Suppression of Richtmyer-Meshkov Instability via Special Pairs of Shocks and Phase Transitions

The classical Richtmyer-Meshkov instability (RMI) is a hydrodynamic instability characterizing the evolution of an interface following shock loading. In contrast to other hydrodynamic instabilities such as Rayleigh-Taylor, it is known for being unconditionally unstable: regardless of the direction of shock passage, any deviations from a flat interface will be amplified. In this article, we show that for negative Atwood numbers, there exist special sequences of shocks which result in a nearly perfectly suppressed instability growth. We demonstrate this principle computationally and experimentally with stepped fliers and phase transition materials. A fascinating immediate corollary is that in specific instances, a phase-transitioning material may self-suppress RMI.

Glucose-sensitive hypothalamic nuclei traced through functional magnetic resonance imaging

Introduction

Hypothalamic glucose-sensitive neural circuits, which regulate energy metabolism and can contribute to diseases such as obesity and type 2 diabetes, have been difficult to study in humans. We developed an approach to assess hypothalamic functional connectivity changes during glucose loading using functional magnetic resonance imaging (fMRI).

Methods

To do so, we conducted oral glucose tolerance tests while acquiring functional images before, and 10 and 45 min after glucose ingestion in a healthy male and cross-sectionally in 20 healthy participants on two different diets.

Results

At group level, 39 fMRI sessions were not sufficient to detect glucose-mediated connectivity changes. However, 10 repeated sessions in a single subject revealed significant intrinsic functional connectivity increases 45 min after glucose intake in the arcuate, paraventricular, and dorsomedial nuclei, as well as in the posterior hypothalamic area, median eminence, and mammillary bodies.

Discussion

Our methodology allowed to outline glucose-sensitive hypothalamic pathways in a single human being and holds promise in delineating individual pathophysiology mechanisms in patients with dysglycemia.

Cerebral blood flow autoregulation assessment by correlation analysis between mean arterial blood pressure and transcranial doppler sonography or near infrared spectroscopy is different: A pilot study

PURPOSE

Recently, cerebral autoregulation indices based on moving correlation indices between mean arterial pressure (MAP) and cerebral oximetry (NIRS, ORx) or transcranial Doppler (TCD)-derived middle cerebral artery flow velocity (Mx) have been introduced to clinical practice. In a pilot study, we aimed to evaluate the validity of these indices using incremental lower body negative pressure (LBNP) until presyncope representing beginning cerebral hypoperfusion as well as lower body positive pressure (LBPP) with added mild hypoxia to induce cerebral hyperperfusion in healthy subjects.

METHODS

Five male subjects received continuous hemodynamic, TCD and NIRS monitoring. Decreasing levels of LBNP were applied in 5-minute steps until subjects reached presyncope. Increasing levels of LBPP were applied stepwise up to 20 or 25 mmHg. Normobaric hypoxia was added until an oxygen saturation of 84% was reached. This was continued for 10 minutes. ORx and Mx indices were calculated using previously described methods.

RESULTS

Both Indices showed an increase > 0.3 indicating impaired cerebral autoregulation during presyncope. However, there was no significant difference in Mx at presyncope compared to baseline (p = 0.168). Mean arterial pressure and cardiac output decreased only in presyncope, while stroke volume was decreased at the last pressure level. Neither Mx nor ORx showed significant changes during LBPP or hypoxia. Agreement between Mx and ORx was poor during the LBNP and LBPP experiments (R2 = 0.001, p = 0.3339).

CONCLUSION

Mx and ORx represent impaired cerebral autoregulation, but in Mx this may not be distinguished sufficiently from baseline. LBPP and hypoxia are insufficient to reach the upper limit of cerebral autoregulation as indicated by Mx and ORx.

Real‐Time Magnetic Resonance Imaging to Study Orthostatic Intolerance Mechanisms in Human Beings: Proof of Concept

Background

Discerning the mechanisms driving orthostatic symptoms in human beings remains challenging. Therefore, we developed a novel approach combining cardiac and cerebral real‐time magnetic resonance imaging, beat‐to‐beat physiological monitoring, and orthostatic stress testing through lower‐body negative pressure (LBNP). We conducted a proof‐of‐concept study in a patient with severe orthostatic hypotension.

