Biomedical subjects
Publications and source records attributed to S Klotz.
We present a neutron diffraction study of liquid water to 6.5 GPa and 670 K. From the measured structure factors we determine radial and angular distributions. It is shown that with increasing density water approaches a local structure common to a simple liquid while distorting only a little the tetrahedral first-neighbor coordination imposed by hydrogen bonds that remain intact.
OBJECTIVE: We report on our experience with the BerlinHeart Excor system in adults and paediatric patients who underwent placement of the mechanical support device under emergency conditions and demonstrate the exceptional advantages and the considerable versatility of the system. METHODS: Since 2003, 29 consecutive patients (25 adults and 4 infants) with ages ranging from 10 months to 54 years underwent implantation of an Excor system. Main underlying heart diseases in adults were acute myocardial infarction (n = 9), dilative cardiomyopathy (n = 6), acute myocarditis (n = 6), whereas most of the children suffered from dilative cardiomyopathy. Ten patients had undergone implantation of an extracorporeal membrane oxygenation system. RESULTS: In 26 cases, a left ventricular assist device (LVAD) was implanted, while 3 patients had biventricular support. The support interval of all patients surviving the perioperative period lasted from 30 to 412 days, mean period of support until heart transplantation or explantation was 184 +/- 117 days. Severe complications were rare. CONCLUSION: The Excor paracorporeal mechanical support system is an excellent and highly versatile device for the support of patients of all ages and different types of underlying heart disease in the mid-term and long-term. The implant procedure and the perioperative management are simple, and complication rates are low.
A key part of the individual patient rights is the renunciation of explicit information on a planned surgical procedure. However, jurisdiction has assigned strict requirements for the validity of such a denial. To ensure legal validity of the denial, the surgeon has to obtain informed consent signed by the patient stating that the patient rejected detailed medical information, but did understand the nature of the planned procedure. The initiative to receive just limited medical information must be taken by the patient himself, not the surgeon. Thus, the patient may choose to receive either detailed or limited information on the surgical procedure. Important to know: A limited time schedule of the surgeon is not a valid justification for a limited informed consent.
We present a neutron diffraction study of the transition between low-density and high-density amorphous ice (LDA and HDA, respectively) under pressure at approximately 0.3 GPa, at 130 K. All the intermediate diffraction patterns can be accurately decomposed into a linear combination of the patterns of pure LDA and HDA. This progressive transformation of one distinct phase to another, with phase coexistence at constant pressure and temperature, gives direct evidence of a classical first-order transition. In situ Raman measurements and visual observation of the reverse transition strongly support these conclusions, which have implications for models of water and the proposed second critical point in the undercooled region of liquid water.
We report measurements of the phonon dispersion of ice Ih under hydrostatic pressure up to 0.5 GPa, at 140 K, using inelastic neutron scattering. They reveal a pronounced softening of various low-energy modes, in particular, those of the transverse acoustic phonon branch in the [100] direction and polarization in the hexagonal plane. We demonstrate with the aid of a lattice dynamical model that these anomalous features in the phonon dispersion are at the origin of the negative thermal expansion (NTE) coefficient in ice below 60 K. Moreover, extrapolation to higher pressures shows that the mode frequencies responsible for the NTE approach zero at approximately 2.5 GPa, which explains the known pressure-induced amorphization (PIA) in ice. These results give the first clear experimental evidence that PIA in ice is due to a lattice instability, i.e., mechanical melting.
We report in situ neutron diffraction studies of high-density amorphous ice (HDA) at 100 K at pressures up to 2.2 GPa. We find that the compression is achieved by a strong contraction ( approximately 20%) of the second neighbor coordination shell, so that at 2.2 GPa it closely approaches the first coordination shell, which itself remains intact in both structure and size. The hydrogen bond orientations suggest an absence of hydrogen bonding between first and second shells and that HDA has increasingly interpenetrating hydrogen bond networks under pressure.
