Why pictures look right when viewed from the wrong place

A picture viewed from its center of projection generates the same retinal image as the original scene, so the viewer perceives the scene correctly. When a picture is viewed from other locations, the retinal image specifies a different scene, but we normally do not notice the changes. We investigated the mechanism underlying this perceptual invariance by studying the perceived shapes of pictured objects viewed from various locations. We also manipulated information about the orientation of the picture surface. When binocular information for surface orientation was available, perceived shape was nearly invariant across a wide range of viewing angles. By varying the projection angle and the position of a stimulus in the picture, we found that invariance is achieved through an estimate of local surface orientation, not from geometric information in the picture. We present a model that explains invariance and other phenomena (such as perceived distortions in wide-angle pictures).     

Hallervorden Spatz Disease

A nine-month-old infant presented with fever and loss of milestones. Examination revealed intermittent rigidity and dystonic movements. Magnetic resonance imaging (MRI) shows decreased signal intensity in globus pallidus and substantia nigra, indicative of iron deposition, suggesting Hallervorden Spatz Disease. The dopamine–neuromelanine system has been postulated to be the possible pathogenesis. Gene mapping has located the defect to be in the coding sequence of a gene called PANK– 2. Prenatal diagnosis is possible. The case is reported because of its rarity and early presentation.     

Modulation of J774.1 macrophage L-arginine metabolism by intracellular Mycobacterium bovis BCG

Using a Mycobacterium bovis BCG mutant (AS1) lacking a Bacillus subtilis L-arginine transporter homolog, we demonstrate here that the interaction between intracellular mycobacteria and the macrophage with respect to L-arginine transport and metabolism is quite complex. Intracellular AS1 stimulates macrophage L-arginine transport and accumulates 2.5-fold more (3)H label derived from L-arginine than does the wild type. These studies suggest that the accumulation of (3)H label reflects the acquisition of metabolites of L-arginine produced by the macrophage.     

Cell-based therapy in the repair of osteochondral defects: a novel use for adipose tissue

Mesenchymal stem cells are currently procured from periosteum and bone marrow. The procurement of stem cells from these sources is tedious and gives a low yield of cells. This study was aimed at circumventing these problems and allowing for a method that would be more acceptable in the clinical setting. Tissue for transplantation was harvested from a single New Zealand White rabbit. Cells were more readily obtained from adipose tissue than from bone marrow or periosteum. The present method also provided a better yield of cells through culture. In vitro studies were performed to assess the differentiation potential of these cells. Successful in vitro transformation into alternative mesenchymal cell lines including cardiomyocytes revealed these cells to have wide differentiation potential. Further characterization morphologically, immunohistochemically, and via gene transfection showed features consistent with mesenchymal stem cells. Cultured cells were then transplanted into defects created in the left medial femoral condyle. The femora were harvested at various intervals and the repair tissue was assessed. Gross osteochondral defect reconstitution and histological grading was superior to periosteum-derived stem cell repair and repair by native mechanisms. Biomechanically, the repair tissue approximated intact cartilage and was superior to osteochondral autografts and repair by innate mechanisms.     

Discordant expression of selectin ligands and sialyl Lewis x-related epitopes on murine myeloid cells

Murine leukocytes are thought to express alpha2-3-sialylated and alpha1-3-fucosylated selectin ligands such as sialyl Lewis x (sLe(x)), although monoclonal antibodies (mAbs) to sLe(x) or Le(x) reportedly do not bind to murine leukocytes. We observed that P- and E-selectin bound to pronase-sensitive ligands on murine monocytic WEHI-3 cells and murine neutrophils, indicating that the ligands for both selectins are glycoproteins. CSLEX-1, HECA-452, and other widely used mAbs to sLe(x) and Le(x) did not bind to WEHI-3 cells and bound at very low levels to murine neutrophils. Only the anti-sLe(x) mAbs 2H5 and KM93, which also recognize nonfucosylated glycans, bound to WEHI-3 cells. 2H5 and KM93 bound to pronase-resistant structures, indicating that the mAbs did not identify selectin ligands. Treatment of WEHI-3 cells with glycosidases or chlorate demonstrated that sialic acid modifications, alpha1-3-galactosylation, or sulfation did not mask epitopes for mAbs to sLe(x) or Le(x). Compared to human promyelocytic HL-60 cells, WEHI-3 cells and murine neutrophils expressed low alpha1-3-fucosyltransferase activities. Consistent with very low endogenous fucosylation, forced fucosylation of intact WEHI-3 cells or murine neutrophils by exogenous alpha1-3-fucosyltransferase FTVI and GDP-fucose created many new epitopes for anti-sLe(x) mAbs such as HECA-452 and CSLEX-1. Nevertheless, forced fucosylation of intact cells did not significantly augment their ability to bind to fluid-phase P- or E-selectin or to roll on immobilized P- or E-selectin under flow. These data suggest that murine myeloid leukocytes fucosylate only a few specific glycans, which interact preferentially with P- and E-selectin.     

