The role of platelet-activating factor (PAF) in experimental glomerular injury

Platelet-activating factor (PAF) is a potent autacoid that participates in inflammation and other pathophysiological processes. In this review we deal with recent evidence suggesting that PAF is a mediator that is released early during glomerular injury. PAF can be synthesized in the glomerulus by infiltrating intrinsic glomerular cells. Normal glomeruli produce PAF upon stimulation, and glomerular PAF synthesis is increased in a variety of experimental glomerulopathies. The local infusion of PAF into the renal artery of isolated blood-free kidneys induces proteinuria. PAF attracts and activates inflammatory cells. Glomerular mesangial, endothelial and epithelial cells are also targets for PAF. Therapy with specific PAF receptor antagonists has prevented or reduced proteinuria and improved glomerular inflammation in several experimental models of proliferative glomerulonephritis and minimal change nephrosis. However, the beneficial effect of administration of PAF antagonists once proteinuria is fully developed has been minimal. PAF may also play a role in the recruitment of inflammatory interstitial cells.

Medulloblastoma presenting as blindness of rapid evolution. A case report

An 18-year-old man reported rapid decrease of visual acuity that progressed to total blindness in 1 month. Computed tomographic scanning showed two neoplastic masses: a large one, intra- and suprasellar, and a smaller cerebellar nodule. Histologically, the former proved to be a large metastasis of the small cerebellar medulloblastoma, which infiltrated and compressed the chiasm. Direct compression of the optic pathways by metastasis of a medulloblastoma is a rare event.

Membrane fusion activity of the influenza virus hemagglutinin: interaction of HA2 N-terminal peptides with phospholipid vesicles

We have investigated the interaction of a number of synthetic 20-residue peptides, corresponding to the HA2 N-terminus of the influenza virus hemagglutinin (X31 strain), with phospholipid vesicles and monolayers. Besides the wild-type sequence, two peptides were studied with mutations corresponding to those previously studied in entire HA's expressed in transfected cells [Gething et al., (1986) J. Cell. Biol. 102, 11-23]. These mutations comprised a single Glu replacement for Gly at the N-terminus ("El" mutant) or at position 4 ("E4") of the HA2 subunit and were shown to produce striking alterations in virus-induced hemolysis and syncytia formation, especially for E1. The X31 "wild-type" (wt) peptide and its E4 variant are shown here to have the capacity to insert into phosphatidylcholine (POPC) large unilamellar vesicle (LUV) membranes in a strictly pH-dependent manner, penetration being marginal at pH 7.4 and significant at pH 5.0. Bilayer insertion was evident from a shift in the intrinsic Trp fluorescence of the wt and E4 peptides and from the induction of calcein leakage from POPC LUV and correlated well with the peptides' ability at pH 5.0 to penetrate into POPC monolayers at initial surface pressures higher than 30 mN/m. By contrast, the E1 peptide was found, at pH 5.0, to bind less tightly to vesicles (assessed by a physical separation method) and to cause much less leakage of POPC LUV than the wt, even under conditions where the peptides were bound to approximately the same extent. Consistent with the correlation between leakage and penetration observed for the wt peptide at pH 5 versus 7, the E1 peptide, even at low pH, showed much less lipid-vesicle-induced shift of its Trp fluorescence than wt, caused a much slower rate of leakage of vesicle contents, and did not insert into POPC monolayers at surface pressures beyond 28.5 mN/m. Circular dichroism spectroscopy measurements of peptides in POPC SUV showed that the conformations of all three peptides are sensitive to pH, but only the wt and E4 peptides became predominantly alpha-helical at acid pH.

Rapid determination of alpha-tocopherol in sarcoplasmic reticulum membranes by reverse phase HPLC

A simple isocratic high performance liquid chromatograph (HPLC) system is described to perform a rapid separation, identification and quantitative determination of vitamin E (alpha-tocopherol) in biological membranes. It makes use of a reverse phase C18 column with pure methanol as the mobile phase, and an ultraviolet detector which enables its quantification in the nanogram scale. This procedure was applied to lipid extracts from whole muscle homogenate and from a preparation of sarcoplasmic reticulum vesicles from skeletal muscle, where the vitamin E contents was determined.

