Effects of double ligation of Stensen's duct on the rabbit parotid gland

Salivary gland duct ligation is an alternative to gland excision for treating sialorrhea or reducing salivary gland size prior to tumor excision. Duct ligation also is used as an approach to study salivary gland aging, regeneration, radiotherapy, sialolithiasis and sialadenitis. Reports conflict about the contribution of each salivary cell population to gland size reduction after ductal ligation. Certain cell populations, especially acini, reportedly undergo atrophy, apoptosis and proliferation during reduction of gland size. Acini also have been reported to de-differentiate into ducts. These contradictory results have been attributed to different animal or salivary gland models, or to methods of ligation. We report here a bilateral double ligature technique for rabbit parotid glands with histologic observations at 1, 7, 14, 30, 60 days after ligation. A large battery of special stains and immunohistochemical procedures was employed to define the cell populations. Four stages with overlapping features were observed that led to progressive shutdown of gland activities: 1) marked atrophy of the acinar cells occurred by 14 days, 2) response to and removal of the secretory material trapped in the acinar and ductal lumens mainly between 30 and 60 days, 3) reduction in the number of parenchymal (mostly acinar) cells by apoptosis that occurred mainly between 14–30 days, and 4) maintenance of steady-state at 60 days with a low rate of fluid, protein, and glycoprotein secretion, which greatly decreased the number of leukocytes engaged in the removal of the luminal contents. The main post- ligation characteristics were dilation of ductal and acinar lumens, massive transient infiltration of mostly heterophils (rabbit polymorphonuclear leukocytes), acinar atrophy, and apoptosis of both acinar and ductal cells. Proliferation was uncommon except in the larger ducts. By 30 days, the distribution of myoepithelial cells had spread from exclusively investing the intercalated ducts pre-ligation to surrounding a majority of the residual duct-like structures, many of which clearly were atrophic acini. Thus, both atrophy and apoptosis made major contributions to the post-ligation reduction in gland size. Structures also occurred with both ductal and acinar markers that suggested acini differentiating into ducts. Overall, the reaction to duct ligation proceeded at a considerably slower pace in the rabbit parotid glands than has been reported for the salivary glands of the rat.     

Monogeneans on native and introduced freshwater fishes from Cuba with the description of a new species of Salsuginus Beverley-Burton, 1984 from Limia vittata (Poeciliidae)

During a parasitological survey carried out between March and September 2003 in Cuba, the following monogeneans were found on the gills of freshwater fishes: Salsuginus cubensis n. sp. on the Cuban molly Limia vittata Guichenot (Poeciliidae); Cichlidogyrus sclerosus Paperna & Thurston, 1969 and C. tilapiae Paperna, 1960 on the African cichlid Tilapia rendalli Boulenger (Cichlidae); Haplocleidus dispar Mueller, 1936 and Pterocleidus acer Mueller, 1936 (all Dactylogyridae) on the sunfish Lepomis macrochirus Rafinesque (Centrarchidae) (new geographical records); and Gyrodactylus sp. (Gyrodactylidae) on the biajaca Nandopsis tetracanthus Valenciennes (Cichlidae) (new host and geographical record). Salsuginus cubensis differs from all other species of the genus in the size and morphology of the copulatory complex. The occurrence of C. sclerosus, C. tilapiae, H. dispar and P. acer in their respective hosts is due to the introduction of these hosts to Cuba. A review of the species composition of the Monogenea in native and introduced freshwater fish from Cuba is presented and the zoogeographical distribution of the species found is briefly discussed.     

New species of Rhabdosynochus Mizelle and Blatz 1941 (Monogenoidea: Diplectanidae) from the gills of centropomid fishes (Teleostei) off the Pacific Coast of Mexico

In the course of the investigations into the fish parasites in the Tres Palos Lagoon in the State of Guerrero off the Pacific coast of Mexico, the following diplectanid species (Monogenoidea) from the gills of centropomids were found: Rhabdosynochus alterinstitus n. sp. from Centropomus nigrescens; Rhabdosynochus lituparvus n. sp., Rhabdosynochus volucris n. sp., and Rhabdosynochus siliquaus n. sp. from Centropomus robalito (Centropomidae). The apparent synapomorphic character supporting a sister relationship of these diplectanids is a single, sheathlike accessory piece comprising 3 distal branches of the male copulatory organ. The origin of the present diplectanid on centropomids is discussed, and it is suggested that this may be the result of allopatric speciation as a result of the uplift of the Panamanian Isthmus, thereby separating the Pacific and Atlantic Oceans during Pleistocene (3-5 million yr ago).     

