Particle velocity profile in an inclined rotating drum

Various experimental and numerical studies have been carried out to study the velocity profiles of the particles inside horizontal rotating drums, but little emphasis has been laid on inclined rotating drums, though these drums are extensively used in granular process industries. In this study, velocity profiles of the particles in a rotating drum with 0o, 5o, 10o, and 15o inclinations have been studied by using the discrete element method. It was found that at the locations of the drum with the volumetric fill in the range of 0.2 0.8, the inclined rotating drum has a similar variation of velocity with the radial height to the horizontal rotating drum. However, the variation of the average particle velocity along the length of the drum differs for horizontal and inclined drums. Furthermore, for the inclined rotating drum, the average velocity increases with the increase in the volumetric fill.

Enhanced fluorescence from CdTe quantum dots self-assembled on the surface of silver nanoparticles

This paper presents an investigation on the fluorescent properties of semiconductor CdTe quantum dots (QDs) self-assembled on the surface of PVP (polyvinylpyrrolidone)-capped silver nanoparticles (NPs) by the ligand field effect. A significant 2.5-fold enhancement in the integrated fluorescence intensities, red shift of fluorescence peak, and obvious decrease of lifetime were observed in the CdTe QDs assembled on the Ag NPs in comparison with the pure CdTe QDs. The fluorescence enhancement factor and red shift were found to depend on the Ag NP concentration. The fluorescence enhancement was attributed to a highly localized electromagnetic field on the Ag NPs generated by the surface plasma and the change in the surface trap state of the CdTe QDs originating from plasma oscillations in the Ag NPs. It is first proposed that the surface passivation of CdTe QDs is also an important factor for metal-enhanced fluorescence. The surface defects of CdTe QDs can be modified by the Cd-O coordination interaction between the CdTe QDs and PVP molecules, which will cause the trap state density and luminescence lifetime to decrease. The surface passivation of CdTe QDs can also improve fluorescence quantum yield and lead to the red shift of the fluorescence peak. Compared with previous reports, the occurrence of the self-assembly of CdTe QDs on the surface of PVP-capped Ag NPs is fairly simple and easy. From a practical point of view, the combination of CdTe QDs with Ag NPs may lead to the fluorescence enhancement, which could be utilized in a variety of chemical and biological detection applications.

Clay-based polymer nanocomposites: research and commercial development

This paper reviews the recent research and development of clay-based polymer nanocomposites. Clay minerals, due to their unique layered structure, rich intercalation chemistry and availability at low cost, are promising nanoparticle reinforcements for polymers to manufacture low-cost, lightweight and high performance nanocomposites. We introduce briefly the structure, properties and surface modification of clay minerals, followed by the processing and characterization techniques of polymer nanocomposites. The enhanced and novel properties of such nanocomposites are then discussed, including mechanical, thermal, barrier, electrical conductivity, biodegradability among others. In addition, their available commercial and potential applications in automotive, packaging, coating and pigment, electrical materials, and in particular biomedical fields are highlighted. Finally, the challenges for the future are discussed in terms of processing, characterization and the mechanisms governing the behaviour of these advanced materials.

The interlayer swelling and molecular packing in organoclays

Understanding the interlayer swelling and molecular packing in organoclays is important to the formation and design of polymer nanocomposites. This paper presents recent experimental and molecular simulation studies on a variety of organoclays that show a linear relationship between the increase of d-spacing and the mass ratio between organic and clay. A denser molecular packing is observed in organoclays containing surfactants with hydroxyl-ethyl units. Moreover, our simulation results show that the head (nitrogen) groups are essentially tethered to the clay surface while the long hydrocarbon chains tend to adopt a layering structure with disordered conformation, which contrasts with the previous assumptions of either the chains lying parallel to the clay surface or being tilted at rather precise angles.

[Effects of the interaction between histone and hAMFR gene promoter on the transcription activity in vitro]

The effects of interaction between histones and human autocrine motility factor receptor (hAMFR) gene promoter on the transcription activity in vitro was investigated by using histones purified from chicken erythrocytes, HeLa cell nuclear extracts and heat-treated supernatants of Xenopus eggs. The results showed that the competitive binding of histones and transcription factors at the promoter of hAMFR gene was very important to the transcription in vitro. If a pre-initiation complex was formed with HeLa cell nuclear extracts on the promoter prior to nucleosome assembly, it would prevent nucleosome-mediated transcription repression. When the nucleosome was assembled on the promoter in advance, the transcription activity could be repressed. When histones and HeLa cell nuclear extracts were mixed in the reaction simultaneously, the transcription activity would depend on the relative amount of histones to that of HeLa cell nuclear extracts.

