A prospective, randomized, controlled trial of metal stents for malignant obstruction of the common bile duct

Endoscopic insertion of biliary stents is the preferred method of palliation for inoperable malignant biliary obstruction; however, migration and clogging are frequent problems with conventional endoprostheses. We sought to determine if expandable metal stents offer improved palliation compared to conventional stents. Sixty-two patients with common bile duct lesions were randomized to receive polyethylene or metal stents. Stents were placed endoscopically or by the combined percutaneous-endoscopic route. Early results (< 1 month) were similar in both groups. Long-term follow-up (n = 28 polyethylene, median: 5 months; n = 27 metal, median: 5 months) showed a higher stent failure rate in the polyethylene (n = 12; 43%) compared to the metal group (n = 6; 22%). The incidence of cholangitis was significantly higher (p < 0.05) in the polyethylene (n = 10; 36%) compared to the metal group (n = 4; 15%). Life-table analysis showed a significantly reduced incidence of stent failure (p = 0.0035) in the metal stent compared to the polyethylene group. The total duration of hospital stay for treatment of stent related problems was significantly higher in the polyethylene (11.8 +/- 3 days) compared to the metal group (4 +/- 1.9 days; p = 0.02). The costs for retreatment because of stent failure were significantly higher in the plastic (DM 5900 +/- 1516) compared to the metal group (DM 2070 +/- 977). As a result, the overall costs (treatment of stent related complications & stents) were higher in the polyethylene group (DM 6000 +/- 1500).(ABSTRACT TRUNCATED AT 250 WORDS)

A method for spatio-temporal (4-D) data representation in confocal microscopy: application to neuroanatomical plasticity

This paper describes a new method for data representation and visualization in four dimensions (three dimensions plus time). Sequential volumes, exhibiting morphological activity, are acquired non-invasively with a confocal scanning laser microscope, where each data set corresponds to a time sample. A pipelined processing includes packing of volumes and specific volume rendering techniques. Subsequent processing in HIS (hue, intensity, saturation)l colour space combines functional, packed images with shaded three-dimensional views. As a result, even subtle changes in morphology become visible and computational time is saved. Experimental findings obtained from investigations of synaptic plasticity in cultured retinal tissue are reported.

cAMP-mediated second messenger mechanisms are involved in spinule formation in teleost cone horizontal cells

A number of light adaptive changes of teleost horizontal cells are mediated by dopamine D1 receptors coupled positively with the cAMP second messenger system. Spinules, finger-like extensions from horizontal cell dendrites directed towards the cone pedicle cytoplasm, are formed in response to a stimulation of D1 receptors. We studied the second messenger mechanism associated with this process using isolated dark-adapted cyprinid retinae. Increasing intracellular cAMP concentrations by adding a membrane permeable analogue, or by stimulating the adenylate cyclase and simultaneously blocking the degradation of cAMP, resulted in a significant increase of spinule numbers in spite of the absence of light. In contradistinction to using isolated retinae for pharmacological experiments, injection of drugs into the vitreous had inconsistent or negative results.

Detection and quantification of latently infected B lymphocytes in Epstein-Barr virus-seropositive, healthy individuals by polymerase chain reaction

We designed a highly sensitive and specific polymerase chain reaction assay for the detection of Epstein-Barr virus (EBV)-related sequences in B-cell DNA of EBV-seropositive healthy individuals. By using this assay, we were able to amplify at least 10 copies of a plasmid containing the BamHI-W region, which is repeated up to 11 times within the EBV genome, in the presence of 1 microgram of EBV-negative DNA, indicating that one virus genome was detectable from 150,000 cells. In 15 of 16 tested individuals, EBV-related sequences were found frequently when the DNA from 10(6) B lymphocytes was examined and 1 microgram of DNA was used in each polymerase chain reaction. When the results of amplifying the diluted plasmid were used as a semiquantitative standard, the number of EBV genomes detected could be estimated to range between 50 and less than 1 from 10(6) B lymphocytes. The results of our study will provide the basis for further investigations of the characteristics of the latent carrier state in healthy EBV-seropositive individuals, such as the determination of the number of virus copies per cell and expression of antigens.

[A prospective study to determine the recanalization time with a guide wire/recanalization catheter system in arterial occlusions]

The success rate and time taken for recanalization was determined in a prospective study of 82 consecutive unselected patients (53 men, 29 women; mean age 65.7 +/- 13, from 28 to 88 years). There were 106 complete occlusions of infrarenal arteries and a hydrophilic guide wire with a special 5-F recanalization catheter was used. Mean occlusion length was 12.97 +/- 10 cm (from 1 cm-45 cm). 79.3% of occlusions were in the femoro-popliteal territory, 6.6% were iliac and 14.1% tibial. 101 of the 106 occlusions were recanalized (95.3%). Mean recanalization time was 120.8 +/- 228.1 s (from 1 s-1440 s), mean recanalization velocity was 0.11 cm/s. The majority of obstructions could be recanalized in less than one minute. The five occlusions which could not be recanalized were distal lesions in the superficial femoral artery and which were longer than 10 cm; two were calcified. There were no complications resulting from the recanalization apart from three perforations which were clinically not apparent. Consequent angioplasty proved successful in 78.1% of these patients.

The circadian component of spinule dynamics in teleost retinal horizontal cells is dependent on the dopaminergic system

During the light phase of a light/dark cycle, dendrites of teleost cone horizontal cells display numerous finger-like projections, called spinules, which are formed at dawn and degraded at dusk, and are thought to be involved in chromatic feedback processes. We have studied the oscillations of these spinules during a normal light/dark cycle and during 48 h of constant darkness in two groups of strongly rhythmic, diurnal fish, Aequidens pulcher. In one group the retinal dopaminergic system had been destroyed by the application of 6-OHDA, while in the other (control) group, the dopaminergic system was intact. In control fish, oscillations of spinule numbers were observed under both normal and constant dark conditions, indicating the presence of a robust circadian rhythm. However, spinule dynamics were severely affected by the absence of retinal dopamine. During the normal light phase, the number of spinules in 6-OHDA injected retinae was strongly reduced, and throughout continual darkness, spinule formation was almost completely suppressed. These results indicate that dopamine is essential for both light-evoked and circadian spinule formation; furthermore, we conclude that there is no circadian oscillator within horizontal cells controlling the formation of spinules.

