Peter Ridefelt

Parathyroid-like regulation of parathyroid-hormone-related protein release and cytoplasmic calcium in cytotrophoblast cells of human placenta

Immunohistochemical staining of human placenta revealed intense reactivity for amino terminal and midregional parathyroid-hormone-related protein (PTHrp) in the cytotrophoblast cells and weaker staining in the syncytiotrophoblasts. The cytotrophoblasts also displayed conspicuous surface staining with the monoclonal antibodies E11 and G11, which recognize a Ca2+ receptor mechanism regulating hormone release of parathyroid cells. Cytotrophoblasts enriched on Percoll gradients or by linking surface-bound E11 to magnetic beads revealed biphasic elevation of cytoplasmic Ca2+ ([Ca2+]i) upon a stepwise rise of external Ca2+ from 0.5 to 3.0 mM, with a half-maximal effect at 1.75 mM. Individual cytotrophoblasts identified by their E11 reactivity disclosed a temporary increase of [Ca2+]i upon elevation of external Mg2+, while Mn2+ triggered both a [Ca2+]i transient and an influx of itself. These effects were efficiently blocked by the G11 antibody. Depolarization with K+ or addition of the voltage-dependent Ca2+ channel blocker verapamil had only marginal effects on [Ca2+]i. Raised extracellular calcium inhibited release of PTHrp from the cells, and this inhibition was blocked by the G11 antibody. The virtually parathyroid-identical Ca2+ regulation of [Ca2+]i may mediate feedback control of PTHrp release from the cytotrophoblasts and thereby participate in the regulation of placental Ca2+ transport.

Interleukin-6 Induced Suppression of Bovine Parathyroid Hormone Secretion

Calcium disturbances in the critically ill coincide with elevations of proinflammatory cytokines. The effects of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) on parathyroid hormone (PTH) secretion were investigated. IL-6 and TNF-α had no acute effect on PTH secretion in extracellular Ca2+ concentrations of 0.5, 1.25 and 3.0 mM. In contrast to TNF-α, cultures for 24 h in the presence of l0 ng/mL of IL-6 showed decreased PTH secretion by 51% and 29% in 0.5 mM and 1.25 mMCa2+ respectively. Neither IL-6 nor TNF-α, affected cytoplasmic Ca2+ of the cells. We conclude that PTH secretion in vitro can be suppressed by IL-6 at clinically relevant concentrations. This suppression may aggravate hypocalcemia of the critically ill and attenuate the conventionally strong stimulation of the PTH release by reduction in serum calcium.

Thrombin, but not bradykinin, stimulates proliferation in isolated human osteoblasts, via a mechanism not dependent on endogenous prostaglandin formation.

Osteolysis or osteosclerosis often occurs in bone tissue adjacent to chronic inflammatory processes. Numerous cytokines and inflammatory mediators have been implicated as osteoclast-activating agents, explaining inflammation-induced bone resorption. In many cases, the cause of the sclerosis seen in these lesions is less thoroughly investigated. We have studied the effects of thrombin and bradykinin, 2 inflammatory mediators, on the rate of proliferation in isolated human osteoblasts (hOBs). Thrombin, at and above 1 U/mL, stimulated the rate of thymidine incorporation into hOBs. The absolute cell number also increased, as measured by an assay based on the detection of cell metabolism. A synthetic peptide ligand for the thrombin receptor enhanced the rate of [3H]thymidine incorporation in hOBs, indicating that thrombin-induced proliferation is mediated via the tetheric thrombin receptor. The thrombin-induced proliferation was not affected by indomethacin, excluding prostanoids as mediators of this effect. Bradykinin did not affect either the rate of thymidine incorporation, or number of cells in long-term cultures of hOBs. In conclusion, the inflammatory mediator, thrombin, stimulates proliferation in isolated human osteoblasts probably via the recently described G-protein-coupled tetheric thrombin receptor. Thrombin may therefore be involved as a mediator of inflammation-induced sclerosis and bone formation.

