Putting it (performance measures) together: an interview with Jerod Loeb. Interview by Steven Berman.
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Accreditation↗
Biomedical subjects
J Loeb
Publications and source records attributed to J Loeb.
Fibroblast growth factors stimulate protein tyrosine phosphorylation and mitogen-activated protein kinase activity in primary cultures of hippocampal neurons.
Fibroblast growth factors (FGFs) are not only mitogens, but they also promote the differentiation of various cell types. For instance, basic FGF (bFGF) provides a critical trophic support for hippocampal neurons in culture. To elicit their biological effects, FGFs interact with high-affinity receptors that are transmembrane proteins with a cytoplasmic portion containing a tyrosine kinase activity. The tyrosine phosphorylation pattern was examined in primary cultures of hippocampal neurons derived from rat embryos. In these cultures grown for 3 days in the absence of serum, the addition of bFGF causes a rapid increase of tyrosine phosphorylation for various proteins with an optimal level after 5 min of bFGF exposure. Concomitantly, bFGF activates mitogen-activated protein kinase (MAP kinase) activity measured with a selective MAP kinase peptide. The activity increased rapidly after the addition of bFGF and remained elevated even when cultures were treated for 1 h with bFGF. Both acidic and basic FGF were able to enhance protein tyrosine phosphorylation and MAP kinase activity, whereas nerve growth factor and epidermal growth factor did not elicit any of these responses. These data indicate that some of the transduction signals (i.e., tyrosine phosphorylation and activation of MAP kinase) that have been described for the proliferative effect of FGFs are also involved when FGFs act as trophic factors for postmitotic neurons in culture.
Animals↗
[Assessment of cerebral autoregulation using transcranial Doppler sonography under lower body negative pressure].
A novel technique for transcranial Doppler sonographic assessment of cerebral autoregulation was tried out in 20 healthy volunteers, ten of them right-handed and ten left-handed. A fall in arterial blood pressure was produced through lower body negative pressure (LBNP) of -50 mmHg during 1 min. The Doppler shift signal of both middle cerebral arteries was recorded simultaneously and analyzed digitally to obtain mean Doppler shift frequency and Doppler signal power. Their product, as an index of volume flow, was calculated on-line. By positioning and coupling of the transducers and keeping the position of the head stable throughout the test, spurious readings due to the effects of gravity or head movement were excluded. With an average fall of mean arterial blood pressure of 10.3 +/- 7.7 mmHg, the TCD flow index as averaged over the entire period of LBNP was 103.6 +/- 19.5% of the value measured under atmospheric pressure, demonstrating a physiological autoregulation. In the right-handed subjects the flow index during LBNP was significantly higher on the right than on the left side. In only one of the ten right-handed individuals the side difference was reversed, while this was the case in five of the ten left-handed subjects.
Adult↗
Zinc-induced tyrosine phosphorylation of hippocampal p60c-src is catalyzed by another protein tyrosine kinase.
Tyrosine phosphorylation of p60c-src induced by Zn2+ in rat hippocampal membranes is shown to inhibit Src tyrosine kinase activity. Zn2+ catalyzes the phosphorylation of p60c-src in the membranes but does not activate autophosphorylation of p60c-src immunoprecipitated with anti-Src monoclonal antibody. Moreover, the immunoprecipitated Src kinase has no Zn(2+)-induced activity in phosphorylation of exogenous substrate, enolase. Cyanogen bromide cleavage of p60c-src phosphorylated in the presence of Zn2+ yields a 4-kDa phosphopeptide corresponding to phosphorylation of a carboxy-terminal tyrosine residue of Src kinase. In conclusion, hippocampal membranes contain a Zn(2+)-stimulated protein tyrosine kinase capable of regulating the p60c-src activity.
Animals↗
Zinc causes tyrosine phosphorylation of hippocampal p60c-src.
