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Biomedical subjects

K G Davis

Publications and source records attributed to K G Davis.

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

A comprehensive analysis of low-back disorder risk and spinal loading during the transferring and repositioning of patients using different techniques.

Although patient handlers suffer from low-back injuries at an alarming rate worldwide, there has been limited research quantifying the risk for the specific tasks performed by the patient handlers. The current study used both a comprehensive evaluation system (low-back disorder risk model) and theoretical model (biomechanical spinal loading model) to evaluate risk of LBD of 17 participants (12 experienced and five inexperienced) performing several patient handling tasks. Eight of the participants were female and nine were male. Several patient transfers were evaluated as well as repositioning of the patient in bed; these were performed with one and two people. The patient transfers were between bed and wheelchair (fixed and removable arms) and between commode chair and hospital chair. A 'standard' patient (a 50 kg co-operative female; non-weight bearing but had use of upper body) was used in all patient handling tasks. Overall, patient handling was found to be an extremely hazardous job that had substantial risk of causing a low-back injury whether with one or two patient handlers. The greatest risk was associated with the one-person transferring techniques with the actual task being performed having a limited effect. The repositioning techniques were found to have significant risk of LBD associated with them with the single hook method having the highest LBD risk and spinal loads that exceeded the tolerance limits (worst patient handling job). The two-person draw sheet repositioning technique had the lowest LBD risk and spinal loads but still had relatively high spinal loads and LBD risk. Thus, even the safest of tasks (of the tasks evaluated in this study) had significant risk. Additionally, the current study represented a 'best' case scenario since the patient was relatively light and co-operative. Thus, patient handling in real situations such as in a nursing home, would be expected to be worse. Therefore, to have an impact on LBD, it is necessary to provide mechanical lift assist devices.

Adult↗
PubMed1999

Effects of box features on spine loading during warehouse order selecting.

Low back disorders in distribution centres or warehouses have been identified as an area of elevated risk in many industries. The task of an order selector requires workers manually to lift boxes from storage bins to a mobile pallet. This study explored the effect of box features and box location when lifting from a pallet in a storage bin upon spine loading. Ten experienced warehouse workers were asked to lift boxes from a pallet while the size, weight, handle features and location of the box on a pallet were changed. An EMG-assisted model was employed to assess spine compression, lateral shear and anterior-posterior shear during the lifts. The position from which the worker lifted a box on a pallet had the most profound effect on spine loading while the lower level of the pallet represented the greatest loadings on the spine. Box weight did not appear to be a feasible means of controlling spine loading unless its position on the pallet could also be controlled. The inclusion of handles had an effect similar to reducing the box weight by 4.5 kg, whereas box size did not effectively affect spine loading. The mechanisms by which these factors affect spine loading are discussed.

Adult↗
PubMed1998

Trunk muscle activities during asymmetric twisting motions.

Axial twisting of the torso has been identified via epidemiologic studies as a significant risk factor for occupationally-related low back disorders. However, only recently have biomechanical studies been able to describe how twisting is accomplished through the use of the trunk musculature. These studies have been performed on subjects whose torso twists were performed in an upright posture. In this study, the electromyographic activity of ten trunk muscles was observed while 12 subjects performed twisting exertions in three different trunk postures. These postures included upright twisting, twisting while the trunk was flexed in the sagittal plane, and twisting while the trunk was flexed and rotated asymmetrically. In addition, twisting velocity and direction of motion were changed under the experimental conditions. Under upright twisting conditions, the twisting torque was generated easily and relatively efficiently through the employment of the oblique (internal and external) and latissimus dorsi muscles. When the trunk was flexed the activity of erector spinae muscles increased (about 10-15%) while the external oblique activity decreased (about 3-5%). Twisting while in asymmetric bent postures was accomplished with a reduction in oblique and latissimus dorsi muscle activities (approximately 5%) while the erector spinae muscle activity remained elevated. The change in muscle activity needed to balance the torso during twisting while bending also increased the amount of lateral torque that was produced by the trunk. These findings suggest that studies observing trunk muscle activities and trunk loading while subjects were in upright postures should be interpreted with caution when evaluating the activity of the trunk during occupational activities. Since many occupational twisting tasks are performed in awkward, asymmetric postures, application of results from upright twisting studies might underestimate the risk of these activities.

