Surgical wound sepsis

With the help of a surgical nurse and using data-processing techniques, a prospective clinical study was conducted to determine the wound infection rate in two hospitals in Calgary. The overall sepsis rate was 5.2% and the clean wound rate 3.5%. The latter is the more meaningful figure as it allows for comparison between hospitals, specialties and individuals and is a good guide for hospital morbidity reviews. The groundwork for succeeding wound infection is laid in the operating theatre, and it is believed that wound infection would be reduced more by attention to Halsted''s principles than by more rigid aseptic techniques. It is estimated that wound sepsis costs the Province of Alberta 1.5 million dollars per year for hospitalization alone. This amounts to roughly $1 per person per year. The annual cost of a prospective study such as the present one is approximately $7000. This is equivalent to the cost of hospitalizing 24 patients with infected wounds for one week (at $300 per week). One dividend of a prospective study is an associated reduction in infection rate. This reduction more than pays for the cost of the program.     

The contralateral coordination of walking legs in the crayfish Astacus leptodactylus

The coupling mechanisms which coordinate the movement of ipsilateral walking legs in the crayfish have been described in earlier investigations. Concerning the coupling between contralateral legs it was only known that these influences are weaker than those acting between ipsilateral legs. The nature of these coupling mechanisms between contralateral legs of the crayfish are investigated here by running left and right legs on separate walking belts at different speeds. The results show that coordination is performed by a phase-dependent shift of the anterior extreme position of the influenced leg. This backward shift leads to a shortening of both the return stroke and the following power stroke. As the coupling influence is only weak, several steps might be necessary to retain normal coordination after a disturbance. This corresponds to v. Holst's relative coordination. The influences act in both directions, from left to right and vice versa. However, one side may be more or less dominant. A gradient was found in the way that anterior leg pairs show less strong coordination than posterior legs. In some cases the coupling between diagonally neighbouring legs was found to be stronger than between contralateral legs of the same segment. The interpretation of this result is still open.     

Fatty acids and lysophospholipids as potential second messengers in auxin action. Rapid activation of phospholipase A2 activity by auxin in suspension-cultured parsley and soybean cells

Activation of cytosolic phospholipase A₂ is a typical signal transduction reaction in animal cells and occurs in plants in response to auxin, elicitors and wounding. Exogenously added fluorescent bis-BODIPY-phosphatidylcholine was taken up and hydrolysed by a cellular phospholipase A₂. Rapid activation of a phospholipase A₂ by auxin in suspension-cultured parsley ( Petrosilenum crispum L.) and soybean ( Glycine max L.) cells was shown by detection and quantification of fluorescent reaction products of phospholipase A₂. Hormone-triggered fluorescent fatty acid accumulation could be detected as early as 5 min. Auxins at 2 μM or higher concentrations activated phospholipase A₂ and fluorescent fatty acids accumulated 1.1- to threefold after 90–120 min, depending on the auxin concentration. Fluorescent lysolipid did not accumulate up to 150 μM auxin. Known inhibitors of phospholipase A₂ inhibited hormone-dependent fluorescent fatty acid accumulation in cell cultures and, previously, elongation growth in etiolated zucchini hypocotyl segments ( Scherer & Arnold (1997 ) Planta 202, 462–469). When lipids were labeled by [¹⁴C]-choline and [¹⁴C]-ethanolamine the corresponding lysophospholipids could be quantified in cell extracts. Radioactive lysophospholipids accumulated as rapidly as 1–2 min after auxin treatment but only at concentrations well above 100 μM auxin. We hypothesize that phospholipase A₂ activation is an early intermediate step between receptor and downstream responses. We hypothesize that fatty acid(s) could be second messengers in several auxin functions, especially in cell elongation. Lysophospholipids seem to be indicators or second messengers for stress caused by high auxin concentrations or may have different auxin-linked functions and are also known to accumulate during elicitor action.     

