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R Walden

Publications and source records attributed to R Walden.

At least 19 recordsLinked to original sources
PubMed2006

[Quantitative Cardiotocography--what does it look like and what can we expect].

BACKGROUND: [corrected] Cardiotocography (CTG) seems to be a non-reliable, expensive but nevertheless practical method for fetal surveillance. Moreover, its diagnostic value is dependent on a long-standing experience of the obstetrician (midwife). It is difficult to define exact diagnostic criteria since nearly all CTG phenomena are lacking precise qualification by the naked eye. Therefore, the idea must be born in mind to analyze fetal heart frequency (FHF) by computer, first off-line then on-line, in order to evaluate its true diagnostic power objectively. METHODS: The FHF of 583 deliveries terminated by the vaginal route were registered prospectively using a PC and an RS422 interface. In 443 cases acid-base measurements (ABL 500, RADIOMETER, Copenhagen) in blood of the umbilical artery (UA) and vein (UV) were available and plausible. In this study only the last 30 min ante-partum were analyzed. The program for FHF analysis was written in MATLAB (The Mathworks Inc., USA). A CTG score was developed using three components of FHF: basal FHF, the deceleration area of all dips, and the micro-fluctuation (MF) of the basal fetal heart rate (FHR). MF denotes the true number of "turning-points" per minute of basal FHR. For each component a maximum of 6 scoring points could be assigned according to empirical cut-off values. These cut-off values were determined using correlation analysis with acid-base parameters in UA blood, especially the actual pH. The accordance between score and pH values was further demonstrated by assignment of 0.036 pH-units to each of the 19 (18 + zero) scoring points, thus covering a pH range between 6.700 and 7.350 (UA). A resulting variable, delta pH (pH measured, UA-pH assigned) was studied and used for further analysis. In order to define criteria for fetal mortality in utero only cases with pH, UA between 7.250 and 7.350 were accepted. RESULTS: Median basal FHF under normal conditions amounted to 138 bpm (mean: 137 +/- 14.9) in 4180 minutes of 372 fetuses. 120 bpm equals the 13.4(th) and 160 bpm the 94.6(th) centile of the distribution. Given fetal normacidity (UA) MF is 58/minute and the mean MF 57.9 +/- 13.4, respectively, with a 10 (th) centile of 41/minute. MF and basal FHF are correlated significantly (r = 0.410, P << 10(-4)). The declaration-area per fetus is significantly correlated with actual pH (UA), r = -0.473, P << 10(-4). the score itself is highly significantly correlated with actual pH (UA) (r = -0.559, P << 10(-4)) and the other parameters of fetal acid-base balance. Nevertheless, prediction variability for pH, especially in score = 1, 2 and zero (minimal CTG pathology) is still present: 80% of all predicted pH values lie in between -0.092 and + 0.071. It is strongly suggested that this score-related predictive pH variability is caused by maternal breathing habits during the last 30 minutes of delivery. CONCLUSION: Adequate quantification of only three variables of FHR using a score leads to fairly good correlations with parameters of the fetal acid-base balance. Thus actual pH (UA) can be predicted in reasonable clinical limits. Still present variability in prediction of pH seems to be, in part, of maternal origin. The maternal influence could be eliminated by continuous (transcutaneous) monitoring of maternal pCO(2). Along these lines the quantitative electronic monitoring of FHR will be realized and instrumented (off-line and on-line) by nexus/gmt, Frankfurt, a.M., Germany.

Acidosis↗
PubMed2002

Patients with Glanzmann thrombasthenia lacking platelet glycoprotein alpha(IIb)beta(3) (GPIIb/IIIa) and alpha(v)beta(3) receptors are not protected from atherosclerosis.

BACKGROUND: Platelets have been suggested to play a role in the early development of atherosclerosis. As one test of this hypothesis, we assessed whether patients with Glanzmann thrombasthenia who lack platelet glycoprotein alpha(IIb)beta(3) (GPIIb/IIIa) complexes or both alpha(IIb)beta(3) and the more ubiquitous alpha(v)beta(3) cell membrane complexes are protected from development of atherosclerosis. METHODS AND RESULTS: Seven patients with Glanzmann thrombasthenia, 45 to 66 years of age, underwent bilateral carotid artery ultrasonography and screening for risk factors of atherosclerosis. Findings consistent with early atherosclerosis evaluated by measurement of intima-media thickness and presence of atherosclerotic plaques were observed in 6 of the 7 patients. Intima-media thickness values higher than the 75th and 90th percentiles of age- and sex-matched white control subjects of the Atherosclerosis Risk in Communities (ARIC) study were observed in 30 and 8 of 56 carotid artery measurements, respectively. Five of the 6 patients with signs consistent with early atherosclerosis lacked both alpha(IIb)beta(3) and alpha(v)beta(3) complexes and 1 only lacked alpha(IIb)beta(3). CONCLUSIONS: Glanzmann thrombasthenia does not protect affected individuals from development of atherosclerosis.

