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Biomedical subjects

P J Whitfield

Publications and source records attributed to P J Whitfield.

At least 19 recordsLinked to original sources
PubMed1995

The plant molluscicide Millettia thonningii (Leguminosae) as a topical antischistosomal agent.

The West African legume Millettia thonningii is used in Ghana as an anthelmintic and as a purgative agent. A chloroform extract of the seeds of Millettia thonningii which is known to be molluscicidal and cercaricidal was topically applied to mouse skin 2 and 24 h prior to exposure to Schistosoma mansoni cercariae. The presence of Millettia thonningii extract components on the surface of the skin appeared to be effective in preventing subsequent establishment of infection. The compound responsible for the activity is thought to be the isoflavonoid alpinumisoflavone.

Administration, Topical↗
PubMed1995

Atanine (3-dimethylallyl-4-methoxy-2-quinolone), an alkaloid with anthelmintic activity from the Chinese medicinal plant, Evodia rutaecarpa.

Phytochemical studies using a range of chromatographic and spectroscopic techniques coupled with in vitro bioassays against larval Schistosoma mansoni, L4 larvae of Ostertagia circumcincta, and adults and larvae of Caenorhabditis elegans have led to the isolation of an active anthelmintic compound in the Chinese medicinal plant Evodia rutaecarpa (Rutaceae) and its identification as atanine (3-dimethylallyl-4-methoxy-2-quinolone). Atanine has not previously been found to possess antiparasitic activity.

Animals↗
PubMed1995

Activity of the molluscicidal plant Millettia thonningii (Leguminosae) toward Biomphalaria glabrata eggs.

A dichloromethane extract of the seeds of the molluscicidal west African legume Millettia thonningii was tested for ovicidal activity toward Biomphalaria glabrata egg masses. The extract was found to be highly ovicidal at concentrations as low as 5 mg/L. Embryonic development of the snails in egg masses was monitored using photomicrographs from which embryonic diameters were estimated. Such measurements revealed that ovicidal effects were developmentally stage specific and normally induced a curtailment of development during the gastrula to trochophore transition.

Animals↗
PubMed1994

Attenuation of Schistosoma mansoni cercariae with a molluscicide derived from Millettia thonningii.

A chloroform extract of molluscicidal plant secondary compounds from the seeds of a West African legume Millettia thonningii was used to attenuate cercariae of Schistosoma mansoni prior to infection of NMRI female mice. Exposure of cercariae to 0.3, 0.6, 1.3, 2.5, 10 or 20 mg/l concentrations of extract for 30 min, immediately before standardized infection, was associated with a concentration-dependent decline in worm establishment at 55 days post-infection. The mean numbers of adult worms established declined from about 17 worms/mouse with control cercariae and those exposed to 0.3 mg/l Millettia to 0.1 worms/mouse after 10 mg/l pre-treatment. Mice exposed to cercariae after 20 mg/l pre-treatment had no adult worms at 55 days post-infection. The activities of cercariae 30 min after exposure to Millettia extract at concentrations up to 2.5 mg/l were similar to those of control larvae: none was immobile. Exposure to higher concentrations of Millettia progressively reduced swimming activity and increased the proportion of immobile cercariae. After pretreatment with 20 mg/l Millettia the majority of larvae were immobile. Levels of anti-parasite antibodies (estimated by ELISA assay using an adult worm-based antigen preparation) rose between 21 and 55 days p.i. with control cercariae and those pre-treated with 2.5 mg/l Millettia. After 5 mg/l pre-treatment, cercariae induced a reduced antibody rise, while mice exposed to cercariae after 10 mg/l pre-treatment showed no rise in anti-parasite antibody levels. These results are discussed in the context of protocols which could possibly use Millettia-attenuated cercariae to induce useful levels of protection in mice towards further cercarial challenge.

Animals↗
PubMed1992

Scanning electron microscope and histological studies of rare triradiate forms of Taenia pisiformis from dogs in Cairo.

Of 5,404 domestic dogs examined for normal and abnormal Taenia pisiformis in Cairo, Egypt, one dog contained 3 triradiate specimens while 3,569 harboured one or more normal cestodes. The study revealed a ratio of one triradiate to 5,620 normal adult worms in the parasite population and a prevalence of 0.02% for the triradiate forms. Polyradiate forms are far less common in this large survey than has been indicated in previous reports.

Animals↗
PubMed1991

The epidemiology of Taenia pisiformis infections in domestic dogs in Cairo.

