High Yield of Rodent Islets with Intraductal Collagenase and Stationary Digestion—A Comparison with Standard Technique

Intraductal distention of the pancreas with collagenase followed by stationary warm incubation improves the recovery of islets of Langerhans in the rat, but controlled studies are needed for valid comparison with standard isolation methods. We have modified Gotoh's technique of stationary digestion for high-yield isolation in the rat (Stationary). The method is subjected herein to rigorous blinded comparison with the standard chopped tissue (Chopped) technique, based on Lacy et al., as performed in our laboratory for over 10 yr. Islet recovery was determined by a single observer ‘blinded’ to the method of isolation used, and only intact islets of diameter ≥ 100 μm were included. Stationary gave 719 ± 114 islets per pancreas (mean ± SD, n = 21 isolations) vs. 487.5 ± 69 for Chopped (n = 36 isolations), a 47.5% increment in yield (p < 0.0001). In vitro islet perifusion showed no statistical difference in stimulation index (SI) or stimulated area under the curve (SAUC) between the two methods, but Stationary showed a trend towards improved phase II insulin release. In vivo function was assessed by isogeneic transplantation of 2,000 islets beneath the renal capsule of streptozotocin diabetic recipients (65 mg/kg Sigma); Stationary recipients (n = 7) became normoglycemic (≤ 8 mmol/L) by 3.3 ± 4.8 days vs. 1.6 ± 1.5 days for Chopped recipients (p = 0.4 ns, mean ± SEM). IVGTT performed at 1 mo posttransplant gave K-values for Stationary of 2.64 ± 0.8 vs. 2.62 ± 0.8 for Chopped (mean ± SD, p = 0.9 ns, n = 6, unpaired t-test), which were not distinguishable from normal control rats (2.59 ± 0.8) (p = 0.9 ns, n = 10). Graft function remained stable until graft bearing nephrectomy induced hyperglycemia uniformly within 1 day. Graft histology showed a healthy well-preserved structure on light microscopy, with well-granulated beta cells on EM. Economic costs of rat, collagenase, and Ficoll were 26% ($50.82) lower per recipient for Stationary. We conclude that modified stationary digestion significantly improves islet recovery with excellent in vitro and in vivo function, and is cost effective.

Up-regulation of miR-888-5p in hepatocellular carcinoma cell lines and its effect on malignant characteristics of cells

MicroRNA (miRNA) expression has been linked to the molecular pathogenesis of hepatocellular carcinoma (HCC). The aberrant expression of miRNA is involved in the processes of tumorigenesis and cancer progression. According to the latest research, miR-888-5p is associated with strong cancer-promoting effect. For instance, miR-888-5p is up-regulated in prostate cancer and breast cancer. Nevertheless, the role of miR-888-5p in HCC has not been investigated to date. In this study, we found that miR-888-5p levels in four HCC cell lines (SMMC7721, HepG2, Huh-7 and Bel7402) were significantly up-regulated compared with human hepatocyte cell line (HHL-5). After transiently transfected with miR-888-5p mimic, our results demonstrated that miR-888-5p plays a major role in promoting the proliferation and metastatic potential of HCC cells. Moreover, miR-888-5p also increased the expression of MMP-2 and MMP-9 proteins which account for cell migration and invasion, and decreased the expression of p53 protein which further promoted malignance of HCC. Therefore, miR-888-5p may be considered a potential biomarker for diagnostics and prognosis of HCC.

Suppression of proximity effect and the enhancement of p-wave superconductivity in the Sr2RuO4-Ru system

We report unexpected phenomena observed on the Sr2RuO4-Ru eutectic phase featuring Ru islands embedded in a bulk crystal of the chiral p-wave superconductor Sr2RuO4. It was found that the Sr2RuO4/Ru interface is atomically sharp, terminated uniformly by a Sr/O layer. Surprisingly, the proximity-induced p-wave superconducting energy gap predicted by theory was not detected inside Ru islands. Our results suggest that the previously observed enhancement of superconductivity in this eutectic phase occurs away from rather than near the Sr2RuO4/Ru interface, where dislocations and phonon hardening were found.

Adult human beta-cell neogenesis?

