Effects of overexpansion on stents' recoil, symmetry/asymmetry, and neointimal hyperplasia in aortas of hypercholesterolemic rabbits.

BACKGROUND: It is not known whether overexpansion modifies stent recoil, symmetric distribution of struts, and neointimal hyperplasia. OBJECTIVES: The objectives were (a) to evaluate whether stent overexpansion modifies the geometric configuration of the stent in the arterial wall, (b) to determine the relationship between overexpansion and stent recoil, and (c) to evaluate the relationship between the distribution of struts and neointimal hyperplasia. METHODS: Twenty tubular stainless steel 316L stents (3.0 and 3.5 mm in diameter) were implanted at 20 and 10 atm, respectively, in the abdominal aorta of New Zealand rabbits fed a hypercholesterolemic diet (1% cholesterol). Sham operations were also performed in seven animals. Eight weeks after implantation or sham operation, an intravascular ultrasound (IVUS) study was performed to measure stent recoil and aid in stent classification (symmetric or asymmetric) according to strut distribution. The degree of injury and neointimal hyperplasia were also evaluated in hematoxylin-eosin stained sections. RESULTS: The symmetry/asymmetry of stents assessed by IVUS, as well as the neointimal hyperplasia, was similar in both groups. Stent recoil was significantly greater in the 3.0-mm stent (overexpanded) group (0.28+/-0.02 mm), as compared with stent recoil in the 3.5-mm stent group (0.10+/-0.01 mm, P<.05). The neointimal hyperplasia in histological slices, independent of the implant technique, was predominantly in zones with higher strut concentration as compared with zones with fewer struts. CONCLUSIONS: Stent overexpansion enhanced stent recoil and did not modify symmetric and asymmetric strut distribution. Neointimal hyperplasia was not modified by the implant technique. Interestingly, significant hyperplasia was observed in locations with greater strut concentration, independent of overexpansion.     

Functional and pharmacological properties of GABArho1delta51 receptors

Gamma-aminobutyrate is the main inhibitory neurotransmitter in the vertebrate brain, and the gamma-aminobutyric acid (GABA) receptor subunit GABArho1delta51 is an alternatively spliced form of the GABArho1 receptor that was recently isolated from human retina cDNA libraries. The rho1delta51 receptor subunit lacks 17 amino acids in the extracellular N-terminal domain and, when expressed in Xenopus oocytes, forms functional homomeric GABA receptors. Unexpectedly, even after a such a big deletion, the fundamental properties of the deleted variant receptors are very similar to those of the complete GABArho1 receptors. For example, both types of receptors are bicuculline resistant, desensitize very little, and are negatively modulated by Zn2+ and positively modulated by La3+. In spite of such similarities, the GABArho1delta51 receptors are more sensitive to GABA, to the specific GABA(C) antagonist (1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid and to Zn2+, than the complete GABArho1 receptors. The GABArho1delta51 receptors extend the variety of inhibitory receptors in the retina. Their functional significance still remains to be determined.     

Results of unrelated cord blood transplant in fanconi anemia patients: risk factor analysis for engraftment and survival.

We retrospectively analyzed results of unrelated cord blood transplantation (UCBT) in 93 Fanconi anemia (FA) patients. Median age at transplantation was 8.6 years (1-45). The units transplanted were HLA-A, -B, or -DRB1 identical in 12 cases, 1 HLA mismatch in 35 cases, and 2 or 3 HLA differences in 45 cases. The median number of nucleated cells (NC) and CD34+ cells infused of recipient weight was 4.9x10(7)/kg and 1.9x10(5)/kg, respectively. Participating centers selected the preparative regimen of their choice, in 57 patients (61%), it included Fludarabine. Graft-versus-host disease (GVHD) prophylaxis consisted mostly of cyclosporine with prednisone. Cumulative incidence (CI) of neutrophil recovery was 60+/-5% at day +60. In multivariate analysis, Fludarabine containing regimen and NC infused>or=4.9x10(7)/kg were associated with higher probability of recovery. CI of grade II-IV acute and of chronic GVHD (aGVHD, cGVHD) was 32%+/-5% and 16%+/-4%, respectively. Overall survival (OS) was 40%+/-5%. In multivariate analysis, factors associated with favorable outcome were use of Fludarabine in the conditioning regimen, number of NC infused>or=4.9x10(7)/kg, and negative cytomegalovirus (CMV) serology in the recipient. In conclusion, factors easily modifiable such as donor selection and a Fludarabine-containing regimen can considerably improve survival in FA patients given a UCBT. These data are the basis for designing prospective protocols.     

Characteristics of transmitter release at regenerating frog neuromuscular junctions

1. A study was made of the onset of transmission and the characteristics of transmitter release from regenerating nerve terminals in frog muscle fibres.

2. Soon after transmission had been restored, some junctions were found which responded to nerve stimulation with only subthreshold end-plate potentials.

3. The evoked transmitter release had a non-linear dependence on the external calcium concentration, like that seen at normal junctions.

4. The synaptic delay was only slightly longer than normal, and the amplitudes of single quantum potentials evoked by nerve stimulation seemed to have a normal distribution.

5. The mean amplitude of the spontaneous miniature end-plate potentials was often substantially smaller than the mean amplitude of the evoked quantal potentials at a given end-plate. Some of these small spontaneous potentials were due to transmitter release from the axon terminal. Possible explanations for this discrepancy in size of spontaneous and evoked potentials are discussed. Two to three weeks after reinnervation began, the amplitude of the spontaneous miniature end-plate potentials returned to normal.

