Response of developing mouse liver irradiated in utero and its modification by 2-mercaptopropionylglycine

Pregnant Swiss albino mice were exposed at gestation days 141/4, 161/4 and 181/4 to 1.5 Gy gamma radiation from 60Co in the presence or absence of 2-mercaptopropionylglycine (MPG). Liver was taken from the litters born to these mothers at different post-partum intervals. The maximum sensitivity was found in 4-week-old animals irradiated at gestation day 141/4. In the MPG treated groups, the number of total cells was higher than in the controls but less than in normals. The increase in pyknotic nuclei and necrotic and binucleate cells was significantly lowered by MPG.

Effects of prenatal gamma-radiation on the development of mice and its modification by 2-mercaptopropionylglycine

Pregnant Swiss albino mice were whole-body exposed to 250, 150 and 50 R gamma-radiation from 60Co in the presence or absence of 2-mercaptopropionylglycine during selective organogenesis and fetal growth periods (days 11.25 and 14.25, 16.25 and 18.25 after conception, respectively). Both the protected and nonprotected pregnant females of 11.25-day gestation showed complete resorption of embryos irradiated with 250 R. With 150 R, in absence of the drug, 11.25-day gestating females showed partial resorption (76.10%). The percentage of parturition improved in the drug-treated females. Non-protected females irradiated with 50 R showed slight resorption, while drug-treated females had normal parturition. Females irradiated during the fetal growth period showed no resorption. Also, no significant alteration in litter size and sex ratio of the newborn animals was noticed when irradiated during this period, both in the control and the experimental groups. Mortality of the young was higher in nonprotected animals as compared to the protected ones.

Depressive effects of morphine and of an enkephalinase inhibitor on responses of ventro-basal thalamic neurones to noxious stimuli

It has been shown that the responses of VB thalamic neurones to noxious mechanical and thermal stimuli are strongly depressed by low doses of Morphine (0,03; 0,1; 1 mg/kg i.v.) and to a lesser extent by ES 52 (a highly potent Thiorphan derivative) injected at higher doses (5; 10 mg/kg i.v). This last effect was less easily reversed by Naloxone than was the depressive effect of Morphine. Moreover, ES 52 can facilitate activity of some thalamic neurones induced by non-noxious mechanical stimuli.

Potentiation of oxygen toxicity in rats by dietary protein or amino acid deficiency

Rats fed 3% casein diets for 6 days showed an increased susceptibility to greater than 98% oxygen [mean survival time 46.9 +/- 4.1 (SD) h] compared with animals fed 25% casein diets (mean survival time 60 +/- 5 h). The 3% casein diet did not reduce the responses to hyperoxia of lung glucose-6-phosphate dehydrogenase, glutathione peroxidase, and glutathione reductase (NAD(P)H), which maintain tissue levels of reduced glutathione or lung superoxide dismutase levels. While supplementation of the 3% casein diet with the sulfur-containing amino acids (cysteine, cystine, or methionine) prevented the increased oxygen toxicity, supplementation with leucine, a nonsulfur-containing amino acid, had no effect on potentiation of toxicity. Animals fed the unsupplemented 3% casein diet failed to show an elevation of lung glutathione in response to hyperoxia. When the 3% casein diet was supplemented with cysteine, total lung glutathione levels increased normally during oxygen exposure. Supplementation of the 25% protein diet with cysteine did not further protect these animals. We conclude that potentiation of oxygen toxicity by dietary protein deficiency in the rat is due to the low sulfur-containing amino acid content of the diet; the mechanism of increased toxicity by hyperoxia is probably related to an inability to increase glutathione levels due to a shortage of the cysteine component of the glutathione tripeptide.

Radioresponse of postnatal erythrocytes and its modification by MPG (2-mercaptopropionylglycine) in mice exposed to gamma radiation in utero

Gamma radiation (150 R) was given in utero at different gestation days, namely 14 1/4, 16 1/4 and 18 1/4, to Swiss albino mice, pretreated with either MPG or double distilled water. Erythrocytes from peripheral blood were counted in young ones at 1, 2, 4 and 6 weeks after birth. The result indicated that erythrocyte count in the MPG treated group was significantly higher than in the unprotected ones at 1 and 2 weeks of postnatal development, after which the values of both control and experimental groups were comparable to that of the normal.

