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PubMed1986

Anticoagulantly active heparin-like molecules from cultured fibroblasts.

Heparin-like molecules, isolated from cultured rat and human skin fibroblasts, accelerated the inactivation of purified human thrombin via purified human antithrombin. Only 15% of the biologic activity of the complex carbohydrates derived from human skin fibroblasts was expressed when the heparin-binding domain an antithrombin was chemically modified at the Trp 49 residue. Human skin fibroblasts were metabolically labeled with [35S]Na2SO4, and radiolabeled heparin-like molecules were isolated utilizing ion-exchange chromatography and fractionated into two separate populations employing immobilized antithrombin. The species which bound with high avidity to the affinity matrix represented about 12% of the radiolabeled heparin-like molecules, accounted for almost 95% of the initial anticoagulant activity, and exhibited a specific activity of 3.98 USP units/10(6) 35S-cpm.

Antithrombins↗

PubMed1994

Localization of bicarbonate transport along the crypt-villus axis in rabbit ileum.

BACKGROUND/AIMS: HCO3- can be absorbed as well as secreted in the rabbit ileum. With 25 mmol/L HCO3- on the serosal side only, a serosa-to-mucosa flux (Jsm) is found; with 25 mmol/L on the mucosal side only, epinephrine elicits a mucosa-to-serosa flux (Jms). This study aimed to localize these two processes along the crypt-villus axis. METHODS: Excised ileal segments were exposed luminally to 2 mol/L Na2SO4 (hypertonic treatment) or to isotonic Ringer's solution for 15 minutes. Mucosa was then chamber-mounted, and measurements were made of Jsm or Jms and of short-circuit current (Isc) responses to glucose plus alanine and to either theophylline or epinephrine. RESULTS: With HCO3-/CO2 added to the serosal side only, hypertonically treated tissues showed a 22% decline in Jsm; a 25% decline in Isc response to theophylline; and a 71% decline in Isc response to glucose plus alanine compared with control. With HCO3-/CO2 added to the mucosal side only, tissues showed 92% and 87% declines in Jms and Isc responses to epinephrine, respectively, and a 87% decline in Isc response to glucose plus alanine. Histological examination showed destruction of villus caused by hypertonic treatment but sparing of crypt cells. CONCLUSIONS: Both HCO3- and Cl- are secreted mainly by crypt cells and absorbed mainly by villus cells.

Animals↗

PubMed1988

Electrophysiology of newt skin: effects of prolactin.

Integumental transepithelial potential (TEP) was measured by both in vivo and in vitro (Ussing chamber) techniques in the same adult terrestrial-phase California newts (Taricha torosa). In both types of preparation, TEP showed a logarithmic relation to external sodium (as Na2SO4) concentrations between 0.1 and 10 meq/liter, with in vivo values exceeding in vitro values at all points. KM was ca. 1 and 5 meq/liter for the in vivo and in vitro preparations, respectively. When terrestrial-phase newts were treated with prolactin (PRL; 50 mIU/g/day), in vivo TEP declined significantly within 3 days. In vivo TEP versus [Na+]ext curves of recently collected aquatic-phase newts were found to be not significantly different from those of PRL-treated terrestrial-phase animals. Current/voltage (I/V) plots likewise showed that skin from aquatic-phase and PRL-treated terrestrial-phase newts was electrophysiologically alike. Estimates and calculations based on the I/V relationship suggest that PRL acts primarily to increase the epithelial electrical resistance in the transcellular pathway, with no effect on the electromotive force of the sodium pump.

Animals↗

PubMed1992

Role of sulfation in post-translational processing of gastric mucins.

1. Gastric mucosal segments were incubated in MEM supplemented with various sulfate concentrations in the presence of [3H]glucosamine, [3H]proline and [35S]Na2SO4, with and without chlorate, an inhibitor of 3'-phosphoadenosine-5'-phosphosulfate formation. 2. Incorporation of glucosamine and sulfate depended upon the sulfate content of the medium and reached a maximum at 300 microM sulfate. Introduction of chlorate into the medium, while having no effect on protein synthesis as evidenced by proline incorporation, caused, at its optimal concentration of 2 mM, a 90% decrease in mucin sulfation and a 40% drop in glycosylation. 3. At low sulfate content in the medium and in the presence of chlorate, the incorporation of sulfate and glucosamine was mainly into the low molecular-weight form of mucin. An increase in sulfate in the medium caused an increase in the high molecular-weight form of mucin and in the extent of sulfation in its carbohydrate chain. 4. The results suggest that the sulfation process is an early event taking place at the stage of mucin subunit assembly and that sulfate availability is essential for the formation of the high molecular-weight mucin polymer.

