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Evaluation of different rodenticidal baits against rodent population in cucumber (Cucumis sativus) crop fields.

The baits used consisted of 2% zinc phosphide and 0.005% bromadiolone. The baitings were carried out at the flowering stage of cucumber crop. Double baiting treatments comprising zinc phosphide and bromadiolone in different combinations resulted in better reduction of rodent population and crop damage. Deployment of different rodenticidal treatments saved yield loss from 7.00 to 11.82q/ha. Thus, accomplishing cost benefit ratio of 1:88 to 1:107. Bromadiolone followed by bromadiolone, the most profitable combination is suggested for control of rodent population in cucumber crop fields.

Animals↗

[Ways to improve the epidemiological surveillance for plague].

The paper deals with the plague epidemiological surveillance in natural foci and with the ways of its improvement. The diversity of methods currently used for surveillance ensures a satisfactory epidemic situation though the problem of plague control among rodents and hares in the natural foci remained unsettled. Therefore the main task of research and practical plague institutions in improving plague epidemiological surveillance in the natural foci is to provide further research evidence for the application of facilities and guidelines to control the carriers and vectors of plague, which can prevent the development of epizootics and reduce a risk for human infection in the enzootic areas.

Animals↗

Field trials of brodifacoum (WBA 8119) against the house mouse (Mus musculus L.).

The anticoagulant rodenticide brodifacoum was tested against house mice (Mus musculus L.) infesting farm buildings. In six trials, treatment success was assessed from the results of census baitings conducted before and after treatment. With 0.005% brodifacoum in canary seed/corn oil bait, the control achieved ranged between 92.7% and 100%, mean 98.8%. Two mouse populations were eradicated in 3 to 4 weeks but a few individuals survived each of the other four treatments which lasted 6 weeks. The effectiveness of brodifacoum against mice is compared with that of 0.1% calciferol and 0.025% warfarin in combination. It is concluded that brodifacoum and calciferol warfarin are equally effective in controlling M. musculus but that brodifacoum treatments need to be conducted for a relatively longer period.

4-Hydroxycoumarins↗

Efficacy of alpha-chlorhydrin in sewer rat control.

A single application of the male chemosterilant, alpha-chlorhydrin, to a problem sewer rat infestation resulted in reductions of rat numbers and distribution which was comparable to effects of warfarin baiting methods. Rat numbers were reduced by more than 85% by both methods. More rapid mortality and recruitment were evident for warfarin effects; the alpha-chlorhydrin treated population had a longer lag phase of growth so that reinfestation of sewer habitat to pre-treatment numbers, and distribution over a 40 square block area, required approximately 1.5-2 times longer after alpha-chlorhydrin treatment when compared with warfarin treatment. Comparisons of changes in rat densities in infested sewers following the two treatments indicate that recovery of warfarin treated populations is achieved by reproductive recruitment followed by dispersal while alpha-chlorhydrin treated populations recover by slower immigration and later reproductive recruitment. Alpha-chlorohydrin should be a useful addition to a limited arsenal of rat control agents because of its specificity for the Norway rat, its single dose effectiveness as a toxicant-chemosterilant, and its short environmental half-life.

Animals↗

Inhibition of 5alpha-reductase enzyme or GABA(A) receptors in the VMH and the VTA attenuates progesterone-induced sexual behavior in rats and hamsters.

