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PubMedDate not supplied

The effect of lead, gold, and silver backings on dose near 125I seeds.

Brachytherapy for ocular melanoma uses 125I seeds backed by a gold shield. Conflicting results are reported in the literature on the effect of the gold on dose close to the seeds. In this work, a small lucite jig was constructed such that the seed-to-detector separation remained fixed as high-Z materials of lead, silver, and gold were moved in and out of position behind the seed. The jig was clamped in place in the water filled tank of a beam scanning system. The response of two p-type silicon diodes was measured at several distances from the seed with and without the high-Z backings. The response with the high-Z backing relative to water, found to be the same for each diode and the same for lead and gold, decreased from about 1.01 at 1.5 mm to about 0.92 at 20 mm. It has been suggested in the literature that L-shell fluorescent x rays of approximately 10 keV from the gold backing might contribute significantly to the dose within 7 mm of the seed. To test this, the response with the gold backing relative to water was measured with an aluminum cap of 1-mm wall thickness covering the diode. The cap transmits about 70% of the 125I influence but is essentially infinitely thick to 10-keV photons. The relative response (gold/water) was the same with and without the cap showing that the contribution of 10-keV x rays is negligible. Compared to water, the silver backing was found to enhance the diode response by about 14% between 5 to 10 mm from the seed.

Biophysical Phenomena↗
PubMed2001

Mast cells are involved in the gastric hyperemic response to acid back diffusion via release of histamine.

Acid back diffusion into the rat stomach mucosa leads to gastric vasodilation. We hypothesized that histamine, if released from the rat mucosa under such conditions, is mast cell derived and involved in the vasodilator response. Gastric blood flow (GBF) and luminal histamine were measured in an ex vivo chamber. Venous histamine was measured from totally isolated stomachs. Mucosal mast cells (MMC), submucosal connective tissue mast cells (CTMC), and chromogranin A-immunoreactive cells (CgA IR) were assessed morphometrically. After mucosal exposure to 1.5 M NaCl, the mucosa was subjected to saline at pH 5.5 (control) or pH 1.0 (H(+) back diffusion) for 60 min. H(+) back diffusion evoked a marked gastric hyperemia, increase of luminal and venous histamine, and decreased numbers of MMC and CTMC. CgA IR cells were not influenced. Depletion of mast cells with dexamethasone abolished (and stabilization of mast cells with ketotifen attenuated) both hyperemia and histamine release in response to H(+) back diffusion. GBF responses to H(+) back diffusion were attenuated by H(1) and abolished by H(3) but not H(2) receptor blockers. Our data conform to the idea that mast cells are involved in the gastric hyperemic response to acid back diffusion via release of histamine.

Acids↗
PubMed2006

Assessment of neuromuscular and haemodynamic activity in individuals with and without chronic low back pain.

BACKGROUND: Biering-Sørenson (1984) found that individuals with less lumbar extensor muscle endurance had an increased occurrence of first episode low back pain. As a result, back endurance tests have been recommended for inclusion in health assessment protocols. However, different studies have reported markedly different values for endurance times, leading some researchers to believe that the back is receiving support from the biceps femoris and gluteus maximus. Therefore, this study was designed to examine the haemodynamic and neuromuscular activity of the erector spinae, biceps femoris, and gluteus maximus musculature during the Biering-Sørenson Muscular Endurance Test (BSME). METHODS: Seventeen healthy individuals and 46 individuals with chronic low back pain performed the Biering-Sørenson Muscular Endurance Test while surface electromyography was used to quantify neuromuscular activity. Disposable silver-silver-chloride electrodes were placed in a bipolar arrangement over the right or left biceps femoris, gluteus maximus, and the lumbosacral paraspinal muscles at the level of L3. Near Infrared Spectroscopy was used simultaneously to measure tissue oxygenation and blood volume changes of the erector spinae and biceps femoris. RESULTS: The healthy group displayed a significantly longer time to fatigue (Healthy: 168.5s, LBP: 111.1s; p < or = 0.05). Significant differences were shown in the median frequency slope of the erector spinae between the two groups at 90-100% of the time to fatigue while no significant differences were noted in the haemodynamic data for the two groups. CONCLUSION: Although the BSME has been recognized as a test for back endurance, individuals with chronic LBP appear to incorporate a strategy that may help support the back musculature by utilizing the biceps femoris and gluteus maximus to a greater degree than their healthy counterparts.

