APX2 Is an Ascorbate Peroxidase-Related Protein that Regulates the Levels of Plastocyanin in Chlamydomonas

The function of ascorbate peroxidase-related (APX-R) proteins, present in all green photosynthetic eukaryotes, remains unclear. This study focuses on APX-R from Chlamydomonas reinhardtii, namely, ascorbate peroxidase 2 (APX2). We showed that apx2 mutants exhibited a faster oxidation of the photosystem I primary electron donor, P700, upon sudden light increase and a slower re-reduction rate compared to the wild type, pointing to a limitation of plastocyanin. Spectroscopic, proteomic and immunoblot analyses confirmed that the phenotype was a result of lower levels of plastocyanin in the apx2 mutants. The redox state of P700 did not differ between wild type and apx2 mutants when the loss of function in plastocyanin was nutritionally complemented by growing apx2 mutants under copper deficiency. In this case, cytochrome c6 functionally replaces plastocyanin, confirming that lower levels of plastocyanin were the primary defect caused by the absence of APX2. Overall, the results presented here shed light on an unexpected regulation of plastocyanin level under copper-replete conditions, induced by APX2 in Chlamydomonas.

Ascorbate Peroxidase 2 (APX2) of Chlamydomonas Binds Copper and Modulates the Copper Insertion into Plastocyanin

Recent phylogenetic studies have unveiled a novel class of ascorbate peroxidases called "ascorbate peroxidase-related" (APX-R). These enzymes, found in green photosynthetic eukaryotes, lack the amino acids necessary for ascorbate binding. This study focuses on the sole APX-R from Chlamydomonas reinhardtii referred to as ascorbate peroxidase 2 (APX2). We used immunoblotting to locate APX2 within the chloroplasts and in silico analysis to identify key structural motifs, such as the twin-arginine transport (TAT) motif for lumen translocation and the metal-binding MxxM motif. We also successfully expressed recombinant APX2 in Escherichia coli. Our in vitro results showed that the peroxidase activity of APX2 was detected with guaiacol but not with ascorbate as an electron donor. Furthermore, APX2 can bind both copper and heme, as evidenced by spectroscopic, and fluorescence experiments. These findings suggest a potential interaction between APX2 and plastocyanin, the primary copper-containing enzyme within the thylakoid lumen of the chloroplasts. Predictions from structural models and evidence from 1H-NMR experiments suggest a potential interaction between APX2 and plastocyanin, emphasizing the influence of APX2 on the copper-binding abilities of plastocyanin. In summary, our results propose a significant role for APX2 as a regulator in copper transfer to plastocyanin. This study sheds light on the unique properties of APX-R enzymes and their potential contributions to the complex processes of photosynthesis in green algae.

Enhanced quality of capacitated spermatozoa from oligoasthenozoospermic men after incubation in test yolk medium

To improve artificially the quality of poor sperm samples to be used in assisted procreation procedures, Test Yolk Buffer (TYB) incubation effect was investigated. After adding the TYB procedure to the standard swim-up technique, a significant (P < 0.001) increase in spermatozoa velocity was observed, while the other seminal parameters were not affected. Three of 11 couples who had not had success after three intraperitoneal inseminations (IPI) with sperm prepared by the usual swim-up technique obtained pregnancies after IPI with TYB-incubated spermatozoa. These preliminary results suggest that TYB incubation for capacitated spermatozoa be employed in the assisted procreation strategies applied for male infertility.

Negative effect of stress of in vitro fertilization program on quality of semen

There are controversial data on the effects of stress on semen quality during treatment for infertility. We have compared the parameters of semen obtained from 84 patients on the day of the ovocyte pick-up during an in vitro fertilization and embryo transfer program (IVF) with those of semen collected from the same patients on the day of admission to the program (up to 3 months earlier). Abnormal semen has been found in 2 of the 84 patients on the day of admission and in 11 on the day of IVF. There were no improvements in semen quality of any patient at the second test. All except two parameters evaluated objectively by the Hamilton-Thorn Motility analyzer were significantly worse (p < 0.001) on the day of IVF, the exceptions were the percentage with moderate or slow motility and the Linear Index. These data indicate that the emotional stress to a subject enrolled in an IVF program negatively affects the quality of semen. Some suggestions are made for improved management of these patients.

IVF: induction of ovulation in poor responders

All IVF programs have a consistent rate of failure in inducing ovulations. Pharmacological induction of ovulation is otherwise crucial for an IVF program because of the need for more than one ovum. Since it is well known that the best candidates for HMG treatment are hypogonadotropic women a short reversible hypogonadotropic state was induced in IVF patients by LH-RH agonist (Buserelin). Superovulation was then achieved with very high initial doses of FSH (Metrodin) in order to maximize the ovarian response. This technique used in 116 IVF women induced a satisfactory follicle growth even in 70% of the patients already poorly responsive to HMG stimulation.

