Vertical Maxillary Measurements using a Virtual External Reference Point in Orthognathic Surgery: Technical Innovation.

It is extremely important to achieve vertical position of the upper jaw in orthognathic surgery. A common method used is measuring distances at surgery using external reference points. Unfortunately, surgeons have been making mistakes when calculating the goal distance of our external reference systems. A possible explanation is that when the author measure the baseline and goal vertical distances, the author usually do not consider the variations produced by the triangulation effect generated due the horizontal or/and transverse movements of the maxilla. A method is proposed to fix this phenomenon in an easy way through the virtual customization of the ERP in computer-assisted surgical simulation. The technique entails creating, in the planning software, the same reference system one will use at surgery. In this virtual system, one measures the difference between the baseline and target distances, and then uses them at surgery.

Nonsurgical Therapies for Basal Cell Carcinoma: A Review. / Terapias no quirúrgicas para el carcinoma basocelular: revisión.

Basal cell carcinoma (BCC) is the most prevalent malignant tumor in humans and the local destruction of tissue that can result from excision has a significant impact on well-being. Treating BCC is costly for health care systems given the high incidence of this tumor, especially in older patients. Standard treatment involves either resection with histologic assessment of margins or Mohs micrographic surgery. Surgery is sometimes contraindicated, however, due to the presence of significant comorbidity or high cosmetic expectations. For such patients, nonsurgical treatments have become available. These alternatives can offer good local control of disease, preserve function, and achieve excellent cosmetic results.

A critical review of the current knowledge regarding the biological impact of nanocellulose.

Several forms of nanocellulose, notably cellulose nanocrystals and nanofibrillated cellulose, exhibit attractive property matrices and are potentially useful for a large number of industrial applications. These include the paper and cardboard industry, use as reinforcing filler in polymer composites, basis for low-density foams, additive in adhesives and paints, as well as a wide variety of food, hygiene, cosmetic, and medical products. Although the commercial exploitation of nanocellulose has already commenced, little is known as to the potential biological impact of nanocellulose, particularly in its raw form. This review provides a comprehensive and critical review of the current state of knowledge of nanocellulose in this format. Overall, the data seems to suggest that when investigated under realistic doses and exposure scenarios, nanocellulose has a limited associated toxic potential, albeit certain forms of nanocellulose can be associated with more hazardous biological behavior due to their specific physical characteristics.

[Enterocolitis associated with Hirschsprung's Disease. Experience in a pediatric teaching hospital]. / Enterocolitis asociada a enfermedad de Hirschsprung. Experiencia en un Hospital Universitario Pediátrico.

Hirschsprung's associated enterocolitis (HAEC) is the most serious and potentially fatal complication of the disease, with a significant morbidity and mortality. The effect of HAEC varies remarkably among the publications since the lack of consensus and the absence of established diagnostic criteria. Patients diagnosed with Hirschsprung's disease (HD) were selected and treated between January 2009 and December 2012 in Fundación HOMI, finding 41 cases of HD, 6 of them with total aganglionosis. 76% of the patients had HAEC, 18 of them during the neonatal period and 6 of them after the final pull-through; 23% presented recurrent enterocolitis episodes. HAEC was the first clinical manifestation in 25 (61%) of the patients with HD. From HD patients limited to the rectum and sigmoid 67% had enterocolitis unlike TCA (total colonic agangliniosis) cases in which all presented HAEC episodes. In our setting, HAEC remains to be an unknown complication; this revision demonstrates its high incidence and mortality.

La enterocolitis asociada a la enfermedad de Hirschsprung (EAEH) es la complicación más grave y potencialmente fatal de la enfermedad, con una morbilidad y mortalidad significativas. La incidencia de EAEH varía notablemente entre las publicaciones dada la falta de consenso y la ausencia de criterios diagnósticos establecidos. Se seleccionaron los pacientes con diagnóstico de enfermedad de Hirschsprung (EH) tratados entre Enero de 2009 a Diciembre de 2012 en la Fundación Hospital de La Misericordia (HOMI) encontrando 41 casos de EH, 6 de ellos con aganglionosis total. En el 76% de los pacientes se realizó el diagnóstico de EAEH, 18 de ellos en el periodo neonatal y 6, tras el descenso definitivo; 23% presentaron episodios de enterocolitis recurrente. La EAEH fue la primera manifestación clínica en 25 (61%) de los pacientes con EH. De los pacientes con EH limitada al recto y sigmoides, un 67% tuvieron enterocolitis a diferencia de los casos de aganglionosis total del colon (ATC), donde todos presentaron episodios de EAEH.

