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"Leitch, Michael A."
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Severe length‐dependent peripheral polyneuropathy in a patient with subacute combined spinal cord degeneration secondary to recreational nitrous oxide abuse: A case report and literature review
2023
Nitrous oxide abuse can have detrimental effects on the central and peripheral nervous systems. This case study report aims to demonstrate a combination of severe generalized sensorimotor polyneuropathy and cervical myelopathy related to vitamin B12 deficiency following nitrous oxide abuse. We present a clinical case study and literature review examining primary research—published between 2012 and 2022—reporting nitrous oxide abuse affecting the spinal cord (myelopathy) and peripheral nerves (polyneuropathy); 35 articles were included in the review with a total of 96 patients, where the mean “patients” age was 23.9 years and were in a 2:1 male/female ratio. Of the 96 cases, within the review, 56% of patients were diagnosed with polyneuropathy, most commonly impacting the nerves of the lower limb (62%), while 70% of patients were diagnosed with myelopathy, most commonly impacting the cervical region (78%) on the spinal cord. In our clinical case study, a 28‐year‐old male underwent a multitude of diagnostic investigations for bilateral “foot drop” and sense of lower limb stiffness as ongoing complications of a vitamin B12 deficiency secondary to recreational nitrous oxide abuse. Both the literature review and our case report emphasize the dangers of recreational nitrous oxide inhalation, colloquially termed “nanging” and the risks it presents to both the central and peripheral nervous systems, which is erroneously considered by many recreational drug users to be less harmful than other illicit substances. Our case report emphasizes the danger of recreational nitrous oxide inhalation and the risks it presents to both the central and peripheral nervous systems, which is considered by many recreational users to be less harmful than other illicit substances.
Journal Article
Alkenones as a Promising Green Alternative for Waxes in Cosmetics and Personal Care Products
2018
The move toward green, sustainable, natural products has been growing in the cosmetic and personal care industry. Ingredients derived from marine organisms and algae are present in many cosmetic products. In this study, a new green ingredient, a wax (i.e., long-chain alkenones) derived from Isochyrsis sp., was evaluated as an alternative for cosmetic waxes. First, the melting point was determined (71.1–77.4 °C), then the alkenones’ thickening capability in five emollients was evaluated and compared to microcrystalline wax and ozokerite. Alkenones were compatible with three emollients and thickened the emollients similarly to the other waxes. Then, lipsticks and lip balms were formulated with and without alkenones. All products remained stable at room temperature for 10 weeks. Lipstick formulated with alkenones was the most resistant to high temperature. Finally, alkenones were compared to three cosmetic thickening waxes in creams. Viscosity, rheology, and stability of the creams were evaluated. All creams had a gel-like behavior. Both viscosity and storage modulus increased in the same order: cream with alkenones < cetyl alcohol < stearic acid < glyceryl monostearate. Overall, alkenones’ performance was comparable to the other three waxes. Alkenones can thus offer a potential green choice as a new cosmetic structuring agent.
Journal Article
Analysis of the giant genomes of Fritillaria (Liliaceae) indicates that a lack of DNA removal characterizes extreme expansions in genome size
2015
Plants exhibit an extraordinary range of genome sizes, varying by > 2000-fold between the smallest and largest recorded values. In the absence of polyploidy, changes in the amount of repetitive DNA (transposable elements and tandem repeats) are primarily responsible for genome size differences between species. However, there is ongoing debate regarding the relative importance of amplification of repetitive DNA versus its deletion in governing genome size.
Using data from 454 sequencing, we analysed the most repetitive fraction of some of the largest known genomes for diploid plant species, from members of Fritillaria.
We revealed that genomic expansion has not resulted from the recent massive amplification of just a handful of repeat families, as shown in species with smaller genomes. Instead, the bulk of these immense genomes is composed of highly heterogeneous, relatively low-abundance repeat-derived DNA, supporting a scenario where amplified repeats continually accumulate due to infrequent DNA removal.
