The secret life of the city rat: a review of the ecology of urban Norway and black rats (Rattus norvegicus and Rattus rattus)

Norway rats (Rattus norvegicus) and black rats (Rattus rattus) are among the most prolific and widespread urban pest species in the world. Yet despite their ubiquity, a unified understanding of the ecology of these species in urban habitats eludes us. A comprehensive understanding of urban rat ecology is important for managing rat populations and mitigating the harmful effects that they may have on urban ecosystems (e.g., structural damage, food contamination, and disease spread). The objective of this systematic review and narrative synthesis is to collate, compare, and contrast data from the published literature regarding the ecology of Norway and black rats in urban centers. Themes emerging from the synthesis process, and discussed in detail, include population dynamics, behavior, movement, and environmental influences on rat populations.     

Using experiential knowledge to understand urban rat ecology: A survey of Canadian pest control professionals

Rats (Rattus rattus and Rattus norvegicus) are among the most prolific and widespread urban pest species in the world. However, there is relatively little contemporary data regarding the ecology of rats in urban centers, preventing the development of effective strategies for urban rat management. Practical constraints associated with field studies suggest the need for more efficient methods of data collection, one of which could involve pest control professionals, who have considerable experiential knowledge of urban rats. The objective of this study was to gather data regarding urban rat ecology through a survey of Canadian pest control professionals and to determine whether such a survey could be useful for the collection of ecological data regarding pest species. Survey results suggested that rat infestations fluctuate seasonally and that there are a variety of environmental factors that may attract rats, particularly exposed garbage, abandoned buildings, and compost. Respondents suggested that rat infestations are most frequent and/or severe in residential areas, commercial areas dealing with food, as well as in neighborhoods of low socioeconomic status. The majority of respondents believed that rats pose at least a moderate health risk to the general public and to themselves, and they also believed that although poison baiting is the cheapest and easiest method of rat control, environmental modification is the most effective way to control rat infestations in the long term. Despite issues with low response rates, these results suggest that pest control professionals may be a valuable source of data regarding urban pest species.     

A comparative assessment of track plates to quantify fine scale variations in the relative abundance of Norway rats in urban slums

Norway rats (Rattus norvegicus) living in urban environments are a critical public health and economic problem, particularly in urban slums where residents are at a higher risk for rat borne diseases, yet convenient methods to quantitatively assess population sizes are lacking. We evaluated track plates as a method to determine rat distribution and relative abundance in a complex urban slum environment by correlating the presence and intensity of rat-specific marks on track plates with findings from rat infestation surveys and trapping of rats to population exhaustion. To integrate the zero-inflated track plate data we developed a two-component mixture model with one binary and one censored continuous component. Track plate mark-intensity was highly correlated with signs of rodent infestation (all coefficients between 0.61 and 0.79 and all p-values?<?0.05). Moreover, the mean level of pre-trapping rat-mark intensity on plates was significantly associated with the number of rats captured subsequently (Odds ratio1.38; 95 % CI 1.19–1.61) and declined significantly following trapping (Odds ratio 0.86; 95 % CI 0.78–0.95). Track plates provided robust proxy measurements of rat abundance and distribution and detected rat presence even when populations appeared ‘trapped out’. Tracking plates are relatively easy and inexpensive methods that can be used to intensively sample settings such as urban slums, where traditional trapping or mark-recapture studies are impossible to implement, and therefore the results can inform and assess the impact of targeted urban rodent control campaigns.     

