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PubMed1984

The population biology of bacterial viruses: why be temperate.

A model of the interactions between populations of temperate and virulent bacteriophage with sensitive, lysogenic, and resistant bacteria is presented. In the analysis of the properties of this model, particular consideration is given to the conditions under which temperate bacteriophage can become established and will be maintained in bacterial populations. The effects of the presence of resistant bacteria and virulent phage on these "existence" conditions for temperate viruses are considered. It is demonstrated that under broad conditions temperate phage will be maintained in bacterial populations and will coexist with virulent phage. Extrapolating from this formal consideration of the population biology of temperate bacteriophage, a number of hypotheses for the conditions under which temperate, rather than virulent, modes of phage reproduction are to be anticipated and the nature of the selective pressures leading to the evolution and persistence of this "benign" type of bacterial virus are reviewed and critically evaluated. Two hypotheses for the "advantages of temperance" are championed: (1) As a consequence of the allelopathic effects of diffusing phage, in physically structured habitats, lysogenic colonies are able to sequester resources and, in that way, have an advantage when competing with sensitive nonlysogens. (2) Lysogeny is an adaptation for phage to maintain their populations in "hard times," when the host bacterial density oscillates below that necessary for phage to be maintained by lytic infection alone.

Bacteriophages↗
PubMed1997

Wear rates of regular and tempered composites.

OBJECTIVES: One of the reasons for using composite inlays is that restorations can be tempered. Composites tempered with heat and light have, at least initially, an enhanced degree of cure which, it is claimed, improves their physical properties, including wear resistance. The aim of this study was to compare the wear rates of a selection of composites in their regular and tempered conditions. METHODS: Two hybrid composites (Brilliant Dentin, Coltène; Occlusin, ICI) and a microfilled material (Heliomolar, Ivoclar-Vivadent) were chosen to provide a variety of filler particle and resin systems. Regular composites were cured normally with light while tempered composites were given an additional 8 min secondary cure at 120 degrees C in the Coltène DI500 heat and light oven. Specimens of an amalgam (Dispersalloy, Johnson & Johnson) and a heat/pressure cured composite (Isosit, Ivoclar-Vivadent) were used for comparison. The specimens were stored for either 7 days or 1 year to determine if prolonged water storage affected wear rate. Wear testing was carried out in a two-body wear machine using a steatite abrader as an enamel substitute. ANOVA was used to test the effects on wear rate of tempering, storage time and type of material. RESULTS: Significant differences were found in wear rate between materials (p < 0.001), but not for tempering or prolonged storage time. CONCLUSION: These findings agree with clinical studies which have shown that tempering has little or no influence on the occlusal wear of composite inlays.

Acrylic Resins↗
PubMed2004

Replica-exchange extensions of simulated tempering method.

In this paper we consider combinations of two well-known generalized-ensemble algorithms, namely, simulated tempering and replica-exchange method. We discuss two examples of such combinations. One is the replica-exchange simulated tempering and the other is the simulated tempering replica-exchange method. In the former method, a short replica-exchange simulation is first performed and the simulated tempering weight factor is obtained by the multiple-histogram reweighting techniques. This process of simulated tempering weight factor determination is faster and simpler than that in the usual iterative process. A long simulated tempering production run is then performed with this weight factor. The latter method is a further extension of the former in which a simulated tempering replica-exchange simulation is performed with a small number of replicas. These algorithms are particularly useful for studying frustrated systems with rough energy landscape. We give the formulations of these two methods in detail and demonstrate their effectiveness taking the example of the system of a 17-residue helical peptide.

Journal Article↗
PubMed1984

DNA-DNA Homology Between Lactic Streptococci and Their Temperate and Lytic Phages.

