Reactions of silicon compounds with organic hydroxyl groups

Thesis (M.A.)--Boston University, 1949. This item was digitized by the Internet Archive

Pathological changes occurring in the endocrine glands in cases of mental disease with special reference to the pituitary

The following thesis is concerned with the histological examination of some of the endocrine glands obtained from cases of mental disease; these have been compared with a series of glands obtained from cases of presumed normal mentality.The following conclusions have been drawn.;1) In a high percentage of cases of mental disease there can be demonstrated an increase of fibrous tissue throughout the endocrine glands. It is important to note, however, that in normal cases there is also a tendency for the fibrous tissue to be increased though the extent of fibrosis is certainly less than in psychotic material.2) In schizophrenic cases there is marked tendency for the nuclear chromatin to be reduced; this is especially marked in the testes of male cases. This is not a constant finding and it should be pointed out that this condition may occur in any chronic disease. The etiology of chromatin deficiency is by no means certain.3) In schizophrenic states there are commonly marked departures from the predicted endocrine weights.4) The cardio- vascular system tends to be underdeveloped in schizophrenics. In manic- depressive states the cardio- vascular system is L:téll developed and may be hypertrophied.There is a curious fine atheroma found in many cases of schizophrenia; this affects the aorta in quite young cases; the cause is obscure but may be toxic.5) In manic states there is usually a well marked preponderance of eosinophil cells in the anterior lobe of the pituitary. In depressive states the basophils tend to predominate. In depressive states it is the rule to find pituitary glands which are well above the average predicted weight. in manic states the weight is average.6) In epilepsy there is a fairly constant increase of fibrous tissue in the anterior lobe of the pituitary. There is a tendency for the nuclear chromatin to be reduced in many of the endocrine glands.A general criticism of the above results is that there are no constant findings which can be related to any definite mental state; this however could hardly be expected. The etiology of mental abnormality must, from the nature of the problem, be very complex. It would be irrational to expect to find a pathology which could be described entirely,- in terms of either morbid anatomy or psycho- pathology.Behaviour, be it normal or abnormal, is the overt reaction of an organism to its environment. The human organism is composed of a multitude of cells which are collected together into functional units; each of these units has to adapt itself to a local envi:. °on: ;nt . Each unit must be working in harmonious cooperation with the others if the whole organism is to be in a state of equilibrium.There is abundant evidence to show the importance of the endocrine gland unit in the biological reactions of all the higher animals. There is a very intimate relationship between the ductless glands and the nervous system; in fact it appears probable that the efficient working of the latter is entirely dependent upon a correctly balanced endocrine system.Histo -pathological methods of investigation have many obvious drawbacks; it is difficult to avoid aretfacts due to post -mortem change and distortion due to fixation; it is still more difficult to estimate the probable degree of physiological activity of the gland from the post-mortem appearances.The only reliable approach to the problem is biological. It is the writer's hope to continue investigations along these lines and to be able to throw some light on the functional activity of the endocrines in mental disease

Bayesian Learning and Predictability in a Stochastic Nonlinear Dynamical Model

Bayesian inference methods are applied within a Bayesian hierarchical modelling framework to the problems of joint state and parameter estimation, and of state forecasting. We explore and demonstrate the ideas in the context of a simple nonlinear marine biogeochemical model. A novel approach is proposed to the formulation of the stochastic process model, in which ecophysiological properties of plankton communities are represented by autoregressive stochastic processes. This approach captures the effects of changes in plankton communities over time, and it allows the incorporation of literature metadata on individual species into prior distributions for process model parameters. The approach is applied to a case study at Ocean Station Papa, using Particle Markov chain Monte Carlo computational techniques. The results suggest that, by drawing on objective prior information, it is possible to extract useful information about model state and a subset of parameters, and even to make useful long-term forecasts, based on sparse and noisy observations

Assembly of the outer retina in the absence of GABA synthesis in horizontal cells

