Microbiome preterm birth DREAM challenge: Crowdsourcing machine learning approaches to advance preterm birth research

Every year, 11% of infants are born preterm with significant health consequences, with the vaginal microbiome a risk factor for preterm birth. We crowdsource models to predict (1) preterm birth (PTB; <37 weeks) or (2) early preterm birth (ePTB; <32 weeks) from 9 vaginal microbiome studies representing 3,578 samples from 1,268 pregnant individuals, aggregated from public raw data via phylogenetic harmonization. The predictive models are validated on two independent unpublished datasets representing 331 samples from 148 pregnant individuals. The top-performing models (among 148 and 121 submissions from 318 teams) achieve area under the receiver operator characteristic (AUROC) curve scores of 0.69 and 0.87 predicting PTB and ePTB, respectively. Alpha diversity, VALENCIA community state types, and composition are important features in the top-performing models, most of which are tree-based methods. This work is a model for translation of microbiome data into clinically relevant predictive models and to better understand preterm birth.

Microbiome Preterm Birth DREAM Challenge: Crowdsourcing Machine Learning Approaches to Advance Preterm Birth Research

Globally, every year about 11% of infants are born preterm, defined as a birth prior to 37 weeks of gestation, with significant and lingering health consequences. Multiple studies have related the vaginal microbiome to preterm birth. We present a crowdsourcing approach to predict: (a) preterm or (b) early preterm birth from 9 publicly available vaginal microbiome studies representing 3,578 samples from 1,268 pregnant individuals, aggregated from raw sequences via an open-source tool, MaLiAmPi. We validated the crowdsourced models on novel datasets representing 331 samples from 148 pregnant individuals. From 318 DREAM challenge participants we received 148 and 121 submissions for our two separate prediction sub-challenges with top-ranking submissions achieving bootstrapped AUROC scores of 0.69 and 0.87, respectively. Alpha diversity, VALENCIA community state types, and composition (via phylotype relative abundance) were important features in the top performing models, most of which were tree based methods. This work serves as the foundation for subsequent efforts to translate predictive tests into clinical practice, and to better understand and prevent preterm birth.

Deep immune phenotyping reveals similarities between aging, Down syndrome, and autoimmunity

[Figure: see text].

Autoreactive T cell receptors with shared germline-like α chains in type 1 diabetes

Human islet antigen reactive CD4⁺ memory T cells (IAR T cells) play a key role in the pathogenesis of autoimmune type 1 diabetes (T1D). Using single-cell RNA sequencing (scRNA-Seq) to identify T cell receptors (TCRs) in IAR T cells, we have identified a class of TCRs that share TCRα chains between individuals (“public” chains). We isolated IAR T cells from blood of healthy, new-onset T1D and established T1D donors using multiplexed CD154 enrichment and identified paired TCRαβ sequences from 2767 individual cells. More than a quarter of cells shared TCR junctions between 2 or more cells (“expanded”), and 29/47 (~62%) of expanded TCRs tested showed specificity for islet antigen epitopes. Public TCRs sharing TCRα junctions were most prominent in new-onset T1D. Public TCR sequences were more germline like than expanded unique, or “private,” TCRs, and had shorter junction sequences, suggestive of fewer random nucleotide insertions. Public TCRα junctions were often paired with mismatched TCRβ junctions in TCRs; remarkably, a subset of these TCRs exhibited cross-reactivity toward distinct islet antigen peptides. Our findings demonstrate a prevalent population of IAR T cells with diverse specificities determined by TCRs with restricted TCRα junctions and germline-constrained antigen recognition properties. Since these “innate-like” TCRs differ from previously described immunodominant TCRβ chains in autoimmunity, they have implications for fundamental studies of disease mechanisms. Self-reactive restricted TCRα chains and their associated epitopes should be considered in fundamental and translational investigations of TCRs in T1D.

