Sequential Appearances Research Articles

Evolution of spinel-bearing ultrahigh-temperature granulite in the Jining complex, North China Craton: constrained by phase equilibria and Monte Carlo methods

The peak temperature and timescale of ultrahigh-temperature (UHT) metamorphism are significant for understanding its thermal budget and geodynamic evolution. The spinel-bearing (sapphirine-absent) UHT granulite at the Xuwujia area in the Jining complex, North China Craton was revealed to have undergone a metamorphic evolution that involves the pre-Tmax (maximum temperature) heating decompression to the Tmax stage with an extreme temperature of ~1125 °C, the post-Tmax cooling to the fluid-absent solidus (~860 °C) at 0.8–0.9 GPa, and sub-solidus decompression. The Tmax condition was recorded by the inferred feldspar-absent peak assemblage of spinel ± garnet. The post-Tmax cooling evolution was indicated by the sequential appearances of plagioclase, K-feldspar, sillimanite and biotite, as well as the core-to-rim ascending grossular component in garnet. Moreover, some texturally zoned spinel has exsolved lamellae of magnetite in the core and shows rim-ward increase of Mg and Al, which suggests a temperature decrease from >1100 °C in local domains isolated from quartz. Spinel with exsolved magnetite lamellae or low Al/(Al + Fe3+) is therefore proposed as an indicator for UHT conditions in metapelites. Probability simulation on the collected zircon ages yields a timescale of ~40 Myr (95% confidence; during 1.90–1.94 Ga) for the supra-solidus cooling stage of the UHT metamorphism in the Jining complex. This extreme UHT metamorphism has reached the rock’s dry solidus (~1125 °C) and undergone slow cooling, which is interpreted to result from a post-orogenic plume activity with sufficient advective heating from hyperthermal mafic intrusions.

Photovoltaic Cycling to-and-fro Actuation of a Water-Microdroplet for Automatic Repeatable Solute Acquisition on Oil-Infused Hydrophobic LN:Fe Surface

Acquiring solute from sources without external aids is a challenging manipulation of water microdroplets for developing LN-based biological lab-on-chips. Herein, a cycling to-and-fro actuation of a water microdroplet stimulated by a laser illumination, with the cycling period controllable by the illumination power, is demonstrated on an oil-infused hydrophobic LN:Fe surface. This cycling to-and-fro movement of the microdroplet, featured by stretching, departing, rebounding, and settling stages, stems from the continuous generation and the intermittent screening of the photovoltaic charges during the laser illumination and it is essentially a natural transportation of net charges from laser spot (high potential) to metal surface (low potential). An analytic model is built to describe the balance between the charge generation and consumption at the laser spot and to predict the dependence of the cycling period on experimental parameters. By utilizing this effect, the water microdroplet is optically manipulated for acquiring fluorescent dye (solute) directly from the metal surface (source) in an automatic and repeatable way. The sequential appearances and fading-away of fluorescent spots inside the microdroplet prove the successful acquisition and dissolution of the fluorescent dye in the microdroplet. The reported technique is crucial to LN-based functionality integration aiming at complicated biological operations.

Concurrent Cooperative J-Aggregates and Anticooperative H-Aggregates.

