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P Rosenberg

Publications and source records attributed to P Rosenberg.

At least 19 recordsLinked to original sources
PubMed1992

Effects of snake venom phospholipase A2 toxins (beta-bungarotoxin, notexin) and enzymes (Naja naja atra, Naja nigricollis) on aminophospholipid asymmetry in rat cerebrocortical synaptosomes.

The effects of snake venom phospholipase A2 (PLA2) toxins (beta-bungarotoxin, notexin) and PLA2 enzymes (Naja nigricollis, Naja naja atra) on aminophospholipid asymmetry in rat cerebrocortical synaptic plasma membranes (SPM) were examined. Incubation of intact synaptosomes with 2 mM 2,4,6-trinitrobenzene sulfonic acid (TNBS) for 40 min, under non-penetrating conditions, followed by SPM isolation, allowed us to calculate the percentage of phosphatidylethanolamine (PE) and phosphatidylserine (PS) in the outer leaflet of the SPM, while incubation with disrupted synaptosomes provided total labeling values with the difference representing labeling of the inner leaflet. We found that 30% of the PE and 2% of the PS were in the outer leaflet, with 54% of the PE and 80% of the PS in the inner leaflet; 16% of the PE and 18% of the PS was inaccessible to TNBS. PLA2 toxins and enzymes increased in a concentration-dependent manner the percentage of PS and, to a lesser extent, the percentage of PE in the outer leaflet of the SPM, due to a redistribution from the inner to the outer leaflet. There was no correlation between the PLA2 enzymatic activities and the increased percentage of PS in the outer leaflet of the SPM induced by the PLA2 toxins and enzymes. Alteration of aminophospholipid asymmetry does not explain the greater presynaptic specificity and potencies of the PLA2 toxins as compared to the PLA2 enzymes, but may be associated with the increased acetylcholine release from synaptosomes induced by both the toxins and enzymes.

Animals↗
PubMed1992

An EDTA.Ca2+ complex inhibits the enzymatic activity but not the lethality of beta-bungarotoxin.

An EDTA.Ca2+ complex inhibits the phospholipase A2 activity of the presynaptic neurotoxin beta-bungarotoxin without affecting its lethal potency. The EDTA.Ca2+ complex induces a conformational change in the enzymatic active site region of beta-BuTx, as indicated by the suppression of the 340 nm tryptophan fluorescence peak. Modification of the enzymatic site without loss of toxicity supports the presence of separate loci for the two activities.

Animals↗
PubMed1992

Haemodynamic changes during spinal anaesthesia with slow continuous infusion or single dose of plain bupivacaine.

Forty elderly patients, scheduled for orthopaedic surgery of the hip or knee were studied. Twenty patients received a single-dose spinal anaesthesia with 3 ml of plain 0.5% bupivacaine (SDSA group). Twenty patients received continuous spinal anaesthesia using a 32- or 22-gauge catheter. A bolus of 1.0 ml of plain 0.5% bupivacaine was given to ten patients and 0.5 ml to another ten, continued by an infusion at a rate of 2 ml/h. The spread of analgesia and haemodynamic changes (central venous pressure, arterial pressures, need for sympathomimetic medication) were registered. The mean dose of bupivacaine was 2.9 ml (range 1.5-5 ml) in the CSA group (3.0 ml in the SDSA group). Eight patients in the CSA group needed medication for pain during surgery compared to five patients in the SDSA group (n.s.). The median level of pinprick analgesia at 60 min was T11 in the CSA and T6.5 in the SDSA group (P less than 0.01). The mean maximum decreases in CVP and MAP were quite similar in the CSA and SDSA group (2.1 vs 2.8 mmHg (0.3 vs 0.4 kPa) and 17 vs 21 mmHg (2.3 vs 2.8 kPa), respectively) (n.s.). Six patients in the SDSA group and four patients in the CSA group needed sympathomimetic medication. It is concluded that titration of bupivacaine for spinal anaesthesia caused only minor haemodynamic changes which were similar to those after single-dose spinal bupivacaine.

Aged↗
PubMed1992

Inhibition of phosphorylation of synapsin I and other synaptosomal proteins by beta-bungarotoxin, a phospholipase A2 neurotoxin.

