Features of 4-aminopyridine sensitive outward current observed in single smooth muscle cells from the rabbit pulmonary artery

The 4-aminopyridine (4AP) sensitive outward current of enzymatically dispersed single smooth muscle cells of the rabbit main pulmonary artery were investigated using the voltage clamp method. When the cell was exposed to physiological salt solution (PSS) in the bath and high K+ in the pipette no inward current was generated by depolarization of the membrane, but when 4AP was present in the bath or when Cs+ with tetraethylammonium+ (Cs+-TEA+) in the pipette, an inward current was generated. This current was enhanced by Ba2+ or high Ca2+ and was blocked by inorganic or organic Ca2+ channel blockers. The outward current was partly inhibited by the Ca2+ channel blockers, Ca2+-free or Mn2+ containing solution. The residual outward current was blocked by external application of 10 mM 4AP, whereas it was inhibited by half with 100 mM TEA+. To investigate further natures of 4AP sensitive outward current, the following experiments were done in the bath solution containing 2.5 mM Mn2+. The reversal potential of this outward current, estimated from the tail current, remained the same in Na+-deficient solution, but shifted to near the K+-equilibrium potential in Cl- deficient solution. Thus, the main current carrier for the outward current seems to be K+, but Cl- may participate to some extent. The amplitude of the outward current decreased slowly. However, the reversal potential was not changed, suggesting the reduction in amplitude of the outward current was not due to the accumulation of K+ on the outer surface of the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytochemical localization of Mn2+-dependent pyrimidine 5'-nucleotidase activity in isolated rod outer segments

A cytochemical method was developed for localization in isolated rod outer segments of manganese-dependent pyrimidine 5'-nucleotidase (MDPNase), an enzyme activity with possible relevance to shedding that we recently reported in photoreceptors and retinal pigment epithelial (RPE) cells in the intact rat retina. The purpose of this study was to eliminate the possibility that the previously observed cytochemical staining of the rods was due to diffusion of reaction product from the RPE cell lysosomes, which were also heavily stained. Rod outer segments (ROS) were isolated on continuous sucrose gradients from retinal homogenates prepared from rats raised in cyclic light (12 hr light:12 hr dark) and killed during the first 2 hr after light onset. ROS-containing bands were removed from the gradients and the isolated rods were fixed in 0.25% glutaraldehyde and pelleted. Chopped sections of the pellets were incubated in cytochemical medium for MDPNase activity and processed for light- and electron-microscopic localization of the enzyme activity. Two patterns of cytochemical staining were seen in ROS isolated from retinas obtained at this time of day. A few of the pellets contained clusters of ROS that were heavily coated along their surfaces and seemingly interconnected by thick strands of highly reactive extracellular material that displayed a punctate pattern of cytochemical staining. This material may have originated from the apical processes of the RPE cells, which were heavily stained in tissue fixed in situ around the time of light onset. The second staining pattern, visible only by electron microscopy, was more commonly observed. In the majority of the isolated ROS profiles, discrete streaks of cytochemical reaction product were seen in association with the internal aspects of the discs, at sites that seemed to correspond to the rims, and to narrow zones within the disc interiors. This distribution of reactive sites closely resembled that observed over most of the length of the ROS in the intact retina fixed at the same time of day. Occasionally, ROS profiles were encountered in which additional reactive sites were localized to the interdisc spaces between the plasma membrane and the rims of the discs. The latter pattern resembled the distribution of reaction product seen during this period over the tips of the ROS fixed in situ. As in the intact retinas, the cytochemical staining of the isolated ROS was inhibited by fluoride ions and strongly stimulated by manganese ions.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification and characterization of major ionic currents in isolated smooth muscle cells using the voltage-clamp technique

