Clinical and genetic aspects of Shiga-like toxin production in traditional enteropathogenic Escherichia coli

Cell culture tests, DNA colony blot hybridization and polymerase chain reaction were used to examine classical enteropathogenic Escherichia coli (EPEC) for the presence of Shiga-like toxin (SLT). Fifteen of 155 strains from West Germany, originally identified as EPEC on the basis of serotyping, were shown to harbor either SLT-I or SLT-II genes. All strains that hybridized with the 20-base oligonucleotide probes which are complementary to slt-IA or slt-IIA sequences derived from the genomic DNA of enterohemorrhagic E. coli O157:H7 strain 933 produced moderate or high levels of cytotoxin in Vero and HeLa cell assays. Four additional strains of low to moderate cytotoxicity did not hybridize with either probe. Five different serogroups producing SLTs were identified: O26, O55, O111, O119 and O128. All three SLT-positive E. coli O26:H11 and four of five E. coli O111:H- isolates hybridized with a 3.4 kilobase fragment (CVD 419 probe) derived from the 60-megadalton plasmid of EHEC O157:H7. Seven of the 15 SLT-gene positive strains were associated with bloody diarrhea, six isolates were from patients with hemolytic uremic syndrome (HUS). Based on their clinical, epidemiological, pathogenic and genetic features SLT-producing E. coli among classical EPEC mimic enterohemorrhagic E. coli O157:H7 and might be considered as EHEC.

Thiazolidine-diones. Biochemical and biological activity of a novel class of tyrosine protein kinase inhibitors

Various derivatives of thiazolidine-diones have been identified as tyrosine protein kinase inhibitors. The epidermal growth factor (EGF) receptor kinase and c-src kinase were inhibited in vitro with IC50 values in the range of 1-7 microM. The v-abl tyrosine protein kinase was not inhibited by thiazolidine-diones. Inhibition was found to be specific for tyrosine protein kinases. Inhibition of serine/threonine protein kinases was not observed. The active derivatives were shown to inhibit EGF-induced receptor autophosphorylation, either in vitro or in intact cells, and were also found to inhibit growth of the EGF-dependent BALB/MK and A431 cell lines (IC50 1-3 microM). Growth of the interleukin-3-dependent myeloid cell line FDC-P1 was inhibited with equal efficiency. Thus, in these cell lines, members of the c-src kinase family are also potential targets for inhibition by the compounds.

[Morphologic changes in the intestine of swine after infection with verotoxin-producing Escherichia coli]

Spontaneous morphologic lesions are described in 12 of 66 pigs submitted for necropsy. All 12 pigs were culture positive for Verotoxin-producing E. coli (VTEC). 10 of them were weaned pigs, one a suckling piglet and one a fattening hog. In 6 cases E. coli serovar 0139:H1 and in one case each the serovars 0139:H40; 0138:H-; 0125ac:H27 and 0154:H- were isolated. From the fecal samples of 2 animals E. coli ONT (O-group non typable):H- were cultured. Macroscopically there were cyanosis, edema of the eye lids, catarrhal enteritis and/or colitis as well as edema of the mesentery, swelling of the mesenteric lymph nodes and congestion of the lung to varying degrees. Histopathologic examination of 5 animals was carried out. In 3 animals atrophy and edema of the villi in the jejunum and ileum were discovered. In one animal an additional infection with corona virus was confirmed electron microscopically. Furthermore there was disseminated necrosis of lymphocytes in Peyer's patches of the small intestine and in secondary follicles of the mesenteric lymph nodes. In one of the animals a hemorrhagic-necrotising ileitis, occurred characterized by necrosis of villi and thrombosis of blood vessels in the mucosa. The highest number of VTEC with seven out of twelve animals was found in weaned pigs in association with the E. coli serovar 0139.

Phenotypic expression of the HLA linked iron-loading gene in males over the age of 40 years: a population study using serial serum ferritin estimations

The frequency of the HLA linked iron-loading gene was assessed in 1783 Afrikaner men over the age of 40 years living in the South Western Cape. Measurements, made on three occasions over a 4.5 year period, included the serum ferritin concentration, a screening test for reduced unsaturated iron-binding capacity and the percentage transferrin saturation. The serum gamma-glutamyl transferase concentration was used as a marker of alcohol abuse. The diagnosis of homozygosity was based on a serum ferritin concentration that was persistently greater than 400 micrograms l-1 and a percentage transferrin saturation greater than 55%. Using these criteria, 17 subjects were diagnosed as homozygous, corresponding to a disease frequency of 0.0095, a gene frequency of 0.0976 and a heterozygote frequency of 0.176 (95% confidence limits: 0.135-0.213). None of the subjects had overt clinical haemochromatosis. Typing for the HLA-A, -B, -C and -DR loci showed that the HLA-A3 allele (frequency 0.6471 and relative risk 4.4) was the only independent marker for the iron-loading gene in this asymptomatic population. Using the present approach it was not possible to distinguish between heterozygotes, alcohol abusers and normal subjects with serum ferritin concentrations at the upper end of the normal range.