The Cyclin-Dependent Kinase 8 (CDK8) Inhibitor DCA Promotes a Tolerogenic Chemical Immunophenotype in CD4+ T Cells via a Novel CDK8-GATA3-FOXP3 Pathway

Immune health requires innate and adaptive immune cells to engage precisely balanced pro- and anti-inflammatory forces. We employ the concept of chemical immunophenotypes to classify small molecules functionally or mechanistically according to their patterns of effects on primary innate and adaptive immune cells. The high-specificity, low-toxicity cyclin-dependent kinase 8 (CDK8) inhibitor 16-didehydro-cortistatin A (DCA) exerts a distinct tolerogenic profile in both innate and adaptive immune cells. DCA promotes regulatory T cells (Treg) and Th2 differentiation while inhibiting Th1 and Th17 differentiation in both murine and human cells. This unique chemical immunophenotype led to mechanistic studies showing that DCA promotes Treg differentiation in part by regulating a previously undescribed CDK8-GATA3-FOXP3 pathway that regulates early pathways of Foxp3 expression. These results highlight previously unappreciated links between Treg and Th2 differentiation and extend our understanding of the transcription factors that regulate Treg differentiation and their temporal sequencing. These findings have significant implications for future mechanistic and translational studies of CDK8 and CDK8 inhibitors.

Spatial Variation of the Native Colon Microbiota in Healthy Adults

The microbiome has been implicated in the development of colorectal cancer and inflammatory bowel diseases. The specific traits of these diseases vary along the axis of the digestive tract. Further, variation in the structure of the gut microbiota has been associated with both diseases. We profiled the microbiota of the healthy proximal and distal mucosa and lumen to better understand how bacterial populations vary along the colon. We used a two-colonoscope approach to sample proximal and distal mucosal and luminal contents from the colons of 20 healthy subjects that had not undergone any bowel preparation procedure. The biopsies and home-collected stool were subjected to 16S rRNA gene sequencing, and random forest classification models were built using taxa abundance and location to identify microbiota specific to each site. The right mucosa and lumen had the most similar community structures of the five sites we considered from each subject. The distal mucosa had higher relative abundance of Finegoldia, Murdochiella, Peptoniphilus, Porphyromonas, and Anaerococcus The proximal mucosa had more of the genera Enterobacteriaceae, Bacteroides, and Pseudomonas The classification model performed well when classifying mucosal samples into proximal or distal sides (AUC = 0.808). Separating proximal and distal luminal samples proved more challenging (AUC = 0.599), and specific microbiota that differentiated the two were hard to identify. By sampling the unprepped colon, we identified distinct bacterial populations native to the proximal and distal sides. Further investigation of these bacteria may elucidate if and how these groups contribute to different disease processes on their respective sides of the colon. Cancer Prev Res; 11(7); 393-402. ©2018 AACR.

Oceanic protists with different forms of acquired phototrophy display contrasting biogeographies and abundance

This first comprehensive analysis of the global biogeography of marine protistan plankton with acquired phototrophy shows these mixotrophic organisms to be ubiquitous and abundant; however, their biogeography differs markedly between different functional groups. These mixotrophs, lacking a constitutive capacity for photosynthesis (i.e. non-constitutive mixotrophs, NCMs), acquire their phototrophic potential through either integration of prey-plastids or through endosymbiotic associations with photosynthetic microbes. Analysis of field data reveals that 40-60% of plankton traditionally labelled as (non-phototrophic) microzooplankton are actually NCMs, employing acquired phototrophy in addition to phagotrophy. Specialist NCMs acquire chloroplasts or endosymbionts from specific prey, while generalist NCMs obtain chloroplasts from a variety of prey. These contrasting functional types of NCMs exhibit distinct seasonal and spatial global distribution patterns. Mixotrophs reliant on 'stolen' chloroplasts, controlled by prey diversity and abundance, dominate in high-biomass areas. Mixotrophs harbouring intact symbionts are present in all waters and dominate particularly in oligotrophic open ocean systems. The contrasting temporal and spatial patterns of distribution of different mixotroph functional types across the oceanic provinces, as revealed in this study, challenges traditional interpretations of marine food web structures. Mixotrophs with acquired phototrophy (NCMs) warrant greater recognition in marine research.

On the intrinsic sterility of 3D printing

3D printers that build objects using extruded thermoplastic are quickly becoming commonplace tools in laboratories. We demonstrate that with appropriate handling, these devices are capable of producing sterile components from a non-sterile feedstock of thermoplastic without any treatment after fabrication. The fabrication process itself results in sterilization of the material. The resulting 3D printed components are suitable for a wide variety of applications, including experiments with bacteria and cell culture.

csrT Represents a New Class of csrA-Like Regulatory Genes Associated with Integrative Conjugative Elements of Legionella pneumophila

