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Biomedical subjects

N Thompson

Publications and source records attributed to N Thompson.

At least 19 recordsLinked to original sources
PubMed2006

Reproductive aging in Japanese quail, Coturnix japonica is associated with changes in central opioid receptors.

Quantitative in vitro autoradiography was used to measure specific mu and delta opioid receptor densities in regions of the Japanese quail, Coturnix japonica, brain that regulates reproductive endocrine and behavioral responses to determine the possible involvement of the opioid system in reproductive decline seen during aging. Densities were measured in selected brain regions of young sexually active (YAM), young photoregressed (YPM), old reproductively senescent (OIM) male, young active (YF), and old senescent female (OF) Japanese quail. Medial and lateral septum (SM, SL), medial preoptic area (POM), and n. intercollicularis (ICo) were of particular interest for reproductive responses. Similar to previous observations, mu and delta opioid receptors showed differential distributions in the areas measured. Some age-related changes were observed, with lower SM mu receptor densities in aged males (OIM) than females or young males (YAM). Densities of mu receptors in the POM and in other areas examined did not vary with sex or age. Similarly, OIM males had lower densities of delta receptors in the SM than young males (YAM and YPM); POM delta receptor densities were also low in OIM males compared to the YPM males, and YAM males were intermediate. Interestingly, photoregressed males (YPM) had higher SL delta receptor densities than any other group. Thus there were age-related differences detected in mu receptor densities among groups in the SM of OIM relative to other groups; and the mu and delta receptor densities did not differ in females with brain region. Additionally for delta receptors specifically, YF and OF did not differ from OIM for any brain region and similarly had lower densities of delta receptors compared to YAM males. These data provide support for regional differences in opioid receptor distribution and for age- and sex-related differences in delta opioid receptor densities. The direction of change presents an interesting dichotomy in that, compared to young active males, delta opioid receptor densities increased with loss of reproductive function in the YPM, whereas receptor densities decreased in the OIM. Plasma androgen levels were relatively low in both these groups compared to the young active males. This observation suggests that there is an age-related loss in the ability of this receptor system to respond to circulating and centrally produced steroid hormones in the POM and in some septal regions, compared to young animals that are responding to environmental cues. Furthermore, these data support an active role of the opioid peptide system in the inhibition of the reproductive axis in photoregression.

Aging↗
PubMed2006

Hydrogen peroxide as an irrigation solution in arthroplasty - a potential contributing factor to the development of aseptic loosening.

The reason for revision of primary total hip arthroplasty is quoted as aseptic loosening in 60.6% of cases between 1979 and 2003 in the Swedish National Hip Arthroplasty Registry. Much research effort has been directed toward enhancing the bone-cement interface of total joint arthroplasties, in an attempt to reduce this complication. Haemostatic agents have been popularized as effective means of retarding the development of potentially harmful debris interposition adjacent to, and blood lamination patterns within, the methylmethacrylate. Such agents include hydrogen peroxide (H(2)O(2)), local freezing saline, saline at room temperature and adrenaline solution. One main concern with the use of hydrogen peroxide is whether it affects the material properties of bone cement such that in the long term it contributes to aseptic loosening. This would have enormous clinical consequences. Preliminary studies indicate that porosity increases and that the tensile strength and yield stresses are reduced by up to a factor of 10 by contaminating samples with increasing concentrations of hydrogen peroxide. We postulate that the current use of hydrogen peroxide as an irrigation solution in arthroplasty contributes to the development of aseptic loosening.

Adhesiveness↗
PubMed2006

Repeatability of a model for measuring multi-segment foot kinematics in children.

This study used a previously tested foot model and adapted it for use with children. A number of variations on this adapted model were implemented and tested for repeatability and accuracy on 15 healthy children on three occasions. These included redefinition of the long axes of the tibia and forefoot, assessment of the flexibility of the forefoot and evaluation of the variability of the wand marker on the heel for both static and dynamic trials. It was found that variations on the model produced only minimal changes in repeatability, the only significant change being elimination of the wand marker on the heel in the static trial, which reduced between-day variability of hindfoot motion in the transverse plane. However, some differences were evident in the mean values for all variations. Based on these results, the most accurate and appropriate version of the model is proposed, and average kinematic curves are presented based on the measurements from 14 healthy children.

