"Fast-track" rehabilitation for elective colonic surgery in Germany--prospective observational data from a multi-centre quality assurance programme

BACKGROUND

The results of "Fast-track" colonic surgery in an unselected population outside of specialised units has been unknown yet.

MATERIALS AND METHODS

Data from 24 German hospitals performing "Fast-track" rehabilitation as the standard peri-operative care for patients undergoing elective colonic resection were collected in a prospective multi-centre study conducted between April 2005 and September 2006 to evaluate local and general morbidity.

RESULTS

One thousand and forty-seven patients undergoing elective "fast-track" colonic resection were included. Compliance to essential parts of "fast-track" rehabilitation was high (epidural analgesia 86,6%, early oral feeding and mobilisation on the day of surgery 85.5 and 85.4%). Surgical morbidity was observed in 148 patients (14.1%) and general morbidity in 95 patients (9.1%), while mortality was 0.8%. Predefined discharge criteria were met within 5 (1-83) days after surgery, but because of economical restraints in the German DRG system, patients were discharged only after 8 (3-83) days. Re-admission rate was 3.9%.

CONCLUSION

"Fast-track" rehabilitation for elective colonic resection was safe and feasible in German hospitals of all sizes and yielded a low general morbidity and re-admission rate. Post-operative recovery was enhanced, but discharge from hospital was delayed because of economical reasons.

Antibiotic Use in Non–University Regional Acute Care General Hospitals in Southwestern Germany, 2001–2002

BACKGROUND

A previous study from Germany showed high antibiotic use in university hospitals, particularly in intensive care units (ICU) and hematology-oncology services, but there has been no information about recent antibiotic use in non-university hospitals. In the present study, we collected data from 40 non-university regional general hospitals located in the southwestern part of the country, and analyzed use density in the medical and surgical services of these hospitals.

MATERIALS AND METHODS

Hospital pharmacy records for the calendar years 2001 and 2002 were evaluated. The number of defined daily doses (DDD, definition according to the WHO/ATC 2001 index) and prescribed daily doses (PDD) per 100 patient days (DDD/100 or PDD/100, respectively) were calculated to compare antibiotic use densities in medical and surgical services. Data for surgery included various subspecialties and gynecology.

RESULTS

Antibiotic use in the participating hospitals increased minimally between 2001 and 2002 both in medicine as well as in surgery. Use density in internal medicine (ICU areas excluded) in the year 2002 ranged between 13.5 and 93.7 DDD/100 with a weighted mean of 49.9 DDD/100 (corresponding to 28.6 PDD/100, respectively). Values for surgery were lower with a weighted mean of 43.4 DDD/100 (corresponding to 26.1 PDD/100, range, 10 to 65.4 DDD/100), respectively. Hospital size was not a strong predictor of use density, while large differences were observed between intensive care areas and normal wards. Mean use densities in intensive care areas in 2002 were 105.6 DDD/100 (or 49.7 PDD/100) in medical intensive care units, 116.9 DDD/100 (or 61.2 PDD/100) in surgical intensive care units, and 112.7 DDD/100 (or 66.7 PDD/100) in mixed, interdisciplinary intensive care units. Betalactams made up > 50% of all PDDs, while fluoroquinolones were the second most frequently prescribed drugs (15% of all PDDs). Fluoroquinolones were usually given orally. Overall glycopeptide and aminoglycoside use was < 1 PDD/100.

CONCLUSION

This recent data from a large regional nonuniversity acute care hospital sample confirms that hospital antibiotic use density largely depends on patient care areas and less on hospital size. Surprisingly low use was observed for glycopeptides and aminoglycosides. The data may be useful as a benchmark for further pharmaco-epidemiologic evaluation and focused drug use control interventions.

