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1 A number of cohort and case-control studies have shown clear, dose-related associations between maternal smoking and infant death. The strongest relationships were found when the mother smoked during pregnancy as well as postnatally. Maternal smoking during pregnancy increases the risk for SIDS in most studies, whereas it appears that maternal smoking only postnatally also leads to an increase in risk. In addition, smoking only by the father appears to increase the risk for SIDS, but this is not seen in all studies. 2 Exposure of children to environmental tobacco smoke (ETS) increases the risk of having night cough and respiratory infections (bronchitis, bronchiolitis, pneumonia), especially during the first 2 years of life. An increased risk is also seen in studies not distinguishing between upper and lower respiratory diagnoses. Long-term breastfeeding may have a protective effect on ETS-increased risk of lower respiratory tract illness. One study of older children reports that ETS combined with allergy increased the risk of acute respiratory tract infections above that due to ETS alone. 3 The number of new episodes and duration of otitis media with effusion in young children is positively correlated with ETS exposure. Especially infants with lower birth weights had a high risk of recurrent otitis media during the first year of life when the mother was a heavy smoker. 4 Passive smoking has been reported as a risk factor in meningococcal disease and tuberculosis in young children. [ABSTRACT FROM AUTHOR]

The effect of different retinoids on morphological transformation and anchorage independent growth of Syrian hamster embryo cells has been studied. Retinoic acid and its derivatives were found to induce morphological transformation of hamster embryo cells, and to synergistically increase the transformation frequency when exposed in combination with benzo[a]pyrene. The increase was maintained when the cells were sequentially exposed to benzo[a]pyrene and retinoids in a similar way as observed for tumor promoting phorbol esters. At the same time retinoids were found to strongly decrease anchorage independent growth of a hamster embryo cell line. The present results support previous findings indicating that retinoids may have an enhancing effect on the early stages in carcinogenesis, and an inhibitory effect on the later stages. [ABSTRACT FROM PUBLISHER]

The possible role of blocked intercellular communication in the process of cell transformation has been studied with Syrian hamster embryo cell lines which are sensitive or resistant to TPA-induced enhancement of morphological transformation. Both the TPA-sensitive () and the TPA-resistant ( and ) cell lines showed gap-junctional communication when measured by a dye-transfer method. However, TPA inhibited the communication only in TPA-sensitive cells, and not in TPA-resistant cells. These results are consistent with the idea that blocked intercellular communication is involved in a late stage of cell transformation and/or expression of the transformed phenotype. [ABSTRACT FROM PUBLISHER]

The mechanism of the activation of rabbit liver fructose 1,6-diphosphatase by sulfhydryl reagents has been studied. Per sulfhydryl group modified, different sulfhydryl reagents stimulated the enzyme to different extents. Disulfides increased the enzyme activity by 80-90% per sulfhydryl group blocked, while the value for the other reagents tested was 15-25%. With all reagents used the stimulation increased linearly with SH blocking until 5-6 sulfhydryl groups had been modified. Further blocking of SH groups led to progressive loss of enzyme activity. Enzymes which had been stimulated by blocking of 5-6 SH groups by 5,5′-dithio-bis(2-nitro- benzoic acid) or para-chloromercuribenzoate had properties different from the native enzyme. The inhibition by AMP and by substrate was increased. unlike the native enzyme, the disulfide modified enzyme precipitated at pH below 4. The remaining free sulfhydryl groups in the two modified enzymes showed different reactivities, and blocking of these SH groups with parachloromercuribenzoate reduced the activity to different extents in the two cases. The data indicate that the stimulation of fructose-1,6-diphosphatase by blocking of sulfhydryl groups is due to conformational changes of the protein. Inhibition of the enzyme by AMP was found to increase with increasing substrate concentration. It is suggested that this may be of significance in the regulatory function of the enzyme. [ABSTRACT FROM AUTHOR]

The effect of acetylation and of sulfhydryl blocking agents on phosphofructokinase from rabbit muscle has been studied. Treatment of phosphofructokinase with N-acetylimidazole led to rapid loss of its allosteric function, as measured by the ability of AMP to stimulate the ATP-inhibited enzyme. The catalytic activity was far less sensitive to acetylation. The loss of allosteric function on acetylation was due to the fact that the modified enzyme was insensitive to ATP inhibition. The presence of ATP during acetylation prevented the loss of allosteric activity. The results indicate that tyrosine residues may play an important role in the inhibitory binding sites of ATP. Incubation of phosphofructokinase with a 50-fold excess of para-chloromercuribenzoate led to complete inactivation of the enzyme, an effect which could be reversed by the addition of excess thiol. Sulfhydryl blocking had no effect on the ability of AMP to stimulate the ATP- inhibited enzyme. The results confirm that sulfhydryl groups are closely associated with the catalytic site of phosphofructokinase, and demonstrate that they are not involved in the inhibition of the enzyme by ATP and its reversal by AMP. [ABSTRACT FROM AUTHOR]

Determination of the enzyme 6-phosphogluconate dehydrogenase in vaginal fluid has previously been suggested as a screening test for uterine cancer. In an attempt to resolve the large discrepancies in the results reported in the literature, some of the factors influencing the stability of the enzyme have been studied. It is demonstrated that the conditions under which the vaginal fluid is handled prior to the assay influence the enzyme activity to a very large extent. Under conditions minimizing denaturation of the enzyme, a considerable activity is found in most women. Evidence is presented that in vaginal fluid from women with uterine cancer the enzyme is more stable than in samples from healthy women. The large variations in the results with the conditions under which the samples are handled render measurement of 6-phosphogluconate dehydrogenase in vaginal fluid an unsuitable method for mass screening of uterine cancer. [ABSTRACT FROM AUTHOR]

Equations are derived without the use of steady state assumptions for the inactivation of enzymes in dilute aqueous solution by ionizing radiation. It is shown that when the exposure times are shorter than the mean life0time of the water radicals, as is frequently the case in experiments involving pulsed radiation, the main part of the enzyme inactivation occurs after the end of the exposure. The total inactivation under such conditions can be described by the same equation as that developed earlier for protracted irradiation. The recent claim that the absolute rate constant for the inactivation of the enzyme can be determined directly from studies of the initial part of the dose inactivation curve, is not supported by the present study. The validity of steady state approximations in the treatment of enzyme inactivation in dilute aqueous solution by ionizing radiation is examined. It is concluded that the requirements for the use of this approximation are satisfied when the exposure time exceeds greatly the life-time of water radicals, as is the case in most enzyme experiments. [ABSTRACT FROM AUTHOR]