Inclusive Approaches for Measuring Demographics of Underrepresented Populations in STEM and Biomedical Research Training Programs.

As federal strategic plans prioritize increasing diversity within the biomedical workforce, and STEM training and outreach programs seek to recruit and retain students from historically underrepresented populations, there is a need for interrogation of traditional demographic descriptors and careful consideration of best practices for obtaining demographic data. To accelerate this work, equity-focused researchers and leaders from STEM programs convened to examine approaches for measuring demographic variables. Gender, race/ethnicity, disability, and disadvantaged background were prioritized given their focus by federal funding agencies. Categories of sex minority, sexual (orientation) minority, and gender minority (SSGM) should be included in demographic measures collected by STEM programs, consistent with recommendations from White House Executive Orders and federal reports. Our manuscript offers operationalized phrasing for demographic questions and recommendations for use across student-serving programs. Inclusive demographics permit the identification of individuals who are being excluded, marginalized, or improperly aggregated, increasing capacity to address inequities in biomedical research training. As trainees do not enter training programs with equal access, accommodations, or preparation, inclusive demographic measures can welcome trainees and inform a nuanced set of program outcomes that facilitate research on intersectionality to support the recruitment and retention of underrepresented students in biomedical research.

A facile strategy for tuning the density of surface-grafted biomolecules for melt extrusion-based additive manufacturing applications.

Melt extrusion-based additive manufacturing (ME-AM) is a promising technique to fabricate porous scaffolds for tissue engineering applications. However, most synthetic semicrystalline polymers do not possess the intrinsic biological activity required to control cell fate. Grafting of biomolecules on polymeric surfaces of AM scaffolds enhances the bioactivity of a construct; however, there are limited strategies available to control the surface density. Here, we report a strategy to tune the surface density of bioactive groups by blending a low molecular weight poly(ε-caprolactone)5k (PCL5k) containing orthogonally reactive azide groups with an unfunctionalized high molecular weight PCL75k at different ratios. Stable porous three-dimensional (3D) scaffolds were then fabricated using a high weight percentage (75 wt.%) of the low molecular weight PCL5k. As a proof-of-concept test, we prepared films of three different mass ratios of low and high molecular weight polymers with a thermopress and reacted with an alkynated fluorescent model compound on the surface, yielding a density of 201-561 pmol/cm2. Subsequently, a bone morphogenetic protein 2 (BMP-2)-derived peptide was grafted onto the films comprising different blend compositions, and the effect of peptide surface density on the osteogenic differentiation of human mesenchymal stromal cells (hMSCs) was assessed. After two weeks of culturing in a basic medium, cells expressed higher levels of BMP receptor II (BMPRII) on films with the conjugated peptide. In addition, we found that alkaline phosphatase activity was only significantly enhanced on films containing the highest peptide density (i.e., 561 pmol/cm2), indicating the importance of the surface density. Taken together, these results emphasize that the density of surface peptides on cell differentiation must be considered at the cell-material interface. Moreover, we have presented a viable strategy for ME-AM community that desires to tune the bulk and surface functionality via blending of (modified) polymers. Furthermore, the use of alkyne-azide "click" chemistry enables spatial control over bioconjugation of many tissue-specific moieties, making this approach a versatile strategy for tissue engineering applications. Supplementary Information: The online version contains supplementary material available at 10.1007/s42242-024-00286-2.

Lecithin cholesterol acyltransferase (LCAT) activity in the presence of Apo-AI-derived peptides exposed to disorder-order conformational transitions.

Although the association of Apo AI with HDLs has been proposed to activate LCAT activity, the detailed molecular mechanisms involved in the process are not known. Therefore, in this study we have investigated how conformational changes in several exposed regions of Apo-AI might cause LCAT activation and for this purpose, designed a strategy to investigate three Apo AI-derived peptides. Since these peptides present the ability to adopt several secondary structure conformations, they were used to determine whether LCAT activity could be modulated in the presence of a particular conformation. Circular dichroism experiments showed that Apo AI-derived peptides in PBS displayed a disordered arrangement, with a strong tendency to adopt ß-sheet and random conformational structures as a function of concentration. However, in the presence of Lyso-C12PC, maximal percentages of α-helical structures were observed. Performed in human plasma, time-course experiments of LCAT activity under control conditions reached the highest level of (3)H-cholesteryl esters after 2.5 h incubation. In the presence of Apo AI-derived peptides, a significant increase in the production of (3)H-cholesteryl esters was observed. The present study provides an important insight into the potential interactions between LCAT and lipoproteins and also suggests that peptides, initially present in a disordered conformation, are able to sense the lipid environment provided by lipoproteins of plasma and following a disorder-to-order transition, change their conformation to an ordered α-helix.

