Effects of X-irradiation and adriamycin on quiescent and proliferating cells of the seminal vesicle in the castrated mouse.

The sensitivity of resting and proliferating cells of the seminal vesicle to X-irradiation and adriamycin has been investigated. Stimulation with testosterone propionate (250 micrograms/day) was started 11 days after castration in BALB/c mice. X-rays (2.5-7.5 Gy total body irradiation) and intraperitoneal injections of adriamycin (4-16 mg/kg body weight) were administered at various times before or after induction of proliferation by testosterone injection. The DNA contents and the weights of the seminal vesicles were determined at 4 days after the start of stimulation. A Do for X-rays of about 10 Gy was found for the seminal vesicle epithelium. For both X-irradiation and adriamycin no significant differences in sensitivity were observed between quiescent (Go) and proliferating (G1; S) seminal vesicle cells.     

TESTOSTERONE-INDUCED CELL PROLIFERATION IN THE ACCESSORY SEX GLANDS OF MICE AT VARIOUS TIMES AFTER CASTRATION

The proliferative response to testosterone in the accessory sex glands (seminal vesicle and coagulating gland) of castrated male Balb/c mice has been examined by pulse and continuous thymidine-labelling experiments, and by the fraction of labelled mitoses technique. Progressive reductions in cellularity followed castration, and by varying the time elapsing between castration and the initiation of testosterone treatment, it was clear that the size of the response depended upon the number of cells in the tissue, relative to the normal complement. Interpretation of FLM data was difficult in periods where proliferative rates changed rapidly. We have attempted to explain the cell kinetic events by postulating a G₀ compartment, from which cells are stimulated to enter the proliferative cycle before subsequently returning to an out of cycle state. It was thought unlikely that substantial changes in cell cycle time occurred. In both the accessory sex glands, the overall form of the continuous thymidine labelling curves showed that most proliferative cells entered DNA synthesis in a shorter time after stimulation at 14 days after castration than they did at 3 days after castration. The data were not consistent with cells moving deeper into G₀ with time after castration. In the seminal vesicle almost all epithelial cells were potentially proliferative by 3 days after castration. In the coagulating gland only 30% were potentially proliferative at 3 days, increasing to 85% at 14 days after castration. However, such proportional increases represented much smaller changes in terms of absolute numbers of cells, because of a concomitant decline in cellularity from 3 to 14 days after castration.     

Combined effects of radiotherapy and endostatin gene therapy in melanoma tumor model

PEgr–Endostatin–EGFP plasmid was constructed to investigate its expression properties induced by ionizing irradiation and the effect of pEgr–Endostatin–EGFP gene-radiotherapy on melanoma tumor-bearing mice. The pEgr–Endostatin–EGFP plasmid was transfected into B16 cell line with liposome. The expression property of endostatin was investigated by RT-PCR and that of EGFP was detected by flow cytometry. Tumor-bearing mice were treated by the plasmid injection and 2 Gy X-irradiation of three fractions. Tumor growth was observed for 18 days after treatment. Change of tumor capillary formation was measured with histochemistry assay at the end of the experiment. The expression of GFP in B16 melanoma cells was detected after X-irradiation with 0.05–20 Gy. Time-course studies showed that the expression of GFP in B16 cells reached its peak at 8 h after irradiation with 2 Gy. The injection of pEgr–Endostatin–EGFP recombinant plasmid into the implanted B16 melanoma in C57BL/6J mice followed by local X-irradiation could significantly inhibit tumor growth with inhibition of intratumor micro-vessel density. The inhibitory effect of pEgr–Endostatin–EGFP gene-radiotherapy on the growth of B16 melanoma is correlated with the marked decrease of intratumoral vascularization. The present data point to the potential of an anti-angiogenic approach in gene-radiotherapy of cancer.     

