The Aetiology of Vascular Discoloration in Cassava Roots after Harvesting: Association with Water Loss from Wounds

When root pieces of cassava, Manihot esculenta Crantz (cv. Yellow Heart or cv. Cuba Sweet), with an area of periderm removed or with a transverse cut uncovered, were held at low humidity and at 22°C, vascular discoloration consistently developed within 2 days. Vascular discoloration was prevented when injured pieces were stored at high humidity or when wounds were covered by a semi-permeable film. When pieces were injured by removal of periderm, at high humidity the respiratory rate was unaltered but at low humidity an increase in respiratory rate occurred after 1 day. When pieces were injured by a transverse cut, at high humidity respiratory rate increased during the first day but decreased thereafter, whereas at low humidity the initial increase was followed by a further increase in respiratory rate after 2 days. It is suggested that vascular discoloration and a respiratory increase may occur in freshly harvested cassava roots as a result of stress produced locally by high rates of water loss at cuts and abrasions.     

Impaired Transduction of R213 and Its Recovery by a Homologous Resident R Factor

Transduction by Plkc of drug-resistance markers of the factor R213 was shown to occur at an exceptionally low frequency (at less than 10(-8) of the input phage), and they could not be transduced by P22. When the recipient cells carried a homologous R factor derived from R213, markers were transduced by Plkc at a normal frequency (at about 10(-5) to 10(-6) of the input phage). Derivative R factors, transducible by Plkc at a normal frequency but being transferred by conjugation at a frequency lower than that of the original R213, were obtained. This type of transductant often segregated R(-) cells. In addition, several transductants contained R factors which were transferred normally by conjugation but were transduced by Plkc at as low a frequency as the original R213. This type of transductant was an effective recipient for transduction by Plkc of R213 when apparently "cured" by acridine treatment. No such effective "cured" recipients were obtained from the transductants with derivatives of R213 transducible at a normal frequency. Two possible interpretations are presented: (i) R213 produces a bacteriocin-like substance upon transduction, or (ii) the genome size of R213 is too large for all of its determinants to be transduced.     

多变鱼腥藻(Anabaena variabilis)藻胆体——类囊体膜光能传递的研究

多变鱼腥藻(Anabaena variabilis)藻胆体一类囊体膜的吸收峰位于678,624,490,438和418nm.当用580nm波长光激发藻胆体一类囊体膜中藻胆蛋白时,室温荧光峰位于662nm,在680nm附近有一肩;液氮温度荧光峰位于655,666,695和730nm.这说明藻胆蛋白捕获的光能能有效地传给叶绿素a.当用436nm波长光激发藻胆体一类囊性膜中叶绿素a时,室温荧光峰(?)于683nm;液氮温室荧光峰在730nm,另一小峰在695nm.表明叶绿素a捕获的光能不能传递给藻胆蛋白.藻胆体一类囊体膜放氧速率为245μmoleO_2/小时,毫克叶绿素,电境照片显示在类囊体膜上有大量藻胆体.用0.3M蔗糖,O.05M磷酸缓冲溶液洗藻胆体一类囊体膜,能使藻胆体与类囊体膜分开.对藻胆体与类囊体之间的光能传递进行了讨论.     

Concentration of Giardia lamblia cysts, Legionella pneumophila, Clostridium perfringens, human enteric viruses, and coliphages from large volumes of drinking water, using a single filtration

Poliovirus, coliphages, Giardia lamblia cysts, Clostridium perfringens spores, and Legionella pneumophila were concentrated simultaneously in a single pass by sequential filtration of large volumes of drinking water through 3- and 1-micron wound electronegative fiberglass cartridge filters (25.4 cm). Filtration was performed under acidic conditions (pH 3.5) in the presence of 0.001 M aluminum chloride to enhance adsorption. Elution of all the microorganisms entrapped or adsorbed to the filters was obtained by a slow backwash elution with a 1.5% beef extract solution, pH 9.75, containing 0.5% Tween 80. Tween 80 was shown to enhance recovery of the bacteriophages, bacteria, and parasites. Giardia cysts were efficiently eluted (71%) and could be reconcentrated by low-speed centrifugation and purified by sucrose density gradient flotation at a final recovery of 52%. Legionella pneumophila cells were eluted at 64% and were further concentrated by low-speed centrifugation at an overall recovery of 55%. C. perfringens spores and coliphages were eluted at efficiencies of 82 and 86%, respectively, and reconcentrated with minimal loss by a detergent - protein flotation method. Poliovirus was eluted at 93% and reconcentrated at 78% efficiency by organic flocculation.     

