Reactive oxygen intermediates mediate a systemic signal network in the establishment of plant immunity.

Recognition of an avirulent pathogen stimulates an oxidative burst generating O2- and H2O2, and these reactive oxygen intermediates (ROIs) cue the induction of defense genes and cell death in the development of a restricted lesion. This localized hypersensitive response (HR) is accompanied by the development of systemic acquired resistance to virulent pathogens. Here we show that inoculation of Arabidopsis leaves with avirulent Pseudomonas syringae induces secondary oxidative bursts in discrete cells in distant tissues, leading to low-frequency systemic micro-HRs. The primary oxidative burst induces these systemic responses, and both the primary burst and the secondary microbursts are required for systemic immunity. Hence, ROIs mediate a reiterative signal network underlying systemic as well as local resistance responses.

Cell walls: structures and signals.

Cell walls harbor proteins and polysaccharides able to condition the development of a plant. In the past year, genes and enzymes modulating the composition and physical properties of walls have been characterized, and wall composition has been linked to the way a cell interacts with another cell, and to the way in which it differentiates. The sum of the signaling and physical activities of a cell wall may explain much about the control of development.

Use of ultrasound to determine need for laparotomy in trauma patients.

STUDY OBJECTIVE: To determine whether abdominal ultrasound can be used routinely as the primary screening test to identify the need for laparotomy in trauma patients. METHODS: Ultrasound was used at a Level II trauma center as a primary screening test for evaluation of intraabdominal injury. We reviewed the charts of all patients from trauma codes presenting between January 1, 1991, and December 31, 1993, to determine the results of abdominal ultrasound evaluation and to learn whether laparotomy was required. RESULTS: A total of 2,013 trauma patients presented during the study interval. Ultrasound was performed in 1,631 patients as the primary screening test for abdominal injury (mean time after arrival, 22.9 minutes), abdominal computed tomography (CT) was performed as the primary screen on 8 (mean time, 68.6 minutes), and 93 patients underwent both ultrasound and CT of the abdomen. Of 86 patients requiring laparotomy who were screened by ultrasound, 80 had positive diagnostic findings, for a sensitivity of 93.0%. Of the 1,545 ultrasound-screened patients who did not require laparotomy, 1,390 had negative findings, for a specificity of 90.0%. None of the patients with negative ultrasound results died or sustained identifiable mortality as a consequence of their negative scans. CONCLUSION: Ultrasound is a sensitive and specific test with which to evaluate trauma patients for abdominal injury requiring surgery. Routine abdominal ultrasound can be performed at the bedside in the emergency department as a timely, noninvasive diagnostic test. This use of a screening abdominal ultrasound examination can improve clinical decision-making for the use of emergency laparotomy. Ultrasound may be a better alternative to CT or diagnostic peritoneal lavage for the initial screening evaluation of abdominal trauma.

Oxidative cross-linking of plasma membrane arabinogalactan proteins.

Monoclonal antibodies which recognize carbohydrate in arabinogalactan proteins (AGPs) have revealed that certain carbohydrate epitopes at the outer plasma membrane surface are developmentally regulated. Some epitopes are expressed according to cell position, and AGPs are thought to play a role in cell-cell interaction during development. This study demonstrates that sugar beet plasma membranes contain two subfamilies of AGPs, with apparent molecular masses of 82 and 97 kDa, and that each subfamily consists of a small number of acidic AGP isoforms. Excision of leaves generates three additional AGP complexes with apparent molecular masses of 120, 170 and 210 kDa, with the 170 kDa complex being the major form induced by excision. The addition of millimolar concentrations of H2O2 to a partially purified fraction of the 82 and 97 kDa AGPs also generates AGP complexes, with the 170 kDa complex as the major form. These results indicate that the plasma membrane AGPs are a target for endogenous H2O2.

Soluble Signals from Cells Identified at the Cell Wall Establish a Developmental Pathway in Carrot.

Cells in a plant differentiate according to their positions and use cell-cell communication to assess these positions. Similarly, single cells in suspension cultures can develop into somatic embryos, and cell-cell communication is thought to control this process. The monoclonal antibody JIM8 labels an epitope on cells in specific positions in plants. JIM8 also labels certain cells in carrot embryogenic suspension cultures. We have used JIM8 and secondary antibodies coupled to paramagnetic beads to label and immunomagnetically sort single cells in a carrot embryogenic suspension culture into pure populations. Cells in the JIM8(+) population develop into somatic embryos, whereas cells in the JIM8(-) population do not form somatic embryos. However, certain cells in JIM8(+) cultures (state B cells) undergo asymmetric divisions, resulting in daughter cells (state C cells) that do not label with JIM8 and that sort to JIM8(-) cultures. State C cells are competent to form somatic embryos, and we show here that a conditioned growth medium from a culture of JIM8(+) cells allows state C cells in a JIM8(-) culture to go on and develop into somatic embryos. JIM8 labels cells in suspension cultures at the cell wall. Therefore, a cell with a role in cell-cell communication and early cell fate selection can be identified by an epitope in its cell wall.

