ABSTBACTNet plankton excretes daily an amount of phosphorus nearly equal to its total phosphorus content. Slightly more than half of the excreted phosphorus is phosphate and the remainder is in soluble organic compounds.Phosphorus excreted by zooplankton may constitute a significant fraction of that required for photosynthesis by the phytoplankton. INTBODUCTIONThe rate of excretion of phosphorus by zooplankton in natural waters has been estimated by several investigators. Several orders of magnitude have been suggested for the rate, and its importance in the cycle of phosphorus has been said to be great by some (Gardiner 1937; Riley 1951; Harris 1959)) and said to be negligible by others (Steele 1959; Rigler I96I).Marshall and Orr ( 1955)) Conover ( 1956)) Cushing ( cited by Rigler 1961)) and Rigler ( 1961) measured the production of phosphate by single species of planktonic crustacea. Marshall and Orr ( 1961) and Conover ( 1961) estimated phosphorus turnover in Calanus finmarchicus from the rate of loss of Ps2. Gardiner ( 1937) and Harris (1959) measured the production of phosphate by freshly collected net plankton. The use of fresh plankton offers a more direct answer to the ecological question of the total excretion of phosphorus by all zooplankton. We estimated the rate of excretion of both orthophosphate and soluble organic phosphorus compounds by zooplankton from three types of water, taking precautions to avoid confusion of bacterial production of phosphorus compounds with excretion of similar compounds by the zooplankton.Plankton was collected from several locations over the continental shelf at a distance of I2 miles from shore, beyond any great

We investigated an hypothesis relating the Duffy-negative blood type with insusceptibility to vivax malaria--and previously associated only with people of West African ancestry--in three population samples of eastern African stock. The samples included Nilotic and Hamitic-Semitic residents of a malarious locale in Ethiopia and Hamito-Semites in Addis Ababa where malaria is not endemic. Fresh red blood cells from 191 subjects were tested with Duffy antisera, anti-Fya and anti-Fyb. Duffy-positive rates in the malarious community were 8% for the Nilotes and 70% for the Hamito-Semites; the Hamito-Semites in Addis Ababa were 98% Duffy-positive. The relative prevalences of Plasmodium vivax in the two study groups at risk to malaria were 2.4% for the Nilotes and 27.3% for the Hamito-Semites, producing a ratio similar to the ratio of Duffy-positive in the two samples. We interpret the data as supportive of the Duffy-vivax hypothesis with reference to a part of eastern Africa, and we suggest that the Duffy-negative genotype may represent the original, rather than the mutant, condition in tropial Africa.

The lack of a quick, simple, and inexpensive diagnostic test has limited the ability of public health officials to rapidly assess and control outbreaks of Giardia lamblia in child day-care centers. We evaluated the performance of a commercially available enzyme-linked immunosorbent assay (ELISA) for the detection of a G. lamblia-associated antigen in stool. Stool specimens were collected from the diapers of 426 children attending 20 day-care centers, fixed in 10% Formalin and polyvinyl alcohol, and examined by microscopy by Formalin concentration and trichrome staining techniques. Specimens were also tested visually and spectrophotometrically by ELISA. Of 99 tests positive by microscopy, 93 were visually positive by ELISA (sensitivity, 93.9%). Of 534 tests negative for G. lamblia by microscopy, 32 (6.0%) were ELISA positive. However, on the basis of examination of multiple specimens from the same child, none of these could be considered false-positive ELISAs; the specfficity of the ELISA was therefore 100%. The sensitivity of both microscopy and ELISA improved as the number of specimens per child increased. An optical density value of >0.040 was 98.0% sensitive and 100% specific for G. lamblia. This ELISA, which appeared to be more sensitive for G. lamblia than did microscopic examination of stool, should be useful as an epidemiologic tool, particularly in day-care settings, and may also have a role in confirming clinical diagnoses of giardiasis.

Axenic cultures of Entamoeba histolytica strains HK-9, HM-1, and Rahman were fractionated to provide plasma membranes, internal, vesiculated membranes, and a soluble cytosol. Each particulate fraction was solubilized and all fractions were analyzed by techniques designed to demonstrate molecular complexity and serologic reactivity. The cytosol contained more antigenic moieties than either membrane fraction; however, the antigens associated with the membranes had very high reactivity and lower nonspecific activity than the cytosol.

