FDA points-to-consider documents: the need for dietary control for the reduction of experimental variability within animal assays and the use of dietary restriction to achieve dietary control

Wild type p53 protein has been shown by recent investigations to be involved in the negative regulation of cell proliferation, whereas aberrant p53 protein has lost this negative regulation of cell growth. Wild type p53 protein, which has a very short half-life, has generally been considered to be undetectable using immunohistochemical methods; however, according to a recent report, wild type p53 protein may accumulate in the nuclei because of a defective ubiquitin pathway. Aberrant p53 protein has a longer half-life, and thus is visible using immunohistochemical methods. In this study, both the proliferative potential represented by the MIB-1 staining index (SI) and the immunoreactivity of p53 protein in 51 intracranial meningiomas were studied applying immunohistochemical staining methods to archival paraffin sections. The correlation among MIB-1 SI, p53 immunoreactivity, histopathologic findings and the clinical course of the meningiomas was also analyzed retrospectively. Although it is not possible with available reagents to distinguish between aberrant p53 protein and wild type p53 protein, statistical analyses show that p53 protein was immunostained both in meningiomas with high MIB-1 SI and in recurrent meningiomas. This demonstrates the close relationship among p53 immunoreactivity, MIB-1 SI, and recurrence; therefore, the presence of p53 protein by immunohistochemical examination may suggest the proliferative activity of meningioma and is capable of serving as a predictor of future recurrence.     

A novel culturing and grafting system for the treatment of leg ulcers

The purpose of this study was to develop and test an efficient culturing and grafting system for the treatment of leg ulcers. The culturing system consisted of a Petriperm culture vessel (20 cm2) aseptically placed in a larger standard Petri dish (60 cm2). Skin cultures were established and cultivated in the Petriperm dish. The cells grew on the bottom of the Petriperm dish, which was made of a gas-permeable 25-micron thick transparent Teflon film. Grafts were produced simply by cutting the film from the bottom of the Petriperm dish with a scalpel. The system was used to produce subconfluent epidermal autografts which were used to heal a 32 cm2 chronic rheumatoid arthritis leg ulcer. The cultured autografts were transferred cell side down on to the cleaned wound bed without an enzymatic digestion. The grafts consisted of autologous keratinocytes, melanocytes and fibroblasts. Caution was taken not to disturb the wound bed for 7-9 days at which time the Teflon film was removed. The wound closed 2 weeks after the last grafting and has remained closed for more than a year post-treatment. The culturing and grafting system presented here will make it possible to develop cellular-based therapies that were previously not possible.     

In vitro evaluation of synthetic heparin-like conjugates comprising different thrombin binding domains

The syntheses of several heparin-like glycoconjugates (i.e., 16a-f) containing identical AT III binding domains (ABD) and spacers but different thrombin binding domains (TBDs) are described. Biological activities of conjugates 16a-f indicate that the thrombin inhibitory activity is mainly determined by the charge density of the TBD moiety.     

Zebrafish visual sensitivity is regulated by a circadian clock

Carbonaceous aerosols are present in many workplace and environmental settings. Some of these aerosols are known or suspect human carcinogens and have been linked to other adverse health effects. Exposure to diesel exhaust is of particular concern because it has been classified as a probable human carcinogen and use of diesel-powered equipment is widespread in industry. Because previously used methods for monitoring exposures to particulate diesel exhaust lack adequate sensitivity and selectivity, a new method was needed. A carbon analysis technique called the thermal-optical method was evaluated for this purpose. In thermal-optical analysis, carbon in a filter sample is speciated as organic and elemental (OC and EC, respectively). When the thermal-optical method was initially evaluated, only one instrument was available, so interlaboratory variability could not be examined. More recently, additional instruments were constructed and an interlaboratory comparison was completed. Eleven laboratories participated in the study, including four in Europe that employ an alternative thermal technique based on coulometric detection of CO2. Good agreement (RSDs less than or equal to 15%) between the total carbon results reported by all laboratories was obtained. Reasonable within-method agreement was seen for EC results, but the EC content found by the two methods was differed significantly. Disagreement between th OC-EC results found by the two methods was expected because organic and elemental carbon are operationally defined. With all filter samples, results obtained with the coulometric method were positively biased relative to thermal-optical results. In addition, the alternative method gave a positive bias in the analysis of two OC standard solutions. About 52% and 70% of the carbon found in two aqueous solutions containing OC only (sucrose and EDTA, respectively) was quantified as elemental,while EC contents of about 1% and 0.1% (respectively) were found by the thermal-optical method. The positive bias in the analysis of the OC standards is attributed largely to inadequate removal of OC during the first part of the analysis; lack of correlation for pyrolytically formed carbon (char) also is a factor. Results obtained with a different thermal program having a higher maximum temperature were in better agreement with the thermal-optical method.     

