Adaptive Wiener Filtering for Improved Acquisition of Distortion Product Otoacoustic Emissions

An innovative acoustic noise canceling method using adaptive Wiener filtering (AWF) was developed for improved acquisition of distortion product otoacoustic emissions (DPOAEs). The system used one microphone placed in the test ear for the primary signal. Noise reference signals were obtained from three different sources: (a) pre-stimulus response from the test ear microphone, (b) post-stimulus response from a microphone placed near the head of the subject and (c) post-stimulus response obtained from a microphone placed in the subjects nontest ear. In order to improve spectral estimation, block averaging of a different number of single sweep responses was used. DPOAE data were obtained from 11 ears of healthy newborns in a well-baby nursery of a hospital under typical noise conditions. Simultaneously obtained recordings from all three microphones were digitized, stored and processed off-line to evaluate the effects of AWF with respect to DPOAE detection and signal-to-noise ratio (SNR) improvement. Results show that compared to standard DPOAE processing, AWF improved signal detection and improved SNR. © 1998 Biomedical Engineering Society. PAC98: 4364Jb, 4360-c, 8790+y     

Immunohistochemical distribution of chromogranins A and B and secretogranin II in neuroendocrine tumours of the gastrointestinal tract

The aim of the present study was to investigate immunohistochemically the distribution of chromogranin A, chromogranin B, and secretogranin II in a series of 152 neuroendocrine tumours of the gastrointestinal tract. Tumour tissues from 25 argyrophil gastric carcinoids, 18 gastrin and 5 somatostatin-producing tumours, 4 gangliocytic paragangliomas, 49 classical argentaffin and 2 L cell appendiceal carcinoids, 27 classical ileal carcinoids, 17 rectal carcinoids, and 5 poorly differentiated neuroendocrine tumours of the stomach and rectum were immunostained with antibodies against chromogranin A, chromogranin B, and secretogranin II. Chromogranin A was the major granin expressed in gastric carcinoids and in serotonin-producing carcinoids of the appendix and the ileum. In contrast, strong chromogranin B and secretogranin II immunoreactivity was found in rectal carcinoids, in which chromogranin A was rarely expressed. Since chromogranin A is a widely used marker for neuroendocrine differentiation, it is of diagnostic importance that some gastrin-producing tumours, gangliocytic paragangliomas, poorly differentiated neuroendocrine carcinomas, and appendiceal L cell carcinoids completely lacked chromogranin A positivity. It is concluded that the various neuroendocrine tumours of the gastrointestinal tract show distinctly different patterns of granin expression, probably reflecting their histogenetical origin.     

Spontaneous reanastomosis between lymphatic vessels following syngeneic transplantation of the small intestine in the rat

Abstract Spontaneous lymphvascular reanastomosis (SLR) following small bowel transplantation in rats is of clinical relevance for the resorption of long chain fatty acids. Detailed morphological and molecular data concerning the process of lymphvascular reanastomosis are not available in the literature. In this study SLR was investigated using microradiology and scanning electron microscopy. Between the 8^th and 21^st postoperative days following transplantation SLR does not occur between the intestinal trunk of the transplant and the thoracic duct of the recipient. Instead, an indirect connection was observed between the inserted advential lymphatic vessels of the mesenteric artery and lymphatic vessels of the aorta or ductus deferens, which are connected with the thoracic duct.     

Negative accumulated oxygen deficit during heavy and very heavy intensity cycle ergometry in humans

