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Biomedical subjects

Peter Young

Publications and source records attributed to Peter Young.

At least 19 recordsLinked to original sources

Convergent methodologies in prosthetic joint infection research: integrating transdisciplinary approaches to understand and prevent biofilm-driven failure of orthopaedic prostheses.

Prosthetic joint infections (PJIs) remain among the most devastating complications of arthroplasty, imposing substantial clinical, economic and patient burdens. Although culture-based diagnostics underpin current clinical practice, PJIs are biofilm-driven infections shaped by taxonomic diversity, spatial organization, host responses and surface interactions, meaning conventional approaches provide only a partial and often decontextualized view of the infection process. We examine how convergent methodologies can transform PJI research by integrating approaches that have traditionally been studied in isolation, including sequencing, transcriptomics, metabolomics, advanced imaging and culture-based characterization. We discuss how whole-genome sequencing, shotgun metagenomics, transcriptomic and metabolomic approaches resolve pathogen identity, functional activity and adaptive persistence and how cross-scale imaging and spatial biology techniques reveal where microbes colonize, interact and survive across implant surfaces. We highlight emerging opportunities to unify these datasets into coherent frameworks that capture both the molecular and physical dimensions of PJIs. Integrating these complementary approaches will enable a multi-layered understanding of PJIs that link composition, function and spatial organization. Ultimately, this provides a foundation for predictive diagnostics, precision antimicrobial strategies and improved implant design and supports a shift towards more effective, mechanism-informed management of implant-associated infection.

Prosthesis-Related Infections↗

Treatment for obstructive sleep apnoea: effect on peripheral nerve function.

BACKGROUND AND OBJECTIVE: Obstructive sleep apnoea (OSA) is suggested to be associated with peripheral nerve damage. A case-control study was conducted to provide further support to this observation. In a longitudinal intervention study, it was examined whether treatment for OSA has a possible beneficial effect on peripheral nerve function. METHODS: Participants were 23 patients with OSA and 23 controls matched for age and body mass index (BMI), all without any known cause of peripheral nerve damage. The sensory nerve action potential (SNAP) amplitudes of both sural nerves were determined. After 6 months of treatment for OSA, treatment compliance was evaluated and nerve conduction studies were repeated. RESULTS: Patients with OSA had significantly lower mean (standard deviation) sural SNAP amplitudes than controls (6.3 (3.5) v 11.2 (5.0), p < 0.001). Multivariate regression analysis including the variables age, BMI and Apnoea-Hypopnea Index (AHI) showed that both age (p < 0.01) and AHI (p < 0.05) were inversely related to the SNAP amplitude. On follow-up, the sural SNAP showed an increase of 2.6 mV on average (p < 0.001). Multivariate regression analysis including the variables age, BMI, AHI, pretreatment SNAP and treatment compliance identified only treatment compliance as being significantly related to the SNAP increase (p < or = 0.005). CONCLUSION: OSA is an independent risk factor for axonal dysfunction of peripheral sensory nerves. Impaired neural function is at least partly reversible with treatment for sleep apnoea.

Action Potentials↗

Pregabalin-associated acute psychosis and epileptiform EEG-changes.

Pregabalin is a novel anticonvulsive and analgesic drug that has been marketed in Europe for more than a year. The typical side effects are dizziness, somnolence and weight gain. We present a patient who, after unintended rapid up-titration of pregabalin, experienced psychotic symptoms associated with rhythmic EEG-changes resolving completely after discontinuation of pregabalin and benzodiazepine administration.

Acute Disease↗

Cell cycle inhibitors p21 and p16 are required for the regulation of Schwann cell proliferation.

