Poly(1-vinyl-2-pyrrolidinone) hydrogels as vitreous substitutes: histopathological evaluation in the animal eye

A homopolymer of 1-vinyl-2 pyrrolidinone and its copolymer with 2-hydroxyethyl methacrylate, both cross-linked with divinyl glycol, were produced as possible substitutes for the vitreous body of the eye. The hydrated polymers behaved like viscoelastic gels, displaying excellent physical and optical properties. The sterile gels (0.7-1.5 ml) were injected into the vitreous cavity of rabbits, which previously underwent gas-mediated vitrectomy. Clinically, the eyes were quiet, with the exception of transient opacities in the vitreous. After 4 weeks, the operated eyes were enucleated and subjected to histopathological analysis using light and transmission electron microscopy. The common feature in all sections was the invasion of inflammatory cells. Vacuoles containing granular material, assumed to be polymer, were seen in the intercellular spaces of the neural retina, in the retinal pigment epithelium cells, and in macrophages. These findings indicated the fragmentation and phagocytosis of synthetic gels. It appeared that the biodegradation of the internalized polymers did not proceed further, however, the fate of polymers and their usefulness as vitreous substitutes should be investigated through long-term experiments.     

Isolation of human osteoblast-like cells and in vitro amplification for tissue engineering

As the field of dental implants continues to grow at a rapid rate so does our quest to find new techniques to enhance bone grafting. Tissue engineering is an exciting new technique in bone grafting. Therefore, the purposes of this study were to develop a simple, reproducible method to isolate human osteoblast-like cells (HOBs) and to evaluate in vitro cell proliferation within 2 different 3-dimensional (3-D) constructs targeted for tissue engineering applications. Ultimately, HOBs that have been amplified within 3-D constructs may be employed for bone regeneration techniques, such as onlay and sinus grafting prior to implant placement. Our cell isolation protocol employed human fetal calvaria tissue sequentially digested with trypsin and collagenase. The HOB cells from only the third and fourth digests were obtained, cultured and evaluated within the constructs. An osteoblast-like phenotype was in part verified for these HOB cells by demonstrating a significantly higher alkaline phosphatase activity than for human gingival fibroblasts, and a comparable level to the osteoblast cell line MG-63. The HOB cells were cultured within either poly (D,L-lactide) (PLA) or a fused fiber ceramic and evaluated for the ability to support in vitro HOB amplification. HOB proliferation was validated by scanning electron microscopy, identifying cells throughout the 3-D constructs. Continuous cell viability was demonstrated for the duration of the 33-day evaluation period and the extent of cell amplification reached approximately 20 times the seeding density. The in vitro amplification results further indicate that tissue engineering strategies with either the PLA or fused fiber construct may be suitable for bone regeneration therapy for dental implants.     

Dystocia, stillbirth, gestation length, and birth weight in Holstein, Jersey, and reciprocal crosses from a planned experiment

Holstein and Jersey cows were mated to 4 Holstein (H) bulls and 4 Jersey (J) bulls to create HH, HJ, JH, and JJ genetic groups (sire breed listed first) in a diallele crossbreeding scheme. Calvings (n = 756) occurred in research herds in Virginia, Kentucky, and North Carolina with 243, 166, 194, and 153 calvings in the HH, HJ, JH, and JJ groups, respectively. Birth weights (BW), dystocia scores (0 for unassisted and 1 for assisted), and stillbirth (0 for alive or 1 for dead within 48 h) were recorded at calving. Gestation lengths (GL) were determined from breeding dates. An animal model was used to analyze BW and GL, and an animal model with logistic regression was used for dystocia and stillbirth. Fixed effects considered for model inclusion were genetic group, herd-year-season, sex, parity (primiparous or multiparous), twin status, and gestation length. Genetic group and effects significant in the model building process were kept in the final model for each trait. Heifer calves had lower BW, shorter GL, and had a lower odds ratio (0.53) for dystocia than bull calves. Twins had lower BW, shorter GL, were 3.86 times more likely to experience dystocia, and 7.80 times more likely to be stillborn than single births. Primiparous cows had calves with lower BW, shorter GL, were 2.50 times more likely to require assistance at birth, and were 2.35 times more likely to produce stillborns than calves from multiparous cows. Genetic group did not affect GL. Least squares means (kg) for BW were 37.7 ± 1.1, 29.1 ± 1.1, 30.3 ± 1.0, and 22.5 ± 1.3 for HH, HJ, JH, and JJ, respectively. Animals in HH weighed more than animals of other genetic groups; the JJ group had the smallest BW, with no differences for BW between HJ and JH. Probability of dystocia in JJ and JH were 5.73% and 18.98% of HH. Calves in HJ and HH were not different for dystocia. Calves in HJ were 3.38 times more likely to be stillborn than calves in JH, but no other genetic group differences were significant for probability of stillbirth. Groups HJ and JH differed for calving traits, with JH crosses experiencing less dystocia than HJ; JJ showed no indication of dystocia. No differences were observed between HH and JJ for stillbirths. Additional investigation of stillbirths in Jerseys is justified.     

Further delineation of spondylo-meta-epiphyseal dysplasia, short limb-abnormal calcification type, with emphasis on diagnostic features

Further delineation of a generalized bone dysplasia which we call spondylo-meta-epiphyseal dysplasia, short limb-abnormal calcification type is presented. This dwarfing condition has several serious complications, with the most common cause of death being spinal cord damage secondary to atlantoaxial instability. It is a heritable condition with an autosomal recessive mode of transmission. Radiologic diagnostic criteria are developed on the basis of studies in 8 patients with the oldest being between 4 and 5 years old. The condition is clinically and radiographically apparent neonatally or in early infancy, and it is probable that all or almost all affected individuals will come to medical attention in the age range screened by this study.     

Superinfection exclusion by bacteriophage T7

Only two of the early genes of bacteriophage T7 were found to play a significant role in exclusion of superinfecting bacteriophage T3 particles; genes 0.3 and 1. Protein synthesis by the preinfecting phage particle was not required for efficient exclusion. These findings are discussed with regard to the known functions of these genes during T7 development.     

Intravenous propranolol administration: a method for rapidly achieving and sustaining desired plasma levels

A model for the intravenous administration of propranolol by a bolus-infusion technique designed to rapidly produce, then maintain, predicted plasma drug concentrations was derived from elimination kinetics in single-dose studies. Prospective testing of this model in 6 adult male subjects revealed a close correlation between predicted and observed drug levels; desired plasma concentrations were achieved within 5 min and maintained over the 30-min study period. By subtracting previously given bolus doses from the dose calculated as needed to produce a desired plasma level, progressive increases in predicted propranolol levels could be effected, with apparent maintenance of equilibrium. Correlations between the bolus doses and infusion rates and the plasma drug levels were consistent and significant, and constitute nomograms from which the dose of drug required to produce a desired plasma level may be approximated. The clearance of propranolol declined slightly as the drug plasma level increased, but did not significantly affect the accuracy of the model.