pH-sensitive expression of calcium-sensing receptor (CaSR) in type-B intercalated cells of the cortical collecting ducts (CCD) in mouse kidney

Background The localization and role of the calcium-sensing receptor (CaSR) along the nephron including the collecting ducts is still open to debate. Methods Using the quantitative, highly sensitive in situ hybridization technique and a double-staining immunohistochemistry technique, we investigated the axial distribution and expression of CaSR along the nephron in mice (C57B/6J) treated for 6 days with acid or alkali diets. Results Under control condition, CaSR was specifically localized in the cortical and medullary thick ascending limb of Henle’s loop (CTAL and MTAL), macula densa (MD), distal convoluted tubule (DCT), and CCD (TALs, MD > DCT, CCD). Along the CCD, CaSR was co-localized with an anion exchanger type 4 (AE4), a marker of the basolateral membrane of type-B intercalated cell (IC-B) in mice. On the contrary, CaSR was not detected either in principal cells (PC) or in type-A intercalated cell (IC-A). CaSR expression levels in IC-B significantly (P < 0.005) decreased when mice were fed NH4Cl (acid) diets and increased when animals were given NaHCO3 (alkali) diets. As expected, cell heights of IC-A and IC-B significantly (P < 0.005) increased in the above experimental conditions. Surprisingly, single infusion (ip) of neomycin, an agonist of CaSR, significantly (P < 0.005) increased urinary Ca excretion without further increasing the hourly urine volume and significantly (P < 0.05) decreased urine pH. Conclusion CaSR, cloned from rat kidney, was localized in the basolateral membrane of IC-B and was more expressed during alkali-loading. Its alkali-sensitive expression may promote urinary alkali secretion for body acid–base balance.

Synthesis and reactivity towards DIBAL-H of Cyclo-Siloxanes cyclo-[R2SiOSi(Ot-Bu)2O]2, cyclo-(t-BuO)2Si(OSiR2)2O, and cyclo-R2Si[Osi(Ot-Bu)2]2O (R=Me, Ph)

The six-, eight- and twelve-membered cyclo-siloxanes, cyclo-[R₂SiOSi(Ot-Bu)₂O]₂ (R = Me (1), Ph (2)), cyclo-(t-BuO)₂Si(OSiR₂)₂O (R = Me (3), Ph (4)), cyclo-R₂Si[OSi(Ot-Bu)₂]₂O (R = Me (5), Ph (6)) and cyclo-[(t-BuO)₂Si(OSiMe₂)₂O]₂ (3a) were synthesized in high yields by the reaction of (t-BuO)₂Si(OH)₂ and [(t-BuO)₂SiOH]₂O with R₂SiCl₂ and (R₂SiCl)₂O (R = Me, Ph). Compounds 1 - 6 were characterized by solution and solid-state ²⁹Si NMR spectroscopy, electrospray mass spectrometry and osmometric molecular weight determination. The molecular structure of 4 has been determined by single crystal X-ray diffraction and features a six-membered cyclo-siloxane ring that is essentially planar. The reduction of 1 - 6 with i-Bu₂AlH (DIBAL-H) led to the formation of the metastable aluminosiloxane (t-BuO)₂Si(OAli-Bu₂)₂ (7) along with Me₂SiH₂ and Ph₂SiH₂.

Influence of pH on hygral expansion, relaxation shrinkage and extensibility of wool fabric

The standard tests for relaxation shrinkage and hygral expansion of wool fabric take no account of pH. It is shown in this work that the pH of the solution in which wool fabric is relaxed as part of the procedure for measuring dimensional properties has a significant influence on the results. At around pH 4.8, which is close to the isoelectric point of wool, the hygral expansion reaches its greatest value and drops at both lower and higher pHs. A similar relationship between pH and extensibility of wool fabric was observed. Values of relaxation shrinkage were found to be dependant on pH. The reasons for the pH dependence of dimensional properties are discussed and these include changes in wool fiber swelling, yarn crimp and polymer relaxation phenomena with changes in pH.

