Red Blood Cell Metabolism in Pyruvate Kinase Deficient Patients

Background: Pyruvate kinase deficiency (PKD) is the most frequent congenital enzymatic defect of glycolysis, and one of the most common causes of hereditary non spherocytic hemolytic anemia. Therapeutic interventions are limited, in part because of the incomplete understanding of the molecular mechanisms that compensate for the metabolic defect.

Methods: Mass spectrometry-based metabolomics analyses were performed on red blood cells (RBCs) from healthy controls (n=10) and PKD patients (n=5).

Results: In PKD patients, decreases in late glycolysis were accompanied by accumulation of pentose phosphate pathway (PPP) metabolites, as a function of oxidant stress to purines (increased breakdown and deamination). Markers of oxidant stress included increased levels of sulfur-containing compounds (methionine and taurine), polyamines (spermidine and spermine). Markers of hypoxia such as succinate, sphingosine 1-phosphate (S1P), and hypoxanthine were all elevated in PKD subjects. Membrane lipid oxidation and remodeling was observed in RBCs from PKD patients, as determined by increases in the levels of free (poly-/highly-unsaturated) fatty acids and acyl-carnitines.

Conclusion: In conclusion, in the present study, we provide the first overview of RBC metabolism in patients with PKD. Though limited in scope, the study addresses the need for basic science to investigate pathologies targeting underrepresented minorities (Amish population in this study), with the ultimate goal to target treatments to health disparities.

Casualties of war: the infection control assessment of civilians transferred from conflict zones to specialist units overseas for treatment

The casualties of global conflict attract media attention and sympathy in public, governmental, and non-governmental circles. Hospitals in developed countries offering specialist reconstructive or tertiary services are not infrequently asked to accept civilian patients from overseas conflict for complex surgical procedures or rehabilitation. Concern about the infection prevention and control risks posed by these patients, and the lack of a good evidence base on which to base measured precautions, means that the precautionary principle of accepting zero risk is usually followed. The aim of this article is to highlight infection control considerations that may be required when treating casualties from overseas conflict, based partly on our own experience. Currently there is a lack of published evidence and national consensus on how to manage these patients. The precautionary principle requires that there is an ongoing search for evidence and knowledge that can be used to move towards more traditional risk management. We propose that only by gathering the experiences of the many individual hospitals that have each cared for small numbers of such patients can such evidence and knowledge be assimilated.

Development of DNA confirmatory and high-risk diagnostic testing for newborns using targeted next-generation DNA sequencing

PURPOSE

Genetic testing is routinely used for second-tier confirmation of newborn sequencing results to rule out false positives and to confirm diagnoses in newborns undergoing inpatient and outpatient care. We developed a targeted next-generation sequencing panel coupled with a variant processing pipeline and demonstrated utility and performance benchmarks across multiple newborn disease presentations in a retrospective clinical study.

METHODS

The test utilizes an in silico gene filter that focuses directly on 126 genes related to newborn screening diseases and is applied to the exome or a next-generation sequencing panel called NBDx. NBDx targets the 126 genes and additional newborn-specific disorders. It integrates DNA isolation from minimally invasive biological specimens, targeted next-generation screening, and rapid characterization of genetic variation.

RESULTS

We report a rapid parallel processing of 8 to 20 cases within 105 hours with high coverage on our NBDx panel. Analytical sensitivity of 99.8% was observed across known mutation hotspots. Concordance calls with or without clinical summaries were 94% and 75%, respectively.

CONCLUSION

Rapid, automated targeted next-generation sequencing and analysis are practical in newborns for second-tier confirmation and neonatal intensive care unit diagnoses, laying a foundation for future primary DNA-based molecular screening of additional disorders and improving existing molecular testing options for newborns.

A homozygous SLITRK6 nonsense mutation is associated with progressive auditory neuropathy in humans

OBJECTIVES/HYPOTHESIS

SLITRK family proteins control neurite outgrowth and regulate synaptic development. In mice, Slitrk6 plays a role in the survival and innervation of sensory neurons in the inner ear, vestibular apparatus, and retina, and also influences axial eye length. We provide the first detailed description of the auditory phenotype in humans with recessive SLITRK6 deficiency.

STUDY DESIGN

Prospective observational case study.

METHODS

Nine closely related Amish subjects from an endogamous Amish community of Pennsylvania underwent audiologic and vestibular testing. Single nucleotide polymorphism microarrays were used to map the chromosome locus, and Sanger sequencing or high-resolution melt analysis were used to confirm the allelic variant.

RESULTS

All nine subjects were homozygous for a novel nonsense variant of SLITRK6 (c.1240C>T, p.Gln414Ter). Adult patients had high myopia. The 4 oldest SLITRK6 c.1240C>T homozygotes had absent ipsilateral middle ear muscle reflexes (MEMRs). Distortion product otoacoustic emissions (DPOAEs) were absent in all ears tested and the cochlear microphonic (CM) was increased in amplitude and duration in young patients and absent in the two oldest subjects. Auditory brainstem responses (ABRs) were dys-synchronised bilaterally with no reproducible waves I, III, or V at high intensities. Hearing loss and speech reception thresholds deteriorated symmetrically with age, which resulted in severe-to-profound hearing impairment by early adulthood. Vestibular evoked myogenic potentials were normal in three ears and absent in one.

CONCLUSION

Homozygous SLITRK6 c.1240C>T (p.Gln414Ter) nonsense mutations are associated with high myopia, cochlear dysfunction attributed to outer hair cell disease, and progressive auditory neuropathy.

Identification of a sporozoite-specific antigen from Toxoplasma gondii

Reduction of risk for human and food animal infection with Toxoplasma gondii is hampered by the lack of epidemiological data documenting the predominant routes of infection (oocyst vs. tissue cyst consumption) in horizontally transmitted toxoplasmosis. Existing serological assays can determine previous exposure to the parasite, but not the route of infection. We have used difference gel electrophoresis, in combination with tandem mass spectroscopy and Western blot, to identify a sporozoite-specific protein (T. gondii embryogenesis-related protein [TgERP]), which elicited antibody and differentiated oocyst- versus tissue cyst-induced infection in pigs and mice. The recombinant protein was selected from a cDNA library constructed from T. gondii sporozoites; this protein was used in Western blots and probed with sera from T. gondii -infected humans. Serum antibody to TgERP was detected in humans within 6-8 mo of initial oocyst-acquired infection. Of 163 individuals in the acute stage of infection (anti- T. gondii IgM detected in sera, or < 30 in the IgG avidity test), 103 (63.2%) had detectable antibodies that reacted with TgERP. Of 176 individuals with unknown infection route and in the chronic stage of infection (no anti- T. gondii IgM detected in sera, or > 30 in the IgG avidity test), antibody to TgERP was detected in 31 (17.6%). None of the 132 uninfected individuals tested had detectable antibody to TgERP. These data suggest that TgERP may be useful in detecting exposure to sporozoites in early T. gondii infection and implicates oocysts as the agent of infection.

