Repellent activity of some essential oils against Simulium species in India.

Use of repellents seems to be most reliable method of personal protection against annoyance and infections associated with haematophagous insects. We have investigated the biting activity of Simulium and tested the repellency of five essential oils extracted from Homalomena aromatica Schott (Alismatales: Araceae), Pogostemon heyneanus Bentham (Lamiales: Lamiaceae), Citrus aurantifolia Swingle (Sapindales: Rutaceae), Vitex negundo L. (Lamiales: Lamiaceae), and Ageratum conzoides L. (Asterales: Asteraceae) on the human volunteers against Simulium (blackflies) in three locations of Arunachal Pradesh, India. Blackflies preferred biting legs (> 79%) as compared to hand and face with profound biting activity during 1000-1100 h (> 23%) and 1500 - 1600 h (> 28%). The essential oil extracted from Homalomena aromatica, Vitex negundo and Ageratum conizoides provided > 2 h protection at 5% concentration and > 5 h protection at 10% concentration in all the three testing locations. The repellency of Homalomena aromatica, Vitex negundo and Ageratum conizoides essential oils after 6 h application was > 50% at 5% concentration and > 90% at 10% concentration. The study provides evidence for the potential of these essential oils in developing new repellents against blackflies.

Field evaluation of repellency of a polyherbal essential oil against blackflies and its dermal toxicity using rat model.

In the present study we have evaluated the repellent activity of mixture of Curcuma longa, Zanthoxylum limonella and Pogostemon heyneanus essential oils in 1:1:2 ratio at 5%, 10% and 20% concentration against blackflies in northeastern India. Initially the essential oil mixture tested here has been found effective against Aedes albopictus mosquitoes. The average protection recorded in 20% concentration (170.56 ± 4.0; 95% CI = 162.09-179.02) was higher as compared to other two concentrations (F = 90.2; p<0.0001; df = 53). Percentage repellency and repellency index was found to be higher in 20% concentration (p ≤ 0.017). No appreciable clinical and behavioral signs were observed in the acute dermal toxicity using rat model. No changes were observed in biochemical profiles of treatment group animals. Similarly, no prominent lesions were observed in vital organs of treatment in both the sexes. The study concludes that tested repellent is safe for use and has multi-insects repellent property.

A cross sectional investigation of malaria epidemiology among seven tea estates in Assam, India.

In the present investigation, the epidemiology of malaria among seven tea estates of Nagaon and Udalguri districts of Assam, India has been described. A cross-sectional open study was carried out to understand the malaria epidemiology and associated risk factors among the tea tribes during March to September 2009. Out of 1,182 peripheral blood smears examined, 506 found positive for malaria (slide positivity rate, SPR = 42.8) with Plasmodium falciparum as predominant species. Dimakuchi tea estate was having highest SPR (P = 0.0275) and contributed more number of P. falciparum cases (P < 0.00001). Tea estates studied in both Udalguri and Nagaon districts were equally affected and the SPR recorded were 41.75 and 43.32% respectively. 154 malaria cases detected were having 'O' blood group but each blood group was found to have similar susceptibility of acquiring malaria infection (χ(2 ) = 3.603; P = 0.3076) and P. falciparum infection (χ(2 ) = 1.818; P = 0.6110). The SPR was highest among children more than 2 years of age group and variation in SPR among the age groups was statistically significant (χ(2 ) = 17.186; P = 0.0018). No gender biasing was observed in malaria distribution. Anemia was found associated with the infection among both the sexes. The findings suggest that tea estates are endemic for stable malaria transmission primarily due to P. falciparum and the prevalence rate decline with age, suggesting the development of protective immunity. Promising intervention measures could be able to reduce the malaria prevalence effectively in the study areas.

