General Linear Statistical Model Research Articles

Sexual dimorphisms in three-dimensional masticatory muscle attachment morphometry regulates temporomandibular joint mechanics

Temporomandibular joint (TMJ) disorders disproportionally affect females, with female to male prevalence varying from 3:1 to 8:1. Sexual dimorphisms in masticatory muscle attachment morphometry and association with craniofacial size, critical for understanding sex-differences in TMJ function, have not been reported. The objective of this study was to determine sex-specific differences in three-dimensional (3D) TMJ muscle attachment morphometry and craniofacial sizes and their impact on TMJ mechanics. Human cadaveric TMJ muscle attachment morphometry and craniofacial anthropometry (10Males; 11Females) were determined by previously developed 3D digitization and imaging-based methods. Sex-differences in muscle attachment morphometry and craniofacial anthropometry, and their correlation were determined, respectively using multivariate general linear and linear regression statistical models. Subject-specific musculoskeletal models of the mandible were developed to determine effects of sexual dimorphisms in mandibular size and TMJ muscle attachment morphometry on joint loading during static biting. There were significant sex-differences in craniofacial size (p = 0.024) and TMJ muscle attachment morphometry (p < 0.001). TMJ muscle attachment morphometry was significantly correlated with craniofacial size. TMJ contact forces estimated from biomechanical models were significantly, 23% on average (p < 0.001), greater for females compared to those for males when generating the same bite forces. There were significant linear correlations between TMJ contact force and both 3D mandibular length (R2 = 0.48, p < 0.001) and muscle force moment arm ratio (R2 = 0.68, p < 0.001). Sexual dimorphisms in masticatory muscle morphology and craniofacial sizes play critical roles in subject-specific TMJ biomechanics. Sex-specific differences in the TMJ mechanical environment should be further investigated concerning mechanical fatigue of TMJ discs associated with TMJ disorders.

Diet is a main source of vitamin D inFinnish pet rabbits (Oryctolagus cuniculus).

During the winter time in Finland, sunlight is inadequate for vitamin D synthesis. Many pet rabbits live as house rabbits with limited outdoor access even during summer and may therefore be dependent on dietary sources of vitamin D. The aims of this study were to report the serum 25-hydroxyvitamin D concentrations in Finnish pet rabbits and to identify factors that influence vitamin D status. Serum 25-hydroxyvitamin D concentrations from 140 pet rabbits were determined using a vitamin D enzyme immunoassay (EIA) kit. Eleven rabbits were excluded from the statistical analysis because of unclear dietary data. The remaining 129 rabbits were divided into groups depending on outdoor access during summer (no access n=26, periodic n=57, regular n=46) as well as daily diet: little or no hay and commercial rabbit food ≤1/2dl (n=12); a lot of hay and no commercial food daily (n=23); a lot of hay and commercial food <1dl (n=59); a lot of hay and commercial food ≥1dl (n=35). The range of serum 25-hydroxyvitamin D concentration was from 4.5 to 67.5ng/ml with a mean of 26.1ng/ml. Statistical general linear model adjusted for weight, age and season indicated that diet was associated with vitamin D concentrations (p=0.001), but outdoor access during summer was not (p=0.41). Mean 25-hydroxyvitamin D concentration was significantly higher in the rabbits receiving a lot of hay and commercial food ≥1dl (33.9±13.2ng/ml) than in rabbits in other diet groups (24.0±8.5ng/ml, 21.7±8.1ng/ml, and 22.2±18.0ng/ml, respectively). This investigation showed wide variation in 25-hydroxyvitamin D concentrations among Finnish pet rabbits. Diet remains a main source since outdoor access seems to be too limited to provide adequate vitamin D synthesis for most of them, and the use of vitamin D supplements is rare.