Trimethylene-bridged tetraorganodistannoxanes{[Me3SiCH2(RCOO)Sn(CH2)3Sn(OOCR)CH2SiMe3]O}n(R=Ph,2,4-Me2C6H3): control of structure by variation of R*

The synthesis of trimethylene-bridged carboxylate-substituted tetraorganodistannoxanes {[Me_3SiCH_2(RCOO)Sn(CH_2)_3Sn(OOCR)CH_2SiMe_3]O}_n (1, R = Ph; 2, R = 2,4-Me_2C_6H_3) is reported. Depending on the structure of R, in the solid state these compounds are either dimers (1, n = 2, cis-isomer) with a ladder-type structure or tetramers (2, n = 4) with a double ladder-type structure.

Dependence of wool fabric dimensions on temperature and pH

Through a series of experimental analysis of temperature and pH value on the expansion of wool fiber and wool fabrics size change. In the pH2.1 solution, the wool fabric size declines with increasing temperature, changing the magnitude depends on the fabric and fabric shape rate. isoelectric point of pH4.8 in the wool, the fibers expand to reach the minimum, while the size of the fabric, along with the solution acidity increases.

Tensile behaviour of wool fabric as a function of fabric pH

Wool fabric extensibility under a 5 N/cm load was observed to be greatest at the wool isoelectric point of pH 4.8 and lower at both pH 2.1 and pH 7.2. The impact of pH on fabric extensibility is similar to the variation in fabric hygral expansion previously observed. Fabric stress-strain curves at different pHs show that for a given fabric extension level, the work required to stretch a fabric was less at pH 2.1 than at pH 4.8. These results confirm the fact that the strength of wool fabric is at a maximum when the pH of the fibres is close to the isoelectric point.

Monolayer behavior of a pyridyl head-group-containing amphiphile and its miscibility with poly(D,L-lactide-co-glycolide) on different pH subphase

In this paper, we investigated the Langmuir film and Langmuir–Blodgett (LB) monolayer film of a nonionic amphiphilic molecule, 4-(6-p-pyridyloxyl)hexyloxyl-4′-dodecyloxylazobenzene (C12AzoC6Py) and its mixture with poly(d,l-lactide-co-glycolide) (PLG) at different subphase pH values (2.0, 2.6, 3.3, 4.4, and 6.5, respectively) by surface pressure–area (π–A) isotherms, in situ interface Brewster angle microscopy (BAM), and ex situ atomic force microscopy (AFM). For pure C12AzoC6Py, its π–A isotherms display a plateau when the subphase pH value is lower than 3.0. The pressure of the plateau increases with the decrease of pH until 2.0. Over the plateau, the π–A isotherms become almost identical to the one under neutral conditions. The appearance of such a plateau can be explained as the coexistence of protonation and unprotonation of pyridyl head groups of the employed amphiphile. In contrast to the homogeneous surface morphology of pure C12AzoC6Py near the plateau by BAM observation, the surface in the case of its mixing with PLG exhibits a dendritic crystalline state under low surface pressure at subphase pH lower than 3.0. The crystalline state becomes soft and gradually melts into homogeneous aggregates with surface pressure increasing to a higher value than that of the plateau. Meanwhile, the hydrolysis of PLG in the mixture system at the interface has been affirmed to be restrained to a very large extent. And the PLG was believed to be compelled to the up layer of the LB film due to the phase separation, which is examined by AFM. Based on the experimental results, the corresponding discussion was also performed.

