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Biomedical subjects

N McClure

Publications and source records attributed to N McClure.

At least 37 records · Page 2Linked to original sources
PubMed2000

Randomly alternating image presentation during laparoscopic training leads to faster automation to the "fulcrum effect".

BACKGROUND AND STUDY AIMS: The aim of this study was to evaluate four training programmes intended to help laparoscopic surgeons automate to the "fulcrum effect". METHODS: A total of 32 participants (16 men, 16 women), were randomly assigned to one of four different image-viewing conditions: full binocular, y-axis inverted, normal laparoscopic and randomly alternating (between y-axis-inverted and normal laparoscopic). The subjects were requested to perform 10 trials of a simple laparoscopic cutting task, each lasting 2 minutes. Each then completed a 2-minute test under normal laparoscopic imaging conditions. RESULTS: In the final test trial, participants who trained under the randomly alternating imaging conditions (y-axis inverted and normal laparoscopic) performed significantly better than those from the other groups. CONCLUSION: Training under a randomly alternating viewing condition helps laparoscopic trainees automate to the "fulcrum effect" faster.

Adolescent↗
PubMed2000

Differences in nuclear DNA fragmentation and mitochondrial integrity of semen and prepared human spermatozoa.

Sperm DNA integrity is essential for accurate transmission of genetic material to offspring. Fragmentation of genomic DNA is an initial hallmark of apoptosis (programmed cell death). The aim of this study was to determine sperm nuclear DNA integrity and mitochondrial function, to quantify possible apoptosis and to investigate any relationship between these parameters. Semen samples (n = 25) were prepared by discontinuous Percoll density centrifugation (95.0:47.5). DNA integrity was determined using a modified alkaline single cell gel electrophoresis (Comet) assay. DNA fragmentation, possibly indicative of apoptosis, was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL). Mitochondrial transmembrane potential was determined using the mitochondrial probe 5,5',6,6'-tetrachloro-1,1', 3,3'-tetraethylbenzimidazolyl carbocyanine iodide (JC-1). The DNA integrity of prepared spermatozoa was significantly greater than that of semen (P < 0.005). Further, the percentage of spermatozoa with fragmented DNA and the degree of fragmentation within these cells in prepared spermatozoa is significantly less than in semen (P < 0.005). There is a significant correlation between DNA damage quantified using the Comet assay and DNA fragmentation determined using TUNEL (R = 0.562, P < 0.01). The percentage of spermatozoa with dysfunctional, possibly apoptotic, mitochondria was significantly lower in prepared spermatozoa than in neat semen samples (P < 0.001). There was a negative correlation between the percentage of spermatozoa with dysfunctional mitochondria and the percentage of progressively motile spermatozoa (R = -0.67, P < 0.01).

Adult↗
PubMed2000

Glutathione and hypotaurine in vitro: effects on human sperm motility, DNA integrity and production of reactive oxygen species.

Sperm DNA integrity is of paramount importance for the accurate conveyance of genetic material. DNA damage may be a major contributory factor in male infertility as DNA from sperm of infertile men has been found to be more susceptible to induced DNA damage in vitro than DNA from fertile men. Reactive oxygen species (ROS) are a significant source of DNA damage and human sperm are extremely sensitive to ROS attack due to their high content of polyunsaturated fatty acids and lack of capacity for DNA repair. Seminal plasma, which contains a wealth of antioxidants, provides sperm with crucial protection against oxidative insult. However, during preparation for use in assisted conception techniques, sperm are separated from seminal plasma and deprived of that essential protection. The aim of this study was to determine the effects of supplementation with glutathione and hypotaurine during sperm preparation on subsequent sperm motility, DNA integrity, induced DNA damage and ROS generation. Semen samples (n = 45) were divided into aliquots and prepared by Percoll density centrifugation (95.0-47.5%) using medium which had been supplemented with these antioxidants to a number of different concentrations all within physiological levels. Control aliquots were included which had no glutathione or hypotaurine added. Sperm motility was determined using computer-assisted semen analysis. DNA damage was induced using H(2)O(2) and DNA integrity was determined using a modified alkaline single cell gel electrophoresis (Comet) assay, while ROS generation was measured using chemiluminescence. Addition of glutathione and hypotaurine, either singly or in combination, to sperm preparation medium had no significant effect on sperm progressive motility or baseline DNA integrity. Despite this, sperm were still afforded significant protection against H(2)O(2)-induced damage and ROS generation.

