PACAP deficiency as a model of aging.

Dysregulation of neuropeptides may play an important role in aging-induced impairments. In the long list of neuropeptides, pituitary adenylate cyclase-activating polypeptide (PACAP) represents a highly effective cytoprotective peptide that provides an endogenous control against a variety of tissue-damaging stimuli. PACAP has neuro- and general cytoprotective effects due to anti-apoptotic, anti-inflammatory, and antioxidant actions. As PACAP is also a part of the endogenous protective machinery, it can be hypothesized that the decreased protective effects in lack of endogenous PACAP would accelerate age-related degeneration and PACAP knockout mice would display age-related degenerative signs earlier. Recent results support this hypothesis showing that PACAP deficiency mimics aspects of age-related pathophysiological changes including increased neuronal vulnerability and systemic degeneration accompanied by increased apoptosis, oxidative stress, and inflammation. Decrease in PACAP expression has been shown in different species from invertebrates to humans. PACAP-deficient mice display numerous pathological alterations mimicking early aging, such as retinal changes, corneal keratinization and blurring, and systemic amyloidosis. In the present review, we summarize these findings and propose that PACAP deficiency could be a good model of premature aging.

Disturbed spermatogenic signaling in pituitary adenylate cyclase activating polypeptide-deficient mice.

PACAP is a neuropeptide with diverse functions in various organs, including reproductive system. It is present in the testis in high concentrations, and in addition to the stage-specific expression within the seminiferous tubules, PACAP affects spermatogenesis and the functions of Leydig and Sertoli cells. Mice lacking endogenous PACAP show reduced fertility, but the possibility of abnormalities in spermatogenic signaling has not yet been investigated. Therefore, we performed a detailed morphological analysis of spermatozoa, sperm motility and investigated signaling pathways that play a role during spermatogenesis in knockout mice. No significant alterations were found in testicular morphology or motility of sperm in homozygous and heterozygous PACAP-deficient mice in spite of the moderately increased number of severely damaged sperms. However, we found robust changes in mRNA and/or protein expression of several factors that play an important role in spermatogenesis. Protein kinase A expression was markedly reduced, while downstream phospho-ERK and p38 were elevated in knockout animals. Expression of major transcription factors, such as Sox9 and phospho-Sox9, was decreased, while that of Sox10, as a redundant factor, was increased in PACAP-deficient mice. The reduced phospho-Sox9 expression was partly due to increased expression and activity of phosphatase PP2A in knockout mice. Targets of Sox transcription factors, such as collagen type IV, were reduced in knockout mice. In summary, our results show that lack of PACAP leads to disturbed signaling in spermatogenesis, which could be a factor responsible for reduced fertility in PACAP knockout mice, and further support the role of PACAP in reproduction.

Changes of expression of endogenous sugar receptors by polymorphonuclear leukocytes after prolonged anaesthesia and surgery.

Anaesthesia and surgery are known to depress granulocyte function in the early postoperative period, leading to deterioration of the immune defence against infection. Carbohydrate-lectin interactions may play an important role in the activities of phagocytic cells in that they facilitate initial host defence in the event of microbial antigenic challenge. A panel of biotinylated (neo)glycoproteins (chemically glycosilated carrier proteins) was used to detect endogenous carbohydrate-binding receptors /lectins/, on peripheral blood polymorphonuclear leukocytes of patients undergoing prolonged anaesthesia for replantation surgery. Four hours after induction of anaesthesia, a progressive decline of expression of endogenous sugar receptors on granulocytes was detected using the labelled (neo)glycoproteins lactose-BSA, N-acetyl-D-glucosamine-BSA, D-mannose-BSA, sialic-acid-BSA and D-xylose-BSA. Concomitant changes in peripheral white blood cell counts and the lack of depression in the absence of general anaesthetic agents suggested the existence of a possible relationship between reduced expression of (neo)glycoprotein receptors to impaired granulocyte function and anaesthetic-induced immunodepression.

Variations in lectin localization in different parts of the bovine heart.

In order to study the distribution of endogenous sugar-binding proteins (lectins) in various areas of the adult bovine heart, we used a battery of biotinylated neoglycoproteins. These tools expose carrier-immobilized carbohydrate moieties as ligands for receptor detection. Characteristic staining patterns depending on the type of carbohydrate ligand were observed in all constituents examined. Comparison to data obtained for lectin distribution in the respective areas of the human heart indicate that the localization of certain types of endogenous sugar receptors can exhibit species-dependent variations.

