Genes conferring specific plant disease resistance.

Genes conferring host resistance to an obligate parasite, grouped together in complex loci provide opportunities to study their structure. By means of an appropriate operational definition of these genes, a modified cis-trans test was used to interpret the position effects of codominant genes mutually recombined within each of two complex loci of flax, with the use of a specially developed method of analysis among F(2) segregants. The different behavior of genes in the M and L groups may reflect a difference in their structure sufficient to raise important implications in the theory of specific host-parasite interactions.

Value of repeated fine needle aspirations of the thyroid: an analysis of over ten thousand FNAs.

OBJECTIVE: Fine needle aspiration (FNA) has been accepted as the diagnostic method of choice in the initial evaluation of thyroid nodules. However, the value of repeated FNAs in the long-term follow-up of lesions initially diagnosed as benign is being questioned. Do the findings on initial FNA really spare patients thyroidectomy or do they only postpone it? The purpose of the present study is our attempt to answer this question. DESIGN: Retrospective review of cytology reports of patients who underwent thyroidal FNAs at Washington Hospital Center from January 1998 through April 2006. All statistical analyses were done using the statistical package Splus. MAIN OUTCOME: Patients who had thyroid nodules diagnosed as benign on FNA performed at our institution had a 90% probability of a benign diagnosis (with 95% confidence interval [0.87, 0.92]), when they underwent surgery. When the benign cytologic diagnosis was confirmed on a repeat aspiration, this probability increased to 98% (with 95% confidence interval [0.94, 1.0]). CONCLUSIONS: Repeated thyroidal FNAs yielding benign diagnoses are nearly always accurate (98%), and therefore the patients can be followed safely without undergoing surgery, unless an unfavorable clinical change occurs.

Black thyroid revisited: cytologic diagnosis in fine-needle aspirates is unlikely.

We report four patients diagnosed with black discoloration of the thyroid gland at surgery and a fifth patient in which the "black thyroid" was an incidental finding at autopsy. The four patients diagnosed at surgery had prior fine-needle aspirations (FNA), which did not reveal any characteristic pigmentation. One patient presented with cervical lymph node metastases from a papillary microcarcinoma of thyroid. The second patient was diagnosed as a cellular adenomatoid nodule, and suppressive therapy was recommended. She elected to have surgery instead. The third patient underwent surgery because of an oxyphilic cell nodule, in a background of lymphocytic thyroiditis, in which a Hürthle cell neoplasm could not be ruled out. His aspirates were reviewed at two other institutions, and no diagnosis of black thyroid was entertained. The fourth patient had an adenomatoid nodule with cystic change and slightly atypical squamous metaplasia. She decided to have surgery, which revealed a black thyroid. Later, it was discovered that the patients had received minocycline for the treatment of acne. FNA does not seem to be a reliable method to diagnose black thyroid preoperatively. Although this is a striking operative finding, diagnosing it on FNA seems to be unlikely and also inconsequential.

Plant resistance to rusts and mildews: genetic control and possible mechanisms.

Genes in plants that confer race-specific resistance to rusts and mildews are widely exploited in agriculture and can prevent huge losses at little cost. However, nothing is known of the molecular basis of their action. Genetic studies, together with observations of responses at the ultrastructural level, can provide broad insights into how resistance is achieved, which may help in cloning resistance genes.

The failure of intrathymic transplantation of nonimmunogenic islet allografts to promote induction of donor-specific unresponsiveness.

Freshly isolated allogenic pancreatic islets transplanted into the thymus of transiently immunosuppressed rats are not rejected but survive indefinitely while also inducing a state of specific unresponsiveness that permits survival of secondary donor-strain islets transplanted extrathymically. Since freshly isolated pancreatic islets contain intraislet antigen-presenting cells as well as endocrine cells it is unclear which cellular component is primarily responsible for mediating unresponsiveness. We therefore examined the impact of pretransplant in vitro culture (a maneuver which selectively depletes intraislet APCs) on the capacity of islet allografts to induce unresponsiveness after intrathymic implantation. APC-depleted pancreatic islets, which are known to have reduced immunogenicity, survived indefinitely in the thymus of allogeneic hosts whether or not brief immunosuppression was employed, but failed to promote survival of subsequent donor-strain islets transplanted to an extrathymic site. These findings emphasize the central role of APCs in the induction of transplantation tolerance in this model, and are consistent with the established role of this population in the development of T cell tolerance in the thymus.