Observation of human dentine by focused ion beam and energy-filtering transmission electron microscopy

Molar dentine was sliced into 100 nm ultrathin sections, by means of a focused ion beam, for observation by energy-filtering transmission electron microscopy (EFTEM). Within the matrix, crystals approximately 10 nm wide and 50-100 nm long were clearly observed. When carbon and calcium were mapped in electron spectroscopic images by EFTEM, carbon failed to localize in crystals. However, it was found in other regions, especially those adjacent to crystals. Because carbon localizations were thought to reflect the presence of organic components, carbon concentration in regions near crystals suggested the interaction of crystals and organics, leading to organic control of apatite formation and growth. Ca was present in almost all regions. The majority of Ca localizing in regions other than crystals may be bound to organic substances present in dentine matrix. These substances are thought to both accumulate Ca and act as reservoirs for crystallization of apatite in dentine.

Comparison of phenytoin serum concentrations in premature neonates following intravenous and oral administration

OBJECTIVE

To compare the serum concentrations attained following intravenous and oral administration of phenytoin in premature neonates.

DESIGN

A prospective, uncontrolled study was conducted over 6 years. Phenhydan concentrate for infusion (Desitin, Hamburg, Germany) was used for intravenous infusion, and Epanutin suspension (Parke-Davis, Freiburg, Germany) was used for oral therapy. Blood samples were analyzed by using a fluorescence polarization immunoassay analyzer TDx model by Abbott Laboratories.

SETTING

A university-affiliated district hospital.

PARTICIPANTS

Twenty premature neonates who were administered intravenous and/or oral phenytoin between February 1991 and February 1997.

MAIN OUTCOME MEASURES

Serum phenytoin concentrations on intravenous and oral phenytoin.

RESULTS

Nine patients received intravenous (group A) and 15 patients received oral (group B) therapy. Mean +/- SD postnatal age (41 +/- 8.7 vs. 48 +/- 17 d; p = 0.03) and actual body weight (1.56 +/- 0.38 vs. 1.88 +/- 0.75 kg; p = 0.02) were slightly higher in group B. There were no significant differences between the groups in mean +/- SD gestational age (26.1 +/- 1.37 vs. 26.9 +/- 3.30 wk), 5-minute Apgar score (8.7 +/- 1.11 vs. 7.7 +/- 2.26), daily dosage (8.1 +/- 3.86 vs. 8.1 +/- 4.21 mg/kg/d), and phenytoin serum concentration (8.7 +/- 7.36 vs. 9.6 +/- 5.83 micrograms/mL).

CONCLUSIONS

Contrary to data in the current literature, reliable serum concentrations in premature neonates were achieved by oral administration of phenytoin suspension. Oral therapy offers a number of advantages and considerably reduces the cost of therapy. Due to substantial variations in phenytoin pharmacokinetics in neonates, close monitoring of serum concentrations is required. Further investigation is required to confirm these results, especially in neonates younger than 20 days' postnatal age and those receiving products other than Epanutin.

Use of a mass-thickness marker to estimate systematic errors and statistical noise in the detection of phosphorus by electron spectroscopic imaging

The element signal obtained from electron-energy-filtered micrographs depends on the systematic error in calculating the background and on the noise in the background-corrected image. Both systematic error and statistical fluctuation of the background can be assessed experimentally with a specimen that combines the element-containing feature with a mass-thickness marker. The approach is described for the mapping of phosphorus in turnip yellow mosaic viruses prepared on a supporting carbon film of variable thickness. The thickness modulations are produced by the additional deposition of heat-evaporated carbon through a second grid used as a mask. The three-window power-law method and the two-window difference method are compared. With the three-window power-law method, the mass-thickness modulations of the marker are still visible in the map, indicating a systematic error for the calculated background. In addition, the intensity profile over the area of the thick carbon film is broader than in the map corrected by the two-window method, indicating a higher level of noise. With the two-window difference method, mass-thickness contrast was practically eliminated due to an improved protocol that uses the mass-thickness marker to calculate the scaling factor: instead of scaling the grey-level of a single background feature, the pre-edge image is scaled to the contrast of the marker area in the image acquired at the element-specific energy loss.

Low risk of bacteremia during catheter replacement in patients with long-term urinary catheters

BACKGROUND

Geriatric patients with long-term urinary catheters have an increased morbidity and mortality. It is conceivable that catheter replacement causes bacteremia and contributes to this morbidity and mortality. The purpose of our study was to determine the incidence and clinical relevance of bacteremia induced by urinary catheter replacements.

