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Biomedical subjects

N Welsh

Publications and source records attributed to N Welsh.

At least 73 records · Page 4Linked to original sources
PubMed1991

GTP-binding proteins may stimulate insulin biosynthesis in rat pancreatic islets by enhancing the signal-recognition-particle-dependent translocation of the insulin mRNA poly-/mono-some complex to the endoplasmic reticulum.

We aimed to elucidate the putative role of GTP-binding proteins in the regulation of insulin biosynthesis. For this purpose, freshly isolated rat islets were incubated in the presence of liposomes containing GDP, guanosine 5'-[beta-thio]diphosphate (GDP[S]), GTP, guanosine 5'-[gamma-thio]triphosphate (GTP[S]), guanosine 5'-[beta gamma-methylene]triphosphate (p[CH2]ppG), guanosine 5'[beta gamma-imido]triphosphate (p[NH]ppG) and ATP, and the effects of the liposomal delivery of these substances on rates of biosynthesis of insulin and total protein were determined. Insulin biosynthesis during a 1 h incubation at 1.67 mM-glucose was stimulated by ATP- and GTP[S]-containing liposomes as compared with control liposomes. At 16.7 mM-glucose, only the GTP[S]-containing liposomes stimulated insulin biosynthesis. No inhibition of islet protein and insulin synthesis was observed with GDP-, GDP[S]-, p[CH2]ppG- and p[NH]ppG-containing liposomes. By determining the subcellular distribution of insulin mRNA, it was found that the mRNA content associated with microsomes was increased and that associated with the cytosolic mono-/poly-somes decreased when the islets were incubated with GTP[S]-containing liposomes, resulting in an approximate doubling of the ratio of microsomal to polysomal-associated insulin mRNA. ATP-containing liposomes produced no effects on the association of insulin mRNA with microsomes. By using photoaffinity labelling and immunoprecipitation techniques, specific binding of GTP[35S] to the alpha-subunit of the signal-recognition particle (SRP) receptor in islet homogenates containing physiological concentrations of GTP and GDP was demonstrated. These findings suggest that the GTP-binding subunit(s) of the SRP receptor, and possibly also of other GTP-binding proteins involved in this process, may regulate insulin biosynthesis by stimulating the translocation of insulin mRNA to the endoplasmic reticulum and by increasing preproinsulin-peptide translocation into the lumen of the reticulum.

Adenosine Triphosphate↗
PubMed1991

Decreased mitochondrial gene expression in isolated islets of rats injected neonatally with streptozotocin.

The aim of the present study was to evaluate the possible role of the expression of the mitochondrial genome for the regulation of insulin production in the pancreatic Beta cell. For this purpose, islets of Langerhans were isolated from adult control rats and rats injected neonatally with streptozotocin and the islet contents of specific mitochondrial DNAs and RNAs together with nuclear-encoded RNAs were determined. The contents of mitochondrial cytochrome b mRNA, the mitochondrial 12 S rRNA and insulin mRNA were all 30-40% lower in islets isolated from the streptozotocin-treated rats as compared to islets from control rats. In contrast, the nuclear mRNA coding for the mitochondrial adenine nucleotide translocator was not decreased in the streptozotocin-treated rats. Contents of mitochondrial DNA, as assessed by the Southern blotting technique, were markedly decreased in the streptozotocin islets. Sequence analysis of mitochondrial DNA from streptozotocin islets and control islets however, did not reveal any differences in nucleotide sequences. In control islets the contents of mitochondrial cytochrome b mRNA increased in response to a high glucose concentration during a 4-h incubation period. Serum deprivation or the addition of theophylline or 4-phorbol 12-myristate 13-acetate failed to affect the cytochrome b mRNA contents in vitro. It is concluded that islets of streptozotocin-treated rats contain low contents of mitochondrial DNA and RNA. Since a lower mitochondrial RNA content may result in a diminished oxidative capacity, it is conceivable that a deficiency of this messenger may contribute to the development of insulin deficiency.

Animals↗
PubMed1991

Decrease in insulin-containing secretory granules and mitochondrial gene expression in mouse pancreatic islets maintained in culture following streptozotocin exposure.

