Validation of a near-infrared probe for detection of thin intracranial white matter structures

OBJECT: The authors have developed an intracranial near-infrared (NIR) probe that analyzes the scattering of light emitted from its tip to measure the optical properties of cerebral tissue. Despite its success in distinguishing graymatter from white matter in humans during stereotactic surgery, the limits of this instrument's resolution remain unclear. In this study, the authors determined the spatial resolution of this new probe by using a rodent model supplemented with phantom measurements and computer simulation. METHODS: A phantom consisting of Intralipid and gelatin was constructed to resemble a layer of white matter overlying a layer of gray matter. Near-infrared measurements were obtained as the probe was inserted through the gray-white matter transition. A computer simulation of NIR measurements through a gray-white matter transition was also performed using Monte Carlo techniques. The NIR probe was then used to study 19 tracks from the cortical surface through the corpus callosum in an in vivo rodent preparation. The animals were killed and histological sections through the tracks were obtained. Data from the phantom models and computer simulations showed that the NIR probe samples a volume of tissue extending 1 to 1.5 mm in front of the probe tip (this distance is termed the "lookthrough" distance). Measurements obtained from an NIR probe passing through a thin layer of white matter consisted of an initial segment of increasing values, a maximum (peak) value, and a trailing segment of decreasing values. The length of the initial segment is the lookthrough distance, the position of the peak indicates the location of the superficial white matter boundary, and the length of the trailing segment is the thickness of the layer. These considerations were confirmed in experiments with rodents. All tracks passed through the corpus callosum, which was demonstrated as a broad peak on each NIR graph. The position of the dorsal boundary of the corpus callosum and its width (based on histological measurements) correlated well with the peak of the NIR curve and its trailing segment, respectively. The initial segments correlated well with estimates of the lookthrough distance. Five of the tracks transected the smaller anterior commissure (diameter 0.2 mm), producing a narrow NIR peak at the correct depth. CONCLUSIONS: Data in this study confirm that the NIR probe can reliably detect and measure the thickness of layers of white matter as thin as 0.2 mm. Such resolution should be adequate to detect larger structures of interest encountered during stereotactic surgery in humans.     

Effects of eyelid closure and disposable and silicone hydrogel extended contact lens wear on rabbit corneal epithelial proliferation

PURPOSE: To examine the rabbit corneal epithelial cell proliferation rate after extended wear of disposable or silicone hydrogel contact lenses or prolonged eyelid closure. METHODS: One randomly chosen eye of 40 New Zealand White rabbits was assigned to silicone hydrogel contact lens wear (n = 15, SH), disposable hydrogel contact lens wear (n = 6, DH), eyelid suturing (n = 15, SUT), or no intervention (n = 4). Contralateral eyes served as the control. After 24 hours or 1 week of lens wear, 5-bromo-2-deoxyuridine (BrdU) was injected intravenously to label dividing corneal epithelial cells, and animals were killed 24 hours after injection. Corneas were stained with monoclonal anti-BrdU antibody and FITC-conjugated secondary antibody. A series of continuous digital images of the wholemounted epithelium were collected from the superior to inferior limbus, and the number of BrdU-labeled cell pairs was counted. RESULTS: SH, DH, and SUT caused a significant decrease in BrdU-labeled pairs of cells over the entire corneal epithelium at day 2 compared with the number in contralateral control eyes (P < 0.001). One week of SUT or SH caused a significant increase centrally in BrdU-labeled cells (P < 0.01). BrdU labeling at the limbus in all groups was not significantly different from the control. Unexpectedly, the proliferation rate of the control corneas was also significantly affected by contralateral lens wear and suturing. CONCLUSIONS: Short-term overnight SH, DH, and SUT all significantly suppressed the cell proliferation rate in the rabbit corneal epithelium. However, adaptation, with central hyperproliferation of cells, appeared to occur at 8 days. The effects of lens wear and eyelid suturing on the cell proliferation rate in contralateral control eyes suggests a central mechanism that regulates corneal epithelial proliferation.     