Osteoporosis-pseudoglioma syndrome: description of 9 new cases and beneficial response to bisphosphonates

Osteoporosis-pseudoglioma syndrome (OPPG) is a rare autosomal recessive disorder of severe juvenile osteoporosis and congenital blindness, due to mutations in the low-density lipoprotein receptor-related protein 5 (LRP5) gene. Approximately fifty cases of OPPG have been reported. We report 9 new cases of OPPG, in three related nuclear families of Conservative Mennonites in Pennsylvania. All 9 children with OPPG were blind and had osteoporosis. Four of six parents had low bone mineral density (BMD) or osteoporosis; 2 were normal. Sequence analysis from genomic DNA revealed homozygosity for a nonsense mutation of exon 6 of LRP5 (W425X) in four OPPG cases tested in families A and C. In family B, OPPG cases were compound heterozygotes for the exon 6 W425X LRP5 mutation and a second exon 6 mutation (T409A); bone phenotype was milder than in family A. Neither of these mutations was present in an unrelated normal. The four treated OPPG patients all responded to bisphosphonates (duration 1.5-6.5 years) with improvement in Z-scores. One patient had a negligible response to teriparatide. In summary, we report 9 new cases of OPPG due to two novel LRP5 mutations, note a milder bone phenotype but similar ocular phenotype in LRP5 W425X/T409A compound heterozygotes than in W425X homozygotes and describe positive response to bisphosphonate treatment in four cases.

Early pregnancy factor in marsupials

Maternal recognition of pregnancy in marsupials occurs in more subtle ways than it does in eutherians. For instance, unlike in eutherians, the plasma progesterone profiles of pregnant and non-pregnant animals are similar during the luteal phase. It is typically during the brief luteal phase that both gestation and parturition occur in marsupials. Yet histological and physiological changes have been documented between gravid and non-gravid uteri in certain monovular marsupials and between pregnant and non-pregnant animals in polyovular marsupials. Early pregnancy factor (EPF), a 10.8-kDa serum protein known to be homologous to chaperonin 10, is associated with maternal immunosuppression, embryonic development and pregnancy in eutherian mammals. It has been reported in two Australian marsupials: the dasyurid Sminthopsis macroura and the phalangerid Trichosurus vulpecula. This paper documents its occurrence in the New World didelphid Monodelphis domestica. EPF is detectable by rosette inhibition assay in the peripheral circulation of pregnant but not of non-pregnant or pseudopregnant animals. Our work focuses on the embryo–maternal signalling role of EPF during pregnancy. Because progesterone-driven changes are similar in pregnant and non-pregnant marsupials, these animals are an excellent laboratory model in which to investigate the role of EPF in orchestrating the physiological changes necessary to sustain pregnancy.

Use of iodoacetylene as a dipolarphile in the synthesis of 5-iodoisoxazole derivatives

Iodoacetylene 1 was prepared in situ from the reactions of ethynylmagnesium bromide or tributyl(ethynyl)tin with iodine. It was used as a dipolarphile in the [2 + 3] cyclization reaction with 1,3-dipolar nitrile oxide derivatives to produce 2-(5-iodoisoxazol-3-yl)pyridine 2 and 3-(4-fluorophenyl)-5-iodoisoxazole 8 in good yield (70-90%). Subsequently, several 5-substituted isoxazole derivatives 3 were obtained by Pd-catalyzed reactions. [reaction: see text]

Significance of serum early pregnancy factor concentrations during pregnancy and embryonic development in Sminthopsis macroura (Spencer) (Marsupialia: Dasyuridae)

Marsupial pregnancy differs from that in eutherians in duration, placentation and hormonal profile so much so that maternal recognition of pregnancy may not occur in polyovular marsupials. However, a comparison of gravid and non-gravid uteri reveals differences indicative of histological and physiological adaptations to pregnancy. In the present study, the hypothesis that embryo-maternal signalling occurs in polyovular marsupials was tested by examining serum from non-pregnant and pregnant Sminthopsis macroura for the presence of early pregnancy factor (EPF), a serum protein secreted by the ovary in response to the presence of a newly fertilized egg in the oviduct. EPF is detectable in the serum of pregnant, but not in non-pregnant, females in all eutherians studied to date. In the present study, EPF was detected in S. macroura serum by the rosette inhibition test during the first 9 days of the 10.7 day gestation period in this marsupial. However, EPF was not detected on day 10, just before parturition, or in non-pregnant or preovulatory animals. Immunohistochemical analysis of ovaries from gravid and non-gravid animals demonstrates that EPF is found in the capillaries, interstitial spaces and secretory cells of the corpus luteum. It is concluded that the spatiotemporal pattern of EPF activity described strongly indicates that maternal recognition of pregnancy in marsupials is mediated, at least in part, by EPF. Because the endocrinological milieu is the same in pregnant and non-pregnant marsupials, the possibility of using marsupials as an experimental system for studying EPF function unconfounded by hormonal effects is presented.

M cell pockets of human Peyer's patches are specialized extensions of germinal centers

M cells in follicle-associated epithelium of Peyer's patches (PP) mediate antigen entrance into the underlying lymphoid tissue. To investigate the functional potential of B cells in this unique microcompartment, the expression of co-stimulatory molecules necessary for B-T cell interaction was examined in histologically normal human PP by three-color immunohistochemistry. In the M cell areas, CD80 / CD86 expression was much more frequent on memory (sIgD(-)CD20(+)) B cells than on naive (sIgD(+)CD20(+)) B cells. M cell areas identified by such co-expression of CD20 and CD80 / CD86 were always spatially related to germinal centers (GC). Contrary to the GC B cell phenotype (sIgD(-)CD20(+)CD80 / 86(hi)CD10(+)Bcl-2(-)), however, M cell-associated B cells with a high level of CD80 / CD86 were CD20(lo)CD10(-)Bcl-2(+), and adjacent memory T cells (CD3(+)CD45R0(+)) often expressed CD40L (CD154). Autologous peripheral blood B-T cell cocultures with purified protein derivative as antigen showed that the sIgD(-)CD80 / CD86(hi)CD20(lo) phenotype could indeed be generated during cognate B-T interactions, concurrent with CD40L up-regulation on memory T cells. Thus, this M cell-associated phenotype might result from B-T cell interactions in the course of antigen presentation by memory B cells, with subsequent CD40 engagement by CD40L-expressing cognate memory T cells. We propose that this M cell-associated event contributes to memory B cell survival and diversification of intestinal immunity, representing a specialized limb of GC function.

