Abstract  CONTEXT: Calcitonin (CT) measurement is crucial to the early diagnosis and the follow-up of medullary thyroid cancer (MTC). If the evaluation of stimulated CT levels is required, a provocative test can be performed, being the high-dose Ca test recently reintroduced in clinical practice.

OBJECTIVE: Our objective was to identify gender-specific thresholds for MTC diagnosis in a large series of patients who underwent the Ca test.

PATIENTS AND METHODS: A total of 91 patients (49 females and 42 males) underwent the Ca test (calcium gluconate, 25 mg/kg) before thyroidectomy and both basal CT (bCT) and stimulated CT (sCT) were compared with histological results by receiver operating characteristic plot analyses. To evaluate possible side effects of Ca administration, cardiac function has been extensively studied.

RESULTS: bCT levels were found to harbor the same accuracy as sCT in the preoperative diagnosis of MTC. The best Ca thresholds for the identification of MTC were >26 and >68 for bCT and >79 and >544 pg/mL for sCT in females and males, respectively. The high tolerability and safety of the Ca test was demonstrated and advice offered to be followed before and during the test.

CONCLUSIONS: Gender-specific bCT and sCT cutoffs for the identification of C-cell hyperplasia and/or MTC have been defined. The bCT and sCT were found to have a similar accuracy, indicating that serum CT assays with improved functional sensitivity may likely decrease the relevance of the stimulation test in several conditions. Finally, systematic cardiac monitoring confirms the safety of the Ca test.

Abstract  This book was written to be used by the clinician who deals with pregnant patients. Everyday in an obstetrical, pediatric or other medical practice, one encounters frequent questions about the use of drugs in pregnancy and lactation. These questions may involve the use of a drug for therapy of an associated condition, an inquiry about some drug a patient has already taken and then decides to ask about or the determination if an untoward pregnancy outcome or an adverse effect observed in the infant was caused by the consumption of some therapeutic agent by the patient. Other health professionals, such as nurses and pharmacists, also are often confronted with questions concerning drug usage in the pregnant or breast feeding woman. Of course, this book is of necessity lacking in giving absolute answers on most drugs in question because experience in humans is not easy to gather. One seldom knows, even when the drug history is thought to be realistic, whether there is an actual cause-effect relationship between a specific drug and an adverse pregnancy outcome. Because the answers are generally inconclusive, physicians caring for pregnant patients should counsel their patients accordingly either when answering a question about some drug already ingested or when explaining the cost/benefit ratio to a patient who is being considered for some specific drug therapy. For the breast feeding patient, the risks from a particular drug are usually much clearer although there are frequent examples where the risk must be inferred from related drugs. Unfortunately, many drugs have not been studied during nursing so the effects on the infant, if any, are completely unknown. A good rule to follow is if the drug can safely be given directly to the infant, it is generally safe to give to the mother during lactation. This book allows the clinician to have at his or her fingertips an up-to-date summary of available data bearing on specific drugs. It is easy to read and organized in a logical manner to save the busy clinician time.

Abstract  The calcium-sensing receptor (CaSR) has been detected in human antral gastrin-secreting cells, where, upon calcium and/or amino acid allosteric activation, it stimulates gastrin secretion. Patients with absorptive hypercalciuria (AH) display an enhanced gastric acid output; therefore, we evaluated the secretion of gastrin in subjects with AH (30 subjects vs. 30 healthy female controls, all postmenopausal) after oral calcium administration (1 g calcium gluconate) and, on a separate occasion, after peptone loading test (protein hydrolyzed, 10 g). Gastrin and monomeric calcitonin responses were higher in AH after both oral calcium administration (P < 0.01) and peptone loading (P < 0.01). Because the activation of CaSR by oral calcium and peptones directly induces gastrin release, the higher gastrin responses to these stimuli suggest an increased sensitivity of gastrin-secreting cells CaSR in patients with AH. A similar alteration in thyroid C cells might explain the enhanced calcitonin responses to both calcium and peptones. If the same alterations should in addition be present in the distal tubule (where CaSR is expressed as well), then a possible explanation for amino acid-induced hypercalciuria in AH would have been identified.

