Robustness Analysis of Reference Surfaces for Surface Guided Radiation Therapy of the Breast

PURPOSE/OBJECTIVE(S)

Surface guided radiation therapy (SGRT) implements an optical imaging system in radiation therapy for positioning and motion management. This system projects visible light onto a patient and the reflected light is used to generate 3D positional information so that clinicians can accurately reproduce body positions. Patient setup shifts are calculated with six degrees of freedom by a registration algorithm comparing a reference surface (RS) of the patient to a live surface map of the patient on treatment day. SGRT has been an effective tool in daily localization for the treatment of breast cancer patients. It is common for patients to have multiple RS throughout the course of their treatment to account for anatomical variation between fractions. We sought to evaluate the robustness of reference surfaces and vendor specific algorithms used for SGRT.

MATERIALS/METHODS

At our institution, positional shift data for five patients treated for right-sided breast cancer were retrospectively analyzed. SGRT performance was compared between RS using bilateral breasts or a single ipsilateral breast. Shift parameters were calculated over the entire treatment course for all patients with a vendor supplied software tool that offers rigid and deformable registration algorithms. The deformable algorithm was used for treatment setups, with the treatment RS encompassing both breasts plus a margin. Two robustness tests were carried out: 1) a trimmed down RS encompassing just the ipsilateral breast and 2) a comparison of deformable vs rigid registration of the clinically used RS. After obtaining translational and angular shift data, the absolute mean differences between shifts were calculated to compare differences between RS size and algorithm performance.

RESULTS

On average, 1.4 new RS were created per patient guided by weekly radiographic imaging to adjust for anatomical changes. The absolute value of the average of the discrepancies between shifts using the clinical RS subtracted from the trimmed external (89 fractions) were <1mm and 1° and the maximum differences were: Lateral: 2.6mm, Longitudinal: 1.4mm, Vertical: 1.1mm, Yaw: 1.1°, Roll: 1.5°, Pitch: 1.7°. Discrepancies between tracking algorithms (83 fractions) were <1.5mm and 1° and the maximum differences were: Lateral: 3.4mm, Longitudinal: 3.5mm, Vertical: 2.0mm, Yaw: 2.4°, Roll: 2.7°, Pitch: 1.9°.

CONCLUSION

Clinically negligible mean discrepancies were observed for both robustness tests showing that neither the reference surface size nor the algorithms investigated caused systematic variations in the shifts for this group of patients. Maximum discrepancies of up to 3 mm and 3° were found between the algorithms, which indicate some variation, but within clinical tolerance. Overall, different selection of reference surfaces and algorithms had a minor effect on clinical shifts for SGRT of the breast.

A Prospective, Multi-Institutional Study of Problematic Plan Detection during Physician Chart Rounds

PURPOSE/OBJECTIVE(S)

We performed a multi-institutional prospective study to determine the detection rate of problematic treatment plans (PP) at physician chart rounds (CR), and to identify factors associated with PP detection.

MATERIALS/METHODS

Curative intent PPs with simulated errors (representative of the most common targets of peer review) were generated. Two breast specialists selected twenty appropriate plans for inclusion and assigned them American Association of Physicists in Medicine (AAPM) Task Group 100 severity and detectability scores. The PPs were blinded and embedded at weekly virtual CR at 2 institutions over 12 months. At site A, both breast and lung cases were reviewed by a mix of breast and lung specialists during CR, and at site B, only breast cases were presented and reviewed by breast specialists. At both sites, breast plans were reviewed via slice-by-slice review in the treatment planning system (TPS), and both used a color-coded tool from the TPS to assess adherence to planning directives. Both sites had systematic approaches to case presentation (without a checklist). Site A was usually prospective CR, while site B was exclusively prospective. The following CR elements were recorded: PP detection, time of detection, length of CR, total number of cases presented, plan elements displayed, number and roles of attendees, and detector's role. Analysis was performed using simple statistics with chi-square testing.

RESULTS

By PP error type classification, 55.0% pertained to "target volume delineation," 25% to "non-target volume delineation or normal tissue sparing," and 20.0% to "dose prescription or written directives." Detectability was rated ≤5 (<5% likelihood of going undetected) for 60% of PPs, and severity was rated ≥7 ("at least potentially serious toxicity or tumor underdose") for only 30% of PPs. CR lasted a median of 64 minutes at site A (IQR 55-82.5) and 70 minutes at site B (IQR 52.5-81.5). PPs were presented at a median of 34 minutes (IQR 22.5-43, site A) and 41.5 minutes (IQR 23.5-56, site B) after CR start. A median of 16 cases (IQR 13-19) at site A and 32 cases (IQR 25-34.5) at site B were presented per CR session, with a median of 1 PP (site A and B) presented per session (range 1-2). The median time spent per case was 4.0 minutes (Site A) and 2.2 minutes (Site B). The median number of attendings at CR was 4 for site A (range 2-6) and 6.5 for Site B (range 5-10). PP detection rate at site A was 20% (n = 4) and at site B was 70% (n = 14) (p = 0.001). Detections were made by an attending physician in 100% (site A, n = 4) and 92.9% (Site B, n = 13) of PP detections. There were no differences in detection rate by PP error type (p = 0.78), detectability (p = 0.60) or severity score (p = 0.68), or by time PP presented after CR start (p = 0.39).

