Systemic and intracellular responses to photooxidative stress in Arabidopsis.

As the sun tracks daily through the sky from east to west, different parts of the canopy are exposed to high light (HL). The extent of and mechanisms by which a systemic acquired acclimation (SAA) response might preacclimate shaded leaves that will be subsequently exposed to full sunlight is largely undefined. We investigated the role of an Arabidopsis thaliana zinc finger transcription factor, ZAT10, in SAA. ZAT10 overexpression resulted in enhanced tolerance to photoinhibitory light and exogenous H2O2, increased expression of antioxidative genes whose products are targeted to multiple subcellular compartments. Partial HL exposure of a leaf or leaves rapidly induced ZAT10 mRNA in distal, shaded photosynthetic tissues, including the floral stem, cauline leaves, and rosette, but not in roots. Fully 86% of fivefold HL-upregulated and 71% of HL-downregulated genes were induced and repressed, respectively, in distal, shaded leaves. Between 15 and 23% of genes whose expression changed in the HL and/or distal tissues were coexpressed in the ZAT10 overexpression plants, implicating ZAT10 in modulating the expression of SAA-regulated genes. The SAA response was detectable in plants with mutations in abscisic acid, methyl jasmonate, or salicylic acid synthesis or perception, and systemic H2O2 diffusion was not detected. Hence, SAA is distinct from pathogen-stimulated systemic acquired resistance and apparently involves a novel signal or combination of signals that preacclimate photosynthetic tissues to HL.

The association between demolition activity and children's blood lead levels.

Urban renewal efforts are a priority for many American cities. As efforts to reconstitute urban centers increase, the demolition of old, deteriorated structures has accelerated. Recent studies have identified demolitions as a potential source of environmental lead exposure. We conducted a study examining the relationship between demolition activity and blood lead levels of children residing in neighborhoods where demolition activity occurred. A retrospective cohort study was conducted in St. Louis City, Missouri. The study period was January 1, 2002 to December 31, 2002. Data were obtained from the Missouri Childhood Lead Poisoning Prevention Program's (CLPPP) lead surveillance system and St. Louis Demolition Permit Database. Children were considered exposed to a demolition if they had a blood lead test within 45 days of any demolition on a census block. Exposure was classified as both a dichotomous (yes/no) and a categorical (none/one/multiple) variable and was analyzed separately. Linear regression models were developed to determine effects of demolitions on blood lead levels. A total of 1196 children 6-72 months of age living in 395 census blocks were included. 314 (26.3%) were exposed and 882 (73.7%) were unexposed to a demolition. In an adjusted model, exposure to multiple demolitions was found to have significant effects on children blood lead levels (coefficient=0.281; 95% CI=0.069, 0.493; P-value=0.010). Age of the child, race, and age of housing where children's resided were also significant predictors. This study suggests that multiple demolitions within a census block may significantly increase children's blood lead levels. The findings may be useful to municipal planners in older cities where demolitions are being used as an urban renewal tool.

Tethered-bilayer lipid membranes as a support for membrane-active peptides.

An immunosensing device, comprising a lipid membrane incorporating ion channels tethered to the surface of a gold electrode, has been reported [Cornell, Braach-Maksvytis, King, Osman, Raguse, Wieczorek and Pace (1997) Nature (London) 387, 580-583]. The present article describes key steps in the assembly of the device and provides further evidence for its proposed sensing mechanism.

There are stable individual differences in performance variability, both from moment to moment and from day to day.

Individual differences in decision speed have been regarded as direct reflections of a "primitive" functional neurophysiological characteristic, which affects performance on all cognitive tasks and so may be regarded as the "biological basis of intelligence", or of age-related changes in mental abilities. More detailed analyses show that variability within an experimental session (WSV) is a stable individual difference characteristic and that mean choice reaction times (CRTs) are gross summary statistics that reflect variability, rather than maximum speed of performance. A total of 98 people aged from 60 to 80 years completed 36 weekly sessions on six different letter categorization tasks. After effects of practice and of circadian variability had been eliminated, individuals with lower scores on the Cattell Culture Fair intelligence test had slower CRTs and greater WSV on all tasks. A simulation study showed that the greater WSVs of low Cattell scorers led directly to the significantly greater variability of their mean CRTs from session to session. However because CRTs on tasks co-varied from session to session it was apparent that, besides being affected by WSV, individuals' between-session variabilities (BSVs) also vary because of state changes that affect their performance from day to day. It seems that both variability in performance from trial to trial during a session and variability in average performance from day to day are correlated, stable, individual difference characteristics that vary inversely with intelligence test performance. Methodological consequences of these results for interpretations of age-related cognitive changes, for variability between as well as within individuals, for individual differences in decision speed, and for circadian variability in performance are discussed.

