PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “PHOSPHOPYRUVIC ACID”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed2006

Evolution of structure and function in the o-succinylbenzoate synthase/N-acylamino acid racemase family of the enolase superfamily.

Understanding how proteins evolve to provide both exquisite specificity and proficient activity is a fundamental problem in biology that has implications for protein function prediction and protein engineering. To study this problem, we analyzed the evolution of structure and function in the o-succinylbenzoate synthase/N-acylamino acid racemase (OSBS/NAAAR) family, part of the mechanistically diverse enolase superfamily. Although all characterized members of the family catalyze the OSBS reaction, this family is extraordinarily divergent, with some members sharing <15% identity. In addition, a member of this family, Amycolatopsis OSBS/NAAAR, is promiscuous, catalyzing both dehydration and racemization. Although the OSBS/NAAAR family appears to have a single evolutionary origin, no sequence or structural motifs unique to this family could be identified; all residues conserved in the family are also found in enolase superfamily members that have different functions. Based on their species distribution, several uncharacterized proteins similar to Amycolatopsis OSBS/NAAAR appear to have been transmitted by lateral gene transfer. Like Amycolatopsis OSBS/NAAAR, these might have additional or alternative functions to OSBS because many are from organisms lacking the pathway in which OSBS is an intermediate. In addition to functional differences, the OSBS/NAAAR family exhibits surprising structural variations, including large differences in orientation between the two domains. These results offer several insights into protein evolution. First, orthologous proteins can exhibit significant structural variation, and specificity can be maintained with little conservation of ligand-contacting residues. Second, the discovery of a set of proteins similar to Amycolatopsis OSBS/NAAAR supports the hypothesis that new protein functions evolve through promiscuous intermediates. Finally, a combination of evolutionary, structural, and sequence analyses identified characteristics that might prime proteins, such as Amycolatopsis OSBS/NAAAR, for the evolution of new activities.

Actinobacteria↗
PubMed2006

Neural stem cells may be uniquely suited for combined gene therapy and cell replacement: Evidence from engraftment of Neurotrophin-3-expressing stem cells in hypoxic-ischemic brain injury.

Previously, we reported that, when clonal neural stem cells (NSCs) were transplanted into brains of postnatal mice subjected to unilateral hypoxic-ischemic (HI) injury (optimally 3-7 days following infarction), donor-derived cells homed preferentially (from even distant locations) to and integrated extensively within the large ischemic areas that spanned the hemisphere. A subpopulation of NSCs and host cells, particularly in the penumbra, "shifted" their differentiation towards neurons and oligodendrocytes, the cell types typically damaged following asphyxia and least likely to regenerate spontaneously and in sufficient quantity in the "post-developmental" CNS. That no neurons and few oligodendrocytes were generated from the NSCs in intact postnatal cortex suggested that novel signals are transiently elaborated following HI to which NSCs might respond. The proportion of "replacement" neurons was approximately 5%. Neurotrophin-3 (NT-3) is known to play a role in inducing neuronal differentiation during development and perhaps following injury. We demonstrated that NSCs express functional TrkC receptors. Furthermore, the donor cells continued to express a foreign reporter transgene robustly within the damaged brain. Therefore, it appeared feasible that neuronal differentiation of exogenous NSCs (as well as endogenous progenitors) might be enhanced if donor NSCs were engineered prior to transplantation to (over)express a bioactive gene such as NT-3. A subclone of NSCs transduced with a retrovirus encoding NT-3 (yielding >90% neurons in vitro) was implanted into unilaterally asphyxiated postnatal day 7 mouse brain (emulating one of the common causes of cerebral palsy). The subclone expressed NT-3 efficiently in vivo. The proportion of NSC-derived neurons increased to approximately 20% in the infarction cavity and >80% in the penumbra. The neurons variously differentiated further into cholinergic, GABAergic, or glutamatergic subtypes, appropriate to the cortex. Donor-derived glia were rare, and astroglial scarring was blunted. NT-3 likely functioned not only on donor cells in an autocrine/paracrine fashion but also on host cells to enhance neuronal differentiation of both. Taken together, these observations suggest (1) the feasibility of taking a fundamental biological response to injury and augmenting it for repair purposes and (2) the potential use of migratory NSCs in some degenerative conditions for simultaneous combined gene therapy and cell replacement during the same procedure in the same recipient using the same cell (a unique property of cells with stem-like attributes).

