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At least 667 records · Page 37Linked to original sources
PubMed1995

A case-control study of hantavirus pulmonary syndrome during an outbreak in the southwestern United States.

In May 1993, an outbreak of hantavirus pulmonary syndrome (HPS) occurred in the southwestern United States. A case-control study determined risk factors for HPS. Seventeen case-patients were compared with 3 groups of controls: members of case-patient households (household controls), members of neighboring households (near controls), and members of randomly selected households > or = 24 km away (far controls). Investigators trapped more small rodents at case households than at near (P = .03) or far control households (P = .02). After the number of small rodents was controlled for, case-patients were more likely than household controls to hand plow (odds ratio [OR], 12.3; 95% confidence interval [CI], 1.1-143.0) or to clean feed storage areas (OR, 33.4; 95% CI, 1.7-666.0). Case-patients were more likely than near controls to plant (OR, 6.2; 95% CI, 1.1-34.0) and more likely than far controls to clean animal sheds (OR, 11.9; 95% CI, 1.4-103.0). Peridomestic cleaning, agricultural activities, and an increased number of small rodents at the household were associated with HPS.

Adolescent↗
PubMed2004

Molecular and cellular correlates of the developmental acquisition of mechanisms modulating ingestive behavior.

Postnatal development in most mammals is accompanied by the acquisition of controls of ingestion. In rodents, the initial and default controller appears to be gastric stretch. In the second week of life, rat pups acquire the ability to sense the presence of nutrients within the gut and appropriately modulate ingestion. In the third week of life, rat pups start to become weaned from the dam's milk and begin independent ingestion. There have been strong indications that neuropeptide Y is a stimulator of ingestion in adults, although there was very little information in pups. Dr. Gerard Smith initiated a series of studies that provide strong evidence to indicate that hypothalamic neuropeptide Y (NPY) neurons are strong candidates for providing the ability of preweaning rat pups to modulate ingestion according to caloric intake. Moreover, the studies also suggest that the overactivity of hypothalamic NPY neurons presage the onset of hyperphagia in syndromes associated with defects in leptin signaling.

Aging↗
PubMed1998

Small mammal survival and trapability in mark-recapture monitoring programs for hantavirus.

Following the 1993 hantavirus pulmonary syndrome (HPS) epidemic in the south-western United States, mammalogists and epidemiologists instituted long-term studies to monitor population density and prevalence of infection in rodents which constitute the reservoir for Sin Nombre virus (SNV). In this study, field techniques used in sampling small mammals for SNV infection were evaluated to determine if trapping and handling protocols were having significant effects on future trapability or mortality of animals. We compared rodent mark-recapture control plots, on which all rodents were simply measured, marked, and released on site, with experimental plots on which all animals were anesthetized with methoxyflurane, sampled for blood and saliva, measured, marked, and released. Blood samples were obtained from anesthetized animals on the experimental plots via a retro-orbital sinus puncture using a heparinized capillary tube. Dacron tipped oral swabs were used to collect buccal cells and saliva from the rodent's oral cavity. Field data were collected monthly from August 1994 to August 1996 at two sites in New Mexico (USA). Analyses were based on 3,661 captures of 1,513 individuals representing 21 species from three rodent families (Rodentia: Muridae, Heteromyidae, Sciuridae) and two species of rabbits (Lagomorpha: Leporidae). Overall, for most murid rodents (including five Peromyscus spp., Neotoma albigula, and Onychomys leucogaster) and one rabbit species (Sylvilagus floridanus), the handling/bleeding procedures had no significant effects on recapture rates or mortality. In contrast, several species of heteromyids (Dipodomys ordii and Perognathus flavus), one murid (Reithrodontomys megalotis) and one leporid (S. auduboni) suffered higher mortality rates, and heteromyid kangaroo rats (D. ordii and D. merriami) exhibited lower trapability as a result of the anesthesia and sampling procedures. In view of the overall non-significant influence of the sampling procedures on murid rodents, the anesthesia and blood/saliva sampling protocols described herein appear to be appropriate for hantavirus research, and may serve as a model for environmental monitoring of other zoonotic agents and their reservoirs.

Animal Welfare↗
PubMed1980

Control of microbial contamination in the use of laboratory rodents.

