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Biomedical subjects

R J Henry

Publications and source records attributed to R J Henry.

At least 19 recordsLinked to original sources
PubMed2005

Robust allele-specific polymerase chain reaction markers developed for single nucleotide polymorphisms in expressed barley sequences.

Many methods have been developed to assay for single nucleotide polymorphisms (SNPs), but generally these depend on access to specialised equipment. Allele-specific polymerase chain reaction (AS-PCR) is a method that does not require specialised equipment (other than a thermocycler), but there is a common perception that AS-PCR markers can be unreliable. We have utilised a three primer AS-PCR method comprising of two flanking-primers combined with an internal allele-specific primer. We show here that this method produces a high proportion of robust markers (from candidate allele specific primers). Forty-nine inter-varietal SNP sites in 31 barley (Hordeum vulgare L.) genes were targeted for the development of AS-PCR assays. The SNP sites were found by aligning barley expressed sequence tags from public databases. The targeted genes correspond to cDNAs that have been used as restriction fragment length polymorphic probes for linkage mapping in barley. Two approaches were adopted in developing the markers. In the first approach, designed to maximise the successful development of markers to a SNP site, markers were developed for 18 sites from 19 targeted (95% success rate). With the second approach, designed to maximise the number of markers developed per primer synthesised, markers were developed for 18 SNP sites from 30 that were targeted (a 60% success rate). The robustness of markers was assessed from the range of annealing temperatures over which the PCR assay was allele-specific. The results indicate that this form of AS-PCR is highly successful for the development of robust SNP markers.

Alleles↗
PubMed2004

Single nucleotide polymorphism, haplotype diversity and recombination in the Isa gene of barley.

The Isa gene from barley--an intronless gene expressed in maternal tissues of the seed--has a likely role in defence against pathogens. The protein product--bi-functional alpha-amylase/subtilisin inhibitor--inhibits the seed's own amylase in addition to the bacterial protease subtilisin and fungal xylanase. Sixteen barley genotypes were targeted to amplify and sequence the Isa gene region to detect sequence polymorphisms, since little is known about genetic diversity at this locus. A total of 80 single nucleotide polymorphisms (SNPs) and 23 indels were detected in 2,164 bp of sequence containing the Isa transcript, promoter and 3' non-transcribed region (overall one SNP per 27 bp and one indel per 94 bp), with eight sequence-based haplotypes distinguishable amongst the 16 varieties. Sequencing a polymorphic region in the promoter in an additional 27 barley genotypes increased the number of sequence-based haplotypes discovered to 11. However there is low haplotype diversity amongst the cultivated barley varieties sampled, with most varieties represented by a single haplotype. There was minor amino acid diversity in the protein, with five out of ten SNP sites in the coding region predicted to produce amino acid substitutions. SNP analysis indicated a history of recombination events--a minimum of seven based on the initial eight haplotypes from the whole sequenced region. Most of the recombination events occurred in the highly polymorphic regions, the 3' non-transcribed region and sequences flanking a microsatellite in the Isa promoter.

Base Sequence↗
PubMed2002

Single nucleotide polymorphisms in cytochrome P450 genes from barley.

Plant cytochrome P450s are known to be essential in a number of economically important pathways of plant metabolism but there are also many P450s of unknown function accumulating in expressed sequence tag (EST) and genomic databases. To detect trait associations that could assist in the assignment of gene function and provide markers for breeders selecting for commercially important traits, detection of polymorphisms in identified P450 genes is desirable. Polymorphisms in EST sequences provide so-called perfect markers for the associated genes. The International Triticeae EST Cooperative data base of 24,344 ESTs was searched for sequences exhibiting homology to P450 genes representing the nine known clans of plant P450s. Seventy five P450 ESTs were identified of which 24 had best matches in Genbank to P450 genes of known function and 51 to P450s of unknown function. Sequence information from PCR products amplified from the genomic template DNA of 11 barley varieties was obtained using primers designed from six barley P450 ESTs and one durum wheat P450 EST. Single nucleotide polymorphisms (SNPs) between barley varieties were identified using five of the seven PCR products. A maximum of five SNPs and three haplotypes among the 11 barley lines were detected in products from any one primer pair. SNPs in three PCR products led to changes between barley varieties in at least one restriction site enabling genotyping and mapping without the expense of a specialist SNP detection system. The overall frequency of SNPs across the 11 barley varieties was 1 every 131 bases.

Base Sequence↗
PubMed2002

Evaluating the potential of SSR flanking regions for examining taxonomic relationships in the Vitaceae.

Three EST-derived microsatellite loci from Vitis vinifera were amplified and sequenced across eight species of Vitaceae from four different genera. Phylogenetic analysis of the microsatellite's flanking regions produced informative results in congruence with previous studies. Generic relationships were respected and the data produced sufficient inter-specific variation to distinguish between Cayratia acris and Cayratia saponaria, two very closely related species. Overall, the sequence alignments showed that priming sites were conserved, whereas microsatellite repeats were present in most cases but structurally variable. The sequence data provided information on the evolutionary patterns of various microsatellite repeats and their correlation to evolutionary relationships among taxa.

Journal Article↗
PubMed1999

Microsatellite variation and assessment of genetic structure in tea tree (Melaleuca alternifolia-Myrtaceae).