Combined mutagenicity of methyl methanesulfonate and ethyl methanesulfonate in Chinese hamster V79 cells.

The combined effects of methyl methanesulfonate (MMS) and ethyl methanesulfonate (EMS) on the induction of 6-thioguanine (6TG)-resistant mutants and chromosome aberrations were examined in Chinese hamster V79 cells. Cells were simultaneously treated with EMS at a concentration of D20 and MMS at various concentrations for 3, 6 or 9 h. In other experiments cells were simultaneously treated with MMS at a concentration of D20 and EMS at various concentrations for 3, 6 or 9 h. The mathematical analysis of the combined effects of both chemicals for cell killing (cytotoxicity) and 6TG-resistant mutations indicates that synergistic interactions were observed for both cell killing and mutations induced by MMS and EMS. The frequency of chromosome aberrations induced by simultaneous treatment with MMS at a concentration of D20 and EMS at various concentrations for 3 h was additive. However, the frequency of chromosome aberrations induced by EMS at a concentration of D20 and MMS at various concentrations for 3 h was not significantly different from those induced by MMS alone.     

Formation of 7-cis- and 13-cis-retinal pigments by irradiating squid rhodopsin.

Squid rhodopsin was irradiated with orange light (greater than 530 nm) at various temperatures from -190 to 10 degrees C until a photo-steady-state mixture was formed. Then the chromophoric retinals were extracted from the photo-steady-state mixtures and their isomer composition was analyzed by high-performance liquid chromatography. In the case of photo-steady-state mixture formed at -85 degrees C, large peaks in the chromatogram were found at the positions of both 7-cis- and 13-cis-retinals. Each peak was further identified by synthesizing the pigments from these retinals with cattle opsin or apobacteriorhodopsin. Both 7-cis- and 13-cis-retinals were also extracted from a photo-steady-state mixture formed by irradiation at -40, at 0, or at 10 degrees C. These isomers were scarcely detected in a photo-steady-state mixture formed by irradiation at -190 degrees C, though 9-cis-retinal was found as a major constituent in this mixture. Irradiation of lumirhodopsin at -190 degrees C, however, produced 7-cis-retinal pigment. These findings suggest that bathorhodopsin may have a conformation to prevent the formation of 7-cis-retinal from the all-trans form and that this particular conformation may be relaxed by the conversion of bathorhodopsin to lumirhodopsin.     

The influence of periphyton, detritus and shelter on invertebrate colonization of aquatic bryophytes

1. Artificial bryophytes were placed in a shaded and an unshaded New Zealand alpine stream to investigate why invertebrates colonized these structures and, by inference, real plants. Three experiments were conducted to investigate the influence of (i) periphyton and detritus (ii) shelter, and (iii) time, on invertebrate colonization. 2. In the first experiment, seven taxa at the unshaded site displayed a preference for substrata with high detrital and periphyton biomass, presumably reflecting a food relationship. At the shaded, less stable site, only two taxa displayed such a relationship. 3. Reducing substratum ‘stem’ density (i.e. ‘shelter’) in the second experiment had little effect on the biomass of periphyton at each site, and only at the shaded site was detrital biomass reduced on low-density substrata. Abundances of most of the twenty-two invertebrate taxa analysed were unaffected by stem density reduction: densities of only four taxa at the unshaded site, and two at the shaded site were reduced. 4. Stepwise multiple regression showed that invertebrate abundance was little affected by stem density at either site. Indeed, shelter was the primary factor influencing abundance of only two of twenty-two taxa at the unshaded site, and none at the shaded site. Abundances of most taxa were related to periphyton or detrital biomass at each site. 5. The third experiment investigated temporal relationships between invertebrate density, periphyton and detrital biomass, and exposure time of artificial bryophytes. Regression analyses indicated that of twenty-two taxa at the stable, unshaded site, eight were influenced by periphyton biomass, three by detrital biomass, and two by exposure time. At the unstable shaded site, abundances of only eight of twenty-two taxa were significantly related to the measured variables, of which exposure time was most important (four taxa).     

