Publications by authors named "Antonis Vakis"

13 Publications

  • Page 1 of 1

Pathogenesis of idiopathic Normal Pressure Hydrocephalus: A review of knowledge.

J Clin Neurosci 2019 Mar 6;61:10-13. Epub 2018 Nov 6.

Department of Neurosurgery, University of Crete, Panepistimiou, 71500 Iraklio, Greece.

Idiopathic Normal Pressure Hydrocephalus (iNPH) is a frequent neuropsychiatric entity. Clinically it is characterised by Hakim's triad: Dementia, gait disturbance and urinary incontinence. While its symptomatology is typical, the etiology and thereby physiopathology of iNPH still remain enigmatic. This review summarizes and synthesizes different etiologic conceptions and physiopathologic aspects of iNPH. A research of literature via the PubMed/MEDLINE and the Cochrane database was conducted. Only English language articles clearly outlining a reasonable concept of physiopathology were included. Most authors advocate that iNPH is a result of chronically altered cerebrospinal fluid (CSF) dynamics, i.e. deranged CSF production, kinetics and reabsorption. In addition, there are vascular, metabolo-neurodegenerative and hereditary factors. Neuroinflammation does not seem to play a significant role in the etiology of iNPH. All in all, iNPH seems to combine several pathogenetic factors leading to a self-reinforcing vicious circle. The majority of studies hint at CSF disturbances on grounds of altered hemodynamics.
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http://dx.doi.org/10.1016/j.jocn.2018.10.147DOI Listing
March 2019

CYP polymorphisms and pathological conditions related to chronic exposure to organochlorine pesticides.

Toxicol Rep 2017 26;4:335-341. Epub 2017 May 26.

Research Group of Clinical Pharmacology and Pharmacogenomics, Faculty of Pharmacy, School of Health Sciences, National and Kapodistrian University of Athens, Greece.

The association between genetic variations in the cytochrome P450 (CYP) family genes and pathological conditions related to long-term exposure to organochlorine compounds (OCs) deserves further elucidation. OCs are persistent organic pollutants with bioaccumulative and lipophilic characteristics. They can act as endocrine disruptors and perturb cellular mechanisms. Prolonged exposure to OCs has been associated with different pathological manifestations. CYP genes are responsible for transcribing enzymes essential in xenobiotic metabolism. Therefore, polymorphisms in these genetic sequences a. alter the metabolic pathways, b. induce false cellular responses, and c. may provoke pathological conditions. The main aim of this review is to define the interaction between parameters a, b and c at a mechanistic/molecular level, with references in clinical cases.
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http://dx.doi.org/10.1016/j.toxrep.2017.05.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5615117PMC
May 2017

Molecular profile of major growth factors in lumbar intervertebral disc herniation: Correlation with patient clinical and epidemiological characteristics.

Mol Med Rep 2017 Apr 20;15(4):2195-2203. Epub 2017 Feb 20.

Laboratory of Virology, Medical School, University of Crete, Heraklion 71003, Greece.

The involvement of growth factors (GFs) in the pathogenesis of lumbar intervertebral disc (ID) herniation and the spontaneous resorption of herniated ID fragments remains only partially elucidated. A simultaneous assessment of the transcript levels of numerous GFs and their association with clinical and epidemiological profiles of human ID herniation would provide valuable insight into the biology and clinical course of the disease. In the present study, we examined simultaneously the transcript levels of vascular endothelial growth factor (VEGF), transforming growth factor β1 (TGF‑β1), basic fibroblast growth factor 2 (bFGF2), platelet derived growth factor (PDGF) isoforms and receptors, epidermal growth factor (EGF) and insulin growth factor‑1 (IGF‑1) in herniated and control ID specimens and investigated their correlation with the clinicopathological profiles of patients suffering from symptomatic lumbar ID herniation. GF mRNA expression levels were determined by RT-qPCR in 63 surgical specimens from lumbar herniated discs and 10 control ID specimens. Multiple positive correlations were observed between the transcript levels of the GFs examined in the ID herniation group. VEGF mRNA expression was significantly increased in the protruding compared with the extruded discs. Intense and acute pain significantly upregulated the PDGF transcript levels. Significant negative correlations were observed between the patient body mass index and the transcript levels of VEGF and PDGF receptors. Our findings support the hypothesis of the involvement of GFs in the natural history of ID herniation. GFs synergistically act in herniated IDs. Increased VEGF expression possibly induces the neovascularization process in the earliest stages of ID herniation. PDGF‑C and ‑D play a role in the acute phase of radiculopathy in a metabolic response for tissue healing. A molecular effect, in addition to the biomechanical effect of obesity in the pathogenesis of ID herniation is also implied.
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http://dx.doi.org/10.3892/mmr.2017.6221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5364887PMC
April 2017

