[Colloid osmotic pressure and neonatal respiratory distress syndrome]

BACKGROUND

The interest of studying colloid osmotic pressure (COP) in neonates is based on a possible relation between low COP and severity of neonatal respiratory distress.

POPULATION AND METHODS

Because this relation has not been accurately established, COP was prospectively measured at birth in 84 infants: 35 with respiratory distress syndrome treated with mechanical ventilation (group RD+: GA = 34.5 +/- 3.5 weeks; BW = 2,190 +/- 830 g); 49 free of severe respiratory disease (group RD-: GA = 37.5 +/- 2.5 weeks; BW = 2,720 +/- 655 g).

RESULTS

On day one after birth COP was significantly lower in the RD+ group (15.0 +/- 2.2 mmHg) as compared with that in the RD- group (17.9 +/- 2.5 mmHg), and was negatively correlated with mean oxygenation index (OI) on day one, with the highest OI over the first five days of life, and with total duration of oxygen support (P < 0.05). COP was significantly reduced in the neonates with systemic hypotension on day one (P < 0.05).

CONCLUSIONS

These results confirm a correlation between COP at birth and incidence and severity of neonatal respiratory distress. The relationship between low COP and systemic hypotension suggests an important role of COP in the ability of maintaining volemia. This study stresses the strong relationship between water homeostasis and neonatal respiratory distress. Nevertheless, it does not allow to conclude that modifying COP is necessary to improve neonatal respiratory disease.

Substance P induces the secretion of gelatinase A from human synovial fibroblasts

We investigated the secretion of the matrix metalloproteinases, interstitial collagenase (matrix metalloproteinase-1), gelatinase A (matrix metalloproteinase-2) and stromelysin-1 (matrix metalloproteinase-3) in human synovial fibroblasts after stimulation with the neuropeptide substance P. Human synovial fibroblasts were stimulated with substance P or interleukin-1 beta (IL-1 beta). In the cell culture media gelatinase A, interstitial collagenase and stromelysin-1 were identified and their activities towards different substrates were determined. Substance P in synovial fibroblasts induced an increase in the overall matrix metalloproteinase activity towards the dinitrophenyl-labelled peptide by 85%, against an increase of 124% after stimulation with IL-1 beta. In case of substance P stimulation, the increase in activity reflects a significantly enhanced secretion of gelatinase A, whereas no significant increase of stromelysin-1 and collagenase secretion could be observed. The matrix metalloproteinase pattern showing the highest gelatinase A secretion was obtained after stimulation with substance P. This pattern was very pronounced and differed very clearly from the pattern seen after IL-1 beta stimulation which caused a significant rise in collagenase and stromelysin-1 activity. We assume that distinct stimulation pathways are involved and that the neuropeptide (substance P), which is always present in the inflamed joint, plays its own and separate role in proliferative processes leading to the cartilage destruction.

[Treatment of neonatal convulsions]

Three important measures are concommitantly recommended in the treatment of neonatal seizures. 1) The maintenance of vital functions by supplying oxygen and using mask ventilation in addition to cardiac monitoring and placing an intravenous line. 2) The search for an etiology through metabolic and infectious laboratory tests. In many cases this will lead to an etiological treatment. 3) The specific treatment of the seizures: intravenous or intrarectal diazepam is the first line treatment. Phenobarbital, then phenytoin and clonazepam are used when diazepam is unsuccessful. Indications and duration of a secondary prophylactic treatment are controversial and must be discussed on the basis of the electroencephalographic data and the risk factors for epileptic seizures during the neonatal period and at 3 months of age.

Relapse of polymyositis after prolonged remission

We describe the case of a patient with polymyositis and anti-Jo-1 antibodies who experienced a relapse of his inflammatory muscle disease after 7 years of clinical remission. Our review of the literature shows that remission is achieved in 25-68% of patients treated with high dose corticosteroids as part of their initial therapy. Relapse rates after complete remission vary from 6 to 43% in the few studies where this information is available. Late relapses after initial remission appear to be unusual, but may be more frequent in patients like this one with antisynthetase syndrome.

