Enhancement of Quasistationary Shocks and Heating via Temporal Staging in a Magnetized Laser-Plasma Jet

We investigate the formation of a laser-produced magnetized jet under conditions of a varying mass ejection rate and a varying divergence of the ejected plasma flow. This is done by irradiating a solid target placed in a 20 T magnetic field with, first, a collinear precursor laser pulse (10^{12}  W/cm^{2}) and, then, a main pulse (10^{13}  W/cm^{2}) arriving 9-19 ns later. Varying the time delay between the two pulses is found to control the divergence of the expanding plasma, which is shown to increase the strength of and heating in the conical shock that is responsible for jet collimation. These results show that plasma collimation due to shocks against a strong magnetic field can lead to stable, astrophysically relevant jets that are sustained over time scales 100 times the laser pulse duration (i.e., >70  ns), even in the case of strong variability at the source.

Improved Measurement of the π→eν Branching Ratio

A new measurement of the branching ratio R_{e/μ}=Γ(π^{+}→e^{+}ν+π^{+}→e^{+}νγ)/Γ(π^{+}→μ^{+}ν+π^{+}→μ^{+}νγ) resulted in R_{e/μ}^{exp}=[1.2344±0.0023(stat)±0.0019(syst)]×10^{-4}. This is in agreement with the standard model prediction and improves the test of electron-muon universality to the level of 0.1%.

Measurements of H-->D-->(gamma-->,pi) and implications for the convergence of the Gerasimov-Drell-Hern integral

We report new measurements of inclusive pi production from frozen-spin HD for polarized photon beams covering the Delta(1232) resonance. These provide data simultaneously on both H and D with nearly complete angular distributions of the spin-difference cross sections entering the Gerasimov-Drell-Hearn (GDH) sum rule. Recent results from Mainz and Bonn exceed the GDH prediction for the proton by 22 microb, suggesting as yet unmeasured high-energy components. Our pi0 data reveal a different angular dependence than assumed in Mainz analyses and integrate to a value that is 18 microb lower, suggesting a more rapid convergence. Our results for deuterium are somewhat lower than published data, considerably more precise, and generally lower than available calculations.

Speculations on potential anti-receptor autoimmune diseases

Many autoimmune disorders have a strong tendency to cluster in a single patient or type of patient. Therefore, in those cases in which anti-receptor antibodies are known to be responsible for one of the diseases in the cluster, it is logical to proceed investigatively on the presumption that the aetiology of other members of the cluster may also have an anti-receptor autoantibody basis. This logic is examined by considering examples of clustering in human diseases involving both organ-specific and non-organ-specific autoimmunities. The strong relationship between clustering among autoimmune diseases and the HLA-B8/DRw3 haplotype may provide a marker for anti-receptor autoimmune diseases.

New limit on the T-violating transverse muon polarization in K+-->pi0mu+nu decays

A search for T-violating transverse muon polarization (P(T)) in the K+-->pi(0)mu(+)nu decay was performed using kaon decays at rest. A new improved value P(T)=-0.0017+/-0.0023(stat)+/-0.0011(syst) was obtained giving an upper limit |P(T)|<0.0050. The T-violation parameter was determined to be Imxi=-0.0053+/-0.0071(stat)+/-0.0036(syst) giving an upper limit |Imxi|<0.016.

Beyond managed care

Even as the federal government tries to prop up Medicare managed care, HMOs continue to pull out of the program. But a Centers for Medicare & Medicaid Services demonstration project aims to show that one concept of managed care can keep chronically ill patients healthier and lower overall costs. The concept, coordinated care, blends case management and disease management, giving patients the resources to manage their own care more actively. But, please, just don't call it managed care.

