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C S Fullmer

Publications and source records attributed to C S Fullmer.

At least 37 records · Page 2Linked to original sources
PubMed1990

Effect of dietary calcium and lead status on intestinal calcium absorption.

Dietary lead intake was demonstrated to result in two very different effects on intestinal calcium absorption and associated parameters, depending on dietary calcium status. Normal growing 14-day-old chicks were fed diets either low (0.05%) or adequate (1.2%) in calcium and containing varying levels of lead (0%-0.8%) for an additional 10 days. In chicks fed the low calcium diet, ingested lead inhibited intestinal 47Ca absorption, and intestinal calbindin D and alkaline phosphatase synthesis in a dose-dependent fashion. Even at the highest levels of lead, however, this inhibition was limited to the stimulation of these parameters by low dietary calcium. In chicks fed the normal calcium diet, lead exposure did not diminish intestinal 47Ca absorption, or calbindin D or alkaline phosphatase synthesis, but actually elevated the values of these parameters at the higher lead exposure levels. The results indicate that the primary effect of lead, in both cases, occurs at or prior to intestinal protein synthesis and most likely involves the cholecalciferol endocrine system rather than any direct interactions between lead and calcium at the intestinal level.

Alkaline Phosphatase↗
PubMed1990

Ion microscopic imaging of calcium transport in the intestinal tissue of vitamin D-deficient and vitamin D-replete chickens: a 44Ca stable isotope study.

The intestinal absorption of calcium includes at least three definable steps; transfer across the microvillar membrane, movement through the cytosolic compartment, and energy-dependent extrusion into the lamina propria, Tracing the movement of calcium through the epithelium has been hampered by lack of suitable techniques and, in this study, advantage was taken of ion microscopy in conjunction with cryosectioning and use of the stable isotope 44Ca to visualize calcium in transit during the absorptive process. The effect of vitamin D, required for optimal calcium absorption, was investigated. Twenty millimolar 44Ca was injected into the duodenal lumen in situ of vitamin D-deficient and vitamin D-replete chickens. At 2.5, 5.0, and 20.0 min after injection, duodenal tissue was obtained and processed for ion microscopic imaging. At 2.5 min. 44Ca was seen to be concentrated in the region subjacent to the microvillar membrane in tissue from both groups. At 5.0 and 20.0 min, a similar pattern of localization was evident in D-deficient tissues. In D-replete tissues, the distribution of 44Ca became more homogenous, indicating that vitamin D increased the rate of transfer of Ca2+ from the apical to the basolateral membrane, a function previously ascribed to the vitamin D-induced calcium-binding protein (28-kDa calbindin-D). Quantitative aspects of the calcium absorptive process were determined in parallel experiments with the radionuclide 47Ca. Complementary information on the localization of the naturally occurring isotopes of calcium (40Ca) and potassium (39K) is also described.

Animals↗
PubMed1990

Intestinal lead and calcium absorption: effect of 1,25-dihydroxycholecalciferol and lead status.

This study was designed to investigate, in some detail, the relative effects of the hormonal form of vitamin D (1,25-dihydroxycholecalciferol) on duodenal Pb and Ca absorption as a function of dietary Pb level. When cholecalciferol-deficient chicks were chronically repleted with physiologic levels of 1,25-dihydroxycholecalciferol (1,25(OH)2D3), as the sole source of the vitamin, 203Pb and 47Ca absorption were enhanced over 4- and 8-fold, respectively. Ingestion of Pb during the repletion period had no significant effect on the intestinal Ca absorption response to 1,25-(OH)2D3 even at a very high dietary Pb level. The efficiency of intestinal 203Pb absorption was, however, significantly diminished by dietary Pb, in an apparent dose-dependent fashion. The results indicate that the extent to which systemic Ca homeostatic mechanisms influence intestinal Pb absorption is dependent, in large part, on Pb status.

Alkaline Phosphatase↗
PubMed1990

Recent studies on the biological actions of vitamin D on intestinal transport and the electrophysiology of peripheral nerve and cardiac muscle.