Animals↗

PubMed1992

Thermodynamic characterization of cytochrome c at low pH. Observation of the molten globule state and of the cold denaturation process.

Several reports have pointed out the existence of intermediate states (both kinetic and equilibrium intermediate) between the native and the denatured states. The molten globule state, a compact intermediate state in which the secondary structure is formed but the tertiary structure fluctuates considerably, is currently being studied intensively because of its possible implication in the folding process of several proteins. We have examined the thermal stability of horse cytochrome c at low pH between 2.0 and 3.2 and different potassium chloride concentrations by absorbance of the Soret band, far and near-ultraviolet circular dichroism (u.v. c.d.) and tryptophan fluorescence using a multidimensional spectrophotometer. The concentration of potassium chloride ranged from 0 M to 0.5 M. The experimental thermal denaturation curves show that: (1) the helical content of cytochrome c remains stable at higher temperature when the concentration of salt is increased; whereas (2) the extent of ordering of the tertiary structure is weakly dependent on salt concentration; and (3) for cytochrome c, the stabilization of the molten globule state is induced by the binding of anions. Other salts such as NaCl, LiCl, potassium ferricyanide (K3Fe(CN)6) and Na2SO4 may also be used to stabilize the molten globule state. The thermodynamic analysis of the denaturation curves of c.d. at 222 nm and c.d. at 282 nm shows that, whereas a two-state (native and denatured) transition is observed at low-salt concentration, the far and near-u.v. c.d. melting curves of cytochrome c do not coincide with each other at high-salt concentration, and a minimum of three different thermodynamic states (IIb, intermediate or IIc, and denatured) is necessary to achieve a sufficient analysis. The intermediate state (called IIc) is attributed to the molten globule state because of its high secondary structure content and the absence of tertiary structure. Therefore, at low pH, cytochrome c is present in at least four states (native, IIb, IIc and denatured) depending on the salt concentration and temperature. The thermodynamic parameters, i.e. the Gibbs free energy differences (delta G), the enthalpy differences (delta H), the midpoint temperatures (Tm) of the transition (IIb in equilibrium intermediate (IIc in equilibrium denatured) are determined. We also give estimates of the heat capacity differences (delta Cp) from the temperature dependence of the enthalpy differences. The enthalpy change and the heat capacity difference of the IIc in equilibrium denatured transition are non-zero. The number of charges (protons or chloride anions) released upon transitions are determined by analysing the pH and chloride anion concentration dependence of the Gibbs free energy.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1983

Serum antibodies against cytosol antigens in multiple sclerosis.

Immunologically pure IgG was isolated from serum of multiple sclerosis (MS) patients and normal controls. The F(ab)2 moiety of IgG was then isolated by salting out between 12.5 and 19.0% Na2SO4 of the pepsin digest of IgG. The ability of the 131I-labelled F(ab)2 to bind to subcellular brain fractions (nuclei, synaptosomes, mitochondria, myelin, microsomes and cytosol) of MS and control brains was assayed and expressed as radioactivity/mg protein of respective fractions. No significant difference could be traced with regard to F(ab)2 binding to the particulate fractions from MS patients and normal controls. MS F(ab)2 did, however, bind about two times more to MS cytosol than to non-MS cytosol antigens and up to 50% more MS than the control F(ab)2 did bind to the MS cytosol. MS F(ab)2 and control F(ab)2 did bind equally to control cytosol. The immunoprecipitate of MS F(ab)2-MS-cytosol was isolated and used for immunization of rabbits. The antiserum formed could be demonstrated by means of crossed immunoelectrophoresis to contain antibodies to one to three MS antigens. Thus it must be concluded that MS serum contains antibodies to one to three MS antigens occurring in MS brain cytosol.

