Populations of NGF-dependent neurones differ in their requirement for BAX to undergo apoptosis in the absence of NGF/TrkA signalling in vivo.

Reports that apoptosis within populations of neurotrophin-dependent neurones is virtually eliminated in BAX-deficient mice and that BAX-deficient neurones survive indefinitely in culture without neurotrophins have led to the view that BAX is required for the death of neurotrophin-deprived neurones. To further examine this assertion in vivo, we have studied two populations of NGF-dependent neurones during the period of naturally occurring neuronal death in mice that lack BAX, NGF or the NGF receptor TrkA, alone and in combination. In the superior cervical ganglion (SCG), naturally occurring neuronal death and the massive loss of neurones that took place in the absence of NGF or TrkA were completely prevented by elimination of BAX. However, in the trigeminal ganglion, naturally occurring neuronal death was only partly abrogated by the elimination of BAX, and although the massive neuronal death that took place in this ganglion in the absence of NGF or TrkA was initially delayed in embryos lacking BAX, this subsequently occurred unabated. Accordingly, BAX-deficient neurones survived in defined without NGF whereas BAX-deficient trigeminal neurones died in the absence of NGF. These results indicate that whereas BAX is required for the death of SCG neurones during normal development and when these neurones are deprived of NGF/TrkA signalling in vivo, the death of trigeminal ganglion neurones occurs independently of BAX when they are deprived of NGF/TrkA signalling. We conclude that BAX is not universally required for neuronal death induced by neurotrophin deprivation, but that there are major differences for the requirement for BAX among different populations of NGF-dependent neurones.     

Structure of a single amino acid mutant of aspartate carbamoyltransferase at 2.5-A resolution: implications for the cooperative mechanism

One of the many interactions important for stabilizing the T state of aspartate carbamoyltransferase occurs between residues Tyr240 and Asp271 within one catalytic chain. The functional importance of this polar interaction was documented by site-directed mutagenesis in which the tyrosine was replaced by a phenylalanine [Middleton, S. A., & Kantrowitz, E. R. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 5866-5870]. In the Tyr240----Phe mutant, the aspartate concentration required to achieve half-maximum velocity is reduced to 4.7 from 11.9 mM for the native enzyme. Here, we report an X-ray crystallographic study of the Tyr240----Phe enzyme at 2.5-A resolution. While employing crystallization conditions identical with those used to grow cytidine triphosphate ligated T-state crystals of the native enzyme, we obtain crystals of the mutant enzyme that are isomorphous to those of the native enzyme. Refinement of the mutant structure to an R factor of 0.219 (only eight solvent molecules included) and subsequent comparison to the native T-state structure indicate that the quaternary, tertiary, and secondary structures of the mutant are similar to those for the native T-state enzyme. However, the conformation of Phe240 in one of the two crystallographically independent catalytic chains contained in the asymmetric unit is significantly different from the conformation of Tyr240 in the native T-state enzyme and similar to the conformation of Tyr240 as determined from the R-state structure [Ke, H.-M., Lipscomb, W. N., Cho, Y. J., & Honzatko, R. B. (1988) J. Mol. Biol. (in press)], thereby indicating that the mutant has made a conformational change toward the R state, localized at the site of the mutation in one of the catalytic chains.     

Development of captive bongos (Tragelaphus eurycerus): Activity budgets and developmental milestones

The development of changes in visual orientation, posture, activity budgets, and behavioral milestones was examined in five bongo calves which were observed from birth to 4 or 6 months of age. The only significant change in the calves' visual orientation was an increase in orientation to food. Reclining declined significantly over weeks, while standing increased and moving did not change. Overall, stationary behaviors dominated the activity budget, but decreased significantly over the study. The category that included locomotion, object exploration, and auto-play did not change, while forage and rumination increased significantly. Contrary to expectation, the decline in suckling was not significant. Affiliative interactions with the dam decreased significantly during the study, but increases in affiliation with other bongos were not significant. Levels of agonistic behavior between the calves and their dams and other herd members were low throughout the study, and did not change significantly. One female calf achieved several developmental milestones later than the others. It is suggested that these differences may have been influenced by the dominance status of her dam. The results conform to the general developmental pattern of “hider” bovids. Bongos, however, show somewhat different patterns of social development than eland, which are reported to be more precocial in expression of aggressive and sexual behaviors. © 1992 Wiley-Liss, Inc.     

