Hb Florida: a novel elongated C-terminal beta-globin variant causing dominant beta-thalassemia phenotype

We report here a new frameshift mutation in exon 3 of the beta-globin gene, a single nucleotide deletion (-C) in between codons 140/141 (GCC/CTG-->GCC/TG), found in an 8-year-old Argentinean girl with clinical picture of thalassemia intermedia. It leads to a beta-chain that is elongated to 156 amino acids [(141)Trp-Pro-Thr-Ser-Ile-Thr-Lys-Leu-Ala-Phe-Leu-Leu-Ser-Asn-Phe-(156)Tyr-COOH]. The resulting hemoglobin, which we named Hb Florida, was not detected in peripheral blood; however, erythroid hyperplasia and dyserythropoiesis with large inclusion bodies on methyl violet staining were observed in bone marrow, suggesting that this is a hyperunstable variant producing a dominant beta-thalassemia phenotype, since the other beta-allele was completely normal.

Long-Term (2???4 Year) Weight Reduction With Metformin Plus Carbohydrate-Modified Diet in Euglycemic, Hyperinsulinemic, Midlife Women (Syndrome W)

Long-term weight reduction remains the ultimate objective and challenge of obesity management. Few long-term dietary or pharmacointervention studies have been conducted and there is a critical need for long-range treatment strategies that are effective, safe, and acceptable. The authors conducted a retrospective cohort analysis of 21 euglycemic, hyperinsulinemic women with progressive, refractory, midlife weight gain (Syndrome W) who had previously lost weight (> or =10% reduction from baseline) with a comprehensive 1-year treatment program that included metformin and a hypocaloric, carbohydrate-modified (low-glycemic index) diet, as well as, other lifestyle modifications. The goal of the analysis was to determine long-term efficacy of the composite intervention using NHLBI criteria for weight stabilization, weight regain < or =3 kg (6.6 lb) in 2 years. Of a total of 26 consecutive women with Syndrome W who achieved goal weight during a 3-year period (1998-2001), 21 women (mean [standard error] age, 55.2 [2.4] years; mean body mass index, 34.2 [1.3] kg/m(2)) continued metformin and returned for annual follow-up visits. Weight maintenance was observed at the final (2-4 year) follow-up visit in 19/21 (90.5%) of women. Mean final follow-up weight (77.5 [2.8] kg) correlated highly with mean weight at 1-year protocol completion (77.2 [2.7] kg), (correlation coefficients r(xy) and sigma(xy) = 0.96, P = 0.000), demonstrating long-term weight reduction in the surveillance phase. Significant and robust decrements in fasting insulin (-28.4% [8.1%] to -43.4% [3.7%]) were observed at all follow-up visits (P < or = 0.002). This preliminary case series suggests that metformin may be an effective long-term adjunct to dietary and other interventions in the treatment of obesity in hyperinsulinemic patients. A randomized clinical trial of the dual regimen should be considered in nondiabetic women with midlife weight gain and hyperinsulinemia (Syndrome W) and, quite possibly, in additional euglycemic overweight and obese subjects with documented hyperinsulinemia and other portentous features of the Metabolic Syndrome.

Altered expression of 3 alpha-hydroxysteroid dehydrogenases in human glaucomatous optic nerve head astrocytes

3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) isoforms (AKR1C1-AKR1C4) are aldo-keto reductases that metabolize steroids and other substances in many tissues including the CNS. Here we demonstrated that in glaucomatous human optic nerve heads, increased expression of 3alpha-HSD was localized to reactive astrocytes in the lamina cribrosa. Similar, optic nerve head astrocytes exhibited increased expression of 3alpha-HSD in response to elevated intraocular pressure in a monkey model of experimental glaucoma, but not in monkeys with unilateral optic nerve transection. In vitro, glaucomatous optic nerve head astrocytes expressed higher levels of AKR1C1, AKR1C2, and AKR1C3 mRNA, than normal astrocytes, with significant differential increase of AKR1C2 expression, and exhibited higher enzymatic activity forming 3alpha-androstanediol a well-recognized neurosteroid. Normal astrocytes exposed to elevated hydrostatic pressure selectively increased AKR1C2 expression. Our findings of increased expression of 3alpha-HSDs in glaucomatous optic nerve head astrocytes offer new insights into possible roles for neurosteroids in the pathophysiology of glaucoma.