Dopamine-1-mediated stimulation of phospholipase C activity in rat renal cortical membranes

Phospholipase C (PL-C) mediates transduction of neurotransmitter signals across membranes via hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2), leading to generation of second messengers inositol-1,4,5-trisphosphate and diacylglycerol. In this study, dopamine-1 (DA-1) but not dopamine-2 (DA-2) agonists were shown to stimulate PL-C activity in renal cortical membranes. The DA-1 agonist, SKF 82526, stimulated the release of inositol phosphates from renal cortical membranes prelabeled with [3H]myoinositol. The majority of the label (75%) was found in phosphatidylinositol followed by PIP2 (15%) and phosphatidylinositol-4-phosphate (10%). A DA-1 specific effect on PL-C activity was also observed in an in vitro assay of PL-C activity in renal cortical membranes and basolateral and brush border membranes using [3H]PIP2 as the substrate. Dopamine and SKF 82526 stimulated the release of inositol phosphates from added [3H]PIP2 in a concentration-dependent manner. This release was blocked by the DA-1 antagonist SCH 23390 but not by the alpha-adrenergic antagonists phentolamine and prazosin. In contrast, the DA-2 agonist LY 171555 had no effect on inositol phosphate release. Guanosine 5'-(3-O-thio)triphosphate enhanced while guanyl-5'-yl thiophosphate attenuated the DA-1 agonist-stimulated PL-C activity. PL-C activity as measured by [3H]PIP2 hydrolysis had a pH optimum of 6.5, was inhibited by Mg2+ concentrations above 1 mM, was linear with time and protein concentration, and was sensitive to phosphatidylserine and calcium concentrations. We conclude that PL-C is activated by DA-1 but not DA-2 agonists in renal cortical membranes as well as both the basolateral and brush border renal tubular membranes. It is speculated that this action may mediate the natriuretic effects of dopamine in renal tubular epithelia.

A patent law primer for clinical chemists and other scientists

Patenting and commercialization by academic scientists, despite potential drawbacks, are on balance highly desirable if technology is to be transferred from the laboratory to the public use, and if the scientist and his institution are to be encouraged to participate in this transfer. If that premise is accepted, there is much that academic institutions can do to foster utilization of their biotechnological discoveries. Such institutions should have a patent policy that is known to all and that includes a professional patent administrator and clear administrative procedures for carrying out such policy. Scientists should be trained to recognize and protect their inventions and to appropriately disclose their inventions to their patent officers. Ideally, scientists should know the rudiments of the patent statutes of their own country and should be aware of what constitutes trade secrets. Scientists should be given guidance in working with patent attorneys in the preparation and prosecution of patent applications. Finally, given human nature, institutions should see to it that their scientists are provided with a suitable environment in which to invent, and appropriate incentives to do so.

A patent law primer for clinical chemists and other scientists

Patenting and commercialization by academic scientists, despite potential drawbacks, are on balance highly desirable if technology is to be transferred from the laboratory to the public use, and if the scientist and his institution are to be encouraged to participate in this transfer. If that premise is accepted, there is much that academic institutions can do to foster utilization of their biotechnological discoveries. Such institutions should have a patent policy that is known to all and that includes a professional patent administrator and clear administrative procedures for carrying out such policy. Scientists should be trained to recognize and protect their inventions and to appropriately disclose their inventions to their patent officers. Ideally, scientists should know the rudiments of the patent statutes of their own country and should be aware of what constitutes trade secrets. Scientists should be given guidance in working with patent attorneys in the preparation and prosecution of patent applications. Finally, given human nature, institutions should see to it that their scientists are provided with a suitable environment in which to invent, and appropriate incentives to do so.

Partial purification of a water-soluble liver protein that regulates adenylate cyclase activity (basal, hormone- and cholera-toxin-activated) and cholera-toxin-catalyzed ADP-ribosylation of the membrane G protein

We have found in water-soluble extracts of rat liver (and RL-PR-C cloned rat hepatocytes), prepared in the absence of detergent, a factor that markedly enhances basal, isoproterenol and cholera toxin activation of adenylate cyclase of rigorously washed hepatocyte membranes, in the absence of added GTP. The factor, which has characteristics of a protein with an Mr of approx. 35000, has been fractionated from crude cytosol by gel filtration, and then further purified over 50-fold by sequential ion-exchange chromatography. The site of action of the protein appears to be at the level of the guanine nucleotide regulatory (G) protein of the plasma membrane adenylate cyclase complex, as the factor, cooperatively with GTP, also permitted cholera toxin to ADP-ribosylate (from 32P-labeled NAD) two integral membrane proteins that migrated on SDS-polyacrylamide gel electrophoresis gels with the mobilities (Mr approx. 46 000 and 48 000) generally observed for the guanine nucleotide regulator protein subunits. In this system, isoproterenol did not stimulate ADP-ribosylation, in either the presence or absence of the liver protein factor.