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.

Australia↗
PubMed1997

The influence of meperidine and nitrous oxide on respiratory depression in rats.

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.

Analgesics, Opioid↗
PubMed1996

Supernumerary and congenitally absent teeth: a literature review.

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.

Anodontia↗
PubMed1995

High-volume aspiration as a supplemental scavenging method for reducing ambient nitrous oxide levels in the operatory: a laboratory study.

Occupational exposure to low levels of nitrous oxide (N2O) have been associated with adverse health effects. The National Institute for Occupational Safety and Health has established a threshold guideline of 25 ppm N2O. The purpose of this laboratory study was to determine the effectiveness of a high-volume dental aspirator as a supplemental device to reduce ambient N2O levels in the operatory. The investigation evaluated four experimental groups that were assigned based on whether or not the aspirator was used and on the rate at which operatory ventilation was established (5 or 10 room air exchanges per hour). Ambient N2O levels were monitored at 30 cm from the nasal hood using an infrared spectrophotometer. The room air exchange rate was measured with a flow hood and then manipulated to the desired ventilation rate. N2O levels were detected with a spectrophotometer and data were recorded with a microprocessor that continuously collected data. The results demonstrated that both utilization of supplemental oral aspiration and increased operatory ventilation significantly reduced ambient N2O levels. It was concluded that a high-volume aspirator, when used in conjunction with the normal scavenging system, can significantly reduce ambient N2O levels to within the guidelines established by the National Institute for Occupational Safety and Health.

Air Pollution, Indoor↗
PubMed1994

A dental complication involving Pseudomonas during chemotherapy for acute lymphoblastic leukemia.

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.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Operatory ventilation and scavenger evacuation rate influence on ambient nitrous oxide levels.

Investigations have shown that greater than Federally-recommended levels of ambient nitrous oxide often exist in the dental workplace. The purposes of this investigation were to examine the influences of (1) operatory ventilation rate and (2) scavenger evacuation rate on ambient nitrous oxide concentrations within a closed dental operatory. This laboratory investigation utilized a scavenging nasal mask assembly (Porter/Brown) to deliver 40% nitrous oxide in oxygen, at a total flow rate of 5 L/min, to a mannequin positioned supinely in a dental chair. Eight experimental groups were assigned based on combinations of operatory air exchange rates (0, 5, 10, or 15 room air changes per hour) and scavenger evacuation rates (18.8 L/min and 21.4 L/min). Ambient nitrous oxide levels were monitored at four locations (0, 15.3, 30.7, and 61.4 cm) from the nasal mask by means of an infrared spectrophotometer (Miran 1B). The operatory air exchange rate was measured with a flow hood (Short Ridge) and manipulated to one of the desired ventilation rates. Time-weighted average (TWA) concentrations of ambient nitrous oxide (ppm) were continuously recorded at 15-second intervals with a microprocessor (DL332F Datalogger) connected directly to a microcomputer. The results demonstrated that significantly reduced (p < 0.05) ambient nitrous oxide levels were achieved with increasing room air exchange rates and the high scavenger evacuation rate. It was concluded that operatory ventilation and scavenger evacuation rates were significant control measures available for reduction of ambient nitrous oxide to Federally recommended levels.

Air Pollution, Indoor↗
PubMed1992

Assessing environmental health concerns associated with nitrous oxide.

Concerns about the effects of occupational exposure to nitrous oxide have existed for a decade. Unfortunately, data are lacking that document biologically tolerable exposure levels. Current guidelines regarding use of N2O are reviewed.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1991

Influence of operatory size and nitrous oxide concentration upon scavenger effectiveness.

Concern regarding environmental health hazards for dental personnel chronically exposed to waste nitrous oxide (N2O) prompted this investigation. The influence on ambient N2O levels of scavenging, operatory size, and N2O concentration delivered to the patient was evaluated during treatment of 36 pediatric dental patients. The results showed that scavenging significantly reduced ambient N2O levels measured at 50-56 cm from the patient's nose. Scavenged ambient N2O levels were also observed to decrease when N2O concentrations administered to the patient were reduced from 50 to 30%. This concentration effect was not observed in the non-scavenged groups. ANOVA showed that operatory size exerted a non-significant influence on ambient N2O. The data collected during routine treatment of pediatric dental patients demonstrated that the scavenging system tested significantly reduced waste N2O in the operator's breathing zone, nearly approximating the 25-ppm recommendation established by the National Institute for Occupational Safety and Health (NIOSH).

Air Pollutants, Occupational↗
PubMed1990

Influence of chronic ethanol exposure on nitrous oxide analgesia in mice.

The purpose of this study was to determine whether sensitivity to nitrous oxide analgesia was altered by chronic ethanol exposure. Control mice exposed to 25%, 50%, and 75% nitrous oxide in oxygen demonstrated a concentration-related analgesic effect, as measured by the acetic acid abdominal constriction test. Other mice previously exposed to ethanol vapors for 72 h exhibited a significantly reduced sensitivity to nitrous oxide analgesia. The dose-response curve of the chronic ethanol-exposed group was shifted to the right of that of the control mice. These findings suggest the possibility that subjects with a history of alcohol abuse might have reduced responsiveness to nitrous oxide in a clinical setting.

Alcoholism↗