Interfacial biomechanical properties of a dual acid-etched versus a chemically modified hydrophilic dual acid-etched implant surface: an experimental study in Beagles

BackgroundThe high survival clinical success rates of osseointegration are requisites for establishing a long-term biomechanical fixation and load-bearing potential of endosseous oral implants. The objective of this preclinical animal study was to evaluate the effect of surface microtopography and chemistry on the early stages of biomechanical rigidity with a sandblasted, dual acid-etched surface, with or without an additional chemical modification (SAE-HD and SAE, respectively), in the tibia of Beagle dogs.MethodsTwo pairs of implants, with the same macrogeometry but different surface technology ((a) dual acid-etched surface treatment with hydrochloric and sulfuric acid followed by microwave treatment and insertion in isotonic saline solution to increase hydrophilicity (SAE-HD) (test, n = 12) and (b) dual acid-etched surface (SAE) (control, n = 12)), were installed bilaterally in the proximal tibia of six Beagle dogs. In order to determine the effect of surface modification on biomechanical fixation, a test protocol was established to assess the torque and a complete set of intrinsic properties. Maximum removal torque (in N cm) was the primary outcome measure, while connection stiffness (N cm/rad) and removal energy (× 10−2J) were the secondary outcome measures and were assessed after 2 and 4 weeks in vivo. A general linear statistical model was used and performed for significant differences with the one-way ANOVA followed by Tukey post hoc test (P < 0.05).ResultsThe removal torque values did not reveal significant statistical differences between SAE-HD and SAE implants at any observation times (P = 0.06). Although a slight increase over time could be observed in both test and control groups. SAE-HD showed higher removal energy at 4 weeks (999.35 ± 924.94 × 10− 2 J) compared to that at 2 weeks (421.94 ± 450.58 × 10− 2 J), while SAE displayed lower values at the respective healing periods (P = 0.16). Regarding connection stiffness, there were no significant statistical differences neither within the groups nor over time. There was a strong, positive monotonic correlation between removal torque and removal energy (=0.722, n = 19, P < 0.001).ConclusionsIn this study, no significant differences were observed between the specific hydrophilic (SAE-HD) and hydrophobic (SAE) surfaces evaluated, in terms of biomechanical properties during the early osseointegration period.

Gene × Environment interaction: What exactly are we talking about?

An ambiguity exists in how psychological scientists use the word “interaction.” This word can refer to physical interactions between components that form the mechanisms in complex systems, but it can also refer to statistical interactions revealed by General Linear Statistical Models (e.g., Analyses of Variance). Statistical interactions indicate that the nature of the relationship between two variables depends on a third variable, but the discovery of such interactions does not constitute evidence of physical interactions between components in a system. Studies conducted using traditional behavioral genetics methods sometimes reveal statistical interactions between genes and environments, but the presence or absence of such interactions tell us surprisingly little about actual, physical interactions between genes and their contexts. This is important, because it is only the latter kinds of interactions that cause the development of behavioral phenotypes, including developmental disabilities. Therefore, when behavioral scientists discover (or fail to discover) Genotype × Environment interactions, it is important to exercise care in interpreting their meaning and in assessing the utility of such findings.

Arterial hypertension treated with angiotensin converting enzyme inhibitors and glucocorticoids are independent risk factors associated with decreased glomerular filtration rate in systemic sclerosis.