Abstract  The assignments of 'structural alerts' by Ashby and associates as predictors of genotoxic carcinogenicity were used as the entries for CASE, an artificial intelligence-based structure-activity relational method. CASE, using this human intelligence-based information, was able to derive structural determinants that duplicate the informational content of the structural alerts (sensitivity, 0.974; specificity, 0.948). The CASE-predicted alerts performed as well as the results of the Salmonella mutagenicity assay or the direct application of structural alerts in predicting carcinogens.

Abstract  With the aid of Sevier-Munger silver stain, parafollicular thyrocytes (C-cells) of rat males were investigated within the period of 10 minutes to 8 hours after the intraperitoneal injection of calcium gluconate solution. In the thyroid glands of both control and experimental animals four types of C-cells at different stages of their secretory cycle were described. Relative rates of these cellular types were found to be objective quantitative criteria of the functional activity of parafollicular cell population.

Abstract  Mutagenicity of 29 food additives including 8 dietary supplements, 13 flavoring agents, 5 bleaching agents and 3 oxidizing agents were examined in Ames' new tester strains, Salmonella typhimurium TA 97 and TA 102. The mutation test was carried out by the preincubation procedure described by Ames et al. These test chemicals were preincubated with S9mix or phosphate buffer (pH 7.4) for 20 min. Potassium bromate showed weak mutagenic activity in TA 97 with S9. The other 28 chemicals were not mutagenic in the new tester strains.

Abstract  The efficacy of dietary calcium glucarate as a chemopreventative agent has been tested in the mouse skin tumorigenesis system. Skin tumorigenesis was initiated in mice of the CD-1 strain with 7,12-dimethylbenz(a)anthracene (DMBA), then promoted with twice weekly applications of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) for 13 weeks. The mice were fed a regular chow diet, or a chow diet fortified with calcium glucarate (128 mmol/kg diet), or with equimolar calcium as calcium gluconate (negative calcium control). When mice were fed calcium glucarate throughout both the initiation and promotion phases papilloma formation was inhibited by over 30%. Transfer of these DMBA-initiated, TPA promoted CD-1 mice to chow diet after 13 weeks on the calcium glucarate-supplemented diet, resulted in an increase in the number of skin papillomas within 3 weeks to the level of those seen in control animals maintained exclusively on the chow diet. When calcium glucarate feeding was restricted to either the initiation or promotion phases, papilloma formation was inhibited by 25%. Dietary calcium gluconate had no effect on papilloma formation in the CD-1 mouse system, but increased the calcium concentration in the skin to the same extent as that of calcium glucarate. The data indicate that the elevation of the normally low levels of glucarate in the body through supplementation, results in a marked alteration in the retention, activity and/or metabolism of xenobiotics.

Abstract  The following researches of calcium pyrrolidinecarboxyiate were tested: a) acute lethality, toxicity and general tolerability; b) influence on normal calcemia and calciuria; c) protective action against death due to sodium ethylenediaminetetraacetate; d) restorative effect in animals fed on calcium-free diet; e) antiflogistic effects; f) effects on ECG, arterial pressure, respiration, isolated heart and duodenal muscle; g) effect on blood clotting; h) effect on plasma recalcification time. In various tests the effects were compared with those of calcium chloride, glutamate, gluconate, lactate and levulinate.

