Catalase can protect spermatozoa of FSH receptor knock-out mice against oxidant-induced DNA damage in vitro.

The aetiology of sperm DNA damage is likely multi-factorial with abnormal compaction of nuclear DNA, abortive apoptosis and oxidative stress implicated as potential causes of DNA damage. The objective of this study was to evaluate DNA damage in spermatozoa from wild-type (WT) and FSH receptor knock-out (FORKO) mice, compare the relative susceptibility of spermatozoa from these animals to oxidative DNA damage, and examine the protective effect of the antioxidant catalase on sperm DNA damage. Epididymal spermatozoa from FORKO mice (n = 5) and WT controls (n = 5) were extracted and incubated with or without catalase. Sperm DNA damage was assessed immediately after epididymal extraction (time 0 control) and following 2-h incubation at 37 °C. DNA damage was measured by the sperm chromatin structure assay and the results expressed as the %DNA fragmentation index or %DFI. Freshly retrieved epididymal spermatozoa from WT mice had a significantly lower mean (±SD) %DFI than that of FORKO mice (2.7 ± 1.8 vs. 6.4 ± 2.9%, p < 0.05). Prolonged (2-h) incubation of FORKO mice spermatozoa resulted in a significant increase in %DFI compared with the time 0 control (17.9 ± 9.2% vs. 6.4 ± 2.9%, respectively, p < 0.05) and the addition of catalase protected these spermatozoa from DNA damage (9.8 ± 4.1 vs. 17.9 ± 9.2%, respectively, p < 0.05). However, incubation of WT mice spermatozoa did not increase %DFI significantly (5.8 ± 5.0 vs. 2.7 ± 1.8, respectively, p > 0.05) and the addition of catalase (vs. no catalase) did not result in a significant reduction in %DFI (5.8 ± 5.0 vs. 7.7 ± 6.5%, respectively, p > 0.05). These data indicate that catalase may protect sperm nuclear DNA from oxidative stress in vitro. The data also demonstrate the differential susceptibility of WT and FORKO mice spermatozoa to oxidative stress.

Jejunal perforation during percutaneous nephrolithotrypsy.

Colonic and duodenal perforations, albeit rare, are known complications of PCNL, however, to our knowledge; jejunal perforation has never been reported. We report a case of an 83-year-old man, underwent left PCNL for a 2cm stone in the renal pelvis, confirmed to have a jejunal perforation. He was successfully managed conservatively. His diagnostic work up and management will be discussed.

Beneficial effect of microsurgical varicocelectomy on human sperm DNA integrity.

BACKGROUND: Human sperm DNA damage may adversely affect reproductive outcomes, and the spermatozoa of infertile men possess substantially more DNA damage than that of fertile men. To date, there is no available treatment for men with high levels of sperm DNA damage. The objective of this study was to examine the effect of varicocelectomy on sperm DNA denaturation (DD, an index of sperm DNA damage) in infertile men with a clinical varicocele. METHODS: We reviewed the reports of 37 men who underwent microsurgical varicocelectomy at our institution from September 2001 to July 2002. Standard semen parameters and the percentage of spermatozoa with DD (monitored by flow cytometry analysis of acridine orange-treated spermatozoa) were assessed before and 6 months after varicocelectomy. RESULTS: The percentage of spermatozoa with DD decreased following varicocelectomy compared with pre-operatively (27.7 versus 24.6%, respectively, P < 0.05). Sperm concentration and the percentages of motile sperm and normal forms (WHO criteria) increased following varicocelectomy, but the difference did not reach statistical significance. CONCLUSIONS: Our data suggest that varicocelectomy can improve human sperm DNA integrity in infertile men with varicocele. These data represent the first report of improved sperm DNA integrity after therapy and further support the beneficial effect of varicocelectomy on human spermatogenesis.

Modular fluorescent-labeled siderophore analogues.