Regulated cell proliferation is a crucial prerequisite for Schwann cells to achieve myelination in development and regeneration. In the present study, we have investigated the function of the cell cycle inhibitors p21 and p16 as potential regulators of Schwann cell proliferation, using p21- or p16-deficient mice. We report that both inhibitors are required for proper withdrawal of Schwann cells from the cell cycle during development and following injury. Postnatal Schwann cells express p21 exclusively in the cytoplasm, first detectable at postnatal day 7. This cytoplasmic p21 expression is necessary for proper Schwann cell proliferation control in the late development of peripheral nerves. After axonal damage, p21 is found in Schwann cell nuclei during the initiation of the proliferation period. This stage is critically regulated by p21, since loss of p21 leads to a strong increase in Schwann cell proliferation. Unexpectedly, p21 levels are upregulated in this phase suggesting that the role of p21 may be more complex than purely inhibitory for the Schwann cell cycle. However, inhibition of Schwann cell proliferation is the overriding crucial function of p21 and p16 in peripheral nerves as revealed by the consequences of loss-of-function in development and after injury. Different mechanisms appear to underlie the inhibitory function, depending on whether p21 is cytoplasmic or nuclear.

Adenoviridae↗

A tighter bound for the echo state property.

This letter provides a brief explanation of echo state networks (ESNs) and provides a rigorous bound for guaranteeing asymptotic stability of these networks. The stability bounds presented here could aid in the design of echo state networks that would be applicable to control applications where stability is required.

Algorithms↗

CRA-026440: a potent, broad-spectrum, hydroxamic histone deacetylase inhibitor with antiproliferative and antiangiogenic activity in vitro and in vivo.

CRA-026440 is a novel, broad-spectrum, hydroxamic acid-based inhibitor of histone deacetylase (HDAC) that shows antitumor and antiangiogenic activities in vitro and in vivo preclinically. CRA-026440 inhibited pure recombinant isozymes HDAC1, HDAC2, HDAC3/SMRT, HDAC6, HDAC8, and HDAC10 in the nanomolar range. Treatment of cultured tumor cell lines grown in vitro with CRA-026440 resulted in the accumulation of acetylated histone and acetylated tubulin, leading to an inhibition of tumor cell growth and the induction of apoptosis. CRA-026440 inhibited ex vivo angiogenesis in a dose-dependent manner. CRA-026440 parenterally given to mice harboring HCT116 or U937 human tumor xenografts resulted in a statistically significant reduction in tumor growth. CRA-026440, when used in combination with Avastin, achieved greater preclinical efficacy in HCT 116 colorectal tumor model. Inhibition of tumor growth was accompanied by an increase in the acetylation of alpha-tubulin in peripheral blood mononuclear cells and an alteration in the expression of many genes in the tumors, including several involved in angiogenesis, apoptosis, and cell growth. These results reveal CRA-026440 to be a novel HDAC inhibitor with potent antitumor activity.

Acetylation↗

An animal model for Charcot-Marie-Tooth disease type 4B1.

Charcot-Marie-Tooth disease (CMT) comprises a family of clinically and genetically very heterogeneous hereditary peripheral neuropathies and is one of the most common inherited neurological disorders. We have generated a mouse model for CMT type 4B1 using embryonic stem cell technology. To this end, we introduced a stop codon into the Mtmr2 locus within exon 9, at the position encoding amino acid 276 of the MTMR2 protein (E276X). Concomitantly, we have deleted the chromosomal region immediately downstream of the stop codon up to within exon 13. The resulting allele closely mimics the mutation found in a Saudi Arabian CMT4B1 patient. Animals homozygous for the mutation showed various degrees of complex myelin infoldings and outfoldings exclusively in peripheral nerves, in agreement with CMT4B1 genetics and pathology. Mainly, paranodal regions of the myelin sheath were affected, with a high degree of quantitative and qualitative variability between individuals. This pathology was progressive with age, and axonal damage was occasionally observed. Distal nerve regions were more affected than proximal parts, in line with the distribution in CMT. However, we found no significant electrophysiological changes, even in aged (16-month-old) mice, suggesting that myelin infoldings and outfoldings per se are not invariably associated with detectable electrophysiological abnormalities. Our animal model provides a basis for future detailed molecular and cellular studies on the underlying disease mechanisms in CMT4B1. Such an analysis will reveal how the disease develops, in particular, the enigmatic myelin infoldings and outfoldings as well as axonal damage, and provide mechanistic insights that may aid in the development of potential therapeutic approaches.