Ovarian stimulation of IVF patients: effects of the reversible hypogonadotrophic state induced by GnRH agonist

Multiple ovulation was induced in 122 hypogonadotrophic IVF patients with large doses of HMG. The hypogonadotrophic state, short and reversible, was obtained by nasal administration of a GnRH agonist (200 micrograms, five times per day). In the 97 induced cycles, a mean of 9.1 follicles was recorded. A comparison of the results obtained for 36 patients who had already been treated with clomiphene and HMG showed both significantly more follicles per cycle (8.5 versus 3.0) and an increase in oocytes retrieved (6.7 versus 1.3) when treated with the agonist and HMG. In addition 11 of 18 already poorly responsive patients had normal responses. The luteal phase was supported by either HCG or progesterone injection. Plasma progesterone profiles were satisfactory and, as expected, the highest progesterone concentrations were associated with HCG treatment.

Long term effects of cryoapheresis and cytostatic treatment in essential mixed cryoglobulinemia

We studied the effects of cryoapheresis combined with different immunosuppressive treatments on the course of the glomerulonephritis of essential mixed cryoglobulinemia. The study was carried out on 11 patients. The effects of immunosuppressive treatments on cryoglobulin rebound after cryoapheresis varied widely. In those responding with sustained reduction in serum cryoglobulin levels, creatinine clearance increased, an effect that lasted several years in 4 patients. In one patient cryoglobulin disappeared, with almost fully recovery of renal function and normalization of blood pressure. One patient died of acute liver failure shortly after the first observation and another entered regular dialysis treatment. All the other patients are still alive after follow-up of 2-9 years. These results compare favourably with those reported by other investigators and suggest that cryoapheresis and cytostatic drugs are beneficial for glomerulonephritis associated with essential mixed cryoglobulinemia.

Suppression of post-apheresis autoantibody rebound in cryoglobulinemia and cold agglutinin hemolytic anemia

We studied the effect of immunosuppressive treatment on the autoantibody rebound that follows autoantibody withdrawal accomplished by extracorporeal plasma treatment. The study was carried out on 9 patients, 8 having essential mixed cryoglobulinemia and 1 cold agglutinin hemolytic anemia. As immunosuppressive drugs we used either cyclophosphamide and prednisolone or arabinoside C and cyclophosphamide. The effect of immunosuppressive treatment on autoantibody rebound (Igm anti-IgG; IgM cold agglutinins) varied widely, a suppressive effect of varying degree having been observed in about half the cases treated with either drug regimen.

Glomerular localization of circulating antiglobulin activity in essential mixed cryoglobulinemia with glomerulonephritis

Kidney biopsy samples from 27 patients with essential mixed cryoglobulinemia of the IgG-IgM(k) type and glomerulonephritis were studied to assess whether glomerular immunodeposits display antiglobulin (AG) activity similar to that of serum cryo-IgM. A preparation of heat-aggregated human IgG (FAIgG) was used to search for tissue AG activity, and blocking tests and reactivity tests were carried out to define the nature of this activity. Glomerular localization of FAIgG was observed in 17 out of 27 kidney specimens, the positive findings being always associated with IgM deposits. Prior exposure of tissue sections to anti-IgM serum blocked the FAIgG reaction, but no such effect was produced by the pretreatment with other antisera. The positive FAIgG tissue specimens yielded a similar fluorescence pattern with aggregated alkylated-reduced IgG, but did not react at all with the aggregated F(ab')2 or aggregated albumin. The IgM recovered in the eluate of a kidney biopsy specimen displayed AG activity. Patients with AG deposits showed more severe histologic changes and a greater renal functional impairment than did those without. The data support the notion that circulating cryo-IgM anti-IgG participates in the formation of glomerular immunodeposits and in the genesis of renal damage.

Preparation of a partially desialylated human chorionic gonadotrophin (hCG) and its use for induction of ovulation after ovarian stimulation with human menopausal gonadotrophin

A method for the large scale preparation of partially desialylated human chorionic gonadotrophin suitable for human use is reported. To obtain the desired grade of desialylation and to avoid the presence of the enzyme in the modified hormone, neuraminidase coupled to Sepharose 4B was used. The preparation showed to be active in vitro (OAAD and SVW tests) and its half-life was found to be 13 min in the rat and 75 min in human beings. This desialo hCG proved to be effective in inducing ovulation in amenorrhoeic women. Among 39 induced cycles 31 ovulations and 5 pregnancies occurred.

