Kinetic properties, and location of nonspecific phosphomonoesterases in subcellular fractions of fasciola hepatica

Optimal activity was recorded at pH 4.5–5 and pH 9.0–9.5 and specific activity was seen to be 0.013 μmoles of p-nitrophenyl phosphate/min/mg protein at 37 C at pH 4.5 and 0.00169 μmoles at pH 9.0. The ratio of acid to alkaline phosphatase was 7.7:1.0. The K_m for acid phosphatase (EC 3.1.3.2) was 0.5 mM with a V_max of 0.0128 units/mg protein and 0.2mM for alkaline phosphatase (EC 3.1.3.1) with a V_max of 0.00175 units/mg protein. Acid phosphatase activity was optimal at 60 C and alkaline at 37 C. Linearity of enzyme activity was observed with time after the first 15 min of incubation and with homogenate concentration. KCN at 20 mM inhibited 82% of activity at pH 9.0 but also 91.5% activity at pH 4.5. NaF at 10^?2M inhibited 92% of activity at pH 4.5 but had no effect at pH 9.0. The two flukicides rafoxanide and nitroxynil at 20mM had little effect on activity at pH 9.0 and pH 4.5. Enzyme activity at pH 4.5 was found to be greatest in the microsomal fraction with high activity in the lysosomal and soluble fractions. Histochemically, alkaline phosphatase was restricted to the excretory system, vitellaria, and uterus while acid phosphatase was found in the integument and gastrodermis.     

The respiratory chain of Paramecium tetraurelia in wild type and the mutant Cl1 I. Spectral properties and redox potentials

1. Purified mitochondria have been prepared from wild type Paramecium tetraurelia and from the mutant Cl₁ which lacks cytochrome aa₃. Both mitochondrial preparations are characterized by cyanide insensitivity. Their spectral properties and their redox potentials have been studied.2. Difference spectra (dithionite reduced minus oxidized) of mitochondria from wild type P. tetraurelia at 77 K revealed the α peaks of b-type cytochrome(s) at 553 and 557 nm, of c-type cytochrome at 549 nm and a-type cytochrome at 608 nm. Two α peaks at 549 and 545 nm could be distinguished in the isolated cytochrome c at 77 K. After cytochrome c extraction from wild type mitochondria, a new peak at 551 nm was unmasked, probably belonging to cytochrome c₁. The a-type cytochrome was characterized by a split Soret band with maxima at 441 and 450 nm. The mitochondria of the mutant Cl₁ in exponential phase of growth differed from the wild type mitochondria in that cytochrome aa₃ was absent while twice the quantity of cytochrome b was present. In stationary phase, mitochondria of the mutant were characterized by a new absorption peak at 590 nm.3. Cytochrome aa₃ was present at a concentration of 0.3 nmol/mg protein in wild type mitochondria and ubiquinone at a concentration of 8 nmol/mg protein both in mitochondria of the wild type and the mutant Cl₁. Cytochrome aa₃ was more susceptible to heat than cytochromes b and c,c₁.4. CO difference spectra at 77 K revealed two different Co-cytochrome complexes. The first, found only in wild type mitochondria, was a typical CO-cytochrome a₃ complex characterized by peaks at 596 and 435 nm and troughs at 613 and 450 nm. The second, found both in mitochondria of the wild type and the mutant, was a CO-cytochrome b complex with peaks at 567, 539 and 420 nm and a trough at 558-549 nm. Both complexes are photo-dissociable.5. Spectral evidence was obtained for interaction of cyanide with the a-type cytochrome (shift of the α peak at 77 K from 608 to 605 nm), but not with the b-type cytochrome.6. The mid-point potentials of the different cytochromes at neutral pH are as follows: cytochrome aa₃ 235 and 395 mV, cytochrome c,c₁ 233 mV, cytochromes b 120 mV.     

