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PubMed1988

Cytology, embryology, and evolution of the developmental arrest syndrome in newts of the genus Triturus (Caudata: Salamandridae).

We have examined embryonic development in three species (T. carnifex, T. cristatus, and T. marmoratus) of European newts of the genus Triturus (subgenus Neotriton) in which developmental arrest occurs in embryos that are homomorphic for a chromosomal heteromorphism involving chromosome 1 (Horner and Macgregor: J. Herpetol., 19:261-270, 1985). Embryonic arrest occurred during tailbud stages in all three species, but at a slightly earlier stage in T. marmoratus. Two phenotypes were identified among the arrested embryos. One of these is indistinguishable in embryonic morphology from normal embryos at all stages up to the time of arrest, but the other is characterized by a protruding yolk plug, which persists from the late gastrula/early neurula stage to the tailbud arrest stage and apparently interferes with normal morphogenesis. Evidence is presented that the two arrested phenotypes, which occur in approximately equal numbers, represent embryos that carry the two alternative homomorphic chromosome pairs of chromosome 1 heteromorphism. We conclude that developmental arrest reflects a balanced lethal heterozygosity probably resulting from an unequal exchange of genic material between the homologues of chromosome 1 which occurred in a common ancestor of the Neotriton species.

Animals↗
PubMed2003

Melatonin, melanogenesis, and hypoxic stress in the newt, Triturus carnifex.

Groups of 6 specimens each of the newt Triturus carnifex were treated with melatonin to see if the hormone inhibited melanogenesis in the Kupffer cells of the liver (melanomacrophages), a process markedly stimulated by hypoxia. A dose of 500 microg/g in 27% ethanol, injected intraperitoneally, induced loss of consciousness and tetany of all the skeletal muscles, which on the contrary appeared relaxed in animals pre-anesthetised by immersion in chlorbutol at 0.2%. Anesthetised specimens injected with melatonin showed a significantly lower increase in hepatic pigmentation after acute hypoxia, a condition attained by sealing each specimen in a 620 mL respiratory chamber with water containing 1.1 ppm of oxygen for the time needed to consume it all (about two hours). If hypoxia is reached gradually, beginning with 8 ppm of oxygen (normoxic condition), the increase in hepatic pigmentation after melatonin injection does not differ significantly from that of non-hormone treated specimens: thus melatonin does not seem to play a direct part in controlling hepatic melanogenesis. Instead, the hormone induces significant increase in oxygen consumption, marked general steatosis of the liver and the almost total disappearance of glycogen. Intraperitoneal injection of 500 microg/g of melatonin in anesthetised animals exposed to the air (normoxic) also causes severe steatosis and an unexpected increase in the hepatic deposits of melanin, as after hypoxic treatment. A dose of 100 ng/g in 1% ethanol, ineffective when injected intraperitoneally, also induces these effects if injected directly into the arterial blood-stream through the conus arteriosus, thus avoiding the hepatic filter. The phenomena observed appear to be induced by a powerful endocrine mechanism that provokes metabolic hypoxia by consuming all the available ATP for synthesizing fat. A less intense form of steatosis can also be observed in animals subjected to hypoxia but without prior hormone treatment, indicating that a natural process triggered by hypoxic stress is pushed to the extreme by exogenous melatonin: the hormone changes the entire energy metabolism of the organism so that it can survive for a long time under adverse environmental conditions.

Animals↗
PubMed2005

Function of the hepatic melanogenesis in the newt, Triturus carnifex.