Prospects for inducing endogenous beta-cell regeneration in the pancreas, one of the most attractive approaches to reverse type 1 and type 2 diabetes, have gained substantially from recent evidence that cells in the adult pancreas exhibit more plasticity than previously recognized. There are two major pathways to beta-cell regeneration, beta-cell replication and beta-cell neogenesis. Substantial evidence for a role for both processes exists in different models. While beta-cell replication clearly occurs during development and early in life, the potential for replication appears to decline substantially with age. In contrast, we have demonstrated that the exocrine compartment of the adult human pancreas contains a facultative stem cell that can differentiate into beta-cells under specific circumstances. We have favoured the idea that, similar to models described in liver regeneration, beta-cell mass can be increased either by neogenesis or replication, depending on the intensity of different stimuli or stressors. Understanding the nature of endocrine stem/progenitor cells and the mechanism by which external stimuli mobilize them to exhibit endocrine differentiation is central for success in therapeutic approaches to induce meaningful endogenous beta-cell neogenesis.

NeuroD1 in the endocrine pancreas: Localization and dual function as an activator and repressor

The basic helix-loop-helix transcription factor NeuroD1 regulates cell fate in the nervous system but previously has not been considered to function similarly in the endocrine pancreas due to its reported expression in all islet cell types in the newborn mouse. Because we found that NeuroD1 potently represses somatostatin expression in vitro, its pattern of expression was examined in both strains of mice in which lacZ has been introduced into the NeuroD1 locus by homologous recombination. Analysis of adult transgenic mice revealed that NeuroD1 is predominantly expressed in beta-cells and either absent or expressed below the limit of lacZ detection in mature alpha-, delta-, or PP cells. Consistent with a previous report, NeuroD1 colocalizes with glucagon as well as insulin in immature islets of the newborn mouse. However, no colocalization of NeuroD1with somatostatin was detected in the newborn. In vitro, ectopic expression of NeuroD1 in TRM-6/PDX-1, a human pancreatic delta-cell line, resulted in potent repression of somatostatin concomitant with induction of the beta-cell hormones insulin and islet amyloid polypeptide. Additionally, NeuroD1 induced expression of Nkx2.2, a transcription factor expressed in beta- but not delta-cells. Transfection studies using insulin and somatostatin promoters confirm the ability of NeuroD1 to act as both a transcriptional repressor and activator in the same cell, suggesting a more complex role for NeuroD1 in the establishment and/or maintenance of mature endocrine cells than has been recognized previously.

Beta-cell differentiation from a human pancreatic cell line in vitro and in vivo

Cell transplantation therapy for diabetes is limited by an inadequate supply of cells exhibiting glucose-responsive insulin secretion. To generate an unlimited supply of human beta-cells, inducibly transformed pancreatic beta-cell lines have been created by expression of dominant oncogenes. The cell lines grow indefinitely but lose differentiated function. Induction of beta-cell differentiation was achieved by stimulating the signaling pathways downstream of the transcription factor PDX-1, cell-cell contact, and the glucagon-like peptide (GLP-1) receptor. Synergistic activation of those pathways resulted in differentiation into functional beta-cells exhibiting glucose-responsive insulin secretion in vitro. Both oncogene-expressing and oncogene-deleted cells were transplanted into nude mice and found to exhibit glucose-responsive insulin secretion in vivo. The ability to grow unlimited quantities of human beta-cells is a major step toward developing a cell transplantation therapy for diabetes.

Differential expression of cholesteryl ester transfer protein in the liver and plasma of fasted and fed transgenic mice