[Effect of sulfur-containing compounds on the ultrastructural organization of the cell wall of Candida utilis yeasts]

The effect of sulfur-containing compounds (cysteine, homocysteine, glutathione, cystine, and methionine) on the ultrastructural organization of the cell wall was studied in Candida utilis 295t by electron microscopy with the aid of staining SH groups by HgCl2. Treatment of the cells with cysteine and homocysteine was found to modify the ultrastructure of the cell wall: the capsule was damaged and the porosity increased, which facilitated the penetration of these compounds into the periplasm. Their further conversion in the cell has been studied.

Potentiation of [D-ala2]enkephalinamide analgesia in rats by thiorphan

The effect of thiorphan, an inhibitor of enkephalin dipeptidyl carboxypeptidase, was tested in the rat tail-flick test. When given alone up to 100 mg/kg s.c., thiorphan had no effect. However, thiorphan (30 mg/kg, s.c.) potentiated intraventricularly administered [D-Ala2,Met5]enkephalinamide (DEAEM) and its [Leu5]-derivative, whereas it had no effect on [D-Ala2,Met5]enkephalin, [D-Met2,Pro5]enkephalinamide, or morphine. Potentiation of DAEAM by thiorphan was dose-responsive and naloxone reversible. The most efficient enhancement of the analgesic effects of DAEAM was seen when the two drugs were co-administrated in rapid succession. Thus, thiorphan potentiation of opioid-peptide induced analgesia in the rat is similar to that seen in the mouse.

Potentiation of stress-induced analgesia (SIA) by thiorphan and its block by naloxone

Exposure of rats to inescapable footshock produces an analgesic effect. To determine if endogenously released enkephalins play a role in this phenomenom, rats were treated with the enkephalinase inhibitor thiorphan (T), exposed to inescapable stress, and tested in the tail-flick test for antinociception. T (10-100 mg/kg sc) caused a dose-related potentiation of both the peak effect and the duration of the SIA. This effect was blocked by doses of naloxone (1 mg/kg sc) that did not affect baseline response latencies.

Thiorphan potentiation of stress-induced analgesia in the mouse

Experiments were done to examine the analgesic effect of thiorphan alone or in combination with stress in mice. Analgesia was assessed by measuring jump latencies from a 55 degrees C hot plate. Thiorphan exhibited weak analgesic properties evidenced by significant increases in jump latencies only after 300 mg/kg i.p. Additional experiments were done to see the effect of i.c.v. administration of thiorphan in the mouse hot plate test. Control experiments revealed that either i.c.v. saline or sham caused naloxone reversible analgesia which was potentiated by thiorphan (100 mg/kg i.p.). Immobilization stress-induced analgesia was also potentiated by thiorphan (100 mg/kg i.p.) and antagonized by naloxone (10 mg/kg i.p.). The results suggest that stress-induced analgesia in the mouse is associated with an endogenous opioid mechanism which is potentiated when enkephalin degradation is inhibited by thiorphan.

Relationship between monensin and sulphur amino acid requirements in broiler chickens

1. Diets containing 80, 100, 125, 150, 175 or 200 mg monensin/kg were fed to broiler chickens from 0 to 28 d in cages that prevented access to excreta. 2. Growth was depressed with 125 mg monensin or more/kg and food intake tended to decrease. Feathering was adversely affected with 175 mg or more/kg. 3. In a similar experiment, diets containing 8.8, 9.1, 9.4, 9.7 and 10.1 g total sulphur amino acids (SAA)/kg were supplemented with 125 or 80 mg monensin/kg and compared with a diet containing 8.8 g SAA and 33 mg robenidie/kg. 4. With 125 mg monensin/kg, body-weight gain was significantly less than that of birds receiving robenidine if dietary SAA content was 9.4 g or less/kg. With 9.7 g SAA or more/kg, gain in birds receiving monensin was similar to that of birds receiving robenidine. 5. Monensin at 125 mg/kg therefore appears to increase SAA requirement.

