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Biomedical subjects

J D Taylor

Publications and source records attributed to J D Taylor.

At least 163 records · Page 9Linked to original sources
PubMed1979

Hormone-induced pigment translocations in amphibian dermal iridophores, in vitro: changes in cell shape.

Hormone-induced pigment translocation studies were conducted at both the light and electron microscopic levels on cultured dermal iridophores from the Mexican leaf frog, Pachymedusa dacnicolor. Two distinct types of dermal iridophores were characterized which differed in (1) their in vivo locations, (2) their overall morphologies in vitro, (3) their responses to alpha-MSH, ACTH, c-AMP or theophylline, (4) their physical alterations of light, and (5) certain ultrastructural features. One iridophore (Type I) was found to be physiologically responsive to the above hormones or agents by a reversible retraction of cellular processes and a thickening of the cell body, an event which is inhibited by cytochalasin B. The other iridophore (Type II) appeared to be unresponsive. Type I iridophores contain cube-like pigmentary organelles, refractosomes, while Type II iridophores contain larger, bar-shaped refractosomes. In addition, both iridophore types contain 60 and 100 A microfilaments as well as microtubules. By in large, micorfilaments were found within microvilli, beneath and parallel to the plasma membrane and in the perinuclear region. Occasionally, bundles of 100 A microfilaments were found between layers of refractosomes in Type I iridophores. These results are discussed in relation to hormone-induced changes in cell shape.

Actins↗
PubMed1979

A transvesical approach to stress incontinence.

Seventy-three patients with urinary incontinence were carefully investigated; only 12 were selected as suitable for operation. In each case the surgical approach was transvesical, as this most rapidly and accurately identified the urethrovesical junction. The outcome was completely successful in 9 of the 12 patients in this highly selective series at the time of review 12 months later.

Female↗
PubMed1978

Actin microfilaments in melanophores of Fundulus heteroclitus. Their possible involvement in melanosome migration.

In melanophores of Fundulus heteroclitus, hormone-stimulated melanosome aggregation is accompanied by cytoplasmic flow from the cellular processes to the perikaryon, and reversal of these events takes place upon hormone-induced melanosome dispersion. These cells contain parallel arrays of microtubules, the majority of which are located in the perikaryon and in cortical regions of the processes. Studies with heavy meromyosin binding demonstrated two types of actin filaments: 11 a decorated meshwork of filaments similar to those usually found in close association with plasma membranes, and 2) filaments decorated in a manner similar to that of stress fibers. There is an apparent increase in the amount of filaments during melanosome aggregation. These results are discussed in relation to intracellular movement.

Actins↗
PubMed1978

Ultrastructural demonstration of hormone-induced movement of carotenoid droplets and endoplasmic reticulum in xanthophores of the goldfish, Carassius auratus L.

The hormone-induced pigment dispersion in primary cultures of xanthophores of goldfish (Carassius auratus L.) has been shown to involve the dispersion of not only carotenoid droplets but also of smooth endoplasmic reticulum. The dispersion of these organelles is inhibited by cytochalasin B and is accompanied by thinning of the cell body, thickening of the processes, and also overall changes in cellular morphology (process extension) under certain conditions. Electron microscopic examination of heavy meromyosin treated glycerinated xanthophores in scales revealed the presence of actin filaments in these cells.

Adrenocorticotropic Hormone↗
PubMed1978

The effects of lumicolchicine, colchicine and vinblastine on pigment migration in fish chromatophores.

The effects of lumicolchicine, colchicine, vinblastine and cold temperature on the pigment migration in melanophores and xanthophores of Fundulus heteroclitus and Oryzias latipes were examined by light and electron microscopy. Xanthophores of both species which contain numerous microfilaments and a poorly developed microtubule system were extremely sensitive to the alkaloids. Lumicolchicine and colchicine induced irreversible dispersion while vinblastine caused permanent aggregation of the pigments. Treatment in lumicolchicine or colchicine at 5 mM for 60 minutes did not disrupt microtubules of melanophores to an appreciable degree, however, melanosome aggregation was partially inhibited by these drug in Oryzias. When melanophores were kept in the cold in the presence of colchicine at 1 mM, almost all microtubules were disrupted and their repolymerization at room temperature was nearly completely inhibited by colchicine. These melanophores lacking in microtubules responded to epinephrine with slow aggregation. Vinblastine at 0.1 mM induced partial aggregation of melanosomes and disruption of microtubules but most melanophores were still able to respond with pigment migration. Vinblastine at 1 mM made all melanophores punctate and immobile. Large vinblastine-induced crystals were frequently seen in the dendritic processes. The results of the present investigation suggest that cytoplasmic microtubules in fish melanophores facilitate melanosome migration only in directional orientation and appear not be responsible for the motive force.