METHODS

We analyzed clinical signs and symptoms and laboratory measures (leukocyte count, C-reactive protein, urine sediment, urine culture) during 120 routine catheter replacements in geriatric patients. In addition, blood cultures were drawn before and at 5, 15, and 30 minutes after catheter replacement.

RESULTS

The urine cultures showed growth of 1 to 5 different microorganisms before replacement. Of 480 blood cultures, 27 (5.6%) were positive. However, the same species grew from blood and urine in only 5 catheter replacements. None of the patients met criteria for systemic inflammatory response syndrome. There were no significant differences in clinical and laboratory findings between patients with and without bacteremia. Coagulase-negative staphylococci grew in 12 blood cultures. Their distribution over time suggested that they mainly represented catheter replacement-related bacteremia rather than contaminants. Consequently, 64 intraurethral catheter segments were additionally cultured. Coagulase-negative staphylococci grew in 10 catheter cultures, but in only 2 simultaneously cultured urine samples.

CONCLUSION

Bacteremia induced by routine replacement of long-term urinary catheters occurred in 4.2% (5/120) of replacements in geriatric patients. Such bacteremia did not have a detectable clinical relevance in our study.

[How safe is short-term inpatient treatment after laparoscopic cholecystectomy]

In 534 patients after laparoscopic cholecystectomy an earliest discharge was intended. The median day of discharge was day 3 postoperatively. The limitations to discharge were; normal physical findings, temperature back to normal and sonographic findings, which did not exceed the usual fluid accumulation in the gallbladder bed. Under strict application of these limitations no postoperative complication was missed. Due to outpatient pre-examination and operation on the day of admission the total length of stay could be limited to 2 days median. Also in this subgroup of 178 patients the chosen procedure was save.

A calcium influx is neither strictly associated with nor necessary for exocytotic membrane fusion in Paramecium cells

Exocytosis of trichocysts in Paramecium cells was generally believed to depend on extracellular Ca, since it is accompanied by a Ca influx and not seen in the absence of Ca. However, by short term removal of Ca we showed recently that only extrusion of secretory contents, but not membrane fusion after stimulation with aminoethyldextran (AED), depends on extracellular Ca. We have now extended these studies to longer times and shown that membrane fusion is stimulated by AED even after 1 min at low Ca (< or = 30 nM). At prolonged times membrane fusion was induced by sole removal of Ca. In the presence of AED, trichocyst contents were slowly extruded followed by resealing of the fused membranes, indicating independency of endocytotic membrane fusion from extracellular Ca (though we observed aberrant resealing). Later on, Ca removal is followed by cell death. By using videomicroscopy, we further provide the first evidence that exocytosis is not necessarily accompanied by an influx of Ca in the presence of the usual high concentrations (1 mM), since local exocytosis at the rear end of the cells is not followed by ciliary reversal which is triggered by Ca influx. We conclude that a Ca influx is neither regularly associated with, nor necessary for, induction of exocytotic membrane fusion in Paramecium cells. As a source for a possible alternative intracellular liberation of calcium during exocytosis, we analyzed the subplasmalemmal alveolar sac system by electron spectroscopic imaging and found indications for Ca redistributions shortly after stimulation.

[Urinary tract infections in general practice]

Urinary tract infections are a frequent problem in ambulatory practices. According to the localization of the infection and to complicating factors we differentiate between various syndromes with different clinical presentations. Relevant diagnostic criteria are a bacteriuria of greater than or equal to 100 organisms par millilitre or a pyuria of greater than or equal to 5 leukocytes per high power field. For acute cystitis, a treatment for three days is recommended. Cotrimoxazole or quinolones are effective drugs, which are more and more recommended for the treatment of acute pyelonephritis, too.

