Showing papers by "University of Göttingen published in 1984"

The role of non-resident cells in Wallerian degeneration.

Abstract: Wallerian degeneration was studied in the phrenic or sciatic nerves of mice following transplantation into Millipore diffusion chambers of 0.22 μm pore size which were implanted in the peritoneal cavity and kept for up to eight weeks. This method positively eliminates the access of nonresident cells to the tissue, at the same time providing proper conditions for tissue survival. Such nerves showed no proliferation of Schwann cells and no evidence for their active role in the removal or digestion of myelin. Schwann cells rejected their sheaths and the latter persisted for weeks, leading either to sheath distension (the sheath becoming wider and thinner) or to collapse (the sheath becoming thicker, collapsing upon the empty axis cylinder). The outer envelope of Schwann cytoplasm separated into pseudopodia rich in microtubules. Sheath rejection led to a slow decay of the myelin in the absence of active phagocytosis. There was profuse fibroblastic proliferation from the epineurium and perineurium, from which cells migrated into the chambers developing fatty change. No evidence was found to link the fatty change in fibroblasts to sheath decay. Diffusion chambers of 5.0 μm pore size were invaded by leukocytes and monocytes. Nerves kept in such chambers showed active phagocytosis of myelin leading to its removal, similar to Wallerian degenerationin situ. Phagocytes were shown to attack selectively the rejected myelin sheaths, distinguishing the latter from the surviving Schwann cells, even though both structures derive from the same cell. The activity of phagocytes in digesting myelin was mediated by a signal which diminished in intensity with time; there was very little active phagocytosis of myelin in nerves that had been predegenerated in 0.22 μm pore chambers. Various modifications of the experiment, including studies with co-cultured peritoneal macrophages or bone marrow, indicate a need for additional activating factors to induce myelin phagocytosis.

Potassium-selective single channels in guard cell protoplasts of Vicia faba

Abstract: In plants, stomata control the gaseous exchange between the intercellular spaces of the leaf and the atmosphere. Fluxes of ions, in particular potassium fluxes, across the membranes of the guard cells produce changes in turgor of the guard cells which in turn result in the opening and closing of the stomatal pore1,2. The molecular mechanisms involved in the uptake or release of ions in guard cells are poorly understood2. Cell-free membrane patches of the plasmalemma, isolated following patch-clamp techniques3–5, allow, for the first time in higher plant cells, the separation of the electrical properties of the plasmalemma from those of the tonoplast. We have applied these techniques to study the properties of single-ion channels in the plasmalemma of guard cell protoplasts of Vicia faba (broad bean). Predominantly a cation-selective channel was observed, which showed a high selectivity for K+, with a permeability ratio / of 11:1 and a single-channel conductance of 37 pS(=37 × 10;−12 Ω−1) in symmetrical 225 mM KC1 solutions. We estimate that this K+ channel contributes significantly to the uptake and release of K+ by guard cells during stomatal movement.

Measurement of Subcellular Metabolite Levels in Leaves by Fractionation of Freeze-Stopped Material in Nonaqueous Media

Abstract: This paper describes a technique for measuring the in vivo metabolite levels in the chloroplast stroma, the cytosol, and the vacuole of spinach (Spinacia oleracea U.S.A. hybrid 424) leaves. Spinach leaves were freeze stopped and the frozen tissue was ground and lyophilized. The dry material was homogenized by sonication in a mixture of carbon tetrachloride and heptane, and fractionated by density gradient centrifugation. Measurements of the activity of marker enzymes in various subcellular compartments show the chloroplastic material mainly appearing in the lightest fractions and the cytosolic material in the middle of the gradient, whereas most of the vacuolar material is found in the heaviest fraction. Using the measured distributions of metabolites and of marker enzymes in each fraction of the gradient, the subcellular distribution of the metabolite can be calculated.As a first application, the new fractionation technique was used to investigate the subcellular contents of malate and sucrose in spinach leaves. The results show striking diurnal changes of sucrose and malate, with both substances primarily located in the vacuolar compartment. About three times more malate is present at the end of the day than at the end of the night. The sucrose content in the vacuole falls from a maximum of 45 millimolars at the end of the day to an almost undetectable value of approximately 1 millimolar at the end of the night.

Respiration and Respiratory Water Loss

Abstract: During the hundreds of million years available for genotypic, periodic, and short-term adaptations in insects the basic need for oxygen uptake and carbon dioxide release in highly changing and highly differing environments has led to a variety of structural and functional adaptations.