The effect of dopamine depletion on light-evoked and circadian retinomotor movements in the teleost retina

The retinae of lower vertebrates undergo a number of structural changes during light adaptation, including the photomechanical contraction of cone myoids and the dispersion of melanin granules within the epithelial pigment. Since the application of dopamine to dark-adapted retinae is known to produce morphological changes that are characteristic of light adaptation, dopamine is accepted as a casual mechanism for such retinomotor movements. However, we report here that in the teleost fish, Aequidens pulcher, the intraocular injection of 6-hydroxydopamine (6-OHDA), a substance known to destroy dopaminergic retinal cells, has no effect on the triggering of light-adaptive retinomotor movements of the cones and epithelial pigment and only slightly depresses the final level of light adaptation reached. Furthermore, the retina continues to show circadian retinomotor changes even after 48 h in continual darkness that are similar in both control and 6-OHDA injected fish. Biochemical assay and microscopic examination showed that 6-OHDA had destroyed dopaminergic retinal cells. We conclude, therefore, that although a dopaminergic mechanism is probably involved in the control of light-induced retinomotor movements, it cannot be the only control mechanism, nor can it be the cause of circadian retinomotor migrations. Interestingly, 6-OHDA injected eyes never reached full retinomotor dark adaptation, suggesting that dopamine has a role to play in the retina's response to darkness.

Contacts of dopaminergic interplexiform cells in the outer retina of the blue acara

Dopaminergic interplexiform cells in the retina of the blue acara were investigated using an antiserum against tyrosine hydroxylase and PAP visualization. In whole-mount preparations, we observed a homogeneous distribution of cell bodies throughout the retina without any indication of regional specialization. At the fine and ultrastructural level, we studied the morphology of labeled telodendria within the outer plexiform layer. Apart from contacts with horizontal cell perikarya and bipolar cell dendrites, we observed direct contacts, mostly in the form of close appositions, with cone pedicles and rod spherules. Quantitative evaluation and reconstruction of serial sections showed that all cone pedicles and most rod terminals were approached in this way. The dopaminergic pathway terminating on horizontal cells and photoreceptors is discussed with respect to the localization of dopamine receptors in the outer retina, and the control of adaptive changes such as retinomotor movements, spinule formation, and horizontal cell coupling.

Self-expanding metal stents for palliation of malignant esophageal obstruction--a pilot study of eight patients

We sought to determine whether the application of a self-expanding metal stent enables palliation of malignant dysphagia with minimal risk. The results of pilot studies from two centers are reported. We treated 8 inoperable patients with a 14 mm self-expanding metal stent (Wallstent). The stent was applied without general anesthesia under mild i.v. sedation. The procedure was successful in all cases. No side effects were noted. In one patient, tumor ingrowth through the meshes of the stent occurred. This patient was additionally treated with a percutaneous gastrostomy. One patient experienced tumor overgrowth of the proximal end, necessitating laser treatment. Three patients were still alive after three months. The mean number of cumulative endoscopic interventions per patient was 2.2 (SD: +/- 2; median 2). The mean observation time was 10.7 weeks +/- 2 (median 12). Dysphagia was graded from 0 (normal swallowing) to 4 (inability to swallow saliva). Dysphagia was significantly (p less than 0.0005) reduced from grade 3.1 (SD: +/- 0.35) to 0.5 (SD: +/- 0.5) immediately after stenting. 62.5% of the patients were able to manage a virtually normal diet (in one of these patients dysphagia recurred six weeks after stent placement due to tumor ingrowth). Six patients (75%) were able to ingest all necessary calories orally. The application of a 14 mm self-expanding metal stent in cases of inoperable malignant esophageal obstruction seems to offer safe and effective palliation of malignant dysphagia.

Technical failure of biliary metal stent deployment in a series of 116 applications

Biliary metal stents are thought to offer improved long-term palliation of malignant biliary obstruction due to a lower incidence of migration and clogging. Placement of these stents is technically more complicated than that of plastic endoprostheses and requires two experienced physicians. We report the incidence and reasons for apparent malfunction of expandable metal stent deployment (Wallstents and Strecker stents). In 116 applications of 82 Wallstents (endoscopic approach: n = 33, transhepatic approach: n = 49), we observed 19 cases of stent malfunction due to technical problems of stent delivery. In 13 cases (15.8%), the restraining membrane of the Wallstent could not be retracted sufficiently to deliver the stent. There were 6 (17.6%) failures in 34 cases of Strecker stent deployment. In 3 cases, we noted difficult balloon removal, including avulsion of the balloon catheter shaft within the endoscope during attempted balloon removal in one case. In one case, the Strecker stent could only be released partially, requiring subsequent endoscopic extraction. In two patients, only partial expansion of one end of the Strecker stent could be achieved. Given the significant malfunction rate of expandable metal stents during stent delivery, further improvements in the delivery system of the metal stents are required.

[Metal or plastic endoprostheses in malignant obstructive jaundice. A randomized and prospective comparison]

In a prospective randomized trial 58 patients (24 men, 34 women, mean age 67 +/- 13 [42-89] years) with inoperable malignant jaundice were treated with synthetic (S; n = 29) or expanding metal endoprostheses (M; n = 29). After endoscopic retrograde cholangiopancreatography patients were divided into a group with hilar (K: n = 7; M: n = 6) or distal involvement (K: n = 22, M: n = 23). In two cases with hilar involvement (28%) a synthetic endoprosthesis could not be implanted, while early prosthesis occlusion (after 2 days) was observed in one case. But in this group it was possible to implant all metal stents. In the group with distal involvement both synthetic and metal endoprostheses were successfully implanted. In the M group the proportion of patients with prosthesis failure (13.6%) was significantly higher than in the S subgroup (40.9%). The cholangitis incidence was 9% in the M group, significantly less (P less than 0.05) than in the K group (40.9%). Duration of hospital stay to treat prosthesis-related complications was significantly less in the M group (average 2.9 days) than the K group (12.9 days). It would be a great advance in palliative tumour treatment if it were possible significantly to reduce, by means of metal stents, the incidence of late cholangitis and the duration of hospital stay necessary to treat late complications. But improvement in the technique of implanting metal stents would be essential before their general use in distal lesions can be recommended.