[Spontaneous kidney rupture]

Spontaneous rupture of the kidney may occur as a complication of various congenital or acquired renal lesions. We describe three patients with non-traumatic rupture of the kidney, recently seen in our hospital. The rupture was related to polyarteritis nodosa in one case, and in the other two respectively to urothelial carcinoma and to acquired renal cystic disease in end-stage renal disease with continuous ambulatory peritoneal dialysis. In all patients the hemorrhagic complication led to a previously unsuspected diagnosis. After nephrectomy all patients did well. While spontaneous rupture of the kidney is very rare, it is important to consider this complication in the evaluation of a corresponding clinical picture. The possible causes of renal rupture are discussed.

Intravenous 1,25(OH)2 vitamin D3 therapy in haemodialysis patients: evaluation of direct and calcium-mediated short-term effects on serum parathyroid hormone concentration

Eleven patients on chronic haemodialysis treatment thrice weekly received 1 microgram 1,25(OH)2D3 i.v. after each dialysis for 3 weeks. Phosphate binders were mainly CaCO3, supplemented in a few patients by moderate amounts of Al(OH)3. Ionised calcium was measured by ion-selective electrode, normal values being 1.28-1.42 mmol/l. PTH was estimated by an N-terminal-sensitive assay; normal values are less than 0.25 ng/ml. Results before and after 1,25(OH)2D3 were: ionised calcium before haemodialysis, 1.19 +/- 0.12 and 1.17 +/- 0.14; ionised calcium after haemodialysis, 1.33 +/- 0.07 and 1.30 +/- 0.09; PTH before haemodialysis, 1.39 +/- 0.71 and 1.38 +/- 0.69; PTH after haemodialysis, 0.64 +/- 0.22 and 0.60 +/- 0.17; Phosphate before haemodialysis, 1.85 +/- 0.48 and 2.18 +/- 0.43 (P less than 0.05). No change of PTH concentration and ionised calcium before and after haemodialysis treatment could be documented after i.v. 1,25(OH)2D3 treatment. Mild and severe hyperparathyroidism were indistinguishable. Increased serum calcium concentrations therefore appear to be required for the suppression of PTH secretion by i.v. 1,25(OH)2D3 therapy.

[Synthesis and cytostatic action of 9-nitronoracronycine]

The synthesis of 9-nitronoracronycine (12) from 1,3-dihydroxy-10-methyl-7-nitroacridone (4) and 2-chlor-2-methyl-3-butyne is reported. Screening tests with the transplantation tumor leukemia P 388 proved 4 and 1-methoxy-10-methyl-7-nitroacridone (14) to be inactive. 12 and 3-methoxy-10-methyl-7-nitroacridone (15) showed cytotoxicity in higher doses. Structure-activity relationships are discussed.

Influence of Ca2+ and temperature on the interaction of gangliosides with valinomycin in mixed monolayers at the air/water interface

The effects of Ca2+ and temperature on mixed ganglioside-valinomycin-monolayers at the air/water interface were studied. Surface pressure-area isotherms of the pure gangliosides (GM1, GD1a) exhibited the typical monolayer characteristics. Pressure-area isotherms of the cyclodepsipeptide, valinomycin, were determined. In mixed monolayers, positive and negative deviation from the mean molecular area indicated the two components were miscible. Especially in GD1a mixtures, the addition of 0.01 mM calcium exhibited, with low molar fractions of valinomycin, a demixing effect in the direction of the phase separation of the components.

[Glomerulonephritis in chronic bacterial infections]

Five patients with chronic bacterial infections (two with osteomyelitis, two with infected vascular prostheses, one with soft tissue abscess), but without endocarditis, developed signs of glomerulonephritis and renal failure. Histological examination in three revealed mainly proliferative glomerular alterations. The outcome of glomerulonephritis paralleled the course of infection. Recovery or marked improvement occurred in three patients in whom the infection was cured, one case with smoldering infection eventually developed endstage renal failure, and one with persistent infection died from severe complications with acute renal failure. If renal failure occurs in the setting of suppurative infection, so-called infection-associated glomerulonephritis must be considered. Prompt and effective eradication of infection has an important bearing on the course of renal function.