Progesterone (P) to the ventromedial hypothalamus (VMH) and the ventral tegmental area (VTA) of ovariectomized (OVX), estradiol benzoate (EB)-primed rats and hamsters produces female sexual behavior similar to that seen in proestrous, receptive rodents. Because P's 5alpha-reduced metabolites can have facilitative effects on female sexual receptivity through actions at GABA(A)/benzodiazepine receptor complexes (GBRs), the role of 5alpha-reductase and GBRs in the VMH and the VTA was investigated. In Experiment 1, 5alpha-reductase immunoreactivity (5alpha-red-IR) and GBR immunoreactivity (GBR-IR) in the VMH and the VTA of OVX, EB (10 microg) and P (500 microg)-primed rats and hamsters was examined. More 5alpha-red-IR and GBR-IR was seen in the VMH and the VTA of receptive (EB and P-primed) compared to non-receptive (sesame oil vehicle) rodents. In Experiment 2, OVX, EB and P-primed rats and hamsters received implants of finasteride, a 5alpha-reductase inhibitor, or no implants to the VMH and the VTA and were tested for sexual receptivity with a male. Ovariectomized EB and P-primed rats and hamsters receiving finasteride to the VMH and the VTA had decreased lordosis compared to rodents receiving control implants to the VMH and the VTA. In Experiment 3, OVX, EB and P-primed rats and hamsters received infusions of picrotoxin, a GBR antagonist, or vehicle infusion to the VMH and the VTA and were tested for sexual receptivity with a male. Ovariectomized EB and P-primed rats and hamsters receiving picrotoxin to the VMH and the VTA had decreased lordosis compared to rodents receiving vehicle infusions to the VMH and the VTA. These data suggest that 5alpha-reductase and GBRs are present in the VMH and VTA, and that inhibiting 5alpha-reductase activity or blocking GBRs in the VMH and the VTA attenuates EB+P-primed sexual receptivity of OVX rats and hamsters.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

Genetic control of acute ethanol-induced behaviors in Drosophila.

BACKGROUND: In most organisms in which acute ethanol exposure has been studied, it leads to similar changes in behavior. Generally, low ethanol doses activate the central nervous system, whereas high doses are sedative. Sensitivity to the acute intoxicating effects of ethanol is in part under genetic control in rodents and humans, and reduced sensitivity in humans predicts the development of alcoholism (Crabbe et al., 1994; Schuckit, 1994). We have established Drosophila melanogaster as a model organism to study the mechanisms that regulate acute sensitivity to ethanol. METHODS: We measured the effects of ethanol vapor on Drosophila locomotor behaviors by using three different assays. Horizontal locomotion was quantified in a locomotor chamber, turning behavior was assayed in narrow tubes, and ethanol-induced loss of postural control was measured in an inebriometer. Mutants with altered sensitivity to the acute effects of ethanol were generated by treatment with ethyl methane sulfonate and isolated by selection in the inebriometer. We ascertained the effects of these mutations on ethanol pharmacokinetics by measuring ethanol levels in extracts of flies at various times during and after ethanol exposure. RESULTS: Among nearly 30,000 potentially mutant flies tested, we isolated 19 mutant strains with reduced and 4 strains with increased sensitivity to the acute effects of ethanol as measured in the inebriometer. Of these mutants, four showed changes in ethanol absorption. Two mutants, named barfly and tipsy to reflect their reduced and increased ethanol sensitivity in the inebriometer, respectively, were analyzed for locomotor behaviors. Both mutants exhibited ethanol-induced hyperactivity that was indistinguishable from wild type. However, barfly and tipsy displayed reduced and increased sensitivity to the sedative effects of ethanol, respectively. Finally, both mutants showed an increased rate of ethanol-induced turning behavior. CONCLUSIONS: The effects of acute ethanol exposure on Drosophila locomotor behaviors are remarkably similar to those described for mammals. The analysis of mutants with altered sensitivity to ethanol revealed that the genetic pathways which regulate these responses are complex and that single genes can affect hyperactivity, turning, and sedation independently.

Absorption↗

Experimental approaches to colon cancer prevention in humans.

Colorectal cancer is a major illness in the Western world. International and migrant studies suggest that environmental causes, notably a fat- and calorie-dense diet (even if adopted in adulthood), are associated with the disease. Case-control studies have not conclusively identified specific etiologic dietary factors, however. In addition, the emphasis placed on migrant studies has led many to overlook potentially important genetic factors that might help to explain some of the discrepancies in the epidemiologic data. Thus, the cause(s) of colorectal cancer remain unclear and hence effective preventive strategies are not presently available. Numerous tenable hypotheses have been generated as a consequence of observational and analytical epidemiologic studies, as well as rodent experiments. Controlled trials to test these hypotheses using colorectal cancer as an endpoint are not justifiable at present. It is possible, however, that "intermediate markers" (such as epithelial cell proliferation rates and others) that are associated with colorectal cancer in both humans and experimental animal systems might provide the means for hypothesis testing in short-term clinical trials. Despite the fact that this approach has several caveats, consistent results obtained in short-term studies would more readily justify the undertaking of a large-scale, long-term controlled study using colon cancer or adenomatous polyp recurrence as an endpoint.

