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Biomedical subjects

A J Thomas

Publications and source records attributed to A J Thomas.

At least 91 records · Page 5Linked to original sources
PubMed1995

Effectiveness of crossover transseptal vasoepididymostomy in treating complex obstructive azoospermia.

OBJECTIVE: To review the indications, surgical technique, and results of crossover transseptal vasoepididymostomies for treatment of complex obstructive azoospermia and oligospermia. DESIGN: Retrospective review of our experience with crossover transseptal end-to-side vasoepididymostomies in 10 men. INTERVENTIONS: Ten men underwent crossover transseptal end-to-side vasoepididymostomies. Nine men had primary and one had secondary infertility. Seven men were azoospermic, and the remaining 3 had severe oligospermia (sperm density < 1 x 10(6)/mL). All had a combination of irreparable ipsilateral ductal obstruction or agenesis with a normal testis and a poorly functional or absent contralateral testis. Contralateral testicular atrophy was associated with a prior hernia repair in 3 men, varicocele-induced atrophy in 2, and severe orchitis in 2. Cryptorchidism, testicular torsion, and one unknown cause were reported for three others. Congenital absence of the vas deferens caused the ipsilateral ductal pathology in 5 men. Three men had a vas injury from pediatric inguinal surgery, and 2 had an idiopathic vas obstruction. RESULTS: Twelve microsurgical crossover transseptal vasoepididymostomies were performed (2 men had repeat procedures). Anastomosis was performed to the caput in five men, the corpus in two, and the cauda in three men. Eight of nine men followed for 6 months or more had sperm in their ejaculate. Two of seven couples have established pregnancies. Total sperm counts ranged from 18 to 201 x 10(6) (mean, 98.1 x 10(6)) with motility of 5% to 37% (mean, 13%). Men with congenital absence of the vas deferens had significantly lower postoperative total sperm counts than men with all other causes of ductal pathology: 37.8 x 10(6) versus 135 x 10(6). No other characteristics (type of infertility, preop semen analysis, cause of testicular pathology, site of epididymal anastomosis) were useful predictors of postoperative sperm counts. CONCLUSIONS: If there is a solitary functioning testis with irreparable excurrent ductal obstruction or agenesis, a crossover transseptal vasoepididymostomy can restore patency in most men.

Adult↗
PubMed1995

Incidence and level of seminal reactive oxygen species in normal men.

OBJECTIVES: Excessive formation of reactive oxygen species (ROS) in human semen has been associated with impaired sperm function and fertility potential. The presence of ROS in semen specimens from normal fertile men emphasizes the importance of defining a normal range of ROS formation. The purpose of this study was to establish a normal range of ROS generation and to investigate the effect of sperm concentration on the ROS level. METHODS: ROS was determined in 15 healthy donors and 20 men with suspected infertility. After the sperm concentration in normal donors was adjusted to 20 x 10(6)/mL, ROS was measured by chemiluminescence using luminol in a Berthold luminometer. A specimen was regarded as positive (abnormal) when the value was at least 10 x 10(4) counts per minute (cpm). ROS was also evaluated at 4 sperm concentrations (60, 30, 15, and 7.5 x 10(6)/mL) from samples obtained from the patients with suspected infertility. In addition, ROS was measured in 7 ROS-positive specimens at a sperm concentration of 15 x 10(6)/mL and 60 x 10(6)/mL. RESULTS: Results showed that ROS formation was negative in all 15 healthy donors (median, 0.9 x 10(4) cpm; interquartile range, 0 to 1.48 x 10(4) cpm). The ROS formation value among all the donors was less than 5.5 x 10(4) cpm. ROS formation was positive in 8 (40%) of the suspected infertile patients. ROS levels were significantly lower at sperm concentrations of 15 x 10(6)/mL or 7.5 x 10(6)/mL compared with 30 x 10(6)/mL or 60 x 10(6)/mL (P = 0.05). The ROS level increased after centrifugation for 10 minutes at 500 g in all 7 specimens at both 15 and 60 x 10(6)/mL. However, the increase in ROS formation at 60 x 10(6)/mL was significantly greater than that at 15 x 10(6)/mL (P < 0.001). CONCLUSIONS: A range of ROS formation of 0 to 5.5 x 10(4) cpm at a sperm concentration of 20 x 10(6)/mL may be considered as normal for healthy donor semen. The positive relationship between ROS formation and sperm concentration at the time of measurement emphasizes the importance of concentration adjustment before analysis when comparing ROS levels between different specimens.