Temperate phages were induced from Streptococcus cremoris R(1), BK(5), and 134. DNA from the three induced phages was shown to be homologous with prophage DNA in the bacterial chromosomes of their lysogenic hosts by the Southern blot hybridization technique. P-labeled DNA from 11 lytic phages which had been isolated on cheese starters was similarly hybridized with DNA from 36 strains of lactic streptococci. No significant homology was detected between the phage and bacterial DNA. Phages and lactic streptococci used included phages isolated in a recently opened cheese plant and all the starter strains used in the plant since it commenced operation. The three temperate phages were compared by DNA-DNA hybridizations with 25 lytic phages isolated on cheese starters. Little or no homology was found between DNA from the temperate and lytic phages. In contrast, temperate phages showed a partial relationship with one another. Temperate phage DNA also showed partial homology with DNA from a number of strains of lactic streptococci, many of which have been shown to be lysogenic. This suggests that many temperate phages in lactic streptococci may be related to one another and therefore may be homoimmune with one another. These findings indicate that the release of temperate phages from starter cells currently in use is unlikely to be the predominant source of lytic phages in cheese plants.

Journal Article↗
PubMed1970

Temperate bacteriophages of Escherichia coli O119:B14.

Lysogeny was detected in 98.8% of the 343 Escherichia coli O119:B14 strains. A suitable indicator strain E. coli KS was selected to demonstrate the presence of temperate phages in this serotype. A great diversity in the temperate population was observed based on their lytic patterns and neutralization studies. No definite relationship could be established between the biochemical reactions and the flagellar antigens of the lysogenic strain and its temperate phage though some temperate phages released by E. coli O119:B14 strains with certain flagellar antigens did give specific lytic patterns and were serologically identical. Lysogenic strains, which did not release temperate phages spontaneously, were u.v. inductible. Cross-reactions with lysogenized colonies which were immune to corresponding phages also confirmed diversity of temperate phages in E. coli O119:B14.

Antigens↗
PubMed2005

Equilibrium sampling of self-associating polymer solutions: a parallel selective tempering approach.

We present a novel simulation algorithm based on tempering a fraction of relaxation-limiting interactions to accelerate the process of obtaining uncorrelated equilibrium configurations of self-associating polymer solutions. This approach consists of tempering (turning off) the attractive interactions for a fraction of self-associating groups determined by a biasing field h. A number of independent configurations (replicas) with overlapping Hamiltonian distributions in the expanded (NVTh) ensemble with constant NVT but different biasing fields, forming a chain of Hamiltonians, were simulated in parallel with occasional attempts to exchange the replicas associated with adjacent fields. Each field had an associated distribution of tempered interactions, average fraction of tempered interactions, and structural decorrelation time. Tempering parameters (number of replicas, fields, and exchange frequencies) were chosen to obtain the highest efficiency in sampling equilibrium configurations of a self-association polymer solution based on short serial simulation runs and a statistical model. Depending on the strength of the relaxation-limiting interactions, system size, and thermodynamic conditions, the algorithm can be orders of magnitude more efficient than conventional canonical simulation and is superior to conventional temperature parallel tempering.

Journal Article↗
PubMed1992

Heat and cold shock protein synthesis in arctic and temperate strains of rhizobia.

We compared heat shock proteins (HSPs) and cold shock proteins (CSPs) produced by different species of Rhizobium having different growth temperature ranges. Several HSPs and CSPs were induced when cells of three arctic (psychrotrophic) and three temperate (mesophilic) strains of rhizobia were shifted from their optimal growth temperatures (arctic, 25 degrees C; temperate, 30 degrees C) to shock temperatures outside their growth temperature ranges. At heat shock temperatures, three major HSPs of high molecular weight (106,900, 83,100, and 59,500) were present in all strains for all shock treatments (29, 32, 36.4, 38.4, 40.7, 41.4, and 46.4 degrees C), with the exception of temperate strains exposed to 46.4 degrees C, in which no protein synthesis was detected. Cell survival of arctic and temperate strains decreased markedly with the increase of shock temperature and was only 1% at 46.4 degrees C. Under cold shock conditions, five proteins (52.0, 38.0, 23.4, 22.7, and 11.1 kDa) were always present for all treatments (-2, -5, and -10 degrees C) in arctic strains. Among temperate strains, five CSPs (56.1, 37.1, 34.4, 17.3, and 11.1 kDa) were present at temperatures down to 0 degrees C. The 34.4- and the 11.1-kDa components were present in all temperate strains at -5 degrees C and in one strain at -10 degrees C. Survival of all strains decreased with cold shock temperatures but was always higher than 50%. These results show that rhizobia can synthesize proteins at temperatures not permissive for growth. In all shock treatments, no correspondence between the number of HSPs or CSPs produced and rhizobial survival was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Biological↗
PubMed1991

Influence of initial flaw size on crack growth in air-tempered porcelain.

