No abstract

Microvessels in the cheek pouch of the hamster were investigated to determine their structural, reactivity, and permeability characteristics after the induction of diabetes. To induce diabetes, hamsters were injected with streptozotocin (50 mg/kg body wt./day, i.p., for 3 days). Vehicle-injected, age-matched hamsters were the controls. Diabetic hamsters were characterized by elevated serum glucose (greater than 300 mg/dl) and triglycerides and decreased serum insulin (50%). Microvascular studies were completed on cheek pouch microvessels suffused with Ringer's solution (37 degrees C, pH 7.4) bubbled with 95% N2-5% CO2. Vascular dimensions and reactivity of selected arterioles and venules to microapplications of norepinephrine were determined with a video micrometer using intravital microscopy. Restrictiveness of the microvascular membranes to fluorescein-labeled dextran fractions (mol wt: 150,000; 40,000; 20,000 daltons) was measured by determining the number of leaky sites. Stimulation of membrane permeability by histamine was investigated. There were no major alterations in arteriolar lumen and wall diameters, whereas venular lumen diameters were increased in hamsters diabetic for two months. Likewise, arteriolar responses to norepinephrine were not altered by diabetes; however, venular responses were decreased at two months. The restrictiveness of the vascular membrane to various dextran fractions was dramatically decreased in the diabetic animals at two months. Histamine did not alter microvascular leakage in the diabetic as it did in the normal hamsters. These studies indicate that microvascular alterations, venular dilation, and increased permeability to large molecules occur in the diabetic hamster within two months after the induction of diabetes.

Postresection villus hyperplasia is a major compensatory mechanism in the short-bowel patient. Substances capable of augmenting postresection mucosal hyperplasia could have therapeutic implications. Human growth hormone (hGH) and human growth hormone releasing factor (hGHRF) stimulate growth of the gastrointestinal tract; however, the diabetogenic actions of growth hormone limit its usefulness in clinical practice. Plerocercoid larvae of the tapeworm Spirometra mansonoides produce an analog of hGH void of diabetogenic side effects. We assessed effects of plerocercoid growth factor (PGF) on mucosal adaptation following 70% proximal jejunoileal resection in young rats. Mucosal weight, DNA, protein, and total sucrase activity per centimeter of bowel were increased in resected PGF-treated animals compared to resected controls. We conclude PGF augments intrinsic postresection mucosal hyperplasia following extensive intestinal resection.

The only observed morphological difference between Spirometra erinacei and S. mansonoides is the uterine shape of the mature proglottid. Two species of worms are thought to be evolutionarily closely related. Biomolecular comparison of the two worms by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis was conducted to observe the genetic distance. The 28s rDNA, mitochondrial cytochrome c oxidase subunit I (mCOI), and ribosomal internal transcribed spacer 1 (ITS1) fragments were obtained from the worms by PCR. The PCR products were cleaved by 5 four-base pair restriction enzyme combinations (Msp I, Hae III, Alu I, Cfo I, Rsa I), electrophoresed and analyzed with PAUP 3.1.1. The fragment patterns of 28S rDNA and ITS1 demonstrated that two worms were in identical systematic tree with bootstrap number 94 and 100, respectively. As for mCOI, bootstrap number was 74 in a different tree. Above results are indicative of recent common ancestry between S. erinacei and S. mansonoides.

Plerocercoids of the tapeworm, Spirometra mansonoides, produce a potent growth stimulating substance which is active in several species of mammals. While most of the actions of the plerocercoid growth factor (PGF) are similar to those of growth hormone (GH), lipid metabolism is one area where their actions are not alike. This report demonstrates that plerocercoid infection not only stimulates growth of intact male hamsters but is lipogenic as well. The lipogenic effects of plerocercoid infection were demonstrated by increases in epididymal fat pad weights, serum triglycerides, cholesterol, and total lipid. The livers of the plerocercoid-infected hamsters also had more cholesterol and more lipid phosphorus than controls. Incorporation studies using [2-14C]acetate showed that infected hamsters incorporated significantly higher levels of the radionuclide in their livers and serum after 1 hr than the controls. The lipogenic effect of plerocercoid infection is distinctly unlike the reported lipolytic action of GH and the lack of any stimulation of [2-14C]acetate incorporation into the epididymal fat pads is unlike the reported acute actions of insulin as well.

No abstract

The effects of bovine growth hormone and the growth factor produced by plerocercoid larvae of the tapeworm, Spirometra mansonoides, on body growth and lipid composition in diabetic-hypophysectomized rats were compared. The diabetic-hypophysectomized control rats gradually lost weight throughout the experiment but both growth hormone and plerocercoids stimulated marked weight gains. Growth hormone treatment resulted in a loss of depot fat from the epididymal fat pads and caused a reduction of liver and serum cholesterol concentrations but had no effect on triglyceride concentrations of either liver or serum. However, plerocercoid infection resulted in increased weights of the epididymal fat pads and increased liver and serum triglyceride concentrations. Serum cholesterol was slightly increased but liver cholesterol was decreased in the plerocercoid-infected rats. Therefore, in the absence of pituitary hormones and insulin, these growth factors had similar effects on body growth but distinctly different effects on lipid metabolism.

A factor produced by the plerocercoid stage of S. mansonoides mimics some, but not all, of the actions reported for hGH. The biological actions of plerocercoid growth factor (PGF) suggest structural similarity to human GH (hGH). Plerocercoid membranes were solubilized, and PGF was purified more than 1000-fold by hGH receptor affinity chromatography. The ability of purified PGF to displace [125I]hGH from monoclonal antibodies specific for four distinct nonoverlapping antigenic determinants of hGH and from an anti-hGH polyclonal antibody was tested in liquid phase RIA. All of the hGH antibodies cross-reacted with PGF, with potencies ranging from more than 60% to less than 1% that of the hGH standard. Of the four major epitopes of hGH defined by the monoclonal antibodies used in this study, only one is not represented to a significant extent in PGF. The epitope of hGH that is only marginally present in PGF is highly conformationally dependent, and a minor difference in the structure of PGF (compared to hGH) could result in a significant conformational change. The dramatic cross-reactivity between anti-hGH antibodies and PGF suggests that the similarities in biological activities between these two substances are based in significant molecular homology.