Serotonin-induced intercellular calcium waves in salivary glands of the blowfly Calliphora erythrocephala

1. Blowfly salivary glands have been used extensively as a model system for the analysis of inositol phosphate-dependent signal transduction. To detect and characterize changes in intracellular free calcium ([Ca2+]i) that might be expected to be triggered by stimulation with serotonin (5-HT), we have carried out digital calcium-imaging experiments on intact glands using the Ca2+-sensitive dye fura-2. 2. 5-HT (1-10 nM) induced repetitive transient increases in [Ca2+]i, i.e. Ca2+ spikes whose frequency was a function of agonist concentration (EC50 = 2.8 nM). 3. Pre-incubation in EGTA decreased the frequency but did not inhibit spiking. Thapsigargin abolished periodic spike activity indicating that the [Ca2+]i rise results from Ca2+ release. Neither caffeine (10 mM) nor ryanodine (10 and 50 microM) induced increases in [Ca2+]i. 4. Oscillatory activity in individual cells was synchronized by regenerative intercellular Ca2+ waves that propagated over distances greater than 400 microm. Colliding waves annihilated each other. 5. Desynchronization of the oscillation pattern by 100 microM 1-octanol suggests the involvement of gap junctions and an intracellular messenger in wave propagation. 6. Local stimulation of glands elicited [Ca2+]i elevations in the stimulated area, but not in adjacent cells, indicating that local increases in [Ca2+]i are not sufficient to trigger Ca2+ waves. However, local stimulation was capable of evoking propagating Ca2+ waves when combined with low-dose 5-HT stimulation of the whole gland. 7. The data are consistent with the hypothesis that: (1) Ca2+ acts as the intercellular messenger and modulates its own release via positive and negative feedback on the inosital 1,4,5-trisphosphate (InsP3) receptor, and (2) sensitization of the InsP3 receptor to Ca2+ by InsP3 is required for the propagation of intercellular Ca2+ waves, as proposed for intracellular Ca2+ waves in Xenopus oocytes.

The rewards outweigh the efforts: breastfeeding outcomes for mothers of preterm infants

This study describes the rewards and efforts of breastfeeding for mothers of preterm infants. Using a semi-structured interview guide, 20 mothers of preterm infants were interviewed in their homes approximately 1 month after infant discharge from a Level III NICU. Mothers described the following rewards of breastfeeding: knowing they were providing the healthiest nutrition for the infant, enhancing closeness between the mother and infant, perceiving infant contentment and tranquility during breastfeeding, providing convenience for the mother, and giving the mother a tangible claim on the infant. Most mothers identified some "efforts" associated with breastfeeding their preterm infants, but indicated that overall, breastfeeding was a rewarding experience. These data provide scientific support for the promotion and facilitation of breastfeeding for mothers of preterm infants, in that mothers perceive specific emotional advantages that they relate to the breastfeeding experience.

Importance of the A-helix of the catalytic subunit of cAMP-dependent protein kinase for stability and for orienting subdomains at the cleft interface

All eukaryotic protein kinases share a conserved catalytic core. In the catalytic (C) subunit of cAMP-dependent protein kinase (cAPK) this core is preceded by a myristylation motif followed by a long helix with Trp 30 at the end of this A-helix filling a hydrophobic cavity between the two lobes of the core. To understand the importance of the A-helix, the myristylation motif (delta 1-14) as well as the entire N-terminal segment (delta 1 -39) were deleted. In addition, Trp 30 was replaced with both Tyr and Ala. All proteins were overexpressed in E. coli and purified to homogeneity. rC(delta 1-14), rC(W30Y), and rC(W30A) all had reduced thermostability, but were catalytically indistinguishable from wild-type C. Based on Surface Plasmon Resonance, all three also formed stable holoenzyme complexes with the RI-subunit, although the appKds were reduced by more than 10-fold due to decrease in the association rate. Surprisingly, however, the holoenzymes were even more thermostable than wild-type holoenzyme. To obtain active enzyme, it was necessary to purify rC(delta 1-39) as a fusion protein with glutathione-S-transferase (GST-rC(delta 1-39), although its thermostability (Tm) was decreased by 12.5 degrees C, was catalytically similar to wild-type C and was inhibited by both the type I and II R-subunits and the heat-stable protein kinase inhibitor (PKI). The Tm for holoenzyme II formed with GST-rC(delta 1-39) was 16.5 degrees C greater than the Tm for free GST-rC(delta 1-39), and the Ka(cAMP) was increased nearly 10-fold. These mutants point out striking and unanticipated differences in how the RI and RII subunits associate with the C-subunit to form a stable holoenzyme and indicate, furthermore, that this N-terminal segment, far from the active site cleft, influences those interactions. The importance of the A-helix and Trp 30 for stability correlates with its location at the cleft interface where it orients the C-helix in the small lobe and the activation loop in the large so that these subdomains are aligned in a way that allows for correct configuration of residues at the active site. This extensive network of contacts that links the A-helix directly to the active site in cAPK is compared to other kinases whose crystal structures have been solved.