BACKGROUND: Patients with severely impaired left-ventricular pump function who are eligible for heart transplantation increasingly undergo high-risk cardiac surgery due to the scarcity of donor organs. If these patients also qualify for long-term mechanical support, the latter can be used as back-up in case of postcardiotomy failure. METHODS: Since 1994, 36 patients (34 male, 2 female; mean age 51 +/- 7 years) underwent coronary bypass surgery/aneurysmectomy (n = 27), aortic valve replacement (n = 4), both (n = 1), or partial left ventriculectomy (n = 4) with a long-term mechanical assist device (Novacor, HeartMate, DeBakey) and were kept on stand-by with the device. Average left ventricular ejection fraction was 23 +/- 9 %, NYHA 2.9 +/- 0.5, and CCS 2.7 +/- 0.9. An intraaortic balloon pump was inserted prior to surgery in 13 patients. RESULTS: In 31 patients, high-risk surgery was performed, whereas 5 patients underwent immediate device placement as coronary revascularization was deemed impossible. 6 patients had postcardiotomy failure after coronary bypass surgery and were immediately provided with a long-term assist system. There were no significant differences in risk factors between the patient subsets. All conservatively operated patients survived and left the institution after 9.4 days and are currently at NYHA 1.5 +/- 0.5 or CCS 1.0 +/- 0, respectively. 6 of the 11 LVAD patients could be bridged to heart transplantation after 43 - 418 days, and 1 patient is still on support. CONCLUSION: High-risk conventional surgery with LVAD stand-by is feasible and seems to be a valuable alternative for heart-transplant candidates.
A species' ecological niche depends on the species' adaptations to its present habitat, but also on the legacy from its ancestors. Most authors argue that such a phylogenetic niche conservatism is of minor importance, although no quantitative analyses across a major taxon is available. Higher plants from central Europe offer a unique opportunity for such an exercise, as the niche positions along various environmental gradients are available for most species. We quantified niche conservatism by two approaches. First, we used a phylogenetic tree and quantified the degree of retention of niches across the tree. Depending on the gradient, the values ranged from 0.43 to 0.22. This was significantly greater than the null expectation. Second, we used a taxonomy and quantified the amount of variance among species that could be explained at higher taxonomic levels. The values ranged from 25 to 72%. Again, this was significantly higher than the null expectation. Thus, both approaches indicated a clear niche conservatism. The distribution of conservatism across taxonomic levels differed considerably among environmental gradients. The differences among environmental gradients could be correlated with the palaeoenvironmental conditions during the radiation of the phylogenetic lineages. Thus, niche conservatism among extant plant species may reflect the opportunities of their ancestors during their diversification.
BACKGROUND: Acute nonocclusive mesenteric ischemia (NOMI) is a rare but often fatal event after cardiac surgery. METHODS: Twenty patients with ongoing ileus after cardiac surgery despite maximal laxative treatment underwent selective mesenteric angiography. In cases of pathological radiographic findings, papaverine was continuously administered via an intraarterial perfusion catheter. RESULTS: Severe NOMI was confirmed in seven patients (mean lactate: 6.9 +/- 8.3 mg/dL), mild to moderate findings in another seven (mean lactate: 1.4 +/- 1.1 mg/dL). One patient had thromboembolic occlusion of the superior mesenteric artery; five patients demonstrated normal imaging findings. In nine of fourteen patients (64%) treated with papaverine, symptoms improved within hours (defecation occurred after 4-29 hours, mean 13 +/- 8.1 hours). No side effects or complications occurred in connection with the papaverine treatment. The clinical condition of five patients deteriorated. Four patients underwent laparotomy with creation of an ileostomy or colostomy, two of whom presented with severe intestinal ischemia and later died. One patient died prior to laparotomy. CONCLUSIONS: Selective mesenteric angiography with continuous papaverine administration is a simple, fast, and effective diagnostic and therapeutic tool to reduce the need for laparotomy for symptoms of ileus after open-heart surgery.
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The phonon dispersion of bcc iron under high pressure to 10 GPa was measured at 300 K by inelastic neutron scattering. Its pressure dependence is surprisingly uniform. Contrary to the behavior found in other bcc elements, there is a lack of any significant pretransitional behavior close to the martensitic bcc-hcp transition which could be related to the Burgers mechanism. This finding confirms predictions by spin-polarized total energy calculations that explain the transition by the effect of pressure on the magnetism of iron. The high pressure frequencies were used to develop a lattice dynamical model from which thermodynamic quantities can be determined at any pressure to 10 GPa.
The full structure of the high-pressure cubic phase I' of hydrogen sulfide has been solved using neutron diffraction data. The molecules are partially rotationally disordered about the <111> axes, as in phase II at ambient pressure but with markedly greater nonuniformity of the toroidal D distribution. The changes in structure at the II-->I' transition signal the onset of significant pressure-induced hydrogen bonding.
