Elevation provenance affects photosynthesis and its acclimation to temperature in the high-Andes alpine herb Phacelia secunda

We analyzed whether Phacelia secunda populations from different elevations exhibit intrinsic traits associated with its diffusive and biochemical components of photosynthesis and if they differ in their acclimation of photosynthesis to warmer temperatures. We hypothesized that P. secunda plants will have similar photosynthetic performances regardless of altitudinal provenance and that plants from high elevations have a lower photosynthetic acclimation capacity to higher temperature than plants from low elevation. Plants from 1600, 2800 and 3600 m elevation in the central Chilean Andes were collected and grown at two thermal regimes (20/16 and 30/26°C day/night). The following photosynthetic traits were measured on each plant at the different growing temperatures: A_N , g_s , g_m , J_max , V_cmax , Rubisco carboxylation k_cat ^c . Under a common growing environment, plants from the highest elevation showed slightly lower CO₂ assimilation rates compared to lower elevations plants. While diffusive components of photosynthesis increased with elevation provenance, the biochemical component decreased, suggesting compensations that explain the similar photosynthetic rates among elevation provenances. Plants from high elevations showed lower photosynthetic acclimation to warmer temperatures compared to plants from low elevation, and these responses were related with elevational changes in diffusional and biochemical components of photosynthesis. Plants of P. secunda from different elevations maintain their photosynthetic traits when growing in a common environment suggesting low plasticity to respond to future climate changes. The fact that plants from high elevation showed lower photosynthetic acclimation to warmer temperature suggest a higher susceptibility to the increase in temperature associated with global warming.

Physiological and ultrastructural characterisation of a desiccation-tolerant filmy fern, Hymenophyllum caudiculatum: Influence of translational regulation and ABA on recovery

The filmy fern Hymenophyllum caudiculatum can lose 60% of its relative water content, remain dry for some time and recover 88% of photochemical efficiency after 30 min of rehydration. Little is known about the protective strategies and regulation of the cellular rehydration process in this filmy fern species. The aim of this study was to characterise the filmy fern ultrastructure during a desiccation-rehydration cycle, and measure the physiological effects of transcription/translation inhibitors and ABA during desiccation recovery. Confocal and transmission electron microscopy were used to compare changes in structure during fast or slow desiccation. Transcription (actinomycin D) and translation (cycloheximide) inhibitors and ABA were used to compare photochemical efficiency during desiccation recovery. Cell structure was conserved during slow desiccation and rehydration, constitutive properties of the cell wall, allowing invagination and folding of the membranes and an important change in chloroplast size. The use of a translational inhibitor impeded recovery of photochemical efficiency during the first 80 min of rehydration, but the transcriptional inhibitor had no effect. Exogenous ABA delayed photochemical inactivation, and endogenous ABA levels decreased during desiccation and rehydration. Frond curling and chloroplast movements are possible strategies to avoid photodamage. Constitutive membrane plasticity and rapid cellular repair can be adaptations evolved to tolerate a rapid recovery during rehydration. Further research is required to explore the importance of existing mRNAs during the first minutes of recovery, and ABA function during desiccation of H. caudiculatum.

Draft genome sequences of bacteria isolated from the Deschampsia antarctica phyllosphere

Genome analyses are being used to characterize plant growth-promoting (PGP) bacteria living in different plant compartiments. In this context, we have recently isolated bacteria from the phyllosphere of an Antarctic plant (Deschampsia antarctica) showing ice recrystallization inhibition (IRI), an activity related to the presence of antifreeze proteins (AFPs). In this study, the draft genomes of six phyllospheric bacteria showing IRI activity were sequenced and annotated according to their functional gene categories. Genome sizes ranged from 5.6 to 6.3 Mbp, and based on sequence analysis of the 16S rRNA genes, five strains were identified as Pseudomonas and one as Janthinobacterium. Interestingly, most strains showed genes associated with PGP traits, such as nutrient uptake (ammonia assimilation, nitrogen fixing, phosphatases, and organic acid production), bioactive metabolites (indole acetic acid and 1-aminocyclopropane-1-carboxylate deaminase), and antimicrobial compounds (hydrogen cyanide and pyoverdine). In relation with IRI activity, a search of putative AFPs using current bioinformatic tools was also carried out. Despite that genes associated with reported AFPs were not found in these genomes, genes connected to ice-nucleation proteins (InaA) were found in all Pseudomonas strains, but not in the Janthinobacterium strain.