Effects of all-trans-retinoyl-beta-D-glucuronide and all-trans-retinoic acid on chondrogenesis and retinoid metabolism in mouse limb bud mesenchymal cells in vitro

Retinoids, derivatives of vitamin A, are essential for many vertebrate functions. Furthermore, several drugs of this class of compounds are valuable in the treatment of certain forms of skin disorders and cancer. However, the therapeutic application of retinoids is limited by their teratogenic potency. The limbs are important sites of retinoid-induced malformations in rodents. Therefore, organoid cultures of limb bud mesenchymal cells have been established for screening of the teratogenic potency of retinoids. We have now applied this system to compare the effects of all-trans-retinoyl-beta-D-glucuronide (all-trans-RAG) with those of all-trans-retinoic acid (all-trans-RA) on chondrogenesis, as assessed by the Alcian blue binding assay and by electron microscopic evaluation including quantitative morphometric analysis. First data of retinoid toxicokinetics in the culture media as well as retinoid concentrations in the cultured mesenchymal limb bud cells were established. While all-trans-RA inhibited chondrogenesis at 10(-7) M by ca. 50%, tenfold higher concentrations of all-trans-RAG were necessary to obtain the same effect. This difference reflects the ratio of RA isomers which were found in the medium after incubation with either all-trans-RAG or all-trans-RA. A pulse experiment (10(-5) M all-trans-RAG or all-trans-RA for the first 2 h of a 6-day incubation period) demonstrated inhibition of chondrogenesis with all-trans-RA, but not with all-trans-RAG. The data indicate that RAG inhibits chondrogenesis upon hydrolysis to RA. Surprisingly, the rather polar RAG isoforms were extensively accumulated in the limb bud mesenchymal cells when compared to the medium. Both all-trans-RAG and all-trans-RA also induced a large increase of retinyl ester concentrations in the chondrocytes compared to vehicle-treated cells. This finding further supports a recent suggestion that RA regulates retinol metabolism via feedback inhibition of retinol oxidation and stimulation of the esterification of retinol.

Endoproteolysis of glucagon-like peptide (GLP)-1 (7-36) amide by ectopeptidases in RINm5F cells

This study concerns whether the pancreatic beta cell expresses cell-surface ectopeptidases that are capable of proteolysis of peptide hormones and neuropeptides that modify glucose-dependent insulin release. These biochemical investigations of the RINm5F cell line found that these cells express ectopeptidases. We have characterized the limited endoproteolysis of GLP-1 (7-36) amide that occurs in the presence of RINm5F plasma membranes. The products and the sensitivity to specific peptidase inhibitors of the proteolysis is characteristic of neutral endopeptidase (NEP) 24.11. Vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase-activating peptide (PACAP), amylin, glucagon, glucose-dependent insulinotropic polypeptide (GIP), and exendin-4 also undergo proteolysis in the presence of RIN cell membranes. NEP 24.11-activity in RIN cell membranes was confirmed using a specific fluorogenic assay, by histochemistry, and by comparison with the recombinant enzyme with respect to the kinetics of proteolysis of GLP-1 (7-36) amide and of a fluorogenic substrate. Specific fluorogenic assays revealed the presence of aminopeptidase N and the absence of aminopeptidase A and of dipeptidylpeptidase IV.

