Everything you wanted to know about the bladder epithelium but were afraid to ask

The mammalian urinary bladder epithelium (urothelium) performs the important function of storing urine for extended periods, while maintaining the urine composition similar to that delivered by the kidneys. The urothelium possesses four properties to perform this function. First, it offers a minimum epithelial surface area-to-urine volume; this reduces the surface area for passive movement of substances between lumen and blood. Second, the passive permeability of the apical membrane and tight junctions is very low to electrolytes and nonelectrolytes. Third, the urothelium has a hormonally regulated sodium absorptive system; thus passive movement of sodium from blood to urine is countered by active sodium reabsorption. Last, the permeability properties of the apical membrane and tight junctions of the urothelium are not altered by most substances found in the urine or blood. The importance of the barrier function of the urothelium is illustrated by infectious cystitis. The loss of the barrier function results in the movement of urinary constituents into the lamina propria and underlying muscle layers, resulting in suprapubic and lower back pain and frequent, urgent, and painful voiding.

First Reports of Aphelenchoides fragariae on Royal Fern and on Hosta and Other Hosts in South Carolina

In September 1999, royal ferns (Osmunda regalis L.) at a South Carolina wholesale nursery were found to be infected by foliar nematodes. Lesions were brown, vein-limited, and often fan shaped. As severity increased, affected leaflets became totally necrotic. Nematodes were extracted by excising and dicing symptomatic leaf sections and placing them in water for up to 24 h. Ten adult nematodes from each of two fern plants were examined microscopically and determined to be Aphelenchoides fragariae (Ritzema Bos) Christie. This is the first report of this nematode infecting royal fern. In August 1996, leaves from several cultivars of Hosta spp. with yellow to tan, vein-limited lesions were submitted from The South Carolina Botanical Garden (Clemson, SC) to the Clemson University Plant Problem Clinic for diagnosis. Nematodes were extracted and examined as described above and identified as A. fragariae. This is the first report of this nematode infecting Hosta spp. in South Carolina. Since 1996, foliar nematodes have been recovered from hostas at several wholesale nurseries in South Carolina. Aphelenchoides spp. also have been detected previously in commercially produced ornamental plants in South Carolina, including a Begonia sp. in 1988; Polygonum bistorta L. 'Super-bum' (snakeweed) in 1997; and a Polystichum sp. (holly fern) in 1997. All plants exhibited angular or vein-limited, necrotic lesions typical of foliar nematode infections.

Inhaled corticosteroid use and bone-mineral density in patients with asthma

BACKGROUND

Inhaled corticosteroids are absorbed into the systemic circulation, but the extent to which they have adverse effects on bone is uncertain. The question is important since 3% of the European population take an inhaled corticosteroid regularly and may do so for many years.

METHODS

We studied the dose-response relation between cumulative inhaled corticosteroid dose and bone-mineral density at the lumbar spine and proximal femur in 196 adults (119 women) with asthma aged 20-40 years. Patients had taken an inhaled corticosteroid regularly for at least 6 months, and had had limited exposure to systemic steroids. Cumulative dose of inhaled corticosteroid was calculated from questionnaires and computerised and written general-practice records, and its effect on bone-mineral density was estimated by multiple regression analysis.

FINDINGS

Median duration of inhaled corticosteroid treatment was 6 years (range 0.5-24), and median cumulative dose was 876 mg (87-4380). There was a negative association between cumulative dose of inhaled corticosteroid and bone-mineral density at the lumbar spine (L2-L4), femoral neck, Ward's triangle, and trochanter, both before and after adjustment for the effects of age and sex. A doubling in dose of inhaled corticosteroid was associated with a decrease in bone-mineral density at the lumbar spine of 0.16 SD (95% CI 0.04-0.28). Similar decreases were found at the femoral neck, Ward's triangle, and trochanter. Adjustment for potential confounding factors including physical activity and past oral, nasal, dermal, and parenteral corticosteroids did not weaken the associations.

INTERPRETATION

This study provides evidence of a negative relation between total cumulative dose of inhaled corticosteroid and bone-mineral density in patients with asthma.

Temperature-dependent gain and noise in fiber Raman amplifiers

An experimental investigation of the temperature dependence of the gain and noise performance of a silica-fiber Raman amplifier is described. A decrease in the Raman scattering cross section in a fiber amplifier cooled from a temperature of 300 K to 77 K was measured and found to be in agreement with theoretical values. No difference between the Raman gain coefficients at these two temperatures was observed.

A chaperone with a hydrophilic surface

The folding of native tubulin involves at least seven different chaperone proteins: prefoldin, the cytosolic chaperonin CCT and five tubulin-specific chaperone proteins named cofactors A-E. The structure of the yeast homolog of cofactor A, Rbl2p, shows it to be a dimer with largely hydrophilic surfaces, reflecting the fact that it interacts with quasi-native, not unfolded, beta-tubulin.

Potassium nitrite reaction with 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid in urine in relation to the drug screening analysis

Recently potassium nitrite has been used as an adulterant to interfere with the analysis of 11-nor-delta 9-tetrahydro-cannabinol-9-carboxylic acid (THC-COOH) in urine. A comprehensive study of the THC-COOH and nitrite reaction chemistry and stability under various conditions is presented. Reverse phase high performance liquid chromatography (HPLC) and negative electrospray mass spectrometry (ESMS) results are given to substantiate the derived reaction mechanism and properties leading to reaction termination. The addition of potassium carbonate as a buffering agent prior to or following sample void as a means of preventing the formation of a nitroso-complexed form of the 11-nor-delta 9+-tetrahydrocannabinol-9-carboxylic acid is evaluated.

Tubulin folding cofactors as GTPase-activating proteins. GTP hydrolysis and the assembly of the alpha/beta-tubulin heterodimer

In vivo, many proteins must interact with molecular chaperones to attain their native conformation. In the case of tubulin, newly synthesized alpha- and beta-subunits are partially folded by cytosolic chaperonin, a double-toroidal ATPase with homologs in all kingdoms of life and in most cellular compartments. alpha- and beta-tubulin folding intermediates are then brought together by tubulin-specific chaperone proteins (named cofactors A-E) in a cofactor-containing supercomplex with GTPase activity. Here we show that tubulin subunit exchange can only occur by passage through this supercomplex, thus defining it as a dimer-making machine. We also show that hydrolysis of GTP by beta-tubulin in the supercomplex acts as a switch for the release of native tubulin heterodimer. In this folding reaction and in the related reaction of tubulin-folding cofactors with native tubulin, the cofactors behave as GTPase-activating proteins, stimulating the GTP-binding protein beta-tubulin to hydrolyze its GTP.

