[Serum levels and urinary excretion of magnesium in pregnancy. Effect of milk intake]

Magnesium levels in serum, as well as 24-hr urine and 2-hr post-fasting urine levels, were studied in 107 pregnant women, who were later separated into two groups. One group was advised to follow their usual intake, and the other, to supplement the diet with 750 cc of milk. The control group (30 healthy non-pregnant women) underwent the same protocol. Magnesium intake in pregnant women was much lower than that recommended for gestation. In both groups of pregnant women, serum magnesium levels were lower than those of the controls, in the second and third trimester of pregnancy. Urinary magnesium in 24-hr urine was higher in each trimester of pregnancy than the controls. Hypomagnesemia and hypermagnesuria not influenced by milk intake was observed.

Ionic calcium levels during pregnancy, at delivery and in the first hours of life

Free calcium ion concentration (mmol/l) and pH were determined in whole blood using a semiautomatic electrode system (ICA-1 Radiometer, Copenhagen, Denmark) in 37 normal women, 90 pregnant women (30 from each trimester of gestation), 28 mothers at delivery and their respective newborns. The blood samples from normal controls, pregnant women, umbilical cord and 40-50-hour-old infants were collected anaerobically in vacuum tubes. Duplicate samples drawn from newborns shortly after birth by heel puncture were collected in special heparinized capillary tubes. We observed that Ca2+ concentrations in the second (1.20 +/- 0.04) and third (1.20 +/- 0.05) trimesters of pregnancy, and at delivery (1.18 +/- 0.05), were lower than in the control group (1.23 +/- 0.04). The [Ca2+] in samples from the umbilical vein (1.44 +/- 0.11) and artery (1.45 +/- 0.08) and from newborns 2-5 min after birth (1.34 +/- 0.12) was greater than in control samples. The [Ca2+] in newborns 40-50 hours after birth was lower (1.16 +/- 0.14) than in the control group.

Developmental studies of the first step of the initiation of brain protein synthesis, role for initiation factor 2

Developmental changes at the level of initiation step of translation in the rat brain were studied. The level of deacylated tRNAimet in rat brain was measured at two stages of postnatal development. Although the amount of tRNA was slightly lower in adult than in young (4 day old) rats, the charging capacity of initiator tRNAimet in vitro was similar at both ages. No differences during development were found in methionyl-tRNA synthetase activity, which throws doubt on its possible participation in regulation of the initiation step. When assayed in the ribosomal salt wash protein fractions, initiation factor 2 activity decreased during brain development, and increased activities were detected in the supernatant of the microsomal fractions. The decrease in eIF-2 activity paralleled the observed decrease in the rat of overall protein synthesis or initiation activity in vitro, suggesting that the regulation of the initiation step of translation during brain development may be tightly linked to changes in initiation factor 2 activity in brain tissue.

Protein kinase activities associated with ribosomes of developing rat brain. Identification of eukaryotic initiation factor 2 kinases

Protein kinases associated with ribosomes in the brains of suckling (4-10 days) and adult (2 months) rats were extracted from ribosomal fraction with 0.5 M KCl. The different protein kinase activities were characterized by their ability to phosphorylate three exogenous substrates: casein, histone IIs and histone IIIs in the presence of different modulators. Ribosomal salt wash fractions contain a high casein kinase activity which was partially inhibited by heparin and stimulated by calmodulin in the presence of Ca2+, indicating the presence of casein kinase I and II and calcium/calmodulin-dependent kinases. Cyclic AMP and cyclic GMP-dependent kinases and protein kinase C (calcium/phospholipids-dependent kinase) were also present. No differences were found in the casein kinase activities of suckling and adult animals, but histone kinase activities were higher in adult than in suckling animals. To identify initiation factor 2 kinases, purified factor from adult brains was used as a protein marker. In addition to the phosphorylation of both factor subunits alpha and beta by casein kinase I or II, an increased phosphorylation was detected of alpha subunit in the presence of cyclic AMP, and beta subunit, in the presence of Ca2+/calmodulin or Ca2+/phospholipids. Present results reinforce our hypothesis that, as occurs in other eukaryotic cells, the decreased rate of protein synthesis during brain development may be regulated by phosphorylation of initiation factor 2.

