The fine structure of the adenohypophysis of Zoarces viviparus L.

Summary In the adenohypophysis of Zoarces viviparus L. three types of acidophils, three types of basophils and two types of pars intermedia cells have been described on the level of light- and electron microscopy. It is pointed out that the seasonal alteration in the activity of the two types of basophils is correlated with the activity of the gonads, and the gonadotropic function of them is postulated. Ultrastructural similarity between the adenohypophyseal cells of Z. viviparus and those of mammals is considered.

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Zusammenfassung In der Adenohypophyse von Zoarces viviparus L. werden aufgrund licht- und elektronenmikroskopischer Untersuchungen drei Typen von acidophilen, drei Typen von basophilen und zwei Typen von Pars intermedia-Zellen beschrieben. Der jahreszeitliche Wechsel in der Aktivität von zwei basophilen Zelltypen ist mit der Aktivität der Gonaden korreliert; eine gonadotrope Funktion dieser beiden Zelltypen wird angenommen. Es wird diskutiert, inwieweit sich die Feinstruktur der Zellen der Adenohypophyse bei Zoarces viviparus und bei Säugern ähnelt.

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The work reported here was carried out with financial support from NATO and the Deutsche Forschungsgemeinschaft.

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This paper was written as a tribute in honour of the 60th birthday of Prof. Dr. med. W. Bargmann.     

Molecular and genetic structure of multiple hemoglobins in the eelpout,Zoarces viviparus L.

Six major hemoglobin components are present in the teleostean fish Zoarces viviparus L. Biochemical characterization has led to a molecular model for the polypeptide chain composition of the individual hemoglobins. Only three different chains are involved. They are determined by three different structural loci, as indicated by the genetic variation of the electrophoretic hemoglobin pattern observed in natural populations. Hemoglobins occur that, despite identical chain compositions, have different electrophoretic mobilities. This may be due to a mechanism, known from man, where part of the hemoglobin is blocked by a hexose.     

Neurosecretory processes projecting from the preoptic nucleus into the third ventricle of Zoarces viviparus L.

Summary The cellular processes loaded with neurosecretory elementary granules penetrate the ependyma and project into the third ventricle at the level of preoptic nucleus of Zoarces viviparus L. These cellular processes seem to be arising from the neurosecretory cells. At this zone, not all but some of the ependymal cells have a cilium. In this paper the possible function of these neurosecretory processes and the ciliated ependymal cells are discussed.This work was aided by a Grant from NATO and the Deutsche Forschungsgemeinschaft.     

Changes in melatonin binding sites under artificial light-dark, constant light and constant dark conditions in the masu salmon brain

To test whether the affinity (Kd) and total binding capacity (Bmax) of melatonin receptors exhibit daily and circadian changes in teleost fish whose melatonin secretion is not regulated by intra-pineal clocks, we examined the changes in melatonin binding sites in the brains of underyearling masu salmon Oncorhynchus masou under artificial light-dark (LD), constant light (LL) and constant dark (DD) conditions. In Experiment 1, fish were reared under a long (LD 16:8) or short (LD 8:16) photoperiod for 69 days. Blood and brains were sampled eight times at 3 h intervals. Plasma melatonin levels were high during the dark phase and low during the light phase in both photoperiodic groups. The Bmax exhibited no daily variations. Although the Kd slightly, but significantly, changed under LD 8:16, this may be of little physiological significance. In Experiment 2, fish reared under LD 12:12 for 27 days were exposed to LL or DD from the onset of the dark phase under LD 12:12. Blood and brains were sampled 13 times at 4 h intervals for two complete 24 h cycles. Plasma melatonin levels were constantly high in the DD group and low in the LL group. No significant differences were observed in the Kd and the Bmax between the two groups, and the Kd and the Bmax exhibited no circadian variation either in the LL or DD groups. These results indicate that light conditions have little effect on melatonin binding sites in the masu salmon brain.     

The structure and cytochemistry of the neurosecretory cells of Fasciola gigantica Cobbold and Fasciola hepatica L.