Properties and biotechnological applications of ice-binding proteins in bacteria

Ice-binding proteins (IBPs), such as antifreeze proteins (AFPs) and ice-nucleating proteins (INPs), have been described in diverse cold-adapted organisms, and their potential applications in biotechnology have been recognized in various fields. Currently, both IBPs are being applied to biotechnological processes, primarily in medicine and the food industry. However, our knowledge regarding the diversity of bacterial IBPs is limited; few studies have purified and characterized AFPs and INPs from bacteria. Phenotypically verified IBPs have been described in members belonging to Gammaproteobacteria, Actinobacteria and Flavobacteriia classes, whereas putative IBPs have been found in Gammaproteobacteria, Alphaproteobacteria and Bacilli classes. Thus, the main goal of this minireview is to summarize the current information on bacterial IBPs and their application in biotechnology, emphasizing the potential application in less explored fields such as agriculture. Investigations have suggested the use of INP-producing bacteria antagonists and AFPs-producing bacteria (or their AFPs) as a very attractive strategy to prevent frost damages in crops. UniProt database analyses of reported IBPs (phenotypically verified) and putative IBPs also show the limited information available on bacterial IBPs and indicate that major studies are required.

NiTi superelastic orthodontic archwires with polyamide coating

Twenty orthodontic archwires with 55.2% Ni and 44.8% Ti (% weight) were subjected to a dipping treatment to coat the NiTi surface by a polyamide polymer. It has been selected a Polyamide 11 due to its remarkable long lasting performance. The transformation temperatures as well as the transformation stresses of the NiTi alloy were determined in order to know whether the coating process can alter its properties. The adhesive wear tests have been demonstrated that the wear rates as well as the dynamic friction coefficients μ of polymer coated wires are much lower than metallic wires. The corrosion studies have shown that the use of this polymer, as coating, seals the NiTi surface to prevent corrosion and the release of nickel ions. The average decrease of Ni ions release due to this coating is around 85%.

Collimator with filtration compensator: clinical adaptation to meet European Union recommendation 4F on radiological protection for dental radiography

OBJECTIVE

Our aim was to develop a compensated filtration collimator for use in paediatric patients undergoing cephalometric radiography that reduces the radiation dose administered and fulfils recommendation 4F of the European guidelines on radiation protection in dental radiology.

METHODS

An easy to use filtration-compensated collimator was constructed of plastic, lead and aluminium and used randomly with a group of 32 children (mean age 11 years) undergoing cephalometric radiography before receiving orthodontic treatment. The radiation doses administered to patients (eye lens and thyroid, submandibular and parotid glands) and to the chassis of the radiographic equipment were determined.

RESULTS

The filtration-compensated collimator is easily fixed to the external surface of the radiographic equipment and results in (a) as collimator, a reduction of 40% in the surface irradiated in the children and of 61.4% in the dose administered to the thyroid glands (P<0.001); (b) as filtration compensator, a reduction of 32.8% administered to the eye lens (P<0.001), 31.45% to the submaxillary gland (P<0.01) and 11.4% to the parotid gland (P<0.05); there was no difference in the dose determined on the radiographic film.

CONCLUSIONS

A radiographic examination can be carried out with children using only a third of the dose normally used with no increase in the time or cost involved.

Low temperature responses of Nothofagus dombeyi and Nothofagus nitida, two evergreen species from south central Chile

