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B J Martin

Publications and source records attributed to B J Martin.

At least 19 recordsLinked to original sources
PubMed2006

A memory-based model for planning target reach postures in the presence of obstructions.

Existing posture prediction and motion simulation models generally lack the capability of simulating human obstruction avoidance during target reach. This compromises the utility of digital human models for ergonomics, as many design problems involve interactions between humans and obstructions. To address this problem, this paper presents a novel memory-based posture planning (MBPP) model, which plans reach postures that avoid obstructions. In this model, the task space is partitioned into small regions called cells. For a given human figure, each cell is linked to a memory that stores various alternative postures for reaching the cell. When a posture planning problem is given in terms of a target and an obstruction configuration, the model examines postures belonging to the relevant cell, selects collision-free ones and modifies them to exactly meet the hand target acquisition constraint. Simulation results showed that the MBPP model is capable of rapidly and robustly planning reach postures for various scenarios.

Biomechanical Phenomena↗
PubMed2006

Prostate specific antigen isoforms and human glandular kallikrein 2--which offers the best screening performance in a predominantly black population?

PURPOSE: Free prostate specific antigen, complexed PSA and human glandular kallikrein 2 have independently been tested against the gold standard of total PSA for prostate cancer screening in largely white populations. With the incidence of prostate cancer much higher in black men, we sought to evaluate these markers simultaneously in a predominantly black population. MATERIALS AND METHODS: A total of 138 men, of whom 108 were black, underwent ultrasound guided biopsy of the prostate for tPSA levels greater than 2.5 ng/ml or an abnormal digital rectal examination. Sera were drawn before biopsy and analyzed for tPSA, fPSA, cPSA and hK2 concentrations using standard methods (hK2 assay is for research use only, not for use in diagnostic procedures). The areas under the receiver operator characteristic curves were determined for each marker as well as biomarker combinations. Additionally, each parameter's specificity, positive and negative predictive values, and theoretical screening efficiency were assessed at or above the 95% sensitivity level. RESULTS: A total of 43 (31.1%) men had prostate cancer by biopsy. While the AUC for %fPSA was statistically the highest (0.822, p <0.001), cPSA offered the highest specificity (31.6%) and positive predictive power (31.7%) of any of the tested biomarkers at comparable sensitivity (greater than 95%). The calculated efficiency of cPSA (51.4%) was also higher than the other markers. Nearly 20% of biopsies would be avoided using cPSA vs standard tPSA screening methods. CONCLUSIONS: Comparing the major PSA isoforms and hK2, cPSA alone appears to offer superior diagnostic discrimination for cancer detection in a predominantly black population.

Black or African American↗
PubMed2005

Effects of low back disability status on lower back discomfort during sustained and cyclical trunk flexion.

A laboratory study was conducted to determine the effects of back disability status on endurance time and perceived discomfort during trunk flexion. Eighty participants (40 with chronic or recurrent low back pain (CRLBP), 40 pain-free) were tested. The trunk was flexed to 15 degrees, 30 degrees, 45 degrees and 60 degrees under three conditions: 1) continuous static flexion; 2) cyclical flexion with 20% rest; and 3) cyclical flexion with 40% rest. Each condition was performed for up to 600 s or until the participant reached his/her pain tolerance limit. Dependent variables included time to distracting discomfort (TDD), total endurance time (TET) and perceived discomfort. For continuous exertions, CRLBP participants had lower TDD (p < 0.001), lower TET (p < 0.001) and greater discomfort (p < 0.001) compared to pain-free controls. In both groups, TDD and TET decreased and perceived discomfort increased as the flexion angle increased. For intermittent exertions, CRLBP participants reported greater discomfort than pain-free participants (p < 0.001). Increasing rest from 20 to 40% reduced discomfort in CRLBP participants, but produced no consistent benefit in pain-free participants. To accommodate persons with CRLBP, consideration should be given to reducing both the magnitude (angle) and duration of trunk flexion required by their jobs.

Adult↗
PubMed2004

Early detection of prostate cancer in African-American men through use of multiple biomarkers: human kallikrein 2 (hK2), prostate-specific antigen (PSA), and free PSA (fPSA).