Acute embolic occlusions of the infrainguinal arteries: percutaneous aspiration embolectomy in 102 patients

Percutaneous aspiration embolectomy (PAE) was performed on acute embolic occlusions of infrainguinal arteries unrelated to percutaneous transluminal angioplasty or chronic atherosclerotic arterial occlusive disease. Of 102 patients, most (62.7% [n = 64]) had limb-threatening ischemia (stages III and IV according to the Fontaine classification); 86.3% (n = 88) had cardiac disease that caused the embolic occlusion. The clinical success rate was 87.3% (n = 89). Major complications occurred in 8.8% (n = 9) of the cases. The 30-day mortality was 3.9% (n = 4). In comparison with Fogarty-catheter embolectomy, PAE has a higher success rate and a lower mortality. PAE has several advantages: It is a simple technique with reduced invasiveness, combines a diagnostic and a therapeutic procedure, enables treatment of tibial and pedal vessels, and can be combined with all other angioplastic methods.

Localization and function of dopamine in the adult vertebrate retina

Dopamine (DA) has satisfied many of the criteria for being a major neurochemical in vertebrate retinae. It is synthesized in amacrine and/or interplexiform cells (depending on species) and released upon membrane depolarization in a calcium-dependent way. Strong evidence suggests that it is normally released within the retina during light adaptation, although flickering and not so much steady light stimuli have been found to be most effective in inducing endogenous dopamine release. DA action is not restricted to those neurones which appear to be in "direct" contact with pre-synaptic dopaminergic terminals. Neurones that are several microns away from such terminals can also be affected, presumably by short diffusion of the chemical. DA thus affects the activity of many cell types in the retina. In photoreceptors, it induces retinomotor movements, but inhibits disc shedding acting via D2 receptors, without significantly altering their electrophysiological responses. DA has two main effects upon horizontal cells: it uncouples their gap junctions and, independently, enhances the efficacy of their photoreceptor inputs, both effects involving D1 receptors. In the amphibian retina, where horizontal cells receive mixed rod and cone inputs, DA alters their balance in favour of the cone input, thus mimicking light adaptation. Light-evoked DA release also appears to be responsible for potentiating the horizontal cell-->cone negative feed-back pathway responsible for generation of multi-phasic, chromatic S-potentials. However, there is little information concerning action of DA upon bipolar and amacrine cells. DA effects upon ganglion cells have been investigated in mammalian (cat and rabbit) retinae. The results suggest that there are both synaptic and non-synaptic D1 and D2 receptors on all physiological types of ganglion cell tested. Although the available data cannot readily be integrated, the balance of evidence suggests that dopaminergic neurones are involved in the light/dark adaptation process in the mammalian retina. Studies of the DA system in vertebrate retinae have contributed greatly to our understanding of its role in vision as well as DA neurobiology generally in the central nervous system. For example, the effect of DA in uncoupling horizontal cells is one of the earliest demonstrations of the uncoupling of electrotonic junctions by a neurally released chemical. The many other, diverse actions of DA in the retina reviewed here are also likely to become model modes of neurochemical action in the nervous system.(ABSTRACT TRUNCATED AT 400 WORDS)

Biocytin: intracellular staining, dye-coupling and immunocytochemistry in carp retina

Correlation of electrophysiological and morphological, including ultrastructural, characteristics of neurones is important for understanding the functional organization of neuronal systems. Further correlation with neurotransmitter content is essential for determining the neurochemical(s) used by a given neurone for propagating its signal. The two main neuronal markers presently available (lucifer yellow and horseradish peroxidase) are not satisfactory for correlating all three aspects. We have devised a new simple procedure whereby retinal interneurones can be labelled with biocytin by positive ionophoresis of an unbuffered solution. Biocytin readily crosses gap junctions thus revealing extensive networks of coupled cells. In the case of H1 horizontal cells, which are known to be GABAergic, the neurotransmitter can also be demonstrated by superimposed immunocytochemistry.

[Rotation aspiration thromboembolectomy]

Rotating aspiration thromboembolectomy (RAT) was performed in 32 patients (11 women and 21 men; mean age 68 [41-92] years with infrainguinal arterial occlusion, various conventional angioplasty techniques having been unsuccessful. Mean length of occlusion was 19.7 cm (2-47 cm). 17 patients were in stage IIb, 8 in stage III and 7 in stage IV (Fontaine classification). RAT consists of mechanical fragmentation of thrombotic or embolic occlusion material during simultaneous infusion of urokinase, followed by aspiration of the material. Primary success (residual stenosis less than or equal to 50%) was demonstrated by angiography in 31 of 32 patients, while primary clinical success (reduction by at least one Fontaine stage) occurred in 29 patients. These results demonstrate that RAT is a suitable method for the percutaneous intraluminal treatment of long thrombotic or embolic occlusions in which conventional angioplasty techniques have previously failed.

Dopamine and plasticity of horizontal cell function in the teleost retina: regulation of a spectral mechanism through D1-receptors

The negative feed-back interaction between horizontal cells (HCs) and cones in the cyprinid fish retina is thought to be mediated by horizontal cell spinules. These are "plastic" structures, largely absent from the dark-adapted retina and formed anew during light adaptation. We have previously shown that horizontal cell feed-back is similarly enhanced by light adaptation. The role of the interplexiform cell transmitter dopamine in both processes has been studied in the roach retina. Application of dopamine to dark-adapted retinae induced spinule formation in a dose-dependent way. The effect of dopamine was mimicked by dibutyryl-cAMP and suppressed selectively by D1 receptor antagonists. The effect of light in inducing spinule formation was lost in retinae depleted of endogenous dopamine. However, application of exogenous dopamine to these retinae triggered normal spinule formation. For all pharmacological treatments used, there was a strong correlation between spinule number and degree of feed-back activity in biphasic horizontal cells. Thus, when the spinule content of the cone pedicles was high, biphasic horizontal cell responses exhibited strong depolarizing components and vice versa. It is concluded that light-evoked formation of spinules in HC dendrites involves the action of dopamine upon D1 receptors. Spinules, in turn, are likely to be presynaptic terminals mediating the dynamic negative feed-back effect of horizontal cells upon cones.

