On parametrizing the N-generation quark mixing matrix.
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Journal Article↗
Biomedical subjects
R Johnson
Publications and source records attributed to R Johnson.
HLA class II regulation and structure. Analysis with HLA-DR3 and HLA-DP point mutants.
Point mutations that affect HLA-DR structure or expression have not previously been described. In the present study, we isolated such mutants by immunoselection of an ethyl methanesulfonate-mutagenized HLA-DR3 cell line with an anti-HLA-DR3 monoclonal antibody, 16.23. To facilitate analysis, we used a parent cell line with a preexisting deletion of one haplotype encompassing DR and DQ alpha and beta. The selection yielded two sets of mutants, one with defects in DR3 structure, the other with defects in different steps leading to DR expression. Of the expression-defective mutants, one had undergone a second deletion removing the remaining DR alpha gene but no other class II genes. It had a normal abundance of DR beta mRNA but had lost binding of DR monomorphic antibodies, indicating that DR beta chains do not form noncognate dimers. A second mutant had an abnormally large DR alpha mRNA, probably resulting from a splice site mutation. Several mutants had marked reductions in DR beta mRNA levels; in two of these, the lesion appeared to be transcriptional because the reduction in DR beta mRNA was paralleled by an altered methylation pattern of one of the DR beta genes. Other expression-defective mutants had different posttranscriptional defects. Some of the mutations were similar to those that have been found in mouse strains defective in I-E expression, whereas others have no known natural counterpart. The matrix of reactivities of anti-HLA class II monomorphic antibodies with these and similar mutants allowed us to define the gene products recognized by these antibodies. A set of seven mutants were "epitope defective," that is, they expressed normal or near normal levels of HLA-DR3 but no longer bound 16.23. Unexpectedly, each of the epitope mutants had decreased DR dimer stability. These mutants should be useful in localizing the DR3 alloepitope and in elucidating its contribution as a restriction element in the presentation of soluble antigen to immune T cells.
Antibodies, Monoclonal↗
Uterine and whole body oxygen extractions in the pregnant rabbit under chronic steady-state conditions.
Seventeen pregnant rabbits were studied under conscious, unstressed conditions after catheterization of the right ventricle (RV), a femoral artery (A), and a uterine vein (UV). Respiratory gas tensions, pH, and oxygen saturations and contents were determined serially throughout the latter half of gestation. The uterine coefficient of oxygen extraction increased with gestational age (R = 0.86) and became 60.6% +/- 0.3% during the last 4 days of pregnancy. To compare uterine perfusion with whole body perfusion in relationship to oxygen demands, the (Ao2 - UVo2/Ao2 - RVo2) ratio was computed. The ratio was greater than or equal to 1 after 20 days of gestation, which demonstrated that in regard to oxygen demands the rabbit uterus is relatively underperfused compared to the rest of the maternal organism in the last part of pregnancy. A comparison with analogous data in other species demonstrates that the pregnant rabbit, like the guinea pig, has a much lower rate of uterine blood flow than does the pregnant sheep. These interspecies differences in the perfusion rate and oxygen extraction of the pregnant uterus are related to differences in placental structure.
Animals↗
Identification of the calmodulin-binding components in bovine lens plasma membranes.
Lens membranes, purified from calf lenses, have been labeled by covalent cross-linking to membrane-bound 125I-calmodulin with dithiobis(succinimidyl propionate). Electrophoretic analysis in sodium dodecyl sulfate demonstrated two major 125I-containing products of Mr = 49 000 and 36 000. That the formation of these two components was specifically inhibited by unlabeled calmodulin, or calmodulin antagonists, would indicate that the formation of these components was calmodulin-specific. The size of these two 125I-labeled components was unchanged over a range of 125I-calmodulin or dithiobis(succinimidyl propionate) concentrations indicating that they represent 1:1 complexes between 125I-calmodulin (Mr = 17 000) and Mr-32 000 and Mr-19 000 lens membrane components respectively. Although formation of both cross-linked components exhibited an absolute dependence on Mg2+, the autoradiographic intensity of these components was enhanced when Ca2+ was included with Mg2+ during the cross-linking reaction. Labeling was maximal in 10 mM MgCl2 and approximately 1 microM Ca2+. Treatment of lens membranes with chymotrypsin resulted in the cleavage of MP26 (the major lens membrane protein), with the appearance of a major proteolytic fragment of Mr = 22 000. This proteolysis was not associated with any significant change in either the size or amount of the 125I-calmodulin-labeled membrane components. These results suggest that calmodulin interacts with two membrane proteins, but not significantly with MP26, in the intact lens cell membrane. Our results indicate the need to maintain caution in interpreting direct calcium plus calmodulin effects on MP26 and lens cell junctions.