Methods and Results

We included a 46‐year‐old man with pure autonomic failure. Without and during −30 mmHg LBNP, we obtained 3T real‐time magnetic resonance imaging of the cardiac short axis and quantitative flow measurements in the pulmonary trunk and middle cerebral artery. Blood pressure was 118/74 mmHg during supine rest and 58/35 mmHg with LBNP. With LBNP, left ventricular stroke volume decreased by 44.6%, absolute middle cerebral artery flow by 37.6%, and pulmonary trunk flow by 40%.

Conclusions

Combination of real‐time magnetic resonance imaging, LBNP, and continuous blood pressure monitoring provides a promising new approach to study orthostatic intolerance mechanisms in human beings.

Integrating services to improve the return-to-work process in depression or anxiety: results from a three-arm parallel randomized trial

Introduction

Depression and anxiety are very frequent and associated with high societal costs, much suffering and functional impairment. Employment is essential and pivotal recovery after sick-leave. In many countries, health care interventions are delivered separately from vocational rehabilitation services. This fragmented placement of interventions often implies lack of coordination, creating despair among sick-listed persons.

Objectives

The aim of this trial was to investigate an integrated mental health care and vocational rehabilitation intervention to improve and hasten the return-to-work process among people sick-listed with anxiety or depression.

Methods

In this RCT, participants were randomly allocated to A) integrated interventions (INT), B) improved mental health care (MHC) or B) service as usual (SAU). Primary outcome was time to return-to-work during 12-month. Secondary outcomes were time to return-to-work at 6-month follow-up; levels of anxiety, depression, stress symptoms and social and occupational functioning at 6-month follow-up; and return-to-work measured as proportion in work at 12-month follow-up.

Results

631 individuals randomized. INT showed higher proportion in work compared with both SAU and MHC at the 12-month follow-up. We found no differences regarding return-to-work time at either the 6- or 12-month follow-up. No differences in symptoms between SAU, MCH or INT were detected, but MHC and INT showed lower scores on Cohen’s perceived stress scale compared with SAU at 12-month follow-up.

Conclusions

Although INT did not hasten return-to-work, it yielded higher proportion in work compared with MHC and SAU.

Disclosure

No significant relationships.

Integrating services improve the return-to-work process for people on sick leave with stress-related disorders: results from a randomized trial (n=666)

Introduction

Stress-related disorders are common and associated withsuffering and a large sociatal burden. While treatment appears to be able to reduce symptoms, evidence of interventions to improve work outcomes is inconsistent. Lack of integration different service domains has been suspected to be a barrier in return-to-work (RTW) processes.

Objectives

We aimed to test the effectiveness of intergrating vocational rehabilitation and mental health care.

Methods

We randomized participants on sick leave to I) service as usual (SAU), I) improved mental health care (MHC) or III) integrated interventions (INT). Primary outcome was RTW-rates measured at 12 months. Secondary outcome were proportion in work at 12 months, RTW-rates measured at 6 months, and symptom levels at 6 months.

Results

We randomized 666 participants. Regarding primary outcome, the SAU group was superior to both MHC and INT. Furthermore, SAU was also superior to INT and MHC on almost all other work-related outcomes. INT and MHC did not show differences on any work-related outcome. On several symptom scales, MHC was observed with lower scores than SAU, whilst INT did not differ from the two other groups.

Conclusions

Both the integrated intervention (INT) and the (non-integrated) mental health care (MHC) intervention lowered return-to-work rates compared with service as usual (SAU), and thereby yielded worse outcomes. However, the MHC group intervention showed a tendency towards having lower symptom levels compared with those in the SAU group; accordingly, the SAU group is not unequivocally superior. INT and MHC showed no general differences.

Disclosure

No significant relationships.

Medullary and Hypothalamic Functional Magnetic Imaging During Acute Hypoxia in Tracing Human Peripheral Chemoreflex Responses

[Figure: see text].

