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Biomedical subjects

S Chopra

Publications and source records attributed to S Chopra.

At least 109 records · Page 6Linked to original sources
PubMed1996

Alleles of the maize P gene with distinct tissue specificities encode Myb-homologous proteins with C-terminal replacements.

The maize P gene is a transcriptional regulator of genes encoding enzymes for flavonoid biosynthesis in the pathway leading to the production of a red phlobaphene pigment. Multiple alleles of the P gene confer distinct patterns of pigmentation to specific floral organs, such as the kernel pericarp and cob tissues. To determine the basis of allele-specific pigmentation, we have characterized the gene products and transcript accumulation patterns of the P-wr allele, which specifies colorless pericarps and red cob tissues. RNA transcripts of P-wr are present in colorless pericarps as well as in the colored cob tissues; however, the expression of P-wr in pericarp does not induce the accumulation of transcripts from the C2 and A1 genes, which encode enzymes for flavonoid pigment biosynthesis. The coding sequences of P-wr were compared with the P-rr allele, which specifies red pericarp and red cob. The P-wr and P-rr cDNA sequences are very similar in their 5' regions. There are only two nucleotide changes that result in amino acid differences; both are outside of the Myb-homologous DNA binding domain. In contrast, the 3' coding region of P-rr is replaced by a unique 210-bp sequence in P-wr. The predicted P-wr protein has a C-terminal sequence resembling a cysteine-containing metal binding domain that is not present in the P-rr protein. These results indicate that the differential pericarp pigmentation specified by the P-rr and P-wr alleles does not result from an absence of P-wr transcripts in pericarps. Rather, the allele-specific patterns of P-rr and P-wr pigmentation may be associated with structural differences in the proteins encoded by each allele.

Alleles↗
PubMed1996

Ablation of the pursuit area in the frontal cortex of the primate degrades foveal but not optokinetic smooth eye movements.

1. Neural pathology which impairs foveal smooth pursuit eye movements typically also degrades optokinetic pursuit of large textures, suggesting that the two kinds of pursuit share a common circuit. This study reports an exception. After sequential bilateral ablation of the pursuit area in the frontal lobe three monkeys displayed degraded pursuit of a small foveal target but performed normally on identical measures of optokinetic pursuit. 2. A related experiment in one subject demonstrated a pursuit deficit when the foveal target moved relative to the background, but not when background and target moved together. The frontal pursuit area may specifically control pursuit of relative motion, and do so by receiving signals primarily from motion detectors in the macular part of the visual field.

Animals↗
PubMed1996

Is sonographic flow imaging useful in the differential diagnosis of adrenal masses?

This prospective study was carried out to assess the ability of colour Doppler ultrasound (CDUS) and power flow imaging to differentiate between benign and malignant adrenal masses. We examined 56 adrenal masses, discovered at CT, in 47 patients who had undergone CT for known extraadrenal malignancy or unrelated benign conditions. The nature of the masses was confirmed by histopathology or assessed for likelihood of malignancy by CT appearance, MRI appearance, recent development or increase in size. In none of the adrenal masses was blood flow detected by colour Doppler or power imaging, despite optimizing scanning parameters for the detection of slow flow. We conclude that colour Doppler ultrasound and power imaging do not help in differentiating benign from malignant adrenal masses.

Adrenal Gland Diseases↗
PubMed1996

Systemic corticosteroids in the phenytoin hypersensitivity syndrome.

A patient is described with the characteristic features of phenytoin hypersensitivity syndrome (PHS) including fever, erythroderma, tibial and facial oedema, pinhead-sized facial pustules and abnormal liver function tests. The use of systemic corticosteroids in this condition is not established. We report the resolution of all the features of PHS with systemic corticosteroids and recurrence on withdrawal, and further remission on reinstitution of systemic corticosteroids.

Anti-Inflammatory Agents↗
PubMed1995

Hepatitis C: a multifaceted disease. Review of extrahepatic manifestations.

PURPOSE: To review the available data on the association between hepatitis C virus (HCV) infection and conditions reportedly related to infection with the virus and to assess the clinical implications of these associations. DATA SOURCES: Pertinent articles were identified using the Paperchase database, which simultaneously searches the MEDLINE (1966 to present), Health (1975 to present), AIDSLINE (1980 to present), and Cancerlit databases. STUDY SELECTION: All studies for a given association were reviewed, but special attention was paid to randomized controlled trials where applicable. RESULTS: According to the available data, HCV infection appears to be strongly associated with essential mixed cryoglobulinemia, membranoproliferative glomerulonephritis, and porphyria cutanea tarda. Evidence strongly suggests that HCV has a direct pathogenetic role in some patients with the first two conditions. The association with Mooren corneal ulcers and autoimmune thyroiditis is suggested, but more data are needed to confirm it. The data for the association between HCV infection and the Sjögren syndrome, lichen planus, and idiopathic pulmonary fibrosis remain weak. Although interferon therapy has been effective in patients with both essential mixed cryoglobulinemia and membranoproliferative glomerulonephritis, a high relapse rate has been noted in the latter condition. CONCLUSIONS: Patients with essential mixed cryoglobulinemia, membranoproliferative glomerulonephritis, and porphyria cutanea tarda should be tested for HCV infection. Conversely, signs and symptoms of these conditions should be sought in patients with chronic HCV infection. Interferon therapy is currently recommended only for patients with symptomatic essential mixed cryoglobulinemia.

Cryoglobulinemia↗