Sporomusa, a new genus of gram-negative anaerobic bacteria including Sporomusa sphaeroides spec. nov. and Sporomusa ovata spec. nov.

Abstract: A new genus of strictly anaerobic, gram-negative, banana-shaped bacteria is described. Cells formed spores and were motile by means of up to 15 laterally inserted flagella. Nitrate or sulfate were not used as electron acceptor. Organic substrates that were fermented included N-methyl compounds, such as betaine, N,N-dimethylglycine and sarcosine, primary alcohols, hydroxy fatty acids, and 2,3-butanediol. In addition, molecular hydrogen and carbon dioxide were fermented to acetate. The latter was the characteristic fermentation product in general. During growth on betaine, trimethylamine was formed in addition. The degradation of N,N-dimethylglycine yielded acetate, monomethylamine, and trimethylamine. The presence of cytochrome b and of ubiquinone in the cells was shown. The deoxyribonuleic acid base composition of the strains was between 41.3 and 47.4 mol% guanine plus cytosine. The name Sporomusa is proposed for this new genus. On the basis of the DNA-DNA homology values obtained, the shape of the spores and some other properties, the isolated strains were assigned to two species. Names proposed: Sporomusa sphaeroides and Sporomusa ovata. The type species is S. sphaeroides and the type strains are strain E, DSM 2875 (S. sphaeroides) and strain H1, DSM 2662 (S. ovata).

Crystal-field excitations in CeB 6 studied by Raman and neutron spectroscopy

Abstract: The ${\ensuremath{\Gamma}}_{8}\ensuremath{-}{\ensuremath{\Gamma}}_{7}$ crystalline-electric-field (CEF) transition of ${\mathrm{CeB}}_{6}$ has been identified near 530 K (46 meV, 372 ${\mathrm{cm}}^{\ensuremath{-}1}$) with use of inelastic neutron and polarized Raman scattering. From the anomalous temperature behavior of the transition energy observed in Raman scattering we deduce a ${\ensuremath{\Gamma}}_{8}$ ground state split by 20 ${\mathrm{cm}}^{\ensuremath{-}1}$ (30 K). The novel CEF level scheme yields a consistent and unified interpretation of so far seemingly unrelated thermal, elastic, and magnetic data.

The Homoaldol Reaction, or How to Overcome Problems of Regio‐ and Stereo‐selectivity

Abstract: Even today, there are conspicuous gaps in the register of organic synthetic methods. Thus, numerous types of homoenolate reagents are listed; yet no generally applicable method for the homologue of the aldol addition, viz. the homoaldol addition, is to be found. The methods documented up to 1980 offer only singular solutions, and, moreover, are not stereoselective. The present article gives an overview of the existing possibilities and then describes how the gap can be closed by using a new class of homoenolate reagents: 2-alkenyl esters of N,N-diisopropylcarbamic acid are lithiated and the resulting allyllithium compounds tailored to high regio- and diastereoselectivity in addition reactions to the carbonyl group via metal exchange. Altogether, the homoaldol reactions now offer a general and reliable, highly stereoselective entry to γ-hydroxycarbonyl compounds, whereby the C(β)C(γ) bond is formed. Furthermore, it is demonstrated how problems associated with the application of allyl anions as synthetic reagents can be solved today.

Hyperinsulinaemia in non-cirrhotic haemochromatosis: impaired hepatic insulin degradation?

Abstract: This study investigated early alterations of glucose metabolism in idiopathic haemochromatosis. Circulating concentrations of glucose, insulin, C-peptide, glucagon, and gastric inhibitory polypeptide (GIF) were measured after a 100-g oral glucose load in 10 men with idiopathic haemochromatosis in the non-cirrhotic stage of the disease. All had normal glucose tolerance and normal body weight. Ten matched healthy subjects were studied as controls. Insulin concentrations increased to significantly higher levels in patients with idiopathic haemochromatosis than in the control subjects from 30 to 180min after the glucose load (p 0.05). Concentrations of glucose, glucagon, C-peptide, and GIF were not significantly different at any time (p> 0.05). Thus, patients with idiopathic haemochromatosis show hyperinsulinaemia and hence insulin resistance without impaired glucose tolerance in the non-cirrhotic stage. Since pancreatic insulin secretion (C-peptide), glucagon secretion, and the entero-insulinar axis (GIP) are not impaired in these non-cirrhotic patients with idiopathic haemochromatosis, iron accumulation in the hepatocytes may be responsible for the impaired insulin effect and may cause impaired hepatic insulin extraction.

