric antigen receptors (CARs) have garnered significant interest due to their clinical success in hematological malignancies. Unfortunately, this success has not been replicated in solid tumors, with only a small fraction of patients achieving complete responses. A number of obstacles to effective CAR-T cell therapy in solid tumors have been identified including tumor antigen heterogeneity, poor T cell fitness and persistence, inefficient trafficking and inability to penetrate into the tumor, immune-related adverse events due to on-target/off-tumor toxicity, and the immunosuppressive tumor microenvironment. Many preclinical studies have focused on improvements to CAR design to try to overcome some of these hurdles. However, a growing body of work has also focused on the use of local and/or regional delivery of CAR-T cells as a means to overcome poor T cell trafficking and inefficient T cell penetration into tumors. Most trials that incorporate locoregional delivery of CAR-T cells have targeted tumors of the central nervous system - repurposing an Ommaya/Rickham reservoir for repeated delivery of cells directly to the tumor cavity or ventricles. Hepatic artery infusion is another technique used for locoregional delivery to hepatic tumors. Locoregional delivery theoretically permits increased numbers of CAR-T cells within the tumor while reducing the risk of immune-related systemic toxicity. Studies to date have been almost exclusively phase I. The growing body of evidence indicates that locoregional delivery of CAR-T cells is both safe and feasible. This review focuses specifically on the use of locoregional delivery of CAR-T cells in clinical trials.

Biochemical Diagnosis of Acute Hepatic Porphyria: Updated Expert Recommendations for Primary Care Physicians

Acute hepatic porphyria (AHP) is a group of rare, metabolic diseases where patients can experience acute neurovisceral attacks, chronic symptoms, and long-term complications. Diagnostic biochemical testing is widely available and effective, but a substantial time from symptom onset to diagnosis often delays treatment and increases morbidity. A panel of laboratory scientists and clinical AHP specialists collaborated to produce recommendations on how to enhance biochemical diagnosis of AHP in the USA. AHP should be considered in the differential diagnosis of unexplained abdominal pain, the most common symptom, soon after excluding common causes. Measurement of porphobilinogen (PBG) and porphyrins in a random urine sample, with results normalized to creatinine, is recommended as an effective and cost-efficient initial test for AHP. Delta-aminolevulinic acid testing may be included but is not essential. The optimal time to collect a urine sample is during an attack. Substantial PBG elevation confirms an AHP diagnosis and allows for prompt treatment initiation. Additional testing can determine AHP subtype and identify at-risk family members. Increased awareness of AHP and correct diagnostic methods will reduce diagnostic delay and improve patient outcomes.

Incorporation of Second-Tier Biomarker Testing Improves the Specificity of Newborn Screening for Mucopolysaccharidosis Type I

Enzyme-based newborn screening for Mucopolysaccharidosis type I (MPS I) has a high false-positive rate due to the prevalence of pseudodeficiency alleles, often resulting in unnecessary and costly follow up. The glycosaminoglycans (GAGs), dermatan sulfate (DS) and heparan sulfate (HS) are both substrates for α-l-iduronidase (IDUA). These GAGs are elevated in patients with MPS I and have been shown to be promising biomarkers for both primary and second-tier testing. Since February 2016, we have measured DS and HS in 1213 specimens submitted on infants at risk for MPS I based on newborn screening. Molecular correlation was available for 157 of the tested cases. Samples from infants with MPS I confirmed by IDUA molecular analysis all had significantly elevated levels of DS and HS compared to those with confirmed pseudodeficiency and/or heterozygosity. Analysis of our testing population and correlation with molecular results identified few discrepant outcomes and uncovered no evidence of false-negative cases. We have demonstrated that blood spot GAGs analysis accurately discriminates between patients with confirmed MPS I and false-positive cases due to pseudodeficiency or heterozygosity and increases the specificity of newborn screening for MPS I.

The critical role of psychosine in screening, diagnosis, and monitoring of Krabbe disease

PURPOSE

Newborn screening (NBS) for Krabbe disease (KD) is performed by measurement of galactocerebrosidase (GALC) activity as the primary test. This revealed that GALC activity has poor specificity for KD. Psychosine (PSY) was proposed as a disease marker useful to reduce the false positive rate for NBS and for disease monitoring. We report a highly sensitive PSY assay that allows identification of KD patients with minimal PSY elevations.

METHODS

PSY was extracted from dried blood spots or erythrocytes with methanol containing d₅-PSY as internal standard, and measured by liquid chromatography-tandem mass spectrometry.

RESULTS

Analysis of PSY in samples from controls (N = 209), GALC pseudodeficiency carriers (N = 55), GALC pathogenic variant carriers (N = 27), patients with infantile KD (N = 26), and patients with late-onset KD (N = 11) allowed for the development of an effective laboratory screening and diagnostic algorithm. Additional longitudinal measurements were used to track therapeutic efficacy of hematopoietic stem cell transplantion (HSCT).

CONCLUSION

This study supports PSY quantitation as a critical component of NBS for KD. It helps to differentiate infantile from later onset KD variants, as well as from GALC variant and pseudodeficiency carriers. Additionally, this study provides further data that PSY measurement can be useful to monitor KD progression before and after treatment.

