A method of imaging viscoelastic parameters with acoustic radiation force

Acoustic radiation force has been proposed as a method of interrogating the mechanical properties of tissue. One simple approach applies a series of focused ultrasonic pulses to generate an acoustic radiation force, then processes the echoes returned from these pulses to estimate the radiation-force-induced displacement as a function of time. This process can be repeated at a number of locations to acquire data for image formation. In previous work we have formed images of tissue stiffness by depicting the maximum displacement induced at each tissue location after a finite period of insonification. While these maximum displacement images are able to differentiate materials of disparate mechanical properties, they exploit only a fraction of the information available. In this paper we show that the time-displacement curves acquired from tissue mimicking phantoms exhibit a viscoelastic response which is accurately described by the Voigt model. We describe how the viscous and elastic parameters of this model may be determined from experimental data. Finally, we show phantom images that depict not only the maximum local displacement, but also the viscous and elastic model parameters. These images offer complementary information about the target.     

Lung injury induced by antibody fragments to angiotensin-converting enzyme.

Rabbits given goat anti-rabbit angiotensin-converting enzyme antibodies or derived antibody fragments develop rapidly fatal pulmonary edema. Endothelial cell injury is manifested by bleb formation and the disintegration of cell membranes. Platelets are found along the injured endothelium and leukocytes block capillary lumens. The pathologic features are similar when immune IgG, F(ab')2, or Fab are given. In vitro studies of complement activation show that solubilized, purified angiotensin-converting enzyme alone activates C1, with consumption of C4 and C3. Addition of immune IgG plus converting enzyme enhances this activation. F(ab')2 plus enzyme enhances only C3 consumption, while Fab with enzyme produces no additional complement utilization. Thus, while complement activation may be involved in the pathogenesis of injury induced by IgG or F(ab')2, the mechanism of Fab-induced endothelial injury remains unclear.     

The suppressive effects of monocytes in the autologous mixed lymphocyte reaction.

The response of isolated T cells to autologous non-T mononuclear cells is called the autologous mixed lymphocyte reaction (AMLR). The responding T cells show immunological memory and specificity. This reaction was present in all thirty normal individuals tested. Since the AMLR in the absence of evidence of in vivo excessive lymphoproliferation must somehow be controlled, we have studied the interactions of enriched T cells, B cells and monocytes in culture as possible means of regulation of this reaction. Increased rate of [3H] thymidine incorporation by T lymphocytes were observed when they were cultured with mitomycin-treated autologous non-T cells. This was increased when the stimulating cells were enriched for B lymphocytes and was significantly decreased when the stimulating cells were enriched for monocytes. Addition of monocyte-enriched cells to B-enriched cells in a 1:1 ratio, significantly suppressed the AMLR (P- less than 0.01). Equivalent numbers of monocytes did not suppress T-cell responses to phytohaemagglutinin (PHA). Monocyte-enriched cells were separated from stimulating B-enriched cells by nucleopore (0.6 mu) or dialysis tubing (0.12 mu) in Marbrook chambers. Soluble products released from monocyte-enriched cells also suppressed the AMLR. The significance of the AMLR in vivo is uncertain but it may be important in immunoregulation, monocytes playing an important role.     

Separation of T lymphocytes from normal individuals and patients with B lymphocyte chronic lymphocytic leukaemia.

Previous studies have shown that lymphocytes from patients with chronic lymphocytic leukaemia have a diminished response to mitogens which stimulate T cells. Chronic lymphocytic leukaemia is most often a disease of accumulating B cells so that T lymphocytes are diluted by large numbers of leukaemic cells. Direct comparison with the responses of normal lymphocytes to mitogenic stimulation is therefore suspect. To circumvent this difficulty, a method of isolating T cells from normal individuals and patients with chronic lymphocytic leukaemia was developed. Lymphocytes containing an average of 16.1 per cent B cells from normal individuals were applied to IgG-anti-IgG-coated Degalan bead columns and held at 4 degrees for 2 hours. The eluted cells contained less than 2 per cent B cells. When chronic lymphocytic leukaemic lymphocytes, containing an average of 68.6 per cent B cells, were applied to IgG-anti-IgG columns, the eluted cells contained 36.4 per cent B cells. To improve the purification of T lymphocytes, columns of uncoated Degalan beads were used to remove non-specifically adherent cells. Eluted lymphocytes were then applied to IgG-anti-IgG columns. This resulted in the recovery of purified populations of T cells with less than 2 per cent contamination with B cells. Patients with chronic lymphocytic leukaemia were found to have lymphocytes with either a normal density or a low density of surface immunoglobulins. B cells were successfully removed from lymphocyte suspensions in all cases of chronic lymphocytic leukaemia with a normal density of lymphocyte surface immunoglobulins. In the three cases of chronic lymphocytic leukaemia with low density surface immunoglobulins, separation by this method was unsuccessful. However, an enriched T-cell population was obtained when leukaemic lymphocytes which had lost all detectable surface immunoglobulins were passed through a column coated with heat-aggregated IgG.     

Enzyme immunoassay for Q fever: comparison with complement fixation and immunofluorescence tests and dot immunoblotting.

