Preferência de oviposição e sua relação com o desempenho de Diaphania hyalinata (L, 1758) (Lepidoptera: Crambidae) em cucurbitáceas / Preferência de oviposição e sua relação com o desempenho de Diaphania hyalinata (L, 1758) (Lepidoptera: Crambidae) em cucurbitáceas

Diaphania hyalinata L. (Lepidoptera, Pyralidae) destaca-se como principal praga da família Cucurbitaceae. Este lepidóptero é oligófago de hábito polífago, que desperta largo interesse de estudos da sua ecologia comportamental por motivos de manejo em culturas de grande importância econômica como o meloeiro (Cucumis melo L.). Dada esta situação, trabalhos básicos de entendimento de aspectos da ecologia são necessários para a melhoria das formas de manejo, principalmente no aspecto do monitoramento populacional. Diante disso, a presente pesquisa teve como objetivo verificar se a escolha do hospedeiro exercida por fêmeas de D. hyalinata corresponde ao melhor desempenho da prole e como os hospedeiros influenciam sua dinâmica populacional. Testes de oviposição com chance de escolha foram realizados em melão, melancia, maxixe, bucha, melãode-são-caetano e pepino, para estabelecimento de um ranking de preferência. Para o desempenho das lagartas e reprodução foi escolhido o melão (dentre o mais preferido) e a bucha e o pepino (dentre os hospedeiros menos preferidos). Os resultados suportam a hipótese de que a escolha de hospedeiro é relacionada com o desempenho da prole e que D. hyalinata demonstrou possuir plasticidade ao lidar com diferentes hospedeiros o que pode ser um indicativo de capacidade de adaptação a recursos alimentares que flutuam em termos de qualidade e disponibilidade. No entanto, de modo geral, esta plasticidade tem custos elevados, principalmente em termos reprodutivos.

Diaphania hyalinata L. (Lepidoptera, Pyralidae) stands out as a major pest of the Cucurbitaceae family. This insect is oligophagous with a polyphagous habit, which arouses wide interest in studies of their behavioral ecology for reasons of pest management in crops of high economic importance such as muskmelon (Cucumis melo L.). Given this situation, basic studies aimed at an understanding of ecological aspects of this pest are needed to improve pest management systems, especially in the aspect of population monitoring. Given this, the present study was aimed to determine whether the choice of the host exerted by females of D. hyalinata corresponds to the best performance of the offspring and how the hosts influence their population dynamics. Oviposition-choice tests were performed on melon, watermelon, cucumber, loofah, balsam apple and cucumber, to establish a ranking of preference. For the performance of larvae and reproduction the melon was chosen (among the most preferred hosts) along with loofah and cucumber (among the least preferred hosts). The results support the hypothesis that the choice of host is related to the performance of the offspring and D. hyalinata has demonstrated plasticity in dealing with different hosts which may be indicative of ability to adapt to fluctuating food resources in terms of quality and availability. However, generally this plasticity is expensive, especially in reproductive terms.

Parasitoids of Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae) collected on tomato plants in lavras, State of Minas Gerais, Brazil.

The objective of this paper was to report on the occurrence of parasitoids of Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) on tomato plants, under greenhouse conditions, in Lavras County (21 degrees 14'43"S; 44 degrees 59'59"W), State of Minas Gerais, Brazil, from August 2001 to February 2002. Three groups of parasitoids were collected: 21 specimens of Bracon sp. (Braconidae), one specimen of Earinus sp. (Braconidae), and 13 specimens of Conura sp. (Chalcididae). The rate of parasitism for the three species was 4.2%, 0.2%, and 2.6%, respectively. This is the first reported occurrence of Earinus sp. parasitizing Tuta absoluta in Brazil.

Parasitoids of Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae) collected on tomato plants in Lavras, state of Minas Gerais, Brazil

Este trabalho teve por objetivo relatar a ocorrência de parasitóides de Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) em plantas de tomate, em condições de casa-de-vegetação, em Lavras (21º14'43"S; 44º59'59"W), Minas Gerais, no período de agosto de 2001 a fevereiro de 2002. Três grupos de parasitóides foram coletados: 21 espécimes de Bracon sp. (Braconidae), um espécime de Earinus sp. (Braconidae) e 13 espécimes de Conura sp. (Chalcididae). A taxa de parasitismo para as três espécies foi de 4,2%, 0,2% e 2,6%, respectivamente. Este estudo relata, pela primeira vez no Brasil, a ocorrência de Earinus sp. parasitando Tuta absoluta.

Mode of action of site-directed irreversible folate analogue inhibitors of thymidylate synthase.