Vitamin D, with parathyroid hormone and calcitonin, is an essential factor in the homeostatic regulation of systemic calcium in most vertebrate species. Targets for this aspect of vitamin D action, through its biologically active metabolites, are primarily the intestine, kidney and bone. Each of these tissues or organs are stimulated by 1,25(OH)2D3 to increase the transport calcium into the extracellular fluid compartment when plasma calcium levels are below normal and/or when there is a greater need for calcium to meet the requirements of physiological processes, such as growth, gestation and lactation. During such periods, the efficiency of the absorption of calcium from the intestine increases, the resorption of calcium salts from bone is stimulated, and the efficiency of the reabsorption of filtered calcium by the renal tubule is increased. In addition to the homeostatic function of vitamin D, there is an increasing amount of evidence that vitamin D has important effects on tissues and organs other than those concerned with calcium homeostasis. With regard to the intestinal epithelial system, the genomic effect of 1,25(OH)2D3 was shown several years ago when the de novo synthesis of a specific vitamin D-induced calcium-binding protein (CaBP, calbindin-D) was demonstrated. In our view, this appears to be an essential factor in the well-documented enhancement of calcium absorption by vitamin D. The function of calbindin-D, a high affinity calcium-binding protein, in the absorptive process is not precisely known but currently considered to act as an intracellular facilitator of the diffusion of calcium from the microvillar pole of the enterocyte to the basal-lateral membrane. There is evidence that vitamin D influences another step in the absorptive process. This step appears to be associated with the entrance of luminal calcium into the enterocyte, the first step in the transepithelial transport process. This response appears to occur relatively early (1 h or less) after 1,25(OH)2D3 is given to vitamin D-deficient animals, whereas the de novo synthesis of transport proteins has a much longer lag time (about 4 h). The in vitro absorption studies of Nemere et al (1984) and the in vivo experiments of our group (Wasserman et al, 1982) accentuate this point. However, the more rapid reaction, i.e., the possible modification of the permeability properties of the brush border membrane, does not result in a substantive increase in overall calcium absorption unless the enterocyte had been "primed" by previous exposure to vitamin D. The "priming" reaction might represent the synthesis of CaBP or some other intracellular component.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

On the molecular mechanism of intestinal calcium transport.

The intestinal absorption of calcium is certainly a complex process, dependent on several factors of which vitamin D, via 1,25(OH)2D3, is the major controlling hormone. The efficiency of calcium absorption is a function of calcium status and calcium need. As the body's demand for calcium increases, the process commonly termed, adaptation, is activated in which the synthesis of 1,25(OH)2D3 from precursor is increased, resulting in the stimulation of the rate of calcium absorption. The increased demand for calcium might result from the ingestion of a diet deficient in calcium, from growth, pregnancy, lactation and egg shell formation in the laying hen. Accomapanying the change in calcium absorptive efficiency are molecular modifications of the transporting enterocytes, some mentioned herein and elsewhere (Wasserman & Chandler, 1985; Wasserman, 1980; Wasserman et al., 1984). Highly correlated with the rate of calcium absorption under a wide variety of conditions is the concentration of the vitamin D-induced calcium-binding protein, calbindin-D28K (avian type) and calbindin-D9K (mammalian intestinal type). The role of calbindin-D in this transport process is not precisely known but is considered to act at the present time as a cytosolic facilitator of Ca2+ diffusion from the brush border membrane to the basolateral membrane. In addition to the induction of calbindin-D synthesis, 1,25(OH)2D3 exerts other effects on the intestinal epithelium that can have consequences on the calcium absorptive process. Some of these effects are summarized in Figure 14. Vitamin D-dependent reactions might be either direct effects of 1,25(OH)2D3 or indirect effects due to elevated intracellular Ca2+ concentrations. These include changes in the fluidity of the brush border membrane, an increase in microvillar alkaline phosphatase-low affinity Ca-activated ATPase activity, an association of calmodulin with the 105 kD brush border cytoskeletal protein and, following calbindin D synthesis, the binding of calbindin D to a 60 kD brush border protein and to microtubules. The latter has been suggested to be related to the proposed transfer of Ca2+ by an endocytotic-exocytotic mechanism. In addition, a vitamin D-dependent intestinal membrane calcium-binding protein has been identified (Kowarski & Schachter, 1980). Playing into this multi-component system is a stimulation of cyclic nucleotide synthesis by 1,25(OH)2D3 which, through activation of cyclic nucleotide-dependent protein kinases, might modify membrane Ca2+ "channels" by phosphorylation reactions.4+ Intracellular organelles, i.e., the endoplasmic reticulum, mitochondria, the Golgi apparatus, are potent sequesters of Ca2+ and could contribute to the protection of the cell from excessively high Ca2+ concentrations by transiently storing absorbed Ca2+.

Animals↗
PubMed1988

Calcium-dependent translocation of calbindin-D28k from intestine to blood.

