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Biomedical subjects

R M Anderson

Publications and source records attributed to R M Anderson.

At least 325 records · Page 18Linked to original sources
PubMed1982

Directly transmitted infections diseases: control by vaccination.

Mathematical models for the dynamics of directly transmitted viral and bacterial infections are guides to the understanding of observed patterns in the age specific incidence of some common childhood diseases of humans, before and after the advent of vaccination programs. For those infections that show recurrent epidemic behavior, the interepidemic period can be related to parameters characterizing the infection (such as latent and infectious periods and the average age of first infection); this relation agrees with the data of a variety of childhood diseases. Criteria for the eradication of a disease are given, in terms of the proportion of the population to be vaccinated and the age-specific vaccination schedule. These criteria are compared with a detailed analysis of the vaccination programs against measles and whooping cough in Britain, and estimates are made of the levels of protection that would be needed to eradicate these diseases.

Age Factors↗
PubMed1982

The population biology and control of Ascaris lumbricoides in a rural community in Iran.

Adults of Ascaris lumbricoides were recovered from 252 persons in the village of Jazin near Esfahan, Iran after treatment with pyrantel pamoate. This horizontal study provides information on age-specific prevalence rates, intensities of infection, frequency distributions, sex ratios and eggs per gram of stool at different parasite intensities. Recruitment of A. lumbricoides was then monitored at 7, 30, 60, 90 and 365 days after treatment in 110 persons. A separate sample population was examined at monthly intervals and, in addition, the stool of each member of a nine-person family was examined for 10 consecutive days. These data are analysed and used to describe the dynamics of transmissions and recruitment of A. lumbricoides in Jazin. The population dynamics of ascariasis are discussed in the context of R the basic reproductive rate of the parasite. The relationships of R with frequency distributions, prevalencies and worm burdens are discussed. Because of the considerable potential of A. lumbricoides to re-infect man in endemic areas, it is shown that it will be difficult to eradicate ascariasis by the use of chemotherapy, even when drugs with a high efficacy are used repeatedly.

Adolescent↗
PubMed1982

Transmission of Schistosoma mansoni from man to snail: experimental studies of miracidial survival and infectivity in relation to larval age, water temperature, host size and host age.

We report the results of experimental work on (a) the influence of temperature on the age-dependent survival and infectivity of the miracidia of Schistosoma mansoni and (b) the relationship between snail age, snail size and susceptibility to infection. The death rate of miracidia declined exponentially with age where life-expectancy was maximal (approximately 16 h) at 15 degrees C. Infectivity also declined rapidly with larval age but, in contrast to larval survival, the rate of infection was at a maximum at 25 degrees C. Snail susceptibility was shown to be more closely correlated with host size rather than host age. Susceptibility declined exponentially with increased host size. Size-dependent susceptibility was shown to generate concave age-prevalence curves for infection within snail populations, where the maximum prevalence is generated in snails of intermediary age. Simple mathematical models are developed to aid estimation of larval survival and infection rates and experimental results are discussed in relation to the overall transmission success of the parasite from man to snail.

Aging↗
PubMed1982

Transmission of Schistosoma mansoni from man to snail: laboratory studies on the influence of snail and miracidial densities on transmission success.

The relationship between infection success, the density of Schistosoma mansoni miracidia and the density of the snail host Biomphalaria glabrata was examined experimentally. Within laboratory infection arenas, the distribution of miracidial infections/snail was approximately uniform and the net rate of snail infection was directly positive binomial to miracidial density. In contrast, however, the rate of infection declined exponentially as snail density increased. Mathematical models are developed to aid in the estimation of infection rates and experimental results are discussed in the context of the transmission dynamics of schistosomiasis.

Animals↗
PubMed1982

Processes influencing the distribution of parasite numbers within host populations with special emphasis on parasite-induced host mortalities.

The paper examines the factors which generate various patterns of dispersion in the distribution of parasites within their host populations. Particular emphasis is placed on the role played by chance elements in the growth and decay of parasite populations and on the influence of different types of demographic processes. It is argued that observed distributions are dynamic, rather than static, entities generated by opposing forces, some acting to create over-dispersion and others acting to generate under-dispersion. Monte Carlo simulation experiments, based on probability models of the growth and decay of host and parasite populations, are used to study the dynamics of parasite dispersion. Attention is specifically focused on the role played by parasite-induced host mortality. It is shown that, for certain types of host-parasite associations, convex curves of mean parasite abundance in relation to age (age-intensity curves), concomitant with a decline in the degree of dispersion in the older age, classes of hosts, may be evidence of the induction in host mortality by parasite infection. Empirical evidence is examined in light of this prediction. In general, however, simulation studies highlight the technical difficulties inherent in establishing clear evidence of parasite-induced host mortality from ecological studies of hosts and parasites in their natural habitats.