Because cholesteryl ester transfer protein (CETP) is considered a potential target in the treatment of atherosclerosis, several reports have focused on the regulation of this enzyme, and there is evidence that insulin may be a regulatory factor. The present study examines the differential expression of the human CETP gene between physiologic conditions that are accompanied by low (fasted) and high (fed) insulin levels. CETP expression was examined in plasma and tissues of transgenic mice expressing the human CETP minigene after 12 hours of fasting (n = 20) or ad libitum feeding (n = 20) with normal mouse chow. Plasma cholesteryl ester transfer activity (CETA) was 20% higher in fed than in fasted mice, reflecting higher levels of CETP (P < 0.05). This observation was accompanied by higher liver mRNA in fed mice (100%, P < 0.05), as determined by ribonuclease protection assays, as well as by higher CETA (23%, P < 0.05) and CETP mass (29%, P < 0.05) in the particulate fraction of liver homogenates. These parameters of liver CETP expression correlated well with each other, as well as with plasma CETA. CETP in the liver particulate fraction was found as a doublet (approximately 70 and 65 kDa), which resolved to a single band (approximately 60 kDa) upon deglycosylation. No differences in CETP expression were observed in pooled adipose tissue samples from fed and fasted mice. Insulin and glucose were not related to any plasma or tissue parameter of CETP expression. In summary, the concerted, differential expression of CETP in the liver of fed and fasted transgenic mice appears to contribute to higher plasma CETP levels in fed mice, but the precise role of insulin and glucose in regulating CETP expression under fasted and fed conditions needs to be defined.

Synthesis and Photophysical Properties of ZnS Colloidal Particles Doped with Silver

The synthesis and photophysical characterization of ZnS:Ag colloid are reported. The presence of mercaptoacetic acid has an important effect not only on the formation of doped and undoped ZnS but also on the photophysical properties. ZnS colloid doped with silver shows a strong green emission upon ultraviolet excitation, the intensity of which was enhanced significantly compared with that of the undoped colloid. The green emission was ascribed to a transition from a donor level such as anion vacancy to the levels of the Ag impurities. Copyright 1998 Academic Press.

The cystic fibrosis transmembrane regulator gene is expressed in the human endocervix throughout the menstrual cycle

OBJECTIVE

To measure cystic fibrosis transmembrane regulator (CFTR) gene expression in cervical secretions during the menstrual cycle.

DESIGN

Prospective, descriptive clinical study.

PATIENTS

Thirteen healthy women with ovulatory menstrual cycles.

INTERVENTIONS

Endocervical cells and secretions were obtained by cytobrushings during the midfollicular, midcycle, and luteal phases. The cells were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) for CFTR and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene expression.

MAIN OUTCOME MEASURES

Detection of CFTR gene expression and a quantitative comparison of the levels of CFTR to GAPDH gene expression.

RESULTS

All endocervical samples exhibited some degree of CFTR gene expression throughout the menstrual cycle; however, the levels of expression were variable. Cystic fibrosis transmembrane regulator gene expression did not correlate with E2 or P levels.

CONCLUSION

The production of copious cervical secretions at the time of ovulation in part may be because of the transport of sodium and water across endocervical cell membranes as a result of E2-stimulated CFTR mRNA and protein. Although cervical mucus becomes thick and scant during the luteal phase, CFTR gene expression is present in these secretions.

High yield of rodent islets with intraductal collagenase and stationary digestion--a comparison with standard technique

Intraductal distention of the pancreas with collagenase followed by stationary warm incubation improves the recovery of islets of Langerhans in the rat, but controlled studies are needed for valid comparison with standard isolation methods. We have modified Gotoh's technique of stationary digestion for high-yield isolation in the rat (Stationary). The method is subjected herein to rigorous blinded comparison with the standard chopped tissue (Chopped) technique, based on Lacy et al., as performed in our laboratory for over 10 yr. Islet recovery was determined by a single observe 'blinded' to the method of isolation used, and only intact islets of diameter > or = 100 microns were included. Stationary gave 719 +/- 114 islets per pancreas (mean +/- SD, n = 21 isolations) vs. 487.5 +/- 69 for Chopped (n = 36 isolations), a 47.5% increment in yield (p < 0.0001). In vitro islet perifusion showed no statistical difference in stimulation index (SI) or stimulated area under the curve (SAUC) between the two methods, but Stationary showed a trend towards improved phase II insulin release. In vivo function was assessed by isogeneic transplantation of 2,000 islets beneath the renal capsule of streptozotocin diabetic recipients (65 mg/kg Sigma); Stationary recipients (n = 7) became normoglycemic (< or = 8 mmol/L) by 3.3 +/- 4.8 days vs. 1.6 +/- 1.5 days for Chopped recipients (p = 0.4 ns, mean +/- SEM). IVGTT performed at 1 mo posttransplant gave K-values for Stationary of 2.64 +/- 0.8 vs. 2.62 +/- 0.8 for Chopped (mean +/- SD, p = 0.9 ns, n = 6, unpaired t-test), which were not distinguishable from normal control rats (2.59 +/- 0.8) (p = 0.9 ns, n = 10). Graft function remained stable until graft bearing nephrectomy induced hyperglycemia uniformly within 1 day. Graft histology showed a healthy well-preserved structure on light microscopy, with well-granulated beta cells on EM. Economic costs of rat, collagenase, and Ficoll were 26% ($50.82) lower per recipient for Stationary. We conclude that modified stationary digestion significantly improves islet recovery with excellent in vitro and in vivo function, and is cost effective.