Aged↗
PubMed1999

Mechanism of organic anion transport across the apical membrane of choroid plexus.

The mechanism and membrane localization of choroid plexus (CP) organic anion transport were determined in apical (or brush border) membrane vesicles isolated from bovine choroid plexus and in intact CP tissue from cow and rat. Brush border membrane vesicles were enriched in Na(+),K(+)-ATPase (20-fold; an apical marker in CP) and demonstrated specific, sodium-coupled transport of proline, glucose, and glutarate. Vesicular uptake of the anionic herbicide 2, 4-dichlorophenoxyacetic acid (2,4-D) was markedly stimulated by an inward sodium gradient but only in the presence of glutarate, indicating the presence of apical dicarboxylate/organic anion exchange. Consistent with this interpretation, an imposed outward glutarate gradient stimulated 2,4-D uptake in the absence of sodium. Under both conditions, uptake was dramatically slowed and overshoot was abolished by probenecid. Likewise, apical accumulation of 2,4-D by intact bovine choroid plexus tissue in vitro was stimulated by external glutarate in the presence of sodium. Glutarate stimulation was abolished by 5 mM LiCl. Identical findings were obtained using rat CP tissue, which showed both sodium/glutarate-stimulated 2,4-D (tissue/medium (T/M) approximately 8) and p-aminohippurate (T/M = 2) transport. Finally, since the renal exchanger (rROAT1) has been cloned in rat kidney, a rROAT1-green fluorescent protein construct was used to analyze exchanger distribution directly in transiently transfected rat CP. As predicted by the functional studies, the fluorescently tagged transporter was seen in apical but not basolateral membranes of the CP.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1999

Surgical resource utilization in urban terrorist bombing: a computer simulation.

BACKGROUND: The objective of this study was to analyze the utilization of surgical staff and facilities during an urban terrorist bombing incident. METHODS: A discrete-event computer model of the emergency room and related hospital facilities was constructed and implemented, based on cumulated data from 12 urban terrorist bombing incidents in Israel. RESULTS: The simulation predicts that the admitting capacity of the hospital depends primarily on the number of available surgeons and defines an optimal staff profile for surgeons, residents, and trauma nurses. The major bottlenecks in the flow of critical casualties are the shock rooms and the computed tomographic scanner but not the operating rooms. The simulation also defines the number of reinforcement staff needed to treat noncritical casualties and shows that radiology is the major obstacle to the flow of these patients. CONCLUSION: Computer simulation is an important new tool for the optimization of surgical service elements for a multiple-casualty situation.

Computer Simulation↗
PubMed1998

The alphabet soup of plant intracellular signalling: enter cyclic nucleotides.

Recent work reveals a role for cyclic nucleotides as secondary signalling molecules in a variety of signal transduction pathways in plants. Evidence is accumulating that cGMP is involved in signalling during photomorphogenesis and that cADP-ribose triggers the release of sequestered Ca2+ during the response of plant cells to abscisic acid. Though more tentative, cAMP has been proposed as playing an important role in ion channel activity and cell cycle progression. Taken together, a picture emerges of differing signalling pathways, possibility interacting with each other, acting on an array of developmental processes.

Abscisic Acid↗
PubMed1997

A plant cation-chloride co-transporter promoting auxin-independent tobacco protoplast division.