Erratum

The paper 'Interference of rheumatoid factor activity by aspartame, a dipeptide methyl ester' by Paul A. Ramsland, Bahereh F. Movafagh, Morris Reichlin and Allen B. Edmundson, J. Mol. Recognit. 1999; 12: 249--257, was published without the required colour plates. The publisher would like to apologise for this omission. The article is reprinted here in full. Please replace the previously published pages with those following. The electronic version of the article, including the colour plates, can be downloaded from the Wiley Interscience website at http://www.interscience.wiley.com. The plates have been included in the original paper, which appeared in Issue 4 of the journal.

The ion channel switch biosensor.

A biosensor technology is described which provides a direct measurement for functional molecular interactions, at the surface of a tethered bilayer membrane, through the electrical transduction of chemically modified ion-channels. High sensitivity of analyte detection is achieved due to the large flux of ions transmitted through the ion channel. The biomimetic sensor surface allows the molecular recognition to be measured in complex biological matrices (such as blood and sera) without compromising sensitivity. We have used the sensor for activity and concentration measurements for a range of analytes, which include bacteria, DNA, proteins and drugs. We have a quantitative model for the biosensor performance which is described by three-dimensional molecular interactions with the membrane surface and two-dimensional molecular interactions within the tethered bilayer.

The gramicidin-based biosensor: a functioning nano-machine.

Biosensors combine a biological recognition mechanism with a physical transduction technique. In nature, the transduction mechanism for high sensitivity molecular detection is the modulation of the cell membrane ionic conductivity through specific ligand-receptor binding-induced switching of ion channels. This effects an inherent signal amplification of six to eight orders of magnitude, corresponding to the total ion flow arising from the single channel gating event. Here we describe the first reduction of this principle to a practical sensing device, which is a planar impedance element composed of a macroscopically supported synthetic bilayer membrane incorporating gramicidin ion channels. The membrane and an ionic reservoir are covalently attached to an evaporated gold surface. The channels have specific receptor groups attached (usually antibodies) that permit switching of gramicidin channels by analyte binding to the receptors. The device may then be made specific for the detection of a wide range of analytes, including proteins, drugs, hormones, antibodies, DNA, etc., currently in the 10(-7)-10(-13) M range. It also lends itself readily to microelectronic fabrication and signal transduction. By adjusting the surface density of the receptors/channel components during fabrication, the optimum sensitivity range of the device may be tuned over several orders of magnitude.

A biosensor that uses ion-channel switches.

Biosensors are molecular sensors that combine a biological recognition mechanism with a physical transduction technique. They provide a new class of inexpensive, portable instrument that permit sophisticated analytical measurements to be undertaken rapidly at decentralized locations. However, the adoption of biosensors for practical applications other than the measurement of blood glucose is currently limited by the expense, insensitivity and inflexibility of the available transduction methods. Here we describe the development of a biosensing technique in which the conductance of a population of molecular ion channels is switched by the recognition event. The approach mimics biological sensory functions and can be used with most types of receptor, including antibodies and nucleotides. The technique is very flexible and even in its simplest form it is sensitive to picomolar concentrations of proteins. The sensor is essentially an impedance element whose dimensions can readily be reduced to become an integral component of a microelectronic circuit. It may be used in a wide range of applications and in complex media, including blood. These uses might include cell typing, the detection of large proteins, viruses, antibodies, DNA, electrolytes, drugs, pesticides and other low-molecular-weight compounds.

The phosphorus-31 spectra of dielectrophoretically reoriented tubules in the HII phase of DOPE.

