Extensive research has documented the experiences and outcomes of women and certain underrepresented racial/ethnic minority groups in STEM educational programs. This paper contributes to current conversations by focusing on the experiences of individuals that identify as both a racial/ethnic and sexual/gender minority (SGM). This paper has two major objectives in mind: (1) provide one of the first empirical studies examining the experiences of SGM students in STEM and (2) interrogate the intersection of racial/ethnic identity and sexual/gender identity within the context of these programs. In order to provide a more robust understanding in these areas, this paper is guided by the following research questions: (1) What are the experiences of students who identify as both a racial/ethnic and sexual/gender minority in STEM educational programs, (2) in what ways do these students' sexual/gender and racial/ethnic identity influence these experiences, (3) do racial/ethnic and sexual/gender minorities feel a sense of belonging within their respective programs and why, and (4) how do racial/ethnic and sexual/gender minorities perceive they are treated by peers, faculty, and staff within these programs. This paper takes a mixed-method approach, incorporating both interviews and quantitative survey data to gain insights into these questions. Upon analysis, major findings demonstrated that students experiences an erasure of student diversity in the classroom, while also experiencing higher salience with their sexual/gender identity when compared to their racial/ethnic identity.

Needle-to-stem unit rate (NESTUR) is a stem growth index of conifer seedling trees that measures the efficiency of stemwood production per unit of needle growth. Five experiments were carried out in this thesis using progenies of two unrelated full-sib radiata pine crosses. The initial experiment (experiment 1) applied the bulked segregant analysis technique to determine whether RAPD analysis could be successfully extended to the development of molecular markers for NESTUR in radiata pine. The NESTUR values of 174 progenies of the full-sib family 12038 x 10946 were determined. Based on the genotypic analysis of the individuals, two quantitative trait loci (QTL) controlling NESTUR were identified at ANOVA P-levels of 0.01-0.001. An absence of RAPD fragment markers generated by primers OPE-06 and OPA-10 was associated with low NESTUR values, while primer UBC-333 generated a 550 bp band that was associated with high NESTUR values. Linkage to components of NESTUR (increments in stem diameter and stem volume) was demonstrated for one of the QTL, while the other was unique to NESTUR, and not shared with the components. There was a significant interaction between the two QTLs. Presence of OPA-101200 locus appeared to inhibit expression of the QTL linked to UBC-333 [subscript 550]. ¶ To further analyse the quantitative trait loci (QTLs) controlling NESTUR, a linkage map was constructed from RAPD markers segregating in 93 haploid progeny of another full sib cross (30040 x 80121) (experiment 2). Two hundred and sixty-two (262) markers were mapped to 14 linkage groups of at least 7 markers, ranging in size from 39 to 183 cM. The 14 linkage groups covered approximately 1511 cM of genetic map distance. ¶ In experiment 3, the linkage map was used to map QTLs controlling NESTUR, as well as increments in seedling stem diameter, volume, and height and needle volume. Altogether, five putative QTLs were detected for NESTUR, with explained variation ranging from 9 to 22%. Of the five QTLs detected, 3 were coincidental with those for stem growth in height, diameter and volume. The two QTL positions that were unique to NESTUR were flanked by QTLs for the component traits. Together, effects of the five QTLs explained 48% of the total phenotypic variation for NESTUR. ¶ Ability of identified markers to predict the phenotype and seedlings with growth potential was assessed in the cross 30040 x 80121, using six RAPD markers associated with NESTUR at ANOVA P-levels of 0.01-0.001 (experiment 4). The correlation between observed NESTUR and predicted values was 0.70. Differences in observed vs. predicted values were not large and did not indicate serious misclassifications, such as classification of an upper ranking individual into the lower group, or vice versa. ¶ Over a two-year growth period, the ability of NESTUR to predict stem growth was strongly affected by seedling age. In contrast, markers linked to NESTUR showed a consistent ability to predict stem growth, irrespective of seedling age. Compared with the top 1% of the original population, seedlings selected for their genotypic values showed a higher stem volume growth of 103% in the first year, and 76% in the second year. ¶ The expression of QTLs for stem volume, stem diameter, height, number of branches, number of whorls, and branches/whorl were compared at 5, 12, and 24 months of age. Two QTLs detected for height showed contrasting expression over two years, one was gradually reduced from LOD of 2.70 to 0.43 and the other increased from 1.12 to 2.45. Compared with the pattern observed for height, LOD scan profiles for diameter and volume showed less temporal change of peaks, suggesting that the genetic control for height growth is probably more unstable than that of diameter. QTLs controlling the phenotype at the time of measurement (ie the final phenotype) showed similar magnitude of effects on that trait's respective increments (or growth rate).