The epidemiology of Taenia pisiformis infections in domestic dogs in Cairo, Egypt. Over 5000 street dogs humanely killed in a culling programme organized by the Egyptian Ministry of the Interior in the winter of 1986 and the spring of 1987 have been utilized to examine the final host epidemiology of the cestode Taenia pisiformis in Cairo. In the winter months the prevalence of infection was 63.4% and the mean intensity 2.82 per dog: by the spring of 1987 these values had risen to 70.8% and 3.78 respectively. These parasite burdens probably represent the highest infection levels with T. pisiformis yet described from urban dog populations anywhere in the world. The dispersion of T. pisiformis within the street dog population was assessed and found to be significantly aggregated and well described by a negative binomial model of overdispersion (variance/mean ratio: 5.16, coefficient k = 0.795). A separate analysis was carried out of infection in each of 18 circumscribed regional areas of Cairo which revealed considerable area-to-area differences with mean intensities varying between 1.62 and 6.54 and prevalences between 43.3% and 91.2%. The size structure of the winter and spring worm samples were very similar with about 45% of worms less than 35 cm in length, about 35% between 35 and 59 cm, about 20% between 60 and 100 cm and less than 5% greater than 100 cm in length. The epidemiological factors which lead to high T. pisiformis infection levels in Cairo dogs have been considered and the consumption of discarded rabbit offal containing Cysticercus pisiformis by street dogs is regarded as a crucial mode of transmission.

Animals↗
PubMed1989

Resistance to Millettia molluscicide in Biomphalaria glabrata: a quantitative genetical approach.

This paper demonstrates the use of a quantitative genetical technique to assess genetic variance in molluscicide resistance in a Millettia thonningii-Biomphalaria glabrata system. Results indicated that there were significant genetic variances in both snail size and survival time in 10 p.p.m. molluscicide suspension. The possibility of wider applications of this technique in examining the genetic basis of molluscicide or pesticide resistance in target species is discussed.

Animals↗
PubMed1987

Vasoactive intestinal polypeptide-like immunoreactive tegumental cells in the digenean helminth Echinostoma liei: possible role in host-parasite interactions.

Immunocytochemical investigations were carried out on the tegument of the digenean platyhelminth Echinostoma liei. Tests with well-characterised antisera to mammalian vasoactive intestinal polypeptide (VIP) reveal a subpopulation of tegumental cells which contain material immunologically similar to VIP. Control experiments with antisera for a related peptide as well as absorption of primary antisera with VIP or secretin confirm the specificity of the reaction. Immunoreactive processes may be traced from the tegumental cells towards the distal cytoplasm of the tegument. Immunoreactivity is also concentrated in the outer layers of that cytoplasm. The finding of VIP-like immunoreactive material in peripheral nonneuronal, nonendocrine cells in this gastrointestinal parasite of mammals is discussed in terms of its implication for both parasite biology and host pathophysiology.

Animals↗
PubMed1986

Surgery for the psyche: a longitudinal study of women undergoing reduction mammoplasty.

This study suggests that surgery is effective in relieving the psychological distress of women requesting reduction mammoplasty for minimal deformity. Eleven young women who applied for operation on the NHS completed measures of psychoneurosis, mood, self-esteem and body perception. Prior to operation they had a distorted body image, low self-esteem and abnormal psychoneurotic profiles. Following surgery body image returned to a normal range; their self-confidence, and view of their femininity and sexual attractiveness were also enhanced. Improvement was maintained during 6 months of follow-up. These results have implications for the NHS provision of cosmetic surgery for such patients.

Adolescent↗
PubMed1985

Interactions of the cysticercoids of Hymenolepis diminuta and raillietina cesticillus in their intermediate host, Tribolium confusum.

This study was based on the experimental exposure of beetles to homologous and heterologous infections of Hymenolepis diminuta and Raillietina cesticillus. The results demonstrated that, for both species over the range of parasite densities employed, the presence of a primary infection had no effect on the establishment success of an homologous challenge infection. The establishment success of R. cesticillus cysticercoids was not affected by the presence of an H. diminuta infection. The existence of an R. cesticillus infection, however, severely reduced the establishment success of an H. diminuta infection. The reduction in H. diminuta establishment was greatest in R. cesticillus infections less than 10 days old. The plausibility of some of the mechanisms that are potentially responsible for the reduction in H. diminuta establishment success is discussed, as is the possible ecological significance of these results.

Animals↗
PubMed1985

Food intake and body weight changes in mice infected with metacestodes of Taenia crassiceps.

General nutritional effects on female CFLP mice harbouring larval Taenia crassiceps were investigated using groups of mice fed ad libitum on purified diets containing 2%, 4%, 8% and 16% (w/w) protein respectively. When uninfected and infected mice were compared over an experimental period of 20 weeks, it was established that a significantly higher proportion of uninfected mice survived the course of the experiment than infected mice. There was no evidence of the presence of the parasites having any effect on the overall food intake of the mice. Infected mice, however, were found to be significantly heavier, on a fresh weight basis, than their uninfected partners, but the pattern was reversed when the dry weights of mouse carcasses were compared following the removal of parasites. In general, more parasite tissue was recovered from mice feeding on the higher protein diets (8% and 16%).

Animals↗
PubMed1983

Presumptive ciliated receptors associated with the fibrillar glands of the spines of the echinoderm Amphipholis squamata.