Septic sacroiliitis

Two cases of septic sacroiliac (SI) joint arthritis are presented to illustrate the difficulty of diagnosing and treating this uncommon osteoarticular infection. The patients presented are a 68-year-old woman with septic sacroiliitis caused by Streptococcus agalactiae and a 20-year-old man with Salmonella infantis infection involving the SI joint. The recent literature is reviewed and compared with previously published series. Of the 177 cases we reviewed, 47 (27%) occurred in pediatric patients. The mean age was 20 years. Only six patients (3%) were older than 60 years of age. Magnetic resonance imaging (MRI) is most useful for defining extent of infection, osteomyelitis, and abscess formation in the SI joint. Computed tomography (CT) is valuable for defining the extent of bone involvement and for guidance of percutaneous needle arthrocentesis. Other imaging modalities are useful primarily in the initial evaluation of patients with a nonspecific presentation. Four to six weeks of intravenous (i.v.) antibiotic therapy is recommended. Indications for surgical intervention include abscess formation, osteomyelitis, sequestrum of necrotic bone, and failure to respond to i.v. antibiotic therapy.

Conditioned blocking in patients with paranoid, non-paranoid psychosis or obsessive compulsive disorder: associations with symptoms, personality and monoamine metabolism

Conditioned blocking (CB) refers to a delay in learning that a new stimulus, added during learning, has the same consequences as the conditioned stimulus already present. In animals such "learned inattention" depends on monoaminergic and limbic function and, thus, CB performance should be informative on selective information processing impairments found in subgroups of psychotic patients. Attenuated CB in acute schizophrenia has been reported to normalize rapidly. This study examines in young patients the specificity of CB performance to illness, and its associations with symptoms, personality traits and monoaminergic metabolic status. CB was attenuated in psychotic patients with non-paranoid symptoms (NP: n = 12, mean age 17 years) with respect to obsessive-compulsive (OCD: n = 13, mean age 16 years) and healthy subjects (CON, n = 29, mean age 18 years), but only a transient attenuation was observed in paranoid hallucinatory patients (PH: n = 14, mean age 19 years). Outgoing personality traits in CON and OCD subjects correlated with CB. In NP patients attenuated CB was associated with increasing neurotic lability. In PH patients CB correlated positively with "manic" but negatively with psychotic or neurotic scores. The severity of negative symptoms in psychosis and specific negative/positive symptoms in the NP/PH groups was associated with reduced CB. Increased dopamine activity (24-h urine samples) correlated positively with CB, but relative increases of noradrenaline metabolism in NP and serotonin metabolism in OCD patients interfered. In summary, marked psychotic or neurotic traits and some symptom-states were associated with reduced CB. The particular selective processing problems of NP patients may reflect inappropriate NA activity.

Transbilayer movement of fluorescent and spin-labeled phospholipids in the plasma membrane of human fibroblasts: a quantitative approach

All phospholipids in the plasma membrane of eukaryotic cells are subject to a slow passive transbilayer movement. In addition, aminophospholipids are recognized by the so-called aminophospholipid translocase, and are rapidly moved from the exoplasmic to the cytoplasmic leaflet of the plasma membrane at the expense of ATP hydrolysis. Though these principal pathways of transbilayer movement of phospholipids probably apply to all eukaryotic plasma membranes, studies of the actual kinetics of phospholipid redistribution have been largely confined to non-nucleated cells (erythrocytes). Experiments on nucleated cells are complicated by endocytosis and metabolism of the lipid probes inserted into the plasma membrane. Taking these complicating factors into account, we performed a detailed kinetic study of the transbilayer movement of short-chain fluorescent (N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl); NBD) and, for the first time, spin-labeled analogues of phosphatidylcholine (PC), -ethanolamine (PE), -serine (PS), and sphingomyelin (SM) in the plasma membrane of cultured human gingival fibroblasts. At 20 degrees C, the passive transbilayer diffusion of NBD analogues was very slow, and the choline-containing NBD analogues were internalized predominantly by endocytosis. Spin-labeled analogues of PC and SM showed higher passive transbilayer diffusion rates, and probably entered the cell by both passive transbilayer movement and endocytosis. In contrast, the rapid uptake of NBD- and spin-labeled aminophospholipid analogues could be mainly ascribed to the action of the aminophospholipid translocase, since it was inhibited by ATP depletion and N-ethylmaleimide pretreatment. The initial velocity of NBD-aminophospholipid translocation was eight to ten times slower than that of the corresponding spin-labeled lipid, and the half-times of redistribution of NBD-PS and spin-labeled PS were 7.2 and 3.6 minutes, respectively. Our data indicate that in human fibroblasts the initial velocity of aminophospholipid translocation is at least one order of magnitude higher than that in human erythrocytes, which should be sufficient to maintain the phospholipid asymmetry in the plasma membrane.

