Immunohistochemical localization of S100A1 and S100A6 in postnatally developing salivary glands of rats

S100 proteins are calcium-binding proteins of the EF-hand superfamily and are involved in the regulation of a number of cellular processes. The present study deals with the immunohistochemical expression of S100A1 and S10100A6 in the rat submandibular and sublingual glands during postnatal development from day 0 to 12 weeks. Expression of S100A1 was particularly concentrated in pillar and transition cells in the granular convoluted tubule (GCT) and in striated duct cells of the submandibular gland age 4 weeks to maturity. None or only weak staining for S100A1 was observed in the duct segment at 0-5 days. On the contrary, immunostaining of S100A6 was present in proacinar cells in undifferentiated submandibular gland at age 3 days to 2 weeks. S100A6 immunoreactivity in rat submandibular gland coexisted with chromogranin reactivity. It is possible that S100A6 regulates secretion of chromogranin in proacinar cells. Secretion of growth factors and biologically active peptides in the GCT are regulated by calcium signals, and S100A1 may be involved in the secretory mechanism of granular cells. S100A1 and S100A6 are potentially of great importance in secretory functions of granular cells and proacinar cells, as well as in rat salivary glands.     

Correction of Fanconi anemia type C phenotypic abnormalities using a clinically suitable retroviral vector infection protocol

Fanconi anemia (FA) is a complex autosomal recessive disease with hematologic manifestations characterized by a progressive hypoplastic anemia, hypersensitivity to clastogenic agents, and an increased incidence of acute myelogenous leukemia. The cDNA that corrects one of four FA complementation subtypes, named Fanconi anemia Type C (FAC) has recently been identified. We constructed a a simplified recombinant retrovirus (vMFGFAC) encoding only the FAC cDNA, and tested its ability to correct the FAC defect in a lymphocytic cell line and primary mobilized blood progenitor cells. In addition, the gene transfer efficiency using a clinically applicable gene transfer protocol into normal primitive hematopoietic progenitor cells, high proliferating potential colony forming cells (HPP-CFC), derived from CD34+ purified cord blood cells was examined. The gene transfer efficiency was significantly enhanced when cells were transduced with supernatant while adherent to a 30/35 KD fragment of fibronectin, FN30/35, and was similar to efficiency obtained by coculture with retrovirus packaging cells. Transduction of an FAC deficient lymphoid cell line with vMFGFAC supernatant resulted in an enhanced cell viability, and G-CSF mobilized peripheral blood cells from an FAC-deficient patient transduced with the vMFGFAC virus demonstrated enhanced progenitor cell colony formation. These data indicate that the vMFGFAC virus allows functional complementation of FAC in lymphoblasts and primary hematopoietic progenitors, and that primitive cord blood hematopoietic stem/progenitor cells can be transduced at an efficiency comparable to protocols using cocultivation if adherent to FN 30/35 fragment.     

Adenovirus-mediated regulable target gene expression in vivo

To regulate expression of a transferred gene in response to an exogenous compound, we have combined a high capacity adenoviral vector devoid of all viral coding sequences with a regulatory system that can be used to express a target gene in vivo in a selected site and at a desired time. This system uses a chimeric transactivator, GLp65, which consists of a mutated progesterone receptor-ligand binding domain fused to the GAL4 DNA binding domain and part of the activation domain of the human p65 protein, a component of the NF-kappaB complex. In the presence of the antiprogestin mifepristone, this chimeric regulator binds to a target gene containing the 17-mer GAL4 binding site, resulting in an efficient ligand-inducible transactivation of the target gene. We inserted the regulator GLp65 and a regulable human growth hormone target gene containing the 17-mer GAL4 binding site into the same adenoviral vector. To obtain tissue-specific expression of the target gene, we coupled the regulator to a liver-specific promoter. Infection of HepG2 cells and experimental mice with the adenovirus resulted in consistently high induction levels of human growth hormone in the presence of mifepristone whereas the transgene expression was undetectable in the absence of the ligand. Taken together, our regulable adenoviral vector represents an important tool for transgene regulation that can be used for potentially diverse applications, ranging from tissue-specific gene expression in transgenic animals to human gene therapy.     

Markers for neuronal degeneration in organotypic slice cultures

This protocol describes ways of monitoring spontaneous or induced neuronal degeneration in organotypic brain slice cultures. Hippocampal cultures (4-week-old) are grown in normal serum-free control medium, or exposed to the neurotoxin trimethyltin (TMT) (0.5-100 microM) for 24 h or the excitotoxic glutamate agonist kainic acid (KA) (5-25 microM) for 48 h followed by 24 h or 48 h, respectively, in normal medium. Corticostriatal slice cultures (also 4-week-old) are exposed to KA (6-24 microM) for 48 h and normal medium for control. The resulting neurodegeneration is estimated by (a) propidium iodide (PI) uptake, (b) lactate dehydrogenase (LDH) efflux to the culture medium, (c) ordinary Nissl cell staining, (d) staining by the neurodegenerative marker Fluoro-Jade (FJ), (e) neuronal microtubule degeneration by immunohistochemical staining for microtubule-associated protein 2 (MAP2), and (f) Timm sulphide silver staining for heavy metal alterations. Both hippocampal and corticostriatal slice cultures show a dose- and time-dependent increase in PI uptake and LDH efflux after exposure to TMT and KA. The mean PI uptake and the LDH efflux into the medium correlate well for both types of cultures. Both TMT and KA exposed hippocampal cultures display in vivo patterns of differential neuronal vulnerability as evidenced by PI uptake, FJ staining and MAP2 immunostaining. Corticostriatal slice cultures exposed to a high dose of KA display extensive striatal and cortical degeneration in FJ staining as suggested by a high PI uptake. A change in Timm sulphide silver staining in deep central parts of some control cultures, corresponds to areas with loss of cells in cell staining, loss of MAP2 staining, PI uptake, and FJ staining. We conclude that organotypic brain slice cultures, in combination with appropriate markers in standardized protocols, represent feasible means for studies of excitotoxic and neurotoxic compounds.     