Adult↗
PubMed1995

Effect of cryopreservation on semen quality in patients with testicular cancer.

OBJECTIVES: Current techniques in cryopreservation of human semen substantially decrease sperm quality. In addition, the pregnancy rate using cryopreserved sperm obtained from testicular cancer patients is lower than when sperm from normal fertile men is used. However, it is still unclear whether cryopreserved sperm from these patients is inherently defective or if the sperm loses its motility after thawing. This study was undertaken to assess the effect of cryopreservation on the quality and motion characteristics of semen from patients with testicular cancer before definitive therapy compared with semen from normal volunteers. METHODS: We compared the sperm quality before and after cryopreservation in samples from 34 patients with testicular cancer and 30 normal volunteers who were referred for sperm banking over a 7-year period. The effects of cancer stage and histologic type on various semen parameters were also examined. A computer-assisted semen analysis was performed before and after cryopreservation on each specimen. The nitrogen vapor technique using Test yolk buffer with glycerol as a cryoprotective agent was used for cryopreservation. The motile sperm count and motion characteristics (motility, velocity, linearity, amplitude of the lateral head movement, motility index) were analyzed before and after cryopreservation and compared between the groups. RESULTS: Semen quality did not significantly differ among patients with Stage I, II, or III cancer. However, semen quality tended to be poorer at higher cancer stages. In general, semen quality was better among patients with pure seminomas than with pure embryonal tumors; quality was worst among patients with mixed germ cell tumors. However, 71.4% of patients with mixed tumors presented with Stage III disease, whereas all patients with seminomas presented with Stage I disease. Significant differences were also seen in prefreeze motility (median, 42% [interquartile range, 24 to 51] versus 60.5% [range, 49 to 73]; P = 0.0004) and motile sperm count (6.7 x 10(6)/mL [range, 3.4 to 14.4] versus 50.0 [range, 24.6 to 72.0]; P = 0.0001) in patients compared with controls, respectively. The motile sperm count and percent motility significantly decreased in both patients and controls after cryopreservation (P = 0.0001). However, the percentage decline in motile sperm count and motion characteristics after cryopreservation did not differ significantly between patients and controls (P > 0.01). CONCLUSIONS: We conclude that the effect of cryopreservation on sperm quality in patients with testicular cancer is identical to its effect on sperm from normal fertile men. Differences in values after preservation are explained by poor semen characteristics before freezing; semen quality declines with more extensive disease. Stage I patients also had poorer quality than control subjects. Thus, we recommend that routine sperm banking be encouraged among all patients with testicular cancer before the initiation of specific medical treatment. We also recommend that future efforts be focused on improving the technique of sperm banking.

Adolescent↗
PubMed1995

Colposcopic genital findings in prepubertal girls assessed for sexual abuse.

After the introduction of the colposcope for the examination of children suspected of being sexually abused in Leeds, a study was undertaken to describe the findings in detail. A total of 109 consecutive prepubertal girls, mean age 70.4 months were assessed including colposcopic genital and anal examination, and peer group review of reports and photographs. Fifty nine children had signs consistent with blunt force penetrating trauma (hymenal transection/major notch, scar, or hymenal attenuation). Transections were encountered most commonly at 6 o'clock (directly posterior). In 46 the hymenal orifice was gaping with thigh abduction only and in 47 the hymenal orifice transverse diameter was greater than 4 mm on labial separation. Overall, physical findings were commonly present and in only two cases were no signs recorded. Non-specific and frequent findings included patterns of labial and introital reddening. Supportive hymenal signs including swelling, rounding of edge, thickening, distortion, and loss of symmetry were common. Labial fusion was present in 20. Urethral dilatation with labial separation was noted in 14. Physical findings including normality are consistent with abuse and even minor anogenital signs as well as negative findings should be documented. Colposcopy and photography are valuable tools in peer review, teaching, and case management.

Age Factors↗
PubMed1995

Modification of conditioned apneas in rats: evidence for cortical involvement.

