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Biomedical subjects

W E Collins

Publications and source records attributed to W E Collins.

At least 199 records · Page 11Linked to original sources
PubMed1985

Electron microscopy of Plasmodium vivax exoerythrocytic schizonts grown in vitro in a hepatoma cell line.

Human hepatoma cells (HepG2-A16) have been shown to be useful for the growth of the exoerythrocytic stages of P. vivax. In order to determine whether the parasites grown in these cells are morphologically similar to those grown in vivo, we performed electron microscopy on the exoerythrocytic (EE) schizonts of P. vivax developed from sporozoites. This study showed for the first time that P. vivax EE schizonts within these cells closely resemble other plasmodial EE schizonts both in vivo and in vitro.

Animals↗
PubMed1985

Identification of Plasmodium vivax sporozoites in mosquitoes using an enzyme-linked immunosorbent assay.

A sandwich enzyme-linked immunosorbent assay (ELISA) for identifying Plasmodium vivax sporozoites in mosquitoes is described. Monoclonal antibodies produced against Thailand P. vivax sporozoites were used in an ELISA to detect and identify homologous sporozoites of Southeast Asian, Mexican and North Korean origin in extracts of frozen or dried infected mosquitoes. The assay was sensitive enough to detect 1 infected mosquito in a pool of 20 insects or 125-250 sporozoites per 30 microliter of mosquito extract. The use of a nonionic detergent and a single freeze-thaw to disrupt the circumsporozoite antigen significantly increased the sensitivity of the method.

Animals↗
PubMed1985

In vitro culture of two populations (dividing and nondividing) of exoerythrocytic parasites of Plasmodium vivax.

Plasmodium vivax sporozoites invaded human hepatoma cells and differentiated into 2 types of exoerythrocytic (EE) parasites. One group was composed of actively dividing schizonts, which released merozoites after 9 days of culture. The second group was nondividing and persisted after the primary schizonts disappeared from the culture. EE schizonts progressively lost reactivity to monoclonal antibodies to the surface-protective protein antigen of P. vivax sporozoites, but the persisting parasites remained strongly reactive. In the 2 strains of P. vivax studied, the ratio of schizonts to persisting parasites was approximately equal.

Animals↗
PubMed1985

Evaluation of sporontocidal compounds using Plasmodium falciparum gametocytes produced in vitro.

A test system that uses infective gametocytes from in vitro cultures was developed for evaluating the sporontocidal activity of antimalarial compounds. In evaluating the system, pyrimethamine and cycloguanil (dihydrofolate reductase inhibitors) and primaquine (8-aminoquinoline) were tested against pyrimethamine-sensitive and pyrimethamine-resistant strains of Plasmodium falciparum. The drugs were administered to Anopheles either in a blood meal containing infective gametocytes or in a noninfective meal 2-4 days later. The mosquitoes were dissected 9-10 days after they received the infective blood meal, and the sporontocidal effect of the drugs was evaluated by the number of oocysts found in the gut. Both cycloguanil and pyrimethamine had marked sporontocidal activity. The susceptibility pattern of the strains to the sporontocidal effect of pyrimethamine and cycloguanil was similar to the susceptibility of their asexual blood stages in vitro to the schizontocidal effect of the compounds. The sporontocidal effect was observed only when the compounds were administered at the same time as the infective blood meal, but not when they were given 2-4 days later. No sporontocidal activity was observed with primaquine. This system permits more reliable quantitative observations than have been possible with previous methods.

Anopheles↗
PubMed1985

Studies on the North Korean strain of Plasmodium vivax in Aotus monkeys and different anophelines.

Twenty-two Aotus monkeys of different karyotypes were infected with the North Korean strain of Plasmodium vivax. Aotus lemurinus griseimembra animals from Colombia produced higher maximum parasitemias and more readily infected mosquitoes than did Aotus monkeys from Bolivia (K-VI) or Peru (K-V and K-X). Comparative feedings indicated that the most susceptible mosquito species was Anopheles stephensi, followed by An. gambiae, An. dirus, An. freeborni, An. quadrimaculatus, An. culicifacies, and An. maculatus.

Animals↗
PubMed1985

Infection of Aotus azarae boliviensis monkeys with different strains of Plasmodium vivax.

Sixty-seven splenectomized Aotus azarae boliviensis were infected with strains of Plasmodium vivax from Southeast Asia (2), New Guinea (2), North Korea (1), and Central America (3). Maximum parasitemias varied among the different strains, with the mean maximum parasitemia for the primary infection period being 16,200 per mm3. Animals previously infected with Plasmodium falciparum and Plasmodium malariae produced maximum parasitemias of 30,200 and 11,900 per mm3, respectively. Gametocytes infective to Anopheles freeborni mosquitoes were produced with 7 of the 8 strains examined.