Journal Article↗
PubMed2005

Are chronic low back pain outcomes improved with co-management of concurrent depression?

OBJECTIVE: To discuss the role of depression in chronic lower back pain and comment on appropriate methods of screening and co-management. DATA SOURCES: The current scientific literature was investigated using the online web databases CINAHL, Medline/PUBMED, Proquest, Meditext and from manual library searches. DATA EXTRACTION: Databases were searched from 1980 to the present (2005). Articles were searched with the key words "depression" and "low back pain". Over three hundred articles were sourced and articles were then selected on their relevance to the chronic spinal pain states that present to manual therapy practitioners. DATA SYNTHESIS: Pain is a subjective awareness of peripheral nociceptive stimulation, projected from the thalamus to the cerebral cortex with each individual's pain experience being mediated by his or her psychological state. Thus a psychological component will often be associated with any painful experience. A number of studies suggest (among other things) that the incidence of depression predicts chronicity in lower back pain syndromes but that chronic lower back pain does not have the reciprocal action to predict depression. CONCLUSION: The aetiology of chronic pain is multifactorial. There is sufficient evidence in the literature to demonstrate a requirement to draw treatment options from many sources in order to achieve a favourable pain relief outcome. The treatment should be multimodal, including mental and emotional support, counseling and herbal advice. While a strong correlation between depression and chronic low back pain can be demonstrated, an apparent paucity of literature that specifically addresses the patient response to chiropractic treatment and concurrent psychotherapy identifies the need for prospective studies of this nature to be undertaken. It is likely that multimodal/multidisciplinary treatment approaches should be encouraged to deal with these chronic lower back pain syndromes.

Journal Article↗
PubMed2003

Contact mechanics of metal-on-metal hip implants employing a metallic cup with a UHMWPE backing.

The contact mechanics in metal-on-metal hip implants employing a cobalt chromium acetabular cup with an ultra-high molecular weight polyethylene (UHMWPE) backing were analysed in the present study using the finite element method. A general modelling methodology was developed to examine the effects of the interfacial boundary conditions between the UHMWPE backing and a titanium shell for cementless fixation, the coefficient of friction and the loading angle on the predicted contact pressure distribution at the articulating surfaces. It was found that the contact mechanics at the bearing surfaces were significantly affected by the UHMWPE backing. Consequently, a relatively constant pressure distribution was predicted within the contact conjunction, and the maximum contact pressure occurred towards the edge of the contact. On the other hand, the interfacial boundary condition between the UHMWPE backing and the titanium shell, the coefficient of friction and the loading angle were found to have a negligible effect on the contact mechanics at the bearing surfaces. Overall, the magnitude of the contact pressure was significantly reduced, compared with a similar cup without the UHMWPE backing. The importance of the UHMWPE backing on the tribological performance of metal-on-metal hip implants is discussed.

Chromium Alloys↗
PubMed1983

Acid back-diffusion and mucosal H+ handling in the rat stomach under normal and stress-induced conditions.

We determined acid back-diffusion and pepsin output simultaneously in vagotomized rats after instillation of HCl into the stomach under normal and stress-induced conditions. With exposure to 6 ml of 100 mM HCl, spontaneous acid back-diffusion increased with the duration of the experiment under both conditions, and the magnitude of the acid back-diffusion was decreased significantly by stress. There was no change in the output of pepsin. While disappearance of luminal acid caused by aspirin or taurocholic acid was not altered by stress, the pepsin output in response to H+ increased significantly in the stressed rats. With exposure to various concentrations of HCl for 3 hr, disappearance of the luminal acid increased linearly with the grade of HCl under both conditions. Except for the concentration of 300 mM, the magnitude of the acid back-diffusion was triple in the normal condition, and the ratio of pepsin output/net flux of H+ was significantly increased by stress. Thus, (1) spontaneous acid back-diffusion decreased with stress, while diffusion induced by chemical barrier breakers remained the same; (2) the action of H+ diffused back into the mucosa did not always parallel the amount of diffusion determined from the loss of H+ in the lumen; (3) intramucosal H+ may be largely dissipated in normal mucosa; and (4) the initiation or aggravation of drug-induced mucosal damages by stress may be related to insufficiency of the H+ dissipating mechanisms.