Voltage-clamp experiments were carried out on freshly dissociated single vertebrate smooth muscle cells from the stomach muscularis of Bufo marinus. Conventional two-microelectrode methodology was used, thus avoiding rapid dialysis of the cytosol. Four major phases of current were identified upon voltage jumps from negative holding levels to more positive levels. The first phase of current was an initial, inward current. This current was blocked by external Mn2+ and was of the correct magnitude to account for the rising phase of the Ca2+-dependent, TTX-independent action potentials found in these cells. Following this initial, inward Ca2+ current, a large outward current was observed which reached its peak over a period of hundreds of milliseconds and then decayed over a period of seconds to a steady-state level. The peak outward current and the steady-state outward current constitute the second and third major currents. The peak outward current was the largest current observed, with a magnitude as large as tens of nanoamps whereas the inward current was at most about one nanoamp. The peak outward current was reduced more than tenfold in the presence of external TEA. It was also decreased or abolished when the preceding inward current was diminished or eliminated by using external Mn2+ or less negative holding potentials. In this way the peak outward current was identified as a Ca2+-activated K+ current whose slow decay was hypothesized to result from removal of internal Ca ions by cellular mechanisms following the initial rise in [Ca2+]i resulting from the inward current. A fourth major current was an early transient outward current observed most clearly upon voltage jumps to more positive potentials when the inward current was eliminated by using less negative holding potentials or external Mn2+. A classical steady-state inactivation relationship as a function of membrane potential was constructed for the inward current. A substantial portion of this inactivation curve lies at potentials negative to the apparent threshold for activation of inward current, suggesting a true voltage-dependent inactivation. Although additional Ca2+-dependent inactivation could not be ruled out, neither could evidence for it be found.

Redistribution of Mn++-dependent pyrimidine 5'-nucleotidase (MDPNase) activity during shedding and phagocytosis

Ultrastructural cytochemistry was used to localize a previously undescribed retinal enzyme activity, ie, "manganese-dependent pyrimidine 5'-nucleotidase" (MDPNase) activity in retinas from rats raised in cyclic light and killed at various times in the lighting cycle. In retinas fixed during the last 3 hr of darkness, at the beginning of the shedding period, heavy cytochemical staining was observed over the extracellular surfaces of the apical processes of the retinal pigment epithelium (RPE) cells. The adjacent distal ends of the rod outer segments (ROS), ensheathed by the apical processes, were also stained along their surfaces. During the first 3 hr after light onset, at the time of maximal shedding and phagocytic activity, the tips of the ROS and ROS phagosomes were heavily labeled with reaction product distributed throughout the interdisc spaces. The RPE apical processes, previously heavily stained, were at this time weakly reactive relative to the ROS tips and phagosomes. After the shedding peak (4-8 hr after light onset), the tips of the ROS were no longer labeled with reaction product, and the apical processes were unreactive. The proximal portions of the ROS were weakly stained throughout the lighting cycle. The observed patterns of redistribution of MDPNase activity before, during, and after the shedding peak suggest that the presence of the enzyme in the ROS tips may be correlated with shedding. Changes in the staining of the RPE apical processes in relation to cyclic light further suggest that this enzyme may be transferred from the apical processes to the ROS tips prior to shedding.

Magnesium and manganese ions modulate Ca2+ uptake and its energetic coupling in sarcoplasmic reticulum

ATP hydrolysis, either coupled or uncoupled from Ca2+ uptake by sarcoplasmic reticulum (SR), is essentially independent of Mg2+ (millimolar range) up to 50 mM. Conversely, a sharp enhancement of Ca2+ uptake by Mg2+ is observed with a consequent increase of pumping efficiency (Ca2+ per ATP). Therefore, Mg2+ modulates pumping efficiency through the molecular mechanism of the pump itself. Manganese ions also stimulate Ca2+ uptake with an apparent efficiency lower than that of Mg2+. Additionally, Mn2+ competes with Ca2+ for the pump system and is accumulated into SR vesicles. Although the affinity of the pump is about three orders of magnitude higher for Ca2+ than for Mn2+, the capacity of the vesicles for Mn2+ is about three times that commonly observed for Ca2+. It is concluded that Mg2+ (millimolar range) couples ATP hydrolysis to Ca2+ uptake and that active transport of cations (Ca2+ and Mn2+) can proceed without a compensatory countertransport of a divalent cation. Finally, it is suggested that the SR pump operates physically as general cation translocator instead of as a Ca2+-specific pump, as commonly assumed.