Syndrome W: a new model of hyperinsulinemia, hypertension and midlife weight gain in healthy women with normal glucose tolerance

To characterize a new insulin resistance syndrome in euglycemic midlife women and the relationship of its features (including hypertension and dyslipidemia), with hyperinsulinemia (AUC insulin > or = 100 microU/mL), retrospective cohort analysis was conducted in 278 consecutive women who presented to a Menopausal Health Program. Of 67 women with midlife weight gain "greater than 20 pounds since their twenties" and body mass indices (BMIs) between 25 and 32 kg/m(2), none of the subjects met criteria for Type 2 diabetes, 5 women had impaired glucose tolerance, and 36 women were hyperinsulinemic. Hyperinsulinemia was a highly statistically significant determinant of hypertension, dyslipidemia, and truncal obesity (Odds Ratios 10.6, 4.0, and 13.7; P values < or = 0.0001, < or = 0.007, and < or = 0.0001) in cross-tabulations. AUC insulin was the best predictor variable of hypertension and dyslipidemia in univariate and multivariate logistic regression models (univariate P values 0.0004 and 0.0088). After adjustment for BMI, age, and estrogen use, the final models, correctly classified, respectively, 74% and 69% of all cases in the dataset (model P values: < or = 0.0001 and < or = 0.0067) and AUC insulin had a log-linear (i.e., dose-dependent) relationship with hypertension and dyslipidemia, which suggests causality. We propose that the constellation of symptoms that includes midlife weight gain, "waist-gain," hypertension, dyslipidemia, and appetite dysregulation in euglycemic women with hyperinsulinemia be titled Syndrome W and suggest that the highly statistically significant relationship of hyperinsulinemia with the characteristic features are evidence of a causal role for insulin in its etiology. The identification of Syndrome W before the onset of overt impaired glucose tolerance, diabetes, or manifestations of coronary artery disease could have important clinical and public health implications for midlife women.

Metformin and carbohydrate-modified diet: a novel obesity treatment protocol: preliminary findings from a case series of nondiabetic women with midlife weight gain and hyperinsulinemia

The authors conducted a retrospective analysis of a new obesity treatment protocol, metformin and hypocaloric, carbohydrate-modified diet, in high-risk, nondiabetic hyperinsulinemic women with progressive midlife weight gain (refractory to diet and exercise). Thirty consecutive nondiabetic women with glucose-mediated area-under-the-curve (AUC) insulin elevations (>or=100 microU/mL) in two body mass index (BMI) categories (group I: 25 to 32.9 kg/m(2) and group II: 33 to 41.7 kg/m(2)) participated in a 1-year treatment program of metformin (mean daily doses of 1,500 mg/day [group I] and 2,000 mg/day [group II]) and carbohydrate-modified dietary regimens. Follow-up body weight (at 3, 6, and 12 months), percentage of patients meeting goal weight attainment (10% reduction in body weight or BMI normalization), and fasting insulin levels (as available) are reported in 26 women (18/18 in group I and 8/12 in group II) who returned for one or more follow-up visits. Significant weight loss was observed at 3, 6, and 12 months in both group I (3.47 [SE 0.68], 6.41 [0.72], and 8.06 [0.96] kg, P < 0.0001) and group II (4.4 [0.8], 9.7 [2.3], 15.1 [3.3], P = 0.001, 0.004, 0.011). Twenty-five of 26 (96%) patients lost >or=5% of their body weight at 6 months and 21/26 (81%) patients lost >or=10% of their body weight at 12 months. Posttreatment fasting insulin decrement (-35.5 [8.2]%) was the most significant predictor of 1-year weight loss (R(2)=0.656, regression coefficient = 0.810, P = 0.005). Following completion of the 1-year intervention study, weight stabilization (within 1 kg) was observed at a 6-month surveillance in 8/9 patients who attained goal weight and continued metformin without additional nutritional counseling, in contrast to weight gain (>or=4 kg or 50% of lost weight) in 5/6 patients who discontinued metformin. The authors concluded that metformin and carbohydrate-modified hypocaloric diet could be an effective novel treatment for long-term weight management in nondiabetic, hyperinsulinemic women.

New perspectives on diagnosis and treatment of obesity

The alarming increase in the prevalence of obesity in the past decade, as demonstrated by ongoing systematic population-based studies, and increased recognition of the adverse health consequences associated with excess body weight have generated widespread interest in the management of obesity. After an extensive review, the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health issued a consensus statement with comprehensive clinical treatment guidelines in 1998 that is relevant to cardiologists as well as primary care physicians. A new focus on obesity research has advanced our understanding of the complexity of this disorder and provided new molecular targets for intervention, including beta(3)-adrenergic receptor agonists, leptin analogues, and uncoupling proteins (UCPs) that stimulate energy expenditure. Two newly available pharmacotherapeutic agents approved by the United States Food and Drug Administration (FDA) and increasing acceptance of bariatric surgery for specific categories of obese patients have expanded current therapeutic options for the management of obesity. Nonetheless, the cornerstone of lifetime weight regulation and the prevention and treatment of obesity inevitably will remain lifestyle modification and long-term vigilance.