Heparin binding lectin of human placenta as a tool for histochemical ligand localization and isolation.

Biotinylated heparin has been used to detect the presence of specific binding sites in sections of human placenta, which has prompted demonstration of expression of lectin activity for this proteoglycan. Purification of this lectin from full-term placenta facilitates the synthesis of its biotinylated derivative, using biotin-amidocaproyl hydrazide, without affecting its activity. It also enables immunization to obtain antibodies. The labeled lectin is shown to bind specifically to nuclear and cytoplasmic locations in various cell types of human placenta, nuclear expression of lectin binding sites being more pronounced at the full-term stage than after 8 weeks of development. The structurally related histone H2B exhibits obvious differences in its binding pattern. The presence of ligands accessible to the lectin whose binding activity can be inhibited by addition of an excess of heparin correlates in most instances with the level of lectin expression detected immunohistochemically. Biochemical information on the nature of the glycohistochemically inferred lectin-specific ligand(s) is obtained by affinity chromatography on resin-immobilized lectin. It leads to isolation of a proteoglycan with similar electrophoretic mobility in agarose-polyacrylamide gel electrophoresis relative to the independently purified heparan sulfate-containing fibronectin binding proteoglycan from human placenta. Both fractions inhibit binding of heparin to the lectin and contain immunologically detected co-purified lectin, emphasizing their ligand properties. Application of labeled tissue lectins in conjunction with lectin-specific antibodies is proposed to obtain valuable insights into the expression of the receptor as well as the ligand part of protein-carbohydrate recognition.

Triosephosphate isomerase deficiency: haemolytic anaemia, myopathy with altered mitochondria and mental retardation due to a new variant with accelerated enzyme catabolism and diminished specific activity.

A new triosephosphate isomerase (TPI) variant is described in an 8-year-old Turkish girl suffering from chronic haemolytic anaemia, myopathy and developmental retardation since early infancy. The enzyme activity profile revealed a generalized deficiency in erythrocytes, granulocytes, mononuclear blood cells, skeletal muscle tissue and cerebrospinal fluid. The concentration of enzyme substrate dihydroxyacetone phosphate was distinctly elevated. Biochemical examination showed accelerated enzyme deamidation, the first step in the normal catabolism of TPI during aging of the erythrocyte. The specific activity of the variant TPI, determined by antibody titration, was reduced to 61% of normal. Its heat stability was markedly decreased. Muscle biopsy and neuropsychological testing further clarified the pathogenesis of the disorder. A prevalent alteration of mitochondria similar to that seen in mitochondrial myopathy and an elevated amount of intracellular glycogen were found. The patient's retarded intellectual development was mainly due to impaired visual perception and sensory-motor co-ordination in addition to a lack of syllogistic reasoning. The findings indicate that the low TPI activity leads to a metabolic block of the glycolytic pathway and hence to a generalized impairment of cellular energy supply.

Familial myopathy with elevated serum angiotensin-converting enzyme, creatine kinase and lactate dehydrogenase isoenzyme 5.

A family is reported in which two members presented with proximal myopathy associated with high serum levels of angiotensin-converting enzyme (SACE), creatine kinase (CK), and lactate dehydrogenase isoenzyme 5. Examination of three relatives revealed elevated SACE levels in all of them, but no myopathy. No evidence of sarcoidosis, the most common disease associated with high SACE levels, could be found. Muscle biopsies of the two affected men revealed myopathic features without granuloma formation. Extensive biochemical, metabolic, immunological, and microbiological studies were all non-contributory. Corticosteroid and, in one patient, azathioprine treatment resulted in an improvement of muscle weakness and in a decrease of SACE as well as CK levels.

Localization of endogenous sugar-binding proteins (lectins) in tumors of the central and peripheral nervous system by biotinylated neoglycoproteins.

