Unraveling the Influence of Thermal Drawing Parameters on the Microstructure and Thermo-Mechanical Properties of Multimaterial Fibers.

Multimaterial thermally drawn fibers are becoming important building blocks in several foreseen applications in surgical probes, protective gears, or medical textiles. Here, the influence of the thermal drawing parameters on the degree of polymer chain orientation, the related thermal shrinkage behavior, and the mechanical properties of the final fibers is investigated via thermo-mechanical testing and small- and wide-angle X-ray scattering (SAXS and WAXS) analyses. This study on polyetherimide fibers reveals that the drawing stress, which depends on the drawing speed and temperature, controls the thermal shrinkage behavior and mechanical properties. Furthermore, SAXS and WAXS analyses show that the degree of chain orientation increases with drawing stresses below 8 MPa and then saturates, which correlates with the amount of observed shrinkage. The use of this process-dependent polymer chain alignment to tune the mechanical and shrinkage properties of the fibers is highlighted and controlled bending multimaterial fibers made of two polymethyl methacrylates having different molecular weights are developed. Finally, a heat treatment procedure is proposed to relax the chain alignment and increase the dimensional stability of devices such as temperature sensors. This deeper understanding can serve as a guide for the processing of complex fibers requiring specific mechanical properties or enhanced thermal stability.

[Perioperative management of patients with hemophilia]. / Perioperatives Management bei Patienten mit Hämophilie.

Hemophilia A and hemophilia B are X chromosome-linked congenital bleeding disorders caused by a deficiency or absence of activity of coagulation factor VIII (hemophilia A) or factor IX (hemophilia B), which are graded in different degrees of severity (mild, moderate, severe). Depending on the severity patients may experience spontaneous bleeding episodes or will develop excessive bleeding in the context of injuries or surgery. Hemophilia should not be a contraindication for an invasive procedure; however, a number of conditions are required to provide successful surgery and an uncomplicated and safe postoperative course. This review provides an overview of hemophilia and the key biochemical laboratory and clinical aspects as well as possible specific and non-specific treatment options and addresses the special needs for the perioperative care of these patients.

Expressiveness of global coagulation parameters in dilutional coagulopathy.

BACKGROUND: Plasma-free volume replacement in haemorrhage often results in dilutional coagulopathy. Prothrombin time index (PTI) and activated partial thromboplastin time (aPTT) are used for monitoring haemostasis but have not yet been clinically evaluated. Our aim was to investigate the effects of haemodilution on the course of global coagulation tests and clotting factors (CFs). METHODS: Blood samples from each of 10 volunteers were diluted with sodium chloride 0.9% (saline) or 6% hydroxyethyl starch 130/0.4 (HAES) by 30-80%. PTI, aPTT, CF, and the thrombelastometric parameters (ROTEM(®)) coagulation time (CT) and maximum clot firmness (MCF) were determined. RESULTS: Dilution-dependent CF decreased in an almost linear manner and was not influenced by the diluent. Critically low activities for CF of ∼30% and a fibrinogen concentration <100 mg dl(-1) were measured at dilutions of between 60% and 75%. Critically low CF activities of about 30% were indicated by a PTI of 35-40%. PTI and MCF decreased continuously, demonstrating a good correlation with CF activities and fibrinogen. aPTT and CT showed a linear course up to a dilution of 65-75% corresponding to CF activities of 30-40%. Thereafter, values became pathological. PTI and aPTT were not influenced by the type of diluent, whereas the diluents had profound differences on results of thromboelastometry. CONCLUSIONS: PTI and MCF are useful for monitoring dilution and intervention points. aPTT and CT reflect intervention points when showing pathological values. The type of diluents does not seem to interfere with PTI and aPTT, but HAES impairs haemostasis in ROTEM(®) more profoundly than saline.

How valid is the determination of hematocrit values to detect blood manipulations?

