A single site in human β-hexosaminidase A binds both 6-sulfate-groups on hexosamines and the sialic acid moiety of GM2 ganglioside

AbstractHuman β-hexosaminidase A (Hex A) (αβ) is composed of two subunits whose primary structures are ∼60% identical. Deficiency of either subunit results in severe neurological disease due to the storage of GM2 ganglioside; Tay–Sachs disease, α deficiency, and Sandhoff disease, β deficiency. Whereas both subunits contain active sites only the α-site can efficiently bind negatively charged 6-sulfated hexosamine substrates and GM2 ganglioside. We have recently identified the αArg424 as playing a critical role in the binding of 6-sulfate-containing substrates, and βAsp452 as actively inhibiting their binding. To determine if these same residues affect the binding of the sialic acid moiety of GM2 ganglioside, an αArg424Gln form of Hex A was expressed and its kinetics analyzed using the GM2 activator protein:[3H]-GM2 ganglioside complex as a substrate. The mutant showed a ∼3-fold increase in its Km for the complex. Next a form of Hex B (ββ) containing a double mutation, βAspLeu453AsnArg (duplicating the α-aligning sequences), was expressed. As compared to the wild type (WT), the mutant exhibited a >30-fold increase in its ability to hydrolyze a 6-sulfated substrate and was now able to hydrolyze GM2 ganglioside when the GM2 activator protein was replaced by sodium taurocholate. Thus, this α-site is critical for binding both types of negatively charge substrates

High prevalence of impaired awareness of hypoglycemia and severe hypoglycemia among people with insulin-treated type 2 diabetes: The Dutch Diabetes Pearl Cohort

Objective People with type 2 diabetes on insulin are at risk for hypoglycemia. Recurrent hypoglycemia can cause impaired awareness of hypoglycemia (IAH), and increase the risk for severe hypoglycemia. The aim of this study was to assess the prevalence and determinants of self-reported IAH and severe hypoglycemia in a Dutch nationwide cohort of people with insulin-treated type 2 diabetes. Research design and methods Observational study of The Dutch Diabetes Pearl, a cohort of people with type 2 diabetes treated in primary, secondary and tertiary diabetes care centers. The presence of IAH and the occurrence of severe hypoglycemia in the past year, defined as an event requiring external help to re

Sex differences in cardiometabolic risk factors, pharmacological treatment and risk factor control in type 2 diabetes: findings from the Dutch Diabetes Pearl cohort

Introduction Sex differences in cardiometabolic risk factors and their management in type 2 diabetes (T2D) have not been fully identified. Therefore, we aimed to examine differences in cardiometabolic risk factor levels, pharmacological treatment and achievement of risk factor control between women and men with T2D. Research design and methods Cross-sectional data from the Dutch Diabetes Pearl cohort were used (n=6637, 40% women). Linear and Poisson regression analyses were used to examine sex differences in cardiometabolic risk factor levels, treatment, and control. Results Compared with men, women had a significantly higher body mass index (BMI) (mean difference 1.79kg/ m2 (95% CI 1.49 to 2.08)), while no differences were found in hemoglobin A1c (HbA1c) and systolic blood pressure (SBP). Women had lower diastolic blood pressure (−1.94mm Hg (95% CI −2.44 to −1.43)), higher total cholesterol (TC

Comparing masticatory performance and mixing ability

Masticatory performance has often been measured by determining an individual's capacity to comminute a test food. Another method to determine masticatory performance, which is now widely used, evaluates the ability to mix and knead a food bolus. Two-coloured chewing gum and paraffin wax have been used as test foods for the quantification of the mixing ability. The aim of our study was to compare the results obtained with the comminution of an artificial test food and the results obtained from mixing of a two-coloured chewing gum. The degree of mixing of the colours of the chewing gum was quantified with an optical method. Twenty young subjects with a natural dentition ( average age 24 years) and twenty elderly subjects, mostly with complete dentures ( average age 72 years), participated in the study. Significant differences in masticatory performance between the two groups were detected with both methods. However, the comminution test was better in discriminating the masticatory performance of the two groups. The mixing ability test with the two-coloured chewing gum proofed to be a good method to determine masticatory function in subjects with a compromised masticatory performance ( elderly subjects). However, the method appeared to be less suitable for subjects with a good masticatory performance ( young subjects)

