Studies on the Indochina I/CDC strain of Plasmodium falciparum in Colombian and Bolivian Aotus monkeys and different anophelines

The Indochina I/CDC strain of Plasmodium falciparum was isolated from a physician returning to the United States after working in the refugee camps along the Thailand-Kampuchean border. The strain was established in splenectomized Aotus monkeys from Colombia after being grown in vitro for 50 days. During the first three passages in Colombian monkeys, the parasites were not infective to Bolivian Aotus monkeys. After six intervening passages in Saimiri sciureus monkeys, the parasites produced high parasitemias in both Colombian and Bolivian Aotus, but gametocytes were no longer produced. Mosquito infections were obtained only during the first three passages in the Colombian monkeys. The most susceptible mosquito was Anopheles freeborni, followed by An. dirus, An. stephensi, An. maculatus, An. culicifacies, and, rarely, An. gambiae. Sporozoites were found in the salivary glands of the An. freeborni, An. dirus, An. stephensi, and An. maculatus.

Studies on the Cambodian I strain of Plasmodium falciparum in Aotus monkeys

The Cambodian I strain of Plasmodium falciparum, originally from Kampuchea was adapted for development in three different types of Aotus monkeys. High-level parasitemias were readily produced in splenectomized Colombian A. trivirgatus griseimembra monkeys. Initially, only minimal parasitemias developed in A. t. trivirgatus monkeys from Colombia. However, in one animal, adaptation occurred and high-level parasitemias were obtained during the second recrudescence of the infection. Passage to other A. t. trivirgatus monkeys indicated that the parasite was well adapted for development in splenectomized animals; low to moderate parasitemias were still produced in intact animals. This line of the parasite produced high level parasitemias when inoculated into splenectomized Aotus monkeys from Peru. Infections in Anopheles freeborni mosquitoes were obtained as late as the 7th passage in A. t. griseimembra monkeys and as late as the 7th recrudescence of the infection in an individual monkey (348 days after inoculation). The sporogonic cycle was completed in An. freeborni mosquitoes, and one transmission to an A. t. griseimembra monkey via the bites of infected mosquitoes was obtained.

A survey of malaria in Indochinese refugees arriving in the United States, 1980

During the months April-June and October-November 1980, a survey was conducted among Indochinese refugees arriving in California to assess the prevalence of malaria. During the two study periods, 3,433 refugees were met and 3,289 (95.8%) of the arriving refugees were screened for malaria by examining thick blood smears and by indirect fluorescent malaria antibody tests of blood absorbed on filter paper. Examination of the blood smears showed that the overall patency rates were 1.7% and 0.6% for the first and second surveys, respectively. The Cambodian Refugees and refugees from camps in Thailand had the highest patency rate in the first survey. In the second survey, the Cambodian refugees and refugees from camps in Indonesia had the highest patency rate. The average malaria seropositivity rate was 15% in the first and 13.6% in the second survey. The Laotian refugees had the highest rate of malaria seropositivity in both surveys. Plasmodium vivax was the most commonly identified species in blood examination, while a higher rate of seropositivity to P. falciparum was found in both surveys. This study indicates that the malaria infection rate was at least 1.7% based on blood smear examination but might be as high as 45% based on serologic examinations. The results of this study when combined with malaria surveillance indicate that the likelihood of introduced malaria in the United States from the Indochinese refugees is low.

Observations on two strains of plasmodium falciparum from Haiti in Aotus monkeys

Two strains of Plasmodium falciparum originating in Haiti were studied in the Aotus monkey. The Haitian I/CDC strain was first adapted to in vitro cultivation and subsequently inoculated into monkeys. The Haitian III/CDC strain was inoculated directly from a human patient into the Aotus monkey. The strains varied in their levels of pathogenicity to the animals. The Haitian I/CDC strain was highly virulent in six splenectomized animals; in one intact animal, the infection could be controlled but not eliminated with periodic doses of quinine and chloroquine. After subsequent splenectomy, the animal developed high parasitemias and died. No gametocytes developed in any of the Haitian I infections. The Haitian III strain was lethal to five of the 14 splenectomized monkeys inoculated, but some were able to control their infections without drug intervention. Gametocytes developed in all infections that persisted for an adequate length of time, and infections of mosquitoes were obtained both during the primary attack and the first recrudescence of the parasitemia. Of the mosquitoes tested, Anopheles freeborni was most susceptible to infection, followed by An. culicifacies, An. dirus, An. maculatus, and An. albimanus. The Haitian III strain was successfully transmitted to four other splenectomized Aotus monkeys via sporozoite inoculation using An. freeborni.

