Carcinosarcoma of the pancreas: a case report and review of the literature

We report the case of a 74-year-old white man with a mass in the head of the pancreas, which was found incidentally on computerized tomographic scan during a workup for deep vein thrombosis. Endoscopy with pancreatic duct brushings yielded a diagnosis of adenocarcinoma. A pancreaticoduodenectomy followed, with complete resection of the tumor. Pathologic examination showed 2 distinct components. One component was a conventional infiltrating pancreatic ductal adenocarcinoma, and the other component was high-grade sarcoma with features of malignant fibrous histiocytoma. To our knowledge, this carcinosarcoma is the seventh reported case of a primary pancreatic neoplasm with mixed carcinomatous and sarcomatous elements.

Regulation mechanisms of intestinal secretion: implications in nutrient absorption

Intestinal secretion is a normal phenomenon, indispensible to solubilize and dilute nutrients and to maintain fluidity in the intestinal lumen. Enterotoxins and certain drugs may disrupt the proabsorptive status maintained by the small intestine under physiologic conditions. Hormones found in nervous and specialized intestinal enterochromaffin cells are responsible, in part, for secretion of fluid into the lumen. Afferent vagal nerve impulses mediated by 5-hydroxytryptamine (serotonin; 5-HT), vasoactive intestinal peptide (VIP) and substance P are the major agents of secretory stimulation. Toxins from pathogenic bacteria, especially some strains of E. coli and V. cholerae, trigger a secretory response and a chain of events involving cGMP and cAMP which result in chloride secretion, coupled to sodium and fluid efflux into the lumen. If secretion is unchecked by natural mechanisms or medications, the consequences are diarrhea, with potential dehydration, hyponatremia and ultimately death. Introduction of absorbable nutrients in the intestinal lumen has a major antisecretory action, both by a nutrient-gene interaction and by proabsorptive hormone expression. In additon, during the absorptive process water is carried into the enterocyte together with solutes. Hydrolysis-resistant peptides of dietary origin and ingested soluble fiber may also have a proabsorptive effect. The gastrointestinal system has a variety of antisecretory or proabsorptive hormonal and protein agonists that balance the outflow of fluid and electrolytes. The more extensively studied are neuropeptide Y/peptide YY (NPY/PYY) and the antisecretory factor (AF). Nitric oxide (NO), a short-lived second messenger, has a major role in secretion by activating cGMP. The intracellular concentration of NO may regulate the absorptive/secretory status of the small intestine, either stimulating absorption or inducing secretion. Specifically targeted 5-HT receptor antagonist drugs and other pharmacologic agents have been clinically tried for the treatment of severe diarrhea, drug-induced malabsorption and reversal of cellular damage.

Zinc supplementation in oral rehydration solutions: experimental assessment and mechanisms of action

BACKGROUND

Zinc deficiency is associated with chronic diarrhea. This condition is generally linked to an overproduction of nitric oxide (NO), which induces secretion and cellular damage as a free radical. Use of oral rehydration solutions (ORS) is an important part of diarrhea treatment, especially early in infancy and for patients with cholera. The presence of zinc in an ORS could be a positive factor in recovery from diarrheal disease.

OBJECTIVE

This study was undertaken to determine whether zinc added to an ORS could regulate the synthesis of NO metabolites in the lumen of zinc deficient rat intestine, acting as a gastrointestinal protector and thus accelerating normalization of intestinal function and zinc status.

METHODS

The effects of zinc on NO metabolism were studied in young male rats fed a zinc deficient diet for three weeks to mimic the condition of patients with recurrent diarrheal episodes. During the fourth week of the zinc deficient feedings, experimental diarrhea was induced using cathartics (magnesium citrate plus phenolphthalein) that exacerbate NO production. A standard ORS with or without 1 mM zinc was given to the rats for the last two days. A control group received a zinc sufficient diet. Rats were killed at each stage. Intestinal nitric oxide synthase (NOS) was assayed, cecal fluid contents were analyzed for nitrates and nitrites, intestinal histology was examined, and activation of nuclear factor NF-kappaB DNA binding activity was determined.

