Naloxone evokes large-amplitude GnRH pulses in luteal-phase ewes

Ewes were sampled during the mid-late luteal phase of the oestrous cycle. Hypophysial portal and jugular venous blood samples were collected at 5-10 min intervals for a minimum of 3 h, before i.v. infusions of saline (12 ml/h; N = 6) or naloxone (40 mg/h; N = 6) for 2 h. During the 2-h saline infusion 2/6 sheep exhibited a GnRH/LH pulse; 3/6 saline infused ewes did not show a pulse during the 6-8-h portal blood sampling period. In contrast, large amplitude GnRH/LH pulses were observed during naloxone treatment in 5/6 ewes. The mean (+/- s.e.m.) amplitude of the LH secretory episodes during the naloxone infusion (1.07 +/- 0.11 ng/ml) was significantly (P less than 0.05) greater than that before the infusion in the same sheep (0.54 +/- 0.15 ng/ml). Naloxone significantly (P less than 0.005) increased the mean GnRH pulse amplitude in the 5/6 responding ewes from a pre-infusion value of 0.99 +/- 0.22 pg/min to 4.39 +/- 1.10 pg/min during infusion. This episodic GnRH secretory rate during naloxone treatment was also significantly (P less than 0.05) greater than in the saline-infused sheep (1.53 +/- 0.28 pg/min). Plasma FSH and prolactin concentrations did not change in response to the opiate antagonist. Perturbation of the endogenous opioid peptide system in the ewe by naloxone therefore increases the secretion of hypothalamic GnRH into the hypophysial portal vasculature. The response is characterized by a large-amplitude GnRH pulse which, in turn, causes a large-amplitude pulse of LH to be released by the pituitary gland.     

Characterisation of the effects of Antimycin A upon high energy state quenching of chlorophyll fluorescence (qE) in spinach and pea chloroplasts

High energy state quenching of chlorophyll fluorescence (qE) is inhibited by low concentrations of the inhibitor antimycin A in intact and osmotically shocked chloroplasts isolated from spinach and pea plants. This inhibition is independent of any effect upon pH (as measured by 9-aminoacridine fluorescence quenching). A dual control of qE formation, by pH and the redox state of an unidentified chloroplast component, is implied. Results are discussed in terms of a role for qE in the dissipation of excess excitation energy within photosystem II.Abbreviations 9-AA_max = Maximum yield of 9-aminoacridine fluorescence - DCMU = 3(3,4-dichlorophenyl)-1,1-dimethylurea; F_max ± Maximum yield of chlorophyll fluorescence - hr = hour - PAR = Photosynthetically Active Radiation - Q_A = Primary stable electron acceptor within photosystem II - qE = High energy state quenching of chlorophyll fluorescence - qI = quenching of chlorophyll fluorescence related to photoinhibition - qP = Quenching of chlorophyll fluorescence by oxidised plastoquinone - qQ = photochemical quenching of chlorophyll fluorescence - qR = (F_max—maximum level of chlorophyll fluorescence induced by the addition of saturating DCMU) - qT = Quenching of chlorophyll fluorescence attributable to state transitions     

Resolution of sulphydryl oxidase from gamma-glutamyltransferase in bovine milk by covalent chromatography on cysteinylsuccinamidopropyl-glass.

1. Sulphydryl oxidase from bovine milk was purified by covalent affinity chromatography on cysteinylsuccinamidopropyl-glass. Selective immobilization of the oxidase occurs through formation of a mixed disulphide between the enzyme and the substrate cysteinyl-glass matrix. Reductive elution of the bound protein can be accomplished with small thiols such as reduced glutathione (GSH), dithiothreitol or cysteine. This method leads to approx. 4000-fold purification of the enzyme from whey. Furthermore, complete resolution of sulphydryl oxidase from gamma-glutamyltransferase was achieved with this procedure. 2. Antibodies prepared against this purified enzyme quantitatively precipitated 95% of the GSH-oxidative activity from detergent-solubilized skim-milk membranes, whereas 100% of the transferase activity remained in the supernatant fraction; these findings confirmed the distinction between these two enzymes. 3. Reverse-phase high-pressure-liquid-chromatographic analyses of assay mixtures containing both enzymes revealed an array of GSH derivatives generated by a combination of the oxidative and hydrolytic activities. However, purified sulphydryl oxidase yielded only GSSG with concomitant stoichiometric loss of GSH. 4. The chromatographic method described is simple and reproducible, and may be applicable to isolation of sulphydryl oxidase from other tissues.     

Direct Comparison of the N-Acetyl-L-Cysteine-Sodium Hydroxide and the Trisodium Phosphate Digestion Methods for the Culture of Mycobacteria

Comparison of sputum digestion procedures utilizing acetylcysteine-sodium hydroxide (AC) and trisodium phosphate for the isolation and culture of mycobacteria indicated that the AC procedure provides faster growth, thus permitting the earlier detection of positives. Also, in untreated patients and those in whom treatment has been recently instituted, the number of positives was slightly larger with the use of the AC procedure. However, of greater interest was finding that the AC procedure provided a larger quantity of positive cultures with sputum from subjects who had been intensively treated with antimicrobials and other drugs. Contamination was higher with the AC procedure, but when the sputa were diluted 1:10 this interference due to contamination was decreased.     

