A randomized double-blind study evaluating anandron associated with orchiectomy in stage D prostate cancer

A randomized double-blind study with a 3-yr follow-up comparing the two arms “orchiectomy + Anandron^® (300 mg)” vs “orchiectomy + placebo” in 125 patients with stage D prostate cancer has confirmed the beneficial effects of the combined Anandron^® therapy on subjective parameters and on the best objective response (NPCP criteria), although these effects were not statistically significant, but failed to detect any improvement in time-to-disease progression or survival. Comparison with the results of other trials emphasizes the urgent need to establish suitable prognostic factors by further clinical research before evaluating the benefits of individual drugs.     

Electroencephalographic Biofeedback in the Treatment of Attention-Deficit/Hyperactivity Disorder

Historically, pharmacological treatments for attention-deficit/hyperactivity disorder (ADHD) have been considered to be the only type of interventions effective for reducing the core symptoms of this condition. However, during the past three decades, a series of case and controlled group studies examining the effects of EEG biofeedback have reported improved attention and behavioral control, increased cortical activation on quantitative electroencephalographic examination, and gains on tests of intelligence and academic achievement in response to this type of treatment. This review paper critically examines the empirical evidence, applying the efficacy guidelines jointly established by the Association for Applied Psychophysiology and Biofeedback (AAPB) and the International Society for Neuronal Regulation (ISNR). On the basis of these scientific principles, EEG biofeedback was determined to be “probably efficacious” for the treatment of ADHD. Although significant clinical improvement was reported in approximately 75% of the patients in each of the published research studies, additional randomized, controlled group studies are needed in order to provide a better estimate of the percentage of patients with ADHD who will demonstrate such gains in clinical practice.     

Androgens in women

The role of androgen treatment in women remains controversial. The proposed “Female Androgen Insufficiency Syndrome” (Fertility and Sterility, April 2002) describes a number of non-specific symptoms including unexplained fatigue, decreased well being/dysphoric mood and/or blunted motivation and diminished sexual function. An estimated 40% of women experience sexual dysfunction, highlighting the need for ongoing research into this field in order to fully define the possible contribution of androgen insufficiency. The increasing availability of products, such as dehydroepiandrosterone (DHEA) supplements also points to the need for controlled studies to assess the safety of these and other preparations.

Measurement of androgens in women requires sensitive assays with the ability to detect low levels and a narrow range with precision. Normal ranges of androgens for women of reproductive and post-reproductive age remain poorly defined. Debate exists as per importance of measurement of free versus total testosterone, with the ‘free androgen index’ offering an alternative method of assessment of testosterone availability.

Testosterone treatment is being developed for women in the form of transdermal patches, gels or cream, with percutaneous implants in common usage in some countries. Recent research has highlighted alternative means of administration, such as oral inhalation or buccal lozenge. DHEA is widely available in some countries. Research to date has demonstrated improvements in libido and sexual function, mood and well being. Evidence points to other potential benefits of androgen treatment, including preservation of bone mass, a possible protective role in breast cancer and beneficial effects on cognition.

Adverse effects of androgen treatment in women are dose-dependent and include virilisation, mood disturbance and acne. These are uncommon if appropriate doses are administered and highlight the need for treatment to be closely monitored clinically and biochemically. Beneficial effects of testosterone treatment in post-menopausal women with lowered androgen levels have been well documented, and preliminary evidence suggests a role for treatment in pre-menopausal women with symptoms and lowered testosterone levels.     

Studies on the local activity of antiandrogens at the molecular and histological level

Androgen dependent skin disorders are important in clinical practice. Effective topical antiandrogens would lead to a breakthrough in their treatment. Although many attempts have been performed to develop such compounds, major successes have not been forthcoming. In the present study three existing antiandrogenic molecules have been compared with regard to their effect on androgen metabolism, receptor competition and on histological parameters in the hamster flank organ test. It appears that the effect on the hamster pigmented spot can be predicted on the basis of molecular mechanism. However, the effects on histological parameters are apparently dependent on additional factors such as metabolism of the active substance before reaching the sebaceous structure or limited penetration through the skin surface. The results indicate that in the development of new antiandrogens pre-screening can be performed with the aid of metabolic and receptor studies, while the histological parameters in the hamster flank organ test provide an animal model with a good predictive value.     

