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Biomedical subjects

J Kingma

Publications and source records attributed to J Kingma.

68 records · Page 4Linked to original sources
PubMed1988

Alkane utilization in Pseudomonas oleovorans. Structure and function of the regulatory locus alkR.

The OCT plasmid-localized alkBAC operon encodes enzymes for alkane hydroxylation and alkanol dehydrogenation. The positively controlled expression of the operon is very efficient in both Pseudomonas putida and Escherichia coli. Two regulatory functions have been ascribed to the regulatory locus alkR: inducer recognition and transcriptional activation of the operon. We have cloned and localized the alkR locus on a 4.9-kilobase pair SalI fragment. The alkR region was analyzed for translation productions in E. coli minicells. Two proteins were identified: a 99- and a 48-kDa peptide. The positions of the cistrons encoding these proteins were established. Both cistrons were shown to be essential for an Alk phenotype. The first cistron (alkS), which encodes the 99-kDa protein, complemented alkR mutations affecting inducer specificity. Furthermore, we found that alkS is responsible for activation of expression of the alkBAC operon since it is required for the induction of the alkB gene product alkane hydroxylase. The second cistron (alkT), which encodes the 48-kDa protein, is required for reconstitution of an Alk phenotype but has no function in regulation of alkBAC expression. Thus, the expression of the alkBAC operon is regulated by a 99-kDa protein, whereas the 48-kDa protein is probably a component of the alkane hydroxylase complex.

Bacterial Proteins↗
PubMed1988

Crystallization of haloalkane dehalogenase from Xanthobacter autotrophicus GJ10.

Haloalkane dehalogenases are enzymes that release chloride or bromide from n-halogenated alkanes. X-ray quality crystals of haloalkane dehalogenase from the 1,2-dichloroethane-degrading bacterium Xanthobacter autotrophicus GJ10 have been grown at room temperature from 64% saturated ammonium sulfate solutions (pH 6.2 to 6.4). The crystals diffract in the X-ray beam to at least 2.4 A resolution (1 A = 0.1 nm). Their space group is P2(1)2(1)2, with cell dimensions a = 94.1 A, b = 72.8 A, c = 41.4 A and alpha = beta = gamma = 90 degrees. There is one monomer (molecular weight 36,000) per asymmetric unit.

Gram-Negative Aerobic Bacteria↗
PubMed1988

Protection afforded by allopurinol in the first 24 hours of coronary occlusion is diminished after 48 hours.

Experiments were performed to test whether the reduction in infarct size afforded by allopurinol following 24 h of permanent coronary artery occlusion is sustained over the subsequent 24 h. A dog's coronary artery was occluded with an embolus followed by injection of radiomicrospheres into the left ventricle to mark the ischemic region and to measure regional blood flow. Dogs were sacrificed either 24 h or 48 hours after embolization. The infarcts were delineated by failure to stain with triphenyl tetrazolium chloride and the ischemic zones were visualized by autoradiography of the heart slices. Dogs in the treatment groups received 600 mg of allopurinol PO 18 h before surgery, and a 10 mg/kg IV bolus 15 minutes before embolization followed by constant IV infusion of 55 mg/kg/24 h until sacrifice. A close correlation in the control animals between the percent of the ischemic zone which infarcted and collateral blood flow was used to predict a nonintervention infarct size in each treatment animal. Allopurinol treatment caused 17.9 +/- 3.3% less of the risk zone to be tetrazolium negative after 24 hours of ischemia than that seen in untreated animals. Less allopurinol induced salvage was observed in the 48 hour drug group with only a 11.1 +/- 3.3% limitation in infarct size. Furthermore, the effect was inconsistent at 48 h with only 2 dogs showing salvage. We conclude that allopurinol delays but does not prevent infarction in the permanent occlusion model.

Allopurinol↗
PubMed1988

Secular trends in abortion attitudes: 1975-1980-1985.

In this study, we compared the attitudes toward abortion of respondents from the National Opinion Research Center's (NORC) General Social Survey (GSS) for the years 1975, 1980, and 1985. The major theme of the GSS is that an adequate description of changes in abortion attitudes is predicted on resolving the question of whether the six abortion items used in the surveys measure one or two dimensions. We used the Mokken method of scale analysis, a stochastic extension of Guttman scaling, to resolve this question. We concluded that the six items are unidimensional and, therefore, create a single scale to measure the changes in abortion attitudes across the three periods. The data revealed virtually no change from 1975 to 1980, but a significant, though small, drop in approval from 1980 to 1985.

Abortion, Induced↗
PubMed1986

Alternative matrix seriation, traditional seriation, and multiple classification.

This study investigated the structural relationships between traditional seriation tasks derived from Piaget's publications and alternative matrix seriation on the one hand, and alternative matrix seriation and multiple classification on the other. Subjects were 464 children from two kindergartens and three primary schools, Grades 1 through 6 who completed these three types of tasks. Factor analysis revealed that the alternative matrix seriation tasks (often used in neo-Piagetian research) did not reflect the same underlying concept as the traditional seriation tasks derived from Piaget's publications. In contrast, we found that alternative matrix seriation referred to the same underlying concept as multiple classification. We concluded that the alternative matrix seriation tasks cannot serve as a replacement for the traditional seriation tasks in assessing a child's seriation capacity.

Child↗
PubMed1985

Heat-labile enterotoxin of Escherichia coli. Characterization of different crystal forms.

