No description available.

Megastigmus spermotrophus is a parasitic chalcid wasp that spends most of its life in the seed of its host, Douglas-fir (Pseudotsuga menziesii). The adult female wasp lays its eggs into the megagametophyte deep within the ovule; the larva prevents an unpollinated ovule from aborting, redirecting resources to feed itself. Host-site selection pressures that influence female oviposition depend on a number of factors. Morphological characteristics of Douglas-fir cones including seed size, seed location, and scale thickness were measured for every ovuliferous scale. Seeds infested by M. spermotrophus as well as seeds fused to galls intiated by a competing conophyte, Contarinia oregonensis were noted. Using a generalized linear mixed effects model, I found that seed position, and the presence of C. oregonensis, were strong predictors of Megastigmus infestation. The percent of M. spermotrophus infested seed was higher in the apical and basal regions of the cone where seeds were smaller, scales were thinner and C. oregonensis were less frequently found. M. spermotrophus was also found to exploit seeds in regions of the cone, where seeds rarely complete development. These data suggest that competitors may not be the only factor influencing infestation; factors of cone morphology are also important. Douglas-fir seed does not show any anatomically detectable defense response to Megastigmus attack. To study mechanisms of host manipulation and defense response of the seed I took a genomics approach. Four types of ovules/seeds were studied: 1. pollinated & uninfested, 2. pollinated & infested, 3. unpollinated & uninfested, and 4. unpollinated and infested. A de novo reference transcriptome was assembled. Transcripts were annotated based on sequence similarity to genes of Pinus taeda, Arabidopsis thaliana, Nasonia vitripennis, and the UniProt database. Expression values were estimated based on the alignment of the original reads back onto the reference transcriptome. Differentially expressed transcripts were identified. Oviposition of M. spermotrophus caused changes in expression of Douglas-fir transcripts. Functional classification of differentially expressed transcripts between infested and uninfested seed revealed genes with possible roles in wounding, but none specific to herbivory. Infested treatments had more transcripts similarly expressed to pollinated than unpollinated seeds suggesting that M. spermotrophus is capable of manipulating gene expression. These transcripts had functional roles related to seed storage, cell division and growth, solute transport, hormone signalling, and programmed cell death among others. Overall, this study reveals a select set of genes that may be involved in stress response to wounding and also genes important for seed development and maturation. / Graduate

D.Sc. / Please refer to full text to view abstract

It is the purpose of this study to ascertain what environmental factors might cause morphological changes exhibited by certain algae, also to determine if this variation in morphology is vegetative, reproductive, or artifactual in nature, and to show what effects these changes in morpohology might have on classification of the organisms in question.

No description available.

Dendritic morphology and microsegregation in the ternary Fe- 1.6% Mn - 0.1 to 0.8 % C alloys have been investigated by quenching the unidirectionally solidified specimens. The microprobe analysis of these specimens showed that the manganese segregation was significantly controlled by the back diffusion. This back diffusion was extremely high in the case of ferritic solidification whereas only a small rise in Cmin was obtained for the austenitic phase. It was found that the manganese microsegregation between the primary arms was always higher than between the secondary arms. The measured segregation ratios indicated a rise with increasing carbon content for both morphologies. No clear effect of cooling rate on segregation was seen for secondary arms and only a sliqht increase was recorded with increasing the cooling rate for primary arms. Secondary dendrite arms solidified to produce asymmecric distribution profiles (saw-tooth or TGZM effect). Measurements of the secondary dendrite arms during qrowth showed that the rate of the coarsening in these manganese steels was higher than other steels resulting in high homogenization between the arms . No tertiary arms have been observed. The primary arms grew mainly in the so-called 'close packed' arrangement and their spacinq did not chanqe with time. By increasing the qrowth rate and the temperature qradient in the liquid a decrease in primary arm spacings was seen. The results agree well with available experimental data in the literature. The microsegregation calculations obtained from the secondary dendrite arm coarseninq model is in a very good agreement with the experimental measurements. The same model without arm coarsening was applied to different primary arm morphologies and the predictions of these models are also in reasonable agreement with observations.