Acetylcholine↗
PubMed2004

Analogs of 1-phosphonooxy-2,2-dihydroxy-3-oxo-5-(methylthio)pentane, an acyclic intermediate in the methionine salvage pathway: a new preparation and characterization of activity with E1 enolase/phosphatase from Klebsiella oxytoca.

The methionine salvage pathway allows the in vivo recovery of the methylthio moiety of methionine upon the formation of methylthioadenosine (MTA) from S-adenosylmethionine (SAM). The Fe(II)-containing form of acireductone dioxygenase (ARD) catalyzes the penultimate step in the pathway in Klebsiella oxytoca, the oxidative cleavage of the acireductone 1,2-dihydroxy-3-oxo-5-(methylthio)pent-1-ene (2) by dioxygen to give formate and 2-oxo-4-(methylthio)butyrate (3). The Ni(II)-bound form (Ni-ARD) catalyzes an off-pathway shunt, forming 3-(methylthio)propionate (4), carbon monoxide, and formate. Acireductone 2 is formed by the action of another enzyme, E1 enolase/phosphatase, on precursor 1-phosphonooxy-2,2-dihydroxy-3-oxo-5-methylthiopentane (1). Simple syntheses of several analogs of 1 are described, and their activity as substrates for E1 enolase/phosphatase characterized. A new bacterial overexpression system and purification procedure for E1, a member of the haloacid dehalogenase (HAD) superfamily, is described, and further characterization of the enzyme presented.

Amino Acid Sequence↗
PubMed2001

Evolution of enzymatic activities in the enolase superfamily: functional assignment of unknown proteins in Bacillus subtilis and Escherichia coli as L-Ala-D/L-Glu epimerases.

The members of the mechanistically diverse enolase superfamily catalyze different overall reactions by using a common catalytic strategy and structural scaffold. In the muconate lactonizing enzyme (MLE) subgroup of the superfamily, abstraction of a proton adjacent to a carboxylate group initiates reactions, including cycloisomerization (MLE), dehydration [o-succinylbenzoate synthase (OSBS)], and 1,1-proton transfer (catalyzed by an OSBS that also catalyzes a promiscuous N-acylamino acid racemase reaction). The realization that a member of the MLE subgroup could catalyze a 1,1-proton transfer reaction, albeit poorly, led to a search for other enzymes which might catalyze a 1,1-proton transfer as their physiological reaction. YcjG from Escherichia coli and YkfB from Bacillus subtilis, proteins of previously unknown function, were discovered to be L-Ala-D/L-Glu epimerases, although they also catalyze the epimerization of other dipeptides. The values of k(cat)/K(M) for L-Ala-D/L-Glu for both proteins are approximately 10(4) M(-1) s(-1). The genomic context and the substrate specificity of both YcjG and YkfB suggest roles in the metabolism of the murein peptide, of which L-Ala-D-Glu is a component. Homologues possessing L-Ala-D/L-Glu epimerase activity have been identified in at least two other organisms.

Alanine Racemase↗
PubMed2004

Human glutaminyl cyclase and bacterial zinc aminopeptidase share a common fold and active site.

BACKGROUND: Glutaminyl cyclase (QC) forms the pyroglutamyl residue at the amino terminus of numerous secretory peptides and proteins. We previously proposed the mammalian QC has some features in common with zinc aminopeptidases. We now have generated a structural model for human QC based on the aminopeptidase fold (pdb code 1AMP) and mutated the apparent active site residues to assess their role in QC catalysis. RESULTS: The structural model proposed here for human QC, deposited in the protein databank as 1MOI, is supported by a variety of fold prediction programs, by the circular dichroism spectrum, and by the presence of the disulfide. Mutagenesis of the six active site residues present in both 1AMP and QC reveal essential roles for the two histidines (140 and 330, QC numbering) and the two glutamates (201 and 202), while the two aspartates (159 and 248) appear to play no catalytic role. ICP-MS analysis shows less than stoichiometric zinc (0.3:1) in the purified enzyme. CONCLUSIONS: We conclude that human pituitary glutaminyl cyclase and bacterial zinc aminopeptidase share a common fold and active site residues. In contrast to the aminopeptidase, however, QC does not appear to require zinc for enzymatic activity.

