Mercury poisoning: prevention by spironolactone

The renal tubular necrosis and calcification as well as the mortality induced by mercuric chloride in the rat are readily prevented by prior treatment with well-tolerated amounts of spironolactone.     

Digitoxin poisoning: prevention by spironolactone

Spironolactone (Aldactone(R)) protects the rat against the production of myocardial necroses and other manifestations of digitoxin poisoning.     

仔猪应激的因素分析与防制对策

应激反应首先是由加拿大内分泌学家Hans Selye提出的。应激反应是机体受到强烈刺激而处于“紧急状态”时,出现的一系列神经内分泌反应,并由此引起各种机能和代谢改变,以提高机体对外环境的适应能力和维持内环境的相对稳定。但是,当应     

奶牛热应激的预防措施

<正> 奶牛热应激是奶牛受到炎热气候的刺激而引起的一系列反应。当夏季气温达到27℃以上时,奶牛往往出现热应激现象,主要表现为食欲不振、采食量减少、精神较差、泌乳量降低(25％-     

Plant moisture stress: evaluation by pressure bomb

The recently developed technique for determining the water stress of a plant by measuring the pressure necessary to force water back to the cut surface of a severed twig is adaptable to both field and laboratory experiments. We have designed and operated an efficient portable system weighing less than 18 kilograms. Sampling variation within and among Douglas fir trees varies from less than +/- I atmosphere under low stress conditions to +/- 10 atmospheres under high stress conditions. In the measurement of plants of comparable height and similar exposure, the variation is reduced to a minimum. Values in internal water stress of Douglas fir vary from 3 to more than 40 atmospheres. Both duration and magnitude of stress are important ecologically. Pressure-bomb measurements are used to demonstrate a relation between plant distribution and internal water stress.     

Chemically induced porphyria: prevention by prior treatment with phenobarbital

The excessive induction of hepatic delta-aminolevulinic acid synthetase in rats after the administration of porphyria-inducing compounds is prevented by prior treatment with phenobarbital. Studies in vivo and in vitro indicate that phenobarbital prevents the induction of chemical porphyria by increasing the rate of detoxification of inducers by way of drug-metabolizing enzymes of the hepatic endoplasmic reticulum.     

Intrinsic mechanisms of pain inhibition: activation by stress

Portions of the brain stem seem normally to inhibit pain. In man and laboratory animals these brain areas and pathways from them to spinal sensory circuits can be activated by focal stimulation. Endogenous opioids appear to be implicated although separate nonopioid mechanisms are also evident. Stress seems to be a natural stimulus triggering pain suppression. Properties of electric footshock have been shown to determine the opioid or nonopioid basis of stress-induced analgesia. Two different opioid systems can be activated by different footshock paradigms. This dissection of stress analgesia has begun to integrate divergent findings concerning pain inhibition and also to account for some of the variance that has obscured the reliable measurement of the effects of stress on tumor growth and immune function.     

Diet-induced hypercholesterolemia in mice: prevention by overexpression of LDL receptors

The current studies were designed to determine whether chronic overexpression of low density lipoprotein (LDL) receptors in the liver would protect mice from the increase in plasma LDL-cholesterol that is induced by high-fat diets. A line of transgenic mice was studied that express the human LDL receptor gene in the liver under control of the transferrin promoter. When fed a diet containing cholesterol, saturated fat, and bile acids for 3 weeks, the transgenic mice, in contrast to normal mice, did not develop a detectable increase in plasma LDL. The current data indicate that unregulated overexpression of LDL receptors can protect against diet-induced hypercholesterolemia in mice.     

Chemical self-defense by termite workers: prevention of autotoxication in two rhinotermitids

Soldiers of the lower termites Prorhinotermes simplex and Schedorhinotermes lamanianus (Isoptera, Rhinotermitidae) have electrophilic contact poisons used in colony defense. Workers of these termites die when exposed to the defense secretion of the other species, but survive when exposed to chemicals from conspecific soldiers. Detoxication occurs by an initial substrate-specific reduction of the electron-deficient double bond of the nitroalkene (Prorhinotermes simplex) or vinyl ketone (Schedorhinotermes lamanianus) followed by complete catabolism to acetate.     

