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PubMed1997

Restoration of function in the paralyzed rabbit orbicularis oculi muscle by direct functional electrical stimulation.

Restoration of the ability to blink and protect the eye in the patient with facial paralysis remains a challenge. Although many treatments exist, no one approach corrects all the deficits associated with the loss of orbicularis oculi function. In this study, the author investigated the feasibility of restoring function by direct electrical stimulation of the paralyzed orbicularis oculi muscle in the rabbit model. Using a pacing device developed by the author, functional restoration of a normal-appearing blink was produced throughout 30 days of continuous pacing in six rabbits with transected facial nerves. Histologic evaluations of the paced tissues demonstrated no evidence of detrimental effects attributable to the electrical stimulation. The findings of this study support the feasibility of employing direct electrical stimulation to restore the function of paralyzed orbicularis oculi muscles. Potential applications may also exist in other areas in which peripheral denervation creates functional impairment.

Animals↗

PubMed2001

Exercise training, vascular function, and functional capacity in middle-aged subjects.

PURPOSE: The aim of this study was to investigate the effect of 8 wk of exercise training on functional capacity, muscular strength, body composition, and vascular function in sedentary but healthy subjects by using a randomized, crossover protocol. METHODS: After familiarization sessions, 19 subjects aged 47 +/- 2 yr (mean +/- SE) undertook a randomized, crossover design study of the effect of 8 wk of supervised circuit training consisting of combined aerobic and resistance exercise. Peak oxygen uptake (.VO(2peak)), sum of 7 maximal voluntary contractions and the sum of 8 skinfolds and 5 segment girths were determined at entry, crossover, and 16 wk. Endothelium-dependent and -independent vascular function were determined by forearm strain-gauge plethysmography and intrabrachial infusions of acetylcholine (ACh) and sodium nitroprusside (SNP) in 16 subjects. RESULTS: Training did not alter ACh or SNP responses. .VO(2peak), (28.6 +/- 1.1 to 32.6 +/- 1.3 mL.kg(-1).min(-1), P < 0.001), exercise test duration (17.4 +/- 1.1 to 22.1 +/- 1.2 min, P < 0.001), and muscular strength (465 +/- 27 to 535 +/- 27 kg, P < 0.001) significantly increased after the exercise program, whereas skinfolds decreased (144 +/- 10 vs 134 +/- 9 mm, P < 0.001). CONCLUSION: These results suggest that moderate intensity circuit training designed to minimize the involvement of the arms improves functional capacity, body composition, and strength in healthy, middle-aged subjects without significantly influencing upper limb vascular function. This finding contrasts with previous studies in subjects with type 2 diabetes and heart failure that employed an identical training program.

Anthropometry↗

PubMed1999

Integration of functional magnetic resonance imaging supported by magnetoencephalography in functional neuronavigation

OBJECTIVE: In this study, the intraoperative visualization of functional data provided by functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) leading to functional neuronavigation is demonstrated in surgery around the motor strip. METHODS: In seven patients with lesions adjacent to the central region, fMRI was performed with a 1.5-Tesla magnetic resonance system, using axial echo-planar imaging with a motor and a sensory task. Somatosensory and motor evoked fields were recorded with a biomagnetometer. fMRI and MEG were matched to an anatomic three-dimensional magnetic resonance image set by a contour fit. Then this three-dimensional image data set was transferred to the navigation microscope and displayed in the eyepieces of the microscope during surgery. Additionally, intraoperative recording of somatosensory evoked potentials was performed for verification of the central sulcus. RESULTS: In all cases, the projection of fMRI and MEG data into the operating viewing field allowed easy identification of the central region, which was confirmed by phase reversal of somatosensory evoked potentials in each case. fMRI and MEG measurements yielded corresponding results in each patient. CONCLUSION: Functional neuronavigation with integration of fMRI and MEG allows the fast identification of eloquent brain areas. The widespread availability of fMRI will result in a broad availability of functional neuronavigation, which will, in turn, contribute to the successful surgery of lesions in eloquent brain areas with lower morbidity.

