美洲绵霉超微结构的初步研究

对美洲绵霉(Achlya americana Humphrey)有性器官的壁结构,细胞核相及一些细胞器的结构进行了初步的超微结构研究,我们发现藏卵器壁由两层组成,卵孢子壁至少由三层组成,而藏卵器横隔膜则由两层壁和中间一层原生质体组成。在细胞核分裂过程中发现有明显的染色体的形成和存在,这是第一次在电子显微镜下看到卵菌的染色体,并对染色体的存在进行了讨论。     

Purification and characterization of pyruvate carboxylase from the honeybee and some properties of related biotin-containing proteins in other insects

Our discovery of a M_r 128 k biotin-containing protein in an extract of the white-fly was an unexpected outcome of the use of an avidin-biotin-peroxidase method to visualize a western blot. This major biotin-containing protein was shown to be present in several tissues of 10 different species of insects by doing a western blot and staining it with streptavidin-linked peroxidase. The amount of this protein in the thorax of the mosquito, Aedes aegypti, increased during development. The non-flying grasshopper, Barytettix psolus, had reduced amounts of this protein in their thoraces compared to a flying grass-hopper, Schistocerca americana. The major biotin-containing protein was purified from the thoraces of honeybee, Apis mellifera, using an avidin Sepharose affinity column. The purified biotin-containing protein was shown to be pyruvate carboxylase, an enzyme that catalyzes the specific transfer of a carboxyl group to pyruvate, yielding oxaloacetate. The purified honeybee pyruvate carboxylase was characterized enzymatically and structurally. This protein had a single subunit of M_r 128 k and formed a native molecule of about M_r 500 k consisting of four of these subunits. The amino acid composition of the protein was also obtained. The enzymatic activity of this protein required acetyl-CoA, ATP, and Mg²⁺. The K_ms of the enzyme for bicarbonate and pyruvate were similar to pyruvate carboxylase from other oganisms. The biotin-containing protein was also partially purified from mosquito thoraces using the same methods and was shown to be pyruvate carboxylase. The comparison between insect pyruvate carboxylase and that of other organisms is provided and the possible physiological role of the pyruvate carboxylase in the thoracic muscles of insects is discussed.     

Regulation by CO2 of 1-aminocyclopropane-1-carboxylic acid conversion to ethylene in climacteric fruits

Cheverry, J. L., Sy, M. O., Pouliquen, J. and Marcellin, P. 1988. Regulation by CO₂ of 1-aminocyclopropane-1-carboxylic acid conversion to ethylene in climateric fruits. - Physiol. Plant. 72: 535–540.
A high CO₂ concentration (20%) at 20°C rapidly and strongly inhibited the development of the climacteric ethylene burst in apple ( Malus domestica Borkh. cv. Granny Smith) and avocado ( Persea americana Mill. cv. Fuerte) fruits and did not change 1-aminocyclopropane-l-carboxylic acid (ACC) content. Treatment with 20% CO₂ markedly decreased ACC-dependent ethylene biosynthesis at 20°C in climacteric pericarp tissues. It is suggested, therefore, that high CO₂ levels inhibit conversion of ACC to ethylene.
Synthesis of the ethylene forming enzyme (EFE) was enhanced when intact preclimacteric apples or early climacteric avocados were pretreated for 40 h with 10 μ11^-1 ethylene. When CO₂ (20%) and ethylene were both applied, a reduced stimulatory effect of ethylene on EFE synthesis was observed. A high CO₂ concentration enhanced EFE acivity in excised tissues of apples and avocados incubated with ACC (2 m M ) and cycloheximide (1 m M ) or 2–5-norbornadiene (5 ml 1^-1). In the autocatalytic process, 20% CO₂ antagonized the stimulation of EFE synthesis by ethylene, but promoted EFE activity.     

Does Removing Coyotes for Livestock Protection Benefit Free-Ranging Ungulates?

Abstract: We studied the effects of coyote (Canis latrans) control for livestock protection on native ungulates during 2003 and 2004 on 7 sites in Utah and Colorado, USA, totaling over 1,900 km². We found no relationships between coyote control variables and offspring/female deer ratios. However, control effort (no. of hr spent aerial gunning for coyotes) and success (no. of coyotes taken) were positively correlated with numbers of mule deer (Odocoileus hemionus) and pronghorn (Antilocapra americana) observed per kilometer of transect. Our results suggest that coyote control for livestock protection may increase densities of mule deer and pronghorn in areas where it is conducted.     

The savannization of moist forests in the Sierra Nevada de Santa Marta, Colombia

In the Rio Ranchería watershed of the Sierra Nevada de Santa Marta, between 500 and 1500 m, savanna vegetation is interspersed with moist forests. The savannas are composed of native savanna grasses like Aristida adscensionis L., Arundinella sp., Panicum olyroides Kunth, and Schyzachyrium microstachyum (Desv.) Roseng., Arrill & Izag and the African Melinis minutiflora P. Beauv. There is also Curatella americana L. and Byrsonima crassifolia (L.) H.B.K., two typical tree species of the neotropical savannas. Although moist forest patches occur more often on lower slopes and narrow valley bottoms, they can also be found on mid- and upper-slopes and less often on ridges. Thus, these forest patches are not gallery forests as are found throughout the neotropics, but the result of deforestation and fractionation of a continuous forest. A comparison of soil profiles between the savannas and remnant forest patches on the same slope, showed the disappearance of the A and B horizons (approx. 50 cm) under savanna vegetation. The sharp difference between the savanna and forest soils at the Rio Ranchería does not appear to be due to a change in soil water status along a toposequence or differences in the underlying bedrock. We hypothesize that the savannas of the Rio Ranchería watershed, are the result of deforestation and land practices on infertile soils derived from granite. The savannization process was likely initiated by Amerindians by means of the frequent use of fire or clearing lands for the cultivation of maize. The introduction of cattle by Spaniards (c. 1530) and the frequent use of fire to maintain grazing fields, contributed to further degradation of the habitat. While some tropical landscapes recovered their forest cover when human pressure was removed approximately 500 years ago, areas such as the Rio Ranchería watershed have suffered permanent damage. The savannas of this region are likely to remain unless fire is suppressed and soil restoration practices implemented.     