Like the majority of lower vertebrates, the newt Triturus carnifex holds varying quantities of melanin and hemosiderin in the Kupffer cells of the liver. Following hypoxic treatment, the amount of these two pigments can increase to such an extent that they can occupy nearly a quarter of the surface of histological sections. A group of six specimens, anesthetised with chlorbutol, were subjected to hypoxic treatment by keeping them in a respiratory chamber containing degassed water under vacuum, with only 1.1 ppm of residual oxygen, until they had consumed the oxygen completely (4 hours, at a temperature of 18 degrees C). Using hematological and histochemical techniques and computerised image analysis, it has been shown that hypoxic animals not only increase the extent of the melanic areas of the liver from about 5-7% to almost 24% compared to control groups kept under two different respiratory conditions (6 anesthetised specimens exposed to the air and 6 submerged in normoxic water), they also went through a remarkable hemolytic process to justify a parallel increase in hemosiderin deposits. Melanin was extracted from the liver by keeping fragments of the organ for one hour at 37 degrees C in an oxidising solution (20 mL of benzyl alcohol, 10 mL of acetone, 5 mL of 10% hydrogen peroxide, and 4 drops of concentrated ammonia solution), then quickly rinsing them in 50% acetone and subsequently letting them stand for 6 hours in 10 mL of distilled water alkalised to pH 12 with a drop of ammonia solution. The extract was then left to sediment at pH 2.5 and the black precipitate washed and dried under vacuum. Elemental and spectrophotometric analyses revealed a significant presence of purines in the melanic pigment. This phenomenon can be explained by the animals' need under hypoxic crisis to rapidly neutralise purines resulting from lysis of the nucleated red blood cells by introducing them into an inert molecular complex. A partial model of structure is proposed here. Synthesis of the mixed polymer is possible through the well-known capacity of ferrous iron to activate tyrosinase (the enzyme responsible for melanogenesis) even in the absence of DOPA.

Animals↗
PubMed2005

Effects of Low pH acute exposure on survival and gill morphology in Triturus italicus larvae.

We examined, from a morphological and ultrastructural point of view, the gill epithelium of Triturus italicus, both in basal conditions and after acute exposure to low pH. Our analysis of gill morphology began with the aim of determining lethal pH levels; we found that the pH value at which 50% of mortality occurs (LC50) is 4.0. We then investigated the effects of the larvae's exposure to a critical value of pH (pH 4.5). No change was observed in the gill during the first 24 hr. After 48 hr, a cellular response was evident and the gills appeared covered with a dense mucous layer. Observations that were carried out by light microscopy (LM) and electron microscopy, both scanning (SEM) and transmission (TEM), showed considerable histological and ultrastructural changes. As regards the principal filament, the alterations resulted in the presence of an external keratinized layer. More changes affected the mitochondria-rich cells (MRCs) in both a qualitative and quantitative way; this cell type shows a wide surface and seems to protrude more than the near pavement cells that, in normal conditions, partially cover the MRCs, thus reducing their external surface. The microvilli were extremely lengthened and often anatomized each other. Changes in the secondary filament affected the thickness of the epithelium, which appeared considerably smaller in the gills of the newts exposed to acid stress. The ciliated cells appeared to be more numerous than in the control specimens and the MRCs showed a widening of the apical surface.

Animals↗
PubMed2004

Effects of noradrenaline administration on the interrenal gland of the newt, Triturus carnifex: evidence of intra-adrenal paracrine interactions.

The existence of paracrine control of steroidogenic activity by adrenochromaffin cells in Triturus carnifex was investigated by in vivo noradrenaline (NA) administration. The effects were evaluated by examination of the ultrastructural morphological and morphometrical features of the tissues as well as the serum levels of aldosterone, NA, and adrenaline (A). In March and July, NA administration increased aldosterone release (from 187.23 +/- 2.93 pg/ml to 878.31 +/- 6.13 pg/ml in March; from 314.60 +/- 1.34 pg/ml to 622.51 +/- 2.65 pg/ml in July) from steroidogenic cells. The cells showed clear signs of stimulation, as evidenced by a strong reduction of lipid content. Moreover, NA administration decreased the mean total number of secretory vesicles in the chromaffin cells in March (from 7.24 +/- 0.18 granules/micro2 to 5.57 +/- 1.88 granules/micro2) and July (from 7.74 +/- 0.74 granules/micro2 to 6.04 +/- 1.13 granules/micro2). In March, however, when T. carnifex chromaffin cells contain both catecholamines, NA (3.88 +/- 0.13 granules/micro2) and A (3.36 +/- 0.05 granules/micro2) in almost equal quantities, NA administration reduced A content (1.29 +/- 1.04 granules/micro2) in the chromaffin cells, enhancing adrenaline secretion (from 681.27 +/- 1.83 pg/ml to 1527.02 +/- 2.11 pg/ml). In July, when the chromaffin cells contain almost exclusively NA granules (NA: 7.42 +/- 0.86 granules/micro2; A: 0.32 +/- 0.13 granules/micro2), NA administration reduced the number of NA granules (5.45 +/- 1.10 granules/micro2), thereby increasing noradrenaline release from the chromaffin cells (from 640.19 +/- 1.65 pg/ml to 1217.0 +/- 1.14 pg/ml). The results of this study indicate that NA influences the steroidogenic cells, eliciting aldosterone release. Noradrenalin effects on the chromaffin cells, increase of NA or A secretion, according to the period of chromaffin cell functional cycle, may be direct and/or mediated through the steroidogenic cells. The existence of intra-adrenal paracrine interactions in T. carnifex is discussed.

