Ancylostoma duodenale and Necator americanus: effect of temperature on egg development and mortality

Parasitology ◽  
1989 ◽  
Vol 99 (1) ◽  
pp. 127-132 ◽  
Author(s):  
G. Smith ◽  
G. A. Schad

SUMMARYThe development and mortality of the eggs of Ancylostoma duodenale and Necator americanus in distilled water were monitored over a range of temperatures between 15 and 35°C. Egg demography was examined within the context of a fourparameter mathematical model of development and mortality. Over the range of temperatures studied, egg mortality (μ) was an increasing exponential function of temperature (T) measured in degrees Celsius. A single model adequately described the mortality of both species (ln [μ] = 0·041*T − 6·87). The minimum time (τ) to hatching was consistently less for A. duodenale (ln [1/T] = −(0·79+53·05*[l/T]) than N. americanus (ln [1/T] = −(0·99 + 53·05*[l/T])). The hatching rate [σ when t > τ) was an increasing function of time and temperature in both cases, but the precise functional relationship was species specific.

1968 ◽  
Vol 2 (4) ◽  
pp. 169-214 ◽  
Author(s):  
Ruy Gomes de Moraes

1 - Foram examinadas as fezes de 2.666 indivíduos, operários e funcionários de duas Emprésas industriais, situadas, uma na cidade do Rio de Janeiro e outra no Estado do Rio (Brasil); 2 - Dos 2.666 indivíduos, 1941 (72.80%) estavam parasitados por um ou mais helmintos e 725 (27,20%) tinham seus exames de fezes negativos; 3 - De cada um dos 2.666 indivíduos foi feito um hemograma completo, tendo sido aproveitada a taxa de eosinófilos que, em associação com os exames de fezes, constituiu o objeto principal dêste trabalho. 4 - Na Tabela A observa-se o número de vêzes em que cada um dos vermes foi observado e seus respectivos percentuais. Embora não seja um trabalho de epidemiologia, verifica-se que 46,81% são infestados pelo Trichuris trichiura; 23,85% pelo Strongyloides stercoralis; 22,46% pelo Necator americanus e/ou Ancylostoma duodenale; 20,51% pelo Ascaris lumbricóides; 1,65% pelo Schistosoma mansoni; 0.67% pelo Enterobius vermicularis; 0,26% por Taenia solium ou T. saginata e 0,11% por Hymenolepis nana; 5 - Os exames de fezes foram feitos pelos métodos de Faust (ou de Ritchie), de Willis, de Baermann e de sedimentação; 6 - A eosinofilia anotada foi a relativa ou em seu percentual, sendo considerada hipereosinofilia uma taxa de eosinófilos igual ou superior a 5% (Eo > 5%); 7 - Foram abordados de modo conciso os fatores que provocam oscilações na eosinofilia normal tais como a idade, a raça, as horas do nictêmero, os fatores físicos, o sexo, os fatores químicos e outros; 8 - Tratou-se de modo mais extenso das diferenças entre as hipereosinofilias parasitárias e não parasitárias, tendo sido focalizada a dinâmica da eosinofilia traduzida na curva de Lavier. 9 - A distribuição dos 2.666 casos foi feita pelos diferentes graus de eosinofilia, tendo sido levantados gráficos e traçadas curvas sôbre a distribuição de cada helminto e de suas associações. 10 - Por ser necessário à explanação do assunto, foi criado o "índice eosinofilico", o qual corresponde à relação entre o número de casos de um determinado grupo com Eo > 5% e Eo < 5%. Para o total de casos positivos, ao "índice eosinofílico" denominamos "índice eosinofílico médio" em para o total dos negativos "índice eosinofílico residual"; 11 - Estabelecendo-se o "índice eosinofílico", pode-se ajuizar a capacidade eosinofilogênica de cada helminto isoladamente, bem como a de suas associações; 12 - Atenção especial foi dada aos problemas da existência da hipereosinofilia nos casos com exames coprológicos negativos para helmintos, tendo-se passado em revista vários dos aspectos biológicos que o assunto comporta; 13 - Outra questão de grande importância clínica explanada neste trabalho é a do encontro de casos de parasitismo por vermes, sem hipereosinofilia. O autor, baseado em seus dados e em outros colhidos na literatura sôbre o assunto, discute a fisiopatologia da eosinopoiese nas helmintoses e ojerece uma interpretação para êste fato ainda não defintivamente esclarecido.