Nothofagus dombeyi (Mirb.) Blume and Nothofagus nitida (Phil.) Krasser are closely related evergreen trees native to south central Chile. Nothofagus dombeyi is a pioneer in habitats subject to high daytime irradiances and nighttime freezing temperatures and has a wider altitudinal and latitudinal distribution than N. nitida, which is restricted to more oceanic climates. We postulated that N. dombeyi has a greater cold-acclimation capacity, expressed as a greater capacity to maintain a functional photosynthetic apparatus at low temperatures, than N. nitida. Because cold-acclimation may be related to the accumulation of cryoprotective substances, we investigated relationships between ice nucleation temperature (IN), freezing temperature (FT), and the temperature causing injury to 50% of the leaf tissues (LT(50)) on the one hand, and concentrations of total soluble carbohydrates (TSC), starch and proline on the other hand. Observations were made throughout a seasonal cycle in adults and seedlings in the field and in seedlings in the laboratory under cold-acclimation inductive and non-inductive conditions. In adults, LT(50) values were lower in N. dombeyi than in N. nitida, suggesting that N. dombeyi is the more frost tolerant species. Adults of both species tolerated freezing in autumn and winter but not in spring and summer. In the fall and winter, seedlings of N. dombeyi had a much lower LT(50) than those of N. nitida. Nothofagus nitida seedlings, in autumn and winter, exhibited freezing avoidance mechanisms. Although elevated TSC and proline concentrations may contribute to freezing tolerance in adults of both species, an increase in proline concentration is unlikely to be the dominant frost tolerance response in adults because proline concentrations were higher in N. nitida than in N. dombeyi. In seedlings, however, there were large differences in proline accumulation between species that may account for the difference between them in freezing tolerance. Starch concentration in both species decreased during winter. Chlorophyll fluorescence indicated that maximal photochemical efficiency (F(v)/F(m)) remained at optimal values (~0.8) throughout the year. The effective photochemical efficiency of PSII (PhiPSII) and relative electron transport rates (ETR(r)) decreased in winter in both species. In seedlings, fluorescence parameters were more affected in winter in N. nitida than in N. dombeyi. We concluded that adults and seedlings of N. dombeyi are hardier than adults and seedlings of N. nitida, which is consistent with its wider latitudinal and altitudinal distribution.

Bond strength of brackets bonded with an adhesion promoter

OBJECTIVE

Enhance-L.C. is an orthodontic adhesion promoter. Our aim was to find out if this product is material-specific as stated by its manufacturers or whether its effects are similar when the promoter is used with other adhesive systems.

DESIGN

In vitro study.

SETTING

Dental Clinic. University of Murcia, Spain, 2002.

MATERIALS AND METHODS

Enhance-L.C. was used with one of the manufacturer's recommended adhesives, Light-Bond, and with a second from another manufacturer, Transbond-XT. One hundred premolars were divided into four groups of 25 premolars: 1)Transbond-XT, 2) Transbond-XT/Enhance-L.C., 3) Light-Bond, 4) Light-Bond/Enhance-L.C.

MAIN OUTCOME MEASURES

Shear bond strength was evaluated with a universal test machine and the adhesive remaining after debonding was determined using image analysis equipment.

RESULTS

Enhance-L.C. did not significantly increase the bond strength of either of the two systems (P > 0.008). However, Light-Bond/Enhance-L.C. provided a bond strength significantly greater (P < 0.008) than Transbond-XT and Transbond-XT/Enhance-L.C. Light-Bond also left significantly (P < 0.05) less adhesive remaining on the enamel than Transbond-XT, whether or not either of the systems were used with Enhance-L.C.

CONCLUSIONS

The use of Enhance-L.C with Light-Bond is to be recommended whenever extra bond strength is needed.

Surgical solutions to periodontal complications of orthodontic therapy

Collaboration of various specialists has become essential in pediatric dental practice. In orthodontics, this collaboration is completely necessary when the patient presents periodontal problems. Even in healthy patients, who do not suffer from periodontal disease, periodontal complications may occur during treatment with fixed appliances. Two cases of young patients, in which periodontal procedures were used to complement the results of orthodontic treatment are presented.