Serial section analysis of clathrin-coated pits in rat liver sinusoidal endothelial cells

Electron microscopy and serial sections were used to examine the shape of clathrin-coated pits in sinusoidal endothelial cells of rat livers. Livers were perfused at 4 degrees C with either concanavalin A-horseradish peroxidase (conA-HRP), or HRP alone, followed by warm-up to 37 degrees C and fixation with glutaraldehyde. Alternatively, the livers were perfused with HRP at 37 degrees C, followed by fixation. All tissue was preserved using a membrane contrast enhancement technique (R-OTO) consisting of sequential osmium-ferrocyanide, thiocarbohydrazide, and osmium-ferrocyanide treatment. Peroxidase reaction product was used to identify structures participating in endocytosis. One hundred and ninety-three clathrin-coated structures were examined. Sixty-six were from livers perfused with conA-HRP at 4 degrees C, 63 were from livers perfused with only HRP at 4 degrees C, and 64 were from livers perfused with HRP at 37 degrees C. These coated structures were morphologically classified into three categories: (a) flat pits; (b) cup-shaped pits; (c) pits with a narrow neck. No isolated coated vesicles were found. In cells perfused at 4 degrees C followed by warming to 37 degrees C, the percentage of coated pits found connected to the cell surface by narrow necks was 31%, using conA-HRP, and 27% using HRP alone. In cells perfused continuously at 37 degrees C, the percentage of coated pits with narrow neck connections was 21% using HRP alone. These results suggest that the formation of coated pits connected to the surface by narrow necks is not an artifact of cell type, of experimental protocol or of incubation with a lectin.     

Effect of seed depth on slug damage to winter wheat

In a field experiment drilled at two depths on three dates in autumn 1988, with or without methiocarb pellets broadcast on the soil surface immediately after drilling, 26% of seeds of winter wheat sown at c. 20 mm depth were killed by slugs compared with only 9% of seeds sown at c. 40 mm. The protection from slug damage provided by this additional 20 mm of depth was comparable with that provided by methiocarb pellets. The effects of seed depth and pellet application did not interact and were consistent on all drilling dates. Thus, fewest seeds and seedlings were killed where methiocarb pellets were broadcast on a seed-bed with seeds sown at 40 mm depth. Intermediate damage was recorded where seeds were sown at 40 mm depth without pellets, or where pellets were broadcast on seeds sown at 20 mm depth. Most seeds and seedlings were killed where seeds were sown at 20 mm depth without pellets. Sublethal damage to seedlings was not affected by sowing depth but was reduced where pellets were broadcast immediately after sowing.     

Nitrification in the intertidal zone: influence of effluent type and effect of tannin on nitrifiers.

Nitrification by intertidal sediments was measured by using a tide simulator that approximated the cycle of seawater on tidal flats. Sediments were chosen from sites affected by industrial and municipal effluents and pastoral seepage and runoff. The ability of sediments from different sites to nitrify endogenous nitrogen varied markedly. All sites exhibited an initial lag before activity commenced. The duration of this lag and the rate of nitrate production were different at each site. The sediments were also capable of oxidizing NH3-N supplied to them in seawater. This "nitrification potential" was highest at sites receiving nitrogenous effluents (slaughterhouse and sewage), but was also substantial in sediments affected by bark extract effluent and pasture runoff. The lowest potential and the longest lag were exhibited by sediments in an apple cannery effluent area. Enrichment cultures of nitrifying microorganisms were obtained from all sites using NH4+ as a source of energy, but enrichments for nitrite oxidizers were unsuccessful. Concentrated pine bark tannins, similar in origin to those in effluents at the well-nitrifying chipmill site, were tested for toxicity to pure cultures of nitrifying bacteria. Two Nitrobacter strains and one Nitrosomonas strain were unaffected by tannins even at 5 mg/ml. A Nitrosolobus and a Nitrosospira strain were inhibited partially at 5 mg/ml and only slightly or not at all at 1 mg/ml.     