Local perception of rodent-associated problems in Sahelian urban areas: a survey in Niamey,Niger

Rodents are involved in the epidemiology of many pathogens and are major pests for agriculture. Local perception and beliefs about rodents and their damages is a key element of control programs. We here present the first survey focusing on the human perception of rodent-associated problems in an African town, namely Niamey, Niger. In total, 170 interviews were conducted in 18 different urban districts where rodents (Mastomys natalensis, Rattus rattus and Mus musculus) are widespread and abundant. Rodent-associated problems were mentioned in almost all instances (96.5 %). Eight different categories of rodent-induced nuisances could be recurrently identified. The most frequently cited one consists in damages on food and food stocks (63.1 %), followed by damages on houses (47.3 %), furniture (19.5 %) and clothes (16.8 %). There was no significant association between damages and districts, which means that the perception of rodent-associated problems did not vary significantly across the city. Our survey strongly suggests that rodents may represent major pests not only for farmers, but also for inhabitants of towns, thus contributing to reinforce economic vulnerability. Finally, no mention of sanitary or medical problems was ever recorded during our survey, thus pointing towards an apparent absence of knowledge about the potential role of rodents in some public health issues.     

Are the closed landfills recovered habitats for small rodents? A case study in a riparian site,Buenos Aires,Argentina

The establishment of landfills in urban areas leads to extensive disturbances. Their development after landfill closure depends on the characteristics of the soil cover, the surrounding communities and the dispersal of plants and animals. This study was carried out in a landfill closed in 2004, surrounded by an urban area, freshwater marshes and a riparian forest. The aim of this study was to determine the role that the closed landfill may play in maintaining rodent communities typical of this zone and its relation to characteristics of the sites. Four rodent and plant samplings were carried out from December 2005 to September 2006 at five sites inside the landfill: three filled cells and two areas of the riparian margin. We recorded a total of 433 individual rodents. The rodent community of the closed landfill included species typical of rural, riparian and rural habitats: Akodon azarae (358), Oligoryzomys flavescens (32), Deltamys kempi (14), Rattus rattus (14), Cavia aperea (11) and Scapteromys aquaticus (4). Rodent species composition varied among sites, but A. azarae was usually the dominant species. We found a rich rodent community mostly composed of wild species. The relictual riparian margin may have served as a major refuge for native rodent community while the landfill was in operation, and after closure it possibly acted as a source for some species to colonize the covered cells.     

Pravastatin improves the impaired nitric oxide-mediated neurogenic and endothelium-dependent relaxation of corpus cavernosum in aged rats

Abstract

Aim: The aim of this study was to investigate the effect of pravastatin treatment on diminished corpus cavernosum (CC) function associated with aging.

Methods: Male rats were divided into three groups as adult rats (12–14 weeks old), aged rats (72–80 weeks old) and aged rats given 10?mg/kg/d pravastatin in drinking water for six weeks. Blood pressure was measured by tail-cuff method. Total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, triglycerides and testosterone levels were estimated in blood. Changes in expression levels of endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (p-eNOS) (Ser-1177), neuronal nitric oxide synthase (nNOS), NADPH oxidase subunit gp91^phox, Rho A and Rho kinase (ROCK2) in CC were assessed by immunohistochemistry. Nitric oxide (NO)-mediated endothelium-dependent and neurogenic CC relaxation were evaluated by acetylcholine (ACh, 0.1?nM–100?µM) and electrical field stimulation (EFS; 30?V, 5?ms, 2–32?Hz), respectively.

Results: In aged rats, NO-mediated, both endothelium-dependent and neurogenic CC relaxation, were significantly impaired as compared to adult rats. Besides, eNOS, p-eNOS and nNOS expressions decreased significantly in CC from aged rats, while gp91^phox, RhoA and ROCK2 expressions increased significantly. The diminished relaxation in response to ACh or EFS as well as the changes in expression of these proteins in aged rats were significantly improved by pravastatin treatment.

Conclusion: Pravastatin improves NO-mediated CC relaxations of aged rats probably by inhibiting NADPH oxidase/Rho kinase pathways, and this effect does not seem to be associated with lipid lowering effect of this drug.     

