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Biomedical subjects

G Forti

Publications and source records attributed to G Forti.

At least 163 records · Page 9Linked to original sources
PubMed1978

Studies on Cation-induced Thylakoid Membrane Stacking, Fluorescence Yield, and Photochemical Efficiency.

Trypsin digestion of photosynthetic membranes isolated from spinach (Spinacia oleracea L.) leaves eliminates the cation stimulation of chlorophyll fluorescence. High concentrations of cations protect the fluorescence yield against trypsin digestion, and the cation specificity for this protection closely resembles that required for the stimulation of fluorescence by cations. Trypsin digestion reverses cation-induced thylakoid stacking, and the time course of this effect seems to parallel that of the reversal of cation fluorescence. High concentrations of cations protect thylakoid stacking and cation-stimulated fluorescence alike. The cation stimulation of photosytem II photochemistry remains intact after trypsinization has reversed both cation-induced thylakoid stacking and fluorescence yield. It is concluded that cation-stimulated fluorescence yield, and not the cation stimulation of photosystem II photochemistry, is associated with thylakoid membrane stacking.

Journal Article↗
PubMed1978

Measurement of 5-androsten-3beta,17beta-diol in spermatic and peripheral venous blood samples from the same human subjects by a radioimmunoassay method.

An original method for 5-androsten-3beta,17beta-diol (A-diol) measurement using an antiserum against A-diol-16-CMO-BSA is described. A-diol and testosterone (T) were determined by radioimmunoassay methods in spermatic and peripheral venous plasma of nine normal subjects during surgical intervention for inguinal hernia repair. In spermatic venous plasma the levels of T and A-diol were, respectively, 25.9 +/- 13.3 and 4.8 +/- 5.1 microgram/100ml (mean +/- SD) with an A-diol/T ratio of 0.19 +/- 0.15 (mean +/- SD); in peripheral plasma the levels of T and A-diol were, respectively, 269 +/- 58 and 91 +/- 25 ng/100 ml (mean +/- SD) with an A-diol/T ratio of 0.35 +/- 0.12 (mean +/- SD) significantly different from spermatic venous plasma (p less than 0.01). From these data a mean testicular A-diol secretion of about 0.70 mg/24 h can be calculated: this value corresponds approximately to the 50% of the blood production rate (BPR) of this steroid. So it can be assumed that a large amount of A-diol in systemic blood comes from sources outside the male gonad.

Adult↗
PubMed1977

Inhibition of photosynthesis by azide and cyanide and the role of oxygen in photosynthesis.

Cyanide and azide inhibit photosynthesis and catalase activity of isolated, intact spinach (Spinacia oleracea) chloroplasts. When chloroplasts are illuminated in the presence of CN(-) or N(3) (-), accumulation of H(2)O(2) is observed, parallel to inhibition of photosynthesis. Photosynthetic O(2) evolution is inhibited to the same extent, under saturating light, whether CO(2) or phosphoglycerate is present as electron acceptor.The illumination of chloroplasts with CN(-) or N(3) (-) inactivates the NADPH- and ATP-dependent phosphoglycerate reduction. This enzyme system can be reactivated by dithiothreitol. In reconstituted, envelope-less chloroplasts, the phosphoglycerate-dependent and the ribose 5-phosphate-dependent O(2) evolution are inhibited to the same extent, while electron transport to NADP is unaffected.It is concluded that the inhibition of photosynthesis by CN(-) and N(3) (-) is due to H(2)O(2) accumulation, which is a consequence of catalase inhibition.The inhibition of phosphoglycerate reduction, but not of CO(2) reduction, is abolished under conditions where ATP is available in excess of NADPH (low light, supply of ATP). This is taken as an indication that electron flow from photosystem I is diverted to O(2) (Mehler reaction, which produces H(2)O(2)) when the unavailability of ATP is limiting the rate of reoxidation of NADPH. The Mehler reaction is considered a physiological process supplying ATP for photosynthesis.

Journal Article↗
PubMed1977

Plasma androgens in women with hyperprolactinaemic amenorrhoea.