RESULTS

Rats fed the zinc-deficient diet for three weeks gained less weight than rats fed a normal zinc content diet and had a lower plasma zinc than controls (51.6 +/- 5.4 [n = 101 vs. 143.6 +/- 7.2 microg/dL [n = 11], p < 0.05). Recovery with ORS+Zn resulted in a higher plasma zinc than with the ORS-Zn (ORS+Zn: 186.5 +/- 12.2; ORS-Zn: 57.5 +/- 6.6 microg/dL, p < 0.05). The zinc-deficient diet did not alter mucosal NOS, as compared to the values of rats fed a normal diet. However, those animals which received five days of cathartic fluids had a small intestinal NOS higher than that of all other groups. Either ORS+Zn or ORS-Zn normalized NOS activity, regardless of cathartic treatment. The rats fed the zinc deficient diet had generally a higher content of NO metabolites in the cecum than rats fed a normal diet. After recovery with either type of ORS, rats given the cathartic remained with higher cecal NO metabolite concentrations than rats that had no induced diarrhea. After recovery with ORS+Zn, intestinal villi showed significant expansion of the lamina propria, an indication of greater absorption of fluid, while with ORS-Zn this was not present. Small intestinal homogenates of rats recovering with ORS+Zn had a decreased NF-kappaB DNA binding activity than tissues from rats consuming ORS-Zn.

CONCLUSIONS

The results are consistent with the hypothesis that addition of Zn to an ORS may contribute to improving the physiologic status of the small intestine and potentially reduce the risks of recurrent diarrhea episodes.

TSP50, a possible protease in human testes, is activated in breast cancer epithelial cells

Initial studies have identified TSP50 as a human testes-specific gene that is demethylated in breast cancer. In this study, we will present new data related to the TSP50 gene. We have found that the TSP50 gene product shares a similar enzymatic structure with many serine proteases. However, the most critical catalytic site, serine, has been replaced by threonine. Western analysis revealed that in human testes, the TSP50 antibody detected two closely positioned protein bands whose estimated molecular masses were 37 kDa, whereas in a large portion of breast cancer tissues, but not normal control tissues, only one band was present. Immunohistochemistry assays found TSP50 proteins located in the spermatocytes of human testes, whereas in situ hybridization and immunohistochemistry confirmed that gene activation in breast tumors took place in malignant mammary epithelial cells. These results suggested that the normal function of the TSP50 gene was involved in spermatogenesis, whereas the up-regulation of TSP50 in many breast cancer patients not only indicated that it might be a novel biomarker for this disease but also encouraged us to further explore the possibility of whether it was an oncogene.

Pulmonary adenocarcinoma simulating malignant mesothelioma

Adenocarcinoma of the lung with pleural involvement frequently resembles pleural epithelioid mesothelioma clinically as well as macro- and microscopically. Special stains, immunohistochemical studies, and electron microscopic studies are needed to differentiate these 2 tumors. We report a case of pleural involvement by adenocarcinoma, mimicking in the hematoxylin-eosin stain an epithelioid mesothelioma, correctly identified only after immunohistochemical and electron microscopic examinations.

Ultrastructure of the periductal area of comedo carcinoma in situ of the breast

We have previously shown that the different biological natures of comedo ductal carcinoma in situ (DCIS) and non-comedo DCIS may, in part, be explained by the different expression patterns of tenascin, a large extracellular matrix protein, as observed by immunohistochemical studies. In the present study, we compared 8 cases of comedo DCIS with 5 cases of non-comedo DCIS by ultrastructural analysis, focusing on the myoepithelium, basal lamina, and tenascin-positive extracellular periductal stromal matrix. Our observations show that the comedo type DCIS frequently has an altered basal lamina, a looser and more disorganized collagenous matrix, and a general increase in stromal cellularity, including fibroblasts, lymphocytes, histiocytes and small blood vessels. In addition, in comedo DCIS, the lateral intercellular spaces between large myoepithelial cells that border the basal lamina are often expanded, compared to those of non-comedo DCIS. These results identify structural characteristics of comedo DCIS that may play a role in its greater preinvasive potential. They may also provide a structural basis for the different strategies that are needed for for clinical management of comedo DCIS, compared to non-comedo DCIS.