Antioxidants↗
PubMed2000

Pathologic features of uterine leiomyomas following uterine artery embolization.

Bilateral uterine artery embolization has recently been employed as an alternative to operational treatment of uterine leiomyomas. The pathologic features induced by uterine artery embolization have not been previously described in detail. Usually patients experience symptomatic improvement with a reduction in size of the leiomyomas. This report describes the pathologic features in a series of 10 uterine leiomyomas where tissue was available for histologic examination following uterine artery embolization. Characteristic histologic features within the leiomyomas included massive necrosis, sometimes with dystrophic calcification, vascular thrombosis, and intravascular foreign material that elicited a histiocytic and foreign-body giant cell reaction. In some cases, intravascular foreign material was present elsewhere in the myometrium, the cervix, or paraovarian region. In occasional cases, there were foci of myometrial necrosis and microabscess formation beyond the confines of the leiomyomas. Foci of extrauterine inflammation were also occasionally identified. Histopathologists should be aware of these findings because the use of uterine artery embolization will possibly become more widespread in the future.

Adult↗
PubMed2000

Serum levels of vascular endothelial growth factor in preeclamptic and normotensive pregnancy.

The purpose of these studies was first to determine if vascular endothelial growth factor (VEGF), a vascular permeability agent, is increased in the serum of women with preclinical and clinical preclampsia (PE), and second to determine how these levels change after delivery. Twenty preeclamptic and 25 normotensive women at term consented to have blood taken pre- and post-delivery. Ten preeclamptic, 10 gestational hypertensive, and 28 normotensive women had blood collected respectively at 12, 20, and 30 weeks gestation and predelivery. Serum was extracted from all samples, and VEGF concentrations were determined by radioimmunoassay. Predelivery, the median serum VEGF concentration in the preeclamptic group was 51.7 ng/mL, and in the control group the concentration was 13.9 ng/mL (P<0.0001). Serum VEGF concentrations fell within 24 hours of delivery in both groups, which resulted in median values of 3.8 ng/mL and 3.2 ng/mL respectively (P<0.3). At 12 and 20 weeks, there was no significant difference between the serum VEGF concentrations in the 3 groups (P<0.3, 0.052 respectively). At 30 weeks, prior to the onset of clinical PE, the serum VEGF levels in the eventual preeclamptic group were elevated significantly compared with the gestational hypertensive and normotensive groups (P<0.001). Predelivery serum VEGF concentrations were significantly elevated in the preeclamptic group and were similar to those in the first study (P<0.0001). These findings suggest that VEGF may be important in the pathophysiology of PE and has the potential to act as a preclinical marker for the condition.

Adult↗
PubMed1999

Antioxidant supplementation in vitro does not improve human sperm motility.

OBJECTIVE: To determine the effects of supplementation of preparation media with ascorbate and alpha-tocopherol on subsequent sperm motility and reactive oxygen species production. DESIGN: Prospective study to analyze postpreparation human sperm motility parameters and reactive oxygen species production following antioxidant supplementation. SETTING: Andrology Laboratory, Royal Maternity Hospital, Belfast, Northern Ireland. PATIENT(S): Sixty patients attending the Andrology Laboratory for semen analysis. INTERVENTION(S): Normozoospermic and asthenozoospermic semen samples (n = 10 for each control and antioxidant group) were prepared by Percoll density centrifugation (95%-47.5%) in media supplemented with ascorbate or alpha-tocopherol to different concentrations within physiologic levels. Controls were included that were not exposed to antioxidant. MAIN OUTCOME MEASURE(S): Sperm motility parameters were assessed using computer-assisted semen analysis. The generation of reactive oxygen species was determined using luminol-dependent chemiluminescence. RESULT(S): The production of reactive oxygen species by sperm was reduced by supplementation in vitro with ascorbate and alpha-tocopherol. However, progressive motility, average path velocity, curvilinear velocity, straight-line velocity, and linearity were decreased significantly, with the greatest inhibition observed with the highest concentrations of antioxidants. CONCLUSION(S): Supplementation of preparation media with ascorbate and alpha-tocopherol, either singly or in combination, is not beneficial to sperm motility.

Antioxidants↗
PubMed1999

Virtual reality training in laparoscopic surgery: a preliminary assessment of minimally invasive surgical trainer virtual reality (MIST VR).

