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Biomedical subjects

M Tu

Publications and source records attributed to M Tu.

10 recordsLinked to original sources
PubMed1994

MODULATION OF NEGATIVE WORK OUTPUT FROM A STEERING MUSCLE OF THE BLOWFLY CALLIPHORA VICINA

Of the 17 muscles responsible for flight control in flies, only the first basalar muscle (b1) is known to fire an action potential each and every wing beat at a precise phase of the wing-beat period. The phase of action potentials in the b1 is shifted during turns, implicating the b1 in the control of aerodynamic yaw torque. We used the work loop technique to quantify the effects of phase modulation on the mechanical output of the b1 of the blowfly Calliphora vicina. During cyclic length oscillations at 10 and 50 Hz, the magnitude of positive work output by the b1 was similar to that measured previously from other insect muscles. However, when tested at wing-beat frequency (150 Hz), the net work performed in each cycle was negative. The twitch kinetics of the b1 suggest that negative work output reflects intrinsic specializations of the b1 muscle. Our results suggest that, in addition to a possible role as a passive elastic element, the phase-sensitivity of its mechanical properties may endow the b1 with the capacity to modulate wing-beat kinematics during turning maneuvers.

Journal Article↗
PubMed1990

Developmental incompatibility between cell nucleus and cytoplasm as revealed by nuclear transplantation experiments in teleost of different families and orders.

Teleosts from different families and orders were used as materials for nuclear transplantation experiments. (1) The nuclei of goldfish (Carassius auratus, family Cyprinidae, order Cypriniformes) were transplanted into the enucleated egg cytoplasm of loach (Paramisgurnus dabryanus, family Cobitidae, order Cypriniformes) and vice-versa. (2) The nuclei of Tilapia (oreochromis nilotica, order Perciformes) were transplanted into the enucleated egg cytoplasm of goldfish (Carassius auratus, order Cypriniformes). The chromosome number of the nucleus donor fish is different from that of the cytoplasmic recipient fish in each of the two combinations. In the first case, only a few early nucleo-cytoplasmic hybrid (NCH) larval fish were obtained in each combination. In second case, even though a high percentage of NCH blastulas were also obtained, the majority of them died at the same developmental stage, except a few which survived until early gastrula stage. The examination of the metaphase chromosome figures of the NCH blastulas or embryos obtained in all three combinations indicated that they were of nucleus-donor type. The developmental rates of all the NCH eggs were similar to those of cytoplasmic-recipient type. Scanning electronmicroscopy examination showed that the morphology of NCH blastula cells, which were obtained from the combination of Tilapia nucleus and goldfish cytoplasm, manifested obviously abnormal features and the cells were arrested at different stages of cell disintegration. Two-dimension polyacrylamide gel electrophoretograms of the homogenates of Tilapia, goldfish and their NCH blastula cells showed that the protein synthetic pattern of NCH blastula was similar to that of Tilapia nucleus type. The results of experiments which failed to obtain NCH adult fish in all three combinations can be explained as a result of developmental incompatibility between the donor nucleus and the enucleated recipient egg cytoplasm, which were from distantly related fish species. And the chromosome numbers of all the component fish of the three combinations which were examined in the experiment and shown to be quite different from each other in the tested fish, should not be overlooked as one of the essential factors causing the developmental incompatibility in NCH fish in this experiment.

Animals↗
PubMed1985

Expression of organ-specific antigens on capillary endothelial cells.

Our central thesis is that the endothelial cells which line capillaries of various organs are not all alike. Using monoclonal and conventional antibodies we demonstrate that capillary endothelial cells express on their cell surface an array of antigens that manifest organ selectivity. Brain-derived endothelial cells possess brain-associated antigens, ovary-derived endothelial cells share antigenic markers with other ovarian cells, and lung-derived endothelium possesses antigens that are primarily expressed on cells of the lung. Our experiments lead us to suggest that organ-associated determinants on the endothelial cell surface may play a role in the selective adhesion of tumor cells during metastasis, in site-limited vascular pathology, and in the regionally limited release of angiogenesis-induced factors.

Animals↗
PubMed1985

A teratocarcinoma-derived endoderm stem cell line (1H5) that can differentiate into extra-embryonic endoderm cell types.

We investigated the ability of the teratocarcinoma-derived, epithelial-type cell line 1H5 to differentiate into either of the two pathways to primary endoderm, and tested the hypothesis that 1H5 represents a state similar to primitive endoderm in the late 4th-day blastocyst. Like other endodermal cell types, 1H5 cells mixed with embryonal-carcinoma cells sort out into "embryoid bodies" or structures that resemble 4th-day mouse embryos. The epithelial line conforms morphologically and biochemically to the few known characteristics typical of primitive endoderm. The present study demonstrates that the formation in vitro of overt visceral endoderm is readily achieved. The spontaneous arrangement of the cells into a cystic form is followed by the appearance of several markers of visceral endoderm, most notably alphafetoprotein, which is detected when 1H5 cells are cultured either in the presence of retinoic acid or when the cells interact with embryonal-carcinoma cells in a specific spatial arrangement after sorting out. However, some less specific properties of visceral endoderm are not expressed. Although 1H5 differentiates histologically into parietal-like endoderm in the tumor form, parietal cells cannot yet be identified with certainty in vitro because of the paucity of parietal-specific markers. The 1H5 cell line could provide a useful system for studying the characteristics and mechanisms underlying visceral-endoderm differentiation in vitro, since it has the distinct advantage that homogeneous cultures are produced, in contrast to other teratocarcinoma cell lines such as F9 which differentiate into a mixture of cell types.

Animals↗
PubMed1982

Monoclonal antibody against angiotensin-converting enzyme: its use as a marker for murine, bovine, and human endothelial cells.

A monoclonal antibody has been prepared against rat angiotensin-converting enzyme (ACE). By selection for antibody binding to endothelial cells of bovine rather than rat origin we have obtained a reagent that has broad cross-species binding properties and that can at the same time serve as a useful marker for the surface of endothelial cells. The IgM-producing clone that we have established, alpha-ACE 3.1.1, has been grown in ascites form to yield ascites fluid that binds selectively to immobilized ACE at a greater than 1:10,000 dilution. By use of enzyme-linked immunosorbent assays, immunofluorescence histology, and flow cytometry, we have demonstrated the presence of ACE on endothelial cells of murine, bovine, and human origin. By means of a fluorescence-activated cell sorter (FACS-IV) we have been able to selectively isolate viable endothelial cells from a mixture of endothelial cells and fibroblasts. We believe the antibody will be useful not only for the selection and in vitro cultivation of endothelial cells but also as a tool for the identification and pharmacological study of ACE.

Animals↗
PubMedDate not supplied

META. 3. A genetic algorithm for metabolic transform priorities optimization.

META is a knowledge-based expert system that simulates the biotransformation of xenobiotics. It operates with the help of a dictionary (knowledge base) to seek target fragments in a compound and transform them to products. Here, a genetic algorithm is introduced to help build the knowledge base and optimize the performance of the methodology.

Algorithms↗