A serological comparison of the three morphological phases of coccidioides immitis: Complement fixation tests with a Pooled antiserum obtained from rabbits with experimental Coccidioidomycosis

Summary A sonicated spherule preparation was more reactive than a sonicated arthrospore antigen in complement fixation tests with a pooled serum from rabbits with experimental coccidioidomycosis. The reactivity of the sonicated spherule approximated the reactivity of coccidioidin. When the sonicated spherule was separated into its supernatant and sediment fractions, both preparations exhibited serological activity.

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Zusammenfassung Ein mit Schallwellen hergestelltes Kügelchen-Präparat war activer in dem Komplement-Tests mit Blutserum von Kaninchen mit einer Coccidioidomycosisinfektion als ein mit Schallwellen hergestelltes Arthrosporantigen. Die Reaktivität der mit Schallwellen hergestellten Kügelchen war der des Coccidioidin ähnlich. Wurden diese Kügelchen in Niederschlag und Lösung getrennt, so hatten beide Präparate serologische Aktivität.

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Part of a dissertation submitted to the Graduate School of Duke University in partial fulfillment of requirements for the Ph.D. degree.This work was supported by contract with the Department of the Army, Fort Detrick, Frederick, Maryland.In conducting the research reported herein, the investigators adhered to Guide for Laboratory Animal Facilities and Care established by the Committee on the Guide for Laboratory Animal Facilities and Care of the Institute of Laboratory Animal Resources, NAS—NRC.     

Spherules in the serology of Coccidioides immitis. II. Complement fixation tests with human sera

Soluble and particulate spherule antigens fixed complement in tests with anti—C. immitis sera. However, the soluble antigen proved more active than the particulate one. Cross reactions were noted between the spherule antigens and anti—H. capsulatum and anti—B. dermatitidis sera. Following enzymatic treatment of the particulate preparation a soluble antigen was obtained which formed two bands with anti—C. immitis serum and one band with anti-H. capsulatum serum in an agar gel double diffusion test.     

Exploitation of marine turtles in the Indian Ocean

Marine turtles long have been of great value to peoples of the Indian Ocean, nutritionally, economically, and culturally. Once directed primarily toward subsistence, the hunting of marine turtles for international trade has increased; today their populations are often so depleted that they are not only insignificant as resources, but are endangered. An understanding of exploitation is imperative to guarantee future populations, yet available information is sketchy. Subsistence hunting is an ambiguous term, since the most intense exploitation is for export. Historically this has involved Chelonia and Eretmochelys, whose populations are now much reduced. Yet, newly discovered populations (Lepidochelys especially) are being exploited, under the stimulus of new foreign markets (e.g., leather), and their fates seem even less hopeful than those of long-exploited populations. Moreover subsistence hunting for immediate local consumption has led to depletion of nesting and feeding populations of turtles in areas where protein sources are in great demand and human population densities high. Neither the future nor the solution to this dilemma is clear, but it is obvious that economic considerations must be carefully considered, and ecological arguments alone are insufficient to manage these resources.     

Endocardiosis in rhesus monkeys

Endocardiosis was diagnosed as an incidental finding in two rhesus monkeys. The gross and histologic appearance of the lesions was described, and the similarity of this lesion to lesions of endocardiosis as found in dogs and man was discussed.The animals used in this study were handled in accordance with the Guide for Laboratory Animal Facilities and Care established by the National Academy of Science, National Research Council.     

Role of mitogen-activated protein kinase pathway in reactive oxygen species-mediated endothelin-1-induced β-myosin heavy chain gene expression and cardiomyocyte hypertrophy