Abstract 041: Hypoxic Peripheral Chemoreceptor Activation Engages Sympathetic Brainstem and Hypothalamic Nuclei in Human Subjects

Peripheral carotid chemoreceptors, which raise sympathetic activation at the brainstem level, may serve as targets for antihypertensive therapy. However, human peripheral chemoreflex regulation in the brainstem is poorly understood due to lack of suitable methodologies. Therefore, we combined measurements of beat-by-beat blood pressure and SpO 2 , and high-resolution functional magnetic resonance imaging (fMRI) to elucidate human brainstem circuits engaged through hypoxic peripheral chemoreceptor activation.

We submitted 12 healthy men (29.7 ±6.6 years; 24.0 ±1.86 kg/m 2 ) to five hypoxic episodes by breathing 10% oxygen for 180 seconds followed by 90 seconds normoxia during multiband fMRI brain acquisitions. We monitored continuous finger arterial blood pressure using customized hardware, ECG, and SpO 2 . Brainstem and hypothalamus fMRI images were analyzed to identify nuclei involved in peripheral chemoreflex processing. Systolic blood pressure (SBP) and SpO 2 time courses were correlated with the blood-oxygen-level dependent signals with a general linear model.

With hypoxia, SpO 2 decreased by 12.32 ±3.68% (p < 0.01), heart rate increased 13.86 ±3.47 bpm (p < 0.01), and SBP decreased with hypoxia 5.45 ±5.5 mmHg (p < 0.01). In the brainstem, the nucleus tractus solitarii (t-values: SpO 2 : 5.9; SBP: 4.79), the caudal ventrolateral medulla (SpO 2 : 5.61; SBP: 5.59), intermediate reticular nucleus (SpO 2 : 4.7, SBP: 5.98), nucleus ambiguus (SpO 2 : 5.03, SBP: 5.59), dorsal motor nucleus of the vagal nerve (SBP: 4.79), and inferior olive (SpO 2 : 4.7, SBP: 6.16) were identified with high sensitivity and corrected for multiple comparisons (p < 0.01). Furthermore, we observed activation of the following hypothalamic nuclei: paraventricular nucleus (SpO 2 : 7.67), anterior and lateral hypothalamic area (SpO 2 : 7.67, SBP: 4.79), supraoptic nucleus, and tuberomammillary nucleus (SpO 2 : 7.07).

High-resolution brainstem fMRI during repeated hypoxia traces brainstem circuits engaged by peripheral chemoreceptors. The methodology can be applied to study peripheral chemoreceptor contributions to human cardiovascular disease and may have utility in identifying patients likely to respond to peripheral chemoreceptor modulation.

Novel Approach to Elucidate Human Baroreflex Regulation at the Brainstem Level: Pharmacological Testing During fMRI

Introduction: Brainstem nuclei govern the arterial baroreflex, which is crucial for heart rate and blood pressure control. Yet, brainstem function is difficult to explore in living humans and is therefore mostly studied using animal models or postmortem human anatomy studies. We developed a methodology to identify brainstem nuclei involved in baroreflex cardiovascular control in humans by combining pharmacological baroreflex testing with functional magnetic resonance imaging. Materials and Methods: In 11 healthy men, we applied eight repeated intravenous phenylephrine bolus doses of 25 and 75 μg followed by a saline flush using a remote-controlled injector during multiband functional magnetic resonance imaging (fMRI) acquisition of the whole brain including the brainstem. Continuous finger arterial blood pressure, respiration, and electrocardiogram (ECG) were monitored. fMRI data were preprocessed with a brainstem-specific pipeline and analyzed with a general linear model (GLM) to identify brainstem nuclei involved in central integration of the baroreceptor input. Results: Phenylephrine elicited a pressor response followed by a baroreflex-mediated lengthening of the RR interval (25 μg: 197 ± 15 ms; 75 μg: 221 ± 33 ms). By combining fMRI responses during both phenylephrine doses, we identified significant signal changes in the nucleus tractus solitarii (t = 5.97), caudal ventrolateral medulla (t = 4.59), rostral ventrolateral medulla (t = 7.11), nucleus ambiguus (t = 5.6), nucleus raphe obscurus (t = 6.45), and several other brainstem nuclei [p < 0.0005 family-wise error (few)-corr.]. Conclusion: Pharmacological baroreflex testing during fMRI allows characterizing central baroreflex regulation at the level of the brainstem in humans. Baroreflex-mediated activation and deactivation patterns are consistent with previous investigations in animal models. The methodology has the potential to elucidate human physiology and mechanisms of autonomic cardiovascular disease.

