Mutations of ANT1, Twinkle, and POLG1 in sporadic progressive external ophthalmoplegia (PEO)

To verify the impact of mutations in ANT1, Twinkle, and POLG1 genes in sporadic progressive external ophthalmoplegia associated with multiple mitochondrial DNA (mtDNA) deletions, DNA samples from 15 Italian and 12 British patients were screened. Mutations in ANT1 were found in one patient, in Twinkle in two patients, and in POLG1 in seven patients. Irrespective of the inheritance mode, screening of these genes should be performed in all patients with progressive external ophthalmoplegia with multiple mtDNA deletions.

Novel heteroplasmic mtDNA mutation in a family with heterogeneous clinical presentations

The protean manifestations of a novel maternally inherited point mutation of the mitochondrial genome are reported. The proband showed isolated, spastic paraparesis. A brother, who had suffered from a multisystem progressive disorder, ultimately died of cardiomyopathy. Another brother is healthy. The proband's mother showed truncal ataxia, dysarthria, severe hearing loss, mental regression, ptosis, ophthalmoparesis, distal cyclones, and diabetes mellitus. A muscle biopsy performed in the proband failed to show the morphological abnormalities typical of mitochondrial disorders; the activities of respiratory chain complexes were normal. However, complex I and IV activities were low in the muscle homogenate of the affected mother and brother. Sequence analysis of mtDNA showed a heteroplasmic mutation of the tRNA(Ile) gene (G4284A). The mutation load was approximately 55%, 80%, and 90% in the muscle mtDNA of the proband, his mother, and his affected brother, respectively. Mutation was undetected in the healthy brother, as well as in 100 control samples. Several cybrid clones containing homoplasmic mutant mtDNA from the proband showed significant reductions of complex IV activity and maximum oxygen consumption rate, compared with homoplasmic wild-type clones derived from the same subject.

New splicing-site mutations in the SURF1 gene in Leigh syndrome patients

The gene SURF1 encodes a factor involved in the biogenesis of cytochrome c oxidase, the last complex in the respiratory chain. Mutations of the SURF1 gene result in Leigh syndrome and severe cytochrome c oxidase deficiency. Analysis of seven unrelated patients with cytochrome c oxidase deficiency and typical Leigh syndrome revealed different SURF1 mutations in four of them. Only these four cases had associated demyelinating neuropathy. Three mutations were novel splicing-site mutations that lead to the excision of exon 6. Two different novel heterozygous mutations were found at the same guanine residue at the donor splice site of intron 6; one was a deletion, whereas the other was a transition [588+1G>A]. The third novel splicing-site mutation was a homozygous [516-2_516-1delAG] in intron 5. One patient only had a homozygous polymorphism in the middle of the intron 8 [835+25C>T]. Western blot analysis showed that Surf1 protein was absent in all four patients harboring mutations. Our studies confirm that the SURF1 gene is an important nuclear gene involved in the cytochrome c oxidase deficiency. We also show that Surf1 protein is not implicated in the assembly of other respiratory chain complexes or the pyruvate dehydrogenase complex.

Molecular characterization of HLA class I in Colombians carrying HLA-A2: high allelic diversity and frequency of heterozygotes at the HLA-B locus

Polymerase chain reaction using sequence-specific oligonucleotide probes (PCR-SSOP) typing was used to analyze HLA class I A, B and C alleles in three different Colombian populations. Fifty-nine samples were from Hispano-American Mestizos living in the urban areas of Cali (referred to here as Aso population). Forty-four and thirty samples were from the African Black populations of Zacarias (Zac) and Punta Soldado (PS), respectively. Samples were selected for expression of HLA-A2 by monoclonal antibody staining and allele-specific hybridization, and their HLA-A2 subtype distribution has been reported previously. Although only a limited number of samples was analyzed, the data suggest the existence of a remarkable degree of HLA class I polymorphism in the populations studied, with representatives of most serological classes. Despite their common African origin, the populations Zac and PS, both resident in malaria endemic regions, showed some striking differences in allelic distribution for all three class I loci. Furthermore, the samples from Aso and PS, but not Zac, showed a low percentage of blank alleles at the HLA-B locus (0 and 0.4%, respectively), suggesting the possibility of a heterozygote advantage for HLA-B alleles in Colombian populations.

[Pre-surgical medical therapy of hyperthyroidism]

The Authors analyze the use and the efficacy of antithyroidal drugs administered to the patients affected by hyperthyroidism, that must undergo thyroidectomy. The aim is that the patients arrive to the operation in euthyroidism: this is very important to avoid the complications that can occur during or just after the thyroidectomy. They believe that till today the most effective treatment of hyperthyroidism before thyroidectomy is based on the use of thyonamide and iodine. In case of intolerance to these drugs or if it is necessary an emergency thyroidectomy or in case of a low compliance of the patient, there is the possibility to use different therapeutic approaches with beta-blockers or betametasone plus iopanoic acid and propranolol administered together for a few days. As concerning the possible complications that can occur during or after the thyroidectomy, the Authors analyze in particular the thyrotoxicosis and the "hungry bone" syndrome.