Phytoestrogens for hormone replacement therapy?

Due to some severe side effects “classical” hormone replacement therapy (HRT) is currently being challenged by a therapy with phytoestrogens. Particularly soy and red clover derived isoflavones are advertised as selective estrogen receptor modulators (SERMs) with only desired and no undesired estrogenic effects. Evidence that this is the case however is scarce. Most studies investigating climacteric complaints did not find beneficial effects. A proposed beneficial effect on mammary cancer is unproven. The majority of studies however indicate an antiosteoporotic effect of isoflavones, while putative beneficial effects in the cardiovascular system are questionable due to the fact that estradiol which—like isoflavones—increase HDL and decrease LDL concentrations appear not to prevent arteriosclerosis in the human. In the urogenital tract, including the vagina, soy and red clover derived isoflavones are without effects.

Cimicifuga racemosa extracts are traditionally used for the treatment of climacteric complaints. Evidence is now available that the yet unknown compounds in Cimicifuga racemosa extracts prevent climacteric complaints and may also have antiosteoporotic effects.     

Differential genotoxic effects of antitumor trans-[PtCl(2)(E-iminoether)(2)] and cisplatin in Escherichia coli

In the present work, we measured survival and the platinum on the genome after treatment of repair-proficient or repair-deficient Escherichia coli strains with trans-[PtCl₂(E-iminoether)₂] and compared these results with the effects of “classical” cisplatin. We found that toxicity of antitumor trans-[PtCl₂(E-iminoether)₂] in repair-deficient trains was much less than that of cisplatin. This markedly reduced toxicity was not a consequence of the reduced uptake or low levels of DNA binding in the bacteria cells but rather appeared to reflect DNA binding mode of this trans-platinum drug different from that of cisplatin.     

On the Specificity of Allopurinol and Oxypurinol as Inhibitors of Xanthine Oxidase. A Pulse Radiolysis Determination of Rate Constants for Reaction of Allopurinol and Oxypurinol with Hydroxyl Radicals

Allopurinol has been employed as a “specific” inhihitor of xanthine oxidase in studies of hypoxic/ reoxygenation injury. Pulse radiolysis was used to establish rate constants for the reactions of allopurinol and its major metabolite oxypurinol with hydroxyl radicals: values were (1.45 ± 0.241 × 10⁹ M^-1 s^-1 for allopurinol and (4.95 ± 0.84) × 10⁹ M^-1 s^-1 for oxypurinol. These rate constants show that, in view of the amounts of allopurinol that have been used in animal studies. hydroxyl radical scavenging by this molecule could contribute to its biological actions. especially if animals are pre-treated with allopurinol. so allowing oxypurinol to form. The ability of allopurinol to protect tissues not containing xanthine oxidase against reoxygenation injury may be related to radical scavenging by allopurinol and oxypurinol.     

Developments in ultrasound--non-medical

Ultrasound is defined as sound of a frequency that is too high for the human ear to detect—i.e. it is inaudible. Nevertheless this “silent sound” has a large range of applications in science, medicine and industry. The study of the effects of ultrasound on materials—known as sonochemistry—is one of the broadest and most exciting areas in current research. In this review some recent developments with major potential are identified from the fields environmental protection and materials processing.

Environmental protection can refer to methods of preventing pollution or to the removal of existing pollution. Here we will look at examples drawn from the latter in which ultrasound has been used for the purification of water (chemical and biological), the decontamination of the atmosphere and soil remediation i.e. the classic three domains of water, air and land.

