Papers by Norman A Ratcliffe
Biochemical Journal, 1993
Pro-phenl oxidase was purified from the haemocytes of the cockroach Blaberus discoidalis by Blue ... more Pro-phenl oxidase was purified from the haemocytes of the cockroach Blaberus discoidalis by Blue Sepharose chromatography, hydrophobic-interaction chromatography on a Phenyl-Superose column and, finally, gel filtration on a Superose 6 column.
British Journal of Cancer, Mar 1, 1971
A possible basis for the differences in malignancy between three closely related sublines of the ... more A possible basis for the differences in malignancy between three closely related sublines of the WBP1 ascites tumour of the rat has been studied by examining the biochemical changes in rat sera during tumour growth in vivo. Death appeared to be due to hypoglycaemia and the ability to induce this condition correlated with the differences in malignancy between the sublines; WBP1 (X) and WBP1 (V), the more malignant sublines, inducing hypoglycaemia earlier and more rapidly than the least malignant subline WBP1 (A). Possible mechanisms whereby the tumour produces these effects are discussed.
Biochemical Journal, Aug 15, 1993
Three agglutinins (lectins), designated BDLl, BDL2 and BDL3, were identified in the haemolymph of... more Three agglutinins (lectins), designated BDLl, BDL2 and BDL3, were identified in the haemolymph of the cockroach Blaberus discoidalis by erythrocyte cross-adsorption and sugar inhibition tests. With the use of (NH4)2SO4 fractionation, anion-exchange and affinity chromatography, BDLI and BDL2 have been purified to homogeneity, and BDL3 has been partially purified to three bands on SDS/PAGE. BDLI has a molecular-mass estimate of 390 kDa by gel filtration and approx. 158 kDa by SDS/PAGE under non-reducing conditions, further reduced to subunits of 36 kDa under reducing conditions. BDL2 has a molecular mass of approx. 140 kDa and is composed of subunits of 67 kDa which can be further reduced to identical subunits of 23 kDa. Isoelectric focusing in agarose gels revealed that BDLI and BDL2 both focused as single bands at pH 6.0 and pH 5.2 respectively. The purified forms of BDLl and BDL2 were stained by the periodic acid/Schiff's reagent showing that both lectins are glycoproteins. In addition, BDL1 was deglycosylated by endo-,8-N-acetylglucosaminidase H. Immunological tests * To whom correspondence should be addressed.
Expert Opinion on Drug Discovery, 2021
Pest Management Science, Aug 30, 2012
BACKGROUND: Studies were carried out to evaluate the effects of Manilkara subsericea extracts and... more BACKGROUND: Studies were carried out to evaluate the effects of Manilkara subsericea extracts and triterpenes on the development of two species of agricultural pest insects, Oncopelus fasciatus and Dysdercus peruvianus.RESULTS: All treatments of insects with M. subsericea extracts induced mortality, delayed development and inhibited moulting. Some extracts assayed (FH, FB and FD in D. peruvianus, and FH, FB and FEA in O. fasciatus) also produced body deformities in the few adults that emerged. Other extracts (FH, FEA, FB, FD and LET in both insects), however, induced either permanent (overaged) or extranumerary nymphs, both of which were unable to achieve the adult stage and reproductive status. The insects were also treated with triterpenes (α‐ and β‐amyrin acetates) which showed high lethality at 30 days after treatment and delayed the intermoult period so that overaged nymphs were detected.CONCLUSION: The results indicate that extracts and triterpenes from Manilkara subsericea act as potent growth inhibitors of phytophagous hemipteran nymphs. It is also concluded that the mixture of several different molecules in the extracts used produces synergic effects that do not occur after using the triterpenes (PFT) alone. These secondary metabolites in the M. subsericea extracts can potentially be used in integrated control programmes against crop pests. Copyright © 2012 Society of Chemical Industry
Frontiers in Physiology, May 11, 2022
Anais Da Academia Brasileira De Ciencias, Sep 1, 2005
This review outlines aspects on the developmental stages of Trypanosoma cruzi and Trypanosoma ran... more This review outlines aspects on the developmental stages of Trypanosoma cruzi and Trypanosoma rangeli in the invertebrate host, Rhodnius prolixus. Special attention is given to the interactions of these parasites with gut and hemolymph molecules and the effects of the organization of midgut epithelial cells on the parasite development. The vector insect's permissiveness to T. cruzi, which develops in the vector gut, largely depends on the host nutritional state, the parasite strain and the molecular interactions with trypanolytic compounds, lectins and resident bacteria in the gut. T. rangeli invades the hemocoel and once in the hemolymph, can be recognized and activates the defense system of its insect vector, i.e., the prophenoloxidase system, phagocytosis, hemocyte microaggregation, superoxide and nitric oxide activity and the eicosanoid biosynthesis pathway. Taken together, these findings not only provide a better understanding of the interactions parasite-insect vector, but also offer new insights into basic physiological processes involved in the parasites transmission.