Integrated optical NIR-evanescent wave absorbance sensorfor chemical analysis

A new, long-path integrated optical (IO) sensor for the detection of non-polar organic substances is described. The sensing layer deposited on a planar multimode IO structure is built by a suitable silicone polymer with lower refractive index (RI). It acts as a hydrophobic matrix for the reversible enrichment of non-polar organic contaminants from water or air. Light from the near-infrared (NIR) range is coupled into the planar structure and the evanescent wave part of the light field penetrating into the silicone layer interacts with the enriched organic species. As a result, light is absorbed at the characteristic frequencies of the corresponding C-H, N-H or O-H overtone and combination band vibrations of the analytes. To perform evanescent field absorbance (EFA) measurements, the arc-shaped strip waveguide structure of 172 mm interaction length was adapted to a tungsten-halogen lamp and an InGaAs diode array spectrograph over gradient index fibers. Dimethyl-co-methly(phenyl)polysiloxanes with varying degrees of phenylation were prepared and used as sensitive coating materials for the IO structure. Light attenuation in the arc-shaped waveguides is high and typical insertion losses in the range of 14-18 dB were obtained. When the coated sensors were brought in contact with aqueous samples, the light transmission decreases, which is due to the formation of H(2)O micro-emulsions in the silicone superstrates. Nevertheless, after reaching constant light transmissions, absorbance spectra of aqueous trichloroethene samples were successfully collected. For gas measurements, where water cross sensitivity problems are absent, the sensitivity of the IO device for trichloroethene was tested as a function of the RI of the silicone superstrate. The slope of the TCE calibration function increases by a factor of 10 by using a poly(methylphenylsiloxane) layer with a RI of 1.449 instead of poly(dimethylsiloxane) (RI: 1.41). A comparison of the IO-EFA and an earlier developed fiber-optic EFA sensor for trichloroethene measurements in the gas phase showed an increase in sensitivity per unit length of the waveguide by a factor of up to 120.

The role of MgADP in force maintenance by dephosphorylated cross-bridges in smooth muscle: a flash photolysis study

The effect of [MgADP] on relaxation from isometric tension, initiated by reducing free [Ca2+] through photolysis of the caged photolabile Ca2+ chelator diazo-2, was determined at 20 degrees C in alpha-toxin permeabilized tonic (rabbit femoral artery, Rf) and phasic (rabbit bladder, Rb) smooth muscle. In Rf, the shape of the relaxation curve was clearly biphasic, consisting of a slow "plateau" phase followed by a monotonic exponential decline with rate constant k. The duration of the plateau (d = 44 +/- 4 s, mean +/- SEM, n = 28) was well correlated (R = 0.92) with the total t1/2 of relaxation that was 66 +/- 3 s (n = 28) in the presence of 20 mM creatine phosphate (CP), and was prolonged in the absence of CP (t1/2 = 83 +/- 3 s, n = 7); addition of 100 microM MgADP further slowed relaxation (t1/2 = 132 +/- 7 s, n = 14). In Rb, a plateau was not detectable and t1/2 (= 15 +/- 2 s, n = 6) was not affected by 100 microM MgADP. In Rf the Q10 between 20 degrees C and 30 degrees C was 4.3 +/- 0.4 for d-1 and 2.8 +/- 0.3 for k (n = 8; p = 0.006). The regulatory myosin light chain (MLC20) in Rf was dephosphorylated at 0.07 +/- 0.02 s-1, from 42 +/- 3% before to 20 +/- 2% after photolysis of diazo-2, reaching basal values at a time when force had fallen by only 40%. We conclude that, in the presence of ATP, as during rigor, the affinity of dephosphorylated cross-bridges for MgADP is significantly higher in tonic than in phasic smooth muscle and contributes to the maintenance of force at low levels of phosphorylation. The MgADP dependence of the post-dephosphorylation phase of relaxation is consistent with its being rate-limited by the slow off-rate of ADP from cross-bridges that were dephosphorylated while in force-generating ADP-bound (AM*D) cross-bridge states. The fourfold faster off-rate of ADP from AM*D in the phasic, Rb, compared to tonic, Rf, smooth muscle is a major determinant of the different kinetics of relaxation in the two types of smooth muscle.