Most of the homoeologous pairing at metaphase I in wheat-rye hybrids is not chiasmatic

The use of telomeric C-bands in wheat-rye hybrids has made it possible to distinguish three types of wheat-wheat (1B^L) and wheat-rye associations (a, end-to-end extremely distal; b, end-to-ed distal; and c, interstitial) between homoeologous chromosomes at different metaphase I stages (early, middle and late) and also to estimate the actual recombination frequencies for such associations at anaphase I. There was a decrease of the a and b association frequencies during the different metaphase I stages, whereas the c type remained without variation in all stages. A good fit between the frequencies of c associations at metaphase I and the number of recombinant chromosomes at anaphase I, assuming a maximum of one chiasma per bond, was found; however, there was no correspondence between metaphase I and anaphase I data when all associations (a + b + c) were considered. In addition, rye-rye homologous pairing was observed at metaphase I, but no evidence for rye-rye recombination was found at anaphase I. The results indicate that most of end-to-end (a and b) homoeologous and nonhomologous associations are actually nonchiasmatic and are a remnant of prophase pairing.     

Inhibition of photosynthesis by chilling in the light

The photosynthetic activity of leaf slices from Spinacia oleracea L., Cucumis sativus L. and Nerium oleander L. was measured in 25° C immediately after preincubation for 2.5 h at various photon flux densities (PFD) with chilling at 4°C, or at a moderate (450 μmol m⁻² s⁻¹) PFD with various temperatures below 25°C. Inhibition of photosynthesis was evident in C. sativus and 45°C-grown N. oleander after preincubation at 4°C at all PFD. The inhibition was most severe at fluxes in excess of the moderate PFD under which the plants were grown. Photosynthesis in S. oleracea and 20°C-grown N. oleander was not inhibited at 4°C unless the PFD was in excess of this moderate PFD. The inhibition of photosynthesis was initiated in C. sativus below 13°C, and in 45°C-grown N. oleander below 8°C. A phase transition in the polar lipids from the thylakoids of these plants was detected at about the same temperatures. For S. oleracea and 20°C-grown N. oleander preincubated under the same conditions, there was no inhibition of photosynthesis and no phase transition above 0°C. These results show that some component of photosynthesis was disrupted in the light at temperatures below that of the phase transition in the thylakoid polar lipids.     

Methanogen genotypes involved in methane formation during anaerobic decomposition of Microcystis blooms at different temperatures

The main goal of this work was to determine which methanogens were present during the anaerobic degradation of Microcystis biomass in the water columns of freshwater lakes. Simulation experiments were performed in which 30 ml Microcystis slurries were anaerobically incubated in 60 ml airtight bottles at three temperatures (15, 25, and 35 °C) for over 90 days. The production of CH₄ was monitored, and the methanogenic community was analyzed by cloning and sequencing the mcrA genes in samples incubated at the three different temperatures. In total, four clusters were detected at different temperatures by phylogenetic analysis of mcrA genes; these included members of Methanomicrobiales, Methanobacteriaceae, and Methanosarcina. An apparent linkage between temperature and phylogeny of the methanogenic community was observed: Methanomicrobiales and Methanobacteriaceae dominated the incubation system at the lower temperatures of 15 and 25 °C, whereas Methanosarcina prevailed at 35 °C. The dominance of these hydrogenotrophic methanogens suggested that, at least at lower temperatures, H₂ and CO₂ might be the primary substrates for CH₄ production during Microcystis anaerobic decomposition.     

Specific photoisomerization of retinal in squid rhodopsin and metarhodopsin

The composition of retinal isomers in the photosteady-state mixtures formed from squid rhodopsin and metarhodopsin was determined by high-pressure liquid chromatography. A large amount of 9-cis-retinal was obtained at liquid N₂ temperature when rhodopsin was irradiated with orange light, but only small quantities of 9-cis-retinal were obtained at 15°C. Scarcely any 9-cis-retinal was produced from metarhodopsin by irradiation at liquid N₂ temperature. A large quantity of 7-cis-retinal was found in the photoproduct of rhodopsin irradiated at solid carbon dioxide temperature, but not at 15°C and liquid N₂ temperature. 7-cis-Retinal was not produced from metarhodopsin at any temperatures. These results indicate that the photoisomerization of retinal is regulated by the structure of the retinal-binding site of this protein. The formation of 9-cis- and 7-cis-retinals is forbidden in the metarhodopsin protein.     

