A comparison, contrast, and criticism of the modern and romantic periods in poetry as exemplified by the lives and works of John Keats and Amy Lowell

Thesis (Ed.M.)--Boston Universit

Permeability Barrier Disruption Coordinately Regulates mRNA Levels for Key Enzymes of Cholesterol, Fatty Acid, and Ceramide Synthesis in the Epidermis

The extracellular lipids of the stratum corneum, which are comprised mainly of cholesterol, fatty acids, and ceramides, are essential for epidermal permeability barrier function. Moreover, disruption of the permeability barrier results in an increased cholesterol, fatty acid, and ceramide synthesis in the underlying epidermis. This increase in lipid synthesis has been shown previously to be due to increased activities of HMG-CoA reductase, acetyl-CoA carboxylase, fatty acid synthase and serine palmitoyl transferase, key enzymes of cholesterol, fatty acid, and ceramide synthesis, respectively. In the present study, we determined whether the mRNA levels for the key enzymes required for synthesis of these three classes of lipids increase coordinately during barrier recovery. By northern blotting, the steady-state mRNA levels for HMG-CoA reductase, HMG-CoA synthase, farnesyl pyrophosphate synthase, and squalene synthase, key enzymes for cholesterol synthesis, all increased significantly after barrier disruption by either acetone or tape stripping. Additionally, the steady-state mRNA levels of acetyl-CoA carboxylase and fatty acid synthase, required for fatty acid synthesis, as well as serine palmitoyl transferase, the rate-limiting enzyme of de novo ceramide synthesis, also increased. Furthermore, artificial restoration of the permeability barrier by occlusion after barrier disruption prevented the increase in mRNA levels for all of these enzymes, except farnesyl pyrophosphate synthase, indicating a specific link of the increase in mRNA levels to barrier requirements. The parallel increase in epidermal mRNA levels for the enzymes required for cholesterol, fatty acid, and ceramide synthesis may be due to one or more transcription factors that regulate lipid requirements for permeability barrier function in keratinocytes

The role of fatty acid desaturases in epidermal metabolism

The lipid composition of skin is important to a variety of functions served by this organ. Therefore, skin expresses multiple enzymes that synthesize and metabolize lipids. An important class of lipid metabolism enzymes expressed in skin is the lipid desaturases. Various isoforms of stearoyl-CoA desaturase, a delta-9 desaturase, as well as a delta-6 desaturase alter the lipid composition of the skin, thereby affecting skin barrier homeostasis and consequently, whole body energy balance. This review will focus on the role of fatty acid desaturases in maintaining epidermal metabolism

Defects in Stratum Corneum Desquamation Are the Predominant Effect of Impaired ABCA12 Function in a Novel Mouse Model of Harlequin Ichthyosis.

Harlequin Ichthyosis is a severe skin disease caused by mutations in the human gene encoding ABCA12. Here, we characterize a novel mutation in intron 29 of the mouse Abca12 gene that leads to the loss of a 5' splice donor site and truncation of the Abca12 RNA transcript. Homozygous mutants of this smooth skin or smsk allele die perinatally with shiny translucent skin, typical of animal models of Harlequin Ichthyosis. Characterization of smsk mutant skin showed that the delivery of glucosylceramides and CORNEODESMOSIN was defective, while ultrastructural analysis revealed abnormal lamellar bodies and the absence of lipid lamellae in smsk epidermis. Unexpectedly, mutant stratum corneum remained intact when subjected to harsh chemical dissociation procedures. Moreover, both KALLIKREIN 5 and -7 were drastically decreased, with retention of desmoplakin in mutant SC. In cultured wild type keratinocytes, both KALLIKREIN 5 and -7 colocalized with ceramide metabolites following calcium-induced differentiation. Reducing the intracellular levels of glucosylceramide with a glucosylceramide synthase inhibitor resulted in decreased secretion of KALLIKREIN proteases by wild type keratinocytes, but not by smsk mutant keratinocytes. Together, these findings suggest an essential role for ABCA12 in transferring not only lipids, which are required for the formation of multilamellar structures in the stratum corneum, but also proteolytic enzymes that are required for normal desquamation. Smsk mutant mice recapitulate many of the pathological features of HI and can be used to explore novel topical therapies against a potentially lethal and debilitating neonatal disease

Effect of age on the pharmacokinetics of busulfan in patients undergoing hematopoietic cell transplantation; an alliance study (CALGB 10503, 19808, and 100103)

