Presynaptic bodies ("ribbons"): from ultrastructural observations to molecular perspectives

The morphological diversity and dynamic aspects of presynaptic bodies are summarised. Molecular characteristics of the presynaptic machinery are discussed and the signals that control the plasticity of the presynaptic bodies are examined. A review is presented of recent findings regarding the physiology of tonically active synapses. The significance of the synaptic bodies and their dynamic changes in retinal and pineal photoreceptors are considered.

Effect of astroglial cell swelling on pH of acidic intracellular compartments

A variety of pathological conditions lead to swelling of astrocytes, which in turn stimulates ion release by activation of ion channels at the plasma membrane. In the present study, acridine orange and fluorescein isothiocyanate coupled to dextran (FITC-dextran) have been used to examine the effect of cell swelling on pH in acidic compartments of cultured astroglial cells. Both NH4Cl (2 mM) and chloroquine (10 microM), known to alkalinize acidic cellular compartments, led to the expected increase in acridine orange fluorescence intensity. Similar, albeit smaller, effects were elicited by a reduction of extracellular osmolarity (-80 mOsm) and treatment of the cells with glutamate (l mM), manoeuvres which enhanced cell volume. Determination of changes in the FITC-dextran fluorescence ratio (485/440 nm) allowed quantification of the pH changes in lysosomal compartments. Treatment with NH4Cl, reduced extracellular osmolarity and glutamate increased lysosomal pH by 0.65 +/- 0.07, 0.85 +/- 0.14 and 0.25 +/- 0.07, respectively. Measurement of cytosolic pH using 2',7',-bis-(2-carboxyethyl)-5- (and -6) carboxyfluorescein (BCECF) demonstrated a pronounced acidification following cell swelling, observed with both reduced extracellular osmolarity (by 0.23 +/- 0.05 pH units) and 1 mM glutamate (by 0.26 +/- 0.02 pH units). In conclusion, pH within lysosomes and possibly other acidic cellular compartments of astrocytes is increased by cell swelling, which may have important consequences for astrocyte function.

Horizontal cell spinule dynamics in fish are affected by rearing in monochromatic light

Blue acaras (Aequidens pulcher, Cichlidae) were reared for 1 yr in white or monochromatic "red", "green" and "blue" lights to study the function and control mechanisms of horizontal cell (HC) spinules in the synaptic pedicles of cones. Ratios of spinules per synaptic ribbon (S/R) were determined in tangential sections in both single and double cones. We found that the S/R ratios in light adapted retinae decreased with decreasing wavelength of the rearing light in all cone types. Conversely, there was an increasing number of incompletely formed spinules with the highest frequency in the blue light group. Dark adaptation resulted in the complete degradation of mature spinules. However, significant numbers of incompletely degraded spinules were observed in the group reared in blue light. Fish reared in blue light which were transferred to white light formed mature spinules when light adapted and still had vestigial spinules when dark adapted. The mechanisms of spinule formation and degradation and the control of spinule dynamics appear to be fully developed in fish reared in monochromatic light. However, long-term chromatic deprivation seems to induce a compensatory modulation of spinule dynamics. A working hypothesis is formulated that interprets the observed effects as manifestations of differences in the activition of dopaminergic interplexiform cells (light adapted) and the sensitivity to glutamate of HCs (dark adapted). Our findings are consistent with the hypothesis that spinules are involved in sign-inverting feedback transmission from HCs to cones.

The eye of the blue acara (Aequidens pulcher, Cichlidae) grows to compensate for defocus due to chromatic aberration

By rearing fish in various monochromatic illuminations we investigated (1) the potential for compensation of refractive error due to chromatic aberration, (2) the contributions of the chromatic channels to emmetropization, and (3) the role of color cues in the control of eye growth. Cichlid fish (Aequidens pulcher) were reared for 6 months (12 h light/12 h dark) in monochromatic lights (623.5, 534.1, 485.0 nm; spectral purity 5-10 nm). Light levels were isoirradiant at 1.1.10(12) quanta/s/cm2. Two control groups were reared in white light with down-welling illuminances of 0.2 and 33 lx. Nasotemporal diameters (NTDs) of the eyes were measured in relation to lens size. Due to the oblique axis of highest acuity vision in cichlids, NTD is considered to be a more important dimension than axial length. Variances in NTD were equally small in all rearing groups. NTDs were enlarged with increasing wavelengths of the rearing lights with highly significant values over controls in the red-light group. The wavelength-dependent size of the eyes matched the changes in focal length due to longitudinal chromatic aberration. Complete recovery from eye enlargement was observed after fish reared in red light were exposed to a white light regime for 5 weeks. Small variances in NTD in all groups indicated stringent control of eye growth in the absence of color cues. The reversibility of the increase in NTD in fish reared in red light suggests that the eyes were emmetropized by visually guided mechanisms. Eye size in fish reared in white light was intermediate between the values expected if only blue-sensitive single or the red- and green-sensitive double cones contributed to the control of eye growth. This suggests that all chromatic channels participate in emmetropizing the fish eye.

Adaptation-dependent changes of bipolar cell terminals in fish retina: effects on overall morphology and spinule formation in Ma and Mb cells

We have investigated the effects of light and dark adaptation on the overall morphology of bipolar cell (BC) terminals in sublaminae a and b of the inner plexiform layer after labelling with Lucifer Yellow (LY) and PKC immunostaining using confocal laser scanning microscopy and serially sectioned material for electron microscopy. Three-dimensional reconstructed terminals showed marked adaptation-dependent changes of their morphology. Terminals of mixed rod-cone BCs in sublamina a (Ma BC) were irregular and scalloped in light adapted, but smooth and regular in dark-adapted specimens. Terminals from mixed rod-cone BCs in sublamina b (Mb BCs) exhibited an opposite behaviour. At the ultrastructural level, bipolar terminals in both sublaminae showed fingerlike extensions (spinules) invaginating presynaptic amacrine cell (AC) processes. Sixty-two percent of the dark-adapted Mb terminals in sublamina b showed spinules, whereas 21% of the light-adapted terminals had spinules. By contrast, 50.6% of the light-adapted Ma terminals in sublamina a formed spinules, compared to 17.8% of the dark-adapted Ma terminals in this sublamina. These observations reflect the functional subdivision of the inner plexiform layer in an inner ON-and an outer OFF-centre lamina. Our findings suggest that the synaptic plasticity of BC axon terminals may be due to differences of BC membrane potential, or the activity of AC input onto bipolar terminals. They may contribute to processes of fine tuning regulating the efficiency of AC-BC interaction under varying adaptation conditions.

Local intraarterial thrombolysis: in vitro comparison between automatic and manual pulse-spray infusion

PURPOSE

Manual and automatic pulse-spray infusion techniques are compared in vitro to evaluate the efficacy of thrombolysis and the distribution of urokinase and saline solution within thrombus using a pulse-spray catheter.

METHODS

A pulse-spray catheter was introduced into a human thrombus within a stenotic flow model. Automatic and manual pulsed infusion of urokinase and automatic pulsed infusion of saline solution were compared. To quantify the efficacy of thrombolysis, pressure gradients were recorded proximal and distal to the thrombus and during the course of infusion. Distribution of infused urokinase was assessed radiographically.