Enzyme-linked immunosorbent assays (ELISA) for the detection of specific immunoglobulin G (IgG) and IgM antibodies were developed by using purified Coxiella burnetii cells. Variables, including type of microtiter plate, blocking agent, incubation conditions, antigen stability, and substrate type, were examined to achieve optimal ELISA performance. The reliabilities of the assay systems were compared with those of complement fixation (CF) and enhanced immunofluorescence (EIF) tests with 600 human serum samples from defined clinical cases of Q fever, routine samples, and serum specimens from farmers. ELISA and EIF test results agreed in all cases. Dot immunoblotting was also used to test some of these sera and gave a rapid, qualitative result, which agreed with ELISA and EIF test results in all cases. No instances were found in which both ELISA and EIF test results were negative and the CF test results was positive. However approximately 5% of the sera were positive by ELISA and the EIF test while the CF test result was either negative or unreadable because of serum anticomplementary activity. We conclude that dot immunoblotting is a useful screening test, whereas ELISA and the EIF test are both rapid and sensitive tests when used for the serodiagnosis of Q fever and should be considered to be replacements for the CF test.     

Characterization of BrkA Expression in Bordetella bronchiseptica

BrkA confers resistance to killing by complement in Bordetella pertussis. Complement resistance in Bordetella bronchiseptica was examined. Four B. bronchiseptica strains possessed the brkA gene; however, only three expressed the protein. Only the strain lacking BrkA was susceptible to complement. Introduction of the B. pertussis brkA gene restored BrkA expression to this strain but did not confer resistance. brkA was mutated in the strains that naturally expressed BrkA, and loss of BrkA did not confer sensitivity to complement. As a species, B. bronchiseptica is more resistant to complement than B. pertussis, and BrkA does not mediate resistance.     

Plaque assay for virulent Legionella pneumophila.

Methods of assessing virulence of Legionella pneumophila, the etiologic agent of Legionnaires disease, include the infection of guinea pigs, fertile chicken eggs, and mammalian and protozoan cell cultures. Guinea pig assays, in particular, are expensive, laborious, or unsuitable for routine screening of Legionella isolates. We have developed a virulence assay that requires the enumeration of viruslike plaques which are the result of virulent L. pneumophila infecting mouse L929 cells. Each plaque is the consequence of the initial infection of an L cell with a single bacterium. A nonvirulent mutant derived from the serial passage of virulent L. pneumophila on Mueller-Hinton agar fails to survive within L cells and consequently fails to produce plaques.     

Microplate technique to determine hemolytic activity for routine typing of Listeria strains.

Because the hemolysis produced by Listeria monocytogenes and Listeria seeligeri on blood agar is frequently difficult to interpret, we developed a microplate technique for the routine determination of hemolytic activity with erythrocyte suspensions. This microtechnique is a simple and reliable test for distinguishing clearly between hemolytic and nonhemolytic strains and could be used instead of the CAMP (Christie-Atkins-Munch-Petersen) test with Staphylococcus aureus in the routine typing of Listeria strains. Furthermore, our results suggest that the quantitation of the hemolytic activity of the Listeria strains, along with the D-xylose, L-rhamnose, and alpha-methyl-D-mannoside acidification tests, allows the differentiation of L. monocytogenes, L. seeligeri, and Listeria ivanovii. We also observed that the treatment of erythrocytes with crude exosubstances of rhodococcus equi, Pseudomonas fluorescens, Acinetobacter calcoaceticus, and S. aureus enhanced the hemolytic activity of all Listeria strains with this characteristic.     

* Immediate allergic reactions to amoxicillin

A large group of patients with suspected allergic reactions to (β-lactam antibiotics was evaluated. A detailed clinical history, together with skin tests, RAST (radioallergosorbent test), and controlled challenge tests, was used to establish whether patients allergic to β-lactam antibiotics had selective immediate allergic responses to amoxicillin (AX) or were cross-reacting with other penicillin derivatives. Skin tests were performed with benzylpenicilloyl-poly-L-lysine (BPO-PLL), benzylpenicilloate, benzylpenicillin (PG), ampicillin (AMP), and AX. RAST for BPO-PLL and AX-PLL was done. When both skin test and RAST for BPO were negative, single-blind, placebo-controlled challenge tests were done to ensure tolerance of PG or sensitivity to AX. A total of 177 patients were diagnosed as allergic to β-lactam antibiotics. We selected the 54 (30.5%) cases of immediate AX allergy with good tolerance of PG. Anaphylaxis was seen in 37 patients (69%), the other 17 (31%) having urticaria and/or angioedema. All the patients were skin test negative to BPO; 49 of 51 (96%) were also negative to MDM, and 44 of 46 (96%) to PG. Skin tests with AX were positive in 34 (63%) patients. RAST was positive for AX in 22 patients (41%) and to BPO in just 5 (9%). None of the sera with negative RAST for AX were positive to BPO. Challenge tests with AX were performed in 23 subjects (43%) to establish the diagnosis of immediate allergic reaction to AX, and in 15 cases (28%) both skin test and RAST for AX were negative. PG was well tolerated by all 54 patients. We describe the largest group of AX-allergic patients who have tolerated PG reported so far. Diagnosis of these patients can be achieved only if specific AX-related reagents are employed. Further studies are necessary to determine the exact extent of this problem and to improve the efficacy of diagnostic methods.