Effects of thiorphan on the antinociceptive actions of intrathecal [D-Ala2,Met5] enkephalin

The intrathecal administration of thiorphan (dl-3-mercapto-2-benzylpropranoyl-glycine) had no effect in doses up to 70 microgram on the rat hot plate and tail flick. Administrations of these doses of thiorphan concurrently or up to 1 h prior to the intrathecal administration of [D-Ala2, Met5] enkephalin resulted in a dose dependent, leftward shift in the peptide dose response curve. The potentiation was maximal with 35 micrograms, higher doses producing no greater potentiation. The potentiated effects of [D-Ala2,Met5] enkephalin were totally antagonized by systemically administered naloxone. Similarly, in the primate, concurrent administration of thiorphan alone in doses up to 70 microgram, had little effect on the hot plate or tail flick in the rat. 200 microgram resulted in a significant increase in hot plate, but not tail flick response latency. The increase observed on the hot plate, was partially antagonized by naloxone. In the primate, doses of intrathecal thiorphan (400-800 microgram) had no effect on the shock titration threshold. Higher doses resulted in an increase in the titration threshold, which was not antagonized by naloxone. These experiments appear to indicate the relevance of the thiorphan-sensitive inactivation system in the spinal cord to the relative potency of exogenously administered opioid peptides.

Angiotensin-converting enzyme inhibitors: importance of the amide carbonyl of mercaptoacyl amino acids for hydrogen bonding to the enzyme

A series of mercaptoacyl amino acids and related compounds was synthesized and evaluated for inhibition of angiotensin-converting enzyme (ACE) in order to determine the nature and importance of the putative interaction between ACE and the amide moiety of inhibitors such as captopril (3-mercapto-2-methylpropanoyl-L-proline). It was concluded that the interaction involves a hydrogen bond from a donor site on ACE to the oxygen of the amide carbonyl. Compounds in which the amide moiety is replaced by other groups (ester, ketone, sulfonamide) capable of accepting a hydrogen bond are effective inhibitors, but compounds in which only the geometrical features of the amide are retained are ineffective inhibitors. The presence of an NH group is not necessary for effective inhibition. The activity of a series of mercaptoacyl cycloalkyl carboxylic acids parallels the activity of the isosteric series of mercaptoacyl imino acids.

2-Mercaptopropionylglycine protection against growth-inhibiting effects in utero irradiated mice

Pregnant Swiss albino mice at different fetal growth periods were exposed to 150 R gamma rays in the presence or absence of 2-mercaptopropionylglycine (MPG), a SH radioprotector. The weights of litters born to these mothers were recorded at different postpartum intervals. There was an initial weight loss at 1 week after birth followed by a second weight loss after 4 weeks in the unprotected control males, whereas females showed continuous gains in weight from initial loss at 1 week. In the MPG-treated groups, the pattern of weight changes remained the same, but the loss was significantly less than in the controls and the second weight loss in the case of males was not obvious.

Some pharmacological properties of tiopronin

Tiopronin (50 mg/kg) and D-penicillamine (50 mg/kg) do not exhibit anti-inflammatory effects in classic animal models (carragenin oedema, granuloma cotton pellets) but suppress pertussis vaccine oedema, an immunological model, when given with a long-lasting dosing regime. Tiopronin and D-penicillamine also fail to inhibit PG release by phagocytosing leucocytes when the concentrations used were in the same range as human blood levels (5-15 micrograms/ml). Indomethacin (1, 3 and 5 mg/kg) instead significantly inhibits both the in vivo and in vitro models considered. This may imply a different mode of action of both tiopronin and D-penicillamine from indomethacin. Tiopronin also possesses similar effects to D-penicillamine suggesting that their overall anti-rheumatic action may have common elements.