Animals↗
PubMed1985

Infectivity of two strains of Plasmodium vivax to Anopheles albitarsis mosquitoes from Colombia.

Anopheles albitarsis obtained from Villavicencio, Colombia, were colonized in the laboratory using force-mating techniques. Laboratory reared mosquitoes were allowed to feed on Aotus monkeys infected with the Salvador II or the Rio Meta strains of Plasmodium vivax from El Salvador and Colombia, respectively. In comparison with other species, the An. albitarsis were less susceptible than Anopheles freeborni, Anopheles culicifacies and strains of Anopheles albimanus from El Salvador, Panama and Colombia and more susceptible than a strain of An. albimanus from Haiti.

Animals↗
PubMed1985

Effects of some motion sickness suppressants on static and dynamic tracking performance.

Two studies examined the influence of three established antimotion sickness drugs on tracking performance in static (stationary) and dynamic (angular acceleration) conditions and on visual fixation ability during motion. In Study I, 40 young men were randomly assigned in equal numbers to either a control (lactose placebo), dimenhydrinate (50 mg), promethazine hydrochloride (25 mg), or mixture (25 mg promethazine plus 10 mg d-amphetamine) group. Study II used 30 new subjects equally divided into control, dimenhydrinate (100 mg), and promethazine (50 mg) groups. Following practice, tests were conducted prior to, and 1, 2, and 4 h after drug ingestion. The depressant drugs had little effect on static tracking, but impaired dynamic tracking performance and reduced ability to maintain visual fixation on a localizer/glide slope instrument due to increased ocular nystagmus. The mixture of promethazine plus d-amphetamine produced none of these deleterious effects.

Aerospace Medicine↗
PubMed1985

An outbreak of Plasmodium inui malaria in a colony of diabetic rhesus monkeys.

Plasmodium inui malaria is an infrequently reported disease of Macaca mulatta. In this report a total of 21 of 48 monkeys in a closed colony of diabetic animals developed hematological evidence of P. inui infection with five showing overt clinical signs of the disease. Diagnosis was confirmed morphologically, serologically and by transmission studies. Since six of these animals were born in the colony, a means of transmission was sought and it was determined that multiple use of a syringe to administer intravenous anesthesia was the probable means of cross transmission.

Animals↗
PubMed1985

Studies on a newly isolated strain of Plasmodium brasilianum in Aotus and Saimiri monkeys and different anophelines.

A strain of Plasmodium brasilianum was isolated from an Aotus vociferans monkey from Peru. The parasite readily infected Aotus monkeys from Bolivia and Columbia and Saimiri sciureus monkeys from Peru and Bolivia. Highest level mosquito infections were obtained by feeding on the Saimiri monkeys. The most susceptible mosquito was Anopheles freeborni, followed by Anopheles dirus, Anopheles stephensi, Anopheles gambiae, Anopheles culicifacies, Anopheles maculatus and Anopheles albimanus. Anopheles quadrimaculatus were also susceptible to infection. Degenerating oocysts were observed in An. dirus mosquitoes infected with this parasite. Transmission via the bites of infected An. maculatus mosquitoes was obtained to 3 Bolivian Saimiri monkeys; prepatent periods were 27, 27, and 29 days.

Animals↗
PubMed1984

Type-I HTLV antibody in urban and rural Ghana, West Africa.

The prevalence of antibodies against the newly described human T-cell lymphoma virus, type I (HTLV-I) in two communities in Ghana, West Africa, is described. There was no difference by community (urban, 3.6% and rural, 4.0%). Prevalence increased with age, being 5.9% among persons greater than 10 years old, but did not differ by sex. There was no difference when data were analysed by housing status or crowding. Non-confirmed reactions in the assay system were frequent and correlated with both prevalence and titer of antibody against malaria. Possible explanations include vector-borne transmission like that of malaria, but the relationship is more probably due to a polyclonal stimulation of B cells, enhancing the potential for detecting reactivity in the assay. Because assay systems vary and because most laboratories do not routinely use a confirmation assay, results presented by different groups must be interpreted cautiously.

Adolescent↗
PubMed1984

Plasmodium fragile: inhibition of cultures by serum from rhesus monkeys immunized with homologous parasites.

Rhesus monkeys, Macaca mulatta, that had previously been immunized with the Nilgiri strain of Plasmodium fragile grown in culture, together with control monkeys with and without inoculation of Freund's adjuvant, were challenged with cultured parasites. After treatment with chloroquine, the monkeys were rechallenged. Serum specimens from three immunized monkeys caused a specific, dose-dependent inhibition of parasite growth in culture. Fifty percent inhibition of in vitro growth was obtained using 5% immune serum combined with 10% normal rhesus serum. The specific inhibitory component of immune serum was shown to be IgG antibody. Results of the study demonstrated that there is good correlation between the inhibitory activity of immune serum, parasite growth in vitro, the in vivo response to challenge, and the indirect fluorescent antibody titer.