In Paradigm Function Morphology, it is usual to model affix position classes with an ordered sequence of inflectional rule blocks. Each rule block determines how (or whether) a particular affix position is filled. In this model, competition among inflectional rules is assumed to be limited to members of the same rule block; thus, the appearance of an affix in one position cannot be precluded by the appearance of an affix in another position. I present evidence that apparently disconfirms this restriction and suggests that a more general conception of rule competition is necessary. The data appear to imply that an affixation rule may in some cases override a rule introducing an affix occupying another, distinct position. I propose that each inflectional rule R carry two indices — the first, as usual, specifying the position of the affix introduced by R. The second, however, specifies the position(s) that R satisfies. By default, these two indices identify the same position. However, where one affix precludes another, the second index of the appearing affix specifies two affix positions: the one in which it appears and the one which it precludes. With both blocks satisfied, no other rules which fill either may be applied.

Light and electron microscopical techniques were employed to make qualitative and quantitative observations on peripheral nerve morphology. Sural nerve biopsies from 4 groups of diabetic patients with different syndromes of polyneuropathy and 6 non-diabetic controls were evaluated. Observations indicated that unequal rates of successful fibre regeneration may underlie an apparent difference in myelinated fibre (MF) loss between painful and painless diaebetic polyneuropathy. MF and unmyelinated fibre (UF) degeneration/regeneration per se are unlikely to be the cause of neuropathic pain in diabetic polyneuropathy since evidence of each was present in patients with remission from painful symptoms and in patients with painless neuropathy. Axonal atrophy may have a role in neuropathic pain generation. Abnormal endoneurial capillary morphology was manifest in all the diabetic patients. Alterations in capillary basement membrane thickness were interdependent with the type and extent of neuropathological change and the clinical expression of the neuropathy. Two patients presented with intractible vomiting due to diabetic gastropathy. The findings of a study of their anterior and posterior abdominal vagus nerves, obtained as biopsy specimens at vagotomy and gastroenterostomy to prevent stomal ulceration, were compared with those of 2 diabetic and 2 non-diabetic patients undergoing vagotomy for duodenal ulceration. Autovagotomy, and its causative role in gastropathy, was not supported since there was persistence of intact and regenerating fibres and evidence of similar MF and UF changes in both groups of diabetic patients. Male Sprague-Dawley rats were employed to make a comparison of the effects of conventional insulin therapy (CIT) and continuous subcutaneous insulin infusion therapy (CSII) in streptozotocin-induced diabetes. CSII was superior to CIT in diurnal and circadian blood glucose homeostasis and in ameliorating a diabetes-related deficit in body weight and skeletal length. Although CSII performed better, neither form of therapy was completely successful in reversing the effects of untreated-diabetes on parameters indexing MF morphology in the tibial nerve. Potentially serious degenerative changes in MFs following the initiation of either form of insulin therapy were found to correlate with the number of detected hypoglycaemic episodes. Normal maturation of MFs in the sural nerve involved the formation of a proximo-distal taper for fibre and axon size. MFs and axons in diabetic rats did not assume a size taper. The effect of diabetes was manifest proximally in the nerve with no evidence of selective involvement of axon or Schwann cell. Male albino Lewis rats were made diabetic with streptozotocin and used to study the effect of early (within 3 weeks= EIT) and delayed (after 6 months= DIT) pancreatic islet transplantation on MF morphology. Optimal diurnal and circadian blood glucose control was achieved for 6 months following EIT and DIT. A body weight deficit in diabetic rats was ameliorated by EIT but not DIT. EIT completely prevented the occurrence of abnormal fibre and axon morphology in the tibial nerves of diabetic rats. DIT completely reversed a deficit in fibre size but not axon size. If these observations were applicable to man the best therapeutic option would be for candidates to receive islet transplantation soon after the onset of diabetes. The occurrence of neuropathy might then be prevented.

M.Sc. / Several characteristics of the homothallic species, Chaetomium aureum, c erraticum, c flavigenum, c rubrogenum and c trilaterale, were examined and compared. Morphological details such as perithecial structure, form and ornamentation of the setae and spores, physiological aspects such as formation of pigment and cellulolytic activity as well as nuclear behaviour during ascosporogenesis were examined to determine their species differentiating potential. Although pigment formation and ornamentation of setae are environment dependent these features could be useful in species delimitation ...

<p> This manual was written specifically as a guide for the beginner dissector to complete a prosected cadaver that will serve as an effective teaching and learning tool. The dissections are written in a manner that facilitates the preservation of more superfi- cial structures on the right side of the cadaver and deeper structures that otherwise would have been concealed on the left side of the cadaver. This format is ideal for students learning anatomy for the first time, as multiple planes can be compared on the same cadaver. The level of structures dissected and identified in these chapters was established with the understanding that the dissector&rsquo;s knowledge of human anatomy is at the level of completion of a general undergraduate anatomy survey course. </p>