Eosinophil peroxidase increases membrane permeability in mammalian urinary bladder epithelium

Eosinophil peroxidase (EPO), a cationic protein found in eosinophils, has been reported to be cytotoxic independent of its peroxidase activity. This study investigated with electrophysiological methods whether EPO is toxic to mammalian urinary bladder epithelium. Results indicate that EPO, when added to the mucosal solution, increases apical membrane conductance of urinary bladder epithelium only when the apical membrane potential is cell interior negative. The EPO-induced conductance was concentration dependent, with a maximum conductance of 411 microseconds/cm2 and a Michaelis-Menten constant of 113 nM. The EPO-induced conductance was nonselective for K+ and Cl-. The conductance was partially reversed using voltage but not by removal of EPO from the bulk solution. Mucosal Ca2+ reversed the EPO-induced conductance by a mechanism involving reversible block of the conductance. Prolonged exposure (up to 1 h) to EPO was toxic to the urinary bladder epithelium, as indicated by an irreversible increase in transepithelial conductance. These results suggest that EPO is indeed toxic to urinary bladder epithelium via a mechanism that involves an increase in membrane permeability.

Tactile illusion-produced number perception in blind and sighted persons

OBJECTIVE

To determine whether tactile receptive communication is possible in both sighted and blind persons through the use of a mechanical device that creates the perception of continuous contact through sequential points of vibration on the skin and whether the ability of these two groups differs.

MATERIAL AND METHODS

The cohort consisted of 20 sighted and 20 blind subjects who had no prior exposure to a tactile communication device that produces a tactile illusion. Each subject was presented number sequences created by the tactile illusion in the form of single-digit, three-digit, and four-digit sequences, and the number of trials needed for correct identification was recorded.

RESULTS

On average, the sighted subjects tended to identify the digit sequences sooner than did the blind subjects by almost one trial; however, this difference was not statistically significant. Younger subjects and female subjects also tended to identify the digit sequences sooner. Nevertheless, the overall correlation between age and number of trials across all replications was relatively minor.

CONCLUSION

Tactile receptive communication is possible through the use of a mechanical device used to create tactile illusions. The tactile illusion of numbers is equally perceived by blind and sighted persons.

Measles infection, measles vaccination and the effect of birth order in the aetiology of hay fever

BACKGROUND

It has recently been suggested that measles infection may reduce the risk of atopy.

OBJECTIVE

To study the independent effect of measles infection and measles vaccination on the occurrence of hay fever in a British national birth cohort.

METHODS

In over 6000 children born in 1970, details of immunizations and childhood diseases were collected by parental interviews at ages 5, 10 and 16 years, and hay fever within the past year at age 16 years.

RESULTS

In univariate analysis, hay fever was less common in those contracting measles infection than in those not infected (OR 0.86, 95% CI 0.76-0.96), and more common in those given measles vaccination than in those not vaccinated (OR 1.16, 95% Cl 1.03-1.31). However, these effects were strongly confounded by birth order, which was closely associated with the likelihood of receiving measles vaccination and with the risk of hay fever. A strong interaction between the effects of measles vaccination and infection, and birth order was found, such that in those with many older sibling contacts, hay fever was significantly and independently reduced in relation to both measles infection and measles vaccination relative to those who were neither infected nor vaccinated.

CONCLUSIONS

Both measles infection and measles vaccination in childhood appear to reduce the risk of hay fever in children with multiple older sibling contacts. Differential exposure or response to the measles virus may explain the effect of birth order on the occurrence of allergic disease.

Diversity Among a Heterodera glycines Field Isolate and Derived Inbreds Based on RAPD Analysis and Reproduction on Soybean Genotypes

A field population of Heterodera glycines was inbred by a combination of controlled male-female matings and inoculation of soybean with second-stage juveniles (J2) from single cysts. The initial and four F inbred populations were subjected to random amplified polymorphic DNA analysis and were also tested for their ability to reproduce on race differentials. The RAPD patterns of the inbred populations had a lower number of total bands and a lower percentage of polymorphic bands among individual cysts than the initial population. The estimated number of polymorphic loci detected by RAPD analysis was about 25% for the initial population and 4% to 7% for the inbred lines. Reproduction of H. glycines decreased for 6 of 24 inbred-soybean combinations. In particular, reproduction of three inbred populations on PI 90763 was greatly reduced. Inbreeding did not decrease variance of cyst number on soybean genotypes. The inbreeding coefficient calculated from RAPD data was greater than that derived from the known inbreeding pedigree.

Consistent effects of high socioeconomic status and low birth order, and the modifying effect of maternal smoking on the risk of allergic disease during childhood

Birth order, maternal age, gestational age, birth weight, maternal smoking, and social class have all been associated with allergic rhinitis, eczema and asthma in childhood, but the consistency of independent effects of these exposures in relation to all of these allergic conditions has not been investigated. We have compared and contrasted the independent effects of these putative risk factors on parent-reported hayfever, eczema and wheeze by age 16 years and in the past 12 months at age 16 using data from the 1970 British birth cohort. The 1970 British birth cohort comprised all children born in England, Scotland and Wales in one week of April 1970, and follow-up surveys at birth, 5, 10 and 16 years of age involved a cumulative total of 17,427 children. We have used data on over 6000 children with complete data at every stage. Social advantage was a risk factor common to each of wheeze at, and hayfever and eczema at and by age 16. Low birth order was an independent risk factor for eczema and hayfever at age 16, but not for wheeze. However, wheeze at age 16 was significantly increased in relation to maternal smoking, with a significant interaction such that the effect of smoking was greatest in those of high birth order and, in the absence of maternal smoking, low birth order was a risk factor for wheeze at age 16. Social advantage and low birth order appear to be the independently consistent determinants of atopic disease. Maternal smoking is an additional risk factor for wheeze, which applies primarily in low socioeconomic groups.

Modulation of polymyxin B effects on mammalian urinary bladder

This report demonstrates that Ca2+, Mg2+, and protons alter the ability of polymyxin B (PX, a cationic antibiotic used clinically as a bactericidal agent) to increase the apical membrane conductance of the rabbit urinary bladder. Using electrophysiological methods, we determine that these alterations occur by two mechanisms. First, they blocked the PX-induced conductance in a rapid and reversible manner; second, they competed with PX for a membrane binding site. In addition, Ca2+ (but not Mg2+ or protons) altered the rate at which the induced conductance could be reversed. When solution pH was greater than 8.8, PX was not able to induce a conductance. This ability of high pH to inhibit the action of PX was due to a decrease in the number of positive charges on PX. Further studies demonstrated that for maximal activity, PX required its fatty acid tail. These data were used to develop a model describing the mechanism by which PX can induce a conductance in the apical membrane of the rabbit urinary bladder.