Antibody Specificity↗

PubMed1995

A seric low molecular weight factor modulates IGFs effects on chick cartilage metabolism.

The effects of recombinant human insulin-like growth factors (rhIGF-I and rhIGF-II) alone and in combination with a partially purified serum low molecular weight growth factor (LMW-GF) were studied by measuring proteoglycan (PG) and total protein synthesis by chick embryo cartilage. rhIGF-I alone did not increase the incorporation of L[3H]serine or [35S]Na2SO4 into whole cartilages. LMW-GF + rhIGF-I markedly increased the incorporation of these precursors. rhIGF-I alone stimulated D[3H]glucosamine uptake, and LMW-GF increased the effect of rhIGF-I. These results for whole cartilage were reproduced with glycosaminoglycans (GAG) extracted from cartilage. LMW-GF acted in synergy with rhIGF-I to stimulate PG core protein synthesis, xylosyl transferase activity and sulfation. Total protein synthesis, as measured by [35S]methionine uptake, was not altered by rhIGF-I. LMW-GF plus rhIGF-I increased the incorporation of this precursor into whole cartilage. The effect of rhIGF-II on PG synthesis was different from that of rhIGF-I. rhIGF-II alone stimulated GAG chain lengthening and sulfation. LMW-GF did not modify the effect of rhIGF-II on these steps. In contrast, rhIGF-II did not stimulate the synthesis of core protein. LMW-GF plus rhIGF-II increased the [3H]serine incorporation into the whole cartilage, but this combination did not stimulate the uptake of [3H]serine into extracted GAG. rhIGF-II plus LMW-GF were also without effect on xylosyl transferase activity. The combination of these factors increased the [35S]methionine incorporation into cartilage total proteins. These results suggest that rhIGF-II does not regulate the PG core protein synthesis, but in combination with LMW-GF, stimulates the synthesis of proteins other than proteoglycan core protein.

Animals↗

PubMed1980

Distal acidification defect induced by phosphate deprivation.

The effect of phosphate deprivation on urinary acidification was investigated in rats fed a phosphate-deficient diet and in control rats fed the same diet supplemented with phosphate. Phosphate-deprived animals developed hypophosphatemia, hypercalcemia, and hypophosphaturia, but failed to develop hyperchloremic metabolic acidosis following 30 or 60 days of phosphate deprivation. Baseline urine pH was significantly higher in phosphate-deprived rats than in controls, but baseline urine HCO3 excretion was not significantly different between the two groups. The pattern of HCO3 reabsorption in phosphate-deprived rats was identical to that of controls at both low and high plasma HCO3 levels. During chronic NH4Cl administration, both 30- and 60-day phosphate-deprived rats had a sigificantly higher minimal urine pH and lower titratable acid and net acid excretion than seen in controls. NH4 excretion was significantly lower than controls in the 60-day phosphate-deprived rats only. During Na2SO4 administration the minimal urine pH was significantly lower in controls than in phosphate-deprived rats, but there was overlap of urine pH values. At comparable levels of urine pH, NH4 excretion was significantly lower in phosphate-deprived rats than in controls. Phosphate-deprived rats were able to raise urine-blood CO2 pressure to the same levels as controls during both HCO3 loading and Tris buffer administration. Phosphate-deprived rats had greater extrarenal buffering capacity than controls as evidenced by a lower decline in blood pH and HCO3 during HCl infusion in phosphate-deprived rats. These data demonstrate that phosphate deprivation is associated with distal acidification defect, impaired NH3 excretion, and increased extrarenal buffering capacity. The increased availability of buffer in phosphate deprivation may play an important role in acid-base homeostasis in this condition.

Acid-Base Imbalance↗

PubMed1991

Taste reactivity in the hamster.

