PubMed Health⌕ Search

Biomedical subjects

T Heinzeller

Publications and source records attributed to T Heinzeller.

11 recordsLinked to original sources
PubMed1991

Pinealocyte subsurface cisterns. I: Cytological aspects including three-dimensional structure.

Subsurface cisterns (ssc) in the pineal gland of Meriones unguiculatus have been characterized with transmission electron microscopy, freeze-fracture, morphometry, and three-dimensional reconstruction. Subsurface cisterns (which are observed only in pinealocytes and never in gliocytes) are cisterns of the endoplasmic reticulum (ER) approaching the plasmalemma at a distance of 15-20 nm. Freeze-fracture preparations show that except for some ribosomes at the cytoplasmic face, the cistern membranes as well as the related portions of the plasmalemma are free of special or specifically arranged particles or pores. All ssc have a lumen of 15-20 nm width and underlie 5.6% of the plasmalemma in a single layer; neither collapsed types nor stacks of ssc could be observed. As seen from reconstructions, large ssc are fenestrated and are situated preferentially in regions where the neighboring pinealocyte also bears large ssc. As a consequence, double-sided ssc, which can be observed in sections of (mostly large) ssc, are not a random phenomenon. In regions of the large ssc, adhering junctions are also concentrated. Tubules of 20-nm diameter link ssc with deeper parts of the ER, particularly with the perinuclear cistern and with the tubulo-cisternal network at the trans-side of the Golgi apparatus. Besides ssc proper, a lot of small endplates of ER-tubules are seen close to the plasmalemma. It is suggested that ssc form by the widening and fusing of such ER-tubules and decrease by retraction of ER-tubules from the cell surface.

Animals↗
PubMed1991

Pinealocyte subsurface cisterns. II: Influence of time of day, sympathectomy, and castration.

Subsurface cisterns (ssc) of the gerbil pinealocyte were studied by electron microscopic morphometry taking account of different external influences: time of day, sympathetic deafferentation, castration with or without substitution of testosterone. Male individuals of Meriones unguiculatus, aged 150 days, were used. Though ssc number is invariant with respect to the light-dark cycle, ssc size follows a highly significant sinusoid curve. The largest ssc were found in the afternoon, the smallest ones in the early morning. Bilateral resection of the superior cervical ganglia reduces the density of pinealocyte ssc markedly, and their size is maximal or, in relation to the scaled-down cell, unusually large. Castration with or without application of testosterone propionate does not alter pinealocyte ssc, neither with respect to density nor size. From these experimental data it is concluded that pinealocyte ssc may play a supportive role in the regulation of pinealocyte sensitivity, in so far as it depends on receptors located in the cell membrane.

Animals↗
PubMed1991

Pinealocyte subsurface cisterns. III: Storage of calcium ions and their probable role in cell stimulation.

Different techniques for the ultrastructural demonstration of calcium have been applied to the pineal gland of Meriones unguiculatus, attention being focussed on the endoplasmic reticulum (ER) and its subsurface cisterns (ssc). By means of a "loading" method [Walz, 1982; Wakasugi et al., 1982] it is shown that the pinealocyte ER-ssc system sequesters calcium with dependency on ATP. Furthermore, a modification of the method of Duce and Keen [1978] is presented which turned out a) to be sensitive enough to demonstrate the cell's own low amounts of calcium as fine granular precipitates, and b) to preserve ultrastructure sufficiently. This method rendered possible comparison of the calcium distribution inside pinealocytes of the following groups: animals fixed during daytime, animals fixed at night, animals fixed at night with prior exposure to bright white light, animals fixed at night but injected at the end of the preceding light period with a pharmacon known to prevent the release of calcium from the ER of muscle fibers (Dantrolen). In contrast to the daytime findings, the pinealocyte ER-ssc system at night is free of precipitable calcium; nocturnal illumination induces reacquisition, Dantrolen hinders nocturnal depletion. From the nocturnal coincidence of pinealocyte activity and calcium release from ssc, and from other cytological and experimental data, it is concluded that the functional significance of ssc refers to the regulation of pinealocyte sensitivity. Vice versa, pinealocyte activity may influence ER expansion and ssc size via the calcium-dependent stability of microtubules.

Animals↗
PubMed1989

Meningeal calcification of the rat pineal organ. Finestructural localization of calcium-ions.