BACKGROUND: The "fulcrum effect" of the body wall on surgical instrument manipulation is a major hurdle for novice endoscopic surgeons. Virtual reality training has not previously been evaluated as a means to overcome this problem. MATERIALS AND METHODS: 16 participants with no experience of endoscopy were required to make multiple defined incisions under laparoscopic laboratory conditions within 2-minute periods. Half of the subjects were randomized to receive initial training on the Minimally Invasive Surgical Trainer, Virtual Reality (MIST VR) computer programme. RESULTS: Participants with MIST VR training made significantly more correct incisions (P = 0.0001) than the control group on test trial 1, and even after extended practice by both groups (P = 0.0001). They were also significantly more likely to actively use both hands to perform the endoscopic evaluation task (P = 0.01). CONCLUSIONS: Virtual reality training represents a potential, viable solution for junior endoscopists, for overcoming the "fulcrum effect", in a replicable, safe learning environment which allows objective and reliable quantification of skill levels by trainers.

Adult↗
PubMed1999

Experienced laparoscopic surgeons are automated to the "fulcrum effect": an ergonomic demonstration.

BACKGROUND AND STUDY AIMS: The inversion of the normal laparoscopic image around the Y-axis has been shown to facilitate the rate of learning of a laparoscopic task in novice subjects. The aim of this study was to investigate the effect of Y-axis image inversion on the performance of experienced laparoscopic surgeons; this had not been previously investigated. METHODS: A total of 16 experienced surgeons,who had already carried out more than 50 operative laparoscopic procedures, and 16 novice participants, who had carried out no procedures, were required to make multiple defined incisions under laparoscopic laboratory conditions within ten 1-minute periods. Participants were randomly allocated to perform the task under either normal or Y-axis inverted imaging conditions (eight experienced surgeons and eight novices in each condition). RESULTS: Y-axis inversion had a significant detrimental effect on the performance of the surgeons, whilst facilitating the performance of novices. The surgeons however, adapted to the inverted condition rapidly, showing a significant improvement in performance over the ten trials. CONCLUSIONS: The Y-axis-inverted image has a detrimental effect on the performance of experienced surgeons, indicating that they have automated to the "fulcrum effect" of the abdominal wall on instrument manipulation. Y-axis-image inversion was found to facilitate significant learning trends, regardless of the participants' level of experience.

Abdomen↗
PubMed1999

A comparison of DNA damage in testicular and proximal epididymal spermatozoa in obstructive azoospermia.

Testicular and epididymal spermatozoa are used routinely for intracytoplasmic sperm injection (ICSI) to treat men with obstructive azoospermia. Little is known of the effects of obstruction and stasis on the DNA of these spermatozoa, particularly in the epididymis where spermatozoa have been retained for long periods. Surgical epididymal aspiration for ICSI could provide spermatozoa that are senescent or dying. Using the Comet assay, the percentage of undamaged DNA of testicular spermatozoa from 20 men with obstructive azoospermia was significantly better (83.0 +/- 1. 2%) than from proximal epididymal spermatozoa (75.4 +/- 2.3%; P < 0. 05). There was no difference between the percentage of undamaged DNA of testicular spermatozoa from 39 men with obstructive azoospermia (84.0 +/- 0.9) or from 10 fertile men at vasectomy (86.8 +/- 1.8) or from ejaculated spermatozoa from five of the controls (78.9 +/- 3.9; P > 0.05). In nine subjects, a second biopsy was carried out 6 months later. There was no significant difference in undamaged DNA on these two occasions (83.5 +/- 5.6 and 84.1 +/- 4.2; P > 0.05). This confirms the reproducibility of the Comet assay for non-ejaculated spermatozoa. Our data suggest that testicular sperm DNA appears to be significantly less damaged than epididymal sperm DNA, and so testicular spermatozoa should be used in preference for ICSI to treat men with obstructive azoospermia.

Adult↗
PubMed1999

The effect of ascorbate and alpha-tocopherol supplementation in vitro on DNA integrity and hydrogen peroxide-induced DNA damage in human spermatozoa.