Effect of Soil Temperature on the Pathogenicity and Reproduction of Meloidogyne chitwoodi and M. hapla on Russet Burbank potato

Meloidogyne chitwoodi and M. hapla were pathogenic to both roots and tubers of Russet Burbank potato. Both species affected root growth at 15, 20, and 25 C, but not 30 C. Meloidogyne chitwoodi reprotluced best at 15, 20, and 25 C and M. hapla at 25 and 30 C. Reproduction of M. chitwoodi was reduced at 30 C; reproduction of M. hapla was reduced at 15 C and less at 20 C. The reproductive potential of M. chitwoodi was higher than that of M. hapla at 15, 20, and 25 C. M. hapla reproduced better at 30 C than did M. chitwoodi. M. chitwoodi infected potato tubers in higher numbers than did M. hapla.     

Studies on phytoplankton pigments in Porto Novo waters (India). I. Mangrove

The annual variations of phytoplankton pigments were studied from January to December, 1971, at two stations of the local mangrove (Pichavaram) environment. At these two stations, chlorophyll a varied from 2.90 to 35.06; chlorophyll b from 0 to 10.02 and chlorophyll c from 0 to 18.12 μg/l. Plant carotenoids varied from 1.56 to 13.83 MSPU/m³ and phaeopigments from 0 to 12.28 μg/l. The main (primary) peak of chlorophyll a was recorded during March at Station 1, and during June at Station 2.Secondary maxima occurred during June and August at Station 1, and during September at Station 2. During the period studied chlorophyll a was the dominant pigment at both the stations, followed by chlorophyll c and chlorophyll b in that order. The increase in the concentration of pigments was mainly due to the presence of phytoplankton species belonging to the genera such as Coscinodiscus, Rhizosolenia, Thalassiothrix, Melosira, Chaetoceros and Biddulphia. During October, phytoplankton was less and the pigment concentration was also low.     

Morphogenetic and diurnal variation of hypericin in some Hypericum species from Turkey during the course of ontogenesis

The genus Hypericum has received considerable interest from scientists, as it is a source of a variety of biologically active compounds including the hypericins. The present study was conducted to determine ontogenetic, morphogenetic and diurnal variation of the total hypericins content in some species of Hypericum growing in Turkey namely, Hypericum aviculariifolium subsp. depilatum var. depilatum (endemic), Hypericum perforatum and Hypericum pruinatum. The Hypericum plants were harvested from wild populations at vegetative, floral budding, full flowering, fresh fruiting and mature fruiting stages four times a day. Plants were dissected into stem, leaf and reproductive tissues, which were dried separately, and subsequently assayed for total hypericin content. The density of dark glands on leaves at full flowering plants was determined for each species. Floral parts had the highest hypericin content in all species tested. But diurnal fluctuation in the hypericin content of whole plant during the course of ontogenesis varied among the species. It reached the highest level at floral budding and tended to increase at night in H. aviculariifolium subsp. depilatum var. depilatum and H. pruinatum, whereas in H. perforatum hypericin content was the highest at full flowering and no diurnal fluctuation was observed. In general, hypericin content of leaves and whole plant was higher in H. aviculariifolium subsp. depilatum var. depilatum whose leaves had more numerous dark glands than those of the two other species.     

Effect of pH,irradiance and population size on the toxicity of Furadan to two species of Anabaena

In two selected nitrogen-fixing cyanobacterial speciesAnabaena fertilissima andAnabaena variabilis pH, irradiance and different inocula sizes considerably modified the toxic effect of 50 % effective concentration (EC 50) dose of the pesticideFuradan (carbofuran 75 DB). Maximum growth and chlorophyll (Chl)a content ofA. fertilissima was observed in the pH range of 8 - 9 and that ofA. variabilis at pH 7-8, while at acidic pH (5 - 6) and at pH above 9 these parameters were considerably retarded. Toxicity of the EC 50 dose ofFuradan was increased further at pH 5-6, whereas reduction in the toxicity to the test cyanobacteria was observed at pH 7.8 - 9.0. The experimental organisms grew comparatively better and synthesized higher amount of Chl a at an irradiance of 12.5 than at 7.5 or 2.5 W m^-2. The toxicity of EC 50 dose of the pesticide gradually decreased with the increasing irradiance. The toxic effect ofFuradan was larger when the initial cyanobacterial population concentration was low andvice versa.     