Oral application of carbon nanofibers in rats increases blood concentration of IL6 and IL10 and decreases locomotor activity.

Environ Toxicol Pharmacol 2017 Mar 24;50:183-191. Epub 2017 Jan 24.

Far Eastern Federal University, Vladivostok, Russian Federation. Electronic address:

Carbon nanofibers (CNF) are versatile nanomaterials that are widely used in various fields of science and technology. As a consequence, animals as well as humans may be exposed to such compounds via different routes. We hypothesized that oral intake of CNF will lead to an inflammatory reaction and consequently induce behavioral impairments. To address this issue, rats were fed with 500mg/kgCNF for 14days and their locomotor activity, emotional status and cognition were quantified by testing the animals in an open field set-up, elevated plus maze and in the universal problem solving box which provides information about motivation and cognition. The behavioral tests were performed 3 times within 10days. At the end of the experiment, blood samples were collected and the plasma concentrations of IL-6, IL-8, IL-1β, IL-10 and IL-18 were measured. Our results demonstrated an inflammatory reaction determined by a significantly elevated IL-6 concentration. This, however, was counteracted by an even more pronounced increase in IL-10. The behavioral effects were restricted mainly to a decrease in locomotor activity which was significant in the open field test, as well as the elevated plus maze. Other parameters indicative of cognitive performance were not influenced and also the emotional status was largely unaffected. In conclusion, our results revealed that oral intake of 500mg/kgCNF induced some adverse effects, which, however, can be still partially compensated by the organism.
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http://dx.doi.org/10.1016/j.etap.2017.01.015DOI Listing
March 2017

Infections in patients undergoing craniotomy: risk factors associated with post-craniotomy meningitis.

J Neurosurg 2015 May 24;122(5):1113-9. Epub 2014 Oct 24.

Department of Internal Medicine, General Hospital of Chalkida;

OBJECT The authors performed a prospective study to define the prevalence and microbiological characteristics of infections in patients undergoing craniotomy and to clarify the risk factors for post-craniotomy meningitis. METHODS Patients older than 18 years who underwent nonstereotactic craniotomies between January 2006 and December 2008 were included. Demographic, clinical, laboratory, and microbiological data were systemically recorded. Patient characteristics, craniotomy type, and pre- and postoperative variables were evaluated as risk factors for meningitis RESULTS Three hundred thirty-four procedures were analyzed (65.6% involving male patients). Traumatic brain injury was the most common reason for craniotomy. Almost 40% of the patients developed at least 1 infection. Ventilator-associated pneumonia (VAP) was the most common infection recorded (22.5%) and Acinetobacter spp. were isolated in 44% of the cases. Meningitis was encountered in 16 procedures (4.8%), and CSF cultures were positive for microbial growth in 100% of these cases. Gram-negative pathogens (Acinetobacter spp., Klebsiella spp., Pseudomonas aeruginosa, Enterobacter cloaceae, Proteus mirabilis) represented 88% of the pathogens. Acinetobacter and Klebsiella spp. demonstrated a high percentage of resistance in several antibiotic classes. In multivariate analysis, the risk for meningitis was independently associated with perioperative steroid use (OR 11.55, p = 0.005), CSF leak (OR 48.03, p < 0.001), and ventricular drainage (OR 70.52, p < 0.001). CONCLUSIONS Device-related postoperative communication between the CSF and the environment, CSF leak, and perioperative steroid use were defined as risk factors for meningitis in this study. Ventilator-associated pneumonia was the most common infection overall. The offending pathogens presented a high level of resistance to several antibiotics.
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http://dx.doi.org/10.3171/2014.8.JNS132557DOI Listing
May 2015

Aggregatibacter aphrophilus brain abscess secondary to primary tooth extraction: Case report and literature review.