Journal Article↗

PubMed2000

An integrated functional magnetic resonance imaging procedure for preoperative mapping of cortical areas associated with tactile, motor, language, and visual functions.

OBJECTIVE: To evaluate an integrated battery of preoperative functional magnetic resonance imaging (fMRI) tasks developed to identify cortical areas associated with tactile, motor, language, and visual functions. METHODS: Sensitivity of each task was determined by the probability that a targeted region was activated for both healthy volunteers (n = 63) and surgical patients with lesions in these critical areas (n = 125). Accuracy of each task was determined by the correspondence between the fMRI maps and intraoperative electrophysiological measurements, including somatosensory evoked potentials (n = 16), direct cortical stimulation (n = 9), and language mapping (n = 5), and by preoperative Wada tests (n = 13) and visual field examinations (n = 6). RESULTS: For healthy volunteers, the overall sensitivity was 100% for identification of the central sulcus, visual cortex, and putative Wernicke's area, and 93% for the putative Broca's area (dominant hemisphere). For patients with tumors affecting these regions of interest, task sensitivity was 97% for identification of the central sulcus, 100% for the visual cortex, 91% for the putative Wernicke's area, and 77% for the putative Broca's area. These sensitivities were enhanced by the use of multiple tasks to target related functions. Concordance of the fMRI maps and intraoperative electrophysiological measurements was observed whenever both techniques yielded maps and Wada and visual field examinations were consistent with fMRI results. CONCLUSION: This integrated fMRI task battery offers standardized and noninvasive preoperative maps of multiple critical functions to facilitate assessment of surgical risk, planning of surgical routes, and direction of conventional, intraoperative electrophysiological procedures. Thus, a greater range of structural and functional relationships is brought to bear in the service of optimal outcomes for neurosurgery.

Adolescent↗

PubMed1983

Functional capacity and rehabilitation of recipients with a functioning renal allograft for ten years or more.

Forty-nine renal transplant recipients who had a single functioning allograft for ten or more years are reviewed. There were 17 cadaver recipients and 32 living-related recipients. Most patients have enjoyed excellent long-term renal function with stable mean daily dosages of azathioprine and prednisone. Fifty-three percent of patients never experienced a rejection episode, and 24% of patients experienced only one rejection episode. Five recipients (10%) developed malignancy following transplantation. Based on the Karnofsky activity scale, 80% of patients enjoyed unrestricted activity at ten years posttransplant. The two major factors contributing to declining activity were progression of systemic diseases such as atherosclerosis or diabetes, and declining allograft function. Following transplantation, all patients developed renewed interest in sexual activity, all men were potent, and all women experienced regular menses. Nine men achieved fatherhood and five women underwent successful pregnancy. Currently, 46 recipients are alive with a functioning allograft. These data confirm the ability of recipients with a long-term functioning renal allograft to return to the work force, participate in preillness levels of activity, and enjoy sexual activity and parenthood.

Activities of Daily Living↗

PubMed2002

Hypertension is an independent predictor of delayed graft function and worse renal function only in kidneys with chronic pathological lesions.

BACKGROUND: Delayed graft function (DGF) has been identified as one of the principal correlates of poor graft survival in cadaveric renal transplantation. However, its risk factors and clinical predictors have been poorly elucidated. METHODS: We analyzed the risk factors of DGF with a specific emphasis on the role of histological damage of donor kidney. Then, we also studied the impact of DGF, and donor factors affecting DGF, on kidney graft function over the first year after engraftment in 100 consecutive cadaveric renal transplant (Tx) recipients. RESULTS: The organs displaying DGF (n=48) had a significantly higher degree of glomerular sclerosis and tubular atrophy (P<0.01), as well as of interstitial fibrosis and vascular damage (P<0.02) in time-zero biopsies. In patients who received an "ideal" organ for Tx (total histological score < or = 4), DGF showed a strong relationship with Deltaage D-R (70% increase of risk for donors 10 years older than recipients), and with the histological score (odds ratio 1.34). In contrast, donor hypertension was the most relevant variable independently associated with DGF (odds ratio 19.4) in patients receiving a suboptimal organ (histological score >4). Moreover, DGF and donor hypertension adversely affected graft function at 1 year, but only in Tx patients with a histological score >4 in time-zero biopsy. Of note, both patients with and those without DGF showed a very low incidence of biopsy-proven acute rejection (8.5 and 6.8%, respectively) and a rather short cold ischemia time (<16 hr). CONCLUSION: Our findings suggest that the quality of the transplanted organ and the occurrence of DGF are strictly related to each other and can influence graft function through apparently nonimmune mechanisms. In addition, long-standing donor hypertension is a strong independent variable affecting both DGF and graft function of suboptimal cadaveric kidneys, at least up to 1 year.