Significance of Linear Extent of Breast Carcinoma at Surgical Margin

Background: Our objective was to correlate the extent of margin positivity and the findings on re-excision specimens of infiltrating mammary carcinoma.Methods: We selected 50 consecutive cases of infiltrating mammary carcinoma, including both infiltrating ductal carcinoma and infiltrating lobular carcinoma, with positive margins followed by re-excision. Margin positivity was defined as the presence of cancer at the inked margin. The extent of margin positivity was assessed by measuring the linear involvement of the inked margin by the carcinoma.Results: Twenty-one of 50 cases (42%) showed positive findings on re-excision, including either infiltrating carcinoma or carcinoma in situ or both. Nine of 14 cases (64%) with ductal carcinoma in situ or infiltrating ductal carcinoma on re-excision and 4 of 7 cases (57%) with lobular carcinoma in situ or infiltrating lobular carcinoma on re-excision had initial linear margins >1.0 cm, whereas 28 of 29 cases (96%) with negative findings on re-excision had initial linear margins &<1.0 cm.Conclusions: Linear measurement of the inked margin involved by infiltrating mammary carcinoma can be used as a predictor of findings on re-excisions.     

Leishmania major Friedlin chromosome 1 has an unusual distribution of protein-coding genes

Leishmania are evolutionarily ancient protozoans (Kinetoplastidae) and important human pathogens that cause a spectrum of diseases ranging from the asymptomatic to the lethal. The Leishmania genome is relatively small [ approximately 34 megabases (Mb)], lacks substantial repetitive DNA, and is distributed among 36 chromosomes pairs ranging in size from 0.3 Mb to 2.5 Mb, making it a useful candidate for complete genome sequence determination. We report here the nucleotide sequence of the smallest chromosome, chr1. The sequence of chr1 has a 257-kilobase region that is densely packed with 79 protein-coding genes. This region is flanked by telomeric and subtelomeric repetitive elements that vary in number and content among the chr1 homologs, resulting in an approximately 27.5-kilobase size difference. Strikingly, the first 29 genes are all encoded on one DNA strand, whereas the remaining 50 genes are encoded on the opposite strand. Based on the gene density of chr1, we predict a total of approximately 9,800 genes in Leishmania, of which 40% may encode unknown proteins.     

A Decade of Change in Obesity Surgery

Background: The International (formerly National) Bariatric Surgery Registry began collecting data in January 1986. The aim of this study was to examine changes in the practice of surgical treatment of severe obesity that occurred during the decade of 1986 through 1995, as observed in the IBSR data. Methods: All data submitted to the IBSR during the decade were transferred to the IBM mainframe computer for analysis. Characteristics of operative type populations were compared over time using analysis of variance (ANOVA) for age, body mass index (BMI), operative weight and Chi-square (χ²) test for gender. Results: There has been a steady increase over the decade in mean patient weight. The operations used have changed from predominantly ‘simple’ operations to more frequent use of ‘complex’ operations. Within the categories of ‘simple’ and ‘complex’, an increase in the variety of operations occurred. As a group, patients with ‘simple’ operations have been heavier, more often male and public pay patients than those who have undergone ‘complex’ operations. One year weight loss was greater for Roux-en-Y gastric bypass (RGB) than vertical banded gastroplasty (VBG), but follow-up rates were too low to study the relative merits of the operations used. The reported incidence of operative mortality and serious complications (leak with peritonitis, abscess and pulmonary embolism) remained low. Conclusions: These observations and their implications can be summarized in three statements which relate to action for improved patient care in the beginning of the new century: (1) increasing weight of candidates for surgical treatment during this decade indicates the need for earlier use of operative treatment before irreversible complications of obesity can develop; (2) low risk of obesity surgery, decreasing postoperative hospital stay, and early weight control support the continued and increased use of surgical treatment; (3) continued widespread use of both ‘simple’ and ‘complex’ operations with increased modifications of standard RGB and VBG procedures emphasizes the need for standardized long-term data and analyses regarding both weight control and postoperative side-effects.     

