Reconstitution of the phosphodiesterase 6 maturation process important for photoreceptor cell function

The sixth family phosphodiesterases (PDE6) are principal effector enzymes of the phototransduction cascade in rods and cones. Maturation of nascent PDE6 protein into a functional enzyme relies on a coordinated action of ubiquitous chaperone HSP90, its specialized cochaperone aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1), and the regulatory Pγ-subunit of PDE6. Deficits in PDE6 maturation and function underlie severe visual disorders and blindness. Here, to elucidate the roles of HSP90, AIPL1, and Pγ in the maturation process, we developed the heterologous expression system of human cone PDE6C in insect cells allowing characterization of the purified enzyme. We demonstrate that in the absence of Pγ, HSP90, and AIPL1 convert the inactive and aggregating PDE6C species into dimeric PDE6C that is predominantly misassembled. Nonetheless, a small fraction of PDE6C is properly assembled and fully functional. From the analysis of mutant mice that lack both rod Pγ and PDE6C, we conclude that, in contrast to the cone enzyme, no maturation of rod PDE6AB occurs in the absence of Pγ. Co-expression of PDE6C with AIPL1 and Pγ in insect cells leads to a fully mature enzyme that is equivalent to retinal PDE6. Lastly, using immature PDE6C and purified chaperone components, we reconstituted the process of the client maturation in vitro. Based on this analysis we propose a scheme for the PDE6 maturation process.

Unique interface and dynamics of the complex of HSP90 with a specialized cochaperone AIPL1

Photoreceptor phosphodiesterase PDE6 is central for visual signal transduction. Maturation of PDE6 depends on a specialized chaperone complex of HSP90 with aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1). Disruption of PDE6 maturation underlies a severe form of retina degeneration. Here, we report a 3.9 Å cryoelectron microscopy (cryo-EM) structure of the complex of HSP90 with AIPL1. This structure reveals a unique interaction of the FK506-binding protein (FKBP)-like domain of AIPL1 with HSP90 at its dimer interface. Unusually, the N terminus AIPL1 inserts into the HSP90 lumen in a manner that was observed previously for HSP90 clients. Deletion of the 7 N-terminal residues of AIPL1 decreased its ability to cochaperone PDE6. Multi-body refinement of the cryo-EM data indicated large swing-like movements of AIPL1-FKBP. Modeling the complex of HSP90 with AIPL1 using crosslinking constraints indicated proximity of the mobile tetratricopeptide repeat (TPR) domain with the C-terminal domain of HSP90. Our study establishes a framework for future structural studies of PDE6 maturation.

Molecular insights into the maturation of phosphodiesterase 6 by the specialized chaperone complex of HSP90 with AIPL1

Phosphodiesterase 6 (PDE6) is a key effector enzyme in vertebrate phototransduction, and its maturation and function are known to critically depend on a specialized chaperone, aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1). Defects in PDE6 and AIPL1 underlie several severe retinal diseases, including retinitis pigmentosa and Leber congenital amaurosis. Here, we characterize the complex of AIPL1 with HSP90 and demonstrate its essential role in promoting the functional conformation of nascent PDE6. Our analysis suggests that AIPL1 preferentially binds to HSP90 in the closed state with a stoichiometry of 1:2, with the tetratricopeptide repeat domain and the tetratricopeptide repeat helix 7 extension of AIPL1 being the main contributors to the AIPL1/HSP90 interface. We demonstrate that mutations of these determinants markedly diminished both the affinity of AIPL1 for HSP90 and the ability of AIPL1 to cochaperone the maturation of PDE6 in a heterologous expression system. In addition, the FK506-binding protein (FKBP) domain of AIPL1 encloses a unique prenyl-binding site that anchors AIPL1 to posttranslational lipid modifications of PDE6. A mouse model with rod PDE6 lacking farnesylation of its PDE6A subunit revealed normal expression, trafficking, and signaling of the enzyme. Furthermore, AIPL1 was unexpectedly capable of inducing the maturation of unprenylated cone PDE6C, whereas mutant AIPL1 deficient in prenyl binding competently cochaperoned prenylated PDE6C. Thus, we conclude neither sequestration of the prenyl modifications is required for PDE6 maturation to proceed, nor is the FKBP-lipid interaction involved in the conformational switch of the enzyme into the functional state.