Adult↗

PubMed2006

Validation of International Classification of Functioning, Disability, and Health (ICF) Core Sets for early postacute rehabilitation facilities: comparisons with three other functional measures.

OBJECTIVE: Short lists of International Classification of Functioning, Disability, and Health (ICF) categories, ICF Core Sets, have been developed as reference standards for clinical practice and research. The objective of this study was to validate the ICF Core Sets for early postacute rehabilitation facilities against the measures most commonly used in early postacute rehabilitation, the FIM instrument, the Functional Assessment Measure, and the Barthel index. DESIGN: Linking study matching the concepts of three commonly used outcome measures to corresponding ICF categories. RESULTS: Corresponding ICF categories could be found for all of the items of the FIM instrument + Functional Assessment Measure and Barthel index. The 40 items of these three measures were linked to 33 different ICF categories. Four items could be linked to ICF categories that were not part of any of the Postacute ICF Core Sets. CONCLUSIONS: The Postacute ICF Core Sets cover the concepts of the most frequently used measures in early postacute rehabilitation. Yet, many aspects of human functioning are not measured by the FIM instrument + Functional Assessment Measure and the Barthel index. If this information is considered relevant, these items would have to be added by using supplementary measures. Our comparison demonstrates the benefit of using a common language when comparing items using different wordings and concepts.

Activities of Daily Living↗

PubMed2001

Partition functions in statistical mechanics, symmetric functions, and group representations.

Partition functions for noninteracting particles are known to be symmetric functions. It is shown that powerful group-theoretical techniques can be used not only to derive these relationships, but also to significantly simplify calculation of the partition functions for particles that carry internal quantum numbers. The partition function is shown to be a sum of one or more group characters. The utility of character expansions in calculating the partition functions is explored. Several examples are given to illustrate these techniques.

Journal Article↗

PubMed1991

Glycaemic thresholds for hypoglycaemic symptoms, impairment of cognitive function, and release of counterregulatory hormones in subjects with functional hypoglycaemia.

Nine patients with food-relieved hypoglycaemic symptoms, in whom insulinoma and other organic diseases presenting with hypoglycaemia had been ruled out, and nine matched controls, participated in the study. Subjects were studied during a 5-h controlled (Biostator) insulin-induced (1-2 mU kg-1 min-1) hypoglycaemic clamp. After 1 h of euglycaemia, we aimed to lower the glucose level in arterialized venous blood in a stepwise manner at 30-min intervals to 3.5, 3.0, and 2.0 mmol l-1, and to withhold these levels for a further 30 min. At euglycaemia and at the end of the latter steps, the visual reaction time and cognitive function (digit span, letter cancellation and trail making) were tested, together with recording symptoms and signs of hypoglycaemia. Counter-regulatory hormones were measured at 20-min intervals. In the patients, clinical signs and symptoms of hypoglycaemia developed at median blood glucose levels of 2.6-2.8 and 2.8-3.1 mmol l-1, respectively. By contrast, the blood glucose levels were 0.4-0.8 mmol l-1 lower in control subjects (P less than 0.05). Similarly, the median threshold for deterioration of visual reaction time was 2.8 mmol l-1 in patients and 2.1 mmol l-1 in controls (P less than 0.01). A similar trend was observed for the results of the neuropsychological tests. Visual reaction time deteriorated in all subjects, whereas the cognitive function of some of the subjects in each group remained unchanged during hypoglycaemia. The glycaemic thresholds for release of cortisol, glucagon and growth hormone were significantly higher in patients (P less than 0.05), whereas the thresholds for catecholamine release showed no significant difference from controls. Despite the comparable glucose infusion rates required to sustain each of the hypoglycaemic levels in the two groups, the control subjects achieved lower glucose levels, suggesting that there is resistance to insulin or glucose in functional hypoglycaemia. In conclusion, the present study suggests that the existence of a higher threshold for symptoms and signs, as well as for deterioration of brain function, may explain every-day hypoglycaemic symptoms, despite normal glucose levels, in subjects with functional hypoglycaemia. However, the hypothesis should be tested further using a blinded approach, including euglycaemic control studies.

