Acid–base physiology: new concepts

The traditional approach to acid–base physiology is based on the Henderson–Hasselbalch equation which is derived from the ${\text{CO}}_2/{{\text{HCO}}_3}^{?}$ buffer system. However, it is becoming increasingly recognized that this is an incomplete analysis as it focuses on only one of the six reactions involving H⁺ and can lead to the incorrect assumption that CO₂ and ${{\text{HCO}}_3}^{?}$ are independently adjusted factors that ultimately determine pH. In 1983, Stewart, a Canadian physiologist, proposed that a fuller understanding of acid–base physiology required consideration of biological fluids as a complex dynamic system, taking into account the interactions of all the chemical species involved. He showed that the true independent variables controlling the pH of any given fluid compartment are: the difference in the concentration of ‘strong ions’; the total concentration of ‘weak acid’; and the PCO₂. Importantly, H⁺ and ${{\text{HCO}}_3}^{?}$ are dependent variables and it is incorrect to think of them as being specifically regulated to manipulate pH. This review will discuss the importance of pH homeostasis and highlight the implications of the Stewart approach in our understanding of acid–base control mechanisms and disorders. In particular, the true mechanisms by which the kidney regulates plasma pH will be discussed, emphasizing key misconceptions that have been propagated as a result of the traditional approach.     

Achieving Best Practice: A Review of Evidence Linked to Occupation-Focused Practice Models

ABSTRACT

The aim of this paper is to identify and synthesize evidence concerning the most widely used contemporary occupation-focused models including Ecology of human performance; Model of human occupation; Occupational adaptation; and Person–environment–occupational performance. The paper characterizes the amount and type of evidence. Evidence found includes illustrations of how the models can be applied to understand and address a particular problem or population, basic studies that test or expand theoretical concepts, psychometric studies, studies that document therapy outcomes, and studies that examine clinical reasoning and/or practice based on the models. The four models differed widely in the amount and type of evidence available.     

Highly selective and sensitive determination of free and total amino acids in Apocynum venetum L. (Luobuma tea) by a developed HPLC–FLD method coupled with pre-column fluorescent labelling

Amino acids (AA) are important chemical constituents of tea leaves remarkably influencing the quality of tea. In this study, free AA and total AA in Apocynum venetum L. (Luobuma tea) were estimated by HPLC equipped with fluorescent detector using 2-[2-(7H-dibenzo[a,g]carbazol-7-yl)-ethoxy] ethyl chloroformate (DBCEEC) as a fluorescent labelling reagent. Different parameters for derivatization and separation were optimized. AA were rapidly derivatized within 3 min at room temperature with DBCEEC. In conjunction with a gradient elution, a baseline resolution of 20 analytes was achieved on a reversed-phase Hypersil BDS C18 column. LC separation for the derivatized AA showed good reproducibility. Twenty AA were detected and showed significant linear responses with correlation coefficients (>0.9992). This developed method offered the low detection limit of 2.88–23.4 fmol.     

Vasculo–Behçet's syndrome with widespread arterial involvement

Abstract

An 18-year-old woman with a history of multiple oral ulcers followed by erythema nodosum was admitted to our hospital because of the lack of a pulse in her upper left extremity and occasional dizziness. High C-reactive protein (CRP) levels were detected in her serum. Arterial angiography showed a widespread narrowing of the major arteries, including both carotid arteries, the left vertebral artery, the left subclavian artery (branches of the aortic arch), the abdominal aorta, and left renal arteries. However, no involvement in the circle of Willis was noted, and this was confirmed by magnetic resonance angiography. Pulmonary scintigraphy showed no perfusion defect. The distribution of the arterial involvement, her youth, and nega-tive human leukocyte antigen (HLA) B51 were consistent with Takayasu arteritis, although the presence of mucocutaneous involvement favored a diagnosis of vasculo-Behçet's syndrome. We treated the patient with prednisolone and warfarin, which resulted in an improvement in CRP levels and no thrombosis-related complications.     

