Comparison of the serum selenium content of healthy adults living in the Antwerp region (Belgium) with recent literature data.

Graphite furnace atomic absorption spectrometry, after improved matrix modification and using Zeeman background correction, was used to measure the serum selenium content of healthy adults living in the Antwerp region (Belgium). The mean serum concentration of 13 men and 13 women, sampled once a month during 1 year, was 84.3 +/- 9.4ng/ml with a broad range of 51.4-121.7 ng/ml. The intra-individual variation was remarkably high. Recent literature on selenium concentrations is reviewed and values are tabulated, with limitation to healthy adults and European countries. The mean serum selenium concentration measured corresponded well to older literature data for Belgium. The obtained values were found to be in the medium range compared with the literature data for other European countries.     

Opposite effects of cholecystokinin octapeptide (CCK-8) and tetrapeptide (CCK-4) after injection into the caudal part of the nucleus accumbens or into its rostral part and the cerebral ventricles

Neurons with colocalized cholecystokinin and dopamine are present predominantly in the ventral tegmental area and project mainly to the caudal part of the medial nucleus accumbens. The activity of this dopamine system can be evaluated by means of the intracranial self-stimulation behavior on male Wistar rats having chronic electrodes implanted into the medial forebrain bundle in the postero-lateral area of the hypothalamus. The direct injection of 150 pmol CCK-8 into the medio-caudal accumbens induced an increase of intracranial self stimulation while a similar administration into its rostral portion produced a slight decrease of intracranial self-stimulation. The administration of 300 pmol CCK-4 into the same medio-caudal part of the accumbens produced an inhibitory action on intracranial self stimulation lasting for 25 min. The injection of 70 to 1300 pmol CCK-4 into the cerebral ventricles produced no change on intracranial self-stimulation. The intracerebroventricular injection of 70 pmol CCK-8 induced a large decrease of intracranial self-stimulation lasting for 20 min. Sodium chloride 0.15 M or unsulphated CCK-8 injection were without effect in either case. These results support the ideas that intracerebroventricular CCK-8 injection inhibits accumbens dopaminergic activity but that CCK-8 injection into the medio-caudal part of the accumbens, where nerve terminals with colocalized CCK and DA are present, facilitates this dopaminergic activity. In addition at the level of medio-caudal accumbens, CCK-8 and CCK-4 have opposite effects.     

Coenzyme binding by 3-hydroxybutyrate dehydrogenase, a lipid-requiring enzyme: lecithin acts as an allosteric modulator to enhance the affinity for coenzyme

The role of phospholipid in the binding of coenzyme, NAD(H), to 3-hydroxybutyrate dehydrogenase, a lipid-requiring membrane enzyme, has been studied with the ultrafiltration binding method, which we optimized to quantitate weak ligand binding (KD in the range 10-100 microM). 3-Hydroxybutyrate dehydrogenase has a specific requirement of phosphatidylcholine (PC) for optimal function and is a tetramer quantitated both for the apodehydrogenase, which is devoid of phospholipid, and for the enzyme reconstituted into phospholipid vesicles in either the presence or absence of PC. We find that (i) the stoichiometry for NADH and NAD binding is 0.5 mol/mol of enzyme monomer (2 mol/mol of tetramer); (ii) the dissociation constant for NADH binding is essentially the same for the enzyme reconstituted into the mixture of mitochondrial phospholipids (MPL) (KD = 15 +/- 3 microM) or into dioleoyl-PC (KD = 12 +/- 3 microM); (iii) the binding of NAD+ to the enzyme-MPL complex is more than an order of magnitude weaker than NADH binding (KD approximately 200 microM versus 15 microM) but can be enhanced by formation of a ternary complex with either 2-methylmalonate (apparent KD = 1.1 +/- 0.2 microM) or sulfite to form the NAD-SO3- adduct (KD = 0.5 +/- 0.1 microM); (iv) the binding stoichiometry for NADH is the same (0.5 mol/mol) for binary (NADH alone) and ternary complexes (NADH plus monomethyl malonate); (v) binding of NAD+ and NADH together totals 0.5 mol of NAD(H)/mol of enzyme monomer, i.e., two nucleotide binding sites per enzyme tetramer; and (vi) the binding of nucleotide to the enzyme reconstituted with phospholipid devoid of PC is weak, being detected only for the NAD+ plus 2-methylmalonate ternary complex (apparent KD approximately 50 microM or approximately 50-fold weaker binding than that for the same complex in the presence of PC). The binding of NADH by equilibrium dialysis or of spin-labeled analogues of NAD+ by EPR spectroscopy gave complementary results, indicating that the ultrafiltration studies approximated equilibrium conditions. In addition to specific binding of NAD(H) to 3-hydroxybutyrate dehydrogenase, we find significant binding of NAD(H) to phospholipid vesicles. An important new finding is that the nucleotide binding site is present in 3-hydroxybutyrate dehydrogenase in the absence of activating phospholipid since (a) NAD+, as the ternary complex with 2-methylmalonate, binds to the enzyme reconstituted with phospholipid devoid of PC and (b) the apodehydrogenase, devoid of phospholipid, binds NADH or NAD-SO3- weakly (half-maximal binding at approximately 75 microM NAD-SO3- and somewhat weaker binding for NADH).(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunohistochemical localization of gastrin-cholecystokinin-like material in the central nervous system of the migratory locust