     

The effect of type D botulinum toxin on frog neuromuscular junctions

1. Botulinum toxin type D blocks neuromuscular transmission in frogs. Motor nerve impulses continue to invade the nerve terminals but cease to evoke the phasic release of transmitter normally associated with them.2. Sensory receptors in the muscle continue to generate impulses even after 4 days of continuous exposure to botulinum toxin.3. Contrary to expectations, spontaneous miniature end-plate potentials did not disappear completely after botulinum intoxication; they still occurred, although with reduced frequency, in most end-plates. These miniature potentials had a skew amplitude distribution instead of the bell-shaped distribution of normal end-plates.4. The electron-microscopic appearance of botulinum-poisoned end-plates was not obviously altered.5. Even though after botulinum nerve impulses fail to release transmitter, tetanic nerve stimulation causes an increase in the frequency of miniature end-plate potentials. Many of the unit potentials which appear during the tetanic period are of an amplitude which is larger than that of spontaneous potentials, indicating that a different class of unit is being released preferentially. Some implications of this finding are briefly discussed.     

Evaluation of the mutagenic and cytotoxic effects of mercurous chloride by the micronuclei technique in golden Syrian hamsters

The aims of this study were to evaluate the mutagenic and cytotoxic activity of mercurous chloride by the micronucleus technique in vivo on the bone marrow of golden Syrian hamsters after a single i.p. drug administration. Forty male golden Syrian hamsters were classified into eight groups: negative control, positive control and six groups treated with different doses of mercurous chloride (1.25, 2.5, 5, 10, 20 and 40 mg/kg). The negative control was injected with physiological saline i.p. and the positive control with cyclophosphamide at a dose of 80 mg/kg i.p. With respect to mutagenic effect, the average number of micronucleated polychromatic erythrocytes (MPE) in hamsters treated with different doses of mercurous chloride was not significant compared with the negative control. With respect to cytotoxic effect, the average polychromatic erythrocyte/red blood cell ratio showed a significant decrease when the doses were higher than the 2.5 mg/kg dose compared with the negative control. In conclusion, this preliminary study shows a cytotoxic effect but not a mutagenic effect of calomel in vivo at one time point (24 h).     

Immune responses induced by the Leishmania (Leishmania) donovani A2 antigen,but not by the LACK antigen,are protective against experimental Leishmania (Leishmania) amazonensis infection

Leishmania amazonensis is one of the major etiologic agents of a broad spectrum of clinical forms of leishmaniasis and has a wide geographical distribution in the Americas, which overlaps with the areas of transmission of many other Leishmania species. The LACK and A2 antigens are shared by various Leishmania species. A2 was previously shown to induce a potent Th1 immune response and protection against L. donovani infection in BALB/c mice. LACK is effective against L. major infection, but no significant protection against L. donovani infection was observed, in spite of the induction of a potent Th1 immune response. In an attempt to select candidate antigens for an American leishmaniasis vaccine, we investigated the protective effect of these recombinant antigens (rLACK and rA2) and recombinant interleukin-12 (rIL-12) against L. amazonensis infection in BALB/c mice. As expected, immunization with either rA2-rIL-12 or rLACK-rIL-12 induced a robust Th1 response prior to infection. However, only the BALB/c mice immunized with rA2-rIL-12 were protected against infection. Sustained gamma interferon (IFN-gamma) production, high levels of anti-A2 antibodies, and low levels of parasite-specific antibodies were detected in these mice after infection. In contrast, mice immunized with rLACK-rIL-12 displayed decreased levels of IFN-gamma and high levels of both anti-LACK and parasite-specific antibodies. Curiously, the association between rA2 and rLACK antigens in the same vaccine completely inhibited the rA2-specific IFN-gamma and humoral responses and, consequently, the protective effect of the rA2 antigen against L. amazonensis infection. We concluded that A2, but not LACK, fits the requirements for a safe vaccine against American leishmaniasis.     

Serotonin antagonizes the human neuronal alpha7 nicotinic acetylcholine receptor and becomes an agonist after L248T alpha7 mutation

The effects of serotonin (5-hydroxytryptamine or 5HT) on chick alpha7 nicotinic receptors have already been described. However similar studies on human alpha7 receptors have been lacking. To begin to fill this deficiency, studies were made on wild-type and mutant human alpha7 (halpha7) receptors expressed in Xenopus oocytes or human BOSC 23 cells. In oocytes wild-type halpha7 receptors were blocked by 5HT, and this block was voltage-dependent. In contrast, 5HT acted as an agonist on halpha7-mutant receptors (L248T). Outside-out membrane-patches from BOSC 23 cells expressing halpha7-mutant receptors exhibited spontaneous channel openings of two conductance levels (59 pS and 76 pS) and short mean open time (0.9 ms). halpha7-Mutant channels activated by nicotine or 5HT displayed similar conductances and high Ca(2+) permeability; but longer duration (2.7 ms) than the spontaneous openings. Mutations at Cys190 and Cys191, in the extracellular N-terminus of the human alpha7 gene, did not prevent receptor expression and incorporation in the oocyte membrane (determined by alpha-bungarotoxin binding). However, both 5HT and nicotine were incapable of gating the channels, indicating that the mutated Cys residues are in, or near, the 5HT- and nicotine-binding site.This is the first report that alpha7 receptors have spontaneous openings; and that 5HT is an agonist of halpha7-mutant receptors, and an antagonist of halpha7-wild-type receptors, through interactions at, or near the acetylcholine-binding sites.