Glass formation and shear elasticity in dense suspensions of repulsive anisotropic particles.

Kinetic vitrification, shear elasticity, and the approach to jamming are investigated for repulsive nonspherical colloids and contrasted with their spherical analog. Particle anisotropy dramatically increases the volume fraction for kinetic arrest. The shear modulus of all systems increases roughly exponentially with volume fraction, and a universal collapse is achieved based on either the dynamic crossover or random close packing volume fraction as the key nondimensionalizing quantity. Quantitative comparisons with recent microscopic theories are performed and good agreement demonstrated.

Microstructure of equilibrium fluid clusters in colloid-polymer suspensions.

Several studies on colloidal depletion systems have reported the existence of a fluid phase consisting of clusters of particles above a critical polymer concentration that acts as a precursor regime to the gel phase at low colloid volume fractions (phi

Scattering for mixtures of hard spheres: comparison of total scattering intensities with model.

The angular dependence of the intensity of x-rays scattered from binary and ternary hard sphere mixtures is investigated and compared to the predictions of two scattering models. Mixture ratio and total volume fraction dependent effects are investigated for size ratios equal to 0.51 and 0.22. Comparisons of model predictions with experimental results indicate the significant impact of the role of particle size distributions in interpreting the angular dependence of the scattering at wave vectors probing density fluctuations intermediate between the sizes of the particles in the mixture.

Identification of prolactin-like proteins synthesized by normal murine lymphocytes.

Cultured murine lymphoid cells release a PRL-like immunoreactive (IR) protein which may be important in immunity, as anti-PRL antisera inhibit lymphocyte proliferation in vitro. We examined culture supernatants (SNs) and cell lysates from concanavalin A (Con A) activated murine thymocytes to identify these proteins. Western blot analysis of cell lysates revealed three specifically-stained PRL-IRs. A doublet of bands at 35.6 and 33.6 kDa was associated with the particulate fraction of the cell. These PRL-IRs were present in lymphocytes independently of mitogen stimulation. In contrast, a 22 kDa PRL-IR was only produced in mitogen stimulated cells, and was specifically immunoprecipitated with anti-PRL antiserum. In addition, all three PRL-like IRs incorporated 35S-methionine in vitro, indicating that they are synthesized by these cells. Only the 22 kDa PRL-like protein was present in culture medium from stimulated cells, suggesting that this may be the PRL bioactivity previously demonstrated in SNs from murine lymphocytes.

Human thymocytes express a prolactin-like messenger ribonucleic acid and synthesize bioactive prolactin-like proteins.

Recent evidence has demonstrated an important immunoregulatory role for pituitary PRL. Moreover, PRLs have been identified as products of transformed human lymphocyte cell lines and normal murine lymphocytes, and implicated as regulators of their proliferative responses. However, PRL synthesis by normal human lymphocytes has not yet been reported. Here we demonstrate that human thymocytes and peripheral blood lymphocytes (PBL) synthesize PRL in primary culture. The principal form produced by thymocytes is 24 kilodaltons (kDa), essentially the same size as pituitary PRL, while PBL produced a 27-kDa variant. Size heterogeneity was evident, with products detected ranging from 21-29 kDa in various tissue samples, a phenomenon also found to occur in human pituitary and decidual PRL. Thymocytes and PBLs also synthesized a low mol wt form (11 kDa) that was released into culture supernatants concurrently with the larger PRL. The 24- and 11-kDa forms expressed PRL-like bioactivity in the Nb2 node lymphoma bioassay, further supporting their PRL-like nature. Expression of these PRLs was regulated by mitogen stimulation in thymocytes, but was constitutively produced in PBL. Northern blot analysis of thymocyte RNA using a human PRL cDNA probe detected a single PRL-like mRNA, which was significantly larger than human pituitary PRL mRNA. This was constitutively present in unstimulated thymocytes. Taken together, these data demonstrate that normal human lymphocytes synthesize bioactive PRLs similar in size to those produced by the pituitary. The presence of a single PRL mRNA suggests that the size variation observed in these proteins is probably due to posttranslational modification, such as proteolysis and glycosylation.

Didemnin B: a new immunosuppressive cyclic peptide with potent activity in vitro and in vivo.

Didemnin B (DB) is a 7-amino-acid, cyclic polypeptide with potent (10(7)-10(10)M) antiproliferative effects in vivo and in vitro against a variety of viruses and tumor cell lines. Because lymphocyte blastogenesis is essential for many immune responses, DB appeared likely to exert immunosuppressive effects as well. Using primary cultures of murine (Balb/c) splenic mononuclear cells to evaluate this possibility, we found that DB was a potent (IC50 = 190 ng/ml) inhibitor of lymphocyte protein synthesis, although RNA synthesis and cell viability were unaffected. However, it markedly inhibited blastogenesis stimulated by concanavalin A (IC50 = 50 pg/ml), lipopolysaccharide (IC50 = less than 100 pg/ml) and alloantigen (IC50 = less than 10 pg/ml) when added to cultures immediately after stimulation. DB added later, at the time of thymidine labeling was much less potent (1/46-1/1430), suggesting that the lymphocyte activation process is particularly sensitive to this agent. Our finding that alloantigen-driven proliferation was exquisitely sensitive to DB (greater than 90% inhibition at 10 pg/ml) led us to test its effects in vivo using the Simonsen parental-to-F1 graft-versus-host reaction (GVHR). Treatment of graft recipients with 0.05, 0.10, and 0.20 mg DB/kg/day for 7 days produced 51%, 40%, and 60% inhibition of splenomegaly induced by the GVHR, and treatment with 0.3 mg/kg/day on days 1, 2, 4, and 6 inhibited 71%. These data show that the in vitro inhibition of alloantigen-driven blastogenesis by DB was reproduced by in vivo treatment as well, even across major histocompatibility differences. This leads us to conclude that DB has potent immunosuppressive activity both in vitro and in vivo.