Eruption of the permanent upper canine: a radiologic study

The early detection of eruptive anomalies of the upper canine requires an understanding of its normal eruptive pattern. We studied this pattern in terms of upper canine inclination and its relation to the lateral incisor, on the basis of the panoramic radiographic records of 305 children aged 4 to 12 years. The study sample comprised 554 maxillary canines in the oral pre-emergence phase of eruption. Subject age, sex, inclination of the canine (CI), its relation to the lateral incisor (RCLI), and development of the lateral incisor (DLI) were evaluated. The results show that the canine erupts, increasing its inclination mesially until a maximum is reached, at about 9 years of age, after which the tooth begins to progressively upright itself. The individual variability of the degree of CI at a given age is considerable. In the initial stages, the RCLI is most commonly characterized by overlapping, a situation rarely seen in the final stages. The DLI effectively discriminates both periods, because when DLI is incomplete, more than half of the cases have an overlapping RCLI. In contrast, when the DLI is complete, this overlapping is seen in only 7% to 11% of the cases. This variable therefore increases the capacity to detect a possible eruptive anomaly at an early stage. In patients with complete DLI and overlapping RCLI, particularly when associated with other clinical signs such as the nonpalpation of the cuspid bulge in the alveolar process, the presence of dental agenesis, ankylosis, malformations, or ectopic eruptions, extraction of the primary canine is advised to prevent impaction.

A comparison of the bond strength to enamel and dentin of two compomers: an in vitro study

The aim of this study was to evaluate the bond strength of two resin-reinforced glass ionomer cements to etched and unetched enamel and to dentin. Thirty-six noncarious human premolar teeth were used. Flat buccal and lingual surfaces were prepared. Dyract and Compoglass were used. The teeth were distributed at random into six groups of six teeth each. The materials were handled according to manufacturers' instructions. In groups 1 and 3 the enamel was etched with 37 percent phosphoric acid. All samples were sheared with an Autograph AG5 machine at a crosshead speed of 0.5 mm/min. Two way ANOVA and comparison with the Tukey test were used to evaluate the results. These showed that on etched enamel Dyract had a significantly higher bond strength (p = 0.02); on unetched enamel Compoglass had a statistically higher bond strength (p = 0.003), and on dentin the materials provided the same bond strength. Overall, disregarding surfaces, there was no difference between the two materials.

Comparison of the changes in facial profile after orthodontic treatment, with and without extractions

A study was made of 31 patients with Angle Class II malocclusion. Fifteen patients did not undergo extraction of teeth (Group A), while 16 underwent extractions of four premolars (Group B). Data was obtained from the corresponding lateral radiographs of the head taken both before and after orthodontic treatment. The main aim of the study was to compare the response of the soft and hard tissues of the facial profile in Class II malocclusion treated with the extraction of four premolars and the response of borderline cases presenting with similar malocclusions, but not subjected to extraction. In this latter group reasonable doubt existed as to whether or not to remove teeth in order to solve the occlusal and aesthetic problems. It is concluded that significant hard tissue differences between the groups at the end of treatment were limited to a more retruded position of the incisors and a reduced overbite amongst those patients subjected to extraction. The main soft tissue differences between the groups at the end of treatment were a more retruded lower lip and a more pronounced lower labial sulcus in those patients subjected to extraction.

Lower molar and incisor displacement associated with mandibular remodeling

The purpose of this study was to quantify the amount of alveolar modeling at the apices of the mandibular incisor and first molar specifically associated with appositional and resorptive changes on the lower border of the mandible during growth and treatment. Cephalometric data from superimpositions on anterior cranial base, mandibular implants of the Björk type, and anatomical "best fit" of mandibular border structures were integrated using a recently developed strategy, which is described. Data were available at annual intervals between 8.5 and 15.5 years for a previously described sample of approximately 30 children with implants. The average magnitudes of the changes at the root apices of the mandibular first molar and central incisor associated with modeling/remodeling of the mandibular border and symphysis were unexpectedly small. At the molar apex, mean values approximated zero in both anteroposterior and vertical directions. At the incisor apex, mean values approximated zero in the anteroposterior direction and averaged less than 0.15 mm/year in the vertical direction. Standard deviations were roughly equal for the molar and the incisor in both the anteroposterior and vertical directions. Dental displacement associated with surface modeling plays a smaller role in final tooth position in the mandible than in the maxilla. It may also be reasonably inferred that anatomical best-fit superimpositions made in the absence of implants give a more complete picture of hard tissue turnover in the mandible than they do in the maxilla.

