The appropriate use of second-generation oral hypoglycemic agents is limited by the lack of definitive guidelines for their use in elderly diabetic patients and controversy over relative dosing ...equivalence. We previously conducted a survey to determine the feasibility and cost of converting diabetic patients from glipizide to glyburide. This new survey provides an extended, 24-month follow-up in 210 patients and focuses on findings in elderly patients. The mean final daily dose of glyburide (11.6 mg) was lower than the preconversion dose of glipizide (18.7 mg) (P < or = 0.0001). One hundred forty-one (67%) patients successfully continued glyburide for 24 months, including 103 (73%) patients who were 65 years of age or older. There was no apparent correlation between age and final dose of glyburide, ability to continue glyburide, or risk of stopping glyburide. The conversion program reduced the mean daily dose after switching from glipizide to glyburide, which was preserved throughout the observation period. The program also conferred a 49% savings in the projected 2-year expenditures for second-generation oral hypoglycemic agents.
Despite extensive clinical experience with second-generation oral hypoglycemic agents, the relative dosing equivalence of glyburide and glipizide remains controversial. A prospective survey was ...conducted to determine the feasibility and cost of converting noninsulin-dependent diabetic patients from glipizide to glyburide. A total of 211 patients previously stabilized on glipizide were converted to glyburide and returned to their respective clinics at least once during the following six months. The mean daily dose (+/- SD) of glipizide before conversion was 18.7 +/- 12.32 mg; the mean daily dose of glyburide after seven months was 9.9 +/- 6.52 mg (P less than 0.001, paired t test). Glyburide was well tolerated. The conversion program appeared to be successful and resulted in a 47% reduction in the mean daily dose after conversion from glipizide to glyburide, which, in turn, conferred a 43% savings in the projected yearly expenditures for second-generation oral hypoglycemics.
Histone acetylation and deposition of H2A.Z variant are integral aspects of active transcription. In
, the single DOMINO chromatin regulator complex is thought to combine both activities
an unknown ...mechanism. Here we show that alternative isoforms of the DOMINO nucleosome remodeling ATPase, DOM-A and DOM-B, directly specify two distinct multi-subunit complexes. Both complexes are necessary for transcriptional regulation but through different mechanisms. The DOM-B complex incorporates H2A.V (the fly ortholog of H2A.Z) genome-wide in an ATP-dependent manner, like the yeast SWR1 complex. The DOM-A complex, instead, functions as an ATP-independent histone acetyltransferase complex similar to the yeast NuA4, targeting lysine 12 of histone H4. Our work provides an instructive example of how different evolutionary strategies lead to similar functional separation. In yeast and humans, nucleosome remodeling and histone acetyltransferase complexes originate from gene duplication and paralog specification.
generates the same diversity by alternative splicing of a single gene.
Keratins are structural proteins that are abundant in human skin, nails, and hair, where they provide mechanical strength. In the present study, we investigate the molecular mobilities and structures ...of three keratin-rich materials with clearly different mechanical properties: nails, stratum corneum (upper layer of epidermis), and keratinocytes (from lower layer of epidermis). We use solid-state NMR on natural-abundance 13C to characterize small changes in molecular dynamics in these biological materials with close to atomistic resolution. One strong advantage of this method is that it detects small fractions of mobile components in a molecularly complex material while it simultaneously gives information on the rigid components in the very same sample. The molecular mobility can be linked to mechanical material properties in different conditions, including hydration or exposure to osmolytes or organic solvents. Importantly, the study revealed that the response to both hydration and addition of urea is clearly different for the nail keratin compared to the stratum corneum keratin. The comparative examination of these materials may provide a better understanding of skin diseases originating from keratin malfunction and contributes to the design and development of new materials.
Acetylation of lysine 16 of histone H4 (H4K16ac) stands out among the histone modifications, because it decompacts the chromatin fiber. The metazoan acetyltransferase MOF (KAT8) regulates ...transcription through H4K16 acetylation. Antibody-based studies had yielded inconclusive results about the selectivity of MOF to acetylate the H4 N-terminus. We used targeted mass spectrometry to examine the activity of MOF in the male-specific lethal core (4-MSL) complex on nucleosome array substrates. This complex is part of the Dosage Compensation Complex (DCC) that activates X-chromosomal genes in male Drosophila. During short reaction times, MOF acetylated H4K16 efficiently and with excellent selectivity. Upon longer incubation, the enzyme progressively acetylated lysines 12, 8 and 5, leading to a mixture of oligo-acetylated H4. Mathematical modeling suggests that MOF recognizes and acetylates H4K16 with high selectivity, but remains substrate-bound and continues to acetylate more N-terminal H4 lysines in a processive manner. The 4-MSL complex lacks non-coding roX RNA, a critical component of the DCC. Remarkably, addition of RNA to the reaction non-specifically suppressed H4 oligo-acetylation in favor of specific H4K16 acetylation. Because RNA destabilizes the MSL-nucleosome interaction in vitro we speculate that RNA accelerates enzyme-substrate turn-over in vivo, thus limiting the processivity of MOF, thereby increasing specific H4K16 acetylation.
Membrane permeability based on mesh analysis Stenqvist, Björn; Ericson, Marica B.; Gregoire, Sebastien ...