Approximation by Brownian motion for Gibbs measures and flows under a function

Abstract: Let denote a flow built under a Holder-continuous function l over the base (Σ, μ) where Σ is a topological Markov chain and μ some (ψ-mining) Gibbs measure. For a certain class of functions f with finite 2 + δ-moments it is shown that there exists a Brownian motion B(t) with respect to μ and σ2 > 0 such that μ-a.e.for some 0 < λ < 5δ/588. One can also approximate in the same way by a Brownian motion B*(t) with respect to the probability . From this, the central limit theorem, the weak invariance principle, the law of the iterated logarithm and related probabilistic results follow immediately. In particular, the result of Ratner ([6]) is extended.

Thyroid Hormones, Gonadal and Adrenocortical Steroids and the Function of the Islets of Langerhans

Abstract: Thyroid hormones, gonadal and adrenocortical steroids, are glucoregulatory hormones. Thyroid hormones increase the provision of glucose to meet the enhanced energy demands which they impose. Glucose tolerance is decreased, associated with increased hepatic glucose production, although the glucose-raising effects of thyroid hormones are partially offset by an increased rate of glucose utilization especially in the postabsorptive state. The insulin secretory capacity of the pancreatic B cells is reduced by an excess of thyroid hormones, and the onset of diabetes may be hastened as pancreatic insulin reserves are depleted. Natural estrogens can improve glucose tolerance through a beta-cytotropic effect and enhanced insulin sensitivity. Progesterone may produce similar effects in the absence of estrogens, but progestins appear to antagonize the effects of estrogens. Testosterone exerts only marginal effects on glucose tolerance. Glucocorticoids decrease glucose tolerance by increased hepatic glucose production and impaired peripheral glucose utilization. Glucocorticoids reduce insulin sensitivity and responsiveness in peripheral tissues. However, the diabetogenic influence of glucocorticoid excess is partly compensated by a beta-cytotropic effect and a condition of diabetes develops when the functional reserve of the endocrine pancreas becomes limiting.

Coupling of ATP synthesis and methane formation from methanol and molecular hydrogen in Methanosarcina barkeri

Abstract: The addition of methanol to a cell suspension of Methanosarcina barken resulted in an increase of the intracellular ATP concentration from 1 nmol/mg to 10 nmol/mg protein and in the formation of a proton-motive force Δp of-130 mV. Δp consisted of more than 90% of the membrane potential ΔΨ. These values were similar under N2 and under H2. The addition of the uncoupler tetrachlorosalicylanilide to the above system under N2 led to a drastic decrease of both, the ATP concentration and the Δp and to a stop of methanogenesis. With methanol and H2, however, methane formation continued, although the effect of the uncoupler on the ATP pool and on Δp was a under N2. The proton-translocating ATPase inhibitor N,N-dicyclohexylcarbodiimide caused a rapid exhaustion of the ATP pool and a discontinuation of methane synthesis, whereas Δp was unaffected. Inhibition of methane formation under these conditions could be relieved by the addition of the uncoupler tetrachlorosalicylanilide. These results demonstrate that methane formation according to the equation CH3OH + H2 CH4+ H2O was coupled to ATP synthesis by a chemiosmotic mechanism and was under the control of ΔΨ: Methane formation only proceeded if the ΔΨ generated was used for ATP synthesis or if an uncoupler was present. Under N2, methane formation according to the equation 4CH3OH CO2+ 3 CH4+ 2H2O was abolished by an uncoupler, because one step in the oxidation of methanol to 1CO2 apparently depended on an energized state of the membrane.

Multimodal interneurons in the cricket brain: properties of identified extrinsic mushroom body cells

Abstract: 322 neurons were recorded intracellularly within the central part of the insect brain and 150 of them were stained with Lucifer Yellow or cobaltous sulphide. Responses to mechanical, olfactory, visual and acoustical stimulation were determined and compared between morphologically different cell types in different regions of the central brain. Almost all neurons responded to multimodal stimulation and showed complex responses. It was not possible to divide the cells into different groups using physiological criteria alone.