The aim of this study was to estimate prevalence and severity of renal insufficiency in systemic sclerosis (SSc) and to assess risk factors associated with reduced glomerular filtration rate (GFR) in SSc patients. Seventy-three consecutive patients with SSc (67 women and 6 men), mean age 56.2years, mean disease duration 6.7years, were included in this cross-sectional study. GFR was measured by creatinine clearance (CCr) in all patients, as well as 24-h proteinuria. We assessed frequency and severity of renal insufficiency in our patients with SSc and estimated the association of renal insufficiency with age, disease duration, subtype of the disease, earlier diagnosed arterial hypertension, and medications for which we assumed to affect renal function-cytostatics, nonsteroidal anti-inflammatory drugs, glucocorticoids, ACE inhibitors, diuretics, and calcium channel blockers (CCB). Fifty-six out of 73 patients with SSc (76.7%) had reduced GFR (CCr lower than 90ml/min), compared to 17/73 (23.3%) of patients with normal renal function. Mild renal insufficiency was noticed in 28/73 (38.4%), moderate in 21/73 (28.8%) and severe renal insufficiency in 5/73 (6.8%). End-stage renal disease (CCr<15ml/min) was found in 2/73 (2.7%) of patients. Using the univariate general linear statistical model, we have found that previously diagnosed arterial hypertension and treatment with glucocorticoids are independent risk factors for reduced GFR. On the other hand, age, disease duration, disease form, as well as antibodies (anticentromere antibodies-ACA and anti-topoisomerase I antibodies-ATA) were excluded as independent risk factors. Patients with SSc and arterial hypertension treated with CCB had significantly higher mean CCr than patients treated with diuretics (90.4 vs 53.5ml/min, p=0.03), or patients treated with ACE inhibitors (90.4 vs 41.7ml/min, p=0.001). Decreased GFR is common in SSc. Most of patients have mild or moderate renal insufficiency. Previously diagnosed arterial hypertension, especially when treated with ACE inhibitors or diuretics, and glucocorticoids are independent risk factors associated with reduced GFR in SSc. These medications should be therefore used with caution in SSc patients.

A General Approach to Panel Data Set-Theoretic Research

Academic research based on general linear statistical models has been rapidly moving toward a greater and richer use of longitudinal and panel data econometric methods. By contrast, set-theoretic empirical research, despite its growing diffusion, has been mainly focused on cross-sectional analysis to date. This article covers this void in panel data set-theoretic research. We provide some diagnostic tools to assess a set-theoretic consistency and coverage both cross-sectionally and across time. The suggested approach is based on the distinction between pooled, between and within consistency and coverage, which can be computed using panel data. We use KLD’s panel (1991–2005) to illustrate how the proposed approach can be applied in the context of set-theoretic longitudinal research.

Skeletal muscle tensile strain dependence: Hyperviscoelastic nonlinearity

IntroductionComputational modeling of skeletal muscle requires characterization at the tissue level. While most skeletal muscle studies focus on hyperelasticity, the goal of this study was to examine and model the nonlinear behavior of both time-independent and time-dependent properties of skeletal muscle as a function of strain. Materials and methodsNine tibialis anterior muscles from New Zealand White rabbits were subject to five consecutive stress relaxation cycles of roughly 3% strain. Individual relaxation steps were fit with a three-term linear Prony series. Prony series coefficients and relaxation ratio were assessed for strain dependence using a general linear statistical model. A fully nonlinear constitutive model was employed to capture the strain dependence of both the viscoelastic and instantaneous components. ResultsInstantaneous modulus (p<0.0005) and mid-range relaxation (p<0.0005) increased significantly with strain level, while relaxation at longer time periods decreased with strain (p<0.0005). Time constants and overall relaxation ratio did not change with strain level (p>0.1). Additionally, the fully nonlinear hyperviscoelastic constitutive model provided an excellent fit to experimental data, while other models which included linear components failed to capture muscle function as accurately. ConclusionsMaterial properties of skeletal muscle are strain-dependent at the tissue level. This strain dependence can be included in computational models of skeletal muscle performance with a fully nonlinear hyperviscoelastic model.

Does knee malalignment predict the efficacy of realignment therapy for patients with knee osteoarthritis?