Growth Response of Three Vegetables to Smooth- and Crenate-Tailed Females of Three Species of Pratylenchus

The effect of morphological variants of females of Pratylenchus penetrans, P. neglectus, and P. crenatus on the growth of three vegetables was studied. Variants were characterized by having either a smooth or crenate tail terminus. Pea was inoculated with variants of P. penetrans, one female per seedling, and grown at light intensities ranging from 1,350 to 21,600 lux in a series of five experiments. Only crenate-tailed females of P. penetrans suppressed the growth of pea and only when pea was grown at 3,900 lux. Radish was inoculated with morphological variants of P. penetrans, P. neglectus, and P. crenatus, four females per seedling, and grown at 3,900 lux in two experiments. Again, truly creuate-tailed females of P. penetrans inhibited growth. The two variants of P. penetrans had a similar infectivity, greater than that of the other two species of Pratylenchus. Only crenate-tailed P. penetrans reproduced on radish. Onion was inoculated with variants of P. penetrans and P. crenatus, four females per seedling, and grown at 14 C at 12,900 lux. Again, only crenate-tailed P. penetrans inhibited growth. The variants of P. penetrans had a similar infectivity, greater than that of P. crenatus. Neither species reproduced on onion at low temperatures.     

Chromosomal Location Plays a Role in Regulation of Aflatoxin Gene Expression in Aspergillus parasiticus

The nor-1 gene in the filamentous fungus Aspergillus parasiticus encodes a ketoreductase involved in aflatoxin biosynthesis. To study environmental influences on nor-1 expression, we generated plasmid pAPGUSNNB containing a nor-1 promoter-β-glucuronidase (GUS) (encoded by uidA) reporter fusion with niaD (encodes nitrate reductase) as a selectable marker. niaD transformants of A. parasiticus strain NR-1 (niaD) carried pAPGUSNNB integrated predominantly at the nor-1 or niaD locus. Expression of the native nor-1 and nor-1::GUS reporter was compared in transformants grown under aflatoxin-inducing conditions by Northern and Western analyses and by qualitative and quantitative GUS activity assays. The timing and level of nor-1 promoter function with pAPGUSNNB integrated at nor-1 was similar to that observed for the native nor-1 gene. In contrast, nor-1 promoter activity in pAPGUSNNB and a second nor-1::GUS reporter construct, pBNG3.0, was not detectable when integration occurred at niaD. Because niaD-dependent regulation could account for the absence of expression at niaD, a third chromosomal location was analyzed using pAPGUSNP, which contained nor-1::GUS plus pyrG (encodes OMP decarboxylase) as a selectable marker. GUS expression was detectable only when pAPGUSNP integrated at nor-1 and was not detectable at pyrG, even under growth conditions that required pyrG expression. nor-1::GUS is regulated similarly to the native nor-1 gene when it is integrated at its homologous site within the aflatoxin gene cluster but is not expressed at native nor-1 levels at two locations outside of the aflatoxin gene cluster. We conclude that the GUS reporter system can be used effectively to measure nor-1 promoter activity and that nor-1 is subject to position-dependent regulation in the A. parasiticus chromosome.     

Properties of a cytostatic factor from Xenopus laevis eggs.

The cytoplasm of mature eggs of Xenopus laevis was found to contain a cytostatic factor (CSF) which induces cleavage arrest at metaphase when microinjected into one blastomere of a two-cell embryo of Xenopus laevis or Rana pipiens. The Rana CSF was found to be incapable of arresting mitosis in Xenopus embryos. Both Xenopus and Rana CSF were stabilized during the transfer procedure by Ca²⁺-chelation in the donor egg. The Xenopus CSF was not present in the germinal vesicle of immature oocytes, but arose in the cytoplasm at the time of germinal vesicle breakdown and subsequently disappeared at the time of fertilization or egg activation.     

Interrelationships of Meloidogyne arenaria and M. incognita on Tolerant Soybean

Reproduction of Meloidogyne arenaria race 2 was excellent on Centennial, Govan, and Kirby soybeans, the latter two of which have tolerance to this species. The M. incognita race 1 isolate reproduced poorly on Centennial, especially at the higher of two temperature regimes. Numbers of galls and egg masses of M. arenaria plus M. incognita in simultaneous equivalent infestations on Centennial did not differ from sequential infestations in which M. arenaria was added first and M. incognita was added to the same pots, 1,2, or 3 weeks later. However, at both 25 and 30 C, suppression of galls and egg masses occurred when inoculation of M. incognita preceded that of M. arenaria by 2 weeks. Generally, M. arenaria reproduced well at 25 or 30 C, whereas M. incognita reproduced better at 30 C. Kirby was tolerant to either nematode species at 25 and 30 C, but in combined infestations of M. arenaria and M. incognita there was evidence of synergistic growth suppression. Govan was tolerant of M. arenaria at 25 C but not at 30 C. Moreover, general plant growth was less vigorous for Govan at the higher temperature, whereas Centennial was much more vigorous at this temperature. Kirby grew equally well at both temperatures.     

