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M J Johnson

Publications and source records attributed to M J Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1992

Protein kinase C stimulatory activity in the pseudopregnant rat ovary.

Ovarian cytosol from pseudopregnant rats was heated to 80-90 degrees C for 2 min and precipitated proteins removed by centrifugation. The supernatant of the heated ovarian cytosol contained no protein kinase C activity but when added to a control preparation containing protein kinase C, enzyme activity was increased to 200% of control. The stimulatory activity was stable to heating for 10 min, was retained on a centrifugal filtration device with a 100,000 M(r) cut-off, did not affect cAMP-dependent protein kinase, was not extractable in petroleum ether or chloroform/methanol (2:1), and enhanced the phosphorylation of protein kinase C-specific peptide substrates. The stimulatory factor was calcium-dependent and could substitute for phosphatidylserine and diacylglycerol in the protein kinase C assay. This stimulatory factor may provide a mechanism whereby the response of protein kinase C to hormonal activation could be regulated by the cell.

Animals↗
PubMed1992

Effect of aldose reductase inhibitors on lenticular dulcitol level in galactose fed rats.

We have shown that galactose cataract development is delayed or inhibited with the administration of aldose reductase inhibitors (ARIs). Dulcitol forms and accumulates in the lens of rats fed galactose. We undertook investigations to study the effectiveness of ARIs in preventing the formation and accumulation of dulcitol in the lens. Young Sprague Dawley rats were fed Purina Rat Chow with 50% galactose either with or without 15 mg sorbinil, 0.15, 0.5, or 1.0 mg E-0722/day/Kg body weight. At desired intervals following the initiation of diets, the lenses were processed for the determination of galactose and dulcitol levels. The lenticular dulcitol increased significantly in all animals fed galactose reaching a maximum level by approximately 15 days with comparatively lower levels in the groups fed ARIs with galactose; this increase was dose dependent in the groups fed E-0722. There was a subsequent, rapid drop in lenticular dulcitol by 18 days in all dietary groups. Interestingly, a second peak of increased lenticular dulcitol was observed in all groups. The correlation between dulcitol accumulation and cataract development is discussed.

Aldehyde Reductase↗
PubMed1992

Hyperamylinemia, hyperinsulinemia, and insulin resistance in genetically obese LA/N-cp rats.

The experimental evidence supporting a direct role for hyperinsulinemia as a cause of insulin resistance remains equivocal. Amylin, an islet beta-cell peptide cosecreted with insulin in response to nutrient stimuli, causes insulin resistance when infused into intact animals or applied to isolated skeletal muscles. We compared measures of amylin and insulin gene expression between control and genetically obese, insulin-resistant Lister Albany/NIH-(LA/N-cp) rats. Pancreatic amylin messenger RNA levels were increased 7.8 +/- 0.7-fold (mean +/- SEM), and plasma amylin-like immunoreactive material was increased 10.9 +/- 1.1-fold (LA/N-lean, 14 +/- 4 pM; LA/N-cp, 153 +/- 16 pM; p less than 0.0001) in obese rats. Pancreatic insulin I mRNA levels were increased 7.4 +/- 0.5-fold, and plasma insulin levels 20.0 +/- 5.0-fold, in these rats (LA/N-lean, 308 +/- 84 pM; LA/N-cp 6,120 +/- 1,540 pM; p less than 0.0001). The EC50 for insulin-stimulated incorporation of glucose into glycogen was about fourfold higher in muscles isolated from obese rats. The present results, coupled with previous observations, support the hypothesis that hyperamylinemia, rather than hyperinsulinemia per se, could have directly caused the insulin resistance in the obese LA/N-cp rats. Hyperamylinemia needs to be considered in future experimental studies probing the relation between hyperinsulinemia and insulin resistance.

Amyloid↗
PubMed1992

Alterations in lens permeability during galactose cataract development in rat.