Our results indicate that a lack of deletion and low turnover of repetitive DNA are major contributors to the evolution of extremely large genomes and show that their size cannot simply be accounted for by the activity of a small number of high-abundance repeat families.
Journal Article
Genome-wide association mapping of date palm fruit traits
by
Krueger, Robert R.
,
Amiri, Khaled M. A.
,
Purugganan, Michael D.
in
45/23
,
45/43
,
631/181/2474
2019
Date palms (
Phoenix dactylifera
) are an important fruit crop of arid regions of the Middle East and North Africa. Despite its importance, few genomic resources exist for date palms, hampering evolutionary genomic studies of this perennial species. Here we report an improved long-read genome assembly for
P. dactylifera
that is 772.3 Mb in length, with contig N50 of 897.2 Kb, and use this to perform genome-wide association studies (GWAS) of the sex determining region and 21 fruit traits. We find a fruit color GWAS at the R2R3-MYB transcription factor
VIRESCENS
gene and identify functional alleles that include a retrotransposon insertion and start codon mutation. We also find a GWAS peak for sugar composition spanning deletion polymorphisms in multiple linked invertase genes. MYB transcription factors and invertase are implicated in fruit color and sugar composition in other crops, demonstrating the importance of parallel evolution in the evolutionary diversification of domesticated species.
Date palm is an important fruit crop in the Middle East and North Africa. Here, the authors report an improved genome assembly of this species and perform GWAS mapping of sex determining region and 21 fruit traits using high density SNP data generated from re-sequencing of the mapping population.
Journal Article
Satellite DNA in Paphiopedilum subgenus Parvisepalum as revealed by high-throughput sequencing and fluorescent in situ hybridization
by
Izan, Shairul
,
Yap, Jing Wei
,
Fay, Michael F.
in
Analysis
,
Animal Genetics and Genomics
,
Biodiversity
2018
Background
Satellite DNA is a rapidly diverging, largely repetitive DNA component of many eukaryotic genomes. Here we analyse the evolutionary dynamics of a satellite DNA repeat in the genomes of a group of Asian subtropical lady slipper orchids (
Paphiopedilum
subgenus
Parvisepalum
and representative species in the other subgenera/sections across the genus). A new satellite repeat in
Paphiopedilum
subgenus
Parvisepalum
, SatA, was identified and characterized using the RepeatExplorer pipeline in HiSeq Illumina reads from
P. armeniacum
(2n = 26). Reconstructed monomers were used to design a satellite-specific fluorescent in situ hybridization (FISH) probe. The data were also analysed within a phylogenetic framework built using the internal transcribed spacer (ITS) sequences of 45S nuclear ribosomal DNA.
Results
SatA comprises c. 14.5% of the
P. armeniacum
genome and is specific to subgenus
Parvisepalum
. It is composed of four primary monomers that range from 230 to 359 bp and contains multiple inverted repeat regions with hairpin-loop motifs. A new karyotype of
P. vietnamense
(2n = 28) is presented and shows that the chromosome number in subgenus
Parvisepalum
is not conserved at 2n = 26, as previously reported. The physical locations of SatA sequences were visualised on the chromosomes of all seven
Paphiopedilum
species of subgenus
Parvisepalum
(2n = 26–28), together with the 5S and 45S rDNA loci using FISH. The SatA repeats were predominantly localisedin the centromeric, peri-centromeric and sub-telocentric chromosome regions, but the exact distribution pattern was species-specific.
Conclusions
We conclude that the newly discovered, highly abundant and rapidly evolving satellite sequence SatA is specific to
Paphiopedilum
subgenus
Parvisepalum
. SatA and rDNA chromosomal distributions are characteristic of species, and comparisons between species reveal that the distribution patterns generate a strong phylogenetic signal. We also conclude that the ancestral chromosome number of subgenus
Parvisepalum
and indeed of all
Paphiopedilum
could be either 2n = 26 or 28, if
P. vietnamense
is sister to all species in the subgenus as suggested by the ITS data.