Older patients with acute myeloid leukemia (AML) and myelodysplastic syndrome have often been excluded from myeloablative-conditioning regimens containing busulfan because of non-disease-related morbidity and mortality. We hypothesized that busulfan clearance (BuCL) in older patients (\u3e 60 years) would be reduced compared to that in younger patients, potentially explaining observed differences in busulfan tolerability. AML patients in three CALGB hematopoietic cell transplantation studies were treated with a conditioning regimen using IV busulfan, dosed at 0.8 mg/kg. Plasma busulfan concentrations were determined by LC-MS and analyzed by non-compartmental methods. BuCL was normalized to actual (ABW), ideal (IBW), or corrected (CBW) body weight (kg). Differences in BuCL between age groups were examined using the Wilcoxon rank sum test. One hundred and eighty-five patients were accrued; 174 provided useable pharmacokinetic data. Twenty-nine patients a parts per thousand yen60 years old (median 66; range 60-74) had a significantly higher BuCL versus those \u3c 60 years old (median 50; range 18-60): BuCL 236 versus 168 mL/min, p = 0.0002; BuCL/ABW 3.0 versus 2.1 mL/min/kg, p = 0.0001; BuCL/IBW 3.8 versus 2.6 mL/min/kg, p = 0.0035; BuCL/CBW 3.4 versus 2.6 mL/min/kg, p = 0.0005. Inter-patient variability in clearance (CV %) was up to 48 % in both age groups. Phenytoin administration, a potential confounder, did not affect BuCL, regardless of weight normalization (p \u3e 0.34). Contrary to our hypothesis, BuCL was significantly higher in older patients compared to younger patients in these studies and does not explain the previously reported increase in busulfan toxicity observed in older patients

Topical 11β-Hydroxysteroid Dehydrogenase Type 1 Inhibition Corrects Cutaneous Features of Systemic Glucocorticoid Excess in Female Mice

Glucocorticoid (GC) excess drives multiple cutaneous adverse effects, including skin thinning and poor wound healing. The ubiquitously expressed enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activates mouse corticosterone from 11-dehydrocorticosterone (and human cortisol from cortisone). We previously demonstrated elevated 11β-HSD1 activity during mouse wound healing, but the interplay between cutaneous 11β-HSD1 and systemic GC excess is unexplored. Here, we examined effects of 11β-HSD1 inhibition by carbenoxolone (CBX) in mice treated with corticosterone (CORT) or vehicle for 6 weeks. Mice were treated bidaily with topical CBX or vehicle (VEH) 7 days before wounding and during wound healing. CORT mice displayed skin thinning and impaired wound healing but also increased epidermal integrity. 11β-HSD1 activity was elevated in unwounded CORT skin and was inhibited by CBX. CORT mice treated with CBX displayed 51%, 59%, and 100% normalization of wound healing, epidermal thickness, and epidermal integrity, respectively. Gene expression studies revealed normalization of interleukin 6, keratinocyte growth factor, collagen 1, collagen 3, matrix metalloproteinase 9, and tissue inhibitor of matrix metalloproteinase 4 by CBX during wound healing. Importantly, proinflammatory cytokine expression and resolution of inflammation were unaffected by 11β-HSD1 inhibition. CBX did not regulate skin function or wound healing in the absence of CORT. Our findings demonstrate that 11β-HSD1 inhibition can limit the cutaneous effects of GC excess, which may improve the safety profile of systemic steroids and the prognosis of chronic wounds

Sphingolipid Activator Proteins Are Required for Epidermal Permeability Barrier Formation

The epidermal permeability barrier is maintained by extracellular lipid membranes within the interstices of the stratum corneum. Ceramides, the major components of these multilayered membranes, derive in large part from hydrolysis of glucosylceramides mediated by stratum corneum beta-glucocerebrosidase (beta-GlcCerase). Prosaposin (pSAP) is a large precursor protein that is proteolytically cleaved to form four distinct sphingolipid activator proteins, which stimulate enzymatic hydrolysis of sphingolipids, including glucosylceramide. Recently, pSAP has been eliminated in a mouse model using targeted deletion and homologous recombination. In addition to the extracutaneous findings noted previously, our present data indicate that pSAP deficiency in the epidermis has significant consequences including: 1) an accumulation of epidermal glucosylceramides together with below normal levels of ceramides; 2) alterations in lipids that are bound by ester linkages to proteins of the cornified cell envelope; 3) a thickened stratum lucidum with evidence of scaling; and 4) a striking abnormality in lamellar membrane maturation within the interstices of the stratum corneum. Together, these results demonstrate that the production of pSAP, and presumably mature sphingolipid activator protein generation, is required for normal epidermal barrier formation and function. Moreover, detection of significant amounts of covalently bound omega-OH-GlcCer in pSAP-deficient epidermis suggests that deglucosylation to omega-OH-Cer is not a requisite step prior to covalent attachment of lipid to cornified envelope proteins