Stimulation of non-sodium-dependent water, electrolyte, and glucose transport in rat small intestine by gum arabic

In experimental models of gastroenterological disease, the soluble fiber gum arabic (GA) acts as a proabsorptive adjuvant. This study investigated which specific transport pathway(s) are affected by GA. Rat jejunum was perfused under anesthesia with a standardized oral rehydration solution (ORS) containing D-glucose, with or without GA (2.5 g/liter). In some preparations either phloridizin, a competitive inhibitor of Na+-coupled D-glucose transport, or phloretin, an inhibitor of basolateral glucose transport, were added to the ORS, with or without GA. Diffusion and paracellular transport changes due to GA were evaluated with L-glucose and [14C]polyethlyene glycol 4000 (PEG). GA partially reversed water, Na+, and D-glucose absorption inhibition induced by phloridzin and normalized water and Na+ absorption in the presence of phloretin. GA also increased absorption of water, Na+, and PEG from an L-glucose ORS. The data suggest that GA does not act via Na+ dependent mechanism(s), but stimulates transcellular and/or transjunctional transport pathways; therefore GA may be useful to increase absorption of solutes transported by diffusion.

Concurrent malakoplakia and papillary urothelial carcinoma of the urinary bladder

A case of malakoplakia and papillary urothelial carcinoma of the urinary bladder is reported. In this case, malakoplakia was an incidental finding in a biopsy of the urinary bladder of a 74-yr old female, who presented with hematuria. The biopsy showed a low-grade papillary urothelial carcinoma in close association with malakoplakia. This is a rare association of these lesions.

Adenocarcinoid tumor of the ovary diagnosed during pregnancy. A case report

BACKGROUND

Adenocarcinoid tumors are uncommon neoplasms with dual morphology, showing components of a neuroendocrine tumor with carcinoid features and an adenocarcinomatous component composed of glands lined with mucin-containing cells, some of which are goblet type.

CASE

A 36-year-old woman had a left adnexal mass found during the second week of pregnancy. Sonography showed it to be increasing in size and eventually to become associated with pelvic pain. During the 20th week of gestation, an exploratory laparotomy was performed, and the left ovary and fallopian tube were excised. A diagnosis of adenocarcinoma was rendered by intraoperative frozen section. A staging procedure was then performed that included removal of the contralateral adenexa, pelvic lymph node sampling, peritoneal biopsies and partial omentectomy. The vermiform appendix and gastrointestinal tract appeared unremarkable. The patient was discharged. Permanent sections of the left ovary revealed an adenocarcinoid tumor.

CONCLUSION

While reports detail ovarian metastases of adenocarcinoid neoplasms from primary appendiceal and other gastrointestinal sites, this case, in the setting of a normal appendix and negative workup for an extraovarian origin, is the fourth documented one of a primary ovarian adenocarcinoid tumor and first diagnosed during pregnancy.

Cholera toxin-induced secretion in rats is reduced by a soluble fiber, gum arabic

Gum arabic (GA), a soluble fiber with emulsifying properties, enhances intestinal water and electrolyte absorption in normal and secreting rats. Our aim was to assess the effect of GA, 2.5 and 5.0 g/liter, on cholera toxin-induced water and electrolyte secretion in rat jejunum in vivo. After a 2-hr exposure to cholera toxin, jejunal segments of adult rats were perfused in vivo with at plasma electrolyte solution containing GA, 0, 2.5 or 5.0 g/liter. 24Na was used as a marker of sodium influx. Cholera toxin-induced secretion was reduced by GA, 2.5 and 5.0 g/liter. 24Na secretion into the lumen was reduced by GA. GA caused a morphological expansion of intercellular spaces in the villi but not crypts. In conclusion, GA promotes lumen to blood intestinal transport of water and sodium despite cholera toxin activation. These observations support a potential role for GA in enhancing the efficacy of ORS.