Journal Article
Changes in the gut microbiota of mice orally exposed to methylimidazolium ionic liquids
by
Leitch, Alistair C.
,
Wright, Matthew C.
,
Dunn, Michael P.
in
Administration, Oral
,
Amino acids
,
Animals
2020
Ionic liquids are salts used in a variety of industrial processes, and being relatively non-volatile, are proposed as environmentally-friendly replacements for existing volatile liquids. Methylimidazolium ionic liquids resist complete degradation in the environment, likely because the imidazolium moiety does not exist naturally in biological systems. However, there is limited data available regarding their mammalian effects in vivo. This study aimed to examine the effects of exposing mice separately to 2 different methylimidazolium ionic liquids (BMI and M8OI) through their addition to drinking water. Potential effects on key target organs-the liver and kidney-were examined, as well as the gut microbiome. Adult male mice were exposed to drinking water containing ionic liquids at a concentration of 440 mg/L for 18 weeks prior to examination of tissues, serum, urine and the gut microbiome. Histopathology was performed on tissues and clinical chemistry on serum for biomarkers of hepatic and renal injury. Bacterial DNA was isolated from the gut contents and subjected to targeted 16S rRNA sequencing. Mild hepatic and renal effects were limited to glycogen depletion and mild degenerative changes respectively. No hepatic or renal adverse effects were observed. In contrast, ionic liquid exposure altered gut microbial composition but not overall alpha diversity. Proportional abundance of Lachnospiraceae, Clostridia and Coriobacteriaceae spp. were significantly greater in ionic liquid-exposed mice, as were predicted KEGG functional pathways associated with xenobiotic and amino acid metabolism. Exposure to ionic liquids via drinking water therefore resulted in marked changes in the gut microbiome in mice prior to any overt pathological effects in target organs. Ionic liquids may be an emerging risk to health through their potential effects on the gut microbiome, which is implicated in the causes and/or severity of an array of chronic disease in humans.
Journal Article
Fluorouracil, epirubicin, and cyclophosphamide (FEC-75) followed by paclitaxel plus trastuzumab versus paclitaxel plus trastuzumab followed by FEC-75 plus trastuzumab as neoadjuvant treatment for patients with HER2-positive breast cancer (Z1041): a randomised, controlled, phase 3 trial
by
McCall, Linda M
,
Suman, Vera J
,
Hunt, Kelly K
in
Adult
,
Aged
,
Antibodies, Monoclonal, Humanized - administration & dosage
2013
Neoadjuvant chemotherapy with trastuzumab for patients with HER2-positive breast cancer can produce a pathological complete response in the breast in 30–65% of patients. We investigated the effect of the timing of trastuzumab administration with anthracycline and taxane neoadjuvant chemotherapy.
This randomised trial was done at 36 centres in the USA and Puerto Rico. Women with operable HER2-positive invasive breast cancer were randomly assigned (1:1) with a biased coin minimisation algorithm, stratified for age, tumour size, and hormone receptor status. Neither patients nor investigators (except for a cardiac safety review panel) were masked to treatment assignment. Patients randomly assigned to sequential treatment received fluorouracil 500 mg/m2, epirubicin 75 mg/m2, and cyclophosphamide 500 mg/m2 (FEC-75) on day 1 of a 21-day cycle for four cycles followed by paclitaxel 80 mg/m2 and trastuzumab 2 mg/kg (after a 4 mg/kg loading dose) once per week for 12 weeks, while those randomly assigned to the concurrent treatment group received paclitaxel and trastuzumab once per week for 12 weeks followed by four cycles of FEC-75 (on day 1 of each 21-day cycle) and once-weekly trastuzumab, in the same doses as the sequential group. Surgery, including evaluation of the axilla, was done within 6 weeks of completion of neoadjuvant treatment. The primary outcome was the percentage of patients who had a pathological complete response in the intention-to-treat population. The study is registered with ClinicalTrials.gov, number NCT00513292.