[Effect of verapamil on rate of restenosis following transluminal angioplasty of renal artery stenoses]

This prospective double-blind randomized study examined the effect of verapamil on restenosis after angioplasty of renal artery stenoses. 31 patients received placebo or 120 mg verapamil two or three times daily until the appointed day of the control angiography after 3 months. All patients received 1.5 g aspirin per day. In the control group (13 stenoses, 12 patients) the degree of stenoses increased from 35 +/- 15% immediately after PTA to 41 +/- 21% at repeat angiography 3 months after PTA, in the verapamil group (20 stenoses, 14 patients) from 35 +/- 16% to 43 +/- 22% (ns). Stenoses recurred in 23% of the stenoses in the placebo group and in 20% of the stenoses in the verapamil group (ns). 5 patients, who interrupted the therapy, were excluded from the evaluation. In the conclusion, verapamil does not decrease the incidence of restenosis after PTA of renal artery stenoses during concurrent therapy with aspirin.

Transient calcium release induced by successive increments of inositol 1,4,5-trisphosphate

Many hormonal, neurotransmitter, and sensory stimuli trigger the formation of inositol 1,4,5-trisphosphate, which in turn releases calcium from intracellular stores. We report here that inositol 1,4,5-trisphosphate-induced calcium release from saponin-permeabilized rat basophilic leukemia cells at 37 degrees C is markedly biphasic, in contrast with nearly monophasic release kinetics at 11 degrees C. Hepatoma, PC-12 neuronal cells, and several other cell types exhibit similar biphasic release at 37 degrees C. The biphasic kinetics are not due to degradation of inositol 1,4,5-trisphosphate or to increased Ca2(+)-ATPase pump activity. Biphasic calcium release was also seen when ATP was quenched to less than 0.4 microM by adding hexokinase and glucose, suggesting that phosphorylation is not involved. External calcium (100 nM-600 nM) range had little influence on the biphasic kinetics. Rapid-mixing experiments revealed that rapid efflux of calcium is followed in approximately 0.5 s by a 30-fold slower efflux. Most striking, successive additions of the same amount of inositol 1,4,5-trisphosphate induced short bursts of calcium release of similar size. This retention of responsiveness, which we term increment detection, may be a distinct mode of signal transduction. Like inactivation and adaptation, increment detection gives rise to transient responses to sustained stimuli. Systems exhibiting inactivation, adaptation, and increment detection differ in their responsiveness (none, partial, and full, respectively) to stepwise increases in stimulus intensity. Increment detection could be advantageous in generating receptor-triggered calcium oscillations.

Squamous cell carcinoma antigen in the diagnosis and treatment follow-up of oral and facial squamous cell carcinoma

The squamous cell carcinoma (SCC) antigen was determined by radioimmunoassay in the serum of 40 untreated patients with SCC of the oromaxillofacial region. The mean (+/- SEM) serum concentration for these patients (3.8 +/- 0.8 ng/ml) was significantly higher than that of 52 disease-free patients coming to routine postoperative care (1.2 +/- 0.1 ng/ml) and of 74 healthy controls (1.1 +/- 0.07 ng/ml). Using a arbitrary limit of 2.2 ng/ml, pathologic serum levels of SCC were observed in 15 (38%) of 40 untreated patients, whereas only four (7.7%) of 52 tumor-free patients revealed an elevated serum SCC. Serial measurements of SCC were pretherapeutically available in 28 patients as well as during individual therapy and further follow-up. All but one of these patients had a normal serum SCC postoperatively. The authors' results demonstrate that the clinical value of SCC lies mainly in monitoring the course of the disease. Careful follow-up studies should be undertaken to determine whether serial determination of SCC is promising in early prediction of tumor reoccurrence.

Kinetics of calcium channel opening by inositol 1,4,5-trisphosphate

The subsecond mobilization of intracellular Ca2+ by IP3 was measured with rapid mixing techniques to determine how cells achieve rapid rises in cytosolic [Ca2+] during receptor-triggered calcium spiking. In permeabilized rat basophilic leukemia cells at 11 degrees C, more than 80% of the 0.7 fmol of Ca2+/cell sequestered by the ATP-driven pump could be released by IP3. Half of the stored Ca2+ was released within 200 ms after addition of saturating (1 microM) IP3. The flux rate was half-maximal at 120 nM IP3. Ca2+ release from fully loaded stores was highly cooperative; the Hill coefficient over the 2-40 nM range was greater than 3. The delay time of channel opening was inversely proportional to [IP3], increasing from 150 ms at 100 nM IP3 to 1 s at 15 nM, indicating that the rate-limiting step in channel opening is IP3 binding. Multiple binding steps are required to account for the observed delay and nonexponential character of channel opening. A simple model is proposed in which the binding of four IP3 molecules to identical and independent sites leads to channel opening. The model agrees well with the data for KD = 18 nM, kon = 1.2 X 10(8) M-1 s-1, and koff = 2.2 s-1. The approximately 1-s exchange time of bound IP3 indicates that the channel gating sites are distinct from binding sites having approximately 100-s exchange times that were previously found with radiolabeled IP3. The approximately 1-1s response time of [Ca2+] to a rapid increase in IP3 level can account for observed rise times of calcium spikes.