Demeclocycline in the prophylaxis of self-induced water intoxication

Demeclocycline, a competitive inhibitor of antidiuretic hormone at renal tubules, was studied in a patient with the syndrome of psychosis, psychogenic polydipsia, and episodic water intoxication. Under double-blind, placebo-controlled conditions, demeclocycline substantially reduced the severity and frequency of hyponatremic episodes.

[Effects of guanfacine on pre- and postsynaptic alpha-adrenoceptors studied in comparison with those of clonidine]

Intravenous injections of guanfacine (1 microgram-3 mg/kg) elevated dose-dependently blood pressure in adrenalectomized, pitched rats. The vasopressor activity of guanfacine was weaker than those of clonidine, an alpha 2-agonist and 1-phenylephrine, an alpha 1-agonist. However, the maximal response produced by guanfacine was the same as that produced by clonidine, while it was much smaller than that produced by 1-phenylephrine. The dose-response curve to guanfacine for increase in blood pressure was shifted in a parallel fashion to the right by 1 mg/kg of yohimbine, an alpha 2-antagonist and by 1 mg/kg of phentolamine, a nonselective alpha 1- and alpha 2-antagonist. However, 0.1 mg/kg of prazosin, a selective alpha 1-antagonist, produced an inhibition of the blood pressure rise induced by higher doses of guanfacine, but not that induced by lower doses. Guanfacine (1 microgram-1 mg/kg) inhibited dose-dependently the tachycardia induced by electrical stimulation of spinal nerves at C7-Th1 in adrenalectomized, pithed rats. The maximal inhibition by guanfacine of heart rate increase induced by electrical stimulation was about 60%. These inhibitory effects were antagonized by yohimbine and phentolamine, but not by prazosin. These results indicate that guanfacine is an alpha 2-agonist with approximately equal potency towards the pre- and postsynaptic alpha 2-adrenoceptors, just as clonidine is, but is weaker as an alpha 2-agonist than clonidine.

[The hypotensive effects and mechanism of SGB-483, a newly-synthesized hypotensive agent]

The effects of SGB-483, a newly-synthesized hypotensive agent, on the blood pressure were studied in unanesthetized and anesthetized rats. SGB-483 produced a significant hypotensive action in the conscious SHR and renal hypertensive (clipping) rats, and it caused reversal of the pressor response to adrenaline in the anesthetized Wistar-Imamichi rats, SHR, and clipping rats. In an isolated guinea pig aorta preparation, SGB-483 competitively inhibited the contractile response to phenylephrine with a pA2 value of 7.64 +/- 0.08. In pithed rats that were pretreated with beta-adrenoceptor blocker, the pressor effect of adrenaline (1 microgram/kg) was not completely blocked by either prazosin (1 mg/kg), an alpha 1-selective blocker, or yohimbine (1 mg/kg), an alpha 2-selective blocker. SGB-483 (1 mg/kg) had no effects on the prazosin-resistant part of the pressor effect of adrenaline, but significantly inhibited the yohimbine-resistant part. Clonidine-induced reversal of the tachycardia induced in the pithed rat by cardiac sympathetic nerve stimulation was unaffected by SGB-483, indicating that SGB-483 is a selective antagonist of the alpha 1-adrenoceptor.

The characterization of lymphocytes migrating through chronically inflamed tissues

Afferent lymphatics draining Freund's adjuvant-induced granulomas and efferent lymphatics from normal subcutaneous lymph nodes were cannulated in sheep. It was previously reported that cells collected from these lymphatics, after being radiolabelled with 111In and returned to the animal intravenously, migrated from the blood back through the granuloma or lymph node into the lymph compartment from which they were originally obtained. Afferent lymph cells preferentially migrated out of the circulation in the granuloma rather than the lymph node. The cell responsible for this selective migration was found to be a small recirculating T lymphocyte. Macrophages and lymphoblasts did not demonstrate this migration. Similarly, B cells did not contribute to the lymphocyte migration observed. The migration of lymphocytes through normal uninflamed skin was examined. Afferent cells migrated through normal skin in the same way as through a granuloma, suggesting that neither antigen nor local inflammatory changes were responsible for this migration.

Serologic and parasitologic studies of Entamoeba histolytica in El Salvador, 1974-1978

Serologic and parasitologic studies were done in El Salvador, C.A., from 1974-1978 to examine the reliability of the diagnosis of Entamoeba histolytica infection in an endemic area and to confirm the estimates of morbidity and mortality due to amebiasis. The results suggest that infection with E. histolytica is common, but the estimated prevalence is too high. Misdiagnosis occurring in hospital and public health laboratories was documented. Data collected from examining family members of persons with E. histolytica infection and disease indicate that most infections are asymptomatic, and support the hypothesis that estimates of morbidity and mortality rates are excessive.

