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Müller cells in the chick retina are generally thought to be a homogeneous population. We show that the transcription factor Pax2 is expressed by Müller cells in the central chick retina and its expression was first observed at stage 32 (embryonic day [E] 7.5). Birth-dating indicated that the majority of Pax2-positive Müller cells are generated between stage 29 and 33 (E5.5-E8). At stage 42 (E16), several Müller cell markers, such as Sox2 and 2M6, had reached the peripheral retina, while the Pax2 labeling extended approximately half-way. A similar pattern was maintained in the 6-month-old chicken. Neither the Pax2-positive nor the Pax2-negative Müller cells could be specifically associated to proliferative responses in the retina induced by growth factors or N-methyl-D-aspartate. Pax2 was not detected in Müller cells in mouse, rat, guinea-pig, rabbit, or pig retinas; but the zebrafish retina displayed a similar pattern of central Pax2-expressing Müller cells.

The Asplenium obovatum group consists of diploid and tetraploid taxa; the origin of the tetraploid A. obovatum subsp. lanceolatum was previously considered to have occurred via autopolyploidy, involving one of the diploids of the group, either A. obovatum subsp. obovatum var. obovatum or var. protobillotii. To test this hypothesis, electrophoretic analyses of eight enzyme systems encoded by fourteen putative loci and cytological studies of the artificial hybrid between both diploid varieties were conducted. Alleles of the loci Lap-1, Mdh-2, Mdh-3, Pgm-1, Pgm-1', and 6Pgd-1 emerged as genetic markers for the diploids and were present in an additive pattern in most of the analyzed individuals of the tetraploid. Cytological results indicated a high degree of genomic homology between the diploids. These results indicated that the tetraploid behaves as a segmental allopolyploid. Our results showed that both diploids were involved in the origin of the tetraploid. We propose the new combination Asplenium obovatum subsp. protobillotii for one of the diploids.

Several studies have dealt with the morphogenesis of the rat hippocampal pyramidal cell, but little is known about how the different pyramidal cell shapes of CA fields differentiate from neuroepithelial cells, or about how the field morphological identity emerges. From our studies of pyramidal cell shapes in the CA1, CA3, and CA4 fields of hippocampi at postnatal developmental stages between P0 and P12, using fresh semidissociated slices and acutely dissociated cells, we identified the sequence of cell shape transformation by which they differentiate from simple bipolar to complex shapes characteristic of adult pyramidal cells of CA1 and CA3. Pyramidal cell morphogenesis does not occur synchronously throughout the CA hippocampus fields, but cells in the CA4 field undergo morphological differentiation at earlier stages, prenatally, than CA3 cells, and these in turn earlier than CA1 cells. Thus, during the P1-P6 stages, a gradient of shapes from less to greater differentiation was clearly observed from CA1 to CA4 in a single slice. Furthermore, a mixture of cells at different degrees of differentiation is observed in CA1 from P1 to P10, and in CA3 from P1 to P5. A gradient of shapes from more to less differentiation was observed at stages P5-P6 from septal to temporal. We describe two processes in the pyramidal cell morphogenesis in the CA1 and CA3 fields, the approximation to the soma of the point of bifurcation of the main apical process, and the acquisition of triangular shape of the soma, showing by a quantitative study of both processes that they occur earlier in CA3 than in CA1. Our study, therefore, provides new insight into rat pyramidal cell morphogenesis, and indicates that this process might be differently regulated in the various CA fields. Hippocampus

The aim of the study was to assess patterns of the use of medicines by the general population older than 0 years. The study was based on the information contained in the computerized database from the 1993 Spanish Household Health Survey. A representative sample of the population older than 0 was identified, and a survey of 26,334 persons was carried out. Of the population 45.3% had taken some medicine in the last 2 weeks prior to the carrying out of the survey. The proportion was greater for women (50.6%) than for men (39.6%). With increasing age, the frequency and amount of medication use increased. A little over 20% of the medicines used were not prescribed by a doctor (self-medication). Data show the frequency of the use of medicines by the Spanish population., (Copyright 1997 by John Wiley & Sons, Ltd.)

The surgical and early postoperative complications and complaints associated with laparoscopic sterilization using electrocoagulation or tubal rings for tubal occlusion were evaluated in a comparative study. Procedures were randomly assigned to subjects (electrocoagulation to 151 subjects and tubal rings to 148 subjects). Difficulties in carrying out the sterillization procedures occurred more frequently when tubal rings were used (6.1%) than when electrocoagulation was used (2.0%). Rates of complications occurring at the time of surgery were similar for the two procedures. However, one patient in the electrocoagulation group had a bowel burn. Postoperative pelvic and abdominal pain were reported by a significantly higher proportion of the tubal ring cases (32.0%) than electrocoagulation cases (19.4%). It appears that although the incidence of surgical difficulties and pain may be somewhat more frequent with the tubal ring, the avoidance of such potentially serious complications as bowel burns may make femal sterilization by the tubal ring method preferable.