Abstract  The stimulus-secretion coupling for hypotonicity-induced insulin release was investigated in BRIN-BD11 cells. A 50 mM decrease in extracellular NaCl caused a twofold increase in insulin release. The release of insulin evoked by hypotonicity progressively decreased in an exponential manner. The response to extracellular hypotonicity displayed a threshold value close to 20 mOsmol/L and a maximal response at about 70 mOsmol/ L. Hypotonicity also caused a rapid increase in cell volume followed by a regulatory volume decrease (RVD), cell membrane depolarization with induction of spike activity, and a rise in cytosolic Ca2+ concentration. 5-Nitro-2-(3-phenylpropylamino)benzoate inhibited the secretory response to hypoosmolarity, failed to affect the early increase in cell volume but prevented the RVD, and suppressed the hypotonicity-induced plasma membrane depolarization. Insulin release provoked by hypotonicity was inhibited by verapamil, absence of Ca2+, thapsigargin, furosemide, tributyltin, and diazoxide. On the contrary, tolbutamide augmented modestly insulin release recorded in the hypoosmolar medium. Last, a rise in extracellular K+ concentration, while augmenting basal insulin output, failed to affect insulin release in the hypoosmolar medium. Thus, the insulin secretory response to hypotonicity apparently represents a Ca2+-dependent process triggered by the gating of volume-sensitive anion channels with subsequent depolarization and gating of voltage-sensitive Ca2+ channels.

Abstract  Gluconic acid (GA) derives from the incomplete oxidation of glucose by some Gluconobacter strains. When fed to nonruminant animals, GA is only poorly absorbed in the small intestine and is primarly fermented to butyric acid in the lower gut. This study investigated the effect of GA on in vitro growth response and metabolism of swine cecal microflora and on animal growth performance, intestinal wall morphology, and intestinal microflora. During a 24-h in vitro cecal fermentation, total gas production and maximum rate of gas production were increased by GA (linear, P < 0.001). Ammonia in cecal liquor was reduced by GA after 4, 8, and 24 h of fermentation (quadratic, P < 0.01). After 24 h of fermentation, total short-chain fatty acids, acetic acid, propionic acid, n-butyric acid, acetic to propionic acid ratio, and acetic + butyric to propionic acid ratio were linearly increased by GA (P < 0.001). In the in vivo study, 48 piglets were divided into 4 groups and housed in individual cages for 6 wk. Piglets received a basal diet with a) no addition (control) or with GA addition at b) 3,000 ppm, c) 6,000 ppm, or d) 12,000 ppm. After 6 wk, 4 animals per treatment were killed, and samples of intestinal content and mucosa were collected. Compared with control, GA tended to increase average daily gain (+13 and +14% for GA at 3,000 and 6,000 ppm, respectively; P of the model = 0.11; quadratic, P < 0.05). Daily feed consumption and gain to feed ratio were not influenced by GA. Intestinal counts of clostridia, enterobacteriaceae, and lactic acid bacteria were not affected by GA. Gluconic acid tended to increase total short-chain fatty acids in the jejunum (+174, +87, and +74% for GA at 3,000, 6,000, and 12,000 ppm, respectively; P of the model = 0.07; quadratic, P = 0.07). Morphological evaluation of intestinal mucosa from jejunum, ileum, and cecum did not show any significant differences among treatments. This study showed that feeding GA influences the composition and activity of the intestinal microflora and may improve growth performance of piglets after weaning.

Abstract  Gluconate derivatives are presented as a category. Gluconic acid and its mineral salts freely dissociate to the gluconate anion and the respective cations. Glucono-delta-lactone (GDL), the 1,5-inner ester of gluconic acid, is formed from the free acid by the removal of water. On the basis of these spontaneous chemical rearrangements, glucono-delta-lactone, gluconic acid and its sodium, calcium and potassium salts can be considered as a category, with all members sharing the same representative moiety, the gluconate anion. Manufacturing and uses of the category members are also interlinked. The data summarized in this report are focused on the environmental and health effects from the gluconate anion and read-across to the lactone but do not deal with specific effects of the cations. Thus toxicological effects related to the cationic components are not part of the present report.

