Exceptional characteristics of heterotetrameric (alpha 2 beta 2) E1p of the pyruvate dehydrogenase complex from Zymomonas mobilis: expression from an own promoter and a lipoyl domain in E1 beta.

In the pyruvate dehydrogenase complex (PDHC) of Zymomonas mobilis the beta subunit of the pyruvate dehydrogenase (E1p) as well as the acetyltransferase (E2p) contain an N-terminal lipoyl domain. Both lipoyl domains were acetylated in vitro using 2-14C-pyruvate as a substrate, demonstrating that both lipoyl domains can accept acetyl groups from the E1 component. As previously shown the structural genes (pdhA alpha beta, pdhB, lpd) encoding the pyruvate dehydrogenase complex of Z. mobilis are located in two distinct gene clusters, pdhA alpha beta and pdhB-orf2-lpd (U. Neveling et al. (1998) J. Bacteriol. 180, 1540-1548). Analysis of pdh gene expression using lacZ fusions revealed that the DNA fragments upstream of pdhA alpha, pdhB and lpd each have promoter activities. These pdh promoter activities were 7-30-fold higher in Z. mobilis than in Escherichia coli.

Gene and subunit organization of bacterial pyruvate dehydrogenase complexes.

Pyruvate dehydrogenase complexes of bacterial origin are compared with respect to subunit composition, organization of the corresponding genes, and the number and location of lipoyl domains. Special attention is given to two unusual examples of pyruvate dehydrogenase complexes, formed by Zymomonas mobilis and Thiobacillus ferrooxidans.

Purification of the pyruvate dehydrogenase multienzyme complex of Zymomonas mobilis and identification and sequence analysis of the corresponding genes.

The pyruvate dehydrogenase (PDH) complex of the gram-negative bacterium Zymomonas mobilis was purified to homogeneity. From 250 g of cells, we isolated 1 mg of PDH complex with a specific activity of 12.6 U/mg of protein. Analysis of subunit composition revealed a PDH (E1) consisting of the two subunits E1alpha (38 kDa) and E1beta (56 kDa), a dihydrolipoamide acetyltransferase (E2) of 48 kDa, and a lipoamide dehydrogenase (E3) of 50 kDa. The E2 core of the complex is arranged to form a pentagonal dodecahedron, as shown by electron microscopic images, resembling the quaternary structures of PDH complexes from gram-positive bacteria and eukaryotes. The PDH complex-encoding genes were identified by hybridization experiments and sequence analysis in two separate gene regions in the genome of Z. mobilis. The genes pdhAalpha (1,065 bp) and pdhAbeta (1,389 bp), encoding the E1alpha and E1beta subunits of the E1 component, were located downstream of the gene encoding enolase. The pdhB (1,323 bp) and lpd (1,401 bp) genes, encoding the E2 and E3 components, were identified in an unrelated gene region together with a 450-bp open reading frame (ORF) of unknown function in the order pdhB-ORF2-lpd. Highest similarities of the gene products of the pdhAalpha, pdhAbeta, and pdhB genes were found with the corresponding enzymes of Saccharomyces cerevisiae and other eukaryotes. Like the dihydrolipoamide acetyltransferases of S. cerevisiae and numerous other organisms, the product of the pdhB gene contains a single lipoyl domain. The E1beta subunit PDH was found to contain an amino-terminal lipoyl domain, a property which is unique among PDHs.

Deep juvenile xanthogranuloma: an unusual presentation.

Juvenile xanthogranuloma (JXG) is a disorder of histiocytes usually associated with cutaneous lesions. It may present a diagnostic dilemma in the absence of cutaneous lesions and when deeply located. Differentiation of JXG from other childhood histiocytosis syndromes, especially Langerhans' cell histiocytosis (LCH), is important. We describe an unusual case of deep JXG in a 27-month-old girl with multiple omental and peritoneal nodules presenting with ascites. Although a diagnosis of LCH was suspected clinically, the absence of Birbeck granules and S-100 protein and T6 antigen negativity, together with CD68 and factor XIIIa positivity, led us to a diagnosis of JXG. Physicians should be aware of the widening spectrum of manifestations of juvenile xanthogranuloma.