In terms of materials processing two examples have been chosen, the treatment of sewage sludge and the control of crystallisation. In both of these cases it is predominantly the mechanical effects of acoustic cavitation, which produce the enhanced digestion, and dewatering of sludge and provide for the control in crystallisation processes.     

Rapporteur report: cellular, animal and epidemiological studies of the effects of static magnetic fields relevant to human health

Three talks were presented in the session on “Cellular, Animal and Epidemiological Studies of the Effects of Static Magnetic Fields Relevant to Human Health”. The first talk presented the in vitro effects of static magnetic fields on cell cultures. The second talk presented the in vivo evidence obtained from animal studies. The final, third talk, presented the evidence obtained from epidemiological studies.

The overall conclusion of the three presentations and the following general discussion was that the scientific evidence available to date is weak and contains large gaps in knowledge either due to the poor quality of published studies or because of the lack of published research on certain health-related topics.

It was emphasized that the rapid development of new technological applications of static magnetic fields (e.g. magnetic levitation trains or magnetic resonance imaging—MRI) results in the human population at large, in certain occupations, and in a selected population of clinical patients being exposed to ever increasing static magnetic field strengths. It is of concern that the knowledge presently available concerning the health effects of these strong static magnetic fields is lagging a long way behind technological development.

In conclusion, it was suggested that there is an urgent need to perform new studies in all research areas (in vitro, in vivo and epidemiology) in order to fill the present gaps in knowledge and provide assurance that this technology will not cause any unwanted and unexpected health side effects.     

Prostate cancer risk in testosterone-treated men

Men with classical androgen deficiency have reduced prostate volume and blood prostate-specific antigen (PSA) levels compared with their age peers. As it is plausible that androgen deficiency partially protects against prostate disease, and that restoring androgen exposure increases risk to that of eugonadal men of the same age, men using ART should have age-appropriate surveillance for prostate disease. This should comprise rectal examination and blood PSA measurement at regular intervals (determined by age and family history) according to the recommendations, permanently revisited, published by ISSAM, EAU, Endocrine Society….

Testosterone replacement therapy is now being prescribed more often for aging men, the same population in which prostate cancer incidence increases; it has been suggested that administration in men with unrecognised prostate cancer might promote the development of clinically significant disease. In hypogonadal men who were candidates for testosterone therapy, a 14% incidence of occult cancer was found. A percentage (15.2%) of prostate cancer has been found in the placebo group (with normal DRE and PSA) in the prostate cancer prevention study investigating the chemoprevention potential of finasteride.

The hypothesis that high levels of circulating androgens is a risk factor for prostate cancer is supported by the dramatic regression, after castration, of tumour symptoms in men with advanced prostate cancer. However these effects, seen at a very late stage of cancer development, may not be relevant to reflect the effects of variations within a physiological range at an earlier stage.

Data from all published prospective studies on circulating level of total and free testosterone do not support the hypothesis that high levels of circulating androgens are associated with an increased risk of prostate cancer. A study on a large prospective cohort of 10,049 men, contributes to the gathering evidence that the long standing “androgen hypothesis” of increasing risk with increasing androgen levels can be rejected, suggesting instead that high levels within the reference range of androgens, estrogens and adrenal androgens decrease aggressive prostate cancer risk. Indeed, high-grade prostate cancer has been associated with low plasma level of testosterone. Furthermore, pre-treatment total testosterone was an independent predictor of extraprostatic disease in patients with localized prostate cancer; as testosterone decreases, patients have an increased likelihood of non-organ confined disease and low serum testosterone levels are associated with positive surgical margins in radical retropubic prostatectomy.

A clinical implication of these results concerns androgen supplementation which has become easier to administer with the advent of transdermal preparations (patch or gel) that achieve physiological testosterone serum levels without supra physiological escape levels. During the clinical development of a new testosterone patch in more than 200 primary or secondary hypogonadal patients, no prostate cancer was diagnosed.     