Effect of three serotonin antagonists on plasma prolactin response to suckling in puerperal women

The effect of the acute administration of three serotonin antagonists on plasma PRL levels and on the PRL response to suckling was investigated in a group of puerperal women. A single oral dose of metergoline or methysergide induced a significant decrease of plasma PRL levels and abolished the PRL response to suckling. Cyproheptadine administration did not modify either the plasma PRL levels or the PRL response to suckling. These results are discussed in light of the known pharmacological properties of the three antiserotonergic drugs.

Antiserotonin treatment of hyperprolactinemic amenorrhea: long-term follow-up with metergoline, methysergide, and cyproheptadine

Twenty patients affected by hyperprolactinemic amenorrhea-galactorrhea have been treated with one or more of the following serotonin antagonists: metergoline, methysergide, and cyproheptadine. Among the 11 patients without evidence of pituitary tumor resumption of menses was observed in five, two of whom had ovulatory cycles; one patient became pregnant; ovulations occurred only during treatment with metergoline. In the group of nine patients with enlarged sellae, three experienced isolated episodes of bleeding, while two had three and four menses each, respectively; all cycles were anovulatory. Plasma prolactin levels and galactorrhea were favorably affected by treatment only in a minority of amenorrhea-galactorrhea patients with and without tumors.

Suppression of puerperal lactation by metergoline

Based on the known stimulatory effect of serotonin on prolactin secretion, a trial of suppression of puerperal lactation by a potent serotonin antagonist, metergoline, was carried out in 30 puerperal women who did not want to nurse. The drug was administered orally at the dose of 4 mg tid for 5 days to all subjects, starting between 24 and 72 hours from delivery. Lactation was either prevented or rapidly suppressed in all subjects. Rebound of lactation after the end of treatment was observed in 10% of cases. Metergoline administration was associated with a significant suppression of the plasma prolactin levels.

Failure of dopamine infusion to suppress the plasma prolactin response to sulpiride in normal and hyperprolactinemic subjects

In eleven normal women dopamine infusion (5 microgram/Kg/min) significantly lowered plasma prolactin levels but failed to suppress the PRL response to sulpiride (10 or 100 mg i.v.), while the same dose of dopamine was effective in abolishing the PRL response to TRH (200 microgram i.v.). In four hyperprolactinemic women showing an impaired PRL response to sulpiride, dopamine infusion was effective both in lowering PRL circulating levels and in restoring an evident response to sulpiride. This finding suggests an impairment of endogenous dopamine activity in hyperprolactinemic amenorrhea.

The effect of alpha1-24-corticotropin on growth hormone release in prepubertal children

The effect of alpha1-24-corticotropin-Zn on the results of pituitary stimulation tests (moderate standardized physical exercise, arginine infusion, insulin-induced hypoglycemia) was studied in 27 prepubertal children with non-endocrine retardation of growth and development. After administration of 1 mg alpha1-24-corticotropin, the basal blood glucose and plasma cortisol levels rose significantly. However, the growth hormone increase after the three stimulation tests was significantly lower than without the corticotropin injection. The results demonstrate the inhibiting effect of alpha1-24-corticotropin on growth hormone secretion.

Muscular exertion: a test of pituitary function in children

The elevated level of growth hormone after moderate standardized physical exercise was compared with that induced by intravenous arginine infusion and by insulin induced hypoglycemia in children with normal pituitary function. Tests were performed on 49 prepubertal children (34 boys and 15 girls); in 42 cases the increase was significant for all three tests, in 5 cases the response was minimal after insulin stimulation but normal after arginine and physical exertion; in 1 case arginine produced no response but the other tests were positive; in 1 case there was a response to arginine but none to insulin or physical exertion. The results indicate that frequently more than one test is necessary for the diagnosis of normal pituitary function; physical exertion being a physiologic test, is simple to perform, acceptable to the children and without side effects. It appears the test of first choice because it can be used in patients seen ambulatorily, other tests being performed in case of doubt or negative response.

Effect of physical exercise on secretion of growth hormone, glucagon, and cortisol in obese and diabetic children

The effect of muscular exertion of moderate intensity on blood sugar (BS), plasma levels of growth hormone (GH), glucagon, and cortisol (F) has been studied in endocrinologically normal children with short stature and compared with children with clinical diabetes mellitus and obese children with normal and diminished carbohydrate tolerance. In diabetic children, physical exertion induces a rise in plasma GH levels comparable to that in controls; in obese children with normal or with diminished glucose tolerance, the rise is considerably smaller. Physical exertion caused no change in F levels in the groups tested, although basal level in the obese children was significantly higher than in the controls. Basal glucagon levels were similar in all groups and showed no change on physical exertion. The behavior of GH and glucagon in diabetic children was comparable to that in the controls even where blood sugar level was high.