Effects of converting-enzyme inhibition on barrier function in diabetic glomerulopathy

Differential solute clearances were used to examine the effects of a 90-day course of enalapril on glomerular barrier function in 16 proteinuric patients with diabetic glomerulopathy. By day 90, plasma renin and prorenin became elevated, and arterial pressure declined. Transglomerular passage of dextrans of broad size distribution (radii 28-60 A) was lowered significantly. In a subset of 8 patients, withdrawal of enalapril was followed after an additional 30 days by a return of renin levels and arterial pressure to pretreatment levels. The dextran-sieving profile also returned to baseline, becoming uniformly elevated above treated day-90 levels. A theoretical analysis of the serial dextran-sieving profiles indicated that enalapril shifted glomerular pore size distribution to smaller size. These changes in barrier size selectivity were associated with a reduction in fractional albumin and IgG clearances during enalapril therapy and a subsequent rise in these quantities after its withdrawal; urinary protein excretion rate tended to vary in parallel. We conclude that inhibition of converting enzyme in humans with established diabetic glomerulopathy diminishes glomerular permeability to proteins by enhancing barrier size selectivity. Because neither enalapril therapy nor its withdrawal influenced the glomerular filtration or renal plasma flow rates significantly, we propose that the primary action of enalapril may be to modulate the intrinsic membrane properties of the glomerular barrier.

Single primer pair for amplifying segments of distinct Shiga-like-toxin genes by polymerase chain reaction

By using a single synthetic oligonucleotide primer pair in the polymerase chain reaction, we amplified specific Shiga-like-toxin (SLT) gene segments from DNAs of 20 clinical Escherichia coli isolates, irrespective of whether they produce SLT-I, SLT-II, or heretofore uncategorized SLTs. These segments were not detectable in any of 20 nontoxigenic E. coli strains. The primers deduced from a conserved region among SLT genes are so-called degenerate-sequence primers; i.e., they contain intentionally introduced sequence ambiguities to overcome minor sequence variations within different SLT genes. In direct gel hybridization with genomic DNA, both primers recognized SLT-I and SLT-II DNA sequences. Amplified sequences of target DNA obtained by polymerase chain reaction were visualized after gel electrophoresis by ethidium bromide staining, and definitive identification of the amplification product as an SLT gene segment was achieved by hybridization to SLT-I- and SLT-II-specific 20-base oligonucleotide probes complementary to a portion of the amplified sequences but not to the primers. The detecting oligonucleotide probes shared only 30% base homology and were shown to recognize specifically SLT-I or SLT-II sequences within genomic DNA. Moreover, they were used to distinguish whether the amplified sequence originated from SLT-I or SLT-II genes. The PCR system with the primers described here is a powerful technique to amplify SLT sequences in E. coli strains that produce serologically distinct SLTs and will facilitate identification of these pathogens, particularly among a multitude of nonpathogenic E. coli strains.

Maternal and fetal sequelae of anticoagulation during pregnancy in patients with mechanical heart valve prostheses

Previous reports indicate an increased risk of thrombotic and embolic events in patients with mechanical heart valve prostheses during pregnancy. We prospectively followed 50 pregnancies in 49 patients with 62 cardiac prostheses from presentation at the antenatal clinic through the remainder of the pregnancy. Of the 60 mechanical prostheses, 39 were Medtronic-Hall, 7 St. Jude Medical, 7 Starr-Edwards and 7 Björk-Shiley. Forty-three patients were in New York Heart Association functional class I or II and 6 were in functional class III or IV. Forty-five patients were in sinus rhythm and 4 had chronic atrial fibrillation. All patients received warfarin during the first and second trimesters. Forty-one pregnancies proceeded beyond 28 weeks. In 23 of these (group I) warfarin was replaced with heparin at 36 weeks gestation. In the remaining 18 (group II) warfarin was not substituted owing to premature onset of labor. The target prothrombin ratio (international normalized ratio) in patients receiving warfarin was 2.0 to 2.5. The partial thromboplastin time was maintained at 1.5 to 2.5 times the control value in patients receiving heparin. Eleven patients received dipyridamole plus warfarin for the duration of pregnancy. There were no maternal thromboembolic complications or deaths associated with pregnancy. Antepartum hemorrhage occurred in 1 patient at 35 weeks gestation. One patient (group I) experienced peripartum hemorrhage. All patients were hemodynamically stable before delivery, but 2 developed pulmonary edema during labor. The mean fetal birth weight was low (2.54 +/- 0.98 kg). There were 9 abortions (18%), 7 stillbirths (14%), 2 neonatal deaths (4%) and 2 instances of warfarin embryopathy (4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of oligonucleotide probes for identification of shiga-like-toxin-producing Escherichia coli

Four synthetic oligonucleotide probes representing different regions of the Shiga-like toxin I (SLT-I) structural genes and one oligonucleotide derived from the SLT-II gene of Escherichia coli serotype O157:H7 strain 933 were examined for the identification of E. coli strains that produce cytotoxins for Vero or HeLa cells. E. coli strains that synthesize SLT-I alone or O157:H7 isolates that coexpress SLT-I and SLT-II hybridized with all four probes that were complementary to the SLT-I genes, suggesting that they have toxin genes with great homology in all the regions examined. In colony hybridization tests, these oligonucleotide probes did not react with E. coli strains that were nontoxigenic for Vero cells or that produced cytotoxins belonging to the SLT-II family. The probe derived from the slt-IIA gene distinguished E. coli strains that produced SLT-II alone from SLT-I-producing strains and hybridized to all E. coli O157:H7 strains that produced both SLT-I and SLT-II. Using two of these oligonucleotide probes that were complementary to slt-IA or slt-IIA sequences, we identified 50 of 52 cytotoxin-producing strains, whereas none of 416 nontoxigenic E. coli strains was reactive. The colony blot hybridization with the oligonucleotide probes described here can serve as a specific and sensitive test with potential diagnostic value.