Phylloporus and Phylloboletellus are no longer alone: Phylloporopsis gen. nov. (Boletaceae), a new smooth-spored lamellate genus to accommodate the American species Phylloporus boletinoides

The monotypic genus Phylloporopsis is described as new to science based on Phylloporus boletinoides. This species occurs widely in eastern North America and Central America. It is reported for the first time from a neotropical montane pine woodland in the Dominican Republic. The confirmation of this newly recognised monophyletic genus is supported and molecularly confirmed by phylogenetic inference based on multiple loci (ITS, 28S, TEF1-α, and RPB1). A detailed morphological description of P. boletinoides from the Dominican Republic and Florida (USA) is provided along with colour images of fresh basidiomata in habitat, line drawings of the main anatomical features, transmitted light microscopic images of anatomical features and scanning electron microscope images of basidiospores. The taxonomic placement, ecological requirements and distribution patterns of P. boletinoides are reviewed and the relationships with phylogenetically related or morphologically similar lamellate and boletoid taxa such as Phylloporus, Phylloboletellus, Phyllobolites and Bothia are discussed.

Solitary plasmacytoma of the medial clavicle

Medial clavicular pain has a broad differential diagnosis that includes traumatic, atraumatic, and neoplastic etiologies. Dedicated imaging studies (eg, computed tomography, magnetic resonance imaging) play an essential role in evaluating and diagnosing disorders of the medial clavicle. In this article, we report a case of medial clavicular pain caused by a rare neoplasm, a solitary plasmacytoma of bone. This case illustrates the importance of accurate diagnosis that is facilitated by thorough evaluation and computed tomographic imaging of the medial clavicle.

Natural history of rhizomelic chondrodysplasia punctata

Rhizomelic chondrodysplasia punctata (RCP) is a rare autosomal recessive disorder with many associated medical complications. Prior to this study, natural history information about RCP was limited and based on experiences with small populations of affected individuals. We delineate the natural history of RCP through systematic analysis of 35 previously unreported individuals (as well as review of 62 literature cases with respect to survival and cause of death). Survival, growth, and developmental expectations and medical needs are summarized based upon experience with this population. Survival is greater among this population than previously reported, with 90% surviving up to 1 year and 50% surviving up to 6 years. Cause of death is most often respiratory problem. All infants with RCP have joint contractures, bilateral cataracts, and severe growth and psychomotor delays. Recommendations for health supervision of children with RCP and for parental counseling are presented.

Differential effect of combined lipase deficiency (cld/cld) on human hepatic lipase and lipoprotein lipase secretion

Combined lipase deficiency (cld) is a recessively inherited disorder in mice associated with a deficiency of LPL and hepatic lipase (HL) activity. LPL is synthesized in cld tissues but is retained in the endoplasmic reticulum (ER), whereas mouse HL (mHL) is secreted but inactive. In this study we investigated the effect of cld on the secretion of human HL (hHL) protein mass and activity. Differentiated liver cell lines were derived from cld mice and their normal heterozygous (het) littermates by transformation of hepatocytes with SV40 large T antigen. After transient transfection with lipase expression constructs, secretion of hLPL activity from cld cells was only 12% of that from het cells. In contrast, the rate of secretion of hHL activity and protein mass per unit of expressed hHL mRNA was identical for the two cell lines. An intermediate effect was observed for mHL, with a 46% reduction in secretion of activity from cld cells. The ER glucosidase inhibitor, castanospermine, decreased secretion of both hLPL and hHL from het cells by approximately 70%, but by only approximately 45% from cld cells. This is consistent with data suggesting that cld may result from a reduced concentration of the ER chaperone calnexin. In conclusion, our results demonstrate a differential effect of cld on hLPL, mHL, and hHL secretion, suggesting differential requirements for activation and exit of the enzymes from the ER.

Determinants of human apolipoprotein [a] secretion from mouse hepatocyte cultures

Efforts to develop an in vitro model system to analyze apolipoprotein [a] (apo[a]) gene transcription, mRNA translation, and protein secretion have been complicated by the limited tissue and species distribution of apo[a] and the presence of regulatory DNA sequences remote from the apo[a] transcription start site. In the current study we examined primary hepatocytes cultured from apo[a] transgenic mice as a model system for analyzing apo[a] biogenesis. Hepatocytes from mice transgenic for a yeast artificial chromosome (YAC) encoding the entire apo[a] gene in its own genomic context (YAC-apo[a] hepatocytes) were unable to maintain apo[a] expression beyond 48 h of culture. This suggests that the apo[a] promoter was not active in cultured YAC-apo[a] hepatocytes. In contrast, apo[a] expression was maintained for at least 7 days in hepatocytes cultured from mice transgenic for an apo[a] cDNA under control of the mouse transferrin promoter (transferrin-apo[a] hepatocytes). Pulse-chase experiments established that more than 80% of apo[a] synthesized by both transferrin-apo[a] and YAC-apo[a] hepatocytes was degraded prior to secretion, independently of the coexpression of human apoB.Thus, low secretion efficiency appears to be a general characteristic of human apo[a] proteins in mouse liver. Apo[a] secretion was increased somewhat (from 18% to 32%) in the presence of lipoprotein-containing serum. Transformed cell lines derived from transferrin apo[a] hepatocytes retained characteristics of apo[a] secretion similar to those observed in primary cells. Primary and transformed apo[a] transgenic hepatocytes may provide valuable additional models with which to study posttranslational mechanisms regulating apo[a] secretion. - Wang, J., J. Boedeker, H. H. Hobbs, and A. L. White. Determinants of human apolipoprotein [a] secretion from mouse hepatocyte cultures. J. Lipid Res. 2001. 42: 60;-69.

