Vaccine efficacy and control measures in pertussis.

An outbreak of pertussis in primary school-children in the St David''s area of Pembrokeshire provided the opportunity to estimate pertussis vaccine efficacy. The estimate of efficacy was 88% when notified cases were used, but this fell to 68% when all children with bouts of coughing for two or more weeks were included. Notified cases were significantly less likely to have been vaccinated than other cases with similar symptoms. Therefore vaccine efficacy estimates based upon notified cases are likely to be biased. However, even the lower estimates suggest that pertussis immunisation is highly desirable and efforts to improve coverage should be increased.     

Effects of Pravastatin on Plasma Lipid Concentrations in Poloxamer 407-Induced Hyperlipidemic Rats

A new animal model of hyperlipidemia is being developed using the nonionic surfactant poloxamer 407 (P-407). We investigated the impact of pravastatin on P-407-induced hyperlipidemia. Twenty rats received P-407 300 mg intraperitoneally to induce hyperlipidemia, and 20 control rats received saline injection. Pravastatin was administered orally to an equal number of rats in both groups using three different regimens. A fourth group did not receive pravastatin. At 24 hours after injection, total cholesterol levels in two of the pravastatin groups were 28% and 34% lower than those in animals that did not receive pravastatin (p≤0.01). At 48 hours, triglyceride levels were significantly lower in all pravastatin groups (21–44%) versus animals not receiving pravastatin. Pravastatin diminished the effects of P-407 on lipoproteins. This new animal model may be useful in screening for investigational antihyperlipidemic agents.     

What some patients can eat during migraine attacks: therapeutic and conceptual implications

Although nausea and vomiting are diagnostic migraine symptoms, most patients can take tablets by mouth and a few say they can eat some food. This study was conducted to determine the proportion who could eat or drink, what was consumable and with what effect. One-hundred-and-nine migraineurs were asked what they could eat or drink at the beginning or height of their attacks; 59 could not take any food by mouth, but 50 could eat during the headache phase of their migraine attacks. Four ate normally, 5 took smaller amounts of their normal dietary intake, and 3 took lighter meals. Dry, carbohydrate foods were consumable by the remaining 38: a few had specific cravings, most stated the precise variety which, when eaten, reduced nausea, headache, other symptoms or length of attacks. Patients should therefore be encouraged to eat what they can tolerate, with their tablets taken as early as possible after the onset of attacks. Simultaneous nausea, tolerance or even craving for specific foods occur in other conditions, particularly high altitude headaches which share other features of migraine attacks. The observations in this paper support the notion that migraine is a central neuronal metabolic disturbance.     

Ethics and statistical methodology in clinical trials.

Statisticians in medicine can disagree on appropriate methodology applicable to the design and analysis of clinical trials. So called Bayesians and frequentists both claim ethical superiority. This paper, by defining and then linking together various dichotomies, argues there is a place for both statistical camps. The choice between them depends on the phase of clinical trial, disease prevalence and severity, but supremely on the ethics underlying the particular trial. There is always a tension present between physicians primarily obligated to their own patients (the weight of 'individual ethics') and ethical committees responsible for the scientific merit of the trial and its long-term implications ('collective ethics'). Individual ethics, it is proposed, favour the Bayesian approach; collective ethics, the frequentist. Though in some situations the choice appears clear-cut, there remain other where both methodologies can be appropriate.     

Water-borne stimuli released by predatory crabs and damaged prey induce more predator-resistant shells in a marine gastropod

Individuals of the morphologically variable, rocky intertidal gastropod Thais (or Nucella) lamellosa developed larger apertural teeth when held in the presence of the predatory crab Cancer productus than when held in its absence, regardless of whether snails were fed or not. In addition, among fed snails larger apertural teeth were produced in the presence of crabs fed conspecific snails than in the presence of crabs fed frozen fish. Because all snails were held in containers through which water flowed from physically separated aquaria holding the crabs, these results indicate that water-soluble chemical cues released by this predatory crab and by damaged conspecifics induced T. lamellosa to improve the defense effectiveness of their shells. Finally, when allowed access to food, snails exposed to these stimuli ate fewer barnacles and grew less than those in the controls.     

Induction of protective immunity to monoclonal-antibody-defined Plasmodium falciparum antigens requires strong adjuvant in Aotus monkeys.

Monoclonal antibodies to the major Plasmodium falciparum merozoite surface coat and rhoptry antigens were produced. A combination of the affinity-purified polypeptides with Freund complete adjuvant which was given three times completely protected an Aotus lemurinus azure (karotype VI) monkey against homologous challenge; however, immunization with the same polypeptides with a muramyl dipeptide derivative [MDP-Lys(L18)] did not protect a second Aotus monkey, even though comparable high antibody titers were induced.     

The immunoprotective Anaplasma marginale major surface protein 2 is encoded by a polymorphic multigene family.

An Anaplasma marginale Florida msp-2 gene was cloned and expressed in Escherichia coli. Pulsed-field gel electrophoresis and Southern blot analysis revealed the presence of multiple msp-2 gene copies that were widely distributed throughout the chromosomes of all three strains examined. Genomic polymorphism among copies was greatest in the 5' end of msp-2 but also occurred in 3' regions. The presence of gene-copy-specific epitopes was indicated by the reactivity of the cloned msp-2 copy with some, but not all, monoclonal antibodies that bound native MSP-2. Multiple antigenically distinct MSP-2 molecules were expressed within strains and were coexpressed by individual A. marginale organisms. These results suggest that expression of polymorphic msp-2 gene copies is responsible for the significant percentages of A. marginale organisms within strains that do not react with individual anti-MSP-2 monoclonal antibodies. Sequence analysis revealed highly significant MSP-2 homology with two rickettsial surface proteins, A. marginale MSP-4 and Cowdria ruminantium MAP-1. Immunization with MSP-4 has been shown to induce protective immunity in a manner similar to that of immunization with MSP-2. These findings support the hypothesis that A. marginale surface proteins are targets of protective immune responses but are antigenically polymorphic.