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Biomedical subjects

J McIntyre

Publications and source records attributed to J McIntyre.

At least 19 recordsLinked to original sources
PubMed2001

Dynamics of the 16O(e, e'p) reaction at high missing energies.

We measured the cross section and response functions for the quasielastic 16O(e,e'p) reaction for missing energies 25< or =E(m)< or =120 MeV at missing momenta P(m)< or =340 MeV/c. For 25<E(m)<50 MeV and P(m) approximately 60 MeV/c, the reaction is dominated by a single 1s(1/2) proton knockout. At larger P(m), the single-particle aspects are increasingly masked by more complicated processes. Calculations which include pion exchange currents, isobar currents, and short-range correlations account for the shape and the transversity, but for only half of the magnitude of the measured cross section.

Journal Article↗
PubMed2001

Measurement of the recoil polarization in the p(e-->, e'p-->)pi(0) reaction at the Delta(1232) resonance.

The recoil proton polarization has been measured in the p(e-->,e'p-->)pi(0) reaction in parallel kinematics around W = 1232 MeV, Q2 = 0.121 (GeV/c)2, and epsilon = 0.718 using the polarized cw electron beam of the Mainz Microtron. All three proton polarization components, Px/P(e) = (-11.4+/-1.3+/-1.4)%, P(y) = (-43.1+/-1.3+/-2.2)%, and P(z)/P(e) = (56.2+/-1.5+/-2.6)%, could be measured simultaneously. The Coulomb quadrupole to magnetic dipole ratio, CMR = (-6.4+/-0.7(stat)+/-0.8(syst))%, was determined from Px in the framework of the Mainz Unitary Isobar Model. The consistency among the reduced polarizations and the extraction of the ratio of longitudinal-to-transverse response is discussed.

Journal Article↗
PubMed2001

Mucoid degeneration of the anterior cruciate ligament mistaken for ligamentous tears.

OBJECTIVE: To describe the MR features of mucoid degeneration of the anterior cruciate ligament (ACL) in a series of patients with MRI findings that were mistaken for tears in the majority of cases but who were found to have an intact ligament at arthroscopy. We will suggest a pathologic entity corresponding to this finding and describe some characteristic features that can be used to identify this entity on MRI. DESIGN: A retrospective analysis of 10 MRI examinations of the knee was performed after arthroscopic evaluation. Prearthroscopic MRI findings had been interpreted as a tear in six patients prospectively and in the remaining four the diagnosis of mucoid degeneration was suggested and ultimately proven. All patients had an intact ACL by preoperative clinical examination, examination under anesthesia, and at arthroscopy. RESULTS: MRI examinations demonstrated an ill-defined ACL, greater in girth than the normal ligament and characterized by increased signal on all sequences. The high-signal ligament was oriented in the normal direction of the ACL. The overall appearance of the ligament was retrospectively described as like a celery stalk. Arthroscopy demonstrated mechanically intact ligaments with a normal to expanded external appearance. Probing of three of the ligaments caused a material to be expressed and pathologic evaluation resulted in the diagnosis of cystic, mucoid degeneration. CONCLUSION: Mucoid degeneration and an intact ACL can be suspected when an apparently thickened and ill-defined ligament with increased signal intensity on all sequences is identified in a patient with a clinically intact ligament.

Adult↗
PubMed2001

Analysis of fluoride levels retained intraorally or ingested following routine clinical applications of topical fluoride products.

