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Biomedical subjects

A Taylor

Publications and source records attributed to A Taylor.

At least 163 records · Page 9Linked to original sources
PubMed2000

Effects of cadmium chloride administration on the macroscopic and microscopic characteristics of ejaculates from Chios ram-lambs.

The effects of cadmium chloride on the volume of the ejaculate, semen density, total number of spermatozoa per ejaculate, viability, grade of motility, and morphological abnormalities were studied in 3-month-old ram-lambs of the Chios breed. Two groups of seven animals each were used. For a period of 7 months, one group was treated with a daily oral dose (3 mg/kg b.w.) of cadmium chloride and the other group received the corresponding volume of doubly distilled water. Blood samples were collected for cadmium determinations, whereas semen was collected weekly. In the cadmium-treated animals, cadmium concentration in the whole blood was increased and the testes weight was lower. The volume of the ejaculate, the semen density and the total number of spermatozoa were significantly reduced by the administration of cadmium chloride. No differences were observed in the viability, the grade motility of spermatozoa, or the percentage of dead and morphologically abnormal spermatozoa between the control and the cadmium-treated animals. Histopathological examination in the cadmium-treated animals revealed the presence of lesions in the Sertoli cells, the seminiferous tubules, the primary and the secondary spermatocytes and the spermatides, whereas in the Leydig cells no significant lesions were evident.

Aging↗
PubMed2000

The effect of vitamin C supplementation on coagulability and lipid levels in healthy male subjects.

Although dietary intake and plasma levels of vitamin C have been inversely associated with cardiovascular disease, the mechanism through which it may exert its effect has not been fully explained. Since thrombosis plays an important role in the onset of cardiovascular disease, we investigated the effect of vitamin C on measures of hemostasis that have been associated with cardiovascular risk. The effect of vitamin C on lipid levels was also evaluated. In a randomized, placebo-controlled, crossover study, we determined the effect of 2 g daily of vitamin C supplementation on platelet adhesion and aggregation, levels of tissue plasminogen activator antigen, plasminogen activator inhibitor, fibrinogen, plasma viscosity, von Willebrand factor, and lipid levels in 18 healthy male volunteers with low normal vitamin C levels. No striking effects of vitamin C on the hemostatic measures were observed, although tissue plasminogen activator antigen levels were inversely related to Vitamin C levels. Von Willebrand factor levels were slightly higher with vitamin C, although within the normal range. Total cholesterol levels were 10% lower when subjects were receiving vitamin C compared to placebo (167+/-7 mg/dL vs. 184+/-7 mg/dL), P=0. 007), although the total cholesterol/HDL ratio was not significantly different. Higher levels of tissue plasminogen activator antigen, which in the present study were associated with lower vitamin C levels, have been shown in prospective studies to convey an increased risk of cardiovascular events. Further studies of the effect of vitamin C on hemostatic measures are required in higher risk populations or those with known cardiovascular disease.

Adult↗
PubMed2000

Calorie restriction modulates age-dependent changes in the retinas of Brown Norway rats.

The present study examined the effect of a 40% reduction in caloric intake (CR) versus ad libitum (AL) feeding on retinal aging. CR- and AL-fed Brown Norway (BN) rats were obtained at 12, 24 and 30 months of age from the National Center for Toxicological Research (NCTR). Age-dependent declines in outer nuclear layer (ONL=photoreceptor) cell densities, ONL height, inner nuclear layer (INL) cell densities, and thicknesses of the inner retina and whole retina were quantified in thick sections at six loci across the circumference of the sensory retina (four peripheral, two central). Data were analyzed by repeated measures, general linear models. Aging in both diet groups was associated with declines in ONL cell density, ONL height, peripheral INL cell density and total retinal thickness (P< or =0.05). However, ONL cell densities, ONL height and retinal thickness were significantly greater in the CR versus AL diet group at all three ages (P< or =0.005). CR was also associated with a trend for greater peripheral INL cell density (P=0.06) and with greater INL thickness at 30 months (Bonferroni P=0.03). Elevated ONL cell densities in the CR-12 cohort relative to the AL-12 cohort could be explained by diet-associated differences in retinal length, i.e. delayed retinal growth in response to CR. Enhanced ONL cell density, ONL height, INL cell density, INL thickness and total retinal thickness in the CR-30 cohort appear to be as a result of reduced rates of retinal cell loss between 24 and 30 months. However, the protective effect of CR in retinas of older animals may also reflect the initial growth-associated enhancements which were observed in 12 month-old animals. The rat retina may provide a useful model for elucidating the neuroprotective mechanism(s) of CR.

