Signal transduction mechanisms involved in ischemic preconditioning in the rat retina in vivo

Ischemic preconditioning (IPC) protects the rat retina against the injury that ordinarily follows severe ischemia. We showed previously that release of adenosine and de novo protein synthesis were required for IPC protection. The mechanisms of IPC were studied in the rat retina by examining the signal transduction mediators responsible, in particular, those theorized to be downstream of adenosine receptors. In addition, we examined the hypothesis that nitric oxide and hydroxyl radicals were involved in the IPC protective phenomenon. Retinal ischemia was produced for 60 min in ketamine/xylazine-anesthetized Sprague-Dawley rats, and recovery was measured using electroretinography. We tested the effects on the protective effect of IPC resulting from antagonism of protein kinase C, potassium ATP channels, nitric oxide synthase, or hydroxyl radicals. The effects of the inhibition of de novo protein synthesis or of protein kinase C, and blockade of potassium ATP channels on the mimicking of IPC by adenosine receptor agonists was examined.IPC protection was strongly attenuated by inhibition of protein kinase C and by blockade of potassium ATP channels, but unaffected by the inhibition of hydroxyl radicals. Blockade of nitric oxide synthase produced a trend toward enhancement of IPC protection. Mimicking of IPC protection by adenosine receptor agonists was inhibited by blockade of protein synthesis or of protein kinase C, as well as by potassium ATP channel antagonism. These results demonstrate that protein kinase C and potassium ATP channels are mediators of the protective effect produced by IPC. In addition, the results show that stimulation of adenosine receptor subtypes A1 and A2a is responsible for IPC protection via downstream stimulation of protein kinase C, the opening of potassium ATP channels, and de novo protein synthesis.

Encephalopathy with epileptic spasms resolved with corticoids in a 69 year-old patient

A 69 year-old man with a history of recent temporal lobe seizures, presented with progressive coma and frequent epileptic spasms. Ictal EEG, PET and SPECT alterations were strikingly similar to those described in infantile spasms. Conventional antiepileptic drugs were ineffective but the introduction of corticoids induced a dramatic improvement with disappearance of the spasms. The etiology remains unknown. Epileptic spasms may occur in the elderly. If conventional antiepileptic drugs are ineffective, corticoids should be tried immediately.

Revision of nonfunctioning kock pouch efferent limb: continent, tissue preserving technique

PURPOSE

Despite extensive surgical experience with the intussuscepted efferent nipple of the Kock pouch, complications are not unusual. Although most repairs are relatively simple, the use of intestinal segments is necessary for reconstruction of the complete efferent limb in cases of severe stenosis, pre-stenotic diverticular enlargement or partial necrosis. We describe the tissue preserving transformation of an inadequate efferent Kock pouch outlet into a flap-valve continence mechanism.

MATERIALS AND METHODS

In 5 women a new efferent limb for the Kock pouch was created by transverse retubularization of the short intact ileal segment of the original limb. Continence was preserved through the construction of a Mitrofanoff-like flap valve, created by embedding the new ileal tube in an extramural trough.

RESULTS

At followup ranging from 6 to 28 months all patients were continent and experienced no problems with catheterization.

CONCLUSIONS

This technique of transverse retubularization of the inadequate efferent ileal limb and creation of a flap valve has obvious advantages. No new small bowel segments are required, thereby simplifying and shortening the procedure. The newly created ileal tube is wide (16 to 18Fr) and easy to catheterize. The mucosal folds are longitudinal and do not impede catheterization. The remaining thin layer of mesentery is set in the center of the tube and permits construction of a straight extramural tunnel.

Interfacial shear rheology of aged and heat-treated beta-lactoglobulin films: displacement by nonionic surfactant

Interfacial shear rheology of adsorbed beta-lactoglobulin films (bulk protein concentration 10(-)(3) wt %) has been studied over the temperature range 20-90 degrees C using a two-dimensional Couette-type viscometer. Effects of the type of interface (air-water, triolein-water, and n-dodecane-water), the pH (2.0, 5.6, 6.0, 7.0, and 9.0), and the extent of the heat treatment have been assessed via measurements of changes in the apparent interfacial shear viscosity and elasticity before and after the addition of increasing amounts of nonionic surfactant Tween 20 (polyoxyethylene sorbitan monolaurate). The highest interfacial viscosities were obtained at the n-dodecane-water interface and the lowest at the air-water interface. Competitive displacement of protein from the interface by Tween 20 was easier at the air-water and n-dodecane-water interfaces as compared to the triolein-water interface. The surface shear viscosity was higher and the displacement by Tween 20 more difficult as the isoelectric point of the protein was approached, which is in agreement with the presence of a more strongly cross-linked protein network at the interface. The effect of heat treatment was dependent on the pH of the aqueous solution. No simple relationship between the surface rheological characteristics and the ease of displacement by Tween 20 could be inferred.

