Preventing percutaneous absorption of industrial chemicals: the "skin" denotation

Percutaneous absorption has received comparatively little attention in occupational health, although this route of entry has repeatedly caused occupation-related intoxications. In practice, the evaluation of skin penetration rates is far from simple. Much evidence has been obtained from studies of chemicals used for cosmetics and topical therapeutics, but the information available on compounds encountered in occupational health is limited. The data obtained from experimental studies have confirmed that the concentration, type of vehicle, skin area, skin condition, and extent of occlusion are important factors in determining the degree of percutaneous absorption, but no general model has been developed. Also, too little is known about the basic chemical properties governing the rate of penetration. Thus, prediction is difficult and bound to be rather inaccurate. Current preventive practice follows the procedure used by ACGIH and is mainly based on a "skin" denotation in official listings of chemicals to which exposure limits have been allocated. The number of substances and groups of chemicals which have received skin denotation in 17 selected countries varies between 24 and 179 and a total of 275 are listed as a skin hazard in one or more countries; ACGIH lists 143. Thus, the denotation practice varies. As an unfortunate result of these discrepancies and the dichotomy of skin denotation, the absence of skin denotation may erroneously indicate that efforts to protect the skin are unnecessary. Thus, an evaluation of skin penetration potentials should be incorporated in occupational health practice as a supplement to the official denotations.     

Microleakage of Class 2 glass-ionomer-silver restorations in primary molars.

The aims of this study were to assess microleakage at the cervical margins of class 2 "sandwich" restorations placed with two glass-ionomer-silver cements in primary molars, to compare the quality of the occlusal margins of these restorations to those prepared with Miracle Mix and Ketac Silver, and to assess by scanning electron microscopy (SEM) the marginal micromorphology of those restorations. Fifty-two class 2 restorations were prepared in extracted primary molars and were restored as follows: 1) Ketac Silver + Estilux Posterior (sandwich), 2) Miracle Mix + Estilux Posterior (sandwich), 3) Ketac Silver only, and 4) Miracle Mix only. No or minimal leakage was evident in most of the occlusal margins, whereas severe leakage was observed in almost 70% of the cervical margins of the Ketac Silver groups. Scanning electron microscopy evaluation demonstrated good adaptation at the buccal and lingual margins of all the restorations. Sixty-seven percent of the Miracle Mix restorations had no defects at the cervical margins, as opposed to only 17% of those with Ketac Silver.     

Brain tissue heterotopia in the nasopharynx. Contribution of MRI to assessment of extension.

The authors report two cases of brain tissue heterotopia in the nasopharynx, without other malformations and, in one of the cases, with a persistent craniopharyngeal canal opening onto the heterotopia. This exceptional malformation is very similar to brain heterotopia in the nose, or "nasal glioma", which is more frequent and less diversified at histology. The malformation is revealed by obstruction of the pharynx with respiratory distress immediately after birth or during the first weeks of life. Total surgical excision provides cure without sequelae. The diagnosis is based on histology. MRI is essential to the diagnostic and pretherapeutic evaluation, notably to avoid missing an ectopic hypophysis, but it is insufficient to diagnose a sphenoidal meningoencephalocele.     

Delayed and atypical D-glyceraldehyde-induced insulin secretion from the perfused duodenum pancreas of chicken

Insulin release by the isolated-perfused pancreas of 5-8 week-old chickens was studied in response to graded concentrations of D-glyceraldehyde (D-GA) (5-20 mM). D-GA was perfused for 30 min in the absence or in the presence of glucose concentrations (2.8 or 14 mM) which do not evoke insulin release alone. D-GA alone or in combination with glucose does not cause a biphasic insulin release. As compared to rodents the release is reduced and delayed (at least 16 min) and requires higher D-GA concentrations which reveals the insensitivity of the chicken pancreas to D-GA. In the absence of glucose, the release is higher at 15 mM D-GA. Glucose (2.8 or 14 mM) sensitized the pancreas to D-GA by eliciting earlier and higher insulin response but never restored an immediate and biphasic secretory response to D-GA. Glucose amplified the response to low D-GA levels (5 and 10 mM) and inhibited the response to higher concentrations (15 and 20 mM). A transient insulin rise ("off-response") related to the D-GA concentration was observed after withdrawal of D-GA either in the absence or in the presence of glucose. Therefore, in addition to glucose, the chicken pancreas is relatively insensitive to D-GA suggesting that the mechanism leading to insulin release in response to nutrient metabolism is different in chickens as compared to that in mammals.     