Towards a body hair atlas of women of caucasian ethnicity

OBJECTIVE

A preliminary study was conducted in 17 female volunteers (mean age 29.8 years) to gain deeper insights into the characteristics of terminal Caucasian female body hair of different body parts. The focus on Caucasian women was driven by the high number of different scalp hair phenotypes in this ethnicity and intended to identify relevant differences between body areas to improve body hair removal approaches.

METHODS

Multiple growth parameters and structural parameters were assessed for hair on the upper arm, forearm, upper leg, lower leg, axilla and intimate area and compared to scalp data.

RESULTS

In particular, macroscopic and much less microscopic or hair surface properties differ strikingly in the investigated body areas. Hair density on the body is much lower than on scalp with the highest hair density in the axilla and intimate area. Multihair follicular units are described for scalp but were also found to a smaller proportion in the axilla and the intimate area. Substantial percentages of hair triplets are only found on the scalp and intimate area. Hair diameter is highest in the intimate area, followed by axillary and lower leg hair and correlates with a faster hair growth rate. The angle of emerging hair is smallest in the intimate area, axilla and on the lower leg. Hair shafts on the lower leg and in the axilla have most overlapping cuticle layers, but independent of body region, no significant differences in the mean thickness of cuticle layers were detectable. In addition, no differences were found in the mean distance between cuticle layer edges along the hair shaft and the hair surface roughness. Hair on the scalp, forearm, upper arm and upper leg had an almost round shape, whereas hair of the lower leg, intimate area and axilla had more elliptical shape. Hairs on the arm showed the highest luminance values and no visible medulla. The darkest hairs were in the axilla and intimate area containing the highest level of visible medulla in hair shafts.

CONCLUSION

To our knowledge, this is the first systematic study comparing terminal hair properties in all cosmetically relevant body regions in Caucasian women.

Relative contributions of technetium Tc 99m sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay to the surgical management of hyperparathyroidism

HYPOTHESIS

Technetium Tc 99m sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay have been used to permit a directed operation in patients with hyperparathyroidism. We hypothesized that the coordinated use of these techniques might be particularly useful in patients who require a second operation for hyperparathyroidism.

DESIGN

Retrospective analysis was performed to determine the specific contribution of these technologies to the surgical management of patients with hyperparathyroidism who underwent evaluation by at least 2 of these techniques between April 1996 and October 1999.

SETTING

Patients were evaluated and treated by an endocrine tumor surgery group within a tertiary care referral center.

PATIENTS

Coordinated application of 99mTc-sestamibi scintigraphy, intraoperative gamma probe detection, and/or the rapid parathyroid hormone assay was performed in 32 patients.

RESULTS

Twenty-eight of 32 patients had primary hyperparathyroidism, 3 had multiple endocrine neoplasia type 1, and 1 had secondary hyperparathyroidism. The surgical procedure was an initial cervical exploration in 19 and a second operative procedure in 13. Parathyroidectomy was successful in all patients. A directed anatomic operation was performed in 24 patients, including 11 patients who underwent second operative procedures and 9 patients who underwent minimally invasive procedures under local anesthesia. A directed operation was facilitated by sestamibi scan in 22 of 24 patients, intraoperative gamma probe detection in 5 of 23 patients, and the rapid parathyroid hormone assay in 15 of 15 patients.

CONCLUSIONS

Coordinated application of 99mTc-sestamibi scintigraphy, intraoperative gamma probe detection, and the rapid parathyroid hormone assay allows for successful directed reoperative parathyroidectomy; a minimally invasive procedure may be performed in selected patients.