Realignment therapies, including knee braces, foot orthoses and shoes are prescribed to patients with medial knee osteoarthritis (OA) with the goal of unloading the medial tibiofemoral (TF) compartment. It is uncertain whether realignment therapies have different effects in those with knee malalignment. We studied whether the efficacy of realignment therapy for pain and function in persons with medial TF OA is predicted by the severity of the baseline knee malalignment. The baseline characteristics of 48 participants with moderate to severe medial knee OA were collected. Participants' pain and function were measured using Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scale before and after 12weeks of realignment therapy using a valgus unloader knee brace plus bilateral neutral foot orthoses and motion control shoes. Anatomical axis (AA) was measured on weight-bearing knee radiographs by a blinded reader and knee malalignment was categorized as either varus malaligned (moderate or severe) or neutral according to the AA angle. We assessed for differences in response to treatment according to alignment category. General linear statistical models were generated to determine which of the measured alignment variables and covariates predicted change in the pain outcome. Anatomical axis knee alignment was not a significant predictor of pain or function change with active treatment. Baseline WOMAC scores were the best predictor of change in WOMAC (P<0.01 and P=0.06 for pain and function, respectively). Baseline knee alignment did not predict the efficacy of 12weeks realignment therapy in participants with medial tibiofemoral OA. [Correction added on 27 August 2015, after first online publication: 'did predict' has been corrected to 'did not predict' in the conclusions of the abstract section.].

Inventory record inaccuracy in supply chains: the role of workers’ behavior

Purpose – The purpose of this paper is to explore the effect of inventory record inaccuracy due to behavioral aspects of workers on the order and inventory variance amplification. Design/methodology/approach – The authors adopt a continuous-time analytical approach to describe the effect of inbound throughput on the inventory and order variance amplification due to the workload pressure and arousal of workers. The model is numerically solved through simulation and results are analyzed with statistical general linear model. Findings – Inventory management policies that usually dampen variance amplification are not effective when inaccuracy is generated due to workers’ behavioral aspects. Specifically, the psychological sensitivity and stability of workers to deal with a given range of operational conditions have a combined and multiplying effect over the amplification of order and inventory variance generated by her/his errors. Research limitations/implications – The main limitation of the research is that the authors model workers’ behavior by inheriting a well-known theory from psychology that assumes a U-shaped relationship between stress and errors. The authors do not validate this relationship in the specific context of inventory operations. Practical implications – The paper gives suggestions for managers who are responsible for designing order and inventory policies on how to take into account workers’ behavioral reaction to work pressure. Originality/value – The logistics management literature does not lack of research works on behavioral decision-making causes of order and inventory variance amplification. Contrarily, this paper investigates a new kind of behavioral issue, namely, the impact of psycho-behavioral aspects of workers on variance amplification.

A General Approach to Longitudinal Set-Theoretic Research in Management

Management research based on general linear statistical models has been rapidly moving toward a greater and richer use of longitudinal (panel data) econometric methods able to cope with critical issues such as endogeneity and reverse causality. By contrast, set-theoretic empirical research in management, despite its growing diffusion, has been solely focused on cross-sectional analysis to date. This article covers this void in longitudinal set-theoretic research. We provide a general framework in which consistency and coverage can be assessed both cross-sectionally and across time. The suggested approach is based on the distinction between pooled, between and within consistency and coverage, which can be computed using panel data. We use KLD’s panel (1991-2005) to illustrate how this approach can be applied in the context of longitudinal research.

Biomechanical Evaluation of Anterior Thoracic Salvage Screws in the Osteoporotic Thoracic Spine

Controlled, cadaveric implantation trial. Evaluation of revision thoracic screw fixation: with revision from unicortical screws to bicortical screws, to larger diameter screws, and the addition of bone cement. Limited data is available regarding the effect of salvage screws on fixation quality in the anterior thoracic spine. Biomechanical studies in the cervical spine and the lumbar spine demonstrate dramatic decreases in fixation in salvage situations. Seventy-two cadaveric thoracic vertebrae from 6 specimens were DEXA scanned at T1-T12. A control screw and a second identical screw were placed in each segment. One screw was then removed and replaced with a revision screw. Varying screw diameter, the number of cortices, and the addition of 1.5 cm of bone cement was evaluated in a pairwise fashion. Comparisons were made using descriptive statistical analysis and a general linear statistical model. Bone mineral density had a significant effect on the pullout force. Pullout force did not vary significantly with control screw diameter. Revision of a smaller diameter bicortical to a larger diameter bicortical screw resulted in a decrease in pullout strength for 4-5 mm screws by 40.1% (P=0.02) and 5-7 mm screws by 63.7% (P=0.05). When a 4 mm bicortical screw is revised to a 5 mm unicortical screw, the pullout force decreases by 67.7% (P<0.001). There was a nonsignificant increase (44%) in pullout with revision of a unicortical 4 mm screw to a bicortical 4 mm screw. If a bicortical screw is revised to a unicortical screw with 1.5 cm of cement, the pullout strength is increased by 240% (P<0.001). When the use of salvage screws is required, the surgeon should anticipate a significant decrease in the holding force compared with the original screw regardless of screw size unless a unicortical screw is revised to a bicortical screw or cement is added to the construct.