A derivative of staurosporine (CGP 41 251) shows selectivity for protein kinase C inhibition and in vitro anti-proliferative as well as in vivo anti-tumor activity

Analogues of staurosporine were synthesized and their ability to inhibit protein kinases was examined. Staurosporine is a potent but non-selective inhibitor of in vitro protein kinase C(PKC) activity (IC50 6.0 nM). The derivative CGP 41 251 had reduced PKC activity with an IC50 of 50 nM but showed a high degree of selectivity when assayed for inhibition of cyclic AMP-dependent protein kinase (IC50 2.4 microM), S6 kinase (IC50 5.0 microM) and tyrosine-kinase-specific activity of epidermal growth factor receptor (IC50 3.0 microM). Staurosporine and CGP 41 251 exerted growth inhibition in the human bladder carcinoma line T-24, human promyelocytic leukemia line HL-60 and bovine corneal endothelial cells at concentrations which correlated well with in vitro PKC inhibition. In addition, both compounds inhibited the release of H2O2 from human monocytes pre-treated with 12-O-tetradecanoyl-phorbol-13-acetate at non-toxic concentrations. In vivo anti-tumor activity was examined in T-24 human bladder carcinoma xenografts in athymic nude mice. Tumor growth inhibition tests revealed significant anti-tumor activity (2p less than 0.001) at 1/10 of the maximum tolerated doses for both compounds. By contrast, a closely related derivative of staurosporine (CGP 42 700) was inactive at concentrations of over 100 microM in all in vitro enzyme and anti-proliferative assays as well as in animal tumor models. Our data suggest an association between PKC inhibition and anti-proliferative and anti-tumor activity.

The amino acid sequence of low-potential cytochrome c550 from the cyanobacterium Microcystis aeruginosa

The low-potential cytochrome c550 has been purified from the cyanobacterium Microcystis aeruginosa and its amino acid sequence has been determined. The protein contains 135 amino acid residues with the Cys-X-X-Cys-His heme binding site at residues 37 to 41. The sequence from residue 28 to 45 shows similarity to cytochrome c553 residues 1 to 18 when the heme binding sites are aligned. Another region of similarity is in the carboxyl-terminal regions of these two proteins. The two aligning regions of cytochrome c553 correspond to helical segments in other related cytochromes. A partial sequence of cytochrome c550 from Aphanizomenon flos-aquae was obtained and showed a 48% identity to the sequence of the M. aeruginosa cytochrome. The single methionine residue in cytochrome c550 of M. aeruginosa occurs at position 119 but there is no methionine in this region in the A. flos-aquae cytochrome, indicating that methionine is not the sixth ligand to the heme iron atom. Histidine 92 is a possible sixth ligand in M. aeruginosa cytochrome c550. The far-uv circular dichroism spectrum indicates that this protein is approximately 17% alpha helix, 42% beta-pleated sheet, and 41% random coil.

Genes coding for Shiga-like toxin and heat-stabile enterotoxin in porcine strains of Escherichia coli

Besides diarrheagenic enterotoxigenic Escherichia coli (ETEC) that produce classical heat stable and/or heat labile enterotoxins (STs, LTs) and the class of Shiga-like toxin-producing entero-hemorrhagic E. coli (EHEC), a new category of E. coli is defined sharing similarities with ETEC and EHEC. DNA hybridization studies indicate that some E. coli serovars from porcine origin harbor genes encoding cytotonic ST and cytotoxic Shiga-like toxin. The presence of two potent toxins might contribute to the virulence of such strains and should be taken into consideration when bio-assays are performed.

A rapid phospholipase A2 bioassay using 14C-oleate-labelled E. coli bacterias

Two methods of phospholipase A2 determination using 14C-labelled E. coli bacterias as substrate were compared. One method works with a filter membrane for separation of cleaved 14C-oleate from remaining phospholipids, the other uses the well-known thin-layer chromatography for lipid analysis. Some features of human serum phospholipase A2 regarding pH and Ca2+ dependency were investigated. Possible sources of errors were discussed. It was shown that either method can differentiate between normal and pathologically elevated phospholipase A2 levels, but that the filter method is superior in terms of sensitivity and workload.

Characterization of phospholipase A2 activity in aspirates of human pancreatic pseudocysts after isolation by reversed-phase high performance liquid chromatography

Phospholipase A (PLA) is able to attack membrane phospholipids and thereby plays a putative role in the pathogenesis of pancreatic pseudocysts. We looked for PLA2-like activity in aspirates from human pancreatic pseudocysts. In material originating from one cyst which occurred shortly after an acute pancreatitis attack, hydrolyzing enzymatic activity measured by a sensitive bioassay system for PLA2 activity was found without prior trypsin activation (67 x 10(3) U/min/100 microliters). A biochemical characterization of this hydrolyzing enzymatic activity was provided after resolution of the respective proteins contained in the cyst fluid by HPLC. High hydrolyzing activities were found in correspondence to one specific, early eluting peak. The purified enzyme had pH optima at 3.5 and 6. Addition of EDTA (5 mM) to the test system abolished the enzymatic activity which mirrored the requirement for calcium ions. The activity was optimal at calcium concentrations ranging from 1-2 mM. Higher calcium concentrations reduced the enzymatic activity. The enzyme showed high heat stability. SDS-gel analysis of the peak showed one single band with a molecular weight of about 20,000 Daltons. Our findings demonstrate the possibility of activated, PLA-like activity in human pancreatic pseudocyst fluid. We speculate that an inappropriate activation of this enzyme in peri- or intrapancreatic "fluid collections" could account for pseudocyst formation after an acute pancreatitis attack.