Completely understanding the working mechanisms of sophisticated supramolecular self-assembly exhibiting competing paths is very important for chemists en route to acquiring the ability of constructing supramolecular systems with controlled structures and designed functions. Here, the self-aggregation behaviors of an N-heterocyclic aromatic dicarboximide molecule 1, boasting two competing paths that give rise to different supramolecular structures and exhibit distinct thermodynamic features, are carefully examined. First, a group of H-aggregates are observed when providing a medium driving force for aromatic stacking, and their formation is manifested as an anticooperative process. When exposed to enhanced strength of aromatic interactions, these H-aggregates are found to transform into J-aggregates via a cooperative assembly mechanism. With the assistance of a mathematic model accommodating two competing polymerization pathways, calculations are conducted to simulate and explain the thermodynamic equilibria of such a unique supramolecular system. The calculation results are highly consistent with the experimental observations, and some important properties are elucidated. Specifically, the anticooperative assembly mechanism generally promotes the formation of low to medium oligomers, whereas the cooperative path is more competent at producing high polymers. If the anticooperative and cooperative routes coexist and compete for the same molecule, the cooperative formations of high polymers are significantly suppressed unless a very high degree of polymerization can be achieved. Such a unique feature of concurring anticooperative and cooperative paths emerges to the H- and J-aggregates of molecule 1 and thus brings about the interesting sequential appearances of the two types of aggregates under conditions of continuously enlarged driving force for self-aggregation. Finally, based on the knowledge acquired from this study and by analyzing the steric features of 1 that influence its supramolecular packing motifs, a slightly modified molecular structure is designed, with which the intermediate H-aggregation state was successfully suppressed, and a single cooperative J-aggregation path is manifested.

Dynamic distributions of long double-stranded RNA in Tetrahymena during nuclear development and genome rearrangements.

Bi-directional non-coding transcripts and their ∼29-nt small RNA products are known to guide DNA deletion in Tetrahymena, leading to the removal of one-third of the genome from developing somatic nuclei. Using an antibody specific for long double-stranded RNAs (dsRNAs), we determined the dynamic subcellular distributions of these RNAs. Conjugation-specific dsRNAs were found and show sequential appearances in parental germline, parental somatic nuclei and finally in new somatic nuclei of progeny. The dsRNAs in germline nuclei and new somatic nuclei are likely transcribed from the sequences destined for deletion; however, the dsRNAs in parental somatic nuclei are unexpected, and PCR analyses suggested that they were transcribed in this nucleus. Deficiency in the RNA interference (RNAi) pathway led to abnormal aggregations of dsRNA in both the parental and new somatic nuclei, whereas accumulation of dsRNAs in the germline nuclei was only seen in the Dicer-like gene mutant. In addition, RNAi mutants displayed an early loss of dsRNAs from developing somatic nuclei. Thus, long dsRNAs are made in multiple nuclear compartments and some are linked to small RNA production whereas others might participate in their regulations.

Epigenetic Regulation of miR-22 in a BPA-exposed Human Hepatoma Cell

Bisphenol A (BPA), an widely used environmental chemical, is encircled to human life. However, we generally do not know whether or not it can cause negative health effects. One of the representative epigenetic changes that inhibit gene expression is DNA methylation, which has been very well studied in association with cancer and development. Gene function is changed by DNA methylation; however, its genetic code does not change. Our study hypothesized that a post-transcriptional change in DNA occurs due to exposure to BPA. These changes then cause regulation of microRNA and gene expression. To identify these successional regulations, we conducted microarraybased assays. For validation, also we conducted bisulfite sequencing, quantitative real-time PCR, miRNA inhibitor assay, and Western blotting. We found 1,751 hypo-methylation changed regions, and several micro- RNA had included methylated-regions. miR-22 was also hypomethylated (chr17:1563947-1564031) by BPA-exposure, and expression of miR-22 was up-regulated in an miRNA array and real-time PCR. miR- 22 has been reported to inhibit estrogen signaling by direct targeting of the estrogen receptor alpha mRNA. Taking notice of this point, we analyzed gene expression profiles that included its predicted targets. In the present study, we found the cause of hypomethylation of miR-22 and negative regulation of its apoptosisrelated target gene expression by BPA-exposure. These results suggests that BPA can alter sequential genomic appearances in HepG2 cells, a potentially affection of BPA toxicity. Also, the results of our study support that toxicology study need to integrated analysis of array-based assays for help in understanding of the molecular action of environmental toxicants.