Ectopic expression of a mutant form of PKCalpha originally found in human tumors: aberrant subcellular translocation and effects on growth control

A point mutation in PKCalpha was originally discovered in a subpopulation of human pituitary tumors characterized by their invasive phenotype, and the same mutation was also seen in some thyroid neoplasms. To investigate the role of this mutation in tumorigenesis, normal and mutant human PKCalpha cDNAs were overexpressed in Rat6 embryo fibroblasts (R6). When extracts of R6 cells that expressed either the normal or mutant PKCalpha were assayed in the presence of calcium, phosphatidylserine and the phorbol ester TPA, for phosphorylation of either histone IIIS or the EGF-receptor peptide, both extracts gave similar results. However, the subcellular localization of the two proteins differed. Immunohistochemistry studies indicated that after treatment with TPA normal PKCalpha mainly translocated to the plasma membrane, but mutant PKCalpha translocated mainly to the perinuclear region and slightly to the nucleus. Furthermore, the cells that expressed the mutant PKCalpha displayed a decreased requirement for serum when compared to the cells expressing the normal human PKCalpha, and they formed small colonies in soft agar. By contrast, the cells expressing the normal human PKCalpha failed to form colonies in soft-agar. Thus, ectopic expression in rat fibroblasts of this mutant human PKCalpha sequence alters the growth properties of these cells and, when activated, the mutant PKCalpha displays aberrant intracellular translocation. Therefore, this mutation in PKCalpha could contribute to the process of tumor progression in certain human tumors.

Decreased 3 alpha-hydroxysteroid dehydrogenase activity in peripheral blood lymphocytes from patients with primary open angle glaucoma

The purpose of the present study was to determine whether peripheral blood lymphocytes (PBL) from primary open angle glaucoma (POAG) patients have reduced 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) activity as was previously found in POAG-derived cultured trabecular meshwork cells. The availability of PBL from both POAG and control patients makes this a useful system for studying the association of decreased 3 alpha-HSD activity with POAG. PBL were isolated from the venous blood of 17 POAG patients and 22 non-glaucoma controls and assayed for 3 alpha-HSD activity with tritiated 5 beta-dihydrocortisol as a substrate. The mean 3 alpha-HSD activity +/- S.E.M., expressed in comparable units of specific activity, of the POAG derived PBL was 13.8 +/- 1.3 U as compared to 32.8 +/- 2.0 U for control cells. This reduction (> 50%) was statistically significant (P < 0.001). Quantitative immunoblot analysis of PBL indicated that the POAG and control cells, despite their difference in 3 alpha-HSD activity, had nearly identical amounts of 3 alpha-HSD protein. The molecular weight of PBL 3 alpha-HSD from both groups of patients was 38,000, the same as previously reported for human liver. The results of this study show an association of decreased PBL 3 alpha-HSD activity and POAG which was not related to antiglaucoma therapy. The reduced levels of 3 alpha-HSD activity in the readily obtainable PBL may serve as a marker for POAG or those at risk for developing the disease.

Treatment of glaucoma with 3 alpha, 5 beta-tetrahydrocortisol: a new therapeutic modality

The effectiveness of 3 alpha, 5 beta-tetrahydrocortisol (3 alpha, 5 beta-THF), a metabolite of cortisol, in lowering intraocular pressure (IOP) in rabbits made ocular hypertensive with glucocorticoids suggested its use in patients with Primary Open Angle Glaucoma (POAG). Patients with well-documented POAG were treated with a 1% suspension of 3 alpha, 5 beta-THF administered to one eye four times daily for up to six weeks. Eight out of nine patients experienced an appreciable decrease in IOP in the treated eye (average decrease 4.9 mm Hg). There was no conjunctival irritation, corneal pathology, visual field changes, alteration in liver or renal function tests or blood count during the treatment period. The present study demonstrates that 3 alpha, 5 beta-THF, a naturally occurring steroid metabolite, is effective in lowering IOP in patients with POAG. Antiglucocorticoids may represent a new therapeutic modality for the management of POAG.

