Density regulation of domestic populations of Triatoma infestans in Brazil

Twenty old houses in a rural area of central Brazil were sampled monthly for Triatoma infestans during 16 months. The samples indicated peak adult emergence between January and May, preceded by peak emergence of stage V, IV and III nymphs respectively. Stage I and II nymphs were rarely taken in the samples. A much smaller peak of adult emergence occurred in September; thus the two peaks of adult emergence during the year were consistent with the approximately six months duration of egg-to-adult development usually recorded in laboratory studies.During January, 1977, when the study began, all houses were searched for dead bugs, exuviae, eggs and eggshells. These samples were used to calculate stage mortalities, from which a simple life-table was constructed. These data were combined with laboratory data concerning stage development times and female longevity and fecundity. Sensitivity analysis of the life-table showed it to be most sensitive to small changes in daily mortality rate and total egg-to-adult development time.The data were used to advance an hypothesis that the size of domestic populations of T. infestans is mainly controlled by changes in the egg-to-adult development time and, to a lesser extent, by changes in female reproductivity. Both these factors are in turn controlled by the nutritional status of the bug population, which, if the supply of food, i.e. number of hosts, is constant, is dependent upon the density of the bug population. It is argued that this mechanism of density regulation functions within limits set by the prevailing ambient temperature.     

Nutritional status of domestic populations of Triatoma infestans

This paper establishes that the weight: length ratio of Triatoma infestans is superior to weight alone as a measure of nutritional status. The weight: length ratios of adults, V and IV stage nymphs correlated with their time since feeding. The weight: length ratio of V stage nymphs correlated with their life expectancy expressed as days until moulting to the adult stage. The weight: length ratio of wild females measured on capture did not correlate with the number of eggs laid during the next 30 days, but after feeding on chicken in the laboratory this correlation was shown.The mean weight: length ratio of different classes of bugs was used to compare the nutritional status of T. infestans populations in three rural houses in central Brazil. One house was recently constructed, containing a newly-established population of bugs. One house was over 15 years old, containing a long-established bug population. The third house had been abandoned for six months and the bug population was in decline. The three houses were carefully demolished to allow a large sample of bugs to be collected from each. The mean weight: length ratios of adults, unfed V stage, fed and unfed IV stage, and fed and unfed III stage nymphs from the newly-colonized house were significantly higher than those of corresponding classes of bugs from the long-established bug population, and from the declining bug population.This evidence fulfils a prediction previously made by the author and supports the hypothesis that the density of domestic population of T. infestans depends on the nutritional status of the bugs which is, in turn, limited by the number of hosts available.     

The maximum density of anopheline mosquitoes that can be permitted in the absence of continuing transmission of filariasis

Using two years of mosquito collections from two fixed stations on Guadalcanal it was possible to compare the average man-biting rate with the prevalence of microfilaraemia. One area was found to be free of infection while the other still had one positive case. The DDT residual spraying had caused a change in biting habits of A. farauti No. 1 allowing a greater density of mosquitoes to bite man at times when they had lower microfilaria densities. This difference was compared with the pre-spray density so that the maximum permissible number of mosquitoes biting man without transmission of filariasis taking place, could be calculated.A theoretical value for m of 19.84 had been worked out previously, this study gave a corrected observed value of m of approximately 20, very close to the calculated theoretical value. The situation studied here probably showed incomplete interruption of transmission, so it was considered preferable to recommend a figure of 0.66 average vector man-biting rate per hour indoors for the critical value.     

The mental health of foreign students

Because of the psychological stress associated with university life and the physical and mental stress associated with migration, researchers have become interested in psychological problems of foreign students. In this study four groups of foreign students from different parts of the world were compared with two British groups on a self-report measure of mental health. No sex differences were found yet the overseas students, as a whole, showed significantly more disturbance than either British control or first-year subjects. However, despite many differences between their countries of origin there were no significant differences between any of the overseas groups on the total scale score or any sub-scores. Further, with the exception of Malaysian students, the British subjects were significantly more satisfied with their social lives than the other groups. These findings are discussed in terms of the literature on life events and illness, culture shock and migration and mental health.     

Mortality during heat waves in New York City July, 1972 and August and September, 1973.

Twelve phthalic acid esters, including those commonly used as plasticizers for biomedical devices, were subjected to various biological tests for acute, short-term, and chronic toxicity. Certain aspects of subtle toxicity were investigated as well as overt toxic manifestations. The acute ip LD₅₀ for these compounds in mice ranged from 3.22 to more than 100 g/kg. A comparison of acute LD₅₀ to chronic LD₅₀ reveals that most of these phthalates are 2–4 times more toxic chronically. However, the chronic toxicity of di-n-octyl phthalate was 21.74 times greater than its acute toxicity, while for di-2-ethylhexyl phthalate the chronic toxicity was 27.99 times greater. Most of these compounds produced a prolongation of pentobarbital sleeping time in mice pretreated with a phthalate ester.     