Comparing masticatory performance and mixing ability

Masticatory performance has often been measured by determining an individual's capacity to comminute a test food. Another method to determine masticatory performance, which is now widely used, evaluates the ability to mix and knead a food bolus. Two-coloured chewing gum and paraffin wax have been used as test foods for the quantification of the mixing ability. The aim of our study was to compare the results obtained with the comminution of an artificial test food and the results obtained from mixing of a two-coloured chewing gum. The degree of mixing of the colours of the chewing gum was quantified with an optical method. Twenty young subjects with a natural dentition ( average age 24 years) and twenty elderly subjects, mostly with complete dentures ( average age 72 years), participated in the study. Significant differences in masticatory performance between the two groups were detected with both methods. However, the comminution test was better in discriminating the masticatory performance of the two groups. The mixing ability test with the two-coloured chewing gum proofed to be a good method to determine masticatory function in subjects with a compromised masticatory performance ( elderly subjects). However, the method appeared to be less suitable for subjects with a good masticatory performance ( young subjects)

Force control in the absence of visual and tactile feedback

Motor control tasks like stance or object handling require sensory feedback from proprioception, vision and touch. The distinction between tactile and proprioceptive sensors is not frequently made in dynamic motor control tasks, and if so, mostly based on signal latency. We previously found that force control tasks entail more compliant behavior than a passive, relaxed condition and by neuromuscular modeling we were able to attribute this to adaptations in proprioceptive force feedback from Golgi tendon organs. This required the assumption that both tactile and visual feedback are too slow to explain the measured adaptations in face of unpredictable force perturbations. Although this assumption was shown to hold using model simulations, so far no experimental data is available to validate it. Here we applied a systematic approach using continuous perturbations and engineering analyses to provide experimental evidence for the hypothesis that motor control adaptation in force control tasks can be achieved using proprioceptive feedback only. Varying task instruction resulted in substantial adaptations in neuromuscular behavior, which persisted after eliminating visual and/or tactile feedback by a nerve block of the nervus plantaris medialis. It is concluded that proprioception adapts dynamic human ankle motor control even in the absence of visual and tactile feedbac

The influence of auditory and visual information on the perception of crispy food

The influence of auditory and/or visual information on the perception of crispy food and on the physiology of chewing was investigated. Participants chewed biscuits of three different levels of crispness under four experimental conditions: no masking, auditory masking, visual masking, and auditory plus visual masking. The order of the four masking condition blocks was randomized. The sound of chewing was masked by loud sounds on a headphone and visual masking of the food was achieved by closing the eyes. We measured skull vibration and the number of chewing cycles until swallowing. Subsequently, texture and sound attributes were scored. Auditory masking led to significant lower scores on the attributes sound and snapping, but only for the participants who started the experiments with auditory plus visual masking. The other participants were not influenced by auditory masking. The memory of the unmodified stimuli helped to maintain accurate sound perception in later trials

Effect of dipyridamole on myocardial reperfusion injury: A double-blind randomized controlled trial in patients undergoing elective coronary artery bypass surgery

Dipyridamole reduces reperfusion-injury in preclinical trials and may be beneficial in patients undergoing coronary angioplasty, but its effect on patients undergoing coronary artery bypass grafting (CABG) is unknown. We hypothesized that dipyridamole limits myocardial reperfusion-injury in patients undergoing CABG. The trial design was a double-blind trial randomizing between pretreatment with dipyridamole or placebo. In all, 94 patients undergoing elective on-pump CABG were recruited between February 2010 and June 2012. The primary endpoint was plasma high-sensitive (hs-) troponin-I at 6, 12, and 24 hours after reperfusion. Secondary endpoints were the occurrence of bleeding, arrhythmias, need for inotropic support, and intensive care unit length of stay. Finally, 79 patients (33 dipyridamole) were included in the per-protocol analysis. Dipyridamole did not significantly affect postoperative hs-troponin-I (change in plasma hs-troponin I -3% [95% confidence interval -23% to 36%]; P > 0.1). Secondary endpoints did not differ between groups. Dipyridamole prior to CABG does not significantly reduce postoperative hs-troponin release