Integrated pest management of two-spotted mite Tetranychus urticae on greenhouse roses using petroleum spray oil and the predatory mite Phytoseiulus persimilis

From 1995 to 1999, four experiments were conducted on greenhouse roses to assess the effectiveness of the nC24 petroleum spray oil (PSO), D-C-Tron Plus, against two-spotted mite, Tetranychus urticae Koch (Acarina: Tetranychidae), and to determine how the oil could be most efficiently and effectively used in combination with the predatory mite Phytoseiulus persimilis Athias-Henriot (Acarina: Phytoseiidae) in an integrated pest management program. The results showed that 0.5% PSO applied fortnightly to roses gave excellent protection from T. urticae infestation when the mite population was not already established. However, PSO applied after roses were infested with T. urticae above the economic threshold only stabilised populations without reducing them below that threshold. Populations of P. persimilis in the upper and lower canopies were unchanged after two sprays of PSO at 7-day intervals, and application of PSO to the upper canopy was as effective in controlling T. urticae in the presence of P. persimilis as spraying the entire plant. Combining PSO with P. persimilis gave better control of T. urticae than using P. persimilis alone. The most cost-effective use of PSO in the presence of P. persimilis is, therefore, to apply spray only to the upper canopy. This will not affect control of powdery mildew with PSO. Comparison of a control program for T. urticae based on the monitored use of synthetic miticides with that based on calendar application of PSO revealed that both gave equally effective control. The benefits of combining PSO and P. persimilis in an integrated pest management program for T. urticae on roses over a program based on synthetic fungicides are discussed.     

Mitochondrial DNA and RAPD polymorphisms in the haploid mite Brevipalpus phoenicis (Acari: Tenuipalpidae)

Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae) is recognized as the vector of citrus leprosis virus that is a significant problem in several South American countries. Citrus leprosis has been reported from Florida in the past but no longer occurs on citrus in North America. The disease was recently reported in Central America, suggesting that B. phoenicis constitutes a potential threat to the citrus industries of North America and the Caribbean. Besides B. phoenicis, B. obovatus Donnadieu, and B. californicus (Banks) have been incriminated as vectors of citrus leprosis virus and each species has hundreds of host plants. In this study, Brevipalpus mite specimens were collected from different plants, especially citrus, in the States of Florida (USA) and São Paulo (Brazil), and reared on citrus fruit under standard laboratory conditions. Mites were taken from these colonies for DNA extraction and for morphological species identification. One hundred and two Random Amplified Polymorphic DNA (RAPD) markers were scored along with amplification and sequencing of a mitochondrial cytochrome oxidase subunit I gene fragment (374 bp). Variability among the colonies was detected with consistent congruence between both molecular data sets. The mites from the Florida and Brazilian colonies were morphologically identified as belonging to B. phoenicis, and comprise a monophyletic group. These colonies could be further diagnosed and subdivided geographically by mitochondrial DNA analysis.     

Melatonin enhances Th2 cell mediated immune responses: Lack of sensitivity to reversal by naltrexone or benzodiazepine receptor antagonists

Chronic administration of melatonin for 5 days to antigen-primed mice increased the production of pro-inflammatory cytokine IL10 but decreased the secretion of antiinflammatory cytokine TNF-. These results further confirm that melatonin activates Th2like immune response. Whether melatoninmediated Th2 response is dependent on opioid or central and peripheral benzodiazepine receptors was also examined. Hence, melatonin was administered to antigen-sensitised mice with either naltrexone (a opioid receptor antagonist) or flumazenil (a central benzodiazepine receptor antagonist) or PK11195 (a peripheral benzoidiazepine receptor antagonist). No significant difference in melatonin-induced Th2 cell response was observed by naltrexone, flumazenil or PK11195 treatment. These findings suggest that the Th2 cell response induced by melatonin in antigen sensitised mice neither dependent on endogenous opioid system nor is modulated through the central or peripheral benzodiazepine receptors.     