Amino Acid Sequence↗
PubMed1995

Morphological and GABA-immunoreactive development of the embryonic chick telencephalon.

The development of neurons utilizing gamma-aminobutyric acid (GABAergic neurons) in prosencephalon and telencephalon from chicken embryonic days 4-14 (E4-E14) was studied by means of immunohistochemistry. Furthermore, routine histology and transmission electron microscopy. respectively, were performed in order to study the morphological development in the designated area. The main finding is that development of GABAergic neurons in the chick telencephalon is rapid; the GABA neurons are appearing in bulk at day 8, being "overexpressed" at days 10-11, decreasing in numbers thereafter and achieving mature morphology on day 14, which is considerably faster than in the rodent. Morphological analysis revealed that the prosencephalon mainly consisted of a thin layer of undifferentiated neuroblasts in the E4 embryo. By E6, the prosencephalon had increased in thickness and occasional cells outside the neuroepithelium showed a more mature morphology with a few cells weakly staining positive for GABA. At E8, the prospective granular and subventricular layers had developed. At E14, the appearance of the telencephalon is approximating that of the adult since both ependymal cells and morphologically mature neurons can be seen.

Animals↗
PubMed1997

[Monoamines, monoamine metabolites, neuron specific enolase and myelin basic protein concentrations in cerebrospinal fluid of resuscitated patients].

Changes of monoamines, monoamine metabolites, neuron specific enolase (NSE) and myelin basic protein (MBP) levels in cerebrospinal fluid were measured in 8 patients for up to 7 days after cardiopulmonary resuscitation. The outcomes were assessed by the Glasgow Outcome Scale. One showed good recovery 3 developed a persistent vegetate state (PVS) and 4 became brain dead (BD). The concentration of NSE increased to a peak about 3 days after resuscitation, then gradually decreased. MBP also showed an increase with time up to 7 days. The time course suggests that neuronal and/or axonal damage progresses for several days after hypoxic or anoxic brain insult. NSE and MBP in the BD group were higher than those in the PVS group, thus CSF levels may be prognostic with regard to hypoxic brain injury. Tyrosine, dopamine, 3-methoxytyramine (3-MT), 3-dihydroxy-4-phenylacetic acid (DOPAC), homovanillic acid (HVA), vanillylmanderic acid (VMA), normetanephrine (NMN), metanephrine (MN), 3-methoxy-4-hydroxyphenylglycol (MHPG), vanillic acid (VA), tryptophan and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were analyzed by HPLC with an electrochemical detector. Concentrations changed within 2 or 3 days after resuscitation, so concentrations at that period may indicate neuronal damage. However, there are some cases with abnormal NSE and MBP levels without abnormal monoamine levels, suggesting that differences in concentrations are not the consequence of the amount of affected neurons, but of the sites of regions.

Adult↗
PubMed1999

Chromogranin A, neuron specific enolase, carcinoembryonic antigen, and hydroxyindole acetic acid evaluation in patients with neuroendocrine tumors.

BACKGROUND: Chromogranin A (CgA), neuron specific enolase (NSE), carcinoembryonic antigen (CEA), and urinary 5-hydroxyindole-3-acetic acid (5-HIAA) are the markers currently used in the diagnosis, prognosis, and follow-up of patients with neuroendocrine tumors (NETs). The authors examined the role of such biomarkers in a large series of patients with NETs. METHODS: One hundred and twenty-seven patients entered the study. Multiple blood and 24-hour urine specimens were assayed for biomarker quantitation. RESULTS: The accuracy of each marker was assessed in patients with (n = 106) and without (n = 21) disease. CgA proved to be the best marker (specificity of 85.7% and sensitivity of 67.9%). Patients with disease had significantly higher CgA and NSE levels compared with disease free patients (P = 0.00003 and P = 0.00240, respectively). NSE and 5-HIAA determination showed a very high specificity (100%) but a rather low sensitivity (32.9% and 35.1%, respectively). CEA was found to have little diagnostic value (sensitivity of 15.4%). CgA was the most sensitive marker for detecting patients with disseminated disease and 5-HIAA displayed the highest sensitivity in identifying syndromic patients. Tumor marker modifications were studied during follow-up. In particular, rises in CgA were associated with progressive disease in 83.3% of cases and stable CgA was associated with stable disease in 53.8% of cases. The relation between CgA modifications and liver lesions during follow-up also was studied; increases in CgA levels were associated with local progression in 100% of cases and stable marker levels were found in 68.7% of the patients with unchanged lesions. CONCLUSIONS: The results of the current study demonstrate that CgA has the highest accuracy and is the most reliable biomarker reflecting the clinical evolution of NETs.