The carbohydrate part of cellular glycoconjugates - glycoproteins, glycoproteins, glycolipids and proteoglycans - and specific endogenous sugar receptors, i.e. lectins, can establish a system of biological recognition based on protein-sugar interactions on the cellular and subcellular levels. To gain insight into the role of proteins in this type of interaction, sections of surgically removed tumor specimens of central and peripheral nervous tissue were analyzed glycohistochemically, using biotinylated neoglycoproteins with different sugar part. A specific staining with this type of probe, exposing different sugar moieties as ligands, indicated the presence of sugar receptors in different types of meningiomas, glioblastomas, gangliocytomas, anaplastic and well-differentiated oligodendrogliomas and ependymomas as well as in neurinomas and neurofibromas of peripheral nerves. In comparison to the well-differentiated ependymomas, the anaplastic form of this tumor exhibited a generally higher capacity to specifically bind the neoglycoproteins, containing alpha- or beta-glucosides. Inverse intensity of the glycohistochemical reaction was observed with galactose-6-phosphate-, galactose-beta(1.3)-N-acetylglucosamine-N-acetyl-D-glucosamine- and mannose- (BSA- biotin), respectively, when anaplastic and differentiated oligodendrogliomas were compared with each other. Tumorously dedifferentiated neurons, i.e. in gangliocytomas, showed a changed spectrum of endogenous sugar receptors in comparison to neurons of normal cerebral cortex. Qualitative and quantitative differences of sugar receptors were observed among the distinct subtypes of meningiomas. Receptors for N-acetyl-D-galactosamine were present only in the anaplastic form, while glucuronic acid-specific receptors were only found in the meningotheliomatous meningiomas. Distinctions in binding spectrum of neoglycoproteins suggest the presence of a possible additional subtype of meningiomas, called submalignant meningioma. Analysis of the spectrum of endogenous sugar receptors can serve to distinguish between different cell populations composing a given tumor, as shown in neurofibromas in the cases of Schwann cells and fibroblastoid cells stained with N-acetyl-D-glucosamine-(BSA-biotin). The analysis of expression of endogenous sugar receptors, as part of an intercellular information code system, may represent a further way of studying the mechanism of tumor differentiation and propagation.

[Histochemical identification of endogenous lectins using labelled neoglycoproteins in human head-and-neck squamous cell carcinoma]. / Histochemische Identifizierung endogener Lektine durch markierte Neoglykoproteine bei humanen Kopf-Hals-Plattenepithelkarzinomen.

According to the "Population-based cancer register" of the Federal Republic of Germany only malignant neoplasms of the buccal cavity, the pharynx and larynx as well as cancers of the respiratory tract show an increasing rate of incidence and mortality. The molecular mechanisms and etiological factors causing this phenomenon are still little understood despite intensive research work. Recognition between receptors on a cellular level may be mediated by specific amino acid sequences on the level of protein-protein recognition. Additionally, the interactions between cell sugars and the corresponding protein receptor may play a decisive role in development, regeneration and organisation of cells and tissue. The high specificity of the binding of biotinylated neoglycoproteins in tissue sections enables to detect glycohistochemically binding sites for the carbohydrate ligands of the glycosylated carrier protein. The evidence of lectins in squamous cell cancer of the oral cavity, oropharynx, larynx, and hypopharynx has not been established so far. Squamous cell cancer tissue samples of twelve patients with different tumour locations were investigated by incubation of sections of paraffin-embedded samples and application of an avidin-biotin-peroxidase complex for visualisation with synthetic biotinylated neoglycoproteins. Altogether 168 stained sections were evaluated including controls. Pronounced cytoplasmatic staining was seen with the following neoglycoproteins: sialic acid-bovine serum albumin (BSA), glucuronic acid-BSA, N-acetylglucosamine (glcNAc)-BSA, N-acetylgalactosamine (beta-galNAc)-BSA, lactose-BSA, maltose-BSA, mannose-BSA, mannose-6-phosphate-BSA. No corresponding lectins seems to exist for the following investigated sugars: fucoidan, heparin, and the alpha-anomeric form of N-acetylgalactosamine, because no specific staining was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme histochemistry of endomyocardial biopsies in idiopathic dilated cardiomyopathy.

The etiology of idiopathic dilated cardiomyopathy (DCM) is yet unknown; this study aimed at further differentiation of the disease by means of enzyme histochemistry. Endomyocardial biopsies from the left ventricle of 40 DCM patients and 5 control specimens had enzymes examined histochemically and semiquantitatively and analyzed according to staining intensities of nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR), succinate dehydrogenase, cytochrome c oxidase, lactate dehydrogenase and acid phosphatase (aPh). In DCM, the NADH-TR activity was elevated as compared to controls, indicating impaired mitochondrial oxidative phosphorylation. However, a concrete relation of enzyme histochemical intensity to anamnestic, hemodynamic or histomorphometric data could not be determined, except for the fact that the intensity of the lysosomal enzyme aPh was elevated in DCM patients with a relatively high left ventricular ejection fraction. The results demonstrate an interindependence of structural, hemodynamic and historical parameters as well as enzyme concentrations in DCM. Thus, a pathological change in the enzyme concentrations tested here cannot be responsible for the functional myocardial impairment in DCM.

