Sisyphus effects in a microwave-excited flux-qubit resonator system.

Sisyphus amplification, familiar from quantum optics, has recently been reported as a mechanism to explain the enhanced quality factor of a classical resonant (tank) circuit coupled to a superconducting flux qubit. Here we present data from a coupled system, comprising a quantum mechanical rf SQUID (flux qubit) reactively monitored by an ultrahigh quality factor noise driven rf resonator and excited by microwaves. The system exhibits enhancement of the tank-circuit resonance, bringing it significantly closer (within 1%) to the lasing limit, than previously reported results.

Cultivation in vitro of the vivax-type malaria parasite Plasmodium cynomolgi.

The vivax-type simian malaria parasite Plasmodium cynomologi was cultured in vitro by both the candle jar method and the continuous flow technique, with rhesus monkey erythrocytes and RPMI 1640 medium supplemented with Hepes buffer and human serum. After 6 weeks in culture, the growth of the parasite had permitted a 5 X 10(6) cumulative dilution of the original inoculum. Cultured parasites remained infective to rhesus monkeys and exhibited a reversible decrease in the ameboid behavior of their trophozoites.

Conventional and functional proteomics using large format two-dimensional gel electrophoresis 24 hours after controlled cortical impact in postnatal day 17 rats.

Conventional and functional proteomics have significant potential to expand our understanding of traumatic brain injury (TBI) but have not yet been used. The purpose of the present study was to examine global hippocampal protein changes in postnatal day (PND) 17 immature rats 24 h after moderate controlled cortical impact (CCI). Silver nitrate stains or protein kinase B (PKB) phosphoprotein substrate antibodies were used to evaluate high abundance or PKB pathway signal transduction proteins representing conventional and functional proteomic approaches, respectively. Isoelectric focusing was performed over a nonlinear pH range of 3-10 with immobilized pH gradients (IPG strips) using supernatant from the most soluble cellular protein fraction of hippocampal tissue protein lysates from six paired sham and injured PND 17 rats. Approximately 1,500 proteins were found in each silver stained gel with 40% matching of proteins. Of these 600 proteins, 52% showed a twofold, 20% a fivefold, and 10% a 10-fold decrease or increase. Spot matching with existing protein databases revealed changes in important cytoskeletal and cell signalling proteins. PKB substrate protein phosphorylation was best seen in large format two-dimensional blots and known substrates of PKB such as glucose transporter proteins 3 and 4 and forkhead transcription factors, identified based upon molecular mass and charge, showed altered phosphorylation 24 h after injury. These results suggest that combined conventional and functional proteomic approaches are powerful, complementary and synergistic tools revealing multiple protein changes and posttranslational protein modifications that allow for more specific and comprehensive functional assessments after pediatric TBI.

Adhesion of carboxylate cements to hydroxyapatite. I. The effect of the structure of aliphatic carboxylates on their uptake by hydroxyapatite.

An investigation was made into the effect of the structure and functionality of aliphatic carboxylates on their sorption onto hydroxyapatite with a view to ascertaining factors affecting the adhesion of polyacrylate cements to tooth materials. In general, the amount of carboxylate sorbed was found to increase with the number of groups contained in the molecule. Thus, polyacrylate was found to be much more strongly sorbed than low molecular weight species. Sorption of the low molecular weight species appeared to be related to stereochemical factors rather than to the stability constants of their calcium chelates.

Plasmodium fragile and Macaca mulatta monkeys as a model system for the study of malaria vaccines.

Pladmodium fragile and the Macaca mulatta monkey are presented as a model system for the study of malarial vaccines. Four animals were immunized with culture-grown P. fragile merozoites and subsequently challenged with culture-produced parasites. One animal failed to develop a detectable parasitemia following primary challenge. Two other immunized animals had primary infections which were short-term. the parasitemias in these three monkeys following secondary challenge were short-term and the immunity was apparently sterilizing. The fourth immunized monkeys had recrudescences of the primary and secondary infection but differed markedly from the four control animals. Indirect fluorescent antibody titers increased as a result of the immunization and were indicative of the level of immunity. Because of the many similarities to the human-P. falciparum model system, the P. fragile-M. mulatta system appears to be particularly well suited for a number of malaria vaccine studies.

The seroepidemiology of malaria in Middle America. V. Antibody responses in an indicator population from an endemic area with attack phase antimalaria activities.

