Pheromones and signature mixtures: defining species-wide signals and variable cues for identity in both invertebrates and vertebrates

Pheromones have been found in species in almost every part of the animal kingdom, including mammals. Pheromones (a molecule or defined combination of molecules) are species-wide signals which elicit innate responses (though responses can be conditional on development as well as context, experience, and internal state). In contrast, signature mixtures, in invertebrates and vertebrates, are variable subsets of molecules of an animal's chemical profile which are learnt by other animals, allowing them to distinguish individuals or colonies. All signature mixtures, and almost all pheromones, whatever the size of molecules, are detected by olfaction (as defined by receptor families and glomerular processing), in mammals by the main olfactory system or vomeronasal system or both. There is convergence on a glomerular organization of olfaction. The processing of all signature mixtures, and most pheromones, is combinatorial across a number of glomeruli, even for some sex pheromones which appear to have 'labeled lines'. Narrowly specific pheromone receptors are found, but are not a prerequisite for a molecule to be a pheromone. A small minority of pheromones act directly on target tissues (allohormone pheromones) or are detected by non-glomerular chemoreceptors, such as taste. The proposed definitions for pheromone and signature mixture are based on the heuristic value of separating these kinds of chemical information. In contrast to a species-wide pheromone, there is no single signature mixture to find, as signature mixtures are a 'receiver-side' phenomenon and it is the differences in signature mixtures which allow animals to distinguish each other.

The search for human pheromones: the lost decades and the necessity of returning to first principles

As humans are mammals, it is possible, perhaps even probable, that we have pheromones. However, there is no robust bioassay-led evidence for the widely published claims that four steroid molecules are human pheromones: androstenone, androstenol, androstadienone and estratetraenol. In the absence of sound reasons to test the molecules, positive results in studies need to be treated with scepticism as these are highly likely to be false positives. Common problems include small sample sizes, an overestimate of effect size (as no effect can be expected), positive publication bias and lack of replication. Instead, if we are to find human pheromones, we need to treat ourselves as if we were a newly discovered mammal, and use the rigorous methods already proven successful in pheromone research on other species. Establishing a pheromone relies on demonstration of an odour-mediated behavioural or physiological response, identification and synthesis of the bioactive molecule(s), followed by bioassay confirmation of activity. Likely sources include our sebaceous glands. Comparison of secretions from adult and pre-pubertal humans may highlight potential molecules involved in sexual behaviour. One of the most promising human pheromone leads is a nipple secretion from the areola glands produced by all lactating mothers, which stimulates suckling by any baby not just their own.

Are vectors able to learn about their hosts? A case study with Aedes aegypti mosquitoes

The way in which vectors distribute themselves amongst their hosts has important epidemiological consequences. While the role played by active host choice is largely unquestioned, current knowledge relates mostly to the innate response of vectors towards stimuli signalling the presence or quality of their hosts. Many of those cues, however, can be unpredictable, and therefore prevent the incorporation of the appropriate response into the vector's behavioural repertoire unless some sort of associative learning is possible. We performed a wide range of laboratory experiments to test the learning abilities of the mosquito, Aedes aegypti. Mosquitoes were exposed to choice procedures in (1) an olfactomenter and (2) a 'visual arena'. Our goal was to determine whether the mosquitoes were able to associate unconditional stimuli (blood feeding, human breath, vibration and electrical shock) with particular odours (citral, carvone, citronella oil and eugenol) and visual patterns (horizontal or vertical black bars) to which they had been previously observed to be responsive. We found no evidence supporting the hypothesis that associative learning abilities are present in adult Ae. aegypti. We discuss the possibilities that the assays employed were either inappropriate or insufficient to detect associative learning, or that associative learning is not possible in this species.

Morbidity and mortality associated with Clostridium difficile ribotype 078: a case-case study

The morbidity and mortality associated with Clostridium difficile ribotype 078 were examined by comparison with other known outbreak strains. A healthcare interaction within eight weeks of a positive specimen significantly increased the likelihood of ribotype 078 compared with ribotype 027. Individuals with ribotype 078 also tended to come from community sources, have a hospital stay post specimen similar to ribotype 027 and a lower 30-day mortality, but these differences were not statistically significant. This study generates several hypotheses and a methodological platform to explore this unique profile.

