Muscle and liver glycogen,protein, and triglyceride in the rat

Summary We have previously found that during exercise net muscle glycogen breakdown is impaired in adrenodemedullated rats, as compared with controls. The present study was carried out to elucidate whether, in rats with deficiencies of the sympatho-adrenal system, diminished exercise-induced glycogenolysis in skeletal muscle was accompanied by increased breakdown of triglyceride and/or protein. Thus, the effect of exhausting swimming and of running on concentrations of glycogen, protein, and triglyceride in skeletal muscle and liver were studied in rats with and without deficiencies of the sympatho-adrenal system. In control rats, both swimming and running decreased the concentration of glycogen in fast-twitch red and slow-twitch red muscle whereas concentrations of protein and triglyceride did not decrease. In the liver, swimming depleted glycogen stores but protein and triglyceride concentrations did not decrease. In exercising rats, muscle glycogen breakdown was impaired by adrenodemedullation and restored by infusion of epinephrine. However, impaired glycogen breakdown during exercise was not accompanied by a significant net breakdown of protein or triglyceride. Surgical sympathectomy of the muscles did not influence muscle substrate concentrations. The results indicate that when glycogenolysis in exercising muscle is impeded by adrenodemedullation no compensatory increase in breakdown of triglyceride and protein in muscle or liver takes place. Thus, indirect evidence suggests that, in exercising adrenodemedullated rats, fatty acids from adipose tissue were burnt instead of muscle glycogen.     

Mutations in the retinal guanylate cyclase (RETGC-1) gene in dominant cone-rod dystrophy

The dominant cone-rod dystrophy gene CORD6 has previously been mapped to within an 8 cM interval on chromosome 17p12-p13. The retinal- specific guanylate cyclase gene (RETGC-1), which maps to within this genetic interval and previously was implicated in Leber's congenital amaurosis, was screened for mutations within this family and in a panel of small families and individuals with various cone and cone- rod dystrophy phenotypes. A missense mutation (E837D) was identified in affected members of the CORD6 family, as well as a second missense mutation (R838C) in three other families with dominant cone-rod dystrophy. RETGC-1 is only the fourth gene to be implicated in cone-rod dystrophy and this is the first report of dominant mutations in this gene.      

Thymic stromal cell specialization and the T-cell receptor repertoire

Ten years ago, we proposed a model for thymus function in which thymic epithelial cells are primarily responsible for imprinting major histocompatibility complex (MHC)-restricted specificity, and bone marrow-derived macrophages or dendritic cells are responsible for the induction of self-tolerance. Since then, transgenic and knockout models have allowed for a dissection of thymic stromal components in vivo, leading to a new understanding of their specialized functions. We have determined that with regard to class II-restricted CD4 T-cell development, two distinct subsets of thymic epithelium help shape the repertoire: Cortical epithelium appears solely responsible for positive selection, whereas a fucose-bearing subset of medullary epithelium is specialized for negative selection. This absolute separation of positive and negative selection into two distinct spatial and temporal compartments leads to a much simpler view of the process of repertoire selection. Finally, a novel view of the function of the thymic medulla is discussed.     

Hot spot mutations in morphological transforming region II (ORF 79) of cytomegalovirus strains causing disease from bone marrow transplant recipients

Summary.  Nested polymerase chain reaction (PCR) amplifying the morphological transforming region II (mtrII) of cytomegalovirus (CMV) has been shown to be useful in the detection of CMV DNA in bone marrow transplant (BMT) recipients. However, there has never been any report on mutation hot spots and subtypes of this open reading frame. Using primers derived from sequences upstream and downstream of mtrII (ORF 79), CMV DNA from peripheral blood leukocytes (PBL) and conventional CMV culture of 16 BMT recipients were amplified by PCR, cloned into pUC118, and sequenced. The amino acid sequences were predicted using the standard triplet code. The DNA sequences obtained from direct amplification of CMV in PBL obtained from the 16 patients were 100% identical to the corresponding ones obtained by amplification of CMV DNA extracted from conventional CMV culture. Within mtrII (ORF 79), hot spot single base mutations were observed at positions +40 (G→A), +123 (A→G), +213 (T→C), and +219 (T→C). However, because of third base degeneracy, only amino acid 14 was changed from valine to isoleucine in the predicted protein of 13 patients. This corresponded to the hot spot mutation at position +40 (GTC→ATC), while the rest were silent mutations. An insertion of 3 bases (ACG) was observed in the CMV DNA of 10 patients at positions +91 to +93, leading to a threonine insertion at amino acid 31 in these patients. For patient no. 147 there was a 65 bp deletion in the CMV DNA amplified later in the course of BMT as compared with that early in the course. This gave rise to a frame shift mutation and a change of more than 70% in the predicted amino acid sequence of the protein. Accepted October 14, 1998 Received May 20, 1998     

