[Artificial intelligence to support telemedicine in Africa]

Telemedizin findet seit Jahrzehnten Anwendung im Alltag von Dermatologen. Insbesondere in afrikanischen Ländern mit begrenzter medizinischer Versorgung, zu überbrückenden geografischen Distanzen und einem zwischenzeitlich relativ gut ausgebauten Telekommunikationssektor liegen die Vorteile auf der Hand. Nationale und internationale Arbeitsgruppen unterstützen den Aufbau von teledermatologischen Projekten und bedienen sich in den letzten Jahren zunehmend KI(künstliche Intelligenz)-gestützter Technologien, um Ärzte vor Ort zu unterstützen. Vor diesem Hintergrund stellen ethnische Variationen eine besondere Herausforderung in der Entwicklung automatisierter Algorithmen dar. Um die Genauigkeit der Systeme weiter zu verbessern und globalisieren zu können, ist es wichtig, die Zahl der verfügbaren klinischen Daten zu erhöhen. Dies kann nur mit der aktiven Beteiligung der lokalen Gesundheitsversorger sowie der dermatologischen Gemeinschaft gelingen und muss stets im Interesse des einzelnen Patienten erfolgen.

Technical aspects of contrast-enhanced ultrasound (CEUS) examinations: tips and tricks

Ultrasound contrast agents have substantially extended the clinical value of ultrasound, allowing the assessment of blood flow and distribution in real-time down to microcapillary level. Selective imaging of contrast agent signals requires a contrast-specific imaging mode on the ultrasound scanner, allowing real-time separation of tissue and contrast agent signals. The creation of a contrast image requires a specific interaction between the insonated ultrasound wave and the contrast agent microbubbles, leading to persistent oscillation of the bubbles. Several technical and procedural parameters have a significant influence on the quality of CEUS images and should be controlled carefully to obtain good image quality and a reliable diagnosis. Achieving the proper balance between the respective parameters is a matter of technical knowledge and experience. Appropriate training and education should be mandatory for every investigator performing CEUS examinations.

CEUS in hepatocellular carcinoma and intrahepatic cholangiocellular carcinoma in 320 patients - early or late washout matters: a subanalysis of the DEGUM multicenter trial

PURPOSE

The aim of the study was the comparison of tumor vascularization and contrast enhancement in contrast-enhanced ultrasound (CEUS) for the characterization of hepatocellular carcinoma (HCC) and intrahepatic cholangiocellular carcinoma (ICC). We present data of the subpopulations HCC and ICC examined in the DEGUM multicenter trial for the characterization of focal liver lesions in clinical practice.

MATERIALS AND METHODS

Based on the data of the DEGUM multicenter trial (1349 patients), all patients with histologically proven HCC (n = 278) and ICC (n = 42) were analyzed. The vascularity pattern and contrast enhancement pattern during the arterial, portal-venous and late phase were compared.

RESULTS

An underlying liver cirrhosis was found in 214/278 patients with HCC (76.9 %) and 7/42 patients with ICC (16.7 %). In CEUS, HCC showed a global arterial hyperenhancement compared to ICC (HCC: tumor center: 60.3 %; tumor periphery: 75 %; ICC: tumor center: 16.7 %; tumor periphery: 40.5 %). ICC showed an initial contrast enhancement primarily at the tumor periphery (ICC: 85.7 % vs. HCC: 61 %) followed by an early portal-venous contrast washout in the tumor center (ICC: 85.8 % vs. HCC: 49.8 %) and tumor periphery (ICC: 66.7 % vs. HCC: 32.6 %). HCC showed a delayed contrast washout (late phase hypoenhancement: HCC: 75 % vs. ICC: 92.9 %).

CONCLUSION

ICCs are rare in cirrhotic livers. CEUS can demonstrate differences in the vascularization patterns between HCC and ICC. HCC showed an arterial global hyperenhancement and delayed contrast washout in the late phase. ICCs are characterized by an arterial contrast enhancement at the tumor periphery with early contrast washout of the vascularized parts of the lesions in the portal-venous and late phase.

