Search PubMed⌕ Search

Biomedical subjects

R N Marshall

Publications and source records attributed to R N Marshall.

At least 37 records · Page 2Linked to original sources
PubMed1999

The pathogenesis of experimental infections of Cryptosporidium muris (strain RN 66) in outbred nude mice.

Three groups of six-week-old nude outbred mice were orally infected with 400, 20,000 and 1,000,000 oocysts of Cryptosporidium muris (strain RN 66) per mouse, respectively. Oocysts were detected in the faeces from 10-18 days post-infection (p.i.) and continued to be shed in large numbers in all groups until the termination of the trial on day 89 p.i. Clinical signs were not observed in any of the infected mice and there was no significant effect on weight gain compared to uninfected controls. Histological examination revealed the presence of parasites confined to the glandular stomach. Parasitised gastric glands were dilated, hypertrophied and filled with numerous parasites. The glands had lost their normal cellular architecture and were lined with many undifferentiated cells. In some mice receiving the largest innoculum, the glandular mucosa was congested and the lamina propria infiltrated with eosinophils, polymorphs and lymphocytes.

Animals↗
PubMed1999

Aircraft control forces and EMG activity: comparison of novice and experienced pilots during simulated take-off and landing.

BACKGROUND: Flying an aircraft requires a considerable degree of coordination, particularly during activities such as takeoff and landing. No studies have examined the magnitude and phasing of muscle activity required to fly an aircraft. The aim of this study was to examine the muscle activation patterns and control forces of novice and experienced pilots during simulated flight. METHODS: Twelve experienced and nine novice pilots were tested on an Aermacchi flight simulator while performing a randomized set of take-off and landing maneuvers. Four different runaway trim settings were used to increase the difficulty of the landings (elevator-up, elevator-down, aileron-left, and aileron-right). Variables recorded included aircraft attitude, pilot applied forces, and electromyographic (EMG) activity. Discriminant function analysis was used to distinguish between novice and experienced pilots. RESULTS: Across all landings, wrist flexors and wrist extensors were the predominant muscles used, with EMG activity consistently around 20-30% maximum voluntary contraction (MVC). In respect to differences in EMG activity between novice and experienced pilots, novices had significantly more activity in wrist extensors during all landings. In contrast, experienced pilots had consistently more vastus lateralis activity for all landings than did novice pilots. Over all landings and take-off, 89.5% of pilots were correctly classified as novice or experienced. When the maneuvers were analyzed individually, normal, elevator-down, and aileron-left landings were the most accurate maneuvers for pilot prediction. EMG and force variables were more important than aircraft attitude in discriminating between novice and experienced pilots (83%, 79%, and 65%, respectively). CONCLUSION: The consistency of the finding that EMG activity and control forces are accurate discriminators of pilot experience is indicative of underlying differences in neuromuscular control strategies between novice and experienced pilots.

Adult↗
PubMed1997

High level expression of equine herpesvirus 1 glycoproteins D and H and their role in protection against virus challenge in the C3H (H-2Kk) murine model.

N and C-terminal truncated forms of equine herpesvirus 1 (EHV 1) glycoproteins gD and gH were expressed in baculovirus resulting in the production of secreted recombinant proteins. A carboxy-terminal histidine tag was included on each of the genes for protein isolation by nickel affinity chromatography. Recombinant gD was recognized by three gD specific monoclonal antibodies, 20C4, 5H6 and F3132. F3132 is a conformationally dependent monoclonal antibody with virus neutralizing activity. Expression of gH was confirmed by reacting the protein with the gH peptide specific antiserum R319. The truncated gD gene was also expressed as a beta-galactosidase fusion protein which was purified from E. coli by nickel affinity chromatography. C3H mice were inoculated with purified recombinant gD or gH or insect cells which had been infected with recombinant baculoviruses. Mice were subsequently challenged with EHV 1. Purified recombinant baculovirus gD provided the most protection and produced high levels of virus neutralizing antibodies. The gD fusion protein was less effective at protecting mice and insect cells infected with either of the recombinant baculoviruses or purified recombinant gH were poor at conferring protection. The results emphasize the importance of using purified proteins in vaccine formulations and of including EHV 1 gD as a component of a subunit vaccine.

Animals↗
PubMed1996

The production of a truncated form of baculovirus expressed EHV-1 glycoprotein C and its role in protection of C3H (H-2Kk) mice against virus challenge.