pH-detachable polymer brushes formed using titanium−diol coordination chemistry and living radical polymerization (RAFT)

pH-detachable poly(styrene) brushes formed on indium−tin oxide (ITO) glass substrates using metal complex chemistry and reversible addition−fragmentation chain transfer (RAFT) polymerization was described. These pH-detachable polymeric brushes were generated using both “graft-from” and “graft-to” methodologies. The methodologies involved either the surface self-assembly of catechol-functional RAFT agents (graft-from) or catechol-terminal polymer chains (graft-to) onto the ITO substrate via titanium−diol coordination. The stepwise functionalization of the ITO glass surfaces was characterized successfully using X-ray photoelectron spectroscopy (XPS) and contact angle measurement. Poly(styrene) brushes generated using the “graft-from” method were denser than those generated using the “graft-to” method, as exemplified by atom force microscopy (AFM) and quantified using cyclic voltammetry. Poly(styrene) brushes assembled using both methods could be detached easily by manipulating the pH of the brush environment. Cyclic voltammetry was utilized to calculate precisely the surface coverage of the RAFT functionality and polymeric brush density.

Synthesis, characterization, and multilayer assembly of pH sensitive graphene−polymer nanocomposites

pH sensitive graphene−polymer composites have been prepared by the modification of graphene basal planes with pyrene-terminated poly(2-N,N′-(dimethyl amino ethyl acrylate) (PDMAEA) and poly(acrylic acid) (PAA) via π−π stacking. The pyrene-terminal PDMAEA and PAA were synthesized using reversible addition−fragmentation chain transfer (RAFT) polymerization with a pyrene-functional RAFT agent. The graphene−polymer composites were found to demonstrate phase transfer behavior between aqueous and organic media at different pH values. Atomic force microscopy (AFM) analysis revealed that the thicknesses of the graphene−polymer sheets were approximately 3.0 nm when prepared using PDMAEA (M_n: 6800 and PDI: 1.12). The surface coverage of polymer chains on the graphene basal plane was calculated to be 5.3 × 10⁻¹¹ mol cm⁻² for PDMAEA and 1.3 × 10⁻¹⁰ mol cm⁻² for PAA. The graphene−polymer composites were successfully characterized using X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR-IR) spectroscopy, and thermogravimetric analysis (TGA). Self-assembly of the two oppositely charged graphene−polymer composites afforded layer-by-layer (LbL) structures as evidenced by high-resolution scanning electron microscopy (SEM) and quartz crystal microbalance (QCM) measurements.

pH-sensitive and targeted PLGA-based drug delivery to colorectal cancer

Investigation on targeted PLGA based drug delivery system for the therapy of colorectal cancer. The results from in-vitro cell experiments indicated that prepared systems have potent cytotoxicity and high affinity to HT-29 cancer cells. Results were published on Biomedical Engineering and Informatics and ICONN conference proceeding.

Why students should learn about negative pH

A common misconception is that the pH scale runs between 0 and 14. The possible origins of this misconception are discussed and strategies to avoid the misconception are presented.

Crosslinking neat ultrathin films and nanofibres of pH-responsive poly(acrylic acid) by UV radiation

Electrospun polyelectrolyte hydrogel nanofibres are being developed for many applications including artificial muscles, scaffolds for tissue engineering, wound dressings and controlled drug release. For electrospun polyelectrolytes, a post-spinning crosslinking process is necessary for producing a hydrogel. Typically, radiation or thermal crosslinking routines are employed that require multifunctional crosslinking molecules and crosslink reaction initiators (free radical producers). Here, ultraviolet subtype-C (UVC) radiation was employed to crosslink neat poly(acrylic acid) (PAA) nanofibres and films to different crosslink densities. Specific crosslink initiators or crosslinking molecules are not necessary in this fast and simple process providing an advantage for biological applications. Scanning probe microscopy was used for the first time to measure the dry and wet dimensions of hydrogel nanofibres. The diameters of the swollen fibres decrease monotonically with increasing UVC radiation time. The fibres could be reversibly swollen/contracted by treatment with solutions of varying pH, demonstrating their potential as artificial muscles. The surprising success of UVC radiation exposure to achieve chemical crosslinks without a specific initiator molecule exploits the ultrathin dimensions of the PAA samples and will not work with relatively thick samples.