Artifacts and pitfalls in contrast-enhanced ultrasound of the liver

Ultrasound technology is always connected to possible artefacts. Since introduction of ultrasound technology the knowledge of those artefacts is eminent to avoid misinterpretations. It is important to know that with the introduction of new ultrasound technology the possibility of artefacts are rising.Whereas artefacts initially were limited to B-mode sonography, every technological step (colour Doppler sonography, contrast enhanced sonography) comes with a range of new artefacts. This article is written to explain the technological basics of ultrasound artefacts and provide the reader with examples in daily practice and how to avoid them.

First results of endocavity evaluation of the microvascularization of malignant prostate tumors using contrast enhanced ultrasound (CEUS) including perfusion analysis: first results

AIM

Detection of prostate cancer lesions using transrectal contrast enhanced ultrasound (CEUS) of the prostate utilizing quantitative perfusion analysis.

METHOD

20 patients (mean age 63 years, 47-71) with biopsy proven prostate cancer underwent transrectal ultrasound (TRUS) prior to radical prostatectomy by 2 experienced examiners using a multifrequency endocavitary probe (5-9 MHZ, LOGIQ E9, GE Healthcare, Chalfont St Giles, UK) to detect cancer-suspect lesions. CEUS was performed dynamically up to 3 Min after bolus injections of 2.4 ml SonoVue® (BRACCO, Italy). Digital cine loops were analyzed by an independent blinded examiner using perfusion quantification software with colour-coded parametric images in order to define suspect regions based on the perfusion-related parameters early wash in rate (WIR), mean transit time (MTT) and rise time (RT). The results of CEUS perfusion analysis were compared with the histopathology after surgery, obtained from whole mount sections.

RESULTS

After prostatectomy and histopathology, 34 prostate cancer foci were found in 20 patients. In 30/34 cases an early enhancement within the tumor was detected by CEUS perfusion analysis without early wash out. By evaluating the MTT and RT tumor detection was possible in 29/34 and 25/34 cases. The highest detection rate of prostate cancers was obtained by analysis of early contrast enhancement (priot to the normal prostate parenchyma), with a sensitivity of 88%, specificity 100%, NPP 60%, PPV 90%, in clinically suspicious cases with good correlation to the postoperative histopathological findings (r = 0.728).

CONCLUSION

This pilot study demonstrates, that quantitaive analysis of perfusion parameters obtained with transrectal CEUS could be helpful for characterization of neoplastic microcirculation of prostate cancer, for preoperative localization of cancer-suspect areas and for therapy guidance and management.

Frequency of tumor entities among liver tumors of unclear etiology initially detected by sonography in the noncirrhotic or cirrhotic livers of 1349 patients. Results of the DEGUM multicenter study

AIM

Investigation of the frequency of various solid focal liver lesions (SFLL) in noncirrhotic and cirrhotic livers with focus on the frequency of metastasis in cirrhotic livers.

MATERIAL AND METHODS

The patient collective in the DEGUM multicenter study (n = 1349) was reevaluated and divided in subcollective A without (n = 1067) and B with cirrhosis (n = 282). 74.6 % of the various tumor entities were confirmed histologically (n = 1006).

RESULTS

In subcollective A there were 385 patients with metastases (36.4 %) and 65 with HCC (6.1 %), whereas the most common benign lesions were hemangioma, with 237 cases (22.4 %) and FNH, with 170 cases (16.1 %). In subcollective B there were 216 cases of HCC (76.6 %) and 12 metastases (4.3 %), as well as 42 benign lesions (14.9 %). CCC was rare in both subcollective A (3.3 %) and subcollective B (2.5 %). A positive oncological history increased the probability of a malignant SFLL in subcollective A by 1.8 times, but did not do so in subcollective B.

CONCLUSION

The frequency of various tumor entities is different in patients with and without cirrhosis of the liver. In noncirrhotic livers, malignant and benign SFLL are equally common. The most common forms are metastases, hemangiomas and FNH, CCC is rare. A positive history of extrahepatic malignancy increases the probability of a malignant SFLL. In cirrhosis, HCC dominates, HCC is 18 times as common as metastases. Benign SFLL and CCC are rare.