The effect of the β-emitting yttrium-90 citrate on the dose–response of dicentric chromosomes in human lymphocytes: a basis for biological dosimetry after radiosynoviorthesis

The production of dicentric chromosomes in human lymphocytes by β-particles of yttrium-90 (Y-90) was studied in vitro to provide a basis of biological dosimetry after radiosynoviorthesis (RSO) of persistent synovitis by intra-articular administration of yttrium-90 citrate colloid. Since the injected colloid may leak into the lymphatic drainage exposing other parts of the body to radiation, the measurement of biological damage induced by β-particles of Y-90 is important for the assessment of radiation risk to the patients. A linear dose–response relationship (α = 0.0229 ± 0.0028 dicentric chromosomes per cell per gray) was found over the dose range of 0.2176–2.176 Gy. The absorbed doses were calculated for exposure of blood samples to Y-90 activities from 40 to 400 kBq using both Monte Carlo simulation and an analytical model. The maximum low-dose RBE, the RBE_M which is equivalent to the ratio of the α coefficients of the dose–response curves, is well in line with published results obtained earlier for irradiation of blood of the same donor with heavily filtered 220 kV X-rays (3.35 mm copper), but half of the RBE_M relative to weakly filtered 220 kV X-rays. Therefore, it can be concluded that for estimating an absorbed dose during RSO by the technique of biological dosimetry, in vitro and in vivo data for the same radiation quality are necessary.     

Ultrastructure of the male reproductive organs in the interstitial annelid Sphaerosyllis hermaphrodita (”Polychaeta”, Syllidae)

 The reproductive organs of the simultaneous hermaphrodite Sphaerosyllis hermaphrodita (Syllidae, Exogoninae) were examined by TEM and reconstructed from ultrathin serial sections. Oocytes are produced in the 11–13th chaetigerous segments and then attached to the outer body surface. The male organs comprise a seminal vesicle, testes, sperm ducts and copulatory chaetae. The unpaired seminal vesicle is an uncompartmented cavity above the gut and within the chaetigerous segments 8–10. Its interior is lined with a layer of gland cells that degenerate as spermatogenesis in the vesicle proceeds. The testes are situated ventrolaterally, close to the seminal vesicle in the 9th chaetigerous segment. They contain cells at early stages of spermatogenesis, which are connected to one another by zonulae collares. The testes and seminal vesicle are enclosed in epithelia. Paired sperm ducts run ventrally from about the midline of the body under the seminal vesicle and into the parapodia of the 9th chaetigerous segment. There they open, together with the protonephridia of this segment, to the outside next to the stout copulatory chaeta. Each sperm duct consists of six cells, the luminal surface of which bears microvilli but no cilia. Only in animals with fully differentiated sperm does the small opening of the proximal duct cell in each duct give access to the seminal vesicle. The mode of sperm transfer is discussed. Accepted: 9 December 1996     

Effect of post-exposure administration of keratinocyte growth factor (Palifermin) on radiation effects in oral mucosa in mice

Oral mucositis is a severe component of the acute radiation syndrome. The present study was initiated to determine the potential of recombinant human keratinocyte growth factor (rHuKGF, Palifermin) to ameliorate oral mucositis in a mouse model after a single radiation exposure. A 3 × 3 mm² area in the center of the lower tongue surface of C3H/Neu mice was irradiated with graded single doses of 25 kV X-rays. Acute mucosal ulceration was used as the quantal end-point for dose–response analyses. Palifermin was applied at a dose of 15 mg/kg on days 0, 1, 2, 3, 4 or 5. For comparison, three injections of 5 or 15 mg/kg on days 1–3 were administered. The ED₅₀ (dose at which ulceration is expected in 50% of the animals) for irradiation alone was 11.6 ± 1.2 Gy. Mean latent time was 9.4 ± 0.2 days; mean ulcer duration was 2.8 ± 0.2 days. Single injections of rHuKGF did not result in a significant increase in isoeffective radiation doses at any of the administration days. However, the latent time to ulceration was significantly shortened by 1–2 days in all protocols. Repeated administration of rHuKGF (15 mg/kg) resulted a significant increase in ED50 to 16.8 ± 4.0 Gy (P = 0.0047); the mean latent time was 4.4 ± 0.9 days. Three injections of 5 mg/kg of Palifermin on days 1–3 yielded an ED50 of 19.4 ± 1.7 Gy. In this protocol, mean latent time was 6.6 ± 0.6 days. In conclusion, Palifermin has a potential to reduce the mucositis burden in patients after a single radiation exposure. Repeated injections are required. For three injections, a negative dose-effect of rHuKGF was observed. The optimum dose, number and timing of the administration require further investigation.     