Abdominal Muscles↗
PubMed1998

Water vapor sorption studies on the physical stability of a series of spray-dried protein/sugar powders for inhalation.

One theory suggests that by maintaining the protein in an amorphous glassy sugar matrix, the physical hindrance encountered by the protein functions to stabilize it. Thus, the nature of the sugar/protein interaction is important as is the maintenance of the sugar in an amorphous form without any recrystallization. Moisture is known to function as a plasticizer and facilitate crystallization and thus loss of the amorphous state. We report the effect of cospray-drying with different proteins on the physical stability of lactose and mannitol. Particle sizing showed their suitability for inhalation, and the effect of exposure of the spray-dried products to moisture vapor was monitored gravimetrically. Bovine liver catalase, bovine pancreatic insulin, and bovine pancreatic ribonuclease A when individually cospray-dried with lactose showed no extensive initial crystallinity by powder X-ray diffraction, but proteins cospray-dried with mannitol generally showed evidence of mannitol component crystallinity. Catalase appeared to inhibit lactose crystallization from an amorphous matrix to a greater extent than insulin when exposed to short-term elevated humidity, but this difference was a kinetic feature. The hygroscopicities of the cospray-dried materials differed and indicated that each protein/sugar system required individual characterization to identify an optimal formulation.

Catalase↗
PubMed1998

Reduction of spinal loading through the use of handles.

A study was performed to investigate how different types of handle coupling affect the loading on the spine. Ten male grocery item selectors performed a laboratory simulation of a warehouse palletizing task. Participants transferred the cases from a pallet in a storage bin to the destination pallet. The trunk motions and muscle activities were monitored by a Lumbar Motion Monitor (LMM) and electromyographic electrodes, respectively, and used as input to an EMG-assisted biomechanical model. The results of the study revealed that the presence of handles reduced the complex loads on the spine. This was particuarly true when lifting to the lowest positions of the pallet, where the highest forces occurred. It was determined that the maximum spinal compression forces were reduced by an average of 6.8% when handles were added to the cases. The presence of handles affected the moments imposed on the trunk in the lower regions on the pallet, indicating a difference in lifting style and/or more sagittal flexion. The results of this study suggest that the multiplier for handle coupling in the 1991 NIOSH Revised Lifting Equation was appropriate for higher lifts (at 133.8 cm), but needs to be more protective for 'poor' coupling conditions with lower vertical heights, which are the most common in industry. Based on these results, it is recommended that handles be designed into the cases that are commonly lifted from low levels in warehousing and other manual materials handling situations.

Adult↗
PubMed1998

Spine loading during asymmetric lifting using one versus two hands.

This study documented three-dimensional spinal loading associated with asymmetric lifting while using either one or two hands to perform the task. Lift asymmetry was defined as a function of the load origin relative to the sagittal plane of the body. Lifts occurred at 0, 30, or 60 degrees off the sagittal plane on both sides of the body (lifting from the right and from the left relative to the sagittal plane). Ten subjects lifted a 13.7 kg box from one of these origins to a sagittally symmetric destination. Spinal loads were estimated through the use of a validated EMG-assisted model. Spine compression and lateral shear forces increased as the lift origin became more asymmetric. However, spinal compression and lateral shear increased by about twice the rate when lifting from origins to the left of the sagittal plane compared to lifting from origins to the right of the sagittal plane. Anterior-posterior spinal shear decreased as asymmetry increased with larger decreases occurring when lift origins occurred to the right of the sagittal plane. One-hand lifting changed the compression and shear profiles significantly. One-hand lifts using the hand on the same side of the body as the load resulted in compression forces that were approximately equal to those observed when lifting with two hands in a sagittally symmetric position. Anterior-posterior shear decreased and lateral shear increased under these conditions. These results reflect the trade-offs that must be considered among spinal forces during asymmetric lifting while using one or two hands. These findings have significant implications for task assessment interpretation and workplace design.

Adult↗
PubMed1997

Biomechanical assessment of lifting dynamics, muscle activity and spinal loads while using three different styles of lifting belt.