Adrenal Cortex↗
PubMed2004

Release of aldosterone and catecholamines from the interrenal gland of Triturus carnifex in response to adrenocorticotropic hormone (ACTH) administration.

The influence of adrenocorticotropic hormone (ACTH) on the interrenal gland of Triturus carnifex was investigated by in vivo administration of synthetic ACTH. The effects were evaluated by examination of the ultrastructural morphological and morphometrical features of the tissues as well as the circulating serum levels of aldosterone, noradrenaline (NA), and adrenaline (A). In June and November, ACTH administration increased aldosterone release (from 281.50 +/- 1.60 pg/ml in carrier-injected newts to 597.02 +/- 3.35 pg/ml in June; from 187.45 +/- 1.34 pg/ml in carrier-injected animals to 651.00 +/- 3.61 pg/ml in November). The steroidogenic cells showed clear signs of stimulation, together with a reduction of lipid content in June and an increase of lipid content in November. Moreover, ACTH administration decreased the mean total number of secretory vesicles in the chromaffin cells in June (from 7.73 +/- 0.60 granules/microm2 in carrier-injected animals to 5.91 +/- 0.40 granules/microm2) and November (from 7.78 +/- 0.75 granules/microm2 in carrier-injected newts to 4.87 +/- 0.40 granules/microm2). In June, however, when T. carnifex chromaffin cells contain almost exclusively NA granules (NA: 7.42 +/- 0.86 granules/microm2; A: 0.32 +/- 0.13 granules/microm2), ACTH decreased NA content (5.52 +/- 0.32 granules/microm2) increasing NA release (from 639.82 +/- 3.30 pg/ml in carrier-injected to 880.55 +/- 4.52 pg/ml). In November, when both catecholamines, NA (3.92 +/- 0.34 granules/microm2) and A (3.84 +/- 0.33 granules/microm2), are present in the chromaffin cells, ACTH administration reduced A content (1.02 +/- 0.20 granules/microm2), enhancing adrenaline secretion (from 681.30 +/- 3.62 pg/ml in carrier-injected newts to 1,335.73 +/- 9.03 pg/ml). The results of this study indicate that ACTH influences the steroidogenic tissue, eliciting aldosterone release. The effects on the chromaffin tissue, increase of NA or A secretion, according to the period of chromaffin cell functional cycle, may be direct and/or mediated through the increase of aldosterone release. Finally, the lack of an increase of A content in the chromaffin cells, or A serum level, following ACTH administration in June might suggest an independence of PNMT enzyme on corticosteroids.

Adrenocorticotropic Hormone↗
PubMed1990

The cycle of follicular and interstitial cells (Leydig cells) in the testis of the marbled newt, Triturus marmoratus (Caudata, Salamandridae).

Ultrastructural examination of the marbled newt (Triturus marmoratus) testis throughout the annual cycle revealed that during the period of testicular quiescence (November-February), primordial germ cells proliferate within cords of filament-rich epithelial cells that will become follicular cells (FCs). Fibroblast-like cells surround the FCs and form the lobule-boundary interstitial cells (ICs). During the period of germ cell development from primordial germ cells to round spermatids (March-June), the FCs surrounding the developing germ cells contain scanty cytoplasm with abundant rough endoplasmic reticulum and scarce filaments. With spermatid elongation (July-August), the FC size grows, its nucleus becomes irregularly outlined, and its cytoplasm displays abundant smooth endoplasmic reticulum, residual bodies, lipid droplets, and large vacuoles. After spermatozoon release by the FCs (August-September), the adjacent ICs increase their size and transform into Leydig cells with abundant smooth endoplasmic reticulum, mitochondria with tubular cristae, and lipid droplets. During the period of testicular quiescence (November-February), the Leydig cells undergo involution, eventually developing the morphological attributes of mesenchymal cells. Intermingled among these cells, cords of filament-rich cells are observed. During this period of the cycle, spermatozoon cysts supported by FCs are present. At the beginning of the germ cell proliferation period (March), these spermatozoa are released, and the adjacent ICs undergo a transformation into Leydig cells similar to those observed in August-September. Maturation and involution of ICs occur when testosterone levels are known to be rising and falling, respectively.