Role of calnexin, calreticulin, and endoplasmic reticulum mannosidase I in apolipoprotein(a) intracellular targeting

Apolipoprotein(a) [apo(a)] is a component of atherogenic lipoprotein(a) [Lp(a)]. Differences in the extent of endoplasmic reticulum (ER) associated degradation (ERAD) of apo(a) allelic variants contribute to the >1000-fold variation in plasma Lp(a) levels. Using human apo(a) transgenic mouse hepatocytes, we analyzed the role of the ER chaperones calnexin (CNX) and calreticulin (CRT), and ER mannosidase I in apo(a) intracellular targeting. Co-immunoprecipitation and pulse-chase analyses revealed similar kinetics of apo(a) interaction with CNX and CRT, peaking 15-30 min after apo(a) synthesis. Trapping of apo(a) N-linked glycans in their monoglucosylated form, by posttranslational inhibition of ER glucosidase activity with castanospermine (CST), enhanced apo(a)-CNX/CRT interaction and prevented both apo(a) secretion and ERAD. Delay of CST addition until 20 or 30 min after apo(a) synthesis [when no apo(a) had yet undergone degradation or Golgi-specific carbohydrate modification] allowed a portion of apo(a) to be secreted or degraded. These results are consistent with a transient apo(a)-CNX/CRT association and suggest that events downstream of CNX/CRT interaction determine apo(a) intracellular targeting. Inhibition of ER mannosidase I with deoxymannojirimycin or kifunensine had no effect on apo(a) secretion, but inhibited proteasome-mediated apo(a) ERAD even under conditions where apo(a)-CNX/CRT interaction was prevented. These results suggest a role for an additional, mannose-specific, ER lectin in targeting secretory proteins to the proteasome for destruction.

Acute laryngeal oedema and the yellow nail syndrome

A complication of yellow nail syndrome after pleurodesis is presented. After endotracheal extubation the patient developed delayed acute laryngeal oedema requiring re-intubation. We postulate that the combination of lymphatic defect and airway trauma from the double lumen endotracheal tube were contributory to the oedema. If endotracheal intubation is performed, these patients should be observed for 48 h.

Role of N-linked carbohydrate processing and calnexin in human hepatic lipase secretion

The addition and endoplasmic reticulum (ER) glucosidase processing of N-linked glycans is essential for the secretion of rat hepatic lipase (HL). Human HL is distinct from rat HL by the presence of four as opposed to two N-linked carbohydrate side chains. We examined the role of N-linked glycosylation and calnexin interaction in human HL secretion from Chinese hamster ovary (CHO) cells stably expressing a human HL cDNA. Steady-state and pulse-chase labeling experiments established that human HL was synthesized as an ER-associated precursor containing high mannose N-linked glycans. Secreted HL had a molecular mass of approximately 65 kDa and contained mature N-linked sugars. Inhibition of N-linked glycosylation with tunicamycin (TM) prevented secretion of HL enzyme activity and protein mass. In contrast, incubation of cells with the ER glucosidase inhibitor, castanospermine (CST), decreased human HL protein secretion by 60%, but allowed 40% of fully active HL to be secreted. HL protein mass and enzyme activity were also recovered from the media of a CHO-derivative cell line genetically deficient in ER glucosidase I activity (Lec23) that was transiently transfected with a human HL cDNA. Co-immunoprecipitation experiments demonstrated that newly synthesized human HL bound to the lectin-like ER chaperone, calnexin, and that this interaction was inhibited by TM and CST. These results suggest that under normal conditions calnexin may increase the efficiency of HL export from the ER. Whereas a significant proportion of human HL can attain activity and become secreted in the absence of glucose trimming and calnexin association, these interrelated processes are nevertheless essential for the expression of full HL activity.

Lipoprotein(a): intrigues and insights

Lipoprotein(a) is an atherogenic, cholesterol ester-rich lipoprotein of unknown physiological function. The unusual species distribution of lipoprotein(a) and the extreme polymorphic nature of its distinguishing apolipoprotein component, apolipoprotein(a), have provided unique challenges for the investigation of its biochemistry, genetics, metabolism and atherogenicity. Some fundamental questions regarding this enigmatic lipoprotein have escaped elucidation, as will be highlighted in this review.

6-Aminohexanoic acid as a chemical chaperone for apolipoprotein(a)

Apolipoprotein (a) (apo(a)) is a component of the atherogenic lipoprotein, Lp(a). The efficiency with which apo(a) escapes the endoplasmic reticulum (ER) and is secreted by the liver is a major determinant of plasma Lp(a) levels. Apo(a) contains a series of domains homologous to plasminogen kringle (K) 4, each of which possesses a potential lysine-binding site. By using primary mouse hepatocytes expressing a 17K4 human apo(a) protein, we found that high concentrations (25-200 mM) of the lysine analog, 6-aminohexanoic acid (6AHA), increased apo(a) secretion 8-14-fold. This was accompanied by a decrease in apo(a) presecretory degradation. 6AHA inhibited accumulation of apo(a) in the ER induced by the proteasome inhibitor, lactacystin. Thus, 6AHA appeared to inhibit degradation by increasing apo(a) export from the ER. Significantly, 6AHA overcame the block in apo(a) secretion induced by the ER glucosidase inhibitor, castanospermine. 6AHA may therefore circumvent the requirement for calnexin and calreticulin interaction in apo(a) secretion. Sucrose gradients and a gel-based folding assay were unable to detect any influence of 6AHA on apo(a) folding. However, non-covalent or small, disulfide-dependent changes in apo(a) conformation would not be detected in these assays. Proline also increased the efficiency of apo(a) secretion. We propose that 6AHA and proline can act as chemical chaperones for apo(a).