Relationship between tumour aromatase activity, tumour characteristics and response to therapy

Aromatase activity has been measured in human breast cancers by incubating tumour minces with [7-³H]testosterone and characterizing purified oestradiol (E₂) fractions by chemical derivative formation. Of 247 primary tumours, 178 showed evidence of oestrogen biosynthesis, levels varying between 0.5 and 12.5 fmol E₂ produced/h/g tissue. These values were quantitatively small but at least comparable with those in other peripheral tissues. There was no correlation between presence or level of aromatase activity and the histopathology of the tumours although oestrogen biosynthesis was more likely to be present in more cellular tumours. Aromatase activity was also unrelated to age, menopausal status, lymph node status and T stage of the patient from which the tumour was derived. In a subgroup of patients presenting without clinical evidence of distant metastatic disease, no significant relation was detected between tumour aromatase and disease-free interval, but tumours without aromatase activity were associated with increased survival at 36 months after primary treatment. A statistically significant correlation was also detected between the presence of tumour aromatase and oestrogen receptors. Furthermore, in small subgroups of patients with “advanced” breast cancer tumour aromatase was related to response to aminoglutethimide but not tamoxifen therapy. Whilst these results do not conclusively define a role for local synthesis of oestrogen in the progression of breast cancer, this possibility still exists and further studies on tumour aromatase are warranted.     

How to evaluate the risk-benefit ratio of the low-dose hormone replacement therapy?

Since the results of the women health initiative study showing an overall negative risk-benefit ratio with 0.625 mg of conjugated estrogens plus 2.5 mg of medroxyprogesterone acetate, the use of the lowest effective dose of steroids in hormone replacement therapy (HRT) is recommended.

A low-dose regimen appears to induce less side effects such as breast tenderness or leg pain than do higher dose preparations.

The decrease in hot flashes with low-dose estrogens, range 60–70%, is less than the 80–90% reduction with standard dosing. But this mean that 60–70% of menopausal women do not need higher doses.

The same applies to bone preservation which is dose dependent: the number of non-respondant women will be higher than with standard doses. However, randomized double-blind, placebo controls trials have defined positive effects on bone of low doses of HRT with adequate calcium and Vitamin D in elderly women. The use of bone densitometry and of biochemical markers of bone turnover is mandatory in women using low or ultra-low-dose preparations.

In spite of the lack of trials conducted with low-dose HRT, this treatment seems to be safer:

• the plasma levels of estradiol are lower; as far as breast cancer risk is concerned, the decrease of this subrogate marker is considered as favourable;

• the increase in breast density is less pronounced;

• the nurses's health study found a dose relationship for stroke, with no increase in risk with low-dose of estrogens;

• the effects on subrogate markers of cardiovascular risk seem to be more favourable.

Beside the low-dose HRT, one must consider some other facts:

• the “critical window” theory: it is biologically plausible that HRT, if started early after the menopause can slow the progression of coronary atherosclerosis;

• the way of administration of HRT: some observational studies have shown no increase in the risk of venous thromboembolism risk among women treated with transdermal estrogens;

• the progestogen used: a French cohort study recently performed found no increase in breast cancer risk with the use of micronized progesterone meanwhile the increase in risk observed with other progestogens was similar to the findings of the WHI study.

In the future, it is conceivable that more comprehensive pharmacogenomic studies will lead to effective algorithms for individualizing the right dose of steroids to be used in HRT.     