Early pregnancy factor suppresses experimental autoimmune encephalomyelitis induced in Lewis rats with myelin basic protein and in SJL/J mice with myelin proteolipid protein peptide 139-151

Early pregnancy factor (EPF) is a secreted protein with immunosuppressive and growth factor properties. During pregnancy, it appears in maternal serum within 6-24 h of fertilization, is present for at least the first two-thirds of pregnancy in all species studied and is essential for embryonic survival. It is a homologue of chaperonin 10, a heat shock protein, but, unlike other members of this family, EPF has an extracellular role. As it has the ability to modulate CD4+ T cell-dependent immune responses, its role in treatment of experimental autoimmune encephalomyelitis (EAE) was investigated. EAE is a CD4+ T cell-mediated disease, the best available animal model of multiple sclerosis (MS). Two models of EAE were investigated, acute EAE induced in Lewis rats by inoculation with myelin basic protein (MBP-EAE) and chronic relapsing EAE induced in SJL/J mice by inoculation with myelin proteolipid protein peptide (residues 139-151) (PLP-EAE). EPF, delivered intraperitoneally or orally to rats or intraperitoneally to mice, suppressed clinical signs of disease. Mice with PLP-EAE were also treated with interferon-beta, with and without EPF. Both EPF and IFN-beta suppressed clinical signs of EAE and, when administered together, gave greater suppression than when given separately. These findings suggest that EPF may be a potential candidate for use in treatment of MS and may be of use in combined therapy with IFN-beta.

Production of a recombinant form of early pregnancy factor that can prolong allogeneic skin graft survival time in rats

Early pregnancy factor (EPF), an extracellular chaperonin 10 homologue, has immunosuppressive and growth factor properties. In order to carry out more extensive studies on the in vivo characteristics of EPF, a recombinant form of the molecule has been prepared. Recombinant human EPF (rEPF) was expressed in Escherichia coli using the plasmid pGEX-2T expression system. Potency of rEPF in vitro in the rosette inhibition test, the bioassay for EPF, was equivalent to that of native EPF (nEPF), purified from human platelets, and synthetic EPF (sEPF). However, the half-life of activity (50% decrease in the log value) in serum, following i.p. injection, was significantly decreased (3.2 h, compared with nEPF 6.2 days, sEPF 5.8 days). This was thought to be due to modification of the N-terminus of the recombinant molecule inhibiting binding to serum carrier proteins. Because EPF can modify Th1 responses, the ability of the recombinant molecule to suppress allogeneic graft rejection was investigated. Following skin grafts from Lewis rats to DA rats and vice versa, rEPF was delivered locally at the graft site and the effect on survival time of the allografts noted. Results demonstrated that rEPF treatment significantly prolonged skin graft survival time by as much as 55% in stringent models of transplantation across major histocompatibility barriers.

Isolation of antibodies which neutralise the activity of early pregnancy factor

Early pregnancy factor (EPF) is a secreted protein with growth regulatory and immunomodulatory properties. It functions as an autocrine growth factor for tumour cells and as an autocrine or paracrine growth factor for regenerating normal cells. Anti-EPF antibodies have demonstrable anti-tumour activity and, as a result, hybridomas which produce such antibodies are unstable. In this study, the phage display antibody techniques have been investigated as a means of producing recombinant anti-EPF antibodies. Mice were immunised with synthetic peptides which correspond to the N or C terminal regions of EPF, and their splenic tissue was used to make combinatorial antibody libraries. The Fab repertoire was displayed on the surface of phage and panned over recombinant EPF. Reactive Fabs were identified by ELISA and their binding was characterised by BIAcore analysis and functional studies. Three libraries with a size of greater than 5x10(7)cfu were constructed and a total of 26 unique Fabs with specific reactivity against EPF were identified. Three Fabs were purified and of these one demonstrated strong EPF neutralising activity, one had intermediate activity and the other was not neutralising. Phage display has provided the means of circumventing the problems of anti-EPF hybridoma development and has resulted in the production of antibodies with potential applications in the diagnosis of pregnancy and the diagnosis and therapy of cancer.

Early pregnancy factor is required at two important stages of embryonic development in the mouse

PROBLEM

The importance of early pregnancy factor (EPF) at the pre-implantation stage of development (days 1-3 post-coitum [p.c.]) has been previously established in this laboratory. However, the role of EPF at the implantation stage (days 4.5-5 p.c.) has not been determined. This present study therefore investigates the role of EPF at this important developmental stage, both in vivo and in vitro.

METHOD OF STUDY

Mated mice were passively immunized with anti-EPF antibodies at the peri-implantation stage (days 3.5-4 p.c.) and embryo implantation recorded. Parallel studies were conducted in vitro, where the effect of anti-EPF antibodies on trophoblast outgrowth of blastocysts was determined.

RESULTS

Administration of anti-EPF antibodies in vivo at the peri-implantation stage of development resulted in failure of embryos to implant. Similarly, trophoblastic outgrowth of blastocysts was adversely affected in the presence of anti-EPF antibodies.

CONCLUSIONS

These results, together with previous findings that anti-EPF antibodies retard embryonic development when administered at the early pre-implantation stage, clearly demonstrate that EPF is required by the embryo at two important developmental stages- the one-two-cell stage and the peri-implantation stage.

Early pregnancy factor: an extracellular chaperonin 10 homologue

Early pregnancy factor (EPF) has been identified as a homologue of chaperonin 10 (cpn10) with immunosuppressive and growth factor properties. As a homologue of cpn10, it belongs to the heat shock family of proteins (hsp) but, unlike other members of this family, EPF is detected extracellularly. Early pregnancy factor was first discovered in pregnancy serum by the rosette inhibition test, and the novelty of its discovery was that its presence could diagnose pregnancy within 6-24 h of a fertile mating. As well as being a monitor of the presence of a viable embryo, it is necessary for embryonic survival. In this capacity it acts as both an immunosuppressant and growth factor. Early pregnancy factor is also a product of proliferating primary and neoplastic cells and functions as an autocrine growth factor both in vivo and in vitro. It has a modifying effect on the outcome of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. Early pregnancy factor is considered to be one of the major factors involved in the modification of multiple sclerosis observed during pregnancy.

