Efficacy of treatment with glycosaminoglycans on experimental collagen-induced arthritis in rats

To evaluate the antioxidant activity of the glycosaminoglycans hyaluronic acid (HYA) and chondroitin-4-sulphate (C4S), we used a rat model of collagen-induced arthritis (CIA). Arthritis was induced in Lewis rats by multiple intradermal injections of 250 μl of emulsion containing bovine type II collagen in complete Freund's adjuvant at the base of the tail and into three to five other sites on the back. Rats were challenged again with the same antigen preparation 7 days later. Disease developed about 11 days after the second immunization. The effects of treatment in the rats were monitored by biochemical parameters and by macroscopic and histological evaluations in blood, synovial tissue and articular cartilage. Arthritis produced the following symptoms: severe periarticular erythema, edema and inflammation in the hindpaws; membrane peroxidation in the cartilage of the joints; endogenous antioxidant wasting; high tumour necrosis factor-α (TNF-α) plasma levels; and synovial neutrophil accumulation. Treatment with HYA and C4S, starting at the onset of arthritis for 10 days, limited the erosive action of the disease in the articular joints of knee and paw, reduced lipid peroxidation, restored the endogenous antioxidants reduced glutathione (GSH) and superoxide dismutase, decreased plasma TNF-α levels, and limited synovial neutrophil infiltration. These data confirm that erosive destruction of the joint cartilage in CIA is due at least in part to free radicals released by activated neutrophils and produced by other biochemical pathways. The beneficial effects obtained with the treatment suggest that HYA and C4S could be considered natural endogenous macromolecules to limit erosive damage in CIA or as a useful tool with which to study the involvement of free radicals in rheumatoid arthritis.     

Age-related nephropathy in laboratory rats

Chronic progressive nephropathy is a spontaneous disease common among aging laboratory rats, often making it difficult to distinguish age-related from drug-related effects in chronic toxicity studies. Morphological changes of the kidney that occur with age include thickening of glomerular and proximal tubular basement membranes, mesangial proliferation, fusion of foot processes, and, ultimately, glomerular sclerosis. Proteinuria (specifically, albuminuria) is the most striking characteristic change in renal function of aging rats and, generally, correlates well with the severity of age-related glomerular pathology. Changes in tubular functions also may occur with aging but have not been investigated sufficiently. The pathogenesis of chronic progressive nephropathy is not known; however, hemodynamic adaptations after ad libitum consumption of protein-rich diets may be a contributing factor. High-protein diets increase glomerular pressures and flows, perhaps facilitating excretion of metabolic end products. These hemodynamic adaptations may impair the permselective properties of the glomerulus, leading to: enhanced accumulation of macromolecules in the mesangium, progressive mesangial expansion, and, ultimately, glomerular sclerosis. Indeed, decreasing total food or protein intake retards or prevents the progression of age-related nephropathy. Inasmuch as chronic toxicity studies are complicated by a high incidence of spontaneous nephropathy, implementation of a restricted dietary regimen may improve detection of drug-induced toxicity.     

Cage size preference in rats in the laboratory

The size of an enclosure is an integral part of how well it accommodates a nonhuman animal's welfare; however, most enrichment studies concentrate on modifying the area inside the enclosure rather than enlarging it. It has been suggested that rats have little need for more cage space, but there is no empirical evidence about rats' need for space. This experiment provides preliminary evidence for the preferences of 5 male and 5 female albino rats using T-maze choices followed by 5 min dwelling times. The rats showed a moderate but significant preference for the larger of 2 cages [540 cm2 vs. 1,620 cm2; binomial z, p <.05]. When the rats shared the chosen cage with 4 familiar cage mates, their preference for the larger cage did not become any stronger [paired t[9] = -.820, p >.05]. The results suggest that rats should be given a somewhat larger space allowance but could share it with up to 4 other rats.     