In vivo inhibition of human CYP1A2 activity by oltipraz.

PURPOSE: Oltipraz is currently undergoing clinical evaluation as a cancer chemopreventive agent, especially with respect to aflatoxin-associated hepatocarcinogenesis. The agent's ability to induce phase II xenobiotic enzymes that detoxify the ultimate carcinogen formed in vivo is thought to be an important mechanism by which disease risk may be attenuated. However, an additional mechanism could be a reduction in the activation of environmental procarcinogens by certain cytochrome P450 (CYP) isoforms. This hypothesis was tested with respect to CYP1A2, by using the clearance of caffeine by N-demethylation as a phenotypic trait measurement of the isoform's catalytic activity. METHODS: Subjects received a single oral dose of caffeine (200 mg) on five separate occasions: on the day prior to oltipraz administration (day 0), 2 h after the first (day 1) of eight daily oral doses of oltipraz (125 mg) and 2 h after the last dose (day 8). In addition, CYP1A2 activity was also measured 2 and 14 days (days 10 and 22, respectively) after discontinuation of oltipraz administration. Plasma concentrations of caffeine and its N-demethylated metabolite, paraxanthine, over 24 h after drug administration, were determined by HPLC. RESULTS: A single 125-mg dose of oltipraz markedly reduced CYP1A2 activity by 75 +/- 13% in nine healthy subjects, resulting in a higher caffeine plasma level and prolongation of the in vivo probe's elimination half-life. Daily administration of 125 mg oltipraz for 8 days resulted in further inhibition so that only 19 +/- 13% of the original baseline level of activity was present. However, 2 days after discontinuation of oltipraz treatment, CYP1A2 activity had returned to 66 +/- 33% of its original level and complete recovery was achieved within 14 days of the chemopreventive agent being stopped. CONCLUSIONS: These results demonstrate that oltipraz is a potent, in vivo inhibitor of CYP1A2 in humans and, because this isoform is importantly involved in procarcinogen activation, they also indicate that such inhibition probably contributes to oltipraz's cancer-chemopreventive effect. In addition, the findings also suggest the likelihood of significant drug interactions between oltipraz and drugs whose metabolism is mediated by CYP1A2.

In vivo CT and MR appearance of prosthetic intraocular lens.

PURPOSE: We present the first in vivo CT and MR imaging description of intraocular lenses (IOLs), which are commonly encountered in elderly patients who have undergone cataract surgery. METHODS: A retrospective review was done of the imaging studies of 20 patients (22 eyes) with IOLs and of three patients (four eyes) with aphakia. CT and MR studies were performed with standard clinical protocols. RESULTS: Sixteen patients with 18 posterior IOLs underwent six CT and 43 MR studies. Four patients with four anterior IOLs had one CT and eight MR studies. The exact position of the optic portion of the IOL could be optimally determined on CT scans with 1-mm-thick sections and on fat-saturated fast T2-weighted MR orbital coil studies performed on a 1.5-T imager. The haptics could not be distinguished from the ciliary body. Three patients with aphakia had eight MR and two CT studies. Aphakia was difficult to identify if the image thickness was greater than the diameter of the pupil (2.5 to 4.0 mm). CONCLUSION: The optic portion of an IOL is visible on either high-quality CT or MR studies. However, the haptic portion is not visible on clinical in vivo images.

El intervalo entre aborto espontáneo y una nueva concepción no afecta el resultado perinatal / Interval between spontaneous abortion and a new pregnancy does not affect perinatal outcome