Swine Cone and Rod Precursors Arise Sequentially and Display Sequential and Transient Integration and Differentiation Potential Following Transplantation

We followed cone and rod development in the pig and we correlated development with the potential for cone and rod precursor integration and differentiation following subretinal transplantation. Rod and cone precursors were identified during development by their position in the outer retina and by immunostaining for markers of differentiation. Embryonic retinal cells from green fluorescent protein (GFP)(+) transgenic pigs at different developmental stages were transplanted into adult retinas and integration and differentiation was followed and quantified by immunostaining for markers of cone and rod differentiation. Pig cones and rods are spatially segregated, allowing us to follow rod and cone development in situ. Gestation in the pig is 114 days. By embryonic day (E) 50, postmitotic cone progenitors had formed the outer two rows of the retina. These cone progenitors are marked by expression of Islet1 (ISL1) and Recoverin (RCVRN) (at this embryonic stage, RCVRN exclusively marks these cone precursors). By contrast, postmitotic neural retina leucine zipper (NRL)(+) rod precursors, located interior to the cone precursors, did not appear until E65. At E50, before NRL(+) rod precursors are evident, transplanted cells gave rise almost exclusively to cones. At, E57, transplanted cells gave rise to equal numbers of rods and cones, but by E65, transplanted cells gave rise almost exclusively to rods. Transplantation of cells at E85 or E105, as precursors initiate opsin expression, led to few integrated cells. Consistent with their sequential appearances in embryonic retina, these results demonstrate sequential and surprisingly narrow developmental windows for integration/differentiation of cone and rod precursors following transplantation.

Repeated and Combined Participation in Workforce, Education and Social Program Services: Preliminary Evidence from Maryland Administrative Data Sources

One justification for extended retention of program administrative data is a resulting capability to study whether and how often repeated, concurrent and sequential appearances are found in multiple program transaction records. The expected return-on-investment from extended retention of administrative data rises when coverage of multiple programmatic interventions is consolidated in an integrated data system. This report is based on a preliminary exploration of linked historical administrative data files containing recorded instances of individual participation in defined education, workforce and social service programs. Our results to date should be treated as illustrative of decision-relevant insights that future refinements can produce. To explore the incidence of repeated, concurrent and sequential participation in more than one government program we accessed two workforce, threepublic education, and two social services administrative data files. We document that many individuals do engage in multiple workforce, education and social services program activities, and in repeated participation within each of the program types. There are many reasons for sustained interest in reliable measurement of repeated and combined program engagements. Some combinations and sequences are looked upon favorably, while others are viewed with some concern. Care should be exercised to avoid hasty conclusions about the benefits and costs that can be assigned to particular combinations of program engagements. Our next steps will include renewed attention to dynamic person identification and program engagement methodologies, while continuing the design and implementation of our study of up to 27 years of multiple program engagements by 1984 credit-course enrollees in Maryland’s public community colleges.

Scale effects on information theory-based measures applied to streamflow patterns in two rural watersheds

Summary Understanding streamflow patterns in space and time is important for improving flood and drought forecasting, water resources management, and predictions of ecological changes. Objectives of this work include (a) to characterize the spatial and temporal patterns of streamflow using information theory-based measures at two thoroughly-monitored agricultural watersheds located in different hydroclimatic zones with similar land use, and (b) to elucidate and quantify temporal and spatial scale effects on those measures. We selected two USDA experimental watersheds to serve as case study examples, including the Little River experimental watershed (LREW) in Tifton, Georgia and the Sleepers River experimental watershed (SREW) in North Danville, Vermont. Both watersheds possess several nested sub-watersheds and more than 30 years of continuous data records of precipitation and streamflow. Information content measures (metric entropy and mean information gain) and complexity measures (effective measure complexity and fluctuation complexity) were computed based on the binary encoding of 5-year streamflow and precipitation time series data. We quantified patterns of streamflow using probabilities of joint or sequential appearances of the binary symbol sequences. Results of our analysis illustrate that information content measures of streamflow time series are much smaller than those for precipitation data, and the streamflow data also exhibit higher complexity, suggesting that the watersheds effectively act as filters of the precipitation information that leads to the observed additional complexity in streamflow measures. Correlation coefficients between the information-theory-based measures and time intervals are close to 0.9, demonstrating the significance of temporal scale effects on streamflow patterns. Moderate spatial scale effects on streamflow patterns are observed with absolute values of correlation coefficients between the measures and sub-watershed area varying from 0.2 to 0.6 in the two watersheds. We conclude that temporal effects must be evaluated and accounted for when the information theory-based methods are used for performance evaluation and comparison of hydrological models.

