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The chromatin structure of yeast ribosomal DNA was analyzed in vivo by crosslinking intact cells with psoralen. We found that in exponentially growing cultures the regions coding for the 35S rRNA precursor fall into two distinct classes. One class was highly accessible to psoralen and associated with nascent RNAs, characteristic for transcriptionally active rRNA genes devoid of nucleosomes, whereas the other class showed a crosslinking pattern indistinguishable from that of bulk chromatin and was interpreted to represent the inactive rRNA gene copies. By crosslinking the same strain growing in complex or minimal medium, we have shown that yeast cells can modulate the proportion of active (non-nucleosomal) and inactive (nucleosomal) rRNA gene copies in response to variations in environmental conditions which suggests that yeast can regulate rRNA synthesis by varying the number of active gene copies, in contrast to the vertebrate cells studied so far. Whereas intergenic spacers flanking inactive rRNA gene copies are packaged in a regular nucleosomal array, spacers flanking active genes show an unusual crosslinking pattern suggesting a complex interaction of regulatory factors and histones with DNA.

The meaning and usefulness of biological indicators in the study of occupational exposure to aluminium (Al) was assessed on the basis of the most recently acquired knowledge on the toxicokinetics of aluminium absorbed by inhalation, results of environmental and biological investigations recently carried out in industrial sectors with low risk of aluminium absorption (refining, casting and pressure moulding covering a total of 8 plants and 119 workers) and the results of investigations on a group of welders exposed to Al concentrations between 5 and 10 mg/m3. It was confirmed that not only the environmental Al concentrations but also certain chemical and physical characteristics (particle size, allotropic state, solubility), simultaneous exposure to other dusts, and mode of exposure (existence of exposure peaks) play a significant role in lung absorption of Al. Urinary Al (AlU) may be considered as an indicator of "recent" exposure with biphase excretion kinetics influenced also by duration of exposure, whereas Al in serum (AlS) can probably furnish indications both on overall exposure and on body burden. In low-level Al exposure (below 0.5 mg/m3), these indicators (especially AlU) permit differentiation of the exposed groups from the general population without, however, any clear relationship with the various environmental Al concentrations. It was also seen that AlU increased with increasing work seniority and was more marked in certain processes, such as casting, and in the first few months or years of work.(ABSTRACT TRUNCATED AT 250 WORDS)

Unlike other apparatuses, the potential effects on the nervous system of occupational exposure to anaesthetic gases have not been exhaustively reviewed. Because of the relevance of these effects, their significance of the quality of life of the exposed subjects and of the increased risk inherent in their delicate work tasks, these themes deserve the greatest attention. This paper briefly examines the data from the international literature as well as the neurobehavioral methods employed, underlines the existing gaps of knowledge and eventually proposes strategies aimed at filling these gaps of knowledge.

Since 1987 at the Spedali Civili of Brescia the problem of anaesthetic gases pollution in operating surgery rooms was managed by means of periodical environmental monitoring and maintenance of the anaesthesiological equipments. The mean nitrous oxide concentrations were generally reduced to values below the limits indicated by the Italian Ministry of Health. On the contrary, a low participation of the operating room personnel was observed in the health surveillance program and this phenomenon is clearly evidenced by the progressive decrease of the number of medical examinations. In order to clarify the usefulness of health surveillance programs and to promote the adoption of "less pollutant" behaviour, a Health Education Program was planned by the Medical Administration, in collaboration with the Occupational Health Service and the Department of Anesthesiology and Intensive Care. This program will be performed at different times, including the administration of a questionnaire, the participation at information meetings, the distribution of brochures and the evaluation of environmental and biological exposure data before and after the education program.