Identification of fur, aconitase, and other proteins expressed by Mycobacterium tuberculosis under conditions of low and high concentrations of iron by combined two-dimensional gel electrophoresis and mass spectrometry

Iron plays a critical role in the pathophysiology of Mycobacterium tuberculosis. To gain a better understanding of iron regulation by this organism, we have used two-dimensional (2-D) gel electrophoresis, mass spectrometry, and database searching to study protein expression in M. tuberculosis under conditions of high and low iron concentration. Proteins in cellular extracts from M. tuberculosis Erdman strain grown under low-iron (1 microM) and high-iron (70 microM) conditions were separated by 2-D polyacrylamide gel electrophoresis, which allowed high-resolution separation of several hundred proteins, as visualized by Coomassie staining. The expression of at least 15 proteins was induced, and the expression of at least 12 proteins was decreased under low-iron conditions. In-gel trypsin digestion was performed on these differentially expressed proteins, and the digestion mixtures were analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry to determine the molecular masses of the resulting tryptic peptides. Partial sequence data on some of the peptides were obtained by using after source decay and/or collision-induced dissociation. The fragmentation data were used to search computerized peptide mass and protein sequence databases for known proteins. Ten iron-regulated proteins were identified, including Fur and aconitase proteins, both of which are known to be regulated by iron in other bacterial systems. Our study shows that, where large protein sequence databases are available from genomic studies, the combined use of 2-D gel electrophoresis, mass spectrometry, and database searching to analyze proteins expressed under defined environmental conditions is a powerful tool for identifying expressed proteins and their physiologic relevance.     

Processing Dutch sentence structures

This paper summarizes existing research on syntactic processing of Dutch sentences by adult native speakers of the language, with an eye to the implications of this work for a general theory of the human sentence processing mechanism (HSPM). The principles underlying the assignment of phrase structure and the binding of traces seem to be the same as those proposed for languages like English or Italian. For example, no delays of analysis exist in parsing the constituents of a phrase even if the phrase is head-final. Also, the obligatory topicalization of a constituent which is required in the highest clause of a Dutch sentence does not appear to result in trace postulation principles distinct from those operative in languages where topicalization is optional. The studies reviewed also address questions concerning the complexity of the dependency between a moved constituent and its trace as measured by the length of a path vs. the length of a chain, the processing of subject gaps following an overt complementizer, the complexity of interpreting an adjunct moved from an obligatory position, and the processing of discontinuous words. Though the studies do not pose a problem for pre-existing views of the HSPM, they do highlight certain areas of parsing theory which remain seriously underdeveloped. Foremost, perhaps, is the specification of the principles governing the architecture of the processing system, which ultimately should explain how the organization of the HSPM and its subcomponents results from acquiring the grammar of any particular language.     

Promotion criteria for clinician-educators in the United States and Canada. A survey of promotion committee chairpersons

CONTEXT: Clinician-educators have concerns about their ability to be promoted and the criteria used by medical school promotion committees. OBJECTIVE: To discover the criteria and methods that medical school promotion committees use to make decisions about the promotion of clinician-educators. METHODS: In June 1996 we mailed a questionnaire to chairpersons of all medical school promotion committees in the United States and Canada. RESULTS: Of 142 schools surveyed, 115 (81%) responded; 45% of respondents had a clinician-educator promotion track. On a scale from 1 (minimally important) to 7 (extremely important), the mean importance ratings of aspects of clinician-educators' performance were the following: teaching skills (6.3), clinical skills (5.8), mentoring (5.7), academic administration (5.3), developing educational programs (5.3), nonresearch scholarship (5.1), clinical research (4.8), service coordination (4.7), and education research (4.5). Methods to evaluate each aspect of performance were rated by respondents for importance and frequency of use. The 4 most important methods for evaluating teaching were awards, peer evaluation, learner evaluation, and teaching portfolio; 70% or more of schools used these frequently or always. The 4 most important methods of evaluating clinical skills were peer evaluation, awards, trainee evaluation, and objective measures, which were used frequently or always by 78%, 65%, 58%, and 29% of schools, respectively. Clinician-educators were expected to have fewer peer-reviewed publications to be promoted than investigators (5.7 vs 10.6, P<.001). Schools with separate clinician-educator tracks differed little in survey responses from schools without such tracks. CONCLUSION: Most, but not all, promotion committees now assign high importance to the special contributions of clinician-educators and use a variety of methods to assess these, regardless of whether they have a separate clinician-educator promotion track.     

Cholelithiasis: current treatment options

Up to 20 percent of the U.S. population may have cholelithiasis, but most of these persons remain asymptomatic. If symptoms or complications develop, several potential management strategies may be used. Open and laparoscopic cholecystectomy are definitive surgical treatments. Nondefinitive methods, such as lithotripsy, indirect dissolution, direct dissolution, sphincterotomy and drainage, have lower success rates but may be indicated in specific cases. Although laparoscopic cholecystectomy is a relatively new technique, its morbidity and mortality rates are comparable to those of open cholecystectomy, and it tends to be less expensive than other surgical methods. For these reasons, laparoscopic cholecystectomy is rapidly becoming the surgical method of choice in the treatment of cholelithiasis.