The Ultrastructure of Myocardial Cells in Normal and Cardiac Lethal Mutant Mexican Axolotls, (Ambystoma Mexicanum)

1970 ◽  
Vol 28 ◽  
pp. 62-63
Author(s):  
Larry F. Lemanski ◽  
Eldridge M. Bertke ◽  
J. T. Justus
Keyword(s):  
Fine Structure ◽  
Heart Development ◽  
Osmium Tetroxide ◽  
Picric Acid ◽  
Ambystoma Mexicanum ◽  
Recessive Mutation ◽  
Acid Mixture ◽  
Myocardial Cells ◽  
Lethal Mutant ◽  
Mexican Axolotl

A recessive mutation has been recently described in the Mexican Axolotl, Ambystoma mexicanum; in which the heart forms structurally, but does not contract (Humphrey, 1968. Anat. Rec. 160:475). In this study, the fine structure of myocardial cells from normal (+/+; +/c) and cardiac lethal mutant (c/c) embryos at Harrison's stage 40 was compared. The hearts were fixed in a 0.1 M phosphate buffered formaldehyde-glutaraldehyde-picric acid-styphnic acid mixture and were post fixed in 0.1 M s-collidine buffered 1% osmium tetroxide. A detailed study of heart development in normal and mutant embryos from stages 25-46 will be described elsewhere.

Z Bands in Developing Heart Muscle of the Mexican Salamander, Ambystoma mexicanum

1972 ◽  
Vol 30 ◽  
pp. 24-25
Author(s):  
Larry F. Lemanski
Keyword(s):  
Plasma Membranes ◽  
Picric Acid ◽  
Structural Features ◽  
Ambystoma Mexicanum ◽  
Acid Mixture ◽  
Myocardial Cells ◽  
Band Formation ◽  
Developing Heart ◽  
Close Proximity ◽  
Band Material

Electron-dense plaques, often seen in association with the plasma membranes of pre-heartbeat salamander myocardial cells, appear to be directly involved in early Z band formation. In differentiating myocardial cells of higher vertebrates, Z band material has been observed in close proximity to the plasma membranes and as isolated electron-dense material in the deep cytoplasm. The present study explores the fine structural features of Z band formation in salamander myocardium from early tailbud embryos (Harrison stage 25) through the adult. Hearts were fixed In a 0.1 M phosphate buffered formaldehyde-glutaraldehyde-picric acid-styphnic acid mixture and were post-fixed and embedded using standard methods.

Fine structure of the tail in the spermatozoa of the Mexican axolotl Ambystoma mexicanum

1983 ◽  
Vol 41 ◽  
pp. 564-565
Author(s):  
Ezzatollah Keyhani
Keyword(s):  
Fine Structure ◽  
Vertical Section ◽  
Neck Region ◽  
Longitudinal Section ◽  
Ambystoma Mexicanum ◽  
Present Communication ◽  
Mexican Axolotl ◽  
Extreme Degree ◽  
The Subject ◽  
Construction Zone

The structure of the spermatozoa represents an extreme degree of diversity among the various species of metazoa. This diversity is most probably a reflection of the adaptation to the variable conditions for fertilization. The Axolotl sperm consists of head and tail. The tail is the subject of the present communication. It consists of neck region, intermediary and principal pieces. I. The neck (∼10μm) is inserted in the nucleus and can be designated as a region between immediately above the mitochondria (a construction zone between nucleus and sustained filament) and the upper region of the anterior centriole. In longitudinal section (Fig.l) it consists of a pair of centrioles and a mass of granular fibrillar substance. The anterior centriole (0.26 x 0.5μm) appears free, while the posterior one is continuous with the flagellum. The appearance of two central filaments indicates the transition between posterior centriole and flagellum. In front of the centrioles,there is a mass of granulo-fibrillar substance (Fig.l) which in vertical section (Fig.4) appear to be semi-circular and relatively thick (0.3μm). The granulo-fibriliar substance protrude outward (Fig.l,3,4) and thus the term protuberance seems appropriate. II.