Summary Brain, corpora cardiaca (CC)-corpora allata (CA) complex, suboesophageal ganglion, thoracic and abdominal ganglia of adults, larvae and embryos of Locusta migratoria have been immunohistochemically screened for gastrin cholecystokinin (CCK-8(s))-like material. In adult, numerous immunoreactive neurons and nerve fibres are located, with a marked symmetry, in various parts of the brain and throughout the ventral nerve cord. In the median part of the brain, cell bodies belonging neither to cellular type A1 nor A2 (following Victoria blue-paraldehyde fuchsin staining) are immunopositive; their processes terminate in the upper protocerebral neuropile. In lateral parts of the brain, external cell bodies send axons into CC and some up to CA, other internal have processes which terminate in the neuropile of the brain. Two of these latter cells react also with methionine-enkephalin antiserum. In the ventral nerve cord, in addition to numerous perikarya, immunore-active arborizations terminate in the neuropile or in close association with the sheath, at the dorsal part of all ganglia.This CCK-8(s) distribution pattern is observed only at the two last larval instars, but is precociously detected in the abdominal nerve cord of embryos, one day before hatching.     

Interactions between membranes and cytolytic peptides

The physico-chemical and biological properties of cytolytic peptides derived from diverse living entities have been discussed. The principal sources of these agents are bacteria, higher fungi, cnidarians (coelenterates) and the venoms of snakes, insects and other arthropods. Attention has been directed to instances in which cytolytic peptides obtained from phylogenetically remote as well as from related sources show similarities in nature and/or mode of action (congeneric lysins). The manner in which cytolytic peptides interact with plasma membranes of eukaryotic cells, particularly the membranes of erythrocytes, has been discussed with emphasis on melittin, thiolactivated lysins and staphylococcal alpha-toxin. These and other lytic peptides are characterized in Table III. They can be broadly categorized into: (a) those which alter permeability to allow passage of ions, this process eventuating in colloid osmotic lysis, signs of which are a pre-lytic induction or latent period, pre-lytic leakage of potassium ions, cell swelling and inhibition of lysis by sucrose. Examples of lysins in which this mechanism is involved are staphylococcal alpha-toxin, streptolysin S and aerolysin; (b) phospholipases causing enzymic degradation of bilayer phospholipids as exemplified by phospholipases C of Cl. perfringens and certain other bacteria; (c) channel-forming agents such as helianthin, gramicidin and (probably) staphylococcal delta-toxin in which toxin molecules are thought to embed themselves in the membrane to form oligomeric transmembrane channels.     

Histochemical changes of substance P, FRAP, serotonin and succinic dehydrogenase in the spinal cord of rats with adjuvant arthritis

Various histochemical changes were found in spinal segments L4-L5 of rats with adjuvant arthritis, predominantly 30 days after inoculation. A slight to marked increase of substance P immunoreactivity occurred in laminae I, II and X. FRAP activity was enhanced in lamina II. Serotonin immunoreactivity was heavier in laminae I, VIII and IX in a few animals. The intensity of the histoenzymological reaction for succinic dehydrogenase increased in certain laminae VIII and X neurons. At day 15 of the disease the increase of substance P and FRAP activities was chiefly restricted to the medial portion of the superficial dorsal horn. There was a significant positive correlation between the scratching behaviour of arthritic rats and the substance P immunoreactivity in laminae X and I. If one accepts that scratching is pain-related, the data are consistent with a possible role of substance P in the chronic pain associated with adjuvant arthritis. They leave undetermined the significance of the other histochemical changes.     

