Allosteric Site Inhibitor Disrupting Auto-Processing of Malarial Cysteine Proteases.

Falcipains are major haemoglobinases of Plasmodium falciparum required for parasite growth and development. They consist of pro- and mature domains that interact via 'hot-spot' interactions and maintain the structural integrity of enzyme in zymogen state. Upon sensing the acidic environment, these interactions dissociate and active enzyme is released. For inhibiting falcipains, several active site inhibitors exist, however, compounds that target via allosteric mechanism remains uncharacterized. Therefore, we designed and synthesized six azapeptide compounds, among which, NA-01 & NA-03 arrested parasite growth by specifically blocking the auto-processing of falcipains. Inhibitors showed high affinity for enzymes in presence of the prodomain without affecting the secondary structure. Binding of NA-03 at the interface induced rigidity in the prodomain preventing structural reorganization. We further reported a histidine-dependent activation of falcipain. Collectively, for the first time we provide a framework for blocking the allosteric site of crucial haemoglobinases of the human malaria parasite. Targeting the allosteric site could provide high selectivity and less vulnerable to drug resistance.

Proteases in Mosquito Borne Diseases: New Avenues in Drug Development.

INTRODUCTION: Mosquito borne diseases continue to propagate and cause millions of deaths annually. They are caused either by protozoan parasites such as Plasmodium, Toxoplasma or by flaviviruses including Dengue and Zika. Among the proteome of such parasitic organisms, proteases play essential roles in events such as host invasion, hemoglobin hydrolysis, replication and immune evasion. Plasmepsin V (PMV), an endoplasmic reticulum resident aspartic protease of Plasmodium spp., is involved in the export of ~400 proteins containing the conserved Plasmodium Export Element motif (PEXEL). Interactions and cleavage of PEXEL proteins by PM V is necessary for export to and across the parasitophorous vacuole membrane. Protease System: Similarly in flaviviruses, a two-component protease system consisting of nonstructural proteins, NS2B and NS3, interacts with other non-structural proteins and plays a major role in viral replication, polyprotein cleavage and virion particle assembly. Thus, proteases involved in indispensable roles in pathogen machinery can be considered as attractive drug targets. Inhibitors against proteases are being used in clinical trials for other communicable and non-communicable diseases. Currently, hydroxyethylamine based inhibitors targeting the catalytic site of PM V with picomolar inhibitory concentrations have been tested in vitro. CONCLUSION: For recently characterized disease such as Zika, no known treatments exist while compound such as Policresulen has high affinity for Dengue NS2B/NS3 complex. Understanding proteases structure-function relationship and protease-inhibitor interactions can provide new insights for novel chemotherapeutic strategies.

A new species of an interesting amphistome Pseudodiplodiscoides Murty, 1970 in Bellamya bengalensis Lamarck, 1882 from water bodies near district Barabanki, U.P.

A new species of an interesting trematode genus Pseudodiplodiscoides (Murty, Zool Anz 185:312-317, 1970), is described from the gut of the snail Bellamya bengalensis Lamarck, 1882, collected from the fresh water bodies near district Barabanki, U.P. After careful examination of several freshly collected specimens, the genus is validated and another species described under the genus Diplodiscus viz., D. minutus (Saksena et al., Indian J Helminthol 4:37-54, 1987) from Indoplanorbis exustus Deshayes has also been transferred to the genus Pseudodiplodiscoides as P. mimutus (1987). The new species is characterised by the shape and size of non operculated eggs, extension of vitellaria and position of genital pore.

Bacillus thuringiensis (Bt) transgenic crop: an environment friendly insect-pest management strategy.