Bacterial evolution is accelerated by mobile genetic elements. To spread horizontally and to benefit the recipient bacteria, genes encoded on these elements must be properly regulated. Among the legionellae are multiple integrative conjugative elements (ICEs) that each encode a paralog of the broadly conserved regulator csrA. Using bioinformatic analyses, we deduced that specific csrA paralogs are coinherited with particular lineages of the type IV secretion system that mediates horizontal spread of its ICE, suggesting a conserved regulatory interaction. As a first step to investigate the contribution of csrA regulators to this class of mobile genetic elements, we analyzed here the activity of the csrA paralog encoded on Legionella pneumophila ICE-βox. Deletion of this gene, which we name csrT, had no observed effect under laboratory conditions. However, ectopic expression of csrT abrogated the protection to hydrogen peroxide and macrophage degradation that ICE-βox confers to L. pneumophila. When ectopically expressed, csrT also repressed L. pneumophila flagellin production and motility, a function similar to the core genome's canonical csrA. Moreover, csrT restored the repression of motility to csrA mutants of Bacillus subtilis, a finding consistent with the predicted function of CsrT as an mRNA binding protein. Since all known ICEs of legionellae encode coinherited csrA-type IV secretion system pairs, we postulate that CsrA superfamily proteins regulate ICE activity to increase their horizontal spread, thereby expanding L. pneumophila versatility.

IMPORTANCE

ICEs are mobile DNA elements whose type IV secretion machineries mediate spread among bacterial populations. All surveyed ICEs within the Legionella genus also carry paralogs of the essential life cycle regulator csrA. It is striking that the csrA loci could be classified into distinct families based on either their sequence or the subtype of the adjacent type IV secretion system locus. To investigate whether ICE-encoded csrA paralogs are bona fide regulators, we analyzed ICE-βox as a model system. When expressed ectopically, its csrA paralog inhibited multiple ICE-βox phenotypes, as well as the motility of not only Legionella but also Bacillus subtilis. Accordingly, we predict that CsrA regulators equip legionellae ICEs to promote their spread via dedicated type IV secretion systems.

Monster potential meets potential monster: pros and cons of deploying genetically modified microalgae for biofuels production

Biofuels production from microalgae attracts much attention but remains an unproven technology. We explore routes to enhance production through modifications to a range of generic microalgal physiological characteristics. Our analysis shows that biofuels production may be enhanced ca fivefold through genetic modification (GM) of factors affecting growth rate, respiration, photoacclimation, photosynthesis efficiency and the minimum cell quotas for nitrogen and phosphorous (N : C and P : C). However, simulations indicate that the ideal GM microalgae for commercial deployment could, on escape to the environment, become a harmful algal bloom species par excellence, with attendant risks to ecosystems and livelihoods. In large measure, this is because an organism able to produce carbohydrate and/or lipid at high rates, providing stock metabolites for biofuels production, will also be able to attain a stoichiometric composition that will be far from optimal as food for the support of zooplankton growth. This composition could suppress or even halt the grazing activity that would otherwise control the microalgal growth in nature. In consequence, we recommend that the genetic manipulation of microalgae, with inherent consequences on a scale comparable to geoengineering, should be considered under strict international regulation.

Placing microalgae on the biofuels priority list: a review of the technological challenges

Microalgae provide various potential advantages for biofuel production when compared with 'traditional' crops. Specifically, large-scale microalgal culture need not compete for arable land, while in theory their productivity is greater. In consequence, there has been resurgence in interest and a proliferation of algae fuel projects. However, while on a theoretical basis, microalgae may produce between 10- and 100-fold more oil per acre, such capacities have not been validated on a commercial scale. We critically review current designs of algal culture facilities, including photobioreactors and open ponds, with regards to photosynthetic productivity and associated biomass and oil production and include an analysis of alternative approaches using models, balancing space needs, productivity and biomass concentrations, together with nutrient requirements. In the light of the current interest in synthetic genomics and genetic modifications, we also evaluate the options for potential metabolic engineering of the lipid biosynthesis pathways of microalgae. We conclude that although significant literature exists on microalgal growth and biochemistry, significantly more work needs to be undertaken to understand and potentially manipulate algal lipid metabolism. Furthermore, with regards to chemical upgrading of algal lipids and biomass, we describe alternative fuel synthesis routes, and discuss and evaluate the application of catalysts traditionally used for plant oils. Simulations that incorporate financial elements, along with fluid dynamics and algae growth models, are likely to be increasingly useful for predicting reactor design efficiency and life cycle analysis to determine the viability of the various options for large-scale culture. The greatest potential for cost reduction and increased yields most probably lies within closed or hybrid closed-open production systems.