Synthetic oligodeoxyribonucleotide probes to detect verocytotoxin-producing Escherichia coli in diseased pigs

Oligonucleotide probes constructed from the sequences published for Shiga-like toxin I (SLT-I) and Shiga-like toxin II (SLT-II) genes and antibody against the purified toxins were used to study the SLT (SLT-IIp) produced by porcine E. coli O138 and O139 strains. By DNA hybridization assays no homology was observed between SLT-I and SLT-IIp. By contrast the oligonucleotide probe derived from the slt-II A gene detected porcine strains of E. coli producing SLT-IIp and E. coli strains associated with human disease producing SLT-II. Homology of nucleotide sequences between SLT-IIp and SLT-II is reflected by serological cross-reactivity as demonstrated by a dot blot ELISA and neutralization of SLT-IIp with anti-SLT-II. The toxins were distinguishable in their ability to kill HeLa S-3 cells. The oligonucleotide probe and anti-SLT-II can facilitate identification of SLT-IIp producing E. coli to further clarify their role in diseased pigs.

Particle counting by fluorescence correlation spectroscopy. Simultaneous measurement of aggregation and diffusion of molecules in solutions and in membranes

A method for simultaneous determination of molar weights (M) and lateral diffusion constants (D) of particles in three- and two-dimensional systems is described. Spontaneous concentration fluctuations in space and time are analyzed, by monitoring fluctuations in the fluorescence from fluorescein-labeled molecules (1 dye/molecule is sufficient), excited by a rotating laser spot. For particles in solution, M values are determined over the range of 3 x 10(2) to 3 x 10(11) daltons, and D values can be determined from approximately 10(-7) to 10(-10) cm2/s. The time for a determination is approximately 1 min. Aggregation can be followed by changes of either M or D. This method is used to study the calcium dependence of vesicle aggregation or fusion, and the time course of aggregate formation of porin (an Escherichia Coli outer membrane protein) in lipid monolayers. Essential parameters for the development of the method are described. Equations to estimate the signal-to-noise ratios and to find the optimal free parameters for a specific application are derived. The theoretical predictions for the correlation function of the signal and for the signal-to-noise ratio are compared with observed values.

ADP-ribosyl proteins formed by pertussis toxin are specifically cleaved by mercury ions

Various types of ADP-ribosyl protein conjugates were synthesized and their chemical stability was compared with that of cysteine-linked ADP-ribosyl groups as formed by incubation of transducin or Gi/Go proteins with NAD and pertussis toxin. Treatment with 0.1 mM HgCl2 specifically cleaved the cysteine-linked conjugates. This may provide a tool for the quantitation of modified Gi/Go proteins as well as of other acceptors modified by ADP-ribose at cysteine residues in the presence of other ADP-ribosyl proteins.

Molecular model for receptor-stimulated calcium spiking

Many cells exhibit periodic transient increases in cytosolic calcium levels rather than a sustained rise when stimulated by a hormone or growth factor. We propose here a molecular model that accounts for periodic calcium spiking induced by a constant stimulus. Four elements give rise to repetitive calcium transients: cooperativity and positive feedback between a pair of reciprocally coupled (crosscoupled) messengers, followed by deactivation and then by reactivation. The crosscoupled messengers in our model are inositol 1,4,5-trisphosphate (InsP3) and cytosolic calcium ions. The opening of calcium channels in the endoplasmic reticulum by the binding of multiple molecules of InsP3 provides the required cooperativity. The stimulation of receptor-activated phospholipase C by released calcium ions leads to positive feedback. InsP3 is destroyed by a phosphatase, and calcium ion is pumped back into the endoplasmic reticulum. These processes generate bistability: the cytosolic calcium concentration abruptly increases from a basal level to a stimulated level at a threshold degree of activation of phospholipase C. Spiking further requires slow deactivation and subsequent reactivation. In our model, mitochondrial sequestration of calcium ion prevents the cytosolic level from increasing above several micromolar and enables the system to return to the basal state. When the endoplasmic reticulum calcium store is refilled to a critical level by the Ca2+-ATPase pump, cooperative positive feedback between the InsP3-gated channel and phospholipase C begins again to give the next calcium spike. The time required for the calcium level in the endoplasmic reticulum to reach a threshold sets the interval between spikes. The amplitude, shape, and period of calcium spikes calculated for this model are like those observed experimentally.