Tribolium embryogenesis: a SEM study of cell shapes and movements from blastoderm to serosal closure

Embryogenesis in the beetle Tribolium is of increasing interest to both molecular and evolutionary biology because it differs from the Drosophila paradigm by its type of segment specification (short- vs. long-germ) and by the extensive epithelial envelopes - amnion and serosa - that are typical of most insects but not of higher dipterans. Using scanning electron microscopy of DAPI staged embryos we document development in Tribolium castaneum from blastoderm to completion of the envelopes, recording many details not otherwise accessible; we also provide a time table of the respective stages at 30 degrees C. The nascent blastoderm cells remain basally confluent with the yolksac until after the 13th (=last synchronous) mitotic cycle. The cells in the prospective serosa - the first domain to segregate visibly from the uniform blastoderm - carry surface protrusions likely to contact the overlying vitelline envelope. The embryonic rudiment, the other (and larger) blastodermal domain, gives rise to amnion and germ anlage. In the latter, visible differentiation begins with a "primitive pit" reminiscent of the posterior midgut rudiment of Drosophila. The subsequent invagination of the mesoderm resembles Drosophila gastrulation, except in the head region where the median groove extends through the entire preoral region. The prospective amnion starts differing visibly from the germ anlage during early gastrulation. It then folds underneath the spreading serosa and, advancing with the latter, closes the amniotic cavity at the ventral face of the germband. The largest (=posterior) amniotic fold covers a crestlike protrusion of the yolksac. Together with marked changes in the shape and arrangement of the amnion cells, this protrusion may contribute to the fold's elevation and early progress.

Combined activities of Gurken and decapentaplegic specify dorsal chorion structures of the Drosophila egg

During Drosophila oogenesis Gurken, associated with the oocyte nucleus, activates the Drosophila EGF receptor in the follicular epithelium. Gurken first specifies posterior follicle cells, which in turn signal back to the oocyte to induce the migration of the oocyte nucleus from a posterior to an anterior-dorsal position. Here, Gurken signals again to specify dorsal follicle cells, which give rise to dorsal chorion structures including the dorsal appendages. If Gurken signaling is delayed and starts after stage 6 of oogenesis the nucleus remains at the posterior pole of the oocyte. Eggs develop with a posterior ring of dorsal appendage material that is produced by main-body follicle cells expressing the gene Broad-Complex. They encircle terminal follicle cells expressing variable amounts of the TGFbeta homologue, decapentaplegic. By ectopically expressing decapentaplegic and clonal analysis with Mothers against dpp we show that Decapentaplegic signaling is required for Broad-Complex expression. Thus, the specification and positioning of dorsal appendages along the anterior-posterior axis depends on the intersection of both Gurken and Decapentaplegic signaling. This intersection also induces rhomboid expression and thereby initiates the positive feedback loop of EGF receptor activation, which positions the dorsal appendages along the dorsal-ventral egg axis.

Cerebrovenous blood temperature-influence of cerebral perfusion pressure changes and hyperventilation: evaluation in a porcine study and in man