LOH–pitfalls of an ambiguous abbreviation

Osteoporosis in elderly men is becoming an important health issue with the aging society. Elderly men with androgen deficiency are exposed to osteoporosis and can be treated with testosterone replacement. In this study, Eurycoma longifolia (EL), a plant with androgenic effects, was supplemented to an androgen-deficient osteoporotic aged rat as alternative to testosterone. Aged 12 months old Sprague-Dawley rats were divided into groups of normal control (NC), sham-operated (SO), orchidectomised-control (OrxC), orchidectomised and supplemented with EL (Orx?+?El) and orchidectomised and given testosterone (Orx?+?T). After 6 weeks of treatment, serum osteocalcin, serum terminal C-telopeptide Type 1 collagen (CTX) and the fourth lumbar bone calcium were measured. There were no significant differences in the osteocalcin levels before and after treatment in all the groups. The CTX levels were also similar for all the groups before treatment. However, after treatment, orchidectomy had caused significant elevation of CTX compared to normal control rats. Testosterone replacements in orchidectomised rats were able to prevent the rise of CTX. Orchidectomy had also reduced the bone calcium level compared to normal control rats. Both testosterone replacement and EL supplementation to orchidectomised rats were able to maintain the bone calcium level, with the former showing better effects. As a conclusion, EL prevented bone calcium loss in orchidectomised rats and therefore has the potential to be used as an alternative treatment for androgen deficient osteoporosis.     

Gender-dependent variations in systemic biomarkers of oxidative protein,DNA, and lipid damage in aged rats

Introduction.?The effect of aging on plasma-protein, lipid and DNA oxidation is well documented. However, none of the studies specify the effect of gender. The purpose of this study is to clarify the ambiguity raised in preliminary reports as to gender dependency of oxidative damage in plasma.

Methods.?In the current study, we investigated the relation between 8-hydroxy-2′-deoxyguanosine levels (8-OHdG), which is a measure of DNA oxidation and protein oxidation parameters such as protein carbonyl (PCO), total thiol (T-SH), and advanced oxidation protein products (AOPP). Our study also covered other oxidative stress parameters, such as lipid hydroperoxides (LHP), malondialdehyde (MDA), erythrocyte glutathione (GSH), superoxide dismutase (Cu-Zn SOD) and the catalase (CAT) activity in plasma of the male and female aged rats.

Results.?8-OHdG and MDA levels in male rats were significantly higher than those in the female group (p?<?0.01 for both parameters). T-SH levels were found to be higher in female rats than in the male (p?<?0.05). Plasma Cu-Zn SOD activities of male rats were significantly higher compared with those of the female rats (p?<?0.05). On the other hand, PCO, AOPP, LHP, GSH levels, and CAT activity were not found to be different between genders.

Conclusions.?We suggest that increased T-SH levels found in female rats may point to an adaptive reaction to oxidative damage, reflecting 8-OHdG and MDA overproduction. We are of the conviction that the increased 8-OHdG and MDA that we have determined in aged male rats may be a risk factor in the extent of oxidation in plasma.     

The modern management of erectile dysfunction: choices available for treatment

Rat parathyroid hormone (PTH) 1-34 (4?μg/kg/day) was applied for 2.5 months to 9 month-old rats immediately after ovariectomy or orchidectomy or to 15 month-old rats with low bone mass which had been castrated 6 months before in order to know the effects on serum biochemistry parameters, lumbar and femoral bone mineral density, histology, cancellous and cortical bone histomorphometry, mineralisation content profile in cortical bone by backscattered-electron microscopy, and femoral torsion biomechanical testing. In ovariectomised rats, preventive PTH treatment avoided cancellous bone loss in tibial metaphysis and partially in lumbar vertebra, while in cortical bone, PTH increased endosteal resorption and periosteal formation. In intervention study, PTH did not restore cancellous bone but a strong endosteal and periosteal new bone formation was detected. In orchidectomised rats, PTH, in preventive study, avoided cancellous bone loss in metaphysis and lumbar vertebra, and a mild new bone formation in cortical bone was found. In intervention study, PTH maintained baseline cancellous bone mass, but in cortical bone a strong endosteal and periosteal new bone formation was detected. The PTH-induced new bone formation was confirmed by histology and by mineral content profiles. After castration, biomechanical properties were affected in females but not in male rats and PTH reverted this effect.     