Eosinophil major basic protein increases membrane permeability in mammalian urinary bladder epithelium

The eosinophil granule protein major basic protein (MBP) is toxic to a wide variety of cell types, by a poorly understood mechanism. To determine whether the action of MBP involves an alteration in membrane permeability, we tested purified MBP on rabbit urinary bladder epithelium using transepithelial voltage-clamp techniques. Addition of nanomolar concentrations of MBP to the mucosal solution caused an increase in apical membrane conductance only when the voltage across the apical membrane was cell interior negative. The magnitude of the MBP-induced conductance was a function of MBP concentration, and the rate of the initial increase in conductance was a function of the transepithelial voltage. The MBP-induced conductance was nonselective for K+ and Cl-. Mucosal Ca2+ reversed the induced conductance, whereas mucosal Mg2+ partially blocked the induced conductance and slowed the rate of the increase in conductance. The induced conductance was partially reversed by changing the voltage gradient across the apical membrane to cell interior positive. Prolonged exposure resulted in an irreversible loss of the barrier function of the urinary bladder epithelium. These results suggest that an increase in cell membrane ion permeability is an initial step in MBP-induced loss of barrier function.

Inoculation Method for Studying Early Responses of Glycine max to Heterodera glycines

An inoculation technique was developed for studying molecular responses of soybean to the soybean cyst nematode (Heterodera glycines). Effect of inoculum age (0-7 days after eggs were released from cysts) and inoculation site (meristem, elongation, or differentiation zone) on infection were tested on four soybean genotypes. Two genotypes (PI 437654 and cv. Peking) were resistant and two (cv. Essex and cv. Hutcheson) were susceptible to race 3 of H. glycines. Inoculum consisting of second-stage juveniles (J2) was prepared by gently agitating nematode eggs at 75 revolutions per minute at 28 degrees C for various intervals. Infection rates were monitored cytologically. The most consistent infection rate was obtained with 48-hour-old inoculum containing more than 80% J2. More than 100 juveniles/root were observed after inoculation with the 48-hour-old inoculum placed at the root elongation zone, in both resistant and susceptible soybeans. Horizontal orientation of roots during inoculation, the use of concentrated J2 inoculurn (500 J2 in 125 mul/root), and restriction of inoculum to the root elongation zone facilitated synchronous root infection.

Prefoldin, a chaperone that delivers unfolded proteins to cytosolic chaperonin

We describe the discovery of a heterohexameric chaperone protein, prefoldin, based on its ability to capture unfolded actin. Prefoldin binds specifically to cytosolic chaperonin (c-cpn) and transfers target proteins to it. Deletion of the gene encoding a prefoldin subunit in S. cerevisiae results in a phenotype similar to those found when c-cpn is mutated, namely impaired functions of the actin and tubulin-based cytoskeleton. Consistent with prefoldin having a general role in chaperonin-mediated folding, we identify homologs in archaea, which have a class II chaperonin but contain neither actin nor tubulin. We show that by directing target proteins to chaperonin, prefoldin promotes folding in an environment in which there are many competing pathways for nonnative proteins.

Tumor necrosis factor-alpha increases sodium and chloride conductance across the tight junction of CACO-2 BBE, a human intestinal epithelial cell line

CACO-2 BBE was used to determine the response of a gastrointestinal epithelium to tumor necrosis factor-alpha (TNF). Incubation of CACO-2 BBE with TNF did not produce any effect on transepithelial resistance (TER) within the first 6 hr but resulted in a 40-50% reduction in TER and a 30% decrease in 1SC (short circuit current) relative to time-matched control at 24 hr. The decrease in TER was sustained up to 1 week following treatment with TNF and was not associated with a significant increase in the transepithelial flux of [14C]-D-mannitol or the penetration of ruthenium red into the lateral intercellular space. Dilution potential and transepithelial 22Na+ flux studies demonstrated that TNF-treatment of CACO-2 BBE cell sheets increased the paracellular permeability of the epithelium to Na+ and Cl-. The increased transepithelial permeability did not associate with an increase in the incidence of apoptosis. However, there was a TNF-dependent increase in [3H]-thymidine labeling that was not accompanied by a change in DNA content of the cell sheet. The increase in transepithelial permeability was concluded to be across the tight junction because: (i) 1 mM apical amiloride reduced the basolateral to apical flux of 22Na+, and (ii) dilution potential studies revealed a bidirectionally increased permeability to both Na+ and Cl-. These data suggest that the increase in transepithelial permeability across TNF-treated CACO-2 BBE cell sheets arises from an alteration in the charge selectivity of the paracellular conductive pathway that is not accompanied by a change in its size selectivity.

Histone-induced damage of a mammalian epithelium: the role of protein and membrane structure

In a previous report [T. J. Kleine, A. Gladfelter, P. N. Lewis, and S. A. Lewis, Am. J. Physiol. 268 (Cell Physiol. 37): C1114-C1125, 1995], we found that the cationic DNA-binding proteins histones H4, H1, and H5 caused a voltage-dependent increase in the transepithelial conductance in rabbit urinary bladder epithelium. In this study, results from lipid bilayer experiments suggest that histones H5-H1 and H4 form variably sized conductive units. Purified fragments of histones H4 and H5 were used to determine the role of histone tertiary structure in inducing conductance. Isolated COOH- and NH2-terminal tails of histone H4, which are random coils, were inactive, whereas the central alpha-helical domain induced a conductance increase. Although the activities of the central fragment and intact histone H4 were in many ways similar, the dose-response relationships suggest that the isolated central domain was much less potent than intact histone H4. This suggests than the NH2- and COOH-terminal tails are also important for histone H4 activity. For histone H5, the isolated globular central domain was inactive. Thus the random-coil NH2- and COOH-terminal tails are important for H5 activity as well. These results indicate that histone molecules interact directly with membrane phospholipids to form a channel and that protein tertiary structure and the degree of positive charge play an important role in this activity.

Cross sectional investigation of the effects of inhaled corticosteroids on bone density and bone metabolism in patients with asthma

BACKGROUND

Bone mineral density has been reduced in patients with asthma taking inhaled corticosteroids in some cross sectional studies and this could be important if treatment is continued for several decades. The possibility of confounding by age, menopausal status, physical activity and, especially, past oral steroid use has not been excluded in most studies. The present study was designed to assess the magnitude of any reduction in bone mineral density in relation to inhaled steroid use after adjusting for these factors.

METHODS

Bone mineral density (BMD), vertebral fractures, and markers of bone metabolism (serum osteocalcin, procollagen peptide I, bone-specific alkaline phosphatase, and urinary deoxypyridinoline cross links) were measured in 81 patients with asthma age 20-40 years; 34 patients (19 men) who had never had inhaled or systemic steroids and 47 (19 men) who had taken inhaled steroids for at least five years with limited exposure to systemic steroids in the past. Data relating to past medication use, physical activity, smoking, and other confounding factors were collected by questionnaire. The relation between inhaled steroid dose and duration and BMD was assessed by linear regression analysis, accounting for potential confounders including weight, exercise, and oral steroid use.