Heat-labile enterotoxin (LT) was obtained in large quantities (several-gram amounts) and great purity from Escherichia coli C600 carrying the LT-coding multicopy plasmid EWD299. By growing this strain on a medium that allows high cell densities in the early stationary phase, we increased the net LT production per milliliter by a factor of 200, compared to natural porcine enterotoxigenic E. coli. Adsorption and redesorption on Controlled-Pore Glass usually resulted in a 50-100-fold purification of LT in one simple step, which was followed by established purification procedures. LT shows a natural tendency to form large crystals, which, however, are disordered. After numerous trials, conditions were found which virtually eliminated the disorder. Much better crystals were obtained by employing CdCl2 and KF as coprecipitating agents. CdCl2 yielded crystals which did not contain A subunits as judged by electrophoresis of dissolved crystals. Adding KF results in beautifully shaped crystals which diffracted beyond 2 A and are suitable for a high resolution structure determination.

Bacterial Toxins↗
PubMed1985

Storage-retrieval processes of normal and learning-disabled children: a stages-of-learning analysis of picture-word effects.

Previous research comparing acquisition performance of learning-disabled and normally achieving children has led to the suggestion that the locus of memory differences lies in either the storage or retrieval components of recall. In this paper we report a free-recall experiment in which a new stages-of-learning model was used to examine the effects of a picture-word manipulation on storage and retrieval differences between nondisabled and disabled grade 2 and 6 children. Although the results of this experiment were consistent with the idea that disabled students are poorer at memory tasks than nondisabled students, the stages-of-learning analysis provided information regarding the precise locus of the deficiencies. Specifically, although disabled and nondisabled children benefited from the presentation of information in pictorial format, normally achieving children were consistently better than their learning-disabled counterparts at storing and learning to retrieve both pictures and words. From a developmental standpoint, the most important finding was that while differences between learning-disabled and normally achieving students at storage remained age invariant, differences in learning to retrieve increased with age. As it turned out, however, differences between disabled and nondisabled children were absent when it came to retaining traces once they had been stored in memory and in retrieval performance between the time a trace was stored and retrieval learning was complete. These results are consistent with previous research in which it has been shown that the ability to learn how to reliably retrieve information that has been stored in memory develops more slowly for disabled than nondisabled children.

Age Factors↗
PubMed1983

Characterization of intracellular inclusions formed by Pseudomonas oleovorans during growth on octane.

The growth of Pseudomonas oleovorans on n-octane was characterized by the formation of intracellular structures. These inclusions were isolated and characterized. Morphologically, they resembled the poly-beta-hydroxybutyrate granules found in Bacillus cereus, as shown by freeze-fracture electron microscopy. The elemental analysis of isolated granules showed, however, that they do not contain poly-beta-hydroxybutyric acid. Instead, the analysis was consistent with a C8 polyester, which interpretation was supported by the fatty acid analysis of hydrolyzed granules. From the evidence presented here, we conclude that P. oleovorans forms poly-beta-hydroxyoctanoate granules when grown on n-octane.

Caprylates↗
PubMed1979

Nature of the regions involved in the insertion of newly synthesized protein into the outer membrane of Escherichia coli.

Outer membrane proteins are synthesized by cytoplasmic membrane-bound polysomes, and inserted at insertion sites which cover about 10% of the total outer membrane when cells grow with a generation time of 1 h. A membrane fraction enriched in outer membrane insertion regions was isolated and partly characterized. The rat at which newly inserted proteins are transferred from such insertion regions into the rest of the outer membrane was found to be very fast; the new protein content of insertion regions and that of the remaining outer membrane equilibrate completely within about 20 s at 25 degrees C. Given the rather rigid structure of the outer membrane and the multiple interactions between outer membrane components and the murein layer, lateral diffusion of newly inserted proteins from insertion sites to the remaining outer membrane is not likely to explain this rapid equilibration. Instead, the data support a model in which insertion regions move along the cell surface, leaving behind stationary, newly inserted outer membrane proteins.

Bacterial Proteins↗
PubMed1978

Insertion of newly synthesized proteins into the outer membrane of Escherichia coli.

The insertion of newly synthesized proteins into the outer membrane of Escherichia coli has been examined. The results show that there is no precurser pool of outer membrane proteins in the cytoplasmic membrane because first, the incorporation of a [35S]methionine pulse into outer membrane proteins completely parallels its incorporation into cytoplasmic membrane proteins, and second, under optimal isolation conditions, no outer membrane proteins are found in the cytoplasmic membrane, even when the membranes are analysed after being labeled for only 15 s. The [35S]methionine present in the outer membrane after a pulse of 15 s was found in protein fragments of varying sizes rather than in specific outer membrane proteins. This label could however be chased into specific proteins within 30--120 s, depending on the size of the protein, indicating that although unfinished protein fragments were present in the outer membrane, they were completed by subsequent chain elongation. Thus, outer membrane proteins are inserted into the outer membrane while still attached to ribosomes. Since ribosomes which are linked to the cell envelope by nascent polypeptide chains are stationary, the mRNA which is being translated by these ribosomes moves along the inner cell surface.

Bacterial Proteins↗
PubMed1978

The effect of toluene on the structure and permeability of the outer and cytoplasmic membranes of Escherichia coli.

The effect of toluene on Escherichia coli has been examined. In the presence of Mg2+, toluene removes very little protein, phospholipid, or lipopolysacharide from E. coli. In the absence of Mg2+, or in the presence of EDTA, toluene removes considerably more cell material, including several specific cytoplasmic proteins such as malate dehydrogenase (EC 1.1.1.37). In contrast, glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and glutamate dehydrogenase (EC 1.4.1.4) are not released at all under the same conditions. Cells treated with toluene in the presence of Mg2+ remain relatively impermeable to pyridne nucleotides, while cells treated with toluene in the presence of EDTA become permeable to these compounds. Freeze-fracture electron microscopy shows that toluene causes considerable damage to the cytoplasmic membrane, while the outer membrane remains relatively intact. These results indicate that the permeability characteristics of toluene-treated cells depend at least partly on the state of the outer membrane after the toluene treatment.

Cell Membrane↗