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Biomedical subjects

J Born

Publications and source records attributed to J Born.

At least 217 records · Page 12Linked to original sources
PubMed1986

Does complement kill E. coli by producing transmural pores?

Three lines of evidence are presented to indicate that C5b-9 kills serum-sensitive E. coli K 12 cells by generating functional pores across the outer and inner bacterial membrane. First, viable cells carrying C5b-8 complexes are impermeable to o-nitrophenyl-beta-D-galactoside (ONPG), but lose viability and become permeable to this marker upon post-treatment with purified C9 in the absence of lysozyme. Cells killed with colicin E1 or gentamicin are also impermeable to ONPG but take up the marker if they are post-treated with lysozyme-free serum. Second, killing by C5b-9 is highly effective, deposition of only a small number of complexes being lethal. This has been demonstrated in experiments where viable cells carrying 2000-4000 C5b-7 complexes per CFU were permitted to multiply in broth culture, and the daughter generations subsequently treated with purified C8 and C9. Fifty percent killing was observed in the fifth to sixth generation, corresponding to a dilution of C5b-7 complexes to 50-100 molecules/CFU. In the presence of 2 mM EDTA, further dilution of C5b-7 down to 8-30 complexes/CFU still caused 50% killing of daughter cells. Third, treatment of C5b-7 cells with purified CC8 and C9 results in the release of intracellular K+, which commences immediately after addition of C8/C9. This was shown in experiments where C5b-7 cells were packed to high density in saline, post-treated with C8 + C9, and K+ directly measured in the cell supernatants. Based on these results, we propose that C5b-9 pores deposited in the outer bacterial membrane periodically fuse with the inner membrane, the transmural pores thus generated permitting rapid K+ efflux, with cell death ensuing through the collapse of membrane potential.

Bacteriolysis↗
PubMed1985

An ACTH 4-9 analog impairs selective attention in man.

Male adults were tested in a dichotic listening task, providing electrophysiological measures of selective attention. Subjects were tested twice, 60 min after oral administration of either 40 mg of ACTH 4-9 analog, or placebo. Averaged auditory evoked potentials (AEPs) to tone pips when attended and when unattended, EEG spectra, heart rate and blood pressure, and behavioral performance were measured during task performance. ACTH 4-9 analog treatment impaired selective attention as indicated a) by a diminished difference between evoked potential waveforms to attended and to unattended tone pips, b) by an impaired behavioral signal detection performance. Furthermore, frontal EEG theta activity slowed down after ACTH 4-9 analog. With time on task, however, there was no decay, but an improvement of selective attention after peptide administration. Differences in attention could not be due to concurrent changes in general cortical and autonomic arousal as indicated by EEG alpha activity, blood pressure and heart rate. Since separate analyses of the AEPs revealed an increased processing of the unattended tone pips in the ACTH 4-9 analog sessions the impaired selective attention under ACTH 4-9 analog may be described as an inability to suppress processing of irrelevant or distracting stimuli.

Adolescent↗
PubMed1985

Adipsic hypernatremia in a patient with pseudotumor cerebri and the primary empty sella syndrome.

Adipsic hypernatremia, a rare disorder, usually secondary to a hypothalamic lesion, is caused by the combination of partial central diabetes insipidus with hypo- or adipsia. We studied a patient who presented with a global hypothalamic dysfunction including adipsic hypernatremia. An extensive work-up disclosed the presence of pseudotumor cerebri and an empty sella turcica. Although endocrine abnormalities including true diabetes insipidus have been reported in conjunction with pseudotumor cerebri or an empty sella, no patient described presented such a global hypothalamic dysfunction or adipsic hypernatremia. The increased intracranial pressure is postulated to be the responsible mechanism for both the empty sella and the hypothalamic dysfunction.

Adult↗
PubMed1985

Effects of an ACTH 4-9 analog on auditory evoked brainstem responses and middle latency responses.

Early and middle latency auditory evoked potentials (EAEPs and MAEPs) were recorded from thirteen male volunteers after oral administration of either 40 mg of an ACTH 4-9 analog (ORG 2766) or placebo. Main results indicate slightly longer latencies of the later components of the EAEPs after ACTH 4-9 analog. Effects of differences in treatment were clearest with very high stimulus rates. Therefore, these effects do not lend themselves for the explanation of ACTH 4-9 analog-induced changes in long latency auditory evoked potentials of cortical origin obtained with comparatively slow stimulus rates in earlier studies. In addition, the ACTH 4-9 analog inhibited a decrease in amplitudes of the Na component of the MAEP across the session. This latter result may be in line with dishabituating actions of the peptide.

Adolescent↗
PubMed1985

An embryonic inducing factor: isolation by high performance liquid chromatography and chemical properties.