Rapid maxillary expansion. A study of the long-term effects

A study was made to determine whether skeletal alterations usually produced by rapid maxillary expansion may be compensated for in time by growth and/or comprehensive orthodontic treatment. In 30 patients, orthodontic treatment was started with rapid maxillary expansion, followed by fixed appliances, not combined with any other form of orthopedic device. Mean treatment time was 3.1 years. Nine measurements from the Ricketts analysis were studied, based on lateral cephalometric radiographs. Records were taken before orthodontic treatment and after completion of active therapy. A statistical analysis was made of the nine variables used, reflecting the vertical and anteroposterior skeletal proportions of the face, contrasting the changes before and after treatment. Of all the variables studied, the four that change with age according to the Ricketts analysis (mandibular plane angle, maxillary height, facial depth and facial convexity), yielded statistically significant differences after treatment, indicative of normal growth. The five remaining variables that remain constant with age according to the Ricketts analysis (facial axis, lower facial height, total facial height, palatal plane inclination and maxillary depth) showed no significant changes after treatment, also indicative of normal growth.

Mandibular remodeling measured on cephalograms: 2. A comparison of information from implant and anatomic best-fit superimpositions

This study quantifies the differences in the perceived pattern of mandibular remodeling when two different methods are used to superimpose roentgenographic images of the mandible. Lateral cephalograms for a group of subjects with metallic implants of the Björk type were superimposed twice; first on the metallic implants and then independently on mandibular anatomic structures according to a common "best fit" rule. In this article, we compare the between-superimposition differences in the perceived displacements of condyle, gonion, menton, pogonion, and Point B. Mean differences between the two superimpositional techniques were smaller than had been anticipated. For the 7-year time interval between 8.5 and 15.5 years, the largest mean differences between methods were 2.70 mm in the horizontal direction at condyle, 1.90 mm in the vertical direction at condyle, and 1.52 mm in the vertical direction at gonion. None of the other between-superimposition differences had a mean value in excess of 1 mm. The individual case variability between the two methods was, however, quite considerable, a finding that we believe has bearing on the confidence that can be placed in individual case analyses in clinical orthodontics. A preliminary attempt has been made to represent and discuss the magnitude of this problem.

Mandibular remodeling measured on cephalograms. 1. Osseous changes relative to superimposition on metallic implants

We report the results of a study aimed at quantifying remodeling of mandibular surfaces in a sample of growing children who represent those usually treated by orthodontists in the mixed and early adult dentition. The sample, 31 patients with metallic implants of the Björk-type, was monitored at annual intervals between 8 1/2 and 15 1/2 years of age. (Maxillary remodeling changes for the sample have been reported earlier.) The present article reports findings concerning changes at condyle, gonion, menton, pogonion, and point B as identified on lateral cephalograms. Data are reported in the Frankfort plane frame of reference with the cephalograms from different time points superimposed on the metallic implants. Mean displacement at condyle was larger than that at any other landmark and was similar in magnitude and direction to the observations of Björk when the difference in orientation of the vertical axis in the two studies is taken into account. The mean displacement of gonion was in an upward and backward direction at an angle of approximately 45 degrees to the Frankfort plane. Mean displacements at menton and pogonion were in a downward and backward direction but were very small. Mean displacement at point B was somewhat greater than that of menton and gonion, oriented in an upward and backward direction. Individual variation for most of the parameters measured was sufficiently large to warrant the inference that caution should be used when mean values are applied to the analysis of individual cases.

Normal maxillary and mandibular growth and dentoalveolar development in Macaca mulatta. A longitudinal cephalometric study from 2 to 5 years of age

Normal maxillary and mandibular growth and dentoalveolar development were examined in a longitudinal study of 10 male Macaca mulatta monkeys. Metallic implants were placed in the jaws of the monkeys as markers, and head films were taken semiannually from 2 to 5 years of age. The results showed that maxillary and mandibular growth is associated with rotational changes that are mostly in an anterior direction and are about twice as great in the mandible (9.4 degrees) as in the maxilla (4.2 degrees). These rotations are largely masked--about 75% in the maxilla and 90% in the mandible--by modeling within the jaws. Similarly, differential vertical dentoalveolar development almost completely masked the rotation of the occlusal plane that results from the rotation of the jaws, which created the impression that the occlusal plane is stable during growth. Peak growth velocity was reached on average at 3 years of age in the maxilla and mandible, with some individual variation. No major growth changes occurred after 3.5 to 4 years of age.