Serologic assessment was carried out in a sample of the population living in an area endemic for malaria in which control measures were being applied. The study area was in El Salvador, Central America, and antimalarial activities consisted of the residual application of the pesticide, propoxur, and drug distribution through a combination of active and passive case detection. Indirect fluorescent antibody (IFA) responses to Plasmodium vivax and P. falciparum antigens were determined on four occasions, at approximately 6-month intervals. The study population consisted of one resident from each of 268 widely distributed houses. Each person was treated with a curative course of chloroquine and primaquine at the beginning of the investigation. An increase in the proportion of positive IFA responses (greater than or equal to 1:20) and an increasing number of serologic conversions (i.e., from negative to positive or a 2-fold increase in titer) during the course of the 18-month study confirmed continued transmission of malaria. The presence of parasites in some individuals without associated serologic changes is discussed.

The enzyme-linked immunosorbent assay (ELISA) for malaria. I. The use of in vitro-cultured Plasmodium falciparum as antigen.

Using the Panama II strain of Plasmodium falciparum obtained from continuous in vitro culture as antigen, the micro enzyme-linked immunosorbent assay (ELISA) was used to test serum samples from 50 persons from the southeastern United States and serum specimens collected weekly from four non-immune and nine semi-immune patients infected with P. falciparum. None of the 50 sera from the United States had ELISA antibody titers greater than 1:80. The nine semi-immune patients had rapid ELISA antibody responses (titers greater than 1:2560) following patent parasitemia. ELISA titers remained elevated despite disappearance of patent parasitemia, and declined gradually following curative antimalarial therapy. The ELISA responses observed in the four non-immune patients were more variable, though positive titers appeared rapidly with patent parasitemia. Maximum titers were lower than those observed in semi-immune patients. These results demonstrate that P. falciparum obtained from continuous in vitro culture is an excellent antigen for the micro-ELISA test for malaria. However, further assessments of the ELISA are needed to identify the conditions associated with positive responses.

The seroepidemiology of malaria in Middle America. I. Longitudinal studies on populations in a low incidence area of El Salvador.

Serologic profiles were established using the indirect fluorescent antibody test in a longitudinal study of six villages in an interior area of El Salvador. Positive serologic responses as well as active cases found through the voluntary collaborator posts occurred primarily in adult males, suggesting that much of the malaria experience in the study area resulted from exposure of this segment of the population in more malarious areas where they traveled to engage in temporary agricultural labor. Malaria incidence was generally low but transmission potential apparently varied markedly even over relatively small distances. Serologic profiles reflected the malaria experience in the population sampled, but many localities were widely dispersed and samples taken from village centers were found in some cases not to be representative of the entire locality population in terms of malaria exposure. The indirect fluorescent antibody technique was found to reflect the malaria experience in the population segments examined. When these data were correlated with the surveillance data from the voluntary collaborator posts, the epidemiology of malaria in the study area was more thoroughly understood.

The seroepidemiology of malaria in Middle America. II. Studies on the Pacific coast of Costa Rica.

Serologic studies for malaria using the indirect fluorescent antibody technique suggest that active transmission is either absent or very low in 6 villages on the Pacific side of Costa Rica. Positive titers (1:20 or higher) were seen in the under-15-year age group in three of the study localities, but only 5 such responses were encountered among 249 people examined in this age range. In the adults (15 years and over) from the same 3 villages there were 68 positive titers among 161 examined. There were 43 positive responses in 189 adults from the remaining 3 villages where none of 307 persons under 15 years of age showed a titer of 1:20 or higher to any of the 3 malaria antigens tested (Plasmodium falciparum, P. vivax and P. malariae). These data suggest that the positive responses in the latter villages are more likely to be associated with old or imported cases than with current local transmission. Serologic responses of 1:80 or higher to the P. falciparum antigen suggested the continued presence of this parasite in the population in spite of the paucity of positive blood smears with this species in recent years. Positive titers with the P. malariae antigen suggest that this parasite is probably still present in the area. Such serologic studies help to indicate areas where malaria transmission is active and provide information on parasite reservoirs in particular populations.

Development of antibodies to Plasmodium vivax as measured by two different serologic techniques.