We have previously described a preferential reduction in the secretory response to nutrient secretagogues in pancreatic mouse islets maintained in culture after in vitro exposure to streptozotocin (SZ). This reduction was associated with an impaired substrate metabolism at the mitochondrial level. To further clarify this issue, mouse pancreatic islets were exposed in vitro to 2.2 mM SZ for 30 min. At 4 h after SZ treatment ultrastructural changes were apparent in the endoplasmic reticulum and Golgi areas of the B-cells. However, 2 and 6 days following SZ exposure the B-cells appeared well preserved, except for a marked decrease in the number of insulin-containing secretory granules. A morphometric analysis of the B-cells 6 days after SZ exposure showed a normal B-cell size and a normal volume fraction of B-cell mitochondria. However, there was a decrease in total islet size and a 13% decrease in the volume fraction of B-cells in the islets. These mouse islets exhibited a decreased content of the mitochondrial DNA-encoded cytochrome b mRNA, as evaluated by dot-blot analysis. As a whole, the data obtained indicate that SZ treatment does not induce a decrease in the number of mitochondria or long-lasting ultrastructural damage to this organelle. However, there is a clear decrease in the cytochrome b mRNA, suggesting that SZ can induce damage to the mitochondrial DNA.

Animals↗
PubMed1991

Interleukin-1 beta-induced nitric oxide production in isolated rat pancreatic islets requires gene transcription and may lead to inhibition of the Krebs cycle enzyme aconitase.

The aim of this study was to characterize the dynamics and functional relevance of interleukin-1 beta (IL-1 beta)-induced nitric oxide production in isolated pancreatic islets. Thus, islets were isolated from adult rats, precultured for 3-5 days in medium RPMI-1640 plus 10% fetal calf serum, and then exposed to IL-1 beta for different time periods, after which islet nitrite production and aconitase activity were determined. IL-1 beta (5 ng/ml) did not increase islet nitrite production during the first hour of incubation. Moreover, the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (Meth-arg; 5 mM) failed to prevent the initial (90 min) IL-1 beta-induced increase in islet insulin release. After 4, 7, and 24 h, however, nitrite production was increased by 50%, 93%, and 139%, respectively. Islet aconitase activity and glucose oxidation rates were decreased by 70% after incubation for 24 h with IL-1 beta. Both Meth-arg and N alpha-p-tosyl-L-lysine chloromethyl ketone (0.1 mM), a protease inhibitor, could completely counteract the IL-1 beta-induced increases in nitrite production and inhibition of aconitase activity and glucose oxidation rates. In a separate series of experiments, islets were incubated for 60 min with or without IL-1 beta and the RNA synthesis inhibitor actinomycin-D (5 micrograms/ml) and subsequently incubated for another 9 h without any additions. The presence of actinomycin-D during the 1-h IL-1 beta incubation period prevented the IL-1 beta-induced rise in nitrite production and the IL-1 beta-induced inhibition of aconitase activity and insulin release. It is concluded that IL-1 beta-induced nitric oxide production is a late event which requires gene transcription and does not mediate the initial stimulatory effects of IL-1 beta on beta-cell function. However, the gradually augmented rate of nitric oxide production may inhibit the enzyme aconitase, leading to a suppressed mitochondrial activity and a defective insulin release in response to nutrient secretagogues.

Aconitate Hydratase↗
PubMed1991

Liposomal delivery of purified heat shock protein hsp70 into rat pancreatic islets as protection against interleukin 1 beta-induced impaired beta-cell function.

Recently it has been demonstrated that heat shock protein 70 (hsp70) is induced in pancreatic islet cells during prolonged exposure to interleukin 1 beta (IL-1 beta). It is unclear whether this represents a cellular defense against the noxious action of IL-1 beta or whether hsp70 is involved in the suppressive action of the cytokine. To assess the role for hsp70 in isolated islets exposed to IL-1 beta, hsp70 was purified and introduced into cells of isolated rat pancreatic islets via the liposome technique. Delivery of hsp70 was efficient according to immunoblot analysis, but delivered hsp70 disappeared within 16 h. Hsp70-containing liposomes did not affect protein synthesis, insulin secretion, or islet insulin mRNA content. However, when hsp70 liposome-incubated islets were further exposed to IL-1 beta (25 U/ml) for 16 h, these islets released more insulin in response to glucose stimulation and contained more insulin mRNA than islets incubated with control liposomes and subsequently exposed to the cytokine. No protective effect of liposomes containing bovine serum albumin or ovalbumin were observed. We conclude that hsp70 may protect against IL-1 beta-induced impairment of pancreatic beta-cell function.