Drug-induced cholestasis. Clinical contribution

We described two cases of drug-induced hepatitis: in both cases we recognised a pathogenesis based on hypersensivity mechanism. The first case, determined by naproxen, presented a serious cholestatic jaundice and histologic pattern due to ductular cholestasis without any inflammatory reaction. The second case, by a-metildopa, was characterized by spread necrosis of liver cells and peri-portal flogistic infiltrated. This chapter of modern epatology is becoming more and more important, because of both the opportunity of studyng physiopathologica mechanism and the increasing morbidity. The peculiarity of these cases was due not only to the morbidity, but also to the seriousnes of clinical symptoms which involved problems of early differential diagnosis and of attentive follow-up.

[Silent myocardial ischemia. Physiopathologic, clinical, and therapeutic considerations and review of the literature]

The need for a modern methodological approach based on recent acquisitions concerning pathophysiology, diagnostics, and therapy of silent ischemic heart disease, as well as the need to establish criteria for prognostic evaluation have prompted the authors to reexamine the subject in light of their own experience and of the current literature.

[Sarcoidosis with pulmonary abscess caused by emerging microorganisms]

The association sarcoidosis-lung abscess due to emerging microorganisms-mycetoma has prompted the authors to report the above clinical case which is interesting in view of the rarity of the disease and of its infective complications. The authors also review the literature on the subject.

Measurement of the Leakage of CO2 from Bundle-Sheath Cells of Leaves during C4 Photosynthesis

During C4 photosynthesis, CO2 is released in bundle-sheath cells by decarboxylation of C4 acids and then refixed via ribulose-1,5-bisphosphate carboxylase. In this study we examined the efficiency of this process by determining the proportion of the released CO2 that diffuses back to mesophyll cells instead of being refixed. This leak of CO2 was assessed by determining the amount of 14CO2 released from leaves during a chase in high [12CO2] following a 70-s pulse in 14CO2. A computer-based analysis of the time-course curve for 14CO2 release indicated a first-order process and provided an estimate of the initial velocity of 14CO2 release from leaves. From this value and the net rate of photosynthesis determined from the 14CO2 fixed in the pulse, the CO2 leak rate from bundle-sheath cells (expressed as a percentage of the rate of CO2 production from C4 acids) could be deduced. For nine species of Gramineae representing the different subgroups of C4 plants and two NAD-malic enzyme-type dicotyledonous species, the CO2 leak ranged between 8 and 14%. However, very high CO2 leak rates (averaging about 27%) were recorded for two NADP-malic enzyme-type dicotyledonous species of Flaveria. The results are discussed in terms of the efficiency of C4 photosynthesis and observed quantum yields.

[Eosinophilic gastroenteritis. A case with predominant involvement of mucosal and muscular layers]

Eosinophilic gastroenteritis is an uncommon disease of unknown aetiology, whose distinctive features are eosinophilia in peripheral blood and eosinophilic infiltration of the bowel wall. Its clinical course shows recurrent crises, even after a period of years, of symptoms that underline the predominant involvement of mucosal, muscular or subserosal layers of the bowel wall. The prognosis of the disease is essentially benign and pharmacologic therapy is not always necessary. A case with predominant involvement of both muscular and mucosal layers is described.

[Rhinocerebral mucormycosis in type 2 diabetes mellitus. Description of a clinical case with favorable outcome]

The case is reported of a 70-year-old man with decompensated non-acidotic type-2 diabetes mellitus and with rhinocerebral mucormycosis, manifested by inflammatory infiltration of the left nasal, paranasal, maxillary, and orbital bone structures with left ophthalmoplegia. The patient was cured after amphotericin B treatment (total dose 2.7 g) and 30 sessions of hyperbaric oxygen (2.8 atmospheres). Cure was confirmed by follow-up over more than 2 years. It is concluded that rhinocerebral mucormycosis must be treated, in addition to control of predisposing factors, and especially by restoring endocrine-metabolic balance, by adequate surgical revision, with specific high-dose amphotericin B treatment and adjunctive hyperbaric oxygen. Further studies are desirable in order to define the advantages of these therapeutic measures.

