Plasticity in the timing of physiological development: physiological heterokairy--what is it, how frequent is it, and does it matter?

The study of developmental sequences of physiological traits could be an important way of placing comparative developmental physiology (CDP) within the research agenda being forged by work on developmental plasticity. Here we focus on the concept of heterokairy defined by Spicer & Burggren in 2003 as changes in the timing of physiological development in an individual. The role of this concept in the future of the CDP is discussed. First we provide an historical perspective of the ideas that have led to the investigation of sequences in CDP. This is followed by a re-examination and clarification of the definition of physiological heterokairy before empirical case studies that (explicitly or implicitly) demonstrate physiological heterokairy are reviewed. We suggest that physiological heterokairy can be demonstrated through a wide range of invertebrate and vertebrate examples. However, care must be taken when inferring that heterokairy as a pattern is always the result of heterokairic processes as there is evidence that physiological heterokairy could result from the altered timing of both homologous or analogous physiological mechanisms. We conclude by discussing the potential link between heterokairy and heterochrony and suggest that the investigation of this link should be a major goal for workers in both CDP and developmental plasticity.     

Microbial transglutaminase—a review of its production and application in food processing

Transglutaminase (EC 2.3.2.13) catalyses an acyl-transfer reaction in which the -carboxamide groups of peptide-bound glutaminyl residues are the acyl donors. The enzyme catalyses in vitro cross-linking in whey proteins, soya proteins, wheat proteins, beef myosin, casein and crude actomysin refined from mechanically deboned poultry meat. In recent years, on the basis of the enzyme's reaction to gelatinize various food proteins through the formation of cross-links, this enzyme has been used in attempts to improve the functional properties of foods. Up to now, commercial transglutaminase has been merely obtained from animal tissues. The complicated separation and purification procedure results in an extremely high price for the enzyme, which hampers a wide application in food processing. Recently studies on the production of transglutaminase by microorganisms have been started. The enzyme obtained from microbial fermentation has been applied in the treatment of food of different origins. Food treated with microbial transglutaminase appeared to have an improved flavour, appearance and texture. In addition, this enzyme can increase shelf-life and reduce allergenicity of certain foods. This paper gives an overview of the development of microbial transglutaminase production, including fermentation and down-stream processing, as well as examples of how to use this valuable enzyme in processing foods of meat, fish and plant origin.     

Pollen season and climate: Is the timing of birch pollen release in the UK approaching its limit?

In light of heightened interest in the response of pollen phenology to temperature, we investigated recent changes to the onset of Betula (birch) pollen seasons in central and southern England, including a test of predicted advancement of the Betula pollen season for London. We calculated onset of birch pollen seasons using daily airborne pollen data obtained at London, Plymouth and Worcester, determined trends in the start of the pollen season and compared timing of the birch pollen season with observed temperature patterns for the period 1995–2010. We found no overall change in the onset of birch pollen in the study period although there was evidence that the response to temperature was nonlinear and that a lower asymptotic start of the pollen season may exist. The start of the birch pollen season was strongly correlated with March mean temperature. These results reinforce previous findings showing that the timing of the birch pollen season in the UK is particularly sensitive to spring temperatures. The climate relationship shown here persists over both longer decadal-scale trends and shorter, seasonal trends as well as during periods of ‘sign-switching’ when cooler spring temperatures result in later start dates. These attributes, combined with the wide geographical coverage of airborne pollen monitoring sites, some with records extending back several decades, provide a powerful tool for the detection of climate change impacts, although local site factors and the requirement for winter chilling may be confounding factors.     

Filamentous freshwater macroalgae in South Africa — a literature review and perspective on the development and control of weed problems

Studies on freshwater filamentous algae have not been undertaken in South Africa for some thirty years. Early investigations were mainly of a taxonomic nature and ecological information is virtually non-existent. However, in the recent years the spread of urban settlement and increasing demand for both industrial and domestic water have highlighted the problems facing current water supplies. Irrigation systems in particular have suffered increasing interferences from filamentous algal blooms, mainly Cladophora glomerata. As nutrient loads have increased in impoundments and rivers, the presence of this alga has become more obvious, causing decreased water flow in canals and an escalation in costs associated with its control. Copper sulphate and predosing with commercial sulphuric acid to reduce pH are now the commonest control method in most of the irrigation systems. A synopsis of current conditions is presented and proposed avenues of research are discussed.     

