Publications by authors named "E G Crichton"

63 Publications

Preservation of the spermatozoa of the dromedary camel (Camelus dromedarius) by chilling and freezing: The effects of cooling time, extender composition and catalase supplementation.

Theriogenology 2020 Sep 5;153:9-18. Epub 2020 May 5.

Camel Reproduction Centre, PO Box, 79914, Dubai, United Arab Emirates.

This study sought to determine the characteristics of dromedary camel sperm following 24 h chilling and cryopreservation, testing two different buffers and cryoprotectants and the presence of catalase (500 IU/mL). Ejaculates were liquefied in Tris-Citric acid-Fructose buffer, and centrifuged through a colloid. For Experiment 1 (n = 5) sperm were cooled 24 h in Green Buffer or INRA-96® containing 0 or 3% glycerol or ethylene glycol. Experiment 2 (n = 5) used the same six treatments to evaluate sperm cryopreserved after 24 h cooling. A test of fertility was run (n = 12 recipients) with split ejaculates of fresh semen cooled 24 h in Green Buffer with and without glycerol. Experiment 3 (n = 7) cryopreserved sperm cooled 2 and 24 h in Green Buffer without cryoprotectant and with and without catalase. Sperm parameters measured before and after treatments included motility, viability and acrosome integrity. Experiment 1 showed no reduction in all sperm parameters after 24 h and no differences between buffers or presence or not of either cryoprotectant. Experiment 2 showed Green Buffer to be better than INRA for supporting sperm frozen after 24 h cooling while, for both buffers, there were few differences in sperm parameters if cryoprotectant was present or absent. Pregnancies were confirmed in 4/6 animals (67%) while no recipients receiving sperm chilled with glycerol were pregnant. In Experiment 3, catalase-supplemented sperm had maintained better motility 2 h post thaw; there were no differences between 2 or 24 h cooled sperm parameters for presence or absence of catalase. There was neither advantage nor disadvantage to coooling sperm 24 h prior to cryopreservation. We concluded that dromedary sperm can be chilled (24 h) and then either inseminated or cryopreserved. While glycerol presence in Green Buffer during chilling did not interfere with cryosurvival it may be toxic to the fertility of fresh chilled sperm. Catalase supplementation during cooling helps maintain sperm motility post thaw.
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http://dx.doi.org/10.1016/j.theriogenology.2020.04.043DOI Listing
September 2020

Superior inhibition of alloantibody responses with selective CD28 blockade is CTLA-4 dependent and T follicular helper cell specific.

Am J Transplant 2021 01 11;21(1):73-86. Epub 2020 Jun 11.

Emory Transplant Center, Atlanta, GA, USA.

Anti-donor antibodies cause immunologic injury in transplantation. CD28 blockade with CTLA-4-Ig has the ability to reduce the incidence of these donor-specific antibodies (DSA), but its mechanism is suboptimal for the inhibition of alloimmunity in that CTLA-4-Ig blocks both CD28 costimulation and CTLA-4 coinhibition. Thus selective CD28 blockade that spares CTLA-4 has potential to result in improved inhibition of humoral alloimmunity. To test this possibility, we utilized a full allogeneic mismatch murine transplant model and T follicular helper (Tfh):B cell co-culture system. We observed that selective blockade with an anti-CD28 domain antibody (dAb) compared to CTLA-4-Ig led to superior inhibition of Tfh cell, germinal center, and DSA responses in vivo and better control of B cell responses in vitro. CTLA-4 blockade enhanced the humoral alloresponse and, in combination with anti-CD28 dAb, abrogated the effects of selective blockade. This CTLA-4-dependent inhibition was Tfh cell specific in that CTLA-4 expression by Tfh cells was necessary and sufficient for the improved humoral inhibition observed with selective CD28 blockade. As CD28 blockade attracts interest for control of alloantibodies in the clinic, these data support selective CD28 blockade as a superior strategy to address DSA via the sparing of CTLA-4 and more potent targeting of Tfh cells.
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http://dx.doi.org/10.1111/ajt.16004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7665991PMC
January 2021

A retrospective analysis of the microbiology of diabetic foot infections at a Scottish tertiary hospital.

BMC Infect Dis 2020 Mar 12;20(1):218. Epub 2020 Mar 12.

Edinburgh Medical School: Biomedical Sciences, Infection Medicine, University of Edinburgh, Chancellor's Building, 49 Little France Crescent, Edinburgh, EH16 4SB, UK.

Background: This study represents the first Scottish retrospective analysis of the microbiology of diabetic foot infections (DFIs). The aims were to compare the microbiological profile of DFIs treated at a Scottish tertiary hospital to that in the literature, gather data regarding antimicrobial resistance and investigate potential trends between the microbiological results and nature or site of the clinical sample taken and age or gender of the patients.