Beta-blocking autoantibodies in pediatric bronchial asthma

We have used the inhibition of binding of a potent beta antagonist, iodohydroxybenzylpindolol, to canine lung-plasma membrane beta-adrenergic receptors as a test for beta-blocking autoantibodies in the sera of 376 mildly and severely asthmatic children. This binding inhibition assay, coupled with a variant test in which the binding assay was performed on selected sera (binding values below 2 SD from the mean) before and after immunodepletion of the sera (removal of IgG and IgA), permitted the conclusion that about 5% of the juvenile asthmatic population studied produce beta-blocking autoantibodies.

Dopamine receptors in the proximal tubule of the rabbit

Our laboratory has characterized dopamine receptors in glomeruli and tubular homogenates. Since the heterogeneity of kidney homogenates limits the interpretation of these studies, the [3H]haloperidol binding site and adenylate cyclase sensitivity to dopamine were studied in the isolated proximal convoluted tubule and pars recta of the rabbit kidney. [3H]Haloperidol binding sites were saturable, stereoselective, and of high affinity. The apparent dissociation constant was 31.5 X 10(-9) M (+/- 8.5) and the maximum receptor density was 0.31 X 10(-15) M (+/- 0.08) per millimeter. In pars recta specific binding was 53% of total [3H]-haloperidol binding. Dopamine stimulated adenylate cyclase activity in a dose-related manner, which was inhibited by cis-flupenthixol but not by trans-flupenthixol or (-)-propranolol. Moreover, the stimulatory effect of the dopamine 1 (D1) agonist SKF 82526 on adenylate cyclase activity was blocked by the D1 antagonist SCH 23390. Dopamine receptors in the proximal convoluted tubule appear to be of the D1 subtype since they are linked to stimulation of adenylate cyclase. This is further substantiated by the stereoselectivity for (+)-sulpiride (a D1 antagonist), which had a greater affinity for the [3H]haloperidol binding site than (-)-sulpiride (a D2 antagonist).

Receptors, antibodies, and disease

Abnormal antibody production is now recognized as the basis of specific endocrine and neurological diseases and their complications. Among the autoimmune diseases, the best understood from a mechanistic point of view are myasthenia gravis, Graves' disease, several variants of insulin resistance, and a variant of bronchial asthma. In each of these human disorders, the clinical symptoms can be traced to the actions of antireceptor antibodies produced by a deranged immune system. The autoantibodies produced in these diseases are functionally heterogeneous. They may produce the clinical symptoms of hormone or neurotransmitter insufficiency either by blocking the binding of these agents to target cell surface receptors or by accelerating the internalization and degradation of these receptors. In other cases, the autoantibodies may produce the clinical signs of hormone excess by mimicking the actions of the hormone, in an uncontrollable fashion. In some cases, functionally different types of autoantibodies will appear in the same patient at different stages of the disease. For all of these autoantibodies, of whatever function, assays for their presence in serum are available, in forms suitable for clinical chemists, as well as for researchers; these will be described in this review. In addition to the known anti-receptor autoimmune diseases, there are a large number of other autoimmune diseases for which there is fragmentary evidence that their clinical symptoms have an anti-receptor autoantibody etiology. Several examples of this group will be discussed, and assays suitable for establishing the presence of anti-receptor antibodies in the sera of such patients will be provided. The disorders to be considered are: type I diabetes mellitus, chronic atrophic gastritis, autoimmune Addison's disease, autoimmune hypoparathyroidism, type II pseudohypoparathyroidism, resistant ovary syndrome, connective tissue diseases, and the HLA-B8/DR3 antigen haplotype as a potential marker for autoimmune diseases of the anti-receptor type.