Thesis (doctoral)--Humboldt-Universiẗat, Berlin, 2005. / Includes bibliographical references (p. 231-260) and index.

Colony-stimulating factor 1 receptor (CSF1R, Fms) is an integral transmembrane glycoprotein with tyrosine specific protein kinase activity that it is found on the mononuclear phagocytes to promote their survival, proliferation and differentiation. Colony-stimulating factor 1 (CSF-1), also known as M-CSF, is a protein ligand that acts on the CSF1R. There is a variable association of Fms with the stem cell marker CD34 on acute myeloid leukemia (AML) cells and this suggests different structures of the AML hierarchy in different patients. Mouse stromal cells (MS-5) were transduced with a plasmid containing human CSF-1 because mouse CSF-1 is inactive on human CSF1R. Results show that AML cells cultured with CSF-1-expressing stroma had a much better growth and survival than the control stroma, suggesting that CSF-1 might be a stimulating factor for the growth of leukemic stem cells.

Construction of the vertebrate nervous system begins with the decision of a group of ectoderm cells to take on a neural fate. Studies using Xenopus ectodermal explants, or with mouse ectoderm cells or embryonic stem (ES) cells, demonstrated that this process of neural determination occurred by default – the ectoderm cells became neural after the removal of inhibitory signals. Whether ectoderm or ES cells directly differentiate into bona fide neural stem cells is not clear. One model suggests that there is an intermediate stage where “primitive” neural stem cells (pNSC) emerge harbouring properties of both ES cells and neural stem cells. The goal of my research was to address this question by evaluating the role of growth factor signaling pathways and their impact on the function of the zinc-finger homeobox transcription factor, Zfhx1b, during mouse neural stem cell development. I tested whether FGF and Wnt signaling pathways could regulate Zfhx1b expression to control early neural stem cell development. Inhibition of FGF signaling at a time when the ectoderm is acquiring a neural fate resulted in the accumulation of too many pNSCs, at the expense of the definitive neural stem cells. Interestingly, over-expression of Zfhx1b was sufficient to rescue the transition from a pNSC to definitive NSC. These data suggested that definitive NSC fate specification in the mouse ectoderm was facilitated by FGF activation of Zfhx1b, whereas canonical Wnt signaling repressed Zfhx1b expression. Next I sought to determine whether Zfhx1b was similarly required during neural lineage development in ES cells. FGF and Wnt signaling modulated expression of Zfhx1b in ES cell cultures in manner resembling my observations from similar experiments using mouse ectoderm. Knockdown of Zfhx1b in ES cells using siRNA did not affect the initial transition of ES cells to pNSC fate, but did limit the ability of these neural cells to further develop into definitive NSCs. Thus, my findings using ES cells were congruent with evidence from mouse embryos and supported a model whereby intercellular signaling induced Zfhx1b, required for the development of definitive NSCs, subsequent to an initial neural specification event that was independent of this pathway.

The studies in this thesis examined piglet gonocyte identification, isolation, purification, preservation and potential for initiation of spermatogenesis after transplantation into irradiated recipient testes. As a first step, we characterized a previously non-described auto-fluorescence in the piglet testis tissue. This auto-fluorescence mainly originated from granules among the testis interstitial cells, and we found that its interference with immuno-fluorescence can be overcome using Sudan black staining. We also showed that porcine gonocytes can be specifically labelled with the lectin Dolichos biflorus agglutinin (DBA). To optimize gonocyte isolation, we found that ~9-fold more live cells could be harvested by enzymatic digestion of testis tissues than with mechanical methods. However, the proportion of gonocytes (~7%) did not differ between the mechanical and enzymatic methods of testis cell isolation. We then developed a novel three-step strategy for isolation of gonocytes by combining enzymatic digestion and vortexing, resulting in a gonocyte proportion of ~40% (~5-fold more than that from conventional methods). For short-term preservation of testis cells, we found that the survival of testis cells under hypothermic conditions was dependent on the cell type, and affected by storage duration, temperature and medium used. More than 80% of live testis cells survived the 6-day hypothermic preservation period in 20% FBS-L15, without visible changes to the cell culture potential or gonocyte proportion. In another experiment where testis tissues were maintained under hypothermic conditions, we found that ~25% of testis cells could survive for 6 days if preserved in HypoThermosol-FRS solution (HTS-FRS), without morphological changes. To purify gonocytes, we showed that centrifugation of testis cells using 17% Nycodenz can lead to precipitation of gonocytes in pellets (with a purity of > 80%). We also found that pre-coating tissue culture plates with both fibronectin and poly-D-lysine can result in the negative selection of gonocytes (with a purity of up to 85%). We subsequently showed that further purification of gonocytes (to > 90%) could be achieved by combining the two latter approaches. To prepare recipients for germ cell transplantation, we used local irradiation of piglet testes which reduced testis growth, decreased seminiferous tubule diameters and completely eliminated spermatogenesis at 4 months post-irradiation. Compared with the absence of endogenous spermatogenesis in the control testes, spermatogenesis up to elongating spermatids was observed in the irradiated testes after gonocyte transplantation. In summary, we investigated several critical elements in the study and manipulation of gonocytes in a large animal model.