Purification and properties of human hepatic 3 alpha-hydroxysteroid dehydrogenase

3 alpha-Hydroxysteroid dehydrogenase (3 alpha-HSD) was purified greater than 500-fold from human liver cytosol. The purification was monitored using 5 beta-[3H]dihydrocortisol (5 beta-DHF) as substrate. Electrophoretically homogeneous enzyme was obtained using a procedure that involved ammonium sulfate precipitation and three successive column chromatography steps: DEAE-cellulose, hydroxylapatite and Blue-Sepharose. The enzyme is a monomer since the native molecular weight was found to be 37,000, using a calibrated Sephadex G-75 column, and the denatured subunit molecular weight was determined to be 38,500, by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The enzyme had a pI of 5.6-5.9. The 3-ketosteroids: cortisol, testosterone, progesterone and androstenedione, were not substrates for 3 alpha-HSD indicating that a saturated 4,5 double bond was required for substrate activity. The conformation at the 5 position, however, did not influence substrate activity since 5 alpha- and 5 beta-DHF and 5 alpha-dihydrotestosterone were all reduced at similar rates. The purified enzyme preferred NADPH to NADH as a cofactor and showed a broad peak of activity in the pH range of 6.8-7.4. The apparent Km for 5 beta-DHF was 18 microM. The enzyme was markedly stabilized by 50 mM phosphate buffer containing 10 to 20% glycerol at 4 degrees C. Freezing and thawing of the enzyme resulted in a large loss of activity during early stages of the purification. This is the first report of the purification to homogeneity of 3 alpha-HSD from human tissue.

Human hepatic 3 alpha-hydroxysteroid dehydrogenase: possible identity with human hepatic chlordecone reductase

3 alpha-Hydroxysteroid dehydrogenase is a cytosolic, monomeric, NADPH-dependent oxidoreductase which reduces 3-keto-5-dihydrosteroids to their tetrahydro products. We present here the first partial amino acid sequence data for the human liver enzyme and show these sequences to be identical to the deduced amino acid sequence for human hepatic chlordecone reductase. In addition, these two enzymes exhibit similar substrate and cofactor specificities and immunological reactivity. The results suggest that the natural substrates for chlordecone reductase are 3-keto-5-dihydrosteroids and that these two proteins may be identical.

5 alpha-dihydrocortisol in human aqueous humor and metabolism of cortisol by human lenses in vitro

Glucocorticoids have long been implicated in the etiology of primary open-angle glaucoma (POAG) and cataract. Cortisol metabolites have biologic activity and may affect aqueous humor dynamics. This study was done to determine whether these metabolites are found in human aqueous humor and can be produced by ocular tissues. Radioimmunoassays (RIA) were developed for 5 alpha-dihydrocortisol (5 alpha-DHF) and 5 beta-dihydrocortisol (5 beta-DHF). These assays, as well as a cortisol RIA, were used to quantify these three steroids in 20 surgically derived aqueous humor specimens from patients with and without POAG. The mean concentrations of cortisol and 5 alpha-DHF were 2.5 and 1.3 ng/ml, respectively. In the small group studied, there was no statistically significant difference between the aqueous humor steroid levels in patients with and without POAG. The amount of 5 beta-DHF was at the lower limits of detection of the assay system and could not be uniquivocally shown. Human lenses metabolized cortisol in vitro to 5 alpha-DHF and 3 alpha,5 alpha-tetrahydrocortisol (3 alpha,5 alpha-THF). There was no 5 beta-DHF or cortisone formed. The 5 alpha-DHF and 3 alpha,5 alpha-THF were identified by their positions on thin-layer chromatography, their retention times on high-performance liquid chromatography, and recrystallization with authentic standards to constant specific activity. The data suggest that the lens is the source of 5 alpha-DHF in aqueous humor.

Human hepatic cortisol reductase activities: enzymatic properties and substrate specificities of cytosolic cortisol delta 4-5 beta-reductase and dihydrocortisol-3 alpha-oxidoreductase(s)

The metabolism of cortisol by human liver homogenates has been studied. Cortisol delta 4-reductase and dihydrocortisol-3-oxidoreductase activities were distributed in all subcellular fractions. The products of the soluble enzymes were identified. Cortisol and 5 beta-dihydrocortisol were reduced to 3 alpha,5 beta-tetrahydrocortisol, and 5 alpha-dihydrocortisol was reduced to 3 alpha,5 alpha-tetrahydrocortisol. The soluble enzymes showed a wide range of substrate specificity. The 21 substituted cortisol derivatives were not metabolized. The apparent Km values of cortisol delta 4-5 beta-reductase and dihydrocortisol-3 alpha-oxidoreductase for their substrates (cortisol, 5 alpha-dihydrocortisol, and 5 beta-dihydrocortisol) all ranged from 18 to 27 microM. Dexamethasone inhibited the reduction of all of these substrates and the inhibition was abolished by 21 substitution of the dexamethasone. Testosterone was a competitive inhibitor of the reduction of cortisol, 5 alpha-dihydrocortisol, and 5 beta-dihydrocortisol with a Ki ranging from 11 to 32 microM. NADPH was the preferred cofactor for the cortisol delta 4-5 beta-reductase and dihydrocortisol-3 alpha-oxidoreductase. No end product inhibition was observed.