Recent studies have reported enhanced prostate cancer detection in Caucasians with serum human glandular kallikrein 2 (hK2) in combination with total- (tPSA) and free-prostate-specific antigen (fPSA). The purpose of this study is to validate these findings in an African-American patient cohort. A total of 137 African-American men were found by routine screening to have tPSA levels above 2.5 ng/ml or an abnormal digital rectal examination. Sera were drawn prior to biopsy of the prostate and Hybritech PSA, FPSA and hK2 (for research use only, not for use in diagnostic procedures) concentrations were determined on Beckman Coulter's Access immunoanalyzer. These independent variables and the ratios of percent fPSA (%fPSA), hK2/tPSA, hK2/fPSA, and hK2*tPSA/fPSA were compared between cancer and non-cancer groups. In all, 49 of 137 men had prostate cancer. hK2 and its calculated ratios outperformed tPSA on receiver operator characteristic (ROC) analysis, but %fPSA had statistically the highest area under the curve (AUC) at 0.801. When restricting the analysis to only the tPSA range of 4.0-10 ng/ml, hK2/fPSA yielded the highest AUC (0.721). The ratio of hK2/fPSA was also found to increase the positive predictive value (PPV) of the %fPSA ranges less than 10 and 10-25%. %fPSA offered the best performance and highest specificity in prostate cancer detection in African-American males over the entire range of tPSA. hK2/fPSA may offer modest improvement in the tPSA range of 4.0-10 ng/ml. Furthermore, hK2/fPSA can enhance the PPV of low %fPSA values. Therefore, the use of multiple biomarkers may ultimately increase the specificity of prostate cancer screening in African-American men.

Black or African American↗
PubMed2003

cPSA and fPSA elimination in African-American men.

In all, 22 African-American males undergoing radical prostatectomy for prostate adenocarcinoma had serum drawn for tPSA, cPSA, and total protein concentrations prior to, during, and after operation to determine the respective elimination rates. African-American cPSA was found to fit best a simple first-order exponential elimination kinetic, with a half-life of 44.6 h. fPSA followed a two-compartment elimination with an alpha-phase elimination of 0.50 h and a beta-phase half-life of 4.2 h. Our results suggest higher rates of elimination for both cPSA and fPSA in an African-American male population with respect to Caucasians and may account for differences in PSA values between races.

Adenocarcinoma↗
PubMed2002

Capillary density and retinal diameter measurements and their impact on altered retinal circulation in glaucoma: a digital fluorescein angiographic study.

AIM: Normal pressure glaucoma (NPG) patients exhibit prolonged retinal arteriovenous passage times in fluorescein angiography and colour Doppler imaging suggests increased resistance downstream from the central retinal and posterior ciliary arteries. The aim of the study was to elucidate the morphological source of decreased perfusion and increased resistance of the ocular circulation in NPG. METHODS: Retinal arteriovenous passage time (AVP) and peripapillary arterial and venous diameters were measured in digital scanning laser fluorescein angiograms. For estimation of retinal capillary density the area of the foveal avascular zone (FAZ) and the perifoveal intercapillary area (PIA) was quantified. 36 patients with NPG (mean age 57 (SD 13) years) and 21 healthy subjects (mean age 51 (13) years) were enrolled in the comparative study. RESULTS: In NPG patients the AVP (2.55 (1.1) seconds) was significantly prolonged (p<0.001) when compared with healthy subject data (AVP: 1.70 (0.39) seconds). No differences for arterial or venous diameter, FAZ, and PIA were observed in NPG patients compared with healthy subjects. FAZ, PIA, arterial and venous diameter were not correlated with visual field indices (except venous diameter with PSD, r=0.35 (p<0.05)) or cup to disc ratios. AVP was significantly correlated (p<0.05) with the size of the optic nerve head (r=-0.28), visual field indices (MD: r=-0.3; PSD: r=0.3; CPSD: r=0.3), and contrast sensitivity (r=-0.34). CONCLUSION: AVP times are significantly prolonged in NPG. The slowing of the retinal transit does not result from capillary dropout, or changes of peripapillary arterial or venous diameters with increased vascular resistance.

Blood Flow Velocity↗
PubMed2002

Outcome, functional recovery and unmet needs following acute stroke. Experience of patient follow up at 6 to 9 months in a newly established stroke service.

OBJECTIVE: To assess outcome at six months post stroke and the unmet needs and adherence to the secondary prevention advice among survivors living at home. SETTING: Stroke Rehabilitation Unit (SRU), Hairmyres Hospital and patients homes. SUBJECTS: Survivors living at home who had been managed in the SRU. RESULTS: Of 572 consecutive patients with confirmed acute stroke, 301 were managed in the SRU and 179 of these were reviewed at home between 6 and 9 months post acute stroke incident. One hundred and thirty seven (76%) survivors at home were living with a carer. Sixty-eight (38%) had had no personal contact with their General Practitioner since discharge from hospital, although 83 (46%) had attended or were attending day hospital. Thirty-two individuals (18%) had resumed smoking. One hundred and forty nine survivors (83%) still required assistance with daily living tasks. One hundred and fifteen patients (64%) required medication advice. One hundred and forty one (79%) had health concerns. Eight subjects had returned to paid employment. Issues raised by survivors included a feeling of being abandoned by the healthcare system, poor access to professional psychological support and a fear of further stroke. CONCLUSION: There is a need for continuing patient education, improved support for stroke survivors and more active involvement of Primary Care Services in the care of stroke patients following hospital discharge.

