Using Bayesian methods to test mediators of intervention outcomes in single-case experimental designs

Abstract

Single-Case Experimental Designs (SCEDs) have lately been recognized as a valuable alternative to large-group studies. SCEDs form a great tool for the evaluation of treatment effectiveness in heterogeneous and low-incidence conditions, which are common in the field of communication disorders. Mediation analysis is indispensable in treatment research because it informs researchers about the mechanism through which the intervention leads to changes (e.g., communication skills) in the outcome of interest (e.g., developmental outcomes). Despite the increasing popularity of both SCEDs and mediation analysis, there are currently no methods for estimating mediated effects for a single individual. This paper describes how Bayesian piecewise regression analysis can be used for mediation analysis in SCEDs. A Playskin Lift^TM dataset from one infant born preterm who is at risk for cognitive developmental delays is used to illustrate two approaches to mediation analysis in SCEDs: Bayesian computation of the mediated effect and Bayesian informative hypothesis testing. Annotated R code is provided so researchers can easily fit the proposed models to their own SCED data set. Advantages and limitations of the method are discussed.     

The phytoestrogen genistein prevents trabecular bone loss and affects thyroid follicular cells in a male rat model of osteoporosis

As a major phytoestrogen of soy, genistein effectively prevents bone loss in both humans and rat models of osteoporosis. However, although the bone‐sparing effects of genistein are achieved directly through estrogen receptors, its mode of action on bone by modulation of other endocrine functions is not entirely clear. Thus, thyroid hormones and calcitonin (CT ) have an essential influence on bone metabolism. Besides its action on bones, in this study we examined the effect of genistein on the activity of two different endocrine cell populations, thyroid follicular and C‐cells. Fifteen‐month‐old Wistar rats were either bilaterally orchidectomized (Orx) or sham‐operated (SO ). Two weeks after surgery, half of the Orx rats were treated chronically with 30 mg kg^?1 b.w. genistein (Orx + G) subcutaneously (s.c.) every day for 3 weeks, while the remaining Orx rats and the SO rats were given the same volume of sterile olive oil to serve as controls. For histomorphometrical analysis of the trabecular bone microarchitecture an ImageJ public domain image processing programme was used. Thyroid sections were analysed histologically and stereologically after visualization of follicular and C‐cells by immunohistochemical staining for thyroglobulin and CT . Thyroid follicular epithelium, interstitium, colloid and CT ‐immunopositive C‐cells were examined morphometrically. Serum concentrations of osteocalcin (OC ), triiodothyronine (T₃), thyroxine (T₄) and CT were determined as well as urinary calcium (Ca²⁺) concentrations. Genistein treatment significantly increased cancellous bone area (B.Ar), trabecular thickness (TbTh) and trabecular number (TbN) (P  < 0.05), but trabecular separation (Tb.Sp) was decreased (P  < 0.05) compared with control Orx rats. In the thyroid, genistein treatment significantly elevated the relative volume density (Vv) of the follicular cells (P  < 0.05) compared with Orx, whereas Vv of the colloid was lower (P  < 0.05) than in the Orx. Evaluation of the biochemical parameters showed significant reductions in serum OC , T₃, T₄ and urinary Ca²⁺ concentrations (P  < 0.05), compared with Orx rats. These data indicate that genistein treatment improves the trabecular microarchitecture of proximal tibia, induces histomorphometrical changes in thyroid glands, and decreases circulating thyroid hormone levels in orchidectomized rat model of male osteoporosis.     

The anti-hyperalgesic effects of carbamazepine and oxcarbazepine are attenuated by treatment with adenosine receptor antagonists

The antinociceptive effects of carbamazepine and oxcarbazepine, and the influence of caffeine, were examined in a paw pressure test in rats. Carbamazepine (10-40 mg/kg; intraperitoneal, i.p.) and oxcarbazepine (40-160 mg/kg; i.p.) caused a significant dose-dependent reduction of the paw inflammatory hyperalgesia induced by concanavalin A (Con A), intraplantarly (i.p1.). A comparable pattern of antinociceptive effect of carbamazepine and oxcarbazepine was observed; the only difference is their potency, in that carbamazepine was about three times more potent than oxcarbazepine. Caffeine (5-20mg/kg; i.p.), a non-selective adenosine receptor antagonist, significantly depressed the antinociceptive effects of carbamazepine and oxcarbazepine, in a dose- and time-dependent manner. Also, a significant depression of the antinociceptive effects of carbamazepine and oxcarbazepine was observed by pretreatment with 1,3-dipropyl-8-cyclopentylxantine (DPCPX, 0.4 and 0.8 mg/kg; i.p.), an adenosine A(1) receptor antagonist. These findings indicate that, in a paw inflammatory hyperalgesia in rats, the antinociceptive effects of both drugs are, at least partially, mediated by adenosine A(1) receptors. In conclusion, the present study suggests the potential clinical importance of carbamazepine and oxcarbazepine in the treatment of inflammatory pain. In addition, caffeine consumption could possibly depress the analgesic effects of both anticonvulsive drugs.     

