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Biomedical subjects

J Lam

Publications and source records attributed to J Lam.

At least 109 records · Page 6Linked to original sources
PubMed1982

Simplified thoracic approach to the ascending and descending aorta in complex coarctation.

Two patients with left ventricular and proximal aortic hypertension secondary to diffuse hypoplasia of the aortic arch have recently been treated by a surgical technique based on: I simultaneous exposure of the ascending and descending thoracic aorta through a left antero-latero-posterior thoracotomy; 2 insertion of a Dacron graft between the aortic root and the descending thoracic aorta. In both cases equal systemic pressures in the ascending and descending thoracic aorta and adequate distal perfusion were obtained.

Aortic Coarctation↗
PubMed1980

Bacterial adhesion to uroepithelial cells: a morphologic study.

Urethral and midstream urine samples from healthy women and from patients with urinary tract infections (UTI) were examined by electron microscopy. Urethral urine samples from healthy subjects contained sparsely and densely colonized uroepithelial cells. The latter had morphologically heterogeneous bacteria adherent to each other and to the epithelial cell by a ruthenium red-positive fibrous matrix, which was present on the surface of all bacteria examined. Urethral urine samples from patients with UTI often had two distinct microcolonies of morphologically similar bacteria adherent to the same uroepithelial cell. Midstream urine samples from these patients contained large microcolonies of morphologically identical bacteria. Urine from patients with catheter-associated infections contained few uroepithelial cells and two distinct varieties of bacterial microcolonies--one of intact homogeneous cells and another of a mixture of damaged and intact bacteria. These in vivo observations indicate that the bacterial surface matrix participates in bacterial adhesion to uroepithelial cells and in bacteria-bacteria adhesion.

Adult↗
PubMed1980

Production of mucoid microcolonies by Pseudomonas aeruginosa within infected lungs in cystic fibrosis.

Direct electron microscopic examination of postmortem lung material from cystic fibrosis patients infected with Pseudomonas aeruginosa has shown that these bacterial cells form distinct fiber-enclosed microcolonies in the infected alveoli. Similar examination of bronchoscopy material from infected cystic fibrosis patients showed that the fibres of the enveloping matrix are definitely associated with the bacterial cells. The fibers of the extracellular matrix stain with ruthenium red and are therefore presumed to be polyanionic. When mucoid strains of P. aeruginosa were recovered from cystic fibrosis patients and grown in a suitable liquid medium, they were found to produce large microcolonies whose component cells were embedded in a very extensive matrix of polyanionic fibers that could be stabilized by reaction with antibodies to prevent collapse during the dehydration steps of preparation for electron microscopy. When these mucoid strains of P. aeruginosa were used to produce pulmonary infections of rats by the agar bead method, the infected alveoli contained large fiber-enclosed bacterial microcolonies. We conclude that the cells of P. aeruginosa that infect cystic fibrosis patients form microcolonies that are enveloped in a fibrous anionic matrix and that these microcolonies can be duplicated in in vitro cultures and in animal model systems.

Cystic Fibrosis↗
PubMed1979

Influence of mucoidy on antibody coating of Pseudomonas aeruginosa.

Antibody-coated bacteria were found in only two of 34 urine sediments from 19 catheterized patients infected with a single epidemic strain of Pseudomonas aeruginosa, whereas 12 of 19 urine sediments from 16 outpatients contained antibody-coated P. aeruginosa. In urine sediments, individual cells and microcolonies of the epidemic strain of P. aeruginosa were enclosed in ruthenium red (polysaccharide)-positive material. This strain was extremely mucoid when grown in a liquid medium for enhancement of mucoid formation. Renal infections was present in some patients, as determined by the bladder washout test and by titers of antibody in serum, and antibody was present in the urine but not coating P. aeruginosa. We conclude that the mucoid layer interfered with antibody coating of the epidemic strain of P. aeruginosa.

Antibodies, Bacterial↗
PubMed1979

Phototoxic polyacetylenes and their thiophene derivatives. (Effects on human skin).

Polyacetylenes and their thiophene derivatives were tested for their effects on human skin. Topically applied alpha-terthienyl evoked bi-phasic phototoxic dermatitis and the appearance of 'sunburn' cells in human epidermis. None of 11 polyacetylenes had the same effect although they mimicked alpha-terthienyl in their phototoxic effects on Candida albicans and certain pathogenic microorganisms. The UV-mediated antibiotic activity of the compounds and their apparent lack of phototoxicity towards the skin suggest a potential topical therapeutic role for them in yeast, fungal and bacterial infections and light-responsive dermatoses. Their topical sensitizing capacity, however, has not yet been studied.