Lens permeability has been shown to be compromised during galactose-induced cataract development in rats. Recent studies have demonstrated permeability and diffusion pathways as well as endocytotic activity in normal lenses of different species using tracers of different molecular weights. We investigated the permeability and diffusion of tracers in normal rat lenses and in lenses during cataract development using three different molecular weight tracers, lanthanum nitrate (LN, MW 430), ruthenium red (RR, MW 858.5) and horseradish peroxidase (HRP, MW 40.000) for this study. Sprague Dawley rats weighing 50gms were fed Purina Rat Chow with or without galactose. Our results, based on transmission electron microscopy, show that all tracers penetrated through the capsule and the basal portion of the intercellular spaces. While the diffusion of RR was restricted to the epithelial cell layer, LN and HRP were observed in intercellular spaces in cortical fiber cells. In the HRP "washout" studies, HRP could be readily removed from the intercellular spaces in the basal region in the epithelial cell layer. This and other observations suggest the presence of a barrier (tight-junction) in the apical region. Our studies also suggest an influx of tracers in the lens, specifically LN and HRP, through the equatorial region. The permeability of the tracers increased and endocytotic vesicles with tracers were often found associated with the lateral and basal membranes of epithelial cells in the galactose-fed rats at the precataractous and mature cataractous stages. This study provides further support for the presence of a tight-junction between epithelial cells and indicates the movement of tracers through the equatorial region. Moreover, it confirms previous observations that indicated alterations in lens permeability during galactose cataractogenesis.

Animals↗
PubMed1991

Fetal movement during labor.

The prognostic significance of antepartum fetal movement is well known; therefore it may be a variable in intrapartum fetal well-being. We report the simultaneous observation of fetal movement with fetal heart rate and uterine contractions by processed Doppler actograph signals during spontaneous labor of 22 normal women with normal fetal outcome. The mean percent incidence of fetal movement during labor was 17.3%. The percentage occurring during uterine contractions was 65.9%. Of all uterine contractions, 89.8% were associated with fetal movement. The proportion of time the fetus spent moving during uterine contractions (21.4%) was higher than between uterine contractions (12.9%). Uterine contractions associated with fetal movement were significantly longer than those not associated with fetal movement (p less than 0.0001). Mean percent incidence of fetal movement did not differ significantly between latent and active-phase labor. This study demonstrates a clear relationship between fetal movement and uterine contractions in labor.

Female↗
PubMed1991

Purification and characterization of a chimeric bifunctional antibody specific for human carcinoembryonic antigen and indium-benzyl-EDTA.

We describe the purification and characterization of a genetically engineered mouse/human chimeric bifunctional antibody specific for human carcinoembryonic antigen and indium-benzyl-EDTA. A clone expressing the bifunctional antibody has been previously described by our group and was found in this investigation also to express monospecific antibodies as well as Ig forms with mismatched light and heavy chains. The physicochemical properties of these various chimeric immunoglobulins were nearly identical. Isoelectric focusing showed that all these immunoglobulins have pI values between 8.47 and 8.80. A purification method that separates the bifunctional antibody from other Ig forms expressed in the same clone has been devised by relying on a unique interaction between the metal chelate binding region of these antibodies and the sulfopropyl functional group of a TSK SP 5-PW column.

Antibodies, Monoclonal↗
PubMed1991

Processing to endoglycosidase H-resistant thyrotropin subunits occurs in the presence of brefeldin-A: evidence favoring the recycling of Golgi membranes to the rough endoplasmic reticulum in mouse thyrotrophs.

In order to assess the localization and physiologic redistribution of Golgi enzymes within mouse thyrotrophs, we studied the carbohydrate processing of TSH subunits in the presence of brefeldin A (BFA). Although this drug clearly causes endoglycosidase (endo) H-sensitive species to accumulate in most cell types, our purpose was to determine whether or not endoglycosidase H-resistant forms of free alpha-subunits and TSH subunits eventually accumulated in small but significant amounts within mouse thyrotrophic tumor cells or pituitary thyrotrophs incubated with BFA. This drug is known to block intracellular transport from the rough endoplasmic reticulum (RER) to the proximal Golgi. Stimulated thyrotrophs have been reported to have some Golgi enzymes active in their dilated RER. Accumulation of endo H-resistant forms in the presence of BFA might be explained by (1) drug-induced enhancement of Golgi to RER membrane recycling with further aberrant distribution of Golgi enzymes or (2) an uncharacteristic trapping of glycoproteins within Golgi elements that might be an unusual action of BFA peculiar to thyrotrophs. Free alpha-subunits and TSH were labeled in mouse thyrotrophic tumor tissue or pituitaries incubated in pulse-chase fashion with [35S]methionine in the absence or presence of BFA, carboxyl cyanide m-chlorophylhydrazone (CCCP), or swainsonine. The results in tumor and pituitary tissue were similar. In incubations without drugs, most TSH subunits (greater than 90%) became endo H-resistant after 5-h chase, and the majority (greater than 85%) were secreted. Doses of CCCP and BFA were selected that generally blocked the secretion of TSH subunits by greater than 85% (in some cases greater than 99%), presumably because of accumulation of secretory proteins in the RER. Yet, in the presence of CCCP, 35% and 42% of intracellular free alpha-subunits and TSH subunits, respectively, became endo H-resistant at 5 h chase. Compared to control incubations, intracellular subunits tended to remain endo H-sensitive in the presence of BFA, yet, compared to CCCP incubations, BFA slightly enhanced the attainment of endo H-resistance by free alpha-subunits and TSH subunits to 55% and 52%, respectively. Pretreatment of tumor tissue with BFA allowed more endo H-resistant species to appear, even during coincubation with CCCP. These data suggest that Golgi enzymes cycle back to the dilated RER of active thyrotrophs and that this phenomenon is enhanced by BFA.