Sera from individuals infected with Plasmodium vivax were tested for the presence of malarial antibodies using the indirect fluorescent antibody (IFA) and the indirect hemagglutination (IGA) tests. The primary infection resulted in the conversion of all sera to a positive response in the IFA test, whereas only 50% gave a positive IGA response. There was a direct relationship between the duration of the primary parasitemia and percentage giving positive IGA response. Relapse resulted in high level positive IFA and IGA responses.

Morphologic variants of Anopheles albimanus and susceptibility to Plasmodium vivax and P. falciparum.

Three morphologically different, true-breeding phenotypes have been isolated from a strain of Anopheles albimanus from Lake Apastepeque, El Salvador. Studies with coindigenous strains of Plasmodium vivax and P. falciparum show that these phenotypes differ significantly in their susceptibility to malaria parasites. This difference is apparent both in the number of mosquitoes that become infected and the level of infection obtained. Variations in malaria susceptibility are markedly greater with P. vivax than with P. falciparum. The significance of genetic variants within a local vector population with respect to the epidemiology of malaria is discussed.

Infection of mosquitoes with Plasmodium vivax from chimpanzees using membrane feeding.

Six splenectomized chimpanzees were infected with the Chesson or the North Korean strains of Plasmodium vivax. Heparinized blood taken from the animals was fed to approximately 45,000 mosquitoes using parafilm membranes. High-level mosquito infections were obtained with the blood from 4 animals. One animal infected mosquitoes only at a very low level. The other chimpanzee failed to produce a parasitemia high enough to warrant mosquito feeding.

Susceptibility of Peruvian Aotus monkeys to infection with different species of Plasmodium.

Splenectomized Aotus trivirgatus monkeys of Peruvian origin were tested for their susceptibility to infection with different species of Plasmodium. Strains of P. vivax from Vietnam and El Salvador produced infections in eight animals with maximum parasite densities ranging from 2,000-180,000 per mm3. A strain of P. falciparum from Cambodia produced maximum parasitemias in five animals ranging from 8-25% of the red blood cells infected. Although two monkeys inoculated with P. fragile had maximum parasitemias of 31% and 42%, treatment was not necessary for animal survival. Three monkeys infected with P. knowlesi via the bites of infected mosquitoes had maximum parasitemias of from 25-41%; these animals died of their infections. Nine animals were infected with P. cynomolgi; maximum parasitemias in seven of these animals with no prior history of malarial infection ranged from 49,500 per mm3 to 11%; two animals with prior experience with P. vivax and P. fragile had maximum P. cynomolgi parasitemias of 65 and 13,200 per mm3. No infections were obtained in animals inoculated with P. coatneyi or P. hylobati.

Serologic studies on onchocerciasis in Guatemala using fixed-tissue sections of adult Onchocerca volvulus.

Sera from 458 residents of a coffee plantation in an area of Guatemala endemic for onchocerciasis were examined for the presence of antibodies to Onchocerca volvulus using a fluorescent antibody (IFA) test with sections of adult worms as the antigen. Antibody response increased with age of the residents and microfilarial density. A total of 70.0% of the residents were serologically positive and 65.1% were positive for microfilariae. Males had higher microfilarial densities and higher IFA responses. Sixty-three individuals were positive for microfilariae and IFA-negative indicating a lack of sensitivity on the part of the test antigen. Seventy-four individuals were negative for microfilariae and IFA-positive, suggesting the possible usefulness of the test in the determination of present or past infection in the absence of microfilariae.

Attempts to immunize monkeys against Plasmodium knowlesi by using heat-stable, serum-soluble antigens.

Thirty-six Macaca mulatta monkeys were immunized with different concentrations and regimens of heat-stable, serum-soluble (S-) antigens of Plasmodium knowlesi prior to challenge with the homologous parasite via sporozoite inoculation. Fewer deaths and reduced maximum parasitemias occurred in those animals inoculated with 10 to 40 mg of S-antigen compared to nonimmunized monkeys or those receiving only Freund's adjuvant. Protection was incomplete, however, suggesting that atibodies to S-antigens may have a limited role in protection of hosts to malarial infection.

Development of different strains of Plasmodium vivax in two species of Anopheles.

Anopheles freeborni mosquitoes with oocyst infections had salivary gland infections at a higher rate of Plasmodium vivax from the New World than with strains from Asia, particularly those from South Vietnam. Anopheles maculatus mosquitoes supported development from oocysts to heavily infected salivary glands for all the strains of P. vivax tested. The results suggest that P. vivax introduced from Vietnam would be less likely to be transmitted by native A. freeborni mosiquitoes than would malaria from some other areas.