Leg muscle pH following sprint running

In an effort to compare the disturbances in leg muscle pH during sprint running, muscle biopsies were obtained from the gastrocnemius and vastus lateralis muscles of six healthy men (three endurance-trained and three nonendurance-trained) before and after a treadmill sprint run (TSR) to fatigue (54-105 s) at roughly 125% of their aerobic capacities. Following the TSR, repeated blood samples were taken from a hand vein and later analyzed for pH, PCO2, and lactic acid (HLa). The muscle specimens were analyzed in duplicate for pH and HLa. Resting-muscle pH was 7.03 +/- 0.02 (means +/- SE) and 7.04 +/- 0.01 for the gastrocnemius and vastus lateralis muscles, respectively. At the termination of the TSR, the pH in these muscles was 6.88 +/- 0.05 and 6.86 +/- 0.03, respectively. After a 400-m timed run on the track, the pH in the gastrocnemius of four of the subjects averaged 6.63 +/- 0.03, while blood pH and HLa were 7.10 +/- 0.03 and 12.3 mM, respectively. Although no differences in pH and HLa were observed between the vastus lateralis and gastrocnemius muscles at the end of the treadmill trial, it is speculated that the lesser disturbance in acid-base balance seen in endurance performers may have been due to a lesser production of metabolites in their running musculature when compared to nonendurance performers.

Electrically conductive, tough hydrogels with pH sensitivity

Electrically conductive, mechanically tough hydrogels based on a double network (DN) comprised of poly(ethylene glycol) methyl ether methacrylate (PPEGMA) and poly(acrylic acid) (PAA) were produced. Poly(3,4-ethylenedioxythiophene) (PEDOT) was chemically polymerized within the tough DN gel to provide electronic conductivity. The effects of pH on the tensile and compressive mechanical properties of the fully swollen hydrogels, along with their electrical conductivity and swelling ratio were determined. Compressive and tensile strengths as high as 11.6 and 0.6 MPa, respectively, were obtained for hydrogels containing PEDOT with a maximum conductivity of 4.3 S cm–1. This conductivity is the highest yet reported for hydrogel materials of high swelling ratios. These hydrogels may be useful as soft strain sensors because their electrical resistance changed significantly when cyclically loaded in compression.

Effect of sodium bicarbonate on [HCO3 -], pH, and gastrointestinal symptoms

Context: Sodium bicarbonate (NaHCO3) is often ingested at a dose of 0.3 g/kg body mass (BM), but ingestion protocols are inconsistent in terms of using solution or capsules, ingestion period, combining NaHCO3 with sodium citrate (Na3C6H5O7), and coingested food and fluid. Purpose: To quantify the effect of ingesting 0.3 g/ kg NaHCO3 on blood pH, [HCO3 -], and gastrointestinal (GI) symptoms over the subsequent 3 hr using a range of ingestion protocols and, thus, to determine an optimal protocol. Methods: In a crossover design, 13 physically active subjects undertook 8 NaHCO3 experimental ingestion protocols and 1 placebo protocol. Capillary blood was taken every 30 min and analyzed for pH and [HCO3 -]. GI symptoms were quantified every 30 min via questionnaire. Statistics used were pairwise comparisons between protocols; differences were interpreted in relation to smallest worthwhile changes for each variable. A likelihood of >75% was a substantial change. Results: [HCO3 -] and pH were substantially greater than in placebo for all other ingestion protocols at almost all time points. When NaHCO3 was coingested with food, the greatest [HCO3 -] (30.9 mmol/kg) and pH (7.49) and lowest incidence of GI symptoms were observed. The greatest incidence of GI side effects was observed 90 min after ingestion of 0.3 g/kg NaHCO3 solution. Conclusions: The changes in pH and [HCO3 -] for the 8 NaHCO3-ingestion protocols were similar, so an optimal protocol cannot be recommended. However, the results suggest that NaHCO3 coingested with a high-carbohydrate meal should be taken 120-150 min before exercise to induce substantial blood alkalosis and reduce GI symptoms. ABSTRACT FROM AUTHOR