Activation of liver cytosol phosphoenolpyruvate carboxykinase by Ca2+ through intracellular redistribution of Mn2+

Calcium has no known direct effect on phosphoenolpyruvate carboxykinase from rat liver cytosol. However, addition of calcium salts to liver postnuclear supernatant led to an increase in assayable enzyme activity in cytosols. This indicates that mitochondria and microsomes present in postnuclear supernatant can participate in observed enzyme activation. The stimulation of phosphoenolpyruvate carboxykinase was prevented by the manganese complexion 1-(2-pyridylazo)-2-naphthol, was not additive with activation by MnCl2 and was inhibited by La3+, Sr2+ and ruthenium red. These data indicate that manganese and mitochondrial or microsomal calcium carriers participate in the mechanism of indirect calcium effect. Measuring of manganese content in cytosols directly, by atomic absorption spectrometry, has provided evidence that there is a pool of manganese associated with mitochondrial and microsomal fraction of rat liver that can be mobilized to the cytosol by calcium ions. The direct addition of this pool of manganese to the cytosol caused the stimulation of phosphoenolpyruvate carboxykinase activity to the same levels as did calcium ions in the postnuclear supernatant. It is postulated that calcium can effect enzyme activity indirectly by releasing manganese from specific cellular compartments into the cytosol.

Physiology and metabolism of essential trace elements: an outline

Man depends on at least nine trace elements--iron, zinc, copper, manganese, iodine, chromium, selenium, molybdenum and cobalt--for optimum metabolic function. These elements serve a variety of functions including catalytic, structural and regulatory activities in which they interact with macromolecules such as enzymes, pro-hormones, pre-secretory granules and biological membranes. These micronutrients are involved, therefore, in all major metabolic pathways at levels which are so fundamental that the features of deficiency of many of them are protean and non-specific. In considering the metabolism of the elements themselves, they fall into two groups: those which exist normally as cations and those present as anions. The latter group are absorbed relatively easily and whole-body homeostasis is mediated mainly by renal excretion. The cations need specific pathways for absorption and their homeostasis is effected by gastrointestinal and biliary secretion. Some elements are absorbed more efficiently as organic complexes. The net achievement of the metabolic pathways for each element is to deliver it to its functional site(s) by exploiting its physicochemical characteristics to avoid interactions with other inorganic nutrients.

Cation-dependent gonadotropin releasing hormone activation of guanylate cyclase

Gonadotropin releasing hormone enhanced guanylate cyclase [E.C.4.6.1.2] two- to threefold in pituitary, testis, liver and kidney. Dose response relationships revealed that at a concentration of 1 nanomolar, gonadotropin releasing hormone caused a maximal augmentation of guanylate cyclase activity and that increasing its concentration to the millimolar range caused no further enhancement of this enzyme. There was an absolute cation requirement for gonadotropin releasing hormone's enhancement of guanylate cyclase activity as there was no increase without any cation present. Gonadotropin releasing hormone could increase guanylate cyclase activity with either calcium or manganese in the incubation medium but more augmentation was observed with manganese. The data in this investigation suggest that guanylate cyclase may play a role in the mechanism of action of gonadotropin releasing hormone.

Manganese action on protein synthesis in diabetic rat pancreas: evidence for a possible physiological role

The actions of manganese on [3H]phenylalanine incorporation into pancreatic acinar protein from streptozotocin-diabetic rats were compared with the actions of several divalent cations, insulin, and pancreatic secretagogues. In the presence of Ca2+, 7 X 10(-4) M manganese greatly enhanced [3H]phenylalanine incorporation. Under similar incubation conditions, magnesium exerted only a slight stimulatory effect on incorporation, whereas cobalt and nickel failed to enhance incorporation. Removal of Ca2+ from incubation medium, or replacement of Ca2+ by either barium or strontium, abolished the stimulatory effect of manganese on incorporation. Lanthanum, at a concentration that inhibits stimulated Ca2+ influx in acini (10(-4) M), also blocked the stimulatory effect of manganese but did not alter the actions of insulin on incorporation. Dibutyryl cyclic GMP, a competitive antagonist of cholecystokinin-octapeptide, and atropine, a competitive antagonist of carbachol, blocked the stimulatory effects of the respective secretagogues on incorporation. Neither antagonist altered the actions of manganese. These findings suggest that in the face of insulin deficiency manganese enhances pancreatic protein synthesis in diabetic rats via a Ca2+-dependent mechanism that is distinct from the actions of other divalent cations, insulin and pancreatic secretagogues.

