Types I and IV collagenolytic and plasminogen activator activities in preovulatory ovarian follicles

During ovulation, enzymatic degradation of the extracellular matrix occurs within and around the graafian follicles. In this study, the activities of several different proteolytic enzymes were measured in the culture media of follicles taken from pregnant mare serum gonadotropin (PMSG)-primed immature rats. At 52 h after PMSG, the follicles were cultured for 2 to 15 h in media with or without human chorionic gonadotropin (hCG). Type I collagenase activity in hCG-stimulated follicles gradually increased within 6 h to 3.3-fold above that of the controls. Relatively pure populations of granulosa cells produced type I collagenase to a similar extent. Likewise, type IV collagenase increased 3.8-fold by 6 h after exposure of the follicles to hCG. In contrast, plasminogen activator activity increased by 3.9-fold at 2 h after hCG, but was negligible at 4, 6, and 15 h after incubation. These results suggest that plasminogen activator may activate both type I and type IV collagenase in hCG-stimulated ovulatory follicles.     

Tree form in a mixed dipterocarp forest in Indonesian Borneo

The form of tropical trees was studied with reference to the production structure of the component individuals of a tropical rain forest stand in Sebulu, East Kalimantan in Indonesian Borneo, since the production structure as a physical or bio-economical basis of tree form still remains obscure in tropical rain forests. The pipe model theory successfully explained the crown shapes of different trees, and its parameter, designated as specific pipe length, suggested an increase in the cost of leaf mass growth with an increase in crown size. A mathematical model consisting of exponential functions of aboveground height was applied for describing stem form, and its properties were examined through changes in its coefficients and by adopting an assumption of the geometrical similarity of individual stem form as a criterion for comparing differences in stem form among individual trees. Furthermore, the cost of buttersses was discussed using the relation between bole- and buttress weight calculated from the mathematical model.     

Pollination systems in a warm temperate evergreen broad-leaved forest on Yaku Island

Animal pollination in a warm temperate evergreen broad-leaved forest was observed on Yaku-shima Island, south of Kyushu, Japan. Three groups of plants were categorized: canopy-flowering tree species, understory-flowering tree species, and climber and epiphyte species. Each of these formed different pollination systems. The canopy-flowering tree species had shallow, dish-shaped flowers and utilized various types of opportunistic pollinators. Most of the climber and epiphyte species had deep, tube-shaped flowers and specialized pollinators, although some climber species which bloomed in the canopy especially in winter, had opportunistic pollinators. The understory-flowering tree species had large dish- or funnel-shaped flowers and endothermic pollinators able to tolerate the dark and cold conditions under the canopy. The individual trees of canopy-flowering tree species produced large numbers of flowers simultaneously (mass-flowering) and had a well synchronized flowering period. Each canopy-flowering tree species segregated its flowering time from those of the anothers. Climber and epiphyte species and most of the understory-flowering tree species produced small numbers of flowers sequentially (extended flowering) and showed a long flowering period.     

Cloning and comparison of Aα mating-type alleles of the basidiomycete Schizophyllum commune

Summary An A mating-type allele (A4) was isolated by walking the chromosome from the closely linked PAB1 gene. A cosmid clone containing the A1 allele isolated from the walk was used as a probe to recover the A1 allele from another cosmid library. Cosmids encoding mating-type activity were identified by transforming Schizophyllum cells and screening for activation of A-regulated development. Putative mating-type transformants were confirmed in mating tests and genetic analyses of progeny. The identity of the specific alleles isolated was demonstrated by showing that their effectiveness in transforming for mating type is limited to recipient strains possessing an A allele different from the one encoded by the cloned sequences. Transforming DNA is active in trans, suggesting that A encodes a diffusible product. Restriction mapping shows that A1 and A4 are coded in the same physical region of the genome, but within a subregion that contains extensive sequence divergence. In addition, Southern analyses show that there is only one copy of A1 or A4 per haploid genome, and that they do not cross-hybridize to one another or to any of the other A alleles. A1 and A4 were subcloned as 2.8 and 1.2 kb fragments, respectively, retaining in transformation all the mating-type activity demonstrated of the original cosmids.     