Neutrophil-rich Ki-1-positive anaplastic large cell lymphoma: a study by fine-needle aspiration biopsy

Fine-needle aspiration biopsy (FNAB) is an accurate, cost-effective method of evaluating lymphomas. The neutrophil-rich variant of anaplastic large cell lymphoma (NR-ALCL) is a rare non-Hodgkin lymphoma. To our knowledge, we present thefirst study of NR-ALCL by FNAB cytology. Histologic confirmation was available for both patients. Both cases were positive for Ki-1 (CD-30) and were either T-cell or null-cell phenotype. FNAB specimens were highly cellular with a single-cell pattern composed of pleomorphic tumor cells, "hallmark" tumor cells, and a background rich in neutrophils that occasionally obscured tumor cells. Diagnosis on FNAB is difficult owing to the rarity of this tumor, its resemblance to Hodgkin lymphoma and other non-Hodgkin lymphomas that express CD30, its similarity to an infectious process, and its occasional confusion with metastatic carcinoma and melanoma. Reproducible cytologic features usually are present, and the diagnosis can be made conclusively by FNAB in conjunction with ancillary studies.     

Regional differentiation of sympathetic activity during hypothalamic heating and cooling in anesthetized rabbits

Summary In anesthetized rabbits immobilized with succinyl choline, the discharges of sympathetic efferents supplying cutaneous and visceral regions were simultaneously recorded. The effects of thermal stimulation of the hypothalamic region were tested on the basis of the integrated discharges. During hypothalamic heating cutaneous sympathetic activity decreased, corresponding to increased ear blood flow, while visceral sympathetic activity increased. During hypothalamic cooling there was, on the average, no significant change of regional sympathetic activity. However, in single experimental periods an increase of cutaneous and a decrease of visceral sympathetic activity was found.The observed responses of regional sympathetic activity were compared with findings about regional cutaneous and intestinal blood flow under the same thermal stimulus and further with corresponding former investigations on regional blood flow and regional sympathetic activity during spinal thermal stimulation. It is suggested by this comparison that regional differentiation of sympathetic activity represents a specific thermoregulatory response of the vasomotor system mediated by the hypothalamic thermoregulatory center.     

Differences between transfer RNA methylase activity in human diploid fibroblasts during in vitro and in vivo aging

The change of the specific activity of S-adenosylmethionine: tRNA methyltransferase in cultures of human diploid fibroblasts at different passages has been measured and compared with that in the same type of cells derived from donors of different ages. Whereas the specific activity of tRNA methylase in the in vitro aged cells was found to decline gradually with increasing passage number of the culture, a different activity--age relationship was observed for this enzyme in cells derived from donors of different ages. The activity of tRNA methylase is high in the fetal cells and drops drastically in the "newborn" cells. After a further 10% decline, the activity of this enzyme reaches a steady low level in the postnatal cells from donors ranging in age from 3 months to 94 years. These findings cast doubt on the validity of the assumption that the results obtained from in vitro aging experiments reflect the biochemistry of aging in vivo. The "fetal" enzyme can methylate the "aged" tRNA but the "aged" enzyme cannot methylate the "fetal" tRNA. The fetal cells contain enzyme activities specific for the formation of m1A, m5C and m1G. These activities are low or deficient in "aged" cells. Control experiments showed that all of these results are due neither to the presence of inhibitor or stimulator in the extract nor to effects related to the population density, sex or growth rate of the culture.