Effects of ionizing radiation on the growth and allyl isothiocyanate accumulation of Wasabia japonica in vitro and ex vitro

Mutations were induced in tissue-cultured wasabi (Wasabia japonica Matsumura) by treating in vitro-derived shoot tips with either γ-rays or X-rays at 0, 10, 20, 40 or 80 Gy. Doses of up to 40 Gy of either γ- or X-ray treatments resulted in a survival rate of more than 60% in culture after 3 mo. The use of γ- or X-rays at doses between 10 Gy and 40 Gy to induce mutation in W. japonica resulted in an alteration of the growth and allyl isothiocyanate (AITC) content of multiple shoots after 3 mo. in culture on Murashige and Skoog medium containing 5 μM N⁶-benzyladenine (BA). Putative mutants from the 40 Gy treatments of either γ- or X-rays exhibited a reduction in shoot weight, number, and height, whereas treatments of either γ-rays or X-rays at 10 Gy and 20 Gy doses showed no significant differences in shoot growth. All shoots treated with 80 Gy were either necrotic or irregenerable, while those treated with 40 Gy produced deformed leaves, from both types of ionizing radiation. Concentrations of AITC were measured by the use of gas chromatography-mass spectrometry (GC-MS). The accumulation of AITC was shown to decrease when doses increased in both γ- and X-ray treatments, compared with the controls. Positive responses were solely occurred at 18 mo. after transfer of in vitro rooted shoots to the shade house. The survival rate, rhizome weight and AITC content of plants derived from shoots treated with 20 Gy or 40 Gy of either γ-rays or X-rays were significantly greater than those of the controls.     

Kinetics of telencephalic neural cell proliferation during the fetal regeneration period following a single X-irradiation at the late organogenesis stage

Summary A sequential study of the acute effects of prenatal X-irradiation on telencephalic cell population dynamics was performed by combining a pathological evaluation with autoradiographic methods. This study confirmed that a dose of 0,95 Gy affects nearly all neuroblasts in the G₁-, G₂-, and M-stage lethally. Within ventricular cells staying in the S-phase at the time of X-irradiation, lethal effects are in the range between 50% and 75%. The surviving remainder of these neuroblasts is responsible for subsequent attempts for regeneration of the telencephalic roof. Two subpopulations of the surviving S-phase cells were observed: The first subpopulation which seems to be restricted to the rudiments of the ventricular zone shows a S/G₂-blockade for 8–12 h after X-irradiation. Thereafter these cells start again with mitotic activity. The second subpopulation is morphologically manifested by the formation of heterotopic cell nests, i.e., so-called rosettes. These cells continue with an intense DNA-replication after the 12th h post irradiation and proceed to the mitosis stage only after about another 4–8 h, i.e., the 16th to 20th hour following X-irradiation. These findings indicate the existence of two different pools of regenerative cells within the telencephalic roof, giving rise to either orthotopic or heterotopic growth processes after irradiation injury.Dedicated to Prof. Dr. H. Kriegel on occasion of his 60th anniversary     

The scanning electron microscopic study of the infection and conidial development of Aspergillus tamarii Kita on its host, the silkworm, Bombyx mori Linn.

Development of Aspergillosis on the integument of the silkworm, Bombyx mori Linn., was examined by scanning electron microscopy. Aspergillosis is a fungal disease caused by an insect mycopathogen Aspergillus tamarii Kita, which infects the silkworms in countries where sericulture (the rearing of silkworms)is prevalent. The present study showed the course of infection and the conidial development of A. tamarii on the integument of B. mori. Five different strains (KA, NB₁₈, NB₄ D₂, NB₇ and PM) of B. mori were inoculated on their body surface with ca. 1 × 10⁶ conidia/ml. Among the five breeds tested, the conidial germination was greatest on the larval surface of KA breed, and least on PM. Most of the conidia germinated on the cuticle approximately 8–12 hours after inoculation, forming a suctorial appressorium within 24 hours. The hyphae reached the hemocoel, where they grew and multiplied extensively, forming a mycelial complex and causing death of the host larva in about 5–6 days. The death of the host was followed by growth of the fungus through mesodermal and epidermal tissues, leading to larval mummification about 6–7 days post-inoculation. Extensive aerial outgrowths of the fungus followed, mostly through the intersegmental regions of larvae. Abundant branched conidiophores developed, forming a confluent yellow brown mat over the entire host body 7 days after inoculation. Each conidiophore had an apical vesicle bearing numerous phialides from which conidia were developed in long chains.     

