Counterion influence on the N-I-N halogen bond

A detailed investigation of the influence of counterions on the [N-I-N]+ halogen bond in solution, in the solid state and in silico is presented. Translational diffusion coefficients indicate close attachment of counterions to the cationic, three-center halogen bond in dichloromethane solution. Isotopic perturbation of equilibrium NMR studies performed on isotopologue mixtures of regioselectively deuterated and nondeuterated analogues of the model system showed that the counterion is incapable of altering the symmetry of the [N-I-N]+ halogen bond. This symmetry remains even in the presence of an unfavorable geometric restraint. A high preference for the symmetric geometry was found also in the solid state by single crystal X-ray crystallography. Molecular systems encompassing weakly coordinating counterions behave similarly to the corresponding silver(i) centered coordination complexes. In contrast, systems possessing moderately or strongly coordinating anions show a distinctly different behavior. Such silver(i) complexes are converted into multi-coordinate geometries with strong Ag-O bonds, whereas the iodine centered systems remain linear and lack direct charge transfer interaction with the counterion, as verified by 15N NMR and DFT computation. This suggests that the [N-I-N]+ halogen bond may not be satisfactorily described in terms of a pure coordination bond typical of transition metal complexes, but as a secondary bond with a substantial charge-transfer character.

Substituent Effects on the [N-I-N](+) Halogen Bond

We have investigated the influence of electron density on the three-center [N–I–N]⁺ halogen bond. A series of [bis(pyridine)iodine]⁺ and [1,2-bis((pyridine-2-ylethynyl)benzene)iodine]⁺ BF₄^– complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO₂, CF₃, H, F, Me, OMe, NMe₂) was confirmed by ¹⁵N NMR and by computation of the natural atomic population and the π electron population of the nitrogen atoms. Formation of the [N–I–N]⁺ halogen bond resulted in >100 ppm ¹⁵N NMR coordination shifts. Substituent effects on the ¹⁵N NMR chemical shift are governed by the π population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N–I–N]⁺ halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine]⁺ complexes. An increased electron density of the halogen bond acceptor stabilizes the [N···I···N]⁺ bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N–I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N–X–N]⁺ halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen]⁺-type synthetic reagents.

Biochemical evidence for the non-inactivation of the steroid sulfatase locus in human placenta and fibroblasts

Steroid sulfatase activities are significantly higher in placentas obtained after the birth of girls than after the birth of boys, and also in female fibroblasts compared to male strains. This constitutes biochemical evidence for the non-inactivation of the X-linked sulfatase locus. No hydrolytic activity is found in the fibroblasts of ichthyotic boys. Heterozygosity is demonstrated in the fibroblasts of the four mothers studied, as they have steroid sulfatase activity of less or equivalent to the normal male value.

Placental sulfatase deficiency: clinical and biochemical study of 16 cases

Clinical and biochemical data of 16 typical cases of placental sulfatase deficiency have been observed. In vivo loading tests with DHA-S allowed us to make a prenatal diagnosis. In vitro experiments gave confirmation, showing zero or virtually zero placental sulfatase activity towards delta 5P or DHA sulfates Aromatase activities, when tested, were normal or more often less than standard values, the latter showing themselves rather large individual variations. All pregnancies were associated with the delivery of male neonates in good health but 3. The 15 living babies have been developing normally since then. These results, together with those reported in the literature, suggest that placental sulfatase deficiency is under control of an X-linked recessive character, this being supported by the recent observation of such a disorder in two sisters simultaneously pregnant. As to the high frequency problem of cesarian section, pointed out by several authors, we cannot conclude, from our own observations, that the defect has an obvious influence on the good outcome of labor, as 10 out of the 16 women delivered vaginally near term.

