Head-bobbing of walking birds

Many birds show a rhythmic forward and backward movement of their heads when they walk on the ground. This so-called “head-bobbing” is characterized by a rapid forward movement (thrust phase) which is followed by a phase where the head keeps its position with regard to the environment but moves backward with regard to the body (hold phase). These head movements are synchronized with the leg movements. The functional interpretations of head-bobbing are reviewed. Furthermore, it is discussed why some birds do bob their head and others do not.     

Ultrastructural immunocytochemistry of gonadotrophs in the goldfish pituitary gland

Summary The immunocytochemical distribution of gonadotropin (GTH) in the goldfish pituitary gland was studied applying the peroxidase-antiperoxidase (PAP) method and the protein A-gold technique at lightand electron-microscopic levels, respectively, with an antiserum raised against silver carp GTH. In the light-microscopic immunocytochemistry, PAS-positive cells in the proximal pars distalis showed strong reaction with the antiserum. Gold particles were concentrated both on globules (large) and on granules (small) of the gonadotrophs (PAS-positive cells) in the electron-microscopic immunocytochemistry. Other cells in the pituitary gland, including thyrotrophs, displayed no immunoreactivity with the antiserum at the dilutions tested. These results indicate, not only immunocytochemical distribution of GTH both in globules and in granules in the gonadotrophs, but also the high purity of the antigen (silver carp GTH) and specificity of the antiserum.     

New observations on the fine structure of the liver in goldfish (Carassius auratus)

Summary A re-examination of goldfish liver was made through the use of SEM of fractured samples and TEM of ultrathin-sections and freeze-etch replicas. Several new hepatic fine structures described in the present study are morphologically similar to those reported previously in many higher vertebrates including mammals. Hepatic sinusoids of goldfish contain fenestrations which are arranged into sieve plates. Although the hepatic plates are made up of two layers of hepatocytes, the parenchymal cells of goldfish liver are morphologically similar to mammalian hepatocytes, particularly with respect to the sinusoidal surfaces which are studded with numerous microvilli. The intercellular surfaces of hepatocytes have both nexus and desmosomal junctions, similar to those found in various epithelial cells of higher vertebrates, as cell attachments and communication foci. Tight junctions are found mainly between the openings of the intracellular bile canaliculi and the intralobular bile ductules which are situated in the center of the bicellular hepatic plate.Supported in part by Grants # GM92 and ES07017     

Ultrastructural identification of catecholaminergic fibers in the goldfish pituitary

Summary The monoaminergic innervation of the goldfish pituitary gland was studied by means of light- and electronmicroscopic radioautography after in vitro administration of ³H-dopamine. The tracer was specifically incorporated and retained by part of the type-B fibers innervating the different lobes of the pituitary. In the rostral pars distalis labeled fibers were most frequently observed in contact with the basement membrane separating the neurohypophysis and the adenohypophysis. In the proximal pars distalis and the pars intermedia, labeled profiles were detected in the neural tissue and in direct contact with the different types of secretory cells.According to the previous data concerning the uptake and retention of tritiated catecholamines in the central nervous system, it is assumed that the labeled fibers are mainly catecholaminergic (principally dopaminergic). This study provides morphological evidence for a neuroendocrine function of catecholamines in the goldfish.     

The role of myosin phosphorylation in anaphase chromosome movement

This work deals with the role of myosin phosphorylation in anaphase chromosome movement. Y27632 and ML7 block two different pathways for phosphorylation of the myosin regulatory light chain (MRLC). Both stopped or slowed chromosome movement when added to anaphase crane-fly spermatocytes. To confirm that the effects of the pharmacological agents were on the presumed targets, we studied cells stained with antibodies against mono- or bi-phosphorylated myosin. For all chromosomes whose movements were affected by a drug, the corresponding spindle fibres of the affected chromosomes had reduced levels of 1P- and 2P-myosin. Thus the drugs acted on the presumed target and myosin phosphorylation is involved in anaphase force production.Calyculin A, an inhibitor of MRLC dephosphorylation, reversed and accelerated the altered movements caused by Y27632 and ML-7, suggesting that another phosphorylation pathway is involved in phosphorylation of spindle myosin. Staurosporine, a more general phosphorylation inhibitor, also reduced the levels of MRLC phosphorylation and caused anaphase chromosomes to stop or slow. The effects of staurosporine on chromosome movements were not reversed by Calyculin A, confirming that another phosphorylation pathway is involved in phosphorylation of spindle myosin.     