Awareness during anesthesia and posttraumatic stress disorder

The prevalence of tarsal coalition is probably 1% or less. The two sites most commonly affected are the calcaneonavicular joint and the middle facet of the talocalcaneal joint. Diagnosis should be suspected in the preteen or teenage patient with insidious or sudden onset of pain in the midfoot to hindfoot associated with a lack of motion in the subtalar joint. Initial treatment with immobilization or an orthosis may relieve symptoms, but most patients will have persistent symptoms that warrant surgical correction. Long-term results indicate that excision of the coalition is moderately successful in relieving symptoms in the calcaneonavicular bar. Long-term success with excision of subtalar bars is less clear, although early relief of symptoms is usually possible.     

Platelet kinetics in autosomal dominant macrothrombocytopenia

A family with autosomal dominant macrothrombocytopenia is described. Despite severe thrombocytopenia, only a moderate hemorrhagic tendency was observed. Kinetic studies revealed a normal platelet survival, normal megakaryocytic numbers, and normal bone marrow responsiveness. The rate of platelet production was set low, despite moderately impaired hemostasis and thrombocytopenia; it apparently was set to maintain another platelet parameter at an optimal level. Measurements of total circulating platelet mass and platelet surface suggested that the platelet production was set to maintain the platelet surface rather than the platelet mass at a normal value.     

Longitudinal endolymph movements induced by perilymphatic injections

Endolymph movements and endocochlear potential (EP) changes were measured during disturbances of perilymphatic pressure. induced by injecting artificial perilymph into scala tympani (ST) or scala vestibuli (SV) of the guinea pig cochlea. Injections were performed either with or without an outlet made in the opposite perilymphatic scala. Injections into ST without an outlet induced large pressure changes but virtually no endolymph movement or EP change. Injection at the same rate into ST with an outlet in SV produced smaller pressure changes which were accompanied by a basally-directed displacement of endolymph and significant EP changes. The magnitude of endolymph displacements and EP changes varied as a function of injection rate. Injections into SV, either with or without an outlet in ST, produced apically-directed endolymph displacement and EP changes. For the SV injections without an outlet, the cochlear aqueduct and round window are likely to provide an outlet and compliance, permitting flow along the perilymphatic scalae to occur even when no ST outlet was provided. We conclude that endolymph movements are not dependent on the absolute pressure of the perilymph, but instead occur when small, sustained pressure gradients are present across the cochlear partition, corresponding to times when perilymph flow is induced. This study demonstrates that in the normal. sealed cochlea, endolymph and EP are insensitive to fluid injections into ST, but are sensitive to fluid injections into SV. Endolymph movements are therefore unlikely to be generated by cerebrospinal fluid pressure fluctuations (such as those produced by respiration, posture changes, coughing, sneezing, etc) which are transmitted to ST by the cochlear aqueduct.     

Open-set speech perception in congenitally deaf children using cochlear implants

A review of the literature examining school-based prevention and treatment intervention programs for smokeless tobacco users is provided. Although few school-based prevention studies have been conducted, the results are promising. Many of the treatment studies that have been conducted, thus far, are limited due to the sample size and the lack of a control group. However, of the studies that have not had these limitations, the results are also promising. In general, studies show that intervention in the dental office can be effective and that group behavioral treatment may also improve cessation rates over minimal contact. On the other hand, pharmacological treatment, which has primarily focused on 2 mg nicotine gum, has not been found to be an effective treatment. Dentists are in an ideal position to advise and assist smokeless tobacco users to quit. The majority of smokeless tobacco users want advice and help from their dentists, and a significant number indicate that discussion of the negative oral effects from the use of smokeless tobacco has an impact on their desire to quit.