Journal of Insect Physiology, 1991
Azadirachtin (1 .O pg/ml) if fed to last&star larvae of Rhodnius prolixus through a blood meal, a... more Azadirachtin (1 .O pg/ml) if fed to last&star larvae of Rhodnius prolixus through a blood meal, affects the immune reactivity as shown by (i) a significant reduction in numbers of haemocytes and nodule formation following challenge with Enterobacter cloacae B12 (ii) a reduction in ability to produce antibacterial and lysozyme activities in the haemolymph when inoculated with bacteria, (iii) a decreased ability of azadirachtin-treated insects to destroy the primary infiction caused by inoculation of E. cloacue cells. However, the present experiments, unlike other immune reactions, fail to demonstrate any interference of azadirachtin with the prophenoloxidase-activating system since the melanin production was not reduced when this system was stimulated by trypsin or by the presence of bacteria in the haemolymph. It is suggested that the immune response is deficient in the azadirachtin-treated insects. The in relation to the general mode of azadirachtin action significance of these results is discussed in insects. azadirachtin; antibacterial and lysozyme activities;
Viruses, Nov 25, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Trends in Parasitology, Dec 1, 2005
In the gut of some insect vectors, parasites ingested with the bloodmeal decrease in number befor... more In the gut of some insect vectors, parasites ingested with the bloodmeal decrease in number before coming into contact with host tissues. Many factors could be responsible for this reduction in parasite number but the potentially important role of the large communities of naturally occurring microorganisms that exist alongside the newly ingested parasites in the vector midgut has been largely overlooked. Some previous reports exist of the inhibition of parasite development by vector gut microbiota and of the killing of Trypanosoma cruzi and Plasmodium spp. by prodigiosin produced by bacteria. Based on this evidence, we believe that the microbiota present in the midgut of vector insects could have important roles as determinants of parasite survival and development in insect vector hosts and, therefore, contribute to the modulation of vector competence for many important diseases.
Journal of Immunology, Feb 15, 2004
Characterizing the Mechanisms of Nonopsonic Uptake of Cryptococci by Macrophages
Developmental & Comparative Immunology, 2021
Lectins are ubiquitous proteins involved in the immune defenses of different organisms and mainly... more Lectins are ubiquitous proteins involved in the immune defenses of different organisms and mainly responsible for non-self-recognition and agglutination reactions. This work describes molecular and biological characterization of a rhamnose-binding lectin (RBL) from Rhodnius prolixus, which possesses a 21 amino acid signal peptide and a mature protein of 34.6 kDa. The in-silico analysis of the primary and secondary structures of RpLec revealed a lectin domain fully conserved among previous insects studied. The three-dimensional homology model of RpLec was similar to other RBLlectins. Docking predictions with the monosaccharides showed rhamnose and galactose-binding sites comparable to Latrophilin-1 and N-Acetylgalactosaminebinding in a different site. The effects of RpLec gene silencing on levels of infecting Trypanosoma cruzi Dm 28c and intestinal bacterial populations in the R. prolixus midgut were studied by injecting RpLec dsRNA into the R. prolixus hemocoel. Whereas T. cruzi numbers remained unchanged compared with the controls, numbers of bacteria increased significantly. The silencing also induced the up regulation of the R. prolixus defC (defensin) expression gene. These results with RpLec reveal the potential importance of this little studied molecule in the insect vector immune response and homeostasis of the gut bacterial microbiota.