Thrombin induces collagen gel contraction partially through PAR1 activation and PKC-epsilon

The ability of fibroblasts to contract three-dimensional collagen gels has been used as an in vitro model of the tissue contraction which characterises both normal repair and fibrosis. Among its actions, thrombin can activate the protease-activated receptor (PAR)1 and, thereby, stimulate inflammation and repair. The current study evaluated whether thrombin could stimulate fibroblast-mediated collagen gel contraction by activating PAR1 and whether its downstream signalling depends on protein kinase C (PKC)-epsilon. Human foetal lung fibroblasts (HFL-1) were cultured in three-dimensional collagen gels and the area of the gels was measured by image analyser. Both thrombin and TFLLR, a selective PAR1 agonist, stimulated collagen gel contraction mediated by HFL-1. After RNA interference-mediated PAR1 knockdown in HFL-1, both thrombin and the PAR1 agonist-induced gel contraction were partially inhibited (by 22.4+/-2.2% and 17.6+/-5.6%, respectively). The gel contraction stimulated by thrombin was also reduced by a nonspecific PKC inhibitor and a calcium-independent PKC-epsilon inhibitor. Both thrombin and TFLLR significantly increased PKC-epsilon activity, and this effect was blocked by PAR1 knockdown. Thrombin stimulates collagen gel contraction at least partially through activation of protease-activated receptor 1 and protein kinase C-epsilon, and may contribute to tissue remodelling in inflammatory airway and lung diseases.

Reproducible research into human chemical communication by cues and pheromones: learning from psychology's renaissance

Despite the lack of evidence that the 'putative human pheromones' androstadienone and estratetraenol ever were pheromones, almost 60 studies have claimed 'significant' results. These are quite possibly false positives and can be best seen as potential examples of the 'reproducibility crisis', sadly common in the rest of the life and biomedical sciences, which has many instances of whole fields based on false positives. Experiments on the effects of olfactory cues on human behaviour are also at risk of false positives because they look for subtle effects but use small sample sizes. Research on human chemical communication, much of it falling within psychology, would benefit from vigorously adopting the proposals made by psychologists to enable better, more reliable science, with an emphasis on enhancing reproducibility. A key change is the adoption of study pre-registration and/or Registered Reports which will also reduce publication bias. As we are mammals, and chemical communication is important to other mammals, it is likely that chemical cues are important in our behaviour and that humans may have pheromones, but new approaches will be needed to reliably demonstrate them. This article is part of the Theo Murphy meeting issue 'Olfactory communication in humans'.

Antibiotic prescribing: the need for a policy in general practice

OBJECTIVE

To see whether changes in prescribing of oral antibacterials in Northern Ireland show the need for a community antibiotics policy.

DESIGN

Analysis of prescribing totals for several oral antibiotics obtained retrospectively from the prescription pricing bureau for the years 1983-7.

SETTING

Audit of anti-infective prescribing in general practice in Northern Ireland over five years.

MAIN OUTCOME MEASURE

Respective usage of agents defined as "common" and "occasional" in 1983.

RESULTS

There was a gradual decrease in the relative use of common agents from 82% of the total in 1983 to 77% in 1987 together with a complementary increase in the use of occasional agents from 5% to 10%. Pronounced changes were noted in the use of amoxycillin, ampicillin, erythromycin, minocycline, doxycycline, and amoxycillin-clavulanic acid.

CONCLUSION

Though this survey found reasonably conservative prescribing, the trend towards increased use of occasional agents has both clinical and cost implications which could be addressed by the use of a prescribing formulary.

Short-lived effects of a formulary on anti-infective prescribing--the need for continuing peer review?

Because of the introduction of indicative drug budgets in the UK and their likely association with prescribing from a drug formulary, we have studied the effect of the introduction without continued reinforcement of a voluntary practice formulary on antimicrobial prescribing in a group practice. Detailed prescribing feedback for two matched periods before and after the launch of the Northern Ireland Faculty of the Royal College of General Practitioners practice formulary was compared. The parameters chosen were adherence to the formulary, generic prescribing and costs. A slight increase in prescriptions dispensed (3.5%) was observed between the two periods but prescribing costs increased by 32%. There was a 5.9% fall in the number of prescriptions for formulary agents following the launch of the formulary and a major increase (60%; P < 0.01) in the use of non-formulary antimicrobials particularly penicillins and tetracyclines. It was concluded that the high level of formulary prescribing prevalent during the production of the formulary was not maintained following its launch probably because of the lack of reinforcement.