Retinal bipolar cells: contrast encoding for sinusoidal modulation and steps of luminance contrast

Contrast encoding for sinusoidal modulations of luminance contrast was investigated by intracellular recording in the intact salamander retina. In what appears to be the first study of this kind for vertebrate bipolar cells, responses of the central receptive-field mechanism of cone-driven cells to modulation of 3 Hz were analyzed quantitatively via both signal averaging and a Fast Fourier Transform (FFT) while the retina was light adapted to 20 cd/m2. Depolarizing and hyperpolarizing bipolar cells showed very similar encoding. Both responded with sinusoidal waveforms whose amplitude varied linearly with modulation depths ranging up to 7-8%. The slope of the modulation/response curve was very steep in this range. Thus, the contrast gain was high, reaching values of 6-7, and the half-maximal response was achieved at modulations of 9% or less. At modulations above approximately 15%, the responses typically showed strong compressive nonlinearity and the waveform was increasingly distorted. At maximum modulation, the higher harmonics of the FFT constituted about 30% of the amplitude of the fundamental. Measurements were also made for cones and horizontal cells. Both cell types showed predominantly linear responses and low contrast gain, in marked contrast to bipolar cells. These results suggest that the high contrast gain and strong nonlinearity of bipolar cells largely arise postsynaptic to cone transmitter release. Further experiments were performed to compare responses to contrast steps versus those to sinusoidal modulation. In the linear range, we show that the contrast gains of cones and horizontal cells are low and virtually identical for both steps and sinusoidal modulations. In bipolar cells, on the other hand, the contrast gain is about two times greater for steps than that for the 3-Hz sine waves. These results suggest that mechanisms intrinsic to bipolar cells act like a high-pass filter with a short time constant to selectively emphasize contrast transients over slower changes in contrast.     

General and specific cognitive deficits in schizophrenia.

BACKGROUND: It is controversial whether the cognitive deficit in schizophrenia is better characterized as generalized or as reflecting relatively independent deficits in different cognitive domains. The issue has implications for assessment practice, intervention design, and the exploration of schizophrenia genetics. METHODS: We used a specialized structural equation modeling approach, single common factor analysis, to explore the relative importance of generalized versus independent cognitive deficits in schizophrenia. Eighteen subtest scores from the Wechsler Adult Intelligence Scale-III and the Wechsler Memory Scale-III were included in the analysis. We analyzed these data for 97 schizophrenia or schizoaffective disorder outpatients and 87 healthy control subjects. RESULTS: Approximately two thirds of the overall effect of a schizophrenia diagnosis on cognitive performance was mediated through a single common factor. The Wechsler subtest scores showed almost uniformly strong relationships with this factor. The independent associations of group status with the subtest scores were smaller in magnitude and only selectively significant. CONCLUSIONS: The relatively greater magnitude of illness effects mediated through the common factor in this analysis, compared with the specific, independent effects, suggests that a generalized cognitive deficit is a core feature of schizophrenia.     

Chewing Gum Headaches

Aspartame, a popular dietetic sweetener, may provoke headache in some susceptible individuals. Herein, we describe three cases of young women with migraine who reported their headaches could be provoked by chewing sugarless gum containing aspartame.     

Three‐dimensional first‐pass myocardial perfusion MRI using a stack‐of‐spirals acquisition

Three‐dimensional cardiac magnetic resonance perfusion imaging is promising for the precise sizing of defects and for providing high perfusion contrast, but remains an experimental approach primarily due to the need for large‐dimensional encoding, which, for traditional 3DFT imaging, requires either impractical acceleration factors or sacrifices in spatial resolution. We demonstrated the feasibility of rapid three‐dimensional cardiac magnetic resonance perfusion imaging using a stack‐of‐spirals acquisition accelerated by non‐Cartesian k‐t SENSE, which enables entire myocardial coverage with an in‐plane resolution of 2.4 mm. The optimal undersampling pattern was used to achieve the largest separation between true and aliased signals, which is a prerequisite for k‐t SENSE reconstruction. Flip angle and saturation recovery time were chosen to ensure negligible magnetization variation during the transient data acquisition. We compared the proposed three‐dimensional perfusion method with the standard 2DFT approach by consecutively acquiring both data during each R–R interval in cardiac patients. The mean and standard deviation of the correlation coefficients between time intensity curves of three‐dimensional versus 2DFT were 0.94 and 0.06 across seven subjects. The linear correlation between the two sets of upslope values was significant (r = 0.78, P < 0.05). Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.