Historically, laboratory rodents have been used in preference to other animal species for biomedical research. Study disruptions and invalidations often have occurred due to microbial contaminants inherent to laboratory rodents. Today, many commercial suppliers and research institutions are controlling a variety of infectious diseases among laboratory rodents by careful design of animal facilities, by adaptation of managerial techniques employing precise operational policies coupled with careful supervision and attention to detail and the use of various diagnostic programs. The continued evolution of epidemiological practices, environment control systems, sophistication of barrier-sustained operations, preventative medicine and sanitation techniques, complemented by an improvement in veterinary diagnostic programs for disease surveillance further minimize microbial contamination of laboratory rodents. Such measures contribute to the fulfillment of various legislative requirements concerned with the quality of animals for biomedical research.

Animal Feed↗
PubMed2003

Control of communicable diseases; restrictions on African rodents, prairie dogs, and certain other animals. Interim final rule; opportunity for public comment.

The Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) are issuing this interim final rule to amend their regulations to establish new restrictions and modify existing restrictions on the import, capture, transport, sale, barter, exchange, distribution, and release of African rodents, prairie dogs, and certain other animals. We are taking this action to prevent the spread of monkeypox, a communicable disease, in the United States.

Africa↗
PubMed1996

Apoptosis, cell replication, and Western-style diet-induced tumorigenesis in mouse colon.

In this study, feeding Western-style diets (WDs) to mice for a duration of two years without any chemical carcinogen led to the development of gross colonic lesions that were histologically classified as dysplastic crypts and focal hyperplasias with or without atypical nuclei. To better understand early biological events contributing to the development of colonic neoplasia, grossly normal colonic mucosa was investigated; mitotic and apoptotic colonic epithelial cells, atypical mitosis, and atypical nuclei were studied. A significant and transient increase of mitotic activity in the basal and intermediate portions of the colonic crypts was seen in young mice after feeding them the WDs. This was accompanied by diffuse activation of apoptosis of the colonic epithelial cells. In the middle of the rodents' life span, after administration of both the WDs and control diet, the rodents developed a marked depletion of apoptotic epithelial cells in the mid-region of the colonic crypts; this was followed by the expansion of an epithelial cell population containing atypical nuclei, and the emergence of the gross lesions noted above. With this sequence of events, prolonged feeding of WDs to mice produced single-crypt dysplastic lesions and focal hyperplasias indicative of tumorigenesis.

Animals↗
PubMed2006

An MLCK-dependent window in late G1 controls S phase entry of proliferating rodent hepatocytes via ERK-p70S6K pathway.

We show that MLCK (myosin light chain kinase) plays a key role in cell cycle progression of hepatocytes: either chemical inhibitor ML7 or RNA interference led to blockade of cyclin D1 expression and DNA replication, providing evidence that MLCK regulated S phase entry. Conversely, inhibition of RhoK by specific inhibitor Y27632 or RhoK dominant-negative vector did not influence progression in late G1 and S phase entry. Inhibition of either MLCK or RhoK did not block ERK1/2 phosphorylation, whereas MLCK regulated ERK2-dependent p70S6K activation. In addition, DNA synthesis was reduced in hepatocytes treated with p70S6K siRNA, demonstrating the key role played by the kinase in S phase entry. Interestingly, after the G1/S transition, DNA replication in S phase was no longer dependent on MLCK activity. We strengthened this result by ex vivo experiments and evidenced an MLCK-dependent window in late G1 phase of regenerating liver after two-thirds partial hepatectomy. In conclusion, our results underline an MLCK-dependent restriction point in G1/S transition, occurring downstream of ERK2 through the regulation of p70S6K activation, and highlighting a new signaling pathway critical for hepatocyte proliferation.

Amides↗
PubMed2002

Sensory, hormonal, and neural control of maternal aggression in laboratory rodents.

Parental animals of many rodent species display fierce and persistent aggression toward unfamiliar conspecifics that appears to protect their often altricial and defenseless young. We herein review studies of the sensory, hormonal, neuroanatomical, and neurochemical mechanisms underlying maternal aggression in laboratory rodents. The relationship between maternal aggression and fearfulness or anxiety is also discussed.

Aggression↗
PubMed1999

Repair of a rodent nasal critical-size osseous defect with osteoblast augmented collagen gel.