CONCLUSION

The effectiveness of PP detection at chart rounds can vary greatly between institutions. The study suggests possible areas for improvement but further study is needed to determine best practices.

Comparing the efficacy of different methods of faecal microbiota transplantation via oral capsule, oesophagogastroduodenoscopy, colonoscopy, or gastric tube

BACKGROUND

The increasing prevalence of multidrug-resistant organism (MDRO) carriage poses major challenges to medicine as healthcare costs increase. Recently, faecal microbiota transplantation (FMT) has been discussed as a novel and effective method for decolonizing MDRO.

AIM

To compare the efficacy of different FMT methods to optimize the success rate of decolonization in patients with MDRO carriage.

METHODS

This prospective cohort study enrolled patients with MDRO carriages from 2018 to 2021. Patients underwent FMT via one of the following methods: oral capsule, oesophagogastroduodenoscopy (EGD), colonoscopy, or gastric tube.

FINDINGS

A total of 57 patients underwent FMT for MDRO decolonization. The colonoscopy group required the shortest time for decolonization, whereas the EGD group required the longest (24.9 vs 190.4 days, P = 0.022). The decolonization rate in the oral capsule group was comparable to that in the EGD group (84.6% vs 85.7%, P = 0.730). An important clinical factor associated with decolonization failure was antibiotic use after FMT (odds ratio = 6.810, P = 0.008). All four groups showed reduced proportions of MDRO species in microbiome analysis after FMT.

CONCLUSION

Compared to other conventional methods, the oral capsule is an effective FMT method for patients who can tolerate an oral diet. The discontinuation of antibiotics after FMT is a key factor in the success of decolonization.

Phenotypes of disease severity in a cohort of hospitalized COVID-19 patients: Results from the IMPACC study

BACKGROUND

Better understanding of the association between characteristics of patients hospitalized with coronavirus disease 2019 (COVID-19) and outcome is needed to further improve upon patient management.

METHODS

Immunophenotyping Assessment in a COVID-19 Cohort (IMPACC) is a prospective, observational study of 1164 patients from 20 hospitals across the United States. Disease severity was assessed using a 7-point ordinal scale based on degree of respiratory illness. Patients were prospectively surveyed for 1 year after discharge for post-acute sequalae of COVID-19 (PASC) through quarterly surveys. Demographics, comorbidities, radiographic findings, clinical laboratory values, SARS-CoV-2 PCR and serology were captured over a 28-day period. Multivariable logistic regression was performed.

FINDINGS

The median age was 59 years (interquartile range [IQR] 20); 711 (61%) were men; overall mortality was 14%, and 228 (20%) required invasive mechanical ventilation. Unsupervised clustering of ordinal score over time revealed distinct disease course trajectories. Risk factors associated with prolonged hospitalization or death by day 28 included age ≥ 65 years (odds ratio [OR], 2.01; 95% CI 1.28-3.17), Hispanic ethnicity (OR, 1.71; 95% CI 1.13-2.57), elevated baseline creatinine (OR 2.80; 95% CI 1.63- 4.80) or troponin (OR 1.89; 95% 1.03-3.47), baseline lymphopenia (OR 2.19; 95% CI 1.61-2.97), presence of infiltrate by chest imaging (OR 3.16; 95% CI 1.96-5.10), and high SARS-CoV2 viral load (OR 1.53; 95% CI 1.17-2.00). Fatal cases had the lowest ratio of SARS-CoV-2 antibody to viral load levels compared to other trajectories over time (p=0.001). 589 survivors (51%) completed at least one survey at follow-up with 305 (52%) having at least one symptom consistent with PASC, most commonly dyspnea (56% among symptomatic patients). Female sex was the only associated risk factor for PASC.

INTERPRETATION

Integration of PCR cycle threshold, and antibody values with demographics, comorbidities, and laboratory/radiographic findings identified risk factors for 28-day outcome severity, though only female sex was associated with PASC. Longitudinal clinical phenotyping offers important insights, and provides a framework for immunophenotyping for acute and long COVID-19.

FUNDING

NIH.