Control of Photosynthetic Sucrose Synthesis by Fructose 2,6-Bisphosphate I. Coordination of CO2 Fixation and Sucrose Synthesis

Abstract: A mechanism is proposed for a feed-forward control of photosynthetic sucrose synthesis, which allows withdrawal of carbon from the chloroplast for sucrose synthesis to be coordinated with the rate of carbon fixation. (a) Decreasing the rate of photosynthesis of spinach (Spinacia oleracea, U.S. hybrid 424) leaf discs by limiting light intensities or CO2 concentrations leads to a 2-to 4-fold increase in fructose 2,6-bisphosphate. (b) This increase can be accounted for by lower concentrations of metabolites which inhibit the synthesis of fructose 2,6-bisphosphate, such as dihydroxyacetone phosphate and 3-phosphoglycerate. (c) Thus, as photosynthesis decreases, lower levels of dihydroxyacetone phosphate should inhibit the cytosolic fructose bisphosphatase via simultaneously lowering the concentration of the substrate fructose 1,6-bisphosphate, and raising the concentration of the inhibitor fructose 2,6-bisphosphate.

DNA restriction fragment length polymorphisms and heterozygosity in the human genome.

Abstract: A list is presented of published reports of DNA polymorphisms found in the human genome by restriction enzyme analysis. While the list indicates the large number of restriction fragment length polymorphisms (RFLPs) detected to date, the information collated is insufficient to permit an estimate of heterozygosity for the genome as a whole. Data from our laboratory are therefore also presented on RFLPs detected using a random sample of cloned DNA segments. Such an analysis has permitted a first unbiassed estimate of heterozygosity for the human genome. Since this figure is an order of magnitude higher than previous estimates derived from protein data, the majority of polymorphic variation present in the human genome must, by implication, occur in noncoding sequences. In addition it was confirmed that enzymes containing the dinucleotide CpG in their recognition sequences detect more polymorphic variation than those that do not contain a CpG. Also presented are the clinical applications of DNA polymorphisms in the diagnosis of human genetic disease.

Electrocardiographic and coronary arteriographic correlations during acute myocardial infarction.

Abstract: One hundred fifty-two patients underwent cardiac catheterization and coronary arteriography within 6.3 ± 6.0 hours from the onset of acute myocardial infarction (AMI). All had standard 12-lead electrocardiograms recorded within 1 hour of cardiac catheterization. The electrocardiographic abnormalities present were correlated with the infarctrelated artery as determined by coronary arteriography. ST-segment elevation was the most common finding in patients with the left anterior descending (LAD) or right coronary artery as the infarct-related artery. ST-segment depression was the most common abnormality in patients with the left circumflex (LC), artery as the infarct-related artery. A classic pattern of anteroseptal AMI was seen in 93% of all patients with the LAD as the infarct-related artery. A classic pattern of inferior AMI was seen in 53% of patients with right or LC narrowing taken as 1 group. The pattern of true posterior and isolated lateral wall AMI in the absence of classic changes in the inferior leads was highly specific and predictive of LC narrowing. In contrast, the pattern of an inferior wall AMI, in the absence of true posterior or lateral wall changes, was highly specific and predictive of right coronary artery narrowing. Fifty-six percent of patients with LC artery as the infarct-related artery presented with non-classic electrocardiographic abnormalities. The electrocardiographic patterns in patients with subtotal occlusions were similar to those of patients with total occlusions. Thus, the electrocardiogram obtained in the first few hours of AMI is reliable in localizing the LAD as the infarct-related artery. Certain patterns are specific but not sensitive in localizing the right coronary artery as opposed to the LC artery as the infarct-related artery. Presentation with signs and symptoms of AMI and a nonclassic electrocardiogram is suggestive of LC narrowing.

Serotonin-immunoreactive neurons in the brain of the honeybee.

Abstract: The distribution of serotonin-immunoreactive neurons in the brain of the worker honey bee Apis mellifera was studied by means of immunocytochemical staining by using a well-characterized antibody to serotonin (5-HT). About 75 immunoreactive perikarya are grouped into clusters in the optic lobe and in the median and dorsal protocerebrum. Immunoreactive fibers were resolved in all areas of the brain. The optic lobe shows restricted layers of 5-HT-immunoreactive fibers in the lamina and medulla organized perpendicular to the retinotopic elements. Immunoreactive fibers in the lobula represent invasions of protocerebral giant wide-field neurons. The nonglomerular neuropil of the brain exhibits a meshwork of immunoreactive fibres invading glomerular neuropil of the mushroom bodies, central body complex, and antennal lobes. Mushroom body stalks and lobes contain immunoreactive fibers arranged perpendicular to the Kenyon cell fibers and matching subcompartments of these corpora pedunculata areas. The calyces are devoid of immunofluorescence. Serotonin-positive fibres in the central body complex are arranged in its subcompartments. No 5-HT immunoreactivity was found in the pons. Antennal glomeruli contain immunoreactive fibers restricted around the margin of the glomeruli. The selective mapping of 5-HT-immunoreactive neurons complements studies on the distribution of monoamine-containing neurons in the bee brain. Serotonin- and catecholamine-containing neurons often occur together in the same brain areas and subcompartments. The immunohistochemical approach in chemoneuroanatomy gives new evidence for a more complicated architecture of the brain than could be deduced from the classical neuroanatomical studies.