Histochemical studies of the nervous system of Fasciola gigantica and Fasciola hepatica were undertaken. Neurosecretory cells were detected by Gomori's aldehydefuchsin, Bargmann's chrome hematoxylin-phloxin, Mallory's triple stain, periodic acid-Schiff, Heidenhain's Azan and alcian blue after potassium permanganate oxidation. Two types of neurosecretory cells were recognized and designated as "A" and "B". Type "A" cells occurred in small numbers in the brain and subesophageal mass and type "B" cells ubiquitous in distribution. The reactions of these cells to the standard stains for neurosecretory substance generally, were less intense than the neurosecretory cells of other animals such as crustaceans and insects. The structure, organisation, distribution and cytochemistry of neurosecretory cells in Fasciola gigantica and Fasciola hepatica is discussed.     

Vitellogenin, lipid and carbohydrate metabolism during vitellogenesis and pregnancy, and after hormonal induction in the blenny Zoarces viviparus (L.).

1. Ovarian vitellogenic growth in Zoarces viviparus lasts about 2 months. Vitellogenesis is immediately followed by ovulation, fertilization and a pregnancy period of 4 months. Vitellogenin is observed in the blood during vitellogenesis, but declines during the first month of pregnancy. 2. The largest amount of liver lipid is found before vitellogenesis is initiated. During pregnancy the liver is depleted of lipid and glycogen, and total lipid and phospholipid is accumulating in the blood. 3. Estradiol treatment during pregnancy results in a dose-dependent increase in vitellogenin and lipids of the blood. 4. In late pregnancy, birth can be provoked with progesterone alone, or with combined progesterone and estradiol treatment.     

Melatonin administration modifies circadian motor activity under constant light depending on the lighting conditions during suckling

Early lighting conditions have been described to produce long-term effects on circadian behavior, which may also influence the response to agents acting on the circadian system. It has been suggested that melatonin (MEL) may act on the circadian pacemaker and as a scavenger of reactive oxygen and nitrogen species. Here, we studied the oxidative and behavioral changes caused by prolonged exposure to constant light (LL) in groups of rats that differed in MEL administration and in lighting conditions during suckling. The rats were exposed to either a light–dark cycle (LD) or LL. At 40 days old, rats were treated for 2 weeks with a daily subcutaneous injection of MEL (10?mg/kg body weight) or a vehicle at activity onset. Blood samples were taken before and after treatment, to determine catalase (CAT) activity and nitrite level in plasma. As expected, LL-reared rats showed a more stable motor activity circadian rhythm than LD rats. MEL treatment produced more reactivity in LD- than in LL rats, and was also able to alter the phase of the rhythm in LD rats. There were no significant differences in nitrite levels or CAT activity between the groups, although both variables increased with time. Finally, we also tested depressive signs by means of sucrose consumption, and anhedonia was found in LD males treated with MEL. The results suggest that the lighting conditions in early infancy are important for the long-term functionality of the circadian system, including rhythm manifestation, responses to MEL and mood alterations.     

The effects of dark and light on the functional recovery following lateral hypothalamic lesions

Treatment with total darkness five days prior to lateral hypothalamic lesions reduced the motor deficiencies consequent to this type of lesion. Constant and cycling light had no effect on the motor impairments.     

Effects of preoptic and hypothalamic lesions in female turkeys during a photoinduced reproductive cycle

Prolactin (Prl) is released by electrical stimulation in the turkey hypothalamus and preoptic area (POA). Possible trajectories for POA efferents to the median eminence (ME) were tested by placing lesions in the POA, the lateral hypothalamus (LHy), or the ventromedial nucleus of the hypothalamus (VMN) of reproductively quiescent turkey hens, then subjecting them to long photoperiods while monitoring their blood Prl levels and nesting activities. In addition, lesions were made in the VMN of a group of incubating hens to learn whether the lesions would cause the elevated Prl levels to fall or interfere with incubation behavior. Lesions in medial POA, LHy, or VMN prevented the onset of incubation and prevented the large rise in Prl associated with it. However, these lesions did not interfere with the initial, more gradual Prl rise caused by increasing daylengths. Lesions in LHy or VMN appeared to interfere with a pathway lying laterally from POA to ME. Electrical stimulation in medial POA, which caused an increase in circulating Prl, failed to do so in hens with LHy or VMN lesions. Lesions in the VMN of incubating hens caused them to leave the nest and suffer a large decline in Prl, both within 48 h. It is tentatively suggested that incubation behavior and its associated elevated Prl are prevented by the POA lesions and that lesions in LHy or VMN, which mimic POA lesion effects, interfere with POA efferents projecting to ME.     