Use of supplemental anti-HBc testing of donors showing non-discriminating reactive results in multiplex nucleic acid testing

BACKGROUND AND OBJECTIVES

The Korean Red Cross began nucleic acid amplification testing (NAT) for HIV and HCV in February 2005, and added HBV NAT beginning in June 2012. The current NAT system utilizes a multiplex assay for simultaneous detection of HBV DNA, HCV RNA and HIV-1 RNA. For samples that are reactive in the multiplex assay, we do specific tests for each virus. However, there have been cases of non-discriminated reactive (NDR) results which appear to be the result of non-specific reactions or cross-contamination, although some cases are considered to arise from the presence of low levels of HBV DNA due to occult hepatitis B infection.

MATERIALS AND METHODS

We examined the incidence of NDR results in previous donations of some NAT-reactive donors. Additionally, for those donors with NDR results, we performed an HBV core antibody (anti-HBc) assay.

RESULTS

From November 2015 to March 2016, there were 408 NAT-reactive donors. Of these, nineteen HBV NAT-reactive donors showed a history of NDR results in the past donations. Seven donors showed NDR results more than once. Of 771 NDR donors, 362 (47·0%) were anti-HBc reactive.

CONCLUSION

The NDR donors had a substantially higher rate of anti-HBc reactivity than other blood donors indicating that some with anti-HBc reactivity represent donors with occult HBV. Therefore, the incorporation of an anti-HBc testing for NDR donors could improve blood safety testing for the Korean Red Cross.

An effective diagnostic strategy for accurate detection of RhD variants including Asian DEL type in apparently RhD-negative blood donors in Korea

BACKGROUND AND OBJECTIVES

The purpose of this study was to provide an effective RHD genotyping strategy for the East Asian blood donors.

MATERIAL AND METHODS

RhD phenotyping, weak D testing and RhCE phenotyping were performed on 110 samples from members of the RhD-negative club, private organization composed of RhD-negative blood donors, in the GwangJu-Chonnam region of Korea. The RHD promoter, intron 4, and exons 7 and 10 were analysed by real-time PCR. Two nucleotide changes (c.1227 G>A, and c.1222 T>C) in exon 9 were analysed by sequencing.

RESULTS

Of 110 RhD-negative club members, 79 (71·8%) showed complete deletion of the RHD gene, 10 (9·1%) showed results consistent with RHD-CE-D hybrid, and 21 (19·1%) showed amplification of RHD promoter, intron 4, and exons 7 and 10. Of the latter group, 16 (14·5%) were in the DEL blood group including c.1227 G>A (N = 14) and c.1222 T>C (N = 2), 2 (1·8%) were weak D, 1(0·9%) was partial D, and 2 (1·8%) were undetermined. The RhD-negative phenotype samples consisted of 58 C-E-c+e+, 19 C-E+c+e+, 3 C-E+c+e-, 21 C+E-c+e-, 6 C+E-c+e+ and 3 C+E-c-e + . Notably, all 58 samples with the C-E-c+e+ phenotype were revealed to have complete deletion of the RHD gene. The C-E-c+e+ phenotype showed 100% positive predictive value for detecting D-negative cases.

CONCLUSIONS

RHD genotyping is not required in half of D-negative cases. We suggest here an effective RHD genotyping strategy for accurate detection of RhD variants in apparently RhD-negative blood donors in East Asia.

Morphological and morphometric study of the androgenetic alopecic scalp using two- and three-dimensional analysis comparing regional differences

BACKGROUND

Androgenetic (male-type) alopecia (AGA) is caused by genetic and androgenetic effects. The progression of baldness results in smaller hair papillae, thinner hair and a shortened hair cycle. Alopecia occurs mainly in the frontal region and, to a lesser extent, in the occipital region.

OBJECTIVES

The morphological differences in the hair follicular units between the alopecic frontal scalp and the vertex and occipital regions were compared using cross-sectional histology and three-dimensional reconstruction.

METHODS

Skin specimens were obtained from the frontal, vertex and occipital regions of 24 male human cadavers with fully progressed AGA, and from the frontal region of 32 normal cadaveric scalps. These specimens were fixed, processed using routine histological methods, serially sectioned at a thickness of 10 μm and then stained with Masson's trichrome. The serial sections were reconstructed three-dimensionally using 'Reconstruct' software.

RESULTS

The ratios between the numbers of terminal and vellus hairs in the frontal and occipital regions in the AGA scalps were 0·2 : 1 and 3·5 : 1, respectively. Almost all of the hair follicles in the frontal region were vellus hair follicles. The sebaceous gland and arrector pili muscle were larger in the frontal region than in the occipital region.

CONCLUSIONS

The morphology of the AGA scalp has been characterized. The terminal-to-vellus hair ratio in the occipital (normal) region was different from that in the frontal (alopecic) region. Moreover, sebaceous glands were larger in the frontal alopecic region than in the occipital region. These larger glands may be associated with other dermatological pathologies, such as seborrhoeic dermatitis.