[Magnet intestinal lesions. Case series]. / Lesiones intestinales por imanes. Serie de casos.

The ingestion of foreign bodies is a common trouble in the pediatric population, and most of cases occur between 6 months and 3 years. In general the vast majority of foreign bodies are not associated with morbidity or mortality. Ingestion of two or more magnets can lead to obstruction, fistulas, ulceration, perforation and bowel volvulus. In this series we present 4 cases of patients ingesting multiple magnets and who due to the ingested foreign body characteristics and clinical profile required surgical treatment.

Single photon emission computed tomography (SPECT) diagnostic accuracy in active unilateral condylar hyperplasia: Retrospective study.

The aim of this study was to assess the diagnostic accuracy of single photon emission tomography (SPECT) in unilateral condylar hyperplasia (UCH). To this end, 3D morphometric changes of the mandibles in one year were assessed (T0 vs. T1) and compared over SPECT results in T1, in a sample of 40 patients. A contingency table was constructed based on these results for SPECT diagnostic accuracy evaluation, classifying patients as SPECT true-positive, true-negatives, false positives and false-negatives. Additionally, the morphometric analysis was used to describe the presentation of mandibular changes using principal component analysis (PCA) and non-parametric statistics. We obtained diagnostic accuracy results of sensitivity 81%, specificity 63%, positive predictor value (PPV) 59%, negative predictor value (NPV) 83% and accuracy 70%, showing that SPECT yields poor results regarding accuracy diagnostic performance. The morphometric analysis showed that individuals without progress of asymmetry and those with more progress differ particularly in a group of landmarks representing the mental region and the right mandibular body. Based on these landmarks, difference among the four SPECT-accuracy groups was statistically significant (p < 0.001), where the landmark showing the largest change within a year had a mean increase of 1.13 + 0.66 mm. Within the limitations of the study, it seems that SPECT alone is not suitable for making surgical decisions regarding condylectomy in active UCH. Follow up with morphological assessment methods are recommended for confirming an active UCH in combination with SPECT.

Alginate-waterborne polyurethane 3D bioprinted scaffolds for articular cartilage tissue engineering.

Articular cartilage defects comprise a spectrum of diseases associated with degeneration or damage of the connective tissue present in particular joints, presenting progressive osteoarthritis if left untreated. In vitro tissue regeneration is an innovative treatment for articular cartilage injuries that is attracting not only clinical attention, but also great interest in the development of novel biomaterials, since this procedure involves the formation of a neotissue with the help of material support. In this work, functional alginate and waterborne polyurethane (WBPU) scaffolds have been developed for articular cartilage regeneration using 3D bioprinting technology. The particular properties of alginate-WBPU blends, like mechanical strength, elasticity and moistening, mimic the original cartilage tissue characteristics, being ideal for this application. To fabricate the scaffolds, mature chondrocytes were loaded into different alginate-WBPU inks with rheological properties suitable for 3D bioprinting. Bioinks with high alginate content showed better 3D printing performance, as well as structural integrity and cell viability, being most suitable for scaffolds fabrication. After 28 days of in vitro cartilage formation experiments, scaffolds containing 3.2 and 6.4 % alginate resulted in the maintenance of cell number in the range of 104 chondrocytes/scaffold in differentiated phenotypes, capable of synthesizing specialized extracellular matrix (ECM) up to 6 µg of glycosaminoglycans (GAG) and thus, showing a potential application of these scaffolds for in vitro regeneration of articular cartilage tissue.

Impact of the COVID-19 pandemic: Community and hospital shared pharmaceutical care model. Satisfaction and acceptability of patients with HIV infection on antiretroviral treatment.

