Hemostatic plug formation in normal and von Willebrand pigs: the effect of the administration of cryoprecipitate and a monoclonal antibody to Willebrand factor

Hemostatic plug (HP) formation was investigated in the ear bleeding time incision in normal and von Willebrand pigs. HP volume was calculated by integrating the areas of serial sections. In normal pigs (n = 11), platelets immediately formed a layer on the surface of the cut channel. Platelet aggregates formed at the ends of transected vessels and gradually enlarged. Finally, all transected vessels were occluded by HP and bleeding stopped. In contrast, large HPs were formed in the incision in von Willebrand's disease (vWD) pigs (n = 4); these HPs did not cover the ends of the transected vessels, which continued to bleed, allowing the formation of large hemostatically ineffective platelet aggregates in the incision. Canals traversed these HPs, and bleeding from the open vessels may have continued through them. After infusion of cryoprecipitate into a vWD pig, the bleeding time shortened, and the morphological findings of the HPs were similar to those of normal pigs. In normal pigs (n = 3) infused with an anti- Willebrand factor monoclonal antibody, which prolonged the bleeding time, a large HP formed in the incision, similar to that observed in the vWD pig. The volume of the normal and vWD HPs increased with time. These in vivo findings suggest that Willebrand factor is involved in the localization of the HP to the damaged vessel and may also play a role in platelet-platelet interaction. A computerized morphometric technique was used for measuring the volume of the hemostatic plugs and the distance of sequential points on the perimeter of the HP from the center of selected bleeding vessels.     

Perceived professional support and the use of blocking behaviours by hospice nurses

A prospective study of the impact of training 41 hospice nurses in assessment skills was used to test hypotheses that blocking behaviours would be used more when patients disclosed feelings and used less when nurses perceived that they had satisfactory professional support Each nurse was asked to assess a patient's current problems before and after feedback training and 8 months later Audiotape recordings of these interviews were rated by trained raters They determined the frequency of nurses' responses which had the function of blocking patient disclosure and the emotional level of patient disclosure Before each patient assessment each nurse was interviewed and questionnaires administered to measure her perceptions of the support she received Blocking behaviours were most evident when patients disclosed their feelings (Kendalls r=0 36, P < 0 001) In interviews containing most patient disclosure of feeling, blocking was significantly less (r= - 0 24, P < 0 5) when the nurse felt that practical help would be available if needed and when the nurse felt that her direct supervisor was concerned about the nurse's own welfare (r= -0 37, P < 0 005)     

