Serum Concentrations of Vitamin D Metabolites in Exclusively Breast-Fed Infants at 70° North

ABSTRACT. The effect of prolonged breast-feeding on the serum concentrations of vitamin D metabolites, calcium, phosphate, and alkaline phosphatase was studied longitudinally in 7 infants from Northern Norway. They were exclusively breast-fed for a median of 71/2 months. Three of the mothers were supplemented with vitamin D throughout lactation. All but one of the infants had 25-hydroxyvitamin D (25-OHD) levels in the rachitic range (< 20 nmol/l) on at least one occasion. Vitamin D supplementation of the mother had no apparent effect on the infants' 25-OHD levels, but the values increased during summer. The infant who had the lowest 25-OHD levels also had decreased 1,25-dihydroxyvitamin D (1,25-(OH)₂D) concentrations, while the others maintained l,25-(OH)₂D levels within normal limits. 24,25-(OH)₂D concentrations were undetectable when the 25-OHD levels were below 35 nmol/l, but the two metabolites were closely correlated for higher values of 25-OHD. Low 25-OHD levels were associated with decreased phosphate concentrations at 6 months. The calcium levels were normal throughout the study period of one year, as were all but two of the alkaline phospatase values. Although none of the infants had clinical or biochemical evidence of rickets, the results suggest that the vitamin D supply from human milk is inadequate, and that routine vitamin D supplementation is advisable for breast-fed infants who are deprived of sunlight exposure.     

Gi-mediated muscarinic adenylyl cyclase inhibition in timolol-treated stunned porcine myocardium

The Gi-mediated muscarinic receptor-adenylyl cyclase system was examined in stunned myocardium induced by either three or five brief ischaemic periods after β-adrenoceptor blockade by timolol (0.1 mg kg^-1). The mid-left anterior descending coronary artery was occluded for 2, 10 and 2 min in four pigs, and for 2, 2, 5, 10 and 2 min in four other pigs. All the ischaemic periods were separated by 30 min of reperfusion and the biopsies were obtained 60 min after the last ischaemic period. Segment length function was measured in the ischaemic region and in the control region supplied by the left circumflex artery. In the two groups, the percentage systolic shortening was reduced equally, to 59±9 and 58±10% of control in the region subjected to ischaemia and only minimally in the control region. The biopsies from the stunned region from both groups showed: (1) no change in either the affinity for carbachol or the number of binding sites of the muscarinic receptors; (2) no alterations in messenger RNA encoding for the α subunit-2 of the inhibitory guanine nucleotide binding protein, as demonstrated by northern blot and solution hybridization; (3) no change in membrane-bound inhibitory guanine nucleotide binding protein, as shown by enzyme immunoassay utilizing a specific anti-peptide antibody, and (4) unchanged inhibition of stimulated adenylyl cyclase activity. These results suggest that there is an intact inhibitory guanine nucleotide binding protein-mediated muscarinic receptor adenylyl cyclase system in the stunned porcine myocardium.     

Sucrolytic enzymes from human dental plaque in saliva

abstract – The total effect of sucrose-splitting activity from three sucrose metabolizing enzymes has been investigated in "resting" saliva in contact with dental plaque material in 356 military recruits. Invertase effect is defined as the splitting of sucrose into equimolar quantities of glucose and fructose, dextransucrase as a glucosyl-transferase producing glucan and free fructose, and levansucrase as a fructosyl-transferase producing fructan and free glucose. Total monohexose and glucose production as well were determined quantitatively in each subject. Monohexose production was related to specific oral conditions, and a difference in tooth decay significant at a 5% level was found between samples with high and low enzyme content. The production of free glucose was lower than that of free fructose, significant at less than a 1 % level. This may indicate that more glucose is bound to form dextran than fructose to form levan in this salivary enzyme system. In the saliva samples with a high level of enzyme content a slight increase in relative effect of dextransucrase was found. This was not statistically significant.     