Animals↗
PubMed2004

Molecular dynamics analysis of structural factors influencing back door pi release in myosin.

The back door has been proposed to be an exit pathway from the myosin active site for phosphate (P(i)) generated by adenosine 5'-triphosphate hydrolysis. We used molecular dynamics simulations to investigate the interaction of P(i) with the back door and the plausibility of P(i) release via this route. Molecular dynamics simulations were performed on the Dictyostelium motor domain with bound Mg.adenosine 5'-diphosphate (ADP) and P(i), modeled upon the Mg.ADP.BeF(x) and Mg.ADP.V(i) structures. Simulations revealed that the relaxation of ADP and free P(i) from their initial positions reduced the diameter of the back door via motions of switch 1 and switch 2 located in the upper and lower 50-kDa subdomains, respectively. In neither simulation could P(i) freely diffuse out the back door. Water molecules, however, could flux through the back door in the Mg.ADP.BeF(x)-based simulation but not in the Mg.ADP.V(i)-based simulation. In neither structure was water observed fluxing through the main (front door) entrance. These observations suggest that the ability of P(i) to leave via the back door is linked tightly to conformational changes between the upper and lower 50-kDa subdomains. The simulations offer structural explanations for (18)O-exchange with P(i) at the active site, and P(i) release being the rate-limiting step in the myosin adenosine 5'-triphosphatase.

Adenosine Diphosphate↗
PubMed2000

Comparison of the effects of add-back therapy with various natural oestrogens on bone metabolism in rats administered a long-acting gonadotrophin-releasing hormone agonist.

The hypoestrogenic state induced by gonadotrophin-releasing hormone agonist (GnRHa) has been shown to be effective in the treatment of oestrogen-dependent disorders but to induce bone loss. Adding back low doses of oestrogen in GnRHa therapy has been proposed to prevent bone loss. The purpose of this study is to assess the efficacy of add-back therapy with different natural oestrogens such as oestrone (OE(1)), oestradiol (OE(2)) and oestriol (OE(3)). Three-month-old female rats (250 g) were subcutaneously administered microcapsules of leuprorelin acetate in doses of 1 mg/kg of body weight every 4 weeks. GnRHa therapy lasted 16 weeks, and pellets of OE(1), OE(2) or OE(3) (0.5 mg/pellet, 60 day release), as an add-back agent, were implanted at 8 weeks of treatment. At the end of treatment, GnRHa alone decreased bone mineral density of the femur and lumbar vertebrae, and increased serum levels of bone metabolic markers such as alkaline phosphatase and osteocalcin levels. As for cancellous bone histomorphometry, GnRHa decreased bone volume while it increased osteoid volume, osteoid surface, eroded surface, mineral apposition rate and bone formation rate. All the oestrogens tested prevented these changes caused by GnRHa therapy. GnRHa induced a significant increase in body weight and a marked reduction in uterine weight, which was not observed in OE(1) or OE(2) add-back group. Body weight and uterine weight of the OE(3) add-back group were the same as those of the GnRHa group. These findings indicate that GnRHa induces high turnover bone loss which can be prevented by concomitant administration of natural oestrogens such as OE(1), OE(2) and OE(3) to the same extent. In addition, OE(3) is unique in that it is much less effective than OE(1) and OE(2) in blocking body weight gain and in promoting growth of uterine tissues. Because of its tissue-selective actions, OE(3) could be considered as one of the most appropriate oestrogens used for GnRHa add-back therapy.

Alkaline Phosphatase↗
PubMedDate not supplied

Hang-back lateral rectus recessions for exotropia.

