Physiologic and pathologic evaluation of chronic extra-aortic counterpulsation with latissimus dorsi flap. Preliminary results

This study attempted to evaluate the efficacy of chronic extra-aortic counterpulsation with a latissimus dorsi neuro vascular flap. Five dogs had a preliminary procedure consisting of the creation of a latissimus dorsi flap and a thoracotomy in which the flap was wrapped around the descending aorta just distal to the left subclavian artery. An epicardial lead was placed on the left ventricle and a nerve stimulating lead placed around the thoraco-dorsal nerve. Three weeks later, both leads were connected to a cardiomyostimulator programmed to function in a counterpulsation mode with a 1:2 assist frequency. Hemodynamic measurements were made at 6 and 8 and 10 and 12 weeks and the dogs were sacrificed. Three dogs had all sets of hemodynamic measurements made. Two of the three dogs demonstrated diastolic augmentation at 6 and 8 and 10 and 12 weeks average 20 to 25 mmHg. The third dog failed to demonstrate any change. All dogs were sacrificed at 12 weeks and specimens were submitted for histologic evaluation. The muscle flap was preserved in all animals. The aorta subjacent to the flap showed, (1) normal intima with no evidence of disruption or thrombus in all animals, (2) in the animals in whom counterpulsation was observed, there appeared to be thinning of the media in the aorta subjacent to the muscle flap, and (3) no evidence of distal emboli. This study demonstrated that chronic counterpulsation can be obtained with a latissimus dorsi flap. The actual hemodynamic benefits are not determined from this study. The medial thinning in the aortic wall may limit the long-term benefit of this procedure.     

Effect of liposome surface charge on the stability of technetium (99mTc) radiolabelled liposomes

Using liposomes radiolabelled by the 99mTechnetium-stannous chloride technique we have investigated the effect of surface charge on the stability of the isotope in vitro and in vivo. Dialysis of 99mTc-labelled positive, negative and neutral liposomes, which had been incubated in either saline or normal rat serum showed no significant loss of the isotope from the liposome surface with only 2 per cent of the isotope dialysed. A comparison of gel chromatography with dialysis confirmed that most of the isotope remained attached to the liposome surface, but it did reveal greater loss of the isotope, between 15 and 23 per cent. The liposome clearance rates obtained from 125I-egg phosphatidylcholine (EPC) and 99mTc dual-labelled positive or neutral liposomes were significantly different. The 99mTc marker was cleared five times faster from the positive liposomes and twice as fast from the neutral liposomes as the 125I-EPC integral membrane marker. The 99mTc attached to liposomes with a negative surface charge was stable in vivo and had the same clearance rate from the circulation as the 125I-EPC marker. These results indicate that the commonly used in vitro techniques for assessing liposome radiolabel stability are unsuitable for predicting the stability of the 99mTc in vivo.     

Interactions of small polypeptides with dimyristoylphosphatidylcholine monolayers: effect of size and hydrophobicity

The effects of size and hydrophobicity of small (molecular weights below 2,000) polypeptides on their predominantly hydrophobic interactions with a neutral phospholipid monolayer were studied. The changes in surface pressure were determined when various concentrations of Gly, Gly-Gly-Gly, -Ala, -Ala- -Ala- -Ala, -Ala-Gly-Gly-Gly-Gly, -Phe- -Leu- -Glu- -Glu- -Leu, adrenocorticotropic hormone fragments 1–10 (ACTH-(1–10)), porcine β-lipotropin, -endorphin and human fibrinopeptide A were injected under dimyristoylphosphatidylcholine (DMPC) monolayers at an initial surface pressure of 10 dyne/cm. In all cases, when peptides with the same number of residues are compared, the concentration needed to increase the surface pressure of the film by 1 dyne/cm was inversely related to its hydrophobicity. A reasonably good correlation was found to exist between the calculated free energy of transfer of a polypeptide from ethanol to water (a measure of its hydrophobicity) and its ability to increase the surface pressure of the DMPC film (a measure of the extent of its interaction with the neutral lipid monolayer).     