Biomimetic analogues 1 of the microbial siderophore (iron carrier) ferrichrome were labeled via piperazine with various fluorescent markers at a site not interfering with iron binding or receptor recognition (compounds 10-12). These iron carriers were built from a tetrahedral carbon symmetrically extended with three strands, each containing an amino acid (G = glycyl, A = alanyl, L = leucyl and P = phenylalanyl) and terminated by a hydroxamic acid, which together define an octahedral iron-binding domain. A fourth exogenous strand provided the site for connecting various fluorescent markers via a short bifunctional linker. Iron(III) titrations, along with fluorescence spectroscopy, generated quenching of fluorescence emission of some of the probes used. The quenching process fits the Perrin model which reinforces the intramolecular quenching process, postulated previously.1 All tested compounds, regardless of their probe size, polarity, or the linker binding them to the siderophore analogue, promote growth of Pseudomonas putida with the same efficacy as the nonlabeled analogues 1, with the added benefit of signaling microbial activity by fluorescence emission. All G derivatives of compounds 10-12 were found to parallel the behavior of natural ferrichrome, whereas A derivatives mediated only a modest iron(III) uptake by P. putida. Incubation of various Pseudomonas strains with iron(III)-loaded G derivatives resulted in the build-up of the labels' fluorescence in the culture medium to a much larger extent than from the corresponding A derivatives. The fluorescence buildup corresponds to iron utilization by the cells and the release of the fluorescent labeled desferrisiderophore from the cell to the media. The fact that the microbial activity of these compounds is not altered by attachment of various fluorescent markers via a bifunctional linker proposes their application as diagnostic tools for detecting and identifying pathogenic microorganisms.

Iron uptake in Ustilago maydis: tracking the iron path.

In this study, we monitored and compared the uptake of iron in the fungus Ustilago maydis by using biomimetic siderophore analogs of ferrichrome, the fungal native siderophore, and ferrioxamine B (FOB), a xenosiderophore. Ferrichrome-iron was taken up at a higher rate than FOB-iron. Unlike ferrichrome-mediated uptake, FOB-mediated iron transport involved an extracellular reduction mechanism. By using fluorescently labeled siderophore analogs, we monitored the time course, as well as the localization, of iron uptake processes within the fungal cells. A fluorescently labeled ferrichrome analog, B9-lissamine rhodamine B, which does not exhibit fluorescence quenching upon iron binding, was used to monitor the entry of the compounds into the fungal cells. The fluorescence was found intracellularly 4 h after the application and later was found concentrated in two to three vesicles within each cell. The fluorescence of the fluorescently labeled FOB analog CAT18, which is quenched by iron, was visualized around the cell membrane after 4 h of incubation with the ferrated (nonfluorescent) compounds. This fluorescence intensity increased with time, demonstrating fungal iron uptake from the siderophores, which remained extracellular. We here introduce the use of fluorescent biomimetic siderophores as tools to directly track and discriminate between different pathways of iron uptake in cells.

Chelation and mobilization of cellular iron by different classes of chelators.

Iron chelators belonging to three distinct chemical families were assessed in terms of their physicochemical properties and the kinetics of iron chelation in solution and in two biological systems. Several hydroxypyridinones, reversed siderophores, and desferrioxamine derivatives were selected to cover agents with different iron-binding stoichiometry and geometry and a wide range of lipophilicity, as determined by the octanol-water partition coefficients. The selection also included highly lipophilic chelators with potentially cell-cleavable ester groups that can serve as precursors of hydrophilic and membrane-impermeant chelators. Iron binding was determined by the chelator capacity for restoring the fluorescence of iron-quenched calcein (CA), a dynamic fluorescent metallosensor. The iron-scavenging properties of the chelators were assessed under three different conditions: (a) in solution, by mixing iron salts with free CA; (b) in resealed red cell ghosts, by encapsulation of CA followed by loading with iron; and (c) in human erythroleukemia K562 cells, by loading with the permeant CA-acetomethoxy ester, in situ formation of free CA, and binding of cytosolic labile iron. The time-dependent recovery of fluorescence in the presence of a given chelator provided a continuous measure for the capacity of the chelator to access the iron/CA-containing compartment. The resulting rate constants of fluorescence recovery indicated that chelation in solution was comparable for the members of each family of chelators, whereas chelation in either biological system was largely dictated by the lipophilicity of the free chelator. For example, desferrioxamine was among the fastest and most efficient iron scavengers in solution but was essentially ineffective in either biological system when used at < or = 200 microM over a 2-hr period at 37 degrees. On the other hand, the highly lipophilic and potentially cell-cleavable hydroxypyridinones and reversed siderophores were highly efficient in all biological systems tested. It is implied that in K562 cells, hydrolysis of these chelators is relatively slower than their ingress and binding of intracellular iron. The chelator-mediated translocation of iron from cells to medium was assessed in 55Fe-transferrin-loaded K562 cells. The speed of iron mobilization by members of the three families of chelators correlated with the lipophilicity of the free ligand or the iron-complexed chelator. The acquired information is of relevance for the design of chelators with improved biological performance.