Formation and properties of cell-size lipid bilayer vesicles

Hydration of single or mixed phospholipids or lipid protein mixtures at low ionic strength results in the formation of a population of large, solvent free, single bilayer vesicles with included volumes of up to 300 microliters/mumol lipid. Their size ranges from 0.1 to 300 microns and they can be sorted out according to size by centrifugation. When formed in distilled water their internal solution has a conductivity of 20-50 microseconds/cm-1, an osmolarity of 0.5-5 mOsM, and a density of 1.0005-1.001. The osmotic pressure produced by the internal solutes cause a surface stress of 25 dyn/cm for a 20-microns vesicle. Their elastic constant ranges from 75-150 dyn/cm. During formation they can internalize particles such as latex beads or cell nuclei. They can be impaled with microelectrodes, or patch clamped. They can also be sealed to a small Vaseline-treated hole in a thin partition between two aqueous compartments. Sealing occurs in two stages. In the first stage sealing resistance is similar to that seen with patch-clamp pipettes. In the second stage, a much tighter seal is obtained. After sealing, the smaller portion of the sealed vesicle can be selectively broken by an electric shock leaving a single membrane across the hole. The capacitance and resistance of such membranes, in the presence of 10 mM NaCl, are approximately 0.7 microF/cm2 and 10(8) omega cm2 for pure lipid vesicles. Gramicidin increases the membrane conductance and monazomycin induces voltage-dependent gating thus providing further evidence that the vesicles are bounded by a single bilayer.     

CCK nerve terminals in the rat striatal and limbic areas originate partly in the brain stem and partly in telencephalic structures

After direct injection of colchicine into the rat rostral caudateputamen, levels of cholecystokinin-like immunoreactive (CCK-IR) material in this part of the nucleus are significantly lowered, and CCK-IR neuronal cell bodies are not demonstrable in the caudateputamen, although numerous ones are revealed in some adjacent telencephalic regions. Direct injection of kainic acid into the rostral caudate-putamen is not followed by a decrease of CCK-IR material in the lesioned region. Twenty one days after injection of 6-hydroxydopamine into the rat ventral mesencephalon, a significant decrease of CCK-IR material is observed in the frontal pole, the pyriform cortex, the nucleus accumbens and the ventral mesencephalon itself, but not in the caudate-putamen. After brain stem hemitransection, no decrease in CCK-IR material is observed in the rostral caudate-putamen.     

Formation of poly(hydroxybutyrate-co-hydroxyvalerate) by Azotobacter vinelandii UWD.

Azotobacter vinelandii UWD formed polyhydroxyalkanoate (PHA) copolymers containing beta-hydroxybutyrate and beta-hydroxyvalerate (HV) when grown in a medium containing glucose as the primary C source and valerate (pentanoate) as a precursor. Copolymer was not formed when propionate was added to the glucose medium but was formed when heptanoate, nonanoate, or trans-2-pentenoate was present. Optimal levels of HV were formed when valerate was added at the time of maximum PHA synthesis, although HV incorporation was not dependent on glucose catabolism. HV content in the polymer was increased from 17 to 24 mol% by adding 10 to 40 mM valerate to glucose medium, but HV insertion into the polymer occurred at a fixed rate. Similarly, the addition of valerate to a fed-batch culture of strain UWD in beet molasses in a fermentor produced 19 to 22 g of polymer per liter, containing 8.5 to 23 mol% HV after 38 to 40 h. The synthesis of HV in these cultures also occurred at a fixed rate (2.3 to 2.8 mol% h-1), while the maximum PHA production rate was 1.1 g liter-1 h-1. During synthesis of copolymer in batch or fed-batch culture, the yield from conversion of glucose into PHA (YP/S) remained at maximum theoretical efficiency (greater than or equal to 0.33 g of PHA per g of glucose consumed). Up to 45 mol% C source, but the PHA produced amounted to less than 1 g/liter. The combination of 30 mM valerate as a sole C source and 0.5 mM 4-pentenoate increased the HV content in the polymer to 52 mol%.(ABSTRACT TRUNCATED AT 250 WORDS)