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At least 1,207 records · Page 67Linked to original sources
PubMed2005

Prevalence and spatial distribution of intraerythrocytic parasite(s) in Puget Sound rockfish (Sebastes emphaeus) from the San Juan Archipelago, Washington (USA).

Two morphologically distinct forms of an intraerythrocytic parasite(s) were detected by microscopic observation of Giemsa-stained blood films in 45.7% of 119 rockfish (Sebastes emphaeus) from the San Juan Archipelago (Washington State, U.S.A.). Infection prevalence for both forms was 53% in males, 44% in females, and 33% in fish of undetermined gender. A binucleate "ring-stage" was present at all 4 geographic sites, with a mean prevalence of 45.7%, while mean prevalence of a larger gamont-like form from the same sites was 5.1%. The relationship of the 2 forms to each other could not be determined. Neither schizogony nor binary fission was evident in any of the infected erythrocytes and the parasites contained no obvious pigment. The possibility of the 2 morphologic forms being 2 distinct species is supported by the observation that no difference in parasitemia was seen in the binucleate form among sites (1.6-1.9%), while parasitemia of the gamont-like form varied significantly among sites, ranging from a high of 4% to a low of 0.1%. Taxonomic status of either form could not be determined at this time based on limited existing morphologic data.

Animals↗
PubMed2006

Spatial distributions of two species of monogeneans on the gills of Siganus fuscescens (Houttuyn) and their seasonal dynamics in caged versus wild-caught hosts.

Two monogeneans species, Polylabris mamaevi Ogawa & Egusa, 1980 and Tetrancistrum nebulosi Young, 1967, are sympatric on the gills of Siganus fuscescens (Houttugn, 1782) in the South China Sea. An investigation into their distribution on the host's gills based on monthly samples from both wild and caged populations revealed that these 2 species co-occurred on the same gill arches, but they were segregated. P. mamaevi attached to the distal half of the gill filaments, whereas T. nebulosi attached to the proximal half. This difference may partly be attributed to microhabitat specialization. Microhabitat distributions were intensity dependent for both species. As intensity increased, monogeneans were increasingly found on the second, third, and even fourth gill arches, and niche breadths increased. The changes in distribution and niche breadths at the host gill arch level in relation to differences in host size and sampling period were considered to represent a functional response to increased intensity. Differences in host resources, in either net-caged or wild populations, did not significantly influence the parasite distributions at the host gill arch level. Simultaneous infections of these 2 species were common, but there was no evidence of negative interspecific interactions.

Analysis of Variance↗
PubMed2005

Spatial distribution of radiation-induced double-strand breaks in plasmid DNA as resolved by atomic force microscopy.

Atomic force microscopy (AFM) has been used to directly visualize, size and compare the DNA fragments resulting from exposure to low- and high-LET radiation. Double-stranded pUC-19 plasmid ("naked") DNA samples were irradiated by electron-beam or reactor neutron fluxes with doses ranging from 0.9 to 10 kGy. AFM scanning in the tapping mode was used to image and measure the DNA fragment lengths (ranging from a few bp up to 2864 bp long). Double-strand break (DSB) distributions resulting from high-LET neutron and lower-LET electron irradiation revealed a distinct difference between the effects of these two types of radiation: Low-LET radiation-induced DSBs are distributed more uniformly along the DNA, whereas a much larger proportion of neutron-induced DSBs are distributed locally and densely. Furthermore, comparisons with predictions of a random DSB model of radiation damage show that neutron-induced DSBs deviate more from the model than do electron-induced DSBs. In summary, our high-resolution AFM measurements of radiation-induced DNA fragment-length distributions reveal an increased number of very short fragments and hence clustering of DSBs induced by the high-LET neutron radiation compared with low-LET electron radiation and a random DSB model prediction.

DNA↗
PubMed2005

Is spatial distribution of the HIV-1-resistant CCR5Delta32 allele formed by ecological factors?

It has been proposed that the Delta32 mutation in the chemokine receptor gene, inducing resistance to HIV-1 and, probably, to other virus infections, has undergone selection in historical times. The frequency of this mutant allele has changed rapidly both in time (during the last two millennia) and in space (across Eurasia). We compiled a global database on Delta32 allele frequencies in 300 populations. Nearly 10 percent of them are our data on 35 East European populations analyzed here for the first time. A detailed map of Delta32 frequency distribution was constructed and statistically analysed. We found a linearly decreasing trend with a maximum in areas surrounding the Baltic and White seas. Significant correlations with ground surface temperature were revealed. However, compared with our previous results, these correlations diminished, indicating that the influence of climate on Delta32 distribution was, if anything at all, indirect. The proposed scenario includes: i) arise and initial spread of the mutation among Uralic-speaking populations; ii) a frequency increase in northeastern Europe as a result of selection and/or genetic drift; iii) secondary spread (with selection continued) due to gene flow and the migrations of northern Europeans across the globe.