Characterization of a GABAergic population of interstitial amacrine cells in the teleost retina

We used postembedding immunocytochemistry with an antiserum against BSA-conjugated GABA to study the inner plexiform layer of a cyprinid teleost, the roach. In this part of the retina, we observed a distinct banding pattern of GABA-positive material. There was a narrow unstained region separating the distal sublamina a from the proximal sublamina b; each sublamina was further subdivided into four (a) and two (b) sublayers of heavier staining, respectively. Using three-dimensional reconstruction of series of half-micron tangential sections, we were able to characterize a population of interstitial amacrine cells which contained GABA-like immunoreactive material. These cells had elliptical dendritic fields (area: about 0.04 mm2) and conspicuous, thick processes (dia. 4-5 microns). In tangential sections, the dendrites of individual cells appeared to be in close contact, occasionally resulting in difficulties in defining the boundaries of a single dendritic field. Two sub-populations of these cells were observed, one in each sublamina. By comparison with a catalogue of Golgi impregnated amacrine cells and cells microinjected with Lucifer Yellow or HRP, the identity of this type of interstitial amacrine cell is established and its possible physiological properties discussed. Apart from this GABA positive type, a second population of interstitial amacrine cell was observed which did not show positive reaction to the GABA antiserum used.

Effects of ipsapirone on spatial and temporal changes in somatosensory evoked potentials after middle cerebral artery occlusion in the rat

The present study investigates the effects of the 5-hydroxytryptamine1A agonist ipsapirone on electroencephalography and somatosensory evoked potentials after middle cerebral artery occlusion in the rat. We implanted 17 silver ball electrodes symmetrically distributed over the skull in 14 rats and registered electroencephalography activity and somatosensory evoked potentials before, 1 hour, and 1 week after permanent occlusion of the left middle cerebral artery. Before vessel occlusion, a symmetric distribution of electroencephalography power was seen over both hemispheres. Middle cerebral artery occlusion caused a complete abolishment of electroencephalography power in the frontolateral aspects of the affected hemisphere. When electroencephalographic recordings 7 days after the insult were superimposed with three-dimensional-reconstructed pictures of the infarct, a close correspondence of the extention and spatial orientation was noted. Two negative and two positive peaks were consistently recorded before middle cerebral artery occlusion. In both control and ipsapirone-treated (30 mg/kg i.p. 30 minutes after induction of ischemia) animals, the vessel occlusion caused a severe reduction in amplitudes of somatosensory evoked potentials in all areas under record (p less than 0.05). One week after middle cerebral artery occlusion, amplitudes of somatosensory potentials over the lesioned hemisphere were still significantly (p less than 0.05) lower than preischemic values in the control group. When compared with the corresponding values 1 hour after middle cerebral artery occlusion, an albeit insignificant tendency toward increased amplitudes was observed in most areas under record. By contrast, in ipsapirone-treated animals, significant differences compared with preischemic values were no longer present 1 week after the vessel occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

GABA and tyrosine hydroxylase immunocytochemistry reveal different patterns of colocalization in retinal neurons of various vertebrates

Colocalization of GABA- and tyrosine hydroxylase-like immunoreactivity was studied in the retinae of various vertebrate species in order to ascertain whether the presumed coexistence of GABA and dopamine, reported earlier for mammals (Kosaka et al.: Exp. Brain Res. 66:191-210, '87: Wässle and Chun: J. Neurosci. 8:3383-3394,'88) is a common phenomenon. GABA-immunopositive cells constituted a separate population from tyrosine hydroxylase-positive cells in fish and amphibians, whilst in higher--i.e., amniote--vertebrates, such as reptiles, birds, and mammals, all dopaminergic cells contained GABA-like immunoreactivity. No clear correlation was found between the type of dopaminergic cell (amacrine/interplexiform) and the presence or absence of colocalization.

Tyrosine hydroxylase immunoreactive interplexiform cells in the lamprey retina

The distribution of tyrosine hydroxylase immunoreactivity was investigated in retinae of metamorphic, postmetamorphic and adult lampreys. Immunoreactive cell bodies were located mainly in the innermost part of the inner nuclear layer, with a few cells scattered throughout the inner plexiform layer. The processes of these neurons ran preferentially in the inner plexiform layer. Additionally, dense plexus of labelled processes were observed in the outer plexiform and nuclear layers. These findings suggest that most of the tyrosine hydroxylase-immunoreactive cells in the lamprey retina are interplexiform cells.

Cyclic changes in dopamine and DOPAC content, and tyrosine hydroxylase activity in the retina of a cichlid fish

Using high-performance liquid chromatography combined with electrochemical detection (HPLC-ED) we measured the content of dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) as well as the activity of tyrosine hydroxylase in the retina of a teleost fish during a normal 12 h dark-light cycle. All 3 parameters showed a distinct diurnal pattern with oscillations during phases of changing illumination and more stable levels throughout the light and dark phase. While tyrosine hydroxylase activity levels roughly paralleled dopamine values, the time course of DOPAC content was a mirror image of dopamine levels. The results suggest that changing dopamine levels provide an adaptational signal for the retinal neural network; its metabolism seems at least in part to be controlled by endogenous factors.

Haloperidol suppresses light-induced spinule formation and biphasic responses of horizontal cells in fish (roach) retina

In retinae of lower vertebrates, negative feed-back interactions between horizontal cells (second-order neurones), and cone photoreceptors lead to generation of spectrally multi-phasic light-evoked responses (S-potentials) in horizontal cells. Spinules (finger-like extensions of horizontal cell dendrites) have been suggested to mediate these interactions in retinae of teleost fish. We have studied whether prevention of light-dependent spinule formation would indeed affect an S-potential component (the red-sensitive depolarization in H2 horizontal cells), known to depend on such negative feed-back. Haloperidol was used as a dopamine antagonist to suppress light-induced formation of spinules in retinae of the cyprinid fish, the roach. In normal (untreated) retinae, biphasic S-potentials were strongly depolarizing and horizontal cell dendrites possessed abundant spinules. However, following application of haloperidol to the vitreous prior to light adaptation, spinule formation was suppressed, and concomitantly, red-sensitive depolarizing S-potentials remained significantly under-developed. The results are consistent, therefore, with the idea that spinules mediate the negative feed-back interaction between horizontal cells and cones.