Taste reactivity, which was first described in the rat, consists of ingestive and aversive response components, the latter seen mostly to bitter-tasting stimuli. The present experiment characterized the hamster's taste reactivity to an array of stimuli (sugars: 1 M sucrose, d-fructose and d-glucose; sodium salts: 1 M NaCl, Na2SO4 and NaNO3; acids: 30 mM HCl, tartaric acid and citric acid; bitter-tasting stimuli: 100 mM quinine hydrochloride and nicotine sulfate and 10 mM denatonium benzoate). These 12 stimuli were chosen to represent 3 examples each of stimuli that taste sweet, salty, sour, or bitter to humans; they were presented in random order via an intraoral fistula, one stimulus each day per animal (n = 10). Infusions of 0.6 ml were delivered over a 1-min period from a syringe pump. Orofacial and somatic motor responses were recorded on videotape for later analysis and were also coded online into a computer. Ingestive responses included forward and lateral tongue protrusions and aversive responses included gaping, chin rubbing, forelimb flailing, fluid rejection, increased locomotion, and aversive posturing. Each stimulus group produced a characteristic pattern of these behaviors, with sugars eliciting only ingestive behaviors and the bitter stimuli evoking predominantly aversive responses. Both sodium salts and acids produced ingestive responses, as seen previously in the rat, although these stimuli also elicited aversive behaviors in the hamster, including apes. The patterns of responses were characterized using multivariate procedures; the stimuli fell into distinct groups that were separated primarily along an hedonic dimension.

Animals↗

PubMed1991

Antiport mediated rounding and endocytosis are enhanced by sulphate.

Rapid cell detachment concomitant with the flat-to-round (FTR) change that is mediated by an upshifted Na+/H+ antiporter via HCO3(-)-dependent H+ pumping, is significantly enhanced by the addition of Na2SO4 (FTR + SO4): (1) a faster and greater reduction in cell surface area and perimeter, and (2) a higher level of macromolecular internalization which is also amiloride sensitive. At a fixed 1 mg/ml extracellular FITC-dextran (FDx) concentration, the intracellular FDx load is similar irrespective of the particle size, in the range from 4400 to 2 million mol.wt which is a 455-fold diversity. This is inconsistent with entry via limited sized portals which would discriminate against the larger molecular weight species, such as the 2 million mol.wt species that measures up to 5 microns in width. Two million mol.wt FDx loads linearly in direct proportion to the extracellular FDx concentration, simulating simple diffusion. Large-channel endocytosis is considered to be a characteristic of specialized cell types such as phagocytes and macrophages. However, the antiporter mediated endocytosis (AME) shown here is demonstrated in two different cell types which are not known for their endocytic prowess, viz. epitheloid human Chang liver cells (ATCC CCL 13) and human lung fibroblasts (ATCC CCL 202). The rounded cells with internalized FDx start reverting back to their flat and protracted form upon flooding with warm growth medium, a round-to-flat (RTF) change. However the cell surface reversion is not associated with efflux of FDx which are sorted out into 'granular patches', the later stage endosomes without membrane outlines in AME. FDx-loaded cells grow as well as trypsinized cells without FDx loaing and they maintain a significant FDx load even after nearly 4 cell divisions. Toad sperms internalized into Chang cells via antiporter activation are also sorted into granular patches. AME provides (a) distinctive access to large particles, simulating small ion influx, and (b) an alternate membrane recycling capability where granular patches are instrumental in sorting. It appears to be not a simple endocytosis-exocytosis pathway.

Amiloride↗

PubMed1994

A method for the determination of environmental contaminants in living marine mammals using microscale samples of blubber and blood.

As part of a study examining the possible effects of organochlorine compounds on juvenile northern elephant seals (Mirounga angustirostris), blubber and blood samples were taken from animals present on the Año Nuevo (California) rookery, and from animals admitted for rehabilitation at The Marine Mammal Center (Sausalito CA). Blubber samples were collected from immobilized seals. A pre-cleaned 6 mm K-medic biopsy punch was used to extract the blubber from a 1 cm incision near the hip, near the dorsal mid point. Blood samples were taken from the extradural vein; two mL of serum was analyzed for organochlorine compounds. Blubber samples (approximately 0.1g) were ground with Na2SO4 and extracted with 20 mL hexane:methylene chloride (1:1). Sera samples were extracted using commercially available disposable C18 columns. The extracts were separated on a micro-Florisil column, and analyzed by HRGC-ECD. Lipid determination in the serum was obtained by colorimetric analysis with 20 microliters samples. Results from the analysis of replicates and standard reference materials showed good recoveries, precision, and accuracy for both the blubber and blood methods.