OBJECTIVE: To demonstrate the influence of different types of lifting belts on trunk motion, muscle activity and spine loading during symmetric and asymmetric lifting exertions. DESIGN. IN VIVO: measurements were achieved representing lifting dynamics, applied trunk moments and myoelectric activity. Dynamic spinal loads were determined from a validated biomechanical model of lifting. BACKGROUND: There is a great deal of controversy as to whether lifting belts are a benefit or a liability to manual materials-handling activities. A review of the literature demonstrates that there is a large amount of conflicting evidence and few definitive, well-executed studies upon which to base an opinion regarding these devices. METHODS: Fifteen subjects lifted boxes of 14 kg and 23 kg from sagitally symmetric and asymmetric origins to an upright posture. Dynamic trunk motions, lifting moments, myoelectric activity and modelled spinal loads were examined as a function of three belt styles (elastic, leather, and orthotic) and compared with results from a no-belt condition. RESULTS: Lifting belts reduced peak trunk angles, velocities and accelerations in the sagittal, lateral and transverse planes. However, only the elastic belt successfully reduced trunk motions in all three dimensions. The orthotic belt significantly increased the lifting moment associated with a given weight. A minor redistribution in muscle activity was observed when wearing an elastic belt. A statistically significant reduction in spinal load was associated with the elastic belt. However, a great deal of variability between subjects was noted. Some subjects experienced increased spinal load while wearing the elastic lifting belt. CONCLUSIONS: These results demonstrate that the biomechanical operation of lifting can be influenced by the type of lifting belts used.

Journal Article↗
PubMed1997

Influence of lift moment in determining MAWL.

An experiment was performed to determine whether maximum acceptable weight of lift (MAWL) estimates were consistent with previously reported values when the MAWL was determined without visual feedback during the weight adjustment period. Twelve healthy male students performed four lifting tasks similar to those often performed in previous psychophysical studies: floor to knuckle at 1 lift per min, floor to knuckle at 4.3 lifts per min, knuckle to shoulder at 1 lift per min, and knuckle to shoulder at 4.3 lifts per min. When compared with the previous studies with similar box dimensions, similar trends between the conditions were present, but a slight reduction in weight was usually chosen by the participant in this study. However, the results of this study agreed with previous psychophysical studies when the distance of the load from the spine (moment arm) was taken into consideration by either comparing the MAWLs with those of a large box or by comparing load moments. Hence this study shows that eliminating visual feedback during the adjustment periods did not significantly alter the MAWLs from previous studies. It also indicates that one must use caution when applying the MAWL in the workplace because the MAWL is very sensitive to moment arm.

Analysis of Variance↗
PubMed1995

Comparison of Pf1 and Fd gene 5 proteins and their single-stranded DNA complexes by NMR spectroscopy and differential scanning calorimetry.

The Pf1 gene 5 protein forms a large helical nucleoprotein complex (Mr = 3.1 x 10(7)) with single-stranded viral DNA, from which a 32 amino acid sequence rich in alanine, proline, and glutamine residues can be removed from the C-terminus by limited proteolysis. Sharp resonances in the 1H NMR spectrum of the Pf1 nucleoprotein complex indicate that the C-terminal region of the protein subunits enjoys remarkable conformational flexibility in the complex. In contrast, the globular N-terminal domain of the protein subunits is rigidly held and does not contribute to the spectrum. The Fd gene 5 protein lacks this C-terminal flexible domain, and no distinct resonances can be observed in the 1H NMR spectrum when this protein is complexed to single-stranded viral DNA. Differential scanning calorimetry shows that the thermal stability of both the Pf1 and Fd gene 5 protein is increased by 8 degrees C in the complex with DNA, and the transition is highly cooperative. Removal of the C-terminal domain of the Pf1 gene 5 protein subunits has no appreciable effect either on the Tm of the DNA-protein complex or on the cooperative nature of the thermal transition. It is suggested that the C-terminal domain of the Pf1 gene 5 protein acts as a dynamic clamp which kinetically stabilizes the nucleoprotein complex.

Amino Acid Sequence↗
PubMed1994

DNA-binding induces a major structural transition in a type I methyltransferase.

