DDT homologues and PCBs in eggs of great crested grebe (Podiceps cristatus) and mallard (Anas platyrhynchos) from Lake Maggiore (Italy).

DDT homologues and PCBs were determined in eggs of two stationary species, great crested grebe (Podiceps cristatus) and mallard (Anas platyrhynchos), in three breeding areas of Lake Maggiore in 1998. As expected, much higher contamination levels of both DDTs and PCBs were found in the fish-eating great crested grebe than in the mallard. In many eggs these values exceeded the safety thresholds proposed for aquatic bird protection. However, no significant correlation could be found between the two classes of pollutants and shell thickness in great crested grebe eggs. While a DDT manufacturer was detected as the main source of DDT pollution in the Lake Maggiore environment, the reason for the surprisingly high PCB level remains unknown.

Spermiogenesis in Seison nebaliae (Rotifera, Seisonidea): further evidence of a rotifer-acanthocephalan relationship.

The spermatozoa of Seison nebaliae are filiform cells about 70 mum long with a diameter of 0.6 mum. They have a slightly enlarged head, 2.5 mum long, followed by a long cell body. The flagellum starts from the head, and runs parallel to the cell body, contained in a groove along it. The head contains an acrosome, two large, paired para-acrosomal bodies, the basal body of the flagellum and the anterior thin extremity of the nucleus. The cell body contains the main portion of the nucleus, a single mitochondrion located in its distal portion, and many accessory bodies with different shapes. The flagellum has a 9 + 2 axoneme. The study of spermiogenesis shows the Golgian origin of the acrosome and the para-acrosomal bodies and reveals some peculiarities: a folding of the perinuclear cisterna is present between the proacrosome and the basal body of the flagellum in early spermatids and the flagellum runs in a canal inside the spermatid cytoplasm. The basal body migrates anteriorly. These characters are shared partly by the Rotifera Monogononta and, to a large extent, by the Acanthocephala studied so far. Many details of the spermiogenetic process are identical to those of Acanthocephala, thus suggesting that the processes in the two taxa are homologous.

Adhesive Papillae of Phallusia mamillata Larvae: Morphology and Innervation.

The swimming larvae of most solitary ascidians belonging to the Ascidiidae family bear three anterior, simple conic adhesive papillae. They secrete adhesive substances that are used to effect transitory settlement at the beginning of the metamorphosis.The adhesive papillae of newly hatched Phallusia mamillata larvae examined by the SEM are covered by the tunic. When the larvae are about to settle, the tunic becomes fenestrated over the central part of the papilla and bulb-ended microvilli protrude through the holes. These papillae have two types of elongated cells: many peripheral cells and few larger central cells with microvilli and bundles of microtubules oriented along the major axis of the cells.We have done immunofluorescence experiments with an anti-beta-tubulin monoclonal antibody (clone 2-28-33) reacting with axonal microtubules. Only the central cells of the papillae were stained and the axons appeared to arise from the proximal ends of these cells. These axons form a long nerve that reaches the brain vesicle. Branches of the same nerve appear to connect to the basal ends of the peripheral cells. By confocal laser microscopy we were able to follow the course of the papillary nerve. The two nerves connecting the dorsal papillae fuse together into a single nerve that runs posteriorly. The nerve connecting the ventral papilla runs posteriorly for a long tract before fusing with the nerve of the dorsal papillae just near the brain.The reported observations raise the hypothesis that the central cells of the adhesive papillae might be primary sensory neurons and that they may have chemosensory function.

Relation of dosing regimen to aminoglycoside ototoxicity: evaluation of auditory damage in the guinea pig.

Groups of guinea pigs were injected intramuscularly for 21 days with netilmicin or amikacin 150 mg/kg/day by one or three daily injections. Amikacin was also tested at 225 mg/kg/day with each dosing regimen. Auditory function was evaluated during the experiment by reflexological and electrophysiological tests. Morphological damage to the inner ear was also evaluated. Netilmicin had no effect on the auditory function nor did it damage the organ of Corti. Conversely, amikacin impaired the auditory function and produced loss of hair cells in a dose-related manner. The effect was equally marked with both dosing regimens of 225 mg/kg/day, whereas a slight decrease of auditory impairment was observed with 150 mg/kg administered once a day. The data suggest that administration of a single daily dose of aminoglycosides does not increase the risk of ototoxicity specifically associated with each compound.

Presence of prolactin-like immunoreactivity and bioactivity in rat spinal cord.

Pursuant to our identification of prolactin-like immunoreactivity (PLI), widely distributed in rat brain, the spinal cord was examined for the presence of this pituitary-hormone-like protein. PLI was present in all spinal cord extracts examined and averaged 500 +/- 53 pg/mg protein. Hypophysectomy, causing a fall in serum prolactin to undetectable levels, was not associated with any change in levels of PLI in spinal cord. Recovery of rat prolactin standards added to spinal cord homogenates was 97.6 +/- 3.9%. When increasing concentrations of spinal cord extract were assayed in a prolactin radioimmunoassay, displacement of rat 125I-Prolactin from antiserum was parallel to that displacement produced by increasing concentrations of rat anterior pituitary standards. Upon subjection to gel permeation chromatography, the elution profiles of immunoreactive prolactin from spinal cord were different from the profiles of anterior pituitary prolactin. In addition to an immunoreactive prolactin peak eluting with pituitary prolactin, spinal cord extracts showed a large void volume peak and late eluting low-molecular-weight materials not seen with anterior pituitary. In the Nb2 lymphoma cell assay, all spinal cord extracts demonstrated prolactin-like bioactivity with a bioactivity/immunoreactivity ratio of 1.05 +/- 0.13. We conclude: (1) PLI, widely distributed in rat brain, is also present in spinal cord; (2) spinal cord prolactin levels are independent of levels in pituitary and peripheral circulation; (3) this immunoreactive prolactin is bioactive, and (4) differing gel permeation chromatographic elution profiles indicate that there may be some molecular differences between pituitary and spinal cord prolactin.

Comparative oto-vestibular effects in the pigmented guinea pig after dibekacin and netilmicin treatment.

We treated groups of pigmented guinea pigs with either intramuscular netilmicin or dibekacin at 100 and 150 mg/kg per day for 3 weeks. Saline was used as the control solution. All animals were tested weekly for both vestibular and auditory functions. The vestibular function was evaluated by the duration of post-rotatory nystagmus (PRN) elicited by interrupting the rotation of the animal around the vertical axis; auditory function was evaluated by the threshold response for the Preyer's pinna reflex (PPR). All animals were then sacrificed and either their labyrinths or Corti organs were processed for further investigations using the scanning electron microscope (SEM). The duration of PRN decreased over the treatment period in all of the groups as a result of adaptation. However, 150 mg/kg dibekacin produced a significant decrease of the PRN responses as compared to the control and other groups. This effect also continued during the recovery period. Likewise, the PPR threshold of the animals receiving 150 mg/kg dibekacin showed a significant increase at the end of the treatments and during the recovery period, while the other dibekacin group had no significant auditory impairment. Netilmicin at both doses did not significantly affect responses following either vestibular or auditory stimulations. SEM observations demonstrated that the sensory epithelia of the labyrinths and Corti organs affected by 150 mg/kg dibekacin had great losses of stereocilia, while comparable doses of netilmicin (150 mg/kg) had only very moderate losses of stereocilia in the labyrinths but not in the Corti organs.