Animals↗
Characterization of the bovine lens plasma membrane substrates for cAMP-dependent protein kinase.
cAMP-dependent protein kinase, derived from either calf lens or bovine heart, promotes the phosphorylation of three lens plasma membrane proteins of molecular mass 28 kDa, 26 kDa and 18 kDa. Correlation of the maximal level of phosphorylation of these components with the Coomassie blue staining intensity of fractionated lens membranes suggests that the phosphorylation of the 28 kDa and 18 kDa components may be approximately stoichiometric. The protein kinase substrates could be dephosphorylated by a cardiac sarcoplasmic-reticulum-bound protein phosphatase activity. The 26 k Da component comigrated with MP26, the major lens membrane component that has been localized to the lens fiber cell junction. Treatment of phosphorylated lens membranes with chymotrypsin did not suggest that any of the three major phosphorylated components was derived from the partial proteolysis of a larger phosphoprotein. After electrophoretic separation of phosphorylated proteins, treatment with N-chlorosuccinimide confirmed that there was little similarity in the structure of the three phosphoproteins. Chymotrypsin did, however, reveal a cryptic phosphorylation site in a 22 kDa fragment that appeared to be derived from MP26. Treatment of phosphorylated membranes with reducing agents resulted in the disappearance of the 28 kDa phosphorylated component and the appearance of a new phosphorylated component of 18 kDa; neither MP26 nor the original 18 kDa component was affected by such treatment. It is not clear whether the original 18 kDa phosphoprotein, present in unreduced samples, is the same as that generated with reducing agents from the 28 kDa phosphorylated lens membrane component.
Animals↗
Model for maximal CP nonconservation.
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Journal Article↗
Delayed choroidal vascular filling after krypton laser photocoagulation.
In four patients treated for macular subretinal neovascularization with krypton red laser photocoagulation, follow-up fluorescein angiograms performed two to ten days after treatment showed wedge-shaped areas of delayed choroidal vascular filling adjacent to and extending directly from the treated areas. There were no immediate or late changes in the fundus corresponding to the areas of delayed choroidal vascular filling. Goldmann visual fields done on two of the patients showed no functional deficit corresponding to the areas of delayed filling. Deep choroidal energy absorption of the krypton wavelength causing choroidal vessel thrombosis could explain this complication.
Aged↗
Charged D production in e+e- annihilation at 29 GeV and a limit on D0-D-bar 0 mixing.
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Journal Article↗
Comparison of Biobrane and Scarlet Red dressings for treatment of donor site wounds.
Two methods of autograft donor site management were tested in 31 patients with burn injuries. Two donor sites of equivalent size were respectively covered with Biobrane and Scarlet Red, two commercial dressing materials available for donor wound coverage. Pain, the amount and type of exudate developing underneath the dressing, adherence, and cellulitis were evaluated on a daily basis, and healing time was determined. Biobrane proved superior to Scarlet Red with respect to control of pain, accumulation of exudate, and healing time; the materials were equal with regard to adherence to the wound, the character of exudate, and the appearance of cellulitis.
Adolescent↗
Action of hydrochloric acid on aluminum hydroxide-magnesium hydroxide gels and magaldrate: 27Al NMR and pH-stat studies.
Neutralization of mixtures of aluminum hydroxide-magnesium hydroxide gels and of magaldrate by hydrochloric acid were studied by 27Al NMR under conditions of both equilibrium and kinetic control. Under conditions where equilibrium has been attained, an aluminum NMR signal is detectable for suspensions of the mixed gels and magaldrate only after enough acid has been added to exhaust the acid-neutralizing capacity of the magnesium hydroxide. Mixed gels seem to form several soluble aluminum-containing species as neutralization proceeds. Under the conditions of the modified Beekman neutralization procedure, in which the species concentrations reflect neutralization kinetics, mixed gels show a sharp burst of the hexaaquoaluminum cation as acid is added followed by a slow loss of that cation from solution and an accompanying slow rise in pH. Magaldrate shows a steady increase in the hexaaquoaluminum cation with added acid. Differences between magaldrate and mixed gels are also apparent in pH-stat titrations in which magaldrate displays a biphasic response, contrasting to the two burst phases with an intervening lag phase observed for mixed gels. The results of the 27Al NMR and pH-stat titrations are consistent with the hypotheses that magaldrate is a homogeneous substance with a hydrotalcite-like structure and that mixed gels consist of a magnesium hydroxide core surrounded by aluminum hydroxide.
Aluminum↗
Preeclampsia complicated by cerebral hemorrhage and brain abscess.
A 34-year-old, preeclamptic woman developed a right basal ganglia hematoma during a vaginal delivery. Her course was later complicated by an infected episiotomy. As a consequence of bacterial seeding most likely from the infected episiotomy, the intracerebral hematoma became infected, developing into a brain abscess. Because of her existing neurological deficits, the developing brain abscess was not recognized until signs and symptoms of increased intracranial pressure developed. This patient illustrates another potentially life-threatening neurological infection that may occur in the peripartum period.
Adult↗
Sequential chemotherapy for advanced epithelial ovarian cancer: platinum combination cytoreduction followed by cyclophosphamide consolidation.