RESULTS

The fastest and most homogeneous dissolution of the thrombus was achieved with automatic pulsed infusion of urokinase, shown by decreasing transthrombotic pressure gradients (p < 0.001, Wilcoxon, matched pairs). Manual pulsed infusion of urokinase or saline solution resulted in inhomogeneous thrombus dissolution and delayed thrombolysis.

CONCLUSION

Application of automatic pulse-spray injectors seems beneficial for more effective and homogeneous intraarterial pulse-spray thrombolysis when compared with conventional manual pulsed technique.

Rod outer segment renewal in the retinae of deep-sea fish

Outer segment renewal involves the synthesis of disc material in the photoreceptor inner segments, the shedding of the tips of the photoreceptor outer segments, and their phagocytosis by the retinal pigment epithelial cells. It has been suggested that in the retinae of deep-sea fish no renewal of outer segments may take place. In order to assess outer segment renewal in deep-sea fish retinae we counted (i) periciliary vesicles in rod inner segments as a parameter for disc-synthesis activity and (ii) phagosomes in retinal pigment epithelial cells as a parameter of shedding and phagocytosis in 12 species of deep-sea fish with multibank or single bank retinae. We also measured the lengths of rod outer segments in order to evaluate the balance between synthesis and phagocytotic activity. In four of these species (Synaphobranchus kaupi, Nematonurus armatus, Coryphaenoides guentheri and Halosauropsis macrochir) we further recorded size-related changes of these parameters and their relation to the position of a given rod within the banks in the retina. The number of periciliary vesicles was highest in inner segments of the most vitread bank and in the periphery of the retina. Phagosomes were most abundant in retinal pigment epithelial cells of the central retina. Long rod outer segments were most frequently recorded in the peripheral retina indicating that in this region new synthesis may outbalance shedding. Vitread rod outer segments were only slightly longer than sclerad ones. Larger animals had shorter rod outer segments than small ones. We present evidence that rod outer segment renewal takes place in the retina of all deep-sea fish. Vitread rods may be more active in this respect than sclerad ones.

Control of rod retinomotor movements in teleost retinae: the role of dopamine in mediating light-dependent and circadian signals

In the retinae of lower vertebrates, several morphological changes, including photomechanical movements of rods, cones and pigment epithelium, occur during light and dark adaptation. We studied the contribution of exogenous and endogenous circadian control mechanisms to rod retinomotor movements in the teleost retina and their dependence on an intact dopaminergic system. Blue acara (Aequidens pulcher) were kept under a 12:12 h light/dark cycle. One population of fish remained untreated; another population was treated with 6-hydroxy-dopamine, selectively to destroy dopaminergic cells. Rod positions were determined in semi-thin radial sections. During the normal light/dark cycle, rods were elongated during the day and contracted at night. Rod retinomotor movements persisted during two cycles of continuous darkness. Expected light levels of rod positions were reduced by about 40% in comparison with normal light phases. Adaptation-dependent retinomotor movements and movements driven by an endogenous circadian clock also occurred in dopamine-depleted retinae. No statistically significant differences were observed between dopamine-containing and dopamine-depleted retinae. We conclude that rod retinomotor movements in teleost retinae are controlled by light and by an endogenous circadian clock. Dopamine plays no essential role in the light-dependent and endogenous control of rod retinomotor movements.

Propofol versus midazolam for sedation during percutaneous transluminal angioplasty

PURPOSE

To prospectively and randomly compare use of propofol versus midazolam for sedation during percutaneous transluminal angioplasty (PTA).

MATERIALS AND METHODS

Forty patients (27 men, 13 women; mean age 64.4 years +/- 12.2) who underwent PTA of the arteries below the diaphragm were prospectively randomized for sedation with propofol or midazolam. Both drugs were administered after an initial bolus injection by means of continuous infusion to achieve conscious sedation at levels II-III according to the Ramsay classification. Patients and interventionalists were blinded to the applied sedative. Both groups were similar with regard to American Society of Anesthesiology status, heart rate, blood pressure, arterial oxygen pressure (pO2), arterial carbon dioxide pressure (pCO2), arterial oxygen saturation (SpO2), and visual analogue scores for general condition, anxiety, and pain. During PTA, heart rate, blood pressure, and pulse oximetry (tpO2) were monitored continually. Every 30 minutes, an arterial blood gas analysis was performed. Visual analogue scores were obtained before, during, and after intervention.

RESULTS

Decreases in SpO2, pO2, and tpO2 were significantly greater after sedation with midazolam (P < .05; t test). The increase in pCO2 was significantly greater after midazolam (P < .05; t test). No significant difference between the drugs was found with regard to any of the other parameters. Both drugs resulted in sufficient sedation and anxiolysis (P < .01 for both drugs for visual analogue score for anxiety before and during PTA; matched pairs test). Satisfaction of the interventionalist was significantly greater for propofol (P < .05; t test).

CONCLUSION

Propofol causes less respiratory depression than midazolam for equivalent sedation and anxiolysis in patients undergoing PTA.

Immunologic properties of Epstein-Barr virus-seronegative adults

Epstein-Barr virus (EBV) seronegativity is rare in people > 20 years old. However, some persons remain EBV-seronegative for nearly their whole lives. The aim of this study was to examine properties of the immune system of EBV-seronegative adults that could contribute to long-term EBV seronegativity. Therefore, differential blood cell counts and lymphocyte subpopulations were determined, and the production of interferon (INF)-alpha and -gamma and interleukin (IL)-6 and -2 in a whole blood assay was investigated. Whereas no differences in the distribution of lymphocyte subpopulations between EBV-seronegative and -positive adults were found, a significant higher percentage of monocytes in EBV-seronegative adults was observed. Significantly more IFN-alpha and IL-6 were detected in culture supernatants of EBV-seronegative persons after stimulation with Newcastle disease virus. In contrast, no differences in the induction of the lymphokines IFN-gamma and IL-2 were seen. These data suggest that faster and higher production of IFN-alpha and IL-6 amy protect EBV-seronegative adults against EBV infection.

[Special treatment methods in general practice--legal medicine viewpoint]

There is only one common medical law which is valid for all physicians. No therapy method can claim a special status or special rights. However, due to the considerable differences in training and qualification, the jurisdiction grants special rights to a healer without medical exam (non-medical practitioner) in comparison to a physician. Additionally, a physician has to take into account the limitations by the social legislation when he uses "special treatment methods" to avoid claims for compensation.

Intra-vitreal injection of substance P antibodies as an antagonist in the vertebrate (fish) retina

A method is described for using substance P (SP) antibodies as an antagonist in the retina of a cyprinid fish, the roach (Rutilus rutilus). Antibody solution (10 microliters) injected into the vitreous was found by immunohistochemical localization to penetrate the neural retina up to the level of the inner margin of the inner nuclear layer. Thus, the inner plexiform layer, where SP would normally be released, was well infiltrated. Similar penetration patterns were observed 2 or 24 h after injection. The physiological effectiveness of the antibody was demonstrated indirectly by measuring its effect upon the spatial coupling of the horizontal cells. Previous work suggested that SP stimulates dopamine release which normally uncouples the horizontal cell somata but not the syncytium of their axon terminals. In retinae isolated from antibody-injected eyes, the horizontal cell somata (but not axon terminals) were indeed found to be significantly more strongly coupled, consistent with the blockage of SP-induced, presumably tonic, release of dopamine. The results suggest that peptide antisera can be useful as pharmacological tools to investigate electrophysiological effects of neuropeptides in the retina as in other parts of the central nervous system.