Production of Endoglucanase, Beta-glucosidase and Xylanase by Bacillus licheniformis Grown on Minimal Nutrient Medium Containing Agriculture Residues

Bacillus licheniformis was grown in minimal nutrient medium containing 1% (w/v) of distillers dried grain with soluble (DDGS), palm kernel meal (PKM), wheat bran (WB) or copra meal (CM), and the enzyme activity of endoglucanase, β-glucosidase, xylanase and reducing sugars was measured to investigate a possibility of using cost-effective agricultural residues in producing cellulolytic and hemicellulolytic enzymes. The CM gave the highest endoglucanase activity of 0.68 units/mL among added substrates at 48 h. CM yielded the highest titres of 0.58 units/ml of β-glucosidase, compared to 0.33, 0.23, and 0.16 units/mL by PKM, WB, and DDGS, respectively, at 72 h. Xylanase production was the highest (0.34 units/mL) when CM was added. The supernatant from fermentation of CM had the highest reducing sugars than other additional substrates at all intervals (0.10, 0.12, 0.10, and 0.11 mg/mL respectively). It is concluded that Bacillus licheniformis is capable of producing multiple cellulo- and hemicellololytic enzymes for bioethanol production using cost-effective agricultural residues, especially CM, as a sole nutrient source.

Upregulation of Fas and downregulation of CD94/NKG2A inhibitory receptors on circulating natural killer cells in patients with new-onset psoriasis

BACKGROUND

Psoriasis has been considered as a T-helper 1 cell-mediated autoimmune disease driven by collaboration with multiple components of innate and acquired immune cells. Natural killer (NK) cells have been shown to bridge innate and acquired immunity, and thus could potentially contribute to the pathophysiology of psoriasis.

OBJECTIVES

To investigate the phenotypic changes of circulating NK cells in patients with new-onset psoriasis.

METHODS

Fifteen patients with plaque psoriasis (eight women and seven men) who visited our clinic after their first episode of psoriasis and did not have a history of previous systemic therapy or phototherapy participated in this study. Peripheral blood mononuclear cells were isolated and stained with a panel of antibodies against cell surface receptors expressed on T and/or NK cells and analysed by flow cytometry.

RESULTS

As compared with normal healthy volunteers, patients with new-onset psoriasis showed no significant changes in numbers of peripheral NK, NK-T or T cells. NK activating receptors 2B4, CD48, NKG2D, CD16 and CD56 were found to be unchanged in new-onset psoriasis. However, the expression of Fas (activation-induced death receptor) was upregulated, whereas the expression of the NK inhibitory receptors CD94 and NKG2A was dramatically reduced on NK cells of new-onset psoriasis. These changes occurred at the level of mean fluorescent intensity, but minimally affected percentages of cells expressing Fas, CD94 and NKG2A.

CONCLUSIONS

Our findings demonstrate that changes in the expression of Fas and CD94/NKG2A receptors on NK cells may occur during new-onset psoriasis, and are likely to contribute to the pathogenesis of psoriasis.

Riboswitches in eubacteria sense the second messenger cyclic di-GMP

Cyclic di-guanosine monophosphate (di-GMP) is a circular RNA dinucleotide that functions as a second messenger in diverse species of bacteria to trigger wide-ranging physiological changes, including cell differentiation, conversion between motile and biofilm lifestyles, and virulence gene expression. However, the mechanisms by which cyclic di-GMP regulates gene expression have remained a mystery. We found that cyclic di-GMP in many bacterial species is sensed by a riboswitch class in messenger RNA that controls the expression of genes involved in numerous fundamental cellular processes. A variety of cyclic di-GMP regulons are revealed, including some riboswitches associated with virulence gene expression, pilus formation, and flagellum biosynthesis. In addition, sequences matching the consensus for cyclic di-GMP riboswitches are present in the genome of a bacteriophage.

Simultaneous determination of delta-aminolevulinic acid, porphobilinogen, levulinic acid and glycine in culture broth by capillary electrophoresis

Capillary electrophoretic simultaneous determination of a mixture containing delta-aminolevulinic acid, porphobilinogen, levulinic acid and glycine was investigated. With increases in the sodium tetraborate buffer concentration (5-70 mM), resolution of the four components was improved, but the migration time was increased. Alternatively, with increases in the applied voltage (5-22.5 kV), a shortened migration time was seen but this adversely affected resolution. The components were separated with high resolution by using a fused-silica capillary column (75 cm x 75 microm I.D.) filled with 30 mM sodium tetraborate buffer (pH 9.3-9.4) under the applied voltage of 20 kV (constant voltage mode). When the established method was applied to the culture broth of Rhodopseudomonas sphaeroides, a photosynthetic bacterium, the four components mentioned above were separated with good resolution. Furthermore, the use of this method would provide a fast, sensitive and specific method for monitoring the administration of delta-aminolevulinic acid in photodynamic cancer therapy, for the measurement of delta-aminolevulinic acid dehydratase activity in erythrocytes, and for testing the delta-aminolevulinic acid assay and for impurities in drug formulation.

