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Biomedical subjects

J Frankel

Publications and source records attributed to J Frankel.

At least 109 records · Page 6Linked to original sources
PubMed1967

Studies on the maintenance of oral development in Tetrahymena pyriformis GL-C. II. The relationship of protein synthesis to cell division and oral organelle development.

The effects of puromycin on synchronized Tetrahymena pyriformis were investigated at two different concentrations, 43 microg per ml and 430 microg per ml. The rate of incorporation of histidine-(14)C into hot TCA-insoluble material was reduced by 30% at the low concentration and by 80-90% at the high concentration. The rate of oxygen uptake was lowered by only 10-20% at both concentrations. Cell division was prevented at both concentrations, if the drug was added prior to a "transition point" at about 45 min after the end of the synchronizing treatment. Development of "anarchic field" oral primordia was arrested, while primordia in early stages of membranelle differentiation were resorbed. Resorption began shortly after addition of the drug, and proceeded most rapidly at the lower concentration. If the drug was added after the "transition point," cell division and oral primordium formation were completed with only slight delay at the low concentration, and with considerable delay (in some cases complete arrest) at the high concentration. The results thus indicate that protein synthesis is involved in the later as well as the earlier stages of development; what specially characterizes the earlier stages, prior to the "transition point," is a dramatic response to partial inhibition of protein synthesis. It is suggested that this response involves the activation or release of a latent intracellular degradative system which is specific for developing structures.

Amino Acids↗
PubMedDate not supplied

Oral assembly in left-handed Tetrahymena thermophila.

We have investigated oral development in a non-genetically derived left-handed (LH) form of Tetrahymena thermophila, in which the large-scale asymmetry of arrangement of cortical structures is reversed whereas the local asymmetry of ciliary architecture remains normal. Approximately 1/2 of the oral apparatuses (OAs) of LH cells develop in the form of superficial mirror-images of OAs of RH cells. In most of these OAs, membranelles are assembled from the cells' anterior to posterior. Nonetheless, the posterior ends of these membranelles undergo the basal body displacements that lead to a "sculptured" appearance, so that the membranelles of LH OAs become organized as rotational permutations of membranelles of normal RH OAs. Many of these membranelles re-orient to a normal orientation near the end of oral development. Membranelles and undulating membranes (UMs) may develop independently of each other, and formation of postciliary microtubules of UMs is separate from that of ribbed wall microtubules. In some cases, the entire OA develops and remains as a 180 degrees rotational permutation of the normal, resembling the inverted OAs of mirror-image doublets and LH cells of Glaucoma scintillans described by Suhama. We present a model for these complex developmental outcomes. These developmental patterns resemble those described previously and less completely for "secondary" OAs of cells with mirror-image global patterns, including janus cells. The present study demonstrates that such alterations in oral development are not a direct outcome of genotypic changes.

Animals↗
PubMedDate not supplied

Morphology and development of mirror-image doublets of Stylonychia mytilus.

This paper describes the cortical anatomy and development of mirror-image doublets of Stylonychia mytilus, analyzed using the protargol technique. The reversed, or "left-handed" (LH) component of these doublets is a mirror image of the normal or "right handed" (RH) component with regard to the arrangement of cortical structures. The mirror-image patterning is imperfect, however, as the individual ciliary structures of the LH component all are of normal internal asymmetry, and the orientation of membranelles is inverted. Certain structures that would be expected to form near the line of symmetry are absent. During cell division and cortical reorganization, ciliary primordia arise and become arranged in a mirror-image pattern that is more perfect than that exhibited by the mature structures. Deviations from a mirror-image pattern appear at late stages when organelle sets differentiate within ciliary primordia: for example, the membranelle set differentiates within the oral primordium of the LH component in a sequence that is an inversion rather than a mirror image of the corresponding sequence of the RH component. This mixed control of oral development by different cortical "informational systems" accounts for some of the characteristic abnormalities of the mature oral structures of the LH component.

Animals↗
PubMedDate not supplied

Morphology and development of left-handed singlets derived from mirror-image doublets of Stylonychia mytilus.

Mirror-image doublets of Stylonychia mytilus include 2 sets of cortical structures, one with the normal "right-handed" (RH) arrangement, the other with a reversed "left-handed" (LH) arrangement. These sets, however, are incomplete, with certain structures, most notably cirri of the right marginal type, missing near the line of symmetry. When a mirror-image doublet is bisected longitudinally to separate the RH and LH components physically, each fragment undergoes a regeneration process that restores a complete set of cortical structures, including the previously missing cirri of the right marginal type. In the resulting LH cell, all ciliary structures are present in an arrangement that is globally reversed in relation to that found in RH cells; in particular, marginal cirri of the left-marginal type are formed at the cell's right margin, and marginal cirri of the right-marginal type are produced at the cell's left margin. Whereas the regenerated RH fragment always divides and initiates a clone of normal singlets, the LH fragment, though structurally nearly complete, in all cases eventually dies without dividing. The cause of death is starvation due to the formation of an abnormal oral apparatus. In the Discussion, we consider the nature and consequences of a reversal of global positional information.