Diagnostic accuracy of CEUS in the differential diagnosis of small (≤ 20 mm) and subcentimetric (≤ 10 mm) focal liver lesions in comparison with histology. Results of the DEGUM multicenter trial

PURPOSE

To evaluate the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) in the differential diagnosis of small and subcentimetric liver tumors in clinical practice.

MATERIALS AND METHODS

1349 patients with a hepatic tumor lacking a definite diagnosis based on B-mode ultrasound and power Doppler ultrasound were examined at 14 hospitals by CEUS using a standardized protocol (pulse/phase inversion imaging, mechanical index < 0.4). Differential diagnosis was based on the vascularity pattern and contrast enhancement pattern during the arterial, portal, and late phase according to the EFSUMB guidelines. 335 patients with focal liver lesions (FLL) ≤ 20  mm were analyzed. The tumor status established after CEUS was compared to histology (73.2 %) or in some cases to CT or MRI.

RESULTS

A definitive diagnosis based on the gold standard was possible in 329 FLLs, while 6 FLLs remained unclear even in the combined gold standard (histology and/or CT and/or MRI). The final diagnoses of ≤ 20  mm FLL with histological confirmation (n = 241) included 87 benign and 154 malignant entities. The overall diagnostic accuracy of CEUS in FLL ≤ 20  mm with histological confirmation was 83.8 %. CEUS correctly identified 144 /154 malignant FLLs (sensitivity 93.5 %) and 58 /87 benign FLLs (specificity 66.7 %). 24 /241 FLLs remained unclear after CEUS (9.9 %). CEUS misclassified 15 /241 FLLs (6.2 %; 12 benign and 3 malignant FLLs). The positive predictive value of CEUS for a malignant FLL was 92.3 % and the negative predictive value was 95.1 %. Out of 241 small FLLs with histological confirmation, 62  FLLs were ≤ 10  mm (diagnostic accuracy of CEUS 80.6 %) and 179 FLLs were > 10  mm and ≤ 20  mm (diagnostic accuracy of CEUS 84.9 %).

CONCLUSION

CEUS has a high diagnostic accuracy for the differential diagnosis of small and subcentimetric FLLs in clinical practice.

Pitfalls and artefacts using contrast enhanced ultrasound

Ultrasound is the method of choice in the detection and characterization of diffuse and focal organic diseases. For B-mode and colour (power) Doppler ultrasound, besides manual skills, (hands-on) a technical knowledge about ultrasound images is of the upmost importance for the investigator. Contrast enhanced ultrasound (CEUS) has become an important diagnostic tool for hepatic, renal, pancreatic indications and several others due to: (a) an increasing rate of studies resulting in sufficient evidence especially in hepatic indications, (b) a rate of adverse events close to zero (1:10,000 in comparison to iodinated contrast agents from 1-12:100) enabling the application of CEUS in patients with severe renal insufficiency or thyroid gland autonomy, and (c) a reasonable price (depends on the country and influence of the health-care system [reimbursement]) and the dosage used. Mini-doses from 0.1 to 0.4 mL are used depending on the contrast agent and applied indication. Therefore a well founded knowledge concerning the technical aspects of CEUS is important for the investigator to avoid misinterpretation especially when artefacts specific for CEUS occur. Special literature is rare. In the presented article we present pitfalls concerning CEUS. The following aspects are considered and illustrated by images: (i) acoustic power (mechanical index) and other aspects resulting in micro bubble destruction, (ii) the possibility of false positive contrast signals in non-vascularized areas, (iii) attenuation caused by too high contrast agent dose, (iv) influence of the frame rate on the spatial resolution, (v) dealing with deep located lesions, (vi) differences in focus positioning in detection and characterization studies, (vii) advantages and disadvantages of replenishment studies, (viii) reliability of contrast enhanced spectral Doppler measurements.

Contrast-enhanced ultrasound (CEUS) for the characterization of focal liver lesions in clinical practice (DEGUM Multicenter Trial): CEUS vs. MRI--a prospective comparison in 269 patients

PURPOSE

The aim of this prospective multicenter study was to assess the diagnostic role of CEUS in the diagnosis of newly discovered focal liver lesions in clinical practice. One important aspect is the comparison of CEUS with magnetic resonance imaging (MRI).