Cellular proliferative responses in squirrel monkeys immunized with recombinant and synthetic Plasmodium vivax circumsporozoite peptides.

The role of circulating peripheral blood momonuclear cells (PBMC) in mediating protective immunity was examined during an immunization trial in Saimiri monkeys. Three engineered constructs representing different but overlapping regions of the circumsporozoite (CS) protein of Plasmodium vivax were used to immunize the Saimiri monkeys. Monkeys were randomly placed into three immunization groups: rPvCS2, rPvCS3, and LCV3 (representing three different but overlapping portions of the P. vivax CS protein) and two control groups: an alum adjuvant control group and an unimmunized control group. Collections of PBMC were made throughout the study at weeks 0, 2, 8, challenge (week 16), and two weeks after challenge. Proliferative responses to all immunogens and pokeweed mitogen were measured in all monkeys. Fourteen of 18 monkeys immunized with either rPvCS2 or rPvCS3 responded on the day of challenge to the appropriate immunogen with a stimulation index less than 2. Immunization with LCV3, which represents the repeat region only, elicited a specific response in only one monkey. However monkeys in both control groups also responded to rPvCS2 and rPvCS3, regardless of immunization, suggesting the presence of epitopes in rPvCS2 and rPvCS3 capable of associating with differing MHC antigens. Furthermore, the frequency of these cells in the periphery was increased by immunization, as demonstrated by a greater number of responding monkeys in the rPvCS2 and rPvCS3 immunized groups.

The enzyme-linked immunosorbent assay (ELISA) for malaria. III. Antibody response in documented Plasmodium falciparum infections.

Serum specimens from patients in El Salvador, Central America, with slide-proven Plasmodium falciparum infections were examined for antibodies to P. falciparum using the enzyme-linked immunosorbent assay (ELISA) and the indirect fluorescent antibody (IFA) methods. Both serologic tests were positive in 78.1% of the 827 samples, both negative in 5.4%, the ELISA positive alone in 6.3%, and the IFA alone in 10.2%. Agreement between the serologic tests was better in the specimens with high positive titers (high IFA = high ELISA). Seropositivity rates and geometric mean titers were higher in the older (greater than or equal to 15 years) age groups for both ELISA and IFA; in such persons, the IFA was positive in 92% and the ELISA in 88%. The lowest seropositivity rates found by the ELISA were observed in children; 27.6% of 98 children less than or equal to 4 years of age were negative. A longer duration of infection as evidenced by the presence of gametocytes on the blood slide resulted in higher positivity rates by both ELISA and IFA. This phenomenon, particularly apparent in young children, supports the belief that the more important variable in determining the proportion of false negatives is previous malaria experience and not age. The results indicate that, while neither serologic test is appropriate as a diagnostic aid, both the ELISA and the IFA would be useful in epidemiologic investigations.

Antibody responses to malarial antigens in the Wopkaimin population of the Star Mountains, Papua New Guinea.

Antibody responses to malarial antigens were determined in 614 serum samples collected from the Wopkaimin population of the Star Mountains of Papua New Guinea. In point prevalence surveys made in 1982-1983, 33.7% of the persons examined were infected with Plasmodium falciparum, P. vivax, or P. malariae. Of these, 72.9% were infected with P. falciparum. In a standard fluorescent antibody test, highest level responses were to P. falciparum, followed by P. malariae, P. vivax, and P. ovale. A strong correlation was found between results of the fluorescent antibody tests and those obtained in an enzyme-linked immunosorbent assay using P. falciparum antigens. The failure of immune responses to eliminate these species of Plasmodium in this highly isolated population is discussed.

Infection of chimpanzees with the Uganda I/CDC strain of Plasmodium malariae.

Nine splenectomized chimpanzees were infected with the Uganda I/CDC strain of Plasmodium malariae. Two had no history of previous malarial infection, whereas 6 had been infected with P. vivax and 1 with P. vivax and P. ovale. The animals with no previous infection had maximum parasitemias of 8,740 and 10,800/mm3. The other animals had maximum parasite counts of 930-75,700/mm3. Anopheles freeborni, An. stephensi, An. dirus, An. maculatus, An. quadrimaculatus, An. culicifacies, An. arabiensis, and An. gambiae were readily infected by feeding through membranes on heparinized blood from these animals.