Imidacloprid Inhibits Behavioral Defences of the Leaf-Cutting Ant Acromyrmex subterraneus subterraneus (Hymenoptera:Formicidae)

Leaf-cutting ants have evolved a range of defensive strategies which complicate the use of entomopathogens for their control. One of these behavioral strategies is self-grooming, which increases when ants detect the presence of fungal conidia on their integuments. We have previously shown that insecticides, when used at ultra-low concentrations, can be synergists of entomopathogenic fungi. It is possible that certain insecticides could modify ant behavior in a way that increases the chances of a fungal infection taking hold. The current study investigated the effects of the neonicotinoid insecticide Imidacloprid (IMI) and the entomopathogenic fungus Beauveria bassiana on self-grooming and locomotion behavior of Acromrymex subterraneus subterraneus workers when ants were exposed to the agents separately or together. Initially 10, 20 and 40 ng/insect IMI was topically administered to worker ants. Four hours after administration, the ants were placed into an experimental arena and self-grooming and locomotion behaviors were recorded for 10 min. Separate groups of ants were exposed to filter paper discs impregnated with conidial suspensions and 4 h later their behavior was monitored for 10 min. Subsequently, ants were treated with 10 ng/insect IMI, immediately exposed to fungal suspensions and 4 h later their behavior was monitored. The 10 ng/insect IMI treatment resulted in higher locomotor activity and lower self-grooming when compared to vehicle, 20 ng and 40 ng IMI treatments. Exposure to fungal conidia produced low locomotion and high self-grooming behaviors. The 10 ng IMI + fungal conidia treatment resulted in lower self-grooming and higher locomotion behavior. These alterations caused by a low concentration of IMI could increase ant susceptibility to infection by entomopathogenic fungi and are thus of interest for future tests in the development of integrated pest management strategies.     

New Bacteriophage of Haemophilus influenzae

Some properties of a newly isolated Haemophilus influenzae bacteriophage are described. The phage is morphologically distinct from previously described H. influenzae phages.     

Capacity for cooperative binding of thyroid hormone (T3) receptor dimers defines wild type T3 response elements.

Thyroid hormone response elements (T3REs) have been identified in a variety of promoters including those directing expression of rat GH (rGH), alpha-myosin heavy chain (rMHC), and malic enzyme (rME). A detailed biochemical and genetic analysis of the rGH element has shown that it consists of three hexamers related to the consensus [(A/G)GGT(C/A)A]. We have extended this analysis to the rMHC and rME elements. Binding of highly purified thyroid hormone receptor (T3R) to T3REs was determined using the gel shift assay, and thyroid hormone (T3) induction was measured in transient tranfections. We show that the wild type version of each of the three elements binds T3R dimers cooperatively. Mutational analysis of the rMHC and rME elements identified domains important for binding T3R dimers and allowed a direct determination of the relationship between T3R binding and function. In each element two hexamers are required for dimer binding, and mutations that interfere with dimer formation significantly reduce T3 induction. Similar to the rGH element, the rMHC T3RE contains three hexameric domains arranged as a direct repeat followed by an inverted copy, although the third domain is weaker than in rGH. All three are required for full function and T3R binding. The rME T3RE is a two-hexamer direct repeat T3RE, which also binds T3R monomer and dimer. Across a series of mutant elements, there was a strong correlation between dimer binding in vitro and function in vivo for rMHC (r = 0.99, P less than 0.01) and rME (r = 0.67, P less than 0.05) T3REs. Our results demonstrate a similar pattern of T3R dimer binding to a diverse array of hexameric sequences and arrangements in three wild type T3REs. Addition of nuclear protein enhanced T3R binding but did not alter the specificity of binding to wild type or mutant elements. Binding of purified T3R to T3REs was highly correlated with function, both with and without the addition of nuclear protein. T3R dimer formation is the common feature which defines the capacity of these elements to confer T3 induction.     

Pollen development in male sterile mangosteen (Garcinia mangostana L.) and male fertile seashore mangosteen (Garcinia celebica L.)

Protoplasma - Mangosteen (Garcinia mangostana L.) is an economically important tropical fruit, yet the reproductive biology of this dioecious plant is complex. Male trees are not known, and female...     

Hierarchical organization of femaleMacaca radiata in captivity

Females of several species of macaques form cohesive matrilineal units in which all members share a collective status. The relationship between rank and kinship inMacaca radiata has not previously been studied. Analysis of observations of social interactions in a large and stable captive group ofM. radiata and longitudinal study of kinship and reproductive success indicate that with few exceptions a matrilineal dominance hierarchy exists in that group. Four young, upwardly mobile females are responsible for the exceptions. Contrary to the pattern noted in other species of macaques, several adult females outrank their daughters. Old age and deteriorating physical condition of mothers appear to be associated with mother-daughter rank reversals. The age and lineage size of females when they entered the group have had a lasting impact. Females who entered the group as adults have achieved higher rank and greater reproductive success than females who entered the group as juveniles without relatives. This research was conducted at the California Primate Research Center in Davis, supported by USPHS grant RR00169.     

An Analysis of Enzyme Kinetics Data for Mitochondrial DNA Strand Termination by Nucleoside Reverse Transcription Inhibitors

Nucleoside analogs used in antiretroviral treatment have been associated with mitochondrial toxicity. The polymerase-γ hypothesis states that this toxicity stems from the analogs'' inhibition of the mitochondrial DNA polymerase (polymerase-γ) leading to mitochondrial DNA (mtDNA) depletion. We have constructed a computational model of the interaction of polymerase-γ with activated nucleoside and nucleotide analog drugs, based on experimentally measured reaction rates and base excision rates, together with the mtDNA genome size, the human mtDNA sequence, and mitochondrial dNTP concentrations. The model predicts an approximately 1000-fold difference in the activated drug concentration required for a 50% probability of mtDNA strand termination between the activated di-deoxy analogs d4T, ddC, and ddI (activated to ddA) and the activated forms of the analogs 3TC, TDF, AZT, FTC, and ABC. These predictions are supported by experimental and clinical data showing significantly greater mtDNA depletion in cell culture and patient samples caused by the di-deoxy analog drugs. For zidovudine (AZT) we calculated a very low mtDNA replication termination probability, in contrast to its reported mitochondrial toxicity in vitro and clinically. Therefore AZT mitochondrial toxicity is likely due to a mechanism that does not involve strand termination of mtDNA replication.     

Mycology at The New York Botanical Garden, 1895–1995

A review of the first 100 years of studies on fungi (including lichens) at The New York Botanical Garden is presented.