Adolescent↗
PubMed2005

Consequences of endocrine disrupting chemicals on reproductive endocrine function in birds: establishing reliable end points of exposure.

It has been difficult to establish reliable indices of exposure to endocrine disrupting chemicals (EDCs) appropriate for a variety of avian species because of a vast array of reproductive strategies. Data from mammals, reptiles and fish provide insight on likely mechanisms of action for EDCs. However, many of the effects of EDCs are weaker than the actions of the native hormones, making it difficult to assess adverse effects in domestic and wild birds. It is clear that differential sensitivity to EDCs exists across species, due to the timing and mode of exposure, compound toxicity and age of the individual. Our studies on EDCs are conducted in the quail model system, with focus on reproductive endocrine, neuroendocrine and behavioral responses. Studies have included EDC exposure, either by egg injection or via diet. Results from egg injection studies showed the following: (1) estradiol administered by embryonic day 12 demasculinized male sexual behavior, altered hypothalamic neurotransmitters and reduced hen day production and fertility in a dose dependent fashion, (2) methoxychlor (MXC) or vinclozolin impaired male sexual behavior in adult quail and (3) DDE exposure impaired reproductive and immune related end points. Two-generation studies were conducted on Japanese and northern bobwhite quail with dietary methoxychlor (MXC) exposure (0, 5 and 10 ppm) beginning in adults (P1), continuing in their offspring (F1), with F2 offspring raised on control diet. MXC exposure impaired male sexual behavior, hypothalamic catecholamines and plasma steroid hormones. Moreover, MXC exposure had reproductive consequences observable at both the lower and higher doses of MXC in F1 and F2 generations. These data demonstrate that embryonic EDC exposure interferes with sexual differentiation of neural systems that direct reproduction.

Androgens↗
PubMed2004

Assessment of sub-division of plantar pressure measurement in children.

Methods for the measurement of plantar pressure are poorly defined particularly when describing sub-sections of the plantar surface of the foot in the presence of deformity. The aim of this study was to assess foot pressure measurement in healthy children, using an automatic technique of sub-area definition that has the potential for objective evaluation of treatment of foot deformity. Twelve healthy children were examined on three occasions. Plantar pressure data were collected and time synchronised with force plate and stereophotogrammetric data. The footprint was divided into five sub-sections by using the position of the markers on the foot at mid-stance projected onto the pressure footprint. Repeatability for peak pressure and peak force was assessed. Automatic sub-area definition based on marker placement was found to be reliable in healthy children. A comparison of results revealed that peak vertical force was a more consistent measure than peak pressure for each of the five sub-areas. This suggests that force may be a more appropriate measurement for outcome studies.

Adolescent↗
PubMed2004

Primary parental preoccupation: circuits, genes, and the crucial role of the environment.

Parental caregiving includes a set of highly conserved behaviors and mental states that may reflect both an individual's genetic endowment and the early experience of being cared for as a child. This review first examines the mental and behavioral elements of early parental caregiving in humans. Second, we consider what is known about the neurobiological substrates of maternal behaviors in mammalian species including some limited human data. Third, we briefly review the evidence that specific genes encode proteins that are crucial for the development of the neural substrates that underlie specific features of maternal behavior. Fourth, we review the emerging literature on the "programming" role of the intrauterine environment and postnatal caregiving environment in shaping subsequent maternal behavior. We conclude that there are critical developmental windows during which the genetically determined microcircuitry of key limbic-hypothalamic-midbrain structures are susceptible to early environmental influences and that these influences powerfully shape an individual's responsivity to psychosocial stressors and their resiliency or vulnerability to various forms of human psychopathology later in life.

Environment↗
PubMed2003

Dynamic foot movement in children treated for congenital talipes equinovarus.

