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Biomedical subjects

J R Saunders

Publications and source records attributed to J R Saunders.

At least 109 records · Page 6Linked to original sources
PubMed1987

The role of capsular polysaccharide K21b of Klebsiella and of the structurally related colanic-acid polysaccharide of Escherichia coli in resistance to phagocytosis and serum killing.

The behaviour of strains of Klebsiella aerogenes of capsular serotype K21 and strains of Escherichia coli producing a structurally related polysaccharide (colanic acid) was analysed by phagocytic and serum-killing assays. The cell-surface characteristics of these strains and of non-capsulate strains derived from them were also investigated by partitioning experiments in aqueous two-polymer phase systems. The possession of K21-type capsule by K. aerogenes or colanic-acid polysaccharide by E. coli conferred a strong negative charge on capsulate bacteria. Negatively charged bacteria of E. coli producing colanic-acid capsules, however, like non-capsulate K. aerogenes, were susceptible to uptake by polymorphonuclear leukocytes. In contrast, K21 polysaccharide conferred on klebsiellae considerable resistance to phagocytic uptake. The finding that ingested non-capsulate derivative strains of K. aerogenes were less rapidly degraded by phagocytes than E. coli strains suggested that other components of the cell surface of Klebsiella, notably lipopolysaccharide, may be involved in protection against phagocytic killing. The presence of colanic-acid capsules on E. coli conferred little resistance to the bactericidal activity of human serum or phagocytic uptake and did not protect against intracellular killing by polymorphonuclear leukocytes.

Blood Bactericidal Activity↗
PubMed1987

Contribution of capsular polysaccharide and surface properties to virulence of Escherichia coli K1.

We examined the surface properties, susceptibility to the bactericidal activity of serum, and susceptibility to phagocytosis of Escherichia coli K1, a laboratory strain of E. coli (LE392), and strain LE392 carrying a plasmid (pKT274) incorporating a 17-kilobase insert of DNA that encodes the ability to produce surface K1 antigen. As determined by electron microscopy, LE392 was nonencapsulated but both E. coli K1 and LE392(pKT274) possessed a thin capsule. By using charged aqueous two-phase polymer systems, both E. coli K1 and LE392(pKT274) were shown to be significantly more negatively charged than LE392. E. coli K1 was resistant to the bactericidal activity of serum, but both LE392 and LE392(pKT274) were completely inhibited by neonatal serum at a concentration of 20% (vol/vol). As measured by counting endocytosed and nonendocytosed bacteria and by chemiluminescent response, E. coli K1 was highly resistant to phagocytic uptake by polymorphonuclear leukocytes, whereas LE392 was rapidly taken up by such cells; LE392(pKT274) was resistant to endocytosis, although less so than E. coli K1. Most intraphagocytic E. coli LK1 remained structurally intact for up to 60 min, whereas both LE392 and LE392(pKT274) were rapidly degraded.

Antigens, Bacterial↗
PubMed1987

Organ culture of rabbit ileum as a model for the investigation of the mechanism of intestinal damage by enteropathogenic Escherichia coli.

Organ culture of rabbit ileum has been established as a model for the investigation of the mechanism of intestinal damage by enteropathogenic Escherichia coli (EPEC). Loops of rabbit ileum were filled in vivo with saline, non-enteropathogenic P-fimbriate E coli (PFEC), or EPEC. After 45 minutes the loops were washed, then mucosal biopsies were taken and cultured for up to 48 hours. The earliest changes discernable by electron microscopy were observed at 18 hours postinfection, at which time EPEC were closely adherent to the surface of enterocytes at the base of microvilli, some of which were elongated. By 24 hours postinfection there were large areas of brush border effacement with pedestal formation around the EPEC. No such damage was seen in biopsies from the control loops (saline, PFEC), and intracellular ultrastructure was extremely well preserved in all preparations for up to 48 hours. While there were no differences at eight hours, biochemical analyses at 24 hours postinfection showed a marked increase in the release of brush border enzymes into the culture medium from EPEC-infected explants compared to explants from the control loops. These findings provide morphological and biochemical evidence for damage to the microvillus membrane by EPEC, and validate organ culture of rabbit ileum as a model for the investigation of EPEC-pathogenicity.

Alkaline Phosphatase↗
PubMed1987

Attempted transmission to cattle of Anaplasma marginale from overwintered Dermacentor andersoni ticks.

Since the 1983 summer outbreak of anaplasmosis in southern Saskatchewan, the role of the tick, Dermacentor andersoni as an overwintering reservoir for Anaplasma marginale has been questioned. The purpose of this study was to determine if spring-collected ticks carried virulent A. marginale. Sixteen splenectomized calves were assigned randomly to two groups of 14 principals and two controls. Adult D. andersoni, collected in April from areas having high transmission rates of A. marginale, were confined to the ears of the principals by special bags and allowed to feed for eight days. The two control calves were subsequently challenged intravenously with blood from a calf infected with the Virginia strain of A. marginale. Principals and controls were monitored for 60 and 50 days postexposure respectively for signs of infection by clinical, hematological and serological procedures. None of the principals developed anaplasmosis but both control calves developed signs of disease.