Regulation of PTH receptor-adenylate cyclase system of canine kidney: influence of Mn2+ on effects of Ca2+, PTH, and GTP

Metal ions play important roles in the regulation of the activation of adenylate cyclase. Previous studies have suggested that an important site of action of metal ions is at or closely related to the nucleotide regulatory protein. The present studies examine the nature of the regulation of enzyme activity by divalent cations and the influence of Mn2+ on hormone binding and stimulation of adenylate cyclase. Studies were performed in canine renal cortical membranes. Substitution of Mg2+ by Mn2+ was associated with a progressive decline in the ability of GTP or PTH to stimulate adenylate cyclase activity. Mn2+ did not alter specific binding of an iodinated PTH analogue. However, in spite of the loss of guanine nucleotide stimulation of enzyme activity, the effects of guanine nucleotide on PTH binding were not altered in the presence of Mn2+. Substitution of Mg2+ by Mn2+ abolished the inhibitory effect of Ca2+ on basal adenylate cyclase activity. Similarly, the effects of GTP or PTH to enhance the inhibitory effects of Ca2+ on enzyme activity were abolished in the presence of Mn2+. Since Mg2+ and Ca2+ compete for a common allosteric site and Mn2+ abolished the effects of these cations, it would appear that Mn2+ also competes for the binding site of Mg2+ and Ca2+. The present studies demonstrating that Mn2+ does not affect hormone binding or the actions of guanine nucleotides on hormone binding yet totally eliminates the effect of GTP on enzyme activity indicate that the effect of Mn2+ occurs at the level of the interactions of the nucleotide regulatory component with the catalytic unit. In addition, these data suggest that there are two functionally distinct sites of guanine nucleotides with different ionic requirements.

Extracellular divalent cations in excitation--contraction coupling: hypertonic solution effects

It is the purpose of this article to point out that the membrane-bound Ca plays an important role in excitation–contraction (E–C) coupling of skeletal muscle fibers and that other divalent cations are unable to substitute for this role of membrane-bound Ca.

Risks and benefits of nutritional supplements during pregnancy

This review emphasizes the role of minerals and vitamins in pregnancy. Of the trace elements, iron, copper, zinc, and iodine have a fundamental role in human nutrition. Supplementation of iron, zinc, and iodine in the diet of all pregnant women, when dietary deficiencies exist, seems justified. The average diet in developed countries contains sufficient amounts of various vitamins, with the exception of folic acid, which may require supplementation. However, in developing nations and among poor populations in which the diet is inadequate, additional supplies of micronutrients are advisable.

The influence of divalent cations and substrate concentration on the incorporation of myo-inositol into phospholipids of isolated bovine oligodendrocytes

The incorporation of myo-inositol into phosphatidylinositol by two routes (CTP-independent and CTP-independent) has been investigated in homogenates prepared from isolated bovine oligodendrocyte perikarya. The CTP-dependent route has the higher maximum velocity of inositol incorporation and can utilise either Mn2+ or Mg2+ as a divalent ion cofactor. This route of inositol incorporation is also strongly inhibited by Ca2+ ions at concentrations less than 1 mM. The primary site of the inhibitory action appears to be the enzyme CDP-diglyceride inositol phosphatidyl transferase (EC 2.7.8.11) though synthesis of CDP-diacylglycerol is also inhibited by endogenous Ca2+ present in the oligodendrocyte homogenate. In contrast, CTP-independent inositol incorporation into phosphatidylinositol is only stimulated by Mn2+ (Zn2+,Cu2+, Mg2+, Ca2+ and Co2+ are ineffective) and is not inhibited by Ca2+, at least up to a concentration of 1 mM.

Effects of divalent metals on the specificity of inhibitors of the cyclic nucleotide phosphodiesterases from bovine heart

Divalent metals used to support phosphodiesterase (EC 3.1.4.-) activity have been found to influence the substrate and enzyme specificity of many phosphodiesterase inhibitors in studies of the hydrolysis of cyclic AMP and cyclic GMP by the calmodulin-dependent and cyclic AMP-specific phosphodiesterases from bovine heart. Many compounds displayed marked differences in substrate specificity and inhibitory potency in the presence of Mg2+, as compared with Mn2+, when studied with the unactivated form of calmodulin-dependent phosphodiesterase, while few compounds displayed differences in the presence of calmodulin. With a single divalent metal, marked differences in inhibitory potency and substrate specificity were also observed in the absence or presence of calmodulin suggesting that alterations in calmodulin and/or Ca2+ levels may greatly affect the response to phosphodiesterase inhibitors. Divalent metals did not alter the effects of inhibitors on the hydrolysis of cyclic AMP by the cyclic AMP-specific phosphodiesterase, however divalent metals would probably indirectly influence the relative cellular level of cyclic AMP hydrolyzed by this enzyme, and therefore the effects of inhibitors, through metal effects on the calmodulin-dependent phosphodiesterase. No correlation was found between the inhibitory activity of the compounds, many of which were cyclic nucleotide analogs, and their ability to activate cyclic AMP-dependent or cyclic GMP-dependent protein kinases or to affect cyclic AMP-dependent protein kinase activity by displacing bound cyclic AMP.

