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Biomedical subjects

R S Menon

Publications and source records attributed to R S Menon.

At least 19 recordsLinked to original sources
PubMed1992

31P NMR spectroscopy of the human heart at 4 T: detection of substantially uncontaminated cardiac spectra and differentiation of subepicardium and subendocardium.

31P NMR spectroscopy of the human heart was undertaken at 4 T to investigate whether spectra localized exclusively to the myocardium can be obtained. Utilizing a Fourier series window approach to spectroscopic imaging, we find that at least two layers across the anterior left ventricle wall can be detected, with voxel sizes of about 8 cm3.

2,3-Diphosphoglycerate↗
PubMed1992

Proton relaxation studies of water compartmentalization in a model neurological system.

Proton relaxation measurements from 18 crayfish abdominal nerve cords (a model of human CNS) are used to demonstrate that the transverse (though not the longitudinal) relaxation can be decomposed into four reproducible components that, in conjunction with optical and electron microscopy of the morphology, can be assigned to three water compartments within the cord and possibly to the mobile lipid protons. The assignments are extraaxonal water protons (32 +/- 9% and mean T2 = 600 +/- 200 ms), axonal water protons (59 +/- 12% and mean T2 = 200 +/- 30 ms), intramyelinic water protons (7 +/- 4% and mean T2 = 50 +/- 20 ms), and finally an unsubstantiated assignment of lipid protons (2.0 +/- 2.0% and mean T2 = 7 +/- 4 ms).

Algorithms↗
PubMed1992

Regional localization of human beta-casein gene (CSN2) to 4pter-q21.

Milk proteins are crucial for the development of all newborn mammals. Caseins that constitute the bulk of the protein in mammalian milk have been shown to be members of a multigene family in at least two species. They are among the most rapidly diverging groups of proteins, and their numbers vary widely among species. beta- and kappa-Caseins are the only caseins present in human milk. Using polymerase chain reaction on genomic DNA from somatic cell hybrids, we have localized the human beta-casein gene (CSN2) to 4pter----q21.

Blotting, Southern↗
PubMed1992

Exon skipping in human beta-casein.

Earlier amino acid alignments of mature beta-caseins showed that the human protein was shifted in alignment relative to other species, with amino acid deletions in the N-terminal region and others inserted in the C-terminal region. Our alignment, based on cDNA sequences and their translation products, has shown that the amino acid deletions correspond exactly to exon 3 in the other species. Cloning and sequencing of a segment of the human beta-casein gene between exons 2 and 4 revealed the presence of an intact exon 3 sequence in the gene. An interruption of the polypyrimidine tract adjacent to the 5' end of exon 3 sequence may account for the omission of the exon from human beta-casein mRNA.

Amino Acid Sequence↗
PubMed1992

Functional brain mapping using magnetic resonance imaging. Signal changes accompanying visual stimulation.

Easily detectable (5%-20%) transient increases in the intensity of water proton magnetic resonance (MR) signals in human primary visual cortex were observed during visual stimulation in gradient echo images at 4-T field strength. The signal intensity increases were predominantly restricted to areas containing gray matter and were used to produce high-spatial-resolution human functional brain maps. Time dependence of the functional brain maps also was monitored during visual stimulation using images acquired every approximately 5 seconds; these images with high spatial and temporal resolution demonstrated that photic stimulation first resulted in signal increases in a large area of the visual cortex followed by a reduction in the size of the area, and that signal intensity increases in the gray matter were time dependent. Reducing the image acquisition echo times reduced the amplitude of the fractional signal change, suggesting that it is produced by a change in T2 or T2*. The amplitude, sign, and echo time dependence of these intrinsic signal changes are consistent with the idea that neural activation increases regional cerebral with the idea that neural activation increases regional cerebral blood flow (rCBF) with a concomitant increase in venous blood oxygenation.

Brain Mapping↗
PubMed1992

Pathology of soft tissue sarcomas. An introduction.

Recent progress in molecular biology, cytogenetics, classification and grading of soft tissue sarcomas is briefly reviewed. It is emphasized that peer review of histopathology is highly desirable. Finally, equipped with modern imaging techniques, the radiologist can anticipate an increasing role in the aspiration cytology of deep seated soft tissue tumors.

Biopsy, Needle↗
PubMed1991

Multiexponential proton relaxation in model cellular systems.

Water proton relaxation measurements obtained from model cellular systems composed of red blood cell (RBC) ghosts are presented. The purpose of the investigation was to evaluate hypotheses concerning the possible sources of multiple exponential components in similar relaxation measurements made on tissue. Both laboratory frame transverse and longitudinal relaxation rates, as well as rotating frame relaxation rates, were measured in preparations of RBC ghosts and "extracellular fluid" that were, (a) uniformly mixed or (b) compartmentalized by layering, as the concentration of serum albumin was varied in the "extracellular fluid." The data show that although transmembrane exchange is too fast to give rise to multiexponential relaxation, multiple components can result from compartmentalization at the level of the cellular organization and do not necessarily require different tissue types. In addition, the data clearly demonstrate the importance of protein adsorption to cellular membranes as a determinant of the concentration of freely mobile solute protein molecules in tissue fluids.

Erythrocyte Membrane↗
PubMed1991

Application of continuous relaxation time distributions to the fitting of data from model systems and excised tissue.