Colorectal Neoplasms↗

Laboratory and field evaluation of pyriminyl as a poison for Rattus norvegicus.

Laboratory tests indicated that the optimum concentration for pyriminyl in rat baits was between 1% and 3%. In field trials in which 0.5% pyriminyl (the concentration in commercial use) was compared with 2.5% zinc phosphide for the control of rats on farms, the pyriminyl treatments were significantly less effective than the zinc phosphide even when the poisoned baits were left down for 7 days instead of 1 day after prebaiting. Both poisons were as effective in medium oatmeal bait as they were in medium oatmeal containing 5% corn oil and 5% sugar.

Animals↗

Field trials of calciferol against warfarin resistant infestations of the Norway rat (Rattus norvegicus Berk).

The effectiveness of calciferol (vitamin D(2)) against Rattus norvegicus was investigated in field trials on twenty-three farms with rat infestations partly resistant to warfarin. At 0.01% combined with warfarin at 0.025% no rodenticidal effect of the calciferol was discernible. At 0.025% with warfarin at the same concentration, results were better, but not appreciably better than is often obtained with warfarin alone against resistant rat populations. When the concentration of calciferol was stepped up to 0.1%, four out of five treatments in which the poison was applied directly gave complete control. The fifth may have partly failed because of poison shyness caused by under-baiting. Five out of six more treatments done after ;pre-baiting' were also successful. The sixth failed for reasons unconnected with the choice of poison.Six further infestations that were not responding adequately to warfarin treatments were quickly controlled when, in three instances, calciferol at 0.1% was used instead and, in three more, it was used together with warfarin. It is concluded that calciferol at 0.1% is an effective poison against R. norvegicus either combined with warfarin or not, but that because at 0.1% its effect is subacute rather than chronic, there may be a case in some environments for using it only after pre-baiting.

Animals↗

[Cereal grain preference of rats].

Cereal grains are usually used as the main material for preparing rodenticide baits. However, the preferences for different grains varies according to species and habitats of rats, and locations. A formula accepted at one location may not be suitable in other places, where rats are accustomed to different types of food. It is therefore important to understand the feeding habits of local rat species before implementing a control program. Seven kinds of grains, including hulled rice, corn, barley, wheat, sorghum, pranuts, and sweet potatoes were tested to study the preferences of rats in the laboratory. The results revealed that Bandicota nemorivaga, Rattus losea and R. norvegicus prefer hulled rice; Apodemus agrarius and Mus musculus prefer peanuts, and R. rattus prefers corn. The influence of quality and nutrient contents of baits on the consumption of the rats is also discussed.

Animals↗

Laboratory evaluation of anticoagulant-treated baits for control of the northern palm squirrel, Funambulus pennanti Wroughton.

Individually caged northern palm squirrels, Funambulus pennanti, were fed with bait containing 0.025% warfarin or fumarin, 0.0075% chlorophacinone or 0.005% brodifacoum for a fixed number of days varying from 1 to 14. Brodifacoum (WBA 8119) was found most toxic since 66% and 70% of the animals died after one and two days' feeding respectively. Chlorophacinone killed 70% of the squirrels after three days' feeding. Squirrels were relatively tolerant to warfarin and fumarin since the mortality after a period of 14 days' feeding was only 58% and 75% respectively.

Animals↗

Quantitative analysis of the age-related fragmentation of hamster 24-h activity rhythms.

The continuous monitoring of spontaneous locomotor activity has emerged as one of the most widely used metrics in rodent circadian research. This behavioral measure is also extremely useful for the description of the effects of aging on circadian rhythms. The present study describes the successful use of a log-survivorship approach to identify discrete bouts of hamster wheel-running activity and provides a detailed description of the age-related fragmentation in the 24-h profile of this behavioral variable. In addition, stepwise discriminant analysis identified the most important quantitative measures for distinguishing between the individual patterns of wheel-running activity of young (3 mo) and old (17-18 mo) golden hamsters. The results suggest that this method of bout analysis can be a valuable tool for the study of genetic, developmental, neurochemical, physiological, and environmental factors involved in the temporal control of rodent locomotor behavior.

