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Biomedical subjects

S Mohan

Publications and source records attributed to S Mohan.

At least 289 records · Page 16Linked to original sources
PubMed1983

Wild mouse retrovirus-induced neurogenic paralysis in laboratory mice. I. Virus replication and expression in central nervous system.

Ecotropic wild mouse retrovirus (1504 M)-induced neurogenic paralytic disease has been studied in inbred strains of mice. The major criterion for the successful transmission of the disease in the laboratory strains of mice is inoculation of high titer ecotropic virus in FV-1n strains of mice at newborn stage (less than or equal to 1 day old), Hybridization studies using 1504 M viral cDNA as probe indicate that in nonparalyzed mice, the inoculated virus replicates primarily in spleen tissue, whereas virus replication is evident in both spleen and central nervous system (CNS) tissue of paralyzed mice. Our studies on virus gene expression indicate that both viral gag gene product p30 and env gene product gp70 are expressed in brain, spinal cord and spleen tissues of paralyzed mice. Together, these results indicate that inoculation of neurotropic wild mouse virus into FV-1n strains of newborn laboratory mice is necessary for the establishment of infection in CNS tissue leading to virus replication and expression and resulting in the paralytic disease.

Animals↗
PubMed1982

Binding studies of a sialic acid-specific lectin from the horseshoe crab Carcinoscorpius rotunda cauda with various sialoglycoproteins.

Interaction of the sialic acid-specific lectin carcinoscorpin with various sialoglycoproteins was studied by using radioiodinated lectin. The binding of carcinoscorpin was dependent not only on sialic acid content but also on the type of glycosidic linkage and form (branched or linear) of the carbohydrate chains. Carcinoscorpin has different classes of binding sites, and binding follows a phenomenon of positive co-operativity. The effect of Ca2+ concentration on the binding was studied, and the optimal concentration was found to be 0.02 M. Effect of pH, temperature and other bivalent metal ions are also reported. From haemagglutination- and precipitation-inhibition studies, it was concluded that carcinoscorpin has multispecificity towards acidic sugars, and its relation to the biological role of the lectin in the horseshoe crab is discussed.

Animals↗
PubMed1982

Binding characteristics of wild mouse type C virus to mouse spinal cord and spleen cells.

Binding characteristics of mouse spinal cord and spleen cells to naturally occurring, ecotropic (paralytogenic and lymphomagenic 1504M virus) and amphotropic (lymphomagenic 1504A virus) retroviruses of wild mice were investigated. 125I-labeled ecotropic (N-tropic) virus bound efficiently to both spinal cord and spleen cells from SWR/J mice (Fv-1n), but labeled amphotropic (N-tropic) virus bound efficiently only to spleen cells. The extent of binding of 1504M virus to the spinal cord cells was related to the time of incubation and to the amount of labeled input virus. 1504M virus bound to both glial and neuronal subpopulations of the spinal cord with almost equal efficiency. Binding of 125I-labeled 1504M virus to SWR/J mouse spinal cord cells was competitively inhibited by unlabeled homologous virus, whereas an excess of unlabeled 1504A virus inhibited only 10% of the ecotropic virus binding. Unlabeled 1504M virus almost completely inhibited the low-level binding of 125I-labeled 1504A virus to spinal cord cells. The different extent of binding of 1504M virus to spinal cord cells from different strains of mice (SWR/J, NIH Swiss, BALB/c-Jax, Lake Casitas wild, and CD-1) correlated with the susceptibility to paralysis in these strains of mice after inoculation with 1504M virus. Although the spinal cord cells of BALB/c mice contained a moderate amount of 1504M virus receptor sites, these mice were resistant to virus-induced paralysis because of their Fv-1b genotype. Our results indicate that the receptor sites for wild mouse ecotropic retrovirus are strain and organ specific and suggest that the presence of such receptors in central nervous system tissue may be a prerequisite for a successful virus infection and paralysis induction in Fv-1n mice.

Animals↗
PubMed1980

Age-related changes in rat muscle collagen.

Age-related studies of collagen in slow, fast and cardiac muscle of the rat indicate that different fractions of collagen as well as total collagen content vary with age and type of muscle. The total collagen level increases by 30% in slow, 40% in fast and 50% in cardiac muscle as age advances from 5 to 25 months. Collagen of the muscles of old animals is less susceptible to the collagen-degrading enzyme when compared to the young, and the activity of the enzyme decreases significantly with age. The decrease in (1) the solubility of collagen; (2) the amount of hydroxyproline released at 65 degrees C, and (3) the increase in the resistance of collagen to the degrading enzyme seen with aging, indicates that the stability of collagen increases in these muscles with aging.

Aging↗
PubMed1980

Age-related changes in cardiac muscle of rat.

Study of the age-related changes in cardiac muscle of 5, 10, 15, 20, and 25 months old albino rats showed that the muscle mass decreased by 10% while the ratio of the weight of cardiac muscle to body weight decreased by 30% between 5 and 25 months. Autolytic and proteolytic activity of sarcoplasmic proteins increased remarkably (70% and 200%, respectively) between 5 and 25 months of age. Although the total protein content decreased, the amount of fibrous protein (collagen) increased by 50%. Levels of salt soluble and labile collagen (free hydroxyproline released at 65 degrees C in Ringer solution) decreased by 65% and 50%, respectively, while insoluble collagen increased by 180% with advance in age from 5 to 25 months. Increase in acid soluble collagen was seen only up to 20 months of age. The acid mucopolysaccharide content decreased, whereas the activity of beta-glucuronidase showed an increase from 110-148 units between 10 and 15 months of age. beta-N-acetylglucosaminidase increased by 25% as the age increased from 5 to 25 months.

