scholarly journals Research Advances of Leptotrombidium scutellare in China

2021 ◽  
Vol 59 (1) ◽  
pp. 1-8
Author(s):  
Rong Xiang ◽  
Xian-Guo Guo
Keyword(s):  
Scrub Typhus ◽  
Natural Infection ◽  
Species Group ◽  
Mountainous Areas ◽  
Epidemiological Evidence ◽  
Experimental Transmission ◽  
Factors Affecting ◽  
Geographical Regions ◽  
Isozyme Spectrum ◽  
Low Precipitation

Leptotrombidium scutellare is one of the 6 main vectors of scrub typhus in China. It has been found in more than 15 provinces of China. Especially in Yunnan, it was found to be mainly distributed in some mountainous areas with high altitude, low temperature and low precipitation. Rodents and some other small mammals were the most common hosts of L. scutellare. To date, more than 40 host species of L. scutellare have been recorded with very low host specificity, and the main hosts varied in different geographical regions. L. scutellare had a strong resistance against the cold environment, and the temperature and humidity were 2 important factors affecting its growth and development. Among different individuals of their rodent hosts, L. scutellare mites often showed an aggregated distribution pattern, which reflected the interspecific cooperation of the mites. The chromosome karyotype of L. scutellare was 2n=16 and all the 8 pairs of chromosomes were short rod-shaped with metacentric or sub-metacentric types. The isozyme spectrum supported that L. scutellare, L. deliense and L. rubellum were in the same species group. Based on the natural infection, experimental transmission and epidemiological evidence, L. scutellare has been eventually confirmed as the second major vector of scrub typhus in China, which is second only to L. deliense.

Transplantation of Adult Dirofilaria roemeri to Grey Kangaroos and Laboratory Rats

1972 ◽  
Vol 46 (1) ◽  
pp. 81-89 ◽  
Author(s):  
David M. Spratt
Keyword(s):  
Aedes Aegypti ◽  
Peritoneal Lavage ◽  
Natural Infection ◽  
Experimental Transmission ◽  
Laboratory Rats ◽  
Saphenous Veins ◽  
Large Numbers ◽  
Grey Kangaroo ◽  
Transmission Studies ◽  
Excellent Source

Adult Dirofilaria roemeri were transplanted subcutaneously into two grey kangaroos and intraperitoneally into seven laboratory rats in an investigation of amicrofilaraemia, and for experimental transmission studies. Low level blood microfilaraemias of only short duration were produced in all but one rat, supporting the hypothesis that the grey kangaroo is an abnormal host of this parasite. Cortisone was instrumental in the success of D. roemeri in rats. Peritoneal lavage of rats harbouring transplanted D. roemeri proved an excellent source of microfilariae. Injection of large numbers of microfilariae into the saphenous veins of rats harbouring transplanted worms failed to alter the number of circulating microfilariae. D. roemeri failed to develop in Aedes aegypti, fed on rats harbouring transplanted worms and exhibiting blood microfilaraemia. One kangaroo, to which worms had been transplanted, was exposed to the bites of Dasybasis hebes (Diptera, Tabanidae) in the study area and acquired a natural infection of D. roemeri.

scholarly journals Compressor type engine brake

2021 ◽  
Vol 1 (3) ◽  
pp. 27-30
Author(s):  
V.V. Verbitskiy ◽  
◽  
V.M. Pogosyan ◽  
Keyword(s):  
Road Transport ◽  
Intake Manifold ◽  
Mountainous Areas ◽  
Accident Rate ◽  
Factors Affecting ◽  
Braking Performance ◽  
Compression Stroke ◽  
Passenger Transportation ◽  
Braking Torque