Organotypic culture system of chicken retina

Analysis of developmental mechanisms during neuroembryogenesis, evaluation of toxicological effects and testing of neuroprotheses rely to an increasing extent on in vivo-like in vitro models. We have developed a novel organotypic culture system of the chick retina. Tissue slices of embryonic retinae were immobilized on glass coverslips by a fibrin clot and permanently rotated between the gas and medium phase, resulting in regular formation and the maintenance of the retinal cytoarchitecture. Selection of embryonic stage, slice thickness and specimen processing were optimized for culturing. Scanning electron microscopy revealed degradation during increasing culture periods of the fibrin clot, which was used for initial immobilization of explants on glass coverslips. Simultaneously, retinal cells became exposed on the tissue surface. Even after several weeks in vitro, formation and maintenance of plexiform and nuclear layers was evident as revealed by two specific monoclonal antibodies. Immunocytochemistry employing two additional photoreceptor- and radial Müller-antibodies indicated differentiation of neuronal and glial cells specific for the retina. The organotypic culture system promises to facilitate developmental studies of retinal development. Quantitative evaluation of Na(+)-channel blocker mexiletine impact on the histogenesis of retinal explants proved the organotypic culture system to be a valuable tool also for neurotoxicological investigations.

Enhancement of antibody dependent cellular cytotoxicity (ADCC) by combination of cytokines

Monoclonal antibodies (MAb) specific for tumor-associated antigens (TAA) can induce an immunological cellular attack of tumor cells by a process termed antibody dependent cellular cytotoxicity (ADCC). Cytokines may augment ADCC by direct activation of immune cells or by enhancement of TAA on tumor cells. Thus, we investigated whether ADCC by MAb 17-1A and BR55-2, which recognize TAA on colorectal tumor cells, can be augmented by 3-day incubation with different concentrations of IL-2, IL-4, IL-6, IL-12, IFN-alpha, IFN-gamma, GM-CSF, M-CSF, and TNF-alpha. ADCC was assessed by a new flowcytometric cytotoxicity assay (Flieger et al. Immunol Methods 1995; 180:1-13) using PKH-2 labeled HT29 cells as targets and PKH-26 labeled peripheral blood mononuclear cells from three healthy volunteers as effector cells. We found three reaction patterns with the cytokines tested: (a) cytokines, which increase ADCC (IL-2, IL-12, IFN-alpha, and IFN-gamma, which represent Thl cytokines); (b) cytokines with no effect (GM-CSF, M-CSF, and TNF-alpha); and (c) cytokines, which decrease ADCC (IL-4 and IL-6, which represent Th2 cytokines). Then, we tested cytokines that increase ADCC in combination with the other cytokines. We found that the combinations IL-2/IFN-alpha, IL-2/IFN-gamma, IL-2/IL-12, and IL-12/IFN-alpha potentiated ADCC. By contrast, IL-4 reduced the IL-2, IL-12, and IFN-alpha-induced ADCC. Since the Thl response, cooperation of monocytes and CD4 cells is involved, we plan to elucidate by magnetic cell sorting (MACS) separation techniques, which cells are involved in cytokine-induced ADCC. Our results may be useful for finding combinations of cytokines and MAb for the locoregional treatment of colorectal cancer.

Similar extent of brain dysmorphology in severely ill women and men with schizophrenia

OBJECTIVE

The purpose of this study was to determine whether women with chronic, severe schizophrenia manifest a widespread deficit in cortical gray matter and ventricular enlargement similar to that seen in men with schizophrenia and whether this deficit is related to age at onset of illness, length of illness, or current illness severity.

METHOD

Volumetric measures of head size, cortical gray matter, white matter and sulci, and lateral and third ventricles were obtained from magnetic resonance images of chronic inpatient schizophrenic women (N = 19) and men (N = 18) and healthy comparison women (N = 19) and men (N = 18). Sex and group differences were assessed by using a two-factor analysis of variance of brain measures. Age was entered as a covariate in assessments of associations between brain measures and age at onset and length of illness.

RESULTS

The schizophrenic patients as a group had less cortical gray matter but comparable white matter and significantly more lateral and third ventricular CSF than the comparison group. Compared to the combined groups of men, women, regardless of diagnosis, had smaller heads, less cortical gray and white matter, and less sulcal, lateral, and third ventricular CSF. There were no group-by-sex interactions, suggesting that in schizophrenia these aspects of gross volumetric morphology in male and female brains are affected equally. There was no relationship between cortical gray matter deficit or ventricular enlargements and age at symptom onset or length of illness in either men or women with schizophrenia, when variance due to age was accounted for statistically.