OBJECTIVES/HYPOTHESIS: Facial skeletal defects are a common challenge for the otolaryngologist. Type I collagen gels have shown promise in the repair of nonhealing critical size defects (CSDs) of facial bone by providing scaffolding for new bone growth by osteoblasts at the defect perimeter. The objective of the present study was to evaluate the effect that suspending osteoblasts within a type I collagen gel has on the repair of a rodent facial CSD. STUDY DESIGN: Randomized controlled trial using a rodent model. METHODS: A previously described facial CSD was created by removing the nasalis bones with a cutting burr to the level of the nasal mucosal membranes on 18 Sprague-Dawley rats. Groups of six animals were treated with an implant containing either 300 microg of type I collagen gel, 12 x 10(5) osteoblasts suspended within type I collagen gel, or 12 x 10(5) fibroblasts suspended within type I collagen gel for comparison. After 30 days the animals-were examined at necropsy with planimetry, histological analysis of new bone growth, and radiodensitometric analysis of bone thickness. RESULTS: All animals had complete coverage with a thin layer of bone. Histological sectioning revealed an increased thickness in the osteoblast augmented group. Radiodensitometric measurements revealed a statistically significant increase in bone repair in the osteoblast group compared with the collagen-only group (P < or = .0005) and the fibroblast group (P < or = .04). CONCLUSION: Type I collagen gels augmented with an osteoblastic suspension significantly enhance the repair of nasal CSDs in a rodent model. The use of cultured bone precursor cells represents a leap forward in osteoengineering.

Animals↗
PubMed1993

Comparative study of the control of basal acid output from rodent isolated stomachs.

1. Isolated, lumen-perfused, whole stomach preparations from mouse and immature rat produced a stable basal acid output which, although not blocked by histamine H2-, acetylcholine M- or CCKB/gastrin receptor antagonists, was almostly completely blocked by the H+/K(+)-ATPase inhibitor, omeprazole, and the metabolic inhibitor, sodium thiocyanate (NaSCN). 2. Fully-defined concentration-effect curves could be obtained on both assays with the phosphodiesterase inhibitor, isobutyl methylxanthine (IBMX) and with dibutyryl cyclic AMP. 3. On the rat stomach assay, histamine H2-receptor blockade had no effect on the IBMX curve. In contrast, the IBMX response in the mouse was abolished by histamine H2-receptor blockade. On both assays responses to dibutyryl cyclic AMP were resistant to H2-receptor blockade. 4. In the absence of suprathreshold endogenous histamine, it is argued that H+/K(+)-ATPase mediated basal acid secretion from the mouse stomach assay is regulated by something other than cyclic AMP.

1-Methyl-3-isobutylxanthine↗
PubMed1973

Mass airflow cabinet for control of airborne infection of laboratory rodents.

A mass airflow cabinet for handling and housing of laboratory rodents has been developed and tested. The unit consists of a high-efficiency particulate air filter and uniform distribution of air at a vertical velocity of 19 cm per s. Animals are maintained without bedding in mesh-bottomed cages that rest on rollers for rotation inside the cabinet. There is an air barrier of 90 cm per s separating the cabinet air from room air. Sampling for airborne bacteria yielded an average of 0.03 colony-forming units (CFU) per ft(3) of air inside the cabinet, whereas 28.8 CFU per ft(3) was simultaneously detected outside the cabinet during housekeeping, a reduction of almost three logs. The efficiency of the air barrier was tested by aerosolization of T3 phage. When phage was aerosolized 5 cm outside the cabinet, no phage could be detected 5 cm inside when the fans were operating; with the fans off an average of 1.6 x 10(4) plaque-forming units (PFU) per ft(3) was detected in six tests. Aerosolization of phage inside the cabinet yielded an average of 9 x 10 PFU per ft(3) outside; an average of 4.1 x 10(6) PFU per ft(3) were detected with the fans not in operation, a reduction of more than four logs. In-use studies on effectiveness showed that the cabinet significantly reduced the incidence of mice originally titer-free to Reo-3 virus. Hemagglutination inhibition antibodies to Reo-3 were detected in 9/22 (42%) mice housed in a conventionally ventilated animal laboratory while no seroconversion was detected in any of 22 mice housed in the mass air flow cabinet in the same laboratory.