Optimizing the accuracy of detecting a functional corpus luteum in dairy cows

The objectives were to evaluate the accuracy of detecting a functional CL by transrectal palpation and ultrasonography, and to optimize the accuracy of detecting a functional CL by ultrasonography in Holstein cows. In Experiment 1, four veterinarians performed transrectal palpation in 1250 cows at 37 d in milk (DIM), two veterinarians repeated transrectal palpation in 823 cows at 58 DIM, and one veterinarian performed 206 ultrasonographic examinations at 37 DIM. In Experiment 2, 987 and 983 ultrasonographic examinations were performed at 21 and 24 d after AI by one veterinarian for detection and measurement of CL. Cows with a blood progesterone concentration > or =1ng/mL were assumed to have a functional CL. Sensitivity and specificity were optimized using receiver operating characteristic analysis. In Experiment 1, sensitivity of transrectal palpation for diagnosing a functional CL ranged from 33.3 to 59.9% at 37 DIM and from 48.3 to 68.4% at 58 DIM, whereas specificity ranged from 76.7 to 93.2% at 37 DIM and from 73.3 to 86.7% at 58 DIM. Sensitivity and specificity for ultrasonography were 89.4 and 45.7%, respectively. In Experiment 2, the sensitivity and specificity of ultrasonography were 97.3 and 38.1% at 21 d after AI, and were 97.9 and 51.0% at 24 d after AI. Sensitivity and specificity were optimized using a cutoff diameter of 23mm at 21 d and 22mm at 24 d, which resulted in sensitivity and specificity of 87.2 and 83.0% at 21 d, and 89.5 and 89.4% at 24 d after AI, respectively. Sensitivity was low and specificity was high for transrectal palpation, whereas ultrasonography resulted in high sensitivity and low specificity. Using a cutoff diameter during ultrasonography improved accuracy of detection of a functional CL compared with either ultrasonography without cutoff or transrectal palpation.     

Studies on the skin of plaice (Pleuronectes platessa L.)

Eighty-nine O-group plaice from a natural population were exposed at 15°C to heavy infection by Cryptocotyle lingua cercariae. Subsequently 45 fish were retained at 15°C, whilst 44 were held at 5°C. Both groups were sampled by killing individual fish at intervals of 6,18,42 h and daily thereafter up to 710 h. Entire fish were fixed immediately in formol saline, transversely sectioned and stained by H & E, PAS, PAS-diastase, JSDB 109, Picro-Mallory, Masson's trichrome, Gram-Weigert and Alcian blue. Histopathological observations showed: (a) epidermal lesions associated with encysted metacercariae in adjacent tissues; (b) myofibrillar necrosis associated with bacteria possibly introduced by the parasite; and (c) a reactive swelling of the intermuscular septa. The progressive development of the parasite cyst and host capsule is described. Development of both was markedly inhibited at the lower temperature, but the inflammatory response at either temperature was slight. This may be evidence of a long-standing host-parasite relationship which has evolved to an advanced state of adaptation on the part of the parasite and tolerance on the part of the host.     

Spectrophotometric study on the oxidation of rutin by horseradish peroxidase and characteristics of the oxidized products

Rutin (3',4',5,7-tetrahydroxyflavone-3-rutinoside) was oxidized by a horseradish peroxidase-H2O2 system to an ascorbate-reducible product which had an absorption maximum at about 290 nm and a shoulder at about 440 nm at pH 4. At pH 7.8, ascorbate-reducible compounds and sodium hydrosulfite-reducible and -nonreducible compounds were formed by the oxidation. The ascorbate-reducible compounds consisted of at least two components, the absorption bands of which were at 460-480 nm and about 620 nm. The sodium hydrosulfite-reducible compounds also consisted of two components, and one of the components which had an absorption maximum at about 480 nm seems to be formed from the ascorbate-reducible component of an absorption maximum at the blue region by a nonenzymatic reaction. A mixture of oxidized products of rutin formed by tert-butyl hydroperoxide-dependent oxidation was similar to that formed by the enzymatic reaction. It is discussed that the 3'- and 4'-OH groups of rutin were oxidized by the horseradish peroxidase-H2O2 system and that the oxidized product which could be reduced by ascorbate is an o-quinone derivative.     