Initiation factor 2 isolated from rat brain contains kinase activities responsible for its phosphorylation

Initiation factor 2 from adult rat brain was isolated from salt-washed microsomes using a three-step purification process consisting of heparin-Sepharose, phosphocellulose and diethylaminoethyl-cellulose (DEAE cellulose) column chromatographies. The initiation factor 2(eIF-2) was phosphorylated in subunits alpha and beta by the endogenous protein kinase activity present in the pruified preparation. This protein kinase activity proved to be mostly a casein kinase, although the possible presence of a very specific alpha kinase activity cannot be dismissed.

Functional heterogeneity of GEF-free initiation factor 2 purified from suckling and adult rat brain

The functional behavior of initiation factor 2 was studied in purified preparations from the brains of suckling (4-12-day-old) and adult (60-day-old) rats. Adult eIF2 has lower GDP and GTP affinity than suckling eIF2, even in the presence of a large excess of GTP, whereas suckling eIF2 has a lower capacity to bind GTP. Since these two factors are free of guanine nucleotide exchange factor (GEF), and ribosomal fractions show an age-dependent difference in GEF activity, the observed functional heterogeneity may be due to a different ratio in eIF2 species (eIF2-GDP, eIF2(alpha P)).

Isolation of eukaryotic initiation factor 2 from rat brain

Eukaryotic initiation factor 2 (eIF-2) was isolated from salt-washed microsomes of 4-day-old rat brain which show a high rate of protein synthesis. A three-step purification scheme was employed, including heparin-Sepharose, phosphocellulose, and DEAE-cellulose column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the isolated factor revealed three polypeptides with molecular weights of 43,000, 54,000, and 59,000 and 90% purity. The rat brain eIF-2 forms ternary complexes with [3H]methionyl-tRNAi and GTP. In terms of specific activity, the purification does not correspond to that revealed by electrophoretic analysis. During purification there is an apparent loss of additional factors that modulates the activity of eIF-2 and explains the high rate of activity of the crude fraction.

Peritoneal vascular reserve characterization through nitroprusside-induced modification of peritoneal mass transfer coefficients

The transport of solutes across the peritoneum may be increased by the topical administration of nitroprusside; the effects of the drug seem to be due to an increase in the number of perfused capillaries and/or in their permeability. We have compared the peritoneal mass transfer coefficients (MTC) for urea, creatinine and parathormone (PTH) under basal conditions and after administration of nitroprusside (4.5 mg/l dialysate) in 15 patients under CAPD therapy. The mean increments of the MTC were 48.8% for urea, 77.5% for creatinine and 323% for PTH. The relative MTC increments for the three molecules (taken in pairs) were: MTCPTH/urea' 2.53 times (mean), MTCPTH/creatinine' 1.7 times, and MTCcreatinine/urea' 0.73-times, with very variable ranges. The overall mean increment (OMI) for all three ratios ranged from -1.25 and +6 times. In six patients, some of the relative increments (and in three of them the OMI) were negative but the epidemiological features of these patients revealed no clear data. The OMI shows a direct correlation with the body surface area and an inverse correlation with the the duration of CAPD and ESRD and with the number of peritonitis episodes, albeit without statistical significance. We conclude that the peritoneal vascular reserve has individual characteristics, and that perhaps the OMI or some other similar index might serve to quantify and characterise it, if our findings are confirmed.