The hang-back recession is a simple, safe alternative to conventional recession. We evaluated the surgical results in 23 consecutive patients undergoing bilateral hang-back lateral rectus recessions and 24 consecutive patients undergoing bilateral conventional lateral rectus recessions. The 6-week postoperative success rate was 78% in the hang-back group and 75% in the conventional group. At the time of the most recent follow-up, the success rate was 64% in the hang-back group and 85% in the conventional group. Dose-response curves were similar for both methods. There were more late overcorrections with the hang-back technique. We suggest modified surgical guidelines for the hang-back recession technique.

Child↗
PubMedDate not supplied

Comparison of hang-back and conventional recession surgery for horizontal strabismus.

PURPOSE: To compare the results of hang-back and conventional recession surgery. METHODS: This randomized, double-blind, matched clinical trial comprised 30 patients with esotropia and 24 with exotropia. All ocular examinations before and at least 1.5 months after surgery were performed by an orthoptist who was unaware of the method of recession. All surgeries were performed by the same surgeon. RESULTS: In patients with esotropia, deviation improved from 31+/-9 prism diopters (delta) preoperatively to 7+/-6 delta postoperatively for hang-back recession (n=15) and from 41+/-14 delta to 6+/-6 delta for conventional recession (n=15). Postoperative horizontal deviation was >10 delta in 40% of patients who underwent hang-back recession and 20% of patients who underwent conventional recession (P<.8). In patients with exotropia, deviation improved from 28.9+/-9 delta preoperatively to 0.5+/-11 delta postoperatively for hang-back recession (n=12) and from 29+/-8 delta to 6+/-6 delta for conventional recession (n=12). Postoperative horizontal deviation was >10 delta in 24% of patients who underwent hang-back recession and 17% of patients who underwent conventional recession (P<.2). Mean follow-up was 7 months. CONCLUSION: Hang-back recession is an alternative to conventional rectus muscle recession, especially in children who have smaller globes and patients with myopia or collagen vascular diseases.

Child↗
PubMed2000

The effect of elastic modulus of the backing material on the fatigue notch factor and stress.

In cemented acetabular cup design it is acknowledged that bone resorption and fatigue fracture of cement may cause the most common problems after total hip replacement. Previous studies have optimized the shape of metal backing (MB) shell used in cemented acetabular components in order to minimize the fatigue notch factor (Kf) in cement, whilst at the same time maximizing Kf in bone at the central part of acetabulum to prevent stress shielding and subsequent bone resorption [1]. The optimal shape was found to be thin at the edges and thick at the dome. The present study describes the effect of changing the elastic modulus of the backing material on Kf and stresses as predicted by the initial shape of the backing shell of (3 mm) thick, and the optimized backing shape of non-uniform thickness in order to find the optimal material for the backing shell. It is recommended to use a backing shell material with elastic modulus equals 70 GPa (which can be readily attained using a fiber reinforced polymer composite). It is shown that such a material will decrease the fatigue notch factor and the stresses in cement at cup edges, at the same time it will increase the stresses and the fatigue notch factor in bone at the central part of acetabulum. Thereby, reducing the possibility of fatigue fracture of cement, whilst at the same time decreasing the stress shielding effect and the resulting bone resorption. The effect of lower bone resorption and lower probability of fatigue fracture of the cement will also reduce the incidence of loosening and premature revision operations.

Aged↗
PubMed2002

Enhancing RGP contact lens performance: comparing back surface options.