Aging↗
PubMed2000

Patterns of fusimotor activity during locomotion in the decerebrate cat deduced from recordings from hindlimb muscle spindles.

1. Recordings have been made from multiple single muscle spindle afferents from medial gastrocnemius (MG) and tibialis anterior (TA) muscles of one hindlimb in decerebrate cats, together with ankle rotation and EMG signals, during treadmill locomotion. Whilst the other three limbs walked freely, the experimental limb was denervated except for the nerves to MG and TA and secured so that it could rotate only at the ankle joint, without any external load. Each afferent was characterised by succinylcholine testing with regard to its intrafusal fibre contacts. Active movements were recorded and then replayed through a servo mechanism to reproduce the muscle length changes passively after using a barbiturate to suppress gamma-motor firing. 2. The difference in secondary afferent firing obtained by subtracting the discharge during passive movements from that during active movements was taken to represent the profile of static fusimotor activity. This indicated an increase before the onset of movement followed by a strongly modulated discharge in parallel with muscle shortening during locomotion. The pattern of static firing matched the pattern of unloaded muscle shortening very closely in the case of TA and with some phase advance in the case of MG. The same effects were observed in primary afferents. 3. Primary afferents with bag1 (b1) contacts in addition showed higher firing frequencies during muscle lengthening in active than in passive movements. This indicated increased dynamic fusimotor firing during active locomotion. There was no evidence as to whether this fluctuated during the movement cycles. 4. When the mean active minus passive difference profile of firing in bag2-chain (b2c) type primary afferents was subtracted from that for b1b2c afferents, the difference was dominated by a peak centred on the moment of maximum lengthening velocity (v). 5. The component of the active minus passive difference firing due to b1 fibre contacts could be modelled by f(t) = av (where a is a constant) during lengthening and by f(t) = 0.2 av during shortening. The remainder of the difference signal matched the predictions of the static fusimotor signal derived from secondary afferents. 6. The findings are discussed in relation to the concept that the modulated static fusimotor pattern may represent a 'temporal template' of the expected movement, though the relationship of the results to locomotion in the intact animal will require further investigation. The analysis of the data indicates that the combined action of muscle length changes and static and dynamic fusimotor activity to determine primary afferent firing can be understood in terms of the interaction between the b1 and b2c impulse initiation sites.

Animals↗
PubMed2000

Mode of delivery and subsequent stress response.

We have shown that a baby's stress (saliva cortisol) and crying response to inoculation at 8 weeks was related to mode of delivery, with the greatest response shown in those born by assisted delivery and the least response in those born by elective caesarean section.

Cesarean Section↗
PubMed2000

Reactive synovitis of the knee joint: MR imaging appearance with arthroscopic correlation.

OBJECTIVE: To evaluate the use of routine MR imaging sequences in detecting and characterizing secondary reactive synovitis of the knee joint using arthroscopy as the standard of reference. DESIGN AND PATIENTS: Fifty consecutive patients with a history of knee pain who were referred for MR imaging and subsequently underwent arthroscopy of the knee comprised the study group. MR images were evaluated for the presence and appearance of synovitis reflected in synovial thickening and irregularity. Synovial thickening was graded on MR imaging as follows: 0=normal, 1=thin line of increased signal intensity, 2=increased signal intensity with frond-like or hair-like projections and a granular appearance of joint fluid. Standard knee imaging protocols were used. RESULTS: The sensitivity, specificity, and accuracy of MR imaging in detecting synovitis compared with arthroscopy were 88%, 97%, and 95%, respectively. Grade 1 synovitis was best seen on proton-density-weighted images, demonstrating increased signal intensity of the synovium against the relatively low signal intensity of the joint fluid. Grade 2 synovitis was best seen on proton-density images and T2-weighted spin echo and fast spin echo images with fat saturation, demonstrating a granular and linear hair-like appearance of joint fluid. Axial and sagittal imaging planes were most helpful in the diagnosis of synovitis. CONCLUSION: Routine MR pulse sequences are useful in identifying the presence and extent of synovial abnormalities. The detection of different stages of synovial pathology should become an important part of the evaluation of the post-traumatic patient as treatment may be altered as a result.

Adult↗
PubMed2000

Coronary calcification: insights from sudden coronary death victims.

We studied 108 cases of sudden coronary death at autopsy. Any calcification was present in 55% of men and women under 40 years; all hearts showed some calcification by age 50 in men, and by age 60 in women. The only risk factor independently associated with increased calcification was diabetes mellitus, in women only. The degree of calcification was greatest for acute and healed plaque ruptures, and the least for plaque erosion. Calcification in coronary atherosclerosis appears to be delayed in women, is greatest in women diabetics, and is associated with one type of plaque instability, namely plaque rupture.