Animals↗
PubMed2002

Implantation of MNNG crystals into a Triturus intact limb affects mitotic and labeling indices, regeneration rate, and morphogenesis in the contralateral, regenerating limb.

Experimental administration of chemical carcinogens to various mammals is highly effective in inducing malignant tumors. In contrast, treatment of regeneration-competent animals even with much higher doses of the same drugs only exceptionally leads to tumor-like growth. Usually, carcinogenic materials implanted or injected into a regenerating limb of urodele amphibia interfere with the regenerative process and frequently lead a). to growth retardation or arrest of regeneration, b). to development of a great variety of abnormal regenerates, and c). to generation of accessory, limb-like structures. Autonomous or experimental incidence of carcinogenesis is extremely low in animals endowed with strong regenerative capabilities. Of exceptional biological significance is the fact that such induced tumors usually regress spontaneously. This unique property of the regeneration-competent animals to resist carcinogenesis provides opportunities to compare non-cancerous alterations in the differentiated state of adult cells to those occurring in neoplasia. The mode of action of the chemical carcinogens on limb regeneration has not yet been clarified with certainty at the cellular and the molecular level. Several scientists claim that the above-mentioned effects might be attributed to local toxic influences of the drugs; therefore the present study was designed to investigate whether the administration of the carcinogen MNNG can affect cell proliferation, histogenesis, and morphogenesis at a region distant from the site of its implantation, even after a relatively long time period. To this end, 40 animals of the species Triturus cristatus had their right hindlimb surgically removed at the distal zeugopod. Then, a small microcrystal (approximately 5 micro g) of MNNG was inserted under the ventral aspect of the skin of the left tarsus in 20 of these animals (groups T and A; see below). Two months later, nine of the MNNG-treated animals were injected intraperitoneally with tritiated thymidine. After 2 h, six of these animals had their right hindlimb amputated at the distal zeugopod, whereas the rest were left to regenerate. The results were evaluated by camera lucida drawings, clearing in methyl benzoate, classical histology, and autoradiography. It was revealed that administration of MNNG at a somatic region (left hindlimb) reduces DNA synthesis and mitosis at a distant place (right hindlimb) even 2 months after MNNG implantation. Despite this, the rate of limb elongation is not substantially reduced. Classical histology revealed normal tissue structure throughout. All regenerated limbs displayed several teratogenic abnormalities.

Amputation, Surgical↗
PubMed1994

A phorbol ester and calcium ionophore regulate sex steroid and prostaglandin release by follicles of the anuran Rana esculenta and the urodele Triturus carnifex.

The aim of this work was to study the relationships among protein kinase C (PKC), calcium, prostaglandins (PGs), and sex steroids in follicles of Rana esculenta and Triturus carnifex. Follicles, oocytes, and wall cells of follicle (theca and granulosa cells) were incubated in vitro with an activator of PKC, phorbol-12-myristate-13-acetate (PMA), a calcium ionophore (A23187), an antagonist of calcium channel, verapamil, PMA + A23187, prostaglandin F2 alpha (PGF2 alpha), and prostaglandin E2 (PGE2). Progesterone, androgens, and 17 beta-estradiol were assessed in incubation media of follicles and wall cells and PGs in incubation media of follicles, oocytes, and wall cells. In both species, PMA increased progesterone; A23187 increased progesterone, 17 beta-estradiol, and PGs; verapamil decreased progesterone and PGs; PMA + A23187 increased progesterone, 17 beta-estradiol, and PGs; PGF2 alpha increased 17 beta-estradiol; PGE2 increased progesterone. These data suggest that PKC and calcium intervene in the regulation of steroidogenesis and PG synthesis by follicles of both R. esculenta and T. carnifex; in particular, calcium seems to regulate PGs synthesis, activating an enzymatic pathway which does not include PKC.

Androgens↗
PubMed1994

Seasonal changes of plasma prolactin concentration in the reproduction of the crested newt (Triturus carnifex Laur).

Plasma prolactin (PRL) and vitellogenin (VTG) concentrations were determined during the annual reproductive cycle of the newt Triturus carnifex Laur. Plasma PRL was measured by a radioimmunoassay using purified newt (Cynops pyrrogaster) PRL as standard and radioligand and its antibodies. Using ELISA, plasma VTG titers were related to ovarian weight. The trends in PRL differed in the two sexes: the PRL changes seemed to be related with vitellogenic processes in the female, whereas they were more related to reproductive behavior in the male.