Kinetics of prephosphorylation reactions and myosin light chain phosphorylation in smooth muscle. Flash photolysis studies with caged calcium and caged ATP

The pre-myosin light chain (MLC20) phosphorylation components of the lag phase (td) of contractile activation were determined in permeabilized smooth muscles activated by photolytic release of ATP from caged ATP and/or Ca2+ from 4-(2-nitrophenyl)-EGTA (NP-EGTA). Calmodulin (CaM) shortened the td (470 ms at 0 added CaM) that followed Ca2+ release, but its effect (td = approximately 200 ms) saturated at 40 microM. Photolysis of caged ATP following preequilibration with identical [Ca4CaM] shortened td to 41 ms. The rate of phosphorylation was very fast (3.5 s-1 at 22 degrees C in the presence of 5 microM exogenous CaM) following photolysis of caged ATP, and, following Ca2+ release, phosphorylation was accelerated by CaM. Simultaneous photolysis of caged ATP and NP-EGTA was followed by a td of 194 ms at 5 microM CaM and a rate of MLC20 phosphorylation intermediate between these parameters following photolysis of, respectively, NP-EGTA and caged ATP. In the presence of the normal, total endogenous CaM content (37 +/- 4 microM) of protal vein smooth muscles td was 565 ms. Steady state maximum force at pCa 5.5 was increased by much lower (100 nM) exogenous [CaM] than was required (> 2.5 microM) to shorten the td. We estimate the endogenous CaM available under steady state conditions in vivo to be approximately 0.25 microM and probably less during a rapid Ca2+ transient. We conclude that the [CaM] dependence of the kinetics of MLC20 phosphorylation and force development (t1/2 and td) initiated by Ca2+ reflects the recruitment of a slowly diffusible component of total CaM. The relatively long duration of td (197 ms) at saturating [CaM] suggests the contribution to td of an additional component, possibly a prephosphorylation activation/isomerization of the Ca4CaM myosin light chain kinase complex (Török, K., and Trentham, D. R. (1994) Biochemistry 33, 12807-12820). The relatively short delay (108 ms in the presence of 40 microM CaM) following simultaneous photolysis of NP-EGTA and caged ATP suggests that preincubation with ATP (prior to photolysis of NP-EGTA) may inhibit the formation of a preactive Ca2CaM myosin light chain kinase complex.

Changes in integrin expression during chondrogenesis in vitro: an immunomorphological study

Integrins are receptors composed of ligand-specific alpha-chains and cell type-specific beta-chains which are involved in cell-cell and cell-matrix interactions. The distribution of alpha 1- and alpha 3-integrins as well as collagen Types I and II, was investigated by immunofluorescence and immunoelectron microscopy during chondrogenesis in organ culture after various culture periods. Mesenchymal cells from limb buds of Day 12 mouse embryos were grown at high density. Within the first 2 days of the culture period, only alpha 1-integrin could be detected. Formation of cartilage-specific matrix on Day 3 was accompanied by the occurrence of alpha 3-integrin. On Day 7, alpha 3 was present only in cartilage nodules, whereas alpha 1 was strongly expressed in the perichondrium and was more or less homogeneously distributed in the surrounding mesenchyme. On Day 14, alpha 1-integrin was again detectable in cartilage. We suggest that the change in collagen formation from Type I to Type II during chondrogenesis is accompanied by a change in integrin expression from alpha 1 to alpha 3. Conversely, dedifferentiation of chondrocytes in aging cartilage is accompanied by the occurrence of collagen Type I and alpha 1-integrin. Therefore, a strict correlation between the collagen type synthesized by the cells and the appropriate receptor presented by the cells is suggested.