How protecting a suburban forest as a natural reserve effected small mammal communities

Restoration of mammal communities was studied between 1975–1984 and 2001–2009 (over ca. 30 years) in two suburban forests in central Poland: one protected as a natural reserve and one not protected. The mammal community in the legally protected forest showed more extensive changes than in the case of the nonprotected forest. In the natural reserve, the numbers of Microtus subterraneus, Apodemus agrarius, Rattus norvegicus and Mus musculus decreased while insectivores (mostly Sorex araneus), bats and Apodemus flavicollis increased in numbers. The community of small mammals in the reserve became more similar to the community from the relatively natural area – Białowieża Primeval Forest (eastern Poland). A protection supported restoration processes of tree stands and consequently started to increase the numbers of mammalian species typical of more natural habitats, as well as to reduce the numbers of synanthropic species and those connected to open areas. In the nonprotected forest, fewer species changed their abundance (M. subterraneus decreased, insectivores, bats and A. flavicollis increased). However, an increase in the percentage of bats and a decrease of M. subterraneus in mammal communities of both forests could reflect general trends in their populations noted in recent decades. The population decline of Warsaw’s urban species – A. agrarius perhaps is the best indicator of the restoration of suburban forests.     

Age-related changes in skeletal-muscle myosin heavy-chain composition: effect of mechanical loading

The purpose of this study was to investigate the effect of compensatory hypertrophy (CH), heavy-resistance exercise training (HRET), and simultaneous CH and HRET on fast-twitch skeletal-muscle myofibrillar-protein synthesis, myosin heavy-chain (MHC) turnover rate, and MHC-isoform composition in young and old rats. In young animals all treatments intensified myofibrillar-protein synthesis, whereas in old animals with CH protein synthesis remained unchanged. The relative content of MHC I and IID in plantaris muscle increases with age, and the relative content of MHC IIB decreases. HRET and simultaneous CH and HRET decreased the proportion of MHC IIB and IIA and increased that of MHC IID in young rat muscle. In old rat muscle, relative content of MHC IID decreased and that of MHC IIB increased. CH decreased relative content of MHC IIB in both age groups and of MHC IIA in old animals. Relative content of MHC IID increased in both groups, and of MHC IIA, in young animals. MHC in plantaris of young rats turned over much faster in all types of mechanical loading but in old rats only during HRET and its combination with CH.     

Endogenous hydrogen sulfide insufficiency as a predictor of sexual dysfunction in aging rats

Objective: Our earlier studies showed that endogenous hydrogen sulfide (H₂S) pathway contributed significantly to erectile function. In this study, we tested the hypothesis that age-dependent changes in the bioavailability of H₂S increased the risk of erectile dysfunction (ED). Methods: Young, adult (3-month) and older (18-month) male Sprague-Dawley rats (n?=?6?8/group) were treated daily with sodium hydrosulfide hydrate (NaHS), DL-propargylglycine, sildenafil or l-NAME for 10 weeks. Subsequent to cavernous nerve electrical stimulation, intracavernosal pressure (ICP) responses were determined, and the samples were collected and processed for hormonal (plasma) and gaseous parameters (plasma and erectile corpus cavernosum [CC]) using standard assay protocols. Results: Aging significantly reduced the ICP response (35.9?±?2.0 mmHg vs. 45.2?±?1.9 mmHg in young controls), which was countered by NaHS (53.5?±?6.0) or sildenafil (52.8?±?9.8) treatment. In these rats, marked increments to testosterone (T) or estradiol resulted from NaHS supplementation. Similar to age-dependent decline in NO, the plasma and CC level of H₂S was significantly lower in senescent rats when compared with young animals (p?<?0.05). Conclusion: Our results confirm that ED with aging may be linked to a derangement in the H₂S pathway accompanied by low T levels. It is likely that a pharmacologic intervention delivering H₂S will provide additional benefits to sexual function from an improved T milieu.     

