This review addresses the 100-year-old Hill equation (published in January 22, 1910), the first formula relating the result of a reversible association (e.g., concentration of a complex, magnitude of an effect) to the variable concentration of one of the associating substances (the other being present in a constant and relatively low concentration). In addition, the Hill equation was the first (and is the simplest) quantitative receptor model in pharmacology. Although the Hill equation is an empirical receptor model (its parameters have only physico-chemical meaning for a simple ligand binding reaction), it requires only minor a priori knowledge about the mechanism of action for the investigated agonist to reliably fit concentration-response curve data and to yield useful results (in contrast to most of the advanced receptor models). Thus, the Hill equation has remained an important tool for physiological and pharmacological investigations including drug discovery, moreover it serves as a theoretical basis for the development of new pharmacological models.

The human precorneal tear film is a special body fluid, since it is a complex mixture of proteins, lipids, small bioactive molecules, and their concentrations and relative distribution represent not only the metabolic state of the ocular surface but also the systemic and local homeostasis of the outer eye and the human body. This suggests that biochemical analysis of the precorneal tear film composition may provide a non-invasive tool for diagnosis and monitoring of disease progression or treatment efficacy in human medicine. However, collecting tears is demanding, and obtaining reproducible and unaltered samples is challenging because of the small sample volumes of tears. Several methods are available for tear collection as a preparatory step of precorneal tear film analysis, and the collection method used has to be assessed since it has a critical impact on the effectiveness of the assays and on the quality of the results. Each sampling method has advantages and disadvantages; therefore, it is not easy to choose the appropriate collecting method for tear collection. To overcome these limitations various methods have been recommended by different authors for special aspects of specific tests. The aim of our review was to evaluate tear sampling methods with regard to our ongoing biochemical analysis. *Contributed equally.

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The present study demonstrates capacity of α-MSH to augment recovery from ischemia/reperfusion (I/R)-induced retinal damage in vivo and correlation of its protective effects with expression of heme oxygenase-1 (HO-1). Used techniques include ocular ischemia and reperfusion, electroretinography, histology, electron microscopy, and molecular-biological techniques. The results demonstrate the α-MSH-mediated inhibition of I/R-induced functional deterioration of the retina. Outcomes suggest that the protective effects of α-MSH occur mainly through HO-1-dependent pathways but HO-1-independent mechanisms may also contribute to protection. The observation that post-ischemic treatment with α-MSH exhibits therapeutic efficacy in the same range as pre-ischemic treatment, is a novel result. This outcome suggests a highly conserved protective role for α-MSH as a major stress response mechanism—and offers the possibility for development of novel therapeutic strategies utilizing this hormone, in particular in treatment of conditions resulting from I/R injury, such as deterioration of retinal microcirculation. The merit of the study lies in the fact that I/R injury contribute significantly to the severity of retinopathies. However, currently there are no evidence-based treatments for retinal I/R injury available for clinical use. Our finding suggests that α-MSH may have a very wide range of uses in the prevention of I/R-mediated pathologies.

The receptorial responsiveness method (RRM) was proposed to characterize changes in the concentration of degradable agonists in the microenvironment of their receptors. The characterization is done by providing concentrations of a stable agonist for the same receptor that is equieffective with the change in concentration to be characterized. RRM is based on the analysis of concentration-effect (E/c) curves reflecting the simultaneous action of the degradable and the stable agonist. In the present study, we investigated whether dissimilar affinity and (or) efficacy of the coacting agonists as well as the steepness of the E/c curves influence the reliability of RRM. E/c curves were simulated based on the operational model and then analyzed with RRM. We found that dissimilarity in affinity of the coacting agonists did not affect the accuracy of RRM estimates. In contrast, accuracy of the estimation depended on the magnitude of the concentration to be assessed, the operational slope factor, and the operational efficacy ratio of the coacting agonists. However, our results suggest that proper choice of a stable agonist for a degradable one can help to ensure reliable results, since information about the change in concentration of a degradable agonist is otherwise difficult to obtain.

Several recent studies have shown the protective effects of resveratrol in various experimental conditions and pathological animal models. Clinical studies also indicate the beneficial effects of resveratrol in different human diseases. Resveratrol produces a cascade against of events from the initial death-provoking signal, DNA fragmentation, and cell death. Researchers recognized the beneficial effect of resveratrol, as an important component, of the overall injury that occurs in various disorders such as oxidative stress, myocardial injury, anticancer activity, antidiabetic activity, and antihypercholesterolemic effects. Many mechanisms have been proposed for the initiation of protective effects of resveratrol in various pathological events, and considerable evidence exists to indicate that many mediators are involved in the resveratrol-induced protection. The present review focuses on the history, and the beneficial effects and mechanisms of resveratrol in oxidative stress, myocardial injury, anticancer-, antidiabetic- and antihypercholesterolemic activities, and discusses those therapeutic tools, which warrant becoming clinically important.

The aim of this study was to evaluate the association between clinical signs and symptoms of dry eye disease (DED) in patients with systemic sclerosis (SSc). This cross-sectional observational study included 19 SSc patients and 19 normal subjects with no ocular symptoms or ocular surface disorders. Clinical parameters included tear film break-up time (tBUT), Schirmer I, lissamine green (LG) dye, and tear film osmolarity tests, tear production, and tear secretion flow. For assessment of the dry eye symptoms, the Ocular Surface Disease Index (OSDI) questionnaire was administered to all patients. The following mean values were found in SSc patients: OSDI 33.6 ± 19.86; osmolarity of the tear fluid 310.8 mOsmol/l ± 14.47; tBUT time 5.158 ± 2.328 s; Schirmer I test 5.395 mm/5 min; LG grading score 2.026 ± 0.8893; collected tear fluid volume 6.397 ± 2.761 µl. The calculated average tear velocity was 4.654 ± 1.963 µl/min. A significant correlation was found between the OSDI as a subjective parameter and disease duration. Early recognition of dry eye symptoms, a possible extra-intestinal manifestation of SSc, should be included in the check up of the disease to reduce ocular complications. The objective tear functional tests were strongly influenced by individual factors like age and disease duration.

Objectives: Systemic sclerosis (SSc) is a rare, chronic connective tissue disease involving multiple organ systems, including the eye. We evaluated the detailed clinical ocular manifestations of outpatients with SSc. Methods: Demographics, disease duration and subtype, nailfold capillaroscopy (NFC) patterns and laboratory parameters encompassing the autoantibody profile of 51 SSc patients were evaluated, and a general ocular examination was performed for each participant. Results: Twenty-nine patients (56.86%) had eyelid skin alterations, 26 (50.98%) had retinal abnormalities, 26 (50.98%) had cataracts, 8 (15.69%) had conjunctival changes, 7 (13.73%) had iris abnormalities, 33 (64.71%) suffered from dry eye disease (DED), and 11 (21.57%) suffered from glaucoma. Significant positive correlations were found between NFC data and both tear breakup time and Ocular Surface Disease Index test values. Conclusions: Eyelid skin abnormalities, DED and retinal abnormalities are among the most common SSc-related ocular involvements. Diverse ophthalmic findings are attributed to the heterogeneity of SSc.