An interchangeable prion-like domain is required for Ty1 retrotransposition

Retrotransposons and retroviruses shape genome evolution and can negatively impact genome function. Saccharomyces cerevisiae and its close relatives harbor several families of LTR-retrotransposons, the most abundant being Ty1 in several laboratory strains. The cytosolic foci that nucleate Ty1 virus-like particle (VLP) assembly are not well understood. These foci, termed retrosomes or T-bodies, contain Ty1 Gag and likely Gag-Pol and the Ty1 mRNA destined for reverse transcription. Here, we report an intrinsically disordered N-terminal prion-like domain (PrLD) within Gag that is required for transposition. This domain contains amino acid composition similar to known yeast prions and is sufficient to nucleate prionogenesis in an established cell-based prion reporter system. Deleting the Ty1 PrLD results in dramatic VLP assembly and retrotransposition defects but does not affect Gag protein level. Ty1 Gag chimeras in which the PrLD is replaced with other sequences, including yeast and mammalian prionogenic domains, display a range of retrotransposition phenotypes from wild type to null. We examine these chimeras throughout the Ty1 replication cycle and find that some support retrosome formation, VLP assembly, and retrotransposition, including the yeast Sup35 prion and the mouse PrP prion. Our interchangeable Ty1 system provides a useful, genetically tractable in vivo platform for studying PrLDs, complete with a suite of robust and sensitive assays. Our work also invites study into the prevalence of PrLDs in additional mobile elements.

An interchangeable prion-like domain is required for Ty1 retrotransposition

Retrotransposons and retroviruses shape genome evolution and can negatively impact genome function. Saccharomyces cerevisiae and its close relatives harbor several families of LTR-retrotransposons, the most abundant being Ty1 in several laboratory strains. The cytosolic foci that nucleate Ty1 virus-like particle (VLP) assembly are not well-understood. These foci, termed retrosomes or T-bodies, contain Ty1 Gag and likely Gag-Pol and the Ty1 mRNA destined for reverse transcription. Here, we report a novel intrinsically disordered N-terminal pr ion-like d omain (PrLD) within Gag that is required for transposition. This domain contains amino-acid composition similar to known yeast prions and is sufficient to nucleate prionogenesis in an established cell-based prion reporter system. Deleting the Ty1 PrLD results in dramatic VLP assembly and retrotransposition defects but does not affect Gag protein level. Ty1 Gag chimeras in which the PrLD is replaced with other sequences, including yeast and mammalian prionogenic domains, display a range of retrotransposition phenotypes from wildtype to null. We examine these chimeras throughout the Ty1 replication cycle and find that some support retrosome formation, VLP assembly, and retrotransposition, including the yeast Sup35 prion and the mouse PrP prion. Our interchangeable Ty1 system provides a useful, genetically tractable in vivo platform for studying PrLDs, complete with a suite of robust and sensitive assays, and host modulators developed to study Ty1 retromobility. Our work invites study into the prevalence of PrLDs in additional mobile elements.

Significance

Retrovirus-like retrotransposons help shape the genome evolution of their hosts and replicate within cytoplasmic particles. How their building blocks associate and assemble within the cell is poorly understood. Here, we report a novel pr ion-like d omain (PrLD) in the budding yeast retrotransposon Ty1 Gag protein that builds virus-like particles. The PrLD has similar sequence properties to prions and disordered protein domains that can drive the formation of assemblies that range from liquid to solid. We demonstrate that the Ty1 PrLD can function as a prion and that certain prion sequences can replace the PrLD and support Ty1 transposition. This interchangeable system is an effective platform to study additional disordered sequences in living cells.

The Opportunistic Pathogen Vibrio vulnificus Produces Outer Membrane Vesicles in a Spatially Distinct Manner Related to Capsular Polysaccharide

Vibrio vulnificus, a bacterial species that inhabits brackish waters, is an opportunistic pathogen of humans. V. vulnificus infections can cause acute gastroenteritis, invasive septicemia, tissue necrosis, and potentially death. Virulence factors associated with V. vulnificus include the capsular polysaccharide (CPS), lipopolysaccharide, flagellum, pili, and outer membrane vesicles (OMVs). The aims of this study were to characterize the morphology of V. vulnificus cells and the formation and arrangement of OMVs using cryo-electron microscopy (cryo-EM). cryo-EM and cryo-electron tomography imaging of V. vulnificus strains grown in liquid cultures revealed the presence of OMVs (diameters of ∼45 nm for wild-type, ∼30 nm for the unencapsulated mutant, and ∼50 nm for the non-motile mutant) in log-phase growth. Production of OMVs in the stationary growth phase was limited and irregular. The spacing of the OMVs around the wild-type cells was in regular, concentric rings. In wild-type cells and a non-motile mutant, the spacing between the cell envelope and the first ring of OMVs was ∼200 nm; this spacing was maintained between subsequent OMV layers. The size, arrangement, and spacing of OMVs in an unencapsulated mutant was irregular and indicated that the polysaccharide chains of the capsule regulate aspects of OMV production and order. Together, our results revealed the distinctive organization of V. vulnificus OMVs that is affected by expression of the CPS.