Tempering of dental porcelain by forced convective cooling in air has been shown previously to inhibit the sizes of cracks induced in porcelain surfaces. However, the depth of compressive stress that is produced by tempering of feldspathic porcelain has not been determined. It can be assumed that the potential of tempered specimens to inhibit crack formation is reduced as the flaw size exceeds some critical value, since the compressive stress decreases with distance from the surface. The objective of this study was to test the hypothesis that the effectiveness of tempering stress in porcelain decreases with the increasing size of initial surface flaws. Body porcelain discs, 16 mm in diameter and 2 mm in thickness, were tempered (T) by forced convective cooling in air from an initial temperature of 982 degrees C at a pressure of 0.34 MPa for 90 s. Nontempered control discs (NT) were slowly cooled by termination of power to the furnace. The half crack-lengths (c) of surface cracks induced by a Vickers microhardness indenter at loads ranging from 2.0 to 39.2 N were determined initially and over a period of 24 h. The initial half crack-lengths, co, for the tempered specimens were significantly smaller (p less than 0.05) than the corresponding values for the slow-cooled specimens. The mean value of the stress corrosion susceptibility coefficient (n), which is inversely related to the slope of log crack size vs. log time, was only slightly smaller for the NT specimen groups (15.3), compared with the mean value for the T groups (17.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Air↗
PubMed1999

Fracture toughness and durability of chemically or thermally tempered metal-ceramic porcelain.

Thermocycling and water storage effects on fracture toughness (KIC) of chemically or thermally tempered metal-ceramic disks were investigated to evaluate the durability of tempering effects with regard to oral aqueous environment. Metal-ceramic disks (phi 10 mm x 2.0 mm) consisting of opaque porcelain (0.2 mm thick), body porcelain (1.3 mm) and Ni-Cr-Be alloy (0.5 mm) were prepared and the porcelain surfaces were polished with 1-micron diamond paste. The disks were subjected to ion exchange (potassium or rubidium) or thermal tempering treatments, then with the as-polished or further annealed disks, thermocycled for 8000, 15,000, and 22,000 cycles between 5 degrees C and 60 degrees C or stored in water at 37 degrees C for 33 days. After aging, KIC values of disks were determined by a Vickers indentation technique. Statistical analyses indicated that the KIC values of ion-exchanged and annealed disks were not significantly affected by the limited number of cycles and water storage, while the thermally tempered and untreated disks revealed a significant decrease in mean KIC from even 8000 cycles and after storage. However, there was no significant difference between thermocycling and water-storage effects on mean KIC of all surface treatment groups. Results indicate that chemical tempering (ion exchange) produced more durable residual stresses than does thermal tempering for metal-ceramic restorations. A low-thermal load only was unlikely to affect the apparent fracture toughness of porcelain.

Chromium Alloys↗
PubMed1977

Responses to temperate, cold, and hot environments and the effect of physical training.

Ten young men underwent several tests before and after a training program: a bicycle ergometer test and 60 min of moderate exercise performed at a temperate 24 degrees C; the same work load performed in heat (40.0 degrees C DB, 30.4 degrees C WB) for 3 h; and cold (10 degrees C) exposure for 60 min. Training consisted of 13 1-h sessions of hard, strenuous, and exhaustive work performed in temperate conditions four times a week. Training resulted in substantial decreases in heart rate and rectal temperature responses to exercise in temperate, minor increases in hot, and no significant changes in cold conditions. Subjects who showed good responses to heat, also showed good responses at 24 degrees C, and poor compensatory responses to cold, which were indicated by relatively low heat production and rectal temperature values, and relatively high body heat loss and extremities temperature values. Subjects who showed poor heat tolerance also showed poor responses in temperate and good compensatory responses in cold conditions. Positive correlation coefficients were found between rectal temperatures in the three environments, and between heart rate and sweat rate responses in temperate and hot conditions. The results indicated that moderately severe training causes minor tolerance improvements in heat and no changes in cold, and that responses in temperate, cold, and hot environments are interdependent.