Radiobiological effects of total body irradiation on the spinal cord

Total body Irradiation (TBI) is often used for conditioning, prior to bone marrow transplantation. Doses of 8–14 Gy in 1–8 fractions over 1–4 days are administered using low dose rate external beam radiotherapy (EBRT). When necessary, consolidation EBRT using conventional doses, fractionation and dose rate is given. The irradiated volume usually contains critical organs such as spinal cord. The purpose of this study was to assess the biologic effect of TBI on the spinal cord in terms of EQD₂ (equivalent dose given in fractions of 2 Gy). EQD₂ values were calculated using the linear-quadratic generalized incomplete repair (IR) model that incorporates IR between fractions and low dose rate irradiation corrections and accounts for mono and bi-exponential repair. Three fractionation schemes were studied as function of dose rate: 8 Gy in 1 and 2 fractions and 12 Gy in 8 fractions. For the 12 Gy in 8 fractions scheme, the influence of dose rate on EQD₂ was limited because the effect of IR between fractions dominates. For the 8 Gy in 1 fraction scheme, significant sparing of the spinal cord may be achieved for low dose rate (5–20 cGy/min). The extent of effects depends on the parameters used. The IR model provides a useful mathematical framework for examination of the effects of fractionated treatments of varying dose rate. Reliable experimental data are needed for accurate assessment of radiation damage to the spinal cord following fractionated low dose rate TBI.     

Chromosome aberration analysis and the influence of mitotic delay after simulated partial-body exposure with high doses of sparsely and densely ionising radiation

The influence of high doses of sparsely and densely ionising radiation on the yield of aberrant human peripheral lymphocytes in simulated partial-body exposures was studied by investigating radiation-induced chromosome aberration frequencies, namely dicentric and centric ring chromosomes. Peripheral blood samples from two volunteers were irradiated with high doses of 200 kV X-rays or neutrons with a mean energy of <E _n>=2.1 MeV and partial-body exposure was simulated by mixing irradiated and non-irradiated blood from the same two donors in proportions of 25, 50, and 75%. Lymphocytes were cultured and first-division metaphase cells were collected after culture times of 48, 56, and 72 h. A significant underrepresentation of dicentric and centric ring chromosomes was observed at the three highest doses of X-rays between the different culture times for nearly all proportions. After neutron irradiation, some significant differences were observed at all doses and all culture times, without however, revealing any systematic pattern. The distribution of dicentric and ring chromosomes showed overdispersion for both radiation types. After simulated partial-body exposures with 200 kV X-rays and <E _n>=2.1 MeV neutrons, strong mitotic delays could be observed, which depended on both the irradiated volume and the applied dose: the smaller the irradiated volume and the higher the dose, the higher was the selective advantage of non-irradiated cells. For the purpose of biological dosimetry after partial body exposure, an extension of the lymphocyte culture time is suggested at least for doses ≥3.0 Gy of 200 kV X-rays and ≥0.5 Gy of <E _n>=2.1 MeV neutrons in order to prevent a systematic underestimation of cytogenetic damage.     

Electroporative deformation of salt filled lipid vesicles

Membrane electroporation, vesicle shape deformation and aggregation of small, NaCl-filled lipid vesicles (of radius a = 50 nm) in DC electric fields was characterized using conductometric and turbidimetrical data. At pulse durations t_E≤ 55 ± 5 ms the increase in the conductivity of the vesicle suspension is due to the field-induced efflux of electrolyte through membrane electropores. Membrane electroporation and Maxwell stress on the vesicle membrane lead to vesicle elongation concomitant with small volume reduction (up to 0.6% in an electric field of E = 1 MV m^–1). At t_E > 55 ± 5 ms, further increases in the conductivity and the optical density suggest electroaggregation and electrofusion of vesicles. The conductivity changes after the electric pulse termination reflect salt ion efflux through slowly resealing electropores. The analysis of the volume reduction kinetics yields the bending rigidity κ = (4.1 ± 0.3) ⋅ 10^–20 J of the vesicle membrane. If the flow of Na⁺ and Cl^– ions from the vesicle interior is treated in terms of Hagen-Poiseuille's equation, the number of permeable electropores is N = 39 per vesicle with mean pore radius r_p = 0.85 ± 0.05 nm at E = 1 MVm^–1 and t_E≤ 55 ± 5 ms. The turbidimetric and conductometric data suggest that small lipid vesicles (a ≤ 50 nm) are not associated with extensive membrane thermal undulations or superstructures. In particular with respect to membrane curvature, the vesicle results are suggestive for the design and optimization of electroporative delivery of drugs and genes to cell tissue at small field strengths (≤1 MVm^–1) and large pulse durations (≤100 ms). Received: 8 July 1997 / Accepted: 15 September 1997     