Dexamethasone induces specific proteins in human trabecular meshwork cells

Previous studies have demonstrated the presence of high-affinity, glucocorticoid-specific receptors in explants of human outflow tissue and in cultured trabecular meshwork. Glucocorticoid-induced responses of scleral fibroblasts and trabecular meshwork cells were evaluated in this study. Incubation of human trabecular meshwork (HTM) and scleral fibroblast (HS) cells with 10(-7) M dexamethasone (DEX) results in a 60% inhibition of prostaglandin production. The effects of glucocorticoid treatment on cellular and secreted proteins using [35S] methionine incorporation were evaluated. Treatment of HTM cells cultured from two normal individuals with DEX induced the expression of [35S] methionine-labelled cellular proteins of 35, 65 and 70 kD, and secreted proteins of 40, 90 and 100 kD. Under the same experimental conditions, a 70 kD molecular weight cellular protein was induced in the HS cells. There were no apparent DEX-induced alterations in HS-secreted proteins. Since a functional common response to glucocorticoid treatment in both HS and HTM cells was inhibition of prostaglandin production, the dexamethasone-induced expression of the 70 kD protein in these cells may be related to this effect. Further studies are required to elucidate specific roles of the steroid-induced proteins in the effects of glucocorticoids on HTM and HS cells.

Arachidonic acid metabolism by cultured bovine corneal endothelial cells

Pathways of arachidonic acid metabolism were identified in freshly prepared and in cultured bovine corneal endothelial cells. The principal pathway of arachidonic acid metabolism in the bovine corneal endothelial cells appears to be the cyclooxygenase pathway with the resultant synthesis of PGI2, PGF2 alpha and PGE2. At least two of these products, PGI2 and PGF2 alpha, are formed by the enzymatic conversion of the substrate, PGH2. Measurements of endogenous prostaglandin production by radioimmunoassay demonstrated that PGE2 was the major arachidonic acid metabolite released, with smaller amounts of PGF2 alpha and the stable hydrolysis product of PGI2, 6-keto PGF1 alpha. The release of all three prostanoids was significantly increased by the addition of the calcium ionophore (A23187), human thrombin, bradykinin and histamine. Basal and stimulated release of prostaglandins by the corneal endothelium may contribute to the regulation of intraocular pressure and also in the modulation of the corneal response to injury.

Human trabecular meshwork cells in culture: morphology and extracellular matrix components

This study demonstrates the presence of laminin and collagen type IV in the extracellular space of human trabecular meshwork (HTM) cells in culture and its absence in cultures of fibroblasts from sclera adjacent to the outflow pathway. These basement membrane components can be detected by standard immunohistochemical techniques. Positive staining for these macromolecules is found only after the HTM cells have reached confluence. The presence of laminin and human collagen type IV in the early passages can serve as additional criteria for identification of HTM cells in culture. These cells provide a useful experimental system for studying the effects of drugs and other factors on the synthesis of components of the extracellular matrix.

Intraocular hypotensive effect of a topically applied cortisol metabolite: 3 alpha, 5 beta-tetrahydrocortisol

3 alpha, 5 beta-tetrahydrocortisol, previously considered an inactive metabolite of cortisol, was found to lower significantly the intraocular pressure (IOP) of rabbits made ocular hypertensive with dexamethasone alone or with threshold levels of dexamethasone plus 5 beta-dihydrocortisol. The ocular hypotensive effect appeared within 3-7 days after the metabolite was started and persisted through the duration of the experiments. The metabolite did not lower the IOP of ocular normotensive untreated animals. Thus, 3 alpha,5 beta-tetrahydrocortisol is a naturally occurring steroid antagonist, which may be of use in the treatment of primary open-angle glaucoma.

Prostaglandin synthesis and release from cultured human trabecular-meshwork cells and scleral fibroblasts

Human trabecular-meshwork (HTM) cells in culture convert arachidonic acid to two products: PGE2 and 6-keto PGF1 alpha. Prostaglandin PGE2 was the major product of arachidonic-acid metabolism. The synthesis and release of PGE2 and 6-keto PGF1 alpha was inhibited by a 15-min pre-treatment with indomethacin (5 X 10(-6) M) or a 4-24-hr incubation with 10(-7) M dexamethasone. The effects of dexamethasone could be prevented by cycloheximide (0.5 micrograms ml-1), or actinomycin D (2 micrograms ml-1). Prostaglandin E2 synthesis and release by these HTM cells from two different individuals could be stimulated by bradykinin, arachidonic acid and the calcium ionophore, A23187.

