Fibrinogen adsorption and platelet adhesion at the surface of modified polypropylene glycol/polysiloxane networks

The protein film adsorbed at an artificial surface ultimately affects platelet adhesion and activation. This study examines the role of fibrinogen in platelet adhesion at the surface of crosslinked polypropylene glycol (PPG)/polyglycidoxy propyl methyl siloxane (PGPMS) networks which contain polyethylene glycol monomethyl ether (PEGME) chains. These crosslinked networks were produced by reacting the epoxy groups of PGPMS with the hydroxyl groups of the polyethers. PEGME chains were attached covalently to the network at only one end while PPG chains were attached at both ends. The incorporation of PEGME resulted in a substantial reduction in fibrinogen adsorption as compared to the model network (PPG + PGPMS only), but the expected concomitant decrease in platelet adhesion was not observed.     

Formaldehyde in cryoprotectant propanediol and effect on mouse zygotes

Cryopreservation of human zygotes and embryos has been routinely performed by in-vitro fertilization clinics for many years. Karran and Legge (1996) first reported that formaldehyde (FA) present in the cryoprotective solutions can have a deleterious effect on mouse oocytes. FA is a cytotoxic, carcinogenic and mutagenic chemical. The effect of FA on mouse zygotes was investigated. In addition, the concentrations of FA in propanediol (PROH) obtained from various sources were determined. Pooled 1-cell embryos were dispensed into droplets of modified Ham's F10 or human tubal fluid containing various concentrations of FA. Since bovine serum albumin (BSA) may minimize toxicity additional trials were done as above in the absence of BSA. FA concentration in the standard 1.5 M PROH, from different sources in water, was measured in the same assay using a standard curve of 0-100 microM FA. FA in a complex medium had a significant deleterious effect on embryo development and hatching but only at 1 mM concentration (P < 0.000001; see Tables I-III). There was no significant effect of FA at 100 microM. However, in a simple medium even 50 microM FA decreased embryo hatching. FA was present in 1.5 M PROH from different sources (range 1.0-35.3 microM concentration). It appears that FA concentrations do not increase with storage because FA concentrations were low even after opening and storage for 3 years on the shelf. This suggests that FA is a contaminant during the manufacturing process and may vary from manufacturer to manufacturer and batch to batch. Until further studies are done to confirm the lack of toxicity to embryos during cryopreservation (with or without FA scavengers) it may be prudent to screen all batches of cryoprotectants for FA as part of quality control.      

Behavioral correlates of oral and postingestive satiety in the rat

Hungry rats display the characteristic "satiety sequence" after drinking a glucose solution: The end of ingestion is accompanied by grooming and exploring, followed by resting. With saccharin solutions over a range of concentrations, however, ingestion is accompanied and followed by persistent grooming and exploring; resting rarely occurs. Gastric preloads of glucose solution promote resting to reinstate the "satiety sequence" after a bout of saccharin ingestion. Therefore, the systemic effects of glucose are sufficient to promote resting. In the absence of postingestive factors, the "satiety sequence" is incomplete following saccharin ingestion as it is after sham-feeding.     

Dental abnormalities in individuals with pathogenic germline variation in DICER1

Pathogenic germline variation in the microRNA processing gene DICER1 gives rise to an autosomal dominant, tumor‐predisposition disorder. Conditional deletion of Dicer1 in murine dental epithelium shows that it controls tooth patterning, size, number, and shape. The human dental phenotype of people with germline pathogenic variation in DICER1 is unknown. DICER1‐carriers (n = 57) and family controls (n = 55) were evaluated at the NIH Clinical Center dental clinic as part of a comprehensive medical evaluation. Digital panoramic radiographs, bite‐wing radiographs, and oral photographs were collected. A single observer, blind to DICER1 status, reviewed the dental records and determined the presence or absence of 11 dental characteristics as described in the clinic notes, radiographs, or oral photographs. Subjective phenotypes were reviewed on radiographs by two examiners (blind to DICER1 status) for the presence or absence of the dental characteristics to reduce inconsistencies. By simple association, bulbous crown, periodontitis, and taurodontism were all significant (p < .05). Logistic regression with chi‐square maximum likelihood estimates showed that bulbous crown and periodontitis remained significant. Recognition of these phenotypes may aid identification of individuals and families at risk for DICER1‐associated neoplasms. These findings may also guide dental care for individuals with germline DICER1 pathogenic variation.     

Intermediate filament expression by normal and diseased human corneal epithelium

Cicatricial conjunctivitis may be a sequel to systemic disorders (eg, Stevens-Johnson syndrome, cicatricial pemphigoid) or local disorders such as chemical burns. The cicatrisation is often associated with corneal epithelial changes that cause visual loss. These have been attributed to encroachment of the conjunctival epithelium over the cornea. However, the epithelial anomalies are poorly understood. We investigated the corneal epithelial changes in cicatricial conjunctivitis with an immunohistochemical study of intermediate filaments in normal and pathological specimens. Our results show that the normal corneal epithelium is immunoreactive for cytokeratin 3 (CK 3) but not cytokeratin 19 (CK 19), whereas normal conjunctival epithelium is CK 3 negative and CK 19 positive. Conjunctiva artificially transposed over the cornea (after therapeutic conjunctival flap reconstruction) retained the normal pattern of conjunctival cytokeratin expression (CK 3 negative, CK 19 positive). Conversely, the entire corneal epithelium exhibited the normal cytokeratin pattern (CK 3 positive, CK 19 negative) in 82% of Stevens-Johnson, 80% of cicatricial pemphigoid, and 69% of chemical burns specimens. The findings suggest that conjunctival encroachment is not responsible for the changes at the corneal surface in cicatricial conjunctivitis and that the abnormal corneal epithelium is derived from native corneal cells in these diseases.     

Involvement of helicase II (uvrD gene product) and DNA polymerase I in excision mediated by the uvrABC protein complex.

The bimodal-incision nature of the reaction of UV-irradiated DNA catalyzed by the Escherichia coli uvrABC protein complex potentially leads to excision of a 12- to 13-nucleotide-long damaged fragment. However, the oligonucleotide fragment containing the UV-induced pyrimidine dimer is not released under nondenaturing in vitro reaction conditions. Also, the uvrABC proteins are stably bound to the incised DNA and do not turn over after the incision event. In this communication it is shown that release of the damaged fragment from the parental uvrABC-incised DNA is dependent upon either chelating conditions or the simultaneous addition of the uvrD gene product (helicase II) and the polA gene product (DNA polymerase I) when polymerization of deoxynucleoside triphosphate substrates is concomitantly catalyzed. The product of this multiprotein-catalyzed series of reactions serves as a substrate for polynucleotide ligase, resulting in the restoration of the integrity of the strands of DNA. The addition of the uvrD protein to the incised DNA-uvrABC complex also results in turnover of the uvrC protein. It is suggested that the repair processes of incision, excision, resynthesis, and ligation are coordinately catalyzed by a complex of proteins in a "repairosome" configuration.