Lectin localization in human nerve by biochemically defined lectin-binding glycoproteins, neoglycoprotein and lectin-specific antibody.

Molecular recognition can be mediated by protein (lectin)-carbohydrate interaction, explaining the interest in this topic. Plant lectins and, more recently, chemically glycosylated neoglycoproteins principally allow to map the occurrence of components of this putative recognition system. Labelled endogenous lectins and the lectin-binding ligands can add to the panel of glycohistochemical tools. They may be helpful to derive physiologically valid conclusions in this field for mammalian tissues. Consequently, experiments were prompted to employ the abundant beta-galactoside-specific lectin of human nerves in affinity chromatography and in histochemistry to purify and to localize its specific glycoprotein ligands. In comparison to the beta-galactoside-specific plant lectins from Ricinus communis and Erythrina cristagalli, notable similarities were especially detectable in the respective profiles of the mammalian and the Erythrina lectin. They appear to account for rather indistinguishable staining patterns in fixed tissue sections. Inhibitory controls within affinity chromatography, within solid-phase assays for each fraction of lectin-binding glycoproteins and within histochemistry as well as the demonstration of crossreactivity of the three fractions of lectin-binding glycoproteins with the biotinylated Erythrina lectin in blotting ascertained the specificity of the lectin-glycoprotein interaction. In addition to monitoring the accessible cellular ligand part by the endogenous lectin as probe, the comparison of immunohistochemical and glycohistochemical detection of the lectin in serial sections proved these methods for receptor analysis to be rather equally effective. The observation that the biotinylated lectin-binding glycoproteins are also appropriate ligands in glycohistochemical analysis warrants emphasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Spatial differences of endogenous lectin expression within the cellular organization of the human heart: a glycohistochemical, immunohistochemical, and glycobiochemical study.

Protein-carbohydrate recognition may be involved in an array of molecular interactions on the cellular and subcellular levels. To gain insight into the role of proteins in this type of interaction, surgically removed specimens of human endomyocardial tissue were processed for histochemical and biochemical analysis. The inherent capacity of these sections to bind individual sugar moieties, which are constituents of the carbohydrate part of cellular glycoconjugates, was assessed using a panel of biotinylated neoglycoproteins according to a standardized procedure. Together with appropriate controls, it primarily allowed localization of endogenous lectins. Differences in lectin expression were observed between layers of endocardial tissue, myocardial cell constituents, connective-tissue elements, and vascular structures. The endocardium proved to be positive with beta-galactoside-bearing probes; with neoglycoproteins carrying beta-xylosides, alpha-fucosides, and galactose-6-phosphate moieties; and with probes containing a carboxyl group within the carbohydrate structure, namely sialic acid and glucuronic acid. In contrast, only fucose-and maltose-specific receptors were apparent in the elastic layers of the endocardium. Aside from ascertaining the specificity of the protein-carbohydrate interaction by controls, i.e., lack of binding of the probe in the presence of the unlabelled neoglycoprotein and lack of binding of the labelled sugar-free carrier protein, respective sugar receptors were isolated from heart extracts by using histochemically effective carbohydrates as immobilized affinity ligand. Moreover, affinity chromatography using immobilized lactose as affinity ligand as well as the use of polyclonal antibodies against the predominant beta-galactoside-specific lectin of heart demonstrated that the lactose-specific neoglycoprotein binding was due to this lectin. Remarkably, the labelled endogenous lectin, preferred to plant lectins for detecting ligands of the endogenous lectin, localized ligands in tissue parts where the lectin itself was detected glycohistochemically as well as immunohistologically. This demonstration of receptor-ligand presence in the same system is a further step toward functional assignment of the recorded protein-carbohydrate interaction. Overall, the observed patterns of lectin expression may serve as a guideline to elucidate the precise physiological relevance of lectins and to analyze pathological conditions comparatively.

Reduced expression of mannose-specific receptors on murine peripheral blood polymorphonuclear leukocytes following prolonged anaesthesia with different inhalation agents.