Chatbots to Support Mental Wellbeing of People Living in Rural Areas: Can User Groups Contribute to Co-design?

Digital technologies such as chatbots can be used in the field of mental health. In particular, chatbots can be used to support citizens living in sparsely populated areas who face problems such as poor access to mental health services, lack of 24/7 support, barriers to engagement, lack of age appropriate support and reductions in health budgets. The aim of this study was to establish if user groups can design content for a chatbot to support the mental wellbeing of individuals in rural areas. University students and staff, mental health professionals and mental health service users (N = 78 total) were recruited to workshops across Northern Ireland, Ireland, Scotland, Finland and Sweden. The findings revealed that participants wanted a positive chatbot that was able to listen, support, inform and build a rapport with users. Gamification could be used within the chatbot to increase user engagement and retention. Content within the chatbot could include validated mental health scales and appropriate response triggers, such as signposting to external resources should the user disclose potentially harmful information or suicidal intent. Overall, the workshop participants identified user needs which can be transformed into chatbot requirements. Responsible design of mental healthcare chatbots should consider what users want or need, but also what chatbot features artificial intelligence can competently facilitate and which features mental health professionals would endorse.

Neurovascular coupling and oxygenation are decreased in hippocampus compared to neocortex because of microvascular differences

The hippocampus is essential for spatial and episodic memory but is damaged early in Alzheimer's disease and is very sensitive to hypoxia. Understanding how it regulates its oxygen supply is therefore key for designing interventions to preserve its function. However, studies of neurovascular function in the hippocampus in vivo have been limited by its relative inaccessibility. Here we compared hippocampal and visual cortical neurovascular function in awake mice, using two photon imaging of individual neurons and vessels and measures of regional blood flow and haemoglobin oxygenation. We show that blood flow, blood oxygenation and neurovascular coupling were decreased in the hippocampus compared to neocortex, because of differences in both the vascular network and pericyte and endothelial cell function. Modelling oxygen diffusion indicates that these features of the hippocampal vasculature may restrict oxygen availability and could explain its sensitivity to damage during neurological conditions, including Alzheimer's disease, where the brain's energy supply is decreased.

Myofunctional therapy. Part 1: Culture, industrialisation and the shrinking human face

Culture, industrialisation and the shrinking human face: Why is it important? Over the past 300,000 years, not only has the way we consume food from birth through our lifetime changed, there have also been changes related to the methods of food preparation, availability, processing, and storage. These diet-related factors, along with other epigenetic factors, have led to a widespread increase in orofacial myofunctional disorders (OMDs) and resultant human malocclusion phenotypes (HMPs) worldwide. Currently there is an increasing need for resolution of HMPs in early childhood and associated OMDs. This review will include reports of cases and describe the nature of the problem and strategies for effective solutions.

Transducin Partners Outside the Phototransduction Pathway

Transducin mediates signal transduction in a classical G protein-coupled receptor (GPCR) phototransduction cascade. Interactions of transducin with the receptor and the effector molecules had been extensively investigated and are currently defined at the atomic level. However, partners and functions of rod transducin α (Gα_{t 1}) and βγ (Gβ₁γ₁) outside the visual pathway are not well-understood. In particular, light-induced redistribution of rod transducin from the outer segment to the inner segment and synaptic terminal (IS/ST) allows Gα_t1 and/or Gβ₁γ₁ to modulate synaptic transmission from rods to rod bipolar cells (RBCs). Protein-protein interactions underlying this modulation are largely unknown. We discuss known interactors of transducin in the rod IS/ST compartment and potential pathways leading to the synaptic effects of light-dispersed Gα_t1 and Gβ₁γ₁. Furthermore, we show that a prominent non-GPCR guanine nucleotide exchange factor (GEF) and a chaperone of Gα subunits, resistance to inhibitors of cholinesterase 8A (Ric-8A) protein, is expressed throughout the retina including photoreceptor cells. Recent structures of Ric-8A alone and in complexes with Gα subunits have illuminated the structural underpinnings of the Ric-8A activities. We generated a mouse model with conditional knockout of Ric-8A in rods in order to begin defining the functional roles of the protein in rod photoreceptors and the retina. Our analysis suggests that Ric-8A is not an obligate chaperone of Gα_t1. Further research is needed to investigate probable roles of Ric-8A as a GEF, trafficking chaperone, or a mediator of the synaptic effects of Gα_t1.

