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Biomedical subjects

R Carter

Publications and source records attributed to R Carter.

At least 307 records · Page 17Linked to original sources
PubMed1984

Characterization of antigens on mosquito midgut stages of Plasmodium gallinaceum. II. Comparison of surface antigens of male and female gametes and zygotes.

Surface proteins of male and female gametes of Plasmodium gallinaceum were radioiodinated by the lactoperoxidase method, immunoprecipitated with stage specific antisera and separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Stage specificity of the surface antigens was further studied by competition between surface iodinated gametes and unlabeled extracts of gametes, zygotes, or asexual parasites during immunoprecipitation reactions. These studies have identified four proteins: 250 kDa (PgZ-1), 215 kDa (PgZ-3) and 56 and 54 kDa (PgZ-13a and b), which were present in indistinguishable antigenic form on both male and female gametes. Three immunogenic proteins, 48 kDa (PgZ-14) and 19 and 17 kDa (PgZ-17a and b), were present on female but not male gametes as were several weakly labeled, non-immunogenic proteins of less than 45 kDa. A 26 kDa protein (PgZ-16) was present on male but not female gametes. Two proteins of 205 and 83 kDa (PgZ-4 and PgZ-11) were labeled on female but not male gametes. Nevertheless preparations of male gametes appeared to contain epitopes cross-reacting with these two proteins since anti-male gamete serum precipitated PgZ-4 and 11. Immune competition studies indicated that each of the surface proteins labeled on sexual stages was antigenically distinct from material present in asexual parasites.

Animals↗
PubMed1984

Characterization of antigens on mosquito midgut stages of Plasmodium gallinaceum. III. Changes in zygote surface proteins during transformation to mature ookinete.

Proteins expressed on the surface of zygotes of Plasmodium gallinaceum during their development from fertilization to mature ookinetes have been examined by lactoperoxidase catalysed surface radioiodination and immunoprecipitation with stage-specific immune rabbit sera and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Surface-labelled proteins of apparent Mr equal to or greater than 55 000 on the female gametes and newly fertilized zygotes were shed during transformation and were recovered quantitatively and apparently intact from the culture supernatant. Zygote surface proteins of Mr 50 000, 19 000 and 17 000 remained bound to the surface throughout the transformation. Three proteins were expressed de novo on the surface of the mature ookinete of which Mr 26 000 and 28 000 represented major surface components and Mr 52 000 a relatively minor component.

Animals↗
PubMed1984

Biosynthesis of the target antigens of antibodies blocking transmission of Plasmodium falciparum.

We have studied the biosynthesis of three proteins of Mr 260 000, 59 000 and 53 000 previously identified on the surface of extracellular gametes of Plasmodium falciparum as the targets of monoclonal antibodies which block infectivity of P. falciparum to mosquitoes. In cultures of P. falciparum pulse labeled with [35S]methionine we have found that these proteins are synthesized by gametocytes from an early stage in their maturation but are not synthesized by asexual blood stage parasites. The target proteins synthesized by the gametocytes become expressed on the surface of the extracellular gametes but the gametes themselves no longer synthesize these proteins. The 59 000 and 53 000 Mr proteins do not result from processing from the 260 000 Mr protein. The 59 000 and 53 000 Mr protein, but not the 260 000 Mr proteins, were glycosylated by either glucosamine or mannose.

Animals↗
PubMed1984

Enrollment and demographic characteristics of physician's assistant students.

The authors in this paper describe enrollment trends and provide demographic information for a representative sample of physician's assistant (PA) students enrolled during 1978-1982 in 46 PA programs accredited by the American Medical Association. In February 1983, there were 2,871 such students enrolled in 54 primary care and three surgeon's assistant programs. The typical PA program, which is two years in length, provides six to nine months of preclinical course work and nine to 15 months of clinical experience. Most programs are based in either medical schools or four-year colleges and offer baccalaureate degrees. From the demographic information obtained by the authors from this sample, the typical PA student is 28 years old and has three to four years of college and one to two years of prior health care experience. There has been a steady increase in the enrollment of women and individuals with four or more years of college. More than half of the PA students enrolled in 1983 were women. Former military medical corpsmen, who once predominated the PA profession, now represent only a small proportion of the PA student population. Most PA students continue to want to practice with family practitioners in small communities.

Adult↗
PubMed1984

New observations on gametogenesis, fertilization, and zygote transformation in Plasmodium gallinaceum.