Serum leptin, IGF-I and insulin levels in preterm infants receiving parenteral nutrition during the first week of life

Leptin is involved in the regulation of body weight through a feedback signal between adipose tissue and the satiety center, to decrease food intake and increase energy expenditure. Newborn infants experience physiological weight loss during the first week of life. The leptin level may be decreased to enhance food intake and to decrease energy expenditure for physiological adaptation during early postnatal days. Insulin-like growth factor-I (IGF-I) and insulin are involved in the regulation of perinatal growth. Leptin might be interrelated with IGF-I or insulin, since both of these have adipogenic and somatotropic effects. We therefore hypothesized that leptin, IGF-I and insulin would be decreased during the first week of life, concurrently with physiological weight loss. Thirty preterm AGA infants (birth weight 1.574+/-313 g; GA 31.9+/-2.2 wk) were studied. All infants received parenteral nutrition from the third day after birth. Leptin was significantly decreased during the first week of life, and insulin was significantly increased at day 7 vs. day 1 and day 3. IGF-I did not change during the first week of life. Leptin was positively correlated with body weight (r = 0.368, p<0.01), body mass index (r = 0.267, p<0.05), and serum IGF-I (r = 0.330, p <0.01), but not with serum insulin. The percent of weight reduction during the first week of life was not correlated with the percent of leptin reduction during the first week of life. In conclusion, leptin was significantly decreased and positively correlated with body weight and IGF-I during the first week of life. Changes of leptin and insulin might be related to postnatal adaptation in metabolism, but the exact role of leptin, IGF-I and insulin in postnatal physiological weight loss is not clear.

Prospective evaluation of perinatal risk factors for cerebral palsy and delayed development in high risk infants

Prematurity, intrauterine infection and perinatal brain injury have been reported to be significant risk factors of cerebral palsy (CP). We examined the perinatal predictors of cerebral palsy and delayed development (DD) in 184 high risk infants. Thirty-five infants were diagnosed as cerebral palsy and delayed development at 12 months corrected age. Antenatal, intrapartum, and neonatal factors were prospectively evaluated in 2 groups of high risk infants compared with controls; Group A (n = 79), infants weighing less than 2,000 g; Group B (n = 43), infants weighing 2,000 g or more. In univariate analysis, there were no significant antenatal and intrapartum factors associated with cerebral palsy and delayed development in either group. We found that significant postnatal risk factors of CP in group A included sepsis (p = 0.008), BPD (bronchopulmonary dysplasia) (p = 0.028), IVH (intraventricular hemorrhage) (p = 0.042), ventriculomegaly (VM) (p = 0.001) and a longer duration of mechanical ventilation (p = 0.001); while in group B, sepsis (p = 0.047) and neonatal seizure (p = 0.027) were significant risk factors. In multivariate analysis, sepsis in group B was a moderate risk factor of CP (OR (odds ratio) 1.47; 95% CI (confidence interval) 1.02-2.13). In conclusion, neonatal sepsis may contribute to the development of cerebral palsy and delayed development. We suggest that high risk infants who have sepsis should be carefully followed for cerebral palsy and delayed development. The prevention of cerebral palsy may be feasible by decreasing neonatal risk factors such as sepsis during the neonatal period.

Neural correlates of a decision in the dorsolateral prefrontal cortex of the macaque

To make a visual discrimination, the brain must extract relevant information from the retina, represent appropriate variables in the visual cortex and read out this representation to decide which of two or more alternatives is more likely. We recorded from neurons in the dorsolateral prefrontal cortex (areas 8 and 46) of the rhesus monkey while it performed a motion discrimination task. The monkey indicated its judgment of direction by making appropriate eye movements. As the monkey viewed the motion stimulus, the neural response predicted the monkey's subsequent gaze shift, hence its judgment of direction. The response comprised a mixture of high-level oculomotor signals and weaker visual sensory signals that reflected the strength and direction of motion. This combination of sensory integration and motor planning could reflect the conversion of visual motion information into a categorical decision about direction and thus give insight into the neural computations behind a simple cognitive act.