Circannual rhythms in the blood picture of laboratory rats

Circannual rhythms of the erythrocyte, total leucocyte, absolute segmented neutrophil and lymphocyte counts in laboratory Wistar rats were found. The highest mean counts occurred in autumn and at the begining of winter. The lowest counts werte recorded in spring and at the begining of summer. A similar circannual rhythm of absolute eosinophil counts in females was also found, but it was not present in males. Circannual rhythms of the relative lymphocyte, segmented neutrophil and eosinophil were not found. The course of seasonal variations in erythrocyte, total leucocyte, absolute segmented neutrophil and lymphocyte counts of males was similar to those of females.     

Spontaneous chromosome aberrations in the oogenesis of laboratory rats]

Cytological preparations were made by Tarkovsky's method from 2335 rat oocytes obtained after an induced superodulation. The chromosomes could be counted exactly in 861 oocytes. In 797 oocytes (92.7%) euploidy (metaphase II with 21 chromosomes) and in 64 oocytes (7.5%) aneuploidy was found. 60 oocytes were hypoploid, but only 4 oocytes (0.4%) were hyperploid (with 22 chromosomes). Hypoploidy can often be due to the presence of artefacts. Probably the rate of spontaneous aneuploidy in rat oogenesis is about 0.8%, this being significantly lower than the rate of spontaneous aneuploidy in mice oogenesis.     

杀蟑胶饵室内药效及德国小蠊对氟虫腈抗药性研究

【目的】本文通过测定杀蟑胶饵对德国小蠊Blattellagermanica(L.)和美洲大蠊Periplaneta americana (L.)的致死效果,以及德国小蠊对杀虫剂氟虫腈的抗性,从而为胶饵选择和蟑螂的化学防治提供参考。【方法】用饲喂法在实验室测定了7种国产杀蟑胶饵及5种美国产杀蟑胶饵或毒饵站对德国小蠊的致死效果,5种国产蟑螂胶饵对美洲大蠊的致死效果,以及对5种国产蟑螂胶饵陈化1个月后对德国小蠊的致死效果。并采用点滴法测定了两个德国小蠊野外品系对氟虫腈的抗性。【结果】7种中国产胶饵中,5种对德国小蠊抗性和非抗性品系在第7天的校正死亡率高于91%。其中韩世和克贝特对德国小蠊的药效显著慢于绿叶、宏宇洁和优士。绿叶、宏宇洁和优士对美洲大蠊在第7天的校正死亡率均高于89%。陈化1个月后的胶饵只有克贝特对蟑螂的致死率有较大降低。美国产胶饵或毒饵站对德国小蠊的致死率均大于82%。点滴法抗性测定结果显示德国小蠊的两个野外品系(Cincy,Irvington)对氟虫腈生理抗性指数分别是4.3和115.1。【结论】不同胶饵对德国小蠊和美洲大蠊的致死效果有明显差异。尽管德国小蠊Irvington品系对氟虫腈表现为高抗性,含0.05%氟虫腈的胶饵仍然对它有效。     

Estrogen treatment during development alters adult partner preference and reproductive behavior in female laboratory rats

There is broad acceptance for the idea that during development estradiol ‘organizes’ many aspects of reproductive behavior including partner preferences in the laboratory rat. With respect to partner preference, this idea is drawn from studies where estrogen action was in someway blocked, either through aromatase or estrogen receptor inhibition, during development in male rats. The lack of estrogens neonatally results in a decrease in the male rat's preference for females. In this study, the effect of early postnatal estradiol treatment on the partner preferences of female rats was examined as a further test of the hypothesis that male-typical partner preference is dependent upon early exposure to estrogens. Our principal finding was that increased postnatal estradiol exposure during development affected partner preference in the expected direction, and this effect was seen under several adult hormonal and behavioral testing conditions. Female rats that received exogenous estradiol during development spent more time with an estrous female and less time with a sexually active male than did cholesterol treated females. The estradiol treatment also disrupted normal female sexual behavior, receptivity, and proceptivity.     

The cage preferences of laboratory rats

Preference tests were used to assess a range of enrichment options for rats kept under standard New Zealand (and similar) caging conditions. The rats did not show significant preferences for most of the options, over an empty cage. The exceptions were shredded paper, a nesting box and a semi-enriched condition incorporating a range of modifications. These cage modifications are recommended for the enrichment of laboratory rats.     