Animals↗
PubMed1984

Integrating pictorial information across eye movements.

Six experiments are reported dealing with the types of information integrated across eye movements in picture perception. A line drawing of an object was presented in peripheral vision, and subjects made an eye movement to it. During the saccade, the initially presented picture was replaced by another picture that the subject was instructed to name as quickly as possible. The relation between the stimulus on the first fixation and the stimulus on the second fixation was varied. Across the six experiments, there was about 100-130 ms facilitation when the pictures were identical compared with a control condition in which only the target location was specified on the first fixation. This finding clearly implies that information about the first picture facilitated naming the second picture. Changing the size of the picture from one fixation to the next had little effect on naming time. This result is consistent with work on reading and low-level visual processes in indicating that pictorial information is not integrated in a point-by-point manner in an integrated visual buffer. Moreover, only about 50 ms of the facilitation for identical pictures could be attributed to the pictures having the same name. When the pictures represented the same concept (e.g., two different pictures of a horse), there was a 90-ms facilitation effect that could have been the result of either the visual or conceptual similarity of the pictures. However, when the pictures had different names, only visual similarity produced facilitation. Moreover, when the pictures had different names, there appeared to be inhibition from the competing names. The results of all six experiments are consistent with a model in which the activation of both the visual features and the name of the picture seen on the first fixation survive the saccade and combine with the information extracted on the second fixation to produce identification and naming of the second picture.

Discrimination Learning↗
PubMed1984

Monoclonal antibody identifies circumsporozoite protein of Plasmodium malariae and detects a common epitope on Plasmodium brasilianum sporozoites.

We produced a hybridoma secreting an immunoglobulin G1 monoclonal antibody against the circumsporozoite protein of the human malaria parasite Plasmodium malariae (Uganda 1/CDC). The monoclonal antibody produces a circumsporozoite precipitation reaction when incubated with viable sporozoites of P. malariae and reacts at high titers with heat-fixed sporozoites in an indirect immunofluorescent antibody test. Using the purified monoclonal antibody and Western blot analysis, we identified two polypeptides with apparent molecular weights of 60,000 (Pm 60) and 48,000 (Pm 48) in extracts of P. malariae sporozoites. Two-dimensional electrophoretic analysis of Pm 60 and the circumsporozoite protein Pm 48 indicated their isoelectric points to be acidic, with values of 5.3 and 4.7 to 5.0, respectively. A two-site immunoradiometric assay showed that the circumsporozoite protein recognized by the monoclonal antibody contains a repetitive epitope. P. malariae monoclonal antibody also reacted strongly with sporozoites of the simian parasite Plasmodium brasilianum, indicating a shared epitope on sporozoites of the two species. The P. malariae antibody did not bind sporozoite antigens of any other primate malarias, including Plasmodium falciparum, Plasmodium vivax, and Plasmodium ovale.

Animals↗
PubMed1984

The effect of oral contraceptives in malaria infections in rhesus monkey.

Rhesus monkeys, Macaca mulatta, were treated with the oral contraceptives Brevicon (norethisterone with ethinylestradiol) and Ovral (norgestrel with ethinylestradiol), and subsequently inoculated with the simian malaria parasites Plasmodium cynomologi bastianellii or P. coatneyi. Parasitological, serological, and serum biochemical studies indicated that although there were some significant differences, in general the patterns of response to infection in both treated and control animals were similar. During the primary infection, however, Brevicon resulted in increased levels of parasitaemia, whereas Ovral resulted in decreased parasitaemias, as compared with the untreated control animals. There were no differences in the responses following secondary parasite infection.

Animals↗
PubMed1984

Malaria in urban and rural areas of southern Ghana: a survey of parasitaemia, antibodies, and antimalarial practices.

A comparative cross-sectional survey was undertaken in two populations, urban and rural, in southern Ghana to assess the impact of urbanization on the prevalence of malaria parasitaemia and antibodies. At the same time, a survey of antimalarial practices was conducted on sample populations in the two communities. The results showed a low parasite rate (1.6%) and correspondingly low titres of malaria antibodies in a significant proportion of the urban community, particularly in children less than 10 years old. This was associated with widespread use in the urban community of antimalarial drugs, particularly chloroquine, as prophylaxis. The parasite rate in the rural community was 22%, and 97% of the sample population over 1 year of age had antibodies against Plasmodium falciparum. These results demonstrate that a substantial proportion of urban children are growing up with little exposure to malaria, even in a region considered endemic for malaria. The implications of these findings are discussed.

Adolescent↗