Endothelin-1 (ET-1) has been found to increase cardiac -myosin heavy chain (-MyHC) gene expression and induce hypertrophy in cardiomyocytes. ET-1 has been demonstrated to increase intracellular reactive oxygen species (ROS) in cardiomyocytes. The exact molecular mechanism by which ROS regulate ET-1-induced -MyHC gene expression and hypertrophy in cardiomyocytes, however, has not yet been fully described. We aim to elucidate the molecular regulatory mechanism of ROS on ET-1-induced -MyHC gene expression and hypertrophic signaling in neonatal rat cardiomyocytes. Following stimulation with ET-1, cultured neonatal rat cardiomyocytes were examined for ³H-leucine incorporation and -MyHC promoter activities. The effects of antioxidant pretreatment on ET-1-induced cardiac hypertrophy and mitogen-activated protein kinase (MAPKs) phosphorylation were studied to elucidate the redox-sensitive pathway in cardiomyocyte hypertrophy and -MyHC gene expression. ET-1 increased ³H-leucine incorporation and -MyHC promoter activities, which were blocked by the specific ET_A receptor antagonist BQ-485. Antioxidants significantly reduced ET-1-induced ³H-leucine incorporation, -MyHC gene promoter activities and MAPK (extracellular signal-regulated kinase, p38, and c-Jun NH₂ -terminal kinase) phosphorylation. Both PD98059 and SB203580 inhibited ET-1-increased ³H-leucine incorporation and -MyHC promoter activities. Co-transfection of the dominant negative mutant of Ras, Raf, and MEK1 decreased the ET-1-induced -MyHC promoter activities, suggesting that the Ras-Raf-MAPK pathway is required for ET-1 action. Truncation analysis of the -MyHC gene promoter showed that the activator protein-2 (AP-2)/specificity protein-1 (SP-1) binding site(s) were(was) important cis-element(s) in ET-1-induced -MyHC gene expression. Moreover, ET-1-induced AP-2 and SP-1 binding activities were also inhibited by antioxidant. These data demonstrate the involvement of ROS in ET-1-induced hypertrophic responses and -MyHC expression. ROS mediate ET-1-induced activation of MAPK pathways, which culminates in hypertrophic responses and -MyHC expression. Tzu-Hurng Cheng, Neng-Lang Shih: These authors have equally contributed to this work     

Onset of coccidioidomycosis in mouse lung after intravenous injection

Summary Intravenous injection of mice with a massive dose ofCoccidioides immitis fungal elements caused a moderate inflammatory response after 6 hours. It was composed of small focal collections of lymphocytes and neutrophils surrounding the rounded fungal elements in the mouse lungs. No further change was noted at 24 hours. Spherules with endospores varying in diameter from 15 to 40 were seen at 48 and 54 hours. Neutrophils persisted throughout this time and increased only minimally; the lymphocytic response was more marked at these later observations.In conducting the research reported here, the investigators adhered to Principles of Laboratory Animal Care as established by the National Society for Medical Research.     

Sulfide oxidation in Ectothiorhodospira abdelmalekii. Evidence for the catalytic role of cytochrome c-551

A cytochrome c-551 was isolated and purified from Ectothiorhodospira abdelmalekii. It is a small acidic haemoprotein with a molecular weight of 9,500, an isoelectric point of 3.5 and a redox potential of-7 mV at pH 7.0. It showed three maxima in the reduced state (=551, =529, =417). The best purity index (A₂₈₀/A₄₁₇) obtained was 0.29. During sulfide oxidation to elemental sulfur a considerable amount of polysulfides were transiently accumulated. The digestion experiment can be taken to indicate that cytochrome c-551 is localized on the outside of the cell membrane. The addition of cytochrome c-551 to a suspension of spheroplasts stimulated the velocity of sulfide oxidation. These experiments support the interpretation that cytochrome c-551 may be a sulfide: acceptor oxidoreductase.In memory of Prof. Yousef Abd-el-Malek, who died in a traffic accident February 12, 1983     

The role of muscle development in the transition to endothermy in nestling bank swallows,Riparia riparia

Summary We examined the transition from ectothermy to endothermy in nestling bank swallows (Riparia riparia) by measuring the peak metabolic response to cold (PMR) in groups of nestlings. Additionally aerobic capacity, as assessed by citrate synthase activity (CS), and contractile function, as assessed by myofibrillar ATPase activity (mATPase) were measured in the pectoralis and mixed leg muscles during development. During the first 65% of their growth (from 2–12 g) bank swallows do not increase their metabolic rate in response to cold (Fig. 1). Between 12 and 16 g the PMR increased from 4 to more than 10 ml O₂ (g·h)^–1. Citrate synthase activity increased throughout development, starting at 20 moles (min·g fresh mass)^–1 in both tissues and increasing to 150 and 50 moles (min·g)^–1 in the pectoralis and leg muscles, respectively (Fig. 5). The augmented aerobic capacity combined with large increases in muscle mass undoubtedly contributes to the improved thermoregulatory abilities of older nestlings. However, muscle mass and aerobic capacity increase continuously and do not show the sharp transition noted in PMR. In the leg muscle mATPase activity is constant throughout growth, but in the pectoralis muscle it undergoes an abrupt increase from 0.5 moles (min·mg myofibrillar protein)^–1 in animals weighing less than 12 g to 0.9 moles (min·mg)^–1 in nestlings weighing more than 15 g (Fig. 6). The similar pattern of development of PMR and mATPase suggests a critical role for muscle development in the transition to endothermy in this species.Abbreviations CS citrate, synthase - mATPase myofibrillar adenosine triphosphatase - PMR peak metabolic rate during cold stress - rate of oxygen consumption     