The accident rate in road transport remains unacceptably high, and in order to reduce it, it is nec-essary to take into account all the factors affecting this process. In this regard, the process of long-term braking deserves special attention, which negative processes require the creation of additional braking systems (retarder brakes) for vehicles operating in mountainous areas, primarily in the field of passenger transportation. Transmission retarder brakes that provide sufficient braking performance have a number of dis-advantages that inhibit their use. Existing engine retarder brakes provide insufficient deceleration, and studies were carried out at the Kuban State Agrarian University (KubSAU) to improve their efficiency. After a theoretical analysis, the compressor brake mode was experimentally investigated. The in-creased pressure was created in the intake manifold and at the end of the compression stroke, air from the cylinder was released through a special valve back into the system, due to which the brak-ing effect was created. The carried out experiments confirmed the possibility of a significant increase in the engine braking torque in the compressor brake mode, when both valves are closed - the exhaust after the exhaust manifold and the intake in front of the carburetor, and compressed air is supplied to the in-take manifold at different pressures. Then the braking torque increases in comparison with engine braking by more than 3 times.

scholarly journals Weed infestation and factors affecting weed incidence in spring cereals in Finland - a multivariate approach

1993 ◽  
Vol 2 (6) ◽  
pp. 525-536 ◽  
Author(s):  
Jukka Salonen
Keyword(s):  
Environmental Factors ◽  
Correspondence Analysis ◽  
Dry Weight ◽  
Organic Soils ◽  
Weed Species ◽  
Data Set ◽  
Factors Affecting ◽  
Geographical Regions ◽  
Weed Flora ◽  
Weed Infestation

Weed vegetation of spring cereal fields in southern and central Finland was analyzed by ordination methods to provide a community level description of weed populations. Attention was paid particularly to the relative importance of environmental factors affecting weed incidence such as crop management, soil properties and weather conditions. A data set of 33 weed taxa from 252 fields was subjected to both indirect and direct gradient analysis. Indirect ordination was obtained with correspondence analysis (CA), and direct gradient analyses were performed with redundancy analysis (RDA) and with canonical correspondence analysis (CCA) relating environmental factors to the occurrence of weeds. Among several management factors, continuous herbicide use explained best the variation in the species composition of weed flora. Weed vegetation was also associated with soil type, moisture conditions and soil pHH2O. Ordination diagrams visualized the species-environment interactions and detected characteristic weed species for different geographical regions. In addition to ordination analyses of weed flora, the level and structure of weed infestation are described. The density of weeds averaged 170 plants m2 (median=124) and the air-dry weight of weeds 320 kg ha-1 (median=183). The average weed density was the same in different soil types, but the weed biomass was lower in clay soils than in coarse mineral and organic soils

scholarly journals The new taxonomic marker of nodulation bacteria of Rhizobium genus and its evolution

2012 ◽  
Vol 10 (2) ◽  
pp. 50-63 ◽  
Author(s):  
Vasily S Zotov ◽  
Natalia V Punina ◽  
Sofia A Khapchaeva ◽  
Svetlana V Didovich ◽  
Tatyana N Melnichuk ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Species Group ◽  
Marker System ◽  
Rhizobium Strains ◽  
Geographical Regions ◽  
Taxonomic Marker

The new taxonomic marker (hin-region) has been proposed, which gives possibility for Rhizobium bacteria study on “species — group of strains” level. Using this marker the groups of Rhizobium strains were determined, which could not be distinguished with other methods, and these results correlated with evolutionary similarity of the bacteria. The developed approach for creating marker systems allows to carry out effective inventory of inter- and intraspecies genetic diversity of nodulating bacteria and to evaluate perspectives of their use in agriculture. The proposed marker system was used for description of Rhizobium bacteria samples isolated from various ecological-geographical regions of Ukraine.

scholarly journals Development of the structure, survey and design of the equatorial overpass of the General Planetary Vehicle

2021 ◽  
Vol 22 (2) ◽  
pp. 205-216
Author(s):  
Anatoli E. Unitsky ◽  
Dmitriy I. Bochkaryov ◽  
Sergey V. Artyushevsky
Keyword(s):  
Rail Transport ◽  
High Tech ◽  
Structural Elements ◽  
Mountainous Areas ◽  
Factors Affecting ◽  
Supporting Structure ◽  
Functional Areas ◽  
Significant Factors