Bispectral index and suppression ratio during hypothermia after cardiac arrest: reply to Aibiki

Dear Editor, We thank Dr. Aibiki [1] for his observation that the bispectral index (BIS) and suppression ratio (SR) may change over time in cardiac arrest survivors receiving neuromuscular blockade (NMB) during therapeutic hypothermia. We agree that the evolution of these electrophysiological parameters may affect the prognostic power of BIS. We believe at least five potential confounders must be considered when interpreting the prognostic utility of BIS (or any other EEGbased variable) in a cardiac arrest survivor treated with hypothermia. The first is interference from muscle activity such as shivering, myoclonus, and seizures. Patients must be fully paralyzed or the BIS1 is not reliable. The second is electrographic seizure activity—anecdotally, we have noted a sudden ‘‘spike’’ in the BIS score when a nonconvulsive seizure begins, and a return to near-baseline BIS values after the seizure ends. The third potential confounder is the variability induced by the time course of cerebral electrical reconstitution following hypoxic-ischemic injury. Because recovery of brain electrical activity is poorly characterized and may vary with severity of brain injury, great caution must be exercised in the interpretation of early BIS1 values. Our patients were evaluated at a mean of 280 min after resuscitation (return of spontaneous circulation, ROSC), but it is possible that patients evaluated very early after ROSC might show false low BIS1 values. Like Dr. Aibiki and colleagues, we have seen changing BIS values in some patients but not others, and agree that this complex issue warrants further study. Reconstitution of cerebral electrical activity has been studied in rats following asphyxial arrest. Electrical bursting is identified as early as 13 min after ROSC, and a longer delay to bursting correlates with worse neurocognitive outcome [2]. Increased bursting of electrical activity at 30–40 min after the ROSC correlates with subsequent development of a continuous EEG background at 90 min, and with good neurological outcome. Conversely, rats with decreased early bursting usually failed to develop a continuous EEG pattern, and had poor neurological outcomes [3]. These time frames and observations have only been reported as experimental rat data, with no known translation to human clinical data. A fourth potential confounder is temperature; again in rat models, hypothermia and fever increased early bursting activity [4, 5] compared to normothermia. The fifth potential confounder of early EEGbased prognostication after cardiac arrest is intensity of analgo-sedation, another area that requires further study. In humans that recover from cardiac arrest, a stereotypical pattern of intermittent cortical electrical activity followed by continuous activity with the sequential appearances of delta, theta, and alpha activities on EEG has been described, whereas the appearance of spikes and sharp waves, or a discontinuous or suppressed background is associated with poor recovery [6, 7]. The time course of this progression, and the influence of clinical factors that may critically influence cerebral blood flow or electrophysiology, such as blood pressure, cardiac index, brain temperature, anticoagulation, electrolyte levels, and partial pressures of oxygen and carbon dioxide in arterial blood, have not been established. BIS1 is a promising and simple technique for early estimation of the severity of brain injury after cardiac arrest, but has potential confounders not yet studied. Further research is required before it can be applied clinically for critical decision-making regarding type of therapeutic intervention and especially before any decisions to limit therapy are made after cardiac arrest. Patients must be given the opportunity to benefit from improved resuscitation, neuroprotective, and critical care therapies, and we must avoid the temptation to declare the neurological prognosis hopeless unless we know the data leading to that conclusion is worthy of such a life-and-death decision.