The Study Group on Occupational Exposure to Inhalation Anaesthetics of the Lombardy Association of Occupational Health and Industrial Hygiene prepared a document that was discussed during the Congress "Occupational Risks due to Inhalation Anaesthetics", held in Brescia, Italy, on May 12, 1992. The same document was then approved by the Directory Council of the Lombardy Association of Occupational Health and Industrial Hygiene. Data on environmental concentrations of Nitrous Oxide collected from 1989 to 1991 in 269 operating rooms of 47 hospitals in Lombardy are reported. The measured levels are considerably lower than those collected from the same Study Group from 1985 to 1987 in 111 operating rooms. The methodologies for exposure control are discussed, regarding both environmental and biological monitoring. These two techniques are complementary and can be used with standardized methods. The review of the literature on the early effects showed, even with some uncertainty at the current exposure levels, effects on liver and Central Nervous System. Still controversial are the data regarding the reproductive toxicity. Health surveillance programs have been organized in the last 5 years in 18 Lombardy hospitals and they indicate no cases of pathologies due to inhalation anesthetics on 1498 subjects. Operative proposals are suggested on the methodology and the frequency of environmental/biological monitoring and health surveillance. The "technical limit values" reported in the document from the Italian Ministry of Health are also discussed. Finally, research topics are suggested in order to assess the early effects of exposure.

In the past years the problem related to occupational exposure to anaesthetic gases in operating rooms has been dealt with in different ways by each hospital administration, and frequently with little cooperation between the health departments involved. At the Spedali Civili of Brescia in the five year period, 1987-1991, a monitoring activity of nitrous oxide (N2O) and halogenated anaesthetics was performed in 30 operating rooms. This lead to a noticeable reduction of environmental concentrations of these substances. Favourable results have been achieved principally by maintenance and/or substitution of anesthesiological machine parts. In order to organize and facilitate this program a close collaboration was accomplished between the Medical Direction of the Hospital and the Occupational Health Department, with the support of the Technical Assistance Department.

High serum bilirubin levels (SBL), over 20-25 mg/dl are toxic for the Central Nervous System (CNS) of newborn infants. However, the possible toxicity on the CNS of "intermediate" SBL both in term and preterm neonates are still a matter of debate. An extensive review of the literature in this respect did not provide conclusive evidence for a dose-response pattern of toxicity for SBL 18-20 mg/dl in infants without hemolysis and/or other risk factors (such as extreme prematurity, hypoxia, hypercapnia, acidosis, sepsis, hyperosmolarity, etc.). Therefore, an aggressive approach to the treatment and/or prophylaxis of neonatal jaundice when SBL are below 20 or even 25 mg/dl is not justified on the basis of the present knowledge. This is particularly true when treatment includes phototherapy and/or exchange-transfusion which are associated with clinically significant complications and side effects. Guidelines for treatment of neonatal hyperbilirubinemia in full-term and preterm infants, with and without added complications and/or risk factors, are provided in the attempt of encouraging a more critical approach to neonatal jaundice, which is coherent with the data available in the literature and which should optimize the risk/benefit ratio.

Audiometric tests performed on 41 workers at a metal engineering factory producing tools for the wood manufacturing industry showed hearing loss at 6 kHz in 45.9% of the cases. A study was therefore carried out to check carefully the physical characteristics of the noise via statistical analysis and octave frequencies band analysis in real time. The measurements revealed higher noise levels at the high and medium high frequencies (3.15-6.3 Hz) both for impulsive and continuous noise. The results of the audiometric tests differed from those of a group of 50 workers employed in two different metal engineering factories, where the noise levels were similar but at medium-low frequencies, with no pure tones. In this group of subjects, hearing loss occurred at 6 kHz in 28% of the cases; the differences thus seemed to be related the particular physical characteristics of the noise levels measured in the first factory. The data are discussed against findings already reported in the literature, in relation to their prevention-related aspects and a more correct interpretation of the audiograms.

Thymic function in myasthenic patients was examined using two biochemical markers which specifically define a population of cortisone-sensitive cortical thymocytes. The enzymatic activities of terminal deoxynucleotidyl transferase (TdT) and adenosine deaminase (ADA) were determined in 13 samples. High contents of both enzymes were found in young patients. The enzymatic activities were easily detectable also in the oldest patients, despite the morphological involution and the decrease in TdT which are known to occur with age in the normal thymus. TdT and ADA-containing cells were almost completely depleted in all the 3 treated patients by the corticosteroid treatment which provides a non-surgical alternative to the elimination of this lymphoid population by thymectomy. The persistence of TdT and ADA activity in old age, and their inhibition by the corticosteroid treatment.