Highly cooperative opening of calcium channels by inositol 1,4,5-trisphosphate

The kinetics of calcium release by inositol 1,4,5-trisphosphate (IP3) in permeabilized rat basophilic leukemia cells were studied to obtain insight into the molecular mechanism of action of this intracellular messenger of the phosphoinositide cascade. Calcium release from intracellular storage sites was monitored with fura-2, a fluorescent indicator. The dependence of the rate of calcium release on the concentration of added IP3 in the 4 to 40 nM range showed that channel opening requires the binding of at least three molecules of IP3. Channel opening occurred in the absence of added adenosine triphosphate, indicating that IP3 acts directly on the channel or on a protein that gates it. The channels were opened by IP3 in less than 4 seconds. The highly cooperative opening of calcium channels by nanomolar concentrations of IP3 enables cells to detect and amplify very small changes in the concentration of this messenger in response to hormonal, sensory, and growth control stimuli.

Identification of rat pancreatic secretory proteins after separation by high-performance liquid chromatography

In the present study an improved method of reversed-phase high-performance liquid chromatography (HPLC) for separation of rat pancreatic juice proteins is introduced. Aliquots of pancreatic juice were saved from conscious rats during basal secretion. The secretory proteins were separated on a wide-pore silica column by use of a multistep acetonitrile/water gradient. Up to 14 individual peaks could be separated by one run. Molecular weight analysis by sodium dodecyl sulfate (SDS)-gels allowed identification of peaks representing amylase, lipase, procarboxypeptidases, proelastase, chymotrypsinogen, and trypsinogen. Injection of pure rat amylase increased one specific peak which was assumed to represent amylase in the juice profile. Small amounts of residual enzymatic activities were measured for amylase, trypsin, and chymotrypsin in material of certain peaks. Activities of lipase, ribonuclease, and carboxypeptidases were not found, which reflected degradation of these enzymes by the separation procedure. High activities of phospholipase A2 were detected in one specific, early-eluting peak. Reversed-phase HPLC offers precise, reproducible, and rapid separation of the major proteins of rat pancreatic juice.

Comparison of the electrical properties of neocortical neurones in slices in vitro and in the anaesthetized rat

Because neurones in isolated brain slices are abnormal in several respects, we have compared the electrical properties of neocortical neurones from the anaesthetized rat with neurones from slices of the same area of neocortex in vitro. Resting potentials were not significantly different but there was a small increase in mean spike amplitude and threshold in slices. The most striking observation was a doubling of the mean apparent input resistance (Rin) of neurones in slices (36 M omega cf. 18 M omega in vivo). To assess the extent to which the loss of surface membrane of neurones in slices might contribute to the raised Rin, we estimated the membrane capacity of neurones in the two samples from calculations of the membrane time constants. The mean membrane capacity was significantly lower in neurones from slices, being 2/3 that of the in vivo sample, showing that recordings were indeed mostly from smaller cells in the slices. Possible causes of the difference in mean input resistance not attributable to neuronal size are also discussed.

Enhancement of N-methyl-N'-nitro-N-nitrosoguanidine-induced DNA amplification in a Simian virus 40-transformed Chinese hamster cell line by 3-aminobenzamide

A Simian virus 40-transformed Chinese hamster cell line (CO 60) amplifies integrated viral DNA sequences as a response to treatment with a variety of carcinogens. To study a possible involvement of poly(ADP-ribose) synthesis, DNA amplification was induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), an alkylating carcinogen that strongly stimulates poly(ADP-ribose) synthesis. In the presence of 3-aminobenzamide (3AB) (2 mM), a competitive inhibitor of poly(ADP-ribose) polymerase, MNNG-induced amplification was increased two to six times the level induced by MNNG alone. Concomitantly, 3AB reduced cellular poly(ADP-ribose) levels and increased MNNG-induced cytotoxicity, as expected. The effect of 3AB on MNNG-induced amplification depended both on the concentration of 3AB and the duration of its presence after MNNG treatment. By contrast, 3-aminobenzoic acid, a noninhibitory structural analogue of 3AB, had no influence on amplification induced by MNNG. These data strongly suggest an involvement of poly(ADP-ribose) in the process of DNA amplification, as it is shown that inhibition of carcinogen-stimulated poly(ADP-ribose) synthesis by 3AB is correlated with an enhancement of inducible DNA amplification in this cell line.

Echocardiographic and hemodynamic correlates of diastolic closure of mitral valve and diastolic opening of aortic valve in severe aortic regurgitation

Acute severe aortic regurgitation (AR) is characterized by a steep increase in left ventricular end-diastolic pressure, exceeding left atrial pressure and occasionally equilibrating with aortic diastolic pressure. These pressure phenomena correlate with the M-mode echocardiographic (echo) findings of diastolic closure of the mitral valve (DCMV) and diastolic opening of the aortic valve (DOAV). Six men, aged 23 to 48 years, with recent-onset, severe AR were evaluated by M-mode echo and pressures at cardiac catheterization. DCMV was seen in all 6 patients and DOAV in 4. Near-constant time intervals from the preceding R wave of the electrocardiogram to DCMV and DOAV were seen, even in 3 patients with varying RR intervals (1 with atrial fibrillation and 2 with asynchronous and demand atrial pacing). When the RR intervals were shorter than these intervals, DCMV and DOAV did not occur. Increasing the heart rate in the 2 patients by atrial pacing resulted in a marked decrease in left ventricular end-diastolic pressure. In conclusion, DCMV and DOAV have a near constant relation to the preceding R wave of the electrocardiogram, DCMV with competence of the mitral valve must be present for DOAV to occur, DOAV indicates that the diastolic blood pressure equals left ventricular end-diastolic pressure, and heart rate is an important factor influencing the hemodynamic and echocardiographic parameters in recent-onset, severe AR.

