Physical-chemical studies on bovine eye lens proteins: I. Light-scattering and viscosity studies of low-molecular weight α-crystallin isolated from adult and embryonic bovine lenses

Low molecular weight α-crystallins, isolated from adult and embryonic bovine lenses, have been characterized using physical-chemical methods. From light-scattering measurements and from the Svedberg relation, a molecular weight of 785 000 ± 30 000 can be concluded. From hydrodynamic data, namely the sedimentation coefficient, the translational diffusion coefficient, the intrinsic viscosity and the rotational diffusion coefficient, a symmetric shape of the molecules in solution with a rather high hydration can be concluded. The low-molecular α-crystallins, isolated from the cortex of adult lenses and from embryonic lenses, have identical hydrodynamic parameters.     

A scanning electron microscope study of preserved allograft tympanic membranes: a comparison with autogenous grafts, xenografts and the normal eardrum

Scanning electron microscopy was used to investigate the surface architecture of the human tympanic membrane. The morphology of the eardrum was compared with the surface structures of preserved tympanic membranes (allografts), fresh air-dried temporalis fascia and preserved calf jugular veins (xenografts). The role of the physical structure and the composition of the extracellular matrix in the regeneration of a tympanic graft is discussed.     

Beneficial effect of tachykinin NK1 receptor antagonism in the development of hapten-induced colitis in mice

The gastro-intestinal tract is highly innervated by both intrinsic and extrinsic sensory nerves and this neuronal component is thought to play a role in local inflammatory responses. This in vivo study was designed to determine the function of substance P and the tachykinin NK1 receptor in the pathogenesis of inflammatory bowel disease by the use of the specific antagonist RP 67580. The dinitrofluorobenzene (DNFB)-induced colonic hypersensitivity model is associated with increased levels of substance P in the colon. The tachykinin NK1 receptor antagonist RP 67580 was used to investigate the role of substance P on the development of diarrhea, mast cell infiltration and activation, colonic tissue damage, hypertrophy of colonic lymphoid structures and leukocyte infiltration. The formation of watery diarrhea could completely be abrogated by treatment with RP 67580 in DNFB-sensitized animals 72 h after challenge. Antagonizing the tachykinin NK1 receptor in these animals also resulted in significantly reduced colonic patch hypertrophy, leukocyte recruitment and tissue damage. Total levels of substance P in the colon of DNFB-sensitized mice treated with the inactive enantiomer of the tachykinin NK1 receptor antagonist were significantly higher compared to DNFB-sensitized mice treated with RP 67580 72 h after challenge. Although RP 67580 was capable of reducing the total number of mast cells present in the colon, mast cell activation was not affected by this treatment. In conclusion, in this chemically-induced immunological model for inflammatory bowel disease we demonstrated an important role for tachykinin NK1 receptors, and its ligand substance P, in the development of colitis downstream from mast cell activation.     

An advantage for detecting dynamic targets in natural scenes

In the present study, we tested the extent to which observers use dynamic information to detect targets in natural scenes. For this purpose, we used composite stimuli in which target sequences were superimposed onto distractor sequences. We varied target visibility in the composite sequence, and the presence or absence of motion. Across four experiments, we found a dynamic advantage for target detection: Observers performed more accurately with dynamic than static target scenes. This advantage depended on the availability of target motion, irrespective of whether the target was upright or inverted in the image plane (Experiments 1-4). The magnitude of this advantage also depended on the availability of segmentation cues (Experiments 1 and 2) and on the distractors used (Experiments 2 and 4). Overall, the dynamic advantage reported extends previous work using isolated dynamic objects to more complex scenes.     

Beta adrenergic blockade Hemodynamics and myocardial energy metabolism in patients with ischemic heart disease

Systemic and coronary hemodynamics and myocardial intermediary metabolism were studied before and after beta adrenergic blockade with propranolol in 9 patients with ischemic heart disease.

A significant reduction was produced in heart rate, left ventricular isometric tension development (dp/dt) and pressure-time per minute, whereas left ventricular end-diastolic pressure rose. Cardiac output and left ventricular mean systolic pressure and mechanical work did not change consistently.

Myocardial oxygen consumption was influenced by left ventricular external work and pressure-time per min., the latter having the predominant effect. Myocardial oxygen consumption was not closely related to the consistent reduction of dp/dt, presumably because of wide variations in stroke volume.

Coronary blood flow was reduced in 5 of 8 patients, changes in coronary diastolic vascular resistance in most cases favoring the preservation of an autoregulatory mechanism. A constant or reduced coronary arteriovenous oxygen extraction in 6 of 9 patients suggested that changes in perfusion rather than in extraction accommodated the altered myocardial oxygen needs. Propranolol appeared to have no direct action on vasomotor tone but probably reduced extravascular compression resistance.

Myocardial efficiency did not change consistently. External efficiency was generally reduced, but internal efficiency rose in 3 patients. When a reduction in efficiency indexes resulted from decreased cardiac work but increased coronary flow and myocardial oxygen consumption, the overstressed myocardium may have benefited.

Total myocardial substrate oxygen extraction ratios exceeded 100 per cent under control conditions and after beta blockade; therefore the respective energy contributions of carbohydrates and fatty acids were obscure, and conversion and storage seemed likely.

The NAD⁺/NADH redox potential gradient was consistently changed to a more positive value. Arterial levels of inorganic phosphate and creatine phosphokinase activity rose, and the myocardial balance of creatine phosphokinase became positive after propranolol.

The antianginal action of propranolol may be related to the following mechanisms: (1) myocardial work is reduced, thus lessening the disparity between oxygen demand and supply; (2) a relative or absolute improvement in coronary perfusion and myocardial oxygen delivery may result, subject to arteriolosclerotic limitations; (3) changes in myocardial intermediary metabolism and enzyme systems favor lessened cellular hypoxia and enhanced aerobiosis.     

Unexpected effect of matrix metalloproteinase down-regulation on vascular intravasation and metastasis of human fibrosarcoma cells selected in vivo for high rates of dissemination

The human tumor/chick embryo model involving grafting of human HT-1080 fibrosarcoma cells on the chorioallantoic membrane was used in conjunction with quantitative real-time Alu PCR to select in vivo a pair of isogenic cell lines (HT-hi/diss and HT-lo/diss), dramatically differing in their ability to disseminate from the primary tumor (i.e., intravasate into the chorioallantoic membrane vasculature and metastasize to the lungs). During an immunohistochemical time course study, HT-hi/diss cells were sequentially visualized having escaped from the primary tumors, engaged with the blood vessels, and eventually observed inside the chorioallantoic membrane capillaries, thus reflecting early intravasating events. In contrast, HT-lo/diss cells seemed restricted to their primary tumor. Importantly, after i.v. inoculation, both variants arrested, extravasated, and proliferated in host tissues with similar efficiencies, highlighting that the observed earlier events at the periphery of the primary tumor could account for their differential dissemination. In a mechanistic probing of these events, we determined that HT-hi/diss intravasation was sensitive to a broad-range matrix metalloproteinase (MMP) inhibitor. To analyze the possible role of individual MMPs, membrane-bound MMP-14 and secreted MMP-9 were individually down-regulated in HT-hi/diss cells with their corresponding small interfering RNAs. Despite efficient down-regulation of MMP-14, neither intravasation nor metastasis of HT-hi/diss cells was affected significantly. However, a substantial down-regulation of MMP-9 was accompanied by a surprising 3-fold increase in intravasation and metastasis. The results emphasize a rising awareness that targeting certain MMPs might result in an enhanced malignancy, exemplified herein at the intravasation level as this step of the metastatic cascade is dissected and quantified.