Adult↗

PubMed2005

The long-term voiding function and sexual function after pelvic nerve-sparing radical surgery for rectal cancer.

BACKGROUND: The aim of the present study is to symptomatically analyze the extent to which pelvic nerve-sparing radical surgery for rectal cancer impacts on long-term voiding and male sexual function. METHODS: A self-administered questionnaire was mailed to 68 patients who underwent pelvic nerve-sparing radical surgery for invasive rectal cancer with 52 responses (28 men and 24 women; 27 complete and 25 incomplete preservation; response rate 76.5%). Each patient was asked to record if there had been any changes in lower urinary tract symptoms after surgery. Sexual function was also investigated in men. RESULTS: Of the 52 patients, 48 (92%) maintained voluntary voiding without catheterization in the long term. Clean intermittent self-catheterization was performed in only four patients with incomplete preservation because of persistent voiding dysfunction. Subjectively, approximately 60% of the patients remained unchanged in lower urinary tract symptoms after surgery. The satisfaction rate regarding the current voiding status was significantly higher in women than in men (83% versus 61%, P = 0.0294), but was not significantly different between those with complete (76%) and incomplete preservation (64%). Despite the acceptable urinary status, 88% of men had some deterioration in the erectile function, regardless of the types of surgical procedures. Overall, 64% of men were unsatisfied with the current sexual function. CONCLUSIONS: Pelvic nerve-sparing radical surgery for rectal cancer preserved the long-term voiding function in the majority of patients. In completely preserved patients and in women, symptomatic outcomes were more satisfactory. Postoperative erectile dysfunction was found to be a serious problem, even in complete nerve-sparing procedure.

Aged↗

PubMed1993

Cytochalasin modulation of nicotinic cholinergic receptor expression and muscarinic receptor function in human TE671/RD cells: a possible functional role of the cytoskeleton.

Previous studies have shown that cells of the TE671/RD human clonal line express muscle-type nicotinic acetylcholine receptors (nAChR) and m3-type muscarinic acetylcholine receptors (mAChR) whose numbers and function are regulated by agonist treatment and second messenger modulation. Here we show that cytochalasin treatment, which causes disruption of actin networks, induces marked changes in the numbers and distribution of nAChR, but not mAChR. Moreover, whereas cytochalasin treatment fails to alter nAChR function significantly, it acutely potentiates mAChR-mediated phosphoinositide hydrolysis. Treatment of TE671/RD cells with different cytochalasin analogues (rank order efficacy at 5 micrograms/ml is H > J = B = C = D > A = E) produces a two- to fourfold increase in numbers of membrane-bound nAChR (Bmax in units of specific 125I-labeled alpha-bungarotoxin binding per milligram of membrane protein). nAChR up-regulation is evident after 1-2 days of cytochalasin B exposure, is maximal after 3-6 days of drug treatment, and is dominated by an approximately 10-fold increase (per cell) in an intracellular nAChR pool. Cytochalasin-induced nAChR up-regulation is similar in magnitude to, but not additive with, up-regulation of nAChR following chronic exposure to nicotine or phorbol ester. Northern blot analysis shows a four- to five-fold coordinate increase in levels of mRNA that encode nAChR alpha, beta, gamma, or delta subunits in cytochalasin-treated cells, suggesting that nAChR up-regulation has a possible transcriptional basis. Studies done using a 86Rb+ efflux assay indicate that cytochalasin treatment has no significant effect on nAChR function. By contrast, cytochalasin treatment has no effect on the numbers of mAChR as assessed by binding studies with the radioantagonist 3H-labeled quinuclidinyl benzilate, but it induces marked enhancement of carbachol-stimulated, but not basal, phosphoinositide hydrolysis. These studies suggest that presumed modulation by cytochalasin treatment of cytoskeletal microfilament integrity can differentially influence expression and function of mAChR (a prototype of the metabotropic receptor superfamily) and nAChR (a prototype of the ligand-gated ion-channel superfamily). The results also suggest possible new roles for the cytoskeleton in regulation of membrane receptor expression, function, and cross talk.