Effect of Staphylococcus enterotoxin B on the concurrent CD8(+) T cell response to influenza virus infection

Bacterial superantigens have potent in vivo effects. Respiratory viral infections are often associated with secondary bacterial infections, raising the likelihood of exposure to bacterial superantigens after the initiation of the anti-viral immune response. In this study, the general and V beta-specific effects of exposure to Staphylococcal enterotoxin B (SEB) during influenza virus infection on both the ongoing acute and the subsequent recall CD8(+) T cell responses were analyzed, using the well-characterized murine influenza model system and tetrameric MHC/peptide reagents to directly identify virus-specific T cells. The results show that although superantigen exposure during the primary viral infection caused delayed viral clearance, there was remarkably little effect of SEB on the magnitude or TCR repertoire of the ongoing cytolytic T cell response or on the recall response elicited by secondary viral infection. Thus, despite the well-characterized immunomodulatory effects of SEB, there was surprisingly little interference with concurrent anti-viral immunity.

The relationship between the dissolved inorganic carbon concentration and growth rate in marine phytoplankton

A range of marine phytoplankton was grown in closed systems in order to investigate the kinetics of dissolved inorganic carbon (DIC) use and the influence of the nitrogen source under conditions of constant pH. The kinetics of DIC use could be described by a rectangular hyperbolic curve, yielding estimations of KG(DIC) (the half saturation constant for carbon-specific growth, i.e. C mu) and mu max (the theoretical maximum C mu). All species attained a KG(DIC) within the range of 30-750 microM DIC. For most species, NH4+ use enabled growth with a lower KG(DIC) and/or, for two species, an increase in mu max. At DIC concentrations of > 1.6 mM, C mu was > 90% saturated for all species relative to the rate at the natural seawater DIC concentration of 2.0 mM. The results suggest that neither the rate nor the extent of primary productivity will be significantly limited by the DIC in the quasi-steady-state conditions associated with oligotrophic oceans. The method needs to be applied in the conditions associated with dynamic coastal (eutrophic) systems for clarification of a potential DIC rate limitation where cells may grow to higher densities and under variable pH and nitrogen supply.

Utilization of dissolved inorganic carbon (DIC) and the response of the marine flagellate Isochrysis galbana to carbon or nitrogen stress

The growth of the marine flagellate Isochrysis galbana was followed in batch cultures at four concentrations of dissolved inorganic carbon (DIC), from C- and N-replete lag phase into C- and/or N-deplete stationary phase. Organic buffers were omitted from the growth medium, and culture pH was maintained at 8.30±0.05 by the addition of acid or alkali. The responses of the flagellate to N stress included an increase in the C∶N ratio, and decreases in the ratios of glutamine (Gln)∶glutamate (Glu) and Chl a∶C, and the cell Chl a quota. Conversely, the responses to C stress included a decrease in the C∶N ratio, and increases in the ratios of Gln∶Glu and Chl a∶C, and the cell Chl a quota. The relationship between carbon-specific growth rate (C-μ), and the concentration of extracellular DIC, [DIC]_ext , exhibited Michaelis-Menten type kinetics with a half saturation constant, K_G(DIC) , of 81 μM. Comparative studies of the diatom Phaeodactylum tricornutum showed similar results, although the value of K_G(DIC) was lower at 30 μM.

In vivo proliferation of naïve and memory influenza-specific CD8(+) T cells

The virus-specific CD8(+) T cell response has been analyzed through the development, effector, and recovery phases of primary and secondary influenza pneumonia. Apparently, most, if not all, memory T cells expressing clonotypic receptors that bind a tetrameric complex of influenza nucleoprotein (NP)(366-374) peptide+H-2D(b) (NPP) are induced to divide during the course of this localized respiratory infection. The replicative phase of the recall response ends about the time that virus can no longer be recovered from the lung, whereas some primary CD8(+)NPP(+) T cells may proliferate for a few more days. The greatly expanded population of CD8(+)NPP(+) memory T cells in the lymphoid tissue of secondarily challenged mice declines progressively in mean prevalence over the ensuing 100 days, despite the fact that at least some of these lymphocytes continue to cycle. The recall of cell-mediated immunity thus is characterized by massive proliferation of the antigen-specific CD8(+) set, whereas the extent of lymphocyte turnover in the absence of cognate peptide is variable, at a low level, and can be influenced by intercurrent infection.