Potentiation of collagen synthesis in explants of the rabbit eye by 5 beta-dihydrocortisol

The biologic effect of 5 beta-dihydrocortisol on collagen synthesis was evaluated. The metabolite was found to potentiate subthreshold levels of dexamethasone in increasing 3H-proline incorporation in cells of the outflow region of the rabbit. Digestion of the tissue with highly purified collagenase indicated that the 3H-proline was incorporated into collagen type protein. This study demonstrates another biologic activity of 5 beta-dihydrocortisol, a metabolite found to accumulate in cells cultured from trabeculectomy specimens from patients with primary open angle glaucoma.

The effect of dexamethasone on the synthesis of collagen in normal human trabecular meshwork explants

This study demonstrates that the trabecular meshwork cells of the human eye incorporate 3H-Proline into collagen during in vitro incubation. Addition of dexamethasone to the incubation mixture produced a marked decrease in this incorporation. Dexamethasone was active at 10(-8) M and higher concentrations. The specificity of the hormone effect was demonstrated by its inability to alter 3H-leucine incorporation in these cells. These results indicate that dexamethasone decreases the synthesis of collagen, a major component of the extracellular matrix, in the trabecular meshwork.

Defects in cortisol-metabolizing enzymes in primary open-angle glaucoma

Assays of cortisol-metabolizing enzymes in homogenates of human trabecular meshwork cells under optimal conditions revealed two defects in primary open-angle glaucoma (POAG): one is a marked increase in delta 4-reductase and the other is a decrease in 3-oxidoreductase. Experiments indicated that the differences in enzyme activities seen between POAG and nonPOAG trabecular meshwork derived cell homogenates were due to altered amounts of enzymes rather than to alterations in cofactor availability, pH, or endogenous activators or inhibitors. This clearly demonstrates an enzymatic defect(s) in POAG which may be the basis for the ocular hypertension and sensitivity to exogenous glucocorticoids seen in this disorder.

5 beta-Dihydrocortisol: possible mediator of the ocular hypertension in glaucoma

5 beta-dihydrocortisol potentiates the action of topically applied dexamethasone in raising the intraocular pressure (IOP) in young rabbits. Dexamethasone (0.06%) plus 5 beta-dihydrocortisol (0.1 and 1.0%) elevated the IOP 7-10 mmHg within 18 days of treatment. By contrast, 0.06% dexamethasone alone raised the IOP 3 to 4 mmHg in a similar period of time. Since 5 beta-dihydrocortisol accumulates abnormally in cultured cells derived from the outflow region of the eye from patients with primary open angle glaucoma (POAG), a similar potentiation in man may account for the sensitivity of these patients to the IOP raising effect of glucocorticoids. Further, this metabolite may potentiate endogenous glucocorticoids resulting in the ocular hypertension characteristic of POAG.

Glucocorticoid target cells in human outflow pathway: autopsy and surgical specimens

Target cells for glucocorticoids were found in trabeculectomy specimens obtained surgically from humans with glaucoma (primary and secondary) and from nonglaucomatous autopsy eyes using an autoradiographic technique. Specific nuclear localization of 3H-dexamethasone was found in cells of the trabecular meshwork, scleral fibroblasts, and in the endothelial lining of both Schlemm's canal and the outflow vessels. Glucocorticoids may alter the outflow facility by a direct effect on the metabolism of these cells. The autoradiographic method is suitable for studying competitors of glucocorticoid binding in small surgical specimens of human tissue involved in the outflow of aqueous humor.

Potentiation of glucocorticoid activity by 5 beta-dihydrocortisol: its role in glaucoma

5 beta-Dihydrocortisol potentiated the threshold level (the smallest dose producing a measurable effect) of topically applied cortisol (0.02 percent) and dexamethasone (0.003 percent) in causing nuclear translocation of the cytosolic glucocorticoid receptor in rabbit iris-ciliary body tissue. 5 beta-Dihydrocortisol accumulates in cells cultured from trabecular meshwork specimens from patients with primary open-angle glaucoma, but not in similar cells derived from nonglaucomatous patients. In view of the sensitivity of patients with primary open-angle glaucoma to the effects of glucocorticoids in raising intraocular pressure, this potentiation may be responsible for the steroid sensitivity and for the ocular hypertension seen in this disorder.

Altered cortisol metabolism in cells cultured from trabecular meshwork specimens obtained from patients with primary open-angle glaucoma

Cells cultured from trabecular meshwork specimens obtained from patients with primary open angle glaucoma (TMPOAG cells) exhibited two major differences in cortisol-metabolizing enzymes when compared with similar cells from nonglaucomatous patients. One is a marked increase (greater than 100-fold) in delta 4-reductase activity and the other is a decrease (4-fold) in 3-oxidoreductase activity. Peripheral lymphocytes from one of these patients as well as from five additional patients with POAG, did not show these abnormalities, indicating that the defects are not found in all cortisol-metabolizing cells. The abnormal metabolism of cortisol by TMPOAG cells may be of significance in the pathogenesis of POAG.