Activities of Daily Living↗
PubMed2001

Ocular perfusion and age-related macular degeneration.

PURPOSE: To review the role of ocular perfusion in the pathophysiology of age-related macular degeneration (AMD), the leading cause of irreversible blindness in the industrialized world. METHODS: Medline search of the literature published in English or with English abstracts from 1966 to 2000 was performed using various combinations of relevant key words. RESULTS: Vascular defects have been identified in both nonexudative and exudative AMD patients using fluorescein angiographic methods, laser Doppler flowmetry, indocyanine green angiography, and color Doppler imaging. CONCLUSION: Although these studies lend some support to the vascular pathogenesis of AMD, it is not possible to determine if the choroidal perfusion abnormalities play a causative role in nonexudative AMD, if they are simply an association with another primary alteration, such as a primary RPE defect or a genetic defect at the photoreceptor level, or if they are more strongly associated with one particular form of this heterogeneous disease. Further study is warranted.

Blood Flow Velocity↗
PubMed2001

A comparison of mobility assessments in a geriatric day hospital.

OBJECTIVE: To assess the sensitivity of the Elderly Mobility Scale (EMS) to detect improvements in mobility after physiotherapy in comparison with the Barthel Index (BI) and Functional Ambulation Category (FAC) in routine clinical day hospital practice. SUBJECTS: Eighty-three patients who completed a course of physiotherapy were studied. METHODS: Each was assessed by an independent physiotherapist before and after a programme of physiotherapy, using the EMS, BI and FAC. RESULTS: The mean age was 79 years (SD 7.7). Fifty-three out of 83 (64%) patients were female and 92% were community dwelling. The median number of physiotherapy sessions undergone by each patient was 9 (range 3-51). All three scales detected an improvement in mobility with physiotherapy (p < 0.001). However, using the EMS, 68 out of 82 (83%) patients had a detectable improvement in mobility compared with only 34 out of 80 (42%) using the BI and 28 out of 81 (35%) using the FAC. Using a matched-pairs comparison, the EMS was significantly more likely to detect an improvement in mobility following physiotherapy within the study group than the BI (p < 0.001) or the FAC (p < 0.001). CONCLUSION: Although all three scales detected improvements in mobility, the EMS detected mobility improvements in a significantly greater number of patients.

Aged↗
PubMed2001

Randomized controlled trial of quadriceps training after proximal femoral fracture.

OBJECTIVE: To determine whether systematic progressive high-intensity quadriceps training increases leg extensor power and reduces disability in patients rehabilitating after proximal femoral fracture. DESIGN: Open parallel group randomized controlled trial comparing the addition of six weeks quadriceps training (40 patients) with standard physiotherapy alone (40 patients). The training group exercised twice weekly, with six sets of 12 repetitions of knee extension (both legs), progressing up to 80% of their one-repetition maximum. SETTING: Orthogeriatric unit, and community follow-up. SUBJECTS: Eighty patients rehabilitating after proximal femoral fracture. MAIN OUTCOME MEASURES: Measurements of leg extensor power (Nottingham Power Rig), functional mobility (elderly mobility score), disability (Barthel Index) and quality of life (Nottingham Health Profile) were made at baseline, after six weeks (at the end of the intervention) and at 16 weeks. RESULTS: Leg extensor power increased significantly in the quadriceps training group (fractured leg mean improvement at six weeks 157% (standard error 16), nonfractured leg 80% (12)) compared with the control group (63% (11) and 26% (8) respectively, unpaired Student's t-test p = 0.007 and p = 0.01 for between-group comparisons). Significant benefits were maintained at 16 weeks. Quadriceps training resulted in a greater increase in elderly mobility scale score compared with standard rehabilitation (between-group difference of 2.5 (95% CI 1.1,3.8) at week 6 and 1.9 (0.4,3.4) at week 16). Barthel score increased significantly from week 0 to 6 in the quadriceps training group compared with controls (Mann-Whitney U-test p = 0.05). Patients in the quadriceps training group scored significantly better in the energy subscore of the Nottingham Health Profile at the end of follow-up (Mann-Whitney U-test p = 0.0185). CONCLUSIONS: Progressive high-intensity quadriceps training in elderly proximal femoral fracture patients increased leg extensor power and reduced disability. This was accompanied by an increase in energy as measured by the Nottingham Health Profile. This intervention may provide a simple practical way of improving outcome in these patients.