Receptors, antibodies, and disease

Abnormal antibody production is now recognized as the basis of specific endocrine and neurological diseases and their complications. Among the autoimmune diseases, the best understood from a mechanistic point of view are myasthenia gravis, Graves' disease, several variants of insulin resistance, and a variant of bronchial asthma. In each of these human disorders, the clinical symptoms can be traced to the actions of antireceptor antibodies produced by a deranged immune system. The autoantibodies produced in these diseases are functionally heterogeneous. They may produce the clinical symptoms of hormone or neurotransmitter insufficiency either by blocking the binding of these agents to target cell surface receptors or by accelerating the internalization and degradation of these receptors. In other cases, the autoantibodies may produce the clinical signs of hormone excess by mimicking the actions of the hormone, in an uncontrollable fashion. In some cases, functionally different types of autoantibodies will appear in the same patient at different stages of the disease. For all of these autoantibodies, of whatever function, assays for their presence in serum are available, in forms suitable for clinical chemists, as well as for researchers; these will be described in this review. In addition to the known anti-receptor autoimmune diseases, there are a large number of other autoimmune diseases for which there is fragmentary evidence that their clinical symptoms have an anti-receptor autoantibody etiology. Several examples of this group will be discussed, and assays suitable for establishing the presence of anti-receptor antibodies in the sera of such patients will be provided. The disorders to be considered are: type I diabetes mellitus, chronic atrophic gastritis, autoimmune Addison's disease, autoimmune hypoparathyroidism, type II pseudohypoparathyroidism, resistant ovary syndrome, connective tissue diseases, and the HLA-B8/DR3 antigen haplotype as a potential marker for autoimmune diseases of the anti-receptor type.

Cortical tubular and glomerular dopamine receptors in the rat kidney

Dopamine receptors in glomeruli and renal cortical tubules were characterized using radioligand binding and adenylate cyclase studies. The binding of [3H]haloperidol to glomeruli and tubules was rapid, saturable with time and ligand concentration, reversible, of high affinity, and demonstrated stereoselectivity and antagonist and agonist rank potency for binding to dopamine receptors. Analysis of kinetic data and Rosenthal plots in glomeruli revealed a single class of [3H]haloperidol binding sites with an apparent dissociation constant (Kd) of 6 nM and maximum receptor density (Bmax) of 0.42 pmol/mg protein. In tubules, at least two binding sites were noted, one with an apparent Kd of 38 nM and Bmax of 1.90 pmol/mg protein and another with an apparent Kd of 183 nM and Bmax of 3.50 pmol/mg protein. Dopamine and apomorphine increased adenylate cyclase in tubular membranes while no increases were noted in glomeruli. These studies suggest that glomeruli have D2 dopamine receptors, while renal cortical tubules contain the D1 dopamine receptor.

On the mechanism of isoproterenol-induced desensitization of adenylate cyclase in cultured differentiated hepatocytes

The adenylate cyclase of cultured differentiated RL-PR-C hepatocytes is desensitized to 1-isoproterenol by exposure to this beta-agonist. Virtually complete desensitization occurred by 60 min (intact cells) or 30 min (isolated plasma membranes). Isoproterenol was maximally effective at 10 micrometers, although substantial desensitization occurred at isoproterenol concentrations as low as 10 nM. Protein synthesis was not required for desensitization. Recovery from desensitization under tissue culture conditions was only 25% complete by 24 h. Maximum desensitization was accompanied by only a modest 35% decrease in binding sites (as determined by binding assays with [3H]dihydroalprenolol), with no change in binding affinity. Adenylate cyclase desensitized to 1-isoproterenol responded normally to guanine nucleotides and to fluoride, suggesting that the regulatory and catalytic proteins were not the sites of the desensitization "defect'. Using N-ethylmaleiimide to inactive the regulatory and catalytic proteins, and dicyclohexylcarbodiimide to inactivate the beta-adrenergic receptor, of intact hepatocytes, various heterologous cell fusion hybrids were produced, and their adenylate cyclases tested for responsiveness to 1-isoproterenol; only hybrids containing "desensitized' receptor failed to respond to isoproterenol. These results suggest that the mechanism of desensitization to isoproterenol involves only the receptor component of the receptor-regulatory protein(s)-adenylate cyclase complex, and that the receptors are reduced in number and/or ability to interact with the regulatory protein as a result of the desensitization process.