OBJECTIVE: The health crisis due to the COVID-19 pandemic is a challenge in the dispensing of outpatient hospital medication (OHM). Models of Antiretroviral Therapy (ART) based on community pharmacy support (ARTCP) have proven to be successful. The aim was to evaluate the degree of satisfaction, acceptability and limitations of the implementation of ARTCP, in the context of a pandemic, in our environment. METHODS: Descriptive cross-sectional study carried out in a Barcelona hospital, during the months of July-November 2020. A telephone survey was carried out via a questionnaire on the quality dimensions of the model (degree of satisfaction, acceptability) and associated inconveniences. Data collected: demographics, antiretroviral treatment (ART), concomitant medication, drug interactions (DDIs), CD4 lymphocyte count and plasma viraemia. Data analysis included descriptive statistics. RESULTS: A total of 533 (78.0%) HIV patients receiving ART were included. 71.9% (383/533) of these patients were very satisfied and 76.2% preferred attending the community pharmacy rather than the hospital. The mean satisfaction rating was 9.3 (DS: 1.4). The benefits reported were: 1) proximity to home (406: 76.1%); 2) lower risk of contagion of COVID-19 (318: 59.7%); 3) shorter waiting time (201: 37.1%); 4) time flexibility (104: 19.5%); 5) reduction of financial expenses (35: 6.57%). A total of 11 (2%) patients reported no benefit. Only 22.9% reported disadvantages associated with ARTCP: 1) lack of privacy (65: 12.2%); 2) lack of coordinationorganization (57: 10.7%). CONCLUSIONS: The COVID-19 pandemic has had an impact on the provision of pharmaceutical care for HIV patients. The ARTPC model has proved efficient, with patients reporting a high degree of satisfaction.

Histologic findings and related diagnostic methods in condylar hyperactivity.

Condylar hyperactivity (CH) is a rare condition that entails a progressive deviation and deformation of the mandible. There is no consensus regarding characteristic histopathological features or a standardized diagnostic process; thus, histopathological analysis of the condyle cannot confirm or exclude an active CH after condylectomy is performed. An electronic search was performed in Medline, Embase, Web of Science, LILACS and grey literature up to December 2019. Additionally, a manual search was performed. Risk of bias of the included studies was assessed using the Newcastle-Ottawa Scale and the Institute of Health Economics Quality Appraisal. All analyses were performed independently and in duplicate. Seventeen articles from 660 were included. Six articles were cross-sectional studies and 11 were case series. Almost all the articles (14) described an augmented thickness of the cartilage layer associated with cartilage islands within the subchondral bone in patients affected by CH. Histological findings seem to be mostly related to the age of the sample rather than a characteristic description of CH. No clear association was found between SPECT/scintigram uptake and a specific histological finding. Hence, there is a necessity for the development of specific tools for evaluating and reporting studies where histology is needed for diagnosis confirmation.

Additive manufactured, highly resilient, elastic, and biodegradable poly(ester)urethane scaffolds with chondroinductive properties for cartilage tissue engineering.

Articular cartilage was thought to be one of the first tissues to be successfully engineered. Despite the avascular and non-innervated nature of the tissue, the cells within articular cartilage - chondrocytes - account for a complex phenotype that is difficult to be maintained in vitro. The use of bone marrow-derived stromal cells (BMSCs) has emerged as a potential solution to this issue. Differentiation of BMSCs toward stable and non-hypertrophic chondrogenic phenotypes has also proved to be challenging. Moreover, hyaline cartilage presents a set of mechanical properties - relatively high Young's modulus, elasticity, and resilience - that are difficult to reproduce. Here, we report on the use of additive manufactured biodegradable poly(ester)urethane (PEU) scaffolds of two different structures (500 µm pore size and 90° or 60° deposition angle) that can support the loads applied onto the knee while being highly resilient, with a permanent deformation lower than 1% after 10 compression-relaxation cycles. Moreover, these scaffolds appear to promote BMSC differentiation, as shown by the deposition of glycosaminoglycans and collagens (in particular collagen II). At gene level, BMSCs showed an upregulation of chondrogenic markers, such as collagen II and the Sox trio, to higher or similar levels than that of traditional pellet cultures, with a collagen II/collagen I relative expression of 2-3, depending on the structure of the scaffold. Moreover, scaffolds with different pore architectures influenced the differentiation process and the final BMSC phenotype. These data suggest that additive manufactured PEU scaffolds could be good candidates for cartilage tissue regeneration in combination with microfracture interventions.

Efficacy of alpha lipoic acid in burning mouth syndrome: a randomized, placebo-treatment study.