The aim of this study was to determine the effects of supplementation with ascorbate and alpha-tocopherol, both singly and in combination, during sperm preparation on subsequent sperm DNA integrity, induced DNA damage and reactive oxygen species (ROS) generation. Semen samples with normozoospermic and asthenozoospermic profiles (n = 15 for each control and antioxidant group) were prepared by Percoll density centrifugation (95.0-47.5%) where the medium had been supplemented with these antioxidants to a number of different concentrations, all within physiological levels. Controls were included which had no ascorbate or alpha-tocopherol added. DNA damage was induced using hydrogen peroxide (H(2)O(2)) and DNA integrity was determined using a modified alkaline single cell gel electrophoresis (Comet) assay, while ROS generation was measured using chemiluminescence. Addition of ascorbate to sperm preparation medium did not affect baseline DNA integrity but did provide sperm with complete protection against H(2)O(2)-induced DNA damage. Generation of H(2)O(2)-induced ROS was also significantly reduced after treatment with ascorbate, although baseline levels were unaffected by this antioxidant. Supplementation of sperm preparation medium with alpha-tocopherol did not influence baseline DNA integrity but provided sperm with dose-dependent protection against H(2)O(2)-induced DNA damage. Generation of H(2)O(2)-induced ROS was significantly reduced after treatment with alpha-tocopherol, although baseline ROS levels were unaffected by this antioxidant. Addition of both ascorbate and alpha-tocopherol in combination to sperm preparation medium actually induced DNA damage and intensified the damage induced by H(2)O(2), however, H(2)O(2)-induced ROS production was significantly reduced in a dose-dependent manner by supplementation with both vitamins.

Antioxidants↗
PubMed1999

Direct effect of alcohol on the motility and morphology of human spermatozoa.

Excessive alcohol consumption has been associated with impaired reproductive function by causing the inhibition of penile tumescence and ejaculatory capability. Alcohol intoxication has also been implicated in impaired spermatogenesis and an increase in sperm structural anomalies. The aim of this study was to determine the direct effects of alcohol on sperm motility and morphology in vitro. Semen samples from 67 subjects were prepared using density centrifugation. Ethanol was added, at concentrations in serum equivalent to social, moderate and heavy drinking, to the medium in which the spermatozoa were cultured. Sperm motility was assessed using computer assisted semen analysis and morphology was assessed by Tygerberg strict criteria after 0, 15, 30, 60, 120, 180 and 240 min exposure. Each concentration of ethanol produced significant decreases in the percentage progressive motility, straight line velocity and curvilinear velocity. The amplitude of lateral head displacement was also depressed by 300 and 500 mg dL-1 of ethanol. A significant decrease in the number of spermatozoa with normal morphology and an increase in irreversible tail defects were observed after exposure to 300 mg dL-1 ethanol. When alcohol is added directly to sperm, at concentrations equivalent to those in serum after moderate and heavy drinking, damaging effects are observed in both sperm motility and morphology.

Ethanol↗
PubMed1998

An ergonomic analysis of the fulcrum effect in the acquisition of endoscopic skills.

BACKGROUND: The loss of three-dimensional visual depth cues has been thought to be the main hindrance to the acquisition of endoscopic skills. However, the "fulcrum effect" of the abdominal wall on the manipulation of instruments has not to our knowledge been previously investigated. METHODS: Subjects with no experience in endoscopy were required to make multiple defined incisions under laparoscopic laboratory conditions, within ten two-minute periods in the first study and 50 in the second. Eleven subjects operated under normal imaging conditions and 11 with the y-axis inverted. RESULTS: Subjects who operated with the image inverted made significantly more incisions and significantly more correct incisions than those working under normal conditions. This effect persisted over 50 trials. CONCLUSIONS: The fulcrum effect has a major detrimental influence on acquisition of endoscopic skills. Further work is required to investigate the role of image inversion in clinical endoscopic training.

Adult↗
PubMed1998

The effects of coital lubricants on sperm motility in vitro.

Infertility affects approximately 15% of couples, and in about one-third the primary cause is a male factor. Patients undergoing infertility investigations frequently experience sexual dysfunction, which often is due to inadequate vaginal lubrication. This can lead to increased use of coital lubricants. The effects of such lubricants on sperm motility have not been widely studied, although sperm motility is one of the best prognostic indicators of fertilization. Using a prospective longitudinal control-based study, we analysed the effect of adding four lubricants: KY jelly, baby oil, olive oil and saliva on sperm motion in 16 samples from patients undergoing infertility investigations. Sperm samples were prepared by density gradient centrifugation prior to mixing with lubricants. Motility parameters were determined using computer-assisted semen analysis after 5, 15 and 30 min. All lubricants except baby oil significantly decreased percentage progressive motility, progressive velocity, curvilinear velocity and lateral head displacement at 12.5% concentration. At a lower concentration of 6.25%, both olive oil and saliva still significantly reduced progressive motility parameters, while KY jelly diminished head movement parameters. Hence, even at these very low concentrations, coital lubricants impair sperm motility and thus may adversely affect fertility.

Cellulose↗