A Prospective Randomized Trial on Preventative Methods for Positional Head Deformity: Physiotherapy versus a Positioning Pillow

To evaluate the impact of stretching exercises versus available bedding pillows on positional head deformities. Fifty children aged 5 months or younger with positional head deformity were included in this prospective clinical trial (n=20 plagiocephaly, n=10 brachycephaly, n=20 combination). A random distribution was performed for treatment with the bedding pillow alone (n=25) or with stretching exercises (n=25) for 6 weeks. Anthropometric caliper measurements were done before and after that interval. Cranial vault asymmetry index (CVAI) and cranial index (CI) were calculated and analyzed using a descriptive statistical general linear model. ΔCVAI in the stretching group was 2.09% for plagiocephaly and 2.34% for combined head deformities. Using the bedding pillow, ΔCVAI was 3.01% in plagiocephal children and 2.86% for combined head deformity. The ΔCI in the stretching group was 0.94% for isolated brachycephal children and 2.24% for combined head deformity. ΔCI in the pillow group was 3.63% for brachycephaly and 3.23% in children with combined head deformities, respectively. Bedding pillows and stretching exercises both resulted in improvements in positional cranial deformation. For children with combined plagiocephaly and brachycephaly, improvement in cranial asymmetry was slightly greater when using bedding pillows versus stretching.

Biomechanical Testing of Microblasted, Acid-Etched/Microblasted, Anodized, and Discrete Crystalline Deposition Surfaces: An Experimental Study in Beagle Dogs

Modifications in implant surface topography and chemistry may alter the early bone response at different levels. This study characterized four implant surfaces and evaluated the biomechanical fixation and histologic response at early implantation times in a canine radius model. External-hexagon Branemark-type implants were used with four experimental surfaces: microblasted (MI), acid-etched and microblasted (AAM), anodized (A), and discrete crystalline deposition (DCD). Surface topography was assessed by scanning electron microscopy, interferometry, and x-ray photoelectron spectroscopy. The implants were placed in the central region of the radii of eight beagle dogs and remained in vivo for 10 or 30 days. The implants were torqued to interface failure, and a general linear statistical model with torque as the dependent variable and implant surface and time in vivo as independent variables was used. All surfaces presented were textured, and different surface chemistries were observed. No significant differences between implant surfaces were observed for torque at 10 days. However, at 30 days, the AAM surface presented significantly higher torque values compared to the DCD and A surfaces. Significantly higher torque values were observed at 30 days compared to 10 days (P < .001). Significantly different biomechanical fixation dependent on surface preparation was observed after 30 days, and all surfaces were biocompatible and osteoconductive.

Hydroseral habitat requirement of the endangered Shining Ramshorn Snail Segmentina nitida

