Hydrogels have successfully proved themselves useful for drug delivery applications and several delivery routes have been developed over the years. The particular interest in this work was to design, synthesise and evaluate in situ forming drug eluting hydrogels, which have the potential to ameliorate the healing of cardiovascular diseases. With this aim the anti-inflammatory and immunosuppressant drugs rapamycin (Ra) and dexamethasone (Dex) were made water soluble by conjugation with polyethylene glycol (PEG). Ra was attached pendant from the terminal of PEGs while Dex was incorporated into dendritic structures grown from PEGs. These conjugates were further crosslinked into hydrogels by either conjugate or thiol-ene addition. The gel degradation was tuned to take between 5 and 27 days by using gel building block combinations that induced either 2 or 4 hydrolytically labile bonds per crosslink or by varying the number of crosslinking sites of the building blocks. The use of thiol-ene addition prolonged the degradation time nearly seven folded compared to conjugate addition as a more stable crosslink was formed. Two different formulations for gelling via conjugate addition were used (acrylate-thiol or vinyl sulphone-thiol) to deliver Ra, which was carried by either a 4- or 2-armed PEG. The elution kinetic for the respective gel formulation was of zero order during 15 and 19 days of gel degradation. In addition, Ra was PEGylated via esters, with a distance of either one or two carbons to a nearby thio-ether functionality. The difference in ester conjugation resulted in a slight but significant change in drug-PEG conjugate stability, which was mirrored by the increased time to reach the half amount of total drug elution; from 9.3 to 10.2 days and from 5.1 to 9.7 days for the two gel formulations, respectively. Dexamethasone was incorporated via an ester into dendrons of first and second generation pending from 2- and 4-armed PEGs at loadings of 2, 4 or 6 Dex molecules per carrier molecule. The resulting elution kinetic was of zero order during degradation periods of 5-27 days. Released Dex still possessed biological activity as determined by an in vitro cell assay. The novelties in this thesis are: (A) slow release of rapamycin obtained by covalent incorporation into hydrogels, (B) the use of unique PEG-based dendrimers to incorporate dexamethasone into a hydrogel and (C) zero order sustained release of dexamethasone at physiological pH. / Hydrogeler har framgångsrikt visat sig användbara för att leverera läkemedel och ett flertal metoder har utvecklats de senaste 20 åren. Fokuset i den här avhandlingen ligger på att designa, framställa och utvärdera läkemedelsutsöndrande hydrogeler som spontanhärdar in situ, vilka har potential att förbättra läkningen efter kardiovaskulär sjukdom. Med det syftet gjordes de anti-inflammatoriska och immunsänkande läkemedlen rapamycin (Ra) och dexametason (Dex) vattenlösliga genom att konjugeras med polyetylenglygol (PEG). Ra fästes kovalent längst ut på PEGar medans Dex inkluderades i dendritiska strukturer vilka byggdes från ändpunkten av PEGar. De här konjugaten tvärbands till hydrogeler via antingen konjugerad addition eller radikal polymerisation. Nedbrytningen av gelerna trimmades till att ta mellan 5 och 27 dagar genom att använda kombinationer av gelbyggstenar som bildar antingen 2 eller 4 hydrolyserbara estrar per tvärbindning eller genom att variera antalet tvärbindningspunkter hos byggstenarna. Användandet av radikal polymerisation i sig ledde till att nedbrytningen av geler tog nära sju gånger längre tid jämfört med geler gjorda via konjugerad addition eftersom stabilare tvärbindningar då formas. Två olika kombinationer för härdning via konjugerad addition (akryl-tiol eller vinylsulfon-tiol) användes för att leverera Ra som bars av antingen en 4- eller 2-armad PEG. Utsöndringskinetiken av Ra för de två kombinationerna var av nollte ordningen under de 15 och 19 dagar som gelerna degraderade. Dessutom, Ra PEGylerades via estrar med ett avstånd på antingen ett eller två kol till en närliggande tioeter. Skillnaden i avstånd ledde till en liten men signifikant skillnad i stabiliteten hos Ra-PEG konjugaten, vilket speglades i den förlängda tiden att nå halva mängden av den totala läkemedelsutsöndringen; från 9.3 till 10.2 dagar och från 5.1 till 9.7 dagar för de två respektive gelkombinationerna. Dex kopplades in via en esterbindning till dendroner av första och andra generationen byggda från PEGar med 2 eller 4 armar, vilket resulterade i att 2, 4 eller 6 Dex levererades per bärarmolekyl. Dex eluerade med nollte ordningens kinetik under degraderingsperioder på mellan 5 och 27 dagar. Vidbehålllen biologisk aktivitet av eluerad Dex bekräftades genom cellexperiment in vitro. Nyheterna i den här avhandlingen består av: (A) kontrollerad utsöndring av rapamycin uppnådd genom kovalent inbindning till hydrogeler, (B) användandet av unika PEGbaserade dendrimerer för kovalent inbindning av dexametason till hydrogeler och (C) nollte ordningens utsöndring av dexametason vid fysiologiskt pH. / <p>QC 20130204</p>