Homogeneous Water Oxidation by Half-Sandwich Iridium(III) N-Heterocyclic Carbene Complexes with Pendant Hydroxy and Amino Groups

Herein, we report three Ir^III Cp* complexes with hydroxy- or amino-functionalized N-heterocyclic carbene (NHC) ligands that catalyze efficient water oxidation induced by addition of ceric ammonium nitrate (CAN). The pendant hydroxy or amino groups are very important for activity, and the complexes with heteroatom-functionalized NHC ligands show up to 15 times higher rates of oxygen evolution in CAN-induced water oxidation than a reference Ir^III Cp* complex without heteroatom functionalization. The formation of molecular high-valent Ir intermediates that are presumably involved in the rate-determining step for water oxidation is established by UV/Vis spectroscopy and ESI-MS under turnover conditions. The hydroxy groups on the NHC ligands, as well as chloride ligands on the iridium center are proposed to structurally stabilize the high-valent species, and thereby improve the catalytic activity. The Ir^III complex with a hydroxy-functionalized NHC shows the highest catalytic activity with a TON of 2500 obtained in 3 h and with >90 % yield relative to the amount of oxidant used.

Incidence of placental sulfatase deficiency on the mode of termination of pregnancy

The mode of termination of pregnancy in case of placental sulfatase deficiency (PSD) has been considered in a 28-case series from our laboratory. After comparison with 75 other cases collected from the literature and also with reports concerned with normal pregnancies it appears that in the case of PSD: first, the gestation length is not increased; second, the parity of the patients has no influence on the mode of delivery; third, spontaneous vaginal delivery can occur (67.8% in our series, 43% in the literature series); fourth, the failure rate of labor, especially when induced, is higher than in a normal population; fifth, the high rate of C-section, largely due to the failure of labor, is enhanced by untimely interventions mostly in case of isolated PSD. If a pejorative incidence of PSD on the mode of delivery exists it must be at a moderate level, and intervention is unnecessary in absence of associated fetal and/or maternal complications.

Testicular steroid sulfatase in a cryptorchid rat strain

Steroid sulfatase (STS) activity was studied in scrotal and abdominal testes from genetically unilateral cryptorchid rats. Specific STS activity was significantly increased in microsomes from abdominal and scrotal testes of the cryptorchid animals as compared to that of control ones. When expressed per gonad, STS activity was only enhanced in the scrotal testis. No difference in the enzyme affinity was observed between descended and undescended testes. Testosterone content was markedly reduced in the abdominal testes. Normal plasma testosterone levels together with elevated LH levels were measured in the cryptorchid rats. The existence of differences in STS expression between descended and undescended testes gives additional support for this enzymatic activity being implicated in testicular function.

Reduced Na(+), K(+)-ATPase activity in erythrocyte membranes from patients with phenylketonuria

Na(+), K(+)-ATPase activity was determined in erythrocyte membranes from 12 phenylketonuric patients of both sexes, aged 8.8 +/- 5.0 y, with plasma phenylalanine levels of 0.64 +/- 0.31 mM. The in vitro effects of phenylalanine and alanine on the enzyme activity in erythrocyte membranes from healthy individuals were also investigated. We observed that Na(+), K(+)-ATPase activity was decreased by 31% in erythrocytes from phenylketonuric patients compared with normal age-matched individuals (p < 0.01). We also observed a significant negative correlation between erythrocyte Na(+), K(+)-ATPase activity and plasma phenylalanine levels (r = -0.65; p < 0.05). All PKU patients with plasma phenylalanine levels higher than 0.3 mM had erythrocyte Na(+), K(+)-ATPase activity below the normal range. Phenylalanine inhibited in vitro erythrocyte Na(+), K(+)-ATPase activity by 22 to 34%, whereas alanine had no effect on this activity. However, when combined with phenylalanine, alanine prevented Na(+) K(+)-ATPase inhibition. Considering that reduction of Na(+), K(+)-ATPase activity occurs in various neurodegenerative disorders leading to neuronal loss, our previous observations showing a significant reduction of Na(+), K(+)-ATPase activity in brain cortex of rats subjected to experimental phenylketonuria and the present results, it is proposed that determination of Na(+), K(+)-ATPase activity in erythrocytes may be a useful peripheral marker for the neurotoxic effect of phenylalanine in phenylketonuria.