RESULTS

The 47 patients taking an inhaled steroid had a mean current dose of 620 micrograms/day (range 100-3000 micrograms), a mean duration of use of 7.8 years, and had had a mean of 0.85 courses of prednisolone in the past. There was no significant difference in mean BMD values between those who were and those who were not on inhaled steroids in men or women. However, on multivariate analysis, cumulative inhaled steroid dose was associated with a reduction in posterior-anterior (P-A) and lateral lumbar spine bone mineral density in women, equivalent to a 0.11 standard deviation reduction in bone density per 1000 micrograms/day inhaled steroid per year after adjustment for potential confounding factors (95% CI for P-A spine 0.01 to 0.22; for lateral spine 0.02 to 0.21). Previous oral steroid use was not an important confounding factor in these patients. Inhaled steroid use was not related to BMD at the wrist or hip in women or at any skeletal site in men. Women taking an inhaled steroid had lower levels of serum osteocalcin than those not taking them, although this was not dose related. Inhaled steroid use was not associated with differences in other markers of bone metabolism in men or women or with the presence of vertebral fractures.

CONCLUSIONS

Although an effect of confounding factors cannot be excluded entirely in a cross sectional study, our findings are in keeping with an effect of inhaled steroid therapy in reducing bone density in the spine in women and provide an estimate of the magnitude of this effect.

Tubulin subunits exist in an activated conformational state generated and maintained by protein cofactors

The production of native alpha/beta tubulin heterodimer in vitro depends on the action of cytosolic chaperonin and several protein cofactors. We previously showed that four such cofactors (termed A, C, D, and E) together with native tubulin act on beta-tubulin folding intermediates generated by the chaperonin to produce polymerizable tubulin heterodimers. However, this set of cofactors generates native heterodimers only very inefficiently from alpha-tubulin folding intermediates produced by the same chaperonin. Here we describe the isolation, characterization, and genetic analysis of a novel tubulin folding cofactor (cofactor B) that greatly enhances the efficiency of alpha-tubulin folding in vitro. This enabled an integrated study of alpha- and beta-tubulin folding: we find that the pathways leading to the formation of native alpha- and beta-tubulin converge in that the folding of the alpha subunit requires the participation of cofactor complexes containing the beta subunit and vice versa. We also show that sequestration of native alpha-or beta-tubulins by complex formation with cofactors results in the destabilization and decay of the remaining free subunit. These data demonstrate that tubulin folding cofactors function by placing and/or maintaining alpha-and beta-tubulin polypeptides in an activated conformational state required for the formation of native alpha/beta heterodimers, and imply that each subunit provides information necessary for the proper folding of the other.

Contemporary use of antibiotics in 1089 adults presenting with acute lower respiratory tract illness in general practice in the U.K.: implications for developing management guidelines

Respiratory symptoms are the most common cause of general practitioner (GP) consultation, and hospital-based specialists are often called on to provide management guidelines, particularly in the area of antibiotic prescribing. The present authors have assessed factors associated with antibiotic use by 115 GPs when managing 1089 adults with an acute lower respiratory tract illness, including cough. They prescribed antibiotics to three-quarters of patients, but felt antibiotics to be definitely indicated in less than one-third of these cases and not needed in one-fifth. Univariate analysis revealed that antibiotics were prescribed more frequently by older GPs for older patients in the presence of underlying disease, discoloured sputum, shortness of breath, wheeze, fever, signs on chest examination, and 'other factors'. Multivariate logistic regression confirmed an independent effect for all these findings except for the presence of underlying disease, shortness of breath and wheeze. 'Other factors' included patient 'pressure' and social factors, and GP work pressure or prior experience with the patient. These factors were an important influence on prescribing, especially if the GP felt an antibiotic was not indicated. Amoxycillin was the first choice (58% of total) except where the patient had recently received antibiotics for the same illness. Broader spectrum antibiotics were used more commonly in patients with chronic lung disease, discoloured sputum, chest signs on examination and where the GP felt antibiotics were indicated. However, these antibiotics were also prescribed to 14% of previously well patients. General practitioners used a wide variety of terms to describe the illness with little consistency or structure. The decision concerning the use and choice of antibiotics and the confidence with which the GP makes that decision is a complex interaction between patient, doctor and disease, being affected not only by clinical features but also by the social and psychological elements of the presenting problem. Such issues need to be appreciated by hospital specialists when called on to advise on developing relevant guidelines for primary care.

Interleukin 10 prevents cytokine-induced disruption of T84 monolayer barrier integrity and limits chloride secretion

BACKGROUND & AIMS

The proinflammatory cytokine interferon gamma (IFN-gamma) disrupts epithelial barrier integrity and attenuates secretagogue-induced chloride secretion. This study tested the efficacy of the anti-inflammatory cytokine interleukin 10 (IL-10) in maintaining epithelial barrier and chloride secretory function in the presence of IFN-gamma.

METHODS

T84 epithelial cell monolayers were treated with IL-10, IFN-gamma, or IFN-gamma plus IL-10. Monolayer barrier integrity was assessed by measurements of electrical conductance, unidirectional mannitol and inulin fluxes, and tight junctional charge selectivity in Ussing chambers. Short-circuit current (Isc) was measured in response to carbachol and forskolin stimulation.

RESULTS

IL-10 attenuated the IFN-gamma-induced increase in electrical conductance and totally prevented the IFN-gamma-induced increase in mannitol and inulin fluxes. IL-10 did not prevent the IFN-gamma-induced abolishment of tight junctional charge selectivity but did attenuate the total increase in sodium and chloride permeability. IFN-gamma and IL-10 both separately reduced peak forskolin and carbachol-stimulated Isc. IL-10 pretreatment further enhanced the IFN-gamma-induced reduction in secretagogue-induced Isc.

CONCLUSIONS

In T84 epithelial monolayers, IL-10 maintains the size, but not the charge, selectivity of the epithelial tight junction in the presence of IFN-gamma. In addition, both IL-10 and IFN-gamma limit carbachol and forskolin-induced increase in Isc.