Assessment of the hemodynamic result of PTA with a Doppler guide wire: initial experience

PURPOSE

To determine the usefulness of a Doppler guide wire for assessing the hemodynamic results of balloon dilation of atherosclerotic arterial obstruction.

MATERIALS AND METHODS

A 0.018-inch 12-MHz Doppler guide wire was used to measure the maximum peak velocity and the time-averaged peak velocity (APV) proximal to, inside, and distal to lesions in 10 consecutively seen patients (six men, four women; mean age, 68 years +/- 11 [standard deviation]). Measurements were made before and after percutaneous transluminal angioplasty (PTA).

RESULTS

The proximal-to-intrastenotic APV ratio was the best predictor of the grade of residual stenosis and correlated well with angiographic measurements (r = .8). Balloon dilation resulted in a significant increase in mean APV distal to the obstruction (12.5 cm/sec before versus 27.6 cm/sec after PTA; P < .05). The mean proximal-to-distal APV ratio also decreased significantly (3.7 before versus 1.0 after PTA; P < .005).

CONCLUSION

The Doppler guide wire can be used for direct intravascular evaluation of the result of balloon dilation in atherosclerotic obstructions.

Determination of the number of Epstein-Barr virus genomes in whole blood and red cell concentrates

The risk of Epstein-Barr virus (EBV) infection after blood transfusion has been controversially discussed. Little is known about EBV transmission via buffy-coat-depleted red cell concentrates (RCC). In this study, we determined the number of EBV genomes in RCC of EBV-seropositive donors in comparison to whole blood. RCC were prepared from whole blood donations by using the 'top and bottom system'. Leucocyte content was significantly reduced in RCC in comparison to whole blood (0.47 x 10(9) vs. 2.3 x 10(9) per unit; P < 0.001). As B cells are expected to harbour EBV genomes, we analysed the number of B lymphocytes in both types of blood products. There was a significant reduction of B cell content from a median value of 90 x 10(6) in whole blood to 0.2 x 10(6) in RCCs (P < 0.001). The number of EBV genomes was estimated at a median value of seven from 10(6) B cells in the peripheral blood of healthy, EBV-seropositive blood donors by means of a polymerase chain reaction (PCR) assay. By calculation, one unit of RCC may contain an average of one to two EBV genomes, in contrast to a whole blood unit, which is likely to harbour an average of 600 to 700 EBV genomes. It is concluded that the use of leucocyte depletion systems significantly reduces the number of EBV genomes in erythrocyte concentrates. Thus, leucocyte reduced blood products appear to minimize the risk of EBV infection.

Localization of dopamine D1-receptors in vertebrate retinae

We used the fluorescent labelled dopamine D1-receptor antagonist Bodipy-SCH 23390 for the cellular localization of D1-ligand binding sites in the retinae of different vertebrates (teleosts, Xenopus, turtle, rat and rabbit). Competition experiments with unfixed cryosections of fish retina were performed to characterize the binding conditions of Bodipy-labelled SCH 23390. Tissue bound [3H]SCH 23390 was displaceable with increased amounts of bodipy-SCH 23390. The pharmacological specificity of the D1 fluorescent antagonist was determined by competition experiments with an excess of unlabelled SCH 23390. This treatment significantly reduced the level of fluorescence of the retina confirming the specificity of the binding. We observed a homogeneously distributed fluorescence signal in both plexiform layers in unfixed cryosections of fish, frog, turtle, rat and rabbit. Similar staining intensities of both plexiform layers were found in frog, turtle, rat and rabbit retina. In teleosts, the label of the outer plexiform layer was markedly more intense. Non-specific label was associated with photoreceptor outer and inner segments. The specific labelling of both plexiform layers indicates a mismatch of dopamine releasing and D1-binding sites, and suggests a possible extrasynaptic localization of the D1-receptor. The physiological significance of the observed distribution of D1-ligand binding sites is discussed with respect to the role of dopamine in controlling adaptational processes in the retina.

A case of an anomalous pulmonary vein of the right middle lobe

A case is reported in which the abnormal course of a pulmonary vein was suggested by computed tomography and confirmed by digital subtraction angiography. The vein drained blood from the right middle lobe into the apical pulmonary vein. This abnormality was probably due to abnormal segmentation of the right lung. Comparable cases have been reported in the literature. It is important to distinguish these benign lesions from more complex malformations because of the therapeutic and prognostic implications. The radiologic findings of this case and a systematic overview of pulmonary vein abnormalities is provided.

Characteristics of viral protein expression by Epstein-Barr virus-infected B cells in peripheral blood of patients with infectious mononucleosis

The frequency of Epstein-Barr virus (EBV) antigen-positive B cells in the peripheral blood of patients with infectious mononucleosis compared with that for latently EBV-infected individuals was examined by immunocytochemistry. B cells positive for Epstein-Barr nuclear antigen (EBNA) 1, EBNA2, and latent membrane protein were frequently found in all peripheral B lymphocyte preparations from 25 patients suffering for 3 to 28 days from infectious mononucleosis by using monoclonal antibodies and the alkaline phosphatase anti-alkaline technique. There was a significant decrease in the number of positive B cells during the course of disease. EBNA1-positive B cells were detected in 0.01 to 2.5% of total B cells (median, 0.8%), EBNA2-positive B cells were detected in 0.01 to 4.5% of total B cells (median, 0.9%), and latent membrane protein-positive B cells were detected in 0.01 to 1.8% of total B cells (median, 0.5%), depending on the duration of clinical signs. In contrast, we did not find any EBNA1- or EBNA2-positive B cells in 2 x 10(6) peripheral blood B lymphocytes of 10 latently EBV-infected individuals, whereas aliquots of the same cell preparations were EBV DNA positive by a PCR assay. Therefore, it appears to be possible to detect infectious mononucleosis by immunocytochemical determination of latent EBV products, which might be of relevance for the diagnosis of EBV reactivations in immunosuppressed patients.

Increase of antigen production in BLV-infected cell lines via additional expression of tax

The selection of animals infected with the bovine leukaemia virus (BLV) is performed by the immunological detection of antibodies against the virus, commonly using the antigen gp51. Furthermore, research is being carried out to develop protective vaccines against BLV that have gp51 as their main component. Taking both of these factors into account, it is clear that there will be an increasing requirement for the virus antigen gp51 for some time to come. The permanently BLV-infected foetal lamb kidney cell line FLK/BLV (and its sublines) has been proved to be the most useful culture for the mass production of the virus antigen. Stable cell lines producing higher quantities of BLV antigen have not been established, either by subcloning of the FLK/BLV or by infection of other permanent cells with BLV. Here, a report is made on efforts to increase the expression of gp51 in BLV-infected cells via the additional expression of homologous transactivating virus protein tax. Selectable tax expression vectors that integrate into the host cell genome were constructed using BL provirus DNA fragments. Highly productive FLK/BLV cells were transfected with these vectors. Following selection with G 418, gp51-producing cell lines were established and tested for their productivity for several months. Some tax-vector-containing cell lines have produced 1.5-2 times more gp51 than the highly productive parental control cell line FLK/BLV 44-1.