Photosynthesis in Phosphoenolpyruvate carboxykinase-type C4 plants: mechanism and regulation of C4 acid decarboxylation in bundle sheath cells

The mechanism and regulation of C4 acid decarboxylation in phosphoenolpyruvate (PEP) carboxykinase-type C4 plants was examined in isolated bundle sheath cell strands. These cells decarboxylated added oxaloacetate to PEP at rates exceeding 2.5 mumol min-1 mg-1 chlorophyll when ATP was added. This requirement for ATP could be replaced by malate plus ADP; under these conditions this cytosol-located decarboxylation of oxaloacetate via PEP carboxykinase was sustained by respiratory ATP. It was confirmed that respiratory ATP production was linked primarily to the oxidative decarboxylation of malate via NAD malic enzyme. This process, measured as pyruvate production, was highly dependent on Pi. Besides being required to generate ATP, Pi had a second role which was probably associated with the transport of malate into mitochondria. Maximum rates of malate decarboxylation via NAD malic enzyme substantially exceeded the minimum rates necessary for providing ATP for cytosolic oxaloacetate decarboxylation. When malate was added with oxaloacetate, ADP and Pi rates of malate decarboxylation of between 3 and 4 mumol min-1 mg-1 chlorophyll were recorded. About half of this activity was sustained by the reoxidation of NADH coupled to reduction of oxaloacetate via malate dehydrogenase. When malate was added without oxaloacetic acid, respiration by these bundle sheath cells was stoichiometrically linked with the oxidation of malate to pyruvate. This malate-dependent respiration was stimulated by adding ADP or phosphorylation uncouplers; it was not significantly inhibited by including oxaloacetate. Possible mechanisms of regulation of the partitioning of C4 acid decarboxylation between PEP carboxykinase in the cytosol and mitochondrial NAD malic enzyme are discussed.

A procedure for the purification of thioredoxin-m from leaves of the C4 plant Zea mays

A simple four-step procedure for the purification of thioredoxin-m from Zea mays leaves is described. The procedure provides pure protein with recoveries of 20-25%. This thioredoxin mediates in the regulation of NADP-malate dehydrogenase involved in photosynthesis in C4 plants.

[Scrofula in an elderly woman. A clinical case]

The case is described of an elderly woman with scrofula. The peculiarity of this case consisted in the comparative rarity of primary tubercular lymphadenopathy (a pathology that in the past used to be common in poor socioeconomic conditions) even considering the present renewed diffusion of tuberculosis; especially as this elderly patient had no previous history of tubercular infection.

Bilevel disulfide group reduction in the activation of c(4) leaf nicotinamide adenine dinucleotide phosphate-malate dehydrogenase

The time course of thioredoxin-mediated reductive activation of isolated Zea mays nicotinamide adenine dinucleotide phosphatemalate dehydrogenase is highly sigmoidal in nature. We examined the factors affecting these kinetics, including the thiol-disulfide status of unactivated and activated forms of the enzyme. The maximum steady rate of activation was increased, and the length of the lag in activation decreased, as the concentrations of thioredoxin-m, dithiothreitol, and KCl were increased. The lag in activation (sigmoidicity) was eliminated by preincubating the unactivated enzyme with 100 mm 2-mercaptoethanol; this pretreatment did not activate the enzyme. Unactivated nicotinamide adenine dinucleotide phosphate-malate dehydrogenase was found to contain approximately two SH groups per subunit, increasing to about four SH per subunit after pretreatment with 2-mercaptoethanol and six SH per subunit after activation by incubating the enzyme with dithiothreitol. We suggest that reduction of one particular higher redox potential disulfide group in unactivated nicotinamide adenine dinucleotide phosphate-malate dehydrogenase facilitates the subsequent reduction of the critical S-S group (regulatory S-S) necessary to generate the active form of the enzyme.

[Micropolyarteritis. The modern nosographic picture and a discussion of a clinical case]

Having observed a patient presenting micropolyarteritis with necrotic skin lesions, hypertension and renal injury, the authors had the opportunity to define more closely a disease that only recently has been recognized as a separate nosological entity within the vast and as yet not fully understood field of arterial disorders. In addition, recent literature on the subject is critically reviewed.

Amino Acid Sequence and Molecular Weight of Native NADP Malate Dehydrogenase from the C(4) Plant Zea mays

N-terminus amino acid analysis of purified corn (Zea mays) NADP malate dehydrogenase showed that the mature protein begins at serine-41 of the preprotein sequence and not threonine-58 as previously concluded; therefore, the transit peptide consists of 40 amino acids. The theoretical molecular weight of the mature subunit protein (392 amino acids) is 42,564, agreeing with an experimental value of about 43,000. The molecular weight of the native unactivated (dark form) and activated (light form) of NADP malate dehydrogenase, determined by analytical ultracentrifugation analysis, was about 84,000, indicating that both forms are dimers. However, conventional and high performance liquid chromatography gel filtration procedures indicated apparent molecular weights of about 110,000 to 120,000 for the unactivated native enzyme and about 143,000 to 150,000 for the active enzyme; in these cases, the molecular weight may be overestimated due to the effect of an unusual molecular conformation on the mobility of the enzyme.