Cortisol, androstenedione, testosterone, dehydroepiandrosterone sulphate (DHAS) and free dehydroepiandrosterone (DHA) were measured in plasma of ten women affected by amenorrhoea with hyperprolactinaemia and eleven women affected by secondary hypothalamic amenorrhoea; twelve normal women at the second day of the menstrual cycle were used as controls. All subjects were hospitalized and 17-ketosteroids, 17OH-corticosteroids and total dehydroepiandrosterone were also measured in urine. Plasma DHAS was increased in all subjects affected by amenorrhoea with hyperprolactinaemia, while plasma DHA and urinary DHA were significantly increased in this group in comparison to other groups. Plasma cortisol, androstenedione and testosterone and urinary 17-oxosteroids and 17OH-corticosteroids were not significantly differnt in the three groups. In subjects affected by amenorrhoea with hyperprolactinaemia treated with bromocriptine a clear decrease of DHAS correlating with a decrease of plasma prolactin was observed. Since in wome DHAS sems to be almost exclusively secreted by the adrenal gland and most of the circulating DHA is dervied from adrenal secretion, these data suggest that human prolactin can stimulate DHAS production by the adrenal cortex.

Adrenal Cortex↗
PubMed1976

Studies on the slow fluorescence decline in isolated chloroplasts.

Data presented here indicate that the slow fluorescence decline in osmotically disrupted chloroplasts is not associated with the well known divalent cation effect on fluorescence yield. Thus the two phenomena have markedly different magnesium concentration requirements, magnesium addition after the fluorescence decline did not stimulate the dark reversal, and the characteristics of the fluorescence induction kinetics of the two processes are not similar. At pH 7.6 the slow fluorescence decline was stimulated by several uncouplers demonstrated to greatly reduce proton pumping, and at pH 9.2 it was stimulated by all uncouplers tested. Acid-base transition was strongly inhibitory, and this inhibition was relieved by coupling factor is suggested by experiments in which phosphorylation substrates were inhibitory, and this inhibition was prevented by uncoupler. These data are explained in terms of coupling factor structural changes which in an unknown manner influence Photosystem II fluorescence emission. Fluorescence induction curves indicate that the slow quenching decreased only the variable fluorescence. The half rise time was decreased along with the sigmoidicity of the rise curve. These data can be accomodated in terms of a model recently proposed by Butler and Kitajima (Biochim. Biophys Acta (1975) 376, 116-125), involving the transfer of energy from the excited, but closed, reaction centres II to the light harvesting chlorophyll system. The slow fluorescence decline is suggested to represent a decrease of this process.

Chlorophyll↗
PubMed1976

Familial male internal pseudohermaphroditism; report on a case.

A rare case of male internal pseudohermaphroditism is described. The patient had normal external male sexual characteristics but unilateral cryptorchidism. Three of his four brothers had also cryptorchidism and were also involuntary infertile. One of them was later operated and a uterus found intra-peritoneallu. The patient's parents were cousins and the possible importance of an inheritable defect is discussed. The patient's karyotype was normal.

Disorders of Sex Development↗
PubMed1976

Dihydrotestosterone in human ovarian venous plasma.

Androstenedione (delta), oestradiol-17beta (Oe2), 5alpha-dihydrotestosterone (DHT), progesterone (P) and testosterone (T) concentrations have been measured by radioimmunoassay in ovarian and peripheral venous blood from 15 women in the luteal phase of the cycle. The ovarian blood samples were obtained during surgical intervention from 15 ovaries containing the corpus luteum and from 5 contralateral ovaries. The mean concentration of DHT in ovarian venous blood was not higher than that found in the cubital vein. However in some cases with high concentrations of testosterone in ovarian venous blood, a small but significant DHT gradient was found.

Adult↗
PubMed1975

Fluorescence induction in intact spinach chloroplasts.