Aging↗

Treatment of monocrotophos-poisoned birds of prey with pralidoxime iodide.

Monocrotophos, and organophosphorus insecticide, was sprayed by farmers to control a plague of levant voles in alfalfa fields. Large numbers of birds of prey attracted by the dying and dead voles developed secondary poisoning after eating the voles. Paralysis of skeletal muscles was the principal clinical finding in these birds. Many of the birds died but some were treated with pralidoxime iodide, 100 mg/kg of body weight, given by intramuscular injection. All treated birds recovered, some in a very short time.

Animals↗

Relationship between autonomic and behavioral thermoregulation in the golden hamster.

Preferred ambient temperature (Ta) of male golden hamsters (Mesocricetus auratus) was measured repeatedly by placing the animals in a temperature gradient for 80 min. A total of 180 observations were made during the last 20 min of treatment in the gradient. The mean preferred Ta was 28.2 +/- 0.2 degrees C. In another experiment the same animals were placed in a temperature-controlled chamber for 80 min while metabolic rate, evaporative water loss, thermal conductance, and colonic temperature were measured at Ta's of 14-34 degrees C. The lower critical Ta, the Ta below which metabolic rate increased above the resting level, was 28 degrees C. This Ta corresponds closely to the mean preferred Ta of the hamster when placed in the temperature gradient. Evaporative water loss was minimal at Ta's of 14 and 16 degrees C and increased gradually with increasing Ta. Thermal conductance was minimal between Ta's of 14 and 28 degrees C and then increased sharply with increasing Ta. The data from the hamster are qualitatively similar to the mouse in that the preferred Ta corresponds with the lower critical Ta. It appears that, for these rodents, the control of preferred Ta is critically related to the animal's metabolic requirements.

Animals↗

Trials of the anticoagulant rodenticides bromadiolone and difenacoum against the house mouse (Mus musculus L.).

Laboratory and field trials were conducted to determine the efficacy of the anticoagulant rodenticide bromadiolone against the house mouse (Mus musculus). In laboratory feeding tests, family groups of warfarin-resistant mice maintained in pens and conditioned to feeding on plain foods were offered pinhead oatmeal bait containing bromadiolone at 0.005%. Overall mortality in replicated 21-day poison treatments was 55/58 or 94.8%. Six field trials were carried out, using the same poison bait, against mice infesting farm buildings. Treatment success, estimated from the results of census baitings conducted before and after treatment, ranged between 60.4% and 100%, mean 92.4%. In equivalent field trials using difenacoum, another newly developed anticoagulant rodenticide, the control achieved ranged between 70.2% and 100%, mean 96.0%. Five field trials, three involving bromadiolone and two difenacoum, were not completely successful and the surviving mice were removed for laboratory examination. In 21-day toxicity tests, each animal was fed the poison bait offered to it earlier in the field. Bromadiolone and difenacoum gave kills of 12/21 (57.1%) and 9/11 (81.8%) respectively. The possible emergence of mouse populations resistant to these anticoagulants is considered.

4-Hydroxycoumarins↗

Some properties of calciferol as a rodenticide.

The potentiality of calciferol (alone and combined with warfarin) for the control of commensal rats and mice has been examined in the laboratory. Nearly all animals fed on 0.1% calciferol for 2 days died. Though illness usually reduced food intake after the first 24 hr. there was no sign of aversion to the poison at 0.1% - which is considered to be the lowest concentration suitable for use against Rattus norvegicus, R. rattus and Mus musculus in the field. There was some indication that resistance to warfarin in R. norvegicus may be correlated with susceptibility to calciferol. Toxicity tests with calciferol combined with warfarin indicated an additive effect between the compounds. No evidence for synergism was found however, although elsewhere there is some evidence for this.

Animals↗