A truncated form of the equine herpesvirus 1 (EHV-1) glycoprotein C (gC) gene was expressed in baculovirus. The gC signal sequence was substituted with the honeybee melittin signal sequence and the transmembrane region was replaced with a histidine tag. The recombinant virus produced high levels of gC in both the cells and supernatants of infected cells. The protein was present by 24 h and maximal secretion occurred at 96 h post-infection. The recombinant protein was antigenically authentic as shown by its reaction with each of a panel of individual monoclonal antibodies specific for the five distinct antigenic sites on EHV-1 gC. Recombinant gC was purified from the supernatant of infected cells by immuno-affinity chromatography and used to immunize C3H (H-2Kk haplotype) mice. This incurred a gC specific antibody response against both the recombinant protein and EHV-1 gC. 'Pepscan' analysis showed that the gC specific antibodies in serum from these mice reacted with the same epitopes on gC as those recognized by antibodies in convalescent equine sera (i.e. antibodies were specific to antigenic sites one and five). A third previously unrecognized antibody binding site at the carboxyl terminus was also detected (Antibody binding domain I). A T-cell proliferative response against EHV-1 was detected in splenocyte populations taken from vaccinated mice. Further, the recovery of virus from the lungs and turbinates following challenge of mice with EHV-1 was significantly reduced. These findings indicate that baculovirus expressed gC may contribute significantly to a subunit vaccine preparation aimed at protecting horses from EHV-1 infection.

Animals↗
PubMed1996

Thoracolumbar disc degeneration in young fast bowlers in cricket: a follow-up study.

OBJECTIVE: To determine the progression of thoracolumbar disc degeneration in young fast bowlers in cricket. DESIGN: Prospective fast bowling technique and MRI follow-up study. BACKGROUND: Previous studies on high-performance young fast bowlers have found that lumbar spine pathology was related to the mixed bowling technique. METHODS: Nineteen young male fast bowlers (mean age 13.6 years) underwent MRI scans to detect the presence of intervertebral disc abnormalities. Subjects were also filmed laterally (200 Hz) and from directly above (100 Hz) whilst bowling two maximum velocity deliveries (session 1). Subjects were tested using an identical methodology 2.7 years later (session 2). RESULTS: At session 1, the incidence of thoracolumbar disc degeneration was 21%; however, at session 2, the incidence significantly (P = 0.008) increased to 58%. Furthermore the increase in the incidence of back pain between session 1 and session 2 was also significant (P = 0.002). The progression of disc degeneration was found to be significantly (P = 0.015) related to the group of fast bowlers who utilized the mixed technique during both session 1 and 2 when compared to those who used this technique during one session only. CONCLUSIONS: Thoracolumbar disc degeneration and back pain increase significantly during the time period examined in this study. Further, bowlers who utilize the mixed bowling technique stand a greater chance of developing degenerative changes of the spine.

Journal Article↗
PubMed1996

Swelling of the knee joint: effects of exercise on quadriceps muscle strength.

OBJECTIVE: To investigate the effects of excessive fluid in the knee joint on the performance of the quadriceps muscles and to determine whether quadriceps muscle performance can be altered by exercising the swollen joint. DESIGN AND SETTING: A before-after trial design was used, and the procedures were performed in a laboratory setting. SUBJECTS: A random sample of 27 adult men with no musculoskeletal problems was divided into intervention and control groups. INTERVENTION: First, in all groups, torque generated by the quadriceps muscle was examined by isokinetic muscle testing undertaken at a joint angular velocity of 120 degrees/sec over a range of motion from 5 degrees to 80 degrees flexion. After this initial test, in group 1, 60mL saline and dextrose was injected into the knee joint and subjects repeated the maximal effort procedure. Subjects then performed submaximal exercise for 3 to 4 minutes, after which maximal effort testing was undertaken again. In group 2, subjects received no injection of fluid, undertook 2 maximum effort tests, then performed submaximal exercise for 3 to 4 minutes, after which maximum effort testing was undertaken again. In group 3 (control group), subjects undertook three maximum effort tests over a time period similar to that for the other groups. MAIN OUTCOME MEASURE: Quadriceps muscle torque generated at 60 degrees from full knee extension. RESULTS: Torque decreased (p < .05) 30% immediately after the injection of fluid. However, torque returned to preinjection levels after submaximal exercise (p > .05). These findings were related to joint capsule compliance and fluid movement. No significant changes (p > .05) in torque were observed for the other two groups. CONCLUSION: Submaximal exercise of swollen knee joints can decrease artificially induced quadriceps muscle inhibition. These findings may have implications for patients with perennial effusions who at times undertake gait activities.

Adult↗
PubMed1996

Transfer movement strategies of individuals with spinal cord injuries.

