[Investigation of electrophysical properties of Listeria monocytogenes cells during the interaction with monoclonal antibodies]

An electrooptical approach was used in studies of Listeria monocytogenes-antibody binding. An electrooptical analyzer, which has been developed at the State Research Center for Applied Microbiology (Obolensk, Russia), was used as a basic instrument for electrooptical measurements. The analyzer consists of the following modules: a sample preparation module, a mixer, an AC field generator, an EO-flow cell, a microcontroller for transfer of liquid, a thermal system, an operator interface, and an image processor. The sample preparation module includes a unit for an automatic filter changing device and a hydraulic system. Since the AC electrokinetic effects depend on the dielectric properties of bioparticles, their composition, morphology, phenotype, the medium, and the frequency of applied electrical field, the electroorientational spectra were used for discrimination of different types of bacteria, a given type being "controlled" (and identified) by the selective choice of binding agents (antibodies). The measurements were performed using a discrete set of frequencies of the orienting electric field (10, 100, 250, and 500 kHz). During biospecific interactions, an antibody is bound to the microorganism, causing a change in the dielectric properties of the microorganism-antibody complex, and the electrooptic signal reaches its maximum at 100-200 kHz. It was shown that the biospecific interactions of Listeria monocytogenes cells with anti-Listeria antibody in the presence of E. coli K-12, and A. brasilense sp7 significantly change the electrooptical signals. Thus, the determination of the presence of particular bacteria within a mixed sample may be achieved by selection and matching of antibodies specific to individual bacterium types and by comparing the spectra of bacterium in the presence and in the absence of specific binding agent (antibody).

[The electrooptical parameters of suspensions of Escherichia coli XL-1 cells interacting with helper phage M13K07]

The electrophysical properties of Escherichia coli XL-1 cells interacting with helper phage M13K07 were studied as a function of the phage-to-cell ratio and the contact time. The electro-optical signal of bacterial cells changed considerably as soon as 10 min after the onset of their incubation with phage particles, presumably due to phage adsorption on the cell surface. The maximum changes in the orientational spectra of cell suspensions were observed when the phage-to-cell ratio was 20. Selectivity studies showed that E. coli XL-1 cells interacting with the helper phage M13K07 in the presence of foreign microflora, such as E. coli K-12 or Azospirillum brasilense Sp7, can be identified by using their electrophysical properties. Changes in the orientational spectra of cell suspensions are interpreted with the stage of phage-bacterium interaction taken into account. The results obtained can probably be used to devise a new rapid method for identification of microorganisms and to study the particular stages of cell infection by bacteriophages.

A precision measurement of the mass of the top quark

The standard model of particle physics contains parameters--such as particle masses--whose origins are still unknown and which cannot be predicted, but whose values are constrained through their interactions. In particular, the masses of the top quark (M(t)) and W boson (M(W)) constrain the mass of the long-hypothesized, but thus far not observed, Higgs boson. A precise measurement of M(t) can therefore indicate where to look for the Higgs, and indeed whether the hypothesis of a standard model Higgs is consistent with experimental data. As top quarks are produced in pairs and decay in only about 10(-24) s into various final states, reconstructing their masses from their decay products is very challenging. Here we report a technique that extracts more information from each top-quark event and yields a greatly improved precision (of +/- 5.3 GeV/c2) when compared to previous measurements. When our new result is combined with our published measurement in a complementary decay mode and with the only other measurements available, the new world average for M(t) becomes 178.0 +/- 4.3 GeV/c2. As a result, the most likely Higgs mass increases from the experimentally excluded value of 96 to 117 GeV/c2, which is beyond current experimental sensitivity. The upper limit on the Higgs mass at the 95% confidence level is raised from 219 to 251 GeV/c2.