The aim of this study was to define objectively gait function in children with treated congenital talipes equinovarus (CTEV) and a good clinical result. The study also attempted an analysis of movement within the foot during gait. We compared 20 children with treated CTEV with 15 control subjects. Clinical assessment demonstrated good results from treatment. Three-dimensional gait analysis provided kinematic and kinetic data describing movement and moments at the joints of the lower limb during gait. A new method was used to study movement within the foot during gait. The data on gait showed significantly increased internal rotation of the foot during walking which was partially compensated for by external rotation at the hip. A mild foot drop and reduced plantar flexor power were also observed. Dorsiflexion at the midfoot was significantly increased, which probably compensated for reduced mobility at the hindfoot. Patients treated for CTEV with a good clinical result should be expected to have nearly normal gait and dynamic foot movement, but there may be residual intoeing, mild foot drop, loss of plantar flexor power with compensatory increased midfoot dorsiflexion and external hip rotation.

Adolescent↗
PubMed2002

Automated recognition of intracellular organelles in confocal microscope images.

Recognition of the localisation of intracellular proteins is essential to the understanding of their function. It is usually made through knowledge of and comparison to the distribution of well-characterised intracellular organelles by experts in cell biology. We have automated this process in order to achieve a more objective and quantitative assessment of the protein distribution within the cell, which can be employed by the less experienced cell biologist and may be utilised as a training program for inexperienced users, or as a high throughput localisation program for novel genes in functional analysis. Here we describe the development and testing of a classification system based on a modular neural network trained with sets of confocal sections through cell lines fluorescently stained for markers of key intracellular structures. The system functioned well in spite of the variability in pattern that occurs between individual cells and performed with 97% accuracy, which gives us confidence in the method and in its future development. It is envisaged that this program will aid the design of further experiments utilising colocalisation with known organelle marker proteins, in order to confirm putative trafficking pathways and protein--protein interactions of the protein of interest.

Animals↗
PubMed2002

Effects of exogenous testosterone on testicular luteinizing hormone and follicle-stimulating hormone receptors during aging.

During aging, the male Japanese quail exhibits a loss of fertility, increased morphological abnormalities in the testes, and a higher incidence of Sertoli cell tumors. Although there is a coincident loss of reproductive behavior, plasma androgen levels remain high until testicular regression occurs in association with senescence. The purpose of this study was to compare mean specific binding of chicken luteinizing hormone (LH) and follicle-stimulating hormone (FSH) as a measure of testicular receptors during identified stages during aging. Males were categorized according to age (young = 9 months, middle aged = 24 months, or old = 36+ months) and sexual behavior (active or inactive). Testicular samples were collected immediately after perfusion with 4% paraformaldehyde from the following groups: young active (n = 8), young photoregressed (n = 5), young photoregressed plus testosterone implant (n = 4), middle-aged active (n = 8), middle-aged inactive (n = 4), old inactive (n = 5), and old inactive plus testosterone implant (n = 6). A crude plasma membrane fraction was prepared from the testes of each bird and an aliquot deriving from 10 mg of testicular tissue was used for binding assay. Specific binding of labeled LH or FSH was expressed as percentage of total radioactive hormone. Results showed significant (P < 0.05) age-related decreases in both FSH and LH receptor numbers. The highest FSH binding was found in young and middle-aged active males, with low binding in old inactive males. Testicular LH binding decreased during aging, with a sharp decrease in middle-aged males, which was similar to old males. Testosterone implants weakly stimulated FSH and LH binding in old males. Both LH and FSH binding decreased in photoregressed young males. However, testosterone implants stimulated increased LH binding, but did not affect FSH binding in young photoregressed males. These results provide evidence for separate regulation of testicular LH and FSH receptors, with testosterone stimulation of LH receptor, but not FSH receptor number in young males. However, during aging there appears to be a loss of this response, potentially because of the reduced efficacy of testosterone stimulation, thereby implying a diminished capacity for response with aging.

Aging↗
PubMed2001

Neuroendocrine and behavioral implications of endocrine disrupting chemicals in quail.