The epidemiology of women's rugby injuries

OBJECTIVE

The purpose of this study was to identify all injuries to members of an elite women's rugby team and to compare these injuries with published data on injuries in other women's contact and collision sports.

DESIGN

This was a prospective cohort observational study conducted using a monthly log completed by the team's certified athletic therapist to closely monitor attendance at practices and games along with the type and severity of injuries.

SETTING

Rugby games and practices held in Ontario, Quebec, and the Netherlands.

PARTICIPANTS

Forty members of the Ontario Women's Senior Provincial Rugby Team over the 1997 season and the 1998 World Championships.

MAIN OUTCOME MEASURES

An injury was defined as a rugby-related event that kept a player out of practice or competition for >24 hours or required the attention of a physician (e.g., suturing lacerations) and in addition included all dental, eye, and nerve injuries and concussions.

RESULTS

There were a total of 35 injuries in 4,958 player-hours and 2,926 athletic exposures. This resulted in a rugby injury rate of 7.1+/-0.4 per 1,000 player-hours and 12.0+/-2 per 1,000 athletic exposures.

CONCLUSION

The incidence of injuries in women's rugby is comparable with that in other women's contact and collision sports, indicating that the sport may be safer than stated in the literature and media.

Presecretory degradation of apolipoprotein [a] is mediated by the proteasome pathway

Plasma levels of atherogenic lipoprotein [a] (Lp[a]) vary over a 1000-fold range and are largely determined by the gene for its unique glycoprotein, apolipoprotein [a] (apo[a]). The apo[a] locus comprises more than 100 alleles, encoding proteins from <300 to >800 kDa. Using primary baboon hepatocyte cultures, we previously demonstrated that differences in the secretion efficiency of apo[a] allelic variants contribute to the variation in plasma Lp[a] levels. In the current study, we investigated the mechanism of apo[a] presecretory degradation. The proteasome inhibitors, acetyl-leucyl-leucyl-norleucinal and lactacystin, prevented apo[a] degradation and increased apo[a] secretion. Transfection with an HA-tagged ubiquitin construct demonstrated the accumulation of ubiquitinated apo[a] in the presence of lactacystin. These results suggest a role for the cytoplasmic proteasome in apo[a] proteolysis. Apo[a] that accumulated intracellularly in the presence of lactacystin remained sensitive to endo-B-N-glucosaminidase H, and apo[a] degradation was reversibly inhibited by brefeldin A, suggesting that transport to a post-endoplasmic reticulum (ER) pre-medial Golgi compartment is required for apo[a] degradation. Newly synthesized apo[a] bound to the ER chaperone calnexin and conditions that enhanced this interaction prevented apo[a] degradation, suggesting that calnexin can protect apo[a] from proteolysis. These studies provide further support for the role of the proteasome in endoplasmic reticulum quality control, and expand this role to one that influences plasma levels of the atherogenic lipoprotein Lp[a].-White, A. L., B. Guerra, J. Wang, and R. E. Lanford. Presecretory degradation of apolipoprotein[a] is mediated by the proteasome pathway.

Biogenesis of Lp(a) in transgenic mouse hepatocytes

Lipoprotein(a) [Lp(a)] biogenesis was examined in primary cultures of hepatocytes isolated from mice transgenic for both human apolipoprotein(a) [apo(a)] and human apoB. Steady-state and pulse-chase labeling experiments demonstrated that newly synthesized human apo(a) had a prolonged residence time (approximately 60 min) in the endoplasmic reticulum (ER) before maturation and secretion. Apo(a) was inefficiently secreted by the hepatocytes and a large portion of the protein was retained and degraded intracellularly. Apo(a) exhibited a prolonged and complex folding pathway in the ER, which included incorporation of apo(a) into high molecular weight, disulfide-linked aggregates. These folding characteristics could account for long ER residence time and inefficient secretion of apo(a). Mature apo(a) bound via its kringle domains to the hepatocyte cell surface before appearing in the culture medium. Apo(a) could be released from the cell surface by apoB-containing lipoproteins. These studies are consistent with a model in which the efficiency of post-translational processing of apo(a) strongly influences human plasma Lp(a) levels, and suggest that cell surface assembly may be one pathway of human Lp(a) production in vivo. Transgenic mouse hepatocytes thus provide a valuable model system with which to study factors regulating human Lp(a) biogenesis.

The needs of women with substance use problems: an expanded vision for treatment

Although the number of females served in United States treatment programs for substance use has increased over the last decade, women continue to be underrepresented. This suggests that the prevalent treatment models, which tend to be male-oriented, may not provide appropriate strategies to meet women's needs. Substance use problems in women appear to be multideterminded phenomena in which genetics, familial history, psychosocial issues, and other environmental factors play contributing roles. Working from a relational theoretical model of female psychosocial development, a continuum of expanded services addressing the entire context of women's lives is discussed.

