An Electron Microscopical Study of the Interaction of Monoclonal Antibodies with Gametes of the Malarial Parasite Plasmodium gallinaceum1

Anti-malarial gamete antibodies prevent the fertilization of gametes in the mosquito midgut and prevent transmission of malaria. Recently, hybridoma cell lines secreting monoclonal antibodies (10G3 and 11C7) against gametes of the malarial parasite have been developed. These antibodies act synergistically to mediate 80–90% suppression of the infectivity of gametocytes, although neither monoclonal antibody alone has a significant effect on gametocyte infectivity. We performed immuno-electron microscopy to characterize the interactions of these monoclonal antibodies with gametes of Plasmodium gallinaceum. Male gametes exposed to either 10G3 or 11C7 agglutinated into loose clusters, while those exposed to a mixture of 10G3 and 11C7 agglutinated into long, rope-like bundles. This difference appears to be related to the distribution of the antibodies on the surface of the gametes. When 10G3 or 11C7 labeled with a ferritin-conjugated anti-mouse Ig were used singly, the ferritin particles were distributed in focal areas over the surface of the parasites. By contrast, when the male gametes were exposed to a mixture of 10G3 and 11C7, the ferritin particles were distributed over their entire surface. Female gametes reacted similarly to these antibodies. These observations indicate that combinations of antibody specificities that reduce fertilization efficiency coat the entire surface of the gametes. On the other hand, focal interactions resulting from a single antibody are unable to block fertilization.     

The effect of male sandfly pheromone and host factors as attractants for female Lutzomyia longipalpis (Diptera: Psychodidae)

Abstract Male Lutzomyia longipalpis (Lutz & Neiva) pheromone extracted from tergal glands combined with heat, carbon dioxide gas and hamster urine was found to be attractive to virgin female sandflies. The host factors if offered in the absence of pheromone or a heat source were, however, unattractive to female flies. Pheromone stored for 6 days and then combined with the same host components remained attractive to female flies but storage failed to enhance its attractiveness. The effects of carbon dioxide gas, hamster urine, chicken uropygial gland extract and octenol plus acetone on the responses of females were inconsistent. A ceramic battery powered heat source was tested with pheromone and host attractants and showed potential for field application in developing a pheromone trap.     

Island models and the coalescent process

Using a coalescent approach, we derive several classical results and extend them to more general models. We find that the classic result for constant population size and constant migration rates holds in models with varying population size and varying migration rates with the obvious substitution of effective population size and mean migration fraction. In addition, the relationship of a 'local' F _ST to local gene flow is derived. This result may be useful for analysing gene flow in a regional subset of a large global population, using only data from the regional subset.     

Episodic Breathing in Frogs: Converging Hypotheses on Neural Control of Respiration in Air Breathing Vertebrates

SYNOPSIS. The episodic, or intermittent, breathing of frogsand many ectothermic vertebrates results in important fluctuationsof arterial blood gases. This pattern of breathing differs fromthe rhythmic and continuous alternation of inspiration observedin most homeotherms, which maintain O₂ and CO₂ levels withinnarrow ranges. These differences in pattern of breathing indicatethat the respiratory control systems of ectotherms and homeothermsdiffer substantially. The results of recent studies using invitro brainstemspinal cord preparations of adult frogs and premetamorphictadpoles (Rana catesbeiana and Rana pipiens) demonstrate, however,that the mechanisms for rhythm generation and pattern formationdescribed previously for mammals are also key features of therespiratory control system of frogs. These findings thereforesupport the hypothesis that the respiratory control system ishighly conserved amongst air breathing vertebrates, whetherthey breathe continuously or episodically.     

Interactions in the Absorption of Monovalent Cations by Excised Radish Roots

Preferential absorption of potassium over sodium has been observedwith excised radish roots using a wide range of concentrationsin the bathing medium. This result is contrary to the situationobserved in most other plants which have been investigated,where it is found that at high external concentrations (>1·0mM) the uptake of potassium is less specific and the rate ofsodium absorption exceeds that of potassium. In radish rootscalcium does not interact with the monovalent cation absorptionin the higher range of concentration and the sodium absorptionis not sensitive to chloride-sulphate substitution. These resultsare discussed in relation to salinity-tolerance and potassium:sodiuminteractions.     

Antagonists of Growth Inhibition of Crithidia by Allopurinol, a Guanine Analog

SYNOPSIS. Allopurinol, 4-hydroxypyrazolo[3,4- d ] pyrimidine, a relatively non-toxic xanthine-oxidase inhibitor used to treat gout, inhibited growth (ID_0–90 1.0 μg/ml) of the trypanosomatid flagellate of insects Crithidia fasciculata in minimal media in respect to biopterin, folic acid and purine. Allopurinol inhibition was antagonized by thymidine (4.0 μg/ml) when a ) biopterin (≥ 1.0 ng) was present alone; traces of folate entering from the inoculum or contamination of chemicals probably sufficed here to satisfy the folate requirement; b) biopterin (5% pure) 1.0 ng was added together with either pteroylglutamic acid (PGA) 4.0 ng or hypoxanthine 0.01 mg. With biopterin absent, full growth was permitted by PGA 10 ng + hypoxanthine 0.03 mg, and completely inhibited by the standard concentration of allopurinol, but in this instance thymidine did not release the inhibition.
Allopurinol is therefore useful for investigating pteridine function via inhibition analysis with the singularity that folate acts uniquely in trypanosomatids as precursor of biopterin, and the complication that both pteridines catalyze multiple biosyntheses. The biosynthetic step between folate and biopterin is postulated to be a site of inhibition of allopurinol in Crithidia.     

A revised numerical chaetotaxy for neotropical Phlebotomine sandfly larvae (Diptera: Psychodidae)

Phlebotomine larval taxonomy is briefly reviewed with particular reference to New World species, of which under one fifth have been adequately described as immature stages. A new numerical chaetotaxy is proposed following studies on the larvae of six species from Brazil. Setal numeration is used in a manner which demonstrates apparent segmental homologies and the use of letter designations for some setae has been reduced. With two exceptions the mesothoracic, metathoracic and abdominal setae are homologized with those of the posterior prothorax, and the anterior prothoracic setae are regarded as atypical.