CONCLUSIONS

The process that contributes to cortical gray matter deficit in schizophrenia appears to affect men and women to a similar extent.

Phase II study of ACNU as first-line treatment in advanced colorectal cancer

Thirty-two patients with metastatic colorectal cancer were entered in a phase II study of ACNU as first-line treatment. ACNU was given at a dose of 100 mg/m2 i.v. every six weeks. In 30 evaluable patients we observed partial responses lasting 5 and 8 months in 2 patients with liver metastases, and stable disease in 4 patients. The toxicity mainly consisted of leuco- and trombocytopenia. We conclude that in this dose and schedule ACNU has only very limited activity in metastatic colorectal cancer.

Changes in brain glucose metabolism in cocaine dependence and withdrawal

OBJECTIVE

The authors investigated changes in brain function associated with cocaine dependence and withdrawal to provide clues regarding the processes that lead to the uncontrollable self-administration of cocaine.

METHOD

They measured regional brain metabolism with [18F]-fluorodeoxyglucose (FDG) and positron emission tomography in 15 outpatients with the diagnosis of cocaine abuse and 17 normal comparison subjects. Ten of the patients were studied less than 1 week after they had last had cocaine, and five were studied 2-4 weeks after withdrawal.

RESULTS

Patients studied within 1 week of cocaine withdrawal but not those studied within 2-4 weeks of cocaine withdrawal had higher levels of global brain metabolism as well as higher levels of regional brain metabolism in the basal ganglia and orbitofrontal cortex than did normal subjects, probably as a consequence of less brain dopamine activity. There was also a significant relationship between the number of days since cocaine withdrawal and regional brain glucose metabolism in the orbitofrontal cortex and in the basal ganglia, and the correlations between cocaine craving and metabolic activity were significant in the prefrontal cortex and the orbitofrontal cortex.

CONCLUSIONS

Although the time-dependent fall in metabolic activity suggests that the higher metabolic activity observed less than a week after cocaine withdrawal may represent a nonspecific expression of drug withdrawal, the selectivity of changes in glucose metabolism for the basal ganglia and for the orbitofrontal cortex suggests that the regional metabolic changes seen in cocaine abusers during detoxification are related to changes in brain dopamine activity.

Proposed delusional depression subtypes: preliminary evidence from a retrospective study of phenomenology and treatment course

An analysis of the phenomenology and treatment course of 52 subjects with delusional depression suggests that there may be various subtypes: bipolar, early-onset unipolar and possibly a late-onset unipolar. The bipolar subgroup tended to relapse in different but always psychotic directions, and was resistant to lithium carbonate treatment alone. Treatment refractoriness, delusional depressive recurrences, and a dementia-like presentation were associated with a small late-onset subgroup. A high rate of delusionally depressive relapses also characterized the early-onset unipolar group, however, patients with single episodes were found only in this subgroup.

Analytical, occupational and toxicologic aspects of the degradation products of polypropylene plastics

Thermooxidative degradation of polypropylene (PP) at close to the industrial processing temperatures was studied with thermogravimetric analysis, infrared spectroscopy, and gas chromatography-mass spectrometry (GC-MS). GC-MS allowed identification of 47 volatile degradation products. Formaldehyde, acetaldehyde, alpha-methylacrolein, acetic acid, and acetone were the major products. Antioxidants markedly slowed down the degradation of polypropylene and the evolution of the degradation products. The relative amounts of the oxidized products were mostly independent of the degradation temperature or the type of antioxidant. Measurements in the plastics industry revealed low airborne concentrations of individual volatile products. The concentration of aerosols, which infrared analysis showed to resemble paraffin fumes, was significant and probably the most important hygienic hazard. The biochemical parameters (the consumption of protecting sulfhydryl groups and the effects on foreign compound metabolism) indicated that the degradation products are biologically reactive, affecting the balance of normal metabolism in exposed animals.