Regulation of the Chlamydomonas cell cycle by light and dark

By growing cells in alternating periods of light and darkness, we have found that the synchronization of phototrophically grown Chlamydomonas populations is regulated at two specific points in the cell cycle: the primary arrest (A) point, located in early G1, and the transition (T) point, located in mid-G1. At the A point, cell cycle progression becomes light dependent. At the T point, completion of the cycle becomes independent of light. Cells transferred from light to dark at cell cycle position between the two regulatory points enter a reversible resting state in which they remain viable and metabolically active, but do not progress through their cycles. The photosystem II inhibitor dichlorophenyldimethylurea (DCMU) mimics the A point block induced by darkness. This finding indicates that the A point block is mediated by a signal that operates through photosynthetic electron transport. Cells short of the T point will arrest in darkness although they contain considerable carbohydrate reserves. After the T point, a sharp increase occurs in starch degradation and in the endogenous respiration rate, indicating that some internal block to the availability of stored energy reserves has now been released, permitting cell cycle progression.     

The effect of light on the tricarboxylic Acid cycle in green leaves: I. Relative rates of the cycle in the dark and the light

Excised green leaves of mung bean (Phaseolus aureus L. var. Mungo) were used to determine the effect of light on the rate of endogenous respiration via the tricarboxylic acid cycle. Illumination with white light at an intensity of 0.043 gram calories cm⁻²min⁻¹ (approximately 8600 lux) of visible radiation (400-700 nm) gave a rate of apparent photosynthesis, measured as net CO₂ uptake, of 21 mg CO₂ dm⁻²hr⁻¹ which was about 11-fold greater than the rate of dark respiration. The feeding of ¹⁴CO₂ or ¹⁴C-labeled acids of the tricarboxylic acid cycle in the dark for 2 hours was established as a suitable method for labeling mitochondrial pools of cycle intermediates.     

Ultrastructure of the frontal ganglion of Chaoborus and observations on neurosecretory cells during the annual cycle

The frontal ganglion contains approximately 20 cells and rests on the two posterior elevator muscles of the roof of the pharynx, thus locating the ganglion ventral and anterior to the brain. Two frontal nerves, a pair of lateral connectives, and the single recurrent nerve connect with the ganglion. There is a centrally located neuropile which is surrounded by the perineurium which in turn is covered by the neural lamella. The perineruium contains numerous glial cells and neurons with two large neurosecretory cells located in a dorsal lateral position of the ganglion.The neurosecretory cells were examined on five occasions during the year, and no significant changes occurred in the fine structure of the organelles or cellular products. The cells appear to be engaged in the synthesis of elementary neurosecretory granules throughout the year. This observation differs from previous studies on diapausing lepidopterous larvae and pupae. Axons from these two cells enter the lateral connectives and extend toward the protocerebrum.     

The structural-functional properties of light and dark hepatoma cells

Morphofunctional analysis of the light and dark solid hepatoma cells of mouse line 22a C3HA and culture of human hepatoma has shown that in both hepatomas the dark cells when compared with the light ones possess increased electronic density of hyaloplasm, and besides the dark cells of solid tumor line have a well-developed endoplasmic reticulum and numerous mitochondria. Both types of cells are able to incorporate labelled RNA and DNA precursors and also to divide themselves mitotically.     

The effect of oxygen on nitrate and nitrite assimilation in leaves of Zea mays L. under dark conditions

The assimilation of nitrate under dark-N₂ and dark-O₂ conditions in Zea mays leaf tissue was investigated using colourimetric and ¹⁵N techniques for the determination of organic and inorganic nitrogen. Studies using ¹⁵N indicated that nitrate was assimilated under dark conditions. However, the rate of nitrate assimilation in the dark was only 28% of the rate under non-saturating light conditions. No nitrite accumulated under dark aerobiosis, even though nitrate reduction occurred under these conditions. The pattern of nitrite accumulation in leaf tissue in response to dark-N₂ conditions consisted of three phases: an initial lag phase, followed by a period of rapid nitrite accumulation and finally a phase during which the rate of nitrite accumulation declined. After a 1-h period of dark-anaerobiosis, both nitrate reduction and nitrite accumulation declined considerably. However, when O₂ was supplied, nitrate reduction was stimulated and the accumulated nitrite was rapidly reduced. Anaerobic conditions stimulated nitrate reduction in leaf tissue after a period of dark-aerobic pretreatment.