The feeding ecology of a carnivorous plant (Pinguicula nevadense): prey analysis and capture constraints

Summary The taxonomic composition and size of arthropods captured by Pinguicula nevadense, an endemic carnivorous plant of the high-mountain zone of the Sierra Nevada (southern Spain), are analysed. The actual prey of P. nevadense and the available arthropods trapped by mimic-traps are compared, in order to identify the capture constraints of the plant. The results show that P. nevadense captures various arthropod taxa. Winged insects, especially Nematocera, make up the main component of the diet. The range of prey sizes in all P. nevadense populations studied is similar. The taxonomic composition of arthropods trapped by the mimic-traps is similar to that of the actual prey of P. nevadense. However, the plant captures prey only below a specific size threshold. These size constraints appear to be the principal factor determining the actual prey of this carnivorous plant.     

Polymerization of the Actin Component of the Cytoskeleton and Formation of the Geometry of a Cultured Nerve Cell (a Model Study)

Using mathematical modeling, we studied the biophysical aspects of the growth of the cell membrane and the growth of the actin network of the cytoskeleton of a neuron cultured on the rigid sublayer and the correlation between these processes. To describe the dynamics of the growth of the cytoskeleton limited by the cell membrane, we used the model of the thermal ratchet. Using the approaches of theoretical biophysics, we obtained a simple biophysical criterion that governs the selection of an alternative scenario of the formation of the cell, either growth of a single neurite or growth of a number of neurites. This criterion depends on the value of the adhesion between the cell and the substrate, the dimension of the actin monomer, and the thermal energy determining the frequency of thermal fluctuations of the cell membrane.     

Comparative susceptibility and possible detoxification mechanisms for selected miticides in banks grass mite and two-spotted spider mite (Acari: Tetranychidae)

The susceptibility and possible detoxification mechanisms of the Banks grass mite (BGM), Oligonychus pratensis (Banks), and the two-spotted spider mite (TSM), Tetranychus urticae Koch, to selected miticides were evaluated with and without synergists. BGM was 112-fold more susceptible to the organophosphate dimethoate, and 24-fold more susceptible to both the pyrethroids bifenthrin and -cyhalothrin than TSM. The synergist triphenyl phosphate (TPP) enhanced the toxicities of bifenthrin and -cyhalothrin against BGM by 3.0- and 4.2-fold, respectively, and enhanced the toxicities of bifenthrin, -cyhalothrin, and dimethoate against TSM by 6.2-, 1.9-, and 1.7-fold, respectively. The synergist diethyl maleate (DEM) enhanced the toxicities of bifenthrin and -cyhalothrin against BGM by 2.2- and 2.9- fold, respectively, and enhanced the toxicity of bifenthrin against TSM by 4.1-fold. On the other hand, the synergist piperonyl butoxide (PBO) increased the toxicities of bifenthrin and -cyhalothrin by 6.0- and 2.6-fold, respectively, against BGM, and by 4.5- and 1.9-fold, respectively, against TSM. The significant synergism with these pyrethroids of all three tested synergists (except for DEM with -cyhalothrin against TSM) suggests that esterases, glutathione S-transferases, and cytochrome P450 monooxygenases all play important roles in their detoxification. However, the toxicity of dimethoate was not enhanced by these synergists in either mite species (except for TPP against TSM). Apparently, these metabolic enzymes play less of a role in detoxification of this organophosphate in these mites.     

Allomonal defence secretions of the American dog tick Dermacentor variabilis (Acari: Ixodidae) promote clustering

The release of the defence secretion from the large wax glands (sensilla sagittiformia) of Dermacentor variabilis ticks modifies the behaviour of other ticks by inducing clustering. A coating of natural tick secretion onto test objects (delipidized ticks, glass beads or filter paper discs) also elicits a clustering response, but a topically applied squalene, its major component, does not have this effect. The clustering response appears to be species specific: D. variabilis cluster on conspecific ticks that secreted but they fail to cluster on Amblyomma americanum or Ixodes scapularis ticks unless coated with secretions from D. variabilis. Volatile components in the defence secretion are involved in recruiting conspecific ticks to those that secreted. When attacked by predatory fire ants, Solenopsis invicta, D. variabilis clustered on individuals that had released the defence secretion. This suggests that the secretion protects ticks from predation by functioning as an alarm pheromone. If confirmed, this is the first report of an alarm pheromone and its glandular source in ticks. The terminology applicable to the integumental glands of ticks is discussed.     