31P electric field nuclear magnetic resonance measurements are described which assess the effect of electric field on the orientation of tubules comprising the HII phase of dioeleoylphosphatidylethanolamine. A model, based on dielectrophoretic effects, was used to predict that a field of 4 MV/m would change the orientation of the lipid tubules in a HII phase. The excitation pulse was biphasic to help discriminate electric field interactions with free ions or permanent dipoles from interactions with induced dipoles, as well as to control the problems of ohmic heating, electrolysis and polarisation associated with dc or unbalanced ac excitation voltages. Spectra consistent with irreversible electrorotation and with reversible and transient electrorotation were observed. No response to the electric field was seen in certain cases. The conditions for irreversible and reversible electrorotation and failure to rotate have been tabulated and are discussed. Finally, some simple models are considered, in order to calculate the energies involved, if the observed NMR spectra are interpreted as arising from lipid HII phase reorientations.

The effect of pulsed electric fields on the phosphorus-31 spectra of lipid bilayers.

A technique is described for measuring the effect of electric fields on the conformation of lipid bilayer membranes by solid state nuclear magnetic resonance. An apparatus was devised to obtain spectra from samples of aligned phospholipid dispersions at varying electric field strengths up to 100 MV/m. Measurements were carried out on membranes made from dioleoylphosphatidylethanolamine and dioleoylphosphatidylcholine, which resulted in electric field induced phase changes. Calibration experiments were performed using bilayers formed from dimyristoylphosphatidylcholine with glycerol and with a nematic liquid crystal. An electric field induced change, from L alpha to HII, was also seen in a dimyristoylphosphatidylcholine/alamethicin bilayer.

Model of antral follicle dynamics during the 5-day cycle in rats based on measurement of antral follicle inflow.

Antral follicles were counted in ovaries from young adult Wistar rats, collected on the 5 days of the ovarian cycle. Follicles were classified as healthy, early atretic or late atretic and divided into five volume classes. From these data, a model was developed in which the inflow of healthy follicles into the various size classes was quantified. This model describes the follicle dynamics during a normal 5-day cycle. It was concluded that the stage of early atresia takes between 20 and 24 h. The inflow of follicles into the antral stage (volume > or = 100 x 10(5) microns2) was continuous but not constant. The highest inflow was found during pro-oestrus and oestrus, at about the time of the first and second FSH surge. The total inflow during each cycle was about 120 follicles of which only 10% ovulated. These ovulating follicles were recruited during the previous pro-oestrus and oestrus. Follicle selection took place in volume classes 1 and 2 (volume 100-350 x 10(5) microns3) during oestrus and dioestrus 1. At dioestrus 2, the follicles that will ovulate have been selected and can be recognized on the basis of their bigger size.

Morphometric analysis of follicular dynamics in pregnant and pseudopregnant rats.

Morphometric analysis of the follicle population greater than or equal to 100 X 10(5) micron 3 or a mean diameter of greater than or equal to 275 micron and assessment of the rate of atresia in ovaries of pregnant and pseudopregnant rats revealed no evidence for the presence of rhythmic follicular maturation during the prolonged dioestrous period. During the first 4-5 days of the dioestrous period, follicles developed to preovulatory size (volume class 5, i.e. greater than or equal to 1000 X 10(5) micron 3 = diam. greater than or equal to 576 micron) reaching the normal number of ovulating follicles in cyclic animals in pregnant rats, but only half that number in pseudopregnant rats. These follicles collapsed on the 5th to 8th days of the dioestrous period and full numbers of preovulatory follicles were not found thereafter until the end of pregnancy and pseudopregnancy. Follicles of smaller sizes (classes 1-4: 100-999 X 10(5) micron 3), however, were present throughout the prolonged dioestrous period. The rate of atresia in the follicle population had increased by the 2nd day and remained from then on at 26.5 +/- 4.5% in the pregnant and 34.3 +/- 1.9% in the pseudopregnant rats. Atretic follicles in the advanced stages of atresia, mostly derived from follicles of classes 1-3, persisted and accumulated at the end of the dioestrous period. The continuous presence of follicles and the constant rate of atresia during the dioestrous period indicate continuous follicular replacements and refute the idea of follicular quiescence during pregnancy and pseudopregnancy. Copulation and electrical stimulation of the cervix seemed to reduce the formation of the new crop of follicles the next morning and the pool of small antral follicles normally maintained after oestrus in cyclic animals. Nevertheless, the smaller crop and pool of follicles seemed able to provide a sufficient number of preovulatory follicles at the end of pregnancy and a sufficient number of ovulations at the end of pseudopregnancy.