Introduction of DDT (dichloro-diphenyl-trichloroethane) and following move towards indiscriminate use of synthetic chemical insecticides led to the contamination of water and food sources, poisoning of non-target beneficial insects and development of insect-pests resistant to the chemical insecticides. Increased public concems about the adverse environmental effects of indiscriminate use of chemical insecticides prompted search of altemative methods for insect-pest control. One of the promising alternatives has been the use of biological control agents. There is well-documented history of safe application of Bt (B. thuringiensis, a gram positive soil bacterium) as effective biopesticides and a number of reports of expression of delta-endotoxin gene(s) in crop plants are available. Only a few insecticidal sprays are required on Bt transgenic crops, which not only save cost and time, but also reduce health risks. Insects exhibit remarkable ability to develop resistance to different insecticidal compounds, which raises concern about the unsystematic use of Bt transgenic technology also. Though resistance to Bt products among insect species under field conditions has been rare, laboratory studies show that insects are capable of developing high levels of resistance to one ormore Cry proteins. Now it is generally agreed that 'high-dose/refuge strategy' is the most promising and practical approach to prolong the effectiveness of Bt toxins. Although manybiosafety concerns, ethical and moral issues exist, area under Bt transgenic crops is rapidly increasing and they are cultivated on more than 32 million hectares world over Even after reservation of European Union (EU) for acceptance of geneticaly modified (GM) crops, 6 out of 25 countries have already adopted Bt crops and many otherindustrial countries will adopt Bt transgenic crops in near future. While the modem biotechnology has been recognized to have a great potential for the promotion of human well-being, adoption of biosafety protocol is necessary to protect human health and environment from the possible adverse effects of the products of genetic engineering. The debate between proponents and opponents of GM technology has created major obstacles in hamessing benefits of the technology It has now become clear that transgenics willbe accepted by the public only when doubts related with general risks and environmental safety are adequately dispelled. Thus, there is need to organize public awareness and present the benefits of Bt transgenic crops to improve social attitude for their rational deployment. In this review, an attempt has been made to discuss social and environmental safety issues of Bt transgenic crops.

Biomarkers of monocrotophos in a freshwater fish Channa punctatus (Bloch).

Activity of a few biomarkers have been investigated on freshwater fish Channa punctatus treated with monocrotophos for acute exposure to 18.56 ppm at 96 hr and subacute exposure viz. 0.46 ppm, 0.96 ppm and 1.86 ppm for 30 days. Biomarkers such as total protein, lipid peroxidation and acetylcholinesterase have been measured in different tissues of fish viz. gills, liver, brain and muscles. The protein levels were found to be depleted in all the tissues after pesticide exposure to lethal and sublethal concentration over the control, where as the lipid levels showed an increase under the stress of pesticide monocrotophos. The increased lipid level may be due to inhibition of lipase activity and other biomarkers of lipid metabolism. A significant inhibition of brain acetylcholinesterase (AChE) indicating its effects on nervous system have also been observed. These parameters can be used as biomarkers to predict the early toxicity of monocrotophos added to aquatic ecosystem.

Monogenoids from the gills of spiny eels (Teleostei: Mastacembelidae) in India and Iraq, proposal of Mastacembelocleidus gen. n., and status of the Indian species of Actinocleidus, Urocleidus and Haplocleidus (Monogenoidea: Dactylogyridae).

Mastacembelocleidus gen. n. (Monogenoidea: Dactylogyridae) is proposed to include two species collected and redescribed from spiny eels (Mastacembelidae) in India and Iraq: Mastacembelocleidus bam (Tripathi, 1959) comb. n. (syn. Ancyrocephalus bam Tripathi, 1959) from the gills of Macrognathus pancalus (new host record) and Macrognathus aculeatus (Synbranchiformes: Mastacembelidae) from Lucknow, India; and Mastacembelocleidus heteranchorus (Kulkami, 1969) comb. n. (syn. Urocleidus heteranchorus Kulkarni, 1969) from the gills of Mastacembelus armatus from Lucknow, India, and Mastacembelus mastacembelus (new host record) from the environs of Erbil, Iraq (new locality record). Urocleidus rhyncobdelli Jain, 1959, Haliotrema tandani Agrawal et Singh, 1982 and Urocleidus raipurensis Dubey, Gupta et Agarwal, 1992 are considered junior subjective synonyms of M. bam.

Redescription of some Indian species of Thaparocleidus Jain, 1952 (Monogenea), with aspects of the developmental biology and mode of attachment of T. pusillus (Gusev, 1976).

