Modelling shellfish growth with dynamic energy budget models: an application for cockles and mussels in the Oosterschelde (southwest Netherlands).

Dynamic energy budget models for growth of individual cockles (Cerastoderma edule) and mussels (Mytilus edulis) are adjusted and calibrated to the Oosterschelde by formulating and parametrizing their functional responses using an extensive set of field observations. The resulting model predictions fit the observations satisfactorily. Results indicate that food quality and the importance of detritus as a food source are site-specific as well as species-specific. Despite these differences in their calibrated parameter values, both species show a very similar functional response. Compared with other systems, however, the functional responses of mussels in the present study are clearly higher than those of mussels in other systems. This may be explained by the absence of intra-specific competition in the measurement set-up that was used, and therefore supports the idea that the generally small functional response of M. edulis is caused by intra-specific competition.

Quantitative steps in the evolution of metabolic organisation as specified by the Dynamic Energy Budget theory.

The Dynamic Energy Budget (DEB) theory quantifies the metabolic organisation of organisms on the basis of mechanistically inspired assumptions. We here sketch a scenario for how its various modules, such as maintenance, storage dynamics, development, differentiation and life stages could have evolved since the beginning of life. We argue that the combination of homeostasis and maintenance induced the development of reserves and that subsequent increases in the maintenance costs came with increases of the reserve capacity. Life evolved from a multiple reserves - single structure system (prokaryotes, many protoctists) to systems with multiple reserves and two structures (plants) or single reserve and single structure (animals). This had profound consequences for the possible effects of temperature on rates. We present an alternative explanation for what became known as the down-regulation of maintenance at high growth rates in microorganisms; the density of the limiting reserve increases with the growth rate, and reserves do not require maintenance while structure-specific maintenance costs are independent of the growth rate. This is also the mechanism behind the variation of the respiration rate with body size among species. The DEB theory specifies reserve dynamics on the basis of the requirements of weak homeostasis and partitionability. We here present a new and simple mechanism for this dynamics which accounts for the rejection of mobilised reserve by busy maintenance/growth machinery. This module, like quite a few other modules of DEB theory, uses the theory of Synthesising Units; we review recent progress in this field. The plasticity of membranes that evolved in early eukaryotes is a major step forward in metabolic evolution; we discuss quantitative aspects of the efficiency of phagocytosis relative to the excretion of digestive enzymes to illustrate its importance. Some processes of adaptation and gene expression can be understood in terms of allocation linked to the relative workload of metabolic modules in (unicellular) prokaryotes and organs in (multicellular) eukaryotes. We argue that the evolution of demand systems can only be understood in the light of that of supply systems. We illustrate some important points with data from the literature.

Advantage of storage in a fluctuating environment.

We will elaborate the evolutionary course of an ecosystem consisting of a population in a chemostat environment with periodically fluctuating nutrient supply. The organisms that make up the population consist of structural biomass and energy storage compartments. In a constant chemostat environment a species without energy storage always out-competes a species with energy reserves. This hinders evolution of species with storage from those without storage. Using the adaptive dynamics approach for non-equilibrium ecological systems we will show that in a fluctuating environment there are multiple stable evolutionary singular strategies (ss's): one for a species without, and one for a species with energy storage. The evolutionary end-point depends on the initial evolutionary state. We will formulate the invasion fitness in terms of Floquet multipliers for the oscillating non-autonomous system. Bifurcation theory is used to study points where due to evolutionary development by mutational steps, the long-term dynamics of the ecological system changes qualitatively. To that end, at the ecological time scale, the trait value at which invasion of a mutant into a resident population becomes possible can be calculated using numerical bifurcation analysis where the trait is used as the free parameter, because it is just a bifurcation point. In a constant environment there is a unique stable equilibrium for one species following the "competitive exclusion" principle. In contrast, due to the oscillatory dynamics on the ecological time scale two species may coexist. That is, non-equilibrium dynamics enhances biodiversity. However, we will show that this coexistence is not stable on the evolutionary time scale and always one single species survives.