Inhalation anaesthetic agents are known to depress phagocytic functions such as mobilization, attachment, chemotactic motility, engulfment and intracellular killing. Mannose-specific sugar receptors on the surface of leukocytes are involved in a series of phagocytosis-related activities. To investigate the effect of anaesthesia on the expression of this type of sugar receptor, mice were anaesthetized with halothane, enflurane and isoflurane. The presence of mannose-binding receptors on peripheral blood polymorphonuclear leukocytes was examined glycocytochemically using the biotinylated neoglycoprotein mannosylated bovine serum albumin. Prolonged administration of inhalation anaesthetic agents, especially halothane, markedly depressed expression of mannose-specific receptors. This reduction may possibly contribute to postoperative immunodepression, resulting from the impaired cellular interaction which is involved in the phagocytic function of granulocytes.

Regional differences in the distribution of endogenous receptors for carbohydrate constituents of cellular glycoconjugates, especially lectins, in cortex, hippocampus, basal ganglia and thalamus of adult human brain.

Ten different types of labelled neoglycoproteins, exposing glycohistochemically pivotal carbohydrate moieties that mostly are constituents of naturally occurring glycoconjugates with an aromatic spacer, were synthesized. The panel was applied to fixed, paraffin-embedded sections of different cortical regions and white matter, of hippocampal gyrus, basal ganglia, thalamus nuclei and adjacent areas of adult human brain to comprehensively map the presence of respective binding sites in these parts. Compliance with accepted criteria for specificity of binding was routinely ascertained. Overall, not a uniform binding pattern, but a distinct distribution with regional differences on the level of specific cytoplasmic and nuclear staining in nerve cells was determined, fiber structures being generally labelled with medium or strong intensity. For example, among the neurons localized in the five cortical laminae the binding of N-acetyl-D-galactosamine varied from strong to undetectable. Biochemical analysis, employing carbohydrate residues as affinity ligands in chromatography, proved that the neuroanatomically different regions exhibited a pattern of receptors with notable similarities. These results on endogenous binding sites for glycoconjugates, especially lectins, are complementary to assessment of localization of cellular glycoconjugates by plant lectins and carbohydrate-specific monoclonal antibodies. They are thus a further obligatory step to substantiate the physiological roles of recognitive protein-carbohydrate interactions in the central nervous system.

Myopathy with altered mitochondria due to a triosephosphate isomerase (TPI) deficiency.

Morphological changes are shown in the muscle biopsy specimens of an 8-year-old girl who suffered from a triosephosphate isomerase (TPI) deficiency, resulting in a chronic, nonspherocytic, hemolytic anemia, mental retardation and neuromuscular impairment. The newly introduced enzyme histochemical reaction for TPI demonstrated a total lack of histochemically detectable enzyme activity, whereas biochemical analysis of muscle tissue revealed less than 10% of the normal enzyme activity. Electron microscopy showed a degenerative myopathy with an increase in the amount of intracellular glycogen. Additionally, mitochondrial changes within the muscle fibers were observed to be similar to those in mitochondrial myopathies. The disturbed balance between glycerin-aldehyde phosphate and dihydroxyacetone phosphate, due to the deficiency of the TPI enzyme, is interpreted as the biochemical background of an impaired electron transport across the mitochondrial membrane, resulting in the coexistence of an impaired glycolytic pathway and an impaired mitochondrial metabolism of muscle cells.

Detection and mapping of endogenous receptors for carrier-immobilized constituents of glycoconjugates (lectins) by labelled (neo)glycoproteins and by affinity chromatography in human adult mesencephalon, pons, medulla oblongata and cerebellum.

Different carrier-immobilized carbohydrate moieties were employed as tools to detect respective binding sites glycohistochemically and glycobiochemically. Besides ascertaining their presence the pattern of endogenous sugar receptors (lectins) in different regions of the human central nervous system was mapped to reveal any non-uniform expression. A strong and specific staining with biotinylated neoglycoproteins, exposing different sugar moieties as ligands, indicated the presence of sugar receptors in the nuclei, neuronal pathways and accessory structures such as ependyma cells, plexus chorioideus, intra- and extracerebral vessels and leptomeninges localized in the mesencephalon, in the pons, in the medulla oblongata and in the cerebellum. Significant differences were seen for various neuroanatomical regions like nerve cells in the basal and central regions of the nuclei pontis in the glycohistochemically detected level of expression of endogenous sugar receptors (lectins). The used approach with carbohydrate constituents of cellular glycoconjugates as ligands in search of specific receptors complemented studies on the localization of glycoconjugates with sugar-specific tools like plant lectins. Exemplary glycobiochemical investigations on the medulla oblongata and cerebellum were performed to investigate the molecular nature of sugar receptors detected glycohistochemically. Despite notable overall similarities, carbohydrate-binding proteins of differing molecular weight can be isolated from these two regions of the central nervous system, namely in the case of receptors with specificity to beta-galactoside termini, to N-acetyl-D-galactosamine and N-acetyl-D-glucosamine and to D-xylose. These combined glycohistochemical and glycobiochemical results serve as a guideline for exploring the physiological relevance of the detected regional differences.