Analysis of electrocorticographic patterns in rats fed standard or hyperlipidic diets in a normal state or during status epilepticus

Objective: The consumption of hyperlipidic diets has grown markedly in recent decades, and several studies have linked this consumption with the development of neurodegenerative diseases. Conversely, hyperlipidic diets have been used as an alternative therapy for refractory epilepsy. The purpose of this study was to evaluate the effects of a hyperlipidic diet on brain electrical activity before and during status epilepticus (SE) using computational and mathematical methods.

Methods: Electrocorticogram (ECoG) was recorded in Wistar rats fed with standard and hyperlipidic diets. Each recording was obtained during 30-minute period (baseline), after this time, the SE was induced by pilocarpine, and recording was continued for another 30?minutes. The ECoG signals were analyzed by the following methods: power spectrum, Lempel–Ziv complexity (LZC), and fractal dimension of the phase space.

Results: Hyperlipidic diet in normal animals caused a decrease in the theta, alpha, and beta rhythm, and reduced the LZC of the brain electrical activity. However, when the animals were induced to SE, these differences between nutritional groups were not observed. SE caused in both dietary groups increase in theta, alpha, and beta rhythm values, and increase in the complexity of brain electrical activity.

Discussion: Hyperlipidic diet consumption attenuated the brain's electrical activity, suggesting that healthy individuals who habitually eat a hyperlipidic diet may develop dysfunctions such as cognitive decline and memory impairment. Furthermore, the antagonistic effect between hyperlipidic diet and SE suggests that this diet could protect against seizures.     

A pH-triggered delayed-release chronotherapeutic drug delivery system of aceclofenac for effective management of early morning symptoms of rheumatoid arthritis

Abstract

Context: Rheumatoid arthritis (RA) is differentiated as an early morning exacerbation of the core arthritis condition associated with increase in pain and stiffness in joints and necessitate for medication. Objective: The aim of the present work was to develop and optimise a pH-triggered delayed-release colon-specific aceclofenac microspheres and to accomplish chronotherapy of RA. Methods: A 3-factor, 3-level Box–Behnken design (BBD) was used to optimise selected variables. Developed formulation was evaluated for in vivo delayed response and anti-arthritis activity in rats. Results: The particle size and encapsulation efficacy of these microspheres were 117.36?±?10.54?µm and 85.06?±?5.85%, respectively. Optimised formulation was analysed by SEM, DSC, X-RPD and FTIR. The in vivo evaluation reveled delayed anti-inflammatory activity in carrageenan-induced rats and anti-arthritic activity in freund’s adjuvant-induced arthritis rats. Conclusion: The optimised aceclofenac microspheres formulation is potential for the chronotherapy of early morning symptoms of RA.     

DNA–chitosan nanoparticles improve DNA vaccine-elicited immunity against Newcastle disease virus through shuttling chicken interleukin-2 gene

In this study, pCAGG-ChIL2 plasmid DNA containing the chicken interleukin-2 (ChIL-2) gene was used to prepare DNA–chitosan nanoparticles (CNPs). The CNPs prepared were spherical, with mean diameters between 100 and 200?nm, have a positive surface charge, and could protect DNA against DNase I degradation. The CNPs prepared were successfully used to transfect the Df-1 cell line with almost no cytotoxicity. CNPs prepared at an amino group to phosphate group ratio (N/P ratio) of 16 provided the highest transfection efficiency (1.1%) in medium with a pH of 6.5. When pCAGG-ChIL2 CNPs were administered to chickens simultaneously with a DNA vaccine against Newcastle disease virus (NDV), haemagglutination inhibition antibody titers and serum interferon-γ (IFN-γ) levels were significantly higher than in chickens immunised with the NDV DNA vaccine alone (p?<?0.05). The results demonstrate that pCAGG-ChIL2 CNPs improve DNA vaccine-elicited immunity against NDV challenge.