Interaction of guanine nucleotides with adenylate cyclase in normal and spontaneously transformed RL-RP-C cloned rat hepatocytes

Spontaneous transformation of RL-PR-C hepatocytes leads to alterations in the adenylate cyclase complex which include a lower than normal basal level of activity, a loss of sensitivity to exogenous GTP, and a decreased sensitivity to isoproterenol. Both normal and transformed membranes possess substantial GTPase activity. Treatment of transformed hepatocyte membranes with either isoproterenol plus GMP or with cholera toxin, under conditions that displace tightly bound GDP, restored the GTP effect on adenylate cyclase, and eliminated the lag in the activation by guanyl-5'-yl-imidodiphosphate. Such pretreatment also enhanced guanine nucleotide effects on the adenylate cyclase of normal hepatocytes. These results are explainable on the basis that transformation increases adenylate cyclase-associated GTPase activity, and increases occupancy of nucleotide regulatory sites by inactive or inhibitory guanine nucleotides, e.g., GDP. Seemingly, both catecholamines and cholera toxin promote an exchange reaction at the regulatory sites, resulting in clearance of these sites of inhibitory nucleotides.

Regulatory states of adenylate cyclase in RL-PR-C cloned rat hepatocytes

The adenylate cyclase of cloned differentiated rat hepatocytes (RL-PR-C) is regulated by cholera toxin, guanine nucleotides and fluoride. The activation of hepatic adenylate cyclase by cholera toxin was additive with that by GTP and synergistic with that by epinephrine. In contrast, when membranes were exposed to cholera toxin in the presence of Gpp(NH)p or fluoride, the response was the same as to these agents in the absence of cholera toxin. Cholera toxin-activated membranes were responsiveness only to epinephrine and GTP, while fluoride-activated membranes responded somewhat to all other agents, and Gpp(NH)p-activated membranes responded to no other agents. These data suggest that responsiveness of hepatic adenylate cyclase to cholera toxin, fluoride and Gpp(NH)p cannot be expressed simultaneously. A model is presented to explain these observations which invokes multiple states of adenylate cyclase, each being sensitive to, or brought about by, a different regulatory agent.

Endogenous and cholera toxin-catalyzed ADP-ribosylation of a plasma membrane protein by RL-PR-C cloned rat hepatocytes

Cholera toxin catalyzed the ADP-ribosylation of a single plasma membrane protein (Mr 55 000) of both RL-PR-C rat hepatocytes and purified rat liver plasma membranes. Labeling of this protein from nicotinamide [2,8-3H]adenine dinucleotide was competitively inhibited by free arginine, but by no other amino acid tested, including lysine. The same protein was ADP-ribosylated from NAD+ endogenously, i.e., in the absence of toxin. This process was, however, not competitively inhibited by added arginine nor by any other amino acid tested lysine. Free ADP-ribose, even in 50-fold molar excess over the nicotinamide [2,8-3H]adenine dinucleotide substrate, did not reduce (by isotope dilution) the endogenous or cholera toxin-catalyzed labeling of the 55 000 dalton membrane protein. It is likely, therefore, that hepatocyte plasma membranes contain an ADP-ribosyltransferase, with a mechanism similar to that of the A subunit of cholera toxin, in that both transfer ADP-ribose to the same membrane protein and in that neither apparently produce free ADP-ribose as an intermediate. It is also clear that the acceptor residue in the 55 000 dalton protein is different for each process. Cholera toxin-catalyzed and endogenous transfer of ADP-ribose to the hepatocyte plasma membrane protein, in contrast to a pigeon erythrocyte system, required no cytosolic factors. The results indicate that ADP-ribosylation in cloned differentiated rat hepatocytes differs from that in pigeon erythrocytes in that the acceptor protein is larger (55 000 compared to 42 000 daltons), cytosolic factors are not required and transfer of ADP-ribose to the acceptor protein occurs endogenously.