MATERIALS AND METHODS

From 05 / 2004 to 12 / 2006, standardized CEUS was performed prospectively on 1349 patients with focal liver lesions that had been newly detected by fundamental ultrasound in order to determine tumor differentiation and tumor entity. 269 patients had a standardized MRI after CEUS. In typical liver hemangioma and focal nodular hyperplasia (FNH), the definitive diagnosis was based on the MRI as the "diagnostic gold standard" and on clinical evidence and additional follow-up (subgroup A) or on histology (subgroup B). 262 patients met the diagnostic standard that had been set.

RESULTS

In the subcollective (n = 262), the tumor differentiation (malignant or benign) of CEUS and MRI was concordant in 225 cases (85.9%), and the assessment of tumor entity in 204 cases (77.9%). In subgroup A (n = 180), concordant results for tumor differentiation were obtained in 169 (93.2%) and for tumor entity in 160 (88.9%) cases. Liver hemangiomas (n = 122) and FNH (n = 43) were most frequent. Subgroup B (n = 82) comprised mainly malignant liver lesions (n = 55), with only a few of hemangiomas (n = 8) or FNH (n = 5). Tumor differentiation was concordant in 56 (68.3%) and tumor entity in 44 cases (53.7%). There were no statistically proven differences between CEUS and MRI.

CONCLUSION

CEUS and MRI are of equal value for the differentiation and specification of newly discovered liver tumors in clinical practice. CEUS and MRI are extremely reliable for the differentiation of benign and malignant lesions, the diagnosis of liver hemangiomas and FNH. The characterization of metastases and HCC is also very reliable.

Contrast-enhanced ultrasound for the characterization of focal liver lesions--diagnostic accuracy in clinical practice (DEGUM multicenter trial)

PURPOSE

To evaluate the diagnostic benefit of contrast-enhanced ultrasound for the differential diagnosis of liver tumors in clinical practice.

MATERIALS AND METHODS

From May 2004 to December 2006 1349 patients (male 677, female 672) with a hepatic tumor lacking a definite diagnosis based on B-mode ultrasound and power Doppler ultrasound were examined at 14 hospitals by contrast-enhanced ultrasound using a standardized protocol (pulse/phase inversion imaging, mechanical index < 0.4). The Tumor status was assessed based on the vascularity pattern and contrast enhancement seen in focal lesions during the arterial, portal, and late phase. The diagnosis established after contrast-enhanced ultrasound was compared to histology (> 75% cases) or in some cases to CT or MRI.

RESULTS

The final diagnosis of hepatic tumors included 573 benign hepatic tumors (hemangiomas n = 242, focal nodular hyperplasia n = 170, hepatocellular adenoma n = 19, other benign lesions n = 142) and 755 malignant hepatic tumors (metastases n = 383, hepatocellular carcinoma n = 279, other malignant lesions n= 93). The overall diagnostic accuracy of contrast-enhanced ultrasound in comparison to the correct final diagnosis based on the combined gold standard was 90.3%. Contrast-enhanced ultrasound was able to correctly assess 723/755 malignant lesions (sensitivity 95.8%) and 476/573 benign lesions (specificity 83.1%). The positive predictive value of contrast-enhanced ultrasound for the diagnosis of a malignant tumor was 95.4% and the negative predictive value of contrast-enhanced ultrasound was 95.7%.

CONCLUSION

Contrast-enhanced ultrasound clearly improves the differential diagnosis of hepatic tumors and is very helpful in clinical practice when B-scan or power Doppler morphological criteria are missing.

Early Postoperative Ultrasound of Kidney Transplants: Evaluation of Contrast Medium Dynamics Using Time-intensity Curves

OBJECTIVE

To evaluate kidney recipients in the early posttransplant phase by semiquantitative analysis of the arterial arrival of ultrasound (US) contrast medium using time-intensity curves.