Streptomyces flavogriseus cellulase: Evaluation under various hydrolysis conditions

Streptomyces flavogriseus CMCase and Avicelase were very stable at 30 degrees C but not at 40 degrees C or higher. beta-Glucosidase was less stable at all temperatures tested. Stabilities were similar at pH values between 5.5 and 7, the optimal range for enzyme activity. Cellulose solubilizing activity was reduced by 40% at a cellobiose concentration of 150mM but glucose inhibited activity by only 10% at this concentration. beta-Glucosidase was inhibited by 40% at a glucose concentration of 10mM (ten times the substrate concentration). Relatively dilute S. flavogriseus cellulase extensively hydrolysed acid-swollen cellulose at concentrations as high as 10%. More highly crystalline forms of cellulose were more resistant to attack.     

Frequency responses of cat rapidly adapting mechanoreceptive fibers

The frequency responses of 11 rapidly adapting (RA) fibers in cat were studied by representing the average firing rate as a function of sinusoidal stimulus amplitude and stimulus frequency. Specifically, rate-intensity functions at different stimulation frequencies were fitted by four-parameter (a0, a1, a2, a3), piece-wise linear functions using nonlinear regression (n = 59; R2 > 0.877). Rate-intensity functions at intermediate frequencies were found by linear interpolation. The result of this analysis is rate-amplitude-frequency functions plotted as two-dimensional surfaces. The surfaces consist of five regions separated and sufficiently defined by four space curves. At 14 different frequencies, the statistical distribution of each rate-intensity-function parameter could be approximated by a particular lognormal distribution (n = 56; R2 > 0.796). The Kolmogorov-Smirnov test fails to reject this hypothesis for each combination of frequency and parameter (56 tests; p > 0.39). Therefore, at a given frequency, the variation of the parameters can be represented by lognormal distributions with specific means and standard deviations. Responses of six RA fibers, which are different from the data-set used for modeling, were compared with the stochastic model at different frequencies. The parameters of those fibers were tested against the null hypotheses that they were sampled from the particular parameter distributions dictated by the model. The Kolmogorov-Smirnov test fails to reject all the hypotheses at the alpha = 0.05 level (44 tests). At the alpha = 0.10 level, only a few test parameters were found to be departing from the model (a0 and a1 at 5 Hz; a2 at 20 Hz; a2 and a3 at 50 Hz). The remaining test parameters could be accurately described by the model. Having confirmed the validity of the model, the logarithmic means and the logarithmic standard deviations of the lognormally distributed rate-intensity-function parameters were estimated in the frequency range of 4-200 Hz. The rate-amplitude-frequency surfaces sampled from the established stochastic model completely characterize the rate responses of RA fibers to sinusoidal stimuli and are superior to tuning curves which require selecting criterion responses. The current rate-response model is promising for future computational work, especially on population modeling.     

Hypothalamic and pituitary periodicity demonstrated by isolated rat adrenal cells

Rats were maintained under standardized conditions of food and water ad libitum and a lighting schedule of 12 h light/we h dark for seven days. Animals were sacrificed at 0500 and 1700 h and tissues were removed and washed. Isolated intact adrenal and pituitary cells were prepared by collagenase treatment. Using a sequential incubation procedure, the release of pituitary ACTH by hypothalamic acid extracts (CRF) was assayed by stimulation of corticosteroid secretion from isolated adrenal cells. Maximum stimulation of adrenal steroids was achieved with hypothalamic extracts and pituitary cells from rats sacrificed at 1700 h, and minimum values were obtained at 0500 h. Intermediate levels were obtained when hypothalamic extracts at one time point were incubated with pituitary cells at the other. The results substantiate the late afternoon peak level of hypothalamic and pituitary secretion occurring prior to the peak activity pattern of the rat.     