A computational model of muscle recruitment for wrist movements

To execute a movement, the CNS must appropriately select and activate the set of muscles that will produce the desired movement. This problem is particularly difficult because a variety of muscle subsets can usually be used to produce the same joint motion. The motor system is therefore faced with a motor redundancy problem that must be resolved to produce the movement. In this paper, we present a model of muscle recruitment in the wrist step-tracking task. Muscle activation levels for five muscles are selected so as to satisfy task constraints (moving to the designated target) while also minimizing a measure of the total effort in producing the movement. Imposing these constraints yields muscle activation patterns qualitatively similar to those observed experimentally. In particular, the model reproduces the observed cosine-like recruitment of muscles as a function of movement direction and also appropriately predicts that certain muscles will be recruited most strongly in movement directions that differ significantly from their direction of action. These results suggest that the observed recruitment behavior may not be an explicit strategy employed by the nervous system, but instead may result from a process of movement optimization.     

Posterior reversible encephalopathy syndrome in a patient with hepatitis B induced type 1 membranoproliferative glomerulonephritis

Posterior reversible encephalopathy syndrome (PRES) is a rare complication of nephrotic syndrome and corticosteroid therapy. Here, we discuss an 18 year old man with type 1 membranoproliferative glomerulonephritis (MPGN) secondary to hepatitis B infection who developed posterior leukoencephalopathy while on therapy with lamivudine and prednisone. He developed seizures and vision loss. He also had hypertension, but no sudden elevation was recorded at any time. Magnetic resonance imaging revealed patchy areas of altered signal intensity involving cortical gray and subcortical white matter in the bilateral frontoparietal regions, occipital cortices, temporal cortices and cerebellar hemispheres, and hyperintensity on T2W and FLAIR sequences. Tapering of prednisone and controlling hypertension resulted in clinical improvement within a few days, and in a month MRI was normal. Diagnosing PRES requires a high index of suspicion when treating similarly susceptible patients. PRES as a complication during the treatment of MPGN secondary to hepatitis B has, to our knowledge, never been reported previously in the literature.     

Intraoperative Inguinal Measurements to Estimate a Single Optimal Mesh Size for Lichtenstein Inguinal Hernioplasty: an Observational Study

In inguinal hernia surgery, use of optimal mesh size during Lichtenstein hernioplasty technique is essential in preventing recurrence. This study was an attempt to determine a single optimal mesh size which can be adapted in vast majority of cases based on intraoperative inguinal measurements. This observational study was done for 1 year in the Department of Surgery, KLES Dr. Prabhakar Kore Hospital and Medical Research Centre, Belagavi, India. A total of 60 patients aged above 18 years who were scheduled for elective inguinal hernioplasty using the Lichtenstein technique for direct or indirect inguinal hernia were subjected to intraoperative measurements. All the patients were male with mean age of 52.75 ± 15.39 years. Mean body mass index (BMI) was 24.51 ± 3.10 kg/m². With regard to hernia characteristics, most of the patients had right-sided hernia (61.7%), indirect (51.67%), and incomplete hernia (81.67%). The mean width of mesh required was 6.65 ± 0.24 cm and mean length was 13.75 ± 0.25 cm. The mesh size was comparable with respect to demographic characteristics, anthropometry, BMI, and type and extent of hernia (p > 0.050) but age and length of mesh size varied significantly in patients with direct and indirect type of hernia (p < 0.050). The present study made an attempt to determine a single optimal mesh size in cases who underwent inguinal hernia repair based on the principles of Lichtenstein hernioplasty, which being 6.7 cm × 13.8 cm. Another significant finding was varying in mesh length size between direct and indirect hernias.     

Hepato-pulmonary amebiasis: a case report

Infections with Entamoeba histolytica are seen worldwide and are more prevalent in the tropics. About 90% of infections are asymptomatic, and the remaining 10% produce a spectrum of clinical syndromes, ranging from dysentery to abscesses of the liver or other organs. Extra-intestinal infection by E. histolytica most often involves liver. Pleuro-pulmonary involvement, seen as the second most common extra-intestinal pattern of infection, is frequently associated with amebic liver abscess. Pulmonary amebiasis occurs in about 2-3% of patients with invasive amebiasis. We report herein the case of a 45-year-old male presenting with hepato-pulmonary amebiasis. The diagnosis was established from direct examination of sputum, in which trophozoites of E. histolytica were detected, and by serology. Following treatment with metronidazole and chloroquine, the clinical evolution improved significantly. On regular follow-up visits, the patient was asymptomatic. This case report reiterates the need for collaboration between clinicians and microbiologists for timely diagnosis of such infections.