PATIENTS AND METHODS

Twenty-two kidney recipients underwent US examination after intravenous bolus administration of 2.4 ml of US contrast medium (SonoVue, Bracco Altana) 5 to 7 days after transplantation. The examinations were performed with the Aplio US system (Toshiba) and a 3.5-MHz wideband transducer using contrast harmonic imaging at a low mechanical index of 0.1. Arterial arrival was documented digitally over 60 sec (image repetition rate: 10 images per sec) for subsequent evaluation of contrast medium kinetics in the main renal artery, interlobar artery, subcapsular area, and renal vein using the system's integrated time-intensity curve (TIC) software. The increase, decrease, and percentage enhancement factor were calculated from the curves. Four patients were excluded from analysis because of perirenal hematoma (n = 3) or a polar perfusion loss demonstrated by power Doppler (n = 1).

RESULTS

Twelve of the remaining 18 patients assigned to the nonrejection group showed an uneventful clinical course. These had uniform TICs with an early and steep increase of similar magnitude in the main renal artery (11.7 +/- 4.5 intensity units/sec), interlobar artery (8.7 +/- 4.6 intensity units/sec), and subcapsular area (8.3 +/- 3.7 intensity units/sec) followed by a washout and subsequent plateau phase. Six patients showed histologically proven acute rejection on day 5 or 6 after transplantation (rejection group). This group had a delayed (time to peak in the subcapsular area: 32.9 +/- 8.3 sec in the rejection group versus 20.9 +/- 4.7 sec in the nonrejection group, p < 0.05) and smaller subcapsular percentage increase (41.2 +/- 21.9 % versus 114.4 +/- 59.8 %, p < 0.05). In the rejection group the subcapsular area (3.8 +/- 2.3 intensity units/sec) showed a less pronounced increase than the main renal artery (7.9 +/- 5.9 intensity units/sec) and interlobar artery (8.7 +/- 3.8 intensity units/sec). The RI in the rejection group was in the normal range at the time of contrast-enhanced US (day 5: 0.78 +/- 0.06) and increased to abnormal levels in the further course (day 7: 0.94 +/- 0.09).

CONCLUSIONS

Quantitative determination of arterial arrival of an US contrast medium in the early phase after kidney transplantation is possible. This new US procedure might identify acute rejection earlier than conventional techniques.

[Improved assessment of the left ventricular endocardial border by intravenous injection of a left heart contrast agent]

PURPOSE

The purpose of this study was to find out whether intravenous injection of a phospholipid-based left heart echo contrast agent improves the delineation of the left ventricular endocardial border. The influence of echo contrast on the quantification of left ventricular volumes, ejection fraction, regional wall function and interobserver variability was also assessed.

METHOD

Prospectively, the apical 4-chamber view was recorded in 20 adult patients before and after intravenous injection of the contrast agent. Left ventricular endocardial border resolution was assessed in 5 segments and left ventricular volumes, ejection fraction, regional wall motion and interobserver variability were measured.

RESULTS

After contrast injection a diagnostically useful left ventricular opacification was present in 18 patients (90%) and an optimal opacification in 14 patients (70%). Without contrast 1.05 endocardial segments could be delineated at end diastole and 1.8 segments at end systole. After contrast injection 3.65 endocardial segments were recognizable at end diastole (p < 0.01), 2.5 segments at end systole (p < 0.02). Left heart contrast improves interobserver-variability of end diastolic volume (p < 0.006), end systolic volume (p < 0.004), ejection fraction (p < 0.0002) and regional wall motion assessment (p < 0.03). Side effects did not occur.

CONCLUSIONS

The intravenous injection of the investigated phospholipid-based echo contrast agent improves left ventricular endocardial border delineation and reproducibility of left ventricular volumes, ejection fraction and regional wall motion assessment.