C19-steroids as androgen receptor modulators: design, discovery, and structure-activity relationship of new steroidal androgen receptor antagonists

Dehydroepiandrosterone (DHEA), the most abundant steroid in human circulating blood, is metabolized to sex hormones and other C19-steroids. Our previous collaborative study demonstrated that androst-5-ene-3beta,17beta-diol (Adiol) and androst-4-ene-3,17-dione (Adione), metabolites of DHEA, can activate androgen receptor (AR) target genes. Adiol is maintained at a high concentration in prostate cancer tissue; even after androgen deprivation therapy and its androgen activity is not inhibited by the antiandrogens currently used to treat prostate cancer patients. We have synthesized possible metabolites of DHEA and several synthetic analogues and evaluated their role in androgen receptor transactivation to identify AR modulators. Steroids with low androgenic potential in PC-3 cell lines were evaluated for anti-dihydrotestosterone (DHT) and anti-Adiol activity. We discovered three potent antiandrogens: 3beta-acetoxyandrosta-1,5-diene-17-one 17-ethylene ketal (ADEK), androsta-1,4-diene-3,17-dione 17-ethylene ketal (OAK), and 3beta-hydroxyandrosta-5,16-diene (HAD) that antagonized the effects of DHT as well as of Adiol on the growth of LNCaP cells and on the expression of prostate-specific antigen (PSA). In vivo tests of these compounds will reveal their potential as potent antiandrogens for the treatment of prostate cancer.     

Antitumor effects of analogs of LH-RH and somatostatin: Experimental and clinical studies

Many clinical approaches for the treatment of hormone-sensitive tumors are being developed based on analogs of LH-RH and somatostatin. Inhibition of the pituitary-gonadal axis forms the basis for oncological applications of LH-RH agonists like [ -Trp⁶]-LH-RH and new LH-RH antagonists free of edematogenic effects such as [Ac- -Nal(2)¹- -Phe(4Cl)²- -Pal(3)³, -Cit⁶, -Ala¹⁰]-LH-RH (SB-75). Agonists and antagonists of LH-RH have been used in patients with prostate cancer and might be also beneficial for the treatment of breast cancer and ovarian, endometrial and pancreatic carcinomas. Some of the effects of LH-RH analogs can be due to direct action since LH-RH receptors have been found in these cancers. The use of sustained delivery systems based on microcapsules of PLG, makes the treatment more efficacious. Octaeptide analogs of somatostatin such as -P s-Trp-NH₂ (RC-160) and related analogs were designed specifically for antitumor activity. These somatostatin analogs, by virtue of having a wide spectrum of activities appear to inhibit various tumors through multiple mechanisms. Direct antiproliferative actions of somatostatin analogs appear to be mediated by specific receptors located on tumor cells. High affinity binding sites for RC-160 and related analogs have been found in human pancreatic, prostate, breast and ovarian cancers and brain tumors such as meningiomas. In vivo administration of analog RC-160 inhibits the growth of Dunning R-3327 prostate cancers in rats, MXT mammary tumors in mice and BOP-induced ductal pancreatic cancers in hamsters. Combination of microcapsules of RC-160 with [ -Trp⁶]-LH-RH results in synergistic potentiation of the inhibition of these cancers. Somatostatin analog RC-160 and LH-RH antagonist SB-75 are the object of further experimental studies and clinical trials aimed at the exploration of their inhibitory effects on the processes of malignant growth.     

Nitric oxide and peroxynitrite. The ugly, the uglier and the not so good: a personal view of recent controversies