Method for the OsO4-free preservation of brain tissue suitable for immunocytochemistry in TEM

Following conventional OsO4-fixation and embedding of brain tissue in Epoxide resins for ultrastructural investigations, on the one hand, the wellknown good depiction of structures is obtained, on the other hand, however, according to these procedures a considerable loss up to 80% of glycolipid-bound and up to 50% of glycoprotein-bound neuraminic acid of important native compounds has to be put up with. The fixation of brain tissue by 1% glutaraldehyde and 1% paraformaldehyde in 0.1 mol/l Na-K-phosphate-buffer, followed by dehydration in acetone or ethanol at--25 degrees C and embedding in Lowicryl K4M preserves for instance amphiphilic glycolipids (gangliosides) to a high degree (95%) and in addition provides a good depiction of neuronal structures. The incubation of ultrathin sections of carp brain, treated as described above, with the specific antibody Q211 against polar gangliosides gave first evidence for a specific labelling of these amphiphilic glycosphingolipids and their localization within the brain tissue.

Seasonal variability of sialo-glycoconjugates in the brain of the Djungarian hamster (Phodopus sungorus)

The influence of season, photoperiod and ambient temperature on the content of proteins, sialo-glycoproteins and gangliosides and on the composition of gangliosides of three different brain regions (cortex, cerebellum and basalbrain) of the Djungarian dwarf hamster (Phodopus sungorus) had been investigated. Concomittantly changes in body wt and fur colouration were recorded. Dwarf hamsters living under natural photoperiod and ambient temperature conditions ("outside") showed a distinct annual cycle in body wt (summer: about 45 g; winter: about 25 g) and fur colouration (summer: dark grey; winter: whitish). Among the three brain regions the mean concentration of proteins ranged between 120 and 155 mg protein/g wet wt. The sialo-glycoprotein content varied between 260 and 410 micrograms NeuAc/g wet wt, and that of gangliosides between 800 and 1650 micrograms NeuAc/g wet wt. Seasonal fluctuations were not found. The composition of brain gangliosides remained uninfluenced throughout the year in the cerebellum, whereas seasonal variations were observed in cortex and basalbrain. Consequently the concentration ratio of the two major mammalian ganglioside fractions GD1a vs GT1b remained almost stable in cerebellum (0.3). In contrast to this the seasonal values of cortex and basalbrain changed from 0.6 and 0.8 in winter to 0.7 and 1.1 in summer. This indicated a higher polarity of the gangliosides in these brain regions during cold adaptation. The results are discussed with regard to modulatory functions of neuronal gangliosides for the process of synaptic transmission during seasonal adaptation.

Ultrastructural localization of calcium in the CNS of vertebrates

The ultrastructural localization of calcium in synaptic areas of the CNS of fish was investigated. Prefixation with phosphate-buffered glutaraldehyde followed by post-fixation with osmium/potassium-bichromate was used to precipitate and visualize endogenous calcium without the addition of external calcium. The presence of calcium in the electron-dense precipitates produced using this method was demonstrated by electron spectroscopic imaging using a Zeiss EM-902 transmission electron microscope, and in various control experiments using the calcium chelator EGTA. In the optic tectum of fish, electron dense precipitates containing calcium were found not only in intracellular compartments, e.g. the smooth endoplasmic reticulum, mitochondria and synaptic vesicles, but also at extracellular locations, particularly in synaptic clefts. In the extracellular sites, only chelate complexes of ionic calcium were found. This would seem to be in agreement with electrophysiological and biochemical data reported in earlier studies. Thus, using the present method, it should be possible to obtain further ultrastructural information concerning the mechanisms of synaptic transmission.

[Adenocarcinoma of the kidney (hypernephroma)]

Adenocarcinomas of the kidney are rare tumors. This malignancy has been called the "internist's tumor" because of its often unusual presentation and systemic symptoms. The diagnosis is largely based on urography, sonography and CT-scan. Radical tumornephrectomy is the only treatment with curative potential. Interventional angiography with tumor embolization has become an important tool for palliation. On the other hand, the results of systemic treatment, such as hormone therapy, chemotherapy or immunotherapy, remain disappointing.