Population-based pediatric reference intervals for hematology, iron and transferrin

Abstract Reference intervals are crucial decision-making tools aiding clinicians in differentiating between healthy and diseased populations. However, for children such values often are lacking or incomplete. Blood samples were obtained from 689 healthy children, aged 6 months to 18 years, recruited in day care centers and schools. Hematology and anemia analytes were measured on the Siemens Advia 2120 and Abbott Architect ci8200 platforms (hemoglobin, erythrocyte volume fraction [EVF], erythrocytes, mean corpuscular volume [MCV], mean corpuscular hemoglobin [MCH], mean corpuscular hemoglobin concentration [MCHC], reticulocytes, leukocytes, lymphocytes, monocytes, neutrophils, eosinophils, basophils, platelets, iron, transferrin, transferrin saturation). Age- and gender-specific pediatric reference intervals were defined by calculating 2.5th and 97.5th percentiles. The data generated is primarily applicable to a Caucasian population, but could be used by any laboratory if verified for the local patient population.

Population-based pediatric reference intervals for general clinical chemistry analytes on the Abbott Architect ci8200 instrument

Abstract Background: Reference intervals are crucial decision-making tools aiding clinicians in differentiating between healthy and diseased populations. However, for children such values often are lacking or incomplete. Methods: Blood samples were obtained from 692 healthy children, aged 6 months to 18 years, recruited in daycare centers and schools. Twelve common general clinical chemistry analytes were measured on the Abbott Architect ci8200 platform; sodium, potassium, chloride, calcium, albumin-adjusted calcium, phosphate, magnesium, creatinine (Jaffe and enzymatic), cystatin C, urea and uric acid. Results: Age- and gender specific pediatric reference intervals were defined by calculating the 2.5th and 97.5th percentiles. Conclusions: The data generated is primarily applicable to a Caucasian population when using the Abbott Architect platform, but could be used by any laboratory if validated for the local patient population.

Neomycin interacts with Ca2+ sensing of normal and adenomatous parathyroid cells

Effects of the polyvalent cationic antibiotic neomycin on regulation of the cytoplasmic Ca2+ concentration ([Ca2+]i) were studied in normal and adenomatous human, and bovine parathyroid cells. Parathyroid hormone (PTH) release was also measured in the bovine cells. Elevation of extracellular Ca2+ from 0.5 to 3 mM caused biphasic increase of [Ca2+]i and inhibition of PTH release. In low external Ca2+ neomycin inhibited PTH release and virtually only triggered the [Ca2+]i transient. In contrast [Ca2+]i was lowered and PTH release stimulated by neomycin in the presence of 3.0 mM Ca2+ or 7 mM Mg2+. These actions of Ca2+ and neomycin on [Ca2+]i were qualitatively similar but less pronounced in the adenomatous than normal human parathyroid cells. Some effects of neomycin were thus similar to those induced by other cationic agents interacting with the Ca2+ receptor mechanism on the parathyroid cell surface, whereas others may involve phospholipase C inhibition, protein kinase C activation or a direct reduction of the Ca2+ influx.

Reference intervals on the Abbot Architect for serum thyroid hormones, lipids and prolactin in healthy children in a population-based study