Zinc cations at concentrations of 0.2 mM and greater catalyzed specific phosphorylation, by ATP, of two membrane-associated proteins from rat hippocampus. These proteins, corresponding to molecular weights of 60 and 49 kDa, were phosphorylated primarily at tyrosine residues. The 60-kDa protein was identified as p60c-src by immunoprecipitation using two different p60src-specific monoclonal antibodies. The 49-kDa protein co-immunoprecipitated with p60c-src. Cyanogen bromide cleavage of p60c-src and the 49-kDa protein phosphorylated in the presence of Zn2+ gave different patterns of phosphopeptides. It is suggested that tyrosine phosphorylation of p60c-src and the p60c-src-associated 49-kDa protein may be a way of zinc participation in hippocampal neurotransmission.
Adenosine Triphosphate↗
Rapid activation of hippocampal casein kinase II during long-term potentiation.
Several studies suggest that protein kinase C and type II Ca2+/calmodulin-dependent protein kinase are activated during induction of long-term potentiation (LTP). We now report that casein kinase II (CK-II), which is present in high concentration in the hippocampus, is also activated in the CA1 region during LTP. CK-II activity increased within 2 min after a train of high-frequency electrical stimulations and reached a maximum (2-fold increase) 5 min later before returning to baseline value. The stimulated protein kinase activity, which was blocked by a selective antagonist of N-methyl-D-aspartate receptors, exhibited specific properties of CK-II, including phosphorylation of the specific substrates of CK-II, marked inhibition by a low heparin concentration, and the use of GTP as a phosphate donor. CK-II activity was also selectively and rapidly augmented in another form of LTP produced by bath application of tetraethylammonium; this LTP (called LTPk) is Ca2+ dependent but N-methyl-D-aspartate independent. Phosphorylation of casein that was not inhibited by heparin (i.e., casein kinase I) remained unchanged. We suggest that an increase in CK-II activity is important in LTP induction.
Adenosine Triphosphate↗
Phosphorylation of the lymphoid cell kinase p56lck is stimulated by micromolar concentrations of Zn2+.
In particulate fractions from LSTRA lymphoma cells, tyrosine phosphorylation of the lymphoid specific tyrosine kinase p56lck is elicited by Zn2+ in the absence of other divalent cations. Zn2+ alone also induces autophosphorylation of immunoprecipitated p56lck. The effect of Zn2+ is dose dependent; it is detected at concentrations of Zn2+ as low as 5 microM and reaches a maximum at 100 microM Zn2+. Among other divalent cations tested, Mn2+, and Co2+ to a lesser extent, were also effective. Zn2+ also stimulated p56lck phosphorylation in the presence of Mg2+ ions at physiological concentration, whereas orthovanadate had no effect. These results suggest that Zn2+ activates the autophosphorylation of p56lck; this fact could be related with the stimulating effect of Zn2+ in the activation of T lymphocytes.
Animals↗
Video-based training of respite care providers: an interactional analysis of presentation format.
We conducted two studies to evaluate a video-based instructional package for training respite care providers and the role of presentation format (viewing the videotapes alone, with a partner, and with structured group training) as a contextual variable. In Study 1, the results of a within-subjects Latin square design nested within a multiple baseline showed that performance during simulated (role-played) respite care situations improved in five of the six skill areas for the 12 trainees following presentation of the videotape, with no differences between presentation formats. Correct responding generalized to respite care situations involving a developmentally disabled child, and in most cases, acquired skills were maintained for up to 6 months. In Study 2, we conducted a clinical replication of Study 1 under conditions more closely approximating those in which the training program would be implemented by respite care agencies. Results of the between-groups analysis were consistent with the findings of Study 1.
Adult↗
The human Pim-1 gene is selectively transcribed in different hemato-lymphoid cell lines in spite of a G + C-rich housekeeping promoter.