Calbindin-D (vitamin D-induced calcium-binding protein; CaBP) is known to be present in blood at concentrations which vary directly with levels in the intestinal mucosa. Employing a sensitive radioimmunoassay and sampling mesentery venous blood, the present experiments demonstrated a direct relationship between intestinal calcium absorption and serum CaBP. Solutions containing 150 mM NaCl and 45Ca-labeled calcium chloride (5 or 20 mM) were placed in the lumen of ligated duodenal preparations in situ and mesentery venous blood sampled with time. The concentration of absorbed 45Ca in serum was maximal at 5 min, followed by a significant increase in mesentery CaBP maximizing at 15-20 min. Elevation of serum CaBP was not observed when calcium in the dosing solution was omitted or replaced by either glucose or glycine. The possible transfer of absorbed calcium from the enterocyte to the circulation as a CaBP complex was ruled out by calculations revealing that considerably more calcium was transferred than could be accounted for by the low and high affinity binding sites on the protein. It is proposed that vitamin D-dependent enhanced transcellular calcium transport constitutes a stimulus for the increased release of intestinal CaBP into the circulation.

Animals↗
PubMed1988

Amino acid sequence and comparative antigenicity of chicken metallothionein.

The complete amino acid sequence of metallothionein (MT) from chicken liver is reported. The primary structure was determined by automated sequence analysis of peptides produced by limited acid hydrolysis and by trypsin digestion. The comparative antigenicity of chicken MT was determined by radioimmunoassay using rabbit anti-rat MT polyclonal antibody. Chicken MT consists of 63 amino acids as compared to 61 found in MTs from mammals. One insertion (and two substitutions) occurs in the amino-terminal region, a region considered invariant among mammalian MTs. Eighteen of the 20 cysteines in chicken MT were aligned with cysteines from other mammalian sequences. Two cysteines near the carboxyl terminus are shifted by one residue due to the insertion of proline in that region. Overall, the chicken protein showed approximately equal to 68% sequence identity in a comparison with various mammalian MTs. The affinity of the polyclonal antibody for chicken MT was decreased by 2 orders of magnitude in comparison to that of a mammalian MT (rat MT isoforms). This reduced affinity is attributed to major substitutions in chicken MT in the regions of the principal determinants of mammalian MTs. Theoretical analysis of the primary structure predicted the secondary structure to consist of reverse turns and random coils with no stable beta or helix conformations. There is no evidence that chicken MT differs functionally from mammalian MTs.

Amino Acid Sequence↗
PubMed1987

Chicken intestinal 28-kilodalton calbindin-D: complete amino acid sequence and structural considerations.

The complete primary structure of the cholecalciferol-induced chicken intestinal 28-kDa calbindin-D is reported. It is a single-chain polypeptide consisting of 261 amino acid residues (computed Mr = 30,042) and is blocked at the amino terminus. Tryptic digestion of the S-pyridylethylated protein followed by HPLC peptide mapping and automated sequence determination provided the bulk of the sequence information. Subsequent chymotryptic and Staphylococcus aureus V8 protease cleavages yielded the sequences of several additional regions as well as extensive overlapping of the tryptic peptides. The primary structure shows six homologous regions of sequence based on the EF-hand concept of calcium binding, four of which are predicted to actually bind calcium. Aside from these regions, there is no overall structural identity or apparent similarity with the mammalian calbindins (9 kDa), calmodulin, or troponin C. It is predicted that the secondary structure of 28-kDa calbindin-D is significantly different from the other proteins of this class, which bind four calcium atoms.

Amino Acid Sequence↗
PubMed1987

Calbindin-D in peripheral nerve cells is vitamin D and calcium dependent.

The vitamin D-induced calcium-binding protein calbindin-D (CaBP) was localized immunohistochemically in some but not all of the cell bodies and axons within the intestinalis nerve of the chicken. Unlike other nerve tissue thus far examined, the CaBP content of the intestinalis nerve was decreased in vitamin D deficiency and increased in chicken adapted to a calcium-deficient diet. These changes are qualitatively similar to the pattern of response of enterocytes. The inclusion of calcium-containing solutions within the duodenal lumen caused, directly or indirectly, a decrease in the amount of CaBP in this nerve in a dose-dependent manner. The exact role of CaBP in intestinalis nerve cells is unknown but may be in the regulation of intracellular ionic Ca2+ concentrations during excitation, although other functions of CaBP cannot be excluded.