Atomic Scale Oxidation of Silicon Nanoclusters on Silicon Carbide Surfaces

The initial stage adsorption of molecular oxygen on the 6H-SiC(0001)-3×3 surface has been studied using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy. STM filled-state imaging reveals the sequential appearances of dark sites upon initial oxygen exposure at room temperature, followed by the appearances of bright sites at higher oxygen exposures. The changes in the STM images are interpreted on the basis of changes in the local density-of-states of the silicon adatom cluster site following the sequential development of different oxygen chemisorption states, beginning with the attachment of oxygen on the dangling bond site to its subsequent insertion in the Si-Si back-bond. Periodic density functional theory calculations supported our interpretations because the most stable chemisorption site was found to occur on the reactive adatom cluster site, as opposed to the adlayer coplanar bonds. The interaction of atomic O beam with the 3 x 3 surface results in the formation of silicon oxide nanoclusters.

An Early Cretaceous age for the Rajmahal traps, Panagarh area, West Bengal: palynological evidence

The discovery of traps in the subsurface Mesozoic succession of the Panagarh area, West Bengal, has drawn attention to their correlation with the traps in the Rajmahal Basin, Bihar. The objective of this paper is to assess the palynological dating of the intertrappean beds with the help of sequential first appearances of the stratigraphically important spore species Cicatricosisporites australiensis, Aquitriradites spinulosus, and Foraminisporis wonthaggiensis. C. australiensis, along with the first appearance of A. spinulosus, denotes the earliest Berriasian. This association is significant for recognition of the Jurassic/Cretaceous boundary. The lowest occurrence of F. wonthaggiensis indicates deposits of Berriasian–Valanginian age. The data on which these observations are based have been obtained from the intertrappean beds of the Rajmahal Formation in six boreholes: PGD-1A, 2, 4, 6, 8 and 9A. Further palynological studies on boreholes PGD-4, 8 and 9A have indicated the approximate time-span for the duration of volcanic activity in the Panagarh area. This seems to have been initiated in the early Berriasian and continued into the Hauterivian, which is earlier than the volcanism associated with the Rajmahal traps in the Rajmahal Basin.

The natural course of neurological recovery following cardiopulmonary resuscitation

In 231 patients resuscitated from circulatory arrest of cardiovascular or pulmonary aetiology brain recovery was evaluated by serial neurological and EEG examinations for up to 1 year. One-hundred and sixteen patients never regained consciousness; 115 patients awakened within 30 days, and 40 eventually recovered completely within 90 days. Patients who had electrocortical activity recorded by the immediate post-resuscitation EEG ( N=106), and patients initially without such activity ( N=125) pursued the same course of recovery: during unconsciousness, interrelated EEG and neurological findings featured a phase of intermittent cortical activity with postural or stereotypic motor responses followed by a phase of continuous cortical activity with sequential appearances of delta, theta, and alpha activities on EEG accompanied by stereotypic or defensive motor responses. After awakening, the sequential return of motor, sensory, and mental faculties differentiated an early phase of severe disability with orientating eye movements and a bilateral Babinski response from the phase of moderate disability featured by speech, locomotor functions, ability to cope with personal necessities and orientation as to personal data, and a normal plantar response. Finally, orientation as to time, place and role of other persons, and retention and recall, defined the phase of slight/no disability. Abnormal courses were identified by incomplete EEG and neurological recoveries or by the appearance of spikes and sharpwaves in the EEG, or by losses of function.

Changes in land plant function over the Phanerozoic: reconstructions based on the fossil record

Major fluctuations in the concentrations of atmospheric CO2and O2are predicted by historical long-term carbon and oxygen cycle models of atmospheric evolution and will have impacted directly on past climates, plant function and evolutionary processes. Here, palaeobotanical evidence is presented from the stomatal density record of fossil leaves spanning the past 400 Myr supporting the predicted changes in atsmopheric CO2. Evidence from experiments on plants exposed to long-term high CO2environments and the newly assembled fossil data indicate the potential for genetic modification of stomatal characters. The influence of the changes in fossil stomatal characteristics and atmospheric composition on the rates of leaf gas exchange over the course of land plant evolution has been investigated through modelling. Three contrasting eras of plant water economies emerge in the Devonian (high), Carboniferous (low) and from the Upper Jurassic to the present-day (high but declining). These patterns of change result from structural changes of the leaves and the impact of atmospheric CO2and O2concentrations on RuBisCo function and are consistent with the fossil evidence of sequential appearances of novel plant anatomical changes. The modelling approach is tested by comparing predicted leaf stable carbon isotope ratios with those measured on fossil plant and organic material. Viewed in a geological context, current and future increases in the concentration of atmospheric CO2might be considered as restoring plant function to that more typically experienced by plants over the majority of their evolutionary history.