Adult↗
PubMed2000

Low serum estradiol concentrations after five days of controlled ovarian hyperstimulation for in vitro fertilization are associated with poor outcome.

OBJECTIVE: To evaluate the prognostic significance of low serum E2 concentrations in controlled ovarian hyperstimulation (COH) cycles for IVF. DESIGN: Retrospective study. SETTING: Assisted conception unit of a university hospital. PATIENT(S): One thousand four hundred and forty patients undergoing COH for IVF. INTERVENTION(S): COH, serum E2 measurement, ultrasonographic scanning of ovarian follicles, oocyte retrieval, and ET. MAIN OUTCOME MEASURE(S): Cancellation and pregnancy rates. RESULT(S): Patients were classified into four groups according to serum E2 levels on the sixth day of COH: group A (E2 level < 50 pg/mL [114 cycles]), group B (E2 level 51-100 pg/mL [189 cycles]), group C (E2 level 101-200 pg/mL [320 cycles]), and group D (E2 level >200 pg/mL [817 cycles]). Group A experienced the highest cancellation rates (65.1%) and lowest pregnancy rates (7.8%) despite requiring significantly more hMG ampules (47.8+/-1.7). The cancellation rate was higher (75.1%) and no pregnancy occurred in a subset of group A in whom COH was initiated with > or =3 ampules (225 IU) of gonadotropins. CONCLUSION(S): In COH cycles using luteal phase buserelin, low initial serum E2 concentrations are associated with poor outcome.

Chorionic Gonadotropin↗
PubMed2000

Aluminum inhibits the lysosomal proton pump from rat liver.

Lysosomes are cytoplasmatic organelles, delimitated by a single lipoprotein membrane, that contain several enzymes mostly belonging to the hydrolases in that they function mainly for intracellular digestion. Lysosomal internal pH is characteristically acidic and it is maintained around pH 4.5 by a proton pump, an ATPase, that uses energy from ATP hydrolysis to translocate H+ ions into lysosomes. In the presence of Al3+ the proton pump activity is markedly reduced compromising acidic vesicles functionality. Among different species utilized, Al2(SO4)3 and AlF3 were the most effective. Aluminum effect was not observed when the delta pH was produced artificially by nigericin.

Adenosine Triphosphate↗
PubMed2000

Variable heating rate thermogravimetric analysis as a mechanism to improve efficiency and resolution of the weight loss profiles of three model pharmaceuticals.

The effect of variable heating rates on the efficiency or resolution of the derivative of the thermogravimetry profiles of three model pharmaceutical compounds was investigated. The variable heating system utilized computer controlled algorithms for the evaluation of crystalline sodium warfarin, DuP 532 and hydrated DuP 925 as model compounds with one, two and three step weight loss profiles, respectively. As the heating modes were increased through each of the eight settings, the minimum heating rate decreased while the efficiency and resolution and the analysis times increased. The observed weight loss remained relatively constant for each of the model compounds as the heating modes were increased. The efficiency of the derivative of the weight loss profile of crystalline sodium warfarin increased from 121 to 621 as the heating mode increased. The resolution between the two steps of the derivative of the weight loss profile of DuP 532 increased from 1.73 to 3.88 as the heating mode increased. For hydrated DuP 925, the resolution increased from 1.49 to 5.46 between steps 1 and 2 of the derivative of the weight loss profile and from 1.87 to 3.24 between steps 2 and 3 of the derivative of the weight loss profile. Variable heating rates provided a valuable aid in obtaining high efficiency/resolution thermograms. The enhanced efficiency/resolution permitted greater separation of the volatilization process, especially for samples with multi-step weight loss profiles. Increasing the heating mode afforded higher efficiencies/resolutions that typically reached a maximum value at mode 6.

Algorithms↗
PubMed2000

Normative data for iliac bone histomorphometry in growing children.

Many insights into normal and pathologic bone development can only be gained by bone histomorphometry. However, the use of this technique in pediatrics has so far been hampered by the lack of reference data. Therefore, we obtained transfixing iliac bone samples from 58 individuals between 1.5 and 22.9 years of age (25 male; tetracycline labeling performed in 48 subjects), who underwent surgery for reasons independent of abnormalities in bone development and metabolism. The results of histomorphometric analyses of cancellous parameters and cortical width are presented as means and standard deviations, as well as medians and ranges in five age groups. In addition, the original data are available from the authors. There were significant age-dependent increases in both cortical width and cancellous bone volume, the latter being due to an increase in trabecular thickness. Osteoid thickness did not vary significantly with age. Bone surface-based indicators of bone formation showed an age-dependent decline, reflecting similar changes in activation frequency. Mineral apposition rate decreased continuously with age. Parameters of bone resorption did not vary significantly between age groups. Paired biopsies from adjacent sites, obtained in eight subjects, were used to examine the reproducibility of histomorphometric parameters in children. The lowest coefficients of variation (<10%) were found for structural measures, as well as mineral apposition rate and wall thickness. The highest variability was found for cellular parameters. The availability of reference material will greatly facilitate the use of histomorphometry in pediatrics.