Aged↗
PubMed2000

Estrogen-replacement therapy: effects on retrobulbar hemodynamics.

PURPOSE: Estrogen-replacement therapy causes vasodilation and increased blood flow in major peripheral arteries. We examined the role that estrogen may play in enhancing perfusion within the watersheds of several major and minor retrobulbar arteries. METHODS: Postmenopausal women receiving estrogen-replacement therapy (n = 16) were compared with both age-matched women not receiving estrogen (n = 16) and with young women (n = 20). Studies involved color Doppler imaging analysis of flow velocities measured in the ophthalmic, central retinal, and nasal and temporal posterior ciliary arteries. RESULTS: In the ophthalmic artery, young women and postmenopausal women receiving estrogen exhibited reduced resistance indexes as compared with postmenopausal women not receiving estrogen (each P <. 001). In contrast, flow velocities in the central retinal artery were similar among the three groups of women. In the posterior ciliary arteries, a different pattern emerged: young women, as compared with either group of postmenopausal women, showed greater peak systolic and end-diastolic velocities at similar resistance index (each P <.05). CONCLUSIONS: Estrogen-replacement therapy in postmenopausal women apparently helps reduce vascular resistance distal to the ophthalmic artery to levels matching those of young women. However, estrogen replacement has little impact on flow velocities in the posterior ciliary arteries. In those vessels, aging per se may reduce perfusion, potentially contributing to the age-dependent risk of major eye diseases, such as glaucoma and age-related macular degeneration.

Adult↗
PubMed1999

Color Doppler imaging discloses reduced ocular blood flow velocities in nonexudative age-related macular degeneration.

PURPOSE: To study ocular perfusion defects in age-related macular degeneration. METHODS: Twenty-five subjects with nonexudative age-related macular degeneration were compared with 25 age-matched control subjects in studies of flow velocities in several retrobulbar vessels. Color Doppler imaging, which was performed by an examiner who was masked to the subjects' assignment to the control or age-related macular degeneration group, measured peak systolic and end diastolic velocity in the ophthalmic, central retinal, and nasal and temporal posterior ciliary arteries of one eye. A resistive index was calculated from the peak systolic and end diastolic velocity. RESULTS: Subjects with nonexudative age-related macular degeneration showed a consistent trend toward lower peak systolic and end-diastolic velocities in the posterior ciliary arteries. For example, in the nasal posterior ciliary artery, the mean end diastolic velocity measured 1.45 +/- 0.34 cm per sec in the age-related macular degeneration group compared with 1.96 +/- 0.66 cm per sec in the control group, yielding a 26% decrease in the age-related macular degeneration group, which represented the largest difference and was highly statistically significant (P = .0012). The resistive index was not significantly altered in the nasal or temporal posterior ciliary artery. Subjects with nonexudative age-related macular degeneration did not differ from control subjects in peak systolic velocity, end diastolic velocity, or resistive index in the ophthalmic artery. In the central retinal artery, the end diastolic velocity was lower (1.37 +/- 1.95 cm per sec vs 1.95 +/- 0.66 cm per sec), whereas the resistive index was higher (0.83 +/- 0.05 vs 0.76 +/- 0.06 cm per sec), in the age-related macular degeneration group; these results were highly statistically significant (P = .0007 and P < .0001, respectively). CONCLUSIONS: Retrobulbar vascular changes in nonexudative age-related macular degeneration subjects include reduced flow velocities in the nasal and temporal posterior ciliary arteries. The reduced peak systolic velocity, combined with the reduced end diastolic velocity at a constant resistive index, seen in nonexudative age-related macular degeneration, is consistent with reduced bulk flow in these vessels, suggesting that choroidal perfusion is abnormal in this form of age-related macular degeneration. The changes in the central retinal artery suggest there may be a more generalized perfusion abnormality beyond the choroid in patients with age-related macular degeneration or that the central retinal artery exhibits a secondary autoregulatory response to a primary change elsewhere.

Aged↗
PubMed1999

Scanning laser ophthalmoscopy-based evaluation of epipapillary velocities: method and physiologic variability.