BACKGROUND: In some cases, rigid gas-permeable (RGP) contact lenses may be the best--or only--means of refractive correction. High Dk RGP materials have markedly reduced hypoxia under those lenses. With aspheric lens back surface designs, post-lens circulation may be enhanced as well by maximizing the provision of nutrients and the clearance of metabolic by-products, toxins, and debris, while minimizing the risk of lens binding. METHODS: Performances of four aspheric back surface RGP designs were compared with a spherical optic zone and peripheral curve back surface reference design. Oxygen uptake rates were measured for each of 40 wearing combinations (five lens designs fitted to each of eight eyes) under non-blink and blink conditions for their effectiveness in reduction of post-lens hypoxia. Hypoxic reductions with blinking were scaled in exchange efficiency (EE) units, and used as relative indicators of post-lens tear exchange. RESULTS: Combined exchange efficiency index (EE) scores (averaged responses across all eight eyes) for each of the five lens back surface designs ranged from a best overall performance of +13.9 EE units down to only +2.5 EE units, with the spherical reference design averaging +8.9 EE units. Tear pump efficiency of each of the eight eyes (averaged responses across all five lens designs) ranged from a high of +12.3 EE units down to -9.8 EE units (i.e., worse than the non-blink condition of 0 EE units). Among the 40 eye-lens back surface design combinations studied here, the highest exchange efficiency score registered was +28.4 EE units, the lowest being -13.8 EE units. CONCLUSIONS: Aspheric lens back surface and/or peripheral curve designs were found to vary significantly in their post-lens exchange efficiency performances, but no "universal problem-solver" design was found among the five we investigated.

Adult↗
PubMed2002

[The influence of expansion maintenance period upon in vivo skin tension and immediate stretch-back rate of the expanded skin].

OBJECTIVE: The study was to investigate the influence of maintenance period of expansion upon skin tension and immediate stretch-back rate of the expanded skin. METHODS: 30 expanders (240 ml) were implanted in six adult dogs, which were divided into four groups: group A with 2-week saline injection of the expander; group B with 6-week injection; group C with sham-operation and group D as the blank control group. The first two groups were subdivided into three groups respectively according to different maintaining times of one week, two weeks and four weeks. When full inflation was finished, a 4 cm x 7 cm expanded flap was created and in vivo skin tension and stretch-back ratio of the flap were measured. The Comparison was made in terms of in vivo skin tension and immediate stretch-back ratio between different injection and different maintenance periods. RESULTS: With expansion maintenance time increasing, the in vivo skin tension and immediate stretch-back ratio decreased. After the capsule of the expand skin flap was removed, the in vivo skin tension and immediate stretch-back rate significantly reduced. Based on the experimental results, 16 patients were treated with implantation of 23 expanders. Their average expander injection time was 14 days and the average maintenance time was 25 days. All expanders obtained good results except one extrusion. CONCLUSION: In skin and soft tissue expansion, in vivo skin tension and immediate stretch-back ratio can be reduced through prolonged maintenance of expansion and capsule removal from the expanded skin flap.

Adolescent↗
PubMed1992

Separation of the polyethylene liner from acetabular cup metal backing. A report of three cases.

In three young patients with cementless Porous Coated Anatomic (PCA) total hip prostheses implanted two to four years previously, the polyethylene liner separated from metal backing. These cups were of the original PCA design, manufactured and packaged as single assembled components, rather than the more recent two-piece components packaged with interchangeable liners separate from the metal backing. Each case of separation was associated with the failure of the thin outer polyethylene rim and central polyethylene peg on the back of the liner that secures it to the metal backing. Cup liners should be securely attached to the metal backing. The possibility of polyethylene failure is considerable when cementless metal-backed acetabular cups are used in active young patients.

Acetabulum↗
PubMed2004

Evidence-based low back pain classification. Improving care at its foundation.

With the cause of most low back pain unknown, patients are often given an unproven, even inventive, diagnosis or pain theory, followed by treatment targeting the clinician's theories and educational background, rather than the patient's characteristics. When recovery occurs, it is attributed to the treatment, despite the recognized positive natural history. The resulting wide variations in care add substantially to the high costs of low back care. Meanwhile, there is a growing number of studies supporting the benefits of classifying low back patients based on a unique form of clinical assessment. This is a brief description and overview of the scientific literature focusing on a form of clinical evaluation that elicits patients' immediate pain patterns in response to a standardized sequence of lumbar mechanical tests consisting of repeated end-range movements and positions. Multiple studies report good/excellent inter-examiner reliability in performing this type of clinical assessment. Most low back patients can be classified into pain response categories with strong evidence that various categories predict both good and poor outcomes. One recent randomized controlled trial of a large low back subgroup identified with this form of assessment reported highly favorable outcomes when treatment was determined by assessment findings rather than prescribing current ''evidence-based'' care for all. By identifying reliable assessment methods that determine validated low back pain subgroups, multiple studies indicate that outcomes can be accurately predicted for most patients, with new evidence that these same assessment findings likely distinguish efficacious from ineffective, even counter-productive, treatments.