Economic impacts of implementing a national smoke-free prison policy

Background

Worldwide, over 600,000 non-smokers are killed annually due to exposure to secondhand smoke (SHS); the UK societal cost of SHS is estimated at £700million per annum. Prior to recent smoke free policy in Scottish prisons smoking rates were very high (70-75%), well above population rates, subjecting people in custody (PiC) and prison staff to high levels of SHS. Eradicating SHS exposure in prisons could lead to improved health in previous smokers and non-smokers alike, and decrease demand on the National Health Service. However, to date, there is little evidence relating to the economic impact of smoking bans in prisons.

Methods

An economic evaluation estimating the short-term and lifetime impacts of smokefree prison policy in Scotland policy used data from the TIPs study (Jun 2016-Nov 2019) for prison staff and PiC. The analyses adopted a public health and personal perspective and key resources included: implementation costs, cessation support services, health service use and personal costs. For the short-term analyses data were sourced from TIPs staff and PiC surveys, and routine data from the Scottish Prison Service and NHS National Services Scotland. Outcomes included SHS exposure, staff sickness absence, violent incidents and quality adjusted life years (QALYs). The life-time analysis used a Markov model to estimate cost per QALY for both staff and PiC.

Results

SHS exposure measures show a median reduction of 91%. Costs and economic outcome results (mean cost pre- and post-ban, cost-consequences balance sheet and incremental cost per QALYs) are confidential until May 2020 due to their sensitivity and will be available to present at EUPHA 2020.

Conclusions

Previous economic evaluations have focussed on smoking bans in public places and raising the smoking age. This is the first economic analysis of a national prison smoking ban and analysis will be of interest to prison services in other jurisdictions which have yet to implement smokefree policy.

Smokefree policy and medication dispensing for people in prison: interrupted time series analysis

Background

Previous evaluations of smokefree prison policies have suggested improvements in self-rated health and some smoking-related symptoms. No studies to date have investigated impacts on medication use as proxy measures of objective ill-health or as indicators of potential negative unintended consequences. These is limited evidence to date on these important outcomes.

Methods

We obtained from NHS National Services Scotland aggregate data on medication items dispensed in prisons, based on individual named patient medication records, and from the Scottish Prison Service data on the prison population, for the period Jan 2013-Nov 2019. Items of interest comprised those for smoking cessation (varenicline and buproprion); nicotine replacement; specific smoking-related health conditions (glyceryl trinitrate; inhaled bronchodilators and steroids; antibiotics; chloramphenicol eye drops; and proton pump inhibitors and H2 receptor antagonists), and potential unintended mental health consequences (anti-depressants). We also included a set of negative controls for which dispensing was not expected to be affected by the new smokefree policy (anticonvulsants, excluding pregabalin and gabapentin). Analyses were undertaken using AutoRegressive Integrated Moving Average (ARIMA) time series methods, with the dates of the policy's announcement and of implementation included as pre-specified breakpoints.

Results

The results of ARIMA modelling of medication dispensing are confidential until May 2020 due to their sensitivity and will be available to present at WCPH 2020.

Conclusions

The use of routinely available dispensing data as an indicator of objective health impacts and potential negative unintended consequences provides novel insights into the effectiveness of smokefree prison policies. Results will be of interest to international jurisdictions considering such policies and to those seeking to harness the potential of administrative data for natural experiments.