Field evaluation of repellency of a polyherbal essential oil against blackflies and its dermal toxicity using rat model

In the present study we have evaluated the repellent activity of mixture of Curcuma longa, Zanthoxylum limonella and Pogostemon heyneanus essential oils in 1:1:2 ratio at 5%, 10% and 20% concentration against blackflies in northeastern India. Initially the essential oil mixture tested here has been found effective against Aedes albopictus mosquitoes. The average protection recorded in 20% concentration (170.56±4.0; 95% CI = 162.09-179.02) was higher as compared to other two concentrations (F = 90.2; p<0.0001; df = 53). Percentage repellency and repellency index was found to be higher in 20% concentration (p<0.017). No appreciable clinical and behavioral signs were observed in the acute dermal toxicity using rat model. No changes were observed in biochemical profiles of treatment group animals. Similarly, no prominent lesions were observed in vital organs of treatment in both the sexes. The study concludes that tested repellent is safe for use and has multi-insects repellent property.

alpha-Tocopherol enhances tumour growth inhibition by cis-dichlorodiammine platinum (II).

Present studies indicate that alpha-tocopherol enhances the efficacy of cisplatin as demonstrated by inoculation of Dalton's lymphoma cells incubated with either cisplatin (5 or 10 microg/ml) alone or cisplatin + alpha-tocopherol (25 or 50 microg/ml) into C3H/He mice. Tumour cells (3 x 10(6) cells/mouse) incubated with cisplatin grow slowly in syngeneic mice as indicated by the late appearance of tumour. However, mice failed to develop tumour when inoculated with tumour cells incubated with cisplatin + alpha-tocopherol. When the animals were challenged with tumour cells (3 x 10(6) cells/mouse) on the 15th day after the initial inoculation, 30-50% survived more than 60 days, with 10% tumour-free survivors being observed in some groups. Antitumour activity was higher in mice receiving lymphoma cells (3 x 10(6) cells/mouse) preincubated with cisplatin + alpha-tocopherol compared to cisplatin alone. Tumour-bearing mice receiving cisplatin in combination with different concentrations of alpha-tocopherol exhibited significantly higher (P<0.001) intratumour platinum content (123-306%) but without any change in the kidney platinum content as compared to those receiving cisplatin (5 or 10 microg/ml) alone. Enhancement of cisplatin-induced tumour growth inhibition is probably due to the modulation of tumour cell membrane permeability by alpha-tocopherol. alpha-Tocopherol might increase the influx of cisplatin into tumour cells, causing the DNA repair machinery to be less efficient due to increased efficiency of adduct formation in the DNA molecule. This effect of alpha-tocopherol can render cisplatin more effective as an antitumour agent.

Alpha-Tocopherol enhances tumour growth inhibition by cis-dichlorodiammine platinum (II)

Present studies indicate that alpha-tocopherol enhances the efficacy of cisplatin as demonstrated by inoculation of Dalton's lymphoma cells incubated with either cisplatin (5 or 10 µg/ml) alone or cisplatin + alpha-tocopherol (25 or 50 µg/ml) into C3H/He mice. Tumour cells (3 x 10(6) cells/mouse) incubated with cisplatin grow slowly in syngeneic mice as indicated by the late appearance of tumour. However, mice failed to develop tumour when inoculated with tumour cells incubated with cisplatin + alpha-tocopherol. When the animals were challenged with tumour cells (3 x 10(6) cells/mouse) on the 15th day after the initial inoculation, 30-50 percent survived more than 60 days, with 10 percent tumour-free survivors being observed in some groups. Antitumour activity was higher in mice receiving lymphoma cells (3 x 10(6) cells/mouse) preincubated with cisplatin + alpha-tocopherol compared to cisplatin alone. Tumour-bearing mice receiving cisplatin in combination with different concentrations of alpha-tocopherol exhibited significantly higher (P<0.001) intratumour platinum content (123-306 percent) but without any change in the kidney platinum content as compared to those receiving cisplatin (5 or 10 µg/ml) alone. Enhancement of cisplatin-induced tumour growth inhibition is probably due to the modulation of tumour cell membrane permeability by alpha-tocopherol. alpha-Tocopherol might increase the influx of cisplatin into tumour cells, causing the DNA repair machinery to be less efficient due to increased efficiency of adduct formation in the DNA molecule. This effect of alpha-tocopherol can render cisplatin more effective as an antitumour agent

Chemo-immunotherapeutical studies on Dalton's lymphoma in mice using cisplatin and ascorbic acid: synergistic antitumor effect in vivo and in vitro.