The ability to transfer in tetraplegia is a focal point of rehabilitation. Many factors have been associated with independence in transferring, yet the majority of these are anecdotal reports. The purpose of this paper is to report preliminary findings of the study of movement strategies of individuals with spinal cord injury attempting a long sitting transfer. Analyses were made from the lateral and posterior views. Pattern recognition techniques show two distinct movement strategies in both views. These were a lift and forward flexion technique from the lateral perspective and a translatory and rotatory technique when viewed from behind. It would seem that the posterior view provides more discriminative information. It is recommended that intervention techniques, such as Functional Electrical Stimulation or orthotic devices be developed within fundamental motion analysis constructs to optimize functional outcome.

Adult↗
PubMed1995

Knee joint effusion and proprioception.

The purpose of this study was to examine the effects of excessive fluid in the knee joint on proprioception. Twenty healthy subjects with no knee pathology participated in this study. Subjects were randomly assigned to control and experimental groups. Baseline measurements of subjects performing a tracking task were then recorded. Specifically, one knee joint was moved passively by a dynamometer through a range of motion from approximately 90 degrees flexion to 10 degrees from full extension at a joint angular velocity of 60 degrees/sec. Subjects were blindfolded and required to track the passively moving joint as accurately as possible for a period of 1.25 minutes with the opposite limb. An electrogoniometer was used to monitor the motion of the active tracking limb. Ninety mL of a solution of saline and dextrose were injected into the knee joint cavity of the experimental subjects, and they repeated the tracking task. After a 5-minute rest, the control group subjects also repeated the task. The results indicated that the injection of fluid did not change the subjects' error in tracking the passively moving limb (p > 0.05). No change in the error associated with tracking was observed for the control group (p > 0.05). It is suggested that the effects of long-term effusions and the nature of the inflammatory fluid might be more responsible for the loss of proprioception observed in some clinical conditions.

Adult↗
PubMed1995

The effect of a 12-over spell on fast bowling technique in cricket.

Nine members of the Western Australian Cricket Association fast bowling development squad were selected to determine the effects that a 12-over spell would have on fast bowling technique and selected physiological variables. Three high-speed cameras operating at 100 Hz filmed the subjects bowling the 5th and 6th balls of their 1st, 6th, 10th and 12th overs. Blood lactate and heart rate were recorded and the bowlers were shown to work at between 80.3% (1st over) to 84.7% (12th over) of their maximum heart rate during the 12-over bowling spell. Data from the 5th and 6th deliveries from each over were averaged to provide representative data, as no significant differences were evident between these two deliveries for the selected kinematic variables. For all subjects, no significant differences were recorded for the selected kinematic variables throughout the duration of the 12-over spell, indicating that in general fast bowling technique does not change over this length of spell. In addition, there was some evidence of change in technique for the bowlers who used a front-on action, where counter-rotation of the shoulders was found to increase; however, this could only be confirmed by a more comprehensive study.

Adolescent↗
PubMed1994

Skeletal muscle mechanics in osteoporotic and nonosteoporotic postmenopausal women.

The purpose of this study was to evaluate single-joint, dynamic muscle function of osteoporotic (OST) and nonosteoporotic (N-OST) women. Knee flexor and extensor function in postmenopausal women (6th decade OST, n = 15; 7th decade OST, n = 10; 6th decade N-OST, n = 6; 7th decade N-OST, n = 5) were evaluated at five angular velocities from 60 degrees.s-1 to 300 degrees.s-1. All subject groups had similar anthropometric measurements, but the 6th decade N-OST group were more physically active than the age-matched OST group. The OST and N-OST women produced peak torque at similar knee angles. The 6th decade N-OST women produced significantly greater knee extensor mean peak torque and angle specific torque, and mean work than any of the other three groups (P < 0.05). However, knee flexor function was equivalent throughout the groups for most comparisons, except those between the 6th decade N-OST and 7th decade OST. While previous research has shown an early loss of flexor muscle function in aging women, our data indicated that women with osteoporosis also experience a deterioration in quadriceps muscle function not encountered within the N-OST subjects. It is possible that such a change is precipitated by reduced physical activity, and may mirror deterioration in bone mineral content.

Aged↗
PubMed1994

Kinematic and kinetic parameters associated with running in different shoes.

The characteristics of the midsole were examined in four pairs of running shoes by a materials test. The variables of interest were the peak acceleration, time to peak acceleration and the kinetic energy absorbed. Ten subjects then ran at a recreational jogging pace (3.5 ms-1) barefoot and in the shoes. An accelerometer secured to the lower tibia was used to measure the peak acceleration and time to peak acceleration associated with footstrike. Subjects were also videoed and a kinematic analysis was undertaken at the knee and ankle joints. The results from the materials test showed that the shoes differed in their midsole characteristics, however, no significant differences (P > 0.05) were observed in the peak acceleration and time to peak acceleration during running in shoes. These variables were significantly greater in the barefoot running condition (P < 0.05), as compared with running in shoes. Small and subtle kinematic differences were observed between the barefoot and shoe conditions. It appears that the differences observed between the shoes in the materials test were not sufficient to elicit the kinematic changes observed between the barefoot and shoe conditions. It is suggested that runners operate within a 'kinetic bandwidth' when responding to impact stresses.

