PubMed Health⌕ Search

Biomedical subjects

B E Matthews

Publications and source records attributed to B E Matthews.

13 recordsLinked to original sources
PubMed1993

Mating in the nematode parasite Strongyloides ratti: proof of genetic exchange.

Strongyloides, a parasitic nematode, has a complex life cycle that represents a transition between free-living and purely parasitic ways of life. By using minisatellite DNA fingerprinting, we have detected a large number of polymorphic loci in cloned lines of S. ratti. In controlled crosses between free-living adults of S. ratti, we show that genetic exchange, consistent with normal sexual reproduction, occurs. This is in contrast to earlier cytological studies which claimed that reproduction in this organism was by pseudogamy, and thus that inheritance was maternal only.

Animals↗
PubMed1992

On the biological and biochemical nature of cloned populations of Strongyloides ratti.

Seven geographically varied isolates of Strongyloides ratti were cloned. Each clone was examined for the degree of homogonic development of the free-living generation and by enzyme electrophoresis. Considerable variation was found between the clones in the degree of development that was homogonic. In contrast, the clones were indistinguishable by enzyme electrophoresis.

Animals↗
PubMed1985

The influence of temperature and osmotic stress on the development and eclosion of hookworm eggs.

Time lapse video micro recording techniques have been used to investigate the development and eclosion of Ancylostoma ceylanicum and A. tubaeforme eggs under a range of temperature and osmotic conditions. Over the range 15 to 35 degrees C increasing temperature resulted in decreased development time, the hyperbolic form of the curve being similar to that found by other workers. The adoption of a developmental parameter to mark the start of timing provided more reproducible results than previously reported. Osmotic stress in the range 0-600 mOsM/kg provided by a number of inorganic salts and organic sugars increased hatching time but did not greatly reduce the percentage that hatched. There was no correlation between the ionic composition of the solution and its effect on the eggs. Solutions of EDTA, carbonates and iodides markedly reduced hatching. Behavioural studies of the pre-hatched larvae suggested that the eggs were permeable and susceptible to osmotic and ionic changes early in their development and well before they were ready to hatch. No appreciable differences were found between the two species of hookworm investigated.

Ancylostoma↗
PubMed1982

Skin penetration by Necator americanus larvae.

Skin penetration by Necator americanus larvae has been investigated in vitro. Larvae were able to penetrate completely human skin from both the epidermal and dermal directions; their passage through the epidermis was marked by cellular destruction. Removal of chloroform soluble skin lipids affected both the percentage of larvae invading and the percentage exsheathing. The larvae released an enzyme at about 37 degrees C, which showed peak activity against azocoll at 37 degrees C and pH 8. It is suggested that initial invasion is a mechanical process and that the enzyme is functional in passage through the germinal layers of the epidermis.

Animals↗
PubMed1982

Behaviour and enzyme release by Anisakis sp. larvae (Nematoda: Ascaridida).

Anisakis sp. larvae when incubated in vitro produced secretions/excretions which released the dye from an azocoll substrate, indicating protease activity. The optimal conditions for enzyme release and activity were a temperature of 37 degrees C and a pH of 7.5. In addition the larvae showed peak behavioural activity at 37 degrees C, the body temperature of the final, marine mammalian host. The results are discussed in relation to their possible significance to the invasion of the various hosts in the life-cycle.

Animals↗
PubMed1982

Survival and behavior of Onchocerca gutturosa microfilariae in vitro.

Microfilariae of Onchocerca gutturosa were extracted from the skin of the bovine naval by teasing in saline and then suspending the skin in a gauze bag overnight in Tyrode's solution with 20% human serum. They survived for ten days in this medium, with antibiotics, in plastic microtitration plates at 11 C. After dispersal in flat containers, microfilariae slowly assumed clumped dispersion patterns. They also accumulated in glass wool, suggesting that aggregation was a tactile phenomenon. Analysis of videotapes of microfilarial movement indicated that activity, expressed as the number of undulations present on the body and the rate of knot formation (where the microfilaria held itself tightly coiled), increased up to 40 C and thereafter declined. The rate of headwave formation, however, appeared constant up to 40 C after which it declined. Where the greatest number of undulations were found on the body the wave amplitude was minimal. Because greater apparent activity was not correlated with increased forward progression, microfilariae at lower temperatures may travel farther than those at 40 C. This may relate to site preference in the host and to uptake by the vector Simulium ornatum.

Animals↗
PubMed1975

Mechanism of skin penetration by Ancylostoma tubaeforme larvae.

Skin penetration by infective Ancylostoma tubaeforme larvae has been investigated cinematographically and using in vitro techniques. The dermal tissue appears to cause little hinderance to larval migration but complete penetration through the skin from the dermal direction did not occur, although total penetration from the epidermal surface was frequently accomplished. No evidence could be found for enzymic secretions emanating from the worms under conditions that gave positive results from Necator americanus and Strongyloides fülleborni infective larvae. The results indicated that A. tubaeforme was able to penetrate without the use of enzymic secretions and an alternative, mechanical mechanism for penetration is advanced.

Adenosine Triphosphate↗