Construction of the vertebrate nervous system begins with the decision of a group of ectoderm cells to take on a neural fate. Studies using Xenopus ectodermal explants, or with mouse ectoderm cells or embryonic stem (ES) cells, demonstrated that this process of neural determination occurred by default – the ectoderm cells became neural after the removal of inhibitory signals. Whether ectoderm or ES cells directly differentiate into bona fide neural stem cells is not clear. One model suggests that there is an intermediate stage where “primitive” neural stem cells (pNSC) emerge harbouring properties of both ES cells and neural stem cells. The goal of my research was to address this question by evaluating the role of growth factor signaling pathways and their impact on the function of the zinc-finger homeobox transcription factor, Zfhx1b, during mouse neural stem cell development. I tested whether FGF and Wnt signaling pathways could regulate Zfhx1b expression to control early neural stem cell development. Inhibition of FGF signaling at a time when the ectoderm is acquiring a neural fate resulted in the accumulation of too many pNSCs, at the expense of the definitive neural stem cells. Interestingly, over-expression of Zfhx1b was sufficient to rescue the transition from a pNSC to definitive NSC. These data suggested that definitive NSC fate specification in the mouse ectoderm was facilitated by FGF activation of Zfhx1b, whereas canonical Wnt signaling repressed Zfhx1b expression. Next I sought to determine whether Zfhx1b was similarly required during neural lineage development in ES cells. FGF and Wnt signaling modulated expression of Zfhx1b in ES cell cultures in manner resembling my observations from similar experiments using mouse ectoderm. Knockdown of Zfhx1b in ES cells using siRNA did not affect the initial transition of ES cells to pNSC fate, but did limit the ability of these neural cells to further develop into definitive NSCs. Thus, my findings using ES cells were congruent with evidence from mouse embryos and supported a model whereby intercellular signaling induced Zfhx1b, required for the development of definitive NSCs, subsequent to an initial neural specification event that was independent of this pathway.

The studies in this thesis examined piglet gonocyte identification, isolation, purification, preservation and potential for initiation of spermatogenesis after transplantation into irradiated recipient testes. As a first step, we characterized a previously non-described auto-fluorescence in the piglet testis tissue. This auto-fluorescence mainly originated from granules among the testis interstitial cells, and we found that its interference with immuno-fluorescence can be overcome using Sudan black staining. We also showed that porcine gonocytes can be specifically labelled with the lectin Dolichos biflorus agglutinin (DBA). To optimize gonocyte isolation, we found that ~9-fold more live cells could be harvested by enzymatic digestion of testis tissues than with mechanical methods. However, the proportion of gonocytes (~7%) did not differ between the mechanical and enzymatic methods of testis cell isolation. We then developed a novel three-step strategy for isolation of gonocytes by combining enzymatic digestion and vortexing, resulting in a gonocyte proportion of ~40% (~5-fold more than that from conventional methods). For short-term preservation of testis cells, we found that the survival of testis cells under hypothermic conditions was dependent on the cell type, and affected by storage duration, temperature and medium used. More than 80% of live testis cells survived the 6-day hypothermic preservation period in 20% FBS-L15, without visible changes to the cell culture potential or gonocyte proportion. In another experiment where testis tissues were maintained under hypothermic conditions, we found that ~25% of testis cells could survive for 6 days if preserved in HypoThermosol-FRS solution (HTS-FRS), without morphological changes. To purify gonocytes, we showed that centrifugation of testis cells using 17% Nycodenz can lead to precipitation of gonocytes in pellets (with a purity of > 80%). We also found that pre-coating tissue culture plates with both fibronectin and poly-D-lysine can result in the negative selection of gonocytes (with a purity of up to 85%). We subsequently showed that further purification of gonocytes (to > 90%) could be achieved by combining the two latter approaches. To prepare recipients for germ cell transplantation, we used local irradiation of piglet testes which reduced testis growth, decreased seminiferous tubule diameters and completely eliminated spermatogenesis at 4 months post-irradiation. Compared with the absence of endogenous spermatogenesis in the control testes, spermatogenesis up to elongating spermatids was observed in the irradiated testes after gonocyte transplantation. In summary, we investigated several critical elements in the study and manipulation of gonocytes in a large animal model.