Asia↗
PubMed1989

The spatial distribution of parenterally administered monoclonal antibodies against CEA in a human colorectal tumour xenograft.

A recently developed experimental model consisting of athymic rats carrying human colonic tumours from the cell line LS 174 T in both hind legs was used. 125I-labelled anti-carcinoembryonic (anti-CEA) monoclonal antibodies were injected either intra-arterially after a bolus injection of mannitol, or intra-peritoneally with or without mannitol. On the fourth day the rats were killed and pieces from the tumours and various organs were measured in a well scintillation counter. Tumour pieces were then submitted to autoradiography and immunohistochemistry for examination of the antibody distribution at the cellular level. In all examined tumours injected with anti-CEA antibodies, most of the antibodies were located in the periphery close to fibrovascular septa. It appears, in addition to the specificity of the antibody for the CEA, that the tumour vascular permeability and anatomy are of utmost importance for tumour targeting in this experimental model with the particular antibody used.

Adenocarcinoma↗
PubMed1993

Structure functional expression and spatial distribution of a cloned cDNA encoding a rat 5-HT1D-like receptor.

Using polymerase chain reaction (PCR) a complementary DNA (cDNA) encoding a 5-hydroxytryptamine (5-HT) receptor was isolated from rat forebrain. The amplified cDNA specifies an open reading frame of 374 amino acids comprising seven putative transmembrane regions. Expression of the cloned cDNA in human embryonic kidney cells (HEK 293) was used to establish the pharmacological profile of the encoded receptor polypeptide. Membranes containing the cloned receptor showed high affinity binding of [3H]-5-HT. Competition binding experiments with a variety of serotonin receptor ligands displayed a rank order of affinities corresponding to a 5-HT1D subtype: 5-CT > 5-HT = metergoline > CGS 12066 > methysergide > sumatriptan > mianserin = (-)alpha-Me-5-HT = yohimbine > 8-OH-DPAT > or = rauwolscine > spiperone > DOI > propranolol > or = 2-Me-5-HT > or = ICS 205930. Ketanserin and ritanserin displaced [3H]-5-HT-binding in a biphasic manner. In situ hybridization revealed highest expression of the corresponding mRNA in the pyramidal layer of the olfactory tubercle and the nucleus caudatus and accumbens.

Amino Acid Sequence↗
PubMed1977

Wave-form characteristics and spatial distribution of evoked spinal electrogram in man.

The evoked spinal electrogram (SEG) in man was recorded from the epidural space, applying the technique of continuous epidural block, and compared with cord dorsum potential (CDP) in wakeful rabbits. Wave-form characteristics of the evoked SEG'S activated by the segmental nerves were almost the same in both cervical and lumbar regions. Somatosensory evoked response from the scalp was clearly demonstrated by stimulation of both the tibial nerve and fifth toe skin, whereas the evoked SEG was produced only by stimulation of the former. This finding might indicate that large nerve fibers are more responsible for producing the evoked SEG. Central latencies to the peaks of the second components of the P2 wave were 29 to 33 and 42 to 48 msec, in cervical and lumbar enlargements, respectively. This probably indicates the presence of a long feedback loop producing the second components. The amplitude of the N1 wave showed a steeper decline along the spinal cord than that of the P2 deflection, indicating between origins of these two components. Polarity of both the N1 and P2 waves became reversed when the recording electrode was situated in the anterior epidural space. The wave-form characteristics of the evoked SEG in man were very similar to those of the CDP in wakeful rabbits.

Adult↗
PubMed2001

Spatial distribution and hatching of overwintered eggs of a fish ectoparasite, Argulus coregoni (Crustacea: Branchiura).

The habitat distribution of overwintered eggs, which were found to be the only source of spring recruitment of Argulus coregoni Thorell, was studied at a commercial fish farm in Central Finland. The frequency of occurrence of egg clutches in the deep parts of the canals and ponds was 50 to 80% and the percentage cover of the surface of stones with egg clutches was 1.7 to 6.4%, while in the shallow parts these values were 8 to 27% and 0.1 to 0.3%, respectively. A greater proportion of empty egg-shells was observed in shallow water in the mid-May, suggesting an earlier hatching there stimulated by the increased temperature and higher illumination. Under laboratory conditions, only elevated UV illumination, but not diurnally fluctuating temperature, significantly accelerated hatching. Normally overwintered eggs produced a pronounced peak of hatched larvae at the end of May and hatching continued at a much slower rate throughout the summer. Eggs that overwintered twice, first normally and then for a second time buried under sediments, were exposed to the same laboratory conditions simultaneously with normally overwintered eggs, but their hatching was delayed until August. The hatching rate was low, but markedly increased in December.

Animals↗
PubMed1998

Impact of spatial distribution of permethrin-impregnated bed nets on child mortality in rural northern Ghana.