cDNA cloning and expression of a potato (Solanum tuberosum) invertase

A cDNA clone encoding an invertase isoenzyme has been isolated from a potato leaf cDNA library. The deduced amino acid sequence shows significant similarities to previously characterised invertases. The highest degree of overall similarity, including the signal peptide sequence, is to carrot cell wall invertase, suggesting that the potato gene encodes an apoplastic enzyme. Expression of the gene, as determined by RT-PCR, is detected in stem and leaf tissue, and at lower levels in tuber, but is absent from roots.     

In vivo effects of vanadium in diabetic rats are independent of changes in PI‐3 kinase activity in skeletal muscle

The PI3 kinase signalling pathway is an important pathway in mediating the glucoregulatory effects of insulin and skeletal muscle (SKM) is the major tissue involved in glucose utilization. In diabetes this pathway is impaired, either due to lack of insulin as in Type 1 diabetes, or due to insulin resistance as in Type 2 diabetes. Bis(maltolato)oxovanadium IV (BMOV), an insulin mimetic/enhancing agent, produces a marked glucose lowering effect in models of both types of diabetes. Some in vitro studies have shown that phosphatidylinositol 3 kinase (PI3 kinase) activity is enhanced by vanadium. In the present study we looked at changes in PI3 kinase expression and activity in SKM from STZdiabetic and fa/fa Zucker rats treated with BMOV for 3 weeks. Although BMOV treatment completely normalized glucose levels in STZdiabetic rats, no effect was observed on basal or insulin-stimulated PI3 kinase activity. In fatty Zucker rats, activation of PI3 kinase activity after insulin injection was impaired as compared to age matched lean controls, but BMOV again did not affect the activity. These results suggest that although PI3 kinase is an important signalling factor in glucose utilization, vanadium treatment does not reduce hyperglycemia through activation of SKM PI3 kinase in vivo.     

Complete resistance to pepper mild mottle tobamovirus mediated by viral replicase sequences partially depends on transgene homozygosity and is based on a gene silencing mechanism

We have previously distinguished two different types of resistance response, complete and delayed, to the pepper mild mottle tobamovirus (PMMoV) in Nicotiana benthamiana plants transformed with the 54kDa region of the viral replicase gene. The present study was undertaken to assess a potential relationship between transgene dose and the type of resistance observed in the 54kDa transgenic plants. By genetic and molecular analysis, we demonstrated that complete resistance against PMMoV infection was strictly correlated with homozygosity of the transgene in the R1 and R2 generation plants. Progeny hemizygous for the TDNA locus showed delayed resistance, but none of the progeny exhibited the complete resistance response. Thus, the resistance to PMMoV varied in a gene dosagedependent manner. However, a limited number of individuals of the R2 progeny from homozygous plants displayed complete resistance, while the remaining plants showed delayed resistanc; the ratio between the two resistance responses was roughly similar to the ratio observed in either the R2 progeny from hemizygous plants or the original R1 generation plants. R2 homozygous plants displaying complete resistance contained undetectable levels of 54kDa mRNA, although the transgene was accurately transcribed in these plants. These results suggest that transgene homozygosity is a necessary but not a sufficient condition to confer complete resistance to PMMoV by a gene silencing mechanism.     