A variety of topical fluorides is now used clinically for the prevention and control of dental caries. It is essential for the dental profession to be fully aware of the relative retention rates of fluoride in saliva and thus its contact with the teeth. These may vary following the use of the different categories and concentrations of agents available and with different methods of use. It is also important to be aware of the amounts of fluoride ion ingested following use of the more concentrated forms and of the resultant elevation in total blood fluoride levels. These parameters were investigated in a series of experiments involving human volunteer subjects using a variety of topical fluoride materials commercially available in Australia. Fluoride mouthrinses appeared to provide the highest salivary retention rates per dose of all forms of topical fluoride. Ingestion rates from concentrated gels were acceptable when effective evacuation methods were applied. The use of custom-made trays resulted in a reduction in amounts of fluoride ion ingested, though simple self-application by toothbrush of smaller quantities proved to be an effective alternative in terms of amount of fluoride ion retained in saliva per amount applied and ingested. None of the concentrated gels used resulted in elevations in total blood fluoride levels which were of concern in adults. It is acknowledged that salivary retention rates of fluoride ion do not necessarily reflect the caries inhibitory effects of topical fluorides. However, these data provide some indication of possible advantages of some products and methods of application over others.

Adult↗
PubMed2001

Studies on dental erosion: an in vitro model of root surface erosion.

Most research on dental erosion has focused on erosion in enamel. However, the increasing retention of teeth into old age has increased the potential for root surface erosion. The nature and kinetics of root surface erosion have not yet been adequately explored. The objective of this project was to develop an in vitro model of root surface erosion in order to investigate the polarised light microscopy of controlled erosion and the histology and rate of demineralisation of this process in root cementum/dentine. The results demonstrate a process quite different in outcome from that in enamel erosion. Erosion results in loss of volume of enamel. However, it leaves a root surface softened though with little volume loss so long as the demineralised collagen remains hydrated. The polarised light histology was similar to that seen in root surface caries. The rate of erosive demineralisation of tooth roots by selected acids was investigated, with differing rates of demineralisation similar to that seen in enamel erosion observed. The process of erosion showed evidence of significant diffusion control.

Acetic Acid↗
PubMed2000

Spatial, not temporal cues drive predictive orienting movements during navigation: a virtual reality study.

A fundamental property of the human brain is the ability to make predictions of future sensory and motor events. We have recently found that steering manoeuvres when walking along curvilinear trajectories are controlled by an anticipatory guidance of the direction of head (and eyes). However it is unclear whether a time-related or space-related signal triggers such anticipatory head orienting movements. By simulating navigation along a multi-legged virtual corridor we show that anticipatory orienting movements are triggered (in standing subjects) by reaching specific locations rather than by the time to the approaching corridor's bend. Similar to what happens in car driving, specific spatial features of the route rather than time to collision seem to drive steering.

Adult↗
PubMed2000

The Gardos channel is responsible for CDNB-induced dense sickle cell formation.

The red blood cells (RBCs) derived from blood taken from homozygous sickle cell (SS) patients demonstrate densities that are inversely proportional to the intracellular reduced glutathione (GSH) content. Addition of 1 mM 1-chloro-2,4-dinitrobenzene (CDNB) to low-density sickle cells (LDSS), at 4 degrees C, results in a shift of LDSS erythrocytes to high-density sickle cells (HDSS), with corresponding decreases in GSH. We have previously demonstrated that this CDNB effect was due to increased K(+) leakage and that dense cell formation could be inhibited by clotrimazole (specific for the Gardos channel) but not DIOA (specific for the K(+)-Cl(-) co-transport system) at pH 7.4 (Shartava et al. Am. J. Hematol. 1999;62:19-24). Here we demonstrate that clotrimazole (10 microM) inhibits dense cell formation at pH 7.1 and 6.8, while DIOA (1 mM) has no effect. As pH 6.8 is the optimal pH for the K(+)-Cl(-) co-transport system, we can now reasonably conclude that damage to the Gardos channel is responsible for CDNB-induced dense cell formation.

Anemia, Sickle Cell↗
PubMed2000

In vitro assessment of the structural integrity of the female condom after multiple wash, dry, and re-lubrication cycles.