Calcium-mediated apoptosis in a plant hypersensitive disease resistance response.

BACKGROUND: Avirulent pathogens elicit a battery of plant defenses, often accompanied by collapse of the challenged cells. In soybean cells, sustained accumulation of H2O2 from an oxidative burst cues localized host cell death. Such hypersensitive cell death appears to be an active process, but little is known about the mechanisms underlying cellular collapse. RESULTS: We show that H2O2 stimulates a rapid influx of Ca2+ into soybean cells, which activates a physiological cell death program resulting in the generation of large (approximately 50 kb) DNA fragments and cell corpse morphology--including cell shrinkage, plasma membrane blebbing and nuclear condensation--characteristic of apoptosis. In contrast, H2O2 induction of the cellular protectant gene glutathione S-transferase is Ca(2+)-independent. Apoptosis in soybean cells and leaf tissue was induced by avirulent Pseudomonas syringae pv. glycinea but was not observed at comparable stages of the compatible interaction with the isogenic virulent strain, which fails to elicit a hypersensitive response. Apoptosis was also observed at the onset of the hypersensitive response in Arabidopsis leaves inoculated with avirulent P. syringae pv. tomato and in tobacco cells treated with the fungal peptide cryptogein, which is involved in the induction of non-host resistance to Phytophthora cryptogea. CONCLUSIONS: These observations establish a signal function for Ca2+ downstream of the oxidative burst in the activation of a physiological cell death program in soybean cells that is similar to apoptosis in animals. That the characteristic cell corpse morphology is also induced in Arabidopsis and tobacco by different avirulence signals suggests that apoptosis may prove to be a common, but not necessarily ubiquitous, feature of incompatible plant-pathogen interactions. Emerging similarities between facets of hypersensitive disease resistance and the mammalian native immune system indicate that apoptosis is a widespread defence mechanism in eukaryotes.

Blunt-trauma carotid artery injury: mild symptoms may disguise serious trouble.

Injury to the carotid artery can occur in athletes by direct blow to the neck or by hyperextension of the neck. After such injury, symptoms may be mild or transient. Catastrophic complications such as stroke can occur if the injury is not recognized and treated. Neurologic changes such as transient weakness or transient unilateral blurred vision that occur after a hyperextension injury or a direct blow to the neck may indicate a carotid artery injury. A careful neurologic examination can help identify most carotid artery injuries, but because the symptoms of injury may not appear immediately, follow-up may be necessary. Treatment may consist of anticoagulation therapy or operative repair.

Cell-context signalling.

In plants, cells differentiate according to their position with relation to their cell neighbours. Monoclonal antibody (MAb) probes to polysaccharide epitopes, present at the surfaces of all plant cells, have defined a family of proteoglycan antigens which signify cellular position. These MAbs have been used to sort the single cells present in carrot somatic cell cultures on the basis of the presence or absence of specific polysaccharide epitopes. This sorting allows embryo initial cells to be cultured among different cell collectives (based on their polysaccharide epitope expression) and thus in altered contextual backgrounds. These experiments have shown that specific populations of embryo initial precursor cells induce and sustain the early development of the embryo initials, revealing that the populations of different cell collectives which are defined by different polysaccharide epitopes (cell-context) serves important regulatory function in early plant development. Somatic embryo initials deprived of the influence of the cell collective-defined by the presence of the polysaccharide epitope recognised by the MAb JIM8-establish unorganised first divisions and develop as callus. However, in the presence of the JIM8-reactive cell collective, or medium conditioned by the collective, the initials develop into somatic embryos. This demonstrates that the cells defined by the JIM8 polysaccharide epitope are necessary to sustain the meristematic activity which drives the renewed development. Transfer of a cell-wall signal from the JIM8-reactive cells to cellular situations in carrot seedlings in which they would not normally occur (out-of-context signals) stimulates lateral root production, thus demonstrating that the inductive signal operative in suspension cultures can be reinterpreted by specific cells later in development and reinitiate meristematic activity. The communication between the precursor cells defined by JIM8 and embryo initials defines an early cell-cell interaction in developing carrot plants. Labelling of flower sections suggests that the same interaction exists between embryo apical and basal cells early in normal development.

Identification of a transitional cell state in the developmental pathway to carrot somatic embryogenesis.