Regulation of C4 photosynthesis: modulation of mitochondrial NAD-malic enzyme by adenylates

Effects of adenylates on the activity of mitochondrial NAD-malic enzyme from NAD-malic-enzyme (NAD-ME)-type and phosphoenolpyruvate-carboxykinase-(PKC)-type C4 plants are examined. At physiological concentrations, ATP, ADP, and AMP all inhibit the enzyme from Atriplex spongiosa and Panicum miliaceum (NAD-ME-type plants), with ATP the most inhibitory species. The degree of inhibition is greater with subsaturating levels of activator, malate, and Mn2+. NAD-malic enzyme from Urochloa panicoides (PCK-type) is activated by ATP (up to 10-fold) and inhibited by ADP and AMP. These effects are discussed in relation to regulation of C4 photosynthesis.

[New prospects in the therapeutic use of somatostatin and its derivatives]

The discovery and subsequent clinical application of somatostatine, a polypeptide neurohormone of 14 amino acids, and of its analogs, opens a novel chapter of neuroendocrinology that is still in full evolution and to a large extent unknown. The isolation of an octapeptide, a selective somatostatine analog, permits to prolong its action, in fact it has a halflife of about 140 min in old subjects and about 100 min. in the young. Thanks to its excellent tolerability, the synthetic hormone can be usefully applied in the treatment of acromegaly, gigantism and hypersomatotropinemic conditions in general, and even in other clinical branches, such as treatment of esophageal hemorrhage due to the rupture of varices in liver cirrhosis or to erosion of gastric blood vessels in patients suffering from peptic ulcer disease.

C4 acid decarboxylation and photosynthesis in bundle sheath cells of NAD-malic enzyme-type C4 plants: mechanism and the role of malate and orthophosphate

The mechanism and possible regulation of C4 acid decarboxylation in NAD-malic enzyme-type C4 plants was studied using isolated bundle sheath cells and mitochondria from Panicum miliaceum. Rates of C4 acid-dependent photosynthetic O2 evolution equalled those observed with saturating NaHCO3; the rates ranged from 3 to 5 mumol min-1 (mg chlorophyll)-1. C4 acid-dependent O2 evolution required the addition of aspartate and 2-oxoglutarate (as a source of oxaloacetate) and also malate and orthophosphate. C4 acid decarboxylation by both isolated cells and mitochondria, measured as pyruvate production, also required all four of these components. The scheme previously proposed to account for aspartate decarboxylation in NAD-malic enzyme-type C4 plants does not envisage a role for externally derived malate. However, the mandatory requirement for malate (with orthophosphate), together with the observation that C4 acid decarboxylation is blocked by an inhibitor of the mitochondrial dicarboxylate transporter, suggests that a net flux of malate from outside the mitochondria is required to sustain this process. Arsenate was found to substitute for orthophosphate favoring a role for orthophosphate in malate transport rather than a metabolic one. The results are discussed in terms of likely mitochondrial metabolite transport mechanisms and regulation of the C4 acid decarboxylation process.

Photosynthesis in phosphoenolpyruvate carboxykinase-type C4 plants: activity and role of mitochondria in bundle sheath cells

Mitochondria from bundle sheath cells of the phosphoenolpyruvate carboxykinase-type C4 species Urochloa panicoides were shown to have metabolic properties consistent with a role in C4 photosynthesis predicted from earlier studies. The rate of O2 uptake in response to added malate plus ADP was at least five times the activity observed with NADH, glycine, or succinate. With malate plus ADP the O2 uptake rate averaged about 150 nmol O2 min-1 mg-1 protein, equivalent to about 0.6 mumol min-1 mg-1 of extracted chlorophyll. About half of this activity was apparently phosphorylation-linked with ADP/O2 ratios of about 4. Studies with electron transport inhibitors suggested that about 65% of this malate oxidation is cytochrome oxidase-terminated with a minor component mediated via the alternative oxidase. These mitochondria supported rapid rates of pyruvate production from malate and this activity was also stimulated by ADP but blocked by inhibitors of electron transport. Adding oxaloacetate increased pyruvate production but inhibited O2 uptake. The results were consistent with the notion that in this subgroup of C4 species mitochondrial-located NAD malic enzyme contributes substantially to total C4 acid decarboxylation. This enzyme is apparently also the primary source of NADH necessary to generate the ATP required for phosphoenolpyruvate carboxykinase-mediated oxaloacetate decarboxylation.