Some snake venom neurotoxins, such as beta-bungarotoxin (beta-BuTX), which possess relatively low phospholipase A2 (PLA2) activity, act presynaptically to alter acetylcholine (ACh) release both in the periphery and in the CNS. In investigating the mechanism of this action, we found that beta-BuTX (5 and 15 nM) inhibited phosphorylation, in both resting and depolarized synaptosomes, of a wide range of proteins, including synapsin I. Naja naja atra PLA2, which has higher PLA2 activity, also inhibited phosphorylation but was less potent than beta-BuTX. At 1 nM, beta-BuTX and N. n. atra PLA2 inhibited phosphorylation of synapsin I only in depolarized synaptosomes. Synaptosomal ATP levels were not affected by 5 or 15 nM beta-BuTX or by 5 nM N. n. atra PLA2. Limited proteolysis, using Staphylococcus aureus V-8 protease, indicated that beta-BuTX inhibited phosphorylation of synapsin I in both the head and the tail regions. The inhibition of phosphorylation was not antagonized by nordihydroguaiaretic acid or indomethacin, suggesting that arachidonic acid derivatives do not mediate this inhibition. Furthermore, inhibition of phosphorylation by beta-BuTX and N. n. atra PLA2 was not altered in the presence of the phosphatase inhibitor okadaic acid, suggesting that stimulation of phosphatase activity is not responsible for this inhibition. Inhibition of protein phosphorylation by PLA2 neurotoxins and enzymes may be associated with an inhibition of ACh release.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1992

Hypotensive anesthesia for middle ear surgery: a comparison of propofol infusion and isoflurane.

An infusion of propofol (2,6-diisopropylphenol) was compared with isoflurane to induce hypotension for middle ear surgery. Forty patients (ASA physical status I-II, 16-55 years) scheduled for elective surgery were included in an open randomized study. The pharmacokinetics of propofol infusion were also studied in 6 patients. Both agents produced controlled hypotension (MAP reduction of 30% from the baseline values) with an acceptable visibility of the surgical field. No major complications occurred. The mean total dose of propofol infusion was 6.4 +/- 2.7 mg/kg and the mean concentration of isoflurane was 0.9 +/- 0.4%. Considerable interindividual pharmacokinetic variability was found and propofol was extensively distributed and rapidly cleared from the body after the infusion. Propofol infusion may be a new alternative as a hypotensive agent in middle ear surgery.

Adolescent↗
PubMed1991

Effects of diisopropyl phosphofluoridate, sarin and soman on the accessibility of proteins, in the electroplax membrane, to lactoperoxidase-catalyzed iodination.

Anticholinesterases (anti-ChE) have some effects on biological properties including behavior, vision, and electroencephalograms, which are often long lasting and which do not appear to be due to cholinesterase (ChE; EC 3.1.1.7) inhibition, but which may be due to alterations in the organization and/or functioning of the cellular membrane. We assessed the effects of anti-ChE agents on the asymmetric organization of proteins in the innervated (excitable) and in the non-innervated (non-excitable) plasma membrane of the electroplax from the electric eel. Lactoperoxidase-catalyzed iodination (LCI) was carried out under impenetrable conditions in intact electroplax (where protein exposure on the external surface is monitored) and in split electroplax (where total protein labeling on both the external and internal monolayers of the plasma membrane bilayer is monitored). Labeling in split electroplax was much greater than in intact electroplax for all molecular weight groupings of proteins (30,000 to greater than 200,000). The anti-ChE agents diisopropyl phosphofluoridate (DFP; 10(-3) M), sarin (10(-4) M) and soman (10(-4) M, 10(-6) M, 2.5 x 10(-9) M) did not alter permeability, protein content or the electrophoretic pattern of the plasma membrane proteins of the electroplax. DFP, sarin and 10(-6) M soman (but not 2.5 x 10(-9) M or 10(-4) M soman) increased labeling of some of the molecular weight fractions in the non-innervated plasma membrane as monitored by LCI in intact electroplax. Under these same conditions, DFP and 10(-4) M soman increased labeling in the innervated plasma membrane while 10(-6) M soman decreased labeling. When LCI was carried out in split electroplax, 10(-4) M soman caused a decrease in labeling in both the innervated and non-innervated plasma membrane indicating a decrease of exposed proteins on the cytoplasmic surface of the plasma membrane. These concentrations of the anti-ChE agents caused almost complete ChE inhibition in the electroplax cells, except for 2.5 x 10(-9) M soman which caused little or no inhibition. These results suggest that alterations in protein asymmetry, as monitored by LCI of accessible proteins, are not directly due to ChE inhibition. These changes in organization of membrane proteins could contribute to a variety of effects of anti-ChE agents which are not due to ChE inhibition.

Animals↗
PubMed1991

Comparative effects of phospholipase A2 neurotoxins and enzymes on membrane potential and Na+/K+ ATPase activity in rat brain synaptosomes.