The concept of the accumulated O₂ deficit (AOD) assumes that the O₂ deficit increases monotonically with increasing work rate (WR), to plateau at the maximum AOD, and is based on linear extrapolation of the relationship between measured steady-state oxygen uptake (O₂) and WR for moderate exercise. However, for high WRs, the measured O₂ increases above that expected from such linear extrapolation, reflecting the superimposition of a "slow component" on the fundamental O₂ mono-exponential kinetics. We were therefore interested in determining the effect of the O₂ slow component on the computed AOD. Ten subjects [31 (12) years] performed square-wave cycle ergometry of moderate (40%, 60%, 80% and 90% ), heavy (40%), very heavy (80%) and severe (110% O_{2 peak}) intensities for 10–15 min, where is the estimated lactate threshold and is the WR difference between and O_{2 peak}. O₂ was determined breath-by-breath. Projected "steady-state" O₂ values were determined from sub- tests. The measured O₂ exceeded the projected value after ~3 min for both heavy and very heavy intensity exercise. This led to the AOD actually becoming negative. Thus, for heavy exercise, while the AOD was positive [0.63 (0.41) l] at 5 min, it was negative by 10 min [–0.61 (1.05) l], and more so by 15 min [–1.70 (1.64) l]. For the very heavy WRs, the AOD was [0.42 (0.67) l] by 5 min and reached –2.68 (2.09) l at exhaustion. For severe exercise, however, the AOD at exhaustion was positive in each case: +1.69 (0.39) l. We therefore conclude that the assumptions underlying the computation of the AOD are invalid for heavy and very heavy cycle ergometry (at least). Physiological inferences, such as the "anaerobic work capacity", are therefore prone to misinterpretation.     

Role of nitric oxide in the biology, physiology and pathophysiology of reproduction

Following its benchmark discovery, nitric oxide (NO) is nowknown to play important functional roles in a variety of physiologicalsystems. Within the vasculature, NO induces vasodilation, inhibitsplatelet aggregation, prevents neutrophil/platelet adhesionto endothelial cells, inhibits smooth muscle cell proliferationand migration, regulates programmed cell death (apoptosis) andmaintains endothelial cell barrier function. NO generated byneurons acts as a neurotransmitter, whereas NO generated bymacrophages in response to invading microbes acts as an antimicrobialagent. Because neurons, blood vessels and cells of the immunesystem are integral parts of the reproductive organs, and inview of the important functional role that NO plays in thosesystems, it is likely that NO is an important regulator of thebiology and physiology of the reproductive system. Indeed, inthe past 10 years, NO has established itself as a polyvalentmolecule which plays a decisive role in regulating multiplefunctions within the female as well as the male reproductivesystem. This review provides an overview of the role of NO invarious reproductive organs under physiological and pathologicalconditions.     

Accuracy of pulse oximetry at various haematocrits and during haemolysis in anin vitro model

In situations in which it may be impossible and/or unethical to evaluate pulse oximetry in humans, an in vitro model with circulating blood may be a necessity. The main objective was to develop such an in vitro model and, in this model, validate the pulse oximetry technique at various haematocrit levels. The pulsating character of arterial blood flow in a tubing system was simulated by using a specially constructed pressure-regulated roller pump. The tubing system was designed to minimise damage to red blood cells. The pulse oximeter readings (SpO₂) were compared with oxygen saturation analyses by a haemoximeter (SaO₂). The pulse oximetry readings were recorded at various haematocrit levels and during haemolysis in the SaO₂ range 60–100 per cent. At a haematocrit level of 41–44 per cent, there was no correlation between SaO₂ and SpO₂ readings. After diluting the blood with normal saline to a haematocrit of 10–11 per cent, a good correlation between SaO₂ and SpO₂ was found. Following haemolysis, the agreement between SaO₂ and SpO₂ was further improved. Using the developed in vitro model, the results indicate that the accuracy of a pulse oximeter may be dependent on the haematocrit level.     

Pneumatised superior turbinate: a common anatomic variation?

Summary Anatomic variations are important in preendoscopic CT evaluation of the paranasal sinuses. In this study, we investigated whether the superior turbinate could become pneumatised like the middle turbinate, pneumatisation of which is well-known. Images of 52 patients who underwent CT examination prior to endoscopic sinus surgery and who had normally aerated posterior ethmoidal cells and an unobscured nasal cavity were retrospectively evaluated. The patients were 12–68 years old (median age, 35 years); 28 were women and 24 were men. Pneumatisation of the superior turbinates was graded in two groups as minimal or marked. Pneumatisation was evident in 25 patients (48%). 13 unilateral (25%), 8 bilateral (15%) pneumatisations were detected in the group graded as minimal, whereas 1 unilateral and 3 bilateral pneumatisations were present in the markedly (8%) pneumatised group of patients. Superior turbinates were seemingly aerated through the posterior ethmoid cells. The superior turbinates can be pneumatised as the middle turbinate is a not frequent anatomic variation that should be taken into account in preendoscopic CT evaluation of the paranasal sinuses.

