Search

A transcriptome analysis reveals the transcripts and alleles differentially expressed in sugarcane genotypes with contrasting lignin composition. Sugarcane bagasse is a highly abundant resource that may be used as a feedstock for the production of biofuels and bioproducts in order to meet increasing demands for renewable replacements for fossil carbon. However, lignin imparts rigidity to the cell wall that impedes the efficient breakdown of the biomass into fermentable sugars. Altering the ratio of the lignin units, syringyl (S) and guaiacyl (G), which comprise the native lignin polymer in sugarcane, may facilitate the processing of bagasse. This study aimed to identify genes and markers associated with S/G ratio in order to accelerate the development of sugarcane bioenergy varieties with modified lignin composition. The transcriptome sequences of 12 sugarcane genotypes that contrasted for S/G ratio were compared and there were 2019 transcripts identified as differentially expressed (DE) between the high and low S/G ratio groups. These included transcripts encoding possible monolignol biosynthetic pathway enzymes, transporters, dirigent proteins and transcriptional and post-translational regulators. Furthermore, the frequencies of single nucleotide polymorphisms (SNPs) were compared between the low and high S/G ratio groups to identify specific alleles expressed with the phenotype. There were 2063 SNP loci across 787 unique transcripts that showed group-specific expression. Overall, the DE transcripts and SNP alleles identified in this study may be valuable for breeding sugarcane varieties with altered S/G ratio that may provide desirable bioenergy traits.

Estimation of genetic diversity in a crop species can assist in the evaluation of germplasm collections as potential gene pools to improve the performance of cultivars. Molecular markers offer the opportunity to assess variation at the DNA sequence level and, as such, have become an important tool in plant genetics (Gebhardt et al.,1991). Restriction fragment length polymorphisms (RFLPs) have led to the integration of DNA markers into molecular genetic studies and plant breeding programmes, and have been used extensively in investigations of genetic diveristy in both wild and cultivated barley (Hordeum spp.) (Graner et al., 1994; Melchinger et al., 1994). RFLPs are co-dominant and locus-specific markers that are unequalled for many applications. In particular, they are well suited for the construction of linkage maps (Graner et al., 1991; Heun et al., 1991) and, because of their locus specificity, allow for synteny studies (Tanksley et al., 1992; Ahn and Tanksley, 1993). However, the procedures involving RFLPs are labour intensive, expensive and few loci are detected per assay. Recently a number of locus-specific PCR-based markers such as sequencetagged sites (Vanichanon et al., 2000) and microsatellites (simple sequence repeats) (Litt and Luty, 1989) have been developed. These marker systems are rapid, technically simple and require only small amounts of DNA. Microsatellites have been used with some success in cereals (Saghai Maroof et al., 1994; Roder et al., 1995) and offer the potential as co-dominant PCR-based markers with uniform genome coverage. Microsatellites show a high level of polymorphism and are particularly suited to identifying a large number of alleles at a specific locus. However, the development of locus-specific markers is time-consuming, expensive and relatively few loci are detected per assay.

Analysis of five microsatellite loci in 500 Melaleuca alternifolia individuals produced 98 alleles that were useful for population genetic studies. Considerable levels of observed heterozygosity were recorded (HO = 0.724), with approximately 90% of the variability being detected within populations. A low level of selfing (14%) was suggested to be the principal cause of excess homozygosity in a number of populations (overall FIS = 0.073). This study showed low levels of inbreeding in certain populations as well as a significant isolation-by-distance model. Only two groups of populations (Queensland and New South Wales) constituted different genetic provenances as a result of geographical isolation. The M. alternifolia data suggest that microsatellite loci did not always arise by a stepwise mutation process but that larger jumps in allele size may be involved in their evolution.

The purpose of this investigation was to compare the pharmacokinetics of midazolam following intravenous, intranasal drop, and nasal-atomizer administration in beagle dogs.Six animals weighing 9-13 kg were used in a repeated-measure design, group assignment based on route of drug administration. Midazolam (1.5 mg/kg) was administered with the delivery route based on group assignment. Blood samples were obtained at baseline and at 1, 3, 5, 7, 10, 15, 20, 30, and 45 min after administration. Cerebrospinal fluid samples (CSF) were obtained at 5 and 10 min after administration. Plasma and CSF concentrations of midazolam were determined by electron-capture gas-liquid chromatography.Comparison between groups and over time demonstrated that both nasal routes resulted in significantly higher CSF concentrations relative to corresponding plasma levels, and that nasal-atomizer administration produced significantly higher CSF concentrations compared to the drop approach.

Narcotic sedation is commonly accomplished with nitrous oxide (N2O) coadministration. Concerns regarding respiratory morbidity and mortality with drug combinations have been reported in the literature, particularly in patients not receiving supplemental oxygen (O2). The purpose of this investigation was to determine the effect of meperidine alone and in combination with N2O on respiration in laboratory rats by evaluating cardiovascular and arterial blood gas data. Fifty-four Sprague-Dawley rats were assigned to one of six groups (nine per group). Groups were allocated based upon the dosage of meperidine administered (0, 4.0, or 8.0 mg/kg intraperitoneally [i.p.]) and exposure to N2O (50% with oxygen) or O2 (100%). Following meperidine administration, animals were placed into a sealed chamber through which flowed either N2O or O2. Arterial blood was obtained, at baseline and at 15-min intervals, from a femoral artery catheter and pH, O2, CO2 (mm Hg), and oxygen saturation (%) were determined. Plasma samples were analyzed using a System 1306 pH/blood gas analyzer. Group comparisons demonstrated that: (a) N2O coadministration, in animals pretreated with meperidine, did not result in increased arterial CO2 levels, and (b) as expected, arterial O2 levels in all groups increased significantly from preexposure baseline values (P < 0.05). This investigation demonstrated that the coadministration of N2O to meperidine-sedated animals did not enhance respiratory depression.