Adenosine Triphosphate↗
PubMed1991

Assessment of fibrin(ogen) degradation products in preeclampsia using immunoblot, enzyme-linked immunosorbent assay, and latex-based agglutination.

Plasma and serum from pregnant women with preeclampsia (N = 35) and normotensive pregnant (N = 71) and nonpregnant (N = 10) controls were screened for fibrin(ogen) degradation products (fibrinogen and cross-linked fibrin degradation products, and fibrin polymers) using three different assay systems (immunoblot, enzyme-linked immunosorbent assay [ELISA], and latex-bead agglutination assay). All tests showed statistically significant differences (P less than .05) between the preeclamptic patients and the other two groups (pregnant and nonpregnant women). The ELISA assay for total fibrin(ogen) degradation products was the most sensitive test, but was less specific than D-dimer latex. Eleven of the 35 preeclamptic women developed HELLP syndrome (hemolysis, elevated liver enzyme, and low platelet counts). Positive tests were as common in the 11 preeclamptic women who developed the syndrome as in the 24 who did not. These results suggest that fibrinolytic disorders are secondary pathophysiologic events in the course of preeclampsia, but further studies with a larger number of patients are needed.

Adolescent↗
PubMed1991

Characterization of monoclonal antibodies to two Treponema denticola serotypes by the indirect fluorescent-antibody assay.

Members of the genus Treponema have been implicated as possible aetiologic agents of periodontal disease. Previously developed murine monoclonal antibodies (MAbs) to two Treponema denticola strains were characterized by an indirect fluorescent-antibody (IFA) technique. Fifteen T. denticola strains and 32 other bacteria commonly isolated from periodontal pockets were used in the screening process. Two monoclonal antibodies to T. denticola ATCC 33521, serotype B, reacted with five T. denticola isolates, and one monoclonal antibody to T. denticola ATCC 33520, serotype c, reacted with two T. denticola isolates. There was no cross-reactivity between MAbs to the two serotypes. Preliminary tests of the MAbs on human periodontal samples show that they are useful in detecting these bacteria in clinical samples.

Antibodies, Bacterial↗
PubMed1991

Permeability studies in neonatal rat lens epithelium.

Lanthanum nitrate (LN) and horseradish peroxidase (HRP) were used as tracers to study intercellular permeability as well as the existence and location of tight junctions and changes in them, if any, in the lens epithelium of Sprague Dawley rats. Thin sections of lenses taken from animals at birth and at three day intervals until the neonates were weaned at approximately 22 days were studied at the electron microscope level. At every age both tracers permeated the intercellular spaces of the anterior region epithelium and between the fiber cells of the equatorial region. The LN precipitates terminated near the apical part of the epithelium in the anterior polar region and were not seen at the epithelial-fiber interface or between fibers in this region. At the site of the tracer termination the intercellular space was found to be considerably constricted or completely sealed. The HRP precipitates, however, were present in these intercellular spaces and by using the HRP "washout" procedure could be washed out of the basolateral site of the intercellular spaces of the epithelium up to the point of constriction if a tight junction were present. The lens area occupied by epithelium with tight junctions was age related being very small in lenses from animals less than 24 hours old and becoming increasingly enlarged as the newborn aged. These findings further confirm the existence of a barrier in the form of tight junctions between epithelial cells in the central anterior region of the maturing rat lens. Moreover, our observations also provide information regarding the pattern of tight junction development and distribution during lens maturation.

Animals↗
PubMed1990

Expression and characterization of a chimeric bifunctional antibody with therapeutic applications.