Lack of influence of glucagon on glucose homeostasis after prolonged exercise in rats

Summary The significance of glucagon for post-exercise glucose homeostasis has been studied in rats fasted overnight. Immediately after exhaustive swimming either rabbit-antiglucagon serum or normal rabbit serum was injected by cardiac puncture. Cardiac blood and samples of liver and muscle tissue were collected before exercise and repeatedly during a 120 min recovery period after exercise. During the post-exercise period plasma glucagon concentrations decreased but remained above pre-exercise values in rats treated with normal serum, while rats treated with antiglucagon serum had excess antibody in plasma throughout. Nevertheless, all other parameters measured showed similar changes in the two groups. Thus after exercise the grossly diminished hepatic glycogen concentrations remained constant, while the decreased blood glucose concentrations were partially restored. Simultaneously concentrations in blood and serum of the main gluconeogenic substrates, lactate, pyruvate, alanine and glycerol declined markedly. During the post-exercise period NEFA concentrations in serum and plasma insulin concentrations remained increased and decreased, respectively, while plasma catecholamines did not differ from basal values. Muscle glycogen concentrations decreased slightly. These findings suggest that in the recovery period after exhaustive exercise the increased glucagon concentrations in plasma do not influence gluconeogenesis.     

Catecholamines and pancreatic hormones during autonomic blockade in exercising man

The importance of autonomic nervous activity for the pancreatic hormonal response to exercise in man was studied. 7 men ran at 58% of V(O2)max (determined without administration of drugs) to exhaustion during alpha-adrenergic blockade with phentolamine (P), during parasympathetic blockade with atropine (A), or without drugs (C). At rest phentolamine increased the plasma concentrations of both insulin and norepinephrine. During exercise norepinephrine concentrations increased and were in P experiments 3 times the concentrations in C experiments. Insulin always declined during exercise but in P experiments never decreased below basal levels. At identical times neither glucagon nor glucose differed significantly in the different expts. Thus during exercise alpha-adrenergic blockade increased insulin concentrations but did not diminish the glucagon response. Nor was this response increased when beta-receptor stimulation in P experiments was intensified by the particularly high catecholamine concentrations. The concentrations of FFA, glycerol and lactate were highest in P experiments and identical in A and C experiments. These findings indicate that during prolonged moderate exercise in man insulin secretion is depressed by stimulation of alpha-adrenergic receptors whereas glucagon secretion is not influenced by adrenergic receptors. Stimulation of beta-adrenergic receptors enhances lipolysis but neither lipolysis nor pancreatic hormonal secretion is influenced by cholinergic activity during exercise.     

Increased expression of osteopontin gene in atypical teratoid/rhabdoid tumor of the central nervous system.

The atypical teratoid/rhabdoid tumor, primary to the central nervous system, is a highly malignant and aggressive neoplasm of infancy and childhood. Although having distinct biological features and clinical outcomes, it is frequently misdiagnosed as primitive neuroectodermal tumor/medulloblastoma. To further distinguish the underlying pathogenesis and to identify biological markers for clinical use, an atypical teratoid/rhabdoid tumor-derived cell line was established and its gene expression pattern analyzed in comparison to the human astrocyte SVG12 cell line and the human DAOY medulloblastoma cell line using a complementary DNA microarray method. The osteopontin gene was found specifically upregulated in atypical teratoid/rhabdoid tumor cells. This specificity was confirmed by immunohistochemistry in pathological sections of tissues from atypical teratoid/rhabdoid tumor patients. Even though the role of osteopontin in the cytopathogenesis of atypical teratoid/rhabdoid tumor still needs to be determined, our data support that overexpressed osteopontin is a potential diagnostic marker for atypical teratoid/rhabdoid tumor.