Modulatory effects of different temperatures and Ca2+ concentrations on gangliosides and phospholipids in monolayers at air/water interfaces and their possible functional role

Gangliosides are neuraminic acid-containing glycolipids preferently localized in nervous membranes and showing physicochemical peculiarities, e.g., drastically changing amphiphilic properties by Ca2+ binding. On account of this they are favorite compounds to act as modulators of membraneous organization and functions during synaptic transmission. Lipid monolayers are suitable experimental systems for the study of the surface behavior of amphipatic molecules and therefore are useful to interpret membraneous organization. The surface pressure/area isotherms of monolayers of different individual gangliosides (GM1, GD1a, GD1b, GT1b) of an artificial reconstituted and a natural ganglioside mixture from bovine brain and of ganglioside mixtures from different brain parts of summer- and winter-adapted dsungarian hamsters were compared at three temperatures (11, 20, and 37 degrees C) with egg phosphatidylcholine (PC) and phosphatidylserine (PS) monolayers. The monolayers were formed in a Teflon trough on a triethanolamine/HCl-buffered (pH 7.4) subphase, in some cases containing different amounts of CaCl2. The surface pressure/area isotherms of ganglioside monolayers, in contrast to phospholipids, generally showed slowly rising slopes, with transitions from the liquid-expanded to the liquid-condensed state at a surface pressure of 20-30 mN/m. Ganglioside monolayers, in particular from GD1a or GT1b versus GD1b or from mixtures from summer- versus winter-adapted hamster brain, were differently affected by temperature and/or by Ca2+. PS monolayers were slightly condensed only by Ca2+. PC monolayers, however, were influenced neither by temperature nor by Ca2+. In mixed monolayers of the unpolar natural lipid cholesterol (Ch) and the disialoganglioside GD1a, intermolecular interactions were indicated. Ganglioside monolayers, in contrast to phospholipids, were shown to be easily modulated by temperature and/or Ca2+ ions, thus enabling gangliosides to act as possible membrane modulators, e.g., during synaptic transmission. In particular, the differences concerning the influences of temperature and/or Ca2+ on the surface behavior of ganglioside mixtures from the brain of summer- compared with winter-adapted hamsters are correlated with other physiologically relevant data.

Binding of Ca2+ to phosphoinositols, phosphatidylserines and gangliosides

The effect of K+, Mg2+ and serotonin on the interaction between Ca2+ and different phospholipids as well as glycosphingolipids (gangliosides) was studied by equilibrium dialysis using 45Ca as tracer. The highly polar phosphatidylinositol-4,5-bisphosphate (TPI) was found to bind more Ca2+ per lipid molecule than all other lipids tested and Ca2+ could not be released as easily as in the other lipids by K+, Mg2+ and serotonin. Ca2+ is released from all lipid-Ca2+ complexes most effectively by Mg2+, serotonin is less effective but enhances K+ in its capacity to displace Ca2+ from the respective binding sites. A remarkable dissociating influence of serotonin on ganglioside-Ca2+ and phosphatidylserine-Ca2+ complexes is observed. This effect is less pronounced with phosphatidylinositol-Ca2+ complexes under comparable comparable conditions. The possible functional role of phospholipids and gangliosides in vivo is discussed with regard to the specific Ca2+-binding properties of these lipids.

Brain gangliosides and thermal adaptation in vertebrates

Comparative studies on brain gangliosides of about 80 species belonging to all classes of vertebrates reveal: a: distinct increases in concentration with phylogenetical progress of nervous organization, b) decreases in number of single fractions, c) changes in the polarity (degree of sialylation, N- or O-acetylation of sialic acids), d) alterations in the preponderance of one of the three possible pathways of biosynthesis. In addition to these phylogenetical trends, clear correlations between the brain ganglioside composition and the state of thermal adaptation were shown: "The lower the environmental (- body) temperature, the higher the polarity of brain gangliosides". This principle was proved for ectotherms being adapted to habitats with extreme temperatures, during seasonal acclimatization and for homeotherms during early neonatal heterothermic development or during hibernation. Surface pressure-area isotherms of monolayers from single ganglioside fractions (GD1a, GD1b) or differently composed ganglioside mixtures from brains of warm- or cold-adapted hamsters as physico-chemical parameters show significant differences in their variability concerning temperature and/or Ca2+-influences. The results are taken as evidence that variations in the composition of synaptic-bound gangliosides may induce alterations in physico-chemical properties of the neuronal membrane, thus modulating synaptic transmission during temperature adaptation.