Protection against a lethal avian influenza A virus in a mammalian system

The question of how best to protect the human population against a potential influenza pandemic has been raised by the recent outbreak caused by an avian H5N1 virus in Hong Kong. The likely strategy would be to vaccinate with a less virulent, laboratory-adapted H5N1 strain isolated previously from birds. Little attention has been given, however, to dissecting the consequences of sequential exposure to serologically related influenza A viruses using contemporary immunology techniques. Such experiments with the H5N1 viruses are limited by the potential risk to humans. An extremely virulent H3N8 avian influenza A virus has been used to infect both immunoglobulin-expressing (Ig+/+) and Ig-/- mice primed previously with a laboratory-adapted H3N2 virus. The cross-reactive antibody response was very protective, while the recall of CD8(+) T-cell memory in the Ig-/- mice provided some small measure of resistance to a low-dose H3N8 challenge. The H3N8 virus also replicated in the respiratory tracts of the H3N2-primed Ig+/+ mice, generating secondary CD8(+) and CD4(+) T-cell responses that may contribute to recovery. The results indicate that the various components of immune memory operate together to provide optimal protection, and they support the idea that related viruses of nonhuman origin can be used as vaccines.

Virus-specific immunity after gene therapy in a murine model of severe combined immunodeficiency

Human severe combined immunodeficiency (SCID) can be caused by defects in Janus kinase 3 (JAK3)-dependent cytokine signaling pathways. As a result, patients are at high risk of life-threatening infection. A JAK3 -/- SCID mouse model for the human disease has been used to test whether transplant with retrovirally transduced bone marrow (BM) cells (JAK3 BMT) could restore immunity to an influenza A virus. The immune responses also were compared directly with those for mice transplanted with wild-type BM (+/+ BMT). After infection, approximately 90% of the JAK3 BMT or +/+ BMT mice survived, whereas all of the JAK3 -/- mice died within 29 days. Normal levels of influenza-specific IgG were present in plasma from JAK3 BMT mice at 14 days after respiratory challenge, indicating restoration of B cell function. Influenza-specific CD4(+) and CD8(+) T cells were detected in the spleen and lymph nodes, and virus-specific CD8(+) effectors localized to the lungs of the JAK3 BMT mice. The kinetics of the specific host response correlated with complete clearance of the virus within 2 weeks of the initial exposure. By contrast, the JAK3 -/- mice did not show any evidence of viral immunity and were unable to control this viral pneumonia. Retroviral-mediated JAK3 gene transfer thus restores diverse aspects of cellular and humoral immunity and has obvious potential for human autologous BMT.

Thymic lymphoproliferative disease after successful correction of CD40 ligand deficiency by gene transfer in mice

Inherited deficiency of the CD40 ligand (X-linked hyper-IgM syndrome) is characterized by failure of immunoglobulin isotype switching and severe defects of cell-mediated immunity. To test the potential for gene transfer therapy to correct this disorder, we transduced murine bone marrow or thymic cells with a retroviral vector containing the cDNA for the murine CD40 ligand (CD40L) and injected them into CD40L-/- mice. Even low-level, constitutive expression of the transgene stimulated humoral and cellular immune functions in these mice. With extended follow-up, however, 12 of 19 treated mice developed T-lymphoproliferative disorders, ranging from polyclonal increases of lymphoblasts to overt monoclonal T-lymphoblastic lymphomas that involved multiple organs. Our findings show that constitutive (rather than tightly regulated), low-level expression of CD40L can produce abnormal proliferative responses in developing T lymphocytes, apparently through aberrant interaction between CD40L+ and TCRalphabeta+CD40+ thymocytes. Current methods of gene therapy may prove inappropriate for disorders involving highly regulated genes in essential positions in proliferative cascades.

Body images and obesity risk among black females: a review of the literature

The prevalence of obesity among Black women has reached epidemic proportions. Some researchers have suggested that the body images of Black females may contribute to their high risk for obesity by inhibiting motivation for weight control. While a number of empirical studies have examined the body images of Black females, findings are complex and at times, inconsistent. For example, some studies show that Black females consider overweight bodies more attractive, while other studies show that Black females prefer normal-weight bodies. Divergent findings may be due, in part, to the multidimensional nature of body image. Inconsistencies may also be due to differences between the Black females sampled. Methodological problems, including the use of measures that have been validated among Black females, the use of various weight-for-height standards, and the inconsistent analyses of or lack of physiological data, also may contribute to conflicting results. This review addresses the complexity of body image findings among a heterogeneous Black female population and the relationship between their body images and obesity risk. Implications for effective obesity treatment programs and suggestions for improvements in future body image studies are also discussed.