Studies in our laboratory have focused on endocrine, neuroendocrine, and behavioral components of reproduction in the Japanese quail. These studies considered various stages in the life cycle, including embryonic development, sexual maturation, adult reproductive function, and aging. A major focus of our research has been the role of neuroendocrine systems that appear to synchronize both endocrine and behavioral responses. These studies provide the basis for our more recent research on the impact of endocrine disrupting chemicals (EDCs) on reproductive function in the Japanese quail. These endocrine active chemicals include pesticides, herbicides, industrial products, and plant phytoestrogens. Many of these chemicals appear to mimic vertebrate steroids, often by interacting with steroid receptors. However, most EDCs have relatively weak biological activity compared to native steroid hormones. Therefore, it becomes important to understand the mode and mechanism of action of classes of these chemicals and sensitive stages in the life history of various species. Precocial birds, such as the Japanese quail, are likely to be sensitive to EDC effects during embryonic development, because sexual differentiation occurs during this period. Accordingly, adult quail may be less impacted by EDC exposure. Because there are a great many data available on normal development and reproductive function in this species, the Japanese quail provides an excellent model for examining the effects of EDCs. Thus, we have begun studies using a Japanese quail model system to study the effects of EDCs on reproductive endocrine and behavioral responses. In this review, we have two goals: first, to provide a summary of reproductive development and sexual differentiation in intact Japanese quail embryos, including ontogenetic patterns in steroid hormones in the embryonic and maturing quail. Second, we discuss some recent data from experiments in our laboratory in which EDCs have been tested in Japanese quail. The Japanese quail provides an excellent avian model for testing EDCs because this species has well-characterized reproductive endocrine and behavioral responses. Considerable research has been conducted in quail in which the effects of embryonic steroid exposure have been studied relative to reproductive behavior. Moreover, developmental processes have been studied extensively and include investigations of the reproductive axis, thyroid system, and stress and immune responses. We have conducted a number of studies, which have considered long-term neuroendocrine consequences as well as behavioral responses to steroids. Some of these studies have specifically tested the effects of embryonic steroid exposure on later reproductive function in a multigenerational context. A multigenerational exposure provides a basis for understanding potential exposure scenarios in the field. In addition, potential routes of exposure to EDCs for avian species are being considered, as well as differential effects due to stage of the life cycle at exposure to an EDC. The studies in our laboratory have used both diet and egg injection as modes of exposure for Japanese quail. In this way, birds were exposed to a specific dose of an EDC at a selected stage in development by injection. Alternatively, dietary exposure appears to be a primary route of exposure; therefore experimental exposure through the diet mimics potential field situations. Thus, experiments should consider a number of aspects of exposure when attempting to replicate field exposures to EDCs.

Animals↗
PubMed2001

Identification and management of intravagal parathyroid adenoma.

Intravagal parathyroid adenomas are rare, with only three cases reported in the English literature. The objective of this report is to describe two additional patients with hyperfunctioning parathyroid glands found within the vagus nerve and to define the anatomy of this finding. Both patients presented with a history of persistent hyperparathyroidism despite multiple therapeutic interventions. A high cervical localization was established in both cases by selective venous sampling. In each patient successful removal of the intravagal parathyroid gland was achieved with subsequent resolution of calcium and parathyroid levels. Each adenoma was located within the vagus nerve below the level of the carotid bifurcation and was enucleated without sacrificing the vagus nerve. In our cases and those reported previously, the parathyroid glands were supernumerary, representing parathyroid tissue embryologically derived from the third branchial pouch. Exploration for hyperparathyroidism requires a complete, meticulous surgical dissection to identify all parathyroid glands and to search for possible accessory tissue in selected cases. Our experience and a review of the literature serve to emphasize that, although rare, intravagal parathyroid adenomas do occur. Examination of the vagus nerve should therefore be strongly considered when four normal glands are found, as intravagal adenomas appear to represent accessory ectopically located parathyroid tissue.

Adenoma↗
PubMed2001

The genome organisation and taxonomy of Sugarcane striate mosaic associated virus.

