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Biomedical subjects

G W Long

Publications and source records attributed to G W Long.

At least 37 records · Page 2Linked to original sources
PubMed1990

The liver as a major site of immunological elimination of murine trypanosome infection, demonstrated with the liver perfusion model.

The isolated liver perfusion model has been used to investigate immunological elimination of bacteria and yeasts but not for analysis of mechanisms of immunological destruction of extracellular parasitic protozoa. Extracellular trypanosomes are eliminated primarily through antibody (and complement?)-promoted hepatic (Kupffer cell) uptake and destruction. We studied the suitability of the isolated liver model system for analyzing the mechanism of immune elimination of mouse-specific Trypanosoma musculi and identified several factors which can complicate such analyses: (i) mechanical trapping of trypanosomes that are quite large (for example, reproducing forms or epimastigotes) or are nonviable and, therefore, nondeformable; (ii) variable species and concentrations of cytadhesive molecules; and (iii) the integrity and composition of the trypanosomal surface coat. There was a substantial difference between hepatic retention of infused T. musculi organisms coated with a specific antibody and those devoid of antibody when both were suspended in normal mouse serum. The difference appeared sufficient to allow accurate quantitative studies of immune destruction in the liver. Studies of whole mice indicated that quantitative investigations of immunological elimination of trypanosomes from the bloodstream are likely to be complicated by problems such as cytadherence of parasites to host endothelial cells and mechanical trapping. Uptake by the liver and spleen appeared more reliable. Thus, the isolated liver perfusion model should significantly benefit studies to elucidate the mechanisms of immune elimination of extracellular trypanosomes.

Animals↗
PubMed1990

Processing and microfiltration of mosquitoes for malaria antigen detection in a rapid dot immunobinding assay.

Data on a technique for the detection of antigen from arthropod vectors in a dot immunobinding assay are presented. In this system, antigen present in the vector was first solubilized in sodium dodecyl sulfate. The homogenate from this process was microfiltered through a two-membrane sandwich; target antigen molecules passed through the first membrane and were immobilized on the second one. The first membrane was nonbinding and served to impinge debris. The second membrane was a high-protein-binding-capacity hydrophobic polyvinylidene difluoride membrane. High signal-to-noise ratios were produced by this method, which is readily adaptable for field use. This assay was used for malaria sporozoites, but it can serve as a general technique that is applicable to other arthropod vectors and etiologic agents.

Animals↗
PubMed1990

Plasmodium falciparum-infected Anopheles stephensi inconsistently transmit malaria to humans.

Malaria was transmitted to only 5 of 10 volunteers bitten by 1-2 Anopheles stephensi carrying sporozoites of the 3D7 clone of the NF54 strain of Plasmodium falciparum in their salivary glands. Parasites were detectable by culture in blood taken 7-10 days following exposure and by thick blood film 14-16.5 days after exposure. Infectivity did not correlate with the numbers of sporozoites in the salivary glands.

Adult↗
PubMed1990

Immunodot assay of Plasmodium falciparum sporozoites in mosquitoes using a direct binding membrane system.

We describe a membrane based immunodot assay for the detection of Plasmodium falciparum sporozoites mixed with mosquitoes. A crude sodium dodecyl sulfate extract of mosquitoes and sporozoites is passed through a bi-layered membrane system, the top layer being a polyvinyldiene difluoride hydrophilic pre-filter which screens out debris but allows the passage of antigen. Sporozoite, as well as mosquito, proteins are bound to the hydrophobic membrane below. This membrane was probed with a monoclonal antibody to the repeat region of the P. falciparum circumsporozoite protein, a peroxidase labeled second antibody and a tetramethyl-benzidine substrate. The method detects as few as 10 sporozoites/mosquito or 100 sporozoites in a pool of 10.

Animals↗
PubMed1990

Rapid diagnosis of Brugia malayi and Wuchereria bancrofti filariasis by an acridine orange/microhematocrit tube technique.

A microhematocrit tube technique for diagnosis of human filariasis has been previously described. A system incorporating heparin, EDTA, and acridine orange into a microhematocrit tube (Quantitative Blood Count, QBC) has been commercially developed for the quantitation of blood counts and has been used for the diagnosis of malaria. We evaluated this test for its usefulness in the diagnosis of filariasis. Upon centrifugation, the parasites were concentrated in the area of the buffy coat and could be observed through the wall of the tube. The parasites were concentrated further by a plastic float that expands the buffy coat and confines the parasites to the periphery of the tube. Acridine orange stains the DNA of the parasite, and morphologic characteristics can be examined by fluorescence microscopy. The terminal and subterminal nuclei and long cephalic space of Brugia malayi, as well as the short cephalic space and caudal nuclei of Wuchereria bancrofti, were easily recognized and differentiated from each other. Microfilariae were detected in samples diluted to a level of approximately 50/ml.

Acridine Orange↗
PubMed1990

T lymphocytes from mice immunized with irradiated sporozoites eliminate malaria from hepatocytes.