Animals↗
PubMed1991

Influence of protease on inhibitory and stimulatory effects of interleukin 1 beta on beta-cell function.

To elucidate the putative role of proteases in the action of interleukin 1 beta (IL-1 beta) on pancreatic beta-cells, we studied the effects on islet function of different protease inhibitors when added together with recombinant IL-1 beta to isolated rat pancreatic islets. It was found that the trypsin inhibitor N alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) counteracted the acute stimulatory effects of IL-1 beta on islet glucose oxidation, insulin release, and biosynthesis. TLCK also partially or completely counteracted the long-term inhibitory effects of IL-1 beta on islet glucose oxidation, insulin biosynthesis, content, and release. This protease inhibitor also counteracted IL-1 beta-induced beta-cell cytotoxicity as assessed by DNA content measurements. Of the other group-specific protease inhibitors investigated, only N-tosyl-L-phenylalanine chloromethyl ketone, N alpha-p-tosyl-L-arginine methyl ester, and chloromercuriphenylsulfonic acid were found to partially protect against IL-1 beta action. We concluded that protease activation, putatively a serine protease, may be an early and perhaps primary event in the action of IL-1 beta on beta-cells.

Animals↗
PubMed1991

Exhibition of specific alterations in activities and mRNA levels of rat islet glycolytic and mitochondrial enzymes in three different in vitro model systems for attenuated insulin release.

We studied the possible relationships between the functional status of the beta-cell and activities or mRNA contents of enzymes involved in the catabolism of glucose. Three different in vitro models with attenuated insulin response were used: rat islets cultured at a low glucose concentration, rat islets incubated in vitro with streptozocin, and fetal rat islets. The fetal and streptozocin-administered islets were compared with adult islets cultured in RPMI-1640 containing 11 mM glucose, and the effects of the in vitro glucose concentrations (3.3, 11, and 28 mM) were assessed on adult islets only. Cellular mRNA levels for the mitochondrial DNA-encoded cytochrome b and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were determined by Northern-blot analysis. Enzymatic activities of high-Km (glucokinase) and low-Km (hexokinase) glucose-phosphorylating enzymes and succinate-cytochrome c reductase were also determined. Islets cultured at 3.3 mM glucose displayed a decreased activity of glucokinase compared with islets cultured at 28 mM glucose (23.3 +/- 12%), whereas there was no difference in hexokinase activity or the level of GAPDH mRNA. The activity of succinate-cytochrome c reductase was similar in islets cultured at the different glucose concentrations. The level of cytochrome b mRNA increased at 28 mM glucose compared with islets cultured at 11 mM glucose (140 +/- 14%). Islets incubated with streptozocin and subsequently cultured for 7 days at 11 mM glucose exhibited a decreased level of cytochrome b mRNA (65 +/- 5%) and no differences in the activities of glucokinase, hexokinase, succinate-cytochrome c reductase, or the level of GAPDH mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Interleukin-1 beta increases the biosynthesis of the heat shock protein hsp70 and selectively decreases the biosynthesis of five proteins in rat pancreatic islets.

Prolonged exposure to high concentrations of human recombinant interleukin-1 beta (rIL-1 beta) has been reported to exert both suppressive and cytotoxic effects on pancreatic beta-cells during culture in vitro. In order to investigate the molecular mechanism(s) underlying the actions of rIL-1 beta on the beta-cell, we have exposed isolated rat pancreatic islets for 3 or for 24 h to 25 U/ml of rIL-1 beta. Subsequently the biosynthesis of heat shock proteins, as assessed by western blot analysis, and total protein biosynthesis patterns were studied, using one and two-dimensional gel electrophoresis of [35S]methionine labelled islet proteins from different subcellular compartments. It was found that rIL-1 beta exerted no specific effects on protein synthesis when added during a 3 h incubation period. However, after a 24 h incubation period, the synthesis of a group of acidic proteins with the approximate molecular weight of 35 kD was specifically inhibited in the rIL-1 beta treated islets. This alteration was predominantly associated with the endoplasmic reticulum fraction. The cytokine also inhibited the synthesis of four cytosolic proteins with the molecular weights 75, 85, 95 and 120 kD. In contrast, rIL-1 beta increased the expression of the heat shock protein hsp70 both in the microsomal and cytosolic fractions, in contrast to the islet nuclei in which no increase was found. These results show that exposure of pancreatic islets to rIL-1 beta is accompanied by specific alterations in the protein synthesis of the islet cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

A role for polyamines in glucose-stimulated insulin-gene expression.