Biomarkers↗
PubMed1997

Uncoupling of cell cycle arrest from the expression of monocytic differentiation markers in HL60 cell variants.

Differentiation generally leads to cell cycle arrest. Human leukemia HL60 cells respond to the presence of 1,25-dihydroxyvitamin D3 (1,25D3) by expressing a number of markers of the monocyte/macrophage phenotype and become arrested predominantly in the G1 phase of the cell cycle. We have recently reported a series (A) of 1,25D3-resistant variants of HL60 cells which proliferate in the presence of 1,25D3 and do not express differentiation markers (Exp. Cell Res. 224, 312, 1996). We now describe another series (B) of such variants, which differ from A series cells grown in similar concentrations of 1,25D3 in that they express the CD14 antigen and nonspecific esterase, characteristic of the monocyte, while continuing to proliferate and they develop hypotetraploid DNA (4C) content at higher concentrations of ambient 1,25D3 than the A series cells. Cells in the B series with 4C DNA content (100B and 200B) also differed from the A series 4C cells by the absence of DNA binding by the full-length Sp1 transcription factor. However, B series cells resembled the A series cells in exhibiting faster growth rates than the parental HL60 cells and showed high levels of vitamin D receptor and retinoid receptor X proteins. These results show that the initial steps in the 1,25D3 signaling pathway are intact in B series resistant cells and lead to the appearance of early markers of monocytic differentiation. However, the progression to subsequent events which comprise terminal differentiation and cell cycle arrest is halted during the adaptation to the presence of 1,25D3 in these cells. Thus, the availability of these variant cells should provide a system for studying the link between differentiation and cell cycle arrest.

Antigens, Differentiation, Myelomonocytic↗
PubMed1987

Histopathological and immunohistochemical changes in neurosurgically resected epileptic foci.

Neurosurgical resection of an epileptic focus was performed in eleven patients suffering from drug resistant focal epilepsy. The clinical result was favourable in nine cases and corresponds to the earlier results. The routinely processed biopsy specimens obtained from the brain resections were stained with haematoxylin-eosin and with specific antisera to GFAP, S-100, NSE, laminin, and fibronectin using the peroxidase-antiperoxidase technique. The main pathological finding was gliosis in eight cases, neuronal degeneration in two cases, and a vascular malformation in one case. The anti-GFAP as a specific marker of astrocytes made the astroglial proliferation clearly visible, demonstrating an astroglial scar in four cases and a moderately to strongly increased amount of astroglial cells in another four cases. Anti-S-100 and anti-fibronectin are not as specific markers. They stained both neurones and glial cells with comparable results to that of anti-GFAP but with a lower specificity and sensitivity. Anti-NSE showed decreased amounts of neurones in most of the heavily gliotic lesions and also stained glial cells in some cases. Anti-laminin stained the pial and vascular basement membranes and revealed an increased vasculature in two cases. From these results, it appears that GFAP immunostaining is a highly demonstrative means for the visualization of astrogliosis in epileptic lesions and may be of help in identifying slight focal changes. An exact demonstration of neuronal loss or other neuronal changes still waits for a more specific marker than NSE. A favourable clinical outcome after neurosurgery seems to be associated with the patients showing a clearly gliotic brain lesion in one temporal lobe.

Adolescent↗
PubMed1986

Calcineurin as a neuronal marker of human brain tumors.