Apneic patterns in breathing can be classically conditioned in rats by brief neonatal exposures to hypoxia, noise, and petting during sleep (A. J. Thomas, W. Austin, L. Friedman, and K. P. Strohl, J. Appl. Physiol. 73: 1530-1536, 1992); thus animals may acquire apneic patterns by exposure to not only respiratory but also nonrespiratory stimuli. We hypothesized that conditioned apneas in these animals can be reduced or abolished by presentation of counterconditioning stimuli, which would prevent the respiratory controller from being influenced by nonrespiratory stimuli and affecting breathing rhythmicity. In five female rats conditioned during neonatal life to exhibit apneic breathing during adulthood and in five female unconditioned control rats, the effect of a brief quiet repetitive auditory stimulus (white noise, 50 Hz, 30 dB) presented for periods of 20 min on and 20 min off was assessed. In conditioned apneic rats, white noise reduced the frequencies of apneas by approximately 79% (P < 0.01) but did not alter the number of apneas in unconditioned control rats. In either group, white noise had no effect on the number of apneas preceded by a sigh. In a second experiment, the effect of Equithesin anesthetic was examined in five female conditioned apneic rats. In contrast to the white noise effect, not only apneic breathing but also apneas preceded by a sign were completely abolished by anesthesia (P < 0.0001). These findings suggest a role for counterconditioning and cortical influences on respiratory rhythm in the adult mammal.

Acoustic Stimulation↗
PubMed1995

A method of human semen centrifugation to minimize the iatrogenic sperm injuries caused by reactive oxygen species.

Current techniques of sperm preparation for in vitro fertilization or intrauterine insemination require centrifugation of human semen to separate spermatozoa from the seminal plasma. Centrifugation increases reactive oxygen species (ROS) formation in semen. Moreover, high levels of ROS are associated with sperm membrane injury through spontaneous lipid peroxidation, which may alter sperm function. We investigated the relationship between centrifugation variables (time and g-force) and ROS production to establish an optimal centrifugation protocol for sperm preparation techniques. Semen from 38 men (24 patients and 14 normal volunteers) was evaluated for the formation of ROS before centrifugation and after centrifugation at 200 g for 2 or 10 min and after 500 g for 2 or 10 min. The absence of white blood cells in semen which can also produce ROS was determined with the myeloperoxidase technique (Endtz test). All specimens were negative (< 1 x 10(6)/ml) by the Endtz test. The formation of ROS was measured by chemiluminescence. ROS formation was regarded as high (positive) when the chemiluminescence response was at least 10 x 10(4) counted photons/min (cpm). The sperm concentration in each sample was adjusted to 15-20 x 10(6) cells/ml before analysis. Eight specimens (7 patients and 1 donor) exhibited high levels of ROS before centrifugation. All 8 showed further, significant increases in ROS formation regardless of g-force or time. The increase in ROS was significantly less when semen was centrifuged for 2 as compared to 10 min (p < 0.001). Six specimens previously ROS-negative became ROS-positive after centrifugation for 10 min at 200 and 500g. We conclude that the time of centrifugation is more important than g-force for inducing ROS formation in semen. Based on these results, we recommend a shorter centrifugation period in the preparation of sperm for assisted reproductive techniques.

Centrifugation↗
PubMed1995

Optimum abstinence time for cryopreservation of semen in cancer patients.

Although an abstinence period of 48 to 72 hours is the most commonly prescribed interval for diagnostic semen analysis, to our knowledge the association between the abstinence period and sperm quality after cryopreservation has not been identified. Patients with a malignant disease who are consulting for semen banking most often require urgent therapy. Consequently, defining the shortest abstinence period that allows for frequent semen collection within a limited interval and the best post-thaw sperm quality is necessary. We investigated the relationship between abstinence period, and the pre-freeze and post-thaw motility variables in semen specimens obtained from cancer patients for sperm banking. Samples collected from 95 patients were divided according to abstinence period: group 1-15 patients at 24 to less than 48 hours, group 2-53 at 48 to less than 72 hours and group 3-27 at more than 72 hours. Pre-freeze and post-thaw motile sperm count and motion variables (motility, velocity, linearity, amplitude of lateral head movement and motility index), and percentage decrease in sperm variables after cryopreservation were analyzed. Semen volume, the pre-freeze and post-thaw motile sperm count, motion parameters and the percentage decrease in semen variables did not differ significantly among the groups. We conclude that semen collection for cryopreservation after 24 to less than 48 hours of abstinence results in post-thaw quality comparable to that after an abstinence of 48 to less than 72 hours or longer. Thus, an abstinence period of 24 to less than 48 hours can be recommended for sperm banking in cancer patients.

Cryopreservation↗
PubMed1995

Development of a new alloplastic spermatocele demonstrating successful sperm retrieval in an animal model.