The objective of the first part of this study was to use an animal model to investigate the relationship between temperature in the cerebrovenous compartment and cerebral perfusion pressure. In the second part of the study, the objective was to examine the influence of hyperventilation and hypothermia on jugular bulb temperature and body temperature in patients undergoing elective neurosurgery. Intracranial pressure was increased artificially by inflating an infratentorial supracerebellar placed balloon catheter in nine pigs under general anesthesia. Temperature was monitored by thermocouples inserted in the sagittal sinus, white matter of the left lobe and abdominal aorta during the ensuing decrease in cerebral profusion pressure (CPP). Cerebrovenous blood temperature (jugular bulb) and body temperature (urinary bladder) were simultaneously monitored in 24 patients undergoing craniotomy. Moderate hyperventilation was performed in all patients. Cerebrovenous blood and core body temperature were recorded and differences between these two temperatures calculated at the beginning and the end of hyperventilation. At the beginning of the intracranial pressure (ICP), increase mean temperatures of cerebrovenous blood and cerebral tissue (left lobe) were lower than core body temperature. During CPP reduction the difference between core body temperature and cerebrovenous blood temperature increased significantly from 0.86+/-0.44 degrees C prior to ICP rise to 1.19+/-0.58 degrees C at maximum ICP. Before hyperventilation, cerebrovenous blood temperature was higher in 19 patients (+/- difference: 0.34 degrees C +/- 0.27) and equal or lower in five patients (difference: -0.08 degrees C +/- 0.11), than core body temperature. At the end of hyperventilation, the difference between cerebrovenous blood temperature and core body temperature increased (+0.42 degrees C +/- 0.24) in those 19 patients who had started with a higher cerebrovenous blood temperature and decreased (-0.10 degrees C +/- 0. 18) in the other five patients. Both studies demonstrated that the temperature of cerebrovenous blood is influenced by maneuvers which are supposed to decrease cerebral blood flow.

Modified seromuscular tube: serosa lined bowel wall imbrication as a continent outlet for continent cutaneous urinary diversion

PURPOSE

We created a simplified modification of the seromuscular tube technique for continent cutaneous urinary diversion.

MATERIALS AND METHODS

We applied a simplified modification of our seromuscular tube technique in 1 woman and 2 men with a mean age of 53 years in whom outlet failure developed after continent cutaneous urinary diversion, and in whom adiposity and postoperative adhesions rendered revision difficult. We constructed a continent outlet conduit by imbricating the whole bowel wall and suturing it into a tube.

RESULTS

At a followup of 4 to 13 months (mean 7) all 3 patients are completely continent without leakage. Catheterization is performed at 3 to 5-hour intervals (mean 4) with 14 to 16Fr catheters.

CONCLUSIONS

The wall imbrication technique involves the flap valve principle, as does the seromuscular tube, and it is easy to perform. To date followup is too short for judging the long-term reliability of this continence mechanism. If the outcome stands the test of time in this series, which represents the worst case scenario, application of this technique may be extended to continent cutaneous urinary diversion.

Ischemic preconditioning attenuates hypoperfusion after retinal ischemia in rats

PURPOSE

Retinal blood flow (RBF) was measured in rats to test the hypotheses that hypoperfusion follows severe ischemia in the retina and that ischemic preconditioning (IPC) attenuates this change in blood flow.

METHODS

Male Sprague-Dawley rats were anesthetized with halothane and mechanically ventilated by tracheostomy to maintain normocarbia and normoxia. Retinal ischemia was induced for 0, 5, 30, 60, 75, or 90 minutes. RBF was measured 60 and 150 minutes after the end of ischemia using the radioactive microsphere blood flow method, and electroretinography was performed during the first 120 minutes after ischemia to quantitate the extent of functional recovery. Additional groups received IPC (5 minutes of ischemia) 24 hours before 30, 60, or 75 minutes of ischemia.

RESULTS

Control (0 minutes' ischemia) RBF was 22+/-3 ml/100 g per minute (mean +/- SE). At 60 minutes after 5, 30, 60, 75, or 90 minutes of ischemia, RBF was 15+/-2 (NS), 11+/-1, 8+/-2, 8+/-1, and 10+/-1 ml/100 g per minute, respectively (significance, P<0.05 versus control). At 150 minutes after 5, 30, 60, 75, or 90 minutes of ischemia, RBF was 18+/-3 (NS), 13+/-1, 12+/-3, 12+/-2, and 11+/-1 ml/100 g per minute respectively (significance, p<0.05 versus control). With prior IPC, RBF after 30 and 60 minutes of ischemia was 21+/-1 and 19+/-3 ml/100 g per minute (both NS compared with control; P<0.05 compared with 30 or 60 minutes of ischemia without IPC). When ischemia was 75 minutes in duration, IPC did not prevent postischemic hypoperfusion. The extent of recovery of the electroretinogram b wave was inversely related to the length of ischemia.