Sea–land breeze in a coastal city and its effect on pollen transport

This paper presents a statistical study of the sea-land breeze in Mar del Plata (Argentina) to characterize the periods of the year when the breeze affects pollen transport, particularly the dispersion of airborne Poaceae pollen between urban and rural areas. In order to analyse the sea breeze circulation, hourly data from coastal, urban and rural meteorological stations were used. The effect of the sea breeze on the particulate matter was analysed from syncronic hourly airborne pollen records from an urban and a rural area. A sea-land breeze appeared between spring and early autumn in the hours of greatest diurnal warming. Results showed that the surface wind direction most probably associated with this phenomenon is NE and E, the time of occurrence shifting to new directions following the counterclockwise rotation, according to theoretical models for the Southern Hemisphere. Poaceae emission takes place in the morning, during the hours of maximum insolation. However, after the occurrence of the breeze, a rise in pollen concentration between 2000 hours and 0200 hours is detected because of pollen reentrainment brought about by air recirculation. The results showed that breeze transport brings a regional component to pollen assemblage.     

Plasticity in the timing of physiological development: Physiological heterokairy — What is it, how frequent is it, and does it matter?

The study of developmental sequences of physiological traits could be an important way of placing comparative developmental physiology (CDP) within the research agenda being forged by work on developmental plasticity. Here we focus on the concept of heterokairy defined by Spicer & Burggren in 2003 as changes in the timing of physiological development in an individual. The role of this concept in the future of the CDP is discussed. First we provide an historical perspective of the ideas that have led to the investigation of sequences in CDP. This is followed by a re-examination and clarification of the definition of physiological heterokairy before empirical case studies that (explicitly or implicitly) demonstrate physiological heterokairy are reviewed. We suggest that physiological heterokairy can be demonstrated through a wide range of invertebrate and vertebrate examples. However, care must be taken when inferring that heterokairy as a pattern is always the result of heterokairic processes as there is evidence that physiological heterokairy could result from the altered timing of both homologous or analogous physiological mechanisms. We conclude by discussing the potential link between heterokairy and heterochrony and suggest that the investigation of this link should be a major goal for workers in both CDP and developmental plasticity.     

PLCζ and its role as a trigger of development in vertebrates

A major unresolved issue in developmental biology is the precise mechanism whereby the sperm activates the oocyte. With the discovery that calcium signals are the primary trigger for oocyte activation, a key remaining question became the identification of the signaling protein that mediates such calcium signals at fertilization. A major step forward came in 2002 with the discovery of a sperm-specific mammalian phospholipase C called phospholipase C zeta (PLCζ), which had the expected properties of the mammalian oocyte activation factor and was subsequently identified in other vertebrate groups. Most recently, defects in PLCζ have been shown to be linked to certain types of male infertility in humans. Despite these advances, many questions remain about the precise mechanism of action of PLCζ and the extent of its role during oocyte activation in the vertebrate kingdom. In this review, we will look at the current state of understanding of PLCζ's mechanism of action and physiological role in mammals and other vertebrates, and identify areas of uncertainty that still remain to be resolved.     

A review of thermoregulation and physiological performance in reptiles: what is the role of phenotypic flexibility?

Biological functions are dependent on the temperature of the organism. Animals may respond to fluctuation in the thermal environment by regulating their body temperature and by modifying physiological and biochemical rates. Phenotypic flexibility (reversible phenotypic plasticity, acclimation, or acclimatisation) in rate functions occurs in all major taxonomic groups and may be considered as an ancestral condition. Within the Reptilia, representatives from all major groups show phenotypic flexibility in response to long-term or chronic changes in the thermal environment. Acclimation or acclimatisation in reptiles are most commonly assessed by measuring whole animal responses such as oxygen consumption, but whole animal responses are comprised of variation in individual traits such as enzyme activities, hormone expression, and cardiovascular functions. The challenge now lies in connecting the changes in the components to the functioning of the whole animal and its fitness. Experimental designs in research on reptilian thermal physiology should incorporate the capacity for reversible phenotypic plasticity as a null-hypothesis, because the significance of differential body temperature–performance relationships (thermal reaction norms) between individuals, populations, or species cannot be assessed without testing that null-hypothesis.     

Pollen donor identity affects timing of stigma receptivity in Collinsia heterophylla (Plantaginaceae): a sexual conflict during pollen competition?

Theory predicts that, during pollen competition, selection may favor a pollen trait that increases donor competitive ability at the expense of the female reproductive function. One such pollen trait could be manipulation of the onset of stigma receptivity. We evaluated the potential occurrence of this kind of sexual conflict by testing female control of the timing of stigma receptivity in the self-compatible annual Collinsia heterophylla. By performing one-donor crosses in the greenhouse, we found that differences in both recipients and pollen donors influenced when stigmas became receptive. Because we did not detect an interaction effect, our result suggests that some donors were consistently better than others at germinating pollen and siring seeds earlier. Unexpectedly, self-pollen was able to fertilize seeds earlier during floral development compared with outcross pollen. These results suggest that female control on timing of stigma receptivity is not complete in this species. In addition, fertilizations that occurred early during floral development resulted in fewer seeds than later fertilizations, possibly indicating a cost of lost control over the onset of receptivity. The ability of pollen donors to influence the timing of stigma receptivity might reflect a conflict between the sexual functions in C. heterophylla.     