Walteriella n. g. (Monogenoidea: Dactylogyridae) from the gills of pimelodid catfishes (Siluriformes: Pimelodidae) from the Peruvian Amazonia based on morphological and molecular data

Systematic Parasitology - On the basis of morphological and molecular data, Walteriella n. g. is proposed to accommodate the dactylogyrid parasites Walteriella conica n. sp. (type-species) from the...     

New and previously described species of Urocleidoides (Monogenoidea: Dactylogyridae) infecting the gills and nasal cavities of Hoplias malabaricus (Characiformes: Erythrinidae) from Brazil

During an investigation of the biodiversity and structure of parasite communities among native populations of the erythrinid fish Hoplias malabaricus (Characiformes) from 7 rivers in Brazil, the following monogenoidean (Dactylogyridae) species were found: Urocleidoides malabaricusi n. sp., Urocleidoides naris n. sp., Urocleidoides cuiabai n. sp., Urocleidoides brasiliensis n. sp., and Urocleidoides eremitus Kritsky, Thatcher, and Boeger, 1986. Specimens considered as a new genus of Dactylogyridae were also found. The new species are mainly distinguished from the other 14 species of Urocleidoides in the general morphology of their copulatory and anchors/bar complexes. These new species and the new dactylogyrid genus are described, as well as supplemental observations and new illustrations of U. eremitus are provided. The present findings expand the known geographical distribution of species of Urocleidoides to southeastern and midwestern Brazil. A high speciation of this genus in the tropics is hypothesized, and it is briefly discussed.     

Sequence of a cDNA for mouse thymidylate synthase reveals striking similarity with the prokaryotic enzyme

We report the nucleotide sequence of a cloned cDNA, pMTS-3, that contains a 1-kb insert corresponding to mouse thymidylate synthase (E.C. 2.1.1.45). The open reading frame of 921 nucleotides from the first AUG to the termination codon specifies a protein with a molecular mass of 34,962 daltons. The predicted amino acid sequence is 90% identical with that of the human enzyme. The mouse sequence also has an extremely high degree of similarity (as much as 55% identity) with prokaryotic thymidylate synthase sequences, indicating that thymidylate synthase is among the most highly conserved proteins studied to date. The similarity is especially pronounced (as much as 80% identity) in the 44-amino-acid region encompassing the binding site for deoxyuridylic acid. The cDNA sequence also suggests that mouse thymidylate synthase mRNA lacks a 3' untranslated region, since the termination codon, UAA, is followed immediately by a poly(A) segment.      

Factors that drive the increasing use of FFPE tissue in basic and translational cancer research

The decision to use 10% neutral buffered formalin fixed, paraffin embedded (FFPE) archival pathology material may be dictated by the cancer research question or analytical technique, or may be governed by national ethical, legal and social implications (ELSI), biobank, and sample availability and access policy. Biobanked samples of common tumors are likely to be available, but not all samples will be annotated with treatment and outcomes data and this may limit their application. Tumors that are rare or very small exist mostly in FFPE pathology archives. Pathology departments worldwide contain millions of FFPE archival samples, but there are challenges to availability. Pathology departments lack resources for retrieving materials for research or for having pathologists select precise areas in paraffin blocks, a critical quality control step. When samples must be sourced from several pathology departments, different fixation and tissue processing approaches create variability in quality. Researchers must decide what sample quality and quality tolerance fit their specific purpose and whether sample enrichment is required. Recent publications report variable success with techniques modified to examine all common species of molecular targets in FFPE samples. Rigorous quality management may be particularly important in sample preparation for next generation sequencing and for optimizing the quality of extracted proteins for proteomics studies. Unpredictable failures, including unpublished ones, likely are related to pre-analytical factors, unstable molecular targets, biological and clinical sampling factors associated with specific tissue types or suboptimal quality management of pathology archives. Reproducible results depend on adherence to pre-analytical phase standards for molecular in vitro diagnostic analyses for DNA, RNA and in particular, extracted proteins. With continuing adaptations of techniques for application to FFPE, the potential to acquire much larger numbers of FFPE samples and the greater convenience of using FFPE in assays for precision medicine, the choice of material in the future will become increasingly biased toward FFPE samples from pathology archives. Recognition that FFPE samples may harbor greater variation in quality than frozen samples for several reasons, including variations in fixation and tissue processing, requires that FFPE results be validated provided a cohort of frozen tissue samples is available.     