Identification of a mutation in liver glycogen phosphorylase in glycogen storage disease type VI

Glycogen storage disease type VI (GSD6) defines a group of disorders that cause hepatomegaly and hypoglycemia with reduced liver phosphorylase activity. The course of these disorders is generally mild, but definitive diagnosis requires invasive procedures. We analyzed a Mennonite kindred with an autosomal recessive form of GSD6 to determine the molecular defect and develop a non-invasive diagnostic test. Linkage analysis was performed using genetic markers flanking the liver glycogen phosphorylase gene ( PYGL ), which was suspected to be the cause of the disorder on biochemical grounds. Mennonite GSD6 was linked to the PYGL locus with a multipoint LOD score of 4.7. The PYGL gene was analyzed for mutations by sequencing genomic DNA. Sequencing of genomic DNA revealed a splice site abnormality of the intron 13 splice donor. Confirmation of the genomic mutation was performed by sequencing RT-PCR products, which showed heterogeneous PYGL mRNA lacking all or part of exon 13 in affected persons. This study is the first to demonstrate that a mutation in the PYGL gene can cause GSD6. This mutation is estimated to be present on 3% of Mennonite chromosomes and the disease affects 0.1% of that population. Determination of this mutation provides a basis for the development of a simple and non-invasive diagnostic test for the disease and the carrier state in this population and confirms biochemical data showing the importance of this gene in glucose homeostasis.

The human early pregnancy factor/chaperonin 10 gene family

cDNA clones corresponding to the sequence for human early pregnancy factor were isolated from a human melanoma library and hybridized to DNA digested with four restriction enzymes obtained from twelve different subjects. Up to 20 cross hybridizing bands were observed. When hybridized to metaphase spreads from four different humans, significant signals were present in nine locations, on eight different chromosome arms. These results suggest that the early pregnancy factor gene is a member of a large gene family. The coding sequence for early pregnancy factor has a high degree of homology with the sequence for human chaperonin 10, and the gene family described here should contain the genes for both of these proteins.

Purification and partial characterization of an early pregnancy factor-induced suppressor factor (EPF-S1)

PROBLEM

The immunomodulatory properties of early pregnancy factor (EPF) are mediated through induction of at least two lymphokines, designated EPF-S1 and EPF-S2 (previously estimated M(r) 15,000 and 55,000 respectively). The activity of the former is MHC-restricted while the latter is restricted to a locus (or loci) outside the MHC. The present study established further criteria by which EPF-S1 and EPF-S2 might be distinguished from each other and compared with other suppressor factors. In addition, techniques have been developed to purify EPF-S1 to homogeneity.

METHOD

Congenic mouse strains were used to map the genetic restriction of EPF-S2 in the rosette inhibition test and high performance gel permeation chromatography was used to demonstrate that EPF-S1 induces EPF-S2 but not vice versa. Further studies then focused on isolation of this first component of the cascade, EPF-S1, from immune ascites (from growth in athymic mice of the anti-EPF-S1 producing rat-mouse hybridoma R2T gamma, in which EPF-S1 is complexed to antibody). Techniques used were acidification followed by application to Sep-pak C18 cartridges, high performance cation-exchange chromatography and two reversed-phased HPLC steps on a C3 column. Purified material was analyzed by SDS-PAGE and Edman degradation.

RESULTS

Approximately 10 micrograms EPF-S1 were isolated fom 60 ml ascitic fluid. Homogeneity of the purified material was demonstrated by SDS-PAGE, where it ran as a single band of approximate M(r) 12,000 coincident with biological activity. Attempts at Edman degradation indicate that the molecule is N-blocked.

CONCLUSION

Definitive primary characterization of EPF-S1 must await the preparation and isolation of proteolytic fragments of the molecule, but the present studies establish conditions which make such structural analysis possible.

A monoclonal antibody to an early pregnancy factor-induced suppressor factor (EPF-S1) disrupts implantation in mice

PROBLEM

The importance of EPF during pregnancy has been established previously but the importance of the EPF-induced suppressor factor EPF-S1 in pregnancy has to date been unaddressed. Investigations were therefore conducted in order to study this.

METHOD

Monoclonal antibodies to EPF-S1 were produced, and one antibody, designated R2T gamma, was characterized. Mated mice were passively immunized with R2T gamma and the effect on implantation determined.

RESULTS

Characterization of anti-EPF-S1 R2T gamma revealed that it cross-reacted with EPF-S1 of different MHC restriction but not with EPF or EPF-S2. When injected into mated mice on days 1 to 4, R2T gamma had no effect on pregnancy but when injections continued to day 5, pregnancy was affected; the number of embryos implanted on day 7 were significantly less than the number of corpora lutea counted, signifying embryonic loss.

CONCLUSION

These studies show that anti-EPF-S1 R2T gamma disrupts implantation in mice when injected on days 1 to 5 of pregnancy but not when injected on days 1 to 4, demonstrating that EPF-S1 exerts its effects around the time of implantation.

Early pregnancy factor in liver regeneration after partial hepatectomy in rats: relationship with chaperonin 10

Early pregnancy factor is not only a product of dividing embryonic and neoplastic cells, as demonstrated previously, but also of normal proliferating cells. Eight hours after partial hepatectomy in rats, early pregnancy factor was detected in serum. It rose to a peak by 48 hr. Neutralization of early pregnancy factor in vivo by passive immunization with specific antibodies, 18 hr after partial hepatectomy, resulted in a significant decrease in the uptake of [3H]thymidine by the liver remnant, measured 4 to 6 hr later. These results suggest that during liver regeneration, early pregnancy factor is essential to the sequence of events that culminates in DNA synthesis and cell division. Recently we purified early pregnancy factor from human platelets and determined by mass spectrometry a precise molecular mass of 10,843 Da. Amino acid sequencing (approximately 72% of the molecule) demonstrated that early pregnancy factor is highly homologous with chaperonin 10, a stress-inducible mitochondrial protein, and that platelet-derived early pregnancy factor and rat chaperonin 10 share similar biochemical and immunological properties. In this study we show that early pregnancy factor, purified from regenerating rat liver and from serum taken 24 hr after hepatectomy, shares these properties. In addition, antibodies to early pregnancy factor, effective in passive immunization studies, recognize chaperonin 10, whereas chaperonin 10 antibodies bind to early pregnancy factor from regenerating liver and posthepatectomy serum. We propose that early pregnancy factor/chaperonin 10 is selectively released from proliferating cells and, in an autocrine or paracrine mode (or both) is involved in DNA synthesis.