The mode of action of restrictocin and mitogillin on eukaryotic ribosomes. Inhibition of brain protein synthesis, cleavage and sequence of the ribosomal RNA fragment

The relationship between the process of rat brain protein synthesis inhibition by restrictocin and mitogillin and the induction of a specific cleavage in 28S rRNA has been examined. Restrictocin or mitogillin at a concentration of 6 nM inhibits protein synthesis to a level of 80%. The inhibition induced by 6 nM alpha-sarcin is of the same order, indicating that those molecules all catalytically inhibit protein synthesis. When restrictocin or mitogillin was reduced and alkylated, a 100-fold higher concentration of these chemically modified molecules was needed in order to obtain the same inhibition as with native molecules, suggesting a close correlation between activity and configuration of the inhibitors. The inhibitory activity of restrictocin or mitogillin was completely lost after oxidation with performic acid. The inhibition of protein synthesis was always correlated with the production of a fragment from the 3'-end of the 28S rRNA. This rRNA fragment had the same electrophoretic mobility as that produced by alpha-sarcin. The 5'-end sequence of the rRNA fragment produced by restrictocin, mitogillin or alpha-sarcin is AGGAA, demonstrating that restrictocin and mitogillin inhibit protein synthesis in the same way as does alpha-sarcin. The conservation of this region of the rRNA from archaebacteria to eukaryotic ribosomes indicates its importance in the elongation process.

The effect of streptozotocin diabetes on brain protein synthesis in the rat

Young normal control rats were compared with a group made diabetic by treatment with streptozotocin and with other normal rats maintained on a restricted diet to obtain a daily body weight change similar to that of the diabetics. In diabetic rats plasma levels of Val, Ile and Leu rose and those of Asp, Thr, Ser, Gln, Gly, Tyr, Orn, Lys, His and Arg decreased, whereas brain concentrations of Leu, Arg and Orn were augmented and those of Thr and Ser reduced. Insulin treatment diminished these differences in comparison with controls values. In food-restricted normal rats plasma and brain amino acid concentrations also differed from values in normal controls but they were of different magnitude and/or direction than those of diabetics. In vitro 3H-Leucine incorporation into proteins by brain postmitochondrial dialyzed supernatants was unaffected in both diabetic and food-restricted rats, whereas in liver preparations the same parameter was significantly reduced in both groups and insulin treatment of the diabetics decreased this difference. Results indicate that brain amino acid concentrations in diabetic animals are a secondary consequence of their circulating levels and of potential modifications of brain amino acid metabolism other than protein synthesis, which is unaffected.

Magnesium excretion in idiopathic hypercalciuria

Given the parallelism in calcium and magnesium metabolisms, we have studied urinary magnesium in normal subjects and in patients with idiopathic hypercalciuria under conditions of basal and restricted diet, fasting, and after oral calcium overload. Serum magnesium values showed no differences between groups. Urinary magnesium levels are increased in absorptive hypercalciuria under free and restricted diet and calcium overload, returning to normal during fasting. Renal hypercalciuria patients maintain a high magnesium excretion under all conditions. This suggests that in idiopathic hypercalciuria there is an impairment of renal magnesium management, dependent on that of calcium because it normalizes when urinary calcium is normal.

Characteristics of the peritoneal mass transfer of parathormone in patients under continuous ambulatory peritoneal dialysis therapy

Recent studies have shown that the mass transfer coefficients (MTC) for low- and middle-molecular-weight substances are maintained at medium terms in patients under continuous ambulatory peritoneal dialysis (CAPD) therapy. We have studied the MTC for parathormone (MW 5,500-6,000) in 29 patients under CAPD. 11 patients were assessed once, 9 patients were assessed twice, and 9 were assessed three times, with 6-month intervals between assessments; in 15 cases nitroprusside (4.5 mg/l) was added to the dialysate, and in 2 cases the assessment was carried out during an episode of peritonitis. A bicompartmental model with exponential ultrafiltration was used, and the generation rates were calculated by mass balance. The MTC was calculated by minimization of the quadratic error, following the procedure of Runge and Kutta. The mean MTC values were 21.2 +/- 5.9 for urea, 10.26 +/- 5.9 for creatinine 2.8 +/- 1.8 for inulin and 1.0 +/- 0.8 for parathormone (PTH), with significant correlation between the MTC values for PTH and inulin (r = 0.5, p less than 0.01). There is a direct correlation between MTCPTH and peritoneal PTH clearance, and an inverse one between MTCPTH and serum PTH, with r = 0.8 and 0.51, respectively. No correlation was found between the MTC for inulin or PTH and the duration of the CAPD therapy, nor with the number of episodes of peritonitis. No significant medium-term variations were detected in the MTC values for PTH and inulin. Both peritonitis and the intraperitoneal administration of nitroprusside induce significant increases in the MTCPTH.