Journal of the Brazilian Chemical Society, 2019
Zika virus (ZIKV) is a mosquito-borne pathogen which is a current global public health concern. T... more Zika virus (ZIKV) is a mosquito-borne pathogen which is a current global public health concern. There are currently no approved vaccines or antivirals against ZIKV infection. Taking into account that naphthoquinones have shown promising antiviral activity, the aim of this study was to describe the screening of two bis-naphthoquinones series against ZIKV. Twenty seven compounds were evaluated against ZIKV using Vero cells. The findings showed that among the compounds analyzed four were promising. Compound 3,3'-((2-nitrophenyl)methylene)bis(2-hydroxynaphthalene-1,4-dione) containing the nitro group at the ortho position showed the best selectivity index, followed by compound 3,3'-(4-chlorophenylmethylene)bis(naphthalene-1,2,4-triyl triacetate) with the chlorophenylmethylene radical. These results demonstrate that these bis-naphthoquinones are largely effective in inhibiting the replication of ZIKV.
Journal of Medicinal Plants Research, 2018
Zika virus (ZIKV), a mosquito-borne member of the family Flaviviridae, is a human pathogen of glo... more Zika virus (ZIKV), a mosquito-borne member of the family Flaviviridae, is a human pathogen of global significance. Recently, ZIKV, has become a public health problem with increases in numbers of cases and a strong association between ZIKV outbreaks and the spread of cases of Guillain-Barré Syndrome and microcephaly. In this study, the extracts of the seaweed Osmundaria obtusiloba (O. obtusiloba) (native to the Brazilian coast) against ZIKV using Vero cells was evaluated. The seaweed extract tested inhibited ZIKV replication in a dose-dependent manner at low concentrations with EC 50 values of 1.82 μg/mL and a selective index (SI) of 288. Other results showed that this extract had significant virucidal effects. In addition, when the extract and Ribavirin were used concomitantly there was a significant synergistic effect. Our promising results suggest that extracts of O. obtusiloba are excellent candidates for further studies, and that marine algae are potentially important sources for the development of novel anti-ZIKV agents.
Experimental parasitology, Jan 24, 2018
Chagas disease, infecting ca. 8 million people in Central and South America, is mediated by the p... more Chagas disease, infecting ca. 8 million people in Central and South America, is mediated by the protozoan parasite, Trypanosoma cruzi. The parasite is transmitted by the bite of blood sucking triatomine insects, such as Rhodnius prolixus, that had previously fed on parasite-infected vertebrate blood and voided their contaminated feces and urine into the wound. The stages of the parasite life cycle in both the insect vector and human host are well-known, but determinants of infection in the insect gut are complex and enigmatic. This paper examines the possible role of the R. prolixus gut agglutinins in the parasite life cycle. The results, derived from gut extracts made from R. prolixus fed on various diets with different vertebrate blood components, and cross adsorption experiments, showed for the first time that R. prolixus has two distinct gut agglutinins originating from their vertebrate blood meal, one for T. cruzi (the parasite agglutinin, PA) and the other for the erythrocytes...
Biochemical Journal, 1995
Endogenous and exogenous lectins have been found to activate the prophenoloxidase (proPO) system ... more Endogenous and exogenous lectins have been found to activate the prophenoloxidase (proPO) system of the cockroach, Blaberus discoidalis, to the same extent as laminarin, a previously known microbial activator of proPO. The lectins can also further enhance this laminarin activation of the proPO system. Non-lectin proteins did not display any activation properties. The time course of proPO activation was studied after reconstitution of the reaction system using purified lectins, a trypsin-like enzyme, a trypsin inhibitor and partially purified lectin-binding proteins from the cockroach haemolymph. Lectin activation of the proPO system is probably not mediated by the lectin sugar-binding sites, as specific inhibitory sugars failed to abrogate the enhanced effect. The results suggest that alternative binding site(s) on the lectins may be involved in the proPO activation process. Evidence also suggests that several different lectins are involved in the regulation of the proPO system thro...