The lipophilic muramyltripeptide MTP-PE, a biological response modifier, is an activator of protein kinase C

The lipophilic immunomodulator MTP-PE is able to activate purified protein kinase C (PKC) by substituting phosphatidyl-serine (PS) or the synthetic diacylglycerol, DiC8, in the assay system. In addition, MTP-PE inhibited [3H]-phorbol-12, 13-dibutyrate ([3H]-PDBu) binding to PKC in a reconstituted receptor system as well as on intact cells (MCF-7). Furthermore, MTP-PE was also able to reduced the epidermal growth factor binding of MCF-7 cells to an extent similar to that found with DiC8 or PDBu. These data indicate that MTP-PE is able to compete for the phorbol ester binding site on PKC both in vivo and in vitro. The components of the MTP-PE molecule, MTP (muramyl-tripeptide) and PE (phosphatidylethanolamine) exerted only marginal effects on PKC activity, did not affect the phorbol ester binding of PKC and the EGF binding of intact MCF-7 cells. Our results suggest that only the complete molecule of the immunomodulator MTP-PE is able to interact with PKC.

[CEA studies in squamous cell carcinomas of the head and neck]

The serum CEA levels of 134 patients with squamous cell carcinoma of the head and neck were studied at the time of diagnosis, at the end of primary therapy and every three months during the follow-up period. Since such patients are mostly nicotine and alcohol addicts, only CEA concentrations above 5 ng/ml were regarded as abnormal. At the time of diagnosis 30% of the patients had clearly abnormal CEA values, more commonly in oropharyngeal and hypopharyngeal tumours than for oral and laryngeal carcinomas. The incidence of pathological CEA concentrations also increased with increasing tumour extension, to a greater extent in well-differentiated than in undifferentiated squamous cell carcinomas. After termination of the primary therapy we found no correlation between success of treatment and serum CEA concentration. Studies of the course of CEA values in tumour-free patients revealed both rising and falling serum values during the period of observation. It was not possible to diagnose tumour recurrence early with the aid of increasing CEA concentrations. CEA exhibits only moderate sensitivity towards squamous cell carcinomas of the head and neck. As correlations between the course of the disease and CEA concentrations in serum could only rarely be observed, the usefulness of this tumour marker for following the course of head and neck squamous cell carcinoma must be regarded as rather low.

Antagonism of interferon induction in spleen and adherent peritoneal cells of mice by the lipophilic antiviral muramyl peptide MTP-PE

The immunomodulator muramyl tripeptide-phosphatidylethanolamine (MTP-PE) has been shown to enhance host resistance against a variety of experimental infections and to cure influenza virus infection in mice when given in a single dose, even at a late stage of the disease. Tests of its capacity to induce alpha/beta- and gamma-interferon (IFN-alpha/beta and -gamma) in vitro demonstrated that it is neither an inducer nor a primer of IFN synthesis. On the contrary, we found that it inhibits the induction of IFN-alpha/beta and -gamma by poly(rI:rC), Newcastle disease virus, lipopolysaccharide, or concanavalin A in adherent cells from the peritoneal cavity and spleen of mice. The antiviral activity of already induced or exogenously added murine IFN was, however, not impaired.

Production of anti-(ADP-ribose) antibodies with the aid of a dinucleotide-pyrophosphatase-resistant hapten and their application for the detection of mono(ADP-ribosyl)ated polypeptides

Previous attempts to produce anti-(ADP-ribose) antibodies by immunization of rabbits with ADP-ribose conjugated to serum albumin had resulted in the production of 5'AMP-specific antibodies [Bredehorst et al. (1978) Eur. J. Biochem. 82, 105-113]. To obtain true anti-(ADP-ribose) antibodies an antigen was constructed that was resistant to enzymic degradation at the pyrophosphate group. The enzymically active beta-methylene derivative of NAD (NAD[CH2]) was synthesized from ADP containing a methylene bridge (CH2) instead of an oxygen in the diphosphate group. NAD[CH2] was converted to its N6-[(2-carboxyethyl)thiomethyl] derivative and hydrolyzed to the corresponding ADP[CH2]-ribose derivative which was then coupled to bovine serum albumin. The antibodies obtained with this antigen were specific for free or protein-bound ADP-ribose groups, except for a cross-reaction with FAD, AMP, ADP, ATP or poly(ADP-ribose) interfered with [3H]ADP-ribose tracer binding only at higher concentrations. No interference was observed with poly(A), RNA and DNA at 6000-fold excess. The antibodies were purified on a novel type of affinity matrix. This was formed from NAD and guanidinobutyrate by a cholera-toxin-catalyzed reaction and the product, ADP-ribosyl guanidinobutyrate, was bound to Affi Gel by carbodiimide-aided condensation. The purified antibodies allowed the detection of ADP-ribose conjugated to polypeptides in amounts lower than 1 pmol as demonstrated by immunoblotting of [14C]ADP-ribosylated elongation factor 2. They also could be used to observe in situ, by indirect immunofluorescence, the increased mono(ADP-ribosyl)ation of nuclear proteins in dimethyl-sulfate-treated cells, and to show that histone H2B was the principal histone acceptor of single ADP-ribose groups in alkylated 3T3 cells.