Effect of Planting Date on Population Densities of Hoplolaimus columbus and Yield of Soybean

During the 1991 and 1992 soybean growing seasons, field plots were established in South Carolina to study the effect of planting date on at-planting nematode densities and subsequent yield losses caused by Hoplolaimus columbus. The susceptible and intolerant soybean cv. Braxton was planted on five dates from to May to 28 June in 1991 and from 12 May to 28 June in 1992. Nematodes were recovered from soil samples collected before nematicide treatment with 1,3-D (Pi), at 6 weeks after planting (Pm), and at harvest (Pf). Initial nematode population densities did not differ among the five dates of planting in either year. The increase in numbers of nematodes from planting to 6 weeks after planting (Pm/Pi) and from planting to harvest (Pf/Pi) were not different among the five planting dates in either year. Root samples also were collected at 6 weeks after planting and at harvest, but planting date did not affect the number of nematodes extracted from roots on any sample date in either year. Altering planting dates between early May and late June was not effective in preventing yield suppression due to H. columbus.

Health care seeking by heartburn sufferers is associated with psychosocial factors

AIM

To determine whether individuals who consult a doctor because of gastroesophageal reflux disease have psychological characteristics and social support patterns that distinguish them from those who remain within the community.

METHODS

Comparison of 138 consecutive patients presenting to a gastrointestinal clinic for the first time because of heartburn with 39 heartburn sufferers who had never sought medical help for their reflux disease and 40 healthy individuals with no heartburn. Instruments used were the State-Trait Anxiety Index, the Crown-Crisp Experiential Index, the Hassles Scale, and the Interview Schedule for Social Interaction.

RESULTS

Heartburn sufferers who remained within the community in no way differed from healthy controls. Patients who sought medical attention were older and their heartburn was more severe than community heartburn sufferers. When these variables were controlled for in the analysis, patients experienced greater phobia, obsessionality, and somatization, more hassles but of significantly lower intensity, and had less-adequate close social support than those who did not seek medical help.

CONCLUSION

Psychological and social factors are associated with individuals with gastroesophageal reflux disease who seek medical help.

Effects of polymyxin B on mammalian urinary bladder

Previous reports have demonstrated that large cationic polypeptides (of molecular mass 5,000 daltons or greater) cause an increase in the apical membrane conductance of the rabbit urinary bladder epithelium. This report investigates the effects of the small cationic molecule polymyxin B (PX: a 1,400 dalton antibiotic) on the permeability of the rabbit urinary bladder. The addition of micromolar concentrations of polymyxin B to the luminal solution of the rabbit urinary bladder resulted in an increase in the transepithelial conductance of the bladder. The magnitude of the increase in the conductance was dependent upon the concentration of PX, and the polarity and magnitude of the apical membrane potential. As the apical membrane potential was made more cell interior negative, the larger was the increase in the membrane conductance. This voltage-dependent increase in conductance was an exponential function of the applied voltage, with a negligible increase in conductance occurring when the membrane potential was cell interior positive. Upon changing the membrane voltage from cell interior positive to negative, there was a delay before there was a measurable change in the membrane conductance. The longer the apical membrane was exposed to PX, the more poorly reversible was its effect on the transepithelial conductance, suggesting a toxic effect of PX on this epithelium.

Permeability properties of the intact mammalian bladder epithelium

Because the mammalian bladder must store urine of composition which differs markedly from that of plasma for prolonged periods, the bladder permeability barrier must maintain extremely low permeabilities to substances which normally cross membranes relatively rapidly, such as water, protons, and small nonelectrolytes like urea and ammonia. In the present studies, permeabilities of the apical membrane of dissected rabbit bladder epithelium to water, urea, ammonia, and protons were measured in Ussing chambers and averaged (in cm/s) for water, 5.15 +/- 0.43 x 10(-5); for urea, 4.51 +/- 0.67 x 10(-6); for ammonia, 5.14 +/- 0.62 x 10(-4); and for protons, 2.98 +/- 1.87 x 10(-3), respectively. These permeability values are exceptionally low and are expected to result in minimal to no leakage of these normally permeable substances across the epithelium. Water permeabilities in intact whole rabbit bladders were indistinguishable from those obtained in the dissected epithelial preparation. Moreover, addition of nystatin to the apical solution of dissected epithelia rapidly increased water permeability in conjunction with loss of epithelial resistance. These results confirm that the apical membrane of the bladder epithelial cells represents the bladder permeability barrier. In addition, they establish a model system that will permit examination of how membrane structure reduces permeability and how epithelial injury compromises barrier function.

Quasi-native chaperonin-bound intermediates in facilitated protein folding

Chaperonins are known to facilitate protein folding, but their mechanism of action is not well understood. The fact that target proteins are released from and rebind to different chaperonin molecules ("cycling") during a folding reaction suggests that chaperonins function by unfolding aberrantly folded molecules, allowing them multiple opportunities to reach the native state in bulk solution. Here we show that the cycling of alpha-tubulin by cytosolic chaperonin (c-cpn) can be uncoupled from the action of cofactors required to complete the folding reaction. This results in the accumulation of folding intermediates which are chaperonin-bound, stable, and quasi-native in that they bind GTP nonexchangeably. We present evidence that these intermediates can be generated without the target protein leaving c-cpn. These data show that, in contrast to prevailing models, target proteins can maintain, and possibly acquire, significant native-like structure while chaperonin-bound.

Cell division does not increase transepithelial permeability of LLC-PK1 cell sheets

The transepithelial electrical resistance (TER) across LLC-PK1 cell sheets is unstable for several days postseeding, even when the cells are trypsinized from a previously confluent culture and replated at confluent density. We therefore followed the TER of LLC-PK1 cells plated at confluent density to elucidate characteristics of the TER fluctuations after plating of the cells. Control cultures reached a maximum TER of 1800 omega.cm2 approximately 24 h after plating. TER then declined sharply, reaching generally stable values (approximately 175 omega.cm2) only after 4 days. Cell cycle activity ([3H]-thymidine incorporation) peaked approximately 22 h after plating, prior to the peak in TER values, and then followed a decline similar to that of the TER. Treatment of cells with EGF at 24 h after plating caused the TER values reached at 3-4 days postseeding to exceed time matched controls by approximately 100%. This EGF-treated group showed a concomitant increase in [3H]thymidine incorporation and cell density compared to control. Transepithelial fluxes of [14C]D-mannitol across control vs EGF-treated cell sheets were not, however, significantly different at the 4-day time point, indicating that a change in tight junction sieving on the basis of size had not occurred. Diffusion and bi-ionic potential studies indicated that the change in TER in EGF-treated cells was instead due to altered charge selectivity at the tight junction and/or intercellular space. We conclude: (1) TER across LLC-PK1 cell sheets does not stabilize until 4 days after seeding at confluent density and (2) cell division and resultant increased cell density in LLC-PK1 cell sheets can correlate with elevated TER values, due to altered ion permeability of the paracellular pathway. Permeability to both Na+ and Cl- decreased as a result of EGF treatment but the decline in chloride permeability was significantly greater. Not only was there a decrease in the permeabilities of all halide anions after exposure of cell sheets to EGF, but the permeability sequence changed after EGF exposure.