Virus-specific CD8+ T cells in primary and secondary influenza pneumonia

Virus-specific CD8+ effector T cells (eCTL) are enriched in the lungs of mice with primary influenza pneumonia, though later detection of memory T cells (mCTL) in the mediastinal lymph nodes (MLN) or spleen by peptide-based staining protocols is at the limits of flow cytometric analysis. Respiratory challenge with an H3N2 virus months after H1N1 priming induces a massive recall response, which reduces virus titers 2-3 days earlier than in nave controls. Influenza-specific mCTL produce interferon-gamma within 6 hr, but still take 4-5 days to localize to the infected respiratory tract. The delay reflects that the recall response develops first in the MLN, which contains relatively few mCTL. The response to a subdominant epitope is less obvious after secondary challenge.

Malignant melanoma simulating a seborrheic keratosis: a case report

This is a case report of malignant melanoma presenting with both clinical and histopathologic features of a seborrheic keratosis. Not a rare phenomenon, this report emphasizes the importance of biopsy to evaluate apparent seborrheic keratoses. We believe that this phenomenon is best considered a presentation of melanoma. Diminished routine histopathologic evaluation of apparent seborrheic keratoses may well increase the number of mistaken diagnoses in such cases.

Evidence for production of paralytic shellfish toxins by bacteria associated with Alexandrium spp. (Dinophyta) in culture

A substantial proportion of bacteria from five Alexandrium cultures originally isolated from various countries produced sodium channel blocking (SCB) toxins, as ascertained by mouse neuroblastoma assay. The quantities of SCB toxins produced by bacteria and dinoflagellates were noted, and the limitations in comparing the toxicities of these two organisms are discussed. The chemical nature of the SCB toxins in selected bacterial isolates was determined as paralytic shellfish toxins by pre- and postcolumn high-performance liquid chromatography, capillary electrophoresis-mass spectrometry, and enzyme immunoassay.

Subungual keratoacanthoma masquerading as a chronic paronychia

Subungual keratoacanthoma is a rare, benign tumor of the digits. Patients present with progressive fusiform swelling, erythema, and tenderness, usually affecting a single digit on the radial side of the hand. A cup-shaped lytic lesion of the distal phalanx is a uniform finding on radiography. Delay in diagnosis and misdiagnosis are common because of the rarity of the lesion and difficulties with histological differentiation from subungual squamous cell carcinoma. Accurate diagnosis requires a high index of suspicion, a careful history, and histological evaluation. The natural progression of the disease appears to be continued growth with ongoing destruction of the distal phalanx. Proper treatment involves surgical removal of the mass by curettage and close follow-up for at least 2 years to monitor for local recurrence.

Relations between carbon and nitrogen during growth of Nannochloropsis oculata (Droop) Hibberd under continuous illumination

Growth of the marine eustigmatophyte Nannochloropsis oculata (Droop) Hibberd was Followed through two periods of batch growth from stationary phase until cessation of net C-fixation. Growth continued for two generations after exhaustion of the N-source (100μM NH₄ ⁺ ), with an increase in the cell C/N mass ratio from 6 to 28. N-deprived cells had a larger mean volume (130%) than N-replete cells. Intracellular concentrations of carotenoids and Chla correlated with cell-N until exhaustion of the N-source, when Chla ml^-1 of culture declined significantly. The contribution of intracellular amino-N to cell-N was less than 3% throughout exponential and stationary phases. The major intracellular amino acids were glutamate (Glu), glutamine (Gln) and alanine; concentrations of tyrosine (on a population basis) increased steadily during N-deprivation. The intracellular concentrations of other amino acids showed fluctuations corresponding with changes in growth rate (e.g. arginine) or cell-N (e.g. glycine). The intracellular ratio of Gln/Glu reached a peak of more than 26 within 3 h of inoculation of stationary phase cells into fresh medium, before falling to around 0.6 during exponential growth, and then remained below 0.1 after NH₄ ^- exhaustion. Of the extracellular amino acids, concentrations of alanine and serine remained relatively constant throughout, while those of glycine, glutamate and of total dissolved free amino acids increased during exponential and early post-exponential phases, before levelling off at 1.4μM amino-N. The behaviour of Nannochloropsis oculata is contrasted with the growth and physiology of Isochrysis galbana.