ATM activation by oxidative stress

The ataxia-telangiectasia mutated (ATM) protein kinase is activated by DNA double-strand breaks (DSBs) through the Mre11-Rad50-Nbs1 (MRN) DNA repair complex and orchestrates signaling cascades that initiate the DNA damage response. Cells lacking ATM are also hypersensitive to insults other than DSBs, particularly oxidative stress. We show that oxidation of ATM directly induces ATM activation in the absence of DNA DSBs and the MRN complex. The oxidized form of ATM is a disulfide-cross-linked dimer, and mutation of a critical cysteine residue involved in disulfide bond formation specifically blocked activation through the oxidation pathway. Identification of this pathway explains observations of ATM activation under conditions of oxidative stress and shows that ATM is an important sensor of reactive oxygen species in human cells.     

Avascular necrosis: occurrence in diving cretaceous mosasaurs

A study of vertebrae of extinct giant marine lizards showed the presence of avascular necrosis in two of the three most common genera of these mosasaurs, Platecarpus and Tylosaurus. This bone disease was invariably present (involving 5 to 66% of vertebrae) in these genera, but absent in a third genus Clidastes. Differential occurrence of avascular necrosis may be related to decompression syndrome, suggesting different habitat and diving habits of the respective genera.     

Pyrazole-induced thyroid necrosis: a distinct organ lesion

One oral dose of pyrazole caused necrosis of rat thyroid follicular epithelial cells but spared the parafollicular (C) cells and the parathyroid glands. Serum thyroxine (T4) and triiodothyronine (T3) were significantly decreased on day 3 after pyrazole administration and were immeasurable on day 5. At day 5 the thyroid was enlarged and the concentration of thyroid-stimulating hormone in the serum was increased, indicating an appropriate pituitary response to a primary lesion in the thyroid. Doses of pyrazole which produced no morphologic change in the thyroids also significantly depressed the concentrations of T4 and T3 in the serum.     

Polyamines and plant stress: activation of putrescine biosynthesis by osmotic shock

The putrescine content of oat leaf cells and protoplasts increases up to 60-fold within 6 hours of exposure to osmotic stress (0.4 to 0.6 molar sorbitol). Barley, corn, wheat, and wild oat leaves show a similar response. Increased arginine decarboxylase activity parallels the rise in putrescine, whereas ornithine decarboxylase remains unchanged. DL-alpha-Difluoromethylarginine, a specific irreversible inhibitor of arginine decarboxylase, prevents the stress-induced rise in increase in arginine decarboxylase activity and putrescine synthesis, indicating the preferential activation of this pathway.     

Brain histamine: rapid apparent turnover altered by restraint and cold stress

Histamine content of rat brain was lowered quickly by inhibitors of histidine decarboxylase, suggesting that a portion of brain histamine turns over rapidly. Restraint and exposure to cold also reduced brain histamine levels and markedly augmented its formation in the hypothalamus.     

Dental caries: prospects for prevention

Combined utilization of measures now available or imminent could reduce caries of the crowns of the teeth to the point of negligibility as a public health problem, if public desire were great enough to motivate changes in some of our habits (64). Universal optimum application of fluoride and substitution of starchy foods for sugary ones (or even simply judicious consumption of sugar) would alone do most of the job. Sealing of susceptible occlusal areas with adhesive polymers promises to protect the sites where fluoride evidently cannot be maximally effective. It seems unlikely that any single measure will be found sufficient to control this multifactorial disease. Consequently, we must continue the search for new means to increase the caries resistance of teeth, to reduce the cariogenicity of foodstuffs, and to check the deleterious activities of cariogenic bacteria. Anticaries food additives and antibacterial agents for intraoral use seem to be approaching practicability. Past performance warrants expectation that ongoing fundamental investigations will produce leads for future development and application.     

Siliceous urinary calculi in calves: prevention by addition of sodium chloride to the diet

Urinary calculi were found in all but one of 14 calves given a ration associated with the formation of siliceous calculi. No calculi were found in a similar group of 14 calves given the same ration with sodium chloride added (4 percent). It is suggested that sodium chloride prevented calculus formation by in creasing water intake and urine volume, with a consequent reduction in the con-centration of silicic acid in the urine