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71.
Leaf decomposition of the exotic evergreen Eucalyptus globulus (eucalyptus), and three native deciduous tree species, Alnus glutinosa (alder), Castanea sativa (chestnut) and Quercus faginea (oak), was compared in a second order stream in Central Portugal. Changes in dry weight, nitrogen and polyphenolic compounds and microbial colonization were periodically assessed for three months.Negative exponential curves fit the leaf weight loss with time for all leaf species. Mass loss rate was in the order alder (K = 0.0161) > chestnut (K = 0.0079) > eucalyptus (K = 0.0068) > oak (K = 0.0037). Microbial colonization followed the same pattern as breakdown rates. Evidence of fungal colonization was observed in alder after 3 days in the stream, whereas it took 21 days in oak leaves to have fungal colonization. Fungal diversity was leaf species-dependent and increased with time. In all cases, percent nitrogen per unit leaf weight increased, at least, at the initial stages of decay while soluble polyphenolics (expressed as percentage per unit leaf weight) decreased rapidly in the first month of leaves immersion.Intrinsic factors such as nitrogen and polyphenolic content may explain differences in leaf decomposition. The possible incorporation of eucalyptus litter into secondary production in a reasonable time span is suggested, although community balance and structure might be affected by differences in allochthonous patterns determined by eucalyptus monocultures. 相似文献
72.
Antonio Bode Benita Casas Emilio Fernández Emilio Marañón Pablo Serret Manuel Varela 《Hydrobiologia》1996,341(3):225-234
Summary Chlorophyll-a and primary production on the euphotic zone of the N-NW Spanish shelf were studied at 125 stations between 1984 and 1992. Three geographic areas (Cantabrian Sea, Rías Altas and Was Baixas), three bathymetric ranges (20 to 60 m, 60 to 150 m and stations deeper than 200 m), and four oceanographic stages (spring and autumn blooms, summer upwelling, summer stratification and winter mixing) were considered. One of the major sources of variability of chlorophyll and production data was season. Bloom and summer upwelling stages have equivalent mean and maximum values. Average chlorophyll-a concentrations approximately doubled in every step of the increasing productivity sequence: winter mixing — summer stratification — high productivity (upwelling and bloom) stages. Average primary production rates increased only 60% in the described sequence. Mean (± sd) values of chlorophyll-a and primary production rates during the high productivity stages were 59.7 ± 39.5 mg Chl-a m–2 and 86.9 ± 44.0 mg C m–2 h–1, respectively. Significant differences in both chlorophyll and primary production resulted between geographic areas in most stages. Only 27 stations showed the effects of the summer upwelling that affected coastal areas in the Cantabrian Sea and Rías Baixas shelf, but also shelf-break stations in the Rías Altas area. The Rías Baixas area had lower chlorophyll than both the Rías Altas and the Cantabrian Sea areas during spring and autumn blooms, but higher during summer upwelling events. On the contrary, primary production rates were higher in the Rías Baixas area during blooms in spring and autumn. Mid-shelf areas showed the highest chlorophyll concentrations during high productivity stages, probably due to the existence of frontal zones in all geographic areas considered. The estimated phytoplankton growth rates were comparable to those of other coastal upwelling systems, with average values lower than the maximum potential growth rates. Doubling rates for upwelling and stratification stages in the northern and Rías Altas shelf areas were equivalent, despite larger biomass accumulations during upwelling events. Low turnover rates of the existing biomass in the Rías Baixas shelf in upwelling stages suggests that the accumulation of phytoplankton was due mainly to the export from the highly productive rías, while the contribution of in situ production to these accumulations was relatively lower. 相似文献
73.
Xp-duplications with and without sex reversal 总被引:5,自引:0,他引:5
Annette Baumstark Gotthold Barbi Mahmoud Djalali Claudia Geerkens Beate Mitulla Torsten Mattfeldt José Carlos Cabral de Almeida Fernando Regla Vargas Juan Clinton Llerena Jr Walther Vogel Walter Just 《Human genetics》1996,97(1):79-86
Duplications in Xp including the DSS (dosage sensitive sex reversal) region cause male to female sex reversal. We investigated two patients from families with Xp duplications. The first case was one of two sisters with karyotype 46,XY, der(22), t(X;22)(p11.3;p11)mat and unambiguous female genitalia. The living sister was developmentally retarded, and showed multiple dysmorphic features and an acrocallosal syndrome. The second case was a boy with a maternally inherited direct duplication of Xp21.3-pter with the breakpoint close to the DSS locus. He had multiple abnormalities and micropenis, but otherwise unambiguous male genitalia. We performed quantitative Southern blot analysis with probes from Xp22.13 to p21.2 to define the duplicated region. Clinical, cytogenetic, and molecular data from both patients were compared with those of previously reported related cases. A comparison of the extragenital symptoms revealed no differences between patients with or without sex reversal. In both cases, the symptoms were non-specific. Among 22 patients with a duplication in Xp, nine had unambiguous female genitalia and a well-documented duplication of the DSS region. Two patients with duplication of DSS showed ambiguous external genitalia. From these data, we conclude that induction of testicular tissue may start in these patients, but that the type of genitalia depends on the degree of subsequent degeneration by a gene in DSS. 相似文献
74.