Didemnin B--an immunosuppressive cyclic peptide that stimulates murine hemagglutinating antibody responses and induces leukocytosis in vivo.

Didemnin B (DB) is a cyclic peptide with potent immunosuppressive activity in vitro and in the murine graft-versus-host-reaction (GVHR), the only measure of in vivo immunity tested in our prior studies. Because continued production of mature leukocytes by bone marrow and an intact antibody response are crucial to defense against infection in immunosuppressed patients, we have evaluated the effects of DB on these processes as well. Anti-sheep red blood cell (SRBC) hemagglutinating antibody (hAb) production was induced by i.p. injection of 5 x 10(7) SRBC in CB6F1 mice (5/group) treated with vehicle or DB once/day for six days. Serum was collected on day 7 and hAb titers measured by SRBC agglutination. Control antibody titers were 1/16, while animals receiving DB doses of 0.025, 0.05, 0.10, and 0.20 mg/kg/day yielded titers of 1/37, 1/74, 1/56, and 1/74, respectively. This stimulation of hAb production (4.6 x control) was confirmed by a second experiment. We then studied DB effects (0.1 mg/kg/day x 6 days) on serum hAb titers in separate groups of five mice at 7, 10, 15, and 20 days postimmunization. Control hAb titers were 1/110 on day 7, then dropped to 1/60 on days 10, 15, and 20. DB-treated animals had titers of 1/130 on day 7, and 1/170 on days 10-20. These data show that DB treatment in vivo causes a persisting increase in anti-SRBC hAb titers. Evaluation of DB effects on proliferation and antibody secretion in vitro by three hybridoma cell lines showed a potent inhibition of cell replication but stimulation of antibody production on a per-cell basis in each clone (+26%-+900%, range), suggesting a direct effect on Ig synthesis. During our first in vivo DB studies (0.1 mg/kg/day x 7 days) in mice, we noted that peripheral blood white counts were elevated on day 8 to 21.3 +/- 2.1 x 10(3)/mm3 compared with control (vehicle only) levels of 13.6 +/- 2.0 x 10(3)/mm3 (P less than .01). Kinetic studies showed that by 24 hr after a single i.p. injection of DB (1.0 mg/kg), blood leukocyte, granulocyte, and lymphocyte counts were elevated by 2.5-, 3-, and 2-fold, respectively, but declined rapidly thereafter. 3H-thymidine incorporation (4 hr) by freshly harvested bone marrow leukocytes from DB-treated mice (0.025, 0.05, and 0.10 mg/kg/day x 7 days) was enhanced up to 40% over control (P less than .05), while bone marrow cellularity was increased 200% (P less than .01).(ABSTRACT TRUNCATED AT 400 WORDS)

Up-regulation of prolactin gene expression and feedback modulation of lymphocyte proliferation during acute allograft rejection.

BACKGROUND: Although recent evidence suggests that prolactin is important in the immune response, bidirectional communication between prolactin and the immune system has not been demonstrated previously. We examined our hypothesis that this communication exists during mouse skin allograft rejection. METHODS: Serum prolactin levels were measured by bioassay, and pituitary prolactin mRNA was examined by use of Northern blots, in BALB/c mice receiving skin allografts from C57BL mice, on days 2, 4, and 6 after grafting. The feedback effects of prolactin on splenic lymphocytes were assessed in one-way mixed lymphocyte reactions, with or without added interleukin-2 (IL-2) or IL-4. RESULTS: Prolactin mRNA was increased significantly in grafted animals compared with sham animals (2.4-fold by day 4). Serum prolactin bioactivity was also elevated on all days tested. Prolactin treatment resulted in dose-dependent modulation of the mixed lymphocyte reaction with lymphocytes from grafted animals but not from sham animals. These effects depended on the time points and the presence of IL-2 or IL-4; the maximal enhancement occurred with day-4 lymphocytes cultured with IL-4 (80%). CONCLUSIONS: This report is the first to implicate in vivo immune regulation of prolactin gene expression. Our observations indicate that bidirectional interaction exists between prolactin and the immune system and provide a rationale for altering prolactin levels to treat allograft rejection.

Cytomegalovirus appendicitis in a patient with human immunodeficiency virus infection. Case report and review of the literature.