PURPOSE: Scanning laser ophthalmoscopy is capable of producing high-resolution fluorescein angiograms. Measurements of capillary blood velocities in the fovea are well established. In this study, we used an identical technique to measure particle velocities in the superficial layers of the optic nerve head. We compared these data with simultaneous velocity measurements in the retinal and macular vasculature. METHODS: Fluorescein angiograms were performed in 30 subjects (12 men, 18 women; mean age, 26 years; standard deviation [SD], 3 years). Off-line, the velocities of hypofluorescent particles through the microvasculature of epipapillary and macular vessels were measured by image-processing techniques. We also assessed the arteriovenous passage (AVP) time of the fluorescein dye front. RESULTS: Epipapillary blood velocities ranged from 2.7 to 6.5 mm/sec (mean, 4.0 mm/sec; SD, 0.99 mm/sec) and differed significantly from macular capillary blood velocities (MCBVs), which ranged from 1.67 to 3.31 mm/sec (mean, 2.53 mm/sec; SD, 0.34 mm/sec). The AVP time in all subjects was 1.74 +/- 0.5 sec (mean +/- SD) and correlated with the MCBV (P < 0.05, r = -0.46). Epipapillary blood velocities showed no correlation with either AVP time or MCBV. CONCLUSIONS: The scanning laser methodology, adapted to objectively assess velocities in the epipapillary vasculature, shows that these measurements are neither correlated with velocities in the perifoveal network, nor inversely correlated with overall retinal transit time. Epipapillary blood velocities were found to be substantially higher than those measured in macular capillaries. This result might be explained by the different anatomy of epipapillary vessels compared with macular capillaries.

Adult↗
PubMed1999

Post-effects of long-term hand vibration on visuo-manual performance in a tracking task.

Movement precision and performance time were evaluated through a visuo-manual tracking task performed before and after 10-min hand vibration exposure. Constant displacement amplitude vibration of 0.2 and 0.3 mm peak to peak at 90, 150, 300 Hz were applied to the hand z-axis by a vertical handle. During exposure a grip force of 5% MVC was exerted for 5 s and then relaxed for 25 s while maintaining fingers-handle contact. The tracking task consisted in moving a ring (phi = 9 mm) attached to a thin rod held between the index finger and thumb along a zig-zagged wire (phi = 3.7 mm). Alterations of tracking errors (ring-wire contact) and tracking time were analysed as a function of the vibration parameters. The tasks were performed by ten healthy participants. Vibration induced a significant increase in tracking errors (ring-wire contact) and a significant decrease in tracking time. These impairments decayed with time after vibration exposure. The recovery period was > 5 min but < 10 min with the exception of 90 Hz vibration, for which recovery could be > 10 min. The number of tracking errors was neither influenced by vibration frequency nor by amplitude. The tracking time decreased as frequency increased and recovery was related to the displacement amplitude. The subjective rating of the performance on a visual analogue scale indicated that the subjects tended to perceive the task as being easier after vibration exposure. Vibration applied to the non-dominant hand while the participant performed the tracking task had no effect. These results show that vibration similar to hand-tool vibration affects precision and velocity control of visually guided hand movements. Furthermore, these performance decrements were not consciously perceived.

Adult↗
PubMed1999

Regional differences in retinal vascular reactivity.

PURPOSE: Although glaucomatous visual field defects are more common in the superior field than in the inferior field, microaneurysms are more frequent in the superior than in the inferior retina in diabetic retinopathy. The authors hypothesized that differences in vascular hemodynamics in the two areas might contribute to these phenomena. METHODS: The blood flow response to hyperoxia and hypercapnia was evaluated in peripapillary retinal tissue superior and inferior to the optic nerve head using confocal scanning laser Doppler flowmetry. In 14 young, healthy persons, blood flow was measured while breathing room air and during isocapnic hyperoxia (100% O2 breathing) and isoxic hypercapnia (PCO2 increased 15% above baseline). Histograms were generated from pixel-by-pixel analysis of retinal portions of superior and inferior temporal quadrants of the entire image. RESULTS: Baseline blood flow in the inferior temporal quadrant was significantly greater than in the superior temporal quadrant (P < 0.05). However, the inferior region failed to increase in perfusion during hypercapnia and experienced significant mean blood flow reduction; flow reduction in the pixels at the 25th, 50th, 75th, and 90th percentile of flow; and an increased percentage of pixels without measurable flow, during hyperoxia (each P < 0.05). In contrast, in the superior temporal region, hyperoxia failed to reduce blood volume, velocity, or flow, whereas hypercapnia significantly increased mean flow; increased flow in the pixels at the 25th, 50th, 75th, and 90th percentile of flow; and reduced the percentage of pixels without measurable flow (each P < 0.05). CONCLUSIONS: The inferior temporal quadrant of the peripapillary retina is, in comparison with the superior temporas region, less responsive to vasodilation and more responsive to vasoconstriction. These differences could contribute to different susceptibility to visual field defect or vascular dysfunction in the superior and inferior retina.

Adolescent↗