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Biomedical subjects

I Reddy

Publications and source records attributed to I Reddy.

7 recordsLinked to original sources
PubMed1998

Coexpression of a constitutively active plasma membrane calcium pump with GFP identifies roles for intracellular calcium in controlling cell sorting during morphogenesis in Dictyostelium.

To examine the potential role of calcium in regulating Dictyostelium development, we reduced free cytosolic and total cell Ca2+ in Dictyostelium cells by expressing a constitutively active form of a human erythrocyte plasma membrane calcium pump. The pump-expressing cells lacked a thapsigargin-mediated increase in cytoplasmic calcium, consistent with a reduced level of total cellular Ca2+. During aggregation, the cells initially formed a large number of aggregation centers, many of which coalesced to form mounds that were smaller than those of wild-type cells, and the cells did not exhibit the normal formation of elongated aggregation streams. The majority of the mounds either arrested at this stage with the formation of small protrusions or formed very aberrant finger-like structures, indicating an essential role for cellular calcium in morphogenesis. We used pump and wild-type cells differentially labeled by expressing different wavelength (green and blue) forms of green fluorescent protein and three-dimensional (3-D) reconstruction of serial fluorescent imaging to visualize the movement of pump and wild-type cells within the aggregate. The results showed that the pump cells exhibited very aberrant cell movement and sorting within the forming mound, suggesting that the reduced cytosolic calcium affects movement required for tip formation. When allowed to form chimeric organisms with wild-type cells, pump cells preferentially localized to two bands, one at the prestalk/prespore boundary and the other in the very posterior of the organism, suggesting that pump cells are unable to properly sort. Expression of the calcium pump had little effect on the induction of prestalk- or prespore-specific genes, whereas extended treatment with EGTA blocked induction of both classes of cell-type-specific genes. Our results suggest a role for intracellular Ca2+ in controlling cell sorting and morphogenesis in Dictyostelium.

Animals↗
PubMed1998

Selective tracheal suctioning to prevent meconium aspiration syndrome.

OBJECTIVE: To analyze the incidence and outcome of meconium aspiration syndrome (MAS) at Al-Yamamah Hospital, Riyadh, Saudi Arabia, where meconium-stained babies have intrapartum obstetrical cleansing of the upper airways, following which depressed/asphyxiated babies are intubated and vigorous babies are observed for 24 h. METHOD: The total live births, records of meconium-stained neonates who had intubations and of those observed, during a 6-year period were reviewed. RESULTS: During this period, there were 85562 live births. One in 325 births (0.27%) was complicated by MAS and the mortality rate was 7%. These figures concur with the reported incidence and mortality of MAS following routine combined obstetric-pediatric suction of airways at birth. Of the 265 cases of MAS that occurred during this period, 237 were in the intubated group and 28 in the observed group. The babies of the former group had severe disease compared with that of the latter. All mortality was from the intubated group. CONCLUSION: Adequate obstetrical cleansing of the upper airway in vigorous babies may obviate the need for endotracheal intubation; intubation of depressed babies following this treatment may be useful.

Asphyxia Neonatorum↗
PubMed1995

Capping protein levels influence actin assembly and cell motility in dictyostelium.

Actin assembly is important for cell motility, but the mechanism of assembly and how it relates to motility in vivo is largely unknown. In vitro, actin assembly can be controlled by proteins, such as capping protein, that bind filament ends. To investigate the function of actin assembly in vivo, we altered the levels of capping protein in Dictyostelium cells and found changes in resting and chemoattractant-induced actin assembly that were consistent with the in vitro properties of capping protein in capping but not nucleation. Significantly, overexpressers moved faster and underexpressers moved slower than control cells. Mutants also exhibited changes in cytoskeleton architecture. These results provide insights into in vivo actin assembly and the role of the actin cytoskeleton in motility.

Actin Depolymerizing Factors↗
PubMed1995

3D analysis of cell movement during normal and myosin-II-null cell morphogenesis in dictyostelium.

To gain insights into the possible guidance mechanisms used by Dictyostelium cells as they undergo morphogenesis, we have used time-lapse computational optical-sectioning microscopy to visualize and quantify the three-dimensional (3D) trajectories of both normal (Ax2) and myosin-II-null cells. To accomplish this, we typically collected 30-60 time-lapse 3D images every 2-3 min at the earliest multicellular stage, the mound. These time-lapse data were used to generate 3D movies of morphogenesis and to construct 3D trajectories for individual cells. In contrast to previous 2D time-lapse cinematography studies which revealed predominantly spiral trajectories of Ax2 cells in the mound, we have found a complex assortment of motile behaviors: some cells jiggled in place; others appeared to follow either linear or spiral trajectories; some cells reversed their directions; and others apparently converted from one motile behavior to another. These results suggest that a number of different, potentially competing cell-guidance mechanisms are operative in the mound. To assess one molecular mechanism underlying this assortment of motile behaviors, we have examined cell locomotion in a mutant, namely, in myosin-II-null cells which never develop beyond the mound. Previous studies had shown that these cells can crawl, albeit somewhat slowly, on a 2D substrate. We also found, at the earliest stages of myosin-II-null mound formation, some directed cell locomotion. But later, as the mound condensed into a tightly packed cell conglomerate, extended cell trajectories disappeared, and instead virtually all of the cells jiggled in place. Thus, our results suggest that myosin-II is absolutely essential for normal 3D ameboid locomotion.

Animals↗