Invited review: β-hydroxybutyrate concentration in blood and milk and its associations with cow performance

Hyperketonemia (HYK) is one of the most frequent and costly metabolic disorders in high-producing dairy cows and its diagnosis is based on β-hydroxybutyrate (BHB) concentration in blood. In the last 10 years, the number of papers that have dealt with the impact of elevated BHB levels in dairy cattle has increased. Therefore, this paper reviewed the recent literature on BHB concentration in blood and milk, and its relationships with dairy cow health and performance, and farm profitability. Most studies applied the threshold of 1.2 mmol/l of BHB concentration in blood to indicate HYK; several authors considered BHB concentrations between 1.2 and 2.9 mmol/l as subclinical ketosis, and values ⩾3.0 mmol/l as clinical ketosis. Results on HYK frequency (prevalence and incidence) and cow performance varied according to parity and days in milk, being greater in multiparous than in primiparous cows, and in the first 2 weeks of lactation than in later stages. Hyperketonemia has been associated with greater milk fat content, fat-to-protein ratio and energy-corrected milk, and lower protein and urea nitrogen in milk. The relationships with milk yield and somatic cell count are still controversial. In general, HYK impairs health of dairy cows by increasing the risk of the onset of other early lactation diseases, and it negatively affects reproductive performance. The economic cost of HYK is mainly due to impaired reproductive performance and milk loss. From a genetic point of view, results from the literature suggested the feasibility of selecting cows with low susceptibility to HYK. The present review highlights that milk is the most promising matrix to identify HYK, because it is easy to sample and allows a complete screening of the herd through BHB concentration predicted using mid-IR spectroscopy during routine milk recording. Further research is needed to validate accurate and convenient methods to discriminate between cows in risk of HYK and healthy animals in field conditions and to support farmers to achieve an early detection and minimise the economic losses.     

Regulation and expression of transgenes in fish—a review

Transgenic fish, owing to a number of advantages which they offer over other species, are proving to be valuable model systems for the study of gene regulation and developmental genetics in addition to being useful targets for the genetic manipulation of commercially important traits. Despite having begun only a decade ago, the production of transgenic fish has become commonplace in a number of laboratories world-wide and considerable progress has been made. In this review, we initially consider the various regulatory elements and coding genes which have been used in fish, and subsequently discuss and compare both the transient and long-term fate and expression patterns of injected DNA sequences in the context of the different factors which are likely to have an effect on the expression of transgenes.     

Modification of chemical reactivity via a novel interaction of light and matter — A review

A new interaction of light, in the VIS region, and matter is presented. Theoretical preliminaries are introduced to support the experiments, in which different physical systems are irradiated with 546 nm; the experimental results show the time of irradiation to be an essential parameter. A tentative theory is presented and the prospect of using the effect in the field of molecular computers is briefly outlined.     

Effect of single-dose administration of FK-506 on allogeneic limb transplantation in rats: is there an optimal timing of its administration?

Although a number of experimental studies have demonstrated that high-dose administration of FK-506 induces the success of limb allogeneic transplantation in rats, some of them have reported occurrences of lethal side effects. Therefore, a more effective regimen with lower-dose administration of this agent must be developed. The objective of this study was to determine an optimal timing of a single-dose administration of FK-506 in rat limb allografts. In the current study, orthotopic hindlimb transplantations were performed using major histocompatibility mismatched pairs of inbred rats. The rats were classified into five groups on the basis of the different time schedules of FK-506 administration as follows: syngeneic group, Lewis-to-Lewis transplantation; control group, ACI-to-Lewis without any immunotherapy; day 0 group, recipients treated with a single-dose administration of FK-506 (5 mg/kg of body weight, intramuscular injection) at day 0 postoperatively; day 1 group, with a single-dose administration of FK-506 at day 1 postoperatively; and day 2 group, with a single-dose administration of FK-506 at day 2 postoperatively. The median graft survival time in each group (n = 5) was 9 days in the control group, 19 days in the day 0 group, 49 days in the day 1 group, and 42 days in the day 2 group. The values in the day 1 and the day 2 groups significantly increased compared with those in other groups. For prolonged survival of a grafted limb, a single-dose administration of FK-506 is more effective at 24 to 48 hours after transplantation.     