Development of the intestinal SGLT1 transporter in rats

Glucose absorption from the small intestine is largely mediated via the sodium-coupled glucose transporter (SGLT1). The goal of this study was to investigate the ontogenesis of the SGLT1, using the rat as an animal model at three stages of development: during lactation, at weaning, and at physiologic maturity. The techniques involved upper small intestinal perfusions with solutions containing 200 mM glucose and 50 mM NaCl, with or without 1 mM phloridzin (Phl), as an inhibitor of SGLT1. Molecular expression of the SGLT1 was also investigated via Western blot analysis from intestinal specimens of the three growth periods. Glucose absorption in weanling rats, in the absence of Phl, was several times higher than in sucklings and approximately double that of mature animals, and the effects of Phl were the greatest in weanlings. Furthermore, the physiologic data correlate to the molecular analysis of the SGLT1 which showed an increase in expression of the SGLT1 in both the weanlings and the adults compared to the sucklings. At all three stages of development Phl abolished Na absorption, and in sucklings there was a net outflow of Na. Due to the coupling between Na and water transport, net water absorption and the influx/efflux ratio, a more sensitive indicator of changes in unidirectional fluid movement, were similarly affected by Phl at the three stages of development. Net water absorption was highest in weanling animals. These findings are consistent with an early development of SGLT1 in rat small intestine and an apparent burst of activity at weaning. Less than complete maturity of other absorptive mechansims is occurring at this time.

Association of increased ubiquitinated proteins with cardiac apoptosis

Intracellular proteases play an important role in the regulation of apoptosis. A study was performed to determine whether inhibition of the cardiac ATP-dependent ubiquitin 26S protease complex affects cardiomyocyte apoptosis. Isolated rat hearts were perfused for up to 80 min with Krebs-Henseleit buffer +/- the 26S-proteasome inhibitor, MG132 (Z-leu-leu-leucinal). TUNEL-staining of hearts perfused with 25 microM MG132 for 50 min revealed a significant increase (p < 0.05) in the apoptotic index from 1.1% to 15.5% when compared with control hearts perfused with buffer only. Histology of adjacent myocardial sections revealed no signs of necrotic or late apoptotic (nuclear condensation) changes, indicating that the TUNEL-positive nuclei were in the early stages of apoptosis. This early stage of apoptosis was associated with a significant (p < 0.05) reduction in cardiac function. There was a 63% decrease in the rate pressure product in hearts perfused with 25 microM MG132 as compared with a 35% decrease in control hearts over the 80-min perfusion period. Soluble ubiquitin-conjugated proteins, as detected by probing with a specific antibody to ubiquitin, were increased in MG132-treated hearts. In hearts perfused with 50 microM MG132, a greater accumulation of ubiquinated proteins was observed accompanied by a more rapid and greater reduction in hemodynamic function. These observations indicate that prolonged inhibition of the ubiquitin-26S-proteasome results in cardiomyocyte apoptosis accompanied by increased ubiquinated proteins, thus suggesting that accumulation of these abnormal proteins may act as a signal to activate the cell death program.

Effect of gum arabic in an oral rehydration solution on recovery from diarrhea in rats

BACKGROUND

It has been shown that gum arabic, a soluble fiber, enhances water, electrolyte, and glucose absorption from oral rehydration solutions in jejunal perfusion of healthy rats and in animals with theophylline-induced secretion or chronic osmotic-secretory diarrhea. This report concerns a study of the effectiveness of an oral rehydration solution supplemented with gum arabic, during recovery from chronic osmotic secretory diarrhea in free-living rats.