In a recent study, we identified Giardia lamblia 65and 70-kDa antigens in the feces of infected Mongolian gerbils. The 65-kDa antigen was from a strain isolated from a human with symptoms of giardiasis, and the 70-kDa antigen was from a strain isolated from a human with no symptoms of giardiasis. In this study, we used preparative electrophoresis and electroelution techniques to purify these antigens to a degree which showed a single discrete protein band on silver-stained polyacrylamide gels. By enzyme-linked immunoelectrotransfer blot, common epitopes on the 65and 70-kDa antigens were indicated by their cross-reactivity with rabbit anti-65-kDa and anti-70-kDa sera. By indirect immunofluorescence assay, the cysts and trophozoites of the two strains cross-reacted with these sera. Of seven lectins tested, only concanavalin A bound to the 70-kDa antigen, suggesting a glycoprotein, and it possessed a low isoelectric point as assessed by preparative isoelectric focusing. Molecular mass estimations of these antigens by sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis were similar to the 65and 70-kDa estimations obtained by native polyacrylamide gradient gel electrophoresis. Although the 65and 70-kDa antigens proved to be resistant to 100°C heat and stable in storage for up to 25 months at-20°C, neither appeared to be the same as a fecal G. lamblia antigen with similar molecular mass found by other investigators. This suggests that variable G. lamblia antigens may be found in

From June 1978 through December 1980, at least 36 cases of amebiasis occurred in persons who had had colonic-irrigation therapy at a chiropractic clinic in western Colorado. Of 10 persons who required colectomy, six did. Of 176 persons who had been to the clinic in the last four months of 1980, 80 had received other forms of treatment. Twenty-one per cent of the colonic-irrigation group had bloody diarrhea, as compared with 1 per cent of the non-irrigation group (P = 0.00013). Thirty-seven per cent of the colonic-irrigation group who submitted specimens had evidence of amebic infection on either stool examination or serum titer, as compared with 2.4 per cent in the non-irrigation group (P = 0.00012). Persons who were given colonic irrigation immediately after a person with bloody diarrhea received it were at the highest risk for the development of amebiasis. Tests of the colonic-irrigation machine after routine cleaning showed heavy contamination with fecal coliform bacteria. The severity of disease in this outbreak may have been related to the route of inoculation.

Two strains of amoebae, one (CDC:0180: 1) from the lung tissue of a patient who died of granulomatous amoebic encephalitis and the other (CDC:0179:1) from the debrided tissue of a mandibular autograft, were isolated and identified as A(anthainoeba (castellatnii based on the morphological and immunofluorescent staining characteristics of the trophozoites and cysts. Both strains of amoebae caused cytopathic effects in mammalian cell cultures and destroyed the cell sheet. However, only the CDC:0180:1 strain, on intranasal instillation into mice, produced the disease manifested by ruffled fur and aimless wandering, followed by coma and death within 30 days. The CDC:0180:1 strain also differed consistently from CDC:0179:1 and another nonpathogenic A. (astellallii strain (ATCC 30,011) in isoenzyme makeup, a dissimilarity which probably reflects its pathogenic potential. Among the many genera of small, free-living amoebae that inhabit soil and fresh water, members of only two genera, i.e., Acanitlharnoeba and Naegleria, cause human disease generally leading to death. Only one species of Naegler-ia, N. fovleri, causes a fulminating, rapidly fatal (within 5 to 7 days) disease called primary amoebic meningoencephalitis. Primary amoebic meningoencephalitis afflicts previously healthy children and young adults, usually after fresh water swimming or skiing (14). Several species of Acantlianoeba, i.e., A. castellanii. A. calber-tsoni, A. polyphaga, and A. astronyxis, on

Trichomonas vaginalis is a widely prevalent, sexually transmitted protozoan infecting both males and females. Despite its prevalence, little is known about its contribution to the morbidity rates for urogenital-tract infections. Currently accepted diagnostic methods are limited to the demonstration of the organism in fresh material, identification in stained material, or in vitro cultivation of organisms from the urogenital tract. We have evaluated the indirect hemagglutination test and the gel diffusion test for efficacy in detecting antibodies in serum samples drawn from two population groups. Sera from patients attending a vaginitis clinic had a seropositivity rate of 69% by indirect hemagglutination and 34% by gel diffusion. Seropositivity rates among culture-positive patients were 78% with indirect hemagglutination and 43% with gel diffusion. A group of normal female hospital employees showed seropositivity rates of 30% by indirect hemagglutination and 3% by gel diffusion. Absorption of reactive sera with Trichomonas antigens reduced or abolished the serological reactivity, confirming the specificity of the test. Serological methods can provide a rapid, sensitive, and economical tool to study the epidemiology of this common protozoan infection.