Comparative efficiencies of bispecific F(ab′γ)2 and chimeric mouse/human IgG antibodies in recruiting cellular effectors for cytotoxicity via Fcγ receptors

Summary The three forms of Fc receptor carried by monocytes (FcRI, II) and natural killer (NK) cells (FcRIII) are all capable of mediating cell lysis. Here we compare the use of F(ab)₂ bispecific antibodies, specifically targetting individual FcR, and chimeric IgG mouse/human antibodies which are capable of targetting all FcR, for their ability to mediate target cell destruction. The derivatives are prepared by linking hinge sulphydryl residues via tandem thioether bonds, using a bismaleimide crosslinker: Fab from an anti-FcR mAb linked to Fab from a common anti-target mAb (BsAb), or Fab from the common anti-target mouse antibody linked to human Fc (FabFc or bisFabFc). All the derivatives targetting chick red blood cells gave efficient lysis, although different effector cell donors yielded differences in both the lytic levels achieved and the comparative efficiencies of derivatives. In contrast, significant lysis of the guinea pig lymphoblastic leukaemia, L₂C, regularly resulted only via the anti-FcRIII BsAb and the chimeric derivatives. These results suggest that the chimeric, Fc-containing derivatives mediate tumour cell lysis principally through FcRIII on NK cells. This is in contrast to the situation with the chick red blood cells where the chimeric derivatives appear capable of lysing erythrocytes by utilizing either monocytes or NK cells, because significant (50%) lysis occurred with effector cell populations magnetically depleted through either FcRII or FcRIII. A major difference between these two types of antibody derivative was their ability to function in the presence of high concentrations of normal human Fc. The lysis mediated by BsAb reactive with FcRI or II was unaffected by the presence of human Fc at 2.5 mg/ml (a concentration comparable with that yielded by IgG in plasma) whereas the BsAb recognizing FcRIII and all the Fc-containing derivatives were completely inhibited.This work has been supported by Tenovus, the Cancer Research Campaign, the Leukaemia Research Fund, Italfarmaco, Milano, Italy and the Imperial Cancer Research Fund     

The ontogenesis of calcium-binding protein in fetal rat kidney

Summary The presence of calcium-binding protein (CaBP) in the nucleus and cytoplasm of epithelial cells of renal tubules varies with the physiologic state. As part of a study to determine whether or not intranuclear CaBP precedes intracytoplasmic CaBP in the same cell, we used peroxidase-labeled antibody against human renal CaBP to localize CaBP in fetal rat kidney tubules. This paper reports examination of kidneys from rats on each day of gestation from the 10th to term (21 days) and on each of the first seven postnatal days. CaBP was first detected in fetal rat kidneys on the 19th gestational day. The histochemical staining reaction that revealed the CaBP was less intense than that produced in kidneys from adult animals, but its distribution was like that in adults, with some cells having no CaBP, others having it in the cytoplasm only, in the nucleus only, or in both. By the seventh postnatal day the staining reaction was similar to the adult patterns in all respects. Send offprint request to:commander,Department of Comparative Medicine, Letterman Army Institute of Research, Attn. : Research Librarian, Presidio of San Francisco, CA 94129, USAIn conducting the research described in this report, the investigators adhered to the Guide for Laboratory Animal Facilities and Care, as promulgated by the Committee on the Guide for Laboratory Animal Resources, National Academy of Sciences-National Research CouncilThe opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense     

Cytochemical evidence for the presence of actin in the nucleus of the voodoo lily appendix

Immunoflorescence microscopy of sections of the voodoo lily Sauromatum guttatum appendix stained with monoclonal antibodies against -smooth muscle actin and cytoplasmic actin revealed different staining intensity of different parts of the cell. The anti-cytoplasmic-actin recognized antigens present mainly in the cytoplasm, and the anti--smooth muscle-actin recognized more intensively antigens present in the nuclei. A positive staining of the nucleus was also obtained with FITC–phalloidin confirming the presence of actin in its filamenous form in the nucleus. The presence of a nuclear -smooth muscle-actin-like protein was further confirmed by confocal laser microscopy. On Western blots, the two anti-actins labelled a protein band that comigrated with standard actin at the approximate molecular weight of 43kDa. Several other proteins interacted with the two antibodies to a different degree. The monoclonal antibodies against -tubulin subunit stained only the periphery of the cytoplasm and anti-pan cytoplasmic myosin stained the cytoplasm weakly. On a Western blot, anti--tubulin subunit primarily recognized a protein band at the appropriate molecular weight of 50kDa. This is the first cytochemical evidence for the presence of -smooth muscle-actin-like protein in the plant nucleus.     