Objetivo: Determinar la probabilidad de un nuevo aborto espontáneo en función del tiempo que transcurre entre un aborto previo y una nueva concepción. Método: Estudio de cohorte retrospectivo, realizado en Clínica Dávila y Hospital Parroquial de San Bernardo, entre enero de 2007 y septiembre de 2008. Se incluyen mujeres sanas, fértiles, con antecedente de un aborto espontáneo y que dentro de 12 meses posteriores a dicho evento vuelven a concebir. La ocurrencia de un nuevo aborto fue definida como variable dependiente y el tiempo entre el aborto espontáneo y una nueva concepción como variable independiente. Dentro de las variables de control se consideró la edad de la paciente, nivel educacional y la paridad. Se utilizó un modelo de regresión logística múltiple para determinar la asociación entre la variable dependiente e independiente. Resultados: 69 mujeres fueron incluidas en el análisis. La tasa de abortos observada fue de 11,9 por ciento. El 86,2 por ciento logró un parto de término con recién nacido sano. El modelo de regresión logística explicó el 50,3 por ciento de la variación de los datos. Los resultados muestran que por cada mes que transcurre entre un aborto y una nueva concepción el OR de un nuevo aborto disminuye en 7 por ciento, sin embargo, esta asociación no es estadísticamente significativa (OR: 0,93; IC95 por ciento: 0,72 a 1,2). Conclusión: En este estudio el intervalo entre un aborto espontáneo y una nueva concepción, no afecta el resultado perinatal.

Objective: To determine the probability of a new spontaneous abortion based on the time between a previous abortion and a new conception. Methods: Retrospective cohort study realized in Clinica Davila and Hospital Parroquial de San Bernardo, Santiago, Chile, between January 2007 and September 2008. Inclusion criteria: multiparous women with no chronic diseases, a history of one spontaneous abortion and a subsequent pregnancy within 12 months. The occurrence of a new abortion was defined as a dependent variable, and the interval between spontaneous abortion and the new conception as an independent variable. The control population was matched by patient age, educational level and parity. A multiple logistic regression model was used to determine the association between the dependent and independent variables. Results: The sample size was 69 women. The spontaneous abortion rate was 11.9 percent. 86.2 percent of the patients continued their pregnancy and achieved a term birth with healthy newborns. The logistic regression model explained 50.3 percent of the variation in the data. The results of this study shows that for every month that passes between a spontaneous abortion and a new conception, the odds ratio of a new abortion decreases up to 7 percent, although this association was not statistically significant (OR: 0.93; 95 percent CI: 0.72 to 1.2). Conclusion: In this study the interval between spontaneous abortion and a new pregnancy, does not affect perinatal outcome.

A review of pulmonary pathology and mechanisms associated with inhalation of freebase cocaine ("crack").

The use of cocaine in the United States has reached near epidemic proportions. A major factor responsible for the dramatic increase in cocaine use is the ability to freebase cocaine and extract essentially pure drug to be smoked as crack. As a result, a variety of respiratory problems temporally associated with crack inhalation have been reported. Cocaine may cause changes in the respiratory tract as a result of its pharmacologic effects exerted either locally or systemically, its method of administration (smoking, sniffing, injecting), or its alteration of central nervous system neuroregulation of pulmonary function. These changes include such diverse disorders as thermal airway injury, pulmonary edema and hemorrhage, hypersensitivity reactions, and interstitial lung disease. However, a review of the pulmonary pathology and dysfunction associated with crack and/or cocaine use indicates that the reported changes are most likely multifactorial, even idiosyncratic, and fails to reveal common features diagnostic of cocaine use. It is likely that the spectrum of cocaine-induced pulmonary disease will continue to enlarge.

Recombination among genes at the L group in flax conferring resistance to rust.

Fourteen of the known genes conferring resistance to rust in flax occur in the L group, and recombinational analysis has been used to study their fine structure. Three important features were observed. (a) Similar to the findings of Shepherd and Mayo, only susceptible recombinants were detected among the testcross progeny of 11 of the 15 heterozygotes involving pairs of L genes. Some of these recombinants showed variation in the degree of their susceptibility and appeared to be unstable in nature. (b) A new class of recombinants exhibiting a modified type of resistance was recovered. They occurred rarely but consistently, with frequencies similar to that of susceptible recombinants. (c) Rare resistant plants occurred among the progeny of susceptible recombinants. In each case, the specificity of the resistant plant corresponded to only one of the parental types. The relative roles of seed contamination, mutation, recombination and the transposition of genetic elements are discussed to account for these features.

Transdermal modification of platelet function. A dermal aspirin preparation selectively inhibits platelet cyclooxygenase and preserves prostacyclin biosynthesis.