Daytime submandibular electrostimulation (dSE) of suprahyoidal muscles was applied to prevent sleep-associated collapse of the tongue into the hypopharyngeal airway. By placing the stimulatory electrodes intra- and extraorally, recruitment of stimulated muscle fibers at low current densities was improved. The significant impact of electrostimulation on suprahyoidal muscle force was initially demonstrated in healthy controls as compared to placebo-treated volunteers. The morphology of suprahyoidal muscles was not affected by this treatment. A patient with obstructive sleep apnea syndrome initially presented with a respiratory disturbance index (RDI) of 13.2, an oxygen desaturation index of 23 and a minimal oxygen saturation of 75%. After two weeks of placebo treatment (TENS-stimulation), respiratory parameters remained unchanged. Two weeks of dSE treatment, however, improved the RDI to 3.9, the oxygen desaturation index from 23 to 2.8 and the minimal oxygen saturation from 75% to 88%. 3D-sonography showed considerable hypertrophy of the stimulated muscles. These results indicate that dSE may prevent episodes of apnea induced by sleep-associated hypopharyngeal collapse of the tongue.
PURPOSE: To evaluate the detectability of acute middle cerebral artery (MCA) infarctions by CT with regard to the time interval after symptom onset and to the infarction size. Analysis of the chronological appearance of signs of ischaemia. MATERIAL AND METHODS: Two examiners retrospectively and independently evaluated CT scans from 171 patients with acute MCA infarctions performed within 24 hours after onset of symptoms. RESULTS: 92, respectively 87% of the Infarctions were correctly diagnosed. The detection rate did not increase after the first hour after onset of symptoms. All MCA infarctions involving the lentiform nucleus, but only 83% of the infarctions covering < 33% of the MCA area, were recognised. The hyperdense middle cerebral artery sign (HMCA5) was present in 75% of the infarctions in the first 90 minutes and in 15% from hour 12 to 24. Hypodensity of the lentiform nucleus appeared within 150 minutes, hypodensity of the convexity cortex at the earliest 60 minutes after onset of symptoms. CONCLUSIONS: The detection rate of acute MCA infarctions corresponds with the infarction size, but does not significantly change after the first hour after symptom onset.
OBJECTIVE: To study the evolution of glomerulosclerosis after renal ablation in a model with abnormal regulation of the renin gene. METHODS: Four-month-old female ovariectomized hypertensive heterozygous transgenic rats (TGR) harbouring the murine REN-2 gene were compared with pressure-matched, pair-fed, stroke-prone, spontaneously hypertensive rats (SHRsp). Both groups were followed for 6 weeks after 70% subtotal nephrectomy (SNX) or sham operation. RESULTS: Blood pressures in the SNX group at the end of the experiment were 193 +/- 3 mmHg in TGR and 199 +/- 5 mmHg in SHRsp. The final C(in) was 306 +/- 68 microliters/min per 100 g body weight in TGR that had undergone SNX and 550 +/- 93 microliters/min per 100 g body weight in SHR that had undergone SNX (P < 0.02), whereas inulin clearance (C(in)) in sham-operated pair-fed TGR and SHRsp controls did not differ from each other. The glomerulosclerosis index was 1.75 +/- 0.08 in perfusion-fixed TGR that had undergone SNX versus 1.21 +/- 0.03 in SHR that had undergone SNX (P < 0.005). In addition, the media thickness of preglomerular vessels was significantly greater in TGR that had undergone SNX (7.48 +/- 0.79 microns) than it was in SHRsp that had undergone SNX (5.27 +/- 1.38 microns, P < 0.02). Rat renal renin messenger RNA (mRNA) expression and, in parallel, mouse REN-2 gene expression were lower in TGR after SNX. Plasma renin and angiotensin II (ANG II) concentrations were reduced to a similar extent in both SNX groups, but plasma prorenin was higher in TGR that had undergone SNX than it was in SHRsp that had undergone SNX. The angiotensin II:I ratio in the kidney was significantly higher in TGR (P < 0.01). There was no significant difference between sham-operated or subtotally nephrectomized TGR and SHRsp with respect to angiotensin type 1 mRNA and angiotensinogen mRNA. The renal angiotensin converting enzyme activity, however, was significantly higher in sham operated and subtotally nephrectomized TGR than it was in sham operated SHRsp and in SHRsp that had undergone SNX. CONCLUSION: Deterioration of renal function is accelerated in subtotally nephrectomized transgenic rats [TGR(mREN2)27] compared with that in comparably hypertensive SHRsp despite suppressed circulating active mRNA and decreased renal renin mRNA. Although alternative explanations are possible, this observation is consistent with a role for local ANG II in the genesis of glomerulosclerosis.
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Explore the source record for details and available documents.