Quartz crystal microbalance investigation of the interaction of bacterial toxins with ganglioside containing solid supported membranes

The binding of cholera toxin, tetanus toxin and pertussis toxin to ganglioside containing solid supported membranes has been investigated by quartz crystal microbalance measurements. The bilayers were prepared by fusion of phospholipid-vesicles on a hydrophobic monolayer of octanethiol chemisorbed on one gold electrode placed on the 5 MHz AT-cut quartz crystal. The ability of the gangliosides G_M1, G_M3, G_D1a, G_D1b, G_T1b and asialo-G_M1 to act as suitable receptors for the different toxins was tested by measuring the changes of quartz resonance frequencies. To obtain the binding constants of each ligand-receptor-couple Langmuir-isotherms were successfully fitted to the experimental adsorption isotherms. Cholera toxin shows a high affinity for G_M1 (K_a = 1.8 ⋅ 10⁸M^–1), a lower one for asialo-G_M1 (K_a = 1.0 ⋅ 10⁷ M^–1) and no affinity for G_M3. The C-fragment of tetanus toxin binds to ganglioside G_D1a, G_D1b and G_T1b containing membranes with similar affinity (K_a∼10⁶ M^–1), while no binding was observed with G_M3. Pertussis toxin binds to membranes containing the ganglioside G_D1a with a binding constant of K_a = 1.6 ⋅ 10⁶ M^–1, but only if large amounts (40 mol%) of G_D1a are present. The maximum frequency shift caused by the protein adsorption depends strongly on the molecular structure of the receptor. This is clearly demonstrated by an observed maximum frequency decrease of 99 Hz for the adsorption of the C-fragment of tetanus toxin to G_D1b. In contrast to this large frequency decrease, which was unexpectedly high with respect to Sauerbrey's equation, implying pure mass loading, a maximum shift of only 28 Hz was detected after adsorption of the C-fragment of tetanus toxin to G_D1a. Received: 14 January 1997 / Accepted: 15 April 1997     

Ornithine decarboxylase activity in rat organs and tissues under artificial hypobiosis

The influence of hypothermia-hypoxia-hypercapnia on ornithine decarboxylase (ODC, EC 4.1.1.17) activities in rat organs and tissues and also on the thymocyte distribution throughout the cell cycle stages was studied. The state of artificial hypobiosis in rats on decrease in the body temperature to 14.4–18.0°C during 3.0–3.5 h was accompanied by drops in the ODC activities in the neocortex and liver by 50–60% and in rapidly proliferating tissues (thymus, spleen, and small intestine mucosa) by 80% of the control value. In kidneys the ODC activity raised to 200% of the control level. Twenty-four hours after termination of the cooling and replacing the rats under the standard conditions, the ODC activities in the neocortex, liver, kidneys, spleen, and intestinal mucosa returned to the control values, but remained decreased in the thymus. Forty-eight hours later the ODC activities in the thymus and spleen exceeded the normal level. The distribution of thymocytes throughout the cell cycle stages did not change in rats in the state of hypothermia (hypobiosis); 24 and 48 h after termination of the cooling the fraction of thymocytes in the S stage was decreased and the fraction of the cells in the G₀+G₁ stage was increased. The normal distribution of thymocytes throughout the cell cycle stages recovered in 72 h. Thus, in the thymus the diminution of the ODC activity preceded the suppression of the cell proliferation rate. The tissue-specific changes in the ODC activity are suggested to reflect adaptive changes in the functional and proliferative activities of organs and tissues during the development of hypobiosis under conditions of hypothermia-hypoxia-hypercapnia.     