The purification of early-pregnancy factor to homogeneity from human platelets and identification as chaperonin 10

Early-pregnancy factor (EPF), first discovered in the early stages of gestation, is associated with and necessary for cell proliferation in a wide variety of biological situations. Like many other growth factors, EPF is present in platelets, and, by titration studies with a neutralising anti-EPF monoclonal antibody, platelets were identified as an extremely rich source of this growth factor. EPF has been purified from clinically outdated human platelets by heat extraction, ion-exchange and affinity chromatographies on SP-Sephadex and heparin-Sepharose respectively, high-performance hydrophobic interaction chromatography and three reverse-phase HPLC steps, with an average yield of 15 micrograms/100 platelet units (equivalent to approximately 50 1 blood). Using SDS/PAGE, EPF migrated as a single band with approximate M(r) 8500, coincident with biological activity. Mass spectrometry provided an accurate and precise determination of the molecular mass as M(r) 10843.5 +/- 2, along with definitive evidence of the homogeneity of the preparation. Attempts at Edman degradation indicated that the molecule was blocked at the N-terminus and sequencing of proteolytic fragments was undertaken. The amino acid sequence of approximately 70% of the molecule was determined which, with a single exception, is identical with rat chaperonin 10. This structural relationship was shown to extend to functional identity by studies using chaperonin 10 and its functional associate chaperonin 60. Investigations with the latter confirmed that chaperonin 10 is the moiety in pregnancy serum which initiates response in the EPF bioassay. Our studies identify EPF as a member of the highly conserved heat-shock family of molecules and demonstrate a molecular chaperone performing an extracellular role.

Early pregnancy factor has immunosuppressive and growth factor properties

Early pregnancy factor (EPF) was first described as a pregnancy-associated substance, although recent studies suggest a more general link with cell development. It is a product of actively dividing cells and its apparent functional importance to them suggests its potential as a regulator of cell proliferation. The recent discovery of EPF in platelets has provided a comparatively rich and readily available source of EPF. The purification procedures employed to isolate EPF from this source have also been applied to pregnancy serum and urine, medium conditioned by oestrous mouse ovaries (stimulated with prolactin and embryo-conditioned medium), medium conditioned by tumour cells, and serum from rats 24 h after partial hepatectomy (PH). In all instances, biological activity followed the same pattern throughout. Furthermore, the final active reversed-phase high-performance liquid chromatography fraction from all sources was bound specifically by immobilized anti-EPF monoclonal antibodies (MAbs), indicating that the active fractions produced from these diverse sources are very closely related, if not identical. Some differences have been observed in the behaviour of EPF in various conditions. EPF is produced by proliferating tumour cells and by liver cells post-PH, and passive immunization studies with anti-EPF MAbs have shown that these cells need EPF for survival. In contrast, EPF has not been detected as a product of the pre-embryo, and addition of anti-EPF MAbs to embryo cultures does not adversely affect development from the 2-cell to the blastocyst stage. Although the pre-embryo is not dependent on EPF for its development in vitro, neutralization of EPF in vivo by anti-EPF MAbs retards its development. Thus, EPF appears to play an indirect role in maintaining the pre-embryo. By virtue of its ability to suppress the delayed-type hypersensitivity reaction, it has been suggested that EPF might act as an immunological response modifier of the maternal immune system. Alternatively, the effect of EPF on lymphocytes may be to reduce the expression of all or some cytokines and this could inhibit development. Whether or not EPF acts more directly as an autocrine growth factor from around the time of implantation, when the embryo first begins synthesis of EPF, is not known and remains to be investigated.

Effect of monoclonal antibodies to early pregnancy factor (EPF) on the in vivo growth of transplantable murine tumours

Neutralisation studies with monoclonal antibodies (mAbs) specific for early pregnancy factor (EPF) have shown it to be essential for the continuation of pregnancy in mice and the growth of some tumour cells in vitro. These studies report that the mAbs are also able to limit the growth of two murine tumour lines transplanted s.c. The development of MCA-2 tumours in CBA mice was unaffected by the injection of 1 mg anti-EPF IgM at the time of tumour cell inoculation. However, four doses of 500 micrograms anti-EPF, injected one dose per day for 4 days after tumour cell inoculation, significantly retarded tumour development such that no tumours were palpable on day 13. A similar dose regimen of control IgM had no effect on tumour size. Dose/response studies revealed that lower doses of anti-EPF administered after tumour cell inoculation were effective in retarding the growth of the MCA-2 tumours. The effects of anti-EPF mAb administration on the growth rate of palpable B16 tumours established s.c. in C57BL/6 mice was also determined. Tumours injected with 6 mg anti-EPF 5/341 or anti-EPF 5/333 mAbs showed significant decrease in the uptake of [3H]thymidine into tumour tissue, measured 16 h after injection. Furthermore, titration of sera for active EPF showed that a significant reduction in the EPF titre was associated with a significant inhibition of tumour DNA synthesis. Thus it appears that neutralisation of EPF retards tumour growth both in vitro and in vivo. In vitro the effects must be due to anti-EPF mAb interfering with a direct mechanism that contributes to the maintenance of cells in the active growing phase. However, in vivo host immunological mechanism that are modified to allow tumour survival may also be affected. The presence of EPF-induced suppressor factor circulating in the serum of tumour-bearing mice has been confirmed and the contribution of such factors to tumour progression must now be investigated.