Different evolution rates within the lens-specificβ-crystallin gene family

Summary We have determined the sequence of a rat A3/A1-crystallin complementary DNA (cDNA) clone and the (partial) sequence of the human B3-crystallin gene. Calculation of the ratio of silent to nonsynonymous substitution between orthologous A3/A1-, B3-, and other - and -crystallin sequences revealed that the region encoding the two globular domains of the A3/A1-crystallin sequence is the best conserved during evolution, much better than the corresponding region of the B1-, B3-, or the -crystallin sequences, and even better (at least in the rodent/frog comparison) that the well-conserved A-crystallin sequence. Remarkably, the rate of change of the A3/A1-crystallin coding sequence does not differ in the rodent and primate lineages, in contrast with previous findings concerning the evolution rates of the A- or -crystallin sequences in these two lineages. Comparison of the regions that encode the four motifs of the -crystallin between orthologous mammalian sequences showed that the extent of nonsynonymous substitution in each of these four homologous motif regions is the same. However, when the orthologous -crystallin genes of more distantly related species (mammals vs chicken or frog) are compared, the extent of nonsynonymous substitution is higher in the regions encoding the external motifs I and III than in the regions encoding the internal motifs II and IV. This phenomenon is also observed when paralogous members of the /-crystallin supergene family are compared.     

“Gomori-positive” neurosecretion in the rat after deafferentation of the medial basal hypothalamus

A portion of the "Gomori-positive" peptidergic neurosecretory (NS) cells in the paraventricular and especially in the supraoptic and postoptic nuclei degenerate three weeks after deafferentation of the medial basal hypothalamus. Most of the remaining NS cells show signs of high activity. Regenerating NS fibres form "muffs" around the blood vessels laterally from the lesion; some of them enter the "isolated" area or persist there if a thin layer of the brain tissue is left somewhere untouched under the basal end of the cut. The regenerating NS fibres are also found outside the nervous tissue: within the scar tissue, in the proliferating connective tissue of the brain sheet below the basal end of the cut and in the mantel plexus area. The NS fibres make close contact with blood vessels invading or penetrating the vascular wall. It is suggested that peptide neurohormones discharged from the "Gomori-positive" NS terminals enter the general blood circulation as well as the portal blood at the site of these newly formed axovasal contacts. It is supposed that under these conditions monoaminergic terminals do not discharge monoamines because no stimulation of monoamine-producing NS cells occurs with deafferentation.     

The Solution Structure of [d(CGC)r(amamam)d(TTTGCG)]2

The solution structure and hydration of a DNARNA hybrid chimeric duplex [d(CGC)r(a_ma_ma_m)d(TTTGCG)]₂ in which the RNA adenines were substituted by 2-O-methylated riboadenines was determined using two-dimensional NMR, simulated annealing, and restrained molecular dynamics. Only DNA residue 7T in the 2-OMe-RNA DNA junction adopted an O4-endo sugar conformation, while the other DNA residues including 3C in the DNA 2-OMe-RNA junction, adopted C1-exo or C2-endo conformations. The observed NOE intensity of 2-O-methyl group to H1 proton of 4a_m at the DNA 2-OMe-RNA junction is much weaker than those of 5a_m and 6a_m. The 2-O-methyl group of 4a_m was found to orient towards the minor groove in the trans domain while the 2-O- methyl groups of 5a_m and 6a_m were found to be in the gauche (+) domain. In contrast to the long-lived water molecules found close to the RNA adenine H2 and H1 protons and the methyl group of 7T in the RNA-DNA junction of [d(CGC)r(aaa)d(TTTGCG)]₂, there were no long-lived water molecules found in [d(CGC)r(a_ma_ma_m)d(TTTGCG)]₂. This is probably due to the hydrophobic enviroment created by the 2-O-methylated riboadenines in the minor groove or due to the wider minor groove width in the middle of the structure. In addition, the 2-O-methylation of riboadenines in pure chimeric duplex increses its melting temperature from 48.5°C to 51.9°C. The characteristic structural features and hydration patterns of this chimeric duplex provide a molecular basis for further therapeutic applications of DNARNA hybrid and chimeric duplexes with 2-modified RNA residues.     