Under conditions in which the Photosystem II quencher is rapidly reduced upon illumination, either after a preillumination or following treatment with dithionite, the fluorescence-induction curve of intact spinich chloroplasts (class I type) displays a pronounced dip. This dip is probably identical with that observed after prolonged anaerobic incubation of whole algal cells ("I-D dip"). It is inhibited by 3(3,4-dichlorophenyl)-1,1-dimethylurea and occurs in the presence of dithionite, sufficient to reduce the plastoquinone pool. It is influenced by far red light, methylviologen, anaerobiosis and uncouplers in a manner consistent with the interpretation that it represents a photochemical quenching of fluorescence by an electron transport component situated between the Photosystem II quencher and plastoquinone. Glutaraldehyde inhibition may indicate that protein structural changes are involved.

Anaerobiosis↗
PubMed1975

Evidence for energy migration from photosystem I to photosystem II and the effect of magnesium.

1. With Euglena chloroplasts 7722 nm light excites a fluorescence induction pattern, measured at l,u nm, typical of the Photosystem II reduction of Q. 2. Both methylviologen and phenazine methosulfate partially quench this fluorescence rise in the absence of electron transport between Photosystem II and Photosystem I, and in a manner consistent with their known role of stimulating Photosystem I photochemistry. 3. The variable fluorescence excited with 22 nm light is reduced to a greater extent than that excited by 638 nm light upon chlorophyll dilution during division in the dark. 4. These observations are interpreted to indicate that in Euglena chloroplasts light absorbed by Photosystem I is transferred energetically "uphill" to Photosystem II, where it can perform Photosystem II photochemistry. 5. Magnesium ions stimulate the variable fluorescence with both 638 nm and 722 nm light to a similar extent, which argues against the concept of magnesium ion interrupting energy transfer between Photosystem II and Photosystem I.

Chlorophyll↗
PubMed1975

A rapid radioimmunoassay for determination of dehydroepiandrosterone sulphate in human plasma.

A rapid radioimmunoassay for the determination of dehydroepiandrosterone sulphate (DHEA-S) in diluted human plasma is described. The radioimmunoassay is performed using an antiserum to DHEA-3-hemisuccinate-BSA. A charcoal-dextran mixture is used for separation of the bound from the free fraction. The reliability criteria of the method in terms of precision, accuracy, sensitivity and specificity have been evaluated. The mean level of DHEA-S in plasma samples from normal men (age range 24-37) is 241-5+/-72-5 mug/dl. In normal premenopausal women the highest values are in the second third of the menstrual cycle (corresponding to the ovulatory phase). In normal old men (age range 64-86) and in post-menopausal women (age range 55-88) the mean values are, respectively, 51-9+/-33-8 and 53-8+/-34-0. The DHEA-S levels found in several cases of adreno-cortical disorders are reported. In primary adrenal insufficiency and in Cushing's syndrome due to adrenal adenoma or bilateral multinodular hyperplasia low values are found; in Cushing's syndrome due to bilateral adrenal hyperplasia normal values are usually found.

Adenoma↗
PubMed1975

Radioimmunoassay of plasma dihydrotestosterone in normal and hypogonodal men.

A radioimmunoassay for determination of dihydrotestosterone (DHT) in man is described. After extraction from plasma, DHT is separated by paper chromatography. The radioimmunoassay is performed using an antiserum to dihydrotestosterone-3-oxime-BSA and a charcoal-dextran mixture is used to separate the free from the bound fraction. The reliability criteria of the method in terms of precision, accuracy, sensitivity and specificity have been evaluated. The mean level of DHT in plasma samples from young (age 21-37) and old (age 65-90) normal men is respectively (mean+/-SD) 54-7+/-19 ng/dl (n = 17) and 39-1+/-19 ng/dl (n = 14). The difference is statistically significant (P less than 0-01). The values found in seven patients with Klinefelter's syndrome (21-0+/-6 ng/dl) are significantly lower than normal young subjects (P less than 0-01). Lastly, the DHT levels found in a mixed group of male hypogonadism (azoospermia, due to tubular failure, germinal cell aplasia and anorchia) are reported.

Adult↗