Zinc, copper, and manganese in immune function and experimental oncogenesis

Dietary deficiency of trace metals among human populations, once thought to be exceedingly rare, has recently gained attention as a potential public health problem. The consumption of highly refined and heavily processed foods reduces the trace element content of the diet. The higher trace element requirements of pregnancy, lactation, growth, development, and chronic disease may further contribute to states of marginal trace metal nutriture. Experimental animal studies have demonstrated that even marginal trace element deprivation during critical periods of growth and development or, alternately, during prolonged deficiency in adults can significantly alter immunologic function. Furthermore, trace metal nutriture has been shown to affect initiation and progression of a large variety of neoplasia. Studies of the interaction of trace metal nutriture and cancer have, however, suffered from many methodological inconsistencies as well as failures to define and quantitate the trace element content of diets and the host alterations in response to neoplastic challenge. Similarly, there has been little information in the critical area of marginal and moderate trace metal deficiency, i.e., those experimentaL situations most analogous to deficiencies that may occur in human populations. In this review, an attempt is made first to place in perspective experimental data relevant to these issues, and second to emphasize the desirability of further investigation in this critical area of human nutrition.

Comparison of Ca2+, Sr2+, and Mn2+ fluxes in mitochondria of the perfused rat heart

The amount of readily exchangeable Ca2+ in mitochondria of an isolated working rat heart is less than 10 ng-ions/g heart. We therefore conclude that either no Ca2+ enters mitochondria or that the Ca+ which does enter is removed continuously. Using Sr2+ and Mn2+, we obtained evidence that the mitochondrial Na+-Ca2+ exchanger was indeed operational in releasing metal from mitochondria of the heart. When Ca2+ in the perfusate was replaced by Sr2+, we found that a significant amount of Sr2+ (approximately 100 ng-ions/g heart) entered mitochondria. When the heart then was returned to a Ca2+-containing perfusate, over 80% of the Sr2+ was washed out of mitochondria within 30 seconds. When low levels of Mn2+ were added to the perfusate, we found that Mn2+ accumulated in mitochondria irreversibly. This is evidence for the operation of the Na+-Ca2+ exchanger because Na+ was found to release Ca2+ and Sr2+ but not Mn2+ from isolated rat heart mitochondria. Our estimates indicate that when the Na+-Ca2+ exchanger is maximally operative, as in the Sr2+-perfused heart, the flux of Sr2+ through mitochondria is at most 10% of the total flux needed for the activation of contraction. The low level of Ca2+ in the mitochondria of Ca2+-perfused hearts suggests a much smaller flux of Ca2+ through the mitochondria in this case. We therefore conclude that mitochondria play little if any role in the beat-to-beat regulation of normal Ca2+ fluxes in the rat heart.

Parameters of unbalanced growth and reversible inhibition of deoxyribnucleic acid synthesis in Brevibacterium ammoniagenes ATCC 6872 induced by depletion of Mn2+. Inhibitor studies on the reversibility of deoxyribonucleic acid synthesis

Unbalanced growth induced by depletion of manganese ions was a prerequisite for production of ribonucleotides in a high salt mineral medium with the wildtype strain Brevibacterium ammoniagenes ATCC 6872. The concentration of manganese strictly controlled the overall deoxyribonucleic acid (DNA) synthesis, whereas ribonucleic acid (RNA), protein and cell wall synthesis remained essentially unimpaired in the manganese-lacking cells. The reversibility of inhibition of overall DNA synthesis was shown by enhanced incorporation (up to threefold compared to the cultures supplied with sufficient manganese) of [8-14C] adenine into alkali-stable, trichloroacetic acid-insoluble material after subsequent addition of 10 microM MnCl2 to 15 h-old depleted cultures. The results of inhibitor studies on the restoration of overall DNA synthesis due to subsequent addition of manganese ions to depleted cultures suggest that ribonucleotide reduction is the primary target of the manganese starvation during nucleotide fermentation with Brevibacterium ammoniagenes ATCC 6872.