Amacrine cells in the retina of a cyprinid fish: functional characterization and intracellular labelling with horseradish peroxidase

Forty amacrine cells in retinae of a cyprinid fish, the roach, were intracellularly labelled with horseradish peroxidase following electrophysiological identification as sustained depolarizing, sustained hyperpolarizing or transient units. Labelled cells were analysed by light microscopy and compared with a catalogue of amacrine cells established in a previous Golgi study on the same species. About 30% of the cell types characterized by the Golgi method were encountered in the present study. When intracellularly labelled cells were differentiated on the basis of their dendritic organization in the plane of the retina, a given electrophysiological response pattern was found to be generated by different morphological types, and vice versa. However, examination of the ramification patterns of the dendrites within the inner plexiform layer (i.e. in the radial dimension of the retina), showed that this morphological parameter of a given amacrine cell could be correlated with its light-evoked response. Several amacrine cell types were found to possess special distal dendrites which arose from the main dendritic branches and extended well over a mm in the retina. Distal dendrites were oriented tangentially with respect to the optic nerve papilla, but did not appear to be involved in any synaptic connectivity. It is concluded that the Golgi-based classification is a valuable tool for identifying intracellularly labelled amacrine cells. However, although the correlation between layering of dendrites in the inner plexiform layer and electrophysiology was generally good, additional physiological parameters would be required to determine whether more extensive parallels exist between structural and functional characteristics of amacrine cells. Alternatively, the considerable morphological diversity of amacrine cells may be of limited physiological significance.

Localization of calcium and phosphorus in early predentin-matrix components by electron spectroscopic imaging (ESI)-analysis in rat molars

The subcellular distribution of the inorganic elements calcium (Ca) and phosphorus (P) was studied in the first-formed dentin matrix during initial mineralization in neonatal rat molars. This most peripheral matrix region is comprised of a proteoglycan-rich ground substance, interwoven by a collagenous network, matrix vesicles, aperiodic fibrils derived from the dental basal lamina, and apical odontoblastic cell processes. All matrix components may possibly serve as templets for mineral deposition during initial calcification of first-formed mantle dentin and predentin. By means of the very sensitive ESI-analysis we studied the subcellular localization of Ca and P and their possible association with distinct organic extracellular matrix components and odontoblasts. Ca-signals were found in the ground substance, at striated collagen fibrils and plasma membranes of odontoblasts in the cuspal early matrix region, but occurred only sparsely in the ground substance of the more distal matrix region where odontoblast processes attach to aperiodic fibrils of the dental basal lamina. Ca was generally absent in matrix vesicles. In contrast, P-signals were found in matrix vesicles, at aperiodic fibrils and at the plasma membranes of odontoblasts. Ca and P co-localized at striated collagen fibrils (type I or II). These results suggest that striated collagen fibrils might serve as primary deposition sites for calcium phosphate during early biological calcification of organic extracellular macromolecules.

Release pattern of endogenous dopamine in teleost retinae during light adaptation and pharmacological stimulation

The release of endogenous dopamine from teleost retinae was studied using high-performance-liquid-chromatography and electrochemical detection. Dopamine was measured in superfusates of isolated retinae after stimulation with flickering light as well as in the presence of GABA, L-glutamate, kainate or taurine. The effect of the receptor antagonists bicuculline, picrotoxin and kynurenic acid was also tested in retinae kept in the dark. We report a low level, basal release of dopamine in the dark (20 pg x 10 min-1/retina), which is transiently increased by stimulation with flickering light. This light evoked release of dopamine is inhibited by GABA and L-glutamate, whilst antagonists of these retinal transmitters stimulate release in the dark.

Rods trigger light adaptive retinomotor movements in all spectral cone types of a teleost fish

Action spectra for light induced cone contraction are described for the two spectral cone types of a dichromatic (red/green) cichlid species (Aequidens pulcher). Criterion response thresholds (50% of maximal response amplitude) were determined for seven wavelengths. After correcting for absorption by cornea and lens, the resulting action spectra were compared with the absorption spectra of the rod and cone visual pigments. We find (i) that the action spectra of red and green sensitive cones are almost identical and (ii) matched most closely the absorption spectrum of the rod visual pigment. We therefore conclude that light adaptive cone contraction is triggered by light absorption in rods, which in the dark adapted state are located next to the external limiting membrane and are therefore in an optimal position to capture the incident light during early dawn. Possible mechanisms of signal transfer from rods to cones are discussed.

Plasticity of cone horizontal cell functioning in cyprinid fish retina: effects of background illumination of moderate intensity

In electrophysiological experiments involving intracellular recording from horizontal cells in the isolated retina of the roach, light adaptation of the retina has been shown to result in potentiation both of (1) the depolarizing component of biphasic chromaticity type S-potentials, and (2) the temporal frequency transfer functions of photopic luminosity type horizontal cells. Under identical light adaptation conditions, the number of spinules on horizontal cell dendrites positioned laterally at cone pedicle ribbon synapses, increase by some threefold. The latter effect occurs equally in pedicles of red- and green-sensitive cones. Thus, horizontal cells are 'plastic' in both structural and electrophysiological respects. Furthermore, since the two electrophysiological parameters studied depend on negative feedback from horizontal cells onto cones, the results suggest that it is the inhibitory synapses that are plastic and that spinules may be sites of the negative feedback interaction. Physiological and behavioural aspects of light-dependent horizontal cell plasticity are also discussed.

Amacrine cells in the retina of a teleost fish, the roach (Rutilus rutilus): a Golgi study on differentiation and layering

We studied 250 amacrine cells in the retina of the tetrachromatic cyprinid Rutilus rutilus (roach) after rapid Golgi impregnation. All cells were recorded in camera lucida drawings from 50 -80 μm sections. For classifications we used independent criteria of presumed functional relevance, most of which could be quantified. These included ‘gross morphological’ features such as size, symmetry and orientation of the dendritic field, pattern of branching and number of ramification points as well as fine structural details like process diameter and the occurrence of spines and varicosities. We also took into account the pattern of radial distribution of dendrites. To obtain information about the subdivision of the inner plexiform layer, we used the relative stratification levels of stratified amacrine cells to plot a frequency distribution diagram showing that the dendrites of these cells are clustered in seven discrete sublayers of unequal width; four sublayers occupy the distal half of the inner plexiform layer (sublamina a) and three sublayers are present in the proximal half (sublamina b). The subdivision was compared with densitometric data of the inner plexiform layer after various staining methods and with previous observations about the location of bipolar terminals and neurochemical bandings. Our findings suggest that this layer is composed of complementary structural components, each of which is subject to a specific layering pattern. On this basis we could distinguish 43 different types of amacrine cell. If individual types occurred in more than one sublayer, they were considered as subtypes; of these, we found 70 different ones. Among the 43 types, 6 were observed only once. In comparison with amacrine cells described in other species, six ‘new’ types were identified. For each individual type, an identity chart was prepared summarizing camera lucida drawings of tangential views at low and high magnification, a semischematical drawing of the radial location of the dendrites, and the most relevant quantitative data. Our observations are discussed in the context of available evidence about light-evoked responses of identified amacrine types in other species, and possible transmitter content. They substantiate a functional concept according to which amacrine cells provide (i) a multicellular aggregate for coupled membrane potential; (ii) unit activity by the action of entire individual cells; and (iii) local microcircuits caused by isolated activation of single dendrites or parts thereof. The great variety of morphological differentiation, and the numerous transmitters found, suggest that within this basic framework individual amacrine types serve highly complex and sophisticated roles in retinal information processing. Our attempt towards a detailed classification and description of amacrine cell types is intended to provide a reference for future intracellular and neurochemical work, to facilitate precise identification.