Relationship between early pregnancy factor, mouse embryo-conditioned medium and platelet-activating factor

The effects of synthetic platelet-activating factor (PAF-acether) and mouse embryo-conditioned medium (a source of embryo-derived PAF (EPAF)) on production of early pregnancy factor (EPF) were compared. Embryo-conditioned medium, itself inactive in the EPF bioassay, stimulated ovarian production of EPF in vitro but PAF-acether did not. In vivo, embryo-conditioned medium induced EPF activity in serum of oestrous female, but not in male, mice in contrast to PAF-acether, which induced activity in serum of both male and female mice. This PAF-induced activity was transitory, declining significantly by 2 h and disappearing by 3 h after injection. Activity induced by embryo-conditioned medium was first evident at 2 h after injection, serum concentrations increasing up to 6 h after injection. By discriminating between the behaviour of PAF-acether and EPAF, these studies reinforce the conclusions of other workers that the molecule produced by the embryo is not PAF. Further investigations into the mechanism of action of PAF-acether revealed that it is a potent inducer of activity in the EPF bioassay, with an absolute requirement for platelets in the spleen cell suspension used in the assay. This platelet-derived active species was bound specifically by an anti-EPF monoclonal antibody, indicating that it is EPF-like. This is consistent with parallel studies showing that platelets are not required for induction of activity by either pregnancy serum or purified EPF. These studies were applied to the PAF-induced leukotriene-like species, which had been found by others to be active in the EPF bioassay. Pregnancy serum induced the appearance of this substance from the spleen cell suspension used in the assay; thus the leukotriene-like substance may be regarded as an effector molecule in vitro or mediator of the initiating stimulus of EPF in the bioassay.

Antibodies to early pregnancy factor retard embryonic development in mice in vivo

Previous work in this laboratory has shown that passive immunization of mice against early pregnancy factor (EPF) leads to failure to maintain pregnancy. The findings presented in this paper demonstrate that this treatment affects the development of the embryos very early in gestation. By Day 3, 54 and 25% of embryos in the 2 groups treated with anti-EPF immunoglobulin (Ig)G and IgM, respectively, had not developed to the 4-cell stage, compared with 12 and 1% in the control groups. None of the embryos in the mice treated with anti-EPF had developed beyond the 8-cell stage. A similar delay in development after treatment was observed on Day 4. The effect apparent during the early stages of cleavage is an indirect rather than a direct one, as 2-cell embryos (32-36 h post coitum), cultured in vitro in the presence of anti-EPF antibodies, developed uninterrupted to the morula and blastocyst stage. The delay in development did not appear to be caused by a disruption of the normal pattern of circulating progesterone, as progesterone concentrations on Day 4 were within the normal range for Quackenbush mice.

Identification of a putative inhibitor of early pregnancy factor in mice

Previous studies have indicated that early pregnancy factor (EPF) produced in the pre- and peri-implantation stage of pregnancy appears to consist of inactive components which combine to produce the active species. This is in contrast with EPF produced later in gestation which appears to consist of a single active species. The original studies on ammonium sulphate fractionation of mouse serum and in-vitro culture of mouse ovaries and oviducts have been repeated but tested in the bioassay for EPF, the rosette inhibition test, over an extended range of dilutions. This revealed that the two components in early pregnancy can be understood as EPF and an inhibitor(s). Once this inhibitor is removed, the active fractions in both early and late pregnancy sera exhibit similar behaviour in the above assay. It was shown also that the ovary alone is the source of activity but that this is modulated by an inhibitory substance(s) from the oviduct. Reversed-phase HPLC studies on purified 'early' EPF confirm that active and inhibitory components are present and demonstrate that the active component exhibits an identical elution pattern to 'late' EPF. Thus as pregnancy proceeds, it is not EPF that alters but rather the inhibitor(s), which disappears from the circulation soon after implantation. This substance(s) is under hormonal control, being present during oestrus as well as the early stages of pregnancy; it may be an important biological regulator of EPF. Its action in the rosette inhibition test has profound implications for further study using this bioassay.

Monoclonal antibodies to early pregnancy factor perturb tumour cell growth

The pregnancy-associated substance early pregnancy factor (EPF) has previously been reported as a product of tumours of germ cell origin. More recently EPF (or an EPF-related substance, tEPF) has also been detected in the serum of patients bearing tumours of non-germ cell origin. We report here the production of tEPF by a variety of cultured transformed and tumour cell lines, of both germ and non-germ cell origin. Antibodies specific for EPF remove all tEPF activity from tumour cell conditioned medium. tEPF production is found to be associated with cell division; tEPF is no longer detected after growth arrest or differentiation. Co-culture of tumour cells with increasing doses of anti-EPF monoclonal antibodies resulted in a significant, dose-dependent decrease in rate of cell growth and viability. Similar anti-EPF concentrations had no effect on the concanavalin A induced proliferation of mouse spleen cells. These studies suggest, therefore, that tEPF is a growth-regulated product of cultured tumour and transformed cells. These cells are also dependent upon tEPF for continued growth, i.e. tEPF is acting in the autocrine mode.

Thromboxane A2 and prostaglandin endoperoxide analogue effects on porcine renal blood flow

Thromboxane A2 (TxA2) has been implicated as a mediator of renal and cardiovascular diseases. However, the direct effects of TxA2 on the renal system have been difficult to study because of the instability of the agonist. In the present study injection of synthetic TxA2 directly into the renal artery of anesthetized pigs produced dose-related decreases in renal blood flow (RBF) from 101 +/- 11 to 12 +/- 3 ml/min at the highest dose (20 ng/kg). The reductions in RBF were similar to those produced by the stable prostaglandin endoperoxide analogue, U-44069, although TxA2 was three times more potent. Under these conditions there were no effects on either mean (MAP) or pulmonary arterial pressures (PAP), or the heart rate (HR). The maximal effects produced by TxA2 and U-44069 on RBF were reproducible and the response remained unchanged after pretreatment with either heparin or indomethacin. Systemically administered TxA2 (200 ng/kg iv) increased PAP from 20 +/- 1 to 34 +/- 3 mmHg and this effect was associated with modest increases in MAP and HR. Intravenous administration of the thromboxane receptor antagonist, L-655,240, inhibited the reductions in RBF produced by intrarenal TxA2 and U-44069 and attenuated the cardiopulmonary effects of TxA2 administered intravenously. The results demonstrate directly that TxA2 is a potent agent for decreasing RBF through interaction with a thromboxane receptor.

Passive immunization of pregnant mice against early pregnancy factor causes loss of embryonic viability

Early pregnancy factor (EPF) is a monitor of the incidence of fertilization and the progress of the early embryo. To determine whether, as well as being a marker of embryonic viability, EPF is also necessary for embryonic survival, passive immunization studies with monoclonal and polyclonal antibodies to EPF were carried out on pregnant mice. In the preparation of monoclonal antibodies, it was noted that most anti-EPF producing hybridomas failed to grow in vitro, while those that did grow produced only low yields of specific IgM antibodies. Two stable hybridoma cell lines were established both producing low affinity anti-EPF IgM; polyclonal anti-EPF IgG was prepared in rabbits. Mice were passively immunized with 500 micrograms monoclonal anti-EPF IgM at 32 and 56 h post coitum (total dose 1 mg) or with 500 micrograms polyclonal anti-EPF IgG at 8, 16, 32 and 40 h post coitum (total dose 2 mg). At 10 days, only 6/18 and 3/6 mice receiving monoclonal antibodies and 2/7 and 1/6 mice receiving polyclonal antibodies had maintained their pregnancies. In contrast, all mice receiving control IgM (N = 14) or control IgG (N = 4) and 22/23 receiving saline were still pregnant at Day 10.