Compounding of a topical drug with prospective natural surfactant-stabilized pharmaceutical bases: Physicochemical and in vitro/in vivo characterization - A ketoprofen case study

Recently, healthcare professionals again began realizing the benefits of preparing customized medications to meet specific patient needs. The objective of this work was to develop and evaluate simple pharmaceutical bases stabilized with natural-origin surfactant of alkyl polyglucoside (APG) type as prospective ready-to-use bases and compare them to widely used pharmacopoeial ones. Additionally, the ability of the formulated bases to sustain isopropyl alcohol was assessed as well as its influence on ketoprofen skin absorption (as a co-solvent and potential penetration enhancer). In order to evaluate the manifold characteristics a topical drug product should possess, a comprehensive characterization was performed using different techniques.Physicochemical characterization demonstrated satisfactory physical stability of APG-stabilized bases upon the addition of alcohol. In vitro release/permeation studies failed to show significant difference in ketoprofen liberation/permeation profiles from different bases. However, the extent of ketoprofen delivery in vivo was clearly increased from APG bases, relative to that obtained from pharmacopoeia quality one, implying a distinct influence of the emulsion systems’ colloidal structures. Taking also into account the rheological behavior of APG bases, revealing their ameliorated sensory characteristics, it could be concluded that the investigated APG bases could be considered as preferential option in drug compounding related to the conventional ones.     

Biodegradable collagen patch with covalently immobilized VEGF for myocardial repair

Vascularization of engineered tissues in vitro and in vivo remains a key problem in translation of engineered tissues to clinical practice. Growth factor signalling can be prolonged by covalent tethering, thus we hypothesized that covalent immobilization of vascular endothelial growth factor (VEGF-165) to a porous collagen scaffold will enable rapid vascularization in vivo. Covalent immobilization may be preferred over controlled release or cell transfection if the effects are desired within the biomaterial rather than the surrounding tissue. Scaffolds were prepared with 14.5 ± 1.4 ng (Low) or 97.2 ± 8.0 ng (High) immobilized VEGF, or left untreated (control), and used to replace a full right ventricular free wall defect in rat hearts. In addition to rapid vascularization, an effective cardiac patch should exhibit neither thinning nor dilatation upon implantation. In vitro, VEGF enhanced the growth of endothelial and bone marrow cells seeded onto scaffolds. In vivo, High VEGF patches had greater blood vessel density (p < 0.01) than control at Day 7 and 28 due to increased cell recruitment and proliferation (p < 0.05 vs. control). At Day 28, VEGF-treated patches were significantly thicker (p < 0.05) than control, and thickness correlated positively with neovascularization (r = 0.67, p = 0.023). Importantly, angiogenesis in VEGF scaffolds contributed to improved cell survival and tissue formation.     

Route-dependent effects of cadmium/cadmium and magnesium acute treatment on parameters of oxidative stress in rat liver

The study was designed to evaluate and compare the effects of single oral (or) and intraperitoneal (i.p.) cadmium (Cd) administration on parameters of oxidative stress in liver of rats. Furthermore, investigation on protective effects of magnesium (Mg) or and i.p. pretreatment on the same parameters was performed. Wistar rats were administrated oral dose of Cd (30 mg Cd/kg b.w.)/Cd+Mg (30 mg Cd/kg b.w., 50 mg Mg/kg b.w.) or i.p. dose of Cd (1.5 mg Cd/kg b.w.)/Cd+Mg (1.5 mg Cd/kg b.w., 3 mg Mg/kg b.w.) and sacrificed after 24 h. In liver homogenates superoxide anion, malondialdehyde, non-protein sulfhydryl groups, total sulfhydryl groups content, and superoxide dismutase activity were determined. Cadmium intoxication caused the increase of superoxide anion and malondialdehyde levels and had negative effect on investigated parameters of antioxidant defense system, except on total sulfhydryl groups. The negative effect was more emphasized after i.p. Cd administration. Oral Mg pretreatment induced more pronounced positive effect than Mg given intraperitoneally that can be attributed, at least partly, to Cd and Mg interactions on the level of GIT. On the basis of the obtained results it can be concluded that both Cd and Cd+Mg effects on parameters of oxidative stress in rats liver are route-dependent.     

Muscle strength and bone density in patients with different rheumatic conditions: cross-sectional study

Aim

To explore the relationship between muscle strength and bone density in patients with different rheumatic diseases and to examine whether inflammatory arthritis was more harmful for muscle strength and bone loss than degenerative joint diseases.

Methods

The study included 361 men and women with a mean ± standard deviation age of 60.5 ± 11.4 years and different rheumatic conditions: regional syndromes, osteoarthritis of the hands, shoulders, knees, and hips, and inflammatory arthritis. Maximum voluntary back strength was measured by isometric dynamometry. Bone mineral density (BMD; g/cm²) of the lumbar spine, femoral neck, and distal radius was measured by dual-energy x-ray absorptiometry. Anthropometry and lifestyle characteristics were also assessed.