Genetic variability of the length of postpartum anoestrus in Charolais cows and its relationship with age at puberty

Fertility records (n = 1 802) were collected from 615 Charolais primiparous and multiparous cows managed in an experimental herd over an 11-year period. The objectives of the study were to describe the genetic variability of the re-establishment of postpartum reproductive activity and the relationship with body weight (BW) and body condition score (BCS) at calving and age at puberty. The length of postpartum anoestrus was estimated based on weekly blood progesterone assays and on twice daily detection of oestrus behaviour. The first oestrus behaviour was observed 69 days (± 25 days s.d.) post-calving and the first positive progesterone measurement (≥ 1 ng mL^-1) was observed at 66 days (± 22 days s.d.) for the group of easy-calving multiparous suckling cows. Estimates of heritability and repeatability were h² = 0.12 and r = 0.38 respectively, for the interval from calving to first oestrus (ICO). Corresponding values were h² = 0.35 and r = 0.60 for the interval from calving to the first positive progesterone test (ICP). The genetic correlation between both criteria was high (r_g = 0.98). The genetic relationships between postpartum intervals and BW and BCS of the female at calving were negative: the genetic aptitude to be heavier at calving and to have high body reserves was related to shorter postpartum intervals. A favourable genetic correlation between age at puberty and postpartum intervals was found (r_g between 0.45 and 0.70). The heifers which were genetically younger at puberty also had shorter postpartum intervals.     

Regulatory characteristics of a fructose bisphosphatase from the blue-green bacterium Anacystis nidulans.

A specific fructose 1,6-bisphosphatase (EC 3.1.3.11) has been partially purified from the obligately autotrophic blue-green bacterium Anacystis nidulans. It was most active at pH 8.0. The K_m for fructose 1,6-bisphosphate was 0.088 mm at pH 8.0 and 0.105 mm at pH 7.0; the K_m for MgCl₂ was 0.95 mm at pH 8.0. Activity at netural pH was particularly sensitive to the MgCl₂ concentration. AMP was an allosteric inhibitor, 50% inhibition being exerted by 0.058 mm AMP at pH 7.0 and 0.085 mm AMP at pH 8.O. The way in which changes in intracellular pH and the concentrations of Mg²⁺ and AMP might influence the activity of the enzyme in the Calvin cycle, the oxidative pentose phosphate pathway and in glycolysis and gluconeogenesis is discussed.     

Esterase and acid phosphatase polymorphism in the fig tree (Ficus carica L.)

The genetics of two enzymatic loci, esterase (Est-D) and acid phosphatase (AcP-A), were studied by means of polyacrylamide gel electrophoresis in the fig tree (Ficus carica L.). Two codominant alleles are described at the Est-D locus and four codominant alleles at the AcP-A locus. Heterozygotes at the AcP-A locus have a hybrid band, thus showing that the AcP-A allozymes, are at least dimer molecules. Both loci are independent of the male sterility factor in F. carica. The polymorphism in four natural populations was investigated for both loci. A significant deficiency of heterozygotes was observed.     

Characterization and properties of an inulinase from a thermophilic bacteria

The inulinase of the thermophilic bacterial strain LCB41 (Bacillus sp.) was produced in fermentor using a mineral medium containing inulin as carbon source. The enzyme content was as high as the known inulinase producers and most of the activity was found in the culture medium. The enzyme was stable at high temperature and active at neutral and slightly basic pH. Fructose is liberated as the sole reaction product of inulin hydrolysis, classifying the enzyme as an exoinulinase. Inulin and sucrose were both hydrolyzed at appreciable rates with an (I/S) ratio of 0·40 and (V_m/K_m)₁/(V_m/K_m)_S = 9·9. The enzyme was less inhibited than yeast invertase or Kluyveromyces fragilis inulinase at high sucrose concentrations. The inulinase of strain LCB41 is a good candidate for industrial hydrolysis of inulin or sucrose.