Differentiation of photoreceptors, glia, and neurons in the retina of the cichlid fish Aequidens pulcher; an immunocytochemical study

Light-microscopic immunocytochemistry was carried out to investigate the developmental dynamics of several neurochemical markers in the retina of blue acara (Aequidens pulcher). As a rule, double-label experiments were performed in order to determine the absolute and relative timing of the appearance of these markers. The diameter of eye-ball (from 0.6 to 1.2 mm) and the body length (from 4.6 to 9.4 mm) enlarged in parallel during the observation period of 2 to 9 days after spawning (day 2-9); hatching took place usually on day 2. Immunoreactive proliferating cell nuclear antigen (ir-PCNA) was present in all neuroblasts (the embryonic homogeneous cell stage; day 1.0-2.0), but was lost progressively in a center-to-periphery and apparent proximal-to-distal sequence as the cells and layers differentiated. In late larvae and juveniles, ir-PCNA was confined to a ring of dividing neuroblasts at the retinal margin and to a population of scattered rod precursors in the outer nuclear layer. Immunoreactive structures of representative antigens progressively appeared after ir-PCNA had decayed. Around hatching, at the synaptic separation stage (day 2.0-2.5), luteinizing hormone-releasing hormone-ir centrifugal fibers, visinin-ir cones, glial fibrillary acidic protein-ir structures and gamma-aminobutyric acid-ir cell bodies appeared, which were followed by the emergence of rhodopsin-ir rods and tyrosine hydroxylase-ir interplexiform cells (on day 2.5-3.0) and serotonin-, neuropeptide Y- and substance P-ir amacrine cells (on day 3.0-4.0). The results indicate that photoreceptor cells, and especially rods start to differentiate at an earlier stage of retinogenesis than has previously been proposed. In addition, an extraretinal tissue in the brain identified as the prospective pineal organ was found to be visinin- and rhodopsin-immunoreactive on day 1.5-2.0 before these photoreceptor-specific antigens became positive in the retina.

Coincidence of Epstein-Barr virus reactivation, cytomegalovirus infection, and rejection episodes in renal transplant recipients

Reactivation of the Epstein-Barr virus was reported to occur frequently under immunosuppressive therapy following organ transplantation. However, little is known about the clinical significance of these EBV reactivations. Therefore, we searched for correlations among the treatment with various immunosuppressive drugs, the incidence of CMV infections, rejection crises, and serological signs of EBV reactivation. EBV-specific antibodies were measured with novel ELISAs, utilizing the recombinant antigens p72 (for anti-EBV nuclear antigen [EBNA]1-IgG), p54, and p138 (anti-early antigen [EA]-IgM, -IgG, -IgA) in a follow-up study of 79 renal transplant recipients. Patients receiving antithymocyte globulin or antilymphocyte globulin therapy showed increasing anti-EA-IgG and -IgA more often than did patients not receiving antithymocyte globulin or antilymphocyte globulin therapy (P < 0.05). In patients receiving OKT3 antirejection therapy, anti-EA-IgM seroconversion was found more frequently (P < 0.01). A significant correlation was also found between groups of patients who had had at least one rejection episode versus patients without any sign of organ rejection, and the incidence of increasing anti-EA-IgG (P < 0.05). Since in most of these patients signs of EBV reactivation followed the appearance of the rejection episode, this may not be due to viral-induced rejection but may be caused by the reinforced immunosuppression during antirejection therapy. As opposed to patients with no signs of CMV infection and with nonsymptomatic CMV infection, patients undergoing symptomatic CMV infection showed anti-EA-IgM seroconversion (P < 0.01), increasing anti-EA-IgA (P < 0.01), and decreasing anti-EBNA-IgG (P < 0.01) more frequently. Our results confirm the role of immunosuppressive therapy in the pathogenesis of EBV reactivation. We further demonstrate a striking coincidence of EBV reactivation and symptomatic CMV infection.

Postmortem evaluation of four randomly selected automated biopsy devices for transthoracic lung biopsy

PURPOSE

To evaluate four automated devices to achieve transthoracic lung biopsy.

METHODS

Transthoracic lung biopsy specimens were obtained randomly from 21 human cadavers with unsuspicious lungs using Biopty (18- and 20-gauge), BIP (18 and 20-gauge), ASAP (18 gauge), and Autovac (18- and 20-gauge) devices. A total of 63 biopsies were carried out with each device and each needle diameter. The same devices and needles were then used randomly for biopsy of peripheral lung metastases. Specimens obtained during both parts of the study were analyzed for the area of tissue on the histologic section, adequacy of tissue for diagnosis, tissue preservation, and crush artifact. The examining pathologist was kept unaware of which procedure was used to obtain the specimens and the cadavers' clinical history.

RESULTS

The Biopty 18-gauge device performed statistically better than any other of the evaluated systems for biopsy of normal lung parenchyma (p < 0.05). For biopsy of lung metastases, the differences between the devices and needle diameters were less, although the Biopty 18-gauge device performed better than the Autovac 18-gauge, BIP 18-gauge, and all 20-gauge devices for the area of tissue on the histologic section (p < 0.05). The results of the full-cut Autovac biopsy system were remarkable because of the large number of biopsies during which no tissue was obtained.

CONCLUSION

Automated biopsy devices can obtain high quality lung specimens sufficient for definite histopathologic diagnosis. However, additional clinical studies on the use of automated biopsy devices for lung biopsy are mandatory.

Patterns of rod proliferation in deep-sea fish retinae

In a sample of 37 species of deep-sea fish species from the sea floor of the Porcupine Seabight and the Gobal spur (North Atlantic) we investigated the overall structure of the retina with special respect for the organization of rods, their length and their arrangement in multiple banks. Using an immunocytochemical marker for cell proliferation (PCNA) we studied the mechanisms of rod proliferation, and, by means of serial section reconstruction followed their integration into the existing population of rods. Furthermore, in three different species we have observed growth related changes in retinal thickness, rod density and proliferation activity. We found evidence for two different principles for the organization of rods in these deep-sea fish retinae. In the first group of species represented by Nematonurus armatus and Coryphaenoides guentheri we found rods to be rather short (20-30 microns) and arranged in three and more banks. In these species rod proliferation occurred in a single band of cells immediately vitread of the external limiting membrane, thus showing a high degree of spatial and temporal order. In these species, young rods are inserted just sclerad of the external limiting membrane and the older outer segments pushed away from the incoming light towards the back of the eye. This may be linked to a progressive loss of function of the older rods and might represent an alternative mechanism to the disk shedding in other vertebrates. In the second population (e.g. Conocara macroptera, Alepocephalus agassizii) we observed considerably longer rod outer segments (60-80 microns) forming no more than two layers. These retinae had rod precursors arranged in disseminated clusters throughout the outer nuclear layer indicating the lack of clear spatio-temporal order in mitotic activity along with a more statistical pattern of integration of the newly formed outer segments. In our sample of species both populations were of about equal size suggesting that the two mechanisms are equally effective and may have arisen independently.

[The value of double contrast colon imaging in inadequate colposcopic diagnosis]

PURPOSE

Prospective evaluation of colon double-contrast enemas in patients with incomplete colonoscopy during routine examination.

MATERIALS AND METHODS

From 1. February 1993 through 31. January 1994 we prospectively evaluated all patients undergoing a double-contrast barium enema following incomplete colonoscopy in the endoscopy unit of the Department of Surgery of the University Hospital Marburg. The examination was carried out using the typical double-contrast technique at least 24 h after colonoscopy. The results of the barium enema were correlated with the findings at colonoscopy with regard to completion of the diagnostic procedure and additional pathological findings.

