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Soumya Chatterjee

Publications and source records attributed to Soumya Chatterjee.

10 recordsLinked to original sources
PubMed2006

Visual spatial summation in macaque geniculocortical afferents.

The spatial summation properties of visual signals were analyzed for geniculocortical afferents in the primary visual cortex (V1) of anesthetized paralyzed macaque monkeys. Afferent input responses were recorded extracellularly during cortical inactivation through superfusion of the cortex with muscimol, allowing investigation of lateral geniculate nucleus of the thalamus (LGN) cell properties in the absence of cortical feedback. Responses from afferent inputs were classified as magno-, parvo-, or koniocellular based on anatomical organization within the cortex, established through histological reconstructions, and visual response wavelength sensitivity. More than 80% of afferents showed strong surround suppression [suppression index (SI) >0.5] and 14% showed negligible surround suppression (SI < 0.2). Afferent responses with weak and strong surround suppression were found throughout cortical input layers 4C and 4A. High-contrast estimates of the spatial extent of the classical surround were similar to the nonclassical surround. The classical and nonclassical surrounds were, on average, 1.5-fold larger than the excitatory center. Unlike neurons within V1, the spatial extent of excitatory summation for geniculocortical afferents was contrast invariant. Nonclassical surround suppression showed slight contrast dependency with estimates larger (20%) at lower contrasts and stronger at higher contrasts (13%). Surround suppression is inherent in cortical input responses and likely derives from lateral inhibition in either the LGN or retina. Although surround suppression within afferent responses increases slightly with contrast, the spatial spread of excitation remains fixed with contrast. This argues for distinct mechanisms of action for contrast-dependent modulation in cortical and subcortical responses.

Action Potentials↗
PubMed2006

Neomycin improves constipation-predominant irritable bowel syndrome in a fashion that is dependent on the presence of methane gas: subanalysis of a double-blind randomized controlled study.

Recent studies have shown that normalization of the lactulose breath test (LBT) with neomycin leads to a significant reduction in irritable bowel syndrome (IBS) symptoms. This subanalysis was done on the constipation-predominant IBS subgroup of patients (C-IBS) to test the ability of neomycin to improve constipation and its correlation with the elimination of methane on breath test. IBS subjects underwent LBT in a blinded fashion. They were then randomly allocated to neomycin or placebo groups. For the purpose of this analysis, only the C-IBS subjects were identified. They were then evaluated for global improvement, abdominal pain, and constipation severity. The ability of neomycin to eliminate methane and its associated improvement in constipation was also determined. One hundred eleven subjects meeting Rome I criteria for IBS were included in the study. Thirty-nine of these had C-IBS. Of these, 20 received placebo and 19 received neomycin. With neomycin, a global improvement of 36.7+/-7.9% was seen, compared to 5.0+/-3.2% for placebo (P < .001) in the intention-to-treat analysis. Constipation was improved by 32.6+/-9.9% with neomycin compared to 18.7+/-7.2% for placebo (P=.26). Of the original 111 subjects, 12 demonstrated methane on breath test. All 12 of these patients were constipation predominant. In the methane producers receiving neomycin or placebo, improvement in constipation was significantly greater in those receiving neomycin (44.0+/-12.3%) compared to placebo (5.0+/-5.1%) (P < .05). Treatment with neomycin improves constipation in C-IBS. This improvement depends on the presence and elimination of methane on breath test.

Adult↗
PubMed2005

Risk of malignancy in scleroderma: a population-based cohort study.

OBJECTIVE: To determine the incidence of cancer in patients with scleroderma (systemic sclerosis) and to compare those rates with cancer rates in the local population. METHODS: Cancer risk in scleroderma patients in the Detroit metropolitan area was assessed by linking patient identification codes of the Michigan Scleroderma Registry to the Metropolitan Detroit Cancer Surveillance System database. Patients were screened between the years 1973 and 2002, with additional followup to 2004. Standardized incidence ratios (SIRs) were calculated for selected malignancies (lung, liver, colon, breast, cervical, and prostate cancers, and non-Hodgkin's lymphomas), with stratification by sex and race. RESULTS: Of 934 patients in the Scleroderma Registry, 538 were included in the study based on tri-county residency (436 females and 102 males). Of these, 45 first malignancies were noted (37 females and 8 males). Lung cancer (10 cases) was found to be the most common cancer in scleroderma patients. However, its incidence was not significantly different from that in the general population of metropolitan Detroit (SIR 1.23). Other types of cancer were examined, and no significant differences were found as compared with the rates in the local population, with 1 exception: black females with scleroderma had significantly higher rates of liver cancer (SIR 45.8). CONCLUSION: Contrary to previous studies, this study did not find statistical evidence of an increased incidence of cancer in scleroderma patients, except for liver cancer. One possible reason is the high background rates of certain cancers in the metropolitan Detroit area. It may be necessary to consider local cancer rates when comparing different scleroderma cohorts.

Adult↗
PubMed2005

Severe proximal myopathy and mononeuritis multiplex in rheumatoid arthritis: manifestations of rheumatoid vasculitis.