The aim of the present study was to evaluate the possible role for polyamines in the glucose regulation of the metabolism of insulin mRNA of pancreatic islet cells. For this purpose islets were prepared from adult mice and cultured for 2 days in culture medium RPMI 1640 containing 3.3 mM- or 16.7 mM-glucose with or without the addition of the inhibitors of polyamine biosynthesis difluoromethylornithine (DFMO) and ethylglyoxal bis(guanylhydrazone) (EGBG). Culture at the high glucose concentration increased the islet contents of both insulin mRNA and polyamines. The synthesis of total RNA, total islet polyamines and polyamines associated with islet nuclei was also increased. When the combination of DFMO and EGBG was added in the presence of 16.7 mM-glucose, low contents of insulin mRNA, spermine and spermidine were observed. Total islet polyamine synthesis was also depressed by DFMO + EGBG, unlike islet biosynthesis of polyamines associated with nuclei, which was not equally decreased by the polyamine-synthesis inhibitors. Total RNA synthesis and turnover was not affected by DFMO + EGBG. Finally, actinomycin D attenuated the glucose-induced enhancement of insulin mRNA, and cycloheximide counteracted the insulin-mRNA attenuation induced by inhibition of polyamine synthesis. It is concluded that the glucose-induced increase in insulin mRNA is paralleled by increased contents and rates of polyamine biosynthesis and that an attenuation of the increase in polyamines prevents the increase in insulin mRNA. In addition, the results are compatible with the view that polyamines exert their effects on insulin mRNA mainly by increasing the stability of this messenger.

Animals↗
PubMed1990

Metabolism and beta-cell function of rat pancreatic islets exposed to human interleukin-1 beta in the presence of a high glucose concentration.

It has been postulated that one of the factors causing immune-mediated pancreatic beta-cell destruction in insulin-dependent diabetes mellitus (IDDM) is interleukin-1 (IL-1). Rat pancreatic islets exposed to human recombinant IL-1 beta (rIL-1 beta) for 48 h in vitro exhibit a markedly reduced glucose-stimulated insulin secretion. Also, a deleterious effect of glucose on beta-cell function, especially under conditions of a reduced beta-cell mass, which may exist in the early phase of IDDM has been suggested. In this study the response of rat pancreatic islets in vitro to a combination of the cytokine and high glucose concentration have therefore been assessed. Thus, islets were cultured for 48 h at either 11.1 or 56 mM glucose with or without 25 U/ml rIL-1 beta. Exposure to the cytokine reduced the islet DNA content at both glucose concentrations by 20-25%. In short-term incubations in the absence of rIL-1 beta after the preceding culture with the cytokine, the glucose-stimulated insulin release was reduced by 70% in islets cultured at 11.1 mM glucose and by only 40% after culture at 56 mM glucose, when compared to the corresponding control islets. The utilization of D-[5-3H]glucose, i.e., the catabolism of glucose in the glycolytic pathway, was the same in all groups of islets. However, the D-[6-14C]glucose oxidation rate, i.e., the metabolism of glucose in the Krebs cycle, was reduced by about 65% in rIL-1 beta exposed islets kept at 11.1 mM glucose and 46% in islets cultured at 56 mM glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1990

Coexpression of the platelet-derived growth factor (PDGF) B chain and the PDGF beta receptor in isolated pancreatic islet cells stimulates DNA synthesis.

Suspensions rich in pancreatic beta cells were transfected by means of electroporation or by using the liposome technique with DNA constructs coding for the B chain of platelet-derived growth factor (PDGF) and the PDGF alpha and beta receptors to induce a mitotic response in this slowly replicating cell type. Transfection with the B-chain construct induced synthesis of the PDGF B-chain homodimer (PDGF-BB) as assessed by the presence of 125I-labeled PDGF-BB competing activity in the conditioned medium of the transfected islet cells. Moreover, islet cells transfected with the PDGF beta-receptor construct exhibited increased immunofluorescence staining with a PDGF beta-receptor antibody. These cells also displayed increased 125I-labeled PDGF-BB binding compared with control transfected cells. Cotransfection with the B-chain construct or the addition of 10% fetal bovine serum or purified PDGF all induced DNA synthesis in islet cells transfected with the PDGF beta-receptor construct. Islet cells transfected with the PDGF alpha-receptor construct did not respond with stimulation of [3H]thymidine incorporation to any of the PDGF isoforms (PDGF-AA, -AB, or -BB). Cotransfection of the PDGF alpha- and beta-receptor constructs resulted in a loss of the DNA synthesis response to PDGF. The beta cells exhibited elevated levels of [3H]inositol trisphosphate after transfection with the B-chain and beta-receptor constructs, indicating activation of phospholipase C. Islet cells transfected with the different receptor constructs exhibited different patterns of tyrosine phosphorylation upon ligand activation. The results demonstrate that pancreatic islet cells can be stimulated to increase DNA synthesis by transfection with the PDGF beta-receptor gene, whereas cotransfection with the alpha-receptor gene may attenuate the growth response.