Heavy Meromyosin Binding Studies of Myocardial Cells in Cardiac Lethal Mutant Salamanders (Ambystoma Meximanum

1975 ◽  
Vol 33 ◽  
pp. 540-541
Author(s):  
Larry F. Lemanski
Keyword(s):  
Heart Development ◽  
Recessive Gene ◽  
Genetic Mutation ◽  
Heart Beat ◽  
Myocardial Cells ◽  
Binding Studies ◽  
Electron Microscopic ◽  
Lethal Mutant ◽  
Microscopic Studies ◽  
Gross Examination

A naturally-occurring genetic mutation, designated c for “cardiac lethal”, was discovered in Ambystoma meximanum. The effect of homozygosity for recessive gene c is the absence of a heart beat, even though initially heart development appears normal. Mutant embryos are first distinguishable form their normal siblings at Harrison stage 34, when the normals develop contracting hearts. The mutant hearts at this stage, upon gross examination appear structurally normal but fail to beat. Nevertheless, the mutants survive through stage 41, which is about 20 days beyond the heart-beat stage and exhibit normal swimming movements indicating that gene c does not affect skeletal muscle. Electron microscopic studies of normal hearts at stage 34 reveal that the myocardial cells contain organized myofibrils; these myofibrils first form directly beneath the plasma membrane. By stage 41, the normal myocardial cells contain numerous well-organized myofibrils and thus have now become highly differentiated muscle cells.

Ultrastructure of the digestive tube of the black mollie

1989 ◽  
Vol 47 ◽  
pp. 914-915
Author(s):  
Thomas Caceci ◽  
Terry C. Hrubec
Keyword(s):  
Smooth Muscle ◽  
Critical Point ◽  
Teleost Fish ◽  
Osmium Tetroxide ◽  
Picric Acid ◽  
Central American ◽  
Acid Mixture ◽  
Digestive Tube ◽  
The Common ◽  
Caudal Segment

The black mollie (Poecilia spp.) is a teleost fish found in Central American estuaries, and taxonomically related to the carps and goldfish. The common strains sold in pet stores are hybrids of P. mexicana and P. sphenops. The ultrastructure of its digestivetract has not previously been described.As with other Cyprinidontiforms, the gut is anatomically simple, consisting of a relatively undifferentiated tube from esophagus to anus. The tube is lined with a simple columnar epithelium and has an external wall composed of two layers of smooth muscle. A serosal investment covers this external muscular tunic. Six intestines were examined by scanning and transmission EM. The fish were anesthetized by chilling and opened on the left side. The gut was removed, unwound, and fixed intact in a 3.0% glutar-aldehyde/ 2.0% formaldehyde/ 2.5% picric acid mixture at RT and buffered with cacodylate at pH 7.4. After primary fixation, each intestine was arbitrarily divided into a cranial, middle, and caudal segment, and four specimens were post-fixed in osmium tetroxide, dehydrated, and embedded for TEM examination. Two specimens for SEM examination were washed, treated with 1.0% tannic acid, then post-fixed in osmium tetroxide, dehydrated, and critical-point dried through CO2.

Induction of myofibrillogenesis in cardiac lethal mutant axolotl hearts rescued by RNA derived from normal endoderm

Development ◽  
1987 ◽  
Vol 99 (2) ◽  
pp. 145-154
Author(s):  
L.A. Davis ◽  
L.F. Lemanski
Keyword(s):  
Organ Culture ◽  
Cardiac Muscle ◽  
Heart Development ◽  
Contractile Activity ◽  
Genetic Defect ◽  
Muscle Differentiation ◽  
Ambystoma Mexicanum ◽  
Normal Embryo ◽  
Heart Tube ◽  
Lethal Mutant

A strain of axolotl, Ambystoma mexicanum, that carries the cardiac lethal or c gene presents an excellent model system in which to study inductive interactions during heart development. Embryos homozygous for gene c contain hearts that fail to beat and do not form sarcomeric myofibrils even though muscle proteins are present. Although they can survive for approximately three weeks, mutant embryos inevitably die due to lack of circulation. Embryonic axolotl hearts can be maintained easily in organ culture using only Holtfreter's solution as a culture medium. Mutant hearts can be induced to differentiate in vitro into functional cardiac muscle containing sarcomeric myofibrils by coculturing the mutant heart tube with anterior endoderm from a normal embryo. The induction of muscle differentiation can also be mediated through organ culture of mutant heart tubes in medium ‘conditioned’ by normal anterior endoderm. Ribonuclease was shown to abolish the ability of endoderm-conditioned medium to induce cardiac muscle differentiation. The addition of RNA extracted from normal early embryonic anterior endoderm to organ cultures of mutant hearts stimulated the differentiation of these tissues into contractile cardiac muscle containing well-organized sarcomeric myofibrils, while RNA extracted from early embryonic liver or neural tube did not induce either muscular contraction or myofibrillogenesis. Thus, RNA from anterior endoderm of normal embryos induces myofibrillogenesis and the development of contractile activity in mutant hearts, thereby correcting the genetic defect.