Abstract Pediatric reference intervals for thyroid hormones, prolactin and lipids are of high clinical importance as deviations might indicate diseases with serious consequences. In general, previous reference intervals are hampered by the inclusion of only hospital-based populations of children and adolescents. The study included 694 children, evenly distributed from 6 months to 18 years of age. They were recruited as volunteers at child care units and schools. All subjects were apparently healthy and a questionnaire on diseases and medications was filled out by parents and by the older children. TSH, free T4, free T3, total cholesterol, LDL, HDL, triglycerides and prolactin were analyzed on Abbott Architect ci8200. Age- and gender-related 2.5 and 97.5 percentiles were estimated. The thyroid hormone levels were similar to previous data for the Abbott Architect platform, but exhibited differences from studies performed with other methods. Prolactin displayed wide reference ranges, but relatively small age-related changes, and a marginal difference between sexes during adolescence. Reference intervals for lipids in the different age groups are known to vary geographically. Levels of LDL and total cholesterol were higher than those reported for children in Canada, but lower than those reported for children in China. The study gives age- and gender- specific pediatric reference intervals, measured with modern methods for a number of important analytes. The results presented here differ from previously recommended reference intervals. In many earlier studies, retrospective hospital-based reference intervals, which may include various sub-groups have been presented. By non-hospital studies it is possible to avoid some of these biases.

Population-based pediatric reference intervals for HbA1c, bilirubin, albumin, CRP, myoglobin and serum enzymes.

Abstract Background. Many previous studies on reference intervals are hampered by the inclusion of only hospital-based populations of children and adolescents. Methods. This study included 694 children, evenly distributed from 6 months to 18 years of age. They were recruited as volunteers at child care units and schools. All subjects were apparently healthy. A questionnaire on diseases and medications was filled out by parents and by the older children. Results. Alanine aminotransferase (ALT), albumin, aspartate aminotransferase (AST), bilirubin, conjugated bilirubin, C-reactive protein (CRP), creatine kinase (CK), Gamma-glutamyltransferase (GGT), HbA1c (mono S and IFCC calibrations), lactate dehydrogenase (LD), myoglobin and panceratic amylase were analyzed on Abbott Architect ci8200, and for HbA1c on Tosoh G7 and a mono S-system. Age- and gender-related 2.5th and 97.5th percentiles were estimated. For some analytes the differences to comparable studies were substantial. Conclusion. The study gives age- and gender-specific pediatric reference intervals, measured with modern methods for a number of important analytes. The results emphasize the importance to evaluate pediatric reference intervals in different populations and ethnic groups including only healthy subjects.

Biomonitoring study of deoxynivalenol exposure and association with typical cereal consumption in Swedish adults

Deoxynivalenol (DON) is a mycotoxin of the trichothecene family commonly found in cereals infested with different Fusarium species. DON acts primarily on the gastrointestinal and immune system and is suspected to be an underlying agent causing several outbreaks of gastrointestinal disorder among humans, which prompts studies of human exposure and estimations of intake among populations. However, assessing human exposure to mycotoxins is associated with several difficulties. Therefore, a study was undertaken among adults (18-80 years) in a subgroup of Riksmaten, the Swedish national survey investigating dietary habits, examining both the association between urinary DON concentration and dietary intake of cereals, and estimations of daily DON intake. The results indicate that exposure to DON is common among Swedish adults, as this mycotoxin was detected in 292 out of 326 urine samples (90%) at levels ranging from non-detectable to 65.8 ng DON/ml urine with a median level of 2.9 ng/ml. Furthermore, urinary D...

Influences of sleep and the circadian rhythm on iron-status indices

OBJECTIVES The aim was to study the influence of sampling time, food intake and sleep on tests used to screen for and monitor conditions of iron deficiency and overload. DESIGN AND METHODS The 24 h variations of iron, transferrin, transferrin saturation (TS) and ferritin were studied in seven healthy individuals during standardised food intake, and during night or day sleep. RESULTS Iron and TS showed clear diurnal variations, with peaks at 12.6 h and 12.8 h respectively, during night sleep, and at 19.7 h and 19.3 h, respectively, during day sleep. Ferritin did not demonstrate any circadian variation. Transferrin and ferritin were unaffected by sleep-condition. Meals did not have any effect except a slight decline of transferrin. CONCLUSIONS Time of day and sleeping patterns had great influence on iron and TS, whereas no or only minor effects are seen on the concentration of ferritin and transferrin. Meals have limited effects.