Osteoporosis is defined as a skeletal disorder characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk. Osteoporosis is well known increasing with age. The number and size of marrow adipocytes increase in a linear manner with age. Early histomorphometric observations suggested that the consequence of the adipose replacement of the marrow functional cell population was a cause of osteoporosis. The replacement of functional cells in the marrow by fat cells is common in several pathological study of osteoporosis. All these evidences clearly demonstrate the reciprocal relationship between osteoblast and adipocyte differentiation. The trans-differentiation of osteoblast to adipocyte is an important mechanism of pathogenesis of osteoporosis. Several reports have indicated that the long-term use of steroids could induce osteonecrosis and osteoporosis. Using a mouse pluripotent mesenchymal cell, D1, as a model, we have demonstrated that dexamethasone, a glucocorticoid, can induce adipogenesis. Peroxisome proliferator-activated receptors-£^ (PPAR£^) plays a critical role in glucose and lipid metabolism, macrophage function, and adipogenesis. It is a nuclear hormone receptor, activated through ligand binding, which results in allosteric changes in receptor conformation, recruitment of coactivators, assembly of a transcriptional complex, there regulates gene expression. Thiazolidinedione (TZD) is one of the agonist of PPAR£^ receptor which has been a medication for diabetic mellitus for years. Treatment with TZDs leads to selective accumulation of subcutaneous adipose tissue. We examined whether adipogenesis induction in D1 cells is initiated by activation of peroxisome proliferator-activated receptor-£^. The results revealed that pioglitazone induces adipogenesis in D1 cells in dosedependent manner and decreases alkaline phosphatase activity in D1 cells. Interestingly, this adipogenesis was not blocked by bisphenol A diglycidyl ether, a peroxisome proliferator-activated receptor-£^ antagonist. A peroxisome proliferator-activated receptor-£^-mediated reporter gene assay showed no response to pioglitazone. We then asked whether dexamethasone-induced adipogenesis can be repressed by mifepristone (RU486), an antagonist of glucocorticoid receptor. The results disclosed that mifepristone cannot counteract dexamethasone-induced adipogenesis, and mifepristone itself induced adipogenesis in D1 cells. Moreover, glucocorticoid receptor-mediated reporter gene assay was not responsive to dexamethasone or mifepristone. We concluded that the adipogenesis induced by pioglitazone and dexamethasone in D1 cells may not occur via a peroxisome proliferator-activated receptor-£^ and glucocorticoid receptor pathway. These results suggested that the adipogenesis induced by glucocorticoids and pioglitazone is directed by a multiple cell signaling pathway. Finally, data from microarray analysis confirmed this adipogenesis pathway, as several adipogenesis-related genes are highly provoked by DEX. We found that the expressions of several adipogenesis-related genes are highly provoked by this agent. Our studies suggest that the adipocyte conversion of bone marrow stromal cells may be the mechanism of bone loss caused by pioglitazone. Considering its widespread clinical use, the detrimental skeletal effects of pioglitazone should be closely monitored.