Acclimatization↗
PubMed1997

Temperance board registration for alcohol abuse in a national sample of Swedish male twins, born 1902 to 1949.

BACKGROUND: Temperance boards were established in Sweden to register and follow up individuals who were seen in legal or medical settings with problems of alcohol abuse. These records, available in a large epidemiologic twin population, have provided an objective and validated measure of alcohol abuse. METHODS: We examined Swedish temperance board registrations from 1929 to 1974 (n = 2516 individual twins) in all male-male Swedish twin pairs of known zygosity from the population-based Swedish Twin Registry; these twin pairs were born from 1902 to 1949 (n = 8935 pairs). RESULTS: The lifetime prevalence and probandwise concordance rates for temperance board registrations were 13.2% and 47.9%, respectively, in monozygotic twins and 14.6% and 32.8%, respectively, in dizygotic twins. Model fitting suggested that genetic and familial-environmental risk factors accounted for 54% (95% confidence interval [CI], 47%-61%) and 14% (95% CI, 8%-19%) of the liability to temperance board registration, respectively; these estimates were stable across birth cohorts. High genetic liability was reflected by large numbers of temperance board registrations and registrations for criminal alcohol use. Elevated familial-environmental liability was indicated by an early age at first registration. CONCLUSIONS: Genetic factors are of major etiologic importance for alcohol abuse in men, while familial environmental factors play a significant but less important role. The etiologic importance of these factors has remained constant in Sweden for men who were born in the first half of the 20th century.

Adult↗
PubMed2004

"A star that gathers lustre from the gloom of night": wives, marriage, and gender in early-nineteenth-century American temperance reform.

This article argues that wives occupied a more central place than mothers in the early nineteenth-century American temperance movement, and that temperance literature portrayed them in two ways. First, temperance writers depicted the drunkard's wife as a pitiable example of the dire effects of male drinking on women and families. Second, they cast wives as potent moral influences on their husbands, capable of preventing the sober from faltering and reclaiming the drunkard. These portrayals coexisted with overtly misogynist views of women within the temperance movement that accused women of making men drunkards through perverted influence and blamed drunkard's wives for their own predicament. The temperance movement's depiction of wives' gender both reflected and contributed to the large ambivalence toward women in American society.

Alcohol Drinking↗
PubMed2004

Recovery of exotic alleles in semiexotic maize inbreds derived from crosses between Latin American accessions and a temperate line.

Genetic diversity of elite maize germplasm in the United States is narrow relative to the species worldwide. Tropical maize represents the most diverse source of germplasm. To incorporate germplasm from tropical maize landraces into the temperate gene pool, 23 Latin American maize accessions were crossed to temperate inbred line Mo44. During inbred line development, selection was practiced in temperate environments, potentially resulting in the loss of substantial proportions of tropical alleles. Genotyping 161 semiexotic inbreds at 51 simple sequence repeat (SSR) loci permitted the classification of their alleles as either Mo44 or tropical and allowed estimation of the proportion of detectable tropical alleles retained in these lines. On average, the percentage of detectable tropical alleles ranged among lines from 15% to 56%, with a mean of 31%. These are conservative, lower-bound estimates of the proportion of tropical germplasm within lines, because it is not known how frequently Mo44 and the tropical maize accession parental populations shared SSR alleles. These results suggest that substantial proportions of exotic germplasm were recovered in the semiexotic lines, despite their selection in temperate environments. The percent of tropical germplasm in semiexotic lines was not correlated to grain yield or moisture of lines testcrossed to a Corn Belt Dent tester, indicating that the incorporation of a substantial percentage of tropical germplasm in an inbred line does not necessarily negatively impact its combining ability. Thus, tropical maize accessions represent a good source of exotic germplasm to broaden the genetic base of temperate maize without hindering agronomic performance.

Agriculture↗
PubMed2000

Effect of hypohydration on core temperature during exercise in temperate and hot environments.

