Esthetic factors in removable partial prosthodontics

For the patient, the appearance of the finished restoration is of paramount importance. To avoid an esthetic failure, the dentist should pay attention to those various components of removable partial dentures which play a role in esthetics.

Alkylation of cytosine and 5-hydroxymethyl-cytosine by methyl methanesulphonate and N-methyl-N-nitrosourea: its relevance to mutagenesis

The reaction of cytosine and 5-hydroxymethyl-cytosine (OHMeCyt) with a variety of monofunctional alkylating agents has been investigated to evaluate further the possible role of cytosine alkylation in mutagenesis and the possibility that the immunity of T-even phages to mutation by methyl methanesulphonate (MMS) was due to the unreactivity of OHMeCyt towards this agent. Both cytosine and OHMeCyt reacted equally well with the methylating agents MMS and N-methyl-N-nitrosourea (MNU) affording 6% and less than 1% respectively of the 3-substituted derivative. No product was isolated following subjection of the bases to reaction with ethyl methane-sulphonate (EMS), N-ethyl-N-nitrosourea (ENU) or iso-propyl methane-sulphonate (iPMS).

Assessing the intellectural consequences of early intervention with high-risk infants

Infants at-risk for mental retardation were divided into a group that received early day-care intervention and a matched control group that did not. The purpose of the intervention was to prevent sociocultural retardation. Children were tested at 7 and 18 months on a simple two-choice visual-discrimination task and on the Bayley Scales of Infant Development to assess the impact of the intervention program on their development. Analyses revealed that the experimental group's performance was reliably superior to that of the control group on both measures and that experimental subjects scoring high on the Bayley Scales reached criterion on the discrimination task on fewer trials than low Bayley scorers. The relationship was particularly strong at 18 months.

Inactivation and mutation of coliphage T4 by aliphatic nitrosamides and methanesulphonates: in vitro recovery of infectivity of T4 inactivated by isopropyl methanesulphonate

The inactivation and mutation (to r phenotype) of extracellular coliphage T4 wild-type by the monofunctional alkylating agents N-methyl- and N-ethyl-N-nitrosourea and isopropyl methanesulphonate were investigated. The rate and extent of change in phage infectivity observed during the post-treatment period were found to correlate with what is known of the mechanisms by which these agents react in vitro. Loss of phage infectivity was found to occur during the period following treatment with these agents, but that resulting from treatment with isopropyl methanesulphonate was preceded, in the first 24 to 48 h, by a recovery of infectivity. This suggested that changes in phage infectivity occurring after treatment with monofunctional alkylating agents are resultant of various processes which diversely promote loss and recovery of infectivity. The mutagenicity of N-methyl-N-nitrosourea was similar to that of its ethyl homologue at a level of phage survival of 4 x 10-3, but less than that of isopropyl methanesulphonate. At a level of survival of 3 x 10-2 ethyl methanesulphonate was a mutagenic as its isopropyl homologue, but methyl methanesulphonate was only slightly if at all mutagenic. These results could not be correlated with the compounds' reaction mechanisms. The efficiency of isopropyl methanesulphonate (compared with its toxicity to phage) was found to decrease as the severity of the dose was increased.

Acquired resistance to daunorubicin in a patient with acute myelogenous leukaemia

Measurement of in vitro and in vivo resistance to daunorubicin in AML patients suggests that there is no simple correlation between the two. In a patient who became clinically resistant and whose cells showed a parallel increased resistance in vitro we found the acquisition of multiple drug resistance. The increased in vitro resistance to daunorubicin could to some extent be overcome by conjugating daunorubicin to DNA.

Mutation of lambda during prophage induction by nitrosamides

Approximately 6% of Escherichia coli K12 (lambda wild-type) cells whose prophage was induced by treatment with N-methyl-N-nitrosourea initiated plaques on E. coli K12S which contained wholly or mostly clear plaque-forming mutants (lambdac). "Fuzzy" plaque-forming mutants (lambdaf) were also recognised, at lesser frequencies. Less marked mutation occurred during prophage induction by N-ethyl-N-nitrosourea, and no apparent mutation occurred during induction by methyl and iso-propyl methanesulphonates, or by a non-inducing treatment of the lysogen with ethyl methanesulphonate. Mutagenic effects of treatment of susceptible host cells or of phage alone, prior to infection, seem not to account for the phenomenon described.

The value of the nose width as an esthetic guide in prosthodontics

A radiographic method was used to measure the interalar and interalar-fold widths of the nose on 80 men and women. These distances were compared to the subjects' intercanine distances as measure on artificial stone casts. In 56 of the subjects, the width of the skeletal nasal aperture was measured and compared to the intercanine distance. From the results of this study, the following conclusions can be drawn. 1. There was no significant relationship between the intercanine distance and the interalar width of the nose in the 80 men and women who served as subjects in this study. 2. There was no significant relationship between the intercanine distance and the interalar-fold width of the nose in the 80 men and women in this study. 3. The presence or absence of a significant relationship between the intercanine distance and the width of the skeletal nasal aperture was not demonstrated conclusively in this study. 4. The results of this study show that the width of the nose would not be a reliable guide for selecting or arranging artificial anterior teeth, provided one concurs that they should be the same size and shape and occupy the same position as their natural predecessors.