Harmonic grey scale imaging of the human brain

Harmonic imaging increases the signal-to-noise ratio in grey-scale imaging. With the use of ultrasound contrast agents (UCA), imaging of brain perfusion seems possible. The authors used an ultrasound system in connection with a 1.8/3.6-MHz harmonic sector transducer and an acoustic densitometry unit for quantification of ultrasound intensity in the thalamus (THAL), the temporoparietal white matter (TPWM), and the lateral fissure (LF). Ten milliliters of BY963, a spherosome-air-based UCA, was injected intravenously in 12 healthy volunteers. Time-intensity curves were calculated. Mean increase of intensity (standard deviation [SD]), mean area under the time-intensity curve (AUC) from baseline (SD), and mean transit time (MTT) (SD) in the region of LF, THAL, and TPWM were 2.2 +/- 1.7, 1.1 +/- 0.6, 0.9 +/- 0.9 dB and 16.7 +/- 22.7, 4.7 +/- 4.7, 3.7 +/- 6.3 as well as 11.1 +/- 3.5, 9.7 +/- 3.1, and 11.9 +/- 8.0, respectively. There was a statistically significant difference for mean AUC (p = 0.02) but none comparing mean intensity increase (p = 0.07) and MTT (p = 0.9). The authors' study indicates that different regions of the human brain show different time-intensity curves. These results suggest that it is possible to measure parameters closely related to perfusion in various regions of the adult human brain.

Interobserver agreement: Cohen's kappa coefficient does not necessarily reflect the percentage of patients with congruent classifications

A widely accepted approach to evaluate interrater reliability for categorical responses involves the rating of n subjects by at least 2 raters. Frequently, there are only 2 response categories, such as positive or negative diagnosis. The same approach is commonly used to assess the concordant classification by 2 diagnostic methods. Depending on whether one uses the percent agreement as such or corrected for that expected by chance, i.e. Cohen's kappa coefficient, one can get quite different values. This short communication demonstrates that Cohen's kappa coefficient of agreement between 2 raters or 2 diagnostic methods based on binary (yes/no) responses does not parallel the percentage of patients with congruent classifications. Therefore, it may be of limited value in the assessment of increases in the interrater reliability due to an improved diagnostic method. The percentage of patients with congruent classifications is of easier clinical interpretation, however, does not account for the percent of agreement expected by chance. We, therefore, recommend to present both, the percentage of patients with congruent classifications, and Cohen's kappa coefficient with 95% confidence limits.

Migration and aggregation of embryonic chicken neurons in vitro: possible functional implication of polysialogangliosides

The presented study reports a primary culture system of embryonic chicken optic lobe neurons, which turned out to be a suitable model for cell migration and aggregation: Freshly dissociated neurons developed short processes, contacted one another and formed fasciculated bundles, on which neurons migrated as long-shaped cells, similar to migrating neurons in vivo. We used this system to study the possible involvement of c-pathway polysialogangliosides for neuronal migration and aggregation. These highly negative charged glycosphingolipids are the predominant gangliosides of migrating and outgrowing neurons in vivo. Addition of a purified ganglioside mixture (50 microM), extracted from brains of the corresponding embryonic stage, strongly enhanced neuronal migration and aggregation, while incubation of the cells with monoclonal antibody Q211, specifically binding c-polysialogangliosides, reduced aggregate formation in a dose-dependent manner. Cultures treated with 10 micrograms/ml Q211, instead, displayed a more divergent growth, leading to the formation of a fine network of single neuronal processes. These results suggest a functional implication of c-polysialogangliosides in neuronal fasciculation, migration and aggregation.

Density-dependent expression of ganglioside GM3 by human skin fibroblasts in an all-or-none fashion, as a possible modulator of cell growth in vitro

The expression of GM3 in human skin fibroblasts (cell type MF II) was investigated biochemically and immunochemically by means of the monoclonal antibody M2590. A cell density-related increase in total gangliosides (about threefold) and especially in GM3 (about sixfold) was found upon attainment of confluency. Immunostaining with mAb M2590 revealed that in preconfluent cultures GM3 is expressed by only a few cells in an all-or-none fashion. The portion of GM3-expressing cells increases in parallel with cell density. In confluent cultures, which are growth-arrested by contact inhibition, all cells are intensely stained by mAb M2590, indicating a high content of GM3 in the plasma membrane. These data suggest that increased cellular M2590 binding is due to an increased GM3 content rather than to an altered conformation or arrangement in the cell membrane. GM3-expressing cells usually show a broad, flat morphology, like that of cells in the resting state (G1/G0-phase) of the cell cycle. The M2590 staining on these cells appear as clusters, orientated along straight lines and indicating an ordered distribution of GM3 in the plasma membrane. A dose-dependent inhibition of cell growth by addition of exogenous gangliosides supports the possible involvement of these glycosphingolipids in the regulation of cell growth.