A simple method is described for the generation of a biologically produced mouse/human chimeric hetero-bifunctional antibody that has dual specificity for human carcinoembryonic Ag and metal chelate haptens. Two large compound chimeric vectors each containing the genetic information to produce a single antibody specificity were sequentially electroporated into the murine nonsecreting hybridoma SP2/0. This led to the isolation of a clone expressing high levels of total IgG (up to 25 micrograms/ml/10(6) cells), 10 to 20% of which showed simultaneous reactivity with both Ag. Binding studies showed that the immunoreactivities and affinity constants for the individual arms of the bifunctional antibody were equivalent to those seen with the parental antibodies.

Animals↗
PubMed1990

cDNA cloning and expression of a metalloproteinase inhibitor related to tissue inhibitor of metalloproteinases.

The purification and characterization of a metalloproteinase inhibitor (MI) from bovine aortic endothelial cells, and the demonstration that it is related to, but distinct from, tissue inhibitor of metalloproteinase (TIMP), have previously been reported [De Clerck, Y. A., Yean, T.-D., Ratzkin, B. J., Lu, H.S. & Langley, K. E. (1989) J. Biol. Chem. 264, 17445-17453]. The cDNA cloning of the bovine MI and its human homolog is now reported. The bovine cDNA cloning used probes designed on the basis of NH2-terminal amino acid sequence of bovine MI. The human cDNA cloning in turn used probes representing parts of the bovine cDNA nucleotide sequence. Both cDNAs encode leader sequences of 26 amino acids and mature protein sequences of 194 amino acids. The amino acid sequences of the mature proteins are 94% identical. The human MI cDNA was expressed in Escherichia coli, and a preparation containing anticollagenase activity was recovered. The amino acid sequence of mature human MI is 38% identical to the sequence for human TIMP, and the 12 cysteines in MI and TIMP are aligned almost identically. Thus MI and TIMP comprise an inhibitor family.

Amino Acid Sequence↗
PubMed1989

Dandy-Walker syndrome: a review of fifteen cases evaluated by prenatal sonography.

Fifteen cases of the Dandy-Walker syndrome evaluated by prenatal sonography were reviewed retrospectively. A posterior fossa cyst communicating with the fourth ventricle was a feature in each case. Hydrocephalus was present in 53% of fetuses. Extracranial congenital malformations were documented in 60% of cases. Cardiac, genitourinary, gastrointestinal, and skeletal anomalies were noted. Of 12 available karyotypes, 4 (33%) were abnormal, including two cases of trisomy 18. Excluding terminated pregnancies, there was an overall mortality of 55%. Associated congenital defects contributed to 83% of the postnatal deaths. The Dandy-Walker syndrome can be accurately diagnosed in utero by sonographic demonstration of characteristic morphologic changes in the fetal posterior fossa. The prenatal examination should include an evaluation of associated supratentorial and extracranial defects. Coexisting structural and chromosomal anomalies occur frequently and adversely affect survival.

Abnormalities, Multiple↗
PubMed1989

Concanavalin-A, lentil, and ricin lectin affinity binding characteristics of human thyrotropin: differences in the sialylation of thyrotropin in sera of euthyroid, primary, and central hypothyroid patients.

TSH from human serum was separated into classes by serial lectin affinity chromatography using Concanavalin-A (ConA), lentil, and ricin lectins. TSH from 10 euthyroid subjects, 40 patients with primary hypothyroidism, and 1 patient with central hypothyroidism was studied. The patterns of ConA and lentil affinity binding were similar for diverse patients; forms of TSH that bound firmly to ConA also tended to bind firmly to lentil. Differences in TSH-ricin binding suggested that there were differences in the sialylation of TSH in sera of euthyroid, primary, and central hypothyroidism patients. For euthyroid subjects, 16.1 +/- 5.4% (mean +/- SD) of the TSH bound to ricin, while after neuraminidase treatment, 38.4 +/- 5.4% bound. For patients with primary hypothyroidism, 23.5 +/- 6.0% of the TSH bound to the ricin, while after neuraminidase treatment, 65.7 +/- 8.8% bound. The increase in ricin binding induced by neuraminidase treatment was significantly higher for TSH from patients with primary hypothyroidism than in that from euthyroid subjects (42.3 +/- 7.6% vs. 22.3 +/- 4.4%; P less than 0.01) and was greater for long term than for short term hypothyroid patients (49.5 +/- 5.0% vs. 36.5 +/- 6.5%; P less than 0.01). While 30% of native TSH from the serum of the patient with central hypothyroidism bound to ricin, the amount bound increased only 17.6% after neuraminidase treatment. McKenzie bioassay of pituitary-derived TSH that was similarly fractionated using ricin failed to show detectable differences in bioactivity among the lectin column fractions. Thus, 1) circulating human TSH can be consistently separated into discrete classes using serial lectin affinity chromatography; 2) there is relatively more core fucosylation of the less processed high mannose and hybrid forms of TSH and less core fucosylation of more processed complex forms; 3) ConA and lentil binding of TSH in primary and central hypothyroidism is similar to that in the euthyroid state; 4) patients with primary hypothyroidism have more sialylated TSH than a patient with central hypothyroidism or euthyroid subjects; and 5) the degree of TSH sialylation increases with prolonged primary hypothyroidism.

