fimA-folD genes linkage in Salmonella identifies a putative junctional site of chromosomal rearrangement in the enterobacterial genome

Abstract Analysis of the Salmonella chromosomal region located upstream of the fimA gene (coding for the major type 1 fimbrial subunit) showed a close linkage of this gene to the folD gene (coding for the enzyme 5,10-methylenetetrahydrofolate dehydrogenase/5, 10-methenyltetrahydrofolate cyclohydrolase), indicating that the fim gene cluster of Salmonella , unlike that of Escherichia coli , has no regulatory genes located upstream of fimA and apparently terminates with this gene. The respective locations of the fim and folD genes in the E. coli and Salmonella genetic maps suggests that the fimA-folD intergenic region of Salmonella encompasses a junctional site of a genetic rearrangement that probably originated from the different chromosomal location of the fim genes in these species.     

Urinary cytologic abnormalities in bone marrow transplant recipients of cyclosporin

The role of urinary cytology in the early diagnosis of cyclosporin nephrotoxicity was studied in 20 bone marrow transplant recipients. There was an evident cyclosporin cytopathy in 35% of bone marrow transplant recipients examined, consisting mainly of degenerative and necrotic abnormalities in cells of the proximal convoluted tubules seen in urinary samples. These findings regressed to normal after reduction of the cyclosporin dose. Urinary cytology proved to be a useful method for the early diagnosis of cyclosporin nephrotoxicity.     

Differences between arterial and mixed venous levels of plasma hydroperoxides following major thoracic and abdominal operations

Fatty acid hydroperoxides in the plasma of 18 patients who were undergoing normal postoperative periods following major thoracic or abdominal operations were measured by using a sensitive assay based upon the activation of the cyclooxygenase activity of prostaglandin H synthase. Following major thoracic operations of nine patients, the mean difference between the arterial (0.49 ± 0.13 μM, mean ± S.E.M.) and mixed venous (−0.09 ± 0.12 μM) level of hydroperoxide was 0.58 ± 0.13 μM (p < 0.01). In marked contrast to this result, major abdominal operations of nine patients led to a mean difference between the arterial (−0.19 ± 0.16 μM) and mixed venous (0.46 ± 0.08 μM) hydroperoxide levels of −0.65 ± 0.17 μM (p < 0.01). Both pulmonary and intraabdominal tissues appear capable of generating significant amounts of fatty acid hydroperoxide in response to standard surgical procedures. The A-MV differences suggest that the blood-borne hydroperoxides were rapidly cleared from the circulation by tissue capillary beds.     

Photodynamic inactivation of red cell uroporphyrinogen decarboxylase by porphyrins

The effects of light and porphyrins on the activity of red cell uroporphyrinogen decarboxylase were studied. Photoinactivation of uroporphyrinogen decarboxylase was dependent on uroporphyrin concentration, irradiation time and temperature. Using 40 W/m2 of UV light intensity, 40-45% decreased activity was produced with 200 microM uroporphyrin I, at 37 degrees C and after 2 hr of illumination. It has been demonstrated that porphyrins photoinactivate uroporphyrinogen decarboxylase and a mechanism for this action in relation to skin lesions is proposed.     

Monolayer black membranes from bipolar lipids of archaebacteria and their temperature-induced structural changes

The membrane of Caldariella acidophila, an extreme thermophilic archaebacterium, is characterized by unusual bipolar complex lipids. They consist of two nonequivalent polar heads, linked by a C40 alkylic component. The molecular organization of these lipids in the plasma membrane is still a matter of study. In this paper, we present current-voltage measurements on artificial bipolar lipid membranes, indicating that molecules are indeed organized as a covalently bound bilayer, in which each molecule is completely stretched and spans its entire thickness. Furthermore, conformational transitions of these artificial membranes (which could be formed only above 70 degrees C from a lipid/squalene dispersion) are analyzed in the 80 to 15 degrees C temperature range. Abrupt variations in capacitance and valinomycin-induced conductance seem to indicate the occurrence of at least two structural changes. Measurements are also extended to different solvent systems. Results are consistent with the picture of a monolayer bipolar lipid membrane in which few solvent molecules align themselves parallel to the lipophilic chains. The amount of solvent as well as the temperature at which conformational transitions occur, depend on the solvent system in which the lipid is dispersed.     

COMPARISON OF THE BEHAVIOUR OF A SOLUBLE AND A MEMBRANE-BOUND ENZYME IN TRANSECTED PERIPHERAL NERVES

Phosphoglucoisomerase (PGI), a soluble enzyme, and AChE, a membrane-bound enzyme were studied in transected peroneal nerves of dog and in isolated segments of these nerves. Although activities of both enzymes increased at the ends of transected nerves, marked differences in their behaviour were observed. The increment in AChE activity was much sharper than that of PGI and continued to grow with time whereas the increase in PGI developed fully within the initial hours after transection and did not change thereafter. In an isolated nerve segment AChE accumulated at both ends with a concomitant decrease in the middle part, whereas changes in PGI activity appeared only in the terminal parts, the rest of the nerve remaining at the normal level. The terminal increase of PGI did not, contrary to that of AChE, depend on the length of the isolated segment. The changes in PGI activity may be features of a local peritraumatic reaction whereas those of AChE indicate involvement of the whole segment along which the enzyme containing organelles are transported.