Beta-Bungarotoxin (beta-BuTX) and notexin are phospholipase A2 (PLA2) neurotoxins which cause an irreversible blockade of neurotransmitter release through specific and potent effects at the presynaptic nerve terminal; however, their mechanism of action is uncertain. We examined the effects of beta-BuTX and notexin on Na+/K+ ATPase activity using Sprague-Dawley rat brain synaptosomes in order to determine if alterations in activity might modulate neurotoxin-induced depolarization. Treatment of synaptosomes with 0.05 to 5 nM beta-BuTX, notexin, and Naja naja atra and Naja nigricollis PLA2 (PLA2 enzymes without selective presynaptic actions) caused a dose-dependent depolarization of synaptosomes with no differences being observed between the effects of the PLA2 neurotoxins and enzymes. N. nigricollis PLA2 (0.5 nM; 20 min) slightly stimulated Na+/K+ ATPase activity while beta-BuTX and notexin (0.5 nM: 10 and 20 min) were without effect. With 50 nM concentrations beta-BuTX and notexin stimulated Na+/K+ ATPase activity, while N. nigricollis and N. n. atra PLA2 inhibited activity. The effects on membrane potential and Na+/K+ ATPase were antagonized or blocked by EDTA (10 mM) and bovine serum albumin (1 mg/ml), suggesting that PLA2 enzymatic activity is essential for their effects on membrane potential and Na+/K+ ATPase activity. Following neurotoxin and enzyme pretreatment, we found a biphasic correlation between synaptosomal free fatty acid (FFA) levels and Na+/K+ ATPase activity, where Na+/K+ ATPase is stimulated by low levels of FFA (0.13 to 0.22 mumol/mg protein) and antagonized by FFA levels in excess of 0.34 mumol/mg protein. In contrast there was a linear correlation between the extent of FFA production and membrane depolarization. We propose that the presynaptic depolarizing actions of beta-BuTX and notexin are not mediated through modulation of Na+/K+ ATPase activity and that the changes observed in ATPase activity and possibly membrane potential are directly due to PLA2 enzymatic activity and the production of FFA.

Animals↗
PubMed1991

A new method for finding long consensus patterns in nucleic acid sequences.

We describe a fast computer algorithm for identifying consensus patterns in DNA sequences. The method requires no prior assumptions about the consensus pattern other than its length. In particular no previous knowledge of the frequency or spacing of consensus patterns is required. However, a priori information about the shape of the consensus pattern, or invariability of individual positions, or the overall conservation level, can be utilized to enhance the selectivity and sensitivity of search. As the number of all possible consensus words increases very rapidly with length, comprehensive searches have usually been restricted to a maximum of 10-12 nucleotides, even when large mainframes are used. Our algorithm enables searching for consensus patterns of this order on current mid-range and powerful microcomputers. Searches may be conducted on single, long sequences or a set of possibly aligned shorter sequences. We give examples of identified consensus patterns in both prokaryotic and eukaryotic DNA sequences, along with some typical program timings.

Base Sequence↗
PubMed1991

Effect of verapamil on right ventricular pressure and atrial tachyarrhythmia after thoracotomy.

We have studied the effect of verapamil on the incidence of ECG changes and right ventricular pressures (RVP) in 25 male patients (aged 62 (SD 9) yr) undergoing thoracotomy in a placebo-controlled double-blind trial. Verapamil 0.01 mg kg-1 h-1 (n = 12) or saline (n = 13) i.v. was started after surgery and continued on the first day after operation with oral verapamil 80 mg or placebo, 8-hourly. Haemodynamic data were collected before operation and on three days after operation with the patients breathing air and then 60% oxygen (FIO2 0.60) for 10 min. Atrial tachyarrhythmia (AT) (4/13) and new ischaemic ECG changes (3/13) occurred only in the control group (P less than 0.05). With an FI02 of 0.21, systolic RVP increased by 54% on the first two days after operation in the control group and by 13% in the verapamil group (P less than 0.02). With an FIO2 of 0.60 for 10 min, systolic RVP decreased more in the control than in the verapamil group (P less than 0.01). In the control group, an increase in end-diastolic RVP (P less than 0.001) and central venous pressure (P less than 0.05) on the first day after operation was predictive of AT occurring on the second day.

Administration, Oral↗
PubMed1991

Phosphatidylcholine asymmetry in electroplax from the electric eel: use of a phosphatidylcholine exchange protein.