The surface of the pineal organ of the rat is covered by a leptomeningeal tissue, the continuation of the corresponding meningeal layers of the diencephalon. The pineal leptomeninx consists of stratified arachnoid and of pia mater cells which follow the vessels into the pineal nervous tissue. The pineal arachnoid contains electron-lucent and electron dense cells differing from each other in their cytoplasmic components. Corpora arenacea of various size and density occur among these arachnoid cells and can grow into the pineal organ alongside pia mater tissue. Acervuli often form groups in circumscribed meningeal "calcification foci". Concrements are absent or rare in the 1- and 2-month-old animal, while they are usually present in the 4- and 6-month-old rats. The electronmicroscopic localization of Ca-ions was studied in 2- and 4-month-old rats by potassium pyroantimonate cytochemistry. In the 4-month-old animals, arachnoid cells containing a varying amount of Ca-pyroantimonate deposits were found first of all around corpora arenacea, but there were also cells free of deposits in the close vicinity of the acervuli. Deposits were preferentially localized to the cytoplasm of electron dense arachnoid cells and to the cell membrane of electron-lucent cells. Most of the precipitates occurred in locally enlarged intercellular spaces. Here, microacervuli were found in 4-month-old animals suggesting that a calcium-rich environment was responsible for the appearance of the concrements. Intermediate stages between the small acervuli and large concentric corpora arenacea may indicate an appositional growth of the acervuli in the calcification foci.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Effects of aggressive encounters on pineal melatonin formation in male gerbils (Meriones unguiculatus, Cricetidae).

Pineal N-acetyl-transferase activity and radioimmunoassayable melatonin levels were determined in adult male gerbils subjected to aggressive encounters using the intruder-model. In the first experiment, a single encounter of 3 min was applied in the afternoon to intact and to animals with sympathetically denervated pineal organs. Compared with controls, both stressed groups demonstrated a drastic decrease in N-acetyl-transferase activity followed by a slow recovery. In both groups there also occurred a marked change in pineal melatonin content: in intact animals pineal melatonin levels were elevated immediately after the encounter; thereafter, melatonin values decreased. In animals bearing denervated pineal organs melatonin levels fell as a consequence of the encounter. In a second experiment, intact gerbils experienced four daily encounters of 1 min for one week. Thereafter the nocturnal formation of melatonin was studied. In comparison with untreated controls, the repeatedly stressed animals demonstrated a temporal delay in the rise of both N-acetyl-transferase activity and melatonin. Since the pineal organ is able to transduce events of the social environment into an endocrine message--as set forth by both our experiments--the pineal organ might play an important role within central processing of social stress.

Acetyltransferases↗
PubMed1986

A single 1- or 5-second light pulse at night inhibits hamster pineal melatonin.

Adult male Syrian hamsters maintained under 6-h light, 18-h dark cycles (lights out daily from 1200-0600 h) were exposed to either 1 or 5 sec light either 8 h (at 2000 h) or 12 h (at 2400 h) into the dark phase. The light had an irradiance of 32,000 microW/cm2. With both light pulse durations and at both times, melatonin levels were depressed to daytime values 30 min after the onset of the light pulse. Whereas pineal melatonin production eventually increased to high nighttime values in hamsters exposed to 1 sec light at either 2000 or 2400 h and in animals receiving a 5-sec light pulse at 2000 h, when the 5-sec light occurred at 2400 h, pineal melatonin levels remained low for the remainder of the night. Thus, both the placement and the duration of light exposure appear to be important in determining the ability of light to depress melatonin production in the Syrian hamster.

Animals↗
PubMed1985

Impact of psychosocial stress on pineal structure of male gerbils (Meriones unguiculatus, cricetidae).