Alkynes↗
PubMed1979

Morphological stabilization of capsules of group B streptococci, types Ia, Ib, II, and III, with specific antibody.

Antibody prepared to the type-specific capsular polysaccharides of group B streptococci was used to demonstrate a stabilizing effect on the capsular glycocalyx. This permitted visualization by electron microscopy of the size of the capsule relative to the rest of the bacterial cell, and clear differences in the dimensions of untreated and antibody-treated capsular material were noted. Antibodies produced against group B streptococci types Ia, Ib, II, and III were used to demonstrate morphologically that the organization and extent of the capsular glycocalyx more closely resembles its natural state on stabilization by reaction with specific antibody.

Animals↗
PubMed1979

Structural and biochemical examination of ghosts derived from a deep rough (heptose-deficient lipopolysaccharide) strain and a smooth strain of Escherichia coli.

Outer membrane derived 'ghosts' can be readily generated from both smooth and deep rough (heptose-deficient LPS) strains of Escherichia coli 08. MORPHOlogical and biochemical studies confirmed that 'ghosts' of both strains are composed of protein (four major proteins), LPS, and phospholipid (cardiolipin and phosphatidylethanolamine) in the form of a single membrane of roughly the same shape as intact normal cells. The ghost membrane cleaves only slightly in freeze-etch preparations of ghosts derived from the smooth strain as compared to the extensive cleavage plane of ghosts derived from the rough strain. The asymmetrical distribution of ghost proteins was visualized, by critical point drying and shadowing with platinum, as a relatively smooth outer surface with some discernible particles (10-15 nm) and an extremely particulate inner surface (10-15-mm particles. Ghosts derived from the smooth strain retained their structure following chloroform-methanol extraction, while ghosts derived from the rough strain fragmented with chloroform-methanol extraction. Evidence is presented that LPS-protein interactions as well as protein-protein interactions are significant in maintaining the ghost structure.

Bacterial Proteins↗
PubMed1978

The importance of the lysophosphatidylcholine and choline moiety of bile phosphatidylcholine in lymphatic transport of fat.

A luminal supply of biliary phosphatidylcholine is important in the translocation of absorbed fat into lymph and in the amount and composition of phosphatidylcholine concurrently synthesized. This study was undertaken to determine whether the effect was due to absorbed lysophosphatidylcholine, to a specific (1-palmitoyl) biliary lysophosphatidylcholine or to extra choline supplied by lysophosphatidylcholine. Rats with bile fistulae and thoracic duct lymph fistulae were given test meals of oleic acid and monoolein (molar ratio 2 : 1) infused duodenally for 8 h. Addition of choline chloride to the test meal increased lymphatic output of triglyceride and phospholipid but not to values found previously in rats with supplements of bile phosphatidylcholine or with bile ducts intact. Addition of dioleoyl phosphatidylcholine increased triglyceride and phospholipid output to values found in rats with intact bile ducts. Since dioleoyl phosphatidylcholine was as efficient as biliary phosphatidylcholine it was concluded that a luminal supply of 1-palmitoyl lysophosphatidylcholine was not essential. It seemed likely from the smaller effect of supplemented choline and from the fatty acid composition of lymph phosphatidylcholine that the essential requirement was a supply of absorbed lysophosphatidylcholine for rapid reacylation to phosphatidylcholine.

Animals↗
PubMed1976

Alpha-Amanitin resistance of RNA polymerase II in mutant Chinese hamster ovary cell lines.