Animals↗
PubMed1985

Lead-binding properties of intestinal calcium-binding proteins.

The bovine and chick vitamin D-induced intestinal calcium-binding proteins (CaBP) bind lead. Bovine CaBP binds 2 atoms of lead/molecule, and chick CaBP binds 4 atoms of lead per molecule and these values are identical to those for calcium binding. 45Calcium-displacement studies indicate significantly higher affinities for lead than for calcium for both proteins. All evidence indicates that lead is bound to the 4 high affinity calcium-binding sites on chick CaBP and to the corresponding 2 high affinity sites on bovine CaBP, and that binding of lead to sulfhydryl groups is, relatively, not significant. Calmodulin, troponin C, and oncomodulin also bind lead with high affinities and in preference to calcium, indicating that lead binding is a general property of proteins belonging to the troponin C superfamily of calcium-binding proteins.

Animals↗
PubMed1985

Intestinal absorption of arsenate in the chick.

The intestinal absorption of arsenate(As(V)) has been investigated in the chick by means of the in situ ligated duodenal loop technique. By this procedure, it was observed that arsenate is rapidly and essentially completely absorbed (80-95%) from the lumen at As(V) concentrations up to 5 mM, declining to about 50% absorption at 50 mM. Transfer from the intestinal lumen to the mucosal cells at low As(V) concentration (0.1 mM) is rapid, while transfer from the mucosal cells to the body occurs more slowly. At stable As(V) concentrations greater than 1 mM, fractional mucosal cell accumulation of As(V) remains constant, while fractional transfer to the body declines. However, total mucosal accumulation of As(V) and that transferred to the body increase in a linear logarithmic fashion from 0.05 to 5 mm As(V). The results indicate that As(V) readily penetrates both the mucosal and serosal surfaces of the epithelial membrane. Furthermore, arsenate and phosphate do not appear to share a common transport pathway in the duodenum and no evidence was obtained for any interaction between the two at this level. Vitamin D3 administration to rachitic chicks was effective in significantly elevating duodenal arsenate absorption, acting primarily to enhance serosal transport.

Administration, Oral↗
PubMed1984

Identification of cysteine-containing peptides in protein digests by high-performance liquid chromatography.

A method is described for the facile identification of half-cystine residues in peptides from protein digests. Combined use of S-beta-(4-pyridylethylation) of cysteine residues with 4-vinyl pyridine and peptide mapping by reversed-phase high-performance liquid chromatography provides the basis for this procedure. Essentially simultaneous, in-line effluent monitoring at 220, 280, and 254 nm provides highly sensitive, specific, and instantaneous identification of all peptide peaks, as well as those containing tryptophan and half-cystine residues, respectively. The resultant cysteine-derivatized peptides are well suited to amino acid compositional and protein sequence analysis, and are protected from loss during enzymatic digestion and/or peptide mapping.

Animals↗
PubMed1984

Characterization of the cysteinyl-containing peptides of the gamma subunit of coupling factor 1.

The cysteinyl peptides of the gamma subunit of chloroplast coupling factor 1 (CF1) have been analyzed by high performance liquid chromatography. Analysis of the reduced enzyme alkylated with 4-vinylpyridine showed that the gamma subunit contains four cysteinyl residues. Two of these residues are involved in a disulfide linkage in CF1 either in solution or bound to washed thylakoid membranes. Two free sulfhydryls, one that is readily attacked by alkylating reagents and another that is less reactive, were also detected. Each of these four cysteinyl residues is present in a separate tryptic peptide derived from the gamma subunit. These results show that 4-vinylpyridine is an excellent reagent for the analysis of cysteinyl-containing peptides and support our analyses of the roles of cysteinyl residues in the gamma subunit in ATP synthesis and hydrolysis.

Amino Acids↗
PubMed1984

Effect of phosphate on the intestinal absorption of lead (203Pb) in chicks.