Since the introduction of the female condom in the early 90s, there have been numerous reports of reuse of the device. In response to these reports, studies were undertaken to evaluate the safety of female condom reuse. If reuse were shown to be safe, then programmatic costs of introduction of the female condom would be reduced allowing it to be more widely available. This article outlines the results of in vitro structural integrity testing of the female condom after multiple wash, dry, and re-lubrication cycles. Devices were tested up to 10 washes using water leakage, burst, and tensile seam testing. All results were compared to the United States Food and Drug Administration (US FDA) standards for an unused female condom. The results of the structural integrity tests for all 6 washing procedures examined in this study were above the FDA minimum standards for seam strength and burst tests. For the water leakage test, 3 of 6 washing procedures tested passed the required FDA minimum standards (no holes detected). From the results of the study, it seems that washing, drying, and re-lubricating the female condom up to 10 times leads to some deterioration in the structural integrity of the device for specified washing procedures. Further studies are currently being conducted to establish the safety of female condom reuse with respect to microbial retention, structural integrity after in vivo use, and viral permeability.

Single-Use Internal Condom↗
PubMed2000

Unlicensed and off label prescribing of drugs in general practice.

AIM: To determine the incidence and nature of unlicensed and off label prescribing of drugs for children in general practice. METHODS: A retrospective analysis of all prescriptions for one year involving children (aged 12 years or under) from a single suburban general practice in the English Midlands. Prescribed drugs were categorised as licensed, unlicensed (without a product licence), or used in an off label way (outside the terms of their product licence). RESULTS: During 1997 there were 3347 prescription items involving 1175 children and 160 different drugs. A total of 2828 (84. 5%) prescriptions were for licensed medicines used in a licensed way; 10 (0.3%) were for unlicensed medicines; and 351 (10.5%) were licensed medicines used in an off label way. For 158 (4.7%) the information was insufficient to determine licence status. CONCLUSION: This is the first study to show that a significant number of drugs prescribed for children by general practitioners are off label and highlights the anomalies and inadequacies of drug information for prescribers.

Child↗
PubMed2000

Analysis of pointing errors reveals properties of data representations and coordinate transformations within the central nervous system.

The execution of a simple pointing task invokes a chain of processing that includes visual acquisition of the target, coordination of multimodal proprioceptive signals, and ultimately the generation of a motor command that will drive the finger to the desired target location. These processes in the sensorimotor chain can be described in terms of internal representations of the target or limb positions and coordinate transformations between different internal reference frames. In this article we first describe how different types of error analysis can be used to identify properties of the internal representations and coordinate transformations within the central nervous system. We then describe a series of experiments in which subjects pointed to remembered 3D visual targets under two lighting conditions (dim light and total darkness) and after two different memory delays (0.5 and 5.0 s) and report results in terms of variable error, constant error, and local distortion. Finally, we present a set of simulations to help explain the patterns of errors produced in this pointing task. These analyses and experiments provide insight into the structure of the underlying sensorimotor processes employed by the central nervous system.

Central Nervous System↗
PubMed1999

Gravity affects the preferred vertical and horizontal in visual perception of orientation.

The aim of this study was to evaluate the influence of gravity on the representation and storage of visual orientation information. On earth, measurements of response time and variability for a task of aligning remembered visual stimuli showed a distinct preference for horizontally and vertically oriented stimuli when the body and gravitational axes were aligned. This preference was markedly decreased or disappeared when the body axis was tilted with respect to gravity but was maintained for tests performed in microgravity. We conclude that subjects acquire and store visual orientation in a multi-modal reference frame that combines proprioceptive and gravitational information when both are available.

Adult↗
PubMed1999

Viewer-centered and body-centered frames of reference in direct visuomotor transformations.