The ultrastructure of the sexual stages of Plasmodium gallinaceum during gametogenesis, fertilization, and early zygote transformation is described. New observations are made regarding the parasitophorous vacuole (PV) of gametocytes and the process of emergence in male and female gametocytes. Whereas female gametocytes readily disrupted both the PV membrane and host cell plasmalemma during emergence, male gametocytes frequently failed to break down the plasmalemma of the host cell. New observations and hypotheses are presented on the behavior of the male gamete nucleus. Following fertilization, the male nucleus appears to travel through a channel of endoplasmic reticulum in the female gamete before fusing with the female nucleus at a region in which the nuclear envelope is thrown into extensive convoluted folds. Polarization of the zygote nucleus, in association with the appearance of a perinuclear spindle of cytoplasmic microtubules, preceded all other changes in the developing zygote. After nuclear polarization becomes apparent, electron-dense material is deposited beneath the zygote pellicle, and a canopy is formed which eventually extends over the entire apical end of the developing ookinete. As the apical end begins to extend outward, polar rings, micronemes, and subpellicular microtubules become visible in this portion and a "virus-like" inclusion known as a crystalloid is formed in the posterior portion of the zygote. When female gametes are prevented from being fertilized, the cytoplasm at 24h after gametogenesis is devoid of most of those organelles found in the developing zygote or the mature ookinete. The cell is surrounded only by a single membrane. Although at various points beneath the membrane there are deposits of electron-dense material reminiscent of those deposited in the zygote, no further development of ookinete structures takes place in the unfertilized female gamete.

Animals↗
PubMed1984

A surface protein expressed during the transformation of zygotes of Plasmodium gallinaceum is a target of transmission-blocking antibodies.

Antibodies against gametes of malarial parasites (Plasmodium spp.) have previously been shown to block infectivity of the parasites to mosquitoes by preventing fertilization of the parasites in the insect midgut. These antibodies did not have any effect on the development of fertilized parasites. We now report that a surface protein of Mr 26,000 synthesized by zygotes of P. gallinaceum is the target of antibodies which block infectivity of the fertilized parasites to mosquitoes. Identification of this target antigen offers a new stage of the parasite against which a malaria transmission-blocking vaccine could be developed.

Aedes↗
PubMed1984

Evaluation of a low-flow oxygen-conserving nasal cannula.

Oxygen therapy is one of the most frequently ordered therapies for patients with chronic obstructive pulmonary disease (COPD). In a large percentage of these cases, oxygen therapy is supplied via nasal cannula. With the rising cost of medical care and the search for more effective means of oxygen delivery, a new oxygen-conserving nasal cannula (CNC) that incorporates a closely coupled 20-ml reservoir was developed. Oxygen is stored in the reservoir during exhalation so that 20 ml of approximately 85% oxygen is the first gas inhaled. To test the hypothesis that the CNC is more efficient than the standard nasal cannula (SNC), 20 patients with COPD were evaluated. All patients were chronically hypoxemic at rest. Results indicate that when the CNC was compared with the SNC, arterial oxygen saturation levels were significantly different (p less than 0.001) at flow rates of 0.5, 1.0, and 2.0 L/min. Oxygen saturation were 2.9% higher at 0.5 L/min, 2.9% higher at 1 L/min, and 2.6% higher at 2 L/min for the CNC than for the SNC. In summary, the CNC offers a more efficient oxygen delivery system for those patients requiring supplemental oxygen administration by nasal cannula.

Aged↗
PubMed1984

Gametocyte production in cloned lines of Plasmodium falciparum.

Gametocyte production by cloned lines of Plasmodium falciparum and their parental isolates has been studied in culture over periods of several months. Many isolates differed significantly from each other in their capacity for gametocyte production. Clones derived from an individual isolate were also widely different in capacity for gametocyte production. Consistent differences in gametocyte production were observed between clones which had always been grown concurrently and thus had identical culture histories. Levels of gametocytogenesis characteristic of individual clones, although subject to transient fluctuations under environmental influence, were stable over several months.

Cell Line↗
PubMed1984

Drug sensitivity and isoenzyme type in cloned lines of Plasmodium falciparum.

Clones have been derived by limiting dilution from recent isolates of Plasmodium falciparum from Africa and Brazil. These clones have been characterized for pyrimethamine and chloroquine sensitivity and/or isoenzyme type. Clones obtained from an isolate containing a mixture of GPI isoenzyme types were found to have (with one exception) only GPI-1 or GPI-2. Clones differing 1,000-fold in pyrimethamine resistance were derived from a single isolate from Brazil which was resistant to both pyrimethamine and chloroquine. Several levels of chloroquine sensitivity were observed in the isolates studied. All clones showed levels of chloroquine sensitivity similar to that of their parent isolates. The KZ1 isolate from East Africa had an intermediate level of chloroquine resistance and a flat dose-response curve and each of its clones had a similar dose-response curve, indicating that the intermediate level of chloroquine resistance did not result from the KZ1 isolate's being a mixture of clones with high and low sensitivity.

Africa↗
PubMed1983

Dopamine stimulates alpha 2-adrenoceptors on the Anolis melanophore.