An improved assay for measuring the transverse redistribution of fluorescent phospholipids in plasma membranes

The internalization of fluorescent 7-nitro-2,1,3-benzoxadiazol-4-yl (NBD)-phospholipids from the plasma membrane can be assessed by the irreversible quenching of analogues in the outer leaflet by dithionite. Here we have utilized this assay to follow the redistribution of short-chain C6-NBD-sphingomyelin and C6-NBD-phosphatidylserine from the cell membrane of human gingiva fibroblasts. The significant uptake of dithionite across the plasma membrane and the subsequent reduction of NBD-analogues exposed to the cytoplasmic lumen does not allow an accurate measurement of the amount of internalized lipid probes even at low temperature. We could show that a precise determination can be achieved by extraction of analogues remaining in the exoplasmic half by a short pretreatment with bovine serum albumin prior to addition of dithionite. The fluorescence of those analogues localized to the cytoplasmic lumen was slowly destroyed by permeating dithionite. The fluorescence of those NBD-probes which are localized in the inner layer of intracellular vesicles remained almost unaffected in the time course of the assay. Thus, this approach allows to distinguish between different routes of internalization of NBD-phospholipids from the plasma membrane.

Characterisation of the processing by human neutral endopeptidase 24.11 of GLP-1(7-36) amide and comparison of the substrate specificity of the enzyme for other glucagon-like peptides

The post-secretory processing of the potent insulinotropic peptide hormone, GLP-1(7-36)amide, probably involves one or more of a small group of membrane-bound ectopeptidases. Reported here, is the characterisation of the endoproteolysis of human GLP-1(7-36)amide by the recombinant human form of neutral endopeptidase (NEP) 24.11, which is one of the best characterised and widely-distributed of ectopeptidases and is involved in the processing of other peptide hormones. The products of the limited endoproteolysis were characterised by mass and primary structure following fractionation using high performance liquid chromatography. The rate of this endoproteolysis by NEP 24.11 was estimated and compared to that of GLP-1(7-36)amide-related peptides. GLP-1(7-36)amide appears to be good substrate for NEP 24.11 with most, but not all potential target bonds being cleaved. Also, the structurally-related peptides, secretin and glucagon appear to be good substrates whereas GIP and exendin-4 are very poor substrates. That the GLP-1(7-36)amide super-agonist, exendin-4 is a poor substrate for NEP 24.11 is significant for the possible use of this peptide as a prototype for the development of clinically-useful peptide agonists. Further studies should reveal whether NEP 24.11 is important for the metabolic clearance of GLP-1(7-36)amide and will be highly relevant for the attempts to realise the suggested therapeutic value of GLP-1(7-36)amide.

Septic bursitis

Nine cases of septic bursitis are presented, and the literature on the subject comprehensively reviewed, with an emphasis on the clinical manifestations of septic bursitis in various anatomic locations. Physical activities associated with increased susceptibility to septic bursitis and systemic conditions that increase the severity of septic bursitis are catalogued. Analysis of the microbiology of cases reported in the literature demonstrates that greater than 80% of cases of septic bursitis are caused by Staphylococcus aureus and other gram-positive organisms. However, a wide variety of gram-negative microorganisms, fungi, and other infectious agents have been reported to cause septic bursitis and may lead to complications in diagnosis and treatment. The nine cases reported here demonstrate the potential severity of septic bursitis and emphasize that significant systemic complications may result from this common musculoskeletal infection. Indications for hospitalization and/or intravenous antibiotic therapy for septic bursitis include the presence of fulminant local infection, evidence for systemic toxicity, or infection in an immunocompromised patient. Patients who fail to respond to intravenous antibiotics and percutaneous aspiration of the bursa may require surgical drainage or bursectomy by one of several methods that have been proposed. There is some recent evidence that intrabursal corticosteroid injection for therapy of nonseptic subcutaneous bursitis may be more effective than systemic antiinflammatory medication or simple bursa aspiration.