We have located a novel carbohydrate epitope in the cell walls of certain single cells in embryogenic, but not in non-embryogenic, suspension cultures of carrot. Expression of this epitope, recognized by the mAb JIM8, is regulated during initiation, proliferation, and prolonged growth of suspension cultures such that changes in the abundance of JIM8-reactive cells always precede equivalent changes in embryogenic potential. Therefore, a direct correlation exists between the presence of the JIM8-reactive cell wall epitope and somatic embryo formation. The JIM8-reactive cell wall epitope is expressed in the cell walls of three types of single cells and one type of cell cluster. One of the single cell types seems able to follow one of two phytohormone-controlled developmental pathways, either a cell elongation pathway that eventually leads to cell death, or a cell division pathway that gives rise to proembryogenic masses. We demonstrate that all JIM8-reactive cell types in embryogenic carrot suspension cultures are developmentally related, and that the switch by one of them to somatic embryogenesis is accompanied by the immediate dissipation of the JIM8-reactive cell wall epitope. The cell wall carbohydrate epitope recognized by JIM8 therefore represents a cell wall marker for a very early transitional cell state in the developmental pathway to carrot somatic embryogenesis.

Can detection of the yolk sac in the first trimester be used to predict the outcome of pregnancy? A prospective sonographic study.

Recent reports have indicated that identification of the yolk sac should precede the detection of the embryo in a normal first-trimester sonographic examination and that failure to visualize a yolk sac strongly suggests an abnormal intrauterine pregnancy. A first-trimester prospective study was performed in 163 normal and 49 abnormal consecutive singleton gestations. All women were examined both abdominally and transvaginally, with pregnancy outcome determined by delivery of a normal infant or a spontaneous abortion. The yolk sac was analyzed in all patients in whom an embryo was not identified (n = 76). When the yolk sac was identified, the following was found: by the abdominal approach with the mean sac diameter (MSD) less than 27 mm (n = 15), nine gestations were normal and six were abnormal, and by the transvaginal approach with the MSD less than 18 mm (n = 13), seven gestations were normal and six were abnormal. The presence of a yolk sac was not consistently predictive of a normal early pregnancy. When the yolk sac was also not identified, the following was found: abdominally with the MSD less than 27 mm (n = 41), 19 gestations were normal and 22 were abnormal, and transvaginally with the MSD less than 18 mm (n = 11), six gestations were normal and five were abnormal. Absence of the yolk sac was not consistently predictive of a spontaneous abortion. When using the MSD range (20-27 mm abdominally and 7-16 mm transvaginally), over which the yolk sac but not the embryo should be identified sonographically, the yolk sac was again not consistently visualized. On abdominal sonograms, the yolk sac was present and absent in three and 10 patients, respectively, for both normal and abnormal pregnancies. On transvaginal sonograms, the yolk sac was present and absent in seven and five normal gestations and in six and four abnormal gestations, respectively. The results of this study suggest that detection of the yolk sac in the first trimester is not an early predictor of pregnancy outcome.

Developmental Regulation of a Plasma Membrane Arabinogalactan Protein Epitope in Oilseed Rape Flowers.

We have identified and characterized the temporal and spatial regulation of a plasma membrane arabinogalactan protein epitope during development of the aerial parts of oilseed rape using the monoclonal antibody JIM8. The JIM8 epitope is expressed by the first cells of the embryo and by certain cells in the sexual organs of flowers. During embryogenesis, the JIM8 epitope ceases to be expressed by the embryo proper but is still found in the suspensor. During differentiation of the stamens and carpels, expression of the JIM8 epitope progresses from one cell type to another, ultimately specifying the endothecium and sperm cells, the nucellar epidermis, synergid cells, and the egg cell. This complex temporal sequence demonstrates rapid turnover of the JIM8 epitope. There is no direct evidence for any cell-inductive process in plant development. However, if cell-cell interactions exist in plants and participate in flower development, the JIM8 epitope may be a marker for one set of them.

Prospective comparison of vaginal and abdominal sonography in normal early pregnancy.