Phosphatidylcholine asymmetry in the inner and outer leaflets of the plasma membrane bilayer of the innervated and noninnervated surfaces of the electroplax cell was determined, using a phosphatidylcholine exchange protein. The exchange protein from bovine liver catalyzed the exchange of phosphatidylcholine from small unilamellar vesicles to the outer monolayer of the plasma membrane bilayer. The exchange protein did not penetrate to the inner monolayer of the plasma membrane, did not modify the permeability of the electroplax, and did not alter the phospholipid or cholesterol content of the electroplax. In the innervated plasma membrane, 42% of the phosphatidylcholine is in the outer leaflet, 33% is in the inner leaflet, and 25% is inaccessible to the exchange protein. Corresponding values for the noninnervated plasma membrane are 56, 26, and 18%, respectively. These results are similar to phosphatidylcholine asymmetry in other biological membranes. This unique cell can be used as a model to test the effects on phospholipid asymmetry of compounds that act on the membrane.

Androgen-Binding Protein↗
PubMed1991

Effect of soman and sarin on phosphatidylcholine asymmetry in the electroplax from the electric eel.

Some effects of organophosphorus anticholinesterase compounds that are unrelated to cholinesterase inhibition and that are sometimes long lasting may be due to alterations at the cellular membrane level. Phosphatidylcholine exchange protein was used to assess the effects of sarin and soman on phosphatidylcholine asymmetry in the inner and outer leaflets of the plasma membrane bilayer of the electroplax. Exposure of electroplax (30 min in vitro) to soman (10(-4), 10(-6) M) or sarin (10(-4), 10(-6), 5 x 10(-9) M) increased the percentage of phosphatidylcholine in the outer monolayer of the innervated plasma membrane bilayer and decreased the percentage in the inner monolayer. These changes by sarin were observed at concentrations that produced 100% cholinesterase inhibition (10(-4), 10(-6) M) and at a concentration (5 x 10(-9) M) where no inhibition occurred, suggesting that these effects are not directly due to cholinesterase inhibition. A 1-week exposure of live eels to soman (10(-8) M) in vivo caused an increase in phosphatidylcholine labeling in the outer monolayer of the innervated and noninnervated surfaces of the electroplax. Two weeks after stopping exposure to soman, increased labeling was still observed, suggesting that this may be a long-term effect. Because the organophosphates did not increase the permeability of the electroplax, all of these changes in labeling appear to be due to a redistribution of phosphatidylcholine from the inner to the outer monolayer of the plasma membrane bilayer.

Animals↗
PubMed1990

Inhibitory effect of EDTA.Ca2+ on the hydrolysis of synaptosomal phospholipids by phospholipase A2 toxins and enzymes.

Phospholipases A2 (PLA2) are Ca2(+)-dependent enzymes that are inhibited by EDTA; this inhibition would be expected to be reversed by restoring the Ca2+ concentration. By examining the hydrolysis of synaptosomal phospholipids by PLA2 enzymes, Naja naja atra and Naja nigricollis, and by toxins with PLA2 activity, beta-bungarotoxin (beta-BuTX) and notexin, we demonstrated a novel inhibitory action of EDTA manifested in the presence of excess Ca2+. We postulate the formation of an EDTA.Ca2+ complex which inhibits PLA2 activity in a concentration-dependent manner. Synaptosomes in which phospholipids are hydrolyzed by PLA2 have membranal damage expressed by increased acetylcholine (ACh) release and decreased osmotic activity. Addition of EDTA.Ca2+, which inhibits phospholipid hydrolysis, also reversed the PLA2 effect on ACh release, but not its effect on osmotic activity. The inhibition of PLA2 was observed on membranal phospholipids as well as on an artificial substrate of phospholipid-Triton mixed micelles. Moreover, we found that another enzyme, lactate dehydrogenase, was also inhibited. Our results indicate a non-specific inhibition exerted on the enzyme rather than on the substrate.

Acetylcholine↗
PubMed1990

Phospholipid hydrolysis and loss of membrane integrity following treatment of rat brain synaptosomes with beta-bungarotoxin, notexin, and Naja naja atra and Naja nigricollis phospholipase A2.