Animals↗
PubMedDate not supplied

The patterning of ciliates.

This past-presidential address considers the relationship between small-scale assembly and large-scale patterning in ciliates. Certain model examples of assembly-based patterning are reviewed, followed by the introduction of Williams and Honts' concept of "meta-assembly" as applied to the development of the oral apparatus. The major part of this review then explores two topics: the nature and origin of large-scale circumferential order, and the manner by which the large-scale order of cell directions influences the organization of membranelles of the oral apparatus. In this review, I summarize an existing formal description of large-scale positional order, allude to a more precise abstract theoretical model, and end with a brief discussion of the problem of searching for molecular mechanisms.

Animals↗
PubMedDate not supplied

Vance Tartar: a unique biologist.

Vance Tartar (1911-1991) has made major discoveries concerning morphogenesis, patterning, and nucleocytoplasmic relations in the giant ciliate Stentor coeruleus, mostly by means of hand-grafting using glass microneedles. This article provides a chronological account of the major events of Vance Tartar's life, a brief description of some of his major scientific achievements, and a discussion of his distinctive personality and multifaceted interests. It concludes with a consideration of how his unique style of life and work contributed to his equally unique scientific contributions.

Animals↗
PubMedDate not supplied

"Fenestrin" and conjugation in Tetrahymena thermophila.

Certain monoclonal antibodies interact with proteins of Tetrahymena thermophila found in the conjugation junction as well as around the gametic nuclei (pronuclei) of conjugating cells; they also react with the oral primordium and fission zone of vegetative cells and with the cytoproct and contractile vacuole pores of all cells. One of these (FXIX-3A7) was investigated in detail. Immunogold labelling suggests that the material labelled by the 3A7 monoclonal antibody, which we call "fenestrin," is located beneath the epiplasm (membrane skeleton). Immunoblots reveal that the major and perhaps sole antigen is a 64 kDa polypeptide, found in two isoelectric variants. Developmental studies implicate fenestrin in two processes involved in conjugation. The first is "tip transformation." During preliminary starvation ("initiation"), labelling of fenestrin first appeared as a spot at the anterior end of starved mature cells, then after mixing of different mating types ("costimulation") it extended posteriorly along the anterior suture. After pairing, this region spread to form a widened plate. The second process is pronuclear transfer. Fenestrations representing channels between the conjugating cells began to appear 0.5 to 1 h after the conjugants united, and eventually merged to form a small number of temporary large holes during exchange of the transfer pronuclei. A fenestrin envelope also enclosed both the transfer and resident pronuclei; a strand of fenestrin connected the two. Shortly after pronuclear transfer, both transfer and resident pronuclei were released from fenestrin caps and fused to produce a zygotic nucleus (synkaryon) not associated with fenestrin Fenestrin thus appears to be intimately involved in the process of pronuclear exchange.

Animals↗
PubMedDate not supplied

Monoclonal antibodies reveal complex structure in the membrane skeleton of Tetrahymena.

Twelve monoclonal antibodies were raised that are specific for the membrane skeleton of Tetrahymena. Five were directed against T. pyriformis and seven were directed against T. thermophila. Some cross-reactivity between species was found. Each monoclonal antibody recognized one of the three major components of epiplasm, i.e. the bands A, B, and C identified in electrophoretic separations of epiplasmic proteins. It was found, using these antibodies, that the epiplasmic proteins A, B and C have overlapping but independent distributions within the cell.

Animals↗
PubMedDate not supplied

Nuclear and cortical regulation in doublets of Paramecium: II. When and how do two cortical domains reorganize to one?

Homopolar doublets with twofold rotational symmetry were generated in Paramecium tetraurelia and in P. undecaurelia by electrofusion or by arrested conjugation. These doublets underwent a complex cortical reorganization over time, which led to their reversion to singlets. This reorganization involved a reduction in number of ciliary rows, a progressive inactivation and loss of one oral meridian, and a reduction and eventual disappearance of one cortical surface (semicell) situated between the two oral meridians. The intermediate steps of this reorganization included some processes that resemble those previously described in regulating doublets of other ciliates, and others that are peculiar to members of the "P. aurelia" species-group and some of its close relatives. The former included a disappearance of one cortical landmark (a contractile vacuole meridian) and transient appearance of another (a third cytoproct) within the narrower semicell. The latter included a reorganization of the paratene zone and the associated invariant (non-duplicating) region to occupy the entire narrower semicell and a redistribution of zones of most active basal-body proliferation within the opposite, wider semicell. The final steps of reorganization involved anterior displacement, invagination, and resorption of one of the two oral apparatuses and eventual disappearance of the associated oral meridian. An oral meridian deprived of its oral apparatus, either by spontaneous resorption or microsurgical removal, could persist for some time in "incomplete doublets" before regulating to the singlet condition. The phylogenetically widespread events encountered in the regulation of doublets to singlets suggest that Paramecium shares some of the global regulatory properties that are likely to be ancestral in ciliates. The more specific events are probably associated with the complex cytoskeletal architecture of this organism and with the frequent occurrence of autogamy that was described in the preceding study (Prajer et al. 1999).

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