Adipose Tissue↗

PubMed1993

Differential scanning calorimetric studies of the effects of ions and pH on ribulose 1,5-bisphosphate carboxylase/oxygenase.

Lucerne rubisco (ribulose 1,5 bisphosphate carboxylase/oxygenase, EC 4.1.1.39) was purified by ammonium sulfate fractionation and gel chromatography. Differential scanning calorimetry (d.s.c.) was used to study the effects of pH in the range 3.5 to 11.4, and the effects, at pH 7.5, of various salts at ionic strength lower than 0.3 (NaH2PO4, (NH4)2SO4, Na2SO4, NaCl, MgCl2, CaCl2) on the thermal denaturation of the protein. Van't Hoff and calorimetric enthalpies, and the change in heat capacity between the native and denatured states were calculated from the experimental data. The effects of salts on the thermal denaturation seem to follow the Hofmeister series. In some cases, the thermal denaturation may be interpreted as a two-step transition of the polypeptide chains. Moreover, comparison of the results with literature data suggests that the thermal denaturation parameters depend on the botanical origin of rubisco and are affected by the conditions of its purification.

Calorimetry, Differential Scanning↗

PubMed1995

Purification of duck immunoglobulins: an evaluation of protein A and protein G affinity chromatography.

Duck serum proteins binding to protein A Sepharose CL-4B and protein G Sepharose 4 Fast Flow and eluted at pH 2.8 or 11.5 were characterized by sodium dodecyl sulphate polyacrylamide gel electrophoresis, radial/immunodiffusion against defined anti-immunoglobulin (Ig) reagents, and by the reactivity in immunoelectrophoresis of antisera raised in rabbits inoculated with the eluates. The results indicated that IgY (previous nomenclature 7.8S IgG) and IgY (delta Fc) (previously 5.7S IgG) bound to protein A efficiently and to protein G weakly, while IgM bound to protein A and protein G weakly. Some binding of non-Ig proteins also occurred. Attempts to separate the non-Ig proteins from the Igs by elution at different pHs (5.0, 4.0, 3.0 and 2.5) were unsuccessful, but it was found that precipitation of Igs in day-old duck serum with Na2SO4, followed by chromatography on protein A Sepharose, yielded relatively pure IgY. The efficient binding of the duck IgYs to protein A resembles high affinity binding of mammalian Igs but cannot be attributed to the Fc, as it is in mammals, since the IgY (delta Fc) does not have an Fc region. Instead, binding probably occurs through unique histidine residues occurring predominantly in the CH1 domain.

Amino Acid Sequence↗

PubMed1984

Salting effects in cinnamoyl-chymotrypsin deacylation.

The influence of inorganic salts on the trans-cinnamoyl-chymotrypsin deacylation kinetics at 25 degrees C and various pH values has been studied: KCl (pH 6.0-13.4), CsCl (pH 9.8 and 13.1), NaCl and Na2SO4 (pH 9.8). Each salt was found to accelerate the reaction with different effectiveness which depended upon pH. The data show that the acyl-enzyme occurs in two forms, which are seen kinetically by different salting effects in deacylation; the equilibrium between the forms is controlled by an ionizing group in the enzyme with pKa about 12.

Acylation↗

PubMed1987

Acid-assisted anion interaction with deoxyhemerythrin.

The interaction of N3-, CNO- and F- with deoxyhemerythrin was monitored from pH 6 to 9 and 3 degrees C to 25 degrees C at an ionic strength 0.5 M (Na2SO4) by using competition with O2. A proton is involved in forming the adduct and is not lost from the protein even at pH values as high as 9. Thermodynamic and kinetic parameters for the interaction of each anion are obtained. It is considered that the proton is introduced as the acid HX and the corresponding parameters for the reaction of HX with deoxyhemerythrin are calculated. These are compared with those for the O2 reaction with deoxyhemerythrin. The adducts are remarkably inert and have dissociation half-lives ranging from 7 s (N3-) to 70 s (CNO- and F-) at 25 degrees C. This stability is ascribed to protonation of a bridged hydroxy group or even bridge-breakage.