Influence of allelic variation on apolipoprotein(a) folding in the endoplasmic reticulum

Plasma levels of lipoprotein(a) (Lp(a)) vary over 1000-fold between individuals and are determined by the gene for its unique apolipoprotein, apo(a), which has greater than 100 alleles. Using primary baboon hepatocyte cultures, we previously demonstrated that differences in the ability of apo(a) allelic variants to escape the endoplasmic reticulum (ER) are a major determinant of Lp(a) production rate. To examine the reason for these differences, the folding of newly synthesized apo(a) was analyzed in pulse-chase experiments. Samples were harvested in the presence of N-ethylmaleimide to preserve disulfide-bonded folding intermediates, and apo(a) was analyzed by immunoprecipitation and SDS-polyacrylamide gel electrophoresis. Apo(a) required a prolonged period (30-60 min) to reach its fully oxidized form. Multiple folding intermediates were resolved, including a disulfide-linked, apo(a)-containing complex. Unexpectedly, all allelic variants examined showed similar patterns and kinetics of folding. Even "null" apo(a) proteins, which are unable to exit the ER, appeared to fold normally. The ER glucosidase inhibitor, castanospermine, prevented apo(a) secretion, but did not inhibit folding. This suggests that an event which is dependent on trimming of N-linked glucoses, and which occurs after the folding events detectable in our assay, is required for apo(a) secretion. Differences in the ability to undergo this event may explain the variable efficiency with which apo(a) allelic variants exit the ER.

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.

Kringle-containing fragments of apolipoprotein(a) circulate in human plasma and are excreted into the urine

Apolipoprotein(a) [apo(a)] contains multiple kringle 4 repeats and circulates as part of lipoprotein(a) [Lp(a)]. Apo(a) is synthesized by the liver but its clearance mechanism is unknown. Previously, we showed that kringle 4-containing fragments of apo(a) are present in human urine. To probe their origin, human plasma was examined and a series of apo(a) immunoreactive peptides larger in size than urinary fragments was identified. The concentration of apo(a) fragments in plasma was directly related to the plasma level of Lp(a) and the 24-h urinary excretion of apo(a). Individuals with low (< 2 mg/dl) plasma levels of Lp(a) had proportionally more apo(a) circulating as fragments in their plasma. Similar apo(a) fragments were identified in baboon plasma but not in conditioned media from primary cultures of baboon hepatocytes, suggesting that the apo(a) fragments are generated from circulating apo(a) or Lp(a). When apo(a) fragments purified from human plasma were injected intravenously into mice, a species that does not produce apo(a), apo(a) fragments similar to those found in human urine were readily detected in mouse urine. Thus, we propose that apo(a) fragments in human plasma are derived from circulating apo(a)/Lp(a) and are the source of urinary apo(a).

Neomycin inhibits secretion of apolipoprotein[a] by increasing retention on the hepatocyte cell surface

Neomycin therapy reduces plasma levels of low density lipoprotein and lipoprotein[a] (Lp[a]). To determine whether neomycin directly alters the biogenesis of Lp[a], we have examined the effect of neomycin on apolipoprotein[a] (apo[a]) synthesis and secretion in primary cultures of baboon hepatocytes. Using this system, we have previously shown that apo[a] is synthesized as a lower molecular weight precursor that upon maturation becomes associated with the cell surface before release into the culture medium. Treatment of hepatocytes with 10 mM neomycin reduced levels of apo[a] in the culture medium by as much as 12-fold. Although a portion of the reduced secretion could be accounted for by a reduction in total protein synthesis, the greatest effect of neomycin on apo[a] secretion was to decrease the release of mature apo[a] from the hepatocyte cell surface into the culture medium. Treatment of hepatocyte cultures with trypsin confirmed that mature apo[a] in neomycin-treated cells was still transported to the cell surface. Examination of related antibiotics demonstrated that inhibition of apo[a] secretion is a general property shared by the deoxystreptamine antibiotics. The mechanism by which neomycin affects the apo[a]-cell surface interaction is not known, but neomycin is known to perturb cell surface membranes, inhibit the interaction of some ligands with their cell surface receptors, and inhibit the metabolism of phosphatidylinositol 4,5 biphosphate. These studies suggest that cell surface association of apo[a] may play a role in Lp[a] biogenesis in vivo.

High prevalence of colorectal cancer in HLA-B27 transgenic F344 rats with chronic inflammatory bowel disease

BACKGROUND/AIMS

Transgenic rats expressing the human major histocompatibility class I molecule HLA-B27 develop a spontaneous multisystem disease that includes a chronic colitis resembling ulcerative colitis. The availability of this phenotype in B27 transgenic rats of 2 different inbred strains provided the opportunity to inquire whether colorectal neoplasia, which occurs with increased frequency in humans with inflammatory bowel disease (IBD), would develop in either or both rat genetic backgrounds.

METHODS

Clinical and histologic evaluation of B27 transgenic rats with chronic inflammatory bowel disease (IBD) on the F344 and LEW inbred backgrounds.

RESULTS

In B27 transgenic rats on an inbred F344 background, hyperplastic lesions evolved in the setting of chronic colitis, with a high frequency of colorectal polyp formation and frequent histologic progression from adenoma to adenocarcinoma. In contrast, no neoplasia occurred in B27 transgenic rats on an inbred LEW background, despite similar colitis.