The role of peristomatal transpiration in the mechanism of stomatal movement

Abstract. Peristomatal transpiration is defined as the relative high local rate of cuticular water loss from external and internal surfaces around the stomatal pore and its decisive role in the control of stomatal movement is re-emphasized. As the resistance towards changes in air humidity is low in the pore surroundings, the state of turgor is particularly unsteady there. Due to the inherent instability the guard cell 'senses' fluctuations in the supply-demand relationship of water and is thus the control unit proper. The environmental variables (supply and demand) are cross-correlated within the subsidiary cell and the information is transmitted to the guard cell through the water potential gradient between the two cells. A conceptual segregation of a 'humidity response' by 'passive' stomatal movements is rejected.
As ions always accumulate at the most distant point of the liquid path and as this point varies with pore width according to the prevailing water potential gradients, it is felt that the water stream is causing the characteristic pattern of ion distribution within the epidermis. Passive import of ions is attributed to local concentration gradients which are steepened by continuous supply and by water uptake into the guard cell in response to starch hydrolysis. A mechanistic model supplements the discussion.     

Functional and morphological regeneration of olfactory tracts and subtracts in goldfish

Goldfish are ideal vertebrates for the study of regeneration within the central nervous system. The present behavioural and neuroanatomical investigations after bilateral transection of the entire olfactory tracts of either lateral or medial subtracts have been designed (1) to examine the relationship between morphological changes and changes in the perception of spontaneously preferred chemosensory stimuli, (2) to investigate the animals' ability to qualitatively discriminate amino acids in olfactory concentrations (below taste threshold, 10^-6–10^-8 M), one of which had been rewarded preoperatively (specific regeneration), and (3) to examine the discriminative ability for amino acids at concentrations above taste threshold (> 10^-5 M) in intact sham-operated, and in operated specimens at various time intervals before functional regeneration. Within 10–14 days after bilateral transection of the lateral olfactory tracts, specific regeneration was observed. After bilateral transection of the medial olfactory tracts, no immediate behavioural change was recorded for 1 week. Thereafter, goldfish behaviour became unstable and dropped to the chance level for 3–4 weeks. Subsequent to this time the goldfish returned to the preoperative level. Following bilateral crushing of the olfactory tracts and after total tractotomy, a specific regeneration was observed after 4 weeks and 6–8 weeks, respectively, post op. HRP studies showed that after bilateral lesioning a qualitative reinnervation of the respective nuclei within the forebrain by the medial and lateral olfactory subtracts was evident.Abbreviations FB funnel biting - FO funnel orientation - HRP horseradish peroxidase - LOT lateral olfactory tract - MOT medial olfactory tract     

Ultrastructural observations on synaptic ribbons in the pineal organ of the goldfish

Summary Synaptic ribbons in the pineal organ of the goldfish were examined electron microscopically with particular attention to their topography. These structures were formed of parallel membranes, which were poorly preserved with OsO₄ fixation and could be extracted from thin sections with pronase indicating their proteinaceous nature. Synaptic ribbons were closely apposed to the plasma membrane bordering dendrites of ganglion cells, but were also related to processes of both photoreceptor and supportive cells. Their close proximity to invaginations of the plasma membrane and portions of the endoplasmic reticulum suggest that they are involved in the turnover of cytoplasmic membranes. Tubular and spherical organelles of unknown function are also described.     

Effects of brain lesions on gonadotrop ultrastructure and serum gonadotropin levels in goldfish

Summary Brain lesions that destroyed the anterior preoptic region or the pituitary stalk in sexually mature (= completed ovarian recrudescence) goldfish caused a significant increase in serum gonadotropin levels for at least 11 days postoperatively. These results confirmed previous findings indicating the presence of a gonadotropin release-inhibitory factor. Electron-microscopic investigation revealed that the gonadotrops were depleted of the small secretory granules, had marked dilations of the cisternae of the endoplasmic reticulum and extensive development of the Golgi apparatus. This indicated both secretion and synthesis, and correlated with the prolonged increase in serum gonadotropin resulting from the lesions.Supported by grants from Natural Sciences and Engineering Research Council of Canada to W.S. Hoar and R.E. Peter     

The anaerobic energy metabolism of goldfish determined by simultaneous direct and indirect calorimetry during anoxia and hypoxia

Summary The energy flow of the anaerobic metabolism of glodfish at 20°C during hypoxia and anoxia was studied by simultaneous direct and indirect calorimetry. During anoxia the heat production as determined by direct calorimetry (180 J · h^–1 · kg^–0.85) is reduced to 30% of the normoxic level (570 J · h^–1 · kg^–0.85), which is the same reduction as found previously. The patterns of substrate utilization are compared with previous results, where the anoxic pattern was established by simultaneous calorimetry without carbon dioxide measurements. The present results, which do include carbon dioxide measurements, show the same pattern: carbohydrate and protein as substrates and carbon dioxide, ethanol and fat as end products. The pattern of substrate utilization at low oxygen levels is a combination of the anoxic pattern with an aerobic component. During anoxia only 5% of the metabolizable energy is used for energy metabolism. Of the remaining part (metabolizable energy for production) 60% is converted into ethanol and 40% into fat. At two hypoxia levels the distribution of the metabolizable energy for production into ethanol and fat is the same.     