Intravenous contrast bolus in computed tomography investigation of mass lesion

Using bolus intravenous contrast (25-75 Renografin 60) and 5-second scanning capability, better definition of vascular anatomy as well as the vascular nature of mass lesions in the chest and abdomen could be demonstrated. The immediate higher concentration of iodine in vessels and organs following initial bolus, improves visualization of these structures dramatically when compared to drip-infusion technique. A description of the technique and examples are shown.

Effects of chronic ingestion of alcohol in the pregnant rat on catecholamine-sensitive adenylate cyclase in the brain of mothers and their offspring

To study the effects of maternal alcohol ingestion on brain adenylate cyclase in offspring, rats were given ethanol in the drinking water before, during and after gestation. Fifteen-day-old pups from alcoholic mothers had reduced body and wet brain weight and protein content with normal concentrations of DNA and RNA in brain; pups from mothers deprived of alcohol from the 21st day of gestation had normal growth and brain protein, DNA, RNA and cyclic nucleotide concentrations. Adenylate cyclase activity was less in homogenates from the diencephalon, mesencephalon and cerebellum of alcoholic and alcohol-deprived mothers than in the corresponding homogenates from control mothers. A reduction of the enzyme activity was only observed in homogenates from diencephalon of offspring from alcoholic and alcohol-deprived mothers as compared with controls. Sensitivity of adenylate cyclase to noradrenaline was reduced in the corpora striata and diencephalon from alcoholic mothers, while these changes were absent in alcohol-deprived mothers and their offspring. Ingestion of ethanol in pregnant mothers does not seem to affect significantly the adenylate system in the brain of the offspring.

Plasma calcitonin concentration in patients treated with chronic dialysis: differences between hemodialysis and CAPD

We have determined plasma calcitonin levels in 72 chronic dialysis patients and investigated their possible correlations with other parameters of calcium and phosphorus metabolism, including plasma levels of calcium, phosphorus, alkaline phosphatase and parathormone, as well as with the duration of treatment. Forty-one of the patients were being treated with hemodialysis (HD) and thirty-one with continuous ambulatory peritoneal dialysis (CAPD). Increased calcitonin levels were detected in 83% of the HD patients and in 79% of the CAPD group. In the former there was a positive correlation between the levels of calcitonin and the calcium, corrected calcium, alkaline phosphatase and parathormone levels and with the duration of treatment, whereas in the latter the calcitonin levels only correlated with the serum calcium. The patients receiving CAPD also showed significantly lower calcium and calcitonin levels than the HD patients. Our conclusion is that, apart from accumulation due to renal failure, the main factor determining the calcitonin level is the blood calcium level, and that the observed increase might play a role in the physiological protection of bone against the action of parathyroid hormone.