[Cardiac failure secondary to hypoparathyroidism. An unusual presentation]. / Insuficiencia cardíaca secundaria a hipoparatiroidismo. Una presentación inusual.

The case of a 37 year old woman with hypoparathyroid congestive heart failure (CHF) is reported. Thyroidectomy had been performed eight years earlier and she had experienced symptoms of hypocalcemia postoperatively. CHF improved rapidly and completely with the treatment of hypocalcemia. Good prognosis is emphasized but it is necessary to think about this cause of ventricular dysfunction in a patient with CHF and a history of neck surgery in order to make an early diagnosis. Pathogenic mechanisms and differential diagnosis are discussed.

Chemical Determinants of antimalarial activity of reversed siderophores.

Reversed siderophores (RSFs) are artificial hydroxamate-based iron chelators designed after the natural siderophore ferrichrome. The modular molecular design of RSF derivatives allowed the synthesis of various congeners with controlled iron-binding capacities and partition coefficients. These two physicochemical properties were assessed by a novel fluorescent method and were found to be the major determinants of RSF permeation across erythrocyte membranes and scavenging of compartmentalized iron. The partition coefficient apparently conferred upon RSFs two major features: (i) the ability to rapidly access iron pools of in vitro-grown Plasmodium falciparum at all developmental stages and to mobilize intracellular iron and transfer it to the medium and (ii) the ability to suppress parasite growth at all developmental stages. These features of RSFs were assessed by quantitative determination of the structure-activity relationships of the biological activities and partition coefficients spanning a wide range of values. The most effective RSF containing the aromatic group of phenylalanine (RSFm2phe) showed 50% inhibitory concentration of 0.60 +/- 0.03 nmol/ml in a 48-h test and a 2-h onset of inhibition of ring development at 5 nmol/ml. The lipophilic compound RSFm2phe and the lipophilic and esterase-cleavable compound RSFm2pee inhibited parasite growth at all developmental stages whether inhibition was assessed in a continuous mode or after discontinuing drug administration. The antimalarial effects of RSFm2phe and cleavable RSFm2pee were potentiated in the presence of desferrioxamine (DFO) at concentrations at which DFO alone had no effect on parasite growth. These studies provide experimental evidence indicating that the effective and persistent antimalarial actions of RSFs are associated with drug access to infected cells and scavenging of iron from intracellular parasites. Moreover, the optimal antimalarial actions of RSFs are apparently also determined by improved accessibility to critical iron pools or by specific interactions with critical parasite targets.

Mode of action of iron(III) chelators as antimalarials. III. Overadditive effects in the combined action of hydroxamate-based agents on in vitro growth of Plasmodium falciparum.

Hydroxamate-based iron(III) chelators exhibit potent antimalarial effects on the asexual stages of Plasmodium falciparum grown in vitro. Antimalarial activity varies with the parasite growth stage and the drug permeation properties. The hydrophilic drug desferrioxamine (DFO) is ineffective on early stages (ring forms) of the parasite due to its poor permeability but irreversibly blocks the growth of advanced stages of parasites. On the other hand, hydrophobic reversed siderophores (RSFs) are more membrane permeable and affect all parasite developmental stages; they affect ring forms irreversibly and trophozoite/schizont forms reversibly and at relatively faster rates, compared with DFO. These observations have provided the basis for postulating a possible overadditive action of the two, distinctly acting, iron chelator types for enhanced antimalarial activity. This was assessed in this study by using novel fast-acting chelators such as RSF derivatives (RSFleum2 and RSFm2) in combination with the relatively slow-acting DFO. Parasite growth was assessed in terms of nucleic acid synthesis and parasitemia. The results indicate that, at any molar ratios of the two types of drugs, the combined inhibitory effect was faster and more potent than the sum of individual effects. The combined drug action showed neither additive nor independent but overadditive properties, as well as sustained inhibition even after drug removal. The potentiating action of RSFs on the long-lasting effects of DFO on parasite growth conformed with the postulated mechanistic model of iron chelator action and iron handling by parasites. Iron chelator combinations might be of therapeutic value.