Relationships between external nitrate availability,nitrate uptake and expression of nitrate reductase in roots of barley grown in N-limited split-root cultures

Despite the large number of studies of nitrate metabolism in plants, it remains undetermined to what extent this key plant system is controlled by overall plant N nutrition on the one hand, and by the nitrate ion itself on the other hand. To investigate these questions, V _max for nitrate uptake (high-affinity range), and nitrate reductase (NR) mRNA and activity, were measured in roots of N-limited barley (Hordeum vulgare L. cv. Golf) grown under conditions of constant relative addition of nitrate, with the seminal roots split between two culture compartments. The total amount of nitrate added per unit time (0.09·d^-1) was distributed between the two root parts (subroots) in ratios of 1000, 982, 955, 9010, 8020, and 5050. These nitrate-addition ratios resulted in nitrate fluxes ranging from 0 to 23 mol nitrate·g^-1 DW root·h^-1, while the external nitrate concentrations varied between 0 and 1.2 M. The apparent V _max for net nitrate uptake showed saturation-type responses to nitrate flux maintained during preceding growth. The flux resulting in half-maximal induction of nitrate uptake was approximately 4 mol nitrate·g^-1 DW root·h^-1, corresponding to an external nitrate concentration of 0.7 M. The activity of NR and levels of NR mRNA did not saturate within the range of nitrate fluxes studied. None of the parameters studied saturated with respect to the steady-state external nitrate concentration. At the zero nitrate addition — the 0%-root — initial uptake activity as determined in short-term ¹⁵N-labelling experiments was insignificant, and NR activity and NR mRNA were not detectable. However, nitrate uptake was rapidly induced, showing that the 0%-root had retained the capacity to respond to nitrate. These results suggest that local nitrate availability has a significant impact on the nitrate uptake and reducing systems of a split-root part when the total plant nitrate nutrition is held constant and limiting.Abbreviation NR nitrate reductase This work was supported by the Lars Hierta Memory Foundation, the Royal Swedish Academy of Sciences, and by the Swedish Natural Science Research Council via project grants (to C.-M.L. and B.I.) and visiting scientist grant (to W.H.C.). We thank Mrs. Ellen Campbell for technical advice, and Mrs. Judith V. Purves, Long Ashton Research Station, Long Ashton, UK, for analyses of ¹⁵N-labelling in tissue samples.     

Locomotor response of the goldfish to polarized light and itse-vector

Summary The locomotor orientation of eleven goldfish, 20–25 cm long, was monitored during periods varying between 24 hours and 8 1/2 days, to verify the response to a depolarized and polarized sky, 100 cm in diameter, and to abrupt 90 ° degree rotation of thee-vector. The monitor consisted of a cylindrical tank with 16 peripheral compartments (Fig. 1) to which the fish had free access. Entry into and exit from each compartment was electronically recorded. The distribution of entries, which had no cyclical relationship with the compartments in depolarized light, became significantly symmetrical and bimodal in polarized light with the preferred compartments oriented parallel with thee-vector. Abrupt 90 ° rotation of the vector counter clockwise maintained this relationship during the entire duration of the recordings (up to 17 hours) (Fig. 2). The mean of the orientation angles of the fish on leaving compartments aligned with thee-vector were significantly higher than those from the remaining compartments (Fig. 3). This behavior tended to keep the locomotor orientation parallel with thee-vector as the fish moved between compartments. A strong cyclical relationship between these orientation angles and the compartments of origin was present in polarized but absent in depolarized light. Counter clockwise 90 ° rotation of thee-vector maintained the cyclic behavior of angles but the relationship between the larger means and thee-vector shifted over one or two compartments. This shift disappeared in clockwise rotation. This phenomenon may be due to one of these directions being unnatural. The results demonstrate a pronounced sensitivity and response toe-vector orientation in the goldfish. The sensory mechanism remains unknown.The authors are greatly indebted to Dr. T. H. Waterman for a critical review and discussion of the results here presented.     