Results

Back strength was lowest in patients with hand and shoulder osteoarthritis (20.0 ± 17.9 kg), followed by patients with inflammatory arthritis (24.8 ± 19.2 kg). Patients with inflammatory arthritis had the lowest BMD at the mid-radius (0.650 ± 0.115 g/cm²) and femoral neck (0.873 ± 0.137 g/cm²), while patients with hand and shoulder osteoarthritis had the lowest BMD at the mid-radius (0.660 ± 0.101). In both sexes, muscle strength was significantly lower in patients who had lower BMD (T score<-1.0). Multiple regression analysis identified significant predictors of back strength to be spine BMD (P = 0.024) and body mass index (P = 0.004) in men and femoral neck BMD in women (P = 0.004).

Conclusion

Muscle strength decline may be connected to bone loss in patients with rheumatic conditions, especially those with inflammatory joint diseases.There is a concomitant decline in muscle strength of the upper and lower limbs and bone density after the fifth decade of the life (1,2). Impaired muscle function is a common consequence in patients with rheumatic diseases, especially those with inflammatory joint diseases. Muscle strength may also be significantly reduced around joints affected with osteoarthritis. Several studies showed greatly reduced isokinetic strength in patients with rheumatoid arthritis (3-5) and patients with knee osteoarthritis (6).It is also known that muscle strengthening can yield a bone-building effect (7). Exercises with greater loading and higher impact activities produce the greatest skeletal benefit (8). Increased muscle weakness can also compound the problem of low bone density by increasing the risk of falls and fracture. A positive correlation between muscle strength and bone density has been shown in several studies (9-17). Some of them demonstrated the association only in postmenopausal women (12,17) but not in men (9,13), while other found a site-specific correlation between muscle strength and bone mineral density (BMD) (4,12). However, several studies did not find a correlation between any measures of muscle strength and BMD (18,19). With such contradictory reports, it is difficult to make clinically relevant conclusions about the relationship between muscle strength and bone mass, although this may be one of the key factors that affect the rehabilitation outcome.The aim of the study was to assess the differences in muscle strength and bone density between patients with different rheumatic conditions. Since muscle strength is an important determinant of bone density, we explored whether the age-related decline in bone density and muscle strength was more pronounced in patients with inflammatory arthritis than in those with degenerative joint diseases.     

Early postnatal castration affects thymic and thymocyte noradrenaline levels and beta-adrenoceptor-mediated influence on the thymopoiesis in adult rats

The interactions among the nervous, endocrine and immune system were studied by examining: i) thymic and thymocyte catecholamine levels in adult rats castrated (Cx) at postnatal day 3 and ii) effects of 14-day-long propranolol (P) treatment on main thymocyte differentiational molecule expression in adult non-Cx and Cx rat. The results demonstrated that castration in early postnatal period lowers levels of both neurally- and thymocyte-derived noradrenaline in adult rats, and thereby diminishes beta-adrenoceptor-mediated fine tuning of the T-cell differentiation/maturation. In non-Cx rats P affected TCRalphabeta-dependent stages of thymocyte differentiation/maturation decreasing frequency of CD4+8+ double positive (DP) TCRalphabeta(low) cells entering selection processes and increasing relative number of positively selected DP TCRalphabeta(high) (most likely due to an increased thymocyte surface density of Thy-1 that is involved in negative control of TCRalphabeta-mediated signaling/selection thresholds) and the most mature CD4+8- TCRalphabeta(high) cells (including CD4+25+ regulatory cells). However, in Cx rats P failed to produce any significant changes in thymocyte subset composition.     

Acetaminophen intake and risk of asthma, hay fever and eczema in early adolescence

A positive association between acetaminophen intake and allergic diseases has recently been reported in developed countries with impaired oxidant/antioxidant balance and promotion of atopy as proposed underlying mechanisms. The aim of the study was to explore the relationship between acetaminophen intake and asthma, hay fever, and eczema in The Republic of Macedonia as a country with acetaminophen intake not physician-controlled, high passive smoke exposure and dietary antioxidant intake, and moderately low prevalence of allergic diseases. Self-reported data obtained through the standardized International Study of Asthma and Allergies in Childhood Phase Three written questionnaires of 3026 adolescents aged 13/14 years from randomly selected schools in Skopje, the capital of Macedonia, were used. The frequency of current acetaminophen intake--both unadjusted and adjusted for confounding factors--was correlated to current and ever-diagnosed asthma, hay fever and eczema by odds ratios (OR, 95% CI) in binary logistic regression. Use of acetaminophen at least once monthly increased the risk of current wheeze (adjusted OR 2.04, 1.31-3.20 p = 0.002), asthma 'ever' (adjusted OR 2.77, 1.06-7.26 p=0.039), current allergic rhinoconjunctivitis (adjusted OR 2.95, 1.79-4.88 p=0.000) and hay fever 'ever' (adjusted OR 2.25, 1.36-3.70 p=0.002). A significant association between frequent acetaminophen intake and atopic eczema and also between infrequent acetaminophen intake and investigated allergic diseases was not established. The findings suggest an increased risk of asthma and hay fever, but not atopic eczema associated with frequent acetaminophen use in a developing country.