OBJECTIVE: To create an alloplastic spermatocele capable of repeated sperm aspiration. The alloplastic spermatocele has long been a theoretical solution to infertility for those patients with congenital absence of the vas deferens or irreversible obstruction of the male reproductive ductal system. Recent studies have suggested that sperm from efferent ducts are capable of fertilization. Clinical use of alloplastic spermatoceles for collection of epididymal sperm has resulted in unacceptably low pregnancy rates. Improvement in spermatocele function may occur if a microsurgical anastomosis is performed to the epididymis. DESIGN: A newly designed alloplastic spermatocele was implanted in 17 mature male rabbits. The faceplate of the device had a 0.7-mm orifice, allowing direct precise microsurgical anastomosis to a specific loop of the epididymal tubule. RESULTS: Sperm retrieval was possible in 16/17 (94%) animals. Repeated successful aspirations (total of 73) were performed in all but one animal. The total number of sperm collected per spermatocele averaged 115 x 10(6) (range 0 to 734 x 10(6)). The sperm motility varied widely between animals and specimens, with a maximum average of 21.6% motile sperm/aspirate per animal. All spermatoceles eventually occluded (mean time of occlusion 14 days; range 3 to 30 days). The prostheses with the attached epididymides were examined histologically. CONCLUSIONS: This prototype alloplastic spermatocele allows repeated high density sperm retrieval over a short period of time. Low sperm motility may be less problematic clinically as new techniques of IVF become available.

Animals↗
PubMed1994

The effect of partial zona dissection on the fertilizing capacity of chronically obstructed mouse caput epididymal sperm.

PURPOSE: Having observed that sperm from the chronically obstructed caput epididymis fertilize poorly in vitro, we investigated the effect of partial zona dissection (PZD) on fertilization in a murine model of unilateral proximal epididymal obstruction. Cleavage rates were compared for zona-intact oocytes and PZD oocytes incubated with sperm from the following epididymal segments: the obstructed caput, the contralateral nonobstructed caput, the contralateral cauda, and a sperm-free preparation to control for parthenogenesis. RESULTS: Unilateral epididymal obstruction resulted in significantly higher sperm counts in the obstructed caput compared to the nonobstructed caput, although there was no difference in motility. Cleavage rates for ova incubated with sperm from the obstructed caput and the nonobstructed caput were uniformly poor and did not differ significantly from those for the sperm-free controls. Cauda sperm fertilized significantly better than all other sperm groups (P < 0.05). Partial zona dissection did not improve cleavage rates in any group. CONCLUSION: We conclude that sperm from the chronically obstructed caput epididymis, like sperm from the normal caput, are unable to fertilize ova, and PZD does not enhance this poor fertilizing capacity. Furthermore, the finding that PZD does not improve the fertilizing capacity of the presumably mature cauda sperm in our mouse model suggests that any beneficial effect of PZD may be strain-specific.

Animals↗
PubMed1994

Safety of transurethral surgery in the early postoperative period following an open cardiac procedure.

A retrospective investigation was performed to determine whether patients undergoing transurethral surgery soon after cardiac surgery experienced increased morbidity or mortality rates. From 1986 to 1990, 24 patients first underwent open heart surgery and then either transurethral prostatectomy, bladder tumor resection or bladder cup biopsy during the same hospital stay. Postoperative complications included significant hematuria in 2 patients (8%), mild stress incontinence in 1 (4%) and bladder perforation in 1. One patient died of a spontaneous pneumothorax 17 days after the urological operation. None of these patients had had a previous myocardial infarction. The outcome of these patients was compared to that of 115 men who underwent transurethral prostatectomy for presumed benign disease during 1990. Complications of transurethral prostatectomy in this group included significant gross hematuria in 5 men, while 6 experienced urinary retention (1), atrial fibrillation (1), delirium (1), myocardial infarction (1), seizure (1) and intraoperative urethral injury (1). There was 1 death from multiple postoperative complications. Morbidity and mortality rates did not differ significantly between the 2 groups. Transurethral surgery performed after cardiac surgery during the same hospital stay appears to be safe, provided the patient is stable.

Aged↗
PubMed1994

Assessment of hepatitis B "e" antigen and "e" antibody status--tests of status or status of tests?