The effects of the phospholipase A2 (PLA2) toxins, beta-bungarotoxin and notexin, and the PLA2 enzymes from Naja naja atra and Naja nigricollis snake venoms on the plasma membrane integrity of synaptosomes were examined. Synaptosomes were isolated from rat brain cerebral cortex, corpus striatum and hippocampus. Osmotic activity, lactate dehydrogenase leakage, and leakage of 2-deoxy-D-(1-3H)-glucose-6-phosphate were monitored (37 degrees C, 10-120 min) following incubation with 0.5, 5 and 50 nM concentrations of toxins and enzymes. Damage to the synaptosomal plasma membrane was time and concentration but not tissue dependent. The potencies of the treatments were as follows: N. n. atra PLA2 greater than or equal to N. nigricollis PLA2 greater than notexin greater than beta-bungarotoxin. Chelation of Ca2+ with 5 mM EDTA completely inhibited plasma membrane disruption caused by beta-bungarotoxin and N. n. atra PLA2. One mg/ml of bovine serum albumin also blocked the disruptive action of N. n. atra PLA2, while 8 mg/ml was required to antagonize beta-bungarotoxin. A correlation between phospholipid hydrolysis and loss of membrane integrity was also observed. The generation of phospholipid hydrolytic products may be critical in the permeabilization of synaptic plasma membranes by these toxins and enzymes, however, they do not explain the presynaptic specificity and potency of beta-bungarotoxin and notexin.

Animals↗
PubMed1990

Inhibition of phosphorylation of rat synaptosomal proteins by snake venom phospholipase A2 neurotoxins (beta-bungarotoxin, notexin) and enzymes (Naja naja atra, Naja nigricollis).

Some snake venom neurotoxins, such as beta-bungarotoxin (beta-BuTX) and notexin, which inhibit the release of neurotransmitter at both peripheral and central presynaptic terminals possess phospholipase A2 activity. In contrast, most snake venom phospholipase A2 enzymes such as those isolated from Naja naja atra and Naja nigricollis are structurally homologous to these neutrotoxins but do not have any specific or potent presynaptic action although they have higher enzymatic activities than the neurotoxins. In order to investigate the mechanisms of presynaptic action of the snake venom neurotoxins, we studied their effects on phosphorylation of rat brain synaptosomal proteins. It is known that phosphorylation of synapsin I, a neuron specific and synaptic vesicle associated phosphoprotein, increases neurotransmitter release. Incubation of cerebral cortical synaptosomes with 32P-orthophosphate at 37 degrees C for 30 min, caused significant phosphorylation of a wide mol. wt range of proteins including most markedly those proteins in the mol. wt range (81,000-86,000) of synapsin I. Both snake venom phospholipase A2 neurotoxins and enzymes (5, 15 and 50 nM) inhibited phosphorylation in a Ca2(+)-dependent manner with the following order of potencies: beta-BuTX greater than N.n. atra phospholipase A2 greater than or equal to notexin greater than N. nigricollis phospholipase A2. Five nanomoles of beta-BuTX, which has the lowest phospholipase A2 activity, inhibited phosphorylation of a wide range of mol. wt proteins (51,000-188,000) by 42-58%. At the same concentration, N.n. atra phospholipase A2 (which possesses the highest enzymatic activity), notexin and N. nigricollis phospholipase A2 caused less inhibition than beta-BuTX, ranging from 0-40% depending on the agent used. These results indicate that there is no correlation between their potencies in inhibiting phosphorylation and the levels of their phospholipase A2 activities. An inhibitory activity on phosphorylation may be at least partially responsible for a presynaptically-induced block of neurotransmitter release.

Animals↗
PubMed1990

Leukotriene and prostaglandin production in rat brain synaptosomes treated with phospholipase A2 neurotoxins and enzymes.

beta-Bungarotoxin (beta-BuTX) and notexin cause an irreversible blockade of neurotransmitter release through specific and potent effects at the presynaptic nerve terminal, however, the mechanism of action is uncertain. We examined the effects of beta-BuTX and notexin on LT and PG production in rat cerebrocortical synaptosomes in order to determine if eicosanoid production might mediate or regulate the pharmacological actions of these phospholipase A2 (PLA2) neurotoxins. The effects of the PLA2 enzymes isolated from Naja naja atra and Naja nigricollis snake venoms (which are not presynaptic selective) on LT and PG production were compared with the effects of beta-BuTX and notexin. N. n. atra PLA2, beta-BuTX, and notexin (all 50 nM) produced a time dependent rise in free fatty acids as measured in synaptic plasma membranes isolated from treated synaptosomes. Both the PLA2 neurotoxins and enzymes stimulated LTC4, LTB4, and PGE2 production, as measured by radioimmunoassay. In all cases, the PLA2 enzymes were more potent than the PLA2 neurotoxins. This observation correlates with their relative enzymatic potencies, as measured by free fatty acid generation. EDTA and BSA antagonized PLA2 induced LTB4 production and BSA also antagonized PLA2 induced PGE2 production. These results suggest that stimulation of eicosanoid production does not mediate the potent and specific presynaptic actions of beta-BuTX and notexin.

Animals↗
PubMed1990

[Autotransfusion].

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Blood Transfusion, Autologous↗