[Binding and interaction of histones and transcription factors on the promoter of hAMFR gene]

In this study, histone H1, core histones H2A-H2B and H3-H4 were purified from chicken erythrocytes by hydroxylapatile chromatography. The nuclear extract was prepared from HeLa cells. We investigated the binding and interaction of histones and transcription factors on the upstream sequence of human autocrine motility factor receptor (hAMFR) gene by gel shift mobility assay. We found that the binding of H1 on the promoter sequence of hAMFR gene was relatively stable. We propose that H1 plays an important role in stablizing chromatosome. We also found that histones and HeLa cell extract could form a ternary complex with the DNA template.

Cell proliferation and oncogene expression after bile duct ligation in the rat: evidence of a specific growth effect on bile duct cells

The proliferative response of the rat liver was measured after temporary or permanent total biliary obstruction (BDO) and in different regions after selective ligation of the lobar ducts draining the right 60% of the hepatic mass. The results were compared with those after 70% partial hepatectomy (PH). Cell proliferation was assessed globally by measuring DNA synthesis and stratified to the separate cell populations with cytostaining techniques that allowed distinction of hepatocytes, duct cells, and nonparenchymal cells (NPCs). In selected experimental groups, gene expression was determined of transforming growth factor-beta 1 (TGF beta-1), prothrombin, c-erb-B2, transforming growth factor alpha (TGF alpha), human Cyclophilin (CyP), and 28S ribosomal RNA. The stimulation of a proliferative response to total BDO required obstruction for longer than 24 hours, but after this deligation did not switch off regeneration. In the first week after permanent BDO, there was progressive infiltration of NPCs, fibrous linkage of some portal areas, and a crescendo of DNA synthesis that was obvious at 24 hours, maximal at 48 hours, and back nearly to baseline at 6 days. At the 2-day mark, the bile duct cells had a 17-fold increase in proliferation, accompanied by a threefold to fourfold increase in hepatocyte renewal. Little or no increase in expression of TGF alpha or the hepatocyte-specific prothrombin gene was detectable in the first 48 hours, whereas levels of the oncogene c-erb-B2 that is associated with cholangiocarcinoma were expressed from 48 to 96 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Modified simple cold storage of rat livers with UW solution

Rat livers were preserved with the conventional use of UW solution for 30, 42, and 48 hr and compared with livers in which the vascular bed was expanded with an additional 10 to 60 ml UW/100 g liver. The extra UW, expressed as % liver weight, was entrapped during final portal infusion by typing off the supra- and infrahepatic inferior vena cava. A beneficial influence of the vascular expansion was most pronounced in the 40% group, with 10/10, 5/10, and 3/10 long-term survivors following transplantation after 30, 42, and 48 hr preservation versus 3/10 and 0/10 after 30 and 42 hr in the 0% controls. In separate experiments, surrogate indices of preservation quality following reperfusion explained this effect. The 40%--and, to a lesser extent, 20%--livers had higher and more uniformly distributed portal blood flow, better tissue oxygenation, smaller increases in postperfusion liver enzymes, higher adenine nucleotides and energy charge, and less histopathologic evidence of hemorrhage and congestion. Pressure changes in the vena cava fluid sump in additional experiments indicated that retrograde infusion of the trapped UW solution occurred in all of the 10-60% groups during the first 6 hr with stable pressures of 1.5 to 3 cm H2O thereafter. Collectively, these data suggest that the much discussed selective vulnerability of the microvasculature of stored allografts is due in part (or principally) to its selective lack of long-term exposure to the UW solution, which drains out of the open vessels but not from the parenchyma. The potential clinical exploitation of this concept is discussed.

Effect on the canine Eck fistula liver of intraportal TGF-beta alone or with hepatic growth factors

Transforming growth factor-beta canceled the hepatocyte proliferation caused by transforming growth factor-alpha when the two substances were mixed and administered through a disconnected central portal vein branch after creation of an Eck fistula. In contrast, transforming growth factor-beta had no antidotal action on the stimulatory effects of insulin or full test doses of insulinlike factor-2, hepatocyte growth factor, epidermal growth factor or triiodothymanine. A minor antidotal effect on hepatic stimulatory substance activity could be detected, but only with hepatic stimulatory substance was given in doses smaller than those known to cause maximum stimulatory response. These results suggest a highly specific pharmacological and physiological interaction between transforming growth factor-alpha and transforming growth factor-beta in the modulation of liver growth control.