Degradation of prolylleucylglycinamide (MIF) by mouse brain

Prolylleucylglycinamide (MIF) at 1.0 mM concentration and pH 7.0 was hydrolyzed by mouse brain homogenate at a rate of 140 nmol/mg protein/hr. Nearly all of this activity can be accounted for by the action of two enzymes, both of which cleave Pro and Leu sequentially from the N-terminus of MIF. At pH 7.0 the predominant enzyme is arylamidase, inhibited by puromycin (1 mM) and Mn2+ (2.5 mM). At pH 8.5, in the presence of Mn2+, a second enzyme with a higher potential activity (570 nmol/mg protein/hr) was observed. While the arylamidase is primarily localized in the cytosol, the Mn2+-stimulated enzyme is equally divided between soluble and particulate fractions. Because of its ability to cleave leucinamide, its high pH optimum, and its Mn2+ dependence, it can be classified as a leucine aminopeptidase (LAP). In its substrate specifically and its preference for Mn2+ over Mg2+ it resembles the LAP from connective tissue more than that from other sources.

Ultrastructural changes in Escherichia coli grown in divalent cation-deficient medium

Escherichia coli strains B and K12 could grow in very limiting conditions of divalent cation deficiency. Growth curves showed a long lag period of about 30 h, followed by an exponential phase bringing the bacterial concentration to about 10(7) ml-1, with a 24 min doubling time, while the growth curves of control cultures were characterized by short lag periods, maximum populations of about 10(9) ml-1 and an 18 min doubling time. The DNA/protein ratio in bacteria grown in deficient medium was 0.48 compared with 0.21 for control bacteria. Significant differences were found in the ultrastructure of the two types of bacteria. Freeze-etched control cells showed the typical appearance with the protoplasmic fracture face of the cytoplasmic membrane (PFC) having a random distribution of intramembranous particles. Bacteria growing in deficient medium in exponential phase presented several particle-free areas on the PFC. At the beginning of the stationary phase, the particle-free zones became larger and crystalline structures were formed. These structural modifications, which increased with culture age, were never observed in bacteria grown in control medium. Optical diffraction analysis of the crystalline structures in freeze-etched cells revealed regular periodic arrays with a rhomboid repeating unit approximately 7.6 x 5.4 nm in dimension and an angle between the axes of about 73 degrees. Negative staining of isolated membranes of bacteria grown in deficient medium showed a more complex organization of the crystalline arrays, each unit being clearly composed of subunits.

Effect of verapamil on 45Ca uptake by synaptosomes

The effect of verapamil on K-stimulated 45Ca uptake (the difference between uptake in 60 mM-Ko medium and 5 mM-Ko medium) was studied using a synaptosomal fraction from rat brain. Verapamil inhibited K-stimulated 45Ca uptake, but not 45Ca uptake in 5 mM-Ko media (1 mM- and 0.1 mM-Cao media). The concentrations of verapamil inducing 50% inhibition of K-stimulated 45Ca uptake (ID50) in 1 mM- and 0.1 mM-Cao media were not significantly different, being about 10(-4) M and 2 X 10(-4) M, respectively. Like verapamil, Mn++ inhibited only K-stimulated 45Ca uptake, but its ID50 values in 1 mM- and 0.1 mM-Cao media were about 1.7 mM and 0.2 mM, respectively. It is considered from these findings that both verapamil and Mn++ specifically inhibit K-stimulated 45Ca uptake, but the modalities of their inhibitory effects on K-stimulated 45Ca uptake are different.

Wound healing: a review. III. Nutritional factors affecting wound healing

Wound healing proceeds more efficiently and quickly in well-nourished individuals who are in good general health at the time that they have to undergo surgery. Per contra, individuals who are malnourished and chronically ill heal less well and are in general at greater risk of complications during and after surgery. For the latter, elective surgery may be deferred until nutritional improvement is attained, but for emergency or urgent operations, institution of measures promoting good nutrition has to be concurrent with necessitous surgery and continued postoperatively. In this paper, the importance to wound healing of proteins, carbohydrates, fats, vitamins, and trace elements and minerals is reviewed.