Persistence and effects of α-methyl-substituted amino acids on 5-hydroxytryptamine and dopamine concentrations in cockroach (Periplaneta americana) nervous tissue

The α-methylated derivatives of tryptophan, tyrosine, and dihydroxyphenylalanine were injected into cockroaches (Periplaneta americana). The levels of these compounds and those of dopamine, 5-hydroxytryptamine, tyrosine, and tryptophan in the nervous tissue, hemolymph, and fat body were measured at various times after drug administration. Levels of 5-hydroxytryptamine and tryptophan in the nervous tissue are significantly reduced by α-methyltryptophan administration. Concentrations of dopamine in nervous tissue are reduced by α-methyltyrosine administration. This effect also persists for several weeks, and α-methyltyrosine is observed in the nervous tissue 3 weeks after injection. Levels of dopamine and 5-hydroxytryptamine in the nervous tissue are unaffected by α-methyldihydroxyphenylalanine, and this compound is less persistent in nervous tissue than α-methyltyrosine or α-methyltryptophan demonstrates that these compounds can be absorbed and affect amine levels in the nervous tissue when included in the diet. Inhibition of tryptophan hydroxylation by crude enzyme preparations of cockroach nervous tissue was demonstrated with both α-methyltryptophan and α-methyltyrosine, with α-methyltryptophan being the more effective inhibitor. Aromatic amino acid decarboxylase activity toward dihydroxyphenylalanine in crude enzyme preparations of cockroach nervous tissue was strongly inhibited by α-methyldihydroxyphenylalanine and monofluoromethyldihydroxyphenylalanine, slightly inhibited by α-methyltyrosine and unaffected by α-methyltryptophan at concentrations up to 10^?3 M. The results indicate that α-methyltyrosine and α-methyltryptophan, but not α-methyldihydroxyphenylalanine, can selectively alter amine concentrations in insect nervous tissue and that insects are only poorly able to metabolize or excrete these compounds. The selective and long-lasting depletion of dopamine or 5-hydroxytryptamine by some of these compounds suggest that they may be useful in behavioral studies designed to elucidate the roles of these amines in insects.     

Volatiles from the symbiotic fungus Raffaelea lauricola are synergistic with Manuka lures for increased capture of the Redbay ambrosia beetle Xyleborus glabratus

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Implications of stunting on morphology of freshwater fishes

The purpose of this study was to assess morphological differences between stunted and non‐stunted white perch Morone americana and green sunfish Lepomis cyanellus. Few female M. americana were captured; thus, morphological differences between adult males and juveniles were assessed for M. americana. Similarly, few immature (juvenile) L. cyanellus were captured for the stunted morphotype; thus, male and female morphological differences were assessed for L. cyanellus. Features of the head tended to be relatively larger in stunted fish of both species, whereas the mid‐body tended to be relatively larger in non‐stunted M. americana, but not in non‐stunted L. cyanellus. Adult and juvenile morphology overlapped considerably in non‐stunted M. americana, but there was a clear distinction between adult and juvenile morphology of stunted M. americana. There was little sexual dimorphism in shape in stunted L. cyanellus, whereas sexual dimorphism was evident in non‐stunted L. cyanellus. It appears that selective forces imposed by predation and food limitation may contribute to morphological diversification between stunted and non‐stunted fishes.     

美洲大蠊水解氨基酸含量测定及营养评价

采用酸水解法,测定美洲大蠊中氨基酸的种类和含量,并对其进行营养评价。结果表明:美洲大蠊含有17种氨基酸(色氨酸被水解破坏而未检出),总氨基酸质量分数为43.14%,其中药效氨基酸占总量的55.43%,呈味氨基酸占总量的20.28%,其氨基酸配比较为合理:E/(E+N)=0.35,E/N=0.55,与WHO/FAO提出的参考蛋白模式接近。美洲大蠊中氨基酸种类齐全,含量丰富,富含必需氨基酸和药效氨基酸,具有很高的食用、药用价值,有较好的开发潜力。     

Effects of multiple founder populations on spatial genetic structure of reintroduced American martens

Reintroductions and translocations are increasingly used to repatriate or increase probabilities of persistence for animal and plant species. Genetic and demographic characteristics of founding individuals and suitability of habitat at release sites are commonly believed to affect the success of these conservation programs. Genetic divergence among multiple source populations of American martens (Martes americana) and well documented introduction histories permitted analyses of post‐introduction dispersion from release sites and development of genetic clusters in the Upper Peninsula (UP) of Michigan <50 years following release. Location and size of spatial genetic clusters and measures of individual‐based autocorrelation were inferred using 11 microsatellite loci. We identified three genetic clusters in geographic proximity to original release locations. Estimated distances of effective gene flow based on spatial autocorrelation varied greatly among genetic clusters (30–90 km). Spatial contiguity of genetic clusters has been largely maintained with evidence for admixture primarily in localized regions, suggesting recent contact or locally retarded rates of gene flow. Data provide guidance for future studies of the effects of permeabilities of different land‐cover and land‐use features to dispersal and of other biotic and environmental factors that may contribute to the colonization process and development of spatial genetic associations.