Pleomorphic Structures in Human Blood Are Red Blood Cell-Derived Microparticles, Not Bacteria

Background

Red blood cell (RBC) transfusions are a common, life-saving therapy for many patients, but they have also been associated with poor clinical outcomes. We identified unusual, pleomorphic structures in human RBC transfusion units by negative-stain electron microscopy that appeared identical to those previously reported to be bacteria in healthy human blood samples. The presence of viable, replicating bacteria in stored blood could explain poor outcomes in transfusion recipients and have major implications for transfusion medicine. Here, we investigated the possibility that these structures were bacteria.

Results

Flow cytometry, miRNA analysis, protein analysis, and additional electron microscopy studies strongly indicated that the pleomorphic structures in the supernatant of stored RBCs were RBC-derived microparticles (RMPs). Bacterial 16S rDNA PCR amplified from these samples were sequenced and was found to be highly similar to species that are known to commonly contaminate laboratory reagents.

Conclusions

These studies suggest that pleomorphic structures identified in human blood are RMPs and not bacteria, and they provide an example in which laboratory contaminants may can mislead investigators.

A rare case of ischaemic pneumatosis intestinalis and hepatic portal venous gas in an elderly patient with good outcome following conservative management

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PI and HPVG caused by ischaemia usually results in death if conservatively managed.

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A 93 year old male survived this despite non-operative management.

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Aggressive surgical intervention is not always in the patients’ best interest.

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Further work is needed to identify patients who may survive conservative treatment.

Introduction

Pneumatosis intestinalis (PI) and hepatic portal venous gas (HPVG) are typically associated and are likely to represent a spectrum of the same disease. The causes of both entities range from benign to life-threatening conditions. Ischaemic causes are known to be fatal without emergency surgical intervention.

Presentation of case

In this case a 93 year old male experienced acute abdominal pain radiating to his back, with nausea and vomiting and a 2-week history of altered bowel habit. Examination revealed abdominal tenderness and distension. He had deranged white cell count (WCC) and renal function. Computed tomography (CT) revealed PI with associated HPVG. The cause was due to ischaemic pathology. The patient was managed conservatively with antibiotics and was discharged 7 days later with resolution of his abdominal pain and WCC.

Discussion

The pathogenesis of HPVG secondary to PI is poorly understood but usually indicates intestinal ischaemia, thought to carry a mortality of around 75%. HPVG in the older patient usually necessitates emergency surgery however this is not always in the patient’s best interest.

Conclusion

There are few reported cases of patient survival following conservative management of PI and HPVG secondary to ischaemic pathology. This case demonstrates the possibility of managing this condition without aggressive surgical intervention especially when surgery would likely result in mortality due to frailty and morbidity. Further work is required to identify suitable patients.

Long-term biostability of self-assembling protein polymers in the absence of covalent crosslinking

Unless chemically crosslinked, matrix proteins, such as collagen or silk, display a limited lifetime in vivo with significant degradation observed over a period of weeks. Likewise, amphiphilic peptides, lipopeptides, or glycolipids that self-assemble through hydrophobic interactions to form thin films, fiber networks, or vesicles do not demonstrate in vivo biostability beyond a few days. We report herein that a self-assembling, recombinant elastin-mimetic triblock copolymer elicited minimal inflammatory response and displayed robust in vivo stability for periods exceeding 1 year, in the absence of either chemical or ionic crosslinking. Specifically, neither a significant inflammatory response nor calcification was observed upon implantation of test materials into the peritoneal cavity or subcutaneous space of a mouse model. Moreover, serial quantitative magnetic resonance imaging, evaluation of pre- and post-explant ultrastructure by cryo-high resolution scanning electron microscopy, and an examination of implant mechanical responses revealed substantial preservation of form, material architecture, and biomechanical properties, providing convincing evidence of a non-chemically or ionically crosslinked protein polymer system that exhibits long-term stability in vivo.