J Microbiol Immunol Infect 2016 Feb 12;49(1):119-22. Epub 2014 Feb 12.

Department of Neurosurgery, University Hospital of Heraklion, Heraklion, Crete, Greece.

We report on a rare case of Aggregatibacter aphrophilus brain abscess of odontogenic origin in a 6-year-old previously healthy boy, who had close contact with a pet dog. The poodle was the most likely source of the infecting organism, which subsequently colonized the patient's oral cavity. The abscess was surgically removed and he recovered completely after prolonged antibiotic treatment with meropenem. We also review the relevant medical literature on A. aphrophilus pediatric brain abscesses.
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http://dx.doi.org/10.1016/j.jmii.2013.12.007DOI Listing
February 2016

Akt/PKB isoforms expression in the human lumbar herniated disc: correlation with clinical and MRI findings.

Eur Spine J 2011 Oct 18;20(10):1676-83. Epub 2011 May 18.

Department of Orthopedics and Traumatology, University Hospital of Heraklion, Crete, Greece.

Intervertebral disc (IVD) degeneration suggests a complex process influenced by genetics, lifestyle and biomechanics, which accounts for the development of low back pain (LBP) and lumbar radiculopathy, a major cause of musculoskeletal disability in humans. The family of Akt/PKB kinases is a principal mediator in the signal transduction pathways, which contribute to transcriptional regulation, cell growth, proliferation, apoptosis, and survival ability. The purpose of this study was to evaluate the transcriptional profile of the AKT family genes in human herniated discs and the involvement of the PI3K-Akt signaling pathway in human IVD degeneration. Real-time PCR analysis was used to assess the mRNA expression pattern of the three Akt/PKB isoforms in 63 herniated and 10 control disc specimens. Our results showed a significant positive correlation between AKT1 and AKT3 mRNA in herniated discs suggesting a synergistic action between these isoforms in disc herniation. Interestingly, AKT2 mRNA was up-regulated in patients with acute pain during the first 12 months, indicating that AKT2 transcriptional activation may be associated with acute rather than chronic inflammation and phagocytosis. Finally, Akt1/PKB transcription presented a stepwise activation as disc herniation deteriorated. Our findings provide evidence on the transcriptional activation of the Akt/PKB pathway indicating that it is involved in lumbar disc degeneration. There is need for further studies to elucidate the exact role and down-stream signaling action of Akt/PKB isoforms in the pathogenesis of lumbar disc herniation.
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http://dx.doi.org/10.1007/s00586-011-1841-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3175883PMC
October 2011

Transcript levels of major MMPs and ADAMTS-4 in relation to the clinicopathological profile of patients with lumbar disc herniation.

Eur Spine J 2011 May 22;20(5):781-90. Epub 2010 Sep 22.

Laboratory of Virology, Medical School, University of Crete, and Department of Orthopedics and Traumatology, University Hospital of Heraklion, P.O. Box 1527, 710 03, Crete, Heraklion, Greece.