Abstract  The purpose of this study is to determine the bioavailability, biodistribution and toxicity of Biocal(TM), a new calcium source. Biocal(TM) is a calcium gluconate stabilized with glycine. A comparative study of this compound versus calcium gluconate was performed in Sprague-Dawley rats. Bioavailability studies were carried out by the labeling of both compounds with Ca-45. We administered a dose of 30 mg of Ca per kg of body weight p.o. to two groups of 7 male adult rats each. The urine elimination of the Ca-45, expressed as total accumulated percentage of Ca-45 activity in urine (Ae(infinity)), between the rats that received Biocal(TM) (Ae(infinity) = 2.436+/-1.337 %) and the rats that received calcium gluconate (Ae(infinity) = 1.241+/-0.473 %) were found to be statistically different (p<0.05). Biodistribution studies showed that the calcium from Biocal(TM) follows the same metabolic pathway as calcium from calcium gluconate. Values of radioactivity concentration of 97.1+/-1.3% and 98.7+/-1.6% were found in bone for Biocal(TM) and calcium gluconate, respectively. Toxicity studies of Biocal(TM) were carried out with 60 female and 60 male rats. The values of oral LD50 for female rats was 13.5 g/kg with a lower limit of 12.8 g/kg and upper limit of 14.3 g/kg. In the case of male rats the LD50 was 13.0 g/kg with a lower limit of 12.2 g/kg and upper limit of 13.9 g/kg. These values are higher with regard to the oral LD50 for calcium gluconate (10 g/kg). Our results demonstrate that calcium from Biocal(TM) has a higher bioavailability with the same metabolic behavior than calcium from calcium gluconate. The value of oral LD50 shows that the toxicity of Biocal(TM) is lower than that of the calcium gluconate. Therefore we conclude that Biocal(TM) has adequate properties to be considered as a promissory calcium compound to be used as dietary supplement or for food fortification. (C) 1999 Elsevier Science Inc.

Abstract  Background Contractile function of the ex vivo, isolated left atrium (LA) has been described by a time-varying elastance, but this atrial chamber property has not been shown in vivo.

Methods and Results Instantaneous LA pressure-volume (P-V) relations were studied in 12 anesthetized, autonomically blocked, atrially paced dogs. LA volume was calculated from orthogonal sonomicrometer pairs using a cast-validated formula. Data were collected during increases in LA pressure produced by a phenylephrine bolus (200 to 400 mu g IV). Isochronal P-V points from 5 beats, representing a wide range of atrial pressures, were fitted by linear regression analysis (range of R(2), .92 to .99). There were significant time-dependent increases in the slopes [E((t))] and small but statistically insignificant decreases in the volume axis intercepts [Vo((t))] of the instantaneous LA P-V relations during atrial contraction; maximal elastance (E(max)) occurred 29+/-16 milliseconds before atrial end systole (minimal LA volume). E(max) was not significantly different than the slopes of either the nonisochronal end-systolic P-V relation (E(es)) or the nonisochronal maximal P-to-V relation (E(maxPV)): 5.5+/-2.8, 4.3+/-1.5, and 5.4+/-4.2 mm Hg/mL, respectively. In 7 dogs, data were collected both before and after a rapid infusion of calcium gluconate (1 to 2 g IV). E(max) increased significantly with a calcium-induced increase in inotropic state (4.5+/-1.6 to 5.7+/-1.8 mm Hg/mL, P<.01), but the volume axis intercept was unchanged (3.6+/-0.7 versus 3.4+/-1.9, P=NS). In 4 additional dogs with heart failure (mean LA pressure, 26+/-6 mm Hg) produced by 3 weeks of rapid right ventricular pacing, LA stroke volume was significantly greater than and elastance determinations were similar to those of normal dogs. However, the effects of calcium infusion on LA function were attenuated in these animals.