RESULTS

Of 448 colonoscopies 168 remained incomplete. Sixty patients underwent an additional double-contrast study of the colon. In 43 patients this study was sufficient to complete the diagnostic procedure. Unknown pathological diagnoses were found in 11 patients. In 2 patients an adenocarcinoma and in 9 patients polypoid lesions were detected.

CONCLUSION

After incomplete colonoscopy a double-contrast barium enema should be performed to complete the diagnostic examination of the whole colon and to reveal unknown additional pathological findings.

[Iatrogenic esophageal perforation in inoperable esophageal carcinoma. Its therapy with a plastic-coated metal stent]

A 60-year-old man was admitted to hospital because of severely impaired swallowing, retrosternal pain and marked weight loss. History and physical examination of the patient, whose general condition was obviously much reduced, pointed to carcinoma of the oesophagus. Contrast-medium swallow demonstrated subtotal stenosis in the oesophagus. Computed tomography and magnetic resonance imaging showed a space-occupying mass originating from the oesophagus, in close relationship to the trachea, main bronchi and descending aorta. Biopsy confirmed the diagnosis of oesophagus carcinoma and exploratory thoracotomy excluded curative surgical treatment. An attempt was made to introduce a feeding tube endoscopically to provide nutritional palliation. But the oesophagus was perforated during this manoeuvre and resulted in an oesophagobronchial fistula with subsequent mediastinitis and mediastinal emphysema. Using a self-expandable plastic-covered metal stent it was possible to cover the perforation and overcome the patient's dysphagia. The mediastinitis healed under intravenous administration of cefotaxim (2 g three times daily), netilmicin (400 mg daily) and metronidazole (500 mg three times daily), for 5 days.

[Percutaneous intraluminal ultrasound studies of the biliary tract in the diagnosis of malignant biliary obstruction]

The diagnostic value of percutaneous intraluminal ultrasound examination of the biliary tract (PIBUS) for the staging of malignancies that had obstructed the biliary tract was assessed in a prospective study. Intrabiliary sonography was performed 25 times in 22 patients (seven women, 15 men; mean age 66.4 +/- 16 years) with obstructive jaundice in whom percutaneous transhepatic drainage of the biliary tract had been undertaken. The obstruction involved the hepatic duct bifurcation in 15 patients, the distal portion of the choledochal duct in five and its central portion as well as hepaticojejunostomy in one patient each. Ultrasound examination made it possible to assess tumour infiltration into the lumen of the biliary tract, its wall or its surrounding structures. Correct T-staging was successful in all 12 patients with carcinoma of the biliary tract (T1: n = 4; T2: n = 2; T3: n = 6), judged against the "gold standard" of exploratory laparotomy in nine. Infiltration of the portal vein was demonstrated in three patients, lymph node metastases in the region of the hepatoduodenal ligament in seven. This experience indicates that PIBUS makes it possible correctly to T-stage carcinoma of the biliary tract, but because of its limited depth penetration it has to be combined with conventional imaging procedures for precise definition of the N and M stages.

Mammalian Müller (glial) cells express functional D2 dopamine receptors

Dopamine plays important functional roles in the vertebrate retina. Here we show that functional D2 dopamine receptors are present on mammalian retinal Müller (glial) cells. Using an antiserum directed to two oligopeptides predicted from rat D2 receptor DNA, patchy label was demonstrated immunocytochemically on virtually all Müller cells enzymatically isolated from guinea-pig and rat retinae. Application of exogeneous dopamine to voltage-clamped isolated living guinea-pig Müller cells caused either a decrease (40%), an increase (32%), or no change (28%) of the input resistance of the membrane. The D2 receptor agonist quinelorane caused an increase of the membrane's input resistance in 100% of the cells. This effect was completely blocked by the D2 receptor antagonist S(-)-sulpiride. When all voltage-activated K+ channels except the delayed rectifiers were blocked by Ba2+, quinelorane had no effect. Further, the reversal potentials of the responses were near the potassium equilibrium potential. We conclude that the activation of Müller cell D2 receptors closes (inwardly rectifying) K+ channels. The presence of functional dopamine receptors on mammalian Müller cells may have important consequences for retinal K+ clearance, and thus, for information processing in the retina.

The occurrence of dopaminergic interplexiform cells correlates with the presence of cones in the retinae of fish

Using light-microscopic immunocytochemistry against tyrosine hydroxylase, we have investigated the morphology of dopaminergic cells in 23 species of fishes representing various systematic classes and subclasses and which live in very different habitats. We have, for the first time, observed teleosts with dopaminergic amacrine cells. Thus, in both bony and cartilaginous fishes, dopaminergic cells are differentiated as interplexiform and amacrine cells. The differentiation of dopaminergic cells into amacrine or interplexiform cells in fishes correlates with the absence or presence of cones. In pure-rod retinae, they occur as amacrine cells, and in mixed rod/cone retinae, they occur as interplexiform cells. We conclude therefore that the differentiation of retinal dopaminergic cells in fish does not depend on the evolutionary or systematic classification of a given species. Rather, it is correlated with the occurrence of rods and/or cones, and thus linked more closely to the habitat. We argue that, in fish, the presence of cones and cone-specific horizontal cells may be responsible for inducing dopaminergic cells to differentiate as interplexiform cells. Possible functions of dopamine in all-rod retinae, which may not require adaptation, may include neuromodulation in the inner plexiform layer for the sensitization of the rod pathway, the shaping of biological rhythms, and the control of eye growth.

Cytokine production in a whole-blood assay after Epstein-Barr virus infection in vivo

Epstein-Barr virus (EBV) has a marked tropism for cells of the immune system, and infection can result in profound immunomodulatory effects. In order to examine the role of cytokines during the acute phase of infectious mononucleosis, we studied the levels of different interleukins (ILs), interferons (IFNs), and the soluble IL-2 receptor (sIL-2R) in serum samples of 20 patients. We found elevated levels of IL-2, IL-6, sIL-2R, and IFN-gamma. Whereas the peak of IL-2 and IL-6 concentration occurred during the first week (P < 0.01), the largest amounts of sIL-2R were measured during the second week (P < 0.01). IFN-gamma levels were only enhanced during the first week. In addition, we investigated the ability to produce cytokines in response to mitogenic stimulation in a whole-blood assay of 11 patients compared with healthy blood donors. In the whole-blood assay of patients compared with controls after stimulation with lipopolysaccharide, we measured more than 10-fold elevated levels of tumor necrosis factor alpha (P < 0.01), 3-fold elevated levels of IL-1 beta (P < 0.01), and about 2-fold increased amounts of IL-6 (P < 0.01). A significant enhancement in sIL-2R and IFN-gamma concentration was found in the assay after stimulation with phytohemagglutinin after 24 h of incubation (P < 0.01). Collectively, our data seem to indicate that monocytes are strongly activated during infectious mononucleosis. Monocytes and monocyte-derived factors may play an important role in the pathogenesis of infectious mononucleosis and, together with T lymphocytes, may be partly responsible for clinical symptoms.

Nitinol prostheses for the treatment of inoperable malignant esophageal obstruction

PURPOSE

This uncontrolled prospective study was undertaken to evaluate a new nitinol stent in the treatment of dysphagia due to inoperable malignant esophageal obstruction.

