A gamma scintigraphic evaluation of the precorneal residence of liposomal formulations in the rabbit

Multilamellar liposomes were prepared from dipalmitoyl phosphatidylcholine or egg lecithin in combination with cholesterol and either dicetyl phosphate or stearylamine. The size and charge of the colloidal preparations were characterized before labelling with [111In]8-hydroxyquinoline. Freshly labelled liposomes were instilled into the eyes of unanaesthetized NZW rabbits and their disposition and drainage followed using gamma scintigraphy. A positive surface charge was found to affect significantly liposomal drainage rate, whereas an increase in size restricted drainage from the inner canthal region. Drainage of the suspending medium was directly compared with liposomes by labelling the medium with [99mTc] sodium pertechnetate and following the simultaneous change in removal of 99mTc and 111In from the precorneal area. Slower drainage rates were obtained for the suspending medium compared with solutions of the isotopes suggesting that the liposomes restricted solution drainage.

A comparison of the effect of viscosity on the precorneal residence of solutions in rabbit and man

The precorneal drainage of radiolabelled solutions containing polyvinyl alcohol (PVA) or hydroxypropyl methylcellulose (HPMC) have been measured in rabbit and man by gamma scintigraphy. Concentration of the polymers was varied to produce solutions with a viscosity range between 10.2 and 102 mPas. Solution drainage was faster in man than in the rabbit with a more pronounced effect of viscosity. Significant retardation of drainage in man was noted at the higher polymer concentrations (0.9% HPMC or 5.85% PVA).

Serratia: a problem in a neonatal nursery

We have noted an increased incidence of Serratia species isolates in our Special Care Nursery recently and have reviewed our experience over the 7 year period from 1976 to 1982. Fifty newborn infants had strains of Serratia isolated, 30 of which were found in 1982. Two strains of Serratia species were isolated: Serratia marcescens in 46 newborn infants and Serratia liquefaciens in six, with both types being found in two infants. All isolates were sensitive initially to gentamicin, kanamycin sulphate, chloramphenicol and co-trimoxazole. However, resistance was documented subsequently to each of these antibiotics. Only 64% of isolates only were sensitive initially to ampicillin; 27% subsequently developed resistance. Recent isolates were sensitive to cefotaxime sodium. Twenty-nine infants (58%) were colonized, and 16 (32%) had minor infections such as conjunctivitis. However in five infants (10%) life threatening illness occurred. Of the five infants with serious infection two had meningitis and three were septicaemic; one infant died. In both infants with meningitis difficulty was experienced in eradicating the organism and porencephaly developed in both.

The structure of a DNA unwinding protein and its complexes with oligodeoxynucleotides by x-ray diffraction

The structure of the gene 5 DNA unwinding protein from bacteriophage fd has been solved to 2.3 A resolution by x-ray diffraction techniques. The molecule contains an extensive cleft region that we have identified as the DNA binding site on the basis of the residues that comprise its surface. The interior of the groove has a rather large number of basic amino acid residues that serve to draw the polynucleotide backbone into the cleft. Arrayed along the external edges of the groove are a number of aromatic amino acid side groups that are in position to stack upon the bases of the DNA and fix it in place. The cleft then acts as an elongated pair of jaws that draws the DNA between them by charge interactions involving the phosphates with the interior lysines and arginines. The jaws then close on the DNA strand through small conformation changes and the rotation of aromatic side-chains into position to stack upon the purines and pyrimidines. Complexes of the gene 5 protein with a variety of oligodeoxynucleotides have been formed and crystallized for x-ray diffraction analysis. The crystallographic parameters of four different unit cells indicate that the fundamental unit of the complex is composed of six gene 5 protein dimers. We believe this aggregate has 622 point group symmetry and is a ring formed by end to end closure of a linear array of six dimers. From our results we have proposed a double helical model for the gene 5 protein-DNA complex in which the protein forms a spindle or core around which the DNA is spooled. 5.0-A x-ray diffraction data from one of the crystalline complexes is currently being analyzed by molecular replacement techniques to obtain what we believe will be the first direct visualization of a protein-deoxyribonucleic acid complex approaching atomic resolution.

Foot vasomotor tone following aortofemoral and femoropopliteal reconstructions for limb ischaemia

A foot arterial resistance index (FARI), determined plethysmographically, was used pre- and postoperatively to compare foot vasomotor tone following arterial reconstructions of the lower limb with and without the addition of lumbar sympathectomy. The index was measured before and during reactive hyperaemia in 40 patients without vascular disease; in 32 patients who underwent aortic reconstructions, 14 of whom were randomly subjected to a concomitant bilateral lumbar sympathectomy; and in 8 patients who had a femoropopliteal bypass for limb salvage. This study indicates that the addition of lumbar sympathectomy to aortic reconstructive operations enhances blood flow to the foot by significantly reducing foot vasomotor tone. Sympathectomy performed to reduce foot arterial resistance in patients undergoing successful femoropopliteal reconstructions may be of no benefit since a persistent marked postoperative hyperaemia of the foot is present.

Effect of allopurinol on tissue ATP, ADP and AMP concentrations in renal ischaemia

The effect of allopurinol on the concentrations of ATP, ADP and AMP in rat kidneys during ischaemia and postischaemic recovery was studied. Significantly higher concentrations of ATP, ADP and AMP were maintained in the allopurinol-treated animals as compared with the control animals during ischaemic and postischaemic recovery.