Nutritional requirements of an aging population with emphasis on subacute care patients

Life expectancy in the United States has increased dramatically during the past century, creating a large population of people with potentially compromised nutritional status. Although requirements were previously believed to decline with aging, recent data suggest that requirements for protein and energy often do not decline and may actually increase during disease exacerbations. Optimal intake of vitamins and minerals is also under reevaluation, and significant segments of the population may have deficiencies based on limited intake or absorption. Social and psychological factors and difficulty chewing and swallowing may interfere with adequate intake. At the end of a hospital stay, many patients need continued skilled transitional care before discharge home. Many patients who have existing nutritional deficits, including weight loss, decreased serum proteins and pressure ulcers are admitted to subacute nursing facilities. Careful initial and periodic reassessment of nutritional status and aggressive nutritional management must be used to prepare patients for optimal independence after discharge. Improved clinical outcome can be achieved with prevention of malnutrition and timely correction of nutritional problems.

Neuronal responses in extrastriate cortex to objects in optic flow fields

During locomotion, observers respond to objects in the environment that may represent obstacles to avoid or landmarks for navigation. Although much is known about how visual cortical neurons respond to stimulus objects moving against a blank background, nothing is known about their responses when objects are embedded in optic flow fields (the patterns of motion seen during locomotion). We recorded from cells in the lateral suprasylvian visual area (LS) of the cat, an area probably analogous to area MT. In our first experiments, optic flow simulations mimicked the view of a cat trotting across a plain covered with small balls; a black bar lying on the balls served as a target object. In subsequent experiments, optic flow simulations were composed of natural elements, with target objects representing bushes, rocks, and variants of these. Cells did not respond to the target bar in the presence of optic flow backgrounds, although they did respond to it in the absence of a background. However, 273/423 cells responded to at least one of the taller, naturalistic objects embedded in optic flow simulations. These responses might represent a form of image segmentation, in that cells detected objects against a complex background. Surprisingly, the responsiveness of cells to objects in optic flow fields was not correlated with preferred direction as measured with a moving bar or whole-field texture. Because the direction of object motion was determined solely by receptive-field location, it often differed considerably from a cell's preferred direction. About a quarter of the cells responded well to objects in optic flow movies but more weakly or not at all to bars moving in the same direction as the object, suggesting that the optic flow background modified or suppressed direction selectivity.

Simulated optic flow and extrastriate cortex. I. Optic flow versus texture

A locomoting observer sees a very different visual scene than an observer at rest: images throughout the visual field accelerate and expand, and they follow approximately radial outward paths from a single origin. This so-called optic flow field is presumably used for visual guidance, and it has been suggested that particular areas of visual cortex are specialized for the analysis of optic flow. In the cat, the lateral suprasylvian visual area (LS) is a likely candidate. To test the hypothesis that LS is specialized for analysis of optic flow fields, we recorded cell responses to optic flow displays. Stimulus movies simulated the experience of a cat trotting slowly across an endless plain covered with small balls. In different simulations we varied the size of balls, their organization (randomly or regularly dispersed), and their color (all one gray level, or multiple shades of gray). For each optic flow movie, a "texture" movie composed of the same elements but lacking optic flow cues was tested. In anesthetized cats, > 500 neurons in LS were studied with a variety of movies. Most (70%) of 454 visually responsive cells responded to optic flow movies. Visually responsive cells generally preferred optic flow to texture movies (69% of those responsive to any movie). The direction in which a movie was shown (forward or reverse) was also an important factor. Most cells (68%) strongly preferred forward motion, which corresponded to visual experience during locomotion.

Simulated optic flow and extrastriate cortex. II. Responses to bar versus large-field stimuli

In the preceding paper we described the responses of cells in the cat's lateral suprasylvian visual area (LS) to large-field optic flow and texture movies. To assess response properties such as direction selectivity, cells were also tested with moving bar stimuli. We expected that there would be good agreement between response properties elicited with optic flow movies and those revealed with bar stimuli. We first asked how well bar response properties predicted responsiveness to optic flow movies. There was no correlation between responsiveness to movies and the degree of end-stopping, length summation, or preference for bars that accelerated and expanded. We then considered only the 322 cells that responded to both bars and optic flow or texture movies and asked how well the strength of their response to movies could be predicted from the direction-tuning curves generated with bar stimuli. One-third of these cells responded much more strongly to movies than could be predicted from their direction-tuning curves. Generally, such cells were rather well tuned for the direction of bar motion and preferred a direction substantially different from what they saw in optic flow movies. Optic flow movies shown in the forward direction were the most effective variety of movie for two-thirds of these cells. To see whether this outcome stemmed from differential direction tuning for bars and large multielement displays, in a second series of experiments we compared direction tuning for bars and large-field texture movies. Many cells showed substantially different direction tuning for the two kinds of stimulus: almost 1/3 of 409 cells had tuning curves that overlapped each other by < 50%. But only a small number of cells (< 10%) responded much better to texture movies than to bars in the predominant direction of image motion in optic flow movies. This result, like that reported in the preceding paper, suggests that cells in LS respond differently to optic flow than to texture displays lacking optic flow motion cues.