Changes in land plant function over the Phanerozoic: reconstructions based on the fossil record

Major fluctuations in the concentrations of atmospheric CO2and O2are predicted by historical long-term carbon and oxygen cycle models of atmospheric evolution and will have impacted directly on past climates, plant function and evolutionary processes. Here, palaeobotanical evidence is presented from the stomatal density record of fossil leaves spanning the past 400 Myr supporting the predicted changes in atsmopheric CO2. Evidence from experiments on plants exposed to long-term high CO2environments and the newly assembled fossil data indicate the potential for genetic modification of stomatal characters. The influence of the changes in fossil stomatal characteristics and atmospheric composition on the rates of leaf gas exchange over the course of land plant evolution has been investigated through modelling. Three contrasting eras of plant water economies emerge in the Devonian (high), Carboniferous (low) and from the Upper Jurassic to the present-day (high but declining). These patterns of change result from structural changes of the leaves and the impact of atmospheric CO2and O2concentrations on RuBisCo function and are consistent with the fossil evidence of sequential appearances of novel plant anatomical changes. The modelling approach is tested by comparing predicted leaf stable carbon isotope ratios with those measured on fossil plant and organic material. Viewed in a geological context, current and future increases in the concentration of atmospheric CO2might be considered as restoring plant function to that more typically experienced by plants over the majority of their evolutionary history.

Sequential acetaldehyde production, lipid peroxidation, and fibrogenesis in micropig model of alcohol-induced liver disease

The pathogenesis of alcohol-induced liver disease involves the adverse effects of ethanol metabolites and oxidative tissue injury. Previous studies indicated that covalent protein adducts with reactive aldehydes may be formed in alcohol consumers. To study the role of such protein adducts in the development of liver injury, we examined the sequential appearances of adducts of the ethanol metabolite acetaldehyde (AA) and of two products of lipid peroxidation, malondialdehyde (MDA) and 4-hydroxynonenol (HNE), in ethanol-fed micropigs. Immunohistochemical stainings using specific antibodies that recognize epitopes of each adduct were performed from liver biopsy specimens obtained at 1, 5, and 12 months from micropigs fed either control diet (n = 5) or ethanol-containing diets (n = 5). After 1 month on the ethanol diet, AA and MDA adducts were observed primarily in the perivenous regions co-localizing with each other and coinciding with increased concentrations of serum aminotransferase markers of liver injury. HNE adducts were usually less intense and more diffuse, and were also seen in some biopsy specimens from control animals. Although the most intense staining reactions at 5 months remained in zone 3, a more widespread distribution was usually seen together with increased evidence of steatonecrosis and focal inflammation. In terminal biopsies at 12 months, perivenous fibrosis was present in three of five biopsy specimens. More extensive pericentral and intralobular fibrosis was noted in one micropig fed ethanol for 21 months. These studies demonstrate that covalent adducts of proteins with reactive aldehydes are formed in early phases of alcoholinduced liver disease. Perivenous adducts of the AA product of ethanol metabolism and the MDA product of lipid peroxidation appear to precede necrosis and fibrosis.