Thaparocleidus wallagonius Jain, 1952, the type-species of the genus, is redescribed from the type-host and locality. T. gomtius (Jain, 1952), T. seenghali (Jain, 1961), T. indicus (Kulkarni, 1969), T. malabaricus (Gusev, 1976) and T. pusillus (Gusev, 1976) were also redescribed, as their original descriptions are incomplete. The following new synonymies for some Indian species are proposed: Urocleidus bhagwanpurensis Agrawal & Singh, 1982, as a junior synonym of T. wallagonius; U. gorakhpurensis Agrawal & Singh, 1982, Murraytrema gorakhpurensis Agrawal & Singh, 1985 and Ancylodiscoides kulkarnii Agrawal & Sharma, 1988 as junior synonyms of T. seenghali; and U. tandani Agrawal & Singh, 1982, A. meerutensis Singh, Agarwal, Kumar & Vibha, 1997 and Silurodiscoides elongatus Singh, Agarwal, Kumar & Vibha, 1997 as junior synonyms of T. indicus. Data on the developmental biology and mode of attachment of T. pusillus from Mystus bleekeri at Lucknow are included.

Mechanism of malarial haem detoxification inhibition by chloroquine.

The haem detoxification pathway of the malaria parasite Plasmodium falciparum is a potential biochemical target for drug development. Free haem, released after haemoglobin degradation, is polymerized by the parasite to form haemozoin pigment. Plasmodium falciparum histidine-rich protein-2 (Pfhrp-2) has been implicated as the catalytic scaffold for detoxification of haem in the malaria parasite. Previously we have shown that a hexapeptide repeat sequence (Ala-His-His-Ala-Ala-Asp), which appears 33 times in Pfhrp-2, may be the major haem binding site in this protein. The haem binding studies carried out by ourselves indicate that up to 18 equivalents of haem could be bound by this protein with an observed K(d) of 0.94 microM. Absorbance spectroscopy provides evidence that chloroquine is capable of extracting haem bound to Pfhrp-2. This was supported by the K(d) value, of 37 nM, observed for the haem-chloroquine complex. The native PAGE studies reveal that the formation of the haem-Pfhrp-2 complex is disrupted by chloroquine. These results indicate that chloroquine may be acting by inhibiting haem detoxification/binding to Pfhrp-2. Moreover, the higher affinity of chloroquine for haem than Pfhrp-2 suggests a possible mechanism of action for chloroquine; it may remove the haem bound to Pfhrp-2 and form a complex that is toxic to the parasite.

Role of An. culicifacies and An. stephensi in malaria transmission in urban Delhi.

Studies on adult densities, vector incrimination and breeding habitats of An. culicifacies and An. stephensi were carried out during June 1984 to May 1986 in three different ecological areas of urban Delhi. Both An. culicifacies and An. stephensi prevailed throughout the year in peri-urban areas with higher densities during the post-monsoon months. In south and northwest areas, low densities of these vector species were recorded. An. culicifacies was found naturally infected with sporozoites in peri-urban and south areas, whereas An. stephensi showed gland infection in south areas only. Out of 827 blood smears collected, 302 were positive for malaria parasites. Of the positives, P. vivax formed 48.3% and P. falciparum 51.7%. Peri-urban areas showed a higher number of malaria cases than south and northwest areas.

Inorganic elements in the adults of Ascaridia galli (Schrank, 1788).

Inorganic analysis of Ascaridia galli has shown the levels of sodium, potassium, copper, magnesium, calcium, zinc, iron, nitrogen, phosphorus, sulphur, chlorine and cobalt (expressed as percentage of dry weight) to be higher in females than in males.

Effect of copper on tissue acid and alkaline phosphates in the green snakehead, Ophiocephalus punctatus (Bloch).

In vitro exposure to 10(-6) and 10(-5) M copper caused a decline in the activity of acid and alkaline phosphatases in both liver and kidney of Ophiocephalus punctatus. While in vivo exposure to 5 and 7.5 mg/l copper resulted in the activation of alkaline phosphatase in the kidney, the activity of this enzyme in the liver was inhibited at the highest concentration. The acid phosphatase was inhibited in the liver and kidney on in vivo exposure to both concentrations. The varied responses of these enzymes to in vitro and in vivo exposure to copper indicate the involvement of different molecular processes.

On a new Telorchis sp. with a redia inside the miracidium.

Adult and miracidium of Telorchis lucknowensis n. sp. from the intestine of Kachuga kachuga in India have been described. The new species is characterised by length of oesophagus, ratio of cirrus sac and metraterm, position of ovary, extension of vitellaria, and the unusual size of eggs containing a miracidium with a well developed redia. This is the first report on the occurrence of miracidia containing a redia in Plagiorchiata. The non-oculate miracidium has bullet shaped body, 2 pairs of penetration glands, and one pair of flame cells. The redia is elongate oval in shape with well developed pharynx, short gut and germ balls.