Glutamate and dopamine modulate synaptic plasticity in horizontal cell dendrites of fish retina

Horizontal cell dendrites protruding into the cone pedicles in fish retina exhibit a light-dependent plasticity. In a light-adapted retina they form numerous spinules having membrane densities at their tips. These spinules disappear during dark adaptation. Experiments with light- or dark-adapted retinas which were incubated in glutamate or its agonists and antagonists, respectively, revealed that this putative cone transmitter is able to reduce the expression of spinules in a light-adapted retina. Dopamine, on the other hand, induces the formation of spinules in a dark-adapted retina and haloperidol reduces the expression in a light-adapted retina. These data suggest a control of spinules plasticity through two retinal neurotransmitter systems.

Distribution of vimentin-type intermediate filaments in Sertoli cells of the human testis, normal and pathologic

The presence, distribution and spatial arrangement of vimentin-type intermediate filaments in Sertoli cells from human testis biopsies, were studied in semithin and ultrathin sections using a polyclonal rabbit antiserum. At the ultrastructural level, vimentin immunoreactivity was seen concentrated around the nuclei, along fibrillary material within the cytoplasm and at the ectoplasmic specializations of the Sertoli cell junctions, as well as throughout the periphery of the Sertoli cell processes. It is therefore well suited as a marker for Sertoli cell configuration. In computer-aided 3D reconstructions of 20 serial sections, Sertoli cells displayed particular configurations of intermediate filaments in the different stages of spermatogenesis. Two basic configurations, named AS (before spermiation, stages V, VI, I and II), and PS (after spermiation, stages III and IV) respectively, could be differentiated. In addition to the reconstruction and morphological analysis of vimentin filaments in Sertoli cells from patients with unaltered spermatogenesis (obstructive azoospermia), pathological specimens (spermatogenetic arrest, Sertoli cells only-syndrome) were studied with respect to vimentin immunohistochemistry. The results indicate that vimentin filaments play an important role in the adaptation of Sertoli cells to the varying configurations of neighbouring cells during spermatogenesis as well as under pathological conditions.

Amacrine cells with neurotensin- and somatostatin-like immunoreactivities in three species of teleosts with different color vision

Neurotensin- and somatostatin-like immunoreactivities were localized by pre-embedding techniques in retinal whole-mounts and radial sections of a monochromatic glass catfish (Kryptopterus bicirrhis), a dichromatic cichlid species (Aequidens pulcher), and the tetrachromatic roach (Rutilus rutilus). Both neuropeptides were observed in perikarya and processes of amacrine cells. For a precise identification of cell types, tangential and radial views were correlated with Golgi-impregnated material. The dendritic pattern defining the morphological subtype of amacrine cells was determined by the given neuropeptide or by the species-specific degrees of complexity of retinal structure and function. Neurotensin-like immunoreactivity was localized in amacrine cells of intermediate size, radial symmetry and dendrites with numerous varicosities; they were monostratified in sublayer 3 of the inner plexiform layer. This cell type was common to all three species. In the mono- and dichromatic retinas, a single type of amacrine cell with somatostatin-like immunoreactivity was found with radially oriented, varicose dendrites in sublayer 5. In the tetrachromatic roach retina, two somatostatin-positive amacrine cell types were found with very different patterns of ramification; furthermore, both of these types occurred in more than one sublayer. Possible functional implications for color vision of neuropeptide-specific amacrine cells with uniform morphology in all three species and those with a more varied morphology in the tetrachromatic roach are discussed.

Destruction of the preganglionic nerves by beta-bungarotoxin does not interfere with normal embryonic development of the rat adrenal medulla

Using beta-bungarotoxin (beta-BTX) as a tool to eliminate the preganglionic cholinergic nerve supply to the embryonic rat adrenal gland, we have investigated whether or not these nerves affect the differentiation of embryonic chromaffin cells (pheochromoblasts). Rat fetuses received a single injection of 1 or 2 micrograms beta-BTX or an identical volume of saline at embryonic day (E) 17 and were taken for morphological and biochemical analyses at E 21. Administration of beta-BTX caused a 15 to 20% reduction in body weight, crown-rump-length and adrenal weight. Spinal cord development was reduced and acetylcholinesterase-positive cells in ventral and lateral columns were virtually absent in toxin-treated animals. In adrenal glands, a decrease of choline acetyltransferase activity to 13% of control levels and a concomitant decrease of ultrastructurally identifiable nerve fibers and axon terminals revealed that application of 2 micrograms beta-BTX effectively reduced the neuronal input to E 21 adrenal glands. Values for total adrenal catecholamines, relative amounts of adrenaline and noradrenaline, tyrosine hydroxylase and phenylethanolamine N-methyltransferase activities were unaltered. All ultrastructural features of pheochromoblasts (except the lack of synapse-like axon terminals) were inconspicuous. Corticosterone levels in adrenals and plasma were identical to controls. These data strongly suggest that normal embryonic development of adrenal chromaffin cells does not require an intact nerve supply.