Immunoreactive arginine vasopressin in the testis: immunocytochemical localization and testicular content in normal and in experimental cryptorchid mouse

The presence of arginine vasopressin (AVP)-like peptide(s) and AVP receptors has been previously demonstrated in the testis of several species. In this study we examined the immunocytochemical localization of AVP and of its associated neurophysin (NPII) within the mouse testis, and the testicular immunoreactive (IR)-AVP content in normal pubertal and adult mice and in unilaterally cryptorchid animals. Immunostaining was conducted on fresh frozen adult testicular sections and on cultured testicular cells using the avidin-biotin immunoperoxidase technique. Immunoreactivities for AVP and NPII were localized at the periphery of the seminiferous tubules. Staining for AVP and NPII was reduced in testes showing impaired spermatogenesis. AVP and NPII immunoreactivities were present in cultured Sertoli cells, but staining was undetectable in cultured Leydig cells. Negative controls were obtained by applying antiserum that had been preabsorbed with excess peptides in place of primary antiserum. Mouse testes were found to contain IR-AVP, which co-eluted with synthetic AVP on HPLC and diluted in parallel in a specific RIA for AVP. Levels of IR-AVP expressed as pg/mg wet-weight testis were significantly higher (p < 0.05) in pubertal (36.6 +/- 1.5) than in adult animals (27.4 +/- 1.5). Experimental unilateral cryptorchidism in adult animals resulted 2 wk later in a marked reduction (p < 0.01) in IR-AVP levels in the abdominal testis (18.1 +/- 1.0 pg/mg testis) as compared to the contralateral scrotal testis (29.8 +/- 1.1 pg/mg testis).(ABSTRACT TRUNCATED AT 250 WORDS)

Local control of Leydig cell arginine vasopressin receptor by naloxone

Arginine vasopressin (AVP) and beta-endorphin are present within the testis where they could act as paracrine effectors of steroidogenesis. In this study we investigated the effect of naloxone, an opioid receptor antagonist on Leydig cell AVP receptor. Intratesticular injection of increasing doses of naloxone (0.1-100 micrograms) resulted 24 h later in a dose-dependent increase in Leydig cell AVP binding capacity. This effect occurred locally since s.c. injection of similar doses of naloxone did not alter the testicular AVP receptor content and intratesticular injection enhanced AVP receptor density only in the naloxone-treated testis but not in the contralateral vehicle-treated testis. Scatchard plot analysis of the data revealed that naloxone locally injected altered AVP binding capacity without change in affinity. These results suggest that in addition to their known paracrine effects in the testis, endogenous opioid peptides may locally control the testicular AVP system by modulating AVP receptor capacity.

Steroid sulfatase activity in homogenates, microsomes and purified Leydig cells from adult rat testis

Steroid sulfatase (STS) activity was studied in the Long-Evans rat testis. The rate of dehydroepiandrosterone sulfate (DHA-S) hydrolysis determined in whole testis homogenates was low compared to that of the corresponding microsomal fractions, which was, in contrast, as high as that expressed in homogenates from purified Leydig cells. Such an increment in STS activity between total homogenates and the corresponding microsomes was not observed for the seminiferous tubules. The STS affinity reported for total testicular microsomes (Km = 3.47 +/- 0.54 microM; mean +/- SEM) was of the same magnitude as that previously reported for Leydig cells, but was about 3 times higher than that measured for whole testis homogenate (Km = 10.11 +/- 0.92 microM). In vivo hCG treatment decreased the STS affinity in total testicular microsomes without affecting this kinetic parameter in whole testis homogenate. These data suggest that the steroid sulfatase expressed in total testicular microsomes (activity and regulation by hCG) could be considered as a good index of Leydig cell STS activity.

