In order to understand the mechanical functions of the cardiac muscle it is important to first understand the microstructure of the tissue. Young et al. (1998) realized that quantitative three-dimensional information about the ventricular myocardium is necessary to analyze myocardial mechanics. They developed a technique using confocal fluorescence laser scanning microscopy to obtain three-dimensional images. While this method worked well in rebuilding the myocardial tissue image by image, it was quite extensive and costly. Costa et al. (1999) developed a method that was used to perform three-dimensional reconstruction as well. Their method, while less expensive and much less time consuming, required sheet assumptions and did not look directly at the cross-fiber plane. From Dr. Criscione's previous work on canines (Ashikaga et al., 2004), we found that the sheet structure can be accurately determined from cross-fiber sections without making any sheet assumptions. We have now expanded on those ideas and created a method to perform the quantitative histological investigation of the rat hearts in a way that is both timely and cost effective. We developed a processing method that preserves the orientation of the fiber and sheet angles. This method was carried out using plastic embedding since the dehydration process used in paraffin embedding has a tendency to grossly distort tissue. Once the heart was fixed in formalin, we then removed the septum and sliced it several times vertically. This allowed us to image the tissue at several depths and find an average fiber angle for each slice. Next, the specimen was hardened, and the sheet orientation was evaluated using polarized light. Once both fiber and sheet angles were obtained from several depths within the septum, we then constructed a three-dimension model of the wall. This method was both cost effective and less time consuming than previous ones and will be a method that can be used in the future to compare the myocardial tissue of diseased and healthy rat hearts so that we may better understand the mechanical functions of the heart as it remodels due to disease.

Thesis (Ph. D.)--University of Hong Kong, 1980.

Thesis (Ph. D.)--University of Hong Kong, 1968. / Typewritten.

<p> A critical factor for successful ovarian transplantation is the expeditious establishment of sufficient blood supply. Recommendations intended to improve recovery, reduce the effects of stress, and decrease the amount of pain for laboratory animals undergoing surgical procedures include post-operative analgesia. The two main types of drugs that are recommended for pain management are opioids and non-steroidal anti-inflammatory drugs (NSAIDs). Buprenorphine, an opioid, and meloxicam, an NSAID, are both widely used and have been shown to affect angiogenesis and vasculogenesis. This study was designed to examine the influence meloxicam and buprenorphine had on new blood vessel formation in the ovarian medullary region of aged female recipient CBA/J mice, transplanted with young ovaries from CBA/J donor females. Medullary vessel analysis was performed by viewing 40 &micro;m thick sections fluorescently labelled with the cell marker CD31/PECAM-1 via confocal microscopy. A multivariate analysis of variance (MANOVA) was performed between treatment groups to analyze how the independent variables of analgesic administration affected multiple dependent variables of deep microvessel quantities. Results demonstrated no significant endothelial microvessel growth or reduction among the meloxicam or buprenorphine-treated mice as compared to saline-treated mice. Results further suggested that neither type of analgesic drugs affected medullary ovarian angiogenesis and vasculogenesis after ovarian transplantation of young ovaries into aged females.</p>