Effects of the distribution in space of permethrin (insecticide)-impregnated bed nets (IIBNS) on child mortality were studied in a randomized controlled trial of IIBNs in a an area highly endemic for Plasmodium falciparum malaria in rural northern Ghana. Eight hundred sixty-two deaths occurred among children 6-59 months of age during 16,841 child-years-at-risk. Mortality increased with the distance from health facilities but not with proximity to identifiable anopheline breeding sites (reservoirs). The efficacy of IIBNs was independent of these distances. Mortality in users of IIBNs was independent of the proximity of nonusers, and mortality rates of nonusers and users living close to each other were similar. Poisson regression estimated a 6.7% increase in mortality among nonusers with each 100-m shift away from the nearest compound with IIBNS, indicating that the insecticide protects nearby nonusers. High coverage of IIBNs achieves maximum impact, but users of IIBNs offer some protection to less fortunate neighbors if coverage is incomplete.

Animals↗
PubMed2000

Density and spatial distribution of Ixodes pacificus (Acari: Ixodidae) in two recreational areas in north coastal California.

The density and distribution of Ixodes pacificus was assessed at 2 parks in north coastal California. The density of I. pacificus adults and nymphs varied significantly between years, trails, and sides of trails. Adult ticks occurred on vegetation along sun-exposed trails in January through March, their density (0-1.93 per 20 m) correlated with brush density, trail width, and presence of an uphill slope. Nymphs (0.06-5.10 per 20 m) occurred in leaf litter along shaded trails in May-July. Adult I. pacificus were rare at picnic sites (0.00-0.24 per 20 m), but nymphal densities (0.93-2.37 per 20 m) were comparable with those along some shaded trails. The prevalence of Borrelia burgdorferi in ticks (2.8% overall) did not differ significantly between locations, years, or stages. We conclude that the risk of acquiring Lyme disease in these sites is low, but varies among trails, seasons, and years.

Animals↗
PubMed2005

Spatial distribution of Salmonella, Escherichia coli O157:H7, and other bacterial populations in commercial and laboratory-scale sprouting mung bean beds.

The reliability of testing spent irrigation water to assess the microbiological status of sprouting mung bean beds has been investigated. In commercial trials, the distribution of opportunistic contaminants within 32 bean sprout beds (25 kg of mung beans per bin) was assessed 48 h after germination. The prevalence of generic Escherichia coli, thermotolerant coliforms, and Aeromonas in sprouts (n = 288) was 5, 11, and 39%, respectively, and 57, 70, and 79% in the corresponding spent irrigation water samples (n = 96). Contamination was heterogeneously distributed within the seedbed. In laboratory trials, beans inoculated with a five-strain cocktail of either Salmonella or E. coli O157:H7 (10(3) to 10(4) CFU/g) were introduced (1 g/500 g of noninoculated seeds) at defined locations (top, middle, or base), and the beans were then sprouted for 48 h. When seeds inoculated with pathogens were introduced at the base or top of the seedbed, the pathogens were typically restricted to these sites and resulted in 44% of the spent irrigation water samples returning false-negative results. Introducing inoculated beans into the middle or at the presoak stage enhanced the distribution of both pathogens within the subsequent sprout bed and resulted in comparable levels recovered in spent irrigation water. The study demonstrated that even though screening a single sample of spent irrigation water is more reliable than testing sprouts directly, it does not provide an accurate assessment of the microbiological status of sprouting mung bean beds. Such limitations may be addressed by ensuring that bean batches are mixed prior to use and by taking spent irrigation water samples from multiple sites at the latter stages of the sprouting process.

Agriculture↗
PubMed1999

QRST integral analysis of body surface electrocardiographic mapping for assessing exercise-induced changes in the spatial distribution of local repolarization properties in patients with coronary artery disease and in patients with previous anterior infarction.

We studied resting, postexercise, difference (postexercise - rest) QRST isointegral maps, and the correlation coefficient between resting and postexercise maps. Study I Fifteen controls and 48 patients without previous myocardial infarction were studied. In coronary syndrome X group (n = 14), no patients showed an abnormally negative area on the postexercise map. In coronary ST depression group (n = 26), 12 patients (46%) showed an abnormally negative area on the postexercise map, and the correlation coefficient was low. Although all control, syndrome X, and coronary ST depression patients showed the global-downward type of difference map, coronary ST elevation patients (n = 8) showed the right-downward and left-upward type, right-upward and left-downward type, or reversed saddle type. Coronary ST depression is related to a globally marked decrease in local repolarization forces. Coronary ST elevation is associated with multidirectional changes in local repolarization forces. Study II Fifty-one patients with previous anterior infarction (29 with residual ischemia and 22 without) were studied. The incidence of the global-positive type of maps was increased and that of the saddle-type map was decreased from rest to postexercise in both groups. The global-upward type or right-downward and left-upward type of difference map was observed in both groups, but the reversed saddle type, right-upward and left-downward type, or global-downward type was observed in the residual ischemia group (34%, 24%, and 14%, respectively). Residual ischemia causes multidirectional changes or a global decrease in local repolarization forces. In both studies, multidirectional changes in local repolarization forces may be related to the vulnerability to ventricular arrhythmias.

Adult↗