PATIENTS AND METHODS

Eighteen consecutive patients (15 men, three women; mean age, 66 years +/- 15) with inoperable malignant obstructions of the esophagus or esophagogastric junction due to esophageal carcinoma (n = 14) or extrinsic obstruction (n = 4) were treated with self-expanding nitinol endoprostheses (diameter, 18 mm). Dysphagia score and activity index were assessed before and every 4 weeks after stent insertion.

RESULTS

Eighteen stents were deployed successfully. One stent expanded insufficiently and was removed inadvertently during retrieval of the application system. Mean time until complete expansion of the stent was 7.1 days +/- 5. Stent placement resulted in a significant decrease in the dysphagia score (2.7 +/- 0.7 before vs 0.6 +/- 0.7 after stent placement, P < .00005 by Wilcoxon matched-pairs test) and a significant increase in the activity index (2.6 +/- 1 before vs 1.7 +/- 0.9 after stent insertion; P < .005). There were no procedure-related complications. Follow-up period (mean, 155 days +/- 100) revealed recurrent dysphagia in four patients. Two patients experienced food bolus impaction, another two had tumor ingrowth through the mesh after 170 and 186 days. Fourteen patients died after a mean survival time of 158 days +/- 106, all with patent stents.

CONCLUSIONS

Self-expanding nitinol esophageal stents are safe and effective in the treatment of malignant esophageal obstructions.

Long-term results of percutaneous aspiration embolectomy

PURPOSE

To evaluate percutaneous aspiration embolectomy (PAE) as a therapeutic alternative to surgical embolectomy.

METHODS

Eighty-five patients underwent 90 PAEs for embolic occlusions below the inguinal ligament between October 1987 and September 1992 in a prospective study with a 96% follow-up.

RESULTS

The first PAE was clinically successful in 77 limbs (86%). In eight cases, major amputation was necessary. Eleven of 13 failures were observed in limbs with acutely threatening ischemia, but the success rate was independent of the time interval from embolism to the PAE procedure. The 30-day mortality rate was 3.5%. The cumulative primary patency rate at 1 and 4 years was 68% and 58%, respectively. The limb salvage rate was 88% after 1 year and 86% after 4 years. The patency rate was significantly better and the mortality was significantly lower in patients receiving long-term anticoagulation with coumadin.

CONCLUSION

PAE is highly effective in the treatment of embolic occlusions of the lower leg arteries and should be considered as an alternative to Fogarty balloon embolectomy.

Dose finding with a novel recombinant plasminogen activator (BM 06.022) in patients with acute myocardial infarction: results of the German Recombinant Plasminogen Activator Study. A study of the Arbeitsgemeinschaft Leitender Kardiologischer Krankenhausärzte (ALKK)

OBJECTIVES

The aim of this study was to determine the appropriate dose of a novel recombinant tissue-type plasminogen activator (BM 06.022) for thrombolysis in patients with acute myocardial infarction.

BACKGROUND

BM 06.022 is a mutant of tissue-type plasminogen activator expressed in Escherichia coli that can be given as a single bolus because of a prolonged half-life, which might obviate the need for complicated regimens.

METHODS

BM 06.022 given as a single bolus was investigated in 142 patients in a multicenter sequential dose-finding study. Efficacy of the drug was assessed from infarct-related artery patency by coronary angiography.

RESULTS

With the first dose of 10 MU of BM 06.022, the predefined minimal 90-min patency of 70% was not achieved, as indicated by the sequential probability ratio test after treatment of 42 patients (group A). The second dose of 15 MU of BM 06.022 was given subsequently in the preset maximum of 100 patients (group B). Angiography 30, 60 and 90 min after the bolus injection of BM 06.022 revealed a patent infarct-related artery (Thrombolysis in Myocardial Infarction trial [TIMI] grade 2 or 3) in 65% and 66%, 73% and 74% and 66% and 75% of patients in groups A and B, respectively. Very early reocclusion up to the 90-min angiogram occurred in 17% and 13%, late reocclusion until predischarge angiography occurred in 7% and 5%, and rescue percutaneous transluminal coronary angioplasty after the 90-min angiogram was performed in 6 and 14 patients in groups A and B, respectively. Plasma fibrinogen decreased from 2.79 g/liter (range 0.94 to 4.75) to 1.69 g/liter (range 0.0 to 3.95) in group A and from 2.54 g/liter (range 0.0 to 5.02) to 0.92 g/liter (range 0.0 to 2.68) in group B. Two bleeding complications requiring transfusion or surgical intervention and one nonfatal intracranial hemorrhage were encountered. Eight patients had a reinfarction, and five patients died, all of cardiac causes.

CONCLUSIONS

With BM 06.022 given as a single bolus, a high early patency rate of the infarct-related coronary artery can be achieved. The speed of thrombolysis seems to be superior to standard thrombolytic drugs. The compound warrants further evaluation with respect to safety and efficacy by clinical end points.

Sex difference in the serostatus of adults to the Epstein-Barr virus

A total of 1047 adults, aged between 18 and 90 years, including blood donors and surgical patients of the Medical University of Lübeck in Germany, were screened for IgG antibodies to the Epstein-Barr Virus, either by standard indirect immunofluorescence or by a novel enzyme-linked immunosorbent assay (Enzygnost Anti-EBV/IgG, Behring, Marburg, Germany). There was a significant sex difference in the serostatus to the Epstein-Barr virus in adults. Male adults were more likely than females (p < 1%) to be EBV-seronegative. The same trend was seen in both a group of 713 blood donors and 334 surgical patients and when different test methods were used. However, this sex difference was not shown in the sera of 86 pediatric patients of the Medical University of Lübeck tested by indirect immunofluorescence for IgG antibodies to the Epstein-Barr virus. Furthermore, titers of IgG antibodies to Epstein-Barr virus specific antigens of female adults, obtained by the enzyme-linked immunosorbent assay (Enzygnost Anti-EBV/IgG), had significantly higher median values than male adults (p < 5%).

Gonadotropin-releasing hormone, a neuropeptide of efferent projections to the teleost retina induces light-adaptive spinule formation on horizontal cell dendrites in dark-adapted preparations kept in vitro

The teleost retina receives efferent projections from neurons of the nucleus olfactoretinalis at the base of the olfactory bulbs. These fibres contain gonadotropin-releasing hormone (GnRH) immunoreactive material and are presynaptic to retinal dopaminergic interplexiform cells. We have incubated isolated dark-adapted retinae and eyecup preparations of roach with salmon-GnRH and found an increase in horizontal cell spinule numbers to 70% light-adaptive levels. This effect was blocked by addition of haloperidol to the incubation medium suggesting that GnRH acts via stimulation of the dopaminergic interplexiform cells. We conclude that GnRH containing efferent fibres are capable of inducing light-adaptive changes in the retina and discuss their implication in the control of endogenous rhythms.