Effects of rapamycin on cultured hepatocyte proliferation and gene expression

Rapamycin, a potent immunosuppressive drug that disrupts normal signal-transduction processes, inhibited hepatocyte proliferation without evidence of inherent cytotoxicity in rat hepatocytes cultured in conventional medium or in a medium enriched with epidermal growth factor. The antiproliferative effect was dose dependent, uninfluenced by the concentration of epidermal growth factor in the medium and long lasting after a brief exposure. The effect of rapamycin was unaltered by the concomitant presence of FK 506 in the medium, suggesting that different binding affinities of these two drugs or even a separate rapamycin binding site may exist. Hepatocytes harvested 12 and 24 hr after partial hepatectomy were progressively less responsive to the antiproliferative effect of rapamycin. The gene expression of transforming growth factor-beta was reduced under in vivo rapamycin treatment, but at the same time the gene expression of albumin and glyceraldehyde-3-phosphate dehydrogenase was unchanged or increased. The experiments confirm that rapamycin has inherent growth-control qualities, and they strengthen the hypothesis that the recently defined immunophilin network is central to many aspects of cellular growth control.

Screening for candidate hepatic growth factors by selective portal infusion after canine Eck's fistula

Completely diverting portacaval shunt (Eck's fistula) in dogs causes hepatocyte atrophy, disruption of hepatocyte organelles, fatty infiltration and low-grade hyperplasia. The effect of hepatic growth regulatory substances on these changes was assessed by constantly infusing test substances for four postoperative days after Eck's fistula into the detached left protal vein above the shunt. The directly infused left lobes were compared histopathologically with the untreated right lobes. In what has been called an hepatotrophic effect, stimulatory substances prevented the atrophy and increased hepatocyte mitoses. Of the hormones tested, only insulin was strongly hepatotrophic; T3 had a minor effect, and glucagon, prolactin, angiotensin II, vasopressin, norepinephrine and estradiol were inert. Insulin-like growth factor, hepatic stimulatory substance, transforming growth factor-alpha and hepatocyte growth factor (also known as hematopoietin A) were powerfully hepatotrophic, but epidermal growth factor had a barely discernible effect. Transforming growth factor-beta was inhibitory, but tamoxifen, interleukin-1 and interleukin-2 had no effect. The hepatotrophic action of insulin was not altered when the insulin infusate was mixed with transforming growth factor-beta or tamoxifen. These experiments show the importance of in vivo in addition to in vitro testing of putative growth control factors. They illustrate how Eck's fistula model can be used to screen for such substances and possibly to help delineate their mechanisms of action.

Screening for candidate hepatic growth factors by selective portal infusion after canine Eck's fistula

Completely diverting portacaval shunt (Eck's fistula) in dogs causes hepatocyte atrophy, disruption of hepatocyte organelles, fatty infiltration and low-grade hyperplasia. The effect of hepatic growth regulatory substances on these changes was assessed by constantly infusing test substances for four postoperative days after Eck's fistula into the detached left protal vein above the shunt. The directly infused left lobes were compared histopathologically with the untreated right lobes. In what has been called an hepatotrophic effect, stimulatory substances prevented the atrophy and increased hepatocyte mitoses. Of the hormones tested, only insulin was strongly hepatotrophic; T3 had a minor effect, and glucagon, prolactin, angiotensin II, vasopressin, norepinephrine and estradiol were inert. Insulin-like growth factor, hepatic stimulatory substance, transforming growth factor-alpha and hepatocyte growth factor (also known as hematopoietin A) were powerfully hepatotrophic, but epidermal growth factor had a barely discernible effect. Transforming growth factor-beta was inhibitory, but tamoxifen, interleukin-1 and interleukin-2 had no effect. The hepatotrophic action of insulin was not altered when the insulin infusate was mixed with transforming growth factor-beta or tamoxifen. These experiments show the importance of in vivo in addition to in vitro testing of putative growth control factors. They illustrate how Eck's fistula model can be used to screen for such substances and possibly to help delineate their mechanisms of action.