The MicroImager is a fast, high resolution, real time, digital autoradiographic imaging tool with broad applications. This study utilizes the MicroImager to evaluate radiolabeled drug behavior in subcutaneous tissue. Experiments were conducted in conjunction with mathematical models to determine the diffusion coefficient (D) and elimination constant (k) for radiolabeled dexamethasone. Osmotic pumps containing [3H]dexamethasone were implanted into rat subcutaneous tissue over 6h, 24 h, and 60 h. Local tissue was explanted and slides were prepared for imaging. The MicroImager was then used to quantify the local concentration of 3H-dexamethasone in the tissue surrounding the tip of the osmotic pump. Betavision+ software was used to obtain local concentration profiles. These were then compared to a mathematical model to determine the diffusion coefficient and elimination constant for the radiolabeled drug. The diffusion coefficient for dexamethasone in rat subcutaneous tissue is 4.11 ± 1.77 x 10-10 m2/s. The elimination constant is 3.65 ± 2.24 x 10-5 s-1.A similar experiment was conducted to determine the diffusion coefficient through different means. [3H]dexamethasone was injected into the rat subcutaneous tissue for a 2.5 min and a 20 min period. A different mathematical model was applied and the diffusion coefficient was found to be 4.01 ± 2.01 x 10-10 m2/s.

No description available.

In this work, transparent and rigid organogels suitable for intravitreal drug delivery applications were produced with pharmaceutical/food grade polar and amphiphilic solvents with HLB values ranging from 0-19. Maximum sterol solubility was obtained with solvents with approximately HLB=6. Solvents with high sterol solubility also required higher sterol concentrations to produce a gel. However, the strength of all the organogels increased with increasing sterol concentration. Furthermore, DSC and SAXS data suggest that the structure of all the organogels was similar. An in vitro release of dexamethasone was performed over a 5.5 month period using novel organogel- dexamethasone implants. The release of dexamethasone varied from 2 to 5.5 months (or more) depending on the organogel used for the implant. These multiple-month release in vitro profiles are comparable and/or exceed the release of commercially available and FDA approved dexamethasone delivery system Ozurdex (~2 month dexamethasone release).

In this work, transparent and rigid organogels suitable for intravitreal drug delivery applications were produced with pharmaceutical/food grade polar and amphiphilic solvents with HLB values ranging from 0-19. Maximum sterol solubility was obtained with solvents with approximately HLB=6. Solvents with high sterol solubility also required higher sterol concentrations to produce a gel. However, the strength of all the organogels increased with increasing sterol concentration. Furthermore, DSC and SAXS data suggest that the structure of all the organogels was similar. An in vitro release of dexamethasone was performed over a 5.5 month period using novel organogel- dexamethasone implants. The release of dexamethasone varied from 2 to 5.5 months (or more) depending on the organogel used for the implant. These multiple-month release in vitro profiles are comparable and/or exceed the release of commercially available and FDA approved dexamethasone delivery system Ozurdex (~2 month dexamethasone release).

Processes that regulate site of fat deposition in beef cattle are poorly understood. For the producer to procure the greatest profit, it is ideal to maximize intramuscular fat. Furthermore, to understand the physiological mechanisms affecting fat depots, it is necessary to evaluate hormones involved in growth regulation. Using a 2 x 2 factorial design of treatments, four experiments were conducted to examine two adipogenic compounds, chlortetracycline and dexamethasone. Synovex-S® and Revalor-S® were used to investigate potential interactions between growth implants and adipogenic compound. Growth performance, carcass quality, organ and fat mass and plasma hormone concentrations were measured in these studies. In Exp. 1, 24 steers received either 0 or 350mg chlortetracycline/d, with or without Synovex-S®. On d 30, 56 and 106, steers received a bolus injection of 1 ug/kg BW thyrotropin-releasing hormone and 0.1 ug/kg BW GH-releasing hormone and serial blood samples were collected. Synovex-S® increased (P ≤ 0.009) rate and efficiency of gain and decreased (P = 0.05) time to peak for GH concentrations. Chlortetracycline attenuated (P ≤ 0.05) the effects of implant on triiodothyronine release, slaughter weight and carcass quality. In Exp. 2, 96 steers received either 0 or 39.6 ppm chlortetracycline/d, with or without Revalor-S®. Implant increased (P < 0.0001) ADG; however, efficiency of gain was greater for implanted steers in the absence of chlortetracycline (interaction, P ≤ 0.03). In Exp. 3, 144 steers received either 0 or 0.09 mg dexamethasone/kg BW on d 0, 28 or 56, with or without Revalor-S®. Average daily gain was lower (P = 0.0003) for implanted steers receiving dexamethasone compared to those receiving no dexamethasone (interaction, P = 0.05). Omental fat mass was greater (P = 0.01) for non-implanted steers receiving dexamethasone compared to no dexamethasone (interaction, P = 0.006). In Exp. 4, 96 steers received either 0 or 0.09 mg dexamethasone/kg BW on d 0, 28, 56 or 84, with or without Revalor-S®. Average daily gain and efficiency of gain were both 13% greater (P ≤ 0.05) with implant. Conversely, DEX lowered ADG by 10% (P = 0.007). There were no effects of treatment on fat mass weights.

