Problems of rodent control in rural tropical areas. (1/25)Rodent control strategies, techniques, and research needs in rural tropical environments are reviewed and discussed with special reference to Mastomys natalensis, the possible reservoir of Lassa fever in West Africa.Public health rodent problems are far more serious and widespread in rural tropical areas than in developed countries. In the latter, only the commensal rodents constitute a major problem, whereas in rural tropical areas, native semidomestic species also serve as disease reservoirs and sources of infection to man. The success of rodent control programmes in developed countries depends in large part on the willingness and ability of people and governments to spend relatively large sums on research and control, on an acquired intolerance of people to rats and disease, and on a substantial economic base. These prerequisites are not usually to be found in rural tropical areas. Consequently, the rodent control techniques and programme organizations of developed countries are not directly applicable to such areas, even though the principles are the same. For this reason, it is suggested that a well-funded, integrated research and control programme should be undertaken in a known Lassa fever area, stressing public education, personnel training, and environmental management as well as rodenticidal approaches. (+info)
Chemosterilant action of trimethylphosphate in rodents. (2/25)Trimethylphosphate, the simplest tri-alkyl ester of phosphoric acid, produces marked antifertility effects in experimental male rodents (Jackson and Jones, 1968). The predominant effect is the "functional" sterilizing action involving spermatids from which intact motile but incompetent sperm continue to be produced. Relatively high doses are required in the mouse (5 X 1 gm/kg orally), whereas it is effective in the rat at 1/10 of this level. Trimethylphosphate is remarkable in that it possesses no anticholinesterase activity, is freshly soluble and stable in water, is effective orally, and has a high level of tolerance. Whereas 500 mg/kg orally render male rats sterile for the ensuing 3 weeks, 5 times this amount, although tolerable, completely disorganizes spermatogenesis without damaging tubular architecture. Such treated rats remain infertile for 20-25 weeks, apparently retaining sexual activity, though a proportion appear to be more permanently sterilized. Rats treated weekly at 5 X 100 mg/kg orally for over 1 year have remained sterile but recover fertility 3-5 weeks from terminating treatment. "Side effects" so far observed are a sedative action and, towards 1 year of treatment, hind leg paresis, although 5 times this dose rate caused progressive loss in weight. Using phosphorus-32-trimethylphosphate the sole phosphorus-containing metabolite is dimethylphosphate (Jackson and Jones, 1968), which has no antifertility activity. With carbon-14-trimethylphosphate, S-methyl cysteine was identified as a urinary metabolite, indicating that trimethylphosphate is involved, at least in its detoxification process, as an alkylating agent. The antifertility action of trimethylphosphate is probably related to methyl alkylation. This would bring it into line with the methyl ester of methanesulphonic acid which also produces the "functional" type of sterility in rats and mice (Jackson, 1964). Like methyl methanesulphonate (Partington and Bateman, 1964), trimethylphosphate in substerilizing doses induces so-called dominant lethal mutations. Preliminary structure/activity studies have shown that tri-n-propyl- and tri-iso-propylphosphates do not affect the fertility of male mice (5 X 1 gm/kg orally). Both these esters together with tri-n-propyl- and tri-n-butyl-phosphates still have the capacity to alkylate, and like trimethylphosphate, the only metabolites in the rat were the di-alkylphosphates and corresponding S-alkyl cysteines. Whereas all these substances interact with cysteine in vitro, only trimethylphosphate reacts readily with glutathione. This might be pertinent to its biological activity. (+info)
Effect of an inactivator of glyceraldehyde-3-phosphate dehydrogenase, a fortuitous arsenate reductase, on disposition of arsenate in rats. (3/25)The environmentally prevalent arsenate (AsV) is reduced in the body to the much more toxic arsenite (AsIII). Recently, we have demonstrated that the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the reduction of AsV in the presence of glutathione, yet the role of GAPDH in AsV reduction in vivo is unknown. Therefore, we examined the effect of (S)-alpha-cholorhydrin (ACH), which forms a GAPDH-inhibitory metabolite, on the reduction of AsV in rats. These studies confirmed the in vitro role of GAPDH as an AsV reductase, inasmuch as 3 h after administration of ACH (100 or 200 mg/kg, ip) to rats both the cytosolic GAPDH activity and the AsV-reducing activity dramatically fell in the liver, moderately decreased in the kidneys, and remained unchanged in the muscle. Moreover, the AsV-reducing activity closely correlated with the GAPDH activity in the hepatic cytosols of control and ACH-treated rats. Two confounding effects of ACH (i.e., a slight fall in hepatic glutathione levels and a rise in urinary AsV excretion) prompted us to examine its influence on the disposition of injected AsV (50 micromol/kg, iv) in rats with ligated bile duct as well as in rats with ligated bile