Behavioral treatment of irritable bowel syndrome: A 1-year follow-up study

Sixteen clients afflicted with irritable bowel syndrome (IBS) were reassessed 1 year following completion of a multicomponent treatment package incorporating progressive muscle relaxation, thermal biofeedback, cognitive therapy, and IBS education. For the 14 patients who kept a 2-week symptom diary, significant reductions in ratings of abdominal pain and tenderness, diarrhea, and flatulence were obtained comparing pretreatment and follow-up symptom-diary ratings. Eleven of 14 clients were improved over pretreatment levels, 57% met the criteria for clinical improvement of at least a 50% reduction in major symptom scores, and all but 1 of 16 rated themselves as subjectively improved.     

New Method for Visualization of Vascular Networks in Nonperfused Fixed Tissues

A new method of visualizing the angioarchitecture of tissues has been developed that uses blood components in nonperfused materials. Tissue blocks are fixed in 4% paraformaldehyde and cut with a vibratome into 50-60 μm sections. Endogenous peroxidase in red blood cells is then reduced in the presence of hydrogen peroxide with the resultant oxidation of the chromogen 3,3'-diaminobenzidine (DAB). This generates a dark, highly insoluble reaction product throughout the vascular system. The visualization of vascular components can be further enhanced by exposing the sections to peroxidase-conjugated IgG to increase the background staining of the blood plasma. The technique minimizes preparation artifact and permits the application of morphometric analytical methods, thus allowing parameters such as the volume density of the vascular bed to be quantified.     

Campylobacter jejuni isolated from patas monkeys with diarrhea

Campylobacter jejuni was isolated from 11 (46%) of 24 patas monkeys with chronic diarrhea. Eight of these 11 (73%) monkey were characterized clinically by mucohemorrhagic diarrhea for periods up to a month followed by loose, semi-formed feces for a 12-month period. Half of the monkeys were treated with erythromycin for 10 days and the other half with tetracycline for 10 days, with all responding to treatment. Despite treatment, all monkeys again had an outbreak of mucohemorrhagic diarrhea. Biopsy specimens were taken from all eight monkeys over a period of 3 months. The clinical signs, treatment, and the gross and microscopic lesions seen in these monkeys were similar to those reported in humans and animals infected with Campylobacter jejuni.     

Fertility of Salmonella typhimurium Crosses with Escherichia coli

At least one factor that causes low fertility of Salmonella typhimurium LT2 strains in crosses with Escherichia coli K-12 Hfr's can be inhibited by growing the female strains in supplemented minimal salts medium rather than in nutrient broth and by incubating the female strains at 50 C immediately before mating with the Hfr. These pretreatments can enhance the recovery of prototrophic recombinants for markers injected early by the Hfr by a factor of as much as 10(4). The heat treatment is effective only on the female in intergeneric crosses and gradually loses (within 50 min) its effectiveness after return of heat-treated cells to 37 C. It is concluded that the restriction system of the female is heat-sensitive. Since markers injected late by the male enter females in which the heat-impaired restriction system has recovered, few recombinants for late markers are found. The presence of the leading end of an E. coli Hfr in an S. typhimurium-E. coli hybrid enhances by up to sevenfold the frequency of lac(+) recombinants in subsequent crosses with an E. coli Hfr if the E. coli segment is integrated into the chromosome of the hybrid; the effect is less marked if the E. coli segment is not integrated.     

The human 5-HT1A receptor expressed in HeLa cells stimulates sodium-dependent phosphate uptake via protein kinase C

Regulation of phosphate uptake was studied in HeLa cell lines after transfection with DNA encoding the human 5-HT1A receptor. Phosphate uptake was saturable and greater than 90% sodium-dependent, with Vmax approximately 30-35% without changing Km. Treatment with 5-HT or the 5-HT1A-specific agonist 8-OH-2-(di-n-propylamino)1,2,3,4-tetrahydronaphthalene increased Vmax approximately 40% without affecting Km. This effect was blocked by pretreatment with the 5-HT1 antagonists, methiothepine and spiperone, or pertussis toxin. Surprisingly, the stimulation was not secondary to an inhibition of adenylyl cyclase because 5-HT stimulated phosphate uptake approximately 20% in the presence of 1 mM 8-Br-cAMP. Rather, the primary pathway linked to the stimulation of phosphate uptake involved activation of protein kinase C because (i) 5-HT measurably activated protein kinase C in these cells, (ii) activators of protein kinase C (phorbol esters and diacylglycerol analogues) stimulated phosphate uptake in these cells (iii) the half-maximal doses for 5-HT-induced phosphatidylinositol hydrolysis and stimulation of phosphate uptake were virtually equivalent, and both effects were equally sensitive to pertussis toxin, and (iv) the stimulation was markedly attenuated in cells made deficient in protein kinase C. These results demonstrate that the stimulation of phosphatidylinositol hydrolysis by the 5-HT1A receptor can generate physiologically measurable effects on cellular transport and suggest that such accessory pathways may play a prominent role in signal transduction.