The expression of the Pim-1 proto-oncogene was studied by using the K562, Daudi, and Jurkat cell lines. In K562, Pim-1 mRNA levels were more than 20-fold higher than in Daudi and 50-fold higher than in Jurkat. Nuclear run-on assay data correlated directly with the steady-state mRNA levels, suggesting that the rate of transcription was responsible for the selective expression of this gene. Furthermore, the half-life of Pim-1 mRNA was shown to be 47 min in K562, 71 min in Daudi, and 35 min in Jurkat. This indicated that selective Pim-1 mRNA expression did not depend on posttranscriptional regulation. Therefore, 1.7 kilobases of the Pim-1 promoter was sequenced and studied in detail. The sequence showed that the region from nucleotide -1 to -873 was G + C rich (71%). Study of promoter deletions defined two major functional regions, a proximal element (nucleotide -104 to -1) and a distal element (nucleotide -427 to -336). DNase I protection assays identified binding sites for the Sp1 and AP2 proteins in these elements. A possible new transcription factor binds at position -348 in the distal element. In our study of the 1.7-kilobase Pim-1 promoter, we found no differences between K562 and Jurkat that could explain large differences in transcription. Therefore, the Pim-1 promoter appears to function constitutively, and we conclude that distant elements must regulate the tissue-selective expression of this gene. Although the Pim-1 gene has a G + C-rich housekeeping promoter, expression is carefully regulated at the level of transcription.
Base Composition↗
The resistance to alkali treatment of the phosphorylation of beta casein versus alpha casein is specific for casein kinase II.
The phosphorylation of mixed casein by casein kinase II shows resistance on beta casein after partial alkali hydrolysis of the proteins separated by gel electrophoresis. This property is specific for casein kinase II among the protein kinases tested and can be used for casein kinase II detection in biological extracts and for characterization of purified casein kinase II.
Alkalies↗
Evaluation of diagnosis-related groups in the National Health Service.
Evaluation of the use of diagnosis-related groups (DRGs) has revealed a number of technical problems in coding of diagnoses and operative procedures, as well as unresolved issues in the clinical acceptability of existing groupings. An investigation of the statistical homogeneity of DRGs, in terms of duration of patient stay, is described. Consideration of data relating to some 990,000 episodes of in-patient care in three English Regions discloses wide variations in statistical homogeneity, both between DRGs and in relation to individual clinical specialties. The greatest homogeneity is found in ENT surgery and gynaecology; and the least in general medicine and orthopaedic surgery. The need for improved data collection and coding procedures is discussed, together with the advisability of sensitivity in the interpretation of DRGs, as well as the need for a co-ordinated approach to their refinement for application in any wider introduction in the NHS.
Diagnosis-Related Groups↗
Lack of detectable somatic hypermutation in the V region of the Ig H chain gene of a human chronic B lymphocytic leukemia.
Monoclonal human B cell tumors are a model system for the study of somatic hypermutation of the Ig genes of humans. It was previously shown that a number of B cell lymphomas exhibited striking V region point mutation, hypothesized to result from the somatic hypermutation mechanism. In this study we have extended the analysis to chronic lymphocytic leukemia. We have cloned and sequenced the productive Vh representing five different cells from a monoclonal chronic lymphocytic leukemia. All five Vh sequences were identical. Therefore, the Vh region in this leukemia was not the subject of detectable somatic mutation. These data suggest that chronic lymphocytic leukemia might lack the mechanism for somatic hypermutation and represent a stage of normal B lymphocyte differentiation in which the somatic hypermutation mechanism is not active.
Amino Acid Sequence↗
Clathrin beta-light chain of rat liver coated vesicles is phosphorylated in vitro and in vivo.
Clathrin beta-light chain of rat liver coated vesicles is phosphorylated in vitro in the presence of poly(L-lysine) by an endogenous protein kinase which appears to be similar to casein kinase II. Clathrin beta-light chain is also phosphorylated in vivo. After injection of [32P]phosphate into rats and preparation of purified coated vesicles in the presence of phosphatase inhibitors, electrophoretic analysis showed the presence of several labeled polypeptides including clathrin beta-light chain. A polypeptide of 50 kDa, which may correspond to the major polypeptide phosphorylated in vitro of coated vesicles, is also labeled in vivo.
Animals↗
Epidermal growth factor stimulated protein kinase shows similar activity in liver of senescent and adult mice.