Morphological Observations on Anterior Endoderm in Cardiac Mutant Mexican Salamanders (Ambystoma Mexicanum)

1975 ◽  
Vol 33 ◽  
pp. 484-485
Author(s):  
Larry F. Lemanski ◽  
Barry S. Marx
Keyword(s):  
Heart Development ◽  
Mutant Gene ◽  
Heart Beat ◽  
Ambystoma Mexicanum ◽  
Myocardial Cells ◽  
Cardiac Defect ◽  
Ultrastructural Studies ◽  
Total Absence ◽  
Reciprocal Transplants ◽  
Recessive Mutant

Humphrey reported the discovery of a recessive mutant gene, designated c for "cardiac lethal" in a dark stock of axolotls, Ambystoma mexicanum, imported from Mexico by Dr. Louis DeLanney. Homozygous recessive embryos exhibit a total absence of heart contractions even though initial heart development appears normal. Ultrastructural studies indicate that the mutant hearts fail to contract because the myocardial cells lack organized myofibrils. In further studies, Humphrey performed transplants of mutant (c/c) heart primordia into the heart regions of normal (+/+) recipients and found the cardiac defect to be corrected. When reciprocal transplants were made, no heart beat was observed. It was further shown that parabiosis of normal embryos with mutant siblings did not correct the cardiac deficiency nor were the normal parabiotic twins adversely affected by this procedure; such conjoined animals lived for up to several months and the mutant twins, except for lacking a functional heart, appeared normal.

Immunofluorescence studies for myosin, α-actinin and tropomyosin in developing hearts of normal and cardiac lethal mutant Mexican axolotls, Ambystoma mexicanum

Development ◽  
1980 ◽  
Vol 55 (1) ◽  
pp. 1-15
Author(s):  
Larry F. Lemanski ◽  
Rebecca A. Fuldner ◽  
Daniel J. Paulson
Keyword(s):  
Heart Function ◽  
Mutant Gene ◽  
Progressive Increase ◽  
Ambystoma Mexicanum ◽  
Myocardial Cells ◽  
Lethal Mutant ◽  
Normal Cells ◽  
Immunofluorescence Studies ◽  
Recessive Mutant ◽  
Mutant Cells

Recessive mutant gene c in axolotl embryos results in an absence of normal heart function. Immunofluorescence studies were done to determine the distributions of myosin, tropomyosin and α-actinin in the hearts of normal and mutant siblings. Anti-myosin specifically stains the A bands of myofibrils in normal hearts and reveals a progressive increase in myofibril organization with development. Mutant hearts display less staining for myosin than normal and localization is mainly in amorphous collections. Anti-α-actinin stains the Z lines of myofibrils in normal myocytes. Mutant cells also have significant staining for α-actinin but show no striations. Antitropomyosin intensely stains the I bands of myofibrils in normal cells; however, there is very little staining for tropomyosin in mutant hearts. Thus, mutant myocardial cells have reduced but significant amounts of actin (Lemanski, Mooseker, Peachey & lyengar, 1976) and myosin, even though non-filamentous, and substantial amounts of α-actinin. The cells appear to contain little tropomyosin.

Arrangement of Mitochondria in Spermatozoa of the Mexican Axolotl, Ambystoma Mexicanum

1973 ◽  
Vol 31 ◽  
pp. 626-627
Author(s):  
Ezzatollah Keyhani ◽  
Larry F. Lemanski ◽  
Sharon L. Lemanski
Keyword(s):  
Plasma Membrane ◽  
Sperm Motility ◽  
Substrate Oxidation ◽  
Ambystoma Mexicanum ◽  
Axial Filament ◽  
Mexican Axolotl ◽  
Middle Piece

Energy for sperm motility is provided by both glycolytic and respiratory pathways. Mitochondria are involved in the latter pathway and conserve energy of substrate oxidation by coupling to phosphorylation. During spermatogenesis, the mitochondria undergo extensive transformation which in many species leads to the formation of a nebemkem. The nebemkem subsequently forms into a helix around the axial filament complex in the middle piece of spermatozoa.Immature spermatozoa of axolotls contain numerous small spherical mitochondria which are randomly distributed throughout the cytoplasm (Fig. 1). As maturation progresses, the mitochondria appear to migrate to the middle piece region where they become tightly packed to form a crystalline-like sheath. The cytoplasm in this region is no longer abundant (Fig. 2) and the plasma membrane is now closely apposed to the outside of the mitochondrial layer.

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