Modulation of epithelial permeability by extracellular macromolecules

Epithelia are sheets of cells joined together by tight junctions. This geometry allows an epithelium to act as a barrier, i.e., restrict the movement of substances between two compartments that it separates (typically 1 compartment is the blood) and also to actively and selectively transport substances between the two compartments. It has been known for a number of years that both the barrier and transport functions of epithelia can be regulated by hormones and neurotransmitters, and this regulation is a central component of plasma electrolyte and nonelectrolyte homeostasis. Less appreciated is that these epithelial functions can be modified by macromolecules other than neurotransmitters and hormones. These macromolecules have been divided into the following categories: proteases, cytokines, cellular constituents, nonbacterial xenobiotics, and bacterial xenobiotics. Such macromolecules can alter epithelial transport and barrier function by a number of different mechanisms. These include proteolysis of epithelial ion channels and tight junctional complexes, conversion of an ion pump into a nonselective cation channel, increase in epithelial membrane permeability resulting in cell swelling and lysis, and up- or downregulation of cellular second messenger systems that can alter ion transport capabilities or prove cytotoxic to the cells. Finally, these modifications can be either transient or chronic in nature and in many circumstances result in a perturbation of the electrolyte and nonelectrolyte status of the host organism.

Intra- and Interpopulation Genome Variation In Meloidogyne arenaria

The genetic heterogeneity of two M. arenaria race 2 populations (designated Pelion and Govan) was examined using RFLP analysis of 12 clonal lines established from single egg masses (six distinct clonal lines from each population). These populations are essentially identical by traditional biochemical and race identification schemes; however, the Govan population is more aggressive than the Pelion population, producing larger galls and exhibiting greater reproductive capabilities on many soybean cultivars and experimental accessions. Variation at the genomic DNA level was examined using probes representative of expressed DNA sequences present in the eukaryotic genome. Ribosomal DNA, interspersed repeated sequences, and cDNA probes were tested for detection of polymorphism within and between single egg mass lines of each population. Cloned cDNAs and ribosomal intergenic spacer sequences detect polymorphism both within and between populations, demonstrating the usefulness of these sequence classes for molecular genetic analysis of population structure and genome evolution.

Specificity in chaperonin-mediated protein folding

Chaperonins are ubiquitous multisubunit toroidal complexes that aid protein folding in an ATP-dependent manner. Current models of folding by the bacterial chaperonin GroEL depict its role as unfolding and releasing molecules that have misfolded, so that they can return to a potentially productive folding pathway in solution. Accordingly, a given target polypeptide might require several cycles of binding and ATP-driven release from different chaperonin complexes before reaching the native state. Surprisingly, cycling of a target protein does not guarantee its folding, and we report here that unfolded beta-actin or alpha-tubulin both form tight complexes when presented to either GroEL or its mitochondrial homologue, and both undergo cycles of release and rebinding upon incubation with ATP, but no native protein is produced. We conclude that different chaperonins produce distinctive spectra of folding intermediates.

Histone-induced damage of a mammalian epithelium: the conductive effect

Human semen has been reported to be cytotoxic to rat descending colon by a mechanism involving polyamines (cationic molecules) and collagenase. In this study, we report that histones, cationic proteins found in human semen, can contribute to semen's cytotoxicity. Histones H1, H4, and H5, when added to the mucosal side of rabbit urinary bladder epithelium, were found to alter the transepithelial conductance (Gt) in a voltage-sensitive manner. When the cell interior was negative, the conductance rapidly increased and plateaued. When the cell interior was positive, the induced conductance decreased to control values. Histone increased the Gt by increasing the apical membrane conductance rather than the tight junction conductance. The magnitude of the Gt increase was dose dependent, and the histone-induced conductance was nonselective for Na+, K+, and Cl-. The induced conductance could be reversed by either increasing mucosal Ca2+ concentration or by removal of histone from the mucosal solution. Prolonged exposure of the epithelium to histone was toxic as determined by the irreversible loss of transepithelial resistance. These results indicate that histone increases membrane ionic permeability, is cytotoxic, and thus may contribute to human semen's toxic effect on colonic epithelium.

Dietary antioxidant vitamin intake and lung function in the general population

We have investigated the relation between lung function and dietary intake of the antioxidant vitamins C and E in the general population in a cross-sectional survey of a random sample of adults from the electoral register of an administrative area of Nottingham. In 2,633 subjects 18 to 70 yr of age, we measured FEV1 and FVC, allergen skin sensitivity to grass pollen, cat fur, and Dermatophagoides pteronyssinus, pack-years smoking exposure by personal recall, and usual dietary intake of vitamins C and E by semiquantitative food frequency questionnaire. After adjustment for the effects of age, sex, height, mean allergen skin wheal diameter, and pack-years smoking history, both FEV1 and FVC were significantly and independently related to mean daily intake of vitamin C, such that a standard deviation (40 mg/d) higher vitamin C intake was associated with a 25.0 (95% CI, 5.2 to 44.8; p = 0.01) ml higher FEV1 and a 23.3 (0.94 to 45.7, p = 0.04) ml higher FVC. There was also an association between vitamin E intake and lung function, such that a standard deviation (2.2 mg) higher intake of vitamin E was associated with a 20.1 (1.3 to 40.4, p = 0.04) ml higher FEV1 and a 23.1 (1.0 to 45, p = 0.04) ml higher FVC. However, vitamin C and vitamin E intakes were significantly correlated (r = 0.29, p < 0.001), and after allowing for the effects of vitamin C there was no additional independent effect of vitamin E on either FEV1 or FVC.(ABSTRACT TRUNCATED AT 250 WORDS)

Stress, personality and social support in gastro-oesophageal reflux disease

BACKGROUND AND AIM

In 40% of patients presenting to medical clinics with heartburn, no objective evidence of gastro-oesophageal reflux disease can be demonstrated. Little research has been performed regarding the psychological characteristics of these patients. The aim of this study was to assess the psycho-social profiles of patients presenting with heartburn in an attempt to discriminate between those with pathological reflux and those with functional disease.

METHODS

One hundred and thirty-eight patients presenting with heartburn underwent endoscopy and oesophageal pH monitoring. They were divided into those with oesophagitis or abnormal degrees of acid reflux into the oesophagus and those with normal endoscopy and normal pH profile. The psychological questionnaires used were the Hassles Scale, the State-Trait Anxiety Index, the Crown-Crisp Experiential Index and the Interview Schedule for Social Interaction.

RESULTS

Patients with functional heartburn did not report any increase in daily hassles nor did they have higher levels of anxiety, depression or other psychological characteristics than those with objective reflux disease. In terms of their available social support, the two groups were similar.