Search for narrow tt resonances in pp collisions at square root of (s)=1.8 TeV

A search for narrow resonances that decay into tt pairs has been performed using 130 pb(-1) of data in the lepton + jets channel collected by the Dphi detector in pp collisions at square root of (s)=1.8 TeV. There is no significant deviation observed from the standard-model predictions at a top-quark mass of 175 GeV/c2. We therefore present upper limits at the 95% confidence level on the product of the production cross section and branching fraction to tt for narrow resonances as a function of the resonance mass MX. These limits are used to exclude the existence of a leptophobic top-color particle with mass MX<560 GeV/c2, using a theoretical cross section for a width GammaX=0.012MX.

Search for large extra dimensions in the monojet+E(T) channel with the DØ detector

We present a search for large extra dimensions (ED) in pp collisions at a center-of-mass energy of 1.8 TeV using data collected by the DØ detector at the Fermilab Tevatron in 1994-1996. Data corresponding to 78.8+/-3.9 pb(-1) are examined for events with large missing transverse energy, one high-p(T) jet, and no isolated muons. There is no excess observed beyond expectation from the standard model, and we place lower limits on the fundamental Planck scale of 1.0 and 0.6 TeV for 2 and 7 ED, respectively.

Search for the production of single sleptons through R-parity violation in pp; collisions at square root (s) =1.8 TeV

We report the first search for supersymmetric particles via s-channel production and decay of smuons or muon sneutrinos at hadronic colliders. The data for the two-muon and two-jets final states were collected by the D0 experiment and correspond to an integrated luminosity of 94+/-5 pb(-1). Assuming that R parity is violated via the single coupling lambda'211, the number of candidate events is in agreement with expectation from the standard model. Exclusion contours are given in the (m(0),m(1/2)) and (m(x),m(v)) planes for lambda(')(211)=0.09, 0.08, and 0.07.

Search for R-parity violating supersymmetry in two-muon and four-jet topologies

We present results of a search for R-parity-violating decay of the neutralino chi;01, taken as the lightest supersymmetric particle, to a muon and two jets. The decay proceeds through a lepton-number violating coupling lambda(')(2jk) (j=1,2; k=1,2,3), with R-parity conservation in all other production and decay processes. In the absence of candidate events from 77.5+/-3.9 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron in pp collisions at sqrt[s]=1.8 TeV, and with an expected background of 0.18+/-0.03+/-0.02 events, we set limits on squark and gluino masses within the framework of the minimal low-energy supergravity-supersymmetry model.

Search for leptoquark pairs decaying into nunu+jets in pp collisions at square root[s] = 1.8 TeV

We present the results of a search for leptoquark (LQ) pairs in (85.2+/-3.7) pb(-1) of pp* collider data collected by the D0 experiment at the Fermilab Tevatron. We observe no evidence for leptoquark production and set a limit on sigma(pp*-->LQLQ-->nunu+jets) as a function of the mass of the leptoquark (m(LQ)). Assuming the decay LQ-->nuq, we exclude scalar leptoquarks for m(LQ) < 98 GeV/c(2), and vector leptoquarks for m(LQ) < 200 GeV/c(2) and coupling which produces the minimum cross section, at a 95% confidence level.

Search for the scalar top quark in pp collisions at square root[s] = 1.8 TeV

We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of pp events corresponding to 108.3 pb(-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, t-->b chi+1 and t-->blnu, no evidence for signal is found. We derive cross-section limits as a function of stop ( t ), chargino ( chi+1), and sneutrino ( nu) masses.

Direct search for charged higgs bosons in decays of top quarks

We present a search for charged Higgs bosons in decays of pair-produced top quarks in pp collisions at sqrt[s] = 1.8 TeV recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( M(H+/-),tan(beta)) parameter space where the decay t--> H(+)b has a branching fraction >0.36 and B(H+/--->tau(nu)(tau)) is large.

Ratio of isolated photon cross sections in pp macro collisions at square root of s = 630 and 1800 GeV

The inclusive cross section for production of isolated photons has been measured in pp macro collisions at square root of s = 630 GeV with the D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy (E(T)) range from 7-49 GeV and have pseudorapidity absolute value of eta < 2.5. This measurement is combined with the previous D0 result at square root of s = 1800 GeV to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the E(T) range.