Carbachol↗

PubMed2005

Cross-functional team processes and patient functional improvement.

OBJECTIVE: To test the hypothesis that higher levels of participation and functioning in cross-functional psychiatric treatment teams will be related to improved patient outcomes. DATA SOURCES/STUDY SETTING: Primary data were collected during the period 1992-1999. The study was conducted in 40 teams within units treating seriously mentally ill patients in 16 Veterans Affairs hospitals across the U.S. STUDY DESIGN: A longitudinal, multilevel analysis assessed the relationship between individual- and team-level variables and patients' ability to perform activities of daily living (ADL) over time. Team data were collected in 1992, 1994, and 1995. The number of times patient data were collected was dependent on the length of time the patient was treated and varied from 1 to 14 between 1992 and 1999. Key variables included: patients' ADL scores (the dependent variable); measures of team participation and team functioning; the number of days from baseline on which a patient's ADLs were assessed; and several control variables. DATA COLLECTION METHODS: Team data were obtained via self-administered questionnaires distributed to staff on the study teams. Additional team data were obtained via questionnaires completed by unit directors contemporaneously with the staff survey. Patient data were collected by trained clinicians at regular intervals using a standard assessment instrument. PRINCIPAL FINDINGS: Results indicated that patients treated in teams with higher levels of staff participation experienced greater improvement in ADL over time. No differences in ADL change were noted for patients treated in teams with higher levels of team functioning. CONCLUSIONS: Findings support our premise that team process has important implications for patient outcomes. The results suggest that the level of participation by the team as a whole may be a more important process attribute, in terms of patient improvements in ADLs, than the team's smooth functioning. These findings indicate the potential appropriateness of managerial interventions to encourage member investment in team processes.

Activities of Daily Living↗

PubMed2004

Factors influencing serum cystatin C levels other than renal function and the impact on renal function measurement.

BACKGROUND: It is well known that serum creatinine may be used as a marker of renal function only if taking into account factors that influence creatinine production, such as age, gender, and weight. Serum cystatin C has been proposed as a potentially superior marker than serum creatinine, because serum cystatin C level is believed to be produced at a constant rate and not to be affected by such factors. However, there are limited data on factors that may influence serum cystatin C levels, and there are limited data comparing cystatin C-based estimates of renal function with creatinine-based estimates that adjust for such factors, especially in individuals with normal, or mildly reduced, renal function. METHODS: This was a cross-sectional study of 8058 inhabitants of the city of Groningen, The Netherlands, 28 to 75 years of age. Serum cystatin C and serum creatinine levels were measured, and creatinine clearance was determined from the average of two separate 24-hour urine collections. We performed multivariate analyses to identify factors independently associated with serum cystatin C levels after adjusting for creatinine clearance. Then, partial Spearman correlations were obtained after adjusting for factors that may influence serum cystatin C and creatinine levels. We also compared the goodness-of-fit (R(2)) of different multivariate linear regression models including serum cystatin C level and serum creatinine level for the outcome of creatinine clearance. RESULTS: Older age, male gender, greater weight, greater height, current cigarette smoking, and higher serum C-reactive protein (CRP) levels were independently associated with higher serum cystatin C levels after adjusting for creatinine clearance. After adjusting for age, weight, and gender, the partial Spearman correlations between creatinine and, respectively, serum cystatin C level and serum creatinine level were -0.29 (P < 0.001) and -0.42 (P < 0.001), respectively. The R(2) values for serum cystatin C level and serum creatinine level adjusted for age, weight, and gender were 0.38 and 0.42, respectively. The addition of cigarette smoking and serum CRP levels did not improve the R(2) value for the multivariate serum cystatin C-based model. CONCLUSION: Serum cystatin C appears to be influenced by factors other than renal function alone. In addition, we found no evidence that multivariate serum cystatin C-based estimates of renal function are superior to multivariate serum creatinine-based estimates.