Effect of a chronic acid load as sulfate or sulfur amino acids on bone metabolism in adult rats

Diets containing an acid load as either sulfur amino acids (SAA) or inorganic sulfate were fed to 45Ca-labeled adult male rats for 10 months. Radioisotope excretion and bone composition data (femur, tibia, mandibles) were compared with those for rats fed a control (15% soy protein) diet. Rats fed the SAA supplement (1.28% cystine plus 0.19% methionine) exhibited a significant reduction in femoral weight and A:R ratio and a tendency toward lower specific gravity, dry weight, fat-free weight and calcium content. Femoral radioautographs indicated a reduction in metaphyseal bone density in six of eight animals. We have postulated that the osteopenia produced by feeding excess free SAA may be due to decreased bone formation caused by a reaction between homocysteine and the aldehyde groups of collagen, as in genetic homo-cystinuric osteoporosis. Sulfate feeding (1.42% of the diet) produced a significant increase in 45Ca excretion, indicative of enhanced bone resorption, lasting about 2 months. There was a tendency for bone mass measurements to be lower than controls after 10 months, but the differences were not significant. Two of eight sulfate-fed rats showed radiographic evidence of osteopenia. No evidence of osteopenia was seen in the controls or in rats previously fed a high protein diet containing the same concentration of SAA.

Stimulation of neutrophil chemotaxis, adhesiveness, phagocytosis, and hexose monophosphate shunt activity by N-(2-mercaptopropionyl)glycine

The effects of the sulfydryl donor drug N-(2-mercaptopropionyl)-glycine (MPG) on neutrophil chemotaxis, adhesiveness, phagocytosis, and hexose monophosphate shunt activity were investigated in vitro. The drug significantly enhanced all the neutrophil functions tested when used at appropriate concentrations. The results, which are in accord with the well known inhibition of neutrophil function by sulfydryl-blocking agents, suggest the possible therapeutic usefulness of the drug in clinical conditions with defective neutrophil function.

Radioprotective effect of MPG (2-mercaptopropionylglycine) on the postnatal growth of mice irradiated in utero

Pregnant mice at gestation days 14 1/4, 16 1/4 and 18 1/4 were exposed to 250 R gamma rays in presence and absence of MPG, a -SH radioprotector. There was a biphasic weight loss in post partum animals born to irradiated mothers. In the MPG treated young ones, the second weight loss was remarkably averted. It was also found that 14 1/4 day of gestation was more radiosensitive than 16 1/4 or 18 1/4 days.

Selective protection of methionine enkephalin released from brain slices by enkephalinase inhibition

Methionine enkephalin release was evoked by depolarization of slices from rat striatum with potassium. In the presence of 0.1 microM thiorphan [(N(R,S)-3-mercapto-2-benzylpropionyl)glycine], a potent inhibitor of enkephalin dipeptidyl carboxypeptidase (enkephalinase), the recovery of the pentapeptide in the incubation medium was increased by about 100 percent. A similar effect was observed with the dipeptide phenylalanylalanine, a selective although less potent enkephalinase inhibitor. Inhibition of other known enkephalin-hydrolyzing enzymes--aminopeptidase by 0.1 mM puromycin or angiotensin-converting enzyme by 1 microM captopril--did not significantly enhance the recovery of released methionine enkephalin. These data indicate that enkephalinase is critically involved in the inactivation of the endogenous opioid peptide released from striatal neurons.

Effect of diet on plasma taurine in the cat

Near adult cats were deprived of dietary taurine until the plasma levels were consistently below 10 microM. The source of dietary lipid (animal versus vegetable), source of protein (soy versus casein versus tuna) and level (17%, 34%, 70%) and the sulfur amino acid content of the diet were then independently varied to determine their respective effects on plasma taurine. Plasma taurine was not influenced by the source of dietary fat but was sensitive to the sulfur amino acid content of the diet independent of total protein when methionine plus cystine was below 1.55% of the diet. Therefore, it is suggested that below 1.55% total sulfur amino acids the taurine requirements of the cat may be a function of the sulfur amino acid content of the diet. No retinal lesions in the area centralis occurred.

