Evidence for interaction of substrate analogs with chicken eggwhite lysozyme after exhaustive reduction of disulfide bonds

In a study of factors that influence the remaining secondary structure of reduced chicken eggwhite lysozyme, N-acetyl-D-glucosamine (NAG) and N, N¹-diacetyl-chitobiose (di-NAG) were found to alter the circular dichroic (CD) spectrum of the reduced protein and its carboxymethyl derivative (Cml). Thus, negative ellipticities in the far u.v. were greater in the presence of the analogs, with NAG being the more effective. For Cml, curve fitting analysis of the CD data indicated an increased helical content in the presence of NAG by an average of 3% of the chain length, while β-structure decreased by an equivalent amount. Other compounds structurally related to NAG produced no similar effects on the CD spectrum of Cml, nor were comparable effects of NAG in evidence on the Cm reduced derivatives of ribonuclease, chymotrypsin, wheat germ agglutinin, or α-lactalbumin. The effect therefore appears specific between NAG and Cml. Conversion of the tryptophan residue at Position 62 of Cml to the oxindole-alanyl derivative prevented these effects of NAG, and this residue may therefore participate in the interaction. During a 4-day incubation at room temperature, the analog preserved the CD spectrum of Cml as well as its concentration. This effect was nearly specific when compared with other Cm reduced proteins and with other carbohydrates. Only one, N-acetyl mannosamine, was effective in preserving the concentration of Cml, but not the CD spectrum. Since D-glucos-amine was entirely without effect on either the CD spectrum of Cml or on its change during incubation, the acetyl group appears essential for the NAG-Cml interaction. The specificity between NAG and Cml is tentatively accounted for in terms of interactions with the primary structure, rather than with the remaining secondary structure. It is suggested that the stabilizing effect noted here could reflect a naturally occurring interaction between a substrate-related ligand     

RNA Synthesis in Cultures of Normal Human Peripheral Blood

RNA and DNA synthesis were measured in cultures of normal human peripheral blood using tritiated cytidine and thymidine and autoradiographictechnics. RNA synthesis preceded DNA synthesis by 24 hours. RNA synthesisoccurred predominantly in the large and medium-sized "blast-like" cells, butdid occur, to a lesser extent, in the small lymphocytes. RNA synthesis did notoccur in the absence of phytohemagglutinin, nor did DNA synthesis. Mechanisms of action of phytohemagglutinin are discussed with particular referenceto its possible antigenic nature.

Submitted on August 12, 1963 Accepted on January 6, 1964     

Effect of Electrode Orientation on Lesion Sizes Produced by Irrigated Radiofrequency Ablation Catheters

Background: Irrigated radiofrequency (RF) ablation catheters may produce different lesion sizes dependent upon the electrode orientation to the tissue. This study examined the effect of irrigated electrode orientation on the lesion size and explores a potential mechanism for this effect.
Methods and Results: Lesions were created in isolated porcine myocardium using an open irrigation, closed irrigation, and nonirrigated RF catheter (all 3.5–4 mm tips). Lesions were created with the electrodes with all permutations of electrode orientation (vertical or horizontal), contact pressure (6 or 20 g), and saline superfusate flow (0.2 or 0.4 m/sec) over tissue interface. The effect of electrode irrigation without RF delivery on tissue temperature was assessed with intramyocardial temperature probes and infrared thermal imaging. For both irrigated catheters, the horizontal orientation produced 25–30% smaller lesion volumes than the vertical orientation despite equal or greater power deliveries. The horizontal orientation produced larger lesion volumes for the nonirrigated catheter. Higher superfusate flow rates were associated with decreased lesion volumes for the irrigated catheters but greater lesion volumes for the nonirrigated catheter. Catheter irrigation alone without RF delivery reduced intramyocardial temperatures up to 4.9°C and the horizontal orientation produced a 2-fold greater area of tissue cooling than the vertical orientation.
Conclusion: Horizontal electrode orientations reduce lesion volumes for irrigated RF catheters. This effect may be in part due to greater areas of active tissue cooling in the horizontal orientation.     

Genotype does not predict severity of behavioural phenotype in juvenile neuronal ceroid lipofuscinosis (Batten disease)

Aim The primary aim of this investigation was to examine genotype and clinical phenotype differences in individuals with juvenile neuronal ceroid lipofuscinosis (JNCL) who were homozygous for a common disease‐causing deletion or compound heterozygous. The secondary aim was to cross‐validate the Child Behavior Checklist (CBCL) and the Unified Batten Disease Rating Scale (UBDRS), a disease‐specific JNCL rating scale. Method Sixty individuals (28 males, 32 females; mean age 15y 1mo, SD 4y 9mo, range 5y 8mo–31y 1mo) with JNCL completed the UBDRS. Results No significant genotype and clinical phenotype differences were identified when comparing individuals homozygous for the deletion with a heterogeneous group of compound heterozygous individuals. There were significant correlations among related behaviour items and scales on the CBCL and UBDRS (Spearman’s rho ranging from 0.39 [p<0.05] to 0.72 [p<0.01]). Behaviour and physical function ratings were uncorrelated, supporting divergent validity of these two constructs in JNCL. Interpretation Previous reports of genotype and clinical phenotype differences were unsupported in this investigation, which did not find differences between individuals homozygous or heterozygous for the CLN3 deletion. The CBCL, an already validated measure of behaviour problems, appears valid for use in JNCL and cross‐validates well with the UBDRS.     