Adolescent↗
PubMed2000

Corpus callosum may be similar in children with ADHD and siblings of children with ADHD.

No previous studies have used morphological neuroimaging to compare children with ADHD with siblings of children with ADHD. To test the hypothesis that the total size of the corpus callosum is altered in children with hyperkinetic disorder, the corpus callosum was outlined from a single midline protondensity weighted slice (containing the septum pellucidum). Fifteen boys with a refined phenotype of ADHD (mean age 10.2 years) and 15 healthy male siblings of children with ADHD (mean age 10.6 years) were enrolled in the study. The two groups were compared for global brain size and the callosal areas of Witelson. No significant differences were found between the study and comparison groups for any of the corpus callosum areas, even after age, global brain size, and handedness were covaried (using MANOVA). In addition, corpus callosum sizes do not seem to differ between children with ADHD and unaffected siblings of children with ADHD. Clinicians should not base their pathophysiological diagnosis of this disorder on an abnormality of callosal development.

Adolescent↗
PubMed2000

Grouping of Salmonella enterica serotype Montevideo strains by ribotyping and IS200 profiling.

One-hundred and twenty-one isolates of Salmonella enterica serotype Montevideo, representing different biotypes and incidents of infection detected in the UK between 1977 and 1995, were analysed by EcoRI ribotyping, PvuII ribotyping and IS200 fingerprinting. Among the isolates examined, 7 EcoRI ribotypes, 5 PvuII ribotypes and 55 IS200 profile types were recognized and 4 arbitrary groups defined. All 33 isolates of biotype 2d belonged to EcoRI/PvuII ribotype 1/1 and IS200 lineage A and comprised Group I. The other 88 isolates of biotype 10di and its variants were assigned to Groups II-IV. All 27 isolates in Group II were of EcoRI/PvuII ribotype 2/2 and IS200 lineage B. Among the 43 isolates in Group III, 42 of which were of EcoRI/PvuII ribotype 3/3, IS200 analysis identified 38 profiles in lineages C-I. Six EcoRI/PvuII ribotypes and 8 IS200 profiles, mostly in lineages C-E, were recognized among the 18 isolates in Group IV. The combined use of biotyping and ribotyping, and to some extent IS200 profiling, has enhanced our understanding of the clonal structure of serotype Montevideo and provides a basis for further study.

Animals↗
PubMed2000

Factors associated with injecting risk behaviour among serial community-wide samples of injecting drug users in Glasgow 1990-94: implications for control and prevention of blood-borne viruses.

AIMS: To examine the association between recipient-sharing of needles and syringes and demographic characteristics, injecting behaviour and needle and syringe exchange utilisation. DESIGN: Self-report data from serial cross-sectional surveys. SETTING: Multiple street, needle and syringe exchange and drug treatment sites throughout Glasgow. PARTICIPANTS: 2576 current injecting drug users (IDUs) recruited during 1990-94. FINDINGS: In the multiple logistic regression analysis, a significantly lower level of recipient-sharing was associated with respondents who resided within 1 mile of a needle and syringe exchange compared to those who lived further away (adjusted OR 1.3; 95% CI 1.0-1.6), and by IDUs who reported obtaining either 6-15, 16-30, or > 30 sterile needles and syringes in an average week from a needle exchange and/or pharmacist (adjusted ORs 0.55, 0.34, 0.25; 95% CIs 0.3-0.9, 0.2-0.6 and 0.2-0.4, respectively) compared to those who obtained no sterile equipment from these sources. Recipient-sharing of needles and syringes in the previous 6 months reduced significantly between 1990 (43%) and 1991-94 (27-33%) (p < 0.0001); this decline was not explained by needle and syringe exchange utilization, suggesting that additional factors were influencing behavioural change at that time. CONCLUSION: Our data indicate that improving injectors' convenience of access to exchange facilities and increasing the numbers of sterile needles and syringes available to them is likely to result in further reductions in recipient-sharing, and thus the potential for blood-borne virus transmission, among IDUs.

Adult↗