5,8-Dideazafolate analogues are tight binding but not irreversible inhibitors of thymidylate synthase (TS). However, when a chloroacetyl (ClAc) group is substituted at the N10-position of 2-desamino-2-methyl-5,8-dideazafolate (DMDDF), the resulting compound, ClAc-DMDDF, although still a reversible inhibitor (KI = 3.4 x 10(-3) M), gradually inactivates thyA-TS irreversibly at a rate of 0.37 min-1. The corresponding iodoacetyl derivative alkylated the enzyme somewhat slower (k3 = 0.15 min-1 ) than ClAc-DMDDF but was bound more tightly (KI = 1.4 x 10(-5) M), resulting in a second-order rate constant (k3/KI) of inactivation that was 100-fold greater than that of ClAc-DMDDF. A tryptic digest of the ClAc-DMDDF-inactivated enzyme yielded a peptide on HPLC, which revealed that cysteine-146, the residue at the active site that is intimately involved in the catalytic process, had reacted with ClAc-DMDDF to form a covalent bond. This derivative was confirmed indirectly by Edman analysis and more directly by mass spectrometry. Deoxyuridine 5'-monophosphate, a substrate in the catalytic reaction, protected against inactivation. Similar to previously described Lactobacillus casei TS inhibition studies with sulfhydryl reagents [Galivan, J., Noonan, J., and Maley, F. (1977) Arch. Biochem. Biophys. 184, 336-345], the kinetics of inhibition suggested that complete inhibition occurs on reaction of only one of the two active site cysteines, although sequence and amino acid analysis revealed that iodoacetate and ClAc-DMDDF had reacted with both active site cysteines. These studies demonstrate that a sulfhydryl reactive compound that is directed to the folate binding site of TS may diffuse to the active site cysteine, and form a covalent bond with this residue. How this inhibition comes about is suggested in a stereoscopic view of the ligand when modeled to the known crystal structure of Escherichia coli TS.

Resurgent Irish immigration to the U.S. in the 1980s and early 1990s: a socio-demographic profile.

PIP: "This article uses U.S. immigration data to assess how the occupational characteristics of recent Irish immigrants compare with prior immigrant cohorts and also examines how Irish immigrants are incorporated into the U.S. economy. Recent Irish immigrants to the U.S. spanned the occupational spectrum.... While the number of entering Irish professionals increased, flows of the less skilled increased even more dramatically, resulting in an overall decline in the occupational selectivity of Irish immigrants." (EXCERPT)^ieng

Changing U.S. immigration law and the occupational selectivity of Asian immigrants.

PIP: This study explored the relationship between US immigration laws and their impact on the immigration of Asian professionals. The article relied on a 1996 Population Association presentation. Data were obtained from the US Immigration and Naturalization Service on legally admitted immigrants to the US. The authors describe the paths to admission, trends in immigration of professionals during 1972-94, and the Immigration Act of 1965 and its 4 amendments. Standardization-decomposition techniques are used to explain the relative differences in professional immigration across 1972-77, 1978-91, and 1992-94. The crude professional rate for all Asians declined by 19% during 1972-91. 62% of the decline was due to changes in the class of admission composition, and 25% was due to a decline in the class-specific professional rates. During 1992-94, the Asian crude professional rate increased 7%, most of which was due to changes in class composition, with the exception of Korean rates. Only the Vietnamese experienced a decline in rates. The 1965 law allowed for equity between countries in admission. The paths of immigration were family ties, job skills, or refugee status. During 1972-77, Chinese took advantage of family reunification, and Indians entered on employment preferences. The legal changes affected the size and share of each class of admission. The revisions indirectly affected the occupational selectivity of immigrant groups. 27% of the flow of Asians during 1972-77 was accounted for by employment preferences. Professionals were 44% of Asian immigrants during 1972-77, 26% during 1978-91, and 33% during 1992-94.^ieng

Immigration to New York City in the '90s: the saga continues.

PIP: The author examines recent immigration flows to New York City, with a focus on their impact on the city's population. Information is included on immigrants by area of the world and country of birth, demographic characteristics, and migration law.^ieng

Properties of an affinity-column-purified human deoxycytidylate deaminase.

Deoxycytidylate deaminase was purified about 7000-fold to homogeneity from a human source (HeLa cells). The final step in the purification employed an affinity column, which increased the specific activity of the enzyme from the previous step by 500-fold. Similar to most other dCMP deaminases, this enzyme is allosterically regulated by microM levels of dCTP and dTTP. However, unlike the other enzymes the most dramatic allosteric responses occur at substrate levels of 0.1 mM dCMP or less, where at least a 10-fold increase in activity is effected by dCTP. The enzyme is particularly sensitive to inhibition by dTTP with 50% inhibition being obtained at 1.5 x (10(-6) M in the absence of dCTP. Antibody to the human enzyme did not cross-react with a dCMP deaminase induced in Escherichia coli by T4-bacteriophage, nor did antibody to the phage-induced enzyme cross-react with the human deaminase. A potential transition-state analogue of the substrate, 2'-beta-D-deoxyribose-pyrimidin-2-one 5'-phosphate was prepared, and found to inhibit dCMP deaminase competitively with a Ki of 1.2 x 10(-8) M.

Studies on the inhibition of human thrombin: effects of plasma and plasma constituents.

The effects of blood plasma and some plasma constituents on several types of thrombin inhibitors were quite varied. Two active esters were rapidly destroyed by serum albumin; one of these reacted initially with Lys-199, the residue that is also acylated by aspirin. Of two sulfonyl fluorides one was unaffected by albumin, and the other bound reversibly to albumin; this binding was greater with albumin acetylated at Tyr-411 near the binding site for medium-chain fatty acids. The effects of a chloromethyl ketone were inhibited, apparently reversibly, by albumin but were practically abolished by glutathione. Of two potent reversible inhibitors one was unaffected by plasma constituents, while the other was over 10-fold less potent in plasma than in fibrinogen. The effect of plasma could be partially explained by binding to albumin and lipoproteins.