Aerosols↗
PubMed1997

Distribution and stability of antisense phosphorothioate oligonucleotides in rodent brain following direct intraparenchymal controlled-rate infusion.

High-flow microinfusion is a novel technique for delivery of compounds directly into the brain parenchyma, bypassing the blood-brain barrier. The feasibility of this technique has been demonstrated with low-molecular-weight compounds, macromolecular dyes, and proteins. Delivery of antisense oligonucleotides into the brain parenchyma represents an additional potential application of this technique not previously described. In this report, the authors examined the distribution and disposition of phosphorothioate oligodeoxynucleotide (PS-ODN) infused for this reason. An 18-mer (35)S-PS-ODN (molecular weight approximately 6000) was infused over 1 hour into the caudate putamen of Fischer 344 rats. At 1, 6, 12, 24, and 48 hours after beginning the infusion, the brains were extracted and analyzed using quantitative autoradiographic techniques. Cerebrospinal fluid (CSF) was also aspirated from the cisterna magna and analyzed for radioactivity and stability of the (35)S-PS-ODN. At 1 hour, the infused ODN was uniformly distributed in brain tissue, with a maximum average concentration of 4806.5 +/- 210.5 nCi/g. This represents a tissue concentration of 19.2 +/- 0.84 microM. Extensive spread into surrounding parenchyma was observed over the ensuing 47 hours. The (35)S-PS-ODN radioactivity peaked in the CSF at the end of the 1-hour infusion, containing 10% (50 +/- 20 nCi) of the infused radioactivity. Activity then decayed exponentially over 11 hours, stabilizing at a lower CSF content of 0.2% (1 +/- 0.1 nCi). The volume of distribution (V(d)) was 105 +/- 7.9 mm3 at 1 hour, representing a ratio of V(d)/V(i) (volume of infusion) of 5.2. The V(d) increased to 443.4 +/- 62.3 mm(3) at the end of 48 hours, whereas the average minimum tissue concentration decreased from 15.2 to 3.2 microM. Undegraded 18-mer was seen throughout the 48-hour period using 20% polyacrylamide/7M urea gel electrophoresis. The animals tolerated the infusion without evidence of toxicity, and minimal structural changes in tissue were observed on histological examination. Thus, PS-ODN can be safely delivered in high concentrations to wide areas of the rat brain by using high-flow microinfusion, and the concentrations remain stable even after 48 hours in situ.

Journal Article↗
PubMed1998

Distribution and stability of antisense phosphorothioate oligonucleotides in rodent brain following direct intraparenchymal controlled-rate infusion.

OBJECT: High-flow microinfusion is a novel technique for delivery of compounds directly into brain parenchyma, bypassing the blood-brain barrier. The feasibility of this technique has been demonstrated with low-molecular-weight compounds, macromolecular dyes, and proteins. Delivery of antisense oligonucleotides into brain parenchyma represents an additional potential application of this technique not previously described. In this report the authors sought to examine the distribution and disposition of phosphorothioate oligodeoxynucleotide (PS-ODN) for this reason. METHODS: An 18-mer 35S-PS-ODN (Mr approximately 6000) was infused over 1 hour into the caudate putamen of Fischer 344 rats. At 1, 6, 12, 24, and 48 hours after beginning the infusion, the brains were extracted and analyzed using quantitative autoradiographic techniques. Cerebrospinal fluid (CSF) was also aspirated from the cisterna magna and was analyzed to determine the radioactivity and stability of the 35S-PS-ODN. At 1 hour, the infused ODN was uniformly distributed in brain tissue, with a maximum average concentration of 4806.5 +/- 210.5 nCi/g. This represents a tissue concentration of 19.2 +/- 0.84 microM. Extensive spread into surrounding parenchyma was observed over the ensuing 47 hours. The 35S-PS-ODN radioactivity peaked in the CSF at the end of the 1-hour infusion, containing 1% (50 +/- 20 nCi) of the infused radioactivity. Activity then decayed exponentially over 11 hours, but stabilized at a lower CSF content of 0.2% (1 +/- 0.1 nCi) thereafter. The volume of distribution was 105 +/- 7.9 mm3 at 1 hour, representing a volume of distribution/volume of infusion ratio of 5.2. The volume of distribution increased to 443 +/- 62.3 mm3 at the end of 48 hours, whereas the average minimum tissue concentration decreased from 15.2 microM to 3.2 microM. Undegraded 18-mer was observed throughout the 48-hour period by means of 20% polyacrylamide/7 M urea gel electrophoresis. The animals tolerated the infusion without evidence of toxicity and minimal structural changes in tissue were observed on histological investigation. CONCLUSIONS: The authors found that PS-ODNs can be safely delivered in high concentrations to wide areas of rat brain by using high-flow microinfusion and are stable even after 48 hours in situ.