Effect of early cold stress on the maturation of rice anthers

Male reproductive development in rice (Oryza sativa Linnaeus is very sensitive to various forms of environmental stresses including low temperature. Here, we present our findings on the proteomic analysis of the later developmental consequences of low temperature treatment on rice anthers. Anther proteins at the trinucleate stage, with or without cold treatment for four days at 12 degrees C at the young microspore stage, were extracted, separated by two-dimensional gel electrophoresis (2-DE) and compared. More than 3000 rice anther proteins of cold-sensitive cultivar Doongara plants at the trinucleate stage were resolved on 2-DE gels over a pH range of 4-7 and detected by silver-staining. Seventy protein spots were differentially displayed after four days of cold treatment at the young microspore stage. Of these, 12 protein spots were newly-induced, 47 were up-regulated, and 11 were down-regulated by cold treatment at the early microspore stage. We identified 18 by matrix-assisted laser desorption/ionization mass spectrometry time of flight (MALDI-TOF) analysis. Of the identified proteins, seven were observed as breakdown (cleavage) products by a combination of 2-DE and MALDI-TOF analysis, thus demonstrating for the first time that cold temperature stress at the young microspore stage enhances and induces partial degradation of proteins in the rice anthers at the trinucleate stage.     

Positive regulation of amidase synthesis in Pseudomonas aeruginosa.

Mutants of Pseudomonas aeruginosa were isolated that were acetamide-negative in growth phenotype at 41 degrees C and constitutive for amidase synthesis at 28 degrees C. Two mutants were derived from the magno-constitutive amidase mutant PAC111 (C11), and a third from a mutant that had enhanced inducibility by formamide, PAC153 (F6). The three temperature-sensitive mutants produced amidases with the same thermal stabilities as the wild-type enzyme. Cultures growing exponentially at 28 degrees C, synthesizing amidase constitutively, ceased amidase synthesis almost immediately on transfer to 41 degrees C. Cultures growing at 41 degrees C were transferred to 28 degrees C and had a lag of about 0.5 of a generation before amidase synthesis became detectable. Pulse-heating for 10 min at 45 degrees C of a culture growing exponentially at 28 degrees C resulted in a lag of about 0.5 of a generation before amidase synthesis recommenced after returning to 28 degrees C. Acetamide-negative mutants that were unable to synthesize amidase at any growth temperature were isolated from an inducible strain producing the mutant B amidase PAC398 (IB10). Two mutants were examined that gave revertants producing B amidase but with novel regulatory phenotypes. It is suggested that amidase synthesis is regulated by positive control exerted by gene amiR.     

Multiple mating and siring success during natural oestrus in the ewe

Ewes were each mated on four separate occasions, at 3, 9, 15 and 21 h after the start of oestrus and at each time by a different ram. The progeny were assigned to sires by blood typing, supplemented by resemblance between lambs and rams. The paternity of 64 lambs, born to 41 ewes, was established: 2 were conceived at a 3-h mating, 27 at 9h, 23 at 15 h and 12 at 21 h. The optimum time for a ram to inseminate, when in competition with others, is therefore 9-15 h after onset of oestrus, and this finding accords with behavioural observations. Ewes tended to lamb during the same half of the day as that when they had come into oestrus.     

Temperature-dependent expression of flagella of Listeria monocytogenes studied by electron microscopy, SDS-PAGE and western blotting

Washed cells of Listeria monocytogenes serotype 4b, grown in broth culture at 20 degrees C and at 37 degrees C, were examined by electron microscopy for the presence of flagella. Many flagella were seen in cells grown at 20 degrees C, whereas at 37 degrees C very few were expressed. Flagella sheared from the cell surface were partially purified by differential centrifugation. Using SDS-PAGE and Western blotting two distinct protein bands were seen in this preparation, both with an apparent molecular mass of approximately 29 kDa. Further purification of these proteins was achieved by gel filtration and ion-exchange chromatography. Whole organisms grown at 20 degrees C and 37 degrees C were examined in Western blots using an affinity-purified polyclonal antibody, and a monoclonal antibody, both directed against 29 kDa putative flagellin. Bacteria grown at 20 degrees C expressed abundant flagellin, whereas only trace amounts could be detected in organisms grown at 37 degrees C. It is concluded that organisms grown at 20 degrees C both produce and assemble flagellin at the cell surface, and that flagellin production is a less marked feature of organisms grown at 37 degrees C.