The influence of crabs on litter processing in high intertidal mangrove forests in tropical Australia

Summary Measurements of litter fall and litter removal by crabs, in conjunction with estimates of litter decay by microbes and tidal export of litter from three high-intertidal mangrove forests were made during a year-long study in tropical northeastern Australia. In forests dominated by Ceriops tagal and Bruguiera exaristata, litter standing stocks remained low on the forest floor (mean 6 g·m^-2), although litter fall was high; 822 and 1022 g·m^-2·y^-1, respectively. Sesarmid crabs removed 580 (Ceriops) and 803 (Bruguiera) g·m^-2·y^-1, or 71 and 79%, of the total annual litter fall from the forest floor. Relative to the rate of litter removal by crabs, microbial turnover of whole, unshredded litter was insignificant, accounting for <1% of annual litter fall. Export of litter by tides was estimated to remove 194 (Ceriops) and 252 (Bruguiera) g·m^-2·y^-1 or 24 and 25% of annual litter fall. In a forest dominated by Avicenniamarina, in which an ocypodid crab was more abundant than sesarmids, litter standing stocks were higher (mean 84 g·m^-2) and crabs removed less litter; 173 g·m^-2·y^-1 or 33% of the annual litter fall of 519 g·m^-2·y^-1. Microbial turnover of intact litter was more important in the Avicennia forest (168 g·m^-2·y^-1 or 32% of annual litter fall), and tides exported 107 g·m^-2·y^-1 or 21% of litter production. In areas where sesarmid crabs were absent or rare in Ceriops forests, there were significantly higher standing stocks of litter and slower rates of leaf removal. Taking into account the probable assimilation efficiencies of sesarmid crabs feeding on mangrove leaves, we estimate that in Ceriops and Bruguiera forests leaf processing by crabs turns litter over at >75 times the rate of microbial decay alone, thus facilitating the high sediment bacterial productivity in these forests. The importance of litter processing by crabs increases with height in the intertidal in tropical Australia, in contrast to New World mangrove forests, where the reverse is true.Contribution No. 445 from the Australian Institute of Marine Science     

Seasonal changes in the pigments, carbohydrates and growth of red spruce as affected by ozone

Two-year-old red spruce seedlings were exposed to various levels ot ozone, from 0.4 to 3 times ambient levels, in open-top chambers in Ithaca, NY, USA. Exposures, which varied with changes in day length, commenced on May 30, 1987 and continued until December 14, 1987. Seedling biomass, carbohydrate contents, pigment contents, and rate of electron transport were assessed twice monthly during the fumigation period. Orthogonal quadratic or cubic polynomials were used to model the response through time each variable measured. A one-way analysis of variance model was fitted to every regression coefficient in each polynomial model to test for ozone effects on seasonal physiological patterns. Ozone did not influence growth, foliar pigment content, foliar starch content, root carbohydrate content, or rate of electron transport. The seasonal change of needle raffinose content differed between exposed to low (0.4 ×, 1×) and high (2×, 3×) ozone levels. There was also a trend towards reduced total soluble sugar content foliage during late autumn in higher ozone treatments.     

Effects of N-immissions on nutrient status and vitality ofPinus sylvestris near a hen-house

Near a hen house (50–600 m), vitality ofPinus sylvestris, N-, P-, K-, Ca-, Mg-contents of the needles, N-, Mg-, K-, Ca- and Al-contents in soil extracts and NH₃/NH ₄ ⁺ -contents of the air were determined. Damage symptoms occurred when N-immissions hit the canopy directly. In contrast no visible decline of the above ground plant could be observed if N was mainly deposited on the soil.     