TEMPERATURE AND DNA TURNOVER IN THE GOLDFISH

Whole body DNA turnover in the goldfish, as measured by the rate of loss of incorporated ¹²⁵I-deoxyuridine, is remarkably invariant over a temperature range of 30 centigrade degrees. Apparently cell proliferation kinetics in this poikilotherm do not simply reflect chemical reaction rates but are under some sort of homeostatic control with respect to temperature. At the nearly lethal temperature of 37°C the rate of cell turnover increases and the absolute number of proliferating cells decreases.     

Transport of the auxin, picloram, through petioles of bean and coleus and stem sections of pea

The transport of the synthetic auxin, picloram (4-amino-3,5,6-trichloropicolinic acid) was investigated in sections of petioles of Phaseolus vulgaris L. and Coleus blumei Benth. and stems of Pisum sativum L. Transport of ¹⁴C-picloram was basipolar in all tissues, although the degree of polarity was dependant on age. The velocity of picloram movement was calculated at between 0.75 and 1.11 mm/hr. The amount moved in a given time, the flux, was dependant on the concentration applied and the length of the sections used. Picloram did not appear to be metabolized by the tissues during the transport experiments. When compared to the movement of other growth regulators, picloram transport bears marked similarities to that of 2,4-dichlorophenoxyacetic acid.     

Preparation of acetylenic sugar derivatives by way of 2-(N-nitroso)acetamido sugars

N-Nitrosation with dinitrogen tetraoxide was used to convert 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-α-D-glucopyranose (1) and 2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-β-D-galactopyranose (4) in high yield into the N-nitroso derivatives 2 and 5, respectively. Similarly, 3-acetamido-1,2,4,6-tetra-O-acetyl-3-deoxy-β-D-glucopyranose (12) and methyl 2-acetamido-3,4,5,6-tetra-O-acetyl-2-deoxy-D-gluconate (15) gave their respective, crystalline N-nitroso derivatives 13 and 16. Various other 2-acetamido sugar derivatives were likewise nitrosated. In ethereal solution, compounds 2 and 16 reacted with potassium hydroxide in isopropyl alcohol to give the C₅ acetylene, 1,2-dideoxy-D-erythro-pent-1-ynitol, isolated as the known triacetate 3. By the same procedure, the galacto derivative 5 was converted in high yield into the 3-epimeric C₅ acetylene, 1,2-dideoxy-D-threo-pent-1-ynitol, isolated as its triacetate 6 and characterized by conversion into the known, crystalline 1,2-dideoxy-3-O-(3,5-dinitrobenzoyl)-4,5-O-isopropylidene-D-threo-pent-1-ynitol (7).     

The effect of angiotensin II and indomethacin on immunoreactive prostaglandin “A” levels in man

The effect of angiotensin II on peripheral levels of immunoreactive prostaglandin A₂ (IR-PGA) was determined in 17 normal male volunteers. IR-PGA rose from 338 ± 65 (SE) pg/ml to 635 ± 142 in response to pressor infusions of angiotensin II (p <0.05 on paired analysis). This increase was not observed when indomethacin, 75 mg p.o., was given to 8 patients two hours prior to a repeat infusion. Five patients of the original group were placed on a low sodium diet (10–20 mEq). The response to angiotensin was now exaggerated (278 ±52 pg/ml to 916 ± 284). These five patients were kept on a low sodium intake and given indomethacin 50 mg p.o. q 6 hourly for 4 days. There was no significant rise with angiotensin infusion (106 ± 31 pg/ml to 120 ± 70). Pressor infusions of angiotensin II raise peripheral levels of IR-PGA, and this response is exaggerated by a low sodium diet and blocked by either acute or chronic indomethacin administration. This data supports the concept that vasodilatory prostaglandins may be released by endogenous angiotensin and thus provide a dynamic antagonism to the renin angiotensin system in man.     

Metabolism of prostaglandins A1 and A2 by human whole blood

The effect of human blood on prostaglandin metabolism in vitro was studied at 37°C and 4°C. Labeled prostaglandins were incubated for up to one hour in whole blood or plasma. After extraction, the prostaglandins were purified by LH-20 Sephadex chromatography. Appropriate ¹⁴C labeled compounds, when available, were used to correct for losses. Metabolism was determined by comparison of incubated samples with zero time controls. There was no reduction in isotopic recovery of prostaglandins B₁, B₂ and E₁ after incubation with whole blood for up to one hour. In contrast, human whole blood, but not plasma, rapidly metabolized prostaglandins A₁ and A₂ at 37°C. The rate of metabolism was temperature dependent, but still continued at 4°C. The products of these reactions were not identified, but they appeared to remain in the aqueous solution after extraction with the neutral organic solvent.