Age Factors↗
PubMed1979

The occurrence and treatment of false positive reactions in enzyme-linked immunosorbent assays (ELISA) for the presence of fungal antigens in clinical samples.

Non-specific positive reactions have been revealed in enzyme-linked immunosorbent assays (ELISA) of sera for the presence of fungal antigen. These false positives were recognized by their occurrence in tests for both Candida albicans and Aspergillus fumigatus antigens and by their response to dithiothreitol, combined with their reaction with non-immune rabbit globulin. A scheme is proposed which differentiates between true and false positive reactions. Use of fractionated anti-fungal globulin in conjugates reduced the incidence of false positive results in sera from hospitalized patients and eliminated them from sera of healthy subjects. The test scheme was applied to two panels of sera containing samples from patients with (a) invasive candidosis and (b) invasive aspergillosis. The relevance of ELISA tests for the detection of fungal antigen in human serum is discussed.

Animals↗
PubMed1978

Age related changes in muscle protein degradation.

In vitro autolytic degradation of sarcoplasmic proteins in red, white and cardiac muscles increases with advance in age and with increase in temperature, the rate varying with age. Higher activity is seen in the alkaline range in all age groups. Ca2+ activated proteolytic activity also increases with advance in age.

Aging↗
PubMed1975

Collagen in aging muscles.

The salt, acid and insoluble collagen fractions were estimated in red, white and cardiac muscles of 10-, 15- and 20-month-old albino rats. The total collagen level with reference to total proteins is more in red than in white and cardiac muscle. Accumulation of more of insoluble collagen and decrease in salt extractable collagen is seen in all three muscles with aging.

Aging↗
PubMedDate not supplied

Temperature differentially affects encounter and docking thermodynamics of antibody--antigen association.

Using BIACORE SPR, we have examined the mechanism of temperature effects on the binding kinetics of two closely related antibody Fabs (H10 and H26) which recognize coincident epitopes on hen egg-white lysozyme (HEL), and whose association and dissociation kinetics are best described by the two-step conformational change model which we interpret as molecular encounter and docking. Time-course series data obtained at a series of six temperatures (6, 10, 15, 25, 30 and 37 degrees C) showed that temperature differentially affects the rate constants of the encounter and docking steps. Docking is more temperature-sensitive than the encounter step, and energetically less favorable at higher temperatures. At elevated temperatures, the time required for docking is longer and the apparent increase in off-rate reflects the greater proportion of the molecules failing to dock and remaining in the less stable encounter state. As a consequence, distribution of free energy change between the encounter and docking steps is altered. At physiological temperature (37 degrees C) the docking step of the H26 complex is energetically unfavorable and most complexes essentially do not dock. There is a significant decrease in total free energy change of the H26 complex at higher temperatures. Elevated temperature changes the rate-limiting step of H26--HEL association from the encounter to the docking step, but not that of H10--HEL. Our results indicate that the mechanism by which elevated temperature reduces the affinities of antigen--antibody complexes is to decrease the net docking rate, and/or stability of the docked complex; at higher temperatures, a smaller proportion of the complexes actually anneal to a more stable docked state. This mechanism may have broad applicability to other receptor--ligand complexes.

Antigen-Antibody Complex↗
PubMedDate not supplied

Wandering spleen with torsion: appearance on CT and ultrasound.

Wandering spleen is a rare entity which may present with symptoms suggestive of other, more common abdominal processes. Torsion of the long pedicle may occur causing abdominal pain. This article describes a case of wandering spleen diagnosed by computed tomography (CT). Liver spleen scintigraphy and sonography supported this diagnosis and suggested torsion. To our knowledge this is only the second case of this entity in which color flow and duplex Doppler findings have been reported.

Humans↗
PubMedDate not supplied

Parathyroid hormone-related protein: primary osteolytic factor produced by breast tumor cells in vitro?

Tumor cells in bone metastases are thought to induce bone resorption primarily by releasing paracrine factors. Parathyroid hormone related protein (PTHrp) has been proposed to mediate osteolytic activity of many tumors. PTHrp is produced by 40% to 60% of breast tumors and is elevated in the serum of up to 50% of patients with breast cancer metastases to bone. Most biologic processes in humans are heterogeneous in nature, so the purpose of this study was to investigate the hypothesis that paracrine factors other than PTHrp could mediate bone resorption by breast tumor cells. Serum-free conditioned medium (CM) was collected from five human breast tumor cell lines and tested for bone resorption-stimulating activity (BRSA) in mouse calvaria organ cultures. CM from all tumor cells studied produced significant bone resorption, comparable to that produced by 10 nM PTH. Small amounts of immunoreactive PTHrp (1.4-12.5 pM) were produced by all breast tumor cell lines. When tested in vitro, equivalent amounts of human PTHrp [1-36] did not produce significant bone resorption. Indomethacin (1 microM) significantly blocked BRSA by CM from all cell lines but did not decrease BRSA by PTHrp. In contrast PTHrp antibody (130 micrograms/ml) completely blocked BRSA by 1 nM PTHrp but did not modify BRSA by CM of breast tumor cells. The results of this study support the hypothesis that breast cancer cells release paracrine factors in vitro that stimulate bone resorption by a mechanism that is partially dependent on prostaglandin synthesis and at least in part different from that of PTHrp.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies↗