The cellular origin of an unusual type of S-potential: an intracellular horseradish peroxidase study in a cyprinid fish retina

L2-type S-potentials are mainly blue/green-sensitive hyperpolarizing responses with a red-sensitive depolarizing component which is either weak or absent. They were first described in the retina of the roach, a cyprinid fish, by Djamgoz (1978, 1984) and Djamgoz & Ruddock (1978, 1979a). The cellular origin of these responses has been determined and characterized by intracellular recording, horseradish peroxidase staining, and light and electron microscopy. They were found to arise in horizontal cells with H2-like morphologies on average (Stell & Lightfoot, 1975). The dendrites of these cells contacted green- and blue-sensitive cone pedicles within which both lateral and central contacts were made at ribbon synapses. The laterally-positioned dendrites had incompletely formed spinules associated with them. A number of similarities between these units and the biphasic, chromaticity (Cb)-type S-potentials have been outlined and it is suggested that L2 units are essentially Cb-units with a weak depolarizing component. In turn, it is suggested that the depolarizing component is reduced as a consequence of the relatively dark-adapted states of the retinae. It is concluded that the negative feed-back pathway that subserves the generation of depolarizing (Cb-type) S-potentials is weak or absent in dark-adapted retinae and that spinules may be the site of this feed-back interaction.

Relation of retinomotor responses and contractile proteins in vertebrate retinas

Photoreceptors of many nonmammalian vertebrate species display pronounced light-dependent movements which are absent in mammalian species. In order to further analyze the molecular basis of receptor movements and of simultaneous migration of melanin granules in pigment epithelial processes, we investigated the distribution of actin, myosin and the actin-binding muscular proteins alpha-actinin and vinculin in the retina of various vertebrate species. The species investigated can be divided in two groups (i) those possessing retinomotor capacity (fish, frog, turtle, chick) and (ii) those in which retinomotor activities are negligible or absent (gecko, mouse, rat). Prominent bundles of actin filaments extending throughout the long axis of photoreceptor inner segments were only found in species possessing retinomotor capacity, while comparable actin filament bundles were absent or poorly developed in photoreceptors of species lacking significant retinomotor capacity. In all species examined, a well developed circumferential band of actin filaments was associated with the zonula adhaerens-like junctions between photoreceptors and Müller (glial) cells forming the external limiting membrane. This area was also identified as the exclusive site of myosin, alpha-actinin and vinculin (only in the chick, alpha-actinin-like immunoreactivity was also found along the photoreceptor actin filament bundles). Thus, the external limiting membrane may be important for both structural support and for providing a possible site of filament sliding for photoreceptor movements. In pigment epithelium actin, myosin, alpha-actinin and vinculin were concentrated circumferentially in the area of the terminal bar which has been previously shown to be contractile. In all species apical pigment-epithelial processes displayed actin-like fluorescence of varying intensities. Another site of actin-like staining were photoreceptor synaptic complexes which represent a well known site for synaptic plasticity. Immunoblotting studies on the avascular chick retina revealed polypeptide bands at Mr approximately 130 000, approximately 100 000, and 42 000 which were specific for vinculin, alpha-actinin and actin, respectively. A faint polypeptide band comigrating with thymus myosin heavy chain indicates myosin to be only a minor component of the retina (chick and fish).

Action spectrum of photomechanical cone contraction in the catfish retina

The action spectrum for the photomechanical contraction of catfish single cones was found to fit the absorbance spectrum of the visual pigment they contain (determined by microspectrophotometry). This indicates that cone contraction is brought about by a direct effect of light on the cones themselves and not, as is the case for the epithelial pigment, by an indirect effect via the rods.

Light-dependent change of cone-horizontal cell interactions in carp retina

Carp H2 horizontal cells were investigated at various stages of dark and light adaptation. Their state of adaptation was verified by evaluating in computer reconstructed serial sections the number of small, fingerlike protrusions originating from H1 processes. These so-called spinules are absent in the dark-adapted state and are reformed during light adaptation. Intracellular recordings showed that long-wave-induced depolarization thought to be mediated by sign-inverted feedback from H1 horizontal cells onto green-sensitive cones could not be demonstrated in completely dark-adapted specimens. This type of response only developed with increasing light adaptation. Following electrophysiological characterization, the cells were injected with horseradish peroxidase and identified light and electronmicroscopically. Our results show a good correlation between the number of spinules and the degree of electrophysiological feedback suggesting that the spinules may be the sites of the feedback synapses in teleost retinas. Several models of synaptic transmission from H1 terminals to cone pedicles are discussed.

Double labelling of retinofugal projections in the cat: a study using anterograde transport of 3H-proline and horseradish peroxidase

A new method is described for combining 3H-proline and horseradish peroxidase (HRP) as anterograde neuronal tracers. By this method the presence of both substances can be demonstrated in the same histological section. We developed this method to investigate the retinofugal projections from the two eyes in the cat. One eye was injected with 3H-proline the other with HRP. Cryostat sections of the brain were mounted on emulsion coated slides in the dark. Sections were first exposed to the emulsion for 2-3 weeks at -40 degrees C and developed for autoradiography. Only then they were reacted for HRP-activity with tetramethylbenzidine (TMB). Keeping to this sequence autoradiographic procedures could not abolish the HRP-reaction product and silver grains and TMB can be visualized on the same slide. The wellknown projection pattern in the lateral geniculate nuclei was confirmed as a control for the new method. In the superior colliculus and in the pretectum a clear overlap of retinal terminals from the two eyes could be demonstrated for the first time.

Permeability of the external glial limiting membrane of rat parietal cortex

As the relevance of previous reports demonstrating the permeability of the glia limitans appears to be not generally accepted, the problem is reinvestigated by examination of the ultrastructure of the glia limitans in combination with tracer studies using Ruthenium Red. The results clearly show that gap junctions are the only type of intercellular contact present in this layer. Measurements of the lengths of cross-sections of junctional regions reveal a decrease in size in absolute terms as well as in relation to total astrocytic surface if one proceeds from the more superficial layers into the depth of the tissue. The intercellular clefts leading from the subarachnoidal space into the interspaces of brain tissue are patent thus allowing the tracer to penetrate to a depth of 0.4-0.6 mm in one hour. Although these observations confirm the idea of an ultimate communication between the cerebrospinal fluid compartments and the extracellular space of brain the discussion shows how the particular arrangement of the intercellular channels and the cells bordering them may be suited to control the local composition of interstitial fluid independently from that of the cerebrospinal fluid.