Although auxin plays a central role in plant development, little is known about the signal transduction pathways triggered by auxin regulating cell elongation, division and differentiation. We describe the molecular analysis of the mutant tobacco line axi 4/1, which was regenerated from an auxin-independent callus created by activation T-DNA tagging. Transcriptional enhancer-mediated deregulated expression of the tagged plant gene axi 4 uncouples division of axi 4/1 protoplasts from external auxin stimuli, whereas in untransformed protoplasts expression of axi 4 and cell division are auxin dependent. axi 4 encodes a 109 kDa protein with significant homology to a family of electroneutral cation-chloride co-transporters (CCCs). We show that overexpression of AXI 4 or another member of the CCC family, the Na+/K+/2Cl--co-transporter from shark, triggers auxin-independent growth of tobacco protoplasts. We suggest that Na+/K+/2Cl--co-transporters may play a role in signalling cell division and that this function is highly conserved between AXI 4 and the shark Na+/K+/2Cl--co-transporter. We also demonstrate that a C-terminal fragment of AXI 4 is sufficient to promote auxin-independent cell division, showing that the C-termini of CCCs are functional subunits triggering cell division. This may allow a molecular dissection of this process not only in plants but also in animal cells.

Amino Acid Sequence↗
PubMed1997

Lipochitooligosaccharide-induced tobacco cells release a peptide as mediator of the glycolipid signal.

Lipochitooligosaccharides (LCOs) are plant growth regulators that promote at subfemtomolar concentrations cell division in tobacco protoplasts. In response to LCO treatment, tobacco cells release a second growth factor that fully mediates the growth-promoting activities of the initial extracellular LCO stimulus. This diffusible growth factor was isolated from the protoplasts' culture filtrate and shown to be a peptide. We report that the LCO-induced mitogen released by tobacco cells and a synthetic heptadecapeptide derived from region 2 of the tobacco homolog of the early nodulin gene ENOD40 are antigenically related and qualitatively indistinguishable in their ability to stimulate cell division.

Amino Acid Sequence↗
PubMed1997

An integrated noninvasive system for monitoring the microcirculatory effects of vasoactive drugs: an experimental study.

BACKGROUND: No information is available on the effects of vasoactive drugs on the microcirculation and on the correlation between their effects on the capillary and the systemic circulation. PURPOSE: To characterize the effects of nitroglycerin (NTG), nitroprusside (NP), and metaraminol infusion on microcirculatory variables using a noninvasive monitoring system. METHODS: Increasing doses of NTG (5-40 microg/kg/min) and NP (5-20 microg/kg/min) were intravenously infused to eight rabbits. The microcirculatory parameters were monitored by a combined noninvasive system which included laser Doppler flowmetry (LDF), photoplethysmograph (PPG), and transcutaneous oxygen tension (tc-PO2). Mean blood pressure (MBP) was measured simultaneously. RESULTS: At maximal rate of NTG infusion, the values of LDF, PPG, tc-PO2, and MBP were 72.2 +/- 23.9, 234.7 +/- 165.6, 103.5 +/- 37.4, and 82.7 +/- 7.4% of baseline, respectively. Following NP infusion the LDF, PPG, tc-PO2, and MBP reached 70.8 +/- 24.1, 190.5 +/- 68.9, 70.0 +/- 14.7, and 75.6 +/- 14.6% of baseline, respectively. The tissue oxygenation was significantly reduced during NP infusion compared to NTG (P < 0.05). The values gradually returned to the baseline 10 min after termination of NP infusion, but not after NTG. After injection of 1 mg metaraminol there was a steep decline in LDF, PPG, and tc-PO2 parallel to a significant increase in MBP. When metaraminol was administered after injection of 0.1 mg phenoxybenzamine, these changes were abolished. CONCLUSIONS: This noninvasive system effectively monitors microcirculatory hemodynamic changes induced by vasoactive drugs. NTG and NP cause similar changes in the systemic and microcirculatory bed, with the exception of peripheral oxygenation, which is reduced only during infusion of NP. The changes in the microcirculatory bed following metaraminol and phenoxybenzamine imply that their effects on the arterioles are mediated by adrenergic alpha-receptors.

Analysis of Variance↗
PubMed1997

Damage control for abdominal trauma.

The damage control concept represents an extension of modern trauma resuscitation into the operating room. This surgical concept has found its most versatile and important use in severe abdominal trauma. The two critical concerns during damage control laparotomy are achieving hemostasis and preventing uncontrolled spillage of intestinal contents or urine. All else is secondary, and contrary to the traditional sequence of abdominal surgery, it is also deliberately disregarded. The common denominator of the many techniques presented in this article for a bail-out laparotomy is the need for a rapid decision, creative improvisation, and awareness that the outcome is determined by the patient's physiologic envelope and not by anatomic integrity, which can be achieved at reoperation.