[Renal acidification mechanism disorders in patients with osteoporosis]. / Trastornos de los mecanismos renales de acidificación en pacientes osteoporóticos.

Eight patients (6 women and 2 men) with osteoporosis caused or aggravated by renal acidification defects are presented. Three of the female patients were premenopausal; the others were 9, 20 and 22 years postmenopausal, and two of them were on hormonal replacement therapy. Two patients had nephrolithiasis: one male with recurrent calcium phosphate stones and a left sided staghorn calculus, and one female with nephrocalcinosis due to medullary sponge kidney and hypercalciuria (patients No. 1 and 2, respectively, Table 1). In the remaining subjects, clinical suspicion was based on: a) Hip fracture in a 44-yr-old premenopausal female without any risk factor (No. 3, Table 2). b) Several vertebral compression fractures in a 45-yr-old male without hypogonadism or other predisposing factors (No. 7, Table 2). c) Lack of response to antiosteoporotic therapy in 3 women (patients No. 4, 6 and 8, Table 2). Serum bicarbonate levels and urine acidification capacity were studied in all patients. Three had low serum bicarbonate (two of whom showed high fractional excretion of bicarbonate), four had a distal defect, and one had a mixed form. Serum creatinine and potassium, and venous blood pH were normal in all cases, suggesting incomplete renal tubular acidosis. Bone mineral density in Z-score (means +/- s.e.m.) was - 1.75 +/- 0.08 in the lumbar spine (n = 8), and - 1.57 +/- 0.09 in the femoral neck (n = 4) [Tables 1 and 2; Figs 1 and 2]. Following one year treatment with oral sodium bicarbonate and potassium citrate, total skeletal calcium increased by 3-10% in five of the patients. Whereas the high prevalence of renal acidification defects among renal stone formers with or without hypercalciuria is well acknowledged, renal tubular acidosis is not included in the list of entities causing secondary osteoporosis. As shown in 6 patients of this series, incomplete RTA should be considered as another disease capable of causing osteoporosis or worsening involutional bone loss.

Antimalarial action of hydroxamate-based iron chelators and potentiation of desferrioxamine action by reversed siderophores.

Hydroxamate-based chelators of iron are potent inhibitors of in vitro growth of Plasmodium falciparum. Two types of such chelators, the natural desferrioxamine and the synthetic reversed siderophore RSFileum2, are prototypes of antimalarial agents whose action spectra differ in the speed of action, stage dependence, and degree of reversibility of effects. This work explores the possibility of improving the antimalarial efficacy of these agents by using them in various combinations on in vitro cultures of P. falciparum. Growth assessment was based both on total nucleic acid synthesis and on parasitemia. The results indicate that the synthetic reversed siderophore more than complements the antimalarial action of desferrioxamine when applied during either ring, trophozoite, or mixed stages. The combined drug effects were significantly higher than the additive effect of the individual drugs. Qualitatively similar results were obtained for both reversible effects and irreversible (i.e., sustained) effects. Following an 8-h window of exposure the combined drug treatment caused parasite growth arrest and prevented its recovery, even 3 days after the treatment. The fact that such a combination of iron chelators displays a wider action spectrum than either drug alone has implications for the design of chemotherapy regimens.

Insulin-like effects of tungstate and molybdate: mediation through insulin receptor independent pathways.