The involvement of matrix metalloproteinases (MMPs) in both the pathogenesis of intervertebral disc (ID) herniation and the spontaneous regression of herniated ID fragments remains only partially elucidated. The purpose of the present study was to simultaneously examine the transcript levels of a large number of MMPs (-1, -3, -8, -9, -13 and -14) and ADAMTS-4 (a disintegrin and metalloproteinase with thrombospondin motifs) and to investigate their correlation with the clinicopathologic profile of patients suffering from symptomatic lumbar ID herniation. mRNA expression levels were determined by means of the real-time polymerase chain reaction in 63 herniated and 10 control ID specimens. Our results showed multiple positive correlations among all MMPs and ADAMTS-4 mRNA in herniated samples, indicating their possible synergistic effect in ID herniation. MMP-9 and -13 mRNA levels were significantly elevated in patients with chronic pain, presumably as a consequence of neovascularization and chronic inflammation. Smoking habits were found to have a negative dose-dependent effect on the transcript levels of MMP-3 and MMP-13 and a positive correlation with pain intensity, suggesting an unfavorable role for smoking in the regression process of herniated disc fragments. Our findings provide evidence of the molecular portrait of MMPs and ADAMTS-4 in lumbar ID herniation, as well as of its association with the clinicopathological profile of the patients included in this study, reinforcing the hypothesis of MMPs involvement in the natural history of ID herniation. However, further studies are necessary to elucidate the exact role of MMPs in the resorption process of herniated lumbar discs.
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http://dx.doi.org/10.1007/s00586-010-1573-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3082673PMC
May 2011

Infections in patients with traumatic brain injury who undergo neurosurgery.

Br J Neurosurg 2011 Feb 22;25(1):9-15. Epub 2010 Jul 22.

Department of Internal Medicine, University Hospital of Heraklion, Crete, Greece.

Objective: Several factors place victims with traumatic brain injury (TBI) at increased risk for infection. The purpose of this study was to delineate the frequency, types and risk factors for infection in patients with TBI who undergo neurosurgery.

Materials And Methods: Retrospective surveillance of infections in patients with TBI, aged  ≥18 years who underwent neurosurgery in University of Crete between 1999 and 2005.

Results: Two hundred fifty-eight patients (76.7% men) who underwent 342 procedures were included. One hundred forty-two infections occurred, mainly lower respiratory tract infections (44.4% of the number of infections) and surgical site infections (SSIs) (25.4%). In multivariate analysis, SSIs were independently associated with the length of stay (p < 0.001), history of malignancy (p = 0.008), CSF leak (p = 0.012), any concomitant infection (p = 0.010), particularly urinary tract infections (p = 0.001) and the use of lumbar and/or ventricular drains (p = 0.005). Meningitis was independently associated with the total length of stay (p < 0.001), the need for intubation and mechanical ventilation beyond surgery (p = 0.028) and the presence of a lumbar and/or ventricular drain (p < 0.001).

Conclusions: Respiratory tract infections were common in patients with TBI who underwent surgery with Acinetobacter spp. being the emerging offending pathogens. Device-related postoperative communication of the CSF and the environment was a significant risk factor for SSI development and meningitis in particular. Malignancy was an independent risk factor for SSIs. The prevalence of the offending pathogens must be determined institution by institution for the establishment of proper antibiotic treatment on suspicion.
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http://dx.doi.org/10.3109/02688697.2010.500411DOI Listing
February 2011

Phylogeny, scaling, and the generation of extreme forces in trap-jaw ants.

J Exp Biol 2008 Jul;211(Pt 14):2358-68

Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

Trap-jaw ants of the genus Odontomachus produce remarkably fast predatory strikes. The closing mandibles of Odontomachus bauri, for example, can reach speeds of over 60 m s(-1). They use these jaw strikes for both prey capture and locomotion - by striking hard surfaces, they can launch themselves into the air. We tested the hypothesis that morphological variation across the genus is correlated with differences in jaw speeds and accelerations. We video-recorded jaw-strikes at 70 000-100 000 frames s(-1) to measure these parameters and to model force production. Differences in mean speeds ranged from 35.9+/-7.7 m s(-1) for O. chelifer, to 48.8+/-8.9 m s(-1) for O. clarus desertorum. Differences in species' accelerations and jaw sizes resulted in maximum strike forces in the largest ants (O. chelifer) that were four times those generated by the smallest ants (O. ruginodis). To evaluate phylogenetic effects and make statistically valid comparisons, we developed a phylogeny of all sampled Odontomachus species and seven outgroup species (19 species total) using four genetic loci. Jaw acceleration and jaw-scaling factors showed significant phylogenetic non-independence, whereas jaw speed and force did not. Independent contrast (IC) values were used to calculate scaling relationships for jaw length, jaw mass and body mass, which did not deviate significantly from isometry. IC regression of angular acceleration and body size show an inverse relationship, but combined with the isometric increase in jaw length and mass results in greater maximum strike forces for the largest Odontomachus species. Relatively small differences (3%) between IC and species-mean based models suggest that any deviation from isometry in species' force production may be the result of recent selective evolution, rather than deep phylogenetic signal.
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http://dx.doi.org/10.1242/jeb.015263DOI Listing
July 2008

Psychosis-like syndrome associated with intermittent intracranial hypertension caused by a large arachnoid cyst of the left temporal lobe.