Talon cusp may occur with other dental anomalies. A case is reported in which talon cusp is associated with a supernumerary tooth, suggesting genetic inheritance as a causative factor.

Asthma affects about 1 in 10 children. The condition is characterized by acute respiratory distress brought on by environmental factors. The condition is treated with medications aimed to reduce reaction to stimulants by the airway. Dental management involves attention to the status of the patient and awareness of stimulants of the reactive airway. Clinical recommendations are provided.

Midazolam in combination with nitrous oxide (N2O) is a commonly used sedative approach for pediatric dental patients. Respiratory morbidity and mortality have been reported with midazolam administration, particularly when used in combination with other drugs in the absence of supplemental oxygen. Thus, the purpose of this investigation was to determine the effect of midazolam alone and in combination with N2O on respiration in laboratory rats by measuring arterial blood gas levels. Sixty-four Sprague-Dawley rats, weighing 250-320 g, were assigned to one of eight groups (eight per group). Groups were allocated based upon the dosage of midazolam administered (0, 1.0, 2.0 or 4.0 mg/kg i.p.) and exposure to N2O/02 (50%/50%) or room air. Arterial blood was obtained from a femoral artery catheter and pH, O2, CO2 (mm Hg), and oxygen saturation (%) were determined. Samples were analyzed using a System 1306 pH/Blood Gas Analyzer. Baseline arterial blood gasses were obtained for each animal and at 15-min intervals following midazolam administration throughout the 45-min experiment. Following midazolam administration, animals were placed into a sealed chamber through which flowed either N2O or room air. Group comparisons demonstrated that: 1) arterial CO2 levels increased in midazolam-exposed animals breathing room air, but not in those exposed to N2O (P0.05), and 2) as expected, N2O/O2-exposed animals showed an increase in arterial O2 and a %saturation that was not observed in room air groups (P0.01). This investigation demonstrated that coadministration of N2O/O to midazolam-exposed animals did not result in hypercarbia, an early indicator of respiratory depression.

This review article examines supernumerary teeth as to prevalence, location, clinical and radiographic appearance, etiology, complications and management of supernumerary teeth; congenital absence of teeth as to prevalence and location, clinical features and complications, etiology, treatment considerations, and coexistance of supernumeraries and congenital absence of teeth.

This is a case report of an 11-year-old white female, diagnosed with acute lymphoblastic leukemia, who developed a dental complication involving endodontic failure and Pseudomonas infection during induction chemotherapy. This unusual set of circumstances resulted in alteration of the child's medical management. Although the oral infection, neutropenia and delayed healing response resulted in interruption of the course of chemotherapy, the child did eventually achieve remission. This case does however demonstrate the importance of dental consultation for oncology patients.

The maxillary quad-helix appliance is a commonly used approach for treatment of maxillary arch constriction and/or posterior crossbite. Concern over excessive force generation during rapid maxillary expansion led to its development and use in growing children. The purpose of this article is to present the clinical application and therapeutic considerations regarding use of the quad-helix appliance in the slow maxillary expansion of mixed dentition cases. Considerable evidence is presented supporting such early expansion and factors for case selection are identified when considering this a treatment option.

This prospective study of 36 children, ages 44-93 months, receiving nitrous oxide-oxygen under standardized conditions during routine dental procedures was conducted to determine what influence eight selected dental procedures and three patient behaviors had on ambient nitrous oxide (N2O) levels in the dentist's breathing zone. Half the children received nitrous oxide-oxygen via a scavenging nasal mask. An infrared spectrophotometer analyzed the ambient N2O level continuously throughout the procedure and the time-weighted average (TWA) for consecutive 15-sec intervals was recorded by a microprocessor. A video camera was used to synchronize the coded dental procedures and patient behaviors to the TWA ambient N2O levels recorded. The results demonstrated that scavenging significantly reduced the dentist's exposure to ambient N2O (P less than 0.05, nonscavenged mean = 284.7 ppm; scavenged mean = 36.6 ppm), but the mean TWA N2O concentration remained significantly higher, P less than 0.05, than the 25-ppm level recommended by the National Institute for Occupational Safety and Health (NIOSH). Supplemental oral evacuation was the only dental procedure capable of reducing ambient N2O to below NIOSH's recommendation when scavenging was employed. The administration of local anesthesia consistently created a significant increase in ambient N2O levels. Patient behaviors of talking, crying, and movement also resulted in significant increases from baseline ambient N2O levels.

Various studies have implicated generalized health problems with chronic exposure to trace levels of nitrous oxide. Recent investigations have reported that higher-than-recommended levels of nitrous oxide exist in the breathing zone of the dental staff. This study was undertaken to accurately determine waste nitrous oxide levels during pediatric sedations and to evaluate the effect of scavenging in reducing environmental exposure. Conscious sedations were performed on 20 uncooperative 2-4-year old children. Each child was assigned randomly to one of two groups, a scavenged group and a nonscavenged control. Sedations were accomplished with oral administration of chloral hydrate and hydroxyzine. All patients received nitrous oxide (40%) in oxygen throughout the procedure. Waste nitrous oxide levels were monitored 22-24 in from the dentist's nose using an infrared spectrophotometer and recorded by a microprocessor. Results indicate that environmental levels of nitrous oxide exceed the National Institute for Occupational Safety and Health (NIOSH) recommendations by 12 times, regardless of whether a scavenging system was employed or not. It is concluded that the scavenging system tested in this investigation may not be as efficient as previously thought at complying with NIOSH recommendations.