The insulin-like effects of tungstate (W) and molybdate (Mo) were studied in rat adipocytes and compared to those of vanadate. Other than being less potent, W and Mo resembled vanadate in stimulating lipogenesis, in activating glucose oxidation, in enhancing rate of hexose uptake, and in inhibiting lipolysis. Tungstate and molybdate did not activate the insulinreceptor tyrosine kinase (InsRTK). Quercetin which blocks InsRTK activity and insulin stimulation of glucose metabolism, failed to inhibit when these bioeffects were stimulated by W or Mo. The metalooxide, however, activated a staurosporine sensitive non receptor, cytosolic protein tyrosine kinase (CytPTK), and staurosporine blocked W or Mo dependent lipogenesis in rat adipocytes. Staurosporine did not prevent Mo and W either from activating hexose transport, or from inhibiting lipolysis. Tungstate and molybdate were less effective than vanadate in inhibiting adipose PTPases in cell free systems. Membranal PTPases were more sensitive to W and Mo inhibition than cytosolic PTPases. While the presence of a nucleophile such as hydroxylamine reversed inhibition of PTPase by vanadate it did not affect inhibition by W or Mo. In summary, the insulinomimetic effects of W and Mo appear to resemble qualitatively that of vanadate in all respects. Both act in an insulin receptor-independent-fashion, activate CytPTK and trigger additional effects that are not mediated by the InsRTK or by CytPTK. The quantitative differences may be attributed to reduced capacity of W and Mo relative to vanadate to inhibit the relevant PTPases in intact cells.

Trastornos de los mecanismos renales de acidificación en pacientes osteoporóticos. / [Renal acidification mechanism disorders in patients with osteoporosis]

Eight patients (6 women and 2 men) with osteoporosis caused or aggravated by renal acidification defects are presented. Three of the female patients were premenopausal; the others were 9, 20 and 22 years postmenopausal, and two of them were on hormonal replacement therapy. Two patients had nephrolithiasis: one male with recurrent calcium phosphate stones and a left sided staghorn calculus, and one female with nephrocalcinosis due to medullary sponge kidney and hypercalciuria (patients No. 1 and 2, respectively, Table 1). In the remaining subjects, clinical suspicion was based on: a) Hip fracture in a 44-yr-old premenopausal female without any risk factor (No. 3, Table 2). b) Several vertebral compression fractures in a 45-yr-old male without hypogonadism or other predisposing factors (No. 7, Table 2). c) Lack of response to antiosteoporotic therapy in 3 women (patients No. 4, 6 and 8, Table 2). Serum bicarbonate levels and urine acidification capacity were studied in all patients. Three had low serum bicarbonate (two of whom showed high fractional excretion of bicarbonate), four had a distal defect, and one had a mixed form. Serum creatinine and potassium, and venous blood pH were normal in all cases, suggesting incomplete renal tubular acidosis. Bone mineral density in Z-score (means +/- s.e.m.) was - 1.75 +/- 0.08 in the lumbar spine (n = 8), and - 1.57 +/- 0.09 in the femoral neck (n = 4) [Tables 1 and 2; Figs 1 and 2]. Following one year treatment with oral sodium bicarbonate and potassium citrate, total skeletal calcium increased by 3-10

in five of the patients. Whereas the high prevalence of renal acidification defects among renal stone formers with or without hypercalciuria is well acknowledged, renal tubular acidosis is not included in the list of entities causing secondary osteoporosis. As shown in 6 patients of this series, incomplete RTA should be considered as another disease capable of causing osteoporosis or worsening involutional bone loss.

Mode of action of iron (III) chelators as antimalarials: II. Evidence for differential effects on parasite iron-dependent nucleic acid synthesis.

Iron chelation treatment of red blood cells infected with Plasmodium falciparum selectively intervenes with iron-dependent metabolism of malaria parasites and inhibits their development. Highly permeant hydroxamate iron chelator RSFileum2 affects all parasite stages when cultures are continuously exposed to drug, but affects primarily ring stages when assessed for irreversible effects, ie, sustained inhibition remaining after drug removal. On the other hand, the hydrophilic and poorly permeant desferrioxamine (DFO) affects primarily trophozoite/schizont stages when tested either in the continuous mode or irreversible mode. Unlike parasites, mammalian cells subjected to similar drug treatment show complete growth recovery once drugs are removed. Our studies indicate that parasites display a limited capacity to recover from intracellular iron depletion evoked by iron chelators. Based on these findings we provide a working model in which the irreversible effects of RSFs on rings are explained by the absence of pathways for iron acquisition/utilization by early forms of parasites. Trophozoite/schizonts can partially recover from RSFileum2 treatments, but show no DNA synthesis following DFO treatment even after drug removal and iron replenishment by permeant iron carriers. At trophozoite stage, the parasite uses a limited pathway for refurnishing its iron-containing enzymes, thus overcoming iron deprivation caused by permeant RSFileum2, but not by DFO because this latter drug is not easily removable from parasites. Their DNA synthesis is blocked by the hydroxamate iron chelators probably by affecting synthesis of ribonucleotide reductase (RNRase). Presumably in parasites, prolonged repression of the enzyme leads also to irreversible loss of activity. The action profiles of RSFileum2 and DFO presented in this study have implications for improved chemotherapeutic performance by combined drug treatment and future drug design based on specific intervention at parasite DNA synthesis.