The purpose of this study was to compare directly the physiological consequences of 5% hypohydration or euhydration during exercise in both temperate (23 degrees C) and hot (33 degrees C) environments. The subjects were eight male volunteers. Each performed four 1-h exercise bouts at 60% maximum oxygen uptake, one in each of the following conditions: hot-hypohydrated, hot-euhydrated, temperate-hypohydrated, and temperate-euhydrated. Heart rate (HR), rectal temperature (Tre), forearm blood flow, and oxygen uptake were measured after 20, 40, and 60 min exercise. Whole-body sweat rate was also determined for each exercise bout. Hypohydration increased Tre significantly (P<0.05) more in the hot environment (0.16 degrees C per 1% decrease in body mass) than in the temperate environment (0.08 degrees C per 1% hypohydration). Furthermore, compared with euhydration, hypohydration decreased forearm blood flow and whole-body sweat rate significantly more during exercise in the hot than in the temperate environment. The reductions in forearm blood flow and whole-body sweat rate appear to have decreased heat loss, thus accounting for the increase in Tre during exercise in the heat while hypohydrated. In conclusion, this study illustrates that the physiological consequences of hypohydration during exercise are exacerbated in the heat.

Adult↗
PubMed2002

Mechanisms promoting higher growth rate in arctic than in temperate shorebirds.

We compared prefledging growth, energy expenditure, and time budgets in the arctic-breeding red knot (Calidris canutus) to those in temperate shorebirds, to investigate how arctic chicks achieve a high growth rate despite energetic difficulties associated with precocial development in a cold climate. Growth rate of knot chicks was very high compared to other, mainly temperate, shorebirds of their size, but strongly correlated with weather-induced and seasonal variation in availability of invertebrate prey. Red knot chicks sought less parental brooding and foraged more at the same mass and temperature than chicks of three temperate shorebird species studied in The Netherlands. Fast growth and high muscular activity in the cold tundra environment led to high energy expenditure, as measured using doubly labelled water: total metabolised energy over the 18-day prefledging period was 89% above an allometric prediction, and among the highest values reported for birds. A comparative simulation model based on our observations and data for temperate shorebird chicks showed that several factors combine to enable red knots to meet these high energy requirements: (1) the greater cold-hardiness of red knot chicks increases time available for foraging; (2) their fast growth further shortens the period in which chicks depend on brooding; and (3) the 24-h daylight increases potential foraging time, though knots apparently did not make full use of this. These mechanisms buffer the loss of foraging time due to increased need for brooding at arctic temperatures, but not enough to satisfy the high energy requirements without invoking (4) a higher foraging intake rate as an explanation. Since surface-active arthropods were not more abundant in our arctic study site than in a temperate grassland, this may be due to easier detection or capture of prey in the tundra. The model also suggested that the cold-hardiness of red knot chicks is critical in allowing them sufficient feeding time during the first week of life. Chicks hatched just after the peak of prey abundance in mid-July, but their food requirements were maximal at older ages, when arthropods were already declining. Snow cover early in the season prevented a better temporal match between chick energy requirements and food availability, and this may enforce selection for rapid growth.

Adaptation, Physiological↗
PubMed2005

A comparison of contaminant dynamics in arctic and temperate fish: A modeling approach.

In order to compare the abilities of arctic and temperate fish to accumulate PCBs we conduct a metabolic analysis to determine how process rates in a mathematical fish contaminant model change with temperature. We evaluate the model by applying the original and adapted models to estimate PCB concentrations in lake trout (Salvelinus namaycush) in Trout Lake, Ontario, Canada, and in arctic char (Salvelinus alphinus) in Lake Øyangen, in the Norwegian high arctic. Modeled concentrations are, for the most part, within 50% of mean measured values and are comparable to the error associated with the fish data. In order to evaluate differences in fish bioaccumulation processes, the model is applied to hypothetical arctic and temperate systems, assuming the same contaminant input values in water and diet. The model predicts that temperate salmonids are able to biomagnify PCBs 6-60% more than arctic salmonids. For all congeners, the lower BMF(MAX) of arctic fish contribute to their lower concentrations. For congeners with log K(ow) < 6.0, the lower concentrations in arctic fish are also attributed to faster loss due to gill ventilation. Faster growth rates for temperate fish reduce the difference in bioaccumulation for congeners with log K(ow) > 7.0. These processes are controlled by the influence of lipid in the fish and their diet as well as the dependence of growth on temperature. We suggest that fish models originally calibrated for temperate systems may be directly applied to arctic lakes after accounting for the lipid content of the fish and their diet as well as water temperature.

