Michael M. Meyer

Statistical Analysis of Multiple Sociometric Relations

Abstract Loglinear models are adapted for the analysis of multivariate social networks, a set of sociometric relations among a group of actors. Models that focus on the similarities and differences between the relations and models that concentrate on individual actors are discussed. This approach allows for the partitioning of the actors into blocks or subgroups. Some ideas for combining these models are described, and the various models and computational methods are applied to the analysis of data for a corporate interlock network of the 25 largest organizations in Minneapolis/St. Paul and for a classic network of 18 monks in a cloister. The computational techniques all involve variations on the standard iterative proportional-fitting algorithm used extensively in the analysis of multidimensional contingency tables.

Synergistic Effects of GDNF and VEGF on Lifespan and Disease Progression in a Familial ALS Rat Model

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of motor neurons in the brain and spinal cord. We have recently shown that human mesenchymal stem cells (hMSCs) modified to release glial cell line-derived neurotrophic factor (GDNF) decrease disease progression in a rat model of ALS when delivered to skeletal muscle. In the current study, we determined whether or not this effect could be enhanced by delivering GDNF in concert with other trophic factors. hMSC engineered to secrete GDNF (hMSC-GDNF), vascular endothelial growth factor (hMSC-VEGF), insulin-like growth factor-I (hMSC-IGF-I), or brain-derived neurotrophic factor (hMSC-BDNF), were prepared and transplanted bilaterally into three muscle groups. hMSC-GDNF and hMSC-VEGF prolonged survival and slowed the loss of motor function, but hMSC-IGF-I and hMSC-BDNF did not have any effect. We then tested the efficacy of a combined ex vivo delivery of GDNF and VEGF in extending survival and protecting neuromuscular junctions (NMJs) and motor neurons. Interestingly, the combined delivery of these neurotrophic factors showed a strong synergistic effect. These studies further support ex vivo gene therapy approaches for ALS that target skeletal muscle.

Loglinear models and categorical data analysis with psychometric and econometric applications

Abstract The past decade has seen the publication of a large number of books and papers on the analysis of multi-way contingency tables using loglinear and logic models. The present article presents a summary of the statistical theory that underlies much of this work, and provides some linkage to models and methods of special interest to psychometricians and econometricians. The discussion includes a review of recent and current research on the computation of maximum likelihood estimates for loglinear and logit models, especially for large multi-way contingency tables.

Male-specific differences in proliferation, neurogenesis, and sensitivity to oxidative stress in neural progenitor cells derived from a rat model of ALS.

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive motor dysfunction and the loss of large motor neurons in the spinal cord and brain stem. A clear genetic link to point mutations in the superoxide dismutase 1 (SOD1) gene has been shown in a small group of familial ALS patients. The exact etiology of ALS is still uncertain, but males have consistently been shown to be at a higher risk for the disease than females. Here we present male-specific effects of the mutant SOD1 transgene on proliferation, neurogenesis, and sensitivity to oxidative stress in rat neural progenitor cells (rNPCs). E14 pups were bred using SOD1G93A transgenic male rats and wild-type female rats. The spinal cord and cortex tissues were collected, genotyped by PCR using primers for the SOD1G93A transgene or the male-specific Sry gene, and cultured as neurospheres. The number of dividing cells was higher in male rNPCs compared to female rNPCs. However, SOD1G93A over-expression significantly reduced cell proliferation in male cells but not female cells. Similarly, male rNPCs produced more neurons compared to female rNPCs, but SOD1G93A over-expression significantly reduced the number of neurons produced in male cells. Finally we asked whether sex and SOD1G93A transgenes affected sensitivity to oxidative stress. There was no sex-based difference in cell viability after treatment with hydrogen peroxide or 3-morpholinosydnonimine, a free radical-generating agent. However, increased cytotoxicity by SOD1G93A over-expression occurred, especially in male rNPCs. These results provide essential information on how the mutant SOD1 gene and sexual dimorphism are involved in ALS disease progression.

Gonadectomy and dehydroepiandrosterone (DHEA) do not modulate disease progression in the G93A mutant SOD1 rat model of amyotrophic lateral sclerosis

Abstract Epidemiological studies have shown a higher incidence of amyotrophic lateral sclerosis (ALS) in men than women. Interestingly, there are clear gender differences in disease onset and progression in rodent models of familial ALS overexpressing mutated human superoxide dismutase-1 (SOD1-G93A). In the present study we sought to determine whether the alterations of serum steroid levels by gonadectomy or chronic treatment of neuroprotective neurosteroids can modulate disease onset and progression in a rat model of ALS (SOD1-G93A transgenic rats). Presymptomatic SOD1-G93A rats were gonadectomized or treated with a neurosteroid dehydroepiandrosterone (DHEA) using silastic tubing implants. Disease onset and progression of the animals were determined by the routine analyses of locomotor testing using the Basso-Beattie-Bresnahan (BBB) score. Although sexual dimorphism was observed in intact and gonadectomized SOD1-G93A rats, there was no significant effect of gonadectomy on disease onset and progression. DHEA treatment did not alter disease progression or survival in SOD1-G93A rats. Our results indicate that gonadal steroids or neurosteroids are not one of the possible modulators for the occurrence or disease progression in a rat model of ALS. Further analysis will be necessary to understand how sexual dimorphism is involved in ALS disease progression.

Acute glial activation by stab injuries does not lead to overt damage or motor neuron degeneration in the G93A mutant SOD1 rat model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease where motor neurons within the brain and spinal cord are lost, leading to paralysis and death. Recently, a correlation between head trauma and the incidence of ALS has been reported. Furthermore, new invasive neurosurgical studies are being planned which involve inserting needles directly to the spinal cord. We therefore tested whether acute trauma to the spinal cord via a knife wound injury would lead to accelerated disease progression in rodent models of ALS (SOD1(G93A) rats). A longitudinal stab injury using a small knife was performed within the lumbar spinal cord region of presymptomatic SOD1(G93A) rats. Host glial activation was detected in the lumbar area surrounding a micro-knife lesion at 2 weeks after surgery in both wild type and SOD1(G93A) animals. However, there was no sign of motor neuron loss in the injured spinal cord of any animal and normal motor function was maintained in the ipsilateral limb. These results indicate that motor neurons in presymptomatic G93A animals are not affected by an invasive puncture wound injury involving reactive astrocytes. Furthermore, acute trauma alone does not accelerate disease onset or progression in this ALS model which is important for future strategies of gene and cell therapies directly targeting the spinal cord of ALS patients.