Calcineurin is one of the calmodulin binding proteins and a Ca2+-dependent and calmodulin-stimulated phosphoprotein phosphatase. We used antisera to the calcineurin as a cell-type-specific marker in order to identify neuronal cells in the rat brain and human neoplasms. In normal rat brain slices, basal ganglia were stained macroscopically, and other areas such as cerebral cortex, corpus callosum, cerebellar cortex, granular layer and pyramidal tract of the spinal cord were lightly identified as well. Under the light microscope, it was found that only the neuronal cells were stained, and astrocytes, oligodendrocytes, ependymal cells and vessels were not. Intracellular distribution of the staining showed various patterns and staining intensity of varying degree. Using the PAP method, localization of the calcineurin in formalin-fixed, paraffin-embedded tissues were studied in 65 human intracranial neoplasms, and in 11 human extracranial neoplasms. The neuronal elements of neuroblastoma, ganglioglioma, ganglioneuroma and retinoblastoma were clearly stained. In contrast, glioblastoma, astrocytoma, oligodendroglioma, ependymoma, meningioma, neurinoma, pituitary adenoma, craniopharyngioma, hemangioblastoma, hamartoma, lymphoma and mesenchymal tumor were all negative. Two cases out of 5 medulloblastomas were stained, but others were not. Although positive tumors disclosed various staining patterns and intensities, these results indicated that calcineurin could be a new neuronal marker in human brain tumors.

Animals↗
PubMed1992

Preferential activation of [3H]phorbol-12,13-dibutyrate binding by AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) in neonatal striatal cell cultures.

Activation of excitatory amino acid receptors increased [3H]phorbol-12,13-dibutyrate ([3H]PdBu) binding in four week cultures of striatal cells from postnatal day 7 rat pups (PN7), and in PN7 cells co-cultured the fourth week with striatal cells from postnatal day 1 rat pups. Kainate (KA), trans-1-amino-cyclopentyl-1,3-dicarboxylate (ACPD), and N-methyl-D-aspartate (NMDA) increased [3H]PdBu binding equally in both types of cultures, but alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) increased binding by 3-fold in the co-cultures. Thus, [3H]PdBu binding in these two types of striatal cultures offers a simple model system for studying the regulation of AMPA/KA receptor responses.

Animals↗
PubMed1991

Abnormalities in the spontaneous firing patterns of cultured rat neocortical neurons after chronic exposure to picrotoxin during development in vitro.

We have used the GABA-A antagonist picrotoxin (PTX) to investigate whether chronic disinhibition, leading to intensified neuronal firing, would induce a specific pattern of physiological alterations in cultured rat neocortex cells. Overall mean spontaneous discharge rates were little affected by 1 microM PTX but firing occurred mainly as repetitive high-frequency bursts of action potentials. This "phasic" pattern contrasted with the irregular, quasi-random, firing usually seen in control units. Neurons tested in normal growth medium after prolonged exposure to 1 microM PTX showed weaker interspike interval dependencies (Markov value) than in controls, along with reduced regularity in the occurrence of bursts. Since all physiological changes were opposite in direction to those reported earlier after chronic suppression of bioelectric activity, the results support the hypothesis that endogenous synaptic and/or action potentials are important for the maturation of neocortical networks. Since experimental alterations were found only in spike-train parameters which reflect ontogenetic changes in untreated control cultures, GABAergic inhibition (by preventing neuronal discharges from becoming too intense) presumably serves to constrain the rate of development within optimal limits.

Action Potentials↗
PubMed2004

Cloning and expression of the enolase gene from Desulfovibrio vulgaris (Miyazaki F).

The gene encoding an enolase from Desulfovibrio vulgaris (Miyazaki F) was cloned and overexpressed in Escherichia coli. A 2.1-kb DNA fragment, isolated from D. vulgaris (Miyazaki F) by double digestion with PstI and BamHI, contained an enolase gene (eno) and part of the methylenetetrahydrofolate dehydrogenase gene (folD). The nucleotide sequence of eno indicates that the protein monomer is composed of 434 amino acids. An expression system for eno under control of the T7 promoter was constructed in E. coli. The purified His-tagged enolase formed a homooctamer and was active in the formation of phosphoenolpyruvate (PEP) as well as in the reverse reaction, the formation of D-(+)-2-phosphoglyceric acid (2-PGA). The pH dependence and kinetic properties of the recombinant enolase from the sulfate-reducing bacterium were also studied. The amounts of eno mRNA when the bacterium was grown on glycerol or glucose were compared to that when D. vulgaris was grown on lactate.

Amino Acid Sequence↗
PubMed2006

The role of the dorsolateral tegmentum in the control of male sexual behavior: a reevaluation.