Journal of colloid and interface science,
03/2023, Letnik:
633
Journal Article
Recenzirano
Odprti dostop
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The main function of a membrane is to control the exchange of matter between the surrounding regions. As such, accurate modeling of membranes is important to properly describe their ...properties. In many cases in both biological systems and technical applications, the membranes are composite structures where transport properties may vary between the different sub-regions of the membrane. In this work we develop a method based on Mesh analysis that is asymptotically exact and can describe diffusion in composite membrane structures. We do this by first reformulating a generalized Fick’s law to include the effects from activity coefficient, diffusion coefficient, and solubility using a single condensed parameter. We then use the derived theory and Mesh analysis to, in essence, retrieve a finite element method approach. The calculated examples are based on a membrane structure that reassembles that of the brick and mortar structure of stratum corneum, the upper layer of our skin. Resulting concentration profiles from this procedure are then compared to experimental results for the distribution of different probes within intact stratum corneum, showing good agreement. Based on the derived approach we further investigate the impact from a gradient in the fluidity of the stratum corneum mortar lipids across the membrane, and find that it is substantial. We also show that anisotropic organisation of the lipid mortar can have large impact on the effective permeability compared to isotropic mortar lipids. Finally, we examine the effects of corneocyte swelling, and their lateral arrangement in the membrane on the overall membrane permeability.
Sugammadex shows a dose–response relationship for reversal of neuromuscular block (NMB) during propofol anaesthesia. Sevoflurane, unlike propofol, can prolong the effect of neuromuscular blocking ...agents (NMBAs), increasing recovery time. This open-label, randomized, dose-finding trial explored sugammadex dose–response relationships, safety, and pharmacokinetics when administered for reversal of moderate rocuronium- or vecuronium-induced NMB during sevoflurane maintenance anaesthesia.
After anaesthesia induction with propofol, adult patients were randomized to receive single-dose rocuronium 0.9 mg kg−1 or vecuronium 0.1 mg kg−1, with maintenance doses as needed. Anaesthesia was maintained with sevoflurane. NMB was monitored using acceleromyography. After the last dose of NMBA, at reappearance of T2, single-dose sugammadex 0.5, 1.0, 2.0, or 4.0 mg kg−1 or placebo was administered. The primary efficacy variable was time from the start of sugammadex administration to recovery of T4/T1 ratio to 0.9. Safety assessments were performed throughout.
The per-protocol population comprised 93 patients (rocuronium, n=46; vecuronium, n=47). A statistically significant dose–response relationship was demonstrated for mean recovery times of T4/T1 ratio to 0.9 with increasing sugammadex dose with both NMBAs: rocuronium, 96.3 min (placebo) to 1.5 min (sugammadex 4.0 mg kg−1); vecuronium, 79.0 min (placebo) to 3.0 min (sugammadex 4.0 mg kg−1). Plasma sugammadex concentrations indicated linear pharmacokinetics, independent of NMBA administered. No study drug-related serious adverse events occurred. Evidence of reoccurrence of block was reported in seven patients sugammadex 0.5 mg kg−1 (suboptimal dose), n=6; 2.0 mg kg−1, n=1.
During sevoflurane maintenance anaesthesia, sugammadex provides well-tolerated, effective, dose-dependent reversal of moderate rocuronium- and vecuronium-induced NMB.
The dosage compensation complex (DCC) of
identifies its X-chromosomal binding sites with exquisite selectivity. The principles that assure this vital targeting are known from the
model: DCC-intrinsic ...specificity of DNA binding, cooperativity with the CLAMP protein, and noncoding roX2 RNA transcribed from the X chromosome. We found that in
, a species separated from
by 40 million years of evolution, all principles are active but contribute differently to X specificity. In
, the DCC subunit MSL2 evolved intrinsic DNA-binding selectivity for rare PionX sites, which mark the X chromosome. In
, PionX motifs are abundant and not X-enriched. Accordingly, MSL2 lacks specific recognition. Here, roX2 RNA plays a more instructive role, counteracting a nonproductive interaction of CLAMP and modulating DCC binding selectivity. Remarkably, roX2 triggers a stable chromatin binding mode characteristic of DCC. Evidently, X-specific regulation is achieved by divergent evolution of protein, DNA, and RNA components.
Abstract
MSL2, the DNA-binding subunit of the Drosophila dosage compensation complex, cooperates with the ubiquitous protein CLAMP to bind MSL recognition elements (MREs) on the X chromosome. We ...explore the nature of the cooperative binding to these GA-rich, composite sequence elements in reconstituted naïve embryonic chromatin. We found that the cooperativity requires physical interaction between both proteins. Remarkably, disruption of this interaction does not lead to indirect, nucleosome-mediated cooperativity as expected, but to competition. The protein interaction apparently not only increases the affinity for composite binding sites, but also locks both proteins in a defined dimeric state that prevents competition. High Affinity Sites of MSL2 on the X chromosome contain variable numbers of MREs. We find that the cooperation between MSL2/CLAMP is not influenced by MRE clustering or arrangement, but happens largely at the level of individual MREs. The sites where MSL2/CLAMP bind strongly in vitro locate to all chromosomes and show little overlap to an expanded set of X-chromosomal MSL2 in vivo binding sites generated by CUT&RUN. Apparently, the intrinsic MSL2/CLAMP cooperativity is limited to a small selection of potential sites in vivo. This restriction must be due to components missing in our reconstitution, such as roX2 lncRNA.
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