Adult↗

PubMed1994

Nutrition and function: is there a relationship between body mass index and the functional capabilities of community-dwelling elderly?

OBJECTIVE: To determine if there is a relationship between body mass index and the ability to perform the usual activities of living in a sample of community-dwelling elderly. DESIGN: Secondary data analysis of The National Health and Nutrition Examination Survey-I Epidemiologic Follow-up Study (1982-1984). Follow-up home interview of a population-based sample originally interviewed between 1971 and 1975 in the National Health and Nutrition Examination Survey-I (NHANES-I). PARTICIPANTS: Survivors of the original NHANES-I cohort who were 65 years of age or older and who were living at home at the time of the second interview (n = 3061). Excluded were those who could not be found, refused participation, or were institutionalized (n = 220), and those without complete height and weight data (n = 194). MAIN OUTCOME MEASURE: Functional status as measured by a 26-item battery. RESULTS: Bivariate analysis revealed a greater risk for functional impairment for subjects with a low body mass index or a high body mass index. The greater the extreme of body mass index (either higher or lower), the greater the risk for functional impairment. Logistic regression analysis indicated that both high and low body mass index continued to be significantly related to functional status when 22 other potential confounders were included in the model. CONCLUSION: The body mass index is related to the functional capabilities of community-dwelling elderly. The inclusion of this simple measurement in the comprehensive assessment of community-dwelling elderly is supported.

Activities of Daily Living↗

PubMed1996

Retrograde migration of the site of functional block: a mechanism underlying resolution of functional retrograde bundle branch block during AV reentrant tachycardia.

INTRODUCTION: Functional bundle branch blocks during supraventricular tachycardia have been described, and their sustainment has been attributed to concealed conduction. Such blocks frequently resolve spontaneously, but the electrophysiologic mechanism of resolution has not been well described. This report describes the resolution of functional bundle branch block through proximal migration of the site of block. METHODS AND RESULTS: During electrophysiologic study of a patient with reentrant antidromic tachycardia via an atriofascicular accessory pathway, functional retrograde right bundle branch block could be readily induced following tachycardia initiation with right ventricular apical pacing. Resolution of this block was associated with shortening of the tachycardia cycle length. Electrogram recordings along the right bundle branch during tachycardia determined that resolution of the functional retrograde right bundle branch block was associated with migration of the site of block from the distal to the proximal right bundle. When the site of block was directly at the recording site, both anterograde and retrograde activation of the right bundle was demonstrated. CONCLUSION: Migration of the site of block is a mechanism of resolution for functional conduction blocks maintained by concealed conduction.

Adult↗

PubMed2006

Functional heartburn patients demonstrate traits of functional bowel disorder but lack a uniform increase of chemoreceptor sensitivity to acid.