Br J Neurosurg 2006 Jun;20(3):156-9

Department of Neurosurgery, University of Crete, Medical School, Heraklion University Hospital, Heraklion, Crete, Greece.

Lesions on certain brain areas can cause psychiatric signs. Symptomatic arachnoid cysts can produce a variety of symptoms like headache, seizures, increased ICP, and rarely psychiatric disorders. We report a case of a young woman with a left temporal lobe arachnoid cyst, presented with headache and an atypical psychosis. A 72-h epidural ICP recording revealed incidental elevation of ICP. After a permanent shunt was placed, patient's symptoms improved substantially, and antipsychotic medication was significantly reduced.
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http://dx.doi.org/10.1080/02688690600776986DOI Listing
June 2006

Use of polytetrafluoroethylene dural substitute as adhesion preventive material during craniectomies.

Clin Neurol Neurosurg 2006 Dec 20;108(8):798-802. Epub 2005 Dec 20.

Department of Neurosurgery, University of Crete, Medical School, Heraklion University Hospital, Voutes, 71 021 Heraklion-Crete, Greece.

Objective: We describe the use of an artificial dural substitute in order to prevent peridural fibrosis in patients who underwent craniectomy and subsequent cranioplasty.

Patients And Methods: In our institution we performed decompressive craniectomy and subsequent cranioplasty, with autologous bone flap, in 52 patients (mean age 32 years) between 1998 and 2004. Most of the craniectomy procedures were performed as emergency, brain swelling relief, measure for various reasons. The standard decompressive craniectomy technique that we perform includes bone removal, meningoplasty and protection from future adhesion formations in 23 of the 52 patients by the use of polytetrafluoroethylene (ePTFE) dural substitute (Preclude((R))). The substitute was applied over dural anasynthesis and under the galea, during craniectomy. The development of adhesion formations between tissue layers was evaluated during reoperation for cranioplasty.

Results: During cranioplasty reoperation we observed that the polytetrafluoroethylene dural substitute succeeds in creating a controlled dissection plane, facilitating access to the epidural space, shortening the operation time by approximately 25% and diminishes the intraoperative blood loss by 37% as compared with the group of patients underwent standard cranioplasty. The difference is of statistical significance (p<0.005). As a result, the use of polytetrafluoroethylene dural substitute as adhesion preventive material could make the cranioplasty operation safer and more successful.

Conclusion: Polytetrafluoroethylene dural substitute is able to prevent peridural scarring and is very efficient in facilitating cranioplasty in patients who underwent craniectomy regardless the indication.
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http://dx.doi.org/10.1016/j.clineuro.2005.11.026DOI Listing
December 2006

Intracerebral CSF collection mimicking cerebral abscess in a patient suffering from cryptococcal meningitis.

J Infect 2005 Nov;51(4):e233-5

Department of Neurosurgery, University of Crete, Medical School, Heraklion University Hospital, Voutes, 71021 Heraklion - Crete, Greece.

We report a case of a large intracerebral CSF collection formed along the course of the catheter of an ommaya-type reservoir (Medtronic 12 mm), implanted in a patient suffered from cryptococcal meningitis in the frame of CLL. This collection was at first diagnosed as intracerebral abscess but emergency craniotomy proves clear CSF collection with no signs of infection. We describe the case and we discuss the issue of CSF pressure pathophysiology and changes in flow dynamics, to patients with cryptococcal meningitis.
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http://dx.doi.org/10.1016/j.jinf.2005.02.007DOI Listing
November 2005