Conclusions We conclude that (1) in the intact heart, LA contraction may be approximated by time-varying elastance with time-dependent changes in E((t)) and that (2) LA systolic P-V relations using either the nonisochronal maximum P-to-V ratio or end systole may be useful as an estimate of E,,, are highly linear and sensitive to calcium-induced changes in inotropic state, and may be useful in identifying LA chamber adaptation to chronic hemodynamic;loads.

Abstract  The effects of 4 weeks of calcium supplementation on free- and total testosterone levels were established in active and sedentary adult males at rest and exhaustion. Thirty healthy male athletes were equally divided into three study groups, as follows: Group 1-non-exercising subjects receiving 35 mg calcium/kg body weight; Group 2-subjects receiving 35 mg calcium/kg body weight undergoing training routines for 90 min/day, 5 days a week and Group 3-subjects undergoing training routines for 90 min/day, 5 days a week. The testosterone levels were determined before and after supplementation, at rest and following a hard training routine. The plasma free- and total testosterone levels increased at exhaustion before and after supplementation relative to resting values (p < 0.05). This was also true when active subjects were compared to inactive subjects (p < 0.05). Our results show that training results in increased testosterone levels in athletes and that the increase is greater if accompanied by calcium supplementation, which may be useful for increasing overall athletic performance.

Abstract  CA1 pyramidal neurons from animals that have acquired hippocampal tasks show increased neuronal excitability, as evidenced by a reduction in the postburst afterhyperpolarization (AHP). Studies of AHP plasticity require stable long-term recordings, which are affected by the intracellular solutions potassium methylsulphate (KMeth) or potassium gluconate (KGluc). Here we show immediate and gradual effects of these intracellular solutions on measurement of the AHP and basic membrane properties, and on the induction of AHP plasticity in CA1 pyramidal neurons from rat hippocampal slices. The AHP measured immediately after establishing whole-cell recordings was larger with KMeth than with KGluc. In general, the AHP in KMeth was comparable to the AHP measured in the perforated-patch configuration. However, KMeth induced time-dependent changes in the intrinsic membrane properties of CA1 pyramidal neurons. Specifically, input resistance progressively increased by 70% after 50 min; correspondingly, the current required to trigger an action potential and the fast afterdepolarization following action potentials gradually decreased by about 50%. Conversely, these measures were stable in KGluc. We also demonstrate that activity-dependent plasticity of the AHP occurs with physiologically relevant stimuli in KGluc. AHPs triggered with theta-burst firing every 30 s were progressively reduced, whereas AHPs elicited every 150 s were stable. Blockade of the apamin-sensitive AHP current (I(AHP)) was insufficient to block AHP plasticity, suggesting that plasticity is manifested through changes in the apamin-insensitive slow AHP current (sI(AHP)). These changes were observed in the presence of synaptic blockers, and therefore reflect changes in the intrinsic properties of the neurons. However, no AHP plasticity was observed using KMeth. In summary, these data show that KMeth produces time-dependent changes in basic membrane properties and prevents or obscures activity-dependent reduction of the AHP. In whole-cell recordings using KGluc, repetitive theta-burst firing induced AHP plasticity that mimics learning-related reduction in the AHP.

Abstract  The relationship between microliths and sialadenitis in man is unclear, so an attempt was made to investigate it experimentally in rats with the use of isoprenaline and calcium gluconate either alone or combined. The acini of the submandibular and parotid glands of rats that were given isoprenaline were enlarged, and degenerate acinar cells were seen, with extravasated secretions in the submandibular gland. Similar changes were seen in the submandibular and parotid glands of rats that were given isoprenaline combined with calcium gluconate; in addition, ductal microliths with regions of atrophic sialadenitis were observed. The results suggest that there is temporary obstruction to the salivary flow after isoprenaline is injected, and in the rats that were also given calcium gluconate some of the stagnant saliva calcified to form microliths, which produced a lasting obstruction and obstructive sialadenitis. This supports the possibility that microliths, which are present in normal salivary glands of man, are a primary etiologic factor in sialadenitis.