published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

<p> Ceratopsian dinosaurs are one of the most diverse dinosaur groups in the Cretaceous, and an outstanding question is how growth strategies of this group evolved in relation to their shift from small bipedal basal ceratopsians to larger quadrupedal ceratopsids. Previous bone histology studies have investigated several basal ceratopsians and centrosaurine ceratopsids (e.g., <i>Centrosaurus, Pachyrhinosaurus, Einiosaurus</i>), but no chasmosaurine ceratopsids have been investigated. I conducted histological analysis of humeri, ulnae, femora, tibiae, ribs, and ossified tendons from multiple specimens of two species of chasmosaurine ceratopsid dinosaurs from the late Campanian (Upper Cretaceous) Kaiparowits Formation of southern Utah, <i>Kosmoceratops richardsoni</i> and <i>Utahceratops gettyi</i>, to examine bone microstructure indicators of growth rate and maturity. I also reexamined the long-bone histology of the ceratopsian dinosaurs <i>Psittacosaurus mongoliensis, Protoceratops andrewsi</i>, and <i>Centrosaurus apertus </i>. All elements of <i>Utahceratops</i> and <i>Kosmoceratops </i> examined are dominated by densely vascularized tissue, indicative of sustained fast growth. Radially-oriented vascular canals as well as dense osteocytes from throughout ontogeny are further indicators of rapid growth. I identified juvenile (UMNH VP 20444, UMNH VP 20454), subadult (UMNH VP 16681) and adult (UMNH VP 16860, UMNH VP 16861, UMNH VP 12198) specimens of <i> Utahceratops</i>, and two subadult to adult specimens (UMNH VP 17000, UMNH VP 21339) of <i>Kosmoceratops</i>. </p><p> I conclude that basal ceratopsians grew more slowly than the large quadrupedal ceratopsids, as evidenced by a generally higher number of definitive growth lines prevalent throughout development. In contrast, the presence of dense osteocytes, and reticular and radially-oriented vascular canals are rapid growth indicators shared by all sampled large ceratopsids, and imply an elevated metabolism for all ceratopsians. Sampled specimens of <i>Utahceratops </i> and <i>Kosmoceratops</i> do not preserve any evidence of annual lines of arrested growth (LAGs). Placed in context with the number of LAGs observed in Alaskan <i>Pachyrhinosaurus, Centrosaurus</i> from Alberta, and <i>Einosaurus</i> from Montana, these data suggest a latitudinal gradient in the number of LAGs, which suggests that bone growth is reacting to the climate.</p>

<p> Spermatogenesis is governed by vitamin A, as shown by vitamin A deficient (VAD) testes, which lack advanced germ cells. Vitamin A signaling is mediated by retinoid receptors. There are two families of retinoid receptors, retinoic acid receptors (RARs) and retinoid X receptors (RXRs), each with alpha, beta and gamma subtypes. Retinoic acid receptor alpha (RARA), plays a significant role in the testis such that <i>Rara</i>-null males are infertile because of severe germ cell loss. </p><p> Striking similarities of the testicular phenotypes are detected between <i> Rara</i>-null and VAD mice: severely degenerated testes, lack of germ cells, sloughing of mature spermatids, and infertility. To discern the molecular function of RARA in germ cells, <i>Rara</i> was conditionally deleted using stimulated by retinoic acid 8 (STRA8)-iCRE. With RARA function disabled in germ cells, morphological abnormalities detected in the testes included lack of germ cell organization, lack of lumen, sloughing cells, and vacuolization. Not surprisingly, germ-cell specific <i>Rara</i> conditional knockout mice (cKO) had a dramatic reduction in epididymal sperm number. Further analysis of cKO testes demonstrated decreased spermatogonial proliferation and differentiation, while meiotic defects such as reduced synapsis, synaptonemal fragmentation, and unrepaired double strand breaks were increased. Furthermore, functional spermatogonial transplantation assays pointed to the possibility that RARA regulates spermatogonial stem cell colonization and proliferation, as shown by the reduction of donor-derived spermatogenesis from the cKO donor germ cells. The lack of RARA in the testes clearly shows quantifiable deficiencies during spermatogonial proliferation, differentiation, and meiosis. </p><p> Microarray gene expression studies of mRNAs from the enriched germ cells from wild type and cKO mice provided molecular evidence that RARA regulates spermatogonial differentiation at postnatal day 4 (P4) and meiosis at P8. Cell differentiation, cell adhesion, cell migration, and other pathways related to the early steps of spermatogonial differentiation were found to be functional categories significant in germ cells from P4. These were very distinct from synapsis, synaptonemal complex formation, and crossover formation related to meiosis, which were functional categories significant in germ cells from P8. In conjunction with phenotypic abnormalities, we provide gene expression evidence that RARA mediates retinoic acid function during spermatogonial proliferation, differentiation, and meiosis.</p>

No description available.

No description available.

No description available.