Thirty-six women with advanced epithelial ovarian cancer were treated with a combination of cisplatin, vinblastine and bleomycin followed by a consolidation regimen of intravenous cyclophosphamide. There was a 53% response rate in previously untreated patients with 25% complete clinical remissions. Sixteen per cent of previously untreated patients remain in a complete clinical remission of greater than 3 yr duration. In a multivariate analysis bulk tumor residuum was not a significant adverse factor in terms of survival, suggesting that intensive chemical cytoreduction followed by non-cross-resistant consolidation may overcome such prognostic variables.
Adult↗
Comparison of the elimination of 10 and 20% TRAVAMULSION lipid emulsion from the blood of beagle dogs.
Metabolic utilization of fat emulsions containing 20% lipid and 10% lipid were compared using beagles. The key parameter measured was elimination of the lipid from the bloodstream, which serves as an indication of the emulsion's availability for metabolism. Nonlinear kinetic analysis was used in this determination. Blood concentrations of free fatty acids, phospholipid, and cholesterol were also measured as additional ways of determining emulsion metabolism. The 10 and 20% emulsions appeared to be equivalent in elimination of the caloric substrate triglyceride from the blood stream. Results also showed an adaptation to emulsion infusion over time at both dosages administered (3 and 6 g/kg of body weight). This was indicated by increased elimination capacity and stabilization of each lipid class measured. However, blood concentrations of phospholipid and cholesterol indicate that the 20% emulsion provides a lesser lipid load for the amount of calories administered when compared to an emulsion containing 10% lipid.
Animals↗
A simplified radioimmunoassay for antibodies causing immune cytopenia.
A two-step, solid-phase radioimmunoassay for the measurement of antibodies directed against platelets, neutrophils, and red blood cells is described. Cells to be tested or standard solutions of human IgG (HIgG) first are incubated with excess 125I goat anti-human IgG. Unbound 125I anti-IgG is adsorbed in a second step to polystyrene balls (PB) coated with excess human IgG. Inhibition of binding in this second step is related directly to the level of cell associated IgG. The amount of cell bound IgG is determined by comparison to a inhibition curve for standard IgG solution. The method was evaluated by quantitating antibody levels in patients with clinical evidence of immune cytopenias.
Antibodies↗
Effects of enflurane, isoflurane, and nitrous oxide on somatosensory evoked potentials during fentanyl anesthesia.
The effects of nitrous oxide, enflurane, and isoflurane on cortical somatosensory evoked potentials (SEPs) were studied in 29 patients undergoing intracranial or spinal operations. Anesthesia was induced with fentanyl (25 micrograms/kg, iv) plus thiopental (0.5-1.0 mg/kg, iv). In one group of patients (n = 12), nitrous oxide (50%) was compared with enflurane (0.25-1.0%), and in another group (n = 12) nitrous oxide (50%) was compared with isoflurane (0.25-1.0%). In a third group of patients (n = 5) with preexisting neurologic deficits, nitrous oxide (50%) was compared with enflurane (0.25-1.0%). In all three groups, one gas was administered for 30 min, and then the alternate gas was administered for 30 min; then the cycle was repeated for a total of two administrations of each of the two anesthetics. SEPs were determined before and after induction of anesthesia and at the end of each 30-min study period. The latencies and amplitudes of the early cortical components of the upper- and lower-extremity SEP were examined. Induction of anesthesia resulted in increases of latency in both upper- and lower-extremity SEPs without any alteration of amplitude. Nitrous oxide, enflurane, and isoflurane each decreased the amplitude of the upper-extremity SEPs compared with the postinduction value. The amplitude of the upper-extremity SEPs was less during nitrous oxide than with either enflurane or isoflurane. Nitrous oxide decreased the amplitude of lower-extremity SEPs below postinduction value, while enflurane and isoflurane had no effect. Isoflurane and enflurane increased the latency of both upper- and lower-extremity SEPs slightly, while nitrous oxide had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)
Anesthesia, General↗
Aminopeptidase activity from germinated jojoba cotyledons.
One major and two minor aminopeptidase activities from germinated jojoba (Simmondsia chinensis) cotyledon extracts were separated by ammonium sulfate precipitation and chromatofocusing. None of the activities were inhibited by 1,10 phenanthroline.The major aminopeptidase, purified 260-fold, showed a pH optimum of 6.9 with leucine-p-nitroanilide as substrate, a molecular weight estimated at 14,200 by electrophoretic analysis, and an isoelectric point of 4.5 according to the chromatofocusing pattern. Activity was inhibited by p-chloromercuribenzoate, slightly stimulated by 1,10 phenanthroline and 2-mercaptoethanol, and not influenced by Mg(2+) or diethyl pyrocarbonate. Inhibition by p-chloromercuribenzoate was prevented by the presence of cysteine in the assay. Leucine-p-nitroanilide and leucine-beta-naphthylamide were the most rapidly hydrolyzed of 11 carboxy-terminal end blocked synthetic substrates tested. No activity on endopeptidase or carboxypeptidase specific substrates was detected. The major aminopeptidase showed activity on a saline soluble, jojoba seed protein preparation and we suggest a possible physiological role for the enzyme in the concerted degradation of globulin reserve proteins during cotyledon senescence.
Journal Article↗
Second thoughts: multiple P300s elicited by a single stimulus.
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Adolescent↗