Inhibition of a nutrient-dependent pinocytosis in dictyostelium discoideum by the amino acid analogue hadacidin

In the present study we examine the effects of the drug hadacidin (N-formyl-N- hydroxyglycine) on pinocytosis in the eukaryotic microorganism dictyostelium discoideum. At concentrations of up to approximately 8 mg/ml, hadacidin inhibited the rate of pinocytosis of fluorescein isothiocyanate (FITC) dextran in cells in growth medium in a concentration-dependent manner but had no effect on cells in starvation medium. Because hadacidin also inhibits cellular proliferation at this concentration, the relationship between growth rate and pinocytosis was studied further using another drug, cerulenin, to produce growth-arrest. These experiments showed no changes in the rate pinocytosis even after complete cessation of cellular proliferation. Other studies showed that the transfer of cells from growth to starvation medium reduced the rate of pinocytosis by approximately 50 percent. A reduction of similar magnitude occurred if cells were transferred from growth to starvation medium containing hadacidin. Also, no additional reduction in pinocytosis occurred when cells that had been treated with hadacidin were transferred to starvation medium containing hadacidin. These cells were able to take up [(14)C]hadacidin in the starvation medium. In contrast to the results with hadacidin-treated cells, cells in a cerulenin-induced state of growth-arrest when transferred to starvation medium exhibited the same 50 percent reduction in pinocytosis observed in cells not previously exposed to either drug. Cells treated with azide, in either growth or starvation medium, exhibited an immediate inhibition of all pinocytotic activity. After the transfer of log-phase cells to starvation medium supplemented with glucose, the reduction in rate was only approximately 10-15 percent. In contrast, a 50 percent reduction was observed after supplementation of starvation medium with sucrose, KCl, or concanavalin A. Maintaining the cells in growth medium containing hadacidin for as long as 16 h had no effect on the rate at which cells aggregated. These results are consistent with the conclusion that D. discoideum exhibits two types of pinocytotic activity: one that is nutrient dependent and the other independent of nutrients. This latter activity persists in starvation medium and is unaffected by hadacidin, whereas the nutrient-dependent activity is present in growth medium and is inhibited by hadacidin.     

Nonrandom location of IS1 elements in the genomes of natural isolates of Escherichia coli

We have studied the spatial distribution of IS1 elements in the genomes of natural isolates comprising the ECOR reference collection of Escherichia coli. We find evidence for nonrandomness at three levels. Many pairs of IS1 elements are in much closer proximity (< 10 kb) than can be accounted for by chance. IS1 elements in close proximity were identified by long-range PCR amplification of the genomic sequence between them. Each amplified region was sequenced and its map location determined by database screening of DNA hybridization. Among the ECOR strains with at least two IS1 elements, 54% had one or more pairs of elements separated by < 10 kb. We propose that this type of clustering is a result of "local hopping," in which we assume that a significant proportion of tranposition events leads to the insertion of a daughter IS element in the vicinity of the parental element. A second level of nonrandomness is found in strains with a modest number of IS1 elements that are mapped through the use of inverse PCR to amplify flanking genomic sequences: in these strains, the insertion sites tend to be clustered over a smaller region of chromosome than would be expected by chance. A third level of nonrandomness is observed in the composite distribution of IS elements across strains: among 20 mapped IS1 elements, none were found in the region of 48-77 minutes, a significant gap. One region of the E. coli chromosome, at 98 min, had a cluster of IS1 elements in seven ECOR strains of diverse phylogenetic origin. We deduce from sequence analysis that this pattern of distribution is a result of initial insertion in the most recent common ancestor of these strains and therefore not a hot spot of insertion. Analysis using long- range PCR with primers for IS2 and IS3 also yielded pairs of elements in close proximity, suggesting that these elements may also occasionally transpose by local hopping.