The effect of phosphate on the intestinal absorption of lead (203Pb2+) was examined in chicks. Absorption was determined by the in situ ligated duodenal loop technique. In one approach, diets differing in phosphate content were fed to 2-week-old chicks for a period of 7 days. With respect to the control group (1.06% P), a severe phosphate deficiency (0.16% P) decreased growth, CaBP synthesis and 203Pb absorption; a moderate phosphate deficiency (0.33% P) resulted in an increase in CaBP production and 203Pb absorption; and the high phosphate diet (2.12%) gave mean values for CaBP synthesis and 203Pb absorption intermediate between those from the chicks fed the 0.33 and 1.06% diets. 203Pb absorption was highly correlated with CaBP concentrations. In another approach, phosphate in varying concentrations was added directly to the dosing solution. In one study, phosphate addition (0.1 mM) depressed 203Pb absorption in rachitic and cholecalciferol-treated chicks. When the data were expressed in terms of absorption of the soluble 203Pb present in the intestinal lumen at the end of the absorption period, an effect of phosphate in addition to the precipitation of the insoluble lead salt was uncovered. In an experiment with normal chicks, it was observed that phosphate in the dosing solution at concentrations of 1 and 2 mM partially and significantly reversed the inhibitory effect of lower concentrations of phosphate (0.01 mM and 0.1 mM). These data demonstrate the complexity of the phosphate-lead interaction, in addition to directly showing an effect of dietary phosphate on intestinal lead absorption.

Animals↗
PubMed1984

Gastrointestinal absorption of lead in chicks: involvement of the cholecalciferol endocrine system.

The role of dietary calcium and phosphorus in modifying the intestinal absorption of lead and also the effect of lead ingestion on the metabolism of cholecalciferol were studied in chicks. The efficiency of absorption of 203Pb and 47Ca was increased when the animals were fed a low calcium diet and treated with cholecalciferol. The synthesis of the vitamin D-induced calcium-binding protein (CaBP) was correspondingly increased. When the chicks were depleted of vitamin D and repleted with 1,25-dihydroxycholecalciferol [1,25(OH)2D3] as their only source of the vitamin, the absorption of both 47Ca and 203Pb was unaffected by dietary calcium levels, and no change in CaBP levels occurred. Low dietary intake of phosphorus resulted in an increase in 47Ca and 203Pb absorption and in CaBP synthesis when the animals were treated with cholecalciferol. However, when the birds were repleted with 1,25(OH)2D3, the intestinal absorption of 47Ca and of 203Pb was increased, as well as the intestinal CaBP levels. Intracardial injection of increasing doses of 1,25(OH)2D3 to rachitic chicks resulted in a concomitant increase in 203Pb absorption in a manner that correlated with the degree of synthesis of CaBP. Ingestion of lead by the chicks was found to impair growth and renal production of 1,25(OH)2D3, resulting in lowered circulating and intestinal content of the hydroxylated metabolites of cholecalciferol.

Animals↗
PubMed1984

Early and direct effect of 1,25-dihydroxycholecalciferol on calcium uptake by duodena of rachitic chicks.

Injection of 1,25 dihydroxycholecalciferol (1,25(OH)2D3, 10 micrograms) directly into the in situ ligated duodenal loop of rachitic chicks significantly elevated the tissue accumulation of 47Ca within 20-30 min. The transfer of 47Ca from lumen to blood, during the same time period, was not increased nor was there any measurable intestinal calcium-binding protein synthesized. Lesser amounts of 1,25(OH)2D3 (1 or 5 micrograms) did not result in any statistically significant elevation of 47Ca tissue accumulation, nor did they have any effect on 47Ca transfer from lumen to blood (transmural). Ten micrograms of 1,24R,25(OH)3D3 was similarly effective in elevating tissue accumulation, whereas 24R,25(OH)2D3 and 25(OH)D3 were not. These results provide additional evidence for an early and direct action of 1,25(OH)2D3 in altering intestinal epithelial membrane transport prior to the induction of synthesis of specific transport proteins.

24,25-Dihydroxyvitamin D 3↗
PubMed1983

Proton-NMR studies of the solution conformations of vitamin-D-induced bovine intestinal calcium-binding protein.

1H NMR is used to study the solution structure of vitamin-D-induced bovine intestinal calcium-binding protein. The study of the native protein is aided by the recently published crystal structure; it is shown that the conformations of the molecule in the crystal and in solution are very similar. The effect of pH and temperature on the native structure is described. The structure of the apo protein is then described, and the effect of pH and temperature on its fold is outlined. A comparison between apo and native protein folds is made which indicates that the folds are very similar. The two folds are related by a calcium titration, which indicates that the protein binds two calcium ions sequentially. Both steps in the Ca2+ titration occur under conditions of slow exchange (kex 80 s-1). The effect of binding Ca2+ ions is to cause twisting motions of helices, with the helices acting as rods, relaying the conformational change induced by Ca2+ binding to the linker regions of the protein.

Animals↗