The inhibitory effect of dopamine on the action of MSH on the Anolis melanophore is blocked by the alpha 2-adrenoceptor antagonists, yohimbine and compound RX 781094, suggesting that the action of dopamine is mediated by alpha 2-adrenoceptors. Apomorphine and sulpiride had no effect on MSH action nor the inhibitory effect of dopamine on MSH action confirming that the Anolis melanophore does not possess dopamine receptors and that the action of dopamine is not mediated by dopamine receptors. Since the kinetics of competition between dopamine and MSH is that described for a single receptor it is concluded that interpretation of classical kinetics of competition in terms of action at a single receptor site requires modification to include an unrelated action at separate receptors, competition occurring at a post-receptor level.

Animals↗
PubMed1983

Plasmodium falciparum: effect of time in continuous culture on binding to human endothelial cells and amelanotic melanoma cells.

An in vitro correlate of the binding in vivo of Plasmodium falciparum-infected erythrocytes to capillary and venular endothelium, using cultured human endothelial cells and amelanotic melanoma cells, was previously developed. The effects of different times in continuous culture on binding of erythrocytes infected with nine different isolates of P. falciparum is now reported. Four isolates, which bound at the time they were first tested, rapidly lost the ability to bind after 26-43 days in culture. One of these, the Cameroun isolate, tested 12 h after the blood was obtained from the patient, had the highest rate of binding of all isolates (680 infected erythrocytes per 100 melanoma cells). After 37 days in culture, only 18 infected erythrocytes per 100 melanoma cells bound. Three isolates first tested after 30-62 days in culture bound poorly. In contrast, two others, the Vietnam (VI) and Brazil (It), continued to bind during the period of study. The Brazil (It) isolate studied after 43 days in culture bound 505 infected erythrocytes per 100 melanoma cells; its clone ItG2G1 continued to bind equally well after 400 days in culture. The ultrastructural morphology of knobs on the binding and nonbinding infected erythrocytes were indistinguishable. Since evidence from other studies indicates that knobs are necessary for binding to endothelium, it is proposed that some parasites in continuous culture may not express the molecules responsible for binding, although the morphologic knobs are still present.

Animals↗
PubMed1983

Characterization of antigens on mosquito midgut stages of Plasmodium gallinaceum. I. Zygote surface antigens.

We have defined the surface protein antigens on Plasmodium gallinaceum zygotes using radioiodination methods and rabbit anti-zygote serum which blocks transmission of the parasite to Aedes aegypti mosquitoes. Fifteen protein bands (1-15) in the molecular weight range of 40 000-240 000 and one band at the bromophenol blue dye marker were labelled by the lactoperoxidase and IODOGEN (1,3,4,6-tetrachloro-3 alpha,6 alpha-diphenylglycoluril) methods. The localization of these radioiodinated components on the cell surface was confirmed in two ways: (1) They were completely degraded by trypsin or Streptomyces griseus protease treatment of intact viable zygotes. (2) They were immunoprecipitated following incubation of intact zygotes with antibody prior to detergent solubilization. Reactivity with immune rabbit serum demonstrated that the major surface immunogens were components with Mr 240 000, 200 000, 180 000, 80 000, 55 000, 50 000 and the band at the dye marker. A band of Mr 180 000 was shown immunologically to be a host serum protein selectively adsorbed to the zygote surface. The identity of this protein and the significance of its adsorption to the surface of the zygote are unknown.

Animals↗
PubMed1983

Immunity to malarial antigens on the surface of Plasmodium falciparum-infected erythrocytes.

An indirect immunofluorescence test with fresh non-fixed infected blood as antigen was used to show that antibody in human sera from the Gambia recognized antigens on the surface of Plasmodium falciparum-infected human erythrocytes. Surface immunofluorescence was detected on 90% of erythrocytes infected with trophozoites and schizonts produced in continuous culture of isolates from the Gambia (FCR 3/K+), Brazil and Thailand. Fluorescence was equally strong with a Gambian parasite clone (FCR 3/K-) that lacked knobs, an ultrastructural modification of the erythrocyte membrane associated with parasite sequestration. Immunofluorescence could not be detected with an isolate from Uganda. The surface antigenicity of parasitized erythrocytes was eliminated by chymotrypsin and trypsin treatment. Fluorescence was specific for the surface of trophozoite- and schizont-infected cells on the condition that fresh erythrocytes were added to cultures every 4-5 days (subculture); if fresh erythrocytes were not added for over 2 weeks, a large percentage of non-infected erythrocytes also bound antibody. Normal erythrocytes incubated with media from these cultures also gave positive surface immunofluorescence. Thus, there are two types of antigenicity on erythrocytes: one expressed on infected erythrocytes and another passively absorbed from media to normal erythrocytes when parasites are not subcultured for long periods.

Absorption↗