[Artificial nutrition in kidney failure]

Renal failure in itself generates a state of malnutrition, due to three main causes: inadequate ingestion (anorexia, vomiting or diet insufficiencies), the existence of catabolic factors (proteins, acidosis, PTH) and extrarenal depuration (which provokes a lack of amino acids and vitamins). Artificial nutrition constitutes a series of measures that can be adopted to act upon each of the above causes. Adequate ingestion compared to inadequate ingestion can be performed orally (especially in chronic renal failure) by parenteral administration (preferable in acute renal failure) and enteral administration (complementary in both cases). The quantity and quality of adequate nutrients is non-dependent on the method of administration; 500 ml, of water should be administered plus diuresis, plus loss from other tracts; the mineral intake of sodium, potassium and phosphorus should be restricted; in the case of vitamins, these should be administered, especially the B and D complexes; there should be sufficient calories to constitute a hypercaloric diet (from 30-50 kg/day), at least 50% in the form of carbohydrates (hypertonic glucose, if administered intravenously, and dextrinolmaltose or starch if administered through the digestive tract) and at least 40% in the form of lipids (preferably of vegetable origin, rich in non-saturated fatty acids); proteins are the mainstay of nutrition in renal failure; thus, with a normal renal function or in dialysis, a dose of 1 g/kg/day is recommended; in chronic renal failure, 0.5 g/kg/day; in cases of renal failure not on dialysis, 0.3 g/kg/day, supplemented by essential amino acids or cetoacids (the effectiveness of the latter is still in dispute).(ABSTRACT TRUNCATED AT 250 WORDS)

[Barrett's esophagus does not revert after medical or surgical therapy for gastroesophageal reflux]

An evaluation was made of 34 patients having Barrett's oesophagus. Medical therapy consisted of antacids, H2 blockers, orthopramides, and postural measures (20 cases, mean follow-up 2.9 years). A Nissen fundoplication was done in 14 cases (mean follow-up 2.5 years). Clinical, endoscopic and histologic evaluation was done in all patients and pH measurements also done in all operated cases. Clinical results have been excellent in 70% of medically treated patients and in 100% of surgically treated ones, pH measurements were between normal limits in all operated patients. However, recovery of the normal epithelium did not occur in any case, except for some partial improvement in one patient treated surgically.

Computer image processing and automatic counting and measuring of fouling organisms

The purpose of this study was to optimize the counting and measuring of marine fouling organisms on experimental panels using automated computer techniques. A script was developed that reduced the time required for the counting and measuring of marine fouling tubeworms by at least one order of magnitude over manual counts, with an error of five percent or less. Small, distinct tubeworms can be successfully counted by computer using a correction factor. Measurements of percentage cover or area should be made with larger tubeworms that have overlapping tubes.

Involvement of lipid mediators in the pathogenesis of experimental nephrosis in rats: its pharmacological modulation

The administration of a single-injection of Adriamycin (ADR) to rats results in marked proteinuria and glomerular morphological changes that are similar to minimal change disease in humans. We have hypothesized that Adriamycin, by itself or through the release of some mediators from resident glomerular cells, could provoke a damage to epithelial glomerular cells. Sprague-Dawley rats received a single injection of Adriamycin, 7.5 mg/kg bw, allocated randomly in several groups and treated throughout 2 weeks of follow-up. All control nontreated animals developed important nephrotic syndrome and degenerative lesions of epithelial glomerular cells. Isolated glomeruli from animals injected with adriamycin 14 days before synthesized thromboxane (TxB2) and platelet activating factor (PAF) in amounts above the rates of control glomeruli. Animals treated with three structurally different PAF receptor antagonists did not present proteinuria or only to a very low extent (p less than 0.0005). In these rats no alterations in epithelial cells were noted. Furthermore, no significant changes in the TxB2 production were noted in rats treated with BN 52021, a PAF receptor antagonist. Leukotrienes also seem to participate since treatment with a 5-lipoxygenase inhibitor partially corrected proteinuria. Moreover, glomeruli from animals with nephrosis and treated with this compound presented only a discrete reduction in the PAF synthesis. On the whole, these data suggest a key role for PAF in the pathogenesis of adriamycin nephropathy. Other lipid meditors, released in cascade simultaneously or thereafter, could perpetuate the renal damage.