Animals↗
PubMed1993

Corticosterone during the annual reproductive cycle and in sexual behavior in the crested newt, Triturus carnifex.

To clarify the role of corticosterone in the male and female crested newt, Triturus carnifex, and the possible involvement of this hormone in the reproductive processes, we monitored the seasonal and daily pattern of this corticosteroid; in addition, corticosterone, testosterone, and 17 beta-estradiol plasma levels were evaluated during the various phases of courtship. In both sexes, the seasonal pattern of corticosterone in plasma showed two peaks: one in winter, at the beginning of the reproduction, and the other one in summer, when the newts leave the pond. The corticosterone daily pattern showed a peak at 05:00 PM. During courtship, corticosterone was lower and testosterone higher in "inactive" male newts than in the courting animals, while estradiol was highest during the approach; in the females corticosterone was lower in "nonreceptive" animals than in "receptive" ones, and sex steroids did not show any difference. These data suggest that corticosterone is involved in the reproductive processes in male and female crested newts.

Animals↗
PubMed1988

Putative neurotransmitters in the retinae of three urodele species (Triturus alpestris, Salamandra salamandra, Pleurodeles waltli).

The immunocytochemical localization of several substances with putative neurotransmitter or modulator properties was investigated in the retinae of three urodele species. Gamma-aminobutyric acid-like immunoreactive labelling appeared in different types of amacrine and horizontal cells. In addition, labelled fibres in the optic nerve were detected. It was not possible to determine whether these fibres were ganglion-cell axons or part of an efferent projection. Endogenous serotonin was found in several populations of amacrine cells including stratified and diffuse types. Glucagon-like immunoreactivity appeared in one bistratified amacrine cell type, and neurotensin-like immunoreactivity was detected in a single monostratified amacrine cell type. Metenkephalin-like-immunoreactive labelling was type. Metenkephalin-like-immunoreactive labelling was rare but found in several sublaminae of the inner plexiform layer. Thus each peptide-like-immunoreactive cell type makes up a distinct and unique population of cells and probably has a special functional role in retinal processing. There are striking similarities in the peptide-like immunoreactive patterns of Triturus alpestris and Necturus maculosus whereas in Ambystomatidae the peptide-like-immunoreactive systems appear to be differently organized. This supports the hypothesis that Salamandridae and Proteidae are more closely related to each other than to the Ambystomatidae.

Animals↗
PubMed1988

Identification of pigment cells during early amphibian development (Triturus alpestris, Ambystoma mexicanum).

The purpose of the present investigation was to provide and apply a methodological manual with which the distribution, patterning and relationship of melanophores and xanthophores can be analyzed during early amphibian development. For demonstration of the methods, which include ultrastructural, histochemical and biochemical approaches, Triturus alpestris and Ambystoma mexicanum (axolotl) embryos are used. These two species differ conspicuously in their larval pigment patterns, showing alternating melanophore bands in horizontal (T. alpestris) and vertical (axolotl) arrangements. With transmission- and scanning electron microscopy melanophores and xanthophores were distinguished by their different pigment organelles and surface structures. The presence of phenol oxidase (tyrosinase) was used to reveal externally invisible or faintly visible melanophores by applying an excess of 3,4 dihydroxy-phenylalanine (dopa). Xanthophores were made visible in fixed and living embryos by demonstrating their pterin fluorescence. In addition, pterins were analyzed by HPLC in embryos before and after pigmentation was visible.

Ambystoma↗
PubMed1975

Observations on peroxisomes in interrenal (adrenocortical) cells of Triturus cristatus and Salamandra salamandra (Urodele Amphibians).

Intracellular organelles (average diameter: 0.3 mu) similar to peroxisomes were observed in the interrenal cells of Triturus cristatus and Salamandra salamandra. Their peroxisomal nature was demonstrated by incubating tissue sections in alkaline 3,3-diaminobenzidine. Oxidation of diaminobenzidine, a characteristic feature of peroxisomes, was observed. These organelles are devoid of a central nucleoid and are surrounded to various degrees by profiles of the smooth endoplasmic reticulum. The matrix of these organelles is sometimes in direct communication with the inside of the smooth tubules. These relationships suggest a possible origin of the peroxisomes from the smooth endoplasmic reticulum.