Sugarcane striate mosaic associated virus (SCSMaV) has slightly flexuous 950 nm x 15 nm filamentous particles and is associated with sugarcane striate mosaic disease in central Queensland, Australia. We report the full sequence of its RNA genome, which comprises 5 open reading frames representing the polymerase, movement function proteins encoded in a triple gene block and coat protein. Phylogenetic analyses based on either the full nucleotide sequence, the polymerase protein, or the coat protein all placed SCSMaV in an intermediate position between the genera Foveavirus and Carlavirus, but outside both genera. In addition, the absence of a sixth open reading frame excludes it from the genus Carlavirus, and the coat protein is approximately half the size of the type member for the genus Foveavirus. Although SCSMaV was most closely allied to Cherry green ring mottle virus by genome analysis, the two viruses are morphologically and biologically dissimilar. SCSMaV may therefore represent a new plant virus taxon.

3' Untranslated Regions↗
PubMed2001

Noncontact dipole effects on channel permeation. IV. Kinetic model of 5F-Trp(13) gramicidin A currents.

Nonlinear least squares fitting was used to assign rate constants for the three-barrier, two-site, double-occupancy, single-filing kinetic model for previously reported current-voltage relations of (5F-Indole)Trp(13) gramicidin A and gramicidin A channels (, 75:2830-2844). By judicious coupling of parameters, it was possible to reduce the parameter space from 64 parameters to 24, and a reasonable fit consistent with other experimental data was obtained. The main features of the fit were that fluorination increased the rate constant for translocation by a factor of 2.33, consistent with a free energy change in the translocation barrier of -0.50 kcal/mol, and increased first-ion binding affinity by a factor of 1.13, primarily by decreasing the first-ion exit rate constant. The translocation rate constant was 5.62 times slower in diphytanoyl phosphatidylcholine (DPhPC) bilayers than in monoolein (GMO) bilayers (coupled for the four combinations of peptide and salt), suggesting a 44.2-mV difference in the projection of the interfacial dipole into the channel. Thus fluorination caused increased currents in DPhPC bilayers, where a high interfacial dipole potential makes translocation more rate limiting because the translocation barrier was reduced, and decreased currents in GMO bilayers, where ion exit or entry is rate limiting because these barriers were increased.

Algorithms↗
PubMed2001

Kinematic analysis of a multi-segment foot model for research and clinical applications: a repeatability analysis.

An unbiased understanding of foot kinematics has been difficult to achieve due to the complexity of foot structure and motion. We have developed a protocol for evaluation of foot kinematics during barefoot walking based on a multi-segment foot model. Stereophotogrammetry was used to measure retroreflective markers on three segments of the foot plus the tibia. Repeatability was evaluated between-trial, between-day and between-tester using two subjects and two testers. Subtle patterns and ranges of motion between segments of the foot were consistently detected. We found that repeatability between different days or different testers is primarily subject to variability of marker placement more than inter-tester variability or skin movement. Differences between inter-segment angle curves primarily represent a shift in the absolute value of joint angles from one set of trials to another. In the hallux, variability was greater than desired due to vibration of the marker array used. The method permits objective foot measurement in gait analysis using skin-mounted markers. Quantitative and objective characterisation of the kinematics of the foot during activity is an important area of clinical and research evaluation. With this work we hope to have provided a firm basis for a common protocol for in vivo foot study.

Biomechanical Phenomena↗
PubMed2000

A randomised controlled trial of intravenous versus inhalational analgesia during outpatient oocyte recovery.

To compare the efficacy and acceptability of conventional intravenous sedation with patient-controlled inhalational isodesox, 57 women undergoing outpatient oocyte recovery were randomly allocated to receive isodesox by face mask, while 55 women were given intravenous fentanyl and midazolam. Women's satisfaction with pain relief, peroperative pain, clouding of memory and the surgeons' assessment of operating conditions were evaluated. Thirty-eight women in the inhalation group (67%) and 41 (75%) women in the intravenous group were 'very satisfied' with their analgesia (p = 0. 41). The mean (SD) pain score in women given isodesox was 46.8 (34. 7), while in the intravenous group it was 34.1 (21.3) (p = 0.02). Oxygen saturation levels < 94% were recorded in one woman using isodesox and in 16 (29%) women given intravenous analgesia. Despite higher pain scores, in comparison with the conventional analgesia, patient-controlled isodesox offers a safer method of pain relief with comparable satisfaction rates.

Administration, Inhalation↗