Fractional conversion of thromboxane A2 and B2 to urinary 2,3-dinor-thromboxane B2 and 11-dehydrothromboxane B2 in the cynomolgus monkey

Following the intravenous administration of thromboxane (TX) B2, the stable hydration product of TXA2, to human and nonhuman primates the most abundant urinary metabolites are 2,3-dinor-TXB2 and 11-dehydro-TXB2. However, it is not known whether fractional conversion of TXB2 to its enzymatic metabolites is an accurate representation of TXA2 metabolism. Thus, we have compared the metabolic disposition of synthetic TXA2 and TXB2 via the beta-oxidation and 11-OH-dehydrogenase pathways in vivo in the monkey. TXA2 or TXB2 (20 ng/kg) was intravenously administered to four cynomolgus monkeys pretreated with aspirin in order to suppress endogenous TXA2 production. Urinary TXB2, 2,3-dinor-TXB2 and 11-dehydro-TXB2 were measured before, during and up to 24 h after thromboxane administration by means of reversed-phase high-performance liquid chromatography radioimmunoassay. Aspirin treatment suppressed urinary 2,3-dinor-TXB2 and 11-dehydro-TXB2 by approx. 75%. A similar fractional conversion of TXA2 and TXB2 into 2,3-dinor-TXB2 and 11-dehydro-TXB2 was found. These results suggest that TXA2 is hydrolyzed to TXB2 prior to enzymatic degradation and that metabolites of the latter represent reliable indices of TXA2 biosynthesis. Due to the variability in the conversion of thromboxanes into 2,3-dinor-TXB2 and 11-dehydro-TXB2, the measurement of both metabolites seems to represent a more reliable index of acute changes in TXA2 production.

Genetically-restricted effector molecules released by human lymphocytes in response to early pregnancy factor

The binding of early pregnancy factor (EPF) to lymphocytes stimulates the release of soluble effector molecules. Studies in mice have shown that it is these factors rather than EPF as such which are inhibitory in the T cell-dependent reactions, the adoptive transfer of contact sensitivity and the rosette inhibition test. Two factors have been identified: mEPF-S1 (Mr approximately 15,000) is major histocompatibility complex (MHC)-restricted while mEPF-S2 (Mr approximately 55,000) is restricted to a locus (or loci) outside the MHC. In the present paper, evidence is presented which shows that EPF also induces the release of soluble mediators from human lymphocytes. With the rosette inhibition test two factors have been detected, both of similar size and genetic restriction to those described previously in the mouse. One factor, designated hEPF-S1 (Mr 14-18,000), is human lymphocyte antigen (HLA)-restricted and the other, hEPF-S2 (Mr 50-60,000), appears to be restricted to a locus (or loci) outside the HLA complex.

L-663,536 (MK-886) (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2 - dimethylpropanoic acid), a novel, orally active leukotriene biosynthesis inhibitor

L-663,536 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2, 2-dimethylpropanoic acid) is a potent inhibitor of leukotriene (LT) biosynthesis in intact human polymorphonuclear leukocytes (PMN) (IC50, 2.5 nM). Similarly, L-663,536 inhibited A23187-induced LTB4 formation by rat peripheral blood and elicited PMN. At concentrations where inhibition of leukotriene biosynthesis occurred in human whole blood (1.1 microM), no effect was seen on cyclooxygenase or 12-lipoxygenase, an effect also observed in washed human platelets. The compound had no effect on rat or porcine 5-lipoxygenase indicating that L-663,536 is not a direct 5-lipoxygenase inhibitor. When administered in vivo L-663,536 was a potent inhibitor of antigen-induced dyspnea in inbred rats pretreated with methysergide (ED50, 0.036 mg/kg p.o.) and of Ascaris-induced bronchoconstriction in squirrel monkeys (1 mg/kg p.o.). The compound inhibited leukotriene biosynthesis in vivo in a rat pleurisy model (ED50, 0.2 mg/kg p.o.), an inflamed rat paw model (ED50, 0.8 mg/kg), a model of leukotriene excretion in rat bile following antigen provocation, and a model in the guinea-pig ear where leukotriene synthesis was induced by topical challenge with ionophore A23187 (ED50, 2.5 mg/kg p.o. and 0.6 micrograms topically). The results indicate that L-663,536 is a potent inhibitor of leukotriene biosynthesis both in vitro and in vivo indicating that the compound is suitable for studying the role of leukotrienes in a variety of pathological situations.

Identification of two suppressor factors induced by early pregnancy factor

The binding of EPF to lymphocytes stimulates the release of soluble mediators, active in T cell dependent reactions, namely the rosette inhibition test and the adoptive transfer of contact sensitivity. On the basis of their ability to inhibit the delayed type hypersensitivity reaction in this latter assay, they have been classified as suppressor factors. This paper describes the identification of two EPF-induced suppressor factors. Unlike EPF which is neither species-restricted nor strain-restricted, these factors are genetically restricted in their action in the rosette inhibition test. EPF-S1 (estimated Mr 14,000) is restricted to the 1 region of the mouse MHC, while EPF-S2 (estimated Mr 55,000) is restricted to a locus (or loci) outside the MHC. Like other antigen non-specific factors, release of these suppressor factors can be stimulated also by Con A.