Vascular injury is considered to be a key finding in the pathogenesis of rheumatoid arthritis (RA). Manifestations are varied depending on the vessel size and the organ system involved. Vasculitis leading to symptomatic inflammatory myositis is a rare complication of RA. We describe a 62-year-old man with seropositive erosive RA of 1-year duration, who presented with severe proximal weakness and mononeuritis multiplex. His joint disease was clinically mild at the time of presentation. Creatine kinase was normal and the electromyogram did not suggest myopathy. However, muscle biopsy revealed extensive small vessel vasculitis and severe inflammatory myositis. This report emphasizes the importance of fully evaluating patients with RA who present with proximal myopathy. The myopathy in our patient was not related to active joint disease, disuse atrophy, or complication of therapy. Rheumatoid vasculitis leading to myositis is a rare and not well-recognized complication of RA for which aggressive immunosuppressive therapy is warranted.

Arthritis, Rheumatoid↗
PubMed2005

Hurler's disease.

Hurler's disease, also known as mucopolysaccharidoses 1H, an autosomal recessive disease due to enzyme alpha-iduronidase deficiency has generally a spectrum of findings involving the eye, skeletal abnormality, organomegaly, joint stiffness, hernia, mental retardation and cardiovascular abnormalities. The two cases presented here are related to each other as brother of 9 years age and sister of 7 years of age with their parents had consanguineous marriage. On ocular examination in both the cases there was dense bilateral corneal opacities. Glycosaminoglycan's level was found to be 4 mg/mmol cr in the first case and 5 mg/mmol cr in the second case. In the first case no ocular treatment was planned and in the second case penetrating keratoplasty was the choice of management.

Child↗
PubMed2004

Increased tyrosine phosphorylation mediates the cooling-induced contraction and increased vascular reactivity of Raynaud's disease.

OBJECTIVE: Increased levels of protein tyrosine kinase (PTK) are mechanistically associated with increased contractile responsiveness to cooling. This study tests the hypothesis that increased PTK activity mediates the increased vascular reactivity to agonists and cooling associated with primary Raynaud's disease (RD). METHODS: The response of dermal arterioles isolated from control (n = 29) and RD (n = 29) subjects to contractile and dilatory agents at 37 degrees C and 31 degrees C was characterized using the microvessel perfusion technique. Fluorescence immunohistochemistry was used to measure tyrosine phosphorylation. RESULTS: At 37 degrees C, arteries from RD patients exhibited similar sensitivity to the specific alpha(2)-adrenergic agonist UK 14,304, to serotonin, and to angiotensin II. At 31 degrees C, however, the response to all 3 agonists was greater in the arterioles from the RD patients than in those from the control subjects. Agonist-induced contraction at both temperatures was reversed by cumulative addition of the PTK inhibitors genistein (1-30 microM) and tyrphostin 47 (0.1-10 microM). All arterioles from control subjects relaxed slightly in response to cooling, whereas more than half of those from RD patients contracted. This cooling-induced contraction was reversed by the cumulative addition of genistein. The 3 agonists elicited large increases in tyrosine phosphorylation only in arterial segments from RD patients at 31 degrees C. Cooling from 37 degrees C to 31 degrees C elicited a large increase in tyrosine phosphorylation in arterioles from RD patients, but not those from control subjects. All increases in tyrosine phosphorylation could be prevented by genistein. CONCLUSION: Increased tyrosine phosphorylation mediates cooling-induced contraction and the increased vascular reactivity of skin arterioles from individuals with RD.

Adrenergic alpha-Agonists↗
PubMed2003

Parallel colour-opponent pathways to primary visual cortex.

The trichromatic primate retina parses the colour content of a visual scene into 'red/green' and 'blue/yellow' representations. Cortical circuits must combine the information encoded in these colour-opponent signals to reconstruct the full range of perceived colours. Red/green and blue/yellow inputs are relayed by the lateral geniculate nucleus (LGN) of thalamus to primary visual cortex (V1), so understanding how cortical circuits transform these signals requires understanding how LGN inputs to V1 are organized. Here we report direct recordings from LGN afferent axons in muscimol-inactivated V1. We found that blue/yellow afferents terminated exclusively in superficial cortical layers 3B and 4A, whereas red/green afferents were encountered only in deeper cortex, in lower layer 4C. We also describe a distinct cortical target for 'blue-OFF' cells, whose afferents terminated in layer 4A and seemed patchy in organization. The more common 'blue-ON' afferents were found in 4A as well as lower layer 2/3. Chromatic information is thus conveyed to V1 by parallel, anatomically segregated colour-opponent systems, to be combined at a later stage of the colour circuit.

Animals↗
PubMed2002

S cone contributions to the magnocellular visual pathway in macaque monkey.

The magnocellular visual pathway is believed to receive input from long (L) and middle (M), but not short (S), wavelength-sensitive cones. Recording from neurons in magnocellular layers of lateral geniculate nucleus (LGN) in macaque monkeys, we found that magnocellular neurons were unequivocally responsive to S cone-isolating stimuli. A quantitative analysis suggests that S cones provided about 10% of the input to these cells, on average, while L:M ratios were far more variable. S cone signals influenced responses with the same sign as L and M cone inputs (i.e., no color opponency). Magnocellular afferent recordings following inactivation of primary visual cortex demonstrated that S cone signals were feedforward in nature and did not arise from cortical feedback to LGN

Action Potentials↗