CONCLUSIONS

Postischemic hypoperfusion is present in the rat retina 60 minutes after ischemia, does not resolve by 150 minutes after ischemia, and is attenuated by IPC when ischemia is 60 minutes or less in duration. Maintenance of postischemic perfusion in the retina may be one of the mechanisms involved in the neuroprotection afforded by IPC.

Effects of low-dose dopexamine on splanchnic oxygenation during major abdominal surgery

OBJECTIVE

To study the influence of low-dose dopexamine on splanchnic oxygenation during major abdominal surgery.

DESIGN

Prospective, randomized, placebo-controlled study.

SETTING

University hospital.

PATIENTS

Eighteen adult patients undergoing elective major abdominal surgery.

INTERVENTIONS

The patients received either dopexamine at 1 microg/kg/min (group A, n = 9) or 0.90% saline as control (group B, n = 9).

MEASUREMENTS AND RESULTS

To assess the splanchnic oxygenation, intestinal tissue PO2 (PtissO2) and gastric intramucosal Pco2 (PmucCO2) were measured, and the PCO2 gap (PmucCO2 - PaCO2) was calculated at baseline (T1) and after an infusion period of 60 mins (T2). There was no difference between the groups in the global oxygen transport parameters. Low-dose dopexamine increases PtissO2 on the serosal side of the small bowel (deltaPtissO2, 17+/-24 mm Hg in group A vs. -5+/-10 in group B). The changes in PtissO2 at the serosal side of the colon after dopexamine demonstrated a nonsignificant increase (deltaPtissO2, 7+/-11 mm Hg in group A vs. -11+/-23 mm Hg in group B). In both groups, the Pco2 gap (group A, 6+/-7 mm Hg [T1] and 5+/-6 mm Hg [T2], vs. group B, 9+/-10 mm Hg [T1] and 12+/-10 mm Hg [T2]) remained unchanged compared with the baseline.

CONCLUSION

It is concluded that low-dose dopexamine improves PtissO2 at the serosal side of the gut, preferably at the small bowel. However, low-dose dopexamine did not improve gastric PmucCO2.

Sevoflurane induced suppression of inhibitory synaptic transmission between soma-soma paired Lymnaea neurons

The cellular and synaptic mechanisms by which general anesthetics affect cell-cell communications in the nervous system remain poorly defined. In this study, we sought to determine how clinically relevant concentrations of sevoflurane affected inhibitory synaptic transmission between identified Lymnaea neurons in vitro. Inhibitory synapses were reconstructed in cell culture, between the somata of two functionally well-characterized neurons, right pedal dorsal 1 (RPeD1, the giant dopaminergic neuron) and visceral dorsal 4 (VD4). Clinically relevant concentrations of sevoflurane (1-4%) were tested for their effects on synaptic transmission and the intrinsic membrane properties of soma-soma paired cells. RPeD1- induced inhibitory postsynaptic potentials (IPSPs) in VD4 were completely and reversibly blocked by sevoflurane (4%). Sevoflurane also suppressed action potentials in both RPeD1 and VD4 cells. To determine whether the anesthetic-induced synaptic depression involved postsynaptic transmitter receptors, dopamine was pressure applied to VD4, either in the presence or absence of sevoflurane. Dopamine (10(-]5) M) activated a voltage-insensitive K(+) current in VD4. The same K(+) current was also altered by sevoflurane; however, the effects of two compounds were nonadditive. Because transmitter release from RPeD1 requires Ca(2+) influx through voltage-gated Ca(2+) channels, we next tested whether the anesthetic-induced synaptic depression involved these channels. Individually isolated RPeD1 somata were whole cell voltage clamped, and Ca(2+) currents were analyzed in control and various anesthetic conditions. Clinically relevant concentrations of sevoflurane did not significantly affect voltage-activated Ca(2+) channels in RPeD1. Taken together, this study provides the first direct evidence that sevoflurane-induced synaptic depression involves both pre- and postsynaptic ion channels.

A biological role for deletions in chromosomal band 13q14 in mantle cell and peripheral t-cell lymphomas?