A comparison of lymphocyte migration through intestinal lymph nodes, subcutaneous lymph nodes, and chronic inflammatory sites of sheep

The migration of 51Cr- and 111In-labeled lymphocytes from blood to various lymph compartments was studied in sheep. When lymphocytes were isolated from lymph, radiolabeled, and returned intravenously to the same animal, nonrandom patterns of lymphocyte migration were observed, which depended on the source of the labeled cells. Lymphocytes isolated from intestinal (jejunum, ileum, or ileocecal junction) efferent lymph always produced greater specific activity in the efferent intestinal lymph than in the efferent lymph of subcutaneous (popliteal or prefemoral) lymph nodes. Conversely, lymphocytes isolated from the efferent lymph of subcutaneous lymph nodes produced greater specific activity in the efferent lymph of subcutaneous lymph nodes than in the intestinal efferent lymph. Unit gravity sedimentation of the free-floating lymphocytes in intestinal efferent lymph demonstrated that small, recirculating lymphocytes, but not lymphoblasts, were responsible for the radioactivity recovered in lymph. The most dramatic examples of nonrandom lymphocyte migration were seen when the migration of lymphocytes was compared between the intestinal efferent lymph and through sites of chronic inflammation.

Comparative studies of three strains of Plasmodium falciparum isolated by the culture method of Trager and Jensen

The ease which Plasmodium falciparum parasites adapt to culture by the method of Trager-Jensen is variable. The strain characteristics of the first three isolates we cultured differed markedly, depending on the ease of adaptation. The West African I, which was cultured readily, proved to be sensitive to all antimalarials assessed by an in-vitro method, caused benign infections in Aotus monkeys, and produced gametocytes both in the cultures and in Aotus monkeys. In contrast, parasites of the Liberian I and Haitian I strains, both of which required an adaptive period of a month or longer proved more tolerant to chloroquine, quinine, and cycloguanil but sensitive to pyrimethamine; commonly produced fatal infections in Aotus monkeys, and did not produce demonstrable gametocytemia. That the differences may be due to the selection of a more virulent and drug tolerant subpopulation is suspected. The implication of these findings, particularly as it may apply to the epidemiology of chloroquine resistant falciparum malaria, is discussed.

Transmission of Plasmodium vivax from Vietnam by four different anophelines

Infections of the SV-I strain of Plasmodium vivax from Vietnam were transmitted via the bites of infected Anopheles stephensi, An. maculatus, and An. balabacensis balabacensis mosquitoes. Infected salivary glands were also found in An. freeborni mosquitoes. In 18 successful transmissions, prepatent periods ranged from 10--17 days. Four black volunteers failed to develop infections even though they were fed upon by heavily infected An. maculatus and An. b. balabacensis mosquitoes.

Measurement of lymphocyte traffic with indium-111

This study was designed to assess the use of 111indium as a radioactive marker for the investigation of lymphocyte recirculation in the sheep. Lymphocytes were collected from sheep with indwelling catheters in the efferent lymphatic ducts of peripheral lymph nodes and labelled with 111In-oxine or Na2 51CrO at doses of 10 microCi and 50 microCi/10(8) cells respectively. After intravenous injection the lymphocyte specific activity (c.p.m./10(7) cells) in blood and lymph was measured for several days. The maximum specific activity in efferent lymph was twelve-fold greater with 111In than with 51Cr-labelled cells. The kinetics of lymphocyte traffic as measured in double labelling experiments was very similar. The modal transit time was 21.6 hr with each isotope. The recovery of 111In-labelled cells was not significantly different from cells labelled with 51Cr. In vivo viability of the labelled cells was further supported by the normal proliferative response observed with 111In-labelled lymphocytes compared to unlabelled cells in the normal lymphocyte transfer reaction. In conclusion, 111In-oxine is an excellent radioactive label for lymphocytes in the sheep. Because of its high counting efficiency and cell labelling characteristics one can label as few as 10 million lymphocytes, or a subpopulation of cells, and assess their recirculation.

Chloroquine-resistant Plasmodium falciparum from East Africa: cultivation and drug sensitivity of the Tanzanian I/CDC strain from an American tourist

A strain of Plasmodium falciparum, designated Tanzanian I/CDC, from an American tourist returning from Tanzania, was isolated in vitro and in the Aotus monkey. Clinically, the infection showed a late recrudescent pattern of chloroquine resistance. In 2 inoculated Aotus monkeys, the infection recrudesced after a dose of chloroquine (40 mg/kg) curative for sensitive P. falciparum strains in the Aotus monkey. In 4 ,dditional monkeys two primary infections and one of the recrudescent parasitaemias were cured with a 100 mg/kg dose of chloroquine; the second recrudescent parasitaemia was cured with an additional 40 mg/kg dose of chloroquine. The 48 h in-vitro chloroquine-sensitivity test demonstrated that the Tanzanian I/CDC strain had a pattern of chloroquine resistance similar to a reference resistant strain, the Vietnam-Oak Knoll (FVO). These studies reinforce reports which suggest that chloroquine-resistant malaria is being transmitted in East Africa.