Mineralization of carbon and nitrogen in soil samples taken from three fertilized pine stands: Long-term effects

Seven years after fertilization the rate of CO₂ production in the soil samples taken from the organic horizons of a poor pine forest site (Calluna vulgaris site type), treated with urea or ammonium nitrate with lime, was lower than that in the unfertilized soil. The same trend was also observed in samples of theEmpetrum-Calluna site type 14 years after fertilization. In the more fertileVaccinium myrtillus site type these rapidly-soluble N fertilizers had a long-term enhancing effect on the production of CO₂. Apatite and biotite eliminated the decreasing effect of urea on the production of CO₂. One reason for this might be the long-term increase in soil pH caused by apatite and biotite, or their constituents (Ca, Mg, K, P). Nitroform (a slow-releasing N fertilizer) had no statistically significant effect on the production of CO₂ in soil samples from any of the forest types. Despite the high N mineralization in the samples from nitroform fertilized soils there was no nitrification, and the high content of total N indicated that after nitroform fertilization the losses of N were low.The correlation between the net mineralization values for C (CO₂ production) and N was poor. However, multiple linear regression analysis, which also took into account the effect of nutrients and pH, indicated that there was a link between the mineralization of C and N.     

Binding and precipitating activities ofErythrina lectins with complex type carbohydrates and synthetic cluster glycosides. A comparative study of the lectins fromE. corallodendron,E. cristagalli,E. flabelliformis,andE. indica

Erythrina lectins possess similar structural and carbohydrate binding properties. Recently, tri- and tetra-antennary complex type carbohydrates with non-reducing terminal galactose residues have been shown to be precipitated as tri- and tetravalent ligands, respectively, with certainErythrina lectins [Bhattacharyya L, Haraldsson M, Brewer CF (1988) Biochemistry 271034-41]. The present work describes a comparative study of the binding and precipitating activities of fourErythrina lectins,viz. E. corallodendron, E. cristagalli, E. flabelliformis, andE. indica, with multi-antennary complex type carbohydrates and synthetic cluster glycosides. The results show that though their binding affinities are very similar, theErythrina lectins show large differences in their precipitating activities with the carbohydrates. The results also indicate significant dependence of the precipitating activities of the lectins on the core structure of the carbohydrates. These findings provide a new dimension to the structure-activity relationship of the lectins and their interactions with asparagine-linked carbohydrates.Abbreviations EAL, ECorL, ECL, EFL, and EIL represent the lectins from the seeds ofErythrina arborescens, - E. corallodendron, E. cristagalli, E. flabelliformis, andE. indica respectively - AFOS thetri-antennary complex type oligosaccharide from asialofetuin - AFGP the tri-antennary glycopeptide from asialofetuin - MeGal methyl -d-galactopyranoside Unless stated otherwise all sugars are in thed-configuration.     

An empirical analysis of the factors contributing to 20-year decrease in soil pH in an old-field plantation of loblolly pine

The pH of weak-acid solutions is controlled by acid concentration (HA + A^–), the degree of acid dissociation (A^–/HA), and the strength of the acids present (pK_a). We developed an empirical approach that allows the relative importance of each of these factors to be estimated for soils. This empirical model was applied to soils collected from an old-field plantation of loblolly pine (Pinus taeda L.) at 5 and 25 years of age. During this period, soil pH dropped by 0.3 to 0.8 units, and extractable calcium, magnesium and potassium declined by 20 to 80%. The empirical model indicates that the decline in pH resulted largely from the reduction in base saturation of the exchange complex. However, the average acid strength of the exchange complex decreased during the 20 years, preventing a greater decline of perhaps 0.1 to 0.2 units in the observed pH. The rate of decrease in the acid neutralizing capacity to pH 3.5 was about 1.3 kmol_c/ha annually, while the increase in base neutralizing capacity was about 2.7 and 1.6 kmol_c/ha annually to pH 5.5 and 8.2, respectively. Extractable alkali and alkaline earth cations declined by about 2.2 kmol_c/ha annually, matched by the rate of increase in aluminium. These changes demonstrated the dynamic nature of poorly buffered soils, and indicated that changes in soil acidity may be expected over a period of decades (especially following changes in land-use).