Similar dose responsiveness of hepatic glycogenolysis and gluconeogenesis to glucagon in vivo

This study was undertaken to determine whether the dose-dependent effect of glucagon on gluconeogenesis parallels its effect on hepatic glycogenolysis in conscious overnight-fasted dogs. Endogenous insulin and glucagon secretion were inhibited by somatostatin (0.8 micrograms X kg-1 X min-1), and intraportal replacement infusions of insulin (213 +/- 28 microU X kg-1 X min-1) and glucagon (0.65 ng X kg-1 X min-1) were given to maintain basal hormone concentrations for 2 h (12 +/- 2 microU/ml and 108 +/- 23 pg/ml, respectively). The glucagon infusion was then increased 2-, 4-, 8-, or 12-fold for 3 h, whereas the rate of insulin infusion was left unchanged. Glucose production (GP) was determined with 3-[3H]glucose, and gluconeogenesis (GNG) was assessed with tracer (U-[14C]alanine conversion to [14C]glucose) and arteriovenous difference (hepatic fractional extraction of alanine, FEA) techniques. Increases in plasma glucagon of 53 +/- 8, 199 +/- 48, 402 +/- 28, and 697 +/- 149 pg/ml resulted in initial (15-30 min) increases in GP of 1.1 +/- 0.4 (N = 4), 4.9 +/- 0.5 (N = 4), 6.5 +/- 0.6 (N = 6), and 7.7 +/- 1.4 (N = 4) mg X kg-1 X min-1, respectively; increases in GNG (approximately 3 h) of 48 +/- 19, 151 +/- 50, 161 +/- 25, and 157 +/- 7%, respectively; and increases in FEA (3 h) of 0.14 +/- 0.07, 0.37 +/- 0.05, 0.42 +/- 0.04, and 0.40 +/- 0.17, respectively. In conclusion, GNG and glycogenolysis were similarly sensitive to stimulation by glucagon in vivo, and the dose-response curves were markedly parallel.     

The quantity of rhodopsin in human eyes

The content of rhodopsin in the eyes of 15 donors (30 eyes) was determined. Both retinal and pigment epithelial fractions were collected from each globe, extracted using 1% CTAB, and the rhodopsin difference spectrum of each fraction was obtained separately. The total amount of rhodopsin, obtained by summing the amounts recovered from the retinal and PE fractions, ranged from 2.00 to 11.94 (median: 6.40) nmoles/eye. Previously reported mean values of about 3.5 to 4.0 nmoles per retina have been obtained using a variety of methods. The present higher values, perhaps largely dependent on procedural details described herein, appear plausible given the known concentrations of rhodopsin in rod outer segments, rod outer segment volumes, and number of rods in the human retina.     

Variation in venom composition and reactivity in two specimens of yellow-faced whip snake (Demansia psammophis) from the same geographical area

Gel filtration chromatography and SDS-PAGE of venom from two specimens of Demansia psammophis showed little similarity. Amidolytic activity of the venoms, however, was in the same order of reactivity against various chromogenic substrates. The venom from both snakes produced precipitin lines with brown snake antivenom but the venom detection kit (Commonwealth Serum Laboratories) identified one venom as brown snake (Pseudonaja sp.) and the other as tiger snake (Notechis sp.). These results raise questions about the phylogeny of this species.     

The usefulness of small-bowel manometry in the diagnosis of gastrointestinal motility disorders

Motility disorders of the gastrointestinal (GI) tract have traditionally been diagnosed by excluding mechanical small-bowel obstruction. In order to diagnose GI motility disorders in a positive fashion, small-bowel manometry was performed on 15 patients who were referred to the authors with intestinal motility disorders. Intestinal manometry was performed after first positioning a 200-cm multilumen tube into the small intestine. Ports located at 10-cm intervals were perfused with sterile water and connected to pressure transducers to record intraluminal pressures with a multichannel chart recorder. This low compliance water perfusion manometry system allowed examination of both fasting and postprandial motility. Intestinal manometry was able to assist in the diagnosis of two patients that had true mechanical small-bowel obstruction. One patient had a stenosis of the gastrojejunostomy and three patients had a functional gastric outlet obstruction secondary to a motility disorder in the Roux limb. One patient had a functional obstruction from a reversed jejunal loop and eight patients were identified as having intestinal pseudo-obstruction. We found intestinal manometry was a helpful adjunct in the diagnosis of GI motility disorders.