The runway for the General Planetary Vehicle is a unique in scale and complexity infrastructural construction - an overpass with a length of 40 000 km, covering the planet along the equator and combined with a string-rail transport of the second level. This high-tech structure is a supporting structure for the General Planetary Vehicle and a communication artery that ensures the movement of passengers and goods, as well as the transfer of large amounts of energy and information. The article discusses the location of the overpass in the plan, indicates the most difficult sections and ways to overcome them. The options for the layout of the General Planetary Vehicle overpass are proposed, the main functional areas and structural elements are described. Significant factors affecting the implementation of the project, the problems inevitable in the development of the main elements, as well as solutions to optimize this transport and infrastructure complex have been identified. Solutions were proposed to optimize the overpass routing to overcome mountainous areas of the earths surface, considering the required takeoff and landing characteristics of the General Planetary Vehicle.

scholarly journals SARS-CoV-2 reinfection in a cohort of 43,000 antibody-positive individuals followed for up to 35 weeks

2021 ◽  
Author(s):  
Laith J. Abu-Raddad ◽  
Hiam Chemaitelly ◽  
Peter Coyle ◽  
Joel A. Malek ◽  
Ayeda A. Ahmed ◽  
...  
Keyword(s):  
Incidence Rate ◽  
Genome Sequencing ◽  
Viral Genome ◽  
Natural Infection ◽  
Antibody Test ◽  
Contact Tracing ◽  
Epidemiological Evidence ◽  
Routine Testing ◽  
Positive Antibody

ABSTRACTBackgroundReinfection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been documented, raising public health concerns. Risk and incidence rate of SARS-CoV-2 reinfection were assessed in a large cohort of antibody-positive persons in Qatar.MethodsAll SARS-CoV-2 antibody-positive persons with a PCR-positive swab ≥14 days after the first-positive antibody test were individually investigated for evidence of reinfection. Viral genome sequencing was conducted for paired viral specimens to confirm reinfection. Incidence of reinfection was compared to incidence of infection in the complement cohort of those antibody-negative.ResultsAmong 43,044 anti-SARS-CoV-2 positive persons who were followed for a median of 16.3 weeks (range: 0-34.6), 314 individuals (0.7%) had at least one PCR positive swab ≥14 days after the first-positive antibody test. Of these individuals, 129 (41.1%) had supporting epidemiological evidence for reinfection. Reinfection was next investigated using viral genome sequencing. Applying the viral-genome-sequencing confirmation rate, the risk of reinfection was estimated at 0.10% (95% CI: 0.08-0.11%). The incidence rate of reinfection was estimated at 0.66 per 10,000 person-weeks (95% CI: 0.56-0.78). Incidence rate of reinfection versus month of follow-up did not show any evidence of waning of immunity for over seven months of follow-up. Meanwhile, in the complement cohort of 149,923 antibody-negative persons followed for a median of 17.0 weeks (range: 0-45.6), risk of infection was estimated at 2.15% (95% CI: 2.08-2.22%) and incidence rate of infection was estimated at 13.69 per 10,000 person-weeks (95% CI: 13.22-14.14). Efficacy of natural infection against reinfection was estimated at 95.2% (95% CI: 94.1-96.0%). Reinfections were less severe than primary infections. Only one reinfection was severe, two were moderate, and none were critical or fatal. Most reinfections (66.7%) were diagnosed incidentally through random or routine testing, or through contact tracing.ConclusionsReinfection is rare. Natural infection appears to elicit strong protection against reinfection with an efficacy ∼95% for at least seven months.

scholarly journals Antibodies in the Sera of Host Species with Pythiosis Recognize a Variety of Unique Immunogens in Geographically Divergent Pythium insidiosum Strains

2008 ◽  
Vol 16 (3) ◽  
pp. 330-336 ◽  
Author(s):  
Ariya Chindamporn ◽  
Raquel Vilela ◽  
Kathleen A. Hoag ◽  
Leonel Mendoza
Keyword(s):  
Host Species ◽  
Natural Infection ◽  
Protein Profile ◽  
Serum Samples ◽  
Pythium Insidiosum ◽  
Geographical Regions ◽  
Human Sera ◽  
Immunogenic Proteins