Immunology of histoplasmosis: Humoral and cellular activity from a polysacchari-de-protein complex and its deproteinized fraction in experimentally immunized mice

In a previous publication it was reported that a polysaccharide-protein complex (PPC), sensitive to -glucosidase, was isolated from Histoplasma capsulatum. This complex was strongly reactive in an agar gel diffusion assay with sera from patients with histoplasmosis, but was unreactive with sera from patients with coccidioidomycosis. Here, the studies with human sera have been expanded and attempts were made to determine the response of mice immunized with nonviable H. capsulatum or Cocccidioides immitis to PPC or its deproteinized fraction (D-PPC) using more sensitive tests for antibody and including also test for cell-mediated immunity. Histoplasmin and coccidioidin were compared with PPC or its deproteinized fraction (D-PPC) in all assays. In a counterimmunoelectrophoresis (CIE) assay, PPC and D-PPC reacted only with sera from patients with histoplasmosis, whereas cross reactions were noted with histoplasmin and coccidioidin using heterologous sera. Cross-reaction were observed with all four antigen preparations and both types of antisera using a micro complement fixation assay. The assay for macrophage migration inhibitory factor (MIF) was also relatively nonspecific, in that inhibition occurred with cells from animals sensitized with Histoplasma or Coccidioides using both homologous and heterologous antigens. In the footpad assay, histoplasmin and coccidioidin were highly cross-reactive in animals sensitized with the heterologous fungus, but the PPC and D-PPC from H. capsulatum elicited significant reactions only in animals sensitized with Histoplasma.     

Differents comportements de 22 souches d'Emmonsia Cifferi et Montemartini, 1959, champignon moniliace,dans les poumons de souris de laboratoire,Comparaison avec leur morphologie parasitaire es vitro

The 22 strains of Emmonsia Ciferri & Montemartini 1959, inoculated intranasally to laboratory mice are not equally virulent. One month after the inoculation, 15 of the strains had produced adiaspores 120 to 190 m in diameter in the lung. Another strain produced adiaspores measuring 44 m and 2 others measuring 20 m or 10 m. The remaining 4 strains did not develop in the lung tissue. Four thermophilic strains, which in vitro have adiaspores measuring 8 to 15 m, had adiaspores reaching 120–180 m in vivo. Neither budding nor endosporulation could be observed in any adiaspore.

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Differents comportements de 22 souches d'Emmonsia Cifferi et Montemartini, 1959, champignon moniliace, dans les poumons de souris de laboratoire, Comparaison avec leur morphologie parasitaire es vitro

Résumé Vingt deux souches d'Emmonsia Ciferri et Montemartini, 1959, inoculées par instillations nasales à des souris de laboratoire, ne présentent pas toutes la même virulence. Un mois après l'inoculation, quinze d'entre elles donnent dans le parenchyme pulmonaire des adiaspores de 120–190 m de diamètre, une souche, des adiaspores de 44 m, une autre, des adiaspores de 20 m et une autre, des adiaspores de 10 m. Les quatre dernières ne se développent pas dans les poumons. Quatre souches thermophiles, donnant in vitro de petites adiaspores de 8–15 m, différencient in vivo des adiaspores de 120–180 m. Aucun phénomène de bourgeonnement ou d'endosporulation n'est observé sur aucune adiaspore.

     

Modeling Virus Adsorption in Batch and Column Experiments

Experiments with batch suspensions, recirculating columns and flow-through columns have been carried out involving a sandy soil and five bacteriophages: MS2, PRD1, X174, Q and PM2. In batch and recirculating column experiments, attachment and detachment rate coefficients were determined by fitting a two-parameter (attachment and detachment) model. In general, attachment and detachment rate coefficients were not found to be significantly different between the two kinds of experiments. There was one exception, however: MS2 appeared to detach faster in the presence of strong advective flow. In the case of flow-through column experiments, it is shown that a two-site model, with adsorption to equilibrium and kinetic sites, fits the breakthrough curves of all the phages, except PM2, satisfactorily. A one-site kinetic model was found to be appropriate for phage PM2. A small proportion of bacteriophages MS2, PRD1, and Q adsorbed to equilibrium sites, whereas a large proportion of X174 adsorbed to equilibrium sites. Such a distinction between adsorption to equilibrium and kinetic sites cannot be made in the case of batch or recirculating column experiments. Kinetic attachment rate coefficients were found to be significantly higher for the bacteriophages with presumably stronger negative charge. This may be ascribed to the presence of multivalent cations. Under these conditions, bacteriophage X174 appears to behave more conservatively than more negatively charged viruses, and may then be a better choice as a relatively conservative tracer for virus transport through the subsurface.     