A protein (vegetalizing factor) which induces amphibian gastrula ectoderm to tissues which in normal development are derived from endoderm and mesoderm has been isolated from chicken embryo trunks by a combination of size exclusion and reversed phase HPLC. An amount of 0.5 ng factor per gastrula evokes inductions in 80-100% of the cases. The protein (apparent Mr approximately 13 000) is split by NaBH4 to polypeptide chains of about half the size under conditions in which disulfide bridges are reduced. The biological activity is lost.

Amino Acids↗
PubMed1984

Ribonucleoprotein particles from Xenopus eggs and embryos. Neural-archencephalic-inducing activity of the protein moiety.

Ribonucleoprotein particles were isolated from unfertilized eggs and gastrula stages of Xenopus laevis. The particles from both stages induce in gastrula ectoderm the formation of large foreheads (neural-archencephalic-inducing activity), whereas ribosomal subunits have no inducing activity. The inducing activity of particles from both stages is largely abolished after treatment with proteolytic enzymes and to some extent with ribonuclease. The protein moiety of gastrula ribonucleoprotein particles was extracted with phenol and the protein reduced with 2-mercaptoethanol. The protein induces foreheads, but at a lower rate than the intact particles. The protein was fractionated by high-performance liquid size-exclusion chromatography on a derivatized silica gel with 75% formic acid as eluent. The fraction which includes proteins from 10 000 to 16 000 Da has the highest neural-archencephalic-inducing activity.

Animals↗
PubMed1984

Human memory and neurohypophyseal hormones: opposite effects of vasopressin and oxytocin.

A classical task of experimental psychology, the retention of lists of words, was given twice to three groups of subjects treated with lysine vasopressin (LVP), oxytocin or saline. From a baseline session (no treatment) to a second session with treatment, the LVP and placebo groups showed an enhancement of the number of words remembered correctly, whereas the oxytocin group did not. Rather, oxytocin impaired memory performance. However, we cannot claim a memory enhancing effect of LVP, because placebo treatment enhanced memory performance to the same extent.

Adult↗
PubMed1984

Dishabituating effects of an ACTH 4-9 analog in a vigilance task.

Ten male adults were tested in a vigilance task after oral administration of either 40 mg ACTH 4-9 analog, ORG 2766, or placebo in a single three hour session. EEG spectra, averaged auditory evoked responses, heart rate and blood pressure, and behavioral performance were measured during a vigilance task. ACTH 4-9 analog treatment led to a decreased inhibition of the central nervous system across the experiment: to less mean power density and faster center frequencies within the alpha band, and to less attenuated amplitudes of the components of the auditory vertex potential (P50, N100, P200). Treatment effects increased towards the end of the session and might indicate a dishabituating effect, probably due to suppression of inhibitory influences of limbic structures on mesencephalic reticular activity.

Adrenocorticotropic Hormone↗
PubMed1984

Behavioral effects of vasopressin.

A single case study was executed to generate hypotheses concerning the role of vasopressin in human behavior. Classic tasks of experimental psychology, introspective and electrophysiological measures were applied in twelve sessions after randomized intake of vasopressin or a placebo. Results indicate that earlier stages of information processing in terms of attentional and arousal processes could be affected by the neuropeptide. Therefore the often claimed enhancement of memory processing seems to be an indirect effect of vasopressin.

Arousal↗
PubMed1984

Two-dimensional echographic localization of intracardiac cerebrospinal fluid shunt catheters.

This study evaluated the ability of two-dimensional echocardiography (2D echo) to detect and localize the distal end of ventriculoatrial shunt catheters in the cardiac chambers of hydrocephalic patients. Twenty-eight patients were studied, and the performances of 2D echo and standard chest x-ray filming were compared. Although standard chest x-ray filming allowed accurate determination of the catheter position in only half of the patients, 2D echo afforded clear visualization and accurate localization of the catheter in all instances. By its precise definition of intracardiac anatomical landmarks and its excellent time determination, 2D echo can provide valuable information on the movements of the catheter's distal end during the cardiac cycle, during head flexion or rotation, and during deep breathing movements. Some interesting observations were made with 2D echo. A to-and-fro motion of the catheter tip through the tricuspid orifice during the cardiac cycle was visualized in two instances. The combination of head movements and deep respiratory movements induced a variation in the position of the catheter tip. The magnitude of this displacement was 6 cm at the most. Two patients underwent reoperation for lengthening or shortening of the catheter. The operative findings confirmed the ultrasonic localization in both cases where the chest x-ray film had failed to identify or adequately locate the catheter tip. It is concluded that 2D echo is a safe, innocuous, and accurate method with which to locate the distal end of a ventriculoatrial shunt. It is the only available technique that provides visualization of intracardiac structures and cardiac cycle reference.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

[Electromanometric studies of the sphincter zone using unperfused probes on children with a healthy anus].