The incorporation of ATP on poly(A) primers catalyzed by poly(A) polymerase was investigated in normal and neoplastic lymphoid cells from animal and human sources. High levels of the enzyme were found in mouse thymus, in chicken bursa and thymus, as well as in neoplastic cells from patients affected by lymphoblastic and Burkitt's lymphomas. Low or very low quantities were found in peripheral blood lymphocytes, chronic lymphocytic leukemia cells, normal lymph nodes and solid lymphoid tissues of Hodgkin's disease. In general, the enzymatic content of neoplastic lymphoid cells reflected those of their normal counterpart. No effect of fasting or cortisone treatment on poly(A) polymerase in mouse spleen, thymus or liver was found. No particular relationships with B, T or non-T, non-B lineages were observed, but some relationship with DNA polymerase alpha was found. Therefore, it may be that poly(A) polymerase levels are related to the proliferative activity of the cellular populations.

The drug scene generally comprises the following four distinct categories of young people: neophytes, addicts who enjoy a high status vis-à-vis other addicts, multiple drug addicts, and non-addicted drug dealers. It has its own evolution, hierarchy, structure and criteria of success and failure. The members are required to conform to the established criteria. The integration of the young addict into the drug scene is not voluntary in the real sense of the word, for he is caught between the culture that he rejects and the pseudo-culture of the drug scene. To be accepted into the drug scene, the neophyte must furnish proof of his reliability, which often includes certain forms of criminal activities. The addict who has achieved a position of importance in the drug world serves as a role model for behaviour to the neophyte. In a more advanced phase of addiction, the personality of the addict and the social functions of the drug scene are overwhelmed by the psychoactive effects of the drug, and this process results in the social withdrawal of the addict. The life-style of addicts and the subculture they develop are largely influenced by the type of drug consumed. For example, it is possible to speak of a heroin subculture and a cocaine subculture. In time, every drug scene deteriorates so that it becomes fragmented into small groups, which is often caused by legal interventions or a massive influx of new addicts. The fragmentation of the drug scene is followed by an increase in multiple drug abuse, which often aggravates the medical and social problems of drug addicts.

To study the pathogenesis of Hodgkin's disease (HD), which today remains obscure, we have undertaken a combined experimental approach: determination of TdT and molecular analysis of rearrangements of immunoglobulin heavy chain (IgH), T-cell receptor (TCR) beta chain and the T-cell rearranging gamma (TRG) genes. TdT determination indicate would the presence of immature cells that are not detected in the normal lymphnode; molecular analysis of the rearrangements of these genes would reveal the presence of even a small monoclonal population of both T and B lineages in the lymphnodes. We believe that the combination of these two types of analysis can indicate whether an expanding lymphoid clone is responsible for this disease. TdT determination was negative in all 41 cases tested. Gene rearrangements were studied in 10 cases for IgH and TCR beta genes and in 5 cases for the TRG gene. No abnormal band beside the germ-line ones was detected in any of our cases, ruling out the presence of a minor neoplastic population. We can explain these results in at least three ways: first, the neoplastic population could represent less than 1% of the total, thus escaping detection by current techniques; second, the neoplastic population is not lymphoid in nature or is composed of mature cells that do not rearrange Ig and TCR genes and therefore belongs to a true non-B, non-T lineage; third, the pathogenesis of HD is completely different from that of non-Hodgkin's lymphomas (NHL) and does not involve the clonal expansion of a cell frozen at a particular maturative stage as is thought to happen in most NHL.

A follow-up study was planned to evaluate the frequency of the breast feeding babies in Rome and its district. 918 subsequently born babies were followed for 6 months. At 3 months of age only the 35,4% of them was still breast fed. We point out that babies born from spontaneous delivery present a higher frequency and a prolonged breast feeding statistically significant v/s babies born from cesarean section, and that the early initiation of breast feeding has a marked positive influence.

Adenosine deaminase (ADA) and terminal deoxynucleotidyl transferase (TdT) activities were determined on 97 biopsy specimens obtained from patients with non-neoplastic diseases (12 cases), Hodgkin (30 cases), and non-Hodgkin lymphomas (55 cases). Thirty additional cases were tested only for TdT. TdT was positive in 10 out of 13 lymphoblastic lymphomas (LL) examined and negative in all the other specimens, including the ten cases of the immunoblastic type. Levels of ADA above 350 U/mg of protein were found in 10 out of 12 LL tested, but not in any other specimen. The 3 TdT- LL had high contents of ADA. Therefore, all LL can be detected using both ADA and TdT markers. The 3 TdT- LL had a heterogeneous phenotype and their possible origin is discussed in view of the possibility that they constitute a rare entity distinct from the more common TdT+ LL. Very low levels of ADA (below 100 U/mg of protein) were found in chronic lymphocytic leukemia and immunocytoma, and in Burkitt's lymphoma. In other B-cell non-Hodgkin lymphomas, intermediate values between 100 and 350 U were often found, and this finding could be relevant to the different cellular origin of the various B-cell neoplasias. We conclude that ADA distribution is solid lymphoid tumors reflects the cellular origin of these neoplasias. Adenosine deaminase alone and in combination with TdT can be useful in the diagnosis and classification of childhood lymphomas in which the immature hystotypes predominate.