METHODS

Chronic diarrhea was induced in 60- to 80-g juvenile rats by providing a magnesium citrate-phenolphthalein solution as the sole fluid source for 7 days. This led to diarrhea characterized by dehydration, soft stools, increased cecal volume, decreased food and fluid intake and failure to gain weight. After 7 days of diarrhea, rats recovered for 24 hours with either tap water or an oral rehydration solution (90 mM Na, 111 mM glucose, 20 mM K, 80 mM chloride, 20 mM citrate) with or without 2.5 g/l gum arabic.

RESULTS

Although all three solutions improved the diarrhea, optimal recovery from diarrhea was achieved with the gum arabic-supplemented oral rehydration solution. After 4 hours and 24 hours, rats drinking the gum arabic-supplemented solution gained more weight and had lower fecal output than rats receiving water or the rehydration solution without gum arabic. All three solutions normalized plasma osmolality after 24 hours.

CONCLUSIONS

The positive effects of the gum arabic-supplemented rehydration solution on fluid and electrolyte absorption seen during jejunal perfusion also occurred during recovery from chronic osmotic secretory diarrhea, when free-living animals drank the solution ad libitum.

Pleomorphic large cell sarcoma of the spleen with rhabdomyosarcomatous differentiation

An unusual case is reported of pleomorphic large cell sarcoma of the spleen with rhabdomyosarcomatous differentiation in a 34-year old male. According to our knowledge, such a neoplasm has never been reported in the literature.

Human serum-resistant retroviral vector particles from galactosyl (alpha1-3) galactosyl containing nonprimate cell lines

Retroviral vector particles (RVP) which are resistant to inactivation by human serum will be needed for many in vivo gene therapy applications. Murine-based producer cell lines generate RVP which are inactivated by human serum, reportedly due to the presence of the galactosyl (alpha1-3) galactosyl carbohydrate moiety (alphaGal) on these and other nonprimate producer cells and RVP. Consequently, human cells (which lack the alphaGal moiety) have been developed as producer cell lines for generation of human serum-resistant RVP. In this study, we report that contrary to earlier reports, the presence of the alphaGal moiety on producer cells and RVP does not necessarily correlate with cell killing or RVP inactivation by human serum. We show that the alphaGal-positive ferret brain cell line, Mpf, is an excellent basal cell line for generation of RVP which have titers and serum resistance levels equal to or greater than RVP produced in human cell lines such as HT1080. Therefore, packaging cell lines need not be limited to those of human or primate origin for production of human serum-resistant RVP.

Modified starch enhances absorption and accelerates recovery in experimental diarrhea in rats

Rice gruels have been used as home remedies to treat dehydration associated with diarrheal illness in developing countries. These preparations have produced conflicting results, most likely due to the heterogeneity of starch used. We investigated whether the modified tapioca starch, Textra (TX), at 5.0 or 10.0 g/L added to a 90 mmol/L Na+-111 mmol glucose oral rehydration solution (ORS) enhanced water and electrolyte absorption in two models of diarrhea. To induce a secretory state (model A), the jejunum of juvenile rats was perfused with 10 mmol/L theophylline (THEO) under anesthesia and then perfused with the solutions indicated above. To produce chronic osmotic-secretory diarrhea (model B), rats had a magnesium citrate-phenolphthalein solution as the sole fluid source for 1 wk, and then were perfused as the THEO-treated rats. Water, electrolyte, and glucose absorption were measured during both perfusions. As an extension of the perfusion studies, we compared how fast rats recovered from chronic osmotic diarrhea by offering them either water, ORS, or ORS containing 5.0 g/L TX along with solid food. Recovery rate markers were measured after 24 h and included weight gain, food and fluid intake, and stool output. In model A, addition of 5.0 g/L TX to ORS reversed Na+ secretion and improved net water as well as K+ and glucose absorption, compared with THEO-treated rats perfused with ORS without TX. In model B, addition of TX to ORS increased water, Na+, K+, and glucose absorption, compared with rats perfused without TX. Increasing TX from 5.0 to 10.0 g/L had no additional benefit. In recovery experiments, animals with free access to ORS with TX had significantly greater weight gain and decreased stool output compared with animals recovering with water or ORS without TX. Our experiments suggest that TX may be a useful additive to standard ORS to promote fluid and electrolyte absorption and may provide additional energy without increasing ORS osmotic load.