We report a case of chronic abdominal pain with subsequent development of acute right lower quadrant tenderness in a patient infected with the human immunodeficiency virus. Ultrasonography and computed tomography revealed an enlarged appendix. On subsequent laparotomy, the patient was found to have appendicitis due to cytomegalovirus. Six additional cases of this infection were identified in a review of the literature. The course of cytomegalovirus appendicitis in these patients was prolonged and atypical compared with noncompromised patients with acute appendicitis. Because perforation may occur, surgery is advocated when this diagnosis is suspected in the patient infected with human immunodeficiency virus.

Dynamic organ culture of precision liver slices for in vitro toxicology.

The lack of a reproducible method for the production of thin tissue slices has hindered the use of liver slices as an in vitro tool for hepatotoxicity studies. Fresh human, rat, and rabbit liver was processed using a mechanical slicer. With this instrument, precision (5% of thickness) liver slices in the submillimeter range could be produced at a rapid rate. Slices were prepared from fresh livers in chilled, oxygenated buffer to minimize trauma. Following incubation for up to 20 h in a dynamic organ culture system, histology of incubated slices suggested that 250 m precision-cut slices were optimum in regard to morphology relative to liver slices incubated under conventional organ culture conditions. Addition of bromobenzene to the culture showed time-dependent hepatotoxicity based on two classic parameters of cell degeneration. Histological evidence is presented which suggests the usefulness of this system for hepatotoxicity studies and the production of focal necrosis in vitro.

Red cell electrophoretic mobility test for early diagnosis of multiple sclerosis.

We have confirmed the red cell electrophoretic mobility-unsaturated fatty acid test for multiple sclerosis, which involves measuring the change in electrophoretic mobility of erythrocytes in Medium 199 upon the addition of linoleic acid. Using defibrinated blood samples, the average decrease in the mobility of red cells upon the addition of linoleic acid of 57 multiple sclerosis patients was 6.7 +/- 2.1% and that of 23 normal control subjects was .09 +/- 1.2% (p less than 0.001). In addition, blood anticoagulated with trisodium citrate was found to give similar test results, and such preparations were found to be simpler and quicker to use.

A rational approach to serious blunt hepatic injury.

Based on our cumulative experience in patients with serious blunt liver trauma, hepatic resection is seldom necessary where cross-clamping the hepatoduodenal ligament (portal triad) effectively stops parenchymal hemorrhage. Oversewing or "hemo-clipping" of intrahepatic disrupted vascular tributaries combined, when appropriate, with lobar hepatic arterial ligation and transposition of an omental pedicle graft into the "fracture" defect is usually sufficient treatment. On the other hand, avulsion of hepatic veins and/or tears of the retrohepatic vena cava require major hepatic resection primarily for exposure. But even in conjunction with internal vena caval bypass shunts, the mortality with this injury remains high.

Kinetics of crystallization in hard-sphere colloidal suspensions.

We propose a kinetic model for describing crystal nucleation kinetics in hard-sphere colloidal suspensions. The model captures the interplay between the enhanced thermodynamic driving force and the reduced particle diffusivity in determining crystal nucleation rates as the particle density is increased in hard-sphere suspensions. Model calculations of nucleation rates and crystal growth velocities agree quantitatively with experimental observations. The dependence of the critical cluster size on volume fraction that emerges differs qualitatively from predictions of classical theories allowing for an experimental validation of the mechanism of crystal nucleation in colloidal suspensions.

Elasticity and clustering in concentrated depletion gels.

X-ray scattering and rheology are employed to study the volume fraction dependence of the collective structure and elastic moduli of concentrated nanoparticle-polymer depletion gels. The nonequilibrium gel structure consists of locally densified nonfractal clusters and narrow random interfaces. The elastic moduli display a power law dependence on volume fraction with effective exponents that decrease with increasing depletion attraction strength. A microscopic theory that combines local structural information with a dynamic treatment of gelation is in good agreement with the observations.

In-vitro hepatotoxicity of three dichlorobenzene isomers in human liver slices.

1 The cytotoxicity of dichlorobenzenes in cultured rat liver slices has previously been shown to be strain specific and biotransformation related. 2 In order to extrapolate animal models to humans, the dichlorobenzenes were incubated with human liver slices to try to clarify their hepatotoxic potential in man. 3 The degree of hepatotoxicity observed with the dichlorobenzenes depended on whether Waymouth's or Krebs-Henseleit was used as the incubation medium. 4 All three dichlorobenzenes (1 mM) produced no significant differences from control when incubated in Waymouth's medium. However, in the Krebs-Henseleit buffer there was a substantial increase in cytotoxicity. 5 In both incubation mediums the dichlorobenzene isomers exhibited the following rank order 1,3-DCB greater than 1,2-DCB greater than 1,4-DCB. 6 1,2-dichlorobenzene hepatotoxicity was blocked by metyrapone, 1,3-dichlorobenzene toxicity was blocked by SKF 525-A and neither one of these inhibitors could block the 1,4-dichlorobenzene cytotoxicity. 7 The use of human liver tissues to evaluate potential toxicants merits consideration since the hepatotoxicity of xenobiotics and drugs in man is the ultimate question.