Alleles↗

Mutations in SEPT9 cause hereditary neuralgic amyotrophy.

Hereditary neuralgic amyotrophy (HNA) is an autosomal dominant recurrent neuropathy affecting the brachial plexus. HNA is triggered by environmental factors such as infection or parturition. We report three mutations in the gene septin 9 (SEPT9) in six families with HNA linked to chromosome 17q25. HNA is the first monogenetic disease caused by mutations in a gene of the septin family. Septins are implicated in formation of the cytoskeleton, cell division and tumorigenesis.

Amino Acid Sequence↗

Increased prevalence of sleep apnea in patients with recurring ischemic stroke compared with first stroke victims.

Since sleep apnea (SA) and stroke have many shared risk factors an independent contribution of SA to the overall risk of stroke is not easily proven and has been questioned recently. To contribute to this controversy, we analysed the frequency of SA in groups of patients with first and recurring ischemic stroke. We prospectively studied 102 patients admitted to our stroke unit. The prevalence of vascular risk factors and a history of previous stroke were recorded. All patients received cardio-respiratory polygraphy during the first 72 hours after admission. CT and MRI scans were evaluated for the location of the acute stroke and the presence of older vascular lesions. Thirty-four women and 68 men with a mean age of 64.5 +/- 13.7 years were included in the study. Cerebral lesions attributable to a previous stroke were identified in 25 patients, of whom 19 reported to have suffered a stroke before. Patients with stroke recurrence had a higher mean apnea-hypopnea index (AHI) (26.6/h vs. 15.1/h, p<0.05) and more often presented with a sleep apnea syndrome (SA) defined by an AHI >or=10/h (80 vs. 52%, p < 0.05) than patients with first ever stroke. Logistic regression analysis including the variables "age", "gender", "cumulative risk factors", "AHI >or=10/h", and "diabetes" identified diabetes (Odd's ratio [OR]=4.5) and AHI >or=10/h (OR=3.5) as independent risk-factors for stroke recurrence. According to our results SA is an independent risk factor for stroke recurrence. We therefore advocate routine sleep-apnea screening in all patients having suffered an ischemic stroke.

Female↗

A case of triploidy.

OBJECTIVE: To report a case of triploidy in a women who conceived after intracytoplasmic sperm injection (ICSI). DESIGN: Case report. SETTING: Maternity unit of a university hospital. PATIENT(S): A 29-year-old woman who was pregnant following intracytoplasmic sperm injection (ICSI). INTERVENTION(S): Ultrasound and serum screening. MAIN OUTCOME MEASURE(S): Amniocentesis and postmortem findings. RESULT(S): Amniocentesis confirmed the karyotype to be 69XXY, and the pregnancy was terminated. CONCLUSION(S): This case refers to diandric triploidy resulting from fertilization by diploid sperm.

Adult↗

Absence of mutations in the prion-protein gene in a large cohort of HMSN patients.

Cellular prion-protein is expressed in axons and Schwann cells of peripheral nerves. Some patients with prion diseases show peripheral nerve involvement and prion-protein deficient mice develop age dependent demyelination of peripheral nerves. Therefore we tested the hypothesis that mutations in the prion-protein gene might also cause hereditary motor and sensory neuropathies. We screened 108 patients with a diagnosis of hereditary motor and sensory neuropathies in whom the common genetic defects causing hereditary motor and sensory neuropathies had previously been excluded for mutations in the protein-coding region of the PRNP gene. Mutations in the coding region of the prion-protein gene were not found. We conclude that mutations in the protein coding region of the prion-protein gene are not a common cause of HMSN (95% CI 0-0.034).