Aging↗
PubMed1982

An evaluation of dynamic pituitary function tests in patients with pituitary tumours.

In a prospective study of 26 patients with macroadenoma of the pituitary (14 secretory and 12 non-secretory), basal and stimulated pituitary hormone levels were used to detect hypothalamic dysfunction and to examine pituitary hormone secretion before and after hypophysectomy. Suprasellar tumour extention with hypothalamic compression occurred in 18 patients but was not consistently associated with hormonal tests indicative of hypothalamic dysfunction. In patients with secretory tumours, secretory activity was adequately assessed by basal hormone levels alone, which showed that surgery reduced hormone levels by a mean 85% in acromegaly and by a mean 55% in prolactinomas. Preoperatively, pituitary reserve of hormones not being hypersecreted was often normal, despite large tumour size and hypothalamic compression. Even after apparently complete pituitary removal at surgery, normal responses to stimulatory tests could sometimes be detected. Conventional dynamic tests are only of limited value in the assessment of hypothalamo-pituitary dysfunction in patients with large pituitary tumours and should not be used indiscriminately in such individuals requiring surgery.

Acromegaly↗
PubMed1982

Cerebellar cortical degeneration with ovarian carcinoma.

A case is described of progressive cerebellar degeneration in association with ovarian carcinoma, with nearly 4 years elapsing between the onset of neurological illness and the discovery of the carcinoma. Neither treatment with prednisolone nor surgical removal of the tumour effected any improvement, CAT scanning late in the illness showed marked cerebellar atrophy. Histology at post-mortem showed complete loss of cerebellar Purkinje cells. The cerebrospinal fluid gave weak binding to multiple neural components in a solid-phase radio-immuno-assay.

Atrophy↗
PubMed1982

Review of the current status of whole-body hyperthermia administered by water circulation techniques.

Since the mid 1970's, whole-body hyperthermia (WBH) has been actively investigated for the treatment of patients with cancer in the United States. Two basic techniques are currently used; one involves transcutaneous transfer of heat by circulation of heated water, and, in the other, extracorporeally circulated blood is heated. Studies which have used the water circulation method are compared as to protocol design, toxicities encountered, and responses observed with and without concomitant chemotherapy. In vitro data indicating that faster rates of heating are associated with greater cytotoxicity due to hyperthermia alone or with several anticancer drugs are discussed in relationship to the design of future techniques for administration of WBH.

Animals↗
PubMed1981

Population dynamics of fox rabies in Europe.

A simple mathematical model for the overall dynamics of the interaction between fox populations and rabies is presented. The model helps to explain epidemiological patterns observed in Europe, including the 3 to 5 year cycle in fox populations infected with rabies, threshold densities and average levels of prevalence of infection. We give a quantitative discussion of the possibilities of controlling rabies by culling or vaccinating foxes (or by a mixture of the two).

Animals↗
PubMed1981

Cycloleucine-induced vacuolation of myelin is associated with inhibition of protein methylation.

Chickens injected with cycloleucine developed vacuolation of myelin similar to that seen in humans with vitamin B12 deficiency. Cycloleucine, an inhibitor of the formation of S-adenosylmethionine, decreased the incorporation of methyl groups into methylarginine in myelin basic protein in vivo. The need for methylcobalamin for the conversion of homocysteine to methionine and the requirement that myelin basic protein may be methylated, offer a rational explanation for the myelin lesions observed in cases of vitamin B12 deficiency where there is increasing evidence that methyl-, rather than adenosylcobalamin is required to prevent dysmyelination.

Amino Acids↗
PubMed1981

The fate of plasma protein which escapes from blood vessels of the choroid plexus of the rat--an electron microscope study.

Fenestrated blood vessels in the rat choroid plexus are permeable to dye-labelled proteins, HRP and ferritin. Most leakage appears to be via fenestrae but some additional escape of marker appears to take place through transient and reversible openings in the junctions between endothelial cells. After they have escaped into the choroidal stroma markers are prevented from entering the CSF by tight junctions between the epithelial cells which cover the choroid plexus, but how they are removed from the extravascular space is not known. Electron microscope study of rats who have been given multiple intravenous injections of ferritin shows that extravascular ferritin is take up both by connective tissue cells in the choroidal stroma and by choroidal epithelial cells. The findings suggest that the ingested protein is subsequently broken down within lysosomal vacuoles in the cytoplasm of these cells. Such intracellular digestion may be the major means of controlling the protein content of the extravascular spaces of the choroid plexus.

Animals↗