Effects of alcohol ingestion in the pregnant rat on daily food intake, offspring growth and metabolic parameters

1. Daily food intake, fluid consumption, offspring growth and metabolic parameters were studied in rats receiving ethanol in the drinking water before, during and after gestation. 2. Ethanol treatment always reduced daily food, liquid and caloric intake in the rat, except during gestation when total daily caloric intake was greater in rats receiving ethanol than in control animals. The increase in both food and liquid intake during lactation in controls was also observed in alcohol-deprived mothers but was significantly reduced in mothers maintained under alcohol treatment. 3. Offspring from alcohol-treated mothers were retarded in body weight and size compared with controls, the differences becoming greater as the suckling period advanced. 4. The 15 day-old pups from alcohol-treated mothers had reduced glucose and augmented beta-hydroxybutyrate levels in blood, and markedly reduced liver glycogen concentrations, indicating their acutely malnourished state. 5. In pups from mothers that received alcohol until the 21st day of gestation, body weight and size were normalized at the 15th day but skeletal maturation and liver glycogen concentration were reduced and blood acetoacetate and beta-hydroxybutyrate were augmented as compared with values in pups from control mothers. If these parameters are interrelated, metabolic changes may be used for early diagnosis of fetal alcohol syndrome.

Effects of maternal ethanol ingestion on cerebral neurotransmitters and cyclic-AMP in the rat offspring

1. To study the effects of maternal alcohol ingestion on brain parameters in offspring, rats were given ethanol for drinking (25% w/v) from the time of mating until sacrifice. Controls drank tap water. 2. Alcohol ingestion reduced daily food and liquid consumption but total caloric intake was only slightly diminished. 3. Maternal body weight increased and offspring body weight, size and brain weight were reduced in the animals receiving alcohol. 4. Brain concentrations of tryptophan, tyrosine and GABA were augmented in ethanol treated mothers at 1 day post-partum. 5. Comparison of brain parameters in offspring of alcoholic mothers with those of controls showed that tryptophan and 5HT concentrations were augmented in 4 day old neonates, NA was increased in 21 day fetuses and 1 day old neonates, and adenylate cyclase activity was also greater in the brains of 21 day fetuses and the cerebellums of 4 day old neonates. 6. Neither phosphodiesterase nor cyclic-AMP concentrations differed in offspring of alcoholic and control mothers. 7. Data showed alterations in brain NA and 5HT systems in the offspring of alcoholic mothers.

Fetal and Early postnatal development of adenylate cyclase and cyclic AMP phosphodiesterase activities in rat brain

Brain cyclic AMP metabolism was studied in rat offspring at 17, 19 and 21 days of intrauterine life and 0, 1 and 4 postnatal days. Wet weight and protein and DNA and RNA concentrations in brain increased in parallel with body weight until the 4th postnatal day although during the perinatal phase some of these parameters suffered a manifest temporal retardation. In the brain, similar qualitative changes were observed in both adenylate cyclase and high Km cyclic AMP phosphodiesterase activity while the low Km enzyme showed a rise from 17-day fetuses to those of 19 days with no further changes. The increase in cyclic AMP concentration was very mild and the values found in the 21-day fetuses were already similar to those in adults. In the mother's brain a significant reduction in adenylate cyclase activity appeared at 19 and 21 days of gestation. The retardation in the ontogenic development of cyclic AMP metabolism during the perinatal phase in offspring is probably a consequence of their specific metabolic situation while in the mother it may be the result of its endocrine preparation for parturition.

Diagnosis of dissecting aortic aneurysm by computed tomography

Computed tomography (CT) of the torso combined with simultaneous intravenous bolus injection of contrast media was used in sixteen patients suspected of having dissected their aorta. All patients had subsequent correlative percutaneous aortography within 24 h of the CT examination. Four patients proved to be normal, one had an aneurysm of the thoracic aorta, and eleven had aortic dissection (five type I, six type III dissection). All eleven patients with aortic dissections were diagnosed by CT and angiography; nine had spontaneous dissections and two had iatrogenic injuries to the aorta. Limitations of this imaging procedure include; inability to detect aortic valvular dysfunction and failure to provide an adequate perspective of aortic branch involvement. Potential benefits include: avoidance of aortogram in some cases, relative non-invasiveness, rapidity and ease of procedure, and less expense, radiation, contrast media, and discomfort to the patient. Early experience with CT-enhancement technique has reliably demonstrated normal as well as abnormal aortic wall morphology. It may have a place as an alternative to the conventional aortogram.