Nitric oxide, a gaseous free radical, is poorly reactive with most biomolecules but highly reactive with other free radicals. Its ability to scavenge peroxyl and other damaging radicals may make it an important antioxidant in vivo, particular in the cardiovascular system, although this ability has been somewhat eclipsed in the literature by a focus on the toxicity of peroxynitrite, generated by reaction of O^·-₂ with NO^· (or of NO^- with O₂). On balance, experimental and theoretical data support the view that ONOO^- can lead to hydroxyl radical (OH^·) generation at pH 7.4, but it seems unlikely that OH^· contributes much to the cytotoxicity of ONOO^-. The cytotoxicity of ONOO^- may have been over-emphasized: its formation and rapid reaction with antioxidants may provide a mechanism of using NO^· to dispose of excess O^·-₂, or even of using O^·-₂ to dispose of excess NO^·, in order to maintain the correct balance between these radicals in vivo. Injection or instillation of “bolus” ONOO^- into animals has produced tissue injury, however, although more experiments generating ONOO^- at steady rates in vivo are required. The presence of 3-nitrotyrosine in tissues is still frequently taken as evidence of ONOO^- generation in vivo, but abundant evidence now exists to support the view that it is a biomarker of several “reactive nitrogen species”. Another under-addressed problem is the reliability of assays used to detect and measure 3-nitrotyrosine in tissues and body fluids: immunostaining results vary between laboratories and simple HPLC methods are susceptible to artefacts. Exposure of biological material to low pH (e.g. during acidic hydrolysis to liberate nitrotyrosine from proteins) or to H₂O₂ might cause artefactual generation of nitrotyrosine from NO^-₂ in the samples. This may be the origin of some of the very large values for tissue nitrotyrosine levels quoted in the literature. Nitrous acid causes not only tyrosine nitration but also DNA base deamination at low pH: these events are relevant to the human stomach since saliva and many foods are rich in nitrite. Several plant phenolics inhibit nitration and deamination in vitro, an effect that could conceivably contribute to their protective effects against gastric cancer development.     

Cytological analysis of partial and total X-chromosome loss induced by X-rays in oocytes of Drosophila melanogaster

With the aid of a cytological technique (analysis of metaphase chromosomes of larval cerebral ganglia) it was shown that, in experiments on X-chromosome loss induced by X-rays in oocytes of Drosophila melanogaster, one has to distinguish between partial and total chromosome loss. For this purpose a scheme has been devised allowing the detection of aberrant F₁ individuals already at the larval stage. After treatment of mature oocytes, X-chromosomal fragments of various sizes were found. On the other hand, most of the X-chromosomal fragments observed after irradiation of immature oocytes had the same size as chromosome IV (“points”). Possibly this finding is, partly at least, simulated by the combined induction of complete X loss and nondisjunction of chromosomes IV. Otherwise preferential breakage close to the X-chromosomal centromere after irradiation of immature oocytes would have to be assumed to account for the observation of “points”.

About 39% (13/33) of the losses induced in mature oocytes by 400 R were shown to be partial ones. Depending on the classification of the “points” observed after treatment of immature oocytes with 3500 R, between 7% (3/43) and 23% (10/43) of the losses were partial ones. No indication was obtained either after irradiation of mature or of immature oocytes that the loss frequencies observed for imagoes and larvae differed from each other, e.g. because of selection.

The two-track component of the dose-effect curve of X-ray-induced (total plus partial) X-chromosome loss seems to be based—completely in the mature, partly in the immature oocyte experiments—on the induction of partial losses requiring two independently produced breaks.     

Improved salt tolerance of melon (Cucumis melo L.) by the addition of proline and potassium nitrate

A pot experiment was carried out under glasshouse conditions with melon (Cucumis melo) cv. “Tempo F1” in a mixture of peat, perlite and sand (1:1:1) to investigate the effects of external proline and potassium nitrate applications to salinity-treated (150 mM) plants with respect to fruit yield, plant growth, some physiological parameters and ion uptake. Treatments were—(i) control (C): plants receiving nutrient solution, (ii) salinity treatment, as for control plus 150 mM NaCl. Salinity treatment was combined with or without either 5 mM supplementary KNO₃ or 10 mM proline. The salt treatment (150 mM NaCl) led to significant decreases in plant growth, fruit yield, relative water content (RWC), stomatal density, uptake of Ca²⁺, K⁺ and N, and chlorophyll a and b contents, accompanied by significant increases in Na⁺ uptake, proline concentration and membrane permeability. Supplementary KNO₃ and proline treatments significantly ameliorated the adverse effects of salinity on plant growth, fruit yield and the physiological parameters examined. This could be attributed to the effects of all the external supplements in maintaining membrane permeability, and increasing concentrations of Ca²⁺, N and K⁺ in the leaves of plants subjected to salt stress.     