Non-steady state ammonium-limited growth of the marine phytoflagellate, Isochrysis galbana Parke

The marine phytoflagellate Isochrysis galbana Parke was followed through two consecutive cycles of ammonium-limited growth. There was a significant (48 h) lag in cell division following the resupply of ammonium but no discernible lag in biomass growth, which led to a transient increase in the mean biomass per cell. Cell carbon and Coulter volume were linearly correlated. Net chlorophyll synthesis was closely linked to the absorption of extracellular N, while carotenoid synthesis continued until C fixation ceased. Photosynthetic activity (C fixation per unit chlorophyll) varied significantly with the cellular N:C ratio. A rapid rise in the ratio of glutamine to glutamate (0.1-6) during the first 24 h after nitrogen supply indicated a temporary imbalance in the flux of C and N into biomass synthesis. Intracellular ammonium accounted for less than 4% of total cell N, while free intracellular amino acids accounted for 3-5%. Nevertheless, cell numbers were able to double after the medium became depleted of ammonium, presumably by recycling and redistributing high molecular weight intracellular N.

Maggot therapy revisited: a case study

This article chronicles a personal experience with the care of a patient with chronic, recalcitrant stasis ulcers who presented with maggot infestation. A case study format is used. A brief history, technique, and benefits of maggot therapy are also included.

Ammonium assimilation by the nitrate-utilizing yeast, Candida nitratophila

Ammonium-nitrogen was assimilated rapidly by nitrogen-replete cultures of the nitrate-utilizing yeast, Candida nitratophila as long as a suitable source of carbon was available. These cultures contained high activities of an NADPH-dependent glutamate dehydrogenase with a relatively high affinity for ammonium (K_m = 0.27 mM) and high glutamine synthetase activity. Both enzyme activities were apparently derepressed when glutamine-grown cultures were starved of nitrogen or transferred to nitrate medium. Nitrogen-deficient cultures also contained NADH-dependent glutamate synthase activity that was inhibited by azaserine in vitro. Ammonium assimilation in vivo, was inhibited by methionine sulphoximine whilst addition of azaserine resulted in an accumulation of intracellular glutamine and an inhibition of glutamate production. Our results suggest that, in C. nitratophila, there is a potential for ammonium assimilation via both the glutamate dehydrogenase pathway and the glutamine synthetase/glutamate synthase pathway with the latter pathway predominating in nitrogen-deficient cells.

Changes in intracellular amino acids and glutamine : glutamate during N-deprivation and feeding in Candida nitratophila

In the yeast, Candida nitratophila Shifrine et Phaff, the intracellular concentrations of α-amino acids decreased rapidly during N-deprivation, with the ratio of glutamine: glutamate (Gln: Glu) falling from 07 in NH₄ ⁺ -grown cells, or 0.5 in NO₃ ^- -grown cells, to 0.1 after 1 h. Addition of NH₄ ⁺ to N-deprived cultures resulted in rapid increases in glutamate, glutamine and alanine with Gln: Glu exceeding 1.5 within 30 min. Recovery of other amino acids, such as arginine, was much slower. Addition of NO³ , resulted in a less rapid increase in the concentration of some intracellular amino acids, including glutamate and glutamine, while levels of arginine continued to fall for 30 min after addition of this N-source. Gln: Glu was slow to rise in NO₃ ^- pulsed cells. Addition of NH₄ ⁺ to cells growing on NO^3- produced little change over the following 2 h other than decreases in arginine and histidine. Carbon deprivation resulted in a rapid decrease in levels of glutamate, glutamine and alanine, but not of aspartate (which this yeast is unable to use as a sole C-source for growth) or arginine. Gln: Glu increased during C-deprivation but fell within 10 min to normal levels on addition of glucose. It is concluded that, in C. nitratophila, Gln:Glu values correlate well with C-N status.

Eyelid pigment implantation: early and late histopathology

Full-thickness sections of upper and lower eyelids were obtained from patients who had eyelid pigment implantation performed by one surgeon. These four patients represented eyelid pigment implantation at varying postoperative stages ranging from 6 months to 4 years. Light microscopic evaluation revealed pigment within dermis and superficial orbicularis muscle. Light and electron microscopic evaluation revealed the vast majority of the pigment to be located intracellularly, primarily within macrophages. No foreign-body reaction was seen around the implanted material. Electron probe analysis of the pigment showed only the presence of iron. Analysis of the unused pigment revealed small amounts of silica and magnesium. These substances could not be identified by electron probe analysis in the eyelid tissues.