Cohort Studies↗

The activation function-1 domain of estrogen receptor alpha in uterine stromal cells is required for mouse but not human uterine epithelial response to estrogen.

The activation function-1 (AF-1) domain of the estrogen receptor alpha (ERalpha) in stromal cells has been shown to be required for epithelial responses to estrogen in the mouse uterus. To investigate the role of the stroma in estrogenic responses of human uterine epithelium (hUtE), human/mouse chimeric uteri composed of human epithelium and mouse stroma were prepared as tissue recombinants (TR) that were grown in vivo under the renal capsule of female nude mouse hosts. In association with mouse uterine stroma (mUtS), hUtE formed normal glands surrounded by mouse endometrial stroma and the human epithelium influenced the differentiation of stroma into myometrium, such that a histologically normal appearing uterine tissue was formed. The hUtE showed a similar proliferative response and increase in progesterone receptors (PR) in response to 17beta-estradiol (E2) in association with either human or mUtS, as TRs. However, under identical endocrine and micro-environmental conditions, hUtE required 5-7 days exposure to E2 rather than 1 day, as shown for mouse uterine epithelium, to obtain a maximal proliferative response. Moreover, this extended length of E2 exposure inhibited mouse epithelial proliferation in the presence of mouse stroma. In addition, unlike the mouse epithelium, which does not proliferate or show regulation of PR expression in response to E2 in association with uterine stroma derived from mice that are null for the AF-1 domain of ERalpha, hUtE proliferates and PR are up-regulated in response to E2 in association genetically identical ERalpha knock-out mouse stromal cells. These results clearly demonstrate fundamental differences between mouse and human uterine epithelia with respect to the mechanisms that regulate estrogen-induced proliferation and expression of PR. Moreover, we show that genetically engineered mouse models could potentially aid in dissecting molecular pathways of stromal epithelial interactions in the human uterus.

Animals↗

Capnography screening for sleep apnea in patients with acute stroke.

Sleep apnea syndrome (SAS) is a prominent clinical feature in acute stroke patients. Diagnosis is usually established by polysomnography or cardio-respiratory polygraphy (CRP). Both diagnostic procedures produce high costs, are dependent on the access to a specialized sleep laboratory, and are poorly tolerated by patients with acute stroke. In this study we therefore investigated whether capnography may work as a simple screening tool in this context. In addition to conventional CRP, 27 patients with acute stroke were studied with capnography provided by our standard monitoring system. The trend graphs of the end-tidal CO(2) values (EtCO(2)) were used to determine the capnography-based estimate of the apnea-hypopnea index (AHI(CO2)). Index events were scored when the EtCO(2) value dropped for > 50% of the previous baseline value. We found that the AHI(CO2) correlated significantly with the apnea-hypopnea index measured with conventional CRP (AHI(CRP)) (r = 0.94; p < 0.001). An AHI(CO2) > 5 turned out to be highly predictive of an AHI(CRP) > 10. According to our findings, routinely acquired capnography may provide a reliable estimate of the AHI(CRP). The equipment needed for this screening procedure is provided by the monitoring systems of most intensive care units and stroke units where stroke patients are regularly treated during the first days of their illness. Therefore, early diagnosis of SAS in these patients is made substantially easier.

Aged↗

The protooncogene Ski controls Schwann cell proliferation and myelination.

Schwann cell proliferation and subsequent differentiation to nonmyelinating and myelinating cells are closely linked processes. Elucidating the molecular mechanisms that control these events is key to the understanding of nerve development, regeneration, nerve-sheath tumors, and neuropathies. We define the protooncogene Ski, an inhibitor of TGF-beta signaling, as an essential component of the machinery that controls Schwann cell proliferation and myelination. Functional Ski overexpression inhibits TGF-beta-mediated proliferation and prevents growth-arrested Schwann cells from reentering the cell cycle. Consistent with these findings, myelinating Schwann cells upregulate Ski during development and remyelination after injury. Myelination is blocked in myelin-competent cultures derived from Ski-deficient animals, and genes encoding myelin components are downregulated in Ski-deficient nerves. Conversely, overexpression of Ski in Schwann cells causes an upregulation of myelin-related genes. The myelination-regulating transcription factor Oct6 is involved in a complex modulatory relationship with Ski. We conclude that Ski is a crucial signal in Schwann cell development and myelination.