Forty-seven sera that gave positive results in tests for hepatitis B surface antigen and core antibody were examined for the presence of "e" antigen and "e" antibody by various commercially available assays. Considerable discordance was observed between results of tests performed on the same sample in different assays. Examination of the sera for the presence of hepatitis B DNA failed to resolve the discrepancies. Increasingly, "e" antigen and its antibody are used as measures of infectivity in carriers of hepatitis B. The absence of reliable tests has implications for patients, for infection control within hospitals and for the implementation of Department of Health guidelines on safe working practices for hepatitis B-infected health care workers.

Carrier State↗
PubMed1993

Characterization of muscarinic agonists in recombinant cell lines.

Using recombinant CHO cells that express Hm1-Hm5 receptors, reference muscarinic agonists have been characterized with respect to their activity in receptor binding and second messenger assays. In whole cell [3H]-N-methyl scopolamine binding, no agonist was found to be truly subtype selective, although some showed marked differences between several of the subtypes (e.g. m1 vs. m2). As a functional index of receptor activation, phosphatidyl-inositol (PI) turnover was measured for m1, m3, and m5 receptors while inhibition of forskolin-stimulated cAMP accumulation was measured for m2 and m4 receptors. Both full and partial agonists were delineated in PI turnover, but all agonists showed similar responses on cAMP. Alkylation studies with propylbenzylcholine mustard showed that both efficacy and potency were markedly affected in the functional assays by the number of free receptors. Thus, receptor reserve appears to play a major role in the determination of subtype selectivity for agonists using functional measures. Even with these limitations, however, the use of transformed cell lines is playing a pivotal role in the discovery of selective agonists.

Animals↗
PubMed1993

Energy balance in healthy elderly women.

There is a paucity of data on which to base estimates of the energy requirements of the elderly. In general, ageing appears to be associated with a reduction in energy requirement arising from a reduction in physical activity and loss of fat-free mass. The aim of the present study was to measure the total energy expenditure (TEE), basal metabolic rate (BMR), and energy expended on physical activity (calculated as TEE-BMR) in a group of healthy elderly women living in the community in Southampton. Mean rates of TEE (9.21 (SD 1.48) MJ/d) and energy expended on physical activity (4.12 (SD 1.19) MJ/d) were higher than those observed in some studies of younger adults in the UK, and higher than the factors used to estimate the average energy requirement for the elderly. The results suggest that an age-related reduction in energy requirement is not inevitable and support the hypothesis that the effects of ageing on physical activity, body composition, and hence energy requirements, are variable.

Aged↗
PubMed1993

Structure of parasternal intercostal muscles in the adult hamster: topographic effects.

The parasternal intercostals are primary inspiratory muscles like the costal and crural diaphragm. However, the structure of the rib cage and its impedance to inspiration and expiration varies regionally. We questioned whether topographic differences in rib cage structure and impedance were associated with regional differences in parasternal intercostal muscle structure. Therefore, we examined the size and percentage of histochemically stained fibers in the parasternal intercostal muscles in the first, second, third, fourth, and sixth interspaces in the hamster. We observed a rostrocaudal gradient in the percentage and size of slow oxidative (SO), fast oxidative-glycolytic, and fast glycolytic (FG) fibers in the parasternal intercostal muscles. In particular, the percentage of SO decreased while the percentage of FG increased in a rostrocaudal direction in the first through sixth interspaces. In addition, the size of SO and FG fibers increased from the first to sixth interspace. Furthermore, changes in the size and percent of the three fiber types produced, in a rostrocaudal direction, significant reductions in the relative mass of the parasternal intercostal muscle made up of SO fibers and increases in the mass of fast fibers. We speculate that topographical differences in the size and percentage of fast and slow twitch fibers in the parasternal intercostal are likely to alter force-generating capacity of the parasternal muscles in a rostrocaudal direction and likely reflect regional differences in muscle load and/or activity.

Analysis of Variance↗
PubMed1993

Acute intestinal ischaemia: options in surgical management.

Seven patients (mean age 67 years, range 52-82 years) presented with acute intestinal ischaemia over a 4-year period. Massive bowel resection was performed in all patients. Exteriorisation and secondary restoration of intestinal continuity was employed in four patients. In two patients a primary anastomosis was performed at the time of resection and one patient underwent a 'second-look' procedure. Massive bowel resection and exteriorisation allows direct observation of stoma viability, avoids the risk of anastomotic breakdown and should be considered in all but moribund patients with acute intestinal ischaemia. In elderly patients resection and primary anastomosis may be an alternative option.

Aged↗