Embryonic stem cells (ESCs) hold great promise for treatment of degenerative disorders such as Parkinson's and Alzheimer's disease, diabetes, and cardiovascular disease. The ability of ESCs to differentiate to all somatic cell types suggests that they may serve as a robust cell source for production of differentiated cells for regenerative medicine and other cell-based therapeutics. In order for ESCs to be used effectively in clinical settings, efficient and reproducible differentiation to targeted cell types must be demonstrated. The overall objective of this project was to engineer microenvironmental control over differentiating ESCs through the formation of embryoid bodies (EBs) uniform in size and shape, and through the incorporation of morphogen-containing polymer microspheres within the interior of EBs. The central hypothesis was that morphogen delivery through incorporated polymer microspheres within a uniform population of EBs will induce controlled and uniform differentiation of ESCs. Rotary suspension culture was developed in order to efficiently produce uniform EBs in high yield. Compared to static suspension culture, rotary suspension significantly improved the production of differentiating cells and EBs over the course of 7 days, while simultaneously improving the homogeneity of EB size and shape compared to both hanging drop and static EBs. The diffusive transport properties of EBs formed via rotary suspension were investigated using a fluorescent, cell permeable dye to model the movement of small morphogenic molecules within EBs. Confocal microscopy, cryosections and EB dissociation all demonstrated that the dye was not able to fully penetrate EB, and that the larger EBs at later time points (7 days) retarded dye movement to a greater extent than earlier EBs (days 2 and 4). Polymer microspheres capable of encapsulating morphogenic factors were incorporated into EBs in order to overcome the diffusional limitations of traditional soluble delivery. The size of microspheres, microsphere coating, microsphere to cell ratio, and rotary mixing speed were all observed to influence incorporation within EBs. The use of microsphere-mediated delivery within EBs to direct cell differentiation was examined. Microsphere-mediated delivery of retinoic acid (RA) induced formation of uniquely cystic spheroids with a visceral endoderm layer enveloping a pseudo-stratified columnar epithelium, and with spatial localization of transcriptional profiles similar to the early primitive streak stage of mouse development. Continued differentiation of RA MS EBs in defined media conditions was assessed. Gene expression demonstrated that regular serum enhanced endoderm induction, serum-free media supported ectoderm differentiation, while mesoderm was most prominent in untreated EBs in full serum. In summary, this work has realized a unique approach for stem cell differentiation through modification of the internal microenvironment of ESC spheroids. This novel inside-out method toward engineering EBs demonstrated that the mode of morphogen delivery significantly affected the course of differentiation. These studies provide the basis for ongoing work, which will utilize the choice of microsphere material, coating, and morphogen in order to uniquely study mechanisms of ESC differentiation and achieve unparalleled engineering of the EB microenvironment.

Clinical trials investigating autologous stem cell transplantation (ASCT) have historically excluded elderly patients due to the risk of treatment-related morbidity related to the administration of high dose chemotherapy. While the availability of this procedure continues to expand, the elderly still represent a population for which the role of ASCT needs to be fully defined. 201 patients who underwent autologous stem cell transplantation (ASCT) for Non Hodgkins lymphoma (NHL) at a single institution following BEAM conditioning between January 1, 2000 and December 31, 2007 were retrospectively identified from the Yale University School of Medicine Bone Marrow Transplant Database. 67 patients were older than 60 years at the time of transplantation (median age 65, range 60 75) and were compared to a matched group of 134 patients transplanted during the same time period. These groups were extremely well-matched for all demographics such as gender, NHL histology, performance status, and comorbidities. Most patients had advanced stage disease at diagnosis and were transplanted at first or second remission. Diffuse large B-cell and mantle cell lymphoma were the most common subtypes but other subtypes were represented. The elderly group experienced significantly more serious toxicities within the first 100 days (63%) when compared to the control group (42%). However, there were no statistical differences (p<0.0001) between the groups regarding specific organ system toxicities. The 1-year non-relapse mortality (3%) was not significantly different when compared to the younger cohort (1%). At a median follow-up of 31 months the median overall survival is 85 months in the elderly group and at a median follow up of 33 months in the younger group the median overall survival has not yet been reached. The overall survival at 3 years is 74% and 75% respectively (p=0.91). The disease-free survival at 3 years is 48% in the elderly group compared to 58% in the control group (p=0.66). By univariate analysis, age >60 years (RR 3.1, 95% CI 1.7 5.7, p=0.004) was the only factor predictive of developing a serious toxicity from ASCT within the first 100 days. HCT-CI score (RR 2, 95% CI 1 4, p=0.043) was the only factor associated with significantly worse overall survival. Autologous stem cell transplantation can be safely performed in selected patients older than 60 years with chemosensitive NHL. Although elderly patients appear more likely to develop acute toxicities, the outcomes are similar to that of younger patients with respect to non-relapse mortality, disease-free survival, and overall survival.