Caloric restriction minimizes aging effects on the femoral medial condyle

This study aimed to analyze the effects of caloric restriction on aged femoral articular cartilage of Wistar rats. Three groups of eight animals each were considered: young (YC) and old (OC) control groups fed with a normal diet and old caloric restriction group (OCR) composed of 18-month-old animals fed with a 31% less caloric diet from 6-months of age. Articular cartilage was studied through morphometry and immunohistochemistry. Body mass was 12% less in the OCR group than in the OC group. The articular cartilage from OC rats show thinner medial condyles, fewer chondrocytes, smaller chondrocytes nuclear volume and, in both condyles, a predominance of collagen type II and less collagen density compared to both YC and OCR groups (p?p?相似文献   

Higher Order Conditioning in the Newborn Rat: Effects of Temporal Disparity Imply Infantile Encoding of Simultaneous Events

Infant rats in the age range 8 to 16 days postnatal (P8–16) outperform older animals at learning an association between neutral olfactory stimuli, but only with simultaneous presentation of the odors; sequential presentation eliminates or reverses the infants' advantage. Such results suggest that infants and older animals differ in how they learn simultaneous events. This study tested whether the infant's special effectiveness with such learning is peculiar to P8–16 or is a general feature of infantile naïvete seen in newborns as well. At 3 hr of age newborn rats exhibited strikingly robust sensory preconditioning and second‐order conditioning, but only for simultaneous odors. Any degree of temporal disparity between odors (even 0 sec) eliminated sensory preconditioning and markedly reduced second‐order conditioning. This suggests that the weak differentiation among simultaneously presented stimuli in newborns may promote something similar to perceptual configuration.     

Prenatal Development of Interlimb Motor Learning in the Rat Fetus

The role of sensory feedback in the early ontogeny of motor coordination remains a topic of speculation and debate. On E20 of gestation (the 20th day after conception, 2 days before birth), rat fetuses can alter interlimb coordination after a period of training with an interlimb yoke, which constrains limb movement and promotes synchronized, conjugate movement of the yoked limbs. The aim of this study was to determine how the ability to express this form of motor learning may change during prenatal development. Fetal rats were prepared for in vivo study at 4 ages (E18–21) and tested in a 65‐min training‐and‐testing session examining hind limb motor learning. A significant increase in conjugate hind limb activity was expressed by El9, but not El 8 fetuses, with further increases in conjugate hind limb activity on E20 and E21. These findings suggest substantial development of the ability of fetal rats to modify patterns of interlimb coordination in response to kinesthetic feedback during motor training before birth.     

Research of stroke combined hyperlipidemia-induced erectile dysfunction in rat model

Abstract

Objective: The study was aimed to evaluate the influences of erectile dysfunction (ED) in a rat model of stroke combined with hyperlipidemia (HLP).

Methods: Male Sprague–Dawley rats were divided into control and hyperlipidemia (HLP) groups. HLP model was constructed by feeding with high-fat and cholesterol diets. Serum levels of total cholesterol (TC), low density lipoprotein (LDL), high density lipoprotein (HDL), triglyceride (TG), and non-HDL were identified to check the model was success. Stroke model was established by FeCl₃. ICP/MAP value was detected to evaluate the erectile function of rats. Serum level of lipoproteins and the expressions of endothelial nitric oxide synthase (eNOS), vascular endothelial growth factor (VEGF) were detected by ELISA. Hematoxylin–eosin (HE) staining of corpus cavernosum and measurement of penis length were utilized to assessment erectile function. Western blot was used.