Interaction of the tetratricopeptide repeat domain of aryl hydrocarbon receptor-interacting protein-like 1 with the regulatory Pγ subunit of phosphodiesterase 6

Phosphodiesterase-6 (PDE6) is key to both phototransduction and health of rods and cones. Proper folding of PDE6 relies on the chaperone activity of aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1), and mutations in both PDE6 and AIPL1 can cause a severe form of blindness. Although AIPL1 and PDE6 are known to interact via the FK506-binding protein domain of AIPL1, the contribution of the tetratricopeptide repeat (TPR) domain of AIPL1 to its chaperone function is poorly understood. Here, we demonstrate that AIPL1-TPR interacts specifically with the regulatory Pγ subunit of PDE6. Use of NMR chemical shift perturbation (CSP) mapping technique revealed the interface between the C-terminal portion of Pγ and AIPL1-TPR. Our solution of the crystal structure of the AIPL1-TPR domain provided additional information, which together with the CSP data enabled us to generate a model of this interface. Biochemical analysis of chimeric AIPL1-AIP proteins supported this model and also revealed a correlation between the affinity of AIPL1-TPR for Pγ and the ability of Pγ to potentiate the chaperone activity of AIPL1. Based on these results, we present a model of the larger AIPL1-PDE6 complex. This supports the importance of simultaneous interactions of AIPL1-FK506-binding protein with the prenyl moieties of PDE6 and AIPL1-TPR with the Pγ subunit during the folding and/or assembly of PDE6. This study sheds new light on the versatility of TPR domains in protein folding by describing a novel TPR-protein binding partner, Pγ, and revealing that this subunit imparts AIPL1 selectivity for its client.

A nonhuman primate model of inherited retinal disease

Inherited retinal degenerations are a common cause of untreatable blindness worldwide, with retinitis pigmentosa and cone dystrophy affecting approximately 1 in 3500 and 1 in 10,000 individuals, respectively. A major limitation to the development of effective therapies is the lack of availability of animal models that fully replicate the human condition. Particularly for cone disorders, rodent, canine, and feline models with no true macula have substantive limitations. By contrast, the cone-rich macula of a nonhuman primate (NHP) closely mirrors that of the human retina. Consequently, well-defined NHP models of heritable retinal diseases, particularly cone disorders that are predictive of human conditions, are necessary to more efficiently advance new therapies for patients. We have identified 4 related NHPs at the California National Primate Research Center with visual impairment and findings from clinical ophthalmic examination, advanced retinal imaging, and electrophysiology consistent with achromatopsia. Genetic sequencing confirmed a homozygous R565Q missense mutation in the catalytic domain of PDE6C, a cone-specific phototransduction enzyme associated with achromatopsia in humans. Biochemical studies demonstrate that the mutant mRNA is translated into a stable protein that displays normal cellular localization but is unable to hydrolyze cyclic GMP (cGMP). This NHP model of a cone disorder will not only serve as a therapeutic testing ground for achromatopsia gene replacement, but also for optimization of gene editing in the macula and of cone cell replacement in general.

False-Positive Monospot in a Returning Traveler with Dengue Fever

The heterophile antibody (Monospot), initial test of choice for Epstein-Barr virus (EBV)-associated infectious mononucleosis, is both sensitive (70-92%) and specific (96-100%). False positives have been demonstrated in cases of viral hepatitis, human immunodeficiency virus, leukemia, lymphoma, pancreatic cancer, systemic lupus erythematosus, and rubella. We present a case of a 46-yr-old male who developed fever, chills, headaches, myalgia, fatigue, and photophobia 1 d after returning from the Philippines. He demonstrated a mild transaminitis and significant thrombocytopenia (12,000 cells/μL). His initial evaluation revealed a positive heterophile antibody test. Without a classic EBV presentation, a fever in returning traveler evaluation was instituted resulting in a positive dengue test by direct fluorescence IgM (8.82 IU) and IgG (7.13 IU), respectively. Both his EBV DNA polymerase chain reaction and IgM by viral capsid antigen were negative. Dengue, an RNA flavivirus, and the dengue antibody have demonstrated cross-reactivity with other flaviviruses including Japanese encephalitis virus, yellow fever virus, West Nile virus, and St. Louis encephalitis. However, EBV is a double-helix DNA herpesvirus and structurally very different. To our knowledge, this is the first reported case of cross-reactivity between dengue and EBV that describes a potential false positive for the heterophile antibody test.