Anesthetic influences on regional hemodynamics in normal and hemorrhaged rats

Abstract: Forty-six male Sprague-Dawley rats were divided in five groups: awake animals and those receiving ketamine, halothane, enflurane, or isoflurane anesthesia. Cannulae were inserted into the left femoral artery and vein and the left ventricle. Inspired concentrations of the volatile anesthetics were adjusted to achieve the minimal alveolar concentration (MAC) of each drug. Ketamine, 125 mg . kg-1, was injected intraperitoneally and then infused at a rate of 1 mg . kg-1 . min-1. All animals breathed spontaneously throughout the experiment (FIO2 = 0.3). Following a 2-h stabilization period, 30% of estimated blood volume was withdrawn gradually over 10 min. Immediately before and 20 min after hemorrhage, cardiac output and regional blood flows were measured by the microsphere method (85Sr, 141Ce-labeled 15-microns microspheres, respectively). Arterial blood samples were analyzed for PO2, PCO2, pH, lactate, and pyruvate at these times also. Prior to hemorrhage, cardiac output (CO) values were similar in awake rats and those receiving ketamine or isoflurane, but CO was reduced moderately by enflurane and to a greater extent by halothane. After hemorrhage, CO was greatest in awake animals and those receiving isoflurane, and awake rats tended to have the greatest organ blood flows. Values of lactate/pyruvate and excess lactate were least in awake animals. Overall results suggested that, in terms of cardiac output and regional blood flows, ketamine approximates the awake state most closely in normovolemic animals, whereas isoflurane anesthesia is most like the awake condition after hemorrhage.

5-Azacytidine-induced undercondensations in human chromosomes

Abstract: The cytosine analogue 5-azacytidine induces very distinct undercondensations in human chromosomes if applied to lymphocyte cultures. The number of induced undercondensations and their chromosomal localization can be varied by the 5-azacytidine dose and the treatment time. “Pulverized” chromosomes or undercondensations in the G-band-positive chromosome regions are produced with high doses and long treatment times. If applied in low doses during the last hours of culture, 5-azacytidine induces specific undercondensations in the heterochromatin of chromosomes 1, 9, 15, 16, and Y. Optimum conditions required for inducing the various types of undercondensation in the chromosomes were determined. Various examples of the use 5-azacytidine in the analysis of chromosome rearrangements involving heterochromatic regions are presented.

Content and localization of FMN, Fe-S clusters and nickel in the NAD-linked hydrogenase of Nocardia opaca 1b.

Abstract: By preparative polyacrylamide gel electrophoresis at pH 8.5, and in the absence of nickel ions, two types of subunit dimers of the NAD-linked hydrogenase from Nocardia opaca 1b were separated and isolated, and their properties were compared with each other as well as with the properties of the native enzyme. The intact hydrogenase contained 14.3 ± 0.4 labile sulphur, 13.6 ± 1.1 iron and 3.8 ± 0.1 nickel atoms and approximately 1 FMN molecule per enzyme molecule. The oxidized hydrogenase showed an absorption spectrum with maxima (shoulders) at 380 nm and 420 nm and an electron spin resonance (ESR) spectrum with a signal at g= 2.01. The midpoint redox potential of the Fe-S cluster giving rise to this signal was + 25 m V. In the reduced state, hydrogenase gave characteristic low-temperature (10 – 20 K) and high-temperature (>40 K) ESR spectra which were interpreted as due to [4Fe–4S] and [2Fe–2S] clusters, respectively. The midpoint redox potentials of these clusters were determined to be -420 mV and -285 mV, respectively. The large hydrogenase dimer, consisting of subunits with relative molecular masses Mr of 64000 and 31000. contained 9.9 ± 0.4 S2− and 9.3 ± 0.5 iron atoms per protein molecule. This dimer contained the FMN molecule, but no nickel. The absorption and ESR spectra of the large dimer were qualitatively similar to the spectra of the whole enzyme. This dimer did not show any hydrogenase activity, but reduced several electron acceptors with NADH as electron donor (diaphorase activity). The small hydrogenase dimer, consisting of subunits with Mr of 56000 and 27000, was demonstrated to have substantially different properties. For iron and labile sulphur average values of 3.9 and 4.3 atoms/dimer molecule have been determined, respectively. The dimer contained, in addition, about 2 atoms of nickel and was free of flavins. In the oxidized state this dimer showed an absorption spectrum with a broad band in the 400-nm region and a characteristic ESR signal at g= 2.01. The reduced form of the dimer was ESR-silent. The small dimer alone was diaphorase-inactive and did not reduce NAD with H2, but it displayed high H2-uptake activities with viologen dyes, methylene blue and FMN, and H2-evolving activity with reduced methyl viologen. Hydrogen-dependent NAD reduction was fully restored by recombining both subunit dimers, although the reconstituted enzyme differed from the original in its activity towards artificial acceptors and the, ESR spectrum in the oxidized state.