To study the efficacy of alpha lipoic acid (ALA) in a group of patients with burning mouth syndrome (BMS). Sixty BMS patients, 30 treated with ALA (Thioderm) 800 mg day(-1) for 8 weeks and 30 patients on the same protocol with a placebo. The symptomatology was measured on a Visual Analogue Scale (VAS). Sixty patients (54 females and 6 males, mean age 64.37 +/- 11.61 years) were included. Thirty-nine patients completed the treatment (23 with ALA and 16 with a placebo). Reviews were carried out at 0, 1 and 2 months. No statistically significant differences were found in the average pre- and post-treatment values for pain with the VAS scores, obtained in the placebo (6.6 +/- 2.5 - 2.8 +/- 25 = 3.8 +/- 3.7) versus ALA (6.3 +/- 2.8 - 4.0 +/- 2.7 = 2.2 +/- 2.6). Only one patient pertaining to the group treated with ALA abandoned because of adverse gastrointestinal side effects. The results showed no significant differences between the two groups.

One-day point prevalence of healthcare-associated infections and antimicrobial use in four countries in Latin America.

BACKGROUND AND AIMS: Experience in the region shows that in some countries there is very good surveillance of Healthcare-associated infections (HAIs) in health services, but there is no national data consistently in all countries. Therefore, we set to estimate the total burden of HAIs and antimicrobial use in acute care hospitals in Brazil, Venezuela, Mexico, and Colombia using the one-day point prevalence methodology. METHODS: The survey was conducted between June and July 2016. In each ward or unit, HAIs and antimicrobial use data were collected on a single day by a trained team of researchers. Also, for each patient, we collected data on risk factors for infections. RESULTS: One out of ten individuals surveyed had at least one healthcare-associated infection (HAI). Pneumonia and surgical site infections were the most relevant among the surveyed countries. Most of the surveyed participants, regardless of their HAI status, received antibiotics except the individuals managed in Brazil. Carbapenems and third-generation Cephalosporins were among the most frequently used antibiotics. CONCLUSION: Our results add to WHO's recent efforts to understand HAIs prevalence and antibiotic consumption in low and middle-income countries, of which we studied three that were not included in their last report.

Semen alterations in porcine rubulavirus-infected boars are related to viral excretion and have implications for artificial insemination.

Porcine rubulavirus (PoRV), also known as blue eye disease (BED) of swine, causes respiratory and reproductive problems in pigs at several developmental stages. To study the effect of PoRV infection on semen production, five boars were infected with 1 x 10(6) TCID(50)/ml of PoRV strain PAC-3 and evaluated for 59 days post inoculation (DPI). Infected boars developed reproductive tract pathology that included swelling of the testes and epididymides. Analysis of the semen showed that the infection had little effect on semen production in four animals, but semen from one boar showed severe alterations in sperm concentration, motility, and morphology. When motility was analyzed in BTS-diluted semen after 24, 48, or 72 h, alterations were detected in all boars. Furthermore, viral antigen was detected in semen, the seminal plasma fraction, or sperm fraction from all boars. These results showed that PoRV is excreted via semen and, therefore, artificial insemination is a potential route of dissemination.

Tissue factor variants induce monocyte transformation and transdifferentiation into endothelial cell-like cells.

Essentials Monocytes (Mo) transdifferentiate into endothelial cell-like (ECL) cells. Mo induce tissue factor (TF) expression and secretion in microvascular endothelial cells (mECs). TF interacts with Mo in a paracrine fashion, inducing their transdifferentiation into ECL cells. TF generates a positive feedback crosstalk between Mo and mECs that promotes angiogenesis. SUMMARY: Background Monocytes (Mo) increase neovascularization by releasing proangiogenic mediators and/or transdifferentiating into endothelial cell-like (ECL) cells. Recently, we have reported that Mo-microvascular endothelial cells (mECs) crosstalk induces mEC-tissue factor (TF) expression and promotes angiogenesis. However, the effect of TF on Mo remains unknown. Objective Here, we analyzed whether TF might exert angiogenic effects by inducing transdifferentiation of Mo. Methods Full-length TF (flTF) and alternatively spliced TF (asTF) were overexpressed in mECs, and their supernatants were added to Mo cultures. CD16 positivity and expression of vascular endothelial cell (VEC) markers in Mo were analyzed by fluorescence activated cell sorting. The capacity to form tube-like structures were visualized in three-dimensional cultures. Results In mECs flTF and asTF expression and release were increased in cultures with Mo-conditioned media. TF variants induced expansion of a CD16+ Mo subset and Mo transdifferentiation into ECL-cells expressing VEC markers that can form new microvessels. CD16+ Mo exposed to TF showed an increased expression of VE-cadherin, von Willebrand factor (VWF) and eNOS. Mo cultured with supernatants obtained from TF-silenced mECs did not transdifferentiate to ECL-cells or expressed VEC markers. Blocking ß1-integrin in Mo significantly blocked the effects of the TF variants. Conclusions Mo induce mECs to express and release TF, which drives CD16- Mo to transform into CD16+ Mo and to transdifferentiate into ECL-cells that can form new microvessels. Our results reveal a TF-mediated positive feedback between mECs and Mo that stimulates Mo differentiation and induces angiogenesis.