[Palliative therapy of complex hilar biliary obstructions using self-expanding metal stents]

Implantation of self-expandable metal stents was planned for 21 patients (12 women, 9 men; mean age 64.7 +/- 11.6 [38-80] years) with malignant obstructive jaundice due to complex hilar biliary obstruction (Bismuth II: n = 5, Bismuth III: n = 13, Bismuth IV: n = 1, state after hepaticojejunostomy: n = 2). Stents were implanted bilaterally in 18 patients (one each on the right and left, n = 12; two stents on right, one stent on left, n = 6), one patient had three stents on one side, another had one unilateral stent. Thus there was a 93.3% success rate (46 of 49 planned stent implantations). The mean bilirubin level fell from 14.7 +/- 7.7 mg/dl before stent implantation to 3.9 +/- 5.4 mg/dl afterwards (P = 0.0001). One patient experienced late bleeding with haemorrhagic shock and consumption coagulopathy after a failed drainage attempt. She died despite superselective embolization, operative suturing of the puncture site, and wide-ranging intensive care measures. Procedure-related death rate was thus 4.8%, the 30-day death rate 9.5%. During the follow-up period, averaging 145 +/- 152 (16-529) days, jaundice recurred in six patients (30%) and was successfully treated by re-intervention in five. 13 patients died after a mean survival time of 98 +/- 119 (16-432) days. It is concluded from these data that self-expandable metal stents provide minimally invasive palliative treatment of complex biliary hilar obstruction in the type of case in which plastic stents are known to fail.

Application of DNA filter hybridization and PCR to distinguish between human and non-human tissues of poor quality

The present report describes a novel approach for the identification of human or non-human specimens after long-term storage in a badly preserved state. The application of the PCR-technique (polymerase chain reaction) using human-specific primers as well as Southern blot (filter) hybridization of the sample DNA to a primate-specific DNA probe enabled us to extend the positive identification beyond the limits of conventional methods such as serological or morphological examinations.

[The premedication of PTA. A double-blind and randomized comparison of midazolam/tramadol versus placebo/tramadol]

A prospective, randomised and double blind comparative study of Midazolam/Tramadol or placebo/Tramadol for premedication before PTA was carried out on 40 patients (12 female and 28 male, average age 66.1 +/- 12). The anxiolytic, analgesic and general findings were quantified by means of a visual analogue score. Pre- and peri-interventional blood gas, blood pressure and pulse rates were determined. The complications of the two schemes were compared. 19 patients received Midazolam/Tramadol and 21 placebo/Tramadol. Patient anxiety was reduced significantly from 25.8 +/- 25 to 4.3 +/- 6 by premedication. Significant increase in the pain score during PTA was observed only in the placebo group (4.3 +/- 12.6 to 27.4 +/- 20.9). There was no difference in the incidence of complications and respiratory depression due to the Midazolam/Tramadol combination was not observed.

[Conventional local intra-arterial fibrinolysis, spray lysis and mechanically accelerated fibrinolysis. An assessment of their position in the spectrum of angioplasty technics]

Intra-arterial local fibrinolysis was performed in 72 patients (51 men, 21 women, mean age 66.8 years) during the course of 78 angioplasties. 11.1% were stage IIa (Fontaine), 38.9% were stage II b, 27.8% were stage III and 22.2% were stage IV. The methods used were conventional fibrinolysis (15.4%), spray lysis (47.4%) and mechanically accelerated fibrinolysis (37.2%). In 66.7% the urokinase dose was < 600,000 I.U., in 17.9% it was > 1,000,000 I.U. Additional balloon dilatation was performed in 72 cases, percutaneous aspiration of thrombo-embolic material in 41 cases and stent implantation in 7 cases. Angiographically the procedure was successful in 90.7%; the Doppler index rose from 0.47 +/- 0.27 to 0.85 +/- 0.3 (p < 0.001). At discharge, staging was: I = 38.9%, IIa = 38.9%, IIb = 5.6%, III = 1.4%, IV = 15.3%. There were no systemic bleeding complications. In 5.1%, complications had to be treated surgically.

[The initial results of the implantation of self-expanding nitinol stents into the esophagus in malignant dysphagia]

Nine patients (mean age 64, range 51-83 years), with dysphagia due to incurable malignant obstruction of the esophagus were treated by the introduction of 10 self-expanding metal endoprostheses (Nitinol stents). All cases were technically and functionally successful. In one patient the stent did not expand completely; it had to be removed and a second introduced. There were no other complications from the stent implantation. During the period of observation of 136 +/- 86 days one stent (11%) was reobstructed by tumor growing into the stent. Two patients died after 60 and 119 days, both with open stents. Early experience with the Nitinol stent indicates that good palliation of malignant dysphagia can be achieved with a much lower complication rate than results from tube implantation. The design and application system of the stent is capable of further improvement.

A controlled trial of an expansile metal stent for palliation of esophageal obstruction due to inoperable cancer

BACKGROUND

Esophageal obstruction due to cancer can produce debilitating dysphagia. Rapid palliation is usually possible with endoscopic placement of a plastic esophageal prosthesis, but this device has a high rate of complications. A new alternative is a metal-mesh stent that collapses to 3 mm in diameter at placement but can then expand up to 16 mm.

METHODS

Patients with esophageal carcinoma (39 patients) or malignant extrinsic obstruction (3 patients) were randomly assigned to treatment with either a plastic prosthesis (16 mm in diameter) or an expansile metal-mesh stent. The patients were evaluated every six weeks until death. The degree of palliation was expressed as a dysphagia score and a Karnofsky performance score.

RESULTS

Complications were significantly less frequent with the metal stents than with the plastic prostheses (no complications vs. nine; P < 0.001). The dysphagia and Karnofsky scores improved significantly and to a similar degree in both treatment groups. The most common causes of recurrent dysphagia were migration of the plastic prostheses (five patients) and ingrowth or overgrowth of the metal stents by tumor (five patients). The rates of reintervention were similar in both treatment groups, as were the 30-day mortality rates. The period of hospitalization after placement of a prosthesis was significantly longer in the group given plastic prostheses than in the group given metal stents (mean +/- SE, 12.5 +/- 2.1 vs. 5.4 +/- 1.0 days; P = 0.005). Despite their higher initial cost, the metal stents were cost effective because of the absence of fatal complications and the decrease in the hospital stay.

CONCLUSIONS

Expansile metal stents are a safe and cost-effective alternative to conventional plastic endoprostheses in the treatment of esophageal obstruction due to inoperable cancer.

Microanatomy of the dopaminergic system in the rainbow trout retina

We have investigated the morphology of dopaminergic interplexiform cells as well as the distribution of two classes of dopamine receptors in the retina of the rainbow trout. Interplexiform cells were visualized using an antiserum against tyrosine hydroxylase and PAP immunocytochemistry. In whole amounts, these cells have a density of between 91 and 182 cells per mm2 with highest values in the lower temporal quadrant. Their cell bodies lie at the inner margin of the inner nuclear layer with only 12-17 cells per retina displaced to the ganglion cell layer. There are three levels of stratification in the inner plexiform layer, one at the distal and proximal borders respectively, and one in the middle. They arise mostly from a radially oriented, stout primary dendrite. Tangential processes are about 1 micron in diameter and show a number of varicosities. The density of processes is greatest in sublayer 5, but no major difference in the general organization is apparent between the three sublayers. In the outer retina, there are two levels of dense ramification confined to the layer of horizontal cells. Light and electron microscopic analysis shows synaptic input to horizontal cells, but not to photoreceptors. The distribution of D1 receptors was assessed by studying the binding pattern of a specific, fluorescent-labelled antagonist, SCH 23390, in unfixed frozen sections. We found displaceable binding in the inner and outer plexiform layers and in the region of horizontal cell perikarya. We used an anti-peptide antibody directed to an extracellular domain of the rat D2 receptor and a fluorescent secondary antiserum to study the localization of D2 receptors. In addition to marked label in both plexiform layers, the outer, and especially the inner segments of rods and cones show specific immunoreactivity. In addition, there is distinct label at the level of the horizontal cell bodies; in the inner retina, specific fluorescence is found in somata of some amacrine cells. The significance of the connectivity pattern and the distribution of the two receptor types is discussed with respect to the role of dopamine in controlling adaptational processes in the outer retina, such as retinomotor movements and changes in horizontal cell morphology and physiology.