CONCLUSION

A high incidence of spontaneous colorectal neoplasia occurs in a line of B27 F344 rats that shares some features of both sporadic and inflammatory bowel disease-associated human colorectal cancer. This represents a novel example of spontaneous colorectal neoplasia in rodents that is not based on germline modification of one or more already-identified cancer-related genes.

Biosynthesis and metabolism of lipoprotein (a)

Significant advances have been made over the past year toward understanding the pathways of lipoprotein (a) biosynthesis and metabolism. Transcriptional and post-translational mechanisms have been identified as important determinants of plasma lipoprotein (a) levels. Assembly of lipoprotein (a) has been shown to be an extracellular event that occurs on the hepatocyte cell surface. The development of lipoprotein (a) transgenic mice has provided a valuable model to study the metabolism of lipoprotein (a).

Current status of coronary artery bypass grafting in patients 70 years of age and older

One hundred and seventy patients 70 years of age and older underwent isolated coronary artery bypass grafting (CABG) from January 1990 to December 1991 at St. Vincent's Hospital, Melbourne, Australia. The clinical records of these patients were analysed to investigate whether elderly patients could undergo safe coronary artery surgery and to determine the factors affecting the outcome. The 30 day or in-hospital mortality was 2.9% (5/170), with 80% (4/5) of the deaths due to cardiac causes. Major postoperative complications occurred in 22.3% (38/170) patients. The median postoperative hospital stay for the patients was 8 days (range 3-103 days). Univariate analysis identified hypertension and female gender as pre-operative risk factors and intraaortic balloon pump, prolonged ventilation, infarct, tamponade, need for inotropes, renal failure and a high APACHE II scores in the intensive care unit as postoperative significant risk factors for operative mortality. There was a trend towards increased mortality with emergency operations; the operative mortality was 2.1% (2/97) for elective operations, 3.1% (2/64) in urgent cases and 11.1% (1/9) for emergencies. Multivariate logistic regression analysis identified prolonged mechanical ventilation, perioperative infarct and APACHE II score as significant independent predictors of mortality. The low operative mortality indicates that elderly patients can undergo safe revascularization. A high incidence of complications necessitates careful monitoring but age per se should not be considered a contraindication to isolated CABG.

Cell surface assembly of lipoprotein(a) in primary cultures of baboon hepatocytes

Lipoprotein(a) (Lp(a)) consists of a low density lipoprotein particle in which apolipoprotein(a) (apo(a)), is disulfide linked to apoB. Lp(a) is produced by the liver, and high plasma levels represent an independent risk factor for cardiovascular diseases. However, pathways of production and metabolism of Lp(a) are poorly understood. We used primary cultures of baboon hepatocytes to analyze the steps involved in Lp(a) biogenesis. The results demonstrated that Lp(a) assembly was extracellular, since it was inhibited when anti-apo(a) antiserum was present in the culture medium. In addition, free apo(a) produced by hepatocytes could associate extracellularly with apoB in either very low density or low density lipoproteins. Lp(a) assembly required lysine-binding pockets in apo(a) kringles, as it was inhibited by the lysine analog, 6-amino hexanoic acid. A portion of apo(a) was also bound to the cell surface via its kringle domains and could be released into the medium by 6-amino hexanoic acid or proline. In add-back experiments, apo(a), but not Lp(a), bound to the cell surface. Addition of low density lipoprotein or very low density lipoprotein to hepatocyte cultures released apo(a) from the cell surface into the lipoprotein fraction of culture medium. We conclude that assembly of Lp(a) can occur at the cell surface. This represents one potential mechanism of Lp(a) production in vivo.

Molecular basis for "null" lipoprotein(a) phenotypes and the influence of apolipoprotein(a) size on plasma lipoprotein(a) level in the baboon

High plasma levels of lipoprotein(a) (Lp(a)) and its unique apolipoprotein, apo(a), are an independent risk factor for cardiovascular disease. Plasma Lp(a) levels vary over a 1000-fold range and are determined by the apo(a) locus, which has at least 34 alleles expressing apo(a) isoforms with molecular weights from < 300,000 to > 800,000. In addition, "null" apo(a) alleles produce no detectable plasma apo(a). We used primary cultures of baboon hepatocytes to investigate the molecular basis for null apo(a) phenotypes. Immunoprecipitation of apo(a) after radiolabeling of hepatocytes revealed that some null alleles gave rise to intracellular protein products that were not secreted. Pulse-chase analysis and endoglycosidase digests demonstrated that these proteins were retained in the endoplasmic reticulum. We also examined the molecular basis for the documented inverse correlation between apo(a) size and plasma Lp(a) concentration. Steady-state labeling and pulse-chase analysis of hepatocytes from animals expressing two isoforms of apo(a) revealed that the endoplasmic reticulum residence time of secreted apo(a) isoforms was determined by their size. This accounted for the inverse relationship between isoform size and level of secretion. We conclude that the efficiency of post-translational processing of apo(a) is a major determinant of plasma Lp(a) concentration.