Ion exchanged Fe-FER through H2O2-assisted decomplexation of organic salts.

Decomplexation of organic ligands through redox titration has been applied to catalyst synthesis, developing an improved preparation method for Fe-ferrierite (Fe-FER), the catalyst showing excellent performance and durability for N2O decomposition under realistic conditions for nitric acid plants.

Cetoacidosis normoglicémica en paciente embarazada con neumonía por COVID-19. Reporte de un caso clínico / Euglycaemic ketoacidosis in a pregnant woman with COVID-19 pneumonia. A case report

RESUMEN Introducción: La cetoacidosis en el embarazo es una emergencia médica que requiere tratamiento en Unidad de Cuidados Intensivos debido a su asociación con morbimortalidad maternofetal. Las gestantes pueden presentar una forma atípica del cuadro llamada cetoacidosis normoglicémica, siendo muy infrecuente en pacientes sin antecedente de diabetes. Caso Clínico: Se presenta una gestante cursando tercer trimestre de embarazo, sin antecedente de diabetes, ingresada en Unidad de Paciente Crítico debido a neumonía por COVID-19 y acidosis metabólica con anión gap aumentado. Se realizó diagnóstico de cetoacidosis normoglicémica posterior al ingreso, iniciándose tratamiento intensivo de trastorno ácido-base con buena evolución. Conclusión: La infección por SARS-CoV-2 puede causar cetoacidosis normoglicémicas en embarazadas no diabéticas; se requiere una alta sospecha clínica para realizar el diagnóstico y tratamiento oportuno.

ABSTRACT Introduction: Ketoacidosis in pregnancy is a medical emergency that requires treatment in an intensive care unit due to its association with maternal-fetal morbimortality. Pregnant women may present an atypical form of the condition called normoglycemic ketoacidosis, being very rare in patients with no history of diabetes. Clinical Case: We present a pregnant woman in the third trimester of pregnancy, without history of diabetes, admitted to a critical patient unit due to COVID-19 pneumonia and metabolic acidosis with an increased anion gap. A diagnosis of normoglycemic ketoacidosis was made after admission, and intensive treatment of acid-base disorder was initiated, with good evolution. Conclusion: SARS-CoV-2 infection can cause normoglycemic ketoacidosis in non-diabetic pregnant women; is required a high clinical suspicion to make the diagnosis and appropriate treatment.

Retention of ionizable compounds on HPLC. 5. pH scales and the retention of acids and bases with acetonitrile-water mobile phases

The pH calibration procedures that lead to the different pH scales in acetonitrile-water mixtures used as mobile phases in reversed-phase liquid chromatography are discussed. Appropriate buffers of known pH value in acetonitrile-water mixtures are selected and used to establish the relationship (delta values) between the two rigorous acetonitrile-water pH scales: sspH and wspH (pH measured in acetonitrile-water mixtures and referred to acetonitrile-water or water, respectively, as standard state). These delta values allow one to convert pH values measured in acetonitrile-water with electrode systems calibrated with aqueous buffers (wspH scale) to sspH values, which are directly related to the thermodynamic acid-base constants. This offers an easy way to measure the pH of acetonitrile-water mobile phases and to relate this pH to the chromatographic retention of acids and bases through the thermodynamic acid-base constants. The relationships are tested for the variation of the retention of acids and bases with the pH of the mobile phase at several mobile-phase compositions and favorably compared with the relationships obtained with the common wwpH scale (pH measured in the aqueous buffer before mixing it with the organic modifier). The use of the rigorous sspH and wspH scales allows one to explain the retention behavior of bases, which in many instances cannot be justified from the pH measurement in the ill-founded wwpH scale.