On the tandemly linked ribosomal genes of Xenopus laevis, the RNA polymerase transcribes past the 3' end of the 40S coding region and terminates at T3 just upstream of the gene promoter. The close proximity of T3 to the gene promoter, and the functional interdependence of these two elements, has led to the suggestion that polymerase terminating at T3 might be passed directly to the gene promoter. Such a mechanism might be necessary to maintain the characteristic high rate of transcription initiation seen on the ribosomal genes. We have performed a direct test of this model by introducing chain-terminating psoralen adducts into a circular plasmid containing a single gene promoter with its attendant T3 region upstream. We find that the psoralen adducts can completely prevent polymerase from traveling around the template circle (and thus prevent polymerase from approaching the promoter from upstream) without affecting the rate of transcription initiation at the gene promoter. This result suggests that recycling of polymerase from T3 to the promoter is not a significant mechanism in maintaining high initiation rates.

Serum lactate dehydrogenase (LDH) levels have been claimed as an independent prognostic factor in non-Hodgkin's lymphomas (NHL). In the present study, the intracellular and serum LDH levels in Hodgkin's (HD) and NHL were investigated. We found that among NHL, the histologic types of high-grade malignancy (lymphoblastic, immunoblastic and centroblastic), according to the Kiel classification, have a significantly higher intracellular (p less than 0.01) and serum (p less than 0.05) content of this enzyme than those of low-grade malignancy. This finding could explain in part the relation between high serum LDH levels and poor prognosis. It is also possible that the stage of the disease at the moment of the serum determination could be related to the serum LDH level, because a large tumor burden is likely to release more enzyme than a smaller one. However, we could not test this hypothesis because in our series there was ony one NHL patient with stage I or II. Serum LDH level could be a predictor of prognosis in NHL because of its relationship with more malignant histological types, and possibly with more advanced diseases.

Isolated nucleoli from exponentially growing microplasmodia of Physarum polycephalum were digested with micrococcal nuclease or DNAase I, or were photoreacted with trimethyl psoralen. In the coding region for the precursor of the ribosomal RNA, micrococcal nuclease and DNAase I digestions show predominantly a smear, and treatment with psoralen leads to a fairly continuous crosslinking of the DNA. All three assays are compatible with the absence of a typical nucleosomal array in most of the gene copies. In contrast, in the central non-transcribed spacer, except in the immediate 5'-flanking region, micrococcal nuclease and DNAase I digestions yield fragments that are multiples of a basic repeat, compatible with a nucleosomal packing of this region. The crosslinking pattern with psoralen confirms this conclusion. In addition, there are three sites over 400 base-pairs long that are inaccessible for psoralen crosslinking. Two of these sites have been mapped to the putative origins of replication. In the terminal non-transcribed spacer, except in the immediate 3'-flanking region, digestions with micrococcal nuclease and DNAase I give a smeared repeat. The crosslinking pattern after treatment with psoralen suggests that this region is packed in nucleosomes, except for about 900 base-pairs constituting the telomere regions of the linear extrachromosomal palindromic rDNA. Micrococcal nuclease digestion of the immediate 5'-flanking region shows a complete absence of any nucleosomal repeat, but digestion with DNAase I leads to a faint ten base-pair repeat. In contrast, in the 3'-flanking regions both nuclease assays indicate a chromatin structure similar to the coding region. Both flanking regions are unusual with respect to psoralen crosslinking, in that crosslinking is reduced both in chromatin and deproteinized DNA. On the basis of the known sequence-dependent psoralen crosslinking and the established sequences in these regions, crosslinking should be expected to occur. However, it does not and we therefore propose the presence of an unusual DNA conformation in these regions.