Hard sphere-like glass transition in eye lens α-crystallin solutions

We study the equilibrium liquid structure and dynamics of dilute and concentrated bovine eye lens α-crystallin solutions, using small-angle X-ray scattering, static and dynamic light scattering, viscometry, molecular dynamics simulations, and mode-coupling theory. We find that a polydisperse Percus–Yevick hard-sphere liquid-structure model accurately reproduces both static light scattering data and small-angle X-ray scattering liquid structure data from α-crystallin solutions over an extended range of protein concentrations up to 290 mg/mL or 49% vol fraction and up to ca. 330 mg/mL for static light scattering. The measured dynamic light scattering and viscosity properties are also consistent with those of hard-sphere colloids and show power laws characteristic of an approach toward a glass transition at α-crystallin volume fractions near 58%. Dynamic light scattering at a volume fraction beyond the glass transition indicates formation of an arrested state. We further perform event-driven molecular dynamics simulations of polydisperse hard-sphere systems and use mode-coupling theory to compare the measured dynamic power laws with those of hard-sphere models. The static and dynamic data, simulations, and analysis show that aqueous eye lens α-crystallin solutions exhibit a glass transition at high concentrations that is similar to those found in hard-sphere colloidal systems. The α-crystallin glass transition could have implications for the molecular basis of presbyopia and the kinetics of molecular change during cataractogenesis.The cytoplasm of the tightly packed fiber cells of the eye lens contains concentrated aqueous protein mixtures that have high refractive indexes, while normally remaining clear enough for vision. Lens clarity depends on short-range order between lens proteins (1, 2) and can be disrupted by both protein aggregation and liquid–liquid phase separation in cataract, a leading cause of blindness. At the high protein concentrations of lens cytoplasm, 25–60% by weight in mammals, small changes in interprotein interactions can disrupt transparency. For human lens proteins with cataractogenic point mutations, and for high-concentration lens protein mixtures, protein interaction changes as small as a fraction of thermal energy, k_BT, can induce phase separation and thus lead to opacification (3–7).In addition to equilibrium phase transitions, dynamical transitions including glass formation and gelation can also occur at high protein concentrations like those of the eye lens (8, 9). Relatively abrupt viscoelastic changes associated with glass formation or gelation could harden the lens and contribute to presbyopia and could alter cataract formation rates by affecting aggregation and phase separation kinetics.Here we study the equilibrium liquid structure and dynamics of concentrated solutions of eye-lens α-crystallin protein solutions, using small-angle X-ray scattering (SAXS), static light scattering (SLS) and dynamic light scattering (DLS), viscometry, liquid-state theory, event-driven molecular dynamics (MD) simulations, and mode-coupling theory (MCT). α-Crystallin is a polydisperse protein with about 40 subunits of two types, αA and αB, and accounts for up to 50% of lens protein mass. The forward scattering intensity from SAXS and light scattering experiments with concentrated α-crystallin solutions can be well represented by monodisperse hard-sphere liquid-structure models that have been key for understanding short-range order needed for lens transparency (1, 2). However, in physiological conditions α-crystallin ranges in molecular weight from 3 × 10⁵ to 2 × 10⁶, with an average near 8 × 10⁵ (10). There have indeed been reports that structure factors obtained from SAXS and small-angle neutron scattering data deviate from predictions for monodisperse hard spheres (11, 12).Accordingly, we first show that a polydisperse hard-sphere liquid-structure model (PHSM) based on the Percus–Yevick (PY) approximation (13) can accurately model SAXS data obtained from the present bovine α-crystallin preparations for volume fractions up to 49%, using a polydispersity of 20%. In contrast, polydispersity did not strongly influence model predictions for the observed SLS, which unlike SAXS probes length scales much larger than molecular sizes.We then test for glassy dynamics of α-crystallin solutions, using DLS and viscometry, and find glass transition features like those previously found for hard spheres. In particular, with increasing α-crystallin concentration, DLS intermediate scattering functions show expected progressively slower relaxations along with fast decays, and the viscosity diverges, both when approaching volume fractions in the vicinity of 58%. Using MCT (14), we obtain semiquantitative models of DLS data and corresponding data from MD simulations of high-concentration polydisperse sphere systems, in which MD polydispersity values were obtained from fits of the PHSM to the SAXS data. We note that for MCT we have used the theory for monodisperse systems, because the majority of the MCT work to date has focused on such systems. Recent results for polydisperse systems (15) support a similar overall picture.In brief, the data show that the present α-crystallin solutions have liquid structure and glassy dynamics similar to those of polydisperse hard-sphere solutions. Thus, eye lens protein solutions show analogs to ordinary glass in linking short-range order, transparency, and arrested dynamics.     

Malignant blue nevus. Case report and literature review

A well-documented case of malignant blue nevus is presented, along with an in-depth review of the literature. Malignant blue nevus is a rare form of malignant melanoma. A cellular blue nevus is the precursor lesion. The scalp is the most common site. The tumor often presents clinically as a progressively enlarging or multinodular blue-black lesion. The histologic pattern is fascicular dense collections of pigmented, pleomorphic spindle cells. Because of marked regional histologic variation within a malignant blue nevus, however, sampling error can cause delay in recognition of malignancy. A high clinical index of suspicion and appropriate biopsy technique are necessary to reach an early diagnosis. The most common site of metastasis of a malignant blue nevus is the lymph node. The phenomenon of benign lymph node nevus cell metastasis, which may occur with benign blue nevi, must be differentiated from a true malignant metastasis of a malignant blue nevus.