Animals↗
PubMed2003

Rangewide phylogeography of a bird-dispersed Eurasian shrub: contrasting Mediterranean and temperate glacial refugia.

We studied the phylogeography of alder buckthorn (Frangula alnus), a bird-dispersed shrub or small tree distributed over most of Europe and West Asia and present in three of the four main refugia of West Palaearctic temperate woody plants: the Iberian Peninsula, the Balkans and Anatolia. A total of 78 populations from 21 countries were analysed for chloroplast DNA variation using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and 21 different haplotypes were distinguished. We found a very strong overall population differentiation (GST = 0.81) and phylogeographical structure, and a sharp contrast between the haplotype-rich refugia and the almost completely uniform area of postglacial colonization. The haplotype network comprises three lineages made up of haplotypes from the Iberian Peninsula, Anatolia with the Caucasus, and temperate Europe. The Iberian and the Anatolian branches represent parts of a major lineage that spans over the whole northern Mediterranean Basin and some neighbouring areas and probably dates back to the Tertiary. Many haplotypes of this lineage are distributed locally and most populations are fixed for a single haplotype; these populations have apparently been very stable since their establishment, experiencing negligible gene flow and few mutations. The temperate European lineage consists of one very widespread and abundant plus six locally distributed haplotypes. Four of them are located in Southeast Europe, the putative refugium of all extant temperate European populations. Contrary to populations from Iberia and Anatolia, F. alnus populations from the southeastern European refugium have most genetic variation within populations. Bird-mediated seed dispersal has apparently allowed not only a very rapid postglacial expansion of F. alnus but also subsequent regular seed exchanges between populations of the largely continuous species range in temperate Europe. In contrast, the disjunct F. alnus populations persisting in Mediterranean mountain ranges seem to have experienced little gene flow and have therefore accumulated a high degree of differentiation, even at short distances. Populations from the southern parts of the glacial refugia have contributed little to the postglacial recolonization of Europe, but their long-term historical continuity has allowed them to maintain a unique store of genetic variation.

DNA, Chloroplast↗
PubMed2006

Responses of crown development to canopy openings by saplings of eight tropical submontane forest tree species in Indonesia: a comparison with cool-temperate trees.

BACKGROUND AND AIMS: Growth in trunk height in canopy openings is important for saplings. How saplings increase height growth in canopy openings may relate to crown architectural constraints. Responses of crown development to canopy openings in relation to trunk height growth were studied for saplings (0.2-2.5 m tall) of eight tropical submontane forest tree species in Indonesia. The results of this study were also compared with those of temperate trees in northern Japan. METHODS: The crown architecture differed among the eight tropical species, i.e. they had sparsely to highly developed branching structures. Crown allometry was compared among the eight species in each canopy condition (closed canopy or canopy openings), and between closed canopy and canopy openings within a species. A general linear regression model was used to analyse how each species increases height growth rate in canopy openings. Crown allometry and its plasticity were compared between tropical and temperate trees by a nested analysis of covariance. KEY RESULTS: Tropical submontane trees had responses similar to cool-temperate trees, showing an increase in height in canopy openings, i.e. taller saplings of sparsely branched species increase height growth rates by increasing the sapling leaf area. Cool-temperate trees have a wider crown projection area and a smaller leaf area per crown projection area to avoid self-shading within a crown compared with tropical submontane trees. Plasticity of the crown projection area is greater in cool-temperate trees than in tropical submontane trees, probably because of the difference in leaf longevity. CONCLUSIONS: This study concluded that interspecific variation in the responses of crown development to canopy openings in regard to increasing height related to the species' branching structure, and that different life-forms, such as evergreen and deciduous trees, had different crown allometry and plasticity.

Indonesia↗