Animals↗
PubMed1990

Use of ELISA to reveal rodent infections in plague surveillance and control programmes.

To assess its potential applications in plague surveillance and control programmes, an enzyme-linked immunosorbent assay (ELISA) that captures the specific Yersinia pestis F1 antigen was used to determine the amounts of this antigen present in samples of blood and spleens from laboratory rats with acute plague, in the buboes of rats with chronic plague, and in tissues from the carcasses of rats that had died from plague. In rats with acute plague, bacteria and F1 antigen were detected in samples of blood 2-4 days after the rats had been subcutaneously inoculated with virulent Y. pestis. Although F1 antigen was not detected in blood samples at the onset of bacteraemia, average antigen levels of 10,240 ng/ml for blood clots and 4829 ng/ml for sera were detected during severe bacteraemia. Immediately after the rats died from acute plague, antigen levels in their spleens of up to 410 micrograms/g of tissue were detected. For rats with chronic plague, ELISA antigen levels of 1600 ng/g to 51 micrograms/g were detected in buboes that contained viable plague bacilli. In samples of spleen, liver, kidney and heart from rat carcasses, F1 antigen was detected up to 20 days after death. In contrast, it was possible to isolate Y. pestis bacilli from these samples only up to 6 days after death.

Animals↗
PubMed1995

Humoral response to a carboxyl-terminal region of the merozoite surface protein-1 plays a predominant role in controlling blood-stage infection in rodent malaria.

The developmental stages of malaria parasites that infect E are responsible for the morbidity and mortality associated with this disease. One of the leading candidates for a blood-stage vaccine against malaria is a surface protein of merozoites, the infectious stages for E, designated merozoite surface protein-1 (MSP-1). The rodent malarial parasite Plasmodium yoelii yoelii (Py) has provided a model system for the study of this Ag, and previous studies from our laboratory had demonstrated that the carboxyl-terminal, cysteine-rich region of MSP-1, when expressed in a native configuration, could immunize mice against a normally lethal challenge infection with Py. We have now prepared a new fusion construct with the glutathione-S-transferase gene of Schistosoma japonicum joined to the carboxyl-terminal 11 kDa of Py MSP-1. This includes only the two epidermal growth factor-like domains of the MSP-1 protein. When expressed in recombinant Escherichia coli, the fusion protein induces a strong protective response in BALB/c mice as judged by the resistance of immunized animals to a virulent challenge infection. Moreover, we demonstrate that this resistance can be transferred passively by immune serum or by purified Ig, establishing a significant role for humoral immunity in protection. No role for CD4+ or CD8+ T cells could be identified in the first 12 days after challenge infection in immune mice selectively depleted of these cells; however, after this time, parasitemias gradually increased in mice depleted of CD4+ T cells, suggesting an active host response is necessary to completely eliminate the infection.

Animals↗
PubMed1995

[The efficacy of Salmocumarín rodenticide in livestock-raising and urban sites].

The activity in burrows at four different sites was calculated, and it went from 80 to 98% during pretreatment. For the first time in our country, average values of days/deaths of synanthropic rodents in natural conditions were obtained, and the reached values were between 16.50 and 19.06 after applying the biorodenticide. In the statistical analysis, a significant difference was found in the set of objectives related with days/deaths averages (H = 8.60*; p < 0.05). Moreover, no significant differences were found in percentages of residual activity in burrows (G = 8,27; p < 0.05). Results obtained show that Salmocumarín biorodenticide is much more effective in places where great populations of this species of cosmopolitan rodents exist.

Animal Husbandry↗