Before the 1950s, the Shining Ramshorn snail Segmentina nitida was widespread across marshes and drainage ditches in Britain, continental Europe and Scandinavia. However, the population has declined rapidly and the IUCN Red Data list highlights the species as seriously vulnerable to extinction. It is now one of the six freshwater molluscan species protected under the UK Biodiversity Action Plan. Most previous research has focused on species decline and conservation issues. The aim of the research reported here was to clarify the habitat requirements of S. nitida in East Kent within the context of a seral classification. Six hydroseral stages were defined according to plant species composition. Segmentina nitida was limited uniquely to the Carex-Juncus-Eleocharis-Oenanthe community, a late seral stage in ditch succession, which confirms the work of other authors. A general linear statistical model applied to data from these sites suggested that (i) the total number of molluscs within each species varied across samples; (ii) the number of molluscs varied between samples with or without S. nitida; (iii) there was no variation in the total number of molluscs across the locations and (iv) there was no relationship between number of molluscs and sample site within location, implying some degree of connectivity between molluscan communities. Also a two-way ANOVA with Factor 1 as the number of mollusc and Factor 2 as the presence/absence of S. nitida showed a significant interaction effect. These observations are novel for these sites in East Kent and have implications for the ecology, life history strategy and conservation management of S. nitida.

Influence of Ethylenediaminetetraacetic Acid on the Active Chlorine Content of Sodium Hypochlorite Solutions When Mixed in Various Proportions

Introduction This study documented the time-related effect on active chlorine content of NaOCl solutions of different concentrations after dilution with ethylenediaminetetraacetic acid (EDTA) in various proportions. Methods Five NaOCl solutions (Milton, Black and Gold domestic bleach, and the surfactant containing products, White King and Hypochlor 1% and 4% forte) were mixed with EDTA in the following proportions: 90:10, 75:25, and 50:50. Changes in active chlorine content were determined at intervals between 5 and 18 minutes. Results Results were analyzed statistically by using general linear statistical models in SPSS. With the exception of White King solutions, EDTA substantially and rapidly reduced available chlorine even in small proportions, with loss being extreme at first and then more gradual. The reaction was exothermic. Results showed that White King mixed 90:10 lost on average only 8% of its active chlorine at its first measurement (approximately 5 minutes) but lost 36% of its active chlorine when mixed 75:25. The Hypochlor products at 90:10 dilution lost on average 27%–31% active chlorine during this time period. Mixing EDTA with NaOCl caused a dramatic loss of active chlorine for all solutions mixed 50:50. NaOCl solutions containing surfactant had less active chlorine loss for the 75:25 and 90:10 admixtures. Conclusions NaOCl and EDTA should not be present in the root canal at the same time if the therapeutic benefits of NaOCl are to be realized, but the order in which they should be used for endodontic irrigation remains a matter of debate.

Optimization of Silicon-Silicon Adhesive Wafer Bonding

Optimization of bonding parameters to develop a low temperature adhesive wafer bonding process for silicon was studied. SU-8 was used as the adhesive. The Key Process Input Variables were soft bake temperature, UV exposure and bonding temperature. The soft bake temperatures were 70 oC, 90 oC and 95 oC. UV exposure energies were 50 mJ/cm2, 100 mJ/cm2 and 150 mJ/cm2 and bonding temperatures of 90 oC, 115 oC and 140 oC were studied to optimize the curing process. The quality of the bonds was determined by two Key Process Output Variables: the fraction of interfacial area in intimate contact, measured by void area, and the strength of the bond interaction, measured by tensile strength. A general linear statistical model was used to determine the impact of the KPIVs on the KPOVs. The optimum conditions are soft bake temperature: 90 oC, UV exposure: 100 mJ/cm2 and bonding temperature: 115 oC.

Ambient and indoor particulate aerosols generated by dairies in the southern High Plains