M.J. ALMEIDA AND C.S. PAIS. 1996. Yeasts were isolated from a variety of home-made bread doughs and identified. A pure culture of Saccharomyces cerevisiae was found in 18% of the doughs. The same species predominated in 80% of the doughs examined whereas Issatchenkia orientalis, Pichia membranaefaciens and Torulaspora delbrueckii were present in about 40% of the samples. About one quarter of the isolates displayed killer activity, strains of P. anomala showing the broadest spectra. Two isolates of S. cerevisiae and three of T. delbrueckii gave biomass values in sucrose medium similar to or higher than those obtained with commercial compressed baker's yeast strains. 相似文献
75.
Factors affecting transient gene expression in cultured radiata pine cotyledons following particle bombardment 总被引:2,自引:0,他引:2
Manuel Rey María Victoria González Ricardo J. Ordás Raffaela Tavazza Giorgio Ancora 《Physiologia plantarum》1996,96(4):630-636
Transfer and expression of the β–glucuronidase gene ( gusA ) in cultured cotyledons of radiata pine ( Pinus radiata D. Don ) were obtained by particle bombardment. Conditions for optimum transient expression were established by using plasmid pB[/12], delivered by gold particles, 1.6 μm in diameter, into 8-day-old cultured cotyledons. Helium pressure of 7.6 MPa, bombardment distance between the stopping screen and the target tissues of 6 cm, and 0.8 μg of plasmid DNA per bombardment proved to be the best parameters for transient expression; using these parameters 79% of bombarded cotyledons showed GUS activity, with 4.3 blue spots per cotyledon. This system was used for studying the expression of several gus-driven promoters the expression of the sunflower ubiquitin gene promoter was higher (99% of positive cotyledons, with 14.2 blue spots per cotyledon) than that of the CaMV 35S promoter, whereas the rice actin and the maize alcohol dehydrogenase gene promoters gave lower gusA expression, as determined histochemically. These results were confirmed by using the gus fluorometric assay. Use of the sunflower ubiquitin gene promoter resulted in gusA expression up to 20 days after bombardment, with a significant level of gus expressing loci per bombarded cotyledon, whereas with the CaMV 35S promoter gusA expression was lost 12 days after bombardment. 相似文献
76.
Verónica Lipperheide Guillermo Quindós Yolanda Jiménez José Pontón José Vicente Bagán-Sebastián José Manuel Aguirre 《Mycopathologia》1996,134(2):75-82
Prevalence of yeasts in 35 leukoplakia and 34 oral lichen planus patients was compared with that observed in persons without oral diseases. Serotype and morphotype were determined on Candida albicans isolates. Yeasts were isolated from the oral cavity specimens of 43.7% of the patients. C. albicans (serotype A) was the predominant species (76% in leukoplakia, 88.2% in lichen planus and 60.8% in healthy persons). Sixteen morphotypes were encountered on malt extract agar, being 732, 733, 734, 753 and 754 the most frequently found. Morphotypes SP1N and SP1Y were the most common on Sabouraud-trypheniltetrazolium agar (68.4% of the isolates from leukoplakia and 73.3% from lichen planus, but only 46.6% of the isolates from healthy oral mucosa showed SP1N morphotype). Presence of oral lesions was associated with a marked reduction in the yeast species and C. albicans biotypes, suggesting that C. albicans and particularly some of its biotypes, show a high potential of adaptation to the changes associated with the development of oral leukoplakia and lichen planus. 相似文献
77.