VITAMIN D NUTRITIONAL STATUS OF PREMATURE INFANTS SUPPLEMENTED WITH 500 IU VITAMIN D2 PER DAY

ABSTRACT. The vitamin D nutritional status of premature infants was assessed by determining plasma 25-hydroxyvitamin D concentrations before and during supplementation with 500 IU vitamin D₂ per day. Fifty-one samples were collected from 25 healthy infants fed breast milk and a vitamin D₃ fortified formula. Gestational age was 32.2±2.4 weeks (mean ± 1 SD). 25-hydroxyvitamin D levels before supplementation correlated well with maternal values ( r =0.81). The infants' mean plasma concentration increased from 30.6±13.7 nmol/l (mean±1 SD) after birth to 46.3±10.5 nmol/l after 9±1 days ( p <0.0025), and to 65.3±16.6 nmol/l after 37±10 days of vitamin D₂ treatment ( p <0.0005). 25-hydroxyvitamin D₂ and 25-hydroxyvitamin D₃ were determined separately, and it appeared that the rise was accounted for by the D₂ fraction while 25-hydroxyvitamin D₃ concentrations were unchanged. The results demonstrate that vitamin D₂ is well absorbed and hydroxylated in the 25 position by premature infants free of associated disease, and that a supplementation of 500 IU per day in addition to breast milk and a regular vitamin D fortified formula is adequate to rapidly establish 25-hydroxyvitamin D levels within the normal adult range.     

Unfavorable prognostic value of CD24 expression in sections from primary and relapsed ovarian cancer tissue

Expression of CD24 represents a poorly recognized, unfavorable prognostic factor. Expression of the protein is supposed to facilitate extravasation of tumor cells. Our study aimed at examination of prognostic significance of CD24 estimation in samples obtained from primary surgeries (PS) and secondary cytoreductions (SCR) (after chemotherapy) in ovarian cancer patients. The analyses were performed on sections originating from 73 tumor samples. Immunohistochemical reactions were performed on paraffin sections of studied tumors, using monoclonal antibodies against CD24. Kaplan-Meier's analysis showed that a significantly shorter overall survival time and progression-free time was demonstrated to characterize cases with cytoplasmic membranous expression of CD24 (CD24c-m) (P < 0.001). The calculations performed demonstrated also a significantly higher proportion of CD24c-m positive cases in sections from SCR as compared to that from PS (P= 0.04) and in cases of progressive disease as compared to complete response at PS and SCR (P= 0.002 and P= 0.05, respectively). Summing up, in this study, we have demonstrated a negative prognostic significance of a cytoplasmic membranous expression of CD24 in cases of ovarian cancer.     

Plasma Concentrations of Vitamin D Metabolites before and during Treatment of Vitamin D Deficiency Rickets in Children

ABSTRACT. Plasma concentrations of 25-hydroxyvitamin D (25-OHD), 1,25-dihydroxyvitamin D (1,25-(OH)₂D), and 24,25-dihydroxyvitamin D (24,25-(OH)₂D) were determined in 17 children with vitamin D deficiency rickets before therapy was started. Thirteen of them also had these tests repeated during treatment. The median 25-OHD concentration was at the lower limit of the reference range before, but increased distinctly within one week of treatment with 1700–4000 IU vitamin D per day (17 vs. 37 nmol/l, p < 0.01). 24,25-(OH)₂D was undetectable in twelve of the patients before therapy. Detectable concentrations were in the range of 1.7 to 3.5 % of the corresponding 25-OHD levels throughout the study, and the two metabolites were closely correlated ( r = 0.84, p < 0.0005). The median l,25-(OH)₂D concentration was near the average of the reference range before, but increased to well above the upper limit of normal within one week of treatment (121 vs. 368 pmol/l, p < 0.01). The levels were largely normal after 10 weeks of therapy, as were the plasma concentrations of calcium, phosphate, and alkaline phosphatase. Parathyroid activity, as judged by serum parathyroid hormone or urinary cyclic AMP concentrations, was stimulated in 11 of 12 children studied prior to treatment. It is concluded that there may be no clear-cut differences between normal nad rachitic values of the different vitamin D metabolites under practical clinical conditions. A low 25-OHD level combined with evidence of a stimulated parathyroid activity, and a rise of l,25-(OH)₂D levels to supernormal values following a few days of vitamin D therapy may be diagnostic clues.     