Biological systems exhibit heterogeneity at many different levels, leading to the expectation of multiple relaxation time components for water protons in tissue samples. Traditional methods which fit the relaxation data to an a priori number of discrete components are open to observer bias in their interpretation of this data, and moreover, are intuitively less realistic for heterogeneous systems than methods which produce continuous relaxation time distributions. Previous validations of continuous distribution techniques have been made on simulated data assuming uniform Gaussian noise. In the current work we have investigated the ability of one particular linear inverse theory technique to reproduce known relaxation time distributions from the data on a controllable model system. Furthermore, using the experience gained on the model system, we have applied this same technique to the analysis of in vitro relaxation time measurements on excised brain tissue and found for water protons in white matter, four reproducible components for the transverse relaxation, whereas gray matter gave rise to only two. The longitudinal relaxation displayed only one component in either white matter or gray matter.

Algorithms↗
PubMed1990

Solvent proton relaxation of aqueous solutions of the serum proteins alpha 2-macroglobulin, fibrinogen, and albumin.

The longitudinal, transverse, and spin-locked rotating frame relaxation rates have been measured for water protons in aqueous solutions of the human serum proteins albumin, fibrinogen, and alpha 2-macroglobulin in the physiological concentration range below 50 g/liter, corresponding to an upper limit for molarity of 725, 147, and 69 microM, respectively. The linear concentration dependence of all the relaxation rates measured at 100 MHz was used to provide the molar sensitivities of each relaxation process for each of the protein solutes. Both the solute dependence and the relaxation-process dependence of the molar sensitivities have been analyzed in terms of a model that has emerged from previous R1 dispersion measurements. This analysis demonstrates consistency between our data and that model for the active motions and their motional rates.

Fibrinogen↗
PubMed1990

Strongyloides stercoralis associated with a bleeding gastric ulcer.

Infection with the helminthic parasite, Strongyloides stercoralis, is usually acquired by skin invasion (or occasionally via ingestion of larvae). After transformation to the adult form, the parasite preferentially localises in the small intestine, especially in the duodenal and jejunal part. A remarkable feature of Strongyloides is its property of endogenous reinfection. In the case of an immunocompromised host a massive infection, called hyperinfections Strongyloides, may occur. Numerous gastrointestinal complications of strongyloides infections, sometimes with a lethal outcome, have been reported. The intestinal manifestations are usually limited to the small bowel, and rarely involve the stomach. We report a patient with complicated strongyloides infection of the stomach.

Aged↗
PubMed1989

Cancer of the breast with nipple involvement.

In the absence of gross deformity of the nipple, such as its retraction or Paget's disease, histological examination of this area is often neglected, or at best confined to a cursory look at a single sagittal section. The inadequacy of this approach is illustrated by this study of 33 consecutive cases of carcinoma of the breast treated with mastectomy. Multiple transverse sections showed tumour in 19 nipples (58%) involving one or more levels. Of these, 17 showed non-invasive tumour, either ductal or lobular type. Invasive tumour was seen in only two nipples, one of which was metastatic extension from the underlying breast tumour. Paget's cells were seen in two cases. The most significant finding was the eccentric location of tumour in 14 nipples. A single central sagittal section would have detected only five cases involving the centrally situated duct. An inexplicable finding was a preponderance of right nipple with tumour. No statistically significant correlation between nipple involvement and the size, location, multicentricity, type of tumour in the breast and metastases in axillary lymph nodes could be found. It became evident from this study that malignant changes in the nipple occur more commonly than is realised, and that it is also one of the sites of multicentric origin of the tumour. This factor will have to be taken into account in planning conservative therapeutic programmes.

Breast↗
PubMed1989

Thymoma: a clinico pathological study of 21 cases and assessment of prognostic features.

This is a retrospective and comprehensive study of 21 cases of thymoma treated during a period of 30 years (1954-1984). The tumors were staged into 3 categories: stage 1 for encapsulated completely resectable tumor, stage 2 for nonresectable intrathoracic tumor and stage 3 for tumor with extrathoracic spread. According to their lymphocytic content tumors were separated into 3 groups: 1) predominantly epithelioid (PE); 2) mixed cellular (MC) and predominantly lymphocytic (PL). Incidence of recurrence and survival were correlated with various treatment modalities. The tumor occurred in all age groups with highest incidence in the fourth decade. Six cases were asymptomatic. Myasthenia gravis was present only in one case. The most important prognostic factor was the stage of the tumor. Five-year survival was 69% for stage 2 and 0% for stage 3. All 12 patients who died with evidence of residual disease had PE tumors. Lymphocytic participation might be indicative of a residual functional competence and appears to confer a more favourable prognosis. This is a tumor of uncertain malignant potential which should be excised or debulked, and staged. Post-operative radiotherapy appears to prevent recurrence and improve the prognosis in stage 2. No therapeutic benefits were seen in the stage 3 cases. The value of chemotherapy is uncertain.

Adolescent↗
PubMed1986

Absence of IgA nephropathy in patients with ankylosing spondylitis.

In 40 patients with ankylosing spondylitis (AS) no evidence for IgA nephropathy was obtained. This conclusion was based on the absence of hematuria and on the inability to find an increased incidence of IgA-containing immunoglobulin deposits in skin biopsies. Increased Clq binding assay was only found in those AS patients with anterior uveitis. In 26% of the skin biopsies perivascular mononuclear cell infiltrates were observed, and immunoglobulin deposits were seen in 65%. These facts suggest that the immunologic system is involved in the pathogenesis of this disease.

Adult↗