UNLABELLED: The aim of this paper is a critical reflection of the practice in competitive cycling to use the hematocrit value (Hct) as an indirect control measure for doping with erythropoietin. To demonstrate the individual physiological variation of Hct values, five different studies were performed: 1) Eight subjects were observed (i) during 23 h after a 1 h lasting bout of cycle exercise at 60% of maximum performance and (ii) during 24h under control conditions. 2) Seven subjects were exposed to a 20 min period of -7 head down tilt (HDT), which was followed by 15 min in sitting position. 3) From four subjects blood samples were taken in a sitting position up to 60 min after they had ingested 1 liter isotonic saline solution. 4) Ten subjects performed a vita maxima test on a cycle ergometer, starting at 100W and increasing the workload by 17W every minute. 5) Four elite cyclists participated in a 10 days competition (1,700 km). RESULTS: 1) During the 24h observation period Hct decreased during the night from 45.3+/-3.1 % to 42.9+/-1.5% and returned to the initial values in the morning. This diurnal variation was even more pronounced after submaximal exercise (-4.1 %). 2) Due to fluid shifts from the interstitial into the intravasal compartment, HDT was accompanied by a 3.1+/-0.5% lower Hct. 3) Drinking of the isotonic saline solution also reduced the hematocrit by 3.3+/-0.5% after one hour. 4) Maximum cycle exercise increased the Hct from 46.8+/-2.4 % to 51.3+/-1.9% which was due to a 15 % decrease in plasma volume. 5) Repeated bouts of cycle-exercise reduced the Hct from 46.4+/-1.5% to 41.3+/-1.6%. CONCLUSIONS: All experiments demonstrate that the Hct is not a constant value but can be considerably changed by physiological measures. Clinical studies show that brain oxygen supply decreases with increasing Hct-values, which are also associated with a higher risk of stroke accidents. We therefore recommend to use a Hct-limit solely under strongly controlled standardized conditions to protect professional cyclists from hazardous manoeuvre until more appropriate methods to detect EPO-doping are developed.

The cellular envelope of oocytes in teleosts.

Structural and functional relationships between oocytes and their envelopes were studied by means of electron microscopy in several teleost species after injection of live fish with horseradish peroxidase. The marker first appeared in the capillaries and the pericapillary spaces of the ovarian stroma. It then entered the collagen-filled spaces between the granulosa and theca cells; these spaces are in direct connection with the pericapillary spaces. The marker penetrated between the follicle cells and into the channels of the zona radiata surrounding the microvilli which traverse these channels. The marker was never found inside the microvilli or in the follicle cells; finally, it reached the surface of the oocytes and was internalized via micropinocytosis. Six stages in the course of folliculogenesis were observed, determined by (1) the formation of follicular and thecal cellular layers and a collagen-filled space between them, (2) the development of microvilli of oocytal and follicular origin, (3) the differentiation of the vitelline envelope and the pore channels, (4) pinocytotic activity of the oocytes, and (5) rapid growth of the oocyte and its envelopes during vitellogenesis.

Phenotypic characterization of acute leukemia with monoclonal antibodies using the microlymphocytotoxicity assay.

Surface antigens of lymphoblasts from 56 pediatric ALL patients were studied with a set of complement fixing monoclonal antibodies. This group of lymphoblasts was comprised of 22 T-cell ALL, 22 CALLA+ Ia+ ALL and 12 non-T-non-B, CALLA- Ia+ ALL. For comparison, two adult T-cell CLL and six B-cell CLL were also studied. It was found that by using the microlymphocytotoxicity technique, the lymphoblasts can be assigned their immunophenotype and thus be classified into their respective lineage and stage of differentiation. In the samples tested, concordant reactivity was observed when FACS fluorescence profile was compared with that of microlymphocytotoxicity suggesting that the latter can be used especially when qualitative estimates are required.

Extravascular circulation in the pituitary of Mugil cephalus (Teleostei).

Extravascular circulation in the pituitary of Mugil cephalus was investigated by injecting live fish with horseradish peroxidase and studying the distribution of the enzyme in the gland. The principal components of the extravascular circulatory system are the pericapillary spaces, and, arising from them, the interlobular and circumhypophyseal spaces. Extensions of these spaces penetrate the glandular parenchyma of the pars distalis, where they merge with pericellular spaces. In the neurohypophysis, pericapillary spaces are connected to the periaxonal spaces. Capillaries penetrating from the proximal neurohypophysis into the pars distalis are accompanied by neurosecretory axons. These axons form a mass of tissue which is limited near the capillaries by the pericapillary spaces and near the adenohypophysis by the interlobular spaces. Toward the interior of the adenohypophysis the amount of nervous tissue accompanying the capillaries progressively diminishes, thus reducing the distance between pericapillary and interlobular spaces. Within the pars distalis, the neurosecretory axons accompanying the capillaries are sparse, and the secretory and stellate cells are mostly located directly adjacent to the pericapillary spaces. In the neurointermediate lobe, interlobular spaces outline the neuro-adenohypophyseal boundary. The relationship between extravascular spaces and hormone-secreting cells varies in the different regions of the adenohypophysis depending upon the type of neurosecretory innervation in the respective region. In the regions of prolactin and gonadotropin cells, where neurosecretory axons are in direct contact with the secretory cells, the hormone-secreting and stellate cells are adjacent to the pericapillary spaces. In the regions of ACTH and STH cells, secretory and stellate cells are found adjacent to the interlobular spaces, which are interposed between the cells and the neurosecretory axons.