Attitudes to alcohol consumption: The attribution of addiction

Research on smoking has found actor—observer differences in the attributions of addictions. Non-smokers were much more likely to label the average smoker as addicted than the smokers were prepared to label themselves as such. This study sought to determine whether the findings from the studies on smokers generalized to those drinking alcohol. Subjects, who were classified as heavy, moderate, light and non-drinkers on the basis of their self-reported weakly consumption, completed a questionnaire. Results showed that although there were some similarities between findings on the attribution of smoking and drinking, drinkers were less concerned about stopping drinking and less likely to label themselves as addicted. The results were discussed in terms of lay beliefs about the health factors related to drinking.     

A comparison of electrophoretic methods for isoenzyme characterization of trypanosomatids. I: Standard stocks of Trypanosoma cruzi zymodemes from northeast Brazil

An investigation of the relative merits of cellulose acetate electophoresis (CAE) and starch-gel electrophoresis (SGE) was made for 18 enzymes of T. cruzi using standard stocks of zymodemes Z1, Z2 and Z3. The 18 enzymes were those shown previously to be the most suited to routine screening of T. cruzi on starch-gel, namely, aspartate aminotransferase (E.C.2.6.1.1. ASAT); alanine aminotransferase (E.C.2.6.1.2. ALAT); phosphoglucomutase (E.C.-2.7.5.1. PGM); glucosephosphate isomerase (E.C.-5.3.1.9. GPI); malate dehydrogenase (oxaloacetate decarboxylating) (NADP⁺) (E.C. 1.1.1.40. ME); glucose-6-phosphate dehydrogenase (E.C.1.1.1.49 G6PD); malate dehydrogenase (E.C. 1.1.1.37. MDH); aconitate hydratase (E.C.4.2.1.3. ACON); isocitrate dehydrogenase (NADP⁺) (E.C.1.1.1.42. ICD); alcohol dehydrogenase (NADP⁺) (E.C.-1.1.1.2. ADH); lactate dehydrogenase (E.C.1.1.1.27. LDH); aminopeptidase (cytosol) (E.G.3.4.11.1. PEP); pyruvate kinase (E.C.2.7.1.40. PK); phosphoglycerate kinase (E.C.2.7.2.3. PGK); enolase (E.C.4.2.1.11. ENO); hexokinase (E.C.2.7.1.1. HK); mannose phosphate isomerase (E.C.5.3.1.8. MPI); and glutamate dehydrogenase (E.C.1.4.1.2. GD). Of these MDH and PEP failed to give satisfactory patterns on CAE. The cellulose acetate zymograms of the other 16 enzymes were as good as, and in some cases better than, those of starch. Increased CAE resolution for ME and G6PD enabled all three zymodemes to be distinguished. Single CAE bands replaced double SGE bands in some cases, and vice versa, without affecting the zymodeme classification. It was concluded that CAE and SGE were both suitable for isoenzyme characterization and were complementary to each other. CAE characterization of T. cruzi was recommended for use in field work and simple laboratories because of its simplicity, transportability, low maintenance requirements and low capital expenditure. Isoelectric focusing (IEF) of ASAT, ALAT, GPI and PGM on Ampholine PAG plates gave poor results, in our hands, and was considered impracticable for routine characterization of T. cruzi.     

Comparison of topical antibacterial agents in the preparation of varicose ulcers for skin grafting

The short-term effects of five topical antibacterial formulations on the microbial flora of 75 varicose ulcers were studied to develop a preparative programme for skin grafting. The flora before treatment was complex including enterobacteria, pseudomonads, streptococci and staphylococci. Chlorhexidine and gentamicin formulations significantly reduced the number of organisms within 48 h but the antibiotic failed to eliminate streptococci.     

Hepatic structure and function in Papua New Guineans with leprosy

Hepatic function, including plasma bromsulphthalein (BSP) clearance was studied in 20 Papua New Guineans with leprosy: 11 lepromatous (LL) (6 had erythema nodosum leprosum (ENL)) (group A), and 9 tuberculoid or borderline (BT or BB) (group B); 12 controls (group C) were also studied. Four of five with abnormal BSP results had significant complicating or additional factors (hepatic amyloidosis, pustular ENL, hepato-cellular carcinoma and a pyogenic abscess), compared with two of 15 with normal results (tuberculous osteitis and pyogenic osteomyelitis). In nine (five from group A, and four from group B) needle liver biopsy histology was assessed: foci of vacuolated phagocytes and histiocytes, and tuberculoid granulomata were the most frequent lesions; none had cirrhosis.Leprosy is not associated with impaired hepatocellular function unless a severe complication or coincident disease is concurrently present. In this limited study therapeutic agents were not associated with abnormal liver structure or function. When liver function is abnormal in leprosy, another cause (e.g. secondary amyloidosis, sepsis or malignancy) should be searched for.     