ABSTRACT Studies by Western blot analyses have shown that antibodies in the sera of host species infected by Pythium insidiosum recognized several prominent proteins expressed by this fungus-like pathogen. Although these studies have utilized sera from infected patients and relevant local strains of P. insidiosum, the results are difficult to compare because of the lack of method standardization. In an effort to resolve this issue, we have utilized standardized methodologies to evaluate six P. insidiosum strains from Asia and the Americas and 15 serum samples from cattle, cats, dogs, horses, and humans with pythiosis from the same geographical regions. Our data show that the antibodies present in these sera recognize a wide variety of unique P. insidiosum immunogenic proteins. Although some of the prominent proteins in this study have been previously reported, several others have yet to be described. For instance, a ∼28-kDa-molecular-mass antigen was detected by the antibodies in all serum samples evaluated. However, this antigen was strongly expressed by only one of the strains evaluated. A diffuse ∼51-kDa protein was not detected by the antibodies in the human sera; but it was recognized by the antibodies in the sera of cattle, cats, dogs, and horses. This antigen was expressed by only two of the strains investigated. Several other similar examples were also observed. The variation of the P. insidiosum protein profile identified by the antibodies in the sera evaluated indicates that some geographically diverged P. insidosum strains expressed some unique immunogens in vitro and that during natural infection (in vivo) P. insidiosum might express a broader number of antigens variably detected by individuals within the same species but especially across species.

scholarly journals Effect of Polymorphisms at Codon 146 of the Goat PRNP Gene on Susceptibility to Challenge with Classical Scrapie by Different Routes

2017 ◽  
Vol 91 (22) ◽  
Author(s):  
Penelope Papasavva-Stylianou ◽  
Marion Mathieson Simmons ◽  
Angel Ortiz-Pelaez ◽  
Otto Windl ◽  
John Spiropoulos ◽  
...  
Keyword(s):  
Prnp Gene ◽  
Transmission Model ◽  
Confirmatory Test ◽  
Enzyme Linked Immunosorbent Assay ◽  
Chi Square ◽  
Peripheral Tissues ◽  
Prolonged Incubation ◽  
Experimental Transmission ◽  
Geographical Regions ◽  
Incubation Periods

ABSTRACT This report presents the results of experimental challenges of goats with scrapie by both the intracerebral (i.c.) and oral routes, exploring the effects of polymorphisms at codon 146 of the goat PRNP gene on resistance to disease. The results of these studies illustrate that while goats of all genotypes can be infected by i.c. challenge, the survival distribution of the animals homozygous for asparagine at codon 146 was significantly shorter than those of animals of all other genotypes (chi-square value, 10.8; P = 0.001). In contrast, only those animals homozygous for asparagine at codon 146 (NN animals) succumbed to oral challenge. The results also indicate that any cases of infection in non-NN animals can be detected by the current confirmatory test (immunohistochemistry), although successful detection with the rapid enzyme-linked immunosorbent assay (ELISA) was more variable and dependent on the polymorphism. Together with data from previous studies of goats exposed to infection in the field, these data support the previously reported observations that polymorphisms at this codon have a profound effect on susceptibility to disease. It is concluded that only animals homozygous for asparagine at codon 146 succumb to scrapie under natural conditions. IMPORTANCE In goats, like in sheep, there are PRNP polymorphisms that are associated with susceptibility or resistance to scrapie. However, in contrast to the polymorphisms in sheep, they are more numerous in goats and may be restricted to certain breeds or geographical regions. Therefore, eradication programs must be specifically designed depending on the identification of suitable polymorphisms. An initial analysis of surveillance data suggested that such a polymorphism in Cypriot goats may lie in codon 146. In this study, we demonstrate experimentally that NN animals are highly susceptible after i.c. inoculation. The presence of a D or S residue prolonged incubation periods significantly, and prions were detected in peripheral tissues only in NN animals. In oral challenges, prions were detected only in NN animals, and the presence of a D or S residue at this position conferred resistance to the disease. This study provides an experimental transmission model for assessing the genetic susceptibility of goats to scrapie.

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