Calcium-induced net potassium uptake of pig hearts in vivo

To determine whether the catecholamine-induced myocardial potassium uptake could be mimicked by increasing extracellular and intracellular calcium concentrations in vivo, we measured changes in myocardial potassium balance in nine anaesthetized open-chest pigs with PVC-valinomycin electrodes in arterial and coronary sinus blood. CaCl₂ infusion (200–400 μmol min^-1) into the left coronary artery increased coronary sinus blood calcium concentration from 2.29 (2.19–2.42) to 4.63 (3.76–5.67) mmol I^-1 (median, 95% confidence interval, P= 0.01) indicating a similar increment in myocardial extracellular calcium concentration. The contractility measure LV dP/dt increased 95 (76–147)%, indicating a substantial increment in intracellular calcium concentration. During the CaCl₂ infusion coronary sinus potassium concentration declined to a nadir 0.12 (0.09–0.17) mmol l^-1 below baseline (P= 0.008) whereas arterial concentration remained unchanged. Peak myocardial potassium uptake was 18 (7–32) μmol min^-1 100 g^-1 and occurred 150 (110–195) s after start of infusion. The response remained unaltered after adrenoceptor blockade by prazosin and propranolol. Prolonged CaCl₂ infusion caused a net myocardial potassium loss which was accompanied by metabolic and haemodynamic indications of myocardial ischaemia. These findings are consistent with enhanced Na-K pump activity in the intact beating pig heart in response to increased extracellular and intracellular calcium concentrations.     

Density of L-type calcium channels in ischaemically preconditioned porcine heart regions

Ischaemic preconditioning by brief ischaemic episodes could be explained by reduced cellular calcium ion (Ca²⁺) influx, reduced cytosolic Ca²⁺ overload and delayed cell-injury during subsequent long-lasting ischaemia. L-type calcium channels (LCC) regulate sarcolemmal Ca²⁺ influx in myocardial cells. The aim of this study was to investigate if preconditioning was associated with reduced density or altered state of LCC in the preconditioned region of the heart. To test this we compared the density and the dissociation constant of (4-)-[³H]isradipine binding to LCC in membranes from preconditioned and control regions of porcine hearts. Eight porcine hearts were regionally preconditioned by two 10-min occlusions of the mid left anterior descending artery, and each occlusion was followed by 30 min of reperfusion. Biopsies were taken from the preconditioned regions and control regions supplied by the circumflex artery at the end of the last reperfusion, and (+)-[³H]isradipine binding to membranes made from the biopsies was measured. The differences in density and dissociation constant of (4-)-[³H]isradipine binding to LCC in membranes from preconditioned and control regions were not significant. In conclusion, the proposed effect of ischaemic preconditioning to reduce Ca²⁺ influx, does not involve local changes in density or state of LCC that could be detected by (+)-[³H]isradipine binding.     

Preparation of cells from pig gastric mucosa

Cells were isolated from pig gastric mucosa by a combination of mechanical and enzymatic treatment. Isopycnic centrifugation on linear density gradients of Percoll provided a simple and rapid procedure for obtaining highly enriched parietal cells and chief cells. Their densities were 1.06 and 1.10 g/ml, respectively. Isolated mucosal cells attached to Petri dishes coated with fibronectin or collagen. Both parietal cells and chief cells adhered more readily to fibronectin than collagen. Mucosal cells and cells from the Percoll gradients were maintained for up to one week as primary cell cultures. The ability of free parietal cells to produce acid was tested by the ¹⁴C-aminopyrine accumulation technique. Maximal accumulation was 2.5 pmol aminopyrine per 10⁴ parietal cells after incubation for 45 min at 10^-4 M histamine. The EC₅₀ for histamine was 5times10^-6 M.The accumulation of aminopyrine at 10^-6 M carbachol and 10^-7 M pentagastrin were for both secretagogues about 0.9 pmol per 10⁴ parietal cells.     

URINARY CYCLIC AMP IN INFANTS ADMITTED TO A NEONATAL INTENSIVE CARE UNIT

ABSTRACT. The urinary excretion of cyclic AMP was studied during the first 3 days of life in 46 randomly selected infants admitted to a neonatal intensive care unit. The data were compared with those of normal newborn infants. Urinary cyclic AMP concentrations were significantly correlated with gestational age (all patients), and with birth weight (all patients except infants of diabetic mothers (IDMs)). The urinary cyclic AMP/creatinine ratio increased from day 1 to day 3 in normal newborns and in IDMs, and tended to increase also in small-for-gestational age (SGA), low birth weight (LBW), and sick, term infants, although the changes in the latter groups were not statistically significant. Four infants studied with parallel determinations showed increased cyclic AMP/creatinine ratio from day 1 to day 3 both in plasma and urine. All urinary cyclic AMP/creatinine ratios were lower than the corresponding ratios found in plasma. In LBW infants, there was an inverse relationship between urinary cyclic AMP and serum calcium. In IDMs a positive correlation was observed between urinary cyclic AMP and blood glucose concentration. In conclusion, the excretion of cyclic AMP in sick newborn infants is influenced by the following factors: gestational age, postnatal age, birth weight, and derangements of serum calcium and blood glucose concentrations.