Alcohol pretreatment does not affect bupivacaine pharmacokinetics in the pig.

We investigated whether alcohol pretreatment sufficient to cause fatty liver change would affect the disposition of bupivacaine after i.v. administration in pigs. Twelve male pigs (22-26 kg) were randomly divided into two groups of six each. Group A received ethanol (1 g kg-1 day-1) via an intragastric tube for 16 days. Group D received an equal volume of isocaloric dextrose 44% in water for this period. On day 17, left internal jugular and carotid cannulae were placed under thiopentone anaesthesia. On recovery from anesthesia, a blood sample was taken for the determination of liver function indices and then bupivacaine hydrochloride (1.2 mg kg-1) was administered over one minute and samples for plasma bupivacaine analysis taken from the arterial cannulae over the next five hours. Right liver lobe biopsies were taken and animals were killed under general anaesthesia. Blind evaluation of liver biopsies confirmed fatty liver changes only in alcohol-pretreated livers. Despite this there were no differences in bupivacaine disposition and liver function indices between the two groups.

Human immunodeficiency virus infection and multilocular thymic cysts.

PURPOSE: Pathologic changes of the thymus, often seen in children with the human immunodeficiency virus (HIV), reflect direct invasion by the virus, followed by involution of the gland. A previously unknown form of thymic response to HIV infection, that of a multilocular thymic cyst, is reported. MATERIALS AND METHODS: Findings were examined in three HIV-positive patients, two children and one adult first seen with large thymic masses. RESULTS: All three had large, septate low-attenuation areas at computed tomography consistent with multilocular thymic cysts. The cystic nature of the lesions was confirmed with magnetic resonance imaging in two. Histopathologic examination, performed in two instances, helped establish the diagnosis. All patients remained in clinically stable condition. They all had parotid gland enlargement and lymphocytic interstitial pneumonia. CONCLUSION: Multilocular thymic cysts are probably another manifestation of the diffuse infiltrative lymphocytosis syndrome, usually associated with a milder course of acquired immunodeficiency syndrome.

Distinct and differently regulated Mo-dependent nitrogen-fixing systems evolved for heterocysts and vegetative cells of Anabaena variabilis ATCC 29413: characterization of the fdxH1/2 gene regions as part of the nif1/2 gene clusters.

Two different fdxH genes (fdxH1, fdxH2) have been isolated from the nitrogen-fixing, heterocyst-forming cyanobacterium Anabaena variabilis ATCC 29413. They are part of two different nif gene clusters, nif1 and nif2. fdxH1 encodes the [2Fe-2S] ferredoxin that is known as the direct electron donor to nitrogenase in heterocysts, and is very similar to FdxH from Anabaena sp. PCC 7120. FdxH2 has more residues in common and shares its oxygen sensitivity with the single FdxH from the non-heterocystous, filamentous cyanobacterium Plectonema boryanum PCC 73110. The latter expresses nitrogenase early (< or = 3-4h) after nitrogen depletion in vegetative cells and exclusively under anaerobic conditions. fdxH2 and the nif2 genes of Anabaena 29413 are also transcribed < or = 4 h after onset of nitrogen-stepdown, exclusively under anaerobic growth conditions and long before functional heterocysts appear. At this time, no fdxH1 and nif1 gene transcription was observed. It occurred later and was associated with nitrogen fixation under aerobic conditions, i.e. within heterocysts. fdxH2 and nifHDK2 were not transcribed during aerobic, nitrogen-fixing growth. In addition, neither was an fdxH2-type gene found nor an anaerobically and early inducible Nif2 system detectable in Anabaena 7120. These data reveal that in filamentous cyanobacteria two different Nif systems have evolved based on molybdenum nitrogenases. It is concluded that a Nif2-type system operates in vegetative cells of non-heterocystous and some, but not all, heterocyst-forming filamentous cyanobacteria. It is environmentally regulated by the levels of both oxygen and combined nitrogen in the habitat. To simultaneously allow for oxygen-evolving photosynthesis and oxygen-sensitive nitrogen fixation, the Nif1-type system probably branched from an ancestral Nif2-type system and has evolved for an exclusive operation within heterocysts. Accordingly, its expression has become an obligate late event in the developmental programme of heterocyst differentiation, irrespective of aerobic or anaerobic growth conditions.