Semagenesis and the parasitic angiosperm Striga asiatica

Over the last several years, intermediates in the reduction of dioxygen have been attributed diverse functional roles ranging from protection against pathogen attack to the regulation of cellular development. Evidence now suggests that parasitic angiosperms, which naturally commit to virulence through the growth of new organs, depend on reduced oxygen intermediates, or reactive oxygen species (ROS), for signal generation. Clearly, the role of ROS in both plant defense and other physiological responses complicates any models that employ these intermediates in host plant recognition. Here we exploit the transparent young Striga asiatica seedling to (i) localize the site of H(2)O(2) accumulation to the surface cells of the primary root meristem, (ii) demonstrate the accumulation of H(2)O(2) within cytoplasmic and apoplastic compartments, and (iii) document precise regulation of H(2)O(2) accumulation during development of the host attachment organ, the haustorium. These studies reveal a new active process for signal generation, host detection and commitment that is capable of ensuring the correct spatial and temporal positioning for attachment.

Unusual infant death: dog attack or postmortem mutilation after child abuse?

An unusual form of fatal child abuse is reported in which investigations by the police and the medical examiner were able to distinguish blunt force head trauma followed by postmortem dismemberment from a fatal dog attack. A discussion of the approaches used to ascertain the correct diagnosis is presented, as well as an overview of dog attacks on humans.

Early decrease in surface expression of HLA-DQ predicts the development of infection in trauma patients

The behaviour of human leucocyte antigen-DR (HLA-DR) following injury has been extensively studied. However, the behaviour of other class II antigens following trauma has not been characterized as well, despite evidence that HLA-DQ genotype influences the response to several bacterial antigens. Our study attempts to characterize and analyse the behaviour of HLA-DQ after trauma in patients with and without infection. Twenty-five patients were studied following major injury. Fifteen of the 25 patients developed infection (men = 11, women = 4); 10 patients developed no infection (men = 9, women = 1). The mean age was 34 +/- 12 years for patients with no infection and 52 +/- 20 years for those with infection. Monocyte HLA-DQ surface expression was determined using FITC-labelled antibodies and flow cytometry. Expression was compared with a control population of 11 healthy volunteers. The percentage of monocytes expressing HLA-DQ following trauma was reduced in patients with infection and in those without infection, but returned to normal (days 8-14) only in those patients who did not develop infection. Monocyte HLA-DQ mean channel fluorescence was reduced on day 1, but quickly returned to normal in those patients who subsequently developed infection. Stimulated with lipopolysaccharide, the initial samples of 13 patients who developed infection showed that surface expression on these monocytes could be elevated into the normal range. We conclude that HLA-DQ is an additional early marker of outcome that may not function merely as an immune suppressor. The maintained ability of HLA-DQ to present self-antigens may be important in the initial stages of the host response to injury.

Differences between bacterial species shown by simultaneous assessment of neutrophil phagocytosis and generation of reactive oxygen intermediates in trauma patients

HYPOTHESIS

Previous studies on alterations in phagocytosis and bacterial killing after trauma have yielded conflicting results. We hypothesize that these changes are variable, depending on the species of bacteria used to assay these variables.

DESIGN

Blood samples from patients were assayed by means of flow cytometry for phagocytosis and reactive oxygen intermediate generation. Several common clinical pathogens were used: Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus. Results were compared with those from controls.

SETTING

Regional level I trauma center.

PATIENTS

Ten consecutive patients were studied with E. coli and K. pneumoniae. Five of these were also studied with S. aureus. Patients were 18 years of age or older, with an Injury Severity Score of 16 or more. Patients who were taking corticosteroids before hospital admission or who were administered corticosteroids before blood was drawn were not studied. Isolated head injuries or limb fractures were also excluded. Controls consisted of healthy volunteers.

MAIN OUTCOME MEASURES

The ingestion of bacteria by neutrophils and the generation of reactive oxygen intermediates.

RESULTS

After trauma, phagocytosis of E. coli was enhanced, whereas ingestion of K. pneumoniae was depressed. Ingestion of S aureus remained unchanged. The generation of reactive oxygen intermediates was depressed after incubation with E. coli and unchanged with K. pneumoniae, but enhanced with S. aureus.

CONCLUSIONS

Neutrophil response to trauma is dependent on which bacterial species the cell is attempting to kill. This may, in part, explain why only a limited number of bacterial species cause a significant proportion of early infections after trauma.