Role of the sulfur-containing amino acids in protein-induced hypercalciuria in men

A human metabolic study was conducted to determine what part sulfur-containing amino acids play in protein-induced hypercalciuria. The effects on the renal handling of calcium of increasing dietary protein from 50 to 150 g protein were compared with those of increasing the sulfur amino acids to simulate the amounts present in the 150 g protein diet; we also evaluated the effects of adding a 1.5 g supplement of phosphorus to the 50 g protein diet containing the sulfur amino acids. An increase in protein intake caused urinary calcium to double, increased glomerular filtration rate and decreased fractional renal tubular reabsorption of calcium and urinary sodium. Sulfur amino acids added to the low protein diet also caused urinary calcium to increase and fractional tubular reabsorption of calcium and urinary sodium to decrease, but the changes were only 43, 44 and 66%, respectively, those caused by the increase in protein. The phosphorus supplement effectively prevented the hypercalciuria caused by adding the sulfur amino acids to the low protein diet.

MPG protection against radiation sickness and weight loss and its correlation with mortality of mice after whole-body gamma-irradiation

The radiation-induced mortality together with the loss of body-weight and development of radiation sickness was studied in young adult Swiss albino mice after exposure to 1500 R of 60Co gamma-radiation in the presence and absence of 2-mercaptopropionyl-glycine (MGP), and results from both the groups were compared. It was found that the time of onset of radiation sickness was delayed in the drug-treated group, the mean survival time was also increased to 6 days as compared to 4.5 days in the untreated control group. These changes showed a direct correlation with the body-weight changes as the loss of weight in the drug-treated group was less marked and more gradual than in the untreated controls.

Effects of N-(2-mercaptopropionyl) glycine on neutrophil locomotion

The effects of the sulphydryl group donor N-(2-mercaptopropionyl) glycine on neutrophil locomotion were evaluated in vitro. The drug, when used at a concentration of 10(-3) M was found to stimulate the random migration and chemotaxis of normal neutrophils as a result of an enhanced rate of locomotion. The true chemotactic response was unaffected. N-(2-mercaptopropionyl) glycine appeared to exert its effect on the whole moving cell population.

Radioresponse of peripheal blood and its modification by MPG (2-mercaptopropionylglycine) in mice. I. Erythrocytes

Radiation-induced peripheral blood erythrocyte changes were studied in male Swiss albino mice after whole-body exposure to different doses of gamma-radiation (250 R, 500 R and 1000 R) with or without the drug, MPG. MPG did not have any effect on the initial cell depression, but it afforded significant protection at later intervals with sublethal gamma doses (250 R and 500 R). However, after lethal exposure (1000 R) the drug did not show any protective effect.

[Influence of propyl-gallate and 2-mercaptopropionylglycine on the development of acute inflammatory reactions and on biosynthesis of PGE2]

Anti-inflammatory activity of Propyl Gallate and 2.mercaptopropionylglycine, administered intraperitoneally to the rat, was evaluated against paw edema induced by Carrageenan, Bradykinin, Serotonin and Dextran. In addition, the influence of these chemicals on PGE2 formation from added arachidonic acid to spleen microsomal fraction incubated "in vitro" was assayed. Our results indicate Propyl Gallate and 2.mercaptopropionylglycine depress significantly the development of acute inflammatory reactions provoked by the above mentioned phlogogens and are able to limit the biosynthesis of PGE2. The last inhibitory activity appears to be less potent than that exerted by some non-steroidal anti-inflammatory agents, namely Indomethacin and Oxametacine, which act primarily by interfering with cyclo-oxigenase activity. In our opinion, the anti-inflammatory effect of Propyl Gallate and 2.mercaptopropionylglycine might be dependent on both the scavenger properties of the two compounds against some final products of lipid peroxides (aldehydes) originated at the inflammation site and the partial inhibition of the formation of PGE2 by acting on the cyclo-oxigenase system.