Antiandrogens: clinical applications

Antiandrogens, preventing androgen action at target tissue level, are used in the treatment of various androgen-dependent diseases. Pharmacologically these substances have either a steroidal structure, like cyproterone acetate (CPA) and spironolactone (SPL), or a non-steroidal structure, like flutamide (FLU). In women with hyperandrogenism (PCO syndrome, idiopathic hirsutism, acne), clinical benefit may be obtained with CPA, which also displays a progestational activity and an antigonadotropic effect. CPA (25-50 mg/day) is used in combination with ethinyl-estradiol (EE) (20-30 micrograms/day) in reversed sequential regimen. SPL, less effective than CPA may be employed in moderate hirsutism and acne at dosages of 100-200 mg/day. During SPL treatment menstrual irregularities are frequent: in this case an association with oral contraceptives is indicated. SPL + bromocriptine (2.5-5 mg/day) has been experienced with success in PCO syndrome. The pure antiandrogen FLU, inducing progressive increase in LH and testosterone secretion, may be used only in combination with oral contraceptives. In men antiandrogens have been tested in BPH and prostatic carcinoma. In BPH the decrease in nuclear receptors and DHT nuclear content during CPA or FLU may represent the rational base of the medical treatment. An improvement in urinary obstructive manifestation has been observed with CPA alone or associated with tamoxifen (100 mg + 100 mg day). In advanced prostatic carcinoma antiandrogens represent a good alternative to estrogen therapy with less side effects and in combination with surgical or medical castration (LH-RH analogues) achieve a complete androgen blockade. An increase in the percentage of remissions and survival has been reported.     

Combination of u.v.-B. and ozone reduces pollen tube growth more than either stress alone

The rate of in vitro Nicotiana tabacum L. “Bel-W3” pollen tube growth was reduced 62 and 44%, respectively, when pollen tubes were exposed to 120 ppb ozone (O₃) for 3 hr or 300 μW/cm² ultraviolet-B (u.v.-B) radiation for 30 min. Petunia hybrida Vilm. “White Cascade” pollen tube growth was reduced 34 and 59%, respectively, upon exposure to O₃ or u.v.-B at the above doses. The combination of u.v.-B at 300 μW/cm² for 30 min, followed by O₃ at 120 ppb for 3 hr, reduced pollen tube growth by 79% for “Bel-W3” and 75% for “White Cascade”. The effect appeared to be additive, implying that different target areas may be affected by the two stressors. In the Northeast, plants are exposed to both u.v.-B and O₃ during the normal growing season. This may result in an unexpectedly higher stress on the reproductive system than had been previously suspected based on these two stressors acting individually.     

The contribution of beta1 integrins to neuronal migration and differentiation depends on extracellular matrix molecules

The interaction of β1 integrin receptors and different extracellular matrix molecules during neuronal development was investigated by comparing both migration and morphological differentiation of D3 wild-type embryonic stem (ES) cell line-derived neural precursor cells with those of the β1 integrin knockout ES cell line G201. Analysing neurosphere explants on laminin and fibronectin as major β1 integrin ligands, the maximal spreading of outward migrating neuronal cells was determined. Compared with gelatine as a standard substrate, migration was found to be significantly increased for D3-derived neurospheres on fibronectin and laminin-1. These matrix effects were found to be even enhanced for G201 preparations. In addition, also the differentiation of wild-type and β1 integrin −/− neurones – as determined by MAP-2- and HNK-1-immunoreactive processes – was found to be increased on fibronectin and laminin when compared to gelatine standards. In the respective knockout preparations on these matrices, again perturbation effects were less pronounced than on gelatine. Our observations indicate that laminin and fibronectin are involved both in β1 integrin-dependent and -independent signalling mechanisms during neurogenesis. Upregulation of compensatory mechanisms such as β1 integrin-independent receptors for laminin and fibronectin might be responsible for the much less pronounced perturbations of G201 neural precursor migration and differentiation on these two substrates than on gelatine.