Cryprosporidium parvum is a coccidian protozoan that colonizes epithelial cells lining respiratory and digestive tracts of animals and humans. Cryptosporidiosis is a well-recognized zoonotic disease infecting primarily neonates and immunocompromised hosts, including human immunodeficiency virus-infected patients. Clinical disease is manifested as a chronic diarrheal illness that is self-limiting in immunocompetent hosts and prolonged and often life-threatening in hosts with compromised immune systems.The lack of a suitable small animal model for screening anti-cryptosporidial drugs and for examining the pathogenicity and immunobiology of chronic cryptosporidiosis was the impetus for this research effort. The objectives of the present study were three-fold: to characterize chronic Cryptosporidium parvum infections in dexamethasone-immunosuppressed mice; evaluate the effects of Cryprosporidium parvum and dexamethasone on B and T lymphocyte proliferation; and determine the effects of the immunomodulator dehydroepiandrosterone on oocyst shedding intensities of mice infected with Cryptosporidium parvum. Adult C57BL/6N mice were immunosuppressed with the synthetic glucocorticoid dexamethasone, then infected with Cryprosporidium parvum (106 oocysts/mouse) investigated for their ability to sustain a four-month chronic infection. Dexamethasone was administered intraperitoneally (125 Jlg/mouse/day) or orally (8 Jlg/ml) in the drinking water ad libitum. Infection chronicity was characterized by evaluating mouse monality, oocyst excretion in the feces, tissue distribution of the parasite, and parasite-induced pathology. A progressive infection with Cryptosporidium parvum occurred in mice immunosuppressed intraperitoneally and orally as long as dexameth sone was administered. Mice receiving dexamethasone given intraperitoneally had a shoner prepatent period and a more consistent, although cyclic, oocyst shedding pattern when compared with mice given dexamethasone orally. Mice given dexamethasone orally exhibited a delayed prepatent period, with a steady increase in oocyst shedding. All mice receiving dexamethasone orally died within three months following oocyst inoculation. Clinical signs included dehydration, icterus, and reduction in spleen and body weights. Clinical signs were more abrupt in mice receiving oral dexamethasone. Parasite colonization involved the entire intestinal tract, including the pyloric ring and Peyer's patches, but was the heaviest in the terminal ileum. Parasites were present in the lungs, gallbladder, and pancreatic ducts. Pathologic abnormalities were isolated to the terminal small intestine and included blunting and fusion of intestinal villi and crypt hyperplasia. Cryptosporidium parvum and dexamethasone administered in vivo reduced B and T lymphocyte responses to the mitogens lipopolysaccharide and concanavalin A. Dehydroepiandrosterone and dehydroepiandrosterone-sulfate resulted in no significant reductions in cryptosporidial activity as determined by oocyst shedding in the feces.

This study aimed to examine potential mechanisms for glucocorticoid (GC)-induced decreases in glucose clearance, and to determine if a reduction in oxidative stress load via dietary pre-treatment with an antioxidant-rich diet has a positive net effect on glucose tolerance following a sub-chronic treatment with the GC analogue dexamethasone (DEX). Rats fed a diet supplemented with 700IU of -tocopherol for two weeks had improved glucose clearance after five days of DEX-treatment relative to unsupplemented rats as well as decreased markers of oxidative stress. Following an intraperitoneal bolus of insulin, phosphorylation of AMP activated protein kinase (AMPK) was preserved in the supplemented groups despite no significant differences in upstream insulin signalling cascade intermediates between DEX-treated groups. This was corroborated by a similar increase (p<0.05) in phosphorylation of the downstream AMPK substrate acetyl CoA carboxylase. This study demonstrated that -tocopherol supplementation can attenuate GC-induced decreases in glucose clearance in an AMPK-dependent manner. / Nutrition and Metabolism

Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 68-76) / Microfiche. / xi, 76 leaves, bound ill. 29 cm