From Sept 15, 2007, to Dec 15, 2011, 282 women were enrolled (140 in the sequential group, 142 in the concurrent group). Two patients in the sequential group withdrew consent before starting treatment. 78 of 138 (56·5%, 95% CI 47·8–64·9) patients who received sequential treatment had a pathological complete response in the breast versus 77 of 142 (54·2%, 95% CI 45·7–62·6) who received concurrent treatment (difference 2·3%, 95% CI −9·3 to 13·9). No treatment-related deaths occurred. The most common severe toxic effects were neutropenia (35 [25·3%] of 138 patients in the sequential group vs 45 [31·7%] of 142 patients in the concurrent group) and fatigue (six [4·3%] vs 12 [8·5%]). Left ventricular ejection fraction dropped below the institutional lower limit of normal at week 12 in one (0·8%) of 130 patients who received sequential treatment and four (2·9%) of 137 patients who received concurrent treatment; by week 24, it had dropped below this limit in nine (7·1%) of 126 patients and in six (4·6%) of 130 patients, respectively.
Concurrent administration of trastuzumab with anthracyclines offers no additional benefit and is not warranted.
US National Cancer Institute.
Journal Article
Interactions between plant genome size, nutrients and herbivory by rabbits, molluscs and insects on a temperate grassland
2019
Angiosperm genome sizes (GS) vary ca 2400-fold. Recent research has shown that GS influences plant abundance, and plant competition. There are also tantalizing reports that herbivores may select plants as food dependent on their GS. To test the hypothesis that GS plays a role in shaping plant communities under herbivore pressure, we exploit a grassland experiment that has experimentally excluded herbivores and applied nutrient over 8 years. Using phylogenetically informed statistical models and path analyses, we show that under rabbit grazing, plant species with small GS generated the most biomass. By contrast, on mollusc and insect-grazed plots, it was the plant species with larger GS that increased in biomass. GS was also shown to influence plant community properties (e.g. competitive strategy, total biomass) although the impact varied between different herbivore guilds (i.e. rabbits versus invertebrates) and nutrient inputs. Overall, we demonstrate that GS plays a role in influencing plant–herbivore interactions, and suggest potential reasons for this response, which include the impact of GS on a plant's response to different herbivore guilds, and on a plant's nutrient quality. The inclusion of GS in ecological models has the potential to expand our understanding of plant productivity and community ecology under nutrient and herbivore stress.
Journal Article
A universe of dwarfs and giants: genome size and chromosome evolution in the monocot family Melanthiaceae
2014
Since the occurrence of giant genomes in angiosperms is restricted to just a few lineages, identifying where shifts towards genome obesity have occurred is essential for understanding the evolutionary mechanisms triggering this process.
Genome sizes were assessed using flow cytometry in 79 species and new chromosome numbers were obtained. Phylogenetically based statistical methods were applied to infer ancestral character reconstructions of chromosome numbers and nuclear DNA contents.
Melanthiaceae are the most diverse family in terms of genome size, with C-values ranging more than 230-fold. Our data confirmed that giant genomes are restricted to tribe Parideae, with most extant species in the family characterized by small genomes. Ancestral genome size reconstruction revealed that the most recent common ancestor (MRCA) for the family had a relatively small genome (1C = 5.37 pg). Chromosome losses and polyploidy are recovered as the main evolutionary mechanisms generating chromosome number change.
Genome evolution in Melanthiaceae has been characterized by a trend towards genome size reduction, with just one episode of dramatic DNA accumulation in Parideae. Such extreme contrasting profiles of genome size evolution illustrate the key role of transposable elements and chromosome rearrangements in driving the evolution of plant genomes.
Journal Article