Combined effects of ascorbic acid (vitamin C) and cisplatin on the growth of Dalton's lymphoma in C3H/He mice was investigated. Chemotherapy with sub-therapeutical dose (3 mg/kg) enabled to increase the survival time of the tumor bearing mice without any tumor free survivors. Ascorbic acid enhances the antitumor effect of cisplatin in vivo resulting in 60/70 day survivors along with tumor free survivors. Ascorbic acid also enhances the efficacy of low dose of cisplatin (5 micrograms/ml) in vitro. Tumor cells incubated with cisplatin and ascorbic acid, when injected into normal mice, exhibited inhibited growth resulting in an increased life span of tumor bearing mice and tumor free survivors. Inoculation of tumor cells incubated with cisplatin (5 micrograms/ml) and different concentrations (25 or 50 micrograms/ml) of ascorbic acid resulted in 30% tumor free mice which was not observed when concentration of cisplatin increased to 10 micrograms/ml in the medium. A possible cause of the enhancement of cisplatin-induced tumor growth inhibition may be the modulation of permeability of tumor cell membrane by ascorbic acid which increases the uptake of cisplatin into tumor cells, making less efficient the DNA repair machinery due to increased efficiency of adduct formation in DNA molecule. Possibly, this effect of ascorbic acid renders cisplatin more effective as an antitumor agent.

A possible mechanism of tumor regression in cisplatin-treated mice.

Immunization of mice with cisplatin results in specific enhancement of host's cellular immune system by stimulating splenocytes and peritoneal exudate cells against the specific tumor antigens. Possible mechanism of tumor cell destruction by splenocytes/PEC was analyzed. Intimate contact between the two cells is the most essential step during the tumor effector cell reaction.

Adoptive immunotherapy of tumor in mice in combination with cyclophosphamide.

Cyclophosphamide causes temporary regression of Dalton's lymphoma when injected at palpable stage. Dose-dependent response to cyclophosphamide was analyzed. Low dose was found to be most effective as compared to the high dose. Adoptive transfer of immunized splenocytes after cyclophosphamide therapy protects the animals from the danger of reappearance of tumor. Such combination therapy is proved to be effective in causing complete and permanent regression of tumor in majority of the treated animals.

Release of protein bound sialic acid from fibrosarcoma cells after cis-dichlorodiammine platinum (II) treatment: the possible role in tumor regression.

Cis-dichlorodiammine platinum (II) (cisplatin) has been successfully used in experimental immunotherapy of syngeneic transplantable fibrosarcoma in mice. Incubation of fibrosarcoma cells with cisplatin in vitro causes release of sialic acid from tumor cells. The estimation of sialic acid in the supernatant have shown a difference in the release of sialic acid from the tumor cells with different concentrations of cisplatin. The removal of sialic acid from fibrosarcoma cells after cisplatin treatment suggests a possible exposure of certain antigenic sites on the tumor cell surfaces. Such membrane changes may be responsible for the increased antigenicity of fibrosarcoma cells.

Studies on the neuroendocrine system of the mangohopper, Idiocerus atkinsoni Leth. (Homoptera : Jassidae).

The neuroendocrine system of the homopteran, Idiocerus atkinsoni has been described, employing a neurosecretory stain. Two groups of medial neurosecretory cells (NSC) of one tinctorial type are present in the pars intercerebralis of the brain. Processes believed to be dendrites of the neurosecretory neurons lie superficially underneath the neurilemma and enclose neurosecretory material (NSM). Both the nervi corporis cardiaci, NCCI and NCCII, are branched. The branches of the former join to form an oesophageal nerve that runs on the oesophageal surface and terminates on the midgut, and those of the latter, innervate the oesophageal dilator muscles. Besides being present in the dendrite-like processes and NSC, the NSM is also seen in the NCCI, anterior part of the aorta and oesophageal nerve but not in the NCCII, corpora cardiaca (CC) and the corpus allatum (CA). It is suggested that the release of NSM into the circulation in this insect occurs through two main routes: the dendrites and the aorta. The evolution of the aorta as an exclusive neurohaemal organ in Hemiptera is discussed.