Unilateral true vocal fold paralysis: cause of right-sided lesions.

At the Georgetown University Center for the Voice, 778 patients were referred for evaluation between July 1, 1990, and June 30, 1995. During this 5-year period, right true vocal fold paralysis or paresis was diagnosed in 24 of these patients (3%). Videostroboscopy, voice analysis, and patient records were reviewed. Ages ranged from 23 to 80 years, and sex distribution approximated a 1:1 ratio. The patients presenting symptoms included hoarseness, dysphagia, choking, voice pitch change, voice weakness, fatigability, and breathiness. Sources of the vocal fold dysfunction included iatrogenic, traumatic, central, and infectious causes.

Glucocorticoids decrease c-fos expression in human nasal polyps in vivo.

BACKGROUND: Activated c-fos binds to jun proteins to form the activation protein 1 (AP-1) transcription factor that regulates cytokine and other proinflammatory genes. c-Fos may play a key role in nasal polyp formation. Glucocorticoids may exert their anti-inflammatory effects through an interaction of glucocorticoid receptors with AP-1 that leads to mutual inactivation of both factors, and a "default" termination of AP-1 mediated gene activation. This may explain the beneficial effects of glucocorticoids in the treatment of nasal polyps. METHODS: To test this hypothesis in humans in vivo the immunohistochemical expression of c-fos-immunoreactive material (c-fos-irm) was assessed in nasal polyps from eight steroid naive subjects, polyps from eight subjects treated with topical beclomethasone dipropionate (BDP), and normal inferior turbinate nasal mucosa (n = 6). RESULTS: mRNA for c-fos was detected in all nasal polyps and normal mucosa. In contrast, c-fos-irm was present in all steroid naive subjects but in only two of the eight subjects treated with BDP (p = 0.007, two-tailed Fisher's exact test). c-Fos-irm was expressed solely in epithelial cells and glandular structures; it was expressed in normal epithelium and glands, but the staining intensity was low. CONCLUSION: Glucocorticoids appear to modulate expression of c-fos-irm and possibly AP-1 in human airway epithelial cells in vivo.

Glucocorticoids induce beta2-adrenergic receptor function in human nasal mucosa.

Glucocorticoids are hypothesized to induce beta2-adrenergic receptors (beta2-R) and their functions. The ability of dexamethasone (DEX) in vitro and beclomethasone dipropionate (BDP) in vivo to induce beta2-R messenger RNA (mRNA) and function was investigated in human nasal mucosa. In this tissue, albuterol does not stimulate exocytosis either in vivo or in vitro (Mullol and coworkers, 1992). Therefore, induction of beta2-R-mediated glandular exocytosis by glucocorticoids was proposed as an unambiguous outcome measure. Human nasal mucosa was cultured for 3 d with and without 1 microM DEX, then challenged with media or 100 microM albuterol. Culture supernatants were collected for measurement of exocytosed glandular products. Explant mRNA was extracted for reverse transcriptase-polymerase chain reaction (RT-PCR), and in situ hybridization of beta2-R mRNA performed. In vivo, normal subjects received saline or BDP for 3 d before albuterol nasal provocation. Concentrations of exocytosed products were measured in nasal secretions. RNA was extracted from nasal epithelial scrapings for RT-PCR. In vitro, DEX treatment induced albuterol-mediated glandular exocytosis (p < 0.04), and increased the steady-state beta2-R/beta-actin mRNA ratio (p < 0.05), and expression of beta2-R mRNA in glands. In vivo, BDP increased the beta2-R/beta-actin mRNA ratio in epithelial scrapings (p < 0.04), but did not induce albuterol-mediated glandular secretion. We conclude that glucocorticoids increase steady-state beta2-R mRNA levels in vivo and in vitro, and can induce beta2-R function as assessed by submucosal gland exocytosis in vitro. While topical BDP induced epithelial beta2-R mRNA, it did not modulate exocytosis from the deeper submucosal glands.