Proabsorptive effect of glycerol as a glucose substitute in oral rehydration solutions

We hypothesized that glycerol, a readily diffusable hydrophilic substance, may effectively substitute for glucose and enhance intestinal water and sodium absorption in an oral rehydration solution (ORS). This was evaluated using a low osmolality (230-240 mOsm/kg) ORS containing 75 mmol/L sodium and a combination of glucose:glycerol (in mmol/L) 75:0, 50:25; 37.5:37.5, 25:50, 10:65, or 0:75 during 3-hour long in vivo rat jejunal perfusions. Water, sodium, potassium, glucose and glycerol absorption, and unidirectional fluid movement (J(in), J(eff)) were determined. Sodium and net water absorptions were maximal at glucose:glycerol ratios between 37.5:37.5 and 10:65 mmol/L. In the absence of glucose (0:75), absorption of water and electrolytes was lower than at any other concentration. The greater net rehydration seemed to be due to a higher J(in) as glycerol was increased up to 65 mmol/L. Potassium absorption followed a similar pattern. With 50 mmol/L glycerol and 25 mmol/L glucose, there was a marked expansion of the lamina propria extracellular space and increased intercellular expansion between enterocytes. These results indicate that glycerol may be an effective partial substitute for glucose in ready-to-use ORS by producing an improved rate of water and electrolyte absorption.

Proabsorptive effects of modified tapioca starch as an additive of oral rehydration solutions

BACKGROUND

Partially hydrolyzed starches from staple cereals, obtained by heat or by enzymatic treatment, are often used in the formulation of homemade or extemporaneously used oral rehydration solutions used in developing countries. Conflicting or anecdotal results obtained thus far could be clarified with a standardized preparation tested under well-controlled laboratory conditions.

METHODS

A modified commercial tapioca starch was tested. Textra (National Starch and Chemical Co. Bridgewater, NJ, U.S.A.) added at 0, 5 or 10 g/l to an oral rehydration solution with 90 mM sodium and 111 mM glucose, in 30 rats malnourished by a protein-deficient diet for 3 weeks and in 26 well-fed control animals, using a one-pass jejunal perfusion.

RESULTS

In protein-deficient rats, Textra stimulated sodium absorption at 5 and 10 g/l (mean +/- SEM); 0 g/l Textra: 160 +/- 13 nmol/min x cm; 5 g/l Textra: 406 +/- 31 (p < 0.0001); and 10 g/l Textra 230 +/- 27 (p < 0.02). Potassium absorption was comparably increased. Textra also improved net water absorption and the water influx:efflux ratio. Glucose absorption was increased only at 10 g/l Textra. In control rats, Textra improved sodium and net water absorption at 5 g/l, but not at 10 g/l Textra; but the influx:efflux ratio and potassium absorption were unaltered.

CONCLUSIONS

These data, obtained in normal and protein-deficient rats, support the view that modified starch is a potentially useful, energy-rich additive for oral rehydration solution, which does not introduce an osmotic penalty.

Intraoral tumor of Chievitz in a child

Juxtaoral organs known as organs of Chievitz are intramuscular embryonic structures found close to the angle of the mandible near the insertion of the pterygomandibular raphae. They are considered of neuroepithelial origin with no known function. We describe the first tumor of the organ of Chievitz which presented intraorally in a child. Immunohistochemically, the Chievitz nests showed positive reaction for vimentin, cytokeratins, and epithelial membrane antigen and ultrastructurally demonstrated cytoplasmic processes and intermediate filament bundles. These observations, together with light microscopic features, suggest that the epithelial nests of the organ of Chievitz are meningothelial rather than neuroepithelial.