BACKGROUND: Functional heartburn (FH) patients have a profound impact on the response to anti-reflux therapy of the nonerosive reflux disease (NERD) group as compared to the response of the erosive esophagitis group. Thus far, there is paucity of information about their physiological and clinical characteristics that may separate them from the other NERD patients. AIM: To compare physiological and clinical characteristics of patients with FH to their counterparts within the NERD group (NERD-positive [NERD+]). METHODS: Subjects with typical heartburn symptoms, at least twice a week, were evaluated by an upper endoscopy. Only those with normal esophageal mucosa were recruited into the study and underwent pH testing to assess esophageal acid exposure. The patients were divided into those with normal pH test (FH) and those with abnormal pH test (NERD+). The groups were compared for demographics, gastroesophageal reflux disease symptom characteristics, psychological profile, and reported quality of life. Additionally, the two patient groups were compared for stimulus response functions to acid, autonomic function response, and rate of Helicobacter pylori infection. RESULTS: Fifty-two patients included 30 with FH and the rest with NERD+. There was no statistical difference in demographics, frequency of hiatal hernia and H. pylori infection between the two groups. Patients with FH had a significantly longer history of heartburn and reported more episodes of chest pain than NERD+ patients (M--7.5 yr and M--once a week vs M--3.5 yr and M--once a month, respectively, p < 0.05). Patients with FH scored significantly higher in the somatization domain than patients with NERD+ (M--60 vs 52.5, p < 0.05), but had similar reported quality of life. Patients with NERD+ demonstrated a significantly shorter time to symptom perception and higher intensity rating (p < 0.05). Only patients with FH demonstrated a statistically significant increase in heart rate and skin conductance after acid perfusion, as compared to those with NERD+ (p < 0.05). CONCLUSION: Patients with FH demonstrate increased reports of chest pain and somatization, an alteration in autonomic function but lack a uniform increase in chemoreceptor sensitivity to acid as compared to those with NERD+. This suggests that while FH patients harbor clinical traits of a functional bowel disorder, hypersensitivity to acid is not a general phenomenon.

Autonomic Nervous System↗

PubMedDate not supplied

Characterization of the point spread function and modulation transfer function of scattered radiation using a digital imaging system.

A digital radiographic system was used to measure the distribution of scattered x radiation from uniform slabs of Lucite at various thicknesses. Using collimation and air gap techniques, [primary + scatter] images and primary images were digitally acquired, and subtracted to obtain scatter images. The scatter distributions measured using small circular apertures were computer fit to an analytical function, representing the circular aperture function convolved with a modified Gaussian point spread function (PSF). On the basis of goodness of fit criterion, the proposed Gaussian function is a very good model for the scatter PSF. The measured scatter PSF's are reported for various Lucite thicknesses. Using the PSF's, the modulation transfer functions are calculated, and this spatial frequency information may have value in analytical scatter removal techniques, grid design, and air gap optimization.

Computers↗

PubMed1975

Bacteriophage P22 virion protein which performs an essential early function. II. Characterization of the gene 16 function.

P16 is a virion protein and, as such, is incorporated into the phage head as a step in morphogenesis. The role of P16 in assembly is not essential since particles are formed without this protein which appear normal by electron microscopy. P16 is essential when the particle infects a cell in the following cycle of infection. In the absence of functional P16, the infection does not appear to proceed beyond release of phage DNA from the capsid. No known genes are expressed, no DNA is transcribed, and the host cell survives the infection, continuing to grow and divide normally. The P16 function is required only during infection for the expression of phage functions. Induction in the absence of P16 proceeds with the expression of early and late genes and results in particle formation. P16 must be incorporated during morphogenesis into progeny particles after both infection and induction for the progeny to be infectious. The P16 function is necessary for transduction as well as for infection. Its activity is independent of new protein synthesis and it is not under immunity control. P16 can act in trans, but appears to act preferentially on the phage or phage DNA with which it is packaged. The data from complementation studies are compatible with P16 release from the capsid with the phage DNA. In the absence of P16 the infection is blocked, but the phage genome is not degraded. The various roles which have been ruled out for P16 are: (i) an early regulatory function, (ii) an enzymatic activity necessary for phage production, (iii) protection of phage DNA from host degradation enzymes, (iv) any generalized alteration of the host cell, (v) binding parental DNA to the replication complex, and (vi) any direct involvement in the replication of P22 DNA. P16 can be responsible for: (i) complete release of the DNA and disengagement from the capsid, (ii) bringing the released DNA to some necessary cell site or compartment such as the cytoplasm, (iii) removal of other virion proteins from the injected DNA, and (iv) alterations of the structure of the injected DNA.

Adsorption↗