Studies on mechanisms of augmentation of liver regeneration by cyclosporine and FK 506

Evidence could not be found of immune modulation of liver regeneration. The powerful immunosuppressive drug FK 506, which augments the response after partial hepatectomy in normal rats, had the same effect in T cell-deficient nude rats. The cytotoxicity of natural killer cells in treated nude rats was not significantly changed by FK 506 therapy. However, the serum of FK 506-treated nude rats increased hepatocyte proliferation when added to third-party hepatocyte cultures, suggesting that FK 506 had induced a serum growth factor in the nude rats or had suppressed an inhibitory factor. A hypothesis was advanced that FK 506 (and cyclosporine) affects hepatic growth by nonimmunological pathways.

Experience with orthotopic rat liver transplantation

300 orthotopic liver transplantations in rats were performed for a variety of reasons. Male rats including Lewis, ACI, Wistar, and SD, with a body weight of 150 to 400 g, were used as liver donors and recipients. A midline abdominal incision was performed in both donor and recipient animals. The donor's liver was perfused through the aorta abdominalis. The recipient's liver was flushed via the protal vein (PV) with 2 ml of lactated Ringer's solution immediately after occlusion of the PV to make intrahepatic blood enter the circulation. The bile duct was reconstructed by end-to-end anastomosis via a Teflon catheter. The cuff technique was applied to anastomoses of the infrahepatic vena cava (VC) and PV. The suprahepatic VC was anastomosed using either suture or cuff technique. The operative success rate was 92.7% (278/300) on the average and 1-week survival rate 88.4% (199/225) in isografting. The model proved reliable for studies of liver transplantation.

Orthotopic liver transplantation and the cytosolic estrogen-androgen receptor status of the liver: the influence of the sex of the donor

Mammalian liver is known to contain cytosolic receptors for both estrogens and androgens. Furthermore, certain mammalian hepatic functions are known to display a sexual dimorphism. However, in clinical liver transplantation, the sex of the donor is not taken into consideration in selection of the donor. In this study, the effect of liver transplantation on the estrogen and androgen receptor content of the liver was determined. Adult male and female rats were subjected to orthotopic liver transplantation, using donors from both the same and the opposite sex as the recipient. The animals were killed on the tenth postoperative day, and the livers were assayed to determine their cytosolic estrogen and androgen receptor content. Transplantation of a liver from a male donor into a male recipient, from a male donor into female recipient and from a female donor into a male recipient produced similar changes in the number of cytosolic estrogen and androgen receptors in hepatic cytosol. In all three situations, the estrogen receptor content in the cytosol of the transplanted liver was the same as that found in an unoperated male liver, and the cytosolic content of the androgen receptor was the same as that of an unoperated female liver. After transplantation of the liver from a female donor into a female recipient, the estrogen and androgen receptor content in the cytosol of the transplanted liver was the same as that of an unoperated female.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol synthesis in bypassed segments of the small intestine in hyperphagic rats

Previous studies have demonstrated that a variety of conditions that result in an increase in food intake lead to an increase in small-intestinal cholesterol synthesis. In the present study, it was determined whether hyperphagia induces an increase in cholesterol synthesis in segments of the small intestine excluded from contact with the food stream and whether this increase would occur in bypassed segments of the proximal or mid-small intestine. In hyperphagic diabetic rats, cholesterol synthesis is increased 91% in the proximal portion of the small intestine excluded from contact with nutrients. In lactating rats, another model of hyperphagia, cholesterol synthesis is increased 2.4-fold in midintestinal segments excluded from contact with the food stream and 2.9-fold in segments of the proximal intestine that have been bypassed. These observations demonstrate that the hyperphagia-induced increase in small-intestinal cholesterol synthesis will occur in portions of the small intestine, even if contact with the food stream is prevented. In addition, this data demonstrated that the mass of the bypassed portion of the small intestine is increased in hyperphagic animals. In diabetic animals, the weight of the bypassed proximal intestine is increased 2.1-fold, whereas in lactating animals the mass is increased 50% in the bypassed midintestine and 74% in the bypassed proximal small intestine. In conclusion, the present study suggests that circulating or neurologic factors, or both, play a role in stimulating intestinal cholesterol synthesis in hyperphagic animals. These findings also suggest that indirect factors play a role in the increase in intestinal mass associated with hyperphagia.