Villous adenoma of the distal appendix

Villous adenoma confined to the distal appendix has not been previously reported in conjunction with acute apendicitis. The presence of an adenoma indicates a need for further investigation due to an association with neoplasia elsewhere.

Response of immunoregulatory lymphocyte subsets to methotrexate in rheumatoid arthritis

In an attempt to define the immunoregulatory mechanisms operating in rheumatoid arthritis, the authors examined peripheral blood functional lymphocyte subsets in 15 patients with active rheumatoid arthritis who were not receiving remittive therapy, as well as 33 healthy controls. The percentage and absolute numbers of total T cells (CD3), T-helper/inducer cells (CD4), and T-suppressor/cytotoxic cells (CD8) did not differ among the groups, nor did the CD4:CD8 ratio or the numbers of T cells coexpressing CD4 and the activation markers Ia or IL-2R. However, rheumatoid arthritis patients did have reduced percentages and numbers of CD4+ cells coexpressing the 2H4 antigen (CD45R-naive T cells) (P less than .0003) and CD8+ cells coexpressing the Leu-15 (CD11b) marker (suppressor/effectors) (P less than .0005). Twelve patients then received oral methotrexate, 7.5 mg weekly. Most showed clinical improvement by 4 weeks and all did by 8 weeks. Although changes in the T-cell subsets were not statistically significant, several tended toward normalization. These findings may help explain the immunoregulatory defect in rheumatoid arthritis and the effectiveness of methotrexate in modifying disease activity.

Metropolitan Forensic Anthropology Team (MFAT) case studies in identification: 2. Identification of a Vietnamese trophy skull

A Vietnamese trophy skull, apparently a victim of the Vietnam war, was recently received for analysis in a New York State homicide case. The skull, which is well preserved except for the missing mandible and maxillary dentition, is compared to trophy skulls of Japanese military personnel, also brought back to the United States by American soldiers following wartime duty in Asia.

Discriminant function analysis of the central portion of the innominate

Terry Collection innominates of 260 American whites and blacks (65 males and 65 females of each race) were analyzed by discriminant function analysis for sex assessment, race known, and for simultaneous race and sex assessment. Measurements from the preservationally favored central portion of the innominate were chosen for their potential usefulness in forensic casework and to objectify long-recognized "formal" differences between the sexes in the greater sciatic notch. These included acetabular diameter, greater sciatic notch height, and position of greatest notch depth. Accuracy of sex prediction when race is known is roughly 90% in both the base sample of 260 and a test sample of 200 (50 additional individuals for each group). For simultaneous race and sex assessment, accuracy of prediction is roughly 60% for each group in both samples. This represents about a 45% reduction in error over random assignment by race and sex.

Metropolitan Forensic Anthropology Team (MFAT) studies in identification: 1. Race and sex assessment by discriminant function analysis of the postcranial skeleton

A case study is presented to demonstrate the utility of the team approach to the identification of human remains, and to illustrate a methodological innovation developed by MFAT. Case 1 represents the first of several planned case studies, each designed to present new methodological solutions to standard problems in identification. The present case describes a test, by application, of race and sex assessment of the postcranial skeleton by discriminant function analysis.

Multiple discriminant function analysis of sex and race in the postcranial skeleton

Terry Collection femora and innominates of 260 American Whites and Blacks (65 males and 65 females of each race) were analyzed by multiple discriminant function analysis. A stepwise procedure produced three optimal discriminant functions using 15 of our 32 measurements. These functions correctly identified 95% of the sample. The first two-one for sex and one for race-are statistically and biologically significant and form the basis of our analysis. The sexing function manifested both size and shape elements. Prominent among the former was joint size--acetabular diameter and epicondylar diameter of the femur. The shape elements included form of the greater sciatic notch and of the inferomedial aspect of the pubic body. The racing function highlighted a pattern of greater innominate dimensions, exclusive of the acetabular joint, in Whites. This was in contrast to the greater length of the Black femur. Overall, the function seems to express the established differences between the races in the ratio of lower limb length to torso length. While these functions have been applied successfully to forensic cases with confirmed identifications, questions regarding the breadth of applicability of discriminant functions make it desirable to validate our results on new material from the Terry and other collections.