The effect of dexamethasone on the in vitro incorporation of precursors of extracellular matrix components in the outflow pathway region of the rabbit eye

The present study demonstrates that the cells of the outflow pathway region incorporate precursors of the extracellular matrix components during in vitro incubation. Addition of dexamethasone (10(-7) M) to the incubation mixture led to changes in precursor incorporation that were precursor and cell specific. The steroid significantly decreased the incorporation of 3H-glucosamine and increased the incorporation of 3H-proline in the outflow pathway cells and in the fibroblasts of the adjacent sclera. The specificity of the hormone effect was demonstrated by its inability to alter 3H-leucine incorporation. By contrast, in iridial fibroblasts dexamethasone caused a decreased incorporation of 3H-glucosamine while not affecting the incorporation of 3H-proline. Our results suggest that dexamethasone causes an increase in collagen synthesis in the target cells most closely related to the outflow pathway. Further, the decreased incorporation of 3H-glucosamine with dexamethasone suggests decreased synthesis of glycosaminoglycans, glycoproteins or possibly glycolipids in these same cells.

Characterization of a glucocorticoid receptor and the direct effect of dexamethasone on herpes simplex virus infection of rabbit corneal cells in culture

Homogenates prepared from a previously established cell line derived from rabbit cornea contain a macromolecule with many properties of a glucocorticoid receptor, namely high affinity (KD = 6 x 10(-9)M) and saturable capacity (135 femtomoles/mg protein) for dexamethasone, extreme heat lability, and a pattern of competition similar to that found in other glucocorticoid target cells. Intact cells specifically bind dexamethasone with an affinity similar to that found in homogenates, and the amount of steroid bound at saturation is approximately 60,000 molecules of dexamethasone per cell. Specific dexamethasone binding was found to be localized to the cell nucleus. The corneal cells were susceptible to infection with herpes simplex virus (HSV). Dexamethasone increased cell susceptibility to the virus and facilitated the spread of the infection throughout the corneal cell culture. This effect was observed at concentrations of dexamethasone as low as 10(-9) M. Tetrahydrocortisol, an inactive glucocorticoid metabolite that does not compete with dexamethasone binding to the receptor, did not enhance HSV infection at a high concentration (10(-5) M). This study demonstrates a direct effect of dexamethasone on corneal cell-HSV interaction in the absence of exogenous immunologic factors. This effect of dexamethasone may be mediated by the glucocorticoid receptor.

Glucocorticoid receptor binding in bovine lens

The present study demonstrates glucocorticoid receptor localization in the nuclei of cells of the anterior epithelium and bow region and its absence in all other regions of the lens. Both autoradiographic and biochemical studies show that triamcinolone acetonide is inactive whereas tetrahydrocortisol (previously considered to be an inactive metabolite of cortisol) is an active competitor of dexamethasone binding to the glucocorticoid receptor in the bovine lens. The consistency of these findings by both techniques supports the validity of this observation. In addition, it indicates that autoradiography can be used for studying glucocorticoid agonist/antagonist relationships in the human lens, where only small amounts of tissue are available.

Corneal-conjunctival uptake of topical 3H-dexamethasone in the rabbit eye

Topically administered 3H-dexamethasone was localized radioautographically to the nuclei of several cell types in the cornea and conjunctiva. In the cornea, label was found in the epithelium and keratocytes. In the conjunctiva, label was found in the epithelium and in the connective tissue cells and blood vessel endothelial cells of the stroma. Prior administration of a 350-fold excess of nonlabeled hormone completely suppressed this localization, indicating that these cells are specific glucocorticoid target cells. There was no localization found in the corneal endothelium. Accumulation of silver grains between corneal stroma and Descemet's membrane suggests that this membrane acts as a partial barrier to diffusion of the steroid.

Glucocorticoid localization by radioautography in the rabbit eye following systemic administration of 3H-dexamethasone

Dexamethasone was localized radioautographically in the nuclei of target cells of the rabbit eye following intravenous administration of the labeled steroid. Specifically bound steroid was found in the nuclei of stromal and endothelial cells of the outflow pathway region. This suggests that the glucocorticoid-induced alteration in outflow facility may be mediated by specific effects in these target cells. Nuclear localization was also found in conjunctiva, iridial smooth muscle, choroidal stroma, retina, and sclera, suggesting a physiologic role for glucocorticoids in these tissues as well.

