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Biomedical subjects

W Chin

Publications and source records attributed to W Chin.

At least 55 records · Page 3Linked to original sources
PubMed1983

A simple field kit for the determination of drug susceptibility in Plasmodium falciparum.

A field kit has been developed which greatly simplifies the performance of the 48-hour in vitro test for drug resistance in Plasmodium falciparum. The kit uses an easily reconstituted lyophilized culture medium, and requires only a fingerprick blood sample. In parallel tests with 13 isolates of P. falciparum in Haiti, the new technique had a success rate equal to that of the previously described method, with comparable results in terms of parasite susceptibility in vitro to chloroquine and pyrimethamine.

Chloroquine↗
PubMed1983

The in vitro cultivation of Plasmodium gonderi.

Plasmodium gonderi, one of the vivax-type simian parasites, has been cultured in vitro by the candle jar method and by the sealed flask method. It showed a 48-hour asexual cycle and maintained its morphologic integrity. The effect of different sera (human, rabbit, and horse) was tested in culture and compared with results using rhesus serum. Growth was lower in rabbit and horse serum, but higher in human serum. Compared with individual human and rhesus serum, the multiplication rate in combined rhesus and human sera (1:1) was greater. In addition, human erythrocytes proved refractory to invasion by P. gonderi in vitro.

Methods↗
PubMed1983

Plasmodium inui and Babesia microti infections in the squirrel monkey, Saimiri sciureus.

The course of Plasmodium inui and Babesia microti infections was studied in seven splenectomized squirrel monkeys (Saimiri sciureus) of Guyanan or Bolivian origin. Three of the monkeys were infected with P. inui either by the inoculations of parasitized blood or by the bite of infected mosquitoes. The remaining four monkeys were infected by the inoculation of parasitized blood, containing P. inui and B. microti in three and with B. microti only in one. The infection in all seven animals was severe, terminating fatally.

Animals↗
PubMed1983

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.

Animals↗
PubMed1983

Studies of the Sal I strain of Plasmodium vivax in the squirrel monkey (Saimiri sciureus).

The Sal I strain of Plasmodium vivax was successfully adapted to three phenotypes of the squirrel monkey, Saimiri sciureus. Through five linear blood passages, parasitemias in excess of 200,000/mm3 blood were attained; Bolivian phenotype Saimiri appear to develop higher peak parasitemias. Sporozoites of the Sal I strain inoculated intravenously produced patent parasitemias in all five squirrel monkeys challenged, with prepatent periods ranging from 21 to 38 days. Anopheles freeborni and An. gambiae were the most susceptible of eight anopheline species fed on infected squirrel monkeys. As a model for in vivo studies of P. vivax the Sal I strain in Saimiri has great potential.

Animals↗
PubMed1982

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.

Adult↗
PubMed1982

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.

Antibodies↗
PubMed1982

[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.

Adrenalectomy↗
PubMed1982

[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.

Adrenergic alpha-Antagonists↗
PubMed1982

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.

Animals↗
PubMed1982

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.

Animals↗
PubMed1982

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.

Animals↗
PubMed1981

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.

Adolescent↗
PubMed1980

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.

Animals↗