NAD[S], an NAD analogue with reduced susceptibility to phosphodiesterase. Chemical synthesis and enzymic properties

The chemical synthesis of adenosine(5') [alpha-thio]diphospho(5')ribofuranosyl-nicotinamide (NAD[S]) is described. The product occurs as a pair of diastereomers with different configuration at the sulfur-bearing phosphorus atom. The diastereomers were separated by high-performance liquid chromatography and their absolute configuration was determined after chemical degradation to the ADP[alpha S] diastereomers and chromatographic comparison with enzymically synthesized ADP[alpha S] diastereomers of known absolute configuration. Additional support for this assignment is based on different rates in the phosphodiesterase-catalyzed hydrolysis. Furthermore the synthesis of [14C]NAD[S] is described. The coenzyme activity of NAD[S] in the reaction with alcohol dehydrogenase from baker's yeast and lactate dehydrogenase from pig heart is very similar to that of beta-NAD. Also, NAD and NAD[S] serve equally well as substrates for NAD glycohydrolase from calf spleen. In contrast, no reaction was detected with NAD pyrophosphorylase, and hydrolysis of the separated NAD[S] diastereomers with snake venom phosphodiesterase showed a 26-fold and a 33-fold slower reaction rate than that of NAD. Nucleotide pyrophosphatase was less sensitive to the S substitution, hydrolyzing NAD[S] 14-times slower than NAD. Poly(ADP-ribose) polymerase from Ehrlich ascites tumor cell nuclei accepted NAD[S] as a substrate but the reaction was significantly slower and approached saturation at much lower values than with NAD. Alkaline hydrolysis of the products insoluble in trichloroacetic acid yielded AMP[S] as the main derivative. It is concluded that with NAD[S] as a substrate the nuclear acceptors were nearly exclusively mono(ADP-ribosyl) ated .

Lupus erythematosus with erythema multiforme (Rowell's syndrome). A case report

A patient who presented with erythema multiforme on clinical and histological examination but who subsequently developed fatal, fulminant systemic lupus erythematosus is reported. The prognostic significance of the development of erythema multiforme-type lesions in lupus erythematosus is discussed with reference to cases reported by Rowell et al. and Provost et al. The term 'Rowell's syndrome' is best avoided.

Combined action of mouse alpha and beta interferons in influenza virus-infected macrophages carrying the resistance gene Mx

In mice, the combined action of alpha and beta interferons (IFNs) against influenza viruses is modulated by the host gene Mx. High concentrations of IFN fail to prevent efficiently the replication of influenza A virus in cultured macrophages lacking the gene Mx, whereas cultured macrophages carrying Mx develop strong antiviral activity even at low concentrations of IFN. Several steps in the replication cycle of influenza virus were compared in Mx/Mx and +/+ mouse macrophages treated with IFN-alpha + beta. Uncoating was not affected. A twofold reduction in the accumulation of primary transcripts was observed in IFN-treated macrophages at the highest concentration of IFN regardless of the genetic constitution of the host cell. No evidence was obtained for inhibition of influenza virus translation in macrophages which lacked Mx when treated with IFN-alpha + beta. In contrast, a marked shut-off of influenza virus polypeptide synthesis occurred in Mx-bearing macrophages treated with these IFNs, although the primary transcripts were active in directing the synthesis of viral polypeptides in a cell-free system. We concluded that a specific inhibitory mechanism for influenza virus translation was induced by IFN-alpha + beta in macrophages bearing the resistance gene Mx.

Molecular structure and biochemical activity of 3,5,3'-triiodothyronamine

The thyroid hormone decarboxylation product, 3,5,3'-triiodothyronamine (T3AM), has been shown to inhibit the cAMP production stimulated by isoproterenol in turkey erythrocytes. This adrenergic receptor binding inhibition was not shown by the thyroid hormones nor by tyramine, but was observed for 3,5-diiodotyramine, 3,5-diiodothyronamine, and thyronamine. T3AM also inhibits prolactin secretion in cultured pituitary cells as well as domperidon binding in rat corpora striata membranes. T3AM has no thyromimetic activity at the nuclear level. The molecular structure of T3AM, determined as a borosalicylate salt by X-ray diffraction techniques, is the first report of a decarboxylated thyroid hormone analogue.

Triiodothyronamine--a beta-adrenergic metabolite of triiodothyronine?

Triiodothyronamine (Triam) is a potential metabolite of triidothyronine (T3), resulting from decarboxylation of the side-chain. In an attempt to elucidate the physiological properties of Triam we have investigated the binding of Triam to beta-adrenergic receptors, using turkey-erythrocytes and performing binding studies with ( (-)(3H)-dihydroalprenolol) ( (-)(3H)-DHA) as a specific beta-adrenergic ligand. The inhibition constant Ki for Triam was determined as 5 X 10(-6) M, compared to dopamine (Ki = 1,3 X 10(-2) M), norepinephrine (Ki = 3 X 10(-4) M), epinephrine (Ki = 5 X 10(-5) M) and isoproterenol (Ki = 3 X 10(-6) M). The inhibition of ( (-)(3H)-DHA)-binding by Triam was further compared with other iodothyronines thyroxine (T4), T3, 3,3',5'-triiodothyronine (rT3) and 3,3'-diiodothyronine (3,3'-T2). It is concluded that Triam binds to beta-adrenergic receptors like naturally occurring amines but different from typical circulating iodothyronines.