Structural aberrations of chromosomal band 13q14 are frequent in B-cell chronic lymphocytic leukemia (B-CLL) and target a putative tumor suppressor gene in the genomic region between the RB1 gene and the genetic marker D13S25. Recently, it has been suggested that alterations of this particular region might also be of relevance for the pathogenesis of mantle cell lymphomas (MCL). We applied dual-color fluorescence in situ hybridization (FISH) using probes for the RB1 and/or D13S25 loci and screened a total of 236 B- and T-cell non-Hodgkin's lymphomas (NHL) for deletions occurring in this genomic region. In MCL, the high rate (12/32; 38%) of hemizygous deletions and especially a deletion pattern similar to B-CLL in four of the cases provide further evidence that a substantial proportion of MCL cases may share a common way of pathogenesis with B-CLL. In other B-cell NHL, the frequency of allelic loss affecting 13q14 was overall low. However, the finding of 13q14 microdeletions in seven cases without detectable alterations of chromosome 13 at G-banding analysis might indicate a possible involvement of this genetic region also for the lymphomagenesis of single cases of B-cell NHL other than B-CLL and MCL. In T-cell NHL, allelic loss at 13q14 was encountered in three of 13 peripheral T-NHL, NOS. Taking into account the very limited cytogenetic data yet available in this entity, our series provides further evidence that 13q14 changes might represent one of the most frequent genetic abnormalities in T-cell NHL.

SMAD genes in juvenile polyposis

Juvenile polyposis (JP) is a dominantly inherited condition characterized by the development of multiple hamartomatous tumors, juvenile polyps, in the gastrointestinal tract. The aim of this study was to clarify the role of SMAD4 in JP. DNA from four unrelated JP kindreds and three sporadic JP cases was available for mutation screening. Two truncating defects (one in a familial and one in a sporadic case) and one missense change (in a familial case) that was absent in 55 control samples were detected. To study the possibility that germline mutations in other genes encoding different components of the TGF-beta signaling pathway may be present in these JP patients, mutation analyses of the SMAD2, SMAD3, and SMAD7 genes were also performed. No mutations of these genes were detected in any of the patients. Our results confirm that SMAD4 is a gene predisposing to JP and suggest the existence of further JP loci other than the SMAD2, SMAD3, or SMAD7 genes. Genes Chromosomes Cancer 26:54-61, 1999.

The role of brinker in mediating the graded response to Dpp in early Drosophila embryos

Brinker (Brk), a novel protein with features of a transcriptional repressor, regulates the graded response to Decapentaplegic (Dpp) in appendage primordia of Drosophila. Here, we show that in the embryo brk also has differential effects on Dpp target genes, depending on the level of Dpp activity required for their activation. Low-level target genes, like dpp itself, tolloid and early zerknullt, show strong ectopic expression in ventrolateral regions of brk mutant embryos; intermediate-level target genes like pannier show weak ectopic expression, while high-level target genes like u-shaped and rhomboid are not affected. Ectopic target gene activation in the absence of brk is independent of Dpp, Tkv and Medea, indicating that Dpp signaling normally antagonizes brk's repression of these target genes. brk is expressed like short gastrulation (sog) in ventrolateral regions of the embryo abutting the dpp domain. Here, both brk and sog antagonize the antineurogenic activity of Dpp so that only in brk sog double mutants is the neuroectoderm completely deleted.

Ileal ureteral substitution in reconstructive urological surgery: is an antireflux procedure necessary?

PURPOSE

Whether antireflux implantation techniques are necessary in adults who undergo ileal ureteral substitution is controversial. We prospectively evaluated the correlation between reflux and renal function in 19 patients who underwent ileal ureteral substitution with no antireflux implantation technique.

MATERIALS AND METHODS

Followup included clinical evaluation, serum creatinine, blood gasses, excretory urogram, cystogram and dynamic selective renographic clearance on technetium mercaptotriglycine renal scans. All patients were followed for a minimum of 4 years except 2 who died 26 and 43 months postoperatively. Mean followup was 57 months (range 48 to 72).

RESULTS

Despite reflux, renal scans indicated a significant increase in renal function in all patients. Vesico-ileal reflux was present in 9 cases and reflux in the renal pelvis occurred in only 3. Reflux occurred in only 3 of 10 patients with ileal segments longer than 15 cm., and did not reach the renal pelvis.

CONCLUSIONS

Reflux appears to have no detrimental effect on renal function in adults with ileal ureters and, therefore, an antireflux procedure is unnecessary. In addition, an ileal segment longer than 15 cm. appears to safeguard the renal pelvis against visible reflux stemming from pro-grade intestinal peristalsis.