Relief of malignant obstructive jaundice by endoscopic or percutaneous insertion of metal stents

From January 1990 through July 1992 we attempted to treat 42 patients (21 men, 21 women; mean age 69 +/- 2 years) with obstructive jaundice due to inoperable malignant biliary obstructions with insertion of metal stents. 67% of the patients had stenoses of the distal common bile duct, 5% of the proximal common bile duct, and 28% had hilar lesions. Obstructions were due to pancreatic cancer (47%), gallbladder cancer (13%), cholangiocarcinoma (20%), and lymphoma of metastatic cancer (20%). We inserted a total of 51 Wallstents and 17 Strecker Stents with a technical success of 100%. The functional success was 95%. The mean bilirubin level decreased from 18.2 +/- 1.7 mg/dl before to 1.5 +/- 0.2 after stent insertion. In the first 30 days one patient (2%) with hilar malignancy developed an early reobstruction due to tumor bleeding and debris. The 30-day mortality rate was 2%. 2 (5%) patients developed recurrent jaundice within the 3-month follow-up period; 1 had tumor overgrowth of the metal stent, 1 had tumor ingrowth through the mesh. Metal biliary endoprotheses offer sufficient initial relief of malignant obstructive jaundice with reduced morbidity and mortality compared to the placement of conventional plastic stents. However, the long-term results are impaired by stent occlusion due to tumor ingrowth or overgrowth.

Spinules: a case for retinal synaptic plasticity

In both vertebrate and invertebrate nervous systems, a population of synapses is characterized by having finger-like indentations of the postsynaptic membrane that project into the presynaptic terminal. These 'spinules' are often transitory structures, and their presence has been associated with increased synaptic activity. We have studied the functional role of spinules in the fish retina, where they are observed in horizontal cells invaginating cone pedicles, and in synaptic terminals of bipolar cells. In the cone-horizontal cell synaptic complex, spinules are present during light adaptation; their formation is triggered by external light stimuli as well as by endogenous factors. Pharmacologically, spinules are degraded following an increase, and formed in response to a decrease of the transmitter glutamate released by the cone cells. Dopamine, released by interplexiform cells and acting via a D1 receptor-mediated increase in cAMP, and a protein-kinase-C-based mechanism are also capable of inducing spinule formation. Functionally, the presence and absence, as well as the timecourse, of spinule formation during light adaptation is closely correlated with the development of biphasic chromatic responses in a class of cone horizontal cells and the manifestation of colour-opponency in ganglion cells. This suggests that in the outer retina of fish, spinules are mediating feedback activity essential for the coding of antagonistic colour information.

Localization of D2 dopamine receptors in vertebrate retinae with anti-peptide antibodies

Dopamine plays an important role in modulating various aspects of retinal signal processing. The morphology of dopaminergic neurons and its physiological effects are well characterized. Two classes of receptor molecules (D1 and D2) were shown pharmacologically to mediate specific actions, with differences between individual groups of vertebrates. In an attempt to better understand dopaminergic mechanisms at the cellular level, we used antisera against D2 receptors and investigated the localization of the dopamine D2 receptor in the retinae of rat, rabbit, cow, chick, turtle, frog, and two fish species with immunofluorescence techniques. Antisera were raised in rabbits to two oligopeptides predicted from rat D2 receptor cDNA; one specific for the splice-variant insertion in the third cytoplasmic loop and the other directed towards the extracellular amino terminal region shared by both short and long isoforms. Preadsorption with the synthetic peptide resulted in a significant reduction of label, indicating the presence of specific binding in all species except turtle and goldfish. The pattern of labelling produced by the two antisera was essentially identical; however, the staining obtained with antiserum to the extracellular motif was always more intense. Specific staining was present in photoreceptor inner and outer segments, and in the outer and inner plexiform layers of all species. In mammals and chick, strongly fluorescent perikarya were observed in the ganglion cell layer and at the proximal margin of the inner nuclear layer. Label may be present in the pigment epithelium but could not be established beyond doubt. This pattern of labelling is in accordance with previous observations on D2 receptor localization by means of radioactive ligand binding and in situ hybridization techniques. It suggests that retinal dopamine acts as a neuromodulator as well as a transmitter. In the distal retina, it may reach its targets via diffusion over considerable distances, even crossing the outer limiting membrane; in the inner and outer plexiform layers, conventional synaptic transmission seems to coexist with paracrine addressing of more distant targets, and D2 receptors are expressed by both amacrine and ganglion cells.

Dark-adaptive cone elongation in the blue acara retina is triggered by green-sensitive cones

In a dichromatic teleost species, we determined the intensity of light of various wavelengths required to prevent cone elongation by exposing fish at the time of their normal "dusk" phase to monochromatic light (479, 623, and 660 nm) at eight to ten different intensities for 75 min. The positions of single and double cones were measured in tangential sections and expressed as cone indices. At all wavelengths, the spectral responses of both cone types were virtually identical. Furthermore, the sensitivity of the blocking effect was highest at shorter wavelengths. When comparing the relative quantal sensitivities of myoid elongation for the two cone types to the spectral sensitivities of the three types of Aequidens pulcher photoreceptor, we found the closest match between the action spectrum and the absorption spectrum of the green-sensitive single cones. This may indicate that this cone type is capable of reacting directly to decreasing levels of illumination. On the other hand, the identical sensitivity of both cone types argues for an indirect control mechanism of dark-adaptive cone elongation, possibly via a neural pathway involving the inner retinal layers, complementary to the neural control of light adaptation. Green-sensitive single cones are well suited to trigger this response, since (1) their sensitivity is inferior to that of double cones; (2) waters inhabited by the blue acara transmit best at long wavelengths; and (3) at dusk, long-wavelength radiation dominates over other parts of the spectrum. Therefore, green-sensitive cone threshold will be reached first at dusk.

Plastic endoprostheses versus metal stents in the palliative treatment of malignant hilar biliary obstruction. A prospective and randomized trial

This prospective and randomized trial sought to compare large-bore plastic endoprostheses (14 French) and self-expanding metal stents (24 French) in the palliative treatment of obstructive jaundice due to biliary hilar malignancies. Twenty patients with Type II-IV (Bismuth classification) hilar obstruction were randomized to treatment with either plastic or metal stents. Both treatment groups were well matched with regard to all assessed clinical criteria before stenting. Stent placement was uniformly successful in the metal group and in 88.9% of the plastic group. Early stent failure (< 30 days) occurred in two patients of the plastic stent group. Longterm (> 30 days), stent failure was observed in 50% of the plastic group and 18.2% of the metal stent group. All differences were not statistically significant. The number of re-interventions required to manage stent-related problems proved to be significantly higher in the plastic group (2.4 +/- 2.6) compared to the metal group (0.4 +/- 0.5). Hospitalization for treatment of stent complications was also significantly higher in the plastic treatment group. The costs calculated for stents and hospital stay for required re-interventions were therefore higher in the plastic stent group. In conclusion, metal stent insertion for palliation of hilar malignancies does not only offer higher success rates and higher patency rates compared to plastic stent insertion, but is also cost-effective since patients require fewer re-interventions.