The objectives were to quantify and size ambient aerosolized dust in and around the facilities of 4 southern High Plains dairies of New Mexico and to determine where health of workers might be vulnerable to particulate aerosols, based on aerosol concentrations that exceed national air quality standards. Ambient dust air samples were collected upwind (background) and downwind of 3 dairy location sites (loafing pen boundary, commodity, and compost field). The indoor milking parlor, a fourth site, was monitored immediately upwind and downwind. Aerosolized particulate samples were collected using high-volume sequential reference air samplers, laser aerosol monitors, and cyclone air samplers. The overall (main effects and estimable interactions) statistical general linear model statement for particulate matter (PM10; particulate matter with an aerodynamic diameter of up to 10 μm) and PM2.5 resulted in a greater mean concentration of dust in the winter (PM10=97.4±4.4μg/m3; PM2.5=32.6±2.6μg/m3) compared with the summer (PM10=71.9±5.0μg/m3; PM2.5=18.1±1.2μg/m3). The upwind and downwind boundary PM10 concentrations were significantly higher in the winter (upwind=64.3±9.5μg/m3; downwind=119.8±13.0μg/m3) compared with the summer (upwind=35.2±7.5μg/m3; downwind=66.8±11.8μg/m3). The milking parlor PM10 and PM2.5 concentration data were significantly higher in the winter (PM10=119.5±5.8μg/m3; PM2.5=55.3±5.8μg/m3) compared with the summer (PM10=88.6.0±5.8μg/m3; PM2.5=21.0±2.1μg/m3). Personnel should be protected from high aerosol concentrations found at the commodity barn, compost field, and milking parlor during the winter.

A randomized crossover trial of conservative snoring treatments: Mandibular repositioning splint and nasal CPAP

To compare the effectiveness of a mandibular repositioning splint (MRS) and nasal continuous positive airway pressure (CPAP) device as first-line treatments for disruptive snoring. Prospective randomized crossover trial. Twenty snorers received 3 months of treatment with both an MRS and nasal CPAP. Snoring Outcomes Survey (SOS), Snoring Bed Partner Survey, and Epworth questionnaires were completed serially. Changes in questionnaire scores were analyzed with a general linear statistical model and by analysis of variance. There was a significant difference between the three preference outcomes for the mean SOS changes (P = 0.003). The mean SOS change was significantly greater for those who preferred MRS to CPAP (mean score difference, 27.15). Eight snorers chose final long-term MRS treatment, five chose nasal CPAP, and seven chose neither. The majority of disruptive snorers can be managed effectively with conservative treatments and therefore avoid surgery.

Secular Decline in Male Testosterone and Sex Hormone Binding Globulin Serum Levels in Danish Population Surveys

Adverse secular trends in male reproductive health have been reported to be reflected in increased testicular cancer risk and decreased semen quality in more recently born men. These secular trends may also be reflected by changes in Leydig cell function. The objective of the study was to examine whether an age-independent time trend in male serum testosterone levels exists. Testosterone and SHBG were analyzed in 5350 male serum samples from four large Danish population surveys conducted in 1982-1983, 1986-1987, 1991-1992, and 1999-2001. Free testosterone levels were calculated. The effects of age, year of birth, and time period on hormone levels were estimated in a general linear statistical model. Testosterone, SHBG, and calculated free testosterone levels in Danish men in relation to age, study period, and year of birth were measured. Serum testosterone levels decreased and SHBG levels increased with increasing age. In addition to this expected age effect, significant secular trends in testosterone and SHBG serum levels were observed in age-matched men with lower levels in the more recently born/studied men. No significant age-independent effect was observed for free testosterone. Adjustment for a concurrent secular increase in body mass index reduced the observed cohort/period-related changes in testosterone, which no longer were significant. The observed cohort/period-related changes in SHBG levels remained significant after adjustment for body mass index. The observed age-independent changes in SHBG and testosterone may be explained by an initial change in SHBG levels, which subsequently lead to adjustment of testosterone at a lower level to sustain free testosterone levels.

SNaPshot Minisequencing and a Panel of Candidate Genes for Complex Routine Testing of Meat Performance Traits in Pigs

The aim of the study was to introduce a convenient method for identification of differences among individual animals in genes supposed to influence meat performance in pigs. The set of seven candidate genes (IGF2, FOS, MC4R, DGAT1, MYF4, MYF, and MC3R) was used. To determine the genotypes, multiplex polymerase chain reaction (PCR) and minisequencing using SNaPshot system (Applied Biosystems; Forster City, CA, USA) were applied. The efficiency of this gene panel for routine testing in pigs was verified in the Black Pied Přeštice pig breed by the statistical general linear model. The results showed that both the method and the gene panel are convenient for meat quality testing and offer reproducible results.