Occurrence,Efficacy, Metabolism,and Toxicity of Triclosan

Triclosan has broad-spectrum anti-microbial activity against most gram-negative and gram-positive bacteria. It is widely used in personal care products, household items, medical devices, and clinical settings. Due to its extensive use, there is potential for humans in all age groups to receive life-time exposures to triclosan, and, indeed, triclosan has been detected in human tissues and the environment. Data gaps exist regarding the chronic dermal toxicity and carcinogenicity of triclosan, which is needed for the risk assessment of triclosan. The US Food and Drug Administration (FDA) nominated triclosan to the National Toxicology Program (NTP) for toxicological evaluations. Currently, the NTP is conducting several dermal toxicological studies to determine the carcinogenic potential of triclosan, evaluate its endocrine and developmental-reproductive effects, and investigate the potential UV-induced dermal formation of chlorinated phenols and dioxins of triclosan. This paper reviews data on the human exposure, environmental fate, efficacy of anti-microbial activity, absorption, distribution, metabolism and elimination, endocrine disrupting effects, and toxicity of triclosan.     

Comparison of Wear-Resistance of Class V Restorative Materials

ABSTRACT: Compomers and resin-modified glass ionomers have been developed to improve the physical properties of traditional glass ionomer cements. This project compared the toothbrush wear-resistance of three compomers (Compoglass, Dyract, Hytac) and three resin-modified glass ionomer restorative materials (Fuji II LC, Photac-Fil, Vitremer) to that of two resin-based composites (Herculite XRV, Silux Plus). Specimens (n = 7) were prepared according to manufacturers' instructions and stored in a humidor for 48 hours prior to testing. The specimens were subjected to 120,000 strokes at 1.5 Hz, using a brush-head force of 200 g on a Manly V-8 cross-brushing machine. The slurry contained a 50:50 (w/w) mixture of toothpaste and deionized water. Abrasion-resistance was calculated by measuring specimen mass-loss prior to and subsequent to brushing. The data were analyzed using a one-way analysis of variance (ANOVA) and the Tukey-Kramer post-hoc test. Significant differences ( p ±.0001) in mass-loss were found, and loss ranged from 0.013 ± 0.003 g (Hytac) to 0.061 ± 0.009 g (Compoglass). No correlation ( p = .959) between wear-resistance and experimentally determined filler content existed. This study showed that all but one hybrid resin-ionomer type material exhibited a resistance to toothbrush wear that was as good as or better than that of the two traditional resin-based composite materials.     

Teratology and Multigeneration Reproduction Studies with Maleic Anhydride in Rats

Teratology and Multigeneration Reproduction Studies with MaleicAnhydride in Rats. SHORT, R.D., JOHANNSEN, F.R., LEVINSKAS,G.J., RODWELL, D.E., AND SCHARDEIN, J.L. (1986). Fundam. AppiToxicol. 7, 359-366. These studies were initiated to evaluatethe effects of maleic anhydride on development and reproductionin CD rats. In the teratology study, pregnant rats (19-23/group)received 0, 30, 90, or 140 mg/kg/day maleic anhydride in cornoil orally from Days 6-15 of gestation and fetuses were examinedfor gross soft tissue and skeletal defects. A reduced weightgain or weight loss was observed in all maleic anhydride-treatedgroups between Days 6 and 9; however, mean weights of all groupswere within 5% of control on Days 15 and 20. No treatment-relatedeffects on fetal development were observed. In the multigenerationstudy, rats (10 males and 20 females/group) received 0, 20,55, or 150 mg/kg/day maleic anhydride in corn oil orally andwere mated to produce two generations, each with two litters.Groups of the same size from the second litter were used forsubsequent generations and were given the same dose of maleicanhydride as were their parents. The high-dose group was terminatedduring the second generation due to treatment-related mortalityin adults. Renal cortical necrosis occurred in high-dose Fomales and females. Increased kidney weights were observed inlow- and mid-dose adult Fl females. No treatment-related effectson reproduction were observed with maleic anhydride at dosesup to 55 mg/kg/day over two generations.     

A Simple Technique for Covering Bilateral IMA

A method of covering mammary grafts with pleura, thymus, and pericardium to separate them from the sternum is described.