A quantitative model of walking incorporating central and peripheral influences

Using the experimental results of Cruse and Saxler (1980a, b) and other authors (Graham, 1972; Pearson, 1972; Bässler, 1977, 1979) a quantitative model is developed in order to describe the behaviour of the systems controlling the leg movements of a walking insect. The whole model consists of six subsystems each of which controls the movement of an individual leg. The single subsystem (Fig. 1) consists of a central part which can assume two modes (protraction, retraction) the transition between which can be controlled by sensory influence. The central part produces the reference input for a feedback loop which controls the leg position. The reference input is however also determined by influences from other subsystems. Four different types of such connections are assumed to exist between the subsystems. Two of these produce alternating (t1, t3), two others in phase coupling (t2, t4) between the subsystems to be connected. These connections can transfer information originating from the central part as well as from the periphery of other subsystems. The model is capable of describing either quantitatively or qualitatively the experimental results of Cruse and Saxler (1980a, b) (see Figs. 3 and 4). In addition it is capable of describing the results of other authors, e.g. the temporal leg coordination of the free walking animal (Graham, 1972).Supported by DFG (Cr 58/1)     

Hexapod Walking: an expansion to Walknet dealing with leg amputations and force oscillations

The control of the legs of a walking hexapod is a complex problem as the legs have three joints each, resulting in a total of 18 degrees of freedom. We addressed this problem using a decentralized architecture termed Walknet, which consists of peripheral pattern generators being coordinated through influences acting mainly between neighbouring legs. Both, the coordinating influences and the local control modules (each acting only on one leg), are biologically inspired. This investigation shows that it is possible to adapt this approach to account for additional biological data by (1) changing the structure of the selector net in a biological plausible way (including force as an analog variable), (2) introducing a biologically motivated coordination influence for coactivation between legs and (3) adding a hypothetical influence between hind and front legs. This network of controllers has been tested using a dynamic simulation. It is able to describe (a) the behaviour of animals walking with one or two legs being amputated and (b) force oscillations that occur in a specific experimental situation, the standing legs of a walking animal.     

Walking in Aretaon asperrimus

This article describes basic parameters characterizing walking of the stick insect Aretaon asperrimus to allow a comparative approach with other insects studied. As in many other animals, geometrical parameters such as step amplitude and leg extreme positions do not vary with walking velocity. However, the relation between swing duration and stance duration is quite constant, in contrast to most insects studied. Therefore, velocity profiles during swing vary with walking velocity whereas time course of leg trajectories and leg angle trajectories are independent of walking velocity. Nevertheless, A. asperrimus does not show a classical tripod gait, but performs a metachronal, or tetrapod, gait, showing phase values differing from 0.5 between ipsilateral neighbouring legs. As in Carausius morosus, the detailed shape of the swing trajectory may depend on the form of the substrate. Effects describing coordinating influences between legs have been found that prevent the start of a swing as long as the posterior leg performs a swing. Further, the treading on tarsus reflex can be observed in Aretaon. No hint to the existence of a targeting influence has been found. Control of rearward walking is easiest interpreted by maintaining the basic rules but an anterior-posterior reversal of the information flow.     

Mast cells promote airway smooth muscle cell differentiation via autocrine up-regulation of TGF-beta 1

Asthma is a major cause of morbidity and mortality worldwide. It is characterized by airway dysfunction and inflammation. A key determinant of the asthma phenotype is infiltration of airway smooth muscle bundles by activated mast cells. We hypothesized that interactions between these cells promotes airway smooth muscle differentiation into a more contractile phenotype. In vitro coculture of human airway smooth muscle cells with beta-tryptase, or mast cells with or without IgE/anti-IgE activation, increased airway smooth muscle-derived TGF-beta1 secretion, alpha-smooth muscle actin expression and agonist-provoked contraction. This promotion to a more contractile phenotype was inhibited by both the serine protease inhibitor leupeptin and TGF-beta1 neutralization, suggesting that the observed airway smooth muscle differentiation was driven by the autocrine release of TGF-beta1 in response to activation by mast cell beta-tryptase. Importantly, in vivo we found that in bronchial mucosal biopsies from asthmatics the intensity of alpha-smooth muscle actin expression was strongly related to the number of mast cells within or adjacent to an airway smooth muscle bundle. These findings suggest that mast cell localization in the airway smooth muscle bundle promotes airway smooth muscle cell differentiation into a more contractile phenotype, thus contributing to the disordered airway physiology that characterizes asthma.     