Abdominal Injuries↗
PubMed1997

T-DNA tagging reveals a novel cDNA triggering cytokinin- and auxin-independent protoplast division.

Activation T-DNA tagging was used to generate four cytokinin-independent (cyi1-4) tobacco cell lines. Plants regenerated from the mutant lines displayed similar phenotypes: reduced apical dominance, poorly developed roots, delayed growth and flowering, and male and female sterility. Tissue culture experiments demonstrated that the mutations in the different lines uncouple cell proliferation from the effects of both cytokinin and auxin. No significant increase of cytokinin or auxin was found in transgenic calli in comparison with untransformed callus. The functional plant sequence tagged in one of the mutant lines, cyi1, was used to isolate an active cDNA, cyi1a, that was able to trigger cytokinin- and auxin-independent protoplast division. Northern analysis shows that the transcript corresponding to cyi1a accumulates to high levels in the untransformed protoplasts shortly before the onset of cell division, and that these levels decrease when protoplasts reach maximum rates of cell division. A small putative open reading frame, starting with the first ATG in cyi1a and encoding a 22 amino acid peptide, has the same activity in tobacco protoplasts as the whole cDNA. This activity is destroyed by a frame shift mutation. Apparently cyi1a encodes a peptide which participates in the events downstream of a joint point of cytokinin and auxin action leading to cell division.

Amino Acid Sequence↗
PubMed1997

Developmental and auxin-induced expression of the Arabidopsis prha homeobox gene.

A single-copy Arabidopsis homeobox gene, prha, which encodes a homeodomain protein with a molecular weight of 90,500 has been characterized. The position of the gene was mapped to the distal part of chromosome 4. Expression of the gene differs in various vegetative and floral plant tissues and is positively influenced by the phytohormone auxin. In Arabidopsis plants, a complex pattern of prha promoter-driven GUS expression is observed, often associated with regions of developing vascular tissue. Exogenously applied auxin strongly increased endogenous prha transcript levels. In addition, the prha promoter is highly responsive to the synthetic auxin, naphthalene acetic acid, in transient assays using tobacco protoplasts. The PRHA protein has the capacity to bind to TAATTG core sequence elements but requires additional adjacent bases for high-affinity binding. These findings are discussed in relation to studies of other plant homeobox genes as well as possible in vivo target genes for PRHA.

Amino Acid Sequence↗
PubMed1997

The impact of Ti-plasmid-derived gene vectors on the study of the mechanism of action of phytohormones.

The molecular basis of tumor formation on dicotyledonous plants by Agrobacterium relies on the transfer to the plant cell of a unique segment of bacterial DNA, the T-DNA. The T-DNA contains genes that are active in the plant cell and encode hormone biosynthetic enzymes, or proteins that deregulate the cell's response to phytohormones. Study of this process has yielded not only knowledge of how alterations in phytohormone homeostasis can affect plant cell growth, but also has provided the essential tools to study phytohormone signaling in transgenic plants. Furthermore, T-DNA insertion into the plant genome forms the basis of gene tagging, a versatile method for isolating genes involved in phytohormone signal transduction and action.

Journal Article↗
PubMed1996

Convergent pathways for lipochitooligosaccharide and auxin signaling in tobacco cells.

Lipochitooligosaccharides (LCOs) are a novel class of plant growth regulators that activate in tobacco protoplasts the expression of AXI1, a gene implicated in auxin signaling. Transient assays with a chimeric P(AXI)-GUS expression plasmid revealed that the N-octadecenoylated monosaccharide GlcN has all structural requirements for a biological active glycolipid, whereas the inactive N-acylated GalN epimer inhibits LCO action. Specific inhibition of LCO and auxin action shows that both signals are transduced within the tobacco cell via separate pathways that converge at or before AXI1 transcription. Cytokinin is suggested to be a common effector of LCO and auxin signaling. We also show that activation of AXI1 correlates with growth factor-induced cell division.

Arabidopsis Proteins↗
PubMed1996

Modification of phytohormone response by a peptide encoded by ENOD40 of legumes and a nonlegume.

The gene ENOD40 is expressed during early stages of legume nodule development. A homolog was isolated from tobacco, which, as does ENOD40 from legumes, encodes an oligopeptide of about 10 amino acids. In tobacco protoplasts, these peptides change the response to auxin at concentrations as low as 10(-12) to 10(-16)M. The peptides encoded by ENOD40 appear to act as plant growth regulators.

Amino Acid Sequence↗