Calcium binding to liposomes composed of negatively charged lipid moieties

Ca2+-binding to liposomes was investigated by means of equilibrium dialysis using 45Ca as tracer. Liposomes composed of various lipids (phospholipids: phosphatidylcholine, -serine, -inositol, -inositol-3, 4-bisphosphate; glycosphingolipids: ganglioside mixture from bovine brain; isolated ganglioside species GM1, GD1a, GT1b; cholesterol) in ratios resembling those of natural cell surface membranes were prepared by the detergent dialysis method. Ca2+ was applied in concentrations ranging from 5 microM to 0.15 mM. Pure phosphatidylcholine liposomes showed only poor Ca2+-binding affinities; however, negatively charged liposomes bound Ca2+ in a rather distinct and specific manner. Ca2+-binding to liposomes containing phosphatidylinositol-3,4-bisphosphate in their bilayers was highest. All the liposomes (except those containing phosphatidylinositol-3,4-bisphosphate) showed no simple Ca2+-binding characteristics, that is, continuous Ca2+-binding was interrupted at a concentration of about 50 microM of total Ca2+ in each Ca2+-binding plot, implying that a certain amount (10%-45%) of previously bound Ca2+ was released. These results are discussed with regard to the different possibilities on the molecular basis of physico-chemical processes as well as in relation to their possible functional role at the process of neuronal synaptic transmission.

Gangliosides and synaptic transmission

Several physiologically relevant findings are reported indicating a functional involvement of gangliosides (sialoglycolipids) in the process of neuronal transmission: a) changes of gangliosides in both concentration and composition during developmental maturation of the CNS and with the level of phylogenetic organization; b) metabolic variations of gangliosides in relation to sensory stimulations; c) involvement of gangliosides in the process of thermal adaptations; d) correlations between long-lasting compensatory changes in the composition of brain gangliosides and long-term changes in the bio-electrical activity of the CNS and the learning ability; e) pronounced ability of gangliosides to complex with Ca2+-ions. On the basis of these experimental data an actualized hypothesis on the molecular interaction of brain gangliosides in the process of synaptic transmission is presented. The main feature of this hypothesis is the assumption that when the negatively charged sialic acids of gangliosides form complexes with Ca2+-ions (cluster-formation) these parts of the synaptic membrane become rigid. Dissociation of the Ca2+-ganglioside-complexes induces an "opening" of the presynaptic zone of interactions by means of an increase of membraneous fluidity, together with Ca2+-influx thus enabling fusion of vesicles and release of transmitter.

[The complexing ability of gangliosides for Ca2, I. Influence of mono- and divalent cations and of acetylcholin (author's transl)]

The binding of Ca2 to single ganglioside species (GGtet1NeuAc, GGtet2aNeuAc, GGtet 3aNeuAc), to their free, reducing sialyl-oligosaccharides and to ganglioside mixtures from chicken brain was investigated by means of ion-sensitive electrodes (potentiometry). Unlike the sialyl-oligosaccharides and free N-acetylneuraminic acid, gangliosides were found to possess two different modes of binding for Ca2, depending on the total concentration of Ca2. This was mainly indicated by a release of up to 75% of previously bound Ca2 after raising the total Ca2-concentration above a critical level of about 5--9 X 10(-5)M. Addition of acetylcholin (9mM), Li, K, and Na, respectively, caused a release of Ca2 from ganglioside-Ca2-complexes (0.1mM Ca2, 0.1mM ganglioside-NeuAc) in the sequence: acetylcholin : Li : K : Na = 4 : 3 : 1 : 1 composed on molar basis (9mM).