Results: TC, TG, LDL, and non-HDL-C in serum were up-regulated, while HDL level was attenuated. After treatment, the serum lipid level recovered. From the ICP/MAP values, the erectile function of both two treatment groups recovered. The expression of PDE5A was up-regulated, while the levels of eNOS and cGMP were suppressed after surgery. The length of penis was decreased, and corpus cavernosum was damaged following HLP and stroke. However, the erectile function was recovered after treatment.

Conclusion: Stroke combined HLP caused ED through NO-cGMP-PDE5 pathway.     

Age-related effects on the zona glomerulosa cells of the rat adrenal cortex

Zona glomerulosa cells of the rat adrenal cortex were studied at 2, 6, 12, 18 and 24 months. Adrenals from unstimulated rats were processed for light and electron microscopy and trunk blood was obtained for the assay of plasma renin activity and aldosterone. Similar assays were made in rats stimulated with adrenocorticotropic hormone (ACTH), 30 min before sacrifice. At light microscopy, no major structural changes were observed; the ultrastructure of most organelles was well preserved and the presence of lipofuscin granules in older animals was remarkable. Acid phosphatase activity was observed in lysosomes and some lipofuscin granules. The quantitative study showed an age-related decrease in cell and nuclear volume (p < 0.01 and p < 0.001 respectively) and an increase in volume density of lipid droplets, lipofuscin granules (p < 0.001), lysosomes and Golgi complex; a decrease in volume density of mitochondria and smooth endoplasmic reticulum (p = 0.052) was also observed. Plasma renin activity and aldosterone level were both reduced (p < 0.001). In stimulated animals, an enhanced aldosterone level was obtained which was higher at 12 months and decreased thereafter. These results show an age-related decrease of aldosterone secretion, consistent with structural and ultrastructural data and related to plasma renin decrement. They also show a decline in the response to aldosterone stimulation by ACTH, indicating a lesser functional ability of zona glomerulosa cells in old animals.     

Demilitarizing disarmament with mine detection rats

ABSTRACT

This paper considers a new technology for mine action in Cambodia: the mine detection rat. Used successfully in Africa for mine detection since 2003, the rats were implemented for the first time in 2015 in Cambodia by the international NGO, APOPO. APOPO entered a small-scale partnership with the state mine action organization, Cambodian Mine Action Centre. The partnership revealed a tension between APOPO’s aspiration to ‘demilitarize’ mine action and the highly militarized nature of mine action under the state. The rats were unique among militaristic structures and experiences and allowed the international NGO to promote an ideal of what demilitarized mine action should look like. But the rats also condition the possibilities for the demilitarization of mine action through their own biological and historical attributes. This paper will use observations from over 14 months of fieldwork among this partnership with mine detection rats, showing tensions between local militarized methods for disarmament and an NGO’s aspirations for global humanitarianism.     

Caloric restriction in trans

Caloric (or dietary) restriction (CR) is the most potent, robust, and reproducible known means of extending longevity and decreasing morbidity in laboratory mammals. Two of the major questions faced by researchers in this field are the applicability to humans and the biochemical mechanism(s) involved in the actions of CR. Studies in nonhuman primates are beginning to address the former; studies in phylogenetically lower organisms such as yeast and Drosophila are beginning to address the latter. de Cabo and colleagues now provide evidence that some aspects of CR can be reproduced in mammalian tissue culture cells exposed to sera from rats and monkeys subjected to CR. This work presents the initial development of a new model with which to approach mechanistic studies of CR and provides a new form of direct evidence that CR exerts at least some of its effects in trans.     

More is less: neurogenesis and age-related cognitive decline in Long-Evans rats

A reduction in the ability to generate new neurons in the brain has been suggested to contribute to cognitive decline with advanced age. In an outbred model strain of Long-Evans rats, cognitive performance as a function of age is variable in assessments of hippocampal-dependent spatial memory. Recent research indicates that greater hippocampal neurogenesis accompanies diminished cognitive abilities in older Long-Evans rats. These findings imply that the role of neurogenesis might change between youth and old age, and that further work is needed to understand the potential benefits and liabilities that new neurons may afford an aging brain.