Application of PCR from the fine needle aspirates for the diagnosis of cervical tuberculous lymphadenitis

Tuberculosis remains a major public health problem worldwide. A definitive and accurate diagnosis of tuberculosis in cervical lymphadenopathy is important because satisfactory results can be achieved with chemotherapy alone, obviating surgery. Recently, fine needle aspiration cytology (FNAC) has provided an alternative and easy procedure for collection of material for cytomorphologic and bacteriologic examination. But the detection rate for M. tuberculosis from the aspirate material is still low with Ziehl-Neelson stain and even with culture. The authors therefore performed polymerase chain reaction (PCR) for mycobacterial DNA sequences in 31 cases of cytodiagnosis of tuberculous lymphadenitis and compared conventional bacteriologic methods. Ziehl-Neelson staining for acid-fast bacilli (AFB) was positive in 3 cases (10%) in direct smears, and the cultures for M. tuberculosis were positive in 6 cases (19%). In 19 (61%) among 31 samples, mycobacterial DNA fragments were detected, using the PCR method. With combined conventional and PCR method, the rate of detection was increased to 68 percent high. In conclusion, PCR is the most sensitive technique in the demonstration of M. tuberculosis in patient with clinically suspected as tuberculosis, who have AFB stain or culture negative cytology. Combined conventional and PCR methods as well as cytologic findings are of further help in the detection and characterization of M. tuberculosis.

Role of suppression in shaping orientation and direction selectivity of complex neurons in cat striate cortex

1. Single binocularly driven complex neurons in cat striate cortex were recorded extracellularly under nitrous oxide-oxygen-halothane anesthesia and muscle relaxant. Orientational/directional tuning was initially derived for each eye in turn, with sine wave gratings of optimal spatial frequency and velocity, while the other eye viewed a uniform field. 2. For the dominant eye, previously concealed suppression was revealed against elevated levels of firing induced with a conditioning grating, drifting continuously in the preferred direction, simultaneously presented to the nondominant eye. During steady-state binocular conditioning, orientational/directional tuning was reestablished for the dominant eye. In a subset of cells, tuning curves during conditioning were also derived for the reverse configuration, i.e., nondominant eye tuning, dominant eye conditioning: results were qualitatively identical to those for conditioning through the nondominant eye. 3. Neurons were initially segregated into five groups, according to the observed suppression profiles induced at nonoptimal orientations/directions during conditioning: Type 1, suppression centered on orthogonal directions; Type 2, suppression around null directions; Type 3, null suppression combined with orthogonal suppression; Type 4, lateral suppression, maximal for directions immediately flanking those inducing excitation; and Type 5, the residue of cells, totally lacking suppression or showing complex or variable suppression. 4. Sharpness of (excitatory) tuning was correlated with directionality and with class of suppression revealed during binocular conditioning. Direction-biased neurons were more sharply orientation tuned than direction-selective neurons; similarly, neurons exhibiting lateral or orthogonal suppression during conditioning were more sharply tuned than neurons with null suppression. 5. Application of suboptimal directions of conditioning weakened the induced suppression but altered none of its main characteristics. 6. The relationship between excitation, suppression, and spatial frequency was investigated by comparing tuning curves for the dominant eye at several spatial frequencies, without and during conditioning. End-stopped neurons preferred lower spatial frequencies and higher velocities of motion than non-end-stopped neurons. Confirming previous reports, suppression in some neurons was still present for spatial frequencies above the cutoff frequency for excitation, demonstrating the tendency for suppression to be more broadly spatial frequency tuned than excitation. 7. Scatterplots of strength of suppression, in directions orthogonal and opposite maximal excitation, partially segregated neurons of Types 1-3. Clearer segregation of Types 1-4 was obtained by curve-fitting to profiles of suppression, and correlating half-width of tuning for suppression with the angle between the directions of optimal suppression and optimal excitation in each neuron. 8. Two interpretations are advanced-the first, based on three discrete classes of inhibition, orthogonal, null and lateral; the second, based on only two classes, orthogonal and null/lateral--in which null and lateral suppression are manifestations of the same inhibitory mechanism operating, respectively, on broadly tuned direction-selective or on sharply tuned direction-biased neurons. Orthogonal suppression may be untuned for direction, whereas lateral and null suppression are broadly direction tuned. Within each class, suppression is more broadly spatial frequency tuned than excitation. 9. It is concluded that orientational/directional selectivity of complex cells at different spatial frequencies is determined by the balance between tuned excitation and varying combinations of relatively broadly distributed or untuned inhibition.

Are the preferred directions of neurons in cat extrastriate cortex related to optic flow?