Acids↗

PubMed1989

Structure-function relationships in the inorganic salt-induced precipitation of alpha-chymotrypsin.

alpha-Chymotrypsin (alpha CT) was used as a model protein to study the effects of salt-induced precipitation on protein conformation. Process parameters investigated included the type and amount of salt used to induce precipitation. The salts studied included Na2SO4, NaCl, NaBr, KBr and KSCN. Precipitate secondary structure content was examined via laser Raman spectroscopy. Conventional and saturation transfer electron paramagnetic resonance spectroscopy were employed to probe the tertiary structure of the active site in spin-labelled alpha CT precipitates. As the molal surface tension increment of the inducing salt increased, the beta-sheet content increased and the alpha-helix content decreased. There was no significant variation in secondary structure with the amount of salt used. The fraction of precipitate that recovered activity on redissolution was correlated with the change in secondary structure content. Spin-labelled precipitate spectra indicated that the active site remains unaltered during precipitation. Molecular modelling was employed to investigate how physical property of alpha CT were affected by these types of conformational change. Estimated physical property changes could not account entirely for observed deviations from current equilibrium theory for salt-induced precipitation. The spectroscopic observations were also combined with activity/solubility results to propose a mechanism for the salt-induced precipitation of globular proteins.

Animals↗

PubMed1991

Secondary structure perturbations in salt-induced protein precipitates.

The secondary structure implications of precipitation induced by a chaotropic salt, KSCN, and a structure stabilizing salt, Na2SO4, were studied for twelve different proteins. alpha-helix and beta-sheet content of precipitate and native structures were estimated from the analysis of amide I band Raman spectra. A statistical analysis of the estimated perturbations in the secondary structure contents indicated that the most significant event is the formation of beta-sheet structures with a concomitant loss of alpha-helix on precipitation with KSCN. The conformational changes for each protein were also analyzed with respect to elements of primary, secondary and tertiary structure existing in the native protein; primary structure was quantified by the fractions of hydrophobic and charged amino acids, secondary structure by x-ray estimates of alpha-helix and beta-sheet contents of native proteins and tertiary structure by the dipole moment and solvent-accessible surface area. For the KSCN precipitates, factors affecting beta-sheet content included the fraction of charged amino acids in the primary sequence and the surface area. Changes in alpha-helix content were influenced by the initial helical content and the dipole moment. The enhanced beta-sheet contents of precipitates observed in this work parallel protein structural changes occurring in other aggregative phenomena.

Chemical Precipitation↗

PubMed1993

Glutamate dehydrogenase from the thermoacidophilic archaebacterium Sulfolobus solfataricus: studies on thermal and guanidine-dependent inactivation.

The hexameric NAD(P)-dependent glutamate dehydrogenase isolated from the thermoacidophilic archaebacterium Sulfolobus solfataricus shows a remarkable thermal stability which is strictly dependent on protein concentration (half-life at 95 degrees C is 0.25 h and 0.5 h at 0.4 and 0.8 mg/ml, respectively). Temperature-dependent inactivation of the enzyme is apparently irreversible; this process is accompanied by a progressive increase in hydrophobic surface area which leads to protein precipitation. 3 M GdnHCl increases the half-life of the enzyme at 90 degrees C and 0.2 mg/ml 6-fold. The hexamer is the only soluble molecular species revealed by glutaraldehyde fixation after thermal inactivation. Lyotropic salts strongly affect the enzyme thermal stability: the half-life at 90 degrees C and 0.2 mg/ml protein concentration increases more than 6-fold in the presence of 0.4 M Na2SO4 and decreases 4-fold in the presence of 0.4 M NaSCN. The maximum protein thermal stability is observed around the isoelectric pH, between pH 5.2 and pH 6.8. Guanidine-dependent inactivation of the enzyme at 20 degrees C is irreversible above 1.5 M GdnHCl. The decline in percentage of reactivation closely parallels the structural changes detected by fluorescence and the loss of hexameric structure accompanied by the dissociation to monomers, as indicated by glutaraldehyde fixation.

Enzyme Activation↗