<p>Abstract</p> <p>Background</p> <p>The inhibitory neurotransmitter gamma-amino-butyric acid (GABA) not only modulates excitability in the mature nervous system but also regulates neuronal differentiation and circuit development. Horizontal cells, a subset of interneurons in the outer retina, are transiently GABAergic during the period of cone photoreceptor synaptogenesis. In rodents, both horizontal cells and cone axonal terminals express GABA_Areceptors. To explore the possibility that transient GABA expression in mouse neonatal horizontal cells influences the structural development of synaptic connectivity in the outer retina, we examined a mutant in which expression of GAD67, the major synthesizing enzyme for GABA, is selectively knocked out in the retina.</p> <p>Results</p> <p>Immunocytochemistry and electron microscopy revealed that the assembly of triad synapses involving cone axonal pedicles and the dendrites of horizontal and bipolar cells is unaffected in the mutant retina. Moreover, loss of GABA synthesis in the outer retina did not perturb the spatial distributions and cell densities of cones and horizontal cells. However, there were some structural alterations at the cellular level: the average size of horizontal cell dendritic clusters was larger in the mutant, and there was also a small but significant increase in cone photoreceptor pedicle area. Moreover, metabotropic glutamate receptor 6 (mGluR6) receptors on the dendrites of ON bipolar cells occupied a slightly larger proportion of the cone pedicle in the mutant.</p> <p>Conclusions</p> <p>Together, our analysis shows that transient GABA synthesis in horizontal cells is not critical for synapse assembly and axonal and dendritic lamination in the outer retina. However, pre- and postsynaptic structures are somewhat enlarged in the absence of GABA in the developing outer retina, providing for a modest increase in potential contact area between cone photoreceptors and their targets. These findings differ from previous results in which pharmacological blockade of GABA_Areceptors in the neonatal rabbit retina caused a reduction in cone numbers and led to a grossly disorganized outer retina.</p

Tribute to Paul Oberst

A tribute to Professor Paul Oberst

Effects of process gas environment on platinum-inclusion density and dissolution rate in phosphate laser glasses

The effects of process gas environment on reducing the density of platinum inclusions in phosphate laser glasses are examined. The platinum inclusions originate from the crucibles used to melt the laser glass and can lead to optical damage in glasses used in highpeak- power lasers. The melting experiments examine the effects of N₂, O₂ and CI₂ gases on inclusion density and platinum dissolution rates. The more oxidizing the process gas conditions, the greater the dissolution rate (O₂ + CI₂ > O₂ » N₂). A thin-film mass transport model is used to analyze dissolution rate data for small plates of platinum over a range of temperatures from 1000 to 1200°C and oxygen fugacity of 10³ to 1 bar. At 1200°C the platinum dissolution rate is approximately 3.0- 10⁻⁸ (Pₒ₂)⁰⁷ (in g/(cm² * s)) where Pₒ₂ is the oxygen fugacity of the process gas in bar. Using CI₂ rather than O₂ causes a measurable increase in the optical absorption of the glass that may be due to either a red-shift and/or a greater absorption coefficient for the platinumchlorine complex

Effects of melting conditions on platinum-inclusion content in phosphate laser glasses

Results from small-scale glass melting experiments aimed at reducing the density of platinum particles in phosphate laser glasses are discussed. The platinum particles originate from the crucibles used to melt the laser glass and can cause optical damage in glasses used in high-peak-power lasers. The melting experiments examine the effects of a) temperature and temperature gradients; b) processing time; and c) O₂ atmosphere on the formation and dissolution of platinum inclusions in LG-750 phosphate laser glass. Results show that most platinum inclusions originate early in the melt cycle, with thermal gradients within the melter being one of the major causes. By using oxidizing conditions (O₂), the platinum inclusions can be dissolved into the glass during the course of the melt cycle. Results from the laboratory-scale melting experiments have been incorporated into a proprietary laser-glass melting process. The laser glass prepared under these conditions has an average of less than 0.1 platinum inclusions/1, which represents a 1000-fold reduction over the previously available phosphate laser glasses