Divergent dimerization properties of mutant beta 1 thyroid hormone receptors are associated with different dominant negative activities

Syndromes of resistance to thyroid hormones are caused by mutations in the T3-binding domain of the c-erbA beta thyroid hormone receptor gene. The S receptor (deletion of THR332) is a potent dominant negative protein cloned from a kindred with generalized resistance to thyroid hormones. The G-H receptor (ARG311HIS) has compromised dominant negative function and was found in both normal individuals and in a patient with severe pituitary resistance to thyroid hormones. We have investigated the mechanism responsible for the difference in receptor phenotypes by analyzing the binding of S and G-H receptors to thyroid hormone response elements with electrophoretic mobility shift analysis. Wild-type human c-erbA beta 1 (WT), S, and G-H receptors were synthesized in reticulocyte lysate, reacted with a thyroid hormone response element consisting of a direct repeat with 4 base pairs (DR+4; AGGTCA CAGG AGGTCA), and the products analyzed by gel shift. G-H receptor homodimerization was greatly impaired; G-H formed predominantly monomeric complex compared with monomeric and homodimeric WT complexes. The G-H receptor was able to form heterodimeric complexes with cellular thyroid hormone receptor auxiliary protein (TRAP) factors including the human retinoid X receptor-alpha. When TRAP was limiting, the levels of G-H heterodimeric complex were 2- to 3-fold reduced compared with WT receptor. In contrast to the WT and G-H receptors, the S receptor formed almost exclusively homodimeric complex with DR+4; the approximate ratio of S:WT:G-H homodimeric complexes at equivalent concentrations of receptors was 60:20:1. A measurable increase (1.2- to 2.6-fold) in heterodimeric complex formation was observed with the S receptor relative to WT when TRAP was at limiting concentration. As reported previously by others, thyroid hormone significantly reduced the WT homodimeric complex with DR+4. There was no effect on the S homodimeric complex. Finally, the WT, S, and G-H receptors formed different complexes with the element consisting of an inverted repeat with 5 base pairs (IR+5; AGGTCA ACAGT TGACCT) and the IR element (AGGTCA TGACCT), which were differently regulated by thyroid hormone. The S receptor bound as a homodimer with IR+5, whereas the WT receptor bound as a homodimer only with thyroid hormone. No homodimeric complex formed with IR+5 and the G-H receptor. Qualitatively similar results were observed with the IR element. We conclude that the ARG311HIS mutation severely perturbs the homodimerization and, to a much less degree, heterodimerization functions of the c-erbA beta 1 receptor. Furthermore, the THR332 deletion mutation augments homodimerization of the c-erbA beta 1 receptor. These results indicate that different mutations in the c-erbA beta 1 thyroid hormone receptor have divergently affected dimerization activities which seem to influence the level of dominant negative activity in man.

Effects of chronic phorbol ester treatment on protein kinase C activity, content, and gene expression in the human monoblastoid U937 cell

