Effects of S100B on Serotonergic Plasticity and Neuroinflammation in the Hippocampus in Down Syndrome and Alzheimer's Disease: Studies in an S100B Overexpressing Mouse Model

S100B promotes development and maturation in the mammalian brain. However, prolonged or extensive exposure can lead to neurodegeneration. Two important functions of S100B in this regard, are its role in the development and plasticity of the serotonergic neurotransmitter system, and its role in the cascade of glial changes associated with neuroinflammation. Both of these processes are therefore accelerated towards degeneration in disease processes wherein S100B is increased, notably, Alzheimer's disease (AD) and Down syndrome (DS). In order to study the role of S100B in this context, we have examined S100B overexpressing transgenic mice. Similar to AD and DS, the transgenic animals show a profound change in serotonin innervation. By 28 weeks of age, there is a significant loss of terminals in the hippocampus. Similarly, the transgenic animals show neuroinflammatory changes analogous with AD and DS. These include decreased numbers of mature, stable astroglial cells, increased numbers of activated microglial cells and increased microglial expression of the cell surface receptor RAGE. Eventually, the S100B transgenic animals show neurodegeneration and the appearance of hyperphosphorylated tau structures, as seen in late stage DS and AD. The role of S100B in these conditions is discussed

Feeding ecology informs parasite epidemiology: prey selection modulates encounter rate with Echinococcus multilocularis in urban coyotes.

We investigated the role of urban coyote feeding ecology in the transmission of Echinococcus multilocularis, the causative agent of Alveolar Echinococcosis in humans. As coyotes can play a main role in the maintenance of this zoonotic parasite within North American urban settings, such study can ultimately aid disease risk management. Between June 2012 and June 2013, we collected 251 coyote feces and conducted trapping of small mammals (n = 971) in five parks in the city of Calgary, Alberta, Canada. We investigated E. multilocularis epidemiology by assessing seasonal variations of coyote diet and the selective consumption of different rodent intermediate host species. Furthermore, accounting for small mammal digestibility and coyote defecation rates we estimated the number of small mammal preys ingested by coyote and consequently, coyote encounter rates with the parasite. Dominant food items included small mammals, fruit and vegetation, although hare and deer were seasonally relevant. The lowest frequency of occurrence per scat of small mammals was recorded in winter (39.4 %), when consumption of deer was highest (36.4 %). However, highest encounter rates (number of infected hosts predated/season) with E. multilocularis (95% CI: 1.0 - 22.4), combined with the lack of predation on non-competent small mammal species, suggest that winter is the critical season for transmission and control of this parasite. Within the small mammal assemblage, voles (Microtus pennsylvanicus and Myodes gapperi) were the selected preys of urban coyotes and likely played a key role for the maintenance of the urban sylvatic life-cycle of E. multilocularis in Calgary

Stress and time-dependent properties of crushed chalk

Although nearly all occurrences of putty/remoulded chalk can be problematic for geotechnical engineers, laboratory studies of its mechanical properties remain infrequent. This paper presents results of a laboratory programme to characterise the mechanical behaviour of reconstituted samples from crushed chalk. Using non-destructive wave velocity propagation measurements by bender elements, a full characterisation of the small-strain shear stiffness (G0) for a range of stress levels and overconsolidation ratios is provided for the first time. The time-related small-strain stiffness and strength gains have also been investigated by ageing fully saturated reconstituted chalk samples under different isotropic stresses for a period up to 72 d. While the increase in strength was found to be negligible, an increase of the soil shear stiffness with time was recorded. Such increase appears to be mostly related to secondary (creep) deformations, although some further increase was also observed when measurable deformations ceased. Beyond the initial shear stiffness, the overall shear behaviour appears to be unaffected by the ageing and is mostly governed by the consolidation stress history and density. These experimental results are expected to benefit the design of geotechnical structures in contact with remoulded or putty chalk, in particular when assessment of small deformation behaviour (serviceability) is required. </jats:p

Fournier's Gangrene due to Masturbation in an Otherwise Healthy Male

Fournier's gangrene is a rare and often fulminant necrotizing fasciitis of the perineum and genital region frequently due to a synergistic polymicrobial infection. This truly emergent condition is typically seen in elderly, diabetic, or otherwise immune-compromised individuals. Here, we report an unusual case of Fournier's gangrene due to excessive masturbation in an otherwise healthy 29-year-old male who presented to the emergency department complaining of two days of fever, vomiting, and diffuse myalgias. Upon further questioning, he also endorsed severe scrotal pain and swelling and frequent masturbation with soap as a lubricant resulting in recurrent penile erythema and minor skin abrasions. Examination of the patient's perineum was consistent with Fournier's gangrene and included significant erythema, edema, and calor of the penis and scrotum with a large malodorous eschar. He was given intravenous antibiotics and immunoglobulin and promptly underwent three surgical debridements of the scrotum and penis with split-thickness skin grafting. Complications from excessive masturbation are exceedingly rare, but as this case illustrates, they can be life threatening

Presynaptic hyperpolarization induces a fast analogue modulation of spike-evoked transmission mediated by axonal sodium channels

In the mammalian brain, synaptic transmission usually depends on presynaptic action potentials (APs) in an all-or-none (or digital) manner. Recent studies suggest, however, that subthreshold depolarization in the presynaptic cell facilitates spike-evoked transmission, thus creating an analogue modulation of a digital process (or analogue–digital (AD) modulation). At most synapses, this process is slow and not ideally suited for the fast dynamics of neural networks. We show here that transmission at CA3–CA3 and L5–L5 synapses can be enhanced by brief presynaptic hyperpolarization such as an inhibitory postsynaptic potential (IPSP). Using dual soma–axon patch recordings and live imaging, we find that this hyperpolarization-induced AD facilitation (h-ADF) is due to the recovery from inactivation of Nav channels controlling AP amplitude in the axon. Incorporated in a network model, h-ADF promotes both pyramidal cell synchrony and gamma oscillations. In conclusion, cortical excitatory synapses in local circuits display hyperpolarization-induced facilitation of spike-evoked synaptic transmission that promotes network synchrony

2001 Research Honors Program Abstracts

Faculty in the College of Agriculture and Life Sciences at Cornell University mentor and guide undergraduate students who have chosen to pursue a research project and graduate with honors. These abstracts reflect the depth of their scholarship and intellectual ability. The research projects encompass work in animal science, biological science, entomology, natural resources, physical science, plant science, and social science