Determination of capillary perfusion pattern in rat brain by timed plasma labeling.

The pattern of capillary perfusion was studied in the brain of anesthetized rats. Two plasma labels were used to demonstrate the density of capillaries perfused during a 10-min period [fluorescein isothiocyanate (FITC) globulin], as well as during a 10-, 3-, or 1-s period [lissamine-rhodamine B 200 (RB200) globulin, infused into the left heart chamber], respectively. A special biopsy cutting-freezing system was used to withdraw brain tissue via a cranial window for histological analysis of dye distribution at the end of the infusion period. Complete labeling of all capillaries was already found after 10 s of dye circulation. However, intra-arterial dye infusion for 3 and 1 s led to reduced filling of capillaries: cortex 86.6 +/- 5.2 and 6.8 +/- 1.8%, hippocampus 95.0 +/- 1.6 and 9.9 +/- 2.1%, and thalamus 97.9 +/- 1.0 and 11.7 +/- 1.8%, respectively. The period of 1 s was found to be the circulation time from left heart chamber to brain capillaries. It can thus be concluded that in the studied brain areas greater than 85% of capillaries are reached by a plasma flow within 2 s and that the remaining small fraction completely fills within 10 s.

Morphometric comparison between human and rat abducens and oculomotor nerves.

A morphologic and morphometric comparison between normal human and rat extraocular muscle nerves was performed using a computer-assisted method to obtain scatter diagrams of relative sheath thickness (g ratio = quotient axon diameter/fiber diameter). Human and rat extraocular muscle nerves (nervus abducens and ramus medialis n. oculomotorii) were excised immediately before the nerve branching at the entering point into the muscle. There was no difference in the absolute number of myelinated fibers between the oculomotor and abducens nerves in both species. The distribution of myelinated fibers was classified according to their g ratios into a two-stage density cluster analysis. Two main populations of nerve fibers for human oculomotor and rat oculomotor and abducens nerves and three main populations for human abducens nerve were differentiated morphometrically and mathematically, differing in their relative sheath thicknesses. There are distinct differences between scatter diagrams of human and rat extraocular muscle nerves, in correlation with the basically different oculomotor functions of these two species. The morphometric differences between human and rat extraocular muscle nerves suggest a difference in the myelination process and the presence of functionally different nerve fibers, strongly indicated by the populations and subpopulations of myelinating nerve fibers peculiar to extraocular muscle. The existence of more than two different types of myelinated fibers in the human nerves implies that the traditional classification based on fiber caliber must be reviewed and a comparison of different classes of nerve and muscle fibers should be performed.

Cervicogenic, hemicranial attacks associated with vascular irritation or compression of the cervical nerve root C2. Clinical manifestations and morphological findings.

Sixteen patients suffering from hemicranial attacks are reported. After many years of unsuccessful conservative treatment (mean = 12.4 years), the patients were treated surgically with good results. The radiological or electrophysiological examinations were non-specific or negative. Only vasoactive tests (provoking or relieving pain) or local anesthesia proved helpful in diagnosing and localizing the origin of pain. Intraoperatively, hemicranial attacks were found to be caused by vascular irritation or compression of the cervical nerve root C2. After decompression (n = 6) or dissection (n = 10) of the nerve root and the ganglion, 12 patients were relieved of their pain, 2 had improved relatively, 1 showed only a slight improvement, and in 1 patient no cause was found and no improvement was achieved. Two patients suffered recurrence of pain postoperatively; one had no further complaints after root extirpation following percutaneous thermorhizotomy. Electron microscopic examination of the nerve root and its ganglion revealed focal morphological changes, including proliferation of connective tissue in the endoneurium and the ganglion itself, the formation of onion-bulb-like structures around single axons, discrete signs of myelin damage and axonal degeneration. These morphological changes are possibly the result of a chronic vascular compression.