GM1 ganglioside reduces cognitive dysfunction after focal cortical ischemia

The functional consequences of cortical focal ischemia and the effect of monosialoganglioside (GM1) treatment on learning/performance of a spatial reversal task were investigated. Cortical focal ischemia was induced by a permanent occlusion of the left common carotid artery and the ipsilateral middle cerebral artery, with a 1-h clamping of the contralateral carotid artery. Twenty-six rats were randomly assigned to three groups: sham controls, a saline-treated ischemic group, and a GM1 ganglioside-treated ischemic group (10 mg/kg/day: IM). Fifteen days after surgery rats were trained on a spatial reversal task in a two-lever operant chamber where food reward was contingent on lever pressing. Training continued from day 15 to day 21 after surgery. Cortical focal ischemia resulted in learning/performance deficits that were reduced by GM1 ganglioside treatment. The cognitive deficits were characterized by a significantly higher number of nonperseverative errors and number of responses to criterion. There was a significant difference between left and right lever performance in the saline-treated ischemic group, which was absent in shams and GM1-treated ischemic rats. On all measures GM1-treated rats were not different from sham controls.

Achalasia of the cardia: long-term results of oesophagomyotomy and posterior partial fundoplication

Forty-eight patients with achalasia of the cardia were treated by Heller's myotomy with a posterior fundoplication of approximately 270 degrees, suturing the gastric fundus to the edges of the myotomy. The mean(s.d.) postoperative follow-up period was 5.4(2.8) years. The clinical results were good to excellent in 44 cases (92 per cent) and fair in four cases (8 per cent) (two with residual dysphagia and two with gastrooesophageal reflux). Barium studies showed a decrease in oesophageal diameter and disappearance of distal narrowing but normal oesophageal emptying did not occur. Postoperative manometric studies (29 patients) revealed a significant decrease in lower oesophageal sphincter pressure and a significant increase in the length of the infradiaphragmatic segment. In the oesophageal body a recovery of peristaltic waves in the proximal third was seen in ten of the patients (34 per cent). Twenty-four-hour pH monitoring showed pathological reflux in only three of 25 patients studied, and one of these was asymptomatic. This technique is effective, improving oesophageal symptoms and controlling long-term reflux.

Evaluation of the magnitude of gastro-oesophageal reflux in Barrett's oesophagus

A manometric study to determine the role of gastro-oesophageal reflux in Barrett's oesophagus was performed on 20 patients with Barrett's oesophagus and 53 patients with reflux oesophagitis without Barrett's oesophagus (25 with mild oesophagitis and 28 with severe oesophagitis). For the same reason, the 20 patients with Barrett's oesophagus also underwent 24 hour continuous oesophageal pH monitoring, and the results obtained were compared with those of 20 oesophagitis patients without Barrett's oesophagus (10 with mild oesophagitis and 10 with severe oesophagitis). The manometric results show that the motor changes found in the Barrett's group are specific but similar to the motor dysfunction associated with reflux oesophagitis. Motor anomalies are probably related more to the inflammatory process in the oesophageal wall than to the metaplastic changes themselves. The pH monitoring results show that while reflux in the Barrett's oesophagus patients was greater overall than in the oesophagitis group without Barrett's oesophagus, the changes are similar when the results are compared with the severe oesophagitis group. In conclusion there are other factors besides gastro-oesophageal reflux involved in the pathogenesis of Barrett's oesophagus.

Factors contributing to the distribution of free fatty acids among phospholipid vesicles

The distribution of free fatty acids at equilibrium after incubation of small sonicated unilamellar vesicles (SUV) with large unilamellar vesicles (LUV) of different lipid composition has been determined. Stearic acid (SA) and oleic acid (OA) showed similar preferences for SUV and LUV of egg yolk phosphatidylcholine (EYPC). Both ionized and protonated forms of the free fatty acids (FFAs) behaved similarly with respect to the equilibrium distribution between EYPC of different size. The charge of the vesicles was found, however, to be important, since both FFAs in their ionized form preferentially associated to vesicles of phosphatidylcholine (PC) as compared with vesicles of phosphatidylglycerol (PC). While SA preferred membranes in the gel state, OA showed preference for the membrane in fluid state. The insertion of both OA and SA in phosphatidylethanolamine (PE)/phosphatidylcholine vesicles is less favourable than in vesicles of pure PC. All these data suggest that membrane lipid content may play a role in determining the distribution of free fatty acids among the membranes of a cell.