Metabolic engineering for direct lactose utilization by Saccharomyces cerevisiae

A recombinant strain of Saccharomyces cerevisiae, secreting -galactosidase from Kluyveromyces lactis, grew efficiently with more than 60 g lactose l^–1. The growth rate (0.23 h^–1) in a cheese-whey medium was close to the highest reported hitherto for other recombinant S. cerevisiae strains that express intracellular -galactosidase and lactose-permease genes. The conditions for growth and -galactosidase secretion in this medium were optimized in a series of factorial experiments. Best results were obtained at 23 °C for 72 h. Since the recombinant strain produced less than 3% ethanol from the lactose, it was also assayed for the production of fructose 1,6-bisphosphate from cheese whey, and 0.06 g l^–1 h^–1 were obtained.     

An efficient adventitious shoot regeneration system for Zhanhua winter jujube (Zizyphus jujuba Mill.) using leaf explants

The direct induction of adventitious shoots from leaf explants obtained from adult plants of Zhanhua winter jujube, an elite variety of Zizyphus jujuba Mill., is reported. The percentage of leaf explants producing shoots and the average number of shoots per explant were significantly improved when 10-day-old leaves were explanted onto Woody Plant Medium and maintained initially in the dark. The plant growth regulator thidiazuron (TDZ) was effective in stimulating shoot regeneration from leaf explants of Zhanhua winter jujube. The highest efficiency of shoot formation was observed with a 20-day culture in the dark on WPM containing 4.54 M TDZ and 2.85 M indoleacetic acid (IAA). The regenerated shoots were transferred to MS medium containing 0.89 M benzyladenine and 5.77 M gibberellic acid for growth. When the shoots were about 2 cm in height, they were transferred to Nitsch medium supplemented with 1.14 M IAA and 2.46 M indolebutyric acid to induce rooting. This system of adventitious shoot production from leaf explants of adult plants could be useful for the genetic engineering and polyploidization of winter jujube.     

Antialgal activity of a hepatotoxin-producing cyanobacterium,Microcystis aeruginosa

Antimicrobial activity of toxin produced by a freshwater bloom-forming cyanobacterium Microcystis aeruginosa has been studied. When tested against certain green algae, cyanobacteria, heterotrophic bacteria and fungi, the toxin inhibited growth of only green algae and cyanobacteria. The toxin has been partially purified employing Thin layer chromatography (TLC) and High-performance liquid chromatography (HPLC) techniques and appears to be microcystin-LR (leucine–arginine). Both crude and purified toxins showed toxicity to mice, the clinical symptoms in test mice being similar to those produced by hepatotoxin. Purified toxin at a concentration of 50 g ml^–1 caused complete inhibition of growth followed by cell lysis in Nostoc muscorum and Anabaena BT1 after 6 days of toxin addition. Addition of toxin (25 g ml^–1) to the culture suspensions of the Nostoc and Anabaena strains caused instant and drastic loss of O₂ evolution. Furthermore a marked reduction (about 87%) in the ¹⁴CO₂ uptake was also observed at a concentration of 50 g ml^–1. Besides its inhibitory effects on photosynthetic processes, M. aeruginosa toxin (50 g ml^–1) also caused 90% loss of nitrogenase activity after 8 h of its addition. Experiments performed with ¹⁴C-labelled toxin indicate that the toxin uptake by cyanobacterial cells occurs both in light and dark. These results demonstrate that the toxin is strongly algicidal and point to the possibility that it may have an important role in establishment and maintenance of toxic blooms of M. aeruginosa in freshwater ecosystems. The relative significance of the hepatotoxic effect and the algicidal effect of the toxin is discussed with reference both to survival and dominance of M. aeruginosa in nature.     

Genetic control of glucokinase activity in mice

Inbred strains of mice were surveyed for liver glucokinase activity. Mice of all strains studied could be distributed into three groups with high, intermediate, and low levels of enzyme activity. Genetic analysis using crosses and backcrosses with prototype high (C3H/HeJ) and low (RF/J) strains revealed that glucokinase activity was controlled by a single gene. The name glucokinase and gene symbol Gk are suggested for this gene. The Gk ^a allele designates the strain with high glucokinase activity, while Gk ^b represents the allele in the strain with the low enzyme activity. The interaction of fasting and diabetes on the activity of glucokinase in these two strains is described.Supported in part by United States Public Health Service Research Grant CA 05873 from the National Cancer Institute. The Jackson Laboratory is fully accredited by the American Association for the Accreditation of Laboratory Animal Care.