Classification and misclassification in sexing the Black femur by discriminant function analysis

Stepwise discriminant function analysis for sex assessment was applied to 130 North American Black femora. The measurements included femoral length and three midshaft dimensions likely to be preserved in archaeologically-derived and forensic remains. The method correctly assigned sex for 76.4% of the sample (range 70.8-81.5%). This compares favorably with results achieved with other skeletal parts; it also compares favorably with results using the femur in sexing other racial groups. Among our other conclusions are: (1) a "general size factor" is one of major significance in correct classification and in misclassification of sex, and most misclassified individuals are anomalous for this factor; (2) the inconsistency in the relation between circumference and femoral length, which characterizes the remaining misclassified individuals, suggests that anomalous functional demands of body weight/musculature are at fault, and affect circumference more than length; and (3) discriminant function analysis of the same variables in Whites produced similar results, suggesting that sex overrides race in sex assessment; this was confirmed by cross-validating the predictive accuracy of Black discriminant function coefficients on White data, and vice versa.

Determination of sex of white femora by discriminant function analysis: forensic science applications

Stepwise multiple discriminant function analysis is used to establish classification functions for sex assessment of North American white femora. The functions correctly assign sex for 82% of a sample consisting of 85 femora of verified age, sex, and race, and for a similarly verified test sample of 30. The objectives are to provide criteria for sexing poorly preserved and fragmentary unknown specimens and a statement of the probable accuracy of such assessments in individual cases. The application of the method to forensic casework is illustrated by a sample case.

Cranial capacity/cranial base relationships and prediction of vault form: a canonical correlation analysis

Canonical correlation analysis was used to test an hypothesized morphological relationship between vault form and cranial capacity relative to length of the chondrocranium. Ninety-five adult male Czech skulls were measured for vault form expressed as length, width and height of the brain case; the chondrocranium was represented by nasion-basion and basion-opisthion lengths. In terms of explained variation, the first and most important dimension of covariation between vault and chondrocranial variables was size. The second most significant dimension of covariation expressed the hypothesized shape relationships--i.e., overall size being equal, the shorter the chondrocranial base relative to cranial capacity, the shorter and wider the vault. Furthermore, the competing hypothesis that vault form is determined by facial length proved untenable since facial length was predictive of vault shape only when measured as prosthion-basion, a measure that incorporates basal length. When corrected for basal length, facial length is unrelated to vault form. The results are consistent with the assumption that phylogenetic and microevolutionary trends toward brachycephaly in man stem from changes in the relationship between two components of skull growth, the chondrocranial base and the brain.

Sex assessment of the femur: a test of a new method

Simple and multiple discriminant functions using mid-shaft femoral circumference for the determination of sex were used to test a sexing method recently proposed by Black. The method was able to correctly assign sex for 82% of the sample, which consisted of 115 North American White femora of verified age and sex. Circumference proved as accurate as any other criteria that have been used in sexing the femur. This suggests a usefulness beyond the limited archaelogical scope originally proposed by Black.

Pharmacology of some acetylcholine homologues

1. The acetates of several long chain (3 to 12 methylene groups) analogues of choline have been prepared and their pharmacological properties studied.2. None of the compounds had a high level of activity at the post-ganglionic parasympathetic acetylcholine receptors. The lower members of the series showed weak agonist activity and the homologues with 8 to 10 methylene groups had very weak anticholinergic activity.3. All the compounds had a depolarizing action at the acetylcholine receptors of the neuromuscular junction and of sympathetic ganglia. At the neuromuscular junction there were two peaks of stimulant activity, one with the hexamethylene and one with the dodecamethylene homologue, whereas at the ganglion there was only one peak, with the hexamethylene homologue.4. The ganglion-stimulant activity of the higher members of the series was blocked by pretreatment with the anticholinesterase drug dyflos, whereas the activity of lower members was either unaffected by such treatment or slightly potentiated.5. The results are discussed in terms of possible spatial arrangements of acetylcholine receptor units in the neuromuscular junction and the ganglion.

The synthesis and pharmacology of some 1,4,5,6-tetrahydropyrimidines

1. Several 1- and 2-substituted, and 1,2-disubstituted, 1,4,5,6-tetrahydropyrimidines have been prepared and their toxicological and pharmacological properties have been investigated.2. In general the compounds were neuromuscular blocking agents with the monosubstituted members of the series showing a depolarizing type of activity and the disubstituted compounds a non-depolarizing type.3. The toxicity to mice of some of the monosubstituted compounds was increased by pretreatment of the animals with SKF 525A, but the toxicity of the disubstituted compounds was unaffected.4. The results obtained with these compounds are not at variance with a suggestion made previously that nicotinic action at the neuromuscular junction can result from an interaction between drug and receptor at two points separated by about 4 A.