Mechanisms of mutant PDE6 proteins underlying retinal diseases

Mutations in PDE6 genes encoding the effector enzymes in rods and cones underlie severe retinal diseases including retinitis pigmentosa (RP), autosomal dominant congenital stationary night blindness (adCSNB), and achromatopsia (ACHM). Here we examined a spectrum of pathogenic missense mutations in PDE6 using the system based on co-expression of cone PDE6C with its specialized chaperone AIPL1 and the regulatory Pγ subunit as a potent co-chaperone. We uncovered two mechanisms of PDE6C mutations underlying ACHM: (a) folding defects leading to expression of catalytically inactive proteins and (b) markedly diminished ability of Pγ to co-chaperone mutant PDE6C proteins thereby dramatically reducing the levels of functional enzyme. The mechanism of the Rambusch adCSNB associated with the H258N substitution in PDE6B was probed through the analysis of the model mutant PDE6C-H262N. We identified two interrelated deficits of PDE6C-H262N: disruption of the inhibitory interaction of Pγ with mutant PDE6C that markedly reduced the ability of Pγ to augment the enzyme folding. Thus, we conclude that the Rambusch adCSNB is triggered by low levels of the constitutively active PDE6. Finally, we examined PDE6C-L858V, which models PDE6B-L854V, an RP-linked mutation that alters the protein isoprenyl modification. This analysis suggests that the type of prenyl modifications does not impact the folding of PDE6, but it modulates the enzyme affinity for its trafficking partner PDE6D. Hence, the pathogenicity of PDE6B-L854V likely arises from its trafficking deficiency. Taken together, our results demonstrate the effectiveness of the PDE6C expression system to evaluate pathogenicity and elucidate the mechanisms of PDE6 mutations in retinal diseases.

The Impact of Mother-Daughter and Father-Daughter Relationships on Drug Refusal Self-Efficacy Among African American Adolescent Girls in Urban Communities

This study yielded interesting findings on the effect of mother-daughter and father-daughter relationships on drug refusal self-efficacy for urban African American girls between the ages of 11 and 14. The questionnaire consisted of assessments on the quality of the girls’ mother and father relationships and their perceived ability to refuse drugs. The quality of the father-daughter relationship significantly predicted drug refusal self-efficacy for urban African American girls. Implications of these findings are discussed.

Aryl Hydrocarbon Receptor-interacting Protein-like 1 Is an Obligate Chaperone of Phosphodiesterase 6 and Is Assisted by the γ-Subunit of Its Client

Phosphodiesterase 6 (PDE6) is the effector enzyme in the phototransduction cascade and is critical for the health of both rod and cone photoreceptors. Its dysfunction, caused by mutations in either the enzyme itself or AIPL1 (aryl hydrocarbon receptor-interacting protein-like 1), leads to retinal diseases culminating in blindness. Progress in research on PDE6 and AIPL1 has been severely hampered by failure to express functional PDE6 in a heterologous expression system. Here, we demonstrated that AIPL1 is an obligate chaperone of PDE6 and that it enables low yield functional folding of cone PDE6C in cultured cells. We further show that the AIPL1-mediated production of folded PDE6C is markedly elevated in the presence of the inhibitory Pγ-subunit of PDE6. As illustrated in this study, a simple and sensitive system in which AIPL1 and Pγ are co-expressed with PDE6 represents an effective tool for probing structure-function relationships of AIPL1 and reliably establishing the pathogenicity of its variants.