Animals↗
PubMed1990

Role of polyamines in mitogenic and secretory responses of pancreatic beta-cells to growth factors.

We have investigated the effects of glucose and the polypeptide growth factor growth hormone (GH), platelet-derived growth factor (PDGF), insulin-like growth factor I (IGF-I), epidermal growth factor (EGF), and transforming growth factor alpha (TGF alpha) on the polyamine content, in relation to proliferation and insulin secretion and content, of pancreatic beta-cells. Fetal rat pancreatic islets containing a high proportion of beta-cells were cultured for 3 days with growth factors. beta-cell replication was significantly increased by glucose, GH, and PDGF plus IGF-I in parallel with increased islet polyamine contents. In contrast, neither EGF nor TGF alpha influenced the islet DNA synthesis rate, polyamine content, insulin content, or insulin accumulation in culture medium. When the increased polyamine content evoked by growth-promoting agents was prevented by inhibitors of polyamine synthesis, elevated DNA synthesis rates persisted or were even augmented. However, subcellular fractionation analysis of islet homogenates revealed that the nuclear polyamine content was not affected by the inhibitors. On the other hand, islet insulin content and glucose-regulated insulin release were decreased by polyamine synthesis inhibitors. Glucose oxidation rates remained unchanged, suggesting that inhibitors were not toxic to islet cells. We conclude that prevention of increases in total cellular content of polyamines in response to glucose, GH, or PDGF plus IGF-I does not prevent mitogenicity of these growth factors. However, when their synthesis is inhibited normal levels of polyamines seem to be maintained in the cell nucleus, an event that may be sufficient to permit a mitotic signal to be translated into a proliferative response.

Animals↗
PubMed1990

In vitro restoration of insulin production in islets from adult rats treated neonatally with streptozotocin.

The aim of this study was to evaluate if the impaired insulin production of the beta-cell deficient islet organ of neonatally streptozotocin (SZ) injected rats is caused by exposure of the beta-cells to a long-lasting functional demand in vivo or a persistent toxic effect of the drug. For this purpose islets were isolated from adult rats which had received an ip injection of SZ (100 mg/kg body weight) on postnatal day 1 or from control rats receiving the solvent only. The islets used were either fresh or after culture for 2, 7, or 14 days in RPMI 1640 supplemented with 5.6, 11.1, or 16.7 mM glucose. After the various culture periods determinations were performed of the islet contents of insulin and insulin mRNA and the rates of (pro)insulin biosynthesis and insulin release. Freshly isolated islets from SZ-treated rats exhibited lower contents of insulin and insulin mRNA, a lower rate of (pro)insulin biosynthesis, and an impaired glucose-sensitive insulin release. Similar results were obtained after 2 days of culture, in each of the glucose concentrations. After 7 days of culture, however, the content of insulin mRNA and the rate of (pro)insulin biosynthesis of the SZ islets were restored to the control levels. When such islets were cultured for 7 days in 5.6 mM glucose, they exhibited a glucose-sensitive insulin release similar to that of the control islets. A difference in the insulin release between the two groups nevertheless persisted after culture for 7 days at either 11.1 and 16.7 mM glucose. Also, after 14 days of culture at 16.7 mM glucose there was an impaired glucose-sensitive insulin release from SZ islets, while islets cultured at 11.1 mM glucose showed a glucose-stimulated insulin release similar to that of the controls. The present data indicate that, as far as storage and biosynthesis of insulin is concerned, the functional aberrations observed in the freshly isolated SZ-islets did not reflect a permanent cytotoxic damage. The persistent impairment of insulin release after culture at 16.7 mM glucose may reflect either an injurious effect of the mildly diabetic metabolism in vivo or of the neonatal streptozotocin injection.