Effect of lidocaine on in vivo hepatic function.

Lidocaine is administered to assess donor or recipient liver function during hepatic transplantation. This study was performed to determine whether lidocaine administered at a constant concentration affected hepatic function or had demonstrable effects on hepatocellular ultrastructure. Fourteen pigs were randomly allocated to receive either a two-stage infusion of lidocaine hydrochloride or of saline. Transhepatic blood samples were taken and ultrasonic portal venous and hepatic arterial blood flow readings made on animals anesthetized with isoflurane in nitrous oxide. Liver biopsies were taken for histological analysis and determination of adenine nucleotide status prior to and after 2 hr of the two-stage infusion. A mean systemic constant plasma lidocaine concentration of 5.9 micrograms/ml was achieved during the second hour of infusion. There were no differences between the two groups in a large number of indices of hepatic function and plasma composition prior to and during the second hour of the respective infusions. Hepatic blood flow was also similar at these times. On histological examination there were no electron microscopic changes that could be specifically attributed to the administration of lidocaine. However, there were progressive changes with time. This study suggests that in anesthetized pigs a constant lidocaine concentration of about 6 micrograms/ml has no detrimental effect on hepatic function. Progressive hepatic ultrastructural changes occurred that could not be attributed to the administration of lidocaine. These may be the result of anesthetic administered or the surgery performed.

Acquired aganglionosis following surgery for Hirschsprung's disease: a report of five cases during a 33-year experience with pull-through procedures.

Acquired Hirschsprung's disease is a rare and controversial form of colonic aganglionosis. Little is known about its aetiology and pathogenesis. We report five cases encountered amongst 173 long-term follow-up patients treated for classical Hirschsprung's disease between 1957 and 1990 at the Red Cross Children's Hospital, Cape Town, and review the current literature. The clinical and pathological findings of the cases have been studied to explore possible aetiological mechanisms. Our cases, like most of those previously reported, developed obstructive symptoms and acquired aganglionosis in pulled-through bowel which had been previously confirmed as ganglionated. Two patients had histological evidence of hyaline fibrosis of blood vessels in the segment of bowel with acquired aganglionosis. Such fibrosis and other features attributable to regional hypoxia were not found in the other three cases. It is suggested that ischaemia with fibrosis may have a pathogenetic role in some, but not all, cases of acquired Hirschsprung's disease. A plea is made for patients developing recurrent symptoms of Hirschsprung's disease, after adequate surgical correction, to be fully studied with repeated sequential biopsies in order to gain a better understanding of the entity.

Fatal meningococcal disease in childhood: an autopsy study of 86 cases.

A retrospective study of the pathology in 86 consecutive autopsies of fatal meningococcal infection in children, performed at the Red Cross War Memorial Children's Hospital during the 19-year period from 1973 to 1991, was undertaken. The most prominent pathological changes found at autopsy were those of an overwhelming bacterial infection with evidence of disseminated intravascular coagulopathy in many organs of the body. The skin, adrenal glands and central nervous system were most commonly involved. Acute myocarditis occurred in 23 cases (27%) and was diagnosed almost exclusively histologically. In only one case was it diagnosed clinically. In addition, the nutritional status and the morphological expression of immune reactivity of our hospital population was better than expected.