A phase II study of capecitabine and oxaliplatin combination chemotherapy in patients with inoperable adenocarcinoma of the gall bladder or biliary tract

BACKGROUND

Advanced biliary tract carcinomas are associated with a poor prognosis, and palliative chemotherapy has only modest benefit. This multi-centre phase II study was conducted to determine the efficacy of capecitabine in combination with oxaliplatin in patients with inoperable gall bladder or biliary tract cancer.

METHODS

This was a Phase II, non-randomised, two-stage Simon design, multi-centre study. Ethics approval was sought and obtained by the North West MREC, and then locally by the West Glasgow Hospitals Research Ethics Committee. Eligible patients with inoperable locally advanced or metastatic adenocarcinoma of the gall bladder or biliary tract and with adequate performance status, haematologic, renal, and hepatic function were treated with capecitabine (1000 mg/m(2) po, twice daily, days 1-14) and oxaliplatin (130 mg/m(2) i.v., day 1) every 3 weeks for up to six cycles. The primary objective of the study was to determine the objective tumour response rates (complete and partial). The secondary objectives included assessment of toxicity, progression-free survival, and overall survival.

RESULTS

Forty-three patients were recruited between July 2003 and December 2005. The regimen was well tolerated with no grade 3/4 neutropenia or thrombocytopenia. Grade 3/4 sensory neuropathy was observed in six patients. Two-thirds of patients received their chemotherapy without any dose delays. Overall response rate was 23.8% (95% CI 12.05-39.5%). Stable disease was observed in a further 13 patients (31%) and progressive disease observed in 12 (28.6%) of patients. The median progression-free survival was 4.6 months (95% CI 2.8-6.4 months; Fig. 1) and the median overall survival 7.9 months (95% CI 5.3-10.4 months; Fig. 2). Fig. 1 Progression-free survival Fig. 2 Overall survival

CONCLUSION

Capecitabine combined with oxaliplatin has a lower disease control and shorter overall survival than the combination of cisplatin with gemcitabine which has subsequently become the standard of care in this disease. However, capecitabine in combination with oxaliplatin does have modest activity in this disease, and can be considered as an alternative treatment option for patients in whom cisplatin and/or gemcitabine are contra-indicated.

Socioeconomic status, human papillomavirus, and overall survival in head and neck squamous cell carcinomas in Toronto, Canada

BACKGROUND

Despite universal healthcare in some countries, lower socioeconomic status (SES) has been associated with worse cancer survival. The influence of SES on head and neck cancer (HNC) survival is of immense interest, since SES is associated with the risk and prognostic factors associated with this disease.

PATIENTS AND METHODS

Newly diagnosed HNC patients from 2003 to 2010 (n=2124) were identified at Toronto's Princess Margaret Cancer Centre. Principal component analysis was used to calculate a composite score using neighbourhood-level SES variables obtained from the 2006 Canada Census. Associations of SES with overall survival were evaluated in HNC subsets and by p16 status (surrogate for human papillomavirus).

RESULTS

SES score was higher for oral cavity (n=423) and p16-positive oropharyngeal cancer (OPC, n=404) patients compared with other disease sites. Lower SES was associated with worse survival [HR 1.14 (1.06-1.22), p=0.0002], larger tumor staging (p<0.001), current smoking (p<0.0001), heavier alcohol consumption (p<0.0001), and greater comorbidity (p<0.0002), but not with treatment regimen (p>0.20). After adjusting for age, sex, and stage, the lowest SES quintile was associated with the worst survival only for OPC patients [HR 1.66 (1.09-2.53), n=832], primarily in the p16-negative subset [HR 1.63 (0.96-2.79)]. The predictive ability of the prognostic models improved when smoking/alcohol was added to the model (c-index 0.71 vs. 0.69), but addition of SES did not (c-index 0.69).

CONCLUSION

SES was associated with survival, but this effect was lost after accounting for other factors (age, sex, TNM stage, smoking/alcohol). Lower SES was associated with greater smoking, alcohol consumption, comorbidity, and stage.