BACKGROUND: Even low doses of oral aspirin inhibit prostacyclin (prostaglandin [PG] I2) formation and cause gastrointestinal toxicity. We examined the skin as a novel route for continuous low-dose aspirin administration and selective inhibition of platelet cyclooxygenase in humans. METHODS AND RESULTS: Aspirin 250 or 750 mg/d for 10 days induced a dose-dependent inhibition of serum thromboxane (TX) B2. At the highest dose, five of six subjects responded, with a mean reduction in serum TXB2 of 95 +/- 3% (P = .003). Urinary 2,3-dinor TXB2, an index of in vivo TXA2 formation, decreased by 68 +/- 7% and recovered slowly, consistent with inhibition of platelet cyclooxygenase in vivo. In contrast, PGI2 biosynthesis, determined as excretion of 2,3-dinor-6-keto PGF1 alpha, was 81 +/- 5% of baseline at 10 days. Intravenous bradykinin increased PGI2 biosynthesis 5.1 +/- 1.6-fold (n = 4) before aspirin treatment. Oral aspirin 75 mg/d for 14 days abolished bradykinin-induced PGI2 formation, whereas dermal aspirin 750 mg/d had no effect despite similar inhibition of TXA2 biosynthesis. In five subjects, plasma aspirin and salicylate were determined after a single application of 750 mg. Aspirin was absorbed slowly, with peak levels of 0.24 +/- 0.11 micrograms/mL at 3 hours. Salicylate levels peaked at 6 to 12 hours, with plasma levels of 0.79 +/- 0.14 micrograms/mL. CONCLUSIONS: Thus, it is possible to achieve selective inhibition of platelet cyclooxygenase by aspirin applied to the skin. This approach may be applicable to other antiplatelet agents and be useful in patients at risk for gastrointestinal bleeding or toxicity.

Suppression of thromboxane A2 but not of systemic prostacyclin by controlled-release aspirin.

BACKGROUND: The antithrombotic efficacy of aspirin is attributed to its inhibition of the enzyme prostaglandin G/H synthase, which is necessary for the formation of thromboxane A2 in platelets. Thromboxane A2 is a potent vasoconstrictor and platelet agonist. However, the formation of prostacyclin by vascular endothelium also requires prostaglandin G/H synthase, and prostacyclin exerts opposite effects on platelet function and vascular tone. We wanted to see whether controlled-release aspirin would affect the formation of thromboxane A2 but not prostacyclin by reducing the aspirin concentration that reaches the posthepatic circulation. METHODS: A controlled-release formulation containing 75 mg of aspirin, designed to release 10 mg per hour, was developed to inhibit prostaglandin G/H synthase in platelets in the prehepatic circulation. The effects of the controlled-release preparation on plasma levels of aspirin and salicylate, serum levels of thromboxane B2, and urinary dinor metabolites of prostacyclin and thromboxane B2 (measured by gas chromatography-mass spectrometry) were compared with those of conventional immediate-release aspirin in normal volunteers. Prostacyclin release was stimulated by intravenous bradykinin. RESULTS: Steady-state inhibition of serum thromboxane B2 required two to four days and appeared slower with 75 mg of controlled-release than with the same amount of immediate-release aspirin. Maximal inhibition was achieved rapidly by adding a single loading dose of 162.5 mg of immediate-release aspirin to the regimen. Over a 28-day period, suppression of thromboxane A2 with this regimen was comparable to that with immediate-release aspirin taken either as 162.5 mg daily or as 325 mg on alternate days, despite the minimal systemic bioavailability of controlled-release aspirin. Bleeding time was prolonged to a similar degree with each of the three regimens. The five- to sixfold increase in the prostacyclin metabolite induced by bradykinin was depressed by pretreatment for four days with 75 mg of immediate-release aspirin, but not by 75 mg of controlled-release aspirin. CONCLUSIONS: Maximal inhibition of platelet thromboxane A2 production was sustained during long-term dosing with controlled-release aspirin, whereas basal prostacyclin biosynthesis fell only slightly and systemic synthesis of prostacyclin stimulated by bradykinin was preserved. Controlled-release aspirin may facilitate determination of the clinical importance of preserving prostacyclin during platelet inhibition in humans.

Combined administration of aspirin and a specific thrombin inhibitor in man.