When mice are immunized with radiation-attenuated sporozoites they are solidly protected against sporozoite challenge by an immune response that has been shown to require CD8+ lymphocytes in several strains of mice. The target of this CD8+ T-cell-dependent immunity has not been established. Immune BALB/c mice were shown to develop malaria-specific, CD8+ T-cell-dependent inflammatory infiltrates in their livers after challenge with Plasmodium berghei sporozoites. Spleen cells from immune BALB/c and C57BL/6 mice eliminated hepatocytes infected with the liver stage of P. berghei in vitro. The activity against infected hepatocytes is not inhibited by antibodies to interferon-gamma and is not present in culture supernatants. It is genetically restricted, an indication that malaria antigens on the hepatocyte surface are recognized by immune T-effector cells. Further subunit pre-erythrocytic stage malaria vaccine development will require identification of the antigens recognized by these T cells and a method of immunization that induces such immunity.

Animals↗
PubMed1989

Sporozoite vaccine induces genetically restricted T cell elimination of malaria from hepatocytes.

The target of the CD8+ T cell-dependent immunity that protects mice immunized with irradiation-attenuated malaria sporozoites has not been established. Immune BALB/c mice were shown to develop malaria-specific, CD8+ T cell-dependent inflammatory infiltrates in their livers after challenge with Plasmodium berghei sporozoites. Spleen cells from immune BALB/c and C57BL/6 mice eliminated hepatocytes infected with the liver stage of P. berghei in vitro. The activity against infected hepatocytes is not inhibited by antibodies to interferon-gamma and is not present in culture supernatants. It is genetically restricted, an indication that malaria antigens on the hepatocyte surface are recognized by immune T effector cells. Subunit vaccine development will require identification of the antigens recognized by these T cells and a method of immunization that induces such immunity.

Animals↗
PubMed1989

Rapid diagnosis of malaria by acridine orange staining of centrifuged parasites.

A rapid diagnostic test for malaria based on acridine orange staining of centrifuged parasites in a microhaematocrit tube ('QBC' tube) was compared with the thick blood smear in 12 volunteers experimentally infected with Plasmodium falciparum, 408 residents of a malaria endemic area, and 180 hospital patients with suspected malaria. In the experimentally infected volunteers, the QBC tube test and the thick blood smear were comparable and the QBC tube could detect as few as 4 parasites/microliter blood. When used for mass screening in the field study, the test had a sensitivity of 70% for the diagnosis of malaria compared with 92% for a single thick blood smear. However, when used to diagnose malaria in hospital patients, the test detected as few as 3 parasites/microliter in 91 of 92 patients with asexual parasitaemia. For the three studies, the QBC tube was highly specific (98.4%), indicating malaria in only 8 of 487 subjects with negative blood films. The species of parasite was correctly identified in 77% of species. Processing the QBC tube was easier and much more rapid than was processing a thick blood smear, taking only 5 min for centrifugation and 5 min for examination. The QBC tube is not a substitute for the blood smear, but its speed and ease of use make it an important new tool for the diagnosis of malaria.

Acridine Orange↗
PubMed1989

Cultivation of the exoerythrocytic stage of Plasmodium berghei in primary cultures of mouse hepatocytes and continuous mouse cell lines.

Plasmodium berghei exoerythrocytic (EE) stages have been cultured in vitro in human continuous cell lines and primary cultures of both human and rat hepatocytes. Although the predominant experimental model of irradiated sporozoite-induced protective immunity is the mouse, P. berghei has not been cultivated in primary mouse hepatocytes or in continuous mouse lines. Because of this, target cells are not available for determining if these immunized mice produce cytotoxic T lymphocytes (CTLs) that recognize P. berghei antigens expressed on hepatocytes in the context of class I major histocompatability (MHC) antigens. We report the development of methods for cultivating the (EE) stage of P. berghei in murine hepatocytes and in two cell lines derived from the livers of BALB/c mice; one line produced from a primary hepatocyte culture and the other produced by fusion of mouse hepatocytes with a continuous rat liver line. Mature parasites were detected by microscopy and by DNA probe in both cell lines, each of which supported complete development of P. berghei liver stages and production of infectious merozoites. Since class I MHC antigens are present on the surface of primary hepatocytes and the mouse X rat hybrid line, these cells can be used to detect cytotoxic T cells against liver stage parasites.

Animals↗
PubMed1988

Chloroquine and quinine: a randomized, double-blind comparison of efficacy and side effects in the treatment of Plasmodium falciparum malaria in the Philippines.