Local regulation of testicular immunoreactive-arginine vasopressin and steroidogenesis by naloxone

The effects of intratesticular injection of naloxone, a universal opioid antagonist, on testicular immunoreactive (IR)-arginine vasopressin (AVP) content and on in vitro testosterone production by Leydig cells were investigated in the mouse. Bilateral intratesticular injection of increasing doses of naloxone (0.1-10 micrograms/testis) resulted 24 h later in a dose-dependent increase in testosterone production by Leydig cells incubated for 3 h in the presence or absence of hCG (100 ng/ml). Unilateral intratesticular injection of naloxone (10 micrograms) similarly enhanced basal and hCG-stimulated testosterone production by Leydig cells, but production was not modified in Leydig cells from the contralateral vehicle-injected testis, nor was it changed when the same dose was injected subcutaneously. Unilateral intratesticular injection of 10 micrograms naloxone led to a dose-dependent increase in the hCG-responsiveness without altering the slope of the hCG dose-response curve. In vitro exposure of Leydig cells to increasing doses of naloxone (10(-9) to 10(-7) M) did not alter either basal or hCG-stimulated testosterone production. Testicular IR-AVP content declined in a dose-dependent manner in naloxone-injected testis, but remained unchanged in the contralateral vehicle-injected testis and in testis from animals that received similar doses of naloxone subcutaneously. Since AVP has been shown to locally exert a negative control on testosterone production within the testis, it might be hypothesized that the increased Leydig cell activity after local naloxone administration results from reduced intratesticular IR-AVP levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Transformation of (1,2-3H)aldosterone in the foetal and placental compartments of the guinea pig

In vivo and in vitro transformation of labelled d-aldosterone (11beta, 21-dihydroxy-3,20-dioxo-4-pregnen-18-al) was studied in the foetal tissues and placenta of guinea pig (35-45 days of gestation). The principal metabolite found in all of these tissues was tetrahydroaldosterone (3alpha, 18,21-trihydroxy-20-oxo-5beta-pregnan-18-al). A large transformation into this metabolite was found in foetal liver (67-68%) and in the placenta (69-82%). Incubation of [3H]- or [14C]aldosterone with the isolated placenta also showed a large conversion to the tetrahydroderivative suggesting that the reductase(s) of ring A of aldosterone is present in this tissue. Most of the unmetabolized aldosterone and tetrahydroaldosterone was found in the unconjugated fraction. Very little of the radioactive material was present in the polar steroids extracted with n-butanol. Aldosterone and tetrahydroaldosterone were liberated from this fraction after enzymatic hydrolysis (beta-glucuronidase and sulphatase) or by solvolysis, suggesting that part of these conjugates is present in the foetal compartment as sulphate esters and glucuronides. Moreover, in this fraction a polar, unconjugated aldosterone metabolite with the characteristics of an acidic compound was detected.

Platelet Na+, K+-ATPase activity as a possible peripheral marker for the neurotoxic effects of phenylalanine in phenylketonuria

The in vitro effects of phenylalanine or alanine alone or combined on Na+, K+-ATPase activity in membranes from human platelets were investigated. The enzyme activity was assayed in membranes prepared from platelet-rich plasma of healthy donors. Phenylalanine or alanine were added to the assay to final concentrations of 0.3 to 1.2 mM, similar to those found in plasma of phenylketonuric patients. Phenylalanine inhibited Na+, K+-ATPase activity by 20-50% [F(4,25)=11.47 ; p<0.001]. Alanine had no effect on Na+, K+-ATPase activity but when combined with phenylalanine prevented the enzyme inhibition. These results, allied to others previously reported on brain Na+, K+-ATPase activity, may reflect a general inhibitory effect of phenylalanine on this important enzyme activity. Therefore, it is possible that measurement of Na+, K+-ATPase activity in platelets from PKU patients may be a useful peripheral marker for the neurotoxic effects of phenylalanine.

Clinical pathological findings in an owl (Athene noctua) with microfilaraemia in Italy

We report the first case of microfilaria infection in a free-flying owl Athene noctua in Italy. A macroparasite, about 10.1-mm long, was observed in the right chamber of the heart. On microscopic examination microfilariae were seen in liver, kidney, myocardium and lungs, although no cellular reaction was present in association with the parasites in any of these tissues. Because of the low pathogenicity of this parasite, infection with microfilaria may be not harmful in wild owls.