Total gastrectomy and small intestinal cholesterol synthesis in diabetic rats

Cholesterol synthesis is increased two- to threefold in the small intestine of diabetic rats. We have observed, in three separate experiments, that the characteristic increase in small intestinal cholesterol synthesis (SICS) in diabetic rats was prevented by total gastrectomy. Food intake was increased twofold, and the small intestine hypertrophied in the gastrectomized diabetic animals. In normal animals, total gastrectomy resulted in only a very small increase in intestinal cholesterol synthesis. In hyperphagic lactating animals, total gastrectomy did not prevent the characteristic increase in SICS that is usually observed in this hyperphagic model. These results indicate that the effects of total gastrectomy on preventing an increase in SICS are relatively specific for the diabetic state. The mechanism by which total gastrectomy prevents the increase in intestinal cholesterol synthesis in diabetic animals is unknown. Vagotomy did not prevent the typical increase in intestinal synthesis in diabetic animals. Additionally, selectively removing either the antrum or fundus of the stomach did not prevent the increase in SICS in diabetic animals, indicating that the inhibition requires the removal of the entire stomach. It can be speculated that the stomach produces a substance that induces the increase in SICS observed in diabetic animals and that total gastrectomy removes this stimulatory substance.

Thyroid cancer: the case for total thyroidectomy

Since there are no prospective studies concerning the treatment of thyroid cancer, there continues to be a considerable disagreement about the 'best' or most appropriate form of surgical treatment for patients with papillary or follicular thyroid cancer. Some surgeons recommend selective treatment depending upon the type of thyroid tumor and stage of the disease. Some advocate thyroid lobectomy and isthmusectomy, some near total thyroidectomy, and some total thyroidectomy for patients with papillary and follicular thyroid cancer. Total thyroidectomy for thyroid cancer would be the treatment of choice for virtually all patients with thyroid cancers if it could be done without complications. We therefore reviewed 160 consecutive patients who had total thyroidectomy for suspected or proven thyroid cancer to determine the complication rate of total thyroidectomy. One hundred and three patients had primary operations, 57 had reoperations with completion of total thyroidectomy and 124 had thyroid cancer. Serious complications (i.e. vocal cord paralysis or hypoparathyroidism) included two cases of transient bilateral recurrent nerve palsy, two patients with presumed transient unilateral vocal cord paralysis, three recurrent laryngeal nerves that were purposely sacrificed because of invasion of the nerve, and one case of permanent hypoparathyroidism. Two other patients developed postoperative wound infections. Only one of the permanent complications, the case of permanent hypoparathyroidism, could have been avoided by a lesser procedure. The experienced surgeon can perform a total thyroidectomy with minimal morbidity, and this procedure has certain theoretical and practical advantages. It should not be done, however, if it will result in a significant complication rate and, in selected patients, it may be preferable to leave a small amount of thyroid tissue to protect the blood supply to the parathyroid glands or recurrent laryngeal nerve.

Localizing studies in patients with persistent or recurrent hyperparathyroidism

Preoperative localizing studies are essential for patients with persistent or recurrent hyperparathyroidism requiring reoperation, because of loss of normal tissue planes and because the hyperfunctioning parathyroid tissue that remains is more likely to be situated in an ectopic position. The value of noninvasive and invasive localizing techniques was evaluated in 59 consecutive patients undergoing reoperation for persistent (40 patients) or recurrent (19 patients) hyperparathyroidism. Magnetic resonance imaging was performed in 17 patients; 11 results (65%) were positive, 3 (18%) were negative, and 3 (18%) were false-positive. Ultrasonography was performed in 52 patients; 29 (56%) were positive, 16 (31%) were negative, and 7 (13%) were false-positive. Computed tomography was performed on 41 patients; 19 (46%) were positive, 16 (39%) were negative, and 6 (15%) were false-positive. Thallium chloride 201-technetium 99m pertechnetate scans were used in 39 patients; 19 (49%) were positive, 11 (28%) were negative, and 9 (13%) were false-positive. One or more of these noninvasive tests was positive in 78% of the cases. Highly selective venous catheterization with measurement of immunoreactive parathyroid hormone concentration localized the abnormal parathyroid gland in 20 of 28 patients (71%) overall and in 8 of the 14 patients (57%) whose tumors were not identified by the noninvasive techniques. Since false-positive results were common, a combination of localizing studies was helpful in identifying the abnormal gland. Fifty-three of the 59 patients (90%) were successfully treated at the initial reoperation and three were successfully treated at a second reoperation. Advances in parathyroid localization have contributed to the improved surgical results in patients with persistent or recurrent hyperparathyroidism.