BACKGROUND: Heparin is of limited value as an antithrombotic drug in the presence of platelet activation and residual thrombus. Greater anticoagulant activity can be achieved in vivo with more specific thrombin inhibitors. Heparin may also increase the risk of bleeding by an effect on platelets that is independent of its thrombin inhibitory activity. METHODS AND RESULTS: The pharmacodynamic and pharmacokinetic effects of a novel thrombin inhibitor, argatroban, were examined alone and in combination with aspirin in normal male volunteers. Argatroban induced a dose-dependent prolongation of the thrombin time and the activated partial thromboplastin time (aPTT). aPTT had returned to its pretreatment value 1 hour after stopping the infusion of argatroban. Six male subjects received an infusion of 1 micrograms/kg/min argatroban after the administration of two doses of 162.5 mg aspirin or a matching placebo. At this dose, aspirin decreased serum thromboxane B2 by a mean of 99% and prolonged the bleeding time (230 +/- 52 versus 320 +/- 113 seconds, p less than 0.01). Argatroban given alone increased thrombin time by 454 +/- 18% and aPTT by 160 +/- 3%. Steady-state plasma concentrations were achieved at 1 hour and declined exponentially with an elimination half-life of 24 +/- 4 minutes. Neither the anticoagulant effects nor the plasma concentrations of argatroban were altered by aspirin. Furthermore, argatroban did not increase the bleeding time when given alone and did not further prolong the bleeding time when combined with aspirin. CONCLUSION: The combination of aspirin and argatroban may prove to be an effective therapeutic strategy in the prevention of coronary thrombosis.

Characterization of the respiratory NADH dehydrogenase of Escherichia coli and reconstitution of NADH oxidase in ndh mutant membrane vesicles.

Highly purified preparations of the cholate-solubilized respiratory NADH dehydrogenase, isolated from genetically amplified Escherichia coli strains [Jaworowski, A., Campbell, H. D., Poulis, M. I., & Young, I. G. (1981) Biochemistry 20, 2041-2047], have been characterized. Enzyme preparations were shown to contain 70% (w/w) lipid, predominantly phosphatidylethanolamine. One mol of noncovalently bound FAD and approximately 1 mol of ubiquinone/mol of enzyme subunit were detected. The purified enzyme was shown to contain only low levels of Fe and acid-labile S, indicating the absence of iron-sulfur clusters. No Cu, Mo, W, or covalently bound P was detected, and no evidence for other chromophores was obtained from visible and ultraviolet absorption spectra of the purified enzyme or of the delipidated polypeptide prepared by gel filtration in sodium dodecyl sulfate. Protein chemical studies verified that the enzyme consists of a single polypeptide species of Mr 47 000, and the N- and C-terminal cyanogen bromide peptides were identified. The pure enzyme was shown to reconstitute membrane-bound, cyanide-sensitive NADH oxidase activity in membrane vesicles prepared from ndh mutant strains.

Increased thromboxane biosynthesis in normal pregnancy is mainly derived from platelets.

Thromboxane biosynthesis was determined in normal pregnant subjects by measurement of its major urinary and plasma metabolites, 2,3-dinor-thromboxane B2 and 11-dehydro-thromboxane B2. Urinary 2,3-dinor-thromboxane B2 increased early in pregnancy (731 +/- 124 pg/mg creatinine) compared with nonpregnancy (less than 350 pg/mg creatinine; p less than 0.001) and the postpartum period (155 +/- 42 pg/mg creatinine, p = 0.015) and remained elevated throughout gestation. Similarly, plasma and urinary 11-dehydro-thromboxane B2 were increased in pregnancy. To determine the cellular origin of the increase in thromboxane biosynthesis in pregnancy, platelet cyclooxygenase was selectively inhibited with aspirin in a dose of 120 mg orally followed by 20 mg twice daily for 7 days (n = 4). Selectivity was confirmed by measurement of urinary 2,3-dinor-6-keto-prostaglandin F1 alpha, an index of prostacyclin biosynthesis. Coincident with a 97% inhibition of serum thromboxane B2, urinary 2,3-dinor-thromboxane B2 was almost completely inhibited and paralleled the recovery of platelet cyclooxygenase after withdrawal of aspirin. This study demonstrates that thromboxane biosynthesis is increased in pregnancy. The increase is mainly platelet derived and is consistent with increased platelet activation throughout pregnancy.