Oral ketoconazole and amphotericin B for the prevention of yeast colonization in patients with acute leukaemia

Forty-eight neutropenic patients with acute leukaemia were randomly allocated to receive, as antifungal prophylaxis, either ketoconazole, 400 mg once daily (K), or amphotericin B tablets and lozenges (A), or both ketoconazole and amphotericin B together (K + A). Antifungal prophylaxis was considered to have failed if (1) there was evidence of increasing colonization of the oropharynx or faeces with Candida spp. or other yeasts, or (2) if systemic antifungal therapy was begun empirically. Prophylaxis failed in nine of 17 patients given K, in four of 19 given A, and in four of 12 given K + A. The differences between the three regimens were not statistically significant, neither was there any significant difference in the mean duration of neutropenia before prophylaxis failed. The absorption of ketoconazole was impaired when patients were neutropenic. We conclude that ketoconazole was neither more nor less effective than amphotericin B in the prevention of yeast colonization in neutropenic patients.     

A survey of intestinal helminths among children of different social communities in Madras,India

Approximately 500 children from five social communites in Madras, Tamilnadu, India were surveyed for intestinal helminth infection. The results of the survey indicated that the extent and degree of helminth infections vary significantly (p < 0.001) between communities in Madras. The frequency and intensity distributions in two of the populations, the elite and the fishing communities are discussed. It is suggested that in view of the wide variability, health education should be geared toward each type of community and its specific routes of helminth dissemination rather than mass education, much of which may be useless to large segments of the general population.     

Psychosocial factors and blood pressure

The evidence linking psychosocial factors to sustained blood pressure elevation is highly suggestive and comes from a variety of sources. Hypertensives show increased responsiveness to emotional and mental stimuli. The hemodynamic characteristics of unstimulated hypertensives are similar to those of normotensives under emotional stress. It is likely that the sympathoadrenomedullary system partly mediates these responses, but the evidence in humans is mixed. Stranger evidence comes from studies of mice showing that symbolic stimuli in the form of disordered social relations lead to hypertension and increased heart size. In humans, the evidence linking psychological traits to hypertension is inconsistent. The prevalence of hypertension varies by social class and ethnic group and increases with acculturation from rural, traditional to modernized societies. One possible explanation for this is the attendant psychosocial changes. A variety of stress-management techniques have been shown to lower blood pressure, adding weight to a stress hypothesis.     

A cellulose acetate membrane precipitin (CAP) test for amoebiasis.

A simple precipitin test (CAP) using cellulose acetate membrane has been devised and evaluated against the gel diffusion precipitin (GDP) test. In 251 sera tested by both methods, the CAP was never negative when the GDP was positive (110 sera). 34 sera were negative by the GDP but positive by the CAP; in all of these the patients either had a past history of amoebiasis or were considered to have active amoebiasis. The CAP is technically very simple, the result is available within four and a half hours, and the membranes can be impregnated with antigen and stored for several months. The CAP is slightly more sensitive than the GDP and remains positive longer after the patient has been cured; it seems to be equally specific.     

The susceptibility of chickens to Trypanosoma brucei subspecies

Chickens were susceptible to infection with three different stocks of the subgenus Trypanozoon: two of presumptive Trypanosoma b. brucei and one of T. b. rhodesiense. Two groups of chickens were used: the first hatched following inoculation with either T. b. brucei or T. b. rhodesiense during embryonic development, and the second were infected as adult birds. In both experimental groups, parasitaemia persisted for prolonged periods, but was mostly subpatent and detectable only by subinoculation of blood into mice. In chickens infected as embryos, parasitaemias were patent for five weeks after hatching, but subpatent thereafter (to weeks 13 to 17). Quantitative estimations of the parasitaemias of seven of the birds hatched from embryos inoculated with T. b. brucei revealed fluctuations in the number of circulating trypanosomes, with an initial peak between days 2 to 9 after hatching. Between weeks 13 to 17 after hatching the chickens appeared to have recovered spontaneously from the trypanosome infections. Homologous challenge at week 20 failed to produce a recrudescence of parasitaemia, indicative of a possible acquired immunity.The infections of ten chickens inoculated with either T. b. brucei or T. b. rhodesiense as adult birds were microscopically subpatent throughout the observation period of six weeks, but subinoculation of blood into mice showed the chickens were parasitaemic from week one and thereafter. Different aspects of infection of avian hosts by the Trypanozoon subspecies are discussed.     

Anti-implantation action of a medicated intrauterine delivery system (MIDS)

The effect of a silastic implant made of polydimethyl siloxane tubing and containing 40 mg of norethindrone acetate has been studied in relation to its effect on the subcutaneous tissue of fifty women. Clinically, induration over the implant was detected in only one of them. The histopathology revealed connective tissue response to the silastic implant. The connective tissue showed progressive condensation and maturation of collagen and was associated with chronic inflammatory cell reaction,mainly mononuclear cells and foreign body giant cells. New capillary formation was also seen. However, no anaplastic changes of the fibroblasts were observed.