Methods: A retrospective analysis of wound microbiology results was performed, data were obtained from one multidisciplinary outpatient foot clinic during the 12 months of the year 2017. Seventy-three patients and 200 microbiological investigations were included. In cases of soft tissue infection, the deepest part of a cleansed and debrided wound was sampled. In cases of osteomyelitis a bone biopsy was obtained. Factors influencing the pattern of microbial growth or prevalence of Staphylococcus aureus were investigated.

Results: Of the 200 microbiological investigations, 62% were culture positive, of which 37.9% were polymicrobial and 62.1% monomicrobial. Among the monomicrobial results (n = 77), most were Gram positive isolates (96.1%) and the most frequently isolated bacteria was S. aureus (84.4%). No methicillin-resistant S. aureus was reported. The prevalence of S. aureus in DFIs was associated with increasing age (p = 0.021), but no evidence of association with gender, anatomical sample site or sample material was found.

Conclusion: The microbiological profile of DFIs in Scotland resembles that reported elsewhere in the UK. In this context, Gram positive organisms, primarily S. aureus, are most frequently isolated from DFIs. The S. aureus isolates identified were largely susceptible to antibiotic therapy. An association between increasing patient age and the prevalence of S. aureus in DFIs was observed.
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http://dx.doi.org/10.1186/s12879-020-4923-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7068857PMC
March 2020

Randomized controlled trial: Flexible sigmoidoscopy as an adjunct to faecal occult blood testing in population screening.

J Med Screen 2020 06 5;27(2):59-67. Epub 2019 Nov 5.

Centre for Research into Cancer Prevention and Screening, University of Dundee, Ninewells Hospital and Medical School, Dundee, UK.

Objectives: Flexible sigmoidoscopy screening at around age 60 can reduce colorectal cancer incidence. Insufficient evidence exists on flexible sigmoidoscopy at age 60 in a population being offered biennial faecal occult blood test screening from age 50. This randomized controlled trial assessed if flexible sigmoidoscopy would be an effective adjunct to faecal occult blood test.

Methods: In the Scottish Bowel Screening Programme between June 2014 and December 2015, 51,769 individuals were randomized to be offered flexible sigmoidoscopy instead of faecal occult blood test at age 60 or to continue faecal occult blood test. Those not accepting flexible sigmoidoscopy and those with normal flexible sigmoidoscopy were offered faecal occult blood test. All with flexible sigmoidoscopy-detected neoplasia or a positive faecal occult blood test result were offered colonoscopy.

Results: Overall flexible sigmoidoscopy uptake was 17.8%, higher in men than women, and decreased with increasing deprivation (25.7% in the least to 9.2% in the most deprived quintile). In those who underwent flexible sigmoidoscopy, detection rate for colorectal cancer was 0.13%, for adenoma 7.27%, and for total neoplasia 7.40%. In those who underwent colonoscopy after a positive flexible sigmoidoscopy, detection rate for colorectal cancer was 0.28%, adenoma 8.66%, and total neoplasia 8.83%. On an intention to screen basis, there was no difference in colorectal cancer detection rate between the study and control groups. Adenoma and total neoplasia detection rate were significantly higher in the study group, with odds ratios of 5.95 (95%CI: 4.69-7.56) and 5.10 (95%CI: 4.09-6.35), respectively.

Conclusions: In a single screening round at age 60, there was low uptake and neoplasia detection rate. Flexible sigmoidoscopy detected significantly more neoplasia than faecal occult blood test alone.
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http://dx.doi.org/10.1177/0969141319879955DOI Listing
June 2020

An update on semen collection, preservation and artificial insemination in the dromedary camel (Camelus dromedarius).

Anim Reprod Sci 2018 Jul 13;194:11-18. Epub 2018 Mar 13.

Centre for Species Survival, Smithsonian Conservation Biology Institute, Front Royal, USA. Electronic address:

Artificial insemination (AI) in domestic animals is an important tool to maximise the use of genetically superior males and thereby insure rapid genetic progress. However, the application of AI in camelids has been hindered by the difficulties involved in collecting, as well as handling the semen due to the viscous nature of the seminal plasma. This review describes the challenges of semen collection and discusses the role of seminal plasma as well as the reasons for the viscosity and how to liquefy it so that ejaculates can be more accurately evaluated. It also reports on the use of various extenders used for liquid storage of fresh and chilled semen and how pregnancy rates are affected by numbers of spermatozoa inseminated, site of insemination and timing of insemination in relation to GnRH injection given to induce ovulation. In addition, this paper reviews the latest research in cryopreservation of camel semen and addresses the various problems involved and possible improvements that can be made so that pregnancy rates can be increased with frozen semen.
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http://dx.doi.org/10.1016/j.anireprosci.2018.03.013DOI Listing
July 2018
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