Animals↗

Genomic organization and mutation analysis of three candidate genes for hereditary neuralgic amyotrophy.

Hereditary neuralgic amyotrophy (HNA) is an autosomal-dominant inherited recurrent focal neuropathy affecting mainly the brachial plexus. In this study we report the genomic structure and mutation analysis of three candidate genes: sphingosine kinase 1 (SPHK1); tissue inhibitor of metalloproteinase 2 (TIMP2); and cytoglobin (CYGB). We did not find any disease-associated mutations, indicating that HNA is not caused by point mutations in these genes. However, we identified several sequencing errors in the cDNA of SPHK1 as well as seven novel single-nucleotide polymorphisms.

Amino Acid Substitution↗

E-cadherin controls adherens junctions in the epidermis and the renewal of hair follicles.

E-cadherin is thought to mediate intercellular adhesion in the mammalian epidermis and in hair follicles as the adhesive component of adherens junctions. We have tested this role of E-cadherin directly by conditional gene ablation in the mouse. We show that postnatal loss of E-cadherin in keratinocytes leads to a loss of adherens junctions and altered epidermal differentiation without accompanying signs of inflammation. Overall tissue integrity and desmosomal structures were maintained, but skin hair follicles were progressively lost. Tumors were not observed and beta-catenin levels were not strongly altered in the mutant skin. We conclude that E-cadherin is required for maintaining the adhesive properties of adherens junctions in keratinocytes and proper skin differentiation. Furthermore, continuous hair follicle cycling is dependent on E-cadherin.

Adherens Junctions↗

E-cadherin is required for the correct formation of autotypic adherens junctions of the outer mesaxon but not for the integrity of myelinated fibers of peripheral nerves.

The calcium-dependent adhesion protein E-cadherin is present in noncompacted regions of myelin sheaths in the peripheral nervous system. There, it is localized to electron-dense structures between membranes of the same Schwann cell referred to as autotypic adherens junctions. It has been suggested that the failure of E-cadherin-mediated adhesion might cause demyelination that proceeds in certain pathological states. To test the requirement of E-cadherin in peripheral nerves, we used tissue-specific gene ablation techniques based on the Cre/LoxP system. We show that E-cadherin deficiency does not cause significant demyelination up to the age of 15 months. Immunostainings for nodal sodium channels, the paranodal protein Caspr1, and the juxtaparanodal potassium channels Kv1.1 and Kv1.2 revealed that E-cadherin is not necessary to maintain the general functional architecture of the nodal region. On the ultrastructural level, we detected a widening of the outer mesaxon accompanied by a loss of electron-dense cytoplasmic areas. We conclude that E-cadherin is required for the proper establishment and/or the maintenance of the outer mesaxon in myelinated PNS fibers but is dispensable for proper nerve function.

Adherens Junctions↗

Clinical features and molecular genetics of hereditary peripheral neuropathies.

Hereditary peripheral neuropathies are the most common monogenetically inherited diseases of the nervous system. The prevalence of the Hereditary Motor and Sensory Neuropathy Type 1A (HMSN 1A or Charcot-Marie-Tooth Neuropathy 1A, CMT1A) alone is estimated to be as high as 1/5000. In 1991, a duplication on chromosome 17p11.2 was identified as the causative genetic defect of CMT1A. Since then causative mutations in 17 genes have been identified. This review summarises the clinical and molecular genetic features of primary inherited neuropathies. It is aimed primarily at clinicians and geneticists. Therefore less emphasis is placed on the pathology and the (often unknown) underlying biological disease mechanisms.

Animals↗