Stable Anticonvulsant Action of Benzodiazepines During Development in Rats

Abstract— The anticonvulsant action of midazolam and clonazepam was studied in 168 immature rats in three age groups (12, 18 and 25 days old). Epileptic after-discharges of the spike-and-wave type accompanied by clonic seizures of facial and forelimb muscles induced by stimulation of sensorimotor cortex were used as a model. The solvent used for clonazepam exhibited a tendency to anticonvulsant action in 12-day-old rats. On the contrary, a proconvulsant action was seen in 25-day-old animals. The action of both benzodiazepines was identical and did not change substantially during development. The highest dose used (1 mg kg^?1, i.p.) shortened the duration of epileptic after-discharges, the two lower doses (0·1 and 0·02 mg kg^?1, i.p.) suppressed the progressive prolongation with repeated stimulations seen under control conditions. Motor correlates of stimulation remained practically uninfluenced by the two benzodiazepines, myoclonic seizures accompanying epileptic after-discharges were attenuated by the highest dose of both drugs.     

Pacing and atrioventricular block

Over the past year, many studies have reported progress in cardiac pacing. Better understanding of the cardiovascular and neuroendocrinologic physiology and sophisticated technologic advances have contributed to the development of new therapeutic approaches. In this review, we discuss the relevant literature on temporary pacing, physiologic mechanisms involved during pacing, the importance of atrioventricular synchrony and rate responsiveness, recent technologic advances, interactions between pacemakers and defibrillators, and reports on therapy. In the field of atrioventricular block, emphasis is on the characterization of new causes and clinical presentation in special populations.     

Septo-optic dysplasia: MR imaging

Septo-optic dysplasia is the diagnosis when optic nerve hypoplasia is seen in conjunction with dysgenesis of the septum pellucidum. Nearly two-thirds of these patients have hypothalamic-pituitary dysfunction, and half have schizencephaly. The disorder is difficult to classify because of the diversity of clinical and pathologic manifestations. Magnetic resonance images of 11 patients with clinical and radiographic evidence of septo-optic dysplasia were reviewed retrospectively. The "syndrome" appears to include two subsets of patients whose abnormalities have different embryogenesis and neuropathologic findings. The existence of these two subsets helps to explain the diversity of the clinical and radiologic findings.     

Aphakic reading adds. An error in traditional teaching

It is traditionally taught in ophthalmic optics that the "effective" bifocal add is greater than the prescribed add in aphakic spectacles. Because the reading segment is fabricated on the front surface of the lens, the added back vertex power is significantly greater than the prescribed add. It is taught that the effective power should be measured at the back surface. The authors explain informally why the effective add is, in truth, exactly equal to the prescribed add and not equal to the difference in back vertex power between the top and bottom segments. Practitioners who prescribe spectacles by the traditional teaching may leave their aphakic patients with suboptimal reading vision.     

Polypeptide composition of normal and neoplastic human breast tissues and cells analyzed by two-dimensional gel electrophoresis

Summary The protein populations of epithelial cells cultured from two neoplastic and five non-neoplastic human breast tissues were resolved and displayed by two-dimensional polyacrylamide gel electrophoresis and silverstaining. With a computer-based image analysis system, we identified eight polypeptides which are present in both of the neoplastic cell lines, but absent from all five of the cultures of non-neoplastic breast cells. The eight polypeptides are not unique to cells cultured from neoplastic breast, because they are also found in cells cultured from non-breast tissues, both neoplastic and non-neoplastic. Two of the eight polypeptides ( M_r 25,000/pI 4.4 and M_r 31,000/pI 5.5) are present in the patterns of whole tissue samples from infiltrating ductal carcinomas and absent in most normal breast tissue.     

Gene conversion,unequal crossing-over and mispairing at a non-tandem duplication during meiosis of Saccharomyces cerevisiae

Summary We have developed a novel system to examine conversion, exchange and mispairing involving a nontandem duplication of the ade8 locus in yeast by monitoring the segregation of heterozygous markers between the duplicated sequence. Plasmid Yrp 17 carries the yeast selectable markers URA3 ⁺ and TRP1 ⁺. Yrpl7 derivatives with a 4 kb insert carrying ade8-18 were used to clone the mutations trpl-1 and ura3-1 by gap repair. Integrants of the resulting plasmids at the Ade8 locus were crossed to yield diploid hybrids with a non-tandem duplication of Ade8 and heterozygosity for the plasmid markers between the duplicated sequences. 1192 complete, unselected asci were analyzed and 270 exhibiting recombination of the markers contributed by the plasmid were analyzed by Southern transfers to detect changes in plasmid sequences. Twenty-seven tetrads had unequal homologous exchanges and five had unequal sister-chromatid exchanges. Seven tetrads carry an additional copy of the integrated plasmid and ten are missing one. We propose that these two classes represent conversions of the entire 11 kb plasmid, which occur after misalignment and formation of an unpaired loop. Mispairing is a frequent event, and occurs in approximately fifty percent of all meioses. The system described provides a means to determine the meiotic rules of conversion, exchange and pairing for duplicated DNA sequences.