Immediate and sustained signal transduction is involved in mediating phorbol ester-induced changes in growth and differentiation. Activation of protein kinase C (PKC) is the initial step in phorbol ester-induced signal transduction. By virtue of preferential down-regulation of individual isoforms and generation of proteolytically derived kinase activities, the signal transduced by sustained activation of this pathway may differ substantially from that generated initially upon application of the phorbol ester. To examine the effect of chronic phorbol ester-induced activation of this pathway, the relationship between PKC activity/content and AP-1 binding activity and gene expression was studied in the U937 cell. Phorbol ester-induced differentiation of the U937 cell into a monocyte/macrophage-like cell requires sustained activation of the PKC pathway. AP-1 binding activity was enhanced by 12-O-tetradecanoylphorbol-13-acetate (TPA) and in a temporally dependent manner, with conversion of a high to low mobility band shift occurring after a 12-h exposure to TPA. After a 72-h exposure, AP-1 binding activity was maximally increased by 1 nM TPA and remained elevated to a similar degree even after treatment with 600 nM TPA. Enhanced AP-1 binding activity was dependent upon continuous exposure to TPA and was not secondary to differentiation. A 72-h treatment with one nM TPA maximally increased expression of c-jun, krox-24, and jun-B mRNA transcripts. Exposure to higher TPA concentrations decreased the content of these transcripts. Maximal expression of collagenase and plasminogen activator receptor transcripts required exposure to much higher TPA concentrations (100 nM).(ABSTRACT TRUNCATED AT 250 WORDS)

Dominant and nondominant negative C-erbA beta 1 receptors associated with thyroid hormone resistance syndromes augment 12-O-tetradecanoyl-phorbol-13-acetate induction of the collagenase promoter and exhibit defective 3,5,3'-triiodothyronine-mediated repression

C-erbA receptors and v-erbA have been shown to functionally interact with 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-inducible gene expression. These proteins enhance trans-activation by c-jun, and the c-erbA receptors in the presence of thyroid hormone repress TPA and c-jun induction of transcription. Also, v-erbA can abrogate T3-mediated repression. We have examined how dominant negative (S and CL) and nondominant negative (G-H) receptors cloned from various patients with thyroid hormone resistance syndromes affect expression of the collagenase promoter induced with TPA. The CL receptor (ARG315HIS mutation) has a 2-fold reduction in T3-binding affinity compared with human c-erbA beta 1 wild-type (WT) receptor, whereas the G-H receptor (ARG311HIS) and S receptor (deletion, THR codon 332) have T3-binding affinities reduced by 100-fold and greater than 100-fold, respectively. These mutant receptors were cotransfected with a collagenase promoter (-1200 to +63 base pairs) chloramphenicol acetyltransferase reporter gene (Col-CAT) into COS-7 cells. Levels of CAT reporter gene expression after transient transfection were determined in the presence or absence of 3-10 nM T3 and the presence or absence of 100 nM TPA. Unoccupied CL receptor and G-H and S receptors stimulated TPA-induced Col-CAT expression 1.5- to 9-fold. The CL receptor with thyroid hormone totally repressed TPA induction of the collagenase receptor. In the presence of thyroid hormone, the enhancing effects by S and G-H receptors on TPA-induced Col-CAT expression were unaffected and minimally diminished, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

An arginine to histidine mutation in codon 311 of the C-erbA beta gene results in a mutant thyroid hormone receptor that does not mediate a dominant negative phenotype

We have examined the c-erbA beta thyroid hormone receptor gene in a kindred, G.H., with a member, patient G.H., who had a severe form of selective pituitary resistance to thyroid hormones (PRTH). This patient manifested inappropriately normal thyrotropin-stimulating hormone, markedly elevated serum free thyroxine (T4) and total triiodothyronine (T3), and clinical hyperthyroidism. The complete c-erbA beta 1 coding sequence was examined by a combination of genomic and cDNA cloning for patient G.H. and her unaffected father. A single mutation, a guanine to adenine transition at nucleotide 1,232, was found in one allele of both these members, altering codon 311 from arginine to histidine. In addition, a half-sister of patient G.H. also harbored this mutant allele and, like the father, was clinically normal. The G.H. receptor, synthesized with reticulocyte lysate, had significantly defective T3-binding activity with a Ka of approximately 5 x 10(8) M-1. RNA phenotyping using leukocytes and fibroblasts demonstrated an equal level of expression of wild-type and mutant alleles in patient G.H. and her unaffected father. Finally, the G.H. receptor had no detectable dominant negative activity in a transfection assay. Thus, in contrast to the many other beta-receptor mutants responsible for the generalized form of thyroid hormone resistance, the G.H. receptor appeared unable to antagonize normal receptor function. These results suggest that the arginine at codon 311 in c-erbA beta is crucial for the structural integrity required for dominant negative function. The ARG-311-HIS mutation may contribute to PRTH in patient G.H. by inactivating a beta-receptor allele, but it cannot be the sole cause of the disease.