duct and renal pedicles. These experiments demonstrated that the hepatic retention of AsV significantly increased, and the combined levels of AsV metabolites (i.e., AsIII plus methylated arsenicals) in the liver decreased in response to ACH; however, ACH failed to delay the disappearance of AsV from the blood of rats with blocked excretory routes. Thus, the GAPDH inactivator ACH inhibits AsV reduction by the liver, but not by the whole body, probably because the impaired hepatic reduction is compensated for by hepatic and extrahepatic AsV-reducing mechanisms spared by ACH. It is most likely that ACH inhibits hepatic AsV reduction predominantly by inactivating GAPDH in the liver; however, a slight ACH-induced glutathione depletion may also contribute. While this study seems to support the conclusion that GAPDH in the liver is involved in AsV reduction in rats, confirmation of the in vivo role of GAPDH as an AsV reductase is desirable. (+info)
Sperm mitochondrial integrity is not required for hyperactivated motility, zona binding, or acrosome reaction in the rhesus macaque. (4/25)(+info)
Historical applications of induced sterilisation in field populations of mosquitoes. (5/25)(+info)
Genome-wide profiling of gene expression in the epididymis of alpha-chlorohydrin-induced infertile rats using an oligonucleotide microarray. (6/25)(+info)
Persistence of thiotepa and tepa in pupae and adults of Culex pipiens fatigans Wiedemann. (7/25)Thiotepa and its oxygen analogue tepa, used to chemosterilize males of Culex pipiens fatigans for genetic control purposes, are toxic and mutagenic. An investigation showed that adult mosquitos that had been treated as pupae showed no detectable chemosterilant in their tissue 24 hours after emergence from the pupal stage. (+info)
Chemosterilization of the tropical house mosquito Culex pipiens fatigans Wied.: laboratory and field cage studies. (8/25)Tris(1-aziridinyl)phosphine sulfide was found to be an excellent sterilant for male Culex pipiens fatigans. When male pupae were exposed to a 0.6% solution for 3 hours, the ensuing adults were rendered permanently sterile with no apparent reduction in their vigour or longevity based on laboratory and field cage studies. Females, however, exposed to the same dosage for the same length of time were partially fertile. (+info)
Chemosterilants are chemical agents that are used to sterilize or inhibit the reproduction of insects and other pests. These chemicals work by interfering with the normal functioning of the reproductive system, either by preventing the formation or maturation of gametes (sex cells) or by preventing the successful fertilization and development of offspring.
Chemosterilants are often used in public health programs to control the spread of disease-carrying insects, such as mosquitoes and ticks. They can also be used in agricultural settings to manage pests that damage crops or stored food products.
Some common chemosterilants include:
* Aziridines: These are a group of chemicals that work by alkylating (adding an alkyl group to) the DNA of cells, which can prevent them from dividing and reproducing. Aziridines are often used to sterilize male insects.
* Dinitrophenols: These chemicals disrupt the energy production in cells, which can lead to sterility or death. Dinitrophenols are sometimes used to sterilize female insects.
* Spinosad: This is a natural compound produced by a soil bacterium that acts as a neurotoxin to insects. It can be used to control a wide range of pests, including flies, mosquitoes, and moths.
It's important to note that chemosterilants are not typically used in medical treatments for humans or other animals. They are primarily used as tools for controlling pest populations in public health and agricultural settings.
Reproductive sterilization is a surgical procedure that aims to prevent reproduction by making an individual unable to produce viable reproductive cells or preventing the union of sperm and egg. In males, this is often achieved through a vasectomy, which involves cutting and sealing the vas deferens, the tubes that carry sperm from the testicles to the urethra. In females, sterilization is typically performed via a procedure called tubal ligation, where the fallopian tubes are cut, tied, or sealed, preventing the egg from traveling from the ovaries to the uterus and blocking sperm from reaching the egg. These methods are considered permanent forms of contraception; however, in rare cases, reversals may be attempted with varying degrees of success.
'Insect control' is not a term typically used in medical definitions. However, it generally refers to the methods and practices used to manage or reduce the population of insects that can be harmful or disruptive to human health, food supply, or property. This can include various strategies such as chemical pesticides, biological control agents, habitat modification, and other integrated pest management techniques.
In medical terms, 'vector control' is a more relevant concept, which refers to the specific practices used to reduce or prevent the transmission of infectious diseases by insects and other arthropods that act as disease vectors (such as mosquitoes, ticks, and fleas). Vector control measures may include the use of insecticides, larvicides, biological control agents, environmental management, personal protection methods, and other integrated vector management strategies.