ST/b and DBA/2 mice differ in brain alpha-bungarotoxin binding and alpha 7 nicotinic receptor subunit mRNA levels: a quantitative autoradiographic analysis

Inbred mouse strains vary in sensitivity to a number of behavioral and physiological effects produced by nicotine. Differences in sensitivity to nicotine are correlated with variance in the number of brain nicotinic receptors as measured in regionally dissected brain tissue. The studies reported here used quantitative autoradiography and in-situ hybridization methods to measure regional levels of alpha-bungarotoxin (alpha BTX) binding and alpha 7 mRNA levels. Two inbred mouse strains, ST/b and DBA/2, were compared because these strains differ maximally in sensitivity to nicotine-induced seizures and in alpha BTX binding measured in regional brain homogenates. The binding of alpha BTX was significantly greater in the St/b strain in 42 of 127 brain regions that were analyzed, and a trend towards increased binding was seen in many additional brain regions. The most consistent strain differences were found in hippocampal, thalamic and pontine nuclei. Strain differences in alpha 7 mRNA levels were also detected, but these were not as widespread as were the alpha BTX binding differences. The alpha 7 mRNA levels were significantly correlated with alpha BTX binding in both mouse strains which suggests that the strain differences in binding are related, in part, to the levels of alpha 7 mRNA.     

Long tube implants in the management of glaucoma

The design, surgical insertion and results of a plastic draining implant for severe glaucoma are reported. The need for pharmacological control of bleb inflammation is stressed and the favourable long-term outlook for patients with such implants is discussed.     

Thyroid gland in dwarf mice: a stereological study

Stereological methods were used to compare thyroids of dwarf mice and of their heterozygote littermates. In the thyroid of dwarf mice unorganized cellular masses, adipous tissue and ultimobranchial cysts are abundant. Follicles are small and their distribution function is unimodal. The number of cells per follicle is considerably lowered if compared with the normal. In control mice the distribution function of thyroid follicles is bimodal. These data show that origin of the thyroid anomaly in dwarf mice is due to a drastic diminution of cell divisions, probably resulting from the lack of growth hormone.     

Enhanced toxicity for mice of combinations of bacterial lipopolysaccharide and vincristine

Sublethal doses of vincristine (VNC) and bacterial lipopolysaccharide (LPS) administered simultaneously to adult male mice resulted in markedly enhanced mortality. All of 10 strains of Pseudomonas aeruginosa tested, 4 of 7 strains of Bacteroides, and 6 of 10 strains of Listeria monocytogenes were able to substitute for purified LPS in enhancing mortality in VNC-treated mice. Inoculation of mice with each of 10 strains of Pseudomonas, each of 7 strains of Bacteroides, and about half of the 10 strains of Listeria tested elicited increased resistance to the lethal action of purified LPS. The patterns of responses of mice receiving a lethal combination of 2 mg of LPS/kg and 1 mg of VNC/kg resembled those of mice receiving a lethal dose of 10 mg of VNC/kg alone or 15 mg of LPS/kg alone with respect to (i) serum glutamic pyruvate transaminase activity, (ii) hematocrit values, and (iii) thrombocytopenia. The patterns of responses of mice receiving a lethal combination of LPS and VNC resembled those of mice receiving a lethal dose of LPS alone with respect to (i) hypothermia, (ii) retention of sulfobromophthalein, (iii) fibrinogen level, (iv) prothrombin activity, (v) blood urea nitrogen levels, and (vi) time of death. These data are consistent with the proposition that the combination of VNC and LPS produces a fatal renal failure. Histological studies confirmed that there was extensive renal damage in mice treated with lethal doses of LPS alone or a lethal combination of LPS and VNC.     

Terminal nitrogen rise

Eighteen-breath nitrogen washouts were performed on eight subjects. Each washout could be simulated by a four-compartment model, each compartment with a different ventilation-to-volume ratio and a variable contribution to expiratory flow. In large breaths initiated near residual volume, a terminal nitrogen rise (TNR) was seen. To account for the TNR with this model, there were relatively small changes in flow from compartments with markedly different nitrogen concentration. Reasons are given for believing these compartments could not be the upper and lower lung. Three of these subjects were studied in the supine, seated, and head-down positions. The TNR was seen at the same lung volume in all positions. At routine bronchospirometry in a second group of subjects, sampling with small catheters during a nitrogen washout showed a TNR in the expirate of lungs, lobes, segments, and subsegments in the upright and supine positions. Apparently a large vertical hydrostatic gradient is unnecessary to produce a TNR. Finally, the TNR was shown to occur at that lung volume where transpulmonary pressure is very small and changing rapidly with volume. This TNR was often followed by a terminal nitrogen fall while the lung was continuing to empty. The TNR occurs when flow from a large poorly ventilated compartment increases relative to the flow from other compartments. A model of lung in which the poorly ventilated compartment develops high specific compliance at low lung volume explains these data.     

Confusions in recognizing phonemes spoken by esophageal speakers: II. Vowels and diphthongs

A methodology was developed to determine the patterns of phonemic errors that listeners would make in receiving the vowels and dipthongs of monosyllables spoken by esophageal speakers. Analyses of the features preserved in the errors were performed. The identified phonemic error patterns and the features found to be poorly preserved in the errors were used to structure multiple-choice intelligibility practice materials for esophageal speakers.