Search for new physics using QUAERO: a general interface to D0 event data

We describe QUAERO, a method that (i) enables the automatic optimization of searches for physics beyond the standard model, and (ii) provides a mechanism for making high energy collider data generally available. We apply QUAERO to searches for standard model WW, ZZ, and t t macro production, to searches for these objects produced through a new heavy resonance, and to the first direct search for W'-->WZ. Through this interface, we make three data sets collected by the D0 experiment at square root of [s] = 1.8 TeV publicly available.

Search for heavy particles decaying into electron-positron pairs in pp collisions

We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.

Structure of the egg envelope of the haddock, Melanogrammus aeglefinus, and effects of microbial colonization during incubation

Haddock (Melanogrammus aeglefinus) eggs from an experimental culture were examined by electron and light microscopy to determine the structure of the egg envelope as preserved by various fixatives and to observe the effects on the envelope of microbial colonization during incubation. The egg envelope consisted of a featureless thin surface coating that readily dissociated into globules and was lost under standard fixation; a thin homogeneous surface layer penetrated by pores; a well-defined intact outer lamella 0.5-1.0 µm thick immediately beneath this; then about three more vaguely defined lamellae of similar thickness beneath which were several broader fibrillar layers. The total envelope thickness was 6.5-8.5 µm. Different fixatives primarily affected the appearance of the thin surface layer, which was well-preserved only by freezing or by fixation in glutaraldehyde with Alcian blue. Egg surfaces were colonized by microorganisms, regardless of early disinfection by various agents, and eggs at hatching were densely populated by bacteria, notably the filamentous genus Leucothrix. However, bacteria did not penetrate the egg envelope beyond the outer layers, where their presence was associated with surface erosion. A dense epiflora did not necessarily prevent normal development of the embryo, although very heavy infestations, as seen on eggs that failed to hatch, may cause suffocation. The envelope structure is compared with that of another gadoid which has been extensively studied and cultured, the Atlantic cod (Gadus morhua).

Vectorial function of major histocompatibility complex class II in a human intestinal cell line

This study explores the expression and the function of major histocompatibility complex class II in the intestinal epithelial cell line CaCo-2, which has been widely used as a model for the human gastrointestinal epithelium. Human leucocyte antigen (HLA)-DR expression on CaCo-2 cells is induceable by interferon-gamma (IFN-gamma), but responsiveness to IFN-gamma is dependent on cell differentiation and IFN-gamma availability at the basolateral cell surface. HLA-DR expression is concentrated in apical cytoplasmic vesicles and on the basolateral cell surface. Invariant chain is expressed in apical vesicles but is absent from the cell surface. Immunoprecipitation studies show a slow rate of dissociation of HLA-DR from Ii. Double labelling shows some overlap between HLA-DR expression and basolateral endosomal markers but no overlap with apical endosomal markers. Functional studies show processing and presentation of lysozyme endocytosed from the basolateral, but not apical surfaces. CaCo-2 cells may provide a useful model with which to dissect the antigen-processing pathways in polarized epithelial cells. The regulated access of antigens taken up from the gut lumen to the processing compartments may prevent overloading the immune system with antigens derived from normal gut contents.

IFN-gamma down-regulates MHC expression and antigen processing in a human B cell line

IFN-gamma is a crucial mediator in the induction of cell-mediated Th1-type responses but is predominantly a negative regulator of B cell differentiation and proliferation. This cytokine is therefore a key factor in determining Th1 vs Th2 differentiation. This study investigates the action of IFN-gamma in modulation of HLA-DR expression and Ag presentation by EBV-transformed human B cell lines. In contrast to its action on the monocyte/macrophage, IFN-gamma down-regulates surface MHC expression on these B cells, and this regulation is posttranscriptional. In parallel with MHC down-regulation, there is a reduced capability to process and present exogenous protein and peptide Ag to T cell hybridomas. IFN-gamma does not change the rates of fluid phase endocytosis or exocytosis in this model system but correlates with an up-regulation of the lysosomal enzymes cathepsins B and D.