Annual rates of deposition of polycyclic aromatic hydrocarbons in different forest ecosystems

Abstract: Using the flux balance of the forest canopy of a beech and a spruce stand annual rates of total deposition — divided into precipitation and interception deposition — were derived for 4 polycyclic aromatic hydrocarbons (PAH). The deposition of PAH is in general higher under spruce because of higher rates of interception deposition as compared to beech. The rate of interception deposition of the various PAH compounds (3.4-Benzopyrene, Indeno (1,2,3-cd)pyrene,1.12 Benzoperylene, Fluoranthene) are significantly different. Substantial amounts of PAH are transferred to the soil by litterfall, which indicates adsorption of PAH on leaf and needle surfaces. The storage of PAH in the soil is equivalent to 34 to 48 yr of the actual deposition for 3.4 Benzopyrene and Indeno (1,2,3-cd)pyrene and is equivalent to 14 to 26yr of actual deposition for the amount of 1.12 Benzoperylene and Fluoranthene in the soil.

Decomposition of 14C-labelled lignin, holocellulose and lignocellulose by mycorrhizal fungi

Abstract: Five different species of known ecto-mycorrhizal fungi: Cenococcum geophilum, Amanita muscaria, Tricholoma aurantium, Rhizopogon luteolus and Rhizopogon roseolus were studied for their ability to metabolize the major components of plant cell walls. All strains were able to decompose 14C-labelled plant lignin, 14C-lignocellulose and 14C-DHP-lignin at a rate which was lower than the one observed for the known white rot fungi Heterobasidion annosum and Sporotrichum pulverulentum. Also 14C-(U)-holocellulose was relatively less degradable for the mycorrhizal fungi than for the white rotters. On the other hand, aromatic monomers like 14C-vanillic acid were decomposed to a much higher extent by two species of mycorrhizal fungi compared to the activity observed for Heterobasidion annosum. The results of the experiments reveal that these stains of mycorrhizal fungi are well able to utilize the major components of plant material and thus can contribute to litter decomposition in the forest floor.

Die Homoaldol-Reaktion oder wie man Probleme der Regio- und Stereoselektivität in den Griff bekommt†‡

Abstract: Auf der Landkarte der Synthesemethoden in der Organischen Chemie finden sich auch heute noch weise Flecken. So weist sie zwar zahlreiche Typen von Homoenolat-Reagentien auf, doch zeigt sie keine allgemein anwendbare Methode fur die zur Aldol-Addition homologe Transformation, die Homoaldol-Addition. Die bis 1980 bekannt gewordenen Verfahren bieten nur singulare Losungen, die zudem nicht stereoselektiv sind. Dieser Beitrag gibt einen Uberblick uber die bestehenden Moglichkeiten und berichtet dann daruber, wie ein weiser Fleck durch eine neue Klasse von Homoenolat-Reagentien ausgefullt wurde: N,N-Diisopropylcarbamidsaure-2-alkenylester werden lithiiert; die resultierenden Allyllithium-Verbindungen werden durch Metallaustausch auf hohe Regio- und Diastereoselektivitat der Carbonyladdition getrimmt. Insgesamt bieten nun Homoaldol-Reaktionen einen allgemeinen und verlaslichen hochstereoselektiven Zugang zu γ-Hydroxycarbonyl-Verbindungen unter Knupfung der C(s)-C(γ)-Bindung. Daruber hinaus wird demonstriert, wie sich Probleme beim Einsatz von Allylanionen als Synthesebausteine heute losen lassen.