Ontogenesis and regulation of steroid sulfatase activity in Leydig cells and seminiferous tubules in the Long-Evans rat

Steroid sulfatase (STS) activity was studied in Long-Evans rat testis. The affinity of the enzyme was shown to increase during postnatal development and to be always higher in purified Leydig cells than in seminiferous tubules. STS activity appeared to be higher in the seminiferous tubules at the earlier stages. In vivo injection of 100 IU hCG resulted in a decrease in the affinity and an increase in the activity of the enzyme expressed in Leydig cells with no such modification in seminiferous tubules. This suggests that STS could play a regulatory role in testosterone production by Leydig cells.

[Deficiency in placental sulfatase. Description of a recent case]

Synthesis of oestrogens occurs, during the greater part of pregnancy, in the placenta starting with two fetal precursors: DHA-S and 16 OH DHA-S. In the case of a deficit in sulphatase, an enzyme which is mainly localised in the placenta, these precursors cannot be transformed so that the level of oestrogens stays very low, without the level of secretion of progesterone being altered. Faced with such hormonal abnormalities it is worth while remembering the diagnosis of placental enzyme deficiency. In fact, this abnormality has no repercussions on the progress of the pregnancy and carries no danger for the fetus. It is therefore unnecessary to carry out untimely treatments thinking: fetal distress or adrenal agenesis be it primary or secondary (due to anencephaly) will occur. The diagnosis depends on simple dynamic tests: the mother receives an injection of free DHA and DHA-S, and enzyme study of the placenta can be confirmed in vitro. There seems to be a link between this abnormality and the sex of the fetus. All cases were followed by the birth of a normal boy. Finally, placental suphatase deficiency is rare, but it would appear that increased usage of hormone levels will reveal a rising number of such cases.

[Deficiency in placental sulfatase. Clinical and biochemical study of 3 cases]

Placental sulfatase deficiency is currently undetected because of the lack of clinical manifestation. However, such a diagnosis should be borne in mind as it would be unadequate to undertake drastic therapy thinking of acute foetal disease or anencephaly. In the case of a clear answer, the dynamic tests allow to diagnose prenatally the defect causing paradoxical low excretion of maternal urinary estrogens and so, to await in perfect safety for the birth of an healthy baby. The enzymatic defect can be confirmed by the biochemical study of placenta tissue in vitro. In the case of an unclear answer to the DHA-S and free DHA tests, we recommend to determine the foetal chromosomal sex before ascertaining the diagnosis.

[Should we still explore placental sulfatase deficiencies? Reflections apropos of a case report]

The finding of low or very low levels of oestrogen during pregnancy should suggest the diagnosis of placental sulfatase deficiency, which is confirmed by performing dynamic biochemical tests. These biochemical tests also enable sulfatase deficiency to be differentiated from other conditions which may be accompanied by an abnormal decrease in oestrogens. The authors report one case and stress the harmlessness of sulfatase deficiency and the associated ichthyosis in boys and they question the value of the dehydroepiandrosterone sulfate test which only confirms an abnormality which is now well known and benign.

Activation of p21ras is not sufficient to ensure a complete G1 phase of the cell division cycle in mouse fibroblasts

In the mouse BP-A31 fibroblasts, mRNAs coding the three isoforms (Ha, Ki, N) of ras are expressed, and there are no activating mutations in the codons 12, 13 or 61. We have produced a subline (Ras2) expressing an oestrogen-inducible v-Ha-ras gene. The contribution of v-Ha-ras to the overall p21ras-GTP content was evaluated by metabolic labelling with 32P. Surprisingly, p21ras-GTP complexes were predominant in the serum-deprived BP-A31 cells as well as in the Ras2 cells. The excess of p21ras-GTP was not due to the lack of the GTPase activating protein. In transient transfection experiments, the serum response element (SRE)-directed CAT was expressed in serum-deprived BP-A31 cells, and insulin caused a further two- to threefold increase in CAT activity. A dominant negative ras mutant (Ha-Ras Asn-17) cancelled both the basal and insulin-induced CAT expression in the BP-A31 but not in the Ras2 cells. Expression of v-Ha-ras in Ras2 cells did not relax their growth factor-dependence and oestradiol had only a minor mitogenic effect. We conclude that p21ras activation does not ensure a complete cell division cycle in these cells, and does not entirely account for the transduction of the mitogenic signal initiated by insulin.