Modified rosette inhibition test with mouse lymphocytes for detection of early pregnancy factor in human pregnancy serum

The rosette inhibition test has been modified so that early pregnancy factor (EPF) in human pregnancy serum can be detected with mouse lymphocytes. Interference with the assay, which would result from incubation of lymphocytes with heterologous serum proteins, is prevented by the introduction of an ion exchange chromatography step. This provides a simple and rapid method for separating EPF from interfering serum proteins. Human pregnancy and non-pregnancy sera were assayed for EPF with human lymphocytes and results compared with those obtained with DEAE-Sephacel fractions of the same sera tested with mouse lymphocytes. The 2 systems showed good agreement but the mouse assay gave greater differentiation between positive and negative results. When monoclonal anti-T cell antibodies, Hu Ly-m1 and anti-Ly-1.1, were substituted for anti-lymphocyte sera in the human and mouse assay systems respectively, similar results were obtained. The mouse assay system has several advantages over the human assay, including stability of the anti-mouse lymphocyte serum and the ready availability of mouse lymphocytes. Moreover the modified method may be applied not only to the assay of human EPF, but also to the assay of EPF from other species. This would be of value if several species were being studied in 1 laboratory, or if sufficient quantities of lymphocytes from a particular species were not available.

Early pregnancy factor (EPF): a link between fertilization and immunomodulation

Early pregnancy factor (EPF) is a pregnancy-dependent, suppressor-releasing hormone, which can be differentiated from other known pregnancy-associated substances by its physiological, biochemical and immunological characteristics. To date studies have shown that the presence of EPF in serum at anytime except during pregnancy is pathological and is associated with tumors of germ cell origin. EPF can be detected in serum within hours of fertilization, thus providing for the first time a means of monitoring in vitro the continuing viability of a fertilized egg in vivo. EPF has been shown to be a link between fertilization and immunomodulation. Fertilization of the ovum initiates a chain of events which includes production of EPF. EPF then binds to lymphocytes, releasing soluble suppressor substances, which in turn modulate the mother's immune system. Thus it is proposed that the conceptus ensures its own defence against immunological rejection.

The appearance and characteristics of early pregnancy factor in the pig

The occurrence of early pregnancy factor in the pig has been established by the rosette inhibition test and by the criteria that gel filtration of serum resulted in a number of peaks of activity similar to those observed in other species. In the pig EPF is present virtually to the end of pregnancy, with a biphasic production in which the titres of EPF decline markedly in mid-pregnancy. Free EPF-A appears concurrently with EPF in the first 3 weeks of pregnancy in some but not all pigs. The presence of excess EPF-A has an inhibitory effect in the rosette inhibition test and modifications, including an initial serum dialysis step, have been introduced into the test to take account of this inhibitory effect.

Detection of an early pregnancy factor-like substance in sera of patients with testicular germ cell tumors

Early pregnancy factor (EPF) is produced by both maternal and fetal tissue1,2 and has been detected previously only during pregnancy.3,4 The present report describes the detection of EPF, or an EPF-like substance (tEPF), in serum from patients with germ cell tumors of the testis. tEPF, or its free components, tEPF-A and tEPF-B, were detected in all 11 patients with nonseminomatous tumors and in 5 of 10 patients with seminoma. It was not detected in serum from healthy male controls nor in patients with non-germ cell tumors or benign testicular disease. It is suggested that tEPF may be an additional serum marker for germ cell tumors and may expand the group already detectable by such markers.

Early pregnancy factor is an immunosuppressive contaminant of commercial preparations of human chorionic gonadotrophin

Early pregnancy factor (EPF) is a pregnancy associated substance detected in human serum and urine throughout the first and second trimesters of pregnancy. It has also been detected in several commercial preparations of human chorionic gonadotrophin (hCG). The various molecular weight forms of EPF which occur in human pregnancy serum, urine and commercial hCG preparations have been partially characterized and found to be similar to each other but distinct from hCG. Further evidence is presented which suggests that it is EPF rather than hCG which is responsible for the immunosuppressive activity of some crude hCG preparations.

Rosette inhibition test: a multicentre investigation of early pregnancy factor in humans

The rosette inhibition test for the detection of early pregnancy factor is described in detail. The extended methodology presented here represents the cumulative experience of three independent laboratories. Special reference is made to the effect on the assay of varying the conditions of rosette formation between lymphocytes and sheep red blood cells. Antilymphocyte sera prepared for use in the rosette inhibition test fell into three categories: (i) with no rosette inhibiting activity, (ii) with rosette inhibiting activity which is not affected by the presence of EPF, and (iii) rosette inhibiting activity which is significantly increased in the presence of EPF. To date, this third reaction has been found to be a specific indication of the presence in serum of early pregnancy factor.

Ovum factor: a first signal of pregnancy?

Previous studies have shown that, in the mouse, a factor is produced by the fertilized ovum within 24 h of mating. It cooperates with prolactin to stimulate ovarian production of component B or early pregnancy factor (EPF). This paper presents an initial characterization of the substance, termed ovum factor (OF). An indirect assay based on the rosette inhibition test for EPF has shown that OF is first released upon penetration of the ovum by the fertilizing spermatozoon. OF continues to be produced at least until blastulation. Processes which parthenogenetically activate the ovum are also capable of stimulating OF release from unfertilized ova. Gel filtration studies reveal that OF exists in multiple MW forms of approximately 160,000; 2,800; and 1,500. A substance with these characteristics has not been described previously; it may represent the first embryonic signal to the mother.

Characterisation and subunit structures of the vicilin storage proteins of pea (Pisum sativum L.)

Investigations of the vicilin fraction of the storage proteins of pea (Pisum sativum L.) have shown that its major components are a number of protein species of Mr 170 000. Convicilin (Mr 280 000, composed of 71 000-Mr subunits) is a separable component of this fraction. The vicilin proteins are composed principally of approximately equal to 50 000-Mr polypeptides, but also contain a number of smaller polypeptides. The sub-unit polypeptide composition of vicilin changes during seed development quantitatively and qualitatively. Vicilin sub-units have been shown to be synthesised as polypeptides of Mr approximately equal to 50 000 by means of pulse-labelling experiments in vivo, and synthesis of vicilin in vitro directed by mRNA, polysomes and microsomes extracted from pea cotyledons in cell-free translation systems. Polypeptides then undergo two distinct types of proteolytic modification: (a) co-translational removal of a small polypeptide (Mr less than 1000); (b) 'nicking' of polypeptide chains in assembled vicilin molecules, which occurs more than 4 h after their initial synthesis. The basic structure of the vicilin molecule is thus a multimer, possibly a trimer, of approximately equal to 50 000-Mr subunits. The heterogeneity of the initially synthesised 50 000-Mr subunits accounts not only for the several different 50 000-Mr polypeptides found in vicilin, but also for the range of minor polypeptides, since the 'nicking' points will differ among subunits. It also accounts for the observed partial separation of vicilin into different molecular species, since different subunit combinations will give rise to molecules with different properties. Vicilin is also glycosylated and this is a source of further variation.