It was recently reported [(1983) Nature 306, 617-620] that tyrosine protein kinase activity associated with EGF receptor was absent from senescent human cultured fibroblasts, which are known to have the same number of receptors as young human cultured fibroblasts. We have measured in both adult and senescent C57 black mice the number of EGF receptors, the activity of their associated tyrosine kinase and the activity of the protein phosphatase which dephosphorylates the EGF receptor. We found our results in both groups of animals to be similar which indicate that the observations made in cultured fibroblasts cannot be generalized to all mammalian tissues.
Aging↗
Protein kinase(s) in bovine brain coated vesicles.
Purified bovine brain coated vesicles contain protein kinase activity which phosphorylates 165, 54 and 50 kDa protein substrates. These phosphorylations do not seem to be induced by a unique protein kinase: indeed, the three substrates present different localizations in coated vesicles, the phosphorylation sites are either serine or threonine residues and vanadate and ATP[gamma S] have different effects on 32P incorporation in the substrates. Comparison of the coated vesicle protein and phosphorylation patterns from different tissues and animal origins shows that only the 50 kDa protein phosphorylation is always observed, compared to the great diversity in other minor phosphorylations which are observed or not in the various coated vesicles. The possible presence of a 50 kDa phosphoprotein phosphatase is also discussed. It is suggested that the 50 kDa protein with its connected specific kinase and phosphatase seems to constitute a regulatory system present in coated vesicles.
Adrenal Glands↗
Characterization of the epidermal-growth-factor-dependent phosphorylation system from normal mouse-liver sinusoidal plasma membranes.
Blood sinusoidal plasma membrane subfractions were isolated from normal mouse liver in the presence of the proteinase inhibitors PhMeSO2F and iodoacetamide. They were purified from smooth microsomal and Golgi vesicle contaminants. The phosphorylation reaction was studied at 33 degrees C, in the presence of 2 mM MnCl2. Addition of epidermal growth factor (EGF) to the preparations stimulated 32P incorporation from [gamma-32P]ATP or [gamma-32P]GTP essentially into one 170 000 Mr protein. Some incorporation was observed in a minor 120 000-Mr component which appears to be a degradation product of the 170 000-Mr component. No EGF-dependent phosphorylation of other membrane proteins or various exogenous proteins could be detected in vitro. The dephosphorylation of the 170 000-Mr component was observed after 4 min of incubation at 33 degrees C. This dephosphorylation reaction was inhibited by addition of 5 mM p-nitrophenyl phosphate but not by addition of micromolar Zn2+, Be2+ or orthovanadate. The 170 000-Mr protein specifically bound 125I-labeled EGF and thus appeared to be the hepatic EGF receptor. The EGF stimulatable kinase activity considerably enhances incorporation of 32P into tyrosine residues of the 170 000-Mr EGF receptor at 33 degrees C. Tryptic peptide maps of the 32P-labeled 170 000-Mr protein revealed a multiplicity of phosphorylated sites. Seven 32P-labeled phosphopeptides were observed after EGF stimulation, three of them being largely prominent. Tryptic peptide maps of the 170 000-Mr protein after it was covalently linked to 125I-labeled EGF showed only one 125I-labeled peptide, the migration of which appeared different from that of 32P-labeled phosphopeptides. These findings were confirmed by V8 protease unidimensional peptide mapping of the 170 000-Mr protein, labeled with 32P or 125I-EGF.
Animals↗
High density lipoprotein exchange reactions.
The term human serum high density lipoprotein (HDL) represents a range of lipid-protein complexes which are identified by their density and hence their relative lipid-protein content. Because HDL composition is variable, any proposed mechanisms for lipid and protein exchange must account for this variability. More importantly, since HDL has been repeatedly shown to be a negative risk factor in atherosclerosis, physical interactions have to be put in a physiological context. In this review, the lipid and protein exchange reactions of HDL with other lipoproteins, phospholipid vesicles, lipid-coated glass beads and isolated cells, will be considered. Particular emphasis will be placed on the role of the two major apoproteins of HDL, namely apo A-I and apo A-II, in these exchange reactions and a model will be presented to explain how these apoproteins might mediate lipid exchange, interconversions of lipoprotein particles, and the egress and excretion of lipid from cells.
Apolipoprotein A-I↗
Atherosclerosis: the role of lipids.
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Aged↗