Stress responses were investigated in 5-month-old male gerbils. Breeders having no pubescent litters served as controls. The first experimental group never left their parents' cage and were thereby fought by higher-ranking males; the second and third groups were stressed for a week by four daily 1-minute encounters with trained fighters, the second group during daytime, the third during the dark period. The first and second groups developed signs of gonadal regression, the third did not. The adrenals of the first group weighed the same as those of controls; the adrenals of both other groups were increased in weight. In the adrenal medulla of all experimental groups, a large number of cells were densely packed with noradrenaline-containing vesicles. In each experimental group the pineal changes included a remarkable decrease in nuclear size of pinealocytes, an increased number of colloidal cysts, and a reduction of that portion of the plasmalemma that is lined by subsurface cisterns. All these changes are interpreted in terms of pineal activation, as are the increased number of membrane whirls found in the first group. The third group exhibited an additional decrease in the size of mitochondria and in the number of "synaptic" structures. This finding and the day-night differences in the gonadal response indicate that stress interferes with the metabolic cyclicity of the pineal gland. However, it remains indiscernible whether the pineal stress reaction signals a general activation of the gland or a change in it's temporal activity patterns.

Adrenal Glands↗
PubMed1985

Responsiveness of pineal N-acetyltransferase and melatonin in the cotton rat exposed to either artificial or natural light at night.

In three separate experiments, the effect of acute exposure to either artificial or natural light during darkness of pineal N-acetyltransferase (NAT) activity and melatonin content was studied in the cotton rat (Sigmodon hispidus). The exposure of animals to an artificial-light irradiance of 160,000 microW/cm2 during darkness for either 1 s, 5 s, or 30 min was followed by a precipitous decline in pineal NAT activity and melatonin content when measured at either 15 or 30 min after light onset. When cotton rats were acutely exposed to light at night for 5 s, irradiances of either 3.2, 32, 320, and 3,200 did not suppress either pineal NAT or melatonin 30 min later; however, if the 5-s exposure had an irradiance of either 32,000 or 160,000 microW/cm2, the pineal enzyme activity and indole content were depressed. Moonlight, which had a maximal irradiance of 0.32 microW/cm2, was unable to suppress pineal NAT activity and melatonin content even when the animals were exposed to the moonlight for 30 min. The treatment of cotton rats with either norepinephrine or its agonist, isoproterenol, before their exposure to light at night retarded slightly the suppressive effect of light on the pineal constituents measured. Also, these drug treatments suppressed the pre-exposure levels of both NAT activity and melatonin content in the cotton rat pineal gland.

Acetyltransferases↗
PubMed1976

Second-order ocellar neurons in the brain of the honeybee (Apis mellifera).

Electrophoretic injection of Procion Yellow M-R4 into the ocellar tract of the worker bee has revealed the following: Two types of giant axon run from the lateral ocellus to the circumesophageal neuropile, where one branches ipsilaterally and the other contralaterally. A third type comes from the median ocellus and can be traced into the cervical connectives. The largest dendritic complex is in the circumesophageal neuropile; in addition, fiber endings have been demonstrated in the following areas: in the subretinal region, along the optic commissure, in the medulla interna, in the subesophageal ganglion and between the neurosecretory cells of the pars intercerebralis. -- The giant fibers are enclosed in a glial sheath. Three types of cell body are described. One is associated with the glia; another, larger cell type comprises giant-axon somata. The third type of cell is small, and cannot yet be identified. Some of the histological results are discussed with respect to the possible function of the ocellus.

Animals↗
PubMedDate not supplied

Gonadal response to psychosocial stress in male tree shrews (Tupaia belangeri) morphometry of testis, epididymis and prostate.

Male tree shrews (46 animals in all) were kept under distinct social conditions. Two kinds of controls were investigated: isolated animals as well as males out of female/male couples. Comparing these two groups only little isolation effect was observed. With the other individuals, initially isolated, dyads were formed which coexisted for 7 or 50 days. In a third group of dyads, after 50 days of coexistence social circumstances were aggravated for 5 more days by providing only half of the cage. All dyads established clear cut dominance relationship. Animals behaving dominantly developed no signs of gonadal regression rather that of stimulation concerning especially with the epididymis. In contrast, animals behaving as subordinates revealed profound regressive changes although differentiated with respect to any parameter, both morphological and conditional. In testis, chronical subordination (50 days, mainly 50 + 5 days) leads to a loss of organ weight, narrowing of seminiferous tubules and to enlarged spermatogonia nuclei. The case is similar in the epididymis: loss of organ weight, lowered epithelium and an enormously increased frequency of immature germ cells within tail segments. Whereas prostate weight drops continuously, striking histological regression occurs already after 7 days (extreme diminution of epithelial height and of epithelial cell nuclei).

Animals↗