The epidemiology and management of candidemia in Northern Ireland during 2002-2011, including a 12-month enhanced case review

In Northern Ireland there are concerns about candidaemia, with rates higher than those reported in England and Wales. Our aim was to explore the epidemiology of candidaemia during a 10 year period and the clinical management upon suspicion of cases during a one year enhanced investigation in Northern Ireland.Candidaemia reports to the Public Health Agency were validated during 2002-2011 and used to examine incidence and antifungal sensitivity trends (during 2007-2011). A clinical proforma was used to collate information for all patients with candidaemia in 2011.The majority (96%) of isolates were captured through voluntary laboratory reporting. There was a year-on-year increase in candidaemia from 2002-2011, from 80 to 131 episodes (incidence rate ratio 1.09 95% CI 1.05-1.13). Rates were highest in males under 1 year and over 75 years. 83/98 (85%) of case notes were available from candidaemia patients during 2011. The most prevalent risk factors were patients on total parenteral nutrition (26 people, 31.3%), surgery in the two months prior to the candidaemia (25 people, 30.1%), significant steroid use in the previous 3 months (24 people, 28.9%) and active neoplastic disease (23 people, 27.7%),This study confirmed an increase in candidaemia rates over time, with the observed incidence in 2011 higher than England and Wales. We identified areas for improvement around the clinical management of candidaemia. We recommend raising the awareness of guidelines for fundoscopy, echocardiography and central venous catheter removal.

A bacteriological investigation of two leisure centre swimming pools disinfected with ozone

A bacteriological study was carried out on the first Leisure Centre swimming pools in the United Kingdom to be disinfected with ozone/chlorine. Results suggested that a free chlorine concentration of approximately 0.8 mg/l was necessary to maintain the pools in a bacteriologically satisfactory condition. This amount of free chlorine was similar to that required when the pool was disinfected with chlorine alone. However, the associated amount of combined chlorine was much lower when disinfection was by ozone/chlorine and this gave more acceptable bathing conditions. Implications for the manamgement of pools disinfected by this method are discussed.

Rapid evidence review to inform safe return to campus in the context of coronavirus disease 2019 (COVID-19)

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted predominantly through the air in crowded and unventilated indoor spaces among unvaccinated people. Universities and colleges are potential settings for its spread. Methods: An interdisciplinary team from public health, virology, and biology used narrative methods to summarise and synthesise evidence on key control measures, taking account of mode of transmission. Results: Evidence from a wide range of primary studies supports six measures.  Vaccinate (aim for > 90% coverage and make it easy to get a jab). Require masks indoors, especially in crowded settings. If everyone wears well-fitting cloth masks, source control will be high, but for maximum self-protection, respirator masks should be worn.  Masks should not be removed for speaking or singing. Space people out by physical distancing (but there is no "safe" distance because transmission risk varies with factors such as ventilation, activity levels and crowding), reducing class size (including offering blended learning), and cohorting (students remain in small groups with no cross-mixing). Clean indoor air using engineering controls-ventilation (while monitoring CO 2 levels), inbuilt filtration systems, or portable air cleaners fitted with high efficiency particulate air [HEPA] filters). Test asymptomatic staff and students using lateral flow tests, with tracing and isolating infectious cases when incidence of coronavirus disease 2019 (COVID-19) is high. Support clinically vulnerable people to work remotely. There is no direct evidence to support hand sanitising, fomite controls or temperature-taking. There is evidence that freestanding plastic screens, face visors and electronic air-cleaning systems are ineffective. Conclusions: The above six evidence-based measures should be combined into a multi-faceted strategy to maximise both student safety and the continuation of in-person and online education provision. Staff and students seeking to negotiate a safe working and learning environment should collect data (e.g. CO 2 levels, room occupancy) to inform conversations.

Further remarks on red tide models

Vertical migration as an accumulation mechanism in the formation of red tide models is discussed with reference to extant mathematical models. Its relationship to other biological and physical factors such as population density changes, tidal rhythms, nutrient limitation and light intensity is evaluated in terms of its possible causal role in red tides.

Mortality of geese as a result of collision with the ground

Two incidents are reported in which groups of migrating wild geese were found dead in agricultural fields in southern Manitoba during spring. In each case, the birds died overnight and poisoning was suspected; however, the birds had lesions of severe traumatic injury. The first incident, in 1985, involved about 150 lesser snow geese (Anser caerulescens caerulescens); the second, in 2003, involved 62 Canada geese (Branta canadensis). Both incidents occurred on dark, moonless nights. One possible explanation is that the birds became disoriented in a manner analogous to spatial disorientation described in aircraft pilots and flew as a flock directly into the earth. In the first incident, geese might have been frightened by sonic booms from aircraft; in the second, there was a thunderstorm with strong gusty winds in the area.