Adrenal Cortex↗
PubMed1980

Endocrine-like cells in the lungs of the newt, Triturus alpestris Laur.

Endocrine-like cells (ELC) scattered in the basal part of the ciliated epithelium were identified in the lungs of the newt, Triturus alpestris. These ELC have a clear cytoplasm containing large amounts of secretory vesicles (69-180 nm in diameter), especially in their basal parts, but do not display formaldehyde-induced fluorescence. The ELC may be associated with nerve fibres.

Animals↗
PubMed1976

Osmium zinc iodide staining of Golgi elements in oocytes of Triturus cristatus.

Developing oocytes of the newt Triturus cristatus were studied in order to clarify the role played by the Golgi apparatus in the formation of yolk. The cytochemical method used for this purpose was that of Maillet (1968) which employs an Osmium Zinc Iodide (OZI) complex. Previtellogenic oocytes reveal a pattern of OZI staining only after hormonal (HCG) stimulation, following which both the Golgi apparatus and the multivesicular bodies are stained. Vitellogenic oocytes taken from non-hormonally stimulated females reveal OZI deposits in a number of vesicles peripheral to the Golgi apparatus as well as within the superficial layer of the forming yolk platelets. Following hormone stimulation, many of the Golgi apparatus located in the central ooplasm of vitellogenic oocytes have all their cisternae blackened by the OZI deposits; other apparatuses,more peripherally located, remain essentially unchanged in their staining pattern. Further, a large number of OZI stained vesicles becomes visible in the vicinity of the Golgi apparatus and within the superficial layer of the forming yolk platelets. The present findings are interpreted as indicating the occurrence of fusion between Golgi derived vesicles and forming yolk platelets. It is also suggested that the vesicles in question function as carriers of Golgi produced enzymes which are presumably required to accomplish the final elaboration of the yolk material.

Animals↗
PubMed1989

The distribution of GABA-like-immunoreactive neurons in the brain of the newt, Triturus cristatus carnifex, and the green frog, Rana esculenta.

The distribution of gamma-aminobutyric acid (GABA) immunoreactivity was studied in the brain of two amphibian species (Triturus cristatus carnifex, Urodela; Rana esculenta, Anura) by employing a specific GABA antiserum. A noteworthy immunoreactive neuronal system was found in the telencephalic dorsal and medial pallium (primordium pallii dorsalis and primordium hippocampi) and in the olfactory bulbs. In the diencephalic habenular nuclei there was a rich GABAergic innervation, and immunoreactive neurons were observed in the dorsal thalamus. In the hypothalamus the GABA immunoreactivity was found in the preoptic area, the paraventricular organ and in the hypothalamo-hypophysial complex. In the preoptic area of the frog some GABA-immunoreactive CSF-contacting cells were shown. In the optic tectum immunolabeled neurons were present in all the cellular layers. A rich GABAergic innervation characterized both the fibrous layers of the tectum and the neuropil of the tegmentum and interpeduncular nucleus. In the cerebellum, in addition to the Purkinje cells showing a variable immunopositivity, some immunoreactive cells bodies appeared in the central grey. Abundant immunolabeled nerve fibers in the acoustico-lateral area and some immunopositive neurons in the region of the raphe nucleus were observed. In conclusion, the GABAergic central systems, well-developed in the amphibian species studied, were generally characterized by close similarities to the pattern described in mammals.

Animals↗
PubMed1980

Scanning and transmission electron microscopic study of the lung of the newt, Triturus alpestris Laur.

The lungs of Triturus alpestris Laur. were investigated with the scanning and transmission electron microscopes. Dimensions of the cell bodies of pneumocytes and ciliated cells, as well as the thickness of the air-blood barrier, were determined. The lungs of the newt form two simple sacs without septa. A ciliated epithelium containing goblet cells lines the pulmonary vein and partially the pulmonary artery. The remainder of the lung surface is covered internally by respiratory epithelium consisting of one type of cell and only occasionally showing the presence of single ciliated cells. All cells, ciliated, goblet and pneumocytes, contain in their cytoplasm lamellar bodies. Multivesicular bodies and numerous vesicles of variable electron density also occur in the cytoplasm of pneumocytes. Atypical mitochondria can be found in all cell types of the lung. Fixation with addition of tannic acid reveals the surface lining film. Tubular myelin figures were not observed.

Animals↗