T-cell lymphoma associated with natural killer-like T-cell reaction

We report a case of T-cell lymphoma showing in the peripheral blood (PB) exclusively T-lymphocytes with suppresser T-cell preponderance and a high percentage of natural killer (NK) marker positive cells by flow cytometry. A T-cell receptor (TCR) gene analysis of the PB leukocytes demonstrated rearrangements of TCRalpha, TCRbeta, and TCRgamma genes. Therefore, the phenotype and genotype appeared to be consistent with an NK-like T-cell leukemia/lymphoma. However, when the PB lymphocytes were separated by size, it was found that 80% of NK marker positive cells were in the smaller cell population, while the neoplastic cells were in the large cell gate. A diagnosis of T-cell lymphoma with reactive NK-like T-cells was finally confirmed by demonstrating the presence of both large atypical lymphoid cells and large granular lymphocytes (LGL) on PB smears. Although immunoperoxidase stain of bone marrow and colon showed positive T-cell markers in the tumor cell population, cytoplasmic granules could not be identified in tissue sections and, thus, a distinction between T-cell lymphoma and NK-like T-cell lymphoma could not be made by light microscopy until NK markers were studied. CD57 was demonstrated immunohistochemically in small lymphocytes but not in the large tumor cells in the colon. Electron microscopy, however, demonstrated LGL reaction to the lymphoma cells in the colonic biopsy. NK-like T-cell lymphoma usually carries a poorer prognosis than peripheral T-cell lymphoma, thus the distinction of these neoplasms is important. This study emphasizes that T-cell lymphoma may cause an LGL reaction or proliferation. If the lymphoma cells were of the same size as LGL, flow cytometric studies may have misled the diagnosis to NK-like T-cell-lymphoma.

Contribution of advanced glycosylation to the amyloidogenicity of islet amyloid polypeptide

The formation of amyloid within the islets of Langerhans is associated with the development of type II diabetes mellitus and occurs by the aggregation and insolubilization of islet amyloid polypeptide (IAPP). Recent in vitro studies suggest that amyloid formation follows a nucleation-dependent polymerization mechanism, i.e. aggregation is initiated by pre-formed aggregates or nucleation seeds. Modification of the Alzheimer's disease amyloid peptide by advanced glycosylation end products (AGEs), which form spontaneously by the non-enzymatic addition of glucose to protein amino groups, has been shown to enhance peptide aggregation in vitro. To explore the possibility that AGEs contribute to islet amyloid formation, we prepared AGE-modified IAPP (AGE-IAPP) in vitro and studied its properties by biochemical and biophysical techniques. AGE modification induced the formation of high-molecular-mass IAPP aggregates and amyloid formation was demonstrated by Congo red green-gold birefringence and by the presence of a characteristic fibrillar structure by electron microscopy. AGE-IAPP also showed an increase in cytotoxicity toward the astroglioma cell line HTB14. When added to soluble IAPP, AGE-IAPP seeds accelerated IAPP aggregation and abolished the nucleation period required for the polymerization of unseeded IAPP. Circular dichroism spectropolarimetry indicated that AGE-IAPP seeds may act as a template to stabilize the beta-sheet conformation of IAPP, thereby promoting its aggregation. Our studies demonstrate that AGE modification of IAPP results in high-molecular mass, fibrillar amyloid structures that nucleate IAPP amyloid formation and suggest a model for intra-islet amyloid deposition that may occur by the progressive advanced glycosylation of IAPP in vivo.

Zinc-bis-histidinate preserves cardiac function in a porcine model of cardioplegic arrest

BACKGROUND

We examined the ability of zinc-bis-histidinate to preserve postarrest myocardial function when added to a standard crystalloid cardioplegic solution.