The medial preoptic area/anterior hypothalamus (MPOA/AH) plays a key role in the control of male sexual behavior. Independently of the type, MPOA/AH lesions permanently eliminate male sexual behavior in the rat. The MPOA/AH projects among other structures to the dorsolateral tegmentum (DLT). Bilateral electrolytic lesions of the DLT or the unilateral electrolytic destruction of the MPOA/HA combined with a contralateral electrolytic lesion of the DLT eliminate male sexual behavior. In the present experiment, we evaluated if neurotoxic lesions of the DLT produce the same behavioral deficits as those observed after electrolytic lesions. This would allow us to evaluate if neurons of the DLT or the fibers passing through this area are important in the control of male sexual behavior. To this aim, sexually experience male rats were tested for socio-sexual behavior, partner preference and motor execution in order to determine if the possible behavioral changes could be attributed to alterations in sexual motivation or motor execution. One week after the bilateral DLT lesions the animals were evaluated in the same behavioral tests. The lesions were identified by glial fibrillary acidic protein (GFAP) and neuronal nuclear protein (Neu-N) immunohistochemistry. No significant consistent effects upon sexual behavior were observed in any of the groups, including the group with clear bilateral damage of the DLT. A reduction in the percentage of males displaying ejaculation in the first post-lesion test was observed for all groups injected with quinolinic acid. No effects upon partner preference or motor coordination were observed after the lesion in any of the groups. The lack of effect of DLT neurotoxic lesions upon mating suggests that neurons of this structure are not involved in the control of male sexual behavior.

Analysis of Variance↗
PubMed2005

Massive gliosis of the retina: report of a case investigated by immunohistochemistry and clonality assays.

We report a rare case of massive retinal gliosis that developed in a 32-year-old woman who had been born with bilateral microphthalmia. The patient had recently noticed left ophthalmos and underwent total resection of the affected eyeball. Histologically, the vitreous body had been totally replaced by massively proliferated spindle cells, which had delicate fibrillary cytoplasm without nuclear atypia. Because the attenuated retinal pigment epithelium and intact sclera were preserved at the periphery of the tumor, the tumor was thought to be retinal in origin. Immunohistochemically, the spindle cells were strongly positive for glial fibrillary acidic protein and neuron-specific enolase and partly positive for S-100 protein. These findings led to a diagnosis of massive gliosis of the retina. Clonality analysis of the tumor using a human androgen receptor assay revealed the polyclonal nature of the proliferating spindle cells. This is the first documentation of the polyclonality of this disease.

Adult↗
PubMed2005

Transmissible spongiform encephalopathies: assessment of exposure risk in the histological working environment using GC-MS detection of fatty acids as marker for central nervous tissues.

To elucidate the risk of occupational exposure to the agent of transmissible spongiform encephalopathies (TSE) in the histological working environment, we assessed the principal suitability of three analytical methods for the detection of tissues of the central nervous system (CNT). We tested a neuron-specific enolase (NSE) Western blot, a glial fibrillary acidic protein (GFAP) ELISA and the GC-MS detection of some CNT typical fatty acids (FAs): omega9-tetracosenic acid, omega7-tetracosenic acid, lignoceric acid, and cerebronic acid. Histological sample processing (formalin fixation, dehydration, paraffin embedding) affected both of the immunochemical approaches considerably. The NSE Western blot produced negative results without exception. The results for the GFAP ELISA were better but still far too insensitive. Thus, both methods were judged to be unsuitable in their present form without major analytical adjustment. GC-MS sensitivity remained unaffected by the formalin fixation process. Sensitivity was reduced in the course of the final dehydration step using xylene in the histological sample processing. However, this reduction was found to be rather moderate (range 42-59%) when compared to the immunochemical methods. Overall, we judged GC-MS to be a promising analytical approach for the assessment of a potential TSE exposure risk via airborne CNT particles in the histological working environment. All the FAs we tested showed very low but detectable baseline contents. Thus, cut-off values must be used in the present GC-MS approach. The most suitable FA turned out to be omega9-tetracosenic acid due to the greatest difference between its content in histological CNT samples and the respective cut-off value (689:1). Preliminary results by GC-MS monitoring of CNT via omega9-tetracosenic acid (and other FAs) on filters of routinely used vacuum cleaners and on filters after air sampling indicate that the airborne CNT/TSE exposure risk in the histological laboratory is minor if existing at all. However, further in depth studies will have to validate our preliminary findings and assess these results in the light of possible future data on human oral and/or pulmonary TSE susceptibility.

Animals↗