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K Buss

Publications and source records attributed to K Buss.

8 recordsLinked to original sources
PubMed2001

Clustering of isochorismate synthase genes menF and entC and channeling of isochorismate in Escherichia coli.

There are two isochorismate synthase genes entC and menF in Escherichia coli. They encode enzymes (isochorismate synthase, EC 5.4.99.6) which reversibly synthesize isochorismic acid from chorismic acid. The genes share a 24.2% identity but are differently regulated. Activity of the MenF isochorismate synthase is significantly increased under anaerobic conditions whereas the activity of the EntC isochorismate synthase is greatly stimulated during growth in an iron deficient medium. Isochorismic acid synthesized by EntC is mainly channeled into enterobactin synthesis whereas isochorismic acid synthesized by MenF is mainly channeled into menaquinone synthesis. When menF or entC were separately placed onto overexpression plasmids and the plasmids introduced into a menF(-)/entC(-) double mutant in two separate experiments, the isochorismate formed was fed into both, the menaquinone and the enterobactin pathway. Moreover, in spite of a high isochorismate synthase activity menaquinone and enterobactin formation were not fully restored, indicating that isochorismate was lost by diffusion. Thus, under these conditions channeling was not observed. We conclude that in E. coli the chromosomal position of both menF and entC in their respective clusters is a prerequisite for channeling of isochorismate in both pathways.

Chorismic Acid↗
PubMed2001

Properties and interaction of heterologously expressed glutamate decarboxylase isoenzymes GAD(65kDa) and GAD(67kDa) from human brain with ginkgotoxin and its 5'-phosphate.

Two isoforms of glutamate decarboxylase (GAD(65kDa) and GAD(67kDa)) from human brain, which had previously been overexpressed in Escherichia coli as fusion proteins containing a glutathione-S-transferase domain, were purified by affinity chromatography on glutathione Sepharose 4B. Both isoforms were also expressed in Saccharomyces cerevisiae. After modification of a HPLC based assay, the enzymes were characterized with respect to their biochemical properties. Comparison of kinetic data, pH, and temperature optima as well as of the mode of interaction with pyridoxal phosphate as a cofactor revealed several significant differences between the two isoenzymes reflecting their somewhat different physiological and molecular features. Investigation of the influence of 4'-O-methylpyridoxine (ginkgotoxin) (1), a neurotoxin occurring in Ginkgo biloba L., on the different isoenzymes, indicates that the phosphorylated form of the toxin, 4'-O-methylpyridoxine-5'-phosphate (2), decreases GAD(65kDa) activity, although in unphysiologically high concentrations, whereas GAD(67kDa) activity seems to be hardly affected.

Brain↗
PubMed1996

Stress reactivity and attachment security.

Seventy-three 18-month-olds were tested in the Ainsworth Strange Situation. These children were a subset of 83 infants tested at 2, 4, 6, and 15 months during their well-baby examinations with inoculations. Salivary cortisol, behavioral distress, and maternal responsiveness measures obtained during these clinic visits were examined in relation to attachment classifications. In addition, parental report measures of the children's social fearfulness in the 2nd year of life were used to classify the children into high-fearful versus average- to low-fearful groups. In the 2nd year, the combination of high fearfulness and insecure versus secure attachment was associated with higher cortisol responses to both the clinic exam-inoculation situation and the Strange Situation. Thus, attachment security moderates the physiological consequences of fearful, inhibited temperament. Regarding the 2-, 4-, and 6-month data, later attachment security was related to greater maternal responsiveness and lower cortisol baselines. Neither cortisol nor behavioral reactivity to the inoculations predicted later attachment classifications. There was some suggestion, however, that at their 2-month checkup, infants who would later be classified as insecurely attached exhibited larger dissociations between the magnitude of their behavioral and hormonal response to the inoculations. Greater differences between internal (hormonal) and external (crying) responses were also negatively correlated with maternal responsiveness and positively correlated with pretest cortisol levels during these early months of life.

Crying↗
PubMed1996

Behavioral inhibition and stress reactivity: the moderating role of attachment security.

The role of the mother-toddler attachment relationship in moderating the relations between behavioral inhibition and changes in salivary cortisol levels in response to novel events was examined in 77 18-month-olds. Behavioral inhibition was determined by observing toddler inhibition of approach to several novel events. Attachment security to mother was assessed using the Ainsworth Strange Situation. Changes in salivary cortisol were used to index activity of the stress-sensitive hypothalamic-pituitary-adrenocortical (HPA) system. In addition, toddler coping behaviors and the behaviors used by mothers to help toddlers manage novel events were examined. Elevations in cortisol were found only for inhibited toddlers in insecure attachment relationships. Mothers in these relationships appeared to interfere with their toddlers' coping efforts. These results are discussed in the context of a coping model of the relations between temperament and stress reactivity.

Adaptation, Psychological↗
PubMed1984

Decerebrate rigidity and vegetative signs in the acute midbrain syndrome with special regard to motor activity and intracranial pressure.

Decerebrate rigidity, intracranial pressure and vegetative signs were studied in 25 patients. Advanced statistical techniques were used to analyse the interrelationships between muscle activity (IEMG), blood pressure (ABP), intracranial pressure (ICP), pulse rate (HR), respiratory rate (RR), and central venous pressure (CVP) occurring during paroxysms of decerebration. The pattern of reaction is influenced by compression or stress imposed on the brain stem at the tentorial incisure and is related to the degree of cisternal obstruction. Significant differences in reaction were disclosed between provoked and spontaneous decerebration posturing.

Adolescent↗
PubMed1982

Intracranial pressure and muscle activity in patients with decerebrate rigidity.

The authors analyse the relationship between the muscle activity during paroxysms of decerebration and the intracranial pressure. These relationships differ, and depend upon the presence or absence of mesencephalic herniation and patency of the perimesencephalic cisterns, as well as on whether the decerebration posturing has been spontaneous or induced by external stimulus. It is suggested that the magnitude of ICP reaction during decerebration is connected with the possibility of compensating the increased intracranial volume and with the strain imposed upon the brain stem at the mesencephalic level. Close correlations between the vegetative variables occuring during spontaneous DR paroxysms suggest a common excitatory neuronal mechanism. In cases when decerebration is provoked by external stimuli the response becomes more complex and not uniform.

Adult↗