Experiment on aggregation of red cells under microgravity on STS 51-C.

Kinetics and morphology of aggregation of red cells were studied using automatic slit-capillary photo-viscometers, one situated on the middeck of the space shuttle 'Discovery', and the other in the ground laboratory at KSC. Experiments were run simultaneously, blood samples being adjusted to haematocrit of 0.30 using native plasma, at temp. of 25 degrees C, and anticoagulated by EDTA. Donors included patients with myocardial infarction, insulin-dependent diabetes, hyperlipidaemia and hypertension. Macro and microphotographs were obtained during flow and stasis. There was a striking difference in the morphology of aggregates formed in space and on the ground. Aggregates formed under zero gravity showed rouleaux formation, while the same blood samples showed severe clumping on the ground, in all patients blood. Normal blood showed rouleaux on the ground, but a random swarm-like pattern in space. The shape of the red cells remained normal under zero gravity.

Precocious ovulation induced by human chorionic gonadotrophin in the immature female rat: comparison of follicle growth induced by treatment with human chorionic gonadotrophin and by electrical stimulation of the hypothalamus.

Precocious first ovulation, preceded by an endogenous preovulatory LH surge, could be predictably induced in immature female rats by administering repeated injections of human chorionic gonadotrophin (hCG). Administration of a dose of 0.05-0.075 i.u. hCG, four times a day from day 28 to day 31 of age resulted in a highly constant ovulatory response: at 4.0 +/- 0.0 days after the start of treatment 7.7 +/- 0.3 (n = 15) ova were found. Use of a higher dose of hCG (0.1 i.u.) resulted in lower numbers of ova (5.6 +/- 0.4, n = 7; P less than 0.005) whereas use of a lower dose of hCG (0.025-0.038 i.u.) resulted in a less constant timing of the induced ovulation at 5.4 +/- 0.2 days after the start of treatment (n = 7; P less than 0.0005). In animals treated with the dose of 0.05-0.075 i.u. hCG, a positive correlation was found between body weight at the start of treatment and the number of ova released (r = 0.75, n = 25; P less than 0.001). Ovarian follicle dynamics were studied on the various days of hCG treatment (dose 0.05-0.075 i.u.) and compared with the follicle changes that take place after electrical stimulation of the hypothalamus, performed on day 28, a treatment known to result in first ovulation 4-5 days later. In both groups a decrease in the number of the smallest and the middle-sized antral follicles as compared with their respective controls was seen, whereas numbers of follicles in the largest, 'ovulatable' size classes gradually increased.(ABSTRACT TRUNCATED AT 250 WORDS)

First haemorheological experiment on NASA space shuttle 'Discovery' STS 51-C: aggregation of red cells.

The 'secret' D.O.D. Mission on flight STS 51-C also carried nearly 100 kg of automated instrumentation of the Australian experiment on aggregation of red cells ("ARC"). The automated Slit-Capillary Photo Viscometer contained blood samples from subjects with history of coronary heart disease, cancer of the colon, insulin-dependent diabetes, etc., as well as normals. The experiment ran for nine hours, according to the program of its microcomputers. When shuttle landed and instrumentation recovered and opened in the presence of NASA quality control officers, it was obvious that experiment was a success. Tentative and preliminary results can be summarized as follows: red cells did not change shape under zero gravity; red cells do aggregate under zero gravity, although the size of aggregates is smaller than on the ground; the morphology of aggregates of red cells appears to be of rouleaux type under zero gravity, notwithstanding the fact that pathological blood was used. These results will have to be confirmed in the future flights. The background and history of development of the project are described, and put into context of our general haemorheological studies.

Rate and course of atresia during follicular development in the adult cyclic rat.