The ultrastructure of the cuticle, fibrillar glands and stäbchen (see Reichensperger 1908) of the arm spines of the brittle star Amphipholis squamata are described. Stäbchen are shown to be cuticular projections into which pass one or more uniciliate cytoplasmic processes. The proximal tips of the cilia protrude into the external environment to a variable extent. Evidence is presented for considering these ciliated endings to be the terminations of sensory neurites. Stäbchen are, in consequence, presumed to have a receptor function. Groups of stäbchen are spatially associated with fibrillar gland openings on the sides of spines while the bases of fibrillar gland cells are in contact with axons from the spine nerve which are laden with 45-270 nm diameter, electron-dense, membrane-bounded granules. The possible functional significance of these relationships is discussed in the context of a hypothesis in which fibrillar gland secretions are considered to act as food-catching mucus.

Animals↗
PubMed1983

Parthenogenesis and asexual multiplication among parasitic platyhelminths.

Among flatworms with parasitic and commensal modes of existence, parthenogenesis and asexual multiplication appear to be largely confined to the Digenea and Cestoda, the only parasitic platyhelminths that routinely utilize indirect life-cycles. Parthenogenesis is apparently restricted to a minority of adult digeneans and cestodes inhabiting their final hosts, and a survey is made of the particular modes of parthenogenesis (i.e. apomictic, automictic and generative) which are employed by such adults. Asexual (amictic) multiplication, in the form of fissioning, is demonstrated by young adults of the cyclophyllidean cestode, Mesocestoides corti, but is otherwise not exhibited by adult cestodes or digeneans, other than in the perplexing phenomenon of proglottid formation in polyzoic tapeworms. Secondary multiplication is of ubiquitous occurrence in digenean life-cycles in the form of the proliferation which takes place within sporocysts and rediae (germinal sacs) located in the first intermediate host. The controversy concerning the nature of this multiplication is reconsidered in the context of recent findings which have centred on cellular aspects. On the basis of present evidence germinal sac multiplication should be regarded as an asexual rather than a parthenogenetic process. The cestode asexual multiplication which occurs in intermediate hosts is a function of the metacestode stage of development. Metacestode proliferation is only known from about 20 species and 6 families of polyzoic cestodes with approximately half the described instances occurring in the family Taeniidae. The organization of these proliferative metacestodes, findings concerning their totipotent stem cells and the ontogeny of buds and new scolices are all reviewed. Finally, the capacity for population expansion of multiplicative larval digeneans and metacestodes are compared, while the ecological roles and the genetical consequences of both parthenogenesis and amictic multiplication in the two taxa are also examined.

Animals↗
PubMed1981

Observations on the development of the ovarian balls of Moniliformis (Acanthocephala).

Observations have been made on the ultrastructure of objects identified as ovarian balls from female Moniliformis after 1, 3, 5, 7 and 9 days in the rat. Similar objects are present in the body cavity of female cystacanths from cockroaches. The ovarian balls from 1-day-old worms are formed of several cells which are enclosed within a surface coat. During development, the ovarian balls increase in size and cell number and the interval organization appears to become more complex. After 9 days of development in the rat, the surface coat of the ovarian balls can no longer be observed and microvilli are present. It also appears that the supporting syncytium has been formed by this time.

Acanthocephala↗
PubMed1978

Experimental studies of infection dynamics: infection of the definitive host by the cercariae of Transversotrema patialense.

The number of cercariae of Transversotrema patialense which attach to the fish host Brachydanio rerio, during a fixed exposure period, is shown to be directly proportional to cercarial density within an experimental infection arena. The distribution of successful infections/host is shown to change from a random pattern to an over-dispersed form as cercarial exposure density or duration of host exposure to infection increases. A stochastic simulation model is used to demonstrate that small differences in host susceptibility to infection, within a population of hosts, can generate patterns of dispersion in parasite numbers/host similar to those observed in the experimental studies. Differences in host behaviour, during the period of exposure to infection, are thought to generate variability in host susceptibility to cercarial infection.

Animals↗
PubMed1977

Experimental investigations on the behaviour of the cercariae of an ectoparasitic digenean Transversotrema patialense: general activity patterns.

The activity patterns of the cercariae of Transversotrema patialense have been examined by monitoring the behaviour of individual larvae. Records of three different behavioural modes, namely active, tail-first swimming, passive dropping and resting periods were made separately. The age- and temperature-dependence of the activity patterns during the spontaneously active life of the cercariae were examined and estimates made of the absolute speeds of swimming and dropping. Through the temperature range 25--32 degrees C, the spontaneously active life of cercariae declined from about 18 h to about 6 h. Within this interval, after an initial period of high activity rates, a gradual decline in activity followed. The decline was a result of a decreasing frequency of swimming events rather than any change in the durations of such events. The neural control and energetic significance of the cercarial activity patterns are discussed.

Animals↗