Nuclear translocation of the cytoplasmic glucocorticoid receptor in the iris--ciliary body of the rabbit

The cytoplasmic glucocorticoid receptor of the iris--ciliary body of the rabbit has been shown to translocate to the cell nucleus within 30 min of an injection of cortisol. Over the next 2 1/2 hr the amount of receptor returns to the control value. The threshold of the loss of receptor from the cytosol was found at 0.04 mg of cortisol per kilogram body weight, with a maximal loss being reached at a cortisol dose of 0.5 mg/kg B.W. The inactive glucocorticoid tetrahydrocortisol and the major sex steroids, dihydrotestosterone, estradiol, and progesterone, had little or no effect on this translocation, indicating the specificity of the cortisol effect. Thus this receptor appears to migrate to the cell nucleus in a manner similar to that found in other steroid-sensitive tissues and is consistent with the accepted mechanism whereby these hormones regulate differential gene expression in the nucleus.

Receptors for glucocorticoids in the lens epithelium of the calf

The calf lens epithelium contains a specific cytoplasmic receptor for glucocorticoids. This binding protein has a high affinity for dexamethasone (average dissociation constant, 8 x 10(-9) mole per liter), a low capacity (average, 550 femtomoles per milligram of protein), extreme heat sensitivity, and exhibits a pattern of competition similar to that of glucocorticoid receptors in other tissues. This provides direct biochemical evidence that these tissues may function as a target organ for glucocorticoids.

Specific glucocorticoid receptor in the iris--ciliary body of the rabbit

The cytoplasm of the iris--ciliary body of the rabbit contains a receptor capable of specifically binding dexamethasone. This binding protein has a high affinity for dexamethasone (average KD = 2.0 X 10(-8) M), a low capacity (average 4.8 X 10(-13) mol of steroid bound per milligram of protein), and extreme heat sensitivity; it exhibits a pattern of competition virtually identical to that obtained with glucocorticoid receptors from other tissues and shows characteristic physicochemical behavior in various salt concentrations. The demonstration of a specific dexamethasone receptor in the iris--ciliary body provides the first direct biochemical evidence that these tissues may function as a target organ for glucocorticoids.

Effects of ethidium bromide on the respiratory chain and oligomycin-sensitive adenosine triphosphatase in purified mitochondria from the cellular slime mold Dicyostelium discoideum

Mitochondria were isolated from the cellular slime mold. Dictyoostelium discoideum, and partially purified by sucrose density gradient fractionation. The most purified mitochondrial fraction from the gradient contained essentially no contaminating lysosomes and minimal amounts of contaminating peroxisomes as determined by the marker enzymes N-acetyl-glucosaminidase and catalase. A mitochondrial fraction with the same amount of lysosomal and peroxisomal contamination was also isolated from cells which had been treated with ethidium bromide for 5 days. The most purified mitochondrial fraction from control and ethidium bromide-treated cells had an identical buoyant density of 1.181 to 1.182 g per ml, suggesting that treatment with the drug does not result in any drastic structural changes in the mitochondrial membrane which would affect its density. In the purified mitochondria from ethidium bromide-treated cells, the content of cytochromes a-a3 was decreased over 80% and that of cytochrome oxidase and oligomycin sensitive ATPase were reduced approximately 50%. By contrast, the specific activities of NADH and succinate dehydrogenases were identical in the purified mitochondria from control and ethidium bromide-treated cells. Previously, we had reported that the specific activities of these two enzymes had nearly doubled in whole cells maintained in ethidium bromide for a time equivalent to six or seven generations after growth had stopped (Stuchell, R. N., Weinstein, B. I., and Beattie, D. S. (1973) Fed. Eur. Biochem. Coc Lett. 37, 23-26). These results suggest that continued formation of new mitochondrial membranes, with an identical complement of succinate and NADH dehydrogenases, must occur despite the cessation of cell growth which occurs as a result of the ethidium bromide induced loss of mitochondrial enzymes. Consequently, the amount of mitochondria, or mitochondrial protein per cell, calculated from the activity of NADH and succinate dehydrogenases has increased nearly 50%. Possible models to explain the control of mitochondrial biogenesis are discussed to explain these results.

Studies of DNA-infected disrupted cell preparations

Procedures for increasing both sensitivity and reproducibility of virus production in disrupted DNA-infected cell preparations have been described. A variety of chemical agents and physical procedures, including fractionation by centrifugation, were tested for effects on the ability of disrupted cell preparations to form virus particles. DNA prepared from lambda-virulent phage, a deletion mutant derived from lambda-temperate phage, was shown to be infectious in disrupted cell preparations. When infectious lambda-virulent and lambda-temperate phage DNA were added simultaneously to frozen and thawed cell preparations, a marked increase in the production of infectious units was observed. This effect was eliminated when the biological activity of either DNA type was destroyed by heat. Phage particles produced by such mixed infections had the same buoyant density as the respective parental phages.