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La pneumatisation du cornet nasal supérieur : une variation anatomique courante ?

Résumé Les variations anatomiques sont importantes à connaitre dans le cadre du bilan tomodensitométrique précédant une chirurgie endoscopique des sinus paranasaux. Dans cette étude, nous avons recherché si le cornet nasal supérieur pouvait être pneumatisé comme l'est le cornet nasal moyen, entité anatomique bien connue. Les images de 52 patients ayant eu une tomodensitométrie avant chirurgie endoscopique et montrant des cellules ethmoïdales postérieures normalement pneumatisées et une cavité nasale nonopaque, ont été évaluées rétrospectivement. Les patients, 28 femmes et 24 hommes, étaient âgés de 12 à 68 ans (moyenne : 35 ans). La pneumatisation du cornet nasal supérieur a été classée en deux groupes; minime et prononçée. Cette pneumatisation était patente chez 25 patients (48 %). Treize pneumatisations unilatérales (25 %) et 8 pneumatisations bilatérales (15 %) furent retrouvées dans le groupe présentant une pneumatisation minime alors que 1 pneumatisation unilatérale et 3 bilatérales (8 %) étaient présentes dans le groupe dont la pneumatisation était plus marquée. Les cornets nasaux supérieurs semblaient être aérés par les cellules ethmoïdales postérieures. Les cornets nasaux supérieurs peuvent être pneumatisés, comme le sont les cornets nasaux moyens, avec une fréquence non-exceptionnelle. Cette variation anatomique mérite d'être prise en considération dans le bilan tomodensitométrique précédant toute chirurgie endoscopique des sinus paranasaux.

     

Impedance plethysmography in human limbs

Electrode design and electrode positioning are important factors in blood flow measurements using impedance plethysmography. Optimal electrode type and accurate positioning will decrease measurement errors and improve the signal-to-noise-ratio. Disk electrodes were found to be superior to tape electrodes because of their better skin-electrode stability and because they prevent limb compression. The distance between current electrodes and potential electrodes should be greater than 2·3 R (disk electrodes) and 1·5 R (tape electrodes) to avoid the influence of the so-called diffusion resistance (R is the radius of the limb at the electrode site).     

Comparative analysis of the polycystic kidney disease 1 (PKD1) gene reveals an integral membrane glycoprotein with multiple evolutionary conserved domains

PKD1 is the major locus of the common genetic disorder autosomal dominant polycystic kidney disease (ADPKD). Analysis of the predicted protein sequence of the human PKD1 gene, polycystin, shows a large molecule with a unique arrangement of extracellular domains and multiple putative transmembrane regions. The precise function of polycystin remains unclear with a paucity of mutations to define key structural and functional domains. To refine the structure of this protein we have cloned the genomic region encoding the Fugu PKD1 gene. Fugu PKD1 spans 36 kb of genomic DNA and has greater complexity with 54 exons compared with 46 in man. Comparative analysis of the predicted protein sequences shows a lower level of homology than in similar studies with identity of 40 and 59% similarity. However key structural motifs including leucine rich repeats (LRR), a C-type lectin and LDL-A like domains and 16 PKD repeats are maintained. A region of homology with the sea urchin REJ protein was also confirmed in Fugu but found to extend over 1000 amino acids. Several highly conserved intra- and extra- cellular regions, with no known sequence homologies, that are likely to be of functional importance were detected. The likely structure of the membrane associated region has been refined with similarity to the PKD2 protein and voltage gated Ca2+ and Na+ channels highlighted over part of this area. The overall protein structure has therefore been clarified and this comparative analysis derived structure will form the basis for the functional study of polycystin and its individual domains.