Role of ubiquitin‐proteasome‐dependent proteolytic process in degradation of muscle protein from diabetic rabbits

The activity of ATP, ubiquitin (Ub)dependent proteases partially purified from skeletal muscle (psoas) from alloxan diabetic rabbits was determined at different periods of insulin deficiency. Two days after alloxan injection, no change was observed in the activity of ATP, Ubdependent proteases, but this activity increased 3 and 5 days after diabetes induction, attaining 181% of control values on the 5th day. However, after this early rise, the activity of muscle ATP, Ubdependent proteases decreased, returning to values that did not differ significantly from controls 7 and 10 days after alloxan injection. After 15 days, the activity of these proteases was 57% lower than in muscle from control rabbits. Both the initial increase and the subsequent fall in the activity of the enzymes were prevented by insulin treatment of alloxan diabetic rabbits. The data suggest that Ubproteasomedependent proteolysis have an important role in the control of muscle protein degradation and may be regulated by insulin.     

Cytoarchitectonic pattern of the hypothalamus in the cobra,Naja naja

Summary The distribution and cytoarchitectonic pattern of the magno- and parvocellular hypothalamic nuclei of the cobra, Naja naja, are described at the light-microscopic level. With respect to their tinctorial affinity to paraldehyde fuchsin (AF) as a representative of the Gomori-type of stains, the magnocellular neurons belong to the AF-positive and the parvocellular neurons to the AF-negative elements. In addition to the supraoptic and paraventricular nuclei proper, two accessory aggregations of magnocellular neurons, the nucleus retrochiasmaticus and nucleus circularis, can be identified. Although in a peculiar location, they may be regarded as subunits of the supraopticoparaventricular neurosecretory complex. As many as 22 AF-negative nuclear areas are identified in the hypothalamus of the cobra. The nucleus periventricularis hypothalami of earlier authors is subdivided into several circumscribed neuronal complexes. The nucleus arcuatus, nucleus hypothalamicus lateralis and nucleus lateralis recessus infundibuli are well developed. An attempt is made to interpret the significance of these nuclei on a comparative and phylogenetic basis.On leave from the Department of Zoology, Nagpur University, Nagpur, India     

The response of the antioxidant defense system in rat hepatocytes challenged with oxysterols is modified by Covi-ox

Suspension cultures of isolated rat hepatocytes were used to investigate whether 7-ketocholesterol and cholestane-3,5,6-triol exert oxidative stress in cells as manifested by increased lipid peroxidation and the induction of the antioxidant enzymes catalase, glutathione peroxidase and superoxide dismutase. The oxysterols were found to increase the levels of both superoxide dismutase and catalase and to have variable effects on glutathione peroxidase activity. Increased lipid peroxidation was not observed, indicating that the endogenous antioxidant defense system was capable of protecting against any oxidative stress that might otherwise by exerted by 7-ketocholesterol or cholestane-3,5,6-triol. Covi-ox, a natural tocopherol blend reduced the effects of both oxysterols on the antioxidant enzymes. A concurrent reduction in the production of thiobarbituric acid-reactive substances in Covi-ox-treated cells is indirect evidence that reactive oxygen species were produced by oxysterols in hepatocyte suspension cultures.     

Exploration of RNA 3′ terminal locations in rat ribosome

The locations of the 3 ends of RNAs in rat ribosome were studied by a fluorescencelabeling method combined with high hydrostatic pressure and agarose electrophoresis. Under physiological conditions, only the 3 ends of 28 S and 5.8 S RNA in 80 S ribosome could be labeled with a high sensitive fluorescent probe – fluorescein 5thiosemicarbazide (FTSC), indicating that the 3 termini of 28 S and 5.8 S RNA were located on or near the surface of 80 S ribosome. The 3 terminus of 5 S RNA could be attacked by FTSC only in the case of the dissociation of the 80 S ribosome into two subunits induced by high salt concentration (1 M KCl) or at high hydrostatic pressure, showing that the 3 end of 5 S RNA was located on the interface of two subunits. However, no fluorescencelabeled 18 S RNA could be detected under all the conditions studied, suggesting that the 3 end of 18 S RNA was either located deeply inside ribosome or on the surface but protected by proteins. It was interesting to note that modifications of the 3 ends of ribosomal RNAs including oxidation with NaIO₄, reduction with KBH₄ and labeling with fluorescent probe did not destroy the translation activity of ribosome, indicating that the 3 ends of RNAs were not involved in the translation activity of ribosome.