Induction of metalloproteinase activity, cartilage matrix degradation and inhibition of endochondral mineralization in vitro by E. coli lipopolysaccharide is mediated by interleukin 1 alpha

Chronic inflammation and degradation of connective tissue in the course of periodontitis are maintained by bacterial products such as lipopolysaccharides (LPS), which probably act via inflammation mediators, e.g. cytokines. We investigated the effects of lipopolysaccharide (LPS) from E. coli and mouse recombinant interleukin 1 alpha (mrIL-1) on chondrogenesis, endochondral mineralization, matrix metalloproteinase activation and matrix degradation in vitro using cartilage organoid cultures. Mesenchymal cells of limb buds from mouse embryos (day 12) were grown at high density on a membrane filter at the medium/air interphase for 14 days. Chondrogenesis occurred during the first 6 days of culture. Endochondral mineralization took place upon addition of 5 mM beta-glycerophosphate from day 7 to 14. Treatment of the cultures with LPS and mrIL-1 on days 2 to 14 and during mineralization on days 7 to 14 resulted in a marked decrease of types I and II collagen, matrix mineralization and proteoglycan content. In the medium, proteoglycan content and metalloproteinase activity were enhanced. LPS induced IL-1 alpha production and release into the medium. LPS antagonist polymyxin B partly abolished the LPS effect, whereas IL-1 receptor antagonist (IL-1ra) partly abolished both LPS and mrIL-1 effects. Reversal of LPS-induced effects by IL-1ra was comparable to the reversal of mrIL-1 effects, only the decrease in type II collagen after LPS treatment was abolished to a lesser extent by IL-1ra.(ABSTRACT TRUNCATED AT 250 WORDS)

Caffeine- and ryanodine-sensitive Ca(2+)-induced Ca2+ release from the endoplasmic reticulum in honeybee photoreceptors

Light stimulation of invertebrate microvillar photoreceptors causes a large rapid elevation in Cai, shown previously to modulate the adaptational state of the cells. Cai rises, at least in part, as a result of Ins(1,4,5)P3-induced Ca2+ release from the submicrovillar endoplasmic reticulum (ER). Here, we provide evidence for Ca(2+)-induced Ca2+ release (CICR) in an insect photoreceptor. In situ microphotometric measurements of Ca2+ fluxes across the ER membrane in permeabilized slices of drone bee retina show that (a) caffeine induces Ca2+ release from the ER; (b) caffeine and Ins(1,4,5)P3 open distinct Ca2+ release pathways because only caffeine-induced Ca2+ release is ryanodine sensitive and heparin insensitive, and because caffeine and Ins(1,4,5)P3 have additive effects on the rate of Ca2+ release; (c) Ca2+ itself stimulates release of Ca2+ via a ryanodine-sensitive pathway; and (d) cADPR is ineffective in releasing Ca2+. Microfluorometric intracellular Ca2+ measurements with fluo-3 indicate that caffeine induces a persistent elevation in Cai. Electrophysiological recordings demonstrate that caffeine mimics all aspects of Ca(2+)-mediated facilitation and adaptation in drone photoreceptors. We conclude that the ER in drone photoreceptors contains, in addition to the Ins(1,4,5)P3-sensitive release pathway, a CICR pathway that meets key pharmacological criteria for a ryanodine receptor. Coexpression of both release mechanisms could be required for the production of rapid light-induced Ca2+ elevations, because Ca2+ amplifies its own release through both pathways by a positive feedback. CICR may also mediate the spatial spread of Ca2+ release from the submicrovillar ER toward more remote ER subregions, thereby activating Ca(2+)-sensitive cell processes that are not directly involved in phototransduction.