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.

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.

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.

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.

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 NO3- 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.

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.

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.

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, KG(DIC) , of 81 µM. Comparative studies of the diatom Phaeodactylum tricornutum showed similar results, although the value of KG(DIC) was lower at 30 µM.

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 (Km = 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.

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.

Photodynamic therapy for superficial bladder cancer.

In photodynamic therapy, a photosensitizing drug is activated by visible light and in the presence of oxygen, results in local cell death. This evolving modality is now being used to treat and palliate a very wide variety of human solid tumors and carcinoma-in-situ lesions. With regard to bladder cancer, advances in drug development and modern light delivery techniques mean that photodynamic therapy shows promise in the treatment of superficial bladder cancer resistant to conventional treatments.

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.

Twenty-four hour access to a CD-ROM surgical database has educational and patient management benefits.

This study determined whether 24 h access to current surgical literature via a personal computer CD-ROM was of relevance to the junior surgeon managing acute surgical referrals. Over a 2 month period, a total of 53 acute surgical referrals were assessed and initially managed by a single basic surgical trainee. The Medline database was searched using Silver Platter software for current surgical literature regarding aetiology and management after the initial patient assessment. Of the 53 searches made (mean search time 7 min 22 s), 20 (38%) were judged to have produced information that increased basic surgical trainee knowledge and a further 9 (17%) changed patient management. By contrast, 24 (45%) of searches did not reveal helpful information. The availability of a surgical database that provides the trainee with abstracts of the current literature is valuable both for the educational development of the surgeon and improvement of patient care.

Suspected testicular torsion: a survey of clinical practice in North West England.

Several aspects of the management of suspected testicular torsion are controversial. A questionnaire was mailed to all 33 consultant urologists in the North West region of England to elicit their policies for routine clinical management. 29 of 33 questionnaires were returned (2 incomplete). As regards radiological investigation, 4 consultants always request ultrasound examination; the others do not favour routine imaging. When the diagnosis of testicular torsion is confirmed at operation, all consultants would perform bilateral testicular fixation, although with considerable variations in technique; most use Vicryl sutures (66%) and three-point fixation (57%). One-third would do an ipsilateral orchidopexy if there was no clear evidence of testicular torsion at operation. The variation revealed by this survey prompted an attempt to formulate a protocol for management. A review of the published work indicates that, in cases of proven testicular torsion, treatment should include bilateral fixation with delayed-absorption or non-absorbable sutures; fixation should be at three points. When torsion is not found at operation, there is no evidence of benefit from orchidopexy.

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.

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.

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.