METHODS

Domestic pigs (35 to 50 kg) on left-sided cardiopulmonary bypass were subjected to 90 minutes of regional ischemia followed by 60 minutes of hypothermic cardioplegic arrest induced by antegrade infusion of 20 mL/kg cold St. Thomas' #2 cardioplegic solution with or without 100 mumol/L of zinc-bis-histidinate and maintained by infusion of 10 mL/kg of the same every 20 minutes. During reperfusion function was assessed at 1 and 3 hours over increasing preloads using the right-sided bypass method.

RESULTS

At roller pump flows up to 2,000 mL/min, stroke work index-end-diastolic pressure curves were significantly (p < 0.05) higher and shifted to the left in treated hearts. In a series of pigs, echocardiography was used to determine end-diastolic and end-systolic volumes. At roller pump flows up to 3,500 mL/min, end-systolic pressure-end-systolic volume curves were significantly higher and shifted to the left in treated hearts. Left ventricular ejection fraction, fractional shortening, stroke volume, and cardiac output were significantly (p < 0.05) higher in treated hearts. Electron microscopy revealed that mitochondria in tissue not at risk appeared more swollen in control hearts.

CONCLUSIONS

The results of this study support the conclusion that zinc-bis-histidinate is effective as a myocardial preservative when added to a crystalloid cardioplegic solution.

Cellulose derivatives and intestinal absorption of water and electrolytes: potential role in oral rehydration solutions

The physicochemical and structural characteristics of several types of carboxymethylcellulose (CMC) and of methylcellulose (MC) were examined in relation to their capacity to modify water and sodium absorption in oral rehydration solutions (ORS) at various concentrations, using a jejunal perfusion procedure in rats. Comparison of intrinsic low-viscosity CMC of various degrees of substitution (DS) revealed that net water absorption increased as the DS was augmented. A stimulatory effect on sodium absorption occurred only at a low (2.5 g/l) CMC concentration. With products of medium DS, stimulation of net water and sodium absorption was observed only with low-viscosity CMC at 2.5 g/l, but not at 5.0 g/l. In perfusions with CMC of medium and high DS there was a reduction of water and sodium absorption, ultimately resulting in net sodium secretion with 5.0 g/l high-DS CMC. MC perfused at 5.0 or 10.0 g/l reduced net water absorption and reversed sodium transport from absorptive to secretory status. These results show that while low-viscosity-grade, low-DS CMC in low concentrations may facilitate solute uptake and concurrent water absorption from ORS by the jejunum, high intrinsic viscosity and possible chemical interaction of solutes with the modified celluloses tend to block water uptake and produce fluid stasis and electrolyte secretion. Thus, the data suggest that only certain types of CMC may be proabsorptive when added to ORS, while high-viscosity and high-DS CMC or MC induce electrolyte malabsorption and eventual catharsis.

Metabolic and structural effects of insulin-like growth factor-I and high-protein diet on dystrophic hamster skeletal muscle

In muscular dystrophy (MD) there is an imbalance between muscle protein synthesis and protein degradation, which results in a net muscle catabolism, along with muscle wasting and weakness. Using a dystrophic hamster model (BIO 53.58), we examined the chronic (8 weeks) effects of two factors that may enhance muscle protein synthesis and inhibit protein degradation, namely, insulin-like growth factor-I (rhIGF-I) and high-protein diet (HPD). Protein synthesis was determined by measuring the incorporation of 14C phenylalanine into perfused leg muscle, while protein degradation was calculated from the release of tyrosine from the same perfused muscle. Urinary 3-methylhistidine excretion was used as an indicator of myofibrillar degradation. Treatment of dystrophic hamsters with rhIGF-I, HPD, or a combination of the two for 8 weeks resulted in significant decreases in total and myofibrillar degradation when compared with untreated dystrophic animals (P < 0.05) but had minimal effects on protein synthesis. Significant morphologic improvements (P < 0.05), including a normalization and greater uniformity of muscle fibers, were also seen in rhIGF-I- and rhIGF-I + HPD-treated animals. rhIGF-I and HPD were effective in reducing the excessive proteolysis seen in dystrophic muscle, and this reduced proteolysis resulted in improvement of muscle morphology.