Endogenous control of spinule formation in horizontal cells of the teleost retina

The process of horizontal cells invaginating teleost cone pedicles are studded with small finger-like projections which are present only in the light-adapted state. The aim of this study was to investigate whether the formation and degradation of these so-called spinules, which are thought to function as feed-back synapses onto the cones, is endogenously controlled. Three types of experiment were carried out involving fish entrained to a 12 h light/dark cycle: 1) The number of spinules was determined in goldfish at various times during exposure to either constant darkness (36 h) or constant light (57 h). 2) The time course of spinule formation and degradation in goldfish was investigated following exposure to light or darkness at various times during the light/dark cycle. 3) The time course of flash-induced spinule formation in tench following dark adaptation at noon was compared to that following dark adaptation at midnight. The results of these experiments show that spinule formation and degradation are partially under endogenous control but that they need light and full expression. This endogenous rhythm is reflected in the time courses of spinule formation and breakdown during different phases of the light/dark cycle.

Morphologic changes in teleost primary and secondary retinal cells following brief exposure to light

Light adaptive morphologic changes in the teleost retina, such as movements of rods, cones, and epithelial pigment and spinule formation on horizontal cell terminals, are normally associated with continual exposure to light. Depending on a variety of factors these processes are generally completed within 30-60 min. In this report we show that a brief exposure to light (1-2 min) preceded and followed by darkness is sufficient to elicit these changes in four species of teleost; the trout (Salmo gairdneri), the tench (Tinca tinca), the carp (Cyprinus carpio), and the goldfish (Carassius auratus). A brief pulse is as effective in causing cone migration and an increase in the number of spinules as continual exposure; however, it is sometimes less effective in causing pigment migration. The photomechanical changes following a brief period of light are always completed more quickly and show greater species variability than the formation of spinules. These results show that the various morphologic manifestations of light adaptation are autonomous processes that need only a short pulse of light to trigger the whole sequence of events. This is of interest when considering their control mechanisms and may have consequences for physiologic work involving experiments on dark-adapted eyes.

Endogenous patterns of photomechanical movements in teleosts and their relation to activity rhythms

The retinal rods, cones and epithelial pigment of most lower vertebrates display rhythmic photomechanical (retinomotor) migrations in response to changes in ambient lighting conditions. This study examines the extent of these migrations in the absence of the daily changes in illumination (constant darkness and constant light) in three species of teleosts. Salmo trutta, a crepuscularly active fish, showed two peaks of light adaptation occurring around dawn and dusk when kept in constant darkness. Tinca tinca, a nocturnal species, also showed an endogenous rhythm during extended periods of darkness, but, unlike Salmo trutta, it was light-adapted throughout what would normally have been "day". At the maximal extent of migration under conditions of continual darkness, the pigment migrated 59% as much as it did during a normal light/dark cycle. Nannacara anomala, a tropical diurnally active species, showed a similar but more pronounced rhythm than Tinca tinca for all 3 days of experimental darkness, behaving essentially identically to fish exposed to a light/dark cycle. Nannacara anomala also displayed a weak rhythm when kept in constant light. It is concluded from these and previous results that the pattern of endogenous photomechanical movement depends both on the activity pattern of a species and on the constancy of the lighting conditions to which it has been exposed during its lifetime.

Pulmonary diffusion capacities for O2 and CO measured by a rebreathing technique

Pulmonary diffusion capacity (D) for O2 and CO was determined from alveolar-mixed venous equilibration kinetics of 16O2, 18O2, and C18O measured during rebreathing by mass spectrometry. During the rebreathing maneuver (15 s) the ventilation was extremely high (about 100 1 X min-1) and PO2 and PCO2 in lung gas were close to their mixed venous values (aveolar hypoxia and hypercapnia). The following mean values (+/- SD) were found in six healthy males (20-33 yr) sitting on a bicycle ergometer (in ml X min-1 X Torr-1): 1) without work load, D18O2 = 54 +/- 10, Dc18O = 47 +/- 11; 2) with the highest work load tested (150 W, O2 uptake 2.1 l X min-1), D18O2 = 62 +/- 12, Dc18O = 54 +/- 8. The ratio D16O2/D18O2 averaged 1.07. The ratio D18O2/Dc18O, averaging 1.2 at rest and at all exercise levels, was close to the estimated O2/CO ratio of Krogh's diffusion constants for tissue and, therefore, was in agreement with the diffusion limitation model. An analysis of the various factors affecting the DO2/DCO ratio does not allow to reliably assess the role of diffusion in red blood cells and reaction with hemoglobin in limiting alveolar-capillary O2 transfer.

Vestibulo-thalamic projection to the anterior suprasylvian cortex of the cat

Suggestive evidence as to the site of a major thalamic relay of the vestibular projection to the anterior suprasylvian (ASS) cortex in the cat has been obtained using the retrograde axonal transport of horseradish peroxidase. The thalamo-cortical neurons are located in several patches surrounding the posterior margins of the ventro-basal complex (VB). This area also was found to receive vestibulo-thalamic projections. It comprises different nuclear groups known to carry somatic, acoustic, visual or combined information, which possibly have certain functions related to kinaesthesia and body orientation in common.

Layer-specific labelling of cat visual cortex after stimulation with visual noise: a [3H]2-deoxy-d-glucose study

Tritiated 2-deoxy-D-glucose (2-DG) was used to demonstrate layer specific uptake of 2-DG at the cellular level in the visual cortex of the cat after stimulation with different kinds of visual stimuli. Two-dimensional static Gaussian visual noise drifting across the visual field led to an increased accumulation of 2-DG in layers III and V as compared to the amount of radioactivity in layer IV. In unstimulated control tissue of visual cortex a homogeneous pattern of labelling was found. Horizontal bars moving vertically across the visual field increased the uptake in layer IV more than in all other layers. Analysis of the 2-DG uptake at the cellular level revealed that visual noise activated two bands of cells, one above and one below layer IV, whereas bar stimuli activated cells mainly in layer IV. Accumulation of 2-DG was always higher in the perikarya than in the surrounding neuropil. These results confirm the physiologically recorded properties of cells in different cortical layers.

Retinal projection to the nucleus of the optic tract in the cat as revealed by retrograde transport of horseradish peroxidase

Retrograde transport of horseradish peroxidase injected iontophoretically into the nucleus of the optic tract of cats revealed that the direction-selective cells in this pretectal nucleus receive direct retinal projections from small retinal ganglion cells, the so-called gamma-cells. These cells from a horizontal band on the contralateral retina. Few labeled cells are found in the ipsilateral temporal retina. The input from the contralateral retina is 10 times more numerous than from the ipsilateral one. In both retinae the highest concentration of labeled cells is near the area centralis.