Zeitschrift f�r Zellforschung und Mikroskopische Anatomie, 1971
1.05genesis in a braconid parasitoid Apanteles glomeratus (L.) is described and compared with tha... more 1.05genesis in a braconid parasitoid Apanteles glomeratus (L.) is described and compared with that in other hymenoptera. 2. The processes are similar, except that there is no uptake of protein for yolk formation with the associated configurations in the follicle cells and the periphery of the oScyte.
Memorias Do Instituto Oswaldo Cruz, Mar 1, 1991
PLOS Pathogens, Nov 24, 2021
Recent reports of the transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2... more Recent reports of the transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) by fully vaccinated people [1] do not undermine the value of injected vaccines that continue to protect against serious illness and hospitalisation. They are, however, an early warning for immediate action to develop new drugs and approaches against Coronavirus Disease 2019 (COVID-19). The logical answer is to target the initial nasal portal of COVID-19 entry into the body with prophylactic drugs, which, together with injected vaccines, could potentially completely prevent infection and subsequent transmission of a range of variants. This paper outlines published work in this vital area in the hope that it becomes an urgent priority for development. COVID-19 variants Over 12,000 mutations have been catalogued in SARS-CoV-2 genomes [2] and have resulted in new SARS-CoV-2 variants, including those identified in South Africa (B.1.351), United Kingdom (B.1.1.7), California (B.1.427 and B.1.429), Brazil (P.1 and P.2), India (B1.617.2 = Delta), Peru (C.37 = Lambda), and Colombia (Mu). Such variants may have increased transmissibility and pathogenicity, higher viral loads, and vaccine resistance [3-5]. A missed opportunity Vaccines provide short-term relief from COVID-19, but rapid evolution of resistant viral variants necessitates additional supportive strategies, including broad-spectrum antiviral agents coupled with innovative prophylactic and therapeutic processes. Antiviral agents against SARS-CoV-2 should have been repurposed drugs, but of all the drugs tested, those effective in the later stages of infection, such as dexamethasone, are the main ones granted approval for emergency use [6]. One exception has been monoclonal antibody therapy [7]. An important missing link has been the lack of innovative drug development for treating the early stages of COVID-19 infection. Disease pathology extols studying the initial interactions of invading pathogens with the body, involving adsorption, colonisation, penetration, multiplication, and host innate immunity [8].
Evidence-based Complementary and Alternative Medicine, 2014
Except for honey as food, and silk for clothing and pollination of plants, people give little tho... more Except for honey as food, and silk for clothing and pollination of plants, people give little thought to the benefits of insects in their lives. This overview briefly describes significant recent advances in developing insect natural products as potential new medicinal drugs. This is an exciting and rapidly expanding new field since insects are hugely variable and have utilised an enormous range of natural products to survive environmental perturbations for 100s of millions of years. There is thus a treasure chest of untapped resources waiting to be discovered. Insects products, such as silk and honey, have already been utilised for thousands of years, and extracts of insects have been produced for use in Folk Medicine around the world, but only with the development of modern molecular and biochemical techniques has it become feasible to manipulate and bioengineer insect natural products into modern medicines. Utilising knowledge gleaned from Insect Folk Medicines, this review describes modern research into bioengineering honey and venom from bees, silk, cantharidin, antimicrobial peptides, and maggot secretions and anticoagulants from blood-sucking insects into medicines. Problems and solutions encountered in these endeavours are described and indicate that the future is bright for new insect derived pharmaceuticals treatments and medicines.
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Papers by Norman A Ratcliffe