The enkephalinase inhibitor thiorphan shows antinociceptive activity in mice

There is both theoretical and therapeutic interest in establishing whether the signals conveyed by the enkephalins are turned off under the action of a specific peptidase which might, in this case, represent a target for a new class of psychoactive agents. Enkephalinase, a dipeptidyl carboxypeptidase cleaving the Gly3-Phe4 bond of enkephalins and distinct fropm angiotensin coverting enzyme (ACE), might be selectively involved in enkephalinergic transmission. It is a membrane-bound enzyme whose localization in the vicinity of opiate receptors in the central nervous system is suggested by parallel regional and subcellular distributions as well as by the effects of lesions. Such a role is further supported by the ontogenetic development of enkephalinase, its substrate specificity accounting for the increased biological activity of several enkephalin analogues and its adaptive increase following chronic treatment with morphine. To investigate the functional role of this enzyme further, we have designed a potent and specific enkephalinase inhibitor. We report here that this compound, thiorphan [(DL-3-mercapto-2-benzylpropanoyl)-glycine; patent no. 8008601] protects the enkephalins from the action of enkephalinase in vitro in nanomolar concentration and in vivo after either intracerebroventricular or systemic administration. In addition, thiorphan itself displays antinociceptive activity which is blocked by naloxone, an antagonist of opiate receptors.

Stimulation of LH and FSH secretion following intraventicular injection of cysteic acid but not taurine

Taurine and related neurally active metabolites, were tested for their ability to influence basal secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH). The animal model used was the unanesthetized, unrestrained adult rat with an indwelling catheter in the jugular vein and a cannula implanted in the right lateral cerebroventricle or anterior pituitary. The proposed inhibitory neurotransmitter traurine, and its metabolic precursor, hypotaurine, did not affect the secretion of LH or FSH following infusion of 0.2 or 2.0 mumol intraventricularly or into the pituitary. In contrast, intraventricular injection of cysteic acid, a neurally excitant amino acid, in doses of 2.0 and 0.2 mumol promoted pituitary secretion of LH in both male and female rats. FSH secretion was also increased slightly by cysteic acid (2.0 mumol). These studies provide additional evidence that excitatory amino acids have a stimulatory role in the release of pituitary gonadotropins.

A comparison of the effects of feeding sulfur amino acids and protein on urine calcium in man

It has been suggested that the sulfur amino acids in protein are responsible for the calciuria observed after protein ingestion. This hypothesis was tested by feeding meals containing either 15 g protein (control), 45 g protein (high protein), or 15 g protein plus sulfur amino acids equivalent to those in the high protein diet. Compared to the control, the high protein diet caused an increase in urinary calcium and sulfate and a decrease in the renal reabsorption of calcium. In contrast, the sulfur amino acid supplement had no effect on calcium excretion or reabsorption. Net acid excretion was unaffected by dietary treatment.

[Study of the changes of some biohumoral parameters related to hepatic function. Special reference to the lipid pattern after treatment with alpha-mercaptopropionylglycine in a group of aged subjects]

A double-blind trial of alpha-mercaptopropionylglycine (1500 mg/day per os) against a placebo was run in 40 aged subjects. Liver function parameters and lipid and sugar metabolism were evaluated before and after the test. The results are discussed, with particular reference to those relating to lipid metabolism.

Effects of methionine supplementation on the incidence of dietary fat induced myocardial lesions in the rat

Purified diets were prepared to evaluate the effect of methionine supplementation on the incidence and severity of vegetable oil-induced myocardial lesions in the rat. The unsupplemented basal diet fed was similar in nutrient composition to typical semipurified diets currently utilized for cardiopathogenic evaluation of dietary rapeseed oils and contained 1.276 mg of S-amino acid per kilocalorie. The methionine-supplemented diet contained an additional 0.25% (w/w) L-methionine or a total of 1.815 mg of S-amino acid per kilocalorie. Feeding trials were conducted in which weanling rats were fed either a diet containing 20% (w/w) soybean oil (SBO), low erucic acid rapeseed oil (LER) or high urucic acid rapeseed oil (HER) for 16 or 28 weeks. Dietary supplementation with methionine was found to reduce the incidence of focal myocardial lesions in SBO-fed animals to zero. These results suggest that marginal deficiencies in methionine may interact with the frequency and severity of myocardial changes reported for Sprague-Dawley rats fed various dietary oils. The results indicate that levels of essential nutrients should be adjusted when the energy level of the diet is increased.