A comprehensive internal quality control system for a large cytology laboratory

The British Columbia Cervical Cytology Program is operated through the Central Laboratory at the Cancer Control Agency in Vancouver and processes all of the gynecologic Papanicolaou smears collected by 3,200 physicians throughout the province of British Columbia. The laboratory receives approximately 2,400 smears per day, and the program currently processes in excess of 500,000 smears annually. This article describes the methods that have been developed for ensuring that adequate quality control is present in the screening and interpretation of half a million smears per year, both at the cytotechnologist and at the cytopathologist level. The results of the quality control program, which was considerably modified in 1985, are also presented. The modified program shows a significant improvement in the number of undercalled and overcalled cases detected in two comparable six-month periods.

EFFECTS OF NITROGEN DEPRIVATION ON RATES OF UPTAKE OF NITROGENOUS COMPOUNDS BY THE DIATOM, PHAEODACTYLUM TRICORNUTUM BOHLIN

A culture of Phaeodactylum tricornutum was suspended in nitrogen-free growth medium under conditions which favoured photosynthesis. Nitrogen deprivation was continued for 60 h and, over this period, samples were removed for measurement of rates of uptake of arginine, guanine, nitrate, nitrite, lysine, methylammonium and urea. In another experiment, the effect of nitrogen deprivation on the ability to take up methylammonium and ammonium was compared. Cells developed, or increased, their abilities to take up all of these nitrogen compounds during nitrogen deprivation but ability to take up the two amino acids increased only slowly whereas the ability to take up the other compounds increased markedly during the first few hours of deprivation. The maximum rates of uptake developed were some 50-100 × higher for methylammonium and ammonium than they were for the other compounds. The rates of uptake are compared with those necessary to sustain growth.

Regressing atypical histiocytosis: a cutaneous proliferation of atypical neoplastic histiocytes with unexpectedly indolent biologic behavior

Regressing atypical histiocytosis (RAH) of skin is a cutaneous noduloulcerative proliferation of atypical neoplastic histiocytes with concomitant polymorphous inflammation, frequently pronounced epidermal hyperplasia, and an unexpectedly indolent biologic course. Spontaneous regression and recurrence without systemic spread were the course in follow-up periods of over six years. Histopathologically, characteristic-appearing atypical mononuclear and multinucleated "RAH" cells showed erythrophagocytosis as well as ultrastructural, surface marker, and enzyme cytochemical features indicating histiocytic differentiation. Cytogenetic analysis showed aneuploidy and several marker chromosomes including 14q+. Its benign biologic course clearly distinguished this entity from malignant histiocytosis, large cell lymphoma, and Hodgkin's disease. The histiocytic atypical cells further distinguished it from the T-cell lesions of the skin, such as mycosis fungoides and lymphomatoid papulosis. This entity is readily confused with malignant lymphoreticular disease, melanoma, or squamous carcinoma.

Treatment of an epithelioma cuniculatum plantare by local excision and a plantar skin flap

Differentiation between benign and malignant lesions on the plantar surfaces is sometimes clinically impossible and requires biopsy. A case of epithelioma cuniculatum plantare is reported that was futilely treated for years as a plantar wart and then upon proper diagnosis was successfully treated by complete excision and rotation of a flap of plantar skin.

The effect of ileal bypass on sterol balance and plasma cholesterol in the White Carneau pigeon

The effect of ileal bypass on steady-state sterol balance and plasma cholesterol was studied in sham operated (SO) and ileal bypass (IB) White Carneau pigeons 6 months (Group I) and 18 months (Group II) after surgery while fed their usual cholesterol-free diet. Unlike what has been noted in other animals, the bile acid (BA) and neutral sterol (NS) excretion (mg/kg per day) in IB was not statistically different from that in SO. Group I: BA, 40.2 (SO) vs 39.0 (IB); NS, 13.3 (SO) vs 17.3 (IB). Group II: BA, 55.7 (SO) vs 54.1 (IB); NS, 9.57 (SO) vs 8.84 (IB). IB pigeons had only slightly lower plasma cholesterol levels (postoperative) than SO pigeons. Group I, 329 (SO) vs 271 (IB) mg/dl (P less than 0.05); Group II, 374 (SO) vs 312 (IB) mg/dl. This study indicates that the response to ileal bypass by White Carneau pigeons in terms of cholesterol excretion and plasma cholesterol changes is different than what has been observed in other species.