2007 ◽  
Vol 59 (3) ◽  
pp. 227-231 ◽  
Author(s):  
S. Zivkovic ◽  
M. Devic ◽  
B. Filipovic ◽  
Z. Giba ◽  
D. Grubisic

The influence of high NaCl concentrations on seed germination in both light and darkness was examined in the species Centaurium pulchellum, C. erythraea, C. littorale, C. spicatum, and C. tenuiflorum. Salt tolerance was found to depend on the life history of the seeds. To be specific, seeds of all five species failed to complete germination when exposed to continuous white light if kept all the time in the presence of 100-200 mM and greater NaCl concentrations. However, when after two weeks NaCl was rinsed from the seeds and the seeds were left in distilled water under white light for an additional two weeks, all species completed germination to a certain extent. The percent of germination not only depended on NaCl concentration in the prior medium, but was also species specific. Thus, seeds of C. pulchellum, C. erythraea, and C. littorale completed germination well almost irrespective of the salt concentration previously experienced. On the other hand, seeds of C. tenuiflorum completed germination poorly if NaCl concentrations in the prior media were greater than 200 mM. When seeds after washing were transferred to darkness for an additional 14 days, they failed to complete germination if previously imbibed on media containing NaCl concentrations greater than 400 mM. However, the seeds of all species, even if previously imbibed at 800 mM NaCl, could be induced to complete germination in darkness by 1 mM gibberellic acid. .


Author(s):  
Volodymyr Fedorov ◽  
Vladislav Kikot ◽  
Nataliya Shtefan

The article considers a two-stage gyrocompass with a rigid torsion suspension of the moving part. The principle of its action is based on balancing the elastic moment of the torsion bars with the gyroscopic moment. When this condition is met, the azimuth of the steady-state position of the rotor axis is calculated from the known kinetic moment , latitude and angular rigidity of the torsion bars, and the measured angle of rotation of the moving part of the gyroscope relative to its initial position. The “aging of the material” of the torsion bars, the effect of temperature on them, etc., leads to an uncontrolled change in the angular stiffness of the torsion bars, which, in turn, leads to an error in determining the position of the meridian. A method is proposed for determining the position of the meridian under conditions when the angular stiffness of the torsion is unknown. The method involves observing the motion of the gyroscope in a mode where the kinetic momentum changes linearly (the rotor accelerates). This movement is associated with the movement of the mathematical model of a two-stage gyrocompass in the same mode in the form of a differential equation of motion or in the form of its solution. As a result of minimizing the discrepancy between the real movement of the gyrocompass and the movement of its mathematical model, the “best estimate” of the parameter characterizing the position of the meridian and the “best estimate” of the angular stiffness of the torsion bars in this dimension are found. The results of modeling the corresponding information processing algorithms are considered. The advantages of the proposed method compared with traditional methods are indicated .


1994 ◽  
Vol 192 (1) ◽  
pp. 107-118 ◽  
Author(s):  
C Zollikofer

The locomotory behaviour of 12 ant species belonging to four different genera (Formicinae: Cataglyphis, Formica, Lasius; Myrmicinae: Myrmica) was studied by filming individuals during walking on smoked-glass plates. Subsequent multivariate analyses of walking kinematics and footfall positions showed marked species-specific as well as size-dependent differences in the locomotory behaviour. The geometric properties of the footfall patterns resulting from the alternating tripod gait scale to leg dimensions in a geometric manner. At high speed, footprint distances between succeeding tripods exceed maximum leg extension, indicating that ants are 'trotting' from one tripod to the next one with intermittent aerial phases. In at least one species (Cataglyphis bombycina), there is evidence for quadrupedal locomotion at the highest speed. The functional relationship between stride length (s, the distance between successive footprints of the same foot) and speed (v) was best described by a curvilinear model, s=avb. Exponent b ranges from 0.3 to 0.6 and reveals differences between species. Within species, exponent b is constant, whereas factor a scales to leg length. Females and males show metachronal interleg coordination patterns rather than the alternating tripod coordination pattern seen in workers of the same species.


1954 ◽  
Vol 31 (3) ◽  
pp. 386-401 ◽  
Author(s):  
JOHN E. TREHERNE

1. The exchange of labelled sodium between the external medium and the haemolymph and whole body has been investigated in the larva of Aedes aegypti. The time for half exchange was of the order of 62 hr. 2. It was found that most of the exchange of labelled sodium occurred through the anal papillae, although smaller amounts enter the haemolymph through the gut and general body surface. Transfer constants have been used to describe the resultant turnover of labelled sodium in the whole system. 3. The rate of uptake of sodium was independent of the external concentrations used in these experiments. 4. Potassium ions do not compete with sodium for uptake, which suggests that separate mechanisms are responsible for the accumulation of these two ions. 5. Larvae were able to retain the sodium in the haemolymph, with relatively little loss, in glass-distilled water. 6. The effect of temperature on the rate of uptake of labelled sodium has been investigated.


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