Helical (spiral) CT of the upper airway with three-dimensional imaging: technique and clinical assessment.

OBJECTIVE: The purpose of this study was to evaluate the application of helical CT-generated three-dimensional images of the upper airway. MATERIALS AND METHODS: Thirty patients, 10 healthy and 20 with upper-airway disease, were studied with helical CT (5-mm collimation). Overlapping images at 2-mm intervals were retrospectively generated. In the group of healthy patients, two radiologists in independently compared overlapping with nonoverlapping images, ranked confidence in identifying small airway structures on a scale of 1-5, and tabulated the number of images demonstrating these structures. In the 20 patients with disease, three-dimensional (3D) surface models were rendered on an independent workstation and were reviewed by two radiologists and one otolaryngologist for image quality, appreciation of lesion morphology, and ability to judge lesion extent, using a similar scale. A phantom was used to optimize parameters for the 3D reconstructions. RESULTS: Viewing of the retrospectively generated overlapping images increased by 122% the number of images in which laryngeal and hypopharyngeal structures could be identified (p < .01). Image confidence scores for the radiologists averaged 3.3 for nonoverlapping and 4.0 for overlapping (p < .05). Radiologists and otolaryngologist rated the quality of the 3D images equally. The otolaryngologist's assessment of the value of the models for understanding the lesion morphology was 3.5 compared with the radiologists assessment of 2.5; and for judging the lesion extent, the otolaryngologist's assessment was 3.8 compared with 2.7 for the radiologist, a statistical significance of p < .01. CONCLUSION: Helical CT with the application of overlapping images and 3D reconstructions significantly assists the understanding of upper-airway disease.

Helical CT of the upper airway: normal and abnormal findings on three-dimensional reconstructed images.

Imaging of the hypopharynx, larynx, and upper airway are effectively achieved with CT and MR imaging. These techniques have proved their diagnostic usefulness in assessing the deep soft tissues not visible with laryngoscopy [1]. However, with axial imaging, large numbers of images often need to be mentally stacked to envision the appearance of the airway. With helical CT, we can create high-quality three-dimensional (3D) reconstructions [2, 3]. Advantages of helical technology include rapid scanning, decreased motion artifact, and minimization of misregistration artifacts. Recent work has suggested a role for multiplanar and 3D reconstructions of helical data for assessing the tracheobronchial tree [3]. The helically derived 3D models illustrate the normal and abnormal findings affecting the airway.

Jet stylets as an aid for replacement of tracheostomy tubes.

Difficulty in tracheostomy tube replacement can be life-threatening in a patient who is dependent on the tracheostomy for ventilation. The use of jet styles for tracheostomy tube replacement in these patients facilitates the tube exchange and allows for jet ventilation if any difficulty is encountered during the tube replacement. We describe two cases in which jet stylets proved to be helpful during tracheostomy tube replacement and discuss considerations that are important for the safe use of these devices.

Three-dimensional imaging of the hypopharynx and larynx by means of helical (spiral) computed tomography. Comparison of radiological and otolaryngological evaluation.

A new computed tomography (CT) technology, helical (spiral) CT, allows the entire neck to be imaged in only 30 seconds. Although multiplanar and three-dimensional (3-D) imaging could be performed with conventional CT, the volumetric acquisition provided by helical (spiral) CT allows significantly improved quality and easier reconstruction for more applications. These 3-D models show an airway appearance similar to that obtained with laryngography. Independent review of the 3-D images in 12 patients with lesions by two radiologists and one otolaryngologist was performed to assess 1) image quality, 2) ability to judge lesion extent, and 3) assistance in understanding the lesion compared to that provided by routine axial scans. Rating scores of 1 to 5 were assigned, with 5 representing the best quality or greatest value. The results showed that both groups scored image quality equally: 4.7. Lesion extent for the radiologists was 2.6, while the otolaryngologist's ranking was 3.7 (p < .01). In assisting understanding of lesions versus axial scans, radiologists ranked 3-D images 2.1, while the otolaryngologist ranked them 3.1 (p < .01). In summary, 3-D models provide a complementary imaging technique in understanding upper airway disease.