Sequential acetaldehyde production, lipid peroxidation, and fibrogenesis in micropig model of alcohol-induced liver disease

The pathogenesis of alcohol-induced liver disease involves the adverse effects of ethanol metabolites and oxidative tissue injury. Previous studies indicated that covalent protein adducts with reactive aldehydes may be formed in alcohol consumers. To study the role of such protein adducts in the development of liver injury, we examined the sequential appearances of adducts of the ethanol metabolite acetaldehyde (AA) and of two products of lipid peroxidation, malondialdehyde (MDA) and 4-hydroxynonenol (HNE), in ethanol-fed micropigs. Immunohistochemical stainings using specific antibodies that recognize epitopes of each adduct were performed from liver biopsy specimens obtained at 1, 5, and 12 months from micropigs fed either control diet (n = 5) or ethanol-containing diets (n = 5). After 1 month on the ethanol diet, AA and MDA adducts were observed primarily in the perivenous regions co-localizing with each other and coinciding with increased concentrations of serum aminotransferase markers of liver injury. HNE adducts were usually less intense and more diffuse, and were also seen in some biopsy specimens from control animals. Although the most intense staining reactions at 5 months remained in zone 3, a more widespread distribution was usually seen together with increased evidence of steatonecrosis and focal inflammation. In terminal biopsies at 12 months, perivenous fibrosis was present in three of five biopsy specimens. More extensive pericentral and intralobular fibrosis was noted in one micropig fed ethanol for 21 months. These studies demonstrate that covalent adducts of proteins with reactive aldehydes are formed in early phases of alcohol-induced liver disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Neonatal renal venous thrombosis: Sequential ultrasonic appearances

The ultrasonic appearances of three cases of renal venous thrombosis are shown. Initially the kidney is enlarged, echogenic and shows echogenic streaking that has a vascular or perivascular distribution. Subsequently thrombosis of renal veins or the inferior vena cava may be demonstrated and ultimately the kidney may recover or atrophy. The ultrasonic appearances will depend on the severity of the thrombosis and the stage at which the examination is performed.

A model for self-recognition and regulation of the incompatibility response of pollen

Recent biochemical studies with Brassica indicate that the pollen grain has a primary role in the control of self incompatibility. Combining this new evidence with that from prior genetic, biochemical, and ultrastructural studies, a working model is hypothesized for the molecular events which occur during self recognition and the subsequent control of pollen germination. Self recognition is postulated to involve the interaction of a presynthesized, genotype-specific recognition molecule (effector) produced by the stigma with a presynthesized receptor molecule produced by and located in or on the pollen grain. The consequence of self recognition is a selective inhibition of pollen protein synthesis within about 2-4 minutes after imbibition. We deduced that protein synthesis is programmed to occur in pollen - unless interrupted as a consequence of self-recognition - and leads to the sequential production of opposing regulators: first a germination inhibitor (G-Inh), then a germination activator (G-Act). These regulators in turn control the activities of presynthesized, and probably sequestered enzymes required for germ tube formation. Sequential appearances of the G-Inh and G-Act occur unless synthesis of the G-Act is blocked as a result of self recognition. Thus, following a self pollination, recognition occurs in sufficient time to block production of the G-Act but not of the G-Inh, and inhibition of germination (incompatibility) results. For a cross pollination, there is no self recognition and production of the G-Act is unimpeded; it then nullifies the effect of the G-Inh and pollen germination (compatibility) results. The model and evidence for its support are discussed in detail.

Hyperacute rejection in human-kidney allografts -- Shwartzman or Arthus reaction?

Abstract The course of three patients indicated that both types of reaction, Shwartzman and Arthus-like, can occur in hyperacute rejection of human-kidney allografts and that the late histologic appearances may be indistinguishable. In the first patient hyperacute failure of the kidney occurred in four hours, in association with the development of a bleeding diathesis. Sequential histologic appearances were those of progressive fibrin deposition resembling a generalized Shwartzman reaction. In the second patient, two consecutive kidneys from the same donor were rejected within minutes of revascularization despite prophylactic heparinization. There was neutrophil infiltration without fibrin deposition. At four days there was cortical necrosis, fibrin thrombi in glomerular capillaries and minimal cellular infiltration. A third patient, without prophylactic heparin, showed both neutrophil infiltration and fibrin deposition at one hour and cortical necrosis at five days.