The role of manganese in growth and sporulation of Bacillus subtilis

Phosphoglycerate phosphomutase of Bacillus subtilis, Bacillus cereus and Bacillus megaterium required Mn2+ as cofactor, whereas the wheat germ and rabbit liver enzymes did not. In the absence of Mn2+, B. subtilis did not sporulate in normal sporulation media but it did sporulate if the proper ratio of glucose or glycerol and malate was used. Decoyinine, an inhibitor of guanosine monophosphate synthesis, induced sporulation in the presence of excess glucose and malate to the same extent with and without Mn2+. Apparently, phosphoglycerate phosphomutase is the only strictly Mn2+-requiring enzyme needed for optimal sporulation in normal sporulation media.

Rationale for adding trace elements to total parenteral nutrient solutions--a brief review

The physiologic importance of trace element supplementation to total parenteral nutrition solutions is discussed. The trace elements discussed are copper, zinc, manganese and iodide.

Propagated spikes and secretion in a coelenterate glandular epithelium

The rete mirabile of Hippopodius (Cl. Hydrozoa, O. Siphonophora) is a sheet of giant endoderm cells penetrated by branches of the ventral radial canal. The cells appear to be highly polyploid. The rough ER is very richly developed and expanded ER cisternae containing amorphous material (presumably synthesized protein) are observed near the outer cell surface. The cells are electrically coupled, and are connected by gap junctions. The rete is electrically excitable and cell to cell conduction of action potentials at 10 cm/s is observed. The action potentials are all-or-none, positive-going events, showing amplitudes of about 70 mV and arising from a 44 mV resting potential. Slowly developing and decaying secondary depolarizations, capable of summing to the 20 mV level, are also observed. After passage of a train of impulses, the rete cells swell and secretion drops appear at the surface, these changes becoming apparent within a few seconds. In 15 mM Mn2+ the response fails to occur, and secondary depolarizations ("secretion potentials") are not seen. Spike propagation is not affected. In Na+-free solutions the spikes are reduced and propagation eventually fails. It is suggested that the spikes are sodium-dependent events which trigger a calcium-dependent secretory process. The composition and biological activity of the secretion are uncertain, but indirect evidence suggests a possible defensive or repellant role for the response.

Muscle contraction during hyperpolarizing currents in the crab

Isolated muscle fibers from the motor legs of the crab Trichodactilus dilocarcinus were submitted to strong hyperpolarizing currents of varied intensities which produced tension during the current pulse. Threshold for tension was obtained with intensities of about 0.2 x 10(-5) A, changing E(m) to ca. -150 mV (starting from a resting potential ofca. -80 mV). At the closure of the anodic square pulse, a second phase of tension usually appeared superimposed upon the one obtained during hyperpolarization. The first phase of tension increased with the increase of Ca(++) concentration in the bath. Sr(++) produced the same type of mechanical output as Ca(++). When added to the normal Ca(++) concentration, Ba(++) and Mn(++) in low concentrations (up to 21.5 mM) also increased the tension of this phase, but at higher concentrations they blocked both phases while Mg(++) did not alter the tension. Of all the divalent cations employed, only Sr(++) is capable of developing tension as a substitute for Ca(++) in the external media. Procaine administered in a dosage (5 x 10(-3) W/V)which would suppress the contracture due to caffeine (10 mM), did not modify the tension developed during the hyperpolarization. The preceding data indicate that the Ca(++) required for tension during hyperpolarization comes from sites which would differ from those usually postulated for tension due to depolarization in the muscle fibers of other crustaceans (American crayfish). Furthermore, the external source of Ca(++) appears to be one mainly implicated in the induction of tension due to inward current pulses.

Liver mitochondria from manganese-deficient and pallid mice: function and ultrastructure

Oxidative phosphorylation was studied in isolated liver mitochondria from manganese-deficient mice and in those from a mutant strain, pallid. In mitochondria from manganese-deficient mice, ratios of adenosine triphosphate formed to oxygen consumed were normal, but oxygen uptake was reduced. Electron microscopy of these mitochondria revealed ultrastructural abnormalities including elongation and reorientation of cristae. No biochemical or structural abnormalities were found in mitochondria from pallid mice.