Social dilemma in the external immune system of the red flour beetle? It is a matter of time

Sociobiology has revolutionized our understanding of interactions between organisms. Interactions may present a social dilemma where the interests of individual actors do not align with those of the group as a whole. Viewed through a sociobiological lens, nearly all interactions can be described regarding their costs and benefits, and a number of them then resemble a social dilemma. Numerous experimental systems, from bacteria to mammals, have been proposed as models for studying such dilemmas. Here, we make use of the external immune system of the red flour beetle, Tribolium castaneum, to investigate how the experimental duration can affect whether the external secretion comprises a social dilemma or not. Some beetles (secretors) produce a costly quinone‐rich external secretion that inhibits microbial growth in the surrounding environment, providing the secretors with direct personal benefits. However, as the antimicrobial secretion acts in the environment of the beetle, it is potentially also advantageous to other beetles (nonsecretors), who avoid the cost of producing the secretion. We test experimentally if the secretion qualifies as a public good. We find that in the short term, costly quinone secretion can be interpreted as a public good presenting a social dilemma where the presence of secretors increases the fitness of the group. In the long run, the benefit to the group of having more secretors vanishes and becomes detrimental to the group. Therefore, in such seminatural environmental conditions, it turns out that qualifying a trait as social can be a matter of timing.     

Production of 6-[18F]fluoro-l-DOPA and its metabolism in vivo—a critical review

This report critically appraises methods for the synthesis of 6-[¹⁸F]fluoro-l-3,4-dihydroxyphenylalanine (6-FDOPA) that are based on labelling by non-regioselective electrophilic fluorination, regioselective fluorodemetalation or nucleophilic substitution. Recommendations for the standardization of labelling procedures, the optimization of radiochemical yield and the assurance of product quality and safety are given. Studies of the metabolism of 6-FDOPA in vivo are also reviewed to emphasize the importance of the biochemical component of the development of this tracer for positron emission tomography (PET).     

Adélie penguin parental activities and reproduction: effects of device size and timing of its attachment during chick rearing period

Summary Effects of device attachment on parental activities and body mass change in instrumented birds and their mates, and on chick growth and survival, were studied in Adélie Penguins Pygoscelis adeliae in Lützow-Holm Bay, Antarclica. Penguins on which small devices were fitted with rubber band harnesses exhibited increased foraging trip duration, and decreased body mass, food delivery rate, chick growth and chick survival. Their mates did not increase food delivery rate. Those on which small or large devices were fitted with epoxy glue did not change foraging trip duration, body mass, or chick survival. However, large devices decreased chick growth. These effects were more obvious; among penguins fitted with devices later in the chick rearing period, and suggest that: 1) parents fitted with devices give a priority to maintenance of their own energy reserve over guarding and food delivery for chicks; and, 2) parents' decreasing energy reserves later in the breeding season might intensify the effects of devices.     

Growth and sex ratio of nestlings in two species of crows: how important is hatching asynchrony?

Summary In experimental studies of avian hatching paterns offspring sex has been neglected. This may be a problem if nestling growth and mortality is sex biased, and if this bias is influenced by hatching spread. In a field study of two crow species, the magpie Pica pica and the hooded crow Corvus corone cornix, we manipulated hatching spread. Both species have asynchronous hatching, and adult males are larger than females by 12–14%. The sex ratios obtained from the different experimental groups on day 24 post-hatch (total sample n = 403) did not deviate significantly from unity, nor did the sex ratios obtained among young newly hatched in an incubator (total sample n = 305). Male and female offspring were of similar size at hatching but males were larger on day 24 post-hatch. Males seemed to be more costly to rear than females, judging by the 20% difference in the mean amounts of food found in the gizzards of the young on day 24 post-hatch. Dimorphism in body size did not seem to be influenced by degree of hatching spread. Asynchronous hatching did not seem to be needed to produce high quality offspring of the larger sex (i.e. males), nor did asynchronous hatching help to ensure equal parental investment in male and female progeny. One reason for the latter negative results may be that the size dimorphism of the two crow species studied were relatively small.     

Effect of diet on cancer development: is oxidative DNA damage a biomarker?

Free radicals and other reactive species are generated in vivo and many of them can cause oxidative damage to DNA. Although there are methodological uncertainties about accurate quantitation of oxidative DNA damage, the levels of such damage that escape immediate repair and persist in DNA appear to be in the range that could contribute significantly to mutation rates in vivo. The observation that diets rich in fruits and vegetables can decrease both oxidative DNA damage and cancer incidence is consistent with this. By contrast, agents increasing oxidative DNA damage usually increase risk of cancer development. Such agents include cigarette smoke, several other carcinogens, and chronic inflammation. Rheumatoid arthritis and diabetes are accompanied by increased oxidative DNA damage but the pattern of increased cancer risk seems unusual. Other uncertainties are the location of oxidative DNA damage within the genome and the variation in rate and level of oxidative damage between different body tissues. In well-nourished human volunteers, fruits and vegetables have been shown to decrease oxidative DNA damage in several studies, but data from short-term human intervention studies suggest that the protective agents are not vitamin C, vitamin E, beta-carotene, or flavonoids.