It has been hypothesized that the end-point position of reaching may be specified in an egocentric frame of reference. In most previous studies, however, reaching was toward a memorized target, rather than an actual target. Thus, the role played by sensorimotor transformation could not be disassociated from the role played by storage in short-term memory. In the present study the direct process of sensorimotor transformation was investigated in reaching toward continuously visible targets that need not be stored in memory. A virtual reality system was used to present visual targets in different three-dimensional (3D) locations in two different tasks, one with visual feedback of the hand and arm position (Seen Hand) and the other without such feedback (Unseen Hand). In the Seen Hand task, the axes of maximum variability and of maximum contraction converge toward the mid-point between the eyes. In the Unseen Hand task only the maximum contraction correlates with the sight-line and the axes of maximum variability are not viewer-centered but rotate anti-clockwise around the body and the effector arm during the move from the right to the left workspace. The bulk of findings from these and previous experiments support the hypothesis of a two-stage process, with a gradual transformation from viewer-centered to body-centered and arm-centered coordinates. Retinal, extra-retinal and arm-related signals appear to be progressively combined in superior and inferior parietal areas, giving rise to egocentric representations of the end-point position of reaching.

Adult↗
PubMed1999

Respiratory depression in children receiving diazepam for acute seizures: a prospective study.

The aim of this study was to determine the incidence of respiratory depression following the use of diazepam in children presenting with seizures. All children presenting with seizures to a children's A & E department over a period of 9 months were studied prospectively. Respiratory depression was defined as a fall in respiratory rate or oxygen saturation, or apnoea resulting in ventilation or resuscitation with bag-and-mask oxygen. There were 130 patient episodes involving 97 children who received treatment for their seizures before admission and/or in the A & E department. Administration of diazepam resulted in 122 patient episodes. The route of administration was rectal in 91 episodes, intravenous in 12 episodes, and both rectal and intravenous in 19 episodes. Eleven children had respiratory depression in relation to diazepam administration. Eight of these children required ventilation. The overall incidence of respiratory depression following the use of diazepam was 9%. The incidence of respiratory depression following diazepam given intravenously or rectally is high. The use of diazepam as first-line therapy for children with acute seizures needs to be reviewed.

Acute Disease↗
PubMed1999

Unlicensed and off label drug use in neonates.

AIM: To determine the extent of use of drugs that are either not licensed (unlicensed), or are outside the terms of their product licence (off label) in a neonatal intensive care unit. METHODS: A prospective study was conducted over 13 weeks. RESULTS: 455 prescription episodes were administered to 70 babies. 63 (90%) patients were given a drug that was either unlicensed or used in an off label way. 54.7% prescription episodes were off label, many for more than one reason, and 9.9% (45) were unlicensed; 35.4% (161) prescription episodes were licensed. CONCLUSION: The use of unlicensed and off label drugs in neonatal intensive care seems to be far greater than other paediatric settings. This highlights the difficulties faced by those trying to ensure safe and effective prescribing for neonates. Urgent action is required to resolve this situation.

Drug Approval↗
PubMed1999

The practice and prevalence of dry sex among men and women in South Africa: a risk factor for sexually transmitted infections?

OBJECTIVES: To establish the prevalence of "dry sex" practice in a South African periurban population. To investigate the reasons for and factors influencing the practice of dry sex and to evaluate dry sex practice as a risk factor for sexually transmitted disease (STD). DESIGN: Cross sectional sample survey. METHODS: A random community sample of men and women aged between 16 and 35 in Gauteng Province, South Africa, were interviewed regarding the practice of dry sex using a structured interviewer administered questionnaire. RESULTS: Dry sex practices were reported by 60% of men and 46% of women. Among younger individuals dry sex practice is far more common among the less educated, but there was no significant difference between education groups in the older respondents. A higher proportion of men practising dry sex than not practising dry sex reported having a past history of STD infection (56% versus 41%) although this difference was only marginally significant (p = 0.05). There was no difference in reported history of STD between women who practised dry sex and those who did not. CONCLUSIONS: This study shows that dry sex practice is common in this community. The younger less educated group were the most likely to practise dry sex. Dry sex practice was associated with an increased prevalence of self reported STDs in men but not in women.

Adolescent↗