Chloroquine (25 mg/kg over 3 d) was compared to quinine (10 mg/kg 3 times daily for 5 d) in 20 adult Filipino males with uncomplicated Plasmodium falciparum malaria in a double-blind, randomized trial. Asexual parasitaemia was cleared in all patients, with no statistically significant difference (P = 0.13) in the rate of clearance between the chloroquine-treated patients (76.1 +/- 29.3 h) and those receiving quinine (60.3 +/- 12.5 h). The duration of fever was also comparable (chloroquine 46.3 +/- 24.7 h; quinine 43.2 +/- 20.0 h; P = 0.76) and 40% of patients in each treatment group experienced mild side effects. Chloroquine, however, is cheaper and easier to administer. In vitro results were strikingly different. P. falciparum parasites from 4 quinine-treated patients were all sensitive to this compound in vitro, whereas 4 of the 5 isolates from the chloroquine group were resistant. Further comparisons of these two antimalarials are indicated, especially in cerebral malaria, and drug use policies should be based on clinical and parasitological response to treatment.

Adolescent↗
PubMed1987

Prevalence of renal involvement in Schistosoma japonicum infection.

244 outpatients and 100 hospitalized patients with confirmed Schistosoma japonicum infection were prospectively surveyed for the presence of nephropathy. There was no association between schistosomiasis and renal disease in the outpatient group. Three hospitalized patients had evidence of significant nephropathy, but this number was not significantly higher than in a control group of 100 hospitalized age and sex-matched control patients without schistosomiasis. One schistosomiasis patient with severe nephrotic syndrome underwent percutaneous renal biopsy. Neither S. japonicum antigen nor antibody was found in the biopsy specimen. 64 of the 100 hospitalized patients had portal hypertension; in 28 patients there was hepatic decompensation. Only one of these hepatosplenic patients had evidence of renal disease. Thus renal involvement was uncommon in patients presenting various manifestations of chronic S. japonicum infection, including those with severe hepatosplenic disease. These results contrast markedly with S. mansoni infection, in which nephropathy associated with advanced liver disease is a distinct, well-recognized clinical entity.

Adolescent↗
PubMed1987

Amodiaquine less effective than chloroquine in the treatment of falciparum malaria in the Philippines.

Amodiaquine was compared to chloroquine in two groups of Filipino patients with uncomplicated falciparum malaria. Every patient received 25 mg/kg of base orally given over three days. In a hospital study, all eight patients receiving chloroquine cleared their parasitemia by day 6, but six of eight patients receiving amodiaquine failed to clear parasitemia and in four patients there was no response at all (RIII resistance); this difference was significant (P less than 0.01). In a village based study, there was initial clearing of parasitemia in each patient. However, recrudescent infection occurred in all five patients receiving amodiaquine (RI resistance). Five of six falciparum infections were sensitive to chloroquine, while parasitemia reappeared in one patient. In this village, resistance to amodiaquine was significantly more common than resistance to chloroquine (P less than 0.05). To our knowledge, this is the first report of amodiaquine being substantially worse than chloroquine in the treatment of Plasmodium falciparum infection.

Adolescent↗
PubMed1987

Comparison of washed and unwashed specimens in the Plasmodium falciparum in vitro microculture drug assay.

The dose response of Plasmodium falciparum isolates in the standard in vitro assay for drug resistance was compared using blood specimens which were centrifuged and washed before cultivation. Washing of the cultures increased the success of cultivation by greater than 100%. Eight cultures which grew using both methods gave similar results in the determination of resistance or sensitivity. The ED50 as determined by probit analysis, was approximately 50% higher in parasites which had been washed before cultivation.

Animals↗
PubMed1987

In vitro drug response of Plasmodium falciparum in the Philippines: increased resistance to amodiaquine.

A long term study was carried out at San Lazaro Hospital, Manila, Philippines, monitoring the in vitro response of Plasmodium falciparum to chloroquine, amodiaquine, mefloquine, and quinine. The in vitro effective dose giving 50% inhibition of schizogony was: 0.68 X 10(-6) M/liter blood for chloroquine; 0.18 X 10(-6) for amodiaquine; 0.2 X 10(-6) for mefloquine; and 1.12 X 10(-6) for quinine. The percent of isolates determined to be resistant in vitro was 85.2% for chloroquine, and 1.2% for both mefloquine and quinine. These figures were relatively unchanged over the course of 3 years studied. The in vitro resistance rate to amodiaquine increased from 5.1% in 1982 to 22.2% in 1984.

Amodiaquine↗
PubMed1986

Praziquantel in treatment of cerebral schistosomiasis.

The effectiveness of standard single-day praziquantel treatment (60 mg/kg) was prospectively evaluated in nine patients with seizures caused by cerebral Schistosoma japonicum infection. Eight patients were cured when discharged from the study, an average of 6 months after receiving praziquantel. They were seizure-free in the absence of anticonvulsants, their electroencephalograms were normal, and no major abnormalities could be detected on neurological examination. Serial computed tomography scanning revealed rapid dissipation of cerebral oedema and complete or near-complete resolution of mass lesions. No serious adverse effects of praziquantel were encountered. The ninth patient was not cured but improved greatly in the months after treatment. Thus, single-day treatment with praziquantel is safe and effective in cerebral schistosomiasis.

Adult↗