CONCLUSION

Differences in psychological characteristics and social support structures do not offer an explanation for the heartburn experienced by patients in the absence of objective evidence of reflux disease. Other explanations, including visceral hypersensitivity, should be sought in these patients.

Acid perception in gastro-oesophageal reflux disease is dependent on psychosocial factors

BACKGROUND

Our aim was to contrast the psychosocial profiles of patients with gastro-oesophageal reflux disease whose symptoms correlate well with acid reflux against those whose symptoms do not.

METHODS

One hundred and one patients presenting with heartburn for the first time underwent oesophageal pH monitoring, and 82 (81%) experienced symptoms during the recording. On the basis of how well their symptoms correlated with acid reflux, patients were divided into symptom-positive and symptom-negative groups. These two groups were then compared on the basis of four questionnaires looking at different psychosocial factors.

RESULTS

Symptom-negative patients displayed significantly higher levels of trait anxiety (44.5 versus 38.7; p < 0.05) and hysteria (5.6 versus 4.1; p < 0.05). The adequacy of their social support structures was significantly lower (6.2 versus 7.3; p < 0.05). No difference in daily hassles or uplifts was found.

CONCLUSION

Significant psychosocial differences are noted in patients with poor symptom-reflux correlation. These differences may help explain the aetiology of such patients' symptoms.

Anti-inflammatory and bronchodilator properties of RP 73401, a novel and selective phosphodiesterase type IV inhibitor

1. We have investigated the effects of RP 73401, a novel, potent and highly selective cyclic nucleotide phosphodiesterase (PDE) type IV inhibitor, in guinea-pig and rat models of bronchoconstriction and allergic inflammation. In some models, the effects of RP 73401 have been compared with those of the standard PDE type IV inhibitor, rolipram. 2. RP 73401 (0.4-400 micrograms kg-1, intratracheally (i.t.) on lactose) inhibited antigen-induced bronchospasm in previously sensitized conscious guinea-pigs (ID50: 7 +/- 1 micrograms kg-1) and in anaesthetized rats (ID50: 100 +/- 25 micrograms kg-1). Rolipram inhibited the antigen-induced bronchospasm in guinea-pigs with an ID50 of 5 +/- 1 micrograms kg-1. In guinea-pig bronchoalveolar lavage (BAL) fluid, total inflammatory cell and eosinophil numbers were reduced by RP 73401 (ID50s: 3.9 +/- 0.8 micrograms kg-1 and 3.2 +/- 0.7 micrograms kg-1, respectively). In the rat, inflammatory cell numbers are less affected. Only the highest dose of RP 73401 (400 micrograms kg-1) significantly inhibited eosinophil influx (41 +/- 16% inhibition). 3. RP 73401 (0.02-100 micrograms kg-1, i.v.) inhibited PAF-induced bronchial hyperreactivity to bombesin in the anaesthetized guinea-pig (ID50: 0.09 +/- 0.03 micrograms kg-1) and inhibited (0.4-40 micrograms kg-1, i.t.) histamine-induced airway microvascular leakage in the anaesthetized guinea-pig by approximately 60% at all doses. 4. RP 73401 relaxed guinea-pig isolated trachea under basal tone (EC50: 9 nM) and when precontracted with histamine (IC50: 2 nM), methacholine (IC50: 29 nM) or leukotriene D4 (LTD4, IC50: 4 nM). 5. RP 73401 (0.4-100 microg kg-1, i.t.) inhibited bronchospasm induced by histamine (ID.%: 34 +/- 6 microg kg-1), methacholine (ID50: 66 +/- 12 pg kg-1) and LTD4 (ID50: <4 microg kg-1) in the anaesthetized guinea pig.Against these same bronchoconstrictors, rolipram (i.t.) had ID5o values of 44 +/- 4, 72 +/- 18 and<4 pg kg- respectively. RP 73401 (4 and 40 pg kg-, i.t.) increased the magnitude and duration of bronchodilatation produced by salbutamol in the anaesthetized guinea-pig. At doses producing significant bronchodilatation, RP 73401 was without effect on heart rate or blood pressure in the anaesthetized guinea-pig. RP 73401 (0.01 -0.25 mg kg-1, i.v.) did not affect heart rate and produced only a small fall in blood pressure in the anaesthetized rat.6. These data demonstrate that RP 73401 and rolipram inhibit antigen- and mediator-induced bronchospasmin guinea-pigs with the same potency. Furthermore, RP 73401 administered directly into the airways, protects against allergic airway inflammation. These results indicate the importance of PDE IV in regulating smooth muscle and inflammatory cell activity. At doses suppressing the inflammatory response in the lung, RP 73401 had little effect in the cardiovascular system. RP 73401 may have a role as a bronchodilator and, more importantly, as a prophylactic anti-inflammatory agent in the treatment of asthma.

Mammalian urinary bladder permeability is altered by cationic proteins: modulation by divalent cations

It was previously demonstrated that protamine sulfate (PS, a cationic polypeptide) as well as synthetic cationic polypeptides (CpP, e.g., polylysine and polyarginine) caused an increase in the apical membrane conductance of the mammalian urinary bladder epithelium that was voltage dependent. The membrane conductance induced by these CpP was mediated by a saturable binding site and was partially blocked by CpP (self-inhibition). The PS-induced membrane conductance can be modified by polyvalent cations at three sites. The first site was to competitively inhibit the interaction of PS with an apical membrane binding site. The second site was to reversibly block the conductance induced by PS. The relative binding affinity (block of PS-induced conductance) sequence was as follows: UO2(2+) > La3+ > Mn2+ > Ba2+ > or = Ca2+ > Sr2+. Although La3+, Mn2+, Ba2+, Ca2+, and Sr2+ inhibited > or = 81% of the PS-induced conductance, UO2(2+) inhibited only 51% and Mg2+ was without effect. The third site was to increase the rate of loss of the PS-induced conductance from the apical membrane. Although neither carbodiimides (carboxyl group reactive reagents) nor neuraminidase (cleaves sialic acid residues) altered the effect of PS on the urinary bladder conductance, PS increased the conductance of lipid bilayers composed of negatively charged phospholipids. A candidate for the binding site might be the negatively charged phosphate groups of membrane lipids.

A novel cochaperonin that modulates the ATPase activity of cytoplasmic chaperonin

The folding of alpha- and beta-tubulin requires three proteins: the heteromeric TCP-1-containing cytoplasmic chaperonin and two additional protein cofactors (A and B). We show that these cofactors participate in the folding process and do not merely trigger release, since in the presence of Mg-ATP alone, alpha- and beta-tubulin target proteins are discharged from cytoplasmic chaperonin in a nonnative form. Like the prokaryotic cochaperonin GroES, which interacts with the prototypical Escherichia coli chaperonin GroEL and regulates its ATPase activity, cofactor A modulates the ATPase activity of its cognate chaperonin. However, the sequence of cofactor A derived from a cloned cDNA defines a 13-kD polypeptide with no significant homology to other known proteins. Moreover, while GroES functions as a heptameric ring, cofactor A behaves as a dimer. Thus, cofactor A is a novel cochaperonin that is structurally unrelated to GroES.