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.

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.

Studies on the West African I strain of Plasmodium falciparum in Aotus trivirgatus monkeys

The West African I strain of Plasmodium falciparum was isolated from a commercial airline pilot who had an overnight stay in Nigeria. Once established in the Aotus trivirgatus griseimembra monkey, the parasite produced high parasitemias and readily infected mosquitoes. Anopheles freeborni and An. maculatus mosquitoes transmitted the infection to additional animals. Infected salivary glands were also seen in An. culcifacies. Comparative infectivity studies indicated the most susceptible mosquito to be An. freeborni, followed by An. culicifacies, An. maculatus, and An. balabacensis balabacensis. Only 2 An. albimanus mosquitoes were infected out of 450 examined. The one A. t. trivirgatus monkey inoculated with this strain had very low levels of parasitemia.

The continuous cultivation of Plasmodium fragile by the method of Trager-Jensen

Using the Trager-Jensen method, a second malaria species, Plasmodium fragile, a simian counterpart to the human malaria P. falciparum, has been cultivated successfully. The average growth rate every 3--4 days was 5-fold and the average number of merozoites observed was 14. To date, only rhesus monkey red blood cells (RBC) would support the long-term cultivation of this parasite. Short-term observations indicate that RBC from the squirrel monkey (Saimiri sciureus) may support growth but human RBC of each of the four major AB-O types failed to support growth of the parasite. Availability of the P. fragile-rhesus monkey model would allow for a second parasite-host system for the in vitro and in vivo study of the immunologic responses of the falciparum-like parasite in a more natural host.

The use of exchange transfusions: a potentially useful adjunct in the treatment of fulminant falciparum malaria

Fulminant falciparum malaria with greater than 500,000/mm3 parasites in the peripheral blood portends a poor prognosis. We recently managed a patient who had greater than 1.2 million/mm3 parasitized erythrocytes in her peripheral blood, following initially inadequate antimalarial therapy, with exchange transfusion in addition to conventional chemotherapy. This patient recovered from her disease despite severe cerebral involvement and acute failure. We feel that exchange transfusion was a useful adjunct and should be considered in patients with life threatening falciparum malaria when conventional measures fail to control the disease.

Protein bound carboxyl-methyl ester as a precursor of methanol formation during oxidation of dimethylnitrosamine in vitro

Protein modification with dimethylnitrosamine was studied in vitro in the presence of hamster liver microsomal fraction. Incorporation of radioactive methyl groups from dimethylnitrosamine into the exogenously added protein was dependent on the microsomal mixed function oxidase system. The methylation yielded chemically labile and stable products. The former was completely hydrolyzed by the mild alkaline treatment, pH 7.4, 100 degrees C, for 5 min and the hydrolytic product was identified as methanol indicating that the activated methyl groups from dimethylnitrosamine were incorporated into a protein as a carboxyl-methyl ester. Thus, it is suggested that methanol, recovered as one of the products during the biodegradation of dimethylnitrosamine [8], is derived, at least in part, from protein carboxyl-methyl ester which is unstable under physiological conditions.

Studies on the Santa Lucia (El Salvador) strain of Plasmodium falciparum in Aotus trivirgatus monkeys

The Santa Lucia strain of Plasmodium falciparum was isolated from El Salvador, Central America, and established in Aotus trivirgatus monkeys. Transmission from monkey to monkey via the bites of infected Anopheles freeborni, A. maculatus, and A, albimanus mosquitoes was obtained in 20 of 27 attempts. Prepatent periods in the monkeys ranged from 17 to 46 days with a mean of 24.3 days. Parasitemias and mortality were higher following sporozoite inoculation into animals which had been previously infected with P. vivax than in those with no previous malaria experience. Monkeys previously infected with P. vivax and P. cynomolgi had lower maximum parasitemias than those previously infected with P. vivax only.

Reduced antibody-dependent cell-mediated cytotoxicity in systemic lupus erythematosus

The peripheral blood mononuclear cells from twenty-three patients with SLE were studied. They showed a reduction in antibody-dependent cell-mediated cytotoxicity. This reduction was significantly related to disease activity. No correlations were found with other clinical features. Some of the possible explanations for this finding are discussed.