Changes in facial morphology in Macaca mulatta: a cephalometric study from 1.5 to 5 years of age

A cross-sectional and longitudinal (3.5 years) study on the craniofacial growth of 10 male rhesus monkeys, using metallic implants and a radiographic cephalometric technique based mainly on angular measurements, led to the following observations. (1) Maxilla and mandible were displaced in a forward and downward direction during growth, the sagittal changes being predominant over the vertical changes. (2) Maxillary and mandibular prognathism increased continuously during the whole time span. This increase was twice as great for the maxilla as for the mandible. (3) The inclination of the palatal plane and the mandibular plane changed very little over time. (4) Mandibular form remained constant, but the cranial base showed a significant flattening between approximately 1.5 and approximately 3 years of age. (5) Upper and lower occlusal plane angles changed little over time. (6) The interincisal angle decreased significantly until approximately 3 years of age in relation to the increase in proclination of the permanent incisors in the maxilla and mandible. The intermolar angle remained fairly constant. Changes in some of the variables reported (maxillary and mandibular prognathism, sagittal jaw relationship, mandibular length, interincisal angle, proclination of the upper and lower incisors, and opening of the cranial base angle) occurred as a function of age. The use of angular measurements allowed us to develop a series of templates that will provide a useful tool for a quick check of normal craniofacial morphology at three representative time points.

Partitioning the components of maxillary tooth displacement by the comparison of data from three cephalometric superimpositions

Using roentgenographic cephalograms from a sample of subjects with metallic implants, appropriately superimposed tracings were used to distinguish developmental and treatment-associated displacements of the maxillary central incisor and first molar associated "local" changes within the periodontium from "secondary" changes which reflect sutural and appositional growth at more distant osseous loci. Tracings were superimposed on anterior cranial base (ACB), on the maxillary implants only (IMP_MAX), and according to the best fit of maxillary anatomic structures without reference to the implants (A_MAX). Using the IMP_MAX superimposition, one could measure total local displacement at any landmark taking into consideration the effects of all appositional and resorptive changes on the superior and anterior surfaces of the palate, whereas using the A_MAX superimposition one could measure local displacement without consideration of surface appositional and resorptive changes. If the second of these measurements were subtracted from the first, the result would be a direct measurement of the effects of surface appositional and resorptive changes as they are expressed at that particular landmark. This strategy has enabled us to quantify and report the amount of accommodation which occurs at the location of each dental landmark in association with the resorptive and appositional changes which occur through time on the superior and anterior surfaces of the hard palate.

Soft tissue facial profile changes after orthodontic treatment with four premolars extracted

A study on the changes occurring in the soft tissue facial profile in a sample of 16 orthodontic female patients treated with extraction of four premolars led to the following observations: (1) The upper and lower lips moved back an average of 3.4 and 3.8 mm to the E line respectively; Sulcus superior and Sulcus inferior moved back an average of 1.6 and 2.3 mm to the E line respectively. (2) The mean change in the labiomental angle after treatment was almost null (0.1 degree). The mean change in the nasolabial angle after treatment showed an increase of 3.7 degrees. There was an important individual variability for both angular measurements. (3) The mean upper and lower lip protrusion relative to the Sn-Pg' line decreased 2.4 and 3.1 mm respectively. (4) The sulcus superior depth measured following Holdaway showed an average decrease of 0.9 mm. The mean changes of the integumental profile of the face relative to the H line after treatment showed that the lower lip moved back an average of 1.4 mm; the distance from Sulcus superior to the H line decreased an average of 2.4 mm, and the distance from Sulcus inferior to the H line increased an average of 0.8 mm. (5) When comparing these changes to acceptable esthetic values for the variables used, we observed that only 12% of patients in our sample finished treatment with a clearly more flattened facial profile. (6) To avoid unesthetic soft tissue profile changes, extraction of premolars should not be performed, if possible, when the pretreatment cephalogram shows any of the following characteristics: Nasolabial angle > or = 110 degrees, Ls to Sn-Pg' line < or = 3 mm, Li to Sn-Pg' line < or = 2 mm, Ss to H line < or = 3 mm, Li to H line < or = 0 mm.