Anaplasmosis↗
PubMed1986

Deletion and rearrangement of plasmid DNA during transformation of Escherichia coli with linear plasmid molecules.

When E. coli was transformed with linearized pBR322 DNA, many transformants contained recircularized plasmids bearing deletions and other rearrangements. Most aberrant molecules were less than monomeric length and had lost the restriction site used for linearization, with the deleted region extending mono- (type Ia) or bi-directionally (type Ib). Type II deletants were greater than monomeric but less than dimeric and contained the pBR322 sequence in direct repeat with deletion at one or both junctions (type IIa) or in inverted repeat with loss of sequence at both junctions (type IIb). Type III deletants were greater than dimeric but less than trimeric, consisting of pBR322 sequences in both direct and inverse repeat with deletions at two or more junctions. Transformation frequencies for linear DNA were drastically reduced in xth-1- bacteria with type IIb deletants predominating in transformants. This indicates that exonuclease III is important for perfect recyclization of plasmids and the generation of type I deletants. In vivo recyclization of in vitro ligation products explains many of the aberrant DNA molecules that are encountered during gene cloning.

Chromosome Deletion↗
PubMed1986

Mechanism of intramolecular recyclization and deletion formation following transformation of Escherichia coli with linearized plasmid DNA.

The deletion end-points of a number of type I (less than monomeric) plasmid deletants obtained by transforming recA+ or recA- E. coli with linear pBR322 DNA were determined by DNA sequencing. In both monodirectional and bidirectional deletions the recyclization point was normally characterized by recombination between directly repeated sequences of between 4 and 10 bp present on each arm of the linearized pBR322 molecule. Frequently, short tracts of uninterrupted homology involved in recombinational recircularization were embedded in regions of relative non-homology. A model predicting the probability of matching sequences in either end of a linear plasmid molecule is presented. It is proposed that exonucleolytic processing of the exposed termini of linear plasmid molecules generates substrates for subsequent recombinational recyclization and deletion. The activity of host recombination and repair functions in recircularizing linear DNA molecules explains the generation of many of the aberrant recombinant DNA constructs obtained during gene cloning procedures.

Base Sequence↗
PubMed1986

Identification and characterisation of PmaCI an endonuclease of novel specificity from Pseudomonas maltophila.

We report the use of MonoQ FPLC (Fast Protein Liquid Chromatography) for the rapid purification of a novel Type II restriction endonuclease PmaCI, from Pseudomonas maltophila, which recognises the sequence 5'-CAC decreases GTG-3'. The resulting enzyme is free of other nucleases to a level suitable for its characterisation by multiple-substrate digestion and DNA sequencing techniques. This method appears to be widely applicable and we have used it for the isolation of restriction endonucleases of comparable purity from a range of other organisms. Also described is a rapid method for screening a library of small inserted regions in recombinant M13 molecules for the presence and subsequent screening of restriction sites of interest.

Base Sequence↗
PubMed1986

Salivary glands.

A review of the more common inflammatory and neoplastic conditions affecting salivary glands has been presented. The use of hydration, massage, antibiotics, and steroids is effective initial treatment for suppurative sialadenitis and usually negates the need for surgical drainage. Total excision of the salivary gland and its duct is necessary in procedures for recurrent infection. Our technique for closure of the floor of the mouth after excision of the submandibular gland and Wharton's duct is described. Salivary neoplasms involving the parotid gland, the submandibular gland, and the minor salivary glands are treated on the basis of their histologic and local findings. Stepwise illustrations of our technique of parotidectomy and surgical considerations, including the counseling of a patient with a parotid mass, are presented to assist surgeons who care for patients with salivary disorders.

Adenocarcinoma↗
PubMed1986

Plasmid-mediated resistance to beta-lactam antibiotics in gram-negative bacteria: the role of in-vivo recyclization reactions in plasmid evolution.

Over 20 different plasmid-encoded beta-lactamases have so far been discovered. This paper considers genetic mechanisms by which beta-lactamase genes encoded by plasmids are disseminated across generic boundaries. Particular emphasis is placed on the evolution of plasmids carrying all or part of Tn3 and encoding TEM-1 beta-lactamase in Haemophilus and Neisseria species. Examples of the acquisition of broad host range plasmids carrying Tn3 sequences and of rescue of transposon sequences to indigenous plasmids or to the host chromosome have been found in these two genera. Studies on nonconjugative beta-lactamase plasmids in Neisseria and Haemophilus are consistent with the evolution of a family of plasmids originating from the insertion of Tn3 into an indigenous progenitor plasmid. A series of subsequent insertional and deletional events, most probably occurring as a consequence of genetic transfer, have given rise to the existing group of small, closely related ampicillin-resistance plasmids found currently in these genera. A general model for deletional and other rearrangements caused by recombinational recyclization during the evolution of resistance plasmids is described.

Anti-Bacterial Agents↗
PubMed1985

Considering the spinal accessory nerve in head and neck surgery.