Gating of spontaneous somatic sensations by movement

Movement is known to attenuate the perception of tactile stimuli delivered on the moving part of the body, and this gating diminishes the greater the distance from the moving part. However, does it influence the perception of sensations occurring spontaneously without external triggers? In Experiment 1, participants were asked to focus on one hand while moving or not moving their thumb, and thereafter to map and describe the spatial and qualitative attributes of sensations perceived over the remaining, motionless part of the hand. The results show that movement reduces the frequency, spatial extent, and intensity of sensations, but also participants’ confidence about their spatial characteristics. As expected, gating decreased the greater the distance from the moving thumb. Furthermore, gating was greater for distal than proximal segments of the hand, suggesting a hierarchical proximo-distal suppression. Experiment 2 ruled out the possibility that these effects were due to tactile sensations elicited by movement. Possible mechanisms of gating in the case of spontaneous sensations are discussed.     

Computer-aided studies of vision in crabs

A system for the back projection of computer-generated visual images onto a screen or screens that cover 240° of the horizontal visual field is described. Its applicability for the study of crab vision is tested by comparing the frequency response of the optokinetic response of the land crab, Cardisoma guanhumi, to sinusoidal oscillation of computer-generated striped patterns and a real striped drum. Significant differences were observed only at the low end of the frequency spectrum. The flexibility of computer-generated visual stimulation and its advantages for the study of optic flow are illustrated by experiments that: (a) demonstrate how well crabs separate the translational and rotational components of optic flow by showing compensatory eye movements to only the latter; (b) show that the ability to compensate for rotation is not impaired by combinations of rotation and translation; (c) show that motion parallax cues are used in addition to previously-described global cues for making the distinction between rotation and translation. Finally, the use of these methods in a successful search for visual interneurones sensitive to optic flow stimuli is demonstrated for the shore crab, Carcinus maenas.     

Time-dependent effects of leptin on food intake and locomotor activity in goldfish

The present study investigates the possible circadian dependence of leptin effects on food intake, locomotor activity, glycemia and plasma cortisol levels in goldfish (Carassius auratus). Fish were maintained under 12L:12D photoperiod and subjected to two different feeding schedules, one group fed during photophase (10:00) and the other one during scotophase (22:00). Leptin or saline were intraperitoneally injected at two different times (10:00 or 22:00), coincident or not with the meal time. To eliminate the entraining effect of the light/dark cycle, goldfish maintained under 24 h light (LL) were fed and leptin-injected at 10:00. A reduction in food intake and locomotor activity and an increase in glycemia were found in goldfish fed and leptin-injected at 10:00. No significant changes in circulating cortisol were observed. Those effects were not observed when leptin was administered during the scotophase, regardless the feeding schedule; neither in fish maintained under LL, suggesting that a day/night cycle would be necessary to observe the actions of leptin administered during the photophase. Changes in locomotor activity and glycemia were only observed in goldfish when leptin was injected at daytime, coincident with the feeding schedule, suggesting that these leptin actions could be dependent on the feeding time as zeitgeber. In view of these results it appears that the circadian dependence of leptin actions in goldfish can be determined by the combination of both zeitgebers, light/dark cycle and food. Our results point out the relevance of the administration time when investigating regulatory functions of hormones.     

Origin of the pituitary innervation in the goldfish

Despite the large number of studies devoted to the pituitary of teleosts, the origin of the direct pituitary innervation is still largely unknown. Although such a model is ideal for applying retrograde transport techniques, these methods involve the difficult in vivo injection of tracers into the pituitary and have never been applied. Recently, a lipophilic fluorescent dye (1-1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanin; DiI) has been introduced and shown to have the capacity of being transported by the membranes of paraformaldehydefixed tissues. Microcrystals of DiI were implanted via a ventral approach into the pituitary of goldfish previously fixed by intracardiac perfusion of paraformaldehyde. The goldfish heads were kept immersed in paraformaldehyde for various periods of time (2–6 weeks). The brains were then dissected and cut transversally using a Vibratome. The results demonstrate that hypophysiotrophic areas are essentially restricted to the preoptic region, the mediobasal hypothalamus and the nucleus dorsolateralis thalami. In addition, cell bodies probably containing gonadotrophin releasing-hormone were also retrogradely stained along a pathway that can be traced up to the olfactory bulbs. The results also confirm that cell bodies, located around the ventral aspect of the preoptic recess and probably corresponding to dopaminergic neurons, project to the pituitary. Large neurons have also been observed in the rostral dorsal midbrain tegmentum just caudal to the posterior commissure. Most neurons of the so-called paraventricular organ remain unstained. Finally, a fiber tract originating from an undetermined territory of the posterior brain has been observed. The results are discussed in relation to the possible chemical nature of the hypophysiotropic neurons.     