The operational stability of the Candida rugosa lipase immobilized in a hydrophilic polyurethane foam was evaluated in consecutive batches for the glycerolysis of olive oil in n-hexane, aimed at the production of monoglycerides.Glycerol controlled the glycerolysis in the system under study, since it is both a substrate and a powerful water binder that reduces the water activity of the reaction medium and of the microenvironment. Two sets of experiments were carried out under different glycerol/triglyceride ratios. After 345 hours of consecutive 23 hours batches no lipase inactivation was observed.List of Symbols aw
thermodynamic activity of water
- DG
diglyceride (s)
- FAME
fatty acid methyl ester (s)
- FFA
free fatty acid (s)
- FID
flame ionization detector Gly glycerol
- MG
monoglyceride (s)
- TG
triglyceride (s)
- TLC
thin layer chromatography
The authors are grateful to Profs. P. Adlercreutz, Technical University of Lund, Sweden, and J.M.S. Cabral, Instituto Superior Técnico, Lisbon, Portugal, for inspiring discussions and advice, to Prof. Helena Pereira, Instituto Superior de Agronomia (ISA), Lisbon, Portugal, for the use of GC equipment and to Mrs. Marlene Dionísio, ISA, for invaluable help with some of the experimental work. 相似文献
78.
M. H. L. Ribeiro D. M. F. Prazeres J. M. S. Cabral M. M. R. da Fonseca 《Bioprocess and biosystems engineering》1995,12(1-2):95-102
l-tryptophan was produced froml-serine and indole by immobilized Escherichia coli cells in organic-aqueous systems. Selective adsorption was the method chosen to enable both product separation andl-serine reutilization. Amongst various adsorbents tested activated carbons and neutral polymeric resins (XAD-4 and XAD-7) showed good performance. The neutral resins could selectively concentrate thel-tryptophan from dilute aqueous solutions and adsorbed only 5% of the unconvertedl-serine. High separation factors (l-tryptophan/l-serine and indole/l-tryptophan) were obtained with these adsorbents. Despite a lower capacity, the XAD-7 resin had the advantage of desorbingl-tryptophan with basic or acidic solutions, while organic solvents were required to desorb, at the same concentration levels, this compound from XAD-4.In a packed bed column filled with XAD-4 resin or activated carbon, totall-tryptophan adsorption and recovery were achieved at linear velocities up to 5.0 cm/min and 3.2 cm/min respectively. Successive sorbent reutilization, following continuous sorption and elution steps, was carried out in packed bed columns with the neutral resins and activated carbon.Thel-form of tryptophan, after crystallization, was identified by HPTLC.List of Symbols HPLC
High Performance Liquid Chromatography
- HPTLC
High Performance Thin Layer Chromatography
- Trp
tryptophan
- Ser
Serine
-
A
amount of sorbent(g)
-
c
equilibrium solute concentration in the aqueous phase (g/dm3)
-
c
i
initial (before adding the sorbent) liquid phase concentration (g/dm3)
-
C
T
tryptophan concentration in the inlet solution (g/dm3)
-
C
To
tryptophan concentration in the outlet solution (g/dm3)
-
E
z
axial dispersion coefficient (m2/s)
-
k
experimental constant (Eq. 1, 2 and 3)
-
K
1
rate constant of adsorption (min–1)
-
L
column length(m)
-
n
experimental constant (eq. 1, 2 and 3)
-
q
equilibrium solid phase concentration (g solute/g sorbent)
-
q
max
maximum capacity of sorbent (g solute/g sorbent)
-
t
time(s)
-
v
liquid velocity (m/s)
-
V
volume of liquid phase(dm3)
-
V
e
eluted volume(dm3)
-
V
r
volume needed to saturate the column (dm3) 相似文献
79.
Silica biomorphs are inorganic self-organized precipitates resulting from a crystal aggregation process controlled by a metal silicate membrane. They display morphological and symmetric properties of living organisms and form under physico-chemical conditions similar to some geochemical conditions suggested for the chemical precipitation of Precambrian chert precursors. In consequence, these inorganic precipitates are proposed as an alternative interpretation to be considered when trying to decipher the biogenicity of putative Precambrian microbiotas. 相似文献
80.
The growth of four strains of the shiitake mushroom Lentinus edodes in solid substrate fermentation in synthetic oak sawdust logs was studied over a 14-week period. Total extracellular phenol oxidase activity and soluble protein were monitored and biomass estimated as the ergosterol content of the fermented sawdust. It was observed that two of the strains had a similar pattern of phenol oxidase activity with two cycles with maxima at 2 and 8 weeks of mycelial growth prior to fruiting. With the other two strains there was a maximum at week 4. For each strain, phenol oxidase activity increased with the cold shock used to induce fruiting. Phenol oxidase activity was not found to be correlated with either soluble protein or total fungal biomass in the fermented sawdust, which were correlated for each strain. Quantification of biomass from submerged liquid culture on the basis of dry weight and ergosterol contents showed that the strains fell into the same two groups with respect to the ergosterol to biomass ratio, which was markedly lower than that for a strain of L. lepideus.Correspondence to: B. C. Okeke 相似文献