PERIPHERAL NERVE BING-NEEL SYNDROME

Background

Bing-Neel syndrome (BNS) is a rare manifestation of Waldenstrom's Macroglobulinaemia (WM) due to direct infiltration of the central nervous system. Isolated peripheral nerve infiltration has not been described but as the blood-nerve-barrier has similar characteristics to the blood-brain-barrier, CNS-penetrating chemotherapy would be required.

Case

A 43 year-old man was diagnosed with WM after presenting with constitutional symptoms; IgMk paraprotein (34.6 g/L) and lymphoplasmacytoid cells in the bone marrow. He received R-CVP (Rituximab, Cyclophosphamide, Vincristine, and Prednisolone) with good partial haematological response and minimal distal sensory vincristine-related neuropathy. Ten months later he developed a rapidly progressive, symmetric sensorimotor deficit in all four limbs with impairment of walking and hand clumsiness, MRC sum score=61/70. Electrophysiology showed a non-length dependant axonal neuropathy with patchy slowing. Sural nerve biopsy revealed a patchy infiltrate WM cells. He tolerated 4 cycles of blood-nerve-barrier penetrating multi-agent chemotherapy, IDARAM (idarubicin, dexamethasone, cytosine arabinoside, methotrexate, cytosine arabinoside plus intrathecal methotrexate). A marked improvement was seen during treatment and by 3 months later MRC score was 70/70. No electrophysiological difference was detectable at this stage.

Discussion

Peripheral BNS is not a recognised neurological manifestation of WM but with appropriate treatment a good outcome may be achieved.

The effects of glucuronic acid and N-acetyl-D-glucosamine on in vitro fertilisation of porcine oocytes

High incidences of polyspermic penetration continue to challenge researchers during porcine in vitro fertilisation (IVF). The aim of this study was to reduce the incidence of polyspermy by increasing the perivitelline space thickness with glucuronic acid and N-acetyl-D-glucosamine (GlcNAc) supplementation during oocyte maturation. After maturation, zona pellucida and perivitelline space thicknesses, intracellular glutathione concentrations and fertilisation kinetics were measured, in addition to embryonic cleavage and blastocyst formation at 48h and 144h after IVF, respectively. There were no significant differences between the treatments for zona pellucida thickness, penetration rates, male pronuclear formation or cortical granule exocytosis. Glucuronic acid supplementation significantly increased (PPPP<0.05) of cleavage and blastocyst formation by 48 and 144h after IVF compared with all other groups. These results indicate that supplementing with 0.005mM glucuronic acid and 0.005mM GlcNAc during oocyte maturation decreases the incidence of polyspermic penetration by increasing perivitelline space thickness and improving embryo development in pigs.

Fasting Serum Glucose and Cholesterol as Predictors of Cardiovascular Reactivity to Acute Stress in a Sample of African American College Students

OBJECTIVE

African Americans are at a greater risk of cardiovascular hyperactivity to stress than Caucasians; however the risk factors for this activity are not clearly delineated for African Americans. The purpose of this study was to determine the ability of fasting serum cholesterol concentration and fasting serum glucose (FSG) to predict cardiovascular reactivity to stress in African Americans.

DESIGN, SETTING, PARTICIPANTS

Serum cholesterol concentration and FSG levels were measured in 48 (40 women, 8 men) African American college students aged 18-30 years. Heart rate, cardiac output, stroke volume, mean arterial pressure and systolic and diastolic blood pressure were measured as the participants viewed a racially noxious scene on a digital video disc. Measurements were taken prior to the scene (pre stressor period), during the scene (stressor period), and while the participant recovered from the scene (recovery period).

RESULTS

A multiple regression analysis revealed that total serum cholesterol and LDL significantly predicted diastolic blood pressure during the pre-stressor period. FSG significantly predicted mean arterial pressure during the recovery period, and predicted stroke volume during the pre-stressor period, stressor period, and the recovery period.

CONCLUSIONS

FSG was a better predictor of cardiovascular reactivity to stress than serum cholesterol concentration, predicting mean arterial pressure and stroke volume. This finding may be due to the association of glucose with diabetes, which is more prevalent in African Americans.