Loss of trapezius muscle function represents the single most important source of long-term morbidity from a radical neck dissection. Its preservation has been one of the central features of the conservative or modified neck dissection. We recently undertook an evaluation of 100 consecutive patients who had undergone composite resection for head and neck cancer and examined them with particular emphasis on the function of the trapezius muscle. The mean interval from the time of radical neck dissection to the time of this evaluation was 6.2 years. The operations included radical neck dissection with sacrifice of the spinal accessory nerve, radical neck dissection with preservation of the spinal accessory nerve, and radical neck dissection with interpositioned cable graft reconstruction. The survey showed that 67 percent of the patients who underwent radical neck dissection with sacrifice of the spinal accessory nerve, although they showed profound atrophy of the trapezius muscle, had few symptoms related to this deficit. Similarly, 47 percent of patients who underwent radical neck dissection with preservation of the spinal accessory nerve showed some signs of muscle atrophy, and 20 percent showed little or no function of the muscle. Interpositioned nerve grafts appeared to function well in 66 percent of the patients. The survey showed that a surprising number of patients treated with a standard radical neck dissection and sacrifice of the spinal accessory nerve had few postoperative symptoms related to the loss of trapezius muscle function. Also unexpected was the number of patients with signs of muscle dysfunction despite nerve preservation.

Accessory Nerve↗
PubMed1985

A comparative analysis of the clinical, sialographic, and pathologic findings in parotid disease.

In review of the clinical and sialographic ability to predict parotid pathology, it was found that the clinical exam was consistently more accurate. Sialographic findings and histopathology were compared in 119 patients who underwent 120 sialograms and subsequent parotidectomies. Sialography alone was able to diagnose a malignant tumor in only 8 per cent (1/13) of the cases. The sialogram proved most helpful for the clinician in the management of patients when the diagnosis was calculus, obstruction, or sialectasia. On the other hand, mass lesions in or adjacent to the parotid, diffuse enlargement of the gland, or conditions such as masseter muscle hypertrophy are probably better evaluated with newer CT techniques in conjunction with sialography or without sialography.

Adolescent↗
PubMed1984

RsrII--a novel restriction endonuclease with a heptanucleotide recognition site.

A sequence-specific endonuclease present in extracts of Rhodopseudomonas sphaeroides 630 has been purified and characterized. The enzyme, Rsr II, recognises and cleaves the palindromic heptanucleotide sequence: (sequence; see test) By virtue of its unusual specificity, RsrII cuts most DNA molecules very infrequently which should facilitate the physical mapping of large genomes.

Base Sequence↗
PubMed1984

Recombination-dependent recircularization of linearized pBR322 plasmid DNA following transformation of Escherichia coli.

Monomeric pBR322 DNA that had been linearized at its unique SalI site transformed wild-type Escherichia coli with 10(2) to 10(3) times less efficiency than CCC plasmid DNA. Dose-response experiments indicated that a single linear plasmid 'molecule' was sufficient to produce a transformant. Transformation with linearized pBR322 DNA was reduced 10 to 40 fold in recA1 , recBC- or recF- backgrounds. In contrast, transformation with CCC DNA was unaffected by the rec status of the host. Transformation with linear pBR322 DNA was increased 3-fold in a DNA ligase-overproducing ( lop11 ) mutant and decreased to a similar degree by transient inactivation of ligase in a ligts7 mutant. A proportion (ranging from about 9% in the wild-type to 42% in a recBC, lop11 mutant) of the transformants obtained with SalI-linearized pBR322 monomeric DNA contained deleted plasmids. Deletion rates were generally higher in rec- strains. Dephosphorylation of the termini on linear DNA or the creation of blunt-ended pBR322 molecules (by end-filling the SalI 5' protrusions or by cleavage with PvuII) decreased the transformation frequency whilst increasing the deletion rate. Linear pBR322 dimeric DNA gave transformation frequencies in recA+ and recA- strains that were reduced only 3 to 7 fold respectively relative to frequencies obtained with dimeric CCC DNA. Furthermore, in contrast to transformation with linear monomeric DNA, deletions were not observed. We propose that the majority of transformants arise, not by simple intracellular reannealing and ligation of the two cohesive SalI-termini of a linear molecule, but by intramolecular recombination.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Proteins↗
PubMed1984

Paraduodenal hernia: diagnosis and surgical management.

Paraduodenal hernia is an unusual cause of intestinal obstruction, but one with which all surgeons should be familiar. We reviewed the anatomy, pathophysiology, initial symptoms, radiographic criteria for diagnosis, and subsequent therapy of five patients treated for paraduodenal hernia at Walter Reed Army Medical Center. Contrast radiography of the small intestine remains the mainstay of preoperative diagnosis. Essential components of treatment include bowel reduction and obliteration of the hernia defect by simple closure or by wide opening of the sac. Further recommendations include sparing the inferior mesenteric vessels during the repair of left paraduodenal hernias and transpositioning the right colon to the left side of the abdomen for repair of right paraduodenal hernias.

Adult↗