Adult↗
PubMed1989

Prefeeding of aldose reductase inhibitor and galactose cataractogenesis.

Our recent investigations have shown that the Eisai compound, E-0722, (2R-4S-6-fluoro-1-2-methylspirochroman 4,4'-imidazolidine 2,5'-dione) is a more potent aldose reductase inhibitor than Sorbinil (D-6-fluorospirochroman 4,4'-imidazolidine 2,5'-dione). In the previous studies these aldose reductase inhibitors were added to the 50% galactose diet fed to rats to determine their effect on galactose-induced alterations in the lens and the development of cataract. In this report we present our results on the effect of prefeeding the aldose reductase inhibitor, E-0722, on the alterations in rat lens following subsequent feeding of galactose. For this study, young Sprague Dawley rats were prefed either rat chow or rat chow plus 50% galactose containing 1mg/day/Kg body weight of E-0722 for 1 or 2 weeks. After this dietary regimen, the animals were transferred to diets containing 50% galactose for different periods. For controls, rats were fed either rat chow or 50% galactose without the prefeeding of E-0722. Our results obtained through gross observation of the lenses, light microscopic studies of lens sections and assay of Na+-K+-ATPase (NPPase) activity show that the prefeeding of E-0722 prior to galactose feeding delays galactose-induced alterations and the development of mature cataract.

Aldehyde Reductase↗
PubMed1987

Human purine nucleoside phosphorylase and adenosine deaminase: gene transfer into cultured cells and murine hematopoietic stem cells by using recombinant amphotropic retroviruses.

Cell lines were established which produced high titers (approximately 10(6) infectious units per ml) of amphotropic, replication-defective recombinant retroviruses which transduced sequences encoding either human purine nucleoside phosphorylase (PNP) or adenosine deaminase (ADA). These viruses also contained a human hypoxanthine phosphoribosyltransferase gene as a selectable marker and a mouse metallothionein promoter (MMP) sequence just upstream from the PNP or ADA genes. Virus structure was maintained through the replication cycle if a short (216-base pair) MMP sequence was used. However, the use of a longer (1,834-base pair) MMP sequence resulted in the deletion of a significant portion of the recombinant virus genome, including the transcriptional regulatory elements of the MMP sequence. Northern analysis indicated a predominance of genome length transcripts in cells infected with deleted virus. The demonstration of substantial human PNP or ADA activity in virus-infected mouse fibroblasts by isozyme analysis suggested that active gene product was translated from either spliced or bicistronic message. The deleted ADA and PNP viruses were introduced into mouse hematopoietic stem cells by cocultivating freshly explanted bone marrow with virus producer cells. The infected marrow cells were injected into irradiated, syngeneic recipient mice, and the presence of integrated ADA or PNP proviral sequences was demonstrated in the DNA of spleen colonies by Southern analysis. Failure of these integrated proviral sequences to express active, human isozyme in spleen colony tissue indicated the existence of some regulatory constraint not active in cultured mouse cells.

Adenosine Deaminase↗
PubMed1987

Lung cancer, immune thrombocytopenia and the lupus inhibitor.

This case report describes the simultaneous occurrence of autoimmune thrombocytopenia and the lupus anticoagulant in a patient with primary adenocarcinoma of the bronchus. Treatment with corticosteroids and plasmapheresis resulted in a return to normal of the partial thromboplastin time and the disappearance of the platelet antibodies. The carcinoma was inoperable.

Adenocarcinoma↗