In vivo priming of T cells against cryptic determinants by dendritic cells exposed to interleukin 6 and native antigen

T cells recognizing poorly displayed self determinants escape tolerance mechanisms and persist in the adult repertoire. The process by which these T cells are primed is not clear, but once activated, they can cause autoimmunity. Here, we show that dendritic cells treated with interleukin 6 (IL-6) process and present determinants from a model native antigen in a qualitatively altered hierarchy, activating T cells in vitro and in vivo against determinants that were previously cryptic because of poor display. IL-6 does not induce conventional maturation of dendritic cells but alters the pH of peripheral, early endosomal compartments and renders the cells more susceptible to killing by chloroquine. Acidification of endosomes by ouabain mimics the effect of IL-6 and allows processing of the same cryptic determinant. These results suggest that cytokines such as IL-6 could initiate and help to propagate an autoimmune disease process by differentiating dendritic cells into a state distinct from that induced by normal maturation.

Soft tissue cervical metastases of squamous carcinoma of the head and neck

Some 497 of 3085 patients with squamous cell carcinoma of the head and neck treated between 1963 and 1990 had a later radical neck dissection at some time after initial treatment. The histological slides were all reviewed, firstly to confirm the presence of squamous cell carcinoma within the neck, and secondly to ascertain whether the metastasis was to soft tissue, to a lymph node or to both. The presence of extracapsular rupture in lymph node deposits was also assessed. Of the 497 patients, 138 had soft tissue deposits only, and 359 had nodal deposits only. Of the patients with nodal deposits 165 had extracapsular rupture and 194 did not. The 5-year survival of the 138 patients with soft tissue metastases was 27% compared with 33% for patients with extracapsular rupture and 50% for patients with no extracapsular rupture. Weighted logistic regression showed that soft tissue deposits were significantly more common in patients in poor general condition, plus poorly differentiated squamous cell carcinoma plus T4 tumours (P < 0.005), and in patients with poorly differentiated squamous cell carcinoma plus T4 tumours (P < 0.025). Cox's multivariate analysis with backward elimination showed that gender, histological differentiation, site of primary tumour and age of patient had no statistically significant effect on survival. The number of nodes (P < 0.0001), the presence of extracapsular rupture (P < 0.0001) and the presence of soft tissue free metastases (P < 0.001) were all highly significant. The N-status at recurrence also reached statistical significance (P < 0.0001).

The use of botulinum toxin for treatment of acquired nystagmus and oscillopsia

PURPOSE

To evaluate the role of botulinum toxin A (BTA) in treating patients with diminished visual acuity secondary to acquired nystagmus and oscillopsia.

METHODS

Twelve patients with acquired nystagmus causing oscillopsia and reduced vision were treated with injection of BTA. Botulinum toxin A was injected directly into the horizontal recti in three patients, and in nine patients retrobulbar BTA was administered. Injections were given at 3- to 4-month intervals and repeated as long as patients noted improvement in their quality of life.

RESULTS

Improvement in visual function varied, and not all patients benefited from the procedure. However, 8 of 12 patients demonstrated a measurable improvement in visual acuity. Transient ptosis was the most common side effect.

CONCLUSION

Retrobulbar BTA provides a simple and safe alternative in managing a condition for which alternative treatments are typically unsatisfactory.

Osseous expansion of the cranial vault by craniotasis

A study of cranial vault lengthening using a custom expandable fixation-distraction (craniotatic) appliance was performed in the young-adult rabbit model. Ten 24-week-old rabbits underwent circumferential suturectomy plus expansion (expanded group), 10 underwent circumferential suturectomy without expansion (sham control group), and 10 served as normal controls. The appliance was lengthened at a rate of 2.5 mm per week for 5 weeks. Serial lateral cephalometry, comparative dry-skull anthropometric measurements, and histologic examinations were performed. The expanded group demonstrated a significantly longer skull, cranial vault, anterior cranial base, posterior face, and orbit as compared with the control groups (p less than 0.05). Callus bone filled the distracted suturectomy and united the frontofacial complex to the posterior cranium. In conclusion, skull lengthening by distraction osteogenesis is possible in the rabbit model and offers a new technique for future investigation in the treatment of coronal synostosis.