The control of walking movements in the leg of the rock lobster

1. Experiments with rock lobsters walking on a treadmill were undertaken to obtain information upon the system controlling the movement of the legs. Results show that the position of the leg is an important parameter affecting the cyclic movement of the walking leg. Stepping can be interrupted when the geometrical conditions for terminating either a return stroke or a power stroke are not fullfilled. 2. The mean value of anterior and posterior extreme positions (AEP and PEP respectively) of the walking legs do not depend on the walking speed (Fig. 1). 3. When one leg is isolated from the other walking legs by placing it on a platform the AEPs and PEPs of the other legs show a broader distribution compared to controls (Figs. 2 and 3). 4. Force measurements (Fig. 4) are in agreement with the hypothesis that the movement of the leg is controlled by a position servomechanism. 5. When one leg stands on a stationary force transducer this leg develops forces which oscillate with the step rhythm of the other legs (Fig. 5). 6. A posteriorly directed influence is found, by which the return stroke of a leg can be started when the anterior leg performs a backward directed movement. 7. Results are compared with those obtained from stick insects. The systems controlling the movement of the individual leg are similar in both, lobster and stick insect but the influences between the legs seem to be considerably different.     

Prevalence of additional positive lymph nodes in complete lymphadenectomy specimens after positive sentinel lymphadenectomy findings for early-stage melanoma of the head and neck

In this study, the prevalence of additional positive lymph nodes in subsequent complete lymphadenectomy specimens for patients with early-stage melanoma of the head and neck, after positive sentinel lymphadenectomy results, was retrospectively analyzed. In the past 5 years at the authors' institution, 23 consecutive patients with clinical stage I or stage II melanoma of the head and neck underwent complete lymphadenectomies after positive sentinel lymph node biopsies and wide local excisions of the primary lesions. Sentinel lymph nodes were identified with intraoperative lymphatic mapping techniques (radiolymphoscintigraphy and vital blue dye injection) and were examined with routine histological methods and immunohistochemical staining for S-100. All lymph nodes harvested in complete lymphadenectomies were examined with routine histological techniques. Twenty-one patients (91.3 percent) demonstrated no additional positive lymph nodes in subsequent complete lymphadenectomy specimens; two patients (8.7 percent) each demonstrated one additional positive lymph node in the complete lymphadenectomy specimens. Both patients had ulcerated primary lesions more than 5 mm in depth. No patient developed a regional nodal recurrence during a mean follow-up period of 23.7 months (range, 2 to 56 months). The low prevalence of additional positive lymph nodes in complete lymphadenectomy specimens suggests that when microscopic metastases exist in the regional nodal basin, most of the time they are confined to the sentinel lymph nodes of patients with early-stage melanoma of the head and neck. Nevertheless, the question of whether subsequent complete lymphadenectomy is still necessary for this subgroup of patients warrants further study.     

Mechanisms of stick insect locomotion in a gap-crossing paradigm

Locomotion of stick insects climbing over gaps of more than twice their step length has proved to be a useful paradigm to investigate how locomotor behaviour is adapted to external conditions. In this study, swing amplitudes and extreme positions of single steps from gap-crossing sequences have been analysed and compared to corresponding parameters of undisturbed walking. We show that adaptations of the basic mechanisms concern movements of single legs as well as the coordination between the legs. Slowing down of stance velocity, searching movements of legs in protraction and the generation of short steps are crucial prerequisites in the gap-crossing task. The rules of leg coordination described for stick insect walking seem to be modified, and load on the supporting legs is assumed to have a major effect on coordination especially in slow walking. Stepping into the gap with a front leg and antennal contact with the far edge of the gap provide information, as both events influence the following leg movements, whereas antennal non-contact seems not to contain information. Integration of these results into the model of the walking controller can improve our understanding of insect locomotion in highly irregular environments.Abbreviations AEP anterior extreme position - fAEP fictive anterior extreme position - PEP posterior extreme position - TOT treading-on-tarsus