Aspartame and dizziness: preliminary results of a prospective, nonblinded, prevalence and attempted cross-over study.

Aspartame is a low-calorie food sweetener recently approved by the FDA for general human consumption. One of us (AJG) treated a patient whose symptoms of episodic vertigo and continuous unsteadiness resolved upon ceasing aspartame intake. A literature review revealed that although dizziness has been associated with aspartame intake, no systematic study of the problem exists. As an initial attempt to ascertain the prevalence of aspartame-related dizziness in an otolaryngologic clinic, we elected to study prospectively all patients entering with the complaint of vertigo by means of a standardized questionnaire. Those patients determined to consume aspartame were further studied in a nonblinded manner to see if aspartame intake could be correlated to symptomatology. A cross-over limb was also attempted, but no patient would participate. This presentation details the case history of the propositus patient and the preliminary results of the currently ongoing prospective study.

Submandibular sialadenitis presenting as Ludwig's angina.

Previous descriptions of Ludwig's angina have focused on the odontogenic etiology and the absence of gland involvement. Incision and drainage of the involved fascial spaces without excision of the submandibular gland has traditionally been the recommended surgical treatment. Two case reports of edentulous patients illustrate acute submandibular sialadenitis spreading onto the fascial spaces described in association with Ludwig's angina. Surgical procedures included incision and drainage, along with excision of the submandibular gland. In select cases clinically resembling Ludwig's angina where submandibular sialadenitis is the etiology, we advocate that gland excision be included with a definitive incision and drainage procedure.

Fertility properties and regulation of antimicrobial substance production by plasmid SCP2 of Streptomyces coelicolor.

Streptomyces coelicolor A3(2) possesses two plasmids (SCP1 and SCP2) that act as sex factors. The plasmid deoxyribonucleic acid isolated from S. coelicolor A3(2) SCP1- strains A617 and A585 had the same molecular weight and endonuclease cleavage pattern as the SCP2 plasmid. The plasmidless strain S18 SCP2- was isolated from the A617 X A585 cross. SCP2 plasmid-containing strains acted as donors of chromosomal markers, whereas the plasmidless strain acted as recipient. The transfer of SCP2+ donor strain markers into the SCP2- recipient occurred at high frequencies (approximately 75%), was unidirectional, was initiated from a fixed region of the chromosome, and had the SCP2 fertility factor transferred first. The introduction of the SCP2 plasmid into a recipient strain greatly reduced the recombination frequency. These fertility properties differed from those previously reported, thereby suggesting that the SCP2 plasmid examined in this investigation may be an additional variant to those described in the literature. The SCP2 plasmid also regulated production of three antibacterial substances and conveyed resistance for S. coelicolor A3(2) strains against growth inhibition by one of them.

Phenoxazinone biosynthesis: accumulation of a precursor, 4-methyl-3-hydroxyanthranilic acid, by mutants of Streptomyces parvulus.

Mutants of Streptomyces parvulus that are blocked in the synthesis of the phenoxazinone-containing antibiotic, actinomycin, were isolated by the 'agar piece' method (after ultraviolet irradiation or treatment with 8-methoxypsoralen plus near-ultraviolet light). Radiolabelling experiments in conjunction with paper, thin-layer and column chromatography revealed that 4-methyl-3-hydroxyanthranilic acid (MHA) is a major metabolite accumulated by these mutants. Studies in vitro and in vivo provided evidence that MHA is a precursor of the phenoxazinone chromophore, actinocin. Normally MHA does not accumulate during growth or antibiotic synthesis by the parental strains. Protoplasts derived from the mutant strain AM5 synthesized MHA in significant amounts. A scheme is proposed for the biosynthesis of actinomycin D that accounts for the accumulation of MHA by the mutants.