A number of mutant Chinese hamster ovary (CHO) cell lines resistant to the cytotoxic action of alpha-amanitin have been isolated. The alpha-amanitin sensitivity of the different mutant cell lines varied widely, but correlated well with the alpha-amanitin sensitivity of the RNA polymerase II activity in each of these mutant cell lines. In comparison with the RNA polymerase II of wild-type cells, three mutants, Ama39, Ama6, and Amal, required respectively 2- to 3-fold, 8- to 10-fold, and about 800-fold higher concentrations of alpha-amanitin for inhibition of their polymerase II activity. Determination of the equilibrium dissociation constants (KD) for complexes between 0-[3H]methyl-demethyl-gamma-amanitin and RNA polymearse II indicated that differences in alpha-amanitin sensitivity were reflected in differences in the ability of the enzymes to bind amanitin. Hybrids formed by fusion of mutants with cells of wild-type sensitivity contained both mutant and wild-type polymerase II activities. Thus, each of the different alpha-amanitin resistance mutations was expressed co-dominantly. A test for complementation between two of these mutations by measurement of both the alpha-amanitin sensitivity and the [3H]amanitin binding by RNA polymerase II in Ama6 X Amal hybrid cells did not reveal any wild-type RNA polymerase II activity. These data provide evidence that the mutation to alpha-amanitin resistance involves structural changes in the gene coding for the alpha-amanitin binding subunit of RNA polymerase II. These changes appear to account for the alpha-amanitin-resistant phenotypes of these mutant cells.

Amanitins↗
PubMed1975

Sindbis virus inhibits phosphatidylcholine biosynthesis in BHK-21 cells.

Sindbis virus inhibits the incorporation of [methyl-3H]choline into the phospholipids of BHK-21 cells and also inhibits the activity of the enzyme that catalyzes the final reaction involved in phosphatidylcholine biosynthesis (cytidine diphosphate-choline:1,2-diacylglycerol cholinephosphotranferase; EC 2.7.8.2).

Cell Line↗
PubMedDate not supplied

Transesophageal echocardiography in pediatric patients: preliminary results.

Transesophageal echocardiography was attempted in 59 pediatric patients with congenital heart disease in the operating room (n = 33) or during heart catheterization or in the intensive care unit (n = 26). Six different commercially available transducers were used with diameters ranging from 7 to 15 mm. Age ranged from 1 day to 16 years, and body weight ranged from 3.7 to 65 kg. Objectives of the study were to determine (1) minimum body weight in which transesophageal echocardiography with various probes is possible, (2) additional diagnostic value, and (3) potential applications. In three cases (one surgical and two nonsurgical) the probe could not be inserted. Minimum body weight was 17 to 20 kg for probes with a diameter of greater than or equal to 13 mm and approximately 12 kg for the 11 mm probes. A 7 mm probe, on the other hand, could be inserted easily in all patients (including a neonate) in whom transesophageal echocardiography was attempted. In 11 of 56 patients, additional diagnostic information was obtained. Thus, transesophageal echocardiography is feasible in the pediatric age group provided that special probes are used in small children. Additional diagnostic information can be obtained, and the technique is of value during cardiac surgery or balloon interventions for evaluation of the efficacy of the procedure and for monitoring ventricular function.

Adolescent↗
PubMedDate not supplied

The role of the microcolony mode of growth in the pathogenesis of Pseudomonas aeruginosa infections.

In nature Pseudomonas aeruginosa grows in two modes, the mobile "swarmer" cell and the glycocalyx-enclosed microcolony. The microcolony mode is numerically dominant perhaps because it provides adhesion in a favorable niche and protection from bacteriophages and phagocytic predators. When this organism colonizes the compromised human host, a broad spectrum of different types of infection is produced, ranging from asymptomatic persistent cystitis to the overwhelming bacteremia seen in neutropenic patients. These infections differ radically both in their degree of toxicity and invasiveness and in their susceptibility to control with specific antibodies and/or antibiotics. These differences may reflect the degree to which intact host defense mechanisms force the bacteria to adopt the defensive, microcolony mode of growth. As examples, the nearly intact host defense mechanisms and vigorous immune response of patients with cystic fibrosis force P. aeruginosa in pulmonary infections into a demonstrably cryptic, microcolony mode of growth that allows its persistence in the face of specific antibodies and antibiotics but limits its toxic activity and its dissemination. In contrast, the ruined defense mechanisms of burned skin allow the spread of bacteria in the mobile mode; toxic effects are seen in neighboring tissues, and a mixed mobile-microcolony reservoir population, whose mobile members can subsequently invade the circulatory system, is built up in the burned tissue. Thus, it is important to define the mode of bacterial growth in each type of P. aeruginosa infection and, where the microcolony mode is predominant, to understand the chemistry of the enveloping exopolysaccharide in order to limit its synthesis and/or facilitate its penetration by antibodies and antibiotics.

Animals↗