Vaginal and abdominal sonography were prospectively compared in 309 consecutive pregnancies of which 175 were normal. Two sonographic criteria of normal were analyzed: (1) the presence of an embryo compared with average gestational sac size and (2) the presence of embryonic cardiac activity compared with crown-rump length. Vaginally, 100% (160/160) of embryos were visualized when the average sac diameter was greater than or equal to 12 mm. Abdominally, an embryo was noted in 99.2% (123/124) of gestational sacs greater than or equal to 27 mm. Vaginal sonography revealed cardiac motion in all embryos of greater than or equal to 5 mm (149/149 cases); abdominal sonography revealed cardiac activity in 100% (132/132) of embryos with a crown-rump length of greater than or equal to 9 mm. One-third of normal embryos less than 5 mm crown-rump length did not demonstrate cardiac activity. The study demonstrates through objective comparison that vaginal sonography is superior to abdominal sonography for detection of an intrauterine embryo and its cardiac activity before 8 menstrual weeks. The diagnosis of embryonic demise should not be made by vaginal sonography in embryos measuring less than 5 mm crown-rump length without a heartbeat, and an empty gestational sac of less than 12 mm average diameter should not be diagnosed as blighted ovum by vaginal scans. In these cases follow-up vaginal sonography is suggested.

Zones of the uterus: discrepancy between US and MR images.

The location of the boundaries among the endometrium, inner myometrium (dark), and outer myometrium (intermediate or bright) were compared on T2-weighted magnetic resonance (MR) and intravaginal ultrasound (US) images obtained within 24 hours of each other. Twelve women with normal reproductive cycles underwent a total of 21 pairs of examinations. The endometrium, inner myometrium (junctional zone), and outer myometrium were measured by three independent observers. The endometrial thickness was thinner with MR imaging (6.5 mm with MR imaging vs 7.9 mm with US early in the cycle [P = .001]; 9.9 mm with MR imaging vs 11.3 mm, respectively, late in the cycle [P = .045]). The junctional zone was thicker with MR imaging (4.4 vs 2.3 mm early [P less than .001]; 3.9 vs 2.2 mm late [P = .003]). The combined thickness of the endometrium and junctional zone was thicker with MR imaging (15.5 vs 12.7 mm early [P = .002]; 17.3 vs 15.8 mm late [P = .064]), confirming that the boundary between the junctional zone and outer myometrium is different with MR imaging versus US.

Ectopic pregnancy: features at transvaginal sonography.

A retrospective review of the transvaginal sonograms of 50 women with laparoscopically confirmed ectopic pregnancy was performed to determine whether certain sonographic findings can be detected to confirm the diagnosis. Forty-seven of the 50 pregnancies were tubal. A tubal ring (a 1-3-cm mass consisting of a 2-4-mm concentric, echogenic rim of tissue surrounding a hypoechoic center) was seen in 23 of 34 (68%) ectopic pregnancies in which the fallopian tube had not ruptured, and the tubal ring could be distinguished from a corpus luteum cyst in most cases. Transvaginal sonography also depicted simple (n = 22) or particulate (bloody) (n = 13) peritoneal fluid associated with ectopic pregnancy. In each case in the series, at least one abnormal uterine, adnexal, or peritoneal finding was detected at transvaginal sonography. Because of its improved resolution of uterine and adnexal structures, transvaginal sonography is recommended as a means for detailed evaluation of patients suspected of having an ectopic pregnancy.

A family of abundant plasma membrane-associated glycoproteins related to the arabinogalactan proteins is unique to flowering plants.

We have identified a family of abundant peripheral plasma membrane glycoproteins that is unique to flowering plants. They are identified by a monoclonal antibody, MAC 207, that recognizes an epitope containing L-arabinose and D-glucuronic acid. Immunofluorescence and immunogold labeling studies locate the MAC 207 epitope to the outer surface of the plasma membrane both in protoplasts and in intact tissues. In some cells MAC 207 also binds to the vacuolar membrane, probably reflecting the movement of the plasma membrane glycoproteins in the endocytic pathway. The epitope recognized by MAC 207 is also present on a distinct soluble proteoglycan secreted into the growth medium by carrot (Daucus carota) suspension culture cells. Biochemical evidence identifies this neutral proteoglycan as a member of the large class of arabinogalactan proteins (AGPs), and suggests a structural relationship between it and the plasma membrane glycoproteins. AGPs have the property of binding to beta-glycans, and we therefore propose that one function of the AGP-related, plasma membrane-associated glycoproteins may be to act as cell surface attachment sites for cell wall matrix polysaccharides.

Hand-held and automated sonomammography. Clinical role relative to X-ray mammography.

A retrospective analysis of 73 patients who had undergone X-ray mammography (XRM), automated sonomammography (ASM), and hand-held sonomammography (HSM) was performed to evaluate the clinical role of both types of sonomammography (SM) relative to XRM. The results were classified on the basis of mammographic and sonographic findings. Clinical and/or surgical proof was obtained in all 73 patients. The SM was complementary to XRM, depending on the radiographic breast density. When comparison was made between ASM (4.5 MHz) and the HSM (7.5 MHz), the pathologic condition was better identified by HSM in 86% of the cases. Moreover, in no cases was ASM better than HSM.