CELL KINETICS OF IRRADIATED EXPERIMENTAL TUMORS: CELL TRANSITION FROM THE NON-PROLIFERATING TO THE PROLIFERATING POOL

Parenchymal tumor cells of murine mammary carcinomas can be divided into two pools, using nucleoli as morphological ‘markers’. Cells with dense nucleoli traverse the cell cycle and divide, thus constituting the proliferating pool. Cells with trabeculate or ring-shaped nucleoli either proceed slowly through G₁ phase or are arrested in it. The role of these non-proliferating, G₁ phase-confined cells in tumor regeneration was studied in vivo after a subcurative dose of X-irradiation in two transplantable tumor lines. Tumor-bearing mice were continuously injected with methyl[³H]thymidine before and after irradiation. Finally, the labeling was discontinued, mice injected with vincristine sulfate and cells arrested in metaphase were accumulated over a 10-hr period. Two clearly delineated groups of vincristinearrested mitoses emerged in autoradiograms prepared from tumor tissue at the time of starting tumor regrowth: one group with the silver-grain counts corresponding to the background level, the other with heavily labeled mitoses. As the only source of unlabeled mitoses was unlabeled G₁ phase-confined cells persisting in the tumor, this observation indicated cell transition from the non-proliferating to the proliferating pool, which took place in the initial phase of the tumor regrowth. Unlabeled progenitors have apparently remained in G₁ phase for at least 5–12 days after irradiation.     

Ontogeny of GTP-binding proteins,Gi and G0, in rat retina

The distribution and the levels of G_i1 (plus G_i3), G_i2, and G₀ in rat retina were studied immunohistochemically and immunochemically during development. At embryonic day (E) 15, G_i1α/G_i3α was observed in the inner layer of the neural retina, the future nerve fiber layer (NFL), while G_i2α was observed both in the inner and outer layers of the neural retina. No immunoreactivity for G₀α was observed. At E18, G_i1α/G_i3α and G_i2α appeared in the inner plexiform layer (IPL), while G₀α was faintly immunoreactive only in the NFL. At birth, G_i2α/G_i3α and G₀α appeared in the ganglion cell layer. G_i2α was intensely immunoreactive in the NFL and IPL. At postnatal day (P) 10, the inner portions of the retina, from the NFL to the outer plexiform layer, were immunoreactive to G_i1α/G_i3α, G_i2α, and G₀α. G_i1α/G_i3α and G₀α were distributed characteristically in a laminated pattern in the IPL, but G_i2α was present homogeneously in the IPL. At P12, G_i2α appeared in the outer nuclear layer. As the postnatal days advanced, the laminated pattern of immunoreactivity to G₀α in the IPL became diffuse, but immunoreactivity to G_i1α/G_i3α remained. The results of enzyme immunoassays showed that the concentration of G₀α increased rapidly from P10 to P15 and reached almost the adult level at P20–P30, while G_i2α decreased until P15 and was almost constant thereafter. These results showed that the distribution of G_i1α/G_i3α, G_i2α, and G₀α differs during development, suggesting that each G protein in the developing retina has a unique function.     

Molecular mechanisms involved in the production of cromosomal aberrations II. Utilization of neurospora endonuclease for the study of aberration production by X-rays in G1 and G2 stages of the cell cycle

Chinese hamster ovary cells (CHO) were X-irradiated in G₁ and G₂ stages of the cell cycle and subsequently Neurospora endonuclease (NE) (E.C.3.1.4), an enzyme which is specific in cleaving single-stranded DNA, was introduced into the cells, after making the cells permeable by treatment with inactivated Sendai virus. With this treatment all classes of X-ray-induced chromatid aberrations increased in G₂ cells, whereas in G₁ cells an increase in cromosome type of aberrations was found, associated with a profound induction of chromatid type of aberrations as well. Duration of the availability of single-strand gaps for the action of NE has been studied in G₂ cells following X-irradiation and the influence of different parts of the G₂ stage on the type and frequencies of chromatid aberrations was discerned. While the increase in chromosome type of aberrations by NE in X-irradiated G₁ cells has been interpreted as due to the conversion of DNA single-strand breaks or gaps to double-strand breaks by NE, the induction of chromatid aberrations in G₁ has been assumed to be due to conversion of some of the damaged bases strand breaks by NE. Biochemical evidence is presented for the conversion by NE of DNA single-strand breaks induced by X-rays into double-strand breaks using neutral sucrose gradient centrifugation.     