Intracellular processing of apo(a) in primary baboon hepatocytes

We have developed a serum-free medium for the long-term culture of highly differentiated primary baboon hepatocytes. Hepatocytes isolated from animals with defined plasma Lp(a) levels and apo(a) glycoprotein phenotypes were used to study the assembly of Lp(a). A combination of steady-state and pulse-chase labeling studies and endoglycosidase digests demonstrated that apo(a) was synthesized as a lower molecular weight precursor. After a prolonged period of time in the endoplasmic reticulum, apo(a) was converted to a mature form and secreted. A proportion of mature apo(a) also had a prolonged residence time in the trans Golgi apparatus. In all experiments, apoB co-immunoprecipitated with apo(a) from the culture medium but not from the cell lysates, supporting an extracellular association of the proteins for the formation of Lp(a). Analysis of hepatic RNA from 29 'null' Lp(a) phenotype baboons revealed that one-third of the animals had detectable apo(a) transcripts, whereas the remainder had no detectable apo(a) mRNA. The baboon hepatocyte system therefore represents a valuable model to examine the effect of allelic variation at the apo(a) locus on Lp(a) assembly.

Intracellular maturation of apolipoprotein[a] and assembly of lipoprotein[a] in primary baboon hepatocytes

The glycoprotein apolipoprotein[a] (apo[a]) is present in plasma at highly variable concentrations and appears as a number of genetically determined size isoforms (400-800 kDa), disulfide linked to apoB-100 in low density lipoprotein to produce lipoprotein [a](Lp[a]). Apo[a] is synthesized by the liver, but the site of association of apo[a] and apoB and factors that regulate its production are unknown. To examine the morphogenesis of the Lp[a] particle, baboon hepatocytes expressing a single, low molecular weight isoform of apo[a] were labeled with [35S]cysteine and methionine, and apo[a] was analyzed by immunoprecipitation and SDS-PAGE. Steady-state labeling revealed two molecular weight forms of apo[a] inside the cell. Only the large form was recovered from the culture medium. Pulse-chase studies and endoglycosidase treatment revealed that the lower molecular weight form of apo[a] represented a precursor with a prolonged residence time in the endoplasmic reticulum or an early Golgi compartment, after which it was processed to the mature form. A proportion of the mature form of apo[a] was rapidly secreted after synthesis, whereas the remainder had a prolonged residence time in a late Golgi compartment. In all experiments, apoB co-precipitated with apo[a] from the culture medium, but not from cell lysates. Density gradient ultracentrifugation and immunoblot analysis revealed that the majority of apo[a] was secreted into the medium in a free form, suggesting that the association between apo[a] and apoB occurred after secretion. Regulation of the movement of apo[a] between intracellular compartments may be one mechanism by which the plasma levels of Lp[a] are influenced.

Pathological lesions associated with Anoplocephala perfoliata at the ileo-caecal junction of horses

The intestinal tracts of 20 horses, killed at a local abattoir and of unknown age, sex and previous clinical history were examined for the presence of Anoplocephala perfoliata attached to the ileo-caecal junction. Four horses had no tape-worms, nine had one to 20 tapeworms attached to the mucosa and seven had more than 100 attached to the mucosa. The histological changes of thickening, ulceration and eosinophil infiltration of the mucosa at the ileo-caecal junction were more severe when more than 100 parasites were present.

Oleate-mediated stimulation of apolipoprotein B secretion from rat hepatoma cells. A function of the ability of apolipoprotein B to direct lipoprotein assembly and escape presecretory degradation

Physiological concentrations of oleate stimulate apolipoprotein (apo) B-containing lipoprotein secretion from HepG2 cells without increasing apoB mRNA levels. The purpose of this study was to determine whether oleate acts by increasing translation of apoB mRNA or through posttranslational effects on the apoB protein. To address the mechanism of oleate-stimulated secretion of apoB, a series of carboxyl terminally truncated apoB constructs was made. Each contained the SV40 early promoter, the apoB 5'-untranslated region, and SV40 polyadenylation signals. Any difference in the response to oleate between endogenous apoB and the proteins encoded by the constructs or between the constructs themselves should thus depend on the protein sequence. Stable transformants were established for each of the constructs in the rat hepatoma cell line McArdle-RH7777. The effect of oleate on secretion of the apoB protein products was determined by labeling with [35S]methionine, immunoprecipitation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Carboxyl-terminal truncation of apoB41 resulted in a loss of the ability of apoB secretion to respond to oleate. Ultracentrifugation of secreted proteins on continuous CsCl gradients from 1.0-1.4 g/ml revealed that this correlated with a decrease in the ability of apoB to be recovered as a buoyant lipoprotein particle. Addition of oleate decreased the densities at which the short forms of apoB secreted as lipoproteins were recovered. Pulse-chase analysis of the secretion of apoB100 and of the truncated proteins revealed that they all underwent rapid posttranslational intracellular degradation. We conclude that oleate has no effect on the translation of apoB mRNA but promotes the secretion of apoB-containing lipoproteins by reducing presecretory degradation of those forms of apoB that can produce buoyant lipoproteins.

Validation of an instrument to measure understanding of pattern by elementary school children

The analysis and validation of an instrument to measure the ability of elementary school children to recognize and extend patterns in different representational forms is presented.