Animals↗
PubMed1978

Ultrasonic effects on mammalian intestinal muscle membrane.

The effects of ultrasound on the bioelectric activities of rat intestinal muscle were studied. It was found that low level ultrasound of 1.5 W/cm2 inhibited action potentials of the intestinal smooth muscle. This biophysical action of ultrasound had accumulative effects. The presence of high Ca++ in the medium (3.4 mM or 2 x normal [Ca++]) prevented this action of ultrasound. These data suggested that ultrasound probably acted on the calcium influx mechanism of the cell membrane.

Action Potentials↗
PubMed1977

Trysinase positive oculocutaneous albinism in the goldfish, Carassius auratus l., and ultrastructural and biochemical study of the eye.

Ultrastructural studies, and cytochemical and biochemical determinations of tyrosinase activity were conducted on the pigment epithelium of albino and xanthic goldfish eyes. In eyes of xanthic goldfish, two types of melanosomes are present, spherical and elongated. Melanized melanosomes are absent in the eyes of the albino goldfish, but elongated lamellar premelanosomes are observed. Internal vesicles are present in both melanosome types in the pigment epithelium of the xanthic goldfish but are absent in premelanosomes of the albino. There are also differences in the distribution of lipid droplets, smooth endoplasmic reticulum and Golgi complexes with the latter two being more abundant in the albino. Tyrosinase was not identified cytochemically; however, the enzyme was demonstrated biochemically in the pigment epithelia of both albino and xanthic goldfish. The enzyme is associated with the particulate and soluble fractions fo both types of eyes. Particulate albino tyrosinase may be solubilized by triton X-100 treatment. Tyrosinase inhibitors are present in the particulate fractions of both albino and xanthic goldfish eyes. Thus, in the goldfish, ocular albinism appears to be a multiple defect at the molecular and ultrastructural levels.

Albinism↗
PubMed1976

Adenosine 3',5'-monophosphate, morphogenetic movements and embryonic neural differentiation in Pleurodeles waltlii.

Evidence is presented for the following hypothesis dealing with dibutyryl-c-AMP induction of neural differentiation in Pleurodeles waltlii embryos: (1) Dibutyryl-c-AMP induces the determination for neural differentiation. (2) Additional dibutyryl-c-AMP is not needed for cytodifferentiation. (3) Cytodifferentiation of induced cells can only take place after morphogenetic movements (in vivo) or extensive cell migrations (in vitro). It is suggested that cell migrations, both in vivo and in vitro, lead to the separation of the induced cells from one another or from unidentified inhibitory cells.

Amphibians↗
PubMed1976

Hormone-induced dispersion or aggregation of carotenoid-containing smooth endoplasmic reticulum in cultured xanthophores from the goldfish, Carrassius auratus L.

A novel organelle movement is described in goldfish xanthophores. Smooth endoplasmic reticulum, containing carotenoids pigments, undergo MSH or c-AMP-induced dispersion. This dispersion is independent of RNA and protein synthesis, not modulated by c-GMP and inhibited by cytochalasin B but only at the relatively high concentration of 10 mug/ml. Epinephrine induces aggregation, a process that is inhibited by colchicine. These results suggest, but do not prove, the involvement of microfilaments in dispersion and microtubules in the aggregation of carotenoid-containing endoplasmic reticulum.

Adrenocorticotropic Hormone↗
PubMed1975

Induction of neural differentiation in cultures of amphibian undetermined presumptive epidermis by cyclic AMP derivatives.

Induction of neural differentiation in cultures of undetermined presumptive epidermis from three amphibian species was achieved by the addition of 1 millimolar dibutyryl adenosine 3',5'-monophosphate, 8-bromadenosine 3',5'-monophosphate, or adenosine C',E'-monophosphate together with theophylline. Adenosine 5'-monophosphate, adenosine 2',3'-monophosphate, dibutyryl guanosine 3',5'-monophosphate, and butyrate at 1 millimolar are ineffective. These results suggest that the action of the primary inductor or inductors may be mediated via adenosine 3',5'-monophosphate.

Amphibians↗