c-pathway polysialogangliosides in the nervous tissue of vertebrates, reacting with the monoclonal antibody Q211

The mouse monoclonal antibody Q211, previously shown to recognize a common epitope of chicken brain GP1c and of two other polysialogangliosides containing 4 and 6 sialic acid residues respectively, is demonstrated to bind to gangliosides with identical thin-layer chromatography (TLC) migration in the brain of representatives of boney fish, rays, reptiles and mammals, including man. In the boney fish brains, the Q211 binding gangliosides were found to be alkali-labile, the Q211 epitope, however, is alkali-stable. After alkaline treatment, the cichlid fish contained at least 4 Q211-binding gangliosides, migrating as GT1c, GQ1c, GP1c and 'GH'. In the trout brain only one Q211 antigenic fraction was found, migrating as GQ1c. In the brains of ray, turtle and embryonic chicken an identical pattern of Q211-binding gangliosides (GQ1c, GP1c, 'GH') occurred. In the embryonic rat and human brain, the content of Q211-binding gangliosides was much lower as compared to the other vertebrate species. The epitope was found in two fractions, migrating like GQ1c (human and rat) and GP1c (rat). The presence of Q211 epitope in all species was confirmed by immunohistochemistry. These data confirm that the Q211-epitope contains a complete c-ganglio-tetraose structure, carrying 3 sialic residues at the inner galactose. They furthermore demonstrate that the expression of c-pathway polysialogangliosides is a general feature of the vertebrate nervous tissue, either during whole life (fish, reptiles) or more or less transient during embryonic development (birds, mammals).

Possible involvement of polysialogangliosides in nerve sprouting and cell contact formation: an ultracytochemical in vitro study

In Cichlid fish (Oreochromis mossambicus) primary cell cultures from whole brain and optic tectum, the differentiation-dependent distribution of polysialogangliosides on the outer cell surface has been followed on an ultrastructural level. For this, a two-step labeling technique with the monoclonal mouse antibody Q211, recognizing a polysialoganglioside-associated epitope, followed by a secondary IgM antibody, coupled to colloidal gold sols as an electron-dense marker, has been used. The gold grains are not uniformly distributed over the whole cell surface, but rather are clearly arranged clusters. In cells from freshly hatched larvae, both cell bodies and nerve fibers strongly exhibit the polysialoganglioside epitope on their surface. With progressing development, neuronal cell labeling is more and more restricted to nerve fibers and especially to cellular adhesion zones, including synaptic terminals, thus suggesting a functional involvement of polysialogangliosides in nerve sprouting and initiation of both cell-to-extracellular matrix and cell-to-cell contacts.

Developmental expression in embryonic rat and chicken brain of a polysialoganglioside-antigen reacting with the monoclonal antibody Q 211

The monoclonal mouse antibody Q 211 binds to an antigen, which is expressed by postmitotic growing neurons of embryonic chicken and rat brain. In chicken, thin layer chromatography (TLC) immunostaining confirms the presence of the Q 211 antigen in at least 3 different polysialoganglioside fractions. One comigrates on TLC plates with GP1c and the others with gangliosides, which have been previously preliminary characterized as GQ1c, and as a hexasialoganglioside. Thus, 3 sialic acid residues linked to the inner galactose of a complete tetraose moiety is suggested as the common epitope of the different Q 211-antigen-active gangliosides. Also in the embryonic rat brain, immunohistochemistry reveals a transient expression of the Q 211 antigen in areas containing growing nerve fibres. Unlike chicken, however, in the rat the staining is restricted to early thalamocortical innervations and to a fibre system (probably long distance projections) connecting the mamillary body with the hippocampus formation. In ganglioside extracts from rat forebrain 2 polysialogangliosides are shown by immuno-TLC to bind Q 211. One of these fractions, occurring transiently and in parallel with histochemical staining, comigrates on TLC plates with chicken GP1c. The other comigrates with the second main Q 211 antigen-containing band of chicken, which was preliminary identified as GQ1c.