Contextual determinants of female-female mounting in laboratory rats

Female-female mounting is widespread among mammalian species, but little is known about the proximal function of this behaviour. While such mounting is often regarded as a 'masculine' trait, its widespread occurrence may indicate that it serves specific functions within the context of female-female social behaviour. We valuated female mounting behaviour in Long-Evans rats in standard observation chambers and in a seminatural enclosure. Under these conditions, we examined a number of potential factors that might influence mounting, including the oestrous cycle, social hierarchy, familiarity and male presence. The female's mounting was not influenced by her own oestrous cycle, but did vary with the oestrous cycle of the stimulus female. Socially dominant females mounted significantly more than subordinate females, and mounting by the dominant female was most frequent when the subordinate female was sexually receptive. Females mounted (and fought with) unfamiliar females significantly more than they did with familiar cagemates. Female-female mounting was dramatically reduced when males were present. Further testing showed that female mounting did not affect the induction of the progestational state of pregnancy, suggesting that female mounting does not function as a pseudomale behaviour that can substitute for genital stimulation provided by the male. Based on these data, female mounting does not appear to function as a sexual behaviour per se, but may serve as a form of female social behaviour related to maintenance of the female's social status within female groups. In this regard, the results of this study suggest that female mounting is part of the normal female's complex behavioural repertoire and does not necessarily reflect masculinization of some underlying neural substrate. Copyright 1999 The Association for the Study of Animal Behaviour.     

Behavioral indexes of poor welfare in laboratory rats

A study compared the behavior of rats kept under standard conditions with the behavior of those from enriched, semi-enriched, and single-housed conditions to determine whether standard conditions have detrimental effects on nonhuman animal welfare. The subjects were 35 female Hooded Norway rats. Using an emergence box, open field, and Hebb-Williams maze, the study measured the subjects' behaviors. Housing conditions significantly affected the behavior of the rats as measured by all 3 procedures. The results of the rats from standard conditions were intermediate between those of the single-housed and the more enriched groups. Thus, enrichng the standard environment would ameliorate behavioral deficits in rats kept under standard conditions.     

Hormonal factors influence the onset of maternal aggression in laboratory rats

This experiment addressed the hypothesis that aggressiveness toward conspecifics is stimulated by hormonal factors known to mediate the onset of maternal care. Subjects included both pregnant and virgin females. Sixteen-day pregnant rats were hysterectomized (H), hysterectomized-ovariectomized and injected with estrogen (HO-EB), or subjected to sham procedures. Nonpregnant females were HO-EB or sham operated. The females were sensitized by continuous exposure to pups and were judged to have initiated maternal care when all pups were retrieved and grouped, Aggressiveness was observed during 5-min intruder tests using unfamiliar males, administered (a) 10 min prior to the introduction of test pups, (b) following the first 3 hr of pup exposure, and (c) after females had initiated maternal care. The results revealed that treatments known to reduce sensitization latencies also increased aggressiveness even prior to exposure to pups. Aggressiveness was displayed before sensitization only in groups having elevated estrogen levels. After initiating maternal behavior, pregnant and pregnancy-terminated females increased further in aggressiveness whereas nonpregnant females did not. Pregnancy-terminated, HO-Oil females became aggressive (only) after initiating maternal behavior, indicating that factors other than estrogen also influence the onset of maternal aggression.     

Blood supply of the main vessels in laboratory rats and rabbits

The vascular bed in 25 rabbits and 25 white rats has been revealed by means of vital injection of Indian ink into the intraorganic vessels, staining of erythrocytes (benzidine reaction) and silver impregnation. In preparations of the aorta, inferior and superior vena cava diameter of the vessels, the wall and middle membrane thickness, amount of elastic membranes have been measured. Ramification of small vessels and capillaries are revealed only in the paravasal tissues, surrounding the aorta and veins. In serial sections it has been stated that at their greatest extent vasa vasorum has no walls and only in places, where the intercostal (or others) vessels get out of the aorta in its middle or external tunics, a limited, as to its spread, network of intramural vessels exists. The morphometrical analysis does not show any regular connection between the vascular diameter, wall thickness, or middle membrane thickness, amount of elastic membranes in it with presence or peculiarities in distribution of the intramural vessels.