Role of intracellular Ca2+ in modulation of tight junction resistance in A6 cells

The role of intracellular Ca2+ in the development and maintenance of epithelial tight junctional integrity is poorly understood. We assessed tight junctional resistance (Rj) in confluent monolayers of A6 cells that were treated with mucosal amiloride such that the transepithelial resistance (Rt) reflects Rj. Solution Ca2+ concentration [Ca2+] was reduced by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) addition to the bathing solutions. Reduction of mucosal [Ca2+] to 1 microM or reduction of serosal Ca2+ to 100 microM did not significantly alter Rt. However, a further decrease of serosal Ca2+ to 40 microM caused the resistance to fall to < 12% of the control value. Following restoration of serosal [Ca2+], Rt increased to a new steady-state value within approximately 15 min. The magnitude of recovery of Rt was inversely correlated with the length of time the epithelium was exposed to low serosal [Ca2+]. To further test the effects of asymmetric Ca2+ removal, the serosal [Ca2+] was chelated using EGTA to reduce Rt. When the Ca2+ ionophore A-23187 was subsequently added to the mucosal solution, Rt increased from 20% to 60% of the control level. In addition, cells were loaded with the fluorescent Ca2+ indicator, Calcium Green, and the temporal relationship between changes in Rt and intracellular Ca2+ was determined. Following removal of serosal Ca2+, cell Ca2+ decreased, followed by a decrease in Rt. In contrast, returning Ca2+ to the serosal bathing solution resulted in a parallel increase of both Rt and cell [Ca2+]. These data strongly suggest that changes in intracellular [Ca2+] play an important role in the regulation of Rj.

Plant-parasitic Nematodes on Soybean in South Carolina

Fields in a concentrated area of soybean production in South Carolina were chosen for soil sampling to determine the distribution of plant-parasitic nematodes. Five hundred sampling sites were distributed over 19 counties according to county soybean acreage. Helicotylenchus and Scutellonema were identified most frequently from soil samples; together, these genera occurred in over 70% of the samples. Pratylenchus and Paratrichodorus were each observed in more than 60% of fields. Meloidogyne spp. were found in 27% of the fields and Hoplolaimus columbus in 14%. Rotylenchulus reniformis and Belonolaimus sp. each occurred in less than 10% of the fields. Tylenchorhynchus and Mesocriconema (Criconemella) were each present in over 40% of the fields, but numbers from each field were low. Of the fields sampled, 14% contained Heterodera glycines. Of these, 47% were race 14 and 32% were race 3. Races 9, 6, and 10 were also observed.

Host Suitability of Graminaceous Crop Cultivars for Isolates of Meloidogyne arenaria and M. incognita

Twenty-two graminaceous plant cultivars were evaluated in the greenhouse for host suitability for three South Carolina isolates of Meloidogyne arenaria race 2 (Ma-R2) designated as Florence, Govan, and Pelion, a Florida isolate of M. arenaria race 1 (Ma-R1), and a South Carolina M. incognita race 3. Host suitability was determined by calculating egg mass index (EMI) reproduction factor (RF) (final egg numbers/initial egg numbers), and number of eggs per gram fresh root. Corn hybrids Pioneer 3147 and Northrup King 508 and oat cv. Florida 502 were nonhosts to all nematode isolates, as no egg masses or eggs were found in roots grown in infested soils. Oat cv. Coker 716 and grain sorghum cvs. Cherokee, Northrup King 2660, and Pioneer 8333 were poor hosts (RF < 1). Good (RF = 1.1-5.0) or excellent (RF > 5.0) hosts for both Ma-R1 and three Ma-R2 isolates included the following: barley cvs. Boone, Keowee, and Redhill; corn hybrid Pioneer 3389; oat cvs. Brooks and Coker 820; rye cvs. Bonel, Florida 401, and Wrens Abruzzi; triticale cvs. Beagle 82 and Florida 201 ; and wheat cvs. Coker 983, Florida 302, and Williams. All cultivars except Coker 716 oat were good or excellent hosts of M. incognita.

Modification of epithelial permeability by cationic polypeptides

It has been demonstrated that protamine sulfate (PS; a cationic polypeptide composed of 70% arginine) increases the apical membrane conductance of the mammalian urinary bladder. In this report, synthetic cationic polypeptides (CpP; e.g., polyarginine) were used to determine whether the response of the bladder to PS was due to its cationic nature (i.e., its arginine content). We demonstrate that CpP induce a large increase in the cation and anion conductance of the apical membrane of the rabbit urinary bladder epithelium. The modulation of the membrane conductance by CpP is dependent upon a number of parameters. 1) The magnitude of the conductance change was voltage dependent. 2) An increase in the total charge per molecule increased the rate of conductance change. 3) An increase in the charge density (ratio of charged amino acids to total amino acids) increased the rate of change of conductance. 4) La3+ inhibited the ability of CpP to alter the membrane conductance. 5) The rate of reversal of the CpP-induced conductance was dependent upon the total charge per molecule as well as the charge density. 6) The level of self-inhibition (ability of solution CpP to inhibit the CpP-induced membrane conductance) was inversely correlated with the charge density and was also concentration dependent, with less inhibition occurring at low mucosal CpP concentrations. These data are consistent with a model developed to describe the effect of PS on the conductive properties of the urinary bladder epithelium.

The mechanism of equilibrium binding of microtubule-associated protein 2 to microtubules. Binding is a multi-phasic process and exhibits positive cooperativity

The mechanism of binding of microtubule-associated protein 2 (MAP2) to taxol-stabilized microtubules (MTs) was examined through Scatchard analysis of equilibrium binding and by immunoelectron microscopy. We demonstrate the following. 1) Binding is a cooperative process as indicated by sigmoidal binding curves, prominent humps in Scatchard plots, and an all-or-none response in binding during ligand titrations. At high tubulin/MAP2 ratios, the Kd for noncontiguous binding (5-25 microM) is estimated to be 100-1500 times greater than that predicted for contiguous binding, suggesting a high degree of cooperativity. 2) Cooperativity is indicated independently by a highly clustered or patchy distribution of MAP2 on MTs as revealed by immunoelectron microscopy. 3) The binding of truncated constructs of mouse MAP2 protein suggests that a domain of MAP2 conferring cooperativity is located in or near the MT binding site near the carboxyl terminus. We speculate that in the cell, cooperativity may generate MTs with uniform biochemical properties and contribute to the segregation of MAPs in neuronal cell processes.