With regard to the measuring technique with unperfused water-filled tubes, many authors report different standards concerning the anorectal pressure zone. In order to define standards, 133 infants with healthy anorectal sphincter from 1 to 12 years of age were examined by this method. As a result, it must be stated that this method cannot reproduce standards. For this reason, very thin perfused tubes with very low rates of perfusion should be used to obtain at least the anorectal pressure profile. The reasons for the poor results achieved with this method, due to the measuring technique, are demonstrated.

Anal Canal↗
PubMed1982

Spontaneous cortical slow-potential shifts and choice reaction time performance.

EEGs from Fz, Cz and Pz locations (reference--right mastoid) were obtained from 36 adults. For experimental trials the Fz slow potentials (SP) were determined for a pretask interval of: a 3 sec baseline, followed by a 2.5 sec SP shift, in either negative (3.5 microV) or positive (1.5 microV) direction, and maintenance at this level for another 2.5 sec. When this criterion was met the stimuli for a choice RT task were presented (potential-related event, PRE), which required a button-press response with the right or left hand for differing stimulus configurations. During subsequent control sessions subjects were tested without pretask criterion SP shifts, with yoked pretask intervals from the experimental sessions. For the experimental conditions the mean RTs were significantly faster and less variable with the negative than with the positive SP shift condition. For the control conditions mean RTs were somewhat faster for the positive than for the negative criterion, which might be attributed to the more variable pretask intervals during the latter polarity condition. For confirmation of the cortical localization of this effect, the experimental session was replicated with corresponding negative and positive SP shift criteria from Pz. No significant differences among means and standard deviations of RTs were found. SP shifts from criterion electrodes (Fz or Pz) were significantly greater in mean amplitude than the concomitant SP shifts from the other electrodes. The present findings demonstrate the feasibility of the PRE methodology for investigations of human brain functions.

Adult↗
PubMed1982

Radioiodination with 125I and reductive methylation with tritium of a vegetalizing inducer protein. Specific radio-activities and effect on biological activity.

An inducer protein, the vegetalizing factor, which causes amphibian ectoderm to differentiate into endoderm was labelled with carrier-free 125I (2000 Ci/m-Atom) to specific activities of 17-32 micronCi/microgram protein. The partial loss of the biological inducing activity is not caused by the iodination of the factor but is due to the oxidation and reduction steps in the iodination procedure. By reductive methylation with formaldehyde and [3H]NaBH4 under mild conditions the factor was labelled to specific activities of 0.8-2.3 micronCi/microgram protein depending on the specific activity of the [3H]NaBH4 (5-15 Ci/mmol). Under these conditions up to 25% of the amino groups of the protein were methylated without a reduction of the biological activity of the factor. The inducing activity of the protein was however considerably reduced, when under more stringent conditions 60-70% of the amino groups were methylated. It was shown by NMR spectroscopy that about one third of protein amino groups is dimethylated under these conditions. The factor could be labelled with N-(propionyloxy)succinimide without a loss of the biological activity, when very few amino groups were substituted. The experiments show that the factor can be labelled to high specific activity without loss of its inducing activity by reductive methylation, which is therefore the most suitable method.

Animals↗
PubMed1981

A vegetalizing inducing factor. Isolation and chemical properties.

A vegetalizing factor which induces the formation of endodermal and mesodermal organs in amphibian gastrula ectoderm was purified from chicken embryos. Preparative sodium dodecyl sulfate polyacrylamide electrophoresis and gel permeation chromatography on sephadex with different eluants were employed. In buffer containing 6 M urea the molecular weight of the factor was estimated to about 28 000-30 000. In buffer containing sodium dodecyl sulfate (SDS) the factor partially dissociates to smaller polypeptide chains. Because an equilibrium between molecules of different size is established, SDS-containing buffers are not suitable for preparative purposes. In 50%-70% formic acid the factor completely dissociates into smaller peptide chains (Mr about 13 000-15 000). Furthermore, very little absorption of the factor to the gel matrices or glass surfaces is observed in formic acid. The final purification can be achieved by high-performance gel permeation chromatography with glycerolpropyl-treated silica gel as column packing and 50% formic acid as eluant.

Animals↗
PubMed1980

R-loop hybridization of collagen DNA: separation in Cs2SO4 gradients.

High molecular weight poly(A)RNA (26-35 S) from chicken embryo trunks which is enriched for collagen mRNA was iodinated and hybridized to DNA under conditions of R-loop formation. The R-loops were separated in Cs2SO4 gradients from the bulk of DNA yielding double stranded DNA enriched for collagen genes.

Animals↗