Journal Article↗
PubMed1992

Back transporting infants from neonatal intensive care units to community hospitals for recovery care: effect on total hospital charges.

Many neonates are referred to neonatal intensive care units (NICUs) for specialized care far from their parents' residence. This distance can add to the stress of the parents and reduce the contact of the parents with their newborn. Small studies have found that back transporting these neonates to hospitals closer to their homes is safe and cost-effective. Despite these findings, the reluctance of many insurers to pay for back transports prevents or delays many back transports. Insurers may not consider the findings of the previous studies to be conclusive, given that the comparisons were between small numbers of neonates back transported and neonates who remained in tertiary care, and the potential for differences in severity of illness between the groups is significant. In this study the effect on hospital charges of back transports was examined by comparing the charges for care in community hospitals with what these charges would have been in a tertiary care center. The advantage of this method is that it avoids case-mix differences between the groups and thus minimizes the potential for small-sample bias. Data were collected for all back transports from a NICU to non-tertiary care centers (n = 90) for a 9-month period. We were able to obtain the itemized bills for the care at community hospitals for 42 of these patients. Each bill was recalculated using the charges for the NICU to determine potential for savings. The average charges for recovery care were about $6200 lower at the community hospital than they would have been at the NICU.(ABSTRACT TRUNCATED AT 250 WORDS)

Convalescence↗
PubMed2006

Effect of same-sided and cross-body load carriage on 3D back shape in young adults.

UNLABELLED: Regular carriage of heavy loads such as backpacks, satchels and mailbags results in a variety of acute medical problems and increased potential for back injury. There is a paucity of information about the specific changes in back posture that occur in response to asymmetrical loading. The purpose of this study was to examine the changes in back shape that occurred in response to asymmetrical load carriage, either on one shoulder (same-side) or across the body (cross-body), in healthy young adults. METHODS: A convenience sample of 21 physiotherapy students randomly performed three trials (unloaded, same-side loaded, cross-body loaded) in standing with a 15% body load. The Microscribe 3DX digitiser (Immersion Group Ltd) recorded the three dimensional coordinates of 15 Key anatomical landmarks on the back in the three conditions. RESULTS: A one-way ANOVA with repeated measures and post-hoc tests was implemented to highlight statistical differences in the data collected (p<0.05). Significant differences were found in the x, y and z coordinates of the anatomical landmarks in the upper back between unloaded and loaded conditions. Results demonstrated significantly less impact on spinal posture from cross-body loading as compared to same-sided loading. CONCLUSION: This study confirms that there are significant three-dimensional changes in back shape in response to asymmetrical loading. Further work is needed to evaluate the optimal carriage type and maximal body load that results in the least spinal impact and injury potential in young adults.

Adult↗
PubMed2006

[Applying back massage protocol to promote an intensive care unit patient's quality of sleep].

This case report concerns the nursing experience of applying back massage to a patient in an intensive care unit (ICU) from 10 May, 2005, in order to improve the patient's quality of sleep. In order to collect information about his quality of sleep of the patient, the author used observation, interview and a Richards-Campbell sleep questionnaire (RCSQ). It was observed that, before massage, the patient's sleep quality was poor, which wa why the protocol with back massage was proposed. The results after back massage was applied that heart beat, respiration. oxygen saturation and blood pressure were not significantly improved. This was probably related to the patient's worry about having his endotracheal tube removed. The patient's perception of sleep, indeed, was obviously improved, a result which may have been related to his/her perception of comfort and care from the nurse. Applying back massage to an ICU patient may therefore be regarded as helpful improving the patient's sleep quality. It is hoped that this case report may serve as a positive reference for health care providers so that it may help patients to recover fully through rest and sleep. Since this report concerned only one patient, however, to understand the real outcome of how back massage could improve the quality of sleep of ICU patients, research is planned on the use of back massage protocol on a large number os such patients.

Aged↗