Absorption↗
PubMed1994

Landing characteristics in subjects with normal and anterior cruciate ligament deficient knee joints.

Sixteen subjects with arthroscopically verified anterior cruciate ligament (ACL) deficiency and 16 subjects without knee problems participated in this study. The functional ability of the ACL-deficient subjects was assessed with the Noyes knee rating system. Each subject completed a landing task in which they hopped from a box 300mm in height to land on one leg. Vertical ground reaction forces and anterior tibial accelerations were recorded, while electrogoniometers measured angular displacement at the knee and ankle joints. Electromyographic (EMG) signals from the vasti lateralis and lateral hamstrings were also recorded. The active stiffness of the hamstring muscles was also assessed in the ACL-deficient subjects. No significant differences (p > 0.05) were observed between the ACL-deficient group and the normal knee group for the landing task. Nor were any significant correlations (p > 0.05) observed between the kinematic, electromyographic variables and the functional ability of the ACL-deficient subjects. However, the active stiffness of the hamstring muscles was positively correlated with functional ability (r = 0.73, p < 0.05), whereas it was negatively related (r = -0.83, p < 0.05) to the magnitude of the EMG activity observed during the landing task. These findings suggest that there is an interplay between the stiffness characteristics of the hamstring muscles and their activation by central processes. It was apparent that not all ACL-deficient subjects take on a landing strategy to minimize stress to their knee joints.

Adult↗
PubMed1993

Giardiasis in lambs at pasture.

Faecal samples from a group of lambs at pasture were screened at weekly intervals for nine weeks for the presence of Giardia species using a modified zinc sulphate flotation method. Fifty-nine of 86 lambs (68.6 per cent) excreted giardia cysts on one or more occasions. They were first detected at approximately three weeks of age and the highest incidence of excretion of cysts occurred when the lambs reached a mean age of 37 days. The lambs had diarrhoea but it was attributed to the presence of Eimeria ovinoidalis.

Animals↗
PubMed1992

Growth hormone therapy in achondroplasia.

A pilot study was carried out to examine the safety and efficacy of recombinant human growth hormone for growth-promoting therapy of achondroplasia. The data suggest that the agent in doses used to treat non-GH-deficient forms of short stature (0.3 mg/kg/wk) modestly increases overall height velocity in some children with achondroplasia. The effect was seen mainly in children with the lowest growth velocities prior to treatment. No untoward effects were noted. Several questions were raised that require further study.

Achondroplasia↗
PubMed1991

Functional torque-velocity and power-velocity characteristics of elite athletes.

Technical limitations of some isokinetic dynamometers have called into question the validity of some data on human muscle mechanics. The Biodex dynamometer has been shown to minimize the impact artefact while permitting automatic gravity correction. This dynamometer was used to study quadriceps muscle torque and power generation in elite power (n = 6) and elite endurance (n = 7) athletes over 12 randomly assigned isokinetic velocities from 30 degrees.s-1 to 300 degrees.s-1. The angle at peak torque varied as a negative, linear function of angular velocity, with the average angle across test velocities being 59.5 degrees (SD 10.2 degrees). Power athletes developed greater peak torque at each angular velocity (P less than 0.05) and experienced a 39.7% decrement in torque over the velocity range tested. Endurance athletes encountered a 38.8% decline in peak torque. Torques measured at 60 degrees of knee flexion followed a similar trend in both groups; however the greatest torques were recorded at 60 degrees.s-1 rather than at 30 degrees.s-1. Leg extensor muscle power increased monotonically with angular velocity in both power (r2 = 0.728) and endurance athletes (r2 = 0.839); however these curves diverged significantly so that the power athletes produced progressively more power with each velocity increment. These inter group differences probably reflected a combination of natural selection and training adaptation.

Adult↗
PubMed1990

Important features associated with acute anterior cruciate ligament injury.

The mechanism of injury and the signs and symptoms associated with initial injury to the anterior cruciate ligament were investigated in 23 subjects. The subjects had injured only their anterior cruciate ligament with no other clinically definable laxity to other major ligamentous structures. The results showed that 70% of subjects had injured their anterior cruciate ligament at footstrike during noncontact situations. In 53% of these subjects the mechanism of injury was internal rotation of the tibia with the knee in slight flexion. A shifting sensation occurring between the tibia and femur was noted by 61% of subjects, while 30% recalled a crack or popping sound at the time of injury. Only 17% of subjects could continue in sports activity immediately following the injury, all with difficulty.

Acute Disease↗