In vivo antimalarial action of a lipophilic iron (III) chelator: suppression of Plasmodium vinckei infection by reversed siderophore.

We assessed in vivo antimalarial action of a lipophilic iron (III) chelator belonging to a new synthetic family of biomimetic siderophores previously termed reversed siderophores (RSFs). The family member, RSF ileum2, was chosen for its high membrane permeability and fast irreversible inhibition of human malaria parasite growth in vitro. [Shanzer A, et al., Proc Natl Acad Sci USA 88:6585, 1991 and Lytton SD, et al., Blood 81:214, 1993]. The lipophilic drug was administered to Swiss mice by subcutaneous route in fractionated coconut oil at a dosage of 0.37 g/kg every 8 hr with no adverse reactions observed. After 3-4 injections demonstrable suppression of Plasmodium vinckei petteri infection was observed and an additional 3-4 injections resulted in 2-3-fold lower parasitemia with prolonged survival time over sham-injected control mice.

Contrast sensitivity and visual acuity in patients with early cataracts.

In a population of 188 nondiabetic patients with early cataracts or nuclear brunescence, we assessed the degree to which contrast sensitivity function (CSF) provided more information about a patient's visual disability than high contrast visual acuity measurements. Data collected included LOCS II cataract classification, Bailey-Lovie visual acuity (LogMAR score), Lotmar interferometric visual acuity (LI VA), and distance contrast sensitivity function (CSF) using the Vistech 6500. Generalized least squares regression models in which CS was the dependent variable and either LogMAR score or LI VA was among the independent variables were used to ascertain whether CSF provided additional information about visual disability to that provided by LogMAR score or LI VA. Contrast sensitivity function was decreased only by nuclear opalescence at high frequencies (12 to 18 cpd); for all other cataract types and nuclear color, CSF testing provided no more information about cataract-related visual loss than LI VA or LogMAR score. Measurement of CSF using the Vistech 6500 system in patients with early cataracts provides information on visual dysfunction beyond that provided by LogMAR score or LI VA only in patients with nuclear opalescence, and that may not be clinically significant.

The antimalarial action of desferal involves a direct access route to erythrocytic (Plasmodium falciparum) parasites.

We designed the N-methylanthranilic-desferrioxamine (MA-DFO) as a fluorescent iron (III) chelator with improved membrane permeation properties. Upon binding of iron (III), MA-DFO fluorescence is quenched, thus allowing traceability of drug-iron (III) interactions. MA-DFO is well tolerated by mammalian cells in culture. Its antimalarial activity is pronounced: IC50 values on in vitro (24-h) growth of Plasmodium falciparum were 3 +/- 1 microM for MA-DFO compared with 30 +/- 8 for DFO. The onset of growth inhibition of rings or trophozoites occurs 2-4 h after exposure to 13 microM MA-DFO. This effect is commensurate with MA-DFO permeation into infected cells. In a 24-h exposure to MA-DFO or DFO, trophozoites take up either compound to approximately 10% of the external concentration, rings to 5%, and noninfected cells to < 1%. Red cells encapsulated with millimolar concentrations of DFO or MA-DFO fully support parasite invasion and growth. We conclude that extracellular MA-DFO and DFO gain selective access into parasites by bypassing the host. The rate-limiting step is permeation through the parasite membrane, which MA-DFO accomplishes faster than DFO, in accordance with its higher hydrophobicity. These views are consistent with the proposed duct, which apparently provides parasitized cells with a window to the external medium.