Computer-aided studies of vision in crabs

A system for the back projection of computer-generated visual images onto a screen or screens that cover 240° of the horizontal visual field is described. Its applicability for the study of crab vision is tested by comparing the frequency response of the optokinetic response of the land crab, Cardisoma guanhumi , to sinusoidal oscillation of computer-generated striped patterns and a real striped drum. Significant differences were observed only at the low end of the frequency spectrum. The flexibility of computer-generated visual stimulation and its advantages for the study of optic flow are illustrated by experiments that: (a) demonstrate how well crabs separate the translational and rotational components of optic flow by showing compensatory eye movements to only the latter; (b) show that the ability to compensate for rotation is not impaired by combinations of rotation and translation; (c) show that motion parallax cues are used in addition to previously-described global cues for making the distinction between rotation and translation. Finally, the use of these methods in a successful search for visual interneurones sensitive to optic flow stimuli is demonstrated for the shore crab, Carcinus maenas .     

Regulation of food intake by melanin-concentrating hormone in goldfish

Melanin-concentrating hormone (MCH), originally discovered in the teleost pituitary, is a hypothalamic neuropeptide involved in the regulation of body color in fish. Although MCH is also present in the mammalian brain, it has no evident function in providing pigmentation. Instead, this peptide is now recognized to be one of the key neuropeptides that act as appetite enhancers in mammals such as rodents and primates. Although there has been little information about the central action of MCH on appetite in fish, recent studies have indicated that, in goldfish, MCH acts as an anorexigenic neuropeptide, modulating the α-melanocyte-stimulating hormone signaling pathway through neuronal interaction. These observations indicate that there may be major differences in the mode of action of MCH between fish and mammals. This paper reviews what is currently known about the regulation of food intake by MCH in fish, especially the goldfish.     

Acoustic response properties of single units in the torus semicircularis of the goldfish,Carassius auratus

Single units of the goldfish torus semicircularis (TS) were recorded in response to pure tones. Response areas (RA) were obtained by recording the number of spikes evoked by tones in a range of frequencies and levels within the units' dynamic range. RAs gave estimates of best sensitivity (BS), characteristic frequency (CF), most excitatory frequency at each level (BF), and Q_10dB. Peri-stimulus-time histograms (PSTH), interspike interval histograms (ISIH), and period histograms were obtained at various frequencies and levels to describe the units' temporal response patterns.The distribution of CF is nonuniform with modes at 155, 455, and 855 Hz. The distribution of the coefficient of synchronization to standard tones is also nonuniform, revealing a dichotomy between units with little or no phase-locking and those that phase-lock strongly. PSTHs for units without significant phase-locking vary widely and include patterns resembling those of the mammalian auditory brainstem. Compared with saccular afferents, torus units tend to have lower spontaneous rates, greater sensitivity, and sharper tuning. Unlike saccular afferents, BF is independent of level for most torus units. Some torus units are similar to saccular afferents while others reveal significant transformations of information between the periphery and the midbrain.Abbreviations BF best frequency - BS best sensitivity - CF characteristic frequency - ISIH inter-spike interval histogram - PSTH peri-stimulus-time histogram - RA response area - TS torus semicircularis     

Two osteoclastic markers expressed in multinucleate osteoclasts of goldfish scales

Complementary DNAs encoding two major osteoclastic markers, tartrate-resistant acid phosphatase (TRAP) and cathepsin K (Cath K) were cloned from the scales of a teleost, the goldfish. This is the first report of the full coding sequence of TRAP and Cath K molecules in fish. In the goldfish scale both TRAP and Cath K mRNAs were expressed in the multinucleate osteoclasts, which showed large numbers of mitochondria and lysosomes, and a well developed ruffled border. These characteristic features of osteoclasts in the scales are similar to those in mammals. Most teleosts use the scale as an internal calcium reservoir during the reproductive season. The expression of TRAP and Cath K mRNAs in the scale significantly increased in April, which is a reproductive season, compared with that in October, a non-reproductive season. Thus, both of these molecular markers should be useful for the study of osteoclasts in the teleost scale.