The type IC DNA methyltransferase M.EcoR124I is a complex multisubunit enzyme that recognizes the non-palindromic DNA sequence GAAN6RTCG. Small angle X-ray scattering has been used to investigate the solution structure of the methyltransferase and of complexes of the enzyme with unmethylated and hemimethylated 30 bp DNA duplexes containing the specific recognition sequence. A major change in the quaternary structure of the enzyme is observed following DNA binding, based on a decrease in the radius of gyration from 56 to 40 A and a reduction in the maximum dimension of the enzyme from 180 to 112 A. The structural transition observed is independent of the methylation state of the DNA. CD shows that there is no change in the secondary structure of the protein subunits when DNA is bound. In contrast, there is a large increase in the CD signal arising from the DNA, suggesting considerable structural distortion which may allow access to the bases targeted for methylation. We propose that DNA binding induces a large rotation of the two HsdM subunits towards the DNA, mediated by hinge bending domains in the specificity subunit HsdS.

Base Sequence↗
PubMed1989

Influence of blood storage time and plasma histamine levels on the pattern of transfusion reactions.

The data from 359 transfusion reactions reported over a 3-year period have been compared with those obtained from 359 matched units given at the same time as the former but not implicated in a reaction. It was found that patients who developed reactions which were not accompanied by a change in body temperature received units with a longer storage time than patients experiencing febrile reactions. In addition it was noted that reactions which included a skin rash also tended to be associated with units stored for longer. In a further prospective assessment plasma histamine levels were measured in a group of 71 patients experiencing 'anaphylactoid', febrile and mixed transfusion reactions as well as in individuals in whom blood transfusions did not cause a reaction. The 'anaphylactoid' reaction group demonstrated a mean plasma histamine level in excess of 1 ng/ml, whereas mean concentrations below 0.50 ng/ml were recorded in the other 3 groups. Our data also suggested that in general, more and 'older' blood was given to the 'anaphylactoid' reactors. The high plasma histamine concentrations could readily contribute to the rash, wheeze and flushing recorded in these individuals. Thus, if a long shelf-life for stored blood is required, strategies which remove histamine from the unit may be worth considering.

Blood Preservation↗
PubMed1989

Educational needs of the terminally ill student.

It is the norm for medical professionals to encourage school reentry for the terminally ill student. Their commitment to and belief in the benefits of school involvement are to be commended. It is essential, however, that the hospital staff be directly involved with facilitating school reentry. Research into the needs of chronically and terminally ill students has historically been done by the medical community. Educators lack basic knowledge and the expertise to ensure that the school experience will be successful. It is hoped that the educational community will become more aware and actively seek to guarantee that every child is provided with an appropriate education in future years. For the time being, however, the medical professional must assume the role of coordinator, bringing together the terminally ill child, parents, peers, and educators, and fostering open, ongoing communication between all. The success of these efforts will bring about healthy attitudes toward death and dying; a rich, rewarding experience for all children involved; and ultimately an opportunity for a dying child to live life to its fullest.

Adolescent↗
PubMed1987

The solution conformations of the subclasses of human IgG deduced from sedimentation and small angle X-ray scattering studies.

The solution conformations of human immunoglobulin G subclass molecules have been investigated by sedimentation and small-angle X-ray scattering techniques. Both methods qualitatively indicate IgG3 to be an extended molecule relative to IgG1. Sedimentation data have been collected for a number of paraproteins of all four subclasses and the hinge-deleted IgG1Dob protein. The known crystal structure of Dob allows the use of this protein as a basis for the proposal of models of the average conformations of IgG subclasses which are consistent with experimental s(0)20,w values. IgG1 is suggested to have a hinge length of 0-15 A and non-coplanar Fab arms; IgG2 to be effectively hingeless with folded-back Fab arms; IgG3 to have an extended hinge of the order of 100 A and IgG4 to be effectively hingeless and T-shaped. The possible correlation of these conformations with subclass function is discussed.

Humans↗
PubMed1987

Effect of microfiltration on the histamine levels in stored human blood.

Plasma and whole blood histamine levels and white cell counts have been monitored over a 6-week period of storage in standard citrate-phosphate-dextrose supplemented with adenine (CPDA) blood packs, add-back blood packs, and also CPDA and add-back packs which were subjected to a microfiltration process at the time of collection. Our results indicate that the plasma histamine level rises and the white blood count falls progressively with time, the former being most marked after the 3rd week of blood storage. At 6 weeks, there was no significant difference between the plasma and whole blood histamine level, suggesting that the entire complement of histamine in blood was now in plasma. Microfiltration substantially reduced the white cell count in the packs, and this was reflected in a greatly reduced whole blood and (subsequently) plasma histamine concentration.

Blood Preservation↗