Animals↗
PubMed1990

Interleukin-1 beta depletes insulin messenger ribonucleic acid and increases the heat shock protein hsp70 in mouse pancreatic islets without impairing the glucose metabolism.

In order to further characterize the actions of recombinant interleukin-1 beta (rIL-1 beta) on the function of insulin-producing cells, the effects of different concentrations of the cytokine were studied on islets obtained from four different mouse strains (NMRI, NOD, C57BL/6, and C57BL/Ks). For this purpose the islets were exposed to rIL-1 beta (25, 50, or 100 U/ml) for a 48-h period in medium RPMI 1640 containing 10% calf serum and 11.1 mM glucose. In all groups and at the various rIL-1 beta concentrations tested, there was a similar 30-50% inhibition in glucose-induced insulin release, a 70-80% decrease in islet insulin content, and no significant differences in islet DNA content or insulin accumulation in the culture medium. To clarify the mechanisms underlying the decreased islet insulin content, rates of (pro)insulin biosynthesis and insulin messenger RNA (mRNA) contents were determined. Exposure of NMRI and C57BL/6 islets to 50 U/ml rIL-1 beta reduced the (pro)insulin biosynthesis by 40-50% and the insulin mRNA contents by 80-90%. The cytokine also induced an increased cellular content of the heat shock protein hsp70, as measured by western blot analysis, and a decrease in DNA biosynthesis, as measured by [methyl-3H]thymidine incorporation. However, exposure to rIL-1 beta did not decrease islet total protein biosynthesis, glucose oxidation, ATP content, ATP/ADP ratio, cAMP content, or polyamine contents. In conclusion, these data suggest that exposure of mouse islets to rIL-1 beta reduces DNA synthesis, insulin mRNA levels, and the biosynthesis of (pro)insulin, without equally impairing other cellular functions. The mechanisms behind these reductions seem to be different from those observed in rat islets, where a rIL-1 beta-induced impairment of substrate metabolism at the mitochondrial level seems to be related to the decrease of several cellular functions.

Animals↗
PubMed1990

Liposome mediated in vitro transfection of pancreatic islet cells.

The aim of this study was to evaluate the suitability of the liposome technique for transfection of pancreatic islet cells in vitro. For this purpose, fetal islets were isolated and cultured free floating for two days after which they were further cultured, either intact or dispersed into islet cell suspensions, with different DNA-liposome preparations. The DNA-construct used were the control plasmid (pSP65) and the viral oncogene v-src contained in the plasmid pSPRIsrc. A previous study showed that islet cells transfected by means of electroporation with pSPRIsrc displayed an increased thymidine incorporation rate, making this plasmid suitable for further transfection studies. The DNA was associated with the liposomes by means of surface adhesion. The liposomes used were either conventional phosphatidylcholine-containing liposomes, phosphatidylethanolamine/oleic acid containing liposomes (pH-sensitive liposomes) or Lipofectin. After the exposure of islet cells to the DNA-liposome preparations, the transfection efficiency was assessed by determination of the uptake of the DNA-constructs (Southern blot analysis) and expression of the gene construct into an mRNA (Northern blot analysis). In addition, the impact of the different DNA-liposome preparations on islet DNA replication (thymidine incorporation rates) was determined. It was found that two days after exposure to the DNA-liposomes, the v-src construct was located in islet cell nuclei and that v-src derived transcripts were transiently expressed in the islet cells. The Lipofectin liposomes were more efficient in transfecting islet cells than the pH-sensitive liposomes as assessed by the blotting techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Maturation of fetal rat islet cells in vitro during tissue culture is associated with increased mitochondrial function.

Tissue culture for one or seven days of pancreatic islets isolated from 21-day old fetal rats was found to be associated with a marked increase in the oxidation of L-(U-14C) glutamine by intact islets and in the activity of both alanine-glutamate and aspartate-glutamate transaminases as well as glutamate dehydrogenase in islet homogenates. This coincided with an increase in the relative amount of mitochondrial DNA. The activities of glucose-phosphorylating enzymes (hexokinase and glucokinase), glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase were less markedly increased during the culture period than those of enzymes involved in amino acid catabolism and located, in part at least, in mitochondria. The combined data suggest that the functional maturation of fetal islets during the culture period is associated with and may be attributable to a preferential maturation of their mitochondria.

Alanine Transaminase↗