It has been proposed that one area of extrastriate cortex in the cat, the lateral suprasylvian area (LS), plays an important role in visual analysis during locomotion (Rauschecker et al., 1987). Cells in LS reportedly tend to prefer directions along a trajectory originating at the center of gaze, and passing outward through the receptive-field center. Such directions coincide with the directions of image motion in an optic flow field, the pattern seen by locomoting observers when they fixate the point towards which they are heading (Gibson, 1950). We re-examined this issue for cells in LS with receptive fields in the lower visual field. Cells recorded posterior to Horsley-Clarke A2 showed a clear correlation between preferred direction and receptive-field location, but not that predicted: preferred directions were generally orthogonal to "optic flow" directions. Since these cells were all located posterior to those in studies showing a bias for "optic flow" directions, we hypothesized that there are two cell populations within LS, an anterior population that tends to prefer radial-outward directions, and a posterior population that tends to prefer directions orthogonal to radial. Data from earlier mapping experiments (Sherk & Mulligan, 1993) supported this idea.

Spatial correlation of suppressive and excitatory receptive fields with direction selectivity of complex cells in cat striate cortex

The aim of the study was to account for direction selectivity of visual cortical neurons through systematic positional mismatch between excitatory and suppressive influences on each neuron. Direction-selective complex neurons were therefore recorded from striate cortex of cats lightly anaesthetized with halothane in nitrous oxide-oxygen. All but small residual eye movements were eradicated with intravenous gallamine triethiodide. Excitatory receptive field (ERF) dimensions and centring were quantified with optimal sine-wave grating stimuli, appropriately windowed to limit them to variable locations along and across the receptive field (RF) centre. Related suppressive receptive fields (SRFS) were similarly mapped during binocular conditioning, induced by an optimal grating applied to the other eye and drifting continuously in each neuron's preferred direction. Its purpose was to elevate ongoing levels of discharge to reveal often concealed null suppression. ERF and SRF profiles were systematically offset, especially along the line of preferred direction such that, for stimuli moving in the non-preferred direction, the SRF lay ahead of the ERF. Derivations of ERFS and SRFS during conditioning, within a single batch of trials, excluded eye movements as a source of positional mismatch. It is concluded that this mismatch may provide the basis for direction selectivity and the emergence of null suppression.

Temperature behavior of dielectric and piezoelectric properties of samarium-doped lead titanate ceramics

The dielectric and electromechanical coupling properties of Sm-doped and Mn-doped PbTiO(3) ceramics were investigated from 4.2 to 300 K. The upper and lower limits of the ceramic dielectric and piezoelectric properties were calculated by averaging the single-domain constants that were determined from a phenomenological theory. Comparisons of the measured and calculated properties were then made. The measured dielectric permittivity epsilon(T)(33) and piezoelectric strain coefficient d(33) appear to be mainly due to the averaging of the intrinsic single-domain response. The large piezoelectric and electromechanical anisotropies present in modified PbTiO(3) ceramics also appear to be an intrinsic property of the material. The piezoelectric coefficient d(31), as well as the planar coupling coefficient k(p), was found to have very small values over two temperature regions, from 120 to 170 K and from 240 to 270 K.

Amino acid sequence of the phosphorylation site of yeast (Saccharomyces cerevisiae) fructose-1,6-bisphosphatase

Fructose-1,6-bisphosphatase from the yeast Saccharomyces cerevisiae has properties similar to other gluconeogenic fructose-1,6-bisphosphatases, but an unusual characteristic of the yeast enzyme is that it can be phosphorylated in vitro by cAMP-dependent protein kinase. Phosphorylation also occurs in vivo, presumably as part of a signalling mechanism for the enzyme's degradation. To probe the structural basis for the phosphorylation of yeast fructose-1,6-bisphosphatase, we have developed an improved procedure for the purification of the enzyme and then performed sequence studies with the in vitro-phosphorylated protein as well as with tryptic and chymotryptic peptides containing the phosphorylation site. As a result of these studies, we have determined that yeast fructose-1,6-bisphosphatase has the following 24-residue NH2-terminal amino acid sequence: Pro-Thr-Leu-Val-Asn-Gly-Pro-Arg-Arg-Asp-Ser-Thr-Glu-Gly- Phe-Asp-Thr-Asp-Ile-Ile-Thr-Leu-Pro-Arg. The site of phosphorylation is located at Ser-11 in the above sequence. The amino acid sequence around the site of phosphorylation contains the sequence - Arg-Arg-X-Ser- associated with many of the better substrates of cAMP-dependent protein kinase. The sequence of residues 15-24 above is highly homologous with the sequence of residues 6-15 of pig kidney fructose-1,6-bisphosphatase, showing 7 out of 10 residues in identical positions. The yeast enzyme, however, has a dissimilar NH2-terminal region which extends beyond the NH2 terminus of mammalian fructose-1,6-bisphosphatases and contains a unique phosphorylation site.