Lack of Mitotic Delays at the Onset of Proliferation in Dormant Root Primordia Challenged by Ionizing Radiation

X-rays at doses between 2.5 and 20 Gy were applied to Allium cepa L. bulbs containing either dormant root primordia (before water imbibition) or actively proliferating meristems. Irradiation of the primordia that were enriched in G₀ cells neither delayed proliferation onset nor root sprouting. Under both protocols, irradiation decreased the final length of the roots to about 60 % (at 20 Gy) of that reached by the unirradiated controls. Irradiation of the proliferating meristems increased the mitotic index at some fixation times. This could not be due to a rise in the cell entry into mitosis, as the rate of root growth decreased simultaneously. The increased mitotic index should be the consequence of a delay in the relative time taken by mitosis in the whole cycle time. Lengthened mitosis probably allows the post-replicative repair of most DNA lesions, as the frequency of interphases with micronuclei was higher in the cells which were irradiated when still dormant than in those irradiated when cycling. Thus, the mitotic delays should be the consequence of a checkpoint pathway activated by the presence of DNA damage. This feedback mechanism seems only to develop after cell proliferation is restored. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effects of testosterone, estradiol, and dihydrotestosterone on male mouse (Mus musculus) ultrasonic vocalizations

Two experiments examined the effects of the free forms of testosterone (T), dihydrotestosterone (DHT), and estradiol (E₂) upon male mouse (Mus musculus) courtship vocalizations and seminal vesicle weight. In the first experiment, administration of T to castrated males was associated with a large number of vocalizations and large seminal vesicle weights, DHT was associated with large seminal vesicle weights but very few vocalizations, whereas E₂ was associated with low measures of both vocalization and seminal vesicle weight. In the second experiment, T and DHT had effects highly similar to those of the previous experiment; however, in contrast to the previous experiment, both low and high dosages of E₂ were associated with large numbers of ultrasonic vocalizations but small seminal vesicles. A mixture of E₂ and DHT was very similar to T in its effect upon both measures. We suggest from these results that hormonal mechanisms similar to those reported for rat sex behavior may interact with situational variables to determine the expression of male mouse courtship.     

A new species of monorchiid digenean from marine fishes in the Southwestern Atlantic Ocean off Patagonia

Proctotrema bartolii n. sp. (Digenea: Monorchiidae) is described based on naturally and experimental obtained adults from the marine fishes Odontesthes smitti (Lahille), O. nigricans (Richardson) (Atherinopsidae) and Eleginops maclovinus (Cuvier) (Eleginopidae) off Patagonia, Argentina, in the Southwestern Atlantic Ocean. Its generic identification is based on the presence of a unipartite terminal organ with the metraterm uniting with its distal region, an unarmed genital atrium, a single testis, a vitellarium follicular lateral to the ovary and ventral sucker, and uterine coils occupying most of hindbody. The new species differs from P. bacilliovatum Odhner, 1911, P. amphitruncatum Fischthal & Thomas, 1969 and P. guptai Ahmad & Dhar, 1987 in having a smaller body (305–650 vs 1,600–3,080, 1,500–1,800 and 2,150–2,670 μm, respectively), a round vs funnel-shaped oral sucker, a smooth vs lobed ovary, a saccular rather than tubular excretory vesicle, the number of vitelline follicles (12–16 vs 8–9, 9 and 6–8, respectively), and wider eggs (25–31 × 15–20 vs 28–37 × 9–12, 24–28 × 7–10, and 24–30 × 8–10 μm, respectively). Moreover, the new species differs from P. bacilliovatum and P. amphitruncatum in having a saccular rather than a coiled seminal vesicle, and from P. bacilliovatum and P. guptai in having its tegument completely vs partly spined. Proctotrema Odhner, 1911 is considered to be restricted to these four species. This is the first report of a species of this genus from South American waters.