The relationship of rat brain weight and pituitary weight to postnatal growth after prenatal exposure to methylazoxymethanol

Teratogens can affect body weight in various ways, but the association of brain damage with postnatal growth abnormalities suggests a role for neuroendocrine growth-controlling systems. Growth deficiencies follow methylazoxymethanol (MAM) exposure during the period when the growth hormone releasing factor (GRF) cells of the hypothalamus form, and the pattern of growth of the animals is like that of animals deficient in growth hormone. The present studies were designed to examine the growth, body proportions, brain weight, and pituitary weight of animals treated with 20 mg/kg MAM on the 13th day of gestation, a peak period for production of GRF neurons. Among the offspring, this treatment produced about 25% dwarfs (animals smaller than the smallest control of the same sex). Significantly more females than males were categorized as dwarfs. The weight effect occurred long after birth, as is characteristic of animals and humans with growth hormone deficiency. Analyses of weights over the course of development indicated that prenatal factors, rather than factors operating between birth and weaning, predicted the adult body weight of dwarfs, while both sets of factors were significant in other animals. The growth reduction was symmetrical, as would be expected if the animals were growth hormone deficient, with an 18% reduction in weight reflecting a 6% reduction in bone length. The remaining treated animals were similar to controls in absolute weight, body proportions, and rate of growth. Neither pituitary weight nor brain weight appears to play the key role in determining which animals will exhibit growth deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of hypothalamic cell numbers in dwarf and normal weight rats exposed prenatally to methylazoxymethanol (MAM)

Growth deficiencies follow MAM exposure during the period when the growth hormone releasing factor (GRF) cells of the hypothalamus form, while animals exposed slightly later in gestation when the inhibitors of growth hormone release are forming, exhibit giantism. Counts of sample regions of the hypothalamus have shown that rats treated in utero on the 14th day of gestation have reductions in the number of GRF cells, increases in the number of SRIF (somatotropin release inhibiting factor) cells, and alterations of pituitary structure. These effects occurred in all treated subjects, even though obvious effects on body size were present in a small fraction of the treated animals. The present study was designed to examine the effect of 20 mg/kg MAM on the 13th day of gestation (a peak period for production of GRF cells) on GRF and SRIF cell numbers, in a large sample of dwarf-treated rats, normal weight-treated rats, and controls. The results of total counts of hypothalamic cells identified by immunocytochemistry demonstrated significant reductions in GRF cells in both dwarf and normal weight rats exposed to MAM, compared to controls, with no difference between the two treated groups. Like pituitary weights, the neuron counts were significantly correlated with body weight only in dwarf animals. SRIF cell numbers were equivalent to those in controls, suggesting that the increase reported earlier may have been due to a rebound effect in proliferation rather than some response of SRIF cells to GRF cell reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Early and late survival after coronary-artery surgery

Between 1970 and 1985, 1801 patients underwent coronary-artery surgery without associated valvular surgery. Eighty-four per cent of patients were male and the mean (+/- SD) age was 55.7 +/- 8.3 years. Of the patients, 18.7% were from the Coronary Care Unit and 6.5% had diabetes. The hospital mortality rate for the whole group was 3.5%. Patients from the Coronary Care Unit had the highest (8.9%) hospital mortality rate compared with those patients who were not from the Coronary Care Unit (2.1%; P less than 0.001). Other factors which increased the hospital mortality rate significantly were the number of diseased vessels (P less than 0.01), the degree of left main coronary-artery stenosis (P less than 0.001), an earlier year of surgery (P less than 0.01) and female sex (P less than 0.01). After these were taken into account, no other factors (for example, age, preoperative infarction, presence of left-ventricular aneurysm, left-ventricular end-diastolic pressure, diabetes, use of mammary-arterial grafts or the need for endarterectomy) affected the mortality rate. Patients were followed-up for a mean (+/- SD) of 4.4 +/- 2.8 years. The five-year survival rate for all patients was 88% and the 10-year survival rate was 65%. Cox regression analysis showed that the significant indicators of decreased long-term survival were undergoing operation directly from the Coronary Care Unit (P less than 0.001), left main coronary-artery stenosis (P less than 0.01), the number of grafted vessels (P less than 0.01), concomitant surgery for aneurysm (P less than 0.001), year of surgery (P less than 0.01). Seventy-nine per cent of patients were free of angina pectoris at five years after operation. The year of surgery (P less than 0.001) and preoperative myocardial infarction (P less than 0.05) were the best predictors of recurrent angina. In the long term, recurrent angina remains a problem, although this may change with the increased use of mammary-arterial grafts.

Open heart surgery in the elderly

Of 3254 open heart surgical cases performed since 1972, 126 patients (3.9%) were 70 years of age or older. The mean age was 72 years, the oldest being 82. Sixty-seven per cent were male. The following procedures were performed: coronary artery bypass grafting (CABG) 51, aortic valve replacement (AVR) 44, AVR + CABG 16, mitral valve replacement (MVR) 3, MVR + CABG 6, MVR + AVR 4, and other, 2. Of those undergoing CABG, 33% came from the Coronary Care Unit and 24% had left main coronary artery stenosis. There was one peri-operative death (2.0%). Of those undergoing AVR, 43% had coronary artery disease and 13% triple vessel disease. Operative mortality for AVR, and AVR + CABG was 11.4% (5/44) and 18.8% (3/16), respectively. Twenty-six per cent of operative survivors had significant postoperative complications (excluding atrial arrhythmias). The postoperative hospital stay for CABG, AVR and other cases was 11, 13 and 16 days, respectively. Seven year survival of all patients was 61.2 +/- 6.5% (+/- 1 SE) and for AVR +/- CABG was 51.5 +/- 8.6%. Five year survival for CABG was 83.9 +/- 6.3%. We conclude that, in selected cases, CABG can be performed safely in the elderly. Although valvular and combined surgery may result in significant morbidity and mortality, the satisfactory long term results in survivors justifies surgery in this group of patients.