Radiation protection of pronormoblasts and normoblasts by 2-mercaptopropionylglycine (MPG)

The pronormoblasts and normoblasts in Swiss albino mice were found to be very sensitive to radiation and their percentage was reduced drastically after exposure to gamma-rays. The degree of damage increased with increase in radiation dose. MPG reduced the initial damage and brought about an early and fast recovery. It is concluded that the drug protects the stem cells and thereby reduces the depletion of the regenerating pool which causes a more efficient and accelerated recovery.

The role of sulfate in the calciuria of high protein diets in adult rats

Diets containing different sources of protein were evaluated for their effect or urinary calcium (Ca) excretion in adult male rats. High protein diets were prepared by adding 24 g N/kg as lactalbumin (Hi-Lact), egg white (Hi-EW), casein (Hi-Cas) or gelatin (Hi-Gel) to a control diet containing 24 g N/kg ascasein (Cas). There were significant differences in the degree of hypercalciuria produced by different dietary protein mixtures. A peak in Ca excretion occurred at about 2 days, when the relative values were as follows (Cas = 100): Hi-Lact, 489; Hi-EW, 429; Hi-Cas, 340, and Hi-Gel, 263. Subsequently urinary Ca declined, but a moderate hypercalciuria persisted to the end of the 8-weekexperiment, when the corresponding values (% Cas) were 200, 183,160 and 136, respectively. The degree of hypercalciuria was proportional to the sulfur content of the diets, i.e., Hi-Lact greater than Hi-EW greater than Hi-Cas greater than Hi-Gel greater than Cas. Supplementing the Cas diet with sulfur amino acids to the level present in the Hi-Lact diet resulted in a comparable increase in Ca excretion. Supplementing the Cas diet with 1.42% sulfate produced a 570% increase in urinary Ca on day 2 and a 306% increase at 5 weeks. There was a linear relationship between Ca excretion and sulfate excretion. It is proposed that a major factor in the hypercalciuria of high protein feeding is the production and excretion of sulfate. Variability in the calciuric effect of different proteins appears to be related mainly to differences in their sulfur amino acid content.

Protein and sulfur amino acid requirements of broiler breeder hens

Two experiments were conducted with Cobb color-sexed broiler breeder hens to determine their protein and sulfur amino acid requirement. A daily intake between 400 and 478 mg of methionine and between 722 and 839 mg of total sulfur amino acids was necessary for maximum egg production, the latter in a diet of 13.07% protein. Slightly lower levels supported maximum body weights. Hens laying at the highest rate consumed 23.4 g of protein per day.

In vitro production of PNH-like red blood cells by 2-mercaptopropionylglycine

2-Mercaptopropionylglycine (2-MPG) transformed normal red blood cells (RBCs) into paroxysmal nocturnal haemoglobinuria (PNH)-like RBCs in vitro, depending on the concentration, pH and time of incubation. The incorporation of radioactive choline in the presence of acetylcholine was reduced, as in RBCs treated with aminoethylisothiouronium salt (AET). In contrast, the uptake in the presence of choline differed when the RBCs were incubated with the two compounds, being reduced in AET-treated RBCs and increased in 2-MPG-treated ones. As true PNH RBCs incorporated to a higher extent the radioactivity in the presence of both acetylcholine and choline, 2-MPG-treated RBCs seemed to resemble the PNH RBCs better than the AET-treated ones. Present results suggest the possibility of modifying selectively the activity of acetylcholinesterase and the transport of choline through the cell membrane.

Modification of radiation-induced spleen weight changes in mice by 2-mercaptopropionylglycine

It was found that the MPG partially protects the spleen against weight loss due to radiation, and exaggerates the compensatory reaction in the tissue during recovery. It is also concluded that MPG protects the stem cells in the spleen, which helps to restore the peripheral blood by extramedullary erythropoiesis.