Ovarian follicles (greater than or equal to 100 X 10(5) microns 3 or a mean diameter of greater than or equal to 275 microns) in adult rats were classified as non-atretic and atretic during the oestrous cycle and recorded in 5 volume classes. The atretic follicles were also categorized in several stages according to the progress of atresia. The degeneration of the entire granulosa wall until the induced changes in the oocyte took at least 24 h. Another 24 h elapsed before the oocyte became denuded. Therefore the % of atretic follicles, i.e. follicles in all stages of atresia, could not be used as indicator for the rate of atresia. The atretic portion in the follicle population greater than or equal to 100 X 10(5) microns 3 increased from early dioestrus 1 to early dioestrus 3, reached a plateau during dioestrus 3 and pro-oestrus, and declined at late oestrus to the level of early dioestrus 1. The sudden decrease in number of atretic follicles after late pro-oestrus was caused by the discard of many atretic follicles in the advanced stages due to various deformities as revealed by histological observation. By using the % of atretic follicles in the earliest stage as indicator of atretic rate, two waves of atresia were found affecting the population of antral follicles during their growth, the first at dioestrus 1 amounting to 15-20% and then at dioestrus 3, affecting 35% of the population. The present study also shows the extension of atresia in the various volume classes of follicles during the oestrous cycle. A pool of approximately 7 follicles in the smallest volume class was maintained after ovulation, grew further in the next cycle with a new cohort of 20 follicles, and seemed to provide the required number of follicles destined to ovulate. This suggests that the follicles that ovulate were already present at an antral stage in the preceding cycle and needed two cycles for their growth to ovulation.

Compensatory ovulatory mechanisms operative after first ovulation in rats unilaterally ovariectomized prepubertally.

Ovarian steroid contents and serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin were measured during the days after first ovulation in rats unilaterally ovariectomized in late prepuberty. In addition, follicle counts were made at second estrus and second metestrus. During the cycle following first ovulation, ovarian estradiol contents in unilaterally ovariectomized (ULO) rats were significantly increased as compared to intact rats on the day of metestrus, on diestrus 1 and on second estrus. Ovarian progesterone was significantly increased on the days of metestrus, on diestrus 1, second proestrus and second estrus, but no differences were seen in ovarian androgen contents. After ULO there was an indication of an augmented FSH surge at the first and the second ovulation. Follicle counts revealed that the total number of healthy as well as of atretic antral follicles on the day of second estrus was significantly increased after ULO, due to increased numbers of the smallest antral follicles. At second metestrus the number of larger antral follicles (350-500 micron 3) and the total number of healthy antral follicles was higher after ULO. It is concluded that the compensatory process after ULO involved increased recruitment of small antral follicles. Activities in the remaining ovary were not simply doubled but a new hormonal balance was established.

Measurement of Aggregation of Red Cells in space--a project for the NASA space shuttle.

Progress is described on the advanced stages in design of an instrument for the study of red blood cell aggregation and blood viscosity under near-zero gravity conditions. This paper gives a brief review of the experiment and its background and a description of the design of the instrument intended for space conditions. Summaries are given of solutions to some problems peculiar to a space experiment, particularly blood storage, microscope focusing, experiment control and data acquisition.

Ovarian follicular development leading to first ovulation and accompanying gonadotrophin levels as studied in the unilaterally ovariectomized rat.

Ovarian follicular development was studied in the rat during a 15-day period preceding first ovulation. Ovaries were obtained by unilateral ovariectomy performed at various ages and the rats were allowed to live until the day after first ovulation. The timing of this ovulation was compared with that in unoperated, paired control rats of the same age. For estimation of gonadotrophin levels, blood was taken from the paired control rats at the time when experimental rats were unilaterally ovariectomized. There was no evidence that unilateral ovariectomy had any influence on the timing of first ovulation. Therefore the ovaries obtained could be dated in relation to first ovulation, and follicular growth during the final prepubertal period could thus be studied in a genuine developmental sequence. Results revealed that follicular growth leading to first ovulation starts at +/- 8 days before this ovulation; follicular processes taking place are comparable to those found during the adult 5-day cycle but proceed more slowly. Gonadotrophin concentrations accompanying the follicular dynamics and measured at 11.00 h, showed a clear tendency for FSH concentrations to decrease with increasing age, i.e. approaching first ovulation. Concentrations of LH did not show a definite pattern and were generally low, although in some individual rats relatively high LH values ( greater than 100 micrograms/l) were found in the period of 5-3 days before first ovulation.