Hemitonic seizures: etiological and diagnostic considerations

Intermittent unilateral tonic posturing of the limbs may relate to focal motor epilepsy, intermittent dystonia or hysteria, and diagnosis may be difficult. Five patients are presented who illustrate two distinct hemitonic syndromes which we believe to be epileptic, namely forced elevation of one arm and paroxysmal hemispasm. It is suggested that these attacks follow an irritative lesion involving the supplementary motor cortex and a deep lesion involving striatothalamic projections respectively. Brevity of episodes, their stereotyped nature and rapid response to anticonvulsant drugs supports an epileptic etiology. The term paroxysmal hemidystonia may not be appropriate for patients with intermittent stereotyped disorders of limb posture, where the clinical features support an epileptic basis and we suggest the designation hemitonic seizures.

Transient compartment syndrome of the forearm resulting from venous congestion from a tourniquet

A case of transient compartment syndrome of the forearm resulting from faulty tourniquet function is described. The patient was followed with serial compartmental pressure measurements. Signs and symptoms subsided within a few hours of limb elevation. Thus, conservative care in the early stages may be therapeutic. Early recognition of tourniquet malfunction, systematic assessment of the source of engorgement, and prompt correction can avoid this post-operative complication.

The Noonan syndrome/cherubism association

Noonan syndrome is characterized by short stature, unusual facies, congenital heart disease, chest deformity, mild mental retardation, and cryptorchidism in males. It may be sporadic or inherited as an autosomal dominant trait and occurs between 1 in 1000 and 1 in 2500 live births. Cherubism is a giant cell lesion of the jaws thought to be transmitted as an autosomal dominant trait. It is usually recognized by age 7 years, follows a variable course, and is not known to be related to other genetic disorders. We herein report on four patients with Noonan syndrome, all of whom had cherubism. Two other probable cases are cited in the literature for a total of six known cases.

Photoreceptor-pigment epithelial cell relationships in rats with inherited retinal degeneration. Radioautographic and electron microscope evidence for a dual source of extra lamellar material

Protein synthesis and displacement in photoreceptor and pigment epithelial cells of inbred normal (Fisher) and mutant (RCS) rats with inherited retinal degeneration has been studied by light and electron microscope radioautography. Groups of animals 14, 15, 17, 19, 27, 35, and 50 days of age were injected with amino acids-H(3) and killed at subsequent time intervals. In normal rats, radioactive protein synthesized in the rod inner segments was incorporated into outer segment saccules and displaced outward; the total renewal time of outer segments at all ages was approximately 9 days. In RCS photoreceptors, outer segment displacement was slowed from the normal rate before day 17 and at all subsequent stages. Most of the newly synthesized protein appeared to migrate only into the basal third of the outer segments. Labeling of pigment epithelial cells in RCS rats was always heavier than in controls. Labeled protein was displaced as early as 1 hr postinjection from pigment epithelial cell somas into the apical processes, and by 2 hr postinjection was located in the adjacent lamellar whorls characteristic of the mutant rat retina. After 1 day, radioactivity was present in the 14, 15, 17, and 19 day series of RCS rats in the apical third of the outer segment layer (occupied mainly by extra lamellar material) while there were few silver grains in the middle third of the layer (occupied mainly by distal parts of outer segments). The RCS pigment epithelial cells thus have an unusual synthetic role and appear to be a source of the extra lamellar material. Electron microscope examination revealed that many intact pigment epithelial cell processes were incorporated into the large whorls of extra lamellae. In addition, many disorganized outer segment saccules were observed in continuity with longer membranous lamellae and large lamellar whorls. The extra lamellar material therefore appears to be derived from both rod outer segments and pigment epithelial cells.